Changes in clusterin expression associated with light-induced retinal damage in rats.

Prolonged periods of high-intensity visible light exposure lead to photoreceptor cell degeneration, but the mechanism of damage is not understood. Increased clusterin mRNA levels have been found in several models of apoptosis, as well as in neurodegeneration. We report here that changes in clusterin mRNA levels are also associated with light-induced retinal damage in adult male albino rats. Animals previously maintained in darkness or a weak cyclic light environment were exposed to intense visible green light for up to 24 h. Some rats were pretreated with a synthetic antioxidant, dimethylthiourea (DMTU), which reduces photoreceptor cell degeneration. Clusterin mRNA steady-state levels increased with the duration of light exposure in both cyclic light and dark reared animals, suggesting that an apoptotic mechanism may be involved. Animals pretreated with DMTU showed a delay in the initial increase in clusterin mRNA levels, suggesting that oxidative damage is involved in the damage mechanism. However, the incomplete suppression of increasing steady-state clusterin mRNA levels by DMTU suggests that either oxidative damage triggers a second pathway or multiple damage mechanisms are induced in the retina by light exposure.