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Long Noncoding RNA NRAV Promotes Respiratory Syncytial Virus Replication by Targeting the MicroRNA miR-509-3p/Rab5c Axis To Regulate Vesicle Transportation [Virus-Cell Interactions]

Respiratory syncytial virus (RSV) is an enveloped RNA virus which is responsible for approximately 80% of lower respiratory tract infections in children. Current lines of evidence have supported the functional involvement of long noncoding RNA (lncRNA) in many viral infectious diseases. However, the overall biological effect and clinical role of lncRNAs in RSV infection remain unclear. In this study, lncRNAs related to respiratory virus infection were obtained from the lncRNA database, and we collected 144 clinical sputum specimens to identify lncRNAs related to RSV infection. Quantitative PCR (qPCR) detection indicated that the expression of lncRNA negative regulator of antiviral response (NRAV) in RSV-positive patients was significantly lower than that in uninfected patients, but lncRNA psoriasis-associated non-protein coding RNA induced by stress (PRINS), nuclear paraspeckle assembly transcript 1 (NEAT1), and Nettoie Salmonella pas Theiler’s (NeST) showed no difference in vivo and in vitro. Meanwhile, overexpression of NRAV promoted RSV proliferation in A549 and BEAS-2B cells, and vice versa, indicating that the downregulation of NRAV was part of the host antiviral defense. RNA fluorescent in situ hybridization (FISH) confirmed that NRAV was mainly located in the cytoplasm. Through RNA sequencing, we found that Rab5c, which is a vesicle transporting protein, showed the same change trend as NRAV. Subsequent investigation revealed that NRAV was able to favor RSV production indirectly by sponging microRNA miR-509-3p so as to release Rab5c and facilitate vesicle transportation. The study provides a new insight into virus-host interaction through noncoding RNA, which may contribute to exploring potential antivirus targets for respiratory virus.

IMPORTANCE The mechanism of interaction between RSV and host noncoding RNAs is not fully understood. In this study, we found that the expression of long noncoding RNA (lncRNA) negative regulator of antiviral response (NRAV) was reduced in RSV-infected patients, and overexpression of NRAV facilitated RSV production in vitro, suggesting that the reduction of NRAV in RSV infection was part of the host antiviral response. We also found that NRAV competed with vesicle protein Rab5c for microRNA miR509-3p in cytoplasm to promote RSV vesicle transport and accelerate RSV proliferation, thereby improving our understanding of the pathogenic mechanism of RSV infection.




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Mutations Near the N Terminus of Vaccinia Virus G9 Protein Overcome Restrictions on Cell Entry and Syncytium Formation Imposed by the A56/K2 Fusion Regulatory Complex [Virus-Cell Interactions]

The entry/fusion complex (EFC) consists of 11 conserved proteins embedded in the membrane envelope of mature poxvirus particles. Poxviruses also encode proteins that localize in cell membranes and negatively regulate superinfection and syncytium formation. The vaccinia virus (VACV) A56/K2 fusion regulatory complex associates with the G9/A16 EFC subcomplex, but functional support for the importance of this interaction was lacking. Here, we describe serially passaging VACV in nonpermissive cells expressing A56/K2 as an unbiased approach to isolate and analyze escape mutants. Viruses forming large plaques in A56/K2 cells increased in successive rounds of infection, indicating the occurrence and enrichment of adaptive mutations. Sequencing of genomes of passaged and cloned viruses revealed mutations near the N terminus of the G9 open reading frame but none in A16 or other genes. The most frequent mutation was His to Tyr at amino acid 44; additional escape mutants had a His-to-Arg mutation at amino acid 44 or a duplication of amino acids 26 to 39. An adaptive Tyr-to-Cys substitution at amino acid 42 was discovered using error-prone PCR to generate additional mutations. Myristoylation of G9 was unaffected by the near-N-terminal mutations. The roles of the G9 mutations in enhancing plaque size were validated by homologous recombination. The mutants exhibited enhanced entry and spread in A56/K2 cells and induced syncytia at neutral pH in HeLa cells despite the expression of A56/K2. The data suggest that the mutations perturb the interaction of G9 with A56/K2, although some association was still detected in detergent-treated infected cell lysates.

IMPORTANCE The entry of enveloped viruses is achieved by the fusion of viral and cellular membranes, a critical step in infection that determines host range and provides targets for vaccines and therapeutics. Poxviruses encode an exceptionally large number of proteins comprising the entry/fusion complex (EFC), which enables infection of diverse cells. Vaccinia virus (VACV), the prototype member of the poxvirus family, also encodes the fusion regulatory proteins A56 and K2, which are displayed on the plasma membrane and may be beneficial by preventing reinfection and cell-cell fusion. Previous studies showed that A56/K2 interacts with the G9/A16 EFC subcomplex in detergent-treated cell extracts. Functional evidence for the importance of this interaction was obtained by serially passaging wild-type VACV in cells that are nonpermissive because of A56/K2 expression. VACV mutants with amino acid substitutions or duplications near the N terminus of G9 were enriched because of their ability to overcome the block to entry imposed by A56/K2.




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Sample multiplexing for targeted pathway proteomics in aging mice [Systems Biology]

Pathway proteomics strategies measure protein expression changes in specific cellular processes that carry out related functions. Using targeted tandem mass tags-based sample multiplexing, hundreds of proteins can be quantified across 10 or more samples simultaneously. To facilitate these highly complex experiments, we introduce a strategy that provides complete control over...




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Cannabinoid exposure in rat adolescence reprograms the initial behavioral, molecular, and epigenetic response to cocaine [Neuroscience]

The initial response to an addictive substance can facilitate repeated use: That is, individuals experiencing more positive effects are more likely to use that drug again. Increasing evidence suggests that psychoactive cannabinoid use in adolescence enhances the behavioral effects of cocaine. However, despite the behavioral data, there is no neurobiological...




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A minor population of macrophage-tropic HIV-1 variants is identified in recrudescing viremia following analytic treatment interruption [Microbiology]

HIV-1 persists in cellular reservoirs that can reignite viremia if antiretroviral therapy (ART) is interrupted. Therefore, insight into the nature of those reservoirs may be revealed from the composition of recrudescing viremia following treatment cessation. A minor population of macrophage-tropic (M-tropic) viruses was identified in a library of recombinant viruses...




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Inner Workings: Molecular biologists offer “wartime service” in the effort to test for COVID-19 [Medical Sciences]

As the novel coronavirus spreads, communities across the United States are struggling to offer public testing. The need is urgent. Testing got off to a delayed start in the United States as a result of technical missteps and a slow response from government officials. Now cities across the country are...




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A genome-wide association study identifies key modulators of complement factor H binding to malondialdehyde-epitopes [Immunology and Inflammation]

Genetic variants within complement factor H (CFH), a major alternative complement pathway regulator, are associated with the development of age-related macular degeneration (AMD) and other complementopathies. This is explained with the reduced binding of CFH or its splice variant factor H-like protein 1 (FHL-1) to self-ligands or altered self-ligands (e.g.,...




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Ammonia emission abatement does not fully control reduced forms of nitrogen deposition [Environmental Sciences]

Human activities and population growth have increased the natural burden of reactive nitrogen (N) in the environment. Excessive N deposition on Earth’s surface leads to adverse feedbacks on ecosystems and humans. Similar to that of air pollution, emission control is recognized as an efficient means to control acid deposition. Control...




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Aerosol-photolysis interaction reduces particulate matter during wintertime haze events [Earth, Atmospheric, and Planetary Sciences]

Aerosol–radiation interaction (ARI) plays a significant role in the accumulation of fine particulate matter (PM2.5) by stabilizing the planetary boundary layer and thus deteriorating air quality during haze events. However, modification of photolysis by aerosol scattering or absorbing solar radiation (aerosol–photolysis interaction or API) alters the atmospheric oxidizing capacity, decreases...




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Matrix mechanotransduction mediated by thrombospondin-1/integrin/YAP in the vascular remodeling [Cell Biology]

The extracellular matrix (ECM) initiates mechanical cues that activate intracellular signaling through matrix–cell interactions. In blood vessels, additional mechanical cues derived from the pulsatile blood flow and pressure play a pivotal role in homeostasis and disease development. Currently, the nature of the cues from the ECM and their interaction with...




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MTV proteins unveil ER- and microtubule-associated compartments in the plant vacuolar trafficking pathway [Cell Biology]

The factors and mechanisms involved in vacuolar transport in plants, and in particular those directing vesicles to their target endomembrane compartment, remain largely unknown. To identify components of the vacuolar trafficking machinery, we searched for Arabidopsis modified transport to the vacuole (mtv) mutants that abnormally secrete the synthetic vacuolar cargo...




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Regulatory mechanism for the transmembrane receptor that mediates bidirectional vitamin A transport [Biochemistry]

Vitamin A has diverse biological functions and is essential for human survival at every point from embryogenesis to adulthood. Vitamin A and its derivatives have been used to treat human diseases including vision diseases, skin diseases, and cancer. Both insufficient and excessive vitamin A uptake are detrimental, but how its...




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Emergence of self-organized multivortex states in flocks of active rollers [Applied Physical Sciences]

Active matter, both synthetic and biological, demonstrates complex spatiotemporal self-organization and the emergence of collective behavior. A coherent rotational motion, the vortex phase, is of great interest because of its ability to orchestrate well-organized motion of self-propelled particles over large distances. However, its generation without geometrical confinement has been a...




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Molecular and isotopic evidence for milk, meat, and plants in prehistoric eastern African herder food systems [Anthropology]

The development of pastoralism transformed human diets and societies in grasslands worldwide. The long-term success of cattle herding in Africa has been sustained by dynamic food systems, consumption of a broad range of primary and secondary livestock products, and the evolution of lactase persistence (LP), which allows digestion of lactose...




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Optimizing Rhizobium-legume symbioses by simultaneous measurement of rhizobial competitiveness and N2 fixation in nodules [Agricultural Sciences]

Legumes tend to be nodulated by competitive rhizobia that do not maximize nitrogen (N2) fixation, resulting in suboptimal yields. Rhizobial nodulation competitiveness and effectiveness at N2 fixation are independent traits, making their measurement extremely time-consuming with low experimental throughput. To transform the experimental assessment of rhizobial competitiveness and effectiveness, we...




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PCARE and WASF3 regulate ciliary F-actin assembly that is required for the initiation of photoreceptor outer segment disk formation [Genetics]

The outer segments (OS) of rod and cone photoreceptor cells are specialized sensory cilia that contain hundreds of opsin-loaded stacked membrane disks that enable phototransduction. The biogenesis of these disks is initiated at the OS base, but the driving force has been debated. Here, we studied the function of the...




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Turning up the heat in turbulent thermal convection [Applied Physical Sciences]

Convection is buoyancy-driven flow resulting from unstable density stratification in the presence of a gravitational field. Beyond convection’s central role in myriad engineering heat transfer applications, it underlies many of nature’s dynamical designs on larger-than-human scales. For example, solar heating of Earth’s surface generates buoyancy forces that cause the winds...




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Multiple antisocial personalities? [Social Sciences]

Engelmann et al. ask whether “personality traits [can] help us better understand economic behavior across strategic contexts” (ref. 1, p. 12781), and, as an answer to this, identify “an antisocial personality profile” (APP) (ref. 1, p. 12785). There is much to like about this investigation; in particular, it illustrates “that...




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E2F6-Mediated Downregulation of MIR22HG Facilitates the Progression of Laryngocarcinoma by Targeting the miR-5000-3p/FBXW7 Axis [Research Article]

Recently, abundant evidence has clarified that long noncoding RNAs (lncRNAs) play an oncogenic or anticancer role in the tumorigenesis and development of diverse human cancers. Described as a crucial regulator in some cancers, MIR22HG has not yet been studied in laryngocarcinoma and therefore the underlying regulatory role of MIR22HG in laryngocarcinoma is worth detecting. In this study, MIR22HG expression in laryngocarcinoma cells was confirmed to be downregulated, and upregulated MIR22HG expression led to suppressive effects on laryngocarcinoma cell proliferation and migration. Molecular mechanism assays revealed that MIR22HG sponges miR-5000-3p in laryngocarcinoma cells. Besides, decreased expression of miR-5000-3p suppressed laryngocarcinoma cell proliferation and migration. Moreover, the FBXW7 gene was reported to be a downstream target gene of miR-5000-3p in laryngocarcinoma cells. More importantly, rescue assays verified that FBXW7 depletion or miR-5000-3p upregulation countervailed the repressive effects of MIR22HG overexpression on laryngocarcinoma progression. In addition, E2F6 was proved to be capable of inhibiting MIR22HG transcription in laryngocarcinoma cells. To sum up, E2F6-induced downregulation of MIR22HG promotes laryngocarcinoma progression through the miR-5000-3p/FBXW7 axis.




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AKT Regulates Mitotic Progression of Mammalian Cells by Phosphorylating MASTL, Leading to Protein Phosphatase 2A Inactivation [Research Article]

Microtubule-associated serine/threonine kinase like (MASTL), also known as Greatwall (Gwl) kinase, has an important role in the regulation of mitosis. By inhibiting protein phosphatase 2A (PP2A), it plays a crucial role in activating one of the most important mitotic kinases, known as cyclin-dependent kinase 1 (CDK1). MASTL has been seen to be upregulated in various types of cancers and is also involved in tumor recurrence. It is activated by CDK1 through phosphorylations in the activation/T-loop, but the complete mechanism of its activation is still unclear. Here, we report that AKT phosphorylates MASTL at residue T299, which plays a critical role in its activation. Our results suggest that AKT increases CDK1-mediated phosphorylation and hence the activity of MASTL, which, in turn, promotes mitotic progression through PP2A inhibition. We also show that the oncogenic potential of AKT is augmented by MASTL activation, since AKT-mediated proliferation in colorectal cell lines can be attenuated by inhibiting and/or silencing MASTL. In brief, we report that AKT plays an important role in the progression of mitosis in mammalian cells and that it does so through the phosphorylation and activation of MASTL.




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Inhaled Corticosteroid Treatment in Chronic Obstructive Pulmonary Disease (COPD): Boon or Bane?

Inhaled corticosteroid (ICS)–based therapy is often used for patients with chronic obstructive pulmonary disease (COPD). However, this approach is under scrutiny because of ICS overuse in patients for whom it is not recommended and because of concerns about adverse events, particularly pneumonia, with long-term ICS use. Evidence suggests ICS may be beneficial in specific patients, namely, those with high blood eosinophil counts (eg, ≥300 cells/µL) or who are at a high risk of exacerbations. According to the Global Initiative for Chronic Obstructive Lung Disease (GOLD) 2020 ABCD assessment tool, these patients belong in group D. For these patients, recommended initial treatment includes ICS in combination with long-acting β2-agonists (LABAs) when blood eosinophil counts are ≥300 cells/µL or LABA + long-acting muscarinic antagonist (LAMA) when patients are highly symptomatic, that is, with greater dyspnea and/or exercise limitation. Follow-up treatments for patients with persistent dyspnea and/or exacerbations may include LABA + ICS, LABA + LAMA, or LABA + LAMA + ICS, with use of ICS being guided by blood eosinophil counts. In this review, differences in the inflammatory mechanism underlying COPD and asthma and the role of ICS treatment in COPD are summarized. Furthermore, findings from recent clinical trials where use of ICS-based dual or triple therapy in COPD was compared with LABA + LAMA therapy and trials in which ICS withdrawal was evaluated in patients with COPD are reviewed. Finally, a step-by-step guide for ICS withdrawal in patients who are unlikely to benefit from this treatment is proposed. A video of the author discussing the overall takeaway of the review article could be downloaded from the link provided: https://www.youtube.com/watch?v=Uq7Sr5jqPDI.




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Marketing Messages in Continuing Medical Education (CME) Modules on Binge-Eating Disorder (BED)

Background:

In 2015, Vyvanse (lisdexamfetamine) became the first Food and Drug Administration (FDA)-approved treatment for binge-eating disorder (BED), a condition first recognized by the DSM–V in 2013. Because pharmaceutical companies use continuing medical education (CME) to help sell drugs, we explored possible bias in CME modules on BED.

Methods:

We utilized a qualitative thematic analysis research approach to identify and classify patterns in CME activities focusing on BED.

Results:

We identified 27 online CME activities on BED in 2015. All were funded by Shire, which manufactures lisdexamfetamine. Seven of 16 presenters disclosed financial ties with Shire. Twenty-nine slides recurred in at least 2 CME modules, and 12 slides were repeated in 5 or more modules. Diagnosis-related themes included: BED is a real, treatable disease; BED is highly prevalent but often missed; BED can occur in anyone; BED results in poor quality of life; many patients with BED are obese; and BED makes losing weight difficult. Treatment-related themes included: lisdexamfetamine is highly effective; topiramate is limited by substantial adverse effects; and other therapeutic options for BED are inferior to lisdexamfetamine because they do not cause weight loss. Although amphetamines can cause addiction, myocardial infarction, stroke, and death, no module mentioned these serious adverse effects.

Conclusions:

It seems that CME is being used to promote lisdexamfetamine for weight loss (a contraindicated use) and to highlight benefits of lisdexamfetamine while underplaying the risks.




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Successful Health Care Provider Strategies to Overcome Psychological Insulin Resistance in United States and Canada

Purpose:

To identify specific actions and characteristics of health care providers (HCPs) in the United States and Canada that influenced patients with type 2 diabetes who were initially reluctant to begin insulin.

Methods:

Patients from the United States (n = 120) and Canada (n = 74) were recruited via registry, announcements, and physician referrals to complete a 30-minute online survey based on interviews with patients and providers regarding specific HCP actions that contributed to the decision to begin insulin.

Results:

The most helpful HCP actions were patient-centered approaches to improve patients’ understanding of the injection process (ie, "My HCP walked me through the whole process of exactly how to take insulin" [helped moderately or a lot, United States: 79%; Canada: 83%]) and alleviate concerns ("My HCP encouraged me to contact his/her office immediately if I ran into any problems or had questions after starting insulin" [United States: 76%; Canada: 82%]). Actions that were the least helpful included referrals to other sources (ie, "HCP referred patient to a class to help learn more about insulin" [United States: 40%; Canada: 58%]).

Conclusions:

The study provides valuable insight that HCPs can use to help patients overcome psychological insulin resistance, which is a critical step in the design of effective intervention protocols.




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Many Family Medicine Successful Interventions and Clinical Reviews for Common Illnesses

Family physician researchers continue to provide assistance to improve family medicine care. Commentaries on social determinants of health lead off this issue. Next, we have several papers on successful interventions by clinicians and/or patients to improve diabetes control, and then other provide information on other practice interventions that make a difference in overall care. Drug advertising continues to mislead. There is costly and nonproductive overuse of specific types of care. Herein is also a Scoping Review of possible indices for determining timely initiation of advance care planning. The issue’s clinical reviews on use of transgender care, cervical myelopathy, and inhaled steroids for chronic obstructive pulmonary disease are pertinent, thorough, and timely.




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Habituation of the cardiovascular response to restraint stress is inhibited by exposure to other stressor stimuli and exercise training [RESEARCH ARTICLE]

Ricardo Benini, Leandro A. Oliveira, Lucas Gomes-de-Souza, Bruno Rodrigues, and Carlos C. Crestani

This study evaluated the effect of exposure to either a chronic variable stress (CVS) protocol or social isolation, as well as treadmill exercise training, in the habituation of the cardiovascular response upon repeated exposure to restraint stress in rats. The habituation of the corticosterone response to repeated restraint stress was also evaluated. For this, animals were subjected to either acute or 10 daily sessions of 60 min of restraint stress. CVS and social isolation protocols lasted for 10 consecutive days, whereas treadmill training was performed for 1 h per day, 5 days per week for 8 weeks. We observed that the increase in serum corticosterone was reduced during both the stress and the recovery period of the 10th session of restraint. Habituation of the cardiovascular response was identified in terms of a faster return of heart rate to baseline values during the recovery period of the 10th session of restraint. The increase in blood pressure and the decrease in tail skin temperature were similar at the 1st and 10th session of restraint. Exposure to CVS, social isolation or treadmill exercise training inhibited the habituation of the restraint-evoked tachycardia. Additionally, CVS increased the blood pressure response at the 10th session of restraint, whereas social isolation enhanced both the tachycardia during the first session and the drop in skin temperature at the 10th session of restraint. Taken together, these findings provide new evidence that pathologies evoked by stress might be related to impairment in the habituation process to homotypic stressors.




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Emergent properties of branching morphologies modulate the sensitivity of coral calcification to high PCO2 [RESEARCH ARTICLE]

Peter J. Edmunds and Scott C. Burgess

Experiments with coral fragments (i.e. nubbins) have shown that net calcification is depressed by elevated PCO2. Evaluating the implications of this finding requires scaling of results from nubbins to colonies, yet the experiments to codify this process have not been carried out. Building from our previous research demonstrating that net calcification of Pocillopora verrucosa (2–13 cm diameter) was unaffected by PCO2 (400 and 1000 µatm) and temperature (26.5 and 29.7°C), we sought generality to this outcome by testing how colony size modulates PCO2 and temperature sensitivity in a branching acroporid. Together, these taxa represent two of the dominant lineages of branching corals on Indo-Pacific coral reefs. Two trials conducted over 2 years tested the hypothesis that the seasonal range in seawater temperature (26.5 and 29.2°C) and a future PCO2 (1062 µatm versus an ambient level of 461 µatm) affect net calcification of an ecologically relevant size range (5–20 cm diameter) of colonies of Acropora hyacinthus. As for P. verrucosa, the effects of temperature and PCO2 on net calcification (mg day–1) of A. verrucosa were not statistically detectable. These results support the generality of a null outcome on net calcification of exposing intact colonies of branching corals to environmental conditions contrasting seasonal variation in temperature and predicted future variation in PCO2. While there is a need to expand beyond an experimental culture relying on coral nubbins as tractable replicates, rigorously responding to this need poses substantial ethical and logistical challenges.




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In vitro insulin treatment reverses changes elicited by nutrients in cellular metabolic processes that regulate food intake in fish [RESEARCH ARTICLE]

Ayelen M. Blanco, Juan I. Bertucci, Jose L. Soengas, and Suraj Unniappan

This research assessed the direct effects of insulin on nutrient-sensing mechanisms in the brain of rainbow trout (Oncorhynchus mykiss) using an in vitro approach. Cultured hypothalamus and hindbrain were exposed to 1 µmol l–1 insulin for 3 h, and signals involved in appetite regulation and nutrient-sensing mechanisms were measured. Additionally, the involvement of the phosphatidylinositide 3-kinase (PI3K)/protein kinase B (Akt) signaling pathway in the actions of insulin was studied by using the inhibitor wortmannin. Treatment with insulin alone did not elicit many changes in the appetite regulators and nutrient-sensing-related genes and enzymes tested in the hypothalamus and hindbrain. However, we found that, when insulin and nutrients were added together, insulin reversed most of the effects exerted by nutrients alone, suggesting that insulin changes responsiveness to nutrients at the central level. Effects reversed by insulin included expression levels of genes related to the sensing of both glucose (slc2a2, slc5a1, gck, pck1, pklr, g6pcb, gys1, tas1r3 and nr1h3 in the hindbrain, and slc2a2, pklr and pck1 in the hypothalamus) and fatty acid (cd36 in the hindbrain, and cd36 and acly in the hypothalamus). Nutrient-induced changes in the activity of Acly and Cpt-1 in the hindbrain and of Pepck, Acly, Fas and Hoad in the hypothalamus were also reversed by insulin. Most of the insulin effects disappeared in the presence of wortmannin, suggesting the PI3K/Akt pathway is a mediator of the effects of insulin reported here. This study adds new information to our knowledge of the mechanisms regulating nutrient sensing in fish.




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Limits to sustained energy intake. XXX. Constraint or restraint? Manipulations of food supply show peak food intake in lactation is constrained [RESEARCH ARTICLE]

Zhi-Jun Zhao, Davina Derous, Abby Gerrard, Jing Wen, Xue Liu, Song Tan, Catherine Hambly, and John R. Speakman

Lactating mice increase food intake 4- to 5-fold, reaching an asymptote in late lactation. A key question is whether this asymptote reflects a physiological constraint, or a maternal investment strategy (a ‘restraint’). We exposed lactating mice to periods of food restriction, hypothesizing that if the limit reflected restraint, they would compensate by breaching the asymptote when refeeding. In contrast, if it was a constraint, they would by definition be unable to increase their intake on refeeding days. Using isotope methods, we found that during food restriction, the females shut down milk production, impacting offspring growth. During refeeding, food intake and milk production rose again, but not significantly above unrestricted controls. These data provide strong evidence that asymptotic intake in lactation reflects a physiological/physical constraint, rather than restraint. Because hypothalamic neuropeptide Y (Npy) was upregulated under both states of restriction, this suggests the constraint is not imposed by limits in the capacity to upregulate hunger signalling (the saturated neural capacity hypothesis). Understanding the genetic basis of the constraint will be a key future goal and will provide us additional information on the nature of the constraining factors on reproductive output, and their potential links to life history strategies.




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The effect of vertical extent of stimuli on cockroach optomotor response [RESEARCH ARTICLE]

Juha Nuutila, Anna E. Honkanen, Kyösti Heimonen, and Matti Weckström

Using tethered American cockroaches walking on a trackball in a spherical virtual reality environment, we tested optomotor responses to horizontally moving black-and-white gratings of different vertical extent under six different light intensities. We found that shortening the vertical extent of the wide-field stimulus grating within a light level weakened response strength, reduced average velocity, and decreased angular walking distance. Optomotor responses with the vertically shortened stimuli persisted down to light intensity levels of 0.05 lx. Response latency seems to be independent of both the height of the stimulus and light intensity. The optomotor response started saturating at the light intensity of 5 lx, where the shortest behaviourally significant stimulus was 1°. This indicates that the number of vertical ommatidial rows needed to elicit an optomotor response at 5 lx and above is in the single digits, maybe even just one. Our behavioural results encourage further inquiry into the interplay of light intensity and stimulus size in insect dim-light vision.




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In vitro-virtual-reality: an anatomically explicit musculoskeletal simulation powered by in vitro muscle using closed loop tissue-software interaction [METHODS [amp ] TECHNIQUES]

Christopher T. Richards and Enrico A. Eberhard

Muscle force-length dynamics are governed by intrinsic contractile properties, motor stimulation and mechanical load. Although intrinsic properties are well-characterised, physiologists lack in vitro instrumentation accounting for combined effects of limb inertia, musculoskeletal architecture and contractile dynamics. We introduce in vitro virtual-reality (in vitro-VR) which enables in vitro muscle tissue to drive a musculoskeletal jumping simulation. In hardware, muscle force from a frog plantaris was transmitted to a software model where joint torques, inertia and ground reaction forces were computed to advance the simulation at 1 kHz. To close the loop, simulated muscle strain was returned to update in vitro length. We manipulated 1) stimulation timing and, 2) the virtual muscle's anatomical origin. This influenced interactions among muscular, inertial, gravitational and contact forces dictating limb kinematics and jump performance. We propose that in vitro-VR can be used to illustrate how neuromuscular control and musculoskeletal anatomy influence muscle dynamics and biomechanical performance.




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The energetics of the New Zealand rockwren (Xenicus gilviventris): could a passerine hibernate? [RESEARCH ARTICLE]

Brian K. McNab and Kerry A. Weston

The thermal physiology of the endangered New Zealand rockwren (Xenicus gilviventris) is examined. It is a member of the Acanthisittidae, a family unique to New Zealand. This family, derived from Gondwana, is thought to be the sister taxon to all other passerines. Rockwrens permanently reside above the climatic timberline at altitudes from 1,000 to 2,900 meters in the mountains of South Island. They feed on invertebrates and in winter face ambient temperatures far below freezing and deep deposits of snow. Their body temperature and rate of metabolism are highly variable. Rockwrens regulate body temperature at ca. 36.4°C, which in one individual decreased to 33.1°C at an ambient temperature of 9.4°C. Its rate of metabolism decreased by 30%; body temperature spontaneously returned to 36°C. The rate of metabolism in a second individual twice decreased by 35%, nearly to the basal rate expected from mass without a decrease in body temperature. The New Zealand rockwren's food habits, entrance into torpor, and continuous residence in a thermally demanding environment suggest that it may hibernate. For that conclusion to be accepted, evidence of its use of torpor for extended periods is required. Those data are not presently available. Acanthisittids are distinguished from other passerines by the combination of their permanent temperate distribution, thermal flexibility, and a propensity to evolve a flightless condition. These characteristics may principally reflect their geographical isolation in a temperate environment isolated from Gondwana for 82 million years in the absence of mammalian predators.




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Magnetoreception in fishes: the effect of magnetic pulses on orientation of juvenile Pacific salmon [RESEARCH ARTICLE]

Lewis C. Naisbett-Jones, Nathan F. Putman, Michelle M. Scanlan, David L. G. Noakes, and Kenneth J. Lohmann

A variety of animals sense Earth's magnetic field and use it to guide movements over a wide range of spatial scales. Little is known, however, about the mechanisms that underlie magnetic field detection. Among teleost fish, growing evidence suggests that crystals of the mineral magnetite provide the physical basis of the magnetic sense. In this study, juvenile Chinook salmon (Oncorhynchus tshawytscha) were exposed to a brief but strong magnetic pulse capable of altering the magnetic dipole moment of biogenic magnetite. Orientation behaviour of pulsed fish and untreated control fish was then compared in a magnetic coil system under two conditions: (1) the local magnetic field; and (2) a magnetic field that exists near the southern boundary of the natural oceanic range of Chinook salmon. In the local field, no significant difference existed between the orientation of the control and pulsed groups. By contrast, orientation of the two groups was significantly different in the magnetic field from the distant site. These results demonstrate that a magnetic pulse can alter the magnetic orientation behaviour of a fish and are consistent with the hypothesis that salmon have magnetite-based magnetoreception.




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Responses of activity rhythms to temperature cues evolve in Drosophila populations selected for divergent timing of eclosion [RESEARCH ARTICLE]

Lakshman Abhilash, Arshad Kalliyil, and Vasu Sheeba

Even though the rhythm in adult emergence and rhythm in locomotor activity are two different rhythmic phenomena that occur at distinct life-stages of the fly life cycle, previous studies have hinted at similarities in certain aspects of the organisation of the circadian clock driving these two rhythms. For instance, the period gene plays an important regulatory role in both rhythms. In an earlier study, we have shown that selection on timing of adult emergence behaviour in populations of Drosophila melanogaster leads to the co-evolution of temperature sensitivity of circadian clocks driving eclosion. In this study, we were interested in asking if temperature sensitivity of the locomotor activity rhythm has evolved in our populations with divergent timing of adult emergence rhythm, with the goal of understanding the extent of similarity (or lack of it) in circadian organisation between the two rhythms. We found that in response to simulated jetlag with temperature cycles, late chronotypes (populations selected for predominant emergence during dusk) indeed re-entrain faster than early chronotypes (populations selected for predominant emergence during dawn) to 6-h phase-delays, thereby indicating enhanced sensitivity of the activity/rest clock to temperature cues in these stocks (entrainment is the synchronisation of internal rhythms to cyclic environmental time-cues). Additionally, we found that late chronotypes show higher plasticity of phases across regimes, day-to-day stability in phases and amplitude of entrainment, all indicative of enhanced temperature sensitive activity/rest rhythms. Our results highlight remarkably similar organisation principles between emergence and activity/rest rhythms.




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Androgenic modulation of extraordinary muscle speed creates a performance trade-off with endurance [RESEARCH ARTICLE]

Daniel J. Tobiansky, Meredith C. Miles, Franz Goller, and Matthew J. Fuxjager

Performance trade-offs can dramatically alter an organism's evolutionary trajectory by making certain phenotypic outcomes unattainable. Understanding how these trade-offs arise from an animal's design is therefore an important goal of biology. To explore this topic, we study how androgenic hormones, which regulate skeletal muscle function, influence performance trade-offs relevant to different components of complex reproductive behaviour. We conduct this work in golden-collared manakins (Manacus vitellinus), a Neotropical bird in which males court females by rapidly snapping their wings together above their back. Androgens help mediate the snap displays by radically increasing the twitch speed of a dorsal wing muscle [scapulohumeralis caudalis (SH)], which actuates the bird's wing-snap. Through hormone manipulations and in situ muscle recordings, we test how these positive effects on SH speed influence trade-offs with endurance. Indeed, this trait impacts the display by shaping signal length. We find that androgen-dependent increases in SH speed incur a cost to endurance, particularly when this muscle performs at its functional limits. Moreover, when behavioural data are overlaid on our muscle recordings, displaying animals appear to balance display speed with fatigue-induced muscle fusion (physiological tetanus) to generate the fastest possible signal while maintaining an appropriate signal duration. Our results point to androgenic hormone action as a functional trigger of trade-offs in sexual performance—they enhance one element of a courtship display, but in doing so, impede another.




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Spatial orientation based on multiple visual cues in non-migratory monarch butterflies [RESEARCH ARTICLE]

Myriam Franzke, Christian Kraus, David Dreyer, Keram Pfeiffer, M. Jerome Beetz, Anna L. Stöckl, James J. Foster, Eric J. Warrant, and Basil el Jundi

Monarch butterflies (Danaus plexippus) are prominent for their annual long-distance migration from North America to their overwintering area in Central Mexico. To find their way on this long journey, they use a sun compass as their main orientation reference but will also adjust their migratory direction with respect to mountain ranges. This indicates that the migratory butterflies also attend to the panorama to guide their travels. While the compass has been studied in detail in migrating butterflies, little is known about the orientation abilities of non-migrating butterflies. Here we studied if non-migrating butterflies - that stay in a more restricted area to feed and breed - also use a similar compass system to guide their flights. Performing behavioral experiments on tethered flying butterflies in an indoor LED flight simulator, we found that the monarchs fly along straight tracks with respect to a simulated sun. When a panoramic skyline was presented as the only orientation cue, the butterflies maintained their flight direction only during short sequences suggesting that they potentially use it for flight stabilization. We further found that when we presented the two cues together, the butterflies incorporate both cues in their compass. Taken together, we here show that non-migrating monarch butterflies can combine multiple visual cues for robust orientation, an ability that may also aid them during their migration.




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Fish embryo vulnerability to combined acidification and warming coincides with low capacity for homeostatic regulation [RESEARCH ARTICLE]

Flemming Dahlke, Magnus Lucassen, Ulf Bickmeyer, Sylke Wohlrab, Velmurugu Puvanendran, Atle Mortensen, Melissa Chierici, Hans-Otto Pörtner, and Daniela Storch

The vulnerability of fish embryos and larvae to environmental factors is often attributed to a lack of adult-like organ systems (gills) and thus insufficient homeostatic capacity. However, experimental data supporting this hypothesis are scarce. Here, by using Atlantic cod (Gadus morhua) as a model, the relationship between embryo vulnerability (to projected ocean acidification and warming) and homeostatic capacity was explored through parallel analyses of stage-specific mortality and in vitro activity and expression of major ion pumps (ATP-Synthase, Na+/K+-ATPase, H+-ATPase) and co-transporters (NBC1, NKCC1). Immunolocalization of these transporters was used to study ionocyte morphology in newly-hatched larvae. Treatment-related embryo mortality until hatch (+20% due to acidification and warming) occurred primarily during an early period (gastrulation) characterized by extremely low ion transport capacities. Thereafter, embryo mortality decreased in parallel with an exponential increase in activity and expression of all investigated ion transporters. Significant changes in transporter activity and expression in response to acidification (+15% activity) and warming (-30% expression) indicate some potential for short-term acclimatization, although likely associated with energetic trade-offs. Interestingly, whole-larvae enzyme capacities (supported by abundant epidermal ionocytes) reached levels similar to those previously measured in gill tissue of adult cod, suggesting that early-life stages without functional gills are better equipped in terms of ion homeostasis than previously thought. This study implies that the gastrulation period represents a critical transition from inherited (maternal) defenses to active homeostatic regulation, which facilitates enhanced resilience of later stages to environmental factors.




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Renal, Cardiovascular, and Safety Outcomes of Canagliflozin by Baseline Kidney Function: A Secondary Analysis of the CREDENCE Randomized Trial

Background

Canagliflozin reduced renal and cardiovascular events in people with type 2 diabetes in the CREDENCE trial. We assessed efficacy and safety of canagliflozin by initial estimated glomerular filtration rate (eGFR).

Methods

CREDENCE randomly assigned 4401 participants with an eGFR of 30 to <90 ml/min per 1.73 m2 and substantial albuminuria to canagliflozin 100 mg or placebo. We used Cox proportional hazards regression to analyze effects on renal and cardiovascular efficacy and safety outcomes within screening eGFR subgroups (30 to <45, 45 to <60, and 60 to <90 ml/min per 1.73 m2) and linear mixed effects models to analyze the effects on eGFR slope.

Results

At screening, 1313 (30%), 1279 (29%), and 1809 (41%) participants had an eGFR of 30 to <45, 45 to <60, and 60 to <90 ml/min per 1.73 m2, respectively. The relative benefits of canagliflozin for renal and cardiovascular outcomes appeared consistent among eGFR subgroups (all P interaction >0.11). Subgroups with lower eGFRs, who were at greater risk, exhibited larger absolute benefits for renal outcomes. Canagliflozin’s lack of effect on serious adverse events, amputations, and fractures appeared consistent among eGFR subgroups. In all subgroups, canagliflozin use led to an acute eGFR drop followed by relative stabilization of eGFR loss. Among those with an eGFR of 30 to <45 ml/min per 1.73 m2, canagliflozin led to an initial drop of 2.03 ml/min per 1.73 m2. Thereafter, decline in eGFR was slower in the canagliflozin versus placebo group (–1.72 versus –4.33 ml/min per 1.73 m2; between-group difference 2.61 ml/min per 1.73 m2).

Conclusions

Canagliflozin safely reduced the risk of renal and cardiovascular events, with consistent results across eGFR subgroups, including the subgroup initiating treatment with an eGFR of 30 to <45 ml/min per 1.73 m2. Absolute benefits for renal outcomes were greatest in subgroups with lower eGFR.

Clinical Trial registry name and registration number

Evaluation of the Effects of Canagliflozin on Renal and Cardiovascular Outcomes in Participants With Diabetic Nephropathy (CREDENCE), NCT02065791.




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A Simple Clinical Tool for Stratifying Risk of Clinically Significant CKD after Nephrectomy: Development and Multinational Validation

Background

Clinically significant CKD following surgery for kidney cancer is associated with increased morbidity and mortality, but identifying patients at increased CKD risk remains difficult. Simple methods to stratify risk of clinically significant CKD after nephrectomy are needed.

Methods

To develop a tool for stratifying patients’ risk of CKD arising after surgery for kidney cancer, we tested models in a population-based cohort of 699 patients with kidney cancer in Queensland, Australia (2012–2013). We validated these models in a population-based cohort of 423 patients from Victoria, Australia, and in patient cohorts from single centers in Queensland, Scotland, and England. Eligible patients had two functioning kidneys and a preoperative eGFR ≥60 ml/min per 1.73 m2. The main outcome was incident eGFR <45 ml/min per 1.73 m2 at 12 months postnephrectomy. We used prespecified predictors—age ≥65 years old, diabetes mellitus, preoperative eGFR, and nephrectomy type (partial/radical)—to fit logistic regression models and grouped patients according to degree of risk of clinically significant CKD (negligible, low, moderate, or high risk).

Results

Absolute risks of stage 3b or higher CKD were <2%, 3% to 14%, 21% to 26%, and 46% to 69% across the four strata of negligible, low, moderate, and high risk, respectively. The negative predictive value of the negligible risk category was 98.9% for clinically significant CKD. The c statistic for this score ranged from 0.84 to 0.88 across derivation and validation cohorts.

Conclusions

Our simple scoring system can reproducibly stratify postnephrectomy CKD risk on the basis of readily available parameters. This clinical tool’s quantitative assessment of CKD risk may be weighed against other considerations when planning management of kidney tumors and help inform shared decision making between clinicians and patients.




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Effect of Low-Sodium versus Conventional Sodium Dialysate on Left Ventricular Mass in Home and Self-Care Satellite Facility Hemodialysis Patients: A Randomized Clinical Trial

Background

Fluid overload in patients undergoing hemodialysis contributes to cardiovascular morbidity and mortality. There is a global trend to lower dialysate sodium with the goal of reducing fluid overload.

Methods

To investigate whether lower dialysate sodium during hemodialysis reduces left ventricular mass, we conducted a randomized trial in which patients received either low-sodium dialysate (135 mM) or conventional dialysate (140 mM) for 12 months. We included participants who were aged >18 years old, had a predialysis serum sodium ≥135 mM, and were receiving hemodialysis at home or a self-care satellite facility. Exclusion criteria included hemodialysis frequency >3.5 times per week and use of sodium profiling or hemodiafiltration. The main outcome was left ventricular mass index by cardiac magnetic resonance imaging.

Results

The 99 participants had a median age of 51 years old; 67 were men, 31 had diabetes mellitus, and 59 had left ventricular hypertrophy. Over 12 months of follow-up, relative to control, a dialysate sodium concentration of 135 mmol/L did not change the left ventricular mass index, despite significant reductions at 6 and 12 months in interdialytic weight gain, in extracellular fluid volume, and in plasma B-type natriuretic peptide concentration (ratio of intervention to control). The intervention increased intradialytic hypotension (odds ratio [OR], 7.5; 95% confidence interval [95% CI], 1.1 to 49.8 at 6 months and OR, 3.6; 95% CI, 0.5 to 28.8 at 12 months). Five participants in the intervention arm could not complete the trial because of hypotension. We found no effect on health-related quality of life measures, perceived thirst or xerostomia, or dietary sodium intake.

Conclusions

Dialysate sodium of 135 mmol/L did not reduce left ventricular mass relative to control, despite improving fluid status.

Clinical Trial registry name and registration number:

The Australian New Zealand Clinical Trials Registry, ACTRN12611000975998.




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Plasma Biomarkers of Tubular Injury and Inflammation Are Associated with CKD Progression in Children

Background

After accounting for known risk factors for CKD progression in children, clinical outcomes among children with CKD still vary substantially. Biomarkers of tubular injury (such as KIM-1), repair (such as YKL-40), or inflammation (such as MCP-1, suPAR, TNF receptor-1 [TNFR-1], and TNFR-2) may identify children with CKD at risk for GFR decline.

Methods

We investigated whether plasma KIM-1, YKL-40, MCP-1, suPAR, TNFR-1, and TNFR-2 are associated with GFR decline in children with CKD and in subgroups defined by glomerular versus nonglomerular cause of CKD. We studied participants of the prospective CKiD Cohort Study which enrolled children with an eGFR of 30–90 ml/min per 1.73 m2 and then assessed eGFR annually. Biomarkers were measured in plasma collected 5 months after study enrollment. The primary endpoint was CKD progression, defined as a composite of a 50% decline in eGFR or incident ESKD.

Results

Of the 651 children evaluated (median age 11 years; median baseline eGFR of 53 ml/min per 1.73 m2), 195 (30%) had a glomerular cause of CKD. Over a median follow-up of 5.7 years, 223 children (34%) experienced CKD progression to the composite endpoint. After multivariable adjustment, children with a plasma KIM-1, TNFR-1, or TNFR-2 concentration in the highest quartile were at significantly higher risk of CKD progression compared with children with a concentration for the respective biomarker in the lowest quartile (a 4-fold higher risk for KIM-1 and TNFR-1 and a 2-fold higher risk for TNFR-2). Plasma MCP-1, suPAR, and YKL-40 were not independently associated with progression. When stratified by glomerular versus nonglomerular etiology of CKD, effect estimates did not differ significantly.

Conclusions

Higher plasma KIM-1, TNFR-1, and TNFR-2 are independently associated with CKD progression in children.




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Protein Kinase C-{delta} Mediates Kidney Tubular Injury in Cold Storage-Associated Kidney Transplantation

Background

Kidney injury associated with cold storage is a determinant of delayed graft function and the long-term outcome of transplanted kidneys, but the underlying mechanism remains elusive. We previously reported a role of protein kinase C- (PKC) in renal tubular injury during cisplatin nephrotoxicity and albumin-associated kidney injury, but whether PKC is involved in ischemic or transplantation-associated kidney injury is unknown.

Methods

To investigate PKC’s potential role in injury during cold storage–associated transplantation, we incubated rat kidney proximal tubule cells in University of Wisconsin (UW) solution at 4°C for cold storage, returning them to normal culture medium at 37°C for rewarming. We also stored kidneys from donor mice in cold UW solution for various durations, followed by transplantation into syngeneic recipient mice.

Results

We observed PKC activation in both in vitro and in vivo models of cold-storage rewarming or transplantation. In the mouse model, PKC was activated and accumulated in mitochondria, where it mediated phosphorylation of a mitochondrial fission protein, dynamin-related protein 1 (Drp1), at serine 616. Drp1 activation resulted in mitochondrial fission or fragmentation, accompanied by mitochondrial damage and tubular cell death. Deficiency of PKC in donor kidney ameliorated Drp1 phosphorylation, mitochondrial damage, tubular cell death, and kidney injury during cold storage–associated transplantation. PKC deficiency also improved the repair and function of the renal graft as a life-supporting kidney. An inhibitor of PKC, V1-1, protected kidneys against cold storage–associated transplantation injury.

Conclusions

These results indicate that PKC is a key mediator of mitochondrial damage and renal tubular injury in cold storage–associated transplantation and may be an effective therapeutic target for improving renal transplant outcomes.




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Tubular STAT3 Limits Renal Inflammation in Autosomal Dominant Polycystic Kidney Disease

Background

The inactivation of the ciliary proteins polycystin 1 or polycystin 2 leads to autosomal dominant polycystic kidney disease (ADPKD). Although signaling by primary cilia and interstitial inflammation both play a critical role in the disease, the reciprocal interactions between immune and tubular cells are not well characterized. The transcription factor STAT3, a component of the cilia proteome that is involved in crosstalk between immune and nonimmune cells in various tissues, has been suggested as a factor fueling ADPKD progression.

Method

To explore how STAT3 intersects with cilia signaling, renal inflammation, and cyst growth, we used conditional murine models involving postdevelopmental ablation of Pkd1, Stat3, and cilia, as well as cultures of cilia-deficient or STAT3-deficient tubular cell lines.

Results

Our findings indicate that, although primary cilia directly modulate STAT3 activation in vitro, the bulk of STAT3 activation in polycystic kidneys occurs through an indirect mechanism in which primary cilia trigger macrophage recruitment to the kidney, which in turn promotes Stat3 activation. Surprisingly, although inactivating Stat3 in Pkd1-deficient tubules slightly reduced cyst burden, it resulted in a massive infiltration of the cystic kidneys by macrophages and T cells, precluding any improvement of kidney function. We also found that Stat3 inactivation led to increased expression of the inflammatory chemokines CCL5 and CXCL10 in polycystic kidneys and cultured tubular cells.

Conclusions

STAT3 appears to repress the expression of proinflammatory cytokines and restrict immune cell infiltration in ADPKD. Our findings suggest that STAT3 is not a critical driver of cyst growth in ADPKD but rather plays a major role in the crosstalk between immune and tubular cells that shapes disease expression.




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Interaction between Epithelial Sodium Channel {gamma}-Subunit and Claudin-8 Modulates Paracellular Sodium Permeability in Renal Collecting Duct

Background

Water and solute transport across epithelia can occur via the transcellular or paracellular pathways. Tight junctions play a key role in mediating paracellular ion reabsorption in the kidney. In the renal collecting duct, which is a typical absorptive tight epithelium, coordination between transcellular sodium reabsorption and paracellular permeability may prevent the backflow of reabsorbed sodium to the tubular lumen along a steep electrochemical gradient.

Methods

To investigate whether transcellular sodium transport controls tight-junction composition and paracellular permeability via modulating expression of the transmembrane protein claudin-8, we used cultured mouse cortical collecting duct cells to see how overexpression or silencing of epithelial sodium channel (ENaC) subunits and claudin-8 affect paracellular permeability. We also used conditional kidney tubule–specific knockout mice lacking ENaC subunits to assess the ENaC’s effect on claudin-8 expression.

Results

Overexpression or silencing of the ENaC -subunit was associated with parallel and specific changes in claudin-8 abundance. Increased claudin-8 abundance was associated with a reduction in paracellular permeability to sodium, whereas decreased claudin-8 abundance was associated with the opposite effect. Claudin-8 overexpression and silencing reproduced these functional effects on paracellular ion permeability. Conditional kidney tubule–specific ENaC -subunit knockout mice displayed decreased claudin-8 expression, confirming the cell culture experiments' findings. Importantly, ENaC β-subunit or α-subunit silencing or kidney tubule–specific β-ENaC or α-ENaC knockout mice did not alter claudin-8 abundance.

Conclusions

Our data reveal the specific coupling between ENaC -subunit and claudin-8 expression. This coupling may play an important role in preventing the backflow of reabsorbed solutes and water to the tubular lumen, as well as in coupling paracellular and transcellular sodium permeability.




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ARHGEF7 ({beta}-PIX) Is Required for the Maintenance of Podocyte Architecture and Glomerular Function

Background

Previous studies showed that Cdc42, a member of the prototypical Rho family of small GTPases and a regulator of the actin cytoskeleton, is critical for the normal development and health of podocytes. However, upstream regulatory mechanisms for Cdc42 activity in podocytes are largely unknown.

Methods

We used a proximity-based ligation assay, BioID, to identify guanine nucleotide exchange factors that activate Cdc42 in immortalized human podocytes. We generated podocyte-specific ARHGEF7 (commonly known as β-PIX) knockout mice by crossing β-PIX floxed mice with Podocin-Cre mice. Using shRNA, we established cultured mouse podocytes with β-PIX knockdown and their controls.

Results

We identified β-PIX as a predominant guanine nucleotide exchange factor that interacts with Cdc42 in human podocytes. Podocyte-specific β-PIX knockout mice developed progressive proteinuria and kidney failure with global or segmental glomerulosclerosis in adulthood. Glomerular podocyte density gradually decreased in podocyte-specific β-PIX knockout mice, indicating podocyte loss. Compared with controls, glomeruli from podocyte-specific β-PIX knockout mice and cultured mouse podocytes with β-PIX knockdown exhibited significant reduction in Cdc42 activity. Loss of β-PIX promoted podocyte apoptosis, which was mediated by the reduced activity of the prosurvival transcriptional regulator Yes-associated protein.

Conclusions

These findings indicate that β-PIX is required for the maintenance of podocyte architecture and glomerular function via Cdc42 and its downstream Yes-associated protein activities. This appears to be the first evidence that a Rho–guanine nucleotide exchange factor plays a critical role in podocytes.




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SerpinB2 Regulates Immune Response in Kidney Injury and Aging

Background

Expression of SerpinB2, a regulator of inflammatory processes, has been described in the context of macrophage activation and cellular senescence. Given that mechanisms for these processes interact and can shape kidney disease, it seems plausible that SerpinB2 might play a role in renal aging, injury, and repair.

Methods

We subjected SerpinB2 knockout mice to ischemia-reperfusion injury or unilateral ureteral obstruction. We performed phagocyte depletion to study SerpinB2’s role beyond the effects of macrophages and transplanted bone marrow from knockout mice to wild-type mice and vice versa to dissect cell type–dependent effects. Primary tubular cells and macrophages from SerpinB2 knockout and wild-type mice were used for functional studies and transcriptional profiling.

Results

Cultured senescent tubular cells, kidneys of aged mice, and renal stress models exhibited upregulation of SerpinB2 expression. Functionally, lack of SerpinB2 in aged knockout mice had no effect on the magnitude of senescence markers but associated with enhanced kidney damage and fibrosis. In stress models, inflammatory cell infiltration was initially lower in knockout mice but later increased, leading to an accumulation of significantly more macrophages. SerpinB2 knockout tubular cells showed significantly reduced expression of the chemokine CCL2. Macrophages from knockout mice exhibited reduced phagocytosis and enhanced migration. Macrophage depletion and bone marrow transplantation experiments validated the functional relevance of these cell type–specific functions of SerpinB2.

Conclusions

SerpinB2 influences tubule-macrophage crosstalk by supporting tubular CCL2 expression and regulating macrophage phagocytosis and migration. In mice, SerpinB2 expression seems to be needed for coordination and timely resolution of inflammation, successful repair, and kidney homeostasis during aging. Implications of SerpinB2 in human kidney disease deserve further exploration.




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Tubule-Specific Mst1/2 Deficiency Induces CKD via YAP and Non-YAP Mechanisms

Background

The serine/threonine kinases MST1 and MST2 are core components of the Hippo pathway, which has been found to be critically involved in embryonic kidney development. Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) are the pathway’s main effectors. However, the biologic functions of the Hippo/YAP pathway in adult kidneys are not well understood, and the functional role of MST1 and MST2 in the kidney has not been studied.

Methods

We used immunohistochemistry to examine expression in mouse kidneys of MST1 and MST2, homologs of Hippo in Drosophila. We generated mice with tubule-specific double knockout of Mst1 and Mst2 or triple knockout of Mst1, Mst2, and Yap. PCR array and mouse inner medullary collecting duct cells were used to identify the primary target of Mst1/Mst2 deficiency.

Results

MST1 and MST2 were predominantly expressed in the tubular epithelial cells of adult kidneys. Deletion of Mst1/Mst2 in renal tubules increased activity of YAP but not TAZ. The kidneys of mutant mice showed progressive inflammation, tubular and glomerular damage, fibrosis, and functional impairment; these phenotypes were largely rescued by deletion of Yap in renal tubules. TNF-α expression was induced via both YAP-dependent and YAP-independent mechanisms, and TNF-α and YAP amplified the signaling activities of each other in the tubules of kidneys with double knockout of Mst1/Mst2.

Conclusions

Our findings show that tubular Mst1/Mst2 deficiency leads to CKD through both the YAP and non-YAP pathways and that tubular YAP activation induces renal fibrosis. The pathogenesis seems to involve the reciprocal stimulation of TNF-α and YAP signaling activities.




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Atorvastatin Reduces In Vivo Fibrin Deposition and Macrophage Accumulation, and Improves Primary Patency Duration and Maturation of Murine Arteriovenous Fistula

Background

Arteriovenous fistulas placed surgically for dialysis vascular access have a high primary failure rate resulting from excessive inward remodeling, medial fibrosis, and thrombosis. No clinically established pharmacologic or perisurgical therapies currently address this unmet need. Statins’ induction of multiple anti-inflammatory and antithrombotic effects suggests that these drugs might reduce arteriovenous fistula failure. Yet, the in vivo physiologic and molecular effects of statins on fistula patency and maturation remain poorly understood.

Methods

We randomized 108 C57Bl/6J mice to receive daily atorvastatin 1.14 mg/kg or PBS (control) starting 7 days before end-to-side carotid artery–jugular vein fistula creation and for up to 42 days after fistula creation. We then assessed longitudinally the effects of statin therapy on primary murine fistula patency and maturation. We concomitantly analyzed the in vivo arteriovenous fistula thrombogenic and inflammatory macrophage response to statin therapy, using the fibrin-targeted, near-infrared fluorescence molecular imaging agent FTP11-CyAm7 and dextranated, macrophage-avid nanoparticles CLIO-VT680.

Results

In vivo molecular-structural imaging demonstrated that atorvastatin significantly reduced fibrin deposition at day 7 and macrophage accumulation at days 7 and 14, findings supported by histopathologic and gene-expression analyses. Structurally, atorvastatin promoted favorable venous limb outward remodeling, preserved arteriovenous fistula blood flow, and prolonged primary arteriovenous fistula patency through day 42 (P<0.05 versus control for all measures).

Conclusions

These findings provide new in vivo evidence that statins improve experimental arteriovenous fistula patency and maturation, indicating that additional clinical evaluation of statin therapy in patients on dialysis undergoing arteriovenous fistula placement is warranted.




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In Vivo Assessment of Size-Selective Glomerular Sieving in Transplanted Human Induced Pluripotent Stem Cell-Derived Kidney Organoids

Background

The utility of kidney organoids in regenerative medicine will rely on the functionality of the glomerular and tubular structures in these tissues. Recent studies have demonstrated the vascularization and subsequent maturation of human pluripotent stem cell–derived kidney organoids after renal subcapsular transplantation. This raises the question of whether the glomeruli also become functional upon transplantation.

Methods

We transplanted kidney organoids under the renal capsule of the left kidney in immunodeficient mice followed by the implantation of a titanium imaging window on top of the kidney organoid. To assess glomerular function in the transplanted human pluripotent stem cell–derived kidney tissue 1, 2, and 3 weeks after transplantation, we applied high-resolution intravital multiphoton imaging through the imaging window during intravenous infusion of fluorescently labeled low and high molecular mass dextran molecules or albumin.

Results

After vascularization, glomerular structures in the organoid displayed dextran and albumin size selectivity across their glomerular filtration barrier. We also observed evidence of proximal tubular dextran reuptake.

Conclusions

Our results demonstrate that human pluripotent stem cell–derived glomeruli can develop an appropriate barrier function and discriminate between molecules of varying size. These characteristics together with tubular presence of low molecular mass dextran provide clear evidence of functional filtration. This approach to visualizing glomerular filtration function will be instrumental for translation of organoid technology for clinical applications as well as for disease modeling.




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The Value of Intravenous Iron: Beyond the Cave of Speculation




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Tubular MST1/2 Deletion and Renal Fibrosis