Our group previously reported that caveolin-1 (cav-1) was down-regulated by nitric oxide (NO) during cerebral ischemia and reperfusion (I/R). However, the role of cav-1 in regulating blood-brain barrier (BBB) permeability is unclear yet. This study aims to address whether the loss of cav-1 induced by NO production affects BBB permeability. Data showed that the expression of cav-1 in isolated cortical microvessels was down-regulated in ischemia-reperfused rat brains subjected to middle cerebral artery occlusion (MCAO). Treatment of NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide synthase inhibitor, reserved cav-1 expression, inhibited matrix metalloproteinases (MMPs) activity and reduced the BBB permeability. Moreover, cav-1 knockdown remarkably increased MMPs activity in the culture medium of brain microvascular endothelial cells. Cav-1 deficiency mice displayed higher MMPs activity and BBB permeability than that of the wild-type mice. Interestingly, the effects of L-NAME on MMPs activity and BBB permeability were partly reversed in cav-1 deficiency mice. These results suggest that cav-1 plays important roles in regulating MMPs activity and BBB permeability in cerebral I/R injury. After completing the mechanism study, I investigated the potential drug candidate that targets cav-1 for protecting BBB and neuronal damage during cerebral I/R. Results showed that calycosin, an isoflavones from Astragali Radix, up-regulated the expression of cav-1 and inhibited MMPs activity, and decreased the BBB permeability in the MCAO ischemia-reperfused rat brains. I further investigated the neuroprotective effects of isoflavones of Astragali Radix, with in vitro oxygen glucose deprivation (OGD) model and in vivo cerebral ischemia-reperfusion models. In addition to calycosin and formononetin, two major isoflavones in Astragali Radix, daidzein was also included because it is a metabolite of formononetin after absorption. Results showed that all three isoflavones decreased infarction volume and neurological scores in MCAO rats and dose-dependently attenuated neuronal death induced by L-glutamate treatment and oxygen-glucose deprivation plus reoxygenation (OGD/RO). The neuroprotective effects were inhibited by estrogen receptors (ER) antagonist ICI 182,780. Interestingly, combine treatment of isoflavones displayed synergistic effects in both OGD/RO and L-glutamate induced neuronal injury models, as well as in MCAO cerebral ischemia-reperfusion rat brains. Mechanistically, estrogen receptor antagonist partly reduced the synergism in these models. PI3K/Akt activation was synergistically induced by treatment of those isoflavones simultaneously. In summary, cav-1 could be a potential therapeutic target for protecting the BBB in the treatment of cerebral I/R injury. Major findings in this thesis include: 1) Cav-1 plays an important role in maintaining BBB integrity through inhibition of MMPs activity. NO induced MMPs activities and BBB leakage are partially mediated by the down-regulation of cav-1 during cerebral I/R injury. 2) Calycosin treatment reserved cav-1 expression and reduced BBB permeability. 3) Isoflavones synergistically protected neurons against I/R-induced neuronal insults both in vitro and in vivo. The works provide a valuable step towards the clarification of the physiological and pathophysiological functions of cav-1, and a new clue for developing isoflavones as agents targeting cav-1 for the prevention or treatment of ischemic stroke. / published_or_final_version / Chinese Medicine / Doctoral / Doctor of Philosophy

Ischemic stroke is a leading cause of disability and death around the world. Higher concentration of glutamate following ischemic stroke is a factor leading to cell death, including neural stem cell death. Up to now no effective treatments of ischemic stroke are available. Notoginsenoside R1 (Noto R1) is the main component of Panax notoginseng, which is a traditional Chinese medicine for the treatment of cardiovascular disease. Its protective effects on the neural cell were noted recently. The main purpose of this experimental study was to investigate the mechanism of Noto R1 against glutamate neurotoxicity on primary cultured mouse cortical neural stem cells in vitro, and its effects on ischemic stroke on mice brain in vivo. In the in vitro part, primary culture of neural stem cells was prepared from 12.5-day-old C57BL/6N mice embryos cortex. Neural stem cells were confirmed by nestin-staining and differentiation study afterwards. Then neural stem cells were incubated with Noto R1 and glutamate for 24 hours. Cells were fixed for TUNEL staining and caspase-3 staining. Protein was collected for western blot for Bax, Bcl-2, phos-AKT, JNK/SAPK, and phospho-p38 MAPK. Results showed that glutamate has cytotoxicity in a dose-dependent manner on neural stem cells. Noto R1 showed remarkable neuro-protective effects on neural stem cells exposed to excessive glutamate by higher viability. Noto R1 significantly reduced caspase-3 expression and TUNEL-positive cells. Furthermore, Noto R1 increased the protein expression of Bcl-2 and phospho-AKT, and reduced Bax expression. Moreover apoptosis pathway study showed phospho-p38 expression was suppressed in the Noto R1 group. In the in vivo part, Noto R1 was administrated systemically to mice of MCAo followed by reperfusion. Behavior score and viability rate were assessed before sacrifice. TTC staining was performed for evaluating infarct area, volume and edema. H&E staining was applied for histological examination. TUNEL staining, IHC staining of Nestin, AQP4 and GFAP were performed. In the first part of Noto R1 of 40 mg/kg or PBS was injected into venous at the onset of blood vessel occlusion for 2 hours, and then followed by 22 hours of reperfusion. Results were all negative. In the second part, Noto R1 was injected intra-peritoneum for 10 days prior to MCAo which lasted for 1 hour 50 minutes, then reperfusion was allowed for 22 hours. Results showed Noto R1 improved behavior score and viability rate. Meanwhile Noto R1 significantly reduced ischemic area, volume and edema percentage. Moreover TUNEL-positive cells in the affected cortex were significantly decreased. Nestin-positive cell in the striatum were significantly increased in the Noto R1 group, and immunoactivity of AQP4 and GFAP was apparently decrease with Noto R1 treatment. In conclusion, this study showed that Noto R1 protected cultured neural stem cells against glutamate neurotoxicity in vitro via p38 MAPK pathway by inhibiting Bax protein expression and enhancing protein expression of Bcl-2 and phospho-AKT. Moreover, it also demonstrated significant preventive effects against ischemic stroke with mice model in vivo. In a word Noto R1 presents a highly potential candidate preventing ischemic stroke clinically in the future. / published_or_final_version / Anatomy / Doctoral / Doctor of Philosophy

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The leading cause of long-term disability among adults in industrialized countries is stroke. Exploration of the brain mechanisms involved during recovery from stroke is likely to yield information that can be used to promote better functional outcome. After focal motor cortical infarcts, reorganization of movement representations in the remaining motor cortex has been linked to both spontaneous recovery and recovery induced by rehabilitative training. However, the mechanisms and nature of cortical reorganization remain poorly understood. The central hypothesis of these dissertation studies is that synaptogenesis and structural reorganization in the cortex near the lesion are linked to spontaneous partial recovery and the beneficial effects of motor rehabilitative training after stroke-like injury. This was tested in a rat model of focal cortical ischemia by both behavioral and neuroanatomical measures in perilesion cortex. In separate studies, it was found that motor rehabilitative training on a skilled reaching task using the impaired forelimb after a unilateral ischemic lesion improved forelimb functional outcome and facilitated synaptogenesis in perilesion cortex. In addition, this improved functional recovery was disrupted by focal protein synthesis inhibition in perilesion cortex, suggesting the structural plasticity in this area plays an important role in regained function. Finally, it was also hypothesized that a therapy that enhances the efficacy of motor rehabilitation also enhances synaptic structural plasticity in perilesion cortex. Cortical electrical stimulation (CS) during motor rehabilitation has previously been shown to improve the efficacy of rehabilitation. Increased density of axodendritic synapses in perilesion cortex was found in rats that received cortical electrical stimulation of perilesion cortex during rehabilitation compared to rehabilitation alone, and the synaptic density was positively correlated with post-rehabilitation reaching performance. These findings suggest that CS-induced functional improvements may be mediated by synaptic structural plasticity in stimulated cortex. Together these studies indicate that, after a cortical lesion in rats, motor rehabilitation alone or in conjunction with other efficacious therapies can greatly enhance synaptic structural plasticity in perilesion cortex. Furthermore, these studies suggest that rehabilitation induced improvements in functional outcome are dependent upon the structural and functional integrity of the reorganized perilesion cortex.

published_or_final_version / Social Work and Social Administration / Master / Master of Social Sciences

published_or_final_version / Social Work / Master / Master of Social Sciences

published_or_final_version / Medicine / Master / Doctor of Medicine

published_or_final_version / Applied Statistics / Master / Master of Social Sciences

published_or_final_version / Psychology / Master / Master of Philosophy

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