First Evidence for a Crosstalk Between Mitochondrial and NADPH Oxidase-Derived Reactive Oxygen Species in Nitroglycerin-Triggered Vascular Dysfunction

Abstract

Chronic nitroglycerin treatment results in development of nitrate tolerance associated with endothelial dysfunction (ED). We sought to clarify how mitochondria- and NADPH oxidase (Nox)-derived reactive oxygen species (ROS) contribute to nitrate tolerance and nitroglycerin-induced ED. Nitrate tolerance was induced by nitroglycerin infusion in male Wistar rats (100 microg/h/4 day) and in C57/Bl6, p47(phox/) and gp91(phox/) mice (50 microg/h/4 day). Protein and mRNA expression of Nox subunits were unaltered by chronic nitroglycerin treatment. Oxidative stress was determined in vascular rings and mitochondrial fractions of nitroglycerin-treated animals by L-012 enhanced chemiluminescence, revealing a dominant role of mitochondria for nitrate tolerance development. Isometric tension studies revealed that genetic deletion or inhibition (apocynin, 0.35 mg/h/4 day) of Nox improved ED, whereas nitrate tolerance was unaltered. Vice versa, nitrate tolerance was attenuated by co-treatment with the respiratory chain complex I inhibitor rotenone (100 microg/h/4 day) or the mitochondrial permeability transition pore blocker cyclosporine A (50 microg/h/4 day). Both compounds improved ED, suggesting a link between mitochondrial and Nox-derived ROS. Mitochondrial respiratory chain-derived ROS are critical for the development of nitrate tolerance, whereas Nox-derived ROS mediate nitrate tolerance-associated ED. This suggests a crosstalk between mitochondrial and Nox-derived ROS with distinct mechanistic effects and sites for pharmacological intervention.

Regulation of VEGF-induced endothelial cell migration by mitochondrial reactive oxygen species

“…This does not preclude the possibility that the NADPH oxidase is an important ROS contributor in this context, but suggests that mitochondrial and Nox pathways may be complementary. Some studies suggest that VEGF may facilitate cross talk between mitochondria and Nox during periods of increased ROS production (14,49). However, this phenomenon is poorly defined and requires further study.…”

“…Nox may function downstream of mitochondria because depletion of mtDNA or inhibition by the mitochondrial respiratory complex inhibitor rotenone or antimycin significantly reduced Nox expression in tumor cells (14). On the other hand, observations from an animal model of nitroglycerin-triggered vascular dysfunction implied that mtROS and Nox-derived ROS may function differentially, because mtROS was important for the initial development of nitrite tolerance whereas Nox-derived ROS were involved in the subsequent endothelial dysfunction (49). Continued investigation is needed of the relationship between mitochondria and Nox in endothelial cells.…”

Antiphospholipid antibodies induce translocation of TLR7 and TLR8 to the endosome in human monocytes and plasmacytoid dendritic cells

“…23,24 In brief, cells were incubated with 50M dihydroethidium (DHE) for 20 minutes at 37°C in PBS buffer. The cells were centrifuged for 5 minutes at 8000g, and the supernatant was discarded.…”

Tetrahydrobiopterin, Endothelial Nitric Oxide Synthase, and Mitochondrial Function in the Heart

“…The importance of mitochondrial ROS formation has also been highlighted recently in endothelial cells in response to angiotensin II, which induced mitochondrial dysfunction via protein kinase C-dependent activation of NADPH oxidase, and a crosstalk between mitochondrialand NADPH-oxidase-derived ROS was also found in nitroglycerin-triggered vascular dysfunction. 8,9 Cardiomyocyte-restricted overexpression of the ROS scavenger metallothionein prevented the DAHP-induced increase in O 2 ⅐Ϫ formation and preserved cardiomyocyte calcium handling and cardiac function. Because elevated blood pressure during DAHP treatment was not normalized by metallothionein overexpression, BH 4 depletion appears to impair cardiac structure and function independent of blood pressure changes.…”