title: Cellular and molecular mechanisms underlying LPS-associated myocyte impairment.
abstract: Recently we reported that Toll-like receptor 4 (TLR4)-positive immune cells of unknown identity were responsible for the LPS-induced depression of cardiac myocyte shortening. The aim of this study is to identify the TLR4-positive cell type that is responsible for the LPS-induced cardiac dysfunction. Neither neutrophil depletion alone nor mast cell deficiency had any impact on the impairment of myocyte shortening during LPS treatment. In contrast, LPS-treated, macrophage-deficient mice demonstrated a partial reduction in shortening compared with saline-treated, macrophage-deficient mice. Because the removal of macrophages could only partially restore myocyte shortening, we also investigated the effects of removing both neutrophils and macrophages on myocyte shortening. Interestingly, endotoxemic, neutrophil-depleted, and macrophage-deficient mice had completely restored myocyte shortening. Because both macrophages and neutrophils can produce nitric oxide (NO) and TNF-alpha, we examined LPS-treated inducible NO synthase knockout (iNOSKO) mice and TNF receptor (TNFR)-deficient mice. Eliminating both TNFR1 and TNFR2 was required to restore myocyte shortening during LPS treatment, whereas iNOS deficiency had no effect. These data suggest that macrophages and to a lesser degree neutrophils cause cardiac impairment, presumably via TNF-alpha.
authors.affiliation: Dept. of Physiology and Biophysics, Univ. of Calgary Medical Centre, AB, Canada.
authors.forename: Samantha A
authors.initials: SA
authors.lastname: Tavener
authors.forename: Paul
authors.initials: P
authors.lastname: Kubes
mesh_terms: D000818:Animals; D019446:Endotoxemia / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D006352:Heart Ventricles; D008070:Lipopolysaccharides; D008264:Macrophages / Q000378:metabolism; D008297:Male; D008407:Mast Cells / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009200:Myocardial Contraction; D032383:Myocytes, Cardiac / Q000378:metabolism*; D009504:Neutrophils / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000172:deficiency; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000172:deficiency; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000172:deficiency; D051197:Toll-Like Receptor 4 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II