Coastal habitats are exposed to increasing pressure of nanopollutants commonly combined with warming due to the seasonal temperature cycles and global climate change. To investigate the toxicological effects of TiO2 nanoparticles (TiO2 NPs) and elevated temperature on the intestinal health of the mussels (Mytilus coruscus), the mussels were exposed to 0.1 mg/L TiO2 NPs with different crystal structures for 14 days at 20 °C and 28 °C, respectively. Compared to 20 °C, the agglomeration of TiO2 NPs was more serious at 28 °C. Exposure to TiO2 NPs led to elevated mortality of M. coruscus and modified the intestinal microbial community as shown by 16S rRNA sequence analysis. Exposure to TiO2 NPs changed the relative abundance of Bacteroidetes, Proteobacteria and Firmicutes. The relative abundances of putative mutualistic symbionts Tenericutes and Fusobacteria increased in the gut of M. coruscus exposed to anatase, which have contributed to the lower mortality in this group. LEfSe showed the combined stress of warming and TiO2 NPs increased the risk of M. coruscus being infected with potential pathogenic bacteria. This study emphasizes the toxicity differences between crystal structures of TiO2 NPs, and will provides an important reference for analyzing the physiological and ecological effects of nanomaterial pollution on bivalves under the background of global climate change.
Nanoplastics (NPs) and antibiotics (ABs) are two of the emerging marine contaminants that have drawn the most attention in recent years. Given the necessity of figuring out the effects of plastic and antibiotic contamination on marine organism life and population in the natural environment, it is essential to apply rapid and effective biological indicators to evaluate their comprehensive toxic effects. In this study, using mussel (Mytilus coruscus) as a model, we investigated the combined toxic effects of NP (80 nm polystyrene beads) and AB (Norfloxacin, NOR) at environmental-relevant concentrations on antioxidant and immune genes. In terms of the antioxidant genes, NPs significantly increased the relative expression of Cytochrome P450 3A-1 (CYP3A-1) under various concentrations of NOR conditions, but they only significantly increased the relative expression of CYP3A-2 in the high concentration (500 μg L-1 NOR) co-exposure group. In the NP-exposure group which exposed to no or low concentrations of NOR, nuclear factor erythroid 2-related factor 2 (Nrf2) was upregulated. In terms of the immune genes, interleukin-1 receptor-associated kinase (IRAK) -1 showed a significant increase in the low-concentration NOR group while a significant inhibition in the high-concentration NOR group. Due to the presence of NPs, exposure to NOR resulted in a significant increase in both IRAK-4 and heat shock protein (HSP) 70. Our findings indicate that polystyrene NPs can exacerbate the effects of NOR on the anti-oxidant and immune defense performance of mussels. This study delves into the toxic effects of NPs and ABs from a molecular perspective. Given the expected increase in environmental pollution due to NPs and ABs, future research is needed to investigate the potential synergistic effect of NPs and ABs on other organisms.
In this work, we describe results of the reproductive health monitoring studies in Mytilus galloprovincialis following spermatozoa hsp70 expression and protamine-like protein properties. Mussels control (ctr) were released within cages for 30 days in three different marine sites near Naples (Campania, Italy): Bagnoli south (BAs) and Bagnoli north (BAn), both close to a disposal metallurgical factory and in Capo Miseno (CM). Studies of hsp70 gene expression carried out, by RT-qPCR, in mussel spermatozoa have shown varied expression levels, particularly 5, 13, and 15-fold more than ctr in CM, BAs, and BAn, respectively, indicating highest involvement of stress proteins in spermatozoa of mussels in Bagnoli. In order to evaluate the possible risk on Mytilus galloprovincialis sustainability loss, electrophoretic analyses were performed on protamine-like proteins (PL) of collected spermatozoa. The results showed that CM PL were apparently unaltered with respect to ctr PL, while BAs and BAn PL appeared in part in the form of peptides and in part as bands with low mobility. Further, CM and BAs PL showed, by electrophoretic mobility shift assay, a decrease in DNA binding ability and a change in their DNA binding mode. The results of this investigation show the usefulness of the study of alterations of spermatozoa hsp70 expression and protamine-like protein properties for eco-toxicological evaluation using Mytilus galloprovincialis as a bioindicator.