title: Early inflammatory damage to intestinal neurons occurs via inducible nitric oxide synthase.
abstract: Intestinal inflammation affects the enteric nervous system (ENS) that lies adjacent to the smooth muscle layers. Previously, we showed that the loss of ENS neurons in animal models such as tri-nitrobenzene sulphonic acid (TNBS)-induced colitis was a limited and early event despite progressive worsening of inflammation. Here, we demonstrated that the rapid appearance of activated immune cells in the intestinal wall is selectively neurotoxic via iNOS-derived NO, using TNBS-induced colitis in both rats and mice, and a co-culture model of ENS neurons and smooth muscle. An influx of neutrophils and macrophages occurred within hours of initiation of rat colitis, correlating with iNOS expression, acutely elevated NO and neuronal death. In vitro, chemical donors of NO selectively caused axonal damage and neuronal death. These outcomes were similar to those seen with combined culture with either activated peritoneal immune cells or the immune cell lines RAW-264 and RBL-2H3. Immune cell-mediated neurotoxicity was blocked by the iNOS inhibitor L-NIL, and neuronal death was inhibited by the RIP-1 kinase inhibitor necrostatin. In a mouse model, the stereotypic loss of myenteric neurons by Day 4 post-TNBS was abrogated by the selective iNOS inhibitors L-NIL or 1400W without effect on other parameters of intestinal inflammation. Preservation of ENS neurons also ameliorated the hyperplasia of smooth muscle that is characteristic of intestinal inflammation, in line with prior work showing neural regulation of smooth muscle phenotype. This identifies a predominant pathway of immune cell damage to the ENS, where early, acute elevation of NO from iNOS can be cytotoxic to myenteric neurons.
authors.affiliation: Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: Shriram
authors.initials: S
authors.lastname: Venkataramana
authors.affiliation: Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Lourenssen
authors.affiliation: Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada.
authors.forename: K G
authors.initials: KG
authors.lastname: Miller
authors.affiliation: Gastrointestinal Diseases Research Unit, Department of Medicine, Queen's University, Kingston, Ontario, Canada. Electronic address: blennerm@queensu.ca.
authors.forename: M G
authors.initials: MG
authors.lastname: Blennerhassett
mesh_terms: D000818:Animals; D002460:Cell Line; D018920:Coculture Techniques; D003092:Colitis / Q000201:enzymology* / Q000473:pathology; D004195:Disease Models, Animal; D017615:Enteric Nervous System / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D005260:Female; D006965:Hyperplasia / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology; D008264:Macrophages / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D008297:Male; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology / Q000276:immunology / Q000473:pathology; D015213:Neuroimmunomodulation / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000201:enzymology* / Q000276:immunology / Q000473:pathology; D009504:Neutrophils / Q000187:drug effects / Q000473:pathology / Q000502:physiology; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017207:Rats, Sprague-Dawley; D014302:Trinitrobenzenesulfonic Acid
chemical_list: D009569:Nitric Oxide; D014302:Trinitrobenzenesulfonic Acid; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C496318:Nos2 protein, rat
keywords: Inducible nitric oxide synthase; Inflammation; Intestine; Myenteric neurons; Neurodegeneration; Nitric oxide