Nociceptin/orphanin FQ increases blood pressure and heart rate via sympathetic activation in sheep

Perioperative changes of serum orphanin in diabetic patients and its relationship with sympathetic nervous system

The occurrence of cardiovascular events in diabetic patients during the perioperative period is related to the activation of sympathetic nerves. Basic research shows that serum nociceptin/orphanin FQ (N/OFQ) levels in diabetic neuropathy rats increased, and N/OFQ reduces the release of norepinephrine (NE). We hypothesize that N/OFQ will affect the sympathetic nervous system during perioperative myocardium of diabetic patients. 66 patients with unilateral knee arthroplasty were divided into diabetes group (D group) and non-diabetes group (N group). Measured blood glucose, serum NE, N/OFQ concentrations at the 30 min before anesthesia (T0), 1 h after surgery (T1), 24 h after surgery (T2) and the cardiac troponinI (cTnI) concentration at T0 and T2. Compared with N group, the concentration of blood glucose, N/OFQ and cTnI in D group was higher and the NE was lower at T0 (P < 0.05). At T1, the blood glucose, N/OFQ, NE concentrations of D group increased, only the blood glucose increased in N group (P < 0.05). Serum N/OFQ of D group from T0 to T1 was correlated with the change trend of blood glucose, NE concentration from T0 to T1 and cTnI from T0 to T2(r = 0.386, P = 0.027; r = 0.350, P = 0.046; r = 0.363, P = 0.038). The outcomes demonstrated that the preoperative serum N/OFQ concentration in diabetic patients was increased, and the increase in N/OFQ concentration during the operation was related to the increase in NE and cTnI concentrations, perioperative N/OFQ may mediate myocardial injury through sympathetic nervous system.

Multi-Omics Characterization of a Human Stem Cell-Based Model of Cardiac Hypertrophy

Cardiac hypertrophy is an important and independent risk factor for the development of cardiac myopathy that may lead to heart failure. The mechanisms underlying the development of cardiac hypertrophy are yet not well understood. To increase the knowledge about mechanisms and regulatory pathways involved in the progression of cardiac hypertrophy, we have developed a human induced pluripotent stem cell (hiPSC)-based in vitro model of cardiac hypertrophy and performed extensive characterization using a multi-omics approach. In a series of experiments, hiPSC-derived cardiomyocytes were stimulated with Endothelin-1 for 8, 24, 48, and 72 h, and their transcriptome and secreted proteome were analyzed. The transcriptomic data show many enriched canonical pathways related to cardiac hypertrophy already at the earliest time point, e.g., cardiac hypertrophy signaling. An integrated transcriptome–secretome analysis enabled the identification of multimodal biomarkers that may prove highly relevant for monitoring early cardiac hypertrophy progression. Taken together, the results from this study demonstrate that our in vitro model displays a hypertrophic response on both transcriptomic- and secreted-proteomic levels. The results also shed novel insights into the underlying mechanisms of cardiac hypertrophy, and novel putative early cardiac hypertrophy biomarkers have been identified that warrant further investigation to assess their potential clinical relevance.

Prospects for Creation of Cardioprotective and Antiarrhythmic Drugs Based on Opioid Receptor Agonists

It has now been demonstrated that the μ, δ1 , δ2 , and κ1 opioid receptor (OR) agonists represent the most promising group of opioids for the creation of drugs enhancing cardiac tolerance to the detrimental effects of ischemia/reperfusion (I/R). Opioids are able to prevent necrosis and apoptosis of cardiomyocytes during I/R and improve cardiac contractility in the reperfusion period. The OR agonists exert an infarct-reducing effect with prophylactic administration and prevent reperfusion-induced cardiomyocyte death when ischemic injury of heart has already occurred; that is, opioids can mimic preconditioning and postconditioning phenomena. Furthermore, opioids are also effective in preventing ischemia-induced arrhythmias.

Deciphering intracellular localization and physiological role of nociceptin and nocistatin

Nociceptin and nocistatin are endogenous ligands of G protein coupled receptor family. Numerous techniques have been used to study the diverse parameters including, localization, distribution and ultrastructure of these peptides. The majority of the study parameters are based on their physiological roles in different organ systems. The present study presents an overview of the different methods used for the study of nociceptin, nocistatin and their receptors. Nociceptin has been implicated in many physiological functions including, nociception, locomotion, stressed-induced analgesia, learning and memory, neurotransmitter and hormone release, renal function, neuronal differentiation, sexual and reproductive behavior, uterine contraction, feeding, anxiety, gastrointestinal motility, cardiovascular function, micturition, cough, hypoxic-ischemic brain injury, diuresis and sodium balance, temperature regulation, vestibular function, and mucosal transport. It has been noted that the use of light and electron microscopy was less frequent, though it may be one of the most promising tools to study the intracellular localization of these neuropeptides. In addition, more studies on the level of circulating nociceptin and nocistatin are also necessary for investigating their clinical roles in health and disease. A variety of modern tools including physiological, light and electron microscopy (EM) are needed to decipher the extent of intracellular localization, tissue distribution and function of these peptides. The intracellular localization of nociceptin and nocistatin will require a high resolution transmission EM capable of identifying these peptides and other supporting molecules that co-localize with them. A tracing technique could also elucidate a possible migratory ability of nociceptin and nocistatin from one cellular compartment to the other.

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 phenylalanine glutamine (FQ) receptor and cardiovascular disease

Nociceptin/Orphanin FQ (N/OFQ) is the endogenous ligand for the N/OFQ receptor. N/OFQ acts directly on blood vessels to elicit vasodilation. This review will describe the peripheral cardiovascular effects of N/OFQ observed in studies conducted in vitro and in vivo, along with those designed to characterize systemic cardiovascular effects resulting from direct injection into brain tissue. Emphasis is placed on the cerebrovascular action of N/OFQ and its function considered in the setting of central nervous system (CNS) pathology. Although N/OFQ is unlikely to cross the blood-brain barrier because of its size, use of N/OFQ antagonists to alleviate the potentially deleterious action of centrally released N/OFQ may be of therapeutic importance in treatment of cerebral ischemia of diverse origin, such as stroke and traumatic brain injury. Targeting N/OFQ may also be of therapeutic importance in alleviating the hyperemia and pain associated with joint inflammation.

Stimulation of sensory neuropeptide release by nociceptin/orphanin FQ leads to hyperaemia in acutely inflamed rat knees

The peripheral effect of the 'opioid-like' peptide nociceptin/orphanin FQ (N/OFQ) on joint blood flow was investigated in acutely inflamed rats. Sensory neuropeptide release from capsaicin-sensitive nerves and the involvement of synovial mast cells and leukocytes on these vasomotor responses were also studied. Blood flow measurements of exposed knee joints were performed in urethane-anaesthetised rats (2 mg kg(-1) intraperitoneal) using laser Doppler perfusion imaging. Topical administration of N/OFQ (10(-13)-10(-8) mol) to acutely inflamed joints caused a dose-dependent increase in synovial perfusion with an ED(50) of 4.0 x 10(-10) mol. This vasodilatatory response was blocked by the selective NOP receptor antagonist [Phe(1)-(CH(2)-NH)-Gly(2)]-Nociceptin(1-13)-NH(2) (10(-9) mol) (P<0.0001).Co-administration of N/OFQ with the neurokinin-1 (NK(1)) receptor antagonist [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-Substance P (10(-12) mol), the vasoactive intestinal peptide (VIP) receptor antagonist VIP(6-28) (10(-9) mol) or the calcitonin gene-related peptide (CGRP) receptor antagonist CGRP(8-37) (10(-9) mol) all blocked the hyperaemic effect of N/OFQ (P<0.0001). Treatment of acutely inflamed knees with capsaicin (8-methyl-N-vanillyl-6-noneamide) to destroy unmyelinated joint afferents also inhibited N/OFQ vasomotor activity. Stabilisation of synovial mast cells with disodium cromoglycate (cromolyn) ameliorated N/OFQ responses, whereas inactivation of circulating leukocytes with the pan-selectin inhibitor fucoidin completely blocked N/OFQ-induced hyperaemia in these joints. These experiments show that in acutely inflamed knee joints, N/OFQ acts on NOP receptors located on synovial mast cells and leukocytes leading to the secondary release of proinflammatory mediators into the joint. These agents subsequently stimulate sensory neuropeptide release from capsaicin-sensitive nerves culminating in vasodilatation and increased articular blood flow.

Nociceptin in rVLM mediates electroacupuncture inhibition of cardiovascular reflex excitatory response in rats

Electroacupuncture (EA) at Neiguan-Jianshi acupoints through an opioid mechanism inhibits the cardiovascular pressor response induced by mechanical stimulation of the stomach. Because nociceptin also may regulate cardiovascular activity through its action in the brain stem, we hypothesized that this neuromodulator serves a role in the EA-related inhibitory effect. Blood pressure in ventilated male Sprague-Dawley rats (400-600 g) anesthetized by ketamine and alpha-chloralose was measured during balloon inflation of the stomach. Gastric distension with 6-8 ml of air induced consistent pressor reflexes of 26 +/- 1 mmHg that could be repeated every 10 min for 100 min. When nociceptin (10 nM) was microinjected into the rostral ventrolateral medulla (rVLM), the pressor response induced by gastric distension was inhibited by 68 +/- 6%. Thirty minutes of EA also decreased the reflex response by 75 +/- 11%; microinjection of saline into the rVLM did not alter the inhibitory effect of EA. In contrast, microinjection of a nociceptin receptor antagonist into the rVLM promptly reversed the EA response. Pretreatment with the opioid receptor antagonist naloxone did not influence the EA-like inhibitory effect of nociceptin on the distension-induced pressor reflex (22 +/- 1 to 8 +/- 2 mmHg). Furthermore, a mu-opioid receptor agonist microinjected into the rVLM after microinjection of a nociceptin receptor antagonist during EA promptly reversed the nociceptin receptor antagonist-related inhibition of the EA effect. Thus, in addition to the classical opioid system, nociceptin, through opioid receptor-like-1 receptor stimulation in the rVLM, participates in the modulatory influence of EA on reflex-induced increases in blood pressure.

Effects of peptides, with emphasis on feeding, pain, and behavior A 5-year (1999-2003) review of publications in Peptides

Novel effects of naturally occurring peptides are continuing to be discovered, and their mechanisms of actions as well as interactions with other substances, organs, and systems have been elucidated. Synthetic analogs may have actions similar or antagonistic to the endogenous peptides, and both the native peptides and analogs have potential as drugs or drug targets. The journal Peptides publishes many leading articles on the structure-activity relationship of peptides as well as outstanding reviews on some families of peptides. Complementary to the reviews, here we extract information from the original papers published during the past five years in Peptides (1999-2003) to summarize the effects of different classes of peptides, their modulation by other chemicals and various pathophysiological states, and the mechanisms by which the effects are exerted. Special attention is given to peptides related to feeding, pain, and other behaviors. By presenting in condensed form the effects of peptides which are essential for systems biology, we hope that this summary of existing knowledge will encourage additional novel research to be presented in Peptides.

The relaxant effect of nociceptin on porcine coronary arterial ring segments

Nociceptin (NC), alias orphanin FQ, has been identified as the endogenous ligand of the opioid receptor-like 1 receptor (ORL1). The purpose of this study was to assess the effect of nociceptin on porcine coronary arteries and to investigate the mechanism of its action, if any. Rings of coronary arteries from porcine hearts were suspended in baths containing Krebs solution, and isometric tension was measured. The response to nociceptin (10(-1)2-10(-5) mol/L) was investigated in porcine coronary arterial rings and also in such rings contracted with prostaglandin F2alpha (PGF2alpha). The effects of endothelium, nitroxide (NO), methylene blue, cyclic GMP (cGMP), naloxone, [Nphe1]NC(1-13)NH2, and propranolol on nociceptin-induced relaxation were also assessed. Our study showed nociceptin relaxed the porcine coronary arterial rings and inhibited the vasocontractivity to PGF2alpha. The relaxing response of nociceptin in coronary arteries was significantly reduced by removal of endothelium and by the presence of L-NNA, cGMP, and [Nphe1]NC(1-13)NH2, the selective nociceptin receptor antagonist, but not by naloxone, the nonselestive opioid receptor blocker or propranolol, which blocks the adrenergic beta-receptor. Our results suggest that nociceptin induces relaxation of isolated coronary artery through NO, cGMP, and ORL1.

Involvement of sympathetic efferents but not capsaicin-sensitive afferents in nociceptin-mediated dual control of rat synovial blood flow

This study set out to examine the vasomotor effects of the opioid-like peptide nociceptin on knee joint capsular blood flow in urethane-anaesthetized rats. Topical application of nociceptin (10(-15)-10(-8) mol) caused a progressive fall in joint perfusion that was significantly inhibited by the specific nociceptin receptor antagonist [Phe(1)-(CH(2)-NH)-Gly(2)] Nociceptin(1-13)-NH(2) as well as the nonspecific opioid antagonist naloxone. To test whether this constrictor response was sympathetically mediated, we administered nociceptin in animals treated with guanethidine to produce sympathetic blockade or in the presence of the alpha-adrenoceptor antagonist phentolamine. Both guanethidine treatment and phentolamine coadministration attenuated the constrictor response to nociceptin. Inhibition of nociceptin-mediated vasoconstriction revealed a supplementary hyperemic response that persisted in animals whose knee joints were treated with 1% capsaicin to destroy the articular unmyelinated nerve supply. These results show that, in the rat knee, peripheral administration of nociceptin primarily causes a sympathetically mediated vasoconstriction. In addition, high-dose nociceptin produces a vasodilatatory response that is likely due to the direct action of nociceptin on vascular smooth muscle and not by a neurogenic mechanism.

Effect of nociceptin/orphanin FQ on venous tone in conscious rats

Nociceptin (orphanin FQ) is an endogenous agonist for the opioid receptor-like1 (ORL1) receptor. We investigated the effects of nociceptin on mean circulatory filling pressure, an index of venous tone. The effects of nociceptin (10, 30 nmol/kg, i.v.) and the vehicle (0.9% NaCl) on mean arterial pressure, heart rate and mean circulatory filling pressure were examined in two groups each of conscious rats: rats with, or without, ganglionic blockade through pretreatment with mecamylamine (1 mg/kg, i.v.) and noradrenaline (2 microg/kg min, i.v.). In the unblocked rats, both doses of nociceptin decreased mean arterial pressure and heart rate, and the high dose also decreased mean circulatory filling pressure. In the ganglionic-blocked rats, nociceptin did not alter heart rate but caused greater reductions of mean arterial pressure and mean circulatory filling pressure. The vehicle had no effects in any group. Therefore, nociceptin is a depressor agent with prominent direct venodilator and bradycardic action.

Regional hemodynamic effects of nociceptin/orphanin FQ in the anesthetized rat

This study examined the vasodilator action of nociceptin, an endogenous opioid receptor-like ligand (ORL1), in thiobutabarbital-anesthetized rats, via the triple-isotope microspheres technique. Nociceptin (10, 30 nmol/kg, left ventricular injection) reduced mean arterial pressure (-27, -29 mm Hg), total peripheral resistance (-36, -41% of baseline) and heart rate (-8, -11% of baseline), but did not significantly affect cardiac output. The vehicle (0.9% NaCl) did not alter hemodynamics. Both doses of nociceptin caused similar changes in arterial flow and conductance of all tissues. Nociceptin increased flows to the skeletal muscle, slightly reduced flows to the caecum and colon, but did not alter flows to other organs and tissues. With flow normalized by pressure to reflect intrinsic vascular tone, nociceptin was found to increase arterial conductance of all tissues, except for the intestine, spleen, caecum and colon. Its dilator influence was greater in the skeletal muscle ( approximately 250% of baseline conductance) than the lungs, heart, liver, stomach, kidneys, skin, testes and brain (140-160% of baseline). Thus, nociceptin causes generalized vasodilatation; its greatest influence is on the skeletal muscle bed.

Sympathoinhibitory action of nociceptin in the rat spinal cord

1. Whole-cell patch recordings were made from antidromically identified sympathetic preganglionic neurons (SPN) of immature rat spinal cord slices. Bath application of nociceptin (0.1-1 micromol/L) suppressed excitatory postsynaptic potentials (EPSP) and hyperpolarized a population of SPN; these effects were naloxone (1 micromol/L) insensitive. 2. Nociceptin suppressed the amplitude of EPSP without causing a concomitant change in glutamate-induced depolarizations, suggesting a presynaptic inhibitory action. 3. Analysis of current-voltage relationships showed that nociceptin hyperpolarized SPN by increasing an inwardly rectifying K+ current. 4. Intrathecal injection of nociceptin (3, 10 and 30 nmol) to urethane-anaesthetized rats dose-dependently reduced the mean arterial pressure and heart rate; these effects were not prevented by prior intravenous injection of naloxone (1 mg/kg). 5. Results from our in vitro and in vivo experiments suggest that nociceptin suppresses spinal sympathetic outflow either by attenuating excitatory synaptic responses or hyperpolarizing SPN.

Characterization of specific [3H]nociceptin binding in rat brain and spinal cord

The present study was undertaken to characterize simultaneously [3H]nociceptin binding to opioid receptor-like 1 (ORL1) receptors in the rat brain and spinal cord. Specific binding of [3H]nociceptin to crude membranes from the rat brain and spinal cord at 25 degrees C was saturable, reversible and of high affinity, and it also exhibited a pharmacological specificity involving the ORL1 receptor. The Kd and Bmax values for [3H]nociceptin in the spinal cord were significantly lower than those in the brain. At 4 degrees C, there was a significant increase in the dissociation constant (Kd) for [3H]nociceptin in the brain and spinal cord with little change in the maximal number of binding sites (Bmax) compared with that at 25 degrees C. Nociceptin and its analogue, [Phe1 psi(CH2-NH)-Gly2]nociceptin(1-13)NH2 were found to be potent inhibitors of [3H]nociceptin binding to crude membranes from the brain and spinal cord, while opioid ligands such as naloxone-benzoylhydrazone, naltrindole and nor-binaltorphimine, exhibited an inhibitory effect only at high concentrations. The Ki values for nociceptin, its analogue and opioid ligands in the spinal cord were significantly lower than those in the brain. There were regional variations in the specific [3H]nociceptin binding to crude membranes from the rat brain: a relatively high density of [3H]nociceptin binding in the cerebral cortex, hippocampus, thalamus and midbrain, moderately dense binding in the corpus striatum and pons/medulla oblongata, and the lowest density of binding in the cerebellum. In conclusion, the present study has shown that [3H]nociceptin binds selectively to ORL1 receptors in the rat brain and spinal cord.

Studies of the cardiovascular effects of nociceptin and related peptides

Nociceptin, a novel opioid peptide, and its ORL(1) receptor share structural similarities with other opioid ligands and receptors. Although NC exerts evident cardiovascular effects at a central and peripheral level, its role in homeostatic mechanisms and disease states are just beginning to be understood, as only recently selective receptor antagonists became available. In this review, some of the new observations regarding the cardiovascular actions of NC, related peptides and newly synthesized receptor antagonists are discussed.

Neurohumoral effects of orphanin FQ/nociceptin: relevance to cardiovascular and renal function

Orphanin FQ/Nociceptin (OFQ/N) is a peptide whose structure resembles that of the endogenous opioid peptides (endorphins). OFQ/N and its receptor are distributed in neural tissue and brain regions involved in the regulation of pituitary hormone release. Functional studies have shown that this peptide evokes a unique pattern of cardiovascular and renal excretory responses. This review will focus on the neural and humoral effects of OFQ/N and how this peptide may participate in the regulation of cardiovascular and renal function.

Pharmacology of nociceptin and its receptor: a novel therapeutic target

Nociceptin (NC), alias Orphanin FQ, has been recently identified as the endogenous ligand of the opioid receptor-like 1 receptor (OP(4)). This new NC/OP(4) receptor system belongs to the opioid family and has been characterized pharmacologically with functional and binding assays on native (mouse, rat, guinea-pig) and recombinant (human) receptors, by using specific and selective agonists (NC, NC(1 - 13)NH(2)) and a pure and competitive antagonist, [Nphe(1)]NC(1 - 13)NH(2). The similar order of potency of agonists and affinity values of the antagonist indicate that the same receptor is present in the four species. OP(4) is expressed in neurons, where it reduces activation of adenylyl cyclase and Ca(2+) channels while activating K(+) channels in a manner similar to opioids. In this way, OP(4) mediates inhibitory effects in the autonomic nervous system, but its activities in the central nervous system can be either similar or opposite to those of opioids. In vivo experiments have demonstrated that NC modulates a variety of biological functions ranging from nociception to food intake, from memory processes to cardiovascular and renal functions, from spontaneous locomotor activity to gastrointestinal motility, from anxiety to the control of neurotransmitter release at peripheral and central sites. These actions have been demonstrated using NC and various pharmacological tools, as antisense oligonucleotides targeting OP(4) or the peptide precursor genes, antibodies against NC, an OP(4) receptor selective antagonist and with data obtained from animals in which the receptor or the peptide precursor genes were knocked out. These new advances have contributed to better understanding of the pathophysiological role of the NC/OP(4) system, and ultimately will help to identify the therapeutic potential of new OP(4) receptor ligands.

Opiate modulating properties of nociceptin/orphanin FQ

The recently discovered peptide nociceptin/orphanin FQ (N/OFQ) and its receptor NOR share many structural similarities with the opioid peptides and their receptors. The anatomical distributions of N/OFQ and NOR are similar to those of opioid peptides and receptors. In addition, NOR and opiate receptors couple via the same G-proteins to similar effectors, such as Ca(2+) channels, K(+) channels, adenylyl cyclase, and several protein kinases. Thus, the behavioral effects of N/OFQ have been investigated in the context of known opiate effects, and a possible connection has been sought between the effects of these two homologous signaling systems. Originally characterized as a nociception-producing peptide, N/OFQ has now been shown to have diverse effects on nociception, as well as effects on many other behaviors. With regard to nociception, the peptide has been reported to produce hyperalgesia, reversal of opioid-mediated analgesia, analgesia, and allodynia. N/OFQ also has effects on other behaviors, such as locomotion, feeding, anxiety, spatial attention, reproductive behaviors, and opiate tolerance. The relationship between opiates and N/OFQ is strengthened by the fact that opiates also affect these behaviors. However, the exact nature of the relationship of N/OFQ with opiates-opiate-like versus antiopiate-remains controversial. This review will detail the diverse effects of N/OFQ and suggest that this peptide, like other putative antiopiate peptides, can be described as 'opiate modulating. '