[Ultrafiltration of Angelicae Sinensis Radix and Astragali Radix inhibits ferroptosis and improves pulmonary fibrosis in rats by regulating Nrf2/xCT/GPX4 signaling pathway].

This study aims to investigate the mechanism of ferroptosis mediated by the nuclear factor-E2-related factor 2(Nrf2)/solute carrier family 7 member 11(SLC7A11, also known as xCT)/glutathione peroxidase 4(GPX4) signaling pathway in radiationinduced pulmonary fibrosis and the intervention effect of Angelicae Sinensis Radix(ASR) and Astragali Radix(AR) ultrafiltration extract. Fifty Wistar rats were randomly divided into five groups, with 10 rats in each group. Except for the blank group without radiation, the rats in each group were anesthetized and subjected to a single local chest irradiation of 40 Gy X-rays once to establish a rat model of radiation-induced pulmonary fibrosis. After radiation, the rats in the intervention groups were orally administered with ASR-AR ultrafiltration extract at doses of 0. 12, 0. 24, and 0. 48 g·kg(-1), respectively, once a day for 30 days. After 30 days of continuous administration, the levels of oxidative stress indicators superoxide dismutase(SOD) activity, reduced glutathione(GSH),malondialdehyde(MDA), and ferrous ion(Fe(2+)) in lung tissues of each group were detected by colorimetry. Immunofluorescence was used to detect reactive oxygen species(ROS) fluorescence expression in lung tissues. Hematoxylin-eosin(HE) and Masson staining were performed to observe pathological changes in lung tissues. Immunohistochemistry and Western blot were used to detect the expression levels of Nrf2/xCT/GPX4 signaling pathway and fibrotic proteins in lung tissues. The results showed that compared with the results in the blank group, the levels of Fe(2+) and MDA in the model group increased, while SOD activity and GSH levels decreased,and ROS levels increased. HE and Masson staining results showed that the structure of lung tissue was seriously damaged, the pulmonary interstitium was significantly proliferated, the alveoli collapsed and consolidated severely, and there were more inflammatory cell aggregates and collagen fiber deposits. Transmission electron microscopy showed that the degree of lung tissue damage in the model group was relatively high, with increased, smaller, and disorganized damaged mitochondria, irregular morphology, shallow matrix,most mitochondria ruptured and shortened, mildly expanded, some mitochondria with increased electron density of the matrix, partial mitochondrial outer membrane rupture, and characteristic changes of ferroptosis-specific mitochondria. Immunohistochemistry showed that the expression of transferrin receptor protein 1(TFR1) in lung tissues was significantly increased, while the expression of GPX4,ferritin heavy chain 1(FTH1), Nrf2, and xCT was significantly decreased. Western blot showed that the expression of α-smooth muscle actin(α-SMA) and collagen Ⅰ protein increased. Compared with the model group, the intervention group with ASR-AR ultrafiltration extract significantly improved lipid peroxidation and antioxidant-related indicators, decreased Fe(2+) levels, alleviated fibrosis, and decreased the expression of TFR1, α-SMA, and collagen Ⅰ proteins in lung tissues, while increased the expression of GPX4, FTH1, Nrf2, and xCT proteins. In summary, ASR-AR ultrafiltration extract has an ameliorative effect on radiation-induced pulmonary fibrosis, and its mechanism may involve the inhibition of ferroptosis by regulating the Nrf2/xCT/GPX4 signaling pathway.