Publication date: Available online 14 February 2018
Source:Journal of Autoimmunity
Author(s): Raphael S. Peres, Paula B. Donate, Jhimmy Talbot, Nerry T. Cecilio, Patricia R. Lobo, Caio C. Machado, Kalil W.A. Lima, Rene D. Oliveira, Vanessa Carregaro, Helder I. Nakaya, Thiago M. Cunha, José Carlos Alves-Filho, Foo Y. Liew, Paulo Louzada-Junior, Fernando Q. Cunha
Rheumatoid arthritis (RA) is an autoimmune arthropathy characterized by chronic articular inflammation. Methotrexate (MTX) remains the first-line therapy for RA and its anti-inflammatory effect is associated with the maintenance of high levels of extracellular adenosine (ADO). Nonetheless, up to 40% of RA patients are resistant to MTX treatment and this is linked to a reduction of CD39 expression, an ectoenzyme involved in the generation of extracellular ADO by ATP metabolism, on circulating regulatory T cells (Tregs). However, the mechanism mediating the reduction of CD39 expression on Tregs is unknown. Here we demonstrated that the impairment in TGF-β signalling lead to the reduction of CD39 expression on Tregs that accounts for MTX resistance. TGF-β increases CD39 expression on Tregs via the activation of TGFBRII/TGFBRI, SMAD2 and the transcription factor CREB, which is activated in a p38-dependent manner and induces CD39 expression by promoting ENTPD1 gene transcription. Importantly, unresponsive patients to MTX (UR-MTX) show reduced expression of TGFBR2 and CREB1 and decreased levels of p-SMAD2 and p-CREB in Tregs compared to MTX-responsive patients (R-MTX). Furthermore, RA patients carrying at least one mutant allele for rs1431131 (AT or AA) of the TGFBR2 gene are significantly (p = 0.0006) associated with UR-MTX. Therefore, we have uncovered a molecular mechanism for the reduced CD39 expression on Tregs, and revealed potential targets for therapeutic intervention for MTX resistance.
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