In this study, the first in vivo and in vitro studies show that MCP-1 and TGF-β1, a powerful profibrogenic cytokine, markedly increase and co-expression within the aortic wall in the thickened intima of aging rats. Furthermore, we document that MCP-1 interacts with TGF-β1 and is centrally located and directly connected with the inflammation cascade, which is closely associated with MMP-2 activation. Age-associated arterial remodeling involves arterial wall collagen deposition and elastin fragmentation, as well as an increase in arterial pressure. We tested the hypothesis that inhibition of MMP activation can decelerate the age-associated arterial proinflammation and its attendant increase in arterial pressure. Indeed, chronic administration of a broad-spectrum MMP inhibitor, PD166739, via a daily gavage, to 16-month-old rats for 8 months markedly blunted the expected age-associated increases in arterial pressure. This was accompanied by the following: (1) inhibition of the age-associated increases in aortic gelatinase and interstitial collagenase activity in situ;(2) preservation of the elastic fiber network integrity;(3) a reduction of collagen deposition;(4) a reduction of monocyte chemoattractant protein 1 and transforming growth factor-beta1 activation;(5) a diminution in the activity of the profibrogenic signaling molecule SMAD-2/3 phosphorylation;(6) inhibition of proendothelin 1 activation;and (7) downregulation of expression of ets-1. Collectively, our results indicate that MMP inhibition retards age-associated arterial proinflammatory signaling, and this is accompanied by preservation of intact elastin fibers, a reduction in collagen, and blunting of an age-associated increase in blood pressure. In addition, there is no proven therapy or prevention for the vascular type Ehlers-Danlos syndrome (vEDS), a genetic disorder associated with increased metalloproteinase (MMP) activity, reduced collagen content in the arterial walls, and spontaneous development of lesions of varying severity in the aorta. We hypothesized that chronic treatment with MMP inhibitor would increase the collagen content and prevent the development of spontaneous aortic lesions. Indeed, heterozygous COL3A1-deficient mice (HT) were treated since weaning with broad spectrum MMP inhibitor, doxycycline, added to food. At the age of 9 months MMP-9 expression was twice as high in tunica media of aorta in untreated HT, while total collagen content was 30% lower and the cumulative score of aortic lesions was 8 times higher than in wild type mice WT. After 9 months of doxycycline treatment, MMP-9 activity, collagen content and lesions in aorta of HT were at the level of WT. In the aneurismal mouse model of collagen III haploinsufficiency, treatment with broad spectrum MMP inhibitor started early in life normalized increased MMP activity and reduced aortic collagen content in adult and prevented development of spontaneous aortic lesions. These findings provide experimental justification for clinical evaluation of the benefit of doxycycline at least in the haploinsufficient variety of vEDS patients. Recent study has shown the Ang II/TGF-β1/vasorin signaling relationship within VSMC with aging. In vivo studies in old (30-month-old) versus young (8-month-old) Fisher 344 Crossbred Norway Brown (FXBN) rat show that aortic transcription and translation of vasorin markedly decreases with aging. In vitro studies in early passage VSMC from old versus young aortae indicate that vasorin protein abundance is substantially reduced with aging. Ang II-associated reduction of vasorin protein abundance in young VSMC and age-associated changes in vasorin protein levels are reversed by the Ang II receptor AT1 antagonist, Losartan (Los), suggesting constitutive activation of AT1 signaling within the arterial wall with aging. Dual immunolabeling and co-immunoprecipitation demonstrate that the co-incidence and physical interaction of vasorin and TGF-β1 within VSMC are significantly decreased with aging. Importantly, exposure of young VSMC to Ang II increases p-SMAD2/3 and collagen type I production, mimicking old cells, and this effect is abolished or substantially mitigated by Los treatment, overexpression of ectopic vasorin, or exogenous recombinant human-vasorin protein. In contrast, exposure of old VSMC to Los decreases p-SMAD2/3 and collagen type I production. Thus, an imbalance of the Ang II/TGF-β1/vasorin signaling cascade, a feature of the aged arterial wall, enhances the collagen production by VSMC. Thus, maintaining the balance of vasorin/TGF-β1 signaling is a novel measure to retard adverse age-associated extracellular matrix remodeling, a determinant of arterial stiffening. 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 and relevant vascular diseases, including aneurysm. Interruption of this vicious cycle is a potential therapeutic approach to arterial health.
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