Protein abundance data of drug-metabolizing enzymes and transporters (DMETs) are useful for scaling in vitro and animal data to humans for accurate prediction and interpretation of drug clearance and toxicity. Targeted DMET proteomics that relies on synthetic stable isotope-labeled surrogate peptides as calibrators is routinely used for the quantification of selected proteins; however, the technique is limited to the quantification of a small number of proteins. Although the global proteomics-based total protein approach (TPA) is emerging as a better alternative for large-scale protein quantification, the conventional TPA does not consider differential sequence coverage by identifying unique peptides across proteins. Here, we optimized the TPA approach by correcting protein abundance data by the sequence coverage, which was applied to quantify 54 DMETs for characterization of 1) differential tissue DMET abundance in the human liver, kidney, and intestine, and 2) interindividual variability of DMET proteins in individual intestinal samples (n = 13). Uridine diphosphate-glucuronosyltransferase 2B7 (UGT2B7), microsomal glutathione S-transferases (MGST1, MGST2, and MGST3) carboxylesterase 2 (CES2), and multidrug resistance-associated protein 2 (MRP2) were expressed in all three tissues, whereas, as expected, four cytochrome P450s (CYP3A4, CYP3A5, CYP2C9, and CYP4F2), UGT1A1, UGT2B17, CES1, flavin-containing monooxygenase 5, MRP3, and P-glycoprotein were present in the liver and intestine. The top three DMET proteins in individual tissues were: CES1>CYP2E1>UGT2B7 (liver), CES2>UGT2B17>CYP3A4 (intestine), and MGST1>UGT1A6>MGST2 (kidney). CYP3A4, CYP3A5, UGT2B17, CES2, and MGST2 showed high interindividual variability in the intestine. These data are relevant for enhancing in vitro to in vivo extrapolation of drug absorption and disposition and can be used to enhance the accuracy of physiologically based pharmacokinetic prediction of systemic and tissue concentration of drugs.

Hydrolases represent an essential class of enzymes indispensable for the metabolism of various clinically essential medications. Individuals exhibit marked differences in the expression and activation of hydrolases, resulting in significant variability in the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs metabolized by these enzymes. The regulation of hydrolase expression and activity involves both genetic polymorphisms and nongenetic factors. This review examines the current understanding of genetic and nongenetic regulators of six clinically significant hydrolases, including carboxylesterase (CES)-1 CES2, arylacetamide deacetylase (AADAC), paraoxonase (PON)-1 PON3, and cathepsin A (CTSA). We explore genetic variants linked to the expression and activity of the hydrolases and their effects on the PK and PD of their substrate drugs. Regarding nongenetic regulators, we focus on the inhibitors and inducers of these enzymes. Additionally, we examine the developmental expression patterns and gender differences in the hydrolases when pertinent information was available. Many genetic and nongenetic regulators were found to be associated with the expression and activity of the hydrolases and PK and PD. However, hydrolases remain generally understudied compared with other drug-metabolizing enzymes, such as cytochrome P450s. The clinical significance of genetic and nongenetic regulators has not yet been firmly established for the majority of hydrolases. Comprehending the mechanisms that underpin the regulation of these enzymes holds the potential to refine therapeutic regimens, thereby enhancing the efficacy and safety of drugs metabolized by the hydrolases.

Mitochondrial dysfunction is a hallmark of many genetic neurodegenerative diseases, but therapeutic options to reverse mitochondrial dysfunction are limited. While recent studies support the possibility of improving mitochondrial fusion/fission dynamics and motility to correct mitochondrial dysfunction and resulting neurodegeneration in Charcot-Marie-Tooth disease (CMT) and other neuropathies, the clinical utility of reported compounds and relevance of preclinical models are uncertain. Here, we describe motor and sensory neuron dysfunction characteristic of clinical CMT type 2 A in a CRISPR/Casp-engineered Mfn2 Thr105Met (T105M) mutant knock-in mouse. We further demonstrate that daily oral treatment with a novel mitofusin activator derived from the natural product piperine can reverse these neurologic phenotypes. Piperine derivative 8015 promoted mitochondrial fusion and motility in Mfn2-deficient cells in a mitofusin-dependent manner and reversed mitochondrial dysfunction in cultured fibroblasts and reprogrammed motor neurons from a human CMT2A patient carrying the MFN2 T105M mutation. Like previous mitofusin activators, 8015 exhibited stereospecific functionality, but the more active stereoisomer, 8015-P2, is unique in that it has subnanomolar potency and undergoes entero-hepatic recirculation which extends its in vivo half-life. Daily administration of 8015-P2 to Mfn2 T105M knock-in mice for 6 weeks normalized neuromuscular and sensory dysfunction and corrected histological/ultrastructural neurodegeneration and neurogenic myoatrophy. These studies describe a more clinically relevant mouse model of CMT2A and an improved mitofusin activator derived from piperine. We posit that 8015-P2 and other piperine derivatives may benefit CMT2A or other neurodegenerative conditions wherein mitochondrial dysdynamism plays a contributory role.

Glioblastoma (GBM) is a disease of the whole brain, with infiltrative tumor cells protected by an intact blood-brain barrier (BBB). GBM has a poor prognosis despite aggressive treatment, in part due to the lack of adequate drug permeability at the BBB. Standard of care GBM therapies include radiation and cytotoxic chemotherapy that lead to DNA damage. Subsequent activation of DNA damage response (DDR) pathways can induce resistance. Various DDR inhibitors, targeting the key regulators of these pathways such as ataxia telangiectasia mutated and Rad3-related (ATR), are being explored as radio- and chemosensitizers. Elimusertib, a novel ATR kinase inhibitor, can prevent repair of damaged DNA, increasing efficacy of DNA-damaging cytotoxic therapies. Robust synergy was observed in vitro when elimusertib was combined with the DNA-damaging agent temozolomide; however, we did not observe improvement with this combination in in vivo efficacy studies in GBM orthotopic tumor-bearing mice. This in vitro–in vivo disconnect was explored to understand factors influencing central nervous system (CNS) distribution of elimusertib and reasons for lack of efficacy. We observed that elimusertib is rapidly cleared from systemic circulation in mice and would not maintain adequate exposure in the CNS for efficacious combination therapy with temozolomide. CNS distribution of elimusertib is partially limited by P-glycoprotein efflux at the BBB, and high binding to CNS tissues leads to low levels of pharmacologically active (unbound) drug in the brain. Acknowledging the potential for interspecies differences in pharmacokinetics, these data suggest that clinical translation of elimusertib in combination with temozolomide for treatment of GBM may be limited.

The development of transforming growth factor βreceptor inhibitors (TGFβRi) as new medicines has been affected by cardiac valvulopathy and arteriopathy toxicity findings in nonclinical toxicology studies. PF-06952229 (MDV6058) selected using rational drug design is a potent and selective TGFβRI inhibitor with a relatively clean off-target selectivity profile and good pharmacokinetic properties across species. PF-06952229 inhibited clinically translatable phospho-SMAD2 biomarker (≥60%) in human and cynomolgus monkey peripheral blood mononuclear cells, as well as in mouse and rat splenocytes. Using an optimized, intermittent dosing schedule (7-day on/7-day off/cycle; 5 cycles), PF-06952229 demonstrated efficacy in a 63-day syngeneic MC38 colon carcinoma mouse model. In the pivotal repeat-dose toxicity studies (rat and cynomolgus monkey), PF-06952229 on an intermittent dosing schedule (5-day on/5-day off cycle; 5 cycles, 28 doses) showed no cardiac-related adverse findings. However, new toxicity findings related to PF-06952229 included reversible hepatocellular (hepatocyte necrosis with corresponding clinically monitorable transaminase increases) and lung (hemorrhage with mixed cell inflammation) findings at ≥ targeted projected clinical efficacious exposures. Furthermore, partially reversible cartilage hypertrophy (trachea and femur in rat; femur in monkey) and partially to fully reversible, clinically monitorable decreases in serum phosphorus and urinary phosphate at ≥ projected clinically efficacious exposures were observed. Given the integral role of TGFβ in endochondral bone formation, cartilage findings in toxicity studies have been observed with other TGFβRi classes of compounds. The favorable cumulative profile of PF-06952229 in biochemical, pharmacodynamic, pharmacokinetic, and nonclinical studies allowed for its evaluation in cancer patients using the intermittent dosing schedule (7-day on/7-day off) and careful protocol-defined monitoring.

Despite a significant decrease in the number of prescriptions for opioids, the opioid crisis continues, fueled in large part by the availability of the phenylpiperidine mu opioid receptor (MOR) agonist fentanyl. In contrast, the number of prescriptions for and the off-label use of gabapentinoids (gabapentin and pregabalin) has increased dramatically, with gabapentinoids commonly detected in opioid overdose victims. Although gabapentinoids can decrease the potency of the opioid receptor antagonist naloxone to reverse heroin-induced hypoventilation in male rats, the specificity and nature of interaction between gabapentinoids and MOR agonists and any potential sex difference in those interactions are not well characterized. Gabapentinoids were studied in female and male rats discriminating fentanyl (0.0032 mg/kg, i.p.) or cocaine (3.2 mg/kg, i.p.). Alone, neither gabapentin nor pregabalin significantly increased fentanyl- or cocaine-appropriate responding. In rats discriminating fentanyl, each gabapentinoid dose-dependently shifted the fentanyl and heroin discrimination dose-effect functions to the left, whereas naloxone dose-dependently shifted the fentanyl and heroin discrimination dose-effect functions to the right. Each gabapentinoid (100 mg/kg) significantly decreased the potency of naloxone to antagonize the discriminative stimulus effect of fentanyl or heroin. In contrast, each gabapentinoid dose-dependently shifted the cocaine and d-methamphetamine discrimination dose-effect functions to the right. There were no significant sex differences in this study. These results suggest that gabapentinoids impact the misuse of opioids, the co-use of opioids and stimulant drugs, and the increasing number of overdose deaths in individuals using opioids, stimulant drugs, and gabapentinoids in mixtures.

Previous studies demonstrated that sigma receptor (R) antagonists alone fail to alter cocaine self-administration despite blocking various other effects of cocaine. However, R antagonists when combined with dopamine transporter (DAT) inhibitors substantially decrease cocaine self-administration. To better understand the effects of this combination, the present study examined the effects of R antagonist and DAT inhibitor combinations in male rats discriminating cocaine (10 mg/kg, i.p.) from saline injections. The DAT inhibitors alone [(–)-2-β-carbomethoxy-3-β-(4-fluorophenyl)tropane 1,5-naphthalenedisulfonate monohydrate (WIN 35,428) and methylphenidate] at low (0.1-mg/kg) doses that were minimally active failed to shift the dose-effect function for discriminative-stimulus effects of cocaine to the left more than 2-fold. At 0.32 mg/kg the DAT inhibitors alone shifted the cocaine dose-effect function leftward 24- or 6.6-fold, respectively. The R antagonists (BD1008, BD1047, and BD1063) failed to fully substitute for cocaine, although BD1008 and BD1047 substituted partially. At 10 mg/kg, BD1008, BD1047, or BD1063 alone shifted the cocaine dose-effect function leftward less than 6.0-fold. In combination with 0.1 mg/kg WIN 35,428, the 10 mg/kg doses of R antagonists shifted the cocaine dose-effect function from 12.3- to 36.7-fold leftward, and with 0.32 mg/kg WIN 35,428 from 14.3- to 440-fold leftward. In combination with 0.1 mg/kg methylphenidate, those R antagonist doses shifted the cocaine dose-effect function from 5.5- to 55.0-fold leftward, and with 0.32 mg/kg methylphenidate from 10.5- to 48.1-fold leftward. The present results suggest that dual DAT/R inhibition produces agonist-like subjective effects that may promote decreases in self-administration obtained in previous studies.

Clinical reports suggest that the most effective strategies for managing opioid use disorder comprise a comprehensive treatment program of both pharmacological and nonpharmacological approaches. However, the conditions under which these combinations are most effective are not well characterized. This study examined whether the presence of an alternative reinforcer could alter the efficacy of Food and Drug Administration–approved opioid antagonist or agonist medications, as well as the nonopioid flumazenil, in decreasing oxycodone choice self-administration in nonhuman primates. Adult squirrel monkeys (n = 7; four females) responded under concurrent second-order fixed-ratio (FR)-3(FR5:S);TO45s schedules of reinforcement for intravenous oxycodone (0.1 mg/kg) or saline on one lever and 30% sweetened condensed milk or water on the other. Doses of naltrexone (0.00032–1.0 mg/kg), nalbuphine (0.32–10 mg/kg), buprenorphine (0.0032–0.032 mg/kg), methadone (0.32–1.0 mg/kg), or flumazenil (1–3.2 mg/kg) were administered intramuscularly prior to oxycodone self-administration sessions that occurred with either milk or water as the alternative. Naltrexone, a μ-opioid receptor antagonist, was >30-fold more potent when milk was available compared with water and abolished oxycodone intake (injections/session) while concomitantly increasing milk deliveries at the highest dose tested. Pretreatment with the low-efficacy μ-agonist nalbuphine was most effective in the presence of milk compared with water, decreasing oxycodone preference to <50% of control values. The higher efficacy μ-agonists, methadone and buprenorphine, and the benzodiazepine antagonist flumazenil did not appreciably alter the reinforcing potency of oxycodone under either condition. These results suggest that antagonist medications used in combination with alternative reinforcers may be an effective strategy to curtail opioid abuse–related behaviors.

Although acute inflammation serves essential functions in maintaining tissue homeostasis, chronic inflammation is causally linked to many diseases. Macrophages are a major cell type that orchestrates inflammatory processes. During inflammation, macrophages undergo polarization and activation, thereby mobilizing pro-inflammatory and anti-inflammatory transcriptional programs that regulate ensuing macrophage functions. Fatty acid binding protein 5 (FABP5) is a lipid chaperone highly expressed in macrophages. FABP5 deletion is implicated in driving macrophages toward an anti-inflammatory phenotype, yet signaling pathways regulated by macrophage-FABP5 have not been systematically profiled. We leveraged proteomic and phosphoproteomic approaches to characterize pathways modulated by FABP5 in M1 and M2 polarized bone marrow-derived macrophages (BMDMs). Stable isotope labeling by amino acids-based analysis of M1 and M2 polarized wild-type and FABP5 knockout BMDMs revealed numerous differentially regulated proteins and phosphoproteins. FABP5 deletion impacted downstream pathways associated with inflammation, cytokine production, oxidative stress, and kinase activity. Toll-like receptor 2 (TLR2) emerged as a novel target of FABP5 and pharmacological FABP5 inhibition blunted TLR2-mediated activation of downstream pathways, ascribing a novel role for FABP5 in TLR2 signaling. This study represents a comprehensive characterization of the impact of FABP5 deletion on the proteomic and phosphoproteomic landscape of M1 and M2 polarized BMDMs. Loss of FABP5 altered pathways implicated in inflammatory responses, macrophage function, and TLR2 signaling. This work provides a foundation for future studies seeking to investigate the therapeutic potential of FABP5 inhibition in pathophysiological states resulting from dysregulated inflammatory signaling.

Cannabinoid and opioid receptor activities can be modulated by a variety of post-translational mechanisms including the formation of interacting complexes. This study examines the involvement of endogenous and exogenous chaperones in modulating the abundance and activity of cannabinoid CB₁ receptor (CB₁R), opioid receptor (DOR), and CB₁R-DOR interacting complexes. Focusing on endogenous protein chaperones, namely receptor transporter proteins (RTPs), we examined relative mRNA expression in the mouse spinal cord and found RTP4 to be expressed at higher levels compared with other RTPs. Next, we assessed the effect of RTP4 on receptor abundance by manipulating RTP4 expression in cell lines. Overexpression of RTP4 causes an increase and knock-down causes a decrease in the levels of CB₁R, DOR, and CB₁R-DOR interacting complexes; this is accompanied by parallel changes in signaling. The ability of small molecule lipophilic ligands to function as exogenous chaperones was examined using receptor-selective antagonists. Long-term treatment leads to increases in receptor abundance and activity with no changes in mRNA supporting a role as pharmacological chaperones. Finally, the effect of cannabidiol (CBD), a small molecule ligand and a major active component of cannabis, on receptor abundance and activity in mice was examined. We find that CBD administration leads to increases in receptor abundance and activity in mouse spinal cord. Together, these results highlight a role for chaperones (proteins and small molecules) in modulating levels and activity of CB₁R, DOR, and their interacting complexes potentially through mechanisms including receptor maturation and trafficking.

Endocannabinoids, which are present throughout the central nervous system (CNS), can activate cannabinoid receptors 1 and 2 (CB1 and CB2). CB1 and CB2 agonists exhibit broad anti-inflammatory properties, suggesting their potential to treat inflammatory diseases. However, careful evaluation of abuse potential is necessary. This study evaluated the abuse potential of lenabasum, a selective CB2 receptor agonist in participants (n = 56) endorsing recreational cannabis use. Three doses of lenabasum (20, 60, and 120 mg) were compared with placebo and nabilone (3 and 6 mg). The primary endpoint was the peak effect (E_max) on a bipolar Drug Liking visual analog scale (VAS). Secondary VAS and pharmacokinetic (PK) endpoints and adverse events were assessed. Lenabasum was safe and well tolerated. Compared with placebo, a 20-mg dose of lenabasum did not increase ratings of Drug Liking and had no distinguishable effect on other VAS endpoints. Dose-dependent increases in ratings of Drug Liking were observed with 60 and 120 mg lenabasum. Drug Liking and all other VAS outcomes were greatest for nabilone 3 mg and 6 mg, a medication currently approved by the US Food and Drug Administration (FDA). At a target therapeutic dose (20 mg), lenabasum did not elicit subjective ratings of Drug Liking. However, supratherapeutic doses of lenabasum (60 and 120 mg) did elicit subjective ratings of Drug Liking compared with placebo. Although both doses of lenabasum were associated with lower ratings of Drug Liking compared with 3 mg and 6 mg nabilone, lenabasum does have abuse potential and should be used cautiously in clinical settings.

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of chemotherapy treatment, routinely manifesting as increased pain sensitivity (allodynia) in distal extremities. Despite its prevalence, effective treatment options are limited. Cannabinoids are increasingly being evaluated for their ability to treat chronic pain conditions, including CIPN. While previous studies have revealed sex differences in cannabinoid-mediated antinociception in acute and chronic pain models, there is a paucity of studies addressing potential sex differences in the response of CIPN to cannabinoid treatment. Therefore, we evaluated the long-term antiallodynic efficacy of cannabinoid receptor type 1 (CB₁)-selective, cannabinoid receptor type 2 (CB₂)-selective, and CB₁/CB₂ mixed agonists in the cisplatin CIPN model, using both male and female mice. CB₁ selective agonism was observed to have sex differences in the development of tolerance to antiallodynic effects, with females developing tolerance more rapidly than males, while the antiallodynic effects of selective CB₂ agonism lacked tolerance development. Compound-specific changes to the female estrous cycle and female plasma estradiol levels were noted, with CB₁ selective agonism decreasing plasma estradiol while CB₂ selective agonism increased plasma estradiol. Chronic administration of a mixed CB₁/CB₂ agonist resulted in increased mRNA expression of proinflammatory cytokines and endocannabinoid regulatory enzymes in female spinal cord tissue. Ovarian tissue was noted to have proinflammatory cytokine mRNA expression following administration of a CB₂ acting compound while selective CB₁ agonism resulted in decreased proinflammatory cytokines and endocannabinoid regulatory enzymes in testes. These results support the need for further investigation into the role of sex and sex hormones signaling in pain and cannabinoid-mediated antinociceptive effects.

Oxidative stress, fibrosis, and inflammasome activation from advanced glycation end product (AGE)–receptor of advanced glycation end product (RAGE) interaction contribute to diabetic cardiomyopathy (DCM) formation and progression. Our study revealed the impact of β-caryophyllene (BCP) on activating cannabinoid type 2 receptors (CB2Rs) against diabetic complication, mainly cardiomyopathy and investigated the underlying cell signaling pathways in mice. The murine model of DCM was developed by feeding a high-fat diet with streptozotocin injections. After the development of diabetes, the animals received a 12-week oral BCP treatment at a dose of 50 mg/kg/body weight. BCP treatment showed significant improvement in glucose tolerance and insulin resistance and enhanced serum insulin levels in diabetic animals. BCP treatment effectively reversed the heart remodeling and restored the phosphorylated troponin I and sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a expression. Ultrastructural examination showed reduced myocardial cell injury in DCM mice treated with BCP. The preserved myocytes were found to be associated with reduced expression of AGE/RAGE in DCM mice hearts. BCP treatment mitigated oxidative stress by inhibiting expression of NADPH oxidase 4 and activating phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/nuclear factor erythroid 2–related factor 2 (Nrf2) signaling. Also, BCP suppressed cardiac fibrosis and endothelial-to-mesenchymal transition in DCM mice by inhibiting transforming growth factor β (TGF-β)/suppressor of mothers against decapentaplegic (Smad) signaling. Further, BCP treatment suppressed nucleotide-binding domain, leucine-rich–containing family, pyrin domain–containing-3 (NLRP3) inflammasome activation in DCM mice and alleviated cellular injury to the pancreatic tissues evidenced by significant elevation of the number of insulin-positive cells. To demonstrate a CB2R-dependent mechanism of BCP, another group of DCM mice were pretreated with AM630, a CB2R antagonist. AM630 was observed to abrogate the beneficial effects of BCP in DCM mice. Taken together, BCP demonstrated the potential to protect the myocardium and pancreas of DCM mice mediating CB2R-dependent mechanisms.

Neuropathic pain is a form of chronic pain that develops because of damage to the nervous system. Treatment of neuropathic pain is often incompletely effective, and most available therapeutics have only moderate efficacy and present side effects that limit their use. Opioids are commonly prescribed for the management of neuropathic pain despite equivocal results in clinical studies and significant abuse potential. Thus, neuropathic pain represents an area of critical unmet medical need, and novel classes of therapeutics with improved efficacy and safety profiles are urgently needed. The cannabidiol structural analog and novel antagonist of GPR55, KLS-13019, was screened in rat models of neuropathic pain. Tactile sensitivity associated with chemotherapy exposure was induced in rats with once-daily 1-mg/kg paclitaxel injections for 4 days or 5 mg/kg oxaliplatin every third day for 1 week. Rats were then administered KLS-13019 or comparator drugs on day 7 in an acute dosing paradigm or days 7–10 in a chronic dosing paradigm, and mechanical or cold allodynia was assessed. Allodynia was reversed in a dose-dependent manner in the rats treated with KLS-13019, with the highest dose reverting the response to prepaclitaxel injection baseline levels with both intraperitoneal and oral administration after acute dosing. In the chronic dosing paradigm, four consecutive doses of KLS-13019 completely reversed allodynia for the duration of the phenotype in control animals. Additionally, coadministration of KLS-13019 with paclitaxel prevented the allodynic phenotype from developing. Together, these data suggest that KLS-13019 represents a potential new drug for the treatment of neuropathic pain.

Patients with arthritis report using cannabis for pain management, and the major cannabinoid delta-9-tetrahydrocannabinol (⁹-THC) has anti-inflammatory properties, yet the effects of minor cannabinoids on arthritis are largely unknown. The goal of the present study was to determine the antiarthritic potential of the minor cannabinoid delta-8-tetrahydrocannabinol (⁸-THC) using the collagen-induced arthritis (CIA) mouse model. Adult male DBA/1J mice were immunized and boosted 21 days later with an emulsion of collagen and complete Freund’s adjuvant. Beginning on the day of the booster, mice were administered twice-daily injections of ⁸-THC (3 or 30 mg/kg), the steroid dexamethasone (2 mg/kg), or vehicle for two weeks. Dorsal-ventral paw thickness and qualitative measures of arthritis were recorded daily, and latency to fall from an inverted grid was measured on alternating days, to determine arthritis severity and functional impairment. On the final day of testing, spontaneous wire-climbing behavior and temperature preference in a thermal gradient ring were measured to assess CIA-depressed behavior. The ⁸-THC treatment (30 mg/kg) reduced paw swelling and qualitative signs of arthritis. ⁸-THC also blocked CIA-depressed climbing and CIA-induced preference for a heated floor without producing locomotor effects but did not affect latency to fall from a wire grid. In alignment with the morphologic and behavioral assessments in vivo, histology revealed that ⁸-THC reduced synovial inflammation, proteoglycan loss and cartilage and bone erosion in the foot joints in a dose-dependent manner. Together, these findings suggest that ⁸-THC not only blocked morphologic changes but also prevented functional loss caused by collagen-induced arthritis.

Chronic pain conditions affect nearly 20% of the population in the United States. Current medical interventions, such as opioid drugs, are effective at relieving pain but are accompanied by many undesirable side effects. This is one reason increased numbers of chronic pain patients have been turning to Cannabis for pain management. Cannabis contains many bioactive chemical compounds; however, current research looking into lesser-studied minor cannabinoids in Cannabis lacks uniformity between experimental groups and/or excludes female mice from investigation. This makes it challenging to draw conclusions between experiments done with different minor cannabinoid compounds between laboratories or parse out potential sex differences that could be present. We chose five minor cannabinoids found in lower quantities within Cannabis: cannabinol (CBN), cannabidivarin (CBDV), cannabigerol (CBG), 8-tetrahydrocannabinol (8-THC), and 9-tetrahydrocannabivarin (THCV). These compounds were then tested for their cannabimimetic and pain-relieving behaviors in a cannabinoid tetrad assay and a chemotherapy-induced peripheral neuropathy (CIPN) pain model in male and female CD-1 mice. We found that the minor cannabinoids we tested differed in the cannabimimetic behaviors evoked, as well as the extent. We found that CBN, CBG, and high-dose 8-THC evoked some tetrad behaviors in both sexes, while THCV and low-dose 8-THC exhibited cannabimimetic tetrad behaviors only in females. Only CBN efficaciously relieved CIPN pain, which contrasts with reports from other researchers. Together these findings provide further clarity to the pharmacology of minor cannabinoids and suggest further investigation into their mechanism and therapeutic potential.

There is a growing interest in the use of medicinal plants to treat a variety of diseases, and one of the most commonly used medicinal plants globally is Cannabis sativa. The two most abundant cannabinoids (⁹-tetrahydrocannabinol and cannabidiol) have been governmentally approved to treat selected medical conditions; however, the plant produces over 100 cannabinoids, including cannabichromene (CBC). Although the cannabinoids share a common precursor molecule, cannabigerol, they are structurally and pharmacologically unique. These differences may engender differing therapeutic potentials. In this review, we will examine what is currently known about CBC with regards to pharmacodynamics, pharmacokinetics, and receptor profile. We will also discuss the therapeutic areas that have been examined for this cannabinoid, notably antinociceptive, antibacterial, and anti-seizure activities. Finally, we will discuss areas where new research is needed and potential novel medicinal applications for CBC.

⁹-Tetrahydrocannabinol (THC) is a psychoactive phytocannabinoid found in the Cannabis sativa plant. THC is primarily metabolized into 11-hydroxy-⁹-tetrahydrocannabinol (11-OH-THC) and 11-nor-9-carboxy-⁹-tetrahydrocannabinol (COOH-THC), which may themselves be psychoactive. There is very little research-based evidence concerning the pharmacokinetics and pharmacodynamics of 11-OH-THC as an individual compound. Male C57BL/6 mice were treated with THC or 11-OH-THC via intraperitoneal injection, tail vein intravenous injection, or oral gavage, and whole-blood compound levels were measured to determine pharmacokinetic parameters [C_max, time to C_max (T_max), elimination half-life, area under the curve, apparent volume of distribution, systemic clearance, terminal rate constant, and absolute bioavailability] while also monitoring changes in catalepsy, body temperature, and nociception. 11-OH-THC achieved a T_max at 30 minutes for all routes of administration. The maximum concentration at 30 minutes was not different between intravenous and intraperitoneal routes, but the oral gavage C_max was significantly lower. THC had a 10-minute time to the maximum concentration, which was the first blood collection time point, for intravenous and intraperitoneal and 60 minutes for oral gavage, with a lower C_max for intraperitoneal and oral gavage compared with intravenous. When accounting for circulating compound levels and ED₅₀ responses, these data suggest that 11-OH-THC was 153% as active as THC in the tail-flick test of nociception and 78% as active as THC for catalepsy. Therefore, 11-OH-THC displayed equal or greater activity than the parent compound THC, even when accounting for pharmacokinetic differences. Thus, the THC metabolite 11-OH-THC likely plays a critical role in the bioactivity of cannabis; understanding its activity when administered directly will aid in the interpretation of future animal and human studies.

The consumption of ⁹-tetrahydrocannabinol (THC)- or cannabis-containing edibles has increased in recent years; however, the behavioral and neural circuit effects of such consumption remain unknown, especially in the context of ingestion of higher doses resulting in cannabis intoxication. We examined the neural and behavioral effects of acute high-dose edible cannabis consumption (AHDECC). Sprague-Dawley rats (six males, seven females) were implanted with electrodes in the prefrontal cortex (PFC), dorsal hippocampus (dHipp), cingulate cortex (Cg), and nucleus accumbens (NAc). Rats were provided access to a mixture of Nutella (6 g/kg) and THC-containing cannabis oil (20 mg/kg) for 10 minutes, during which they voluntarily consumed all of the provided Nutella and THC mixture. Cannabis tetrad and neural oscillations were examined 2, 4, 8, and 24 hours after exposure. In another cohort (16 males, 15 females), we examined the effects of AHDECC on learning and prepulse inhibition and serum and brain THC and 11-hydroxy-THC concentrations. AHDECC resulted in higher brain and serum THC and 11-hydroxy-THC levels in female rats over 24 hours. AHDECC also produced: 1) Cg, dHipp, and NAc gamma power suppression, with the suppression being greater in female rats, in a time-dependent manner; 2) hypolocomotion, hypothermia, and antinociception in a time-dependent manner; and 3) learning and prepulse inhibition impairments. Additionally, most neural activity and behavior changes appear 2 hours after ingestion, suggesting that interventions around this time might be effective in reversing/reducing the effects of AHDECC.

People with sickle cell disease (SCD) often experience chronic pain as well as unpredictable episodes of acute pain, which significantly affects their quality of life and life expectancy. Current treatment strategies for SCD-associated pain primarily rely on opioid analgesics, which have limited efficacy and cause serious adverse effects. Cannabis has emerged as a potential alternative, yet its efficacy remains uncertain. In this study, we investigated the antinociceptive effects of ⁹-tetrahydrocannabinol (THC), cannabis’ intoxicating constituent, in male HbSS mice, which express >99% human sickle hemoglobin, and male HbAA mice, which express normal human hemoglobin A, as a control. Acute THC administration (0.1–3 mg/kg^–1, i.p.) dose-dependently reduced mechanical and cold hypersensitivity in human sickle hemoglobin (HbSS) but not human normal hemoglobin A (HbAA) mice. In the tail-flick assay, THC (1 and 3 mg/kg^–1, i.p.) produced substantial antinociceptive effects in HbSS mice. By contrast, THC (1 mg/kg^–1, i.p.) did not alter anxiety-like behavior (elevated plus maze) or long-term memory (24-hour novel object recognition). Subchronic THC treatment (1 and 3 mg/kg^–1, i.p.) provided sustained relief of mechanical hypersensitivity but led to tolerance in cold hypersensitivity in HbSS mice. Together, the findings identify THC as a possible therapeutic option for the management of chronic pain in SCD. Further research is warranted to elucidate its mechanism of action and possible interaction with other cannabis constituents.

Targeting the endocannabinoid (eCB) signaling system for pain relief is an important treatment option that is only now beginning to be mechanistically explored. In this review, we focus on two recently appreciated cannabinoid-based targeting strategies, treatments with cannabidiol (CBD) and α/β-hydrolase domain containing 6 (ABHD6) inhibitors, which have the exciting potential to produce pain relief through distinct mechanisms of action and without intoxication. We review evidence on plant-derived cannabinoids for pain, with an emphasis on CBD and its multiple molecular targets expressed in pain pathways. We also discuss the function of eCB signaling in regulating pain responses and the therapeutic promises of inhibitors targeting ABHD6, a 2-arachidonoylglycerol (2-AG)-hydrolyzing enzyme. Finally, we discuss how the novel cannabinoid biosensor GRAB_eCB2.0 may be leveraged to enable the discovery of targets modulated by cannabinoids at a circuit-specific level.

The National Center for Complementary and Integrative Health (NCCIH), which is part of the US National Institutes of Health (NIH), has a broad interest in studying the biologic activities of natural products, especially those for which compelling evidence from preclinical research suggests biologic activities that may be beneficial to health or have a potential role in disease treatment, as well as products used extensively by the American public. As of 2023, use of cannabis for medical purposes is legal in 38 states and Washington, D.C. Such use continues to climb generally without sufficient knowledge regarding risks and benefits. In keeping with NCCIH’s natural product research priorities and recognizing this gap in knowledge, NCCIH formally launched a research program in 2019 to expand research on the possible benefits for pain management of certain substances found in cannabis: minor cannabinoids and terpenes. This Viewpoint provides additional details and the rationale for this research priority at NCCIH. In addition, NCCIH’s efforts and initiatives to facilitate and coordinate an NIH research agenda focused on cannabis and cannabinoid research are described.

Cannabis and its products have been used for centuries for both medicinal and recreational purposes. The recent widespread legalization of cannabis has vastly expanded its use in the United States across all demographics except for adolescents. Meanwhile, decades of research have advanced our knowledge of cannabis pharmacology and particularly of the endocannabinoid system with which the components of cannabis interact. This research has revealed multiple targets and approaches for manipulating the system for therapeutic use and to ameliorate cannabis toxicity or cannabis use disorder. Research has also led to new questions that underscore the potential risks of its widespread use, particularly the enduring consequences of exposure during critical windows of brain development or for consumption of large daily doses of cannabis with high content ⁹-tetrahydrocannabinol. This article highlights current neuroscience research on cannabis that has shed light on therapeutic opportunities and potential adverse consequences of misuse and points to gaps in knowledge that can guide future research.

Low-efficacy mu opioid receptor (MOR) agonists may serve as novel candidate analgesics with improved safety relative to high-efficacy opioids. This study used a recently validated assay of pain-depressed behavior in mice to evaluate a novel series of MOR-selective C9-substituted phenylmorphan opioids with graded MOR efficacies. Intraperitoneal injection of dilute lactic acid (IP acid) served as a noxious stimulus to depress locomotor activity by mice in an activity chamber composed of two compartments connected by an obstructed door. Behavioral measures included (1) crosses between compartments (vertical activity over the obstruction) and (2) movement counts quantified as photobeam breaks summed across compartments (horizontal activity). Each drug was tested alone and as a pretreatment to IP acid. A charcoal-meal test and whole-body-plethysmography assessment of breathing in 5% CO₂ were also used to assess gastrointestinal (GI) inhibition and respiratory depression, respectively. IP acid produced a concentration-dependent depression in crosses and movement that was optimally alleviated by intermediate- to low-efficacy phenylmorphans with sufficient efficacy to produce analgesia with minimal locomotor disruption. Follow-up studies with two low-efficacy phenylmorphans (JL-2-39 and DC-1-76.1) indicated that both drugs produced naltrexone-reversible antinociception with a rapid onset and a duration of ~1 h. Potency of both drugs increased when behavior was depressed by a lower IP-acid concentration, and neither drug alleviated behavioral depression by a non-pain stimulus (IP lithium chloride). Both drugs produced weaker GI inhibition and respiratory depression than fentanyl and attenuated fentanyl-induced GI inhibition and respiratory depression. Results support further consideration of selective, low-efficacy MOR agonists as candidate analgesics.

We primary care clinicians, scholars, and leaders ascribe value to Barbara Starfield’s core tenets of primary care—the 4 Cs: first contact, comprehensiveness, coordination, and continuity. In today’s era of rapid technological advancements and dwindling resources, what are the implications for face-to-face interactions of patient-clinician relationships? We propose adding a 5th C: "Contiguity." Contiguity—or physical proximity and presence—is a key dimension that not only enables the necessary technical aspects of a physical exam but also authenticates the most human aspects of a relationship and occurs specifically when we are physically vulnerable and responsible for the other before us. This, in turn, may best enable us to bridge difference and nurture trust with our patients. We measure what we value and, thus, naming Contiguity as a core tenet assures that we will not lose sight of this keystone in a patient’s relationship with their personal physician.

Practicing family medicine is really hard; the emotional toll of sharing patients’ distress, vulnerability, and trauma can build up and become overwhelming. A family physician experienced such a moment during one particularly complex morning. Feeling nearly ready to walk out of patient care, she reached out to the team nurse, who helped her get through the moment and re-engage with the waiting patients. Sharing vulnerability in the moment, and later reflecting and deciding to write about it shows the power of prioritizing teamwork in practice.

The usual challenges of conducting primary care research, including randomized trials, have been exacerbated, and new ones identified, during the COVID-19 pandemic. HOMER (Home versus Office for Medication Enhanced Recovery; subsequently, Comparing Home, Office, and Telehealth Induction for Medication Enhanced Recovery) is a pragmatic, comparative-effectiveness research trial that aims to answer a key question from patients and clinicians: What is the best setting in which to start treatment with buprenorphine for opioid use disorder for this patient at this time? In this article, we describe the difficult journey to find the answer. The HOMER study began as a randomized trial comparing treatment outcomes in patients starting treatment with buprenorphine via induction at home (unobserved) vs in the office (observed, synchronous). The study aimed to enroll 1,000 participants from 100 diverse primary care practices associated with the State Networks of Colorado Ambulatory Practices and Partners and the American Academy of Family Physicians National Research Network. The research team faced unexpected challenges related to the COVID-19 pandemic and dramatic changes in the opioid epidemic. These challenges required changes to the study design, protocol, recruitment intensity, and funding conversations, as well as patience. As this is a participatory research study, we sought, documented, and responded to practice and patient requests for adaptations. Changes included adding a third study arm using telehealth induction (observed via telephone or video, synchronous) and switching to a comprehensive cohort design to answer meaningful patient-centered research questions. Using a narrative approach based on the Greek myth of Homer, we describe here the challenges and adaptations that have provided the opportunity for HOMER to thrive and find the way home. These clinical trial strategies may apply to other studies faced with similar cultural and extreme circumstances.

PURPOSE

HIV pre-exposure prophylaxis (PrEP) may increase rates of bacterial sexually transmitted infections (STIs) among gay, bisexual, and other men who have sex with men (GBM) through risk compensation (eg, an increase in condomless sex or number of partners); however, longitudinal studies exploring the time-dependent nature of PrEP uptake and bacterial STIs are limited. We used marginal structural models to estimate the effect of PrEP uptake on STI incidence.

PURPOSE

Chest pain frequently poses a diagnostic challenge for general practitioners (GPs). Utilizing risk stratification tools might help GPs to rule out acute coronary syndrome (ACS) and make appropriate referral decisions. We conducted a systematic review of studies evaluating risk stratification tools for chest pain in primary care settings, both with and without troponin assays. Our aims were to assess the performance of tools for ruling out ACS and to provide a comprehensive review of the current evidence.

Patient expectations of receiving antibiotics for common symptoms can trigger unnecessary use. We conducted a survey (n = 564) between January 2020 to June 2021 in public and private primary care clinics in Texas to study the prevalence and predictors of patients’ antibiotic expectations for common symptoms/illnesses. We surveyed Black patients (33%) and Hispanic/Latine patients (47%), and over 93% expected to receive an antibiotic for at least 1 of the 5 pre-defined symptoms/illnesses. Public clinic patients were nearly twice as likely to expect antibiotics for sore throat, diarrhea, and cold/flu than private clinic patients. Lack of knowledge of potential risks of antibiotic use was associated with increased antibiotic expectations for diarrhea (odds ratio [OR] = 1.6; 95% CI, 1.1-2.4) and cold/flu symptoms (OR = 2.9; 95% CI, 2.0-4.4). Lower education and inadequate health literacy were predictors of antibiotic expectations for diarrhea. Future antibiotic stewardship interventions should tailor patient education materials to include information on antibiotic risks and guidance on appropriate antibiotic indications.

The aim of this work is to test whether the use of a transparent capsule affects the residual capsule weight after inhalation as a surrogate of the inhaled delivered dose for patients with non-reversible chronic airway disease. Researchers conducted an observational cross-sectional study with patients using a single-dose dry powder inhaler. The weight of the capsule was measured with a precision microbalance before and after inhalation. Ninety-one patients were included, of whom 63 (69.2%) used a transparent capsule. Inhalation with a transparent capsule achieved a weight decrease of 30.1% vs 8.6% for devices with an opaque capsule (P <0.001). These data reinforce the need to provide patients with mechanisms that verify the correct inhalation technique.

PURPOSE

The impact of digital health on medically underserved patients is unclear. This study aimed to determine the early impact of a digital innovation to grow quality care through an interprofessional care team (DIG IT) on the blood pressure (BP) and 10-year atherosclerotic cardiovascular disease (ASCVD) risk score of medically underserved patients.

PURPOSE

Meeting scholarly activity requirements continues to be a challenge in many family medicine (FM) residency programs. Studies comprehensively describing FM resident scholarship have been limited. We sought to identify institutional factors associated with increased scholarly output and meeting requirements of the Accreditation Council for Graduate Medical Education (ACGME).

PURPOSE

We undertook a trial to test the efficacy of a technology-assisted health coaching intervention for weight management, called Goals for Eating and Moving (GEM), within primary care.

PURPOSE

Despite being key to better health outcomes for patients from racial and ethnic minority groups, the proportion of underrepresented in medicine (URiM) physicians remains low in the US health care system. This study linked a nationally representative sample of family physicians (FPs) with Medicaid claims data to explore the relative contributions to care of Medicaid populations by FP race and ethnicity.

PURPOSE

Currently, 40% of counties in the United States do not have an obstetrician or midwife, and in rural areas the likelihood of childbirth being attended to by a family medicine (FM) physician is increasing. We sought to characterize the effect of the FM presence on unit culture and a key perinatal quality metric in Iowa hospital intrapartum units.

BACKGROUND

For many patients with post–COVID-19 condition (long COVID), primary care is the first point of interaction with the health care system. In principle, primary care is well situated to manage long COVID. Beyond expressions of disempowerment, however, the patient’s perspective regarding the quality of long COVID care is lacking. Therefore, this study aimed to analyze the expectations and experiences of primary care patients seeking treatment for long COVID.