Calpain-1 Activity and Central Arterial Aging

血管紧张素II （Ang II）信号，包括基质金属蛋白酶II型（MMP2）激活，与血管平滑肌细胞（VSMC）迁移能力的年龄相关增加以及动脉衰老的其他促炎特征有关。在成纤维细胞中MMP2的表达需要Calpain-1的激活，并且在心肌细胞中由Ang II诱导。然而，calpain-1与其底物在控制动脉壁中与年龄相关的促炎和钙化前状态中的作用仍不清楚。

Angiotensin II (Ang II) signaling, including matrix metalloproteinase type II (MMP2) activation, has been linked to an age-associated increase in migration capacity of vascular smooth muscle cells (VSMC), and to other proinflammatory features of arterial aging. Calpain-1 activation is required for MMP2 expression in fibroblasts and is induced in cardiomyocytes by Ang II. The consequences of engagement of calpain-1 with its substrates, however, in governing the age-associated proinflammatory and procalcification status within the arterial wall, remain unknown. In this study, our results first demonstrate an age-associated increase of calpain-1 gene transcripts, protein levels and activity in the old aortic wall; increased Ang II induces calpain-1 expression in the aortic walls in vivo and ex vivo and VSMC in vitro; the Ang II mediated age-associated increased MMP2 activity, is blocked by calpain inhibitor 1 or CAST, indicating that calpain activity is required for MMP activation by Ang II treatment. An increase in old VSMC migratory capacity is mimicked in young VSMC by over-expression of calpain-1. Collectively, these findings point to increased calpain-1 activity, as a central component of the exaggerated Ang II signaling pathway, which is involved in age-associated arterial remodeling. Thus, Calpain-1 activation is a pivotal molecular event in the age-associated arterial Ang II/MMP2 signaling cascade that is linked to cytoskeleton protein restructuring, and VSMC migration. Furthermore, age-associated arterial alterations are characterized both by a shift of VSMC from a contractile to synthetic phenotype, i.e., cytoskeleton restructuring and enhancement of migratory capability, and extracellular matrix remodeling (ECM), ie., collagen types I and III, which could be degenerated by proteases and become immature collagen to form a procalcification niche. Our recent study indicates that calpain-1, increases within VSMC; and orchestrates an angiotensin II cascade which mediates a VSMC phenotype shift within the aged aortic wall, and plays an important role in generating arterial matrix alterations that lead to procalcification. Our results show that over-expression of ectopic calpain-1 by a recombinant adenovirus harboring full length cDNA (pAd/CANP1) in young VSMC increased Col I and III up to the levels of untreated old control cells. Further, over-expression of calpain-1 in young VSMC decreases the counter-calcification molecules osteopontin (OPN) and osteonectin (ON), which mimics aging. In contrast, young VSMC infected with recombinant adenovirus containing calpastatain cDNA (pAd/CAST), an endogenous inhibitor of calpain), increases OPN and ON. An age-associated increase of calpain-1 activity within VSMCs results in enhanced collagen production and reduced counter-calcification molecules, favoring a procacification status, which is a potential molecular mechanism of arterial matrix remodeling with aging. Thus, targeting calpain-1 is a potential approach to delay or reverse the age-associated arterial pro-inflammation and -calcification state that is also associated with diseases such as hypertension, atherosclerosis, and stroke.