Acute toxic responses of the rockfish (Sebastes schlegeli) to Iranian heavy crude oil: Feeding disrupts the biotransformation and innate immune systems

• We observed the variation of innate immune and biotransformation system in Iranian Heavy crude oil-fed fish.
• Some of immune disturbance was shown in the fish exposed to Iranian Heavy crude oil.
• Immune disturbance may allow pathogens to more easily affect fish including infectious diseases.
• The present work is the first account of the “Hebei spirit” spilled oil on fish innate immune system.

To clarify the toxic effects of Iranian Heavy Crude Oil (IHCO) from the “Hebei spirit” oil spill, innate immune toxic effects defending on biotransformation pathway have been investigated on fish exposed to IHCO. Juvenile rockfish were exposed to IHCO in gelatin capsules by feeding. The effects on multiple fish biotransformation enzymes (Cytochrome P4501A and glutathione-S-transferase) and the expression level of the several immune response genes, including interleukin-1beta, granulocyte colony-stimulating factor and Cathepsin L, were measured in the liver, spleen and kidney. The tissue-specific expression patterns of these genes demonstrated that the highest expression levels of Cytochrome P4501A, glutathione-S-transferase, interleukin-1beta, granulocyte colony-stimulating factor, interferon stimulated gene 15 and Cathepsin L were found in the liver and that the TNF receptor was high in spleen. The oil-fed fish had significantly higher concentrations of biliary fluorescent metabolites and Cytochrome P4501A expression during the initial stage (12 ∼ 48 h after exposure) than those in the liver and kidney of the sham group. Similarly, the highest mRNA expression levels of interleukin-1beta and granulocyte colony-stimulating factor were detected in the liver at the early stages of exposure (12 h after exposure). Following exposure, the levels of interferon stimulated gene 15 and granulocyte colony-stimulating factor mRNA remained high at 120 h after exposure in the liver but the levels of interleukin-1beta and Cathepsin L gradually decreased to an expression level equal to or less than the sham group. Our data suggest that the innate immune and hepatodetoxification responses in oil-fed fish were induced at the initial stage of exposure to the IHCO at the same time but several immune-related genes decreased to less than that of the sham group after the initial stage of response. Therefore, immune disturbances in fish exposed to IHCO may allow the pathogens, including the infectious diseases, to more easily affect the oil exposed fish.