Interaction between metabolism and transport of benzo[a]pyrene and its metabolites in enterocytes.
Epithelial cells of the small intestine are responsible for the resorption of different food components as well as potentially toxic agents such as benzo[a]pyrene (B[a]P), a particular contaminant of charcoal-grilled meat. This study was undertaken to investigate any functional relationship between the metabolism of B[a]P and the unidirectional transport of metabolites back into the intestinal lumen mediated by ATP-binding cassette (ABC) transport proteins. The human intestinal Caco-2 cell line was used. In addition, mdr1- and mrp2-transfected MDCK cells were employed to characterize the possible role of these ABC transport proteins in the polarized transport. After incubations of Caco-2 cells with B[a]P, HPLC analysis revealed that the primary metabolites of B[a]P were B[a]P-1-sulfate and B[a]P-3-sulfate. Other metabolites, such as B[a]P-3-glucuronide, B[a]P-9,10-diol, or B[a]P-3,6-quinone, could be detected only in small amounts. The transport experiments using Transwell chambers clearly showed that B[a]P-1- and B[a]P-3-sulfate were actively transported toward the apical (luminal) region. This transport increased after induction of CYP1A1/CYP1B1 (Phase 1)-metabolism, although a decrease was observed during concomitant inhibition. Inhibition studies using chemical inhibitors of P-glycoprotein, MRPs, showed no effects. A comparison between the transport of B[a]P-1- and B[a]P-3-sulfate in wild-type and mrp2-transfected MDCKII cells revealed no differences at all. The results indicate that B[a]P is metabolized by Caco-2 cells mainly to B[a]P-1- and B[a]P-3-sulfate, which are subject to an apically directed transport. Furthermore ABC transport proteins P-glycoprotein, MRP1, and MRP2 are not involved in this polarized B[a]P-sulfate secretion.
Buesen
Roland
R
Department of Food Toxicology, School for Veterinary Medicine, Bischofsholer Damm 15, 30173 Hannover, Germany.
Mock
Melissa
M
Seidel
Albrecht
A
Jacob
Jürgen
J
Lampen
Alfonso
A
D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics; D001564:Benzo(a)pyrene / Q000378:metabolism*; D001692:Biological Transport; D018938:Caco-2 Cells; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics; D065633:Cytochrome P-450 CYP1B1; D020895:Enterocytes / Q000378:metabolism*; D004790:Enzyme Induction; D015870:Gene Expression; D006801:Humans; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D012333:RNA, Messenger; D001564:Benzo(a)pyrene; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1