Evidence for apoptosis in the lens after in vivo exposure to ultraviolet radiation

Abstract

SummaryThe eye is exposed to ultraviolet radiation (UVR) in daylight. Epidemiological studies suggest a dose dependent association between UVR and cataract development. Experimental data confirm that UVR induces damage in the lens epithelium and trigger apoptosis. The time delay between exposure and onset of apoptosis in the lens varies depending on the dosage of UVR. The higher the in vivo UVR dose, the faster the onset of apoptosis and the development of lens opacification. Apoptotic events in the epithelium precede macroscopic cataractogenesis. Lens epithelium is a primary target for UVR exposure. Immunohistochemistry shows that the expression of apoptotic markers, caspase 3 and p53, increase in the lens epithelium after radiation. TUNEL‐labeling visualizes the transient increase of apoptosis products after UVR. After higher doses of UVR, apoptosis features are observed 1 h after radiation. Transmission electron microscopy shows the multi‐layered stack of epithelial cells, membrane infolds, nuclear fragmentation and chromatin condensation, phagosomes and apoptotic bodies, phagocytosis of apoptotic bodies and pyknosis. UVR causes apoptosis in the lens epithelial cells. The onset of apoptosis depends on the radiation dose.