Citrus Alkaline Extract Delayed the Progression of Pulmonary Fibrosis by Inhibiting p38/NF-κB Signaling Pathway-Induced Cell Apoptosis

OBJECTIVE: To investigate the intervention effect and functioning mechanism of citrus alkaline extract (CAE) on bleomycin- (BLM-) induced pulmonary fibrosis in mice. METHODS: 42 C57BL/6 male mice were assigned randomly to the normal group, model group, low (16mg/kg), medial (32mg/kg) and high (64mg/kg) CAE dosage groups, prednisone group (6mg/kg), and pirfenidone group (100mg/kg), respectively. One day after model construction, intragastric administration was applied to the mice once a day for 28 days and then killed. Body weights of mice were recorded. Their pulmonary tissues were subjected to HE staining and Masson's staining and then their degree of pulmonary alveolitis as well as pulmonary fibrosis was scored. Contents of hydroxyproline (HYP) and prostaglandin E2 (PGE2) in pulmonary tissues and levels of interleukin-17 (IL-17) in serum and bronchoalveolar lavage fluid (BALF) were determined by ELISA method. Expression of collagen I, collagen III, and Prosurfactant protein C (Pro-SPC) proteins in pulmonary tissue were measured immunohistochemically and that of nuclear transcription factor κB (NF-κB) and vimentin was determined by the immunofluorescence method. Apoptosis of pulmonary tissue was tested by the Tunel staining method, while the expression of MAPK-related protein was recorded by Western Blot assay. RESULTS: After CAE treatment, the body weight, PGE2 level, and Pro-SPC protein expression of pulmonary fibrosis mice were increased, while the score of pulmonary alveolitis and pulmonary fibrosis, levels of HYP and cell apoptosis, IL-17 contents of serum and BALF in pulmonary tissues, and expression of collagen I, collagen III, vimentin, NF-κB, and p-p38 were reduced. CONCLUSION: CAE effectively delayed the progression of BLM-induced pulmonary fibrosis in pulmonary fibrosis mice and a possible mechanism is the inhibition of cell apoptosis of NF-κB/p38-mediated signaling pathway.