Role of type-II pathway in apoptotic cell death induction by photosensitized CDRI-97/78 under ambient exposure of UV-B.

Novel trioxane 97/78, developed by Central Drug Research Institute (CDRI), Lucknow has shown promising antimalarial activity. Clinical experience of anti-malarial drugs registered the occurrence of phototoxicity in patients exposed with sunlight subsequent to medication. Photodegradation study has identified one photo-product up to 4h under UV-B/Sunlight by LC-MS/MS. UV-B irradiated 97/78 compound produced ¹O₂ via type-II dependent reaction mechanism, corroborated by its specific quencher. 2'-dGuO degradation and % tail development in photochemical as well as comet test, advocated the genotoxic potential of 97/78. The photocytotoxicity assays (MTT and NRU) on HaCaT cell line revealed the considerable decline in cell viability by 97/78. Cell cycle and Annexin V/PI double stain along with AO/EB demonstrated the G2/M phase arrest and apoptosis. Significant caspase-3 activity was measured in photoexcited 97/78 by colorimetric assay. Fluorescence stain with AO/JC-1 confirmed the lysosomal disruption and mitochondrial membrane destabilization by UV-B irradiated 97/78. Gene expression by RT-PCR showed significant upregulation of p21 and pro-apoptotic Bax, but no change observed in Bcl-2. In conclusion, the study highlights ROS mediated DNA damage, lysosomal and mitochondrial destabilization via upregulation of Bax and activation of caspase-3 which further leads to apoptosis.