78 kDa Glucose-Regulated Protein Attenuates Protein Aggregation and Monocyte Adhesion Induced by Angiotensin II in Vascular Cells

Abstract

Investigations of vascular smooth muscle cell (VSMC) phenotypic modulation due to angiotensin II (AngII) stimulation are important for understanding molecular mechanisms contributing to hypertension and associated vascular pathology. AngII induces endoplasmic reticulum (ER) stress in VSMCs, which has been implicated in hypertensive vascular remodeling. Under ER stress, 78 kDa glucose-regulated protein (GRP78) acts as an endogenous chaperone, as well as a master controller of unfolded protein response (UPR) to maintain protein quality control. However, the potential downstream consequences of ER stress induced by AngII on protein quality control and pro-inflammatory phenotype in VSMCs remain elusive. This study aims to identify protein aggregation as evidence of the disruption of protein quality control in VSMCs, and to test the hypothesis that preservation of proteostasis by overexpression of GRP78 can attenuate the AngII-induced pro-inflammatory phenotype in VSMCs. Increases in protein aggregation and enhanced UPR were observed in VSMCs exposed to AngII, which were mitigated by overexpression of GRP78. Moreover, GRP78 overexpression attenuated enhanced monocyte adhesion to VSMCs induced by AngII. Our results thus indicate that the prevention of protein aggregation can potentially mitigate an inflammatory phenotype in VSMCs, which may suggest an alternative therapy for the treatment of AngII-associated vascular disorders.