Role of nociceptin/orphanin FQ (Noc/oFQ) in murine experimental colitis

Current overview of opioids in progression of inflammatory bowel disease; pharmacological and clinical considerations

Inflammatory bowel diseases (IBD) belong to a subgroup of persistent, long-term, progressive, and relapsing inflammatory conditions. IBD may spontaneously develop in the colon, resulting in tumor lesions in inflamed regions of the intestine, such as invasive carcinoma. The benefit of opioids for IBD treatment is still questionable, thereby we investigated databases to provide an overview in this context. This review demonstrates the controversial role of opioids in IBD therapy, their physiological and pharmacological functions in attenuating the IBD symptoms, and in improving inflammatory, oxidative stress, and the quality of life factors in IBD subjects. Data were extracted from clinical, in vitro, and in vivo studies in English, between 1995 and 2019, from PubMed, Google Scholar, Scopus, and Cochrane library. Based on recent reports, there are promising opportunities to target the opioid system and control the IBD symptoms. This study suggests a novel approach for future treatment of functional and inflammatory disorders such as IBD.

N/OFQ-NOP System in Peripheral and Central Immunomodulation

Classical opioids (μ: mu, MOP; δ: delta, DOP and κ: kappa, KOP) variably affect immune function; they are immune depressants and there is good clinical evidence in the periphery. In addition, there is evidence for a central role in the control of a number of neuropathologies, e.g., neuropathic pain. Nociceptin/Orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ peptide receptor, NOP; peripheral and central activation can modulate immune function. In the periphery, NOP activation generally depresses immune function, but unlike classical opioids this is in part driven by NOP located on circulating immune cells. Peripheral activation has important implications in pathologies like asthma and sepsis. NOP is expressed on central neurones and glia where activation can modulate glial function. Microglia, as resident central 'macrophages', increase/infiltrate in pain and following trauma; these changes can be reduced by N/OFQ. Moreover, the interaction with other glial cell types such as the ubiquitous astrocytes and their known cross talk with microglia open a wealth of possibilities for central immunomodulation. At the whole animal level, clinical ligands with wide central and peripheral distribution have the potential to modulate immune function, and defining the precise nature of that interaction is important in mitigating or even harnessing the adverse effect profile of these important drugs.

Blockade of nociceptin/orphanin FQ receptor signaling reverses LPS-induced depressive-like behavior in mice

Nociceptin/orphanin FQ is the natural ligand of a Gi-protein coupled receptor named NOP. This peptidergic system is involved in the regulation of mood states and inflammatory responses. The present study aimed to investigate the consequences of blocking NOP signaling in lipopolysaccharide (LPS)-induced sickness and depressive-like behaviors in mice. LPS 0.8mg/kg, ip, significantly induced sickness signs such as weight loss, decrease of water and food intake and depressive-like behavior in the tail suspension test. Nortriptyline (ip, 60min prior the test) reversed the LPS-induced depressive states. The NOP receptor antagonist SB-612111, 30min prior LPS, did not modify LPS-induced sickness signs and depressive-like behavior. However, when injected 24h after LPS, NOP antagonists (UFP-101, icv, and SB-612111, ip) significantly reversed the mood effects of LPS. LPS evoked similar sickness signs and significantly increased tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) plasma levels 6h post-injection in wild-type ((NOP(+/+)) and NOP knockout ((NOP(-/-)) mice. However, LPS treatment elicited depressive-like effects in NOP(+/+) but not in NOP(-/-) mice. In conclusion, the pharmacological and genetic blockade of NOP signaling does not affect LPS evoked sickness signs while reversing depressive-like behavior.

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-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.

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.

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.

Nociceptin/orphanin FQ receptor antagonists as innovative antidepressant drugs

Nociceptin/orphanin FQ (N/OFQ) and its receptor (NOP) were identified in the mid 90s as a novel peptidergic system structurally related to opioids. A growing body of preclinical evidence suggests that blockade of NOP receptors evokes antidepressant-like actions. These have been explored using a range of compounds (peptide and non peptide antagonists), across different species (rat and mouse) and assays (behavioral despair and chronic mild stress) suggesting a robust and consistent antidepressant-like effect. Moreover, rats and mice knockout for the NOP receptor gene display an antidepressant-like phenotype in behavioral despair assays. Electrophysiological, immunohistochemical and neurochemical studies point to an important role played by monoaminergic systems, particularly 5-HTergic, in mediating the antidepressant-like properties of NOP antagonists. However other putative mechanisms of action, including modulation of the CRF system, circadian rhythm and a possible neuroendocrine-immune control might be involved. A close relationship between the N/OFQ-NOP receptor system and stress responses is well described in the literature. Stressful situations also alter endocrine, behavioral and neurochemical parameters in rats and chronic administration of a NOP antagonist restored these alterations. Interestingly, clinical findings showed that plasma N/OFQ levels were significantly altered in major and post-partum depression, and bipolar disease patients. Collectively, data in the literature support the notion that blockade of NOP receptor signaling could be a novel and interesting strategy for the development of innovative antidepressants.

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

Nociceptin/orphanin FQ (N/OFQ) and nociceptin orphanin peptide (NOP) receptors represent an endogenous system modulating gastrointestinal functions and inflammation. We investigated the peripheral effect of N/OFQ and of UFP-101, the NOP antagonist, in a model of colitis induced by TNBS (2,4,6 trinitrobenzenesulphonic acid; 60mg/kg). Male rats received two intraperitoneal injections per day of N/OFQ, UFP-101 or saline for 3 days after colitis induction. Four days after TNBS, animals were sacrificed and colonic histological damage, myeloperoxidase (MPO) activity and cytokine (IL-1β and IL-10) levels were evaluated. N/OFQ plasmatic levels were assessed by radioimmunoassay. TNBS increased all the inflammatory variables considered. In colitic rats, N/OFQ (0.02 and 0.2nmol/kg) improved microscopic damage, MPO activity and decreased IL-1β levels in comparison with TNBS group, whereas at the highest dose (20nmol/kg) the peptide worsened colitis. UFP-101 at the dose of 1nmol/kg, without pharmacological activity, antagonised the protective effect of N/OFQ (0.2nmol/kg) on colitis, but at a dose level of 3 and 10nmol/kg worsened inflammation, revealing the endogenous N/OFQergic system protective role. N/OFQ plasmatic levels were not modified in TNBS-treated rats compared with controls, whereas they were reduced in rats treated with the doses of UFP-101 aggravating colitis. In conclusion, peripheral low doses of N/OFQ have a beneficial effect on colonic inflammation in rats. In contrast, N/OFQ at a dose 100-1000-fold higher than those that protect worsens colitis, probably through different mechanisms. The peripheral N/OFQergic system can represent a new field of investigation in some intestinal inflammatory conditions.

The effects of nociceptin peptide (N/OFQ)-receptor (NOP) system activation in the airways

The heptadecapeptide nociceptin/orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ peptide (NOP) receptor. It is cleaved from a larger precursor identified as prepronociceptin (ppN/OFQ). NOP is a member of the seven transmembrane-spanning G-protein coupled receptor (GPCR) family. ppN/OFQ and NOP receptors are widely distributed in different human tissues. Asthma is a complex heterogeneous disease characterized by variable airflow obstruction, bronchial hyper-responsiveness and chronic airway inflammation. Limited therapeutic effectiveness of currently available asthma therapies warrants identification of new drug compounds. Evidence from animal studies suggests that N/OFQ modulates airway contraction and inflammation. Interestingly up regulation of the N/OFQ-NOP system reduces airway hyper-responsiveness. In contrast, inflammatory cells central to the inflammatory response in asthma may be both sources of N/OFQ and respond to NOP activation. Hence paradoxical dysregulation of the N/OFQ-NOP system may potentially play an important role in regulating airway inflammation and airway tone. To date there is no data on N/OFQ-NOP expression in the human airways. Therefore, the potential role of N/OFQ-NOP system in asthma is unknown. This review focuses on its physiological effects within airways and potential value as a novel asthma therapy.

Nociceptin/orphanin FQ inhibition with SB612111 ameliorates dextran sodium sulfate-induced colitis

Inflammatory bowel diseases, primarily Crohn's disease and ulcerative colitis, are chronic inflammatory disorders of the gastrointestinal tract with unknown etiology. The majority of current therapeutic agents focus on controlling proinflammatory molecules. The neuropeptide nociceptin/orphanin FQ (N/OFQ) has been described as a potential immunomodulator for inflammatory bowel diseases. In this study, we asked whether the small molecule N/OFQ antagonist (-)-cis-1-methyl-7-[[4-(2,6-dichlorophenyl)piperidin-1-yl]methyl]-6,7,8,9-tetrahydro-5H-benzocyclohepten-5-ol (SB612111) would inhibit the development of dextran sodium sulfate-induced colitis in C57BL/6 mice. Inhibition of the N/OFQ receptor (NOP) by SB612111 significantly ameliorated the clinical disease course in these animals, as indicated by reduced fecal bleeding, improved recovery from diarrhea and weight loss, and a reduction in histopathological alterations. In addition, the inflammatory response in the colon was diminished, as demonstrated by reduced cytokine protein and messenger RNA expression for CXCL1/keratinocyte-derived chemokine, interferon-γ, interleukin-1β, interleukin-6, and tumor necrosis factor-α, some of which are known targets for the treatment of this devastating disease. Our results strongly support a role for the receptor-ligand pair NOP-N/OFQ in the pathogenesis of colitis. We conclude that inhibition of NOP receptors with small molecule inhibitors may constitute a novel, urgently needed approach for the treatment of inflammatory bowel diseases.

NOP Receptor Ligands as Potential Agents for Inflammatory and Autoimmune Diseases

Nociceptin/orphanin FQ (N/OFQ) is a seventeen-amino acid peptide that is the endogenous ligand of a G-protein-coupled receptor (NOP). Various immune cells express the precursor protein and secrete N/OFQ as well as display binding sites for this peptide. The functional capacity of NOP receptor was demonstrated in vitro and in vivo studies by the ability of N/OFQ to induce chemotaxis of immune cells, to regulate the expression of cytokines and other inflammatory mediators, and to control cellular and humoral immunity. In this context, N/OFQ could modulate the outcome of some inflammatory diseases, such as sepsis and autoimmune pathologies by mechanisms not clearly elucidated yet. In fact, human body fluid revealed increased levels of N/OFQ under sepsis, arthritis, and Parkinson's diagnose. Preclinical studies pointed to the blockade of NOP receptor signaling as successful in treating these experimental conditions. Further preclinical and clinical studies are required to investigate the potential of NOP ligands in treating inflammatory diseases.

Long-term peripheral infusion of nociceptin/orphanin FQ promotes hyperplasia, activation and migration of mucosal mast cells in the rat gastric fundus

The endogenous neuropeptide nociceptin/orphanin FQ (N/OFQ) modulates behavioral and gastrointestinal responses to stress. Mucosal mast cells (MMCs) are primary mediators of stress-related responses in the gastrointestinal tract. We investigated the influence of N/OFQ and of the N/OFQ peptide (NOP) receptor antagonist, UFP-101, on MMCs in the rat gastric fundus. N/OFQ was infused subcutaneously for 52 h at 0.1, 1 and 10 μg/kg/h and at 1 μg/kg/h for 4h, 52 h, 7 days and 14 days via Alzet osmotic minipumps. Density of MMCs and connective tissue mast cells (CTMCs) was assessed histochemically and immunohistochemically. Activation and location of MMCs were assessed by transmission electron microscopy. Contacts between MMCs and nerve elements were assessed by double immunofluorescence. N/OFQ (1 μg/kg/h) and UFP-101 (10 and 30 μg/kg/h) were infused subcutaneously in the absence and presence of acute cold-restraint stress and density of MMCs was assessed. Peripheral N/OFQ dose-dependently increased the density of MMCs, while not influencing CTMCs. The increasing effect was maintained up to 14 days following continuous infusion, while after termination of the 4-h infusion, the effect declined rapidly. The peptide promoted the activation of MMCs and their migration from the lamina propria toward the epithelial layer. The association between MMCs and nerve fibers was time-dependently down-regulated following N/OFQ infusion. The stress-induced hyperplasia of MMCs was not influenced by N/OFQ and abolished by UFP-101. UFP-101 alone was ineffective. The present results suggest that endogenous N/OFQ could be considered a potential component of the circuit neuropeptides-mast cells-stress.

Nociceptin/orphanin FQ in inflammation and sepsis

Nociceptin/orphanin FQ, N/OFQ, and its receptor NOP represent a non-opioid branch of the opioid superfamily that were first studied for their effects on pain responses. Both N/OFQ and NOP are involved in a wide range of 'non-pain' responses including immunomodulation and cardiovascular control. There is now growing interest in this system in inflammation and sepsis, which is the focus of this review article. The N/OFQ-NOP system is present in immune cells and N/OFQ modifies immunocyte function. On the basis of various in vitro and in vivo studies, N/OFQ increases the inflammatory response in healthy anaesthetized animals and in those with a septic or inflammatory process. It affects tissue perfusion, increases capillary leakage and inflammatory markers, and leads to immune cell chemotaxis. Moreover, NOP activation produces bradycardia and hypotension. Systemic N/OFQ administration also increased mortality in an animal model of sepsis, and there is limited evidence for increased plasma N/OFQ concentrations in patients with sepsis who died compared with those who survived. There is a need for further observational and mechanistic studies in patients with established inflammatory processes or sepsis. These studies may facilitate the design of appropriate clinical studies to evaluate NOP ligands as modifiers of the inflammatory response.

Nociceptin/orphanin FQ suppresses adaptive immune responses in vivo and at picomolar levels in vitro

Nociceptin/orphanin FQ (N/OFQ), added in vitro to murine spleen cells in the picomolar range, suppressed antibody formation to sheep red blood cells in a primary and a secondary plaque-forming cell assay. The activity of the peptide was maximal at 10(-12) M, with an asymmetric U-shaped dose-response curve that extended activity to 10(-14) M. Suppression was not blocked by pretreatment with naloxone. Specificity of the suppressive response was shown using affinity-purified rabbit antibodies against two N/OFQ peptides and with a pharmacological antagonist. Antisera against both peptides were active, in a dose-related manner, in neutralizing N/OFQ-mediated immunosuppression, when the peptide was used at concentrations from 10(-12.3) to 10(-11.6) M. In addition, nociceptin given in vivo by osmotic pump for 48 h suppressed the capacity of spleen cells placed ex vivo to make an anti-sheep red blood cell response. These studies show that nociceptin directly inhibits an adaptive immune response, i.e., antibody formation, both in vitro and in vivo.

Nociceptin-induced modulation of human T cell function

There is an accumulating evidence for the immunoregulatory role of the neuropeptide, nociceptin/orphanin FQ (N/OFQ) however its role on T cell function requires elucidation. This study has demonstrated an inhibitory role for N/OFQ on SEB-activated T cell function. N/OFQ decreases T cell proliferation, which is abrogated when the costimulatory receptors CD80 and CD86 are blocked. In addition, evidence suggests that the immunoregulatory cytokines TGF-beta, IFN-gamma and nitric oxide (NO) are involved in the N/OFQ effect. N/OFQ also, through involvement of IFN and NO, induces the expression of the immunosuppressive modulator indoleamine 2,3-dioxygenase (IDO), suggesting a central role for IDO in the N/OFQ effect on T cell proliferation. The data presented in this report indicate a multi-faceted mechanism of action used by N/OFQ to modulate T cell function.

Peripheral anti-nociceptive effect of nociceptin/orphanin FQ in inflammation and stress-induced colonic hyperalgesia in rats

Nociceptin/orphanin FQ (N/OFQ) and its NOP receptors are present in the central nervous system and in the periphery playing important roles in the modulation of gastrointestinal functions and pain. The aim of this study was to investigate the role of central and peripheral N/OFQ-NOP receptor system in the nociceptive response to colorectal distension (CRD) in basal condition and in two models of gut hypersensitivity triggered by both inflammation and stress. Male Wistar rats were tested in basal and in post-inflammatory conditions, i.e., 5 days after IC TNBS instillation (80 mg/Kg) and received N/OFQ (2 nmol/Kg IP), UFP-101 (a selective NOP receptor antagonist, 10 nmol/Kg IP), N/OFQ+UFP-101, N/OFQ (0.5 nmol/rat ICV) or vehicle. Female rats were tested in basal and after partial restraint stress receiving the same pharmacological treatment. CRD was performed using barostat and abdominal contractions were recorded by electromyography. In basal condition, N/OFQ, ICV and IP injected, did not modify basal visceral sensitivity. Both in TNBS and stress-induced hyperalgesia, IP but not ICV injection of N/OFQ significantly decreased the number of abdominal contractions. Peripheral injection of UFP-101 antagonized N/OFQ effect. Moreover, in post-inflammatory colitis, UFP-101, injected alone, exacerbated visceral hyperalgesia to CRD compared with vehicle. These findings indicate that in rats, N/OFQ, only peripherally injected, reduces visceral hypersensitivity triggered by inflammation or stress without affecting basal sensitivity. N/OFQ visceral anti-hyperalgesic effect involves peripheral NOP receptors. In a post-inflammatory, but not in an acute stress colitis model, N/OFQergic system is endogenously activated.

Nociceptin and urotensin-II concentrations in critically ill patients with sepsis

BACKGROUND

The systemic inflammatory response to infection (sepsis) involves widespread organ dysfunction, including changes in immune modulation, cardiovascular derangements, and neural activation. Two neuropeptide/receptor systems, nociceptin/orphanin FQ (N/OFQ) which acts at the non-classical opioid receptor NOP and urotensin-II (U-II) which acts at the urotensin receptor (UT), have been implicated in neural, immune, and cardiovascular system function. In this study, we make measurements of these peptides in critically ill patients.

METHODS

Plasma samples from 21 critically ill patients with sepsis were collected over four consecutive days. Plasma N/OFQ and U-II concentrations were determined by radioimmunoassay and compared with biochemical and clinical markers of illness severity, including serum creatinine, bilirubin, platelet and white cell counts, admission APACHE II and serial SOFA scores.

RESULTS

Median (inter-quartile range) admission plasma N/OFQ concentrations in sepsis were higher in patients who died within 30 days (n=4) compared with survivors (n=17); 3.0 (2.5-5.0) vs 1.0 (1.0-2.5) pg ml(-1) (P=0.028). Plasma N/OFQ concentrations were increased in a subgroup of five patients who had undergone major gastrointestinal surgery. There were no significant changes in plasma U-II concentrations. There were no correlations between plasma U-II and N/OFQ concentrations and markers of illness severity and organ system dysfunction.

CONCLUSIONS

Plasma N/OFQ concentrations were increased in critically ill patients with sepsis who had undergone major gastrointestinal surgery and in patients who subsequently died. Further work is required to clarify the significance of plasma N/OFQ concentrations in sepsis.

Endogenous opiates and behavior: 2005

This paper is the 28th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2005 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 (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).