title: Rac1 mediates sex difference in cardiac tumor necrosis factor-alpha expression via NADPH oxidase-ERK1/2/p38 MAPK pathway in endotoxemia.
abstract: The purpose of this study was to investigate the role of Rac1 and estrogen in sex difference of cardiac tumor necrosis factor-alpha (TNF-alpha) expression during endotoxemia. Endotoxemia was induced in male and female mice by peritoneal injection of lipopolysaccharide (LPS, 4 mg/kg). Compared with female mice, male mice produced more TNF-alpha in the heart 4 h after LPS treatment, which were correlated with higher Rac1 and NADPH oxidase activity, more phosphorylation of ERK1/2 and p38 MAPK, and up-regulation of toll-like receptor-4 (TLR-4) expression in male mice. Cardiac specific Rac1 knockout or administration of 17beta-estradiol down-regulated Rac1 expression, attenuated gp91(phox)-NADPH oxidase expression and activity, decreased phosphorylation of ERK1/2/p38 MAPK and inhibited cardiac TNF-alpha expression induced by LPS, suggesting an important role of Rac1 and estrogen in LPS-stimulated TNF-alpha expression in the heart. More importantly, the sex difference in TNF-alpha expression was abrogated by Rac1 knockout or gp91(phox) knockout and by administration of apocynin or N-acetylcysteine in LPS-stimulated mice. To investigate the functional significance of sex difference in endotoxemia, heart function was measured in isolated hearts with a Langendorff system. Male mice exhibited worse myocardial dysfunction compared with female in endotoxemia. Treatment of male mice with 17beta-estradiol attenuated myocardial dysfunction during endotoxemia. In conclusion, LPS induces Rac1 activation, which contributes to NADPH oxidase activity and phosphorylation of ERK1/2/p38 MAPK, leading to TNF-alpha expression in the heart. The sex difference in TNF-alpha expression is estrogen-dependent and mediated via Rac1 dependent NADPH oxidase/ERK1/2 and p38 MAPK pathway in LPS-stimulated hearts.
authors.affiliation: Critical Illness Research, Lawson Health Research Institute, London Health Sciences Center, London, Ontario, Canada.
authors.forename: Huaqing
authors.initials: H
authors.lastname: Zhu
authors.forename: Limei
authors.initials: L
authors.lastname: Shan
authors.forename: Tianqing
authors.initials: T
authors.lastname: Peng
mesh_terms: D000818:Animals; D019446:Endotoxemia / Q000201:enzymology* / Q000503:physiopathology; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D006334:Heart Function Tests; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D009206:Myocardium / Q000201:enzymology* / Q000473:pathology; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D012727:Sex Characteristics; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D008070:Lipopolysaccharides; D008562:Membrane Glycoproteins; D017382:Reactive Oxygen Species; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D004958:Estradiol; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D048051:p38 Mitogen-Activated Protein Kinases; D020830:rac1 GTP-Binding Protein