Post-stroke acute inhibition of aquaporin 4 (AQP4) is known to exacerbate inflammation and apoptosis, yet the underlying mechanisms are not fully understood. The objective of this study was to investigate the specific mechanism of inflammation and apoptosis following cerebral ischemia–reperfusion (I/R) injury using the AQP4-specific inhibitor, N-(1,3,4-thiadiazol-2-yl) pyridine-3-carboxamide dihydrochloride (TGN-020). Ischemic stroke was induced in mice using the middle cerebral artery occlusion (MCAO) model. The C57/BL6 mice were randomly divided into three groups as follows: sham operation, I/R 48 h, and TGN-020 + I/R 48 h treatment. All mice were subjected to a series of procedures. These procedures encompassed 2,3,5-triphenyltetrazolium chloride (TTC) staining, neurological scoring, fluorescence tracing, western blotting, immunofluorescence staining, and RNA sequencing (RNA-seq). The glymphatic function in the cortex surrounding cerebral infarction was determined using tracer, glial fibrillary acid protein (GFAP), AQP4 co-staining, and beta-amyloid precursor protein (APP) staining; differential genes were detected using RNA-seq. The influence of TGN-020 on the extracellular signal-regulated kinase 1/2 (ERK) 1/2 pathway was confirmed using the ERK1/2 pathway agonists Ro 67–7467. Additionally, we examined the expression of inflammation associated with microglia and astrocytes after TGN-020 and Ro 67–7467 treatment. Compared with I/R group, TGN-020 alleviated glymphatic dysfunction by inhibiting astrocyte proliferation and reducing tracer accumulation in the peri-infarct area. RNA-seq showed that the differentially expressed genes were mainly involved in the activation of astrocytes and microglia and in the ERK1/2 pathway. Western blot and immunofluorescence further verified the expression of associated inflammation. The inflammation and cell apoptosis induced by I/R are mitigated by TGN-020. This mitigation occurs through the improvement of glymphatic function and the inhibition of the ERK1/2 pathway.

Both glymphatic system dysfunction and inflammatory response aggravate neurological dysfunction after subarachnoid hemorrhage (SAH). Studies have shown that β-hydroxybutyrate (BHB) may mitigate painful diabetic neuropathy (PDN) by upregulating SNTA1 expression and reinstating AQP4 polarity. However, the potential of BHB to ameliorate glymphatic system function and inflammatory response in SAH mice remains uncertain. The SAH models were constructed by injection of arterial blood into cisterna Magana. Three groups of C57 mice were randomly assigned: Sham, SAH, and BHB. All mice were subjected to neurological function assessment, western blot, immunofluorescence double staining, and RNA-seq. Glymphatic system function was examined with tracer and immunofluorescence double staining, and the differential genes were examined with RNA-seq. In addition, the expression of related inflammation was detected. Compared with the SAH group, BHB reinstated AQP4 polarization by upregulating SNTA1 protein to enhance the glymphatic system. According to RNA-seq, the different genes were primarily connected to microglia activation, astrocytes, and inflammation. Western blot and immunofluorescence further confirmed that the related inflammatory protein expression levels were upregulated. BHB attenuated neuroinflammation after SAH. Ultimately, it can mitigate the neurological deficits in SAH mice. The study reveals a novel mechanism that BHB treatment mitigates neurologic impairment in SAH mice. We propose that BHB may play a neuroprotective effect by enhancing glymphatic system function and attenuating neuroinflammatory subarachnoid hemorrhage.

Limb ischemic postconditioning (LPostC) is an innovative treatment for ischemia/reperfusion injury (IRI). However, its mechanisms have not yet been elucidated. Herein, we assessed the importance of SIRT1/PGC-1α signaling in LPostC neuroprotection following cerebral I/R injury in rats. In this study, we used 40 male SD rats that were separated into sham, I/R, LPostC, and LPostC + EX-527 (SIRT1 inhibitor) groups (each with 10 rats), with a middle cerebral artery occlusion (MCAO) model used to induce IRI. LPostC was induced via three cycles of bilateral femoral artery occlusion and non-occlusion. At 24 h, we examined SIRT1 and PGC-1α protein levels by western blotting in ischemic areas. The mRNA levels of SIRT1, PGC-1α, NRF-1 and CytoC1 in the ischemic area were assessed by qRT-PCR. We also quantified neurological deficit scores and evaluated cerebral infarct volume by TTC staining. TUNEL staining was used to evaluate the apoptotic rates in neurons. In addition, antioxidant SOD activity and MDA levels were measured by the Microplate Reader. Our findings indicated that LPostC increased the protein and mRNA levels of SIRT1 and PGC-1α in cerebral ischemic tissue, then up-regulated the downstream protein NRF-1, down-regulated CytoC1, and improved mitochondrial function, thereby reducing brain damage. LPostC relieved cerebral IRI via reducing the size of the cerebral infarct, neuronal apoptosis, and neurological deficits. Meanwhile LPostC increased SOD activity and reduced MDA content in brain tissue. Treatment with EX-527 reversed the protection of LPostC after IRI (all P < 0.05). This suggests that LPosC may protect against cerebral IRI at least in part via up-regulating the SIRT1/PGC-1α signaling pathway, thereby increasing the individual's ability to resist oxidative stress.

Delayed neuronal damage can be caused or aggravated after cerebral ischemia-reperfusion (I/R) injury. Recent studies have shown that glymphatic system dysfunction after cerebral ischemia-reperfusion injury is involved in ischemic brain edema and neuroinflammation, thereby regulating cerebral ischemia-reperfusion injury. The aim of this study is to investigate the changes of glymphatic system after cerebral ischemia-reperfusion injury and whether limb remote ischemic postconditioning (LRIP) can improve the function of glymphatic system to protect the brain. To establish a focal brain I/R injury mouse model, this study utilized the middle cerebral artery occlusion/reperfusion (MCAO/R) method. The present study classified eight-week-old C57BL/6 male mice into three groups. The changes in glymphatic function in different periods of ischemia and reperfusion were analyzed through immunofluorescence, transmission electron microscopy (TEM), and Western-Blot (WB) assays. The contents of the evaluation included cerebrospinal fluid flow, swelling degree of brain tissue, aquaporin-4 (AQP4) expression and polarization, and amyloid-β (Aβ) excretion. In the early stages of cerebral ischemia, cerebrospinal fluid (CSF) flow is disturbed, accompanied by a decrease in AQP4 polarization. The polarity of AQP4 decreased from 12 h to 72 h of reperfusion, the Aβ deposition. LRIP can increase the expression of β-DG and AQP4 polarization, reduce the deposition of Aβ, improve the function of the glymphatic system, and reduce the expression of AQP4 to play A protective role in brain. Glymphatic system impaired after cerebral ischemia-reperfusion injury in mice. LRIP may play a neuroprotective role by improving glymphatic function after I/R.

Background: The function of the glymphatic system (GS) in patients with depressive disorders (DDs), as well as its relationship with clinical characteristics and plasma glial fibrillary acidic protein (GFAP) levels, remains poorly understood. In this study, the Diffusion Tensor Imaging-Analysis along the Perivascular Space (DTI-ALPS) method was applied to assess glymphatic function in individuals with DDs. Correlations between the DTI-ALPS index, clinical features of DDs, and plasma GFAP concentrations were analyzed to explore potential underlying mechanisms of DDs. Methods: Between August 2022 and March 2024, a total of 72 patients diagnosed with DD at the Department of Psychiatry and Psychology at the Affiliated Hospital of Guilin Medical University and 44 healthy controls (HCs) were enrolled in the study. Detailed information was collected and recorded for all participants, including demographic characteristics (sex, age, and education level), disease-related data (smoking and alcohol history, illness duration, and relevant clinical scales), neuroimaging parameters [brain magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) metrics], and fasting morning venous blood samples. GS function was assessed using the DTI-ALPS index, and plasma GFAP concentration was measured via enzyme-linked immunosorbent assay (ELISA). Chi-squared tests, non-parametric tests, and partial Spearman’s rank correlation analyses were employed to examine the relationships between the DTI-ALPS index and clinical features of depression, as well as plasma GFAP levels. Results: The DTI-ALPS index was significantly lower in the persistent depressive disorder (PDD) group compared to both the HC (P<0.001) and non-persistent depressive disorder (NPDD) (P<0.001) groups. Conversely, plasma GFAP concentrations were significantly elevated in the PDD group relative to the HC (P<0.001) and NPDD (P0.05). Partial Spearman’s rank correlation analyses were performed controlling for sex, age, and smoking. P values were adjusted for multiple comparisons using the Benjamini-Yekutieli false discovery rate (FDR) procedure, and are reported as q values. These analyses showed that the DTI-ALPS index across all the study participants was negatively correlated with the plasma GFAP levels (r=−0.290, q=0.009), indicating a significant correlation. No other variables showed statistically significant associations with the DTI-ALPS index (all q>0.05). Further, GFAP concentrations were positively correlated with illness duration, Hamilton Depression Rating Scale (HAMD-17), Patient Health Questionnaire-9 (PHQ-9), and Pittsburgh Sleep Quality Index (PSQI) scores (all q<0.05), and negatively correlated with Mini-Mental State Examination (MMSE) scores (r=–0.230, q=0.012). Conclusions: The DTI-ALPS index was found to be lower in the PDD group compared to both the HC and NPDD groups, and was correlated with plasma GFAP levels. These findings suggest that the covariation between glymphatic dysfunction and glial activation may represent a potential biological feature in the progression of DDs.

Background The acute inhibition of glymphatic after stroke has been shown to aggravate post-stroke inflammation and apoptosis; however, the related mechanisms remain ambiguous. This study aimed to assess the specific mechanism of inflammation and apoptosis after cerebral ischemia-reperfusion (I/R) injury by improving glymphatic dysfunction. Materials and Methods Ischemic stroke was induced using the mice middle cerebral artery occlusion (MCAO) model. The C57/BL6 mice were randomly divided into three groups as follows: sham operation, Ischemia-reperfusion (I/R) 48 hours, and N-(1,3,4-thiadiazol-2-yl) pyridine-3-carboxamide dihydrochloride (TGN-020) + I/R 48 hours treatment. Neurological examination, TTC, fluorescence tracer, western blot, and immunofluorescence staining were performed in all mice in sequence. The glymphatic function in the cortex surrounding cerebral infarction was determined using tracer, glial fibrillary acid protein (GFAP), aquaporin-4 (AQP4) co-staining, and beta-amyloid precursor protein (APP) staining, differential genes were detected using RNA-seq. Iba-1, IL-1β, TNF-α, cleaved caspase 3, and tunel staining were used to verify inflammation and apoptosis after TGN-020 treatment. Results Compared with I/R group, the degree of neurological deficit was alleviated in TGN-020 group. TGN-020 alleviated glymphatic dysfunction by improving astrocyte proliferation and reducing tracer accumulation in the peri-infarct area. RNA-seq showed that the differentially expressed genes were mainly involved in the activation of astrocytes and microglia, and involved in the ERK pathway. RNA-seq was verified by western blot and immunofluorescence. Conclusions The inflammation of astrocytes and microglia after cerebral ischemia-reperfusion (I/R) is closely related to the glymphatic system. The improvement of glymphatic function may play a neuroprotective role after cerebral I/R by inhibiting inflammation through ERK pathway.