Comparative effects of cytokines on constitutive and inducible expression of the gene encoding for the cytochrome P450 3A6 isoenzyme in cultured rabbit hepatocytes: consequences on progesterone 6beta-hydroxylation.
Cultured rabbit hepatocytes were used to compare the relative activities of cytokines to inhibit the constitutive or rifampicin (RIF)-induced expression of the cytochrome P450 3A6 gene (CYP3A6). Human recombinant cytokines tested were interleukin-1beta (IL-1beta) (2 U/mL), interleukin-2 (IL-2) (5,000 U/mL) and interferon-gamma (IFN-gamma) (50 U/mL). Hepatocytes were cultured in the presence or absence of 25 microM RIF for 24 hr, with or without cytokines alone or in combination. All these cytokines inhibited RIF-induced P4503A6 expression without apparent cellular toxicity. By contrast, only IFN-gamma treatment provided a significant decrease (41%) in the constitutive P4503A6 protein level. Moreover, cytokines differed in their ability to repress RIF-dependent transcriptional induction of CYP3A6: IL-1beta and IL-2 were approximately equipotent, causing an almost 40-50% suppression of CYP3A6 mRNA and protein levels, whereas IFN-gamma exerted repressive effects only on P4503A6-related erythromycin N-demethylase activity and inducible protein expression. In fact, although strongly reducing P4503A6 protein content (an approximate 70% decrease), IFN-gamma did not exhibit any influence on CYP3A6 mRNAs with the exception of its association with interleukins. All these results suggest that IL-1beta and IL-2 mainly promote a transcriptional repression mechanism, given the absence of effect of these cytokines on the basal P4503A6 level, whereas IFN-gamma exerts a post-transcriptional suppressive action on both induced and constitutive P4503A6 expression. Consequently, P4503A6-dependent progesterone 6beta-hydroxylase activity also presented a cytokine-specific pattern of inhibition, with a much greater sensitivity than P4503A6 immunoreactive protein to IL-1beta and IL-2 + IFN-gamma treatments. Thus, this study underlines the significant impact of inflammation on steroid metabolism.
Calleja
C
C
Laboratoire de Pharmacologie-Toxicologie INRA, Toulouse, France.
Eeckhoutte
C
C
Dacasto
M
M
Larrieu
G
G
Dupuy
J
J
Pineau
T
T
Galtier
P
P
D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases; D002478:Cells, Cultured; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics* / Q000378:metabolism; D016207:Cytokines / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D007371:Interferon-gamma / Q000494:pharmacology; D007375:Interleukin-1 / Q000494:pharmacology; D007376:Interleukin-2 / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D008297:Male; D011374:Progesterone / Q000378:metabolism; D011817:Rabbits
D016207:Cytokines; D007375:Interleukin-1; D007376:Interleukin-2; D011374:Progesterone; D007371:Interferon-gamma; D003577:Cytochrome P-450 Enzyme System; D001189:Aryl Hydrocarbon Hydroxylases; C100638:cytochrome P-450 CYP3A6 (rabbit)