Methotrexate treatment in recent onset RA does not change the NO dynamics of the lung

Patients with established rheumatoid arthritis (RA) and recent onset RA have lower nitric oxide (NO) levels in the alveolar compartment (CANO) and in the airway wall (CawNO), but also a higher diffusion capacity for NO in the airways (DawNO) compared with matched controls. The aim was to study recent onset RA subjects, before treatment and 3 months of immunosuppressive treatment with methotrexate (MTX). RA subjects, ACPA positive, were recruited. Disease activity was measured using Disease Activity Score for 28 joints (DAS28), and disability according to Health Assessment Questionnaire (HAQ). The NO dynamics (median (IQR)) were estimated by the Hogman-Merilainen algorithm. When the non-smoking RA subjects (n=22) were compared with smoking subjects (n=8) there were differences in FENO50 of 19 (12, 25) ppb and 9 (5, 14) ppb resp. (p=0.004) and in NO dynamics CANO 2.1 (1.1, 2.3) ppb and 0.9 (0.3, 1.2) ppb resp. (p=0.007), while no differences were found in CawNO 65 (38, 119) ppb and 21 (17, 61) ppb resp. (p=0.12), and DawNO 16 (8, 31) mL/s and 17 (8, 27) mL/s resp. (p=0.68). The weekly MTX dose was 20 (15, 20) mg. There were reductions of DAS28, HAQ and s-CRP on MTX treatment with no differences between non-smokers and current smokers. Neither FENO50 nor any of the NO parameters changed after MTX. There were no correlations between FENO50 and NO parameters with DAS28, HAQ and s-CRP before or after treatment. The altered NO dynamics of the lung in ACPA positive RA patients are present in the early stage of the disease, before any treatments are initiated and do not change after MTX therapy. The HMA can be an additional tool to study the early pulmonary events in the development of the RA pathology.