Suppression of superoxide production by chlorothalonil in striped bass (Morone saxatilus) macrophages: the role of cellular sulfhydryls and oxidativestress

Chlorothalonil (TCIN) is the most commonly applied fungicide in the USA, wi th substantial use in the Chesapeake Bay area. Little is known about the su blethal toxicity of TCIN to fish, but since it is structurally similar to t he immunotoxicant pentachlorophenol, the potential for immunomodulation exi sts. Previous studies have indicated that in vitro exposure of macrophages to TCIN modulates immunostimulated reactive oxygen species (H2O2/hypochloro us acid) and NADPH production in striped bass (Morone saxatilus). The goals of this study were to determine if TCIN inhibits superoxide (O-2(-)) produ ction by macrophage NADPH oxidase, to examine the role of cellular sulfhydr yl groups in TCIN-induced macrophage dysfunction, and to identify the exten t to which lipid peroxidation contributes to the observed toxic effects. Th e results of lucigenin-augmented chemiluminescence assays indicated that TC IN suppressed both baseline and stimulated O-2 production in a dose-depende nt manner. Similar results were obtained using both the particulate stimula ted zymosan and the lipid-soluble stimulant phorbol 12-myristate-13-acetate . Inhibition of glutathione synthesis by pre-treatment with buthionine sulf oximine (BSO) enhanced the suppression of O-2(-) production. The protection of sulfhydryl groups bq culturing macrophages with dithiothreitol (DTT) re duced TCIN-induced macrophage dysfunction. TCIN did not initiate lipid pero xidation in macrophages, as measured by the thiobarbituric acid reactive su bstances (TBARS) assay, nor did pre-treatment with BSO potentiate lipid per oxidation. Because the observed TCIN-induced suppression of O-2 was modulat ed by altering cellular sulfhydryl status with BSO and DTT, it is possible that toxicity results fi um the inhibition of NADPH oxidase activity by TCI N binding to its functional sulfhydryl groups. (C) 2000 Elsevier Science B. V. All rights reserved.