Stroke risk factors prepare rat brainstem tissues for modified local Shwartzman reaction

Rhinosinusitis and Stroke: A Systematic Review

Rhinosinusitis is one of the most common inflammatory diseases. It has been recognized that intracranial vessels are involved and there might be an association with stroke occurrence. The aim of this study was to evaluate the association between rhinosinusitis and cardiovascular diseases, especially stroke, through a literature review. The review was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We performed on PubMed a literature search from February 2000 to February 2022, using the search terms 'rhinosinusitis' OR 'chronic rhinosinusitis' AND 'stroke' OR 'ischemic stroke'. Fourteen studies were eligible and included in the analysis. Overall, the studies encompassed a total of 1,006,338 patients included in this review. All studies concluded that there is a statistically significant correlation between clinical or radiological sinus inflammation and the risk of stroke, which is independent of traditional stroke risk factors. In conclusion, rhinosinusitis is associated with an increased incidence of stroke.

Incidental COVID-19 related lung apical findings on stroke CTA during the COVID-19 pandemic

BACKGROUND

Authors have noticed an increase in lung apex abnormalities on CT angiography (CTA) of the head and neck performed for stroke workup during the coronavirus disease 2019 (COVID-19) pandemic.

OBJECTIVE

To evaluate the incidence of these CTA findings and their relation to COVID-19 infection.

METHODS

In this retrospective multicenter institutional review board-approved study, assessment was made of CTA findings of code patients who had a stroke between March 16 and April 5, 2020 at six hospitals across New York City. Demographic data, comorbidities, COVID-19 status, and neurological findings were collected. Assessment of COVID-19 related lung findings on CTA was made blinded to COVID-19 status. Incidence rates of COVID-19 related apical findings were assessed in all code patients who had a stroke and in patients with a stroke confirmed by imaging.

RESULTS

The cohort consisted of a total of 118 patients with mean±SD age of 64.9±15.7 years and 57.6% (68/118) were male. Among all code patients who had a stroke, 28% (33/118) had COVID-19 related lung findings. RT-PCR was positive for COVID-19 in 93.9% (31/33) of these patients with apical CTA findings.Among patients who had a stroke confirmed by imaging, 37.5% (18/48) had COVID-19 related apical findings. RT-PCR was positive for COVID-19 in all (18/18) of these patients with apical findings.

CONCLUSION

The incidence of COVID-19 related lung findings in stroke CTA scans was 28% in all code patients who had a stroke and 37.5% in patients with a stroke confirmed by imaging. Stroke teams should closely assess the lung apices during this COVID-19 pandemic as CTA findings may be the first indicator of COVID-19 infection.

A murine model of inflammation-induced cerebral microbleeds

BACKGROUND

Cerebral microhemorrhages (CMH) are tiny deposits of blood degradation products in the brain and are pathological substrates of cerebral microbleeds. The existing CMH animal models are β-amyloid-, hypoxic brain injury-, or hypertension-induced. Recent evidence shows that CMH develop independently of hypoxic brain injury, hypertension, or amyloid deposition and CMH are associated with normal aging, sepsis, and neurodegenerative conditions. One common factor among the above pathologies is inflammation, and recent clinical studies show a link between systemic inflammation and CMH. Hence, we hypothesize that inflammation induces CMH development and thus, lipopolysaccharide (LPS)-induced CMH may be an appropriate model to study cerebral microbleeds.

METHODS

Adult C57BL/6 mice were injected with LPS (3 or 1 mg/kg, i.p.) or saline at 0, 6, and 24 h. At 2 or 7 days after the first injection, brains were harvested. Hematoxylin and eosin (H&E) and Prussian blue (PB) were used to stain fresh (acute) hemorrhages and hemosiderin (sub-acute) hemorrhages, respectively. Brain tissue ICAM-1, IgG, Iba1, and GFAP immunohistochemistry were used to examine endothelium activation, blood-brain barrier (BBB) disruption, and neuroinflammation. MRI and fluorescence microscopy were used to further confirm CMH development in this model.

RESULTS

LPS-treated mice developed H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. No surface and negligible H&E-positive CMH were observed in saline-treated mice (n = 12). LPS (3 mg/kg; n = 10) produced significantly higher number, size, and area of H&E-positive CMH at 2 days. LPS (1 mg/kg; n = 9) produced robust development of PB-positive CMH at 7 days, with significantly higher number and area compared with saline (n = 9)-treated mice. CMH showed the highest distribution in the cerebellum followed by the sub-cortex and cortex. LPS-induced CMH were predominantly adjacent to cerebral capillaries, and CMH load was associated with indices of brain endothelium activation, BBB disruption, and neuroinflammation. Fluorescence microscopy confirmed the extravasation of red blood cells into the brain parenchyma, and MRI demonstrated the presence of cerebral microbleeds.

CONCLUSIONS

LPS produced rapid and robust development of H&E-positive (at 2 days) and PB-positive (at 7 days) CMH. The ease of development of both H&E- and PB-positive CMH makes the LPS-induced mouse model suitable to study inflammation-induced CMH.

Heat stress presenting with encephalopathy and MRI findings of diffuse cerebral injury and hemorrhage

Background

Heat stress results in multiorgan failure and CNS injury. There a few case reports in the literature on the neurological consequences of heat stress.

Case presentation

We describe a patient with heat stress presenting with encephalopathy and bilateral cerebral, cerebellar, and thalamic lesions and intraventricular hemorrhage on MRI.

Conclusion

Heat stress should be in the differential diagnosis of patients presenting with encephalopathy and elevated serum inflammatory markers especially if the history suggests a preceding episode of hyperthermia.

Common infections and the risk of stroke

The occurrence of stroke in populations is incompletely explained by traditional vascular risk factors. Data from several case-control studies and one large study using case series methodology indicate that recent infection is a temporarily acting, independent trigger factor for ischemic stroke. Both bacterial and viral infections, particularly respiratory tract infections, contribute to this association. A causal role for infection in stroke is supported by a graded temporal relationship between these conditions, and by multiple pathophysiological pathways linking infection and inflammation, thrombosis, and stroke. Furthermore, observational studies suggest that influenza vaccination confers a preventive effect against stroke. Case-control and prospective studies indicate that chronic infections, such as periodontitis, chronic bronchitis and infection with Helicobacter pylori, Chlamydia pneumoniae or Cytomegalovirus, might increase stroke risk, although considerable variation exists in the results of these studies, and methodological issues regarding serological results remain unresolved. Increasing evidence indicates that the aggregate burden of chronic and/or past infections rather than any one single infectious disease is associated with the risk of stroke. Furthermore, genetic predispositions relating to infection susceptibility and the strength of the inflammatory response seem to co-determine this risk. Here, we summarize and analyze the evidence for common acute and chronic infectious diseases as stroke risk factors.

How inflammation modulates central nervous system vessel activation and provides targets for intervention--a personal perspective

I here describe a line of research that grew out of studies of spinal cord-damaging decompression sickness, focused on the blood-endothelial interface, that was influenced by the local Shwartzman phenomenon, addressed innate immune and inflammatory mechanisms, and ultimately arrived at mucosal tolerance approaches to prevent stroke. Intranasal instillation of E-selectin is under development as a novel means of targeting immunomodulation to activating blood vessels within the vascular tree supplying the brain. The goal of this form of focused immunomodulation is to prevent recurrent strokes in patients that have previously suffered transient ischemic attacks or strokes.

Modulation of cannabinoid receptor activation as a neuroprotective strategy for EAE and stroke

Recognition of the importance of the endocannabinoid system in both homeostasis and pathologic responses raised interest recently in the development of therapeutic agents based on this system. The CB(2) receptor, a component of the endocannabinoid system, has significant influence on immune function and inflammatory responses. Inflammatory responses are major contributors to central nervous system (CNS) injury in a variety of diseases. In this report, we present evidence that activation of CB(2) receptors, by selective CB(2) agonists, reduces inflammatory responses that contribute to CNS injury. The studies demonstrate neuroprotective effects in experimental autoimmune encephalomyelitis, a model of multiple sclerosis, and in a murine model of cerebral ischemia/reperfusion injury. In both cases, CB(2) receptor activation results in reduced white cell rolling and adhesion to cerebral microvessels, a reduction in immune cell invasion, and improved neurologic function after insult. In addition, administration of the CB(1) antagonist SR141716A reduces infarct size following ischemia/reperfusion injury. Administration of both a selective CB(2) agonist and a CB(1) antagonist has the unique property of increasing blood flow to the brain during the occlusion period, suggesting an effect on collateral blood flow. In summary, selective CB(2) receptor agonists and CB(1) receptor antagonists have significant potential for neuroprotection in animal models of two devastating diseases that currently lack effective treatment options.

Mucosal tolerance to E-selectin promotes the survival of newly generated neuroblasts via regulatory T-cell induction after stroke in spontaneously hypertensive rats

Neuroblasts in the subventricular zone (SVZ) proliferate markedly after brain ischemia, and migrate to the site of injury along with blood vessels. However, a large fraction of stroke-generated neuroblasts die shortly after being born, in part, because of local inflammation. In spontaneously hypertensive rats (SHRs) subjected to permanent middle cerebral artery occlusion, we primed E-selectin-specific regulatory T cells (Tregs) by repetitive intranasal administration of recombinant E-selectin to target local secretion of immunomodulating, antiinflammatory cytokines to activating blood vessel segments. E-selectin-tolerized SHRs had decreased infarction volumes, and increased numbers of Tregs in the cervical lymph nodes and ischemic brain. The brain Tregs were distributed primarily in periinfarct regions. E-selectin tolerization did not alter cellular proliferation in the ipsilateral SVZ after stroke, but the expression of tumor necrosis factor on vascular niche blood vessels was suppressed and both doublecortin protein levels and the number of newly generated neuroblasts or neurons were increased in the brain. This enhanced survival of neural progenitor cells and neurons was paralleled by improved functional performance. These studies suggest that E-selectin-specific Tregs can modulate the efficacy of neurogenesis after ischemia and promote repair after brain injury.

Mucosal tolerization to E-selectin protects against memory dysfunction and white matter damage in a vascular cognitive impairment model

Vascular cognitive impairment (VCI) is the second most prevalent type of dementia in the world. The white matter damage that characterizes the common subcortical ischemic form of VCI can be modeled by ligating both common carotid arteries in the Wistar rat to induce protracted cerebral hypoperfusion. In this model, we find that repetitive intranasal administration of recombinant E-selectin to induce mucosal tolerance and to target immunomodulation to activating blood vessels potently suppresses both white matter (and possibly gray matter) damage and markers of vessel activation (tumor necrosis factor and E-selectin); it also preserves behavioral function in T-maze spontaneous alternation, T-maze spatial discrimination memory retention, and object recognition tests. Immunomodulation may be an effective novel strategy to prevent progression of VCI.

Place of drug therapy in the treatment of carotid stenosis

Carotid stenosis is an important cause of transient ischaemic attacks and stroke. The cause of carotid stenosis is most often atherosclerosis; contributing to the pathogenesis of the lesion are endothelial injury, inflammation, lipid deposition, plaque formation, fibrin, platelets and thrombin. Carotid stenosis accounts for 10-20% of cases of brain infarction, depending on the population studied. Despite successful treatment of selected patients who have had an acute ischaemic stroke with tissue plasminogen activator and the promise of other experimental therapies, prevention remains the best approach to reducing the impact of ischaemic stroke. High-risk or stroke-prone patients can be identified and targeted for specific interventions. At this juncture, treatment of carotid stenosis is a well established therapeutic target and a pillar of stroke prevention. There are two main strategies for the treatment of carotid stenosis. The first approach is to stabilise or halt the progression of the carotid plaque through risk factor modification and medication. Hypertension, diabetes mellitus, smoking, obesity and high cholesterol levels are closely associated with carotid stenosis and stroke; control of these factors may decrease the risk of plaque formation and progression. The second approach is to eliminate or reduce carotid stenosis through carotid endarterectomy or carotid angioplasty and stenting. Carotid endarterectomy, which is the mainstay of therapy for severe carotid stenosis, is beyond the scope of this review. Anticoagulants seem to play little role (if any) in the medical (i.e. non-surgical) treatment of carotid stenosis. Adoption of a healthy lifestyle combined with the reduction of risk factors has been shown to lead to a reduction in the extent of carotid stenosis. The medical treatment of carotid stenosis should be based on the triad of the reduction of risk factors, patient education, and use of antiplatelet agents.

Mucosal tolerance to E-selectin provides cell-mediated protection against ischemic brain injury

We have demonstrated that induction of mucosal tolerance to E-selectin, a cytokine-inducible adhesion molecule restricted to activating blood vessels, prevents ischemic and hemorrhagic stroke in spontaneously hypertensive, genetically stroke-prone (SHR-SP) rats. We now examine whether mucosal tolerance to E-selectin has protective effects in ischemic brain damage after permanent middle cerebral artery occlusion (MCAO) in SHR-SP rats and whether these effects are related to generation of regulatory T cells. Rats were exposed to intranasal administration of E-selectin every other day for 10 days (single tolerization group) or on two tolerization schedules separated by 11 days (booster tolerization group). Control groups received PBS on corresponding schedules. MCAO was performed 48 h after the last dose of E-selectin or PBS. There were 45.8% and 37.9% (P < 0.05) decreases of infarction volume in the E-selectin booster group compared with the PBS group at 6 and 48 h, respectively. Single tolerization with E-selectin had only a slight trend toward a decrease in infarction volume (6.3%). CD8-positive cells were decreased in brains of E-selectin booster animals (46.6%, P < 0.01) compared with controls; splenocyte-culture supernatant levels of IL-10 were increased (59.3%, P < 0.05) in E-selectin booster animals. A decrease of infarction volume (34%, P < 0.05) was also observed in SHR-SP rats subjected to MCAO after adoptive transfer of splenocytes from E-selectin-tolerized compared with PBS-tolerized donors. The results indicate that, in addition to preventing stroke, mucosal tolerance to E-selectin is cytoprotective. Thus, immunomodulation targeted to activated blood vessel segments can both reduce stroke occurrence and attenuate brain damage if a stroke supervenes.

Increased cytokine release by leucocytes in survivors of stroke at young age

BACKGROUND

Enhanced stimulus-induced release of pro-inflammatory cytokines by leucocytes may contribute to the pathogenesis of ischaemic stroke.

DESIGN

We investigated the lipopolysaccharide-induced release of interleukin-1beta (IL-1beta), IL-6, IL-8, and tumour necrosis factor-alpha (TNF-alpha) in whole blood from 20 patients with a history of ischaemic stroke under the age of 50, 20 patients with a history of cervical artery dissection (CAD) and 21 age- and sex-matched healthy control subjects.

RESULTS

Release of IL-8 was higher (P = 0.006) and release of TNF-alpha and IL-6 tended to be higher (P < 0.1) in young stroke patients than in control subjects. No increased release existed in CAD patients. Vascular risk factors or history of infection before stroke did not modify IL-8 production. A common T(250) --> A polymorphism in the IL-8 gene promotor was newly identified but did not correlate with the variability of IL-8 release. The C(260) --> T polymorphism in the gene of the monocytic LPS-receptor CD14--a risk factor for myocardial infarction--was not associated with increased cytokine release.

CONCLUSIONS

We conclude that high inducible release of IL-8--and possibly of TNF-alpha and IL-6--may contribute to the odds of ischaemic stroke in young adults.

Brain vessels normally undergo cyclic activation and inactivation: evidence from tumor necrosis factor-alpha, heme oxygenase-1, and manganese superoxide dismutase immunostaining of vessels and perivascular brain cells

Studies of vascular biology during the past decade have identified an expanding list of agonists and antagonists that regulate local hemostasis, inflammation, and reactivity in blood vessels. Interactions at the blood-endothelial interface are intricate and complex and have been postulated to play a role in the initiation of stroke and the progression of brain injury during early hours of ischemia, particularly in conjunction with reperfusion injury (Hallenbeck, 1996). In the current study of normal and activated vessels in rat brain, immunoreactive tumor necrosis factor-alpha (TNF-alpha), heme oxygenase-1 (HO-1), and manganese superoxide dismutase (MnSOD) exhibit concentric perivascular rings involving vessel wall and surrounding parenchyma that appear to coincide with one another in serial sections. The ring patterns suggest periodic radial expansion of these molecules released through a process of cyclic activation and inactivation of brain vessel segments. In this process, the rings appear randomly scattered instead of affecting all vessels within a high power field (HPF) synchronously. The average number of vessels per HPF (mean +/- SD) with perivascular cuffs of immunoreactive MnSOD increased from 51 +/- 28 in Wistar, 72 +/- 46 in Wistar-Kyoto, and 84 +/- 30 in Sprague Dawley rats (no spontaneous strokes) to 184 +/- 72 in spontaneously hypertensive stroke-prone rats (spontaneous strokes). Perivascular immunoreactive cuffs are also increased in spontaneously hypertensive rats by induction of cytokine expression by lipopolysaccharide (64 +/- 15 vs. 131 +/- 32 /HPF). The patterns of TNF-alpha, HO-1, and MnSOD in naïve animals are interpreted to indicate that focal hemostatic balance normally fluctuates in brain vessels and influences surrounding parenchymal cells. Perivascular immunoreactive cuffs representing this process are more frequent in animals with lipopolysaccharide-induced endothelial activation or genetic stroke proneness.

Therapeutic potential of anti-inflammatory drugs in focal stroke

The importance of cytokines, especially TNF-alpha and IL-1beta, are emphasised in the propagation and maintenance of the brain inflammatory response to injury. Much data supports the case that ischaemia and trauma elicit an inflammatory response in the injured brain. This inflammatory response consists of mediators (cytokines, chemokines and adhesion molecules) followed by cells (neutrophils early after the onset of brain injury and then a later monocyte infiltration). De novo upregulation of pro-inflammatory cytokines, chemokines and endothelial-leukocyte adhesion molecules occurs soon after focal ischaemia and trauma, as well as at the time when the tissue injury is evolving. The significance of this brain inflammatory response and its contribution to brain injury is now becoming more understood. In this review, we discuss the role of TNF-alpha and IL-1beta in traumatic and ischaemic brain injury and associated inflammation and the co-operative actions of chemokines and adhesion molecules in this process. We also address novel approaches to target cytokines and reduce the brain inflammatory response and thus brain injury, in stroke and neurotrauma. The mitogen-activated protein kinase (MAPK), p38, has been linked to inflammatory cytokine production and cell death following cellular stress. Stroke-induced p38 enzyme activation in the brain has been demonstrated and treatment with a second generation p38 MAPK inhibitor, SB-239063, provides a significant reduction in infarct size, neurological deficits and inflammatory cytokine expression produced by focal stroke. SB-239063 can also provide direct protection of cultured brain tissue to in vitro ischaemia. This robust SB-239063-induced neuroprotection emphasises a significant opportunity for targeting MAPK pathways in ischaemic stroke injury and also suggests that p38 inhibition should be evaluated for protective effects in other experimental models of nervous system injury and neurodegeneration.

Brain injury and cerebrovascular fibrin deposition correlate with reduced antithrombotic brain capillary functions in a hypertensive stroke model

Hemostasis factors may influence the pathophysiology of stroke. The role of brain hemostasis in ischemic hypertensive brain injury is not known. We studied ischemic injury in spontaneously hypertensive rats in relation to cerebrovascular fibrin deposition and activity of different hemostasis factors in brain microcirculation. In spontaneously hypertensive rats subjected to transient middle cerebral artery occlusion versus normotensive Wistar-Kyoto (W-K) rats, infarct and edema volumes were increased by 6.1-fold (P < 0.001) and 5.8-fold (P < 0.001), respectively, the cerebral blood flow (CBF) reduced during middle cerebral artery occlusion (MCAO) by 55% (P < 0.01), motor neurologic score increased by 6.9-fold (P < 0.01), and cerebrovascular fibrin deposition increased by 6.8-fold (P < 0.01). Under basal conditions, brain capillary protein C activation and tissue plasminogen activator activity were reduced in spontaneously hypertensive rats compared with Wistar-Kyoto rats by 11.8-fold (P < 0.001) and 5.1-fold (P < 0.001), respectively, and the plasminogen activator inhibitor-1 antigen and tissue factor activity were increased by 154-fold (P < 0.00001) and 74% (P < 0.01), respectively. We suggest that hypertension reduces antithrombotic mechanisms in brain microcirculation, which may enhance cerebrovascular fibrin deposition and microvascular obstructions during transient focal cerebral ischemia, which results in greater neuronal injury.

Advances in the vascular pathophysiology of ischemic stroke

The cerebral vascular supply is constructed to protect the cerebral hemispheres and brainstem from the consequences of blood flow cessation. Reversal of blood flow around local obstructions is a feature of the microvascular beds of the striatum and cerebral cortex. Cerebral capillaries of these beds consist of endothelial cells, basal lamina, and astrocyte end-feet that sit in close apposition. The interaction of astrocytes with neurons indicates the close relationship of microvessels to neurons. These relationships are altered when blood flow ceases in the supplying artery. Increased endothelial cell permeability and endocytoses lead to edema formation, and matrix degradation is associated with hemorrhage. Autoregulation is lost. Ischemia initiates leukocyte adhesion receptor expression, which is promoted by cytokine generation from the neuropil and activated monocytes. "Preactivation" may further augment the inflammatory responses to ischemia. The activation of cerebral microvessels by ischemia is heterogeneous, involving alterations in integrin-matrix interactions, leukocyte-endothelial cell adhesion, permeability changes, and the "no-reflow" phenomenon due to platelet activation, fibrin formation, and leukocyte adhesion. Ischemia produces swelling of the microvascular endothelium, and rapid detachment and swelling of the astrocyte end-feet. Ischemic injury targets the microvasculature, where the inflammatory responses are initiated and contribute to tissue injury.

Sinusitis and carotid artery stroke

The relationship between sinusitis and ischemic stroke is unexplored. The anatomic proximity between the paranasal sinuses and the internal carotid artery suggests that inflammation of the sinuses could easily extend to the intracranial vasculature. We report 4 patients with acute ischemic stroke and extensive disease of the paranasal sinuses. All patients had large vessel stroke involving the internal carotid artery territory. All patients had extensive disease of the sphenoid and other sinuses. The sinus disease was demonstrated by magnetic resonance imaging. These case report observations suggest a relationship between inflammation of the paranasal sinuses, particularly sphenoid sinusitis, and ischemic stroke.

The interleukin-1 type I receptor is expressed in human hypothalamus

Several lines of evidence suggest that interleukin-1 (IL-1) acts directly on the central nervous system, probably within the hypothalamus, causing effects such as fever, activation of the immune response and sickness behaviour. IL-1 has also been shown to be involved in the aetiology of several neuronal diseases, including neurodegeneration, stroke and Alzheimer's disease. However, the question as to whether the full-length type I IL-1 receptor (IL-1RI) is expressed in the human hypothalamus has yet to be addressed. Using the polymerase chain reaction, we cloned a full-length cDNA encoding the human hypothalamic IL-1RI from human hypothalamic cDNA. The DNA sequence of the human hypothalamic receptor was identical to that of the human fibroblast IL-1RI. The IL-1RI receptor protein was detected in astrocytes of normal human hypothalamic brain sections using immunocytochemical techniques. To ascertain that the cloned receptor was functional, Chinese hamster ovary (CHO) cells were transfected with a plasmid vector containing the IL-1RI coding region. IL-1RI-mediated-signal transduction was assessed by microphysiometry and activation of p38 MAP (mitogen-activated protein) kinase. We report the first demonstration that both the type I IL-1 transcript and the protein are expressed in the human hypothalamus. The receptor was expressed in a stable CHO cell line, providing a tool with which to embark on a thorough analysis of the signalling mechanisms mediated by IL-1 via this receptor.

Inflammatory mediators and stroke: new opportunities for novel therapeutics

Contrary to previous dogmas, it is now well established that brain cells can produce cytokines and chemokines, and can express adhesion molecules that enable an in situ inflammatory reaction. The accumulation of neutrophils early after brain injury is believed to contribute to the degree of brain tissue loss. Support for this hypothesis has been drawn from many studies where neutrophil-depletion blockade of endothelial-leukocyte interactions has been achieved by various techniques. The inflammation reaction is an attractive pharmacologic opportunity, considering its rapid initiation and progression over many hours after stroke and its contribution to evolution of tissue injury. While the expression of inflammatory cytokines that may contribute to ischemic injury has been repeatedly demonstrated, cytokines may also provide "neuroprotection" in certain conditions by promoting growth, repair, and ultimately, enhanced functional recovery. Significant additional basic work is required to understand the dynamic, complex, and time-dependent destructive and protective processes associated with inflammation mediators produced after brain injury. The realization that brain ischemia and trauma elicit robust inflammation in the brain provides fertile ground for discovery of novel therapeutic agents for stroke and neurotrauma. Inhibition of the mitogen-activated protein kinase (MAPK) cascade via cytokine suppressive anti-inflammatory drugs, which block p38 MAPK and hence the production of interleukin-1 and tumor necrosis factor-alpha, are most promising new opportunities. However, spatial and temporal considerations need to be exercised to elucidate the best opportunities for selective inhibitors for specific inflammatory mediators.

Neonatal cytokines and coagulation factors in children with cerebral palsy

We explored the association of inflammatory mediators and markers of autoimmune and coagulation disorders with cerebral palsy (CP), examining 53 analytes in dried neonatal blood of 31 children with spastic CP, most born at term, and 65 control children. Ultramicroanalysis was performed by recycling immunoaffinity chromatography coupled with laser-enhanced fluorescence and chemiluminescence detection. Reactive antibodies to lupus anticoagulant, anticardiolipin, antithrombin III, and the translational product of the factor V Leiden mutation were isolated by recycling immunoaffinity chromatography and measured by capillary electrophoresis with chemiluminescence-enhanced immunoassay. Higher concentrations of interleukins (ILs) 1, 8, 9, tumor necrosis factor-alpha, and RANTES were observed in these children with CP than in any control child. There were also substantial elevations of IL-6, 11, 13, and other chemokines and colony-stimulating factors in children with CP. Antiphospholipid antibody was present in a titer of 1:100 or greater in 4 children with CP and no control child. Using cuts empirically chosen by recursive partitioning, we found higher concentrations of antibody to antithrombin III, to a translational product of factor V Leiden mutation, and to proteins C and S in children with CP than in controls. We conclude that inflammation and these coagulation abnormalities, which have interacting pathways, are important in the etiology of CP.

Cerebral lupus vasculopathy. Mechanisms and clinical relevance

The most common neuropathological findings in SLE are a small vessel cerebral vasculopathy and microinfarcts. These findings may reflect the end result of repeated episodes of acute inflammation in the small vessels in the brain. There is experimental support for the local Shwartzman reaction as a paradigm to explain some of the CNS manifestations in SLE. Activation or "priming" of cerebral microvascular endothelial cells by anticardiolipin antibodies or other immunoglobulins in concert with intravascular activation of the complement system may combine to elicit leukothrombosis in the brain. Therapies aimed at inhibiting leukocyte-endothelial cell interactions in the brain may be of use in CNS lupus.

Cytokines and adhesion molecules in stroke and related diseases

Once thought as immunologically naive, cells from the central nervous system have been shown to become immunologically reactive and produce various substances including cytokines and adhesion molecules. Recent investigations have revealed that mRNAs of certain cytokines such as tumor necrosis factor, interleukin-1, and interleukin-6 are expressed in the ischemic brain of the animals. Chemokines including CINC, MCP-1, and MIP-1, as well as adhesion molecules such as ICAM-1. ELAM and P-selectin were also found to be expressed. Although identification of the cells producing these cytokines were often difficult, neurons, endothelia, activated astrocytes and microglia/macrophages were the likely sources. The induction of these molecules in ischemic brain is time-locked and appears to be controlled in a highly regulated manner during the process of ischemic cascade. The functional role, interrelationship, and basic mechanism of action of these molecules are being increasingly recognized, while trials such as antiadhesion antibody molecules, growth factors, and anticytokine antibodies have been successful in reducing the neuronal damage in animals subjected to ischemic injury. Furthermore, changes of certain cytokines or adhesion molecules have been detected in the serum or cerebrospinal fluid of patients with stroke and related diseases suggesting that these molecules play a role in the pathogenesis of human stroke. Understanding of these cytokine-adhesion molecule cascades in the ischemic brain may allow us to develop new strategies for the treatment of stroke.

The association of leukocyte count, fibrinogen and C-reactive protein with vascular risk factors and ischemic vascular diseases

In 154 subjects (age 63 +/- 11 years; 63 women and 91 men) randomly selected from the population, we tested the hypothesis that inflammatory parameters are associated with vascular risk factors and particularly with a history of ischemic vascular diseases. The subjects were part of the control group (n = 197) in a case-control study investigating recent infection as a risk factor for acute cerebrovascular ischemia and had been matched for sex and age with patients suffering from acute ischemic stroke or transient ischemic attack. Subjects with malignant or inflammatory diseases, with recent trauma, surgery or vascular diseases (n = 43) were excluded from the present analysis. In multivariate analysis, current smoking, diabetes mellitus, age > or = 65 years, and a history of stroke independently increased the leukocyte count. Hypertriglyceridemia, peripheral arterial disease, and diabetes mellitus were positively associated with C -reactive protein (CRP). Age > or = 65 years and diabetes mellitus independently increased fibrinogen. (p < 0.05, respectively) Subjects with a history of cerebrovascular, cardiovascular or peripheral arterial disease had higher leukocyte counts, fibrinogen and CRP than subjects without vascular risk factors and higher leukocytes and fibrinogen than subjects with one or more risk factors. Subjects under the age of 65 with vascular risk factors but without ischemic diseases had higher leukocyte count, fibrinogen and CRP and subjects older than 65 with risk factors had higher CRP than subjects without risk factors or ischemic diseases in the same age group. (p < 0.05, respectively) These results support the hypotheses that low-grade inflammation is associated with vascular risk factors and that inflammatory mechanisms may contribute to the risk of organ ischemia.

Cerebral protection in homozygous null ICAM-1 mice after middle cerebral artery occlusion. Role of neutrophil adhesion in the pathogenesis of stroke

Acute neutrophil (PMN) recruitment to postischemic cardiac or pulmonary tissue has deleterious effects in the early reperfusion period, but the mechanisms and effects of neutrophil influx in the pathogenesis of evolving stroke remain controversial. To investigate whether PMNs contribute to adverse neurologic sequelae and mortality after stroke, and to study the potential role of the leukocyte adhesion molecule intercellular adhesion molecule-1 (ICAM-1) in the pathogenesis of stroke, we used a murine model of transient focal cerebral ischemia consisting of intraluminal middle cerebral artery occlusion for 45 min followed by 22 h of reperfusion. PMN accumulation, monitored by deposition of 111In-labeled PMNs in postischemic cerebral tissue, was increased 2.5-fold in the ipsilateral (infarcted) hemisphere compared with the contralateral (noninfarcted) hemisphere (P < 0.01). Mice immunodepleted of neutrophils before surgery demonstrated a 3.0-fold reduction in infarct volumes (P < 0.001), based on triphenyltetrazolium chloride staining of serial cerebral sections, improved ipsilateral cortical cerebral blood flow (measured by laser Doppler), and reduced neurological deficit compared with controls. In wild-type mice subjected to 45 min of ischemia followed by 22 h of reperfusion, ICAM-1 mRNA was increased in the ipsilateral hemisphere, with immunohistochemistry localizing increased ICAM-1 expression on cerebral microvascular endothelium. The role of ICAM-1 expression in stroke was investigated in homozygous null ICAM-1 mice (ICAM-1 -/-) in comparison with wild-type controls (ICAM-1 +/+). ICAM-1 -/- mice demonstrated a 3.7-fold reduction in infarct volume (P < 0.005), a 35% increase in survival (P < 0.05), and reduced neurologic deficit compared with ICAM-1 +/+ controls. Cerebral blood flow to the infarcted hemisphere was 3.1-fold greater in ICAM-1 -/- mice compared with ICAM-1 +/+ controls (P < 0.01), suggesting an important role for ICAM-1 in the genesis of postischemic cerebral no-reflow. Because PMN-depleted and ICAM-1-deficient mice are relatively resistant to cerebral ischemia-reperfusion injury, these studies suggest an important role for ICAM-1-mediated PMN adhesion in the pathophysiology of evolving stroke.

Agonist-stimulated release of von Willebrand factor and procoagulant factor VIII in rats with and without risk factors for stroke

Lipopolysaccharide (LPS)-induced (i.v. or i.c.v., 1.8 mg/kg) release of von Willebrand factor (vWF) was examined in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. SHR rats released significantly (P < 0.05) more vWF than WKY rats in response to LPS. LPS also inhibited factor VIII procoagulant activity (FVIII:c) which may indicate an increase in thrombin activity. Cultured cerebrovascular endothelial cells (EC) derived from both SHR and WKY rats, as well as human umbilical vein EC (HUVEC) cultures constitutively released vWF. Treatment with agonists including LPS, thrombin and tumor necrosis factor-alpha (TNF alpha) did not affect the in vitro secretion of vWF by cerebrovascular EC cultures but significantly upregulated vWF release by HUVEC cultures. Preincubation of cerebrovascular EC cultures with interleukin-1 (IL-1) +/- TNF alpha or co-culturing in the presence of LPS-activated syngeneic monocytes had no effect on vWF secretion. The findings demonstrate that conditions of hypertension may affect endothelial cells and make them more responsive to agonist stimulation and thereby increase secretion of vWF, an important factor in hemostasis as well as thrombosis. The capacity of LPS to significantly affect the in vivo secretion of vWF in SHR and WKY rats but not cultured cerebrovascular EC indicates that observed elevations in plasma vWF were not derived from cerebrovascular EC. It is suggested that hypertension may function as a risk factor for thrombotic stroke by influencing factors involved in coagulation processes, such as vWF and factor VIII:c.

Quantitation of perivascular monocytes and macrophages around cerebral blood vessels of hypertensive and aged rats

The numbers of monocytes and macrophages in the walls of cerebral blood vessels were counted on perfusion-fixed frozen brain sections (16 microns) of spontaneously hypertensive rats (SHR), stroke-prone SHR (SHR-SP), normotensive Wistar-Kyoto (WKY) rats, and young (16-week-old) and old (2-year-old) normotensive Sprague-Dawley rats (SD-16w and SD-2y, respectively) using monoclonal antibodies against rat macrophages (ED2). The staining was visualized with fluorescein-labeled second antibodies. The ED2-specific staining in brain sections was restricted to macrophages in a perivascular location. The number of perivascular cells per square millimeter of high-power field was significantly greater in SHR-SP (8.6 +/- 2.1; n = 4) and SHR (6.7 +/- 0.9; n = 6) than in normotensive WKY (4.0 +/- 0.5; n = 6; p < 0.01). The number of perivascular macrophages was also greater in SD-2y (7.5 +/- 2.7; n = 9) than in SD-16w (2.9 +/- 1.8; n = 8; p < 0.01). No ED2 staining was found in the resident microglia or in the endothelial cells, which were identified by double staining with rhodamine-labeled anti-factor VIII-related antigen antibodies. The results suggest that the stroke risk factors hypertension and advanced age are associated with increased subendothelial accumulation of monocytes and macrophages. This accumulation could increase the tendency for the endothelium to convert from an anticoagulant to a procoagulant surface in response to mediators released from these subendothelial cells.

In vivo relationship of interleukin-2 and soluble IL-2 receptor to blood-brain barrier impairment in patients with active multiple sclerosis

Interleukin (IL)-2 has well-recognized effects on cerebral endothelial cells and, therefore, may mediate disruption of the blood-brain barrier in patients with multiple sclerosis (MS). To evaluate the in vivo relationship of the IL-2 system to blood-brain barrier impairment in MS, levels of IL-2 and soluble IL-2 receptors (sIL-2R) in cerebrospinal fluid (CSF) and serum samples from 50 patients with active MS and 49 controls were correlated with values of the CSF to serum albumin ratio. Intrathecal levels of IL-2 and sIL-2R were significantly higher in MS compared with the control groups and correlated with albumin ratios in MS patients. Intrathecal levels of IL-2 and sIL-2R also correlated with the degree of barrier damage in these patients. It is suggested that intrathecal levels of IL-2 and sIL-2R are related to barrier impairment in MS and may be important in understanding some of the pathological changes of this condition.

Comparison of stimulated tissue factor expression by brain microvascular endothelial cells from normotensive (WKY) and hypertensive (SHR) rats

The amounts of tissue factor (TF) expressed by brain microvascular endothelial cells (BMECs) from normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR) were compared after stimulating the cells with different doses of lipopolysaccharide (LPS), thrombin, phorbol myristic acid (PMA), Ca(2+)-ionophore (A23187), or tumor necrosis factor (TNF) and interleukin-1 (IL-1). Treatment of cultured BMECs from WKY and SHR with all of these factors dose-dependently increased their total amount of TF; no substantive differences in the levels of enhanced TF expression were observed between WKY and SHR BMECs. We conclude that stimulated endothelium from rats with hypertension, a major stroke risk factor, is not hyperresponsive with respect to TF expression when compared to normotensive controls.

Possible involvement of interleukin-1 in ischemic brain edema formation

To determine the contribution of interleukin 1 (IL-1) on ischemic brain edema formation, the effect of recombinant human interleukin 1 beta (rhIL-1 beta), or zinc protoporphyrin (ZnPP) as an IL-1 blocker, on brain edema was studied in rats. The animals were subjected to 60 min of ischemia in a middle cerebral artery occlusion model. Immediately after reperfusion, rhIL-1 beta at a dose of 10 ng/2 microliters, or ZnPP at doses of 1 and 10 micrograms/2 microliters were topically applied into lateral cerebroventricle. In rhIL-1 beta-treated rats, ischemic brain edema formation was significantly increased in the dorsal and ventral areas of the caudate putamen 24 h after reperfusion, compared to that of vehicle-treated control rats. Furthermore, in ZnPP-treated rats, brain edema was decreased in both caudate-putamen areas. This suggests that IL-1 plays an important role in pathogenesis for post-ischemic brain edema.

Genetic hypertension and increased susceptibility to cerebral ischemia

A review of the sensitivity of genetically hypertensive rats to cerebral ischemia was presented together with original data describing the systematic comparison of the effects of focal ischemia (permanent and temporary with reperfusion) performed in hypertensive and normotensive rats (i.e., blood pressures verified in conscious instrumented rats). Microsurgical techniques were used to isolate and occlude the middle cerebral artery (MCAO) of spontaneously hypertensive (SHR), Sprague-Dawley (SD) and Wistar Kyoto (WKY) rats at the level of the inferior cerebral vein. Following permanent (24 h) MCAO, persistent and similar decreases in local microvascular perfusion (i.e., to 15.6 +/- 1.7% of pre-MCAO levels) were verified in the primary ischemic zone of the cortex for all strains using Laser-Doppler flowmetry. A contralateral hemiplegia that occurred following MCAO, evidenced by forelimb flexion and muscle weakness, was greater in SHR (neurological grade = 2.0 +/- 0.1) than SD (1.0 +/- 0.4) or WKY (0.7 +/- 0.4) rats (N = 7-9, p less than 0.05). SHR also exhibited sensory motor deficits following MCAO compared to sham-operation, with decreased normal placement response of the hindlimb (% normal = 20 vs. 83, N = 23-30, p decreased rota-rod (41 +/- 7 vs. 126 +/- 19 on rod, N = 10-15, p less than 0.05) and balance beam (25 +/- 5 vs. 116 +/- 29 s on beam, N = 5-7, p less than 0.05) performance. However, an index of general motor activity was not affected by permanent MCAO. Triphenyltetrazolium-stained forebrain tissue analyzed by planimetry revealed a significantly larger and more consistent cortical infarction in SHR (hemispheric infarction = 27.9 +/- 1.5%) compared to SD (15.4 +/- 4.1%) and WKY (4.0 +/- 2.4%) rats (N = 7-9, p less than 0.05), occupying predominantly the frontal and parietal areas. Also, a significant degree of ipsilateral hemispheric swelling (4.6 +/- 0.9%, N = 7-9, p less than 0.05) and increased brain water content (78.4 +/- 0.3% to 80.4 +/- 0.2%, N = 8-9, p less than 0.05) was identified in SHR that was not observed in SD or WKY rats. A novel model of temporary MCAO also was evaluated in the hypertensive and normotensive rat strains. Initially, the effect of increasing MCAO-time followed by 24 h reperfusion in SHR was studied. During temporary MCAO (20 to 300 min), persistent and stable decreases in local microvascular perfusion (i.e., to 15-20% of pre-MCAO levels) were verified in the primary ischemic zones of the cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Functions and mechanisms of interleukin 1 in the brain

Interleukin 1 (IL-1), a cytokine with diverse actions, has been proposed as a mediator of both beneficial and detrimental responses to inflammation and injury. Many of the actions of IL-1, such as those on behaviour, neuroendocrine function, sleep, fever and metabolism, are mediated by the CNS, as described here by Nancy Rothwell. IL-1 can be synthesized and act locally within the brain to influence neuronal and glial function, and has been strongly implicated in normal brain development and responses to brain injury. A number of distinct sites and mechanisms of action have been proposed to explain these diverse effects of IL-1 in the brain, probably involving multiple receptor subtypes and complex interactions with neurotransmitters and neuropeptides.

Extracellular matrix permits the expression of von Willebrand's factor, uptake of di-I-acetylated low density lipoprotein and secretion of prostacyclin in cultures of endothelial cells from rat brain microvessels

Microvascular endothelial cells from the adult rat brain were cultured on Matrigel and found to express many differentiated properties including secretion of prostacyclin (PGI2) and von Willebrand's factor (vWF). Brain microvascular endothelial cells (BMECs) were purified by dextran and percoll gradients after enzymatic treatment and cultured under various conditions. BMECs that were plated on Matrigel stained positively for factor VIII-related antigen and incorporated Di-I-acetylated low density lipoprotein, whereas BMEC plated on fibronectin, gelatin, or uncoated dishes did not express any of the above properties which are characteristic of endothelial cells. vWF was measured by a sensitive ELISA in the culture media of BMECs plated on different types of matrices. Specificity of the anti-human vWF antibodies for the rat vWF was verified by immunoabsorption on a solid phase, sodium dodecyl sulfate, and Western blot analysis. BMECs also secreted vWF into the culture media only when the cells were plated on Matrigel, and this secretion was augmented after a 6 h incubation with an interleukin-1 tumor necrosis factor-alpha mixture, but not by lipopolysaccharide. From different matrices tested, only Matrigel permitted the secretion of PGI2 by BMECs. Cells also proved to be sensitive to mechanical stimulation and became refractory to secretagogue if the mechanical stimulation was serially repeated. Under the best conditions, stimulation of the cells with bradykinin (1 microM) substantially increased PGI2 secretion. These data indicate that growth of BMECs on Matrigel in vitro permits the expression of classical endothelial cell markers in a manner similar to the behavior of these cells in situ.

Seizures and cerebritis associated with administration of OKT3

The development of a self-limited aseptic meningitis usually following the first dose administration of OKT3 therapy (an anti-pan-T-cell monoclonal antibody) in the treatment of renal transplantation rejection is well-documented. This report describes a patient with renal transplantation rejection who developed lateralizing seizures and cerebritis documented by magnetic resonance imaging. These findings were associated with the initiation of OKT3 therapy. To our knowledge, both cerebritis and seizures have not been described in association with OKT3 therapy.

Lipopolysaccharide-induced production of tumor necrosis factor activity in rats with and without risk factors for stroke

Rats produced more TNF activity in cerebrospinal fluid (CSF) than in blood after intracerebroventricular (i.c.v.) injection of lipopolysaccharide (LPS). After intravenous (i.v.) LPS, blood TNF levels exceeded CSF levels. Thus, brain cells appear to produce TNF in response to LPS. Rats with the stroke-risk factors hypertension or combined hypertension and genetic stroke-proneness produce more TNF in response to a provocative dose of LPS i.v. than control animals free of these risk factors. The possible relevance to stroke vulnerability is discussed.