Inflammatory reaction after brain damage and prospective therapy against damage impending cerebral infarction

Silent Brain Infarction – A Review of Recent Observations

Silent brain infarction is a cerebral ischaemic event evident on brain imaging without any clinical symptom. Silent brain infarction is often detected in apparently healthy, elderly people and in different selected patient groups as well. Lately, several studies were carried out in order to identify the clinical conditions leading to silent brain infarction. A large number of clinical and paraclinical parameters were found to increase silent brain infarction prevalence, and the continuously growing list of risk factors revealed that the majority of them are similar to those related to stroke. Accordingly, some consider silent brain infarction the preclinical stage of clinically overt stroke. This point of view emphasizes the early recognition and management of silent brain infarction-related risk factors, and a great need for comparative studies, which could elicit the most sensitive indicators of the increased silent brain infarction risk, especially the ones that could be cost-effectively screened in the large populations as well.

Soluble adhesion molecules and C-reactive protein in the progression of silent cerebral infarction in patients with type 2 diabetes mellitus

The purpose of this study was to investigate the association between the progression of silent cerebral infarction (SCI) and levels of soluble adhesion molecules and high-sensitivity C-reactive protein (hs-CRP) in type 2 diabetic patients. One hundred twenty middle-aged and elderly diabetic patients without histories of vascular events were followed up for a period of 3 years. We measured levels of soluble intercellular adhesion molecule 1 (sICAM-1), vascular cell adhesion molecule 1, E-selectin, and hs-CRP and assessed brain ischemic lesions by magnetic resonance imaging at baseline and 3 years later. Silent cerebral infarction was observed in 13% of the patients at baseline, and these patients were significantly older and had significantly higher blood pressure than those without SCI. Thirty-two patients had newly diagnosed SCI after 3 years. There were no significant differences in factors such as age, blood pressure, and diabetic control between patients without SCI and those in whom it was newly diagnosed. However, only sICAM-1 levels, but not the other soluble adhesion molecules or hs-CRP, were associated with the progression of SCI, and this relationship remains after adjustment for risk factors. On the other hand, higher levels of sICAM-1 and hs-CRP at baseline were observed in 7 patients who were excluded from the present study because of the onset of symptomatic cerebral infarction during follow-up. Our present study suggests that sICAM-1 levels may be a potential marker for SCI, which may lead to future stroke and vascular dementia, and that this marker could be useful in monitoring disease progression and as a surrogate marker in treatment studies.

Synthetic fibronectin peptide exerts neuroprotective effects on transient focal brain ischemia in rats

Leukocytes have been investigated during the past decade for their roles in secondary tissue damage after ischemia/reperfusion injury. Peptide PRARIY, a synthetic fibronectin peptide, has shown an anti-adhesion effect in in vitro studies. Previous studies have demonstrated that anti-adhesion agents lead to reductions in apoptosis. The purpose of the present study was to determine whether the peptide PRARIY displays anti-inflammatory, anti-apoptotic, and neuroprotective effects following transient focal brain ischemia in rats. Twenty-six male Sprague-Dawley rats (300-350 g) were randomly divided into three groups: phosphate-buffered saline (PBS) controls, PRARI controls, and PRARIY treatments. The right middle cerebral artery was transiently occluded using a 4-0 nylon suture. One hour later, the occluder was withdrawn, and reperfusion was maintained for 48 h. Immediately after reperfusion, the peptides (20 mg/kg, dissolved in PBS) and the same volume of PBS were continuously infused through the right external carotid artery using an osmotic minipump for 24 h. Neurological deficits were examined at 3, 24, and 48 h after ischemia. Forty-eight hours after reperfusion, the rats were sacrificed for determining infarction size, leukocyte infiltration, and apoptosis in the ischemia area. Unexpectedly, PRARIY did not influence leukocyte infiltration. However, PRARIY-treated rats showed significantly functional outcome, reduction of infarction size, decrease of TUNEL positive cells, and increase of Bcl-2 (anti-apoptotic protein) positive cells in the ischemic areas when compared to the controls. These data indicate that the peptide PRARIY exerts its neuroprotective effects via supporting neural cell survival rather than anti-leukocyte recruitment following brain ischemia/reperfusion injury.

Heterogeneity affecting outcome from acute stroke therapy: making reperfusion worse

BACKGROUND

Stroke patients are heterogeneous not only with respect to etiology but also in terms of preexisting clinical conditions. Approximately one fifth of patients with acute stroke are hyperglycemic and/or have had a recent infectious or inflammatory condition. Summary of Review-- Experimental research indicates that these factors can alter and accelerate the evolution of stroke and reperfusion injury, although these effects are complex and some may have a favorable impact. Both conditions involve activation of inflammatory and reactive oxygen mechanisms. In addition, hyperglycemia has concomitant deleterious vascular and metabolic effects that worsen infarct size and encourage hemorrhagic transformation in reperfusion models. Clinical data are less extensive but in general support an adverse impact on outcome.

CONCLUSIONS

After examining these data in detail, we concluded that the presence of these clinical conditions could assist in identification of those at increased risk for complications of reperfusion therapy. Furthermore, consideration of these factors may provide a rational basis for combination therapy and improve the clinical relevance of experimental stroke models.

Reperfusion injury after focal cerebral ischemia: the role of inflammation and the therapeutic horizon

Recent evidence indicates that thrombolysis may be an effective therapy for the treatment of acute ischemic stroke. However, the reperfusion of ischemic brain comes with a price. In clinical trials, patients treated with thrombolytic therapy have shown a 6% rate of intracerebral hemorrhage, which was balanced against a 30% improvement in functional outcome over controls. Destruction of the microvasculature and extension of the infarct area occur after cerebral reperfusion. We have reviewed the existing data indicating that an inflammatory response occurring after the reestablishment of circulation has a causative role in this reperfusion injury. The recruitment of neutrophils to the area of ischemia, the first step to inflammation, involves the coordinated appearance of multiple proteins. Intercellular adhesion molecule-1 and integrins are adhesion molecules that are up-regulated in endothelial cells and leukocytes. Tumor necrosis factor-alpha, interleukin-1, and platelet-activating factor also participate in leukocyte accumulation and subsequent activation. Therapies that interfere with the functions of these factors have shown promise in reducing reperfusion injury and infarct extension in the experimental setting. They may prove to be useful adjuncts to thrombolytic therapy in the treatment of acute ischemic stroke.

Cytokine autoantibodies in multiple sclerosis, aseptic meningitis and stroke

BACKGROUND

We have recently described the induction of anti-cytokine autoantibodies during bacterial infections and autoimmune diseases as a mechanism for cytokine regulation.

METHODS

Herein, we study the occurrence of autoantibodies to pro- and anti-inflammatory cytokines in cerebrospinal fluid and plasma from patients with multiple sclerosis, aseptic meningitis and stroke.

RESULTS

Increased levels of autoantibodies to interferon gamma, tumour necrosis factor alpha, interleukin 4 and interleukin 10 were detected in both compartments of multiple sclerosis and aseptic meningitis patients. Interestingly, in cerebrospinal fluid from stroke patients, only autoantibodies to interleukin 4 and interleukin 10, but not interferon alpha or tumour necrosis factor alpha were detected. No significant autoantibody levels were registered in plasma from stroke patients against all four cytokines compared with healthy control subjects. The latter revealed very low autoantibody levels in plasma and no detectable autoantibodies in cerebrospinal fluid.

CONCLUSIONS

Our data show for the first time the occurrence of cytokine autoantibodies in these diseases, but their biological significance is unclear.

Gene expression induced by cerebral ischemia: an apoptotic perspective

The flow of new information on gene expression related to apoptosis has been relentless in the last several years. This has also been the case with respect to gene expression after cerebral ischemia. Many of genes associated with an apoptotic mode of cell death have now been studied in the context of experimental cerebral ischemia from the immediate early genes through modulating genes such as bcl-2 to genes in the final execution phase such as interleukin-1β converting enzyme (ICE)-related proteases. It was impossible to adequately cite all primary reports on these subjects. However, many excellent reviews have appeared in the last year, which together, cover all these areas of interest. In this review, we have elected to cite only reports published since January 1996 and use an extensive collection of reviews (indicated in italics) to guide the reader to the earlier literature. Our intent is to provide the reader with a timely and useful analysis of the current state of the art. It is hoped that this approach does not cause offense with our colleagues whose contributions before 1996 laid the foundation for much of this work.