Modulation of Reactive Oxygen Species and Collagen Synthesis by Angiotensin II in Cardiac Fibroblasts

摘要

Angiotensin II increases the NAD(P)H-dependent superoxide anion production and the intracellular generationof reactive oxygen species in cardiac fibroblasts and apocynin, a NAD(P)H oxidase inhibitor, abrogates this rise. Themembrane associated NAD(P)H oxidase complex is the predominant source of superoxide anion and reactive oxygenspecies generation in angiotensin II-stimulated adult cardiac fibroblasts. Inhibition of this NAD(P)H oxidase complexwith apocynin completely blocks the angiotensin II-stimulated collagen production, collagen I and III protein and mRNAexpression.Superoxide anion production is also increased by the Cu,Zn-superoxide dismutase (SOD) inhibitor diethyldithiocarbamicacid (DETC) and decreased by the superoxide scavenger tempol in control and ANG II-treated fibroblasts. ANG II andDETC stimulate the collagen production and the collagen I and fibronectin content in fibroblasts. The SOD mimeticstempol and EUK-8 as well as polyethyleneglycol-SOD reduce the collagen production.ANG II also decreases the activity and mRNA and protein expression of the mitochondrial antioxidants Mn-SOD andperoxiredoxin-3. Upon phosphorylation of Akt by ANG II, P-Akt is translocated from the cytoplasm to the nucleus andnuclear phosphorylation of FOXO3a by P-Akt leads to relocalisation of FOXO3a from the nucleus to the cytosol,resulting in a decrease in its transcriptional activity and in Mn-SOD expression. These data indicate that ANG IIinactivates FOXO3a by activating Akt and this leads to a reduction in the expression of the antioxidant Mn-SOD. A roleof SOD and the formed reactive oxygen species in the regulation and organization of collagen in cardiac fibroblasts issuggested.