Novel Role of Thbs‐1/CD47‐Drp1 signaling following ischemia reperfusion in the aging heart

Abstract

Ischemia reperfusion (IR) injury leads to activation of dynamin‐related protein (Drp‐1), causing mitochondrial fission and generation of reactive oxygen species (ROS), but the molecular mechanisms that activate Drp‐1 are not known. The purpose of this study was to establish the signaling pathway between Thbs‐1/CD47 and fission protein (Drp‐1) through PGC‐1 following IR in advancing age.MethodsFemale Fischer‐344 rats were divided into 4 groups: Young Control, Young+IR, Old Control and Old+IR. Echocardiography measurements were done at baseline and 72 hours after IR (30 minutes of ischemia,72 hrs of reperfusion). After evaluation of heart function and coronary flow using vevo3100, hearts were explanted and mitochondrial ROS generation was measured using MitoPY1 (O2·−), as well as protein levels of Thbs‐1, PGC‐1, and Drp‐1. In vitro, rat aortic endothelial cells (RAEC) received hypoxic conditions to mimic IR in vivo model. Cells were treated with SiRNA for PGC‐1 or control scrambled SIRNA and then underwent hypoxia challenge to evaluate PGC‐1 effect on Drp‐1. Cell lysate was collected for Western Blot after 36 hours of transfection.ResultsMitochondrial O2·− generation in heart tissue increased in both age groups following IR. Old animals experiencing diastolic dysfunction at the baseline, after IR they exhibited reduced systolic function and exacerbated diastolic dysfunction compared to young controls. IR induces Thbs‐1 and Drp‐1 expression in young and old hearts. SiRNA to PGC‐1 enhanced levels of Drp‐1 in RAECs and increases ROS generation after hypoxia.ConclusionLeft ventricular diastolic dysfunction during IR is potentiated due to increased generation of ROS. These results highlight a novel signaling pathway by which Thbs‐1 regulates mitochondrial fission (Drp‐1) and ROS generation during hypoxia, and presumably, following IR. Inhibiting Thbs‐1 immediately after IR may prevent Drp‐1‐mediated mitochondrial fission and is likely to improve diastolic function of the heart by reducing ROS‐mediated cardiomyocyte damage in the aged population.Support or Funding InformationNIH R01 AG05358 Gheen's FoundationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.