Effect of CDNB on filarial thioredoxin reductase : A proteomic and biochemical approach

Thioredoxin reductase plays a crucial role in the maintenance of cellular redox homeostasis. In this study, we have targeted TrxR in Setaria cervi, a bovine filarial parasite using its inhibitor CDNB. It caused significant decrease in the motility and viability of these parasites leading to their death. Inhibition of TrxR leads to the downregulation of the antioxidant system followed by generation of oxidative stress in these parasites. The increased ROS level induced lipid peroxidation and protein carbonyl formation which might alter the mitochondrial membrane permeability leading to release of cytochrome c. CDNB significantly downregulated the level of ced-9 and activity of tyrosine phosphatases, cytochrome c oxidase. It also upregulated ced-3, homolog of mammalian caspase 3 suggesting initiation of intrinsic pathway of apoptosis. The proteomic profile of CDNB treated parasites showed marked alteration in abundance of different protein spots with 20% downregulated and 13% unregulated spots in comparison to control parasites. We observed a downregulation in the glycolytic enzymes such as enolase, PGK, and GAPDH thereby blocking the ATP formation in the parasite. This study suggests that TrxR inhibition disrupts the cellular homeostasis thereby generating oxidative stress followed by mitochondrial mediated apoptosis in filarial parasites leading to the death of the parasites.

Lymphatic filariasis is one of the most prevalent tropical diseases caused by tissue dwelling parasitic nematodes viz., Wuchereria bancrofti, Brugia malayi and Brugia timori. Currently available antifilarial drugs effectively eliminate larval stages of the parasite but are ineffective against the adult worms. Therefore, there is an urgent need for finding proteins/enzymes which play a crucial role in the persistence of these parasites. Our study for the first time reports the important role played by S. cervi TrxR in its survival. Thus, suggesting filarial TrxR as a potent chemotherapeutic target against lymphatic filariasis. This would help in screening of new compounds having macrofilaricidal activity.