Treg cell-derived osteopontin promotes microglia-mediated white matter repair after ischemic stroke.

The precise mechanisms underlying the beneficial effects of regulatory T (Treg) cells on long-term tissue repair remain elusive. Here, using single-cell RNA sequencing and flow cytometry, we found that Treg cells infiltrated the brain 1 to 5 weeks after experimental stroke in mice. Selective depletion of Treg cells diminished oligodendrogenesis, white matter repair, and functional recovery after stroke. Transcriptomic analyses revealed potent immunomodulatory effects of brain-infiltrating Treg cells on other immune cells, including monocyte-lineage cells. Microglia depletion, but not T cell lymphopenia, mitigated the beneficial effects of transferred Treg cells on white matter regeneration. Mechanistically, Treg cell-derived osteopontin acted through integrin receptors on microglia to enhance microglial reparative activity, consequently promoting oligodendrogenesis and white matter repair. Increasing Treg cell numbers by delivering IL-2:IL-2 antibody complexes after stroke improved white matter integrity and rescued neurological functions over the long term. These findings reveal Treg cells as a neurorestorative target for stroke recovery.

Leveraging single-cell RNA sequencing to unravel the impact of aging on stroke recovery mechanisms in mice.

Aging compromises the repair and regrowth of brain vasculature and white matter during stroke recovery, but the underlying mechanisms remain elusive. To understand how aging jeopardizes brain tissue repair after stroke, we performed single-cell transcriptomic profiling of young adult and aged mouse brains at acute (3 d) and chronic (14 d) stages after ischemic injury, focusing a priori on the expression of angiogenesis- and oligodendrogenesis-related genes. We identified unique subsets of endothelial cells (ECs) and oligodendrocyte (OL) progenitors in proangiogenesis and pro-oligodendrogenesis phenotypic states 3 d after stroke in young mice. However, this early prorepair transcriptomic reprogramming was negligible in aged stroke mice, consistent with the impairment of angiogenesis and oligodendrogenesis observed during the chronic injury stages after ischemia. In the stroke brain, microglia and macrophages (MG/MΦ) may drive angiogenesis and oligodendrogenesis through a paracrine mechanism. However, this reparative cell-cell cross talk between MG/MΦ and ECs or OLs is impeded in aged brains. In support of these findings, permanent depletion of MG/MΦ via antagonism of the colony-stimulating factor 1 receptor resulted in remarkably poor neurological recovery and loss of poststroke angiogenesis and oligodendrogenesis. Finally, transplantation of MG/MΦ from young, but not aged, mouse brains into the cerebral cortices of aged stroke mice partially restored angiogenesis and oligodendrogenesis and rejuvenated sensorimotor function and spatial learning and memory. Together, these data reveal fundamental mechanisms underlying the age-related decay in brain repair and highlight MG/MΦ as effective targets for promoting stroke recovery.

Regulatory T cell expansion promotes white matter repair after stroke.

Recent research highlights the function of regulatory T cells (Tregs) in white matter integrity in CNS diseases. Approaches that expand the number of Tregs have been utilized to improve stroke recovery. However, it remains unclear if Treg augmentation preserves white matter integrity early after stroke or promotes white matter repair. This study evaluates the effect of Treg augmentation on white matter injury and repair after stroke. Adult male C57/BL6 mice randomly received Treg or splenocyte (2 million, iv) transfer 2 h after transient (60 min) middle cerebral artery occlusion (tMCAO). Immunostaining showed improved white matter recovery after tMCAO in Treg-treated mice compared to mice received splenocytes. In another group of mice, IL-2/IL-2 antibody complexes (IL-2/IL-2Ab) or isotype IgG were administered (i.p) for 3 consecutive days starting 6 h after tMCAO, and repeated on day 10, 20 and 30. The IL-2/IL-2Ab treatment boosted the number of Tregs in blood and spleen and increased Treg infiltration into the ischemic brain. Longitudinal in vivo and ex vivo diffusion tensor imaging analysis revealed an increase in fractional anisotropy 28d and 35d, but not 14d, after stroke in IL-2/IL-2Ab-treated mice compared to isotype-treated mice, suggesting a delayed improvement in white matter integrity. IL-2/IL-2Ab also improved sensorimotor functions (rotarod test and adhesive removal test) 35d after stroke. There were correlations between white matter integrity and behavior performance. Immunostaining confirmed the beneficial effects of IL-2/IL-2Ab on white matter structures 35d after tMCAO. IL-2/IL-2Ab treatment starting as late as 5d after stroke still improved white matter integrity 21d after tMCAO, suggesting long-term salutary effects of Tregs on the late-stage tissue repair. We also found that IL-2/IL-2Ab treatment reduced the number of dead/dying OPCs and oligodendrocytes in the brain 3d after tMCAO. To confirm the direct effect of Tregs on remyelination, Tregs were cocultured with lysophosphatidyl choline (LPC)-treated organotypic cerebella. LPC exposure for 17 h induced demyelination in organotypic cultures, followed by gradual spontaneous remyelination upon removal of LPC. Co-culture with Tregs accelerated remyelination in organotypic cultures 7d after LPC. In conclusion, Boosting the number of Tregs protects oligodendrocyte lineage cells early after stroke and promotes long-term white matter repair and functional recovery. IL-2/IL-2Ab represents a feasible approach of Treg expansion for stroke treatment.

Matching entropy based disparity estimation from light field data.

A major challenge for matching-based disparity estimation from light field data is to prevent mismatches in occlusion and smooth regions. An effective matching window satisfying three characteristics: texture richness, disparity consistency, and anti-occlusion should be able to prevent mismatches to some extent. According to these characteristics, we propose matching entropy in the spatial domain of the light field to measure the amount of correct information in a matching window, which provides the criterion for matching window selection. Based on matching entropy regularization, we establish an optimization model for disparity estimation with a matching cost fidelity term. To find the optimum, we propose a two-step adaptive matching algorithm. First, the region type is adaptively determined to identify occluding, occluded, smooth, and textured regions. Then, the matching entropy criterion is used to adaptively select the size and shape of matching windows, as well as the visible viewpoints. The two-step process can reduce mismatches and redundant calculations by selecting effective matching windows. The experimental results on synthetic and real data show that the proposed method can effectively improve the accuracy of disparity estimation in occlusion and smooth regions and has strong robustness for different noise levels. Therefore, high-precision disparity estimation from 4D light field data is achieved.

The interleukin-4/PPARγ signaling axis promotes oligodendrocyte differentiation and remyelination after brain injury.

The repair of white matter damage is of paramount importance for functional recovery after brain injuries. Here, we report that interleukin-4 (IL-4) promotes oligodendrocyte regeneration and remyelination. IL-4 receptor expression was detected in a variety of glial cells after ischemic brain injury, including oligodendrocyte lineage cells. IL-4 deficiency in knockout mice resulted in greater deterioration of white matter over 14 d after stroke. Consistent with these findings, intranasal delivery of IL-4 nanoparticles after stroke improved white matter integrity and attenuated long-term sensorimotor and cognitive deficits in wild-type mice, as revealed by histological immunostaining, electron microscopy, diffusion tensor imaging, and electrophysiology. The selective effect of IL-4 on remyelination was verified in an ex vivo organotypic model of demyelination. By leveraging primary oligodendrocyte progenitor cells (OPCs), microglia-depleted mice, and conditional OPC-specific peroxisome proliferator-activated receptor gamma (PPARγ) knockout mice, we discovered a direct salutary effect of IL-4 on oligodendrocyte differentiation that was mediated by the PPARγ axis. Our findings reveal a new regenerative role of IL-4 in the central nervous system (CNS), which lies beyond its known immunoregulatory functions on microglia/macrophages or peripheral lymphocytes. Therefore, intranasal IL-4 delivery may represent a novel therapeutic strategy to improve white matter integrity in stroke and other brain injuries.

Aged microglia promote peripheral T cell infiltration by reprogramming the microenvironment of neurogenic niches.

BACKGROUND: The immune cell compartment of the mammalian brain changes dramatically and peripheral T cells infiltrate the brain parenchyma during normal aging. However, the mechanisms underlying age-related T cell infiltration in the central nervous system remain unclear. RESULTS: Chronic inflammation and peripheral T cell infiltration were observed in the subventricular zone of aged mice. Cell-cell interaction analysis revealed that aged microglia released CCL3 to recruit peripheral CD8+ memory T cells. Moreover, the aged microglia shifted towards a pro-inflammation state and released TNF-α to upregulate the expression of VCAM1 and ICAM1 in brain venous endothelial cells, which promoted the transendothelial migration of peripheral T cells. In vitro experiment reveals that human microglia would also transit to a chemotactic phenotype when treated with CSF from the elderly. CONCLUSIONS: Our research demonstrated that microglia play an important role in the aging process of brain by shifting towards a pro-inflammation and chemotactic state. Aged microglia promote T cell infiltration by releasing chemokines and upregulating adhesion molecules on venous brain endothelial cells.

Mer regulates microglial/macrophage M1/M2 polarization and alleviates neuroinflammation following traumatic brain injury.

BACKGROUND: Traumatic brain injury (TBI) is a leading cause of death and disability worldwide. Microglial/macrophage activation and neuroinflammation are key cellular events following TBI, but the regulatory and functional mechanisms are still not well understood. Myeloid-epithelial-reproductive tyrosine kinase (Mer), a member of the Tyro-Axl-Mer (TAM) family of receptor tyrosine kinases, regulates multiple features of microglial/macrophage physiology. However, its function in regulating the innate immune response and microglial/macrophage M1/M2 polarization in TBI has not been addressed. The present study aimed to evaluate the role of Mer in regulating microglial/macrophage M1/M2 polarization and neuroinflammation following TBI. METHODS: The controlled cortical impact (CCI) mouse model was employed. Mer siRNA was intracerebroventricularly administered, and recombinant protein S (PS) was intravenously applied for intervention. The neurobehavioral assessments, RT-PCR, Western blot, magnetic-activated cell sorting, immunohistochemistry and confocal microscopy analysis, Nissl and Fluoro-Jade B staining, brain water content measurement, and contusion volume assessment were performed. RESULTS: Mer is upregulated and regulates microglial/macrophage M1/M2 polarization and neuroinflammation in the acute stage of TBI. Mechanistically, Mer activates the signal transducer and activator of transcription 1 (STAT1)/suppressor of cytokine signaling 1/3 (SOCS1/3) pathway. Inhibition of Mer markedly decreases microglial/macrophage M2-like polarization while increases M1-like polarization, which exacerbates the secondary brain damage and sensorimotor deficits after TBI. Recombinant PS exerts beneficial effects in TBI mice through Mer activation. CONCLUSIONS: Mer is an important regulator of microglial/macrophage M1/M2 polarization and neuroinflammation, and may be considered as a potential target for therapeutic intervention in TBI.

Ceria nanoparticles ameliorate white matter injury after intracerebral hemorrhage: microglia-astrocyte involvement in remyelination.

BACKGROUND: Intracerebral hemorrhage (ICH) can induce excessive accumulation of reactive oxygen species (ROS) that may subsequently cause severe white matter injury. The process of oligodendrocyte progenitor cell (OPC) differentiation is orchestrated by microglia and astrocytes, and ROS also drives the activation of microglia and astrocytes. In light of the potent ROS scavenging capacity of ceria nanoparticles (CeNP), we aimed to investigate whether treatment with CeNP ameliorates white matter injury by modulating ROS-induced microglial polarization and astrocyte alteration. METHODS: ICH was induced in vivo by collagenase VII injection. Mice were administered with PLX3397 for depleting microglia. Primary microglia and astrocytes were used for in vitro experiments. Transmission electron microscopy analysis and immunostaining were performed to verify the positive effects of CeNP in remyelination and OPC differentiation. Flow cytometry, real-time polymerase chain reaction, immunofluorescence and western blotting were used to detect microglia polarization, astrocyte alteration, and the underlying molecular mechanisms. RESULTS: CeNP treatment strongly inhibited ROS-induced NF-κB p65 translocation in both microglia and astrocytes, and significantly decreased the expression of M1 microglia and A1 astrocyte. Furthermore, we found that CeNP treatment promoted remyelination and OPC differentiation after ICH, and such effects were alleviated after microglial depletion. Interestingly, we also found that the number of mature oligodendrocytes was moderately increased in ICH + CeNP + PLX3397-treated mice compared to the ICH + vehicle + PLX3397 group. Therefore, astrocytes might participate in the pathophysiological process. The subsequent phagocytosis assay indicated that A1 astrocyte highly expressed C3, which could bind with microglia C3aR and hinder microglial engulfment of myelin debris. This result further replenished the feedback mechanism from astrocytes to microglia. CONCLUSION: The present study reveals a new mechanism in white matter injury after ICH: ICH induces M1 microglia and A1 astrocyte through ROS-induced NF-κB p65 translocation that hinders OPC maturation. Subsequently, A1 astrocytes inhibit microglial phagocytosis of myelin debris via an astrocytic C3-microglial C3aR axis. Polyethylene glycol-CeNP treatment inhibits this pathological process and ultimately promotes remyelination. Such findings enlighten us that astrocytes and microglia should be regarded as a functional unit in future works.

Melatonin attenuates neuronal apoptosis through up-regulation of K(+) -Cl(-) cotransporter KCC2 expression following traumatic brain injury in rats.

Traumatic brain injury (TBI) initiates a complex cascade of neurochemical and signaling changes that leads to neuronal apoptosis, which contributes to poor outcomes for patients with TBI. The neuron-specific K(+) -Cl(-) cotransporter-2 (KCC2), the principal Cl(-) extruder in adult neurons, plays an important role in Cl(-) homeostasis and neuronal function. This present study was designed to investigate the expression pattern of KCC2 following TBI and to evaluate whether or not melatonin is able to prevent neuronal apoptosis by modulating KCC2 expression in a Sprague Dawley rat controlled cortical impact model of TBI. The time course study showed decreased mRNA and protein expression of KCC2 in the ipsilateral peri-core parietal cortex after TBI. Double immunofluorescence staining demonstrated that KCC2 is located in the plasma membrane of neurons. In addition, melatonin (10 mg/kg) was injected intraperitoneally at 5 minutes and repeated at 1, 2, 3, and 4 hours after brain trauma, and brain samples were extracted 24 hours after TBI. Compared to the vehicle group, melatonin treatment altered the down-regulation of KCC2 expression in both mRNA and protein levels after TBI. Also, melatonin treatment increased the protein levels of brain-derived neurotrophic factor (BDNF) and phosphorylated extracellular signal-regulated kinase (p-ERK). Simultaneously, melatonin administration ameliorated cortical neuronal apoptosis, reduced brain edema, and attenuated neurological deficits after TBI. In conclusion, our findings suggested that melatonin restores KCC2 expression, inhibits neuronal apoptosis and attenuates secondary brain injury after TBI, partially through activation of BDNF/ERK pathway.

The efficacy and safety of cilostazol for the secondary prevention of ischemic stroke in acute and chronic phases in Asian population--an updated meta-analysis.

BACKGROUNDS: While previous meta-analysis have investigated the efficacy of cilostazol in the secondary prevention of ischemic stroke, they were criticized for their methodology, which confused the acute and chronic phases of stroke. We present a new systematic review, which differs from previous meta-analysis by distinguishing between the different phases of stroke, and includes two new randomized, controlled trials (RCTs). METHODS: All RCTs investigating the effect of cilostazol on secondary prevention of ischemic stroke were obtained. Outcomes were analyzed by Review Manager, including recurrence of cerebral infarction (ROCI), hemorrhage stroke or subarachnoid hemorrhage (HSSH), all-cause death (ACD), and modified Rankin Scale score (mRS). The Grading of Recommendations Assessment, Development and Evaluation (GRADE) assessed the quality of the evidence. RESULTS: 5491 patients from six studies were included in the current study. In secondary prevention of ischemic stroke in chronic phase, cilostazol was associated with a 47% reduction in ROCI (relative risk [RR] 0.53, 95% confidence interval [CI] 0.34 to 0.81, p = 0.003), while no significant difference in HSSH and ACD compared with placebo; and 71% reduction in HSSH (RR 0.29, 95% CI 0.15 to 0.56, p = 0.0002) compared with aspirin, but not in ROCI and ACD. In the secondary prevention of ischemic stroke in acute phase, cilostazol did not show any effect in the ROCI, HSSH, ACD and mRS compared to placebo or aspirin. The quality of the evidence from chronic phase was high or moderate, and those from acute phase were moderate or low when analyzed by GRADE approach. CONCLUSION: Cilostazol provided a protective effect in the secondary prevention of the chronic phase of ischemic stroke.

Decreased plasma neuroactive amino acids and increased nitric oxide levels in melancholic major depressive disorder.

BACKGROUND: Amino acid neurotransmitters and nitric oxide (NO) are involved in the pathogenesis of major depressive disorder (MDD). Here we want to establish whether changes in their plasma levels may serve as biomarker for the melancholic subtype of this disorder. METHODS: Plasma levels of glutamic acid (Glu), aspartic acid (Asp), glycine (Gly), gamma-aminobutyric acid (GABA), and NO were determined in 27 medicine-naïve melancholic MDD patients and 30 matched controls. Seven of the MDD patients participated also in a follow-up study after 2 months' antidepressant treatment. The relationship between plasma and cerebral-spinal fluid (CSF) levels of these compounds was analyzed in an additional group of 10 non-depressed subjects. RESULTS: The plasma levels of Asp, Gly and GABA were significantly lower whereas the NO levels were significantly higher in melancholic MDD patients, also after 2 months of fluoxetine treatment. In the additional 10 non-depressed subjects, no significant correlation was observed between plasma and CSF levels of these compounds. CONCLUSION: These data give the first indication that decreased plasma levels of Asp, Gly and GABA and increased NO levels may serve as a clinical trait-marker for melancholic MDD. The specificity and selectivity of this putative trait-marker has to be investigated in follow-up studies.

Novel subsets of peripheral immune cells associated with promoting stroke recovery in mice.

AIMS: Peripheral immune cells infiltrating into the brain trigger neuroinflammation after an ischemic stroke. Partial immune cells reprogram their function for neural repair. Which immune cells promote ischemic brain recovery needs further identification. METHODS: We performed single-cell transcriptomic profiling of CD45high immune cells isolated from the ischemic hemisphere at subacute (5 days) and chronic (14 days) stages after ischemic stroke. RESULTS: A subset of phagocytic macrophages was associated with neuron projection regeneration and tissue remodeling. We also identified a unique type of T cells with highly expressed macrophage markers, including C1q, Apoe, Hexb, and Fcer1g, which showed high abilities in tissue remodeling, myelination regulation, wound healing, and anti-neuroinflammation. Moreover, natural killer cells decreased cytotoxicity and increased energy and metabolic function in the chronic stage after ischemic stroke. Two subgroups of neutrophils upregulated CCL signals to recruit peripheral immune cells and released CXCL2 to keep self-recruiting at the chronic stage. CONCLUSIONS: We identified subsets of peripheral immune cells that may provide potential therapeutic targets for promoting poststroke recovery.

Effects of curcumin on glucose metabolism in the brains of rats subjected to chronic unpredictable stress: a 18 F-FDG micro-PET study.

BACKGROUND: Chronic unpredictable stress (CUS) can cause behavioral and physiological abnormalities that are important to the prediction of symptoms of depression that may be associated with cerebral glucose metabolic abnormalities. Curcumin showed potential antidepressant effects, but whether or not it can reverse cerebral functional abnormalities and so ameliorate depression remains unknown. METHODS: To investigate the effects of curcumin on brain activity in CUS rats, rats were subjected to 3 weeks of CUS and then treated with curcumin orally at a dose of 40 mg/kg/day for one month. 18 F fluorodeoxyglucose (18 F-FDG)-micro positron emission tomography (micro-PET) neuroimaging was used to detect changes in cerebral metabolism. Body weight, sucrose preference, and open field tests were used to record depressive behaviors during CUS and after curcumin treatment. RESULTS: Three weeks of CUS significantly decreased body weight, sucrose preference, sucrose consumption, total distance travelling, and the number of rearing events. It also induced metabolic alterations in several parts of the brain, showing increased glucose metabolism in the right hemisphere. After curcumin treatment for one month, sucrose preference, sucrose consumption, total distance travelling, and the number of rearing events returned to normal levels. Curcumin treatment also induced strong deactivation of the left primary auditory cortex and activation of amygdalohippocampal cortex. CONCLUSION: Curcumin was found to ameliorate the abnormalities in the behavior and brain glucose metabolism caused by CUS, which may account for its antidepressive effects.

A novel phenotype of B cells associated with enhanced phagocytic capability and chemotactic function after ischemic stroke.

Accumulating evidence has demonstrated the involvement of B cells in neuroinflammation and neuroregeneration. However, the role of B cells in ischemic stroke remains unclear. In this study, we identified a novel phenotype of macrophage-like B cells in brain-infiltrating immune cells expressing a high level of CD45. Macrophage-like B cells characterized by co-expression of B-cell and macrophage markers, showed stronger phagocytic and chemotactic functions compared with other B cells and showed upregulated expression of phagocytosis-related genes. Gene Ontology analysis found that the expression of genes associated with phagocytosis, including phagosome- and lysosome-related genes, was upregulated in macrophage-like B cells. The phagocytic activity of macrophage-like B cells was verified by immunostaining and three-dimensional reconstruction, in which TREM2-labeled macrophage-like B cells enwrapped and internalized myelin debris after cerebral ischemia. Cell-cell interaction analysis revealed that macrophage-like B cells released multiple chemokines to recruit peripheral immune cells mainly via CCL pathways. Single-cell RNA sequencing showed that the transdifferentiation to macrophage-like B cells may be induced by specific upregulation of the transcription factor CEBP family to the myeloid lineage and/or by downregulation of the transcription factor Pax5 to the lymphoid lineage. Furthermore, this distinct B cell phenotype was detected in brain tissues from mice or patients with traumatic brain injury, Alzheimer's disease, and glioblastoma. Overall, these results provide a new perspective on the phagocytic capability and chemotactic function of B cells in the ischemic brain. These cells may serve as an immunotherapeutic target for regulating the immune response of ischemic stroke.

Age-Related Alterations in Peripheral Immune Landscape with Magnified Impact on Post-Stroke Brain.

Immunosenescence refers to the multifaceted and profound alterations in the immune system brought about by aging, exerting complex influences on the pathophysiological processes of diseases that manifest upon it. Using a combination of single-cell RNA sequencing, cytometry by time of flight, and various immunological assays, we investigated the characteristics of immunosenescence in the peripheral blood of aged mice and its impact on the cerebral immune environment after ischemic stroke. Our results revealed some features of immunosenescence. We observed an increase in neutrophil counts, concurrent with accelerated neutrophil aging, characterized by altered expression of aging-associated markers like CD62L and consequential changes in neutrophil-mediated immune functions. Monocytes/macrophages in aged mice exhibited enhanced antigen-presentation capabilities. T cell profiles shifted from naive to effector or memory states, with a specific rise in T helper 1 cells and T helper 17 cells subpopulations and increased regulatory T cell activation in CD4 T cells. Furthermore, regulatory CD8 T cells marked by Klra decreased with aging, while a subpopulation of exhausted-like CD8 T cells expanded, retaining potent immunostimulatory and proinflammatory functions. Critically, these inherent disparities not only persisted but were further amplified within the ischemic hemispheres following stroke. In summary, our comprehensive insights into the key attributes of peripheral immunosenescence provide a vital theoretical foundation for understanding not only ischemic strokes but also other age-associated diseases.

[Research progress on role of ghrelin in brain].

The brain-gut peptide ghrelin, a endogenous ligand for the growth hormone secretagogue hormone receptor, is mainly produced by gastric cells in the periphery, regulating energy metabolism via stimulating the appetite. Inside the brain, ghrelin is mainly expressed in the pituitary and in the hypothalamic arcuate nucleus, regulating the synthesis and secretion of neuropeptides that are correlated with feeding behavior, reproduction, and stress responses. Recently, more and more researches focused on the regulating roles of ghrelin on learning and memory, and mood regulation have indicated that ghrelin may inhibit neuronal apoptosis, improve cognitive function, and regulate the activities of neuroendocrine systems such as the hypothalamo-pituitary-adrenal axis and the hypothalamo-pituitary-gonadal axis thus get involved in the pathogenesis of neuropsychiatric diseases. The aim of this review is to summarize the main findings in this field, with the purpose of promoting further studies on the role of ghrelin in the brain.

InterCellDB: A User-Defined Database for Inferring Intercellular Networks.

Recent advances in single cell RNA sequencing (scRNA-seq) empower insights into cell-cell crosstalk within specific tissues. However, customizable data analysis tools that decipher intercellular communication from gene expression in association with biological functions are lacking. The authors have developed InterCellDB, a platform that allows a user-defined analysis of intercellular communication using scRNA-seq datasets in combination with protein annotation information, including cellular localization and functional classification, and protein interaction properties. The application of InterCellDB in tumor microenvironment research is exemplified using two independent scRNA-seq datasets from human and mouse and it is demonstrated that InterCellDB-inferred cell-cell interactions and ligand-receptor pairs are experimentally valid.

Dual roles of hexokinase 2 in shaping microglial function by gating glycolytic flux and mitochondrial activity.

Microglia continuously survey the brain parenchyma and actively shift status following stimulation. These processes demand a unique bioenergetic programme; however, little is known about the metabolic determinants in microglia. By mining large datasets and generating transgenic tools, here we show that hexokinase 2 (HK2), the most active isozyme associated with mitochondrial membrane, is selectively expressed in microglia in the brain. Genetic ablation of HK2 reduced microglial glycolytic flux and energy production, suppressed microglial repopulation, and attenuated microglial surveillance and damage-triggered migration in male mice. HK2 elevation is prominent in immune-challenged or disease-associated microglia. In ischaemic stroke models, however, HK2 deletion promoted neuroinflammation and potentiated cerebral damages. The enhanced inflammatory responses after HK2 ablation in microglia are associated with aberrant mitochondrial function and reactive oxygen species accumulation. Our study demonstrates that HK2 gates both glycolytic flux and mitochondrial activity to shape microglial functions, changes of which contribute to metabolic abnormalities and maladaptive inflammation in brain diseases.

Distinct proteomic profiles in prefrontal subareas of elderly major depressive disorder and bipolar disorder patients.

We investigated for the first time the proteomic profiles both in the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC) of major depressive disorder (MDD) and bipolar disorder (BD) patients. Cryostat sections of DLPFC and ACC of MDD and BD patients with their respective well-matched controls were used for study. Proteins were quantified by tandem mass tag and high-performance liquid chromatography-mass spectrometry system. Gene Ontology terms and functional cluster alteration were analyzed through bioinformatic analysis. Over 3000 proteins were accurately quantified, with more than 100 protein expressions identified as significantly changed in these two brain areas of MDD and BD patients as compared to their respective controls. These include OGDH, SDHA and COX5B in the DLPFC in MDD patients; PFN1, HSP90AA1 and PDCD6IP in the ACC of MDD patients; DBN1, DBNL and MYH9 in the DLPFC in BD patients. Impressively, depending on brain area and distinct diseases, the most notable change we found in the DLPFC of MDD was 'suppressed energy metabolism'; in the ACC of MDD it was 'suppressed tissue remodeling and suppressed immune response'; and in the DLPFC of BD it was differentiated 'suppressed tissue remodeling and suppressed neuronal projection'. In summary, there are distinct proteomic changes in different brain areas of the same mood disorder, and in the same brain area between MDD and BD patients, which strengthens the distinct pathogeneses and thus treatment targets.

Neuroprotection against ischemic stroke requires a specific class of early responder T cells in mice.

Immunomodulation holds therapeutic promise against brain injuries, but leveraging this approach requires a precise understanding of mechanisms. We report that CD8+CD122+CD49dlo T regulatory-like cells (CD8+ TRLs) are among the earliest lymphocytes to infiltrate mouse brains after ischemic stroke and temper inflammation; they also confer neuroprotection. TRL depletion worsened stroke outcomes, an effect reversed by CD8+ TRL reconstitution. The CXCR3/CXCL10 axis served as the brain-homing mechanism for CD8+ TRLs. Upon brain entry, CD8+ TRLs were reprogrammed to upregulate leukemia inhibitory factor (LIF) receptor, epidermal growth factor-like transforming growth factor (ETGF), and interleukin 10 (IL-10). LIF/LIF receptor interactions induced ETGF and IL-10 production in CD8+ TRLs. While IL-10 induction was important for the antiinflammatory effects of CD8+ TRLs, ETGF provided direct neuroprotection. Poststroke intravenous transfer of CD8+ TRLs reduced infarction, promoting long-term neurological recovery in young males or aged mice of both sexes. Thus, these unique CD8+ TRLs serve as early responders to rally defenses against stroke, offering fresh perspectives for clinical translation.