Notch Signaling Mediates TNF-α-Induced IL-6 Production in Cultured Fibroblast-Like Synoviocytes from Rheumatoid Arthritis

Zhijun Jiao,Huaxi Xu,Shengjun Wang,Zhaoliang Su,Wenhong Wang,Jie Ma

doi:10.1155/2012/350209

Abstract

It has been reported that Notch family proteins are expressed in synovium tissue and involved in the proliferation of synoviocyte from rheumatoid arthritis (RA). The aim of this paper was to investigate whether Notch signaling mediated TNF-α-induced cytokine production of cultured fibroblast-like synoviocytes (FLSs) from RA. Exposure of RA FLSs to TNF-α (10 ng/ml) led to increase of Hes-1, a target gene of Notch signaling, and a marked upregulation of Notch 2, Delta-like 1, and Delta-like 3 mRNA levels. Blockage of Notch signaling by a γ-secretase inhibitor (DAPT) inhibited IL-6 secretion of RA FLSs in response to TNF-α while treatment with recombinant fusion protein of Notch ligand Delta-like 1 promoted such response. TNF-α stimulation also induced IL-6 secretion in OA FLSs; however, the Hes-1 level remained unaffected. Our data confirm the functional involvement of Notch pathway in the pathophysiology of RA FLSs which may provide a new target for RA therapy.

Highlights

Rheumatoid arthritis (RA) is characterized by chronic and progressive inflammation of multiple joints, resulting in leukocyte invasion, formation of pannus, progressive degradation of the cartilage, and erosion of the bones [1]
We first determined the effect of tumor necrosis factor-α (TNF-α) on the expression of Notch signaling molecules in RA fibroblast-like synoviocytes (FLSs) by real-time PCR
Exposure of RA FLSs to TNF-α led to a gradual, timedependent increase of hairy-enhancer of split-like 1- (Hes-1) mRNA levels, a target gene

Summary

Introduction

Rheumatoid arthritis (RA) is characterized by chronic and progressive inflammation of multiple joints, resulting in leukocyte invasion, formation of pannus, progressive degradation of the cartilage, and erosion of the bones [1]. Cytokines secreted by RA synoviocytes include tumor necrosis factor-α (TNF-α), interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and granulocyte macrophage-colony stimulating factor (GM-CSF) [3]. Among these cytokines, TNF-α appears to be the major proinflammatory cytokine because it is known to strongly induce the production of IL-6, IL-8, GM-CSF, and even itself in synoviocytes; the precise molecular mechanism of cytokines production in response to TNF-α stimulation is not clarified [4]. Four Notch receptors (Notch 1–4) and five of their ligands (Delta-like 1, 3, 4; Jagged-1, 2) have been identified in mammals. The intracellular domain (ICD) of the receptor is proteolytically cleaved and translocated into the nucleus, where it associates with the RBP-Jκ transcription factor and regulates expression of several target genes, such as the basic helix-loop-helix (bHLH) proteins hairy-enhancer of split-like 1- (Hes-1) and Hes-5 [6]

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