Combination therapy of 17beta-estradiol and recombinant tissue plasminogen activator for experimental ischemic stroke

Impact of 17β-Estradiol on the Shape, Survival, Osteogenic Transformation, and mRNA Expression of Gingiva-Derived Stem Cell Spheroids

Background and Objectives: Mesenchymal stem cells hold promise for tissue regeneration, given their robust growth and versatile differentiation capabilities. An analysis of bone marrow-sourced mesenchymal stem cell proliferation showed that 17β-estradiol could enhance their growth. This study aims to investigate the influence of 17β-estradiol on the shape, survival, osteogenic differentiation, and mineralization of human mesenchymal stem cells. Materials and Methods: Spheroids made from human gingiva-derived stem cells were cultivated with varying concentrations of 17β-estradiol: 0, 0.01, 0.1, 1, and 10 nM. Morphology was assessed on days 1, 3, and 5. The live/dead kit assay was employed on day 3 for qualitative cell viability, while cell counting kit-8 was used for quantitative viability assessments on days 1, 3, and 5. To evaluate the osteogenic differentiation of the spheroids, a real-time polymerase chain reaction assessed the expressions of RUNX2 and COL1A1 on day 7. Results: The stem cells formed cohesive spheroids, and the inclusion of 17β-estradiol did not noticeably alter their shape. The spheroid diameter remained consistent across concentrations of 0, 0.01, 0.1, 1, and 10 nM of 17β-estradiol. However, cellular viability was boosted with the addition of 1 and 10 nM of 17β-estradiol. The highest expression levels for RUNX2 and COL1A1 were observed with the introduction of 17β-estradiol at 0.1 nM. Conclusions: In conclusion, from the results obtained, it can be inferred that 17β-estradiol can be utilized for differentiating stem cell spheroids. Furthermore, the localized and controlled use, potentially through localized delivery systems or biomaterials, can be an area of active research. While 17β-estradiol holds promise for enhancing stem cell applications, any clinical use requires a thorough understanding of its mechanisms, careful control of its dosage and delivery, and extensive testing to ensure safety and efficacy.

Worsened Stroke Outcome in a Model of Preeclampsia is Associated With Poor Collateral Flow and Oxidative Stress

BACKGROUND

Preeclampsia increases the incidence of maternal stroke, a devastating condition that is on the rise. We investigated stroke outcome in a model of experimental preeclampsia with and without treatment with clinically relevant doses of magnesium sulfate (experimental preeclampsia+MgSO4) compared to normal late-pregnant and nonpregnant rats.

METHODS

Transient middle cerebral artery occlusion was used to induce focal stroke for either 1.5 or 3 hours. Infarct volume and hemorrhagic transformation were determined as measures of stroke outcome. Changes in core middle cerebral artery and collateral flow were measured by dual laser Doppler. The relationship between middle cerebral artery perfusion deficit and infarction was used as a measure of ischemic tolerance. Oxidative stress and endothelial dysfunction were measured by 3-nitrotyrosine and 8-isoprostane, in brain and serum, respectively.

RESULTS

Late-pregnant animals had robust collateral flow and greater ischemic tolerance of brain tissue, whereas experimental preeclampsia had greater infarction that was related to poor collateral flow, endothelial dysfunction, and oxidative stress. Importantly, pregnancy appeared preventative of hemorrhagic transformation as it occurred only in nonpregnant animals. MgSO4 did not provide benefit to experimental preeclampsia animals for infarction.

CONCLUSIONS

Stroke outcome was worse in a model of preeclampsia. As preeclampsia increases the risk of future stroke and cardiovascular disease, it is worth understanding the influence of preeclampsia on the material brain and factors that might potentiate injury both during the index pregnancy and years postpartum.

Extracellular matrix metalloproteinase-9 (MMP-9) is required in female mice for 17β-estradiol enhancement of hippocampal memory consolidation

Hippocampal plasticity and memory are modulated by the potent estrogen 17β-estradiol (E₂). Research on the molecular mechanisms of hippocampal E₂ signaling has uncovered multiple intracellular pathways that contribute to these effects, but few have questioned the role that extracellular signaling processes may play in E₂ action. Modification of the extracellular matrix (ECM) by proteases like matrix metalloproteinase-9 (MMP-9) is critical for activity-dependent remodeling of synapses, and MMP-9 activity is required for hippocampal learning and memory. Yet little is known about the extent to which E₂ regulates MMP-9 in the hippocampus, and the influence this interaction may have on hippocampal memory. Here, we examined the effects of hippocampal MMP-9 activity on E₂-induced enhancement of spatial and object recognition memory consolidation. Post-training bilateral infusion of an MMP-9 inhibitor into the dorsal hippocampus of ovariectomized female mice blocked the enhancing effects of E₂ on object placement and object recognition memory, supporting a role for MMP-9 in estrogenic regulation of memory consolidation. E₂ also rapidly increased the activity of dorsal hippocampal MMP-9 without influencing its protein expression, providing further insight into hippocampal E₂/MMP-9 interactions. Together, these results provide the first evidence that E₂ regulates MMP-9 to modulate hippocampal memory and highlight the need to further study estrogenic regulation of extracellular modification.

Fisetin Prolongs Therapy Window of Brain Ischemic Stroke Using Tissue Plasminogen Activator: A Double-Blind Randomized Placebo-Controlled Clinical Trial

Recombinant tissue plasminogen activator (rt-PA) can be utilized to treat ischemic stroke with safety and effectiveness but limited by a narrow therapeutic window. In the present clinical trial among patients with stroke, we sought to evaluate the potential of fisetin to extend the therapeutic window of rt-PA treatment. Patients with stroke were divided based on their onset-to-treatment time (OTT) and then randomly assigned to receive the rt-PA treatment combined with fisetin or placebo. Primary outcome was evaluated using the National Institutes of Health Stroke scale (NIHSS), and secondary outcome was assessed by serum levels of matrix metalloproteinase (MMP) 2, MMP 9, and C-reactive protein (CRP). Fisetin dramatically improved the treatment outcomes of the patients with stroke in the delayed OTT strata, as revealed by lower NIHSS scores. The beneficial effect of fisetin was likely attributable to reduced levels of MMP-2, MMP-9, and CRP in the serum, as evidenced by strong linear correlations between serum levels of such markers with the NIHSS scores in all enrolled patients. Fisetin may possess the potential to supplement traditional rt-PA treatments among patients with stroke, particularly for those with delayed OTT, and thereby extend the otherwise narrow therapeutic window and improve the treatment outcomes.

β-Estradiol Protects Against Acidosis-Mediated and Ischemic Neuronal Injury by Promoting ASIC1a (Acid-Sensing Ion Channel 1a) Protein Degradation

Background and Purpose- Sex differences in the incidence and outcome of stroke have been well documented. The severity of stroke in women is, in general, significantly lower than that in men, which is mediated, at least in part, by the protective effects of β-estradiol. However, the detailed mechanisms underlying the neuroprotection by β-estradiol are still elusive. Recent studies have demonstrated that activation of ASIC1a (acid-sensing ion channel 1a) by tissue acidosis, a common feature of brain ischemia, plays an important role in ischemic brain injury. In the present study, we assessed the effects of β-estradiol on acidosis-mediated and ischemic neuronal injury both in vitro and in vivo and explored the involvement of ASIC1a and underlying mechanism. Methods- Cultured neurons and NS20Y cells were subjected to acidosis-mediated injury in vitro. Cell viability and cytotoxicity were measured by methylthiazolyldiphenyl-tetrazolium bromide and lactate dehydrogenase assays, respectively. Transient (60 minutes) focal ischemia in mice was induced by suture occlusion of the middle cerebral artery in vivo. ASIC currents were recorded using whole-cell patch-clamp technique while intracellular Ca2+ concentration was measured with fluorescence imaging using Fura-2. ASIC1a expression was detected by Western blotting and quantitative real-time polymerase chain reaction. Results- Treatment of neuronal cells with β-estradiol decreased acidosis-induced cytotoxicity. ASIC currents and acid-induced elevation of intracellular Ca2+ were all attenuated by β-estradiol treatment. In addition, we showed that β-estradiol treatment reduced ASIC1a protein expression, which was mediated by increased protein degradation, and that estrogen receptor α was involved. Finally, we showed that the level of ASIC1a protein expression in brain tissues and the degree of neuroprotection by ASIC1a blockade were lower in female mice, which could be attenuated by ovariectomy. Conclusions- β-estradiol can protect neurons against acidosis-mediated neurotoxicity and ischemic brain injury by suppressing ASIC1a protein expression and channel function. Visual Overview- An online visual overview is available for this article.

Hesperidin reduces adverse symptomatic intracerebral hemorrhage by promoting TGF-β1 for treating ischemic stroke using tissue plasminogen activator

Treatment with recombinant tissue plasminogen activator (rt-PA) is the most effective therapeutic option against brain ischemic stroke at the present time. However, elevated incidence of symptomatic intracerebral hemorrhage (SIH) greatly hinders ideal treatment outcome of rt-PA. We sought to assess the impacts of hesperidin on SIH following rt-PA therapies. Patients with ischemic stroke were assigned into two groups in a random fashion, to receive either rt-PA + placebo (Pc) or rt-PA + hesperidin. Treatment outcome was evaluated 24 h after the initial reperfusion using the transcranial Doppler ultrasonography (TCD) and the NIH Stroke Scale (NIHSS). Further, serum concentrations of transforming growth factor (TGF)-β1, matrix metalloproteinase (MMP)-2, and MMP-9 were examined. Following the initial administration, stroke patients continued to receive either daily Pc or daily hesperidin, and the treatment outcome after 7 days was examined using the TCD, NIHSS, Glasgow Outcome Scale (GOS), and the Modified Rankin Scale (MRS). Combined treatment of rt-PA with hesperidin yielded significant improvement of outcomes, as revealed by better TCD and NIHSS scores as well as decreased SIH incidences, which could be attributable to elevation of TGF-β1 and reduction in serum levels of both MMP-2 and MMP-9 caused by hesperidin. Follow-up hesperidin treatment for 7 consecutive days also markedly enhanced the recovery of stroke patients, as indicated by TCD, MRS, GOS, and NIHSS. Findings of the present study strongly suggested potential clinical application of hesperidin supplement in rt-PA therapies to reduce SIH and thereby improve the treatment outcomes of rt-PA in patients with ischemic stroke.

The effect of exercise preconditioning on stroke outcome in ovariectomized mice with permanent middle cerebral artery occlusion

Exercise preconditioning has been shown to be effective in improving behavioral and neuropathological indices after cerebral ischemia. We evaluated the effect of exercise preconditioning, 17β-estradiol, and their combination on stroke outcome using an experimental model of stroke in ovariectomized (OVX) mice. OVX mice were randomly assigned to 4 groups as follows: control (stroke), exercise (exercise and stroke), estradiol (17β-estradiol and stroke), and exercise+estradiol (exercise and 17β-estradiol and stroke). Exercise preconditioning was performed on a treadmill 5 days/week, 40 min/day, at a speed of 18 m/min for 4 weeks. 17β-estradiol was gavaged (40 μg/kg per day) for 4 weeks. Stroke was induced by permanent middle cerebral artery occlusion (pMCAO), and neurological deficits were evaluated 1, 2, and 7 days after stroke. Then, the serum concentrations of matrix metalloproteinase-9 (MMP-9) and interleukin-10 (IL-10) and infarct volumes were assessed. Exercise preconditioning and 17β-estradiol induced a better outcome compared with the control ischemic mice, which was manifested by decrease in MMP-9, increase in IL-10, diminished infarct volume, and improved neurological deficits. Concomitant administration of 17β-estradiol and exercise also significantly improved these parameters. Exercise preconditioning or administration of 17β-estradiol alone or in combination before pMCAO induced significant neuroprotection in OVX mice.

Neuroprotective effects of estrogen in CNS injuries: insights from animal models

Among the estrogens that are biosynthesized in the human body, 17β-estradiol (estradiol or E2) is the most common and the best estrogen for neuroprotection in animal models of the central nervous system (CNS) injuries such as spinal cord injury (SCI), traumatic brain injury (TBI), and ischemic brain injury (IBI). These CNS injuries are not only serious health problems, but also enormous economic burden on the patients, their families, and the society at large. Studies from animal models of these CNS injuries provide insights into the multiple neuroprotective mechanisms of E2 and also suggest the possibility of translating the therapeutic efficacy of E2 in the treatment SCI, TBI, and IBI in humans in the near future. The pathophysiology of these injuries includes loss of motor function in the limbs, arms and their extremities, cognitive deficit, and many other serious consequences including life-threatening paralysis, infection, and even death. The potential application of E2 therapy to treat the CNS injuries may become a trend as the results are showing significant therapeutic benefits of E2 for neuroprotection when administered into the animal models of SCI, TBI, and IBI. This article describes the plausible mechanisms how E2 works with or without the involvement of estrogen receptors and provides an overview of the known neuroprotective effects of E2 in these three CNS injuries in different animal models. Because activation of estrogen receptors has profound implications in maintaining and also affecting normal physiology, there are notable impediments in translating E2 therapy to the clinics for neuroprotection in CNS injuries in humans. While E2 may not yet be the sole molecule for the treatment of CNS injuries due to the controversies surrounding it, the neuroprotective effects of its metabolite and derivative or combination of E2 with another therapeutic agent are showing significant impacts in animal models that can potentially shape the new treatment strategies for these CNS injuries in humans.

Epigallocatechin Gallate Extends Therapeutic Window of Recombinant Tissue Plasminogen Activator Treatment for Brain Ischemic Stroke: A Randomized Double-Blind and Placebo-Controlled Trial

OBJECTIVES

Recombinant tissue plasminogen activator (rt-PA) is a safe and effective treatment for acute brain ischemia stroke, albeit with a narrow therapeutic window. We aimed to assess the effect of epigallocatechin gallate (EGCG) in extending the rt-PA treatment window in this clinical trial among stroke patients.

METHODS

Patients were randomly assigned according to their onset-to-treatment time (OTT) and were then treated with rt-PA simultaneously with EGCG or placebo. Treatment outcome was assessed by the National Institutes of Health stroke scale (NIHSS) and plasma levels of matrix metalloproteinases (MMP)-2 and 9.

RESULTS

Administration of EGCG significantly improved treatment outcomes of patients in the delayed OTT strata, as evidenced by improved NIHSS scores. This improved treatment outcome was likely attributed to reduction in plasma levels of both MMP-2 and 9, as indicated by strong linear correlations between both MMPs and NIHSS scores in all patients.

CONCLUSIONS

Epigallocatechin gallate could potentially be used as a supplement of traditional rt-PA treatment among stroke patients, particularly those with delayed OTT, to extend the otherwise narrow therapeutic window and improve the outcome in late stroke treatment.

Increased Plasma Matrix Metalloproteinase-9 Levels Contribute to Intracerebral Hemorrhage during Thrombolysis after Concomitant Stroke and Influenza Infection

BACKGROUND

Thrombolysis is the only approved therapy for acute stroke. However, life-threatening complications such as intracerebral hemorrhage (ICH) can develop after intravenous administration of tissue plasminogen activator (tPA). Both infection and thrombolysis during cerebral ischemia disrupt the blood-brain barrier (BBB). tPA can induce matrix metalloproteinase-9 (MMP-9), which is known to be involved in BBB disruption. However, it has still not been investigated whether preexisting influenza virus infection during thrombolysis after acute stroke affects systemic levels of MMP-9 and its inhibitor TIMP-1 and whether increased systemic MMP-9 levels affect ICH. This study aimed to investigate the influence of influenza virus infection on plasma levels of MMP-9 and TIMP-1 after thrombolysis in acute stroke, and to determine whether the infection correlates with intracerebral bleeding.

METHODS

C57BL/6 mice were infected by administering 1 × 105 plaque-forming units of human influenza (H1N1) virus intranasally. After 3 days of infection the middle cerebral artery was occluded for 45 min and then reperfused. Intravenous tPA (10 mg/kg) treatment was started 10 min after stroke onset. Twenty-four hours after stroke onset, mice were deeply anesthetized with ketamine, venous blood was drawn from the caval vein and centrifuged at 2,000 rpm, and the supernatant was collected and frozen at -80°C. Plasma levels of MMP-9 and TIMP-1 were quantified by using ELISA.

RESULTS

After stroke, plasma MMP-9 was significantly increased in mice with a concomitant influenza infection that were treated with tPA (9.99 ± 0.62 ng/ml, n = 7) as compared to noninfected control mice that were treated with tPA (4.74 ± 0.48 ng/ml, n = 8). Moreover, plasma levels of TIMP-1, an inhibitor of MMP-9, were also significantly increased in mice treated with tPA after concomitant infection and stroke (42.17 ± 7.02 ng/ml, n = 7) as compared to noninfected control mice that were treated with tPA after stroke (20.22 ± 2.12 ng/ml, n = 8). MMP-9 values significantly correlated with intracerebral hemoglobin levels in animals treated with tPA after stroke (p = 0.028, r = 0.76, n = 8) and after concomitant stroke and infection (p = 0.039, r = 0.78, n = 7).

CONCLUSION

Preexisting influenza A virus infection led to increased plasma MMP-9 and TIMP-1 levels in mice undergoing thrombolysis after induced stroke. MMP-9 levels closely correlated with intracerebral bleeding after thrombolysis during concomitant infection and stroke. Thus, our data indicate that thrombolysis may be dangerous during influenza infection. MMP-9 inhibitors might be considered to reduce the side effects of thrombolysis during concomitant infection and stroke.

Resveratrol improves delayed r-tPA treatment outcome by reducing MMPs

OBJECTIVES

Although recombinant tissue plasminogen activator (r-tPA) is currently the most effective treatment for brain ischemic stroke, the 3-h narrow therapeutic windows severely limits its clinical efficacy. We aim to investigate the effect of resveratrol on improving treatment outcomes of delayed r-tPA administration.

MATERIALS & METHODS

Patients were randomly divided according to their onset-to-treatment time (OTT), as early OTT or delayed OTT. Then, they were either treated with r-tPA + placebo or with r-tPA + resveratrol. Twenty-four hours after the treatment, outcomes were assessed with NIH stroke scale (NIHSS), and plasma levels of MMP-2 and MMP-9 were also examined with ELISA.

RESULTS

In patients receiving delayed r-tPA treatment, co-administration of resveratrol significantly improves their treatment outcomes compared with those receiving placebo, as indicated by improved NIHSS scores. This improved outcome was be caused by resveratrol-induced reduction in plasma levels of both matrix metalloproteinase (MMP)-2 and MMP-9, as a positive correlation was observed between reductions in both MMPs and patient NIHSS scores.

CONCLUSIONS

Resveratrol could be potentially administered as an adjuvant with r-tPA treatment, which extends the clinical therapeutic window of r-tPA, therefore improving the outcome of patients receiving late stroke treatment.

Combination therapies for neurobehavioral and cognitive recovery after experimental traumatic brain injury: Is more better?

Traumatic brain injury (TBI) is a significant health care crisis that affects two million individuals in the United Sates alone and over ten million worldwide each year. While numerous monotherapies have been evaluated and shown to be beneficial at the bench, similar results have not translated to the clinic. One reason for the lack of successful translation may be due to the fact that TBI is a heterogeneous disease that affects multiple mechanisms, thus requiring a therapeutic approach that can act on complementary, rather than single, targets. Hence, the use of combination therapies (i.e., polytherapy) has emerged as a viable approach. Stringent criteria, such as verification of each individual treatment plus the combination, a focus on behavioral outcome, and post-injury vs. pre-injury treatments, were employed to determine which studies were appropriate for review. The selection process resulted in 37 papers that fit the specifications. The review, which is the first to comprehensively assess the effects of combination therapies on behavioral outcomes after TBI, encompasses five broad categories (inflammation, oxidative stress, neurotransmitter dysregulation, neurotrophins, and stem cells, with and without rehabilitative therapies). Overall, the findings suggest that combination therapies can be more beneficial than monotherapies as indicated by 46% of the studies exhibiting an additive or synergistic positive effect versus on 19% reporting a negative interaction. These encouraging findings serve as an impetus for continued combination studies after TBI and ultimately for the development of successful clinically relevant therapies.

Therapeutic benefits of combined treatment with tissue plasminogen activator and 2-(4-methoxyphenyl)ethyl-2-acetamido-2-deoxy-β-d-pyranoside in an animal model of ischemic stroke

Tissue plasminogen activator (tPA) is the only approved therapy for acute ischemic stroke, but tPA therapy is limited by a short therapeutic window and some adverse side effects. 2-(4-Methoxyphenyl)ethyl-2-acetamido-2-deoxy-β-d-pyranoside, a salidroside analog (code-named SalA-4g), has shown potent neuroprotective effects. In this study, a rat model of embolic middle cerebral artery occlusion (MCAO) was used to mimic ischemic stroke. The embolic MCAO rats were intravenously (iv) injected with tPA alone, SalA-4g alone, or a combination of tPA and SalA-4g. Compared to treatment with tPA alone at 4h post MCAO, combined treatment with tPA at 4h post MCAO and SalA-4g starting at 4h post MCAO and continuing for 3days at an interval of 24h significantly reduced neurological deficits and infarct volume, and significantly inhibited the intracerebral bleeding, edema formation, neuronal loss, and cellular apoptosis in the ischemic brain. Our results suggested that additive neuroprotective actions of SalA-4g contributed to widening the therapeutic window of tPA therapy and ameliorating its side effects in treating MCAO rats. The therapeutic benefits of combined treatment with tPA and SalA-4g for ischemic stroke might be associated with its effects on cerebral glucose metabolism.

High-dose estrogen treatment at reperfusion reduces lesion volume and accelerates recovery of sensorimotor function after experimental ischemic stroke

Estrogens have previously been shown to protect the brain against acute ischemic insults, by potentially augmenting cerebrovascular function after ischemic stroke. The current study hypothesized that treatment with sustained release of high-dose 17β-estradiol (E2) at the time of reperfusion from middle cerebral artery occlusion (MCAO) in rats would attenuate reperfusion injury, augment post-stroke angiogenesis and cerebral blood flow, and attenuate lesion volume. Female Wistar rats underwent ovariectomy, followed two weeks later by transient, two-hour right MCAO (tMCAO) and treatment with E2 (n=13) or placebo (P; n=12) pellets starting at reperfusion. E2 treatment resulted in significantly smaller total lesion volume, smaller lesions within striatal and cortical brain regions, and less atrophy of the ipsilateral hemisphere after six weeks of recovery. E2-treated animals exhibited accelerated recovery of contralateral forelimb sensorimotor function in the cylinder test. Magnetic resonance imaging (MRI) showed that E2 treatment reduced the formation of lesion cysts, decreased lesion volume, and increased lesional cerebral blood flow (CBF). K(trans), a measure of vascular permeability, was increased in the lesions. This finding, which represents lesion neovascularization, was not altered by E2 treatment. Ischemic stroke-related angiogenesis and vessel formation was confirmed with immunolabeling of brain tissue and was not altered with E2 treatment. In summary, E2 treatment administered immediately following reperfusion significantly reduced lesion size, cyst formation, and brain atrophy while improving lesional CBF and accelerating recovery of functional deficits in a rat model of ischemic stroke.

Ginsenoside Represses Symptomatic Intracerebral Hemorrhage after Recombinant Tissue Plasminogen Activator Therapy by Promoting Transforming Growth Factor-β1

BACKGROUND

Currently, the most effective treatment for brain ischemic stroke is recombinant tissue plasminogen activator (rt-PA); however, increased incidence of symptomatic intracerebral hemorrhage severely reduced its favorable treatment outcome.

METHODS

We aimed to investigate the effect of ginsenoside (Gs) on symptomatic intracerebral hemorrhage after rt-PA treatment. Stroke patients were randomly divided into 2 treatment groups, one receiving rt-PA + placebo (Pc) and the other rt-PA + Gs. Twenty-four hours after the treatment, outcomes were assessed with transcranial Doppler (TCD) ultrasonography and National Institutes of Health Stroke Scale (NIHSS), and plasma levels of transforming growth factor-β1 (TGF-β1), matrix metalloproteinase (MMP)-2, and MMP-9 were also measured. After initial cotreatment, the patients were continuously administered with either Pc or Gs, and the treatment outcomes at 7 days were assessed with TCD, NIHSS, modified Rankin scale (MRS), and Glasgow outcome scale (GOS).

RESULTS

Cotreatment of rt-PA with Gs significantly improved outcomes in patients compared to the Pc group, as indicated by improved TCD and NIHSS scores and reduced incidence of symptomatic intracerebral hemorrhage, which could be attributed to a Gs-induced increase in TGF-β1 and a decrease in both MMP-2 and MMP-9 serum levels. Seven days of Gs treatment also significantly improved outcomes in patients compared to the Pc group, assessed by TCD, NIHSS, MRS, and GOS.

CONCLUSION

Our study supports the clinical use of Gs as a potential supplement with rt-PA treatment, which reduces symptomatic intracerebral hemorrhage, therefore improving the treatment outcome of stroke patients.

Demethylation of Circulating Estrogen Receptor Alpha Gene in Cerebral Ischemic Stroke

Background

Estrogen is involved in neuron plasticity and can promote neuronal survival in stroke. Its actions are mostly exerted via estrogen receptor alpha (ERα). Previous animal studies have shown that ERα is upregulated by DNA demethylation following ischemic injury. This study investigated the methylation levels in the ERα promoter in the peripheral blood of ischemic stroke patients.

Methods

The study included 201 ischemic stroke patients, and 217 age- and sex-comparable healthy controls. The quantitative methylation level in the 14 CpG sites of the ERα promoter was measured by pyrosequencing in each participant. Multivariate regression model was used to adjust for stroke traditional risk factors. Stroke subtypes and sex-specific analysis were also conducted.

Results

The results demonstrated that the stroke cases had a lower ERα methylation level than controls in all 14 CpG sites, and site13 and site14 had significant adjusted p-values of 0.035 and 0.026, respectively. Stroke subtypes analysis showed that large-artery atherosclerosis and cardio-embolic subtypes had significantly lower methylation levels than the healthy controls at CpG site5, site9, site12, site13 and site14 with adjusted p = 0.039, 0.009, 0.025, 0.046 and 0.027 respectively. However, the methylation level for the patients with small vessel subtype was not significant. We combined the methylation data from the above five sites for further sex-specific analysis. The results showed that the significant association only existed in women (adjusted p = 0.011), but not in men (adjusted p = 0.300).

Conclusions

Female stroke cases have lower ERα methylation levels than those in the controls, especially in large-artery and cardio-embolic stroke subtypes. The study implies that women suffering from ischemic stroke of specific subtype may undergo different protective mechanisms to reduce the brain injury.

17β-estradiol inhibits MMP-9 and SUR1/TrpM4 expression and activation and thereby attenuates BSCB disruption/hemorrhage after spinal cord injury in male rats

Blood-spinal cord barrier (BSCB) disruption and progressive hemorrhage after spinal cord injury (SCI) lead to secondary injury and the subsequent apoptosis and/or necrosis of neuron and glia, causing permanent neurological deficits. In this study, we examined the effect of 17β-estradiol (E2) on BSCB breakdown and hemorrhage as well as subsequent inflammation after SCI. After a moderate contusion injury at the 9th thoracic segment of spinal cord, E2 (300 μg/kg) was administered by iv injection immediately after SCI, and the same dose of E2 was then administered 6 and 24 hours after injury. Our data show that E2 attenuated BSCB permeability and hemorrhage and reduced the infiltration of neutrophils and macorphages after SCI. Consistent with this finding, the expression of inflammatory mediators was significantly reduced by E2. Furthermore, E2 treatment significantly inhibited the expression of sulfonylurea receptor 1 and transient receptor potential melastatin 4 after injury, which are known to mediate hemorrhage at an early stage after SCI. Moreover, the expression and activation of matrix metalloprotease-9 after injury, which is known to disrupt BSCB, and the degradation of tight junction proteins, such as zona occludens-1 and occludin, were significantly inhibited by E2 treatment. Furthermore, the protective effects of E2 on BSCB disruption and functional improvement were abolished by an estrogen receptor antagonist, ICI 182780 (3 mg/kg). Thus, our study provides evidence that the neuroprotective effect of E2 after SCI is, in part, mediated by inhibiting BSCB disruption and hemorrhage through the down-regulation of sulfonylurea receptor 1/transient receptor potential melastatin 4 and matrix metalloprotease-9, which is dependent on estrogen receptor.

Salutary Effects of Estrogen Sulfate for Traumatic Brain Injury

Estrogen plays an important role as a neuroprotector in the central nervous system (CNS), directly interacting with neurons and regulating physiological properties of non-neuronal cells. Here we evaluated estrogen sulfate (E2-SO4) for traumatic brain injury (TBI) using a Sprague-Dawley rat model. TBI was induced via lateral fluid percussion (LFP) at 24 h after craniectomy. E2-SO4 (1 mg/kg BW in 1 mL/kg BW) or saline (served as control) was intravenously administered at 1 h after TBI (n=5/group). Intracranial pressure (ICP), cerebral perfusion pressure (CPP), and partial brain oxygen pressure (pbtO2) were measured for 2 h (from 23 to 25 h after E2-SO4 injection). Brain edema and diffuse axonal injury (DAI) were assessed by diffusion tensor imaging (DTI), and cerebral glycolysis was measured by (18)F-labeled fluorodeoxyglucose (FDG) positron emission tomography (PET) imaging, at 1 and 7 days after E2-SO4 injection. E2-SO4 significantly decreased ICP, while increasing CPP and pbtO2 (p<0.05) as compared with vehicle-treated TBI rats. The edema size in the brains of the E2-SO4 treated group was also significantly smaller than that of vehicle-treated group at 1 day after E2-SO4 injection (p=0.04), and cerebral glycolysis of injured region was also increased significantly during the same time period (p=0.04). However, E2-SO4 treatment did not affect DAI (p>0.05). These findings demonstrated the potential benefits of E2-SO4 in TBI.

TGF-β1 prevents blood-brain barrier damage and hemorrhagic transformation after thrombolysis in rats

Transforming growth factor-beta1 (TGF-β1) is well known to promote extracellular matrix accumulation. Recent studies demonstrated that TGF-β1 protects against blood-brain barrier (BBB) disruption in the condition of inflammatory pain and stroke. In the present study, we investigated whether TGF-β1 can maintain BBB integrity and prevent hemorrhagic transformation (HT) after recombinant tissue plasminogen activator (rt-PA) treatment in a rat model of thromboembolic middle cerebral artery occlusion (MCAO). Three hours after MCAO, rats were given saline, rt-PA alone or rt-PA combined with TGF-β1 intravenously. Animals were sacrificed 24h after surgery. HT was calculated as hemorrhagic score. Evans blue dye extravasation was measured for BBB disruption. Basement membrane damage was observed by electron microscopy and quantified by collagen IV and laminin immunostaining. Gelatin zymography was used to measure the activities of matrix metalloproteinase (MMP)-2 and MMP-9. Western blot was performed for the expressions of MMP-2, MMP-9 and plasminogen activator inhibitor type-1 (PAI-1). Rats treated with rt-PA showed elevations in basement membrane damage, BBB disruption and HT. These phenomena were reduced in rats treated by TGF-β1. We also showed that TGF-β1 inhibited rt-PA mediated induction of MMP-2 and MMP-9. Meanwhile, TGF-β1 upregulated PAI-1 expression which was reduced by rt-PA. Taken together, these results suggest that TGF-β1 can reduce rt-PA induced basement membrane degradation, BBB disruption and HT. One possible mechanism is associated with the elevation of PAI-1. Suppression of MMP-2 and MMP-9 elevated by rt-PA may be another mechanism contributing to the protective effects of TGF-β1.

Neuroprotective effect of masitinib in rats with postischemic stroke

This study evaluated the therapeutic potential of masitinib, an oral tyrosine kinase inhibitor with activity against c-Kit and platelet-derived growth factor receptors (PDGFR), to reduce ischemic brain area and neurological deficit. Using a well-established filament model of ischemic stroke in rats, the responses to oral treatment with masitinib alone or in combination with recombinant tissue plasminogen activator (rt-PA) were compared to those after rt-PA (10 mg/kg intravenously (i.v.)) monotherapy. In both cases, two doses of masitinib were used--25 or 100 mg/kg, twice per day. Ischemic brain area and the neurological deficit were assessed using the triphenyltetrazolium chloride (TTC) method and behavioral neurological tests, respectively. Masitinib, as a single agent, reduced significantly the infarct size, as compared with the stroke control group. Brain ischemic area decreased from 9.14 to 4.36 % (25 mg/kg) or 2.60 % (100 mg/kg). Moreover, a combined treatment of masitinib with rt-PA produced a stronger effect than the one observed after each of the compound alone. The size of the brain ischemic area (rt-PA 1.67 %) was further reduced to 0.83 or 0.7 % at masitinib doses of 25 and 100 mg/kg, respectively. Masitinib reduced significantly brain ischemia induced by experimental stroke and potentiated the therapeutic effect of rt-PA.

Effects of edaravone, a free radical scavenger, on circulating levels of MMP-9 and hemorrhagic transformation in patients with intravenous thrombolysis using low-dose alteplase

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) plays a key role for the blood-brain barrier disruption and intravenous tissue plasminogen activator (iv-tPA) therapy increases MMP-9. Edaravone, a free radical scavenger, reduces MMP-9-related blood-brain barrier disruption. We aimed to investigate whether edaravone would suppress the MMP-9 increase after iv-tPA using low-dose alteplase (0.6 mg/kg).

SUBJECTS

Patients hospitalized within 12 hours after ischemic stroke onset between April 2008 and June 2013 were retrospectively examined. Patients with slight deficits (National Institutes of Health Stroke Scale score ≤ 4), stroke caused by arterial dissection, severe inflammatory disease or autoimmune disease, or regular use of steroid were excluded. Serum concentrations of high-sensitivity C-reactive protein, interleukin-6, MMP-2, and MMP-9 were serially measured at admission, after 24 hours, day 7, and day 14. General linear models were used to compare changes in concentrations of these biomarkers over time.

RESULTS

A total of 63 patients (38 men, aged 74.48 ± 13.8 years) were studied. Patients were divided into 2 groups according to the iv-tPA therapy, that is, tPA group (n = 32) and non-tPA group (n = 31). Edaravone was administered routinely except for contraindication (90.6% in the tPA group and 87.1% in the non-tPA group). Significant interaction of group × time factor was observed only in MMP-9 concentrations by repeated-measure analysis of variance (P = .004). Association between iv-tPA therapy and subsequent hemorrhagic transformation was highly significant, but MMP-9 concentrations at any point did not predictive of subsequent hemorrhagic transformation (area under the receiver operating characteristic curve, .681).

CONCLUSIONS

Low-dose iv-tPA increases MMP-9 concentration even in combination with Edaravone. The effect of higher dosage of Edaravone on circulating MMP-9 concentration and subsequent hemorrhagic transformation should be investigated.

Remote ischemic perconditioning is effective after embolic stroke in ovariectomized female mice

Remote ischemic conditioning is neuroprotective in young male rodents after experimental stroke. However, it has never been tested in females whom remain at higher risk of stroke injury after menopause. We tested remote ischemic perconditioning therapy (RIPerC) at 2 h after embolic stroke in ovariectomized (OVX) female mice with and without intravenous tissue plasminogen activator (IV-tPA) treatment. We assessed cerebral blood flow (CBF), neurobehavioral outcomes, infarction, hemorrhage, edema, and survival. RIPerC therapy with and without IV-tPA improved the CBF and neurobehavioral outcomes and reduced the infarction, hemorrhage, and edema significantly. Late IV-tPA alone at 4 h post-stroke neither improved the neurobehavior nor reduced the infarction but aggravated hemorrhage and mortality in OVX mice. RIPerC therapy prevented the increased mortality during late IV-tPA. Our study demonstrates for the first time that RIPerC therapy is effective in OVX females.

Impact of methodology on estrogens' effects on cerebral ischemia in rats: an updated meta-analysis

Background

Although most animal stroke studies have demonstrated potent neuroprotective effects of estrogens, there are a number of articles reporting the opposite. In 2009, we made the case that this dichotomy was related to administered estrogen dose. Several other suggestions for the discordant results have also been propagated, including the age of the experimental animals and the length of hypoestrogenicity prior to estrogen administration. These two suggestions have gained much popularity, probably because of their kinship with the window of opportunity hypothesis, which is commonly used to explain the analogous dichotomy among human studies. We were therefore encouraged to perform an updated meta-analysis, and to improve it by including all relevant variables in a large multiple regression model, where the impact of confounders could be controlled for.

Results

The multiple regression model revealed an indisputable impact of estrogen administration mode on the effects of estrogens in ischemic stroke. Subcutaneous slow-release pellets differed from the injection and silastic capsule treatments in terms of impact of estrogens on ischemic stroke, showing that the first mentioned were more prone to render estrogens damaging. Neither the use of elderly animals nor the adoption of longer wash-out periods influenced estrogens’ effects on experimental ischemic stroke in rats.

Conclusions

We conclude that the discordant results regarding estrogens’ effects in rat models of ischemic stroke are a consequence of differences in estrogen administration modes. These results are not only of importance for the ongoing debate regarding menopausal hormone therapy, but also have an important bearing on experimental stroke methodology and the apparent translational roadblock for suggested stroke interventions.

Coadministration of FTY720 and rt-PA in an experimental model of large hemispheric stroke-no influence on functional outcome and blood-brain barrier disruption

BACKGROUND

Systemic thrombolysis with recombinant tissue plasminogen activator (rt-PA) is the standard of acute stroke care. Its potential to increase the risk of secondary intracerebral hemorrhage, especially if administered late, has been ascribed to its proteolytic activity that has detrimental effects on blood-brain barrier (BBB) integrity after stroke. FTY720 has been shown to protect endothelial barriers in several disease models such as endotoxin-induced pulmonary edema and therefore is a promising candidate to counteract the deleterious effects of rt-PA. Besides that, every putative neuroprotectant that will be eventually forwarded into clinical trials should be tested in conjunction with rt-PA.

METHODS

We subjected C57Bl/6 mice to 3 h filament-induced tMCAO and postoperatively randomized them into four groups (n = 18/group) who received the following treatments directly prior to reperfusion: 1) vehicle-treatment, 2) FTY720 1 mg/kg i.p., 3) rt-PA 10 mg/kg i.v. or 4) FTY720 and rt-PA as a combination therapy. We measured functional neurological outcome, BBB disruption by quantification of EB extravasation and MMP-9 activity by gelatin zymography.

RESULTS

We observed a noticeable increase in mortality in the rt-PA/FTY720 cotreatment group (61%) as compared to the vehicle (33%), the FTY720 (39%) and the rt-PA group (44%). Overall, functional neurological outcome did not differ significantly between groups and FTY720 had no effect on rt-PA- and stroke-induced BBB disruption and MMP-9 activation.

CONCLUSIONS

Our data show that FTY720 does not improve functional outcome and BBB integrity in large hemispheric infarctions, neither alone nor in conjunction with rt-PA. These findings stand in contrast to a recently published study that showed beneficial effects of FTY720 in combination with thrombolysis in a thrombotic model of MCAO leading to circumscript cortical infarctions. They might therefore represent a caveat that the coadministration of these two drugs might lead to excess mortality in the setting of a severe stroke.

Transient focal cerebral ischemia induces long-term cognitive function deficit in an experimental ischemic stroke model

Vascular dementia ranks as the second leading cause of dementia in the United States. However, its underlying pathophysiological mechanism is not fully understood and no effective treatment is available. The purpose of the current study was to evaluate long-term cognitive deficits induced by transient middle cerebral artery occlusion (tMCAO) in rats and to investigate the underlying mechanism. Sprague-Dawley rats were subjected to tMCAO or sham surgery. Behavior tests for locomotor activity and cognitive function were conducted at 7 or 30days after stroke. Hippocampal long term potentiation (LTP) and involvement of GABAergic neurotransmission were evaluated at 30days after sham surgery or stroke. Immunohistochemistry and Western blot analyses were conducted to determine the effect of tMCAO on cell signaling in the hippocampus. Transient MCAO induced a progressive deficiency in spatial performance. At 30days after stroke, no neuron loss or synaptic marker change in the hippocampus were observed. LTP in both hippocampi was reduced at 30days after stroke. This LTP impairment was prevented by blocking GABAA receptors. In addition, ERK activity was significantly reduced in both hippocampi. In summary, we identified a progressive decline in spatial learning and memory after ischemic stroke that correlates with suppression of hippocampal LTP, elevation of GABAergic neurotransmission, and inhibition of ERK activation. Our results indicate that the attenuation of GABAergic activity or enhancement of ERK/MAPK activation in the hippocampus might be potential therapeutic approaches to prevent or attenuate cognitive impairment after ischemic stroke.

Window of opportunity: estrogen as a treatment for ischemic stroke

The neuroprotection research in the last 2 decades has witnessed a growing interest in the functions of estrogens as neuroprotectants against neurodegenerative diseases including stroke. The neuroprotective action of estrogens has been well demonstrated in both in vitro and in vivo models of ischemic stroke. However, the major conducted clinical trials so far have raised concern for the protective effect of estrogen replacement therapy in postmenopausal women. The discrepancy could be partly due to the mistranslation between the experimental stroke research and clinical trials. While predominant experimental studies tested the protective action of estrogens on ischemic stroke using acute treatment paradigm, the clinical trials have mainly focused on the effect of estrogen replacement therapy on the primary and secondary stroke prevention which has not been adequately addressed in the experimental stroke study. Although the major conducted clinical trials have indicated that estrogen replacement therapy has an adverse effect and raise concern for long term estrogen replacement therapy for stroke prevention, these are not appropriate for assessing the potential effects of acute estrogen treatment on stroke protection. The well established action of estrogen in the neurovascular unit and its potential interaction with recombinant tissue Plasminogen Activator (rtPA) makes it a candidate for the combined therapy with rtPA for the acute treatment of ischemic stroke. On the other hand, the "critical period" and newly emerged "biomarkers window" hypotheses have indicated that many clinical relevant factors have been underestimated in the experimental ischemic stroke research. The development and application of ischemic stroke models that replicate the clinical condition is essential for further evaluation of acute estrogen treatment on ischemic stroke which might provide critical information for future clinical trials. This article is part of a Special Issue entitled Hormone Therapy.

Vascular protection to increase the safety of tissue plasminogen activator for stroke

Thrombolytic therapy with tissue plasminogen activator (tPA) remains the most effective treatment for acute ischemic stroke, but can cause vascular damage leading to edema formation and hemorrhagic transformation (HT). In this review, we discuss how tPA contributes to the pathogenesis of vascular damage and highlight evidence to support combination therapy of tPA with pharmacological agents that are vascular protective. There is an unmet need to develop therapeutic interventions which target the underlying mechanisms of vascular damage after acute ischemic stroke in order to prevent HT and improve the safety and impact of tPA.

Does inhibiting Sur1 complement rt-PA in cerebral ischemia?

Hemorrhagic transformation (HT) associated with recombinant tissue plasminogen activator (rt-PA) complicates and limits its use in stroke. Here, we provide a focused review on the involvement of matrix metalloproteinase 9 (MMP-9) in rt-PA-associated HT in cerebral ischemia, and we review emerging evidence that the selective inhibitor of the sulfonylurea receptor 1 (Sur1), glibenclamide (U.S. adopted name, glyburide), may provide protection against rt-PA-associated HT in cerebral ischemia. Glyburide inhibits activation of MMP-9, ameliorates edema formation, swelling, and symptomatic hemorrhagic transformation, and improves preclinical outcomes in several clinically relevant models of stroke, both without and with rt-PA treatment. A retrospective clinical study comparing outcomes in diabetic patients with stroke treated with rt-PA showed that those who were previously on and were maintained on a sulfonylurea fared significantly better than those whose diabetes was managed without sulfonylureas. Inhibition of Sur1 with injectable glyburide holds promise for ameliorating rt-PA-associated HT in stroke.

Evaluation of combination therapy in animal models of cerebral ischemia

Combination therapy has been identified as a promising strategy to improve stroke management. We conducted a systematic review and meta-analysis of evidence from animal models of ischemic stroke to determine whether combining treatments improved efficacy. Multiple databases were searched and data were extracted from focal ischemia experiments comparing control groups, single treatments, and combination treatments. Of 11,430 papers identified, 142 met the inclusion criteria; these tested 126 treatments in 373 experiments using 8,037 animals (I(2)=85 to 96%). Taken together, single treatments reduced infarct size by 20% and improved neurological score by 12% compared with control; a second therapy improved efficacy by an additional 18% and 25%, respectively. Publication bias may affect combination efficacy for infarct size but not neurological score. Combining thrombolysis with other therapies may extend the time window from 4.4 to 8 hours in animal models, although testing beyond 6 hours is required to confirm this. Benefits of additional therapy decreased as the efficacy of the primary treatment increased, with combination efficacy reaching a ceiling at 60% to 80% protection. Combining treatments may bring benefits and extend the time window for treatment. More evidence is needed due to potential publication bias and heterogeneity.

A dominant negative ERβ splice variant determines the effectiveness of early or late estrogen therapy after ovariectomy in rats

The molecular mechanisms for the discrepancy in outcome of initiating estrogen therapy (ET) around peri-menopause or several years after menopause in women are unknown. We hypothesize that the level of expression of a dominant negative estrogen receptor (ER) β variant, ERβ2, may be a key factor determining the effectiveness of ET in post-menopausal women. We tested this hypothesis in ovariectomized nine month-old (an age when irregular estrous cycles occur) female Sprague Dawley rats. Estradiol treatment was initiated either 6 days (Early ET, analogous to 4 months post-menopause in humans), or 180 days (Late ET, analogous to 11 years post-menopause in humans) after ovariectomy. Although ERβ2 expression increased in all OVX rats, neurogenic and neuroprotective responses to estradiol differed in Early and Late ET. Early ET reduced ERβ2 expression in both hippocampus and white blood cells, increased the hippocampal cell proliferation as assessed by Ki-67 expression, and improved mobility in the forced swim test. Late ET resulted in either no or modest effects on these parameters. There was a close correlation between the degree of ERβ2 expression and the preservation of neural effects by ET after OVX in rats, supporting the hypothesis that persistent elevated levels of ERβ2 are a molecular basis for the diminished effectiveness of ET in late post-menopausal women. The correlation between the expression of ERβ2 in circulating white blood cells and brain cells suggests that ERβ2 expression in peripheral blood cells may be an easily accessible marker to predict the effective window for ET in the brain.

Impact of tissue plasminogen activator on the neurovascular unit: from clinical data to experimental evidence

About 15 million strokes occur each year worldwide. As the number one cause of morbidity and acquired disability, stroke is a major drain on public health-care funding, due to long hospital stays followed by ongoing support in the community or nursing-home care. Although during the last 10 years we have witnessed a remarkable progress in the understanding of the pathophysiology of ischemic stroke, reperfusion induced by recombinant tissue-type plasminogen activator (tPA-Actilyse) remains the only approved acute treatment by the health authorities. The objective of the present review is to provide an overview of our present knowledge about the impact of tPA on the neurovascular unit during acute ischemic stroke.

Potential age-dependent effects of estrogen on neural injury

In 2000, approximately 10 million women were receiving hormone replacement therapy (HRT) for alleviation of menopausal symptoms. A number of prior animal studies suggested that HRT may be neuroprotective and cardioprotective. Then, in 2003, reports from the Women's Health Initiative (WHI) indicated that long-term estrogen/progestin supplementation led to increased incidence of stroke. A second branch of the WHI in women with prior hysterectomy found an even stronger correlation between estrogen supplementation alone and stroke incidence. Follow-up analyses of the data, as well as data from other smaller clinical trials, have also demonstrated increased stroke severity in women receiving HRT or estrogen alone. This review examines the studies indicating that estrogen is neuroprotectant in animal models and explores potential reasons why this may not be true in postmenopausal women. Specifically, age-related differences in estrogen receptors and estrogenic actions in the brain are discussed, with the conclusion that animal models of disease must closely mimic human disease to produce clinically relevant results.

17β-estradiol attenuates breakdown of blood-brain barrier and hemorrhagic transformation induced by tissue plasminogen activator in cerebral ischemia

Tissue plasminogen activator (tPA) remains the only approved thrombolytic agent for the early treatment of ischemic stroke. However, treatment with tPA may lead to disruption of the blood-brain barrier and hemorrhagic transformation. 17β-estradiol (E2) has demonstrated efficacy in reduction of infarct volume in ischemic stroke models. The effects of acute administration of E2 on permeability of the blood-brain barrier and its ability to prevent hemorrhagic transformation in ischemic rats treated with tPA have not previously been studied. Here, we show that neurological deficits, brain water content, and Evan's blue extravasation were increased in ovariectomized female Wistar rats treated with tPA and attenuated in rats receiving E2+tPA. We also show that intracerebral hemoglobin and matrix metalloproteinase-9 activity were elevated with tPA treatment, and these increases were reduced by E2 treatment. Taken together, these data demonstrate that acute administration of E2 is capable of ameliorating some of the adverse effects of tPA administration, including the increase of matrix metalloproteinase-9 activity, blood-brain barrier permeability, and hemorrhagic transformation. These findings suggest a potential role for estrogen in thrombolytic treatment for ischemic stroke.

Gonadal steroids prevent cell damage and stimulate behavioral recovery after transient middle cerebral artery occlusion in male and female rats

17β-estradiol (E) and progesterone (P) are neuroprotective factors in the brain preventing neuronal death under different injury paradigms. Our previous work demonstrates that both steroids compensate neuronal damage and activate distinct neuroprotective strategies such as improving local energy metabolism and abating pro-inflammatory responses. The current study explored steroid hormone-mediated protection from brain damage and restoration of behavioral function after 1h transient middle cerebral artery occlusion (tMCAO). Male and ovariectomized female rats were studied 24h after stroke. Both steroid hormones reduced the cortical infarct area in males and females to a similar extent. A maximum effect of ~60-70% reduction of the infarct size was evident after P and a combined treatment with both hormones. No infarct protection was seen in the basal ganglia. Testing of motor and sensory behavioral revealed an equal high degree of functional recovery in all three hormone groups. Gene expression studies in the delineated penumbra revealed that estrogen receptor (ER) alpha and beta are locally up-regulated. tMCAO-mediated induction of the pro-inflammatory chemokines CCL2, CCL5 and interleukin 6 was attenuated by E and P, whereas the expression of vascular endothelial growth factor (VEGF) was fortified. Local expression of microglia/macrophage/lymphocyte markers, i.e. Iba1, CD68 and CD3, were significantly reduced in the penumbra after hormone treatment suggesting attenuation of microglia and lymphocyte attraction. These results demonstrate the neuroprotective potency of a combined treatment with E and P under ischemic conditions in both sexes and point at the regulation of chemokine-microglia/lymphocyte interactions as a supposable mechanism implicated in cell protection.

Regulation of matrix metalloproteinase 2 by oligomeric amyloid β protein

Matrix metalloproteinases (MMPs) are a group of proteinases that degrade components of the extracellular matrix (ECM). There is increasing evidence for a link between the activation of MMPs and Alzheimer's disease (AD) pathogenesis, in which both beneficial and detrimental actions of MMPs have been suggested. It has been demonstrated that MMPs could degrade amyloid β (Aβ) and play important roles in the extracellular Aβ catabolism and clearance. On the other hand, MMPs could contribute to AD pathogenesis by compromising the blood brain barrier and promoting neurodegeneration. In the present study, we observed that oligomeric Aβ regulates MMP2 expression in a paradoxical manner. In rat primary astrocyte cultures, oligomeric Aβ down-regulated MMP2 transcription and reduced its extracellular activity. However, in a widely used mouse model for AD, immunohistochemistry demonstrated an increase of MMP2 expression in astrocytes surrounding senile plaques in APP/PS1 transgenic mice brains. Using real-time PCR, we found that the MMP2 mRNA level was elevated in APP/PS1 transgenic mice brains. In addition, elevated mRNA levels of MMP stimulating cytokines such as IL-1β and TGFβ were found in the brains of APP/PS1 mice. Our study suggests a complex regulation of MMP2 expression by oligomeric Aβ in astrocytes. While oligomeric Aβ directly down-regulates MMP2 expression and activation in astrocytes, it induces production of proinflammatory cytokines which could serve as strong stimulators for MMP2. Therefore, the ultimate outcome of the oligomeric Aβ on MMP2 activation in astrocytes might be the combination of its direct inhibitory action on astrocyte MMP2 expression and the secondary action of inducing inflammatory cytokines.

Angiogenesis in old-aged subjects after ischemic stroke: a cautionary note for investigators

Angiogenesis represents a form of neovascularisation of exceptional importance in numerous pathological conditions including stroke. In this context it is directly related to neuroregeneration which is seen in close proximity. However, numerous experimental data have been drawn from studies that have ignored the age criterion. This is extremely important as angiogenesis is different in young versus old subjects. Extrapolating data obtained from studies performed in young subjects or "in vitro" to old-age patients could lead to inexact conclusions since the dynamics of angiogenesis is age-dependent.

The current review covers the key features of brain senescence including morphological and functional changes related to the brain parenchyma, its vascular network and blood flow which could possibly influence the process of angiogenesis. This is followed by a description of post-stroke angiogenesis and its relationship to neuroregeneration and its modulation by vascular endothelial growth factor (VEGF) and insulin-like growth factor 1 (IGF 1), the most important factors active in old brain after ischemic injury.