Kappa Opioid Research Articles

Discovery of an Ortho-Substituted N-Cyclopropylmethyl-7α-phenyl-6,14-endoethano-tetrahydronorthebaine Derivative as a Selective and Potent Kappa Opioid Receptor Agonist with Subsided Sedative Effect.

Research into kappa opioid receptor (KOR) agonists with attenuated central-nervous-system side effects is a critical focus for developing productive and safe analgesics. Herein, a series of ortho-substituted N-cyclopropylmethyl-7α-phenyl-6,14-endoethano-tetrahydronorthebaines were designed, synthesized, and subjected to bioassays. Compound 7a exhibited high subtype selectivity and potent agonistic activity toward KOR (KOR, Ki = 3.9 nM, MOR/KOR = 270, DOR/KOR = 1075; [35S]GTPγS binding, EC50 = 3.4 nM). Additionally, this compound exhibited robust and persistent antinociceptive effects in rodent models with different animal strains (hot plate test, ED50 = 0.20-0.30 mg/kg, i.p.; abdominal constriction test, ED50 = 0.20-0.60 mg/kg, i.p.), with its KOR-mediated mechanism for antinociception firmly established. Notably, compound 7a, unlike conventional KOR agonists, displayed minimal sedation and aversion at the antinociceptive ED50 dose. This feature addresses a crucial limitation in existing KOR agonists, positioning compound 7a as a promising novel therapeutic agent.

Efficacy and safety of aticaprant, a kappa receptor antagonist, adjunctive to oral SSRI/SNRI antidepressant in major depressive disorder: results of a phase 2 randomized, double-blind, placebo-controlled study

This was a double-blind, randomized, phase 2 study of adults (18–64 years) with DSM−5 diagnosis of major depressive disorder (MDD), with moderate-to-severe episode severity (Montgomery–Åsberg Depression Rating Scale [MADRS] ≥25) despite an adequate course with ongoing antidepressant for ≥6 weeks to ≤12 months. Following a double-blind placebo lead-in period (up to 3 weeks), participants were randomized to receive once daily aticaprant 10 mg or continue placebo, added to their ongoing treatment, for 6 weeks. Of 184 participants enrolled, 169 were included in safety analyses (aticaprant n = 85, placebo n = 84) and 166 in full intent-to-treat (fITT) efficacy analyses; 121 placebo lead-in non-responders (<30% reduction in MADRS total score) in fITT were included in enriched ITT (eITT) analyses. Improvement (least squares mean difference [upper limit 1-sided 80% CI] versus placebo) in MADRS total score at week 6 for aticaprant was significant versus placebo (eITT: −2.1 [−1.09], 1-sided p = 0.044; effect size (ES) 0.23; fITT −3.1 [2.21], 1-sided p = 0.002; ES 0.36). The between-group difference was larger among participants with Snaith–Hamilton Pleasure Scale (SHAPS) score greater/equal to versus less than baseline median SHAPS. The most common treatment-emergent adverse events reported for aticaprant (versus placebo) were headache (11.8% versus 7.1%), diarrhea (8.2% versus 2.4%), nasopharyngitis (5.9% versus 2.4%), and pruritus (5.9% versus 0%). One participant (1.2%) in each arm discontinued treatment due to an adverse event. In this study of participants with MDD and inadequate response to SSRI/SNRI, adjunctive treatment with aticaprant significantly reduced depressive symptoms versus placebo, without resulting in significant safety signals, supporting further investigation in larger trials.

Effects of sex and hydration status on kappa opioid receptor-mediated diuresis in rats.

Understanding the function of the kappa opioid receptor (KOP) is crucial for the development of novel therapeutic interventions that target KOP for the treatment of pain, stress-related disorders and other indications. Activation of KOP produces diuretic effects in rodents and man. Sex is a vital factor to consider when assessing drug response in pre-clinical and clinical studies. In this study, the diuretic effect of the KOP agonist, U50488 (1-10 mg/kg), was investigated in both adult female and male Wistar rats that were either normally hydrated or water-loaded. The KOP antagonist norbinaltorphimine (norBNI, 10 mg/kg) was administered 24 h prior to U50488 to confirm the involvement of KOP. U50488 elicited a significant diuretic response at doses ≥ 3 mg/kg in both female and male rats independent of hydration status. U50488 diuretic effects were inhibited by norBNI pre-administration. Water-loading reduced data variability for urine volume in males, but not in females, compared with normally hydrated rats. Sex differences were also evident in U50488 eliciting a significant increase in sodium and potassium ion excretion only in males. This may suggest different mechanisms of U50488 diuretic action in males where renal excretion mechanisms are directly affected more than in females.

In Vitro and In Vivo Pharmacological Profiles of LENART01, a Dermorphin-Ranatensin Hybrid Peptide.

Diverse chemical and pharmacological strategies are currently being explored to minimize the unwanted side effects of currently used opioid analgesics while achieving effective pain relief. The use of multitarget ligands with activity at more than one receptor represents a promising therapeutic approach. We recently reported a bifunctional peptide-based hybrid LENART01 combining dermorphin and ranatensin pharmacophores, which displays activity to the mu-opioid receptor (MOR) and dopamine D2 receptor (D2R) in rat brains and spinal cords. In this study, we investigated the in vitro binding and functional activities to the human MOR and the in vivo pharmacology of LENART01 in mice after subcutaneous administration. In vitro binding assays showed LENART01 to bind and be selective to the human MOR over the other opioid receptor subtypes and delta, kappa and nociceptin receptors. In the [35S]GTPγS binding assay, LENART01 acted as a potent and full agonist to the human MOR. In mice, LENART01 produced dose-dependent antinociceptive effects in formalin-induced inflammatory pain, with increased potency than morphine. Antinociceptive effects were reversed by naloxone, indicating MOR activation in vivo. Behavioral studies also demonstrated LENART01's properties to induce less adverse effects without locomotor dysfunction and withdrawal syndrome compared to conventional opioid analgesics, such as morphine. LENART01 is the first peptide-based MOR-D2R ligand known to date and the first dual MOR-dopamine D2R ligand for which in vivo pharmacology is reported with antinociceptive efficacy and reduced opioid-related side effects. Our current findings may pave the way to new pain therapeutics with limited side effects in acute and chronic use.

Efficacy and safety of difelikefalin in the treatment of hemodialysis patients with pruritus: A meta-analysis and systematic review.

The incidence of pruritus associated with hemodialysis (HD) patients can be as high as 70%, and ~40% of patients suffer from moderate to severe systemic pruritus. Difelikefalin (CR845), a peripheral restrictor κ-opioid receptor agonist, activates opioid receptors on peripheral neurons and immune cells to relieve pruritus in patients. However, the clinical effect of difelikefalin on HD-related pruritus is unclear. Therefore, the purpose of this meta-analysis and systematic review was to investigate the safety and efficacy of difelikefalin in the treatment of HD-associated pruritus. This study explored the efficacy and safety of difelikefalin in the treatment of pruritus in HD patients by systematic review and meta-analysis. Randomized controlled trials on difelikefalin in the treatment of pruritus in HD patients were retrieved from PubMed, Embase, Cochrane Library, and Web of Science electronic databases. The retrieval deadline was January 1, 2023. Stata 15.0 software was used for data analysis of the included studies. A total of 4 randomized controlled trials were included, totaling 1,268 patients (736 patients in the experimental group and 532 patients in the control group). Results of the meta-analysis showed that, compared with the control group, difelikefalin could significantly improve the Worst Itch Numeric Rating Scale score (improvement &gt; 3; risk ratio (RR)=1.28, 95% confidence interval (CI) (1.07, 1.53)), decrease the 5-D itch score (standardized mean difference=-0.43, 95% CI (-0.55, -0.30)), and significantly improve adverse events (RR=1.33, 95% CI (1.13, 1.56)). Although difelikefalin can improve itching symptoms in HD patients, it can also increase adverse reactions based on the current literature. Therefore, more studies are needed to further explore the safety and efficacy of difelikefalin treatment.

Dexamethasone attenuates neuropathic pain through spinal microglial expression of dynorphin A via the cAMP/PKA/p38 MAPK/CREB signaling pathway

This study aimed to elucidate the opioid mechanisms underlying dexamethasone-induced pain antihypersensitive effects in neuropathic rats. Dexamethasone (subcutaneous and intrathecal) and membrane-impermeable Dex-BSA (intrathecal) administration dose-dependently inhibited mechanical allodynia and thermal hyperalgesia in neuropathic rats. Dexamethasone and Dex-BSA treatments increased expression of dynorphin A in the spinal cords and primary cultured microglia. Dexamethasone specifically enhanced dynorphin A expression in microglia but not astrocytes or neurons. Intrathecal injection of the microglial metabolic inhibitor minocycline blocked dexamethasone-stimulated spinal dynorphin A expression; intrathecal minocycline, the glucocorticoid receptor antagonist Dex-21-mesylate, dynorphin A antiserum, and κ-opioid receptor antagonist GNTI completely blocked dexamethasone-induced mechanical antiallodynia and thermal antihyperalgesia. Additionally, dexamethasone elevated spinal intracellular cAMP levels, leading to enhanced phosphorylation of PKA, p38 MAPK and CREB. The specific adenylate cyclase inhibitor DDA, PKA inhibitor H89, p38 MAPK inhibitor SB203580 and CREB inhibitor KG-501 completely blocked dexamethasone-induced anti-neuropathic pain and increased microglial dynorphin A exprression. In conclusion, this study reveal that dexamethasone mitigateds neuropathic pain through upregulation of dynorphin A in spinal microglia, likely involving the membrane glucocorticoid receptor/cAMP/PKA/p38 MAPK/CREB signaling pathway.

Isolation, characterization and pharmacological potentials of methanol extract of Cassia fistula leaves: Evidenced from mice model along with molecular docking analysis

The purpose of the current investigation was to conduct a detailed analysis of the chemical components and medicinal properties of the methanolic crude extract derived from the leaves of Cassia fistula. This analysis was carried out using both experimental (in vivo) and computational (in silico) methods. Eleven chemicals were chromatographically isolated using GC-MS/MS, which utilizes a library of NIST and Wiley 2020 versions. FTIR analysis of the extract was performed to identify the functional group of the compounds. The glucose-lowering capacity, analgesic, and anti-diarrheal activities of methanolic crude extract were analyzed utilizing a well-known oral glucose tolerance test, tail immersion method, writhing assay, and castor oil-induced diarrheal mice methods, respectively. After 60 min, 120 min, and 180 min of loading the drugs, a significant reduction of blood glucose levels was examined (p < 0.05) in all the extracts of this plant (200 mg/kg, 400 mg/kg and 600 mg/kg) utilized in this research at a time-dependent manner. Similarly, all the crude extracts showed significant (p < 0.05) effects against pain centrally and peripherally compared to the standard drug morphine (2 mg/kg bw) and diclofenac sodium (50 mg/kg bw). Moreover, the methanol extract (400 mg/kg bw) manifested anti-diarrheal efficacy by inhibiting 72.0 % of the diarrheal episode in mice compared to the standard drug loperamide (inhibition = 80.0%). The results of the computational investigations corroborated existing in-vivo findings. Greater or close to equivalent binding affinity to the active binding sites of kappa opioid receptor, glucose transporter 3 (GLUT 3), and cyclooxygenase 2 was indicative of the potential anti-diarrheal, hypoglycemic, and analgesic characteristics of the isolated compounds (COX-2). Moreover, anticancer and antimicrobial potentiality was also found impressive through evaluation of binding affinity with epidermal growth factor receptor (EGFR) and dihydrofolate reductase (DHFR) receptors. Results from this study indicated that C. fistula might be a beneficial natural resource for treating diarrhea, hyperglycemia, and pain. However, additional research is required to conduct a comprehensive phytochemical screening and establish precise action mechanisms of the crude extract or the plant-derived compounds.

Kappa-opioid receptor stimulation in the nucleus accumbens shell and ethanol drinking: Differential effects by rostro-caudal location and level of drinking

Although the kappa-opioid receptor (KOR) and its endogenous ligand, dynorphin, are believed to be involved in ethanol drinking, evidence on the direction of their effects has been mixed. The nucleus accumbens (NAc) shell densely expresses KORs, but previous studies have not found KOR activation to influence ethanol drinking. Using microinjections into the NAc shell of male and female Long-Evans rats that drank under the intermittent-access procedure, we found that the KOR agonist, U50,488, had no effect on ethanol drinking when injected into the middle NAc shell, but that it promoted intake in males and high-drinking females in the caudal NAc shell and high-drinking females in the rostral shell, and decreased intake in males and low-drinking females in the rostral shell. Conversely, injection of the KOR antagonist, nor-binaltorphimine, stimulated ethanol drinking in low-drinking females when injected into the rostral NAc shell and decreased drinking in high-drinking females when injected into the caudal NAc shell. These effects of KOR activity were substance-specific, as U50,488 did not affect sucrose intake. Using quantitative real-time PCR, we found that baseline gene expression of the KOR was higher in the rostral compared to caudal NAc shell, but that this was upregulated in the rostral shell with a history of ethanol drinking. Our findings have important clinical implications, demonstrating that KOR stimulation in the NAc shell can affect ethanol drinking, but that this depends on NAc subregion, subject sex, and ethanol intake level, and suggesting that this may be due to differences in KOR expression.

Nalmefene, an opioid receptor modulator, aggravates atherosclerotic plaque formation in apolipoprotein E knockout mice by enhancing oxidized low-density lipoprotein uptake in macrophages

Nalmefene, an antagonist of mu- and delta-opioid receptors and a partial agonist of kappa-opioid receptors, has shown promise in reducing alcohol consumption among patients with alcohol dependence. Opioid receptors play pivotal roles in various physiological processes, including those related to peripheral inflammatory diseases such as colitis and arthritis, as well as functions in the immune system and phagocytosis. Atherosclerosis, a chronic inflammatory disease, progresses through the phagocytosis and uptake of oxidized low-density lipoprotein (oxLDL) by macrophages in atherosclerotic plaques. Despite this knowledge, it remains unclear whether nalmefene influences the formation of atherosclerotic plaques and increases the risk of serious cardiovascular events. This study aims to elucidate the impact of nalmefene on atherosclerosis in apolipoprotein E knockout (ApoE KO) mice and peritoneal macrophages in vitro.In this experiment, 8-week-old male ApoE KO mice were fed a high-fat diet intraperitoneally administered either vehicle (saline) or nalmefene (1 mg and 3 mg kg−1 day−1) for 21 days. Oil red O-staining and immunohistochemistry with an anti-MOMA2 (monocyte/macrophage) antibody showed that a dose-dependent increase in atherosclerotic plaque formation and augmentation of macrophage-rich plaque formation in ApoE-KO mice. Further investigations focused on the effects of nalmefene on the expression of scavenger receptor CD36 in RAW264.7 cells, conducted through western blotting analysis. Nalmefene demonstrated a significant increase in CD36 protein expression in RAW264.7 cells. To explore the impact on oxidized LDL uptake in peritoneal macrophages, cells were treated with nalmefene (300 μg/mL) for 24 h, followed by the addition of DiI-labeled oxLDL (DiI-oxLDL) for 4 h. Nalmefene significantly enhanced DiI-oxLDL uptake in macrophages. Additionally, treatment with nalmefene (300 μg/mL) for 24 h decreased the mRNA expression of mu-, delta-, and kappa-opioid receptors in RAW264.7 cells.In conclusion, nalmefene may augment oxLDL uptake by macrophages through increased CD36 expression and decreased opioid receptor, thereby contributing to atherosclerotic plaque formation and vulnerability. Consequently, the use of nalmefene may be associated with an elevated risk of cardiovascular events.

Efficacy and safety of nalbuphine for epidural labor analgesia at high altitude: An observational study.

Xining is located at the eastern edge of the Qinghai-Tibet Plateau, with an average altitude of >7000 feet (>2000 m). Nalbuphine is a kappa-opioid receptor agonist that can provide analgesia with fewer side effects than other opioid analgesics. This study aimed to evaluate pain control, side effects, and neonatal outcomes from combining nalbuphine with sufentanil and ropivacaine in 600 women during epidural anesthesia while giving birth at a high altitude in Xining, China. A total of 600 parturients receiving epidural labor analgesia were randomly divided into 2 groups, each group 300 parturients. The nalbuphine group received nalbuphine, sufentanil, and ropivacain, the control group only received sufentanil and ropivacain. The analgesic effect was evaluated through the Visual Analogue Scale scores. Neonatal outcomes were mainly evaluated through the Apgar Scores. Compared to the control group, the nalbuphine group showed lower Visual Analogue Scale scores at all time points after analgesia (P < .05). In comparison with the control group, parturients in the nalbuphine group showed lower incidence rates of fever at delivery, 24-hour postpartum bleeding, and pruritus (P < .05). However, between the 2 groups, there were no statistically significant differences in the remaining maternal and infant outcomes and neonatal outcomes (P > .05). Moreover, no adverse effects on neonatal outcomes were observed. The findings from this study support findings from previous studies that nalbuphine provided safe epidural analgesia without significant side effects for the mother and infant, and showed both safety and efficacy when used during labor at high altitude.

Abstract 7496: The piritramide-based perioperative analgesia can affect the cancer dissemination in colorectal cancer patients

Abstract Introduction: Colorectal cancer (CRC) stands as a prominent contributor to global cancer-related mortality. Post-surgical management of CRC patients often involves the administration of opioid analgesics. These analgesics operate through opioid and cannabinoid receptors, pathways implicated in tumor progression and metastasis, potentially impacting patient survival adversely. This investigation delves into the influence of piritramide and morphine on cancer dissemination, encompassing in vitro and in vivo assessments, cytotoxicity analyses, and elucidation of their mode of action. Methods: The presence of circulating tumor cells (CTCs) in the blood of 131 CRC patients was quantitatively assessed using the real-time polymerase chain reaction (qPCR) method. Cytotoxic effects of morphine and piritramide were evaluated via colony-forming assays (CFA) utilizing HCT116 and HT29 cell lines. The impact of piritramide and morphine on opioid receptor activity was gauged through transfected reporter cell lines and fluorescence imaging plater reader (FLIPR) calcium assays. In vivo models involving subcutaneous and intrasplenic administration in SCID and BALB mice, respectively, utilizing HCT116 and HT29 cell lines, were conducted. Morphological profiling, employing the cell painting assay, facilitated high-content image-based analysis on both cell lines. Results: Perioperative analgesia with piritramide exhibited a tendency towards longer time to recurrence (TTR) survival in CRC patients (HR=1.8, p=0.104). Conversely, morphine-treated patients demonstrated a twofold increase in TTR events (HR=4.7, p=0.011). Piritramide, but not morphine, significantly inhibited colony growth in HCT116 and HT-29 cell lines in the CFA, consistent with cytotoxicity test results. Functional assays revealed agonistic effects of both piritramide and morphine on opioid receptor kappa 1 (OPRK1) and mu 1 (OPRM1), with piritramide exhibiting greater potency as an OPRK1 agonist. In the SCID mice model, subcutaneous application of HT29 cell lines resulted in significantly reduced tumor growth in piritramide-treated mice. In the intrasplenic model utilizing BALB mice, mice treated with piritramide exhibited diminished tumor growth and a reduction in both the number and size of metastases. Comparative analysis with reference compounds revealed a distinct phenotypic profile of piritramide affecting the endoplasmic reticulum. Conclusion: Piritramide, as opposed to morphine, demonstrated cytotoxic effects on both in vitro and in vivo CRC cell lines, resulting in reduced tumor growth and dissemination. Perioperative analgesia with piritramide exhibited potential in improving time to recurrence survival in CRC patients. Acknowledgement: This study received support from the European Union - Next Generation EU (LX22NPO5102) and Palacky University Olomouc (LF 2023_006). Citation Format: Josef Srovnal, Emil Berta, Monika Vidlarova, Alona Rehulkova, Katerina Jecmenova, Miroslav Popper, Alzbeta Srovnalova, Petr Prasil, Pavel Skalicky, Tomas Gabrhelik, Jan Maca, Pavel Michalek, Marian Hajduch. The piritramide-based perioperative analgesia can affect the cancer dissemination in colorectal cancer patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7496.

Co-targeting the kappa opioid receptor and dopamine transporter reduces motivation to self-administer cocaine and partially reverses dopamine system dysregulation

Cocaine disrupts dopamine (DA) and kappa opioid receptor (KOR) system activity, with long-term exposure reducing inhibiton of DA uptake by cocaine and increasing KOR system function. Single treatment therapies have not been successful for cocaine use disorder; therefore, this study focuses on a combination therapy targeting the dopamine transporter (DAT) and KOR. Sprague Dawley rats self-administered 5 days of cocaine (1.5 mg/kg/inf, max 40 inf/day, FR1), followed by 14 days on a progressive ratio (PR) schedule (0.19 mg/kg/infusion). Behavioral effects of individual and combined administration of phenmetrazine and nBNI were then examined using PR. Additionally, ex vivo fast scan cyclic voltammetry was then used to assess alterations in DA and KOR system activity in the nucleus accumbens before and after treatments. Chronic administration of phenmetrazine as well as the combination of phenmetrazine and nBNI—but not nBNI alone—significantly reduced PR breakpoints. In addition, the combination of phenmetrazine and nBNI partially reversed cocaine-induced neurodysregulations of the KOR and DA systems, indicating therapeutic benefits of targeting the DA and KOR systems in tandem. These data highlight the potential benefits of the DAT and KOR as dual-cellular targets to reduce motivation to administer cocaine and reverse cocaine-induced alterations of the DA system.

Enhancing Docking Accuracy with PECAN2, a 3D Atomic Neural Network Trained without Co-Complex Crystal Structures

Decades of drug development research have explored a vast chemical space for highly active compounds. The exponential growth of virtual libraries enables easy access to billions of synthesizable molecules. Computational modeling, particularly molecular docking, utilizes physics-based calculations to prioritize molecules for synthesis and testing. Nevertheless, the molecular docking process often yields docking poses with favorable scores that prove to be inaccurate with experimental testing. To address these issues, several approaches using machine learning (ML) have been proposed to filter incorrect poses based on the crystal structures. However, most of the methods are limited by the availability of structure data. Here, we propose a new pose classification approach, PECAN2 (Pose Classification with 3D Atomic Network 2), without the need for crystal structures, based on a 3D atomic neural network with Point Cloud Network (PCN). The new approach uses the correlation between docking scores and experimental data to assign labels, instead of relying on the crystal structures. We validate the proposed classifier on multiple datasets including human mu, delta, and kappa opioid receptors and SARS-CoV-2 Mpro. Our results demonstrate that leveraging the correlation between docking scores and experimental data alone enhances molecular docking performance by filtering out false positives and false negatives.

LY2444296, a κ-opioid receptor antagonist, selectively reduces alcohol drinking in male and female Wistar rats with a history of alcohol dependence

Alcohol use disorder (AUD) remains a major public health concern. The dynorphin (DYN)/κ-opioid receptor (KOP) system is involved in actions of alcohol, particularly its withdrawal-associated negative affective states. This study tested the ability of LY2444296, a selective, short-acting, KOP antagonist, to decrease alcohol self-administration in dependent male and female Wistar rats at 8 h abstinence. Animals were trained to orally self-administer 10% alcohol (30 min/day for 21 sessions) and were made dependent via chronic intermittent alcohol vapor exposure for 6 weeks or exposed to air (nondependent). After 6 weeks, the effect of LY2444296 (0, 3, and 10 mg/kg, p.o.) was tested on alcohol self-administration at 8 h of abstinence. A separate cohort of rats was prepared in parallel, and their somatic withdrawal signs and alcohol self-administration were measured after LY2444296 administration at 8 h, 2 weeks, and 4 weeks abstinence. LY2444296 at 3 and 10 mg/kg significantly reduced physical signs of withdrawal in dependent rats at 8 h abstinence, only. Furthermore, 3 and 10 mg/kg selectively decreased alcohol self-administration in dependent rats at only 8 h abstinence. These results highlight the DYN/KOP system in actions of alcohol during acute abstinence, suggesting KOP antagonism could be beneficial for mitigating acute withdrawal signs and, in turn, significantly reduce excessive alcohol consumption associated with AUD.

In and out Beauty and Sensitive Skin, a Psychophysiological Exploration: Myth or Reality?

Knowing that biomolecules, such as β-amyrin and α-amyrin, have some pharmacological effects, the aim of this study was directed towards exploring the protective effect of Tomato Peel and Seed Extract (TPSE) for its soothing function but also for its capacity to modulate the adrenal axis, which is involved in stress response. Ex vivo tests were carried out on skin explants to evaluate the effectiveness of TPSE formulated at 0.5% on Calcitonin Gene-Related Peptide (CGRP) and IL-10 release, Kappa Opioid Receptor (KOR), and Caspase 14 expression. An in vivo study combined a clinical evaluation of skin homogeneity and psychological parameters as well as an analysis of salivary cortisol and dehydroepiandrosterone concentrations. All measurements were carried out at the beginning and after 28 days of applying a TPSE face cream. TPSE regulated not only the release of CGRP, IL-10, and the expression of Caspase 14, reflecting anti-neurogenic and anti-inflammatory properties, but also modulated KORs. Twenty-eight days of TPSE application induced a significant decrease in intensity and extent erythrosis, a lower output of salivary cortisol, and a significant increase in pleasant emotions when compared to placebo. These results provide encouragement to continue exploring the impact of cosmetic ingredients on psychophysiological parameters to improve skin health and well-being.

Abstract 1275 Autophagy leads to stress-driven synaptic alterations mediated by κ-opioid receptor activation

Abstract 1275 Autophagy leads to stress-driven synaptic alterations mediated by κ-opioid receptor activation

NCP, a dual kappa and mu opioid receptor agonist, is a potent analgesic against inflammatory pain without reinforcing or aversive properties.

While agonists of mu (MOR) and kappa (KOR) opioid receptors have analgesic effects, they produce euphoria and dysphoria, respectively. Other side effects include respiratory depression and addiction for MOR agonists and sedation for KOR agonists. We reported that 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-{[4'-(2'-cyanopyridyl)]carboxamido}cmorphinan (NCP) displayed potent KOR full agonist and MOR partial agonist activities (58%) with 6.5x KOR-over-MOR selectivity in vitro Herein, we characterized pharmacological effects of NCP in rodents. In mice, NCP exerted analgesic effects against inflammatory pain in both the formalin test and the acetic acid writhing test, with A50 values of 47.6 and 14.4 microg/kg (s.c.), respectively. The analgesic effects in the acetic acid writhing test were mediated by the KOR. NCP at doses much higher than those effective in reducing inflammatory pain did not produce antinociception in the hot plate and tail flick tests, inhibit compound 48/80-induced scratching, cause conditioned place aversion (CPA) or preference, impair rotarod performance, inhibit locomotor activity, cause respiratory depression, or precipitate morphine withdrawal. However, NCP (10~100 microg/kg) inhibited gastrointestinal transit with a maximum of ~40% inhibition. In MOR knockout mice, NCP caused CPA, demonstrating that its lack of CPA is due to combined actions on the MOR and KOR. Following s.c. injection, NCP penetrated into the mouse brain. In rats trained to self-administer heroin, NCP (1~320 microg/kg/infusion) did not function as a reinforcer. Thus, NCP produces potent analgesic effects via KOR without side effects except constipation. Therefore, dual full KOR/partial MOR agonists with moderate KOR-over-MOR selectivity may be promising as non-addictive analgesics for inflammatory pain. Significance Statement Developing non-addictive analgesics is crucial for reducing opioid overdose deaths, minimizing drug misuse, and promoting safer pain management practices. Herein, pharmacology of a potential non-addictive analgesic, NCP, is reported. NCP has full KOR agonist / partial MOR agonist activities with a 6.5 x selectivity for KOR over MOR. Unlike MOR agonists, analgesic doses of NCP do not lead to self-administration or respiratory depression. Furthermore, NCP does not produce aversion, hypolocomotion, or motor incoordination, side effects typically associated with KOR activation.

Characterization of a Nonselective Opioid Receptor Functional Antagonist: Implications for Development as a Novel Opioid Dependence Medication.

Opioids represent the most extensive category of abused substances in the United States, and the number of fatalities caused by these drugs exceeds those associated with all other drug overdoses combined. The administration of naltrexone, a potent pan-opioid receptor antagonist, to an individual dependent on opioids can trigger opioid withdrawal and induce severe side effects. There is a pressing demand for opioid antagonists free of opioid withdrawal effects. In our laboratory, we have identified a compound with affinity to mu, delta, and kappa opioid receptors in the range of 150-250 nM. This blood-brain barrier (BBB)-permeant compound was metabolically stable in vitro and in vivo. Our in vivo work demonstrated that 1-10 mg/kg intraperitoneal administration of our compound produces moderate efficacy in antagonizing morphine-induced antiallodynia effects in the chemotherapy-induced peripheral neuropathy (CIPN) model. The treatment was well-tolerated and did not cause behavioral changes. We have observed a fast elimination rate of this metabolically stable molecule. Furthermore, no organ toxicity was observed during the chronic administration of the compound over a 14-day period. Overall, we report a novel functional opioid antagonist holds promise for developing an opioid withdrawal therapeutic.

Diagnosis and management of pruritus associated with chronic kidney disease in hemodialyzed patients

Chronic kidney disease-associated pruritus (CKD-aP) is a disabling symptom which is frequent and often underestimated. Pa-MRC has a negative impact on quality of life, and is frequently accompanied by sleep disorders and depression. The approval of difelikefalin – a kappa opioid receptor agonist – in this indication requires updated recommendations. As a first step, secondary causes of pruritus without skin lesions must be ruled out, and general measures taken (emollients, psychological support, optimization of dialysis, normalization of serum calcium, phosphate and PTH in the range proposed by the KGIDO guidelines, treatment of iron deficiency). A therapeutic test with a non-sedating oral antihistamine may be proposed. If this test is negative, Pa-MRC must be strongly suspected, and its intensity (WI-NRS scale) and impact on quality of life assessed. In the case of mild Pa-MRC (WI-NRS ≤ 3), only general measures are implemented. If Pa-MRC is moderate to severe (WI-NRS ≥ 4), specific treatment with difelikefaline can be initiated for 6 months in addition to general measures. At 3 months, if the response is complete (WI-NRS score ≤ 1) or partial (decline ≥ 3 points), treatment is continued. At 6 months, if the response is complete, treatment may be discontinued with the patient’s agreement; treatment is maintained if the response is partial. At 3 or 6 months, if response is insufficient (decline < 3 points) and/or in the event of intolerance, treatment is discontinued and an alternative treatment (e.g., gabapentinoids, UVB) may be considered after dermatological consultation.

The Role of δ2-Opioid Receptors in the Regulation of Tolerance of Isolated Cardiomyocytes to Hypoxia and Reoxygenation.

Hypoxia (20 min) and reoxygenation (30 min) were simulated on isolated rat cardiomyocytes to evaluate the cytoprotective effect of selective δ2-opioid receptor agonist deltorphin II, opioid receptor antagonist naloxone methiodide, μ-opioid receptor antagonist CTAP, κ-opioid receptor antagonist nor-binaltorphimine, ε1-opioid receptor antagonist BNTX, and δ2-opioid receptors naltriben. Deltorphin II was administered 5 min before reoxygenation, antagonists were administered 10 min before reoxygenation. The cytoprotective effect of deltorphin II was assessed by the number of cardiomyocytes survived after hypoxia/reoxygenation, as well as by the lactate dehydrogenase content in the incubation medium. It has been established that the cytoprotective effect of deltorphin II occurs at a concentration of 64 nmol/liter and is associated with activation of δ2-opioid receptors.