Interleukin-1 alpha and phorbol ester inhibit collagen synthesis in osteoblastic MC3T3-E1 cells by a transcriptional mechanism.
The effects of recombinant human interleukin-1 alpha (IL-1) on procollagen gene expression were examined in the clonal mouse osteoblastic cell line MC3T3-E1. Cells were grown in Dulbecco's Modified Eagle's Medium containing 10% fetal calf serum and 50 micrograms/ml ascorbic acid. Collagen synthesis was assessed as [3H]proline incorporation into collagenase-digestible protein (CDP). Procollagen mRNA levels were determined by Northern blot analysis using a 32P-labeled alpha 1(I) cDNA. Transcription rates were determined by nuclear run-off assay. IL-1 at 1-1000 pg/ml caused a concentration-dependent inhibition of CDP, which was maximally reduced by 75-80%, and a parallel reduction of procollagen alpha 1(I) mRNA levels. The effects of IL-1 were mimicked by the tumor promoter phorbol 12-myristate 13-acetate (PMA) at 1-100 nM, which inhibited CDP and reduced procollagen alpha 1(I) mRNA levels to a similar extent. The effects of IL-1 and PMA were independent of prostaglandin production, since indomethacin did not alter the inhibitory effect of either agent on CDP. Neither IL-1 (up to 10 ng/ml) nor PMA (100 nM) affected adenylate cyclase activity, while forskolin (10 microM), PTH (10 nM) and prostaglandin E2 (1 microM) stimulated adenylate cyclase activity 3- to 5-fold. However, forskolin (10 microM) and (Bu)2cAMP (100 microM) failed to alter CDP or procollagen alpha 1(I) mRNA levels. IL-1 (1 ng/ml) and PMA (100 nM) reduced transcription of the alpha 1(I) procollagen gene by 70% and 80%, respectively, while alpha 2(I) transcription was decreased by 59% and 53%. Neither IL-1 nor PMA affected transcription of the beta-actin or beta-tubulin genes.(ABSTRACT TRUNCATED AT 250 WORDS)
Harrison
J R
JR
Department of Medicine, University of Connecticut Health Center, Farmington 06032.
Vargas
S J
SJ
Petersen
D N
DN
Lorenzo
J A
JA
Kream
B E
BE
D000818:Animals; D003094:Collagen / Q000096:biosynthesis*; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D007375:Interleukin-1 / Q000494:pharmacology*; D051379:Mice; D010017:Osteoma, Osteoid / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology; D010703:Phorbol Esters / Q000494:pharmacology*; D011347:Procollagen / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology; D014407:Tumor Cells, Cultured / Q000187:drug effects / Q000378:metabolism / Q000473:pathology
D007375:Interleukin-1; D010703:Phorbol Esters; D011347:Procollagen; D003094:Collagen