Mechanistic Role of the Calcium-Dependent Protease Calpain in the Endothelial Dysfunction Induced by MPO (Myeloperoxidase)

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 71; no. 4; pp. 761 - 770
• Main Authors: Etwebi, Zienab, Landesberg, Gavin, Preston, Kyle, Eguchi, Satoru, Scalia, Rosario
• Format: Journal Article
• Language: English
• Published: United States American Heart Association, Inc 01.04.2018
• Subjects: Animals; Animals, Genetically Modified; Aorta - metabolism; Aorta - pathology; Calpain - metabolism; Cell Adhesion - physiology; Cell Adhesion Molecules - metabolism; Cell Culture Techniques; Endothelial Cells - immunology; Endothelial Cells - metabolism; Inflammation - immunology; Leukocytes - physiology; Mice; Peroxidase - metabolism; Protein Phosphatase 2 - metabolism; Signal Transduction; Up-Regulation; Vascular Diseases - immunology; Vascular Diseases - metabolism; calpain; cell adhesion molecules; endothelial cells; inflammation; peroxidase
• DOI: 10.1161/HYPERTENSIONAHA.117.10305
• ISSN: 0194-911X

MPO (myeloperoxidase) is a peroxidase enzyme secreted by activated leukocytes that plays a pathogenic role in cardiovascular disease, mainly by initiating endothelial dysfunction. The molecular mechanisms of the endothelial damaging action of MPO remain though largely elusive. Calpain is a calcium-dependent protease expressed in the vascular wall. Activation of calpains has been implicated in inflammatory disorders of the vasculature. Using endothelial cells and genetically modified mice, this study identifies the µ-calpain isoform as novel downstream signaling target of MPO in endothelial dysfunction. Mouse lung microvascular endothelial cells were stimulated with 10 nmol/L MPO for 180 minutes. MPO denitrosylated µ-calpain C-terminus domain, and time dependently activated µ-calpain, but not the m-calpain isoform. MPO also reduced Thr AMPK (AMP-activated protein kinase) and Ser eNOS (endothelial nitric oxide synthase) phosphorylation via upregulation of PP2A (protein phosphatase 2) expression. At the functional level, MPO increased endothelial VCAM-1 (vascular cell adhesion molecule 1) abundance and the adhesion of leukocytes to the mouse aorta. In MPO-treated endothelial cells, pharmacological inhibition of calpain activity attenuated expression of VCAM-1 and PP2A, and restored Thr AMPK and Ser eNOS phosphorylation. Compared with wild-type mice, µ-calpain deficient mice experienced reduced leukocyte adhesion to the aortic endothelium in response to MPO. Our data first establish a role for calpain in the endothelial dysfunction and vascular inflammation of MPO. The MPO/calpain/PP2A signaling pathway may provide novel pharmacological targets for the treatment of inflammatory vascular disorders.