Analysis of cytotoxicity induced by proinflammatory cytokines in the human alveolar epithelial cell line A549.

Epithelial cell injury under hyperinflammatory conditions is critical in the development of septic acute lung injury (ALI). The aim of the present study is to analyze the cytotoxic effects of a mixture of proinflammatory cytokines in the human alveolar epithelial cell line A549. The cytotoxicity of proinflammatory cytokines were assessed in A549 cells by measuring lactate dehydrogenase released into the culture medium and by crystal violet staining of surviving cells. Activation of the caspase-dependent apoptotic pathway was evaluated by monitoring cleavage of cytokeratin 18 by caspases using enzyme-liked immunosorbent assay (ELISA). To estimate the cytotoxic signaling pathways responsible for epithelial injury, agents with antiinflammatory or antioxidative properties were extensively screened for cytoprotective effects in the inflammation-associated epithelial injury model. The present study revealed that inflammatory cytokines exerted cytotoxicity in A549 cells. A mixture of interleukin-1beta (IL-1β), tumor necrosis factor-alpha (TNF-α) and interferon-gamma (IFN-γ), designated as cytomix, augmented cytotoxicity compared with each individual cytokine. Treatment with glucocorticoid (dexamethasone), tetracycline-derived antiinflammatory antibiotics (minocycline or doxycycline), angiotensin II receptor blockers (losartan or telmisartan), or antioxidants (dimethyl sulfoxide, catalase) attenuated cytomix-induced cytotoxicity, including caspase activation. These results implied that inflammatory cytokines alone could cause alveolar epithelial injury in the pathophysiology of septic ALI. Caspase-dependent apoptosis was speculated to be one mechanism responsible for the cytokine-induced cytotoxicity. Agents with antiinflammatory or antioxidative properties such as glucocorticoid, tetracycline-derived antibiotics, angiotensin II receptor blockers, or direct antioxidants showed substantial effect in attenuating cytokine-induced cytotoxicity and may be candidates for treatment options.