Early atorvastatin reduces hemorrhage after acute cerebral ischemia in diabetic rats

Effect of CYP2C19 genetic variants on bleeding and major adverse cardiovascular events in a cohort of Arab patients undergoing percutaneous coronary intervention and stent implantation

INTRODUCTION

One-third of patients have clopidogrel resistance that may lead to major adverse cardiac events (MACEs). By contrast, it was found that some clopidogrel-treated patients have hyperresponsive platelets that are associated with higher bleeding risk. Several studies have shown that polymorphisms in the gene encoding the CYP2C19 contribute to the variability in response to clopidogrel. Data on genetic and nongenetic factors affecting clopidogrel response in the Arab population are scarce. In this prospective cohort study, we sought to assess the association between the increased function allele (CYP2C19*17) and bleeding events, and validate the effect of the CYP2C19 genetic variants and nongenetic factors on the incidence of MACEs.

METHODS

Blood samples were collected from patients that were undergoing percutaneous coronary intervention and receiving clopidogrel at the Heart Hospital, a specialist tertiary hospital in Doha, Qatar. Patients were followed for 12 months. Genotyping was performed for CYP2C19*2, *3, and *17 using TaqMan assays.

RESULTS

In 254 patients, the minor allele frequencies were 0.13, 0.004, and 0.21 for *2, *3, and *17, respectively. Over a 12-month follow-up period, there were 21 bleeding events (8.5 events/100 patient-year). CYP2C19*17 carriers were found to be associated with increased risk of bleeding (OR, 21.6; 95% CI, 4.8-96.8; P < 0.0001). CYP2C19*2 or *3 carriers were found to be associated with increased risk of baseline and incident MACE combined (OR, 8.4; 95% CI, 3.2-23.9; P < 0.0001).

CONCLUSION

This study showed a significant association between CYP2C19*17 allele and the increased risk of bleeding, and CYP2C19*2 or *3 with MACE outcomes.

Drug Development for Central Nervous System Diseases Using In vitro Blood-brain Barrier Models and Drug Repositioning

An important goal of biomedical research is to translate basic research findings into practical clinical implementation. Despite the advances in the technology used in drug discovery, the development of drugs for central nervous system diseases remains challenging. The failure rate for new drugs targeting important central nervous system diseases is high compared to most other areas of drug discovery. The main reason for the failure is the poor penetration efficacy across the blood-brain barrier. The blood-brain barrier represents the bottleneck in central nervous system drug development and is the most important factor limiting the future growth of neurotherapeutics. Meanwhile, drug repositioning has been becoming increasingly popular and it seems a promising field in central nervous system drug development. In vitro blood-brain barrier models with high predictability are expected for drug development and drug repositioning. In this review, the recent progress of in vitro BBB models and the drug repositioning for central nervous system diseases will be discussed.

Comorbidity and age in the modelling of stroke: are we still failing to consider the characteristics of stroke patients?

Stroke is a significant cause of mortality and morbidity for which there are limited treatment options. Virtually all drug interventions that have been successful preclinically in experimental stroke have failed to translate to an effective treatment in the clinical setting. In this review, we examine one of the factors likely contributing to this lack of translation, the failure of preclinical studies to consider fully the advanced age and comorbidities (eg, hypertension or diabetes) present in most patients with stroke. Age and comorbidities affect the likelihood of suffering a stroke, disease progression and the response to treatment. Analysing data from preclinical systematic reviews of interventions for ischaemic stroke we show that only 11.4% of studies included an aged or comorbid model, with hypertension being the most frequent. The degree of protection (% reduction in infarct volume) varied depending on the comorbidity and the type of intervention. We consider reasons for the lack of attention to comorbid and aged animals in stroke research and discuss the value of testing a potential therapy in models representing a range of comorbidities that affect patients with stroke. These models can help establish any limits to a treatment's efficacy and inform the design of clinical trials in appropriate patient populations.

Considering risk factors for the effectiveness of translational therapies in brain stroke

Multiple studies on cerebral ischemia have been performed in animal models to propose different strategies of neuroprotection that mitigate either the early or late consequences of the disease. These therapies have been successful in reducing the volume of infarction, the proinflammatory cascade, and the amount of free radicals, as well as reversing markers of neurodegeneration, among other events. However, when those strategies are translated to clinical studies, their effectiveness is not reproduced. This review will focus on highlighting some of the main limitations of the animal models of stroke that lead to unsuccessful translational therapies and the common risk factors in humans that should be carefully considered in the experimental design of future studies to generate a more realistic spatiotemporal physiopathology and improve therapeutic efficacy in cerebral ischemia.

The effects of statins with a high hepatoselectivity rank on the extra-hepatic tissues; New functions for statins

Statins, as the most common treatment for hyperlipidemia, exert effects beyond their lipid-lowering role which are known as pleiotropic effects. These effects are mainly due to the inhibition of isoprenoids synthesis and consequently blocking prenylation of proteins involved in the cellular signaling pathways regulating cell development, growth, and apoptosis. Statins target cholesterol synthesis in the liver as the major source of cholesterol in the body and so reduce whole-body cholesterol. The reduced level of cholesterol forces other organs to an adaptive homeostatic reaction to increase their cholesterol synthesis capacity, however, this only occurs when statins have unremarkable access to the extra-hepatic tissues. In order to reduce the adverse effects of statin on the skeletal muscle, most recent efforts have been towards formulating new statins with the highest level of hepatoselectivity rank and the least level of access to the extra-hepatic tissues; however, the inaccessibility of statins for the extra-hepatic tissues may induce several biological reactions. In this review, we aim to evaluate the effects of statins on the extra-hepatic tissues when statins have unremarkable access to these tissues.

Statin Therapy in Ischemic Stroke Models: A Meta-Analysis

Statins, drugs known for lipid lowering capabilities and reduction of cardiovascular disease, have demonstrated neuroprotective effects following ischemic stroke in retrospective clinical and animal studies. However, dosing (methods, time, type of statin, and quantity) varies across studies, limiting the clinical applicability of these findings. Furthermore, a comprehensive review of statins in edema and blood-brain barrier (BBB) breakdown is needed to provide insight on diverse, less explored neuroprotective effects. In the present study, we conduct a meta-analysis of publications evaluating statin administration in animal models of ischemic stroke. We review statins' most effective dosing regimen in four outcomes-infarct, edema, BBB breakdown, and functional outcome-to characterize several parameters of benefit associated with statin administration. A search term was constructed to identify experimental murine studies exploring statin use after transient middle cerebral artery occlusion (tMCAO) in PubMed, Web of Science, and Embase. Extracted data included statin type, dose, time and method of administration, and the four predetermined outcomes (functional outcome, edema, BBB breakdown, and infarction). A meta-analysis and stratified meta-regression were conducted using the standardized mean difference (SMD) method for continuous measurements. Included publications were assessed for bias using SYRCLE's RoB tool for animal studies. A total of 24 studies were included. Statin administration significantly reduced infarct volume (p < 0.0001), edema volume (p < 0.002), and neurological deficit (p < 0.0001). Simvastatin and pravastatin were most effective in reducing infarct volume when compared with atorvastatin (p = 0.0475, p = 0.0004) and rosuvastatin (p = 0.0036, p < 0.0001). Pravastatin outperformed all others in functional outcome. Subcutaneous (SC) injection was most effective in all outcomes. Statin therapy reduced BBB breakdown according to our systematic review. Mean study quality was 4.6/10. While statin therapy evidently improves neurological outcome following ischemic stroke, this analysis adds to our understanding of dosing and statins' effects on edema and BBB breakdown. These findings will aid the design of future studies investigating statin use and have larger implications for the clinical care of ischemic stroke patients.

Atorvastatin inhibits osteoclastogenesis and arrests tooth movement

INTRODUCTION

In addition to their cholesterol-lowering effects, the statin class of drugs appears to enhance osteogenesis and suppress bone resorption, which could be a clinical concern during orthodontic treatment. In this animal study, we aimed to determine whether atorvastatin (ATV) affects orthodontic tooth movement (OTM) through osteoclast inhibition. Furthermore, we analyzed the potential adverse effects of ATV on long-bone turnover and endochondral ossification.

METHODS

Rats were administered ATV (15 mg/kg) or saline solution via gavage (n = 12 animals/group), starting 2 weeks before initial OTM. Tooth displacement was measured after 7, 14, and 21 days. Histologic sections of the maxilla and femur were obtained after 14 and 21 days of OTM and stained (hematoxylin and eosin; TRAP assay) for histomorphometric analysis.

RESULTS

ATV was associated with significant (P <0.05) reductions in OTM and osteoclast counts. Independently of drug administration, OTM increased the number of osteoclasts and reduced the bone-volume ratio compared with the control maxillae without OTM. Long-term statin administration did not appear to affect femoral endochondral ossification.

CONCLUSIONS

This experimental study showed that the long-term use of ATV can significantly promote osteoclast inhibition and slow the OTM in the first week in rats. Under physiologic conditions, the drug did not affect bone turnover and endochondral ossification.

Atorvastatin attenuates the ovarian damage induced by cyclophosphamide in rat: An experimental study

BACKGROUND

Cyclophosphamide (CP), as an anticancer agent, causes ovarian toxicity and subsequent infertility in women. Atorvastatin (ATV) at a low dose has antioxidant and anti-inflammatory properties.

OBJECTIVE

The aim of this study was to investigate the protective effect of ATV against CP-induced ovarian injury in rat.

MATERIALS AND METHODS

In this experimental study, thirty-two female Wistar rats were randomly divided into four groups as I) control, II) ATV (10 mg/kg), III) CP (150 mg/kg), and IV) CP +ATV. The ATV treated groups were received ATV for 10 days via oral gavage. In the CP+ATV group, ATV was administrated on 5 days before and 5 days after CP injection. Histological structure, apoptosis (caspase-3), oxidative stress parameters as malondialdehyde, reactive oxygen species, protein carbonyl levels and cell viability were evaluated in ovary tissue by histological scores, immunohistochemistry, histochemical and biochemical assays. The levels of estrogen and progesterone hormones were measured on the 12th day of study.

RESULTS

ATV pretreatment significantly decreased the levels of oxidative stress biomarkers as malondialdehyde, reactive oxygen species and protein carbonyl levels and increased cell death in CP-treated rats as compared with the CP alone group. ATV significantly increased estrogen and progesterone levels in CP-treated rats. In addition, the histological examination showed ATV mitigated acute inflammation, degenerative cells in stroma and follicles, stromal edema, vacuolization, atresia of the follicles and congestion of blood vessels in the CP-treated animals. Furthermore, ATV significantly reduced immunoreactivity level of caspase-3 in CP-treated rats.

CONCLUSION

Our results showed that the ATV with antioxidant and anti-apoptosis (caspase-3) activities protected ovarian against CP-induced toxicity.

The role of KATP channels in cerebral ischemic stroke and diabetes

ATP-sensitive potassium (KATP) channels are ubiquitously expressed on the plasma membrane of cells in multiple organs, including the heart, pancreas and brain. KATP channels play important roles in controlling and regulating cellular functions in response to metabolic state, which are inhibited by ATP and activated by Mg-ADP, allowing the cell to couple cellular metabolic state (ATP/ADP ratio) to electrical activity of the cell membrane. KATP channels mediate insulin secretion in pancreatic islet beta cells, and controlling vascular tone. Under pathophysiological conditions, KATP channels play cytoprotective role in cardiac myocytes and neurons during ischemia and/or hypoxia. KATP channel is a hetero-octameric complex, consisting of four pore-forming Kir6.x and four regulatory sulfonylurea receptor SURx subunits. These subunits are differentially expressed in various cell types, thus determining the sensitivity of the cells to specific channel modifiers. Sulfonylurea class of antidiabetic drugs blocks KATP channels, which are neuroprotective in stroke, can be one of the high stoke risk factors for diabetic patients. In this review, we discussed the potential effects of KATP channel blockers when used under pathological conditions related to diabetics and cerebral ischemic stroke.

Atorvastatin mitigates cyclophosphamide-induced hepatotoxicity via suppression of oxidative stress and apoptosis in rat model

Cyclophosphamide (CP), as a chemotherapy drug, induces hepatotoxicity through causing oxidative stress. Atorvastatin (ATV) at a low dose has antioxidant and anti-inflammatory properties. The present study was designed to investigate the protective effects of ATV against CP-induced hepatotoxicity in rat. In this experimental study, 32 rats were treated with ATV orally at a dose of 10 mg/kg for 10 consecutive days, 5 days before and 5 days after the administration of a single intraperitoneal injection of CP (150 mg/kg). The hepatoprotective effect of ATV was evaluated by measuring liver function markers, oxidative markers, histological and immunohistochemical assays. The biochemical results showed that administration of CP increased hepatic biomarkers enzymes as aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels. CP increased malondialdehyde (MDA), protein carbonyl (PC) and decreased glutathione (GSH) content in rats. Moreover, administration of CP was associated with periportal leucocyte infiltration, dilation sinusoids, hepatocyte vacuolation, congestion and hemorrhage in livers of rats. CP significantly increased immunoreactivity of caspase-3 as a marker of apoptosis in liver tissue. ATV markedly mitigated liver injury through reduction in oxidative stress biomarkers, histopathological findings and apoptosis. The antioxidant and anti-apoptotic activities of ATV are main proposed mechanisms involved in its hepatoprotective effects against CP-induced hepatic injury.

Cerebral ischemic damage in diabetes: an inflammatory perspective

Stroke is one of the leading causes of death worldwide. A strong inflammatory response characterized by activation and release of cytokines, chemokines, adhesion molecules, and proteolytic enzymes contributes to brain damage following stroke. Stroke outcomes are worse among diabetics, resulting in increased mortality and disabilities. Diabetes involves chronic inflammation manifested by reactive oxygen species generation, expression of proinflammatory cytokines, and activation/expression of other inflammatory mediators. It appears that increased proinflammatory processes due to diabetes are further accelerated after cerebral ischemia, leading to increased ischemic damage. Hypoglycemia is an intrinsic side effect owing to glucose-lowering therapy in diabetics, and is known to induce proinflammatory changes as well as exacerbate cerebral damage in experimental stroke. Here, we present a review of available literature on the contribution of neuroinflammation to increased cerebral ischemic damage in diabetics. We also describe the role of hypoglycemia in neuroinflammation and cerebral ischemic damage in diabetics. Understanding the role of neuroinflammatory mechanisms in worsening stroke outcome in diabetics may help limit ischemic brain injury and improve clinical outcomes.

The enhanced atorvastatin hepatotoxicity in diabetic rats was partly attributed to the upregulated hepatic Cyp3a and SLCO1B1

Liver injury is a common adverse effect of atorvastatin. This study aimed to investigate atorvastatin-induced hepatotoxicity in diabetic rats induced by high-fat diet combined with streptozotocin. The results showed that 40 mg/kg atorvastatin was lethal to diabetic rats, whose mean survival time was 6.2 days. Severe liver injury also occurred in diabetic rats treated with 10 mg/kg and 20 mg/kg atorvastatin. The in vitro results indicated that atorvastatin cytotoxicity in hepatocytes of diabetic rats was more severe than normal and high-fat diet feeding rats. Expressions and activities of hepatic Cyp3a and SLCO1B1 were increased in diabetic rats, which were highly correlated with hepatotoxicity. Antioxidants (glutathione and N-Acetylcysteine), Cyp3a inhibitor ketoconazole and SLCO1B1 inhibitor gemfibrozil suppressed cytotoxicity and ROS formation in primary hepatocytes of diabetic rats. In HepG2 cells, up-regulations of CYP3A4 and SLCO1B1 potentiated hepatotoxicity and ROS generation, whereas knockdowns of CYP3A4 and SLCO1B1 as well as CYP3A4/SLCO1B1 inhibitions showed the opposite effects. Phenobarbital pretreatment was used to induce hepatic Cyp3a and SLCO1B1 in rats. Phenobarbital aggravated atorvastatin-induced hepatotoxicity, while decreased plasma exposure of atorvastatin. All these findings demonstrated that the upregulations of hepatic Cyp3a and SLCO1B1 in diabetic rats potentiated atorvastatin-induced hepatotoxicity via increasing ROS formation.

Impact of Comorbidities on Acute Injury and Recovery in Preclinical Stroke Research: Focus on Hypertension and Diabetes

Human ischemic stroke is very complex, and no single preclinical model can comprise all the variables known to contribute to stroke injury and recovery. Hypertension, diabetes, and hyperlipidemia are leading comorbidities in stroke patients. The use of predominantly young adult and healthy animals in experimental stroke research has created a barrier for translation of findings to patients. As such, more and more disease models are being incorporated into the research design. This review highlights the major strengths and weaknesses of the most commonly used animal models of these conditions in preclinical stroke research. The goal is to provide guidance in choosing, reporting, and executing appropriate disease models that will be subjected to different models of stroke injury.

Treatment of acute cerebral ischemia using animal models: a meta-analysis

BACKGROUND

There are numerous potential treatments assessed for acute cerebral ischemia using animal models. This study aimed to assess the effect of these treatments in terms of infarct size and neurobehavioral change. This meta-analysis was conducted to determine if any of these treatments provide a superior benefit so that they might be used on humans.

METHODS

A systematic search was conducted using several electronic databases for controlled animal studies using only nonsurgical interventions for acute cerebral ischemia. A random-effects model was used.

RESULTS

After an extensive literature search, 145 studies were included in the analysis. These studies included 1408 treated animals and 1362 control animals. Treatments that had the most significant effect on neurobehavioral scales included insulin, various antagonists, including N-methyl-D-aspartate (NMDA) receptor antagonist ACEA1021, calmodulin antagonist DY-9760e, and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor antagonist YM872, and antiviral agents. Treatments providing the greatest effect on infarct size included statins, sphingosine-1-phosphate agonist (fingolimod), alcohol, angiotensin, and leukotrienes. Treatments offering the greatest reduction in brain water content included various agonists, including sphingosine-1-phosphate agonist fingolimod, statins, and peroxisome proliferator-activated receptor gamma (PPAR-γ). Treatment groups with more than one study all had high heterogeneity (I² > 80%), however, using meta-regression we determined several sources of heterogeneity including sample size of the treatment and control groups, the occlusion time, but not the year when the study was conducted.

CONCLUSIONS

Some treatments stand out when compared to others for acute cerebral ischemia in animals. Greater replication of treatment studies is required before any treatments are selected for future human trials.

Cerebral neovascularization in diabetes: implications for stroke recovery and beyond

Neovascularization is an innate physiologic response by which tissues respond to various stimuli through collateral remodeling (arteriogenesis) and new vessel formation from existing vessels (angiogenesis) or from endothelial progenitor cells (vasculogenesis). Diabetes has a major impact on the neovascularization process but the response varies between different organ systems. While excessive angiogenesis complicates diabetic retinopathy, impaired neovascularization contributes to coronary and peripheral complications of diabetes. How diabetes influences cerebral neovascularization remained unresolved until recently. Diabetes is also a major risk factor for stroke and poor recovery after stroke. In this review, we discuss the impact of diabetes, stroke, and diabetic stroke on cerebral neovascularization, explore potential mechanisms involved in diabetes-mediated neovascularization as well as the effects of the diabetic milieu on poststroke neovascularization and recovery, and finally discuss the clinical implications of these effects.

Hyperglycemia, acute ischemic stroke, and thrombolytic therapy

Ischemic stroke is a leading cause of disability and is considered now the fourth leading cause of death. Many clinical trials have shown that stroke patients with acute elevation in blood glucose at onset of stroke suffer worse functional outcomes, longer in-hospital stay, and higher mortality rates. The only therapeutic hope for these patients is the rapid restoration of blood flow to the ischemic tissue through intravenous administration of the only currently proven effective therapy, tissue plasminogen activator (tPA). However, even this option is associated with the increased risk of intracerebral hemorrhage. Nonetheless, the underlying mechanisms through which hyperglycemia (HG) and tPA worsen the neurovascular injury after stroke are not fully understood. Accordingly, this review summarizes the latest updates and recommendations about the management of HG and coadministration of tPA in a clinical setting while focusing more on the various experimental models studying (1) the effect of HG on stroke outcomes, (2) the potential mechanisms involved in worsening the neurovascular injury, (3) the different therapeutic strategies employed to ameliorate the injury, and finally, (4) the interaction between HG and tPA. Developing therapeutic strategies to reduce the hemorrhage risk with tPA in hyperglycemic setting is of great clinical importance. This can best be achieved by conducting robust preclinical studies evaluating the interaction between tPA and other therapeutics in order to develop potential therapeutic strategies with high translational impact.

Neurovascular injury in acute hyperglycemia and diabetes: A comparative analysis in experimental stroke

BACKGROUND

Admission hyperglycemia impacts ischemic stroke deleteriously but the relative role of acute hyperglycemia (HG) versus diabetes in the pathogenesis of this poor outcome is not clear.

PURPOSE

To determine the effect of acute HG on neurovascular outcomes of stroke under control and diabetic conditions.

METHODS

Moderate acute HG (140-200 mg/dl) was achieved by glucose injection before middle cerebral artery occlusion (MCAO) in control Wistar and diabetic Goto-Kakizaki (GK) rats. Following 3 h MCAO/21 h reperfusion, we measured infarct size, hemorrhagic transformation (HT) frequency, excess hemoglobin, neurobehavioral outcome and plasma and MCA matrix metalloprotease (MMP) activity.

RESULTS

Infarct size was significantly smaller in diabetic rats. Moderate acute HG increased neuronal damage in diabetic but not in control rats. HT frequency and hemoglobin were significantly higher in diabetic rats. HG augmented vascular damage in control rats and had no additional effect on bleeding in diabetic rats. Baseline plasma MMP-9 activity was significantly higher in diabetic rats. HG increased MMP-9 activity in control and diabetic rats. Neurological deficit was greater in diabetic rats and was worsened by HG.

CONCLUSIONS

The finding that functional outcome is poorer in both acute HG and diabetes without a significant increase in infarct size suggests that amplified vascular damage contributes to neurological deficit in hyperglycemia. These results highlight the importance of vascular protection to improve neurological outcome in acute ischemic stroke.

Continuous oral administration of atorvastatin ameliorates brain damage after transient focal ischemia in rats

AIMS

Pre-treatment with statins is known to ameliorate ischemic brain damage after experimental stroke, and is independent of cholesterol levels. We undertook pre- vs post-ischemic treatment with atorvastatin after focal cerebral ischemia in rats.

MAIN METHODS

Male Sprague-Dawley rats underwent transient 90-min middle cerebral artery occlusion (MCAO). Atorvastatin (20mg/kg/day) or vehicle was administered orally. Rats were divided into vehicle-treated, atorvastatin pre-treatment, atorvastatin post-treatment, and atorvastatin continuous-treatment groups. In the pre-treatment, rats were given atorvastatin or vehicle for 7 days before MCAO. In the post-treatment, rats received atorvastatin or vehicle for 7 days after MCAO. Measurement of infarct volume, as well as neurological and immunohistochemical assessments, were done 24h and 7 days after reperfusion.

KEY FINDINGS

Each atorvastatin-treated group demonstrated significant reductions in infarct and edema volumes compared with the vehicle-treated group 24h after reperfusion. Seven days after reperfusion, infarct volumes in the post-treatment group and continuous-treatment group (but not the pre-treatment group) were significantly smaller than in the vehicle-treated group. Only the continuous-treatment group had significantly improved neurological scores 7 days after reperfusion compared with the vehicle group. Post-treatment and continuous-treatment groups had significantly decreased lipid peroxidation, oxidative DNA damage, microglial activation, expression of tumor necrosis factor-alpha, and neuronal damage in the cortical ischemic boundary area after 7 days of reperfusion.

SIGNIFICANCE

These results suggest that continuous oral administration (avoiding withdrawal) with statins after stroke may reduce the extent of post-ischemic brain damage and improve neurological outcome by inhibiting oxidative stress and inflammatory responses.

Therapeutic Effects of Policosanol and Atorvastatin against Global Brain Ischaemia-Reperfusion Injury in Gerbils

Stroke is the third cause of death and the first of permanent adult disability. Pretreatment with policosanol and atorvastatin has been effective in experimental models of cerebral ischaemia in rodents. The objective was to compare the therapeutic effects of policosanol and atorvastatin in a model of global cerebral ischaemia in gerbils. Gerbils were distributed into seven groups, a negative control and six with ischaemia-reperfusion-induced global cerebral ischemia (one vehicle positive control, two policosanol (100 and 200 mg/kg), two atorvastatin (10 and 20 mg/kg) and one aspirin (60 mg/kg) group). Treatments were given 4 h after ischaemia induction. Effects on ischemia-reperfusion-induced symptoms, hyperlocomotion, damage of pyramidal hipoccampal neurons and increased plasma oxidative markers were investigated. Positive, not negative controls, exhibited clinical symptoms, hyperlocomotion, neuronal damage and increased plasma oxidative markers. Policosanol (100 and 200 mg/kg) reduced significantly ischemia-reperfusion-induced symptoms, the frequency of symptomatic animals, histological scores of neuronal damage and plasma oxidative markers as compared with the positive control group. Atorvastatin (10 and 20 mg/kg) decreased significantly the symptoms and histological scores, but unchanged the frequency of symptomatic gerbils and oxidative variables. Only the highest dose of policosanol (200 mg/kg) and atorvastatin (20 mg/kg) reduced significantly ischemia reperfusion-induced hyperlocomotion, policosanol being the most effective. Aspirin 60 mg/kg lowered significantly symptom score, the rate of symptomatic gerbils and hyperlocomotion versus the positive controls, but failed to modify oxidative parameters. In conclusion, postreperfusion treatment with policosanol and atorvastatin was effective for ameliorating symptoms, hyperlocomotion and neurological damage of hippocampal CA1 neurons in gerbils with ischemia-reperfusion-induced global cerebral ischemia, but only policosanol reduced increased plasma oxidative variables.

Comparative analysis of the neurovascular injury and functional outcomes in experimental stroke models in diabetic Goto-Kakizaki rats

Diabetes worsens functional outcome and is associated with greater hemorrhagic transformation (HT) after ischemic stroke. We have shown that diabetic Goto-Kakizaki (GK) rats develop greater HT and neurological deficit despite smaller infarcts after transient middle cerebral artery occlusion (MCAO) with the suture model. However, the impact of (1) the duration of ischemia/reperfusion (I/R); (2) the method of ischemia; and (3) acute glycemic control on neurovascular injury and functional outcome in diabetic stroke remained unanswered. Wistar and GK rats were subjected to variable MCAO by suture or embolus occlusion. A group of GK rats were treated with insulin or metformin before stroke with suture occlusion. In all groups, infarct size, edema, HT occurrence and severity, and functional outcome were measured. Infarct size at 24h was smaller in GK rats with both suture and embolic MCAO, but expanded with longer reperfusion period. Edema and HT were increased in GK rats after 90min and 3h occlusion with the suture model, but not in the embolic MCAO. Neurological deficit was greater in diabetic rats. These findings suggest that diabetes accelerates the development of HT and amplifies vascular damage in the suture model where blood flow is rapidly reestablished. Acute metformin treatment worsened the infarct size, HT, and behavior outcome, whereas insulin treatment showed a protective effect. These results suggest that the impact of ischemia/reperfusion on neurovascular injury and functional outcome especially in disease models needs to be fully characterized using different models of stroke to model the human condition.

Cerebrovascular complications of diabetes: focus on stroke

Cerebrovascular complications make diabetic patients 2-6 times more susceptible to a stroke event and this risk is magnified in younger individuals and in patients with hypertension and complications in other vascular beds. In addition, when patients with diabetes and hyperglycemia experience an acute ischemic stroke they are more likely to die or be severely disabled and less likely to benefit from the one FDA-approved therapy, intravenous tissue plasminogen activator. Experimental stroke models have revealed that chronic hyperglycemia leads to deficits in cerebrovascular structure and function that may explain some of the clinical observations. Increased edema, neovascularization and protease expression as well as altered vascular reactivity and tone may be involved and point to potential therapeutic targets. Further study is needed to fully understand this complex disease state and the breadth of its manifestation in the cerebrovasculature.

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.

Angiopoietin/Tie2 pathway mediates type 2 diabetes induced vascular damage after cerebral stroke

We investigated the changes and the molecular mechanisms of cerebral vascular damage after stroke in type-2 diabetic (T2DM) mice. Adult male db/db T2DM and wild-type (WT) mice were subjected to transient middle cerebral artery occlusion (MCAo) and sacrificed 24 hours after MCAo. T2DM-mice exhibited significantly increased blood glucose, brain hemorrhagic rate, mortality and cerebrovascular density, but decreased cerebrovascular diameter, arteriolar density and arterial mural cell numbers in the ischemic brain compared with WT mice. The hemorrhagic rate was significantly correlated with the mortality (r = 0.85). T2DM-mice also exhibited increased blood-brain barrier leakage and concomitantly, increased Angiopoietin2, but decreased Angiopoietin1, Tie2 and tight junction protein expression in the ischemic brain. Angiopoietin1 gene expression also significantly decreased in the common carotid artery (CCA) in T2DM-mice compared with WT mice after stroke. To further test the effects of T2DM on cerebrovascular damage, we performed in vitro studies. The capillary-like tube formation of primary cultured mouse brain endothelial cells (MBECs) significantly increased, but artery cell migration in the primary CCA cultures significantly decreased both in Sham and MCAo T2DM-mice compared with the WT mice. Angiopoietin1 treatment significantly increased artery cell migration in T2DM-CCA after MCAo. Tie2-FC, a neutralized Tie2 antibody, significantly decreased artery cell migration in WT-CCA after MCAo. Therefore, decreased Angiopoietin1/Tie2 and increased Angiopoietin2 expression may contribute to diabetes-induced vascular damage after stroke.

Diabetes-induced peroxynitrite impairs the balance of pro-nerve growth factor and nerve growth factor, and causes neurovascular injury

AIMS/HYPOTHESIS

Diabetic retinopathy, the leading cause of blindness in working-age Americans, is characterised by reduced neurotrophic support and increased proinflammatory cytokines, resulting in neurotoxicity and vascular permeability. We sought to elucidate how oxidative stress impairs homeostasis of nerve growth factor (NGF) and its precursor, proform of NGF (proNGF), to cause neurovascular dysfunction in the eye of diabetic patients.

METHODS

Levels of NGF and proNGF were examined in samples from human patients, from retinal Müller glial cell line culture cells and from streptozotocin-induced diabetic animals treated with and without atorvastatin (10 mg/kg daily, per os) or 5,10,15,20-tetrakis (4-sulfonatophenyl)porphyrinato iron (III) chloride (FeTPPs) (15 mg/kg daily, i.p.) for 4 weeks. Neuronal death and vascular permeability were assessed by TUNEL and extravasation of BSA-fluorescein.

RESULTS

Diabetes-induced peroxynitrite formation impaired production and activity of matrix metalloproteinase-7 (MMP-7), which cleaves proNGF extracellularly, leading to accumulation of proNGF and reducing NGF in samples from diabetic retinopathy patients and experimental models. Treatment of diabetic animals with atorvastatin exerted similar protective effects that blocked peroxynitrite using FeTPPs, restoring activity of MMP-7 and hence the balance between proNGF and NGF. These effects were associated with preservation of blood-retinal barrier integrity, preventing neuronal cell death and blocking activation of RhoA and p38 mitogen-activated protein kinase (p38MAPK) in experimental and human samples.

CONCLUSIONS/INTERPRETATION

Oxidative stress plays an unrecognised role in causing accumulation of proNGF, which can activate a common pathway, RhoA/p38MAPK, to mediate neurovascular injury. Oral statin therapy shows promise for treatment of diabetic retinopathy.

Exacerbated brain damage, edema and inflammation in type-2 diabetic mice subjected to focal ischemia

One of the limiting factors in stroke therapeutic development is the use of animal models that do not well represent the underlying medical conditions of patients. In humans, diabetes increases the risk of stroke incidence as well as post-stroke mortality. To understand the mechanisms that render diabetics to increased brain damage, we evaluated the effect of transient middle cerebral artery occlusion in adult db/db mice. The db/db mouse is a model of type-2 diabetes with four times higher blood sugar than its normoglycemic genetic control(db/+ mouse). Following transient middle cerebral artery occlusion, the db/db mice showed significantly higher mortality, bigger infarcts, increased cerebral edema, worsened neurological status compared to db/+ mice. The db/db mice also showed significantly higher post-ischemic inflammatory markers (ICAM1(+) capillaries, extravasated macrophages/neutrophils and exacerbated proinflammatory gene expression) compared to db/+ mice. In addition, the post-ischemic neuroprotective heat-shock chaperone gene expression was curtailed in the db/db compared to db/+ mice.

Endothelin-1-mediated cerebrovascular remodeling is not associated with increased ischemic brain injury in diabetes

Diabetes increases the risk of as well as poor outcome after stroke. Matrix metalloprotease (MMP) activation disrupts blood-brain barrier integrity after cerebral ischemia. We have previously shown that type 2 diabetes promotes remodeling of middle cerebral arteries (MCA) characterized by increased media/lumen (M/L) ratio and MMP activity in an endothelin (ET)-1-dependent manner in the Goto-Kakizaki (GK) rat model. In the present study, we examined the effects of ET-1-mediated vascular remodeling on neurovascular damage following cerebral ischemic injury in GK rats 5 and 12 weeks after the onset of diabetes. The MCA structure, cerebral perfusion as well as infarct size, and hemorrhage were measured in control and diabetic rats subjected to transient MCA occlusion. M/L ratio was increased after 12 but not 5 weeks of diabetes. The baseline cerebral perfusion was lower and the infarct volume smaller in diabetic rats in both age groups. The incidence of hemorrhagic transformation was higher after 5 weeks of diabetes as compared to that after 12 weeks or in the control groups. These findings provide evidence that ET-1-mediated cerebrovascular remodeling does not worsen the neurovascular damage of ischemic brain injury in diabetes. It is possible that this early remodeling response is compensatory in nature to regulate vascular tone and integrity, especially when ischemia is layered on diabetic vascular disease.

Drug repurposing for vascular protection after acute ischemic stroke

The attempts to develop new treatments for acute ischemic stroke have been fraught with costly and spectacularly disappointing failures. Repurposing of safe, older drugs provides a lower risk alternative. Vascular protection is a novel strategy for improving stroke outcome. Promising targets for vascular protection after stroke have been identified, and several of these targets can be approached with "repurposed" old drugs, including statins, angiotensin receptor blockers (ARBs), and minocycline. We tested the vascular protection (ability to reduce hemorrhagic transformation) of three marketed drugs (candesartan, minocycline, and atorvastatin) in the experimental stroke model using three different rat strains [Wistar, spontaneously hypertensive rats (SHR) and type 2 diabetic Goto-Kakizaki (GK) rats]. All agents decreased the infarct size, improved the neurological outcome and decreased bleeding. Mechanisms identified include inhibition of MMP-9, activation of Akt, and increased expression of proangiogenic growth factors. Premorbid vascular damage (presence of either diabetes or hypertension) increased the likelihood of vascular injury after ischemia and reperfusion and improved the response to vascular protection.

Vascular protection in diabetic stroke: role of matrix metalloprotease-dependent vascular remodeling

Temporary focal ischemia causes greater hemorrhagic transformation (HT) in diabetic Goto-Kakizaki (GK) rats, a model with increased cerebrovascular matrix metalloprotease (MMP) activity and tortuosity. The objective of the current study was to test the hypotheses that (1) diabetes-induced cerebrovascular remodeling is MMP dependent and (2) prevention of vascular remodeling by glucose control or MMP inhibition reduces HT in diabetic stroke. Control and GK rats were treated with vehicle, metformin, or minocycline for 4 weeks, and indices of remodeling including vascular tortuosity index, lumen diameter, number of collaterals, and middle cerebral artery (MCA) MMP activity were measured. Additional animals were subjected to 3 hours MCA occlusion/21 hours reperfusion, and infarct size and HT were evaluated as indices of neurovascular injury. All remodeling markers including MMP-9 activity were increased in diabetes. Infarct size was smaller in minocycline-treated animals. Both metformin and minocycline reduced vascular remodeling and severity of HT in diabetes. These results provide evidence that diabetes-mediated stimulation of MMP-9 activity promotes cerebrovascular remodeling, which contributes to greater HT in diabetes. Metformin and minocycline offer vascular protection, which has important clinical implications for diabetes patients who are at a fourfold to sixfold higher risk for stroke.

Comparison of the post-embolization effects of tissue-plasminogen activator and simvastatin on neurological outcome in a clinically relevant rat model of acute ischemic stroke

Data has emerged, largely from non-thromboembolic animal models of stroke, that suggests that statins, which have efficacy in preventing strokes when given pre-ischemically, may have a positive effect on stroke even when given post-ischemically, possibly through pleitropic cerebrovascular effects. The goal of this study was to characterize the effects of IV tPA in a clinically relevant model of stroke utilizing a vascular occlusion with a freshly formed clot, and evaluate the effects of post-ischemic administration of simvastatin on stroke outcome in this model. Neurological deficit, clot burden, and lesion volume were assessed after treatment with tPA in one experiment, and after treatment with simvastatin in another. In the tPA experiment, treatment with 10mg/kg of tPA IV (with 20% given as an initial bolus, and 80% given as an infusion over the remaining 30 min), starting within an hour after stroke, resulted in significant reductions, compared with control animals, in neurological deficit (mean+/-SD neuroscores of 21.5+/-21.1 and 30+/-29.3, respectively, p=0.005), clot burden (p=0.010) and lesion volume (p=0.049) at 24h. In the simvastatin experiment on the other hand, treatment with a 20mg/kg of simvastatin as a single intraperitoneal dose within an hour after stroke resulted in no salutary effects on neurological deficit, clot burden or lesion volume compared with controls at 24h. These results suggest that more research needs to be done to fully ascertain the therapeutic potential and optimal dosing paradigm of a post-ischemic treatment with a statin.

Diverse effects of statins on angiogenesis: new therapeutic avenues

Angiogenesis is an important process for a variety of physiologic and pathologic conditions. Different angiogenic modulating targets are under extensive investigation both experimentally and clinically. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) are the first-line agents used in hypercholesterolemia. They are also characterized by having other benefits apart from their lipid-lowering effects. Among these pleiotropic effects are the pro- and antiangiogenic properties of statins. The pleiotropic effects of statins and how they modulate new blood vessel formation are discussed in this review. The currently available data from both animal and human studies regarding the effects of statins on angiogenesis in ischemic heart disease, stroke, ocular diseases, and cancer are also reviewed. Statins are safe, orally available agents that may acquire novel therapeutic indications through their angiogenic modulating effects.