Progression of Arterial Aging: the Local MCP-1/MMP-2/TGF-beta 1 Signaling Loop

在这项研究中，双染色显示，随着年龄的增长，MCP-1和tgf - β 1（一种强大的促纤维化细胞因子）在大鼠、非人灵长类动物和人类增厚的内膜中显著增加并在主动脉壁内共定位。心血管信号网络分析表明，MCP-1与TGF-beta1相互作用，位于中心，与炎症级联直接相关，与MMP-2激活密切相关。体外研究表明，MCP-1通过CCR-2信号传导，以剂量或时间依赖的方式提高MMP2， MMP2是一种已知的潜伏tgf - β 1的激活剂，在培养的年轻（8个月）大鼠主动脉血管平滑肌细胞（VSMC）中达到老年细胞（30个月）的水平。MCP-1处理增加激活的细胞内和细胞外tgf - β 1及其下游分子胶原I型和III型，这在年轻VSMC中依赖于MMP-2的激活，达到未处理的老年细胞的水平。此外，随着年龄的增长，细胞活化的tgf - β 1在包括细胞质、细胞器和细胞核在内的VSMC亚组分中分布和增加。有趣的是，通过siRNA敲低MCP-1或通过腺病毒转染过表达异位TIMP-2，可以降低MMP-2和tgf - β 1的激活，并以MMP-2激活依赖的方式降低年轻细胞的侵袭能力，类似于未经处理的老年细胞。CCR-2和MMP抑制剂GM 6001显著降低了这些影响。值得注意的是，tgf - β 1治疗在年轻VSMC中以剂量依赖的方式增加MCP-1、MMP-2和VSMC侵袭性，直至未治疗的老年细胞水平。

In this study, dual staining shows that with aging MCP-1 and TGF-beta1, a powerful profibrogenic cytokine, markedly increase and co-localize within the aortic wall in the thickened intima of rats, nonhuman primates, and humans. Cardiovascular signaling network analysis indicates that MCP-1 interacts with TGF-beta1 and is centrally located and directly connected with the inflammation cascade, which is closely associated with MMP-2 activation. In vitro study shows that MCP-1 elevates MMP2, a known activator of latent TGF-beta1 in a dose- or time-dependent manner through CCR-2 signaling in cultured vascular smooth muscle cells (VSMC) from young (8 mo) rat aortae, reaching the levels of old cells (30mo). MCP-1 treatment increases activated intracellular and extracellular TGF-beta1 and its downstream molecules collagen types I and III, which is dependent upon MMP-2 activation in young VSMC, reaching levels of untreated old cells. Furthermore, cellular activated TGF-beta1 is distributed and increased in VSMC sub-fractions, including cytosol, the organelles and the nuclei, with aging. Interestingly, knockdown of MCP-1 via siRNA or overexpression of ectopic TIMP-2 by adenovirus transfection reduces activation of MMP-2 and TGF-beta1 and production of invasive capacity of young cells in an MMP-2 activation-dependent manner, resembling that of untreated old cells. These effects are substantially reduced by both CCR-2 and an MMP inhibitor, GM 6001. Of note, TGF-beta1 treatment increases MCP-1, MMP-2, and VSMC invasiveness in a dose-dependent manner in young VSMC, up to levels of old untreated cells. Furthermore, we demonstrate that a novel protein, Vasorin, is markedly down-regulated in the aged arterial wall, which is closely associated with an increase of TGF-beta1 activity and arterial fibrosis. Further in vitro studies indicate that aging also upregulated TGF-beta1, SMAD 2 and collagen I expression within VSMC; Ang II treatment of young VSMC upregulated the levels of TGF-beta1, SMAD 2 and collagen I expression up to the same levels as from old cells; aging down-regulated Vasorin expression in old rat VSMC as compared with young; TGF-beta1 interacts with Vasorin in rat VSMC; aging affects the interaction of TGF-beta1 with Vasorin; overexpression of Vasorin counteracts TGF-beta1 signaling pathway and collagen I expression in VSMC from old rats; overexpression of Vasorin counteracts TGF-beta1 signaling pathway and collagen I expression induced by Ang II treatment in VSMC from young rats. Taken together, this complex local signaling loop of MCP-1/MMP-2/TGF-beta1 plays a bedrock role in the initiation and progression of age-associated arterial intimal cellularity and fibrosis. Interruption of this vicious cycle is a potential therapeutic approach to arterial health in the elderly.