Nox-derived ROS are acutely activated in pressure overload pulmonary hypertension: indications for a seminal role for mitochondrial Nox4

Abstract

Pulmonary arterial hypertension is a severe progressive disease with marked morbidity and high mortality in which right ventricular (RV) failure is the major cause of death. Thus knowledge of the mechanisms underlying RV failure is an area of active interest. Previous studies suggest a role of NADPH oxidase in cardiomyocyte dysfunction in the left heart. Here we postulate that acute pressure overload induced by pulmonary artery banding (PAB) leads to a Nox4-initiated increase in reactive oxygen species (ROS) in mouse RV that may lead to feed-forward induction of Nox2. To test our hypothesis, ROS production was measured in RV and left ventricle homogenates. The data show that hydrogen peroxide (H2O2), but not superoxide anion (O2(·-)), was increased in the early phases (within 6 h) of PAB in RV and that this increase was diminished by catalase and diphenyleneiodonium chloride but not by SOD, N(ω)-nitro-l-arginin methyl ester, febuxostat, or indomethacin. H2O2 production in RV was not attenuated in Nox2 null mice subjected to 6 h PAB. Moreover, we observed an upregulation of Nox4 mRNA after 1 h of PAB and an increase in mitochondrial Nox4 protein 6 h post-PAB. In contrast, we observed an increase in Nox2 mRNA 1 day post-PAB. Expression of antioxidant enzymes SOD, catalase, and glutathione peroxidase did not change, but catalase activity increased 6 h post-PAB. Taken together, these findings show a role of mitochondria-localized Nox4 in the early phase of PAB and suggest an involvement of this isozyme in early ROS generation possibly contributing to progression of RV dysfunction and failure.

Cyclic stretch stimulates mitochondrial reactive oxygen species and Nox4 signaling in pulmonary artery smooth muscle cells

“…3, D and E). Interestingly, Nox4 protein has been reported to localize to the mitochondria in the right ventricles of a mouse model of pressure overload pulmonary hypertension (14) and in breast epithelial cells (17). These data suggest the possibility of a feed-forward mechanism involving cytosolic and mitochondrial ROS, although the mechanisms involved remain to be determined.…”

Updates of reactive oxygen species in melanoma etiology and progression

“…Emerging evidence show that mitochondria-generated ROS and cytosolic ROS (for example, NOX-generated ROS) interact with each other and may enhance the total cellular ROS production [88]; or some NOX isoforms may locate in mitochondria and become a source of mitochondrial ROS in addition to the ROS generated by electron transport complexes [89]. …”

Single oral acute fluoride exposure causes changes in cardiac expression of oxidant and antioxidant enzymes, apoptotic and necrotic markers in male rats

“…Recent studies showed that Nox4 mediated oxidative stress is a major cause in the failing heart [8], diabetic cardiomyopathy [39] and hypercholesterolemia induced cardiac dysfunction [40] and pressure overload pulmonary hypertension [41]. Thus, Nox4 mediated oxidative stress could be one of the possible mechanisms associated with acute F -induced cardiac dysfunction.…”