Biocide mixture (CMIT/MIT) induces neurotoxicity through the upregulation of the MAPKs signaling pathways

The biocides 5-chloro-2-methyl-2h-isothiazolin-3-one and 2-methyl-2h-isothiazolin-3-one (CMIT/MIT) are widely used and can be found in many different types of water-soluble consumer products, such as shampoo, dentifrice, and germicide. Recent reports have suggested that it may be harmful to the skin and lungs. Although not known to be linked to pathogenic cellular and molecular pathways, it is a recognized risk factor for endangering public health. Therefore, the aim of this study was to examine the impact of CMIT/MIT (in 3:1 ratio) in SH-SY5Y human neuroblastoma cells. SHSY-5Y cells were exposed to different concentration (0, 12.5, 25, and 50 μM) of CMIT/MIT for 24 h. Cellular proliferation was considerably reduced in the MTT assay after CMIT/MIT exposure. In addition, the results showed an increase in lactate dehydrogenase (LDH) release and lipid peroxidation and a decrease in physiological antioxidant defense. We also observed an activation of Nrf-2/HO-1 signaling pathway by Western blot and qRT-PCR. Exposure to CMIT/MIT (in 3:1 ratio) also increased the release of proinflammatory cytokines, such as IL-1β, IL-6, and TNF-α. Furthermore, in SHSY-5Y, CMIT/MIT (in 3:1 ratio) raised the levels of phosphorylated ERK1/2, phosphorylated p38, and phosphorylated JNK1/2 proteins. The activation of these pathways was strongly connected with the cell cycle-related genes p53 and p21 and the activation of apoptotic cascade. These results imply that the Nrf-2/HO-1, p38-JNK1/2-ERK1/2, and Bax/Bcl-2 signaling pathways are responsible for inducing cellular damage and accelerating neuronal aging in response to CMIT/MIT (in 3:1 ratio) exposure.<b>NEW & NOTEWORTHY</b> 5-Chloro-2-methyl-2h-isothiazolin-3-one and 2-methyl-2h-isothiazolin-3-one (CMIT/MIT) are widely used, but they may be harmful to the skin and lungs. CMIT/MIT reduces cell viability and induces lactate dehydrogenase (LDH) release in SHSY5Y cell line. CMIT/MIT induces oxidative stress, lipid peroxidation, and activates endogenous antioxidant system. CMIT/MIT induces proinflammatory cytokines release. CMIT/MIT promoted the upregulation of MAPKs and induces apoptosis.