Table 4.
List of OA signaling pathways that has a relation with IDO activity
| Pathway | Function | Situ in The Joint | IDO Relation | Reference |
|---|---|---|---|---|
| RNAKL/NF-KBP65/IGFBP5/GDF5/BMP-7/PPRA/ACVR2B/SMAD2/IRAK1/iNOS2/TRFA6/CHRD1/TIR/CCN2 | Signaling | Synovial fluid/subchondral bone | These pathways induce IDO secretion and function | [177,178,179] |
| RALA | Sox9 regulation | Synovial | Inhibits IDO | [173] |
| MMP13 /MMP-1/2/3/9/ADAMTS4 | Matrix degradation | Synovial fluid/subchondral bone | These pathways could be stimulated by IDO1 | [7,59,176] |
| COX2/TNFα/JAK2/STAT3 | Induce inflammations | Synovial fluid | These factors have a potential to induce IDO production | [59,68,102,201,207] |
| COLA1/COL2A1/ACAN | Intracellular matrix | Articular cartilage | IDO1 regulates COAL2A1 production while enhances COLA1 | [87,97,188] |
| SOX9/NF-κB | Transcription | Synovial fluid/articular cartilage | IDO1 regulates soxy9 expression | [198,200] |
| TGF-β | Regulatory | Synovial fluid/subchondral bone/articular cartilage | Induces IDO activity and massively expressed in the presence of IDO | [32,60,120,140] |