Lectin-like oxidized low-density lipoprotein receptor 1 mediates matrix metalloproteinase 3 synthesis enhanced by oxidized low-density lipoprotein in rheumatoid arthritis cartilage.
OBJECTIVE
To investigate for the presence of oxidized low-density lipoprotein (ox-LDL) and lectin-like oxidized LDL receptor 1 (LOX-1) in cartilage specimens from rheumatoid arthritis (RA) joints and to determine whether the interaction of ox-LDL with LOX-1 can induce matrix metalloproteinase 3 (MMP-3) in articular cartilage explant culture.


METHODS
Human articular cartilage specimens obtained from patients with RA, osteoarthritis (OA), and femoral neck fractures were examined for LOX-1 and ox-LDL by confocal fluorescence microscopy. The association between ox-LDL and LOX-1 was evaluated by immunofluorescence analysis. Articular cartilage specimens from patients with femoral neck fractures were incubated with ox-LDL, with or without preincubation with neutralizing anti-LOX-1 antibody. MMP-3 synthesis by chondrocytes in explant cartilage was evaluated by immunofluorescence, and protein secretion into conditioned medium was monitored by immunoblotting and enzyme-linked immunosorbent assay.


RESULTS
The majority of the RA chondrocytes stained positively with both anti-LOX-1 and anti-ox-LDL antibodies; however, no positive cells were found in OA and normal cartilage specimens. Anti-LOX-1 antibody suppressed the binding of DiI-labeled ox-LDL to chondrocytes in explant culture, suggesting that the interaction was mediated by LOX-1. In contrast to native LDL, ox-LDL induced MMP-3 synthesis by articular chondrocytes in association with the induction of LOX-1, which resulted in enhanced secretion of MMP-3 into the culture medium. Anti-LOX-1 antibody reversed ox-LDL-stimulated MMP-3 synthesis to control levels.


CONCLUSIONS
Ox-LDL, principally mediated by LOX-1, enhanced MMP-3 production in articular chondrocytes. Increased accumulation of ox-LDL with elevated expression of LOX-1 in RA cartilage indicates a specific role of the receptor-ligand interaction in cartilage pathology in RA.
Kakinuma
Takumi
T
Department of Orthopaedic Surgery, Kyoto University Graduate School of Medicine, 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507, Japan.
Yasuda
Tadashi
T
Nakagawa
Takefumi
T
Hiramitsu
Teruko
T
Akiyoshi
Miki
M
Akagi
Masao
M
Sawamura
Tatsuya
T
Nakamura
Takashi
T
D000906:Antibodies / Q000494:pharmacology; D001172:Arthritis, Rheumatoid / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D002358:Cartilage, Articular / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D019902:Chondrocytes / Q000187:drug effects / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D015151:Immunoblotting; D008077:Lipoproteins, LDL / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D019278:Matrix Metalloproteinase 3 / Q000096:biosynthesis*; D008856:Microscopy, Fluorescence; D011973:Receptors, LDL / Q000276:immunology / Q000378:metabolism*; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; D046509:Tissue Culture Techniques
D000906:Antibodies; D008077:Lipoproteins, LDL; C495137:OLR1 protein, human; D011973:Receptors, LDL; D051131:Receptors, Oxidized LDL; D051127:Scavenger Receptors, Class E; C099252:oxidized low density lipoprotein; D019278:Matrix Metalloproteinase 3