2,3,7,8-Tetrachlorodibenzo-p-dioxin and diindolylmethanes differentially induce cytochrome P450 1A1, 1B1, and 19 in H295R human adrenocortical carcinoma cells.
Diindolylmethane (DIM) is an acid-catalyzed condensation product of indole-3-carbinol, a constituent of cruciferous vegetables, and is formed in the stomach. DIM alters estrogen metabolism and inhibits carcinogen-induced mammary tumor growth in rodents. DIM is a weak agonist for the aryl hydrocarbon (Ah) receptor and blocks the effects of estrogens via inhibitory Ah receptor-estrogen receptor cross-talk. DIM and various structural analogs were examined in H295R cells for effects on 3 cytochrome P450 (CYP) enzymes involved in estrogen synthesis and/or metabolism: CYP1A1, CYP1B1, and CYP19 (aromatase). Aromatase activity was measured by conversion of 1 beta-(3)H-androstenedione to estrone and (3)H(2)O. H295R cells were exposed to the test chemicals dissolved in dimethyl sulfoxide for 24 h prior to analyses. 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) (0--30 nM) and DIM (0--10 microM) induced ethoxyresorufin-O-deethylase (EROD) activity, as a measure of CYP1A1 and possibly 1B1 activity, with EC(50) values of about 0.3 nM and 3 microM, respectively. DIM, but not TCDD, induced aromatase activity with an apparently maximal 2-fold increase at 10 microM; higher concentrations of DIM and many of its analogs were cytotoxic. TCDD (30 nM) significantly increased CYP1A1 and 1B1 mRNA levels, but had no effect on mRNA for CYP19. DIM (3 microM) significantly increased mRNA levels for all three CYPS: DIM analogs with substitutions on the 5 and 5' position (3 microM) induced aromatase and EROD activity, together with mRNA levels of CYP1A1, 1B1, and 19; analogs that were substituted on the central carbon of the methane group showed little or no inductive activity toward the CYPS: In conclusion, DIM and several of its analogs appear to induce CYPs via multiple yet distinct pathways in H295R human adrenocortical carcinoma cells.
Sanderson
J T
JT
Research Institute for Toxicology, Utrecht University, P.O. Box 80176, 3508 TD Utrecht, The Netherlands. t.sanderson@ritox.vet.uu.nl
Slobbe
L
L
Lansbergen
G W
GW
Safe
S
S
van den Berg
M
M
D000302:Adrenal Cortex / Q000201:enzymology / Q000378:metabolism; D018268:Adrenocortical Carcinoma / Q000201:enzymology* / Q000378:metabolism*; D001141:Aromatase / Q000032:analysis / Q000187:drug effects*; D047072:Aromatase Inhibitors; D001189:Aryl Hydrocarbon Hydroxylases; D002460:Cell Line; D002470:Cell Survival; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis / Q000037:antagonists & inhibitors / Q000187:drug effects*; D065633:Cytochrome P-450 CYP1B1; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D005562:Formazans / Q000032:analysis; D006801:Humans; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D007457:Iodine Radioisotopes; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D012333:RNA, Messenger / Q000096:biosynthesis; D011863:Radioimmunoassay; D018336:Receptors, Aryl Hydrocarbon / Q000037:antagonists & inhibitors*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013329:Structure-Activity Relationship; D013778:Tetrazolium Salts / Q000032:analysis; D014316:Tritium; D014407:Tumor Cells, Cultured
D047072:Aromatase Inhibitors; D065607:Cytochrome P-450 Enzyme Inhibitors; D005562:Formazans; D007211:Indoles; D007457:Iodine Radioisotopes; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D018336:Receptors, Aryl Hydrocarbon; D013778:Tetrazolium Salts; D014316:Tritium; C079782:MTT formazan; D003577:Cytochrome P-450 Enzyme System; D001141:Aromatase; D001189:Aryl Hydrocarbon Hydroxylases; C585496:CYP1B1 protein, human; D019363:Cytochrome P-450 CYP1A1; D065633:Cytochrome P-450 CYP1B1; C016392:3,3'-diindolylmethane