Environmental and occupational genotoxins
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Investigations on the consequences of contamination of environmental compartments with genotoxins are in progress over the past 60 years leading to the development of the field of genetic toxicology as a discipline in its own right. The genotoxicity testing of nanomaterials has gained increasing importance in recent years. Such environmental and occupational genotoxins interfere directly or indirectly with the functions and the structure of the DNA leading to mutagenesis and may cause cancer. It was therefore desired to bring a dedicated issue of the journal on ‘Environmental and Occupational Genotoxins’ to provide an overview on the current state of important environmentally relevant chemicals and their contamination as genotoxins in diverse organisms both in vitro and in vivo.
The contributions in this issue reflect the importance of nanoparticles as hot topic as environmental genotoxins and also includes reports concerning the release of DNA damaging chemicals of anthropogenic source. The application of nano-materials in diverse fields and their increasing use in healthcare and consumer products pose serious concerns about their environmental and human health impact. The most commonly used parameters of DNA damage in the field of ecogenotoxicology are at present measurements of the comet formation (in single gel cell electrophoresis assays) and induction of micronuclei. The current issue contains a contribution which describes the use of this approach for the detection of DNA damage in tobacco BY-2 cells, Chinese hamster Ovarian cell lines (CHO-K1) and other cancer and non cancerous cell lines.
The articles included in this issue begin with the investigations of aquatic ecosystems utilizing fish to study genotoxic effects in sweet water and marine ecosystems. Experiments with widely used species namely Clarias gariepinus (cat fish) demonstrated significant increase in micronuclei and nuclear aberrations by lead [ https://doi.org/10.1007/s13237-019-00289-w]. Such increased genomic instability may lead to increase of health defects including neoplasms and genetic related disorders, cell dysfunction and/or cell death.
The application of crown gall tumor assay using potato discs has recently been used for analysis of tumor inducing potential of different environmental samples. To check the tumor inducing potential of lead acetate the authors have elegantly established that different concentrations of lead alone and in combination with Agrobaterium tumefaciens were able to induce tumor. The crown gall tumor disc bioassay can be used as a potential and reliable tool for screening the tumor inducing potential of various test agents [ https://doi.org/10.1007/s13237-019-00283-2].
Experts in the field have been recognizing that nanomaterials possess special features that make them challenging from a safety assessment point of view. The genotoxicity testing of nanomaterial has gained increasing importance in recent years. DNA damage (strand breaks), chromosomal damage (chromosomal aberrations, micronuclei) and altered DNA repair signaling pathways are some of the outcomes reported following nanomaterial exposure in the research papers. The cytotoxic and genotoxic potential of zero valent iron nanoparticles (nZVI), unravels further prospects in the safety evaluation of nanomaterials of ecotoxicological relevance [ https://doi.org/10.1007/s13237-019-00294-z].
Silver nano particle (AgNPs) of three different sizes ranging from 15 to 22 nm were studied in Chinese Hamster ovary cell line (CHO-K1) cells for genotoxicity and cytotoxicity. AgNPs were able to internalize in CHO-K1 cells and cause cyto-genotoxicity at size ~ 15 nm [ https://doi.org/10.1007/s13237-019-00295-y]. Testing of magnesium oxide nanoparticles (MgO NPs) on established cell lines at cellular levels using toxicological endpoints provided valuable information about their adverse effects using cytotoxicity, genotoxicity, oxidative stress, cellular apoptosis and cellular uptake studies in cancer (HepG2) and non-cancer (NRK 49F) cell lines [ https://doi.org/10.1007/s13237-019-00298-9]. The anticancer efficacy of graphene oxide-functionalized gold nanoparticles (GO-AuNPs) in human breast cancer cell lines MCF7 and MDA-MB-231 detected detrimental effect in cancer cells through apoptosis. The expression pattern of several proteins established the intrinsic apoptosis pathway in these cell lines after GO-AuNP exposure. GO-AuNPs were found effective in both types of human breast cancer cells viz. hormone-responsive MCF7 and chemoresistant MDA-MB-231 and can be considered as a highly potential anticancer agent in breast cancer therapy[ https://doi.org/10.1007/s13237-019-00284-1]. A simple method to screen suspected genotoxins especially following occupational exposures that is a mechanism-based spectrophotometric titration of nano-alumina powder with calf thymus ds-DNA was carried out at two temperature levels with a view to generating possible mode of interaction between the industrially useful nanopowder and DNA [ https://doi.org/10.1007/s13237-019-00301-3].
Nanoparticles (NPs) provide versatile means to reduce the toxicity enhanced bioactivity and improve targeting of cells. The antioxidant and pro-oxidant effects, or bioavailability and toxicity, of selenium depend on its chemical form and is exploited in the treatment of chemotherapy. The effects of nano-selenium (Nano-Se) were compared with inorganic and organic selenium in Swiss albino mice. Nano-Se was less genotoxic to the mice and possessed ability to modulate the antioxidative defense system and reduce oxidative stress induced and can be promoted as an effective supplement for chemoprevention and incorporated in the formulation of Se- containing pharmaceuticals available in the market [ https://doi.org/10.1007/s13237-019-00303-1].
Furthermore, the present volume contains additionally a review article concerning the cytotoxic and mutagenic effects of green silver nanoparticles in cancer and normal cells [ https://doi.org/10.1007/s13237-019-00293-0] and a follow up short report on the frequency of micronuclei in population of Bhopal exposed to methyl isocyanate in 1984 [ https://doi.org/10.1007/s13237-019-00300-4].
Through this issue an attempt has been made to provide an overview of the current state of the art, challenges and future directions of the assessment of environmental and occupational genotoxins and nanomaterials in particular. It is hoped that the articles contained in this issue will be informative and stimulate the readers to carry out further research aimed at understanding the effects of the release of genotoxins in the environment. A better understanding shall help in prevention of adverse effects in humans and ecosystems from contamination of the biosphere with DNA damaging agents.
The special theme issue is a tribute to Professor Archana Sharma, co-founder of the journal Nucleus. She was instrumental in introducing human genetics, environmental mutagenesis and genetic toxicology in the post graduate curriculum since 1972, and initiated researches in this area at the University of Calcutta. We are thankful to all the authors for their dedication to contribute the articles, to the editors of the Nucleus for their help from time to time, and M/s Springer Nature, their publication team for necessary support for timely processing and publication of this special theme issue.