Modulation of gamma ray-induced genotoxic effect by thymol, a monoterpene phenol derivative of cymene

P. R. Archana, B. Nageshwar Rao, B. S. Satish Rao

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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.

Original languageEnglish
Pages (from-to)374-383
Number of pages10
JournalIntegrative Cancer Therapies
Volume10
Issue number4
DOIs
Publication statusPublished - 12-2011

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All Science Journal Classification (ASJC) codes

  • Oncology
  • Complementary and alternative medicine

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