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.
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.
Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio 44272.
Abdul
A
Haseeb
Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio 44272.
Mohammad Shahidul
MS
Makki
Department of Anatomy and Neurobiology, Northeast Ohio Medical University, Rootstown, Ohio 44272. Electronic address: thaqqi@neomed.edu.
Tariq M
TM
Haqqi
D044503:5-Methylcytosine / Q000031:analogs & derivatives; D019902:Chondrocytes / Q000737:chemistry / Q000378:metabolism*; D003596:Cytosine / Q000031:analogs & derivatives* / Q000032:analysis / Q000378:metabolism; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D044127:Epigenesis, Genetic; D006801:Humans; D053583:Interleukin-1beta / Q000494:pharmacology / Q000502:physiology*; D007521:Isocitrate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics; D007656:Ketoglutaric Acids / Q000378:metabolism*; D006899:Mixed Function Oxygenases; D061251:Primary Cell Culture; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology
D004268:DNA-Binding Proteins; D053583:Interleukin-1beta; D007656:Ketoglutaric Acids; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; C011865:5-hydroxymethylcytosine; D044503:5-Methylcytosine; D003596:Cytosine; D006899:Mixed Function Oxygenases; C462539:TET1 protein, human; D007521:Isocitrate Dehydrogenase
5-hmC; Chondrocytes; Cytokine; DNA Methylation; Dioxygenase; Epigenetics; IL-1; TNF-α