Adverse effect of tannery waste leachates in transgenic Drosophila melanogaster: role of ROS in modulation of Hsp70, oxidative stress and apoptosis

Abstract

Leachate is a complex chemical mixture of chemicals produced as a result of leaching of solid wastes. The potential toxicity of leachates is a major environmental health concern. The present study evaluated the role of ROS in tannery leachates induced Hsp70 expression, antioxidant enzymes and apoptosis in Drosophila. Different concentrations (0.05-2.0%) of leachates prepared from tannery waste at different pH (7.00, 4.93 and 2.88) were mixed with Drosophila food and fed to the larvae for 2-48 h to examine the different stress and apoptotic markers. A concentration- and time-dependent significant increase in Hsp70 expression, ROS generation, antioxidant enzymes activities and MDA content were observed in the exposed larvae. Activities of antioxidant enzymes were delayed compared with Hsp70 expression and MDA level in the exposed organisms. Apoptotic cell death was observed in the exposed larvae at higher concentrations concurrent with a significant regression in Hsp70 along with a higher level of ROS generation. A positive correlation drawn between ROS generation and apoptotic markers and a negative correlation between apoptotic markers and Hsp70 expression at these concentrations indicated the important role of ROS in the induction of cellular damage in the exposed organisms. There was a significant generation of ROS in the larvae exposed to 0.5% of leachates which did not interfere with the protection of their cells by Hsp70 and antioxidant enzymes. However, generation of significantly higher levels of ROS in the larvae exposed to 1.0% and 2.0% leachates may decrease Hsp70 expression thus leading to mitochondria-mediated caspase-dependent apoptotic cell death.

Heat shock proteins in toxicology: How close and how far?

“…Although elevated temperature is the classic inducer of heat shock proteins, it is now clear that a variety of other stresses including pesticides, heavy metals, solvents and effluents can induce heat shock proteins (Stringham et al 1992;Stringham and Candido 1994;Guven and de Pomerai 1995;Candido and Jones 1996;Mutwakil et al 1997;Chowdhuri et al 1999;Gupta et al 2005a,b;Nazir et al 2006;Gupta et al 2007a,b;Siddique et al 2007Siddique et al , 2008Siddique et al , 2009Bhargav et al 2008;Singh et al 2009). Under stress conditions, the newly synthesized stress proteins play an essential role in maintaining cellular homeostasis by assisting correct folding of nascent and stressaccumulated misfolded proteins, preventing protein aggregation or promoting selective degradation of misfolded or denatured proteins (Schlesinger 1990;Morimoto 1993;Sikora and Grzesiuk 2007;Saluja and Dudeja 2008).…”

“…hsp70, hsp83 and hsp26 tagged with reporter genes like β-galactosidase or GFP have been used to detect cellular stress caused by environmental chemicals or their mixtures. The assays designed allow for quantification of the extent of stress gene expression following environmental chemicals exposure, suggesting the extent of cellular toxicity inflicted by the chemicals (Chowdhuri et al 1999;Gupta et al 2005aGupta et al ,b, 2007aNazir et al 2006;Siddique et al 2007Siddique et al , 2008Siddique et al , 2009Bhargav et al 2008;Singh et al 2009). Another model organism, Caenorhabditis elegans, with both its hsp70 and hsp16 promoters tagged with the lacZ reporter gene, has been used to a great extent to examine the cellular toxicity of heavy metals or their mixtures (Stringham et al 1992;Stringham and Candido 1994;Guven and de Pomerai 1995;Candido and Jones 1996).…”

Detection of DNA Damage in Drosophila and Mouse

“…Drosophila has hence found extensive use as a model organism in various fields including toxicology testing. [33][34][35][36][37][38] Concerns have been raised about the ethics and use of animals for toxicology research and testing, and emphasis now is given to the use of alternatives to mammals in research as well as education. The European Centre for the Validation of Alternative Methods (ECVAM) promotes scientific and regulatory acceptance of alternative methods for reducing, refining or replacing the use of laboratory animals 39,40 and recommends D. melanogaster as an alternative to animal models for testing and research.…”

Drosophotoxicology: The growing potential for Drosophila in neurotoxicology

“…Hsp70 is a highly responsive stress gene with fairly low specificity with respect to environmental stressor. Nonetheless, this reporter has served as a rapid readout of toxicity in larval and adult feeding assays of specific organophosphates as well as complex mixtures of industrial leachates [43,92]. In addition, immunohistochemical analysis of the reporter reveals tissue specific patterns of toxic insult that expose sex-linked differences in response [43].…”

“…Reporter gene response could be monitored at any stage of development using modes of delivery summarized in Figure 1. For example, a simple assay would involve feeding E(spl)-lacZ larvae on media containing various concentrations or compositions of agents for a defined time and determining β-galactosidase levels in homogenates of larvae by standard chemical substrate assays [92]. Through optimization of larval sample handling techniques this approach could be adapted to a multi-well format for high throughput.…”