Isoprostane F2α-VI, a new marker of oxidative stress, increases following light damage to the mouse retina

PURPOSE A number of studies have suggested that retinal light damage involves oxidative stress. These include demonstration of protection by antioxidants, immunohistochemical detection of oxidative stress markers, and upregulation of antioxidant enzymes. Recently a new specific marker of lipid peroxidation (LPO), isoprostane F(2alpha)-VI, has been developed. This prostaglandin isomer is produced by nonenzymatic oxidation of membrane-linked arachidonic acid. Because it provides an unusually stable and specific measure of LPO, we sought to determine whether its levels would increase following retinal light damage. METHODS Balb/c mice were exposed to bright fluorescent light for 7 h. Twenty-eight h after light exposure, photoreceptor death was assessed by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analysis. Isoprostane F(2alpha)-VI was quantified in retinal extracts by gas chromatography/mass spectrometry. Retinal isoprostane was localized by immunofluorescence. RESULTS TUNEL analysis demonstrated photoreceptor cell death after light exposure. Compared with controls, retina extracts from mice exposed to fluorescent light had a significant increase in isoprostane F(2alpha)-VI levels following light damage. Immunohistochemistry confirmed an increase in retinal isoprostane. CONCLUSIONS Elevated levels of isoprostane F(2alpha)-VI, a stable, highly specific marker of lipid peroxidation, confirm earlier reports of light-mediated retinal lipid peroxidation, potentially an important mechanism of retinal degeneration. Further, since levels of isoprostane F(2alpha)-VI are readily quantified, its measurement provides a new means to specifically monitor retinal oxidative damage caused by prooxidants such as light.