Osteogenic protein-1 and interleukin-6 with its soluble receptor synergistically stimulate rat osteoblastic cell differentiation.
Osteogenic Protein-1 (OP-1, BMP-7), a member of the bone morphogenetic protein family, stimulates synthesis of biochemical markers characteristic of the osteoblastic and chondrocytic phenotypes and induces new bone formation. Interleukin-6 (IL-6), a cytokine produced by a wide variety of cells, appears to interact with other factors producing different biological effects. In the present study, we showed that OP-1 action in fetal rat calvaria (FRC) cells was enhanced by the combination of IL-6 and the soluble receptor IL-6sR. OP-1 alone induced alkaline phosphatase (AP) activity by 4- to 5-fold above the control. Exogenous IL-6 soluble receptor (IL-6sR) synergistically stimulated the OP-1-induced AP activity and mineralized bone nodule formation by an additional 3-fold. The stimulation was IL-6sR concentration-dependent. The combination of IL-6 and IL-6sR synergistically stimulated OP-1 action by an additional 6- to 7-fold. BMPR-II receptor mRNA expression in FRC cells treated with OP-1 and IL-6 plus IL-6sR was stimulated further, while BMPR-IA, -IB, and ActR-I expressions were not affected. The intracellular signaling molecules Smad2 and Smad5 mRNA expressions were not changed under these conditions. The expression of selected BMP family members (BMP-3, -4, and -6) was altered in FRC cells treated with OP-1 in combination with IL-6 and IL-6sR. The combination of IL-6 and IL-6sR reduced the OP-1-stimulated BMP-3 mRNA levels and enhanced the suppressive effect of OP-1 on BMP-4 and -6 mRNA expressions. In conclusion, the present results demonstrate that exogenous IL-6 and IL-6sR synergistically stimulate OP-1 action in primary cultures of rat osteoblastic cells. One possible mechanism of synergy involves differential regulation of the effects of OP-1 on the expression of the type II BMP receptor and several other BMPs.
Yeh
Lee-Chuan C
LC
Department of Biochemistry, The University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA. carolyeh@biochem.uthscsa.edu
Zavala
Michelle C
MC
Lee
John C
JC
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000235:genetics / Q000494:pharmacology*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis; D004268:DNA-Binding Proteins / Q000235:genetics; D004357:Drug Synergism; D004622:Embryo, Mammalian; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D015850:Interleukin-6 / Q000494:pharmacology*; D010006:Osteoblasts / Q000166:cytology* / Q000187:drug effects; D010750:Phosphoproteins / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D019947:Receptors, Interleukin-6 / Q000235:genetics / Q000502:physiology*; D012886:Skull / Q000166:cytology / Q000196:embryology; D051899:Smad2 Protein; D051902:Smad5 Protein; D012995:Solubility; D015534:Trans-Activators / Q000235:genetics; D016212:Transforming Growth Factor beta
C525821:Bmp7 protein, rat; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D004268:DNA-Binding Proteins; D015850:Interleukin-6; D010750:Phosphoproteins; D019947:Receptors, Interleukin-6; D051899:Smad2 Protein; C497784:Smad2 protein, rat; D051902:Smad5 Protein; C497799:Smad5 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D004247:DNA; D000469:Alkaline Phosphatase