Melanocortins counteract inflammatory and apoptotic responses to prolonged myocardial ischemia/reperfusion through a vagus nerve-mediated mechanism

A Review of Inflammatory Bowel Disease: A Model of Microbial, Immune and Neuropsychological Integration

Objective: Inflammatory bowel diseases (IBDs) are complex chronic inflammatory disorders of the gastro-intestinal (GI) tract with uncertain etiology. IBDs comprise two idiopathic disorders: Crohn’s disease (CD) and ulcerative colitis (UC). The aetiology, severity and progression of such disorders are still poorly understood but thought to be influenced by multiple factors (including genetic, environmental, immunological, physiological, psychological factors and gut microbiome) and their interactions. The overarching aim of this review is to evaluate the extent and nature of the interrelationship between these factors with the disease course. A broader conceptual and longitudinal framework of possible neuro-visceral integration, core microbiome analysis and immune modulation assessment may be useful in accurately documenting and characterizing the nature and temporal continuity of crosstalk between these factors and the role of their interaction (s) in IBD disease activity. Characterization of these interactions holds the promise of identifying novel diagnostic, interventions, and therapeutic strategies.

Material and Methods: A search of published literature was conducted by exploring PubMed, EMBASE, MEDLINE, Medline Plus, CDSR library databases. Following search terms relating to key question were set for the search included: “Inflammatory bowel diseases,” “gut microbiota,” “psychological distress and IBD,” “autonomic reactivity and IBD,” “immune modulation,” “chronic inflammation,” “gut inflammation,” “enteric nervous system,” “gut nervous system,” “Crohn’s disease,” “Ulcerative colitis”, “depression and IBD”, “anxiety and IBD”, “quality of life in IBD patients,” “relapse in IBDs,” “remission in IBDs,” “IBD disease activity,” “brain-gut-axis,” “microbial signature in IBD,” “validated questionnaires in IBD,” “IBD activity indices,” “IBD aetiology,” “IBDs and stress,” “epidemiology of IBDs”, “autonomic nervous system and gut inflammation”, “IBD and environment,” “genetics of IBDs,” “pathways of immune response in IBDs,” “sleep disturbances in IBD,” “hypothalamic-pituitary-adrenal axis (HPA),” “sympatho-adrenal axis,” “CNS and its control of gut function” “mucosal immune response,” “commensal and pathogenic bacteria in the gut,” “innate and adaptive immunity.” Studies evaluating any possible associations between gut microbiome, psychological state, immune modulation, and autonomic function with IBDs were identified. Commonly cited published literatures with high quality research methodology/results and additional articles from bibliographies of recovered papers were examined and included where relevant.

Results: Although there is a substantial literature identifying major contributing factors with IBD, there has been little attempt to integrate some factors over time and assess their interplay and relationship with IBD disease activity. Such contributing factors include genetic and environmental factors, gut microbiota composition and function, physiological factors, psychological state and gut immune response. Interdependences are evident across psychological and biological factors and IBD disease activity. Although from the available evidence, it is implausible that a single explanatory model could elucidate the interplay between such factors and the disease course as well as the sequence of the effect during the pathophysiology of IBD.

Conclusion: Longitudinal monitoring of IBD patients and integrating data related to the contributing/risk factors including psychological state, physiological conditions, inflammatory/immune modulations, and microbiome composition/function, could help to explain how major factors associate and interrelate leading to exacerbation of symptoms and disease activity. Identifying the temporal trajectory of biological and psychosocial disturbances may also help to assess their effects and interdependence on individuals’ disease status. Moreover, this allows greater insight into understanding the temporal progressions of subclinical events as potential ground for disease severity in IBD. Furthermore, understanding the interaction between these risk factors may help better interventions in controlling the disease, reducing the costs related to disease management, further implications for clinical practice and research approaches in addition to improving patients’ mental health and quality of life.

Chrysin rescues rat myocardium from ischemia-reperfusion injury via PPAR-γ/Nrf2 activation

Pharmacological strategies aimed at co-activating peroxisome proliferator-activated receptor-gamma (PPAR-γ)/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway have shown promising results in alleviating myocardial injury. The aim of the study was to evaluate the role of chrysin, a PPAR-γ agonist, in ischemia-reperfusion (IR)-induced myocardial infarction (MI) in rats and to explore the molecular mechanism driving this activity. To evaluate this hypothesis, chrysin (60 mg/kg, orally), PPAR-γ antagonist (GW9662, 1 mg/kg, intraperitoneally), or both were administered to rats for 28 days. On the 29th day, one-stage ligation of left anterior descending coronary artery for 45 min followed by 60 min of reperfusion was performed. Chrysin significantly decreased infarct size and improved cardiac functions following IR-induced MI. This improvement was corroborated by augmented PPAR-γ/Nrf2 expression as confirmed by immunohistochemistry and western blotting analysis. Chrysin exhibited strong anti-oxidant property as demonstrated by increased GSH and CAT levels and decreased 8-OHdG and TBARS levels. Our findings also imply that chrysin significantly inhibited inflammatory response as validated by decreased NF-κB, IKK-β, CRP, TNF-α and MPO levels. In addition, chrysin decreased TUNEL/DAPI positivity, a marker of apoptotic response and normalized cardiac injury markers. The histopathological and ultrastructural analysis further supported the functional and biochemical outcomes, showing preserved myocardial architecture. Intriguingly, co-administration with GW9662 significantly diminished the cardioprotective effect of chrysin as demonstrated by depressed myocardial function, decreased PPAR-γ/Nrf2 expression and increased oxidative stress. In conclusion, the present study demonstrates that co-activation of PPAR-γ/Nrf2 by chrysin may be crucial for its cardioprotective effect.

Activation of Melanocortin Receptors as a Potential Strategy to Reduce Local and Systemic Reactions Induced by Respiratory Viruses

The clinical hallmarks of infections caused by critical respiratory viruses consist of pneumonia, which can progress to acute lung injury (ALI), and systemic manifestations including hypercoagulopathy, vascular dysfunction, and endotheliitis. The disease outcome largely depends on the immune response produced by the host. The bio-molecular mechanisms underlying certain dire consequences of the infection partly arise from an aberrant production of inflammatory molecules, an event denoted as "cytokine storm". Therefore, in addition to antiviral therapies, molecules able to prevent the injury caused by cytokine excess are under investigation. In this perspective, taking advantage of melanocortin peptides and their receptors, components of an endogenous modulatory system that exerts marked anti-inflammatory and immunomodulatory influences, could be an effective therapeutic strategy to control disease evolution. Exploiting the melanocortin system using natural or synthetic ligands can form a realistic basis to counteract certain deleterious effects of respiratory virus infections. The central and peripheral protective actions exerted following melanocortin receptor activation could allow dampening the harmful events that trigger the cytokine storm and endothelial dysfunction while sustaining the beneficial signals required to elicit repair mechanisms. The long standing evidence for melanocortin safety encourages this approach.

Hype or hope: Vagus nerve stimulation against acute myocardial ischemia-reperfusion injury

Acute myocardial infarction (MI) is a major cause of death worldwide. Although timely and successful reperfusion could reduce myocardial ischemia injury, limit infarct size, and improve ventricular dysfunction and reduce acute mortality, restoring blood flow might also lead to unwanted myocardial ischemic-reperfusion (I/R) injury. Pre-clinical studies have demonstrated that multiple approaches are capable of attenuating the myocardial I/R injury. However, there is still no effective therapy for preventing myocardial I/R injury for the clinical setting. It is known that myocardial I/R injury could induce cardiac autonomic imbalance with over-activated sympathetic tone and reduced vagal activity, in turn, contributing to pathogenesis of myocardial I/R injury. Cumulative evidence shows that the enhancement of vagal activity, so called vagus nerve stimulation (VNS), is able to reduce injury and promote recovery of injured myocardium. Therefore, VNS might be a potentially novel strategy choice for preventing/attenuating myocardial I/R injury. In this review, we describe the protective role of VNS in myocardial I/R injury and related potential mechanisms. Then, we discuss the challenge and the opportunity of VNS in the treatment of acute myocardial I/R injury.

Fenoprofen-An Old Drug Rediscovered as a Biased Allosteric Enhancer for Melanocortin Receptors

It is time-consuming and costly to bring new drugs to market, making it necessary and urgent to exploit existing drugs for new uses. Recently, fenoprofen was demonstrated as an allosteric modulator at melanocortin receptors (MCRs), although the exact mode of action has not been clarified. MCRs regulate multiple functions, including pigmentation, adrenal steroidogenesis, inflammation, energy homeostasis, and exocrine gland secretion. In this study, we showed that fenoprofen failed to displace the orthosteric agonist Nle⁴-d-Phe⁷-α-melanocyte stimulating hormone from binding to MC3-5R while possessing positive allosteric modulator activities at these receptors. In addition, fenoprofen induced biased signaling at MC3-5R, as it selectively activated ERK1/2 cascade but not the canonical cAMP signaling. Notably, fenoprofen stimulated biased signaling at MC3-5R, but not at MC1R, hence acting selectively among this highly conserved family of receptors. Moreover, PAM activity and biased signaling induced by fenoprofen were observed not only at wild-type but also at naturally occurring mutant MC3Rs, suggesting that this biased allosteric enhancer action might constitute as novel therapeutic opportunity for obese patients harboring these mutations. Our study might guide novel therapeutic applications for repurposing current drugs or designing new drugs combining allosteric and biased properties.

The Role of the Vagus Nerve in Cancer Prognosis: A Systematic and a Comprehensive Review

This article reviews the role of the vagus nerve in tumor modulation and cancer prognosis. We present a systematic review of 12 epidemiological studies examining the relationship between heart rate variability, the main vagus nerve index, and prognosis in cancer patients (survival and tumor markers). These studies show that initially high vagal nerve activity predicts better cancer prognosis, and, in some studies, independent of confounders such as cancer stage and treatments. Since the design of the epidemiological studies is correlational, any causal relationship between heart rate variability and cancer prognosis cannot be inferred. However, various semi-experimental cohort studies in humans and experimental studies in animals have examined this causal relationship. The second part of this paper presents a comprehensive review including human and animal cohort and experimental studies showing that vagotomy accelerates tumor growth, while vagal nerve activation improves cancer prognosis. Based on all reviewed studies, it is concluded that the evidence supports a protective role of the vagus nerve in cancer and specifically in the metastatic stage.

Protein kinases are involved in the cardioprotective effects activated by platelet glycoprotein IIb/IIIa inhibitor tirofiban at reperfusion in rats in vivo

The thrombolytic effect of platelet glycoprotein IIb/IIIa inhibitors (GP IIb/IIIa inhibitors) in myocardial infarction has been well established. Nevertheless, data on the mechanism of the cardioprotective effect of GP IIb/IIIa inhibitors in ischemic-reperfusion injury (IR) are lacking. Sprague-Dawley rats received 120 min of coronary ischemia and 180 min of reperfusion. A GP IIb/IIIa inhibitor was given via continuous intravenous infusion at a rate of 2 μg/kg/min 30 min prior to reperfusion with/without inhibitors of PKCε (chelerythrine), PI3 kinase and Akt (wortmannin), p38 MAPK (SB203582), p42/44 MAPK (PD98059) and ERK1/2 (u0126) 15 min prior to the GP IIb/IIIa inhibitor. Protein isolation and analysis were performed by Western blot analysis. The cardioprotective effects were measured as the ratio of myocardial necrotic area to the area at risk (AAR) and the apoptotic index (AI) calculated as the percentage of myocytes positive for terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling of all myocytes stained by 4', 6-diamidino-2-phenylindole. The GP IIb/IIIa inhibitor reduced the ratio of myocardial necrotic area to AAR and AI, and also exerted an immediate cardioprotective effect by activating multiple signaling pathways including phosphorylation and activation of PKCε, PI3 kinase, Akt, p38 MAPK, p42/44 MAPK and ERK1/2. However, there were no significant increases in the phosphorylation of Raf and MEK1/2. We concluded that the GP IIb/IIIa inhibitor reduced the extent of cardiac IR and significantly ameliorate the apoptosis of myocytes in the rats. In addition, the cardioprotective effect was mediated through the activation of multiple signal transduction pathways.

Long Term Osmotic Mini Pump Treatment with Alpha-MSH Improves Myocardial Function in Zucker Diabetic Fatty Rats

The present investigation evaluates the cardiovascular effects of the anorexigenic mediator alpha-melanocyte stimulating hormone (MSH), in a rat model of type 2 diabetes. Osmotic mini pumps delivering MSH or vehicle, for 6 weeks, were surgically implanted in Zucker Diabetic Fatty (ZDF) rats. Serum parameters, blood pressure, and weight gain were monitored along with oral glucose tolerance (OGTT). Echocardiography was conducted and, following sacrifice, the effects of treatment on ischemia/reperfusion cardiac injury were assessed using the isolated working heart method. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity was measured to evaluate levels of oxidative stress, and force measurements were performed on isolated cardiomyocytes to determine calcium sensitivity, active tension and myofilament co-operation. Vascular status was also evaluated on isolated arterioles using a contractile force measurement setup. The echocardiographic parameters ejection fraction (EF), fractional shortening (FS), isovolumetric relaxation time (IVRT), mitral annular plane systolic excursion (MAPSE), and Tei-index were significantly better in the MSH-treated group compared to ZDF controls. Isolated working heart aortic and coronary flow was increased in treated rats, and higher Hill coefficient indicated better myofilament co-operation in the MSH-treated group. We conclude that MSH improves global heart functions in ZDF rats, but these effects are not related to the vascular status.

Old drugs with new skills: fenoprofen as an allosteric enhancer at melanocortin receptor 3

The efficiency of drug research and development has paradoxically declined over the last decades despite major scientific and technological advances, promoting new cost-effective strategies such as drug repositioning by systematic screening for new actions of known drugs. Here, we performed a screening for positive allosteric modulators (PAMs) at melanocortin (MC) receptors. The non-steroidal anti-inflammatory drug fenoprofen, but not the similar compound ibuprofen, presented PAM activity at MC₃, MC₄, and MC₅ receptors. In a model of inflammatory arthritis, fenoprofen afforded potent inhibition while ibuprofen was nearly inactive. Fenoprofen presented anti-arthritic actions on cartilage integrity and synovitis, effects markedly attenuated in Mc3r−/− mice. Fenoprofen displayed pro-resolving properties promoting macrophage phagocytosis and efferocytosis, independently of cyclooxygenase inhibition. In conclusion, combining repositioning with advances in G-protein coupled receptor biology (allosterism) may lead to potential new therapeutics. In addition, MC₃ PAMs emerged as a viable approach to the development of innovative therapeutics for joint diseases.

Vagal Modulation of the Inflammatory Response in Sepsis

The vagus nerve can sense peripheral inflammation and transmit action potentials from the periphery to the brainstem. Vagal afferent signaling is integrated in the brainstem, and efferent vagus nerves carry outbound signals that terminate in spleen and other organs. Stimulation of efferent vagus nerve leads to the release of acetylcholine in these organs. In turn, acetylcholine interacts with members of the nicotinic acetylcholine receptor (nAChR) family, particularly with the alpha7 nicotinic acetylcholine receptor (α7nAChR), which is expressed by macrophages and other cytokine-producing cells. Ultimately, the production of proinflammatory cytokines is markedly inhibited. This neuroimmune communication is termed "the inflammatory reflex". The uncontrolled inflammation as a result from sepsis can lead to multiple organ failure, and even death. Experimental data show that regulation of the inflammatory reflex appears to be a useful interventional strategy for septic response. Herein, we review recent advances in the understanding of the inflammatory reflex and discuss potential therapeutics that vagal modulation of the immune system for the treatment of severe sepsis and septic shock.

Anti-apoptotic effects of myocardin-related transcription factor-A on rat cardiomyocytes following hypoxia-induced injury

Myocardin-related transcription factor-A (MRTF-A) can transduce both biomechanical and humoral signals, which can positively modulate cardiac damage induced by acute myocardial infarction. However, the molecular mechanism that underlies the contribution that MRTF-A provides to the myocardium is not completely understood. The objective of this study was to investigate the effects of MRTF-A on myocardium apoptosis and its mechanisms. Our experiment results showed that MRTF-A expression increased and Bcl-2 expression reduced during myocardial ischemia–reperfusion in rat. Meanwhile, primary cardiomyocytes were pretreated with wild-type MRTF-A or siRNA of MRTF-A before exposure to hypoxia. We found that overexpression of MRTF-A in myocardial cells inhibited apoptosis and the release of cytochrome c. MRTF-A enhanced Bcl-2, which contributes to MRTF-A interaction with Bcl-2 in the nuclei of cardiomyocytes. MRTF-A upregulation expression of Bcl-2 in cardiomyocytes induced by hypoxia was inhibited by PD98059, an ERK1/2 inhibitor. In conclusions, MRTF-A improved myocardial cell survival in a cardiomyocyte model of hypoxia-induced injury; this effect was correlated with the upregulation of anti-apoptotic gene Bcl-2 through the activation of ERK1/2.

NDP-α-MSH attenuates heart and liver responses to myocardial reperfusion via the vagus nerve and JAK/ERK/STAT signaling

Melanocortin peptides afford cardioprotection during myocardial ischemia/reperfusion via janus kinases (JAK), extracellular signal-regulated kinases (ERK) and signal transducers/activators of transcription (STAT) pathways. Here we investigated whether melanocortin-induced modulation of the JAK/ERK/STAT signaling occurs via the cholinergic anti-inflammatory pathway, focusing our study on cardiac and hepatic responses to prolonged myocardial ischemia/reperfusion. Ischemia was produced in rats by ligature of the left anterior descending coronary artery for 30min; effects of ischemia/reperfusion were evaluated using Western blot of heart and liver proteins. Intravenous treatment, during coronary artery occlusion, with the melanocortin analog (Nle(4), D-Phe(7))α-melanocyte-stimulating hormone (NDP-α-MSH) induced a left ventricle up-regulation of the cardioprotective transcription factors pJAK2, pERK1/2 and pTyr-STAT3 (JAK-dependent), and a reduction in the levels of the inflammatory mediators tumor necrosis factor-α (TNF-α) and pJNK (a transcription factor also involved in apoptosis), as assessed at the end of the 2-h reperfusion period. Further, these beneficial effects of NDP-α-MSH were associated with heart over-expression of the pro-survival proteins heme oxygenase-1 (HO-1) and Bcl-XL, and decrease of ventricular arrhythmias and infarct size. In the liver NDP-α-MSH induced a decrease in the pJAK2 and pTyr-STAT3 levels, and strongly reduced pERK1/2 expression. In the liver of ischemic rats NDP-α-MSH also blunted pJNK activity and TNF-α expression, and up-regulated Bcl-XL. Bilateral cervical vagotomy prevented all effects of NDP-α-MSH, both in the heart and liver. These results indicate that melanocortins inhibit heart and liver damage triggered by prolonged myocardial ischemia/reperfusion likely, as main mechanism, via the vagus nerve-mediated modulation of the JAK/STAT/ERK signaling pathways.

Pinocembrin reduces cardiac arrhythmia and infarct size in rats subjected to acute myocardial ischemia/reperfusion

Oxidative stress plays an important role in the pathogenesis of ischemia/reperfusion (I/R) injury induced by cardiac dysfunction. Pinocembrin (5,7-dihydroxyflavanone) is a flavonoid found in propolis and in rhizomes of fingerroot (Boesenbergia pandurata) that is reported to have pharmacological properties including antimicrobial, antioxidant, and anti-inflammatory activities. The cardioprotective effects of pinocembrin in an I/R model were investigated in this study. Male Wistar rats (n = 20) were randomly divided into 2 groups to receive either pinocembrin (30 mg/kg body weight) or the vehicle intravenously. Thirty minutes later, the left anterior descending coronary artery of each rat was ligated for 30 min, and then reperfusion was allowed for 120 min. Cardiac function improved in the pinocembrin-treated group: the time to first ventricular fibrillation (VF) was significantly longer in the treated group (550 ± 54 s) than in the vehicle-only control group (330 ± 27 s) (p < 0.05). VF incidence and arrhythmia score were lower and infarcts were 49% smaller in the pinocembrin-treated group than in the control group (p < 0.05). In the pinocembrin-treated group, malondialdehyde levels and Bax/Bcl-2 ratios decreased, and the ratio of phosphorylated connexin 43 (phospho-Cx43) to total Cx43 increased in infarcted tissues compared with the non-infarcted area (p < 0.05). Pinocembrin exhibited cardioprotective effects during I/R, evidenced by improved cardiac function, fewer arrhythmias, and smaller infarcts in treated hearts than in controls. These benefits may be due to pinocembrin’s antiapoptotic and anti-oxidative stress effects and its ability to increase the phosphorylation of Cx43 in ischemic myocardium.

Melanocortin-4 receptor agonists alleviate intestinal dysfunction in secondary intra-abdominal hypertension rat model

BACKGROUND

Intra-abdominal hypertension (IAH) is a potentially life-threatening disease. Melanocortin-4 (MC4) receptor activation exhibits life-saving properties. The aim of the present study was to examine whether treatment with the MC4 receptor agonist RO27-3225 ameliorates intestinal injury in IAH rats.

METHODS

A total of 72 male Sprague-Dawley rats were randomized into six groups. Group 1 was the sham group. Group 2, the sham + RO group, received RO27-3225 (180 μg/kg, intraperitoneally). IAH was induced in group 3, the IAH group, by blood draw (mean arterial pressure = 30 mm Hg for 90 min) followed by shed blood and/or Ringer solution reinfusion. Intra-abdominal pressure was increased to 20 mm Hg by injecting air into the peritoneal cavity. Group 4, the RO group, was administered RO27-3225 at 5 min after blood draw. Groups 5 and 6 were the chlorisondamine (Chl) and HS024 groups, in which the rats were pretreated with the nicotinic acetylcholine receptor antagonist Chl or selective MC4 receptor antagonist (HS024), respectively, at 2 min before RO27-3225 was administered.

RESULTS

RO27-3225 restored mean arterial pressure, reduced tumor necrosis factor-α, and interleukin-1β messenger RNA expression increased by IAH, alleviated histologic damage, and improved superoxide dismutase activity in the intestine. Compared with the IAH group, the levels of intestinal fatty acid-binding protein, intestinal edema and intestinal permeability were lower in the RO group. Furthermore, the RO27-3225 treatment increased the expression of Rho-associated coiled-coil-containing protein kinase 1 and phosphorylated myosin light chain. Chl and HS024 abrogated the protective effects of RO27-3225.

CONCLUSIONS

These data indicate that the MC4 receptor agonist counteracts the intestinal inflammatory response, ameliorating intestinal injury in experimental secondary IAH by MC4 receptor-triggered activation of the cholinergic anti-inflammatory pathway. It may represent a promising strategy for the treatment of IAH in the future.

Protective effects of the melanocortin analog NDP-α-MSH in rats undergoing cardiac arrest

We previously reported that melanocortins afford cardioprotection in conditions of experimental myocardial ischemia/reperfusion, with involvement of the janus kinases (JAK), extracellular signal-regulated kinases (ERK) and signal transducers and activators of transcription (STAT) signalings. We investigated the influence of the melanocortin analog [Nle(4), D-Phe(7)]α-melanocyte-stimulating hormone (NDP-α-MSH) on short-term detrimental responses to cardiac arrest (CA) induced in rats by intravenous (i.v.) administration of potassium chloride, followed by cardiopulmonary resuscitation (CPR) plus epinephrine treatment. In CA/CPR rats i.v. treated with epinephrine (0.1 mg/kg) and returned to spontaneous circulation (48%) we recorded low values of mean arterial pressure (MAP) and heart rate (HR), alteration of hemogasanalysis parameters, left ventricle low expression of the cardioprotective transcription factors pJAK2 and pTyr-STAT3 (JAK-dependent), increased oxidative stress, up-regulation of the inflammatory mediators tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), and down-regulation of the anti-inflammatory cytokine IL-10, as assessed at 1h and 3h after CPR. On the other hand, i.v. treatment during CPR with epinephrine plus NDP-α-MSH (340 μg/kg) almost completely restored the basal conditions of MAP and HR, reversed metabolic acidosis, induced left ventricle up-regulation of pJAK2, pTyr-STAT3 and IL-10, attenuated oxidative stress, down-regulated TNF-α and IL-6 levels, and improved survival rate by 81%. CA/CPR plus epinephrine alone or in combination with NDP-α-MSH did not affect left ventricle pSer-STAT3 (ERK1/2-dependent) and pERK1/2 levels. These results indicate that melanocortins improve return to spontaneous circulation, reverse metabolic acidosis, and inhibit heart oxidative stress and inflammatory cascade triggered by CA/CPR, likely via activation of the JAK/STAT signaling pathway.

Atorvastatin protects against cerebral ischemia/reperfusion injury through anti-inflammatory and antioxidant effects

In addition to its lipid-lowering effect, atorvastatin exerts anti-inflammatory and antioxidant effects as well. In this study, we hypothesized that atorvastatin could protect against cerebral ischemia/reperfusion injury. The middle cerebral artery ischemia/reperfusion model was established, and atorvastatin, 6.5 mg/kg, was administered by gavage. We found that, after cerebral ischemia/reperfusion injury, levels of the inflammation-related factors E-selectin and myeloperoxidase were upregulated, the oxidative stress-related marker malondialdehyde was increased, and superoxide dismutase activity was decreased in the ischemic cerebral cortex. Atorvastatin pretreatment significantly inhibited these changes. Our findings indicate that atorvastatin protects against cerebral ischemia/reperfusion injury through anti-inflammatory and antioxidant effects.

Resolution of inflammation: examples of peptidergic players and pathways

Appreciation for the resolution of inflammation has increased in recent years, with the detailing of specific mediators and pathways and the identification of (receptor) targets that could be exploited for innovative anti-inflammatory drug discovery programmes. Thus, acute inflammation resolves by the intervention of endogenous anti-inflammatory mediators that reduce white blood cell recruitment and promote removal of migrated leukocytes by apoptosis and phagocytosis by resident 'cleaners', such as the macrophages, resulting ultimately in the repair of the inflamed or injured tissue. Here, we explore a selection of pro-resolving proteinaceous mediators and targets, such as melanocortins and galectins.

The anti-apoptotic and cardioprotective effects of salvianolic acid a on rat cardiomyocytes following ischemia/reperfusion by DUSP-mediated regulation of the ERK1/2/JNK pathway

The purpose of this study was to observe the effects of salvianolic acid A (SAA) pretreatment on the myocardium during ischemia/reperfusion (I/R) and to illuminate the interrelationships among dual specificity protein phosphatase (DUSP) 2/4/16, ERK1/2 and JNK pathways during myocardial I/R, with the ultimate goal of elucidating how SAA exerts cardioprotection against I/R injury (IRI). Wistar rats were divided into the following six groups: control group (CON), I/R group, SAA+I/R group, ERK1/2 inhibitor PD098059+I/R group (PD+I/R), PD+SAA+I/R group, and JNK inhibitor SP600125+I/R group (SP+I/R). The cardioprotective effects of SAA on the myocardium during I/R were investigated with a Langendorff device. Heart rate (HR), left ventricular systolic pressure (LVSP), left ventricular end-diastolic pressure (LVEDP), maximum rate of ventricular pressure rise and fall (±dp/dt_max), myocardial infarction areas (MIA), lactate dehydrogenase (LDH), and cardiomyocytes apoptosis were monitored. To determine the crosstalk betwee JNK and ERK1/2 via DUSP2/4/16 with SAA pretreatment, siRNA-DUSP2/4/16 were performed. The expression levels of Bcl-2, Bax, caspase 3, p-JNK, p-ERK1/2 and DUSP2/4/16 in cardiomyocytes were assayed by Western blot. Our results showed that LDH, MIA and cell apoptosis were decreased, and various parameters of heart function were improved by SAA pretreatment and SP application. In the I/R group, the expression levels of p-ERK1/2 and DUSP4/16 were not significantly different compared with the CON group, however, the protein expression levels of p-ERK1/2, Bcl-2 and DUSP4/16 were higher, while p-JNK, Bax, caspase 3 and DUSP2 levels were reduced among the SAA+I/R, PD+SAA+I/R and SP+I/R groups. The above indices were not significantly different between the SAA+I/R and SP+I/R groups. Compared with the SAA+I/R group, p-ERK1/2 was increased and p-JNK was decreased in the SAA+si-DUSP2+I/R, however, p-ERK was downregulated and p-JNK was upregulated in SAA+si-DUSP4+I/R group. SAA exerts an anti-apoptotic role against myocardial IRI by inhibiting DUSP2-mediated JNK dephosphorylation and activating DUSP4/16-mediated ERK1/2 phosphorylation.

NDP-MSH inhibits neutrophil migration through nicotinic and adrenergic receptors in experimental peritonitis

Melanocortin is a potent anti-inflammatory molecule. However, little is known about the effect of melanocortin on acute inflammatory processes such as neutrophil migration. In the present study, we investigated the ability of [Nle4, D-Phe7]-melanocyte-stimulating hormone (NDP-MSH), a semisynthetic melanocortin compound, in the inhibition of neutrophil migration in carrageenin-induced peritonitis model. Herein, subcutaneous pretreatment with NDP-MSH decreased neutrophil trafficking in the peritoneal cavity in a dose-dependent manner. NDP-MSH inhibited vascular leakage, leukocyte rolling, and adhesion and reduced peritoneal macrophage inflammatory protein 2, but not TNF-alpha, IL-1beta, IL-10, and keratinocyte-derived chemokine production. In addition, the effect on neutrophil migration was reverted by the pretreatment with both propranolol (a nonselective beta-adrenergic antagonist) and mecamylamine (a nonselective nicotinic antagonist) but not by splenectomy surgery. Moreover, NDP-MSH intracerebroventricular administration inhibited neutrophil migration, indicating participation of the central nervous system. Our results propose that the NDP-MSH effect may be due to a spleen-independent neuro-immune pathway that efficiently regulates excessive neutrophil recruitment to tissues.

The clinical importance of the anti-inflammatory vagovagal reflex

Excessive activation of the immune system is prevented by anti-inflammatory mediators such as corticosteroids and anti-inflammatory cytokines. Recently, it became clear that the brain not only senses peripheral inflammation through vagal afferent nerve fibers, but also provides an integrated response dampening the immune system through vagal efferents. This so-called anti-inflammatory pathway has been introduced as a third system by which the immune system is modulated. In sepsis, the anti-inflammatory effect is mediated by modulation of splenic macrophages, whereas in the gut, vagal nerve fibers synapse with enteric cholinergic neurons interacting with resident intestinal macrophages. In this chapter, the preclinical data underscoring the importance of this pathway are summarized, and its clinical significance is reviewed. Finally, the current data supporting its relevance to human disease and its therapeutic potential will be discussed. Insight in the mechanisms underlying these crucial properties will lead to better understanding of immune-mediated diseases and ultimately to improved anti-inflammatory therapies.

Postconditioning with vagal stimulation attenuates local and systemic inflammatory responses to myocardial ischemia reperfusion injury in rats

OBJECTIVE

To assess effects of postconditioning with the vagal stimulation (VS) on the local and systematic inflammatory responses to acute myocardial ischemia reperfusion injury (IRI).

METHODS

Sixty male Sprague-Dawley rats were randomly allocated into three groups: sham group, ischemia reperfusion group (IR group), and postconditioning with the VS group (POVS group). Serum levels of inflammatory cytokines during reperfusion and myocardial levels of inflammatory cytokines in both ischemic and non-ischemic regions at the end of the experiment were assayed. The infarct size was assessed by Evans blue and triphenyltetrazolium chloride staining.

RESULTS

The infarct size was significantly reduced in the POVS group compared to the IR group. Serum levels of TNF-α at 30, 60, and 120 min of reperfusion and serum levels of HMGB-1, ICAM-1, IL-1, and IL-6 at 120 min of reperfusion were significantly lower in the POVS group than in the IR group. Myocardial levels of TNF-α, HMGB-1, ICAM-1, IL-1, and IL-6 in both ischemic and non-ischemic regions were also significantly reduced in the POVS group compared with the IR group.

CONCLUSIONS

Postconditioning with the VS can significantly attenuate the local and systemic inflammatory responses to myocardial IRI, and provide an obvious cardioprotection.

Melanocortins as potential therapeutic agents in severe hypoxic conditions

Melanocortin peptides with the adrenocorticotropin/melanocyte-stimulating hormone (ACTH/MSH) sequences and synthetic analogs have protective and life-saving effects in experimental conditions of circulatory shock, myocardial ischemia, ischemic stroke, traumatic brain injury, respiratory arrest, renal ischemia, intestinal ischemia and testicular ischemia, as well as in experimental heart transplantation. Moreover, melanocortins improve functional recovery and stimulate neurogenesis in experimental models of cerebral ischemia. These beneficial effects of ACTH/MSH-like peptides are mostly mediated by brain melanocortin MC(3)/MC(4) receptors, whose activation triggers protective pathways that counteract the main ischemia/reperfusion-related mechanisms of damage. Induction of signaling pathways and other molecular regulators of neural stem/progenitor cell proliferation, differentiation and integration seems to be the key mechanism of neurogenesis stimulation. Synthesis of stable and highly selective agonists at MC(3) and MC(4) receptors could provide the potential for development of a new class of drugs for a novel approach to management of severe ischemic diseases.

Drug-induced activation of the nervous control of inflammation: a novel possibility for the treatment of hypoxic damage

Together with undernutrition and, on the opposite, overeating and obesity, sudden tissue hypoperfusion is the most important cause of mortality and disability worldwide. Tissue hypoperfusion/hypoxia rapidly triggers an unrestrained inflammatory cascade that is the main responsible for the severity of the eventual outcome. The brain plays a key role in inflammation, either through activation of the hypothalamic-pituitary-adrenal humoral response or through activation of the vagal "cholinergic anti-inflammatory pathway". Both humoral and nervous brain responses to inflammation are under the regulatory control of melanocortins, which have moreover a direct anti-inflammatory effect on inflammatory cells. Abundant experimental and clinical evidence indicates that MC(3)/MC(4) melanocortin receptor agonists and cholinergic receptor agonists (mainly at the α7-nicotinic subtype) should by now be considered as completely innovative, effective drugs for the treatment of hypoxic conditions; melanocortin agonists being practically devoid of harmful side effects.

Melanocortin MC₄ receptor agonists counteract late inflammatory and apoptotic responses and improve neuronal functionality after cerebral ischemia

Indirect evidence indicates that, in cerebral ischemia, melanocortins have neuroprotective effects likely mediated by MC₄ receptors. To gain direct insight into the role of melanocortin MC₄ receptors in ischemic stroke, we investigated the effects of a highly selective MC₄ receptor agonist. Gerbils were subjected to transient global cerebral ischemia by occluding both common carotid arteries for 10 min. In saline-treated stroke animals, an impairment in learning and memory occurred that, at day 11 after stroke, was associated with hippocampus up-regulation of tumor necrosis factor-α (TNF-α), BAX, activated extracellular signal-regulated kinases (ERK1/2), c-jun N-terminal kinases (JNK1/2) and caspase-3, down-regulation of Bcl-2, and neuronal loss. Treatment for 11days with the selective melanocortin MC₄ receptor agonist RO27-3225, as well as with the well known non-selective [Nle⁴,D-Phe⁷]α-melanocyte-stimulating hormone (NDP-α-MSH) as a reference non-selective melanocortin, counteracted the inflammatory and apoptotic responses, as indicated by the changes in TNF-α, BAX, ERK1/2, JNK1/2, caspase-3 and Bcl-2 protein expression. Furthermore, melanocortin treatment reduced neuronal loss and dose-dependently improved learning and memory. These positive effects were associated with overexpression of Zif268, an immediate early gene involved in injury repair, synaptic plasticity and memory formation. Pharmacological blockade of MC₄ receptors with the selective MC₄ receptor antagonist HS024 prevented all effects of RO27-3225 and NDP-α-MSH. These data give direct evidence that stimulation of MC₄ receptors affords neuroprotection and promotes functional recovery from stroke, by counteracting prolonged and/or recurrent inflammatory and apoptotic responses, and likely by triggering brain repair pathways.

Melanocortins protect against multiple organ dysfunction syndrome in mice

BACKGROUND AND PURPOSE

Melanocortins reverse circulatory shock and improve survival by counteracting the systemic inflammatory response, and through the activation of the vagus nerve-mediated cholinergic anti-inflammatory pathway. To gain insight into the potential therapeutic value of melanocortins against multiple organ damage following systemic inflammatory response, here we investigated the effects of the melanocortin analogue [Nle⁴ D-Phe⁷]α-MSH (NDP-α-MSH) in a widely used murine model of multiple organ dysfunction syndrome (MODS).

EXPERIMENTAL APPROACH

MODS was induced in mice by a single intraperitoneal injection of lipopolysaccharide followed, 6 days later (= day 0), by zymosan. After MODS or sham MODS induction, animals were randomized to receive intraperitoneally NDP-α-MSH (340 µg·kg⁻¹ day) or saline for up to 16 days. Additional groups of MODS mice were concomitantly treated with the melanocortin MC₄ receptor antagonist HS024, or the nicotinic acetylcholine receptor antagonist chlorisondamine, and NDP-α-MSH.

KEY RESULTS

At day 7, in the liver and lung NDP-α-MSH, significantly reduced mRNA expression of tumour necrosis factor-α (TNF-α), increased mRNA expression of interleukin-10 and improved the histological picture, as well as reduced TNF-α plasma levels; furthermore, NDP-α-MSH dose-dependently increased survival rate, as assessed throughout the 16 day observation period. HS024 and chlorisondamine prevented all the beneficial effects of NDP-α-MSH in MODS mice.

CONCLUSIONS AND IMPLICATIONS

These data indicate that NDP-α-MSH protects against experimental MODS by counteracting the systemic inflammatory response, probably through brain MC₄ receptor-triggered activation of the cholinergic anti-inflammatory pathway. These findings reveal previously undescribed effects of melanocortins and could have clinical relevance in the MODS setting.

The pulse of inflammation: heart rate variability, the cholinergic anti-inflammatory pathway and implications for therapy

Biological therapeutics targeting TNF, IL-1 and IL-6 are widely used for treatment of rheumatoid arthritis, inflammatory bowel disease and a growing list of other syndromes, often with remarkable success. Now advances in neuroscience have collided with this therapeutic approach, perhaps rendering possible the development of nerve stimulators to inhibit cytokines. Action potentials transmitted in the vagus nerve culminate in the release of acetylcholine that blocks cytokine production by cells expressing acetylcholine receptors. The molecular mechanism of this cholinergic anti-inflammatory pathway is attributable to signal transduction by the nicotinic alpha 7 acetylcholine receptor subunit, a regulator of the intracellular signals that control cytokine transcription and translation. Favourable preclinical data support the possibility that nerve stimulators may be added to the future therapeutic armamentarium, possibly replacing some drugs to inhibit cytokines.