Background/Purpose: Myeloid cells with a monocyte/macrophages phenotype are present in large numbers in the rheumatoid arthritis (RA) joint, significantly contributing to disease. This study aimed to assess whether peripheral monocytes in RA are pre-programmed to become M1 pro-inflammatory macrophages.

Methods: Blood was collected from healthy donors, at-risk individuals (Those with arthralgia, ACPA+/RF+, normal CRP and no evidence of synovitis) and established RA patients. CD14+ monocytes were isolated from peripheral blood mononuclear cells using a CD14 magnetic bead separation kit. Cells were stimulated with LPS (100ng/ml) for 3-24 hours and to assess the effects of STAT3 inhibition, cells were pre-treated with STATTIC (10µM) for 30mins. A Human Cytokine and Chemokine PCR array was carried out and those genes most differentially expression were further validated in a larger cohort of patients using RT-PCR. The metabolic profile of cells was analysed using Seahorse XFE Technology, which concomitantly analysis glycolysis and mitochondrial respiration in real-time. Gene and protein expression of key inflammatory and glycolytic markers was also carried out by RT-PCR, western blotting and ELISA.

Results: CD14+ RA monocytes are hyper-inflammatory upon stimulation, with significantly higher expression of IL-1β, TNFα, IL-6, IL-27, CXCL10 and CXCL11 compared to healthy controls, which is indicative of a M1-like pro-inflammatory phenotype. These hyper-inflammatory cells are highly glycolytic, with increased expression of HIF1α and PFKFB3, a key glycolytic enzyme. Both baseline glycolysis and the maximal glycolytic capacity are increased in RA CD14+ monocytes, with no changes observed in mitochondrial respiration. This hyper-inflammatory, hyper-glycolytic phenotype is mediated by STAT3, as selective STAT3 inhibition can significantly decrease M1-like cytokines and PFKFB3 expression. Finally, this pro-inflammatory phenotype in evident in CD14+ monocytes from arthralgia ACPA+/RF+ people at risk of developing disease, demonstrating that these processes may precede clinical manifestations in RA.

Conclusion: This study demonstrates the unique inflammatory and metabolic phenotype of RA monocytes, suggesting that peripheral CD14+ monocytes may be pre-programmed to become M1-like pro-inflammatory macrophages. In addition, the observation of this phenotype in at-risk individuals indicates that these features may precede clinical manifestations of RA and therefore could be useful as a biomarker for early diagnosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/rheumatoid-arthritis-peripheral-cd14-monocytes-are-hyper-inflammatory-hyper-glycolytic-and-retain-a-memory-bias-toward-m1-macrophages/