Bone marrow stromal cells-derived exosomes reduce neurological damage in traumatic brain injury through the miR-124-3p/p38 MAPK/GLT-1 axis.

BACKGROUND: Mounting evidence indicates that stem cell-derived exosomal miRNAs have therapeutic effects on traumatic brain injury (TBI). This research is focused on exploring the molecular processes of miR-124-3p obtained from bone marrow stromal cells-derived exosomes (BMSCs-Exos) in attenuating posttraumatic glutamate-mediated excitotoxicity. METHODS: We created a TBI rat model and analyzed the expression profile of miRNA through miRNA microarray. The miR-124-3p and p38 MAPK levels were analyzed utilizing RT-qPCR and western blotting. Dual-luciferase reporter (DLR) assay showed the targeting relationship between miR-124-3p and p38 MAPK. We subsequently conducted a TUNEL assay and flow cytometry to evaluate the neuronal apoptotic rate in an in vitro glutamate-mediated excitotoxicity model treated with BMSCs-Exos enriched with miR-124-3p (BMSCs-ExosmiR-124-3p). Moreover, the levels of p38 MAPK and glutamate transporter-1 (GLT-1) were measured by western blotting. Furthermore, BMSCs-ExosmiR-124-3p were administered to the TBI rats, and their neuroprotective effects were observed using western blotting, immunohistochemistry, histological staining, magnetic resonance imaging (MRI), and Morris water maze (MWM). RESULTS: The results revealed that the brains of TBI rats exhibited lowered miR-124-3p and enhanced p38 MAPK levels. DLR assay demonstrated miR-124-3p's role in targeting p38 MAPK and negatively regulating its expression. In vitro and in vivo studies confirmed that BMSCs-ExosmiR-124-3p attenuated glutamate-mediated excitotoxicity by downregulating p38 MAPK and upregulating GLT-1 expressions via transferring exosomal miR-124-3p. Moreover, histopathological evaluation and MRI results showed that BMSCs-ExosmiR-124-3p remarkably alleviated neuronal cell death and minimized the lesion volumes post-TBI. MWM outcomes illustrated that BMSCs-ExosmiR-124-3p treatment could substantially improve neurological function post-TBI. Furthermore, the effects of treatment with p38 MAPK inhibitor SB203580 were similar to BMSCs-ExosmiR-124-3p. CONCLUSION: Overall, the outcomes of the current report highlighted that BMSCs-ExosmiR-124-3p can lead to the upregulation of GLT-1 in TBI rat models by inhibiting the p38 MAPK signaling pathway, hence alleviating glutamate-mediated excitotoxicity and attenuating neurological damage post-TBI.

MTHFD2 suppresses glioblastoma progression via the inhibition of ERK1/2 phosphorylation.

Glioblastoma (GBM) is a WHO grade 4 tumor and is the most malignant form of glioma. Methylenetetrahydrofolate dehydrogenase 2 (MTHFD2), a mitochondrial enzyme involved in folate metabolism, has been reported to be highly expressed in several human tumors. However, little is known about the role of MTHFD2 in GBM. In this study, we aimed to explore the biological functions of MTHFD2 in GBM and identify the associated mechanisms. We performed experiments such as immunohistochemistry, Western blot, and transwell assays and found that MTHFD2 expression was lower in high-grade glioma than in low-grade glioma. Furthermore, a high expression of MTHFD2 was associated with a favorable prognosis, and MTHFD2 levels showed good prognostic accuracy for glioma patients. The overexpression of MTHFD2 could inhibit the migration, invasion, and proliferation of GBM cells, whereas its knockdown induced the opposite effect. Mechanistically, our findings revealed that MTHFD2 suppressed GBM progression independent of its enzymatic activity, likely by inducing cytoskeletal remodeling through the regulation of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation, thereby influencing GBM malignance. Collectively, these findings uncover a potential tumor-suppressor role of MTHFD2 in GBM cells. MTHFD2 may act as a promising diagnostic and therapeutic target for GBM treatment.

Exosomes derived from bone marrow mesenchymal stem cells attenuate neurological damage in traumatic brain injury by alleviating glutamate-mediated excitotoxicity.

BACKGROUND: Traumatic brain injury (TBI) is one of the major contributors to disability and death worldwide. Glutamate-mediated excitotoxicity, one of the secondary injuries occurring after TBI, leads to extreme neuronal apoptosis, and can be a potential target for intervention. Bone marrow mesenchymal stem cells-derived exosomes (BMSCs-Exos) have demonstrated neuroprotective effects on TBI. However, their precise role and the underlying mechanism by which they regulate glutamate-mediated excitotoxicity have not yet been determined. Therefore, this study aimed to determine whether BMSCs-Exos alleviate glutamate excitotoxicity post-TBI and their associated mechanism. METHODS: BMSCs-Exos were extracted from the BMSCs incubation medium and identified by transmission electron microscopy, nanoparticle trafficking analysis, and western blotting. The neuroprotective effects of BMSCs-Exos on glutamate excitotoxicity were investigated in the glutamate-mediated excitotoxicity neuronal cell model and the TBI rat model (TBI induced by controlled cortical impact) using western blotting and TUNEL assay. Cortical lesion samples were collected post-TBI on day-1 and day-14 to study histology. In addition, cortical lesion volume on days 1, 3 and 7 following TBI was determined using T2-weighted magnetic resonance imaging (MRI), and cognitive function was assessed at 4 weeks following TBI using the Morris water maze (MWM) test. RESULTS: BMSCs-Exos were observed to be spherical with a mean diameter of 109.9 nm, and expressed exosomal markers CD9, CD81 and TSG101. BMSCs-Exos were efficiently endocytosed by astrocytes after co-incubation for 24 h. In vitro studies revealed that 125 µM of glutamate significantly induced neuronal apoptosis, which was attenuated by BMSCs-Exos in astrocyte-neuron co-cultures. This attenuation was mediated by the upregulation of glutamate transporter-1 (GLT-1) level and the downregulation of p-p38 MAPK level in astrocytes. Similar results were obtained in vivo, wherein we verified that PKH67-labeled BMSCs-Exos administered intravenously could reach the perilesional cortex crossing the blood-brain barrier and significantly reduce glutamate levels in the perilesional cortex of the TBI rat, accompanied by increased GLT-1 level and downregulation in p-p38 MAPK level. Additionally, western blotting and TUNEL staining also revealed that BMSCs-Exos significantly downregulated the expression of pro-apoptosis markers, including cleaved caspase-3 and cleaved caspase-9, and attenuated neuronal apoptosis following TBI. Immunohistochemical analysis and Nissl staining showed that BMSCs-Exos significantly increased GLT-1-positive cells, and the number of apoptotic neurons decreased in the perilesional cortex. Moreover, MRI and MWM results revealed that BMSCs-Exos significantly minimized cortical lesion volume and ameliorated cognitive function after TBI. The underlying neuroprotective mechanism of BMSCs-Exos may be due to an increase in GLT-1 level in astrocytes by blocking the p38 MAPK signaling pathway. CONCLUSION: Taken together, our findings demonstrate that the implementation of BMSCs-Exos may be an effective prospective therapy for attenuating post-TBI neurological damage.