Hypoxia induces T Helper 17 cell upregulation in cultured peripheral blood mononuclear cells from chronic stage patients of severe cerebral infarction

Curcumol ameliorates neuroinflammation after cerebral ischemia-reperfusion injury via affecting microglial polarization and Treg/Th17 balance through Nrf2/HO-1 and NF-κB signaling

Neuroinflammation caused by microglia and other immune cells plays pivotal role in cerebral ischemia/reperfusion injury and recovery. Modulating microglial polarization or Treg/Th17 balance from pro-inflammatory phenotype to anti-inflammatory phenotype are promising strategies for the treatment of cerebral ischemia. Curcumol has potential to fight against oxidative stress and inflammation, but whether it has protective effect in cerebral ischemia is uncertain. In the present study, cerebral ischemia was induced in C57BL/6 mice via middle cerebral artery occlusion (MCAO). MCAO mice were treated with curcumol for 7 days, then post-stroke ischemic injury, neurological deficits, microglial polarization and brain leukocyte infiltration were evaluated by TTC staining, behavioural tests, flow cytometry, western blot and immunofluorescence. We found that poststroke administration of curcumol reduced infarct volume, attenuated neuronal damage and inflammation, and improved motor function recovery of MCAO mice. Curcumol skewed microglial polarization toward anti-inflammatory phenotype in MCAO mice in vivo or after oxygen-glucose deprivation and reoxygenation (OGD/R) in vitro. In addition, curcumol reduced local T cell infiltration in ischemic brain of MCAO mice and impaired Treg/Th17 balance. Curcumol inhibited ROS production and regulated Nrf2/HO-1 and NF-κB signaling in microglia. Finally, inhibiting Nrf2/HO-1 signaling or activating NF-κB signaling abrogated the influence of curcumol on microglial polarization. In conclusion, curcumol treatment reduced brain damage and neuroinflammation via modulating anti-inflammatory microglial polarization and Treg/Th17 balance through Nrf2/HO-1 and NF-κB signaling. Curcumol might be a promising treatment strategy for stroke patients.

Drivers of Chronic Pathology Following Ischemic Stroke: A Descriptive Review

Stroke is the third leading cause of death and long-term disability in the world. Considered largely a disease of aging, its global economic and healthcare burden is expected to rise as more people survive into advanced age. With recent advances in acute stroke management, including the expansion of time windows for treatment with intravenous thrombolysis and mechanical thrombectomy, we are likely to see an increase in survival rates. It is therefore critically important to understand the complete pathophysiology of ischemic stroke, both in the acute and subacute stages and during the chronic phase in the months and years following an ischemic event. One of the most clinically relevant aspects of the chronic sequelae of stroke is its extended negative effect on cognition. Cognitive impairment may be related to the deterioration and dysfunctional reorganization of white matter seen at later timepoints after stroke, as well as ongoing progressive neurodegeneration. The vasculature of the brain also undergoes significant insult and remodeling following stroke, undergoing changes which may further contribute to chronic stroke pathology. While inflammation and the immune response are well established drivers of acute stroke pathology, the chronicity and functional role of innate and adaptive immune responses in the post-ischemic brain and in the peripheral environment remain largely uncharacterized. In this review, we summarize the current literature on post-stroke injury progression, its chronic pathological features, and the putative secondary injury mechanisms underlying the development of cognitive impairment and dementia. We present findings from clinical and experimental studies and discuss the long-term effects of ischemic stroke on both brain anatomy and functional outcome. Identifying mechanisms that occur months to years after injury could lead to treatment strategies in the chronic phase of stroke to help mitigate stroke-associated cognitive decline in patients.

Crosstalk between the aging intestinal microflora and the brain in ischemic stroke

Aging is an inevitable phenomenon experienced by animals and humans, and its intensity varies from one individual to another. Aging has been identified as a risk factor for neurodegenerative disorders by influencing the composition of the gut microbiota, microglia activity and cognitive performance. The microbiota-gut-brain axis is a two-way communication path between the gut microbes and the host brain. The aging intestinal microbiota communicates with the brain through secreted metabolites (neurotransmitters), and this phenomenon leads to the destruction of neuronal cells. Numerous external factors, such as living conditions and internal factors related to the age of the host, affect the condition of the intestinal microflora in the form of dysbiosis. Dysbiosis is defined as changes in the composition and function of the gut microflora that affect the pathogenesis, progress, and response to treatment of a disease entity. Dysbiosis occurs when changes in the composition and function of the microbiota exceed the ability of the microflora and its host to restore equilibrium. Dysbiosis leading to dysfunction of the microbiota-gut-brain axis regulates the development and functioning of the host’s nervous, immune, and metabolic systems. Dysbiosis, which causes disturbances in the microbiota-gut-brain axis, is seen with age and with the onset of stroke, and is closely related to the development of risk factors for stroke. The review presents and summarizes the basic elements of the microbiota-gut-brain axis to better understand age-related changes in signaling along the microbiota-gut-brain axis and its dysfunction after stroke. We focused on the relationship between the microbiota-gut-brain axis and aging, emphasizing that all elements of the microbiota-gut-brain axis are subject to age-related changes. We also discuss the interaction between microbiota, microglia and neurons in the aged individuals in the brain after ischemic stroke. Finally, we presented preclinical and clinical studies on the role of the aged microbiota-gut-brain axis in the development of risk factors for stroke and changes in the post-stroke microflora.

Aging Microbiota-Gut-Brain Axis in Stroke Risk and Outcome

The microbiota-gut-brain-axis (MGBA) is a bidirectional communication network between gut microbes and their host. Many environmental and host-related factors affect the gut microbiota. Dysbiosis is defined as compositional and functional alterations of the gut microbiota that contribute to the pathogenesis, progression and treatment responses to disease. Dysbiosis occurs when perturbations of microbiota composition and function exceed the ability of microbiota and its host to restore a symbiotic state. Dysbiosis leads to dysfunctional signaling of the MGBA, which regulates the development and the function of the host's immune, metabolic, and nervous systems. Dysbiosis-induced dysfunction of the MGBA is seen with aging and stroke, and is linked to the development of common stroke risk factors such as obesity, diabetes, and atherosclerosis. Changes in the gut microbiota are also seen in response to stroke, and may impair recovery after injury. This review will begin with an overview of the tools used to study the MGBA with a discussion on limitations and potential experimental confounders. Relevant MGBA components are introduced and summarized for a better understanding of age-related changes in MGBA signaling and its dysfunction after stroke. We will then focus on the relationship between the MGBA and aging, highlighting that all components of the MGBA undergo age-related alterations that can be influenced by or even driven by the gut microbiota. In the final section, the current clinical and preclinical evidence for the role of MGBA signaling in the development of stroke risk factors such as obesity, diabetes, hypertension, and frailty are summarized, as well as microbiota changes with stroke in experimental and clinical populations. We conclude by describing the current understanding of microbiota-based therapies for stroke including the use of pre-/pro-biotics and supplementations with bacterial metabolites. Ongoing progress in this new frontier of biomedical sciences will lead to an improved understanding of the MGBA's impact on human health and disease.

Age-related immune alterations and cerebrovascular inflammation

Aging is associated with chronic systemic inflammation, which contributes to the development of many age-related diseases, including vascular disease. The world's population is aging, leading to an increasing prevalence of both stroke and vascular dementia. The inflammatory response to ischemic stroke is critical to both stroke pathophysiology and recovery. Age is a predictor of poor outcomes after stroke. The immune response to stroke is altered in aged individuals, which contributes to the disparate outcomes between young and aged patients. In this review, we describe the current knowledge of the effects of aging on the immune system and the cerebral vasculature and how these changes alter the immune response to stroke and vascular dementia in animal and human studies. Potential implications of these age-related immune alterations on chronic inflammation in vascular disease outcome are highlighted.

Upregulated expression of hypoxia reactive genes in peripheral blood mononuclear cells from chronic liver disease patients

Liver fibrosis induces intrahepatic microcirculation disorder and hypoxic stress. Hypoxic stress has the potential for an increase in the possibility of more liver fibrosis and carcinogenesis. Liver biopsy is a standard method that evaluates of intrahepatic hypoxia, however, is invasive and has a risk of bleeding as a complication. Here, we investigated the hypoxia reactive gene expressions in peripheral blood mononuclear cells (PBMC) from chronic liver disease patients to evaluate intrahepatic hypoxia in a non-invasive manner. The subjects enrolled for this study were composed of 20 healthy volunteers (HV) and 48 patients with chronic liver disease (CLD). CLD patients contained 24 patients with chronic hepatitis（CH）and 24 patients with liver cirrhosis (LC). PBMC were isolated from heparinized peripheral blood samples. We measured the transcriptional expression of hypoxia reactive genes and inflammatory cytokines by quantitative RT-PCR. mRNA expression of adrenomedullin (AM), vascular endothelial growth factor A (VEGFA) superoxide dismutase (SOD), glutathione peroxidase (GPx) (p < 0.05), Interleukin-6 (IL-6), transforming growth factor-beta (TGF-β) and heme oxygenase-1 (HO-1) in CLD group were significantly higher than HV. AM mRNA expression is correlated with serum lactate dehydrogenase (LDH), serum albumin (Alb), IL6, and SOD mRNA expression. The hypoxia reactive gene expression in PBMCs from CLD patients was more upregulated than HV. Especially, angiogenic genes were notably upregulated and correlated with liver fibrosis. Here, we suggest that mRNA expression of AM in PBMCs could be the biomarker of intrahepatic hypoxia.

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The hypoxia reactive genes in PBMC were elevated in patients with chronic liver disease.

^•Angiogenic genes were upregulated and correlated with liver fibrosis in patients with chronic liver disease.

^•Adrenomedullin mRNA expression in PBMC was correlated with liver function.

^•mRNA expression of adrenomedullin in PBMC could be the biomarker of intrahepatic hypoxia.

Delayed diapedesis of CD8 T cells contributes to long-term pathology after ischemic stroke in male mice

OBJECTIVE

Stroke is a debilitating disorder with significant annual mortality and morbidity rates worldwide. Immune cells are recruited to the injured brain within hours after stroke onset and can exhibit either protective or detrimental effects on recovery. However, immune cells, including CD8 T cells, persist in the injured brain for weeks, suggesting a longer-term role for the adaptive immune system during functional recovery. The aim of this study was to determine if the delayed secondary diapedesis of CD8 T cells into the ischemic brain negatively impacts functional recovery after transient ischemic stroke in male mice.

RESULTS

Mice exhibited an increased number of leukocytes in the ipsilesional hemispheres at 14 days (3-fold; p < 0.001) and 30 days (2.2-fold; p = 0.02) after transient middle cerebral artery occlusion (tMCAo) compared to 8 days post-tMCAo, at which time acute neuroinflammation predominantly resolves. Moreover, mice with higher ipsilesional CD8 T cells at 30 days (R² = 0.52, p < 0.01) exhibited worse functional recovery. To confirm a detrimental role of chronic CD8 T cell diapedesis on recovery, peripheral CD8 T cells were depleted beginning 10 days post-tMCAo. Delayed CD8 T cell depletion improved motor recovery on the rotarod (F_(1,28) = 4.264; p = 0.048) compared to isotype control-treated mice. CD8 T cell-depleted mice also exhibited 2-fold (p < 0.001) reduced leukocyte infiltration at 30 days post-tMCAo. Specifically, macrophage, neutrophil, and CD4 T cell numbers were reduced in the ipsilesional hemisphere of the CD8 T cell-depleted mice independent of inflammatory status of the post-stroke CNS (e.g. microglial phenotype and cytokine production). RNAseq identified a unique profile for brain infiltrating CD8 T cells at 30 days post-tMCAo, with 46 genes differentially expressed relative to CD8 T cells at 3 days post-tMCAo.

CONCLUSION

Our data reveal a role for CD8 T cells in the chronic phase post-stroke that can be therapeutically targeted. We demonstrate long-term CD8 T cell recruitment into the ipsilesional hemisphere that affects both immune cell numbers present in the injured brain and functional recovery through one month after stroke onset.

Characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment

AIM

To investigate the characteristics of the peripheral T cell immune response of patients at different stages of vascular cognitive impairment (VCI).

METHODS

61 Arterial atherosclerotic cerebral infarct induced VCI patients, including 28 vascular dementia (VaD) cases, 33 no dementia (VCI-ND) cases, and 25 atherosclerotic cerebral infarct patients with normal cognitive function (CI-NC) as controls were enrolled. Peripheral CD8(+)T, CD4(+)CD25(+) Treg, CD4(+)IL-17(+) Th17 cells proportion, and IL-1β, IL-2, IL-6, IFN-γ levels, and neuropsychological function were assessed.

RESULTS

There was no difference in average age, gender ratio, years of education, and risk factors of infarct among the three groups. Peripheral CD4(+)CD25(+) Treg in VCI-ND and VaD groups were significantly lower than that in controls, and CD8(+) T cells were markedly elevated in VaD group. The IL-17(+) Th17 cell proportion did not differ significantly among three groups. IL-6 and IFN-γ expression levels in VaD group were higher than those in other two groups. The VDAS-Cog executive function subscale score was negatively correlated with CD4(+)CD25(+) Treg proportion in VCI patients, and positively correlated with IL-6 levels.

CONCLUSION

VCI patients demonstrated a decrease in peripheral CD4(+) Treg proportion and increased IL-6 expression, and both parameters were correlated with the decline of executive functions.

Metabolic control of the Treg/Th17 axis

The interplay of the immune system with other aspects of physiology is continually being revealed and in some cases studied in considerable mechanistic detail. A prime example is the influence of metabolic cues on immune responses. It is well appreciated that upon activation, T cells take on a metabolic profile profoundly distinct from that of their quiescent and anergic counterparts; however, a number of recent breakthroughs have greatly expanded our knowledge of how aspects of cellular metabolism can shape a T-cell response. Particularly important are findings that certain environmental cues can tilt the delicate balance between inflammation and immune tolerance by skewing T-cell fate decisions toward either the T-helper 17 (Th17) or T-regulatory (Treg) cell lineage. Recognizing the unappreciated immune-modifying potential of metabolic factors and particularly those involved in the generation of these functionally opposing T-cell subsets will likely add new and potent therapies to our repertoire for treating immune mediated pathologies. In this review, we summarize and discuss recent findings linking certain metabolic pathways, enzymes, and by-products to shifts in the balance between Th17 and Treg cell populations. These advances highlight numerous opportunities for immune modulation.

Interleukin-17 in post-stroke neurodegeneration

Stroke is a leading cause of physical disability with neurodegenerative sequelae such as dementia and depression causing significant excess morbidity. Stroke severity can be exacerbated by apoptotic cell death in ischemic tissue, of which inflammatory activity is a key determinant. Studies have identified harmful and beneficial sets of T lymphocytes that infiltrate the brain post-stroke and their activation signals, suggesting that they might be targeted for therapeutic benefit. Animal models and human studies implicate interleukin(IL)-17 and its congeners (e.g. IL-23, IL-21) as mediators of tissue damage in the delayed phase of the inflammatory cascade and the involvement of T lymphocytes in propagating IL-17 release. In this review, we highlight the current understanding of IL-17 secreting cells, including sets of CD4(+) αβ and CD4(-) γδ T lymphocytes, as potentially important mediators of brain pathology post-stroke. Interactions between the IL-17 axis and innate pathways, positive feedback mechanisms that prolong or amplify IL-17, and IL-17 regulatory pathways may offer intervention targets to enhance recovery, prevent long-term decline, and improve quality of life.

Suppression of the inflammatory response by diphenyleneiodonium after transient focal cerebral ischemia

Diphenyleneiodonium (DPI), a NADPH oxidase inhibitor, reduces production of reactive oxygen species (ROS) and confers neuroprotection to focal cerebral ischemia. Our objective was to investigate whether the neuroprotective action of DPI extends to averting the immune response. DPI-induced gene changes were analyzed by microarray analysis from rat brains subjected to 90 min of middle cerebral artery occlusion, treated with NaCl (ischemia), dimethylsulfoxide (DMSO), or DMSO and DPI (DPI), and reperfused for 48 h. The genomic expression profile was compared between groups using ingenuity pathway analysis at the pathway and network level. DPI selectively up-regulated 23 genes and down-regulated 75 genes more than twofold compared with both DMSO and ischemia. It significantly suppressed inducible nitric oxide synthase signaling and increased the expression of methionine adenosyltransferasesynthetase 2A and adenosylmethionine decarboxylase 1 genes, which are involved in increasing the production of the antioxidant glutathione. The most significantly affected gene network comprised genes implicated in the inflammatory response with an expression change indicating an overall suppression. Both integrin- and interleukin-17A-signaling pathways were also significantly associated and suppressed. In conclusion, the neuroprotective effects of DPI are mediated not only by suppressing ischemia-triggered oxidative stress but also by limiting leukocyte migration and infiltration.

Dynamic regulation of Th17 differentiation by oxygen concentrations

Naive CD4(+) T cells are activated by antigen-presenting cells (APCs) and differentiate into distinct types of helper T (T(h)) cells in the lymph node or spleen. Oxygen (O(2)) tension is generally low in these secondary lymphoid tissues compared with the bloodstream or atmosphere. However, the effect of changes in O(2) concentration on the differentiation of T(h) cells remains unclear. Here, we established a novel model of T(h)-cell differentiation, which mimics physiological O(2) conditions. We primed naive CD4(+) T cells under 5% O(2), which has been observed in the lymph node or spleen and reoxygenated under normoxia that mimicked the O(2) concentration in blood. In this model, the differentiation of T(h)17 cells, but not T(h)1 or iTreg cells, was enhanced. Under the condition of 5% O(2), mammalian target of rapamycin complex 1 (mTORC1) was activated and led to the stabilization of hypoxia-inducible factor 1α (HIF-1α) in T(h)17 cells. The activation of mTORC1 and the acceleration of T(h)17-cell differentiation, which occurred when cells were primed under 5% O(2), were not observed in the absence of HIF-1α but were accelerated in the absence of von Hippel-Lindau tumor suppressor protein (vHL), a factor critical for HIF-1α degradation. Thus, a positive feedback loop between HIF-1α and mTORC1 induced by hypoxia followed by reoxygenation accelerates T(h)17-cell differentiation.