Hydrogen peroxide production and bactericidal activity in pronephros phagocyte sub-populations from Fundulus heteroclitus following exposure to pentachlorophenol

Antimicrobial activities of phagocytic cells serve as a first line of defense against invading pathogens; therefore, suppression of these functions by exposure to environmental contaminants should ultimately lead to decreased resistance to infectious diseases. To test this hypothesis, the ability of pronephric phagocytes from an estuarine fish, Fundulus heteroclitus, to produce reactive oxygen intermediates (ROIs) and kill a pathogenic strain of bacteria was studied following in vitro exposure to sublethal doses of pentachlorophenol (PCP). Enriched cultures of macrophages and eosinophils were exposed to 0–20 mg/liter PCP. The cells were then assayed for hydrogen peroxide (H2O2) production and bactericidal activity against Listonella anguillarum, the etiological agent responsible for vibriosis in marine and estuarine fish. In the absence of PCP, the production of H2O2 and bactericidal capacity were significantly greater in eosinophils than in macrophages. Macrophage and eosinophil bactericidal activity was inhibited by PCP concentrations ≥ 5 mg/liter and ≥ 10 mg/liter, respectively; at 20 mg/liter, bactericidal activity was essentially eliminated in both cell types. Although changes in H2O2 production were not detected in either phagocyte population following exposure to PCP, previous studies have shown such treatment significantly inhibits phagocytosis and the production of Superoxide. Taken with the current results, these data indicate that suppression of these activities by chronic PCP exposure could result in decreased cell-mediated protective capacity against pathogens.