Antioxidant tempol suppresses heart cytosolic phospholipase A2α stimulated by chronic intermittent hypoxia
Abstract
Adaptation to chronic intermittent hypoxia (CIH) is associated with reactive oxygen species (ROS) generation implicated in the improved cardiac tolerance against acute ischemia-reperfusion injury. Phospholipases A2 (PLA(2)s) play an important role in cardiomyocyte phospholipid metabolism influencing membrane homeostasis.
Here we aimed to determine the effect of CIH (7000 m, 8 h/day, 5 weeks) on the expression of cytosolic PLA(2) (cPLA(2)α), its phosphorylated form (p-cPLA(2)α), calcium-independent (iPLA(2)), and secretory (sPLA(2)IIA) at protein and mRNA levels, as well as fatty acids (FA) profile in left ventricular myocardium of adult male Wistar rats. Chronic administration of antioxidant tempol was used to verify the ROS involvement in CIH effect on PLA2s expression and phospholipid FA remodeling.
While CIH did not affect PLA2s mRNA levels, it increased the total cPLA(2)α protein in cytosol and membranes (by 191% and 38%, respectively) and p-cPLA(2)α (by 23%) in membranes. Onthe contrary, both iPLA(2) and sPLA(2)IIA were downregulated by CIH.
CIH further decreased phospholipid n-6 polyunsaturated FA (PUFA) and increased n-3 PUFA proportion. Tempol treatment prevented only CIH-induced cPLA(2)α up-regulation and its phosphorylation on Ser505.
Our results show that CIH diversely affect myocardial PLA(2)s and suggest that ROS are responsible for the activation of cPLA(2)α under these conditions.