Mesenchymal stem cells ameliorate hyperglycemia-induced endothelial injury through modulation of mitophagy

Wuzheng Zhu,Guangneng Liao,Lan Li,Jingping Liu,Yujia Yuan,Younan Chen,Yanrong Lu,Jingqiu Cheng,Jie Zhang

doi:10.1038/s41419-018-0861-x

Abstract

Mitochondrial dysfunction and excessive mitochondrial reactive oxygen species (ROS) are fundamental contributors to endothelial injury in diabetic states. Mesenchymal stem cells (MSCs) have exhibited an extraordinary cytoprotective effect that extends to the modulation of mitochondrial homeostasis. However, the underlying mechanisms have not been clearly defined. Emerging evidence has suggested that mitophagy could counteract mitochondrial-derived oxidative stress through the selective elimination of impaired or dysfunctional mitochondria. Therefore, we investigated whether MSCs could ameliorate high-glucose-induced endothelial injury through the modulation of mitophagy. We observed that exposure of human umbilical vein endothelial cells (HUVECs) to high glucose triggers mitochondrial impairment with excessive mitochondrial fragmentation and ROS generation, loss of membrane potential and reduced ATP production. Furthermore, mitophagy was blunted upon high glucose insult, which accelerated dysfunctional mitochondrial accumulation, initiating the mitochondrial apoptotic pathway and, eventually, endothelial dysfunction. MSCs treatment notably attenuated these perturbations accompanied by an enhancement of Pink1 and Parkin expression, whereas these beneficial effects of MSCs were abolished when either Pink1 or Parkin was knocked down. In aortas of diabetic rats, defective mitophagy was observed, which coincided with marked mitochondrial dysfunction. Ultrastructurally, RAECs from diabetic rats revealed a significant reduction in autophagic vacuoles and a marked increase in fragmented mitochondria. Importantly, the infusion of MSCs restored Pink1/Parkin-mediated mitophagy, ameliorated mitochondrial dysfunction and attenuated apoptosis in endothelial cells in diabetic rats. These results suggest that MSCs may protect endothelial cells from hyperglycemia-induced injury by ameliorating mitochondrial dysfunction via Pink1/Parkin –mediated mitophagy

Highlights

Diabetic vasculopathy that affects both the micro- and macrovasculature is the leading cause of morbidity and mortality in diabetic patients[1]
SiRNA targeting Pink[1] or Parkin suppressed the ability of Mesenchymal stem cells (MSCs) to improve the migration under HG conditions (Figs. 7g, h). These results demonstrate that Pink1/Parkin-mediated mitophagy is essential for MSCs to protect human umbilical vein endothelial cells (HUVECs) against HG-induced apoptosis and endothelial dysfunction
Our finding demonstrated that HG resulted in mitochondrial dysfunction and subsequent mitochondrial ROS (mtROS) overproduction; concurrently, mitophagy was blocked, leading to an accumulation of damaged mitochondria and promoting mitochondrial compromise, which further accelerated the deterioration of mitochondrial dysfunction and triggered the mitochondrial apoptotic cascade, eventually causing endothelial injury

Summary

Result

HG induces mitophagy inhibition, mitochondrial dysfunction and apoptosis in HUVECs We first determined whether HG alters mitophagy in HUVECs. MSCsmediated LC3-II accumulation and reduction of P62 levels were attenuated by administration of autophagy inhibitor 3-MA (Fig. 2d) These data collectively suggest that this restoration of autophagic flux in HG environment could be attributed to MSCs. Mitochondrial fragmentation has recently been found to be an important contributing factor to ROS overproduction under HG conditions, in which it causes deleterious vascular cell signaling and subsequent endothelial dysfunction[21,22]. MSCs treatment markedly reduced the expression of proapoptotic factor Bax and cleaved Caspase-3 (C-Casp3), but increased the anti-apoptotic molecule Bcl-2 compared with those of HG group, whereas either Pink[1] or Parkin knockdown abrogated the anti-apoptotic effect of MSCs in HG conditions (Fig. 7b). These unfavorable manifestations were markedly reversed in MSCs-treated diabetic rats These data suggest that MSC treatment inhibited hyperglycemia-induced mtROS overproduction, improved mitochondrial fitness and reduced cell apoptosis in diabetic rat aortas

Discussion

Findings

Materials and methods