Effects of selenium deficiency on expression of selenoproteins in bovine arterial endothelial cells

Damage to the vascular endothelium by reactive oxygen species causes many c ardiovascular diseases including atherosclerosis. Such damage can be preven ted by selenium (Se), which is thought to exert its actions mainly through the expression of selenoproteins. Se deficiency increased the susceptibilit y to tert-butylhydroperoxide (t-BuOOH) and enhanced lipid peroxidation in b ovine arterial endothelial cells (BAEC), We investigated the effects of Se deficiency on the expression of the selenoproteins in BAEC, Se-75 metabolic labeling analysis and RT-PCR analysis revealed that BAEC expressed two glu tathione peroxidase (GPx) isozymes, cytosolic GPx (cGPx) and phospholipid h ydroperoxide GPx (PHGPx), three thioredoxin reductase (TrxR) isozymes, TrxR 1, TrxR2 and TrxR3, and selenoprotein P (SelP), Se deficiency reduced both enzyme activity and mRNA level of cGPx, but did not affect those of PHGPx. SelP mRNA level was also reduced by Se deficiency, although the extent of r eduction was much smaller than that of cGPx mRNA, We further found that Trx R activity was also decreased by Se deficiency but none of the mRNA levels of TrxR isozymes were reduced, These results indicate that vascular endothe lial cells express several selenoproteins including cGPx, PHGPx, TrxR isozy mes and SelP which might play important roles in the defense system against oxidative stresses and that the expressions of these selenoproteins are di fferently regulated by Se status.