title: Non-selective toxicological effects of the insect juvenile hormone analogue methoprene. A membrane biophysical approach.
abstract: The Gram-positive bacterium, Bacillus stearothermophilus, was used as a model organism to identify the non-selective toxic effects of the currently used insecticide methoprene (isopropyl(2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate). A significant decrease of the yield of bacterial cultures and a premature appearance of ultrastructural abnormalities in cells cultured in the presence of the insecticide were taken as indicators of cytotoxicity. A putative correlation of this cytotoxicity with methoprene-induced perturbations on membrane lipid organization was investigated, using differential scanning calorimetry and the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and its propionic acid derivative (DPH-PA). The membrane physical effects depended on the lipid bilayer composition and packing. The most striking effect was a progressive broadening and shifting to lower temperatures, with increasing methoprene concentrations, of the main transition phase of the dimyristoyl- or dipalmitoylphosphatidylcholine bilayers and of the lateral phase separation of liposomes reconstituted with the lipid extracts of B. stearothermophilus.
authors.affiliation: Centro de Neurociências e Biologia Celular, Department of Biochemistry, University of Coimbra, 3001-401 Coimbra, Portugal.
authors.forename: João P
authors.initials: JP
authors.lastname: Monteiro
authors.forename: Romeu A
authors.initials: RA
authors.lastname: Videira
authors.forename: Manuel J
authors.initials: MJ
authors.lastname: Matos
authors.forename: Augusto M
authors.initials: AM
authors.lastname: Dinis
authors.forename: Amália S
authors.initials: AS
authors.lastname: Jurado
mesh_terms: D000818:Animals; D002152:Calorimetry, Differential Scanning; D004161:Diphenylhexatriene / Q000031:analogs & derivatives / Q000737:chemistry; D005454:Fluorescence Polarization; D001411:Geobacillus stearothermophilus / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure; D007605:Juvenile Hormones / Q000737:chemistry / Q000633:toxicity*; D008051:Lipid Bilayers / Q000737:chemistry; D008081:Liposomes / Q000737:chemistry; D008726:Methoprene / Q000737:chemistry / Q000633:toxicity*; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D013696:Temperature
chemical_list: D007605:Juvenile Hormones; D008051:Lipid Bilayers; D008081:Liposomes; D004161:Diphenylhexatriene; C037385:1-(4'-carboxyethyl)-6-diphenyl-1,3,5-hexatriene; D008726:Methoprene