title: Modulation of gamma ray-induced genotoxic effect by thymol, a monoterpene phenol derivative of cymene.
abstract: The radioprotective effect of thymol (TOH), a monoterpene phenol, on radiation-induced DNA damage was analyzed in vitro. Chinese hamster lung fibroblast cells (V79) were treated with different concentrations of TOH (0-100 µg/mL) for 1 hour before exposure to 3 Gy gamma irradiation, and then cytokinesis-blocked micronucleus and single-cell gel electrophoresis (comet assay) assays were used to evaluate the radiation-induced cytogenetic damage and genotoxic effects. Furthermore, the modulating effect of TOH on radiation-induced cell death was assessed by apoptotic and necrotic cell detection by staining with ethidium bromide/acridine orange using fluorescence microscopy. To understand the mechanism of TOH-imparted cytoprotection, mitochondrial membrane potential (MMP) was detected by flow cytometry after staining the cells with Rhodamine 123. Pretreatment of V79 cells with various concentrations of TOH (0-100 µg/mL) for 1 hour reduced the radiation-induced micronuclei as well as percent tail DNA and mean Olive tail moment with a maximum protective effect observed at TOH (25 µg/mL). Apoptosis by microscopic, MMP measurements indicated that the V79 cells exposed to gamma radiation alone showed a maximal increase in the number of early and late apoptotic and necrotic cell death associated with a significant loss of the MMP. Pretreatment with TOH (25 µg/mL) showed a significant (P < .01) decrease in the level of apoptotic fraction as well as necrotic cells and suppressed the radiation-induced collapse of MMP when compared with the radiation alone group. These results suggest that TOH suppresses radiation-induced genotoxicity, apoptosis, and necrosis primarily by the free radical scavenging and modulation of oxidative stress.
authors.affiliation: Manipal University, Manipal, India.
authors.forename: P R
authors.initials: PR
authors.lastname: Archana
authors.forename: B
authors.initials: B
authors.lastname: Nageshwar Rao
authors.forename: B S
authors.initials: BS
authors.lastname: Satish Rao
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D002478:Cells, Cultured; D020552:Comet Assay; D006224:Cricetinae; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects; D005347:Fibroblasts / Q000187:drug effects* / Q000528:radiation effects*; D005720:Gamma Rays / Q000009:adverse effects*; D008168:Lung / Q000187:drug effects / Q000528:radiation effects; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects / Q000528:radiation effects; D015162:Micronucleus Tests; D011832:Radiation Injuries / Q000517:prevention & control; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013943:Thymol / Q000494:pharmacology*
chemical_list: D011837:Radiation-Protective Agents; D013943:Thymol