Central cholinergic activation of a vagus nerve-to-spleen circuit alleviates experimental colitis

Heterophyllin B alleviates cognitive disorders in APP/PS1 model mice via the spleen-gut microbiota-brain axis

BACKGROUND

Accumulating evidence implicates both the brain-spleen axis and the gut microbiota-brain axis in Alzheimer's disease (AD) pathogenesis. While our previous work demonstrated heterophyllin B (HB) rectifies splenic Th1/Th2 imbalance and ameliorates cognitive deficits in Aβ1-42-induced AD mice, its potential modulation of the vagus nerve-spleen circuit remains unexplored.

METHODS

Using 8-month-old male APP/PS1 mice with/without splenic denervation (SD), we systematically investigated HB's therapeutic mechanisms via the spleen-gut microbiota-brain axis. Cognitive function was assessed through novel object recognition (ORT) and object location memory (OLT) tests. Immunofluorescence (IF) and enzyme-linked immunosorbent assay (ELISA) were employed to analyze Aβ plaques, phosphorylated tau (p-Tau) levels, and associated neuroinflammatory responses. Flow cytometry was utilized to examine the subtypes of splenic lymphocytes. Hematoxylin and eosin (H&E) staining, along with immunohistochemical (IHC) experiments, was conducted to evaluate the protective effects of HB on the intestinal barrier. Gut microbiota composition was analyzed using 16S rRNA sequencing.

RESULTS

HB administration significantly improved cognitive performance (ORT discrimination index: +28.7 %; OLT discrimination index: +26.6 %), reduced brain and serum Aβ1-42 and p-Tau levels, downregulated the Th1/Th2 ratio in the spleen, and alleviated intestinal permeability and neuroinflammation, which were abolished in SD APP/PS1 mice. Gut microbiota shifts showed HB-induced enrichment of cognition-associated Dubosiella and Muribaculaceae, with concurrent suppression of pathogenic Lachnospiraceae_NK4A136 and ASF356.

CONCLUSION

This study provides first evidence that HB ameliorates AD pathology through vagus nerve-dependent regulation of the spleen-gut microbiota-brain axis, establishing its multimodal therapeutic potential for neural-immune-gut circuit modulation in neurodegenerative diseases.

Tobacco smoking and sarcoidosis revisited-Evidence, mechanisms, and clinical implications: a narrative review

Sarcoidosis is a multisystem inflammatory disease with unclear etiology, influenced by genetic predisposition and environmental exposures. Smoking has been widely studied for its potential role in sarcoidosis, with conflicting evidence regarding its impact on disease risk, severity, and treatment response. While some epidemiologic studies suggest that smoking is associated with a lower risk of sarcoidosis, others highlight variations based on geography, ethnicity, and smoking history. Assessing the effects of smoking is particularly challenging because of the complex composition of tobacco smoke, which contains thousands of chemicals with diverse biologic effects. Nicotine, a major component of tobacco, has demonstrated both pro- and anti-inflammatory properties, further complicating its role in sarcoidosis. This narrative review explored the complex relationship between smoking and sarcoidosis by examining smoking's effects on immune modulation, disease presentation and prognosis, and response to immunosuppressive therapy. By summarizing current evidence, this paper aimed to clarify the impact of smoking and nicotine on sarcoidosis and identify key areas for future research, particularly in understanding the mechanisms underlying smoking-related immune modulation and treatment outcomes.

Inflammatory bowel disease and neuropsychiatric disorders: Mechanisms and emerging therapeutics targeting the microbiota-gut-brain axis

Crohn's disease (CD) and ulcerative colitis (UC) are the two major entities of inflammatory bowel disease (IBD). These disorders are known for their relapsing disease course and severe gastrointestinal symptoms including pain, diarrhoea and bloody stool. Accumulating evidence suggests that IBD is not only restricted to the gastrointestinal tract and that disease processes are able to reach distant organs including the brain. In fact, up to 35 % of IBD patients also suffer from neuropsychiatric disorders such as generalized anxiety disorder and major depressive disorder. Emerging research in this area indicates that in many cases these neuropsychiatric disorders are a secondary condition as a consequence of the disturbed communication between the gut and the brain via the microbiota-gut-brain axis. In this review, we summarise the current knowledge on IBD-associated neuropsychiatric disorders. We examine the role of different pathways of the microbiota-gut-brain axis in the development of CNS disorders highlighting altered neural, immunological, humoral and microbial communication. Finally, we discuss emerging therapies targeting the microbiota-gut-brain axis to alleviate IBD and neuropsychiatric symptoms including faecal microbiota transplantation, psychobiotics, microbial metabolites and vagus nerve stimulation.

Neurotransmitter and neuropeptide regulation of gut immunity

It is increasingly clear that the nervous system and immune system share a common molecular dialogue for intersystem communication. One of the key mechanisms of this communication is via neurotransmitters and neuropeptides. Diverse neuronal subtypes interact with various immune cell populations via the release of a wide variety of these neuromodulators that bind to receptors on immune cells. In the gut, this communication occurs via gut-intrinsic enteric neurons, extrinsic sensory and autonomic neurons. Here, we highlight a few key neurotransmitters and neuropeptides that have been shown to play a role in gut inflammation and host defense by acting on immune cells. Aberrations in this communication can lead to disorders including autoimmunity and tissue inflammation. We also discuss the need to better understand the molecular code of neuroimmune communication, which could lead to approaches to improve gut function and health.

Vagal Splenic-Dependent Effects Influence Glucose Homeostasis, Insulin Secretion, and Histopathology of the Endocrine Pancreas in Hypothalamic Obese Male Rats: Vagus Nerve and Spleen Interactions Affect the Endocrine Pancreas

Vagus nerve (VN) and spleen dysfunctions are often associated with obesity (Ob). Aim: We evaluated the effects of VN and spleen ablation on adiposity, metabolism, and insulin secretion in hypothalamic obese male rats. Methods: Ob was induced by neonatal subcutaneous injection of monosodium glutamate (4 g/kg). At 60 days of life, Ob animals were randomly distributed into four groups (n = 16 rats/group): sham operation (SHAM), vagotomy (VAG), splenectomy (SPL), and VAG + SPL. Body weight and food intake were monitored for 8 weeks postsurgery. Intraperitoneal glucose tolerance test (ipGTT) and intraperitoneal pyruvate tolerance test (ipPTT) were performed at 148 days of life, and VN activity was recorded at 150 days. After euthanasia (150 days), adiposity, plasma biochemical parameters, glucose-induced insulin secretion (GIIS), and cholinergic and adrenergic islet responsiveness were evaluated. The pancreas was submitted for histopathological analysis, and the protein content of OXPHOS and IL-10 was evaluated in isolated pancreatic islets. Results: Decreased VN activity was confirmed in the Ob-VAG groups, associated with lower visceral adiposity, triglycerides, and plasma insulin, together with improved insulin sensibility and pyruvate tolerance, compared to Ob-SHAM rats. Spleen absence reduced VN activity and cholinergic insulinotropic responses, with deleterious effects on the endocrine pancreas. Furthermore, Ob-VAG + SPL rats presented greater reductions in GIIS and more severe endocrine pancreas histopathology, compared to the Ob-SHAM group, without altered islet size or number or protein content of OXPHOS or IL-10. Conclusion: Vagal and splenic interactions contribute to glucose homeostasis control in hypothalamic obese rats, modulating insulin secretion and pancreas histology.

Targeted spleen modulation: a novel strategy for next-generation disease immunotherapy

The spleen, the largest lymphatic organ, comprises a diverse array of immunocytes in approximately one quarter of the body, including T cells, B cells, natural killer cells, and myeloid cells (such as dendritic cells, neutrophils, myeloid-derived suppressor cells, and macrophages). These immune cells undergo dynamic transitions and mobilization, enabling the spleen to execute a wide range of immunological functions. The spleen's structural organization and multicellular composition, along with its reservoir of lymphocytes, facilitate the capture and clearance of blood-borne antigens while also orchestrating both innate and adaptive immune responses. Additionally, the spleen plays critical roles in hematopoiesis and the removal of aged or damaged red blood cells. Despite being innervated by sympathetic (catecholaminergic) nerve fibers, the spleen lacks parasympathetic (vagal or cholinergic) innervation. The neuroimmune axis, particularly the interplay between sympathetic and parasympathetic nervous system immune circuits, significantly influences disease onset and progression. Extensive research employing physical, genetic, and pharmacological approaches has sought to directly modulate splenic immunocytes and activate neuroimmune interactions to restore immune homeostasis and counteract disease. Two primary mechanisms underlie these immunomodulatory interventions: (1) the cholinergic anti-inflammatory pathway, wherein norepinephrine released by splenic catecholaminergic fibers binds to β2-adrenergic receptors on CD4⁺ T cells, triggering acetylcholine secretion, which in turn suppresses inflammatory cytokine production in macrophages via α7 nicotinic acetylcholine receptor signaling, and (2) direct immunomodulation of splenic immunocytes, which regulates key genes and signaling pathways, alters cytokine secretion, and modulates ion flux to influence cellular functions. Among various therapeutic strategies, physical methods, particularly electrical stimulation and splenic ultrasound stimulation, have demonstrated the greatest promise for clinical applications in splenic immunomodulation and disease management.

The spleen in ischaemic heart disease

Ischaemic heart disease is a consequence of coronary atherosclerosis, and atherosclerosis is a systemic inflammatory disease. The spleen releases various immune cells in temporally distinct patterns. Neutrophils, monocytes, macrophages, B cells and T cells execute innate and adaptive immune processes in the coronary atherosclerotic plaque and in the ischaemic myocardium. Prolonged inflammation contributes to ischaemic heart failure. The spleen is also a target of neuromodulation through vagal, sympathetic and sensory nerve activation. Efferent vagal activation and subsequent activation of the noradrenergic splenic nerve activate β2-adrenergic receptors on splenic T cells, which release acetylcholine that ultimately results in attenuation of cytokine secretion from splenic macrophages. Coeliac vagal nerve activation increases splenic sympathetic nerve activity and drives the release of T cells, a process that depends on placental growth factor. Activation of the vagosplenic axis protects acutely from ischaemia-reperfusion injury during auricular tragus vagal stimulation and remote ischaemic conditioning. Splenectomy abrogates all these deleterious and beneficial actions on the cardiovascular system. The aggregate effect of splenectomy in humans is a long-term increase in mortality from ischaemic heart disease. The spleen has been appreciated as an important immune organ for inflammatory processes in atherosclerosis, myocardial infarction and heart failure, whereas its complex interaction with circulating blood factors and with the autonomic and somatic nervous systems, as well as its role in cardioprotection, have emerged only in the past decade. In this Review, we describe this newly identified cardioprotective function of the spleen and highlight the potential for translating the findings to patients with ischaemic heart disease.

Exploring the efficacy of Transcutaneous Auricular Vagus nerve stimulation (taVNS) in modulating local and systemic inflammation in experimental models of colitis

BACKGROUND

Current inflammatory bowel disease (IBD) treatments often fail to achieve lasting remission and have adverse effects. Vagus nerve stimulation (VNS) offers a promising therapy due to its anti-inflammatory effects. Its invasive nature, however, has led to the development of non-invasive methods like transcutaneous auricular VNS (taVNS). This study assesses taVNS's impact on acute colitis progression, inflammatory, anti-inflammatory, and apoptosis-related markers.

METHODS

Male C57BL/6 mice (11-12 weeks) were used for dextran sulfate sodium (DSS)- and dinitrobenzene sulfonic acid (DNBS)-induced colitis studies. The administration of taVNS or no stimulation (anesthesia without stimulation) for 10 min per mouse began one day before colitis induction and continued daily until sacrifice. Ulcerative colitis (UC)-like colitis was induced by administering 5% DSS in drinking water for 5 days, after which the mice were sacrificed. Crohn's disease (CD)-like colitis was induced through a single intrarectal injection of DNBS/ethanol, with the mice sacrificed after 3 days. Disease activity index (DAI), macroscopic evaluations, and histological damage were assessed. Colon, spleen, and blood samples were analyzed via qRT-PCR and ELISA. One-way or two-way ANOVA with Bonferroni and Šídák tests were applied.

RESULTS

taVNS improved DAI, macroscopic, and histological scores in DSS colitis mice, but only partially mitigated weight loss and DAI in DNBS colitis mice. In DSS colitis, taVNS locally decreased colonic inflammation by downregulating pro-inflammatory markers (IL-1β, TNF-α, Mip1β, MMP 9, MMP 2, and Nos2) at the mRNA level and upregulating anti-inflammatory TGF-β in non-colitic conditions at both mRNA and protein levels and IL-10 mRNA levels in both non-colitic and colitic conditions. Systemically, taVNS decreased splenic TNF-α in non-colitic mice and increased serum levels of TGF-β in colitic mice and splenic levels in non-colitic and colitic mice. Effects were absent in DNBS-induced colitis. Additionally, taVNS decreased pro-apoptotic markers (Bax, Bak1, and caspase 8) in non-colitic and colitic conditions and increased the pro-survival molecule Bad in non-colitic mice.

CONCLUSIONS

This study demonstrates that taVNS has model-dependent local and systemic effects, reducing inflammation and apoptosis in UC-like colitis while offering protective benefits in non-colitic conditions. These findings encourage further research into underlying mechanisms and developing adjunct therapies for UC.

Neuroimmune communication of the cholinergic system in gut inflammation and autoimmunity

Neuroimmune communication in the body forms a bridge between two central regulatory systems of the body, i.e., nervous and immune systems. The cholinergic system is a crucial modulatory neurotransmitter in the central and peripheral nervous system. It includes the neurotransmitter acetylcholine (ACh), the enzyme required for the synthesis of ACh (choline acetyltransferase, ChAT), the enzyme required for its degradation (acetylcholinesterase, AChE), and cholinergic receptors (Nicotinic acetylcholine receptors and muscarinic acetylcholine receptors). The cholinergic system in neurons is well known for its role in cognitive function, sensory perception, motor control, learning, and memory processes. It has been shown that the non-neuronal cholinergic system (NNCS) is present in various tissues and immune cells and forms a neuroimmune communications system. In the present review, we discussed the NNCS on immune cells, its role in homeostasis and inflammatory reactions in the gut, and how it can be exploited in treating inflammatory responses.

Splenic nerve denervation attenuates depression-like behaviors in Chrna7 knock-out mice via the spleen-gut-brain axis

BACKGROUND

Growing evidence highlights the role of the spleen-brain axis in inflammation-associated depression. The α7-subtype of nicotinic acetylcholine receptor (α7 nAChR, encoded by the Chrna7 gene) is implicated in systemic inflammation, with Chrna7 knock-out (KO) mice displaying depression-like behaviors. Yet, the influence of spleen nerve on depression-like behaviors in these KO mice remains to be elucidated.

METHODS

We investigated the effects of the splenic nerve denervation (SND) on depression-like behaviors, the protein expression in the prefrontal cortex (PFC), and the gut microbiota composition in Chrna7 KO mice.

RESULTS

SND markedly alleviated depression-like behaviors and the reduced expression of GluA1 and postsynaptic density protein-95 (PSD-95) in the PFC of Chrna7 KO mice. No changes in α-diversity of gut microbiota were noted among the control, KO + sham, and KO + SND groups. However, significant differences in β-diversity of gut microbiota were noted among the groups. Notable alterations in various microbiota (e.g., Fluviimonas_pallidilutea, Maribacter_arcticus, Parvibacter_caecicola) and plasma metabolites (e.g., helicide, N-acetyl-L-aspartic acid, α-D-galactose 1-phosphate, choline, creatine) were observed between KO + sham and KO + SND groups. Interestingly, correlations were found between the relative abundance of specific microbiota and other outcomes, including synaptic proteins, metabolites and behavioral data.

LIMITATIONS

The underlying mechanisms remain to be fully understood.

CONCLUSIONS

Our findings indicate that the splenic nerve contributes to depression-like phenotypes in Chrna7 KO mice via the spleen-gut-brain axis.

Stress-sensitive neural circuits change the gut microbiome via duodenal glands

Negative psychological states impact immunity by altering the gut microbiome. However, the relationship between brain states and microbiome composition remains unclear. We show that Brunner's glands in the duodenum couple stress-sensitive brain circuits to bacterial homeostasis. Brunner's glands mediated the enrichment of gut Lactobacillus species in response to vagus nerve stimulation. Cell-specific ablation of the glands markedly suppressed Lactobacilli counts and heightened vulnerability to infection. In the forebrain, we mapped a vagally mediated, polysynaptic circuit connecting the central nucleus of the amygdala to Brunner's glands. Chronic stress suppressed central amygdala activity and phenocopied the effects of gland lesions. Conversely, excitation of either the central amygdala or parasympathetic vagal neurons activated Brunner's glands and reversed the effects of stress on the gut microbiome and immunity. The findings revealed a tractable brain-body mechanism linking psychological states to host defense.

Role of stress and early-life stress in the pathogeny of inflammatory bowel disease

Numerous preclinical and clinical studies have shown that stress is one of the main environmental factor playing a significant role in the pathogeny and life-course of bowel diseases. However, stressful events that occur early in life, even during the fetal life, leave different traces within the central nervous system, in area involved in stress response and autonomic network but also in emotion, cognition and memory regulation. Early-life stress can disrupt the prefrontal-amygdala circuit thus favoring an imbalance of the autonomic nervous system and the hypothalamic-pituitary adrenal axis, resulting in anxiety-like behaviors. The down regulation of vagus nerve and cholinergic anti-inflammatory pathway favors pro-inflammatory conditions. Recent data suggest that emotional abuse at early life are aggravating risk factors in inflammatory bowel disease. This review aims to unravel the mechanisms that explain the consequences of early life events and stress in the pathophysiology of inflammatory bowel disease and their mental co-morbidities. A review of therapeutic potential will also be covered.

An Amygdalar-Vagal-Glandular Circuit Controls the Intestinal Microbiome

Psychological states can regulate intestinal mucosal immunity by altering the gut microbiome. However, the link between the brain and microbiome composition remains elusive. We show that Brunner's glands in the duodenal submucosa couple brain activity to intestinal bacterial homeostasis. Brunner's glands mediated the enrichment of gut probiotic species in response to stimulation of abdominal vagal fibers. Cell-specific ablation of the glands triggered transmissible dysbiosis associated with an immunodeficiency syndrome that led to mortality upon gut infection with pathogens. The syndrome could be largely prevented by oral or intra-intestinal administration of probiotics. In the forebrain, we identified a vagally-mediated, polysynaptic circuit connecting the glands of Brunner to the central nucleus of the amygdala. Intra-vital imaging revealed that excitation of central amygdala neurons activated Brunner's glands and promoted the growth of probiotic populations. Our findings unveil a vagal-glandular neuroimmune circuitry that may be targeted for the modulation of the gut microbiome. The glands of Brunner may be the critical cells that regulate the levels of Lactobacilli species in the intestine.

The immunomodulatory effect of oral NaHCO3 is mediated by the splenic nerve: multivariate impact revealed by artificial neural networks

Stimulation of the inflammatory reflex (IR) is a promising strategy for treating systemic inflammatory disorders. Recent studies suggest oral sodium bicarbonate (NaHCO3) as a potential activator of the IR, offering a safe and cost-effective treatment approach. However, the mechanisms underlying NaHCO3-induced anti-inflammatory effects remain unclear. We investigated whether oral NaHCO3's immunomodulatory effects are mediated by the splenic nerve. Female rats received NaHCO3 or water (H2O) for four days, and splenic immune markers were assessed using flow cytometry. NaHCO3 led to a significant increase (p < 0.05, and/or partial eta squared > 0.06) in anti-inflammatory markers, including CD11bc + CD206 + (M2-like) macrophages, CD3 + CD4 + FoxP3 + cells (Tregs), and Tregs/M1-like ratio. Conversely, proinflammatory markers, such as CD11bc + CD38 + TNFα + (M1-like) macrophages, M1-like/M2-like ratio, and SSChigh/SSClow ratio of FSChighCD11bc + cells, decreased in the spleen following NaHCO3 administration. These effects were abolished in spleen-denervated rats, suggesting the necessity of the splenic nerve in mediating NaHCO3-induced immunomodulation. Artificial neural networks accurately classified NaHCO3 and H2O treatment in sham rats but failed in spleen-denervated rats, highlighting the splenic nerve's critical role. Additionally, spleen denervation independently influenced Tregs, M2-like macrophages, Tregs/M1-like ratio, and CD11bc + CD38 + cells, indicating distinct effects from both surgery and treatment. Principal component analysis (PCA) further supported the separate effects. Our findings suggest that the splenic nerve transmits oral NaHCO3-induced immunomodulatory changes to the spleen, emphasizing NaHCO3's potential as an IR activator with therapeutic implications for a wide spectrum of systemic inflammatory conditions.

Brain-Gut Axis: Invasive and Noninvasive Vagus Nerve Stimulation, Limitations, and Potential Therapeutic Approaches

Inflammatory bowel disease (IBD) is a chronic relapsing condition with no known etiology and is characterized by disrupted gut homeostasis, chronic inflammation, and ulcerative lesions. Although current treatments can reduce disease activity, IBD frequently recurs once treatments are discontinued, indicating that treatments are ineffective in providing long-term remission. The lack of responsiveness and reluctance of some affected persons to take medications because of potential adverse effects has enhanced the need for novel therapeutic approaches. The vagus nerve (VN) is likely important in the pathogenesis of IBD, considering the decreased activity of the parasympathetic nervous system, especially the VN, and the impaired interaction between the enteric nervous system and central nervous system in patients with IBD. Vagus nerve stimulation (VNS) has demonstrated anti-inflammatory effects in various inflammatory disorders, including IBD, by inhibiting the production of inflammatory cytokines by immune cells. It has been suggested that stimulating the vagus nerve to induce its anti-inflammatory effects may be a potential therapeutic approach for IBD. Noninvasive techniques for VNS have been developed. Considering the importance of VN function in the brain-gut axis, VNS is a promising treatment option for IBD. This review discusses the potential therapeutic advantages and drawbacks of VNS, particularly the use of noninvasive transcutaneous auricular vagus nerve stimulation.

Activating α7nAChR suppresses systemic inflammation by mitigating neuroinflammation of the medullary visceral zone in sepsis in a rat model

Our previous studies have shown that activating α7nAChRs suppresses systemic inflammation and immunity through the cholinergic anti-inflammatory pathway (CAP) in early sepsis. Now that the medullary visceral zone (MVZ) is the center of CAP and responsible for regulating systemic inflammation, what changes will occur in MVZ's pathology and function in sepsis, especially when interfering with α7nAChRs? Does activation of MVZ's α7nAChRs contribute to the inhibition of systemic inflammation? To clarify these issues, we explored the systemic inflammation and immunity state by detecting serum levels of TNF-α, IL-6, HMGB1, sCD14, and CD4+CD25+Treg and TH17 lymphocytes percentage, meanwhile, we analyzed the apoptosis of cholinergic and catecholaminergic neurons and the expressions of tyrosine hydroxylase (TH) and choline acetyltransferase (CHAT) in MVZ in sepsis and the interfering effects on α7nAChRs. In this study, we found that in sepsis, serum TNF-α, IL-6, HMGB1, sCD14, CD4+CD25+Treg, and TH17 lymphocytes significantly increased and the ratio of Treg/TH17 significantly decreased, cholinergic and catecholaminergic neurons underwent apoptosis with low expressions of TH and CHAT in MVZ; activation of α7nAChRs not only significantly decreased the levels of septic serum TNF-α, IL-6, HMGB1, sCD14, and TH17 lymphocytes (P ＜ 0.05), but also significantly reduced cholinergic and catecholaminergic neurons' apoptosis, and promoted expressions of TH/CHAT. Our study reveals that sepsis undermines MVZ through neuroinflammation which contributes to the uncontrolled systemic inflammation. Activating central α7nAChRs is not only helpful to restore MVZ's structure and function but also beneficial to subside the inflammatory storm in sepsis. Even if MVZ is damaged in sepsis, cholinergic neurons in MVZ still regulate the systemic inflammation stably.

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.

Galantamine ameliorates experimental pancreatitis

BACKGROUND

Acute pancreatitis is a common and serious inflammatory condition currently lacking disease modifying therapy. The cholinergic anti-inflammatory pathway (CAP) is a potent protective anti-inflammatory response activated by vagus nerve-dependent α7 nicotinic acetylcholine receptor (α7nAChR) signaling using splenic CD4+ T cells as an intermediate. Activating the CAP ameliorates experimental acute pancreatitis. Galantamine is an acetylcholinesterase inhibitor (AChEI) which amplifies the CAP via modulation of central muscarinic ACh receptors (mAChRs). However, as mAChRs also activate pancreatitis, it is currently unknown whether galantamine would be beneficial in acute pancreatitis.

METHODS

The effect of galantamine (1-6 mg/kg-body weight) on caerulein-induced acute pancreatitis was evaluated in mice. Two hours following 6 hourly doses of caerulein (50 µg/kg-body weight), organ and serum analyses were performed with accompanying pancreatic histology. Experiments utilizing vagotomy, gene knock out (KO) technology and the use of nAChR antagonists were also performed.

RESULTS

Galantamine attenuated pancreatic histologic injury which was mirrored by a reduction in serum amylase and pancreatic inflammatory cytokines and an increase the anti-inflammatory cytokine IL-10 in the serum. These beneficial effects were not altered by bilateral subdiaphragmatic vagotomy, KO of either choline acetyltransferase+ T cells or α7nAChR, or administration of the nAChR ganglionic blocker mecamylamine or the more selective α7nAChR antagonist methyllycaconitine.

CONCLUSION

Galantamine improves acute pancreatitis via a mechanism which does not involve previously established physiological and molecular components of the CAP. As galantamine is an approved drug in widespread clinical use with an excellent safety record, our findings are of interest for further evaluating the potential benefits of this drug in patients with acute pancreatitis.

Transcutaneous auricular vagus nerve stimulation in the treatment of disorders of consciousness: mechanisms and applications

This review provides an in-depth exploration of the mechanisms and applications of transcutaneous auricular vagus nerve stimulation (taVNS) in treating disorders of consciousness (DOC). Beginning with an exploration of the vagus nerve's role in modulating brain function and consciousness, we then delve into the neuroprotective potential of taVNS demonstrated in animal models. The subsequent sections assess the therapeutic impact of taVNS on human DOC, discussing the safety, tolerability, and various factors influencing the treatment response. Finally, the review identifies the current challenges in taVNS research and outlines future directions, emphasizing the need for large-scale trials, optimization of treatment parameters, and comprehensive investigation of taVNS's long-term effects and underlying mechanisms. This comprehensive overview positions taVNS as a promising and safe modality for DOC treatment, with a focus on understanding its intricate neurophysiological influence and optimizing its application in clinical settings.

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.

Alpha 7 nicotinic acetylcholine receptors signaling boosts cell-cell interactions in macrophages effecting anti-inflammatory and organ protection

Activation of the cholinergic anti-inflammatory pathway (CAP) via vagus nerve stimulation has been shown to improve acute kidney injury in rodent models. While alpha 7 nicotinic acetylcholine receptor (α7nAChR) positive macrophages are thought to play a crucial role in this pathway, their in vivo significance has not been fully understood. In this study, we used macrophage-specific α7nAChR-deficient mice to confirm the direct activation of α7nAChRs in macrophages. Our findings indicate that the administration of GTS-21, an α7nAChR-specific agonist, protects injured kidneys in wild-type mice but not in macrophage-specific α7nAChR-deficient mice. To investigate the signal changes or cell reconstructions induced by α7nAChR activation in splenocytes, we conducted single-cell RNA-sequencing of the spleen. Ligand-receptor analysis revealed an increase in macrophage-macrophage interactions. Using macrophage-derived cell lines, we demonstrated that GTS-21 increases cell contact, and that the contact between macrophages receiving α7nAChR signals leads to a reduction in TNF-α. Our results suggest that α7nAChR signaling increases macrophage-macrophage interactions in the spleen and has a protective effect on the kidneys.

Low-Intensity Focused Ultrasound Ameliorates Ischemic Heart Failure Related to the Cholinergic Anti-Inflammatory Pathway

OBJECTIVES

This study aims to determine the effect of low-intensity focused ultrasound (LIFU) in ischemic heart failure (IHF) and explore the potential neuroimmune mechanism.

METHODS

Sprague-Dawley rats were subjected to ultrasound (US) with specific parameters, and electrocardiograms were recorded to analyze the effect of LIFU and/or vagal denervation on heart rate. Thereafter, myocardial infarction (MI) was induced by left anterior artery ligation, and LIFU was performed three times a day for 25 days after MI. Echocardiography, Masson staining, and ELISA were used to evaluate the effect of LIFU on the structure and function of the heart. Finally, ELISA, flow cytometry, qRT-PCR, and Western blot analysis were performed to determine the effect of LIFU on the inflammation and the expression of the cholinergic anti-inflammatory pathway (CAP)-related mediators.

RESULTS

LIFU reduced heart rate in rats (control vs LIFU, P < .01), and vagotomy (VT) eliminated this effect of LIFU on heart rate (VT vs LIFU + VT, P > .01). LIFU-ameliorated IHF in terms of cardiac structure and function (MI vs MI + LIFU, P < .01), but VT abrogated the beneficial effect of LIFU (MI + VT vs MI + LIFU + VT, P > .01). After the treatment of LIFU, decreased levels of inflammatory cytokines, increased proportion of anti-inflammatory macrophages, and increased expression of CAP-related mediators (MI vs MI + LIFU, P < .01).

CONCLUSIONS

LIFU ameliorates IHF whereas the CAP plays a promising role. LIFU has the potential to be a novel nonpharmacological and noninvasive therapy for the treatment of coronary artery disease and other cardiovascular diseases.

Can a basic solution activate the inflammatory reflex? A review of potential mechanisms, opportunities, and challenges

Stimulation of the inflammatory reflex (IR) is a promising strategy to treat systemic inflammatory disorders. However, this strategy is hindered by the cost and side effects of traditional IR activators. Recently, oral intake of sodium bicarbonate (NaHCO3) has been suggested to activate the IR, providing a safe and inexpensive alternative. Critically, the mechanisms whereby NaHCO3 might achieve this effect and more broadly the pathways underlying the IR remain poorly understood. Here, we argue that the recognition of NaHCO3 as a potential IR activator presents exciting clinical and research opportunities. To aid this quest, we provide an integrative review of our current knowledge of the neural and cellular pathways mediating the IR and discuss the status of physiological models of IR activation. From this vantage point, we derive testable hypotheses on potential mechanisms whereby NaHCO3 might stimulate the IR and compare NaHCO3 with classic IR activators. Elucidation of these mechanisms will help determine the therapeutic value of NaHCO3 as an IR activator and provide new insights into the IR circuitry.

Role of neurotransmitters in immune-mediated inflammatory disorders: a crosstalk between the nervous and immune systems

Immune-mediated inflammatory diseases (IMIDs) are a group of common heterogeneous disorders, characterized by an alteration of cellular homeostasis. Primarily, it has been shown that the release and diffusion of neurotransmitters from nervous tissue could result in signaling through lymphocyte cell-surface receptors and the modulation of immune function. This finding led to the idea that the neurotransmitters could serve as immunomodulators. It is now manifested that neurotransmitters can also be released from leukocytes and act as autocrine or paracrine modulators. Increasing data indicate that there is a crosstalk between inflammation and alterations in neurotransmission. The primary goal of this review is to demonstrate how these two pathways may converge at the level of the neuron and glia to involve in IMID. We review the role of neurotransmitters in IMID. The different effects that these compounds exert on a variety of immune cells are also reviewed. Current and future developments in understanding the cross-talk between the immune and nervous systems will undoubtedly identify new ways for treating immune-mediated diseases utilizing agonists or antagonists of neurotransmitter receptors.

Vagus Nerve Stimulation: A Personalized Therapeutic Approach for Crohn's and Other Inflammatory Bowel Diseases

Inflammatory bowel diseases, including Crohn's disease and ulcerative colitis, are incurable autoimmune diseases characterized by chronic inflammation of the gastrointestinal tract. There is increasing evidence that inappropriate interaction between the enteric nervous system and central nervous system and/or low activity of the vagus nerve, which connects the enteric and central nervous systems, could play a crucial role in their pathogenesis. Therefore, it has been suggested that appropriate neuroprosthetic stimulation of the vagus nerve could lead to the modulation of the inflammation of the gastrointestinal tract and consequent long-term control of these autoimmune diseases. In the present paper, we provide a comprehensive overview of (1) the cellular and molecular bases of the immune system, (2) the way central and enteric nervous systems interact and contribute to the immune responses, (3) the pathogenesis of the inflammatory bowel disease, and (4) the therapeutic use of vagus nerve stimulation, and in particular, the transcutaneous stimulation of the auricular branch of the vagus nerve. Then, we expose the working hypotheses for the modulation of the molecular processes that are responsible for intestinal inflammation in autoimmune diseases and the way we could develop personalized neuroprosthetic therapeutic devices and procedures in favor of the patients.

Galantamine attenuates autoinflammation in a mouse model of familial mediterranean fever

BACKGROUND

Autoinflammatory diseases, a diverse group of inherited conditions characterized by excessive innate immune activation, have limited therapeutic options. Neuroimmune circuits of the inflammatory reflex control innate immune overactivation and can be stimulated to treat disease using the acetylcholinesterase inhibitor galantamine.

METHODS

We tested the efficacy of galantamine in a rodent model of the prototypical autoinflammatory disease familial Mediterranean fever (FMF). Multiple chronic disease markers were evaluated in animals that received long-term galantamine treatment compared to vehicle.

RESULTS

Long-term treatment with galantamine attenuated the associated splenomegaly and anemia which are characteristic features of this disease. Further, treatment reduced inflammatory cell infiltration into affected organs and a subcutaneous air pouch.

CONCLUSIONS

These findings suggest that galantamine attenuates chronic inflammation in this mouse model of FMF. Further research is warranted to explore the therapeutic potential of galantamine in FMF and other autoinflammatory diseases.

Ion channel regulation of gut immunity

Mounting evidence indicates that gastrointestinal (GI) homeostasis hinges on communications among many cellular networks including the intestinal epithelium, the immune system, and both intrinsic and extrinsic nerves innervating the gut. The GI tract, especially the colon, is the home base for gut microbiome which dynamically regulates immune function. The gut's immune system also provides an effective defense against harmful pathogens entering the GI tract while maintaining immune homeostasis to avoid exaggerated immune reaction to innocuous food and commensal antigens which are important causes of inflammatory disorders such as coeliac disease and inflammatory bowel diseases (IBD). Various ion channels have been detected in multiple cell types throughout the GI tract. By regulating membrane properties and intracellular biochemical signaling, ion channels play a critical role in synchronized signaling among diverse cellular components in the gut that orchestrates the GI immune response. This work focuses on the role of ion channels in immune cells, non-immune resident cells, and neuroimmune interactions in the gut at the steady state and pathological conditions. Understanding the cellular and molecular basis of ion channel signaling in these immune-related pathways and initial testing of pharmacological intervention will facilitate the development of ion channel-based therapeutic approaches for the treatment of intestinal inflammation.

Altered neutrophil-to-lymphocyte ratio in sepsis secondary to canine parvoviral enteritis treated with and without an immunomodulator in puppies

Neutrophil-to-lymphocyte ratio (NLR) is a cheap and easy-to-obtain biomarker that mirrors the balance between innate and adaptive immunity. Cortisol and catecholamines have been identified as major drivers of NLR. High cortisol levels increase neutrophils while simultaneously decreasing lymphocyte counts. Likewise, endogenous catecholamines may cause leukocytosis and lymphopenia. Thus, NLR allows us to monitor patient severity in conditions such as sepsis. Twenty-six puppies with sepsis secondary to canine parvoviral enteritis were treated with and without an immunomodulator. Our group determined the NLR and the plasmatic cortisol levels by chemiluminescence, and norepinephrine (NE) and epinephrine (E) by HPLC during the first 72 h of clinical follow-up. Our results showed that at admission puppies presented an NLR value of 1.8, cortisol of 314.9 nmol/L, NE 3.7, and E 3.3 pmol/mL. Both treatments decreased admission NLR values after 24 h of treatment. However, only the puppies treated with the immunomodulator (I) remained without significant changes in NLR (0.7-1.4) compared to the CT group, and that showed a significant difference (P < 0.01) in their NLR value (0.4-4.6). In addition, we found significant differences in the slope values between the admission and final values of NLR (P < 0.005), cortisol (P < 0.02), and E (P < 0.05) between treatments. Then, our data suggest that the immunomodulator positively affects the number of lymphocytes and neutrophils involved in NLR as well as major drivers like cortisol and epinephrine, which is reflected in clinical parameters and survival.

Bioelectronic medicine: Preclinical insights and clinical advances

The nervous system maintains homeostasis and health. Homeostatic disruptions underlying the pathobiology of many diseases can be controlled by bioelectronic devices targeting CNS and peripheral neural circuits. New insights into the regulatory functions of the nervous system and technological developments in bioelectronics drive progress in the emerging field of bioelectronic medicine. Here, we provide an overview of key aspects of preclinical research, translation, and clinical advances in bioelectronic medicine.

Electrical neuromodulation therapy for inflammatory bowel disease

Inflammatory bowel disease (IBD) is an inflammatory disease of the gastrointestinal (GI) tract. It has financial and quality of life impact on patients. Although there has been a significant advancement in treatments, a considerable number of patients do not respond to it or have severe side effects. Therapeutic approaches such as electrical neuromodulation are being investigated to provide alternate options. Although bioelectric neuromodulation technology has evolved significantly in the last decade, sacral nerve stimulation (SNS) for fecal incontinence remains the only neuromodulation protocol commonly utilized use for GI disease. For IBD treatment, several electrical neuromodulation techniques have been studied, such as vagus NS, SNS, and tibial NS. Several animal and clinical experiments were conducted to study the effectiveness, with encouraging results. The precise underlying mechanisms of action for electrical neuromodulation are unclear, but this modality appears to be promising. Randomized control trials are required to investigate the efficacy of intrinsic processes. In this review, we will discuss the electrical modulation therapy for the IBD and the data pertaining to it.

Divergent Adaptations in Autonomic Nerve Activity and Neuroimmune Signaling Associated With the Severity of Inflammation in Chronic Colitis

BACKGROUND

The autonomic nervous system (ANS) is thought to play a critical role in the anti-inflammatory reflex pathway in acute colitis via its interaction with the spleen and colon. Inflammation in the intestine is associated with a blunting of vagal signaling and increased sympathetic activity. As a corollary, methods to restore sympatho-vagal balance are being investigated as therapeutic strategies for the treatment of intestinal inflammation. Nevertheless, it is indefinite whether these autonomic signaling adaptations in colitis are detrimental or beneficial to controlling intestinal inflammation. In this study, models of moderate and severe chronic colitis are utilized to resolve the correlations between sympatho-vagal signaling and the severity of intestinal inflammation.

METHODS

Spleens and colons were collected from Winnie (moderate colitis), Winnie-Prolapse (severe colitis), and control C57BL/6 mice. Changes to the size and histomorphology of spleens were evaluated. Flow cytometry was used to determine the expression of adrenergic and cholinergic signaling proteins in splenic B and T lymphocytes. The inflammatory profile of the spleen and colon was determined using a RT-PCR gene array. Blood pressure, heart rate, splanchnic sympathetic nerve and vagus nerve activity were recorded.

RESULTS

Spleens and colons from Winnie and Winnie-Prolapse mice exhibited gross abnormalities by histopathology. Genes associated with a pro-inflammatory response were upregulated in the colons from Winnie and further augmented in colons from Winnie-Prolapse mice. Conversely, many pro-inflammatory markers were downregulated in the spleens from Winnie-Prolapse mice. Heightened activity of the splanchnic nerve was observed in Winnie but not Winnie-Prolapse mice. Conversely, vagal nerve activity was greater in Winnie-Prolapse mice compared with Winnie mice. Splenic lymphocytes expressing α1 and β2 adrenoreceptors were reduced, but those expressing α7 nAChR and producing acetylcholine were increased in Winnie and Winnie-Prolapse mice.

CONCLUSIONS

Sympathetic activity may correlate with an adaptive mechanism to reduce the severity of chronic colitis. The Winnie and Winnie-Prolapse mouse models of moderate and severe chronic colitis are well suited to examine the pathophysiology of progressive chronic intestinal inflammation.

Manipulation of the inflammatory reflex as a therapeutic strategy

The cholinergic anti-inflammatory pathway is the efferent arm of the inflammatory reflex, a neural circuit through which the CNS can modulate peripheral immune responses. Signals communicated via the vagus and splenic nerves use acetylcholine, produced by Choline acetyltransferase (ChAT)+ T cells, to downregulate the inflammatory actions of macrophages expressing α7 nicotinic receptors. Pre-clinical studies using transgenic animals, cholinergic agonists, vagotomy, and vagus nerve stimulation have demonstrated this pathway's role and therapeutic potential in numerous inflammatory diseases. In this review, we summarize what is understood about the inflammatory reflex. We also demonstrate how pre-clinical findings are being translated into promising clinical trials, and we draw particular attention to innovative bioelectronic methods of harnessing the cholinergic anti-inflammatory pathway for clinical use.

Electrical stimulation of the splenic nerve bundle ameliorates dextran sulfate sodium-induced colitis in mice

BACKGROUND

Vagus nerve stimulation has been suggested to affect immune responses, partly through a neuronal circuit requiring sympathetic innervation of the splenic nerve bundle and norepinephrine (NE) release. Molecular and cellular mechanisms of action remain elusive. Here, we investigated the therapeutic value of this neuromodulation in inflammatory bowel disease (IBD) by applying electrical splenic nerve bundle stimulation (SpNS) in mice with dextran sulfate sodium (DSS)-induced colitis.

METHODS

Cuff electrodes were implanted around the splenic nerve bundle in mice, whereupon mice received SpNS or sham stimulation. Stimulation was applied 6 times daily for 12 days during DSS-induced colitis. Colonic and splenic tissues were collected for transcriptional analyses by qPCR and RNA-sequencing (RNA-seq). In addition, murine and human splenocytes were stimulated with lipopolysaccharide (LPS) in the absence or presence of NE. Single-cell RNA-seq data from publicly available data sets were analyzed for expression of β-adrenergic receptors (β-ARs).

RESULTS

Colitic mice undergoing SpNS displayed reduced colon weight/length ratios and showed improved Disease Activity Index scores with reduced Tumor Necrosis Factor α mRNA expression in the colon compared with sham stimulated mice. Analyses of splenocytes from SpNS mice using RNA-seq demonstrated specific immune metabolism transcriptome profile changes in myeloid cells. Splenocytes showed expression of β-ARs in myeloid and T cells. Cytokine production was reduced by NE in mouse and human LPS-stimulated splenocytes.

CONCLUSIONS

Together, our results demonstrate that SpNS reduces clinical features of colonic inflammation in mice with DSS-induced colitis possibly by inhibiting splenic myeloid cell activation. Our data further support exploration of the clinical use of SpNS for patients with IBD.

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.

Neuroimmune Interactions in Peripheral Organs

Interactions between the nervous and immune systems were recognized long ago, but recent studies show that this crosstalk occurs more frequently than was previously appreciated. Moreover, technological advances have enabled the identification of the molecular mediators and receptors that enable the interaction between these two complex systems and provide new insights on the role of neuroimmune crosstalk in organismal physiology. Most neuroimmune interaction occurs at discrete anatomical locations in which neurons and immune cells colocalize. Here, we describe the interactions of the different branches of the peripheral nervous system with immune cells in various organs, including the skin, intestine, lung, and adipose tissue. We highlight how neuroimmune crosstalk orchestrates physiological processes such as host defense, tissue repair, metabolism, and thermogenesis. Unraveling these intricate relationships is invaluable to explore the therapeutic potential of neuroimmune interaction. Expected final online publication date for the Annual Review of Neuroscience, Volume 45 is July 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Exploring the vagus nerve and the inflammatory reflex for therapeutic benefit in chronic spinal cord injury

PURPOSE OF REVIEW

To describe features and implications of chronic systemic inflammation in individuals with spinal cord injury (SCI) and to summarize the growing therapeutic possibilities to explore the vagus nerve-mediated inflammatory reflex in this context.

RECENT FINDINGS

The discovery of the inflammatory reflex provides a rationale to explore neuromodulation modalities, that is, electrical vagus nerve stimulation and pharmacological cholinergic modalities to regulate inflammation after SCI.

SUMMARY

Inflammation in individuals with SCI may negatively impact functional recovery and medical consequences after SCI. Exploring the potential of the vagus nerve-based inflammatory reflex to restore autonomic regulation and control inflammation may provide a novel approach for functional improvement in SCI.

Artemisia argyi extract alleviates inflammation in a DSS-induced colitis mouse model and enhances immunomodulatory effects in lymphoid tissues

Background

The incidence of inflammatory bowel disease (IBD), an inflammatory disorder of the gastrointestinal system has increased. IBD, characterized by aberrant immune responses against antigens, is thought to be caused by the invasion of enterobacteria. The pathogenesis of IBD is complicated, hence novel effective therapeutic agents are warranted. Therefore, this study evaluates the potential of Artemisia argyi, a medicinal herb, in alleviating IBD.

Methods

The effectiveness of the A. argyi ethanol extract was verified both in vitro and in vivo. Inflammation was induced in RAW 264.7 cells by 1 μg/mL of lipopolysaccharide (LPS) and by 3% dextran sodium sulfate (DSS) in a DSS-induced colitis mouse model. During the ten-day colitis induction, 200 mg/kg of A. argyi ethanol extract was orally administered to the treatment group. Levels of inflammation-related proteins and genes were analyzed in the colon, serum, and lymphoid tissues, i.e., Peyer’s patches (PPs) and spleen. The chemical constituent of the A. argyi ethanol extract was identified using an ultra-high performance liquid chromatography mass spectrometry (UPLC-MS/MS) analysis.

Results

A. argyi ethanol extract treatment ameliorated IBD symptoms and reduced the expression of inflammation-related proteins and genes in the colon and serum samples. Furthermore, A. argyi treatment induced the activation of anti-oxidative associated proteins, such as nuclear factor-erythroid factor 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1); and the treatment have also inhibited nuclear factor-κB (NF-κB), a central mediator of inflammatory responses. A. argyi enhanced the immunomodulatory effects in the PPs and spleen, which may stem from interleukin-10 (IL-10) upregulation. Chemical analysis identified a total of 28 chemical compounds, several of which have been reported to exert anti-inflammatory effects.

Conclusions

The effectiveness of the A. argyi ethanol extract in alleviating IBD was demonstrated; application of the extract successfully mitigated IBD symptoms, and enhanced immunomodulatory responses in lymphoid tissues. These findings suggest A. argyi as a promising herbal medicine for IBD treatment.

The Effect of α7nAChR Signaling on T Cells and Macrophages and Their Clinical Implication in the Treatment of Rheumatic Diseases

Rheumatoid arthritis (RA) is one of the most common autoimmune disease and until now, the etiology and pathogenesis of RA is not fully understood, although dysregulation of immune cells is one of the leading cause of RA-related pathological changes. Based on current understanding, the priority of anti-rheumatic treatments is to restore immune homeostasis. There are several anti-rheumatic drugs with immunomodulatory effects available nowadays, but most of them have obvious safety or efficacy shortcomings. Therefore, the development of novel anti-rheumatic drugs is still in urgently needed. Cholinergic anti-inflammatory pathway (CAP) has been identified as an important aspect of the so-called neuro-immune regulation feedback, and the interaction between acetylcholine and alpha 7 nicotinic acetylcholine receptor (α7nAChR) serves as the foundation for this signaling. Consistent to its immunomodulatory functions, α7nAChR is extensively expressed by immune cells. Accordingly, CAP activation greatly affects the differentiation and function of α7nAChR-expressing immune cells. As a result, targeting α7nAChR will bring profound therapeutic impacts on the treatment of inflammatory diseases like RA. RA is widely recognized as a CD4+ T cells-driven disease. As a major component of innate immunity, macrophages also significantly contribute to RA-related immune abnormalities. Theoretically, manipulation of CAP in immune cells is a feasible way to treat RA. In this review, we summarized the roles of different T cells and macrophages subsets in the occurrence and progression of RA, and highlighted the immune consequences of CAP activation in these cells under RA circumstances. The in-depth discussion is supposed to inspire the development of novel cell-specific CAP-targeting anti-rheumatic regimens.

Cholinergic immunomodulation in inflammatory bowel diseases

Inflammatory bowel diseases (IBD) are chronic intestinal disorders characterized by dysregulated immune responses to resident microbiota in genetically susceptible hosts. The activation of the cholinergic system has been proposed for the treatment of IBD patients according to its potential anti-inflammatory effect in vivo. The α-7-nicotinic-acetylcholine receptor (α7nAChR) is involved in the inhibition of inflammatory processes, modulating the production of cytokines, suppressing dendritic cells and macrophage activity, leading to the suppression of T cells. In this review, we address the most recent studies and clinical trials concerning cholinergic signaling and its therapeutic potential for inflammatory bowel diseases.

Cholinergic anti-inflammatory pathway and COVID-19

The cholinergic anti-inflammatory pathway (CAP) first described by Wang et al, 2003 has contemporary interest arising from the COVID-19 pandemic. While tobacco smoking has been considered an aggravating factor in the severity of COVID-19 infections, it has been suggested by some that the nicotine derived from tobacco could lessen the severity of COVID-19 infections. This spotlight briefly describes the CAP and its potential role as a therapeutic target for the treatment of COVID-19 infections using vagus nerve stimulation or selective alpha7 nicotinic acetylcholine receptor agonists.

Peripheral nerve stimulation and immunity: the expanding opportunities for providing mechanistic insight and therapeutic intervention

Pre-clinical research advances our understanding of the vagus nerve-mediated regulation of immunity and clinical trials successfully utilize electrical vagus nerve stimulation in the treatment of patients with inflammatory disorders. This symbiotic relationship between pre-clinical and clinical research exploring the vagus nerve-based 'inflammatory reflex' has substantially contributed to establishing the field of bioelectronic medicine. Recent studies identify a crosstalk between the vagus nerve and other neural circuitries in controlling inflammation and delineate new neural immunoregulatory pathways. Here we outline current mechanistic insights into the role of vagal and non-vagal neural pathways in neuro-immune communication and inflammatory regulation. We also provide a timely overview of expanding opportunities for bioelectronic neuromodulation in the treatment of various inflammatory disorders.

Rise in Postprandial GLP-1 Levels After Roux-en-Y Gastric Bypass: Involvement of the Vagus Nerve-Spleen Anti-inflammatory Axis in Type 2 Diabetic Rats

PURPOSE

The mechanism underlying postprandial glucagon-like peptide-1 (GLP-1) changes after metabolic surgery remains mostly unclarified. This investigation aimed to address whether the vagus nerve-spleen anti-inflammatory axis is involved in the rise in postprandial GLP-1 levels in type 2 diabetes mellitus (T2DM) rats following metabolic surgery.

MATERIALS AND METHODS

T2DM rat model was established with a high-fat diet and a low dose of streptozotocin and subjected to Roux-en-Y gastric bypass (RYGB) and splenic denervation. A mixed-meal tolerance test for postprandial GLP-1 response was performed. TNF-α in the plasma, spleen, and ileum was measured by ELISA, and alpha 7 nicotinic acetylcholine receptor (α7nAChR) expression in the spleen was analyzed by Western blot.

RESULTS

Postprandial GLP-1 improvement by RYGB was accompanied by the reduction of TNF-α levels in spleen and ileum and up-regulation of splenic α7nAChR in T2DM rats. Splenic denervation abrogates a rise in postprandial GLP-1 levels in response to the mixed-meal challenge, along with higher TNF-α levels in spleen and ileum and down-regulation of splenicα7nAChR, compared with denervated sham rats.

CONCLUSION

Our results reveal that the vagus nerve-spleen anti-inflammatory axis mediates the rise of postprandial GLP-1 response after RYGB through lowering TNF-α contents in the intestinal tissue in T2DM rats.

Vagus Nerve Stimulation Reduces Indomethacin-Induced Small Bowel Inflammation

Crohn's disease is a chronic, idiopathic condition characterized by intestinal inflammation and debilitating gastrointestinal symptomatology. Previous studies of inflammatory bowel disease (IBD), primarily in colitis, have shown reduced inflammation after electrical or pharmacological activation of the vagus nerve, but the scope and kinetics of this effect are incompletely understood. To investigate this, we studied the effect of electrical vagus nerve stimulation (VNS) in a rat model of indomethacin-induced small intestinal inflammation. 1 min of VNS significantly reduced small bowel total inflammatory lesion area [(mean ± SEM) sham: 124 ± 14 mm2, VNS: 62 ± 14 mm2, p = 0.002], intestinal peroxidation and chlorination rates, and intestinal and systemic pro-inflammatory cytokine levels as compared with sham-treated animals after 24 h following indomethacin administration. It was not known whether this observed reduction of inflammation after VNS in intestinal inflammation was mediated by direct innervation of the gut or if the signals are relayed through the spleen. To investigate this, we studied the VNS effect on the small bowel lesions of splenectomized rats and splenic nerve stimulation (SNS) in intact rats. We observed that VNS reduced small bowel inflammation also in splenectomized rats but SNS alone failed to significantly reduce small bowel lesion area. Interestingly, VNS significantly reduced small bowel lesion area for 48 h when indomethacin administration was delayed. Thus, 1 min of electrical activation of the vagus nerve reduced indomethacin-induced intestinal lesion area by a spleen-independent mechanism. The surprisingly long-lasting and spleen-independent effect of VNS on the intestinal response to indomethacin challenge has important implications on our understanding of neural control of intestinal inflammation and its potential translation to improved therapies for IBD.

Small intestinal bacterial overgrowth in Alzheimer's disease

The results of animal studies and clinical data support the gut microbiota contribution to the pathogenesis of Alzheimer’s disease (AD). The aim of this pilot study was to evaluate the prevalence of small intestinal bacterial overgrowth (SIBO) and fecal markers of intestinal inflammation and permeability in AD patients. The study was conducted in 45 AD patients and 27 controls. Data on comorbidities, pharmacotherapy, and gastrointestinal symptoms were acquired from medical records and a questionnaire. SIBO was evaluated using lactulose hydrogen breath test. Fecal calprotectin and zonulin levels were assessed by ELISA assays. The positive result of SIBO breath test was found in 49% of the AD patients and 22% of the controls (p = 0.025). The comparative analysis between SIBO-positive and SIBO-negative AD patients with respect to the degree of cognitive impairment, comorbidities and used medications did not reveal any statistically significant difference, except for less common heartburn in SIBO-positive AD patients than in SIBO-negative ones (9 vs 35%, p = 0.038). The median fecal calprotectin and zonulin levels in the AD group compared to the control group amounted to 43.1 vs 64.2 µg/g (p = 0.846) and 73.5 vs 49.0 ng/ml (p = 0.177), respectively. In the AD patients there was no association between the presence of SIBO and fecal calprotectin level. Patients with AD are characterized by higher prevalence of SIBO not associated with increased fecal calprotectin level that may be related to anti-inflammatory effect of cholinergic drugs used in the treatment of AD.

The Regulation Effect of α7nAChRs and M1AChRs on Inflammation and Immunity in Sepsis

The inflammatory storm in the early stage and immunosuppression in the late stage are responsible for the high mortality rates and multiple organ dysfunction in sepsis. In recent years, studies have found that the body's cholinergic system can spontaneously and dynamically regulate inflammation and immunity in sepsis according to the needs of the body. Firstly, the vagus nerve senses and regulates local or systemic inflammation by means of the Cholinergic Anti-inflammatory Pathway (CAP) and activation of α7-nicotinic acetylcholine receptors (α7nAChRs); thus, α7nAChRs play important roles for the central nervous system (CNS) to modulate peripheral inflammation; secondly, the activation of muscarinic acetylcholine receptors 1 (M1AChRs) in the forebrain can affect the neurons of the Medullary Visceral Zone (MVZ), the core of CAP, to regulate systemic inflammation and immunity. Based on the critical role of these two cholinergic receptor systems in sepsis, it is necessary to collect and analyze the related findings in recent years to provide ideas for further research studies and clinical applications. By consulting the related literature, we draw some conclusions: MVZ is the primary center for the nervous system to regulate inflammation and immunity. It coordinates not only the sympathetic system and vagus system but also the autonomic nervous system and neuroendocrine system to regulate inflammation and immunity; α7nAChRs are widely expressed in immune cells, neurons, and muscle cells; the activation of α7nAChRs can suppress local and systemic inflammation; the expression of α7nAChRs represents the acute or chronic inflammatory state to a certain extent; M1AChRs are mainly expressed in the advanced centers of the brain and regulate systemic inflammation; neuroinflammation of the MVZ, hypothalamus, and forebrain induced by sepsis not only leads to their dysfunctions but also underlies the regulatory dysfunction on systemic inflammation and immunity. Correcting the neuroinflammation of these regulatory centers and adjusting the function of α7nAChRs and M1AChRs may be two key strategies for the treatment of sepsis in the future.

Platinized graphene fiber electrodes uncover direct spleen-vagus communication

Neural interfacing nerve fascicles along the splenic neurovascular plexus (SNVP) is needed to better understand the spleen physiology, and for selective neuromodulation of this major organ. However, their small size and anatomical location have proven to be a significant challenge. Here, we use a reduced liquid crystalline graphene oxide (rGO) fiber coated with platinum (Pt) as a super-flexible suture-like electrode to interface multiple SNVP. The Pt-rGO fibers work as a handover knot electrodes over the small SNVP, allowing sensitive recording from four splenic nerve terminal branches (SN 1–4), to uncover differential activity and axon composition among them. Here, the asymmetric defasciculation of the SN branches is revealed by electron microscopy, and the functional compartmentalization in spleen innervation is evidenced in response to hypoxia and pharmacological modulation of mean arterial pressure. We demonstrate that electrical stimulation of cervical and sub-diaphragmatic vagus nerve (VN), evokes activity in a subset of SN terminal branches, providing evidence for a direct VN control over the spleen. This notion is supported by adenoviral tract-tracing of SN branches, revealing an unconventional direct brain-spleen projection. High-performance Pt-rGO fiber electrodes, may be used for the fine neural modulation of other small neurovascular plexus at the point of entry of major organs as a bioelectronic medical alternative.

Gonzalez-Gonzalez et al. use high-performance platinized graphene fiber electrodes to interface individual neurovascular plexus that innervate the spleen. Their approach provides evidence for distinct function of individual spleen terminal branches in organ function.

Treating disorders across the lifespan by modulating cholinergic signaling with galantamine

Advances in understanding the regulatory functions of the nervous system have revealed neural cholinergic signaling as a key regulator of cytokine responses and inflammation. Cholinergic drugs, including the centrally acting acetylcholinesterase inhibitor, galantamine, which are in clinical use for the treatment of Alzheimer's disease and other neurodegenerative and neuropsychiatric disorders, have been rediscovered as anti-inflammatory agents. Here, we provide a timely update on this active research and clinical developments. We summarize the involvement of cholinergic mechanisms and inflammation in the pathobiology of Alzheimer's disease, Parkinson's disease, and schizophrenia, and the effectiveness of galantamine treatment. We also highlight recent findings demonstrating the effects of galantamine in preclinical and clinical settings of numerous conditions and diseases across the lifespan that are characterized by immunological, neurological, and metabolic dysfunction.

Regulation of the Autonomic Nervous System on Intestine

Intestine is composed of various types of cells including absorptive epithelial cells, goblet cells, endocrine cells, Paneth cells, immunological cells, and so on, which play digestion, absorption, neuroendocrine, immunological function. Intestine is innervated with extrinsic autonomic nerves and intrinsic enteric nerves. The neurotransmitters and counterpart receptors are widely distributed in the different intestinal cells. Intestinal autonomic nerve system includes sympathetic and parasympathetic nervous systems, which regulate cellular proliferation and function in intestine under physiological and pathophysiological conditions. Presently, distribution and functional characteristics of autonomic nervous system in intestine were reviewed. How autonomic nervous system regulates intestinal cell proliferation was discussed. Function of autonomic nervous system on intestinal diseases was extensively reviewed. It might be helpful to properly manipulate autonomic nervous system during treating different intestinal diseases.

Vagus nerve-mediated intestinal immune regulation: therapeutic implications for inflammatory bowel diseases

The pathophysiology of inflammatory bowel disease (IBD) involves immunological, genetic and environmental factors. Through its ability to sense environmental stimuli, the autonomic nervous system plays a key role in the development and persistence of IBD. The vagus nerve (VN), which contains sensory and motor neurons, travels throughout the body to innervate the gut and other visceral organs in the thoracic and abdominopelvic cavities. Recent studies show that the VN has anti-inflammatory effects via the release of acetylcholine, in what is known as the cholinergic anti-inflammatory pathway (CAIP). In the gut immune system, the CAIP is proposed to be activated directly by signals from the gut and indirectly by signals from the liver, which receives gut-derived bioactive substances via the portal vein and senses the status of the gut. The gut-brain axis and liver-brain-gut reflex arc regulate a wide variety of peripheral immune cells to maintain homeostasis in the gut. Therefore, targeting the neural reflex by methods such as VN stimulation is now under investigation for suppressing intestinal inflammation associated with IBD. In this review, we describe the role of the VN in the regulation of intestinal immunity, and we discuss novel therapeutic approaches for IBD that target neuroimmune interactions.