BackgroundAstrocyte-mediated neuroinflammation plays a critical role in ischemic stroke-induced secondary cerebral injury. Previous studies have suggested that the dopamine D2 receptor (DRD2) acts as a key target in regulating the neuroinflammatory response. However, the underlying molecular mechanisms are still unknown, and effective DRD2 agonists are lacking. In the present study, we examined the anti-inflammatory and neuroprotective effects of sinomenine (Sino), a monomeric compound with potential immunoregulatory properties in nervous system.MethodsTTC staining, apoptosis assay, evaluation of brain edema, and neurological assessment were performed in the middle cerebral artery occlusion (MCAO) mouse model. Primary astrocytes exposed to oxygen glucose deprivation (OGD) were used in the in vitro experiments. Quantitative PCR was applied to assess the levels of inflammatory cytokines. Multi-labeling immunofluorescence, Western blot, co-immunoprecipitation, and electrophoretic mobility shift assay (EMSA) were also used to investigate the molecular mechanisms underlying the Sino-mediated anti-inflammatory effects in vivo and in vitro.ResultsSino remarkably attenuated the cerebral infarction and neuronal apoptosis, reduced the levels of inflammatory cytokines, and alleviated neurological deficiency in MCAO mice. Sino significantly inhibited astrocytic activation and STAT3 phosphorylation as well as increased DRD2 and αB-crystallin (CRYAB) expression after MCAO. In vitro, Sino blocked OGD-induced activation of STAT3 and generation of pro-inflammatory cytokines in primary astrocytes, and these effects were significantly abolished by either DRD2 or CRYAB knockdown. Additionally, Sino induced up-regulation and nuclear translocation of CRYAB in astrocytes and enhanced the interaction between CRYAB and STAT3, which further inhibited the activation and DNA-binding activity of STAT3.ConclusionsOur study demonstrates that Sino activates astrocytic DRD2 and thereby suppresses neuroinflammation via the CRYAB/STAT3 pathway, which sheds some light on a promising therapeutic strategy for ischemic stroke.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-016-0739-8) contains supplementary material, which is available to authorized users.
We aimed to investigate the blood brain barrier (BBB) change caused by subarachnoid hemorrhage (SAH) and to explore the molecular mechanisms of acute brain injury after SAH. The SD rat model of SAH was firstly established by endovascular filament perforation technique. The changes of regional cerebral blood flow (rCBF), BBB permeability and ultrastructure of brain tissue at different time points after SAH were respectively observed by Doppler flowmetry, evans blue extravasation and transmission electron microscopy. Meanwhile, the expression changes of Claudin-5, Occludin, Zo-1 and Caveolin-1 were detected by immunohistochemistry and Western blot. Furthermore, the expressions of Akt, P-Akt and Foxo1A were also measured by Western blot. The change of BBB permeability showed two peaks at 3 and 72 h after SAH, corresponding to the change of rCBF. The BBB tight junction opening can be observed after SAH, and the largest opening was occurred at 3 h and 72 h. There was no significant change in Caveolin-1, Claudin-5 and Akt expressions after SAH (P > 0.05), while Zo-1 and Occludin were significantly down-regulated (P < 0.05). The expression of P-Akt was obviously reduced at 30 min and then increased at 1 and 24 h, while Foxo1A was up-regulated at 1 and 24 h after SAH (P < 0.05). Down-regulated Zo-1 and Occludin, as well as Akt/FOXO signaling pathway may be involved in the regulation of tight junction opening and the BBB permeability in the early stage after SAH.
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