Churala Pal

Mitochondria-Dependent Reactive Oxygen Species-Mediated Programmed Cell Death Induced by 3,3′-Diindolylmethane through Inhibition of F0F1-ATP Synthase in Unicellular Protozoan Parasite Leishmania donovani

Mitochondria are the principal site for the generation of cellular ATP by oxidative phosphorylation. F0F1-ATP synthase, a complex V of the 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 F0F1-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 F0F1-ATP synthase activity causes depletion of mitochondrial ATP levels and significant stimulation of mitochondrial reactive oxygen species (ROS) production, followed by depolarization of mitochondrial membrane potential (ΔΨm). Because ΔΨm is the driving force for mitochondrial ATP synthesis, loss of ΔΨm results in depletion of cellular ATP level. The loss of ΔΨm causes the cellular ROS generation and in turn leads to the oxidative DNA lesions followed by DNA fragmentation. In contrast, loss of ΔΨm 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 mitochondrial DNA-depleted cells are insensitive to DIM to induce PCD. Therefore, mitochondria are necessary for cytotoxicity of DIM in kinetoplastid parasites. Taken together, our study indicates for the first time that DIM-induced mitochondrial dysfunction by inhibition of F0F1-ATP synthase activity leads to PCD in Leishmania spp. parasites, which could be exploited to develop newer potential therapeutic targets.

Hydroxychavicol, a Piper betle leaf component, induces apoptosis of CML cells through mitochondrial reactive oxygen species-dependent JNK and endothelial nitric oxide synthase activation and overrides imatinib resistance.

Alcoholic extract of Piperbetle (Piper betle L.) leaves was recently found to induce apoptosis of CML cells expressing wild type and mutated Bcr‐Abl with imatinib resistance phenotype. Hydroxychavicol (HCH), a constituent of the alcoholic extract of Piper betle leaves, was evaluated for anti‐CML activity. Here, we report that HCH and its analogues induce killing of primary cells in CML patients and leukemic cell lines expressing wild type and mutated Bcr‐Abl, including the T315I mutation, with minimal toxicity to normal human peripheral blood mononuclear cells. HCH causes early but transient increase of mitochondria‐derived reactive oxygen species. Reactive oxygen species‐dependent persistent activation of JNK leads to an increase in endothelial nitric oxide synthase‐mediated nitric oxide generation. This causes loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, cleavage of caspase 9, 3 and poly‐adenosine diphosphate‐ribose polymerase leading to apoptosis. One HCH analogue was also effective in vivo in SCID mice against grafts expressing the T315I mutation, although to a lesser extent than grafts expressing wild type Bcr‐Abl, without showing significant bodyweight loss. Our data describe the role of JNK‐dependent endothelial nitric oxide synthase‐mediated nitric oxide for anti‐CML activity of HCH and this molecule merits further testing in pre‐clinical and clinical settings. (Cancer Sci 2012; 103: 88–99)

Antibacterial Activity and Anticorrosive Efficiency of Aqueous Methanolic Extract of Artemisia pallens (Asteraceae) and its major Constituent

An aqueous-methanolic [methanol:water (1:1)] extract of the whole plant of Artemisia pallens (Family: Asteraceae) has shown good antibacterial activity against Pseudomonas aeruginosa and Shigella flexneri at the concentration of 100 mg/mL. The activity-guided fractionation has led to isolation of compound 4-hydroxyphenyl-?-D-glucopyranoside (which is known as arbutin), as a major constituent and exhibited the same antibacterial activity at a concentration of 17 mg/mL. Both the crude extract and arbutin also showed 94% anticorrosive efficiency against mild steel in 1M HCl at concentration of 200 mg/L.

An Overview on the Thermodynamic Techniques used in Food Chemistry

The thermal behaviour of food strongly depends on its composition. The goals of food processing are to inactivate spoilage and pathogenic microorganisms and to maintain this status in storage. Using calorimetric techniques, many physicochemical effects can be observed in the temperature range between -50°C and 300°C. Biophysical techniques namely isothermal titration (ITC) and Differential Scanning Calorimetry (DSC) are used to characterize the structure and properties of food materials before and after processing to develop a fundamental understanding of the impact of processing and storage conditions. The data resulting from such studies can be used to predict the physical properties of foods under optimized condition.