Bioaccumulation of pollutants in the green-lipped mussel Perna viridis: Assessing pollution abatement in Victoria Harbour and its adjacent aquaculture area, Hong Kong, and the minimal human health risks from mussel consumption

The green-lipped mussel Perna viridis was utilised for pollution biomonitoring in Victoria Harbour and its adjacent aquaculture area in Hong Kong. P. viridis was collected from a reference site and redeployed at five study sites for five weeks during the dry and wet seasons of 2019. Our study found various polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the mussel tissue, while polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) were not detected. P. viridis at the reference site generally displayed lower levels of pollutants. Comparing with previous research in the 1980s and 2000s, we observed substantial reduction in the tissue levels of PAHs, PCBs, OCPs and heavy metals in P. viridis. The human health risks associated with consuming these mussels were determined to be insignificant. Our findings imply that the Harbour Area Treatment Scheme has been effective in improving the water quality in Victoria Harbour and its adjacent aquaculture area.

Chronic Methylmercury Exposure Induces Production of Prostaglandins: Evidence From A Population Study and A Rat Dosing Experiment

Methylmercury (MeHg) is a well-known environmental neurotoxicant affecting millions worldwide who consume contaminated fishes and other food commodities. Exposure to MeHg has been shown to associate positively with some chronic diseases including cardiovascular diseases, but the mechanism is poorly characterized. MeHg had been shown to affect prostaglandin (PG) regulations in in vitro studies, but neither in vivo nor human studies investigating the effects of MeHg on PG regulations has been reported. Thus, the current study aimed to investigate the association between MeHg exposure and serum PG concentrations in a cross-sectional study among human adults followed by a validation investigation on the cause-effect relationship using a rat model. First, a total of 121 women were recruited from two cities: Wanshan and Leishan in Guizhou, China. Statistical analysis of the human data showed a positive association between blood total mercury (THg) levels and serum concentrations of PGF2α, 15-deoxy-PGJ2, and PGE2 after adjusting for site effects. In the animal study, adult female Sprague-Dawley rats were dosed with 40 μg MeHg/kg body weight/day for 12 weeks. Serum 15-deoxy-PGJ2 and 2,3 d-6-keto-PGF1α concentrations were found to increase significantly after 6 and 10 weeks of MeHg dosing, respectively, while serum PGF2α concentration increased significantly after 12 weeks of MeHg dosing. Combined results of our human and rat studies have shown that chronic MeHg exposure induced dysregulation of PG metabolism. As PGs are a set of mediators with very diverse functions, its abnormal production may serve as the missing mechanistic link between chronic MeHg exposure and various kinds of associated clinical conditions including neurodegeneration and cardiovascular diseases.

Dietary chitosan-selenium nanoparticle (CTS-SeNP) enhance immunity and disease resistance in zebrafish

Selenium (Se) is an essential micronutrient for human and animals. It plays an important role in antioxidative stress, selenoenzymes regulation and immunomodulation. In this study, two common immunostimulants chitosan (CTS) and Se were used to synthesize nanoparticles (CTS-SeNP). Immunomodulation of CTS-SeNP were explored in wild-type zebrafish (Danio rerio). Dietary supplementation of CTS-SeNP enhanced lysozyme activity, phagocytic respiratory burst as well as splenocytes proliferation stimulated by LPS and ConA. CTS-SeNP showed immunomodulation effect from 5 to 20 μg/g but the best outcome was observed at 10 μg/g. Immunomodulation effect were rapidly induced after 3-9d and can sustain to 60. The zebrafish fed with 10 μg/g CTS-SeNP also showed 26.7% higher survival rate than the control after intraperitoneal injection of common bacterium Aeromonas hydrophila. Our results suggested that CTS-SeNP is an effective immunostimulant to fish and has potential application in aquaculture.

Chronic exposure of adult rats to low doses of methylmercury induced a state of metabolic deficit in the somatosensory cortex

Because of the ever-increasing bioaccumulation of methylmercury (MeHg) in the marine food chain, human consumers are exposed to low doses of MeHg continually through seafood consumption. Epidemiological studies strongly suggest that chronic prenatal exposure to nanomolar of MeHg has immense negative impacts on neurological development in neonates. However, effects of chronic exposure to low doses (CELDs) of MeHg in adult brains on a molecular level are unknown. The current study aims to investigate the molecular effects of CELD of MeHg on adult somatosensory cortex in a rat model using proteomic techniques. Young adult rats were fed with a low dose of MeHg (40 μg/kg body weight/day) for a maximum of 12 weeks. Whole proteome expression of the somatosensory cortex (S1 area) of normal rats and those with CELD to MeHg were compared. Levels of MeHg, total calcium, adenosine triphosphate (ATP), and pyruvate were also measured. Comparative proteomic studies of the somatosensory cortexes revealed that 94 proteins involved in the various metabolic processes (including carbohydrate metabolism, generation of precursors for essential metabolites, energy, proteins, cellular components for morphogenesis, and neurotransmission) were down-regulated. Consequently, levels of important end products of active metabolism including ATP, pyruvate, and total calcium were also found to be significantly reduced concomitantly. Our results showed that CELD of MeHg induced a state of metabolic deficit in the somatosensory cortex of adult rats.

Abstract P6-08-04: AP-1 Activation and a Functional SNP242 Regulate the LY-6K Gene Expression in Human Breast Cancer Cells

Background: Lymphocyte antigen 6 complex locus K(LY-6K), a member of cancer-testis antigen, is a novel breast cancer biomarker. Elevated LY-6K induces cell invasion and metastasis through activating the Raf-1/MEK/ERK signaling pathway. And in a previous study, breast cancer patients have single nucleotide polymorphism (SNP) within promoter of LY-6K. However, the molecular mechanisms that mediate regulation of human LY-6K gene expression are completely unknown. Material and Methods: The human breast carcinoma cells used in these studies include the MCF7 and adriamycin resistant MCF7. Within the pGL3 reporter vector, the -3050/+182 bp fragment and truncated fragment (deleted from -500 to -1 bp and from -1550 to -1050 bp) upstream of the LY-6K gene was subcloned and measured promoter activity. Next, multiple cis elements were identified using several gene tool software (TFSEARCH, TRANSFAC, PROMO and MATCHTM) in the promoter of human LY-6K gene. Substitution of two base pair of transcription factor binding site or single base pair of SNP was subcloned within pGL3 vector using site-directed mutagenesis and measured transcriptional activity. Chromatin immunoprecipitation (ChIP), electrophoretic mobility shift assay (EMSA) and supershift assays were used to demonstrate in vitro interactions between the transcription factor and transcription factor binding site within the promoter of LY-6K.

Results: We found that a novel AP-1 binding site in the LY-6K promoter. The substitution from C to G at the 242 nucleotide position in the promoter region is a functional LY-6K single nucleotide polymorphism (called SNP242), which increase AP-1 transcription binding affinity to LY-6K promoter. Ongoing studies are investigating to identify the relationship between LY-6K transcription and SNP756 which located at the 756 nucleotide position within LY-6K promoter and to find binding partner of LY-6K. We are also manipulating LY-6K transgenic mouse and knock-out mouse to investigate the mechanism of LY-6K in vivo. Discussion: The activity of the AP-1 transcription factor plays an important role in cell mobility of breast cancer cells via the promoting of LY-6K gene expression. LY-6K expression is dependent on not AP-1 transcription factor, but also SNP242 G allele by increasing AP-1 binding affinity. We demonstrated that metastasis of breast cancer cells depend on LY-6K expression turn on ERK signaling. These results suggested that LY-6K SNP242 G allele increases the risk of cancer and metastasis and LY-6K communicate with integrin-GPCR to cell migration via activating Ras/ERK signaling pathway.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P6-08-04.