[EngO4-3] Synergistic cytoprotection by co-treatment with dexamethasone and rapamycin against inflammatory cytokine-induced alveolar epithelial cell injury
(Background)Massive production of inflammatory mediators is one of the main pathophysiological manifestations in sepsis. These inflammatory mediators can directly activate the cellular apoptotic signaling pathway, whereas sepsis-related organ dysfunction is assumed to be deeply associated with cellular apoptosis. Although clinical trials targeting inflammatory mediators to mitigate organ dysfunction in sepsis have been extensively performed, the clinical outcomes of such trials remain far from satisfactory, especially when evaluated on a single-treatment basis. Given the need for better sepsis treatments, we screened various agents with anti-inflammatory properties for cytoprotective effects and identified dexamethasone and rapamycin as candidates with favorable synergistic effects in vitro. The purpose of the present study was to further explore the underlying mechanism of augmented cytoprotection exerted by co-treatment with dexamethasone and rapamycin against inflammatory cytokine-induced cytotoxicity.
(Methods)Human alveolar epithelial cell-derived A549 cells were stimulated with a mixture of inflammatory cytokines (cytomix: IL-1beta, TNF-alpha, and IFN-gamma), which induced cellular injury, including apoptosis. This in vitro model was designed to simulate acute lung injury associated with sepsis. The cells were pretreated with dexamethasone and rapamycin before the cytomix stimulation. Conditioned medium and cell lysate were subjected to further analysis to determine the degree of cytotoxicity inhibition, and also to identify the cytoprotective signaling pathway exerted by the simultaneous treatment of dexamethasone and rapamycin.
(Results)Either dexamethasone or rapamycin significantly attenuated the cytomix-induced cytotoxicity in A549 cells in a dose-dependent manner. In addition, the simultaneous administration of dexamethasone and rapamycin had a synergistical cytoprotective effect. The applied doses of dexamethasone (10 nM) and rapamycin (1 nM) were considerably below the presumed clinical blood concentrations of each drug. Interestingly, distinct augmentation of c-Jun inhibition and Akt activation was observed when the cells were co-treated with both drugs.
(Conclusions)The synergistic cytoprotective effect of dexamethasone and rapamycin was observed against cytokine-induced cytotoxicity in A549 cells. Augmentation of c-Jun inhibition and Akt activation was inferred to be responsible for the synergism. The combined administration of distinct anti-inflammatory drugs, such as dexamethasone and rapamycin, offers a promising treatment option for alveolar epithelial injury associated with sepsis.
(Methods)Human alveolar epithelial cell-derived A549 cells were stimulated with a mixture of inflammatory cytokines (cytomix: IL-1beta, TNF-alpha, and IFN-gamma), which induced cellular injury, including apoptosis. This in vitro model was designed to simulate acute lung injury associated with sepsis. The cells were pretreated with dexamethasone and rapamycin before the cytomix stimulation. Conditioned medium and cell lysate were subjected to further analysis to determine the degree of cytotoxicity inhibition, and also to identify the cytoprotective signaling pathway exerted by the simultaneous treatment of dexamethasone and rapamycin.
(Results)Either dexamethasone or rapamycin significantly attenuated the cytomix-induced cytotoxicity in A549 cells in a dose-dependent manner. In addition, the simultaneous administration of dexamethasone and rapamycin had a synergistical cytoprotective effect. The applied doses of dexamethasone (10 nM) and rapamycin (1 nM) were considerably below the presumed clinical blood concentrations of each drug. Interestingly, distinct augmentation of c-Jun inhibition and Akt activation was observed when the cells were co-treated with both drugs.
(Conclusions)The synergistic cytoprotective effect of dexamethasone and rapamycin was observed against cytokine-induced cytotoxicity in A549 cells. Augmentation of c-Jun inhibition and Akt activation was inferred to be responsible for the synergism. The combined administration of distinct anti-inflammatory drugs, such as dexamethasone and rapamycin, offers a promising treatment option for alveolar epithelial injury associated with sepsis.