Lipopolysaccharide regulates proinflammatory cytokine expression in mouse myoblasts and skeletal muscle.
The purpose of the present study was to examine the regulation of tumor necrosis factor (TNF)-alpha and interleukin (IL)-6 by lipopolysaccharide (LPS) in C2C12 myoblasts and mouse skeletal muscle. LPS produced dose- and time-dependent increases in TNF-alpha and IL-6 mRNA content in C2C12 myoblasts. The LPS-induced cytokine response could be mimicked by peptidoglycan from the cell wall of Staphylococcus aureus but not by zymosan A, a cell wall component from Saccharomyces cerevisiae. Ongoing protein synthesis was not necessary for the increase in the two cytokine mRNAs. The transcriptional inhibitor 5,6-dichloro-beta-D-ribofuranosyl-benzimidazole blocked LPS-stimulated IL-6 mRNA expression without changing its mRNA half-life. The anti-inflammatory glucocorticoid dexamethasone selectively blocked LPS-stimulated IL-6 mRNA accumulation but not TNF-alpha. In contrast, the proteasomal inhibitor MG-132 blocked TNF-alpha mRNA expression but not IL-6. Exposure of myoblasts to LPS was associated with a rapid decrease in the inhibitor of nuclear factor-kappaB (I kappaB, alpha, and epsilon), and this response was also blocked by MG-132. Treatment of myocytes with IL-1 or TNF-alpha also increased IL-6 mRNA content, but the increase in IL-6 mRNA due to LPS could not be prevented by pretreatment with antagonists to either IL-1 or TNF. Under in vivo conditions, LPS increased the plasma concentration of TNF-alpha and IL-6 and stimulated the accumulation of their mRNAs in multiple tissues including skeletal muscle from wild-type mice. In contrast, the ability of LPS to stimulate the same cytokines was markedly decreased in mice that harbor a mutation in the Toll-like receptor 4. Our data suggest that LPS stimulates cytokine expression not only in classical immune tissues but also in skeletal muscle.
Frost
Robert A
RA
Department of Cellular and Molecular Physiology, The Pennsylvania State University, College of Medicine, Hershey, Pennsylvania 17033, USA. rfrost@psu.edu
Nystrom
Gerald J
GJ
Lang
Charles H
CH
D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D001425:Bacterial Outer Membrane Proteins / Q000494:pharmacology; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000276:immunology; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6 / Q000235:genetics*; D007976:Leupeptins / Q000494:pharmacology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008809:Mice, Inbred C3H; D018485:Muscle Fibers, Skeletal / Q000166:cytology / Q000187:drug effects / Q000276:immunology*; D018482:Muscle, Skeletal / Q000166:cytology* / Q000276:immunology; D014176:Protein Biosynthesis / Q000276:immunology; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000494:pharmacology
D000893:Anti-Inflammatory Agents; D000970:Antineoplastic Agents; D001425:Bacterial Outer Membrane Proteins; D007375:Interleukin-1; D015850:Interleukin-6; D007976:Leupeptins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D003907:Dexamethasone; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde