In this study, we have performed a comprehensive quantitative proteomic study to analyze aortic proteins from young (8 mo) and old (30 mo) rats. Using 2-D DIGE, we have obtained 2-D gel maps of 301 identified non-redundant proteins from rat aorta and observed 18 proteins that significantly change abundance with aging. Utilizing iTRAQ, 921 proteins were quantified and between both methods, 50 proteins were shown to have significantly different age-associated abundance. The two methods have produced complemented each other and therefore, increased the confidence of the results. Totally, 981 proteins were detected by two methods. The majority (240, 80%) of the proteins detected by 2DE are also quantified by iTRAQ. Approximately 5 % of the proteins identified have significantly different abundance with aging (Table). Of the proteins found to differ with aging, 5 proteins had post-translation modifications (PTM). Acidic calponin3 is a phosphoprotein while the milk fat globule protein epidermal growth factor 8 (MFG-E8), Alpha-1-inhibitor III, kininogen 1 and periostin were detected as N-linked glycoproteins. Furthermore, proteomic analysis shows that one protein of interest, MFG-E8, significantly increases in abundance in old rat aorta. Transcription and translation analysis demonstrated that aortic MFG-E8 mRNA and protein levels increase with aging in several mammalian species including humans. Dual immunolabeling shows that MFG-E8 colocalizes with both angiotensin II (Ang II) and monocyte chemoattractant protein-1 (MCP-1) within vascular smooth muscle cells (VSMCs) of the thickened aged aortic wall. Exposure of early passage VMSCs from young aorta to Ang II markedly increases MFG-E8 and enhances invasive capacity to levels observed in VSMCs from old rats. Treatment of VSMCs with MFG-E8 increases MCP-1 and VSMCs invasion that are inhibited by the MCP-1 receptor blocker, vCCI. Silencing MFG-E8 RNA substantially reduces MFG-E8 expression and VSMCs invasion capacity. Taken together, the proteome changes observed in this study including cytoskeletal remodeling, apoptosis/cell death and cell cycle/proliferation, and extracellular-related matrix reveal that the aged aorta is affected in concert by numerous signaling proteins, including MFG-E8. The further findings indicate that arterial MFG-E8 significantly increases with aging and is a pivotal relay element within the Ang II MCP-1/VSMC invasion signaling cascade. Thus, targeting of MFG-E8 within this signaling axis pathway is a potential novel therapy for prevention and treatment of the quintessential age-associated diseases, i.e., arthrosclerosis and diseases involved in inflammation and smooth muscle cells invasion.
Showing the most recent 10 out of 18 publications
