Received for publication July 1, 2008.
Revised August 12, 2008.
Accepted for publication August 13, 2008.

Mitochondria dependent ROS-mediated programmed cell death (PCD) induced by 3,3'-Diindolylmethane (DIM) through Inhibition of FoF1-ATP synthase in unicellular protozoan parasite Leishmania donovani

Abstract

Mitochondria are the principal site for the generation of cellular ATP by oxidative phosphorylation. FoF1-ATP synthase, a complex V of electron transport chain, is an important constituent of mitochondria dependent-signaling pathways involved in apoptosis. In the present study, we have shown for the first time that 3,3'-Diindolylmethane (DIM), a DNA topoisomerase I poison inhibits mitochondrial FoF1-ATP synthase of Leishmania donovani and induces programmed cell death (PCD), which is a novel insight into the mechanism in protozoan parasites. DIM-induced inhibition of FoF1-ATP synthase activity causes depletion of mitochondrial ATP levels and significant stimulation of mitochondrial ROS production, followed by depolarization of mitochondrial membrane potential (m). Since, m is the driving force for mitochondrial ATP synthesis, loss of m results in depletion of cellular ATP level. The loss of m causes the cellular ROS generation and in turn led to the oxidative DNA lesions followed by DNA fragmentation. On the other hand, loss of m leads to release of cytochrome c into the cytosol and subsequently activates the caspase-like proteases, which lead to oligonucleosomal DNA cleavage. We have also shown that mt-DNA depleted cells are insensitive to DIM to induce PCD. Therefore, mitochondria are necessary for cytotoxicity of DIM in kinetoplastid parasites. Taken together, our studies indicate for the first time that DIM-induced mitochondrial dysfunction by inhibition of FoF1-ATP synthase activity leads to PCD in Leishmania parasites, which could be exploited to develop newer potential therapeutic targets.

Key words: Apoptosis, Oxidative stress, Topoisomerases