ABSTRACT
In the present study we investigated the radioprotective activity of hydroalcoholic leaf extracts of Psidium guajava (P.G) against rats exposed to X rays. Exposure to ionizing radiation like X rays induces oxidative damage in normal tissues leading to their death or transforming them into cancerous tissues. To study the optimum dose of radioprotection, rats were administered with different doses (50,100,200,400 mg/kg body weight) of Psidium guajava leaf extracts daily for five consecutive days. One hour after last administration of leaf extracts the rats were treated with 6.6 Gy of x rays.200 mg/kg body weight was selected as an optimum dose for radioprotection based on survival analysis. Pretreatment of 200 mg/kg body weight of P.G leaf extract increased the levels of antioxidant enzymes such as superoxide dismutase, catalase, reduced glutathione and lowered the levels of lipid peroxidation, protein carbonyls and nitric oxide when compared to irradiated group in liver tissue homogenates. DNA damage indicators analyzed through comet assay showed a reduction in Olive tail movement and percentage DNA in tail significantly in P.G pretreated group when compared to irradiated group alone. Pretreatment of P.G leaf extract at a dose of 200mg/kg body weight protected cells from apoptosis which was analyzed microscopically by Ethidium bromide /Acridine orange staining. Our findings demonstrate the role of P.G leaf extract as a radio modulator in vivo, consequent to its powerful antioxidant activity in vitro and could be beneficial in combating radiation induced damage in living systems.
ABSTRACT
Response of a transplantable tumor, S180, grown intradermally in inbred Balb/c mice, was assessed by using micronucleus assay after treating the solid tumors with bleomycin (BLM), radiation (RT) and hyperthermia (HT) vis-a-vis multimodality approach. The frequency of micronuclei (MN) though did not vary greatly during the one week of observation in untreated tumors, it significantly increased in the drug and RT groups at 24 hr post-treatment. However, MN frequency was non-significant in the HT group from the control. A drug dose dependent linear increase in the frequency of MN induction was evident in 10, 15 and 20 mg/kg body weight BLM alone treated groups. Combination of radiation with BLM or HT further increased the MN counts in the bimodality groups. But, MN induction at 24 hr post-treatment in the trimodality group (BLM + RT + HT) was non-significant from that of the bimodality treatments. However, the tumors treated with trimodality treatment presented severe tumor necrosis, indicating increased cell loss, and resulting in immediate tumor regression. In all the bi-modality groups MN counts though declined 3 or 5 days post-treatment, the values remained significantly higher than the control, on day 7 post-treatment. Micronucleus assay could be used as a predictive parameter for the assessment of post-irradiation tumor regression response. However, the tumor response assessment with MN assay alone may not be sufficient and the role of other parameters, such as apoptosis and necrosis, in immediate tumor regression, especially radiosensitive/thermosensitive tumors can not be ignored while taking multimodality approach into consideration for cancer therapy.