ADORA2A and rheumatoid arthritis: Previous works had shown that MTX inhibited NF-κB activation by increasing both adenosine release and the activation of the adenosine receptor A2a in rheumatoid arthritis [31] and that MTX decreased the TNF-α-mediated activation of NF-κB in Jurkat through the inhibition of IκBα phosphorylation and degradation [3], as well as by releasing adenosine, although the dose (10 μM) and length of treatment (60 min) varied significantly from our experimental conditions.