The combined effects of microplastics and bisphenol-A on the innate immune system response and intestinal microflora of the swimming crab Portunus trituberculatus

Microplastics (MPs) and bisphenol-A (BPA) have been shown to have toxic effects on aquatic organisms. However, data on the combined effects of MPs and BPA on the innate immune system response and intestinal microorganisms of crabs are limited. Here, Portunus trituberculatus were exposed to BPA (at a concentration of 100 mu g/L), MPs (microbeads of polystyrene with a particle size of 1 mu m and at a concentration of 1 x 106 particles/L) or BPA+MPs for 21 days were tested at the tissue, cellular, and molecular levels. The results showed that neither the single nor combined exposure of MPs and BPA had a significant impact on the growth of crabs. However, intestinal histology study found that the intestinal villi of crabs in the BPA treated group, MP treated group and MP+BPA treated group appeared abnormal. Overall, compared with the control group and the single pollutant exposure group, co-exposure to the MP and BPA generally led to a significant increase in MDA and SOD activity and a significant decrease in CAT activity, and the activation of MyD88, Crustin-1, TARF6, Cu/Zn-SOD, Lyz, Toll -2 and NOX gene expression levels were significantly up-regulated. Co-exposure induced disorders of the intestinal microbial community of crabs, resulting in an increase in the abundance of harmful bacteria and a decrease in the abundance of beneficial bacteria. This study shows that the combined exposure of MPs and BPA can exacerbate the intestinal toxicity of a single pollutant to P. trituberculatus.