Precision biochemistry tracks DNA damage in fish

Research over the past several years has demonstrated the adverse effects of industrial pollutants in water and sediment on the health of fish in the lower Duwamish River. The Duwamish flows through an industrialized section of south Seattle, Wash., and in 2001 a section of the lower river was added to the Environmental Protection Agency’s Superfund list because of contaminants including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), mercury and other metals, and phthalates. In previous research on Duwamish fish, PNRI used an infrared spectroscopy method to document DNA damage in the gills of English sole.

In a new joint paper, the researchers report on several biomarkers, including pollution-induced P450 enzyme changes, and on infrared spectral analysis of DNA and measurements of specific modifications to DNA from fish gills and livers using liquid and gas chromatography combined with mass spectrometry (LC/MS,GC/MS). Precision chemical analysis techniques at NIST allowed the researchers to identify and measure damage to adenine and guanine, specific chemical components or bases of DNA, at extraordinarily low levels–five lesions out of a 100 million bases in one case. The results correlated well with earlier research and revealed similar damage to liver DNA (more likely tied to the fish’s food) and gill DNA (more probably reflecting pollutants in water).

The results suggest that these DNA lesions, and others like them, can be used as very sensitive biomarkers to provide a direct measure of the impact of contaminants on fish populations. Moreover, since natural DNA repair processes may gradually reverse the damage in the absence of further insults, these biomarkers also might be used to help assess the efficacy of pollution remediation efforts. The work was funded in part by the National Institute of Environmental Health Sciences (NIH).