Journal of Neuroinflammation最新文献

Background: Neonatal hypoxic-ischemic brain damage (HIBD) is a leading cause of neurological deficits and death in neonates. In HIBD, the death of endothelial cells and disruption of the blood-brain barrier (BBB) are closely related to the severity of brain damage and long-term clinical outcomes. There is increasing evidence that a glycolytic enzyme, pyruvate kinase M2 (PKM2), is essential for managing metabolic processes in endothelial cells, but its role (and underlying molecular mechanism) in hypoxic-ischemic (HI)-associated endothelial cell metabolism, cell survival, and BBB function remains unknown.

Methods: We established an in vivo HI-induced brain injury rat model and an in vitro model in which human cerebral microvascular endothelial cells (hCMECs) underwent oxygen-glucose deprivation (OGD). Infarct volume was measured and neurobehavioral tests were conducted to assess brain damage, and Evans blue extravasation and FITC-dextran were used to evaluate the BBB. RNA sequencing, qRT-PCR, western blotting, and immunofluorescence labeling were conducted to identify the molecular mechanisms underlying HIBD.

Results: PKM2 expression was upregulated in the brains of HIBD rats and in OGD-treated hCMECs. The inhibition of PKM2 greatly upregulated the expression of pyroptosis-associated proteins, including NLRP3, cleaved caspase-1, GSDMD, IL-1β, and IL-18. In contrast, the activation of PKM2 preserved junctional proteins and maintained the integrity of the BBB, which together improved functional recovery in HIBD rats. Mechanistically, preconditioning of PKM2 contributed to lactate-mediated cellular defense mechanisms, including the activation of nuclear factor erythroid 2-related factor 2 (NRF2) and thioredoxin (TRX), and to the downregulation of thioredoxin-interacting protein (TXNIP) via a modest increase in reactive oxygen species.

Conclusions: Our analyses provide compelling evidence that PKM2 preconditioning attenuates endothelial cell pyroptosis and BBB disruption in neonatal HIBD by causing oxidative stress resistance and activating the NRF2/TRX/TXNIP pathway. Therefore, PKM2 represents a promising pharmacological target for treating HIBD.

Background: Traumatic brain injury (TBI) causes severe disruption of the blood-brain barrier (BBB), a key event that contributes to secondary neurological damage. Interleukin-25 (IL-25) has recently emerged as an important regulator of neuroinflammation, yet its role in BBB repair after TBI remains unclear. This study investigated the protective effects of IL-25 on BBB integrity and neurological function in mice following TBI and explored the underlying mechanisms.

Methods: IL-25 expression in mouse serum and cortical tissue after TBI was quantified using enzyme-linked immunosorbent assays, and its cellular sources were identified via immunofluorescence staining. The impact of exogenous IL-25 on BBB integrity was evaluated by measuring, tight junction proteins (ZO-1, occludin, and claudin-5), Evans Blue extravasation, and cerebral edema on magnetic resonance imaging. Mechanistic, investigations using flow cytometry and in vitro oxygen glucose deprivation/reoxygenation models assessed whether IL-25 acted directly on brain microvascular endothelial cells (BMECs) or indirectly through immune pathways. Cytokine array and Western blot analyses were used to identify downstream mediators, and single-cell RNA sequencing was performed to characterize IL-25-induced transcriptional changes. Neurological function was assessed using the modified Neurological Severity Score, rotarod test, and Morris water maze.

Results: IL-25 levels increased significantly in the cortex and serum after TBI, peaking at day 3, with neurons and BMECs identified as the main sources. Exogenous IL-25 administration alleviated BBB dysfunction, restored tight junction protein expression, reduced Evans Blue leakage, and diminished cerebral edema. Mechanistically, IL-25 acted indirectly by activating brain-resident group 2 innate lymphoid cells to secrete interleukin-13 (IL-13), rather than acting directly on BMECs. IL-13 preserved BBB integrity by suppressing C-X-C motif chemokine ligand 10 (CXCL-10) expression and inhibiting endothelial pyroptosis. Single-cell RNA sequencing confirmed upregulation of BBB-protective genes such as Tiam1, Hsp90aa1, and Hes1, along with activation of tight junction and transforming growth factor-β signaling pathways. IL-25 treatment improved both motor coordination and cognitive performance after TBI.

Conclusions: IL-25 promotes BBB repair and enhances neurological recovery following TBI by inducing ILC2-derived IL-13, which suppresses CXCL-10 and endothelial pyroptosis. These findings identify IL-25 as a potential therapeutic target for mitigating BBB damage and improving outcomes after TBI.

Astrocytes are the primary source of high mobility group box-1 (HMGB1) which is intimately associated with aging and related disease in central nervous system (CNS). However, the multi-localization and multifunctional characteristics of HMGB1 indicate that it may regulate brain aging through various pathways and mechanisms which are not yet clearly defined. In this study, we find that the expression of HMGB1 decreases with aging in both human and mouse astrocytes. Conditional knockout of Hmgb1 in astrocytes induces the exacerbation of mice aging. Specifically, by establishing a nuclear HMGB1 depletion model and interfering extracellular HMGB1, we find that nuclear HMGB1 is anti-senescent whereas extracellular HMGB1 is pro-senescent. Inhibiting HMGB1 nuclear export to enhance its nuclear retention effectively alleviates astrocyte senescence. Together, promoting the nuclear retention of HMGB1 is a new strategy for attenuating brain aging and related disorders.

Progranulin (PGRN) is a neurotrophic and anti-inflammatory factor produced mainly by neurons and microglia in the central nervous system. Progranulin haploinsufficiency causes frontotemporal dementia (FTD). It is unclear to what extent neuronal versus microglial PGRN deficiency contributes to FTD pathology. In this study, we restored progranulin in neurons in progranulin knockout mice using Nestin-driven expression of mouse Grn transgene in a knockout background (NesGrn KOBG). They were compared with full PGRN KO mice and floxed control mice that carry a loxP flanked STOP codon in front of mGrn transgene (Grn-flfl). The expected neuron-only PGRN rescue was confirmed at RNA and protein level in brain tissue and primary cells, and single nucleus RNA sequencing. Despite neuronal PGRN-restoration, there was no difference in microgliosis, astrogliosis, and microglia phenotypes as assessed by histology, microglia morphometry and bulk RNAseq showing strong upregulation of microglia-associated genes equally in both KO lines. However, a microglial subpopulation with a phagocyte signature expressing Gpnmb, Lgals3, Atp6v0d2 and Apobec1 occurred only in PGRN KO brain, and accordingly, the loss of synapses and dendritic spines, which is caused by excessive synaptic pruning in PGRN KO mice, was partially attenuated in NesGrn KOBG mice. Lipidomic studies showed that phosphatidylserine eat-me-signals were increased in PGRN KO but not in NesGrn KOBG brain. Furthermore, some neuronal genes involved in axonal structure and dynamics were co-restored with progranulin in NesGrn KOBG mice. However, the modest improvement of neuronal health was not associated with an improvement of FTD-like behavior including hyperactivity, compulsive licking and impaired avoidance learning and memory. The results suggest that (still) viable neurons do not provide (sufficient) progranulin to prevent microgliosis but may shape the phenotype by presenting or hiding eat-me signals. Nonetheless, neuron-only-progranulin restoration may be insufficient to halt the progression of FTD.

MicroRNAs (miRNAs) canonically regulate post-transcriptional gene expression, but they can also serve as ligands for Toll-like receptors (TLRs). These receptors and their associated signalling pathways contribute to inflammatory responses involved in various central nervous system (CNS) diseases, including Alzheimer's disease (AD). Here, we investigated the effects of extracellularly delivered miRNA in the context of neuroinflammation. We identified several miRNAs specifically dysregulated in AD and/or neuroinflammatory states, which directly activate the single-stranded RNA sensors mouse TLR7 and human TLR7/8. Among them, extracellular miR-29a-5p induced cytokine and chemokine release from murine primary microglia, altered expression of TLR signalling elements, and enhanced Aβ phagocytosis. Furthermore, this miRNA induced neuronal injury dependent on microglial TLR7 expression, but also in a cell-autonomous fashion, in vitro. Intrathecal injection of miR-29a-5p into mice led to microglial accumulation and neuronal injury in the cerebral cortex through TLR7 after 3 days. Brains of wild-type and APP/PS1 mice, an established AD mouse model, treated with multiple intrathecal miR-29a-5p injections over 120 days exhibited changes in cytokine/chemokine expression and neuronal injury. RNAseq analysis of the cerebral cortex of both miRNA-treated genotypes revealed downregulation of MAPK-associated pathways.Our study establishes AD-associated miRNAs such as miR-29a-5p as TLR7 agonists and signalling molecules for microglia, thereby altering the neuroinflammatory response.