CMIT/MIT induce apoptosis and inflammation in alveolar epithelial cells through p38/JNK/ERK1/2 signaling pathway

Backgrounds The 5-chloro-2-methyl-2h-isothiazolin-3-one and 2-methyl-2h-isothiazol-3-one (CMIT/MIT) are widespread biocides that commonly found in variety of water-soluble consumer products including dentifrice, germicide and shampoo etc. Recently, in Korea, it has been reported that general population was exposed to humidifier sterilizer with CMIT/MIT as disinfectant components, and eventually more than 530 victims had been suffered severe lung disease since they had used. Although it is known to be a certain risk factor threatening public health, it is unknown to be associated with pathological cellular- and molecular-mechanisms. Therefore, in this study, we investigated the cytotoxic effect of CMIT/MIT in mouse alveolar type II epithelial cells, MLE-12 cells. Methods MLE-12 cells were treated with CMIT/MIT (0-50 μM) for 24 hours. Results In MTT assay, cellular proliferation was significantly decreased in response to CMIT/MIT treatment. In western blot analysis, protein levels of BAX/Bcl-2 and cleaved caspase-3 were significantly increased. Moreover, cell cycle-related gene were also increased. In ELISA, CMIT/MIT increased the release of pro-inflammatory cytokine of TNF-α and IL-1β. Moreover, CMIT/MIT increased the phosphorylated-ERK1/2, phosphorylated-p38, and phosphorylated-JNK1/2 protein levels in MLE-12 cells. Conclusion These findings suggest that CMIT/MIT exposure induce the injury of alveolar epithelial cells with inflammatory response via the p38-JNK1/2-ERK1/2 signaling pathway.