Research on genotoxic effects of pollutants

About the Institute

The Institute of Hygiene & Occupational Medicine (Institut für Hygiene und Arbeitsmedizin) is part of the University of Duisberg-Essen, and is located in the University Hospital in Essen, Germany. The primary function of the institute concerns occupational health and environmental pollutants affecting health.

Professor Dr. Elke Dopp is the Chief Scientist & Head of the Division of In-vitro & Molecular Toxicology and the main focus of her research is genotoxicity of environmental pollutants in water, airborne particles and nanoparticles. Professor Dr. Dopp also holds the position of Lecturer for Environmental Hygiene at the University Hospital, Essen.

Comet Assay in the research

The Comet assay has played a significant role in the research carried out since it was first conducted at The Institute of Hygiene & Occupational Medicine in 2002. Depending upon the number of projects running, there are usually between eight and ten people utilizing the assay for genotoxicity studies of pollutants. Projects which have involved the comet assay to date include:

Genotoxicity of metal(oid) organic compounds.
Genotoxicity of Titanium dioxide nanoparticles
Analysis of early genomic changes in arsenic-exposed human urothelial cells
Investigations into toxic oxidation by-products in waste water
Toxicity tests of water pollutants

Currently, there are two major projects which utilise the Comet Assay and involve collaboration with the following institutes:

Research Institute for Prevention and Occupational Medicine of the German Social Accident Insurance, Ruhr University, Bochum, Germany (IPA)
Institute of Energy and Environmental Technology, Duisburg, Germany (IUTA)
IWW Water Centre, Mülheim, Germany
Institute of Biological Sciences, Cell Biology and Biosystems Technology, University of Rostock, Germany
FOCAS Institute, Dublin Institute of Technology, Ireland

Assessment and prevention of toxic oxidation by-products during oxidative waste water treatment.

The main purpose of this research is to provide a basis for the improvement of advanced oxidation processes during the treatment of complex urban waste water. It is therefore important that substances are not only eliminated but also that no toxic oxidation by-products are generated.

The in-vitro, alkaline comet assay is performed as described by Singh and his co-workers (Singh et al., 1988) using the Chinese hamster ovary, CHO-9 cell-line with minor modifications. SYBR-Green® is the fluorescent dye used to stain the DNA. Slides are examined under excitation with a Leica DMLB microscope (40x objective) and scored using Perceptive Instruments Comet Assay IV system. Olive Tail Moment is the parameter chosen to quantify the level of DNA damage following exposure.

Early molecular changes in the genome of arsenic-exposed human urothelial cells depending on cellular uptake and biotransformation.

Epidemiological studies have indicated that exposure of humans to inorganic arsenic in drinking water is associated with the occurrence of bladder cancer. The World Health Organisation currently classifies arsenic as the most harmful toxin in drinking water worldwide (WHO, 2001). Although temporary high doses are applied in cancer therapy, chronic low dose exposure may increase the risk of cancers such as bladder cancer (for review, see Tseng, 2007).

The aim of this research is to elucidate mechanisms by which arsenic and its metabolites may induce this malignancy. One study which has already been published studied the uptake capabilities of the UROtsa cell-line (immortalized human urothelial cells) and the HepG2 cell-line (human hepatoma cells). The comet assay was used to study the genotoxicity of different arsenic compounds in these two cell types (Dopp et al., 2008).

The study showed that the uptake of arsenic compounds appeared to be highly dependent upon cell type and arsenic species. Non-methylating urothelial cells accumulate higher amounts of arsenic species than the methylating hepatocytes. Both cyto- and genotoxic effects are more distinct in hepatocytes.

Further work is continuing to elucidate the role of speciation and methylation for the toxicity and carcinogenicity of arsenic.

Comet Assay IV

The Perceptive Instruments Comet Assay IV was chosen as the scoring system to use in her comet assay studies for its speed, reproducibility and ease of use.

Professor Dr. Dopp will continue using the comet assay for ongoing and future investigations into genotoxicity of pollutants in the workplace and wider environment.

Publications/References

Titanium dioxide nanoparticles induce oxidative stress and DNA-adduct formation but not DNA-breakage in human lung cells. Bhattacharya, K., Davoren, M, Boertz, J; Schins, R.P.F., Hoffmann, E. & Dopp, E. Particle and Fibre Toxicology (2009), 6(1):17.

Subcellular distribution of inorganic and organic arsenic compounds in human urothelial cells and human hepatocytes. Dopp, E., von Recklinghausen, U. Hartmann, L.M., Stueckradt, I., Pollok, I., Rabieh, S., Ping, Y., Nüssler, A., Katier, C., Hirner, A.V., Rettenmeier, A.W. Drug Metabolism and Disposition. (2008), 36:5, 971-979.

Cellular uptake, subcellular distribution and toxicity of arsenic compounds. Dopp, E., von Recklinghausen, U., Rabieh, S., Nussler, A.K., Boertz, J., Hirner, A.V., Rettenmeier, A.W. Environmental Research. (2010), 110:5, 435-442.

A simple technique for the quantitation of low levels of DNA damage in individual cells. Singh, N.P., McCoy, M.T., Tice, R.R., Schneider, E.L. Experimental Cell Research. (1988), 175: 184-191.

Arsenic methylation, urinary arsenic metabolites and human diseases: current perspective Tseng, C.H. Journal of Environmental Science and Health, Part C. Environmental Carcinogenesis & Ecotoxicology Reviews. (2007), 25: 1-22.

Arsenic and arsenic compounds. International Programme on Chemical Safety. World Health Organisation. Environmental Health Criteria (2001), 224.