1
|
Murray KM, Rude KM, Sladek J, Reardon C. Electrical activation of vagal efferent or afferent neurons elicits two distinct mechanisms of anti-inflammatory actions. The Journal of Immunology 2021. [DOI: 10.4049/jimmunol.206.supp.13.08] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/10/2023]
Abstract
Abstract
Inhibition of inflammation by reducing macrophage activation and pro-inflammatory cytokine production by electrical vagal nerve stimulation is well documented. Despite this ability to regulate inflammation, the mechanisms and intermediaries in this process are not completely understood. Vagal efferent neurons are thought to be the primary source of anti-inflammatory activity, despite the composition of the vagus nerve, which is predominantly vagal afferent neurons. Activation of vagal efferent neurons ameliorates lipopolysaccharide (LPS)-induced sepsis and is dependent on acetylcholine (ACh) derived from choline acetyltransferase (ChAT+) T-cells. Recent studies have identified vagal afferent fibers as anti-inflammatory as well, however the circuitry, including whether these vagal-mediated anti-inflammatory mechanisms converge, is unknown. Here, we show that VNS is capable of eliciting two distinct, anti-inflammatory mechanisms orchestrated by vagal efferent or afferent neurons. Using ChAT+ T-cell conditional KO mice, we show that afferent VNS reduced LPS-induced inflammation independently of T-cell derived ACh by measuring serum and lymphatic organ TNF-α and IL-6 levels. Using a highly selective β2-adrenergic receptor (β2-AR) antagonist, we show that intact, efferent, and notably afferent VNS regulates immunity in a β2-AR-dependent fashion. Together, these findings demonstrate that VNS is capable of eliciting two unique neuro-immune circuits with distinct mechanistic elements. Continued development of these circuits will inform the design of future vagal nerve stimulators, that may improve the efficacy of these devices in the regulation of immunity.
Collapse
|
2
|
Ramirez VT, Sladek J, Godinez DR, Rude KM, Chicco P, Murray K, Brust-Mascher I, Gareau MG, Reardon C. Sensory Nociceptive Neurons Contribute to Host Protection During Enteric Infection With Citrobacter rodentium. J Infect Dis 2021; 221:1978-1988. [PMID: 31960920 DOI: 10.1093/infdis/jiaa014] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Accepted: 01/15/2020] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND Neurons are an integral component of the immune system that functions to coordinate responses to bacterial pathogens. Sensory nociceptive neurons that can detect bacterial pathogens are found throughout the body with dense innervation of the intestinal tract. METHODS In this study, we assessed the role of these nerves in the coordination of host defenses to Citrobacter rodentium. Selective ablation of nociceptive neurons significantly increased bacterial burden 10 days postinfection and delayed pathogen clearance. RESULTS Because the sensory neuropeptide CGRP (calcitonin gene-related peptide) regulates host responses during infection of the skin, lung, and small intestine, we assessed the role of CGRP receptor signaling during C rodentium infection. Although CGRP receptor blockade reduced certain proinflammatory gene expression, bacterial burden and Il-22 expression was unaffected. CONCLUSIONS Our data highlight that sensory nociceptive neurons exert a significant host protective role during C rodentium infection, independent of CGRP receptor signaling.
Collapse
Affiliation(s)
- Valerie T Ramirez
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Jessica Sladek
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Dayn Romero Godinez
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Kavi M Rude
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Pamela Chicco
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Kaitlin Murray
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Ingrid Brust-Mascher
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Melanie G Gareau
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| | - Colin Reardon
- Department of Anatomy, Physiology, & Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, California, USA
| |
Collapse
|
3
|
Murray K, Rude KM, Sladek J, Reardon C. Divergence of neuroimmune circuits activated by afferent and efferent vagal nerve stimulation in the regulation of inflammation. J Physiol 2021; 599:2075-2084. [PMID: 33491187 DOI: 10.1113/jp281189] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 01/20/2021] [Indexed: 12/11/2022] Open
Abstract
KEY POINTS It has previously been shown that afferent and efferent vagal nerve stimulation potently inhibits lipopolysaccharide (LPS)-induced inflammation Our data show inhibition of inflammation by efferent but not afferent vagal nerve stimulation requires T-cell derived acetylcholine We show that afferent and efferent neuroimmune circuits require β2 -adrenergic receptor signalling ABSTRACT: Chronic inflammation due to inappropriate immune cell activation can have significant effects on a variety of organ systems, reducing lifespan and quality of life. As such, highly targeted control of immune cell activation is a major therapeutic goal. Vagus nerve stimulation (VNS) has emerged as a therapeutic modality that exploits neuroimmune communication to reduce immune cell activation and consequently inflammation. Although vagal efferent fibres were originally identified as the primary driver of anti-inflammatory actions, the vagus nerve in most species of animals predominantly comprises afferent fibres. Stimulation of vagal afferent fibres can also reduce inflammation; it is, however, uncertain how these two neuroimmune circuits diverge. Here we show that afferent VNS induces a mechanism distinct from efferent VNS, ameliorating lipopolysaccharide (LPS)-induced inflammation independently of T-cell derived acetylcholine (ACh) which is required by efferent VNS. Using a β2 -adrenergic receptor antagonist (β2 -AR), we find that immune regulation induced by intact, afferent, or efferent VNS occurs in a β2- AR-dependent manner. Together, our findings indicate that intact VNS activates at least two distinct neuroimmune circuits each with unique mechanisms of action. Selective targeting of either the vagal efferent or afferent fibres may provide more personalized, robust and effective control over inappropriate immune responses.
Collapse
Affiliation(s)
- Kaitlin Murray
- Department of Anatomy, Physiology, and Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, CA, USA
| | - Kavi M Rude
- Department of Anatomy, Physiology, and Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, CA, USA
| | - Jessica Sladek
- Department of Anatomy, Physiology, and Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, CA, USA
| | - Colin Reardon
- Department of Anatomy, Physiology, and Cell Biology, UC Davis School of Veterinary Medicine, UC Davis, Davis, CA, USA
| |
Collapse
|
4
|
Keogh CE, Rude KM, Gareau MG. Role of pattern recognition receptors and the microbiota in neurological disorders. J Physiol 2021; 599:1379-1389. [PMID: 33404072 DOI: 10.1113/jp279771] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 12/28/2020] [Indexed: 12/12/2022] Open
Abstract
In recent years, the gut microbiota has been increasingly implicated in the development of many extraintestinal disorders, including neurodevelopmental and neurodegenerative disorders. Despite this growing connection, our understanding of the precise mechanisms behind these effects is currently lacking. Pattern recognition receptors (PRRs) are important innate immune proteins expressed on the surface and within the cytoplasm of a multitude of cells, both immune and otherwise, including epithelial, endothelial and neuronal. PRRs comprise four major subfamilies: the Toll-like receptors (TLRs), the nucleotide-binding oligomerization domain leucine rich repeats-containing receptors (NLRs), the retinoic acid inducible gene 1-like receptors and the C-type lectin receptors. Recognition of commensal bacteria by PRRs is critical for maintaining host-microbe interactions and homeostasis, including behaviour. The expression of PRRs on multiple cell types makes them a highly interesting and novel target for regulation of host-microbe signalling, which may lead to gut-brain signalling. Emerging evidence indicates that two of the four known families of PRRs (the NLRs and the TLRs) are involved in the pathogenesis of neurodevelopmental and neurodegenerative disorders via the gut-brain axis. Taken together, increasing evidence supports a role for these PRRs in the development of neurological disorders, including Alzheimer's disease, Parkinson's disease and multiple sclerosis, via the microbiota-gut-brain axis.
Collapse
Affiliation(s)
- Ciara E Keogh
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| | - Kavi M Rude
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| | - Mélanie G Gareau
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, 95616, USA
| |
Collapse
|
5
|
Salvo E, Stokes P, Keogh CE, Brust-Mascher I, Hennessey C, Knotts TA, Sladek JA, Rude KM, Swedek M, Rabasa G, Gareau MG. A murine model of pediatric inflammatory bowel disease causes microbiota-gut-brain axis deficits in adulthood. Am J Physiol Gastrointest Liver Physiol 2020; 319:G361-G374. [PMID: 32726162 PMCID: PMC7509259 DOI: 10.1152/ajpgi.00177.2020] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Inflammatory bowel diseases (IBDs) are chronic intestinal diseases, frequently associated with comorbid psychological and cognitive deficits. These neuropsychiatric effects include anxiety, depression, and memory impairments that can be seen both during active disease and following remission and are more frequently seen in pediatric patients. The mechanism(s) through which these extraintestinal deficits develop remain unknown, and the study of these phenomenon is hampered by a lack of murine pediatric IBD models. Herein we describe microbiota-gut-brain (MGB) axis deficits following induction of colitis in a pediatric setting. Acute colitis was induced by administration of 2% dextran sodium sulfate (DSS) for 5 days starting at weaning [postnatal day (P)21] causing reduced weight gain, colonic shortening, and colonic inflammation by 8 days post-DSS (P29), which were mostly resolved in adult (P56) mice. Despite resolution of acute disease, cognitive deficits (novel object recognition task) and anxiety-like behavior (light/dark box) were identified in the absence of changes in exploratory behavior (open field test) in P56 mice previously treated with DSS at weaning. Behavioral deficits were found in conjunction with neuroinflammation, decreased neurogenesis, and altered expression of pattern recognition receptor genes in the hippocampus. Additionally, persistent alterations in the gut microbiota composition were observed at P56, including reduced butyrate-producing species. Taken together, these results describe for the first time the presence of MGB axis deficits following induction of colitis at weaning, which persist in adulthood.NEW & NOTEWORTHY Here we describe long-lasting impacts on the microbiota-gut-brain (MGB) axis following administration of low-dose dextran sodium sulfate (DSS) to weaning mice (P21), including gut dysbiosis, colonic inflammation, and brain/behavioral deficits in adulthood (P56). Early-life DSS leads to acute colonic inflammation, similar to adult mice; however, it results in long-lasting deficits in the MGB axis in adulthood (P56), in contrast to the transient deficits seen in adult DSS. This model highlights the unique features of pediatric inflammatory bowel disease.
Collapse
Affiliation(s)
- Eloisa Salvo
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Patricia Stokes
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Ciara E. Keogh
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Ingrid Brust-Mascher
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Carly Hennessey
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Trina A. Knotts
- 2Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, California
| | - Jessica A. Sladek
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Kavi M. Rude
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Michelle Swedek
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Gonzalo Rabasa
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| | - Mélanie G. Gareau
- 1Department of Anatomy, Physiology and Cell Biology, University of California, Davis, California
| |
Collapse
|
6
|
Murray K, Barboza M, Rude KM, Brust-Mascher I, Reardon C. Functional circuitry of neuro-immune communication in the mesenteric lymph node and spleen. Brain Behav Immun 2019; 82:214-223. [PMID: 31445965 PMCID: PMC6800652 DOI: 10.1016/j.bbi.2019.08.188] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 08/20/2019] [Accepted: 08/21/2019] [Indexed: 12/23/2022] Open
Abstract
The peripheral nervous system is an active participant in immune responses capable of blocking aberrant activation of a variety of immune cells. As one of these neuro-immune circuits, the cholinergic anti-inflammatory pathway has been well established to reduce the severity of several immunopathologies. While the activation of this pathway by vagal nerve stimulation requires sympathetic innervation of the spleen, the neuro-immune circuitry remains highly controversial. Neuro-immune pathways in other lymphoid tissues such as mesenteric lymph nodes (MLN) that are critical to the surveillance of the small intestine and proximal colon have not been assessed. Using conditionally expressed Channelrhodopsin, selective stimulation of sympathetic post-ganglionic neurons in the superior mesenteric ganglion (SMG) prevented macrophage activation and LPS-induced TNFα production in the spleen and MLN, but not in the inguinal LN. Site selective stimulation of the SMG induced the release of norepinephrine, resulting in β2AR dependent acetylcholine release in the MLN and spleen. VNS-evoked release of norepinephrine and acetylcholine in the MLN and spleen was significantly reduced using selective optogenetic blockade applied at the SMG. Additionally, this optogenetic blockade restored LPS-induced TNFα production, despite VNS. These studies identify the superior mesenteric ganglion as a critical node in a neuro-immune circuit that can inhibit immune function in the MLN and the spleen.
Collapse
Affiliation(s)
- Kaitlin Murray
- Department. of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Mariana Barboza
- Department. of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Kavi M. Rude
- Department. of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Ingrid Brust-Mascher
- Department. of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, California, United States of America
| | - Colin Reardon
- Department of Anatomy, Physiology, and Cell Biology, School of Veterinary Medicine, University of California Davis, Davis, CA, USA.
| |
Collapse
|
7
|
Rude KM, Pusceddu MM, Keogh CE, Sladek JA, Rabasa G, Miller EN, Sethi S, Keil KP, Pessah IN, Lein PJ, Gareau MG. Developmental exposure to polychlorinated biphenyls (PCBs) in the maternal diet causes host-microbe defects in weanling offspring mice. Environ Pollut 2019; 253:708-721. [PMID: 31336350 PMCID: PMC6719698 DOI: 10.1016/j.envpol.2019.07.066] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 07/12/2019] [Accepted: 07/12/2019] [Indexed: 05/05/2023]
Abstract
The gut microbiota is important for maintaining homeostasis of the host. Gut microbes represent the initial site for toxicant processing following dietary exposures to environmental contaminants. The diet is the primary route of exposure to polychlorinated biphenyls (PCBs), which are absorbed via the gut, and subsequently interfere with neurodevelopment and behavior. Developmental exposures to PCBs have been linked to increased risk of neurodevelopmental disorders (NDD), including autism spectrum disorder (ASD), which are also associated with a high prevalence of gastrointestinal (GI) distress and intestinal dysbiosis. We hypothesized that developmental PCB exposure impacts colonization of the gut microbiota, resulting in GI pathophysiology, in a genetically susceptible host. Mouse dams expressing two heritable human mutations (double mutants [DM]) that result in abnormal Ca2+ dynamics and produce behavioral deficits (gain of function mutation in the ryanodine receptor 1 [T4826I-RYR1] and a human CGG repeat expansion [170-200 CGG repeats] in the fragile X mental retardation gene 1 [FMR1 premutation]). DM and congenic wild type (WT) controls were exposed to PCBs (0-6 mg/kg/d) in the diet starting 2 weeks before gestation and continuing through postnatal day 21 (P21). Intestinal physiology (Ussing chambers), inflammation (qPCR) and gut microbiome (16S sequencing) studies were performed in offspring mice (P28-P30). Developmental exposure to PCBs in the maternal diet caused significant mucosal barrier defects in ileum and colon (increased secretory state and tight junction permeability) of juvenile DM mice. Furthermore, PCB exposure increased the intestinal inflammatory profile (Il6, Il1β, and Il22), and resulted in dysbiosis of the gut microbiota, including altered β-diversity, in juvenile DM mice developmentally exposed to 1 mg/kg/d PCBs when compared to WT controls. Collectively, these findings demonstrate a novel interaction between PCB exposure and the gut microbiota in a genetically susceptible host that provide novel insight into environmental risk factors for neurodevelopmental disorders.
Collapse
Affiliation(s)
- Kavi M Rude
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Matteo M Pusceddu
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Ciara E Keogh
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Jessica A Sladek
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Gonzalo Rabasa
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Elaine N Miller
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Sunjay Sethi
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Kimberly P Keil
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Isaac N Pessah
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Pamela J Lein
- Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States
| | - Mélanie G Gareau
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, Davis, CA, 95616, United States.
| |
Collapse
|
8
|
Rude KM, Keogh CE, Gareau MG. The role of the gut microbiome in mediating neurotoxic outcomes to PCB exposure. Neurotoxicology 2019; 75:30-40. [PMID: 31454514 DOI: 10.1016/j.neuro.2019.08.010] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 07/25/2019] [Accepted: 08/21/2019] [Indexed: 12/19/2022]
Abstract
A series of complex physiological processes underlie the development of the microbiota, gut, and brain in early life, which together communicate via the microbiota-gut-brain axis to maintain health and homeostasis. Disruption of these processes can lead to dysbiosis of the microbiota, pathophysiology of the gut and behavioral deficits including depression, anxiety and cognitive deficits. Environmental exposures, particularly in early life, can interfere with development and impact these pathways. This review will focus on the role of the microbiome and the gut in neurodevelopment and neurodegeneration as well as the impacts of environmental exposures, particularly to the neurotoxicant polychlorinated biphenyls (PCBs), given that the gut serves as the primary exposure route. There exists extensive research on the importance of the microbiome in the developing brain and connections with autism spectrum disorder (ASD) and increasing links being established between the microbiome and development of Alzheimer's disease (AD) in the elderly. Finally, we will speculate on the mechanisms through which PCBs can induce dysbiosis and dysregulate physiology of the gut and brain.
Collapse
Affiliation(s)
- Kavi M Rude
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, United States
| | - Ciara E Keogh
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, United States
| | - Mélanie G Gareau
- Department of Anatomy, Physiology and Cell Biology, School of Veterinary Medicine, University of California, Davis, CA, United States.
| |
Collapse
|