Expression of CXCR-1 and CXCR-2 chemokine receptors on synovial neutrophils in inflammatory arthritides: Does persistent or increasing expression of CXCR-2 contribute to the chronic inflammation or erosive changes?

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ObjectiveTo analyze the CXCR-1 and CXCR-2 chemokine receptor expression on peripheral blood neutrophils (PBN) and synovial fluid neutrophils (SFN) of patients with rheumatoid arthritis (RA) and Behçet's disease (BD) (characterized by erosive and non-erosive arthritis, respectively), and to compare them with those of patients with osteoarthritis (OA). MethodsWe used flow cytometry to investigate the expression of CXCR-1 and CXCR-2 chemokine receptors on PBN and SFN of fifty-five (22 RA, 22 BD and 11 OA) age and sex-matched patients. ResultsIn respect to chemokine receptor expression on neutrophils isolated from patients with RA, mean fluorescein intensity (MFI) of CXCR-1 chemokine receptors on PBN from active and inactive RA patients, and SFN from patients with RA were 151 (90–395), 129 (81–539) and 136 (64–220), respectively, and there were not statistically significant difference each other. But MFI of CXCR-2 chemokine receptors on SFN of patients with RA was 18 (10–32), and significantly higher than PBN of active and inactive RA patients (MFI: 10 (6–15) and 12 (7–16), P=0.002 and 0.037, respectively). In respect to chemokine receptor expression on neutrophils isolated from patients with BD, MFI of CXCR-1 chemokine receptors on PBN of active BD patients was 245 (97–844), and higher than PBN of active RA patients and SFN of BD patients (MFI: 151 (90–395) and 134 (61–231), P=0.047 and 0.017, respectively). MFI of CXCR-2 chemokine receptors on PBN of active and inactive BD patients, and SFN of patients BD were 10 (6–14), 10 (2–16), and 12 (8–24), respectively, there were not statistically significant difference each other. MFI of CXCR-1 chemokine receptors on SFN from patients with RA, BD, and OA were 136 (64–220), 134 (61–231), and 114 (60–180), respectively, and there was no difference between the study groups. MFI of CXCR-2 chemokine receptors on SFN of patients with RA was 18 (10–32), and higher than patients with BD and OA (MFI: 12 (8–24) and 11 (9–18), P=0.037 and 0.005, respectively), though there was no difference between last two groups. ConclusionOur study points that CXCR-1 and CXCR-2 chemokine receptors of SFN may have diverse functions in the course of inflammatory arthritides. These results indicate that CXCR-2 chemokine receptor might play more critical role in long lasting accumulation of neutrophils within the synovial fluid of patients with RA.