title: Cytotoxic and radioprotective effects of Podophyllum hexandrum.
abstract: Podophyllum hexandrum, a herb thriving in Himalayas has already been reported to exhibit antitumor and radioprotective properties. Present study was undertaken to unravel the possible mechanism responsible for the cytotoxic and radioprotective properties of REC-2001, a fraction isolated from the rhizome of P. hexandrum using murine peritoneal macrophages and plasmid DNA as model systems. Cell death, levels of intracellular reactive oxygen species (ROS) and apoptosis were studied employing trypan blue exclusion assay, dichlorofluorescein diacetate and DNA fragmentation assay, respectively. Superoxide anions, hydroxyl radicals and DNA damage were estimated following nitroblue tetrazolium, 2-deoxyribose degradation and plasmid DNA relaxation assays, respectively. Pre-irradiation administration of REC-2001 to peritoneal macrophages in the concentration range of 25-200μg/ml significantly reduced radiation induced ROS generation, DNA damage, apoptosis and cell killing in comparison to radiation control group indicating radioprotective potential. Studies with plasmid DNA indicated the ability of REC-2001 to inhibit 20Gy induced single and double strand breaks further supporting the antioxidative potential. However, REC-2001 in a dose-dependent fashion induced cell death, ROS and DNA fragmentation indicating the cytotoxic nature. REC-2001, in presence of 100μM copper sulfate, generated significant amount of hydroxyl radicals and superoxide anions indicating ability to act as a pro-oxidant in presence of metal ions. The superoxide anion generation was found to be sensitive to metal chelators like EDTA and deferoxamine mesylate (DFR). These results suggest that the ability of REC-2001 to act as a pro-oxidant in presence of metal ions and antioxidant in presence of free radicals might be responsible for cytotoxic and radioprotective properties.
authors.affiliation: Division of Radiopharmaceuticals and Radiation Biology, Institute of Nuclear Medicine and Allied Sciences, Brig. SK Mazumdar Marg, Delhi 110054, India.
authors.forename: Sandeep Kumar
authors.initials: SK
authors.lastname: Shukla
authors.forename: Pankaj
authors.initials: P
authors.lastname: Chaudhary
authors.forename: Indracanti
authors.initials: I
authors.lastname: Prem Kumar
authors.forename: Farhat
authors.initials: F
authors.lastname: Afrin
authors.forename: Satish Chandra
authors.initials: SC
authors.lastname: Puri
authors.forename: Ghulam Nabi
authors.initials: GN
authors.lastname: Qazi
authors.forename: Rakesh Kumar
authors.initials: RK
authors.lastname: Sharma