MicroRNA-204-3p inhibits lipopolysaccharide-induced cytokines in familial Mediterranean fever via the phosphoinositide 3-kinase γ pathway

Objective. We sought to identify the microRNA (miRNA) profile and potential biomarkers in FMF and to clarify their gene targets to elucidate the pathogenesis of FMF. Methods. We performed an miRNA microarray using serum from FMF patients in attack and in remission. We then examined the expression of miRNAs in macrophages derived from THP-1 cells stimulated with toll-like receptor (TLR) ligands. Macrophages derived from THP-1 cells transfected with pre-miRNA were stimulated with lipopolysaccharides (LPSs) for the quantification of inflammatory cytokine production. To identify the target genes, we overexpressed their miRNA and performed a complementary DNA microarray. Transfection with reporter construct and the precursor miRNA was performed to confirm the suppression of target mRNA. Results. We found that miR-204-3p was greatly decreased in the serum from FMF patients in attack. The expression of miR-204-3p was suppressed by LPS stimulation in the macrophages derived from THP-1 cells and the inhibition of miR-204-3p significantly induced the production of TLR4-related cytokines. The bioinformatic analysis showed that miR-204-3p is predicted to target genes implicated in the TLR pathway through the regulation of PI3K gamma signalling. The reporter assay revealed that miR-204-3p directly suppressed the luciferase activity of 3'-UTR of PIK3CG reporter construct. The inhibition of PI3K gamma resulted in decreased amounts of IL-6 and IL-12p40 in monocytes from FMF patients. Conclusion. These data suggest that serum miR-204-3p has potential as a useful biomarker in FMF patients and that miR-204-3p serves as a suppressor of inflammatory cytokine production in FMF by targeting the PI3K gamma pathway.