Macrophages from the synovium of active rheumatoid arthritis exhibit an activin A‐dependent pro‐inflammatory profile

Abstract

Rheumatoid arthritis (RA) is a chronic inflammatory disease whose pathogenesis and severity correlates with the presence of macrophage-derived pro-inflammatory cytokines within the inflamed synovium. Macrophage-derived cytokines fuel the pathological processes in RA and are targets of clinically successful therapies. However, although macrophage polarization determines cytokine production, the polarization state of macrophages in RA joints remains poorly defined. To dissect the molecular basis for the tissue-damaging effects of macrophages in RA joints, we undertook the phenotypic and transcriptomic characterization of ex vivo isolated CD14(+) RA synovial fluid (RA-SF) macrophages. Flow cytometry and gene profiling indicated that RA-SF macrophages express pro-inflammatory polarization markers (MMP12, EGLN3, CCR2), lack expression of markers associated with homeostatic and anti-inflammatory polarization (IGF1, HTR2B) and exhibit a transcriptomic profile that resembles the activin A-dependent gene signature of pro-inflammatory in vitro-generated macrophages. In fact, high levels of Smad-activating activin A were found in RA-SF and, accordingly, the Smad signalling pathway was activated in ex vivo-isolated RA-SF macrophages. In vitro experiments on monocytes and macrophages indicated that RA-SF promoted the acquisition of pro-inflammatory markers (INHBA, MMP12, EGLN3, CCR2) but led to a significant reduction in the expression of genes associated with homeostasis and inflammation resolution (FOLR2, SERPINB2, IGF1, CD36), thus confirming the pro-inflammatory polarization ability of RA-SF. Importantly, the macrophage-polarizing ability of RA-SF was inhibited by an anti-activin A-neutralizing antibody, thus demonstrating that activin A mediates the pro-inflammatory macrophage-polarizing ability of RA-SF. Moreover, and in line with these findings, multicolour immunofluorescence evidenced that macrophages within RA synovial membranes (RA-SM) also express pro-inflammatory polarization markers whose expression is activin A-dependent. Altogether, our results demonstrate that macrophages from RA synovial fluids and membranes exhibit an MMP12(+) EGLN3(+) CCR2(+) pro-inflammatory polarization state whose acquisition is partly dependent on activin A from the synovial fluid.

Methotrexate selectively targets human proinflammatory macrophages through a thymidylate synthase/p53 axis

“…Previously, we have shown that macrophages from RA joints exhibit a GM-CSF-dependent transcriptomic and phenotypical proinflammatory polarisation state 26. As macrophages represent an important MTX target in RA, the expression of TS was determined in normal and active RA synovium.…”

Urokinase plasminogen activator and receptor promote collagen-induced arthritis through expression in hematopoietic cells

“…Additionally macrophages produce a spectrum of proteases (in addition to uPA) such as matrix metalloproteinases that drive tissue destruction in RA. [30][31][32] In CIA, macrophages play a preeminent role in driving disease. Targeting molecules that promote macrophage proliferation, accumulation or activation (eg, CSF-1, granulocytemacrophage colony-stimulating factor, TNF-a, IL-1b, and IL-6) [33][34][35][36][37][38][39][40] suppresses CIA in mice.…”

Reshaping of Human Macrophage Polarization through Modulation of Glucose Catabolic Pathways

“…M-MØ respond to hypoxia by changing their metabolic profile and acquiring a GM-MØ-like transcriptomic and functional profile, with both changes dependent on both HIF-1a and HIF-2a. This hypoxia-driven response could explain the elevated number of proinflammatory macrophages found in the synovium of rheumatoid arthritis patients (43), where the severe hypoxic milieu might promote or contribute to the activin A-dependent M-MØ to GM MØ switch (5, 6, 43). In contrast, hypoxia does not modify GM-MØ at the transcriptional (expression of polarization-associated genes) or functional (cytokine production) level (Fig.…”