Atorvastatin induction of VEGF and BDNF promotes brain plasticity after stroke in mice

Blocked angiogenesis in Galectin-3 null mice does not alter cellular and behavioral recovery after middle cerebral artery occlusion stroke

Angiogenesis is thought to decrease stroke size and improve behavioral outcomes and therefore several clinical trials are seeking to augment it. Galectin-3 (Gal-3) expression increases after middle cerebral artery occlusion (MCAO) and has been proposed to limit damage 3days after stroke. We carried out mild MCAO that damages the striatum but spares the cerebral cortex and SVZ. Gal-3 gene deletion prevented vascular endothelial growth factor (VEGF) upregulation after MCAO. This inhibited post-MCAO increases in endothelial proliferation and angiogenesis in the striatum allowing us to uniquely address the function of angiogenesis in this model of stroke. Apoptosis and infarct size were unchanged in Gal-3(-/-) mice 7 and 14 days after MCAO, suggesting that angiogenesis does not affect lesion size. Microglial and astrocyte activation/proliferation after MCAO was similar in wild type and Gal-3(-/-) mice. In addition, openfield activity, motor hemiparesis, proprioception, reflex, tremors and grooming behaviors were essentially identical between WT and Gal-3(-/-) mice at 1, 3, 7, 10 and 14 days after MCAO, suggesting that penumbral angiogenesis has limited impact on behavioral recovery. In addition to angiogenesis, increased adult subventricular zone (SVZ) neurogenesis is thought to provide neuroprotection after stroke in animal models. SVZ neurogenesis and migration to lesion were overall unaffected by the loss of Gal-3, suggesting no compensation for the lack of angiogenesis in Gal-3(-/-) mice. Because angiogenesis and neurogenesis are usually coordinately regulated, identifying their individual effects on stroke has hitherto been difficult. These results show that Gal-3 is necessary for angiogenesis in stroke in a VEGF-dependant manner, but suggest that angiogenesis may be dispensable for post-stroke endogenous repair, therefore drawing into question the clinical utility of augmenting angiogenesis.

Combining statins with tissue plasminogen activator treatment after experimental and human stroke: a safety study on hemorrhagic transformation

AIMS

Statins may afford neuroprotection against ischemic injury, but it remains controversial whether combined treatment with tissue plasminogen activator (tPA) after stroke increases the risk of hemorrhagic transformation (HT), the major tPA-related complication. We evaluated the safety of combining statin with tPA administration during the acute phase of both experimental and human stroke.

METHODS

The occurrence and severity of HT, infarct volume, and neurological outcome were evaluated in spontaneous hypertensive rats (SHR) subjected to embolic middle cerebral arterial occlusion (MCAO), which received vehicle or simvastatin (20 mg/kg), 15 min after ischemia and tPA (9 mg/kg) 3 h after ischemia. Additionally, HT rate was evaluated in stroke patients who were treated with tPA (0.9 mg/kg) within 3 h after symptom onset, considering whether or not were under statins treatment when the stroke occurred.

RESULTS

In the experimental study, no differences in HT rates and severity were found between treatment groups, neither regarding mortality, neurological deficit, infarct volume, or metalloproteinases (MMPs) brain content. In the clinical study, HT rates and hemorrhage type were similar in stroke patients who were or not under statins treatment.

CONCLUSION

This study consistently confirms that the use of statins does not increase HT rates and severity when is combined with tPA administration.

Brain-derived neurotrophic factor G196A polymorphism predicts 90-day outcome of ischemic stroke in Chinese: a novel finding

BACKGROUND AND PURPOSE

Recovery after stroke varies considerably between individuals. An abundance of evidence suggests that genetic factors contribute to stroke recovery. The aim of this study was to determine whether or not the BDNF G196A polymorphism independently influences the occurrence, severity, and 90-day functional outcome in Chinese patients with ischemic stroke (IS).

METHODS

BDNF G196A genetic variants were investigated in 494 IS and 346 controls. Severity was assessed by the National Institutes of Health Stroke Scale at the time of admission. Three hundred and eight patients were assessed 90 days post-stroke using the Modified Rankin Scale to determine stroke outcome.

RESULTS

We showed that a significant association existed between the BDNF G196A AA genotype and the occurrence of IS (P=0.021), even after adjustment for covariates (P=0.028). The AA genotype of the BDNF G196A was associated with a poor outcome of recovery 3 months after stroke onset (P=0.008) was a novel finding, independent of other known predictors of poor outcome (P=0.012).

CONCLUSIONS

The BDNF G196A polymorphism was significantly associated with the occurrence and long-term outcomes of IS, thus BDNF G196A may be used as a prognostic biomarker and therapeutic target in IS.

The sonic hedgehog pathway mediates brain plasticity and subsequent functional recovery after bone marrow stromal cell treatment of stroke in mice

Bone marrow stromal cells (MSCs) improve neurologic recovery after middle cerebral artery occlusion (MCAo). To examine whether in vivo blockage of the endogenous sonic hedgehog (Shh) pathway affects grafted MSC-induced neurologic benefits, MCAo mice were administered: vehicle (control); cyclopamine (CP)- a specific Shh pathway inhibitor; MSC; and MSC and cyclopamine (MSC-CP). Neurologic function was evaluated after MCAo. Electron microscopy and immunofluorescence staining were employed to measure synapse density, protein expression of tissue plasminogen activator (tPA), and Shh in parenchymal cells in the ischemic boundary zone (IBZ), respectively. Marrow stromal cell treatment significantly enhanced functional recovery after ischemia, concurrent with increases of synaptophysin, synapse density, and myelinated axons along the IBZ, and significantly increased tPA and Shh expression in astrocytes and neurons compared with control. After treatment with MSC-CP or CP, the above effects were reversed. Co-culture of MSCs with cortical neurons confirmed the effect of Shh on MSC-mediated neurite outgrowth. Our data support the hypothesis that the Shh pathway mediates brain plasticity via tPA and thereby functional recovery after treatment of stroke with MSCs.

Effect of an inductive hydrogel composed of urinary bladder matrix upon functional recovery following traumatic brain injury

Traumatic brain injury (TBI) is a major public health problem with no effective clinical treatment. Use of bioactive scaffold materials has been shown to be a promising strategy for tissue regeneration and repair in a number of injury models. Of these scaffold materials, urinary bladder matrix (UBM) derived from porcine bladder tissue, has demonstrated desirable properties for supporting and promoting the growth of neural cells in vitro, suggesting its potential as a scaffold for brain tissue repair in the treatment of TBI. Herein we evaluate the biocompatibility of UBM within brain tissue and the effects of UBM delivery upon functional outcome following TBI. A hydrogel form of UBM was injected into healthy rat brains for 1, 3, and 21 days to examine the tissue response to UBM. Multiple measures of tissue injury, including reactive astrocytosis, microglial activation, and neuron degeneration showed that UBM had no deleterious effects on normal brain. Following TBI, the brains were evaluated histologically and behaviorally between sham-operated controls and UBM- and vehicle-treated groups. Application of UBM reduced lesion volume and attenuated trauma-induced myelin disruption. Importantly, UBM treatment resulted in significant neurobehavioral recovery following TBI as demonstrated by improvements in vestibulomotor function; however, no differences in cognitive recovery were observed between the UBM- and vehicle-treated groups. The present study demonstrated that UBM is not only biocompatible within the brain tissue, but also can exert protective effects upon injured brain.

Axonal remodeling of the corticospinal tract in the spinal cord contributes to voluntary motor recovery after stroke in adult mice

BACKGROUND AND PURPOSE

We sought to demonstrate the contribution of axonal remodeling of the corticospinal tract (CST) in the spinal cord to functional outcome after stroke.

METHODS

Bilateral pyramidotomy (BPT) or sham-BPT was performed in mice with transgenic yellow fluorescent protein labeling in the CST subjected to middle cerebral artery occlusion (MCAo). Foot-fault and single pellet reaching tests were performed 3 days after MCAo and weekly thereafter. Mice were euthanized at day 14 or 28 after stroke. Immunofluorescent staining for growth-associated protein-43 and Synaptophysin was performed on cervical sections.

RESULTS

Functional improvements were evident during the initial 14 days in both MCAo-sham-BPT and MCAo-BPT mice (P<0.01, versus day 3). Progressive recovery was present during the subsequent 14 days in MCAo-sham-BPT mice (P<0.001, versus day 14) but not in MCAo-BPT mice. In the stroke-affected cervical gray matter of MCAo-sham-BPT mice, growth-associated protein-43-Cy3 staining on CST axons were significantly increased at day 14 after stroke compared with normal mice (P<0.001), and CST axonal density and Synaptophysin-Cy3 staining of CST-yellow fluorescent protein axonal terminals were significantly increased at day 28 compared with day 14 after MCAo (P<0.001).

CONCLUSIONS

Our data demonstrate that voluntary motor recovery is associated with CST axonal outgrowth and synaptic formation in the denervated side of the spinal gray matter during the later phase after stroke, suggesting that the CST axonal plasticity in the spinal cord contributes to neurological recovery.

Acute atorvastatin treatment exerts antidepressant-like effect in mice via the L-arginine-nitric oxide-cyclic guanosine monophosphate pathway and increases BDNF levels

Atorvastatin is a synthetic and lipophilic statin that presents a good effect in decreasing cholesterol levels and is safe and well tolerated. Population-based studies have suggested a positive role of statins in reducing depression risk. This study aimed at investigating the atorvastatin effect in the tail suspension test (TST) and in the forced swimming test (FST). The participation of NMDA receptors and L-arginine-NO-cGMP in an atorvastatin antidepressant-like effect in the TST was evaluated. Acute atorvastatin administration (0.1-30 mg/kg) reduced the immobility time both in TST and FST. A similar effect was observed by using imipramine as a positive control in the TST and FST (1 and 0.1-1 mg/kg, p.o., respectively). An atorvastatin (0.1 mg/kg) antidepressant-like effect was prevented by the pretreatment of mice with NMDA (0.1 pmol/site, i.c.v.), L-arginine (750 mg/kg, i.p.) or sildenafil (5 mg/kg, i.p.). The administration of MK-801 (0.001 mg/kg, i.p.), ketamine (0.1 mg/kg, i.p.), 7-nitroindazole (50 mg/kg, i.p.), methylene blue (20 mg/kg, i.p.), or ODQ (30 pmol/site i.c.v.) in combination with a subeffective dose of atorvastatin (0.01 mg/kg, p.o.) reduced the immobility time in the TST compared to drugs alone, showing the participation of the pathway L-arginine-NO-cGMP. The administration of drugs did not produce any significant alteration in locomotor activity in the open-field test. Acute atorvastatin treatment (0.1-10.0 mg/kg, v.o.) increased the hippocampal BDNF levels, which is an effect that has not been observed in imipramine-treated mice. These results demonstrate that atorvastatin exerts an antidepressant-like effect and point to dependence on the inhibition of NMDA receptors and NO-cGMP synthesis, and on the increase of hippocampal BDNF levels.

Vascular endothelial growth factor promotes pericyte coverage of brain capillaries, improves cerebral blood flow during subsequent focal cerebral ischemia, and preserves the metabolic penumbra

BACKGROUND AND PURPOSE

Therapeutic angiogenesis aims at improving cerebral blood flow by amplification of vascular sprouting, thus promoting tissue survival under conditions of subsequent ischemia. It remains unknown whether induced angiogenesis leads to the formation of functional vessels that indeed result in hemodynamic improvements. Observations of hemodynamic steal phenomena and disturbed neurovascular integrity after vascular endothelial growth factor delivery questioned the concept of therapeutic angiogenesis.

METHODS

Mice were treated with recombinant human vascular endothelial growth factor (0.02 μg/d; intracerebroventricular) for 3 to 21 days and subsequently exposed to 90-minute middle cerebral artery occlusion. Angiogenesis, histological brain injury, IgG extravasation, cerebral blood flow, protein synthesis and energy state, and pericyte coverage on brain capillaries were evaluated in a multiparametric approach combining histochemical, autoradiographic, and regional bioluminescence techniques.

RESULTS

Vascular endothelial growth factor increased brain capillary density within 10 days and reduced infarct volume and inflammation after subsequent middle cerebral artery occlusion, and, when delivered for prolonged periods of 21 days, enhanced postischemic blood-brain barrier integrity. Increased cerebral blood flow was noted in ischemic brain areas exhibiting enhanced angiogenesis and was associated with preservation of the metabolic penumbra, defined as brain tissue in which protein synthesis has been suppressed but ATP preserved. Vascular endothelial growth factor enhanced pericyte coverage of brain endothelial cells via mechanisms involving increased N-cadherin expression on cerebral microvessels.

CONCLUSIONS

That cerebral blood flow is increased during subsequent ischemic episodes, leading to the stabilization of cerebral energy state, fosters hope that by promoting new vessel formation brain tissue survival may be improved.

Multipotent mesenchymal stromal cells decrease transforming growth factor β1 expression in microglia/macrophages and down-regulate plasminogen activator inhibitor 1 expression in astrocytes after stroke

Multipotent mesenchymal stromal cells (MSCs) decrease the expression of transforming growth factor β1 (TGFβ1) in astrocytes and subsequently decrease astrocytic plasminogen activator inhibitor 1 (PAI-1) level in an autocrine manner. Since activated microglia/macrophages are also a source of TGFβ1 after stroke, we therefore tested whether MSCs regulate TGFβ1 expression in microglia/macrophages and subsequently alters PAI-1 expression after ischemia. TGFβ1 and its downstream effector phosphorylated SMAD 2/3 (p-SMAD 2/3) were measured in mice subjected to middle cerebral artery occlusion (MCAo). MSC treatment significantly decreased TGFβ1 protein expression in both astrocytes and microglia/macrophages in the ischemic boundary zone (IBZ) at day 14 after stroke. However, the p-SMAD 2/3 was only detected in astrocytes and decreased after MSC treatment. In vitro, RT-PCR results showed that the TGFβ1 mRNA level was increased in both astrocytes and microglia/macrophages in an astrocyte-microglia/macrophage co-culture system after oxygen-glucose deprived (OGD) treatment. MSCs treatment significantly decreased the above TGFβ1 mRNA level under OGD conditions, respectively. OGD increased the PAI-1 mRNA in astrocytes in the astrocyte-microglia/macrophage co-culture system, and MSC administration significantly decreased this level. PAI-1 mRNA was very low in microglia/macrophages compared with that in astrocytes under different conditions. Western blot results also verified that MSC administration significantly decreased p-SMAD 2/3 and PAI-1 level in astrocytes in astrocyte-microglia/macrophage co-culture system under OGD conditions. Our in vivo and in vitro data, in concert, suggest that MSCs decrease TGFβ1 expression in microglia/macrophages in the IBZ which contribute to the down-regulation of PAI-1 level in astrocytes.

Assessing post-stroke behavior in mouse models of focal ischemia

Experimental treatment strategies and neuroprotective drugs that showed therapeutic promise in animal models of stroke have failed to produce beneficial effects in human stroke patients. The difficulty in translating preclinical findings to humans represents a major challenge in cerebrovascular research. The reasons behind this translational road block might be explained by a number of factors, including poor quality control in various stages of the research process, the validity of experimental stroke models, and differences in drug administration and pharmacokinetics. Another major difference between animal studies and clinical trials is the choice of end point or outcome measures. Here, we discuss the necessity of poststroke behavioral testing to bridge the gap between clinical and experimental end points. We review established sensory-motor tests for outcome determination after focal ischemia based on the published literature as well as our own personal experience. Selected tests are described in more detail and good laboratory practice standards for behavioral testing are discussed. This review is intended for stroke researchers planning to use behavioral testing in mice.

Atorvastatin requires geranylgeranyl transferase-I and Rac1 activation to exert neuronal protection and induce plasticity

Statins are widely used cholesterol-lowering drugs that may reduce the incidence of stroke and the progression of Alzheimer's disease (AD). However, how statins exert these beneficial effects remains poorly understood. Thus, this study evaluated the roles of Rac1 geranylgeranylation and the relationship between Rac1 and αN-catenin in the protective activity of atorvastatin (ATV) in a cortical neuronal culture model of glutamate (GLU) excitotoxicity. We found that ATV-induced neuroprotection and plasticity were blocked by isoprenoids, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), inhibition of farnesylation (FTI-277) and geranylgeranylation (GGTI-286), down-regulation of GGTase-Iβ and Rac activity and promotion of active RhoA. Additionally, ATV rescued the distribution of dendritic αN-catenin and increased the number and length of dendritic branches; these effects were reversed by GGTI-286, GGTase-Iβ shRNA, Rac1 shRNA and a dominant-negative version of Rac1 (T17N). In summary, our findings suggest that ATV requires GGTase-Iβ, prenylation and active Rac1 to induce protection and plasticity. In this regard, αN-catenin is a marker for stable interactions between adhesion proteins and the actin cytoskeleton and is necessary for the neuroprotective action of ATV.

Simvastatin attenuates stroke-induced splenic atrophy and lung susceptibility to spontaneous bacterial infection in mice

BACKGROUND AND PURPOSE

Statins are widely used in the primary and secondary prevention of ischemic stroke, but their effects on stroke-induced immunodepression and poststroke infections are elusive. We investigated the effects of simvastatin treatment on stroke-induced splenic atrophy and lung susceptibility to bacterial infection in acute experimental stroke in mice.

METHODS

Ischemic stroke was induced by transient middle cerebral artery occlusion, followed by reperfusion. In some experiments, splenectomies were performed 2 weeks before middle cerebral artery occlusion. Animals were randomly assigned to sham and middle cerebral artery occlusion groups treated subcutaneously with vehicle or simvastatin (20 mg/kg per day). Brain infarction, neurological function, brain interferon-γ expression, splenic atrophy and apoptosis, and lung infection were examined.

RESULTS

Simvastatin reduced stroke-induced spleen atrophy and splenic apoptosis via increased mitochrondrial antiapoptotic Bcl-2 expression and decreased proapoptotic Bax translocation from cytosol into mitochondria. Splenectomy reduced brain interferon-γ (3 days) and infarct size (5 days) after stroke, and these effects were reversed by adoptive transfer of splenocytes. Simvastatin inhibited brain interferon-γ (3 days) and reduced infarct volume and neurological deficits (5 days) after stroke, and these protective effects were observed not only in naive stroke mice but also in splenectomied stroke mice adoptively transferred with splenocytes. Simvastatin also decreased the stroke-associated lung susceptibility to spontaneous bacterial infection.

CONCLUSIONS

Results provide the first direct experimental evidence that simvastatin ameliorates stroke-induced peripheral immunodepression by attenuating spleen atrophy and lung bacterial infection. These findings contribute to a better understanding of the beneficial effects of statins in the treatment of stroke.

Interleukin 6-preconditioned neural stem cells reduce ischaemic injury in stroke mice

Transplantation of neural stem cells provides a promising therapy for stroke. Its efficacy, however, might be limited because of massive grafted-cell death after transplantation, and its insufficient capability for tissue repair. Interleukin 6 is a pro-inflammatory cytokine involved in the pathogenesis of various neurological disorders. Paradoxically, interleukin 6 promotes a pro-survival signalling pathway through activation of signal transducer and activator of transcription 3. In this study, we investigated whether cellular reprogramming of neural stem cells with interleukin 6 facilitates the effectiveness of cell transplantation therapy in ischaemic stroke. Neural stem cells harvested from the subventricular zone of foetal mice were preconditioned with interleukin 6 in vitro and transplanted into mouse brains 6 h or 7 days after transient middle cerebral artery occlusion. Interleukin 6 preconditioning protected the grafted neural stem cells from ischaemic reperfusion injury through signal transducer and activator of transcription 3-mediated upregulation of manganese superoxide dismutase, a primary mitochondrial antioxidant enzyme. In addition, interleukin 6 preconditioning induced secretion of vascular endothelial growth factor from the neural stem cells through activation of signal transducer and activator of transcription 3, resulting in promotion of angiogenesis in the ischaemic brain. Furthermore, transplantation of interleukin 6-preconditioned neural stem cells significantly attenuated infarct size and improved neurological performance compared with non-preconditioned neural stem cells. This interleukin 6-induced amelioration of ischaemic insults was abolished by transfecting the neural stem cells with signal transducer and activator of transcription 3 small interfering RNA before transplantation. These results indicate that preconditioning with interleukin 6, which reprograms neural stem cells to tolerate oxidative stress after ischaemic reperfusion injury and to induce angiogenesis through activation of signal transducer and activator of transcription 3, is a simple and beneficial approach for enhancing the effectiveness of cell transplantation therapy in ischaemic stroke.

CART peptide induces neuroregeneration in stroke rats

Utilizing a classic stroke model in rodents, middle cerebral artery occlusion (MCAo), we describe a novel neuroregenerative approach using the repeated intranasal administration of cocaine- and amphetamine-regulated transcript (CART) peptide starting from day 3 poststroke for enhancing the functional recovery of injured brain. Adult rats were separated into two groups with similar infarction sizes, measured by magnetic resonance imaging on day 2 after MCAo, and were treated with CART or vehicle. The CART treatment increased CART level in the brain, improved behavioral recovery, and reduced neurological scores. In the subventricular zone (SVZ), CART enhanced immunolabeling of bromodeoxyuridine, a neural progenitor cell marker Musashi-1, and the proliferating cell nuclear antigen, as well as upregulated brain-derived neurotrophic factor (BDNF) mRNA. AAV-GFP was locally applied to the SVZ to examine migration of SVZ cells. The CART enhanced migration of GFP(+) cells from SVZ toward the ischemic cortex. In SVZ culture, CART increased the size of neurospheres. The CART-mediated cell migration from SVZ explants was reduced by anti-BDNF blocking antibody. Using (1)H-MRS (proton magnetic resonance spectroscopy), increases in N-acetylaspartate levels were found in the lesioned cortex after CART treatment in stroke brain. Cocaine- and amphetamine-regulated transcript increased the expression of GAP43 and fluoro-ruby fluorescence in the lesioned cortex. In conclusion, our data suggest that intranasal CART treatment facilitates neuroregeneration in stroke brain.

The BDNF val(66)met polymorphism is not related to motor function or short-term cortical plasticity in elderly subjects

The brain derived neurotrophic factor (BDNF) val(66)met polymorphism affects function of the motor system in young subjects, but little is known about motor system effects in the elderly. The current study assessed motor system physiology and behavior, plus a measure of short-term motor cortex plasticity using transcranial magnetic stimulation, in 38 elderly subjects, then examined whether findings varied in relation to BDNF genotype. Baseline data were also collected from 14 young subjects. At baseline, elderly subjects had poorer motor performances, larger motor cortex maps, and smaller motor evoked potentials compared to young subjects. Degree of age-related differences in neurophysiology correlated inversely with motor performance, for example, larger map area correlated with weaker pinch grip force (r=-0.42, P=0.01). In elderly subjects, baseline behavior and neurophysiology did not differ in relation to BDNF genotype. In addition, although map area increased significantly (P=0.03) across 30 min of exercise, this change did not vary according to BDNF genotype. Aging is associated with changes in neurophysiology that might represent a compensatory response. The data do not support an association between BDNF genotype and behavior, neurophysiology, or short-term cortical plasticity in the motor system of healthy elderly subjects.

Ipsilateral versus contralateral spontaneous post-stroke neuroplastic changes: involvement of BDNF?

Stroke is a leading cause of death and disability in industrialized countries. Although surviving patients exhibit a certain degree of restoration of function attributable to brain plasticity, the majority of stroke survivors has to struggle with persisting deficits. In order to potentiate post-stroke recovery, several rehabilitation therapies have been undertaken and many experimental studies have reported that brain-derived neurotrophic factor (BDNF) is central to many facets of neuroplastic processes. However, although BDNF role in brain plasticity is well characterized through strategies that manipulate its content, the involvement of this neurotrophin in spontaneous post-stroke recovery remains to be clarified. Besides, while the neuroplastic role of BDNF is restricted to its mature form, most studies investigating the proper effect of ischemia on post-stroke BDNF metabolism focused on mRNA or total protein expressions. In addition, these studies are mainly performed in brain regions collected either at or around the lesion site. Therefore, the objective of the present study was to investigate in both hemispheres, the long-term expression (up to one month) of both pro- and mature BDNF forms in rats subjected to photothrombotic ischemia. These assessments were performed in the cortex and in the hippocampus, two regions known to subserve functional recovery after stroke and were coupled to the study of synaptophysin expression, a marker of synaptogenesis. Our study reports that stroke induces an early and transient increase (4h) in mature BDNF expression in the cortex of both hemispheres that was associated with a delayed rise (30d) in synaptophysin levels ipsilateraly. In both hippocampal territories, the pattern of mature BDNF expression shows a more delayed increase (from 8 to 30d), which coincides with the evolution of synaptophysin expression. Interestingly, in these hippocampal territories, pro-BDNF levels evolve differently suggesting a differential gene regulation between the two hemispheres. While highlighting the complexity of changes in BDNF metabolism after stroke, our data suggest that BDNF involvement in spontaneous post-stroke plasticity is region-dependent.

Neuroinflammation after traumatic brain injury: opportunities for therapeutic intervention

Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide, yet despite extensive efforts to develop neuroprotective therapies for this devastating disorder there have been no successful outcomes in human clinical trials to date. Following the primary mechanical insult TBI results in delayed secondary injury events due to neurochemical, metabolic and cellular changes that account for many of the neurological deficits observed after TBI. The development of secondary injury represents a window of opportunity for therapeutic intervention to prevent progressive tissue damage and loss of function after injury. To establish effective neuroprotective treatments for TBI it is essential to fully understand the complex cellular and molecular events that contribute to secondary injury. Neuroinflammation is well established as a key secondary injury mechanism after TBI, and it has been long considered to contribute to the damage sustained following brain injury. However, experimental and clinical research indicates that neuroinflammation after TBI can have both detrimental and beneficial effects, and these likely differ in the acute and delayed phases after injury. The key to developing future anti-inflammatory based neuroprotective treatments for TBI is to minimize the detrimental and neurotoxic effects of neuroinflammation while promoting the beneficial and neurotrophic effects, thereby creating optimal conditions for regeneration and repair after injury. This review outlines how post-traumatic neuroinflammation contributes to secondary injury after TBI, and discusses the complex and varied responses of the primary innate immune cells of the brain, microglia, to injury. In addition, emerging experimental anti-inflammatory and multipotential drug treatment strategies for TBI are discussed, as well as some of the challenges faced by the research community to translate promising neuroprotective drug treatments to the clinic.

Neural stem cells and stroke

Acute ischemic stroke causes a disturbance of neuronal circuitry and disruption of the blood-brain barrier that can lead to functional disabilities. At present, thrombolytic therapy inducing recanalization of the occluded vessels in the cerebral infarcted area is a commonly used therapeutic strategy. However, only a minority of patients have timely access to this kind of therapy. Recently, neural stem cells (NSCs) as therapy for stroke have been developed in preclinical studies. NSCs are harbored in the subventricular zone (SVZ) as well as the subgranular zone of the brain. The microenvironment in the SVZ, including intercellular interactions, extracellular matrix proteins, and soluble factors, can promote NSC proliferation, self-renewal, and multipotency. Endogenous neurogenesis responds to insults of ischemic stroke supporting the existence of remarkable plasticity in the mammalian brain. Homing and integration of NSCs to the sites of damaged brain tissue are complex morphological and physiological processes. This review provides an update on current preclinical cell therapies for stroke, focusing on neurogenesis in the SVZ and dentate gyrus and on recruitment cues that promote NSC homing and integration to the site of the damaged brain.

MRI measurement of angiogenesis and the therapeutic effect of acute marrow stromal cell administration on traumatic brain injury

Using magnetic resonance imaging (MRI), the present study was undertaken to investigate the therapeutic effect of acute administration of human bone marrow stromal cells (hMSCs) on traumatic brain injury (TBI) and to measure the temporal profile of angiogenesis after the injury with or without cell intervention. Male Wistar rats (300 to 350 g, n=18) subjected to controlled cortical impact TBI were intravenously injected with 1 mL of saline (n=9) or hMSCs in suspension (n=9, 3 × 10(6) hMSCs) 6 hours after TBI. In-vivo MRI acquisitions of T2-weighted imaging, cerebral blood flow (CBF), three-dimensional (3D) gradient echo imaging, and blood-to-brain transfer constant (Ki) of contrast agent were performed on all animals 2 days after injury and weekly for 6 weeks. Sensorimotor function and spatial learning were evaluated. Volumetric changes in the trauma-induced brain lesion and the lateral ventricles were tracked and quantified using T2 maps, and hemodynamic alteration and blood-brain barrier permeability were monitored by CBF and Ki, respectively. Our data show that transplantation of hMSCs 6 hours after TBI leads to reduced cerebral atrophy, early and enhanced cerebral tissue perfusion and improved functional outcome compared with controls. The hMSC treatment increases angiogenesis in the injured brain, which may promote neurologic recovery after TBI.

Adjudin attenuates lipopolysaccharide (LPS)- and ischemia-induced microglial activation

Neuroinflammation caused by microglial activation plays a key role in ischemia, neurodegeneration and many other CNS diseases. In this study, we found that Adjudin, a potential non-hormonal male contraceptive, exhibits additional function to reduce the production of proinflammatory mediators. Adjudin significantly inhibited LPS-induced IL-6 release and IL-6, IL-1β, TNF-α expression in BV2 microglial cells. Furthermore, Adjudin exhibited anti-inflammatory properties by suppression of NF-κB p65 nuclear translocation and DNA binding activity as well as ERK MAPK phosphorylation. To determine the in vivo effect of Adjudin, we used a permanent middle cerebral artery occlusion (pMCAO) mouse model and found that Adjudin could reduce ischemia-induced CD11b expression, a marker of microglial activation. Furthermore, Adjudin treatment attenuated brain edema and neurological deficits after ischemia but did not reduce infarct volume. Thus, our data suggest that Adjudin may be useful for mitigating neuroinflammation.

Post-stroke infections exacerbate ischemic brain injury in middle-aged rats: immunomodulation and neuroprotection by progesterone

We investigated the effect of delayed, prolonged systemic inflammation on stroke outcomes and progesterone (P4) neuroprotection in middle-aged rats. After transient middle cerebral artery occlusion/reperfusion (MCAO) surgery, rats received P4 (8 or 16 mg/kg) or vehicle injections at 2h, 6h and every 24h until day 7 post-occlusion. At 24h post-injury systemic inflammation was induced by giving three doses of lipopolysaccharide (LPS; 50 μg/kg, at 4h intervals) to model post-stroke infections. We measured serum brain-derived neurotrophic factor (BDNF), pro-inflammatory cytokines, and behavioral parameters at multiple times. Serum BDNF levels decreased more in the vehicle+LPS group compared to vehicle-alone at 3 and 7 days post-injury (P<0.05). Vehicle-alone showed a significant increase in interleukin-1β, interleukin-6, and tumor necrosis factor alpha levels at different times following stroke and these levels were further elevated in the vehicle+LPS group. P4 at both doses produced a significant (P<0.05) decline in cytokine levels compared to vehicle and vehicle+LPS. P4 restored BDNF levels at 3 and 7 days post-stroke (P<0.05). Behavioral assessment (rotarod, grip strength, sensory neglect and locomotor activity tests) at 3, 5 and 7 days post-stroke revealed that the vehicle group had significant (P<0.05) deficits in all tests compared to intact controls, and performance was worse in the vehicle+LPS group. P4 at both doses produced significant functional improvement on all tests. Systemic inflammation did not show an additive effect on infarct volume but P4 at both doses showed significant infarct reduction. We suggest that post-stroke infection exacerbates stroke outcomes and P4 exerts neuroprotective/modulatory effects through its systemic anti-inflammatory and BDNF regulatory actions.

Emerging therapies in neurorehabilitation

Just as advancing technology has furthered our understanding of how the nervous system recovers, technology also enables the development of novel approaches to treatment. Because nervous system disease and injury often lead to severely impaired function, patients and families are willing to try anything, so therapies are often adopted with little evidence that they actually work. Evidence shows that comprehensive rehabilitation programs produce better outcomes, but it is still not understood what components of these multifaceted programs are critical to their success. Functional neuroimaging and other modalities now allow monitoring of neurophysiologic changes that can be paired with assessments detailing clinical changes, furthering our understanding of the factors that influence the recovery process. This article discusses several novel and emerging therapies in neurorehabilitation as well as recent multistudy reviews of selected treatments.

Neuroprotective action of lithium in disorders of the central nervous system

Substantial in vitro and in vivo evidence of neurotrophic and neuroprotective effects of lithium suggests that it may also have considerable potential for the treatment of neurodegenerative conditions. Lithium's main mechanisms of action appear to stem from its ability to inhibit glycogen synthase kinase-3 activity and also to induce signaling mediated by brain-derived neurotrophic factor. This in turn alters a wide variety of downstream effectors, with the ultimate effect of enhancing pathways to cell survival. In addition, lithium contributes to calcium homeostasis. By inhibiting N-methyl-D-aspartate receptor-mediated calcium influx, for instance, it suppresses the calcium-dependent activation of pro-apoptotic signaling pathways. By inhibiting the activity of phosphoinositol phosphatases, it decreases levels of inositol 1,4,5-trisphosphate, a process recently identified as a novel mechanism for inducing autophagy. These mechanisms allow therapeutic doses of lithium to protect neuronal cells from diverse insults that would otherwise lead to massive cell death. Lithium, moreover, has been shown to improve behavioral and cognitive deficits in animal models of neurodegenerative diseases, including stroke, amyotrophic lateral sclerosis, fragile X syndrome, and Huntington's, Alzheimer's, and Parkinson's diseases. Since lithium is already FDA-approved for the treatment of bipolar disorder, our conclusions support the notion that its clinical relevance can be expanded to include the treatment of several neurological and neurodegenerative-related diseases.

Repetitive acute intermittent hypoxia increases expression of proteins associated with plasticity in the phrenic motor nucleus

Acute intermittent hypoxia (AIH) initiates plasticity in respiratory motor control, including phrenic long term facilitation (pLTF). Since pLTF is enhanced by preconditioning with repetitive exposure to AIH (rAIH), we hypothesized that a rAIH protocol consisting of 3 AIH exposures per week for 10 weeks (3×wAIH; AIH: 10, 5-min episodes of 10.5% O(2); 5-min normoxic intervals) would enhance expression of molecules that play key roles in pLTF within the phrenic motor nucleus. Immunohistochemical analyses revealed that 3×wAIH for 10 weeks increased serotonin terminal density in the C4 phrenic motor nucleus and serotonin 2A (5-HT(2A)) receptor expression in presumptive phrenic motor neurons. Immunoreactive brain derived neurotrophic factor (BDNF) and its high affinity receptor (TrkB) also increased following 3×wAIH. 3×wAIH also increased expression of another hypoxia-sensitive growth factor known to elicit phrenic motor facilitation, vascular endothelial growth factor (VEGF), and its receptor (VEGFR-2). Kinases "downstream" from TrkB and VEGFR-2 were up-regulated in or near presumptive phrenic motor neurons, including phosphorylated extracellular-signal regulated kinase (p-ERK) and protein kinase B (p-AKT). Thus, 3×wAIH up-regulates neurochemicals known to be associated with phrenic motor plasticity. Since 3×wAIH upregulates pro-plasticity molecules without evidence for CNS pathology, it may be a useful therapeutic tool in treating disorders that cause respiratory insufficiency, such as spinal injury or motor neuron disease.

MRI detects brain reorganization after human umbilical tissue-derived cells (hUTC) treatment of stroke in rat

Human umbilical tissue-derived cells (hUTC) represent an attractive cell source and a potential technology for neurorestoration and improvement of functional outcomes following stroke. Male Wistar rats were subjected to a transient middle cerebral artery occlusion (tMCAo) and were intravenously administered hUTC (N = 11) or vehicle (N = 10) 48 hrs after stroke. White matter and vascular reorganization was monitored over a 12-week period using MRI and histopathology. MRI results were correlated with neurological functional and histology outcomes to demonstrate that MRI can be a useful tool to measure structural recovery after stroke. MRI revealed a significant reduction in the ventricular volume expansion and improvement in cerebral blood flow (CBF) in the hUTC treated group compared to vehicle treated group. Treatment with hUTC resulted in histological and functional improvements as evidenced by enhanced expression of vWF and synaptophysin, and improved outcomes on behavioral tests. Significant correlations were detected between MRI ventricular volumes and histological lesion volume as well as number of apoptotic cells. A positive correlation was also observed between MRI CBF or cerebral blood volume (CBV) and histological synaptic density. Neurological functional tests were also significantly correlated with MRI ventricular volume and CBV. Our data demonstrated that MRI measurements can detect the effect of hUTC therapy on the brain reorganization and exhibited positive correlation with histological measurements of brain structural changes and functional behavioral tests after stroke. MRI ventricular volumes provided the most sensitive index in monitoring brain remodeling and treatment effects and highly correlated with histological and functional measurements.

Multimodal neuroprotection induced by PACAP38 in oxygen-glucose deprivation and middle cerebral artery occlusion stroke models

Pituitary adenylate cyclase activating peptide (PACAP), a potent neuropeptide which crosses the blood-brain barrier, is known to provide neuroprotection in rat stroke models of middle cerebral artery occlusion (MCAO) by mechanism(s) which deserve clarification. We confirmed that following i.v. injection of 30 ng/kg of PACAP38 in rats exposed to 2 h of MCAO focal cerebral ischemia and 48 h reoxygenation, 50 % neuroprotection was measured by reduced caspase-3 activity and volume of cerebral infarction. Similar neuroprotective effects were measured upon PACAP38 treatment of oxygen-glucose deprivation and reoxygenation of brain cortical neurons. The neuroprotection was temporally associated with increased expression of brain-derived neurotrophic factor, phosphorylation of its receptor-tropomyosin-related kinase receptor type B (trkB), activation of phosphoinositide 3-kinase and Akt, and reduction of extracellular signal-regulated kinases 1/2 phosphorylation. PACAP38 increased expression of neuronal markers beta-tubulin III, microtubule-associated protein-2, and growth-associated protein-43. PACAP38 induced stimulation of Rac and suppression of Rho GTPase activities. PACAP38 downregulated the nerve growth factor receptor (p75(NTR)) and associated Nogo-(Neurite outgrowth-A) receptor. Collectively, these in vitro and in vivo results propose that PACAP exhibits neuroprotective effects in cerebral ischemia by three mechanisms: a direct one, mediated by PACAP receptors, and two indirect, induced by neurotrophin release, activation of the trkB receptors and attenuation of neuronal growth inhibitory signaling molecules p75(NTR) and Nogo receptor.

Increased levels of circulating endothelial progenitor cells in patients with ischaemic stroke treated with statins during acute phase

BACKGROUND AND PURPOSE

Endothelial progenitor cells (EPCs) have been suggested to be a therapeutic option in ischaemic stroke. Our aim was to study whether statin treatment during acute phase could increase circulating EPCs after acute ischaemic stroke.

METHODS

We studied 48 patients with a first-ever non-lacunar ischaemic stroke (<12 h from stroke onset). Sixteen patients received statin treatment (20 mg atorvastatin/day) during the first 4 days. We defined the EPC increment during the first week as the difference in the number of early outgrowth colony-forming unit-endothelial cell (CFU-EC) between day 7 and at admission (previous to atorvastatin treatment). Serum levels of vascular endothelial growth factor and active matrix metalloproteinase 9 (determined by ELISA), and nitric oxide metabolites (NOx) (determined by high-performance liquid chromatography) were measured at admission, 24 and 72 h, and day 7.

RESULTS

Colony-forming unit-endothelial cells were similar at baseline between patients treated (n = 16) and non-treated (n = 32) with statins (10.1 ± 3.9 vs. 7.9 ± 6.9 CFU-EC, P = 0.223). However, patients treated with statins showed a higher EPC increment (24.0 ± 17.3 vs. 6.0 ± 17.8 CFU-EC, P = 0.002) during the first week. An EPC increment ≥ 4 CFU-EC predicted with the highest sensitivity (88%) and specificity (92%) the probability of good outcome (area under the curve 0.903, P < 0.0001). Statin treatment (OR, 13.1; CI 95%, 2.2-76.9, P = 0.004) was independently associated with an EPC increment ≥ 4 CFU-EC after adjustment for confounder factors, but this association was lost when adjusting for NOx levels.

CONCLUSIONS

Statin treatment for 4 days may increase circulating EPC levels, probably by NO-related mechanisms.

Neuroprotective and neurorestorative effects of thymosin β4 treatment initiated 6 hours after traumatic brain injury in rats

OBJECT

Thymosin β4 (Tβ4) is a regenerative multifunctional peptide. The aim of this study was to test the hypothesis that Tβ4 treatment initiated 6 hours postinjury reduces brain damage and improves functional recovery in rats subjected to traumatic brain injury (TBI).

METHODS

Traumatic brain injury was induced by controlled cortical impact over the left parietal cortex in young adult male Wistar rats. The rats were randomly divided into the following groups: 1) saline group (n = 7); 2) 6 mg/kg Tβ4 group (n = 8); and 3) 30 mg/kg Tβ4 group (n = 8). Thymosin β4 or saline was administered intraperitoneally starting at 6 hours postinjury and again at 24 and 48 hours. An additional group of 6 animals underwent surgery without TBI (sham-injury group). Sensorimotor function and spatial learning were assessed using the modified Neurological Severity Score and the Morris water maze test, respectively. Animals were euthanized 35 days after injury, and brain sections were processed to assess lesion volume, hippocampal cell loss, cell proliferation, and neurogenesis after Tβ4 treatment.

RESULTS

Compared with saline administration, Tβ4 treatment initiated 6 hours postinjury significantly improved sensorimotor functional recovery and spatial learning, reduced cortical lesion volume and hippocampal cell loss, and enhanced cell proliferation and neurogenesis in the injured hippocampus. The high dose of Tβ4 showed better beneficial effects compared with the low-dose treatment.

CONCLUSIONS

Thymosin β4 treatment initiated 6 hours postinjury provides both neuroprotection and neurorestoration after TBI, indicating that Tβ4 has promising therapeutic potential in patients with TBI. These data warrant further investigation of the optimal dose and therapeutic window of Tβ4 treatment for TBI and the associated underlying mechanisms.

Inflammatory regulators of redirected neural migration in the injured brain

Brain injury following stroke or trauma induces the migration of neuroblasts derived from subventricular zone neural precursor cells (NPCs) towards the damaged tissue, where they then have the potential to contribute to repair. Enhancing the recruitment of new cells thus presents an enticing prospect for the development of new therapeutic approaches to treat brain injury; to this end, an understanding of the factors regulating this process is required. During the neuroinflammatory response to ischemic and traumatic brain injuries, a plethora of pro- and anti-inflammatory cytokines, chemokines and growth factors are released in the damaged tissue, and recent work indicates that a variety of these are able to influence injury-induced migration. In this review, we will discuss the contribution of specific chemokines and growth factors towards stimulating NPC migration in the injured brain.

Progesterone is neuroprotective against ischemic brain injury through its effects on the phosphoinositide 3-kinase/protein kinase B signaling pathway

We tested the hypothesis that the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) pathway mediates some of the neuroprotective effects of progesterone (PROG) after ischemic stroke. We examined whether PROG acting through the PI3K/Akt pathway could affect the expression of vascular endothelial growth factor (VEGF) and brain-derived neurotrophic factor (BDNF). Rats underwent permanent focal cerebral ischemia by electrocoagulation and received intraperitoneal injections of PROG (8 mg/kg) or vehicle at 1 h post-occlusion and subcutaneous injections at 6, 24, and 48 h. PAkt/Akt levels, apoptosis and apoptosis-related proteins (phosphorylated Bcl-2-associated death promoter (pBAD), BAD, caspase-3, and cleaved caspase-3) were analyzed by TUNEL assays, Western blotting and immunohistochemistry at 24 h post-pMCAO. VEGF and BDNF were analyzed at 24, 72 h and 14 days post-pMCAO with Western blots. Following pMCAO, PROG treatment significantly (P<0.05) reduced ischemic lesion size and edema. Treatment with PROG significantly (P<0.05) decreased VEGF at 24 and 72 h but increased VEGF expression 14 days after injury. The treatment also increased BDNF, and attenuated apoptosis by increasing Akt phosphorylation compared with vehicle alone. The selective PI3K inhibitor wortmannin compromised PROG-induced neuroprotective effects and reduced the elevation of pAkt levels in the ischemic penumbra. Our findings lead us to suggest that the PI3K/Akt pathway can play a role in mediating the neuroprotective effects of PROG after stroke by altering the expression of trophic factors in the brain.

Therapeutic benefit of treatment of stroke with simvastatin and human umbilical cord blood cells: neurogenesis, synaptic plasticity, and axon growth

The therapeutic efficacy of cell-based therapy after stroke can be enhanced by making the host brain tissue more receptive to the administered cells, which thereby facilitates brain plasticity. We hypothesized that simvastatin increases human umbilical cord blood cell (HUCBC) migration into the ischemic brain and promotes brain plasticity and neurological functional outcome after stroke. Rats were subjected to 2-h middle cerebral artery occlusion (MCAo) and administered subtherapeutic doses of simvastatin (0.5 mg/kg, gavaged daily for 7 days), HUCBCs (1 × 10(6), one time injection via tail vein), or combination simvastatin with HUCBCs starting at 24 h after stroke. Combination treatment of stroke showed an interactive effect in improvement of neurological outcome compared with simvastatin or HUCBC monotherapy groups. In addition, combination treatment significantly increased brain-derived neurotrophic factor/TrkB expression and the number of engrafted HUCBCs in the ischemic brain compared with HUCBC monotherapy. The number of engrafted HUCBCs was significantly correlated with functional outcome (modified neurological severity score). Combination treatment significantly increased neurogenesis and synaptic plasticity in the ischemic brain, and promoted neuroblast migration in cultured subventricular zone explants. Using primary cultured neurons (PCNs), we found that combination treatment enhanced neurite outgrowth compared with nontreatment control, simvastatin or HUCBC supernatant monotherapy. Inhibition of TrkB significantly attenuated combination treatment-induced neurite outgrowth. Our data indicate that combination simvastatin and HUCBC treatment of stroke increases BDNF/TrkB expression, enhances HUCBC migration into the ischemic brain, amplifies endogenous neurogenesis, synaptic plasticity and axonal growth, and thereby improves functional outcome after stroke.

Impact of inhibition of erythropoietin treatment-mediated neurogenesis in the dentate gyrus of the hippocampus on restoration of spatial learning after traumatic brain injury

Our previous study demonstrates that delayed (initiated 24h post injury) erythropoietin (EPO) therapy for traumatic brain injury (TBI) significantly improves spatial learning. In this study, we investigated the impact of inhibition of EPO treatment-mediated neurogenesis on spatial learning after experimental TBI. Young male Wistar rats (318+/-7 g) were subjected to unilateral controlled cortical impact injury. TBI rats received delayed EPO treatment (5000 U/kg in saline) administered intraperitoneally once daily at 1, 2, and 3 days post injury and intracerebroventricular (icv) infusion of either a mitotic inhibitor cytosine-b-D-arabinofuranoside or vehicle (saline) for 14 days. Another 2 groups of TBI rats were treated intraperitoneally with saline and infused icv with either a mitotic inhibitor Ara-C or saline for 14 days. Animals receiving sham operation were infused icv with either Ara-C infusion or saline. Bromodeoxyuridine (BrdU) was administered to label dividing cells. Spatial learning was assessed using a modified Morris water maze test. Animals were sacrificed at 35 days after injury and brain sections stained for immunohistochemical analyses. As compared to the saline treatment, immunohistochemical analysis revealed that delayed EPO treatment significantly increased the number of BrdU-positive cells and new neurons co-stained with BrdU and NeuN (mature neuron marker) in the dentate gyrus in TBI rats. EPO treatment improved spatial learning after TBI. Ara-C infusion significantly abolished neurogenesis and spatial learning recovery after TBI and EPO treatment. Both EPO and Ara-C reduced the number of astrocytes and microglia/macrophages in the dentate gyrus after TBI. Our findings are highly suggestive for an important role of EPO-amplified dentate gyrus neurogenesis as one of the mechanisms underlying EPO therapeutic treatments after TBI, strongly indicating that strategies promoting endogenous neurogenesis may hold an important therapeutic potential for treatment of TBI.

Systematic Review and Meta-Analysis of the Efficacy of Statins in Experimental Stroke

Background and purpose

Statins are postulated as candidate drugs for the treatment of acute stroke. The aim of this study was to critically appraise the evidence for the efficacy of statins administered after the onset of experimental focal cerebral ischemia.

Methods

We undertook a systematic review and meta-analysis of animal studies reporting the efficacy of any statin administered following middle cerebral artery occlusion. The primary outcome measure was infarct volume. Assessment of study quality and range of evidence were undertaken, and prespecified sub-group analyses were performed.

Results

Eighteen published studies describing outcome in 472 animals were identified. Statins reduced infarct volume by 11·2% (95% confidence interval 8·1% to 14·3%, P < 0·001) and improved the neurological severity score by 0·7 points (95% confidence interval 0·4 to 1·1, P < 0·0001). Efficacy was evident up to three-hours post-middle cerebral artery occlusion. Median study quality score was 7 of 13 (interquartile range, 4 to 11). No studies tested efficacy in aged, female, or hypertensive animals; or in species other than rodents.

Conclusions

These findings suggest that statins administered after middle cerebral artery occlusion have modest efficacy. Effects of potential sources of bias are considered likely to reduce the estimated effect from this review.

Evidence for epistatic gene interactions between growth factor genes in stroke outcome

BACKGROUND AND PURPOSE

Growth factors are thought to modulate neurological function in stroke recovery through effects in angiogenesis, neurogenesis, and neuroprotection.

METHODS

We tested the association of variants in the brain-derived neurotrophic factor (BDNF), fibroblast growth factor 2 (FGF2) and vascular endothelial growth factor A (VEGFA) genes, and epistatic interactions between them, with functional outcome in a sample of 546 stroke patients.

RESULTS

While none of the tested genes was independently associated with stroke outcome, two significant gene-gene interaction models were identified. One model combined one BDNF and three FGF2 markers, with a global odds ratio (OR) (95% confidence interval [CI]) of 4.15 [2.86-6.04]. The second model included one FGF2 and two VEGFA markers with a global OR [95% CI] = 2.54 [1.76-3.67].

CONCLUSIONS

The results provide evidence for gene interactions in stroke outcome, highlighting the complexity of the recovery mechanisms after a stroke event.

Statins Enhance Expression of Growth Factors and Activate the PI3K/Akt-mediated Signaling Pathway after Experimental Intracerebral Hemorrhage

Previous studies have demonstrates that statins improve neurological outcome and promote neurovascular recovery after ICH. This study is designed to examine whether simvastatin and atorvastatin affect levels of growth factors and activate the Akt signaling pathway during the recovery phase after intracerebral hemorrhage (ICH) in rats. Sixty (60) male Wistar rats were subjected to ICH by stereotactic injection of 100 μL of autologous blood into the striatum and were treated with or without simvastatin or atorvastatin. Neurological functional outcome was evaluated by behavioral tests (mNSS and corner turn test) at different time points after ICH. Brain extracts were utilized for Enzyme-linked immunosorbent assay (ELISA) analyses to measure vascular endothelial growth factor (VEGF); brain-derived neurotrophin factor (BDNF) expression, and nerve growth factor (NGF). Western blot was used to measure the changes in the Akt-mediated signaling pathway. Both the simvastatin- and atorvastatin-treated animals had significant neurological improvement at 2 weeks post-ICH. Simvastatin and atorvastatin treatment increased the expression of BDNF, VEGF and NGF in both low- and high-dose groups at 7 days after ICH (p < 0.05). Phosphorylation of Akt, glycogen synthase kinase-3β (GSK-3β), and cAMP response element-binding proteins (CREB) were also increased at 7 days after statin treatment. These results suggest that the therapeutic effects of statins after experimental ICH may be mediated by the transient induction of BDNF, VEGF and NGF expression and the activation of the Akt-mediated signaling pathway.

Circulating and brain BDNF levels in stroke rats. Relevance to clinical studies

Background

Whereas brain-derived neurotrophic factor (BDNF) levels are measured in the brain in animal models of stroke, neurotrophin levels in stroke patients are measured in plasma or serum samples. The present study was designed to investigate the meaning of circulating BDNF levels in stroke patients.

Methods and Results

Unilateral ischemic stroke was induced in rats by the injection of various numbers of microspheres into the carotid circulation in order to mimic the different degrees of stroke severity observed in stroke patients. Blood was serially collected from the jugular vein before and after (4 h, 24 h and 8 d) embolization and the whole brains were collected at 4, 24 h and 8 d post-embolization. Rats were then selected from their degree of embolization, so that the distribution of stroke severity in the rats at the different time points was large but similar. Using ELISA tests, BDNF levels were measured in plasma, serum and brain of selected rats. Whereas plasma and serum BDNF levels were not changed by stroke, stroke induced an increase in brain BDNF levels at 4 h and 24 h post-embolization, which was not correlated with stroke severity. Individual plasma BDNF levels did not correlate with brain levels at any time point after stroke but a positive correlation (r = 0.67) was observed between individual plasma BDNF levels and stroke severity at 4 h post-embolization.

Conclusion

Circulating BDNF levels do not mirror brain BDNF levels after stroke, and severe stroke is associated with high plasma BDNF in the very acute stage.

Simvastatin protects auditory hair cells from gentamicin-induced toxicity and activates Akt signaling in vitro

Background

Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, known as statins, are commonly used as cholesterol-lowering drugs. During the past decade, evidence has emerged that statins also have neuroprotective effects. Research in the retina has shown that simvastatin, a commonly used statin, increases Akt phosphorylation in vivo, indicating that the PI3K/Akt pathway contributes to the protective effects achieved. While research about neuroprotective effects have been conducted in several systems, the effects of statins on the inner ear are largely unknown.

Results

We evaluated whether the 3-hydroxy-3-methylglutaryl-coenzyme A reductase is present within the rat cochlea and whether simvastatin is able to protect auditory hair cells from gentamicin-induced apoptotic cell death in a in vitro mouse model. Furthermore, we evaluated whether simvastatin increases Akt phosphorylation in the organ of Corti. We detected 3-hydroxy-3-methylglutaryl-coenzyme A reductase mRNA in organ of Corti, spiral ganglion, and stria vascularis by reverse transcriptase-polymerase chain reaction (RT-PCR). Moreover, we observed a dose-dependent and significant reduction of hair cell loss in organs of Corti treated with simvastatin in addition to gentamicin, as compared to samples treated with gentamicin alone. The protective effect of simvastatin was reversed by addition of mevalonate, a downstream metabolite blocked by simvastatin, demonstrating the specificity of protection. Finally, Western blotting showed an increase in organ of Corti Akt phosphorylation after simvastatin treatment in vitro.

Conclusion

These results suggest a neuroprotective effect of statins in the inner ear, mediated by reduced 3-hydroxy-3-methylglutaryl-coenzyme A reductase metabolism and Akt activation.

Intense training overcomes effects of the Val66Met BDNF polymorphism on short-term plasticity

The val(66)met polymorphism in the brain-derived neurotrophic factor (BDNF) gene impacts activity-dependent secretion of BDNF and modifies short-term cortical plasticity. The current study examined whether sustained training overcomes polymorphism effects on short-term plasticity and also examined polymorphism effects on long-term plasticity. Twenty-four subjects completed a 12-day protocol of daily training on a marble navigation task that required intense use of the first dorsal interosseus (FDI) muscle. In parallel, transcranial magnetic stimulation (TMS) mapping was used to assess serial measures of short-term cortical motor map plasticity, plus long-term cortical motor map plasticity, of the cortical FDI map. On Day 1, subjects with the polymorphism did not show significant short-term cortical motor map plasticity over 30 min of FDI activity, but subjects without the polymorphism did. After 5 days of intense training, a genotype-based difference in short-term cortical motor map plasticity was no longer found, as both groups showed short-term plasticity across the 30 min of FDI activity. Also, across 12 days of training, map area decreased significantly, in a manner that did not vary in relation to genotype. Training of sufficient intensity and duration overcomes effects that the val(66)met polymorphism has on short-term cortical motor map plasticity. The polymorphism-related differences seen with short-term plasticity are not found with long-term cortical motor map plasticity.

The effects of potential neuroprotective agents on rat facial function recovery following facial nerve injury

OBJECTIVE

To evaluate whether a series of pharmacologic agents with potential neuroprotective effects accelerate and/or improve facial function recovery after facial nerve crush injury.

STUDY DESIGN

Randomized animal study.

SETTING

Tertiary care facility.

METHODS

Eighty female Wistar-Hannover rats underwent head restraint implantation and daily conditioning. Animals then underwent unilateral crush injury to the main trunk of the facial nerve and were randomized to receive treatment with atorvastatin (n = 10), sildenafil (n = 10), darbepoetin (n = 20), or a corresponding control agent (n = 40). The return of whisking function was tracked throughout the recovery period.

RESULTS

All rats initiated the return of whisking function from nerve crush by day 12. Darbepoetin-treated rats (n = 20) showed significantly improved whisking amplitude and velocity across the recovery period, with several days of significant pairwise differences vs comparable control rats (n = 16) across the first 2 weeks of whisking function return. In contrast, rats treated with sildenafil (n = 10) and atorvastatin (n = 10) did not show significant improvement in whisking function recovery after facial nerve crush compared to controls. By week 8, all darbepoetin-treated animals and comparable nerve crush control animals fully recovered whisking function and were statistically indistinguishable.

CONCLUSION

Among the 3 potentially neuroprotective agents evaluated, only darbepoetin administration resulted in accelerated recovery of whisking parameters after facial nerve crush injury. Further efforts to define the mechanism of action and translate these findings to the use of darbepoetin in the care of patients with traumatic facial paralysis are needed.