Role of lymphotoxin in expression of interleukin 6 in human fibroblasts. Stimulation and regulation.
IL-6 is a cytokine with a number of biological functions, including stimulation of immunoglobulin synthesis and proliferation of early hematopoietic stem cells. We showed that lymphotoxin stimulated accumulation of IL-6 mRNA in human fibroblasts (W138) in a dose-responsive fashion; tumor necrosis factor-alpha (TNF-alpha) was about threefold more potent than lymphotoxin. Further experiments suggested that stimulation by lymphotoxin was independent of protein kinase C activity, did not require new protein synthesis, and was at least in part a result of increased stabilization of IL-6 mRNA. t1/2 of the IL-6 transcripts increased from 0.3 h in unstimulated cells to 0.85 h in cells stimulated with lymphotoxin. In addition, stimulators of protein kinase C, including phorbol esters and teleocidin, enhanced accumulation of IL-6 mRNA. Cycloheximide (CHX), inhibitor of protein synthesis, also markedly increased levels of IL-6 mRNA. Both CHX and activators of protein kinase C increased by greater than 16-fold the stability of IL-6 mRNA. Further, dose-response studies showed that sodium fluoride (NaF), activator of G-binding proteins, and ouabain, inhibitor of Na+/H+ pump, increased levels of IL-6 mRNA. NaF stimulated IL-6 mRNA levels independent of protein kinase C activity. These results suggest that stimulators of several pathways of signal transduction increase levels of IL-6 mRNA and posttranscriptional stabilization is, in part, the mechanism that many of these signals, including lymphotoxin, use to increase levels of IL-6 RNA.
Akashi
M
M
Division of Hematology/Oncology, University of California, Los Angeles 90024.
Loussararian
A H
AH
Adelman
D C
DC
Saito
M
M
Koeffler
H P
HP
D002460:Cell Line; D003513:Cycloheximide / Q000494:pharmacology; D015342:DNA Probes; D005347:Fibroblasts / Q000187:drug effects / Q000276:immunology; D015870:Gene Expression / Q000187:drug effects*; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D007700:Kinetics; D008233:Lymphotoxin-alpha / Q000494:pharmacology*; D008235:Lyngbya Toxins / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D012313:RNA / Q000096:biosynthesis / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D011994:Recombinant Proteins / Q000494:pharmacology; D012969:Sodium Fluoride / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic / Q000187:drug effects; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D015342:DNA Probes; D015850:Interleukin-6; D008233:Lymphotoxin-alpha; D008235:Lyngbya Toxins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D014409:Tumor Necrosis Factor-alpha; C022176:teleocidins; D010042:Ouabain; D012313:RNA; D012969:Sodium Fluoride; D003513:Cycloheximide; D011493:Protein Kinase C; D013755:Tetradecanoylphorbol Acetate