Hypothermia for Acute Ischemic Stroke: Not Just Another Neuroprotectant

Pharmacological hypothermia induced neurovascular protection after severe stroke of transient middle cerebral artery occlusion in mice

Therapeutic hypothermia is a potential protective strategy after stroke. The present study evaluated the neurovascular protective potential of pharmacological hypothermia induced by the neurotensin receptor 1 agonist HPI-201 after severe ischemic stroke. Adult C57BL/6 mice were subjected to filament insertion-induced occlusion of the middle cerebral artery (60 min MCAO). HPI-201 was i.p. injected 120 min after the onset of MCAO to initiate and maintain the body temperature at 32-33°C for 6 hrs. The infarct volume, cell death, integrity of the blood brain barrier (BBB) and neurovascular unit (NVU), inflammation, and functional outcomes were evaluated. The hypothermic treatment significantly suppressed the infarct volume and neuronal cell death, accompanied with reduced caspase-3 activation and BAX expression while Bcl-2 increased in the peri-infarct region. The cellular integrity of the BBB and NVU was significantly improved and brain edema was attenuated in HPI-201-treated mice compared to stroke controls. The hypothermic treatment decreased the expression of inflammatory factors including tumor necrosis factor-α (TNF-α), MMP-9, interleukin-1β (IL-1β), the M1 microglia markers IL-12 and inducible nitric oxide synthase (iNOS), while increased the M2 marker arginase-1 (Arg-1). Stroke mice received the hypothermic treatment showed lower neurological severity score (NSS), performed significantly better in functional tests, the mortality rate in the hypothermic group was noticeably lower compared with stroke controls. Taken together, HPI-201 induced pharmacological hypothermia is protective for different neurovascular cells after a severely injured brain, mediated by multiple mechanisms.

Differential effects of hypothermia on neurovascular unit determine protective or toxic results: Toward optimized therapeutic hypothermia

Therapeutic hypothermia (TH) benefits survivors of cardiac arrest and neonatal hypoxic-ischemic injury and may benefit stroke patients. Large TH clinical trials, however, have shown mixed results. Given the substantial pre-clinical literature supporting TH, we explored possible mechanisms for clinical trial variability. Using a standard rodent stroke model (n = 20 per group), we found smaller infarctions after 2 h pre- or post-reperfusion TH compared to 4 h. To explore the mechanism of this discrepancy, we used primary cell cultures of rodent neurons, astrocytes, or endothelial cells subjected to oxygen-glucose deprivation (OGD). Then, cells were randomly assigned to 33℃, 35℃ or 37℃ for varying durations after varying delay times. Both 33 and 35℃ TH effectively preserved all cell types, although 33℃ was superior. Longer cooling durations overcame moderate delays to cooling initiation. In contrast, TH interfered with astrocyte paracrine protection of neurons in a temperature-dependent manner. These findings suggest that longer TH is needed to overcome delays to TH onset, but shorter TH durations may be superior to longer, perhaps due to suppression of astrocytic paracrine support of neurons during injury. We propose a scheme for optimizing TH after cerebral injury to stimulate further studies of cardiac arrest and stroke.

Bilirubin and Ischemic Stroke: Rendering the Current Paradigm to Better Understand the Protective Effects of Bilirubin

Novel and innovative methods are critical in fostering new treatments and improving clinical outcomes in patients who suffer from ischemic stroke. Bilirubin has long been considered metabolic waste that can be harmful to the body; however, it is now becoming recognized as one of the body's most potent antioxidant, anti-inflammatory, and neuroprotective molecules. These properties facilitate bilirubin's anti-atherogenic effects to impede and prevent the formation of thrombi in ischemic stroke. These functions allow for protection from neuronal injury during an ischemic state and suggest that elevated bilirubin levels may be linked to a lower rate of morbidity and mortality. Therefore, here we discuss the pathophysiology of stroke and the molecular properties of bilirubin to better understand their beneficial relationship. We outline clinical studies looking at the relationship between serum bilirubin levels and ischemic stroke prevalence. At this time, few studies have rigorously looked at the relationship between bilirubin and ischemic stroke, whether it is positive or negative. Thus, rigorous research is needed to provide evidence supporting the current studies, expand on these studies, and facilitate their translation to bedside therapy for patients who suffer from ischemic stroke.

Limb Remote Ischemic Conditioning: Mechanisms, Anesthetics, and the Potential for Expanding Therapeutic Options

Novel and innovative approaches are essential in developing new treatments and improving clinical outcomes in patients with ischemic stroke. Remote ischemic conditioning (RIC) is a series of mechanical interruptions in blood flow of a distal organ, following end organ reperfusion, shown to significantly reduce infarct size through inhibition of oxidation and inflammation. Ischemia/reperfusion (I/R) is what ultimately leads to the irreversible brain damage and clinical picture seen in stroke patients. There have been several reports and reviews about the potential of RIC in acute ischemic stroke; however, the focus here is a comprehensive look at the differences in the three types of RIC (remote pre-, per-, and postconditioning). There are some limited uses of preconditioning in acute ischemic stroke due to the unpredictability of the ischemic event; however, it does provide the identification of biomarkers for clinical studies. Remote limb per- and postconditioning offer a more promising treatment during patient care as they can be harnessed during or after the initial ischemic insult. Though further research is needed, it is imperative to discuss the importance of preclinical data in understanding the methods and mechanisms involved in RIC. This understanding will facilitate translation to a clinically feasible paradigm for use in the hospital setting.

ALA-PpIX mediated photodynamic therapy of malignant gliomas augmented by hypothermia

Background

Malignant gliomas are highly invasive, difficult to treat, and account for 2% of cancer deaths worldwide. Glioblastoma Multiforme (GBM) comprises the most common and aggressive intracranial tumor. The study hypothesis is to investigate the modification of Photodynamic Therapy (PDT) efficacy by mild hypothermia leads to increased glioma cell kill while protecting normal neuronal structures.

Methods

Photosensitizer accumulation and PDT efficacy in vitro were quantified in various glioma cell lines, primary rat neurons, and astrocytes. In vivo studies were carried out in healthy brain and RG2 glioma of naïve Fischer rats. Hypothermia was induced at 1 hour pre- to 2 hours post-PDT, with ALA-PpIX accumulation and PDT treatments effects on tumor and normal brain PDT quantified using optical spectroscopy, histology, immunohistochemistry, MRI, and survival studies, respectively.

Findings

In vitro studies demonstrated significantly improved post-PDT survival in primary rat neuronal cells. Rat in vivo studies confirmed a neuroprotective effect to hypothermia following PpIX mediated PDT by T₂ mapping at day 10, reflecting edema/inflammation volume reduction. Mild hypothermia increased PpIX fluorescence in tumors five-fold, and the median post-PDT rat survival time (8.5 days normothermia; 14 days hypothermia). Histology and immunohistochemistry show close to complete cellular protection in normal brain structures under hypothermia.

Conclusions

The benefits of hypothermia on both normal neuronal tissue as well as increased PpIX fluorescence and RG2 induced rat survival strongly suggest a role for hypothermia in photonics-based surgical techniques, and that a hypothermic intervention could lead to considerable patient outcome improvements.

Neuroprotective effect of epidermal growth factor plus growth hormone-releasing peptide-6 resembles hypothermia in experimental stroke

BACKGROUND

Combined therapy with epidermal growth factor (EGF) and growth hormone-releasing peptide 6 (GHRP-6) in stroke models has accumulated evidence of neuroprotective effects from several studies, but needs further support before clinical translation. Comparing EGF + GHRP-6 to hypothermia, a gold neuroprotection standard, may contribute to this purpose.

OBJECTIVES

The aims of this study were to compare the neuroprotective effects of a combined therapy based on EGF + GHRP-6 with hypothermia in animal models of (a) global ischemia representing myocardial infarction and (b) focal brain ischemia representing ischemic stroke.

METHODS

(a) Global ischemia was induced in Mongolian gerbils by a 15-min occlusion of both carotid arteries, followed by reperfusion. (b) Focal brain ischemia was achieved by intracerebral injection of endothelin 1 in Wistar rats. In each experiment, three ischemic treatment groups - vehicle, EGF + GHRP-6, and hypothermia - were compared to each other and to a sham-operated control group. End points were survival, neurological scores, and infarct volume.

RESULTS

(a) In global ischemia, neurological score at 48-72 h, infarct volume, and neuronal density of hippocampal CA1 zone in gerbils treated with EGF + GHRP-6 were similar to the hypothermia-treated group. (b) In focal ischemia, the neurologic score and infarct volume of rats receiving EGF + GHRP-6 were also similar to animals in the hypothermia group.

DISCUSSION

With hypothermia being a good standard neuroprotectant reference, these results provide additional proof of principle for EGF and GHRP-6 co-administration as a potentially neuroprotective stroke therapy.

Very Mild Hypothermia (35°C) Postischemia Reduces Infarct Volume and Blood/Brain Barrier Breakdown Following tPA Treatment in the Mouse

Reperfusion therapies for stroke diminish in effectiveness and safety as time to treatment increases. Hypothermia neuroprotection for stroke is established, but its clinical translation has been hampered by uncertainties regarding optimal temperature and complications associated with moderate hypothermia. Also, hypothermia targeting temperatures of 32-33°C is associated with clinical and logistical problems related to induction and adverse side effects. We hypothesized that ischemic damage and tPA-exacerbated blood/brain barrier (BBB) breakdown produced following 30 minutes of middle cerebral artery occlusion and either 1 hour of saline or tPA infusion would be reduced by treatment with very mild cooling of 1.5°C for 48 hours followed by 24 hours of gradual rewarming. Infarct volume was reduced by 29.6% (p<0.001) and 41.9% (p<0.001) in hypothermic-tPA (Hypo_tPA)-treated and hypothermic-saline (Hypo_Sal)-treated animals compared to normothermic-tPA (Norm_tPA) and saline (Norm_Sal)-treated animals, respectively. Hypothermia also reduced IgG extravasation in tPA-treated, but not saline-treated groups compared to their normothermic controls (p<0.001). The ipsilateral-contralateral changes in optical density for IgG extravasation were 18.4% greater in the Norm_tPA than Norm_Sal (p<0.001) group. The ipsilateral-contralateral changes in optical density for IgG extravasation were reduced by 17.8% (p<0.001) in the Hypo_tPA compared to Norm_tPA group. No significant mean difference in IgG extravasation was seen between Hypo_tPA and Hypo_Sal groups (p>0.05). Very modest hypothermia to reduce the BBB breakdown could improve the availability and safety of reperfusion treatments for stroke.

A mathematical model of cellular metabolism during ischemic stroke and hypothermia

Stroke is a major cause of death and disability worldwide. Therapeutic hypothermia is a potentially useful neuroprotective treatment. A mathematical model of brain metabolism during stroke is extended here to simulate the effect of hypothermia on cell survival. Temperature decreases were set to reduce chemical reaction rates and slow diffusion through ion channels according to the Q10 rule. Heat delivery to tissues was set to depend on metabolic heat generation rate and perfusion. Two cooling methods, scalp and vascular, were simulated to approximate temperature variation in the brain during treatment. Cell death was assumed to occur at continued cell membrane depolarization. Simulations showed that hypothermia to 34.5 °C induced within 1-1.5 h of stroke onset could extend cell survival time by at least 5 h in tissue with perfusion reduced by 80% of normal. There was good agreement between simulated metabolite dynamics and those reported in rat model studies.

A case of commotio cordis treated with therapeutic hypothermia

BACKGROUND

Therapeutic hypothermia is used as a neuroprotective strategy for patients who have persistent neurologic compromise after return of spontaneous circulation from cardiac arrest. The 2010 American Heart Association Guidelines recommend the use of therapeutic hypothermia in adult cardiac arrest patients when the initial rhythm is ventricular fibrillation. These recommendations are based on primary research in patients with a cardiac cause of their ventricular fibrillation.

CASE REPORT

A 43-year-old male was brought to our emergency department (ED) with commotio cordis. He was struck in the chest with a baseball bat, after which he collapsed at the scene and was pulseless. Return of spontaneous circulation was achieved after defibrillation by treating paramedics, and the patient remained comatose on arrival to the ED. He was transferred to the intensive care unit and treated with therapeutic hypothermia at target temperature of 32-34°C. He was extubated on day 3, and discharged home on day 8 with good neurologic function. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: We report a case of commotio cordis in which the adult patient was treated with therapeutic hypothermia and had a favorable outcome. To our knowledge, this is the first reported case of its kind. Evidence for the use of therapeutic hypothermia is incomplete in patients with a traumatic cause of cardiac arrest, such as commotio cordis, despite probable similarities in the pathophysiology of anoxic brain injury. Our case illustrates that there may be benefit from use of therapeutic hypothermia for a broader population than is currently recommended.

Guidelines for the early management of patients with acute ischemic stroke: a guideline for healthcare professionals from the American Heart Association/American Stroke Association

BACKGROUND AND PURPOSE

The authors present an overview of the current evidence and management recommendations for evaluation and treatment of adults with acute ischemic stroke. The intended audiences are prehospital care providers, physicians, allied health professionals, and hospital administrators responsible for the care of acute ischemic stroke patients within the first 48 hours from stroke onset. These guidelines supersede the prior 2007 guidelines and 2009 updates.

METHODS

Members of the writing committee were appointed by the American Stroke Association Stroke Council's Scientific Statement Oversight Committee, representing various areas of medical expertise. Strict adherence to the American Heart Association conflict of interest policy was maintained throughout the consensus process. Panel members were assigned topics relevant to their areas of expertise, reviewed the stroke literature with emphasis on publications since the prior guidelines, and drafted recommendations in accordance with the American Heart Association Stroke Council's Level of Evidence grading algorithm.

RESULTS

The goal of these guidelines is to limit the morbidity and mortality associated with stroke. The guidelines support the overarching concept of stroke systems of care and detail aspects of stroke care from patient recognition; emergency medical services activation, transport, and triage; through the initial hours in the emergency department and stroke unit. The guideline discusses early stroke evaluation and general medical care, as well as ischemic stroke, specific interventions such as reperfusion strategies, and general physiological optimization for cerebral resuscitation.

CONCLUSIONS

Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke remains urgently needed.

Taboos and opportunities in sonothrombolysis for stroke

Systemic thrombolysis with tissue plasminogen activator (tPA) is the only approved treatment for acute ischaemic stroke that improves functional outcome if given up to 4.5 h from symptom onset. At least half of treated patients have unfavourable outcomes long-term though, emphasising the need to amplify the only approved acute stroke therapy. Ultrasound targeting of an intra-arterial occlusive clot and delivering mechanical pressure to its surrounding fluids (referred to as sonothrombolysis) accelerates the thrombolytic effect of tPA. Higher recanalisation rates produce a trend towards better functional outcomes that could be safely achieved with the combination of 2 MHz frequency ultrasound and systemic tPA. To further accelerate the clot-dissolving effect of ultrasound, a variety of frequencies and intensities as well as other adjuvant treatment elements are being studied. However, literature reports argue efficacy and safety of these novel approaches doubting promptly translation into the clinical practice. This review will summarise our current knowledge about potentially harmful (taboos) directions and what we think are promising avenues for these future stroke therapies. We also give a prospect for novel technologies such as operator-independent devices that aim to further spread the use of sonothrombolysis for stroke.

A novel stroke therapy of pharmacologically induced hypothermia after focal cerebral ischemia in mice

Compelling evidence from preclinical and clinical studies has shown that mild to moderate hypothermia is neuroprotective against ischemic stroke. Clinical applications of hypothermia therapy, however, have been hindered by current methods of physical cooling, which is generally inefficient and impractical in clinical situations. In this report, we demonstrate the potential of pharmacologically induced hypothermia (PIH) by the novel neurotensin receptor 1 (NTR1) agonist ABS-201 in a focal ischemic model of adult mice. ABS-201 (1.5-2.5 mg/kg, i.p.) reduces body and brain temperature by 2-5°C in 15-30 min in a dose-dependent manner without causing shivering or altering physiological parameters. Infarct volumes at 24 h after stroke are reduced by ∼30-40% when PIH therapy is initiated either immediately after stroke induction or after 30-60 min delay. ABS-201 treatment increases bcl-2 expression, decreases caspase-3 activation, and TUNEL-positive cells in the peri-infarct region, and suppresses autophagic cell death compared to stroke controls. The PIH therapy using ABS-201 improves recovery of sensorimotor function as tested 21 d after stroke. These results suggest that PIH induced by neurotensin analogs represented by ABS-201 are promising candidates for treatment of ischemic stroke and possibly for other ischemic or traumatic injuries.

Neuroprotection by hypothermia plus alkalinization of dorsal root ganglia neurons through ischemia

Brain and spinal cord (CNS) trauma typically directly kill some neurons leading to permanent neurological deficits. However, they also lead to a number of triggers which in turn frequently kill a vastly larger number of neurons than were killed by the initial insult. The best mechanism for reducing the extent of neurological deficits is to minimize the number of neurons that die immediately due to the trauma, and post-trauma sequelae. Neuroprotection techniques have taken many diverse forms with a breadth too great for a short review. Therefore, this review is focused on the roles of only a small number of neuroprotective agents, with its primary focus being on neuroprotection provided by hypothermia, alone and when combined with the other methods. Included are also recent results involving a novel neuroprotective technique, tested on adult human dorsal root ganglion neurons, comparing the influences of hypothermia and alkalinization singly, providing fourfold and eightfold increases in neuroprotection, respectively, but when combined providing a 26-fold increase in neuroprotection. This combinatorial approach to neuroprotection holds great promise for enhancing the degree of neuroprotection clinically following CNS trauma, leading to the preservation of maximal neurological functions.

Effect of hypothermia therapy after outpatient cardiac arrest due to ventricular fibrillation

BACKGROUND

Several investigators have emphasized the positive effect of hypothermia therapy on patients who have suffered from cardiac arrest. Salvaging patients from circulatory collapse is a pivotal task, but it is unclear whether additional hypothermia can practically contribute to an improvement in the neurological outcome.

METHODS AND RESULTS

Since December 2005, our hospital has been using hypothermia therapy. Forty-six comatose patients after recovery of spontaneous circulation were consecutively enrolled in the present study. Twenty-five of the enrolled patients received hypothermia therapy and 21 did not because they were treated prior to 2005. The time from collapse to spontaneous circulation (P=0.09), the rates of performance of bystander CPR (P=0.370) and presence of a witnessed collapse (P=0.067) were not significantly different between the recovery group (n=28) and the non-recovery group (n=18). The additional hypothermia therapy was an independent predictor of neurological recovery (P=0.005, OR 6.5, 95%CI 1.74-24.27). The recovery rate was significantly higher in patients who received hypothermia therapy (80%) compared to those who did not (38%).

CONCLUSIONS

Hypothermia therapy is very useful for treating patients who have had an out-of-hospital cardiac arrest; it should be induced rapidly and smoothly.

Clinical application of therapeutic hypothermia in stroke

OBJECTIVE

Hypothermia has long been known to be a potent neuroprotectant. In this mini-review, we highlighted clinical experience that hypothermia protects the brain from cerebral injury. We discussed the clinical practice of hypothermia in ischemic stroke.

RESULTS

Multiple factors play a significant role in the mechanisms. Clinical application drew first from two clinical trials with comatose patients after cardiac arrest is attractive. The Australian and European study have led to renewed interest in these patients. More and more evidences bring the insight into its effects on cerebral ischemia. The type of cooling technique to be used, the duration of cooling and speed of rewarming appear to be key factors in determining whether hypothermia is effective in preventing or mitigating neurological injury. Although until now, there are no clear therapeutic standards of the parameters in therapeutic hypothermia, it is well accepted that cooling should be initiated as soon as possible. By combining hypothermia with other neuroprotectants, it may be possible to enhance protective effects, reduce side effects and lengthen the maximum time.

CONCLUSION

In addition to its neuroprotective properties, hypothermia may extend the therapeutic window for other neuroprotective treatment. Thus, combination therapies with neuroprotective, anti-inflammatory and thrombolytic agents are likely to be investigated in the clinical setting in the future.

Ultrasound-enhanced thrombolysis with tPA-loaded echogenic liposomes

BACKGROUND AND PURPOSE

Currently, the only FDA-approved therapy for acute ischemic stroke is the administration of recombinant tissue plasminogen activator (tPA). Echogenic liposomes (ELIP), phospholipid vesicles filled with gas and fluid, can be manufactured to incorporate tPA. Also, transcranial ultrasound-enhanced thrombolysis can increase the recanalization rate in stroke patients. However, there is little data on lytic efficacy of combining ultrasound, echogenic liposomes, and tPA treatment. In this study, we measure the effects of pulsed 120-kHz ultrasound on the lytic efficacy of tPA and tPA-incorporating ELIP (t-ELIP) in an in-vitro human clot model. It is hypothesized that t-ELIP exhibits similar lytic efficacy to that of rt-PA.

METHODS

Blood was drawn from 22 subjects after IRB approval. Clots were made in 20-microL pipettes, and placed in a water tank for microscopic visualization during ultrasound and drug treatment. Clots were exposed to combinations of [tPA]=3.15 microg/ml, [t-ELIP]=3.15 microg/ml, and 120-kHz ultrasound for 30 minutes at 37 degrees C in human plasma. At least 12 clots were used for each treatment. Clot lysis over time was imaged and clot diameter was measured over time, using previously developed imaging analysis algorithms. The fractional clot loss (FCL), which is the decrease in mean clot width at the end of lytic treatment, was used as a measure of lytic efficacy for the various treatment regimens.

RESULTS

The fractional clot loss FCL was 31% (95% CI: 26-37%) and 71% (56-86%) for clots exposed to tPA alone or tPA with 120 kHz ultrasound. Similarly, FCL was 48% (31-64%) and 89% (76-100%) for clots exposed to t-ELIP without or with ultrasound.

CONCLUSIONS

The lytic efficacy of tPA containing echogenic liposomes is comparable to that of tPA alone. The addition of 120 kHz ultrasound significantly enhanced lytic treatment efficacy for both tPA and t-ELIP. Liposomes loaded with tPA may be a useful adjunct in lytic treatment with tPA.

A new technique allowing prolonged temporary cerebral artery occlusion

OBJECT

Clipping of complex cerebral aneurysms often requires temporary vessel occlusion. The risk of stroke, however, increases exponentially with occlusion time. The authors hypothesized that prolonged temporary occlusion might be tolerated if the occluded vessels were perfused with cold physiological saline solution (CPSS). A low-flow perfusion rate would permit surgical manipulation of an aneurysm distal to the occlusion.

METHODS

To test this hypothesis, the authors temporarily occluded the middle cerebral artery (MCA) with an endovascular catheter in 6 rats. Three animals, the treatment group, were perfused with 5-ml CPSS/hour through the occluding endovascular catheter into the MCA, and the other 3 served as an ischemic control group. In both groups, the catheter was removed after 90 minutes of occlusion. The brain temperature was monitored with a stereotactically placed probe in the caudate-putamen in 2 separate experimental groups (11 animals).

RESULTS

Magnetic resonance imaging perfusion scanning during vessel occlusion confirmed similar reduction of cerebral blood flow during MCA occlusion in both the simple-occlusion and perfusion-occlusion groups. Magnetic resonance imaging diffusion scans performed 24 hours after temporary occlusion revealed infarcts in the ischemic control group of 138.3 +/- 28.0 mm(3) versus 9.9 +/- 9.9 mm(3) in the cold saline group (p < 0.005). A focal cooling effect during perfusion with CPSS was demonstrated (p < 0.05).

CONCLUSIONS

Prolonged temporary cerebral vessel occlusion can be tolerated using superselective CPSS perfusion through an occluding endovascular catheter into the ischemic territory. This technique could possibly be applied in neurosurgery practice to the management of complex intracranial aneurysms.

Therapeutic hypothermia for global and focal ischemic brain injury--a cool way to improve neurologic outcomes

BACKGROUND

Therapeutic hypothermia (TH) has been employed as a neuroprotective strategy for a wide array of clinical problems since the late 1940s. Animal studies have determined that the neuroprotective effect of hypothermia is pleiotropic, impacting many steps in both the ischemic cascade and reperfusion injury. Interest in the neuroprotective effects of TH for ischemic brain injury has been resurgent, fueled by both recent positive and negative clinical trials. A review of preclinical and clinical reports on TH in adult patients is provided in this article.

REVIEW SUMMARY

Animal data and several large clinical studies of mild to moderate TH (32 degrees C-34 degrees C) for global cerebral ischemia describe favorable neurologic outcomes, with few adverse effects. However, clinical implementation for global ischemia remains poor. Some animal data support a role for TH in focal cerebral ischemia, if instituted soon after the onset of ischemia, and in the setting of reperfusion. Clinical studies of TH for focal cerebral ischemia have so far been equivocal. The available data suggest that, despite sharing some common components in the ischemic cascade, focal and global cerebral ischemia are pathophysiologically disparate, and may respond to different neuroprotective strategies.

CONCLUSION

TH is a safe, effective neuroprotective strategy for global cerebral ischemia. Because of the neuroprotective efficacy of TH in adult comatose survivors of cardiac arrest, neurologists should advocate the implementation of this strategy. TH for focal ischemia is a promising therapeutic option, but requires more basic and clinical investigation.

The Continued Promise of Neuroprotection for Acute Stroke Treatment

Stroke is the second leading cause of death. However, effective pharmocologic treatment options are still extremely limited and applicable to only a small fraction of patents. The translational failure in finding an effective neuroprotectant for ischemic strokes has generated an active discussion in this field. One focus has been on validating systems for testing neuroprotectants. This review discusses some fundamental issues in experimental stroke that are worthy of further exploration. We begin with a general review of the current status of experimental stroke research and then move on to a discussion of the determining factors and processes that control and differentiate the fate of ischemic ischemic cells and tissue. We propose several strategies of neuroprotection for ischemic strokes with an emphasis on manipulating cellular energy state.

Novel thyroxine derivatives, thyronamine and 3-iodothyronamine, induce transient hypothermia and marked neuroprotection against stroke injury

BACKGROUND AND PURPOSE

Mild hypothermia confers profound neuroprotection in ischemia. We recently discovered 2 natural derivatives of thyroxine, 3-iodothyronamine (T(1)AM) and thyronamine (T(0)AM), that when administered to rodents lower body temperature for several hours without induction of a compensatory homeostatic response. We tested whether T(1)AM- and T(0)AM-induced hypothermia protects against brain injury from experimental stroke.

METHODS

We tested T(1)AM and T(0)AM 1 hour after and 2 days before stroke in a mouse model of focal ischemia. To determine whether T(1)AM and T(0)AM require hypothermia to protect against stroke injury, the induction of hypothermia was prevented.

RESULTS

T(1)AM and T(0)AM administration reduced body temperature from 37 degrees C to 31 degrees C. Mice given T(1)AM or T(0)AM after the ischemic period had significantly smaller infarcts compared with controls. Mice preconditioned with T(1)AM before ischemia displayed significantly smaller infarcts compared with controls. Pre- and postischemia treatments required the induction of hypothermia. T(1)AM and T(0)AM treatment in vitro failed to confer neuroprotection against ischemia.

CONCLUSIONS

T(1)AM and T(0)AM, are potent neuroprotectants in acute stroke and T(1)AM can be used as antecedent treatment to induce neuroprotection against subsequent ischemia. Hypothermia induced by T(1)AM and T(0)AM may underlie neuroprotection. T(1)AM and T(0)AM offer promise as treatments for brain injury.

Guidelines for the Early Management of Adults With Ischemic Stroke

Purpose— Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

Methods— Members of the panel were appointed by the American Heart Association Stroke Council’s Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council’s Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

Results— Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Guidelines for the early management of adults with ischemic stroke: a guideline from the American Heart Association/American Stroke Association Stroke Council, Clinical Cardiology Council, Cardiovascular Radiology and Intervention Council, and the Atherosclerotic Peripheral Vascular Disease and Quality of Care Outcomes in Research Interdisciplinary Working Groups: the American Academy of Neurology affirms the value of this guideline as an educational tool for neurologists

PURPOSE

Our goal is to provide an overview of the current evidence about components of the evaluation and treatment of adults with acute ischemic stroke. The intended audience is physicians and other emergency healthcare providers who treat patients within the first 48 hours after stroke. In addition, information for healthcare policy makers is included.

METHODS

Members of the panel were appointed by the American Heart Association Stroke Council's Scientific Statement Oversight Committee and represented different areas of expertise. The panel reviewed the relevant literature with an emphasis on reports published since 2003 and used the American Heart Association Stroke Council's Levels of Evidence grading algorithm to rate the evidence and to make recommendations. After approval of the statement by the panel, it underwent peer review and approval by the American Heart Association Science Advisory and Coordinating Committee. It is intended that this guideline be fully updated in 3 years.

RESULTS

Management of patients with acute ischemic stroke remains multifaceted and includes several aspects of care that have not been tested in clinical trials. This statement includes recommendations for management from the first contact by emergency medical services personnel through initial admission to the hospital. Intravenous administration of recombinant tissue plasminogen activator remains the most beneficial proven intervention for emergency treatment of stroke. Several interventions, including intra-arterial administration of thrombolytic agents and mechanical interventions, show promise. Because many of the recommendations are based on limited data, additional research on treatment of acute ischemic stroke is needed.

Estimation of the hypothermic component in neuroprotection provided by cannabinoids following cerebral ischemia

Cannabinoids have neuroprotective potentials, and the expression of endocannabinoids as well as cannabinoid receptors is induced after cerebral ischemia. They also induce hypothermia by lowering the hypothalamic set point. We have estimated the significance of such hypothermia in ischemic neuroprotection following systemic administration of WIN 55,212-2, a synthetic cannabinoid receptor agonist. Results showed that WIN 55,212-2 significantly reduced infarct volumes of rats subjected to focal cerebral ischemia (middle cerebral artery occlusion) and significantly decreased ischemic CA1 damage in rats subjected to global cerebral ischemia (two-vessel occlusion). A significant (approximately 50%) part of this neuroprotection was provided by WIN 55,212-2 induced hypothermia (33.7+/-1.1 degrees C/34.9+/-1.6 degrees C), because prevention of hypothermia by maintaining body core temperatures between 37.0 and 38.0 degrees C dissolved the neuroprotective effect into a hypothermic component and an unidentified component. Finally, the ability of WIN 55,212-2 to reduce levels of the proinflammatory cytokine IFNgamma in the infarcted hemisphere of rats subjected to focal cerebral ischemia required hypothermia. For the cannabinoid WIN 55,212-2, we have isolated and directly demonstrated that hypothermia is only part of, although significant, cannabinoid mediated neuroprotection in both global and focal cerebral ischemia. We conclude that cannabinoids are reliable candidates for drug-induced hypothermia and neuroprotection. These neuroprotective effects of cannabinoids could provide the basis for potential therapeutic uses of cannabinoids and/or endocannabinoids in stroke.

Apoptosis: Future Targets for Neuroprotective Strategies

Focal permanent or transient cerebral artery occlusion produces massive cell death in the central core of the infarction, whereas in the peripheral zone (penumbra) nerve cells are subjected to various determining survival and death signals. Cell death in the core of the infarction and in the adult brain is usually considered a passive phenomenon, although events largely depend on the partial or complete disruption of crucial metabolic pathways. Cell death in the penumbra is currently considered an active process largely dependent on the activation of cell death programs leading to apoptosis. Yet cell death in the penumbra includes apoptosis, necrosis, intermediate and other forms of cell death. A rather simplistic view implies poor prospects regarding cell survival in the core of the infarction and therapeutic expectations in the control of cell death and cell survival in the penumbra. However, the capacity for neuroprotection depends on multiple factors, primarily the use of the appropriate agent, at the appropriate time and during the appropriate interval. Understanding the mechanisms commanding cell death and survival area is as important as delimiting the therapeutic time window and the facility of a drug to effectively impact on specific targets. Moreover, the detrimental effects of homeostasis and the activation of multiple pathways with opposing signals following ischemic stroke indicate that better outcome probably does not depend on a single compound but on several drugs acting in combination at the optimal time in a particular patient.

Neuroprotective effect of recombinant human granulocyte colony-stimulating factor in transient focal ischemia of mice

Cerebral ischemia induces the expression of several growth factors and cytokines, which protect neurons against ischemic insults. Recent studies showed that granulocyte colony-stimulating factor (G-CSF) has a neuroprotective effect through the signaling pathway for the antiapoptotic cascade. The current study was designed to assess the neuroprotective mechanisms of G-CSF in ischemia/reperfusion injury using bone marrow chimera mice known to express enhanced green fluorescent protein (EGFP). Mice were subjected to ischemia/reperfusion and divided into two groups: those treated with G-CSF (G-CSF group) and vehicle (control group) (n = 35 in each group). Immunohistochemistry and immunoblotting for antiapoptotic protein, nitrotyrosine, and inducible nitrate oxide synthase (iNOS) were performed. G-CSF significantly reduced stroke volume (34%, P < 0.006). G-CSF upregulated Stat3, pStat3, and Bcl-2 (P < 0.05), and suppressed iNOS and nitrotyrosine expression. In EGFP chimera mice, G-CSF decreased the migration of Iba-1/EGFP-positive bone marrow-derived monocytes/macrophages and increased intrinsic microglia/macrophages at ischemic penumbra (P < 0.05), suggesting that bone marrow-derived monocytes/macrophages are not involved in G-CSF-induced reduction of ischemic injury size. Our study indicated that G-CSF exerts a neuroprotective effect through the direct activation of antiapoptotic pathway, and suggested that G-CSF is important for expansion of the therapeutic time window in patients with cerebral ischemia.

Delayed profound local brain hypothermia markedly reduces interleukin-1beta gene expression and vasogenic edema development in a porcine model of intracerebral hemorrhage

White matter (lobar) intracerebral hemorrhage (ICH) can cause edema-related deaths and life-long morbidity. In our porcine model, ICH induces oxidative stress, acute interstitial and delayed vasogenic edema, and up-regulates interleukin-1beta (IL-1beta), a proinflammatory cytokine-linked to blood-brain barrier (BBB) opening. In brain injury models, hypothermia reduces inflammatory cytokine production and protects the BBB. Clinically, however, hypothermia for stroke treatment using surface and systemic approaches can be challenging. We tested the hypothesis that an alternative approach, i.e., local brain cooling using the ChillerPad System, would reduce IL-1beta gene expression and vasogenic edema development even if initiated several hours after ICH. We infused autologous whole blood (3.0 mL) into the frontal hemispheric white matter of 20 kg pentobarbital-anesthetized pigs. At 3 hours post-ICH, we performed a craniotomy for epidural placement of the ChillerPad. Chilled saline was then circulated through the pad for 12 hours to induce profound local hypothermia (14 degrees C brain surface temperature). We froze brains in situ at 16 hours after ICH induction, sampled perihematomal white matter, extracted RNA, and performed real-time RT-PCR. Local brain cooling markedly reduced both IL-1beta RNA levels and vasogenic edema. These robust results support the potential for local brain cooling to protect the BBB and reduce injury after ICH.

A rat model of smoke inhalation injury: Influence of combustion smoke on gene expression in the brain

Acute smoke inhalation causes death and injury in victims of home and industrial fires as well as victims of combat situations. The lethal factors in combustion smoke inhalation are toxic gases and oxygen deficiency, with carbon monoxide (CO) as a primary cause of death. In survivors, inhalation of smoke can result in severe immediate and delayed neuropathologies. To gain insight into the progression of molecular events contributing to smoke inhalation sequelae in the brain, we developed a smoke inhalation rat model and conducted a genome-wide analysis of gene expression. Microarray analysis revealed a modified brain transcriptome with changes peaking at 24 h and subsiding within 7 days post-smoke. Overall, smoke inhalation down regulated genes associated with synaptic function, neurotransmission, and neurotrophic support, and upregulated genes associated with stress responses, including nitric oxide synthesis, antioxidant defenses, proteolysis, inflammatory response, and glial activation. Notably, among the affected genes, many have been previously implicated in other types of brain injury, demonstrating the usefulness of microarrays for analysis of changes in gene expression in complex insults. In accord with previously described modulations of nitric oxide homeostasis in CO poisoning, microarray analysis revealed increased brain expression of nitric oxide synthase (NOS) and NOS ligand after inhalation of smoke. Furthermore, immunostaining showed significant elevations in perivascular NOS and in protein nitration, corroborating the involvement of nitric oxide perturbations in post-smoke sequelae in the brain. Thus, the new rat model, in combination with microarray analyses, affords insight into the complex molecular pathophysiology of smoke inhalation in the brain.

Local brain hypothermia for neuroprotection in stroke treatment and aneurysm repair

Hypothermia is well known to provide neuroprotection following various brain insults in experimental animals. Two recently completed clinical trials of whole body hypothermia in out-of-hospital cardiac arrest patients' demonstrated significantly improved survival rates and neurologic outcomes. These results provide new excitement and encouragement for clinical application of hypothermia in cerebrovascular disease. However, the intensive care challenges and adverse events (e.g. prolonged times to target temperatures, shivering and sedation, pneumonia) during the management of hypothermia, dampen enthusiasm for widespread application especially in elderly stroke patients. In this manuscript, we review recent hypothermia trials for stroke. We describe an alternate approach, i.e. local brain cooling, and discuss this new technique with reference to the extensive literature on the marked efficacy of hypothermia. We describe a new technology, the ChillerPad(TM) and ChillerStrip(TM) Systems developed by Seacoast Technologies, Inc. (Portsmouth, NH, USA). The latter device has received FDA approval and will be employed in a trial of local hypothermia for cerebral aneurysm repair. We present our experimental findings that profound local hypothermia does not damage cortical neurons. We also report that local hypothermia protects the blood-brain barrier and markedly reduces vasogenic edema development in an experimental intracerebral hemorrhage model. Lastly, we review potential mechanisms through which hypothermia provides blood-brain barrier protection and reduces edema formation. Clearly, hypothermia has a bright future for cerebrovascular disease treatment if brain cooling can be delivered in a manner that does not compromise the patient or the neurosurgical and intensive care settings. Local brain cooling may be just that new treatment approach.

Effect of mild hypothermia on the thrombolytic efficacy of 120 kHz ultrasound enhanced thrombolysis in an in-vitro human clot model

INTRODUCTION

Ischemic stroke causes substantial death and disability. Currently, recombinant tissue plasminogen activator (rt-PA) is the only FDA approved therapy. However, there are dangerous side effects and therapy must start within 3 h of onset. Therefore, there is interest in adjunctive therapies such as ultrasound enhanced thrombolysis (UET) and hypothermia. Recently, transcranial ultrasound during rt-PA therapy was shown to improve vessel recanalization. Also hypothermia (32-34 degrees C) was shown to be safe and possibly improve outcome. This suggests combining UET and hypothermia to treat ischemic stroke. Little is known about the effects of hypothermia on UET, and in-vitro rt-PA efficacy is reduced for T<37 degrees C. Here, the effects of hypothermia on UET in in-vitro human clot are presented. It is hypothesized that UET efficacy at 33 degrees C is less than at 37 degrees C.

MATERIALS AND METHODS

Whole blood was drawn from volunteers. Clots were made, incubated at 37 degrees C and aged for 2 days for maximal lytic resistance. Clots were exposed to human fresh-frozen plasma (control), hFFP and rt-PA ([rt-PA]=3.2 microg/ml), hFFP and 120 kHz ultrasound (US), and hFFP, rt-PA and ultrasound (UET) at 33 degrees C and 37 degrees C. Clot percent mass loss (Deltam) was measured to determine thrombolytic efficacy. Data were analyzed using mixed-model analysis of variance.

RESULTS AND CONCLUSIONS

US and rt-PA independently increased Deltam (3.5+/-1.0% and 5.1+/-0.9% respectively; p<0.01) over control. UET increased Deltam an additional 8.1+/-1.3% (p=0.026) The effect of temperature on Deltam (-1.6+/-0.7%) was not significant (p=0.09). Hypothermia did not reduce UET efficacy in this in-vitro model.