Effects of interleukin-1 beta and tumor necrosis factor-alpha on osteoblastic expression of osteocalcin and mineralized extracellular matrix in vitro.
Osteoblasts play a pivotal role during the bioresponse of bone to agents that stimulate bone resorption and/or inhibit bone formation including hormones, polypeptide growth factors, and cytokines. We examined the cytokines interleukin-1-beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) for their effects on osteoblastic proliferation and development and expression of alkaline phosphate and the osteoblast-specific protein osteocalcin in a mineralizing environment. Primary rat osteoblast-like cells (ROB) and osteoblastic cell lines derived from rat (ROS 17/2.8) and human (MG-63) osteosarcomas were studied. IL-1 beta and TNF-alpha were chosen because of their critical importance during the host response to local inflammatory stimuli. Qualitatively similar two- to threefold inhibition of osteocalcin synthesis by IL-1 beta and TNF-alpha were observed in all three postconfluent bone-forming model systems. Because of the readily measurable concentrations of osteocalcin produced in our culture protocol, it was not necessary to enhance osteoblastic synthesis of osteocalcin by supplementation with 1,25(OH)2-vitamin D3, a treatment which exerts pleiotropic effects on osteoblasts. Under the constraints of our protocol, where alkaline phosphatase and mineralization were already elevated at the 14-day onset of treatment, neither of these phenotypic properties was sensitive to a three-day cytokine exposure. Differences were noted in proliferation, where only TNF-alpha stimulated DNA synthesis in ROB cells, while both cytokines stimulated MG-63 cells. IL-1 beta and TNF-alpha failed to alter ROS 17/2.8 DNA synthesis except at the highest doses (25 pM IL-1 beta and 1 nM TNF-alpha) where inhibition was observed. These results further support the view that cytokine-mediated osteoblastic regulation can be relatively selective.
Taichman
R S
RS
Department of Periodontology, Harvard School of Dental Medicine, Boston, MA 02115.
Hauschka
P V
PV
D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D015152:Blotting, Northern; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis; D005109:Extracellular Matrix / Q000737:chemistry / Q000187:drug effects*; D005470:Fluorometry; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D008903:Minerals / Q000032:analysis*; D010006:Osteoblasts / Q000187:drug effects* / Q000378:metabolism; D015675:Osteocalcin / Q000032:analysis / Q000096:biosynthesis*; D012333:RNA, Messenger / Q000187:drug effects; D011863:Radioimmunoassay; D051381:Rats; D014407:Tumor Cells, Cultured; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D007375:Interleukin-1; D008903:Minerals; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D015675:Osteocalcin; D004247:DNA; D000469:Alkaline Phosphatase