Tumor necrosis factor-alpha decreases insulin-like growth factor-I messenger ribonucleic acid expression in C2C12 myoblasts via a Jun N-terminal kinase pathway

Endocrinology. 2003 May;144(5):1770-9. doi: 10.1210/en.2002-220808.

Abstract

IGF-I is a major anabolic hormone for skeletal muscle in vivo. Yet the mechanisms by which GH and cytokines regulate IGF-I expression remain obscure. Lipopolysaccharide (LPS) dramatically alters the circulating concentration of both TNF alpha and IGF-I, and TNF alpha in part mediates the cachectic activity of LPS. Little is known about the local synthesis of IGF-I and TNF alpha in skeletal muscle per se. The purpose of the present study was to determine whether LPS alters the expression of TNF alpha and IGF-I in mouse skeletal muscle and whether TNF alpha directly inhibits IGF-I mRNA expression in C2C12 myoblasts. Intraperitoneal injection of LPS in C3H/SnJ mice increased the expression of TNF alpha protein in plasma (16-fold) and TNF alpha mRNA in skeletal muscle (8-fold). LPS also decreased the plasma concentration of IGF-I (30%) and IGF-I mRNA in skeletal muscle (50%, between 6 and 18 h after LPS administration). Addition of LPS or TNF alpha directly to C2C12 myoblasts decreased IGF-I mRNA by 50-80%. The TNF alpha-induced decrease in IGF-I mRNA was both dose and time dependent and occurred in both myoblasts and differentiated myotubes. TNF alpha selectively decreased IGF-I but not IGF-II mRNA levels, and the effect of TNF alpha was blocked by a specific TNF-binding protein. TNF alpha did not alter IGF-I mRNA levels in the presence of the protein synthesis inhibitor cycloheximide. TNF alpha did not change the half-life of IGF-I mRNA. TNF alpha completely prevented GH-inducible IGF-I mRNA expression, but this GH resistance was not attributable to impairment in signal transducer and activator of transcription-3 or -5 phosphorylation. TNF alpha increased both nitric oxide synthase-II mRNA and protein, and the nitric oxide donor sodium nitroprusside decreased IGF-I mRNA levels in C2C12 cells. Yet inhibitor studies indicate that nitric oxide did not mediate the effect of TNF alpha on IGF-I mRNA expression. TNF alpha stimulated the phosphorylation of c-Jun and specific inhibition of the Jun N-terminal kinase pathway, but not other MAPK pathways, completely prevented the TNF alpha-induced drop in IGF-I mRNA. These data suggest that LPS stimulates TNF alpha expression in mouse skeletal muscle and autocrine-derived cytokines may contribute to the reduced expression of IGF-I in this tissue.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cell Line
  • DNA-Binding Proteins / metabolism
  • Dose-Response Relationship, Drug
  • Growth Hormone / pharmacology
  • Insulin-Like Growth Factor I / antagonists & inhibitors*
  • Insulin-Like Growth Factor I / genetics
  • JNK Mitogen-Activated Protein Kinases
  • Lipopolysaccharides / pharmacology
  • Mice
  • Mice, Inbred C3H
  • Milk Proteins*
  • Mitogen-Activated Protein Kinases / metabolism*
  • Muscle, Skeletal / metabolism
  • Myoblasts / metabolism*
  • Nitric Oxide Donors / pharmacology
  • Nitric Oxide Synthase / physiology
  • Phosphorylation
  • Protein Biosynthesis / physiology
  • RNA, Messenger / antagonists & inhibitors
  • RNA, Messenger / metabolism
  • STAT3 Transcription Factor
  • STAT5 Transcription Factor
  • Time Factors
  • Trans-Activators / metabolism
  • Transcription, Genetic / physiology
  • Tumor Necrosis Factor-alpha / administration & dosage
  • Tumor Necrosis Factor-alpha / genetics
  • Tumor Necrosis Factor-alpha / pharmacology*

Substances

  • DNA-Binding Proteins
  • Lipopolysaccharides
  • Milk Proteins
  • Nitric Oxide Donors
  • RNA, Messenger
  • STAT3 Transcription Factor
  • STAT5 Transcription Factor
  • Stat3 protein, mouse
  • Trans-Activators
  • Tumor Necrosis Factor-alpha
  • Insulin-Like Growth Factor I
  • Growth Hormone
  • Nitric Oxide Synthase
  • JNK Mitogen-Activated Protein Kinases
  • Mitogen-Activated Protein Kinases