Melatonin can suppress the cytotoxic effects of chlorpyrifos on human hepG2 cell lines

The cytotoxic effect of chlorpyrifos (CP) on human HepG2 cell lines and the protective role of melatonin were investigated. TD50 of CP for HepGZ cells was also determined. The viability of HepGZ cells decreased with CP treatment in a dose-dependent manner (P <0.05). Preincubation with melatonin prior to CP application caused an increase in cell viability (P <0.05). TD50 of CP for HepG2 was determined as 84.5 microg/mL. A 1-hour melatonin treatment caused a decrease in TD50 from 84.5 to 34.1 microg/mL. The level of thiobarbituric acid reactive substance (TBARS) and the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were determined in cell lines with or without melatonin administration to find out the possible mechanism of melatonin. CP caused a significant decrease in SOD, GSH-Px and CAT activities and an increase in TBARS level (P <0.05). Pre-incubation of cells with melatonin prevented an increase in TBARS. Melatonin also reduced the CP-caused inhibition of the activities of GSH-Px and CAT (P <0.05). It was suggested that CP shows a cytotoxic effect on HepG2 cell lines and melatonin can suppress cytotoxicity caused by CP with its antioxidant properties. Melatonin also reduces TD50 of CP for HepG2 cell lines.

Photooxidation of lens alpha-crystallin by hypericin (active ingredient in St. John's Wort)

Hypericin is the active ingredient in the over the counter antidepressant medication St. John's Wort. Hypericin produces singlet oxygen and other excited state intermediates that indicate it should be a very efficient phototoxic agent in the eye. Furthermore it absorbs in the UV and visible range, which means it can potentially damage both the lens and the retina. Lens alpha-crystallin, isolated from calf lenses, was irradiated in the presence of hypericin (5 x 10(-5) M, 10 mM ammonium bicarbonate, pH 7.0) and in the presence and absence of light (> 300 nm, 24 mW/cm2). Hypericin-induced photosensitized photopolymerization as assessed by sodium dodecylsulfate-polyacrylamide gel electrophoresis. Further analysis of the oxidative changes occurring in alpha-crystallin using mass spectrometry showed specific oxidation of methionine, tryptophan and histidine residues, which increased with irradiation time. Hypericin did not damage the lens protein in the dark. Damage to alpha-crystallin could undermine the integrity of the lens directly by protein denaturation and indirectly by disturbing chaperone function. Therefore, in the presence of light, hypericin can induce changes in lens protein that could lead to the formation of cataracts. Appropriate precautions should be taken to protect the eye from intense sunlight while on this antidepressant medication.

Electron-topological investigation of structure-antitubercular activity relationship of thiosemicarbazone derivatives

Within the framework of the electron-topological approach the structure-antitubercular activity relationship was investigated in a series of thiosemicarbazone derivatives. The series in view included 71 compounds. For each compound conformational and quantum-chemical calculations were carried out. An activity feature gave a satisfactory description of the class of active compounds: two parameters, alpha a and Pa, estimating the probabilities of its realization had the values equal to 0.935 and 0.914, correspondingly. At the same time the feature of inactivity found ("the break of activity") was realized within the class of inactive compounds with the probabilities alpha b = 0.749 and Pb = 0.950. Eight compounds not included in the teaching sample were tested for features presence. The results of the test demonstrated a high ability of the electron-topological method to predict the activity needed.