Project description:Both exposure to ionizing radiation and obesity have been associated with various pathologies including cancer. There is a crucial need in better understanding the interactions between ionizing radiation effects (especially at low doses) and other risk factors, such as obesity. In order to evaluate radiation responses in obese animals, C3H and C57BL/6 mice fed a control low fat or a high fat (HF) diet were exposed to fractionated doses of X-rays (4×0.75 Gy). Bone marrow micronucleus assays did not suggest a modulation of radiation-induced genotoxicity by HF diet. Both HF diet and irradiation resulted in increased oxidative damage, H2AX levels and proliferation in C57BL/6 mouse liver. Using methylation-specific PCR, we observed that the promoters of p16 and Dapk genes were methylated in the livers of C57BL/6 mice fed a HF diet (irradiated and non-irradiated); Mgmt promoter was methylated in irradiated and/or HF diet-fed mice. In addition, methylation PCR arrays identified Ep300 and Socs1 (whose promoters exhibited higher methylation levels in non-irradiated HF diet-fed mice) as potential targets for further studies. We then compared microRNA regulations after radiation exposure in the livers of C57BL/6 mice fed a normal or an HF diet, using microRNA arrays. Interestingly, radiation-triggered microRNA regulations observed in normal mice were not observed in obese mice. All together, our results suggested the existence of dietary effects on radiation responses (especially epigenetic regulations) in mice, possibly in relationship with obesity-induced chronic oxidative stress. C57BL/6J mice were fed a normal or a high-fat diet and exposed to 4 x 0.75 Gy X-rays. miRNA expression was measured in the livers of 3 mice for each experimental group.
Project description:Both exposure to ionizing radiation and obesity have been associated with various pathologies including cancer. There is a crucial need in better understanding the interactions between ionizing radiation effects (especially at low doses) and other risk factors, such as obesity. In order to evaluate radiation responses in obese animals, C3H and C57BL/6 mice fed a control low fat or a high fat (HF) diet were exposed to fractionated doses of X-rays (4×0.75 Gy). Bone marrow micronucleus assays did not suggest a modulation of radiation-induced genotoxicity by HF diet. Both HF diet and irradiation resulted in increased oxidative damage, H2AX levels and proliferation in C57BL/6 mouse liver. Using methylation-specific PCR, we observed that the promoters of p16 and Dapk genes were methylated in the livers of C57BL/6 mice fed a HF diet (irradiated and non-irradiated); Mgmt promoter was methylated in irradiated and/or HF diet-fed mice. In addition, methylation PCR arrays identified Ep300 and Socs1 (whose promoters exhibited higher methylation levels in non-irradiated HF diet-fed mice) as potential targets for further studies. We then compared microRNA regulations after radiation exposure in the livers of C57BL/6 mice fed a normal or an HF diet, using microRNA arrays. Interestingly, radiation-triggered microRNA regulations observed in normal mice were not observed in obese mice. All together, our results suggested the existence of dietary effects on radiation responses (especially epigenetic regulations) in mice, possibly in relationship with obesity-induced chronic oxidative stress.
Project description:Treatment of tumors with ionizing radiation for cancer therapy induces biological responses that include changes in cell cycle, activation of DNA repair mechanisms, and induction of apoptosis or senescence programs. What is not known is whether ionizing radiation induces an epigenetic DNA methylation response or whether epigenetic changes occur in genes in pathways classically associated with the radiation response. We exposed breast cancer cells to 0, 2, or 6 Gy and determined global DNA methylation at 1, 2, 4, 8, 24, 48, and 72 hours post-irradiation. We found that radiation treatment resulted in a DNA methylation response and that cell cycle, DNA repair, and apoptosis pathways were enriched in genes are were differentially-methylated. DNA methylation profiling of ionizing radiation treated cells using the Infinium HumanMethylation450 BeadChip.
Project description:In this study we show that, in embryonic fibroblasts from mice on a high fat diet and treated with Forskolin, ionizing radiation exposure or both, phosphorylation of CREB-binding protein (CREB) by ATM (ataxia-telangiectasia-mutated) and casein kinases 1 and 2 (CK1 and CK2) on a cluster of five phosphorylation sites (the ATM/CK cluster) within the unstructured kinase-inducible domain (KID) provides an additional level of regulation through dynamic modulation of CREB DNA binding activity. Stoichiometric phosphorylation of the ATM/CK cluster in response to DNA damage inhibited cAMP-induced CREB target gene expression, CREB DNA binding activity, and CREB-CRTC2-DNA ternary complex formation proportional to the number of phosphate residues modified. Substoichiometric phosphorylation of the ATM/CK cluster promoted cAMP/Ca2+-regulated transcriptional coactivators (CRTCs) recruitment and CREB activation via an ATM-independent, PKA-dependent pathway. Mice expressing a non-phosphorylatable CREBS111A allele exhibited phenotypes consistent with CREB deregulation, including fasting hyperglycemia, susceptibility to diet-induced obesity, and reduced expression of gluconeogenic genes. Two genotypes: CREB+/+ (wild type) and CREBS111A (non-phosphorylatable CREB KID S111A mutant allele) each control treated, exposed to forskolin, ionizing radiation or both in triplicate and in two batches toataling 48 arrays