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

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.

Non-invasive vagus nerve stimulation in anti-inflammatory therapy: mechanistic insights and future perspectives

Non-invasive vagus nerve stimulation (VNS) represents a transformative approach for managing a broad spectrum of inflammatory and autoimmune conditions, including rheumatoid arthritis and inflammatory bowel disease. This comprehensive review delineates the mechanisms underlying VNS, emphasizing the cholinergic anti-inflammatory pathway, and explores interactions within the neuro-immune and vagus-gut axes based on both clinical outcomes and pre-clinical models. Clinical applications have confirmed the efficacy of VNS in managing specific autoimmune diseases, such as rheumatoid arthritis, and chronic inflammatory conditions like inflammatory bowel disease, showcasing the variability in stimulation parameters and patient responses. Concurrently, pre-clinical studies have provided insights into the potential of VNS in modulating cardiovascular and broader inflammatory responses, paving the way for its translational application in clinical settings. Innovations in non-invasive VNS technology and precision neuromodulation are enhancing its therapeutic potential, making it a viable option for patients who are unresponsive to conventional treatments. Nonetheless, the widespread adoption of this promising therapy is impeded by regulatory challenges, patient compliance issues, and the need for extensive studies on long-term efficacy and safety. Future research directions will focus on refining VNS technology, optimizing treatment parameters, and exploring synergistic effects with other therapeutic modalities, which could revolutionize the management of chronic inflammatory and autoimmune disorders.

Effects of Different Cow-Milk Beta-Caseins on the Gut-Brain Axis: A Narrative Review of Preclinical, Animal, and Human Studies

The gut and brain communicate through bidirectional neural, endocrine, and immune signals to coordinate central nervous system activity with gastrointestinal function. Dysregulated inflammation can promote immune cell activation and increase entero-endocrine signaling and intestinal permeability; hence, a functional gut-brain axis is necessary for a healthy digestive system. The consumption of milk products can lead to gut discomfort via effects on gastrointestinal tract function and the inflammatory state, which, in turn, affect the brain. A1 β-casein and A2 β-casein are major components of bovine-milk protein, and their digestion may result in different physiological effects following the consumption of milk products. Peptides derived from A1 β-casein, such as β-casomorphins, may increase gut dysfunction and inflammation, thereby modulating the availability of bioactive metabolites in the bloodstream and contribute to changes in cognitive function. This narrative review examines the functional interrelationships between the consumption of cow-milk-derived β-caseins and their effect on the brain, immune system, and the gut, which together comprise the gut-brain axis.

Feasibility Trial Exploring Immune-Related Biomarkers Pertaining to Rapid Immune Surveillance and Cytokine Changes after Consuming a Nutraceutical Supplement Containing Colostrum- and Egg-Based Low-Molecular-Weight Peptides

Immune protection associated with consuming colostrum-based peptides is effective against bacterial and viral insults. The goal for this study was to document acute changes to immune surveillance and cytokine levels after consuming a single dose of a nutraceutical blend in the absence of an immune challenge. A double-blind, randomized, placebo-controlled, cross-over pilot study involved healthy participants attending two clinic visits. Blood draws were performed pre-consumption and at 1, 2, and 24 h after consuming a blend of bovine colostrum- and hen's egg-based low-molecular-weight peptides (CELMPs) versus a placebo. Immunophenotyping was performed by flow cytometry, and serum cytokines were measured by multiplex cytokine arrays. Consumption of CELMPs triggered increased immune surveillance after 1 h, involving monocytes (p < 0.1), natural killer (NK) cells (p < 0.1), and natural killer T (NKT) cells (p < 0.05). The number of NKT cells expressing the CD25 immunoregulatory marker increased at 1 and 2 h (p < 0.1). Increased serum levels of monocyte chemoattractant protein-1 (MCP-1) was observed at 2 and 24 h (24 h: p < 0.05). Selective reduction in pro-inflammatory cytokines was seen at 1, 2, and 24 h, where the 2-h reduction was highly significant for IL-6, IFN-γ, and IL-13. The rapid, transient increase in immune surveillance, in conjunction with the reduced levels of inflammatory markers, suggests that the CELMP blend of natural peptides provides immune benefits of use in preventive medicine. Further studies are warranted in chronic inflammatory conditions.

Exploring Electrical Neuromodulation as an Alternative Therapeutic Approach in Inflammatory Bowel Diseases

Background and Objectives: This review systematically evaluates the potential of electrical neuromodulation techniques-vagus nerve stimulation (VNS), sacral nerve stimulation (SNS), and tibial nerve stimulation (TNS)-as alternative treatments for inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's Disease (CD). It aims to synthesize current evidence on the efficacy and safety of these modalities, addressing the significant burden of IBD on patient quality of life and the limitations of existing pharmacological therapies. Materials and Methods: We conducted a comprehensive analysis of studies from PubMed, focusing on research published between 1978 and 2024. The review included animal models and clinical trials investigating the mechanisms, effectiveness, and safety of VNS, SNS, and TNS in IBD management. Special attention was given to the modulation of inflammatory responses and its impact on gastrointestinal motility and functional gastrointestinal disorders associated with IBD. Results: Preliminary findings suggest that VNS, SNS, and TNS can significantly reduce inflammatory markers and improve symptoms in IBD patients. These techniques also show potential in treating related gastrointestinal disorders during IBD remission phases. However, the specific mechanisms underlying these benefits remain to be fully elucidated, and there is considerable variability in treatment parameters. Conclusions: Electrical neuromodulation holds promise as a novel therapeutic avenue for IBD, offering an alternative to patients who do not respond to traditional treatments or experience adverse effects. The review highlights the need for further rigorous studies to optimize stimulation parameters, understand long-term outcomes, and integrate neuromodulation effectively into IBD treatment protocols.

Complementary role of peripheral and central autonomic nervous system on insulin-like growth factor-1 activation to prevent fatty liver disease

BACKGROUND

Insulin-like growth factor-1 (IGF-1) is involved in the pathology of non-alcoholic fatty liver disease (NAFLD) and ameliorates fatty infiltration in the liver. It is activated by growth hormone (GH); however, the role of GH-IGF-1 axis in NAFLD developmental phase has not been well identified. Therefore, in this study, we focused on the effect of IGF-1 in NAFLD pathology and GH excretion activation from the pituitary gland by peripheral autonomic neural pathways relaying liver-brain-gut pathway and by central neuropeptides.

METHODS

GH and IGF-1 levels were assessed in wild-type and melanocortin-4 receptor knockout mice upon the development of diet-induced NAFLD. The contribution of the peripheral autonomic nervous system connecting the liver-brain-gut axis was assessed by its blockade using capsaicin and that of the central nervous system was assessed by the expression of hypothalamic brain-derived neurotrophic factor (BDNF) and corticotropin-releasing factor (CRH), which activates GH release from the pituitary gland.

RESULTS

In the NAFLD mouse models, the levels of GH and IGF-1 increased (p < .05). Further, hepatic fatty infiltration was suppressed even under peripheral autonomic nervous system blockade (p < .001), which inhibited gastric ghrelin expression. In mice with peripheral autonomic nervous blockade, hypothalamic BDNF and CRH were inhibited (p < .05), resulting in GH and IGF-1 excretion, whereas other neuropeptides of somatostatin and cortistatin showed no changes. These complementary effects were canceled in melanocortin-4 receptor knockout mice, which diminished BDNF and CRH release control.

CONCLUSIONS

Our study demonstrates that the release of IGF-1 by the nervous system is a key factor in maintaining the pathological homeostasis of NAFLD, suggesting its therapeutic potential.

Vagus nerve stimulation as a therapeutic option in inflammatory rheumatic diseases

The vagus nerve forms intricate neural connections with an extensive number of organs, particularly the digestive system. The vagus nerve has a pivotal role as a fundamental component of the autonomic nervous system, exhibiting an essential effect. It establishes a direct link with the parasympathetic system, consequently eliciting the synaptic release of acetylcholine. Recent studies have revealed the potential anti-inflammatory function of the vagus nerve. The activation of the hypothalamic system through the stimulation of vagal afferents is fundamentally involved in regulating inflammation. This activation process leads to the production of cortisol. The other mechanism, defined as the cholinergic anti-inflammatory pathway, is characterized by the involvement of vagal efferents. These fibers release the neurotransmitter acetylcholine at particular synaptic connections, involving interactions with macrophages and enteric neurons. The mechanism under consideration is ascribed to the α-7-nicotinic acetylcholine receptors. The fusion of acetylcholine receptors is responsible for the restricted secretion of inflammatory mediators by macrophages. A potential mechanism for anti-inflammatory effects involves the stimulation of the sympathetic system through the vagus nerve, leading to the control of immunological responses within the spleen. This article offers an extensive summary of the present knowledge regarding the therapeutic effectiveness of stimulating the vagus nerve in managing inflammatory rheumatic conditions based on the relationship of inflammation with the vagus nerve. Furthermore, the objective is to present alternatives that may be preferred while applying vagus nerve stimulation approaches.

CDP-choline modulates cholinergic signaling and gut microbiota to alleviate DSS-induced inflammatory bowel disease

Inflammatory bowel diseases (IBD) represent chronic gastrointestinal inflammatory disorders characterized by a complex and underexplored pathogenic mechanism. Previous research has revealed that IBD patients often have a deficiency of choline and its metabolites, including acetylcholine (ACh) and phosphatidylcholine (PC), within the colon. However, a comprehensive study linking these three substances and their mechanistic implications in IBD remains lacking. This study aimed to investigate the efficacy and underlying mechanism of cytidine diphosphate (CDP)-choline (citicoline), an intermediate product of choline metabolism, in a mouse model of IBD induced by dextran sulfate sodium salt (DSS). The results demonstrated that CDP-choline effectively alleviated colonic inflammation and deficiencies in choline, ACh, and PC by increasing the raw material. Further detection showed that CDP-choline also increased the ACh content by altering the expression of high-affinity choline transporter (ChT1) and acetylcholinesterase (AChE) in DSS-induced mice colon. Moreover, CDP-choline increased the expression of alpha7 nicotinic acetylcholine receptor (α7 nAChR) and activated the cholinergic anti-inflammatory pathway (CAP), leading to reduced colon macrophage activation and proinflammatory M1 polarization in IBD mice, thus reducing the levels of TNF-α and IL-6. In addition, CDP-choline reduced intestinal ecological imbalance and increased the content of hexanoic acid in short-chain fatty acids (SCFAs) in mice. In conclusion, this study elucidates the ability of CDP-choline to mitigate DSS-induced colon inflammation by addressing choline and its metabolites deficiencies, activating the CAP, and regulating the composition of the intestinal microbiome and SCFAs content, providing a potential prophylactic and therapeutic approach for IBD.

Rapid increase in immune surveillance and expression of NKT and γδT cell activation markers after consuming a nutraceutical supplement containing Aloe vera gel, extracts of Poria cocos and rosemary. A randomized placebo-controlled cross-over trial

GOAL

To evaluate the acute impact of a nutraceutical blend on immune surveillance.

STUDY DESIGN

A randomized, double-blind, placebo-controlled, cross-over trial was conducted in 11 healthy subjects. Blood samples were taken immediately before and at 1, 2, and 3 hours after consuming placebo or 500 mg of UP360, which is a blend of botanicals from Aloe vera, Poria cocos, and rosemary (APR extract). Immunophenotyping and flow cytometry quantified numbers of monocytes, NK cells, NKT cells, CD8+ cytotoxic T cells, γδT cells, and total T cells, and expression of CD25 and CD69 activation markers. Plasma was tested for cytokines, chemokines, growth factors, and enzymatic activity of superoxide dismutase and catalase.

RESULTS

Compared to the placebo, consumption of APR extract triggered rapid increases in chemokine levels starting at 1 hour, including IP-10 (P<0.05) and MCP-1 (P<0.1), which peaked at 2 hours (P<0.01) and 3 hours (P<0.05), respectively. The stem cell-mobilizing growth factor G-CSF increased at 2 hours (P<0.05). Increased immune surveillance involved a transient effect for monocytes at 1 hour, followed by NKT cells, CD8+ cytotoxic T cells, and γδT cells at 2-3 hours. Increased immune cell alertness was seen at 1 hour by increased CD25 expression on monocytes (P<0.01), NKT cells (P<0.01), and T cells (P<0.05). NKT cells showed upregulation of CD69 at 2 hours (P<0.01). Increased enzymatic activity was seen at 2 hours for the antioxidant enzymes superoxide dismutase (P<0.05) and catalase (P<0.01).

CONCLUSION

Consumption of APR extract triggered acute changes to chemokine levels. In addition, immune alertness was increased via the expression of activation markers on multiple types of innate immune cells, followed by increased immune surveillance and antioxidant protection. This suggests a beneficial enhancement of natural immune surveillance, likely via a combination of gut-mediated cytokine release and vagus nerve communication, in combination with cellular protection from oxidative stress.

Unveiling the Link: Exploring Mitochondrial Dysfunction as a Probable Mechanism of Hepatic Damage in Post-Traumatic Stress Syndrome

PTSD is associated with disturbed hepatic morphology and metabolism. Neuronal mitochondrial dysfunction is considered a subcellular determinant of PTSD, but a link between hepatic mitochondrial dysfunction and hepatic damage in PTSD has not been demonstrated. Thus, the effects of experimental PTSD on the livers of high anxiety (HA) and low anxiety (LA) rats were compared, and mitochondrial determinants underlying the difference in their hepatic damage were investigated. Rats were exposed to predator stress for 10 days. Then, 14 days post-stress, the rats were evaluated with an elevated plus maze and assigned to HA and LA groups according to their anxiety index. Experimental PTSD caused dystrophic changes in hepatocytes of HA rats and hepatocellular damage evident by increased plasma ALT and AST activities. Mitochondrial dysfunction was evident as a predominance of small-size mitochondria in HA rats, which was positively correlated with anxiety index, activities of plasma transaminases, hepatic lipids, and negatively correlated with hepatic glycogen. In contrast, LA rats had a predominance of medium-sized mitochondria. Thus, we show links between mitochondrial dysfunction, hepatic damage, and heightened anxiety in PTSD rats. These results will provide a foundation for future research on the role of hepatic dysfunction in PTSD pathogenesis.

[The abdominal brain: neuroanatomic perspectives for the abdominal surgeon]

The "abdominal brain" does not only consist of a separate enteric nervous system but also of bidirectional connections to the autonomous nerve system with parasympathicus und sympathicus as well as brain and spinal cord. Novel studies have shown that these connections can quickly transfer information on the ingested nutrients to the brain to conduct the feeling of hunger and more complex behaviour, such as "reward-related learning". However, even emotional experience, in particular, stress, has a strong impact onto the gastrointestinal system. The immune system, motility and barrier function of the gastrointestinal tract are modulated by the intestinal microbiota. Local bacteria may directly influence neuronal communication by released metabolic products and neuropeptides as well as may control inflammatory factors. Intensive research over the last 10 years was able to provide evidence that intestinal microbiota may affect emotional and cognitive aspects of our behaviour and, thus, it might be in the focus of numerous neuropsychiatric diseases, such as depressions and anxiety disorders.The presented review is to provide a short summary of the I): anatomic basics of the so-called gut-brain axis and II): modi of the bidirectional regulation. Through indirect connections to the limbic system, gut-brain axis can substantially influence stress and anxiety but also the pain processing. In addition, the role of microbiota is outlined and future paths are shown, e.g., how the (microbiota-)gut-brain axis may alter emotional experience, pain processing and intestinal function. Such associations are relevant for further development of visceral medicine, and, thus, also for the abdominal surgeon to derive future treatment concepts with interdisciplinary orientation.

Gastrointestinal Dysfunction in Stroke

Gastrointestinal (GI) complications are seen in over 50% of ischemic stroke survivors; the most common complications are dysphagia, constipation, and GI bleeding. The bidirectional relationship of the gut-brain axis and stroke has recently gained traction, wherein stroke contributes to gut dysbiosis (alterations in the normal host intestinal microbiome) and gut dysbiosis perpetuates poor functional neurologic outcomes in stroke. It is postulated that the propagation of proinflammatory cells and gut metabolites (including trimethylamine N-oxide and short-chain fatty acids) from the GI tract to the central nervous system play a central role in gut-brain axis dysfunction. In this review, we discuss the known GI complications in acute ischemic stroke, our current knowledge from experimental stroke models for gut-brain axis dysfunction in stroke, and emerging therapeutics that target the gut-brain axis.

Are gut dysbiosis, barrier disruption, and endotoxemia related to adipose tissue dysfunction in metabolic disorders? Overview of the mechanisms involved

Recently, compelling evidence points to dysbiosis and disruption of the epithelial intestinal barrier as major players in the pathophysiology of metabolic disorders, such as obesity. Upon the intestinal barrier disruption, components from bacterial metabolism and bacteria itself can reach peripheral tissues through circulation. This has been associated with the low-grade inflammation that characterizes obesity and other metabolic diseases. While circulating bacterial DNA has been postulated as a common feature of obesity and even type 2 diabetes, almost no focus has been given to the existence and effects of bacteria in peripheral tissues, namely the adipose tissue. As a symbiont population, it is expected that gut microbiota modulate the immunometabolism of the host, thus influencing energy balance mechanisms and inflammation. Gut inflammatory signals cause direct deleterious inflammatory responses in adipose tissue and may also affect key gut neuroendocrine mechanisms governing nutrient sensing and energy balance, like incretins and ghrelin, which play a role in the gut-brain-adipose tissue axis. Thus, it is of major importance to disclose how gut microbiota and derived signals modulate neuroendocrine and inflammatory pathways, which contribute to the dysfunction of adipose tissue and to the metabolic sequelae of obesity and related disorders. This review summarizes the current knowledge regarding these topics and identifies new perspectives in this field of research, highlighting new pathways toward the reduction of the inflammatory burden of metabolic diseases.

Enlarged cross-sectional area of the left vagus nerve in patients with major depressive disorder

Purpose

Autonomic dysfunction and a chronic low-grade inflammation are supposed to play a role in the etiology of major depressive disorder (MDD). The vagus nerves (VN) form a major part of the parasympathetic nervous system and of the gut-brain axis. They are supposed to exert anti-inflammatory and epithelial barrier protective effects in the gut. A reduced vagal activity was described in patients with MDD. We aimed to examine the VN in patients with MDD with high-resolution ultrasound (HRUS) and hypothesized that the cross-sectional area (CSA) and the echogenicity of the VNs were altered in comparison to healthy controls.

Materials and methods

The echogenicity (gray scale mean) and the CSA of the cervical VNs at the level of the thyroid gland and both median nerves were examined with HRUS in 50 patients with MDD and 50 matched healthy controls.

Results

The left VN-CSA was significantly larger in the MDD group compared to the control group (1.7 ± 0.4 mm2 versus 1.5 ± 0.4 mm2; p = 0.045). The CSA of the right VN and both median nerves (MN) were similar between groups. In MDD subgroup analyses, recurrent depressive disorders were the main contributing factor for the left VN-CSA enlargement. Echogenicity was not altered in the VN and MN between groups.

Conclusion

The enlargement of the left VN-CSA in patients with MDD, and especially in these patients with recurrent depressive disorders, might turn out as a promising imaging biomarker. Longitudinal studies are warranted to examine whether the VNs-CSA change in the course of MDD.

Modulating functionally-distinct vagus nerve fibers using microelectrodes and kilohertz frequency electrical stimulation

Modulation of functionally distinct nerve fibers with bioelectronic devices provides a therapeutic opportunity for various diseases. In this study, we began by developing a computational model including four major subtypes of myelinated fibers and one unmyelinated fiber. Second, we used an intrafascicular electrode to perform kHz-frequency electric stimulation to preferentially modulate a population of fibers. Our model suggests that fiber physical properties and electrode-to-fascicle distance severely impacts stimulus-response relationships. Large diameter fibers (Aα- and Aβ-) were only minimally influenced by the fascicle size and electrode location, while smaller diameter fibers (Aδ-, B- and C-) indicated a stronger dependency.Clinical Relevance- Our findings support the possibility of selectively modulating functionally-distinct nerve fibers using electrical stimulation in a small, localized region. Our model provides an effective tool to design next-generation implantable devices and therapeutic stimulation strategies toward minimizing off-target effects.

Network Approaches to Uncover Pathogenesis and Therapeutic Targets of Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are currently recognized to involve chronic intestinal inflammation in genetically susceptible individuals. Patients with IBD mainly develop gastrointestinal inflammation, but it is sometimes accompanied by extraintestinal manifestations such as arthritis, erythema nodosum, episcleritis, pyoderma gangrenosum, uveitis, and primary sclerosing cholangitis. These clinical aspects imply the importance of interorgan networks in IBD. In the gastrointestinal tract, immune cells are influenced by multiple local environmental factors including microbiota, dietary environment, and intercellular networks, which further alter molecular networks in immune cells. Therefore, deciphering networks at interorgan, intercellular, and intracellular levels should help to obtain a comprehensive understanding of IBD. This review focuses on the intestinal immune system, which governs the physiological and pathological functions of the digestive system in harmony with the other organs.

Organ- and function-specific anatomical organization of vagal fibers supports fascicular vagus nerve stimulation

Vagal fibers travel inside fascicles and form branches to innervate organs and regulate organ functions. Existing vagus nerve stimulation (VNS) therapies activate vagal fibers non-selectively, often resulting in reduced efficacy and side effects from non-targeted organs. The transverse and longitudinal arrangement of fibers inside the vagal trunk with respect to the functions they mediate and organs they innervate is unknown, however it is crucial for selective VNS. Using micro-computed tomography imaging, we tracked fascicular trajectories and found that, in swine, sensory and motor fascicles are spatially separated cephalad, close to the nodose ganglion, and merge caudad, towards the lower cervical and upper thoracic region; larynx-, heart- and lung-specific fascicles are separated caudad and progressively merge cephalad. Using quantified immunohistochemistry at single fiber level, we identified and characterized all vagal fibers and found that fibers of different morphological types are differentially distributed in fascicles: myelinated afferents and efferents occupy separate fascicles, myelinated and unmyelinated efferents also occupy separate fascicles, and small unmyelinated afferents are widely distributed within most fascicles. We developed a multi-contact cuff electrode to accommodate the fascicular structure of the vagal trunk and used it to deliver fascicle-selective cervical VNS in anesthetized and awake swine. Compound action potentials from distinct fiber types, and physiological responses from different organs, including laryngeal muscle, cough, breathing, and heart rate responses are elicited in a radially asymmetric manner, with consistent angular separations that agree with the documented fascicular organization. These results indicate that fibers in the trunk of the vagus nerve are anatomically organized according to functions they mediate and organs they innervate and can be asymmetrically activated by fascicular cervical VNS.

Injection of amyloid-β to lateral ventricle induces gut microbiota dysbiosis in association with inhibition of cholinergic anti-inflammatory pathways in Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is the most common neurodegenerative disease and its pathogenesis is still unclear. There is dysbiosis of gut microbiota in AD patients. More importantly, dysbiosis of the gut microbiota has been observed not only in AD patients, but also in patients with mild cognitive impairment (MCI). However, the mechanism of gut microbiota dysbiosis in AD is poorly understood. Cholinergic anti-inflammatory pathway is an important pathway for the central nervous system (CNS) regulation of peripheral immune homeostasis, especially in the gut. Therefore, we speculated that dysfunction of cholinergic anti-inflammatory pathway is a potential pathway for dysbiosis of the gut microbiota in AD.

METHODS

In this study, we constructed AD model mice by injecting Aβ_1-42 into the lateral ventricle, and detected the cognitive level of mice by the Morris water maze test. In addition, 16S rDNA high-throughput analysis was used to detect the gut microbiota abundance of each group at baseline, 2 weeks and 4 weeks after surgery. Furthermore, immunofluorescence and western blot were used to detect alteration of intestinal structure of mice, cholinergic anti-inflammatory pathway, and APP process of brain and colon in each group.

RESULTS

Aβ_1-42 i.c.v induced cognitive impairment and neuron damage in the brain of  mice. At the same time, Aβ_1-42 i.c.v induced alteration of gut microbiota at 4 weeks after surgery, while there was no difference at the baseline and 2 weeks after surgery. In addition, changes in colon structure and increased levels of pro-inflammatory factors were detected in Aβ_1-42 treatment group, accompanied by inhibition of cholinergic anti-inflammatory pathways. Amyloidogenic pathways in both the brain and colon were accelerated in Aβ_1-42 treatment group.

CONCLUSIONS

The present findings suggested that Aβ in the CNS can induce gut microbiota dysbiosis, alter intestinal structure and accelerate the amyloidogenic pathways, which were related to inhibiting cholinergic anti-inflammatory pathways.

Immunological Tolerance in Liver Transplant Recipients: Putative Involvement of Neuroendocrine-Immune Interactions

The transplantation world changed significantly following the introduction of immunosuppressants, with millions of people saved. Several physicians have noted that liver recipients that do not take their medication for different reasons became tolerant regarding kidney, heart, and lung transplantations at higher frequencies. Most studies have attempted to explain this phenomenon through unique immunological mechanisms and the fact that the hepatic environment is continuously exposed to high levels of pathogen-associated molecular patterns (PAMPs) or non-pathogenic microorganism-associated molecular patterns (MAMPs) from commensal flora. These components are highly inflammatory in the periphery but tolerated in the liver as part of the normal components that arrive via the hepatic portal vein. These immunological mechanisms are discussed herein based on current evidence, although we hypothesize the participation of neuroendocrine-immune pathways, which have played a relevant role in autoimmune diseases. Cells found in the liver present receptors for several cytokines, hormones, peptides, and neurotransmitters that would allow for system crosstalk. Furthermore, the liver is innervated by the autonomic system and may, thus, be influenced by the parasympathetic and sympathetic systems. This review therefore seeks to discuss classical immunological hepatic tolerance mechanisms and hypothesizes the possible participation of the neuroendocrine-immune system based on the current literature.

Neuroimmune crosstalk in the gut and liver

It has long been assumed that the nervous system exerts distinct effects on immune functions, given the large number of immune disorders that are affected by mental stress. In fact, many different immune cells have been shown to possess a wide variety of neurotransmitter receptors and receive signals of various neurotransmitters, including acetylcholine and noradrenaline. Compared with the findings on local neuroimmune interactions, limited experimental techniques have so far failed to capture a comprehensive overview of neuroimmune interactions between distant organs and the autonomic nervous system in vivo, and the molecular mechanisms underlying local immune regulation of the nervous system have long remained unclear. However, the recent rapid progress in genetic recombination, microscopy and single-cell analysis has deepened our understanding of the anatomical and physiological functions of peripheral nerves at each organ to which they belong. Furthermore, the development of optogenetic and chemogenetic methods has enabled the artificial modulation of specific neuronal activities, and there has been remarkable progress in elucidation of the interaction between nerves and immune cells in vivo, particularly in barrier organs such as the gastrointestinal tract, respiratory tract and skin. This review focuses on the immunoregulatory mechanisms governed by the autonomic nervous system and outlines the latest findings in the regulation of enteric and hepatic immunity by the nervous system.

The Cholinergic Anti-Inflammatory Pathway Attenuates the Development of Atherosclerosis in Apoe-/- Mice through Modulating Macrophage Functions

(1) Background: The cholinergic anti-inflammatory pathway (CAP) has been implicated in the regulation of various diseases, including chronic inflammatory cardiovascular disorders such as atherosclerosis (AS). This study aims to explore the underlying regulatory mechanisms of CAP activity in the progression of AS. (2) Methods: The Apoe^-/- mice were subjected to sham, bilateral cervical vagotomy surgery (VGX), and VGX supplemented with Gainesville Tokushima scientists (GTS)-21 (4 mg/kg/d) and then fed with a high-fat diet for 10 weeks. Atherosclerotic lesion size and inflammation levels were investigated by histology and inflammatory cytokines analysis. The blood M1/M2 macrophages were analyzed by flow cytometry. Primary mouse bone marrow-derived macrophages (BMDM), peritoneal macrophages, and RAW264.7 cells were treated with CAP agonists acetylcholine (Ach) and GTS-21 to study their effects on macrophage functions. (3) Results: Compared with the sham group, inhibition of CAP by the VGX resulted in growing aortic lipid plaque area, deteriorated inflammatory levels, and aberrant quantity of M1/M2 macrophages in Apoe^-/- mice. However, these detrimental effects of VGX were significantly ameliorated by the reactivation of CAP through GTS-21 treatment. The in vitro study using macrophages revealed that stimulation with CAP agonists suppressed M1, but promoted M2 macrophage polarization through the upregulation of TNFAIP3 and phosphorylation STAT3 levels, respectively. Moreover, the activation of CAP inhibited the formation of macrophage foam cells in the peritoneal cavity by regulating genes related to cholesterol metabolism. (4) Conclusions: This study provides novel evidence and mechanisms that the CAP plays an important role in the regulation of AS development by controlling macrophage functions, implying a potential use of CAP activation as a therapeutic strategy for AS treatment.