title: Activation of a stress-induced gene by insecticides in the midge, Chironomus yoshimatsui.
abstract: Stress proteins (heat shock proteins, HSPs) have been proposed as general biomarkers for environmental monitoring. In the present study, we evaluated the environmental stress-burden on the aquatic midge Chironomus yoshimatsui using hsp70 expression. Larvae collected from streams receiving polluted runoff (field strain) were resistant to the organophosphorus insecticide, fenitrothion (F), and the synthetic pyrethroid, ethofenprox (E), whereas a strain originally collected from an unpolluted area (susceptible strain) showed low resistance to insecticide exposure. To examine the expression of an HSP70 gene in C. yoshimatsui, an hsp70 cDNA probe was prepared using RNA obtained from the field strain larvae and used for Northern blot analyses. The expression of this HSP70 gene in larvae collected from two field sites in May about 1 week after insecticide spraying in the fields was 2.3 (p = 0.018) to 3.3 fold higher than that in the susceptible strain and was also 4.6 and 1.4 (p = 0.033) fold higher than those collected in November 3 months after the cessation of insecticide spraying. In order to identify potential inducers of the HSP70 gene of the field strain, larvae of the susceptible strain were exposed to F or E for 24 h and hsp70 mRNA levels determined. Exposures to F at 0.4 microg/L and E at 1.1 microg/L increased hsp70 mRNA levels 2.7 (p = 0.049) and 4.4 (p = 0.043) fold over controls, respectively. These results suggest that larvae collected from polluted areas are burdened by environmental stressors and the tested insecticides are potential inducers of HSP70. The results also support the suggestion that HSP70 gene expression is a sensitive indicator of low level (nonlethal) exposures to certain insecticides.
authors.affiliation: Laboratory of Environmental Molecular Physiology, School of Life Science, Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo 192-0392, Japan. yocchan@ls.toyaku.ac.jp
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Yoshimi
authors.forename: Kozue
authors.initials: K
authors.lastname: Minowa
authors.forename: Natalie K
authors.initials: NK
authors.lastname: Karouna-Renier
authors.forename: Chiharu
authors.initials: C
authors.lastname: Watanabe
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Sugaya
authors.forename: Takashi
authors.initials: T
authors.lastname: Miura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002219:Carbamates / Q000633:toxicity; D002683:Chironomidae / Q000187:drug effects / Q000235:genetics*; D004784:Environmental Monitoring; D005278:Fenitrothion / Q000633:toxicity; D005786:Gene Expression Regulation; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics*; D007306:Insecticides / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000235:genetics; D007928:Lethal Dose 50; D008969:Molecular Sequence Data; D048448:Phenylcarbamates; D011722:Pyrethrins / Q000633:toxicity; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: D002219:Carbamates; D018840:HSP70 Heat-Shock Proteins; D007306:Insecticides; D048448:Phenylcarbamates; D011722:Pyrethrins; D012333:RNA, Messenger; C076840:ethofenprox; C052034:fenoxycarb; D005278:Fenitrothion