Oxidized LDL binding to LOX-1 enhances MCP-1 expression in cultured human articular chondrocytes

Objective: It has been suggested that oxidized low-density lipoprotein (ox-LDL) has some roles in progression of osteoarthritis. The purpose of this study is to investigate whether ox-LDL binding to lectin-like ox-LDL receptor 1 (LOX-1) enhances monocyte chemoattractant protein I (MCP-1) expression in cultured human articular chondrocytes (HACs). Method. The time course and dose response of MCP-1 mRNA expression and MCP-1 protein release into medium following ox-LDL stimulation were investigated using quantitative Real time PCR (delta-delta Ct method) and enzyme-linked immunosorbent assay (ELISA), respectively. To examine the receptor specificity of ox-LDL action, HACs were preincubated with anti-human LOX-1 monoclonal antibody (TS92). Results: A time-course study revealed that MCP-1 mRNA expression increased 5.09 +/- 0.86 fold 12 h after ox-LDL stimulation compared to time-0. ox-LDL stimulation increased MCP-1 protein level in conditioned medium in a time-dependent manner. Increased MCP-1 level was evident 6 h after stimulation, reaching 830 +/- 91 pg/ml at 24 h (33 +/- 8 pg/ml at time-0). Dose responses of MCP-1 expression were also evident in mRNA and protein levels. Pretreatment with TS92 markedly suppressed these stimulating effects of ox-LDL, although that with non-specific IgG did not. Native LDL did not affect MCP-1 expression. Conclusion: Our results suggest that ox-LDL enhances MCP-1 expression in HACs and supports the hypothesis that ox-LDL is involved in cartilage degeneration. (C) 2008 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.