ORL1 Research Articles

Effect of chronic delivery of the NOP/MOR partial agonist AT-201 and NOP antagonist J-113397 on heroin relapse in a rat model of opioid maintenance.

The opioid crisis persists despite availability of effective opioid agonist maintenance treatments (methadone and buprenorphine). Thus, there is a need to advance novel medications for the treatment of opioid use and relapse. We recently modeled maintenance treatment in rats and found that chronic delivery of buprenorphine and the mu opioid receptor (MOR) partial agonist TRV130 decreases relapse to oxycodone seeking and taking. In contrast, chronic delivery of the buprenorphine analog BU08028 had mixed effects on different heroin relapse-related measures. Here, we tested the effect of the mixed nociceptin (NOP) receptor/MOR partial agonist AT-201 and the NOP receptor antagonist J-113397 on different heroin relapse-related measures. We trained male and female rats to self-administer heroin (6-h/d, 14-d) in context A and then implanted osmotic minipumps containing AT-201 (0, 3.8, or 12mg/kg/d) or J-113397 (0, 12.6, or 40mg/kg/d). Next, we tested the effect of chronic delivery of the compounds on (1) incubation of heroin seeking in a non-drug context B, (2) extinction responding reinforced by heroin-associated discrete cues in context B, (3) context A-induced reinstatement of heroin seeking, and (4) reacquisition of heroin self-administration in context A. In females, AT-201 modestly increased reacquisition of heroin self-administration and J-113397 modestly decreased incubation of heroin seeking. The compounds had no effect on the other relapse-related measures in females, and no effect on any of the measures in males. The NOP/MOR partial agonist AT-201 and the NOP antagonist J-113397 did not mimic buprenorphine's inhibitory effects on relapse in a rat model of opioid maintenance treatment.

GPCR Function in Autophagy Control: A Systematic Approach of Chemical Intervention

Autophagy facilitates the degradation of cellular content via the lysosome and is involved in cellular homeostasis and stress response pathways. As such, malfunction of autophagy is linked to a variety of diseases ranging from organ-specific illnesses like cardiomyopathy to systemic illnesses such as cancer or metabolic syndromes. Given the variety of autophagic functions within a cell and tissue, regulation of autophagy is complex and contains numerous positive and negative feedback loops. While our knowledge of mechanisms for cargo selectivity has significantly improved over the last decade, our understanding of signaling routes activating individual autophagy pathways remains rather sparse. In this resource study, we report on a well-characterized chemical library containing 77 GPCR-targeting ligands that was used to systematically analyze LC3B-based autophagy as well as ER-phagy flux upon compound treatment. Upon others, compounds TC-G 1004, BAY 60-6583, PSNCBAM-1, TC-G 1008, LPA2 Antagonist 1, ML-154, JTC-801 and ML-290 targeting adenosine receptor A2a (ADORA2A), adenosine receptor A2b (ADORA2B), cannabinoid receptor 1 (CNR1), G-protein coupled receptor 39 (GPR39), lysophosphatidic acid receptor 2 (LPAR2), neuropeptide S receptor 1 (NPSR1), opioid related nociceptin receptor 1 (OPRL1), and relaxin receptor 1 (RXFP1), respectively, were hit compounds for general autophagy flux. From these compounds, only JTC-801 markly increased ER-phagy flux. In addition, the global impact of these selected hit compounds were analyzed by TMT-based mass spectrometry and demonstrated the differential impact of targeting GPCRs on autophagy-associated proteins. This chemical screening exercise indicates to a significant cross-talk between GPCR signaling and regulation of autophagy pathways.

Methods of machine learning and big data analysis to establish the molecular mechanisms of the effects of racetams on the metabolism of adipose tissue

Racetams exhibit not only nootropic effects, but also affect the metabolism of fats and carbohydrates. Experimental studies have indicated the possibility of using phenylpiracetam in the treatment of obesity. At the same time, the molecular mechanisms of this pharmacological effect of phenylpiracetam are practically unknown. The paper presents the results of a new artificial intelligence (AI) method for comparative chemoreactome analysis of fonturacetam, piracetam, aniracetam, pramiracetam and levetiracetam. Another AI method, chemoneurocytological analysis, made it possible to compare the neuroprotective effects of molecules on neurons in culture. Despite the similarity of the proteomic interaction profiles of the studied molecules, differential analysis made it possible to establish the molecular mechanisms of the effect of phenylpiracetam on weight loss. Phenylpiracetam can activate β3-adrenoceptors, adenosine, glucagon-like peptide, sphingosine phosphate, and peroxisome proliferator receptors (PPARG); specifically inhibit cannabinoid, opioid, histamine, glutamate, nociceptin, neuropeptide Y and orexin receptors, which is important for normalizing appetite and improving the metabolism of adipose tissue. The synthetic AI method - pharmacoinformatic analysis indicated the advisability of taking phenylpiracetam together with vitamins C, D and group B.

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.

P522 Post hoc analysis reveals limited efficacy of induction therapy in ileum only Crohn´s disease

Abstract Background Crohn´s disease (CD) can affect any part of the GI tract, although has a predilection for the terminal ileum and colon. Approximately 30% of patients have inflammation restricted to the small intestine, another 30% have disease limited to the colon, and the remainder have a combination of small and large bowel involvement. Despite studies suggesting that ileal and colonic CD may be distinct disease phenotypes and might therefore respond differently to treatment, CD patients are typically enrolled into clinical trials irrespective of the site of gastrointestinal involvement. The aim of this systematic review and meta-analysis was to assess treatment efficacy in patients with small bowel disease. Methods Embase and PubMed databases were searched until October 2023 for randomised, placebo-controlled, clinical trials that reported induction efficacy, based on clinical remission (CDAI <150), in ileal-only Crohn’s disease between 2010 and 2023. The following search criteria were employed: Crohn´s disease AND [2010-2023] AND (small bowel OR ileum OR ileal OR L1) AND (CDAI OR clinical remission AND induction AND placebo). Additional studies, not identified through this search strategy were also considered. Resultant studies were systematically reviewed before a random-effects meta-analysis was undertaken to assess induction efficacy, based on clinical remission, in ileal only CD. Results A total of 9 studies, involving 709 adult patients, were identified: two via Embase and PubMed; six from supplementary search materials; and one post-hoc analysis of brazikumab data (not published). The studies provided CDAI remission results by disease location subset. The induction treatment times ranged from 6-12 weeks, and both bio-naïve and bio-failure patients were included. The studies were relatively homogenous (I2 = 38.5%, Q = 13.0 (p-value = 0.112)) with a random effect meta-analytic estimate of difference versus placebo in CDAI remission of 2.1% (95% CI -6% to 11%). Two studies used clinical response (defined as ≥ 100 point decrease or score < 150) as indicated in the figure. Conclusion This is the first systematic meta-analysis of treatment effects in ileal-only CD. The available evidence suggests treatment effect heterogeneity, with inferior outcomes in ileal disease versus a broader patient population with ileocolonic or colonic involvement. Previous systematic review1 on clinical remission after induction treatment demonstrate placebo adjusted values in the range of 12-20% in a no defined disease site population. This indicates the need for novel therapies with a mechanism of action directly tailored to heal the small intestine in patients with CD.

Expression heterogeneity, tumor immune characteristics and the prognosis effects of OPRL1 in patients with tumors: a pan-cancer study combined with bioinformation analyses and in vitro validation

PurposeOpioids are currently the most frequently prescribed analgesics in clinical practice. However, their effect on cancer progression remains a topic of debate. Opioid receptors (ORs) are present in various types of tumor cells and their expression levels vary depending on the type of tumor. This study aims to explore and preliminarily characterize the association between four different ORs (μ, δ, κ, and nociception/orphanin FQ peptide receptor) and the prognosis of different types of tumors for comparison, with a focus on nociception/ orphanin FQ peptide receptor.MethodsThe expression levels of four ORs in normal tissues and immune cells were obtained from Human Protein Atlas (HPA) RNA-seq dataset, Monaco dataset, and Consensus dataset. Pan-cancer analysis was performed using the The Cancer Genome Atlas (TCGA) dataset, which included the expression of four ORs in different cancer types, significant copy-number alterations (sCNA), gene mutations of the four ORs, survival analysis, co-expression genes analysis, functional enrichment analyses, and correlations between ORs and immune cell infiltration levels. Based on the results of bioinformatic analysis, we selected 10 cancer cell lines for validation in vitro using specific agonists for the four ORs.ResultsOPRL1 (opioid related nociceptin receptor 1 gene) exhibited the highest abundance across different types of cancers, while OPRM1 (opioid receptor mu 1 gene) and OPRD1 (opioid receptor delta 1 gene) were barely detectable in multiple cancer types. Pan-cancer survival analysis revealed the overall worse/better prognosis of the four ORs in certain cancer types. Elevated levels of OPRM1 appear to be associated with poorer outcomes in breast invasive carcinoma and kidney renal clear cell carcinoma. Elevated OPRD1 levels are connected to worsen outcomes in kidney renal clear cell carcinoma and liver hepatocellular carcinoma, but better prognosis in bladder urothelial carcinoma. Increased OPRK1 (opioid receptor kappa 1 gene) expression is linked to a poorer prognosis in kidney renal papillary cell carcinoma. Furthermore, high OPRL1 expression relates to worse outcomes in bladder urothelial carcinoma and liver hepatocellular carcinoma, but better outcomes in breast invasive carcinoma and pancreatic adenocarcinoma. Functional enrichment analyses found that immune-related pathways were enriched in OPRK1 and OPRL1, with OPRL1 exhibiting the highest correlation with immune cell infiltration. Different effects on cell growth, migration, and invasion were observed in different cancer types upon the administration of agonists for the four ORs.ConclusionOPRL1 may play a vital role in monocytes and regulating the immune response and tumor-infiltrating macrophages. Due to its high abundance in different types of tumors, it may hold greater clinical significance for oncology patients. OPRK1 also participates in immune-related pathways. OPRL1 could potentially serve as therapeutic targets for different types of cancers.Graphical

Acute single non-sedative doses of NOP receptor agonists affect acquisition of object location memory but repeated high doses do not induce long-lasting deficits

The Nociceptin/Orphanin FQ (N/OFQ) system has been shown to modulate various aspects of long-term memory. It is therefore important to study the effects on memory impairment by nociceptin receptor (NOP) agonists under preclinical development. In the present study, we investigated the effect of systemic injection of two small molecule selective NOP agonists, AT-202 and AT-524, in the object location memory task in male and female mice. Since high doses of NOP agonists have been shown to induce sedation, we first determined the sedative doses for the two compounds and found them to be higher in female than in male mice. We then observed that sub-sedative doses of NOP agonists administered before learning, induced memory impairment during a test session performed 24 h later. Again, female mice were less sensitive to the amnesic effects than males. On the contrary, in male mice, NOP agonists did not produce amnesia when they were injected after learning, suggesting that they do not affect the consolidation of object location memory. Finally, repeated administration of high doses of NOP agonists over 7 days did not impair long-term spatial memory. Together, our data show for the first time that NOP receptor agonists impair the acquisition of object location memory with sex-dependent potency but do not affect memory consolidation, and that repeated stimulation of the receptor does not compromise long-term episodic-like spatial memory.

A dual nociceptin and mu opioid receptor agonist exhibited robust antinociceptive effect with decreased side effects

The compelling demand of a consummate analgesic medication without addiction is rising due to the clinical mistreatment. Additionally, the series of severe untoward effects usually deterred the utilization while coping with serious pain. As a possible turning point, we revealed that compound 14 is a dual agonist of mu opioid receptor (MOR) and nociceptin-orphanin FQ opioid peptide (NOP) receptor in this study. More importantly, compound 14 achieves pain relieving at very small doses, meanwhile, reduces several unwanted side effects such as constipation, reward, tolerance and withdrawal effects. Here, we evaluated the antinociception and side effects of this novel compound from wild type and humanized mice to further develop a safer prescription analgesic drug.

Heterodimerization of apelin and opioid receptor-like 1 receptors mediates apelin-13-induced G protein biased signaling

The apelin receptor (APJ) and the opioid-related nociceptin receptor 1 (ORL1) are family A G protein-coupled receptors that participate in a variety of physiological processes. The distribution and function of APJ and ORL1 in the nervous system and peripheral tissues are similar; however, the detailed mechanism of how these two receptors modulate signaling and physiological effects remains unclear. Here, we examined whether APJ and ORL1 form dimers, and investigated signal transduction pathways. The endogenous co-expression of APJ and ORL1 in SH-SY5Y cells was confirmed by western blotting and RT-PCR. Bioluminescence and fluorescence resonance energy transfer assays, as well as a proximity ligation assay and co-immunoprecipitation experiments, demonstrated that APJ and ORL1 heterodimerize in HEK293 cells. We found that the APJ-ORL1 heterodimer is selectively activated by apelin-13, which causes the dimer to couple to Gαi proteins and reduce the recruitment of GRKs and β-arrestins to the dimer. We showed that the APJ-ORL1 dimer exhibits biased signaling, in which G protein-dependent signaling pathways override β-arrestin-dependent signaling pathways. Our results demonstrate that the structural interface of the APJ-ORL1 dimer switches from transmembrane domain TM1/TM2 in the inactive state to TM5 in the active state. We used mutational analysis and BRET assays to identify key residues in TM5 (APJ L2185.55, APJ I2245.61, and ORL1 L2295.52) responsible for the receptor–receptor interaction. These results provide important information on the APJ-ORL1 heterodimer and may assist the design of new drugs targeting biased signaling pathways for treatment of pain and cardiovascular and metabolic diseases.

Machine-learning analysis of opioid use disorder informed by MOR, DOR, KOR, NOR and ZOR-based interactome networks

Opioid use disorder (OUD) continuously poses major public health challenges and social implications worldwide with dramatic rise of opioid dependence leading to potential abuse. Despite that a few pharmacological agents have been approved for OUD treatment, the efficacy of said agents for OUD requires further improvement in order to provide safer and more effective pharmacological and psychosocial treatments. Proteins including mu, delta, kappa, nociceptin, and zeta opioid receptors are the direct targets of opioids and play critical roles in therapeutic treatments. The protein–protein interaction (PPI) networks of the these receptors increase the complexity in the drug development process for an effective opioid addiction treatment. The report below presents a PPI-network informed machine-learning study of OUD. We have examined more than 500 proteins in the five opioid receptor networks and subsequently collected 74 inhibitor datasets. Machine learning models were constructed by pairing gradient boosting decision tree (GBDT) algorithm with two advanced natural language processing (NLP)-based autoencoder and Transformer fingerprints for molecules. With these models, we systematically carried out evaluations of screening and repurposing potential of more than 120,000 drug candidates for four opioid receptors. In addition, absorption, distribution, metabolism, excretion, and toxicity (ADMET) properties were also considered in the screening of potential drug candidates. Our machine-learning tools determined a few inhibitor compounds with desired potency and ADMET properties for nociceptin opioid receptors. Our approach offers a valuable and promising tool for the pharmacological development of OUD treatments.

Inhibitory Effects of a Novel μ-Opioid Receptor Nonpeptide Antagonist, UD-030, on Morphine-Induced Conditioned Place Preference

Although opioids are widely used to treat moderate to severe pain, opioid addiction and the opioid overdose epidemic are becoming more serious. Although opioid receptor antagonists/partial agonists, such as naltrexone and buprenorphine, have relatively low selectivity for the μ-opioid receptor (MOP), they have been used for the management of opioid use disorder. The utility of highly selective MOP antagonists remains to be evaluated. Here, we biologically and pharmacologically evaluated a novel nonpeptide ligand, UD-030, as a selective MOP antagonist. UD-030 had more than 100-fold higher binding affinity for the human MOP (Ki = 3.1 nM) than for δ-opioid, κ-opioid, and nociceptin receptors (Ki = 1800, 460, and 1800 nM, respectively) in competitive binding assays. The [35S]-GTPγS binding assay showed that UD-030 acts as a selective MOP full antagonist. The oral administration of UD-030 dose-dependently suppressed the acquisition and expression of morphine-induced conditioned place preference in C57BL/6J mice, and its effects were comparable to naltrexone. These results indicate the UD-030 may be a new candidate for the treatment of opioid use disorder, with characteristics that differ from traditional medications that are in clinical use.

Computational Design of Plant-Based Antistress Agents Targeting Nociceptin Receptor.

Stress is the body's reaction to the challenges it faces, and it produces a multitude of chemical molecules known as stressors as a result of these reactions. It's also a misalignment of the sympathetic and parasympathetic nervous systems causing changes in a variety of physiological reactions and perhaps leading to stress disorders. The reduction in neurotransmitter & neurohormonal hormones is mainly governed by the nociceptin receptor as G-protein coupled receptor and increased the level of reactive oxygen species. Various synthetic medicines that target nociceptin receptors were utilized to reduce the effects of stress but they come up with a variety of side effects. Because of the widespread utilization and renewed interest in medicinal herbal plants considered to be alternative antistress therapy. Our present work is an approach to decipher the molecular nature of novel herbal leads by targeting nociceptin receptor, under which herbal compounds were screened and validated through in-silico methods. Among screened leads, withanolide-B showed stable association in the active site of the nociceptin receptor as an antistress agent with no side effects. Furthermore, the selected lead was also evaluated for stability by molecular dynamic stimulation as well as for pharmacokinetics and toxicity profile. It has been concluded stable conformation of withanolide-B without presence of any major toxic effects. As a result, the in silico molecular docking technique is a highly successful method for selecting a prospective herbal lead molecule with respect to a specific target, and future research can pave the way for further exploration in the drug development field.

Opioid-Modulated Receptor Localization and Erk1/2 Phosphorylation in Cells Coexpressing μ-Opioid and Nociceptin Receptors.

We attempted to examine the alterations elicited by opioids via coexpressed μ-opioid (MOP) and nociceptin/orphanin FQ (NOP) receptors for receptor localization and Erk1/2 (p44/42 MAPK) in human embryonic kidney (HEK) 293 cells. Through two-photon microscopy, the proximity of MOP and NOP receptors was verified by fluorescence resonance energy transfer (FRET), and morphine but not buprenorphine facilitated the process of MOP-NOP heterodimerization. Single-particle tracking (SPT) further revealed that morphine or buprenorphine hindered the movement of the MOP-NOP heterodimers. After exposure to morphine or buprenorphine, receptor localization on lipid rafts was detected by immunocytochemistry, and phosphorylation of Erk1/2 was determined by immunoblotting in HEK 293 cells expressing MOP, NOP, or MOP+NOP receptors. Colocalization of MOP and NOP on lipid rafts was enhanced by morphine but not buprenorphine. Morphine stimulated the phosphorylation of Erk1/2 with a similar potency in HEK 293 cells expressing MOP and MOP+NOP receptors, but buprenorphine appeared to activate Erk1/2 solely through NOP receptors. Our results suggest that opioids can fine-tune the cellular localization of opioid receptors and phosphorylation of Erk1/2 in MOP+NOP-expressing cells.

A Crosstalk between the Cannabinoid Receptors and Nociceptin Receptors in Colitis-Clinical Implications.

Inflammatory bowel diseases (IBD) refer to a group of gastrointestinal (GI) disorders with complex pathogenesis characterized by chronic intestinal inflammation with a variety of symptoms. Cannabinoid and nociceptin opioid receptors (NOPs) and their ligands are widely distributed in the GI tract. The nociceptin opioid receptor is a newly discovered member of the opioid receptor family with unique characteristics. Both cannabinoid and NOP systems exhibit antinociceptive and anti-inflammatory activity and contribute to maintaining proper motility, secretion and absorption in the GI tract. Furthermore, they influence high and low voltage calcium channels, which play a crucial role in the processing of pain, and share at least two kinases mediating their action. Among them there is NF-κB, a key factor in the regulation of inflammatory processes. Therefore, based on functional similarities between cannabinoid and nociceptin receptors and the anti-inflammatory effects exerted by their ligands, there is a high likelihood that there is an interaction between cannabinoid receptors 1 and 2 and the nociceptin receptor in colitis. In this review, we discuss potential overlaps between these two systems on a molecular and functional level in intestinal inflammation to create the basis for novel treatments of IBD.

Epigenetic Modulation of Opioid Receptors by Drugs of Abuse.

Chronic exposure to drugs of abuse produces profound changes in gene expression and neural activity associated with drug-seeking and taking behavior. Dysregulation of opioid receptor gene expression is commonly observed across a variety of abused substances including opioids, cocaine, and alcohol. Early studies in cultured cells showed that the spatial and temporal gene expression of opioid receptors are regulated by epigenetic mechanisms including DNA and histone modifications and non-coding RNAs. Accumulating evidence indicate that drugs of abuse can modulate opioid receptor gene expression by targeting various epigenetic regulatory networks. Based on current cellular and animal models of substance use disorder and clinical evidence, this review summarizes how chronic drug exposure alters the gene expression of mu, delta, kappa, and nociceptin receptors via DNA and histone modifications. The influence of drugs of abuse on epigenetic modulators, such as non-coding RNAs and transcription factors, is also presented. Finally, the therapeutic potential of manipulating epigenetic processes as an avenue to treat substance use disorder is discussed.

Investigation of the μ and κ-opioid receptor activation by eight new synthetic opioids using the [35S]-GTPγS assay: U-47700, isopropyl U 47700, U-49900, U-47931E, N-methyl U-47931E, U-51754, U-48520 and U-48800

Since their first occurrence in 2008, a rapid increase of new psychoactive substances (NPS) on the recreational drug market has been observed. One class of NPS are synthetic opioids, which poses a health risk due to the high affinity and high potency of most of these compounds for the opioid receptors. Four opioid receptor subtypes are known, the mü-opioid (MOR), the delta-opioid (DOR), the kappa-opioid (KOR) and the nociceptin receptor, which are G protein-coupled receptors (GCPRs). MOR and DOR agonists often express mood-enhancing and euphoric properties. However, opioid overdoses can lead to respiratory depression and result in death. Nevertheless, for many NPS, including new synthetic opioids, data on toxicological and toxicokinetic properties are scarce. The aim of the present study was to investigate eight structurally closely related U-opioids (U-47700, isopropyl U-47700, U-49900, U-47931E, N-methyl U-47931E, U-48520, U-51754, and U-48800) for their potential of MOR and KOR activation, due to the relative lack of pharmacological data for the U-opioids. The [35S]-GTPγS assay, was used to study receptor activation and is based on the exchange of GDP with radiolabelled GTP. This exchange is one of the first events of the GPCR-signal cascade. For each receptor two respective and well-studied compounds were chosen as reference compounds: hydromorphone and fentanyl for MOR, and U-69593 and U-50488 for KOR. Owing to their close structural similarity of the investigated U-compounds, structure activity relationships have also been derived. The most prevalent compound of this set, U-47700, was also the most potent compound of the test set at MOR, with an EC50 value of 111 nM. However, the two MOR reference compounds hydromorphone and fentanyl had lower EC50 values of 6.75 nM and 24.9 nM, respectively, hence, being 16 and 4 times more potent than U-47700. At KOR, U-51754 was the most potent substance out of the test set, with an EC50 value of 120 nM. Nevertheless, the two U-opioids U-69593 and U-50488, which have been used as KOR reference compounds, were 4 and 5 times more potent than U-51754 at KOR, with EC50 of 29.3 nM and 24.8 nM, respectively. The studied compounds can be categorized into the U-47700 and U-50488 group. It has been previously reported that the compounds of the U-47700 group show higher receptor binding affinities for MOR and compounds of the U-50488 group for KOR, hence the presence or absence of the methylene group has an influence on the receptor binding affinity at MOR and KOR. In general, our results on the receptor activation of MOR and KOR are in good alignment with reported receptor binding affinities, confirming that the U-47700 group has a higher affinity and activity at MOR and the U-50488 group at KOR. The following structural features were advantageous for activating MOR: two chlorine substituents in 3,4-position at the aromatic ring, the absence of the methylene group between the amide group and the aromatic ring, a methyl group at the amide nitrogen, and/or a dimethylamine residue at the amine nitrogen of the cyclohexane ring. Further, the following structural features were beneficial for KOR activation: a methylene group between the amide group and the aromatic ring, a pyrrolidine residue at the amine nitrogen of the cyclohexane ring, a methyl group at the amide nitrogen, and/or chlorine substitution in 3,4-position at the aromatic ring. While synthetic opioids are often considered more potent than conventional opioids, there are some occurring on the NPS market, which are less potent. Hence, performing these studies is important to identify the effect of structural alterations on the receptor activity and in understanding the potential risk to the public health.

Copper-Mediated Radiocyanation of Unprotected Amino Acids and Peptides.

This report describes a copper-mediated radiocyanation of aryl halides that is applicable to complex molecules. This transformation tolerates an exceptionally wide range of functional groups, including unprotected amino acids. As such, it enables the site-specific introduction of [11C]CN into peptides at an iodophenylalanine residue. The use of a diamine-ligated copper(I) mediator is crucial for achieving high radiochemical yield under relatively mild conditions, thus limiting racemization and competing side reactions of other amino acid side chains. The reaction has been scaled and automated to deliver radiolabeled peptides, including analogues of adrenocorticotropic hormone 1-27 (ACTH) and nociceptin (NOP). For instance, this Cu-mediated radiocyanation was leveraged to prepare >40 mCi of [11C]cyano-NOP to evaluate biodistribution in a primate using positron emission tomography. This investigation provides preliminary evidence that nociceptin crosses the blood-brain barrier and shows uptake across all brain regions (SUV > 1 at 60 min post injection), consistent with the known distribution of NOP receptors in the rhesus brain.

The nociceptin receptor promotes autophagy through NF-kB signaling and is transcriptionally regulated by E2F1 in HCC

Opioids and their receptors are involved in cancer progression. However, the roles of the nociceptin receptor (NOP) and its antagonist (JTC801) in hepatocellular carcinoma (HCC) are poorly understood. The prognostic value of NOP expression was evaluated using tissue microarray and immunohistochemical staining analyses in a human HCC cohort. The biological role and mechanism of NOP in HCC tumor growth were determined in vitro and in vivo. We found that NOP was associated with the clinicopathological features and survival outcomes of HCC patients. NOP overexpression promoted HCC growth in vitro and in vivo. Mechanistically, NOP activated NF-kB signaling to promote autophagy, which inhibited apoptosis, in HCC cells. An inhibitor of autophagy, 3-MA, and an inhibitor of NF-kB, JSH-23, attenuated the function of NOP in HCC. E2F1 was identified as a transcription factor of NOP. The oncogenic role of NOP was positively regulated by E2F1. Furthermore, JTC801, a selective antagonist of NOP, abolished the function of NOP by inhibiting NF-kB signaling and autophagy. Our study demonstrates that NOP is an oncogene in HCC. We provide a potential therapeutic candidate and prognostic predictor for HCC. JTC801 could become a potential drug for HCC therapy.

Interactions between the Nociceptin and Toll-like Receptor Systems.

Nociceptin and the nociceptin receptor (NOP) have been described as targets for treatment of pain and inflammation, whereas toll-like receptors (TLRs) play key roles in inflammation and impact opioid receptors and endogenous opioids expression. In this study, interactions between the nociceptin and TLR systems were investigated. Human THP-1 cells were cultured with or without phorbol myristate acetate (PMA 5 ng/mL), agonists specific for TLR2 (lipoteichoic acid, LTA 10 µg/mL), TLR4 (lipopolysaccharide, LPS 100 ng/mL), TLR7 (imiquimod, IMQ 10 µg/mL), TLR9 (oligonucleotide (ODN) 2216 1 µM), PMA+TLR agonists, or nociceptin (0.01–100 nM). Prepronociceptin (ppNOC), NOP, and TLR mRNAs were quantified by RT-qPCR. Proteins were measured using flow cytometry. PMA upregulated ppNOC mRNA, intracellular nociceptin, and cell membrane NOP proteins (all p < 0.05). LTA and LPS prevented PMA’s upregulating effects on ppNOC mRNA and nociceptin protein (both p < 0.05). IMQ and ODN 2216 attenuated PMA’s effects on ppNOC mRNA. PMA, LPS, IMQ, and ODN 2216 increased NOP protein levels (all p < 0.05). PMA+TLR agonists had no effects on NOP compared to PMA controls. Nociceptin dose-dependently suppressed TLR2, TLR4, TLR7, and TLR9 proteins (all p < 0.01). Antagonistic effects observed between the nociceptin and TLR systems suggest that the nociceptin system plays an anti-inflammatory role in monocytes under inflammatory conditions.

Mechanistic Characterization of the Pharmacological Profile of HS-731, a Peripherally Acting Opioid Analgesic, at the µ-, δ-, κ-Opioid and Nociceptin Receptors.

Accumulated preclinical and clinical data show that peripheral restricted opioids provide pain relief with reduced side effects. The peripherally acting opioid analgesic HS-731 is a potent dual μ-/δ-opioid receptor (MOR/DOR) full agonist, and a weak, partial agonist at the κ-opioid receptor (KOR). However, its binding mode at the opioid receptors remains elusive. Here, we present a comprehensive in silico evaluation of HS-731 binding at all opioid receptors. We provide insights into dynamic interaction patterns explaining the different binding and activity of HS-731 on the opioid receptors. For this purpose, we conducted docking, performed molecular dynamics (MD) simulations and generated dynamic pharmacophores (dynophores). Our results highlight two residues important for HS-731 recognition at the classical opioid receptors (MOR, DOR and KOR), particular the conserved residue 5.39 (K) and the non-conserved residue 6.58 (MOR: K, DOR: W and KOR: E). Furthermore, we assume a salt bridge between the transmembrane helices (TM) 5 and 6 via K2275.39 and E2976.58 to be responsible for the partial agonism of HS-731 at the KOR. Additionally, we experimentally demonstrated the absence of affinity of HS-731 to the nociceptin/orphanin FQ peptide (NOP) receptor. We consider the morphinan phenol Y1303.33 responsible for this affinity lack. Y1303.33 points deep into the NOP receptor binding pocket preventing HS-731 binding to the orthosteric binding pocket. These findings provide significant structural insights into HS-731 interaction pattern with the opioid receptors that are important for understanding the pharmacology of this peripheral opioid analgesic.