Biology subjects

Anrather, J.

Publications and source records attributed to Anrather, J..

18 recordsLinked to original sources

bioRxiv2026

Intravital pH Imaging using the sensor ApHID Reveals Incomplete Lysosomal Acidification in Resident Meningeal Phagocytes.

Tracking lysosomes and quantifying their pH in the living, intact brain has been challenging owing to the lack of suitable in vivo tools. Here we report the use of dextran polymers labeled with the pH sensor ApHID to visualize and quantify lysosomal pH in mouse brain resident phagocytes. ApHID-dextrans delivered systemically are rapidly endocytosed by phagocytes in the meninges -mainly dural and subdural macrophages- and accumulate in lysosomal compartments. Intravital pH imaging revealed a striking heterogeneity in lysosomal acidification, with only ~5% of meningeal phagocytes reaching pH values below 5.0, in marked contrast with measurements in macrophage cell cultures. Photothrombotic ischemic lesions induced progressive lysosomal acidification in local phagocytes, while acute chloroquine treatment led to rapid alkalinization. Our methodology enables direct, quantitative pH measurements without genetic manipulations, and unveils a previously unappreciated heterogeneity in lysosomal acidification among brain-resident myeloid cells.

neuroscience↗

bioRxiv2026

ABERRANT HIPPOCAMPAL NEUROGENESIS IS A CONSERVED RESPONSE TO STROKE IN MICE: A MULTI-CENTER MULTIMODEL STUDY

BackgroundAdult hippocampal neurogenesis is markedly altered after cerebral ischemia. Although stroke increases the production of newborn neurons, many of these cells display aberrant morphological and positional features that impair their functional integration and contribute to long-term cognitive decline. Given the clinical heterogeneity of ischemic stroke and the persistent translational failures of preclinical approaches relying on single-model studies it remains unknown whether post-stroke neurogenic alterations are conserved across different experimental paradigms. This study aimed to define common and model-specific features of hippocampal neurogenesis across complementary focal ischemia models. MethodsWe performed a multi-center, multimodel analysis within the STROKE-IMPaCT consortium using permanent and transient middle cerebral artery occlusion (MCAO) paradigms (MCAO via ligation or cauterization under normoxic (dMCAO) or hypoxic conditions (dMCAO+Hypoxia); and filament-based tMCAO across six international sites. Brains from adult C57BL/6J mice were collected 3 days, 7 days, or 2 months after ischemia, sham, or naive conditions. Hippocampal cell proliferation (Ki67) and neuroblast density (DCX) were quantified, and the morphological maturation of newborn neurons was evaluated using high-resolution analyses of dendritic architecture and somatodendritic polarity. All analyses were performed blind to experimental group. ResultsAcross all stroke models, ischemia induced a robust bilateral increase in hippocampal cell proliferation, most pronounced at 3 days and still elevated at 7 days, with levels returning to baseline by 2 months. Neuroblast density was similarly increased at 7 days, particularly in the ipsilateral hippocampus, but normalized by 2 months. Despite recovery in cell number, long-term morphological analysis revealed a consistent reduction in apical dendrite length and a higher proportion of neurons exhibiting aberrant features including ectopic localization, multipolar or inverted polarity, and abnormal lateral growth across all models. These abnormalities were observed both when pooling data across sites and when analyzing each model or center individually. ConclusionsIschemia induces an early, transient increase in hippocampal neurogenesis across diverse stroke paradigms, but the newborn neurons generated after stroke consistently display maladaptive morphological features. These cross-model, cross-site abnormalities indicate that aberrant hippocampal neurogenesis represents a robust hallmark of post-stroke pathology within the investigated species, independent of ischemia type or surgical approach, despite known differences in the spatial distribution of primary injury across experimental stroke models. Our findings support the concept that maladaptive neurogenesis may contribute to chronic post-stroke cognitive impairment and underscore the need to consider the quality not only the quantity of newborn neurons when developing therapeutic strategies.

animal behavior and cognition↗

bioRxiv2025

Assessing post-stroke cognition in pre-clinical models: lessons and recommendations from a multi-center study

Cognitive decline is a significant long-term consequence of stroke and has no available treatments. To aid in therapy development, we sought to achieve robust detection of cognitive performance after stroke in a multi-site design. Ischemic stroke was induced in adult and middle-aged male C57BL/6J mice utilizing three well-established models: distal middle cerebral artery occlusion (dMCAO), dMCAO with hypoxia and transient MCAO. Cognitive outcomes were assessed via Novel Object Recognition (NOR) and Barnes Maze (BM) tests prior to surgery, and during sub-acute (1-2 weeks) and chronic (8 weeks) phases post-stroke. Histology and immunostaining were used to assess infarct size, tissue damage and neuronal loss, and plasma neurofilament light was quantified. We did not detect a reliable cognitive deficit after stroke using NOR but saw a promising signal from BM (single site tested only). Overall, our study highlights the often-encountered challenges in detecting post-stroke cognitive impairment within the pre-clinical stroke community, as well as a number of complexities in the design and execution of pre-clinical stroke cognition studies, particularly as applied to a multi-site structure. We provide recommendations and suggest important aspects of stroke cognition studies to consider in the future, whether operating as an individual lab or a multi-site group.

animal behavior and cognition↗

bioRxiv2025

Hypertension-Induced Neurovascular and Cognitive Dysfunction at Single-Cell Resolution

Arterial hypertension is a leading cause of cognitive impairment, attributed to cerebrovascular insufficiency, blood-brain barrier disruption, and white matter damage. However, the molecular mechanisms by which hypertension affects brain cells remain unclear. Using scRNA-seq in a mouse model of hypertension induced by angiotensin II, we mapped neocortical transcriptomic changes before (3 days) and after (42 days) onset of neurovascular and cognitive deficits. Surprisingly, evidence of endothelial transport disruption and senescence, stalled oligodendrocyte differentiation, interneuronal hypofunction and network imbalance emerged after just 3 days. By 42 days, when cognitive impairment becomes apparent, deficits in myelination and axonal conduction, as well as neuronal mitochondrial dysfunction developed. These findings reveal a previously unrecognized early vulnerability of endothelial cells, interneurons, and oligodendrocytes, and provide the molecular bases for the subsequent neurovascular dysfunction and cognitive impairment in hypertension. In addition, the data constitute a valuable resource for future mechanistic studies and therapeutic target validation.

neuroscience↗

bioRxiv2025

Neutrophil stalling does not mediate the increase in tau phosphorylation and the cognitive impairment associated with high salt diet

High dietary salt intake has powerful effects on cerebral blood vessels and has emerged as a risk factor for stroke and cognitive impairment. In mice, high salt diet (HSD) leads to reduced cerebral blood flow (CBF), tau hyperphosphorylation and cognitive dysfunction. However, it is still unclear whether the reduced CBF is responsible for the effects of HSD on tau and cognition. Capillary stalling has emerged as a cause of CBF reduction and cognitive impairment in models of Alzheimers disease and diabetes. Therefore, we tested the hypothesis that capillary stalling also contributes to the CBF reduction and cognitive impairment in HSD. Using two-photon imaging, we found that HSD increased stalling of neutrophils in brain capillaries and decreased CBF. Neutrophil depletion reduced the number of stalled capillaries and restored resting CBF but did not prevent tau phosphorylation or cognitive impairment. These novel findings show that, capillary stalling contribute to CBF reduction in HSD, but not to tau phosphorylation and cognitive deficits. Therefore, the hypoperfusion caused by capillary stalling is not the main driver of the tau phosphorylation and cognitive impairment.

neuroscience↗

bioRxiv2025

Endothelial Sphingosine-1-Phosphate Receptor (S1PR) 1, a Functional S1PR in the Human Cerebrovascular Endothelium, Limits Blood Brain Barrier Permeability and Neuronal Injury following Subarachnoid Hemorrhage in Mice.

Hypoxia-induced blood-brain barrier (BBB) permeability has been identified as a key contributor to the progression of ischemic-hypoxic brain injury and neuronal dysfunction in stroke and other cerebrovascular diseases. Emerging clinical evidence highlights that the vasoprotective signaling properties of high-density lipoprotein (HDL), mediated through its bioactive lipid component sphingosine-1-phosphate (S1P), may be impaired in cardiovascular and inflammatory conditions. Nonetheless, the precise contributions and mechanistic roles of S1P signaling within the cerebral microvasculature remain insufficiently characterized. In this study, we aimed to elucidate the role of S1P signaling via its endothelial receptor S1PR1 in the pathophysiology of early brain injury following subarachnoid hemorrhage (SAH), a particularly severe form of stroke. Additionally, we sought to evaluate the relevance of the endothelial S1PR1 pathway in the human cerebrovascular endothelium, its functional role in hypoxia-induced cerebral endothelial barrier dysfunction, and its underlying molecular mechanisms. To address these objectives, we utilized endothelial-specific S1PR1 knockout mice subjected to the endovascular rupture model of aneurysmal SAH, performed mechanistic studies in primary human cerebral microvascular endothelial cells, and characterized S1PR1 expression in human brain tissue using validated protocols. Our findings reveal robust expression of S1PR1 in the cerebrovascular endothelium of both mice and humans. Functional analyses demonstrated that S1PR1 is critical for maintaining BBB integrity and mitigating neuronal injury in the context of SAH. Mechanistic in vitro studies indicated that S1PR1 exerts a vasoprotective effect by limiting hypoxia-induced BBB dysfunction in human primary brain microvascular endothelial cells through inhibition of Rho-associated kinase (ROCK)-mediated phosphorylation of myosin light chain (MLC), suppression of stress fiber formation and caveolin-1-dependent endosomal trafficking. These results highlight the pivotal role of endothelial S1PR1 signaling in preserving cerebral vascular integrity and provide a strong scientific foundation for developing novel therapeutic approaches targeting the S1P pathway in the endothelium to enhance neurovascular protection.

neuroscience↗

bioRxiv2024

A minimally invasive thrombotic stroke model to study circadian rhythm in awake mice

Experimental stroke models in rodents are essential for mechanistic studies and therapeutic development. However, these models have several limitations negatively impacting their translational relevance. Here we aimed to develop a minimally invasive thrombotic stroke model through magnetic particle delivery that does not require craniotomy, is amenable to reperfusion therapy, can be combined with in vivo imaging modalities, and can be performed in awake mice. We found that the model results in reproducible cortical infarcts within the middle cerebral artery (MCA) with cytologic and immune changes similar to that observed with more invasive distal MCA occlusion models. Importantly, the injury produced by the model was ameliorated by tissue plasminogen activator (tPA) administration. We also show that MCA occlusion in awake animals results in bigger ischemic lesions independent of day/night cycle. Magnetic particle delivery had no overt effects on physiologic parameters and systemic immune biomarkers. In conclusion, we developed a novel stroke model in mice that fulfills many requirements for modeling human stroke.

neuroscience↗

bioRxiv2024

Molecular and functional alterations in the cerebral microvasculature in an optimized mouse model of sepsis-associated cognitive dysfunction.

Systemic inflammation has been implicated in the development and progression of neurodegenerative conditions such as cognitive impairment and dementia. Recent clinical studies indicate an association between sepsis, endothelial dysfunction, and cognitive decline. However, the investigations of the role and therapeutic potential of the cerebral microvasculature in systemic inflammation-induced cognitive dysfunction have been limited by the lack of standardized experimental models for evaluating the alterations in the cerebral microvasculature and cognition induced by the systemic inflammatory response. Herein, we validated a mouse model of endotoxemia that recapitulates key pathophysiology related to sepsis-induced cognitive dysfunction, including the induction of an acute systemic hyperinflammatory response, blood-brain barrier (BBB) leakage, neurovascular inflammation, and memory impairment after recovery from the systemic inflammatory response. In the acute phase, we identified novel molecular (e.g. upregulation of plasmalemma vesicle associated protein, a driver of endothelial permeability, and the pro-coagulant plasminogen activator inhibitor-1, PAI-1) and functional perturbations (i.e., albumin and small molecule BBB leakage) in the cerebral microvasculature along with neuroinflammation. Remarkably, small molecule BBB permeability, elevated levels of PAI-1, intra/perivascular fibrin/fibrinogen deposition and microglial activation persisted 1 month after recovery from sepsis. We also highlight molecular neuronal alterations of potential clinical relevance following systemic inflammation including changes in neurofilament phosphorylation and decreases in postsynaptic density protein 95 and brain-derived neurotrophic factor suggesting diffuse axonal injury, synapse degeneration and impaired neurotrophism. Our study serves as a standardized model to support future mechanistic studies of sepsis-associated cognitive dysfunction and to identify novel endothelial therapeutic targets for this devastating condition. SIGNIFICANCEThe limited knowledge of how systemic inflammation contributes to cognitive decline is a major obstacle to the development of novel therapies for dementia and other neurodegenerative diseases. Clinical evidence supports a role for the cerebral microvasculature in sepsis-induced neurocognitive dysfunction, but the investigation of the underlying mechanisms has been limited by the lack of standardized experimental models. Herein, we optimized a mouse model that recapitulates important pathophysiological aspects of systemic inflammation-induced cognitive decline and identified key alterations in the cerebral microvasculature associated with cognitive dysfunction. Our study provides a reliable experimental model for mechanistic studies and therapeutic discovery of the impact of systemic inflammation on cerebral microvascular function and the development and progression of cognitive impairment.

neuroscience↗

bioRxiv2023

Brain and blood single-cell transcriptomics in acute and subacute phases after experimental stroke

Cerebral ischemia triggers a powerful inflammatory reaction involving both peripheral leukocytes and brain resident cells. Recent evidence indicates that their differentiation into a variety of functional phenotypes contributes to both tissue injury and repair. However, the temporal dynamics and diversity of post-stroke immune cell subsets remain poorly understood. To address these limitations, we performed a longitudinal single-cell transcriptomic study of both brain and mouse blood to obtain a composite picture of brain-infiltrating leukocytes, circulating leukocytes, microglia and endothelium diversity over the ischemic/reperfusion time. Brain cells and blood leukocytes isolated from mice 2 or 14 days after transient middle cerebral artery occlusion or sham surgery were purified by FACS sorting and processed for droplet-based single-cell transcriptomics. The analysis revealed a strong divergence of post-ischemic microglia, macrophages, and neutrophils over time, while such diversity was less evident in dendritic cells, B, T and NK cells. Conversely, brain endothelial cells and brain associated-macrophages showed altered transcriptomic signatures at 2 days post-stroke, but low divergence from sham at day 14. Pseudotime trajectory inference predicted the in-situ longitudinal progression of monocyte-derived macrophages from their blood precursors into day 2 and day 14 phenotypes, while microglia phenotypes at these two time points were not connected. In contrast to monocyte-derived macrophages, neutrophils were predicted to be continuously de-novo recruited from the blood. Brain single-cell transcriptomics from both female and male aged mice did not show major changes in respect to young mice, but aged and young brains differed in their immune cell composition. Furthermore, blood leukocyte analysis also revealed altered transcriptomes after stroke. However, brain-infiltrating leukocytes displayed higher transcriptomic divergence than their circulating counterparts, indicating that phenotypic diversification into cellular subsets occurs within the brain in the early and the recovery phase of ischemic stroke. In addition, this resource report contains a searchable database https://anratherlab.shinyapps.io/strokevis/ to allow user-friendly access to our data. The StrokeVis tool constitutes a comprehensive gene expression atlas that can be interrogated at the gene and cell type level to explore the transcriptional changes of endothelial and immune cell subsets from mouse brain and blood after stroke.

immunology↗

bioRxiv2023

Comparative multi-omics analyses of cardiac mitochondrial stress in three mouse models of frataxin deficiency

Cardiomyopathy is often fatal in Friedreich Ataxia (FA). However, the FA heart maintains adequate function until disease end stage, suggesting that it can initially adapt to the loss of frataxin (FXN). Conditional knockout mouse models with no Fxn expression show transcriptional and metabolic profiles of cardiomyopathy and mitochondrial integrated stress response (ISRmt). However, ISRmt has not been investigated in models with disease-relevant, partial decrease of FXN. We characterized the heart transcriptomes and metabolomes of three mouse models of partial FXN loss, YG8-800, KIKO-700, and FxnG127V. Few metabolites were significantly changed in YG8-800 mice and did not provide a signature of cardiomyopathy or ISRmt. Instead, several metabolites were altered in FxnG127V and KIKO-700 hearts. Transcriptional changes were found in all models, but differentially expressed genes consistent with cardiomyopathy and ISRmt were only identified in FxnG127V hearts. However, these changes were surprisingly mild even at an advanced age (18-months), despite a severe decrease in FXN levels to 1% of WT. These findings indicate that the mouse heart has extremely low reliance on FXN, highlighting the difficulty in modeling genetically relevant FA cardiomyopathy. Summary statementThe mitochondrial integrated stress response in the heart of a Friedreich Ataxia mouse model is surprisingly mild, despite a severe decrease in frataxin levels below 1% of normal.

molecular biology↗

bioRxiv2022

Calcium transients in nNOS neurons underlie distinct phases of the neurovascular response to barrel cortex activation in awake mice

Neuronal nitric oxide (NO) synthase (nNOS), a Ca2+ dependent enzyme, is expressed by distinct populations of neocortical neurons. Although neuronal NO is well known to contribute to the blood flow increase evoked by neural activity, the relationships between nNOS neurons activity and vascular responses in the awake state remain unclear. We imaged the barrel cortex in awake, head-fixed mice through a chronically implanted cranial window. The Ca2+ indicator GCaMP7f was expressed selectively in nNOS neurons using adenoviral gene transfer in nNOScre mice. Air-puffs directed at the contralateral whiskers or spontaneous motion induced Ca2+ transients in 30.2{+/-}2.2% or 51.6{+/-}3.3% of nNOS neurons, respectively, and evoked local arteriolar dilation. The greatest dilatation (14.8{+/-}1.1%) occurred when whisking and motion occurred simultaneously. Ca2+ transients in individual nNOS neurons and local arteriolar dilation showed various degrees of correlation, which was strongest when the activity of whole nNOS neuron ensemble was examined. We also found that some nNOS neurons became active immediately prior to arteriolar dilation, while others were activated gradually after arteriolar dilatation. Discrete nNOS neuron subsets may contribute either to the initiation or to the maintenance of the vascular response, suggesting a previously unappreciated temporal specificity to the role of NO in neurovascular coupling.

neuroscience↗

bioRxiv2022

Meningeal IL-17 producing T cells mediate cognitive impairment in salt-sensitive hypertension

Hypertension, a disease afflicting over one billion individuals worldwide, is a leading cause of cognitive impairment, the mechanisms of which remain poorly understood. In a mouse model of hypertension, we found that the neurovascular and cognitive dysfunction depends on IL-17, a cytokine elevated in hypertensive individuals. However, neither circulating IL-17 or brain angiotensin signaling could account in full for the dysfunction. Rather, IL-17 produced by T-cells in the dura mater was the major culprit by reaching the cerebrospinal fluid and activating IL-17 receptors on brain associated macrophages. Accordingly, depleting brain macrophages, deleting IL17-RA in brain macrophages, or suppressing meningeal T cells completely rescued cognitive function without attenuating blood pressure elevation, circulating IL-17 or brain angiotensin signaling. The data unveil a critical role of meningeal T-cells and macrophage IL-17 signaling in the neurovascular and cognitive dysfunction of hypertension and suggest novel therapies to counteract the devastating effects of hypertension on cognitive health.

neuroscience↗

bioRxiv2021

A preclinical randomized multicenter trial of anti-IL-17A treatment for acute ischemic stroke

Multiple consensus statements have called for preclinical randomized controlled trials (pRCT) to improve translation in stroke research. Here, we investigated the efficacy of IL-17A neutralizing antibodies in a multicentric pRCT using a murine stroke model. C57/Bl.6 mice were subjected to transient middle cerebral artery occlusion (tMCAO). Mice were randomly allocated (1:1). Either anti-IL-17A (500 {micro}g) or isotype antibody (500 {micro}g) were administered 1 h after tMCAO. Primary analysis of infarct volumes was done by MRI after three days. Secondary analysis included mortality, neurological score, neutrophil infiltration and the impact of the gut microbiome on treatment effects. Out of 136 mice, 109 mice were included in the analysis. Mixed model analysis revealed that the IL-17A neutralization significantly reduced infarct sizes (anti IL-17A: 61.77 {+/-} 31.04 mm3; IgG control: 75.66 {+/-} 34.79 mm3; p=0.01). Secondary outcome measures showed a decrease in mortality (Hazard Ratio=3.43, 95% CI = 1.157 - 10.18; p=0.04) and neutrophil invasion into ischemic cortices. There was no difference in the neurological score. The analysis of the gut microbiome showed significant differences between centers. Taken together, this is the first positive pRCT in an ischemia reperfusion model. It suggests IL-17A neutralization as a potential target in stroke.

neuroscience↗

bioRxiv2020

DNA damage independent inhibition of NF-κB transcription by anthracyclines

Anthracyclines are among the most used and effective anticancer drugs. Their activity has been attributed to DNA double-strand breaks resulting from topoisomerase II poisoning and to eviction of histones from select sites in the genome. Here we show that the extensively used anthracyclines Doxorubicin, Daunorubicin and Epirubicin, decrease the transcription of nuclear factor kappa B (NF-{kappa}B)-dependent gene targets, but not interferon responsive genes. Using an NMR-based structural approach, we demonstrate that anthracyclines disturb the complexes formed between the NF-{kappa}B subunit RelA and its DNA binding sites. The variant anthracyclines Aclarubicin, Doxorubicinone and the newly developed Dimethyl-doxorubicin, which share anticancer properties with the other anthracyclines but do not induce DNA damage, also suppressed inflammation, thus uncoupling DNA damage from the effects on inflammation. These findings have implications for anticancer therapy and for the development of novel anti-inflammatory drugs with limited side effects for life-threatening conditions such as sepsis.

immunology↗

bioRxiv2018

Dietary salt promotes cognitive impairment through tau phosphorylation

Dietary habits and vascular risk factors promote both Alzheimers disease and cognitive impairment caused by vascular factors1-3. Furthermore, accumulation of hyperphosphorylated tau, a microtubule associated protein and a hallmark of Alzheimers pathology, is also linked to vascular cognitive impairment4-7. In mice, a salt-rich diet leads to cognitive dysfunction associated with a nitric oxide deficit in cerebral endothelial cells and cerebral hypoperfusion8. Here we report that dietary salt induces tau hyperphosphorylation followed by cognitive dysfunction, effects prevented by restoring endothelial nitric oxide production. The nitric oxide deficiency reduces neuronal calpain nitrosylation resulting in enzyme activation, which, in turn, leads to tau phosphorylation by activating cyclin dependent kinase-5. Salt-induced cognitive impairment is not observed in tau-null mice or in mice treated with anti-tau antibodies, despite persistent cerebral hypoperfusion and neurovascular dysfunction. These findings unveil a causal link between dietary salt, endothelial dysfunction and tau pathology, independent of hemodynamic insufficiency. Avoiding excessive salt intake and maintaining vascular health may help stave off vascular and neurodegenerative pathologies underlying late-life dementia.

neuroscience↗

bioRxiv2018

Exacerbation of blood brain barrier dysfunction and brain injury after aneurysmal subarachnoid hemorrhage in endothelial specific S1PR1 knock out mice.

Blood brain barrier (BBB) dysfunction upon ischemia and hypoxia has been implicated in the exacerbation of neuronal injury in stroke. Despite the therapeutic potential of the cerebrovascular endothelium, the limited understanding of the endothelial signaling pathways governing BBB function restricts progress towards developing novel therapeutic approaches specifically targeting the endothelium. Sphingosine-1-phosphate (S1P) is a potent modulator of endothelial function via its receptors (S1PR). Recent human and mouse studies indicate that vasoprotective endothelial S1P signaling via S1PR1 may be impaired in cardiovascular and inflammatory diseases. Herein, we investigated the expression of S1PR1 in the mouse and human cerebrovascular endothelium and the role of endothelial-specific S1PR1 signaling in brain injury in a mouse model of aneurysmal subarachnoid hemorrhage (SAH), the most devastating type of stroke. We found that S1PR1 is the most abundant S1PR transcript in the mouse brain and in mouse and human brain endothelial cells (20-100 mRNA copies per cell). S1PR1 transcripts were significantly enriched (~6 fold) in mouse cortical microvessels compared to total brain. Using the S1PR1-eGFP knock in mouse, we found that S1PR1-eGFP is abundantly expressed in the cerebrovascular endothelium in the mouse brain. A similar pattern of expression was observed in human brain samples. Endothelial specific deletion of S1PR1 in adult mice (S1pr1 flox/floxxCdh5-CreERT2, referred to as S1pr1iECKO), resulted in exacerbation of brain edema, neuronal injury and worsened neurological outcomes upon SAH compared to S1pr1 flox/flox littermates. No differences in the subarachnoid blood, hemostasis or cerebral blood flow changes during and after SAH were found between groups. Mechanistically, S1pr1iECKO exhibited aggravated BBB dysfunction and increased phosphorylation of myosin light chain (MLC) in isolated cortical microvessels, a downstream effector of the Rho-ROCK pathway implicated in endothelial inflammation and barrier dysfunction. Taken together, our data indicate that S1PR1 is an endogenous protective signaling pathway in the endothelium, critical to maintain BBB function and to mitigate neuronal injury in pathological conditions. Thus, the therapeutic and diagnostic potential of the endothelial sphingosine-1-phosphate pathway in stroke deserves further study.

neuroscience↗

bioRxiv2018

Endogenous protection from ischemic brain injury by preconditioned monocytes

Exposure to low dose lipopolysaccharide prior to cerebral ischemia is neuroprotective in stroke models, a phenomenon termed preconditioning. While it is well established that lipopolysaccharide-preconditioning induces central and peripheral immune responses, the cellular mechanisms modulating ischemic injury remain unclear. Here, we investigated the role of immune cells in the brain protection afforded by preconditioning and we tested whether monocytes may be reprogrammed by ex vivo lipopolysaccharide exposure thus modulating the inflammatory injury after cerebral ischemia in male mice. We found that systemic injection of low-dose lipopolysaccharide induces a distinct subclass of CD115+Ly6Chi monocytes that protect the brain after transient middle cerebral artery occlusion in mice. Remarkably, adoptive transfer of monocytes isolated from preconditioned mice into naive mice 7 hours after transient middle cerebral artery occlusion reduced brain injury. Gene expression and functional studies showed that IL-10, iNOS and CCR2 in monocytes are essential for the neuroprotection. This protective activity was elicited even if mouse or human monocytes were exposed ex vivo to lipopolysaccharide and then injected into male mice after stroke. Cell tracking studies showed that protective monocytes are mobilized from the spleen and reach brain and meninges, wherein they suppressed post-ischemic inflammation and neutrophils influx into the brain parenchyma. Our findings unveil a previously unrecognized subpopulation of splenic monocytes capable to protect the brain with an extended therapeutic window, and provide the rationale for cell therapies based on the delivery of autologous or allogeneic protective monocytes into patients with ischemic stroke.\n\nSignificance StatementInflammation is a key component of the pathophysiology of the brain in stroke, a leading cause of death and disability with limited therapeutic options. Here, we investigate endogenous mechanisms of protection against cerebral ischemia. Using LPS preconditioning as an approach to induce ischemic tolerance in mice, we found the generation of neuroprotective monocytes within the spleen from where they traffic to the brain and meninges suppressing post-ischemic inflammation. Importantly, systemic LPS preconditioning can be mimicked by adoptive transfer of in vitro-preconditioned mouse or human monocytes at translational relevant time points after stroke. This model of neuroprotection may facilitate clinical efforts to increase the efficacy of bone marrow mononuclear cell treatments in acute neurological diseases such as cerebral ischemia.

neuroscience↗

bioRxiv2018

A master regulatory network restoring brain glutamate homeostasis is coordinately activated in stroke

Post-transcriptional regulation by miRNAs is essential for complex molecular responses to physiological insult and disease. Although many disease-associated miRNAs are known, their global targets and culminating network effects on pathophysiology remain poorly understood. We applied AGO CLIP to systematically elucidate altered miRNA-target interactions in brain following ischemia/reperfusion (I/R) injury. Among 1,190 identified, most prominent was the cumulative loss of target regulation by miR-29 family members. Integration of translational and time-course RNA profiles revealed a dynamic mode of miR-29 target de-regulation, led by acute translational activation and later increase in RNA levels, allowing rapid proteomic changes to take effect. These functional regulatory events rely on canonical and non-canonical miR-29 binding and engage glutamate reuptake signals to control local glutamate levels. These results uncover a miRNA target network that acts acutely to maintain brain homeostasis after ischemic stroke.

neuroscience↗