Endothelial cell-derived SSAO can increase MLC₂₀ phosphorylation in VSMCs

Area of Science:

• Physiology
• Biochemistry
• Molecular Biology

Background:

• Vascular hyporesponsiveness is a critical factor in shock decompensation and mortality.
• Myosin light chain 20 (MLC20) phosphorylation regulates vascular reactivity, but its regulation by semicarbazide-sensitive amine oxidase (SSAO) during hypoxia is unclear.

Purpose of the Study:

• To investigate the effect of semicarbazide-sensitive amine oxidase (SSAO) expression on myosin light chain 20 (MLC20) phosphorylation during hypoxia.
• To elucidate the underlying molecular mechanisms involving inducible nitric oxide synthase (iNOS) and RhoA/ROCK1 signaling.

Main Methods:

• Constructed an amine oxidase copper containing 3 (AOC3) overexpressing adenovirus vector to increase SSAO expression in rat intestinal microvascular endothelial cells (RIMECs).
• Co-cultured RIMECs with rat intestinal microvascular smooth muscle cells (RIMSCs) to assess signaling pathway changes.
• Measured SSAO, iNOS, RhoA/ROCK1 expression, and MLC20 phosphorylation levels.

Main Results:

• Increased SSAO expression via AOC3 overexpression reduced iNOS expression and activity post-hypoxia.
• RIMSCs co-cultured with AOC3-overexpressing RIMECs showed elevated ROCK1 protein levels and MLC20 phosphorylation compared to controls.
• SSAO overexpression inhibited iNOS activity and promoted RhoA/ROCK pathway activation.

Conclusions:

• SSAO overexpression enhances MLC20 phosphorylation by inhibiting iNOS and activating the RhoA/ROCK pathway.
• This mechanism may offer a therapeutic strategy to alleviate vascular hyporesponsiveness in shock decompensation.