DcR3 induces cell proliferation through MAPK signaling in chondrocytes of osteoarthritis

Introduction: Decoy receptor 3 (DcR3), a soluble receptor belonging to the tumor necrosis factor (TNF) receptor superfamily, competitively binds and inhibits the TNF family including Fas-ligand (Fas-L), lymphotoxin-like inducible protein that competes with glycoprotein D for binding herpesvirus entry mediator on T-cells (LIGHT) and TNF-like ligand 1A (TL1A). In this study, we investigated the functions of DcR3 on osteoarthritis (OA) chondrocytes.

Methods: Expressions of DcR3 in chondrocytes were measured by realtime Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR). Expression of DcR3 in sera and joint fluids was measured by enzyme-linked immunosorbent assay (ELISA). Chondrocytes were incubated with DcR3-Fc chimera protein (DcR3-Fc) before induction of apoptosis by Fas-L and apoptosis was detected with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labelling labeling (TUNEL) staining and Western blotting of caspase 8 and poly (ADP-ribose) polymerase (PARP). Chondrocytes were incubated with DcR3-Fc and the proliferation was analyzed by 4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate (WST) assay. Phosphorylation of Extracellular Signal-Regulated Kinase (ERK), P38 mitogen-activated protein kinase (MAPK) and Jun N-terminal Kinase (JNK) in chondrocytes was measured by Western blotting after incubation with DcR3-Fc, Mitogen-activated protein kinase kinase (MEK1/2) inhibitor, or P38 MAPK inhibitor. Chondrocytes were treated with DcR3-Fc after pre-incubation with blocking antibody of Fas-L, LIGHT and TL1A, and proliferation or phosphorylation of ERK was analyzed.

Results: DcR3 was expressed in OA and normal chondrocytes. DcR3-Fc protects chondrocytes from Fas-induced apoptosis. DcR3-Fc increased chondrocytes proliferation and induced the phosphorylation of ERK specifically. DcR3-induced chondrocytes proliferation was inhibited by pre-incubation of PD098059 or blocking Fas-L antibody. DcR3 increased chondrocytes proliferation in OA chondrocytes, but did not in normal.

Conclusion: DcR3 regulates the proliferation of OA chondrocytes via ERK signaling and Fas-induced apoptosis.