Decreased thioredoxin reductase activity in endothelial cells exposed to high glucose is associated with protein tyrosine nitration and interaction with caveolin 1

Abstract

Thioredoxin reductase 1 (TrxR1) is an important antioxidant enzyme that controls cellular redox homeostasis. Here we wanted to determine the effects of elevated glucose levels on TrxR1activity in human endothelial cells. Human coronary and aortic endothelial cells (HCAEC and HAEC, respectively) were exposed to high glucose conditions (HG= 25mM) for 5 days and/or iso‐osmotic control (L‐glucose). We found that HG diminished TrxR1 activity (30% reduction, p<0.005), stimulated its association with caveolin‐1 and its subcellular localization to caveolae. Immunoprecipitation analysis revealed that HG‐promoted TrxR1 tyrosine nitration. Pre‐treatments of the cells with the peroxynitrite decomposition catalyst FeTPPS (25μM) partially rescued TrxR1 activity and prevented its interaction with caveolin‐1. FeTPPS also attenuated HG‐induced increases in caspase 3 activity and induction of apoptosis in endothelial cells. Our results suggest that inhibition of TrxR1 activity by HG in human endothelial cells is a result of its nitration and interaction with caveolin‐1. Restoration of TrxR1 activity may be a potentially beneficial therapeutic strategy for the prevention of diabetes‐induced vascular complications.