p38 MAPK regulates IL-1beta induced IL-6 expression through mRNA stability in osteoblasts

Immunol Invest. 2004 May;33(2):213-33. doi: 10.1081/imm-120034231.

Abstract

Osteoblast-derived IL-6 functions in coupled bone turnover by supporting osteoclastogenesis favoring bone resorption instead of bone deposition. Gene regulation of IL-6 is complex occurring both at transcription and post-transcription levels. The focus of this paper is at the level of mRNA stability, which is important in IL-6 gene regulation. Using the MC3T3-E1 as an osteoblastic model, IL-6 secretion was dose dependently decreased by SB203580, a p38 MAPK inhibitor. Steady state IL-6 mRNA was decreased with SB203580 (2 microM) ca. 85% when stimulated by IL-1beta (1-5 ng/ml). These effects require de novo protein synthesis as they were inhibited by cycloheximide. p38 MAPK had minor effects on proximal IL-6 promoter activity in reporter gene assays. A more significant effect on IL-6 mRNA stability was observed in the presence of SB203580. Western blot analysis confirmed that SB203580 inhibited p38 MAP kinase, in response to IL-1beta in a dose dependent manner in MC3T3-E1 cells. Stably transfected MC3T3-E1 reporter cell lines (MC6) containing green fluorescent protein (GFP) with the 3'untranslated region of IL-6 were constructed. Results indicated that IL-1beta, TNFalpha, LPS but not parathyroid hormone (PTH) could increase GFP expression of these reporter cell lines. Endogenous IL-6 and reporter gene eGFP-IL-6 3'UTR mRNA was regulated by p38 in MC6 cells. In addition, transient transfection of IL-6 3'UTR reporter cells with immediate upstream MAP kinase kinase-3 and -6 increased GFP expression compared to mock transfected controls. These results indicate that p38 MAPK regulates IL-1beta-stimulated IL-6 at a post transcriptional mechanism and one of the primary targets of IL-6 gene regulation is the 3'UTR of IL-6.

Publication types

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

MeSH terms

  • 3' Untranslated Regions / genetics
  • Animals
  • Base Sequence
  • Cell Line
  • Enzyme Inhibitors / pharmacology
  • Gene Expression Regulation / drug effects*
  • Genetic Vectors / genetics
  • Interleukin-1 / pharmacology*
  • Interleukin-6 / chemistry
  • Interleukin-6 / genetics*
  • Interleukin-6 / metabolism
  • Mice
  • Molecular Sequence Data
  • Osteoblasts / drug effects*
  • Osteoblasts / metabolism*
  • Promoter Regions, Genetic / genetics
  • RNA Stability / drug effects*
  • RNA, Messenger / genetics
  • RNA, Messenger / metabolism
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Signal Transduction
  • p38 Mitogen-Activated Protein Kinases / antagonists & inhibitors
  • p38 Mitogen-Activated Protein Kinases / metabolism*

Substances

  • 3' Untranslated Regions
  • Enzyme Inhibitors
  • Interleukin-1
  • Interleukin-6
  • RNA, Messenger
  • Recombinant Proteins
  • p38 Mitogen-Activated Protein Kinases