Activated Protein C Inhibits Proliferation and Tumor Necrosis Factor α-Stimulated Activation of p38, c-Jun NH2-Terminal Kinase (JNK) and Akt in Rheumatoid Synovial Fibroblasts

Sohel M Julovi,Nikita Minhas,Lyn March,Christopher J Jackson,Kaitlin Shen,Kelly Mckelvey

doi:10.2119/molmed.2013.00034

Sohel M Julovi, Nikita Minhas + Show 4 more

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https://doi.org/10.2119/molmed.2013.00034

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Abstract

Synovial fibroblast proliferation is a hallmark of the invasive pannus in the rheumatoid joint. Activated protein C (APC) is a natural anticoagulant that exerts antiinflammatory and cyto-protective effects in various diseases via endothelial protein C receptor (EPCR) and proteinase-activated receptor (PAR)-mediated pathways. In this study, we investigated the effect and the underlying cellular signaling mechanisms of APC on proliferation of human rheumatoid synovial fibroblasts (RSFs). We found that APC stimulated proliferation of mouse dermal fibroblasts (MDFs) and normal human dermal fibroblasts (HDFs) by up to 60%, but robustly downregulated proliferation of RSFs. APC induced the phosphorylation of extracellular signal-regulated protein kinase (ERK) and enhanced expression of p21 and p27 in a dose-dependent manner in RSFs. The latter effect was inhibited by pre-treatment with the ERK inhibitors PD98059 and U0126 but not by p38 inhibitor SB203580. In addition, APC significantly downregulated tumor necrosis factor (TNF)α-stimulated cell proliferation and activation of p38, c-Jun NH2-terminal kinase (JNK) and Akt in RSFs. These results provide the first evidence that APC selectively inhibits proliferation and the inflammatory signaling pathways of RSFs. Thus, APC may reduce synovial hyperplasia and pannus invasion in rheumatoid arthritis.

Highlights

Rheumatoid synovial fibroblasts (RSFs) are one of the major cell types in the synovial pannus and contribute actively to inflammation in rheumatoid arthritis (RA) [1,2,3]. These cells respond to cytokines, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α through the activation of multiple intracellular signaling pathways, including the mitogenactivated protein kinases (MAPKs) extracellular signal–regulated protein kinase (ERK), c-Jun NH2-terminal kinase (JNK)
We investigated the effects of Activated protein C (APC) on RSF proliferation and, surprisingly, our results show that APC inhibits proliferation of RSFs and that it acts via induction of p21/p27 and activation of ERK1/2
Treatment with APC (0.1–10 μg/mL) for 24 h stimulated the proliferation of normal mouse dermal fibroblasts (MDFs) and normal human dermal fibroblasts (HDFs) by up to 60% (Figure 1A)

Summary

Introduction

Rheumatoid synovial fibroblasts (RSFs) are one of the major cell types in the synovial pannus and contribute actively to inflammation in rheumatoid arthritis (RA) [1,2,3] These cells respond to cytokines, such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α through the activation of multiple intracellular signaling pathways, including the mitogenactivated protein kinases (MAPKs) extracellular signal–regulated protein kinase (ERK), c-Jun NH2-terminal kinase (JNK). The Cip/Kip family contains proteins such as p21/WAF1 and p27/KIP that bind to cyclin/cyclin-dependent kinase complexes and prevent kinase activation These cyclin-dependent kinase inhibitors play a key role in RA pathogenesis by affecting proliferation and inflammatory cytokine production in human RSFs and mouse synovial fibroblasts [11,12]

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