Involvement of Cytochrome P450 1A in the toxicity of aryl hydrocarbon receptor agonists : alteration arachidonic acid metabolism and production of reactive oxygen species
Schlezinger, Jennifer J.
MetadataShow full item record
Two cytochrome P4501A-dependent mechanisms of aryl hydrocarbon receptor (AhR) agonist toxicity were examined in the marine teleost scup (Stenotomus chrysops), alteration of arachidonic acid (AA) metabolism and production of reactive oxygen species (ROS). In scup hepatic microsomes, cytochrome P450s including CYP1A and CYP2B-like proteins catalyzed regioselective metabolism of AA to eicosatrienoic and hydroxyeicosatetraenoic acids. Benzo[a]pyrene (BP) treatment induced liver microsomal AA metabolism, but that effect varied with season. Endogenous AA epoxides were recovered from scup liver, heart, and kidney, and their composition in the liver was altered by treatment with BP or 2,3,7,8-tetrachlorodibenzo-p-dioxin. In scup and mammals, the formation of ROS was stimulated by binding of 3,3',4,4-tetrachlorobiphenyl (TCB) to CYP1A, apparently CYP1Al. Attack of that ROS inactivated scup CYP1A. ROS release and inactivation of CYP1A were stimulated only by substrates of CYP1A that are slowly metabolized. In vivo, 3,3',4,4',5- pentachlorobiphenyl (PeCB) potently induced CYP1A mRNA, protein and catalytic activity at low doses (0.01-0.1 mg/kg), suppressed induction of CYP1A protein and catalytic activity at a high dose (1 mg/kg) and transiently induced oxidative stress in scup liver. The suppression of CYP1A induction was organ-dependent, with hepatic CYP1A being most susceptible to inactivation. The results suggest that ROS could be involved in the in vivo suppression of scup liver CYP1A by planar halogenated aromatic hydrocarbons. The reactive oxygen sensitive transcription factor, nuclear factor-KB (NF-KB), was characterized in scup. An NF-KB consensus binding sequence bound specifically to 3 proteins in scup liver, heart and kidney. One protein was recognized by an antibody to mammalian p50. Injection alone appeared to activate NF-KB. BP did not increase the activation ofNF-KB, and PeCB activated NF-KB in only 1 of 2 experiments. Last, CYP1A induction in endothelial cells of the American eel (Anguilla rostrata), a site which may be particularly susceptible to alterations in AA metabolism and ROS production, was described. Eel liver CYP1A responded to BP, 13-naphthoflavone and TCB in a dose-dependent fashion, and induction was correlated with hepatic inducer concentration. Endothelial CYP1A was inducible in a number of organs and was metabolically active. In the rete mirabile, penetration of endothelial CYP1A induction increased with increasing dose of AhR agonists, corresponding with an increase in inducer concentration. A transition from endothelial to epithelial staining occurred in the gill, heart and kidney at high inducer doses.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1998
Suggested CitationThesis: Schlezinger, Jennifer J., "Involvement of Cytochrome P450 1A in the toxicity of aryl hydrocarbon receptor agonists : alteration arachidonic acid metabolism and production of reactive oxygen species", 1998-08, DOI:10.1575/1912/5152, https://hdl.handle.net/1912/5152
Showing items related by title, author, creator and subject.
Diversity and characterization of novel Cytochrome P450 2 genes in the marine teleost Fundulus Heteroclitus Oleksiak, Marjorie F. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1997-09)The multiplicity and roles of cytochrome P450 CYP genes in the 2 family are not well known in fish. Characterizations of CYP2 genes were done in the killifish, Fundulus heteroclitus. Multiple cDNAs from three CYP2 ...
Xenobiotic monooxygenase activity and the response to inducers of cytochrome P-450 during embryonic and larval development in fish Binder, Robert L. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1981-08)Data demonstrating the presence and inducibility of the xenobiotic monooxygenase system in fish embryos and larvae are described. The ontogeny of benzo(a)pyrene monooxygenase (BPM) activity, and NADPH- and NADH-cytochrome ...
Purification and characterization of the hepatic microsomal monooxygenase system from the coastal marine fish Stenotomus chrysops Klotz, Alan V. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1983-08)Three cytochrome P-450 forms were highly purified (8-12 nmol/mg) from the hepatic microsomes of the untreated coastal marine fish Stenotomus chrysops (scup) by detergent solubilization and column chromatography. Scup ...