Objective: To study the signaling pathway of the up-regulation of claudin-5 expression by Xuebijing injection.
Methods: Animal and cell models of acute respiratory distress syndrome (ARDS) were induced by lipopolysaccharide (LPS). (1) In vivo study, 20 male Sprague-Dawley (SD) rats were randomly divided into 4 groups: control group, LPS group (LPS injection 10 mg/kg for 12 hours), Xuebijing control group (Xuebijing injection 1 mg/kg, twice a day, for 3 days), and Xuebijing intervention group (LPS injection after pretreatment of Xuebijing injection), according to random number method with 5 rats in each group. The lung tissues were taken to detect lung dry/wet weight ratio (W/D) and the morphological changes in each group. Claudin-5, phosphorylated forkhead box transcription factor O1 (p-FOXO1), total FOXO1 (t-FOXO1), phosphorylated Akt (p-Akt) and total Akt (t-Akt) in lung tissues were detected by immunohistochemical staining (IHC) and Western blotting. (2) In vitro study, human pulmonary microvascular endothelial cells (HPMECs) were divided into 6 groups (5 holes in each group): control group, Xubijing control group (incubated with 2 g/L Xubijing for 24 hours), phosphoinositide 3-kinases (PI3K) signaling pathway LY294002 control group (incubated with 10 μmol/L LY294002 for 1 hour), LPS group (incubated with 1 mg/L LPS for 12 hours), Xubijing intervention group (incubated with 2 g/L Xuebijing for 24 hours, then with 1 mg/L LPS for 12 hours) and LY294002 intervention group (incubated with 10 μmol/L LY294002 for 1 hour, then with 2 g/L and Xubijing for 24 hours, and then with 1 mg/L LPS for 12 hours). The expression levels of claudin-5, p-FOXO1, t-FOXO1, p-Akt and t-Akt of HPMECs in each group were assessed by Western blotting.
Results: In vivo study: (1) Compared with the control group, the lung W/D ratio increased significantly in LPS group (6.79±0.42 vs. 4.19±0.13), and decreased significantly after the intervention of Xuebijing (4.92±0.38 vs. 6.79±0.42, P < 0.01). (2) Morphological changes of lung tissue: compared with the control group, the injury of lung tissue in LPS group was more serious, which was significantly improved after Xuebijing intervention. (3) Expression levels of claudin-5, p-Akt/t-Akt and p-FOXO1/t-FOXO1: the expression levels of claudin-5, p-Akt/t-Akt and p-FOXO1/t-FOXO1 in LPS group were significantly decreased as compared with the control group (claudin-5/GAPDH: 0.33±0.03 vs. 1.03±0.07, p-Akt/t-Akt: 0.18±0.02 vs. 1.01±0.13, p-FOXO1/t-FOXO1: 0.16±0.06 vs. 1.00±0.19, all P < 0.01). After the intervention of Xuebijing, the expression levels were significantly increased as compared with the LPS group (claudin-5/GAPDH: 0.53±0.05 vs. 0.33±0.03, p-Akt/t-Akt: 0.56±0.12 vs. 0.18±0.02, p-FOXO1/t-FOXO1: 0.68±0.10 vs. 0.16±0.06, all P < 0.01). In vitro study: compared with the control group, the expression level of claudin-5 in the LPS group was significantly decreased (claudin-5/β-actin: 0.45±0.03 vs. 1.01±0.15, P < 0.01), and the expression level of claudin-5 in Xuebijing intervention group was also significantly decreased (claudin-5/β-actin: 0.80±0.08 vs. 1.01±0.15, P < 0.01). After the intervention of LY294002, the expression of claudin-5 was significantly decreased as compared with the Xubijing intervention group (claudin-5/β-actin: 0.41±0.02 vs. 0.80±0.08, P < 0.01).
Conclusions: Xuebijing injection improve pulmonary vascular barrier function in rats with ARDS by up-regulating claudin-5 expression through PI3K/Akt/FOXO1 signaling pathway.