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

Charles H. Lang, Gerald J. Nystrom, Robert A. Frost

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78 Scopus citations

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-α (TNF-α), 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-1 β, TNF-α, and IL-6 with maximal 8- to 10-fold increases in IGFBP-1 production. Although the maximal responsiveness of cells treated with TNF-α and IL-6 was 20-30% less than that with IL-1β, cells demonstrated a similar sensitivity to all cytokines (half-maximal responsive dose of ~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 ~4 h and not altered by IL-1β. 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- κB 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.

Original languageEnglish (US)
Pages (from-to)G719-G727
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume276
Issue number3 39-3
DOIs
StatePublished - Mar 1999

All Science Journal Classification (ASJC) codes

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)

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