Albumin therapy improves local vascular dynamics in a rat model of primary microvascular thrombosis: a two-photon laser-scanning microscopy study

mPR-Specific Actions Influence Maintenance of the Blood–Brain Barrier (BBB)

Cerebral cavernous malformations (CCMs) are characterized by abnormally dilated intracranial microvascular sinusoids that result in increased susceptibility to hemorrhagic stroke. It has been demonstrated that three CCM proteins (CCM1, CCM2, and CCM3) form the CCM signaling complex (CSC) to mediate angiogenic signaling. Disruption of the CSC will result in hemorrhagic CCMs, a consequence of compromised blood–brain barrier (BBB) integrity. Due to their characteristically incomplete penetrance, the majority of CCM mutation carriers (presumed CCM patients) are largely asymptomatic, but when symptoms occur, the disease has typically reached a clinical stage of focal hemorrhage with irreversible brain damage. We recently reported that the CSC couples both classic (nuclear; nPRs) and nonclassic (membrane; mPRs) progesterone (PRG)-receptors-mediated signaling within the CSC-mPRs-PRG (CmP) signaling network in nPR(−) breast cancer cells. In this report, we demonstrate that depletion of any of the three CCM genes or treatment with mPR-specific PRG actions (PRG/mifepristone) results in the disruption of the CmP signaling network, leading to increased permeability in the nPR(−) endothelial cells (ECs) monolayer in vitro. Finally, utilizing our in vivo hemizygous Ccm mutant mice models, we demonstrate that depletion of any of the three CCM genes, in combination with mPR-specific PRG actions, is also capable of leading to defective homeostasis of PRG in vivo and subsequent BBB disruption, allowing us to identify a specific panel of etiological blood biomarkers associated with BBB disruption. To our knowledge, this is the first report detailing the etiology to predict the occurrence of a disrupted BBB, an indication of early hemorrhagic events.

The cerebral collateral circulation: Relevance to pathophysiology and treatment of stroke

The brain's collateral circulation consists of arterial anastomotic channels capable of providing nutrient perfusion to brain regions whose normal sources of flow have become compromised, as occurs in acute ischemic stroke. Modern CT-based neuroimaging is capable of providing detailed information as to collateral extent and sufficiency and is complemented by magnetic resonance-based methods. In the present era of standard-of-care IV thrombolysis for acute ischemic stroke, and following the recent therapeutic successes of randomized clinical trials of acute endovascular intervention, the sufficiency of the collateral circulation has been convincingly established as a key factor influencing the likelihood of successful reperfusion and favorable clinical outcome. This article reviews the features of the brain's collateral circulation; methods for its evaluation in the acute clinical setting; the relevance of collateral circulation to prognosis in acute ischemic stroke; the specific insights into the collateral circulation learned from recent trials of endovascular intervention; and the major influence of genetic factors. Finally, we emphasize the need to develop therapeutic approaches to augment collateral perfusion as an adjunctive strategy to be employed along with, or prior to, thrombolysis and endovascular interventions, and we highlight the possible potential of inhaled nitric oxide, albumin, and other approaches. This article is part of the Special Issue entitled 'Cerebral Ischemia'.

Toward a scientific understanding of the effectiveness, material basis and prescription compatibility of a Chinese herbal formula Dan-hong injection

Since traditional Chinese medicine (TCM) is a complex mixture of multiple components, the application of methodologies for evaluating single-components Western medicine in TCM studies may have certain limitations. Appropriate strategies that recognize the integrality of TCM and connect to TCM theories remain to be developed. Here we use multiple unique approaches to study the scientific connotation of a TCM formula Dan-hong injection (DHI) without undermining its prescription integrity. The blood circulation improving and healing promoting effects of DHI were assessed by a qi stagnation blood stasis rat model and a mouse model of laser irradiation induced cerebral microvascular thrombosis. By UFLC-PDA-Triple Q-TOF-MS/MS and relevance analysis between chemical characters and biological effects, 82 chemical constituents and nine core components, whose blood circulation promoting effects were found comparable to that of whole DHI, were successfully identified. What’s more, the rationality of DHI prescription compatibility could be reflected not only in the maximum efficacy of the original ratio, but also in the interactions of compounds from different ingredient herbs, such as complementary activities and facilitating tissues distribution. This study provides scientific evidences in explanation of the clinical benefits of DHI, and also gives a good demonstration for the comprehensive evaluation of other TCM.

Neuroprotective strategies and the underlying molecular basis of cerebrovascular stroke

Stroke is a leading cause of disability in the US. Although there has been significant progress in the area of medical and surgical thrombolytic technologies, neuroprotective agents to prevent secondary cerebral injury and to minimize disability remain limited. Only limited success has been reported in preclinical and clinical trials evaluating a variety of compounds. In this review, the authors discuss the most up-to-date information regarding the underlying molecular biology of stroke as well as strategies that aim to mitigate this complex signaling cascade. Results of historical research trials involving N-methyl-d-aspartate and α-amino-3-hydroxy-5-methyl-4-isoxazole propionate receptor antagonists, clomethiazole, antioxidants, citicoline, nitric oxide, and immune regulators have laid the groundwork for current progress. In addition, more recent studies involving therapeutic hypothermia, magnesium, albumin, glyburide, uric acid, and a variety of other treatments have provided more options. The use of neuroprotective agents in combination or with existing thrombolytic treatments may be one of many exciting areas of further development. Although past trials of neuroprotective agents in ischemic stroke have been limited, significant insights into mechanisms of stroke, animal models, and trial design have incrementally improved approaches for future therapies.

Expanding the concept of neuroprotection for acute ischemic stroke: The pivotal roles of reperfusion and the collateral circulation

This review surveys the efforts taken to achieve clinically efficacious protection of the ischemic brain and underscores the necessity of expanding our purview to include the essential role of cerebral perfusion and the collateral circulation. We consider the development of quantitative strategies to measure cerebral perfusion at the regional and local levels and the application of these methods to elucidate flow-related thresholds of ischemic viability and to characterize the ischemic penumbra. We stress that the modern concept of neuroprotection must consider perfusion, the necessary substrate upon which ischemic brain survival depends. We survey the major mechanistic approaches to neuroprotection and review clinical neuroprotection trials, focusing on those phase 3 multicenter clinical trials for acute ischemic stroke that have been completed or terminated. We review the evolution of thrombolytic therapies; consider the lessons learned from the initial, negative multicenter trials of endovascular therapy; and emphasize the highly successful positive trials that have finally established a clinical role for endovascular clot removal. As these studies point to the brain's collateral circulation as key to successful reperfusion, we next review the anatomy and pathophysiology of collateral perfusion as it relates to ischemic infarction, as well as the molecular and genetic influences on collateral development. We discuss the current MR and CT-based diagnostic methods for assessing the collateral circulation and the prognostic significance of collaterals in ischemic stroke, and we consider past and possible future therapeutic directions.

Cerebral collateral circulation in experimental ischemic stroke

Cerebral collateral circulation is a subsidiary vascular network, which is dynamically recruited after arterial occlusion, and represents a powerful determinant of ischemic stroke outcome. Although several methods may be used for assessing cerebral collaterals in the acute phase of ischemic stroke in humans and rodents, they are generally underutilized. Experimental stroke models may play a unique role in understanding the adaptive response of cerebral collaterals during ischemia and their potential for therapeutic modulation. The systematic assessment of collateral perfusion in experimental stroke models may be used as a “stratification factor” in multiple regression analysis of neuroprotection studies, in order to control the within-group variability. Exploring the modulatory mechanisms of cerebral collaterals in stroke models may promote the translational development of therapeutic strategies for increasing collateral flow and directly compare them in term of efficacy, safety and feasibility. Collateral therapeutics may have a role in the hyperacute (even pre-hospital) phase of ischemic stroke, prior to recanalization therapies.

Albumin Administration in Acute Ischemic Stroke: Safety Analysis of the ALIAS Part 2 Multicenter Trial

BACKGROUND

Albumin treatment of ischemic stroke was associated with cardiopulmonary adverse events in previous studies and a low incidence of intracranial hemorrhage. We sought to describe the neurological and cardiopulmonary adverse events in the ALIAS Part 2 Multicenter Trial.

METHODS

Ischemic stroke patients, aged 18-83 and a baseline NIHSS ≥ 6, were randomized to treatment with ALB or saline control within 5 hours of stroke onset. Neurological adverse events included symptomatic intracranial hemorrhage, hemicraniectomy, neurological deterioration and neurological death. Cardiopulmonary adverse events included pulmonary edema/congestive heart failure, acute coronary syndromes, atrial fibrillation, pneumonia and pulmonary thromboembolism.

RESULTS

Among 830 patients, neurological and cardiopulmonary adverse events were not differentially associated with poor outcome between ALB and saline control subjects. The rate of symptomatic intracranial hemorrhage in the first 24h was low overall (2.9%, 24/830) but more common in the ALB treated subjects (RR = 2.4, CI95 1.01-5.8). The rate of pulmonary edema/CHF in the first 48h was 7.9% (59/830) and was more common among ALB treated subjects (RR = 10.7, CI95 4.3-26.6); this complication was expected and was satisfactorily managed with mandated diuretic administration and intravenous fluid guidelines. Troponin elevations in the first 48h were common, occurring without ECG change or cardiac symptoms in 52 subjects (12.5%).

CONCLUSIONS

ALB therapy was associated with an increase in symptomatic ICH and pulmonary edema/congestive heart failure but this did not affect final outcomes. Troponin elevation occurs routinely in the first 48 hours after acute ischemic stroke.

TRIAL REGISTRATION

ClincalTrials.gov NCT00235495.

Impaired leptomeningeal collateral flow contributes to the poor outcome following experimental stroke in the Type 2 diabetic mice

Collateral status is an independent predictor of stroke outcome. However, the spatiotemporal manner in which collateral flow maintains cerebral perfusion during cerebral ischemia is poorly understood. Diabetes exacerbates ischemic brain damage, although the impact of diabetes on collateral dynamics remains to be established. Using Doppler optical coherent tomography, a robust recruitment of leptomeningeal collateral flow was detected immediately after middle cerebral artery (MCA) occlusion in C57BL/6 mice, and it continued to grow over the course of 1 week. In contrast, an impairment of collateral recruitment was evident in the Type 2 diabetic db/db mice, which coincided with a worse stroke outcome compared with their normoglycemic counterpart db/+, despite their equally well-collateralized leptomeningeal anastomoses. Similar to the wild-type mice, both db/+ and db/db mice underwent collateral growth 7 d after MCA stroke, although db/db mice still exhibited significantly reduced retrograde flow into the MCA territory chronically. Acutely induced hyperglycemia in the db/+ mice did not impair collateral flow after stroke, suggesting that the state of hyperglycemia alone was not sufficient to impact collateral flow. Human albumin was efficacious in improving collateral flow and outcome after stroke in the db/db mice, enabling perfusion to proximal MCA territory that was usually not reached by retrograde flow from anterior cerebral artery without treatment. Our results suggest that the impaired collateral status contributes to the exacerbated ischemic injury in mice with Type 2 diabetes, and modulation of collateral flow has beneficial effects on stroke outcome among these subjects.

Symptomatic intracranial hemorrhage in the ALIAS Multicenter Trial: relationship to endovascular thrombolytic therapy

BACKGROUND

In the ALIAS (Albumin in Acute Stroke) Part 2 Multicenter Trial, 85% of subjects received standard-of-care intravenous tissue plasminogen activator, and 21% received some form of endovascular thrombolysis. The overall rate of symptomatic intracranial hemorrhage was within the expected range but was higher in albumin-treated subjects than in saline-treated subjects.

AIMS AND METHODS

Using the trial's Public Use Dataset, we analyzed factors contributing to symptomatic and asymptomatic intracranial hemorrhage in the 'safety sample' of 830 subjects.

RESULTS

Four hundred sixteen subjects received albumin therapy, and 414 received saline. Intravenous tissue plasminogen activator was given to 68.2%; intravenous tissue plasminogen activator plus endovascular intervention in 16.4%; and endovascular therapy alone in 43%. Symptomatic intracranial hemorrhage occurred in 41 subjects - within the first 12 h in one-third of cases, and within the first day in ∼60%. Intravenous tissue plasminogen activator had been used in 78% of symptomatic intracranial hemorrhage subjects - no higher than in the overall cohort. In contrast, 48.8% of subjects with symptomatic intracranial hemorrhage had received endovascular therapy - a rate markedly higher than the 20.7% rate for the entire cohort (P = 0.0001). Sixty-eight point three percent of subjects with symptomatic intracranial hemorrhage had received albumin, and 31.7% saline (risk ratio 2.14, P = 0.025). Other factors associated with symptomatic intracranial hemorrhage were baseline NIHSS and ASPECTS scores and the SEDAN score. Forty-one point four percent of subjects with symptomatic intracranial hemorrhage died. The odds ratio for symptomatic intracranial hemorrhage was 3.89 (95% confidence interval 2.04-7.41) with endovascular therapy and 2.15 (confidence interval 1.08-4.25) with albumin.

CONCLUSIONS

Endovascular thrombolysis was the major factor predisposing to symptomatic intracranial hemorrhage, and albumin contributed to this predisposition. The latter may be mediated by albumin's influence on platelet aggregation or collateral perfusion.

In Vivo Imaging of the Mouse Neurovascular Unit Under Chronic Cerebral Hypoperfusion

Background and Purpose—

Proper brain function is maintained by an integrated system called the neurovascular unit (NVU) comprised cellular and acellular elements. Although the individual features of specific neurovascular components are understood, it is unknown how they respond to ischemic stress as a functional unit. Therefore, we established an in vivo imaging method and clarified the NVU response to chronic cerebral hypoperfusion.

Methods—

Green mice (b-act-EGFP) with SR101 plasma labeling were used in this experiment. A closed cranial window was made over the left somatosensory cortex. To mimic chronic cerebral hypoperfusion, mice were subjected to bilateral common carotid artery stenosis operations using microcoils. In vivo real-time imaging was performed using 2-photon laser-scanning microscopy during the preoperative period, and after 1 day and 1 and 2 weeks of bilateral common carotid artery stenosis or sham operations.

Results—

Our method allowed 3-dimensional observation of most of the components of the NVU, as well as dynamic capillary microcirculation. Under chronic cerebral hypoperfusion, we did not detect any structural changes of each cellular component in the NVU; however, impairment of microcirculation was detected over a prolonged period. In the pial small arteries and veins, rolling and adhesion of leukocyte were detected, more prominently in the latter. In the deep cortical capillaries, flow stagnation because of leukocyte plugging was frequently observed.

Conclusions—

We established an in vivo imaging method for real-time visualization of the NVU. It seems that under chronic cerebral hypoperfusion, leukocyte activation has a critical role in microcirculation disturbance.

Discovery of prognostic biomarker candidates of lacunar infarction by quantitative proteomics of microvesicles enriched plasma

Background

Lacunar infarction (LACI) is a subtype of acute ischemic stroke affecting around 25% of all ischemic stroke cases. Despite having an excellent recovery during acute phase, certain LACI patients have poor mid- to long-term prognosis due to the recurrence of vascular events or a decline in cognitive functions. Hence, blood-based biomarkers could be complementary prognostic and research tools.

Methods and Finding

Plasma was collected from forty five patients following a non-disabling LACI along with seventeen matched control subjects. The LACI patients were monitored prospectively for up to five years for the occurrence of adverse outcomes and grouped accordingly (i.e., LACI-no adverse outcome, LACI-recurrent vascular event, and LACI-cognitive decline without any recurrence of vascular events). Microvesicles-enriched fractions isolated from the pooled plasma of four groups were profiled by an iTRAQ-guided discovery approach to quantify the differential proteome. The data have been deposited to the ProteomeXchange with identifier PXD000748. Bioinformatics analysis and data mining revealed up-regulation of brain-specific proteins including myelin basic protein, proteins of coagulation cascade (e.g., fibrinogen alpha chain, fibrinogen beta chain) and focal adhesion (e.g., integrin alpha-IIb, talin-1, and filamin-A) while albumin was down-regulated in both groups of patients with adverse outcome.

Conclusion

This data set may offer important insight into the mechanisms of poor prognosis and provide candidate prognostic biomarkers for validation on larger cohort of individual LACI patients.

Vascular remodeling after ischemic stroke: mechanisms and therapeutic potentials

The brain vasculature has been increasingly recognized as a key player that directs brain development, regulates homeostasis, and contributes to pathological processes. Following ischemic stroke, the reduction of blood flow elicits a cascade of changes and leads to vascular remodeling. However, the temporal profile of vascular changes after stroke is not well understood. Growing evidence suggests that the early phase of cerebral blood volume (CBV) increase is likely due to the improvement in collateral flow, also known as arteriogenesis, whereas the late phase of CBV increase is attributed to the surge of angiogenesis. Arteriogenesis is triggered by shear fluid stress followed by activation of endothelium and inflammatory processes, while angiogenesis induces a number of pro-angiogenic factors and circulating endothelial progenitor cells (EPCs). The status of collaterals in acute stroke has been shown to have several prognostic implications, while the causal relationship between angiogenesis and improved functional recovery has yet to be established in patients. A number of interventions aimed at enhancing cerebral blood flow including increasing collateral recruitment are under clinical investigation. Transplantation of EPCs to improve angiogenesis is also underway. Knowledge in the underlying physiological mechanisms for improved arteriogenesis and angiogenesis shall lead to more effective therapies for ischemic stroke.

High-dose albumin treatment for acute ischaemic stroke (ALIAS) Part 2: a randomised, double-blind, phase 3, placebo-controlled trial

BACKGROUND

In animal models of ischaemic stroke, 25% albumin reduced brain infarction and improved neurobehavioural outcome. In a pilot clinical trial, albumin doses as high as 2 g/kg were safely tolerated. We aimed to assess whether albumin given within 5 h of the onset of acute ischaemic stroke increased the proportion of patients with a favourable outcome.

METHODS

We did a randomised, double-blind, parallel-group, phase 3, placebo-controlled trial between Feb 27, 2009, and Sept 10, 2012, at 69 sites in the USA, 13 sites in Canada, two sites in Finland, and five sites in Israel. Patients aged 18-83 years with ischaemic (ie, non-haemorrhagic) stroke with a baseline National Institutes of Health stroke scale (NIHSS) score of 6 or more who could be treated within 5 h of onset were randomly assigned (1:1), via a central web-based randomisation process with a biased coin minimisation approach, to receive 25% albumin (2 g [8 mL] per kg; maximum dose 750 mL) or the equivalent volume of isotonic saline. All study personnel and participants were masked to the identity of the study drug. The primary endpoint was favourable outcome, defined as either a modified Rankin scale score of 0 or 1, or an NIHSS score of 0 or 1, or both, at 90 days. Analysis was by intention to treat. Thrombolytic therapies were permitted. This trial is registered with ClinicalTrials.gov, number NCT00235495.

FINDINGS

422 participants were randomly assigned to receive albumin and 419 to receive saline. On Sept 12, 2012, the trial was stopped early for futility (n=841). The primary outcome did not differ between patients in the albumin group and those in the saline group (186 [44%] vs 185 [44%]; risk ratio 0·96, 95% CI 0·84-1·10, adjusted for baseline NIHSS score and thrombolysis stratum). Mild-to-moderate pulmonary oedema was more common in patients given albumin than in those given saline (54 [13%] of 412 vs 5 [1%] of 412 patients); symptomatic intracranial haemorrhage within 24 h was also more common in patients in the albumin group than in the placebo group (17 [4%] of 415 vs 7 [2%] of 414 patients). Although the rate of favourable outcome in patients given albumin remained consistent at 44-45% over the course of the trial, the cumulative rate of favourable outcome in patients given saline rose steadily from 31% to 44%.

INTERPRETATION

Our findings show no clinical benefit of 25% albumin in patients with ischaemic stroke; however, they should not discourage further efforts to identify effective strategies to protect the ischaemic brain, especially because of preclinical literature showing convincing proof-of-principle for the possibility of this outcome.

FUNDING

National Institute of Neurological Disorders and Stroke, US National Institutes of Health; and Baxter Healthcare Corporation.

Histone induced platelet aggregation is inhibited by normal albumin

INTRODUCTION

Histones are small, nuclear proteins that serve to package DNA. Recent reports suggest that extracellular histones, including histone H4, may contribute to the pathogenesis of sepsis; they promote platelet aggregation and thrombosis when released into the circulation during inflammation or cell death. The mechanisms by which the body minimizes the deleterious effects of circulating histones are unclear. Because histones can bind to plasma proteins, including albumin, we hypothesized that normal albumin can prevent histones from activating platelets.

MATERIALS AND METHODS

Platelets and platelet-free plasma were obtained from healthy, adult subjects. The dose-dependent effects of histone H4 on platelet aggregation were studied by optical aggregometry. The effects of native and albumin-depleted plasma (prepared by affinity chromatography) on histone-induced platelet aggregation were also assessed. The effects of normal and surface-neutralized albumin (through modification of carboxyl groups) on histone-induced platelet activation and aggregation were evaluated using flow cytometry and aggregometry.

RESULTS

Histone H4 induced platelet aggregation in a dose-dependent manner. This histone-induced platelet aggregation was inhibited by both plasma and human serum albumin in a dose-dependent fashion. Furthermore, depletion of albumin from plasma reduced its ability to inhibit aggregation. Finally, surface neutralization of albumin decreased its ability to inhibit histone-induced activation and aggregation.

DISCUSSION

These data suggest that normal albumin serves a role in preventing histone-induced platelet aggregation in a charge-dependent manner.

The failure of animal models of neuroprotection in acute ischemic stroke to translate to clinical efficacy

The discrepancy in results regarding neuroprotective agents in animal experiments compared to clinical trials is a major problem. While many neuroprotective agents have been proven effective in a variety of animal ischemic stroke models, none have been shown to work in phase III clinical trials. This review retrospectively summarizes the neuroprotectants selected for human randomized controlled trials (RCT) and explores the reasons behind the clinical translational failure of these agents. Here, we suggest that there are many factors (model selection, anesthetic choice, physiological monitoring, model success criteria, embolus property, reperfusion damage, infarction area, therapeutic time window, drug penetration, blood concentration, gender difference, and outcome evaluation) responsible for this phenomenon. Ultra-early treatment using a "home run" drug and multi-target therapy may be the most promising for future consideration.

Albumin therapy enhances collateral perfusion after laser-induced middle cerebral artery branch occlusion: a laser speckle contrast flow study

Laser speckle contrast (LSC) was used to compare the extent of cortical ischemia in two inbred mouse strains that differed in their degree of collateral circulation, after laser occlusion of the distal middle cerebral artery, and after treatment with 25% albumin (ALB) or saline (control). Sequential LSC images acquired over ∼90 minutes were coaligned, converted to relative flow, and normalized to baseline. After 3-day survival, infarction was quantified by triphenyl tetrazolium chloride or magnetic resonance imaging. In the sparsely collateralized BALB/c strain, mean flow fell to 13% to 14% and 33% to 34% of baseline in central (core) and peripheral (penumbral) regions of interest, and ALB treatment at 30 minutes enhanced perfusion in both regions by ∼2-fold relative to saline, restoring flow to the benign-oligemic range centrally, and to the hyperemic range peripherally. The ALB-induced increment in parenchymal perfusion was disproportionate to the subtle flow increase in the occluded artery itself, suggesting that ALB improved collateral circulation. Cortical infarction in BALB/c mice was reduced 45% by ALB treatment. In contrast to BALB/c mice, the better-collateralized CD-1 strain developed milder ischemia, had smaller infarcts, and showed no differential benefit of ALB. We conclude that where native collateralization is insufficient (BALB/c strain), ALB treatment exerts a significant therapeutic effect after ischemia by augmenting collateral perfusion.

Docosahexaenoic acid complexed to human albumin in experimental stroke: neuroprotective efficacy with a wide therapeutic window

BACKGROUND

Docosahexaenoic acid (DHA) complexed to human serum albumin (Alb) is neuroprotective after experimental stroke. Here we tested using lower concentrations of albumin as part of the complex to achieve neuroprotection. We found that lower Alb concentrations extend the therapeutic window of protection beyond 5 h after stroke onset.

METHODS

Sprague-Dawley rats were received 2 h middle cerebral artery occlusion (MCAo). The behavior was evaluated on day 1, 2, 3 and 7 after MCAo. In the dose-response study, animals were given either DHA (5mg/kg), Alb (0.63g/kg), DHA-Alb (5mg/kg + 0.32, 0.63 or 1.25 g/kg) or saline, i.v. 3 h after onset of stroke (n=6-8 per group). In the therapeutic window study, DHA-Alb (5mg/kg + 1.25g/kg) was administered i.v. at either 3, 4, 5, 6 or 7 h after onset of stroke (n=7-9 per group). Alb (1.25g/kg) was given at 3 h or 5 h and saline at 3h after onset of reperfusion. Seven days after MCAo, infarct volumes and number of GFAP, ED-1, NeuN, SMI-71 positive cells and vessels were counted.

RESULTS

Moderate DHA-Alb doses (0.63 and 1.25 g/kg) improved neurological scores compared to albumin-treated rats on days 1, 2, 3 and 7. All DHA-Alb doses (0.32, 0.63 and 1.25 g/kg) markedly reduced cortical (by 65-70%), striatal (by 52-63%) and total infarct volumes (by 60-64%) compared to native Alb group. In the therapeutic window study DHA-Alb led to improved neurological score and significant reductions of infarct volumes (especially in the cortical or penumbral region), even when treatment was initiated as late as 7 hours after onset of MCAo.

CONCLUSIONS

The DHA-Alb complex affords high-grade neurobehavioral neuroprotection in focal cerebral ischemia, equaling or exceeding that afforded by native Alb or DHA, at considerably moderate doses. It has a broad therapeutic window extending to 7 h after stroke onset. Taken together, these finding support the potential clinical feasibility of administering DHA-Alb therapy to patients with acute ischemic stroke.

In vivo real-time two-photon microscopic imaging of platelet aggregation induced by selective laser irradiation to the endothelium created in the beta-actin-green fluorescent protein transgenic mice

Although thrombus formation in vivo has recently been reported, all previous laser induced thrombus models have been associated with vessel wall disruption. This study aimed to evaluate in vivo real-time platelet aggregation after selective endothelial injury, and to visualize thrombus formation without disruption and swelling of the arterial intima induced by two-photon laser irradiation. Cecal arteriole thrombi were created in beta-actin-green fluorescent protein transgenic mice by selective endothelial injury using two-photon laser-scanning microscopy (TPLSM). The in vivo real-time process of thrombus formation was assessed. Anticoagulant drug efficiency for thrombi was also analyzed in detail. TPLSM allowed visualization of microvessel components from the arterial smooth muscle to the intimal layer. Immediately after selective laser irradiation of the intimal layer, platelet adhesion and aggregation were seen only at the area of injury of the intimal layer after forming linear adhesions downstream of the injured area. When shear stress was overcome, thrombus formation began at the downstream edge of the injured area. Thrombus volume plateaued approximately 60 min after laser irradiation. The thrombolytic effects of anticoagulant drugs were precisely assessed; therefore, our model appears the most advanced model in point of real-time imaging of pathophysiological processes in vivo currently reported. In vivo real-time imaging of thrombus formation can be achieved using TPLSM in combination with an organ stabilizing system. The high magnification and resolution of TPLSM allows investigation of the mechanisms of thrombus formation along with assessment of antithrombotic drug efficacy with little interexperimental variation.

Current perspectives on potential role of albumin in neuroprotection

Albumin is the most abundant plasma protein synthesised mainly in the liver. It is also a major component of extracellular fluids including cerebrospinal fluid, interstitial fluid and lymph. Albumin has several biochemical properties including regulation of colloid osmotic pressure of plasma, transportation of hormones, fatty acids, drugs and metabolites across plasma, regulation of microvascular permeability, antioxidant activity, anti-thrombotic activity and anti-inflammatory activity. This multifunctional protein has been implicated in many neurological diseases owing to its ability to regulate hemodynamic properties of the brain circulation as well as the direct neuroprotective actions on neuronal and glial cells. In this review, we summarise various neuroprotective actions of the albumin in the brain. In experimental ischemic stroke, exogenous human serum albumin administration has been found to be neuroprotective via reducing brain swelling, prevention of post-ischemic thrombosis, anti-oxidant activity, hemodilution and increasing the perfusion to the ischemic tissue. Also, human serum albumin administration is currently under clinical trials for treatment of cerebral ischemia. In the experimental models of Alzheimer's disease, albumin has been implicated in neuroprotection by inhibiting polymerisation and enhancing the clearance of amyloid β. The direct neuroprotective actions on neuronal and glial cells are mediated via endogenously produced albumin or cellular uptake of blood derived albumin. These neuroprotective effects of albumin are partly attributed to anti-oxidant property and modulation of intracellular signalling of neuronal or glial cells. The recent finding of de novo synthesis of albumin in microglial cells directs us to explore newer roles of this endogenously produced multifunctional protein in normal as well as pathological conditions of the brain.

The Albumin in Acute Stroke Part 1 Trial: an exploratory efficacy analysis

BACKGROUND AND PURPOSE

The Albumin in Acute Stroke (ALIAS) Part 2 Trial is directly testing whether 2 g/kg of 25% human albumin (ALB) administered intravenously within 5 hours of ischemic stroke onset results in improved clinical outcome. Recruitment into Part 1 of the ALIAS Trial was halted for safety reasons. ALIAS Part 2 is a new, reformulated trial with more-stringent exclusion criteria. Our aim was to explore the efficacy of ALB in the ALIAS Part 1 data and to assess the statistical assumptions underlying the ALIAS Part 2 Trial.

METHODS

ALIAS is a multicenter, blinded, randomized controlled trial. Data on 434 subjects, comprising the ALIAS Part 1 subjects, were analyzed. We examined both the thrombolysis and nonthrombolysis cohorts combined and separately in a "target population" by excluding subjects who would not have been eligible for the ALIAS Part 2 Trial; the latter comprised patients >83 years of age, those with elevated baseline troponin values, and those with in-hospital stroke. We examined the differences in the primary composite outcome, defined as a modified Rankin Scale score of 0 to 1 and/or a National Institutes of Health Stroke Scale score of 0 to 1 at 90 days after randomization.

RESULTS

In the combined thrombolysis plus nonthrombolysis cohorts of the target population, 44.7% of subjects in the ALB group had a favorable outcome compared with 36.0% in the saline group (absolute effect size=8.7%; 95% CI, -2.2% to 19.5%). Among thrombolyzed subjects of the target population, 46.7% had a favorable outcome in the ALB group compared with 36.6% in the saline group (absolute effect size=10.1%; 95% CI, -2.0% to 20.0%).

CONCLUSIONS

Preliminary results from the ALIAS Part 1 suggest a trend toward a favorable primary outcome in subjects treated with ALB and support the validity of the statistical assumptions that underlie the ALIAS Part 2 Trial. The ALIAS Part 2 Trial will confirm or refute these results.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov/ALIAS. Unique identifier: NCT00235495.

The albumin in acute stroke (ALIAS) multicenter clinical trial: safety analysis of part 1 and rationale and design of part 2

BACKGROUND AND PURPOSE

enrollment in the Albumin in Acute Stroke (ALIAS) Trial was suspended in late 2007 due to a safety concern. We present the safety data of that Trial ("Part 1") and the rationale for the design of Part 2.

METHODS

ALIAS Part 1 was designed to assess whether 25% albumin (ALB) started within 5 hours of stroke onset would confer neuroprotection in subjects with acute ischemic stroke and baseline National Institutes of Health Stroke Scale of ≥ 6. Exclusion criteria included recent or current congestive heart failure, myocardial infarction, or cardiac surgery. The study comprised 2 cohorts: subjects who received thrombolysis and those who did not, each with 1:1 randomization to ALB or placebo. The primary outcome was the National Institutes of Health Stroke Scale and modified Rankin Scales at 90 days. The intended sample size was 1800.

RESULTS

four hundred thirty-four subjects were enrolled, and 424 were used in the safety analysis (ALB 207, saline 217). There were 36 deaths within the first 30 days in the ALB group and 21 in the saline group. In contrast, death rates after 30 days were similar by treatment. Large strokes were the predominant cause of early death in both groups. In subjects >83 years of age, 90-day death rates were 2.3-fold higher with ALB than with saline (95% CI, 1.04 to 5.12). Similarly, 90-day deaths in subjects receiving excessive fluids were 2.10-fold greater with ALB than with saline (CI, 1.10 to 3.98).

CONCLUSIONS

The ALIAS Part 2 Trial, which started in early 2009, was modified as follows to enhance safety: upper age limit of 83 years; requirement for normal baseline serum troponin level; restriction of total intravenous fluids in the first 48 hours to ≤ 4200 mL; mandatory diuretic at 12 to 24 hours; and detailed site retraining. Because of insufficient nonthrombolysed subjects (22%) in Part 1, the 2-cohort design was eliminated. The Data Safety Monitoring Board has reviewed the safety data of Part 2 3 times and has approved continuation of the trial.

Albumin activates astrocytes and microglia through mitogen-activated protein kinase pathways

Following acute brain injury, albumin may gain access to the brain parenchyma. Clinical studies indicate a protective role for albumin in stroke but an increase in mortality associated with albumin administration following traumatic brain injury. We investigated the effects of albumin on astrocyte and microglial activation, and the role of mitogen-activated protein kinases (MAPK) in these responses. Albumin activated ERK1/2, p38 MAPK and JNK signaling pathways in astrocytes, and induced the production of interleukin (IL)-1beta, inducible nitric oxide (NO) synthase, the NO metabolite nitrite, and the chemokine CX3CL1 while reducing the level of S100B. The release of inflammatory markers by astrocytes was partially dependent on p38 MAPK and ERK1/2 pathways, but not JNK. In microglia, albumin exposure activated all three MAPK pathways and produced an increase in IL-1beta and nitrite. Inhibition of p38 MAPK in microglia leads to an increased level of IL1beta, while inhibition of all three MAPKs suppressed the release of nitrite. These results suggest that albumin activates astrocytes and microglia, inducing inflammatory responses involved both in the mechanisms of cellular injury and repair via activation of MAPK pathways, and thereby implicate glial activation in the clinical responses to administration of albumin.

Elevated albumin in retinas of monkeys with experimental glaucoma

PURPOSE

To establish the identity of a prominent protein, approximately 70 kDa, that is markedly increased in the retina of monkeys with experimental glaucoma compared with the fellow control retina, the relationship to glaucoma severity, and its localization in the retina.

METHODS

Retinal extracts were subjected to 2-D gel electrophoresis to identify differentially expressed proteins. Purified peptides from the abundant 70 kDa protein were analyzed and identified by liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS) separation, and collision-induced dissociation sequencing. Protein identity was performed on MASCOT (Matrix Science, Boston, MA) and confirmed by Western blot. The relationship between the increase in this protein and glaucoma severity was investigated by regression analyses. Protein localization in retina was evaluated by immunohistochemistry with confocal imaging.

RESULTS

The abundant protein was identified as Macaca mulatta serum albumin precursor (67 kDa) from eight non-overlapping proteolytic fragments, and the identity was confirmed by Western blot. The average increase in retinal albumin content was 2.3 fold (P = 0.015). In glaucoma eyes, albumin was localized to some neurons of the inner nuclear layer, in the inner plexiform layer, and along the vitreal surface, but it was only found in blood vessels in control retinas.

CONCLUSIONS

Albumin is the abundant protein found in the glaucomatous monkey retinas. The increased albumin is primarily localized to the inner retina where oxidative damage associated with experimental glaucoma is known to be prominent. Since albumin is a major antioxidant, the increase of albumin in the retinas of eyes with experimental glaucoma may serve to protect the retina against oxidative damage.

Multifunctional actions of approved and candidate stroke drugs

Ischemic stroke causes brain damage by multiple pathways. Previous stroke trials have demonstrated that drugs targeting one or only a few of these pathways fail to improve clinical outcome after stroke. Drugs with multimodal actions have been suggested to overcome this challenge. In this review, we describe the mechanisms of action of agents approved for secondary prevention of ischemic stroke, such as antiplatelet, antihypertensive, and lipid-lowering drugs. These drugs exhibit considerable properties beyond their classical mechanisms, including neuroprotective and neuroregenerative properties. In addition, candidate stroke drugs currently studied in clinical phase III trials are described. Among these, albumin, hematopoietic growth factors, and citicoline have been identified as promising agents with multiple mechanisms. These drugs offer hope that additional treatment options for the acute phase after a stroke will become available in the near future.

Albumin therapy augments the effect of thrombolysis on local vascular dynamics in a rat model of arteriolar thrombosis: a two-photon laser-scanning microscopy study

BACKGROUND AND PURPOSE

Results of our recent pilot clinical trial suggest that the efficacy of thrombolytic therapy in acute ischemic stroke may be enhanced by the coadministration of high-dose albumin. Here, we explored the microvascular hemodynamic effects of this combined therapy in a laboratory model of cortical arteriolar thrombosis.

METHODS

We studied the cortical microcirculation of physiologically monitored rats in vivo by two-photon laser-scanning microscopy after plasma-labeling with fluorescein-dextran. We induced focal thrombosis in 30- to 50-microm cortical arterioles by laser irradiation and measured arteriolar flow velocity by repeated line-scanning. At 30 minutes post-thrombosis, we treated animals with the thrombolytic agent, reteplase, which was coadministered with either human albumin, 2 g/kg, or with saline control.

RESULTS

Baseline arteriolar flow velocity averaged 3.8+/-0.7 mm/s, was immediately reduced by thrombosis to 22% to 25% of control values, and remained unchanged before treatment. Subthrombolytic doses of reteplase combined with saline led to a median increase in flow velocity to 37% of control distal to the thrombus (P=nonsignificant versus pretreatment). By contrast, reteplase combined with albumin therapy resulted in a prompt, highly significant increase of median flow velocity to 58% of control levels (P=0.013 versus reteplase+saline), which remained significantly higher than the reteplase+saline group at multiple time-points over the subsequent hour.

CONCLUSIONS

The beneficial effect of subthrombolytic doses of reteplase on microvascular hemodynamics distal to a cortical arteriolar thrombosis is markedly enhanced by the coadministration of high-dose albumin therapy; these results have important clinical implications for the management of patients with acute ischemic stroke.

Neuroprotection for ischemic stroke: past, present and future

Neuroprotection for ischemic stroke refers to strategies, applied singly or in combination, that antagonize the injurious biochemical and molecular events that eventuate in irreversible ischemic injury. There has been a recent explosion of interest in this field, with over 1000 experimental papers and over 400 clinical articles appearing within the past 6 years. These studies, in turn, are the outgrowth of three decades of investigative work to define the multiple mechanisms and mediators of ischemic brain injury, which constitute potential targets of neuroprotection. Rigorously conducted experimental studies in animal models of brain ischemia provide incontrovertible proof-of-principle that high-grade protection of the ischemic brain is an achievable goal. Nonetheless, many agents have been brought to clinical trial without a sufficiently compelling evidence-based pre-clinical foundation. At this writing, around 160 clinical trials of neuroprotection for ischemic stroke have been initiated. Of the approximately 120 completed trials, two-thirds were smaller early-phase safety-feasibility studies. The remaining one-third were typically larger (>200 subjects) phase II or III trials, but, disappointingly, only fewer than one-half of these administered neuroprotective therapy within the 4-6h therapeutic window within which efficacious neuroprotection is considered to be achievable. This fact alone helps to account for the abundance of "failed" trials. This review presents a close survey of the most extensively evaluated neuroprotective agents and classes and considers both the strengths and weakness of the pre-clinical evidence as well as the results and shortcomings of the clinical trials themselves. Among the agent-classes considered are calcium channel blockers; glutamate antagonists; GABA agonists; antioxidants/radical scavengers; phospholipid precursor; nitric oxide signal-transduction down-regulator; leukocyte inhibitors; hemodilution; and a miscellany of other agents. Among promising ongoing efforts, therapeutic hypothermia, high-dose human albumin therapy, and hyperacute magnesium therapy are considered in detail. The potential of combination therapies is highlighted. Issues of clinical-trial funding, the need for improved translational strategies and clinical-trial design, and "thinking outside the box" are emphasized.