Abstract 17101: Mitochondrial Ros Activates Golgi Resident eNOS in the Vascular Endothelium Following Hypoxia-Reoxygenation (h/r): Role of Oxygen Sensing in Cellular Adaptation

Abstract

Adaptation to hypoxia (H) is achieved by the cell's ability to sense alterations in O 2 and respond accordingly. Changes in cellular oxygenation trigger signaling pathways with reactive oxygen species (ROS) and nitric oxide (NO) playing critical roles. ROS and NO also regulate the tissue inflammation and injury associated with ischemia/reperfusion as occurs in unstable coronary syndromes. While moderate periods of H followed by reoxygenation (R) can induce vascular protection, questions remain regarding how this occurs. Therefore, studies were performed to elucidate the mechanisms responsible for protection of vascular endothelium following H/R with particular focus on ROS-induced NO production and its downstream targets, in endothelial cells (BAECs). We hypothesize that mitochondrial ROS-mediated activation of Golgi eNOS-NO is integral in inducing the vasculoprotective mechanisms critical for cellular adaptation to H/R. BAECs were subjected to H (2 hr) and R (10 - 60 min). H triggered clustering of mitochondria toward nuclei and upon R perinuclear ROS production was seen (Fig). This was associated with activation of Golgi resident ser/thr kinase (Akt) as evidenced by the presence of pAkt in the Golgi fraction that in turn activates Golgi resident eNOS. The H/R-induced activation of Golgi eNOS was attenuated by pretreatment with complex III inhibitor, myxothiazol confirming the role of mitochondrial ROS. NO produced at the vicinity of the Golgi inhibited vWF release. Thus, in response to R, eNOS in endothelial cells is activated due to serine 1179 phosphorylation within the Golgi by mitochondrial ROS-induced activation of PI3K/Akt. A discrete intracellular NOS pool is activated by H/R that serves to inhibit exocytosis of WPB that in turn can decrease inflammation and thrombosis. This knowledge of how cells sense and adapt following hypoxia provides a framework to understand the role of H/R in cardiovascular diseases that can be ultimately used toward treatment.