Radiation possible effects
Original title: DNA protective properties of vanillin against gamma-radiation under different conditions: Possible mechanisms.
By Maurya DK, Adhikari S, Nair CK, Devasagayam TP., Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Published on 17 June 2007.
Abstract: Ionizing radiation is an important genotoxic agent. Protecting against this form of toxicant, especially by a dietary component, has several potential applications. In the present study, we have examined the ability of vanillin (4-hydroxy-3-methoxybenzaldehyde), a naturally occurring food flavouring agent, to inhibit radiation-induced DNA damage measured as strand breaks under in vitro, ex vivo and in vivo conditions besides the possible mechanisms behind the observed protection. Our study showed that there was a concentration-dependent inhibition of the disappearance of super-coiled (ccc) form of plasmid pBR322 (in vitro) upon exposure to 50Gy of gamma-radiation. Presence of 0.5mM vanillin has a dose-modifying factor (DMF) of 6.75 for 50% inactivation of ccc form. Exposure of human peripheral blood leucocytes (ex vivo) to gamma-radiation causes strand breaks in the cellular DNA, as assessed by comet assay. When leucocytes were exposed to 2Gy of gamma-radiation there was an increase in parameters of comet assay such as %DNA in tail, tail length, 'tail moment' and 'Olive tail moment'. The presence of 0.5mM vanillin during irradiation significantly reduced these parameters. Damage to DNA in mouse peripheral blood leucocytes after whole-body exposure of mice (in vivo) to gamma-radiation was studied at 1 and 2h post-irradiation. There was recovery of DNA damage in terms of the above-mentioned parameters at 2h post-irradiation. This was more than that observed at 1h. The recovery was more in vanillin treated mice. Hence our studies showed that vanillin offers protection to DNA against radiation-induced damage possibly imparting a role other than modulation of DNA repair. To examine the possible mechanisms of radioprotection, in terms of radiation-derived radicals, we carried out the reaction of vanillin with ABTS(+) radical spectrophotometrically besides with DNA peroxyl and carbonyl radicals by using pulse radiolysis. Our present investigations show that vanillin has ability to protect against DNA damage in plasmid pBR322, human and mouse peripheral blood leucocytes and splenic lymphocytes besides enhancing survival in splenic lymphocytes against gamma-radiation, and that the possible mechanism may involve scavenging of radicals generated during radiation, apart from modulation of DNA repair observed earlier.