Pharmacological inhibition of MALT1 protease activity suppresses endothelial activation via enhancing MCPIP1 expression

Mucosa associated lymphoid tissue lymphoma translocation protein 1 (MALT1) is not only an intracellular signaling scaffold protein but also a paracaspase that plays a key role in the signal transduction and cellular activation of lymphocytes and macrophages. However, its role in endothelial cells remains unknown. Here we report that pharmacological inhibition of MALT1 protease activity strongly suppresses endothelial activation via enhancing MCPIP1 expression. Treatment with MALT1 protease inhibitors selectively inhibited TNFα-induced VCAM-1 expression in HUVECs and LPS-induced VCAM-1 expression in mice. In addition, Inhibition of MALT1 protease activity also significantly inhibited TNFα-induced adhesion of THP-1 monocytic cells to HUVECs. To explore the mechanisms, MALT1 inhibitors does not affect the activation of NF-κB signaling pathway in HUVEC. However, they can stabilize MCPIP1 protein and significantly enhance MCPIP1 protein level in endothelial cells. These results suggest that MALT1 paracaspase also targets MCPIP1 and degrade MCPIP1 protein in endothelial cells similar as it does in immune cells. Taken together, the study suggest inhibition of MALT1 protease activity may represent a new strategy for prevention/therapy of vascular inflammatory diseases such as atherosclerosis.