miR-155 induction in microglial cells suppresses Japanese encephalitis virus replication and negatively modulates innate immune responses

Abstract

BackgroundMicroglial cells, which are resident macrophages of the central nervous system, play important roles in immune responses and pathogenesis. Japanese encephalitis virus (JEV) is a neurotropic virus that infects microglial cells in brain. Several microRNAs including miR-155 and miR-146a play an important role in defining the microglia inflammatory profile. In this study, we have investigated the effect of miR-155 and miR-146a modulation on JEV infection as well as innate immune responses in human microglial cells.MethodsIn vitro studies were performed in JEV-infected human microglial CHME3 cells. miR-155 or miR-146a were overexpressed and total RNA and protein were extracted following JEV-infection. Expression of genes involved in innate immune responses was studied by PCR array, quantitative real-time PCR (qPCR), western blot and Fluorescence activated cell sorter (FACS). JEV replication was monitored by studying the viral RNA by qPCR, protein by western blot, and titres by plaque assay.ResultsOverexpression of miR-155 in CHME3 cells resulted in significantly reduced JEV replication whereas miR-146a overexpression had an insignificant effect. Additionally, interferon regulatory factor 8 (IRF8) and complement factor H (CFH) were induced during JEV infection; however, this induction was attenuated in miR-155 overexpressing cells following JEV infection. Further, JEV-induced NF-κB regulated downstream gene expression was attenuated. Interestingly, an increased level of CD45, a negative regulator of microglia activation and a reduced phosphorylated-Signal Transducers and Activators of Transcription (p-STAT1) expression was observed in miR-155 overexpressing cells upon JEV infection.ConclusionInduction of miR-155 in human microglial cells may negatively modulate JEV-induced innate immune gene expression and may have a beneficial role in limiting JEV replication in human microglial cells.

MicroRNA-15b Modulates Japanese Encephalitis Virus–Mediated Inflammation via Targeting RNF125

“…Thus, in this study, we aimed to address the role of miRNA-regulated pathways in the JEV-induced neuroinflammation model. Recently, the roles of miR-29b and miR-155 in microglial activation during JEV-induced neuroinflammation were studied (42,53,54). In this study, we demonstrated that miR-15b is stimulated both in vitro and in vivo, and miR-15b regulates the inflammatory response following JEV infection by targeting RNF125.…”

The complement system and toll-like receptors as integrated players in the pathophysiology of atherosclerosis

“…Distinct types of miRNAs may affect innate immunity, and specifically miR-146a is shown to be a negative regulator of TLR signaling, which could be of importance in neurodegenerative diseases [114]. Another miRNA, miR-155, may affect the complement system by attenuating FH in a human cell model of Japanese encephalitis [115]. Lastly, the complement system may affect miRNAs.…”

An update on the role of miRNA-155 in pathogenic microbial infections

“…In human microglial CHME3 cells, infection with the neurotropic flavivirus Japanese encephalitis virus (JEV) resulted in the up-regulation of miR-155 [53]. Nevertheless, miR-155 over-expression was associated to a restriction in JEV replication, a significant reduction in JEV-induced IFN-b and an attenuation of the expression of complement factor H (CFH), a negative regulator of complement activation, and interferon regulatory factor 8 (IRF8), an IFN-b inducer.…”