Abstract
Purpose :
Gamma crystallins are the main constituents of the lens nucleus where they remain transparent for decades due to a combination of chaperone activity by alpha B crystallins, low oxidative environment, and unique physico-chemical properties. Progressive age-related breakdown of these defenses contributes to protein destabilization, aggregation and opacification. We hypothesize that alpha-crystallin mimetic drugs exist among FDA approved drugs that can be developed as anti-cataract drugs.
Methods :
Bovine lens crystallins were extracted according to Ortwerth (Exp Eye Res 47:1988) and separated over Sephadex G-200 to isolate Pool 1 (a-crystallin polymers), Pool 2 (alpha-crystallin oligomers), Pool 3 beta-H and beta-L crystallins, and Pool 4 (monomeric gamma crystallins). Pools 1-3 and 2560 drugs (500-50 uM) were tested for their ability to protect bovine gamma crystallin (Pool 4, 3 mg/ml) aggregation upon exposure to oxidative (OS) and/or heat shock stress (HSS). Absorbance at 600 nm was used as index of turbidity.
Results :
Aggregation of gamma crystallins by HSS/OS was potently inhibited by Pool 1 proteins (alpha crystallins) at sub-stoichiometric ratio of 0.5:1 confirming earlier findings. Among 2560 drugs tested at 1:1 drug: protein ratio, 63 had turbidity protecting activity. 4 drugs had antioxidant activity, 31 chaperone activity and 26 had dual antioxidant & chaperone activity. At 0.5: 1 ratio, 7 compounds were obtained that had strong protective activity against gamma crystallin destabilization (see Table).
Conclusions :
These results suggest that alpha-crystallin mimetic drugs exist in the US Pharmacopeia that could be potentially repositioned toward the prevention of age-related cataract.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.