The acute and sub-chronic exposures of goldfish to naphthenic acids induce different host defense responses

► Acute exposure (one week) of goldfish to naphthenic acids (NAs) enhanced pro-inflammatory gene expression in gills, spleen and kidney. ► Macrophages obtained from fish exposed to NAs for one week produced higher levels of reactive oxygen and reactive nitrogen intermediates. ► Goldfish exposed to NAs for one week were more resistant to infection with Trypanosoma carassii. ► Sub-chronic exposure of goldfish (8-12 weeks) to higher (20 mg/L) but not lower (5 mg/L) concentrations of NAs caused a down-regulation in pro-inflammatory gene expression in different tissues. ► Sub-chronic exposure of goldfish to 20 mg/L NAs abrogated the ability of fish to control the infection with T. carassii and caused higher mortality in infected fish.