Molecular neurobiology
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Molecular neurobiology · Dec 2016
GSK-3β inhibitor TWS119 attenuates rtPA-induced hemorrhagic transformation and activates the Wnt/β-catenin signaling pathway after acute ischemic stroke in rats.
Hemorrhagic transformation (HT) is a devastating complication for patients with acute ischemic stroke who are treated with tissue plasminogen activator (tPA). It is associated with high morbidity and mortality, but no effective treatments are currently available to reduce HT risk. Therefore, methods to prevent HT are urgently needed. ⋯ In addition, Western blot analysis showed that TWS119 increased the protein expression of β-catenin, claudin-3, and ZO-1 while suppressing the expression of GSK-3β. These results suggest that TWS119 reduces rtPA-induced HT and attenuates blood-brain barrier disruption, possibly through activation of the Wnt/β-catenin signaling pathway. This study provides a potential therapeutic strategy to prevent tPA-induced HT after acute ischemic stroke.
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Molecular neurobiology · Dec 2016
Traumatic Brain Injury Increases the Expression of Nos1, Aβ Clearance, and Epileptogenesis in APP/PS1 Mouse Model of Alzheimer's Disease.
To test the hypothesis that an amyloidogenic genetic background predisposes to worsening of post-TBI outcome, we investigated whether traumatic brain injury (TBI) in amyloid precursor protein (APP)/PS1 mice aggravates epileptogenesis and/or enhances somatomotor and cognitive impairment. To elaborate the mechanisms of worsening outcomes, we studied changes in the expression of genes involved in APP processing and Tau pathways in the perilesional cortex, ipsilateral thalamus, and ipsilateral hippocampus 16 weeks post-TBI. Mild (mTBI) or severe TBI (sTBI) was triggered using controlled cortical impact in 3-month-old APP/PS1 mice and wild-type (Wt) littermates. ⋯ Motor impairment correlated (p < 0.001) with the increased cortical expression of genes encoding proteins related to β-amyloid (Aβ) clearance, including Clu (r = 0.83), Abca1 (r = 0.78), A2m (r = 0.76), Apoe (r = 0.70), and Ctsd (r = 0.63). Immunohistochemical analysis revealed a focal reduction in Aβ load lateral to lesion core in APP/PS1-sTBI mice compared to APP/PS1-sham mice (p < 0.05). The present study provides the first comprehensive evidence of exacerbated epileptogenesis and its molecular mechanisms in Alzheimer's disease (AD)-related genetic background after TBI.
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Molecular neurobiology · Dec 2016
bFGF Protects Against Blood-Brain Barrier Damage Through Junction Protein Regulation via PI3K-Akt-Rac1 Pathway Following Traumatic Brain Injury.
Many traumatic brain injury (TBI) survivors sustain neurological disability and cognitive impairments due to the lack of defined therapies to reduce TBI-induced blood-brain barrier (BBB) breakdown. Exogenous basic fibroblast growth factor (bFGF) has been shown to have neuroprotective function in brain injury. The present study therefore investigates the beneficial effects of bFGF on the BBB after TBI and the underlying mechanisms. ⋯ Both the in vivo and in vitro effects are related to the activation of the downstream signaling pathway, PI3K/Akt/Rac-1. Inhibition of the PI3K/Akt or Rac-1 by specific inhibitors LY294002 or si-Rac-1, respectively, partially reduces the protective effect of bFGF on BBB integrity. Overall, our results indicate that the protective role of bFGF on BBB involves the regulation of tight junction proteins and RhoA in the TBI model and OGD-induced HBMECs injury, and that activation of the PI3K/Akt /Rac-1 signaling pathway underlies these effects.
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Molecular neurobiology · Nov 2016
Intracerebral Glycine Administration Impairs Energy and Redox Homeostasis and Induces Glial Reactivity in Cerebral Cortex of Newborn Rats.
Accumulation of glycine (GLY) is the biochemical hallmark of glycine encephalopathy (GE), an aminoacidopathy characterized by severe neurological dysfunction that may lead to early death. In the present study, we evaluated the effect of a single intracerebroventricular administration of GLY on bioenergetics, redox homeostasis, and histopathology in brain of neonatal rats. Our results demonstrated that GLY decreased the activities of the respiratory chain complex IV and creatine kinase, induced reactive species generation, and diminished glutathione (GSH) levels 1, 5, and 10 days after GLY injection in cerebral cortex of 1-day-old rats. ⋯ Regarding the histopathological analysis, GLY increased S100β staining in cerebral cortex and striatum, and GFAP in corpus callosum of 1-day-old rats 5 days after injection. Finally, we verified that melatonin prevented the decrease of complex IV and CK activities and GSH concentrations, and the increase of MDA levels and S100β staining caused by GLY. Based on our findings, it may be presumed that impairment of redox and energy homeostasis and glial reactivity induced by GLY may contribute to the neurological dysfunction observed in GE.
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Molecular neurobiology · Oct 2016
Phosphoinositide 3-Kinase γ Restrains Neurotoxic Effects of Microglia After Focal Brain Ischemia.
Phosphoinositide 3-kinase γ (PI3Kγ) is linked to neuroinflammation and phagocytosis. This study was conducted to elucidate conjectural differences of lipid kinase-dependent and kinase-independent functions of PI3Kγ in the evolvement of brain damage induced by focal cerebral ischemia/reperfusion. Therefore, PI3Kγ wild-type, knockout, and kinase-dead mice were subjected to middle cerebral artery occlusion followed by reperfusion. ⋯ Lastly, PI3Kγ-deficient microglia exhibited strongly increased cAMP levels in comparison with wild-type microglia or cells expressing kinase-dead PI3Kγ after oxygen/glucose deprivation and recovery. Our data suggest PI3Kγ kinase activity-independent control of cAMP phosphodiesterase as a crucial mediator of microglial cAMP regulation, MMP-9 expression, and phagocytic activity following focal brain ischemia/recirculation. The suppressive effect of PI3Kγ on cAMP levels appears critical for the restriction of ischemia-induced immune cell functions and in turn tissue damage.