Interferon-alpha downregulates expression of the oxytocin receptor in cultured human myometrial cells.
Previous studies in the endometrium of ruminants showed that type I interferon (IFN) prevents oxytocin receptor (OTR) formation. We studied the effect of IFN-alpha on human myometrial cells in culture expressing a high density of biologically active OTR. We found that IFN-alpha induced a 35-50% decrease in OTR mRNA and protein and that this inhibition was time and dose dependent. Maximal inhibition of OTR mRNA was obtained after 2-3 days, whereas 1-(beta-mercapto-beta, beta-cyclopentamethyl-enepropionic acid,2-O-Me-Tyr,Thr4,Orn8,Tyr9-amide)-[125I]vasotocin ([125I]OTA) binding reached a nadir after 3-4 days, with half-maximal inhibitory concentration (IC50) = 1,100 U/ml. Mathematical analysis of multiple homologous competition curves for [125I]OTA indicated that IFN-alpha treatment (5,000 U/ml x 3 days) reduced just the binding capacity (Bmax) without changing the binding affinity. Accordingly, the same treatment with IFN-alpha did not affect the half-maximally effective concentration (EC50) for the oxytocin-induced increase in intracellular calcium but significantly decreased maximal responsiveness (Emax) of myometrial cells to OT stimulation. In conclusion, our data demonstrate, for the first time, a negative regulation by IFN-alpha of the steady-state expression of OTR mRNA in cultured human myometrial cells obtained from nonpregnant uteri. This inhibition was followed by a parallel decrease in both the Bmax for [125I]OTA and Emax for oxytocin, suggesting a decreased OTR protein availability.
Maggi
M
M
Department of Clinical Physiopathology, University of Florence, Italy.
Peri
A
A
Baldi
E
E
Mancina
R
R
Granchi
S
S
Fantoni
G
G
Finetti
G
G
Forti
G
G
Raggi
C C
CC
Serio
M
M
D001483:Base Sequence; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D017931:DNA Primers; D004305:Dose-Response Relationship, Drug; D015536:Down-Regulation / Q000187:drug effects*; D005260:Female; D006801:Humans; D000077190:Interferon alpha-2; D016898:Interferon-alpha / Q000494:pharmacology*; D007700:Kinetics; D009215:Myometrium / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000096:biosynthesis; D011869:Radioligand Assay; D018045:Receptors, Oxytocin / Q000096:biosynthesis*; D011994:Recombinant Proteins; D014158:Transcription, Genetic / Q000187:drug effects*
D017931:DNA Primers; D000077190:Interferon alpha-2; D016898:Interferon-alpha; D012333:RNA, Messenger; D018045:Receptors, Oxytocin; D011994:Recombinant Proteins; D002118:Calcium