Objective: To observe the protective effect of forsythiaside A on acute lung injury (ALI) in septic rats.
Methods: Male Sprague-Dawley (SD) rats were randomly divided into normal control group, sham operation group, sepsis model group, and forsythiaside A intervention group, with 10 rats in each group. The rats in the normal control group did not receive any intervention; the rats in the sham operation group only underwent abdominal surgery; and those in the model group and forsythiaside A intervention group received cecal ligation and puncture (CLP) to establish the sepsis rat model. The rats in the forsythiaside A intervention group were given 75 mL/kg of forsythiaside A within 0.5 hour after operation, and repeated after 6 hours. The rats in the sham operation group and model group were given the same amount of normal saline at the same time points. The lung tissues were collected for pathological examination 12 hours after operation. The lung homogenate was prepared, and enzyme-linked immunosorbent assay (ELISA) was used to detect tumor necrosis factor-α (TNF-α), interleukins (IL-1β, IL-6). The activity of superoxide dismutase (SOD) was detected by xanthine oxidase method, and the content of malonaldehyde (MDA) was detected by colorimetry. The expression of nuclear factor-κB p65 (NF-κB p65) was detected by Western blotting.
Results: There was no significant pathological change of lung tissue in both normal control group and sham operation group, and there was no significant difference in each parameter between the two groups. The rats in the model group had interstitial infiltration of inflammatory cells, alveolar structure destruction, alveolar septum thicken, extensive alveolar hemorrhage, telangiectasia; the levels of TNF-α, IL-1β, IL-6, MDA and NF-κB p65 protein expression in lung tissue were significantly higher than those in the normal control group and sham operation group [TNF-α (ng/L): 132.81±16.15 vs. 45.08±5.98, 46.10±6.72, IL-1β (ng/L): 137.32±15.22 vs. 51.03±7.89, 50.92±8.13; IL-6 (ng/L): 138.39±14.28 vs. 51.68±7.03, 52.48±7.36; MDA (kU/g): 1.79±0.13 vs. 0.96±0.05, 0.97±0.05; NF-κB p65 protein (NF-κB p65/GAPDH): 2.82±0.23 vs. 1.76±0.12, 1.82±0.13; all P < 0.05], the activity of SOD decreased significantly (kU/g: 45.90±5.46 vs. 92.11±10.13, 93.36±10.56, both P < 0.05). The changes in lung histopathology in the forsythiaside A intervention group were obviously improved as compared with the model group, which showed less inflammatory cell infiltration, less alveolar septum thickening, less bleeding and more intact structures; the levels of TNF-α, IL-1β, IL-6, MDA and the expression of NF-κB p65 protein in lung tissue were significantly lower than those in the model group [TNF-α (ng/L): 72.48±9.78 vs. 132.81±16.15, IL-1β (ng/L): 83.85±12.46 vs. 137.32±15.22, IL-6 (ng/L): 81.88±11.89 vs. 138.39±14.28, MDA (kU/L): 1.29±0.09 vs. 1.79±0.13, NF-κB p65 protein (NF-κB p65/GAPDH): 2.29±0.19 vs. 2.82±0.23, all P < 0.05], SOD activity increased significantly (kU/g: 66.03±7.98 vs. 45.90±5.46, P < 0.05).
Conclusions: Forsythiaside A can effectively alleviate ALI in septic rats. The mechanism may be related to down-regulate the expression of NF-κB p65 and reduce the level of inflammatory factors and free radicals in lung tissue, thereby against acute lung injury in septic rats.