Mechanosignaling with ischemia‐reperfusion: restart of flow triggers a signaling cascade (1180.11)

Abstract

We concluded earlier that endothelial mechanotransduction with ischemia in the lung activates a signaling cascade comprised of KATP channel closure that leads to NOX2 activation and reactive oxygen species (ROS) production. We studied the mechanosignaling with reperfusion. Isolated perfused mouse lungs and pulmonary endothelial cells showed a 2 fold increase in ROS production with ischemia that increased by 3‐3.5 fold upon reperfusion. This response is not due to hypoxia or reoxygenation since alveolar pO2 is unchanged in these ventilated lungs. ROS production was not observed in lungs and cells from NOX2 null, KATP channel null mice or lungs pre‐treated with KATP agonist (cromakalim) or a NOX2 activation inhibitor (MJ33). Wild type mice (WT) showed ~1.8 fold increase in oxidative lung damage (as assessed by 8‐isoprostanes, TBARS, alveolar permeability) with pulmonary ischemia and a ~2.5 fold increase with reperfusion; no significant change was observed in NOX2 null mice. Calcium influx, observed with ischemia in WT cells increased further with reperfusion; this was not observed in KATP and NOX2 null cells. Reperfusion thus amplifies the effects of the mechanosignaling cascade that is associated with ischemia. Prevention of the cascade with inhibitors such as MJ33 or cromakalim has potential application in lung transplantation which requires reperfusion of a previously ischemic lung.Grant Funding Source: NIHRO1HL‐075587