Toxicological assessment of 2-methylisothiazol-3(2H)-one on physiological and antioxidant parameters in Mytilus galloprovincialis

Isothiazolinones are biocides that play a key role in many industries, particularly as preservatives and antimicrobial agents. Among this class is 2-methylisothiazol-3(2H)-one (MIT), which has been classified as a human skin sensitizer by the European Commission Regulation (EC) No 1272/2008 (EC Regulation, 2008). In the current post-pandemic COVID-19 era, the increased use of these compounds has led to higher concentrations in various aquatic ecosystems. Therefore, the present study aimed to assess the effects induced by MIT using the Mediterranean mussel (Mytilus galloprovincialis) exposed to different concentrations of MIT (E1: 0.2 mg L^-1 and E2: 0.4 mg L^-1) for 14 days. Physiological and antioxidant responses in selected target tissues, including the haemolymph, gills, and digestive gland (DG), were evaluated. The alteration of the immune response was assessed through assays of haemocyte viability and phagocytosis capacity that showed significant alterations in the exposed groups compared to the control (CTRL) group. In addition, the cytotoxicity of DG cells was investigated by evaluating hepatocyte viability, showing a significant decrease in the E1 groups. Also, their ability to regulate cell volume when subjected to a hypotonic solution (Regulatory Volume Decrease assay, RVD). Furthermore, measurement of enzymatic markers such as superoxide dismutase (SOD) activity, lipid peroxidation (LPO), protein carbonylation, and acetylcholinesterase (AChE) activity in gills and DG, were performed. Data from these biochemical analyses also demonstrated significant alterations in the exposed groups with respect to the CTRL. Overall, findings showed significant alterations in physiological and antioxidant parameters in MIT-exposed groups, highlighting the potential toxicological impact of this compound. These results emphasize the need for further research to deepen our understanding of the mechanisms underlying MIT toxicity.