Journal of Neuroinflammation最新文献

The thrombolytic protease tissue plasminogen activator (tPA) is expressed in the CNS, where it regulates diverse functions including neuronal plasticity, neuroinflammation, and blood-brain-barrier integrity. However, its role in different brain regions such as the substantia nigra (SN) is largely unexplored. In this study, we characterize tPA expression, activity, and localization in the SN using a combination of retrograde tracing and β-galactosidase tPA reporter mice. We further investigate tPA's potential role in SN pathology in an α-synuclein mouse model of Parkinson's disease (PD). To characterize the mechanism of tPA action in α-synuclein-mediated pathology in the SN and to identify possible therapeutic pathways, we performed RNA-seq analysis of the SN and used multiple transgenic mouse models. These included tPA deficient mice and two newly developed transgenic mice, a knock-in model expressing endogenous levels of proteolytically inactive tPA (tPA Ala-KI) and a second model overexpressing proteolytically inactive tPA (tPA Ala-BAC). Our findings show that striatal GABAergic neurons send tPA⁺ projections to dopaminergic (DA)-neurons in the SN and that tPA is released from SN-derived synaptosomes upon stimulation. We also found that tPA levels in the SN increased following α-synuclein overexpression. Importantly, tPA deficiency protects DA-neurons from degeneration, prevents behavioral deficits, and reduces microglia activation and T-cell infiltration induced by α-synuclein overexpression. RNA-seq analysis indicates that tPA in the SN is required for the upregulation of genes involved in the innate and adaptive immune responses induced by α-synuclein overexpression. Overexpression of α-synuclein in tPA Ala-KI mice, expressing only proteolytically inactive tPA, confirms that tPA-mediated neuroinflammation and neurodegeneration is independent of its proteolytic activity. Moreover, overexpression of proteolytically inactive tPA in tPA Ala-BAC mice leads to increased neuroinflammation and neurodegeneration compared to mice expressing normal levels of tPA, suggesting a tPA dose response. Finally, treatment of mice with glunomab, a neutralizing antibody that selectively blocks tPA binding to the N-methyl-D-aspartate receptor-1 (NMDAR1) without affecting NMDAR1 ion channel function, identifies the tPA interaction with NMDAR1 as necessary for tPA-mediated neuroinflammation and neurodegeneration in response to α-synuclein-mediated neurotoxicity. Thus, our data identifies a novel pathway that promotes DA-neuron degeneration and suggests a potential therapeutic intervention for PD targeting the tPA-NMDAR1 interaction.

Background: Traumatic brain injury (TBI) is characterized by high mortality and disability rates. Disease-associated microglia (DAM) are a newly discovered subtype of microglia. However, their presence and function in the acute phase of TBI remain unclear. Although glycolysis is important for microglial differentiation, its regulatory role in DAM transformation during the acute phase of TBI is still unclear. In this study, we investigated the functions of DAM-like cells in the acute phase of TBI in mice, as well as the relationship between their transformation and glycolysis.

Methods: In this study, a controlled cortical impact model was used to induce TBI in adult male wild-type (WT) C57BL/6 mice and adult male TREM2 knockout mice. Various techniques were used to assess the role of DAM-like cells in TBI and the effects of glycolysis on DAM-like cells, including RT‒qPCR, immunofluorescence assays, behavioural tests, extracellular acidification rate (ECAR) tests, Western blot analysis, cell magnetic sorting and culture, glucose and lactate assays, and flow cytometry.

Results: DAM-like cells were observed in the acute phase of TBI in mice, and their transformation depended on TREM2 expression. TREM2 knockout impaired neurological recovery in TBI mice, possibly due in part to their role in clearing debris and secreting VEGFa and BDNF. Moreover, DAM-like cells exhibited significantly increased glycolytic activity. TREM2 regulated the AKT‒mTOR‒HIF-1α pathway and glycolysis in microglia in the acute phase of TBI. The increase in glycolysis in microglia partially contributed to the transformation of DAM-like cells in the acute phase of TBI in mice.

Conclusions: Taken together, the results of our study demonstrated that DAM-like cells were present in the acute phase of TBI in mice. TREM2 might influence DAM-like cell transformation by modulating the glycolysis of microglia. Our results provide a new possible pathway for intervening TBI.

Lipid droplets (LDs), serving as the convergence point of energy metabolism and multiple signaling pathways, have garnered increasing attention in recent years. Different cell types within the central nervous system (CNS) can regulate energy metabolism to generate or degrade LDs in response to diverse pathological stimuli. This article provides a comprehensive review on the composition of LDs in CNS, their generation and degradation processes, their interaction mechanisms with mitochondria, the distribution among different cell types, and the roles played by these cells-particularly microglia and astrocytes-in various prevalent neurological disorders. Additionally, we also emphasize the paradoxical role of LDs in post-cerebral ischemia inflammation and explore potential underlying mechanisms, aiming to identify novel therapeutic targets for this disease.

Background: Immunothrombosis is the process by which the coagulation cascade interacts with the innate immune system to control infection. However, the formation of clots within the brain vasculature can be detrimental to the host. Recent work has demonstrated that Toxoplasma gondii infects and lyses central nervous system (CNS) endothelial cells that form the blood-brain barrier (BBB). However, little is known about the effect of T. gondii infection on the BBB and the functional consequences of infection on cerebral blood flow (CBF) during the different stages of infection.

Main body: We demonstrate that brain endothelial cells upregulate the adhesion molecules ICAM-1 and VCAM-1 and become morphologically more tortuous during acute T. gondii infection of mice. Longitudinal two-photon imaging of cerebral blood vessels during infection in mice revealed vascular occlusion in the brain, prompting an analysis of the coagulation cascade. We detected platelet-fibrin clots within the cerebral vasculature during acute infection. Analysis of CBF using longitudinal laser-speckle imaging during T. gondii infection demonstrated that CBF decreased during acute infection, recovered during stable chronic infection, and decreased again during reactivation of the infection induced by IFN-γ depletion. Finally, we demonstrate that treatment of mice with a low-molecular-weight heparin, an anticoagulant, during infection partially rescued CBF in T. gondii-infected mice without affecting parasite burden.

Conclusions: Our data provide insight into the host-pathogen interactions of a CNS parasite within the brain vasculature and suggest that thrombosis and changes in cerebral hemodynamics may be an unappreciated aspect of infection with T. gondii.

Background: Alzheimer's disease (AD) is a prevalent neurodegenerative disorder worldwide, and microglia are thought to play a central role in neuroinflammatory events occurring in AD. Chemerin, an adipokine, has been implicated in inflammatory diseases and central nervous system disorders, yet its precise function on microglial response in AD remains unknown.

Methods: The APP/PS1 mice were treated with different dosages of chemerin-9 (30 and 60 µg/kg), a bioactive nonapeptide derived from chemerin, every other day for 8 weeks consecutively. The primary mouse microglia were stimulated by amyloid beta 42 (Aβ₄₂) oligomers followed by treatment with chemerin-9 in vitro. ChemR23 inhibitor α-NETA was further used to investigate whether the effects of chemerin-9 were ChemR23-dependent.

Results: We found that the expression of chemerin and ChemR23 was increased in AD. Intriguingly, treatment with chemerin-9 significantly ameliorated Aβ deposition and cognitive impairment of the APP/PS1 mice, with decreased microglial proinflammatory activity and increased phagocytic activity. Similarly, chemerin-9-treated primary microglia showed increased phagocytic ability and decreased NLRP3 inflammasome activation. However, the ChemR23 inhibitor α-NETA abolished the neuroprotective microglial response of chemerin-9.

Conclusions: Collectively, our data demonstrate that chemerin-9 ameliorates cognitive deficits in APP/PS1 transgenic mice by boosting a neuroprotective microglial phenotype.

Background: Disturbances of the sleep-wake cycle and other circadian rhythms typically precede the age-related deficits in learning and memory, suggesting that these alterations in circadian timekeeping may contribute to the progressive cognitive decline during aging. The present study examined the role of immune cell activation and inflammation in the link between circadian rhythm dysregulation and cognitive impairment in aging.

Methods: C57Bl/6J mice were exposed to shifted light-dark (LD) cycles (12 h advance/5d) during early adulthood (from ≈ 4-6mo) or continuously to a "fixed" LD12:12 schedule. At middle age (13-14mo), the long-term effects of circadian rhythm dysregulation on cognitive performance, immune cell regulation and hippocampal microglia were analyzed using behavioral, flow cytometry and immunohistochemical assays.

Results: Entrainment of the activity rhythm was stable in all mice on a fixed LD 12:12 cycle but was fully compromised during exposure to shifted LD cycles. Even during "post-treatment" exposure to standard LD 12:12 conditions, re-entrainment in shifted LD mice was marked by altered patterns of entrainment and increased day-to-day variability in activity onset times that persisted into middle-age. These alterations in light-dark entrainment were closely associated with dramatic impairment in the Barnes maze test for the entire group of shifted LD mice at middle age, well before cognitive decline was first observed in aged (18-22mo) animals maintained on fixed LD cycles. In conjunction with the effects of circadian dysregulation on cognition, shifted LD mice at middle age were distinguished by significant expansion of splenic B cells and B cell subtypes expressing the activation marker CD69 or inflammatory marker MHC Class II Invariant peptide (CLIP), differential increases in CLIP+, 41BB-Ligand+, and CD74 + B cells in the meningeal lymphatics, alterations in splenic T cell subtypes, and increased number and altered functional state of microglia in the dentate gyrus. In shifted LD mice, the expansion in splenic B cells was negatively correlated with cognitive performance; when B cell numbers were higher, performance was worse in the Barnes maze. These results indicate that disordered circadian timekeeping associated with early exposure to shift work-like schedules alone accelerates cognitive decline during aging in conjunction with altered regulation of immune cells and microglia in the brain.

Following recent advances in post-thrombectomy stroke care, the role of neuroinflammation and neuroprotective strategies in mitigating secondary injury has gained prominence. Yet, while neuroprotection and anti-inflammatory agents have re-emerged in clinical trials, their success has been limited. The neuroinflammatory response in cerebral ischemia is robust and multifactorial, complicating therapeutic approaches targeting single pathways. In this study, we aimed to characterize early inflammatory gene dysregulation following ischemic stroke using translational in-silico and in-vivo approaches. Using an in vivo ischemic stroke model, transcriptomic analysis revealed significant dysregulation of inflammatory genes. Graph theory analysis then showed a rich-club organization among stroke-related genes, with highly connected core nodes. The expression levels of the core genes identified within this network significantly explained radiological outcomes, including T2-signal hyperintensity (R² = 0.57, P < 0.001), mean diffusivity (R² = 0.52, P < 0.001), and mean kurtosis (R² = 0.65, P < 0.001), correlating more strongly than non-core genes. Similar findings were observed with functional and cognitive outcomes, showing R² values of 0.58, 0.7, 0.54, and 0.7 for neurological severity scores, corner tasks, passive avoidance, and novel object recognition tasks, respectively (P < 0.001). Using in-silico analysis, we identified a set of upstream regulators directly interacting with core network nodes, leading to simulations that highlighted C3-targeted therapy as a potential treatment. This hypothesis was then confirmed in vivo using a targeted C3 inhibitor (CR2-fH), which reversed gene dysregulation in the neuroinflammatory network and improved radiological and functional outcomes. Our findings underscore the significance of neuroinflammation in stroke pathology, supporting network-based therapeutic targeting and demonstrating the benefits of targeted complement inhibition in enhancing outcomes through modulation of the neuroinflammatory network core. This study's approach, combining graph theory analysis along with in-silico modeling, offers a promising translational pipeline applicable to stroke and other complex diseases.

Background: Intracerebral hemorrhage (ICH) causes prominent deposition of extracellular matrix molecules, particularly the chondroitin sulphate proteoglycan (CSPG) member neurocan. In tissue culture, neurocan impedes the properties of oligodendrocytes. Whether therapeutic reduction of neurocan promotes oligodendrogenesis and functional recovery in ICH is unknown.

Methods: Mice were retro-orbitally injected with adeno-associated virus (AAV-CRISPR/Cas9) to reduce neurocan deposition after ICH induction by collagenase. Other groups of ICH mice were treated with vehicle or a drug that reduces CSPG synthesis, 4-4-difluoro-N-acetylglucosamine (difluorosamine). Rota-rod and grip strength behavioral tests were conducted over 7 or 14 days. Brain tissues were investigated for expression of neurocan by immunofluorescence microscopy and western blot analysis. Brain cryosections were also stained for microglia/macrophage phenotype, oligodendrocyte lineage cells and neuroblasts by immunofluorescence microscopy. Tissue structural changes were assessed using brain magnetic resonance imaging (MRI).

Results: The adeno-associated virus (AAV)-reduction of neurocan increased oligodendrocyte numbers and functional recovery in ICH. The small molecule inhibitor of CSPG synthesis, difluorosamine, lowered neurocan levels in lesions and elevated numbers of oligodendrocyte precursor cells, mature oligodendrocytes, and SOX2⁺ nestin⁺ neuroblasts in the perihematomal area. Difluorosamine shifted the degeneration-associated functional state of microglia/macrophages in ICH towards a regulatory phenotype. MRI analyses showed better fiber tract integrity in the penumbra of difluorosamine mice. These beneficial difluorosamine results were achieved with delayed (2 or 3 days) treatment after ICH.

Conclusion: Reducing neurocan deposition following ICH injury is a therapeutic approach to promote histological and behavioral recovery from the devastating stroke.

Multiple Sclerosis (MS), a neuroinflammatory disease of the central nervous system, is one of the commonest causes of non-traumatic disability among young adults. Impaired cognition arises as an impactful symptom affecting more than 50% of the patients and with substantial impact on social, economic, and individual wellbeing. Despite the lack of therapeutic strategies, many efforts have been made to understand the mechanisms behind cognitive impairment in MS patients. Here, we aimed to investigate whether microglia-derived synaptic elimination and immune interactions are exacerbated in MS patients with impaired cognition when compared to non-demented controls (NDC) and cognitively preserved MS patients, that may clarify the role of immune cell interplay in MS cognitive deficits. Postmortem hippocampal samples were obtained from NDCs and MS patients. Sixteen MS patients were categorized based on their cognitive status: preserved cognition (MSCP) and impaired cognition (MSCI). Immunohistochemistry studies were conducted to explore the density of microglia, their role in synaptic engulfment, and their interaction with CD8⁺ immune cells in the context of cognitive impairment in MS. In high synaptic density hippocampal regions, MSCI patients exhibited a massive presence of microglia cells actively engulfing both excitatory and inhibitory synapses, accompanied by morphological alterations. Additionally, there was an increased expression of the complement protein C1q particularly localized at inhibitory synapses within microglia cells, suggesting a preferential engulfment of complement-tagged inhibitory synapses in MSCI patients. Furthermore, in hippocampal lesions of MSCI patients, we detected a significant infiltration of microglia and CD8 T cells that may be contributing to the smouldering MS and cognitive deterioration. These findings demonstrate that cognitive deficits occurring in MS are associated with microglia engulfment of C1q-tagged inhibitory synapses, which may be driven by direct or indirect stimulation from CD8+ T cells.

The immune system has garnered attention due to its association with disease progression in amyotrophic lateral sclerosis (ALS). However, the role of peripheral immune cells in this context remains controversial. Here, we conducted single-cell RNA-sequencing of peripheral blood mononuclear cells to comprehensively profile immune cells concerning the rate of disease progression in patients with ALS. Our analysis revealed increased frequencies of T helper 17 cells (Th17) relative to regulatory T cells, effector CD8 T cells relative to naïve CD8 T cells, and CD16^highCD56^low mature natural killer cells relative to CD16^lowCD56^high naïve natural killer cells in patients with rapidly progressive ALS. Additionally, we employed serum proteomics through a proximity extension assay combined with next-generation sequencing to identify inflammation-related proteins associated with rapid disease progression. Among these proteins, interleukin-17 A correlated with the frequency of Th17, while killer cell lectin-like receptor D1 (CD94) correlated with the frequency of effector CD8 T cells. These findings further support the active roles played by these specific immune cell types in the progression of ALS.