Chondrocytes from three patients subjected to ACT, and another three individuals subjected to total knee arthroplasty, were in separate experiments challenged with 10 nM or 100 nM chemerin21 157 for 24 h, and subsequently a panel of cytokines was measured in the cell supernatants. The results show an increased concentration of TNF a, IL 1b, IL 6 and IL 8 as a result of chemerin stimulation in comparison to unstimulated control cells. The levels of IL 6 and IL 8 were markedly increased, whereas a rather modest effect was observed in terms of altered levels of IL 1b and TNF a. Joint inflammation is associated with deterioration of the cartilage matrix requiring a clarification as to whether chemerin21 157 affects chondrocyte secretion of matrix metalloproteases.
Cell cultures from six indivi duals were arranged and challenged with 10 nM or 100 nM chemerin21 157 for 24 h, and subsequently a panel of eight different MMPs was measured in the supernatants. Significantly elevated levels of MMP 1, MMP 2, MMP 3, MMP 8, and selleck inhibitor MMP 13 were detected. The metalloproteases MMP 7, MMP 9, and MMP 12 could not be detected. Discussion Recent studies addressing the role of chondrocytes in joint inflammation have revealed that these cells secrete Spleen Tyrosine Kinase inhibitors and bind a variety of cytokines and chemokines and that they possess immunoregulatory cap abilities. The present study adds further informa tion to this issue by demonstrating that chondrocytes in both native cartilage and cell culture express the chemokine receptor ChemR23, a property primarily ascribed to leukocytes.
Using the ligand recombinant human chemerin21 157, we demonstrated that chemerinChemR23 binding eli cits intracellular signalling leading to the phosphoryla tion of p4442 MAPKs and Akt, both of which are involved in central signal transduction pathways that convey inflammatory signalling. Hence, the cleavage product of prochemerin chemerin21 157 mediates pro inflammatory signalling in chondrocytes as judged by the observed promotion of cytokine secretion. The enzymes reported to generate chemerin21 157 from prochemerin include the neutrophil serine pro teases cathepsin G and elastase. This indicates that, regardless of the source of prochemerin in joints, it can be cleaved by the enzymes produced by neutro phils into isoforms of chemerin that further promote inflammation by recruiting leukocytes, and that pro mote chondrocyte secretion of pro inflammatory cyto kines. Previous studies have reported that chemerin21 157 can be detected in arthritic synovial fluid and prochemerin from the circulation could likely be the source.