A2A Adenosine Receptors Are Differentially Modulated by Pharmacological Treatments in Rheumatoid Arthritis Patients and Their Stimulation Ameliorates Adjuvant-Induced Arthritis in Rats

Fabrizio Vincenzi,Marcello Govoni,Martina Targa,Katia Varani,Melissa Padovan,Sarah Giacuzzo,Carmen Corciulo,Stefania Merighi,Stefania Gessi,Pier Andrea Borea,Victor Sanchez-Margalet

doi:10.1371/journal.pone.0054195

Abstract

A2A adenosine receptors (ARs) play a key role in the inhibition of the inflammatory process. The purpose of this study was to evaluate the modulation of A2AARs in rheumatoid arthritis (RA) patients after different pharmacological treatments and to investigate the effect of A2AAR stimulation in a rat model of arthritis. We investigated A2AAR density and functionality in RA progression by using a longitudinal study in RA patients before and after methotrexate (MTX), anti-TNFα agents or rituximab treatments. A2AARs were analyzed by saturation binding assays in lymphocytes from RA patients throughout the 24-month study timeframe. In an adjuvant-induced arthritis model in rats we showed the efficacy of the A2AAR agonist, CGS 21680 in comparison with standard therapies by means of paw volume assessment, radiographic and ultrasonographic imaging. Arthritic-associated pain was investigated in mechanical allodynia and thermal hyperalgesia tests. IL-10 release following A2AAR stimulation in lymphocytes from RA patients and in serum from arthritic rats was measured. In lymphocytes obtained from RA patients, the A2AAR up-regulation was gradually reduced in function of the treatment time and the stimulation of these receptors mediated a significant increase of IL-10 production. In the same cells, CGS 21680 did not affected cell viability and did not produced cytotoxic effects. The A2AAR agonist CGS 21680 was highly effective, as suggested by the marked reduction of clinical signs, in rat adjuvant-induced arthritis and associated pain. This study highlighted that A2AAR agonists represent a physiological-like therapeutic alternative for RA treatment as suggested by the anti-inflammatory role of A2AARs in lymphocytes from RA patients. The effectiveness of A2AAR stimulation in a rat model of arthritis supported the role of A2AAR agonists as potential pharmacological treatment for RA.

Highlights

Rheumatoid Arthritis (RA) is a chronic autoimmune disease that primarily affects joints and causes pain, stiffness, swelling and limited motion [1,2]
We have investigated the involvement of A2AARs in RA by evaluating their affinity and density in lymphocytes from RA patients at different time points after the treatment with classic or biologic disease modifying anti-rheumatic drugs (DMARDs)
We have found an up-regulation of A2AARs in untreated RA patients that was gradually reduced in function of the treatment time and in different ways depending on the type of drug used

Summary

Introduction

Rheumatoid Arthritis (RA) is a chronic autoimmune disease that primarily affects joints and causes pain, stiffness, swelling and limited motion [1,2]. In RA the inflammatory process leads to progressive cartilage degradation with synovial hyperplasia, change in underlying bone with erosions and high levels of proinflammatory mediators [3,4]. Diagnosis and therapy are crucial in order to prevent unfavourable outcome avoiding joint deterioration and functional disability [7]. The introduction of anti-TNFa agents (e.g. adalimumab, etanercept) or the use of antiCD20 B cell targeted therapy (rituximab, RTX) have provided a marked improvement in RA even if some patients do not respond or fail to maintain adequate response to these treatments [10,11]. The availability of alternative therapeutic options, targeting the pathways associated to inflammatory processes in RA, could be very useful to assist clinicians in making alternative pharmacological treatment choices [12,13]

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