Medical therapy for intracerebral hematoma with the gamma-aminobutyric acid-A agonist muscimol

A Multi-Model Pipeline for Translational Intracerebral Haemorrhage Research

Apart from acute and chronic blood pressure lowering, we have no specific medications to prevent intracerebral haemorrhage (ICH) or improve outcomes once bleeding has occurred. One reason for this may be related to particular limitations associated with the current pre-clinical models of ICH, leading to a failure to translate into the clinic. It would seem that a breakdown in the 'drug development pipeline' currently exists for translational ICH research which needs to be urgently addressed. Here, we review the most commonly used pre-clinical models of ICH and discuss their advantages and disadvantages in the context of translational studies. We propose that to increase our chances of successfully identifying new therapeutics for ICH, a bi-directional, 2- or 3-pronged approach using more than one model species/system could be useful for confirming key pre-clinical observations. Furthermore, we highlight that post-mortem/ex-vivo ICH patient material is a precious and underused resource which could play an essential role in the verification of experimental results prior to consideration for further clinical investigation. Embracing multidisciplinary collaboration between pre-clinical and clinical ICH research groups will be essential to ensure the success of this type of approach in the future.

The role of hemorrhage following spinal-cord injury

Spinal-cord injury is characterized by primary damage as a direct consequence of mechanical insult, and secondary damage that is partly due to the acute inflammatory response. The extent of any hemorrhage within the injured cord is also known to be associated with the formation of intraparenchymal cavities and has been anecdotally linked to secondary damage. This study was designed to examine the contribution of blood components to the outcome of spinal-cord injury. We stereotaxically microinjected collagenase, which causes localized bleeding, into the spinal cord to model the hemorrhage associated with spinal cord injury in the absence of significant mechanical trauma. Tissue damage was observed at the collagenase injection site over time, and was associated with localized disruption of the blood-spinal-cord barrier, neuronal cell death, and the recruitment of leukocytes. The magnitude of the bleed was related to neutrophil mobilization. Interestingly, the collagenase-induced injury also provoked extended axonal damage. With this model, the down-stream effects of hemorrhage are easily discernible, and the impact of treatment strategies for spinal-cord injury on hemorrhage-related injury can be evaluated.

Treatment of intracerebral hemorrhage in animal models: meta-analysis

OBJECTIVE

Interventions that improve functional outcome after acute intracerebral hemorrhage (ICH) in animals might benefit humans. Therefore, we systematically reviewed the literature to find studies of nonsurgical treatments tested in animal models of ICH.

METHODS

In July 2009 we searched Ovid Medline (from 1950), Embase (from 1980), and ISI Web of Knowledge (from 1969) for controlled animal studies of nonsurgical interventions given after the induction of ICH that reported neurobehavioral outcome. We assessed study quality and performed meta-analysis using a weighted mean difference random effects model.

RESULTS

Of 13,343 publications, 88 controlled studies described the effects of 64 different medical interventions (given a median of 2 hours after ICH induction) on 38 different neurobehavioral scales in 2,616 treated or control animals (median 14 rodents per study). Twenty-seven (31%) studies randomized treatment allocation, and 7 (8%) reported allocation concealment; these studies had significantly smaller effect sizes than those without these attributes (p < 0.001). Of 64 interventions stem cells, calcium channel blockers, anti-inflammatory drugs, iron chelators, and estrogens improved both structural outcomes and neurobehavioral scores in >1 study. Meta-regression revealed that together, structural outcome and the intervention used accounted for 65% of the observed heterogeneity in neurobehavioral score (p < 0.001, adjusted r(2) = 0.65).

INTERPRETATION

Further animal studies of the interventions that we found to improve both functional and structural outcomes in animals, using better experimental designs, could target efforts to translate effective treatments for ICH in animals into randomized controlled trials in humans.

Vascular Dysfunction in Brain Hemorrhage: Translational Pathways to Developing New Treatments from Old Targets

Hemorrhagic stroke which is a form of stroke that affects 20% of all stroke patients is a devastating condition for which new treatments must be developed. Current treatment methods are quite insufficient to reduce long term morbidity and high mortality rate, up to 50%, associated with bleeding into critical brain structures, into ventricular spaces and within the subarachnoid space. During the last 10-15 years, significant advances in the understanding of important mechanisms that contribute to cell death and clinical deficits have been made. The most important observations revolve around a key set of basic mechanisms that are altered in brain bleeding models, including activation of membrane metalloproteinases, oxidative stress and both inflammatory and coagulation pathways. Moreover, it is now becoming apparent that brain hemorrhage can activate the ischemic stroke cascade in neurons, glial cells and the vascular compartment. The activation of multiple pathways allows comes the opportunity to intervene pharmacologically using monotherapy or combination therapy. Ultimately, combination therapy or pleiotropic compounds with multi-target activities should prove to be more efficacious than any single therapy alone. This article provides a comprehensive look at possible targets for small molecule intervention as well as some new approaches that result in metabolic down-regulation or inhibition of multiple pathways simultaneously.

Additive neuroprotection of GABA A and GABA B receptor agonists in cerebral ischemic injury via PI-3K/Akt pathway inhibiting the ASK1-JNK cascade

Co-activation of GABA A and GABA B receptors results in neuroprotection during in vitro ischemia. However, it is unclear whether this mode of action is responsible for its neuroprotective effects in animal models of ischemia in vivo, and the precise mechanisms are also unknown. This study compared the neuroprotective efficacies of muscimol, a GABA A receptor agonist, and a GABA B receptor agonist baclofen in rat brain ischemia. The additive neuroprotection could be obtained in the hippocampal CA1 pyramidal cells prominently when muscimol and baclofen were co-applied. In particular, our study showed that co-activation of GABA A and GABA B receptors could strongly increase Akt activation and inhibit ASK1 activation by phosphorylation of serine 83 of ASK1. PI-3K inhibitor LY294002 reversed the increasing Akt activation and ASK1 (S83) phosphorylation. Moreover, MKK4/MKK7-JNK signaling activation was inhibited during ischemia/reperfusion (I/R) by co-treatment of muscimol with baclofen. JNK substrate, Bcl-2 and c-jun phosphorylation were also attenuated. Our results indicated that co-activation of GABA A receptor and GABA B receptor exerted neuroprotective effect via PI-3K/Akt pathway, which could inhibit the ASK1-c-Jun N-terminal protein kinase (JNK) cascade.

A mouse model of intracerebral hemorrhage using autologous blood infusion

The development of controllable and reproducible animal models of intracerebral hemorrhage (ICH) is essential for the systematic study of the pathophysiology and treatment of hemorrhagic stroke. In recent years, we have used a modified version of a murine ICH model to inject blood into mouse basal ganglia. According to our protocol, autologous blood is stereotactically infused in two stages into the right striatum to mimic the natural events of hemorrhagic stroke. Following ICH induction, animals demonstrate reproducible hematomas, brain edema formation and marked neurological deficits. Our technique has proven to be a reliable and reproducible means of creating ICH in mice in a number of acute and chronic studies. We believe that our model will serve as an ideal paradigm for investigating the complex pathophysiology of hemorrhagic stroke. The protocol for establishing this model takes about 2 h.

Advances in hemorrhagic stroke therapy: conventional and novel approaches

Treatments for spontaneous intracerebral, thrombolytic-induced and intraventricular hemorrhages (IVH) are still at the preclinical or early clinical investigational stages. There has been some renewed interest in the use of surgical evacuation surgery or thrombolytics to remove hematomas, but these techniques can be used only for specific types of brain bleeding. The STICH (Surgical Trial in Intracerebral Haemorrhage) clinical trials should provide some insight into the potential for such techniques to counteract hematoma-induced damage and subsequently, morbidity and mortality. More recently, clinical trials (ATACH [Antihypertensive Treatment in Acute Cerebral Hemorrhage] and INTERACT [Intensive Blood Pressure Reduction in Acute Cerebral Hemorrhage Trial]) have begun testing whether or not regulating blood pressure affects the well-being of hemorrhage patients, but the findings thus far have not conclusively demonstrated a positive result. More promising trials, such as the early stage CHANT (Cerebral Hemorrhagic And NXY-059 Treatment) and the late stage FAST (Factor VIIa for Acute Hemorrhagic Stroke Treatment), have addressed whether or not manipulating oxidative stress and components of the blood coagulation cascade can achieve an improved prognosis following spontaneous hemorrhages. However, CHANT was halted prematurely because although it showed that the spin trap agent NXY-059 was safe, it also demonstrated that the drug was ineffective in treating acute ischemic stroke. In addition, the recombinant activated factor VII FAST trial recently concluded with only modestly positive results. Despite a beneficial effect on the primary end point of reducing hemorrhage volume, controlling the coagulation cascade with recombinant factor VIIa did not decrease the mortality rate. Consequently, Novo Nordisk has abandoned further development of the drug for the treatment of intracerebral hemorrhaging. Even though progress in hemorrhage therapy that successfully reduces the escalating morbidity and mortality rate associated with brain bleeding is slow, perseverance and applied translational drug development will eventually be productive. The urgent need for such therapy becomes more evident in light of concerns related to uncontrolled high blood pressure in the general population, increased use of blood thinners by the elderly (e.g., warfarin) and thrombolytics by acute ischemic stroke patients, respectively. The future of drug development for hemorrhage may require a multifaceted approach, such as combining drugs with diverse mechanisms of action. Because of the substantial benefit of factor VIIa in reducing hemorrhage volume, it should be considered as a prime drug candidate included in combination therapy as an off-label use if the FAST trial proves that the risk of thromboembolic events is not increased with drug administration. Other promising drugs that may be considered in combination include uncompetitive NMDA receptor antagonists (such as memantine), antioxidants, metalloprotease inhibitors, statins and erythropoietin analogs, all of which have been shown to reduce hemorrhage and behavioral deficits in one or more animal models.

Tumor necrosis factor-alpha increases in the brain after intracerebral hemorrhage and thrombin stimulation

OBJECTIVE

The goals of this study were 1) to determine the effects of intracerebral hemorrhage (ICH) on brain tumor necrosis factor (TNF)-alpha levels, which are still controversial; 2) to investigate the role of TNF-alpha in ICH-induced brain injury; 3) to examine the effects of thrombin on brain TNF-alpha levels; and 4) to elucidate the role of TNF-alpha in thrombin-induced neuroprotection.

METHODS

Autologous whole blood and thrombin were injected into the right caudate of rats or mice. Brain TNF-alpha was then determined by enzyme-linked immunosorbent assay and immunohistochemistry. Brain edema and neurological deficits were also examined.

RESULTS

Perihematomal TNF-alpha levels increased after ICH. ICH-induced brain edema was less in TNF-alpha knockout mice compared with wild-type mice (P < 0.05). Intracerebral infusion of thrombin also caused an increase in brain TNF-alpha levels. Thrombin preconditioning reduced thrombin-induced brain edema, but this effect was not blocked by a neutralizing TNF-alpha antibody.

CONCLUSION

Increase of perihematomal TNF-alpha levels contributes to brain edema formation after ICH. Thrombin may be a major mediator of ICH-induced TNF-alpha production, but thrombin-induced brain tolerance may not be TNF-alpha mediated.

Brain genomics of intracerebral hemorrhage

After intracerebral hemorrhage (ICH), many changes of gene transcription occur that may be important because they will contribute to understanding mechanisms of injury and recovery. Therefore, gene expression was assessed using Affymetrix microarrays in the striatum and the overlying cortex at 24 h after intracranial infusions of blood into the striatum of adult rats. Intracerebral hemorrhage regulated 369 of 8,740 transcripts as compared with saline-injected controls, with 104 regulated genes shared by the striatum and cortex. There were 108 upregulated and 126 downregulated genes in striatum, and 170 upregulated and 69 downregulated genes in the cortex. Real-time reverse transcriptase-polymerase chain reaction (RT-PCR) confirmed upregulation of IL-1-beta, Lipcortin 1 (annexin) and metallothionein 1,2, and downregulation of potassium voltage-gated channel, shaker-related subfamily, beta member 2 (Kcnab2). Of the functional groups of genes modulated by ICH, many metabolism and signal-transduction-related genes decreased in striatum but increased in adjacent cortex. In contrast, most enzyme, cytokine, chemokine, and immune response genes were upregulated in both striatum and in the cortex after ICH, likely in response to foreign proteins from the blood. A number of these genes may contribute to brain edema and cellular apoptosis caused by ICH. In addition, downregulation of growth factor pathways and the phosphatidylinositol 3-kinase (PI3K)/Akt pathway could also contribute to perihematoma cell death/apoptosis. Intracerebral hemorrhage-related downregulation of GABA-related genes and potassium channels might contribute to perihematoma cellular excitability and increased risk of post-ICH seizures. These genomic responses to ICH potentially provide new therapeutic targets for treatment.

Mmp-9 deficiency enhances collagenase-induced intracerebral hemorrhage and brain injury in mutant mice

Matrix metalloproteinase-9 (MMP-9) participates in the disregulation of blood-brain barrier during hemorrhagic transformation, and exacerbates brain injury after cerebral ischemia. However, the consequences of long-term inhibition or deficiency of MMP-9 activity (which might affect normal collagen or matrix homeostasis) remains to be determined. The authors investigated how MMP-9 gene deficiency enhances hemorrhage and increases mortality and neurologic deficits in a collagenase-induced intracerebral hemorrhage (ICH) model in MMP-9-knockout mice. MMP-9-knockout and corresponding wild-type mice at 20 to 35 weeks were used to model an aged population (because advanced age is a significant risk factor in human ICH). Collagenase VII-S (0.5 microL, 0.075 U) was injected into the right basal ganglia in mice and mortality, neurologic deficits, brain edema, and hemorrhage size measured. In addition, MMP-9 activity, brain collagen content, blood coagulation, cerebral arterial structure, and expressions of several MMPs were examined. Increased hemorrhage and brain edema that correlated with higher mortality and neurologic deficits were found in MMP-9-knockout mice. No apparent structural changes were observed in cerebral arteries, even though brain collagen content was reduced in MMP-9-knockout mice. MMP-9-knockout mice did exhibit an enhanced expression of MMP-2 and MMP-3 in response to ICH. The results indicate that a deficiency of MMP-9 gene in mutant mice increases collagenase-induced hemorrhage and the resulting brain injury. The intriguing relationship between MMP-9 deficiency and collagenase-induced ICH may reflect the reduction in collagen content and an enhanced expression of MMP-2 and MMP-3.

Pathophysiology of brain edema formation

A number of mechanisms seem to be involved in edema formation after an ICH. At least three phases of edema are involved in ICH. These include a very early phase (first several hours) involving hydrostatic pressure and clot retraction, a second phase (first 2 days) involving the activation of the coagulation cascade and thrombin production, and a third phase (after 3 days) involving RBC lysis and hemoglobin-induced neuronal toxicity. Activation of the complement system in brain parenchyma also plays an important role in the second and third phases. There are potential therapeutic strategies to address each of these mechanisms. Because the adverse effect of an ICH seems to result from a toxic effect of blood components on brain tissue, early clot removal may be the best strategy, because it results in the removal of all the toxic components [93]. Hematoma aspiration after tissue plasminogen activator (tPA) infusion has also been shown to be relatively safe and effective in animal models. Kaufman et al [94] reported that tPA lysed the hematoma in minutes and did not cause inflammation or bleeding in rabbits. Because clots lysed with tPA can be aspirated through a needle or catheter, mechanical brain injury by this method is minimized. In a rat model, aspiration of clot with tPA reduced clot volume and brain injury [95,96]. Recently, Wagner et al [97] infused tPA into hematomas in a porcine model at 3 hours after induction and aspirated the liquified clots 1 hour later. Clot removal after tPA treatment resulted in a 72% reduction in hematoma volume compared with untreated controls. Clot removal also reduced brain edema volume and BBB disruption and improved cerebral tissue pressure [93]. Six randomized trials have been accomplished, but surgical evacuation of the clot remains controversial [98-103]. Recently, thrombolysis and aspiration under CT guidance reduced the hematoma volume effectively [104]. Infusion of tPA directly into the hematoma before clot aspiration has also been used in human beings. Up to 90% of the original hematoma volume can be removed [105, 106]. Schaller et al [107] injected tPA directly into a hematoma 72 hours after the ictus in patients. The hematomas were lysed, and the liquified clots were drained in 14 patients. Two patients died, but none had recurrent hemorrhage. In conclusion, much has been learned about the basic mechanisms involved in edema formation after ICH. Animal models indicate that a number of components of blood are capable of inducing brain injury and brain edema. Now, it is time to translate that basic information into clinical trials.

Experimental animal models of intracerebral hemorrhage

Experimental animal ICH models are able to reproduce the overall important pathophysiologic events documented in human ICH, including edema development, markedly reduced metabolism, and tissue pathologic responses. Thus, ICH models serve as an important tool for new understanding of the mechanisms underlying brain injury after an intracerebral bleed. Currently, ongoing studies in several laboratories using these models investigating secondary inflammatory responses as well as intracellular signaling and molecular events are expected to provide therapeutic targets for treating ICH. Future studies should also be directed at one aspect of ICH modeling that has received little attention--potential differences in the hemostatic systems and physical and biochemical properties of clots in animals that might make their susceptibility to aspiration and/or fibrinolytic drugs and rates of rehemorrhage different than in human beings. Also, future efforts should be directed toward the development of a model that mimics the pathophysiologic processes that lead to spontaneous ICH, progression of hemorrhage, and the recurrence of bleeding in human beings. This model would not only provide better understanding of the dynamic events leading to ICH and tissue injury but should also lead to the development of highly effective pharmacologic and surgical treatments.

Evidence for apoptosis after intercerebral hemorrhage in rat striatum

The overall hypothesis that cell death after intracerebral hemorrhage is mediated in part by apoptotic mechanisms was tested. Intracerebral hemorrhage was induced in rats using stereotactic infusions of 0.5 U of collagenase (1-microL volume) into the striatum. After 24 hours, large numbers of TUNEL-positive stained cells with morphologies suggestive of apoptosis were present in the center and periphery of the hemorrhage. Double staining with Nissl and immunocytochemical labeling with antibodies against neuronal nuclei and glial fibrillary acidic protein suggested that these TUNEL-positive cells were mostly neurons and astrocytes. Electrophoresis of hemorrhagic brain extracts showed evidence of DNA laddering into approximately 200-bp fragments. Western blots showed cleavage of the cytosolic caspase substrate gelsolin. The density of TUNEL-positive cells at 24 and 48 hours after hemorrhage was significantly reduced by treatment with the broad-spectrum caspase inhibitor zVADfmk. It was unlikely that apoptotic changes were due to neurotoxicity of injected collagenase because TUNEL-positive cells and DNA laddering were also obtained in an alternative model of hemorrhage where autologous blood was infused into the striatum. Furthermore, equivalent doses of collagenase did not induce cell death in primary neuronal cultures. These results provide initial evidence that apoptotic mechanisms may mediate some of the injury in brain after intracerebral hemorrhage.

Protective effects of free radical inhibitors in intracerebral hemorrhage in rat

Iron compounds formed in the degradation of a hematoma can accelerate the formation of free radicals in adjacent ischemic or hypoperfused tissue. The purpose of this study was to examine the efficacy of compounds that quench free radicals in improving the outcome in rats with experimental intracerebral hemorrhage. Intracerebral hemorrhage was induced in rats by injection of bacterial collagenase and heparin into the caudate nucleus. Rats were treated with alpha-tocopherol plus ascorbic acid starting before hemorrhage, or with dimethylthiourea or alpha-phenyl-N-tert-butyl nitrone starting 2 h after hemorrhage, with treatment continued for 10 days after induction of hemorrhage. Outcome was assessed by behavioral analyses, magnetic resonance imaging, and histopathology. A trend towards behavioral improvement was found for rats treated with alpha-tocopherol/ascorbic acid, while behavior was significantly improved following intracerebral hemorrhage in rats treated with dimethylthiourea or alpha-phenyl-N-tert-butyl nitrone. These results suggest that free radicals may play a role in the development of brain injury following intracerebral hemorrhage, and that compounds that interrupt the free radical cascade may improve outcome. However, treatment did not significantly affect edema, resolution of the hematoma, or neuronal injury in tissue adjacent to the hemorrhage.