Upregulated thioredoxin and its reductase prevent H2O2-induced growth inhibition and death in human pulmonary artery smooth muscle cells

Abstract

The thioredoxin (Trx) system controls cellular redox in vascular smooth muscle cells. The present study investigated the roles of Trx1 and Trx reductase1 (TrxR1) proteins in regulation of cell growth, death, reactive oxygen species (ROS) and glutathione (GSH) levels in hydrogen peroxide (H2O2)-treated human pulmonary artery smooth muscle (HPASM) cells. H2O2 induced growth inhibition and cell death in HPASM cells over 24 h. Overexpression of Trx1 and TrxR1 using adenoviruses significantly weakened cell growth inhibition and cell death caused by H2O2. Increases in ROS levels including mitochondrial superoxide anion (O2•−) were observed as early as 5–30 min after H2O2 addition. Administration of adTrxR1 attenuated H2O2-induced increases in ROS levels at 30–180 min. adTrx1 and adTrxR1 significantly reduced the increases in O2•− level in H2O2-treated HPASM cells at 24 h. Furthermore, HPASM cells transfected with Trx1 or TrxR1 siRNA showed increases in ROS levels with or without H2O2 at 5 min. While H2O2 transiently decreased GSH level at 5 min, Trx1 and TrxR1 siRNA intensified the decrease in GSH level. In conclusion, upregulation of Trx1 and TrxR1 significantly attenuated cell growth inhibition and death in H2O2-treated HPASM cells. As a whole, Trx-related adenoviruses diminished H2O2-induced ROS level in HPASM cells whereas Trx-related siRNAs increased ROS levels and decreased GSH level in these cells.