PEROXIDE-INDUCED DAMAGE IN LENSES OF TRANSGENIC MICE WITH DEFICIENT AND ELEVATED LEVELS OF GLUTATHIONE-PEROXIDASE

Transgenic mice with elevated glutathione peroxidase (GSHPx) activity and gene knockout animals with a deficiency of the enzyme were used to investigate the role of GSHPx in defending the lens against H2O2-indu ced damage. The effects of peroxide on cultured lenses were determined by using light and transmission electron microscopy to evaluate morph ological changes occurring in the epithelium and superficial cortex of the central and equatorial regions of the lens. DNA single-strand bre aks in the epithelium were also examined. Following a 30-min exposure to 25 mu M H2O2, lenses from normal animals showed distinct changes in the morphology of both the epithelium and superficial cortex. The dam age to these cells was extensive in lenses of gene knockout mice in wh ich activity of GSHPx was undetectable. In marked contrast, lenses of transgenic mice, which had 5-fold higher activities of GSHPx, were abl e to resist the cytotoxic effects. Similar to damage to cell morpholog y, the extent of DNA strand breaks was significantly lower (40% of con trol) in H2O2-exposed lenses as compared to normal lenses while DNA da mage in gene knockout lenses was 5 times greater than that of GSHPx-ri ch transgenic lenses. The present studies extend our previous findings on the role of the glutathione redox cycle in the detoxification of p eroxide and demonstrate that an increase in GSHPx activity protects th e lens against peroxide-induced changes in cell morphology and DNA str and breaks.