Endothelial cell-derived SSAO can increase MLC phosphorylation in VSMCs.

Vascular hyporesponsiveness in the shock decompensation period is an important factor leading to death. Myosin light chain 20 (MLC) is the main effector protein that regulates vascular reactivity. However, whether the change in semicarbazide-sensitive amine oxidase (SSAO) expression during hypoxia can change the MLC phosphorylation level, and its underlying mechanism were not clear. The amine oxidase copper containing 3 (AOC3) overexpressing adenovirus vector was constructed and transfected into rat intestinal microvascular endothelial cells (RIMECs) to overexpress SSAO, and the RIMECs were co-cultured with rat intestinal microvascular smooth muscle cells (RIMSCs). The changes in SSAO/inducible nitric oxide synthase (iNOS)/Rho associate coiled-coil containing protein kinase 1 (ROCK1) expression levels and MLC phosphorylation level were detected. Here we found that the increased SSAO by AOC3 overexpression can decrease the iNOS expression level and its activity after hypoxia. In addition, RIMSCs co-cultured with RIMECs overexpressed with AOC3 gene had significantly higher ROCK1 protein level and MLC phosphorylation level than RIMSCs co-cultured with normal RIMECs. Our study demonstrated that SSAO overexpression can significantly inhibit iNOS activity, promote RhoA/ROCK pathway activation, and increase the phosphorylation level of MLC, which might be the potential mechanism in relieving the vascular hyporesponsiveness during shock decompensation.