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.


The Smoking-Induced Heat Shock Protein DNAjC6 Is Downregulated in Rheumatoid Arthritis.

Ospelt1,  Caroline, Stanczyk2,  Joanna, Kolling3,  Christoph, Gay1,  Renate E., Gay4,  Steffen

Center of Experimental Rheumatology and Center of Integrative Human Physiology, Zurich, Switzerland
Center of Experimental Rheumatology and Center of Integrative Human Physiology, Zurich, Switzerland
Schulthess Clinic Zurich, Switzerland
University Hospital Zurich, Zurich, Switzerland

Background:

Previously we had found that the heat shock protein DNAjC6 is upregulated in joints of mice after exposure to cigarette smoke as well as in the synovium of human smokers compared to non-smokers. Smoking has repeatedly been shown to be a risk factor for the development of rheumatoid arthritis (RA) in susceptible individuals. On the other hand nicotine has also been found to have anti-inflammatory properties and smoke exposure delays the onset of collagen-induced arthritis in mice. Also heat shock proteins have been described to protect cells from environmental damage and act as tumor suppressors, as well as to elicit aberrant immune responses. In the current work we aimed at elucidating the effect of increased levels DNAjC6 in joints of smokers and its possible role in pathogenesis of RA.

Material and Methods:

Expression of DNAjs, MMPs, IL-6, IL-8 and microRNAs (miRs) in synovial fibroblasts (SFs) and tissues was measured by Real-time PCR. Relative quantification with 18S or let7a as reference genes was used to quantify levels of gene expression. Synovial fibroblasts were transfected with siRNA targeting DNAjC6 or siRNA control by nucleoporation.

Results:

Basal mRNA expression levels of 6 DNAj family members representing different subtypes of DNAjs namely DNAjA3, B4, B9, C6, C9 and C15 were measured in RA (n=6) and osteoarthritis (OA; n=8) SFs. Except for DNAjB9, SFs expressed all of the measured DNAjs, but only DNAjC6 was differentially expressed between RA and OA. Thereby, transcript levels of DNAjC6 were 2.3 fold downregulated in RASFs compared to OASFs (dCT 13.6 ±0.4 vs 12.4 ±0.2; p=0.04). Decreased expression of DNAjC6 in RA was also measured in synovial tissues, where it was 3.3 fold lower in RA (n=16) than in OA patients (n=6) (dCT 13.7 ±0.2 vs 12.0 ±0.6; p=0.01). To see the effect of lowered DNAjC6 levels in SFs we silenced its expression in OASFs (n=4) and measured expression levels of MMPs, IL-6 and IL-8. Whereas the expression of the interleukins, MMP-9 and MMP-13 was not altered, expression of MMP-1 and MMP-3 significantly increased by silencing of DNAjC6 (1.9 ±0.2 and 1.7 ±0.2 respectively; p=0.03). In search of mechanisms leading to lowered expression of DNAjC6 in RA, we used computational miR target prediction programs and found that miR-323 potentially targets DNAjC6, but no other members of the DNAj family. In accordance, expression of miR-323 was significantly higher in RASFs (n=6) than in OASFs (n=4) (dCT 8.6 ±0.3 vs 9.4 ±0.1; p=0.04) and basal expression levels of miR-323 in SFs (n=10) negatively correlated with expression of DNAjC6 (Spearman r: -0.8; p=0.006).

Conclusion:

In the current work, we identified a novel pathway contributing to the imprinted activated phenotype of SFs in RA. Elevated expression of miR-323 in RASFs causes downregulation of DNAjC6 mRNA which leads to higher expression of MMPs promoting joint destruction. Therefore, increased expression of DNAjC6 in joints of smokers might be a protective mechanism against environmental damage.

To cite this abstract, please use the following information:
Ospelt, Caroline, Stanczyk, Joanna, Kolling, Christoph, Gay, Renate E., Gay, Steffen; The Smoking-Induced Heat Shock Protein DNAjC6 Is Downregulated in Rheumatoid Arthritis. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1093
DOI: 10.1002/art.28860

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