Human cellular inflammation in the pathology of acute cerebral ischaemia

Neuroprotective strategies for neonatal hypoxic-ischemic brain damage: Current status and challenges

Neonatal hypoxic-ischemic brain damage (HIBD) is a prominent contributor to both immediate mortality and long-term impairment in newborns. The elusive nature of the underlying mechanisms responsible for neonatal HIBD presents a significant obstacle in the effective clinical application of numerous pharmaceutical interventions. This comprehensive review aims to concentrate on the potential neuroprotective agents that have demonstrated efficacy in addressing various pathogenic factors associated with neonatal HIBD, encompassing oxidative stress, calcium overload, mitochondrial dysfunction, endoplasmic reticulum stress, inflammatory response, and apoptosis. In this review, we conducted an analysis of the precise molecular pathways by which these drugs elicit neuroprotective effects in animal models of neonatal hypoxic-ischemic brain injury (HIBD). Our objective was to provide a comprehensive overview of potential neuroprotective agents for the treatment of neonatal HIBD in animal experiments, with the ultimate goal of enhancing the feasibility of clinical translation and establishing a solid theoretical foundation for the clinical management of neonatal HIBD.

The new insight into the inflammatory response following focused ultrasound-mediated blood-brain barrier disruption

BACKGROUND

Despite the great potential of FUS-BBB disruption (FUS-BBBD), it is still controversial whether FUS-BBBD acts as an inducing factor of neuro-inflammation or not, and the biological responses after FUS-BBBD triggers the inflammatory process are poorly understood. The aim of this study is to investigate the safety window for FUS levels based on a comprehensive safety assessment.

METHODS

The mice were treated with two different ultrasound parameters (0.25 MPa and 0.42 MPa) in the thalamus region of brain. The efficacy of BBB opening was verified by dynamic contrast-enhanced MRI (DCE-MRI) and the cavitation monitoring. The transcriptome analysis was performed to investigate the molecular response for the two BBBD conditions after FUS-mediated BBB opening in time-dependent manners. Histological analysis was used for evaluation of the tissue damage, neuronal degeneration, and activation of glial cells induced by FUS-BBBD.

RESULTS

The BBBD, as quantified by the K_trans, was approximately threefold higher in 0.42 MPa-treated group than 0.25 MPa-treated group. While the minimal tissue/cellular damage was found in 0.25 MPa-treated group, visible damages containing microhemorrhages and degenerating neurons were detected in 0.42 MPa-treated group in accordance with the extent of BBBD. In transcriptome analysis, 0.42 MPa-treated group exhibited highly dynamic changes in the expression levels of an inflammatory response or NF-κB pathway-relative genes in a time-dependent manner whereas, 0.25 MPa was not altered. Interestingly, although it is clear that 0.42 MPa induces neuroinflammation through glial activation, neuroprotective properties were evident by the expression of A2-type astrocytes.

CONCLUSIONS

Our findings propose that a well-defined BBBD parameter of 0.25 MPa could ensure the safety without cellular/tissue damage or sterile inflammatory response in the brain. Furthermore, the fact that the excessive sonication parameters at 0.42 MPa could induce a sterile inflammation response via glial activation suggested the possibility that could lead to tissue repair toward the homeostasis of the brain microenvironment through A2-type reactive astrocytes.

Adhesion of Leukocytes to Cerebral Venules Precedes Neuronal Cell Death and Is Sufficient to Trigger Tissue Damage After Cerebral Ischemia

Background

Leukocytes contribute to tissue damage after cerebral ischemia; however, the mechanisms underlying this process are still unclear. This study investigates the temporal and spatial relationship between vascular leukocyte recruitment and tissue damage and aims to uncover which step of the leukocyte recruitment cascade is involved in ischemic brain injury.

Methods

Male wild-type, ICAM-1-deficient, anti-CD18 antibody treated, or selectin-deficient [fucusyltransferase (FucT IV/VII^−/−)] mice were subjected to 60 min of middle cerebral artery occlusion (MCAo). The interaction between leukocytes and the cerebrovascular endothelium was quantified by in vivo fluorescence microscopy up to 15 h thereafter. Temporal dynamics of neuronal cell death and leukocyte migration were assessed at the same time points and in the same tissue volume by histology.

Results

In wild-type mice, leukocytes started to firmly adhere to the wall of pial postcapillary venules two hours after reperfusion. Three hours later, neuronal loss started and 13 h later, leukocytes transmigrated into brain tissue. Loss of selectin function did not influence this process. Application of an anti-CD18 antibody or genetic deletion of ICAM-1, however, significantly reduced tight adhesion of leukocytes to the cerebrovascular endothelium (-60%; p < 0.01) and increased the number of viable neurons in the ischemic penumbra by 5-fold (p < 0.01); the number of intraparenchymal leukocytes was not affected.

Conclusions

Our findings suggest that ischemia triggers only a transient adhesion of leukocytes to the venous endothelium and that inhibition of this process is sufficient to partly prevent ischemic tissue damage.

Immune responses in perinatal brain injury

The perinatal period has often been described as immune deficient. However, it has become clear that immune responses in the neonate following exposure to microbes or as a result of tissue injury may be substantial and play a role in perinatal brain injury. In this article we will review the immune cell composition under normal physiological conditions in the perinatal period, both in the human and rodent. We will summarize evidence of the inflammatory responses to stimuli and discuss how neonatal immune activation, both in the central nervous system and in the periphery, may contribute to perinatal hypoxic-ischemic brain injury.

Early monitoring and quantitative evaluation of macrophage infiltration after experimental traumatic brain injury: A magnetic resonance imaging and flow cytometric analysis

The inflammatory response following traumatic brain injury (TBI) is regulated by phagocytic cells. These cells comprising resident microglia and infiltrating macrophages play a pivotal role in the interface between early detrimental and delayed beneficial effects of inflammation. The aim of the present study was to monitor the early effect of monocyte/phagocytic accumulation and further to explore its kinetics in TBI mice. Localized macrophage population was monitored using ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle enhanced in vivo serial magnetic resonance imaging (MRI). Flow cytometry based gating study was performed to discriminate between resident microglia (Ly6G^-CD11b⁺CD45^low) and infiltrating macrophages (Ly6G^-CD11b⁺CD45^high) at the injury site. The T₂* relaxation analysis revealed that maximum macrophage infiltration occurs between 66 and 72h post injury (42-48h post administration of USPIO) at the site of inflammation. This imaging data was well supported by iron oxide specific Prussian blue staining and macrophage specific F4/80 immunohistochemistry (IHC) analysis. Quantitative real-time PCR analysis found significant expression of monocyte chemoattractant protein-1 (MCP-1) at 72h post injury. Also, we found that flow cytometric analysis demonstrated a 7-fold increase in infiltrating macrophages around 72h post injuries as compared to control. The MR imaging in combination with flow cytometric analysis enabled the dynamic measurement of macrophage infiltration at the injury site. This study may help in setting an optimal time window to intervene and prevent damage due to inflammation and to increase the therapeutic efficacy.

Expression of aryl hydrocarbon receptor in rat brain lesions following traumatic brain injury

Background

Aryl Hydrocarbon Receptor (AhR) is a ligand-activated transcription factor with multiple functions operating in a variety of organs, including the brain. Recent studies have revealed that AhR played a functional role in traumatic injuries. This paper aims to study the expression of AhR during the early phase following a traumatic brain injury (TBI) in rat brains by immunohistochemistry.

Methods

Weight-drop induced TBI was performed in rats. The expression of AhR in brain of TBI rats were examined by immunohistochemistry.

Results

Neuron expression of AhR in the rat brains of experiment group had been upregulated since day 3 in lesional hemisphere compared to that of the control group and mainly located in the cytoplasm, indicating an inactivated state. Interestingly, the accumulation of AhR⁺ non-neuron cells became significant as early as 18 h after injury, which had kept increasing until 24 h post injury and then decreased slowly. For AhR⁺ non-neuron cells, the AhR mainly located in cell nucleus, indicating a reactive status. Furthermore, double staining showed that most AhR⁺ non-neuron cells co-localized with W3/13, a marker for T lymphocytes, but not with ED-1 (for activated microglia/macrophages) or GFAP (for activated astrocytes), suggesting that most AhR⁺ non-neuron cells were T lymphocytes.

Conclusion

This is the first study concerning AhR expression in brains following TBI, and our data demonstrated that AhR was upregulated and activated in T lymphocytes following TBI. More research is needed to make a more conclusive conclusion.

Omega-3 Fatty Acids: Possible Neuroprotective Mechanisms in the Model of Global Ischemia in Rats

Background. Omega-3 (ω3) administration was shown to protect against hypoxic-ischemic injury. The objectives were to study the neuroprotective effects of ω3, in a model of global ischemia. Methods. Male Wistar rats were subjected to carotid occlusion (30 min), followed by reperfusion. The groups were SO, untreated ischemic and ischemic treated rats with ω3 (5 and 10 mg/kg, 7 days). The SO and untreated ischemic animals were orally treated with 1% cremophor and, 1 h after the last administration, they were behaviorally tested and euthanized for neurochemical (DA, DOPAC, and NE determinations), histological (Fluoro jade staining), and immunohistochemical (TNF-alpha, COX-2 and iNOS) evaluations. The data were analyzed by ANOVA and Newman-Keuls as the post hoc test. Results. Ischemia increased the locomotor activity and rearing behavior that were partly reversed by ω3. Ischemia decreased striatal DA and DOPAC contents and increased NE contents, effects reversed by ω3. This drug protected hippocampal neuron degeneration, as observed by Fluoro-Jade staining, and the increased immunostainings for TNF-alpha, COX-2, and iNOS were partly or totally blocked by ω3. Conclusion. This study showed a neuroprotective effect of ω3, in great part due to its anti-inflammatory properties, stimulating translational studies focusing on its use in clinic for stroke managing.

Cytokines, chaperones and neuroinflammatory responses in heroin-related death: what can we learn from different patterns of cellular expression?

Heroin (3,6-diacetylmorphine) has various effects on the central nervous system with several neuropathological alterations including hypoxic-ischemic brain damage from respiratory depressing effects and neuroinflammatory response. Both of these mechanisms induce the release of cytokines, chemokines and other inflammatory mediators by the activation of many cell types such as leucocytes and endothelial and glial cells, especially microglia, the predominant immunocompetent cell type within the central nervous system. The aim of this study is to clarify the correlation between intravenous heroin administration in heroin related death and the neuroinflammatory response. We selected 45 cases among autopsies executed for heroin-related death (358 total cases); immunohistochemical studies and Western blotting analyses were used to investigate the expression of brain markers such as tumor necrosis factor-α, oxygen-regulated protein 150, (interleukins) IL-1β, IL-6, IL-8, IL-10, IL-15, cyclooxygenase-2, heat shock protein 70, and CD68 (MAC387). Findings demonstrated that morphine induces inflammatory response and cytokine release. In particular, oxygen-regulated protein 150, cyclooxygenase-2, heat shock protein 70, IL-6 and IL-15 cytokines were over-expressed with different patterns of cellular expression.

Epigenetic mechanisms in cerebral ischemia

Treatment efficacy for ischemic stroke represents a major challenge. Despite fundamental advances in the understanding of stroke etiology, therapeutic options to improve functional recovery remain limited. However, growing knowledge in the field of epigenetics has dramatically changed our understanding of gene regulation in the last few decades. According to the knowledge gained from animal models, the manipulation of epigenetic players emerges as a highly promising possibility to target diverse neurologic pathologies, including ischemia. By altering transcriptional regulation, epigenetic modifiers can exert influence on all known pathways involved in the complex course of ischemic disease development. Beneficial transcriptional effects range from attenuation of cell death, suppression of inflammatory processes, and enhanced blood flow, to the stimulation of repair mechanisms and increased plasticity. Most striking are the results obtained from pharmacological inhibition of histone deacetylation in animal models of stroke. Multiple studies suggest high remedial qualities even upon late administration of histone deacetylase inhibitors (HDACi). In this review, the role of epigenetic mechanisms, including histone modifications as well as DNA methylation, is discussed in the context of known ischemic pathways of damage, protection, and regeneration.

Use of imaging to study leukocyte trafficking in the central nervous system

The migration of leukocytes from the bloodstream into the central nervous system (CNS) is a key event in the pathogenesis of inflammatory neurological diseases and typically involves the movement of cells through the endothelium of post-capillary venules, which contains intercellular tight junctions. Leukocyte trafficking has predominantly been studied in animal models of multiple sclerosis, stroke and infection. However, recent evidence suggests that immune cells and inflammation mechanisms play an unexpected role in other neurological diseases, such as epilepsy and Parkinson's disease. Imaging leukocyte trafficking in the CNS can be achieved by epifluorescence intravital microscopy (IVM) and multiphoton microscopy. Epifluorescence IVM is ideal for the investigation of leukocyte-endothelial interactions, particularly tethering and rolling, signal transduction pathways controlling integrin activation, slow rolling, arrest and adhesion strengthening in CNS vessels. Multiphoton microscopy is more suitable for the investigation of intraluminal crawling, transmigration and motility inside CNS parenchyma. The mechanisms of leukocyte trafficking in the CNS are not well understood but the use of in vivo imaging techniques to unravel the underlying regulatory pathways will provide insight into the mechanisms of brain damage and may contribute to the development of novel therapeutic strategies. In this review, we discuss recent work in this field, highlighting the development and use of in vivo imaging to investigate leukocyte recruitment in the CNS.

E-selectin deficiency attenuates brain ischemia in mice

AIMS

To determine whether E-selectin deficiency can attenuate brain ischemia in a mouse model of focal cerebral ischemia.

METHODS

E-selectin was determined in spontaneously hypertensive rats (SHRs) and stroke-prone spontaneously hypertensive rats (SHR-SPs). E-selectin knockout (Es(-/-) ) mice and wild-type control (WT) mice underwent permanent distal middle cerebral artery occlusion (MCAO). Behavioral analyses were performed followed by the measurement of infarct areas. Myeloperoxidase (MPO) protein was determined by Western blot. IL-6, IL-1β, and TNF-α were detected by ELISA. In situ detection of apoptotic cells was performed by TUNEL staining.

RESULTS

The brain and serum E-selectin levels were higher in SHR-SPs than in SHRs (P < 0.05) after salt intake. E-selectin deficiency improved neurological function and reduced infarct area in cerebral ischemic mice. MPO and IL-1β were lower in Es(-/-) mice than in WT mice. In addition, the number of apoptotic cells in Es(-/-) mice was significantly less than in WT mice after MCAO.

CONCLUSIONS

E-selectin deficiency presents protective effect on cerebral ischemia. This protective effect is likely achieved by the inhibition of inflammation and apoptosis.

Concussions: What a neurosurgeon should know about current scientific evidence and management strategies

BACKGROUND

There has been a tremendous amount of interest focused on the topic of concussions over the past few decades. Neurosurgeons are frequently consulted to manage patients with mild traumatic brain injuries (mTBI) that have radiographic evidence of cerebral injury. These injuries share significant overlap with concussions, injuries that typically do not reveal radiographic evidence of structural injury, in the realms of epidemiology, pathophysiology, outcomes, and management. Further, neurosurgeons often manage patients with extracranial injuries that have concomitant concussions. In these cases, neurosurgeons are often the only "concussion experts" that patients encounter.

RESULTS

The literature has been reviewed and data have been synthesized on the topic including sections on historical background, epidemiology, pathophysiology, diagnostic advances, clinical sequelae, and treatment suggestions, with neurosurgeons as the intended target audience.

CONCLUSIONS

Neurosurgeons should have a fundamental knowledge of the scientific evidence that has developed regarding concussions and be prepared to guide patients with treatment plans.

A3 adenosine receptor agonist reduces brain ischemic injury and inhibits inflammatory cell migration in rats

A3 adenosine receptor (A3AR) is recognized as a novel therapeutic target for ischemic injury; however, the mechanism underlying anti-ischemic protection by the A3AR agonist remains unclear. Here, we report that 2-chloro-N(6)-(3-iodobenzyl)-5'-N-methylcarbamoyl-4'-thioadenosine (LJ529), a selective A3AR agonist, reduces inflammatory responses that may contribute to ischemic cerebral injury. Postischemic treatment with LJ529 markedly reduced cerebral ischemic injury caused by 1.5-hour middle cerebral artery occlusion, followed by 24-hour reperfusion in rats. This effect was abolished by the simultaneous administration of the A3AR antagonist MRS1523, but not the A2AAR antagonist SCH58261. LJ529 prevented the infiltration/migration of microglia and monocytes occurring after middle cerebral artery occlusion and reperfusion, and also after injection of lipopolysaccharides into the corpus callosum. The reduced migration of microglia by LJ529 could be related with direct inhibition of chemotaxis and down-regulation of spatiotemporal expression of Rho GTPases (including Rac, Cdc42, and Rho), rather than by biologically relevant inhibition of inflammatory cytokine/chemokine release (eg, IL-1β, TNF-α, and MCP-1) or by direct inhibition of excitotoxicity/oxidative stress (not affected by LJ529). The present findings indicate that postischemic activation of A3AR and the resultant reduction of inflammatory response should provide a promising therapeutic strategy for the treatment of ischemic stroke.

Neutralization of interleukin-1β reduces cerebral edema and tissue loss and improves late cognitive outcome following traumatic brain injury in mice

Increasing evidence suggests that interleukin-1β (IL-1β) is a key mediator of the inflammatory response following traumatic brain injury (TBI). Recently, we showed that intracerebroventricular administration of an IL-1β-neutralizing antibody was neuroprotective following TBI in mice. In the present study, an anti-IL-1β antibody or control antibody was administered intraperitoneally following controlled cortical injury (CCI) TBI or sham injury in 105 mice and we extended our histological, immunological and behavioral analysis. First, we demonstrated that the treatment antibody reached target brain regions of brain-injured animals in high concentrations (> 11 nm) remaining up to 8 days post-TBI. At 48 h post-injury, the anti-IL-1β treatment attenuated the TBI-induced hemispheric edema (P < 0.05) but not the memory deficits evaluated using the Morris water maze (MWM). Neutralization of IL-1β did not influence the TBI-induced increases (P < 0.05) in the gene expression of the Ccl3 and Ccr2 chemokines, IL-6 or Gfap. Up to 20 days post-injury, neutralization of IL-1β was associated with improved visuospatial learning in the MWM, reduced loss of hemispheric tissue and attenuation of the microglial activation caused by TBI (P < 0.05). Motor function using the rotarod and cylinder tests was not affected by the anti-IL-1β treatment. Our results suggest an important negative role for IL-1β in TBI. The improved histological and behavioral outcome following anti-IL-1β treatment also implies that further exploration of IL-1β-neutralizing compounds as a treatment option for TBI patients is warranted.

Visualization of the ischemic core on native human brain slices by potassium staining method

The potassium staining method is based on the formation of potassium cobaltnitrite crystals after the treatment by sodium cobaltnitrite of brain tissue. The degree of staining correlates with the distinct potassium content of infracted and non-infarcted brain areas. The aim of the present study was to prove that potassium staining technique is a reliable method for localization of ischemic core on native whole hemisphere cryosections of stroke patients. Furthermore, potassium stained sections have been compared with appropriate postmortem MRI images of respective brains. Brains of stroke patients were removed within 24h after death and postmortem MRI scanning was performed. Horizontal cryosections of frozen brains were taken and potassium staining was performed. Using the stained whole hemisphere sections as "map" tissue sampling has been made in order to determine water and potassium content. Potassium content of infarcted samples was significantly decreased in comparison with intact regions (0.7346+/-0.2142 mg/L and 1.928+/-0.447 mg/L, respectively, p<0.01) (mean values+/-SD). Water content of affected areas (expressed in percents) has been found to be above non-infarcted regions (81.657%+/-4.07 and 72.96%+/-6.37, respectively, p<0.01). According to our results the potassium staining method of human whole hemisphere brain sections reliably differentiates focal ischemic areas from intact brain regions. In conclusion, the postmortem examination of ischemic brain could be started with making the potassium map of infarcted whole hemisphere cryosections providing guidance for targeted tissue sampling and base of comparison for further examinations.

Inflammation and brain injury: acute cerebral ischaemia, peripheral and central inflammation

Inflammation is a classical host defence response to infection and injury that has many beneficial effects. However, inappropriate (in time, place and magnitude) inflammation is increasingly implicated in diverse disease states, now including cancer, diabetes, obesity, atherosclerosis, heart disease and, most relevant here, CNS disease. A growing literature shows strong correlations between inflammatory status and the risk of cerebral ischaemia (CI, most commonly stroke), as well as with outcome from an ischaemic event. Intervention studies to demonstrate a causal link between inflammation and CI (or its consequences) are limited but are beginning to emerge, while experimental studies of CI have provided direct evidence that key inflammatory mediators (cytokines, chemokines and inflammatory cells) contribute directly to ischaemic brain injury. However, it remains to be determined what the relative importance of systemic (largely peripheral) versus CNS inflammation is in CI. Animal models in which CI is driven by a CNS intervention may not accurately reflect the clinical condition; stroke being typically induced by atherosclerosis or cardiac dysfunction, and hence current experimental paradigms may underestimate the contribution of peripheral inflammation. Experimental studies have already identified a number of potential anti-inflammatory therapeutic interventions that may limit ischaemic brain damage, some of which have been tested in early clinical trials with potentially promising results. However, a greater understanding of the contribution of inflammation to CI is still required, and this review highlights some of the key mechanism that may offer future therapeutic targets.

Rapid brain penetration of interleukin-1 receptor antagonist in rat cerebral ischaemia: pharmacokinetics, distribution, protection

BACKGROUND AND PURPOSE

Limited data on the brain penetration of potential stroke treatments have been cited as a major weakness contributing to numerous failed clinical trials. Thus, we tested whether interleukin-1 receptor antagonist (IL-1RA), established as a potent inhibitor of brain injury in animals and currently in clinical development, reaches the brain via a clinically relevant administration route, in experimental stroke.

EXPERIMENTAL APPROACH

Male, Sprague-Dawley rats [either naïve or exposed to middle cerebral artery occlusion (MCAo)] were given a single s.c. dose of IL-1RA (100 mg*kg(-1)). The pharmacokinetic profile of IL-1RA was assessed in plasma and CSF up to 24 h post-administration. Brain tissue distribution of administered IL-1RA was assessed using immunohistochemistry. In a separate experiment, the neuroprotective effect of the single s.c. dose of IL-1RA in MCAo was assessed versus a placebo control group.

KEY RESULTS

A single s.c. dose of IL-1RA reduced damage caused by MCAo by 33%. This dose resulted in sustained, high concentrations in plasma and CSF, penetrated brain tissue exclusively in areas of blood-brain barrier breakdown and co-localized with morphologically viable neurones. CSF concentrations did not reflect massive parenchymal infiltration of IL-1RA in MCAo animals compared to naïve.

CONCLUSIONS AND IMPLICATIONS

These data are the first to show that a potential treatment for stroke, IL-1RA, rapidly reaches salvageable brain tissue via an administration route that is clinically relevant. This allows confidence that IL-1RA, as a candidate for further clinical development, is able to confer its protective actions both peripherally and centrally.

Mast cells as early responders in the regulation of acute blood-brain barrier changes after cerebral ischemia and hemorrhage

The inflammatory response triggered by stroke has been viewed as harmful, focusing on the influx and migration of blood-borne leukocytes, neutrophils, and macrophages. This review hypothesizes that the brain and meninges have their own resident cells that are capable of fast host response, which are well known to mediate immediate reactions such as anaphylaxis, known as mast cells (MCs). We discuss novel research suggesting that by acting rapidly on the cerebral vessels, this cell type has a potentially deleterious role in the very early phase of acute cerebral ischemia and hemorrhage. Mast cells should be recognized as a potent inflammatory cell that, already at the outset of ischemia, is resident within the cerebral microvasculature. By releasing their cytoplasmic granules, which contain a host of vasoactive mediators such as tumor necrosis factor-alpha, histamine, heparin, and proteases, MCs act on the basal membrane, thus promoting blood-brain barrier (BBB) damage, brain edema, prolonged extravasation, and hemorrhage. This makes them a candidate for a new pharmacological target in attempts to even out the inflammatory responses of the neurovascular unit, and to stabilize the BBB after acute stroke.

In vivo assessment of macrophage CNS infiltration during disruption of the blood-brain barrier with focused ultrasound: a magnetic resonance imaging study

Focused ultrasound has been discovered to locally and reversibly increase permeability of the blood-brain barrier (BBB). However, inappropriate sonication of the BBB may cause complications, such as hemorrhage and brain tissue damage. Tissue damage may be controlled by selecting optimal sonication parameters. In this study, we sought to investigate the feasibility of labeling cells with superparamagnetic iron oxide particles to assess the inflammatory response during focused-ultrasound-induced BBB opening. We show that infiltration of phagocytes does not occur using optimal parameters of sonication. Taken together, the results of our study support the usefulness and safety of focused-ultrasound-induced BBB opening for enhancing drug delivery to the brain. These findings may have implications for the optimization of sonication parameters.

Chapter 4 - Applications of nanotechnology in molecular imaging of the brain

Rapid advances in the field of nanotechnology promise revolutionary improvements in the diagnosis and therapy of neuroinflammatory disorders. An array of iron oxide nano- and microparticle agents have been developed for in vivo molecular magnetic resonance imaging (mMRI) of cerebrovascular endothelial targets, such as vascular cell adhesion molecule-1 (VCAM-1), E-selectin, and the glycoprotein receptor GP IIb/IIIa expressed on activated platelets. Molecular markers of glioma cells, such as matrix metalloproteinase-2 (MMP-2), and markers for brain tumor angiogenesis, such as alpha (v) beta (3) integrin (alpha(v)beta(3)), have also been successfully targeted using nanoparticle imaging probes. This chapter provides an overview of targeted, iron oxide nano- and microparticles that have been applied for in vivo mMRI of the brain in experimental models of multiple sclerosis (MS), brain ischemia, cerebral malaria (CM), brain cancer, and Alzheimer's disease. The potential of targeted nanoparticle agents for application in clinical imaging is also discussed, including multimodal and therapeutic approaches.

A rapid and transient peripheral inflammatory response precedes brain inflammation after experimental stroke

Increasing evidence suggests that peripheral inflammatory responses to stroke and other brain injuries have an important role in determining neurological outcome. The mediators of this response and the temporal relationships between peripheral and central inflammatory alterations are poorly understood. In this study, we show that experimental stroke in mice induces a peripheral inflammatory response that peaks 4 h after stroke, and precedes the peak in brain inflammation 24 h after stroke. This peripheral response is dominated by the induction of the chemokine CXCL-1 and the proinflammatory cytokine interleukin-6 and could serve as an accessible target for therapy and as a source of biomarkers predictive of prognosis.

Neutralization of interleukin-1beta modifies the inflammatory response and improves histological and cognitive outcome following traumatic brain injury in mice

Interleukin-1beta (IL-1beta) may play a central role in the inflammatory response following traumatic brain injury (TBI). We subjected 91 mice to controlled cortical impact (CCI) brain injury or sham injury. Beginning 5 min post-injury, the IL-1beta neutralizing antibody IgG2a/k (1.5 microg/mL) or control antibody was infused at a rate of 0.25 microL/h into the contralateral ventricle for up to 14 days using osmotic minipumps. Neutrophil and T-cell infiltration and microglial activation was evaluated at days 1-7 post-injury. Cognition was assessed using Morris water maze, and motor function using rotarod and cylinder tests. Lesion volume and hemispheric tissue loss were evaluated at 18 days post-injury. Using this treatment strategy, cortical and hippocampal tissue levels of IgG2a/k reached 50 ng/mL, sufficient to effectively inhibit IL-1betain vitro. IL-1beta neutralization attenuated the CCI-induced cortical and hippocampal microglial activation (P < 0.05 at post-injury days 3 and 7), and cortical infiltration of neutrophils (P < 0.05 at post-injury day 7). There was only a minimal cortical infiltration of activated T-cells, attenuated by IL-1beta neutralization (P < 0.05 at post-injury day 7). CCI induced a significant deficit in neurological motor and cognitive function, and caused a loss of hemispheric tissue (P < 0.05). In brain-injured animals, IL-1beta neutralizing treatment resulted in reduced lesion volume, hemispheric tissue loss and attenuated cognitive deficits (P < 0.05) without influencing neurological motor function. Our results indicate that IL-1beta is a central component in the post-injury inflammatory response that, in view of the observed positive neuroprotective and cognitive effects, may be a suitable pharmacological target for the treatment of TBI.

Systemic infection, inflammation and acute ischemic stroke

Extensive evidence implicates inflammation in multiple phases of stroke etiology and pathology. In particular, there is growing awareness that inflammatory events outside the brain have an important impact on stroke susceptibility and outcome. Numerous conditions, including infection and chronic non-infectious diseases, that are established risk factors for stroke are associated with an elevated systemic inflammatory profile. Recent clinical and pre-clinical studies support the concept that the systemic inflammatory status prior to and at the time of stroke is a key determinant of acute outcome and long-term prognosis. Here, we provide an overview of the impact of systemic inflammation on stroke susceptibility and outcome. We discuss potential mechanisms underlying the impact on ischemic brain injury and highlight the implications for stroke prevention, therapy and modeling.

Monocyte count is an underlying marker of lacunar subtype of hypertensive small vessel disease

BACKGROUND

In the hypertensive small vessel disease (HSVD), it remains unclear why some patients develop lacunar infarcts (LIs) whilst others develop deep intracerebral hemorrhages (dICHs). Inflammation might be related to LI, and leukocyte and monocyte counts are regarded as an inflammatory marker of ischemic stroke.

OBJECTIVE

We investigated the relationship between leukocyte and monocyte counts determined in the first 24 h after stroke onset in HSVD patients.

METHODS

We prospectively studied 236 patients with first acute stroke because of HSVD (129 LI and 107 dICH). We analyzed demographic data, vascular risk factors, and white blood cell count subtypes obtained in the first 24 h after stroke.

RESULTS

The multivariate analysis showed that LI subtype of HSVD was correlated with hyperlipidemia (P < 0.0001), a higher monocyte count (P = 0.002), and showed a trend with current smoking (P = 0.051), whereas dICH subtype was correlated with low serum total cholesterol (P = 0.003), low serum triglycerides (P < 0.0001), and high neutrophil count (P = 0.050).

CONCLUSIONS

In patients who developed HSVD-related stroke, high monocyte count, current smoking, and hyperlipidemia are prothrombotic factors related to LI, whereas low cholesterol and triglyceride values are related to dICH. Monocyte count might be an inflammatory risk marker for the occlusion of small vessels in hypertensive patients.

MRI of monocyte infiltration in an animal model of neuroinflammation using SPIO-labeled monocytes or free USPIO

Magnetic resonance imaging (MRI) has been applied to visualize monocyte infiltration with the use of intravenously injected ultrasmall superparamagnetic iron oxide (USPIO). However, USPIO uptake in vivo remains elusive, and the heterogeneous enhancement patterns observed by MRI point to multiple pathophysiological events. This study focused on specific imaging of monocyte infiltration into the brain by transfusion of superparamagnetic iron oxide (SPIO)-labeled monocytes in a rat model of neuroinflammation, experimentally induced photothrombosis (PT). At day 5 after lesion induction, animals were transfused with SPIO-labeled monocytes (5 x 10(6) cells) or free USPIO (17 mg Fe/kg). MRI was performed 24, 72 and, 120 h later. To investigate temporal changes directly after intravenous USPIO administration, MRI was performed repeatedly up to 8 h. Relaxation measurements showed that rat monocytes were efficiently labeled in vitro using SPIO (R2=12+/-0.9 s(-1)). After transfusion of SPIO-labeled monocytes, a significant increase in contrast enhanced area (340%+/-106%) in the PT lesion was observed not before 72 h. Contrast enhancement after USPIO injection increased up to 407%+/-39% at a much earlier point of time (24 h) and diminished thereafter. Repetitive MRI directly after USPIO injection showed significant contrast enhancement in the lesion within 2 h. Our study shows that MRI enables in vivo tracking of SPIO-labeled monocytes longitudinally. Moreover, our data suggest that contrast enhancement after injection of free USPIO does not primarily represent signals from peripherally labeled monocytes that migrated toward the inflammatory lesion. The use of SPIO-labeled monocytes provides a better tool to specifically assess the time window of monocyte infiltration.

Systemic inflammation and stroke: aetiology, pathology and targets for therapy

There is growing evidence that systemic inflammation is involved in multiple aspects of stroke aetiology and pathology. In the present review, we provide an overview of these roles and, in particular, outline recent evidence that the underlying systemic inflammatory profile can critically alter the response to ischaemic brain injury. We also highlight the need for stroke models to more adequately account for the involvement of underlying systemic inflammation.

Elevated soluble intercellular adhesion molecule-1 levels are associated with poor short-term prognosis in middle-aged patients with acute ischaemic stroke

BACKGROUND

There is increasing evidence that cellular adhesion molecules (CAMs) play an important role in the pathophysiology of acute ischaemic stroke. We examined the prognostic value of soluble intercellular adhesion molecule-1 (sICAM-1) and soluble vascular cell adhesion molecule-1 (sVCAM-1) on in-hospital mortality in patients with ischaemic stroke.

METHODS

We recruited 241 consecutive patients <or=65 years of age who were admitted with acute ischaemic stroke. Serum levels of sICAM-1 and sVCAM-1 were determined within 12 h from admission. Seventy-six subjects without evidence of cardiovascular disease, matched for age and sex, served as controls.

RESULTS

Patients with acute ischaemic stroke had higher sICAM levels compared to controls [267 (220-325) versus 200 (179-225) ng/ml, p<0.001]. Sixteen (6.6%) patients died during hospitalization. sICAM-1 and sVCAM-1 levels were significantly higher in patients who died compared to those who survived [370 (324-453) versus 260 (219-313) ng/ml, p<0.001 and 790 (495-985) versus 576 (494-671) ng/ml, p=0.01, respectively] but only sICAM-1 levels were independently associated with early death, after adjusting for various confounding factors. For 10 ng/ml increase in sICAM-1 levels there was a 9% higher risk of dying. Cut-off point analysis revealed that sICAM-1 levels >322 ng/ml were the optimal points that discriminated those who died from the rest of the patients.

CONCLUSIONS

High sICAM-1 levels on admission are associated with early death in ischaemic middle-aged stroke patients suggesting a pathogenetic role of inflammation in the evolution of ischaemic stroke.

Pathophysiology of ischaemic stroke: insights from imaging, and implications for therapy and drug discovery

Preventing death and limiting handicap from ischaemic stroke are major goals that can be achieved only if the pathophysiology of infarct expansion is properly understood. Primate studies showed that following occlusion of the middle cerebral artery (MCA)--the most frequent and prototypical stroke, local tissue fate depends on the severity of hypoperfusion and duration of occlusion, with a fraction of the MCA territory being initially in a 'penumbral' state. Physiological quantitative PET imaging has translated this knowledge in man and revealed the presence of considerable pathophysiological heterogeneity from patient to patient, largely unpredictable from elapsed time since onset or clinical deficit. While these observations underpinned key trials of thrombolysis, they also indicate that only patients who are likely to benefit should be exposed to its risks. Accordingly, imaging-based diagnosis is rapidly becoming an essential component of stroke assessment, replacing the clock by individually customized management. Diffusion- and perfusion-weighted MR (DWI-PWI) and CT-based perfusion imaging are increasingly being used to implement this, and are undergoing formal validation against PET. Beyond thrombolysis per se, knowledge of the individual pathophysiology also guides management of variables like blood pressure, blood glucose and oxygen saturation, which can otherwise precipitate the penumbra into the core, and the oligaemic tissue into the penumbra. We propose that future therapeutic trials use physiological imaging to select the patient category that best matches the drug's presumed mode of action, rather than lumping together patients with entirely different pathophysiological patterns in so-called 'large trials', which have all failed so far.

Inflammation and ischaemic stroke

PURPOSE OF REVIEW

Inflammation is implicated in ischaemic stroke as a general cardiovascular risk factor, a possible immediate trigger, a component (and possible exacerbating factor) of the response to tissue injury, a marker of future risk, and as a therapeutic target. Each aspect is reviewed.

RECENT FINDINGS

Evidence of epidemiological association of inflammatory markers, particularly C-reactive protein, has accrued, but the independence of inflammation from more conventional risk indicators is under question. Other inflammatory markers are associated with intermediate phenotypes such as hypertension. Tissue inflammation in atherosclerotic plaque is of probable relevance in identifying recently symptomatic carotid disease. Both humoral and cellular inflammation are evident following stroke, with evidence that these responses may exacerbate tissue injury. Blockade of interleukin-1, or of neutrophil chemotaxis, has reduced infarct volume in models of stroke but has yet to show benefit in clinical trials. Other anti-inflammatory strategies are promising.

SUMMARY

Inflammation is implicated in several aspects of acute ischaemic stroke. It remains to be established whether the inflammatory response is a truly independent risk factor in general, or whether specific anti-inflammatory interventions are beneficial either in prevention or acute treatment.

Tacrolimus depresses local immune cell infiltration but fails to reduce cortical contusion volume in brain-injured rats

The immunosuppressant drug tacrolimus (FK-506) failed to show an anti-edematous effect despite suppressing pro-inflammatory cytokines in cerebrospinal fluid following focal traumatic brain injury. By questioning the role of the inflammatory response as a pharmacological target, we investigated the effects of FK-506 on immune cell infiltration in brain-injured rats. Following induction of a cortical contusion, male Sprague-Dawley rats received FK-506 or physiological saline intraperitoneally. Brains were removed at 24 h, 72 h or 7 days, respectively. Frozen brain sections (7 microm) were stained immunohistologically for markers of endothelial activation (intercellular adhesion molecule-1--ICAM-1), neutrophil infiltration (His-48), and microglial and macrophage activation (Ox-6; ED-1), respectively. Immunopositive cells were counted microscopically. Contusion volume (CV) was quantified morphometrically 7 days after trauma. Inflammatory response was confined to the ipsilateral cortex and hippocampal formation, predominating in the contusion and pericontusional cortex. Strongest ICAM-1 expression coincided with sustained granulocyte accumulation at 72h which was suppressed by FK-506. Ox-6+ cells prevailing at 72 h were also significantly reduced by FK-506. ED-1+ cells reaching highest intensity at 7 days were significantly attenuated at 72 h. Cortical CV was not influenced. FK-506 significantly decreased post-traumatic local inflammation which, however, was not associated with a reduction in cortical CV. These results question the importance of post-traumatic local immune cell infiltration in the secondary growth of a cortical contusion.

Dual regulation of astrocyte gap junction hemichannels by growth factors and a pro-inflammatory cytokine via the mitogen-activated protein kinase cascade

Evidence that glutamate and ATP release from astrocytes can occur via gap junction hemichannels (GJHCs) is accumulating. However, the GJHC is still only one possible release mechanism and has not been detected in some studies, although this may be because the levels were below those detectable by the system used. Because of these conflicting results, we hypothesized that release from astrocyte GJHCs might depend on different astrocyte states, and screened for factors affecting astrocyte GJHC activity by measuring fluorescent dye leakage via GJHCs using a conventional method for GJHC acivation, i.e. removal of extracellular divalent cations. Astrocytes cultured in Dulbecco's minimal essential medium containing 10% fetal calf serum, a medium widely used for astrocyte studies, did not show dye leakage, whereas those cultured in a defined medium showed substantial dye leakage, which was confirmed pharmacologically to be due to GJHCs and not to P2x7 receptors. EGF and bFGF inhibited the GJHC activity via the mitogen-activated protein kinase cascade, and the effect of the growth factors was reversed by interleukin-1beta. These factors altered GJHC activity within 10 min, but did not affect connexin 43 expression. GJHC activity in hippocampal slice culture preparations was measured using the same methods and found to be regulated in a similar manner. These results indicate that astrocyte GJHC activity is regulated by brain environmental factors.

Brain oedema in focal ischaemia: molecular pathophysiology and theoretical implications

Focal cerebral ischaemia and post-ischaemic reperfusion cause cerebral capillary dysfunction, resulting in oedema formation and haemorrhagic conversion. There are substantial gaps in understanding the pathophysiology, especially regarding early molecular participants. Here, we review physiological and molecular mechanisms involved. We reaffirm the central role of Starling's principle, which states that oedema formation is determined by the driving force and the capillary "permeability pore". We emphasise that the movement of fluids is largely driven without new expenditure of energy by the ischaemic brain. We organise the progressive changes in osmotic and hydrostatic conductivity of abnormal capillaries into three phases: formation of ionic oedema, formation of vasogenic oedema, and catastrophic failure with haemorrhagic conversion. We suggest a new theory suggesting that ischaemia-induced capillary dysfunction can be attributed to de novo synthesis of a specific ensemble of proteins that determine osmotic and hydraulic conductivity in Starling's equation, and whose expression is driven by a distinct transcriptional program.

Suppression of inflammatory cell recruitment by histamine receptor stimulation in ischemic rat brains

Inflammation is a crucial factor in the development of ischemia-induced brain injury. Since facilitation of central histaminergic activity ameliorates reperfusion injury, effects of postischemic administration of L-histidine, a precursor of histamine, and thioperamide, a histamine H3 receptor antagonist, on inflammatory cell infiltration were evaluated in a rat model of transient occlusion of the middle cerebral artery. After reperfusion for 12, 24, or 72 h following 2 h of occlusion, brain slices were immunohistochemically stained with antibodies against myeloperoxidase and CD68, which were markers of polymorphonuclear leukocytes and macrophages/microglia, respectively. After reperfusion for 12-24 h, the number of neutrophils on the ischemic side increased markedly, whereas the increase was not observed on the contralateral side. Administration of L-histidine (1000 mg/kg x 2, i.p.), immediately and 6 h after reperfusion, reduced the number of neutrophils to 52%. Simultaneous administration of thioperamide (5 mg/kg, s.c.) further decreased the number of neutrophils to 32%. Likewise, the ischemia induced increase in the number of CD68-positive cells after 24 h was suppressed by L-histidine injections. The L-histidine administration decreased the number of CD4+ T lymphocytes on both ischemic and contralateral sides after 12 h, and concurrent administration of thioperamide prolonged the effect. Although administration of mepyramine (3 nmol, i.c.v.) did not affect suppression of leukocyte infiltration, ranitidine tended to reverse the effect of L-histidine. These data suggest that enhancement of central histaminergic activity suppresses inflammatory cell recruitment after ischemic events through histamine H2 receptors, which may be a mechanism underlying the protective effect of L-histidine.

Intrinsic activated microglia map to the peri-infarct zone in the subacute phase of ischemic stroke

BACKGROUND AND PURPOSE

Microglial activation is an important component of the neuroinflammatory response to ischemic stroke. Experimental studies have outlined such patterns temporally and spatially. In vivo studies in stroke patients have relied on positron emission tomography and (R)-PK11195, a ligand that binds peripheral benzodiazepine binding sites. In this study we sought to establish temporal and spatial patterns of microglial activation in ischemic stroke with particular emphasis on a defined peri-infarct zone.

METHODS

Using this technique, we studied carotid territory ischemic stroke patients in 3 time windows up to 30 days after ictus. Controls were studied in a single session. [11C](R)-PK11195 injection was followed by 3-dimensional acquisition over 60 minutes. Cerebral blood volume (CBV) was measured afterward with the use of standard C15O paradigms. Analysis employed the reference tissue model in which ipsilateral cerebellum was used to generate parametric binding potential maps corrected for CBV. Data were coregistered to T1-based MRI. Using control data to identify 99% confidence limits, a region of interest analysis was applied to identify significant binding in core infarction, contralateral hemisphere, and within a defined peri-infarct zone.

RESULTS

Four patients (mean age, 66 years) were imaged across 9 sessions. Four age-matched controls were studied. Within this model, ipsilateral cerebellum was validated as a reference tissue. With the use of control-derived confidence limits and correction for CBV, significant binding potential rises were identified beyond 72 hours and extending to 30 days in core infarction, contralateral hemisphere, and peri-infarct zone.

CONCLUSIONS

In ischemic stroke patients, minimal activation of microglia is seen before 72 hours. Beyond this, binding potential rises in core infarction, peri-infarct zone, and contralateral hemisphere to 30 days. This may represent a therapeutic opportunity that extends beyond time windows traditionally reserved for neuroprotection.

Stroke and T-cells

The microvasculature of the brain region affected by a stroke assumes an inflammatory phenotype that is characterized by endothelial cell activation and barrier dysfunction and the recruitment of adherent leukocytes. Although most attention has been devoted to the possible role of neutrophils in the tissue responses to ischemic stroke there is evidence that T-lymphocytes also accumulate in the postischemic brain. Although comparable detailed analyses of lymphocyte involvement in ischemic brain injury have not been performed, emerging findings suggest a role for T-cells in the pathogenesis of ischemic stroke. The recruitment of T-cells to the site of brain injury is critically dependent on the coordinated expression of adhesion molecules on the activated capillary endothelium. Whether the recruited lymphocytes are acting directly on brain tissue or indirectly through activation of other circulating blood cells and/or extravascular cells remain unclear. Cytotoxic CD8+ T-cells may induce brain injury through molecules released from their cytotoxic granules. CD4+ T-helper 1 (TH1) cells, which secrete proinflammatory cytokines, including interleukin-2 (IL-2), IL-12, interferon-gamma, and tumor necrosis factor-alpha, may play a key role in the pathogenesis of stroke, whereas CD4+TH2 cells may play a protective role through anti-inflammatory cytokines such as IL-4, IL-5, IL-10, and IL-13. T-cells should be considered as therapeutic targets for ischemic stroke. However, because infection is a leading cause of mortality in the postacute phase of ischemic stroke, and considering anti-inflammatory role of CD4+TH2, treatment targeting T-cells should be carefully designed to reduce deleterious and enhance protective actions of T-cells.

The complexity of tissue-type plasminogen activator: can serine protease inhibitors help in stroke management?

Stroke, the third leading cause of death in industrialised countries, represents a major burden on healthcare authorities. The elucidation of molecular events sustaining infarct evolution in experimental models has allowed the development of putative therapeutic agents. However, despite marked benefits in animals, most of them have failed in clinical trials. At present, the only approved therapy for stroke is early reperfusion by intravenous injection of the thrombolytic agent, tissue-type plasminogen activator (tPA). tPA-dependent thrombolysis sometimes promotes haemorrhage, but improves neurological outcome in a great proportion of patients, provided it is performed within the recommended therapeutic window. In addition to the benefit of tPA injection in the vascular compartment, this endogenously produced serine protease could also promote excitotoxic processes within the cerebral parenchyma. This article reviews the various aspects of tPA during stroke, and discusses potential improvements to current clinical management, with a particular emphasis on targeting the deleterious actions of tPA through endogenous serine protease inhibitors (serpins).

Association of Soluble Intercellular Adhesion Molecule 1 with Neurological Deterioration of Ischemic Stroke: The Chongqing Stroke Study

BACKGROUND

Adhesion molecules play important roles in the pathophysiology of ischemic stroke. The aim of the present study was to investigate whether serum levels of soluble intercellular adhesion molecule 1 (sICAM-1), soluble vascular cellular adhesion molecule 1 (sVCAM-1) and soluble E-selectin were associated with neurological deterioration of ischemic stroke.

METHODS

238 consecutive patients with ischemic stroke examined within 24 h from onset were enrolled into the study. The stroke severity was daily assessed with the NIH Stroke Scale (NIHSS) within the first week after admission. Serum levels of sICAM-1, sVCAM-1 and sE-selectin after admission were measured using enzyme-linked immunosorbent assay. Multivariate logistic regression was used to analyze the association of serum levels of sICAM-1, sVCAM-1 and sE-selectin on admission with the neurological deterioration of ischemic stroke, adjusted for potential confounders.

RESULTS

52 (21.8%) out of 238 stroke patients suffered from neurological deterioration. Serum levels of sICAM-1 on admission of stroke patients were significantly higher than those of healthy controls. Compared with patients without deterioration, patients with neurological deterioration had higher levels of sICAM-1, but not of sVCAM-1 and sE-selectin. On multivariate logistic regression, the serum level of sICAM-1 on admission was associated with neurological deterioration of stroke (OR 2.92, 95% CI 1.41-6.05). Other variables associated with neurological deterioration were fasting serum glucose (OR 1.65, 95% CI 1.24-2.20), baseline fibrinogen (OR 1.31, 95% CI 1.13-1.52) and NIHSS score (OR 1.23, 95% CI 1.15-1.32).

CONCLUSIONS

The serum level of sICAM-1 on admission is associated with neurological deterioration of ischemic stroke.

How healthy is the acutely reperfused ischemic penumbra?

Because it is the main determinant of clinical recovery, early reperfusion of the ischemic penumbra has become the mainstay of acute stroke therapy. Although early permanent recanalization can be associated with spectacular and complete recovery, some patients in fact exhibit delayed or incomplete recovery, even despite small infarcts on late structural imaging. This might result from tissue inflammation and selective neuronal death/damage, two probably inter-related cellular events well described in the animal literature, precluding full functional restoration in the salvaged penumbra. However, impact of these processes on recovery may be complex because of the interplay with ongoing plasticity and the possible promoting effect of inflammation on the latter. Preliminary results from imaging studies of inflammation and selective neuronal loss after middle cerebral artery territory stroke, using radioligands of the central benzodiazepine receptor and the activated microglia, respectively, reviewed here, suggest these phenomena also exist in man, although their relationship with acute-stage hypoperfusion and their impact on clinical recovery, if any, remain poorly understood. Furthermore, their inter-relationships in the salvaged penumbra have not been addressed. Better understanding of these potentially harmful processes might help to maximize benefits from thrombolysis, and could also have implications for patients who enjoy spontaneous recanalization.

Increased plasma levels of TNF-α but not of IL1-β in MPTP-treated monkeys one year after the MPTP administration

The cause of Parkinson's disease remains unknown although some evidence suggests that an inflammatory reaction, mediated by cytokines such as TNF-alpha and IL-1beta, is related with dopaminergic degeneration in the brain. In the present work we measured the plasma levels of TNF-alpha and IL-1beta in parkinsonian monkeys one year after MPTP administration. TNF-alpha levels were seen to have increased in parkinsonian monkeys reflecting the clinical symptoms observed, while IL-1beta levels remained unchanged. These results suggest that TNF-alpha plays a role in sustaining of dopaminergic degeneration in chronic parkinsonism.

A randomised phase II study of interleukin-1 receptor antagonist in acute stroke patients

OBJECTIVES

The cytokine interleukin (IL)-1 mediates ischaemic brain damage in rodents. The endogenous, highly selective, IL-1 receptor antagonist (IL-1ra) protects against ischaemic cerebral injury in a range of experimental settings, and IL-1ra causes a marked reduction of cell death when administered peripherally or at a delay in transient cerebral ischaemia. We report here the first randomised, double blind, placebo controlled trial of recombinant human IL-1ra (rhIL-1ra) in patients with acute stroke.

METHODS

Patients within 6 hours of the onset of symptoms of acute stroke were randomised to rhIL-1ra or matching placebo. Test treatment was administered intravenously by a 100 mg loading dose over 60 seconds, followed by a 2 mg/kg/h infusion over 72 h. Adverse events and serious adverse events were recorded for up to 3 months, serial blood samples were collected for biological markers up to 3 months, and 5-7 day brain infarct volume was measured by computed tomography.

RESULTS

No adverse events were attributed to study treatment among 34 patients randomised. Markers of biological activity, including neutrophil and total white cell counts, C reactive protein, and IL-6 concentrations, were lower in rhIL-1ra treated patients. Among patients with cortical infarcts, clinical outcomes at 3 months in the rhIL-1ra treated group were better than in placebo treated.

CONCLUSIONS

These data suggest that rhIL-1ra is safe and well tolerated in acute stroke. In addition, rhIL-1ra exhibited biological activity that is relevant to the pathophysiology and clinical outcome of ischaemic stroke. Our findings identify rhIL-1ra as a potential new therapeutic agent for acute stroke.

Glucocorticoid therapy in neurologic critical care

BACKGROUND

The pivotal role of inflammation and edema across the spectrum of central nervous system injury has driven extensive investigation into the therapeutic potential of glucocorticoids.

OBJECTIVE

To review the experimental and clinical data relating to the efficacy and adverse effects of glucocorticoids in conditions encountered in critical neurologic and neurosurgical illness.

DATA SOURCE

Search of MEDLINE and Cochrane databases, manual review of article bibliographies.

DATA SYNTHESIS AND CONCLUSIONS

The efficacy of glucocorticoids is well established in ameliorating edema associated with brain tumors and in improving outcome in subsets of patients with bacterial meningitis. Despite frequently encouraging experimental results, clinical trials of glucocorticoids in ischemic stroke, intracerebral hemorrhage, aneurysmal subarachnoid hemorrhage, and traumatic brain injury have not shown a definite therapeutic effect. The evidence supporting glucocorticoid therapy for spinal cord injury is controversial; however methylprednisolone continues to be widely employed in this setting.

Caffeine suppresses TNF-alpha production via activation of the cyclic AMP/protein kinase A pathway

This study investigated the effect of in vitro exposure to caffeine, and its major metabolite paraxanthine, at concentrations relevant to typical caffeine consumption in humans, on lipopolysaccharide (LPS)-stimulated cytokine production in human whole blood. In addition, a role for the cyclic AMP/protein kinase A (PKA) pathway in the immunomodulatory effect of caffeine was investigated. Diluted whole blood (taken following >/=15 h abstinence from caffeine-containing food and beverages) was preincubated with caffeine or paraxanthine (10-100 microM) and stimulated with LPS (1 proportional, variant g/ml) for 24 h. The proinflammatory cytokines tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-12, and the antiinflammatory cytokine IL-10 were measured in cell-free supernatants. Whilst caffeine and paraxanthine had little or no effect on IL-10, IL-1beta, or IL-12 production, TNF-alpha production was suppressed in all individuals studied. The effect was statistically significant at 100 microM and consistent across seven experiments performed. Although not statistically significant, a similar effect was observed with paraxanthine. Caffeine (100 microM) also increased intracellular cyclic AMP concentrations in LPS-stimulated monocytes isolated from whole blood. Moreover, the effect of caffeine on TNF-alpha production was abolished by pretreatment with the protein kinase A inhibitor Rp-8-Br-cAMPS (10(-4) and 10(-5)M). To conclude, this study demonstrates that concentrations of caffeine that are relevant to human consumption consistently suppress production of the proinflammatory cytokine TNF-alpha in human blood and that this effect is mediated by the cyclic AMP/protein kinase A pathway.

Adverse hepatic drug reactions: inflammatory episodes as consequence and contributor

Susceptibility to drug toxicity is influenced by a variety of factors, both genetic and environmental. The focus of this article is the evidence addressing the hypothesis that inflammation is both a result of and a susceptibility factor for drug toxicity, with an emphasis on liver as a target organ. Results of studies suggesting a role for inflammatory mediators in the hepatotoxicity caused by acetaminophen or ethanol are discussed. For several drugs, the evidence from animal models that concurrent inflammation increases injury is presented. In addition, the occurrence of adverse drug reactions in people with preexisting inflammatory diseases is considered. The special case of idiosyncratic drug reactions is discussed and the potential raised for development of animal models for this type of drug toxicity. The conclusion is that inflammatory factors should be considered as determinants of sensitivity to adverse drug reactions.