Anti-inflammatory mixture alleviates acute lung injury induced by sepsis in rats by modulating Beclin-1-mediated autophagy

Abstract

To investigate the protective effects of an anti-inflammatory mixture on acute lung injury (ALI) induced by sepsis in rats, as well as its possible mechanisms. A total of 40 Sprague-Dawley (SD) rats were randomly divided into the sham group, septic ALI model group (model group), 3-methyladenine (3-MA) control group, and anti-inflammatory mixture pretreatment group, with 10 rats in each group. Cecal ligation and perforation (CLP) was performed to reproduce a septic ALI model. The rats in the sham group only underwent opening and closing the abdomen without perforation and ligation. Both groups were given saline gavage and intraperitoneal injection for 3 consecutive days before surgery. The 3-MA control group was given intraperitoneal injection of saline and autophagy inhibitor 3-MA 15 mg/kg for 3 consecutive days before modeling. The anti-inflammatory mixture pretreatment group was given 8.8 mL/kg of anti-inflammatory mixture by gavage [the composition of anti-inflammatory mixture: rhubarb 15 g (after the next), coptis chinensis 15 g, baical skullcap root 12 g, magnoliae cortex 12 g, dahurian patrinia herb 30 g] and saline intraperitoneal injection for 3 consecutive days before modeling. The rats in each group were anesthetized 24 hours after surgery and died due to abdominal aortic blood collection. Enzyme-linked immunosorbent assay (ELISA) was used to detect the levels of serum inflammatory cytokines interleukins (IL-1β and IL-6). Lung tissue was taken and then the bronchoalveolar lavage fluid (BALF) was collected, and the levels of IL-1β and IL-6 were detected by ELISA. Lung wet/dry weight (W/D) ratio was measured. After hematoxylin-eosin (HE) staining, the histopathological changes of the lungs were observed under light microscopy. Western blotting was used to detect the expression of autophagy markers microtubule-associated protein 1 light chain 3- II/I (LC3- II/I) and Beclin-1 protein in lung tissue. Autophagosomes in lung tissue were observed with transmission electron microscopy. Compared with the sham group, the rats in the model group exhibited severe destruction of lung tissue structure, with significant infiltration of inflammatory cells, the lung W/D ratio and the levels of IL-1β and IL-6 in serum and BALF were significantly increased, the expressions of LC3- II/I and Beclin-1 protein were down-regulated, the autophagosomes were more. The rats in the 3-MA control group exhibited more severe lung tissue injury as compared with the model group, the lung W/D ratio and the levels of inflammatory cytokines in serum and BALF were further increased, the expressions of LC3- II/I and Beclin-1 protein still showed a decrease tendency as compared with the sham group, and the autophagosomes were less than that in the model group. Compared with the model group, the anti-inflammatory mixture pretreatment group showed milder lung tissue injury with a minimal amount of inflammatory cell infiltration, the lung W/D ratio was significantly reduced (7.07±1.02 vs. 11.33±1.85, P < 0.05), the levels of IL-1β and IL-6 in both serum and BALF were significantly decreased [IL-1β (ng/L): 26.04±3.86 vs. 40.83±5.46 in serum, 17.75±2.02 vs. 26.86±4.32 in BALF; IL-6 (ng/L): 91.28±10.15 vs. 129.44±13.05 in serum, 76.06±7.51 vs. 120.91±7.47 in BALF, all P < 0.05], and the ratio of LC3- II/I and Beclin-1 protein expression were significantly increased [LC3- II/I ratio: 1.23±0.02 vs. 0.60±0.02, Beclin-1 protein (Beclin-1/GAPDH): 2.37±0.33 vs. 0.62±0.05, both P < 0.05]. Furthermore, an increase in the number of autophagosomes was observed. The anti-inflammatory mixture improves lung injury in rats with sepsis induced by CLP and reduce inflammation levels, potentially through upregulation of Beclin-1-mediated autophagy.