Radioprotective effects and mechanism of Dicliptera chinensis polysaccharide on submandibular gland injury induced by radiation in rats

Ionizing radiation can cause damage to the structure and function of submandibular glands through oxidative stress and apoptosis. The polysaccharide of Dicliptera chinensis is a kind of natural antioxidant, which has the radiation protection effect and can prevent the damage caused by ionizing radiation. The aim of this study is to investigate the protective effect of Dicliptera chinensis polysaccharide on radiation-induced submandibular gland injury and its mechanism. Sprague-Dawley rats were irradiated with 18Gy X-rays and treated with Dicliptera chinensis polysaccharide (200 mg/kg) or amifostine (250 mg/kg). In this study, the changes of salivary gland secretion function were observed by measuring saliva flow rate, the histamathological changes of submandibular gland were observed by hematoxylin-eosin staining and immunohistochemistry, the expression of oxidative stress-related indicators (ROS, T-AOC) and their markers (NOX4, SOD2) in submandibular gland tissues were detected by ELISA, TUNEL and WB experiments, and the expression of apoptosis-related proteins (p-p53, Bax, Bcl2, caspase 9, caspase 3) was detected by western blotting assay. The results showed that Dicliptera chinensis polysaccharide protected salivary gland secretory function by alleviating the damage of AQP-5 protein on submandibular gland epithelial cell membrane, reduced the oxidative stress injury of submandibular gland by regulating the expression of NOX4 and SOD2 proteins. Furthermore, Dicliptera chinensis polysaccharide reduced apoptosis by regulating the p53-bax/bcl2 pathway. In summary, Dicliptera chinensis polysaccharide could be used as a radiation protection agent to prevent radiation damage of submandibular glands in the future.