Argemone oil induced cellular damage in the reproductive tissues of transgenic Drosophila melanogaster: protective role of 70 kDa heat shock protein

Potential risk of organophosphate exposure in male reproductive system of a non-target insect model Drosophila melanogaster

Based on several adverse reports of pesticides on reproductive efficiency of various organisms, studies on "reproductive toxicity" have gained importance. Fecundity, reflecting reproductive success of any organism, is governed by several factors from female and male reproductive systems. This present study explored morphological and biochemical alterations in the male reproductive system of a non-target model organism, Drosophila melanogaster following chronic sub-lethal exposure (1^st instar larvae differentially exposed to 1-6 μg/mL until adulthood) to the organophosphate (OP) pesticide, acephate (chronic LC₅₀ 8.71 μg/mL). This study demonstrates altered testis structure, decreased germ cell viability and gross body weight, increased activities of oxidative stress marker lipid peroxidase (LPO), and the endogenous antioxidant enzyme catalase (CAT)in addition with altered expression of reproductive marker proteins like vitellogenin and mitoferrin in acephate-exposed flies when compared to control counterparts. Altered reproductive behavior, indicated by a significant decline in the number of mating pairs, validates the adverse effect of chronic acephate exposure on male reproduction in the non-target insect model D. melanogaster.

Toxicity assessment of sodium fluoride in Drosophila melanogaster after chronic sub-lethal exposure

Sodium fluoride (NaF), one of the most frequently used fluoride compound is composed of Na⁺ and F^-. Apart from its use in water fluoridation, NaF also acts as a major component for different dental products like toothpastes, gels and mouth rinses etc. The present study was carried out to explore the toxic impact of chronic NaF exposure on a non-target organism, Drosophila melanogaster. The larvae exposed to different concentrations of NaF through food showed a significant increase in HSP70 expression both qualitatively and quantitatively. The altered tail length and tail intensity in Comet assay validate the increased DNA damage in treated larvae. The activity of AChE, oxidative stress marker enzymes, phase I and phase II detoxifying enzymes were found to be significantly inhibited in the treated larvae when compared to control though there was no evidence of dose dependent change in each case. The alterations in the mentioned parameters can be due to increased body Fluoride ion (F^-) concentration since the analysis with ion electrode analyzer revealed that F^- concentration increased significantly with NaF treatment. Hence, the results suggest that D. melanogaster manifest prominent toxic response when subjected to chronic exposure to sub-lethal NaF concentrations.

High mobility group protein DSP1 negatively regulates HSP70 transcription in Crassostrea hongkongensis

HSP70 acts mostly as a molecular chaperone and plays important roles in facilitating the folding of nascent peptides as well as the refolding or degradation of the denatured proteins. Under stressed conditions, the expression level of HSP70 is upregulated significantly and rapidly, as is known to be achieved by various regulatory factors controlling the transcriptional level. In this study, a high mobility group protein DSP1 was identified by DNA-affinity purification from the nuclear extracts of Crassostrea hongkongensis using the ChHSP70 promoter as a bait. The specific interaction between the prokaryotically expressed ChDSP1 and the FITC-labeled ChHSP70 promoter was confirmed by EMSA analysis. ChDSP1 was shown to negatively regulate ChHSP70 promoter expression by Luciferase Reporter Assay in the heterologous HEK293T cells. Both ChHSP70 and ChDSP1 transcriptions were induced by either thermal or CdCl2 stress, while the accumulated expression peaks of ChDSP1 were always slightly delayed when compared with that of ChHSP70. This indicates that ChDSP1 is involved, very likely to exert its suppressive role, in the recovery of the ChHSP70 expression from the induced level to its original state. This study is the first to report negative regulator of HSP70 gene transcription, and provides novel insights into the mechanisms controlling heat shock protein expression.

Evaluation of the toxic potential of calcium carbide in the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ)Bg(9)

In the present study the toxic potential of calcium carbide (CaC2) was studied on the third instar larvae of transgenic Drosophila melanogaster (hsp70-lacZ)Bg(9). The third instar larvae were exposed to 2, 4, 8, 16 and 32×10(-3)g/ml of CaC2 in diet for 24h. The results reveal that the dose 2×10(-3)g/ml was not toxic but the remaining doses showed a dose dependent significant increase in the hsp70 expression, β-galactosidase activity, tissue damage, oxidative stress markers (lipid peroxidation and protein carbonyl content), glutathione-S-transferase activity, expression of Caspase 3 and 9, apoptotic index and DNA damage (midgut cells). A significant reduction as compared to control group in total protein, glutathione content and acetylcholinesterase activity was also observed. The Inductively Coupled Plasma Atomic Emission Spectroscopy analysis (ICPAES) reveals the presence of copper, iron, sodium, aluminium, manganese, calcium, nickel and mercury. The toxic effects of CaC2 in the present study may be attributed to the impurities present in it.

The mitochondrial uncoupler 2,4-dinitrophenol attenuates sodium nitroprusside-induced toxicity in Drosophila melanogaster: potential involvement of free radicals

The toxicity of sodium nitroprusside (SNP) (an inducer of oxidative/nitrosative stress) and the attenuation of SNP effects by 2,4-dinitrophenol (DNP) (that induces mild uncoupling of respiration) were evaluated in the Drosophila melanogaster model system. Fly larvae were raised on food supplemented with 1.0 mM SNP, 0.5 or 1.25 mM DNP, or with mixtures 1.0 mM SNP plus 0.5 or 1.25 mM DNP. Food supplementation with SNP decreased larval viability and pupation height whereas supplementation with DNP substantially reversed these changes. Biochemical analyses of oxidative stress markers and activities of antioxidant and associated enzymes were carried out on 2-day-old flies emerged from control larvae and larvae fed on food supplemented with SNP, DNP, or SNP/DNP mixtures. Larval exposure to SNP lowered activities of aconitase, while the presence of DNP reduced the negative impact of SNP by raising aconitase activity back to near control levels. Larval treatment with SNP also elevated the contents of carbonyl protein, uric acid and low molecular mass thiols and produced higher activities of superoxide dismutase, glutathione S-transferase, glucose-6-phosphate dehydrogenase and thioredoxin reductase in adult flies. However, the presence of DNP in the food mixtures prevented SNP-induced changes in thioredoxin reductase and glucose-6-phosphate dehydrogenase activities, as well as uric acid and low-molecular-mass thiol content. The potential mechanisms by which DNP exerts protective effects against SNP toxicity are discussed.

Environmental chemical mediated male reproductive toxicity: Drosophila melanogaster as an alternate animal model

Industrialization and indiscriminate use of agrochemicals have increased the human health risk. Recent epidemiological studies raised a concern for male reproduction given their observations of reduced sperm counts and altered semen quality. Interestingly, environmental factors that include various metals, pesticides and their metabolites have been causally linked to such adversities by their presence in the semen at levels that correlate to infertility. The epidemiological observations were further supported by studies in animal models involving various chemicals. Therefore, in this review, we focused on male reproductive toxicity and the adverse effects of different environmental chemicals on male reproduction. However, it is beyond the scope of this review to provide a detailed appraisal of all of the environmental chemicals that have been associated with reproductive toxicity in animals. Here, we provided the evidence for reproductive adversities of some commonly encountered chemicals (pesticides/metals) in the environment. In view of the recent thrust for an alternate to animal models in research, we subsequently discussed the contributions of Drosophila melanogaster as an alternate animal model for quick screening of toxicants for their reproductive toxicity potential. Finally, we emphasized the genetic and molecular tools offered by Drosophila for understanding the mechanisms underlying the male reproductive toxicity.

Hazardous effect of tannery solid waste leachates on development and reproduction in Drosophila melanogaster: 70kDa heat shock protein as a marker of cellular damage

Rapid industrialization has increased the burden of chemicals in the environment. These chemicals may be harmful to development and reproduction of any organism. We therefore analyzed the adverse effects of leachates from a tannery solid waste on development and reproduction using Drosophila. We show a significant delay in mean emergence of flies observed at the higher concentrations of the leachates, indicating their effect on the organism's development. Significant leachate-induced effect on reproduction of the organism was also observed. Sub-organismal analyses revealed Hsp70 expression and tissue damage in a sex-specific manner. Refractoriness of Hsp70 expression in accessory glands of male flies and ovaries of females was concurrent with tissue damage. Genes encoding certain seminal proteins (Acp70A and Acp36DE) from accessory glands were significantly down-regulated at higher concentrations of the leachates. The study suggests that (i) sub-organismal adverse responses are reflected at organismal level, (ii) tannery waste leachates cause adverse effects on the expression of genes encoding seminal proteins that facilitate normal reproduction and (iii) Hsp70 may be used as a marker of cellular damage for reproductive organs.

Comet assay: a reliable tool for the assessment of DNA damage in different models

New chemicals are being added each year to the existing burden of toxic substances in the environment. This has led to increased pollution of ecosystems as well as deterioration of the air, water, and soil quality. Excessive agricultural and industrial activities adversely affect biodiversity, threatening the survival of species in a particular habitat as well as posing disease risks to humans. Some of the chemicals, e.g., pesticides and heavy metals, may be genotoxic to the sentinel species and/or to non-target species, causing deleterious effects in somatic or germ cells. Test systems which help in hazard prediction and risk assessment are important to assess the genotoxic potential of chemicals before their release into the environment or commercial use as well as DNA damage in flora and fauna affected by contaminated/polluted habitats. The Comet assay has been widely accepted as a simple, sensitive, and rapid tool for assessing DNA damage and repair in individual eukaryotic as well as some prokaryotic cells, and has increasingly found application in diverse fields ranging from genetic toxicology to human epidemiology. This review is an attempt to comprehensively encase the use of Comet assay in different models from bacteria to man, employing diverse cell types to assess the DNA-damaging potential of chemicals and/or environmental conditions. Sentinel species are the first to be affected by adverse changes in their environment. Determination of DNA damage using the Comet assay in these indicator organisms would thus provide information about the genotoxic potential of their habitat at an early stage. This would allow for intervention strategies to be implemented for prevention or reduction of deleterious health effects in the sentinel species as well as in humans.

Diphenyl diselenide [(PhSe)2] inhibits Drosophila melanogaster delta-aminolevulinate dehydratase (delta-ALA-D) gene transcription and enzyme activity

The main objective of the present study was to compare the inhibitory effect of diphenyl diselenide (PhSe)(2) and Pb(2+) on mice and fruit fly delta-Aminolevulinate dehydratase (delta-ALA-D). Optimum pH was quite different for mice (pH 6.5) and flies (pH 8.5). At pH 8.5, the inhibitory potency of (PhSe)(2) was higher for the fruit flies (IC(50) 8.2 micromol/l) than for mice (IC(50) 19.5 micromol/l). Pb(2+) inhibited mice delta-ALA-D at pH 6.5 (IC(50) 6.2 micromol/l) and 8.5 (IC(50) 5.6 micromol/l) with higher potency than the fly enzyme (IC(50) 43.7 micromol/l). delta-ALA-D transcription was reduced by 15% in flies exposed to 0.3 mmol/kg (PhSe)(2), which is similar to the reduction observed in activity measured in the presence of dithiothreitol. The three-dimensional prediction by SWISS-PROT mouse and fly delta-ALA-D revealed differences in the number of hydrogen bonds and turns for the 2 enzymes. Sulfhydryl groups (-SH) that could be oxidized by (PhSe)(2) are conserved in the two sources of enzyme. Distinct responsiveness to pH, (PhSe)(2) and Pb(2+) of these enzymes may be related to subtle differences in tertiary or quaternary structure of mouse and fly delta-ALA-D. Furthermore, mechanism underlying enzyme inhibition after in vivo exposure seems to be different for Drosophila melanogaster and rodent enzymes.

Validation of Drosophila melanogaster as an in vivo model for genotoxicity assessment using modified alkaline Comet assay

The single cell gel electrophoresis or Comet assay is one of the most popular techniques for genotoxicity assessment. The present study was undertaken to validate our previously modified version of the Comet assay for genotoxicity assessment in Drosophila melanogaster (Oregon R(+)) with four well-known mutagenic and carcinogenic alkylating agents, i.e. ethyl methanesulfonate (EMS), methyl methanesulfonate (MMS), N-ethyl-N-nitrosourea (ENU) and cyclophosphamide (CP). Third instar larvae (74 +/- 2 h) of D.melanogaster were fed different concentrations of EMS, MMS, ENU and CP (0.05, 0.5 and 1.0 mM) mixed standard Drosophila food for 24 h. At 98 +/- 2 h, the anterior midgut from control and treated larvae were dissected out, single-cell suspensions were prepared and Comet assay was performed. Our results show a dose-dependent increase in DNA damage with all the four alkylating agents, in comparison to control. The lower concentration (0.05 mM) of the test chemicals, except MMS, did not induce any DNA damage in the gut cells of the exposed larvae. When comparison of Comet parameters was made among the chemicals, MMS was found to be the most potent genotoxicant and ENU the least. The present study validated our previous observation and shows that D.melanogaster is a sensitive and suitable model for the in vivo assessment of genotoxicity using our modified alkaline Comet assay.

Heat shock response:hsp70 in environmental monitoring

Heat shock proteins (Hsps) are a ubiquitous feature of cells in which these proteins cope with stress-induced denaturation of other proteins. Among the different families of Hsps, the 70 kDa family (hsp70) is the most highly conserved and has been most extensively studied. Apart from their primary role in cellular defense under stress condition, a number of studies in recent years have shown the immense potential of hsp70 in pollution monitoring using even transgenic approach both in vivo and in vitro. This article reviews the recent developments in the widespread application of hsp70 in environmental risk assessment.