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Brain, Behavior, and Immunity Jul 2024The vagus nerve, a pivotal link within the gut-brain axis, plays a critical role in maintaining homeostasis and mediating communication between the gastrointestinal...
The vagus nerve, a pivotal link within the gut-brain axis, plays a critical role in maintaining homeostasis and mediating communication between the gastrointestinal tract and the brain. It has been reported that gastrointestinal infection by Salmonella typhimurium (S. typhimurium) triggers gut inflammation and manifests as anxiety-like behaviors, yet the mechanistic involvement of the vagus nerve remains to be elucidated. In this study, we demonstrated that unilateral cervical vagotomy markedly attenuated anxiety-like behaviors induced by S. typhimurium SL1344 infection in C57BL/6 mice, as evidenced by the open field test and marble burying experiment. Furthermore, vagotomy significantly diminished neuronal activation within the nucleus of the solitary tract and amygdala, alongside mitigating aberrant glial cell activation in the hippocampus and amygdala. Additionally, vagotomy notably decreases serum endotoxin levels, counters the increase in splenic Salmonella concentration, and modulates the expression of inflammatory cytokines-including IL-6, IL-1β, and TNF-α-in both the gastrointestinal tract and brain, with a concurrent reduction in IL-22 and CXCL1 expression. This intervention also fostered the enrichment of beneficial gut microbiota, including Alistipes and Lactobacillus species, and augmented the production of gamma-aminobutyric acid (GABA) in the gut. Administration of GABA replicated the vagotomy's beneficial effects on reducing gut inflammation and anxiety-like behavior in infected mice. However, blockade of GABA receptors with picrotoxin abrogated the vagotomy's protective effects against gut inflammation, without influencing its impact on anxiety-like behaviors. Collectively, these findings suggest that vagotomy exerts a protective effect against infection by promoting GABA synthesis in the colon and alleviating anxiety-like behavior. This study underscores the critical role of the vagus nerve in relaying signals of gut infection to the brain and posits that targeting the gut-brain axis may offer a novel and efficacious approach to preventing gastrointestinal infections and associated behavioral abnormalities.
Topics: Animals; Anxiety; Mice; Vagus Nerve; Gastrointestinal Microbiome; Mice, Inbred C57BL; Vagotomy; Male; gamma-Aminobutyric Acid; Salmonella typhimurium; Cytokines; Brain-Gut Axis; Brain; Salmonella Infections; Behavior, Animal; Hippocampus; Gastrointestinal Tract; Inflammation; Amygdala
PubMed: 38663772
DOI: 10.1016/j.bbi.2024.04.034 -
Osteoarthritis and Cartilage Open Jun 2024Low vagal tone is common in osteoarthritis (OA) comorbidities and results in greater peripheral inflammation. Characterizing vagal tone's role in OA pathogenesis may...
OBJECTIVE
Low vagal tone is common in osteoarthritis (OA) comorbidities and results in greater peripheral inflammation. Characterizing vagal tone's role in OA pathogenesis may offer insights into OA's influences beyond the articular joint. We hypothesized that low vagal tone would accelerate onset of OA-related gait changes and worsen joint damage in a rat knee OA model.
METHODS
Knee OA was induced in male Sprague Dawley rats by transecting the medial collateral ligament and medial meniscus. Then, left cervical vagus nerve transection (VGX, n = 9) or sham VGX (non-VGX, n = 6) was performed. Gait and tactile sensitivity were assessed at baseline and across 12 weeks, with histology and systemic inflammation evaluated at endpoint.
RESULTS
At week 4, VGX animals showed limping gait characteristics through shifted stance times from their OA to non-OA limb (p = 0.055; stance time imbalance = 1.6 ± 1.6%) and shifted foot strike locations (p < 0.001; spatial symmetry = 48.4 ± 0.835%), while non-VGX animals walked with a balanced and symmetric gait. Also at week 4, while VGX animals had a mechanical sensitivity (50% withdrawal threshold) of 13.97 ± 7.70 compared to the non-VGX animal sensitivity of 29.74 ± 9.43, this difference was not statistically significant. Histologically, VGX animals showed thinner tibial cartilage and greater subchondral bone area than non-VGX animals (p = 0.076; VGX: 0.80 ± 0.036 mm; non-VGX: 0.736 ± 0.066 mm). No group differences in systemic inflammation were observed at endpoint.
CONCLUSIONS
VGX resulted in quicker onset of OA-related symptoms but remained unchanged at later timepoints. VGX also had thinner cartilage and abnormal bone remodeling than non-VGX. Overall, low vagal tone had mild effects on OA symptoms and joint remodeling, and not at the level seen in common OA comorbidities.
PubMed: 38655014
DOI: 10.1016/j.ocarto.2024.100467 -
Heliyon Apr 2024The use of proton pump inhibitors in the acute phase of cerebral infarction may lead to adverse long-term outcomes, this study aims to explore the potential of...
BACKGROUND
The use of proton pump inhibitors in the acute phase of cerebral infarction may lead to adverse long-term outcomes, this study aims to explore the potential of electroacupuncture (EA) in replacing omeprazole in exerting post-stroke gastrointestinal protection.
METHODS
A permanent middle cerebral artery infarction model was established using the modified Longa thread occlusion technique. Gastrointestinal motility, gastrointestinal mucosal damage, cerebral infarct volume, and alterations in choline acetyltransferase (ChAT)-positive neurons within the dorsal motor nucleus of the vagus nerve (DMV) were assessed after 7 days of EA at Zusanli (ST36) or omeprazole intervention. To evaluate the role of the vagal nerve in mitigating post-stroke gastrointestinal dysfunction, we employed subdiaphragmatic vagotomy and the ChAT-specific inhibitor α-NETA. Additionally, we utilized methyllycaconitine (MLA), a selective inhibitor of the α7-type nicotinic acetylcholine receptor (α7nAChR), and PNU282987, an agonist, to identify the target of EA.
RESULTS
EA restored ChAT neurons lost in the DMV, activated the vagus nerve and conferred cerebroprotection while ameliorating gastrointestinal mucosal injury and gastrointestinal motility disorders. In addition, following the administration of the α7nAChR antagonist, the attenuation of gastric mucosal injury and inflammatory factors induced by EA was hindered, although gastrointestinal motility still exhibited improvement.
CONCLUSION
EA at ST36 promotes the restoration of cholinergic signaling in the DMV of stroke-afflicted rats, and its excitation of the vagal nerve inhibits gastrointestinal inflammation after stroke via α7nAChR, while improvement in gastrointestinal motility could be mediated by other acetylcholine receptors.
PubMed: 38638995
DOI: 10.1016/j.heliyon.2024.e29426 -
PLoS Pathogens Apr 2024Influenza A virus (IAV) is a common respiratory pathogen and a global cause of significant and often severe morbidity. Although inflammatory immune responses to IAV...
Influenza A virus (IAV) is a common respiratory pathogen and a global cause of significant and often severe morbidity. Although inflammatory immune responses to IAV infections are well described, little is known about how neuroimmune processes contribute to IAV pathogenesis. In the present study, we employed surgical, genetic, and pharmacological approaches to manipulate pulmonary vagal sensory neuron innervation and activity in the lungs to explore potential crosstalk between pulmonary sensory neurons and immune processes. Intranasal inoculation of mice with H1N1 strains of IAV resulted in stereotypical antiviral lung inflammation and tissue pathology, changes in breathing, loss of body weight and other clinical signs of severe IAV disease. Unilateral cervical vagotomy and genetic ablation of pulmonary vagal sensory neurons had a moderate effect on the pulmonary inflammation induced by IAV infection, but significantly worsened clinical disease presentation. Inhibition of pulmonary vagal sensory neuron activity via inhalation of the charged sodium channel blocker, QX-314, resulted in a moderate decrease in lung pathology, but again this was accompanied by a paradoxical worsening of clinical signs. Notably, vagal sensory ganglia neuroinflammation was induced by IAV infection and this was significantly potentiated by QX-314 administration. This vagal ganglia hyperinflammation was characterized by alterations in IAV-induced host defense gene expression, increased neuropeptide gene and protein expression, and an increase in the number of inflammatory cells present within the ganglia. These data suggest that pulmonary vagal sensory neurons play a role in the regulation of the inflammatory process during IAV infection and suggest that vagal neuroinflammation may be an important contributor to IAV pathogenesis and clinical presentation. Targeting these pathways could offer therapeutic opportunities to treat IAV-induced morbidity and mortality.
Topics: Animals; Mice; Vagus Nerve; Orthomyxoviridae Infections; Sensory Receptor Cells; Influenza A Virus, H1N1 Subtype; Lung; Mice, Inbred C57BL; Male; Female; Influenza, Human
PubMed: 38626267
DOI: 10.1371/journal.ppat.1011635 -
International Journal of Biological... 2024It had been shown that selective cardiac vagal activation holds great potential for heart regeneration. Optogenetics has clinical translation potential as a novel means...
It had been shown that selective cardiac vagal activation holds great potential for heart regeneration. Optogenetics has clinical translation potential as a novel means of modulating targeted neurons. This study aimed to investigate whether cardiac vagal activation via optogenetics could improve heart regenerative repair after myocardial infarction (MI) and to identify the underlying mechanism. We used an adeno-associated virus (AAV) as the vector to deliver ChR2, a light-sensitive protein, to the left nodose ganglion (LNG). To assess the effects of the cardiac vagus nerve on cardiomyocyte (CM) proliferation and myocardial regeneration the light-emitting diode illumination (470 nm) was applied for optogenetic stimulation to perform the gain-of-function experiment and the vagotomy was used as a loss-of-function assay. Finally, sequencing data and molecular biology experiments were analyzed to determine the possible mechanisms by which the cardiac vagus nerve affects myocardial regenerative repair after MI. Absence of cardiac surface vagus nerve after MI was more common in adult hearts with low proliferative capacity, causing a poor prognosis. Gain- and loss-of-function experiments further demonstrated that optogenetic stimulation of the cardiac vagus nerve positively regulated cardiomyocyte (CM) proliferation and myocardial regeneration . More importantly, optogenetic stimulation attenuated ventricular remodeling and improved cardiac function after MI. Further analysis of sequencing results and flow cytometry revealed that cardiac vagal stimulation activated the IL-10/STAT3 pathway and promoted the polarization of cardiac macrophages to the M2 type, resulting in beneficial cardiac regenerative repair after MI. Targeting the cardiac vagus nerve by optogenetic stimulation induced macrophage M2 polarization by activating the IL-10/STAT3 signaling pathway, which obviously optimized the regenerative microenvironment and then improved cardiac function after MI.
Topics: Adult; Humans; Interleukin-10; Optogenetics; Myocardial Infarction; Vagus Nerve; Myocytes, Cardiac
PubMed: 38617528
DOI: 10.7150/ijbs.89883 -
Biochemical Pharmacology Jun 2024Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's...
Intestinal barrier dysfunction, leaky gut, is implicated in various diseases, including irritable bowel syndrome (IBS) and neurodegenerative conditions like Alzheimer's disease. Our recent investigation revealed that basal forebrain cholinergic neurons (BFCNs), critical for cognitive function, receive signals from butyrate and orexin, playing a role in regulating intestinal barrier function through adenosine A2B signaling and the vagus. This study explores the involvement and function of brain histamine, linked to BFCNs, in the regulation of intestinal barrier function. Colonic permeability, assessed by quantifying absorbed Evans blue in rat colonic tissue, showed that histamine did not affect increased colonic permeability induced by LPS when administered subcutaneously. However, intracisternal histamine administration improved colonic hyperpermeability. Elevating endogenous histamine levels in the brain with SKF91488, a histamine N-methyltransferase inhibitor, also improved colonic hyperpermeability. This effect was abolished by intracisternal chlorpheniramine, an histamine H1 receptor antagonist, not ranitidine, an H2 receptor antagonist. The SKF91488-induced improvement in colonic hyperpermeability was blocked by vagotomy, intracisternal pirenzepine (suppressing BFCNs activity), or alloxazine (an adenosine A2B receptor antagonist). Additionally, intracisternal chlorpheniramine injection eliminated butyrate-induced improvement in colonic hyperpermeability. These findings suggest that brain histamine, acting via the histamine H1 receptor, regulates intestinal barrier function involving BFCNs, adenosine A2B signaling, and the vagus. Brain histamine appears to centrally regulate intestinal barrier function influenced by butyrate, differentiating its actions from peripheral histamine in conditions like IBS, where mast cell-derived histamine induces leaky gut. Brain histamine emerges as a potential pharmacological target for diseases associated with leaky gut, such as dementia and IBS.
Topics: Animals; Histamine; Rats; Male; Receptor, Adenosine A2B; Cholinergic Neurons; Rats, Sprague-Dawley; Vagus Nerve; Colon; Permeability; Prosencephalon
PubMed: 38608783
DOI: 10.1016/j.bcp.2024.116201 -
Scientific Reports Apr 2024The vagus nerve is the only pathway for transmitting parasympathetic signals between the brain and thoracoabdominal organs, thereby exhibiting anti-inflammatory...
The vagus nerve is the only pathway for transmitting parasympathetic signals between the brain and thoracoabdominal organs, thereby exhibiting anti-inflammatory functions through the cholinergic anti-inflammatory pathway. Despite often being resected during lymph node dissection in upper gastrointestinal cancer surgery, the impact of vagotomy on postoperative outcomes in gastric cancer patients remains unclear. Sub-diaphragmatic vagotomy was performed on C57BL/6 mice. Three weeks later, syngeneic murine gastric cancer cell line YTN16P was injected into the peritoneal cavity, and the number of peritoneal metastases (PM) on the mesentery and omentum compared with control mice. The phenotypes of immune cells in peritoneal lavage and omental milky spots one day after tumor inoculation were analyzed using flow cytometry and immunohistochemistry. Intraperitoneal transfer of 3 × 10 YTN16P significantly increased the number of metastatic nodules on the mesentery in the vagotomy group compared to the control group. The omental metastasis grade was also significantly higher in the vagotomy group. Phenotypic analysis of immune cells in peritoneal lavage did not reveal significant differences after vagotomy. However, vagotomized mice exhibited a notable increase in milky spot area, with a higher presence of cytokeratin(+) tumor cells, F4/80(+) macrophages, and CD3(+) T cells. Vagus nerve signaling appears to regulate the immune response dynamics within milky spots against disseminated tumor cells and inhibits the development of PM. Preserving the vagus nerve may offer advantages in advanced gastric cancer surgery to reduce peritoneal recurrence.
Topics: Humans; Mice; Animals; Peritoneal Neoplasms; Stomach Neoplasms; Mice, Inbred C57BL; Omentum; Vagus Nerve
PubMed: 38570542
DOI: 10.1038/s41598-024-58440-w -
American Journal of Physiology.... Jun 2024Unacylated ghrelin (UAG), the unacylated form of ghrelin, accounts for 80%-90% of its circulation. Accumulated studies have pointed out that UAG may be used to treat...
Unacylated ghrelin (UAG), the unacylated form of ghrelin, accounts for 80%-90% of its circulation. Accumulated studies have pointed out that UAG may be used to treat metabolic disorders. This study aimed to investigate the effect of intestinal perfusion of UAG on metabolically associated fatty liver disease (MAFLD) induced by a high-fat diet and its possible mechanisms. Neuronal retrograde tracking combined with immunofluorescence, central administration of a glucagon-like peptide-1 receptor (GLP-1R) antagonist, and hepatic vagotomy was performed to reveal its possible mechanism involving a central glucagon-like peptide-1 (GLP-1) pathway. The results showed that intestinal perfusion of UAG significantly reduced serum lipids, aminotransferases, and food intake in MAFLD rats. Steatosis and lipid accumulation in the liver were significantly alleviated, and lipid metabolism-related enzymes in the liver were regulated. UAG upregulated the expression of GLP-1 receptor (GLP-1R) in the paraventricular nucleus (PVN) and GLP-1 in the nucleus tractus solitarii (NTS), as well as activated GLP-1 neurons in the NTS. Furthermore, GLP-1 fibers projected from NTS to PVN were activated by the intestinal perfusion of UAG. However, hepatic vagotomy and GLP-1R antagonists delivered into PVN before intestinal perfusion of UAG partially attenuated its alleviation of MAFLD. In conclusion, intestinal perfusion of UAG showed a therapeutic effect on MAFLD, which might be related to its activation of the GLP-1 neuronal pathway from NTS to PVN. The present results provide a new strategy for the treatment of MAFLD. Intestinal perfusion of UAG, the unacylated form of ghrelin, has shown promising potential for treating MAFLD. This study unveils a potential mechanism involving the central GLP-1 pathway, with UAG upregulating GLP-1R expression and activating GLP-1 neurons in specific brain regions. These findings propose a novel therapeutic strategy for MAFLD treatment through UAG and its modulation of the GLP-1 neuronal pathway.
Topics: Animals; Ghrelin; Male; Glucagon-Like Peptide 1; Glucagon-Like Peptide-1 Receptor; Rats; Rats, Sprague-Dawley; Signal Transduction; Liver; Diet, High-Fat; Lipid Metabolism; Non-alcoholic Fatty Liver Disease; Perfusion; Paraventricular Hypothalamic Nucleus; Vagotomy
PubMed: 38564323
DOI: 10.1152/ajpgi.00217.2023 -
Brain, Behavior, and Immunity Jul 2024The sympathetic arm of the inflammatory reflex is the efferent pathway through which the central nervous system (CNS) can control peripheral immune responses. Diminazene...
The sympathetic arm of the inflammatory reflex is the efferent pathway through which the central nervous system (CNS) can control peripheral immune responses. Diminazene aceturate (DIZE) is an antiparasitic drug that has been reported to exert protective effects on various experimental models of inflammation. However, the pathways by which DIZE promotes a protective immunomodulatory effects still need to be well established, and no studies demonstrate the capacity of DIZE to modulate a neural reflex to control inflammation. C57BL/6 male mice received intraperitoneal administration of DIZE (2 mg/Kg) followed by lipopolysaccharide (LPS, 5 mg/Kg, i.p.). Endotoxemic animals showed hyperresponsiveness to inflammatory signals, while those treated with DIZE promoted the activation of the inflammatory reflex to attenuate the inflammatory response during endotoxemia. The unilateral cervical vagotomy did not affect the anti-inflammatory effect of DIZE in the spleen and serum. At the same time, splenic denervation attenuated tumor necrosis factor (TNF) synthesis in the spleen and serum. Using broad-spectrum antibiotics for two weeks showed that LPS modulated the microbiota to induce a pro-inflammatory profile in the intestine and reduced the serum concentration of tryptophan and serotonin (5-HT), while DIZE restored serum tryptophan and increased the hypothalamic 5-HT levels. Furthermore, the treatment with 4-Chloro-DL-phenylalanine (pcpa, an inhibitor of 5-HT synthesis) abolished the anti-inflammatory effects of the DIZE in the spleen. Our results indicate that DIZE promotes microbiota modulation to increase central 5-HT levels and activates the efferent sympathetic arm of the inflammatory reflex to control splenic TNF production in endotoxemic mice.
Topics: Animals; Male; Mice; Spleen; Diminazene; Lipopolysaccharides; Mice, Inbred C57BL; Gastrointestinal Microbiome; Inflammation; Serotonin; Sympathetic Nervous System; Endotoxemia; Brain; Brain-Gut Axis; Anti-Inflammatory Agents; Tumor Necrosis Factor-alpha
PubMed: 38548186
DOI: 10.1016/j.bbi.2024.03.037 -
Surgery Jun 2024Gastric surgery is a crucial component of general surgery training. However, there is a paucity of high-quality data on operative volume and the diversity of surgical...
BACKGROUND
Gastric surgery is a crucial component of general surgery training. However, there is a paucity of high-quality data on operative volume and the diversity of surgical procedures that general surgery residents are exposed to.
METHODS
We conducted a retrospective analysis of operative case logs of all general surgery residents graduating from the American College of Graduate Medical Education-accredited program from 2009 to 2022. Data on the mean number of gastric procedures, including the mean in each subcategory, were retrieved. A Mann-Kendall trend test was used to investigate trends in operative volume.
RESULTS
Between 2009 and 2022, the mean overall logged gastric procedures rose significantly (τ = 0.722, P < .001) from 36.2 in 2009 to 49.2 in 2022 (35.9% increase). The most substantial growth was seen in laparoscopic gastric reduction for morbid obesity (mean 1.9 in 2017 to 19 in 2022; τ = 0.670, P = .009). A statistically significant increase was also seen in laparoscopic partial gastric resections, repair of gastric perforation, and "other major stomach procedures" (P < .05 for all comparisons). Open gastrostomy, open partial gastric resections, and open vagotomy all significantly decreased (P < .05 for all comparisons). There was no significant change in the volume of laparoscopic gastrectomy, total gastric resections, and non-laparoscopic gastric reductions for morbid obesity (P > .05 for all comparisons).
CONCLUSION
There has been a substantial increase in the volume of gastric surgery during residency over the past 14 years, driven mainly by an increase in laparoscopic gastric reduction. However, there may still be a need for further gastric surgical training to ensure well-rounded general surgeons.
Topics: Humans; Retrospective Studies; Internship and Residency; United States; General Surgery; Clinical Competence; Laparoscopy; Gastrectomy; Female; Male
PubMed: 38503604
DOI: 10.1016/j.surg.2024.02.012