DNA Double-Strand Breaks in Arctic Char (Salvelinus alpinus) from Bjørnøya in the Norwegian Arctic

An overview on the legacy and risks of Polychlorinated Biphenyls (PCBs) and Organochlorinated Pesticides (OCPs) in the polar regions

Polychlorinated Biphenyls (PCBs) and Organochlorinated Pesticides (OCPs) are 'trapped' in a variety of environmental media and can therefore undergo further processing by geochemical cycles. By reviewing a wide range of research studies, we present and discuss the main progresses that affect legacy contaminants, such as migration and transformation processes, biological effects assessment across all Arctic media. PCBs and OCPs demonstrated an overall decreasing concentration trend over time in the Arctic. Ecological risk assessment was undertaken by comparison with two standards, suggesting that there was no ecological risk in either soil or sediment. The concentrations of HCB, ΣHCHs, ΣDDTs, chlordane, mirex, and ΣPCBs increased with trophic levels (TLs), showing a significant linear correlation (P < 0.001). The calculated trophic magnification factors (TMFs) values ranged from 0.0004 to 26.63, among which DDTs had the highest value. Future research need to focus on the long-term fate of PCBs and OCPs.

Expression of DNA repair genes in arctic char (Salvelinus alpinus) from Bjørnøya in the Norwegian Arctic

High levels of organochlorines (OCs) have been measured in arctic char (Salvelinus alpinus) from Lake Ellasjøen on Bjørnøya, Norway (74.30°N, 19.0°E). In a nearby lake, Laksvatn, the OC-levels in arctic char were low. A previous study has shown that char from Ellasjøen had significantly higher levels of DNA double strand breaks (DSBs) than char from Lake Laksvatn. Even though there is increasing evidence of the genotoxic effects of OCs, little is known about the effects of OCs on the DNA repair system. The aim of the present study was to determine if the two main DNA DSB repair mechanisms, homologous recombination (HR) and non-homologous end-joining (NHEJ), are affected by the higher OC and DSB level in char from Ellasjøen. This was analysed by comparing the transcript level of 11 genes involved in DNA DSB repair in char liver samples from Ellasjøen (n = 9) with char from Laksvatn (n = 12). Six of the investigated genes were significantly upregulated in char from Ellasjøen. As the expression of DNA DSB repair genes was increased in the contaminant-exposed char, it is likely that the DNA DSB repair capacity is induced in these individuals. This induction was positively correlated with the DNA DSB and negatively correlated with one or several OCs for four of these genes. However, the strongest predictor variable for DNA repair genes was habitat, indicating genetic differences in repair capacity between populations. As char from Ellasjøen still had significantly higher levels of DSBs compared to char from Laksvatn, it is possible that chronic exposure to OCs and continued production of DSB has caused selective pressure within the population for fixation of adaptive alleles. It is also possible that DSB production was exceeding the repair capacity given the prevailing conditions, or that the OC or DSB level was above the threshold value of inhibition of the DNA repair system resulting in the rate of DNA damage exceeding the rate of repair.

A simple method for isolation and culture of primary hepatocytes from Salvelinus leucomaenis (White-spotted Charr)

White-spotted charr (Salvelinus leucomaenis, S. I.) is an anadromous cold water-adapted fish, distributed in the Far East. We have previously reported the complete mitochondrial DNA sequences of white-spotted chars (S. l. imbrius and S. l. pluvius) in Japan. In general, fish hepatocytes are useful for cellular and biochemical studies of fish. In this study, we isolated hepatocytes from the liver of white-spotted charr and used basic methods, such as enzyme digestion and low centrifugation, to analyze the molecular mechanisms involved in specific cellular responses. The isolated hepatocytes could be cultured at 5-20 °C but not 37 °C. The morphology of hepatocytes was altered in a temperature-dependent manner. The properties of hepatocyte were similar to those of living fish. Moreover, the proliferation rate and damage of isolated hepatocytes depended on the concentration of fetal bovine serum in the culture medium. Taken together, this study demonstrates that this simple method for isolation and culture of hepatocytes from white-spotted charr may be useful for other biochemical and cellular studies.