Laminar Shear Stress Increases the Cytosolic Pool of PINK1 in Endothelial Cells and Enhances Mitophagic Sensitivity Toward Dysfunctional Mitochondria

Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1) is an essential molecule in mitophagy process in mammalian cells. Mutation or deficiency of PINK1 has been closely related to several disease conditions. The purpose of this study was to determine PINK1 expression levels and subcellular localization under exercise-mimic laminar shear stress (LSS) condition in human aortic endothelial cells (HAECs) or in exercising mice, and its implication on endothelial homeostasis and cardiovascular disease (CVD) prevention. First, LSS significantly elevated both full-length PINK1 (FL-PINK1) mRNA and protein expressions in ECs. Mitochondrial fractionation assays and confocal microscopic analysis showed reduced FL-PINK1 accumulation on mitochondria with an increase in a cytosolic pool of FL-PINK1 under LSS. Mitophagy flux, determined by a mtKeima probe, decreased with intact mitochondrial morphology and membrane potential under LSS, suggesting that elevated cytosolic PINK1 is not utilized for immediate mitophagy inductions. However, increased cytosolic PINK1 seems to elevate mitophagic sensitivity toward dysfunctional mitochondria in pathological conditions. LSS-preconditioned ECs showed lower angiotensin II (AngII)-induced mtDNA lesions and displayed rapid Parkin recruitment and mitophagy induction in response to mitochondrial uncoupler (CCCP) treatment. Exercise-preconditioned mice, a physiological LSS-enhanced model, showed elevated PINK1 expression in ECs of the thoracic aorta compared to sedentary control. In addition, exercise enhanced AngII-induced mitophagy induction in ECs and reduced AngII-induced mtDNA lesion formation in the mouse aorta. Taken together, LSS increases a cytosolic pool of FL-PINK1, which may elevate the mitophagic sensitivity toward dysfunctional mitochondria in ECs.