ABSTRACT: Osteoarthritis (OA) is a common degenerative disease that is associated with the degradation of articular cartilage. Accumulating evidence has confirmed that LIM mineralization protein-1 (LMP-1) is an important agent of bone formation and has been shown to be osteoinductive in various types of disease. However, the underlying mechanisms of LMP-1 in the pathogenesis of OA remain unknown. The present study aimed to evaluate the role and potential mechanism of LMP-1 in IL-1β-stimulated OA chondrocytes. CHON-001 cells were transfected with pcDNA3.1-LMP-1, pcDNA3.1, negative control-small interfering (si)RNA or LMP-1 siRNA for 24 h and then induced by IL-1β for 12 h to establish an OA model in vitro. Cell viability, apoptosis and inflammatory cytokine (IL-6, IL-8 and TNF-α) release were assessed using MTT assay, flow cytometry and ELISA, respectively. The expression levels of LMP-1, cleaved-caspase 3, phosphorylated (p)-p65, p65, p-JNK and JNK were analyzed using reverse transcription-quantitative PCR and western blotting. Overexpression of LMP-1 notably alleviated the IL-1β-induced inflammatory response in CHON-001 cells, as shown by increased cell viability, decreased apoptosis, suppressed expression of cleaved-caspase 3 and a decreased cleaved-caspase 3/caspase 3 ratio. Moreover, IL-1β-induced secretion of IL-6, IL-8 and TNF-α in CHON-001 cells; this was reversed by pcDNA3.1-LMP-1. However, knocking down LMP-1 expression exert opposite effects on the IL-1β-induced inflammatory response in CHON-001 cells, as evidenced by the decreased cell viability, increased apoptosis, enhanced expression of cleaved-caspase 3 and cleaved-caspase 3/caspase 3 ratio and enhanced secretion of IL-6, IL-8 and TNF-α observed. The present data demonstrated that LMP-1 siRNA notably inhibited LMP-1 expression, suppressed cell viability, promoted apoptosis and enhanced cleaved-caspase 3 expression and cleaved-caspase 3/caspase 3 ratio. In addition, LMP-1 siRNA promoted the release of inflammatory factors in CHON-001 cells. It was also found that pcDNA3.1-LMP-1 inhibited p-p65 and p-JNK expression, as well as decreasing the p-p65/p65 and p-JNK/JNK ratio. Nevertheless, there was no significant difference in the mRNA expression levels of p65 and JNK between the groups. Taken together, these findings indicated that overexpression of LMP-1 alleviated IL-1β-induced chondrocytes injury by regulating the NF-κB and MAPK/JNK pathways, suggesting that LMP-1 may be a valuable therapeutic agent for OA treatment.
