In vitro UV-B Effect on Lens Protein Solutions

Abstract

To investigate the effects of UV-B exposure on the protein solutions of different lens parts, rabbit lenses were separated into the equator (Eq), anterior cortex (Ac), nucleus (Nu) and posterior cortex (Pc). After homogenization, the water-soluble protein from each part was irradiated with UV-B at 0 to 0.225 J/cm². Alterations in the content of protein SH, carbonyl groups, light scattering intensity and SDS-PAGE pattern were measured to compare the effect of UV-B on the protein solutions of various lens parts with or without additional GSH to test its preventive effect. The results showed that after UV-B irradiation, the protein sulfhydryl groups are gradually reduced. The nonprotein thiol (GSH added to the protein solution) was lost more rapidly than the protein sulfhydryl. The high molecular bands on the SDS-PAGE pattern mainly aggregated with disulfide. UV-B damage also increased the content of carbonyl groups and light scattering, irrespective of the lens parts. Lens proteins from the equator suffered the least damage while those of the nucleus were most strongly affected by UV-B exposure. This study suggests that the lens proteins from various lens parts have different responses to UV-B exposure; the sensitivity was in the following order: Eq < Ac ≤ Pc < Nu.

Carnosine Ameliorates Lens Protein Turbidity Formations by Inhibiting Calpain Proteolysis and Ultraviolet C-Induced Degradation

“…Exposure of lens proteins to UV-C irradiation results in ROS production 36 and proteolytic degradation, whereas UV-B does not increase proteolytic susceptibility to the same extent but promotes the formation of cross-linked proteins 16,17 and increased content of carbonyl and disulfide bonding to form insoluble lens protein. 37 Even though ultraviolet light is filtered by the dwindling ozone layer, increased exposure to UV-B is now considered to be a factor for increased cataract incidence. The observed UV-B-induced aggregation of γ-crystallins at ∼44 kDa (formation of dimers), similar to those of Andley et al, 29 may be related to intermolecular disulfide bond formations induced by UV irradiation.…”

“…Even though the current results revealed that CAR required 100 or 200 mM or higher concentrations to protect γ-crystallins from UV-C or UV-B insults, doses of CAR needed for delaying lens opacity formation induced by daily light ultraviolet may be lower than the concentrations used in the current assays. Exposure of lens proteins to UV-C irradiation results in ROS production and proteolytic degradation, whereas UV-B does not increase proteolytic susceptibility to the same extent but promotes the formation of cross-linked proteins , and increased content of carbonyl and disulfide bonding to form insoluble lens protein …”

UV DAMAGE TO THE EYE LENS: Further Results from Animal Model Studies: A review

“…In addition in-vivo as well as in-vitro investigations on organ and cell levels in culture systems provide further insight into characteristics and underlying mechanisms of UV damage to the eye lens 18,19,20,21) (Figure 8). …”