The Effect Of Tea Polyphenols On Apoptosis And Proliferation Of Submandibular Gland Induced By Irradiation

Objective: To observe the effects of tea polyphenols (TP) in submandibular gland cells apoptosis and proliferation induced by radiation in rat.Methods: Seventy rats were randomly divided into Normal group(N-group) 10 rats﹑ radiation group(R-group) 30 rats and tea polyphenols-radiation group(TPR-group) 30 rats. R-group and TPR-group were irradiated with a single exposure dose of 15 Gy of 60Coγrays delivered to the head and neck area. The two groups'rats were intragastrically administered with normal sodium(R-group) or TP(TPR-group) from 14 days before radiation to the experiment ended. On day 3,day 6,day30 after radiation, ten submandibular glands were taken from each groups to do examination. Terminal deoxynucleotidyl transferase(TdT)-mediated dUTP-digoxigenin nick end labeling method (TUNEL) was used to examine apoptosis of the submandibular glands cells, immunohistochemical technique was used to detect the proliferating cell nuclear antigen(PCNA)﹑B cell lymphoma/lewkmia-2(Bcl-2) and Bcl-2 assaciated X protein(Bax) expression in the glands. The morphologic changes of submandibular glands were observed by transmission electron microscopy.Results: 1. Apoptosis index in the cells of submandibular glands were significant increased on days 3,days 6 and 30 after irradiation compared with N-group (P﹤0.01); After gavaged with TP, apoptosis index in the cells of submandibular glands were significant decreased on days 3,days 6 and 30 after irradiation compared with R-group (P﹤0.01).2. PCNA expression in the cells of submandibular glands were significant increased on day 3 and day 6 after irradiation compared with N-group(P﹤0.01), TP could significant decrease PCNA expression in the cells of submandibular glands on day 3 and day 6 after irradiation compared with R-group(P﹤0.01).3.Expression of Bcl-2 and Bax were not significant difference between the R-group and TPR-group (P > 0.05). 4.Transmission electron microscopy morphological changes: heterochromatinization of the nuclear and the changes of nuclear tending to apoptosis can be observered after irradiation in the cells of submandibular gland. After gavaged with TP, the gland injury after radiation was alleviated by histological examinations. The lesions of submandibular glands in TPR-group were gentle from electron microscope study, and the apoptosis in cell nuclear was not typical.Conclusion: 1. Tea polyphenols has the effect against irradiation-induced apoptosis in submandibular glands. 2. Tea polyphenols can influence the expression of PCNA in submandibular glands induced by radiation. 3. TP can protect the injury of ultrastructure in sumandibular glands from radiation injuries.