Protective and worsening peripheral nociceptin/orphanin FQ receptor-mediated effect in a rat model of experimental colitis

Endometriosis and Opioid Receptors: Are Opioids a Possible/Promising Treatment for Endometriosis?

Endometriosis (EM), defined as the presence of endometrial-like tissue with surrounding smooth muscle cells outside the uterus, is a disregarded gynecological disease reported to affect 6-10% of women of reproductive age, with 30-50% of them suffering from chronic pelvic pain and infertility. Since the exact pathogenic mechanisms of EM are still unclear, no curative therapy is available. As pain is an important factor in EM, optimal analgesia should be sought, which to date has been treated primarily with non-steroidal anti-inflammatory drugs (NSAIDs), metamizole or, in extreme cases, opioids. Here, we review the pain therapy options, the mechanisms of pain development in EM, the endogenous opioid system and pain, as well as the opioid receptors and EM-associated pain. We also explore the drug abuse and addiction to opioids and the possible use of NOP receptors in terms of analgesia and improved tolerability as a target for EM-associated pain treatment. Emerging evidence has shown a promising functional profile of bifunctional NOP/MOP partial agonists as safe and nonaddictive analgesics. However, until now, the role of NOP receptors in EM has not been investigated. This review offers a thought which still needs further investigation but may provide potential options for relieving EM-associated pain.

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.

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.

2,4,6-trinitrobenzenesulfonic acid-induced colitis in Rattus norgevicus: a categorization proposal

Reproducibility in animal research is crucial for its reliance and translational relevance. The 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced model of inflammatory bowel disease (IBD) is widely used but inconsistently and incompletely characterized throughout the literature. This hinders comparisons between studies and influences the low rate of translation of effective preclinical molecules. The purpose of this study was to categorize TNBS-induced colitis, based on macroscopic and microscopic scoring systems, and to identify basic routine parameters that could anticipate those categories. We retrospectively analysed male Wistar Rattus norvegicus (n=28 for the control group and n=87 for the TNBS group) and categorized TNBS-induced colitis in three phenotypes: Mild, Moderate and Severe colitis, as for human IBD. Also, we showed that the time course of food intake and fecal excretion (but not body weight, fluid intake or welfare scores) could foresee those categories. So, routine evaluation of food intake and fecal excretion may guide researchers in planning their experiments, selecting the animals with the severity of colitis that better matches their aims, or applying early humane endpoints to animals that will not be used in the experiments. In conclusion, categorizing TNBS-induced colitis enhances the reproducibility of data gathered with this experimental model and strengths its translational relevance.

Haem iron reshapes colonic luminal environment: impact on mucosal homeostasis and microbiome through aldehyde formation

BACKGROUND

The World Health Organization classified processed and red meat consumption as "carcinogenic" and "probably carcinogenic", respectively, to humans. Haem iron from meat plays a role in the promotion of colorectal cancer in rodent models, in association with enhanced luminal lipoperoxidation and subsequent formation of aldehydes. Here, we investigated the short-term effects of this haem-induced lipoperoxidation on mucosal and luminal gut homeostasis including microbiome in F344 male rats fed with a haem-enriched diet (1.5 μmol/g) 14-21 days.

RESULTS

Changes in permeability, inflammation, and genotoxicity observed in the mucosal colonic barrier correlated with luminal haem and lipoperoxidation markers. Trapping of luminal haem-induced aldehydes normalised cellular genotoxicity, permeability, and ROS formation on a colon epithelial cell line. Addition of calcium carbonate (2%) to the haem-enriched diet allowed the luminal haem to be trapped in vivo and counteracted these haem-induced physiological traits. Similar covariations of faecal metabolites and bacterial taxa according to haem-induced lipoperoxidation were identified.

CONCLUSIONS

This integrated approach provides an overview of haem-induced modulations of the main actors in the colonic barrier. All alterations were closely linked to haem-induced lipoperoxidation, which is associated with red meat-induced colorectal cancer risk.

N/OFQ-NOP System in Food Intake

While lifestyle modifications should be the first-line actions in preventing and treating obesity and eating disorders, pharmacotherapy also provides a necessary tool for the management of these diseases.However, given the limitations of current anti-obesity drugs, innovative treatments that improve efficacy and safety are needed.Since the discovery that the activation of the Nociceptin/Orphanin (N/OFQ) FQ peptide (NOP) receptor by N/OFQ induces an increase of food intake in laboratory animals, and the finding that this effect can be blocked by NOP antagonists, many NOP agonists and antagonists have been synthesized and tested in vitro and in vivo for their potential regulation of feeding behavior. Promising results seem to suggest that the N/OFQergic system may be a potential therapeutic target for the neural control of feeding behavior and related pathologies, especially in binge-like eating behavior.

Nociceptin/orphanin FQ antagonizes lipopolysaccharide-stimulated proliferation, migration and inflammatory signaling in human glioblastoma U87 cells

Glioblastoma is among the most aggressive brain tumors and has an exceedingly poor prognosis. Recently, the importance of the tumor microenvironment in glioblastoma cell growth and progression has been emphasized. Toll-like receptor 4 (TLR4) recognizes bacterial lipopolysaccharide (LPS) and endogenous ligands originating from dying cells or the extracellular matrix involved in host defense and in inflammation. G-protein coupled receptors (GPCRs) have gained interest in anti-tumor drug discovery due to the role that they directly or indirectly play by transactivating other receptors, causing cell migration and proliferation. A proteomic analysis showed that the nociceptin receptor (NOPr) is among the GPCRs significantly expressed in glioblastoma cells, including U87 cells. We describe a novel role of the peptide nociceptin (N/OFQ), the endogenous ligand of the NOPr that counteracts cell migration, proliferation and increase in IL-1β mRNA elicited by LPS via TLR4 in U87 glioblastoma cells. Signaling pathways through which N/OFQ inhibits LPS-mediated cell migration and elevation of [Ca2+]i require β-arrestin 2 and are sensitive to TNFR-associated factor 6, c-Src and protein kinase C (PKC). LPS-induced cell proliferation and increase in IL-1β mRNA are counteracted by N/OFQ via β-arrestin 2, PKC and extracellular signal-regulated kinase 1/2; furthermore, the contributions of the transcription factors NF-kB and AP-1 were investigated. Independent of LPS, N/OFQ induces a significant increase in cell apoptosis. Contrary to what was observed in other cell models, a prolonged exposure to this endotoxin did not promote any tolerance of the cellular effects above described, including NOPr down-regulation while N/OFQ loses its inhibitory role.

The TNBS-induced colitis animal model: An overview

Background

Despite recent advances the pathogenesis of Crohn's disease remains incompletely understood. A variety of animal models have been utilized in an effort to provide further insights and develop more therapeutic options. In order to simulate, to an extent, the pathogenesis and the clinical course of the disease, TNBS induced colitis is often used. Various approaches for inducing TNBS -colitis have been described in the literature.

Methods/results

In this review, we sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model. Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

Data sources

The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model. Two investigators independently reviewed the abstracts and appropriate articles were included in this review. Additional articles were gathered and evaluated.

Conclusion

The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

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We sought to present the animal model of TNBS induced colitis and outline the pathogenesis, pathophysiology, clinical course and pathological characteristics of the model.

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Furthermore, we describe the differences among those protocols regarding types of animals and colitis induction.

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The MEDLINE database was thoroughly searched using the keywords: TNBS, colitis, Crohn's disease, animal model.

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Two investigators independently reviewed the abstracts and appropriate articles were included in this review.

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The aim of this study was to thoroughly present an updated review of the TNBS-induced colitis protocols that are implemented by researchers.

Anti-inflammatory effect of dual nociceptin and opioid receptor agonist, BU08070, in experimental colitis in mice

Endogenous opioid and nociceptin systems are widely distributed in the gastrointestinal tract where they seem to play a crucial role in maintaining the intestinal homeostasis. The aim of our study was to assess whether activation of nociceptin (NOP) and µ-opioid (MOP) receptors by a mixed NOP/MOP receptor agonist, BU08070, induces anti-inflammatory response in experimental colitis. The anti-inflammatory effect of BU08070 (1 mg/kg i.p.) was characterized in the mouse model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis, based on the assessment of the macroscopic and microscopic total damage scores and determination of myeloperoxidase (MPO) activity and TNF-α level in the colon. The effect of BU08070 on cell viability and NF-κB was characterized in THP-1 Blue cell line. The antinociceptive activity of BU08070 was examined in mustard oil-induced mouse model of abdominal pain. A potent anti-inflammatory effect of BU08070 (1 mg/kg i.p.) was observed as indicated by decrease in macroscopic damage score (1.88±0.39 vs. 5.19±0.43 units in TNBS alone treated mice), MPO activity (2.29±0.37 vs. 9.64±2.55 units) and TNF-α level in the colon (35.85±2.45 vs. 49.79±3.81 pg/ml). The anti-inflammatory effect of BU08070 was reversed by selective NOP and MOP receptor antagonists. BU08070 produced concentration-dependent inhibition of TNF-α and LPS-induced NF-κB activation. BU08070 exerted antinociceptive action in mice with experimental colitis. In conclusion, BU08070 significantly reduced the severity of colitis in TNBS-treated mice compared with controls. These results suggest that BU08070 is a potential therapeutic agent for inflammatory bowel diseases therapy.

Nociceptin/orphanin FQ and stress regulate synaptophysin expression in the rat fundic and colonic mucosa

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the N/OFQ peptide (NOP) receptor, is a neuropeptide regulating gastrointestinal functions. The present study investigated the influence of acute cold-restraint stress and of short- and long-lasting peripheral infusion of N/OFQ on the level of synaptophysin, an exocytotic protein involved in neural plasticity. Exposure to cold-restraint stress for 3h or subcutaneous infusion of N/OFQ, 1 μg/kg/h for 4h, induced a significant increase of the area of synaptophysin-immunoreactive nerve fibers in the fundic mucosa, while prolonged subcutaneous infusion of N/OFQ, 1 μg/kg/h for 52 h and for 14 days, did not modify the synaptophysin-immunostained fibers. In the colonic mucosa stress exposure and subcutaneous infusion of N/OFQ, at any time point considered, had no significant effect on the area of synaptophysin-immunoreactive nerve fibers. Synaptophysin immunoreactive nerve fibers were decreased in knockout rats for the NOP receptor gene both in the fundic and colonic mucosa. Synaptophysin-immunoreactivity was demonstrated in cells located in the basal portion of the fundic mucosa. Our study is the first to show that the N/OFQ/NOP receptor system influences the expression of synaptophysin and hence the process of exocytosis both in nerve terminals and in cells.

Nociceptin/orphanin FQ-NOP receptor system in inflammatory and immune-mediated diseases

The neuropeptide nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand of the G-protein-coupled receptor NOP. Cells from the immune system express the precursor preproN/OFQ and the NOP receptor, as well as secrete N/OFQ. The activation of the N/OFQ-NOP pathway can regulate inflammatory and immune responses. Several immune activities, including leukocyte migration, cytokine and chemokine production, and lymphocytes proliferation are influenced by NOP activation. It was demonstrated that cytokines and other stimuli such as Toll-like receptor agonist (e.g., lipopolysaccharide) induce N/OFQ production by cells from innate and adaptive immune response. In this context, N/OFQ could modulate the outcome of inflammatory diseases, such as sepsis and immune-mediated pathologies by mechanisms not clearly elucidated. In fact, clinical studies revealed increased levels of N/OFQ under sepsis, arthritis, and Parkinson's disease. Preclinical and clinical studies pointed to the blockade of NOP receptor signaling as successful strategy for the treatment of inflammatory diseases. This review is focused on experimental and clinical data that suggest the participation of N/OFQ-NOP receptor activation in the modulation of the immune response, highlighting the immunomodulatory potential of NOP antagonists in the inflammatory and immunological disturbances.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

The endogenous nociceptin/orphanin FQ-NOP receptor system as a potential therapeutic target for intestinal disorders

In 1995, by reverse pharmacology approach, used here for the first time in the history of pharmacology, nociceptin/orphanin FQ (N/OFQ) has been discovered as the endogenous ligand of a preidentified receptor named opioid receptor like 1. Subsequent studies showed that N/OFQ and its receptor (N/OFQergic system) are widely distributed in central and peripheral nervous systems as well as in peripheral organs of human and animals, and represent a system that is involved in a very large range of biological functions such as pain perception, intestinal motility and secretion, immune modulation, stress. From the time of its discovery to now, a high number of NOP agonists and antagonists have been synthesized and tested in various pathologies. Nevertheless, none of the molecules targeting N/OFQergic system have currently succeeded in going through clinical trials concerning gut pathologies, indicating that further studies are required. The work from Dr. Fichna et al., published in the present issue of Neurogastroenterology and Motility, adds another brick in the wall of understanding the role of N/OFQergic system in IBS-D pathology by the pharmacological evaluation of a new NOP receptor agonist, SCH 221510, in animal models of intestinal alterations (diarrhea and visceral hyperalgesia). Interestingly, authors report clinical data confirming the involvement of N/OFQergic system in IBS-D patients and, consequently, suggest this system as a valuable therapeutic target for IBS-D pathology. This minireview aims to give a brief summary of experimental and clinical studies focusing on the N/OFQergic system as pharmacological target for the therapeutic treatment of intestinal pathologies such as IBS and IBD.

Nociceptin system as a target in sepsis?

The nociceptin system comprises the nociceptin receptor (NOP) and the ligand nociceptin/orphanin FQ (N/OFQ) that binds to the receptor. The archetypal role of the system is in pain processing but the NOP receptor is also expressed on immune cells. Activation of the NOP receptor is known to modulate inflammatory responses, such as mast-cell degranulation, neutrophil rolling, vasodilation, increased vascular permeability, adhesion molecule regulation and leucocyte recruitment. As there is a loss of regulation of inflammatory responses during sepsis, the nociceptin system could be a target for therapies aimed at modulating sepsis. This review details the known effects of NOP activation on leucocytes and the vascular endothelium and discusses the most recent human and animal data on the role of the nociceptin system in sepsis.

Anti-inflammatory and antinociceptive action of an orally available nociceptin receptor agonist SCH 221510 in a mouse model of inflammatory bowel diseases

The nociceptin receptors (NOPs) are expressed in the gastrointestinal (GI) tract on muscle cell membranes and neurons, as well as the immune cells that infiltrate the mucosa. The involvement of NOPs in the pathophysiology of GI inflammation has been suggested, but due to the lack of selective NOP agonists, it never fully elucidated. Our aim was to characterize the anti-inflammatory and antinociceptive effect of the NOP agonist, SCH 221510 [3-endo-8-[bis(2-methylphenyl)methyl]-3-phenyl-8-azabicyclo [3.2.1]octan-3-ol], as a potential therapeutic strategy in the treatment of inflammatory bowel diseases (IBD). The anti-inflammatory action of SCH 221510 was determined after intraperitoneal, oral, and intracolonic administration of SCH 221510 (0.1-3.0 mg/kg once or twice daily) in mice treated with 2,4,6-trinitrobenzenesulfonic acid (TNBS). Antinociceptive action of SCH 221510 was evaluated in the mouse model of mustard oil (MO)-induced abdominal pain. Relative NOP mRNA expression was assessed in patients with IBD using real-time reverse transcriptase-polymerase chain reaction. We found that the expression of NOP mRNA was significantly decreased in patients with IBD. The administration (0.1 and 1.0 mg/kg i.p. twice daily and 3 mg/kg p.o. twice daily) of SCH 221510 attenuated TNBS colitis in mice. This effect was blocked by a selective NOP antagonist [J-113397 [(±)-1-[(3R*,4R*)-1-(cyclooctylmethyl)-3-(hydroxymethyl)-4-piperidinyl]-3-ethyl-1,3-dihydro-2H-benzimidazol-2-one]]. The intracolonic injections of SCH 221510 did not improve colitis in mice. The antinociceptive effect of SCH 221510 was observed after oral administration of SCH 221510 in MO-induced pain tests in mice with acute colitis. In conclusion, our results show a potent anti-inflammatory and antinociceptive effect upon selective activation of NOP receptors and suggest that the NOP agonist SCH 221510 is a promising drug candidate for future treatment of IBD.

The role of orphanin FQ/nociceptin in neuroplasticity: relationship to stress, anxiety and neuroinflammation

The neuropeptide, orphanin FQ/nociceptin (OFQ/N or simply, nociceptin), is expressed in both neuronal and non-neuronal tissue, including the immune system. In the brain, OFQ/N has been investigated in relation to stress, anxiety, learning and memory, and addiction. More recently, it has also been found that OFQ/N influences glial cell functions, including oligodendrocytes, astrocytes, and microglial cells. However, this latter research is relatively small, but potentially important, when observations regarding the relationship of OFQ/N to stress and emotional functions is taken into consideration and integrated with the growing evidence for its involvement in cells that mediate inflammatory events. This review will first provide an overview and understanding of how OFQ/N has been implicated in the HPA axis response to stress, followed by an understanding of its influence on natural and learned anxiety-like behavior. What emerges from an examination of the literature is a neuropeptide that appears to counteract anxiogenic influences, but paradoxically, without attenuating HPA axis responses generated in response to stress. Studies utilized both central administration of OFQ/N, which was shown to activate the HPA axis, as well as antagonism of NOP-R, the OFQ/N receptor. In contrast, antagonist or transgenic OFQ/N or NOP-R knockout studies, showed augmentation of HPA axis responses to stress, suggesting that OFQ/N may be needed to control the magnitude of the HPA axis response to stress. Investigations of behavior in standard exploratory tests of anxiogenic behavior (eg., elevated plus maze) or learned fear responses have suggested that OFQ/N is needed to attenuate fear or anxiety-like behavior. However, some discrepant observations, in particular, those that involve appetitive behaviors, suggest a failure of NOP-R deletion to increase anxiety. However, it is also suggested that OFQ/N may operate in an anxiolytic manner when initial anxiogenic triggers (eg., the neuropeptide CRH) are initiated. Finally, the regulatory functions of OFQ/N in relation to emotion-related behaviors may serve to counteract potential neuroinflammatory events in the brain. This appears to be evident within the glial cell environment of the brain, since OFQ/N has been shown to reduce the production of proinflammatory cellular and cytokine events. Given that both OFQ/N and glial cells are activated in response to stress, it is possible that there is a possible convergence of these two systems that has important repercussions for behavior and neuroplasticity.