Advances in neuroprotective strategies: potential therapies for intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is associated with higher mortality and morbidity than any other form of stroke. However, there currently are no treatments proven to improve outcomes after ICH, and therefore, new effective therapies are urgently needed. Growing insight into ICH pathophysiology has led to the development of neuroprotective strategies that aim to improve the outcome through reduction of secondary pathologic processes. Many neuroprotectants target molecules or pathways involved in hematoma degradation, inflammation or apoptosis, and have demonstrated potential clinical benefits in experimental settings. We extensively reviewed the current understanding of ICH pathophysiology as well as promising experimental neuroprotective agents with particular focus on their mechanisms of action. Continued advances in ICH knowledge, increased understanding of neuroprotective mechanisms, and improvement in the ability to modulate molecular and pathologic events with multitargeting agents will lead to successful clinical trials and bench-to-bedside translation of neuroprotective strategies.     

Molecular pathophysiology of cerebral hemorrhage: secondary brain injury

Intracerebral hemorrhage (ICH) is an often fatal type of stroke that kills approximately 30,000 people annually in the United States. If the patient survives the ictus, then the resulting hematoma within brain parenchyma triggers a series of adverse events causing secondary insults and severe neurological deficits. This article discusses selected aspects of secondary brain injury after ICH and outlines key mechanisms associated with hematoma toxicity, oxidative stress, and inflammation. Finally, this review discusses the relevance of hematoma resolution processes as a target for ICH therapy and presents potential clinically relevant molecular targets that could be harnessed to treat secondary injury associated with ICH injury.     

Intranasal insulin ameliorates neurological impairment after intracerebral hemorrhage in mice

In Alzheimer’s disease and ischemic stroke,intranasal insulin can act as a neuroprotective agent.However,whether intranasal insulin has a neuroprotective effect in intracerebral hemorrhage and its potential mechanisms remain poorly understood.In this study,a mouse model of autologous blood-induced intracerebral hemorrhage was treated with 0.5,1,or 2 IU insulin via intranasal delivery,twice per day,until 24 or 72 hours after surgery.Compared with saline treatment,1 IU intranasal insulin treatment significantly reduced hematoma volume and brain edema after cerebral hemorrhage,decreased blood-brain barrier permeability and neuronal degeneration damage,reduced neurobehavioral deficits,and improved the survival rate of mice.Expression levels of p-AKT and p-GSK3βwere significantly increased in the perihematoma tissues after intranasal insulin therapy.Our findings suggest that intranasal insulin therapy can protect the neurological function of mice after intracerebral hemorrhage through the AKT/GSK3βsignaling pathway.The study was approved by the Ethics Committee of the North Sichuan Medical College of China(approval No.NSMC(A)2019(01))on January 7,2019.     

Frameless stereotactic aspiration and thrombolysis of deep intracerebral hemorrhage is associated with reduced levels of extracellular cerebral glutamate and unchanged lactate pyruvate ratios

Introduction  

Intracerebral hemorrhage (ICH) is a devastating form of stroke commonly resulting in severe morbidity and high mortality. Secondary brain injury often occurs in the days following the initial hemorrhage and is associated with significant neurological deterioration. The neurochemistry associated with secondary injury is poorly understood The purpose of this study is to characterize the neurochemical changes, in perihematomal tissue during frameless minimally invasive evacuation of spontaneous hematomas     

Protective role of tuftsin fragment 1-3 in an animal model of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) causes morbidity and mortality and commonly follows the reperfusion after an ischemic event. Tissue plasminogen activator (tPA), a fibrinolytic serine protease, is routinely given for the treatment of stroke. However, tPA also can promote neuronal death, suggesting that caution should be exercised when using it. Furthermore, tPA upon brain injury mediates microglial activation and modulates neuronal survival. To investigate the role of tPA and microglia during brain hemorrhage, we induced experimentally ICH by intracerebral injection of collagenase. Seven days after the introduction of ICH, it persisted in tPA-deficient (tPA(-/-)) mice but is drastically reduced in size in wild-type mice. Three weeks after ICH, there are still red blood cells in tPA(-/-) but not in wild-type animals. Activated microglia persist around the injury site. When microglial activation is inhibited by tuftsin fragment 1-3 macrophage/microglial inhibitory factor (MIF), the stroke injury volume is significantly reduced, and the neurobehavioral deficits exhibited by the mice are improved. Our results suggest that endogenous tPA assists in the clearance of intracerebral hemorrhage, presumably by affecting microglial activation, and MIF could be a valuable neuroprotective agent for the treatment of ICH.     

Annexin A1 attenuates neuroinflammation through FPR2/p38/COX-2 pathway after intracerebral hemorrhage in male mice

Spontaneous intracerebral hemorrhage (ICH) is the deadliest stroke subtype and neuroinflammation is a critical component of the pathogenesis following ICH. Annexin A1-FPR2 signaling has been shown to play a protective role in animal stroke models. This study aimed to assess whether Annexin A1 attenuated neuroinflammation and brain edema after ICH and investigate the underlying mechanisms. Male CD-1 mice were subjected to collagenase-induced ICH. Annexin A1 was administered at 0.5 hr after ICH. Brain water content measurement, short-term and long-term neurobehavioral tests, Western blot and immnunofluorescence were performed. Results showed that Annexin A1 effectively attenuated brain edema, improved short-term neurological function and ameliorated microglia activation after ICH. Annexin A1 also improved memory function at 28 days after ICH. However, these beneficial effects were abolished with the administration of FPR2 antagonist Boc-2. Furthermore, AnxA1/FPR2 signaling may confer protective effects via inhibiting p38-associated inflammatory cascade. Our study demonstrated that Annexin A1/FPR2/p38 signaling pathway played an important role in attenuating neuroinflammation after ICH and that Annexin A1 could be a potential therapeutic strategy for ICH patients.     

Lack of Aquaporin 9 Reduces Brain Angiogenesis and Exaggerates Neuronal Loss in the Hippocampus Following Intracranial Hemorrhage in Mice

Intracranial hemorrhage (ICH) is a common subtype of stroke with high morbidity and mortality. However, few clinical therapies that can reduce ICH-induced brain injury and promote the recovery outcome in ICH patients are available to improve the recovery from ICH. Given that aquaporin 9 (AQP9) plays a critical role in brain edema after ischemic stroke and traumatic brain injury and is involved in the regulation of angiogenesis, we examined the role of AQP9 in preventing neuronal loss and in neovascularization in the dorsal hippocampus (DH) after ICH. We found that intra-DH collagenase-induced ICH increased AQP9 protein levels in the hippocampus, which was associated with behavioral deficits in wild-type mice. However, ICH robustly enhanced behavioral deficits in the AQP9-null mice, as compared with the wild-type mice. Furthermore, neovascularization and proliferation of brain microvascular endothelial cells following ICH were severely impaired in the AQP9-null mice, as compared with the wild-type mice. Finally, hippocampal neuronal loss following ICH became severer in the AQP9-null mice, relative to the wild-type mice. Taken together, our findings indicated that AQP9 in the brain may play a compensatory role in response to ICH, promote brain angiogenesis, and prevent subsequent neuronal death, thus preventing the deterioration of neurological outcome of ICH.     

Ultra-early hemostatic therapy for primary intracerebral hemorrhage: a review

Stroke is a major health problem worldwide, causing high morbidity and mortality. Intracerebral hemorrhage (ICH) accounts for 10% of stroke cases in the United States and Europe and up to 30% in Asian populations. Intracerebral hemorrhage is less treatable than other forms of stroke and causes higher morbidity and disability. Data suggest that early hematoma growth is the principal cause of early neurological deterioration after ICH. Prospective and retrospective studies indicate that early hematoma growth occurs in 18-38% of patients scanned within three hours of ICH onset, and that hematoma volume is an important predictor of 30-day mortality. Recombinant activated factor VII (rFVIIa, NovoSeven), a powerful initiator of hemostasis, is approved for the treatment of bleeding in patients with hemophilia and inhibitors, and can also promote hemostasis in patients with normal coagulation. A Phase-IIB randomized, double-blind, placebo-controlled, dose-ranging trial has been conducted in 399 patients with ICH to investigate the potential of rFVIIa as an ultra-early hemostatic therapy. A reduction in hematoma growth in non-coagulopathic ICH patients was evident with reduced mortality and improved clinical outcome at three months. The significance of these findings for neurocritical care is discussed.     

Therapeutic hypothermia in experimental models of focal and global cerebral ischemia and intracerebral hemorrhage

Experimental evidence shows that therapeutic hypothermia (TH) protects the brain from cerebral injury in multiple ways. In different models of focal and global cerebral ischemia, mild-to-moderate hypothermia reduces mortality and neuronal injury and improves neurological outcome. In models of experimental intracerebral hemorrhage (ICH), TH reduces edema formation but does not show consistent benefi cial effects on functional outcome parameters. However, the number of studies of hypothermia on ICH is still limited. TH is most effective when applied before or during the ischemic event, and its neuroprotective properties vary according to species, strains and the model of ischemia used. Intrinsic changes in body and brain temperature frequently occur in experimental models of focal and global cerebral ischemia, and may have infl uenced studies on other neuroprotectants. This might be one explanation for the failure of a large amount of translational clinical neuroprotective trials. Hypothermia is the only neuroprotective therapeutic agent for cerebral ischemia that has successfully managed the transfer from bench to bedside, and it is an approved therapy for patients after cardiac arrest and children with hypoxic-ischemic encephalopathy. However, the implementation of hypothermia in the treatment of stroke patients is still far from routine clinical practice. In this article, the authors describe the development of TH in different models of focal and global cerebral ischemia, point out why hypothermia is so efficient in experimental cerebral ischemia, explain why temperature regulation is essential for further neuroprotective studies and discuss why TH for acute ischemic stroke still remains a promising but controversial therapeutic option.     

Neuroprotective effect of minocycline against acute brain injury in clinical practice: A systematic review

Acute brain injury is a leading cause of morbidity and mortality worldwide. The term is inclusive of traumatic brain injury, cerebral ischemia, subarachnoid hemorrhage, and intracerebral hemorrhage. Current pharmacologic treatments have had minimal effect on improving neurological outcomes leading to a significant interest in the development neuroprotective agents. Minocycline is a second-generation tetracycline with high blood brain barrier penetrance due to its lipophilic properties. It functions across multiple molecular pathways involved in secondary-injury cascades following acute brain injury. Animal model studies suggest that minocycline might lead to improved neurologic outcomes, but few such trials exist in humans. Clinical investigations have been limited to small randomized trials in ischemic stroke patients which have not demonstrated a clear advantage in neurologic outcomes, but also have not been sufficiently powered to draw definitive conclusions. The potential neuroprotective effect of minocycline in the setting of traumatic brain injury, subarachnoid hemorrhage, and intracerebral hemorrhage have all been limited to pilot studies with phase II/III investigations pending. The authors aim to synthesize what is currently known about minocycline as a neuroprotective agent against acute brain injury in humans.     

Magnesium:pathophysiological mechanisms and potential therapeutic roles in intracerebral hemorrhage

Intracerebral hemorrhage(ICH) remains the second-most common form of stroke with high morbidity and mortality.ICH can be divided into two pathophysiological stages:an acute primary phase,including hematoma volume expansion,and a subacute secondary phase consisting of blood-brain barrier disruption and perihematomal edema expansion.To date,all major trials for ICH have targeted the primary phase with therapies designed to reduce hematoma expansion through blood pressure control,surgical evacuation,and hemostasis.However,none of these trials has resulted in improved clinical outcomes.Magnesium is a ubiquitous element that also plays roles in vasodilation,hemostasis,and blood-brain barrier preservation.Animal models have highlighted potential therapeutic roles for magnesium in neurological diseases specifically targeting these pathophysiological mechanisms.Retrospective studies have also demonstrated inverse associations between admission magnesium levels and hematoma volume,hematoma expansion,and clinical outcome in patients with ICH.These associations,coupled with the multifactorial role of magnesium that targets both primary and secondary phases of ICH,suggest that magnesium may be a viable target of study in future ICH studies.     

Neuroinflammation after traumatic brain injury: Opportunities for therapeutic intervention

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

Preclinical and clinical evidence of IGF-1 as a prognostic marker and acute intervention with ischemic stroke

Ischemic strokes are highly prevalent in the elderly population and are a leading cause of mortality and morbidity worldwide. The risk of ischemic stroke increases in advanced age, corresponding with a noted decrease in circulating insulin growth factor-1 (IGF-1). IGF-1 is a known neuroprotectant involved in embryonic development, neurogenesis, neurotransmission, cognition, and lifespan. Clinically, several studies have shown that reduced levels of IGF-1 correlate with increased mortality rate, poorer functional outcomes, and increased morbidities following an ischemic stroke. In animal models of ischemia, administering exogenous IGF-1 using various routes of administration (intranasal, intravenous, subcutaneous, or topical) at various time points prior to and following insult attenuates neurological damage and accompanying behavioral changes caused by ischemia. However, there are some contrasting findings in select clinical and preclinical studies. This review discusses the role of IGF-1 as a determinant factor of ischemic stroke outcomes, both within the clinical settings and preclinical animal models. Furthermore, the review provides insight on the role of IGF-1 in mechanisms and cellular processes that contribute to stroke damage.     

Genetic deletion of the prostaglandin E2 E prostanoid receptor subtype 3 improves anatomical and functional outcomes after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) is a stroke subtype associated with high mortality and morbidity. Following ICH, excitotoxicity and inflammation significantly contribute to secondary brain injury and poor outcomes. Prostaglandin E₂ (PGE₂) levels rise locally with insult to the nervous system, and PGE₂ is known to modulate these processes mainly through its E prostanoid (EP) receptors, EP1‐4. EP receptor subtype 3 (EP3) is the most abundant EP receptor in the brain and we have previously shown that signaling through the PGE₂–EP3 axis exacerbates excitotoxicity and ischemic stroke outcomes. This study aimed to investigate the contribution of this pathway in modulating anatomical outcomes and functional recovery following ICH. Genetic deletion of EP3 resulted in 48.2 ± 7.3% less ICH‐induced brain injury (P < 0.005) and improved functional recovery (P < 0.05), as identified by neurological deficit scoring. To start investigating the mechanisms involved in neuroprotection with impaired PGE₂–EP3 signaling, histological staining was performed to evaluate blood and ferric iron accumulation, neuroinflammation, blood–brain barrier dysfunction, and peripheral neutrophil infiltration. After ICH, EP3 knockout mice demonstrated 49.5 ± 8.8% and 42.8 ± 13.1% less blood (P < 0.01) and ferric iron (P < 0.05), respectively. Furthermore, EP3 knockout mice had significantly reduced astrogliosis, microglial activation, blood–brain barrier breakdown, and neutrophil infiltration. Collectively, these results suggest an injurious role for the PGE₂–EP3 signaling axis in modulating brain injury, inflammation, and neurological functional recovery after ICH. Modulation of the PGE₂–EP3 signaling axis may represent a putative therapeutic avenue for the treatment of ICH.     

Aspects of intracerebral hematomas--an update

Background – In Norway, there are approximately 16000 strokes each year and 15% of these are caused by intracerebral hematomas. Intracerebral hemorrhage (ICH) results from the rupture of blood vessels within the brain parenchyma. ICH occurs as a complication of several diseases, the most prevalent of which is chronic hypertension. When hemorrhage develops in the absence of a pre‐existing vascular malformation or brain parenchymal lesion, it is denoted primary ICH. Secondary ICH refers to hemorrhage complicating a pre‐existing lesion. Primary ICH is the most common type of hemorrhagic stroke, accounting for approximately 10% of all strokes. Despite aggressive management strategies, the 30‐day mortality remains high, at almost 50%, with the majority of deaths occurring within the first 2 days. At 6 months, only 20–30% achieve independent status. Material and methods – This article is based on clinical experience, modern therapeutic guidelines for the treatment of intracerebral hematomas and up‐to‐date medical literature found in Medline. The article discusses the pathophysiology, clinical aspects, treatment, and the prognosis of intracerebral hematomas. Results and discussion – Advances in diagnosis, prognosis, pathophysiology, and treatment over the past few decades have significantly advanced our knowledge of ICH; however, much work still needs to be carried out. Future genetic and epidemiologic studies will help identify at‐risk populations and hopefully allow for primary prevention. Randomized controlled studies focusing on novel therapeutics should help to minimize secondary injury and hopefully improve morbidity and mortality.     

Experimental intracerebral hemorrhage: avoiding pitfalls in translational research

Intracerebral hemorrhage (ICH) has the highest mortality of all stroke subtypes, yet treatments are mainly limited to supportive management, and surgery remains controversial. Despite significant advances in our understanding of ICH pathophysiology, we still lack preclinical models that accurately replicate the underlying mechanisms of injury. Current experimental ICH models (including autologous blood and collagenase injection) simulate different aspects of ICH-mediated injury but lack some features of the clinical condition. Newly developed models, notably hypertension- and oral anticoagulant therapy-associated ICH models, offer added benefits but further study is needed to fully validate them. Here, we describe and discuss current approaches to experimental ICH, with suggestions for changes in how this condition is studied in the laboratory. Although advances in imaging over the past few decades have allowed greater insight into clinical ICH, there remains an important role for experimental models in furthering our understanding of the basic pathophysiologic processes underlying ICH, provided limitations of animal models are borne in mind. Owing to differences in existing models and the failed translation of benefits in experimental ICH to clinical practice, putative neuroprotectants should be trialed in multiple models using both histological and functional outcomes until a more accurate model of ICH is developed.     

脑出血后继发性脑损伤的机制与治疗

脑出血具有高发病率和高死亡率的特点。近年研究表明，脑出血产生的继发性脑损伤机 制主要涉及凝血酶诱导、红细胞裂解、毒性反应、氧化损伤和炎症反应等多个方面。根据不同的损 伤机制，应运而生了多种脑出血的治疗策略，但是否能成功应用于临床还有待进一步研究。本文对脑 出血后继发性损伤的潜在机制和新兴治疗方法进行了综述。