Patients with
rheumatoid arthritis (RA) suffer from
pain and joint disability. The transient receptor potential
ankyrin 1 (
TRPA1) channel expressed on sensory neurones and non-neuronal cells mediates
pain transduction and
inflammation and it has been implicated in RA. However, there is little information on the contribution of TRPA1 for human disease. Here, we investigated the expression of TRPA1 on peripheral blood leukocytes and the circulating levels of its endogenous activators
4-hydroxynonenal (4-HNE) and
hydrogen peroxide (H2O2) in RA patients treated or not with the anti-rheumatic
leflunomide (LFN) or the anti-TNFα
adalimumab (ADA). We also assessed whether TRPA1 expression correlates with
joint pain and disability, in addition to the immune changes in RA. TRPA1 expression on peripheral blood leukocytes correlated with
pain severity and disability. TRPA1 levels on these cells were associated with the numbers of polymorphonuclear and the activation of CD14+ cells. No correlations were found between the lymphocyte population and TRPA1 expression,
pain or disability. Patients recently diagnosed with RA expressed increased levels of TRPA1 on their leukocytes whilst treatment with either LFN or ADA down-regulated this receptor probably by reducing the numbers of polymorphonuclears and the activation of CD14+ cells. We suggest that the activation levels of CD14+ cells, the numbers of PMNs in the peripheral blood and the expression of TRPA1 on peripheral blood leukocytes correlate with RA progression, affecting
joint pain sensitivity and loss of function.