IL-6 signal blockade ameliorates the enhanced osteoclastogenesis and the associated joint destruction in a novel FcγRIIB-deficient rheumatoid arthritis mouse model.

Abstract

OBJECTIVE:

We earlier found that TNFα but not interleukin (IL)-17 is indispensable in the pathogenesis of spontaneously occurring rheumatoid arthritis (RA)-like disease in our newly established FcγRIIB-deficient C57BL/6 (B6) mouse model, designated KO1. Here, we examined the role of IL-6 in the pathogenesis of RA features in KO1, with particular reference to cartilage and bone destruction in arthritic joints.

METHODS:

To evaluate the preventive effect of MR16-1, a rat anti-mouse IL-6 receptor (IL-6R) mAb, 4-month-old preclinical KO1 mice were divided into three groups: the first treated with MR16-1 for 6 months, the second treated with normal rat IgG, as a control, and the third left untreated. The incidence and severity of arthritis, immunological abnormalities, and transcription levels of receptor activator of NF-κB ligand (RANKL), osteoprotegerin (OPG), and inflammatory cytokines/chemokines in ankle joint tissues were compared among the three groups. The therapeutic effect of MR16-1 was examined by treating 7-month-old KO1 mice in the early stages of arthritis for 2 months.

RESULTS:

Compared with the findings in the KO1 mice left untreated or treated with normal rat IgG, the development of arthritis was markedly suppressed in mice with MR16-1 treatment started from preclinical stages. The suppression was associated with the decrease in production of autoantibodies, rheumatoid factors (RF), and anti-cyclic citrullinated peptide (CCP). Histologically, marked synovitis, pannus formation, and cartilage and bone destruction associated with the increase in tartrate-resistant acid phosphatase (TRAP)-positive osteoclast generation were evident in the two control groups; however, these findings were virtually absent in MR16-1-treated mice. Real-time PCR analysis revealed that the up-regulated expression levels of MCP-1, IL-6, and TNFα, and the aberrantly high RANKL/OPG expression ratio in synovial joint tissues from the two control groups of mice with overt arthritis were significantly suppressed in MR16-1-treated mice. In mice with therapeutic MR16-1 treatment, there was no progression in arthritis score and the RANKL/OPG ratio in joint tissues was significantly suppressed.

CONCLUSIONS:

Administration of an anti-IL-6R mAb ameliorated spontaneously occurring RA-like disease features, indicating that IL-6, as well as TNFα, plays a pivotal role in the pathogenesis of RA in KO1 mice. Current studies showed that, in addition to the role in enhancing autoantibody production, IL-6 promotes synovial tissue inflammation and osteoclastogenesis, leading to the severe synovitis with pannus formation and the progressive cartilage and bone destruction in multiple joints.

• Authors: Mareki Ohtsuji, Qingshun Lin, Keiko Nishikawa, Naomi Ohtsuji, Hideki Okazaki, Hiromichi Tsurui, Hirofumi Amano, Toshikazu Shirai, Norihiro Nishimoto, Hiroyuki Nishimura, Sachiko Hirose
• Journal: Modern rheumatology (Mod Rheumatol) Vol. 25 Issue 2 Pg. 270-7 (Mar 2015) ISSN: 1439-7609 [Electronic] England
• PMID: 25159156 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Monoclonal
• Autoantibodies
• Cytokines
• Fc gamma receptor IIB
• Osteoprotegerin
• RANK Ligand
• Receptor Activator of Nuclear Factor-kappa B
• Receptors, IgG
• Receptors, Interleukin-6

Topics

• Animals
• Antibodies, Monoclonal (pharmacology, therapeutic use)
• Arthritis, Rheumatoid (drug therapy, genetics, pathology)
• Autoantibodies (immunology)
• Cytokines (genetics, metabolism)
• Disease Models, Animal
• Joints (drug effects, immunology, pathology)
• Mice
• Osteoclasts (drug effects, immunology, pathology)
• Osteoprotegerin (genetics, metabolism)
• RANK Ligand (genetics, metabolism)
• Receptor Activator of Nuclear Factor-kappa B (genetics, metabolism)
• Receptors, IgG (genetics, metabolism)
• Receptors, Interleukin-6 (immunology)
• Severity of Illness Index