Abstract 16785: Molecular Mechanisms of the Crosstalk Between Mitochondrial and NADPH Oxidase Derived Reactive Oxygen Species in White Blood Cells - Implications for Cardiovascular Diseases
Background: Many diseases and drug-induced complications are associated or even based on an imbalance between the formation of reactive oxygen and nitrogen species (ROS/RNS) and antioxidant enzymes catalyzing the break-down of these harmful oxidants. Previously we and others have reported on a crosstalk between different sources of oxidative stress. With the present study we sought to determine the underlying mechanism for this crosstalk.
Methods and results: Human neutrophils were used to study the induction of Nox-dependent oxidative burst by mitochondrial ROS (mtROS) in response to antimycin A or myxothiazol. Activation of Nox2 was measured by extracellular detection of ROS by a peroxidase-coupled chemiluminescence assay. We used different inhibitors for the involved signaling cascade such as cyclosporine A (inhibits the mitochondrial permeability transition pore [mPTP]), chelerythine (inhibitor of protein kinase C) and apocynin (inhibitor of NADPH oxidase). All of these inhibitors suppressed the antimycin A/myxothiazol-triggered extracellular ROS signal, whereas exogenous hydrogen peroxide mimicked the effect of mitochondrial ROS formation and caused extracellular superoxide formation (lucigenin ECL). According to preliminary data, this crosstalk between mtROS and NADPH oxidase was also suppressed in white blood cells from mice deficient of p47phox (an essential subunit for activation of Nox2) or cyclophilin D (a regulatory subunit of the mPTP), whereas this crosstalk was amplified in white blood cells from GPx-1 deficient mice or from MnSOD+/- mice. We also observed that increases in blood pressure, in endothelial dysfunction as well as in NADPH oxidase activity were more pronounced in MnSOD+/- mice as compared to their wild type littermates.
Conclusions: Previous data have demonstrated that NADPH oxidase derived ROS/RNS stimulate mitochondrial oxidative stress contributing to overall angiotensin-II dependent cellular dysfunction. Our data now show that mitochondrial ROS trigger the activation of NADPH oxidase, which may have severe effects on progression of cardiovascular diseases representing a feedback loop creating a vicious circle of oxidative stress.
- © 2011 by American Heart Association, Inc.