High shear stress-induced pulmonary hypertension alleviated by endothelial progenitor cells independent of autophagy.

BACKGROUND: Pulmonary hypertension (PH) is a progressive disease characterized by lung endothelial cell dysfunction and vascular remodeling. Endothelial progenitor cells (EPCs) have been proved to be a potential therapeutic strategy to treat PH. Autophagy has been found to be protective to hypoxia-induced PH. In this study, we applied high shear stress (HSS)-induced PH, and examined whether EPCs confer resistance against HSS-induced PH through autophagy.
METHODS: Pulmonary microvascular endothelial cells (PMVECs) were cultured under HSS with pro-inflammatory factors in an artificial capillary system to mimic the PH condition. Levels of p62, a selective autophagy substrate, were quantified by western blotting. Cell viability was determined by trypan blue exclusion test.
RESULTS: The p62 level in PMVECs was increased at 4 hours after HSS, peaked at 12 hours and declined at 24 hours. The cell viability gradually decreased. Compared with PMVECs cultured by empty medium, in cells cultured by EPC-conditioned medium (EPC-CM), the cell viability was significantly higher; however, p62 levels were also significantly higher, suggesting inhibition of autophagy by EPC-CM. Adding choloquine to suppress autophagy decreased the cell viability of PMVECs under PH.
CONCLUSIONS: EPC-CM could suppress the autophagic activity of PMVECs in HSS-induced PH. However, suppression of autophagy leads to cell death. EPCs could fight against PH through cellular or molecular pathways independent of autophagy. But it is not proved if induction of autophagy could be a potential strategy to treat HSS-induced PH as hypoxia-induced PH.