Steroid hormones and retinoic acid interact in the regulation of calcitonin and calcitonin gene-related peptide secretion and messenger ribonucleic acid levels in CA-77 C cells.
Northern hybridizations were used to evaluate the modulated action of retinoic acid (R.A.) in presence of dexamethasone (Dex) and/or calcitriol (1,25-(OH)2D3) on calcitonin (CT) and calcitonin gene-related peptide (CGRP) mRNA steady state levels in the murine CA-77 C cell line. Dex was found to increase both CT and CGRP mRNAs in a time-and-dose-dependent way without changing the alternative splicing. A slight but significant increase in the steady-state CT mRNA level was found 3 days after addition of 10(-10) M Dex; the same dose slightly decreased the CGRP mRNA level; concentrations of Dex > or = 10(-9) M elevated both mRNAs. Calcium from 1-4 mM in short-term (1 hr. and 4 hrs.) or long-term stimulations (1 day and 4 days), with or without Dex cotreatment was ineffective. Dex alone (10(-6) M) elicited a 2-fold increase in CGRP mRNA and a 9-fold increase in CT mRNA steady state levels after 6 days of treatment whereas addition of 5.10(-5) M R.A. alone for 6 days decreased both the CGRP and the CT mRNA steady state level (12- and 4-fold decreases, respectively). Our results showed that 5.10(-7) M R.A. blunted in part (-30%) the rise of CT and CGRP mRNA induced under Dex; whereas doses > or = 5.10(-6) M maximally decreased both CT and CGRP mRNA (2- and 9-fold decreases, respectively). The fall under R.A. alone was enhanced when CA-77 cells were cotreated during 6 days with 10(-7) M 1,25-(OH)2D3 (-68% versus -37%). Moreover, the fall in CGRP mRNA (18-fold) of CA-77 cells treated simultaneously with 10(-6) M Dex, 5.10(-6) M R.A. and 10(-7) M 1,25-(OH)2D3 was greater than the decrease (9-fold) observed when the same dose of R.A. blunted the Dex induction. The results obtained by RIA for the CT and CGRP C cell content and release in the culture medium strengthened those observed on both CT and CGRP mRNAs, since a good parallelism was observed between the peptide biosynthesis, secretion and the mRNA levels. Our data suggest that R.A. and 1,25-(OH)2D3 exert a stronger inhibition of the CT gene by a likely coupled action of the two compounds probably via the formation of an heterodimer receptor.
Lamari
Y
Y
Université Pierre et Marie Curie, Paris, France.
Tahri
E H
EH
Collignon
H
H
Garel
J M
JM
D017398:Alternative Splicing; D000818:Animals; D002116:Calcitonin / Q000235:genetics / Q000378:metabolism*; D015740:Calcitonin Gene-Related Peptide / Q000235:genetics / Q000378:metabolism*; D018276:Carcinoma, Medullary / Q000378:metabolism*; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005938:Glucocorticoids / Q000494:pharmacology*; D051379:Mice; D012333:RNA, Messenger / Q000032:analysis; D013964:Thyroid Neoplasms / Q000378:metabolism*; D014212:Tretinoin / Q000494:pharmacology*
D005938:Glucocorticoids; D012333:RNA, Messenger; D014212:Tretinoin; D003907:Dexamethasone; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide