Effect of Metalloprotease Inhibition on Age-Associated Arterial Remodeling

National Institute On Aging

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Abstract

Age-associated arterial structural and functional remodeling includes intimal vascular smooth muscle cell (VSMC) invasion and proliferation, VSMC senescence, collagen deposition, elastin fragmentation, calcification, amyloidosis, and increased arterial stiffening and blood pressure. This adverse remodeling is linked to proinflammatory molecular signaling cascades involving angiotensin II (Ang II), milk fat globule EGF-8 (MFG-E8) and its fragment medin, transforming growth factor-beta1 (TGF-β1), monocyte chemoattractant protein 1 (MCP-1), and proendothelin 1 (pro-ET1). These signals activate matrix metalloproteinases (MMPs) such as MMP2 via transcription factors ETS-1 and nuclear factor kappa B (NF-κB), while reducing anti-inflammatory molecules like vasorin and nuclear factor erythroid 2-related factor 2 (Nrf2). Inhibiting MMP activation decelerates age-associated arterial remodeling and decreases arterial blood pressure. Chronic administration (8 months) of the broad-spectrum MMP inhibitor, PD166793, to 16-month-old FXBN rats alleviates age-associated increases in arterial pressure and mitigates increases in aortic gelatinase and interstitial collagenase activity, aortic wall thickening, elastic fiber destruction, collagen deposition, MCP-1 and TGF-β1 activity, phosphorylation of profibrogenic molecule SMAD-2/3, pro-ET1 activation, and ETS-1 upregulation. In vitro studies show that pro-ET1 treatment of VSMCs increases ETS-1 transcription and translation, which is reduced by PD166793. Overexpressing ETS-1 in VSMCs elevates TGF-β1 and MCP-1 protein levels, indicating that MMP inhibition impedes age-associated arterial proinflammatory signaling, preserving elastin fiber integrity and reducing collagen and systolic blood pressure. The glycosylated protein vasorin interacts with TGF-β1, attenuating its profibrogenic and proinflammatory effects in arterial VSMCs. Ang II amplifies TGF-β1 activation in aging VSMCs by decreasing vasorin signaling through MMP2 cleavage. Vasorin mRNA and protein expression are significantly reduced in the aortic wall and primary cultured VSMCs from old versus young FXBN rats. Ang II treatment of young VSMCs lowers vasorin protein expression to levels seen in old untreated cells, while Losartan treatment increases vasorin levels in old VSMCs. Vasorin and TGF-β1 interactions are reduced in old VSMCs. Ang II treatment of young VSMCs increases MMP2 activation and TGF-β1 downstream signaling, which is inhibited by vasorin overexpression. Treating young rats with Ang II for 28 days reduced vasorin expression and worsened arterial health, but MMP inhibition increased vasorin levels in the aortic wall. Thus, reduced vasorin amplifies Ang II profibrotic signaling via MMP2 activation in aging arterial VSMCs. Aging increases cardiovascular disease incidence due to arterial proinflammatory shifts at molecular, cellular, and tissue levels. Calorie restriction (CR) in rats improves cardiovascular health and lifespan by blocking arterial inflammation. Our study examined how CR affects the proinflammatory landscape within the arterial wall. Aortae from young (6-month-old) and old (24-month-old) Fisher 344 rats, either fed ad libitum (AL) or on a 40% CR diet, were analyzed. CR markedly reduced age-associated intimal medial thickening, collagen deposition, and increased elastin fraction. Aortic wall immunostaining/blotting showed CR prevented age-associated increases in PDGF-BB density, MMP2 activity, TGF-β1, and p-SMAD-2/3 signaling. In VSMCs from both AL and CR rat aortae, CR alleviated age-associated phenotypic shifts, profibrogenic signaling, and PDGF-BB response. CR reduces adverse matrix remodeling and cellular proinflammation in aging arterial walls, likely via PDGF signaling inhibition, preserving a youthful aortic wall phenotype. We also found that auto-antibody production is related to MMP2 activation during experimental atherosclerosis in ApoE-/- mice. B cells and antibodies function differently based on antibody isotype, with IgM being protective and IgG inflammatory. ApoE-/- Aid-/- mice, which cannot produce IgG but maintain high plasma cholesterol, showed reduced plaque burdens and MMP2 expression compared to ApoE-/- mice. Both ApoE-/- and ApoE-/- Aid-/- mice had elevated IgM antibody titers, but ApoE-/- Aid-/- mice had higher levels of antibodies specific to malondialdehyde-oxidized low-density lipoprotein (MDA-oxLDL), which blocks macrophage infiltration into plaques. Conversely, ApoE-/- mice had antibodies specific to numerous self-proteins. Elevated MDA-oxLDL-specific IgM antibodies inhibit plaque formation and MMP2 expression, suggesting both IgM and IgG are involved in age-associated atherogenesis.