Overexpression of antioxidant enzyme peroxiredoxin 5 protects human tendon cells against apoptosis and loss of cellular function during oxidative stress

Oxidative stress and apoptosis are implicated in tendon degeneration. Peroxiredoxin 5 (PRDX5) is a novel thioredoxin peroxidase recently identified in mammals, participating directly in eliminating hydrogen peroxide (H2O2) and neutralizing other reactive oxygen species (ROS). We have previously reported that PRDX5 is upregulated in degenerative human tendon. However, the effects of this upregulation on human tendon cell function remain unknown, in particular, with regards to oxidative stress conditions. Here we report that exposure of human tendon cells to 50 muM H2O2 for 24 h (in vitro oxidative stress) caused a significant increase in the percentage of apoptotic cells (P < 0.05) as assessed by flow cytometric analysis of Annexin V binding, accompanied by increased PRXD5 mRNA and protein expression. Overexpression of PRDX5 in human tendon cells via transfection inhibited H2O2-induced tendon cell apoptosis by 46% (P < 0.05), and prevented the decrease in tendon cell collagen synthesis which occurs under H2O2 challenge, although the decrease in collagen synthesis was small. Results from our study indicate that the antioxidant enzyme PRDX5 plays a protective role in human tendon cells against oxidative stress by reducing apoptosis and maintaining collagen synthesis. (C) 2004 Elsevier B.V. All rights reserved.