Stroke-induced Immunodepression Research Articles

Neutrophil-to-lymphocyte Ratio as a New Predictor of Sepsis in Critically-ill Stroke Patients

BACKGROUND: Several studies have reported that many severe stroke patients developed sepsis during their acute phase, which leads to poor outcomes. In stroke, there is a shift from predominant Th1 lymphocytes, which have proinflammatory characteristics, to predominant Th2 lymphocytes which activate anti-inflammatory responses that induce hyporesponsiveness of the immune system against an invasion of pathogen, known as stroke-induced immunodepression syndrome. AIM: This study aims to examine whether the neutrophils-to-lymphocytes ratio (NLR) could predict the development of sepsis in acute stroke patients. METHODS: Patients were admitted to Fatmawati hospital intensive care unit from September 2019 to May 2020. RESULTS: The mean NLR of acute stroke patients during their stay in ICU was 16.8 ± 12.5. We performed Mann–Whitney test, which revealed that the mean rank of several NLR parameters, such as initial NLR, day-3 NLR, highest NLR, and dNLR in stroke patients at ICU, was associated with the incidence of sepsis. The median difference in day-3 NLR, highest NLR, and dNLR in the stroke group with sepsis differed from those of the non-sepsis group. CONCLUSION: NLR is assumed to have potential as an early predictor to distinguish septic conditions from non-septic conditions, to prevent delay in establishing diagnosis and management of sepsis, especially in acute, critically-ill stroke patients.

Abstract TMP112: Stroke-associated Pneumonia Impairs Pulmonary Host Defense While Infection Impairs Stroke Recovery

Introduction: Stroke-associated pneumonia (SAP) is a common clinical complication implicated in increased morbidity and mortality after stroke. Dysphagia and stroke-induced immunodepression may contribute to SAP. However, a better understanding of the processes underlying the infection-induced immune response in the recovering brain remains to be unveiled. Methods: Stroke was modeled in mice by tMCAO (1h) followed by reperfusion; at day 3 mice received an oropharyngeal Klebsiella inoculation. To examine how lung infection affects the brain immune response, we compared tMCAo+infection vs tMCAo+vehicle. Functional outcomes and brain leukocyte cytokine expression were analyzed. To investigate how stroke affects the host response to pulmonary infection we compared Sham+infection vs tMCAo+ infection. Bacterial burden in the lung and spleen, tissue injury and immune cell profile in the lungs were evaluated at day 2 post-infection. Results/Conclusions: We detected similar brain leukocyte numbers between the tMCAo infected vs vehicle groups. However, in the tMCAo infected group, cytotoxic T-cells (CD8+) produced less IL-6 and IFNγ and granulocytes/neutrophils produced less INFγ. tMCAo infected animals also exhibited a worse functional recovery (Fig 1a). Klebsiella CFUs were increased in spleen in mice with stroke compared to sham, while lung (BAL) white blood cells counts were reduced in the stroke group, with altered cellular composition (Fig 1b).Our investigation has revealed that lung infection attenuates cytokine production in the brain after stroke. That could have a dual effect, positive for brain injury but detrimental for fighting infection. Stroke affects the response to lung infection by reducing lung leukocyte counts and increasing bacterial dissemination. Advancing our understanding of the mechanisms driving altered immune responses in SAP important for identifying potential treatment targets.

Orexin-A inhibits cerebral ischaemic inflammatory injury mediated by the nuclear factor-κB signalling pathway and alleviates stroke-induced immunodepression in mice

Cerebral ischaemia is accompanied by infectious complications due to immunosuppression, known as stroke-induced immunodepression (SIID). Orexin-A (OXA), a neuropeptide produced in the hypothalamus, has been reported to have neuroprotective properties after stroke and is known to modulate inflammatory processes in peripheral tissues. The aim of this study was to determine the effects of orexin-A (OXA) on cerebral ischaemic inflammatory injury and SIID following experimental stroke. Cerebral ischaemia was induced in C57/BL6 mice by middle cerebral artery occlusion (MCAO). A mouse model of pneumonia and poststroke pneumococcal pneumonia was established by intratracheal inoculation with S. pneumoniae in a normal mouse or MCAO mouse model on the third day. We found that OXA postconditioning inhibited cerebral ischaemic inflammatory injury. The mechanism involved downregulation of the NF-κB signalling pathway. In addition, OXA may serve as a potential treatment target for attenuating stroke-induced immunodepression in mice.

Pneumonia in patients with stroke: risk factors, identification of at-risk patients, and methods of prevention

Stroke-associated pneumonia (SAP) is the most common complication of the early stage of ischaemic stroke. The prevalence of SAP is difficult to determine precisely, but it is estimated to affect 2–22% of patients in the acute phase of stroke. Strokeassociated pneumonia is a clinically significant problem, as it markedly increases the risk of death compared to the population of acute stroke patients without pneumonia. In addition, SAP is associated with poorer final functional status, greater dependence on other people’s help after hospital discharge, extended hospital stay, and higher treatment costs. The paper presents the risk factors for stroke-related pneumonia, including the two best documented: dysphagia and stroke-induced immunodepression syndrome (SIDS). An attempt is made to identify patients in the acute phase of stroke who should be evaluated for the risk of developing pneumonia, and tools useful in the identification of such patients (A2DS2, ISAN scoring systems) are discussed. Also, based on expert recommendations, measures to minimise the risk of stroke-related pneumonia are proposed, and the recommended therapeutic regimen is described.

Stroke-associated pneumonia and stroke-induced immunodepression

卒中相关性肺炎（SAP）是急性缺血性卒中的主要并发症，与患者的病死率和医疗费用增加密切相关。发生SAP的病理生理学机制可能与误吸及卒中诱导的免疫抑制有关，后者是在卒中发生后通过复杂的循环性和神经性通路包括下丘脑-垂体-肾上腺轴、交感/副交感神经系统而诱发。.

Very Low Frequency Heart Rate Variability Predicts the Development of Post-Stroke Infections.

Stroke-induced immunodepression is a major risk factor for severe infectious complications in the immediate post-stroke period. We investigated the predictive value of heart rate variability (HRV) to identify patients at risk of post-stroke infection, systemic inflammatory response syndrome, or severe sepsis during the post-acute interval from days 3 to 5 after stroke onset. A prospective, observational monocentric cohort study was conducted in a university hospital stroke unit of patients with ischemic infarction in the territory of the middle cerebral artery without an ongoing infection at admission. Standard HRV indices were processed from Holter ECG. Recording started within the first day after the onset of stroke. Infection (primary endpoint: pneumonia, urinary tract, unknown localization) was assessed between days 3 and 5. The predictive value of HRV adjusted for clinical data was analyzed by logistic regression models and area under the receiver operating characteristic curve (AUC). From 287 eligible patients, data of 89 patients without event before completion of 24-h Holter ECG were appropriate for prediction of infection (34 events). HRV was significantly associated with incident infection even after adjusting for clinical covariates. Very low frequency (VLF) band power adjusted for both, the National Institutes of Health Stroke Scale (NIHSS) at admission and diabetespredicted infection with AUC = 0.80 (cross-validation AUC = 0.74). A model with clinical data (diabetes, NIHSS at admission, involvement of the insular cortex) performed similarly well (AUC = 0.78, cross-validation AUC = 0.71). Very lowfrequency HRV, an index of integrative autonomic-humoral control, predicts the development of infectious complications in the immediate post-stroke period. However, the additional predictive value of VLF band power over clinical risk factors such as stroke severity and insular involvement was marginal. The continuous HRV monitoring starting immediately after admission might probably increase the predictive performance of VLF band power. That needs to be clarified in further investigations.

Influence of beta-blocker therapy on the risk of infections and death in patients at high risk for stroke induced immunodepression.

BackgroundStroke-induced immunodepression is a well characterized complication of acute ischemic stroke. In experimental studies beta-blocker therapy reversed stroke-induced immunodepression, reduced infection rates and mortality. Recent, heterogeneous studies in stroke patients could not provide evidence of a protective effect of beta-blocker therapy. Aim of this study is to investigate the potential preventive effect of beta-blockers in subgroups of patients at high risk for stroke-induced immunodepression.MethodsData from a prospectively derived registry of major stroke patients receiving endovascular therapy between 2011–2017 in a tertiary stroke center (University Medical Center Göttingen. Germany) was used. The effect of beta-blocker therapy on pneumonia, urinary tract infection, sepsis and mortality was assessed using multivariate logistic regression analysis.ResultsThree hundred six patients with a mean age of 72 ± 13 years and a median NIHSS of 16 (IQR 10.75–20) were included. 158 patients (51.6%) had pre-stroke- and continued beta-blocker therapy. Beta-blocker therapy did not reduce the incidence of pneumonia (OR 0.78, 95% CI 0.31–1.92, p = 0.584), urinary tract infections (OR 1.51, 0.88–2.60, p = 0.135), sepsis (OR 0.57, 0.18–1.80, p = 0.334) or mortality (OR 0.59, 0.16–2.17, p = 0.429). Strokes involving the insula and anterio-medial cortex increased the risk for pneumonia (OR 4.55, 2.41–8.56, p<0.001) and sepsis (OR 4.13, 1.81–9.43, p = 0.001), while right hemispheric strokes increased the risk for pneumonia (OR 1.60, 0.92–2.77, p = 0.096). There was a non-significantly increased risk for urinary tract infections in patients with beta-blocker therapy and insula/anterio-medial cortex strokes (OR 3.12, 95% CI 0.88–11.05, p = 0.077) with no effect of beta-blocker therapy on pneumonia, sepsis or mortality in both subgroups.ConclusionsIn major ischemic stroke patients, beta-blocker therapy did not lower post-stroke infection rates and was associated with urinary tract infections in a subgroup with insula/anterio-medial strokes.

Immunomodulatory treatment with systemic GM-CSF augments pulmonary immune responses and improves neurological outcome after experimental stroke

Stroke-induced immunodepression is an independent risk factor for stroke-associated pneumonia (SAP). Granulocyte-macrophage colony stimulating factor (GM-CSF) has neuroprotective properties in experimental stroke and been demonstrated to reverse immunodepression in sepsis patients. However, whether GM-CSF restores immune function after stroke preventing SAP and improving outcome is unknown. Here, we demonstrated that GM-CSF treatment improved peripheral and pulmonary leukocyte numbers, peripheral cytokine responses, lowered lung bacterial burden in the early course and improved long-term functional outcome after experimental stroke. These data suggest that GM-CSF is promising for stroke treatment since it not only acts neuroprotective in the ischemic brain but may also protect against detrimental post-stroke infections.

Stroke-induced immunodepression and dysphagia independently predict stroke-associated pneumonia – The PREDICT study

Stroke-associated pneumonia is a frequent complication after stroke associated with poor outcome. Dysphagia is a known risk factor for stroke-associated pneumonia but accumulating evidence suggests that stroke induces an immunodepressive state increasing susceptibility for stroke-associated pneumonia. We aimed to confirm that stroke-induced immunodepression syndrome is associated with stroke-associated pneumonia independently from dysphagia by investigating the predictive properties of monocytic HLA-DR expression as a marker of immunodepression as well as biomarkers for inflammation (interleukin-6) and infection (lipopolysaccharide-binding protein). This was a prospective, multicenter study with 11 study sites in Germany and Spain, including 486 patients with acute ischemic stroke. Daily screening for stroke-associated pneumonia, dysphagia and biomarkers was performed. Frequency of stroke-associated pneumonia was 5.2%. Dysphagia and decreased monocytic HLA-DR were independent predictors for stroke-associated pneumonia in multivariable regression analysis. Proportion of pneumonia ranged between 0.9% in the higher monocytic HLA-DR quartile (≥21,876 mAb/cell) and 8.5% in the lower quartile (≤12,369 mAb/cell). In the presence of dysphagia, proportion of pneumonia increased to 5.9% and 18.8%, respectively. Patients without dysphagia and normal monocytic HLA-DR expression had no stroke-associated pneumonia risk. We demonstrate that dysphagia and stroke-induced immunodepression syndrome are independent risk factors for stroke-associated pneumonia. Screening for immunodepression and dysphagia might be useful for identifying patients at high risk for stroke-associated pneumonia.

Neuroanatomical correlates of stroke-associated infection and stroke-induced immunodepression

BackgroundInfections represent the most frequent medical complications in stroke patients. Their main determinants are dysphagia and a transient state of immunodepression. We analyzed whether distinct anatomical brain regions were associated with the occurrence of stroke-associated infections or immunodepression. Materials and methodsIn 106 patients with acute ischemic stroke, we evaluated the incidence of pneumonia, urinary tract infection, or other infections together with the characterization of biomarkers of immunodepression. Twenty control subjects served to provide reference values. Using voxel-based lesion-symptom mapping, the involvement of gray and white matter structures was correlated with clinical and laboratory findings in crude analyses and in volume adjusted models to rule out associations reflecting differences in the size of the infarction. ResultsStroke-associated infection occurred in 22 (21%) patients and prevailed in patients with larger infarcts. Volume adjusted voxel-based lesion-symptom mapping revealed the involvement of the superior and middle temporal gyri, the orbitofrontal cortex, the superior longitudinal fasciculus and the inferior fronto-occipital fasciculus amongst infected patients. These associations were similar for pneumonia but not for urinary tract infections. Lymphopenia was associated with lesions of the superior and middle temporal gyri. Laterality did not influence stroke-associated infections or the presence of immunodepressive traits after volume control. The greatest overlap in the neuroanatomical correlates occurred between pneumonia and dysphagia. ConclusionInfarct volume plays a relevant role in the occurrence of stroke-associated infections, but lesions in specific brain locations such as the superior and lateral temporal lobe and the orbitofrontal cortex are also associated with increased infectious risk, especially pneumonia.

Antigen Presentation After Stroke.

Stroke induces a local inflammatory reaction and a plethora of innate immune responses in the brain where antigen-presenting cells become prominent. However, to date, it is still unclear whether antigen presentation is relevant to the neuropathological and functional outcome of stroke. Stroke does not trigger overt autoimmune reactions, but neural antigens have been found in lymphoid tissues of patient with stroke and it is unknown whether they promote tolerance or immune reactions that under certain conditions might contribute to the functional worsening observed in some patients. Autoantibodies to neural molecules have also been reported in patients with stroke, but the subclass of antibodies is important for their function, and the contribution of such findings to stroke outcome is not yet clear. Notably, stroke induces immunodepression highlighted by a transient lymphopenia, lymphoid organ atrophy, and monocyte deactivation. While these effects might reduce the chances of autoreactivity, they increase the risk of infection in patients with stroke and most frequently in those with severe stroke. Therefore any potential brain protective effect of stroke-induced immunodepression by attenuating or preventing lymphocyte-mediated brain damage is confounded by stroke severity and an increased incidence of infections. Systemic inflammation due to a number of comorbidities that are frequent in patients with stroke is also associated to a poor outcome. Herein, we review some relevant findings regarding the identification of neural antigens in stroke and discuss their potential contribution to the functional outcome of stroke.

Stroke induces specific alteration of T memory compartment controlling auto-reactive CNS antigen-specific T cell responses

Whether and when auto-reactivity after stroke occurs is still a matter of debate. By using overlapping 15mer peptide pools consisting of myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG) we show increased frequencies of immunodominant MOG- and MBP T cell responses in acute ischemic stroke which were associated with reduced frequencies of naïve T cells as well as CD8+ TEMRA cells. Auto-reactive CNS antigen-specific T cells responses as well as alterations of T cell subpopulations normalized in long-term follow up after stroke. Our findings suggest that stroke-induced immunodepression might function as an adaptive mechanism in order to inhibit harmful and long-lasting CNS antigen-specific immune responses.

T Cells and Cerebral Ischemic Stroke.

Stroke results in cerebral inflammation that causes brain injury and triggers immunodepression, resulting in an increased incidence of morbidity and mortality secondary to remote infection. It is well known that T cells modulate brain inflammation after ischemic stroke, and targeting T cells may be an innovative therapeutic strategy for stroke treatment. T cell deficiency is neuro-protective, but the observed protective effects differ between ischemic models. Recent studies suggest different T cell subsets may have distinct effects on the injured brain. In addition to their role in cerebral inflammation, T cells also play a role in stroke-induced immunodepression. Therefore, T cell-targeted therapies designed to provide protection against brain inflammation might paradoxically contribute to remote organ infection and mortality. Further investigations are required to determine the role of specific T cell subsets in cerebral inflammation and stroke-induced immunodepression, the optimal therapeutic window for treatment, and the appropriate dose of anti-T cell therapy.

Blocking stroke-induced immunodeficiency increases CNS antigen-specific autoreactivity but does not worsen functional outcome after experimental stroke.

Stroke-induced immunodepression (SIDS) is an essential cause of poststroke infections. Pharmacological inhibition of SIDS appears promising in preventing life-threatening infections in stroke patients. However, SIDS might represent an adaptive mechanism preventing autoreactive immune responses after stroke. To address this, we used myelin oligodendrocyte glycoprotein (MOG) T-cell receptor transgenic (2D2) mice where >80% of peripheral CD4(+) T cells express a functional receptor for MOG. We investigated in a murine model of middle cerebral artery occlusion the effect of blocking SIDS by inhibiting body's main stress axes, the sympathetic nervous system (SNS) with propranolol and the hypothalamic-pituitary-adrenal axis (HPA) with mifepristone. Blockade of both stress axes robustly reduced infarct volumes, decreased infection rate, and increased long-term survival of 2D2 and C57BL/6J wild-type mice. Despite these protective effects, blockade of SIDS increased CNS antigen-specific Type1 T helper cell (Th1) responses in the brains of 2D2 mice 14 d after middle cerebral artery occlusion. One month after experimental stroke, 2D2 mice developed signs of polyradiculitis, which were diminished by SIDS blockade. Adoptive transfer of CD4(+) T cells, isolated from 2D2 mice, into lymphocyte-deficient Rag-1KO mice did not reveal differences between SIDS blockade and vehicle treatment in functional long-term outcome after stroke. In conclusion, inhibiting SIDS by pharmacological blockade of body's stress axes increases autoreactive CNS antigen-specific T-cell responses in the brain but does not worsen functional long-term outcome after experimental stroke, even in a mouse model where CNS antigen-specific autoreactive T-cell responses are boosted.

Lipopolysaccharide binding protein, interleukin-10, interleukin-6 and C-reactive protein blood levels in acute ischemic stroke patients with post-stroke infection.

BackgroundIschemic stroke patients are prone to infection by stroke-induced immunodepression. We hypothesized that levels of lipopolysaccharide binding protein (LBP), interleukin-10 (IL-10), IL-6 and C-reactive protein (CRP) are early predictors for the development of stroke-associated infection.MethodsFifty-six patients with ischemic stroke (n = 51) and transient ischemic attack (TIA) (n = 5) who presented within 6 hours after symptom onset and who were free of detectable infection on admission were included in the study. Of these, 20 developed early infections during the first week. Blood samples were taken at 6, 12, and 24 hours and at 3 and 7 days after stroke onset. Levels of LBP, Il-10, IL-6 and CRP, as well as S100B, were measured as markers of inflammation and brain damage by commercially available immunometric tests.ResultsIn the univariate analysis, levels of LBP, IL-10, IL-6 and CRP significantly differed between patients who developed an infection and those who did not. In the binary logistic regression analysis, which was adjusted for National Institutes of Health Stroke Scale (NIHSS) on admission, stroke subtype and S100B peak levels, as indicator of the extent of brain damage, IL-10 at 6 hours, CRP at 6 hours and NIHSS on admission were identified as independent predictors of infection (IL-10: P = 0.009; CRP: P = 0.018; NIHSS: P = 0.041). The area under the curve (AUC) of the receiver operating characteristic (ROC) curves in relation to the dichotomized status of the infection (infection versus no infection) was 0.74 (95% confidence interval: 0.59 to 0.88) for CRP at 6 hours, 0.76 (0.61 to 0.9) for IL-10 at 6 hours, 0.83 (0.71 to 0.94) for NIHSS on admission and 0.94 (0.88 to 1) for the combination of CRP, IL-10 and NIHSS. In a subanalysis, 16 patients with early infections were matched with 16 patients without infection according to S100B peak levels. Here, the temporal pattern of LBP, IL-10, IL-6 and CRP significantly differed between the patient groups.ConclusionsOur data show that blood levels of inflammation markers may be used as early predictors of stroke-associated infection. We propose prospective studies to investigate if the calculated cut-offs of CRP, IL-10 and NIHSS might help to identify patients who should receive early preventive antibiotic treatment.

Rat middle cerebral artery occlusion is not a suitable model for the study of stroke-induced spontaneous infections.

BackgroundInfections related to stroke-induced immunodepression are an important complication causing a high rate of death in patients. Several experimental studies in mouse stroke models have described this process but it has never been tested in other species such as rats.MethodsOur study focused on the appearance of secondary systemic and pulmonary infections in ischemic rats, comparing with sham and naive animals. For that purpose, male Wistar rats were subjected to embolic middle cerebral artery occlusion (eMCAO) or to transient MCAO (tMCAO) inserting a nylon filament. Forty-eight hours after ischemia, blood and lung samples were evaluated.ResultsIn eMCAO set, ischemic rats showed a significant decrease in blood-peripheral lymphocytes (naive = 58.8±18.1%, ischemic = 22.9±16.4%) together with an increase in polymorphonuclears (PMNs) (naive = 29.2±14.7%, ischemic = 71.7±19.5%), while no change in monocytes was observed. The increase in PMNs counts was positively correlated with worse neurological outcome 48 hours after eMCAO (r = 0.55, p = 0.043). However, sham animals showed similar changes in peripheral leukocytes as those seen in ischemic rats (lymphocytes: 40.1±19.7%; PMNs: 51.7±19.2%). Analysis of bacteriological lung growth showed clear differences between naive (0±0 CFU/mL; log10) and both sham (3.9±2.5 CFU/mL; log10) and ischemic (4.3±2.9 CFU/mL; log10) groups. Additionally, naive animals presented non-pathological lung histology, while both sham and ischemic showed congestion, edema or hemorrhage. Concordant results were found in the second set of animals submitted to a tMCAO.ConclusionsInflammatory and infection changes in Wistar rats subjected to MCAO models may be attributed not only to the brain ischemic injury but to the surgical aggression and/or anaesthetic stress. Consequently, we suggest that stroke-induced immunodepression in ischemic experimental models should be interpreted with caution in further experimental and translational studies, at least in rat stroke models that entail cervicotomy and cranial trepanation.

Are We Ready to Translate T-Cell Transmigration in Stroke?

See related article, p 1799. Changes in the adaptive immune system after focal cerebral ischemia are increasingly recognized to critically influence the outcome after stroke.1 In particular, T lymphocytes have been implicated as mediators of inflammatory brain tissue damage, but also as modulators of tissue remodeling. In addition, reductions in T-lymphocyte cellularity and function are prominent features of stroke-induced immunodepression and may increase the susceptibility to infection after stroke.2 T cells are, therefore, promising targets for developing novel stroke treatments. Recent experimental studies demonstrated that specific inhibition of T-cell trafficking into the ischemic brain by blockade of very late antigen-4 or vascular cell adhesion molecule-1 improved stroke outcome.3–5 These results in rodent stroke models led to the initiation of a phase II trial testing natalizumab in acute ischemic stroke, which is currently recruiting patients.6 In the present …

Role of the sympathetic nervous system and spleen in experimental stroke-induced immunodepression.

BackgroundThe mechanism of stroke-induced immunodepression syndrome (SIDS) remains uncertain. Some studies suggest that hyperactivation of the sympathetic nervous system (SNS) may be the key factor underlying SIDS. Catecholamines impair early lymphocyte response, which can increase the risk of stroke-associated infection (SAI).Material/MethodsOur study focused on dynamic changes of metanephrine (MN), normetanephrine (NMN), cytokines, and spleen volume in the rat middle cerebral artery occlusion (MCAO) model.ResultsAfter MCAO, there is hyperactivation of SNS and pro-/anti-inflammatory imbalance, indicating systemic immunodepression. In addition, rat spleen size was reduced. Correlation analysis indicated that MCAO-induced spleen size reduction correlated with the changes in MN, NMN, and cytokines. Blocking SNS with propranolol can partly reverse the immunodepression and the reduction in spleen volume.ConclusionsTaken together, these findings suggest that acute ischemic stroke induces over-activation of the SNS, which lowers the threshold of infection and increases the risk of infection.

Moderate Hypothermia Inhibits Brain Inflammation and Attenuates Stroke‐Induced Immunodepression in Rats

Stroke causes both brain inflammation and immunodepression. Mild-to-moderate hypothermia is known to attenuate brain inflammation, but its role in stroke-induced immunodepression (SIID) of the peripheral immune system remains unknown. This study investigated the effects in rats of moderate intra-ischemic hypothermia on SIID and brain inflammation. Stroke was induced in rats by permanent distal middle cerebral artery occlusion combined with transient bilateral common carotid artery occlusion, while body temperature was reduced to 30°C. Real-time PCR, flow cytometry, in vitro T-cell proliferation assays, in vivo delayed-type hypersensitivity (DTH) reaction and confocal microscopy were used to study SIID and brain inflammation. Brief intra-ischemic hypothermia helped maintain certain leukocytes in the peripheral blood and spleen and enhanced T-cell proliferation in vitro and delayed-type hypersensitivity in vivo, suggesting that hypothermia reduces SIID. In contrast, in the brain, brief intra-Ischemic hypothermia inhibited mRNA expression of anti-inflammatory cytokine IL-10 and proinflammatory mediators INF-γ, TNF-α, IL-2, IL-1β and MIP-2. Brief intra-Ischemic hypothermia also attenuated the infiltration of lymphocytes, neutrophils (MPO(+) cells) and macrophages (CD68(+) cells) into the ischemic brain, suggesting that hypothermia inhibited brain inflammation. Brief intra-ischemic hypothermia attenuated SIID and protected against acute brain inflammation.

Ischemic postconditioning protects against focal cerebral ischemia by inhibiting brain inflammation while attenuating peripheral lymphopenia in mice

BackgroundIschemic postconditioning (IPostC) has been shown to attenuate brain injury in rat stroke models, but a mouse model has not been reported. This study establishes an IPostC model in mice and investigates how IPostC affects infiltration of leukocytes in the ischemic brain and lymphopenia associated with stroke-induced immunodepression. Material and methodsA total of 125 mice were used. IPostC was performed by a repeated series of brief occlusions of the middle cerebral artery (MCA) after reperfusion, in a focal ischemia model in mice. Infarct sizes, neurological scores, inflammatory brain cells and immune cell populations in lymph nodes, spleen and bone marrow were analyzed with fluorescence-activated cell sorting (FACS). ResultsIPostC performed immediately, 2min and 3h after reperfusion significantly reduced infarct sizes and attenuated neurological scores as measured up to 3days post-stroke. In the group with strongest protection, infarct sizes were reduced from 49.6±2.8% (n=16) to 27.9±2.9% (n=10, P<.001). The spared infarct areas were seen in the ischemic penumbra or ischemic margins, i.e., the border zones between the cortical territories of the anterior cerebral artery and those of the MCA, as well as in the ventromedial and dorsolateral striata. FACS analyses showed that IPostC significantly blocked increases in the numbers of microglia (CD45intCD11b+), macrophages (CD45hiCD68+), CD4 T cells (CD45+CD4+) and CD8 T cells (CD45+CD8+) as well as B lymphocytes (CD45+CD19+) in the ischemic brain (n=5/group). Reduced-immune cell numbers in the peripheral blood and spleen were increased by IPostC while immune cell populations in the bone marrow were not altered by IPostC. ConclusionsIPostC reduced brain infarction and mitigated neurological deficits in mice, likely by blocking infiltration of both innate and adaptive immune cells in the ischemic brain. In addition, IPostC robustly attenuated peripheral lymphopenia and thus improved systemic immunodepression.