The acute neurotoxicity of inorganic mercury in Mactra chinensis philippi.

Inorganic mercury (IHg) is hazardous to marine organisms especially resulting in neurotoxicity, bivalves are sensitive to pollutants as "ocean sentinel", but data on the neurotoxicity of IHg in bivalves are sparse. So we chosed M. chinensis philippi with typical neural structures in bivalves to investigate the neurotoxicity of IHg, which could be helpful to understand the specificity of neural regulation and the response characteristics of bivalves. After acute exposed to IHg (HgCl2) for 24 h, the metabolites of ganglion tissues in M. chinensis philippi were evaluated using 1H-nuclear magnetic resonance based metabolomics; Ca2+, neurotransmitters (nitric oxide, glutamate, acetylcholine) and related enzymes (calcineurin, nitric oxide synthase and acetylcholinesterase) were measured using biochemical detection. Compared to the control group, the levels of the nitric oxide (81.04 ± 12.84 µmol/g prot) and acetylcholine (30.93 ± 12.57 µg/mg prot) in M. chinensis philippi of IHg-treated were decreased, while glutamate (2.11 ± 0.61 mmol/L) increased significantly; the activity of nitric oxide synthase (679.34 ± 135.33 U/mg prot) was increased, while acetylcholinesterase (1.39 ± 0.44 U/mg prot) decreased significantly, and the activity of calcineurin (0.52 ± 0.02 U/mg prot) had a statistically insignificant increasing tendency. The concentration of Ca2+ (0.92 ± 0.46 mmol/g prot) in the IHg-treated group was significantly higher than that in the control group. OPLS-DA was performed to reveal the difference in metabolites between the control and IHg-challenged groups, the metabolites of glucose, glutamine, inosine, succinate, glutamate, homarine, and alanine were sensitive to IHg, subsequently metabolic pathways that were affected including glucose metabolism, glutamine metabolism, nucleotide metabolism, Krebs cycle, amino acid metabolism and osmotic regulation. In our study, IHg interfered with metabolites in M. chinensis philippi, thus the corresponding metabolic pathways were changed, which influenced the neurotransmitters subsequently. Furthermore, Ca2+overload affected the synthesis or degradation of the neurotransmitters, and then the altered neurotransmitters involved in changes in metabolic pathways again. Overall, we hypothesized that the neurotoxic effects of IHg on bivalve were in close contact with metabolism, neurotransmitters, related enzymes and Ca2+, which could be effective neurotoxic biomarkers for marine environmental quality assessment, and also provide effective data for the study of the regulatory mechanism of the nervous system in response to IHg in bivalves.

Comparative proteomics study of exosomes in Vibrio harveyi and Vibrio anguillarum.

Exosomes are a class of extracellular vesicles released by bacteria and contain diverse biomolecules. In this study, we isolated exosomes from Vibrio harveyi and Vibrio anguillarum, which are both serious pathogens in mariculture, using a supercentrifugation method, and the proteins in the exosomes of these two vibrios were analyzed by LC-MS/MS proteomics. Exosome proteins released by V. harveyi and V. anguillarum were different; they not only contained virulence factors (such as lipase and phospholipase in V. harveyi, metalloprotease and hemolysin in V. anguillarum), but also participated in the important life activities of bacteria (such as fatty acid biosynthesis, biosynthesis of antibiotics, carbon metabolism). Subsequently, to verify whether the exosomes participated in bacterial toxicity, after Ruditapes philippinarum was challenged with V. harveyi and V. anguillarum, the corresponding genes of virulence factors from exosomes screened by proteomics were tested by quantitative real-time PCR. All the genes detected were upregulated which suggested that exosomes were involved in vibrio toxicity. The results could provide an effective proteome database for decoding the pathogenic mechanism of vibrios from the exosome perspective.