title: Inverse dose-rate-effects on the expressions of extra-cellular matrix-related genes in low-dose-rate gamma-ray irradiated murine cells.
abstract: Based on the results of previous microarray analyses of murine NIH3T3/PG13Luc cells irradiated with continuous low-dose-rate (LDR) gamma-ray or end-high-dose-rate-irradiations (end-HDR) at the end of the LDR-irradiation period, the inverse dose-rate-effects on gene expression levels were observed. To compare differences of the effects between LDR-irradiation and HDR-irradiation, HDR-irradiations at 2 different times, one (ini-HDR) at the same time at the start of LDR-irradiation and the other (end-HDR), were performed. The up-regulated genes were classified into two types, in which one was up-regulated in LDR-, ini-HDR-, and end-HDR irradiation such as Cdkn1a and Ccng1, which were reported as p53-dependent genes, and the other was up-regulated in LDR- and ini-HDR irradiations such as pro-collagen TypeIa2/Col1a2, TenascinC/Tnc, and Fibulin5/Fbln5, which were reported as extra-cellular matrix-related (ECM) genes. The time dependent gene expression patterns in LDR-irradiation were also classified into two types, in which one was an early response such as in Cdkn1a and Ccng1 and the other was a delayed response such as the ECM genes which have no linearity to total dose. The protein expression pattern of Cdkn1a increased dose dependently in LDR- and end-HDR-irradiations, but those of p53Ser15/18 and MDM2 in LDR-irradiations were different from end-HDR-irradiations. Furthermore, the gene expression levels of the ECM genes in embryonic fibroblasts from p53-deficient mice were not increased by LDR- and end-HDR-irradiation, so the delayed expressions of the ECM genes seem to be regulated by p53. Consequently, the inverse dose-rate-effects on the expression levels of the ECM genes in LDR- and end-HDR-irradiations may be explained from different time responses by p53 status.
authors.affiliation: Department of Radiobiology, Institute for Environmental Sciences, Kamikita, Aomori, Japan. sugihara@ies.or.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Sugihara
authors.forename: Hayato
authors.initials: H
authors.lastname: Murano
authors.forename: Kimio
authors.initials: K
authors.lastname: Tanaka
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Oghiso
mesh_terms: D000818:Animals; D002460:Cell Line; D002478:Cells, Cultured; D004307:Dose-Response Relationship, Radiation; D005109:Extracellular Matrix / Q000235:genetics*; D005347:Fibroblasts / Q000166:cytology; D005720:Gamma Rays; D015870:Gene Expression / Q000528:radiation effects*; D016158:Genes, p53 / Q000502:physiology; D051379:Mice; D011829:Radiation Dosage