Abstract 5469: Low dose ionizing radiation induces persistent activation of NADPH oxidase pathway in mouse colon

Abstract

Abstract Exposure to ionizing radiation has been linked to persistent oxidative stress. The purpose of the current study was to characterize the role of NADPH oxidase pathway in radiation-induced increased oxidant production in colon epithelial cells. Mice (C57BL/6J; 6-8 weeks, male) were exposed to either sham or 0.5 Gy γ radiation, and NADPH oxidase pathway and oxidative stress markers were assessed in colon samples 60 d after exposure. Radiation exposure led to higher elevation of 4-HNE and 8-oxo-dG staining relative to unirradiated control. We also observed increased staining for the proliferative marker phospho-histone H3 in colon sections of irradiated mice. PCR analysis showed increased expression of two NADPH oxidase isoforms, Nox1 and Nox3, in irradiated samples. Additionally, expression of NoxA1 and Noxo1 along with Hif1α were also increased after radiation. Immunoblot analysis confirmed the PCR results, and ChIP assay revealed greater binding of stress response factor GATA6 and Hif1α to Nox1 and Nox3, and Nox3 promoters respectively after radiation exposure relative to control. Co-immunoprecipitation experiments show enhanced binding of Rac1, an activator of NADPH oxidase, to Nox1 and Nox3. In summary, we demonstrated that exposure to a low dose of γ radiation caused long-term upregulation of NADPH oxidase isoforms as well as its regulators and activators such as NoxA1, Noxo1, Hif1α, TLR4, GATA6, Doux1, and Doux2. When considered along with our results on oxidative stress and proliferative markers, our observations on NADPH oxidase pathway provides new insight into molecular events contributing to radiation-induced persistent oxidative stress and cell proliferation in colon, and have implications for colorectal carcinogenesis. Note: This abstract was not presented at the meeting. Citation Format: Santosh Kumar, Shubhankar Suman, Bo-Hyun Moon, Albert J. Fornace, Kamal Datta. Low dose ionizing radiation induces persistent activation of NADPH oxidase pathway in mouse colon [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5469. doi:10.1158/1538-7445.AM2017-5469