Acute toxic effects and molecular mechanisms of combined pollution by microplastics and petroleum on Tegillarca granosa in intertidal sediments based on biochemical indicators, histopathology, DNA damage and gene expression.

The harmful effects of marine microplastic pollution on organisms have attracted widespread attention, but research on the toxic effects of combined pollution formed by microplastics adsorbing petroleum in intertidal sediments is relatively scarce. In this study, acute toxicity of the single and combined pollution of Polyethylene microplastics (PE MPs) and diesel on Tegillarca granosa after 96 hours exposure was investigated in terms of oxidative stress related biochemical indicators, histopathology, DNA damage and gene expression, respectively. The results showed that microplastics-diesel combined exposure resulted in increased SOD activity in both the gills and the visceral mass of T. granosa, whereas GPx and GST activities were inhibited. However, no significant change in MDA content was observed under short-term exposure conditions. The Integrated Biological Responses version 2 (IBRv2) index revealed that the gills exhibited higher sensitivity to the combined pollutant. High-concentration combined exposure induced histopathological alterations (gill swelling, digestive tubule necrosis of the visceral mass) and DNA damage. Furthermore, high-concentration combined pollution upregulated the gene expression of cytochrome P450 Family 2 (CYP2 family), GST, CAT, GPX, and SOD1, while downregulating the KEAP1. It indicated that combined pollutants can regulate antioxidant genes by activating the cytochrome P450 (CYPs) enzyme system and the KEAP1-NRF2 signaling pathway, interfere with the antioxidant defense system of T. granosa, and produce an enhanced toxic effect. The research revealed the toxic effects and molecular mechanisms of microplastic-petroleum combined pollution on T. granosa, providing a scientific basis for assessing the ecological risks of combined pollution in marine environments.