Regulation of IGF binding protein-1 in hep G2 cells by cytokines and reactive oxygen species

Am J Physiol. 1999 Mar;276(3):G719-27. doi: 10.1152/ajpgi.1999.276.3.G719.

Abstract

The liver is a major site of synthesis for insulin-like growth factor binding protein (IGFBP)-1. Because IGFBP-1 inhibits many anabolic actions of IGF-I, increases in IGFBP-1 may be partly responsible for the decrease in lean body mass observed in catabolic/inflammatory conditions. This study aimed to determine in Hep G2 cells 1) the sensitivity of IGFBP-1 synthesis to treatment with interleukin (IL)-1, tumor necrosis factor-alpha (TNF-alpha), and IL-6, 2) the ability of reactive oxygen species (ROS) to enhance IGFBP-1 production, and 3) the role of ROS in mediating cytokine-induced increases in IGFBP-1. Hep G2 cells responded to IL-1beta, TNF-alpha, and IL-6 with maximal 8- to 10-fold increases in IGFBP-1 production. Although the maximal responsiveness of cells treated with TNF-alpha and IL-6 was 20-30% less than that with IL-1beta, cells demonstrated a similar sensitivity to all cytokines (half-maximal responsive dose of approximately 10 ng/ml). A low concentration (3 ng/ml) of all three cytokines had an additive effect on IGFBP-1 production. Cytokines also increased IGFBP-1 mRNA. The half-life of IGFBP-1 mRNA was approximately 4 h and not altered by IL-1beta. Incubation with ROS, including H2O2 and nitric oxide (NO) donors, resulted in a relatively smaller increase in IGFBP-1. However, preincubating Hep G2 cells with various free radical scavengers and NO synthase and eicosanoid inhibitors failed to prevent or attenuate cytokine-induced increases in IGFBP-1. Finally, preincubating cells with pyrrolidinedithiocarbamate (PDTC) but not SN50 (inhibitors of nuclear factor-kappaB activation and nuclear translocation, respectively) attenuated increases in IGFBP-1 induced by IL-1. These results indicate that 1) proinflammatory cytokines directly enhance IGFBP-1 synthesis by stimulating transcription without altering mRNA stability, 2) addition of exogenous ROS also stimulates IGFBP-1 production but to a smaller extent than cytokines, and 3) the cytokine-induced increase in IGFBP-1 production is not mediated by endogenous production of ROS or eicosanoids but appears to at least partially involve a PDTC-sensitive pathway.

Publication types

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

MeSH terms

  • Cytokines / pharmacology
  • Cytokines / physiology*
  • Eicosanoids / physiology
  • Humans
  • Insulin-Like Growth Factor Binding Protein 1 / metabolism*
  • Interleukin-1 / pharmacology
  • Interleukin-6 / pharmacology
  • Liver / metabolism*
  • NF-kappa B / physiology
  • Oxidative Stress / physiology
  • Reactive Oxygen Species / physiology*
  • Tumor Cells, Cultured
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Cytokines
  • Eicosanoids
  • Insulin-Like Growth Factor Binding Protein 1
  • Interleukin-1
  • Interleukin-6
  • NF-kappa B
  • Reactive Oxygen Species
  • Tumor Necrosis Factor-alpha