Pivotal role of NOX‐2‐containing NADPH oxidase in early ischemic preconditioning

Abstract

Reactive oxygen species (ROS)‐mediated signaling is implicated in early ischemic preconditioning (PC). A NOX‐2‐containing NADPH oxidase is a recognized major source of ROS in cardiac myocytes, whose activity is augmented by preconditioning mimetics, such as angiotensin II. We hypothesized that this oxidase is an essential source of ROS in PC. Hearts from wild‐type (WT) and NOX‐2 knockout (KO) mice were Langendorff perfused and subjected to 35 min ischemia/reperfusion with or without preceding PC or drug treatment. Infarct size was measured by triphenyl tetrazolium chloride staining, and NADPH oxidase activity by lucigenin chemiluminescence. PC significantly attenuated infarct size in WT (26±2% vs. control, 38±2%, P<0.05) yet was ineffective in KO hearts (33±3% vs. control, 34±3%). Concomitantly, PC significantly increased NADPH oxidase activity in WT (+41±13%; P<0.05), but not in KO (−5±18%, P=NS). The ROS scavenger MPG (N‐2‐mercaptopropionyl glycine, 300 µmol/L) abrogated PC in WT (39±2% vs. control, 33±1%). CCPA (2‐chloro N6 cyclopentyl adenosine, 200 nmol/L), a putative ROS‐independent PC trigger, significantly attenuated infarct size in WT, MPG‐treated WT and KO hearts (24±2, 23±1, and 20±3%, respectively, P<0.05). Furthermore, CCPA did not augment NADPH oxidase activity over control (+22±11%, P=NS). Inhibition of protein kinase C (PKC) with chelerythrine (CHE, 2 µmol/L) completely abrogated both PC (38±2% vs. CHE alone, 35±2%) and associated increases in oxidase activity (+3±10%, P=NS). PKC‐dependent activation of a NOX‐2‐containing NADPH oxidase is pivotally involved in early ischemic PC. However, adenosine receptor activation can trigger a ROS and NOX‐2 independent PC pathway.

20-HETE increases NADPH oxidase-derived ROS production and stimulates the L-type Ca2+ channel via a PKC-dependent mechanism in cardiomyocytes

“…The phosphorylation of p47 phox subunits induces their translocation from the cytosolic compartment to the cellular membrane, where they combine with other NADPH subunits to assemble the fully activated NADPH oxidase complexes that generate superoxide. Moreover, PKC-dependent activation of NADPH oxidase is reportedly involved in early ischemic preconditioning in the heart (2) and also in the action of ANG II in the regulation of neuronal activity in the brain (30). Several isoforms of PKC have been identified that phosphorylate the regulatory p47 phox subunits of NADPH oxidase to augment the production of superoxide radicals.…”

“…Recent studies have suggested a role for NADPH oxidase-derived ROS in cardiac pathology. Mice lacking gp91ds phox , a subunit of NADPH oxidase, do not develop ANG II-induced cardiac hypertrophy (2). On the other hand, excessive intracellular Ca 2ϩ accumulation is another factor mediating ischemia-induced cardiac injury.…”

SGLT2 inhibitors: hypotheses on the mechanism of cardiovascular protection

“…Reactive oxygen species (ROS) play a highly regulated role in normal physiological signalling and are involved in cellular adaptions to cellular stress (for example, gp91 phox NADPH oxidase-linked ischaemic conditioning 5 ). However, excess ROS production leads to pathological states such as heart failure and exacerbation of ischaemic cell death as occurs in ischaemia/reperfusion injury and heart failure.…”

NADPH oxidase signaling and cardiac myocyte function

“…While mitochondrial-derived ROS are widely considered to be involved in the pathway, there is also evidence for a signaling role of NADPH oxidase-derived ROS in the proximal pathways of preconditioning. Bell et al [110] studied ischemic preconditioning in isolated buffer-perfused hearts from mice with a global deficiency of Nox2 (Nox2−/− mice) and matched wild-type mice, and showed that Nox2 knockout mice failed to precondition in response to brief global ischemia. In contrast, hearts of wild-type mice had enhanced NADPH oxidase activity and showed attenuated infarct sizes after preconditioning.…”

“…Further investigation into the signaling mechanisms involved in the above effects revealed that protein kinase C was essential for the activation of Nox2 oxidase in ischemic preconditioning [110]. In angiotensin II-dependent preconditioning, NADPH oxidase-induced activation of ASK-1 and p38MAPK were suggested to trigger mitochondrial ROS generation and consequent cardioprotection [111], whilst in tachycardia/exercise-mediated preconditioning NADPH oxidase-induced modulation of SR Ca2+ release was proposed as the mechanism mediating the protective response [44].…”