Negative feedback loop of ERK/CREB/miR-212-3p inhibits HBeAg-induced macrophage activation

The activation of liver macrophages is closely related to liver injury after HBV Infection. Our previous results demonstrated that HBeAg played a key role in inducing macrophage activation. As we all know, miRNAs are involved in the regulation of multiple immune cell functions. Meanwhile, we have shown that miR-155 positively regulates HBeAg-induced macrophage activation and accelerates liver injury. Subsequently, based on our previous miRNA Sequencing results, we further evaluated the role of miR-212-3p called 'neurimmiR' in HBeAg-induced macrophages in this study. First, miR-212-3p expression was significantly elevated in HBeAg-treated macrophages. Meanwhile, we found up-regulation of miR-212-3p significantly decreased the production of cytokines, whereas knockdown of miR-212-3p held the opposite effect by gains and losses of function. Mechanically, although MAPK signal pathway, including ERK, JNK and p38, was activated in HBeAg-induced macrophages, only ERK promoted the expression of miR-212-3p via transcription factor CREB, which was able to bind to the promoter of miR-212-3p verified by ChIP assay. Moreover, we further indicated that up-regulated miR-212-3p inhibited HBeAg-induced inflammatory cytokine production through targeting MAPK1. In conclusion, miR-212-3p was augmented in HBeAg-stimulated macrophages via ERK/CREB signal pathway and the elevated miR-212-3p suppressed inflammatory cytokine production induced by HBeAg through targeting MAPK1.