Synergistic Enhancement of Isoforskolin and Dexamethasone Against Sepsis and Acute Lung Injury Mouse Models

Sepsis is initiated by the dysfunctional response of the host immune system to infection. Septic shock and acute lung injury (ALI) are the main etiology of death caused by sepsis. Glucocorticoids, which are commonly used in clinic to antagonize the inflammatory response of sepsis, may cause serious side effects. Isoforskolin (ISOF) from the plant stimulates adenylyl cyclase, increases the cAMP level and inhibits inflammatory response. The aim of this study was to investigate the synergistic effect of ISOF with dexamethasone (DEX) to prevent and ameliorate septic inflammation. Lipopolysaccharide (LPS) of 30 and 5 mg/kg (iv.) was used to induce sepsis and ALI mice model respectively in vivo. BEAS-2B cells stimulated by LPS were applied as cell model in vitro. The cumulative survival of mice with LPS-induced sepsis and the histopathological changes of lungs in mice with acute lung injury were observed, and the secretion of pro-inflammatory cytokines was analyzed by ELISA. The expression of RGS2 in BEAS-2B cells was detected by immunoblotting assay and PCR. In the sepsis mice model, ISOF (10 mg/kg) combined with DEX (10 mg/kg.) (ip.) pretreatment significantly increased mice survival rate from 33.3% to 58.3%, which was significantly higher than that of ISOF or DEX treated alone. In the ALI mice model, ISOF, DEX pretreatment alone and combined application attenuated pulmonary pathological changes in ALI mice. Furthermore, ISOF, DEX alone or combined administration decreased MPO, MDA, IL-6, and IL-8 levels, while significantly synergistic effects were observed in the combined treatment group compared with ISOF or DEX alone. In BEAS-2B cells, combined pretreatment with ISOF and DEX significantly decreased the expression of IL-8 and increased the expression of RGS2. The results indicated that ISOF in combination with DEX synergistically improves survival rate and attenuates ALI in mice model through anti-inflammatory and antioxidant effects.