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Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection.

ABSTRACT: INTRODUCTION:Stroke-associated pneumonia (SAP) is a major cause of mortality in patients who have suffered from severe ischemic stroke. Although multifactorial in nature, stroke-induced immunosuppression plays a key role in the development of SAP. Previous studies using a murine model of transient middle cerebral artery occlusion (tMCAO) have shown that focal ischemic stroke induction results in functional defects of lymphocytes in the spleen, thymus, and peripheral blood, leading to spontaneous bacterial infection in the lungs without inoculation. However, how ischemic stroke alters immune cell niche and the expression of cytokines and chemokines in the lungs has not been fully characterized. METHODS:Ischemic stroke was induced in mice by tMCAO. Immune cell profiles in the brain and the lungs at 24- and 72-hour time points were compared by flow cytometric analysis. Cytokine and chemokine expression in the lungs were determined by multiplex bead arrays. Tissue damage and bacterial burden in the lungs following tMCAO were evaluated. RESULTS:Ischemic stroke increases the percentage of alveolar macrophages, neutrophils, and CD11b+ dendritic cells, but reduces the percentage of CD4+ T cells, CD8+ T cells, B cells, natural killer cells, and eosinophils in the lungs. The alteration of immune cell niche in the lungs coincides with a significant reduction in the levels of multiple chemokines in the lungs, including CCL3, CCL4, CCL5, CCL17, CCL20, CCL22, CXCL5, CXCL9, and CXCL10. Spontaneous bacterial infection and tissue damage following tMCAO, however, were not observed. CONCLUSION:This is the first report to demonstrate a significant reduction of lymphocytes and multiple proinflammatory chemokines in the lungs following ischemic stroke in mice. These findings suggest that ischemic stroke directly impacts pulmonary immunity.

SUBMITTER: Farris BY

PROVIDER: S-EPMC6842816 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection.

Farris Breanne Y BY Monaghan Kelly L KL Zheng Wen W Amend Courtney D CD Hu Heng H Ammer Amanda G AG Coad James E JE Ren Xuefang X Wan Edwin C K ECK

Immunity, inflammation and disease 20191105 4

<h4>Introduction</h4>Stroke-associated pneumonia (SAP) is a major cause of mortality in patients who have suffered from severe ischemic stroke. Although multifactorial in nature, stroke-induced immunosuppression plays a key role in the development of SAP. Previous studies using a murine model of transient middle cerebral artery occlusion (tMCAO) have shown that focal ischemic stroke induction results in functional defects of lymphocytes in the spleen, thymus, and peripheral blood, leading to spo ...[more]

PMID: 31691533

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Project description:The peripheral immune system plays a critical role in aging and in the response to brain injury. Emerging data suggest inflammatory responses are exacerbated in older animals following ischemic stroke; however, our understanding of these age-related changes is poor. In this work, we demonstrate marked differences in the composition of circulating and infiltrating leukocytes recruited to the ischemic brain of old male mice after stroke compared to young male mice. Blood neutrophilia and neutrophil invasion into the brain were increased in aged animals. Relative to infiltrating monocyte populations, brain-invading neutrophils had reduced phagocytic potential, and produced higher levels of reactive oxygen species and extracellular matrix-degrading enzymes (i.e., MMP-9), which were further exacerbated with age. Hemorrhagic transformation was more pronounced in aged versus young mice relative to infarct size. High numbers of myeloperoxidase-positive neutrophils were found in postmortem human brain samples of old (> 71 years) acute ischemic stroke subjects compared to non-ischemic controls. Many of these neutrophils were found in the brain parenchyma. A large proportion of these neutrophils expressed MMP-9 and positively correlated with hemorrhage and hyperemia. MMP-9 expression and hemorrhagic transformation after stroke increased with age. These changes in the myeloid response to stroke with age led us to hypothesize that the bone marrow response to stroke is altered with age, which could be important for the development of effective therapies targeting the immune response. We generated heterochronic bone marrow chimeras as a tool to determine the contribution of peripheral immune senescence to age- and stroke-induced inflammation. Old hosts that received young bone marrow (i.e., Young → Old) had attenuation of age-related reductions in bFGF and VEGF and showed improved locomotor activity and gait dynamics compared to isochronic (Old → Old) controls. Microglia in young heterochronic mice (Old → Young) developed a senescent-like phenotype. After stroke, aged animals reconstituted with young marrow had reduced behavioral deficits compared to isochronic controls, and had significantly fewer brain-infiltrating neutrophils. Increased rates of hemorrhagic transformation were seen in young mice reconstituted with aged bone marrow. This work suggests that age alters the immunological response to stroke, and that this can be reversed by manipulation of the peripheral immune cells in the bone marrow.

Project description:ObjectiveHyperglycemia is a common comorbidity for ischemic stroke and is associated with worsened neurological outcomes. Platelets are central mediators of ischemic stroke and hyperglycemia mediates platelet hyperactivity. In this study, we investigated the contribution of platelet glucose metabolism to ischemic stroke.MethodsMice lacking both Glut1 and Glut3 specifically in platelets (DKO) and their littermate controls (WT) were subjected to 1-hour transient middle cerebral artery occlusion under normoglycemic and streptozotocin-induced hyperglycemic conditions after which stroke outcomes, platelet activation, and platelet-neutrophil aggregate (PNA) formation were examined.ResultsUnder normoglycemic conditions, DKO mice were protected from ischemic stroke with smaller brain infarct volumes and improved cerebral blood flow. In addition, DKO mice had reduced platelet activation, PNA, and cerebral neutrophil recruitment after stroke. Hyperglycemia significantly increased infarct size and cerebral Evans blue extravasation and worsened neurological outcomes and cerebral blood flow in both WT and DKO mice, abolishing the protective effect witnessed under normoglycemic conditions. Flow cytometric analysis after stroke demonstrated increased platelet activation and neutrophil trafficking to the brain, independent of platelet glucose metabolism. Finally, platelets from healthy DKO mice were unable to become procoagulant upon dual agonist stimulation. Conversely, hyperglycemia increased platelet mitochondrial reactive oxygen species production which potentiated procoagulant platelet formation in WT mice and restored procoagulant platelet formation in DKO mice.ConclusionHyperglycemia aggravates ischemic stroke outcome independent of platelet glucose uptake. Furthermore, we demonstrated that hyperglycemia primes procoagulant platelet formation. This underlines the therapeutic potential for strategies targeting procoagulant platelet formation for the treatment of acute ischemic stroke.

Project description:Background: Previous study showed that stroke may be a potential first sign of neoplasia. But the relationship between them remains unclear. Besides, ischemic stroke is a complex brain disease, which involves cell death or complex immune regulation. Thus, it is necessary to reveal the association of tumor immune microenvironment and cell death with ischemic stroke. Methods: Here, a photothrombosis-induced ischemic injury models of brain and skull was established. We compared and analyzed the pattern of gene expression profile between brain and skull after ischemic injury by transcriptome analysis. Further, we investigated the enrichment of relevant differential genes in cancer pathways and cell death pathways, and analyzed changes in the immune microenvironment after ischemic injury. Moreover, the pan-cancer genomic and prognosis analysis of ischemic injury related gene set were performed. Results: The results showed that the gene expression patterns were different in temporal and spatial locations after ischemic injury. We found that the effect on the transcriptome of the brain after skull ischemic injury was particularly large, but it could be recovered in a short period, while the effect on the skull after brain ischemic injury was long-lasting. The expression of genes related to ischemic injury is also associated with cell death and cancer hallmark pathways. In addition, changes in the abundance of immune cells indicate that brain ischemic injury may disrupt its immune microenvironment for a longer time, while skull can better balance the stability of immune microenvironment. Moreover, the brain ischemic injury-related gene sets are highly correlated with a variety of tumors, especially GBM, KIRC, LGG and UVM after stroke have a greater risk of death. Conclusion: This study gives us a new understanding of the role of the skull in brain ischemic injury, and reveals the association of tumor immune microenvironment and cell death with ischemic stroke.

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Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection.

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Ischemic stroke alters immune cell niche and chemokine profile in mice independent of spontaneous bacterial infection.

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