• Wei-Chiao Chiu, Jiun-Yang Chiang, and Fu-Tien Chiang.
• Graduate Institute of Physiology, College of Medicine, National Taiwan University, Taipei, Taiwan.
• J Formos Med Assoc. 2021 Oct 1; 120 (10): 1863-1868.

Background/PurposeThe small-molecule compounds Y16 and Rhosin can inhibit the activation of leukemia-associated Rho guanine nucleotide exchange factor (LARG) and small G-protein RhoA, respectively, in breast cancer cells and inhibit their growth and migration. However, it remains unclear whether they have inhibitory effects on the vascular smooth muscle cells (VSMCs) of spontaneously hypertensive rats (SHRs).MethodsPrimary cultured VSMCs from SHRs were treated with different concentrations of Y16 or Y16 plus Rhosin for 24 h, followed by 10-min stimulation with 10-7 M angiotensin II (Ang II). The cells were then harvested, and the total protein was extracted. The co-immunoprecipitation method, Western blot analysis, and MTT assay were performed to determine the LARG-RhoA interaction, the protein levels of RhoA and MYPT1, and cell viability, respectively.ResultsY16 dose-dependently inhibited the LARG-RhoA complex formation induced by Ang II. With 50 μM of Y16, the effect of inhibition was statistically significant. Y16 also reduced the formation of phospho-MYPT1 stimulated by Ang II. With 5 μM of Y16, the inhibitory effect was statistically significant. When 25 μM of Y16 and 25 μM of Rhosin were combined, the inhibitory effect on LARG-RhoA interaction was statistically significant. When Y16 and Rhosin were combined, a significantly reduced concentration could effectively inhibit MYPT1 phosphorylation (2.5 μM compared with 5 μM for Y16 alone).ConclusionTreating SHR VSMCs with Y16 can suppress the activation of LARG, prevent LARG binding to RhoA, and decrease the phosphorylation of MYPT1, thus weakening the activation of the calcium (Ca2+) sensitization pathway in SHR VSMCs.Copyright © 2021. Published by Elsevier B.V.

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