UV-B AS A PRO-AGING AND PRO-CATARACT FACTOR

One of the functions of the human lens is filter light between 300-400 nm from reaching the retina. The lens is therefore continually under photooxidative stress. In the young lens the primary absorbing species is the O-beta glucoside of 3-hydroxykynurenine (3-HKG) which has a ma ximum at 365 nm. Photophysical studies have demonstrated that absorpti ons by this compound in the short term are relatively benign to the le ns, but in the long term can lead to the photochemical loss of 3-HKG w ith the concomitant yellowing of lens proteins. It will be proposed th at part of this yellowing is due to the photochemically induced attach ment of 3-HKG to lens proteins. The yellowing of lens proteins leads t o a drastic increase in the number of photons absorbed by the lens. Th is, along with the age-related losses of antioxidants such as GSH will increase the photooxidative stress on the lens. Considering the foreg oing and various epidemiological, model and biochemical studies, it ca n be concluded that light is most likely one of the causative factors in cataractogenesis.