The role of cytokines in the neuropathology of stroke and neurotrauma

Evaluating the effect of post-traumatic hypoxia on the development of axonal injury following traumatic brain injury in sheep

Damage to the axonal white matter tracts within the brain is a key cause of neurological impairment and long-term disability following traumatic brain injury (TBI). Understanding how axonal injury develops following TBI requires gyrencephalic models that undergo shear strain and tissue deformation similar to the clinical situation and investigation of the effects of post-injury insults like hypoxia. The aim of this study was to determine the effect of post-traumatic hypoxia on axonal injury and inflammation in a sheep model of TBI. Fourteen male Merino sheep were allocated to receive a single TBI via a modified humane captive bolt animal stunner, or sham surgery, followed by either a 15 min period of hypoxia or maintenance of normoxia. Head kinematics were measured in injured animals. Brains were assessed for axonal damage, microglia and astrocyte accumulation and inflammatory cytokine expression at 4 hrs following injury. Early axonal injury was characterised by calpain activation, with significantly increased SNTF immunoreactivity, a proteolytic fragment of alpha-II spectrin, but not with impaired axonal transport, as measured by amyloid precursor protein (APP) immunoreactivity. Early axonal injury was associated with an increase in GFAP levels within the CSF, but not with increases in IBA1 or GFAP+ve cells, nor in levels of TNFα, IL1β or IL6 within the cerebrospinal fluid or white matter. No additive effect of post-injury hypoxia was noted on axonal injury or inflammation. This study provides further support that axonal injury post-TBI is driven by different pathophysiological mechanisms, and detection requires specific markers targeting multiple injury mechanisms. Treatment may also need to be tailored for injury severity and timing post-injury to target the correct injury pathway.

Pharmacological therapy to cerebral ischemia-reperfusion injury: Focus on saponins

Secondary insult from cerebral ischemia-reperfusion injury (CIRI) is a major risk factor for poor prognosis of cerebral ischemia. Saponins are steroid or triterpenoid glycosides with various pharmacological activities that are effective in treating CIRI. By browsing the literature from 2001 to 2021, 55 references involving 24 kinds of saponins were included. Saponins were shown to relieve CIRI by inhibiting oxidation stress, neuroinflammation, and apoptosis, restoring BBB integrity, and promoting neurogenesis and angiogenesis. This review summarizes and classifies several common saponins and their mechanisms in relieving CIRI. Information provided in this review will benefit researchers to design, research and develop new medicines to treat CIRI-related conditions with saponins.

The Immunological Roles of Olfactory Ensheathing Cells in the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) is a devastating type of neurological disorder of the central nervous system (CNS) with high mortality and disability. The pathological processes of SCI can usually be described as two stages, namely, primary and acute secondary injuries. Secondary injury produces more significant exacerbations of the initial injury. Among all the mechanisms of secondary damage, infection and inflammatory responses, as the principle culprits in initiating the second phase of SCI, can greatly contribute to the severity of SCI and numerous sequelae after SCI. Therefore, effectively antagonizing pro-inflammatory responses may be a promising treatment strategy to facilitate functional recovery after SCI. Olfactory ensheathing cells (OECs), a unique type of glial cells, have increasingly become potential candidates for cell-based therapy in the injured CNS. Strikingly, there is growing evidence that the mechanisms underlying the anti-inflammatory role of OECs are associated with the immune properties and secretory functions of these cells responsible for anti-neuroinflammation and immunoregulatory effects, leading to maintenance of the internal microenvironment. Accordingly, a more profound understanding of the mechanism of OEC immunological functions in the treatment of SCI would be beneficial to improve the therapeutic clinical applications of OECs for SCI. In this review, we mainly summarize recent research on the cellular and molecular immune attributes of OECs. The unique biological functions of these cells in promoting neural regeneration are discussed in relation of the development of novel therapies for CNS injury.

Targeting C–C Chemokine Receptor 5: Key to Opening the Neurorehabilitation Window After Ischemic Stroke

Stroke is the world’s second major cause of adult death and disability, resulting in the destruction of brain tissue and long-term neurological impairment; induction of neuronal plasticity can promote recovery after stroke. C–C chemokine receptor 5 (CCR5) can direct leukocyte migration and localization and is a co-receptor that can mediate human immunodeficiency virus (HIV) entry into cells. Its role in HIV infection and immune response has been extensively studied. Furthermore, CCR5 is widely expressed in the central nervous system (CNS), is engaged in various physiological activities such as brain development, neuronal differentiation, communication, survival, and learning and memory capabilities, and is also involved in the development of numerous neurological diseases. CCR5 is differentially upregulated in neurons after stroke, and the inhibition of CCR5 in specific regions of the brain promotes motor and cognitive recovery. The mechanism by which CCR5 acts as a therapeutic target to promote neurorehabilitation after stroke has rarely been systematically reported yet. Thus, this review aims to discuss the function of CCR5 in the CNS and the mechanism of its effect on post-stroke recovery by regulating neuroplasticity and the inflammatory response to provide an effective basis for clinical rehabilitation after stroke.

Neurotensin agonist PD 149163 modulates the neuroinflammation induced by bacterial endotoxin lipopolysaccharide in mice model

OBJECTIVE

The disruption of bidirectional communication between neuroendocrine and immune components by stressors leads to mental problems. The immunomodulation therapy of neuroinflammation-led psychiatric illness is an emerging area of research. Therefore, the present study aimed to evaluate immune modulation efficacy of PD 149163 (PD) against the lipopolysaccharide (LPS)-induced neuroinflammation.

MATERIALS AND METHODS

The Swiss albino mice (female/12 weeks) were divided into six groups (6 mice/group): (I) Control: 0.9% NaCl; (II) LPS: 1 mg/kg BW, for 5 days; (III) LPS + PD Low: LPS 1 mg/kg BW (for 5 days) after that PD 100 µg/kg BW (for 21 days); (IV) LPS + PD High: LPS 1 mg/kg BW (for 5 days) after that PD 300 µg/kg BW (for 21 days); (V) PD Low: PD 100 µg/kg BW (for 21 days); (VI) PD High: PD 300 µg/kg BW (for 21 days). All treatments were given intraperitoneal.

RESULTS

The LPS-induced weight loss (body and brain) was normalized to control after PD treatment. The PD enhanced superoxide dismutase (SOD) activity while decreased lipid hydroperoxide (LOOH) level altered in LPS-exposed mice. The significantly increased pro-inflammatory cytokines (IL-6 and TNF-α) in LPS exposure were also decreased by PD. Likewise, the LPS-induced HPA axis activation was stabilized by PD. In the hippocampus, the pyramidal cell layer thickness, pyramidal neurons number and size of CA1 and CA3 regions were reduced along with misalignment, shrinkage, and impairment of cytoarchitecture. In the co-treated group, the LPS-induced hippocampus disruption was reversed after PD exposure.

CONCLUSION

We suggested that the PD modulates the LPS-induced neuroinflammation and psychiatric illness in a dose-dependent manner.

Systemic Inflammatory Response Syndrome is Associated with Hematoma Expansion in Intracerebral Hemorrhage

OBJECTIVES

Systemic inflammatory response syndrome (SIRS) and hematoma expansion are independently associated with worse outcomes after intracerebral hemorrhage (ICH), but the relationship between SIRS and hematoma expansion remains unclear.

MATERIALS AND METHODS

We performed a retrospective review of patients admitted to our hospital from 2013 to 2020 with primary spontaneous ICH with at least two head CTs within the first 24 hours. The relationship between SIRS and hematoma expansion, defined as ≥6 mL or ≥33% growth between the first and second scan, was assessed using univariable and multivariable regression analysis. We assessed the relationship of hematoma expansion and SIRS on discharge mRS using mediation analysis.

RESULTS

Of 149 patients with ICH, 83 (56%; mean age 67±16; 41% female) met inclusion criteria. Of those, 44 (53%) had SIRS. Admission systolic blood pressure (SBP), temperature, antiplatelet use, platelet count, initial hematoma volume and rates of infection did not differ between groups (all p>0.05). Hematoma expansion occurred in 15/83 (18%) patients, 12 (80%) of whom also had SIRS. SIRS was significantly associated with hematoma expansion (OR 4.5, 95% CI 1.16 - 17.39, p= 0.02) on univariable analysis. The association remained statistically significant after adjusting for admission SBP and initial hematoma volume (OR 5.72, 95% CI 1.40 - 23.41, p= 0.02). There was a significant indirect effect of SIRS on discharge mRS through hematoma expansion. A significantly greater percentage of patients with SIRS had mRS 4-6 at discharge (59 vs 33%, p=0.02).

CONCLUSION

SIRS is associated with hematoma expansion of ICH within the first 24 hours, and hematoma expansion mediates the effect of SIRS on poor outcome.

Inflammatory Factors as Potential Markers of Early Neurological Deterioration in Acute Ischemic Stroke Patients Receiving Endovascular Therapy - The AISRNA Study

BACKGROUND AND PURPOSE

This study aimed to explore several peripheral blood-based markers related to the inflammatory response in a total of 210 patients with acute ischemic stroke (AIS) caused by large artery occlusion in the anterior circulation who received endovascular therapy (EVT) from an observational study of clinical significance of circulating non-coding RNA in acute ischemic stroke (AISRNA).

METHODS

We collected baseline characteristics of 210 AIS patients participating in an observational acute stroke cohort: the AISRNA study. The following inflammatory factors were measured in these participants: interleukin-2 [IL-2], IL-4, IL-6, IL-10, tumor necrosis factor-α [TNF-α], and interferon-γ [IFN-γ]. The National Institute of Health Stroke Scale score increase of ≥4 within 24 hours after EVT defined as early neurological deterioration (END).

RESULTS

Compared with patients without END, patients with END had a higher incidence of atrial fibrillation (P=0.012), and also had higher levels of IL-6 and IL-10 (P<0.01). Furthermore, we found that the area under the curves (AUCs) of IL-6 and IL-10 for predicting END were 0.768 (0.697-0.829), and 0.647 (0.570-0.719), respectively. Adjusting for age, sex, and atrial fibrillation, the odds ratios (ORs; 95% confidence interval) for incident END for IL-6 and IL-10 were 1.98 (1.05-6.69) and 1.18 (1.04-1.33), respectively. Additionally, we found significant changes over time in the expression levels of IL-4, IL-6, and IL-10 in patients with END compared with patients without END (P<0.05).

CONCLUSION

IL-6 and IL-10 levels at admission may be potential markers of END after EVT, and the time course of IL-4, IL-6, and IL-10 is correlated with stroke progression. Further larger studies are needed to confirm the current findings.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04175691. Registered November 21, 2019, https://www.clinicaltrials.gov/ct2/show/NCT04175691.

The Prognostic Value of Serum Cytokines in Patients with Acute Ischemic Stroke

The inflammatory response is an unavoidable process and contributes to the destruction of cerebral tissue during the acute ischemic stroke (AIS) phase and has not been addressed fully to date. Insightful understanding of correlation of inflammatory mediators and stroke outcome may provide new biomarkers or therapeutic approaches for ischemic stroke. Here, we prospectively recruited 180 first-ever AIS patients within 72 hrs after stroke onset. We used the National Institutes of Health Stroke Scale (NIHSS) to quantify stroke severity and modified Rankin scale (mRS) to assess the 3-month outcome for AIS patients. Initially, we screened 35 cytokines, chemokines, and growth factors in sera from 75 AIS patients and control subjects. Cytokines that were of interest were further investigated in the 180 AIS patients and 14 heathy controls. We found that IL-1RA, IL-1β, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-13, IL-15, EGF, G-CSF, Flt-3L, GM-CSF and Fractalkine levels were significantly decreased in severe stroke patients. In particular, IL-1β, IL-4, IL-5, IL-7, IL-9, IL-10, IL-15, G-CSF and GM-CSF were significantly reduced in AIS patients with poor outcome, compared to those with good prognosis. IL-6 was notably higher in the poor outcome group. Only IL-9 level decreased in the large infarct volume group. After adjusting for confounders, we found that IL-5 was an independent protective factor for prognosis in AIS patients with an adjusted OR of 0.042 (P = 0.007), whereas IL-6 was an independent risk predictor for AIS patients with an adjusted OR of 1.293 (P = 0.003). Our study suggests the levels of serum cytokines are related to stroke severity, short-term prognosis and cerebral infarct volume in AIS patients.

Protein microarray analysis identifies key cytokines associated with malignant middle cerebral artery infarction

INTRODUCTION

We aimed to explore potential cytokines involved in the malignant middle cerebral artery infarction (MMI) and elucidate their underlying regulatory mechanisms.

METHODS

We first developed a cytokine profile by Quantibody^® Human Cytokine Antibody Array7000 using serum samples from eight patients with MMI and eight patients with non-acute cerebral infarction (NACI). The differentially expressed cytokines were then identified in patients with MMI using two-tailed Student's t-test and Fisher's Exact Test compared with patients with NACI. Gene Ontology and pathway enrichment analyses were performed using DAVID. Protein-protein interaction (PPI) network was constructed based on STRING database.

RESULTS

A total of 10 differentially expressed cytokines were identified from 320 unique inflammatory cytokines in serums. Among them, four cytokines, like NCAM1 (neural cell adhesion molecule 1), IGFBP-6 (insulin-like growth factor binding protein 6), LYVE1 (lymphatic vessel endothelial hyaluronan receptor 1), and LCN2 (Lipocalin2), were up-regulated, while another six cytokines, such as TGFB1 (transforming growth factor, beta 1, also known as LAP), EGF (epidermal growth factor), PDGFA (platelet-derived growth factor alpha polypeptide), MMP-10 (matrix metallopeptidase 10), IL-27 (interleukin 27), and CCL2 (chemokine (C-C motif) receptor 2), were down-regulated. Moreover, cytokine-cytokine receptor interaction pathway was significantly enriched.

CONCLUSIONS

Our findings indicate that 10 differentially expressed cytokines, such as NCAM1, LCN2, IGFBP-6, LYVE1, MMP-10, IL-27, PDGFA, EGF, CCL2, and TGFB1 may participate in the development of MMI. Moreover, cytokine-cytokine receptor interaction pathway may be an important mechanism involved in this disease. These differentially expressed cytokines may serve as diagnostic biomarkers or drug targets for MMI.

Secondary Hematoma Expansion and Perihemorrhagic Edema after Intracerebral Hemorrhage: From Bench Work to Practical Aspects

Intracerebral hemorrhages (ICH) represent about 10-15% of all strokes per year in the United States alone. Key variables influencing the long-term outcome after ICH are hematoma size and growth. Although death may occur at the time of the hemorrhage, delayed neurologic deterioration frequently occurs with hematoma growth and neuronal injury of the surrounding tissue. Perihematoma edema has also been implicated as a contributing factor for delayed neurologic deterioration after ICH. Cerebral edema results from both blood-brain barrier disruption and local generation of osmotically active substances. Inflammatory cellular mediators, activation of the complement, by-products of coagulation and hemolysis such as thrombin and fibrin, and hemoglobin enter the brain and induce a local and systemic inflammatory reaction. These complex cascades lead to apoptosis or neuronal injury. By identifying the major modulators of cerebral edema after ICH, a therapeutic target to counter degenerative events may be forthcoming.

Astrocytes and Brain Hypoxia

Astrocytes provide the structural and functional interface between the cerebral circulation and neuronal networks. They enwrap all intracerebral arterioles and capillaries, control the flux of nutrients as well as the ionic and metabolic environment of the neuropil. Astrocytes have the ability to adjust cerebral blood flow to maintain constant PO2 and PCO2 of the brain parenchyma. Release of ATP in the brainstem, presumably by local astrocytes, helps to maintain breathing and counteract hypoxia-induced depression of the respiratory network. Astrocytes also appear to be involved in mediating hypoxia-evoked changes in blood-brain barrier permeability, brain inflammation, and neuroprotection against ischaemic injury. Thus, astrocytes appear to play a fundamental role in supporting neuronal function not only in normal conditions but also in pathophysiological states when supply of oxygen to the brain is compromised.

Chronic Inflammation After Severe Traumatic Brain Injury: Characterization and Associations With Outcome at 6 and 12 Months Postinjury

OBJECTIVE

Examine associations between chronic inflammatory profiles and outcome 6 to 12 months following severe traumatic brain injury (TBI).

SETTING

University-affiliated level 1 trauma center and community.

PARTICIPANTS

Adults with severe TBI (n = 87); healthy controls (n = 7).

DESIGN

Prospective cohort study.

MAIN MEASURES

Glasgow Outcome Scale; serum cytokines (interleukin [IL]-1β, IL-4, IL-5, IL-6, IL-7, IL-8, IL-10, IL-12, tumor necrosis factor α), 2 weeks to 3 months, 4- to 6-month averages, 6- and 12-month levels.

RESULTS

Serum levels of IL-1β, IL-6, IL-8, IL-10, and tumor necrosis factor α were elevated over 3 months following TBI. Multivariate analysis showed that increased cytokine load score was associated with a 1.21 (95% confidence interval, 1.06-1.38) and 1.18 (95% confidence interval, 1.02-1.37) increase in odds of unfavorable Glasgow Outcome Scale score at 6 and 12 months, respectively. Also, elevated IL-6/IL-10 ratios were associated with increased odds of unfavorable outcomes at 6 months (adjusted odds ratio = 1.76; 95% confidence interval, 1.08-2.88).

CONCLUSIONS

Chronic inflammation has not been well characterized following TBI. Our subacute cytokine load score classifies individuals at risk for unfavorable outcomes following injury. Higher proinflammatory burden with IL-6, relative to the anti-inflammatory marker IL-10, is significantly associated with outcome. Further research should examine whether inflammatory genes and other inflammatory biomarkers affect risk for unfavorable outcomes and TBI complications.

Neuroinflammation in hepatic encephalopathy: mechanistic aspects

Hepatic encephalopathy (HE) is a major neurological complication of severe liver disease that presents in acute and chronic forms. While elevated brain ammonia level is known to be a major etiological factor in this disorder, recent studies have shown a significant role of neuroinflammation in the pathogenesis of both acute and chronic HE. This review summarizes the involvement of ammonia in the activation of microglia, as well as the means by which ammonia triggers inflammatory responses in these cells. Additionally, the role of ammonia in stimulating inflammatory events in brain endothelial cells (ECs), likely through the activation of the toll-like receptor-4 and the associated production of cytokines, as well as the stimulation of various inflammatory factors in ECs and in astrocytes, are discussed. This review also summarizes the inflammatory mechanisms by which activation of ECs and microglia impact on astrocytes leading to their dysfunction, ultimately contributing to astrocyte swelling/brain edema in acute HE. The role of microglial activation and its contribution to the progression of neurobehavioral abnormalities in chronic HE are also briefly presented. We posit that a better understanding of the inflammatory events associated with acute and chronic HE will uncover novel therapeutic targets useful in the treatment of patients afflicted with HE.

Alcohol exposure after mild focal traumatic brain injury impairs neurological recovery and exacerbates localized neuroinflammation

Traumatic brain injury (TBI) represents a leading cause of morbidity and mortality among young individuals. Alcohol abuse is a risk factor associated with increased TBI incidence. In addition, up to 26% of TBI patients engage in alcohol consumption after TBI. Limited preclinical studies have examined the impact of post-injury alcohol exposure on TBI recovery. The aim of this study was to determine the isolated and combined effects of TBI and alcohol on cognitive, behavioral, and physical recovery, as well as on associated neuroinflammatory changes. Male Sprague-Dawley rats (∼300g) were subjected to a mild focal TBI by lateral fluid percussion (∼30PSI, ∼25ms) under isoflurane anesthesia. On day 4 after TBI, animals were exposed to either sub-chronic intermittent alcohol vapor (95% ethanol 14h on/10h off; BAL∼200mg/dL) or room air for 10days. TBI induced neurological dysfunction reflected by an increased neurological severity score (NSS) showed progressive improvement in injured animals exposed to room air (TBI/air). In contrast, TBI animals exposed to alcohol vapor (TBI/alcohol) showed impaired NSS recovery throughout the 10-day period of alcohol exposure. Open-field exploration test revealed an increased anxiety-like behavior in TBI/alcohol group compared to TBI/air group. Additionally, alcohol-exposed animals showed decreased locomotion and impaired novel object recognition. Immunofluorescence showed enhanced reactive astrocytes, microglial activation, and HMGB1 expression localized to the injured cortex of TBI/alcohol as compared to TBI/air animals. The expression of neuroinflammatory markers showed significant positive correlation with NSS. These findings indicated a close relationship between accentuated neuroinflammation and impaired neurological recovery from post-TBI alcohol exposure. The clinical implications of long-term consequences in TBI patients exposed to alcohol during recovery warrant further investigation.

Seizure-induced oxidative stress in temporal lobe epilepsy

An insult to the brain (such as the first seizure) causes excitotoxicity, neuroinflammation, and production of reactive oxygen/nitrogen species (ROS/RNS). ROS and RNS produced during status epilepticus (SE) overwhelm the mitochondrial natural antioxidant defense mechanism. This leads to mitochondrial dysfunction and damage to the mitochondrial DNA. This in turn affects synthesis of various enzyme complexes that are involved in electron transport chain. Resultant effects that occur during epileptogenesis include lipid peroxidation, reactive gliosis, hippocampal neurodegeneration, reorganization of neural networks, and hypersynchronicity. These factors predispose the brain to spontaneous recurrent seizures (SRS), which ultimately establish into temporal lobe epilepsy (TLE). This review discusses some of these issues. Though antiepileptic drugs (AEDs) are beneficial to control/suppress seizures, their long term usage has been shown to increase ROS/RNS in animal models and human patients. In established TLE, ROS/RNS are shown to be harmful as they can increase the susceptibility to SRS. Further, in this paper, we review briefly the data from animal models and human TLE patients on the adverse effects of antiepileptic medications and the plausible ameliorating effects of antioxidants as an adjunct therapy.

The use of microRNAs to modulate redox and immune response to stroke

SIGNIFICANCE

Cerebral ischemia is a major cause of death and disability throughout the world, yet therapeutic options remain limited. The interplay between the cellular redox state and the immune response plays a critical role in determining the extent of neural cell injury after ischemia and reperfusion. Excessive amounts of reactive oxygen species (ROS) generated by mitochondria and other sources act both as triggers and effectors of inflammation. This review will focus on the interplay between these two mechanisms.

RECENT ADVANCES

MicroRNAs (miRNAs) are important post-transcriptional regulators that interact with multiple target messenger RNAs coordinately regulating target genes, including those involved in controlling mitochondrial function, redox state, and inflammatory pathways. This review will focus on the regulation of mitochondria, ROS, and inflammation by miRNAs in the chain of deleterious intra- and intercellular events that lead to brain cell death after cerebral ischemia.

CRITICAL ISSUES

Although pretreatment using miRNAs was effective in cerebral ischemia in rodents, testing treatment after the onset of ischemia is an essential next step in the development of acute stroke treatment. In addition, miRNA formulation and delivery into the CNS remain a challenge in the clinical translation of miRNA therapy.

FUTURE DIRECTIONS

Future research should focus on post-treatment and potential clinical use of miRNAs.

Shock wave trauma leads to inflammatory response and morphological activation in macrophage cell lines, but does not induce iNOS or NO synthesis

BACKGROUND

Experimental CNS trauma results in post-traumatic inflammation for which microglia and macrophages are vital. Experimental brain contusion entails iNOS synthesis and formation of free radicals, NO and peroxynitrite. Shock wave trauma can be used as a model of high-energy trauma in cell culture. It is known that shock wave trauma causes sub-lytic injury and inflammatory activation in endothelial cells. Mechanical disruption of red blood cells can induce iNOS synthesis in experimental systems. However, it is not known whether trauma can induce activation and iNOS synthesis in inflammatory cell lines with microglial or macrophage lineage. We studied the response and activation in two macrophage cell lines and the consequence for iNOS and NO formation after shock wave trauma.

METHODS

Two macrophage cell lines from rat (NR8383) and mouse (RAW264.7) were exposed to shock wave trauma by the Flyer Plate method. The cellular response was investigated by Affymetrix gene arrays. Cell survival and morphological activation was monitored for 24 h in a Cell-IQ live cell imaging system. iNOS induction and NO synthesis were analyzed by Western blot, in cell Western IR-immunofluorescence, and Griess nitrite assay.

RESULTS

Morphological signs of activation were detected in both macrophage cell lines. The activation of RAW264.7 was statistically significant (p < 0.05), but activation of NR8383 did not pass the threshold of statistical significance alpha (p > 0.05). The growth rate of idle cells was unaffected and growth arrest was not seen. Trauma did not result in iNOS synthesis or NO induction. Gene array analyses showed high enrichment for inflammatory response, G-protein coupled signaling, detection of stimulus and chemotaxis. Shock wave trauma combined with low LPS stimulation instead led to high enrichment in apoptosis, IL-8 signaling, mitosis and DNA-related activities. LPS/IFN-ɣ stimulation caused iNOS and NO induction and morphological activation in both cell lines.

CONCLUSIONS

Shock wave trauma by the Flyer Plate method caused an inflammatory response and morphological signs of activation in two macrophage cell lines, while iNOS induction appeared to require humoral signaling by LPS/IFN-ɣ. Our findings indicated that direct energy transfer by trauma can activate macrophages directly without humoral mediators, which comprises a novel activation mechanism of macrophages.

Temporal profile of cerebrospinal fluid, plasma, and brain interleukin-6 after normothermic fluid-percussion brain injury: effect of secondary hypoxia

Interleukin-6 (IL-6) is a proinflammatory cytokine that may play multiple roles in the pathogenesis of traumatic brain injury (TBI). The present study determined time-dependent changes in IL-6 concentrations in vulnerable brain regions, cerebrospinal fluid (CSF) samples, and plasma after normothermic TBI. Because secondary insults are common in head injured patients, we also assessed the consequences of a post-traumatic secondary hypoxic insult on this pleiotropic cytokine. Male Sprague-Dawley rats were intubated, anesthetized, and underwent a moderate parasagittal fluid-percussion brain injury (1.8-2.1 atm, 37°C) followed by either 30 minutes of normoxic or hypoxic (pO₂ = 30-40 mmHg) gas levels. Rats were sacrificed 3, 6, or 24 hours after TBI or shamoperated procedures. Brain samples, including the ipsilateral cerebral cortex and hippocampus were dissected and analyzed. Plasma and CSF samples were collected at similar times and stored at -80°C until analysis. IL-6 levels were significantly increased ( p < 0.05) at 3, 6, and 24 hours in the cerebral cortex and at 6 hours in the hippocampus after TBI. IL-6 levels in the TBI normoxic group for both structures returned to control levels by 24 hours. Plasma levels of IL-6 were elevated at all time points, while CSF levels were high at 3 and 6 hours, but normalized by 24 hours. Post-traumatic hypoxia led to significantly elevated ( p < 0.05) IL-6 protein levels in the cerebral cortex at 24 hours compared to sham-operated controls. These findings demonstrate that moderate TBI leads to an early increase in IL-6 brain, plasma, and CSF protein levels. Secondary post-traumatic hypoxia, a common secondary injury mechanism, led to prolonged elevations in plasma IL-6 levels that may participate in the pathophysiology of this complicated TBI model.

Stem cell transplantation in neurological diseases: improving effectiveness in animal models

Neurological diseases afflict a growing proportion of the human population. There are two reasons for this: first, the average age of the population (especially in the industrialized world) is increasing, and second, the diagnostic tools to detect these pathologies are now more sophisticated and can be used on a higher percentage of the population. In many cases, neurological disease has a pharmacological treatment which, as in the case of Alzheimer's disease, Parkinson's disease, Epilepsy, and Multiple Sclerosis can reduce the symptoms and slow down the course of the disease but cannot reverse its effects or heal the patient. In the last two decades the transplantation approach, by means of stem cells of different origin, has been suggested for the treatment of neurological diseases. The choice of slightly different animal models and the differences in methods of stem cell preparation make it difficult to compare the results of transplantation experiments. Moreover, the translation of these results into clinical trials with human subjects is difficult and has so far met with little success. This review seeks to discuss the reasons for these difficulties by considering the differences between human and animal cells (including isolation, handling and transplantation) and between the human disease model and the animal disease model.

Neuroinflammation and neuroimmune dysregulation after acute hypoxic-ischemic injury of developing brain

Hypoxic-ischemic (HI) injury to developing brain results from birth asphyxia in neonates and from cardiac arrest in infants and children. It is associated with varying degrees of neurologic sequelae, depending upon the severity and length of HI. Global HI triggers a series of cellular and biochemical pathways that lead to neuronal injury. One of the key cellular pathways of neuronal injury is inflammation. The inflammatory cascade comprises activation and migration of microglia - the so-called "brain macrophages," infiltration of peripheral macrophages into the brain, and release of cytotoxic and proinflammatory cytokines. In this article, we review the inflammatory and immune mechanisms of secondary neuronal injury after global HI injury to developing brain. Specifically, we highlight the current literature on microglial activation in relation to neuronal injury, proinflammatory and anti-inflammatory/restorative pathways, the role of peripheral immune cells, and the potential use of immunomodulators as neuroprotective compounds.

Acute alcohol intoxication prolongs neuroinflammation without exacerbating neurobehavioral dysfunction following mild traumatic brain injury

Traumatic brain injury (TBI) represents a leading cause of death and disability among young persons with ∼1.7 million reported cases in the United States annually. Although acute alcohol intoxication (AAI) is frequently present at the time of TBI, conflicting animal and clinical reports have failed to establish whether AAI significantly impacts short-term outcomes after TBI. The objective of this study was to determine whether AAI at the time of TBI aggravates neurobehavioral outcomes and neuroinflammatory sequelae post-TBI. Adult male Sprague-Dawley rats were surgically instrumented with gastric and vascular catheters before a left lateral craniotomy. After recovery, rats received either a primed constant intragastric alcohol infusion (2.5 g/kg+0.3 g/kg/h for 15 h) or isocaloric/isovolumic dextrose infusion followed by a lateral fluid percussion TBI (∼1.4 J, ∼30 ms). TBI induced apnea and a delay in righting reflex. AAI at the time of injury increased the TBI induced delay in righting reflex without altering apnea duration. Neurological and behavioral dysfunction was observed at 6 h and 24 h post-TBI, and this was not exacerbated by AAI. TBI induced a transient upregulation of cortical interleukin (IL)-6 and monocyte chemotactic protein (MCP)-1 mRNA expression at 6 h, which was resolved at 24 h. AAI did not modulate the inflammatory response at 6 h but prevented resolution of inflammation (IL-1, IL-6, tumor necrosis factor-α, and MCP-1 expression) at 24 h post-TBI. AAI at the time of TBI did not delay the recovery of neurological and neurobehavioral function but prevented the resolution of neuroinflammation post-TBI.

Leg ischaemia before circulatory arrest alters brain leucocyte count and respiratory chain redox state

OBJECTIVES

Remote ischaemic preconditioning and its neuroprotective abilities are currently under investigation and the method has shown significant effects in several small and large animal studies. In our previous studies, leucocyte filtration during cardiopulmonary bypass reduced cerebrocortical adherent leucocyte count and mitigated cerebral damage after hypothermic circulatory arrest (HCA) in piglets. This study aimed to obtain and assess direct visual data of leucocyte behaviour in cerebral vessels after hypothermic circulatory arrest following remote ischaemic preconditioning.

METHODS

Twelve native stock piglets were randomized into a remote ischaemic preconditioning group (n = 6) and a control group (n = 6). The intervention group underwent hind-leg ischaemia, whereas the control group received a sham-treatment before a 60-min period of hypothermic circulatory arrest. An intravital microscope was used to obtain measurements from the cerebrocortical vessel in vivo. It included three sets of filters: a violet filter to visualize microvascular perfusion and vessel diameter, a green filter for visualization of rhodamine-labelled leucocytes and an ultraviolet filter for reduced nicotinamide adenine dinucleotide (NADH) analysis. The final magnification on the microscope was 400. After the experiment, cerebral and cerebellar biopsies were collected and analysed with transmission electron microscope by a blinded analyst.

RESULTS

In the transmission electron microscope analysis, the entire intervention group had normal, unaffected rough endoplasmic reticulum's in their cerebellar tissue, whereas the control group had a mean score of 1.06 (standard deviation 0.41) (P = 0.026). The measured amount of adherent leucocytes was lower in the remote ischaemic preconditioning group. The difference was statistically significant at 5, 15 and 45 min after circulatory arrest. Statistically significant differences were seen also in the recovery phase at 90 and 120 min after reperfusion. Nicotinamide adenine dinucleotide autofluorescence had statistically significant differences at 10 min after cooling and at 120 and 180 min after hypothermic circulatory arrest.

CONCLUSIONS

Remote ischaemic preconditioning seems to provide better mitochondrial respiratory chain function as indicated by the higher NADH content. It simultaneously provides a reduction of adherent leucocytes in cerebral vessels after hypothermic circulatory arrest. Additionally, it might provide some degree of cellular organ preservation as implied by the electron microscopy results.

Chemokines and neurodegeneration in the early stage of experimental ischemic stroke

Neurodegeneration is a hallmark of most of the central nervous system (CNS) disorders including stroke. Recently inflammation has been implicated in pathogenesis of neurodegeneration and neurodegenerative diseases. The aim of this study was analysis of expression of several inflammatory markers and its correlation with development of neurodegeneration during the early stage of experimental stroke. Ischemic stroke model was induced by stereotaxic intracerebral injection of vasoconstricting agent endothelin-1 (ET-1). It was observed that neurodegeneration appears very early in that model and correlates well with migration of inflammatory lymphocytes and macrophages to the brain. Although the expression of several studied chemotactic cytokines (chemokines) was significantly increased at the early phase of ET-1 induced stroke model, no clear correlation of this expression with neurodegeneration was observed. These data may indicate that chemokines do not induce neurodegeneration directly. Upregulated in the ischemic brain chemokines may be a potential target for future therapies reducing inflammatory cell migration to the brain in early stroke. Inhibition of inflammatory cell accumulation in the brain at the early stage of stroke may lead to amelioration of ischemic neurodegeneration.

Limb ischemic preconditioning attenuates cerebral ischemic injury in rat model

Ischemic brain injury is not uncommon after open-heart surgery with cardiopulmonary bypass and seriously undermines the patients' life quality. Therefore, potential protective effects of limb ischemic preconditioning (LIP) on subsequent ischemic injury of the brain were investigated by evaluating anti-inflammatory effects and apoptosis of pyramidal neurons in the CA1 hippocampus. One hundred and eight Sprague-Dawley rats were divided into the middle cerebral artery occlusion (MCAO) group (n=54) and the LIP group (n=54). A thread was used to occlude the middle cerebral artery in the MCAO group and the LIP group animals were pretreated with LIP followed by MCAO. In the two groups, nine samples were collected at each time-point of 0, 6, 12, 24, 48 and 72 h after MCAO to detect IL-6 and IL-17 and their mRNA levels. Neurological severity scores (NSS) were examined before the animals were sacrificed. Compared with the LIP group, cerebral histopathological changes in the MCAO group were most distinct and significantly more infiltrated inflammatory and apoptotic neuronal cells were observed at 24, 48 and 72 h post-surgery. IL-17 and IL-6 mRNA levels analyzed by quantitative real-time polymerase chain reaction (PCR) (qRT-PCR) were significantly reduced in the LIP group compared with the MCAO group at the 12, 24 and 48 h time-points. A significant reduction in IL-17 expression level was determined by enzyme-linked immunosorbent assay (ELISA) in the LIP group at 12, 24 and 48 h, while IL-6 was significantly reduced at the 24 and 48 h time-points. The NSSs were not significantly different between the groups. Therefore, in a MCAO rat model, we have proved that LIP pretreatment can protect the brain from infarction after ischemic injury and induce ischemic tolerance, potentially, by reducing IL-17 to provide anti-inflammatory effects and attenuate apoptosis of hippocampal neuronal cells.

Monocyte chemoattractant protein-1-deficiency results in altered blood-brain barrier breakdown after experimental stroke

BACKGROUND AND PURPOSE

Stroke-induced blood-brain barrier (BBB)-disruption can contribute to further progression of cerebral damage. There is rising evidence for a strong involvement of chemokines in postischemic BBB-breakdown. In a previous study, we showed that monocyte chemoattractant protein-1 (MCP-1)-deficiency results in a markedly reduced inflammatory reaction with decreased levels of interleukin-6, interleukin-1β, and granulocyte colony-stimulating factor after experimental stroke. With MCP-1 as one of the key players in stroke-induced inflammation, in this study, we investigated the influence of MCP-1 on poststroke BBB-disruption as well as transcription/translation of BBB-related genes/proteins after cerebral ischemia.

METHODS

Sixteen wild-type and 16 MCP-1(-/-) mice were subjected to 30 minutes of middle cerebral artery occlusion. By injecting high molecular-tracer, we compared the degree of BBB-disruption after middle cerebral artery occlusion. Real-time polymerase chain reactions and Western blot technique were used to compare tight-junction gene expression, protein secretion, and BBB-leakage.

RESULTS

Here, we report that MCP-1-deficiency results in a reduced BBB-leakage and a diminished expression of BBB-related genes occludin, zonula occludens-1, and zonula occludens-2. Real-time polymerase chain reactions and Western blot analysis revealed elevated claudin-5-levels in MCP-1(-/-) animals. MCP-1-deficiency resulted in reduced infarct sizes and an increased vascular accumulation of fluorescein-isothiocyanate-albumin.

CONCLUSIONS

The results of the study provide further insights into the molecular mechanisms of BBB-opening and may help to better understand the mechanisms of infarct development after cerebral ischemia.

Hydrogen sulfide reduces neutrophil recruitment in hind-limb ischemia-reperfusion injury in an L-selectin and ADAM-17-dependent manner

BACKGROUND

Reperfusion following ischemia leads to neutrophil recruitment into injured tissue. Selectins and β2-integrins regulate neutrophil interaction with the endothelium during neutrophil rolling and firm adhesion. Excessive neutrophil infiltration into tissue is thought to contribute to ischemia-reperfusion injury damage. Hydrogen sulfide mitigates the damage caused by ischemia-reperfusion injury. This study's objective was to determine the effect of hydrogen sulfide on neutrophil adhesion receptor expression.

METHODS

Human neutrophils were either left untreated or incubated in 20 μM hydrogen sulfide and/or 50 μg/ml pharmacologic ADAM-17 inhibitor TAPI-0; activated by interleukin-8, fMLP, or TNF-α; and labeled against P-selectin glycoprotein ligand-1, leukocyte function associated antigen-1, Mac-1 α, L-selectin, and β2-integrin epitopes CBRM1/5 or KIM127 for flow cytometry. Cohorts of three C57BL/6 mice received an intravenous dose of saline vehicle or 20 μM hydrogen sulfide with or without 50 μg/ml TAPI-0 before unilateral tourniquet-induced hind-limb ischemia for 3 hours followed by 3 hours of reperfusion. Bilateral gastrocnemius muscles were processed for histology before neutrophil infiltration quantification.

RESULTS

Hydrogen sulfide treatment significantly increased L-selectin shedding from human neutrophils following activation by fMLP and interleukin-8 in an ADAM-17-dependent manner. Mice treated with hydrogen sulfide to raise bloodstream concentration by 20 μM before ischemia or reperfusion showed a significant reduction in neutrophil recruitment into skeletal muscle tissue following tourniquet-induced hind-limb ischemia-reperfusion injury.

CONCLUSIONS

Hydrogen sulfide administration results in the down-regulation of L-selectin expression in activated human neutrophils. This leads to a reduction in neutrophil extravasation and tissue infiltration and may partially account for the protective effects of hydrogen sulfide seen in the setting of ischemia-reperfusion injury.

Effect of IMOD™ on the inflammatory process after acute ischemic stroke: a randomized clinical trial

Background and purpose of the study

Considering the role of inflammation in acute cerebrovascular accidents, anti-inflammatory treatment has been considered as an option in cerebrovascular diseases. Regarding the properties of Setarud (IMOD™) in immune regulation, the aim of the present study was to evaluate the role of this medication in treating patients with acute ischemic stroke.

Methods

In this randomized clinical trial, 99 patients with their first ever acute ischemic stroke were divided into two groups of IMOD™ (n = 49) and control (n = 50). The control group underwent routine treatment and the intervention group underwent routine treatment plus daily intermittent infusion of IMOD™ (250mg on the first day and then 375mg into DW5% serum during a 30-minute period for 7 days). The serum levels of inflammatory markers were evaluated on the first day (baseline) and on 4th and 7th days. Data were analyzed and the results were compared.

Results and major conclusion

58 males (58.6%) and 41 females (41.4%) with a mean age of 67.00 ± 8.82 years, who had their first ever stroke attack, were enrolled in this trial. Treatment with IMOD™ showed a decreasing trend in IL-6 levels compared to the control group (p = 0.04). In addition, the treatment resulted in the control of increasing serum levels of hsCRP after 7 days compared to the control group (p = 0.02). There was an insignificant decrease in TNF-α and IL-1 levels in the IMOD™ group. Considering the prominent role of inflammation after an ischemic cerebral damage, it appears that treatment with IMOD™ improves the inflammatory profile. Therefore, IMOD™ (Setarud) might be considered as a therapeutic option in the acute ischemic stroke. However, future studies are necessary on its long-term results and clinical efficacy.

Hyperglycemia as a Risk Factor of Ischemic Stroke

Diabetes is considered a major risk factor for stroke and is associated with worsened stroke outcomes. Here, we discuss and summarize the mechanisms that have been associated with the increased risk of stroke due to the hyperglycemia in diabetes mellitus. In diabetic stroke models, hyperglycemia exaggerates the following damaging processes: acidosis, accumulation of reactive oxygen species/reactive nitrogen, inflammation and mitochondrial dysfunction. Understanding the mechanism of diabetes acting as a stroke risk factor will definitely assist to reveal issues related to drug metabolism and toxicity in diabetic stroke. In addition, it is suggested that future studies may focus on the mechanisms mediating blood-brain barrier and astrocytes dysfunction under hyperglycemic stroke.

Matrix metalloproteinases in human spontaneous intracerebral hemorrhage: an update

BACKGROUND

In default of a plausible and satisfactory causal treatment for hemorrhagic stroke, a role of matrix metalloproteinases (MMPs) in the pathogenesis of cerebrovascular diseases has recently been widely discussed. The well-known impact of MMPs on extracellular matrix destruction triggered by inflammation as a foundation for several diseases, including stroke, is very much in evidence. Newly, some additional aspects of MMP function considering their intracellular activity crucial for neuronal death following ischemic brain damage have emerged. The effect of blood-brain barrier disruption caused by MMPs on the prognosis in patients suffering from spontaneous intracerebral hemorrhage (ICH) has been of interest since it throws a new light upon the pathogenesis, course and possible therapeutic approaches for this least treatable and at the same time most life-threatening form of stroke. Hence, we primarily aimed to review the current clinical knowledge on the significance of metalloproteinase activation in the course of spontaneous intracranial hemorrhage in humans. We also provide a brief characterization of the MMP enzyme family and report on the latest findings on issues arising from experimental studies.

METHODS

A Medline search using the following key words was performed: matrix metalloproteinases + spontaneous intracerebral hemorrhage/intracranial hemorrhage/bleeding/hemorrhagic stroke. We accepted studies reporting on MMP expression in adult patients with spontaneous ICH, as well as its relation to radiological and clinical features and patients' outcome. For the final review, 18 clinical studies were considered. MMP inhibition was reviewed on the basis of 11 relevant experimental studies. Also, some relevant reports on the biology of MMPs and their pathophysiology in ICH were reviewed.

RESULTS AND CONCLUSIONS

Many studies provide convincing evidence of a detrimental role of MMPs in ICH, stressing their association with neuroinflammation. The role of MMPs in hemorrhagic stroke appears critical for hematoma and brain edema growth as well as for neuronal death, which are understood as secondary brain injury and may have a considerable clinical impact. Although data on human spontaneous ICH are scarce and mostly based on small populations, they reveal the apparent correlation between MMPs and clinical and radiological ICH features as well as the functional outcome, which might rationalize future therapeutic strategies. However, attempts at MMP inhibition in spontaneous ICH have solely been made under experimental conditions and were associated with a wide range of possible side effects. Therefore, further comprehensive, elucidating investigations in this field are vital before any conclusions could be translated to humans.

Role of cerebral endothelial cells in the astrocyte swelling and brain edema associated with acute hepatic encephalopathy

Brain edema is an important complication of acute hepatic encephalopathy (AHE), and astrocyte swelling is largely responsible for its development. Elevated blood and brain ammonia levels have been considered as major etiological factors in this edema. In addition to ammonia, recent studies have suggested that systemic infection, inflammation (and associated cytokines (CKs)), as well as endotoxin (lipopolysaccharide (LPS)) are also involved in AHE-associated brain edema. As endothelial cells (ECs) are the first resident brain cells exposed to blood-borne "noxious agents" (i.e., ammonia, CKs, LPS) that are present in AHE, these cells may be in a critical position to react to these agents and trigger a process resulting in astrocyte swelling/brain edema. We therefore examined the effect of conditioned media (CM) from ammonia, LPS and cytokine-treated cultured brain ECs on cell swelling in cultured astrocytes. CM from ammonia-treated ECs when added to astrocytes caused significant cell swelling, and such swelling was potentiated when astrocytes were exposed to CM from ECs treated with a combination of ammonia, LPS and CKs. We also found an additive effect when astrocytes were exposed to ammonia along with CM from ammonia-treated ECs. Additionally, ECs treated with ammonia showed a significant increase in the production of oxy-radicals, nitric oxide (NO), as well as evidence of oxidative/nitrative stress and activation of the transcription factor nuclear factor kappa B (NF-κB). CM derived from ECs treated with ammonia, along with antioxidants (AOs) or the NF-κB inhibitor BAY 11-7082, when added to astrocytes resulted in a significant reduction in cell swelling, as compared to the effect of CM from ECs-treated only with ammonia. We also identified increased nuclear NF-κB expression in rat brain cortical ECs in the thioacetamide (TAA) model of AHE. These studies suggest that ECs significantly contribute to the astrocyte swelling/brain edema in AHE, likely as a consequence of oxidative/nitrative stress and activation of NF-κB.

Lipoxin A4 inhibits 5-lipoxygenase translocation and leukotrienes biosynthesis to exert a neuroprotective effect in cerebral ischemia/reperfusion injury

Lipoxin A(4) (LXA(4)), a biologically active eicosanoid with anti-inflammatory and pro-resolution properties, was recently found to have neuroprotective effects in brain ischemia. As 5-lipoxygenase (5-LOX) and leukotrienes are generally considered to aggravate cerebral ischemia/reperfusion (I/R) injury, we investigated their effects on LXA(4)-mediated neuroprotection by studying middle cerebral artery occlusion (MCAO)/reperfusion in rats and oxygen-glucose deprivation (OGD)/recovery in neonatal rat astrocyte primary cultures. LXA(4) effectively reduced infarct volumes and brain edema, and improved neurological scores in the MCAO/reperfusion experiments; this effect was partially blocked by butoxycarbonyl-Phe-Leu-Phe-Leu-Phe (Boc2), a specific antagonist of the LXA(4) receptor (ALXR). Total 5-LOX expression did not change, regardless of treatment, but LXA(4) could inhibit nuclear translocation induced by MCAO or OGD. We also found that LXA(4) inhibits the upregulation of both leukotriene B(4) (LTB(4)) and leukotriene C(4) (LTC(4)) and the phosphorylation of extracellular signal-regulated kinase (ERK) induced by MCAO or OGD. The phosphorylation of the 38-kDa protein kinase (p38) and c-Jun N-terminal kinase (JNK) was not altered throughout the experiment. These results suggest that the neuroprotective effects of LXA(4) are probably achieved by anti-inflammatory mechanisms that are partly mediated by ALXR and through an ERK signal transduction pathway.

Role of histamine and its receptors in cerebral ischemia

Histamine is recognized as a neurotransmitter or neuromodulator in the brain, and it plays a major role in the pathogenic progression after cerebral ischemia. Extracellular histamine increases gradually after ischemia, and this may come from histaminergic neurons or mast cells. Histamine alleviates neuronal damage and infarct volume, and it promotes recovery of neurological function after ischemia; the H1, H2, and H3 receptors are all involved. Further studies suggest that histamine alleviates excitotoxicity, suppresses the release of glutamate and dopamine, and inhibits inflammation and glial scar formation. Histamine may also affect cerebral blood flow by targeting to vascular smooth muscle cells, and promote neurogenesis. Moreover, endogenous histamine is an essential mediator in the cerebral ischemic tolerance. Due to its multiple actions, affecting neurons, glia, vascular cells, and inflammatory cells, histamine is likely to be an important target in cerebral ischemia. But due to its low penetration of the blood-brain barrier and its wide actions in the periphery, histamine-related agents, like H3 antagonists and carnosine, show potential for cerebral ischemia therapy. However, important questions about the molecular aspects and pathophysiology of histamine and related agents in cerebral ischemia remain to be answered to form a solid scientific basis for therapeutic application.

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.

Pathogenesis of cognitive dysfunction in patients with obstructive sleep apnea: a hypothesis with emphasis on the nucleus tractus solitarius

OSA is characterized by the quintessential triad of intermittent apnea, hypoxia, and hypoxemia due to pharyngeal collapse. This paper highlights the upstream mechanisms that may trigger cognitive decline in OSA. Three interrelated steps underpin cognitive dysfunction in OSA patients. First, several risk factors upregulate peripheral inflammation; these crucial factors promote neuroinflammation, cerebrovascular endothelial dysfunction, and oxidative stress in OSA. Secondly, the neuroinflammation exerts negative impact globally on the CNS, and thirdly, important foci in the neocortex and brainstem are rendered inflamed and dysfunctional. A strong link is known to exist between neuroinflammation and neurodegeneration. A unique perspective delineated here underscores the importance of dysfunctional brainstem nuclei in etiopathogenesis of cognitive decline in OSA patients. Nucleus tractus solitarius (NTS) is the central integration hub for afferents from upper airway (somatosensory/gustatory), respiratory, gastrointestinal, cardiovascular (baroreceptor and chemoreceptor) and other systems. The NTS has an essential role in sympathetic and parasympathetic systems also; it projects to most key brain regions and modulates numerous physiological functions. Inflamed and dysfunctional NTS and other key brainstem nuclei may play a pivotal role in triggering memory and cognitive dysfunction in OSA. Attenuation of upstream factors and amelioration of the NTS dysfunction remain important challenges.

[Haemophagocytic lymphohistiocytosis syndrome: a possible cause of multi-organ failure in severe head trauma?]

We report the case of a 26-year-old patient who was victim of severe head trauma following a trafic road accident. Two days after trauma, she had fever, pancytopenia and multi-organ failure. The haemophagocytic lymphohistiocytosis syndrome was suspected. This diagnosis was confirmed by biologic findings (elevated serum levels of ferritin and triglycerid) and histological findings (examination of bone marrow smears showing histiocytes phagocytosing blood cells). The evolution was unfavorable despite of corticotherapy and symptomatic measures.

Effect of laser phototherapy on wound healing following cerebral ischemia by cryogenic injury

Laser phototherapy emerges as an alternative or auxiliary therapy for acute ischemic stroke, traumatic brain injury, degenerative brain disease, spinal cord injury, and peripheral nerve regeneration, but its effects are still controversial. We have previously found that laser phototherapy immunomodulates the response to focal brain damage. Following direct cortical cryogenic injury the effects of laser phototherapy on inflammation and repair was assessed after cryogenic injury (CI) to the central nervous system (CNS) of rats. The laser phototherapy was carried out with a 780 nm AlGaAs diode laser. The irradiation parameters were: power of 40 mW, beam area of 0.04 cm(2), energy density of 3 J/cm(2) (3s) in two points (0.12 J per point). Two irradiations were performed at 3 h-intervals, in contact mode. Rats (20 non-irradiated - controls and 20 irradiated) were used. The wound healing in the CNS was followed in 6 h, 1, 7 and 14 days after the last irradiation. The size of the lesions, the neuron cell viability percentages and the amount of positive GFAP labeling were statistically compared by ANOVA complemented by Tukey's test (p<0.05). The distribution of lymphocytes, leukocytes and macrophages were also analyzed. CI created focal lesions in the cortex represented by necrosis, edema, hemorrhage and inflammatory infiltrate. The most striking findings were: lased lesions showed smaller tissue loss than control lesions in 6 h. During the first 24 h the amount of viable neurons was significantly higher in the lased group. There was a remarkable increase in the amount of GFAP in the control group by 14 days. Moreover, the lesions of irradiated animals had fewer leukocytes and lymphocytes in the first 24 h than controls. Considering the experimental conditions of this study it was concluded that laser phototherapy exerts its effect in wound healing following CI by controlling the brain damage, preventing neuron death and severe astrogliosis that could indicate the possibility of a better clinical outcome.

Neuroprotection by rosiglitazone in transient focal cerebral ischemia might not be mediated by glutamate transporter-1

Glutamate transport represents a key mechanism for maintaining low level of glutamate in the extracellular milieu to restrict the excitotoxic action of glutamate released during ischemia/reperfusion (I/R) injury. Recently, it has been reported that glutamate transporter-1 (GLT-1) is a novel target for peroxisome proliferator-activated receptor-γ (PPARγ) agonist, which shows neuroprotection following oxygen glucose deprivation (OGD) in neuronal-astrocytic cocultures. Hence, the present study was undertaken to investigate the role of rosiglitazone in neuroprotection mediated by GLT-1 following focal cerebral I/R injury in rat. We found that rosiglitazone (2 mg/kg i.p) administered pre- or post-I/R injury significantly improved behavioral outcome and decreased cerebral infarct volume. However, no significant changes were observed in GLT-1 mRNA and protein expression in rosiglitazone-treated rats following 1 hr of ischemia/24 hr of reperfusion (1/24 hr I/R) injury. Interestingly, bioinformatics analysis also does not reveal any PPAR response element on the GLT-1/EAAT2 promoter region. Further rosiglitazone neither increased [(3) H]glutamate uptake in glia-enriched preparations nor caused any change in glutamine synthetase activity. On the other hand, there was a significant (P < 0.05) downregulation in tumor necrosis factor-α and interleukin-1β gene expression, which were more pronounced in the posttreatment group. The posttreatment with rosiglitazone also significantly reduced the increase in prostaglandin E2 level in the ischemic brain. Therefore, the present findings suggest that the neuroprotective effect of rosiglitazone does not seem to be mediated by modulation of GLT-1 protein expression/activity in a focal cerebral ischemia model. However, the results do provide increasing evidence that the neuroprotective effect may be mediated by its antiinflammatory action.

Immunoexcitotoxicity as a central mechanism in chronic traumatic encephalopathy-A unifying hypothesis

Some individuals suffering from mild traumatic brain injuries, especially repetitive mild concussions, are thought to develop a slowly progressive encephalopathy characterized by a number of the neuropathological elements shared with various neurodegenerative diseases. A central pathological mechanism explaining the development of progressive neurodegeneration in this subset of individuals has not been elucidated. Yet, a large number of studies indicate that a process called immunoexcitotoxicity may be playing a central role in many neurodegenerative diseases including chronic traumatic encephalopathy (CTE). The term immunoexcitotoxicity was first coined by the lead author to explain the evolving pathological and neurodevelopmental changes in autism and the Gulf War Syndrome, but it can be applied to a number of neurodegenerative disorders. The interaction between immune receptors within the central nervous system (CNS) and excitatory glutamate receptors trigger a series of events, such as extensive reactive oxygen species/reactive nitrogen species generation, accumulation of lipid peroxidation products, and prostaglandin activation, which then leads to dendritic retraction, synaptic injury, damage to microtubules, and mitochondrial suppression. In this paper, we discuss the mechanism of immunoexcitotoxicity and its link to each of the pathophysiological and neurochemical events previously described with CTE, with special emphasis on the observed accumulation of hyperphosphorylated tau.

Levosimendan decreases intracranial pressure after hypothermic circulatory arrest in a porcine model

OBJECTIVES

Hypothermic circulatory arrest (HCA) provides an optimal operating field in aortic arch surgery, but it is associated with neurological complications. Levosimendan is an inotropic agent with clinical indications for open-heart surgery. Through peripheral vasodilatation, cardiac contractility enhancement and anti-inflammatory function it has a potential to improve cerebral protection after HCA.

DESIGN

Eighteen piglets were randomly assigned to a levosimendan group (n = 9) and a placebo group (n = 9) and underwent a 60-minute period of hypothermic circulatory arrest at 18°C. A levosimendan or placebo infusion (0.2 μg/kg/min) was commenced at the onset of anesthesia and continued for 24 hours. Animals were followed for one week and their neurological recovery was assessed daily. Finally the animals were electively sacrificed and their brain was harvested for histopathological examination.

RESULTS

Levosimendan decreased intracranial pressure during the experiment. There were no differences between the groups in terms of hemodynamic or metabolic data, brain metabolism, neurological recovery or histopathology of the cerebral tissue. In the levosimendan group, cardiac enzymes were slightly more elevated.

CONCLUSIONS

Levosimendan decreased intracranial pressure during the experiment, but in terms of cerebral metabolism, neurological recovery and histopathology of the brain tissue levosimendan did not improve brain protection in this experimental setting.

Serum levels of cytokines and C-reactive protein in acute ischemic stroke patients, and their relationship to stroke lateralization, type, and infarct volume

There is increasing evidence that inflammation plays an important role in the progression of acute ischemic stroke (AIS). The primary aims of this study were to examine the serum levels of 13 cytokines, C-reactive protein (CRP), glucose, and hemoglobin in AIS patients, and their relationship to stroke lateralization, type, and infarct volume. Forty-five patients with AIS were evaluated. Blood samples were taken within 72 h, and volumetric analyses performed within 1–7 days after AIS onset. Cytokines were measured in serum from all patients and from 40 control subjects using Luminex Bio-Plex XMap technology. The levels of interleukin (IL)-1ra (p < 0.001), IL-6 (p < 0.001), IL-8 (p < 0.001), IL-9 (p = 0.038), IL-10 (p = 0.001), IL-12 (p = 0.001), IL-18 (p < 0.001), and GRO-α (CXCL1) (p = 0.017) were significantly higher in the AIS patients than in the controls. The IL-8 level was significantly correlated with age in the patient group (r = 0.52, p < 0.001). None of the variables were found to be associated with stroke lateralization. Infarct volume was significantly positively correlated with CRP level (r = 0.47, p = 0.005). Patients with radiologically confirmed infarctions had significantly elevated serum levels of GRO-α (p = 0.023). The cytokine profile of the AIS patients supports not only earlier findings of a proinflammatory response but also early activation of endogenous immunosuppressive mechanisms. Novel findings of this study are elevated serum levels of IL-9 and GRO-α. Elevated GRO-α in AIS patients with radiologically confirmed infarctions suggests that GRO-α is specific for stroke of known etiology. Our results indicate that CRP plays an important role in the progression of cerebral tissue injury.

Focal cerebral ischemia and mitochondrial dysfunction in the TNFα-transgenic rat

Post-ischemic neurodegeneration may be accelerated by a cytokine-receptor mediated apoptotic pathway, as shown in a transgenic rat overexpressing tumor necrosis factor-alpha (TNFα) in brain. To further investigate the mechanism of ischemic cellular injury in this animal, we tested the hypothesis that increased synthesis of TNFα augments neuronal death by promoting mitochondrial dysfunction, calcium dysregulation, and oxidative stress. Adult male TNFα-transgenic (TNFα-Tg) and non-transgenic (non-Tg) littermates underwent reversible middle cerebral artery occlusion (MCAO) for 1 hour followed by 1 hour of reperfusion. Cortical mitochondria were isolated from injured (ipsilateral) and uninjured (contralateral) hemispheres of ischemic rats or from pooled hemispheres of control animals. ATP synthesis was attenuated in non-ischemic TNFα-Tg rats, demonstrated by reduction of state III and respiratory control ratio, increased production of reactive oxygen species, and earlier formation of the calcium-induced membrane permeability transition pore. After MCAO, mitochondrial dysfunction was augmented more significantly in ischemic TNFα-Tg brain mitochondria than in non-Tg rats. These results show that mitochondrial dysfunction may be caused by increased brain levels of TNFα without physiological stress but will be exacerbated after MCAO. We conclude that ischemic stress and synthesis of inflammatory cytokines synergistically augment mitochondrial dysfunction to promote neuronal death.

Dynamics of neuroinflammation in the macrosphere model of arterio-arterial embolic focal ischemia: an approximation to human stroke patterns

Background

Neuroinflammation evolves as a multi-facetted response to focal cerebral ischemia. It involves activation of resident glia cell populations, recruitment of blood-derived leucocytes as well as humoral responses. Among these processes, phagocyte accumulation has been suggested to be a surrogate marker of neuroinflammation. We previously assessed phagocyte accumulation in human stroke by MRI. We hypothesize that phagocyte accumulation in the macrosphere model may resemble the temporal and spatial patterns observed in human stroke.

Methods

In a rat model of permanent focal ischemia by embolisation of TiO₂-spheres we assessed key features of post-ischemic neuroinflammation by the means of histology, immunocytochemistry of glial activation and influx of hematogeneous cells, and quantitative PCR of TNF-α, IL-1, IL-18, and iNOS mRNA.

Results

In the boundary zone of the infarct, a transition of ramified microglia into ameboid phagocytic microglia was accompanied by an up-regulation of MHC class II on the cells after 3 days. By day 7, a hypercellular infiltrate consisting of activated microglia and phagocytic cells formed a thick rim around the ischemic infarct core. Interestingly, in the ischemic core microglia could only be observed at day 7. TNF-α was induced rapidly within hours, IL-1β and iNOS peaked within days, and IL-18 later at around 1 week after ischemia.

Conclusions

The macrosphere model closely resembles the characteristical dynamics of postischemic inflammation previously observed in human stroke. We therefore suggest that the macrosphere model is highly appropriate for studying the pathophysiology of stroke in a translational approach from rodent to human.