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Sévoz-Couche C, Liao W, Foo HYC, Bonne I, Lu TB, Tan Qi Hui C, Azhar SH, Peh WYX, Yen SC, Wong WSF. Direct vagus nerve stimulation: A new tool to control allergic airway inflammation through α7 nicotinic acetylcholine receptor. Br J Pharmacol 2024; 181:1916-1934. [PMID: 38430056 DOI: 10.1111/bph.16334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 11/24/2023] [Accepted: 01/08/2024] [Indexed: 03/03/2024] Open
Abstract
BACKGROUND AND PURPOSE Asthma is characterized by airway inflammation, mucus hypersecretion, and airway hyperresponsiveness. The use of nicotinic agents to mimic the cholinergic anti-inflammatory pathway (CAP) controls experimental asthma. Yet, the effects of vagus nerve stimulation (VNS)-induced CAP on allergic inflammation remain unknown. EXPERIMENTAL APPROACH BALB/c mice were sensitized and challenged with house dust mite (HDM) extract and treated with active VNS (5 Hz, 0.5 ms, 0.05-1 mA). Bronchoalveolar lavage (BAL) fluid was assessed for total and differential cell counts and cytokine levels. Lungs were examined by histopathology and electron microscopy. KEY RESULTS In the HDM mouse asthma model, VNS at intensities equal to or above 0.1 mA (VNS 0.1) but not sham VNS reduced BAL fluid differential cell counts and alveolar macrophages expressing α7 nicotinic receptors (α7nAChR), goblet cell hyperplasia, and collagen deposition. Besides, VNS 0.1 also abated HDM-induced elevation of type 2 cytokines IL-4 and IL-5 and was found to block the phosphorylation of transcription factor STAT6 and expression level of IRF4 in total lung lysates. Finally, VNS 0.1 abrogated methacholine-induced hyperresponsiveness in asthma mice. Prior administration of α-bungarotoxin, a specific inhibitor of α7nAChR, but not propranolol, a specific inhibitor of β2-adrenoceptors, abolished the therapeutic effects of VNS 0.1. CONCLUSION AND IMPLICATIONS Our data revealed the protective effects of VNS on various clinical features in allergic airway inflammation model. VNS, a clinically approved therapy for depression and epilepsy, appears to be a promising new strategy for controlling allergic asthma.
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Affiliation(s)
- Caroline Sévoz-Couche
- INSERM, UMRS1158 Neurophysiologie Respiratoire et Clinique, Sorbonne Université, Paris, France
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Wupeng Liao
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
| | - Hazel Y C Foo
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
| | - Isabelle Bonne
- Electron Microscopy Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Thong Beng Lu
- Electron Microscopy Unit, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Department of Microbiology & Immunology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Caris Tan Qi Hui
- Advanced imaging and Histology Core, Immunology Program, Life Science Institute, National University of Singapore, Singapore
| | - Syaza Hazwany Azhar
- Advanced imaging and Histology Core, Immunology Program, Life Science Institute, National University of Singapore, Singapore
| | - Wendy Yen Xian Peh
- The N.1 Institute for Health, National University of Singapore, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore
| | - Shih-Cheng Yen
- The N.1 Institute for Health, National University of Singapore, Singapore
- Department of Electrical and Computer Engineering, National University of Singapore, Singapore
| | - W S Fred Wong
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Singapore-HUJ Alliance for Research and Enterprise (SHARE), National University of Singapore, Singapore
- Drug Discovery and Optimization Platform, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Mu X, Liu Z, Zhao X, Yuan L, Li Y, Wang C, Xiao G, Mu J, Qiu J, Qian Y. Bisphenol A Analogues Induce Neuroendocrine Disruption via Gut-Brain Regulation in Zebrafish. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:1022-1035. [PMID: 38165294 DOI: 10.1021/acs.est.3c05282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2024]
Abstract
There is epidemiological evidence in humans that exposure to endocrine-disrupting chemicals such as bisphenol A (BPA) is tied to abnormal neuroendocrine function with both behavioral and intestinal symptoms. However, the underlying mechanism of this effect, particularly the role of gut-brain regulation, is poorly understood. We exposed zebrafish embryos to a concentration series (including environmentally relevant levels) of BPA and its analogues. The analogue bisphenol G (BPG) yielded the strongest behavioral impact on zebrafish larvae and inhibited the largest number of neurotransmitters, with an effective concentration of 0.5 μg/L, followed by bisphenol AF (BPAF) and BPA. In neurod1:EGFP transgenic zebrafish, BPG and BPAF inhibited the distribution of enteroendocrine cells (EECs), which is associated with decreased neurotransmitters level and behavioral activity. Immune staining of ace-α-tubulin suggested that BPAF inhibited vagal neural development at 50 and 500 μg/L. Single-cell RNA-Seq demonstrated that BPG disrupted the neuroendocrine system by inducing inflammatory responses in intestinal epithelial cells via TNFα-trypsin-EEC signaling. BPAF exposure activated apoptosis and inhibited neural developmental pathways in vagal neurons, consistent with immunofluorescence imaging studies. These findings show that both BPG and BPAF affect the neuroendocrine system through the gut-brain axis but by different mechanisms, revealing new insights into the modes of bisphenol-mediated neuroendocrine disruption.
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Affiliation(s)
- Xiyan Mu
- Institute of Quality Standard and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Zaiteng Liu
- Institute of Quality Standard and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Xiaoyu Zhao
- Institute of Quality Standard and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Lilai Yuan
- Fishery Resource and Environment Research Center, Chinese Academy of Fishery Sciences, Beijing 214081, China
| | - Yingren Li
- Fishery Resource and Environment Research Center, Chinese Academy of Fishery Sciences, Beijing 214081, China
| | - Chengju Wang
- College of Sciences, China Agricultural University, Beijing 100083, China
| | - Guohua Xiao
- Hebei Ocean and Fisheries Science Research Institute, Qinhuangdao 066000, China
- Hebei Marine Living Resources and Environment Key Laboratory, Qinhuangdao 066004, China
| | - Jiandong Mu
- Hebei Ocean and Fisheries Science Research Institute, Qinhuangdao 066000, China
- Hebei Marine Living Resources and Environment Key Laboratory, Qinhuangdao 066004, China
| | - Jing Qiu
- Institute of Quality Standard and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, China
| | - Yongzhong Qian
- Institute of Quality Standard and Testing Technology for Agro-Products, Chinese Academy of Agricultural Sciences, Beijing 100081, China
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Wei Y, Peng S, Lian C, Kang Q, Chen J. Anorexia nervosa and gut microbiome: implications for weight change and novel treatments. Expert Rev Gastroenterol Hepatol 2022; 16:321-332. [PMID: 35303781 DOI: 10.1080/17474124.2022.2056017] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
INTRODUCTION Host-microbiota interactions may be involved in many physical and psychological functions ranging from the digestion of food, maintenance of immune homeostasis, to the regulation of mood and cognition. Microbiome dysbiosis has been consistently described in many diseases. The pathogenesis and weight regulation mechanism in anorexia nervosa (AN) also seem to be implicated in the dynamic bidirectional adjustment of the microbiota-gut-brain axis. This review aims at elucidating this relationship. AREA COVERED This review starts with a description of pathogenic gut-brain pathways. Next, we focus on the latest research on the associations between gut microbiota and weight change in the condition of AN. The strategies to alter the intestinal microbiome for the treatment of this disorder are discussed, including dietary, probiotics, prebiotics, synbiotics, and fecal microbiota transplantation. EXPERT OPINION Gut microbiome is inextricably linked to AN. It may regulate weight gain in the process of refeeding via the microbiota-gut-brain axis, while the specific mechanism has yet to be clearly established. In the future, a better understanding of gut microbiome could have implications for developing microbiome-based prevention, diagnostics and therapies.
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Affiliation(s)
- Yaohui Wei
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Sufang Peng
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Cheng Lian
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Qing Kang
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jue Chen
- Shanghai Mental Health Center, Shanghai Jiao Tong University School of Medicine, Shanghai, China
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The autonomic nervous system in septic shock and its role as a future therapeutic target: a narrative review. Ann Intensive Care 2021; 11:80. [PMID: 33999297 PMCID: PMC8128952 DOI: 10.1186/s13613-021-00869-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2021] [Accepted: 05/05/2021] [Indexed: 02/06/2023] Open
Abstract
The autonomic nervous system (ANS) regulates the cardiovascular system. A growing body of experimental and clinical evidence confirms significant dysfunction of this regulation during sepsis and septic shock. Clinical guidelines do not currently include any evaluation of ANS function during the resuscitation phase of septic shock despite the fact that the severity and persistence of ANS dysfunction are correlated with worse clinical outcomes. In the critical care setting, the clinical use of ANS-related hemodynamic indices is currently limited to preliminary investigations trying to predict and anticipate imminent clinical deterioration. In this review, we discuss the evidence supporting the concept that, in septic shock, restoration of ANS-mediated control of the cardiovascular system or alleviation of the clinical consequences induced by its dysfunction (e.g., excessive tachycardia, etc.), may be an important therapeutic goal, in combination with traditional resuscitation targets. Recent studies, which have used standard and advanced monitoring methods and mathematical models to investigate the ANS-mediated mechanisms of physiological regulation, have shown the feasibility and importance of monitoring ANS hemodynamic indices at the bedside, based on the acquisition of simple signals, such as heart rate and arterial blood pressure fluctuations. During the early phase of septic shock, experimental and/or clinical studies have shown the efficacy of negative-chronotropic agents (i.e., beta-blockers or ivabradine) in controlling persistent tachycardia despite adequate resuscitation. Central α-2 agonists have been shown to prevent peripheral adrenergic receptor desensitization by reducing catecholamine exposure. Whether these new therapeutic approaches can safely improve clinical outcomes remains to be confirmed in larger clinical trials. New technological solutions are now available to non-invasively modulate ANS outflow, such as transcutaneous vagal stimulation, with initial pre-clinical studies showing promising results and paving the way for ANS modulation to be considered as a new potential therapeutic target in patients with septic shock.
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TLR4 Signaling Selectively and Directly Promotes CGRP Release from Vagal Afferents in the Mouse. eNeuro 2021; 8:ENEURO.0254-20.2020. [PMID: 33318075 PMCID: PMC7877464 DOI: 10.1523/eneuro.0254-20.2020] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 12/03/2020] [Accepted: 12/03/2020] [Indexed: 12/14/2022] Open
Abstract
There has been a long-standing debate regarding the role of peripheral afferents in mediating rapid-onset anorexia among other responses elicited by peripheral inflammatory insults. Thus, the current study assessed the sufficiency of peripheral afferents expressing toll-like receptor 4 (TLR4) to the initiation of the anorexia caused by peripheral bacterial lipopolysaccharide (LPS). We generated a Tlr4 null (Tlr4LoxTB) mouse in which Tlr4 expression is globally disrupted by a loxP-flanked transcription blocking (TB) cassette. This novel mouse model allowed us to restore the endogenous TLR4 expression in specific cell types. Using Zp3-Cre and Nav1.8-Cre mice, we produced mice that express TLR4 in all cells (Tlr4LoxTB X Zp3-Cre) and in peripheral afferents (Tlr4LoxTB X Nav1.8-Cre), respectively. We validated the Tlr4LoxTB mice, which were phenotypically identical to previously reported global TLR4 knock-out mice. Contrary to our expectations, the administration of LPS did not cause rapid-onset anorexia in mice with Nav1.8-restricted TLR4. The later result prompted us to identify Tlr4-expressing vagal afferents using in situ hybridization (ISH). In vivo, we found that Tlr4 mRNA was primarily enriched in vagal Nav1.8 afferents located in the jugular ganglion that co-expressed calcitonin gene-related peptide (CGRP). In vitro, the application of LPS to cultured Nav1.8-restricted TLR4 afferents was sufficient to stimulate the release of CGRP. In summary, we demonstrated using a new mouse model that vagally-expressed TLR4 is selectively involved in stimulating the release of CGRP but not in causing anorexia.
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Direct measurement of vagal tone in rats does not show correlation to HRV. Sci Rep 2021; 11:1210. [PMID: 33441733 PMCID: PMC7807082 DOI: 10.1038/s41598-020-79808-8] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Accepted: 12/07/2020] [Indexed: 02/07/2023] Open
Abstract
The vagus nerve is the largest autonomic nerve, innervating nearly every organ in the body. “Vagal tone” is a clinical measure believed to indicate overall levels of vagal activity, but is measured indirectly through the heart rate variability (HRV). Abnormal HRV has been associated with many severe conditions such as diabetes, heart failure, and hypertension. However, vagal tone has never been directly measured, leading to disagreements in its interpretation and influencing the effectiveness of vagal therapies. Using custom carbon nanotube yarn electrodes, we were able to chronically record neural activity from the left cervical vagus in both anesthetized and non-anesthetized rats. Here we show that tonic vagal activity does not correlate with common HRV metrics with or without anesthesia. Although we found that average vagal activity is increased during inspiration compared to expiration, this respiratory-linked signal was not correlated with HRV either. These results represent a clear advance in neural recording technology but also point to the need for a re-interpretation of the link between HRV and “vagal tone”.
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Carrara M, Herpain A, Baselli G, Ferrario M. Vascular Decoupling in Septic Shock: The Combined Role of Autonomic Nervous System, Arterial Stiffness, and Peripheral Vascular Tone. Front Physiol 2020; 11:594. [PMID: 32733257 PMCID: PMC7358433 DOI: 10.3389/fphys.2020.00594] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Accepted: 05/12/2020] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Acute inflammation and sepsis are known to induce changes in vascular properties, leading to increased arterial stiffness; at the same time, the autonomic nervous system (ANS) also affects vascular properties by modulating the arterial smooth muscle tone, and it is widely reported that sepsis and septic shock severely impair ANS activity. Currently, clinical guidelines are mainly concerned to resuscitate septic shock patients from hypotension, hypovolemia, and hypoperfusion; however, if the current resuscitation maneuvers have a beneficial effect also on vascular properties and autonomic functionality is still unclear. The objective of this work is to assess the effects of standard resuscitation at vascular level and to verify if there is any association between alterations in vascular properties and ANS activity. METHODS Six pigs underwent a protocol of polymicrobial septic shock and resuscitation (fluids and noradrenaline). The arterial blood pressure (ABP) waveform was recorded in the central aorta and in the peripheral radial and femoral artery. The characteristic arterial time constant was computed at the three arterial sites based on the two-element Windkessel model, to characterize the overall arterial vascular tree. Moreover, independent estimates of total arterial compliance (AC) and total peripheral resistance (TPR) were performed. Baroreflex sensitivity (BRS), low frequency (LF, 0.04-0.15 Hz) spectral power of diastolic blood pressure, and indices of heart rate variability (HRV) were computed to assess ANS functionality. RESULTS Septic shock induced a severe vascular disarray, decoupling the usual pressure wave propagation from central to peripheral sites; this phenomenon appeared as an inversion of the physiological pulse pressure (PP) amplification, with a higher PP in the central aorta than in the peripheral arteries. The time constant was decreased, together with AC and TPR. ANS dysfunction was described by a reduced BRS, decreased LF power, and suppressed HRV. This compromised condition was not resolved by administration of fluids and noradrenaline. Thus, a persistent vascular and autonomic dysfunction were reported also in the resuscitated animals, and they were found to be significantly correlated. CONCLUSION Measures of vascular function and ANS activity could add information to standard hemodynamic and clinical markers, and the current resuscitation strategies could benefit from the adjunction of these additional functional indices.
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Affiliation(s)
- Marta Carrara
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Antoine Herpain
- Experimental Laboratory of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
- Department of Intensive Care, Erasme Hospital, Université Libre de Bruxelles, Brussels, Belgium
| | - Giuseppe Baselli
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy
| | - Manuela Ferrario
- Department of Electronics, Information and Bioengineering, Politecnico di Milano, Milan, Italy
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Carrara M, Herpain A, Baselli G, Ferrario M. A Mathematical Model of dP/dt Max for the Evaluation of the Dynamic Control of Heart Contractility in Septic Shock. IEEE Trans Biomed Eng 2019; 66:2719-2727. [PMID: 30872214 DOI: 10.1109/tbme.2019.2894333] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
OBJECTIVE Septic shock (SS) patients often show elevated heart rate (HR) despite resuscitation, and this condition is considered an early manifestation of myocardial dysfunction due to an impairment of autonomic nervous system (ANS). We aimed at proposing a mathematical model to assess the autonomic control of ventricular contractility (VC) and HR to track changes in heart functionality during an experimental animal model of SS and resuscitation. METHODS SS was induced in six adult swine by polymicrobial peritonitis. We analyzed the beat-to-beat variability of the maximum positive time derivative of left ventricular pressure (dP/dt max), heart period (HP), and aortic blood pressure (ABP). We identified the transfer functions relating fluctuations in ABP and HP to dP/dt max to characterize the static and dynamic properties of the arterial baroreflex and the force-frequency relation mechanisms, respectively. Standard indices of autonomic dysfunction have also been considered as HR variability (HRV) and baroreflex sensitivity (BRS). RESULTS During baseline, the baroreflex is predominant in controlling VC with a gain value of -5.8 (-7.5,-3) s-1, compared to -1.2 (-1.9,-0.5) mmHg/s ms-1 of the force-frequency autoregulation. During shock, both mechanisms increase their extent in VC control (higher gains and slightly faster dynamics for the baroreflex). After resuscitation, the physiological control of VC is not restored and all the animals still exhibit high HR and reduced HRV and BRS. CONCLUSION A condition of cardiovascular inefficiency is persistent after resuscitation and this could be due to autonomic dysfunction. SIGNIFICANCE The ANS in SS is crucial to restore homeostasis. Our model could be used to evaluate the efficacy of treatments on VC and related control mechanisms.
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Diet, gut microbiota composition and feeding behavior. Physiol Behav 2018; 192:177-181. [DOI: 10.1016/j.physbeh.2018.03.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2017] [Revised: 03/23/2018] [Accepted: 03/23/2018] [Indexed: 02/07/2023]
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Han T, Tang Y, Li J, Xue B, Gong L, Li J, Yu X, Liu C. Nitric oxide donor protects against acetic acid-induced gastric ulcer in rats via S-nitrosylation of TRPV1 on vagus nerve. Sci Rep 2017; 7:2063. [PMID: 28522805 PMCID: PMC5437002 DOI: 10.1038/s41598-017-02275-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/10/2017] [Indexed: 12/19/2022] Open
Abstract
This study was conducted to investigate the effects of nitric oxide (NO) in acetic acid-induced gastric ulcer of rats and the underlying mechanisms. We found that peritoneal injection of sodium nitroprusside (SNP), a NO donor, decreased the ulcer area, inflammatory cell infiltration and MPO degree in acetic acid-induced gastric ulcer in rats. This effect was abolished by a transient receptor potential vanilloid 1 (TRPV1) antagonist or prior subdiaphragmatic vagotomy. SNP increased the jejunal mesenteric afferent discharge in a dose-depended manner, which was largely diminished by pretreatment of S-nitrosylation blocker N-ethylmaleimide, TRPV1 antagonist capsazepine, genetic deletion of TRPV1, or vagotomy. Whole-cell patch clamp recording showed that SNP depolarized the resting membrane potential of NG neurons, and enhanced capsaicin-induced inward current, which were both blocked by N-ethylmaleimide. Our results suggest that NO donor SNP alleviates acetic acid-induced gastric ulcer in rats via vagus nerve, while S-nitrosylation of TRPV1 may participate in this route. Our findings reveal a new mechanism for vagal afferent activation, and a new potential anti-inflammatory target.
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Affiliation(s)
- Ting Han
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Yan Tang
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jing Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Bing Xue
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Liping Gong
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Jingxin Li
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Xiao Yu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China
| | - Chuanyong Liu
- Department of Physiology, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China. .,Provincial Key Lab of Mental Disorder, School of Basic Medical Sciences, Shandong University Cheeloo Medical College, Shandong, China.
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Page AJ, Kentish SJ. Plasticity of gastrointestinal vagal afferent satiety signals. Neurogastroenterol Motil 2017; 29. [PMID: 27781333 DOI: 10.1111/nmo.12973] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Accepted: 09/19/2016] [Indexed: 12/21/2022]
Abstract
The vagal link between the gastrointestinal tract and the central nervous system (CNS) has numerous vital functions for maintaining homeostasis. The regulation of energy balance is one which is attracting more and more attention due to the potential for exploiting peripheral hormonal targets as treatments for conditions such as obesity. While physiologically, this system is well tuned and demonstrated to be effective in the regulation of both local function and promoting/terminating food intake the neural connection represents a susceptible pathway for disruption in various disease states. Numerous studies have revealed that obesity in particularly is associated with an array of modifications in vagal afferent function from changes in expression of signaling molecules to altered activation mechanics. In general, these changes in vagal afferent function in obesity further promote food intake instead of the more desirable reduction in food intake. It is essential to gain a comprehensive understanding of the mechanisms responsible for these detrimental effects before we can establish more effective pharmacotherapies or lifestyle strategies for the treatment of obesity and the maintenance of weight loss.
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Affiliation(s)
- A J Page
- Centre for Nutrition and Gastrointestinal Disease, Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia.,Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, SA, Australia.,Department of Gastroenterology and Hepatology, Royal Adelaide Hospital, Adelaide, SA, Australia
| | - S J Kentish
- Centre for Nutrition and Gastrointestinal Disease, Discipline of Medicine, University of Adelaide, Adelaide, SA, Australia.,Nutrition and Metabolism, South Australian Health and Medical Research Institute, Adelaide, SA, Australia.,School of Medicine, University of Queensland, St Lucia, QLD, Australia
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Browning KN, Verheijden S, Boeckxstaens GE. The Vagus Nerve in Appetite Regulation, Mood, and Intestinal Inflammation. Gastroenterology 2017; 152:730-744. [PMID: 27988382 PMCID: PMC5337130 DOI: 10.1053/j.gastro.2016.10.046] [Citation(s) in RCA: 197] [Impact Index Per Article: 28.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2016] [Revised: 09/27/2016] [Accepted: 10/27/2016] [Indexed: 02/07/2023]
Abstract
Although the gastrointestinal tract contains intrinsic neural plexuses that allow a significant degree of independent control over gastrointestinal functions, the central nervous system provides extrinsic neural inputs that modulate, regulate, and integrate these functions. In particular, the vagus nerve provides the parasympathetic innervation to the gastrointestinal tract, coordinating the complex interactions between central and peripheral neural control mechanisms. This review discusses the physiological roles of the afferent (sensory) and motor (efferent) vagus in regulation of appetite, mood, and the immune system, as well as the pathophysiological outcomes of vagus nerve dysfunction resulting in obesity, mood disorders, and inflammation. The therapeutic potential of vagus nerve modulation to attenuate or reverse these pathophysiological outcomes and restore autonomic homeostasis is also discussed.
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Affiliation(s)
- Kirsteen N. Browning
- Department of Neural and Behavioral Science Penn State College of Medicine 500 University Drive MC H109 Hershey, PA 17033
| | - Simon Verheijden
- Translational Research Center of Gastrointestinal Disorders (TARGID) KU Leuven Herestraat 49 3000 Leuven, Belgium
| | - Guy E. Boeckxstaens
- Translational Research Center of Gastrointestinal Disorders (TARGID) KU Leuven Herestraat 49 3000 Leuven, Belgium,Division of Gastroenterology & Hepatology University Hospital Leuven Herestraat 49 3000 Leuven, Belgium,Address of correspondence: Prof. dr. Guy Boeckxstaens,
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Phillips Campbell RB, Duffourc MM, Schoborg RV, Xu Y, Liu X, KenKnight BH, Beaumont E. Aberrant fecal flora observed in guinea pigs with pressure overload is mitigated in animals receiving vagus nerve stimulation therapy. Am J Physiol Gastrointest Liver Physiol 2016; 311:G754-G762. [PMID: 27562060 DOI: 10.1152/ajpgi.00218.2016] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 08/17/2016] [Indexed: 01/31/2023]
Abstract
Altered gut microbial diversity has been associated with several chronic disease states, including heart failure. Stimulation of the vagus nerve, which innervates the heart and abdominal organs, is proving to be an effective therapeutic in heart failure. We hypothesized that cervical vagus nerve stimulation (VNS) could alter fecal flora and prevent aberrations observed in fecal samples from heart failure animals. To determine whether microbial abundances were altered by pressure overload (PO), leading to heart failure and VNS therapy, a VNS pulse generator was implanted with a stimulus lead on either the left or right vagus nerve before creation of PO by aortic constriction. Animals received intermittent, open-loop stimulation or sham treatment, and their heart function was monitored by echocardiography. Left ventricular end-systolic and diastolic volumes, as well as cardiac output, were impaired in PO animals compared with baseline. VNS mitigated these effects. Metagenetic analysis was then performed using 16S rRNA sequencing to identify bacterial genera present in fecal samples. The abundance of 10 genera was significantly altered by PO, 8 of which were mitigated in animals receiving either left- or right-sided VNS. Metatranscriptomics analyses indicate that the abundance of genera that express genes associated with ATP-binding cassette transport and amino sugar/nitrogen metabolism was significantly changed following PO. These gut flora changes were not observed in PO animals subjected to VNS. These data suggest that VNS prevents aberrant gut flora following PO, which could contribute to its beneficial effects in heart failure patients.
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Affiliation(s)
| | - Michelle M Duffourc
- Department of Biomedical Sciences, East Tennessee State University, Johnson City, Tennessee
| | - Robert V Schoborg
- Department of Biomedical Sciences, East Tennessee State University, Johnson City, Tennessee
| | - Yanji Xu
- Shaun & Lilly International, Collierville, Tennessee; and
| | - Xinyi Liu
- Shaun & Lilly International, Collierville, Tennessee; and
| | | | - Eric Beaumont
- Department of Biomedical Sciences, East Tennessee State University, Johnson City, Tennessee;
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Calzetta L, Luongo L, Cazzola M, Page C, Rogliani P, Facciolo F, Maione S, Capuano A, Rinaldi B, Matera MG. Contribution of sensory nerves to LPS-induced hyperresponsiveness of human isolated bronchi. Life Sci 2015; 131:44-50. [PMID: 25914087 DOI: 10.1016/j.lfs.2015.03.023] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2014] [Revised: 03/11/2015] [Accepted: 03/29/2015] [Indexed: 10/23/2022]
Abstract
AIMS Bacterial lipopolysaccharide (LPS) can induce bronchial hyperresponsiveness (BHR), but the underlying mechanisms remain to be determined. Here, the possible contribution of sensory nerves to LPS-induced BHR was examined in human isolated bronchi to pharmacologically identify the mechanisms underlying this phenomenon. MAIN METHODS Human isolated bronchial tone was induced by electrical field stimulation (EFS). The responses of airways to LPS, with or without capsaicin desensitization or thiorphan treatment were studied and the transient receptor potential vanilloid type 1 (TRPV1) expression was assessed. We performed similar experiments in the presence of a TRPV1 or a neurokinin (NK) 2 receptor antagonist using SB366791 and GR159897, respectively. KEY FINDINGS LPS increased (≃2.3-fold, P<0.001) the contraction induced by EFS, compared to control tissues. Acute administration of capsaicin enhanced (≃2.3-fold, P<0.001) the EFS-mediated contraction, but did not potentiate the effect of LPS. Thiorphan increased (≃1.3-fold, P<0.05) the contractile response of LPS treated tissues and, at lower frequencies, it enhanced (≃1.7-fold, P<0.001) the capsaicin-induced contraction. In capsaicin-desensitized bronchi, LPS did not modify (P>0.05) the EFS contractile response, nor after treatment with thiorphan. Capsaicin desensitization reduced (≃0.4-fold, P<0.001) the LPS-induced BHR. SB366791 and GR159897 prevented the LPS-induced BHR and the release of NKA. LPS increased (+85.3±9.5%, P<0.01) the surface membrane expression of TRPV1 in parasympathetic ganglia. SIGNIFICANCE Our results demonstrate the involvement of capsaicin-sensitive sensory nerves and neutral endopeptidases in LPS-induced BHR of the human bronchi, associated with an upregulation of TRPV1 and release of NKA.
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Affiliation(s)
- Luigino Calzetta
- Department of Systems Medicine, University of Rome "Tor Vergata", Rome, Italy
| | - Livio Luongo
- Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - Mario Cazzola
- Department of Systems Medicine, University of Rome "Tor Vergata", Rome, Italy.
| | - Clive Page
- The Sackler Institute of Pulmonary Pharmacology, Institute of Pharmaceutical Science, King's College London, London, UK
| | - Paola Rogliani
- Department of Systems Medicine, University of Rome "Tor Vergata", Rome, Italy
| | | | - Sabatino Maione
- Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - Annalisa Capuano
- Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - Barbara Rinaldi
- Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy
| | - Maria Gabriella Matera
- Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy
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Kentish SJ, Page AJ. The role of gastrointestinal vagal afferent fibres in obesity. J Physiol 2014; 593:775-86. [PMID: 25433079 DOI: 10.1113/jphysiol.2014.278226] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 11/21/2014] [Indexed: 12/16/2022] Open
Abstract
Gastrointestinal (GI) vagal afferents are a key mediatory of food intake. Through a balance of responses to chemical and mechanical stimuli food intake can be tightly controlled via the ascending satiety signals initiated in the GI tract. However, vagal responses to both mechanical and chemical stimuli are modified in diet-induced obesity (DIO). Much of the research to date whilst in relatively isolated/controlled circumstances indicates a shift between a balance of orexigenic and anorexigenic vagal signals to blunted anorexigenic and potentiated orexigenic capacity. Although the mechanism responsible for the DIO shift in GI vagal afferent signalling is unknown, one possible contributing factor is the gut microbiota. Nevertheless, whatever the mechanism, the observed changes in gastrointestinal vagal afferent signalling may underlie the pathophysiological changes in food consumption that are pivotal for the development and maintenance of obesity.
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Affiliation(s)
- Stephen J Kentish
- Discipline of Medicine, University of Adelaide, Frome Road, Adelaide, SA, 5005, Australia; Royal Adelaide Hospital, North Terrace, Adelaide, SA, 5000, Australia
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Daulatzai MA. Chronic functional bowel syndrome enhances gut-brain axis dysfunction, neuroinflammation, cognitive impairment, and vulnerability to dementia. Neurochem Res 2014; 39:624-44. [PMID: 24590859 DOI: 10.1007/s11064-014-1266-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2013] [Revised: 02/10/2014] [Accepted: 02/25/2014] [Indexed: 12/15/2022]
Abstract
The irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal disorder world wide that lasts for decades. The human gut harbors a diverse population of microbial organisms which is symbiotic and important for well being. However, studies on conventional, germ-free, and obese animals have shown that alteration in normal commensal gut microbiota and an increase in pathogenic microbiota-termed "dysbiosis", impact gut function, homeostasis, and health. Diarrhea, constipation, visceral hypersensitivity, and abdominal pain arise in IBS from the gut-induced dysfunctional metabolic, immune, and neuro-immune communication. Dysbiosis in IBS is associated with gut inflammation. Gut-related inflammation is pivotal in promoting endotoxemia, systemic inflammation, and neuroinflammation. A significant proportion of IBS patients chronically consume alcohol, non-steroidal anti-inflammatories, and fatty diet; they may also suffer from co-morbid respiratory, neuromuscular, psychological, sleep, and neurological disorders. The above pathophysiological substrate is underpinned by dysbiosis, and dysfunctional bidirectional "Gut-Brain Axis" pathways. Pathogenic gut microbiota-related systemic inflammation (due to increased lipopolysaccharide and pro-inflammatory cytokines, and barrier dysfunction), may trigger neuroinflammation enhancing dysfunctional brain regions including hippocampus and cerebellum. These as well as dysfunctional vago-vagal gut-brain axis may promote cognitive impairment. Indeed, inflammation is characteristic of a broad spectrum of neurodegenerative diseases that manifest demntia. It is argued that an awareness of pathophysiological impact of IBS and implementation of appropriate therapeutic measures may prevent cognitive impairment and minimize vulnerability to dementia.
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Affiliation(s)
- Mak Adam Daulatzai
- Sleep Disorders Group, EEE Department, Melbourne School of Engineering, The University of Melbourne, Grattan Street, 3rd Floor, Room No. 344, Parkville, VIC, 3010, Australia,
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Babic T, Travagli RA. Acute pancreatitis decreases the sensitivity of pancreas-projecting dorsal motor nucleus of the vagus neurones to group II metabotropic glutamate receptor agonists in rats. J Physiol 2014; 592:1411-21. [PMID: 24445314 DOI: 10.1113/jphysiol.2013.270108] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Recent studies have shown that pancreatic exocrine secretions (PES) are modulated by dorsal motor nucleus of the vagus (DMV) neurones, whose activity is finely tuned by GABAergic and glutamatergic synaptic inputs. Group II metabotropic glutamate receptors (mGluR) decrease synaptic transmission to pancreas-projecting DMV neurones and increase PES. In the present study, we used a combination of in vivo and in vitro approaches aimed at characterising the effects of caerulein-induced acute pancreatitis (AP) on the vagal neurocircuitry modulating pancreatic functions. In control rats, microinjection of bicuculline into the DMV increased PES, whereas microinjections of kynurenic acid had no effect. Conversely, in AP rats, microinjection of bicuculline had no effect, whereas kynurenic acid decreased PES. DMV microinjections of the group II mGluR agonist APDC and whole cell recordings of excitatory currents in identified pancreas-projecting DMV neurones showed a reduced functional response in AP rats compared to controls. Moreover, these changes persisted up to 3 weeks following the induction of AP. These data demonstrate that AP increases the excitatory input to pancreas-projecting DMV neurones by decreasing the response of excitatory synaptic terminals to group II mGluR agonist.
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Affiliation(s)
- Tanja Babic
- Department of Neural and Behavioral Sciences, Penn State College of Medicine, 500 University Drive, MC H109, Hershey, PA 17033, USA.
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18
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Riley TP, Neal-McKinney JM, Buelow DR, Konkel ME, Simasko SM. Capsaicin-sensitive vagal afferent neurons contribute to the detection of pathogenic bacterial colonization in the gut. J Neuroimmunol 2013; 257:36-45. [PMID: 23481698 DOI: 10.1016/j.jneuroim.2013.01.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 01/16/2013] [Accepted: 01/22/2013] [Indexed: 12/22/2022]
Abstract
Vagal activation can reduce inflammation and disease activity in various animal models of intestinal inflammation via the cholinergic anti-inflammatory pathway. In the current model of this pathway, activation of descending vagal efferents is dependent on a signal initiated by stimulation of vagal afferents. However, little is known about how vagal afferents are activated, especially in the context of subclinical or clinical pathogenic bacterial infection. To address this question, we first determined if selective lesions of capsaicin-sensitive vagal afferents altered c-Fos expression in the nucleus of the solitary tract (nTS) after mice were inoculated with either Campylobacter jejuni or Salmonella typhimurium. Our results demonstrate that the activation of nTS neurons by intraluminal pathogenic bacteria is dependent on intact, capsaicin sensitive vagal afferents. We next determined if inflammatory mediators could cause the observed increase in c-Fos expression in the nTS by a direct action on vagal afferents. This was tested by the use of single-cell calcium measurements in cultured vagal afferent neurons. We found that tumor necrosis factor alpha (TNFα) and lipopolysaccharide (LPS) directly activate cultured vagal afferent neurons and that almost all TNFα and LPS responsive neurons were sensitive to capsaicin. We conclude that activation of the afferent arm of the parasympathetic neuroimmune reflex by pathogenic bacteria in the gut is dependent on capsaicin sensitive vagal afferent neurons and that the release of inflammatory mediators into intestinal tissue can be directly sensed by these neurons.
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Affiliation(s)
- T P Riley
- Programs in Neuroscience, Washington State University, Pullman, WA 99164, USA.
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Liang H, Xu L, Zhou C, Zhang Y, Xu M, Zhang C. Vagal activities are involved in antigen-specific immune inflammation in the intestine. J Gastroenterol Hepatol 2011; 26:1065-71. [PMID: 21371121 DOI: 10.1111/j.1440-1746.2011.06710.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/09/2022]
Abstract
BACKGROUND AND AIMS The mechanism of intestinal immune inflammation, such as food allergy, remains to be further understood. The present study aims to investigate the role of the vagal nerve in the pathogenesis of skewed T-helper 2 (Th2) responses in the intestine. METHODS The expression of the immunoglobulin E (IgE) receptor on the vagus nerve in the mouse intestine was observed by immunohistochemistry. Vagus ganglion neurons (VGN) were isolated from mice and cultured in vitro. The IgE receptor/IgE complex on vagus neurons was examined by immune precipitation assay. A food allergy mouse model was developed; the effect of the partial removal of the vagal nerve (PRVn) via surgery or administration with anticholinergic agents on the suppression of Th2 inflammation was evaluated. RESULTS The high-affinity IgE receptor was detected on the intestinal vagus nerve. An increase in the expression of the IgE receptor on the vagus nerve was observed in the intestines of mice with intestinal immune inflammation. Isolated mouse VGN express IgE receptor I, which could form complexes with IgE. Re-exposure to specific antigens activated the sensitized VGN, manifesting the release of transmitter glutamate that could activate dendritic cells by increasing the expression of CD80 and major compatibility complex class II and suppressing interleukin-12. The PRVn suppressed Th2 inflammation in the intestine. CONCLUSIONS The intestinal vagus nerve in mice expresses a high-affinity IgE receptor. An antigen-specific immune response can activate the vagus nerve in the intestine and induces the release of transmitters to modulate dendritic cell phenotypes that facilitate the development of skewed Th2 polarization in the intestine.
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Affiliation(s)
- Hong Liang
- Department of Neurosurgery, Daping Hospital of the Third Military Medical University, Yuzhong District, Chongqing, China
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20
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Mueller MH, Karpitschka M, Gao Z, Mittler S, Kasparek MS, Renz B, Sibaev A, Glatzle J, Li Y, Kreis ME. Vagal innervation and early postoperative ileus in mice. J Gastrointest Surg 2011; 15:891-900; discussion 900-1. [PMID: 21437764 DOI: 10.1007/s11605-011-1481-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 02/27/2011] [Indexed: 01/31/2023]
Abstract
INTRODUCTION Postoperative ileus is characterized by infiltrates of leukocytes in the gut wall 24 h after surgery, which is subject to vagal modulation. We hypothesized that vagal modulation is irrelevant during earlier hours of postoperative ileus and aimed to determine whether afferent neuronal feedback to the central nervous system is altered by vagal innervation during this early period. METHODS C57BL6 mice were laparotomized and received standardized small bowel manipulation to induce postoperative ileus. Subgroups were vagotomized 3-4 days prior to experiments while control animals were sham-operated. Three or 9 h later a 2-cm jejunal segment was harvested for multi-unit mesenteric afferent nerve recordings in vitro. Intestinal motility was monitored continuously and intestinal muscularis was stained for myeloperoxidase to determine infiltration of leukocytes. RESULTS Peak amplitudes of intestinal motility and afferent nerve discharge at baseline were not different in all subgroups. Afferent discharge to 5-HT (500 μM) was virtually absent following vagotomy at 3 and 9 h of postoperative ileus (POI) compared to controls (p < 0.05). Maximum afferent nerve discharge to bradykinin and peak firing during maximum distension at 60 mmHg was not different in all subgroups while luminal distension from 10 to 30 mmHg was lower at 3 h of POI following vagotomy compared to controls (p < 0.05). The number of myeloperoxidase positive cells was similar at 3 h of POI in both subgroups; however, at 9 h of POI, ileus counts were increased to 713 ± 99 cells following vagotomy compared to 47 ± 6 cells per square millimeter in control animals. CONCLUSIONS Vagal afferents mediate sensitivity to low-threshold distension and 5-HT during postoperative ileus but not to high-threshold distension and bradykinin. Vagal inhibition of the intestinal immune response is present at 9 h but not detectable earlier, i.e., at 3 h of postoperative ileus when spinal reflex inhibition may prevail.
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Affiliation(s)
- Mario H Mueller
- Walter-Brendel Institute for Surgical Research, Ludwig-Maximilian's University, Munich, Germany.
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21
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De Winter BY, De Man JG. Interplay between inflammation, immune system and neuronal pathways: Effect on gastrointestinal motility. World J Gastroenterol 2010; 16:5523-35. [PMID: 21105185 PMCID: PMC2992670 DOI: 10.3748/wjg.v16.i44.5523] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Sepsis is a systemic inflammatory response representing the leading cause of death in critically ill patients, mostly due to multiple organ failure. The gastrointestinal tract plays a pivotal role in the pathogenesis of sepsis-induced multiple organ failure through intestinal barrier dysfunction, bacterial translocation and ileus. In this review we address the role of the gastrointestinal tract, the mediators, cell types and transduction pathways involved, based on experimental data obtained from models of inflammation-induced ileus and (preliminary) clinical data. The complex interplay within the gastrointestinal wall between mast cells, residential macrophages and glial cells on the one hand, and neurons and smooth muscle cells on the other hand, involves intracellular signaling pathways, Toll-like receptors and a plethora of neuroactive substances such as nitric oxide, prostaglandins, cytokines, chemokines, growth factors, tryptases and hormones. Multidirectional signaling between the different components in the gastrointestinal wall, the spinal cord and central nervous system impacts inflammation and its consequences. We propose that novel therapeutic strategies should target inflammation on the one hand and gastrointestinal motility, gastrointestinal sensitivity and even pain signaling on the other hand, for instance by impeding afferent neuronal signaling, by activation of the vagal anti-inflammatory pathway or by the use of pharmacological agents such as ghrelin and ghrelin agonists or drugs interfering with the endocannabinoid system.
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22
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Keenan DM, Iranmanesh A, Veldhuis JD. Analytical construct of reversible desensitization of pituitary-testicular signaling: illustrative application in aging. Am J Physiol Regul Integr Comp Physiol 2010; 300:R349-60. [PMID: 21084679 DOI: 10.1152/ajpregu.00477.2010] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Luteinizing hormone (LH) administered in pharmacological amounts downregulates Leydig cell steroidogenesis. Whether reversible downregulation of physiological gonadotropin drive operates in vivo is unknown. Most of the analytical models of dose-response functions that have been constructed are biased by the assumption that no downregulation exists. The present study employs a new analytical platform to quantify potential (but not required) pulsatile cycles of LH-testosterone (T) dose-response stimulation, desensitization, and recovery (pulse-by-pulse hysteresis) in 26 healthy men sampled every 10 min for 24 h. A sensitivity-downregulation hysteresis construct predicted marked hysteresis with a median time delay to LH dose-response inflection within individual T pulses of 23 min and with median T pulse onset and recovery LH sensitivities of 1.1 and 0.10 slope unit, respectively (P < 0.001). A potency-downregulation model yielded median estimates of one-half maximally stimulatory LH concentrations (EC(50) values) of 0.66 and 7.5 IU/l for onset and recovery, respectively (P < 0.001). An efficacy-downregulation formulation of hysteresis forecasts median LH efficacies of 20 and 8.3 ng·dl(-1)·min(-1) for onset and offset of T secretory burst, respectively (P = 0.002). Segmentation of the LH-T data by age suggested greater sensitivity, higher EC(50) (increased LH potency), and markedly (2.7-fold) attenuated LH efficacy in older individuals. Each of the three hysteresis models yielded a marked (P < 0.005) reduction in estimated model residual error compared with no hysteresis. In summary, model-based analyses allowing for (but not requiring) reversible pituitary-gonadal effector-response downregulation are consistent with a hypothesis of recurrent, brief cycles of LH-dependent stimulation, desensitization, and recovery of pulsatile T secretion in vivo and an age-associated reduction of LH efficacy. Prospective studies would be required to prove this aging effect.
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Affiliation(s)
- Daniel M Keenan
- Department of Statistics, University of Virginia, Charlottesville, USA
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23
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Ochoa-Cortes F, Ramos-Lomas T, Miranda-Morales M, Spreadbury I, Ibeakanma C, Barajas-Lopez C, Vanner S. Bacterial cell products signal to mouse colonic nociceptive dorsal root ganglia neurons. Am J Physiol Gastrointest Liver Physiol 2010; 299:G723-32. [PMID: 20576919 DOI: 10.1152/ajpgi.00494.2009] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
This study examined whether bacterial cell products that might gain access to the intestinal interstitium could activate mouse colonic nociceptive dorsal root ganglion (DRG) neurons using molecular and electrophysiological recording techniques. Colonic projecting neurons were identified by using the retrograde tracer fast blue and Toll-like receptor (TLR) 1, 2, 3, 4, 5, 6, 9, adapter proteins Md-1 and Md-2, and MYD88 mRNA expression was observed in laser-captured fast blue-labeled neurons. Ultrapure LPS 1 microg/ml phosphorylated p65 NF-kappaB subunits increased transcript for TNF-alpha and IL-1beta and stimulated secretion of TNF-alpha from acutely dissociated DRG neurons. In current-clamp recordings from colonic DRG neurons, chronic incubation (24 h) of ultrapure LPS significantly increased neuronal excitability. In acute studies, 3-min superfusion of standard-grade LPS (3-30 microg/ml) reduced the rheobase by up to 40% and doubled action potential discharge rate. The LPS effects were not significantly different in TLR4 knockout mice compared with wild-type mice. In contrast to standard-grade LPS, acute application of ultrapure LPS did not increase neuronal excitability in whole cell recordings or afferent nerve recordings from colonic mesenteric nerves. However, acute application of bacterial lysate (Escherichia coli NLM28) increased action potential discharge over 60% compared with control medium. Moreover, lysate also activated afferent discharge from colonic mesenteric nerves, and this was significantly increased in chronic dextran sulfate sodium salt mice. These data demonstrate that bacterial cell products can directly activate colonic DRG neurons leading to production of inflammatory cytokines by neurons and increased excitability. Standard-grade LPS may also have actions independent of TLR signaling.
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Yüce B, Kemmer M, Qian G, Müller M, Sibaev A, Li Y, Kreis ME, Storr M. Cannabinoid 1 receptors modulate intestinal sensory and motor function in rat. Neurogastroenterol Motil 2010; 22:672-e205. [PMID: 20158615 DOI: 10.1111/j.1365-2982.2010.01473.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
BACKGROUND Cannabinoid receptors are involved in visceral pain perception and control of intestinal motility in vivo. The underlying mechanisms are not well characterized. We aimed to determine whether the cannabinoid-1 (CB(1)) receptor modulates intestinal afferent nerve discharge and the peristaltic reflex. METHODS Rats were anesthetized and intestinal segments were removed. Afferent nerve discharge from a mesenteric nerve was investigated in vitro in the presence of the CB(1) antagonist SR 141716A or the CB(1) agonist WIN 55212-2. The myenteric peristaltic reflex was induced by electrical field stimulation and influence of SR 141716A or WIN 55212-2 was recorded. KEY RESULTS Afferent nerve discharge to the algesic mediator bradykinin was reduced to 11 +/- 5.1 imp s(-1) following pretreatment with SR 141716A and unchanged after WIN 55212-2 compared to 63 +/- 15.4 imp s(-1) in controls. At maximum distension pressure (80 cmH(2)O) during ramp distension, 92 +/- 12.4 imp s(-1) were reached following SR 141716A compared to 260 +/- 13.2 in vehicle controls and 227 +/- 15.4 in WIN 55212-2 pretreated animals. In contrast, afferent discharge to 5-HT (500 micromol L(-1)) was increased to 75 +/- 24.6 imp s(-1) following WIN 55212-2 compared to 18 +/- 5.9 imp s(-1) in controls, whereas SR 141716A had no effect. Ascending neuronal contractions were dose-dependently attenuated in the presence of SR 141716A and latency of these contractions was reduced. WIN 55212-2 had opposite effects that were abolished by SR 141716A. CONCLUSIONS & INFERENCES Activation of the CB(1) receptor differentially alters afferent intestinal nerve sensitivity to bradykinin, 5-HT, and noxious mechanical distension, while it strengthens ascending neuronal contractions. Further studies are needed to determine the physiological relevance of these observations.
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Affiliation(s)
- B Yüce
- Department of Internal Medicine II, Ludwig Maximilians University, 81377 Munich, Germany.
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25
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Role of the vagus nerve on the development of postoperative ileus. Langenbecks Arch Surg 2010; 395:407-11. [PMID: 20333399 DOI: 10.1007/s00423-010-0594-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 01/07/2010] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Postoperative ileus involves reflex inhibition of intestinal motility within hours after surgery and a subsequent intestinal inflammatory response that is characterized by efferent vagal modulation via acetylcholine receptors on intestinal macrophages. We aimed to characterize the role of vagal modulation of intestinal motility during the early hours after surgery. METHODS C57BL6 mice underwent laparotomy and standardized small bowel manipulation to induce postoperative ileus. Subgroups were vagotomized 3-4 days prior to experiments or received pharmacological inhibition of the acetylcholine alpha7 subunit with the inhibitor alpha-bungarotoxin, while control animals were sham operated and remained otherwise untreated. Three hours later, a 2-cm jejunal segment was harvested with the mesentery attached. Mesenteric afferent nerve recordings were established in an organ bath generating a multiunit signal with subsequent computerized analysis. Intraluminal pressure was continuously recorded to assess intestinal motility. Afferent nerve responses were quantified at baseline and to chemical stimulation with bradykinin (0.5 microM) or serotonin (5-HT; 500 microM) and following mechanical stimulation by continuous ramp distension to 60 mmHg. RESULTS Peak amplitudes of intestinal motility and afferent nerve discharge at baseline were not different following chronic vagotomy, alpha-bungarotoxin or sham operation. Maximum afferent discharge to 5-HT following alpha-bungarotoxin was comparable to sham controls, while the response was reduced in chronically vagotomized animals (p < 0.05). Maximum afferent nerve discharge to bradykinin and peak firing during maximum distension at 60 mmHg was similar in the different subgroups. At luminal distension from 10 to 30 mmHg, afferent discharge was lower in vagotomized animals compared to sham controls (p < 0.05) but unchanged after alpha-bungarotoxin. CONCLUSIONS Sensitivity to low-threshold distension and 5-HT is mediated via vagal afferents during postoperative ileus, while sensitivity to high-threshold distension and bradykinin is independent of vagal afferent innervation. Early inhibition of intestinal motility at 3 h after onset of postoperative ileus does not appear to depend on vagal innervation.
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Buchholz BM, Bauer AJ. Membrane TLR signaling mechanisms in the gastrointestinal tract during sepsis. Neurogastroenterol Motil 2010; 22:232-45. [PMID: 20377787 PMCID: PMC2951022 DOI: 10.1111/j.1365-2982.2009.01464.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Our bacterial residents are deadly Janus-faced indwellers that can lead to a sepsis-induced systemic inflammatory response syndrome and multiple organ failure. Over half of ICU patients suffer from infections and sepsis remains one of the top 10 causes of death worldwide. Severe ileus frequently accompanies sepsis setting up an insidious cycle of gut-derived microbial translocation and the copious intestinal production of potent systemic inflammatory mediators. Few therapeutic advances have occurred to prevent/treat the sequelae of sepsis. Here, we selectively review studies on cellular membrane-bound Toll-like receptor (TLR) mechanisms of ileus. Virtually, no data exist on Gram-positive/TLR2 signaling mechanisms of ileus; however, TLR2 is highly inducible by numerous inflammatory mediators and studies using clinically relevant scenarios of Gram-positive sepsis are needed. Specific Gram-negative/TLR4 signaling pathways are being elucidated using a 'reverse engineering' approach, which has revealed that endotoxin-induced ileus is dually mediated by classical leukocyte signaling and by a MyD88-dependent non-bone marrow-derived mechanism, but the specific roles of individual cell populations are still unknown. Like TLR2, little is also know of the role of flagellin/TLR5 signaling in ileus. But, much can be learned by understanding TLR signaling in other systems. Clearly, the use of polymicrobial models provides important clinical relevancy, but the simultaneous activation of virtually all pattern recognition receptors makes it impossible to discretely study specific pathways. We believe that the dissection of individual TLR pathways within the gastrointestinal tract, which can then be intelligently reassembled in a meaningful manner, will provide insight into treatments for sepsis.
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Affiliation(s)
- Bettina M. Buchholz
- Department of Medicine/Gastroenterology, University of Pittsburgh, Pittsburgh, PA, Department of Surgery, Rheinische Friedrich-Wilhelms-Universität Bonn, Germany
| | - Anthony J. Bauer
- Department of Medicine/Gastroenterology, University of Pittsburgh, Pittsburgh, PA
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ENHANCED EXPRESSION OF CARDIAC NERVE GROWTH FACTOR AND NERVE SPROUTING MARKERS IN RATS FOLLOWING GASTRIC PERFORATION. Shock 2010; 33:170-8. [DOI: 10.1097/shk.0b013e3181ab9ee0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Goehler LE, Lyte M, Gaykema RPA. Infection-induced viscerosensory signals from the gut enhance anxiety: implications for psychoneuroimmunology. Brain Behav Immun 2007; 21:721-6. [PMID: 17428636 PMCID: PMC1986672 DOI: 10.1016/j.bbi.2007.02.005] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/01/2007] [Revised: 02/26/2007] [Accepted: 02/27/2007] [Indexed: 12/20/2022] Open
Abstract
Infection and inflammation lead to changes in mood and cognition. Although the "classic" sickness behavior syndrome, involving fatigue, social withdrawal, and loss of appetites are most familiar, other emotional responses accompany immune activation, including anxiety. Recent studies have shown that gastrointestinal bacterial infections lead to enhanced anxiety-like behavior in mice. The bacteria-induced signal is most likely carried by vagal sensory neurons, and occurs early on (within 6h) during the infection. These signals induce evidence of activation in brain regions that integrate viscerosensory information with mood, and potentiate activation in brain regions established as key players in fear and anxiety. The findings underline the importance of viscerosensory signals arising from the gastrointestinal tract in modulation of behaviors appropriate for coping with threats, and suggest that these signals may contribute to affective symptoms associated with gastrointestinal disorders.
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Affiliation(s)
- Lisa E Goehler
- Department of Psychology, University of Virginia, Charlottesville, VA 22904-4400, USA.
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