Arthritis & Rheumatism, Volume 62,
November 2010 Abstract Supplement

Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Atlanta, Georgia November 6-11, 2010.


Defective ERK Signaling in Hematopoietic Progenitor Cells in Rheumatoid Arthritis.

Colmegna2,  Ines, Pryschep1,  Sergei, Oishi3,  Hisashi, Goronzy3,  Jorg J., Weyand3,  Cornelia M.

Georgia Institute of Technology
McGill University, Montreal, QC, Canada
Stanford University

Background:

The main functional property of hematopoietic progenitor cells (CD34+ HPC) is their proliferative response to hematopoietins. HPC from patients with rheumatoid arthritis (RA) are hypo-responsive to growth factor stimulation leading to a decreased cell cycle entry and progression and thus to a restricted expansion capacity. Kinase-based signal transduction pathways are key integration points that link extracellular stimuli to proliferation, differentiation and cell survival. We tested the hypothesis of whether a defect of the extracellular signal-regulated kinase (ERK) pathway underlies the proliferative defect of RA HPC.

Methods:

CD34+ cells from patients with rheumatoid factor-positive RA and demographically matched healthy controls were MACS sorted from PBMC. A minimum of 12 RA samples and 12 matched controls were included per experiment. The surface expression of cytokine receptors (IL-3 and IL-6 receptor subunits, c-kit and FLT3) was evaluated by FACS. Baseline and post-cytokine (IL-3, IL-6, FLT3-L and SCF) activation phosphorylation states of ERK 1/2 were determined by flowcytometric single-cell phospho-protein analysis (Phospho-Flow). Transcripts of ERK target genes (c-Myc and Cyclin D) were quantified by RT-PCR. The co-localization of K-Ras/ Raf-B, proximal events in the activation of ERK, was assessed by confocal microscopy in CD34+ cells.

Results:

The frequency and density of cytokine receptor expression was similar in RA and controls CD34+ cells. Baseline and post-cytokine activation phosphorylated ERK (pERK) was decreased in RA CD34 compared to demographically matched controls (baseline p=0.04, 10' activation p=0.005, 15' activation p=0.006). Transcripts of ERK modulated genes involved in cell cycle progression (Cyclin D3, and c-Myc) were significantly reduced in RA (p<0.02). Confocal microscopy studies demonstrated significantly lower cytokine-induced Ras/Raf colocalization in RA CD34+ cells than in controls. (p=0.04) implicating proximal events in the defective ERK activation.

Conclusions:

Cytokine evoked signaling responses of the ERK signaling pathway, a key integration network linking extracellular stimuli to proliferation, are defective in RA HPC. Insufficient clustering of K-Ras and Raf-B complexes, decreased phosphorilation of ERK and downregulation of the expression of ERK dependent genes involved in proliferative responses are all consistent with a defect in the ERK pathway.

To cite this abstract, please use the following information:
Colmegna, Ines, Pryschep, Sergei, Oishi, Hisashi, Goronzy, Jorg J., Weyand, Cornelia M.; Defective ERK Signaling in Hematopoietic Progenitor Cells in Rheumatoid Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :351
DOI: 10.1002/art.28120

Abstract Supplement

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