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Leukocyte Calpain Deficiency Reduces Angiotensin II-Induced Inflammation and Atherosclerosis But Not Abdominal Aortic
Deborah A Howatt1, Anju Balakrishnan1, Jessica J Moorleghen1
1From the Saha Cardiovascular Research Center (D.A.H., A.B., J.J.M., L.M., D.L.R.), and Department of Physiology (V.S.), University of Kentucky, Lexington; Department of Chronic Kidney Disease and Cardiovascular Disease, Okayama University School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan (H.A.U.); Laboratory for Proteolytic Neuroscience, RIKEN Brain Science Institute, Saitama, Japan (J.T., T.C.S.); Department of Developmental, Molecular, and Chemical Biology, Tufts University School of Medicine, Boston, MA (A.H.C.); and INSERM, Université Pierre et Marie Curie-Paris, Paris, France (L.B.).
Objective:
Angiotensin II (AngII) infusion profoundly increases activity of calpains, calcium-dependent neutral cysteine proteases, in mice. Pharmacological inhibition of calpains attenuates AngII-induced aortic medial macrophage accumulation, atherosclerosis, and abdominal aortic aneurysm in mice. However, the precise functional contribution of leukocyte-derived calpains in AngII-induced vascular pathologies has not been determined. The purpose of this study was to determine whether calpains expressed in bone marrow (BM)-derived cells contribute to AngII-induced atherosclerosis and aortic aneurysms in hypercholesterolemic mice.
Approach And Results:
To study whether leukocyte calpains contributed to AngII-induced aortic pathologies, irradiated male low-density lipoprotein receptor(-/-) mice were repopulated with BM-derived cells that were either wild-type or overexpressed calpastatin, the endogenous inhibitor of calpains. Mice were fed a fat-enriched diet and infused with AngII (1000 ng/kg per minute) for 4 weeks. Overexpression of calpastatin in BM-derived cells significantly attenuated AngII-induced atherosclerotic lesion formation in aortic arches, but had no effect on aneurysm formation. Using either BM-derived cells from calpain-1-deficient mice or mice with leukocyte-specific calpain-2 deficiency generated using cre-loxP recombination technology, further studies demonstrated that independent deficiency of either calpain-1 or -2 in leukocytes modestly attenuated AngII-induced atherosclerosis. Calpastatin overexpression significantly attenuated AngII-induced inflammatory responses in macrophages and spleen. Furthermore, calpain inhibition suppressed migration and adhesion of macrophages to endothelial cells in vitro. Calpain inhibition also significantly decreased hypercholesterolemia-induced atherosclerosis in the absence of AngII.
Conclusions:
The present study demonstrates a pivotal role for BM-derived calpains in mediating AngII-induced atherosclerosis by influencing macrophage function.
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