Abstract
BackgroundIntracranial infection, one of the complications of traumatic brain injury, is usually associated with inflammation. Several microRNAs (miRNAs), including miR-155, have been reported to be critical modulators in peripheral and central nervous system inflammation. In this study, we investigated the role of miR-155 in lipopolysaccharide (LPS)-induced inflammatory injury in mouse microglia BV2 cells.ResultsThe expression level of miR-155 was significantly up-regulated after LPS stimulation in BV2 cells. LPS administration decreased BV2 cell viability, promoted apoptosis and increased the release of pro-inflammatory cytokines; while miR-155 knockdown rescued BV2 cell from LPS-induced injury. RACK1 was a directly target of miR-155. Interestingly, miR-155 knockdown did not attenuate LPS-induced inflammatory injury when RACK1 was knocked down. The mechanistic study indicated that miR-155 knockdown deactivated MAPK/NF-κB and mTOR signaling pathways under LPS-treated conditions.ConclusionsKnockdown of miR-155 protected mouse microglia BV2 cells from LPS-induced inflammatory injury via targeting RACK1 and deactivating MAPK/NF-κB and mTOR signaling pathways.
Highlights
Intracranial infection, one of the complications of traumatic brain injury, is usually associated with inflammation
BV2 cells were administrated with LPS, LPS + scramble, LPS + miR-155 mimic, LPS+ inhibitor control, and LPS + miR-155 inhibitor. a Cell viability was measured by Cell Counting Kit-8 (CCK-8) assay (n = 3). b Cell apoptosis was measured by flow cytometry (n = 3). c Expression of anti-apoptotic (Bcl-2) and pro-apoptotic (Bax, caspase-3, and caspase-9) proteins were measured by western blot analysis. d Relative mRNA expressions of IL-1β, IL-6, IL-8, and TNF-α were measured by quantitative RT-PCR (n = 3). e-h Concentrations of IL-1β, IL-6, IL-8, and TNF-α were measured by Enzyme-linked immunosorbent assay (ELISA) (n = 3)
We evaluated the impact of RACK1 on inflammatory cytokines by Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and ELISA. qRT-PCR results showed that transfection of miR-155 inhibitor alone in LPS-induced cells decreased the relative mRNA expression levels of IL-1β, IL-6, IL-8, and TNF-α, while transfection with both miR-155 inhibitor and si-RACK1 increased the expression of these pro-inflammatory cytokines (P < 0.05 or P < 0.01, Fig. 6d)
Summary
Intracranial infection, one of the complications of traumatic brain injury, is usually associated with inflammation. Several microRNAs (miRNAs), including miR-155, have been reported to be critical modulators in peripheral and central nervous system inflammation. We investigated the role of miR-155 in lipopolysaccharide (LPS)-induced inflammatory injury in mouse microglia BV2 cells. Post traumatic intracranial infection is generally due to contamination that caused by foreign body entered into the brain parenchyma after the injury [2]. MiRNAs are abundant in brain tissues and play a variety of regulatory functions in the central nervous system (CNS) [11]. It has been reported that miRNAs played key roles in the process of nerve development and injury repair [8, 12, 13].
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