Background/Purpose:

Tofacinitib (Pfizer) is an oral Janus kinase inhibitor, recently approved for the treatment of rheumatoid arthritis (RA) and psoriatic arthritis (PsA). Although its mechanism of action has been explored in circulating cells, in particular neutrophils and lymphocyte, its effect on dendritic cells development and function remains still to be elucidated.
Monocyte-derived dendritic cells are a subset of inflammatory DC derived from circulating monocytes and have a key role in inflammation and infection. The aim of this project is to evaluate the effect of Tofacitinib on inflammatory monocyte-derived dendritic cells (Mo-DC) from RA and PsA patients, and in particular on the ability of monocyte to differentiate into dendritic cells, an important step in innate immunity.

Methods: Monocytes were isolated from blood of healthy donor (HC), RA and PsA patients by magnetic separation and plated in presence/absence of GM-CSF/IL-4 cocktail for 7 days, to acquire immature dendritic cells (DC) phenotype. To evaluate the effect of Tofacinitib on Mo-DC differentiation, monocyte were treated with 1µM Tofacinitib (or DMSO as control) for 15 minute prior to cytokine stimulation. CD209 (immature DC marker) and CD14 (monocyte marker) were evaluated by flow cytometry in the CD11c positive population. Non-specific macropinocytosis (using Lucifer Yellow) and receptor-mediated endocytosis (using DQ^TM Ovalbumin) were investigated by flow cytometry. Western blot analysis was utilized for analysis of the effect of Tofacinitib on NADPH oxidases (NOX) 5 and 2, known player in Mo-DC differentiation. Finally, the frequency of CD209 cells was evaluated by flow cytometry in both peripheral blood (PBMC) and synovial fluid (SFMC) mononuclear cells from RA and PsA patients.

Results: Pre-treatment of Mo-DC with Tofacinitib inhibited Mo-DC differentiation in RA and PsA patients, as shown by reduced CD209 marker expression, paralleled by an increase of CD14 marker expression. The decreased ability of monocytes to differentiate into DC in the presence of Tofacinitib was translated into a function impairment of phagocytic ability, in particular in PsA patients, as observed by the decreased uptake of both DQ^TM Ovalbumin (receptor-mediated endocytosis) and Lucifer Yellow (micropinocytosis).
When comparing the ability of monocyte to differentiate into DC, we observed that RA monocytes differentiated faster than HC and PsA, expressing CD209 marker already at day 1.
NOX5 has previously been shown to play a key role in Mo-DC differentiation, therefore we sought to investigate whether the effect of Tofacinitib on Mo-DC differentiation is mediated through modulating NOX5. Interestingly, Tofacinitib decreased NOX5 and increased NOX2 protein expression in Mo-DC in both PsA and RA Mo-DC. Finally, we identified the CD209 population in PBMC cells from RA and PsA patients, and we observed an increased frequency of this population at the site of inflammation in SFMC cells from PsA and RA patients.

Conclusion: Together, these observations suggest a novel mechanism of action of Tofacinitib in RA and PsA, by inhibiting Mo-DC development, which may alter migration of DC to the joint and subsequent activation of the immune response.

« Back to 2018 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/tofacitinib-impairs-monocyte-derived-dendritic-cell-differentiation-in-rheumatoid-arthritis-and-psoriatic-arthritis/