Bifunctional modulating effects of an indigo dimer (bisindigotin) to CYP1A1 induction in H4IIE cells.
In this study, we measured and characterized the bifunctional effects of a newly identified natural compound-bisindigotin (SLY-1), isolated from leaf extracts of Isatis indigotica, to CYP1A1/EROD activities in H4IIE cells. The compound, SLY-1 (1muM) elicited a transitory and significant induction of CYP1A1 RNA/protein levels and EROD activities in the cells. Maximum levels of CYP1A1 expression and EROD induction were attained at 8 and 12h of post-treatment, respectively. Thereafter the induction decreased significantly. Similar profile of CYP1A2 and CYP1B1 mRNA induction was observed. In contrast TCDD elicited CYP1A1/EROD induction was persistent. The transitory effect by SLY-1 is most likely due to the clearance of SLY-1 by cellular metabolism. Taken together the observation indicated that SLY-1 is an Ah receptor agonist for CYP1A1/CYP1A2/CYP1B1/EROD induction. Interestingly in the TCDD/SLY-1 cotreatment study, although synergistic effects on CYP1A1 expression and EROD induction were observed at 4-8h, significant inhibitory effects to TCDD induced CYP1A1 protein and EROD activity were detected at 12-24h of post-treatment. Because there was no significant reduction of CYP1A1, CYP1A2 or CYP1B1 transcript levels between TCDD- and TCDD/SLY-1 treated cells, the data pointed to the translational and/or post-translational inhibitory effect. The cellular signal transduction system may be modulated following exposure to SLY-1. To investigate the possible mechanisms involved, various specific kinase inhibitors or activators (chelerythrin, PD98059, U0126, ZM336372, SB202190, PKA inhibitor PKI (6-22) amide, and dbcAMP) were used for the assessment. Chelerythrine, PD98059 or dbcAMP treatment in TCDD induced cells showed significant inhibitory effects on CYP1A1 mRNA/protein expressions and EROD activities. U0126 had no observable EROD inhibitory effect. ZM336372 or SB202190 showed inhibition only at EROD activities. The results indicated that the SLY-1 inhibitory effect was possibly not mediated by the cAMP/PKA, PKC or MEK pathways. Nevertheless our results indicate that SLY-1 is not only an inducer of the CYP1A1 system, but also a potent inhibitor of CYP1A1 enzyme.
Lai
K P
KP
Croucher Institute of Environmental Sciences and Department of Biology, Hong Kong Baptist University, Kowloon Tong, Hong Kong, PR China.
Mak
N K
NK
Wei
X
X
Wong
R N S
RN
Wong
M H
MH
Wong
Chris K C
CK
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D001564:Benzo(a)pyrene / Q000378:metabolism; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000201:enzymology; D002460:Cell Line; D045744:Cell Line, Tumor; D019363:Cytochrome P-450 CYP1A1 / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000096:biosynthesis; D065633:Cytochrome P-450 CYP1B1; D020536:Enzyme Activators / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D007203:Indigo Carmine; D007211:Indoles / Q000494:pharmacology*; D031219:Isatis / Q000737:chemistry; D010770:Phosphotransferases / Q000037:antagonists & inhibitors; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction
D020536:Enzyme Activators; D004791:Enzyme Inhibitors; D007211:Indoles; D000072317:Polychlorinated Dibenzodioxins; D012333:RNA, Messenger; D001564:Benzo(a)pyrene; D007203:Indigo Carmine; D001189:Aryl Hydrocarbon Hydroxylases; C585499:Cyp1b1 protein, rat; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D065633:Cytochrome P-450 CYP1B1; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010770:Phosphotransferases