Proinflammatory and vasodilator effects of nociceptin/orphanin FQ in the rat mesenteric microcirculation are mediated by histamine

The Nociceptin/Orphanin FQ peptide receptor antagonist, SB-612111, improves cerebral blood flow in a rat model of traumatic brain injury

Traumatic brain injury (TBI) affects more than 2.5 million people in the U.S. each year and is the leading cause of death and disability in children and adults ages 1 to 44. Approximately 90% of TBI cases are classified as mild but may still lead to acute detrimental effects such as impaired cerebral blood flow (CBF) that result in prolonged impacts on brain function and quality of life in up to 15% of patients. We previously reported that nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor antagonism reversed mild blast TBI-induced vestibulomotor deficits and prevented hypoxia. To explore mechanisms by which the NOP receptor-N/OFQ pathway modulates hypoxia and other TBI sequelae, the ability of the NOP antagonist, SB-612111 (SB), to reverse TBI-induced CBF and associated injury marker changes were tested in this study. Male Wistar rats randomly received sham craniotomy or craniotomy + TBI via controlled cortical impact. Injury severity was assessed after 1 h (modified neurological severity score (mNSS). Changes in CBF were assessed 2 h post-injury above the exposed cortex using laser speckle contrast imaging in response to the direct application of increasing concentrations of vehicle or SB (1, 10, and 100 µM) to the brain surface. TBI increased mNSS scores compared to baseline and confirmed mild TBI (mTBI) severity. CBF was significantly impaired on the ipsilateral side of the brain following mTBI, compared to contralateral side and to sham rats. SB dose-dependently improved CBF on the ipsilateral side after mTBI compared to SB effects on the respective ipsilateral side of sham rats but had no effect on contralateral CBF or in uninjured rats. N/OFQ levels increased in the cerebral spinal fluid (CSF) following mTBI, which correlated with the percent decrease in ipsilateral CBF. TBI also activated ERK and cofilin within 3 h post-TBI; ERK activation correlated with increased CSF N/OFQ. In conclusion, this study reveals a significant contribution of the N/OFQ-NOP receptor system to TBI-induced dysregulation of cerebral vasculature and suggests that the NOP receptor should be considered as a potential therapeutic target for TBI.

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.

Functional pharmacological characterization of SER100 in cardiovascular health and disease

BACKGROUND AND PURPOSE

SER100 is a selective nociceptin (NOP) receptor agonist with sodium-potassium-sparing aquaretic and anti-natriuretic activity. This study was designed to characterize the functional cardiovascular pharmacology of SER100 in vitro and in vivo, including experimental models of cardiovascular disease.

EXPERIMENTAL APPROACH

Haemodynamic, ECG parameters and heart rate variability (HRV) were determined using radiotelemetry in healthy, conscious mice. The haemodynamic and vascular effects of SER100 were also evaluated in two models of cardiovascular disease, spontaneously hypertensive rats (SHR) and murine hypoxia-induced pulmonary hypertension (PH). To elucidate mechanisms underlying the pharmacology of SER100, acute blood pressure recordings were performed in anaesthetized mice, and the reactivity of rodent aorta and mesenteric arteries in response to electrical- and agonist-stimulation assessed.

KEY RESULTS

SER100 caused NOP receptor-dependent reductions in mean arterial blood pressure and heart rate that were independent of NO. The hypotensive and vasorelaxant actions of SER100 were potentiated in SHR compared with Wistar Kyoto. Moreover, SER100 reduced several indices of disease severity in experimental PH. Analysis of HRV indicated that SER100 decreased the low/high frequency ratio, an indicator of sympatho-vagal balance, and in electrically stimulated mouse mesenteric arteries SER100 inhibited sympathetic-induced contractions.

CONCLUSIONS AND IMPLICATIONS

SER100 exerts a chronic hypotensive and bradycardic effects in rodents, including models of systemic and pulmonary hypertension. SER100 produces its cardiovascular effects, at least in part, by inhibition of cardiac and vascular sympathetic activity. SER100 may represent a novel therapeutic candidate in systemic and pulmonary hypertension.

Hepatoprotective and anti-tumor effects of targeting MMP-9 in hepatocellular carcinoma and its relation to vascular invasion markers

The current study aims to evaluate the hepatoprotective and antitumor efficacy of doxycycline, as an matrix metalloproteases-9 (MMP-9) inhibitor, in an in vivo model of hepatocellular carcinoma (HCC). HCC was induced experimentally by thiocetamide (200 mg/kg) in rats that were treated with doxycycline (5 mg/kg for 16 weeks). Tumor severity was evaluated by measuring α-fetoprotein (AFP) levels, histopathologically by investigating liver sections stained with hematoxylin/eosin and assessing the survival rate. Liver homogenates were used for the measurements of MMP-9, fascin and hepatic heparan sulfate proteoglycan (HSPG) levels. Oxidative stress markers [malonaldehyde (MDA) and glutathione] as well as fibroblast growth factor-2 (FGF-2) gene expression were also among the assessed indicators. HCC in human and animal samples showed significant elevation in the levels of MMP-9 (231.7, 90 %), fascin (33.17, 140 %), as well as FGF-2 gene expression (342 % in animal samples; all respectively), associated with a significant decrease in hepatic HSPG level. Treatment of rats with doxycycline increased the animal survival rate (90 %) and decreased serum AFP level. Moreover, doxycycline ameliorated fibrosis and the induced massive hepatic tissue breakdown. It also restored the integrity of hepatic HSPGs and showed a magnificent inhibitory effect of tumor invasion cascade by significantly reducing the activities of MMP-9 (42 %) and fascin (50 %), as well as reducing the gene expression of FGF-2 (85.7 %). Furthermore, the antioxidant impact of doxycycline was evidenced by the significant elevation in glutathione level and depressing MDA level. To this end, doxycycline, proved promising hepatoprotective and antitumor activity and opens, thereby, a new horizon against vascular migration ability of the tumor 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.

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.

Exploring LPS-induced sepsis in rats and mice as a model to study potential protective effects of the nociceptin/orphanin FQ system

The nociceptin receptor (NOP) and its ligand nociceptin/orphanin FQ (N/OFQ) have been shown to exert a modulatory effect on immune cells during sepsis. We evaluated the suitability of an experimental lipopolysaccharide (LPS)-induced sepsis model for studying changes in the nociceptin system. C57BL/6 mice BALB/c mice and Wistar rats were inoculated with different doses of LPS with or without a nociceptin receptor antagonist (UFP-101 or SB-612111). In C57BL/6 mice LPS 0.85 mg/kg injection produced no septic response, whereas 1.2mg/kg produced a profound response within 5h. In BALB/c mice, LPS 4 mg/kg produced no response, whereas 7 mg/kg resulted in a profound response within 24h. In Wistar rats LPS 15 mg/kg caused no septic response in 6/10 animals, whereas 25mg/kg resulted in marked lethargy before 24h. Splenic interleukin-1β mRNA in BALB/c mice, and serum TNF-α concentrations in Wistar rats increased after LPS injection in a dose-dependent manner, but were undetectable in control animals, indicating that LPS had stimulated an inflammatory reaction. IL-1β and TNF-α concentrations in LPS-treated animals were unaffected by administration of a NOP antagonist. Similarly NOP antagonists had no effect on survival or expression of mRNA for NOP or ppN/OFQ (the N/OFQ precursor) in a variety of tissues. In these animal models, the dose-response curve for LPS was too steep to allow use in survival studies and no changes in the N/OFQ system occurred within 24h. We conclude that LPS-inoculation in rodents is an unsuitable model for studying possible changes in the NOP-N/OFQ system in sepsis.

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.

Functional plasticity of the N/OFQ-NOP receptor system determines analgesic properties of NOP receptor agonists

Despite high sequence similarity between NOP (nociceptin/orphanin FQ opioid peptide) and opioid receptors, marked differences in endogenous ligand selectivity, signal transduction, phosphorylation, desensitization, internalization and trafficking have been identified; underscoring the evolutionary difference between NOP and opioid receptors. Activation of NOP receptors affects nociceptive transmission in a site-specific manner, with antinociceptive effects prevailing after peripheral and spinal activation, and pronociceptive effects after supraspinal activation in rodents. The net effect of systemically administered NOP receptor agonists on nociception is proposed to depend on the relative contribution of peripheral, spinal and supraspinal activation, and this may depend on experimental conditions. Functional expression and regulation of NOP receptors at peripheral and central sites of the nociceptive pathway exhibits a high degree of plasticity under conditions of neuropathic and inflammatory pain. In rodents, systemically administered NOP receptor agonists exerted antihypersensitive effects in models of neuropathic and inflammatory pain. However, they were largely ineffective in acute pain while concomitantly evoking severe motor side effects. In contrast, systemic administration of NOP receptor agonists to non-human primates (NHPs) exerted potent and efficacious antinociception in the absence of motor and sedative side effects. The reason for this species difference with respect to antinociceptive efficacy and tolerability is not clear. Moreover, co-activation of NOP and μ-opioid peptide (MOP) receptors synergistically produced antinociception in NHPs. Hence, both selective NOP receptor as well as NOP/MOP receptor agonists may hold potential for clinical use as analgesics effective in conditions of acute and chronic pain.

Angiopoietin-1 regulates microvascular reactivity and protects the microcirculation during acute endothelial dysfunction: role of eNOS and VE-cadherin

The growth factor angiopoietin-1 (Ang-1) plays an essential role in angiogenesis and vascular homeostasis. Nevertheless, the role of Ang-1 in regulating vascular tone and blood flow is largely unexplored. Endothelial nitric oxide synthase (eNOS) and the junctional protein VE-cadherin are part of the complex signalling cascade initiated by Ang-1 in endothelial cells. In this study, we aimed to investigate the mechanisms underlying acute effects of Ang-1 on microvascular reactivity, permeability and blood flow, and hypothesise that eNOS and VE-cadherin underpin Ang-1 mediated vascular effects that are independent of angiogenesis and proliferation. Myography of isolated microarterioles from male C3H/HeN mice (7-10 weeks) was employed to measure vascular reactivity in vitro. Microcirculatory function in vivo was evaluated by intravital microscopy and Doppler fluximetry in dorsal window chambers. Ang-1 and its stable variant MAT.Ang-1 induced a concentration-dependent vasodilation of arterioles in vitro, which was blocked with nitric oxide (NO) synthesis inhibitor l-NAME. In vivo, MAT.Ang-1 restored to control levels l-NAME induced peripheral vasoconstriction, decreased blood flow and microvascular hyperpermeability. Tissue protein expression of VE-cadherin was reduced by NOS inhibition and restored to control levels by MAT.Ang-1, whilst VE-cadherin phosphorylation was increased by l-NAME and subsequently reduced by MAT.Ang-1 administration. Moreover, MAT.Ang-1 alone did not modulate systemic levels of angiogenetic factors. Our novel findings report that Ang-1 induces arteriolar vasodilation via release of NO, suggesting that Ang-1 is an important regulator of microvascular tone. As MAT.Ang-1 ameliorates detrimental effects on the microcirculation induced by inhibition of NO synthesis and stabilizes the endothelial barrier function through VE-cadherin, we propose that this Ang-1 variant may serve as a novel therapeutic agent to protect the microcirculation against endothelial dysfunction.

The Nociceptin/Orphanin FQ system is modulated in patients admitted to ICU with sepsis and after cardiopulmonary bypass

BACKGROUND AND OBJECTIVES

Nociceptin/Orphanin FQ (N/OFQ) is a non-classical endogenous opioid peptide that modulates immune function in vitro. Its importance in inflammation and human sepsis is unknown. The objectives of this study were to determine the relationship between N/OFQ, transcripts for its precursor (pre-pro-N/OFQ [ppNOC]) and receptor (NOP), inflammatory markers and clinical outcomes in patients undergoing cardiopulmonary bypass and with sepsis.

METHODS

A prospective observational cohort study of 82 patients admitted to Intensive Care (ICU) with sepsis and 40 patients undergoing cardiac surgery under cardiopulmonary bypass (as a model of systemic inflammation). Sixty three healthy volunteers, matched by age and sex to the patients with sepsis were also studied. Clinical and laboratory details were recorded. Polymorph ppNOC and NOP receptor mRNA were determined using quantitative PCR. Plasma N/OFQ was determined using ELISA and cytokines (TNF- α, IL-8, IL-10) measured using radioimmunoassay. Data from patients undergoing cardiac surgery were recorded before, 3 and 24 hours after cardiopulmonary bypass. ICU patients with sepsis were assessed on Days 1 and 2 of ICU admission, and after clinical recovery.

MAIN RESULTS

Plasma N/OFQ concentrations increased (p<0.0001) on Days 1 and 2 of ICU admission with sepsis compared to matched recovery samples. Polymorph ppNOC (p= 0.019) and NOP mRNA (p<0.0001) decreased compared to healthy volunteers. TNF-α, IL-8 and IL-10 concentrations increased on Day 1 compared to matched recovery samples and volunteers (p<0.0001). Similar changes (increased plasma N/OFQ, [p=0.0058], decreased ppNOC [p<0.0001], increased IL-8 and IL-10 concentrations [both p<0.0001]) occurred after cardiac surgery but these were comparatively lower and of shorter duration.

CONCLUSIONS

The N/OFQ system is modulated in ICU patients with sepsis with similar but reduced changes after cardiac surgery under cardiopulmonary bypass. Further studies are required to clarify the role of the N/OFQ system in inflammation and sepsis, and the mechanisms involved.

Nociceptin receptor signaling in sympathetic neurons from septic rats

BACKGROUND

The endogenous opioid peptide, nociception (Noc), contributes to the regulation of systemic blood pressure and regional blood flow. Recent clinical and animal studies have reported that Noc and its receptor (nociceptin/orphanin FQ [NOP]) are involved in inflammation and sepsis. The purpose of the present study was to examine the modulation of Ca(2+) channels by Noc in acutely isolated stellate ganglion (SG) neurons from control and septic rats.

MATERIALS AND METHODS

Sepsis was induced in male Sprague-Dawley rats via cecal ligation and puncture. SG neurons were isolated 24 and 72 h after sepsis induction. Thereafter, the concentration-response relationships for the Noc-stimulated NOP receptor Ca(2+) current inhibition were determined using the whole-cell patch clamp technique. In addition, the Noc precursor (prepronociceptin [PNOC]) and NOP receptor messenger RNA (mRNA) levels were determined by quantitative real-time polymerase chain reaction, and PNOC protein levels were measured by Western blot analysis.

RESULTS

Comparison of the Noc concentration-response relationships in SG neurons from control and septic rats 24 h after sepsis revealed similar potency and efficacy. Moreover, 72 h after sepsis, neurons from control and septic rats exhibited an increased potency compared with both groups at the 24-h time point--an effect that was more pronounced in neurons from septic rats. PNOC mRNA levels were significantly greater in SG neurons isolated from septic rats compared with control neurons, but NOP receptor mRNA levels remained unchanged during the 72-h period.

CONCLUSIONS

Our study demonstrates the cecal ligation and puncture model-induced temporal upregulation of components within the NOP receptor signaling pathway in rat sympathetic neurons. As SG neurons provide the main sympathetic input to the heart, an increased Noc release and potency during sepsis may compromise cardiovascular function.

The nociceptin/orphanin FQ receptor antagonist UFP-101 reduces microvascular inflammation to lipopolysaccharide in vivo

Microvascular inflammation occurs during sepsis and the endogenous opioid-like peptide nociceptin/orphanin FQ (N/OFQ) is known to regulate inflammation. This study aimed to determine the inflammatory role of N/OFQ and its receptor NOP (ORL1) within the microcirculation, along with anti-inflammatory effects of the NOP antagonist UFP-101 (University of Ferrara Peptide-101) in an animal model of sepsis (endotoxemia). Male Wistar rats (220 to 300 g) were administered lipopolysaccharide (LPS) for 24 h (-24 h, 1 mg kg(-1); -2 h, 1 mg kg(-1) i.v., tail vein). They were then either anesthetised for observation of the mesenteric microcirculation using fluorescent in vivo microscopy, or isolated arterioles (~200 µm) were studied in vitro with pressure myography. 200 nM kg(-1) fluorescently labelled N/OFQ (FITC-N/OFQ, i.a., mesenteric artery) bound to specific sites on the microvascular endothelium in vivo, indicating sparse distribution of NOP receptors. In vitro, arterioles (~200 µm) dilated to intraluminal N/OFQ (10(-5)M) (32.6 + 8.4%) and this response was exaggerated with LPS (62.0 +7.9%, p=0.031). In vivo, LPS induced macromolecular leak of FITC-BSA (0.02 g kg(-1) i.v.) (LPS: 95.3 (86.7 to 97.9)%, p=0.043) from post-capillary venules (<40 µm) and increased leukocyte rolling as endotoxemia progressed (p=0.027), both being reduced by 150 nmol kg(-1) UFP-101 (i.v., jugular vein). Firstly, the rat mesenteric microcirculation expresses NOP receptors and secondly, NOP function (ability to induce dilation) is enhanced with LPS. UFP-101 also reduced microvascular inflammation to endotoxemia in vivo. Hence inhibition of the microvascular N/OFQ-NOP pathway may have therapeutic potential during sepsis and warrants further investigation.

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.

Pkd2 mesenteric vessels exhibit a primary defect in endothelium-dependent vasodilatation restored by rosiglitazone

Patients with autosomal dominant polycystic kidney disease have a high prevalence of hypertension and structural vascular abnormalities, such as intracranial aneurysms. Hypertension can develop in childhood and often precedes a significant reduction in the glomerular filtration rate. The major aim of this study was to investigate whether a primary endothelial defect or a vascular smooth muscle (VSM) defect was present in murine polycystic kidney disease (Pkd)2 heterozygous mesenteric vessels before the development of renal failure or hypertension. Using pressure myography, we observed a marked defect in ACh-stimulated endothelium-dependent vasodilatation in Pkd2 arterioles. In contrast, Pkd2 vessels responded normally to sodium nitroprusside, phenylephrine, KCl, and pressure, indicating unaltered VSM-dependent responses. Pretreatment with the peroxisome proliferator-activated receptor-γ agonist rosiglitazone significantly restored ACh-dependent vasodilation in Pkd2 mice. Isolated heterozygous Pkd2 endothelial cells displayed normal ACh-stimulated Ca(2+) and nitric oxide production. However, isolated Pkd2 heterozygous VSM cells displayed basal increases in superoxide and sodium nitroprusside-stimulated peroxynitrite formation, which were both suppressed by rosiglitazone. Furthermore, we observed a defective response of Pkd2 mesenteric venules to ACh in vivo, which was more marked after ischemia-reperfusion injury. In conclusion, the results of our study suggest that the defect in vasodilatation in Pkd2 heterozygous vessels is primarily due to a reduction in nitric bioavailability secondary to increased vascular oxidative stress. The ability of rosiglitazone to correct this phenotype suggests that this defect is potentially reversible in patients with autosomal dominant polycystic kidney disease.

Angiopoietin-1 variant reduces LPS-induced microvascular dysfunction in a murine model of sepsis

Introduction

Severe sepsis is characterised by intravascular or extravascular infection with microbial agents, systemic inflammation and microcirculatory dysfunction, leading to tissue damage, organ failure and death. The growth factor angiopoietin (Ang-1) has therapeutic potential but recombinant Ang-1 tends to aggregate and has a short half-life in vivo. This study aimed to investigate the acute effects of the more stable Ang-1 variant matrilin-1-angiopoietin-1 (MAT.Ang-1) on the function of the microcirculation in an experimental model of sepsis, and whether any protection by MAT-Ang-1 was associated with modulation of inflammatory cytokines, angiogenic factors or the endothelial nitric oxide synthase (eNOS)-Akt and vascular endothelial (VE)-cadherin pathways.

Methods

Aluminium window chambers were implanted into the dorsal skinfold of male C3H/HeN mice (7 to 10 weeks old) to expose the striated muscle microcirculation. Endotoxemia was induced by intraperitoneal injection of lipopolysaccharide (LPS, 1 mg/kg at 0 and 19 hours). MAT.Ang-1 was administered intravenously 20 hours after the onset of sepsis. Microcirculatory function was evaluated by intravital microscopy and Doppler fluximetry.

Results

Endotoxemia resulted in macromolecular leak, which was ameliorated by MAT.Ang-1 post-treatment. LPS induced a dramatic reduction in tissue perfusion, which was improved by MAT.Ang-1. Proteome profiler array analysis of skeletal muscle also demonstrated increased inflammatory and reduced angiogenic factors during endotoxemia. MAT.Ang-1 post-treatment reduced the level of IL-1β but did not significantly induce the expression of angiogenic factors. MAT.Ang-1 alone did not induce leak or increase angiogenic factors but did reduce vascular endothelial growth factor expression in controls.

Conclusion

Administration of MAT.Ang-1 after the onset of sepsis protects the microcirculation from endotoxemia-induced vascular dysfunction through reducing inflammation but without pro-angiogenic actions, thus representing a novel, potential pharmacotherapeutic agent for the treatment of sepsis.

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.

Immunohistochemical and biomolecular identification of orphanin FQ, eNOS, atrial natriuretic factor and oxytocin in rat seminal vesicles

In previous studies performed on rodents, we detected the presence of adreno-cholinergic and peptidergic innervation in seminal vesicles and other organs of the male genital system, such as prostate and deferent duct, in which we also investigated the expression of NOS and NADPH-diaphorase. During this project, we focused our attention on the expression of some peptides involved in local control of smooth muscle relaxation, contractility, vasodilatation and control of blood flow in rat seminal vesicles. We investigated, through immunohistochemistry and RT-PCR, the presence of four peptides: orphanin, eNOS, ANF and oxytocin. Immunohistochemistry was used to detect the presence of the proteins, whereas RT-PCR analysis confirmed gene expression of orphanin, eNOS and ANF, but not oxytocin. In our opinion, orphanin, eNOS and ANF could have paracrine effects regulating the function of seminal vesicles, whereas oxytocin, which may reach this anatomical district through the blood flow, may have a hormonal action. This is a pilot study that, with further investigation, may allow to better clarify the role of these molecules in the control of seminal vesicle tissues' homeostasis.

In vivo effects of N/OFQ(1–13)NH2 and its structural analogue [ORN9]N/OFQ(1–13)NH2 on carrageenan-induced inflammation: rat-paw oedema and antioxidant status

The effects of nociceptin(1–13)NH2 (N/OFQ(1–13)NH2) and its structural analogue [Orn9]N/OFQ(1–13)NH2 on acute carrageenan (CG)-induced peripheral inflammation and paw antioxidant status were studied. CG was injected intraplantarly in the right hind paw of rats and the volume of the inflamed paw was measured each 30 min for a period of 4h. When administered simultaneously with CG, N/OFQ(1–13)NH2 decreased the paw volume, whereas if injected 15 min before CG it had no effect. [Orn9]N/OFQ(1–13)NH2 produced the opposite effects at the same time-intervals of its administration. We also investigated whether these neuropeptides influence CG-induced changes in cell antioxidant system, especially at the 4th hour of CG administration. CG alone decreased the glutathione level and superoxide dismutase activity, as measured in post-nuclear homogenate of the inflamed paw. However, CG injection increased glutathione peroxidase and glucose-6-phospate dehydrogenase activities, while the activity of glutathione reductase was unchanged. The peptides themselves did not change all measured parameters. Moreover, neither N/OFQ(1–13)NH2 nor [Orn9]N/OFQ(1–13)NH2 modified CG-induced changes in the antioxidant status, regardless of the time of their injection (simultaneously or 15 min before CG). The present results suggest that N/OFQ(1–13)NH2 and [Orn9]N/OFQ(1–13)NH2 most likely affect the neuronal inflammation, rather than act as pro- or antioxidants.

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.

Endogenous opiates and behavior: 2007

This paper is the thirtieth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2007 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.