Objective To investigate the ability of
Angelica Sinensis to affect the radiation-induced TGF-β_1 release in the animal model,
so as to find an effective method to reduce the lung toxicity after thoracic
irradiation. Methods The thoraces of C57BL/6 mice were exposed to either sham irradiation or single fraction of 12 Gy. Four study groups were defined: those that received neither irradiation nor
Angelica Sinensis (NT group), those that received Angelica Sinensis but no irradiation (AS group), those that underwent irradiation without Angelica Sinensis (XRT group) and those that received both Angelica Sinensis and irradiation (AS/XRT group). Treated and sham-irradiated control mice were sacrificed at times corresponding to the latent period (1, 24, 72 hours and 1 week postirradiation), the pneumonic phase (2, 4, 8, and 16 weeks postirradiation), and the beginning of the fibrotic phase (24 weeks postirradiation). The TGF-β_1 mRNA expressions in the lung tissue were quantified by real-time quantitative reverse transcription polymerase chain reaction (RT-PCR). Immunohistochemical Streptavidin-Peroxidase method and positive cell counting were used for objective quantification of TGF-β_1 protein expression. Results NT and AS groups exhibited low levels of TGF-β_1 protein expression with positive cell counts between 9 and 31. And there is an significantly elevated level of TGF-β_1 positive inflammatory cells in XRT group(P<0.01). The number of the positive cells in AS/XRT group is between the NT and AS groups and the XRT-group, and the difference between AS/XRT group and XRT group was significant(P<0.01). The results of qRT-PCR show that the relative mRNA expressions of cytokine TGF-β_1 in XRT group was significantly higher than the nonirradiated groups(P<0.01), the lung tissue of the mice which were treated by Angelica Sinensis (AS/XRT group) revealed only a minor radiation-mediated TGF-β_1 response on mRNA level, but the statistical comparison of the TNF-α mRNA expression between the XRT and AS/XRT treatment-group was not significant(P=0.054). Conclusion This study demonstrates a significant radiation-induced increase of TGF-β_1 (on mRNA and protein level) in the lung tissue, and the predominant localisation of TGF-β_1 in areas of inflammatory cell infiltrates suggests involvement of this cytokine in the pathogenesis of radiation-induced lung injury. In addition, we observed a pronounced decrease of mRNA and protein production of the TGF-β_1 in the AS/XRT group as compared to the XRT group. Therefore our results indicate that Angelica Sinensis down-regulates the radiation-induced TGF-β_1 release in the lung tissue, and it is maybe one of the possible mechanisms of this drug to reduce the lung toxicity after thoracic irradiation.;