RESUMO
PURPOSE: Oxidative stress is an essential component of innate response against microbes. The oxidative impact has a very subtle connection with apoptosis. Our previous work indicated presumptive evidence of apoptosis by the chalcone derivatives against the human lymphatic filarial parasite. Evidence suggests the involvement of glutathione-S-transferase (GST) in the mechanism of action of chalcone drugs. In the present study, we explored the implications of redox status in apoptosis of the parasite by this drug. RESULTS: Treatment with the representative drug, 4t, significantly decreased GSH level and increased GST activity in the Brugia malayi microfilariae (Mf) in comparison to Mf without 4t treatment. Drug-induced loss of motility of the parasites was reversed by the treatment with GSH (41%) and NAC (19%). A significant fall in rGST activity was observed due to drug addition, which could be reversed by the addition of GSH co-substrate, but not with the re-addition of rGST, indicating a vital role of GSH. In silico study demonstrated a favorable drug-GST enzyme interaction. Oxidative stress was reflected by increased protein carbonylation and intracellular reactive oxygen species level, in the drug-treated parasite. Mitochondrial oxygen consumption was reduced by the drug, which was reversed on the addition of GSH. Mitochondrial dysfunction was confirmed by MTT and cytochrome c assay. Apoptosis was confirmed by the inhibition in PARP activity. CONCLUSION: We conclude that the depletion of GSH by chalcone with concomitant mitochondrial dysfunction revealed a novel rationale of apoptosis in the parasite. Such a mechanism might have wide therapeutic implications.
