Early signaling of inflammation in acute ischemic stroke: clinical and rheological implications

Investigating the relationship between interleukin-6 serum levels and outcome in acute ischemic CVA

INTRODUCTION

Interleukin-6 (IL-6) is among the inflammatory mediators exhibiting elevated levels in ischemic stroke (IS) patients. The present study set out to evaluate the relationship between serum levels of interleukin-6 with long-term and at-hospital outcomes of acute ischemic stroke in patients hospitalized at Imam Khomeini Hospital, Urmia, Iran, from 2017 to 2018.

METHOD AND MATERIALS

This cross-sectional descriptive study enrolled 29 and 31 acute stroke patients for long-term and at-hospital observation, respectively. Evaluation of stroke severity was performed using the National Institute of Health Stroke Scale (NIHSS) and the modified Rankin Scale (mRS) on days 1, 5, and 90. Serum IL-6 level was measured via enzyme-linked immunosorbent assay (ELISA) on days one and five.

RESULTS

In the present cohort study, the following population were enrolled: for long-term evaluation, 11 (38%) men and 18 (63%) women with a mean age of 64.5 ± 14.9 years, and for at-hospital evaluation: 11 (37.5%) men and 20 (64.5%) with a mean age of 65.25 ± 14.37 years. A significant positive correlation was observed between IL-6 levels with NIHSS and mRS scores of the patients from time of admission until the end of the follow-up period (long-term: p < .001; at-hospital: 0.022).

CONCLUSION

The evidence from the present study suggests that IL-6 contributes to the determination of the severity of ischemic strokes and may be useful in predicting prognosis. However, larger scale studies are required to further establish these finds.

Influence of Interleukin-6 (IL-6) Promoter Gene Polymorphisms (-174G>C, -572G>C, and -597G>A) on IL-6 Plasma Levels and Their Impact in the Development of Acute Ischemic Stroke in Young Indians

This study aimed to determine whether there is an influence of interleukin 6 (IL-6) gene promoter polymorphisms on IL-6 plasma levels and its role in the development of ischemic stroke in young Indians. One hundred young patients with ischemic stroke (age ≥ 45 years) and equal number of age- and sex-matched controls were genotyped for 174G>C, -572G>C, and -597G>A promoter polymorphisms by polymerase chain reaction-restriction fragment length polymorphism. Plasma IL-6 levels were measured by enzyme-linked immunosorbent assay. Plasma IL-6 levels were significantly higher in patients as compared to controls (patients: 28.61 ± 8.61 pg/mL, controls: 7.60 ± 4.10 pg/mL, P = .001). Both -174G>C (allelic χ2/P value: 4.79/.028, genotypic χ2/P value: 5.3/.021) and -572G>C (allelic χ2/P value: 9.63/.00113 Genotypic χ2/P value: 74/.0002) polymorphisms exhibited genotypic as well as allelic significant association with the disease phenotype. Comparison was made between patients and controls for all 3 polymorphisms using a recessive model with respect to plasma IL-6 levels; no polymorphism showed any significant correlative association with the increased IL-6 levels (P = .31, .51, .32). Interleukin 6 is an inflammatory marker that is considerably influenced by nongenetic factors and is not a good candidate gene for studying genetic components associated with ischemic stroke. It seems that the variability in IL-6 levels is an integrated effect of nongenetic influences and the inflammatory events that follow ischemic stroke instead of being its cause. It is suggested that there is no direct association between -174G>C, -572G>C, and -597G>A polymorphisms and elevated IL-6 levels in the development of ischemic stroke.

Quantitative Measurement of Erythrocyte Aggregation as a Systemic Inflammatory Marker by Ultrasound Imaging: A Systematic Review

This systematic review is aimed at answering two questions: (i) Is erythrocyte aggregation a useful biomarker in assessing systemic inflammation? (ii) Does quantitative ultrasound imaging provide the non-invasive option to measure erythrocyte aggregation in real time? The search was executed through bibliographic electronic databases CINAHL, EMB Review, EMBASE, MEDLINE, PubMed and the grey literature. The majority of studies correlated elevated erythrocyte aggregation with inflammatory blood markers for several pathologic states. Some studies used "erythrocyte aggregation" as an established marker of systemic inflammation. There were limited but promising articles regarding the use of quantitative ultrasound spectroscopy to monitor erythrocyte aggregation. Similarly, there were limited studies that used other ultrasound techniques to measure systemic inflammation. The quantitative measurement of erythrocyte aggregation has the potential to be a routine clinical marker of inflammation as it can reflect the cumulative inflammatory dynamics in vivo, is relatively simple to measure, is cost-effective and has a rapid turnaround time. Technologies like quantitative ultrasound spectroscopy that can measure erythrocyte aggregation non-invasively and in real time may offer the advantage of continuous monitoring of the inflammation state and, thus, may help in rapid decision making in a critical care setup.

Reduction of the systemic inflammatory induced by acute cerebral infarction through ultra-early thrombolytic therapy

Acute ischemic stroke induces systemic inflammation, exhibited as changes in body temperature, white blood cell counts and C-reactive protein (CRP) levels. The aim of the present study was to observe the effects of intravenous thrombolytic therapy on inflammatory indices in order to investigate the hypothesis that post-stroke systemic inflammatory response occurs in response to the necrosis of brain tissues. In this study, 62 patients with acute cerebral infarction and indications for intravenous thrombolysis were divided into three groups on the basis of their treatment and response: Successful thrombolysis (n=36), failed thrombolysis (n=12) and control (n=14) groups. The body temperature, white blood cell counts and high-sensitivity (hs)-CRP levels were recorded pre-treatment and on post-stroke days 1, 3, 5 and 7. Spearman's correlation analysis showed that the pre-treatment National Institutes of Health Stroke Scale (NIHSS) score positively correlated with body temperature, white blood cell count and hs-CRP levels. On day 3 of effective intravenous thrombolysis, the body temperature and white blood cell were decreased and on days 3 and 5, the serum levels of hs-CRP were reduced compared with those in the failed thrombolysis and control groups. The results indicate that the systemic inflammatory response following acute cerebral infarction was mainly caused by ischemic injury of local brain tissue; the more serious the stroke, the stronger the inflammatory response. Ultra-early thrombolytic therapy may inhibit the necrosis of brain tissue and thereby reduce the inflammatory response.

Immunological biomarkers improve the accuracy of clinical risk models of infection in the acute phase of ischemic stroke

Infection is an independent risk factor for adverse outcome in stroke patients. The risk of developing an infection in this setting is partly related to a stroke-induced immunodepression, in which a shift to a predominant Th2 (immunosuppressive) phenotype has been postulated to play a major role. Our aim was to study whether clinical variables or changes in plasma cytokine expression can predict poststroke infections.

PATIENTS AND METHODS

Medical records of 92 stroke patients were reviewed, and the baseline concentration of cytokines from the Th1/Th2 system was determined. Clinical and serological predictors of incident infections and their prognostic significance were sought by means of univariate and multivariate analysis, and two predictive models for developing an infection were constructed by combining independent predictors (strictly clinical in one, and both clinical and serological in the other) for this outcome. The improvement conferred by the addition of immunological markers to the clinical model was assessed by comparing their respective ROC curves and by improvement (Net Reclassification Index and Integrated Discriminator Improvement) analysis.

RESULTS

Nineteen patients (20.7% of the study sample) developed an infection. Ongoing antiplatelet therapy at symptom onset (OR 0.02, 95% CI 0.001-0.23, p = 0.001), diabetes mellitus (OR 9.96, 95% CI 1.32-75.29, p = 0.03), IL-13 level <33 pg/ml (OR 84.16, 95% CI 2.53-2795.18, p = 0.01) and interferon-γ level >8.4 pg/ml (OR 60.17, 95% CI 1.78-2037.23, p = 0.02) were independently associated with the development of infections during hospital admission. The combined regression model predicted infection with an accuracy of 93.4%, an improvement in the predictive capacity of 17% (p < 0.001). Infection was associated with a worse neurological status at hospital discharge (median NIHSS score 11 (6-18) vs. 4 (1-11.5), p = 0.014).

CONCLUSIONS

This study shows that bloodstream biomarkers are useful to improve the accuracy of clinical prognostic models for infection in the acute phase of stroke. The clinical predictors of infection in the acute phase of stroke are relatively well established in the medical literature, but further research to identify the optimal combination of biomarkers (possibly inflammatory and stress markers) to be included in a clinically useful model is needed. Such a model could be subsequently used in clinical trials to assess the effect of prophylactic and/or early antibiotic therapy in this setting, a currently controversial issue in this field.

Predictors for Poststroke Outcomes: The Tel Aviv Brain Acute Stroke Cohort (TABASCO) Study Protocol

Background

Recent studies have demonstrated that even survivors of mild stroke experience residual damage, which persists and in fact increases in subsequent years. About 45% of stroke victims remain with different levels of disability. Identifying factors associated with poststroke cognitive and neurological decline could potentially yield more effective therapeutic opportunities.

Aims and hypothesis

We hypothesize that data based on biochemical, neuroimaging, genetic and psychological measures can, in aggregate, serve as better predictors for subsequent disability, cognitive and neurological deterioration, and suggest possible interventions.

Design

The Tel-Aviv Brain Acute Stroke Cohort (TABASCO) study is an ongoing, prospective cohort study that will recruit approximately 1125 consecutive first-ever mild–moderate stroke patients. It is designed to evaluate the association between predefined demographic, psychological, inflammatory, biochemical, neuroimaging and genetic markers, measured during the acute phase, and long-term outcome: subsequent cognitive deterioration, vascular events (including recurrent strokes), falls, affect changes, functional everyday difficulties and mortality.

Discussion

This study is an attempt to comprehensively investigate the long-term outcome of mild–moderate strokes. Its prospective design will provide quantitative data on stroke recurrence, the incidence of other vascular events and the evaluation of cognitive, affective and functional decline. Identifying the factors associated with poststroke cognitive and functional decline could potentially yield more effective therapeutic approaches.

Correlation between proinflammatory serum markers: high sensitivity C-reactive protein, interleukin-6 with disability score in acute ischemic stroke

Stroke being the third leading cause of death and foremost cause of disability, if potential diagnostic utility of blood borne protein biomarkers in predicting acute stroke is established, it would be a substantial adjunct to computerized tomography and magnetic resonance imaging which have their own limitations. This study was done to correlate serum Interleukin 6, high sensitivity C reactive protein at the time of admission with neurological worsening assessed by NIHSS at the time of admission and 7 days after admission. 46 Patients admitted in neurology department SAIMS, Indore with first ever ischemic stroke within 72 h of onset were included in the study. All patients with history of stroke of more than 72 h onset, Infection & peripartum stroke were excluded from the study. Disability scoring was done by NIHSS and their serum samples assayed for hsCRP, IL6 by commercially available quantitative sandwich enzyme-linked immunoadsorbent assay kits. Serum samples of 50 control cases which included healthy volunteers and staff from SAIMS were also analyzed for hsCRP, IL6 for comparative study. A significant correlation was observed between NIHSS scoring and serum hsCRP and IL6 at the time of admission. Patients with initial high serum IL6 and hsCRP also showed significant clinical deterioration as assessed by NIHSS scoring 7 days after admission. Elevated hsCRP and IL6 within 72 h of admission strongly correlated with functional disability in study population in India and may serve as useful adjunct to CT Scan in emergency 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.

Correlation and association of plasma interleukin-6 and plasma platelet-derived microparticles, markers of activated platelets, in healthy individuals

INTRODUCTION

The aim of this study was to clarify the correlation and association of plasma IL-6 and PDMPs, both of which are associated with metabolic syndrome, in healthy individuals.

MATERIALS AND METHODS

We conducted a cross-sectional study of 464 healthy Japanese volunteers (210 men and 254 women, median age 39 and 35years, respectively) who had no signs, symptoms or history of cardiovascular- or cerebrovascular disease and took no medications. We assayed their IL-6 levels with a conventional ELISA kit and their PDMP levels by ELISA and monoclonal antibodies against CD42b and CD42a (glycoprotein Ib and IX).

RESULTS

By multivariate analysis, the plasma level of PDMP was correlated with diastolic blood pressure (p=0.015), platelet count (p<0.001), high sensitivity C-reactive protein, and the plasma level of IL-6 (p<0.001) in men (R(2)=0.454, p<0.001) and was correlated with platelet count (p<0.001) and the plasma level of IL-6 (p<0.001) in women (R(2)=0.159, p<0.001). Quartile range of plasma level of IL-6 was associated with plasma level of PDMP after adjustment for diastolic blood pressure, platelet count, and high sensitivity C-reactive protein in men (p<0.001) and associated with plasma level of PDMP after adjustment for platelet count in women (p<0.001).

CONCLUSIONS

These results suggest the plasma IL-6 is correlated and associated with the plasma PDMPs, markers of activated platelets in healthy individuals.

Interleukin-6 as an early predictor for one-year survival following an ischaemic stroke/transient ischaemic attack

BACKGROUND

Early biomarkers for survival in an acute ischaemic stroke/transient ischaemic attack might serve as a useful tool for the clinician. Several studies have highlighted the role of inflammatory biomarkers as an early signal for acute ischaemic stroke prognosis.

AIMS

This study examines the potential advantage of using high-sensitivity interleukin-6 as a possible biomarker at the early stages of acute stroke for identifying patients at a high risk for 12-month mortality.

METHODS

Inflammatory biomarkers and neurological scores were determined in 250 patients following mild to moderate acute ischaemic stroke within 24 h of hospital admission. Outcome data on mortality were collected after 12 months. The signal detection methodology was used to identify subgroups that were at a high risk for 12-month mortality.

RESULTS

Twelve months following the event, 234 of the 250 stroke patients survived. Signal detection identified predictors that distinguished individuals likely to die from those with a better recovery prediction. Plasma interleukin-6 concentration emerged as the optimal predictor, with a cut point of 6.47 pg/ml, chi(2) (l, N=250)=20.5, P<0.001. Interleukin-6 above 6.47 pg/ml during the acute phase predicted subsequent non-survival (P=0.006, odds ratio 8.0).

CONCLUSIONS

This study demonstrates the clinical potential of using high-sensitivity interleukin-6 as an early signal for acute ischaemic stroke survival and suggests a clear cut point for patients at a high risk who might benefit from closer clinical surveillance and/or administration of therapeutic interventions.

Inflammatory markers and poor outcome after stroke: a prospective cohort study and systematic review of interleukin-6

BACKGROUND

The objective of this study was to determine whether: (a) markers of acute inflammation (white cell count, glucose, interleukin-6, C-reactive protein, and fibrinogen) are associated with poor outcome after stroke and (b) the addition of markers to previously validated prognostic models improves prediction of poor outcome.

METHODS AND FINDINGS

We prospectively recruited patients between 2002 and 2005. Clinicians assessed patients and drew blood for inflammatory markers. Patients were followed up by postal questionnaire for poor outcome (a score of>2 on the modified Rankin Scale) and death through the General Register Office (Scotland) at 6 mo. We performed a systematic review of the literature and meta-analysis of the association between interleukin-6 and poor outcome after stroke to place our study in the context of previous research. We recruited 844 patients; mortality data were available in 844 (100%) and functional outcome in 750 (89%). After appropriate adjustment, the odds ratios for the association of markers and poor outcome (comparing the upper and the lower third) were interleukin-6, 3.1 (95% CI: 1.9-5.0); C-reactive protein, 1.9 (95% CI: 1.2-3.1); fibrinogen, 1.5 (95% CI: 1.0-2.36); white cell count, 2.1 (95% CI: 1.3-3.4); and glucose 1.3 (95% CI: 0.8-2.1). The results for interleukin-6 were similar to other studies. However, the addition of inflammatory marker levels to validated prognostic models did not materially improve model discrimination, calibration, or reclassification for prediction of poor outcome after stroke.

CONCLUSIONS

Raised levels of markers of the acute inflammatory response after stroke are associated with poor outcomes. However, the addition of these markers to a previously validated stroke prognostic model did not improve the prediction of poor outcome. Whether inflammatory markers are useful in prediction of recurrent stroke or other vascular events is a separate question, which requires further study. Please see later in the article for the Editors' Summary.

Social isolation alters neuroinflammatory response to stroke

Social isolation has dramatic long-term physiological and psychological consequences; however, the mechanisms by which social isolation influences disease outcome are largely unknown. The purpose of the present study was to investigate the effects of social isolation on neuronal damage, neuroinflammation, and functional outcome after focal cerebral ischemia. Male mice were socially isolated (housed individually) or pair housed with an ovariectomized female before induction of stroke, via transient intraluminal middle cerebral artery occlusion (MCAO), or SHAM surgery. In these experiments, peri-ischemic social isolation decreases poststroke survival rate and exacerbates infarct size and edema development. The social influence on ischemic damage is accompanied by an altered neuroinflammatory response; specifically, central interleukin-6 (IL-6) signaling is down-regulated, whereas peripheral IL-6 is up-regulated, in isolated relative to socially housed mice. In addition, intracerebroventricular injection of an IL-6 neutralizing antibody (10 ng) eliminates social housing differences in measures of ischemic outcome. Taken together, these data suggest that central IL-6 is an important mediator of social influences on stroke outcome.

Cytokines and myelination in the central nervous system

Myelin abnormalities that reflect damage to developing and mature brains are often found in neurological diseases with evidence of inflammatory infiltration and microglial activation. Many cytokines are virtually undetectable in the uninflamed central nervous system (CNS), so that their rapid induction and sustained elevation in immune and glial cells contributes to dysregulation of the inflammatory response and neural cell homeostasis. This results in aberrant neural cell development, cytotoxicity, and loss of the primary myelin-producing cells of the CNS, the oligodendrocytes. This article provides an overview of cytokine and chemokine activity in the CNS with relevance to clinical conditions of neonatal and adult demyelinating disease, brain trauma, and mental disorders with observed white matter defects. Experimental models that mimic human disease have been developed in order to study pathogenic and therapeutic mechanisms, but have shown mixed success in clinical application. However, genetically altered animals, and models of CNS inflammation and demyelination, have offered great insight into the complexities of neuroimmune interactions that impact oligodendrocyte function. The intracellular signaling pathways of selected cytokines have also been highlighted to illustrate current knowledge of receptor-mediated events. By learning to interpret the actions of cytokines and by improving methods to target appropriate predictors of disease risk selectively, a more comprehensive understanding of altered immunoregulation will aid in the development of advanced treatment options for patients with inflammatory white matter disorders.