title: Induction of hsp70, hsp60, hsp83 and hsp26 and oxidative stress markers in benzene, toluene and xylene exposed Drosophila melanogaster: role of ROS generation.
abstract: Exposure to benzene, toluene and xylene in the human population may pose a health risk. We tested a working hypothesis that these test chemicals cause cellular toxicity to a non-target organism, Drosophila melanogaster. Third instar larvae of D. melanogaster transgenic for hsp70, hsp83 and hsp26 and Oregon R(+) strain were exposed to 1.0-100.0 mM benzene, toluene and xylene for 2-48 h to examine the heat shock proteins (hsps), ROS generation, anti-oxidant stress markers and developmental end points. The test chemicals elicited a concentration- and time-dependent significant (p<0.01) induction of the hsps in the exposed organism in the order of hsp70>hsp83>or=hsp26 as evident by beta-galactosidase activity after 24 h. RT-PCR amplification studies in Oregon R(+) larvae revealed a similar induction pattern of these genes along with hsp60 in the order of hsp70>hsp60>hsp26>or=hsp83. Under similar experimental conditions, a significant induction of ROS generation and oxidative stress markers viz. superoxide dismutase, catalase, glutathione S-transferase, thioredoxin reductase, glutathione, malondialdehyde and protein carbonyl content was observed. Sub-organismal response was propagated towards organismal response i.e., a delay in the emergence of flies and their reproductive performance. While hsp70 was predominantly induced in the organism till 24 h of treatment with the test chemicals, a significant or insignificant regression of Hsp70 after 48 h was concurrent with a significant induction (p<0.01) of hsp60>hsp83>or=hsp26 in comparison to the former. A significant positive correlation was observed between ROS generation and these hsps in the exposed organism till 24 h and a negative correlation between ROS generation and hsp70 in them after 48 h indicating a modulatory role of ROS in the induction of hsps. The study suggests that among the tested hsps, hsp70 may be used as an early bioindicator of cellular toxicity against benzene, toluene and xylene and D. melanogaster as an alternative animal model for screening the risk posed by environmental chemicals.
authors.affiliation: Embryotoxicology Section, Indian Institute of Toxicology Research, P.O. Box No. 80, Mahatma Gandhi Marg, Lucknow- 226 001, Uttar Pradesh, India.
authors.forename: Mahendra Pratap
authors.initials: MP
authors.lastname: Singh
authors.forename: M M Krishna
authors.initials: MM
authors.lastname: Reddy
authors.forename: N
authors.initials: N
authors.lastname: Mathur
authors.forename: D K
authors.initials: DK
authors.lastname: Saxena
authors.forename: D Kar
authors.initials: DK
authors.lastname: Chowdhuri
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001554:Benzene / Q000633:toxicity*; D018834:Chaperonin 60 / Q000096:biosynthesis*; D029721:Drosophila Proteins / Q000096:biosynthesis*; D004331:Drosophila melanogaster; D005298:Fertility / Q000187:drug effects; D008401:Gas Chromatography-Mass Spectrometry; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006358:Hot Temperature; D015227:Lipid Peroxidation / Q000187:drug effects; D018384:Oxidative Stress / Q000502:physiology*; D050050:Protein Carbonylation / Q000187:drug effects; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012098:Reproduction / Q000187:drug effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D052617:Solid Phase Microextraction; D012997:Solvents; D014050:Toluene / Q000633:toxicity*; D014992:Xylenes / Q000633:toxicity*
chemical_list: D000975:Antioxidants; D018834:Chaperonin 60; D029721:Drosophila Proteins; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; C087442:Hsp26 protein, Drosophila; C089272:Hsp83 protein, Drosophila; D017382:Reactive Oxygen Species; D012997:Solvents; D014992:Xylenes; D014050:Toluene; D012313:RNA; D001554:Benzene