Radiation-induced Cellular DNA Damage Research Articles

Urinary 8-Hydroxy-2′-Deoxyguanosine: A Biomarker for Radiation-Induced Oxidative DNA Damage in Pediatric Cardiac Catheterization

To determine the utility of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) as a sensitive biomarker for radiation-induced cellular DNA damage in children undergoing cardiac catheterization. We enrolled pediatric patients with congenital heart diseases requiring cardiac catheterization in conjunction with healthy children and children under sedation as control. Demographic, clinical, laboratory and invasive hemodynamic data, urinary 8-OHdG levels, and radiation exposure measurements were collected prospectively. Nineteen patients, 10 healthy children and 9 children under sedation, were studied. In 19 patients who underwent cardiac catheterization, the median level of 8-OHdG in urine obtained at 24-48 hours after the procedure was significantly higher than at baseline (44.0 vs 17.3 ng/mg creatinine, P = .0001). Furthermore, the urinary 8-OHdG level after the procedure increased in 18 of the 19 study subjects. In contrast, there was no significant difference in 8-OHdG levels between the 2 spot urine samples obtained at arbitrary intervals of 24-48 hours in 10 healthy children (P = .7213), and at baseline and 24-48 hours following echocardiography in 9 children under sedation (P = .1097). Stepwise multiple regression analysis revealed that the cumulative air kerma during the cardiac catheterization was the variable which was strongly and significantly associated with the ratio of post- to precardiac catheterization urinary 8-OHdG levels among the evaluated variables (R(2) = 0.7179, F = 11.0256, P = .0007). Urinary 8-OHdG could be a useful biomarker for radiation-induced cellular DNA damage in children undergoing diagnostic cardiac catheterization.

Spectrum of Radiation-Induced Clustered Non-DSB Damage - A Monte Carlo Track Structure Modeling and Calculations.

The aim of this report is to present the spectrum of initial radiation-induced cellular DNA damage [with particular focus on non-double-strand break (DSB) damage] generated by computer simulations. The radiation types modeled in this study were monoenergetic electrons (100 eV-1.5 keV), ultrasoft X-ray photons Ck, AlK and TiK, as well as some selected ions including 3.2 MeV/u proton; 0.74 and 2.4 MeV/u helium ions; 29 MeV/u nitrogen ions and 950 MeV/u iron ions. Monte Carlo track structure methods were used to simulate damage induction by these radiation types in a cell-mimetic condition from a single-track action. The simulations took into account the action of direct energy deposition events and the reaction of hydroxyl radicals on atomistic linear B-DNA segments of a few helical turns including the water of hydration. Our results permitted the following conclusions: a. The absolute levels of different types of damage [base damage, simple and complex single-strand breaks (SSBs) and DSBs] vary depending on the radiation type; b. Within each damage class, the relative proportions of simple and complex damage vary with radiation type, the latter being higher with high-LET radiations; c. Overall, for both low- and high-LET radiations, the ratios of the yields of base damage to SSBs are similar, being about 3.0 ± 0.2; d. Base damage contributes more to the complexity of both SSBs and DSBs, than additional SSB damage and this is true for both low- and high-LET radiations; and e. The average SSB/DSB ratio for low-LET radiations is about 18, which is about 5 times higher than that for high-LET radiations. The hypothesis that clustered DNA damage is more difficult for cells to repair has gained currency among radiobiologists. However, as yet, there is no direct in vivo experimental method to validate the dependence of kinetics of DNA repair on DNA damage complexity (both DSB and non-DSB types). The data on the detailed spectrum of DNA damage presented here, in particular the non-DSB type, provide a good basis for testing mechanistic models of DNA repair kinetics such as base excision repair.

Radioprotective effect of Terminalia Chebula Retzius extract against γ-irradiation-induced oxidative stress

The present study was undertaken to evaluate the radioprotective effect of Terminalia chebula Retzius extract against γ-irradiation-induced oxidative stress in rats. Major phenolic compounds such as total phenolics, flavonoids and triterpenoids contents of Terminalia chebula extract (TCE) were measured. Potential antioxidant activity of TCE was tested by free radical scavenging activity (FRSA) using 1,1,2,2-diphenyl-p-picryl hydrazyl (DPPH), total antioxidant power (TAP) using ferric reducing antioxidant power (FRAP), metal chelating activity (MCA) and inhibition of DNA damage of plasmid (pBR322). In vitro studies showed that TCE possesses potential antioxidant activity and protected plasmid DNA against breakage induced by Fenton reactants. Endogenous spleen colony forming unit (CFU) assay, DNA damage using rat peripheral blood by single cell gel electrophoresis (comet assay) and intestinal histopathological studies in rats were performed in order to find the radioprotective effect of TCE. Animals were divided into various groups and pretreated with TCE (80mg/kg body weight, i.p.) for 5 days prior to whole body γ-irradiation. The results showed that TCE administration prior to γ-irradiation significantly enhanced the CFU counts, reduced radiation-induced cellular DNA damage and gastrointestinal cell death. The results suggested that TCE is able to protect from γ-irradiation-induced oxidative stress and may considered as probable radioprotector.

Radioprotective Effects of Gallic Acid in Mice

Radioprotecting ability of the natural polyphenol, gallic acid (3,4,5-trihydroxybenzoic acid, GA), was investigated in Swiss albino mice. Oral administration of GA (100 mg/kg body weight), one hour prior to whole body gamma radiation exposure (2–8 Gy; 6 animals/group), reduced the radiation-induced cellular DNA damage in mouse peripheral blood leukocytes, bone marrow cells, and spleenocytes as revealed by comet assay. The GA administration also prevented the radiation-induced decrease in the levels of the antioxidant enzyme, glutathione peroxidise (GPx), and nonprotein thiol glutathione (GSH) and inhibited the peroxidation of membrane lipids in these animals. Exposure of mice to whole body gamma radiation also caused the formation of micronuclei in blood reticulocytes and chromosomal aberrations in bone marrow cells, and the administration of GA resulted in the inhibition of micronucleus formation and chromosomal aberrations. In irradiated animals, administration of GA elicited an enhancement in the rate of DNA repair process and a significant increase in endogenous spleen colony formation. The administration of GA also prevented the radiation-induced weight loss and mortality in animals (10 animals/group) exposed to lethal dose (10 Gy) of gamma radiation. (For every experiment unirradiated animals without GA administration were taken as normal control; specific dose (Gy) irradiated animals without GA administration serve as radiation control; and unirradiated GA treated animals were taken as drug alone control).

Phenolic compounds isolated from Pilea microphylla prevent radiation-induced cellular DNA damage

Six phenolic compounds namely, quercetin-3- O-rutinoside (1), 3- O-caffeoylquinic acid (2), luteolin-7- O-glucoside (3), apigenin-7- O-rutinoside (4), apigenin-7- O- β- d-glucopyranoside (5) and quercetin (6) were isolated from the whole plant of Pilea microphylla using conventional open-silica gel column chromatography and preparative HPLC. Further, these compounds were characterized by 1D, 2D NMR techniques and high-resolution LC–MS. Compounds 1–3 and 6 exhibited significant antioxidant potential in scavenging free radicals such as DPPH, ABTS and SOD with IC 50 of 3.3–20.4 μmol/L. The same compounds also prevented lipid peroxidation with IC 50 of 10.4–32.2 μmol/L. The compounds also significantly prevented the Fenton reagent-induced calf thymus DNA damage. Pre-treatment with compounds 1–3 and 6 in V79 cells attenuated radiation-induced formation of reactive oxygen species, lipid peroxidation, cytotoxicity and DNA damage, correlating the antioxidant activity of polyphenols with their radioprotective effects. Compounds 1, 3 and 6 significantly inhibited lipid peroxidation, presumably due to 3′,4′-catechol ortho-dihydroxy moiety in the B-ring, which has a strong affinity for phospholipid membranes. Oxidation of flavonoids, with catechol structure on B-ring, yields a fairly stable ortho-semiquinone radical by facilitating electron delocalization, which is involved in antioxidant mechanism. Hence, the flavonoid structure, number and location of hydroxyl groups together determine the antioxidant and radioprotection mechanism.

Empetrum nigrumvar.japonicumExtract Suppresses γ-Ray Radiation-Induced Cell Damage via Inhibition of Oxidative Stress

The ethylacetate fraction of Empetrum nigrum var. japonicum (ENE) was shown to reduce intracellular reactive oxygen species (ROS) generated by γ-radiation and activate antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and gluthathion peroxidase (GPx). ENE protected cells against radiation-induced cellular DNA damage, membrane lipid peroxidation, and protein modification, which are the main points of radiation-induced damage. In addition, ENE recovered cell viability by inhibiting apoptosis after cells were treated with radiation. ENE treatment also reduced γ-radiation induced Bax, and caspase 9 and 3 expression in irradiated cells. However, irradiated cells with ENE recovered Bcl-2 expression, which was reduced by radiation. This anti-apoptotic effect of ENE was due to the inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1)-c-Jun NH(2)-terminal kinase (JNK) cascades induced by γ-radiation. In summary, these results suggest that ENE protects cells against γ-radiation-induced oxidative stress via the reduction of ROS and attenuation of apoptosis.

Effect of silver nanoparticle and glycyrrhizic acid (SN-GLY) complex on repair of whole body radiation-induced cellular DNA damage and genomic instability in mice

Silver nanoparticles (SN) were redispersed in aqueous solution of Pluronic F127 and complexed with the phytoceutical, glycyrrhizic acid (GLY) to obtain SN-GLY complex. The ability of the SN-GLY complex to offer protection against ionising radiation in post-irradiation scenarios was evaluated in ex vivo and in vivo models using Swiss albino mice. Treatment of mouse blood leucocytes with SN-GLY immediately after 4 Gy gamma radiation exposure, ex vivo, enhanced the rate of repair of cellular DNA damages as revealed by comet assay. Exposure of mice to 4 Gy whole body gamma radiation induced formation of strand breaks in cellular DNA and the unrepaired double strand breaks eventually caused the formation of micronuclei. The post-irradiation administration of SN-GLY resulted in a faster decrease in the comet parameters indicating enhanced cellular DNA repair process and reduction in micronucleus formation. Thus the studies showed effective radiation protection by SN-GLY in post-irradiation conditions.

Eckol protects V79-4 lung fibroblast cells against γ-ray radiation-induced apoptosis via the scavenging of reactive oxygen species and inhibiting of the c-Jun NH 2-terminal kinase pathway

The radioprotective effect of eckol against γ-ray radiation-induced oxidative stress and its possible protective mechanisms were investigated. Eckol was found to reduce the intracellular reactive oxygen species generated by γ-ray radiation. Moreover, eckol also protected against radiation-induced cellular DNA damage and membrane lipid peroxidation, which are the main targets of radiation-induced damage. In addition, eckol recovered the cell viability damaged by radiation via the inhibition of apoptosis. Irradiated cells with eckol treatment reduced the expression of bax, the activation of caspase 9 and caspase 3, which were induced by radiation. However, irradiated cells with eckol recovered the expression of bcl-2 and mitochondrial cytochrome c which were decreased by radiation. The anti-apoptotic effect of eckol exerted via the inhibition of mitogen-activated protein kinase kinase-4 (MKK4/SEK1)-c-Jun NH 2-terminal kinase (JNK)-activator protein 1 (AP-1) cascades induced by radiation. In summary, the results suggest that eckol protects cells against the oxidative stress induced by radiation via the reduction of reactive oxygen species and the attenuation of activation in SEK1-JNK-AP-1 pathway.

Radiation-Induced Cellular DNA Damage Repair Response Enhances Viral Gene Therapy Efficacy in the Treatment of Malignant Pleural Mesothelioma

Malignant pleural mesothelioma (MPM) treated with radiotherapy (RT) has incomplete responses as a result of radiation-induced tumoral stress response that repairs DNA damage. Such stress response is beneficial for oncolytic viral therapy. We hypothesized that a combination of RT and NV1066, an oncolytic herpes virus, might exert an additive or synergistic effect in the treatment of MPM. JMN, a MPM cell line, was infected with NV1066 at multiplicities of infection of .05 to .25 in vitro with and without radiation (1 to 5 Gy). Virus replication was determined by plaque assay, cell kill by lactate dehydrogenase assay, and GADD34 (growth arrest and DNA damage repair 34, a DNA damage-repair protein) by real-time reverse transcriptase-polymerase chain reaction and Western blot test. Synergistic cytotoxicity dependence on GADD34 upregulation was confirmed by GADD34 small inhibitory RNA (siRNA). Synergism was demonstrated between RT and NV1066 across a wide range of doses. As a result of such synergism, a dose-reduction for each agent (up to 5500-fold) can be accomplished over a wide range of therapeutic-effect levels without sacrificing tumor cell kill. This effect is correlated with increased GADD34 expression and inhibited by transfection of siRNA directed against GADD34. RT can be combined with oncolytic herpes simplex virus therapy in the treatment of malignant pleural mesothelioma to achieve synergistic efficacy while minimizing dosage and toxicity.