MicroRNA-205-5b inhibits HMGB1 expression in LPS-induced sepsis

Inflammatory cytokines belonging to high mobility group box (HMGB) 1 play a key role in sepsis through yet unknown mechanisms. The inflammatory response is modulated by microRNAs (miRNAs or miRs) at multiple levels and is poorly understood. In this study, the regulation of HMGB1 by miRNAs was evaluated using 3-(2,4-dimethoxybenzylidene) anabaseine (GTS-21) to activate the cholinergic anti-inflammatory pathway (CAP) and decrease HMGB1 expression in RAW264.7 cells. Microarray-based miRNA expression profiling of RAW264.7 cells was used to screen target miRNAs through genetic screening, GO analysis and hierarchical clustering. The expression of miRNA targets in the serum, colon, spleen, livers and lungs of BALB/c mice was quantified by RT-qPCR. Serum protein levels were quantified by ELISA. Western blot analysis and RT-qPCR were used for verification in vitro. Using miRNA array analysis, we screened 3 miRNAs (miR-205-5b, miR-196a and miR-193b). Animal experiments with miR-205-5b indicated its high degree of expression in the serum, colon, spleen, liver and lungs following the downregulation of HMGB1 in the tissues. RAW264.7 cells transfected with miR-205-5b mimics downregulated HMGB1 protein expression, suggesting translational regulation. HMGB1 expression negatively correlated with miR-205-5b expression in LPS-induced sepsis. By contrast, HMGB1 expression in LPS-stimulated RAW264.7 cells was increased following transfection with miR-205-5b inhibitor. miR-205-5b is a critical mediator of cholinergic anti-inflammatory activity in late sepsis. The upregulation of miR-205-5b as a potential therapeutic target for the treatment of inflammatory diseases is a possible novel therapeutic strategy against late sepsis. The mechanisms involved include the by post-transcriptional suppression of HMGB1 in cells and tissues.