Background
Acetaminophen is commonly recommended for the early analgesia of osteoarthritis. However, the molecular mechanism by which it acts remains unknown. The
Conclusion
Acetaminophen affects inflammatory factors secretion and extracellular matrix synthesis of human chondrocytes by regulating RNA N6-methyladenosine level and N6-methyladenosine-related protein expression. Stimulation of the normal chondrocyte cell line C28/I2 with the cytokine IL-1β (10 μM) mimics the inflammatory state in vitro. Acetaminophen (Ace, 50 μg/mL) changes the m6A related proteins expression and the total RNA m6A levels in IL-1β-treated chondrocyte cells. Furthermore, regulation of RNA m6A levels (by methylation inhibitor Cyc and/or Ace) affects IL-1β-induced inflammatory cytokines secretion and extracellular matrix synthesis in C28/I2 cells.
Methods
The normal chondrocyte cell line C28/I2 was treated with interleukin-1β to mimic the inflammatory state. Acetaminophen and the methylation inhibitor (cycloleucine) were used to treat interleukin-1β-induced C28/I2 cells. The expression of RNA N6-methyladenosine -related proteins was detected by RT-qPCR and western blot. The total RNA N6-methyladenosine level was measured by dot blot analysis and enzyme linked immunosorbent assay. The levels of interleukin-6, interleukin-8 and anti-tumor necrosis factor-α were measured by enzyme linked immunosorbent assay. The extracellular matrix synthesis and degradation were examined by western blot.
Results
After interleukin-1β stimulated C28/I2 cells, the intracellular RNA N6-methyladenosine level increased, and the expression of regulatory proteins also changed, mainly including the increased expression of methyltransferase like 3 and the downregulated expression of AlkB family member 5. The use of cycloleucine inhibited interleukin-1β-induced inflammation and extracellular matrix degradation by inhibiting RNA N6-methyladenosine modification. In contrast, acetaminophen treatment counteracted interleukin-1β-induced changes in RNA N6-methyladenosine levels and regulatory protein expression. Furthermore, acetaminophen treatment of interleukin-1β-induced C28/I2 cells inhibited the secretion of interleukin-6, interleukin-8 and anti-tumor necrosis factor-α, down-regulated the expression of matrix metalloproteinase-13 and Collagen X, and up-regulated the expression of collagen II and aggrecan. In addition, AlkB family member 5 overexpression activated interleukin-1β-induced chondrocyte viability and suppressed inflammation and extracellular matrix degradation.