Background: Radiation-induced bystander effect (RIBE) is defined as a phenomenon that occurs when radiation signals are transmitted from irradiated cells to non-irradiated ones, inducing radiation effects in them. RIBE has an effective role in radiation response at low doses as well as in radiotherapy due to affecting normal tissues adjacent or far from the irradiated tumor. Reactive oxygen species have an important role in RIBE induction; therefore, the present research was conducted to investigate the possible inhibitory effects of garlic as an antioxidant-containing plant on RIBE.
Materials and Methods: MCF7 cells treated with raw garlic extract were irradiated by 60Co gamma rays, and their culture medium was transferred to autologous non-irradiated (bystander) cells. Percentage cell viability and micronucleus formation in both irradiated and bystander cells were examined, and were compared with corresponding cell groups not treated with garlic.
Results: Treatment with garlic extract reduced the number of cells containing micronucleus in both irradiated and bystander cells. However, it only increased the percentage cell viability in bystander cells and not irradiated ones.
Conclusion: RIBE was effectively suppressed by raw garlic. Inhibitory effects of raw garlic may be of particular importance for exposures to environmentally relevant low doses, and partially for addressing the limited therapeutic gain of radiotherapy. Therefore, raw garlic is recommended in human diets, and should be prescribed for radiotherapy patients.
Key words: Allium sativum, Antioxidant, Radiation-induced bystander effect, Raw garlic
Ionizing radiations interact with organic compounds and water in the cells. Interaction between radiation and water molecules results in the generation of free radicals which attack DNA and act as genotoxin. DNA lesions lead to gene mutation and subsequent cancerous transformation. Based on the above description, DNA is the main target of ionizing radiation (target theory), and the magnitude of DNA legions determines the probability of cancer development. However, radiation-induced bystander effect (RIBE), which is defined as radiation effects induced in non-irradiated cells, may contribute to cancer induction as well. As a result, RIBE complicates the radiation dose-response relationship, especially at low doses, in which direct radiation effects predominate.
It is accepted that Reactive Oxygen Species (ROS) including free radicals have an important role in the induction of RIBE, as in some studies the inhibitory effects of ROS scavengers on the legions induced by RIBE has been proved (1-7). Also it has been illustrated that external antioxidants such as vitamin E, and vitamin C are able to decrease the number of micronucleus formed in bystander cells (8).
Garlic (Allium sativum, L.) is a plant, which has been used in herbal medicine as early as 3700 BC because of its therapeutic efficacy (9). It contains...