Modulation of ten-eleven translocation 1 (TET1), Isocitrate Dehydrogenase (IDH) expression, α-Ketoglutarate (α-KG), and DNA hydroxymethylation levels by interleukin-1β in primary human chondrocytes

J Biol Chem. 2014 Mar 7;289(10):6877-85. doi: 10.1074/jbc.M113.512269. Epub 2014 Jan 27.


5-Hydroxymethylcytosine (5-hmC) generated by ten-eleven translocation 1-3 (TET1-3) enzymes is an epigenetic mark present in many tissues with different degrees of abundance. IL-1β and TNF-α are the two major cytokines present in arthritic joints that modulate the expression of many genes associated with cartilage degradation in osteoarthritis. In the present study, we investigated the global 5-hmC content, the effects of IL-1β and TNF-α on 5-hmC content, and the expression and activity of TETs and isocitrate dehydrogenases in primary human chondrocytes. The global 5-hmC content was found to be ∼0.1% of the total genome. There was a significant decrease in the levels of 5-hmC and the TET enzyme activity upon treatment of chondrocytes with IL-1β alone or in combination with TNF-α. We observed a dramatic (10-20-fold) decrease in the levels of TET1 mRNA expression and a small increase (2-3-fold) in TET3 expression in chondrocytes stimulated with IL-1β and TNF-α. IL-1β and TNF-α significantly suppressed the activity and expression of IDHs, which correlated with the reduced α-ketoglutarate levels. Whole genome profiling showed an erasure effect of IL-1β and TNF-α, resulting in a significant decrease in hydroxymethylation in a myriad of genes including many genes that are important in chondrocyte physiology. Our data demonstrate that DNA hydroxymethylation is modulated by pro-inflammatory cytokines via suppression of the cytosine hydroxymethylation machinery. These data point to new mechanisms of epigenetic control of gene expression by pro-inflammatory cytokines in human chondrocytes.

Keywords: 5-hmC; Chondrocytes; Cytokine; DNA Methylation; Dioxygenase; Epigenetics; IL-1; TNF-α.

Publication types

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

MeSH terms

  • 5-Methylcytosine / analogs & derivatives
  • Chondrocytes / chemistry
  • Chondrocytes / metabolism*
  • Cytosine / analogs & derivatives*
  • Cytosine / analysis
  • Cytosine / metabolism
  • DNA Methylation*
  • DNA-Binding Proteins / biosynthesis*
  • DNA-Binding Proteins / genetics
  • Epigenesis, Genetic*
  • Humans
  • Interleukin-1beta / pharmacology
  • Interleukin-1beta / physiology*
  • Isocitrate Dehydrogenase / biosynthesis*
  • Isocitrate Dehydrogenase / genetics
  • Ketoglutaric Acids / metabolism*
  • Mixed Function Oxygenases
  • Primary Cell Culture
  • Proto-Oncogene Proteins / biosynthesis*
  • Proto-Oncogene Proteins / genetics
  • RNA, Messenger / biosynthesis
  • RNA, Messenger / genetics
  • Tumor Necrosis Factor-alpha / pharmacology
  • Tumor Necrosis Factor-alpha / physiology


  • DNA-Binding Proteins
  • Interleukin-1beta
  • Ketoglutaric Acids
  • Proto-Oncogene Proteins
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • 5-hydroxymethylcytosine
  • 5-Methylcytosine
  • Cytosine
  • Mixed Function Oxygenases
  • TET1 protein, human
  • Isocitrate Dehydrogenase