iNOS upregulation mediates oxidant-induced disruption of F-actin and barrier of intestinal monolayers.
Using oxidant-induced hyperpermeability of monolayers of intestinal (Caco-2) cells as a model for the pathophysiology of inflammatory bowel disease (IBD), we previously showed that oxidative injury to the F-actin cytoskeleton is necessary for the disruption of monolayer barrier integrity. We hypothesized that this cytoskeletal damage is caused by upregulation of an inducible nitric oxide (NO) synthase (iNOS)-driven pathway that overproduces reactive nitrogen metabolites (RNMs) such as NO and peroxynitrite (OONO(-)), which cause actin nitration and disassembly. Monolayers were exposed to H(2)O(2) or to RNMs with and without pretreatment with antioxidants or iNOS inhibitors. H(2)O(2) concentrations that disassembled and/or disrupted the F-actin cytoskeleton and barrier integrity also caused rapid iNOS activation, NO overproduction, and actin nitration. Added OONO(-) mimicked H(2)O(2); iNOS inhibitors and RNM scavengers were protective. Our results show that oxidant-induced F-actin and intestinal barrier disruption are caused by rapid iNOS upregulation that further increases oxidant levels; a similar positive feedback mechanism may underlie the episodic recurrence of the acute IBD attack. Confirming these mechanisms in vivo would provide a rationale for developing novel anti-RNM therapies for IBD.
Banan
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Division of Digestive Diseases, Department of Internal Medicine, Rush University Medical Center, Chicago, Illinois 60612, USA. ali_banan@rush.edu
Fields
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Zhang
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Keshavarzian
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D000199:Actins / Q000187:drug effects*; D018938:Caco-2 Cells; D003599:Cytoskeleton / Q000187:drug effects; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000187:drug effects* / Q000473:pathology; D009566:Nitrates / Q000502:physiology; D009569:Nitric Oxide / Q000502:physiology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D016877:Oxidants / Q000494:pharmacology*; D018384:Oxidative Stress; D010539:Permeability; D015854:Up-Regulation
D000199:Actins; D009566:Nitrates; D016877:Oxidants; C039642:peroxynitric acid; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; C496319:NOS2 protein, human; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II