Tumor necrosis factor-alpha autoregulates interleukin-6 synthesis via activation of protein kinase C. Function of sphingosine 1-phosphate and phosphatidylcholine-specific phospholipase C.
We investigated the mechanism of interleukin-6 (IL-6) synthesis induced by tumor necrosis factor-alpha (TNF) in osteoblast-like MC3T3-E1 cells. TNF stimulated the synthesis of IL-6 dose dependently in the range between 1 and 30 ng/ml. Staurosporine and calphostin C, inhibitors of protein kinase C (PKC), significantly enhanced the TNF-induced synthesis of IL-6. 1-Oleoyl-2-acetylglycerol, a specific activator of PKC, inhibited the TNF-induced IL-6 synthesis. The stimulative effect of TNF was markedly increased in the PKC down-regulated cells. TNF produced diacylglycerol. TNF had little effect on the formation of inositol phosphates and choline. On the contrary, TNF significantly stimulated the formation of phosphocholine dose dependently. D-609, an inhibitor of phosphatidylcholine-specific phospholipase C, suppressed the TNF-induced diacylglycerol production. The TNF-induced IL-6 synthesis was significantly enhanced by D-609. TNF induced sphingomyelin hydrolysis. Neither C2-ceramide nor sphingosine but sphingosine 1-phosphate significantly stimulated the synthesis of IL-6. PKC down-regulation amplified the IL-6 synthesis by sphingosine 1-phosphate. These results strongly suggest that sphingosine 1-phosphate may act as a second messenger for TNF-induced IL-6 synthesis and that TNF autoregulates IL-6 synthesis due to PKC activation via phosphatidylcholine-specific phospholipase C in osteoblast-like cells.
Kozawa
O
O
Department of Pharmacology, Gifu University School of Medicine, Gifu 500, Japan.
Suzuki
A
A
Kaida
T
T
Tokuda
H
H
Uematsu
T
T
D016475:3T3 Cells; D000818:Animals; D001952:Bridged-Ring Compounds / Q000494:pharmacology; D002794:Choline / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation; D006706:Homeostasis; D007295:Inositol Phosphates / Q000378:metabolism; D015850:Interleukin-6 / Q000096:biosynthesis*; D007700:Kinetics; D008246:Lysophospholipids; D051379:Mice; D009636:Norbornanes; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D010767:Phosphorylcholine / Q000378:metabolism; D011493:Protein Kinase C / Q000378:metabolism*; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology; D013859:Thiocarbamates; D013871:Thiones / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*; D010738:Type C Phospholipases / Q000378:metabolism*
D001952:Bridged-Ring Compounds; D004075:Diglycerides; D007295:Inositol Phosphates; D015850:Interleukin-6; D008246:Lysophospholipids; C064769:N-acetylsphingosine; D009636:Norbornanes; D013859:Thiocarbamates; D013871:Thiones; D014409:Tumor Necrosis Factor-alpha; D010767:Phosphorylcholine; C060506:sphingosine 1-phosphate; C046498:tricyclodecane-9-yl-xanthogenate; D011493:Protein Kinase C; D010727:Phosphoric Diester Hydrolases; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C105598:phosphatidylcholine-specific phospholipase C; D002794:Choline; D013110:Sphingosine