Abstract 20332: Oxidative Inactivation of Protein Tyrosine Phosphatases Underlies Aging-associated Increases in Inflammation in VSMC and Atherosclerosis in ApoE−/− Mice

The incidence of cardiovascular diseases (CVD) increases with age. Numerous studies have implicated oxidative stress induced activation of receptor and cytosolic tyrosine kinases in the pathogenesis of CVD. However, the role of protein tyrosine phosphatases (PTPs) in age-associated vascular dysfunction and increase in CVD has received much less attention. We previously reported that reactive oxygen species generation was significantly increased in aortic vascular smooth muscle cells (VSMC) isolated from aged mice than from young mice. Here, we hypothesize that oxidative inactivation of PTPs with aging enhances inflammatory mechanisms that increase atherosclerosis susceptibility. We investigated age-related changes in PTP activity using VSMC isolated from young (4 months) and aged (16 months) wild-type (C57BL/6) mice. Total PTP, PTP1B and dual-specificity lipid and protein phosphatase PTEN activities were decreased in aged VSMC compared with young VSMC. Decrease in PTP1B and PTEN activities correlated with enhanced oxidation of these proteins as determined using anti-oxidized PTP active site antibody. Aged VSMC had significantly enhanced TNF-α-induced phosphorylation of transcription factors STAT3 and NF-kB as well as upregulated E-selectin, P-selectin, VCAM-1 and ICAM-1 mRNA expression (6.1, 2.6, 1.7 and 3.3 fold increases, respectively) compared to young VSMC. Monocyte adhesion to VSMC monolayers was two-fold higher in aged than in young VSMC (p<0.01). The increases in proinflammatory signaling, adhesion molecule expression and monocyte adherence were significantly inhibited when aged cells were pre-treated with the antioxidant N-acetylcysteine or overexpression of dominant negative IkBα or JSH-23, both NF-kB inhibitors. Atherosclerosis increased 4-fold in aged apoE−/− mice compared to young apoE−/− mice. The increase in atherosclerosis in aged apoE−/− mice was correlated with decreased aortic total PTP, PTP1B and PTEN activities and increased E-selectin, VCAM-1 and ICAM-1 expression. In conclusion, our data indicate that oxidative stress-induced inhibition of PTP activities increases atherosclerotic burden in aged mice on hypercholesterolemic background by enhancing the activity of inflammatory signaling pathways.