Neural signaling in the spleen controls B-cell responses to blood-borne antigen

M1 cholinergic signaling in the brain modulates cytokine levels and splenic cell sub-phenotypes following cecal ligation and puncture

BACKGROUND

The contribution of the central nervous system to sepsis pathobiology is incompletely understood. In previous studies, administration of endotoxin to mice decreased activity of the vagus anti-inflammatory reflex. Treatment with the centrally-acting M1 muscarinic acetylcholine (ACh) receptor (M1AChR) attenuated this endotoxin-mediated change. We hypothesize that decreased M1AChR-mediated activity contributes to inflammation following cecal ligation and puncture (CLP), a mouse model of sepsis.

METHODS

In male C57Bl/6 mice, we quantified basal forebrain cholinergic activity (immunostaining), hippocampal neuronal activity, serum cytokine/chemokine levels (ELISA) and splenic cell subtypes (flow cytometry) at baseline, following CLP and following CLP in mice also treated with the M1AChR agonist xanomeline.

RESULTS

At 48 h. post-CLP, activity in basal forebrain cells expressing choline acetyltransferase (ChAT) was half of that observed at baseline. Lower activity was also noted in the hippocampus, which contains projections from ChAT-expressing basal forebrain neurons. Serum levels of TNFα, IL-1β, MIP-1α, IL-6, KC and G-CSF were higher post-CLP than at baseline. Post-CLP numbers of splenic macrophages and inflammatory monocytes, TNFα+ and ILβ+ neutrophils and ILβ+ monocytes were higher than baseline while numbers of central Dendritic Cells (cDCs), CD4+ and CD8+ T cells were lower. When, following CLP, mice were treated with xanomeline activity in basal forebrain ChAT-expressing neurons and in the hippocampus was significantly higher than in untreated animals. Post-CLP serum concentrations of TNFα, IL-1β, and MIP-1α, but not of IL-6, KC and G-CSF, were significantly lower in xanomeline-treated mice than in untreated mice. Post-CLP numbers of splenic neutrophils, macrophages, inflammatory monocytes and TNFα+ neutrophils also were lower in xanomeline-treated mice than in untreated animals. Percentages of IL-1β+ neutrophils, IL-1β+ monocytes, cDCs, CD4+ T cells and CD8+ T cells were similar in xanomeline-treated and untreated post-CLP mice.

CONCLUSION

Our findings indicate that M1AChR-mediated responses modulate CLP-induced alterations in serum levels of some, but not all, cytokines/chemokines and affected splenic immune response phenotypes.

Sensory neurons regulate stimulus-dependent humoral immunity

Sensory neurons sense pathogenic infiltration, serving to inform immune coordination of host defense. However, sensory neuron-immune interactions have been predominantly shown to drive innate immune responses. Humoral memory, whether protective or destructive, is acquired early in life - as demonstrated by both early exposure to streptococci and allergic disease onset. Our study further defines the role of sensory neuron influence on humoral immunity in the lung. Using a murine model of Streptococcus pneumonia pre-exposure and infection and a model of allergic asthma, we show that sensory neurons are required for B-cell and plasma cell recruitment and antibody production. In response to S. pneumoniae , sensory neuron depletion resulted in a larger bacterial burden, reduced B-cell populations, IgG release and neutrophil stimulation. Conversely, sensory neuron depletion reduced B-cell populations, IgE and asthmatic characteristics during allergen-induced airway inflammation. The sensory neuron neuropeptide released within each model differed. With bacterial infection, vasoactive intestinal polypeptide (VIP) was preferentially released, whereas substance P was released in response to asthma. Administration of VIP into sensory neuron-depleted mice suppressed bacterial burden and increased IgG levels, while VIP1R deficiency increased susceptibility to bacterial infection. Sensory neuron-depleted mice treated with substance P increased IgE and asthma, while substance P genetic ablation resulted in blunted IgE, similar to sensory neuron-depleted asthmatic mice. These data demonstrate that the immunogen differentially stimulates sensory neurons to release specific neuropeptides which specifically target B-cells. Targeting sensory neurons may provide an alternate treatment pathway for diseases involved with insufficient and/or aggravated humoral immunity.

Neuroimmune Modulation Through Vagus Nerve Stimulation Reduces Inflammatory Activity in Crohn's Disease Patients: A Prospective Open-label Study

BACKGROUND AND AIMS

Crohn's disease [CD] is a debilitating, inflammatory condition affecting the gastrointestinal tract. There is no cure and sustained clinical and endoscopic remission is achieved by fewer than half of patients with current therapies. The immunoregulatory function of the vagus nerve, the 'inflammatory reflex', has been established in patients with rheumatoid arthritis and biologic-naive CD. The aim of this study was to explore the safety and efficacy of vagus nerve stimulation in patients with treatment-refractory CD, in a 16-week, open-label, multicentre, clinical trial.

METHODS

A vagus nerve stimulator was implanted in 17 biologic drug-refractory patients with moderately to severely active CD. One patient exited the study pre-treatment, and 16 patients were treated with vagus nerve stimulation [4/16 receiving concomitant biologics] during 16 weeks of induction and 24 months of maintenance treatment. Endpoints included clinical improvement, patient-reported outcomes, objective measures of inflammation [endoscopic/molecular], and safety.

RESULTS

There was a statistically significant and clinically meaningful decrease in CD Activity Index at Week 16 [mean ± SD: -86.2 ± 92.8, p = 0.003], a significant decrease in faecal calprotectin [-2923 ± 4104, p = 0.015], a decrease in mucosal inflammation in 11/15 patients with paired endoscopies [-2.1 ± 1.7, p = 0.23], and a decrease in serum tumour necrosis factor and interferon-γ [46-52%]. Two quality-of-life indices improved in 7/11 patients treated without biologics. There was one study-related severe adverse event: a postoperative infection requiring device explantation.

CONCLUSIONS

Neuroimmune modulation via vagus nerve stimulation was generally safe and well tolerated, with a clinically meaningful reduction in clinical disease activity associated with endoscopic improvement, reduced levels of faecal calprotectin and serum cytokines, and improved quality of life.

M1 Cholinergic Signaling Modulates Cytokine Levels and Splenocyte Sub-Phenotypes Following Cecal Ligation and Puncture

Background

The contribution of the central nervous system to sepsis pathobiology is incompletely understood. In previous studies, administration of endotoxin to mice decreased activity of the vagus anti-inflammatory reflex. Treatment with the centrally-acting M1/M4 muscarinic acetylcholine (ACh) receptor (M1/M4AChR) attenuated this endotoxin-mediated change. We hypothesize that decreased M1/M4AChR-mediated activity contributes to inflammation following cecal ligation and puncture (CLP), a mouse model of sepsis.

Methods

Basal forebrain cholinergic activity (immunostaining), serum cytokine/chemokine levels (ELISA) and splenocyte subtypes (flow cytometry) were examined at baseline and following CLP in male C57BL/6 male mice.

Rersults

At 48hrs. post-CLP, activity in basal forebrain cells expressing choline acetyltransferase (ChAT) was half of that observed at baseline. Lower activity was also noted in the hippocampus, which contains projections from ChAT-expressing basal forebrain neurons. Serum levels of TNFα, IL-1β, MIP-1α, IL-6, KC and G-CSF were higher post-CLP than at baseline. Post-CLP numbers of splenic macrophages and inflammatory monocytes, TNFa+ and ILb+ neutrophils and ILb+ monocytes were higher than baseline while numbers of central Dendritic Cells (cDCs), CD4+ and CD8+ T cells were lower. When, following CLP, mice were treated with xanomeline, a central-acting M1AChR agonist, activity in basal forebrain ChAT-expressing neurons and in the hippocampus was significantly higher than in untreated animals. Post-CLP serum concentrations of TNFα, IL-1β, and MIP-1α, but not of IL-6, KC and G-CSF, were significantly lower in xanomline-treated mice than in untreated mice. Post-CLP numbers of splenic neutrophils, macrophages, inflammatory monocytes and TNFα+ neutrophils also were lower in xanomeline-treated mice than in untreated animals. The effects of CLP on percentages of IL-1β+ neutrophils, IL-1β+ monocytes, cDCs, CD4+ T cells and CD8+ T cells were similar in xanomeline - treated and untreated post-CLP mice.

Conclusion

Our findings indicate that M1/M4AChR-mediated responses modulate CLP-induced alterations in the distribution of some, but not all, leukocyte phenotypes and certain cytokines and chemokines.

Pharmacological and Electroceutical Targeting of the Cholinergic Anti-Inflammatory Pathway in Autoimmune Diseases

Continuous dialogue between the immune system and the brain plays a key homeostatic role in various immune responses to environmental cues. Several functions are under the control of the vagus nerve-based inflammatory reflex, a physiological mechanism through which nerve signals regulate immune functions. In the cholinergic anti-inflammatory pathway, the vagus nerve, its pivotal neurotransmitter acetylcholine, together with the corresponding receptors play a key role in modulating the immune response of mammals. Through communications of peripheral nerves with immune cells, it modulates proliferation and differentiation activities of various immune cell subsets. As a result, this pathway represents a potential target for treating autoimmune diseases characterized by overt inflammation and a decrease in vagal tone. Consistently, converging observations made in both animal models and clinical trials revealed that targeting the cholinergic anti-inflammatory pathway using pharmacologic approaches can provide beneficial effects. In parallel, bioelectronic medicine has recently emerged as an alternative approach to managing systemic inflammation. In several studies, nerve electrostimulation was reported to be clinically relevant in reducing chronic inflammation in autoimmune diseases, including rheumatoid arthritis and diabetes. In the future, these new approaches could represent a major therapeutic strategy for autoimmune and inflammatory diseases.

Outcomes of nicotinic modulation on markers of intestinal IgA antibody response

Acetylcholine (ACh), as a ligand of nicotinic acetylcholine receptors (nAChRs), plays a key role in the cholinergic anti-inflammatory pathway; however, its role in the immunoglobulin A (IgA) response remains unknown. Therefore, the present study aimed to investigate the role of ACh in the intestinal biomarkers involved in IgA synthesis and the polymeric immunoglobulin receptor (pIgR) involved in IgA transcytosis. Groups of mice were administered GTS-21 (an α7nAChR agonist) or mecamylamine (a non-selective nAChR antagonist) intraperitoneally for 7 days. Intestinal fluids were used for antibody concentration assessment by ELISA, cell suspensions from Peyer's patches and the lamina propria were obtained for flow cytometric analysis of plasma cells, and CD4⁺ T-cells expressing intracellular transforming growth factor (TGF)-β and IgA-producing interleukin (IL)-4, -5, -6 and -10, and isolated epithelial cells to determine the levels of pIgR mRNA using reverse transcription-quantitative PCR. Regarding to the untreated control group, the concentration of IgA was reduced in the mecamylamine group and unaltered in the GTS-21 group while IgM levels exhibited no differences; the percentage of IgA⁺ plasma cells from Peyer's patches and the lamina propria, and the percentage of TGF-β⁺/CD4⁺ T-cells from Peyer's patches were greater in the GTS-21-group. In both treatment groups, the percentages of IgM⁺ plasma cells and IL-6⁺/IL-10⁺ CD4⁺ T cells were greater in both compartments; pIgR mRNA expression levels decreased in epithelial cells. The percentage of IL-4 CD4⁺ T-cells were greater in Peyer's patches and lower in the lamina propria in the mecamylamine group, and the percentage of IL-5 CD4⁺ T-cells in the lamina propria were decreased in both treatment groups. These findings require further examination to address the impact of cholinergic modulation on IgA-transcytosis via pIgR. The present study may be an experimental reference for clinical trials that address the role of nicotinic system in intestinal dysfunctions as postoperative ileus.

Elevated levels of IgA and IgG2 in individuals with chronic spinal cord injury

OBJECTIVES

To determine circulating levels of antibodies (IgA, IgM, IgG1-4) in individuals with SCI as compared to uninjured individuals.

STUDY DESIGN

Prospective, observational study.

SETTING

Outpatient clinic of a Department of Physical Medicine and Rehabilitation and research institute in an academic medical center.

PARTICIPANTS

Individuals with chronic (≥ 1 year from injury) SCI and uninjured individuals.

OUTCOME MEASURES

Serum antibody titers were determined by commercial multiplex ELISA.

RESULTS

Blood samples were collected from individuals with chronic SCI (N = 29, 83% males) and uninjured individuals (N = 25, 64% males). Among participants with SCI, the distribution of American Spinal Injury Association Impairment Scale (AIS) grades was: A (n = 15), B (n = 2), C (n = 4), D (n = 8). Neurological levels of injury were: cervical (n = 17), thoracic (n = 10), and lumbar (n = 2). IgA levels were significantly elevated in participants with SCI compared to uninjured participants (median: 1.98 vs. 1.21 mg/ml, P < 0.0001), with levels most elevated in individuals with motor complete injuries compared to uninjured participants (P < 0.0003). IgG2 antibodies were also significantly elevated in participants with SCI compared to uninjured participants (median: 5.98 vs. 4.37 mg/ml, P < 0.018).

CONCLUSIONS

To our knowledge, this study provides the first evidence of elevated IgA, the antibody type most prevalent at respiratory, genitourinary and gastrointestinal tracts, common sites of infections in individuals with SCI. IgG2 levels were also elevated in individuals with SCI. These data support further investigations of IgA and other antibody types in individuals with chronic SCI, which may be increasingly important in the context of emerging novel infectious diseases such as SARS-CoV-2.

A Prospective Viewpoint on Neurological Diseases and Their Biomarkers

Neurodegenerative diseases (NDDs) are disorders that affect both the central and peripheral nervous systems. To name a few causes, NDDs can be caused by ischemia, oxidative and endoplasmic reticulum (ER) cell stress, inflammation, abnormal protein deposition in neural tissue, autoimmune-mediated neuron loss, and viral or prion infections. These conditions include Alzheimer's disease (AD), Lewy body dementia (LBD), and Parkinson's disease (PD). The formation of β-sheet-rich aggregates of intra- or extracellular proteins in the CNS hallmarks all neurodegenerative proteinopathies. In systemic lupus erythematosus (SLE), numerous organs, including the central nervous system (CNS), are affected. However, the inflammatory process is linked to several neurodegenerative pathways that are linked to depression because of NDDs. Pro-inflammatory signals activated by aging may increase vulnerability to neuropsychiatric disorders. Viruses may increase macrophages and CCR5+ T cells within the CNS during dementia formation and progression. Unlike medical symptoms, which are just signs of a patient's health as expressed and perceived, biomarkers are reproducible and quantitative. Therefore, this current review will highlight and summarize the neurological disorders and their biomarkers.

Autonomic Regulation of Nociceptive and Immunologic Changes in a Mouse Model of Complex Regional Pain Syndrome

Chronic pain frequently develops after limb injuries, and its pathogenesis is poorly understood. We explored the hypothesis that the autonomic nervous system regulates adaptive immune system activation and nociceptive sensitization in a mouse model of chronic post-traumatic pain with features of complex regional pain syndrome (CRPS). In studies sympathetic signaling was reduced using 6-hydroxydopamine (6-OHDA) or lofexidine, while parasympathetic signaling was augmented by nicotine administration. Hindpaw allodynia, unweighting, skin temperature, and edema were measured at 3 and 7 weeks after fracture. Hypertrophy of regional lymph nodes and IgM deposition in the skin of injured limbs were followed as indices of adaptive immune system activation. Passive transfer of serum from fracture mice to recipient B cell deficient (muMT) mice was used to assess the formation of pain-related autoantibodies. We observed that 6-OHDA or lofexidine reduced fracture-induced hindpaw nociceptive sensitization and unweighting. Nicotine had similar effects. These treatments also prevented IgM deposition, hypertrophy of popliteal lymph nodes, and the development of pronociceptive serum transfer effects. We conclude that inhibiting sympathetic or augmenting parasympathetic signaling inhibits pro-nociceptive immunological changes accompanying limb fracture. These translational results support the use of similar approaches in trials potentially alleviating persistent post-traumatic pain and, possibly, CRPS. PERSPECTIVE: Selective treatments aimed at autonomic nervous system modulation reduce fracture-related nociceptive and functional sequelae. The same treatment strategies limit pain-supporting immune system activation and the production of pro-nociceptive antibodies. Thus, the therapeutic regulation of autonomic activity after limb injury may reduce the incidence of chronic pain.

Somatosensory and autonomic neuronal regulation of the immune response

Bidirectional communication between the peripheral nervous system (PNS) and the immune system is a crucial part of an effective but balanced mammalian response to invading pathogens, tissue damage and inflammatory stimuli. Here, we review how somatosensory and autonomic neurons regulate immune cellular responses at barrier tissues and in peripheral organs. Immune cells express receptors for neuronal mediators, including neuropeptides and neurotransmitters, allowing neurons to influence their function in acute and chronic inflammatory diseases. Distinct subsets of peripheral sensory, sympathetic, parasympathetic and enteric neurons are able to signal to innate and adaptive immune cells to modulate their cellular functions. In this Review, we highlight recent studies defining the molecular mechanisms by which neuroimmune signalling mediates tissue homeostasis and pathology. Understanding the neural circuitry that regulates immune responses can offer novel targets for the treatment of a wide array of diseases.

Role of the Cholinergic Anti-Inflammatory Reflex in Central Nervous System Diseases

In several central nervous system diseases, it has been reported that inflammation may be related to the etiologic process, therefore, therapeutic strategies are being implemented to control inflammation. As the nervous system and the immune system maintain close bidirectional communication in physiological and pathological conditions, the modulation of inflammation through the cholinergic anti-inflammatory reflex has been proposed. In this review, we summarized the evidence supporting chemical stimulation with cholinergic agonists and vagus nerve stimulation as therapeutic strategies in the treatment of various central nervous system pathologies, and their effect on inflammation.

Inflammation neuroscience: neuro-immune crosstalk and interfaces

Inflammation is a key process in antimicrobial defence and tissue repair, and failure to properly regulate inflammation can result in tissue damage and death. Neural circuits play important roles throughout the course of an inflammatory response, and the neurophysiological and molecular mechanisms are only partly understood. Here, we review key evidence for the neural regulation of inflammation and discuss emerging technologies to further map and harness this neurophysiology, a cornerstone in the rapidly evolving field of inflammation neuroscience.

Exercise prevents HFD-induced insulin resistance risk: involvement of TNF-α level regulated by vagus nerve-related anti-inflammatory pathway in the spleen

OBJECTIVES

Regular physical exercise can improve insulin resistance in insulin target tissues. However, the mechanisms about the beneficial effect of exercise on insulin resistance are not yet fully resolved. This study was carried out to address whether insulin resistance improvement by exercise is involved in an anti-inflammatory pathway in the spleen in high-fat diet (HFD) feeding mice.

METHODS

Male C57Bl/6J mice with or without subdiaphragmatic vagotomy (sVNS) were subjected to medium-intensity treadmill exercise during HFD feeding. Glucose tolerance test and insulin tolerance test were detected, and spleen acetylcholine level, choline acetyltransferase activity (ChAT), protein kinase C (PKC) and tumor necrosis factor-alpha (TNF-α) were assayed.

RESULTS

We found that exercise significantly improves HFD-induced glucose intolerance and insulin resistance, along with an increase in acetylcholine level, ChAT activity, and PKC activity, and decrease in TNF-α level in the system and the spleen from HFD-fed mice. However, sVNS abolished the beneficial effect of exercise on glucose intolerance and insulin resistance, decreased acetylcholine level, ChAT activity, and PKC activity, and increase TNF-α level of the spleen in HFD-mice exercise intervention.

CONCLUSIONS

These data reveal that the prevention of HFD-associated insulin resistance by exercise intervention involves reducing splenic TNF-α level, which is mediated by cholinergic anti-inflammatory activity via influencing PKC activity, ChAT activity, and acetylcholine concentration in mice spleen.

Cholinergic modulation of the immune system - A novel therapeutic target for myocardial inflammation

The immune system and the nervous system depend on each other for their fine tuning and working, thus cooperating to maintain physiological homeostasis and prevent infections. The cholinergic system regulates the mobilization, differentiation, secretion, and antigen presentation of adaptive and innate immune cells mainly through α7 nicotinic acetylcholine receptors (α7nAChRs). The neuro-immune interactions are established and maintained by the following mechanisms: colocalization of immune and neuronal cells at defined anatomical sites, expression of the non-neuronal cholinergic system by immune cells, and the acetylcholine receptor-mediated activation of intracellular signaling pathways. Based on these immunological mechanisms, the protective effects of cholinergic system in animal models of diseases were summarized in this paper, such as myocardial infarction/ischemia-reperfusion, viral myocarditis, and endotoxin-induced myocardial damage. In addition to maintaining hemodynamic stability and improving the energy metabolism of the heart, both non-neuronal acetylcholine and neuronal acetylcholine in the heart can alleviate myocardial inflammation and remodeling to exert a significant cardioprotective effect. The new findings on the role of cholinergic agonists and vagus nerve stimulation in immune regulation are updated, so as to develop improved approaches to treat inflammatory heart disease.

The Link Between Autonomic Nervous System and Rheumatoid Arthritis: From Bench to Bedside

Neuronal stimulation is an emerging field of research focused on the management and treatment of various diseases through the reestablishment of physiological homeostasis. Electrical vagus nerve stimulation has recently been proposed as a revolutionary therapeutic option for rheumatoid arthritis (RA) in combination with or even as a replacement for conventional and biological drugs. In the past few years, disruption of the autonomic system has been linked to RA onset and activity. Novel research on the link between the autonomic nervous system and the immune system (immune-autonomics) has paved the way for the development of innovative RA management strategies. Clinical evidence supports this approach. Cardiovascular involvement, in terms of reduced baroreflex sensitivity and heart rate variability-derived indices, and mood disorders, common comorbidities in patients with RA, have been linked to autonomic nervous system dysfunction, which in turn is influenced by increased levels of circulating pro-inflammatory cytokines. This narrative review provides an overview of the autonomic nervous system and RA connection, discussing most of the common cardiac and mental health-related RA comorbidities and their potential relationships to systemic and joint inflammation.

Bioelectronic Medicine: From Preclinical Studies on the Inflammatory Reflex to New Approaches in Disease Diagnosis and Treatment

Bioelectronic medicine is an evolving field in which new insights into the regulatory role of the nervous system and new developments in bioelectronic technology result in novel approaches in disease diagnosis and treatment. Studies on the immunoregulatory function of the vagus nerve and the inflammatory reflex have a specific place in bioelectronic medicine. These studies recently led to clinical trials with bioelectronic vagus nerve stimulation in inflammatory diseases and other conditions. Here, we outline key findings from this preclinical and clinical research. We also point to other aspects and pillars of interdisciplinary research and technological developments in bioelectronic medicine.

Neural Control of Inflammation: Bioelectronic Medicine in Treatment of Chronic Inflammatory Disease

Inflammation is important for antimicrobial defense and for tissue repair after trauma. The inflammatory response and its resolution are both active processes that must be tightly regulated to maintain homeostasis. Excessive inflammation and nonresolving inflammation cause tissue damage and chronic disease, including autoinflammatory and cardiovascular diseases. An improved understanding of the cellular and molecular mechanisms that regulate inflammation has supported development of novel therapies for several inflammatory diseases, including rheumatoid arthritis and inflammatory bowel disease. Many of the specific anticytokine therapies carry a risk for excessive immunosuppression and serious side effects. The discovery of the inflammatory reflex and the increasingly detailed understanding of the molecular interactions between homeostatic neural reflexes and the immune system have laid the foundation for bioelectronic medicine in the field of inflammatory diseases. Neural interfaces and nerve stimulators are now being tested in human clinical trials and may, as the technology develops further, have advantages over conventional drugs in terms of better compliance, continuously adaptable control of dosing, better monitoring, and reduced risks for unwanted side effects. Here, we review the current mechanistic understanding of common autoinflammatory conditions, consider available therapies, and discuss the potential use of increasingly capable devices in the treatment of inflammatory disease.

Functions of acetylcholine-producing lymphocytes in immunobiology

Recent advances in neuroscience and immunology have shown that cholinergic signals are vital in the regulation of inflammation and immunity. Choline acetyltransferase⁺ (ChAT⁺) lymphocytes have the capacity to biosynthesize and release acetylcholine, the cognate ligand for cholinergic receptors. Acetylcholine-producing T cells relay neural signals in the 'inflammatory reflex' that regulate cytokine release in spleen. Mice deficient in acetylcholine-producing T cells have increased blood pressure, show reduced local vasodilatation and viral control in lymphocytic choriomeningitis virus infection, and display changes in gut microbiota compared with littermates. These observations indicate that ChAT⁺ lymphocytes play physiologically important roles in regulation of inflammation and anti-microbial defense. However, the full scope and importance of ChAT⁺ lymphocytes in immunity and vascular biology remains to be elucidated. Here, we review key findings in this emerging area.

Neural reflex control of vascular inflammation

Atherosclerosis is a multifactorial chronic inflammatory disease that underlies myocardial infarction and stroke. Efficacious treatment for hyperlipidemia and hypertension has significantly reduced morbidity and mortality in cardiovascular disease. However, atherosclerosis still confers a considerable risk of adverse cardiovascular events. In the current mechanistic understanding of the pathogenesis of atherosclerosis, inflammation is pivotal both in disease development and progression. Recent clinical data provided support for this notion and treatment targeting inflammation is currently being explored. Interestingly, neural reflexes regulate cytokine production and inflammation. Hence, new technology utilizing implantable devices to deliver electrical impulses to activate neural circuits are currently being investigated in treatment of inflammation. Hopefully, it may become possible to target vascular inflammation in cardiovascular disease using bioelectronic medicine. In this review, we discuss neural control of inflammation and the potential implications of new therapeutic strategies to treat cardiovascular disease.

Intimate neuro-immune interactions: breaking barriers between systems to make meaningful progress

The nervous system is often viewed as an isolated system that integrates information from the environment and host. Recently, there has been a renewed focus exploring the concept that the nervous system also communicates across biological systems. Specifically, several high profile studies have recently highlighted the importance of neuro-immune communication in the context of homeostasis, central nervous system disorders, host defense and injury. Here, we discuss the history of shared mechanisms and interconnectedness of the nervous, immune and epithelial compartments. In light of these overlapping mechanisms, it is perhaps unsurprising that neuro-immune-epithelial signaling plays a key role in regulating diverse biological phenomena. In this review, we explore recent breakthroughs in understanding neuro-immune signaling to highlight the importance of interdisciplinary approaches to biomedical research and the future development of novel therapeutics.

Review article: the role of the autonomic nervous system in the pathogenesis and therapy of IBD

BACKGROUND

There is a growing body of evidence implicating a role for the brain-gut axis in the pathogenesis of inflammation in patients with IBD.

AIMS

To perform a narrative review of published literature regarding the association of the autonomic nervous system and intestinal inflammation and to describe the rationale for and emerging use of autonomic manipulation as a therapeutic agent METHODS: Current relevant literature was summarised and critically examined.

RESULTS

There is substantial pre-clinical and clinical evidence for a multifaceted anti-inflammatory effect of the vagus at both systemic and local intestinal levels. It acts via acetylcholine-mediated activation of α-7-acetylcholine receptors involving multiple cell types in innate and adaptive immunity and the enteric nervous system with subsequent protective influences on the intestinal barrier, inflammatory mechanisms and the microbiome. In patients with IBD, there is evidence for a sympatho-vagal imbalance, functional enteric neuronal depletion and hyporeactivity of the hypothalamic-pituitary-adrenal axis. Direct or transcutaneous vagal neuromodulation up-regulates the cholinergic anti-inflammatory pathway in pre-clinical and clinical models with down-regulation of systemic and local intestinal inflammation. This is supported by two small studies in Crohn's disease although remains to be investigated in ulcerative colitis.

CONCLUSIONS

Modulating the cholinergic anti-inflammatory pathway influences inflammation both systemically and at a local intestinal level. It represents a potentially underutilised anti-inflammatory therapeutic strategy. Given the likely pathogenic role of the autonomic nervous system in patients with IBD, vagal neuromodulation, an apparently safe and successful means of increasing vagal tone, warrants further clinical exploration.

Noninvasive ultrasound stimulation of the spleen to treat inflammatory arthritis

Targeted noninvasive control of the nervous system and end-organs may enable safer and more effective treatment of multiple diseases compared to invasive devices or systemic medications. One target is the cholinergic anti-inflammatory pathway that consists of the vagus nerve to spleen circuit, which has been stimulated with implantable devices to improve autoimmune conditions such as rheumatoid arthritis. Here we report that daily noninvasive ultrasound (US) stimulation targeting the spleen significantly reduces disease severity in a mouse model of inflammatory arthritis. Improvements are observed only with specific parameters, in which US can provide both protective and therapeutic effects. Single cell RNA sequencing of splenocytes and experiments in genetically-immunodeficient mice reveal the importance of both T and B cell populations in the anti-inflammatory pathway. These findings demonstrate the potential for US stimulation of the spleen to treat inflammatory diseases.

Neurological and Inflammatory Manifestations in Sjögren's Syndrome: The Role of the Kynurenine Metabolic Pathway

For decades, neurological, psychological, and cognitive alterations, as well as other glandular manifestations (EGM), have been described and are being considered to be part of Sjögren's syndrome (SS). Dry eye and dry mouth are major findings in SS. The lacrimal glands (LG), ocular surface (OS), and salivary glands (SG) are linked to the central nervous system (CNS) at the brainstem and hippocampus. Once compromised, these CNS sites may be responsible for autonomic and functional disturbances that are related to major and EGM in SS. Recent studies have confirmed that the kynurenine metabolic pathway (KP) can be stimulated by interferon-γ (IFN-γ) and other cytokines, activating indoleamine 2,3-dioxygenase (IDO) in SS. This pathway interferes with serotonergic and glutamatergic neurotransmission, mostly in the hippocampus and other structures of the CNS. Therefore, it is plausible that KP induces neurological manifestations and contributes to the discrepancy between symptoms and signs, including manifestations of hyperalgesia and depression in SS patients with weaker signs of sicca, for example. Observations from clinical studies in acquired immune deficiency syndrome (AIDS), graft-versus-host disease, and lupus, as well as from experimental studies, support this hypothesis. However, the obtained results for SS are controversial, as discussed in this study. Therapeutic strategies have been reexamined and new options designed and tested to regulate the KP. In the future, the confirmation and application of this concept may help to elucidate the mosaic of SS manifestations.

Molecular and Functional Neuroscience in Immunity

The nervous system regulates immunity and inflammation. The molecular detection of pathogen fragments, cytokines, and other immune molecules by sensory neurons generates immunoregulatory responses through efferent autonomic neuron signaling. The functional organization of this neural control is based on principles of reflex regulation. Reflexes involving the vagus nerve and other nerves have been therapeutically explored in models of inflammatory and autoimmune conditions, and recently in clinical settings. The brain integrates neuro-immune communication, and brain function is altered in diseases characterized by peripheral immune dysregulation and inflammation. Here we review the anatomical and molecular basis of the neural interface with immunity, focusing on peripheral neural control of immune functions and the role of the brain in the model of the immunological homunculus. Clinical advances stemming from this knowledge within the framework of bioelectronic medicine are also briefly outlined.

Association Between Splenic Contraction and the Systemic Inflammatory Response After Acute Ischemic Stroke Varies with Age and Race

Animal models have demonstrated the deleterious contribution of splenic immunocytes on secondary brain injury after stroke. While previous work has demonstrated splenic contraction (SC) in patients with acute ischemic stroke (AIS) and intracranial hemorrhage (ICH), no clinical studies have examined the relationship between the systemic inflammatory response syndrome (SIRS) with SC in stroke patients. This is a retrospective analysis of a previous prospective observational study where daily spleen sizes were evaluated in 178 acute stroke patients. Spleen contraction was based on previously established normograms of healthy volunteers from the same study. SC from the first 24 h of stroke onset was evaluated against criteria for SIRS for the first 5 days of admission after AIS. Ninety-one patients had verified AIS without concurrent infection at admission. SIRS was not associated with SC at admission. African-American patients with early SIRS had higher odds of having SC. Older patients with persistent SIRS at 72 h had lower odds of SC. At 48 h, there was significantly higher lymphocytosis and lower neutrophils present in patients with SC. Patients with SIRS at 72 h were more likely to have worse discharge mRS. This study provides evidence for an association among SC and SIRS in African-American patients suggesting that spleen changes could be a biomarker for detecting SIRS in this population. Our data also indicate a counter association between SC and a lack of SIRS in patients older than 75. Further studies are needed to ascertain how age affects this association.

Vagal influences in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic immune-mediated inflammatory disease with a prevalence of 0.5-1% in Western populations. Conventionally, it is treated with therapeutic interventions that include corticosteroids, disease-modifying anti-rheumatic drugs, and biological agents. RA exerts a significant socio-economic burden and despite the use of existing treatments some patients end up with disabling symptoms. The autonomic nervous system (ANS) is a brain-body interface that serves to regulate homeostasis by integrating the external environment with the internal milieu. The main neural substrate of the parasympathetic branch of the ANS is the vagus nerve (VN). The discovery of the role of the ANS and the VN in mediating and dampening the inflammatory response has led to the proposal that modulation of neural circuits may serve as a valuable therapeutic tool. Recent studies have explored the role of the VN in this inflammatory reflex and have provided evidence that stimulation may represent a novel new therapeutic intervention. Accumulating evidence suggests that modulation of the parasympathetic tone results in a broad physiological multi-level response, including decreased pro-inflammatory cytokine response in terms of tumour necrosis factor-α, interleukin-1 (IL-1), and IL-6, and may result in an enhanced macrophage switch from M1 to M2 cells and potentially an increased level of the anti-inflammatory cytokine IL-10. Therefore, therapeutic electrical modulation of the VN may serve as an alternative, non-pharmacological, neuroimmunomodulatory intervention in RA in the future. This review gives a focused introduction to the mechanistic link between the ANS and the immune system.

Neuroanatomy of the spleen: Mapping the relationship between sympathetic neurons and lymphocytes

The nervous system plays a profound regulatory role in maintaining appropriate immune responses by signaling to immune cells. These immune cells, including B- and T-cells, can further act as intermediary messengers, with subsets of B- and T-cells expressing choline acetyltransferase (ChAT), the enzyme required for acetylcholine (ACh) synthesis. Neural control of ACh release from ChAT⁺ T-cells can have powerful immune implications, regulating lymphocyte trafficking, inflammation, and prevent death due to experimental septic shock. Although ACh release from T-cells has been proposed to occur following norepinephrine (NE) released from sympathetic nerve terminals in the spleen, it is unknown how this communication occurs. While it was proposed that tyrosine hydroxylase (TH⁺) axons form synapse-like structures with ChAT⁺ T-cells, there is scant evidence to support or refute this phenomenon. With this in mind, we sought to determine the relative abundance of ChAT⁺ B- and T-cells in close proximity to TH⁺ axons, and determine what factors contribute to their localization in the spleen. Using confocal microscopy of tissue sections and three-dimensional imaging of intact spleen, we confirmed that ChAT⁺ B-cells exceed the number of ChAT⁺ T-cells, and overall few ChAT⁺ B- or T-cells are located close to TH⁺ fibers compared to total numbers. The organized location of ChAT⁺ lymphocytes within the spleen suggested that these cells were recruited by chemokine gradients. We identified ChAT⁺ B- and T-cells express the chemokine receptor CXCR5; indicating that these cells can respond to CXCL13 produced by stromal cells expressing the β2 adrenergic receptor in the spleen. Our findings suggest that sympathetic innervation contributes to organization of ChAT⁺ immune cells in the white pulp of the spleen by regulating CXCL13. Supporting this contention, chemical sympathectomy significantly reduced expression of this chemokine. Together, we demonstrated that there does not appear to be a basis for synaptic neuro-immune communication, and that sympathetic innervation can modulate immune function through altering stromal cell chemokine production.

Mechanisms and Therapeutic Relevance of Neuro-immune Communication

Active research at the frontiers of immunology and neuroscience has identified multiple points of interaction and communication between the immune system and the nervous system. Immune cell activation stimulates neuronal circuits that regulate innate and adaptive immunity. Molecular mechanistic insights into the inflammatory reflex and other neuro-immune interactions have greatly advanced our understanding of immunity and identified new therapeutic possibilities in inflammatory and autoimmune diseases. Recent successful clinical trials using bioelectronic devices that modulate the inflammatory reflex to significantly ameliorate rheumatoid arthritis and inflammatory bowel disease provide a path for using electrons as a therapeutic modality for targeting molecular mechanisms of immunity. Here, we review mechanisms of peripheral sensory neuronal function in response to immune challenges, the neural regulation of immunity and inflammation, and the therapeutic implications of those mechanistic insights.

Low-Level Vagus Nerve Stimulation Suppresses Post-Operative Atrial Fibrillation and Inflammation: A Randomized Study

OBJECTIVES

This study sought to examine the efficacy of low-level vagus nerve stimulation (LLVNS) in suppressing post-operative atrial fibrillation (POAF) and inflammatory cytokines in patients undergoing cardiac surgery.

BACKGROUND

POAF often complicates cardiac surgery.

METHODS

Patients undergoing cardiac surgery were randomized to active or sham LLVNS. In all patients, a bipolar wire was sutured to the vagus nerve pre-ganglionic fibers alongside the lateral aspect of the superior vena cava. High-frequency (20 Hz) stimulation, 50% below the threshold for slowing the heart rate, was delivered for 72 h in the LLVNS group. The development of POAF was monitored continuously during the entire hospital stay by use of telemetry. Blood was collected on arrival in the intensive care unit and at 24 and 72 h for measurement of inflammatory cytokines. Patients were followed up within 1 month after cardiac surgery.

RESULTS

A total of 54 patients were randomized to either active LLVNS (n = 26) or sham control (n = 28). The baseline characteristics of the patients were balanced in the 2 groups. POAF occurred in 3 patients (12%) in the LLVNS group and 10 patients (36%) in the control group (hazard ratio: 0.28; 95% confidence interval: 0.10 to 0.85; p = 0.027). None of the patients developed any complications as a result of wire placement. At 72 h, serum tumor necrosis factor-α and interleukin-6 levels were significantly lower in the LLVNS group than in the control group.

CONCLUSIONS

These data suggest that LLVNS suppresses POAF and attenuates inflammation in patients undergoing cardiac surgery. Further studies are warranted.

Essential Neuroscience in Immunology

The field of immunology is principally focused on the molecular mechanisms by which hematopoietic cells initiate and maintain innate and adaptive immunity. That cornerstone of attention has been expanded by recent discoveries that neuronal signals occupy a critical regulatory niche in immunity. The discovery is that neuronal circuits operating reflexively regulate innate and adaptive immunity. One particularly well-characterized circuit regulating innate immunity, the inflammatory reflex, is dependent upon action potentials transmitted to the reticuloendothelial system via the vagus and splenic nerves. This field has grown significantly with the identification of several other reflexes regulating discrete immune functions. As outlined in this review, the delineation of these mechanisms revealed a new understanding of immunity, enabled a first-in-class clinical trial using bioelectronic devices to inhibit cytokines and inflammation in rheumatoid arthritis patients, and provided a mosaic view of immunity as the integration of hematopoietic and neural responses to infection and injury.

Neural Crest Cells Contribute an Astrocyte-like Glial Population to the Spleen

Neural crest cells (NCC) are multi-potent cells of ectodermal origin that colonize diverse organs, including the gastrointestinal tract to form the enteric nervous system (ENS) and hematopoietic organs (bone marrow, thymus) where they participate in lymphocyte trafficking. Recent studies have implicated the spleen as an anatomic site for integration of inflammatory signals from the intestine with efferent neural inputs. We have previously observed alterations in splenic lymphocyte subsets in animals with defective migration of NCC that model Hirschsprung's disease, leading us to hypothesize that there may be a direct cellular contribution of NCC to the spleen. Here, we demonstrate that NCC colonize the spleen during embryogenesis and persist into adulthood. Splenic NCC display markers indicating a glial lineage and are arranged anatomically adjacent to blood vessels, pericytes and nerves, suggesting an astrocyte-like phenotype. Finally, we identify similar neural-crest derived cells in both the avian and non-human primate spleen, showing evolutionary conservation of these cells.

Neural regulation of immunity: molecular mechanisms and clinical translation

Studies bridging neuroscience and immunology have identified neural pathways that regulate immunity and inflammation. Recent research using methodological advances in molecular genetics has improved our understanding of the neural control of immunity. Here we outline mechanistic insights, focusing on translational relevance and conceptual developments. We also summarize findings from recent clinical studies of bioelectronic neuromodulation in inflammatory and autoimmune diseases.

Neuronal Circuits Modulate Antigen Flow Through Lymph Nodes

When pathogens and toxins breech the epithelial barrier, antigens are transported by the lymphatic system to lymph nodes. In previously immunized animals, antigens become trapped in the draining lymph nodes, but the underlying mechanism that controls antigen restriction is poorly understood. Here we describe the role of neurons in sensing and restricting antigen flow in lymph nodes. The antigen keyhole-limpet hemocyanin (KLH) injected into the mouse hind paw flows from the popliteal lymph node to the sciatic lymph node, continuing through the upper lymphatics to reach the systemic circulation. Re-exposure to KLH in previously immunized mice leads to decreased flow from the popliteal to the sciatic lymph node as compared with naïve mice. Administering bupivacaine into the lymph node region restores antigen flow in immunized animals. In contrast, neural activation using magnetic stimulation significantly decreases antigen trafficking in naïve animals as compared with sham controls. Ablating Na_V1.8 + sensory neurons significantly reduces antigen restriction in immunized mice. Genetic deletion of FcγRI/FcεRI also reverses the antigen restriction. Colocalization of PGP9.5-expressing neurons, FcγRI receptors and labeled antigen occurs at the antigen challenge site. Together, these studies reveal that neuronal circuits modulate antigen trafficking through a pathway that requires Na_V1.8 and FcγR.

Circulating T cell subsets are altered in individuals with chronic spinal cord injury

Traumatic spinal cord injury (SCI) induces changes in the immune system, both acutely and chronically. To better understand changes in the chronic phase of SCI, we performed a prospective, observational study in a research institute and Department of Physical Medicine and Rehabilitation of an academic medical center to examine immune system parameters, including peripheral immune cell populations, in individuals with chronic SCI as compared to uninjured individuals. Here, we describe the relative frequencies of T cell populations in individuals with chronic SCI as compared to uninjured individuals. We show that the frequency of CD3+ and CD3+ CD4+ T cells are decreased in individuals with chronic SCI, although activated (HLA-DR+) CD4+ T cells are elevated in chronic SCI. We also examined regulatory T cells (T_regs), defined as CD3+ CD4+ CD25+ CD127lo and CCR4+, HLA-DR+ or CCR4+ HLA-DR+. To our knowledge, we provide the first evidence that CCR4+, HLA-DR+ or CCR4+ HLA-DR+ T_regs are expanded in individuals with SCI. These data support additional functional studies of T cells isolated from individuals with chronic SCI, where alterations in T cell homeostasis may contribute to immune dysfunction, such as immunity against infections or the persistence of chronic inflammation.

Neural circuitry and immunity

Research during the last decade has significantly advanced our understanding of the molecular mechanisms at the interface between the nervous system and the immune system. Insight into bidirectional neuro-immune communication has characterized the nervous system as an important partner of the immune system in the regulation of inflammation. Neuronal pathways, including the vagus nerve-based inflammatory reflex, are physiological regulators of immune function and inflammation. In parallel, neuronal function is altered in conditions characterized by immune dysregulation and inflammation. Here, we review these regulatory mechanisms and describe the neural circuitry modulating immunity. Understanding these mechanisms reveals possibilities to use targeted neuromodulation as a therapeutic approach for inflammatory and autoimmune disorders. These findings and current clinical exploration of neuromodulation in the treatment of inflammatory diseases define the emerging field of Bioelectronic Medicine.

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.

Galantamine Attenuates Type 1 Diabetes and Inhibits Anti-Insulin Antibodies in Nonobese Diabetic Mice

Type 1 diabetes in mice is characterized by autoimmune destruction of insulin-producing pancreatic β-cells. Disease pathogenesis involves invasion of pancreatic islets by immune cells, including macrophages and T cells, and production of antibodies to self-antigens, including insulin. Activation of the inflammatory reflex, the neural circuit that inhibits inflammation, culminates on cholinergic receptor signals on immune cells to attenuate cytokine release and inhibit B-cell antibody production. Here, we show that galantamine, a centrally acting acetylcholinesterase inhibitor and an activator of the inflammatory reflex, attenuates murine experimental type 1 diabetes. Administration of galantamine to animals immunized with keyhole limpet hemocyanin (KLH) significantly suppressed splenocyte release of immunoglobulin G (IgG) and interleukin (IL)-4 and IL-6 during KLH challenge ex vivo. Administration of galantamine beginning at 1 month of age in nonobese diabetic (NOD) mice significantly delayed the onset of hyperglycemia, attenuated immune cell infiltration in pancreatic islets and decreased anti-insulin antibodies in serum. These observations indicate that galantamine attenuates experimental type 1 diabetes in mice and suggest that activation of the inflammatory reflex should be further studied as a potential therapeutic approach.

Systemic inflammation and the brain: novel roles of genetic, molecular, and environmental cues as drivers of neurodegeneration

The nervous and immune systems have evolved in parallel from the early bilaterians, in which innate immunity and a central nervous system (CNS) coexisted for the first time, to jawed vertebrates and the appearance of adaptive immunity. The CNS feeds from, and integrates efferent signals in response to, somatic and autonomic sensory information. The CNS receives input also from the periphery about inflammation and infection. Cytokines, chemokines, and damage-associated soluble mediators of systemic inflammation can also gain access to the CNS via blood flow. In response to systemic inflammation, those soluble mediators can access directly through the circumventricular organs, as well as open the blood–brain barrier. The resulting translocation of inflammatory mediators can interfere with neuronal and glial well-being, leading to a break of balance in brain homeostasis. This in turn results in cognitive and behavioral manifestations commonly present during acute infections – including anorexia, malaise, depression, and decreased physical activity – collectively known as the sickness behavior (SB). While SB manifestations are transient and self-limited, under states of persistent systemic inflammatory response the cognitive and behavioral changes can become permanent. For example, cognitive decline is almost universal in sepsis survivors, and a common finding in patients with systemic lupus erythematosus. Here, we review recent genetic evidence suggesting an association between neurodegenerative disorders and persistent immune activation; clinical and experimental evidence indicating previously unidentified immune-mediated pathways of neurodegeneration; and novel immunomodulatory targets and their potential relevance for neurodegenerative disorders.

Approaching the next revolution? Evolutionary integration of neural and immune pathogen sensing and response

Mammalian immunity evolved by the process of natural selection that produced differential survival and reproduction advantages through combinations of hereditary traits underlying the response to pathogens. Primitive animals sense the presence of microbial pathogens through recognition of pathogen-derived molecules in their rudimentary immune and nervous systems. No molecular biological mechanism assigns primacy of pathogen sensing mechanisms to immune cells over neurons. Rather, in animals as diverse as Caenorhabditis elegans to mammals, neural reflexes are activated by the presence of pathogens and transduce neural mechanisms that control the development of immunity. A coming revolution in immunological thinking will require immunologists to incorporate neural circuits into understanding pathogen signal transduction, and the molecular mechanisms of learning, that culminate in immunity.

Assessment of immune cells and function of the residual spleen after subtotal splenectomy due to splenomegaly in cirrhotic patients

Background

The spleen is thought to be central in regulating the immune system, a metabolic asset involved in endocrine function. Overwhelming postsplenectomy infection leads to a mortality rate of up to 50%. However, there is still controversy on performing subtotal splenectomy as treatment of splenomegaly due to portal hypertension in cirrhotic patients. In the present study, immunocytes and the indexes of splenic size, hemodynamics, hematology and immunology in the residual spleen were analyzed to support subtotal splenectomy due to splenomegaly.

Results

In residual spleen, T lymphocytes mainly were focal aggregation in the periarterial lymphatic sheath. While B lymphocytes densely distributed in splenic corpuscle. In red pulp, macrophages were equally distributed in the xsplenic cord and adhered to the wall of splenic sinus with high density. The number of unit area T and B lymphocytes of splenic corpuscle and marginal zone as well as macrophages of red pulp were obviously increased in the residual spleen, while the number of macrophages didn’t be changed among the three groups in white pulp. While there were some beneficial changes (i.e., Counts of platelet and leucocyte as well as serum proportion of CD3+ T cells, CD4+ T cells, CD8+ T cells were increased markedly; serum levels of M-CSF and GM-CSF were decreased significantly; The proportion of granulocyte, erythrocyte, megakaryocyte in bone marrow were changed obviously; But serum IgA, IgM, IgG, Tuftsin level, there was no significant difference; splenic artery flow volume, portal venous diameter and portal venous flow volume, a significant difference was observed in residual spleen) in the clinical indices.

Conclusion

After subtotal splenectomy with splenomegaly due to portal hypertension in cirrhotic patients, the number of unit area T and B lymphocytes, and MØ in red pulp of residual spleen increased significantly. However, whether increase of T, B lymphocytes and MØs in residual splenic tissue can enhance the immune function of the spleen, still need further research to confirm.

Neurostimulation of the cholinergic anti-inflammatory pathway ameliorates disease in rat collagen-induced arthritis

INTRODUCTION

The inflammatory reflex is a physiological mechanism through which the nervous system maintains immunologic homeostasis by modulating innate and adaptive immunity. We postulated that the reflex might be harnessed therapeutically to reduce pathological levels of inflammation in rheumatoid arthritis by activating its prototypical efferent arm, termed the cholinergic anti-inflammatory pathway. To explore this, we determined whether electrical neurostimulation of the cholinergic anti-inflammatory pathway reduced disease severity in the collagen-induced arthritis model.

METHODS

Rats implanted with vagus nerve cuff electrodes had collagen-induced arthritis induced and were followed for 15 days. Animals underwent active or sham electrical stimulation once daily from day 9 through the conclusion of the study. Joint swelling, histology, and levels of cytokines and bone metabolism mediators were assessed.

RESULTS

Compared with sham treatment, active neurostimulation of the cholinergic anti-inflammatory pathway resulted in a 52% reduction in ankle diameter (p = 0.02), a 57% reduction in ankle diameter (area under curve; p = 0.02) and 46% reduction overall histological arthritis score (p = 0.01) with significant improvements in inflammation, pannus formation, cartilage destruction, and bone erosion (p = 0.02), accompanied by numerical reductions in systemic cytokine levels, not reaching statistical significance. Bone erosion improvement was associated with a decrease in serum levels of receptor activator of NF-κB ligand (RANKL) from 132±13 to 6±2 pg/mL (mean±SEM, p = 0.01).

CONCLUSIONS

The severity of collagen-induced arthritis is reduced by neurostimulation of the cholinergic anti-inflammatory pathway delivered using an implanted electrical vagus nerve stimulation cuff electrode, and supports the rationale for testing this approach in human inflammatory disorders.

Neural control of the immune system

Neural reflexes support homeostasis by modulating the function of organ systems. Recent advances in neuroscience and immunology have revealed that neural reflexes also regulate the immune system. Activation of the vagus nerve modulates leukocyte cytokine production and alleviates experimental shock and autoimmune disease, and recent data have suggested that vagus nerve stimulation can improve symptoms in human rheumatoid arthritis. These discoveries have generated an increased interest in bioelectronic medicine, i.e., therapeutic delivery of electrical impulses that activate nerves to regulate immune system function. Here, we discuss the physiology and potential therapeutic implications of neural immune control.

Expression of recombinant human IL-4 in Pichia pastoris and relationship between its glycosylation and biological activity

Secretory human interleukin 4 (hIL4) is an N-glycosylated pleiotropic cytokine. It is unknown if these N-linked glycans are required and essential for hIL4 protein stability, expression, secretion, and activity in vivo, and hIL4 expressed from Pichia pastoris yeast has not been tested to date. In this study, we successfully expressed human hIL4 in P. pastoris, the methylotrophic yeast, with a yield of 15.0mg/L. Using the site-directed mutagenesis technique, we made two mutant hIL4 cDNA clones (N38A and N105L) and subsequently expressed them in P. pastoris to analyze the relevant function of each N-glycosylation site on hIL4. Our results demonstrate that the glycosylation only occurs at position Asn38, but not Asn105. The glycosylated form of hIL4 unexpectedly has lower biological activity and lower stability when compared to its non-glycosylated form. The implications of this are discussed.

Neuronal and nonneuronal cholinergic structures in the mouse gastrointestinal tract and spleen

Accumulating evidence demonstrates that acetylcholine can directly modulate immune function in peripheral tissues including the spleen and gastrointestinal tract. However, the anatomical relationships between the peripheral cholinergic system and immune cells located in these lymphoid tissues remain unclear due to inherent technical difficulties with currently available neuroanatomical methods. In this study, mice with specific expression of the tdTomato fluorescent protein in choline acetyltransferase (ChAT)-expressing cells were used to label preganglionic and postganglionic cholinergic neurons and their projections to lymphoid tissues. Notably, our anatomical observations revealed an abundant innervation in the intestinal lamina propria of the entire gastrointestinal tract principally originating from cholinergic enteric neurons. The aforementioned innervation frequently approached macrophages, plasma cells, and lymphocytes located in the lamina propria and, to a lesser extent, lymphocytes in the interfollicular areas of Peyer's patches. In addition to the above innervation, we observed labeled epithelial cells in the gallbladder and lower intestines, as well as Microfold cells and T-cells within Peyer's patches. In contrast, we found only a sparse innervation in the spleen consisting of neuronal fibers of spinal origin present around arterioles and in lymphocyte-containing areas of the white pulp. Lastly, a small population of ChAT-expressing lymphocytes was identified in the spleen including both T- and B-cells. In summary, this study describes the variety of cholinergic neuronal and nonneuronal cells in a position to modulate gastrointestinal and splenic immunity in the mouse.

Noradrenergic neurons regulate monocyte trafficking and mortality during gram-negative peritonitis in mice

Effective host defense requires a robust, yet self-limited response to pathogens. A poorly calibrated response can lead to either bacterial dissemination due to insufficient inflammation or organ injury due to excessive inflammation. Recent evidence suggests that the cholinergic anti-inflammatory reflex helps calibrate the immune response. However, the influence of peripheral noradrenergic neurons, which are primarily sympathetic neurons, in regulating immunity remains incompletely characterized. Using a model of 6-hydroxydopamine-mediated noradrenergic nerve ablation, we show that elimination of noradrenergic neurons improves survival during Klebsiella pneumoniae peritonitis (67 versus 23%, p < 0.005) in mice. The survival benefit results from enhanced MCP-1-dependent monocyte recruitment and a subsequent decrease in bacterial loads. Splenectomy eliminated both the survival benefit of 6-hydroxydopamine and monocyte recruitment, suggesting that monocytes recruited to the peritoneum originate in the spleen. These results suggest that noradrenergic neurons regulate the immune response through two pathways. First, sympathetic nerve-derived norepinephrine directly restrains MCP-1 production by peritoneal macrophages during infection. Second, norepinephrine derived from the vagally innervated splenic nerve regulates splenic monocyte egress. Removal of these two modulators of the immune response enhances antibacterial immunity and improves survival. These results may have implications for how states of catecholamine excess influence the host response to bacterial infections.

Cholinergic control of inflammation in cardiovascular diseases

A neuroimmunological reflexive signaling pathway with potent anti-inflammatory capacity has been discovered recently. Within this so called cholinergic anti-inflammatory pathway the vagus nerve plays a central role in both signal integration and signal output, by measuring and influencing levels of circulating pro-inflammatory cytokines. Our group has recently shown that parasympathomimetic stimulation of the vagus nerve has the potential to inhibit inflammatory processes in experimental autoimmune myocarditis. Although vagus nerve stimulation has been shown to be protective in several inflammatory diseases, its potential as a therapeutic strategy has not been studied extensively in clinical settings. In this review we will discuss general molecular mechanisms of the cholinergic anti-inflammatory pathway with emphasis on autoimmune myocarditis. Furthermore, clinical and experimental studies that investigate the role of vagus nerve stimulation in cardiovascular diseases will be discussed.

Rethinking inflammation: neural circuits in the regulation of immunity

Neural reflex circuits regulate cytokine release to prevent potentially damaging inflammation and maintain homeostasis. In the inflammatory reflex, sensory input elicited by infection or injury travels through the afferent vagus nerve to integrative regions in the brainstem, and efferent nerves carry outbound signals that terminate in the spleen and other tissues. Neurotransmitters from peripheral autonomic nerves subsequently promote acetylcholine-release from a subset of CD4(+) T cells that relay the neural signal to other immune cells, e.g. through activation of α7 nicotinic acetylcholine receptors on macrophages. Here, we review recent progress in the understanding of the inflammatory reflex and discuss potential therapeutic implications of current findings in this evolving field.