Calpain-1 Activity and Central Arterial Aging

National Institute On Aging

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Abstract

Angiotensin II (Ang II) signaling, including matrix metalloproteinase type II (MMP2) activation, is linked to age-associated increases in migration, invasion, proliferation, profibrosis, procalcification, senescence, and proinflammation of vascular smooth muscle cells (VSMCs). This project addresses the consequences of calpain-1 activation and its substrates, such as vitronectin, in governing the age-associated proinflammatory status and remodeling within the arterial wall. Our findings demonstrate that the transcription, translation, and activation of calpain-1 are significantly upregulated in rat aortae and early-passage aortic VSMCs from old (30-month) Fisher 344 crossbreed Brown Norway (FXBN) rats compared to young (8-month) animals or cells. Dual immunolabeling indicates that the colocalization of calpain-1 and Ang II protein increases within the aged aortic wall and VSMCs. To explore the molecular relationship between calpain-1 and Ang II, we chronically infused young rats with Ang II or treated cultured aortic rings and VSMCs with Ang II. The results indicate that Ang II induces calpain-1 protein expression and activation in the aortic walls in vivo and in aortic rings ex vivo and VSMCs in vitro. The Ang II-mediated, age-associated increases in MMP2 activation, migration, and synthetic phenotypic shifts of VSMCs are all blocked by the calpain-1 inhibitor, calpastatin. Overexpression of calpain-1 in young VSMCs results in the cleavage of intact vimentin, an increased migratory capacity, and MMP2 activity, mimicking that of old untreated VSMCs, which is blocked by the MMP inhibitor, GM6001. Age-associated changes in the central arterial system, including endothelial dysfunction and stiffening, are linked to extracellular matrix (ECM) remodeling, such as fibrosis, elastolysis, and calcification. Ang II induces both MMP2 and calpain-1 expression and activation in the arterial wall and VSMCs. We have found that calpain-1 plays an important role in MMP2 activation and ECM remodeling in the arterial walls and VSMCs. Dual immunolabeling demonstrates increased colocalization of calpain-1 and MMP2 within old rat VSMCs and old arterial walls compared to young animals or cells. Overexpression of calpain-1 upregulates MMP2 mRNA and protein levels, and its activity, in part, by increasing the ratio of membrane-type 1 MMP (MT1-MMP), an activator of MMP2, to tissue inhibitor of metalloproteinases 2 (TIMP2), an inhibitor of MMP2. The effect of calpain-1 overexpression-induced MMP2 activation is associated with increased collagen I, II, and III production and vascular calcification in the arterial wall and VSMCs with aging.