Alpha7 cholinergic-agonist prevents systemic inflammation and improves survival during resuscitation

Post-Translational Modification of HMGB1 Disulfide Bonds in Stimulating and Inhibiting Inflammation

High mobility group box 1 protein (HMGB1), a highly conserved nuclear DNA-binding protein, is a “damage-associated molecular pattern” molecule (DAMP) implicated in both stimulating and inhibiting innate immunity. As reviewed here, HMGB1 is an oxidation-reduction sensitive DAMP bearing three cysteines, and the post-translational modification of these residues establishes its proinflammatory and anti-inflammatory activities by binding to different extracellular cell surface receptors. The redox-sensitive signaling mechanisms of HMGB1 also occupy an important niche in innate immunity because HMGB1 may carry other DAMPs and pathogen-associated molecular pattern molecules (PAMPs). HMGB1 with DAMP/PAMP cofactors bind to the receptor for advanced glycation end products (RAGE) which internalizes the HMGB1 complexes by endocytosis for incorporation in lysosomal compartments. Intra-lysosomal HMGB1 disrupts lysosomal membranes thereby releasing the HMGB1-transported molecules to stimulate cytosolic sensors that mediate inflammation. This HMGB1-DAMP/PAMP cofactor pathway slowed the development of HMGB1-binding antagonists for diagnostic or therapeutic use. However, recent discoveries that HMGB1 released from neurons mediates inflammation via the TLR4 receptor system, and that cancer cells express fully oxidized HMGB1 as an immunosuppressive mechanism, offer new paths to targeting HMGB1 for inflammation, pain, and cancer.

A critical review on marine serine protease and its inhibitors: A new wave of drugs?

Marine organisms are rich sources of enzymes and their inhibitors having enormous therapeutic potential. Among different proteolytic enzymes, serine proteases, which can be obtained from various marine organisms show a potential to biomedical application as thrombolytic agents. Although this type of proteases plays a crucial role in almost all biological processes, their uncontrolled activity often leads to several diseases. Accordingly, the actions of these types of proteases are regulated by serine protease inhibitors (SPIs). Marine SPIs control complement activation and various other physiological functions, such as inflammation, immune function, fibrinolysis, blood clotting, and cancer metastasis. This review highlights the potential use of serine proteases and their inhibitors as the new wave of promising drugs.

Neural Regulation of Interactions Between Group 2 Innate Lymphoid Cells and Pulmonary Immune Cells

Emerging evidence supports the involvement of nervous system in the regulation of immune responses. Group 2 innate lymphoid cells (ILC2), which function as a crucial bridge between innate and adaptive immunity, are present in large numbers in barrier tissues. Neuropeptides and neurotransmitters have been found to participate in the regulation of ILC2, adding a new dimension to neuroimmunity. However, a comprehensive and detailed overview of the mechanisms of neural regulation of ILC2, associated with previous findings and prospects for future research, is still lacking. In this review, we compile existing information that supports neurons as yet poorly understood regulators of ILC2 in the field of lung innate and adaptive immunity, focusing on neural regulation of the interaction between ILC2 and pulmonary immune cells.

Anatomical and clinical implications of vagal modulation of the spleen

The vagus nerve coordinates most physiologic functions including the cardiovascular and immune systems. This mechanism has significant clinical implications because electrical stimulation of the vagus nerve can control inflammation and organ injury in infectious and inflammatory disorders. The complex mechanisms that mediate vagal modulation of systemic inflammation are mainly regulated via the spleen. More specifically, vagal stimulation prevents organ injury and systemic inflammation by inhibiting the production of cytokines in the spleen. However, the neuronal regulation of the spleen is controversial suggesting that it can be mediated by either monosynaptic innervation of the splenic parenchyma or secondary neurons from the celiac ganglion depending on the experimental conditions. Recent physiologic and anatomic studies suggest that inflammation is regulated by neuro-immune multi-synaptic interactions between the vagus and the splanchnic nerves to modulate the spleen. Here, we review the current knowledge on these interactions, and discuss their experimental and clinical implications in infectious and inflammatory disorders.

Gut Inflammation in Association With Pathogenesis of Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease that is generally thought to be caused by multiple factors, including environmental and genetic factors. Emerging evidence suggests that intestinal disturbances, such as constipation, are common non-motor symptoms of PD. Gut inflammation may be closely associated with pathogenesis in PD. This review aims to discuss the cross-talk between gut inflammation and PD pathology initiation and progression. Firstly, we will highlight the studies demonstrating how gut inflammation is related to PD. Secondly, we will analyze how gut inflammation spreads from the gastro-intestine to the brain. Here, we will mainly discuss the neural pathway of pathologic α-syn and the systemic inflammatory routes. Thereafter, we will address how alterations in the brain subsequently lead to dopaminergic neuron degeneration, in which oxidative stress, glutamate excitotoxicity, T cell driven inflammation and cyclooxygenase-2 (COX-2) are involved. We conclude a model of PD triggered by gut inflammation, which provides a new angle to understand the mechanisms of the disease.

Central serotonin prevents hypotension and hypothermia and reduces plasma and spleen cytokine levels during systemic inflammation

An exceptionally high mortality rate is observed in sepsis and septic shock. Systemic administration of lipopolysaccharide (LPS) has been used as an experimental model for sepsis resulting in an exacerbated immune response, brain neurochemistry adjustments, hypotension, and hypothermia followed by fever. Central serotonergic pathways not only modulate systemic inflammation (SI) but also are affected by SI, including in the anteroventral region of the hypothalamus (AVPO), which is the hierarchically most important region for body temperature (Tb) control. In this study, we sought to determine if central serotonin (5-HT) plays a role in SI induced by intravenous administration of LPS (1.5 mg/kg) in male Wistar rats (280-350 g) by assessing 5-HT levels in the AVPO, mean arterial pressure, heart rate, and Tb up to 300 min after LPS administration, as well as assessing plasma and spleen cytokine levels, nitric oxide (NO) plasma levels, and prostaglandin (PG) E₂ levels in the AVPO at 75 min and 300 min after LPS administration. We observed reduced AVPO 5-HT levels, hypotension, tachycardia, hypothermia followed by fever, as well as observing increased plasma NO, plasma and spleen cytokines and AVPO PGE₂ levels in SI. Intracerebroventricular (icv) administration of 5-HT 30 min before LPS administration prevented hypotension and hypothermia, which were accompanied by reduced plasma NO, as well as plasma TNF-α, IL-1β, IL-6, and IL-10 and spleen TNF-α and IL-10 levels. We suggest that SI reduced 5-HT levels in the AVPO favor an increased pro-inflammatory status both centrally and peripherally that converge to hypotension and hypothermia. Moreover, our results are consistent with the notion that exogenous 5-HT given icv prevents hypotension and hypothermia probably activating the splenic anti-inflammatory pathway.

Glucose Activates Vagal Control of Hyperglycemia and Inflammation in Fasted Mice

Sepsis is a leading cause of death in hospitalized patients. Many experimental treatments may have failed in clinical trials for sepsis, in part, because they focused on immune responses of healthy animals that did not mimic the metabolic settings of septic patients. Epidemiological studies show an association between metabolic and immune alterations and over 1/3 of septic patients are diabetic, but the mechanism linking these systems is unknown. Here, we report that metabolic fasting increased systemic inflammation and worsened survival in experimental sepsis. Feeding and administration of glucose in fasted mice activated the vagal tone without affecting blood pressure. Vagal stimulation attenuated hyperglycemia and serum TNF levels in sham but only hyperglycemia in splenectomized mice. Vagal stimulation induced the production of dopamine from the adrenal glands. Experimental diabetes increased hyperglycemia and systemic inflammation in experimental sepsis. Fenoldopam, a specific dopaminergic type-1 agonist, attenuated hyperglycemia and systemic inflammation in diabetic endotoxemic mice. These results indicate that glucose activates vagal control of hyperglycemia and inflammation in fasted septic mice via dopamine.

Exercise activates vagal induction of dopamine and attenuates systemic inflammation

Physical exercise is one of the most important factors improving quality of life, but it is not feasible for patients with morbidity or limited mobility. Most previous studies focused on high-intensity or long-term exercise that causes metabolic stress or physiological adaption, respectively. Here, we studied how moderate-intensity swimming affects systemic inflammation in 6-8 week old C57BL/6J male mice during endotoxemia. One-hour swimming prevented hypokalemia, hypocalcemia, attenuated serum levels of inflammatory cytokines, increased anti-inflammatory cytokines but affected neither IL6 nor glycemia before or after the endotoxic challenge. Exercise attenuated serum TNF levels by inhibiting its production in the spleen through a mechanism mediated by the subdiaphragmatic vagus nerve but independent of the splenic nerve. Exercise increased serum levels of dopamine, and adrenalectomy prevented the potential of exercise to induce dopamine and to attenuate serum TNF levels. Dopaminergic agonist type-1, fenoldopam, inhibited TNF production in splenocytes. Conversely, dopaminergic antagonist type-1, butaclamol, attenuated exercise control of serum TNF levels. These results suggest that vagal induction of dopamine may contribute to the anti-inflammatory potential of physical exercise.

From neuroimunomodulation to bioelectronic treatment of rheumatoid arthritis

Neuronal stimulation is an emerging field in modern medicine to control organ function and reestablish physiological homeostasis during illness. The nervous system innervates most of the peripheral organs and provides a fine tune to control the immune system. Most of these studies have focused on vagus nerve stimulation and the physiological, cellular and molecular mechanisms regulating the immune system. Here, we review the new results revealing afferent vagal signaling pathways, immunomodulatory brain structures, spinal cord-dependent circuits, neural and non-neural cholinergic/catecholaminergic signals and their respective receptors contributing to neuromodulation of inflammation in rheumatoid arthritis. These new neuromodulatory networks and structures will allow the design of innovative bioelectronic or pharmacological approaches for safer and low-cost treatment of arthritis and related inflammatory disorders.

GTS-21 reduces microvascular permeability during experimental endotoxemia

INTRODUCTION

No effective pharmacological therapy is currently available to attenuate tissue edema formation due to increased microvascular permeability in sepsis. Cholinergic mediators have been demonstrated to exert anti-inflammatory effects via the α7 nicotinic acetylcholine receptor (α7nAChR) during inflammation. GTS-21, a partial α7nAChR agonist, is an appealing therapeutic substance for sepsis-induced microvascular inflammation due to its demonstrated cholinergic anti-inflammatory properties and its favorable safety profile in clinical trials. This study evaluated the effect of GTS-21 on microvascular permeability and leukocyte adhesion during experimental endotoxemia.

METHODS

Male Wistar rats (n=60) were anesthetized and prepared for intravital microscopy (IVM). Sevoflurane inhalation combined with propofol (10mg/kg) and fentanyl (5μg/kg) was used for anesthesia induction, followed by continuous intravenous anesthesia with propofol (10-40mg/kg/h) and fentanyl (10μg/kg/h). The rat mesentery was prepared for evaluation of macromolecular leakage, leukocyte adhesion and venular wall shear rate in postcapillary venules using IVM. Following baseline IVM recording, GTS-21 (1mg/kg) was applied simultaneously with, 1h prior to and 1h after administration of lipopolysaccharide (LPS, 5mg/kg). Test substances (crystalloid solution, LPS, GTS-21) were administered as volume equivalent intravenous infusions over 5min in the respective treatment groups. The consecutive IVMs were performed at 60, 120 and 180min after the baseline IVM. The systemic inflammatory response was evaluated by measuring TNF-α levels after the 180min IVM.

RESULTS

Microvascular permeability was significantly reduced in animals treated with GTS-21 simultaneously and 1h after induction of endotoxemia. Leukocyte adhesion, venular wall shear rate and TNF-α levels were not affected by GTS-21 treatment compared to the untreated endotoxemic animals.

CONCLUSION

GTS-21 has a protective effect on microvascular barrier function during endotoxemia. Considering its anti-inflammatory efficacy and safety profile, its clinical use might prove beneficial for the treatment of capillary leakage in sepsis therapy.

Neuroanatomy and Physiology of Brain Dysfunction in Sepsis

Sepsis-associated encephalopathy (SAE), a complication of sepsis, is often complicated by acute and long-term brain dysfunction. SAE is associated with electroencephalogram pattern changes and abnormal neuroimaging findings. The major processes involved are neuroinflammation, circulatory dysfunction, and excitotoxicity. Neuroinflammation and microcirculatory alterations are diffuse, whereas excitotoxicity might occur in more specific structures involved in the response to stress and the control of vital functions. A dysfunction of the brainstem, amygdala, and hippocampus might account for the increased mortality, psychological disorders, and cognitive impairment. This review summarizes clinical and paraclinical features of SAE and describes its mechanisms at cellular and structural levels.

Neural Control of Inflammation: Implications for Perioperative and Critical Care

Inflammation and immunity are regulated by neural reflexes. Recent basic science research has demonstrated that a neural reflex, termed the inflammatory reflex, modulates systemic and regional inflammation in a multiplicity of clinical conditions encountered in perioperative medicine and critical care. In this review, the authors describe the anatomic and physiologic basis of the inflammatory reflex and review the evidence implicating this pathway in the modulation of sepsis, ventilator-induced lung injury, postoperative cognitive dysfunction, myocardial ischemia-reperfusion injury, and traumatic hemorrhage. The authors conclude with a discussion of how these new insights might spawn novel therapeutic strategies for the treatment of inflammatory diseases in the context of perioperative and critical care medicine.

MicroRNA-205‑5b inhibits HMGB1 expression in LPS-induced sepsis

Inflammatory cytokines belonging to high mobility group box (HMGB)1 play a key role in sepsis through yet unknown mechanisms. The inflammatory response is modulated by microRNAs (miRNAs or miRs) at multiple levels and is poorly understood. In this study, the regulation of HMGB1 by miRNAs was evaluated using 3-(2,4-dimethoxybenzylidene)anabaseine (GTS-21) to activate the cholinergic anti-inflammatory pathway (CAP) and decrease HMGB1 expression in RAW264.7 cells. Microarray-based miRNA expression profiling of RAW264.7 cells was used to screen target miRNAs through genetic screening, GO analysis and hierarchical clustering. The expression of miRNA targets in the serum, colon, spleen, livers and lungs of BALB/c mice was quantified by RT-qPCR. Serum protein levels were quantified by ELISA. Western blot analysis and RT-qPCR were used for verification in vitro. Using miRNA array analysis, we screened 3 miRNAs (miR‑205‑5b, miR‑196a and miR‑193b). Animal experiments with miR‑205‑5b indicated its high degree of expression in the serum, colon, spleen, liver and lungs following the downregulation of HMGB1 in the tissues. RAW264.7 cells transfected with miR‑205‑5b mimics downregulated HMGB1 protein expression, suggesting translational regulation. HMGB1 expression negatively correlated with miR‑205‑5b expression in LPS-induced sepsis. By contrast, HMGB1 expression in LPS-stimulated RAW264.7 cells was increased following transfection with miR‑205‑5b inhibitor. miR‑205‑5b is a critical mediator of cholinergic anti-inflammatory activity in late sepsis. The upregulation of miR‑205‑5b as a potential therapeutic target for the treatment of inflammatory diseases is a possible novel therapeutic strategy against late sepsis. The mechanisms involved include the by post-transcriptional suppression of HMGB1 in cells and tissues.

Attenuation of Collagen-Induced Arthritis in rat by nicotinic alpha7 receptor partial agonist GTS-21

This research was performed to observe the effect of GTS-21 on Collagen Induced Arthritis (CIA). CIA model was used and after the onset of arthritis, the rats were divided into three groups based on their clinical symptoms score. Two groups were intraperitoneally (IP) injected daily with GTS-21 (1 mg/kg, 2.5 mg/kg) for a week, whereas phosphate buffered saline (PBS) was used for the control group. Cytokine titers, radiological, and histological examinations were performed at different time points after treatment with GTS-21. Compared with those of the control, the levels of TNF-α, IL-1, and IL-6 in the serum were significantly reduced after GTS-21 management. In addition, radiological results show that bone degradation was inhibited as well. Moreover, the hematoxylin and eosin (H&E) staining indicated that the histological score was significantly alleviated in the therapeutic group. Tartrate-resistant acid phosphatase (TRAP) stain-positive cells were also detected in the destruction of the articular cartilage, which was significantly reduced compared with the control group. This study provides the first evidence on the effect of GTS-21 as a potential treatment for RA.

Dopamine mediates vagal modulation of the immune system by electroacupuncture

Previous anti-inflammatory strategies against sepsis, a leading cause of death in hospitals, had limited efficacy in clinical trials, in part because they targeted single cytokines and the experimental models failed to mimic clinical settings. Neuronal networks represent physiological mechanisms, selected by evolution to control inflammation, that can be exploited for the treatment of inflammatory and infectious disorders. Here, we report that sciatic nerve activation with electroacupuncture controls systemic inflammation and rescues mice from polymicrobial peritonitis. Electroacupuncture at the sciatic nerve controls systemic inflammation by inducing vagal activation of aromatic L-amino acid decarboxylase, leading to the production of dopamine in the adrenal medulla. Experimental models with adrenolectomized mice mimic clinical adrenal insufficiency, increase the susceptibility to sepsis and prevent the anti-inflammatory effects of electroacupuncture. Dopamine inhibits cytokine production via dopamine type 1 (D1) receptors. D1 receptor agonists suppress systemic inflammation and rescue mice with adrenal insufficiency from polymicrobial peritonitis. Our results suggest a new anti-inflammatory mechanism mediated by the sciatic and vagus nerves that modulates the production of catecholamines in the adrenal glands. From a pharmacological perspective, the effects of selective dopamine agonists mimic the anti-inflammatory effects of electroacupuncture and can provide therapeutic advantages to control inflammation in infectious and inflammatory disorders.

Identification of pharmacological modulators of HMGB1-induced inflammatory response by cell-based screening

High mobility group box 1 (HMGB1), a highly conserved, ubiquitous protein, is released into the circulation during sterile inflammation (e.g. arthritis, trauma) and circulatory shock. It participates in the pathogenesis of delayed inflammatory responses and organ dysfunction. While several molecules have been identified that modulate the release of HMGB1, less attention has been paid to identify pharmacological inhibitors of the downstream inflammatory processes elicited by HMGB1 (C23-C45 disulfide C106 thiol form). In the current study, a cell-based medium-throughput screening of a 5000+ compound focused library of clinical drugs and drug-like compounds was performed in murine RAW264.7 macrophages, in order to identify modulators of HMGB1-induced tumor-necrosis factor alpha (TNFα) production. Clinically used drugs that suppressed HMGB1-induced TNFα production included glucocorticoids, beta agonists, and the anti-HIV compound indinavir. A re-screen of the NIH clinical compound library identified beta-agonists and various intracellular cAMP enhancers as compounds that potentiate the inhibitory effect of glucocorticoids on HMGB1-induced TNFα production. The molecular pathways involved in this synergistic anti-inflammatory effect are related, at least in part, to inhibition of TNFα mRNA synthesis via a synergistic suppression of ERK/IκB activation. Inhibition of TNFα production by prednisolone+salbutamol pretreatment was also confirmed in vivo in mice subjected to HMGB1 injection; this effect was more pronounced than the effect of either of the agents administered separately. The current study unveils several drug-like modulators of HMGB1-mediated inflammatory responses and offers pharmacological directions for the therapeutic suppression of inflammatory responses in HMGB1-dependent diseases.

Parasympathetic stimulation via the vagus nerve prevents systemic organ dysfunction by abrogating gut injury and lymph toxicity in trauma and hemorrhagic shock

We tested if vagus nerve stimulation (VNS) would prevent gut injury, mesenteric lymph toxicity, and systemic multiple organ dysfunction syndrome following trauma-hemorrhagic shock (T/HS). Four groups of experiments were performed. The first tested whether VNS (5 V for 10 min) would protect against T/HS-induced increases in gut and lung permeability as well as neutrophil priming. In the second experiment, mesenteric lymph was collected from rats subjected to T/HS or trauma-sham shock with or without VNS and then injected into naive mice to assess its biologic activity. Lung permeability, neutrophil priming, and red blood cell deformability were measured. Next, the role of the spleen in VNS-mediated protection was tested by measuring gut and lung injury in splenectomized rats subjected to sham or actual VNS. Lastly, the ability of nicotine to replicate the gut-protective effect of VNS was tested. Vagus nerve stimulation protected against T/HS-induced gut injury, lung injury, and neutrophil priming (P < 0.05). Not only did VNS limit organ injury after T/HS, but in contrast to the mesenteric lymph collected from the sham-VNS T/HS rats, the mesenteric lymph from the VNS T/HS rats did not cause lung injury, neutrophil priming, or loss of red blood cell deformability (P < 0.05) when injected into naive mice. Removal of the spleen did not prevent the protective effects of VNS on gut or lung injury after T/HS. Similar to VNS, the administration of nicotine also protected the gut from injury after T/HS. Vagus nerve stimulation prevents T/HS-induced gut injury, lung injury, neutrophil priming, and the production of biologically active mesenteric lymph. This protective effect of VNS was not dependent on the spleen but appeared to involve a cholinergic nicotinic receptor, because its beneficial effects could be replicated with nicotine.

Electrical vagus nerve stimulation attenuates systemic inflammation and improves survival in a rat heatstroke model

This study was performed to gain insights into novel therapeutic approaches for the treatment of heatstroke. The central nervous system regulates peripheral immune responses via the vagus nerve, the primary neural component of the cholinergic anti-inflammatory pathway. Electrical vagus nerve stimulation (VNS) reportedly suppresses pro-inflammatory cytokine release in several models of inflammatory disease. Here, we evaluated whether electrical VNS attenuates severe heatstroke, which induces a systemic inflammatory response. Anesthetized rats were subjected to heat stress (41.5°C for 30 minutes) with/without electrical VNS. In the VNS-treated group, the cervical vagus nerve was stimulated with constant voltage (10 V, 2 ms, 5 Hz) for 20 minutes immediately after completion of heat stress. Sham-operated animals underwent the same procedure without stimulation under a normothermic condition. Seven-day mortality improved significantly in the VNS-treated group versus control group. Electrical VNS significantly suppressed induction of pro-inflammatory cytokines such as tumor necrosis factor-α and interleukin-6 in the serum 6 hours after heat stress. Simultaneously, the increase of soluble thrombomodulin and E-selectin following heat stress was also suppressed by VNS treatment, suggesting its protective effect on endothelium. Immunohistochemical analysis using tissue preparations obtained 6 hours after heat stress revealed that VNS treatment attenuated infiltration of inflammatory (CD11b-positive) cells in lung and spleen. Interestingly, most cells with increased CD11b positivity in response to heat stress did not express α7 nicotinic acetylcholine receptor in the spleen. These data indicate that electrical VNS modulated cholinergic anti-inflammatory pathway abnormalities induced by heat stress, and this protective effect was associated with improved mortality. These findings may provide a novel therapeutic strategy to combat severe heatstroke in the critical care setting.

Vagal nerve stimulation modulates gut injury and lung permeability in trauma-hemorrhagic shock

BACKGROUND

Hemorrhagic shock is known to disrupt the gut barrier leading to end-organ dysfunction. The vagus nerve can inhibit detrimental immune responses that contribute to organ damage in hemorrhagic shock. Therefore, we explored whether stimulation of the vagus nerve can protect the gut and recover lung permeability in trauma-hemorrhagic shock (THS).

METHODS

Male Sprague-Dawley rats were subjected to left cervical vagus nerve stimulation at 5 V for 10 minutes. The right internal jugular and femoral artery were cannulated for blood withdrawal and blood pressure monitoring, respectively. Animals were then subjected to hemorrhagic shock to a mean arterial pressure between 30 mm Hg and 35 mm Hg for 90 minutes then reperfused with their own whole blood. After observation for 3 hours, gut permeability was assessed with fluorescein dextran 4 in vivo injections in a ligated portion of distal ileum followed by Evans blue dye injection to assess lung permeability. Pulmonary myeloperoxidase levels were measured and compared.

RESULTS

Vagal nerve stimulation abrogated THS-induced lung injury (mean [SD], 8.46 [0.36] vs. 4.87 [0.78]; p < 0.05) and neutrophil sequestration (19.39 [1.01] vs. 12.83 [1.16]; p < 0.05). Likewise, THS gut permeability was reduced to sham levels.

CONCLUSION

Neuromodulation decreases injury in the THS model as evidenced by decreased gut permeability as well as decreased lung permeability and pulmonary neutrophil sequestration in a rat model.

Restoring the balance of the autonomic nervous system as an innovative approach to the treatment of rheumatoid arthritis

The immunomodulatory effect of the autonomic nervous system has raised considerable interest over the last decades. Studying the influence on the immune system and the role in inflammation of the sympathetic as well as the parasympathetic nervous system not only will increase our understanding of the mechanism of disease, but also could lead to the identification of potential new therapeutic targets for chronic immune-mediated inflammatory diseases, such as rheumatoid arthritis (RA). An imbalanced autonomic nervous system, with a reduced parasympathetic and increased sympathetic tone, has been a consistent finding in RA patients. Studies in animal models of arthritis have shown that influencing the sympathetic (via α- and β-adrenergic receptors) and the parasympathetic (via the nicotinic acetylcholine receptor α7nAChR or by electrically stimulating the vagus nerve) nervous system can have a beneficial effect on inflammation markers and arthritis. The immunosuppressive effect of the parasympathetic nervous system appears less ambiguous than the immunomodulatory effect of the sympathetic nervous system, where activation can lead to increased or decreased inflammation depending on timing, doses and kind of adrenergic agent used. In this review we will discuss the current knowledge of the role of both the sympathetic (SNS) and parasympathetic nervous system (PNS) in inflammation with a special focus on the role in RA. In addition, potential antirheumatic strategies that could be developed by targeting these autonomic pathways are discussed.

β2-Adrenoreceptors of regulatory lymphocytes are essential for vagal neuromodulation of the innate immune system

The nervous system is classically organized into sympathetic and parasympathetic systems acting in opposition to maintain physiological homeostasis. Here, we report that both systems converge in the activation of β2-adrenoceptors of splenic regulatory lymphocytes to control systemic inflammation. Vagus nerve stimulation fails to control serum TNF levels in either β2-knockout or lymphocyte-deficient nude mice. Unlike typical suppressor CD25(+) cells, the transfer of CD4(+)CD25(-) regulatory lymphocytes reestablishes the anti-inflammatory potential of the vagus nerve and β2-agonists to control inflammation in both β2-knockout and nude mice. β2-Agonists inhibit cytokine production in splenocytes (IC(50)≈ 1 μM) and prevent systemic inflammation in wild-type but not in β2-knockout mice. β2-Agonists rescue wild-type mice from established polymicrobial peritonitis in a clinically relevant time frame. Regulatory lymphocytes reestablish the anti-inflammatory potential of β2-agonists to control systemic inflammation, organ damage, and lethal endotoxic shock in β2-knockout mice. These results indicate that β2-adrenoceptors in regulatory lymphocytes are critical for the anti-inflammatory potential of the parasympathetic vagus nerve, and they represent a potential pharmacological target for sepsis.

Cholinergic regulatory lymphocytes re-establish neuromodulation of innate immune responses in sepsis

Many anti-inflammatory strategies that are successful in treating sepsis in healthy animals fail in clinical trials, in part because sepsis normally involves immunocompromised patients, and massive lymphocyte apoptosis prevents immunomodulation. In this article, we report a new set of regulatory lymphocytes that are able to re-establish the cholinergic anti-inflammatory modulation and to provide therapeutic advantages in sepsis. The vagus nerve controls inflammation in healthy, but not in septic, mice. Likewise, vagus nerve and cholinergic agonists fail to control inflammation in splenectomized and nude animals. Unlike typical suppressor CD25(+) cells, CD4(+)CD25(-) lymphocytes re-establish the anti-inflammatory potential of the vagus nerve and cholinergic agonists in immunocompromised and septic animals. These cholinergic lymphocytes re-establish splenic protection and the potential of cholinergic agonists to rescue immunocompromised animals from established sepsis. The study results revealed these new regulatory lymphocytes as, to our knowledge, the first known physiological target for neuromodulation of the innate immune responses and a potential therapeutic target for sepsis.

HMGB1 is a therapeutic target for sterile inflammation and infection

A key question in immunology concerns how sterile injury activates innate immunity to mediate damaging inflammation in the absence of foreign invaders. The discovery that HMGB1, a ubiquitous nuclear protein, mediates the activation of innate immune responses led directly to the understanding that HMGB1 plays a critical role at the intersection of the host inflammatory response to sterile and infectious threat. HMGB1 is actively released by stimulation of the innate immune system with exogenous pathogen-derived molecules and is passively released by ischemia or cell injury in the absence of invasion. Established molecular mechanisms of HMGB1 binding and signaling through TLR4 reveal signaling pathways that mediate cytokine release and tissue damage. Experimental strategies that selectively target HMGB1 and TLR4 effectively reverse and prevent activation of innate immunity and significantly attenuate damage in diverse models of sterile and infection-induced threat.

Acetylcholine inhibits hypoxia-induced tumor necrosis factor-α production via regulation of MAPKs phosphorylation in cardiomyocytes

Recent findings have reported that up-regulation of tumor necrosis factor-alpha (TNF-α) induced by myocardial hypoxia aggravates cardiomyocyte injury. Acetylcholine (ACh), the principle vagal neurotransmitter, protects cardiomyocytes against hypoxia by inhibiting apoptosis. However, it is still unclear whether ACh regulates TNF-α production in cardiomyocytes after hypoxia. The concentration of extracellular TNF-α was increased in a time-dependent manner during hypoxia. Furthermore, ACh treatment also inhibited hypoxia-induced TNF-α mRNA and protein expression, caspase-3 activation, cell death and the production of reactive oxygen species (ROS) in cardiomyocytes. ACh treatment prevented the hypoxia-induced increase in p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK) phosphorylation, and increased extracellular signal-regulated kinase (ERK) phosphorylation. Co-treatment with atropine, a non-selective muscarinic acetylcholine receptor antagonist, or methoctramine, a selective type-2 muscarinic acetylcholine (M(2) ) receptor antagonist, abrogated the effects of ACh treatment in hypoxic cardiomyocytes. Co-treatment with hexamethonium, a non-selective nicotinic receptor antagonist, and methyllycaconitine, a selective alpha7-nicotinic acetylcholine receptor antagonist, had no effect on ACh-treated hypoxic cardiomyocytes. In conclusion, these results demonstrate that ACh activates the M(2) receptor, leading to regulation of MAPKs phosphorylation and, subsequently, down-regulation of TNF-α production. We have identified a novel pathway by which ACh mediates cardioprotection against hypoxic injury in cardiomyocytes.

α7-cholinergic receptor mediates vagal induction of splenic norepinephrine

Classically, sympathetic and parasympathetic systems act in opposition to maintain the physiological homeostasis. In this article, we report that both systems work together to restrain systemic inflammation in life-threatening conditions such as sepsis. This study indicates that vagus nerve and cholinergic agonists activate the sympathetic noradrenergic splenic nerve to control systemic inflammation. Unlike adrenalectomy, splenectomy and splenic neurectomy prevent the anti-inflammatory potential of both the vagus nerve and cholinergic agonists, and abrogate their potential to induce splenic and plasma norepinephrine. Splenic nerve stimulation mimics vagal and cholinergic induction of norepinephrine and re-establishes neuromodulation in α7 nicotinic acetylcholine receptor (α7nAChR)-deficient animals. Thus, vagus nerve and cholinergic agonists inhibit systemic inflammation by activating the noradrenergic splenic nerve via the α7nAChR nicotinic receptors. α7nAChR represents a unique molecular link between the parasympathetic and sympathetic system to control inflammation.

Neural pathways in allergic inflammation

Allergy is on the rise worldwide. Asthma, food allergy, dermatitis, and systemic anaphylaxis are amongst the most common allergic diseases. The association between allergy and altered behavior patterns has long been recognized. The molecular and cellular pathways in the bidirectional interactions of nervous and immune systems are now starting to be elucidated. In this paper, we outline the consequences of allergic diseases, especially food allergy and asthma, on behavior and neural activity and on the neural modulation of allergic responses.

Ethyl pyruvate prevents inflammatory responses and organ damage during resuscitation in porcine hemorrhage

Hemorrhage remains a common cause of death despite the recent advances in critical care, in part because conventional resuscitation fluids fail to prevent lethal inflammatory responses. Here, we analyzed whether ethyl pyruvate can provide a therapeutic anti-inflammatory potential to resuscitation fluids and prevent organ damage in porcine hemorrhage. Adult male Yorkshire swine underwent lethal hemorrhage with trauma and received no resuscitation treatment or resuscitation with Hextend alone, or supplemented with ethyl pyruvate. Resuscitation with ethyl pyruvate did not improve early hemodynamics but prevented hyperglycemia, the intrinsic coagulation pathway, serum aspartate aminotransferase, and myeloperoxidase in the major organs. Resuscitation with ethyl pyruvate provided an anti-inflammatory potential to restrain serum TNF and high-mobility group B protein 1 levels. Ethyl pyruvate inhibited nuclear factor [kappa]B in the spleen but not in the other major organs. In contrast, ethyl pyruvate inhibited NO in all the major organs, and it also inhibited TNF production in the major organs but in the lung and heart. The most significant effects were found in the terminal ileum where ethyl pyruvate inhibited cytokine production, restrained myeloperoxidase activity, preserved the intestinal epithelium, and prevented the systemic distribution of bacterial endotoxin. Ethyl pyruvate can provide therapeutic anti-inflammatory benefits to modulate splenic nuclear factor [kappa]B, restrain inflammatory responses, and prevent hyperglycemia, the intrinsic coagulation pathway, and organ injury in porcine hemorrhage without trauma.

Novel insights for systemic inflammation in sepsis and hemorrhage

The inflammatory responses in sepsis and hemorrhage remain a major cause of death. Clinically, it is generally accepted that shock in sepsis or hemorrhage differs in its mechanisms. However, the recognition of inflammatory cytokines as a common lethal pathway has become consent. Proinflammatory cytokines such as tumor necrosis factor (TNF) or high-mobility group box1 (HMGB1) are fanatically released and cause lethal multiorgan dysfunction. Inhibition of these cytokines can prevent the inflammatory responses and organ damage. In seeking potential anti-inflammatory strategies, we reported that ethyl pyruvate and alpha7 nicotinic acetylcholine receptor (alpha7nAChR) agonists effectively restrained cytokine production to provide therapeutic benefits in both experimental sepsis and hemorrhage. Here, we review the inflammatory responses and the anti-inflammatory strategies in experimental models of sepsis and hemorrhage, as they may have a consistent inflammatory pathway in spite of their different pathophysiological processes.

Survival and inflammatory responses in experimental models of hemorrhage

BACKGROUND

Alternative experimental models of hemorrhage mimic particular conditions of clinical settings and provide advantages to analyze novel resuscitation treatments. Here, we compared alternative models of hemorrhage and analyzed the effects of resuscitation with Hextend.

METHODS

Adult male Sprague-Dawley rats underwent alternative models of hemorrhage: anesthetized without trauma, anesthetized with trauma, or conscious (unanesthetized) hemorrhage. Each model of hemorrhage includes three experimental groups: (C) control without hemorrhage or resuscitation treatment; (NR) animals with hemorrhage but without resuscitation; and (HX) animals with hemorrhage and resuscitation treatment with Hextend.

RESULTS

Conscious animals required the highest hemorrhagic volume, whereas hemorrhage with trauma required the lowest blood volume withdrawal to achieve the same arterial pressure. Conscious hemorrhage exhibited the fastest mortality, but anesthetized animals with or without trauma had similar mortality kinetic. These survival rates did not correlate with blood chemistry, hemodynamic responses, or serum TNF and HMGB1 levels. Hemorrhage in conscious animals or anesthetized animals with trauma increased serum TNF levels by approximately 2-fold compared with hemorrhage in anesthetized animals without trauma. Animals in conscious hemorrhage had similar TNF increases in all the organs, but trauma induced a specific TNF overproduction in the spleen. Resuscitation with Hextend improved survival in all the experimental models, yet its survival benefits were statistically greater in anesthetized animals with trauma. The only two markers similar to the survival benefits of Hextend were the TNF levels in the lung and liver. Hextend significantly improved survival and inhibited pulmonary and hepatic TNF levels in all the experimental models.

CONCLUSIONS

The survival benefits of resuscitation with Hextend depended on the experimental models and did not correlate with blood chemistry, hemodynamic, or serum cytokine levels. However, resuscitation with Hextend inhibited TNF levels in the lung and the liver with a pattern that resembled the survival benefits.