In vivo inhibition of miR-155 significantly alters post-stroke inflammatory response

Abstract

BackgroundMicroRNA miR-155 is implicated in modulation of the inflammatory processes in various pathological conditions. In our previous studies, we demonstrated that in vivo inhibition of miR-155 promotes functional recovery after mouse experimental stroke. In the present study, we explored if this beneficial effect is associated with miR-155 inhibition-induced alterations in post-stroke inflammatory response.MethodsIntravenous injections of a specific miR-155 inhibitor were initiated at 48 h after mouse distal middle cerebral artery occlusion (dMCAO). Temporal changes in the expression of cytokines and key molecules associated with cytokine signaling were assessed at 7, 14, and 21 days after dMCAO, using mouse cytokine gene and protein arrays and Western blot analyses. Electron and immunofluorescence confocal microscopy techniques were used to evaluate the ultrastructural changes, as well as altered expression of specific phenotypic markers, at different time points after dMCAO.ResultsIn the inhibitor-injected mice (inhibitor group), there was a significant decrease in CCL12 and CXCL3 cytokine expression at 7 days and significantly increased levels of major cytokines IL-10, IL-4, IL-6, MIP-1α, IL-5, and IL-17 at 14 days after dMCAO. These temporal changes correlated with altered expression of miR-155 target proteins SOCS-1, SHIP-1, and C/EBP-β and phosphorylation levels of cytokine signaling regulator STAT-3. Electron microscopy showed decreased number of phagocytically active peri-vascular microglia/macrophages in the inhibitor samples. Immunofluorescence and Western blot of these samples demonstrated that expression of leukocyte/ macrophage marker CD45 and phagocytosis marker CD68 was reduced at 7 days, and in contrast, significantly increased at 14 days after dMCAO, as compared to controls.ConclusionsBased on our findings, we propose that in vivo miR-155 inhibition following mouse stroke significantly alters the time course of the expression of major cytokines and inflammation-associated molecules, which could influence inflammation process and tissue repair after experimental cerebral ischemia.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0753-x) contains supplementary material, which is available to authorized users.

Inhibition of MicroRNA‐155 Supports Endothelial Tight Junction Integrity Following Oxygen‐Glucose Deprivation

“…We, therefore, assessed the NO release in all HBMEC experimental groups, but found no significant differences at 48 hours after the oligonucleotide transfections (Figure 3B). As a major inflammatory miRNA, miR‐155 regulates cytokine expression, which could significantly influence the endothelial TJs 19. It is also known, that OGD triggers the endothelial cell activation leading to increased cytokine release.…”

“…Improved TJ integrity in the inhibitor‐injected animals was accompanied by increased levels of the TJ protein ZO‐1 in brain tissue extracts 18. In addition, we proposed that miR‐155 inhibition–induced stabilization of TJs could be associated with altered poststroke inflammatory response 19. Our in vivo studies involving systemic anti–miR‐155 injections did not precisely determine whether miR‐155 inhibition directly influenced the vascular endothelium.…”

Brain-immune interactions in perinatal hypoxic-ischemic brain injury

“…In the adult stroke model, the expression of miR-155 is significantly affected. Inhibition of miR-155 reduces the ischemic inflammatory responses, which contributes to the reduced brain tissue damage and promotes brain repair and functional recovery (Caballero-Garrido et al , 2015; Pena-Philippides et al , 2016). …”

Targeting vascular inflammation in ischemic stroke: Recent developments on novel immunomodulatory approaches

“…Tail vein injection of a specific anti-miR-155 inhibitor was reported to promote functional recovery in a mouse model of stroke when carried out 48 h later (Caballero- Garrido et al, 2015; Pena-Philippides et al, 2016). This action was associated with improved blood flow, reduced infarct size and edema, attenuated neuronal damage and inflammatory cytokine/chemokine presence, and preserved microvascular integrity in the peri-infarct area.…”