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Objective: Interleukin (IL)-23/IL-17 pathway involves in the pathogenesis of ankylosing spondylitis (AS). The exact mechanism implicated in overexpression of IL-23 and activation of the IL-23/IL-17 axis is not clear. The aim of the study was to clarify whether macrophages of AS patients undergo unfolded protein response (UPR) and secret increased IL-23., Methods: Peripheral blood monocyte isolated from 10 HLA-B27 + patients and five HLA-B27 + normal subjects were differentiated to macrophages by macrophage-colony stimulating factor (M-CSF) for seven days. Flow cytometry was used to detect monocyte purity and expression of macrophage markers. Analysis of mRNA expression for HLA-B and B27, UPR-associated proteins (BiP, CHOP, MDG1, and XBP1) and IL-23 was performed by RT-qPCR., Results: RT-qPCR data showed a significant overexpression of HLA-B27, UPR genes (BiP, CHOP, and XBP1), and IL-23 in M-CSF-derived macrophages from AS patients compared to healthy controls. Increased expression of MDG1 was not significant., Conclusions: Our data suggest that UPR activation occurs in M-CSF-derived macrophages of AS patients and is accompanied by overexpression of HLA-B27. UPR appears to be associated with overproduction of IL-23 in AS macrophages.

• A 2A AR agonist decreases TNF-α secretion by macrophages of AS patients. • A 2A AR activation increases IL23A mRNA expression by macrophages of AS patients. • A 2A AR activation did not have any influence on macrophages of healthy individuals. Ankylosing spondylitis (AS) is an auto-inflammatory debilitating disorder with a complex pathogenesis. The adenosinergic pathway is an immunologic regulating pathway with a potential role in AS pathophysiology. In the present study, we have aimed to investigate the influence of A 2A adenosine receptor (A 2A AR) activation on tumor necrosis factor-α (TNF-α) and interleukin-23 (IL-23) expression and secretion by monocyte-generated macrophages of AS patients. Whole-blood separated monocytes were extracted from 14 AS patients and 14 healthy controls. Macrophages were differentiated by macrophage colony-stimulating factor (M-CSF), and surface markers were confirmed by flow cytometer. Cells were treated with CGS-21680 as a known agonist of A 2A AR. Analysis of ADORA2A , TNFA , and IL23A gene expression was performed by SYBR green real-time PCR. The concentration of secreted cytokines was also measured by ELISA kits. Based on our analysis, CGS-21680 significantly decreased TNF-α secretion by monocyte-derived macrophages of AS patients. Moreover, A 2A AR agonist increased the IL23A mRNA expression level in monocyte-derived macrophages of AS patients considerably. Whereas, CGS-21680 did not have any influence on macrophages of healthy individuals. According to our results, it appears that A 2A AR activation can increase IL-23 secretion by monocyte-derived macrophages of AS patients. Although the TNF-α reducing effect of A 2A AR agonists can be a potential target in AS treatment, robust increasing of IL-23 should be considered as the undesirable effect of these agents. [ABSTRACT FROM AUTHOR]