The Effect of miR-132, miR-146a, and miR-155 on MRP8/TLR4-Induced Astrocyte-Related Inflammation.

Astrocyte activation, associated with the release of pro-inflammatory cytokines interleukin 1-β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF-α), is a hallmark of multiple brain diseases, including mesial temporal lobe epilepsy. In recent years, several microRNAs have emerged as important controllers of Toll-like receptor (TLR) signaling. In this study, we investigated the effect of miR-132, miR-146a, and miR-155 on myeloid-related protein-8 (MRP8) induced astrocyte-related inflammation. Using quantitative polymerase chain reaction (qPCR) and western blot, we found clear upregulation of TLR4 and downstream inflammatory cytokines, along with dysregulation of miR-132, miR-146a, and miR-155 in in vitro astrocytes after exposing them to different concentrations of MRP8. In addition, we focused on the effect of miR-132 on astrocyte-related inflammation induced by MRP8 via lentiviral infection then evaluated the expression of its possible target genes: acetylcholinesterase (AChE) and interleukin-1 receptor-associated kinase (IRAK4). Our results show that miR-132 is a negative feedback regulator of IL-1β and IL-6, but not TNF-α, by targeting IRAK4. Together, our findings demonstrate the novel role of TLR4-related microRNAs, especially miR-132, in the regulation of MRP8-induced astrocyte activation and highlight the importance of miR-132 in the modulation of innate immune response induced by endogenous ligands in neurological diseases.