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(PP133) The in vivo study on adenovirus mediate smad7 gene expression regulated by irradiation via Egr-1 promoter.
Li, Wang*,1, Yan, Feng1, Xiaorong, Fu1, Xuwei, Cai1, 1 Fudan University, Shanghai, China
ABSTRACT- Purpose/Objective: To investigate the time-effect relationship and dose-effect relationship of the expression of adenovirus mediating Smad7 gene regulated by irradiation via Egr-1 promoter in the lungs of C57BL mouse. Materials/Methods: The recombinant adenovirus (AD.Egr-Smad7) made up of replication-defective adenovirus enclosed radio-inducible elements from the Egr-1 gene promoter and cDNA encoding Smad7. Mice were infected by intratracheal instillation with AD.Egr-Smad7 and irradiated to their whole lungs after 24 hours.144 mice were randomly divided into 2 groups,the irradiated group and the unirradiated group. The mouse in each group were infected by intratracheal instillation with AD.Egr-Smad7 or replication-defective adenovirus respectively with 108,5*108,109 pfu.The lungs were harvested 6 hours after irradiation to evaluated the dose-effect relationship of Smad7 gene expression with different adenovirus dose. 324 mice were randomly divided into 6 groups, the lungs were harvested at different time point following irradiation with single dose of 8Gy to observe the time-effect relationship of Smad7 gene expression with different time interval. 108 mice were randomly divided into 3 groups, they were irradiated respectively by different single irradiation dose and the lungs were harvested 5 hours after irradiation to evaluate the dose-effect relationship of Smad7 gene expression with different irradiation dose. The expression of exogenous Smad7 was detected by Western blotting analysis. Results: The expression of adenovirus mediating Smad7 gene which is regulated by Egr-1 promoter could be induced by irradiation markedly compared with control groups (P< 0.01).The degree of Smad7 gene expression has relationship with adenovirus dose, irradiation dose and time interval after irradiation. The expression degree of Smad7 gene increased in a dose-dependent manner when the AD.Egr-Smad7 dose was at108,5*108,109 pfu (P< 0.01)and the expression degree of Smad7 gene also increased in a dose-dependent manner when the irradiation dose was at 0-12Gy, then it decreased when the irradiation dose was at 15Gy. The expression degree of Smad7 gene appeared to reach a peak at 2-9 hours after initiation of irradiation (P< 0.05) and then regulated down and almost returned to the normal standard 15 hours later. Conclusions: he in vivo investigation demonstrates that gama irradiation markedly induce adenovirus mediating Smad7 gene expression regulated by Egr-1 promoter. The expression of Smad7 gene has correlation with AD.Egr-Smad7 dose,irradiation dose and time interval after irradiation. It deserves further study to block the signal transduction of TGF beta locally as a novel strategy for gene therapy aiming at preventing radiation-induced lung fibrosis.
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