Increased microRNA-146a/b, TRAF6 gene and decreased IRAK1 gene expressions in the peripheral mononuclear cells of patients with Sjögren's syndrome.

MicroRNA-146a (miR-146a) is a microRNA supposed to regulate innate immune, inflammatory response and antiviral pathway negatively. Recently, its potential use as a biomarker for disease diagnosis, prevention and treatment has become widely investigated. In the current study, we measured the expression of miR-146a/b, and their target genes, IRAK1, IRAK4, TRAF6 in the peripheral mononuclear cells of patients with Sjögren's syndrome (n=21) and healthy controls (n=10) by quantitative reverse transcription polymerase chain reaction. We found that both miR-146a and miR-146b, furthermore, the gene of TRAF6 were significantly overexpressed in the Sjögren's patients, whereas the expression of IRAK1 gene was significantly decreased. The expression of IRAK4 did not differ significantly. These results suggest that in the peripheral mononuclear cells of Sjögren's patients, the transcriptional repression of IRAK1 is taking place, whereas the other NF-κB pathway regulating gene, TRAF6 is overexpressed. As IRAK1 has been regarded a crucial gene in the pathogenesis of systemic lupus erythematosus, TRAF6 can be a Sjögren's syndrome specific biomarker, confirming and partly explaining the existance of different pathogenic pathways in the two diseases. These observations, however, need still wider confirmations.