Retinol binding protein 4 promotes the phenotypic transformation of vascular smooth muscle cells under high glucose condition via modulating RhoA/ROCK1 pathway

Phenotypic switch of vascular smooth muscle cells (VSMCs) contributes to the pathogenesis of atherosclerosis (AS). High level of retinol binding protein 4 (RBP4) is regarded as a risk factor in cardiac-cerebral vascular disease. This study is performed to clarify the biological function of RBP4 in modulating the phenotypic switch of VSMCs induced via RhoA/ROCK1 signaling pathway. In vivo experiment, all the rats were divided into control group (NC), diabetic group (DM) and diabetic atherosclerosis group (DAS). The expressions of biochemical indicators, RhoA and Rho associated coiled-coil containing protein kinase 1 (ROCK1) were detected. In vitro experiment, VSMCs were cultured under high glucose condition, and ectogenic RBP4, HA-1100, rapamycin, or 3-methyladenine (3-MA) were supplemented to treat the VSMCs, respectively. The proliferation and migration of VSMCs were evaluated. The regulatory relationship between RBP4 and ROCK1 was predicted by bioinformatics analysis, and validated by qRT-PCR and Western blot. The regulatory effects of RBP4 on contractile phenotypic markers such as calponin, MYH11, α-SMA and autophagy markers including LC3II, LC3I, and Beclin-1 as well as mTOR were also detected. Moreover, VSMCs were cultured exposed to ROCK1 overexpressed plasmid or short hairpin RNA (shRNA), the proliferation and migration of VSMCs were evaluated and the regulatory effects of RhoA/ROCK1 signaling pathway on contractile phenotypic markers and autophagy markers were also detected. In vivo, RhoA, ROCK1, and mTOR were highly expressed in the rats intraperitoneally injected with RBP4. In vitro, the expressions of calponin, MYH11, α-SMA, LC3II, LC3I, and Beclin-1 were decreased in VSMCs treated with ROCK1-OA under high glucose condition, conversely, the expressions were increased in VSMCs exposed to ROCK1-shRNA. After incubated with rapamycin additionally, the expressions of calponin, MYH11, α-SMA, LC3II/I and Beclin-1 were up-regulated and the expression of p-mTOR was decreaed in VSMCs of HG+ROCK1-OA. Conversely, after incubated with 3-MA additionally, the expressions of calponin, MYH11, α-SMA, LC3II/I and Beclin-1 were down-regulated and the expression of p-mTOR was elevated in VSMCs of HG+ROCK1-shRNA. Ectogenic RBP4 facilitated high glucose-induced proliferation and migration of VSMCs, and it repressed the expression of calponin, MYH11, α-SMA, LC3II/I, and Beclin-1 in VSMCs. As expected, ROCK1 inhibit or counteracted the biological effects of RBP4 on VSMCs. In addition, the expressions of contractile phenotypic markers, LC3II/I, and Beclin-1 were promoted and mTOR were decreased after the VSMCs treated with autophagy agonist, whereas no significant difference was observed in the expressions of ROCK1, RhoA. RBP4 is an injurious factor in the pathogenesis of diabetic AS, and it promotes the phenotypic switch of VSMCs via activating RhoA/ROCK1 pathway and inhibiting autophagy.