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BACKGROUND: Gut dysmotility is common after ischemic stroke, but the mechanism underlying this response is unknown. Under homeostasis, gut motility is regulated by the neurons of the enteric nervous system that control contractile/relaxation activity of muscle cells in the gut wall. More recently, studies of gut inflammation revealed interactions of macrophages with enteric neurons are also involved in modulating gut motility. However, whether poststroke gut dysmotility is mediated by direct signaling to the enteric nervous system or indirectly via inflammatory macrophages is unknown. METHODS AND RESULTS: We examined these hypotheses by using a clinically relevant permanent intraluminal midcerebral artery occlusion experimental model of stroke. At 24 hours after stroke, we performed in vivo and ex vivo gut motility assays, flow cytometry, immunofluorescence, and transcriptomic analysis. Stroke-induced gut dysmotility was associated with recruitment of muscularis macrophages into the gastrointestinal tract and redistribution of muscularis macrophages away from myenteric ganglia. The permanent intraluminal midcerebral artery occlusion model caused changes in gene expression in muscularis macrophages consistent with an altered phenotype. While the size of myenteric ganglia after stroke was not altered, myenteric neurons from post-permanent intraluminal midcerebral artery occlusion mice showed a reduction in neuronal nitric oxide synthase expression, and this response was associated with enhanced intestinal smooth muscle contraction ex vivo. Finally, chemical sympathectomy with 6-hydroxydopamine prevented the loss of myenteric neuronal nitric oxide synthase expression and stroke-induced slowed gut transit. CONCLUSIONS: Our findings demonstrate that activation of the sympathetic nervous system after stroke is associated with reduced neuronal nitric oxide synthase expression in myenteric neurons, resulting in impaired smooth muscle relaxation and dysregulation of gut transit.
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Sistema Nervioso Entérico , Accidente Cerebrovascular , Ratones , Animales , Óxido Nítrico Sintasa de Tipo I/genética , Óxido Nítrico Sintasa de Tipo I/metabolismo , Sistema Nervioso Entérico/metabolismo , Neuronas/fisiología , Relajación Muscular , Accidente Cerebrovascular/metabolismoRESUMEN
Inflammatory bowel disease (IBD) is becoming more common in the Western world due to changes in diet-related microbial dysbiosis, genetics and lifestyle. Incidences of gut permeability can predate IBD and continued gut barrier disruptions increase the exposure of bacterial antigens to the immune system thereby perpetuating chronic inflammation. Currently, most of the approved IBD therapies target individual pro-inflammatory cytokines and pathways. However, they fail in approximately 50% of patients due to their inability to overcome the redundant pro inflammatory immune responses. There is increasing interest in the therapeutic potential of T regulatory cells (Tregs) in inflammatory conditions due to their widespread capability to dampen inflammation, promote tolerance of intestinal bacteria, facilitate healing of the mucosal barrier and ability to be engineered for more targeted therapy. Intestinal Treg populations are inherently shaped by dietary molecules and gut microbiota-derived metabolites. Thus, understanding how these molecules influence Treg-mediated preservation of the intestinal barrier will provide insights into immune tolerance-mediated mucosal homeostasis. This review comprehensively explores the interplay between diet, gut microbiota, and immune system in influencing the intestinal barrier function to attenuate the progression of colitis.
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Tissue injury induced by stroke is traditionally thought to be localised to the brain. However, there is an accumulating body of evidence to demonstrate that stroke promotes pathophysiological consequences in peripheral tissues including the gastrointestinal system. In this study, we investigated the mechanisms underlying gut permeability after stroke. We utilised the clinically relevant experimental model of stroke called permanent intraluminal middle cerebral artery occlusion (pMCAO) to examine the effect of cerebral ischaemia on the gut. We detected stroke-induced gut permeability at 5 h after pMCAO. At this timepoint, we observed significantly elevated intestinal epithelial cell death in post-stroke mice compared to their sham-operated counterparts. At 24 h after stroke onset when the gut barrier integrity is restored, our findings indicated that post-stroke intestinal epithelium had higher expression of genes associated with fructose metabolism, and hyperplasia of intestinal crypts and goblet cells, conceivably as a host compensatory mechanism to adapt to the impaired gut barrier. Furthermore, we discovered that stroke-induced gut permeability was mediated by the activation of the sympathetic nervous system as pharmacological denervation decreased the stroke-induced intestinal epithelial cell death, goblet cell and crypt hyperplasia, and gut permeability to baseline levels. Our study identifies a previously unknown mechanism in the brain-gut axis by which stroke triggers intestinal cell death and gut permeability.
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Adolescent idiopathic scoliosis (AIS) is a noticeable spinal deformity in both adult and adolescent population. In majority of the cases, the gold standard of treatment is surgical intervention. Technological advancements in medical imaging and 3D printing have revolutionised the surgical planning and intraoperative decision making for surgeons in spinal surgery. However, its applicability for planning complex spinal surgeries is poorly documented with human subjects. The objective of this study is to evaluate the accuracy of 3D printed models for complex spinal deformities based on Cobb angles between 40° to 95°.This is a retrospective cohort study where, five CT scans of the patients with AIS were segmented and 3D printed for evaluating the accuracy. Consideration was given to the Inter-patient and acquisition apparatus variability of the CT-scan dataset to understand the effect on trueness and accuracy of the developed CAD models. The developed anatomical models were re-scanned for analysing quantitative surface deviation to assess the accuracy of 3D printed spinal models. Results show that the average of the root mean square error (RMSE) between the 3DP models and virtual models developed using CT scan of mean surface deviations for the five 3d printed models was found to be 0.5±0.07 mm. Based on the RMSE, it can be concluded that 3D printing based workflow is accurate enough to be used for presurgical planning for complex adolescent spinal deformities. Image acquisition and post processing parameters, type of 3D printing technology plays key role in acquiring required accuracy for surgical applications.
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Previous studies investigating innate leukocyte recruitment into the brain after cerebral ischemia have shown conflicting results. Using distinct cell surface and intracellular markers, the current study evaluated the contributions of innate immune cells to the poststroke brain following 1-h middle cerebral artery occlusion (tMCAO) or permanent MCAO (pMCAO), and assessed whether these cells ascribed to an inflammatory state. Moreover, we examined whether there is evidence for leukocyte infiltration into the contralateral (CL) hemisphere despite the absence of stroke infarct. We observed the recruitment of peripheral neutrophils, monocytes and macrophages into the hemisphere ipsilateral (IL) to the ischemic brain infarct at 24 and 96 h following both tMCAO and pMCAO. In addition, we found evidence of increased leukocyte recruitment to the CL hemisphere but to a lesser extent than the IL hemisphere after stroke. Robust production of intracellular cytokines in the innate immune cell types examined was most evident at 24 h after pMCAO. Specifically, brain-associated neutrophils, monocytes and macrophages demonstrated stroke-induced production of tumor necrosis factor-α (TNF-α) and interleukin (IL)-1ß, while only monocytes and macrophages exhibit a significant expression of arginase 1 (Arg1) after stroke. At 96 h after stroke, brain-resident microglia demonstrated production of TNF-α and IL-1ß following both tMCAO and pMCAO. At this later timepoint, neutrophils displayed TNF-α production and brain-associated macrophages exhibited elevation of IL-1ß and Arg1 after tMCAO. Further, pMCAO induced significant expression of Arg1 and IL-1ß in monocytes and macrophages at 96 h, respectively. These results revealed that brain-associated innate immune cells display various stroke-induced inflammatory states that are dependent on the experimental stroke setting.
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Encéfalo , Inmunidad Innata , Inflamación , Accidente Cerebrovascular Isquémico , Leucocitos , Encéfalo/inmunología , Encéfalo/patología , Isquemia Encefálica/inmunología , Isquemia Encefálica/patología , Inmunidad Innata/inmunología , Inflamación/inmunología , Inflamación/patología , Accidente Cerebrovascular Isquémico/inmunología , Accidente Cerebrovascular Isquémico/patología , Leucocitos/inmunología , Leucocitos/patología , Microglía/inmunología , Microglía/patología , Monocitos/inmunología , Monocitos/patología , Accidente Cerebrovascular/inmunología , Accidente Cerebrovascular/patología , Factor de Necrosis Tumoral alfa/inmunologíaRESUMEN
Ulcerative colitis is an inflammatory disease of the colon that is associated with colonic neutrophil accumulation. Recent evidence indicates that diet alters the composition of the gut microbiota and influences host-pathogen interactions. Specifically, bacterial fermentation of dietary fiber produces metabolites called short-chain fatty acids (SCFAs), which have been shown to protect against various inflammatory diseases. However, the effect of fiber deficiency on the key initial steps of inflammation, such as leukocyte-endothelial cell interactions, is unknown. Moreover, the impact of fiber deficiency on neutrophil recruitment under basal conditions and during inflammation in vivo is unknown. Herein, we hypothesized that a fiber-deficient diet promotes an inflammatory state in the colon at baseline and predisposes the host to more severe colitis pathology. Mice fed a no-fiber diet for 14 days showed significant changes in the gut microbiota and exhibited increased neutrophil-endothelial interactions in the colonic microvasculature. Although mice fed a no-fiber diet alone did not have observable colitis-associated symptoms, these animals were highly susceptible to low dose (0.5%) dextran sodium sulphate (DSS)-induced model of colitis. Supplementation of the most abundant SCFA, acetate, prevented no-fiber diet-mediated enrichment of colonic neutrophils and colitis pathology. Therefore, dietary fiber, possibly through the actions of acetate, plays an important role in regulating neutrophil recruitment and host protection against inflammatory colonic damage in an experimental model of colitis.
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Quimiotaxis de Leucocito/inmunología , Colitis/etiología , Fibras de la Dieta/deficiencia , Microbioma Gastrointestinal , Infiltración Neutrófila/inmunología , Animales , Biomarcadores , Adhesión Celular , Colitis/metabolismo , Colitis/patología , Sulfato de Dextran/efectos adversos , Dieta , Modelos Animales de Enfermedad , Células Endoteliales , Recuento de Leucocitos , Masculino , Metagenómica/métodos , Ratones , ARN Ribosómico 16SRESUMEN
The composition of the gut microbiota depends on many factors, including our lifestyle, diet, metabolism, antibiotic use and hygiene. The contribution of these factors in shaping the gut microbiota and the subsequent effects on the prevention and development of stroke has been under intense investigation. Furthermore, several reports have uncovered the impact of stroke on intestinal dysfunction and gut dysbiosis, highlighting the delicate interplay between the brain, gut and microbiome following this acute brain injury. Despite our growing appreciation of the gut microbiota in shaping brain health, the immune system, host metabolism and disease progression, its therapeutic capability in stroke is yet to be fully exploited. This review will explore the microbiota-gut-brain axis in stroke, and examine the potential role of the gut microbiota in the onset, progression and recovery phase of stroke.
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Microbiota , Accidente Cerebrovascular , Progresión de la Enfermedad , Disbiosis , Microbioma Gastrointestinal , HumanosRESUMEN
Bacterial infection a leading cause of death among patients with stroke, with elderly patients often presenting with more debilitating outcomes. The findings from our retrospective study, supported by previous clinical reports, showed that increasing age is an early predictor for developing fatal infectious complications after stroke. However, exactly how and why older individuals are more susceptible to infection after stroke remains unclear. Using a mouse model of transient ischaemic stroke, we demonstrate that older mice (>12 months) present with greater spontaneous bacterial lung infections compared to their younger counterparts (7-10 weeks) after stroke. Importantly, we provide evidence that older poststroke mice exhibited elevated intestinal inflammation and disruption in gut barriers critical in maintaining colonic integrity following stroke, including reduced expression of mucin and tight junction proteins. In addition, our data support the notion that the localized pro-inflammatory microenvironment driven by increased tumour necrosis factor-α production in the colon of older mice facilitates the translocation and dissemination of orally inoculated bacteria to the lung following stroke onset. Therefore, findings of this study demonstrate that exacerbated dysfunction of the intestinal barrier in advanced age promotes translocation of gut-derived bacteria and contributes to the increased risk to poststroke bacterial infection.
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Envejecimiento/metabolismo , Colon/metabolismo , Neumonía/metabolismo , Accidente Cerebrovascular/metabolismo , Infecciones Urinarias/metabolismo , Enfermedad Aguda , Anciano , Animales , Estudios de Cohortes , Modelos Animales de Enfermedad , Femenino , Humanos , Masculino , Ratones , Ratones Endogámicos C57BL , Estudios Retrospectivos , Factores de RiesgoRESUMEN
BACKGROUND: High-fat feeding and hyperglycemia, key risk factors for the development of metabolic syndrome (MetS), are emerging to associate with increased risk of developing dementia and cognitive decline. Despite this, clinical and experimental studies have yet to elucidate the specific contributions of either high-fat feeding or hyperglycemia to potential neuroinflammatory components. In this study, we delineate these individual components of MetS in the development of neuroinflammation. METHODS: Male C57Bl/6 J adult mice were treated with either citrate vehicle (CIT) or streptozotocin (STZ; 55 mg/kg) 3, 5 and 7 days before commencement of either a normal or high-fat diet for 9 or 18 weeks. By creating separate models of high-fat feeding, STZ-induced hyperglycemia, as well as in combination, we were able to delineate the specific effects of a high-fat diet and hyperglycemia on the brain. Throughout the feeding regime, we measured the animals' body weight and fasting blood glucose levels. At the experimental endpoint, we assessed plasma levels of insulin, glycated haemoglobin and performed glucose tolerance testing. In addition, we examined the effect of high fat-feeding and hyperglycemia on the levels of systemic inflammatory cytokines, gliosis in the hippocampus and immune infiltration in cerebral hemispheric tissue. Furthermore, we used intravital multiphoton microscopy to assess leukocyte-endothelial cell interactions in the cerebral vasculature of mice in vivo. RESULTS: We showed that acute hyperglycemia induces regional-specific effects on the brain by elevating microglial numbers and promotes astrocytosis in the hippocampus. In addition, we demonstrated that chronic hyperglycemia supported the recruitment of peripheral GR1+ granulocytes to the cerebral microvasculature in vivo. Moreover, we provided evidence that these changes were independent of the systemic inflammation associated with high-fat feeding. CONCLUSIONS: Hyperglycemia alone preferentially induces microglial numbers and astrocytosis in the hippocampus and is associated with the peripheral recruitment of leukocytes to the cerebrovasculature, but not systemic inflammation. High-fat feeding alone, and in combination with hyperglycemia, increases the systemic pro-inflammatory cytokine milieu but does not result in brain-specific immune gliosis. These results shed light on the specific contributions of high-fat feeding and hyperglycemia as key factors of MetS in the development of neuroinflammation.
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Dieta Alta en Grasa/efectos adversos , Encefalitis/etiología , Hiperglucemia/complicaciones , Sistema Inmunológico/patología , Síndrome Metabólico/complicaciones , Síndrome Metabólico/etiología , Animales , Antibióticos Antineoplásicos/toxicidad , Glucemia , Proteínas de Unión al Calcio/metabolismo , Citocinas/metabolismo , Modelos Animales de Enfermedad , Encefalitis/inmunología , Encefalitis/patología , Ayuno/sangre , Hiperglucemia/inducido químicamente , Hiperglucemia/patología , Insulina/sangre , Leucocitos/efectos de los fármacos , Leucocitos/metabolismo , Leucocitos/patología , Masculino , Ratones , Ratones Endogámicos C57BL , Proteínas de Microfilamentos/metabolismo , Microglía/efectos de los fármacos , Microglía/metabolismo , Microglía/patología , Proteínas del Tejido Nervioso/metabolismo , Neuronas/efectos de los fármacos , Neuronas/metabolismo , Estreptozocina/toxicidadRESUMEN
Invariant natural killer T (iNKT) cells and neutrophils play an increasingly important part in the pathogenesis of inflammatory diseases, but their precise roles in modulating colitis remain unclear. Previous studies have shown important interplays between host immune system and the gut microbiota, and the resulting modulation of inflammation. However, the interactions between iNKT cells, neutrophil and gut microbiota in regulating colitis pathology are poorly understood. Here, we show iNKT cell-deficient Jα18-/- mice display reduced dextran sodium sulfate (DSS)-induced colonic inflammation compared to their wild-type (WT) counterparts. We reveal that there is a distinct gut microbiota shaped by the absence of iNKT cells, which comprises of microorganisms that are associated with protection from colonic inflammation. Additionally, the reduced inflammation in Jα18-/- mice was correlated with increased expressions of neutrophil chemoattractant (Cxcl1 and Cxcl2) and increased neutrophil recruitment. However, these neutrophils were recruited to the colon at day 3 of our model, prior to observable clinical signs at day 5. Further analysis shows that these neutrophils, primed by the microbiota shaped by the lack of iNKT cells, exhibit anti-inflammatory and immune-modulatory properties. Indeed, depletion of neutrophils in DSS-treated Jα18-/- mice demonstrates that neutrophils confer an anti-colitogenic effect in the absence of iNKT cells. Thus, our data supports a changing dogma that neutrophils possess important regulatory roles in inflammation and highlights the complexity of the iNKT cell-microbiota-neutrophil axis in regulating colonic inflammation.
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Colitis/inmunología , Microbioma Gastrointestinal/inmunología , Inflamación , Intestinos/inmunología , Células T Asesinas Naturales/inmunología , Infiltración Neutrófila/inmunología , Animales , Quimiocina CXCL1/genética , Quimiocina CXCL1/inmunología , Quimiocina CXCL2/genética , Quimiocina CXCL2/inmunología , Colitis/inducido químicamente , Sulfato de Dextran , Modelos Animales de Enfermedad , Masculino , Ratones , Ratones Endogámicos C57BL , Ratones NoqueadosRESUMEN
Neutrophils are becoming recognized as highly versatile and sophisticated cells that display de novo synthetic capacity and potentially prolonged lifespan. Emerging concepts such as neutrophil heterogeneity and plasticity have revealed that, under pathological conditions, neutrophils may differentiate into discrete subsets defined by distinct phenotypic and functional characteristics. Indeed, these newly described neutrophil subsets will undoubtedly add to the already complex interactions between neutrophils and other immune cell types for an effective immune response. The interactions between neutrophils and monocytes/macrophages enable the host to efficiently defend against and eliminate foreign pathogens. However, it is also becoming increasingly clear that these interactions can be detrimental to the host if not tightly regulated. In this review, we will explore the functional cooperation of neutrophil and monocytes/macrophages in homeostasis, during acute inflammation and in various disease settings. We will discuss this in the context of cardiovascular disease in the form of atherosclerosis, an autoimmune disease mainly occurring in the kidneys, as well as the unique intestinal immune response of the gut that does not conform to the norms of the typical immune system.