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.


Ankylosing Spondylitis Macrophages Produce Greater IL-23 in Response to Lipopolysaccharide without Significant Unfolded Protein Response Induction.

Zeng,  Ling, Lindstrom,  Mary, Smith,  Judith

Purpose:

Inflamed tissue from Ankylosing Spondylitis (AS) patients display a preponderance of macrophages. Previous work from an HLA-B27 transgenic rat model suggests that macrophages from arthritic animals develop an intracellular stress response called the Unfolded Protein Response (UPR) and as a result, secrete increased cytokines in response to Toll like receptor agonists such as lipopolysaccharide (LPS). Our objective was to determine if macrophages from AS patients undergo a UPR and secrete increased cytokines/chemokines in response to LPS.

Methods:

Peripheral blood monocytes were isolated from 10 AS patients (median age 46.5y, 90% male, 70%HLA-B27+ and 2ND) and 10 controls (HC, median age 45y, 90%male, all HLA-B27-), and differentiated in vitro with M-CSF for 5 days. Select samples were then treated with 1000U/mL IFN-g for 24h to up-regulate MHC class I prior to stimulation with LPS for 3h (for RNA collection), or 8–24h (supernatants). UPR induction was assessed by up-regulation of ERdj4, BiP and CHOP mRNA detected by quantitative PCR. Supernatants were analyzed for cytokine/chemokine production by ELISA or Luminex. Statistical analysis involved 2-sample Wilcoxon tests for cytokine data, and a linear mixed effect model following log transformation of gene expression data.

Results:

In response to LPS alone, AS macrophages secreted more CXCL9, IL-10, IL-12p70, IL-23, and TNFa than HC macrophages (p< or = 0.02). We did not detect significant differences between AS and HC for IL-6, IL-8, CXCL10, IL-1b, IFN-b or MCP-1. IFN pre-treatment tended to minimize differences between AS and HC for all cytokines/chemokines except IL-12p70. The most striking difference between AS and HC macrophages was for IL-23 production (median HC 9pg/mL vs. AS 265 pg/mL at 24h, p=0.0007). 3h LPS treatment had no effect on UPR gene expression. Although IFN treatment up-regulated HLA-B expression by 2–3 fold, it did not enhance BiP or CHOP expression. ERdj4 expression weakly increased (2-fold, p=0.03–0.06) in IFN+LPS AS samples only.

Conclusions:

Gene association studies and animal models have implicated the IL-23/Th17 pathway in pathogenesis. These results showing greater IL-23 production by AS patient macrophages in response to LPS further support the development of IL23-directed therapy. Since we were unable to detect significant UPR induction in AS macrophages, the relationship between UPR and inflammatory cytokine production remains unclear.

To cite this abstract, please use the following information:
Zeng, Ling, Lindstrom, Mary, Smith, Judith; Ankylosing Spondylitis Macrophages Produce Greater IL-23 in Response to Lipopolysaccharide without Significant Unfolded Protein Response Induction. [abstract]. Arthritis Rheum 2010;62 Suppl 10 :1965
DOI: 10.1002/art.29730

Abstract Supplement

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