Humic Substances and Crude Oil Induce Cytochrome P450 1A Expression in the Amazonian Fish Species Colossoma macropomum (Tambaqui)

Abstract

Cytochrome P450 1A (CYP1A) induction is used widely as a biomarker of exposure to pollutants, such as petroleum hydrocarbons, yet CYP1A inducibility has been characterized in few tropical fish. Using Western blot analysis, catalytic assay, and immunohistochemistry, we evaluated CYP1A induction in an Amazonian fish (tambaqui; Colossoma macropomum) acclimated to humic substances (HS) and acutely exposed to crude oil. HS are ubiquitous in Amazonian waters, and they are known to affect the bioavailability of pollutants. CYP1A activity was also measured in fish exposed for 10 days to a range of concentrations of HS from both natural and commercial sources. Crude oil induced CYP1A expression in tambaqui, as expected. Exposure to both HS and crude oil resulted in greater levels of CYP1A expression relative to that in fish exposed to petroleum alone. Interestingly, CYP1A induction was also observed in fish exposed to HS alone. Induction by HS was concentration-dependent, and activity was higher in fish exposed to HS from the commercial source than in fish exposed to the HS from the natural source. The use of CYP1A as a biomarker of exposure to pollutants such as petroleum hydrocarbons in fish living in environments rich in humic substances should be considered with caution given that HS themselves induce CYP1A expression. Our results suggest that there may be as yet unknown CYP1A inducing components (aryl hydrocarbon receptor agonists) in humic substances.

Organic carbon source in formulated sediments influences life traits and gene expression of Caenorhabditis elegans

“…In the present study, only one concentration was applied. However, it was previously shown with fish and cladocerans that the response follows exposure concentrations (Meems et al 2004;Matsuo et al 2006). Consequently, the impact of SOM on life trait variables of C. elegans is surely modulated, if the SOM concentration varies.…”

“…Overall, the phenotypic and molecular reactions of C. elegans indicate that the worm tends to recognize not yet characterized P constituents as weak ''natural'' xenobiotics which induced Phase I and II genes. In previous papers, the potential of HSs to induce even the synthesis of the concerning enzymes was shown (Matsuo et al 2006). From a previous whole genomic DNA microarray study with C. elegans exposed to two different humic substance sources (Menzel et al 2005b), it is well understood that the transcription patterns as well as the induction strengths strongly vary from source to source.…”

Different natural organic matter isolates cause similar stress response patterns in the freshwater amphipod, Gammarus pulex

“…G. pulex is reported to be intolerant to changes in oxygen regime and is considered an indicator of "clean water" (Mason 1981). Specimens of G. pulex were collected from several shallow creeks in the vicinity of Kiel (Schleswig-Holstein, Northern Germany).…”

Exposure to humic material modulates life history traits of the cladoceransMoina macrocopaandMoina micrura

“…• transcriptionally controlled induction of stress proteins and antioxidant enzymes [7]; • development of oxidative stress symptoms, including lipid peroxidation [8]; and • induction and modulation of biotransformation enzymes [6,[8][9][10][11][12].…”