Overexpression of TLR7 and TLR9 Occurs Before Onset Symptoms In First-Degree Relatives of Rheumatoid Arthritis Patients.

BACKGROUND: Autoantibodies have a central role in the physiopathology of Rheumatoid Arthritis (RA). However, the responsible factors that trigger and perpetuate the autoantibodies production are unknown. Toll-like receptors (TLRs) have been considered as promotors of autoantibodies production to break down the immunotolerance in RA. AIM OF THE STUDY: Evaluate the expression levels of TLR7 and TLR9 as well as their correlation with autoantibodies in first-degree relatives (FDR) of RA patients (seropositive and seronegative to ACPA), respect to early RA (eRA) and chronic RA (cRA) patients. METHODS: We selected 32 RA patients (16 as eRA and 16 as cRA) and 32 FDR of RA patients (16 seropositive and 16 seronegative to ACPA). Expression levels of TLR7 and TLR9 in whole blood samples from each group were measured by real-time PCR using total RNA extracted from each subject. Also, correlation analysis between TLRs expression and autoantibodies was performed. RESULTS: The expression of TLR7 and TLR9 was diminished in RA patients (p <0.01) but elevated in ACPA- FDR (p <0.0001) and ACPA+ FDR (p <0.05) with a positive correlation between them (r = 0.749, p <0.000). Moreover, the expression levels of TLR7 correlate positively with ACPA levels in both seropositive ACPA+ FDR subjects (r = 0.582, p = 0.018) and eRA patients (r = 0.593, p = 0.020). CONCLUSIONS: Our results showed overexpression of TLR7 and TLR9 may occur in preclinical RA subjects. TLR7 overexpression correlated with ACPA levels' production, suggesting TLR7 may play a role in ACPA development.

Subclinical inflammation in the preclinical phase of rheumatoid arthritis might contribute to articular joint damage.

The first degree relatives of rheumatoid arthritis (RA) patients have a higher risk of developing RA, which is related to the expression of autoantibodies against citrullinated proteins (ACPA). Remarkably, prior to the onset of RA, cartilage damage is already initiated, whereas ACPA autoantibodies are already expressed. Here we show that both TNF-α and IL-6 are also increased prior to the onset of RA. Furthermore, when the levels of DKK1 and Sclerostin were evaluated in first degree relatives of RA patients, we found that the serum levels of TNF- α correlate with the expression levels of both DKK1 and Sclerostin. Interestingly, when the disease is already established, the correlation of TNF- α with DKK1 is lost in RA patients, whereas the correlation of Sclerostin with both TNF- α and IL-6 is further increased. Our data suggest a subclinical inflammation in patients at high risk of developing RA, which might lead to an increase in the levels of both DKK1 and Sclerostin, contributing to joint damage in the preclinical phase of the disease linked to the expression of ACPA autoantibodies.