IL-1 down-regulates platelet-derived growth factor-alpha receptor gene expression at the transcriptional level in human osteoblastic cells.
Regulation of the platelet-derived growth factor (PDGF)-alpha receptor is thought to play an important role in pathophysiologic processes. Previously, we have reported that IL-1 has the potential to regulate PDGF-induced biologic activity in both normal human osteoblastic cells and the human osteoblastic cell line, MG-63, by decreasing the expression of PDGF-alpha receptor mRNA. In the present studies, we analyzed the effects of IL-1 on transcription rates and the stability of PDGF-alpha receptor mRNA in MG-63 cells. The data indicate that the t1/2 of PDGF-alpha receptor mRNA is approximately 3.3 h after incubation with the RNA II polymerase transcription inhibitor 5,6-dichloro-1 beta-D-ribofuranosylbenzimidazole (DRB). Approximately the same t1/2 (3.1 h) was obtained when osteoblastic cells were incubated with IL-1. The t1/2 for PDGF-alpha receptor mRNA for cells incubated with both IL-1 and DRB was 3 h. This finding suggests that the levels of PDGF-alpha receptor mRNA transcripts are not regulated by post-transcriptional mechanisms. Results of nuclear run-on analysis were consistent with this conclusion, demonstrating that IL-1 modulates PDGF-alpha receptor gene expression at the transcriptional level. Surprisingly, incubation of cells with cycloheximide also caused down-regulation of PDGF-alpha receptor mRNA, which suggests that synthesis of a labile factor is necessary for constitutive expression. The functional consequence of down-regulation of PDGF-alpha receptors by IL-1 was also assessed. By using chemotaxis assays, we demonstrated that IL-1 significantly inhibited PDGF-AA-mediated migration in human MG-63 osteoblastic sarcoma cells.
Xie
J F
JF
Department of Oral Biology, Boston University School of Graduate Dentistry, MA.
Stroumza
J
J
Graves
D T
DT
D002633:Chemotaxis / Q000187:drug effects; D003513:Cycloheximide / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism* / Q000494:pharmacology; D012333:RNA, Messenger / Q000235:genetics; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014407:Tumor Cells, Cultured
D007375:Interleukin-1; D010982:Platelet-Derived Growth Factor; D012333:RNA, Messenger; D003513:Cycloheximide; D017479:Receptors, Platelet-Derived Growth Factor