MicroRNA and interleukin 6 interplay in the adipose tissue of rheumatoid arthritis patients.

Abstract

MicroRNAs (miRs) are non-translated RNA sequences that elicit negative control over protein expression. The adipose tissue (AT) is considered the major producer of miRs and inflammatory interleukin 6 (IL-6). This study aims to investigate the relationship between production of IL-6 and miRs in AT. IL-6 gene expression was analysed in RNA extracts from subcutaneous AT of 75 patients with rheumatoid arthritis (RA), with qPCR. Genome-wide profile of human miRs (2565 miRs, 96.6%) was analysed in 35 AT samples on 3D microarray. The miR-processing proteins Dicer, Drosha and DGCR8 were analysed with qPCR. In silico prediction of protein targets for the differentially expressed (DE) miRs (p<0.05; log2FC >±0.5) was conducted by DIANA software. Seven AT samples were stimulated in vitro with IL-6 or IL-6+IL-6R antibody tocilizumab and analysed for the miR processing proteins. We identified 30 DE miRs between AT with high and low IL-6 mRNA, of which 26 miRs were inversely related with IL-6 levels. DE miRs were predicted to interfere in oestrogen (p=0.001), FoxO (p=0.006) and insulin (p=0.03) signalling pathways. High expression of IL-6 in AT was associated with significantly higher expression of Dicer (p=0.04) and Drosha (p=0.04), while inhibition of IL-6 signalling with tocilizumab decreased the levels of total miRs processing enzymes (p=0.003). IL-6 mRNA production in AT has a negative effect on the miRs expression profile and it increases miR-production capacity.