5-Lipoxygenase inhibitors attenuate TNF-α-induced inflammation in human synovial fibroblasts.

Han-Ching Lin,Tzu-Hung Lin,Ming-Yueh Wu,Houng-Chi Liou,Mann-Jen Hour,Chih-Hsin Tang,Yung-Cheng Chiu,Wen-Mei Fu,Huang-Ju Tu,Rong-Sen Yang,Chuen-Mao Yang

doi:10.1371/journal.pone.0107890

Abstract

The lipoxygenase isoform of 5-lipoxygenase (5-LOX) is reported to be overexpressed in human rheumatoid arthritis synovial tissue and involved in the progress of inflammatory arthritis. However, the detailed mechanism of how 5-lipoxygenase regulates the inflammatory response in arthritis synovial tissue is still unclear. The aim of this study was to investigate the involvement of lipoxygenase pathways in TNF-α-induced production of cytokines and chemokines. Human synovial fibroblasts from rheumatoid patients were used in this study. 5-LOX inhibitors and shRNA were used to examine the involvement of 5-LOX in TNF-α-induced cytokines and chemokines expression. The signaling pathways were examined by Western Blotting or immunofluorescence staining. The effect of 5-LOX inhibitor on TNF-α-induced chemokine expression and paw edema was also explored in vivo in C57BL/6 mice. Treatment with 5-LOX inhibitors significantly decreased TNF-α-induced pro-inflammatory mediators including interleukin-6 (IL-6) and monocyte chemo-attractant protein-1 (MCP-1) in human synovial fibroblasts. Knockdown of 5-LOX using shRNA exerted similar inhibitory effects. The abrogation of NF-κB activation was involved in the antagonizing effects of these inhibitors. Furthermore, 5-LOX inhibitor decreased TNF-α-induced up-regulation of serum MCP-1 level and paw edema in mouse model. Our results provide the evidence that the administration of 5-LOX inhibitors is able to ameliorate TNF-α-induced cytokine/chemokine release and paw edema, indicating that 5-LOX inhibitors may be developed for therapeutic treatment of inflammatory arthritis.

Highlights

Rheumatoid arthritis (RA) is a chronic and systemic autoimmune syndrome, which is characterized by massive synovial proliferation and inflammation and leads to the destruction of joint cartilage and bone [1]
Rabbit anti-5-LOX antibody was from Novus (Littleton, CO, USA). 5-LOX inhibitors, including MK-886, Nordihydroguaiaretic acid (NDGA); leukotriene B4 and leukotriene B4 receptor antagonist LY29311 were from Cayman Chemical Company (Ann Arbor, MI, USA)
Synovial fibroblasts contribute to synovium inflammation, angiogenesis, matrix degradation by its abilities to produce inflammatory cytokines, matrix degradation enzymes and angiogenic factor [22]

Summary

Introduction

Rheumatoid arthritis (RA) is a chronic and systemic autoimmune syndrome, which is characterized by massive synovial proliferation and inflammation and leads to the destruction of joint cartilage and bone [1]. Many kinds of cells infiltrate into the joint cavity during arthritis, including immune cells (such as macrophage, T cells and B cells) and erosive cells such as bone resorptive osteoclasts. Pruzanski et al [2] reported that the phospholipase A2 (PLA2) activity is increased in arthritis. Cytokines including TNF-a, IL-1 are reported to stimulate the activity of PLA2 [3,4]. Both cyclooxygenase (COX) and lipoxygenase (LOX) pathways are involved in the inflammatory actions related to AA [5]

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