Nociceptive effects and gene alterations of CMIT/MIT mixture in zebrafish embryos and larvae

Nociception is a critical biological process that facilitates detecting and avoiding harmful stimuli. Methylisothiazolinone (MIT) and methylchloroisothiazolinone (CMIT) are biocidal agents widely used in disinfectants and cosmetics, however, their effects on nociceptive pathways and neurotoxicity remain insufficiently understood. This study investigated the neurotoxic and nociceptive effects of CMIT/MIT mixtures in zebrafish models. Zebrafish embryos were exposed to CMIT/MIT, and their behavioral and molecular responses to nociceptive stimuli were assessed. Acute exposure (4 -72 h post-fertilization) to CMIT/MIT (15 and 30 μg/L) led to heightened behavioral responses to noxious stimuli, significantly increasing velocity and neuronal activity. Molecular analysis revealed the upregulated expression of nociception-related and inflammatory markers. Subchronic exposure (4 hpf to 28 days post-fertilization) to lower CMIT/MIT concentrations resulted in prolonged freezing responses and reduced the movement in zebrafish larvae. Protein-protein interaction analysis further identified key pathways, including calcium signaling, MAPK, and neuroinflammation, affected by CMIT/MIT exposure. This study provides evidence that even low levels of CMIT/MIT exposure can enhance nociceptive responses by activating sensory neurons and modulating inflammatory pathways, raising concerns about the neurotoxic potential of these widely used biocidal compounds.