β-sitosterol improves the permeability of lung epithelial cells by inhibiting the NF-kB pathway

Abstract Objective: To investigate the mechanism of the protective effect of beta-sitosterol (BS) on sepsis-induced lung injury. METHODS: A mouse model of sepsis-induced lung injury was established by cecum ligation and puncture (CLP). The murine lung epithelial (MLE-12) cells injury model was established by challenging LPS. Evans blue staining, lung wet/dry mass ratio (W/D), and the total protein concentration in bronchoalveolar lavage fluid (BALF) were used to assess the changes in lung tissue permeability. HE staining was performed to observe the histopathological changes in lung tissues. ELISA was examined to determine IL-6 and TNF-α inflammatory factors in each group of lung tissues and cells. The protein levels of claudin-4, claudin-5, Bcl-2, Bax, p65 and p-p65 were detected by western blotting or immunofluorescence. Fluorescein isothiocyanate (FITC)-dextran extravasation as a measure of MLE-12 cells permeability. RESULTS: BS attenuated lung tissue pathological changes caused by sepsis, reduced the level of inflammatory factors and decreased the permeability of lung tissue and MLE-12 cells. Moreover, BS inhibited NF-kB signaling pathway to upregulate tight junction proteins claudin-4 and claudin-5 thereby improving septic lung epithelial cell permeability. CONCLUSION: BS reduces the level of inflammatory factors by inhibiting NF-kB signaling pathway and regulates the expression of tight junction proteins claudin-4 and claudin-5 to improve the barrier function of lung epithelial cells, thus improving lung injury caused by sepsis.