Thrombospondin‐1 mediates Drp‐1 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. Methods Female 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. Results Mitochondrial 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. Conclusion Left 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 Information NIH R01 AG05358 Gheen's Foundation This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Coronary microvascular injury in myocardial infarction: perception and knowledge for mitochondrial quality control

“…A recent study ( in vivo and in vitro ) showed that thrombospondin mediates Drp1 signaling after ischemia/reperfusion in aged hearts. Using RAEC, an association was shown between thrombospondin and Drp1 through PGC1a 132 . In post-ischemic heart, loss of PGC1α levels facilitated mitochondrial fragmentation and promotes cardiac dysfunction 132 .…”

“…Using RAEC, an association was shown between thrombospondin and Drp1 through PGC1a 132 . In post-ischemic heart, loss of PGC1α levels facilitated mitochondrial fragmentation and promotes cardiac dysfunction 132 . This suggests that PGC1α-related mitochondrial biogenesis can potentially alleviate pathogenesis underlying mitochondrial dynamics-related disorders.…”

SIRT1/SIRT3 Modulates Redox Homeostasis during Ischemia/Reperfusion in the Aging Heart

“…A previous study demonstrated that ischemic damage increased the formation of oxyradicals conducted by complex III in the aging heart which overlapped with the pre-existing aging defects [ 91 ]. Increased myocyte apoptosis and the oxidative modification of mitochondrial proteins also supports the greater mitochondria-derived oxidative damage in the aged heart during I/R [ 93 , 94 ]. Moreover, the impairment of mitochondrial OXPHOS and the excessive ROS with aging during myocardial I/R exacerbates impaired metabolic flexibility [ 93 ], resulting in more severe contractile dysfunction [ 95 ] and the intolerance to I/R stress in the aged heart [ 36 , 84 , 93 ].…”

Thrombospondin 1 in Metabolic Diseases

“…Drp-1 is a key protein involved in mitochondrial fission and ROS signaling. Inhibitors of TSP1 may potentially reduce cardiomyocyte damage and aging by reducing production of Drp-1 ( 32 ).…”