Structure-activity relationships for the impact of selected isothiazol-3-one biocides on glutathione metabolism and glutathione reductase of the human liver cell line Hep G2.
To investigate the toxic mode of action of isothiazol-3-one biocides the four compounds N-methylisothiazol-3-one (MIT), 5-chloro-N-methylisothiazol-3-one (CIT), N-octylisothiazol-3-one (OIT) and 4,5-dichloro-N-octylisothiazol-3-one (DCOIT) were purified and tested as single chemical entities for their effects on the human hepatoblastoma cell line Hep G2 and on isolated and cellular glutathione reductase GR). The two chlorinated substances CIT and DCOIT significantly decreased the amount of total cellular glutathione (GSx) in a dose and time dependent manner. Concomitantly, an increase in the level of oxidised glutathione (GSSG) was observed. The resulting shift in the GSH/GSSG ratio entailing the breakdown of the cellular thiol reduction potential was accompanied by necrotic morphological changes like swelling of the plasma membrane and subsequent lysis of the cells. Additionally, CIT and DCOIT were found to inhibit cellular GR in the cells in a concentration dependent manner. The T-SAR-based (thinking in terms of structure-activity relationships) comparison of the chlorine-substituted structures CIT and DCOIT with their non-chlorinated and less active analogues MIT and OIT identified the chlorine substituents and the resulting reaction mechanisms to be the key structural mediators of the observed toxic effects. Furthermore, differences in the activity of both chlorinated substances could be explained using the T-SAR approach to link the lipophilicity and the intrinsic glutathione-reactivity of the compounds to the expected target site concentrations inside the cells.
Arning
Jürgen
J
UFT - Centre for Environmental Research and Technology, University of Bremen, Leobener Strabe, D-28359 Bremen, Germany. jarning@uni-bremen.de
Dringen
Ralf
R
Schmidt
Maike
M
Thiessen
Anette
A
Stolte
Stefan
S
Matzke
Marianne
M
Bottin-Weber
Ulrike
U
Caesar-Geertz
Birgit
B
Jastorff
Bernd
B
Ranke
Johannes
J
D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000473:pathology; D004202:Disinfectants / Q000737:chemistry / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D019803:Glutathione Disulfide / Q000378:metabolism*; D005980:Glutathione Reductase / Q000378:metabolism*; D022781:Hepatocytes / Q000187:drug effects* / Q000201:enzymology; D006801:Humans; D021281:Quantitative Structure-Activity Relationship; D013844:Thiazoles / Q000633:toxicity*
D004202:Disinfectants; D013844:Thiazoles; D005980:Glutathione Reductase; D019803:Glutathione Disulfide