Regulation of Cataractogenesis in Culture Bovine Lenses by 5-Phenyldithiole-3-Thione-NSAID Hybrid Molecules
Although cataract is one of the leading causes of blindness worldwide, there is no pharmacological management for the disease. There is evidence that L-cysteine, a substrate for the endogenous production of hydrogen sulfide (H2S) and Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen can mitigate cataractogenesis. Therefore, this study investigated the pharmacological actions and mechanisms by which ATB 343 (indomethacin & H2S donor) and ATB 337 (diclofenac & H2S donor) regulate time-dependent and hydrogen peroxide (H2O2)-induced cataractogenesis in cultured bovine lenses, ex vivo. Dulbecco's Modified Eagle's medium (DMEM)-cultured lenses exhibited a time-dependent decrease in transmittance and a corresponding loss of lens optical clarity up to 72 hours. Except for ATB 343 (10-7 mM) that increased transmittance by 26.91% (n=16; p<0.01) after 24 hours, all concentrations of ATB 343 and ATB 337 tested (10-8 M - 10-4 M) decreased transmittance in cultured bovine lenses. Moreover, neither indomethacin (10-8 M - 10-4 M), diclofenac (10-8 M - 10-4 M), nor elevation of pH attenuated time-dependent lens degradation, ex vivo. Interestingly, H2O2 accelerated lens opacification in a concentration-dependent manner, achieving a significant (p<0.001) inhibition of 45.11% (10 mM; n=24) and 42.77% (50 mM; n=12) after 72 hours. Whereas ATB 343 (10-8 M, 10-7M & 10-6 M) partially attenuated H2O2 (10 mM)-induced loss in transmittance up to 72 hours, achieving the highest magnitude of attenuation after 6 hours of 33.21% (n=6; p<0.001); 29.40% (n=6; p<0.001) and 15.20% (n=6; p<0.05), it partially attenuated H2O2 (50 mM)-induced lens opacification in cultured bovine lenses up to 24 hours by 39.30% (n=12; p<0.001), 46.11% (n=9; p<0.001) and 9.30% (n=24; p>0.05) (24 hours), respectively. Similarly, ATB 337 (10-8M to 10-6M) partially reversed H2O2 (10 mM and 50 mM)-induced degradation up to 72 hours. After 48 hours, ATB 343 and ATB 337 (10-7M) significantly (n=3; p<0.05) enhanced time-dependent GSH depletion by 3.6% ± 0.05% and 2.7 ± 0.5% and H2O2-induced GSH depletion by 12.3 ± 0.1% (n=3; p<0.01) and 8.7 ± 0.4% (n=3; p<0.05), respectively. ATB 343 enhanced time-dependent SOD depletion by 35.3 ± 2.7% (n=3; p<0.001) but attenuated H2O2-induced SOD depletion by 56.6 ± 3.1% (n=3; p<0.001) (t=48 h). ATB 337 enhanced time-dependent loss in SOD by 48.9 ± 4.4% (n=3; p<0.001) but reversed H2O2-induced SOD loss by 31.8 ± 4.9% (n=3; p<0.001) (t=48 h). In conclusion, ATB 343 and ATB 337 partially protected cultured bovine lenses from cataract formation, presumably via an effect on lenticular SOD concentrations. In addition to delineating the exact mechanism by which H2S-NSAIDs regulate cataractogenesis in bovine and other in vitro models of cataract, future studies should be conducted to replicate these studies in animal model of cataracts. Globally, successful identification of pharmacological cataract treatments is likely to have a significant impact of the prognosis of the disease, especially in developing nations that lack access to cataract surgery.
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