Cross-Talk Between Mitochondria and NADPH Oxidase: Effects of Mild Mitochondrial Dysfunction on Angiotensin II-Mediated Increase in Nox Isoform Expression and Activity in Vascular Smooth Muscle Cells

Abstract Mitochondria and NADPH oxidase activation are concomitantly involved in pathogenesis of many vascular diseases. However, possible cross-talk between those ROS-generating systems is unclear. We induced mild mitochondrial dysfunction due to mitochondrial DNA damage after 24 h incubation of rabbit aortic smooth muscle (VSMC) with 250 ng/mL ethidium bromide (EtBr). VSMC remained viable and had 29% less oxygen consumption, 16% greater baseline hydrogen peroxide, and unchanged glutathione levels. Serum-stimulated proliferation was unaltered at 24 h. Although PCR amplification of several mtDNA sequences was preserved, D-Loop mtDNA region showed distinct amplification of shorter products after EtBr. Such evidence for DNA damage was further enhanced after angiotensin-II (AngII) incubation. Remarkably, the normally observed increase in VSMC membrane fraction NADPH oxidase activity after AngII was completely abrogated after EtBr, together with failure to upregulate Nox1 mRNA expression. Conversely, basal No...