Environmental Toxicology

Overview

The environment has changed unimaginably since its existence, to support life, offering optimal ecological niches, across the course of evolution to more than 1.7 million of the world's species, covering every possible taxon. The global trend of industrialization, urbanization and tremendous anthropogenic activities has resulted in the contamination of habitats with various synthetic chemicals to alarming levels that can potentially threaten the very existence of life. Environmental toxicology refers to the scientific study of the potential effects of these anthropogenic compounds on organisms, populations and by extension, the ecosystem. The significant challenge in this study area is to create efficient ways to predict toxic potency and exposure levels for chemicals that lack toxicological and exposure data in environmental settings. The demand to assess large numbers of chemicals for hazard identification in a cost- and time-efficient manner, therefore, generated the need for high-throughput assays. The need for high-throughput toxicity testing coupled with ethical concerns over animal testing necessitated the pursuit of better tools for ecotoxicological studies. Hence, the development, validation and application of high throughput alternate models as well as alternative to animal models for ecotoxicity studies are high priority in eco-toxicology. The information on usage, exposure and effects obtained from quantitative structure-activity relationships, read-across methods, thresholds of toxicological concern and in vitro tests prior to in vivo testing are ideal route for more rapid, efficient, and cost effective risk assessment of chemicals. A major challenge is the development of diagnostic capabilities to precisely determine the cause-effect relationships within impaired ecosystems. This will help in determining the extent to which existing remediation strategies/technologies are effective, and the refinements needed in risk management.

Mission and goals
Generation of knowledge/tools useful for protection as well as management of ecosystem integrity and to advance the understanding of ecotoxicological problems across different ecological strata at cellular, genetic and organismal levels in order to improve environmentally relevant ecological risk assessment.

Competencies

  • Mechanism of toxicity of environmental pollutants
  • Development of sensors and markers for detection of biological contaminants
  • Remediation of hazardous and persistent chemical substances from soil and waste waters
  • Ecotoxicity and environmental impact assessment

MIRNA profiling provides insights on adverse effects of Cr(VI) in the midgut tissues of Drosophila melanogaster

Cr(VI), a well-known environmental chemical, is reported to cause various adverse effects on exposed organisms including genomic instability and carcinogenesis. Despite available information on the underlying mechanism of Cr(VI) induced toxicity, studies regarding toxicity modulation by epigenetic mechanisms are limited. It was therefore, hypothesized that the global miRNA profiling in Cr(VI) exposed Drosophila, a genetically tractable model organism, will provide information about mis-regulated miRNAs along with their targeted genes and relevant processes. Third instar larvae of Drosophila melanogaster (Oregon R+) were exposed to 5.0-20.0 ?g/ml of Cr(VI) for 24 and 48 h. Following miRNA profile analysis on an Agilent platform, 28 of the 36 differentially expressed miRNAs were found to be significantly mis-regulated targeting major biological processes viz., DNA damage repair, oxidation-reduction processes, development and differentiation. Down-regulation of mus309 and mus312 under DNA repair, acon to oxidation-reduction and pyd to stress activated MAPK cascade respectively belonging to these gene ontology classes concurrent with up-regulation of dme-miR-314-3p, dme-miR-79-3p and dme-miR-12-5p confirm their functional involvement against Cr(VI) exposure. These findings assume significance since majority of the target genes in Drosophila have functional homologues in humans. The study further recommends Drosophila as a model to explore the role of miRNAs in xenobiotic induced toxicity. Chandra et al (2015) J Hazardous Materials 283:558-67.

Exposure to endosulfan influences sperm competition in Drosophila melanogaster

Dwindling male fertility due to xenobiotics is of global concern. Accordingly, male reproductive toxicity assessment of xenobiotics through semen quality analysis in exposed males, and examining progeny production of their mates is critical. These assays, in part, are biased towards monogamy. Females soliciting multiple male partners (polyandry) is the norm in many species. Polyandry incites sperm competition and allows females to bias sperm use. However, consequences of xenobiotic exposure to the sperm in the light of sperm competition remain to be understood. Therefore, we exposed Drosophila melanogaster males to endosulfan, and evaluated their progeny production as well as the ability of their sperm to counter rival control sperm in the storage organs of females sequentially mated to control/exposed males. Endosulfan (2?g/ml) had no significant effect on progeny production and on the expression of certain genes associated with reproduction. However, exposed males performed worse in sperm competition, both as 1st and 2nd male competitors. These findings indicate that simple non-competitive measures of reproductive ability may fail to demonstrate the harmful effects of low-level exposure to xenobiotics on reproduction and advocate consideration of sperm competition, as a parameter, in the reproductive toxicity assessment of xenobiotics to mimic situations prevailing in the nature. Misra et al (2014) Sci Rep 4: 7433.

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