A nonpsychotropic cannabinoid, HU-211, has cerebroprotective effects after closed head injury in the rat

Efficacy of N-Methyl-D-Aspartate (NMDA) Receptor Antagonists in Treating Traumatic Brain Injury-Induced Brain Edema: A Systematic Review and Meta-analysis of Animal Studies

Traumatic brain injury leads to glutamate release, which overstimulates N-methyl-D-aspartate (NMDA) receptors, leading to neurotoxicity and cytotoxic edema. NMDA receptor antagonists may offer neuroprotection by blocking this pathway. The objective of this systematic review is to assess the efficacy of NMDA receptor antagonists for traumatic brain injury-induced brain edema in rodent models. This systematic review followed Cochrane Handbook guidelines and registered its protocol in PROSPERO (ID: CRD42023440934). Here, we included controlled rodent animal models comparing NMDA antagonist use with a placebo treatment. Outcome measures included the reduction of cerebral edema, Neurobehavioral Severity Scale, and adverse effects. The search strategy used Medical Subject Headings terms related to traumatic brain injury and NMDA receptor antagonists. The Collaborative Approach to Meta Analysis and Review of Animal Experimental Studies (CAMARADES) checklist and Systematic Review Centre for Laboratory Animal Experimentation's (SYRCLE's) tools were used to measure the quality and bias of included studies. The synthesis of results was presented in a meta-analysis of standard mean difference. Sixteen studies were included, with the predominant drugs being ifenprodil, MK-801, magnesium, and HU-211. The subjects consisted of Sprague-Dawley or Sabra rats. The analysis showed a significant reduction in brain edema with NMDA antagonist treatment (Standardized mean difference [SMD] - 1.17, 95% confidence interval [CI] - 1.59 to - 0.74, p < 0.01), despite high heterogeneity (I2 = 72%). Neurobehavioral Severity Scale also significantly improved (mean difference - 3.32, 95% CI - 4.36 to - 2.28, p < 0.01) in animals receiving NMDA antagonists. Administration within 1 h after injury showed a modest enhancement in reducing brain edema compared with the baseline (SMD - 1.23, 95% CI - 1.69 to - 0.77, p < 0.01). Studies met standards for animal welfare and model appropriateness. Although baseline comparability and selective reporting bias were generally addressed, key biases such as randomization, allocation concealment, and blinding were often unreported. Overall, NMDA antagonists exhibit promising efficacy in the treatment of traumatic brain injury. Notably, our systematic review consistently demonstrated a significant reduction in brain edema with compounds including HU-211 and NPS 150.

Cannabinoids and endocannabinoids as therapeutics for nervous system disorders: preclinical models and clinical studies

Cannabinoids are lipophilic substances derived from Cannabis sativa that can exert a variety of effects in the human body. They have been studied in cellular and animal models as well as in human clinical trials for their therapeutic benefits in several human diseases. Some of these include central nervous system (CNS) diseases and dysfunctions such as forms of epilepsy, multiple sclerosis, Parkinson's disease, pain and neuropsychiatric disorders. In addition, the endogenously produced cannabinoid lipids, endocannabinoids, are critical for normal CNS function, and if controlled or modified, may represent an additional therapeutic avenue for CNS diseases. This review discusses in vitro cellular, ex vivo tissue and in vivo animal model studies on cannabinoids and their utility as therapeutics in multiple CNS pathologies. In addition, the review provides an overview on the use of cannabinoids in human clinical trials for a variety of CNS diseases. Cannabinoids and endocannabinoids hold promise for use as disease modifiers and therapeutic agents for the prevention or treatment of neurodegenerative diseases and neurological disorders.

Blood-brain barrier disruption and edema formation due to prolonged starvation in wild-type mice

INTRODUCTION

Different types of diseases have been treated by restricted caloric intake or fasting. Although during this long time, fasting protective measures, for example, supplements, are given to the patients to protect vital organs such as the liver and kidney, little attention is given to the brain. The current research aims to investigate hypoglycemia due to prolonged fasting disrupts blood-brain barrier (BBB) in mice.

MATERIALS AND METHODS

Immunohistochemistry (IHC) and in situ hybridization (ISH) techniques were used to examine the expression of different genes. Evans blue extravasation and wet-dry technique were performed to evaluate the integrity of BBB and the formation of brain edema, respectively.

RESULTS

We confirmed that hypoglycemia affected mice fasting brain by examining the increased expression of glucose transporter protein 1 and hyperphosphorylation of tau protein. We subsequently found downregulated expression of some genes, which are involved in maintaining BBB such as vascular endothelial growth factor (VEGF) in astrocytes and claudin-5 (a vital component of BBB) and VEGF receptor (VEGFR1) in endothelial cells by ISH. We also found that prolonged fasting caused the brain endothelial cells to express lipocalin-2, an inflammatory marker of brain endothelial cells. We performed Evans blue extravasation to show more dye was retained in the brain of fasted mice than in control mice as a result of BBB disruption. Finally, wet-dry method showed that the brain of prolonged fasted mice contained significantly higher amount of water confirming the formation of brain edema. Therefore, special attention should be given to the brain during treatment with prolonged fasting for various diseases.

CONCLUSIONS

Our results demonstrated that hypoglycemia due to prolonged fasting disrupts BBB and produces brain edema in wild-type mice, highlighting the importance of brain health during treatment with prolonged fasting.

Surface-fill H2S-releasing silk fibroin hydrogel for brain repair through the repression of neuronal pyroptosis

Traumatic brain injury (TBI) remains the major cause of disability and mortality worldwide due to the persistent neuroinflammation and neuronal death induced by TBI. Among them, pyroptosis, a specific type of programmed cell death (PCD) triggered by inflammatory signals, plays a significant part in the pathological process after TBI. Inhibition of neuroinflammation and pyroptosis is considered a possible strategy for the treatment of TBI. In our previous study, exogenous hydrogen sulfide(H₂S) exerted a neuroprotective effect after TBI. Here, we developed a surface-fill H₂S-releasing silk fibroin (SF) hydrogel (H₂S@SF hydrogel) to achieve small-dose local administration and avoid volatile and toxic side effects. We used a controlled cortical impact (CCI) to establish a mild TBI model in mice to examine the effect of H₂S@SF hydrogel on TBI-induced pyroptosis. We found that H₂S@SF hydrogel inhibited the expression of H₂S synthase in neurons after TBI and significantly inhibited TBI-induced neuronal pyroptosis. In addition, immunofluorescence staining results showed that the necroptosis protein receptor-interacting serine/threonine-protein kinase 1 (RIPK1) partially colocalized with the pyroptosis protein Gasdermin D (GSDMD) in the same cells. H₂S@SF hydrogel can also inhibit the expression of the necroptosis protein. Moreover, H₂S@SF hydrogel also alleviates brain edema and the degree of neurodegeneration in the acute phase of TBI. The neuroprotective effect of H₂S@SF hydrogel was further confirmed by wire-grip test, open field test, Morris water maze, beam balance test, radial arm maze, tail suspension, and forced swimming test. Lastly, we also measured spared tissue volume, reactive astrocytes and activated microglia to demonstrate H₂S@SF hydrogel impacts on long-term prognosis in TBI. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel. STATEMENT OF SIGNIFICANCE: Silk fibroin (SF) hydrogel controls the release of hydrogen sulfide (H₂S) to inhibit neuronal pyroptosis and neuroinflammation in injured brain tissue. In this study, we synthesized a surface-fill H₂S-releasing silk fibroin hydrogel, which could slowly release H₂S to reshape the homeostasis of endogenous H₂S in injured neurons and inhibit neuronal pyroptosis in a mouse model of traumatic brain injury. Meanwhile, H₂S@SF hydrogel could alleviate brain edema and the degree of neurodegeneration, improve motor dysfunction, anxious behavior and memory impairment caused by TBI, reduce tissue loss and ameliorate neuroinflammation. Our study provides a new theoretical basis for the treatment of H₂S after TBI and the clinical application of H₂S@SF hydrogel.

Deficiency of autism-related Scn2a gene in mice disrupts sleep patterns and circadian rhythms

Autism spectrum disorder (ASD) affects ~2% of the population in the US, and monogenic forms of ASD often result in the most severe manifestation of the disorder. Recently, SCN2A has emerged as a leading gene associated with ASD, of which abnormal sleep pattern is a common comorbidity. SCN2A encodes the voltage-gated sodium channel NaV1.2. Predominantly expressed in the brain, NaV1.2 mediates the action potential firing of neurons. Clinical studies found that a large portion of children with SCN2A deficiency have sleep disorders, which severely impact the quality of life of affected individuals and their caregivers. The underlying mechanism of sleep disturbances related to NaV1.2 deficiency, however, is not known. Using a gene-trap Scn2a-deficient mouse model (Scn2atrap), we found that Scn2a deficiency results in increased wakefulness and reduced non-rapid-eye-movement (NREM) sleep. Brain region-specific Scn2a deficiency in the suprachiasmatic nucleus (SCN) containing region, which is involved in circadian rhythms, partially recapitulates the sleep disturbance phenotypes. At the cellular level, we found that Scn2a deficiency disrupted the firing pattern of spontaneously firing neurons in the SCN region. At the molecular level, RNA-sequencing analysis revealed differentially expressed genes in the circadian entrainment pathway including core clock genes Per1 and Per2. Performing a transcriptome-based compound discovery, we identified dexanabinol (HU-211), a putative glutamate receptor modulator, that can partially reverse the sleep disturbance in mice. Overall, our study reveals possible molecular and cellular mechanisms underlying Scn2a deficiency-related sleep disturbances, which may inform the development of potential pharmacogenetic interventions for the affected individuals.

Implantation of injectable SF hydrogel with sustained hydrogen sulfide delivery reduces neuronal pyroptosis and enhances functional recovery after severe intracerebral hemorrhage

Hydrogen sulfide (H₂S), an important endogenous signaling molecule, plays an important neuroprotective role in the central nervous system. However, there is no ideal delivery material or method involving the sustained and controlled release of H₂S for clinical application in brain diseases. Silk fibroin (SF)-based hydrogels have become a potentially promising strategy for local, controlled, sustained drug release in the treatment of various disorders. Here, we show a silk fibroin (SF)-based hydrogel with sustained H₂S delivery (H₂S@SF hydrogel) is effective in treating brain injury through stereotactic orthotopic injection in a severe intracerebral hemorrhage (ICH) mouse model. In this study, we observed H₂S@SF hydrogel sustained H₂S release in vitro and in vivo. The physicochemical properties of H₂S@SF hydrogel were studied using FE-SEM, Raman spectroscopy and Rheological analysis. Treatment with H₂S@SF hydrogel attenuated brain edema, reduced hemorrhage volume and improved the recovery of neurological deficits after severe ICH following stereotactic orthotopic injection. Double immunofluorescent staining also revealed that H₂S@SF hydrogel may reduce cell pyroptosis in the striatum, cortex and hippocampus. However, when using endogenous H₂S production inhibitor AOAA, H₂S@SF hydrogel could not suppress ICH-induced cell pyroptosis. Hence, the therapeutic effect of the H₂S@SF hydrogel may be partly the result of the slow-release of H₂S and/or the effect of the SF hydrogel on the production of endogenous H₂S. Altogether, the results exhibit promising attributes of injectable silk fibroin hydrogel and the utility of H₂S-loaded injectable SF hydrogel as an alternative biomaterial toward brain injury treatment for clinical application.

Shape effect of cerium oxide nanoparticles on mild traumatic brain injury

The catalytic performance and therapeutic effect of nanoparticles varies with shape. Here, we investigated and compared the therapeutic outcomes of ceria nanospheres (Ceria NSs) and ceria nanorods (Ceria NRs) in an in vivo study of mild traumatic brain injury (mTBI). In vivo TBI was induced in a mouse model of open head injury using a stereotaxic impactor. Outcomes including cytoprotective effects, cognitive function, and cerebral edema were investigated after retro-orbital injection of 11.6 mM of ceria nanoparticles. Ceria nanoparticles significantly reduced fluoro-jade B (FJB)-positive cells and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL)-positive cells, and restored mRNA levels of superoxide dismutase 1 (SOD1) and SOD2. They also decreased the cyclooxygenase-2 (COX-2) expression compared with the untreated control group. Comparing the two nanomaterials, Ceria NRs showed less stable and high-energy (100) and (110) planes, which increased the number of active sites. The Ce3+/Ce4+ molar ratio of Ceria NRs (0.40) was greater than that of Ceria NSs (0.27). Ceria NRs (0.059 ± 0.021) appeared to exhibit better anti-inflammatory effect than Ceria NSs (0.133 ± 0.024), but the effect was statistically insignificant (p = 0.190). Ceria nanoparticles also improved cognitive impairment following mTBI compared with the control group, but the effect did not differ significantly according to the nanoshape. However, Ceria NRs (70.1 ± 0.5%) significantly decreased brain water content compared with Ceria NSs (73.7 ± 0.4%; p = 0.0015), indicating a more effective reduction in brain edema (p = 0.0015). Compared with Ceria NSs, the Ceria NRs are more effective in alleviating cerebral edema following in vivo mTBI.

Global Trends in Cannabis and Cannabidiol Research from the Year 1940 to 2019

Legalization of Cannabis in countries, like Canada, and global demand for non-hallucinating chemical components, such as Cannabidiols (CBD), have stimulated the increased interest from academics, industry, and regulatory agencies. Subsequent research publications in scientific journals in this field are expected to grow rapidly. However, there have been few research reviews that have quantified patterns in research publications concerning cannabis, nor a literature-based perspective on the historical development, current status, and future direction of cannabis research. Here, a bibliometric analysis is performed to address this gap in the scientific literature. A total of 1167 relevant articles (Supplementary file 1) were screened and analyzed using three software tools: HistCite, CiteSpace, and Bibliometric Online Analysis Platform. The performances of relevant countries, institutions, authors, and journals were presented, and the evolutionary trends of different categories were revealed. The historical development of cannabis and CBD research can be clearly divided into three stages, which focus on the chemistry, pharmacology, and molecular biology aspects of Cannabis sativa in general and then a focus on CBD related publications. A timeline was drawn to highlight the major trends in the literature, including scientific discoveries. In the end, several suggestions for future research directions in this field are provided.

Ruxolitinib exerts neuroprotection via repressing ferroptosis in a mouse model of traumatic brain injury

Traumatic brain injury (TBI) is a major cause of death and disability worldwide. Various forms of cells death are involved in the pathological process of TBI, without exception to ferroptosis, which is mainly triggered by iron-dependent lipid peroxidation. Although there have been studies on ferroptosis and TBI, the effect of ruxolitinib (Ruxo), one type of FDA approved drugs for treating myelofibrosis, on the process of ferroptosis post-TBI is remained non-elucidated. Therefore, using a controlled cortical impact device to establish the mouse TBI model, we examined the effect of Ruxo on TBI-induced ferroptosis, in which the inhibitor of ferroptosis, Ferrostatin-1 (Fer-1) was used as a positive control. Moreover, we also respectively explored the effects of these two interventions on neurological deficits caused by TBI. We firstly examined the expression patterns of ferroptosis-related markers at protein level at different time points after TBI. And based on the expression changes of these markers, we chose 12 h post-TBI to prove the effect of Ruxo on ferroptosis. Importantly, we found the intensely inhibitory effect of Ruxo on ferroptosis, which is in parallel with the results obtained after Fer-1-treatment. In addition, these two treatments both alleviated the content of brain water and degree of neurodegeneration in the acute phase of TBI. Finally, we further confirmed the neuroprotective effect of Ruxo or Fer-1 via the wire-grip test, Morris water maze and open field test, respectively. Thereafter, the lesion volume and iron deposition were also measured to certificate their effects on the long-term outcomes of TBI. Our results ultimately demonstrate that inhibiting ferroptosis exerts neuroprotection, and this is another neuroprotective mechanism of Ruxo on TBI.

The synthetic cannabinoid JWH-018 modulates Saccharomyces cerevisiae energetic metabolism

Synthetic cannabinoids are a group of novel psychoactive substances with similar properties to Δ9-THC. Among the vast number of synthetic cannabinoids, designed to be tested in clinical trials, JWH-018 was the first novel psychoactive substance found in the recreational drug marketplace. The consumption of JWH-018 shows typical effects of CB1 agonists including sedation, cognitive dysfunction, tachycardia, postural hypotension, dry mouth, ataxia and psychotropic effects, but appeared to be more potent than Δ9-THC. However, studies on human cells have shown that JWH-018 toxicity depends on the cellular line used. Despite these studies, the underlying molecular mechanisms to JWH-018 action has not been clarified yet. To understand the impact of JWH-018 at molecular and cellular level, we used Saccharomyces cerevisiae as a model. The results showed an increase in yeast growth rate in the presence of this synthetic cannabinoid due to an enhancement in the glycolytic flux at expense of a decrease in pentose phosphate pathway, judging by 2D-Gel proteomic analysis, qRT-PCR experiments and ATP measurements. Overall, our results provide insights into molecular mechanisms of JWH-018 action, also indicating that Saccharomyces cerevisiae is a good model to study synthetic cannabinoids.

Platelet regulates neuroinflammation and restores blood-brain barrier integrity in a mouse model of traumatic brain injury

Neuroinflammation accompanied by microglial activation triggers multiple cell death after traumatic brain injury (TBI). The secondary injury caused by inflammation may persist for a long time. Recently, platelet C-type lectin-like 2 receptor (CLEC-2) has been shown to regulate inflammation in certain diseases. However, its possible effects on TBI remain poorly understood. Here, we aimed to investigate the role of platelet CLEC-2 in the pathological process of neuroinflammation after TBI. In this study, mice were subjected to sham or controlled cortical impact injury, and arbitrarily received recombinant platelet CLEC-2. In parallel, BV2 cells were treated with lipopolysaccharide (LPS) to mimic microglial activation after TBI. Primary endothelial cells were also subjected to LPS in order to replicate the inflammatory damage caused by TBI. We used western blot analysis, reverse transcription polymerase chain reaction (RT-PCR), and immunostaining to evaluate the role of platelet CLEC-2 in TBI. In conditional knock out platelet CLEC-2 mice, trauma worsened the integrity of the blood-brain barrier and amplified the release of inflammatory cytokines. In wild type mice subjected to controlled cortical impact injury, recombinant platelet CLEC-2 administration altered the secretion of inflammatory cytokines, reduced brain edema, and improved neurological function. In vitro, the polarization phenotype of microglia induced by LPS was transformed by recombinant platelet CLEC-2, and this conversion depended on the mammalian target of rapamycin (mTOR) pathway. Endothelial cell injury by LPS was ameliorated when microglia expressed mostly M2 phenotype markers. In conclusion, platelet CLEC-2 regulates trauma-induced neuroinflammation and restores blood-brain barrier integrity.

Exogenous Hydrogen Sulfide Offers Neuroprotection on Intracerebral Hemorrhage Injury Through Modulating Endogenous H2S Metabolism in Mice

Hydrogen sulfide (H₂S), an important endogenous signaling molecule, has a significant neuroprotective role in the central nervous system. In this study, we examined the protective effects of exogenous H₂S against intracerebral hemorrhage (ICH), as well as its underlying mechanisms. We investigated the effects of exogenous H₂S on ICH using Western blotting, injury volume, measurement of brain edema, propidium iodide (PI) staining, and behavior assessment, respectively. We found that endogenous H₂S production was downregulated in the brain after ICH, which is caused by the decrease in cystathionine β-synthase (CBS) as the predominant cerebral H₂S-generating enzyme in the brain. Treatment with sodium hydrosulfide (NaHS; an H₂S producer) could restore the H₂S production and the expression of CBS. NaHS could also attenuate brain edema, injury volume, and neurological deficits in the Morris water maze test after ICH. Western blotting results indicated that H₂S pretreatment reversed the increase in caspase 3 cleavage and the decrease in Bcl-2, suppressed the activation of autophagy marker (LC3II and Beclin-1), and maintained the p62 level in injured striatum post-ICH. However, H₂S could not restore brain CBS expression and H₂S content, reduce brain edema, and improve motor performance and memory function after ICH through modulating autophagy and apoptosis when pretreated with the CBS inhibitor aminooxyacetic acid (AOAA). We also found that AOAA reduced the endogenous H₂S production through inhibiting the enzyme activity of CBS rather than modulating the expression of CBS protein level. These present results indicate that H₂S may possess potential therapeutic value in the treatment of brain injury after ICH, and the protective effect of exogenous H₂S against ICH may be not a direct action but an indirect effect through inducing endogenous H₂S metabolism responses.

A Systematic Review of Closed Head Injury Models of Mild Traumatic Brain Injury in Mice and Rats

Mild TBI (mTBI) is a significant health concern. Animal models of mTBI are essential for understanding mechanisms, and pathological outcomes, as well as to test therapeutic interventions. A variety of closed head models of mTBI that incorporate different aspects (i.e., biomechanics) of the mTBI have been reported. The aim of the current review was to compile a comprehensive list of the closed head mTBI rodent models, along with the common data elements, and outcomes, with the goal to summarize the current state of the field. Publications were identified from a search of PubMed and Web of Science and screened for eligibility following PRISMA guidelines. Articles were included that were closed head injuries in which the authors classified the injury as mild in rats or mice. Injury model and animal-specific common data elements, as well as behavioral and histological outcomes, were collected and compiled from a total of 402 articles. Our results outline the wide variety of methods used to model mTBI. We also discovered that female rodents and both young and aged animals are under-represented in experimental mTBI studies. Our findings will aid in providing context comparing the injury models and provide a starting point for the selection of the most appropriate model of mTBI to address a specific hypothesis. We believe this review will be a useful starting place for determining what has been done and what knowledge is missing in the field to reduce the burden of mTBI.

Understanding the endocannabinoid system as a modulator of the trigeminal pain response to concussion

Post-traumatic headache is the most common symptom of postconcussion syndrome and becomes a chronic neurological disorder in a substantial proportion of patients. This review provides a brief overview of the epidemiology of postconcussion headache, research models used to study this disorder, as well as the proposed mechanisms. An objective of this review is to enhance the understanding of how the endogenous cannabinoid system is essential for maintaining the balance of the CNS and regulating inflammation after injury, and in turn making the endocannabinoid system a potential modulator of the trigeminal response to concussion. The review describes the role of endocannabinoid modulation of pain and the potential for use of phytocannabinoids to treat pain, migraine and concussion.

Cannabinoid receptors and TRPA1 on neuroprotection in a model of retinal ischemia

Retinal ischemia is a pathological event present in several retinopathies such as diabetic retinopathy and glaucoma, leading to partial or full blindness with no effective treatment available. Since synthetic and endogenous cannabinoids have been studied as modulators of ischemic events in the central nervous system (CNS), the present study aimed to investigate the involvement of cannabinoid system in the cell death induced by ischemia in an avascular (chick) retina. We observed that chick retinal treatment with a combination of WIN 55212-2 and cannabinoid receptor antagonists (either AM251/O-2050 or AM630) decreased the release of lactate dehydrogenase (LDH) induced by retinal ischemia in an oxygen and glucose deprivation (OGD) model. Further, the increased availability of endocannabinoids together with cannabinoid receptor antagonists also had a neuroprotective effect. Surprisingly, retinal exposure to any of these drugs alone did not prevent the release of LDH stimulated by OGD. Since cannabinoids may also activate transient receptor potential (TRP) channels, we investigated the involvement of TRPA1 receptors (TRPA1) in retinal cell death induced by ischemic events. We demonstrated the presence of TRPA1 in the chick retina, and observed an increase in TRPA1 content after OGD, both by western blot and immunohistochemistry. In addition, the selective activation of TRPA1 by mustard oil (MO) did not worsen retinal LDH release induced by OGD, whereas the blockage of TRPA1 completely prevented the extravasation of cellular LDH in ischemic condition. Hence, these results show that during the ischemic event there is an augment of TRPA1, and activation of this receptor is important in cell death induction. The data also indicate that metabotropic cannabinoid receptors, both type 1 and 2, are not involved with the cell death found in the early stages of ischemia. Therefore, the study points to a potential role of TRPA1 as a target for neuroprotective approaches in retinal ischemia.

Antidepressant effects of curcumin and HU-211 coencapsulated solid lipid nanoparticles against corticosterone-induced cellular and animal models of major depression

Major depression is a complex neuropsychiatric disorder with few treatment approaches. The use of nontargeted antidepressants induced many side effects with their low efficacy. A more precise targeting strategy is to develop nanotechnology-based drug delivery systems; hence, we employed solid lipid nanoparticles (SLNs) to encapsulate HU-211 and curcumin (Cur). The antidepressant effects of the dual-drug nanoparticles (Cur/SLNs-HU-211) for major depression treatment were investigated in corticosterone-induced cellular and animal models of major depression. Cur/SLNs-HU-211 can effectively protect PC12 cells from corticosterone-induced apoptosis and can release more dopamine, which may be associated with the higher uptake of Cur/SLNs-HU-211 shown by cellular uptake behavior analysis. Additionally, Cur/SLNs-HU-211 significantly reduced the immobility time in forced swim test, enhanced fall latency in rotarod test, and improved the level of dopamine in mice blood. Cur/SLNs-HU-211 can deliver more Cur to the brain and thus produce a significant increase in neurotransmitters level in brain tissue, especially in the hippocampus and striatum. The results of Western blot and immunofluorescence revealed that Cur/SLNs-HU-211 can significantly enhance the expression of CB1, p-MEK1, and p-ERK1/2. Our study suggests that Cur/SLNs-HU-211 may have great potential for major depression treatment.

Management of Elevated Intracranial Pressure

Elevated intracranial pressure (ICP) is a primary cause of morbidity and mortality for many neurologic disorders. The relationship between ICP and brain volume is influenced by autoregulatory processes that can become dysfunctional. As a result, neurologic damage can occur by systemic and intracranial insults such as ischemia and excitatory amino acids. Therefore, survival is dependent on optimizing ICP and cerebral perfusion pressure. Treatment of intracranial hypertension requires intensive monitoring and aggressive therapy. Intracranial pressure monitoring techniques such as intraventricular catheters are useful for determining ICP elevations before changes in vital signs and neurologic status. Therapeutic modalities, generally aimed at reducing cerebral blood volume, brain tissue, and cerebrospinal fluid (CSF) volume, include nonpharmacologic (CSF removal, controlled hyperventilation, and elevating the patient’s head) and pharmacologic management. Mannitol and sedation are first-line agents used to lower ICP. Barbiturate coma may be beneficial in patients with elevated ICP refractory to conventional treatment. The use of prophylactic antiseizure therapy and optimal nutrition prevents significant complication. Currently, investigations are directed at discovering useful neuroprotective agents that prevent secondary neurologic injury.

Brain Volume Determination in Subarachnoid Hemorrhage Using Rats

Brain edema is routinely measured using the wet-dry method. Volume, however, is the sum total of all cerebral tissues, including water. Therefore, volumetric change following injury may not be adequately quantified using percentage of edema. We thus tested the hypothesis that dried brains can be reconstituted with water and then re-measured to determine the actual volume. Subarachnoid hemorrhage (SAH) was induced by endovascular perforation in adult male Sprague-Dawley rats (n = 30). Animals were euthanized at 24 and 72 h after evaluation of neurobehavior for determination of brain water content. Dried brains were thereafter reconstituted with equal parts of water (lost from brain edema) and centrifuged to remove air bubbles. The total volume was quantified using hydrostatic (underwater) physics principles that 1 ml water (mass) = 1 cm(3) (volume). The amount of additional water needed to reach a preset level marked on 2-ml test tubes was added to that lost from brain edema, and from the brain itself, to determine the final volume. SAH significantly increased both brain water and volume while worsening neurological function in affected rats. Volumetric measurements demonstrated significant brain swelling after SAH, in addition to the brain edema approach. This modification of the "wet-dry" method permits brain volume determination using valuable post hoc dried brain tissue.

Weight Drop Models in Traumatic Brain Injury

Weight drop models in rodents have been used for several decades to advance our understanding of the pathophysiology of traumatic brain injury. Weight drop models have been used to replicate focal cerebral contusion as well as diffuse brain injury characterized by axonal damage. More recently, closed head injury models with free head rotation have been developed to model sports concussions, which feature functional disturbances in the absence of overt brain damage assessed by conventional imaging techniques. Here, we describe the history of development of closed head injury models in the first part of the chapter. In the second part, we describe the development of our own weight drop closed head injury model that features impact plus rapid downward head rotation, no structural brain injury, and long-term cognitive deficits in the case of multiple injuries. This rodent model was developed to reproduce key aspects of sports concussion so that a mechanistic understanding of how long-term cognitive deficits might develop will eventually follow. Such knowledge is hoped to impact athletes and war fighters and others who suffer concussive head injuries by leading to targeted therapies aimed at preventing cognitive and other neurological sequelae in these high-risk groups.

Treatment of traumatic brain injury with anti-inflammatory drugs

Traumatic brain injury rapidly induces inflammation. This inflammation is produced both by endogenous brain cells and circulating inflammatory cells that enter from the brain. Together they drive the inflammatory response through a wide variety of bioactive lipids, cytokines and chemokines. A large number of drugs with anti-inflammatory action have been tested in both preclinical studies and in clinical trials. These drugs either have known anti-inflammatory action or inhibit the inflammatory response through unknown mechanisms. The results of these preclinical studies and clinical trials are reviewed. Recommendations are suggested on how to improve preclinical testing of drugs to make them more relevant to evaluate for clinical trials.

Methylene blue attenuates traumatic brain injury-associated neuroinflammation and acute depressive-like behavior in mice

Traumatic brain injury (TBI) is associated with cerebral edema, blood brain barrier breakdown, and neuroinflammation that contribute to the degree of injury severity and functional recovery. Unfortunately, there are no effective proactive treatments for limiting immediate or long-term consequences of TBI. Therefore, the objective of this study was to determine the efficacy of methylene blue (MB), an antioxidant agent, in reducing inflammation and behavioral complications associated with a diffuse brain injury. Here we show that immediate MB infusion (intravenous; 15-30 minutes after TBI) reduced cerebral edema, attenuated microglial activation and reduced neuroinflammation, and improved behavioral recovery after midline fluid percussion injury in mice. Specifically, TBI-associated edema and inflammatory gene expression in the hippocampus were significantly reduced by MB at 1 d post injury. Moreover, MB intervention attenuated TBI-induced inflammatory gene expression (interleukin [IL]-1β, tumor necrosis factor α) in enriched microglia/macrophages 1 d post injury. Cell culture experiments with lipopolysaccharide-activated BV2 microglia confirmed that MB treatment directly reduced IL-1β and increased IL-10 messenger ribonucleic acid in microglia. Last, functional recovery and depressive-like behavior were assessed up to one week after TBI. MB intervention did not prevent TBI-induced reductions in body weight or motor coordination 1-7 d post injury. Nonetheless, MB attenuated the development of acute depressive-like behavior at 7 d post injury. Taken together, immediate intervention with MB was effective in reducing neuroinflammation and improving behavioral recovery after diffuse brain injury. Thus, MB intervention may reduce life-threatening complications of TBI, including edema and neuroinflammation, and protect against the development of neuropsychiatric complications.

Neuroprotective effects of the cannabinoid agonist HU210 on retinal degeneration

Cannabinoids have been demonstrated to exert neuroprotective effects on different types of neuronal insults. Here we have addressed the therapeutic potential of the synthetic cannabinoid HU210 on photoreceptor degeneration, synaptic connectivity and functional activity of the retina in the transgenic P23H rat, an animal model for autosomal dominant retinitis pigmentosa (RP). In P23H rats administered with HU210 (100 μg/kg, i.p.) from P24 to P90, ERG recordings showed an amelioration of vision loss, as compared to vehicle-administered animals. Under scotopic conditions, the maximum a-wave amplitudes recorded at P60 and P90 were higher in HU210-treated animals, as compared to the values obtained in untreated animals. The scotopic b-waves were significantly higher in treated animals than in untreated rats at P30, P60 and P90. This attenuation of visual deterioration correlated with a delay in photoreceptor degeneration and the preservation of retinal cytoarchitecture. HU210-treated animals had 40% more photoreceptors than untreated animals. Presynaptic and postsynaptic elements, as well as the synaptic contacts between photoreceptors and bipolar or horizontal cells, were also preserved in HU210-treated P23H rats. These results indicate that HU210 preserves cone and rod structure and function, together with their contacts with postsynaptic neurons, in P23H rats. These data suggest that cannabinoids are potentially useful to delay retinal degeneration in RP patients.

Brain water content. A misunderstood measurement?

Brain edema is a major contributor to poor outcome following ischemic and hemorrhagic stroke. In animal models, edema has historically been quantified as a change in % brain water content (water content/wet weight). As described in this communication, this number can be misleading, as 'small' changes in % brain water content actually reflect much bigger changes in brain swelling. Using either water content, expressed as g/g dry weight, or a measure of brain swelling, better reflect the impact of edema after stroke and brain injury.

Hydrogen sulfide offers neuroprotection on traumatic brain injury in parallel with reduced apoptosis and autophagy in mice

Hydrogen sulfide (H₂S), a novel gaseous mediator, has been recognized as an important neuromodulator and neuroprotective agent in the central nervous system. The present study was undertaken to study the effects of exogenous H₂S on traumatic brain injury (TBI) and the underlying mechanisms. The effects of exogenous H₂S on TBI were examined by using measurement of brain edema, behavior assessment, propidium iodide (PI) staining, and Western blotting, respectively. Compared to TBI groups, H₂S pretreatment had reduced brain edema, improved motor performance and ameliorated performance in Morris water maze test after TBI. Immunoblotting results showed that H₂S pretreatment reversed TBI-induced cleavage of caspase-3 and decline of Bcl-2, suppressed LC3-II, Beclin-1 and Vps34 activation and maintained p62 level in injured cortex and hippocampus post TBI. The results suggest a protective effect and therapeutic potential of H₂S in the treatment of brain injury and the protective effect against TBI may be associated with regulating apoptosis and autophagy.

The role of potassium BK channels in anticonvulsant effect of cannabidiol in pentylenetetrazole and maximal electroshock models of seizure in mice

Cannabidiol is a nonpsychoactive member of phytocannabinoids that produces various pharmacological effects that are not mediated through putative CB1/CB2 cannabinoid receptors and their related effectors. In this study, we examined the effect of the i.c.v. administration of potassium BK channel blocker paxilline alone and in combination with cannabidiol in protection against pentylenetetrazol (PTZ)- and maximal electroshock (MES)-induced seizure in mice. In the PTZ-induced seizure model, i.c.v. administration of cannabidiol caused a significant increase in seizure threshold compared with the control group. Moreover, while i.c.v. administration of various doses of paxilline did not produce significant change in the PTZ-induced seizure threshold in mice, coadministration of cannabidiol and paxilline attenuated the antiseizure effect of cannabidiol in PTZ-induced tonic seizures. In the MES model of seizure, both cannabidiol and paxilline per se produced significant increase in percent protection against electroshock-induced seizure. However, coadministration of cannabidiol and paxilline did not produce significant interaction in their antiseizure effect in the MES test. The results of the present study showed a protective effect of cannabidiol in both PTZ and MES models of seizure. These results suggested a BK channel-mediated antiseizure action of cannabidiol in PTZ model of seizure. However, such an interaction might not exist in MES-induced convulsion.

Poloxamer-188 attenuates TBI-induced blood-brain barrier damage leading to decreased brain edema and reduced cellular death

Plasmalemma permeability plays an important role in the secondary neuronal death induced by traumatic brain injury (TBI). Previous works showed that Poloxamer 188 (P188) could restore the intactness of the plasma membrane and play a cytoprotective action. However, the roles of P188 in blood-brain barrier (BBB) integrity and TBI-induced neural cell death are still not clear. In this study, mice were induced TBI by controlled cortical impact (CCI), and cerebral water content was measured to explore the profile of brain edema after CCI. Further, the regimen of P188 in mouse CCI models was optimized. The neurological test and BBB integrity assessment were performed, and the numbers of TBI-induced neural cell death were counted by propidium iodide (PI) labeling. The expression of apoptotic pathway associated proteins (Bax, cyt-c, caspase-8, caspase-9, caspase-3, P53) and aquaporin-4 (AQP4) was assessed by RT-PCR or immunoblotting. The data showed that the brain edema peaked at 24 h after TBI in untreated animals. Tail intravenous injection of P188 (4 mg/ml, 100 μl) 30 min before TBI or within 30 min after TBI could attenuate TBI-induced brain edema. P188 pre-treatment restored BBB integrity, suppressed TBI-induced neural cell death, and improved neurological function. TBI induced an up-regulation of Bax, cyt-c, caspase-8, caspase-9, caspase-3, and the expression of p53 was down-regulated by P188 pre-treatment. AQP4 mainly located on endothelial cells and astrocytes, and its expression was also regulated by P188 pretreatment. All these results revealed that P188 attenuates TBI-induced brain edema by resealing BBB and regulating AQP4 expression, and suppressed apoptosis through extrinsic or intrinsic pathway. Plasmalemma permeability may be a potential target for TBI treatment.

New insights into the role of peroxisome proliferator-activated receptors in regulating the inflammatory response after tissue injury

Major trauma results in a strong inflammatory response in injured tissue. This posttraumatic hyperinflammation has been implied in the adverse events leading to a breakdown of host defense mechanisms and ultimately to delayed organ failure. Ligands to peroxisome proliferator-activated receptors (PPARs) have recently been identified as potent modulators of inflammation in various acute and chronic inflammatory conditions. The main mechanism of action mediated by ligand binding to PPARs is the inhibition of the nuclear transcription factor NF-κB, leading to downregulation of downstream gene transcription, such as for genes encoding proinflammatory cytokines. Pharmacological PPAR agonists exert strong anti-inflammatory properties in various animal models of tissue injury, including central nervous system trauma, ischemia/reperfusion injury, sepsis, and shock. In addition, PPAR agonists have been shown to induce wound healing process after tissue trauma. The present review was designed to provide an up-to-date overview on the current understanding of the role of PPARs in the pathophysiology of the inflammatory response after major trauma. Therapeutic options for using recombinant PPAR agonists as pharmacological agents in the management of posttraumatic inflammation will be discussed.

Peroxisome proliferator-activated receptors: "key" regulators of neuroinflammation after traumatic brain injury

Traumatic brain injury is characterized by neuroinflammatory pathological sequelae which contribute to brain edema and delayed neuronal cell death. Until present, no specific pharmacological compound has been found, which attenuates these pathophysiological events and improves the outcome after head injury. Recent experimental studies suggest that targeting peroxisome proliferator-activated receptors (PPARs) may represent a new anti-inflammatory therapeutic concept for traumatic brain injury. PPARs are “key” transcription factors which inhibit NFκB activity and downstream transcription products, such as proinflammatory and proapoptotic cytokines. The present review outlines our current understanding of PPAR-mediated neuroprotective mechanisms in the injured brain and discusses potential future anti-inflammatory strategies for head-injured patients, with an emphasis on the putative beneficial combination therapy of synthetic cannabinoids (e.g., dexanabinol) with PPARα agonists (e.g., fenofibrate).

Therapeutic Potential of Non-Psychotropic Cannabidiol in Ischemic Stroke

Cannabis contains the psychoactive component delta⁹-tetrahydrocannabinol (delta⁹-THC), and the non-psychoactive components cannabidiol (CBD), cannabinol, and cannabigerol. It is well-known that delta⁹-THC and other cannabinoid CB₁ receptor agonists are neuroprotective during global and focal ischemic injury. Additionally, delta⁹-THC also mediates psychological effects through the activation of the CB₁ receptor in the central nervous system. In addition to the CB₁ receptor agonists, cannabis also contains therapeutically active components which are CB₁ receptor independent. Of the CB₁ receptor-independent cannabis, the most important is CBD. In the past five years, an increasing number of publications have focused on the discovery of the anti-inflammatory, anti-oxidant, and neuroprotective effects of CBD. In particular, CBD exerts positive pharmacological effects in ischemic stroke and other chronic diseases, including Parkinson’s disease, Alzheimer’s disease, and rheumatoid arthritis. The cerebroprotective action of CBD is CB₁ receptor-independent, long-lasting, and has potent anti-oxidant activity. Importantly, CBD use does not lead to tolerance. In this review, we will discuss the therapeutic possibility of CBD as a cerebroprotective agent, highlighting recent pharmacological advances, novel mechanisms, and therapeutic time window of CBD in ischemic stroke.

Valproate administered after traumatic brain injury provides neuroprotection and improves cognitive function in rats

BACKGROUND

Traumatic brain injury (TBI) initiates a complex series of neurochemical and signaling changes that lead to pathological events including neuronal hyperactivity, excessive glutamate release, inflammation, increased blood-brain barrier (BBB) permeability and cerebral edema, altered gene expression, and neuronal dysfunction. It is believed that a drug combination, or a single drug acting on multiple targets, may be an effective strategy to treat TBI. Valproate, a widely used antiepileptic drug, has a number of targets including GABA transaminase, voltage-gated sodium channels, glycogen synthase kinase (GSK)-3, and histone deacetylases (HDACs), and therefore may attenuate a number of TBI-associated pathologies.

METHODOLOGY/PRINCIPAL FINDINGS

Using a rodent model of TBI, we tested if post-injury administration of valproate can decrease BBB permeability, reduce neural damage and improve cognitive outcome. Dose-response studies revealed that systemic administration of 400 mg/kg (i.p.), but not 15, 30, 60 or 100 mg/kg, increases histone H3 and H4 acetylation, and reduces GSK-3 activity, in the hippocampus. Thirty min post-injury administration of 400 mg/kg valproate improved BBB integrity as indicated by a reduction in Evans Blue dye extravasation. Consistent with its dose response to inhibit GSK-3 and HDACs, valproate at 400 mg/kg, but not 100 mg/kg, reduced TBI-associated hippocampal dendritic damage, lessened cortical contusion volume, and improved motor function and spatial memory. These behavioral improvements were not observed when SAHA (suberoylanilide hydroxamic acid), a selective HDAC inhibitor, was administered.

CONCLUSION/SIGNIFICANCE

Our findings indicate that valproate given soon after TBI can be neuroprotective. As clinically proven interventions that can be used to minimize the damage following TBI are not currently available, the findings from this report support the further testing of valproate as an acute therapeutic strategy.

Pursuing paradoxical proconvulsant prophylaxis for epileptogenesis

There are essentially two potential treatment options for any acquired disorder: symptomatic or prophylactic. For acquired epilepsies that follow a variety of different brain insults, there remains a complete lack of prophylactic treatment options, whereas at the same time these epilepsies are notoriously resistant, once they have emerged, to symptomatic treatments with antiepileptic drugs. The development of prophylactic strategies is logistically challenging, both for basic researchers and clinicians. Nevertheless, cannabinoid-targeting drugs provide a very interesting example of a system within the central nervous system (CNS) that can have very different acute and long-term effects on hyperexcitability and seizures. In this review, we outline research on cannabinoids suggesting that although cannabinoid antagonists are acutely proconvulsant, they may have beneficial effects on long-term hyperexcitability following brain insults of multiple etiologies, making them promising candidates for further investigation as prophylactics against acquired epilepsy. We then discuss some of the implications of this finding on future attempts at prophylactic treatments, specifically, the very short window within which prevention may be possible, the possibility that traditional anticonvulsants may interfere with prophylactic strategies, and the importance of moving beyond anticonvulsants-even to proconvulsants-to find the ideal preventative strategy for acquired epilepsy.

Multifunctional drugs for head injury

Traumatic brain injury (TBI) remains one of the leading causes of mortality and morbidity worldwide in individuals under the age of 45 years, and, despite extensive efforts to develop neuroprotective therapies, there has been no successful outcome in any trial of neuroprotection to date. In addition to recognizing that many TBI clinical trials have not been optimally designed to detect potential efficacy, the failures can be attributed largely to the fact that most of the therapies investigated have been targeted toward an individual injury factor. The contemporary view of TBI is that of a very heterogenous type of injury, one that varies widely in etiology, clinical presentation, severity, and pathophysiology. The mechanisms involved in neuronal cell death after TBI involve an interaction of acute and delayed anatomic, molecular, biochemical, and physiological events that are both complex and multifaceted. Accordingly, neuropharmacotherapies need to be targeted at the multiple injury factors that contribute to the secondary injury cascade, and, in so doing, maximize the likelihood of a successful outcome. This review focuses on a number of such multifunctional compounds that have shown considerable success in experimental studies and that show maximum promise for success in clinical trials.

Disruption of IFN-gamma- mediated antiviral activity in neurons: the role of cannabinoids

Interferon-gamma (IFN-gamma) has potent antiviral activity in neurons which is affected by the production of nitric oxide (NO). This study examines the interactions between cannabinoid receptor-1 (CB(1)), IFNgamma-induced pathways, and inhibition of vesicular stomatitis virus (VSV) replication in neuronal cells. CB(1) is abundantly expressed in neurons of the CNS and the NB41A3 neuroblastoma cell line. CB(1) activation of NB41A3 cells by the synthetic cannabinoid, WIN55,212-2, is associated with an inhibition of Ca(2+) mobilization, leading to diminished nitric oxide synthase (NOS)-1 activity and the production of NO, in vitro. This ultimately results in antagonism of IFN-gamma-mediated antiviral activity and enhanced viral replication. Therefore, activation of cells expressing CB(1) by endogenous (or exogenous) ligands may contribute to decreased inflammation and to increased viral replication in neurons and disease in the CNS.

Cannabinoids as therapeutic agents for ablating neuroinflammatory disease

Cannabinoids have been reported to alter the activities of immune cells in vitro and in vivo. These compounds may serve as ideal agents for adjunct treatment of pathological processes that have a neuroinflammatory component. As highly lipophilic molecules, they readily access the brain. Furthermore, they have relatively low toxicity and can be engineered to selectively target cannabinoid receptors. To date, two cannabinoid receptors have been identified, characterized and designated CB(1) and CB(2). CB(1) appears to be constitutively expressed within the CNS while CB(2) apparently is induced during inflammation. The inducible nature of expression of CB(2) extends to microglia, the resident macrophages of the brain that play a critical role during early stages of inflammation in that compartment. Thus, the cannabinoid-cannabinoid receptor system may prove therapeutically manageable in ablating neuropathogenic disorders such as Alzheimer's disease, multiple sclerosis, amyotrophic lateral sclerosis, HIV encephalitis, closed head injury, and granulomatous amebic encephalitis.

Enhancing expression of Nrf2-driven genes protects the blood brain barrier after brain injury

The integrity of the blood-brain barrier (BBB) is critical for normal brain function, and its compromise contributes to the pathophysiology of a number of CNS diseases and injuries. Using a rodent model of brain injury, the present study examines the pathophysiology of BBB disruption. Western blot and immunohistochemical analyses indicate that brain injury causes a loss of capillary endothelial cells and tight junction proteins, two critical components of the BBB. Activation of the transcription factor NF-E2-related factor-2 (Nrf2) by sulforaphane, a naturally occurring compound present in high levels in cruciferous vegetables, significantly increased the expression of endogenous cytoprotective genes in brain tissue and microvessels as indicated by real-time PCR analysis. Postinjury administration of sulforaphane reduced the loss of endothelial cell markers and tight junction proteins and preserved BBB function. These protective effects were dependent on the activity of Nrf2. Injured rats pretreated with decoy oligonucleotides containing the binding site of Nrf2, and mice lacking the nrf2 gene, did not benefit from sulforaphane administration. These findings indicate a potential therapeutic usefulness for Nrf2-activating molecules to improve the function of the neurovascular unit after injury.

The endocannabinoid system as an emerging target of pharmacotherapy

The recent identification of cannabinoid receptors and their endogenous lipid ligands has triggered an exponential growth of studies exploring the endocannabinoid system and its regulatory functions in health and disease. Such studies have been greatly facilitated by the introduction of selective cannabinoid receptor antagonists and inhibitors of endocannabinoid metabolism and transport, as well as mice deficient in cannabinoid receptors or the endocannabinoid-degrading enzyme fatty acid amidohydrolase. In the past decade, the endocannabinoid system has been implicated in a growing number of physiological functions, both in the central and peripheral nervous systems and in peripheral organs. More importantly, modulating the activity of the endocannabinoid system turned out to hold therapeutic promise in a wide range of disparate diseases and pathological conditions, ranging from mood and anxiety disorders, movement disorders such as Parkinson's and Huntington's disease, neuropathic pain, multiple sclerosis and spinal cord injury, to cancer, atherosclerosis, myocardial infarction, stroke, hypertension, glaucoma, obesity/metabolic syndrome, and osteoporosis, to name just a few. An impediment to the development of cannabinoid medications has been the socially unacceptable psychoactive properties of plant-derived or synthetic agonists, mediated by CB(1) receptors. However, this problem does not arise when the therapeutic aim is achieved by treatment with a CB(1) receptor antagonist, such as in obesity, and may also be absent when the action of endocannabinoids is enhanced indirectly through blocking their metabolism or transport. The use of selective CB(2) receptor agonists, which lack psychoactive properties, could represent another promising avenue for certain conditions. The abuse potential of plant-derived cannabinoids may also be limited through the use of preparations with controlled composition and the careful selection of dose and route of administration. The growing number of preclinical studies and clinical trials with compounds that modulate the endocannabinoid system will probably result in novel therapeutic approaches in a number of diseases for which current treatments do not fully address the patients' need. Here, we provide a comprehensive overview on the current state of knowledge of the endocannabinoid system as a target of pharmacotherapy.

[Anti-inflammatory modulators in traumatic brain injury]

Traumatic brain injury leads to primary and secondary brain injuries. Primary brain injury results from mechanical forces applied to the head at the time of impact. Secondary brain injury occurs at some time after the primary impact. Numerous pathophysiological mechanisms have been postulated to explain the progressive tissue damage produced by secondary injuries. The endogenous neuroinflammatory response after traumatic brain injury contributes to the development of blood-brain barrier breakdown, cerebral oedema and neuronal cell death and this has led to various pharmacological therapies to try to limit this type of damage. Studies employing glutamate receptor antagonist for cerebral protection have yielded promising results in laboratory animals but failed to produce clinically significant improvements. The present review will summarize the mechanisms of post traumatic cerebral inflammation with a special focus on the anti-inflammatory drug targets.

Targeting the endocannabinoid system in treating brain disorders

Recent cannabinoid research has a primary focus on developing therapeutics against human diseases. Many studies on cannabinoids indicate important progress for protection against several neurodegenerative disorders. Agonists of cannabinoid receptors activate signalling pathways in the brain that are linked to neuronal repair and cell maintenance, and endogenous ligands can also activate neuroprotective responses. These endocannabinoids are bioactive fatty acid amides and esters that are synthesised in the brain and include arachidonoyl ethanolamide (anandamide) and 2-arachidonoyl glycerol. Endocannabinoids are released in response to pathogenic events, thus representing a potential compensatory repair mechanism. Enhancing this on-demand action of endocannabinoids is a strategy with which to promote endogenous repair signalling. For such enhancement, considerable work has gone into modulating the availability of endocannabinoids by blocking the processes of their deactivation. The targets include the anandamide-hydrolysing enzyme fatty acid amide hydrolase, the carrier-mediated anandamide transport system and 2-arachidonoyl glycerol-deactivating enzyme monoacylglycerol lipase. The activity of endocannabinoids is terminated through transport and degradation and, accordingly, selective inhibitors of these processes effectively exploit the protective nature of cannabinergic responses. This review highlights recent studies implicating the endocannabinoid system in neuroprotection against different disorders of the CNS.

Sulforaphane enhances aquaporin-4 expression and decreases cerebral edema following traumatic brain injury

Brain edema, the infiltration and accumulation of excess fluid causing an increase in brain tissue volume, often leads to a rise in intracranial pressure and is a key contributor to the morbidity and mortality associated with traumatic brain injury (TBI). The cellular and molecular mechanisms contributing to the development/resolution of TBI-associated brain edema are poorly understood. Aquaporin-4 (AQP4) water channel is expressed at high levels in brain astrocytes, and the bidirectional transport of water through these channels is critical for the maintenance of brain water homeostasis. By using a rodent injury model, we show that TBI decreased AQP4 level in the injury core and modestly increased it in the penumbra region surrounding the core. Postinjury administration of sulforaphane (SUL), an isothiocyanate present in abundance in cruciferous vegetables such as broccoli, attenuated AQP4 loss in the injury core and further increased AQP4 levels in the penumbra region compared with injured animals receiving vehicle. These increases in AQP4 levels were accompanied by a significant reduction in brain edema (assessed by percentage water content) at 3 days postinjury. These findings suggest that the reduction of brain edema in response to SUL administration could be due, in part, to water clearance by AQP4 from the injured brain.

Cannabidiol-induced intracellular Ca2+ elevations in hippocampal cells

The phytocannabinoid cannabidiol (CBD) is at the forefront of therapeutic cannabinoid research due to its non-psychotropic properties. Research supports its use in a variety of disorders, yet the cellular mechanisms of its action remain unclear. In this study, the effect of CBD upon Ca2+ homeostasis in hippocampal cells was characterised. CBD (1 microM) elevated intracellular Ca2+ ([Ca2+]i) by approximately +45% of basal Ca2+ levels in both glia (77% responders) and neurones (51% responders). Responses to CBD were reduced in high excitability HEPES buffered solution (HBS), but not affected in low excitability/low Ca2+ HBS. CBD responses were also significantly reduced (by 50%) by the universal Ca2+ channel blocker cadmium (50 microM) and the L-type specific Ca2+ channel blocker nifedipine (20 microM). Interestingly, intracellular store depletion with thapsigargin (2 microM) had the most dramatic effect on CBD responses, leading on average to a full block of the response. Elevated CBD-induced [Ca2+]i responses (>+100%) were observed in the presence of the CB1 receptor antagonist, AM281 (1 microM), and the vanilloid receptor antagonist, capsazepine (CPZ, 1 microM). Overall, our data suggest that CBD modulates hippocampal [Ca2+]i homeostasis via intracellular Ca2+ stores and L-type VGCC-mediated Ca2+ entry, with tonic cannabinoid and vanilloid receptor signalling being negatively coupled to this pathway.

Recent advances in the development of multifactorial therapies for the treatment of traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of death and disability in the industrialised world and remains a major health problem with serious socioeconomic consequences. So far, despite encouraging preclinical results, almost all neuroprotection trials have failed to show any significant efficacy in the treatment of clinical TBI. This may be due, in part, to the fact that most of the therapies investigated have targeted an individual injury factor. It is now recognised that TBI is a very heterogeneous type of injury that varies widely in its aetiology, clinical presentation, severity and pathophysiology. The pathophysiological sequelae of TBI are mediated by an interaction of acute and delayed molecular, biochemical and physiological events that are both complex and multifaceted. Accordingly, a successful TBI treatment may have to simultaneously attenuate many injury factors. Recent efforts in experimental TBI have, therefore, focused on the development of neuropharmacotherapies that target multiple injury factors and thus improve the likelihood of a successful outcome. This review will focus on three such novel compounds that are currently being assessed in clinical trials; progesterone, dexanabinol and dexamethasone, and provide an update on the progress of both magnesium and cyclosporin A.

[Therapeutic use of cannabinoids in neurology]

This review gives insight into the potential therapeutical role of cannabinoids in neurology. Preclinical data are presented which could give a rationale for the clinical use of cannabinoids in the fields of multiple sclerosis, spasticity, epilepsy, movement disorders, and neuroprotection after traumatic head injury or ischemic stroke. Besides, clinical data (case reports, open-label and randomised controlled studies) dealing with the therapeutical use of cannabinoids in these fields are reported and discussed. At present, clinical data are insufficient to recommend the use of cannabinoids in any neurological disease as standard therapy. Several questions still have to be answered (which cannabinoid? which way of administration? stimulation of endogenous cannabinoids? separation between desired and undesired effects?), and controlled studies are still needed to clarify the potential therapeutical role of cannabinoids in neurology.

Combination of dexanabinol and tempol in focal cerebral ischemia: is there a ceiling effect?

Because ischemic neuronal death is triggered by several parallel mechanisms, a combination of drugs active against individual death-promoting mechanisms may have synergistic effects. Dexanabinol is a noncompetitive NMDA antagonist with anti-inflammatory effects and tempol is a nitroxide antioxidant. Therefore, we explored whether their combined use results in smaller infarct volumes as compared with their individual administration. Rats underwent permanent middle cerebral artery occlusion (PMCAO) and were given vehicle, dexanabinol alone, tempol alone, or a combination of dexanabinol and tempol (n = 13 per group) 1 h later. Five animals in each group were evaluated with a motor rating scale 24 h after PMCAO and the infarct volumes were then measured. The remaining animals were examined with motor and behavioral scales up to 30 days after PMCAO and their infarct volumes were then determined. Motor disability and water maze latencies at all time points examined and infarct volumes at days 1 and 30 were significantly reduced in all active treatment groups when compared with vehicle. However, no significant differences were observed between the active treatment groups. In conclusions, combination therapy with dexanabinol and tempol does not appear to have additional neuroprotective effects compared to those conferred by each agent alone even when administered at optimal timing and dosing. Therefore, a ceiling neuroprotective effect that is impossible to overcome may exist.

Closed-head minimal traumatic brain injury produces long-term cognitive deficits in mice

Victims of minimal traumatic brain injury (mTBI) do not show clear morphological brain defects, but frequently suffer lasting cognitive deficits, emotional difficulties and behavioral disturbances. In the present study we adopted a non-invasive closed-head weight-drop mouse model to produce mTBI. We examined the effects of 20, 25, or 30 g weight drop 7, 30, 60 and 90 days following injury on mice's ability to perform the Morris water maze. The mice suffered profound long-lasting learning and memory deficits that were force- and time-dependent. Although the injured mice could acquire the task, they could not improve their initial escape latency by more than 50%, while normal mice improved by up to 450% (P<0.001). In order to directly compare the learning ability of individual mice following our mTBI we have devised a new measure which we term learning rate. We define learning rate as the rate the mouse improved its own performance in consecutive trials in a given experimental day. The learning rate of control mice increased linearly throughout the testing period with a slope of approximately 0.9. Injured mice that sustained 20 and 25 g weight drop could also improve their learning rate linearly but with a slope of only 0.2. Mice who sustained 30 g weight drop could not improve their learning rate linearly and reached a plateau after the third experimental learning day. These results indicate that the severity of injury may correlate with the degree of integration of the learning task. These cognitive deficits occurred without any other clear neurological damage, no evident brain edema, no notable damage to the blood-brain barrier and no early anatomical changes to the brain (observed by magnetic resonance imaging imaging). These results demonstrate that persistent deficits of cognitive learning abilities in mice, similar to those observed in human post-concussive syndrome, can follow mTBI without any anatomical damage to the brain and its surrounding tissue.

Dexanabinol (HU-211) has a beneficial effect on axonal sprouting and survival after rat optic nerve crush injury

Dexanabinol (HU-211) is a synthetic non-psychotropic cannabinoid and a non-competitive NMDA-receptor antagonist. The beneficial effect of dexanabinol on prevention of degeneration and promotion of regeneration was studied on the crush-injured rat optic nerve model. Sprague-Dawley rats were subjected to a calibrated crush injury of the optic nerve and treated with a single intraperitoneal injection of dexanabinol (7 mg/kg), its vehicle only or were untreated. Transmission electron microscopic analysis of the excised optic nerves was performed after 30 days. In the dexanabinol treated rats, the site of injury was traversed by unmyelinated and thinly myelinated axons, possibly indicative of regenerative growth. No such growth was detectable in the controls. Viable axons were found 0.5 mm distal to the site of injury in 6 of 8 dexanabinol treated rats, but in only 1 of 10 rats in the control groups. These results have clinical implications for the prevention of secondary degeneration and promotion of regeneration after injuries to the central nervous system.

The therapeutic potential of the cannabinoids in neuroprotection

After thousands of years of interest the last few decades have seen a huge increase in our knowledge of the cannabinoids and their mode of action. Their potential as medical therapeutics has long been known. However, very real concerns over their safety and efficacy have lead to caution and suspicion when applying the legislature of modern medicine to these compounds. The ability of this diverse family of compounds to modulate neurotransmission and act as anti-inflammatory and antioxidative agents has prompted researchers to investigate their potential as neuroprotective agents. Indeed, various cannabinoids rescue dying neurones in experimental forms of acute neuronal injury, such as cerebral ischaemia and traumatic brain injury. Cannabinoids also provide symptomatic relief in experimental models of chronic neurodegenerative diseases, such as multiple sclerosis and Huntington's disease. This preclinical evidence has provided the impetus for the launch of a number of clinical trials in various conditions of neurodegeneration and neuronal injury using compounds derived from the cannabis plant. Our understanding of cannabinoid neurobiology, however, must improve if we are to effectively exploit this system and take advantage of the numerous characteristics that make this group of compounds potential neuroprotective agents.

Novel therapies in development for the treatment of traumatic brain injury

In industrialised countries, the mean per capita incidence of traumatic brain injury (TBI) that results in a hospital presentation is 250 per 100,000. In Europe and North America alone, this translates to > 2 million TBI presentations annually. Approximately 25% of these presentations are admitted for hospitalisation. Despite the significance of these figures, there is no single interventional pharmacotherapy that has shown efficacy in the treatment of clinical TBI. This lack of efficacy in clinical trials may be due, in part, to the inherent heterogeneity of the traumatic brain injury population. However, it is the multifactorial nature of secondary injury that also poses a major hurdle, particularly for those therapies that have been designed to specifically target an individual injury factor. It is now becoming increasingly recognised that any successful TBI therapy may have to simultaneously affect multiple injury factors, somewhat analogous to other broad spectrum interventions. Recent efforts in experimental TBI have therefore focussed on developing novel pharmacotherapies that may affect multiple injury factors and thus improve the likelihood of a successful outcome. While a number of interventions are noteworthy in this regard, this review will focus on three novel compounds that show particular promise: magnesium, substance P antagonists and cyclosporin A.

Stilbazulenyl nitrone, a novel azulenyl nitrone antioxidant: improved neurological deficit and reduced contusion size after traumatic brain injury in rats

OBJECT

Stilbazulenyl nitrone (STAZN) is a second-generation azulenyl nitrone that has markedly enhanced antioxidant properties compared with those of conventional alpha-phenyl nitrones. In this study, the authors assessed the potential efficacy of STAZN in a rodent model of fluid-percussion brain injury, which results in a consistent cortical contusion.

METHODS

After anesthesia had been induced in normothermic Sprague-Dawley rats (brain temperature 36-36.5 degrees C) by halothane-nitrous oxide, the animals were subjected to a right parietooccipital parasagittal fluid-percussion injury (1.5-2 atm). The agent (STAZN, 30 mg/kg: eight animals) or vehicle (dimethyl sulfoxide; eight animals) was administered intraperitoneally at 5 minutes and 4 hours after trauma. The neurological status of each rat was evaluated on Days 1, 2, and 7 postinjury (normal score 0, maximum injury 12). Seven days after trauma, the rat brains were perfusion fixed, coronal sections at various levels were digitized, and areas of contusion were measured. Treatment with STAZN significantly improved neurological scores on Days 2 and 7 postinjury compared with vehicle-treated rats. Administration of STAZN also significantly reduced the total contusion area by 63% (1.8 +/- 0.5 mm2 in STAZN-treated animals compared with 4.8 +/- 2.1 mm2 in vehicle-treated animals; p = 0.04) and the deep cortical contusion area by 60% (1.2 +/- 0.2 mm2 in STAZN-treated animals compared with 2.9 +/- 1.2 mm2 in vehicle-treated animals; p = 0.03). By contrast, hippocampal cell loss in the CA3 sector was unaffected by STAZN treatment.

CONCLUSIONS

Therapy with STAZN, a novel potent antioxidant, administered following traumatic brain injury, markedly improves neurological and histological outcomes. Azulenyl nitrones appear to represent a promising class of neuroprotective agents for combating this devastating condition.