Exploring the Potential Interference of Estuarine Sediment Contaminants with the DNA Repair Capacity of Human Hepatoma Cells

Abstract

Estuaries may be reservoirs of a wide variety of pollutants, including mutagenic and carcinogenic substances that may impact on the ecosystem and human health. A previous study showed that exposure of human hepatoma (HepG2) cells to extracts from sediment samples collected in two areas (urban/industrial and riverine/agricultural) of an impacted estuary (Sado, Portugal), produced differential cytotoxic and genotoxic effects. Those effects were found to be consistent with levels and nature of sediment contamination. The present study aimed at evaluating whether the mixtures of contaminants contained in those extracts were able to modulate DNA repair capacity of HepG2 cells. The residual level of DNA damage was measured by the comet assay in cells exposed for 24 or 48 h to different extracts, after a short preexposure to a challenging concentration range of ethyl methanesulfonate (EMS), as a model alkylating agent. The results suggested that the mixture of contaminants present in the tested samples, besides a potential direct effect on the DNA molecule, may also interfere with DNA repair mechanisms in HepG2 cells, thus impairing their ability to deal with genotoxic stress and, possibly, facilitating accumulation of mutations. Humans are environmentally/occupationally exposed to mixtures rather than to single chemicals. Thus, the observation that estuarine contaminants induce direct and indirect DNA strand breakage in human cells, the latter through the impairment of DNA repair, raises additional concerns regarding potential hazards from exposure and the need to further explore these endpoints in the context of environmental risk assessment.

A review on impact of water pollution on freshwater fish species and their aquatic environment

“…Aquatic ecosystems are delicate and at high risk mostly due to the majority of pollutants derived from domestic, urban and industrial sources i.e. various agricultural practices ( Figure 1) result in the release of pollutants into the riverine system (Kaur and Dua, 2014;Pinto et al, 2015;Byrne et al, 2015). Mainly in aquatic ecosystem, the most frequent contaminants are in the forms of heavy metals and pesticides (Khoshnood, 2016).…”

Water physicochemical factors and oxidative stress physiology in fish, a review

“…Any inadvertent alteration to an ecosystem's natural characteristics brought on by adjustments to its physical, chemical, and biological components is referred to as "pollution" (Subhendu, 2000). Aquatic ecosystems are vulnerable and at great risk as a result of a large number of pollutants coming from home, urban, and industrial sources, as well as various farming practices that leak contaminants into the river system (Byrne et al, 2015;Kaur and Dua, 2015;Pinto et al, 2015).…”

Current aspects of DNA damage and repair in ecotoxicology: a mini-review

“…One of the simplest, yet effective, methods to determine the extent to which pollutants interfere with DNA repair is to elicit damage using a model genotoxicant or mutagen such as ethyl methanesulfonate (EMS) and see if cells can repair it while exposed to the target pollutants compared to a control or reference. For example, Pinto et al (2015) revealed that sediment extracts from impacted estuarine areas containing complex mixtures of organic and inorganic pollutants could cause DNA damage and inhibit DNA repair in human HepG2 cells. The authors made use of EMS and the common alkaline single-cell gel electrophoresis assay, or as it is more commonly known, the Comet assay (Singh et al 1988) to determine DNA damage.…”