Role of rno-miR-124-3p in regulating MCT1 expression in rat brain after permanent focal cerebral ischemia

Exosomes derived from microglia overexpressing miR-124-3p alleviate neuronal endoplasmic reticulum stress damage after repetitive mild traumatic brain injury

JOURNAL/nrgr/04.03/01300535-202409000-00033/figure1/v/2024-01-16T170235Z/r/image-tiff We previously reported that miR-124-3p is markedly upregulated in microglia-derived exosomes following repetitive mild traumatic brain injury. However, its impact on neuronal endoplasmic reticulum stress following repetitive mild traumatic brain injury remains unclear. In this study, we first used an HT22 scratch injury model to mimic traumatic brain injury, then co-cultured the HT22 cells with BV2 microglia expressing high levels of miR-124-3p. We found that exosomes containing high levels of miR-124-3p attenuated apoptosis and endoplasmic reticulum stress. Furthermore, luciferase reporter assay analysis confirmed that miR-124-3p bound specifically to the endoplasmic reticulum stress-related protein IRE1α, while an IRE1α functional salvage experiment confirmed that miR-124-3p targeted IRE1α and reduced its expression, thereby inhibiting endoplasmic reticulum stress in injured neurons. Finally, we delivered microglia-derived exosomes containing miR-124-3p intranasally to a mouse model of repetitive mild traumatic brain injury and found that endoplasmic reticulum stress and apoptosis levels in hippocampal neurons were significantly reduced. These findings suggest that, after repetitive mild traumatic brain injury, miR-124-3 can be transferred from microglia-derived exosomes to injured neurons, where it exerts a neuroprotective effect by inhibiting endoplasmic reticulum stress. Therefore, microglia-derived exosomes containing miR-124-3p may represent a novel therapeutic strategy for repetitive mild traumatic brain injury.

Astrocyte-derived extracellular vesicles inhibit the abnormal activation of immune function in neonatal mice with hypoxic-ischemic brain damage by carrying miR-124-3p

OBJECTIVE

Hypoxic-ischemic brain damage (HIBD) is among the leading causes of neonatal death worldwide. miR-124-3p can be utilized as a potential diagnostic and prognostic biomarker for perinatal asphyxia and HI encephalopathy in newborns. This study investigated the protective effect and mechanism of miR-124-3p in astrocyte-derived extracellular vesicles (ADEVs) in HIBD.

METHODS

    The neonatal mouse model of HIBD was established. Astrocytes were transfected with the miR-124-3p inhibitor, followed by isolation and identification of ADEVs (ADEVs + inhi miR). HIBD mice were injected with ADEVs or ADEVs + inhi miR through the lateral ventricle, and neurological function was evaluated based on the modified neurological severity score (mNSS). The infarct volume of mice and the morphological modifications of neurons were observed by TTC staining and hematoxylin-eosin staining. The contents of SOD, GSH-Px, CAT, and MDA in the hippocampus were measured. The neuronal apoptosis, the activation of MPO+ neutrophils, NK cells, and CD3+ cells in CA1 region of the hippocampus was determined by means of TUNEL staining and immunofluorescence.

RESULTS

ADEVs alleviated HIBD in neonatal mice. ADEVs could intrinsically protect mice from HIBD by reducing oxidative stress and apoptosis in hippocampal tissue. ADEVs inhibited the positive expression of MPO+ neutrophils, NK cells, and CD3+ cells in HIBD neonatal mice. ADEVs inhibited the hippocampal immune cells by delivering miR-124-3p in neonatal HIBD mice.

CONCLUSION

ADEVs can inhibit the abnormal activation of immune function in HIBD by delivering miR-124-3p, thereby eliciting a protective effect on brain damage in neonatal mice.

miRNA-124 alleviated memory impairment induced by d-galactose rapidly in male rats via microglia polarization

MiRNA-124 has been considered to play a significant role in the formation of memory and a variety of neurodegenerative diseases. In this study, the aim is to verify whether miRNA-124 is involved in memory impairment induced by d-galactose, and explore the underlying neuroprotective mechanism. The results revealed that rapid administration of d-galactose (1000 mg/kg subcutaneously) in mice caused memory impairments, as determined by Novel Object Recognition test, Morris Water Maze test, and histological assessments. MiRNA-124 agomir is stereotactic injected into hippocampus, thus alleviated memory impairment induced by d-galactose and reversed the neural damage and neuroinflammation. Furthermore, the results of molecular biological analysis and immunohistochemistry revealed that miRNA-124 markedly reduced neuroinflammation induced by d-galactose through polarization of microglia as determined by detection of ionized calcium binding adapter molecule 1 (Iba-1), inducible nitric oxide synthase (iNOS) and arginase-1(Arg-1), which also downregulated inflammatory mediators, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and upregulated IL-4 and IL-10. Hence, taken together, the results of the present study suggested that miRNA-124 showed a significant negative correlation with memory impairment and neuroinflammation induced by d-galactose rapidly, possibly via polarization of microglia from M1 to M2. It is possible that miRNA-124 can be used as a new target for the pathogenesis of memory impairment, including age-associated neurodegenerative diseases such as Alzheimer's disease.

Purpurogallin Reverses Neuronal Apoptosis and Enhances "M2" Polarization of Microglia Under Ischemia via Mediating the miR-124-3p/TRAF6/NF-κB Axis

Purpurogallin (PPG) has been demonstrated to exert an anti-inflammatory function in neurological diseases. This study aimed at investigating the role of PPG on microglial polarization post ischemic stroke as well as the underlying mechanism. Mouse hippocampal neurons HT-22 and microglial BV2 cells were treated by oxygen and glucose deprivation to simulate an in-vitro ischemia model. qRT-PCR and ELISA examined expression of cytokines in microglia. CCK8 and flow cytometry measured HT-22 cell viability and apoptosis, respectively. The levels of miR-124-3p and TRAF6/NF-κB were determined. A mouse cerebral ischemia model was set up using middle cerebral artery occlusion (MCAO) method. After being dealt with PPG, the neurological functions, brain edema, neuronal apoptosis, and microglia activation of the mice were evaluated. As suggested by the results, PPG transformed "M1" to "M2" polarization of BV2 cells, and abated HT-22 cell apoptosis. PPG enhanced the neurological functions, alleviated brain edema, and decreased neuroinflammatory responses, and neuronal apoptosis in the brain lesions of MCAO mice. Furthermore, PPG enhanced miR-124-3p and repressed the TRAF6/NF-κB pathway. miR-124-3p suppressed the TRAF6/NF-κB pathway by targeting TRAF6. Collectively, PPG alleviates ischemia-induced neuronal damage and microglial inflammation by modulating the miR-124-3p/TRAF6/NF-κB pathway.

Transcranial Direct-Current Stimulation Regulates MCT1-PPA-PTEN-LONP1 Signaling to Confer Neuroprotection After Rat Cerebral Ischemia-Reperfusion Injury

Propionic acid (PPA) is a critical metabolite involved in microbial fermentation, which functions to reduce fat production, inhibit inflammation, and reduce serum cholesterol levels. The role of PPA in the context of cerebral ischemia-reperfusion (I/R) injury has yet to be clarified. Increasing evidence indicate that transcranial direct-current stimulation (tDCS) is a safe approach that confers neuroprotection in cerebral ischemia injury. Here, we show that the levels of PPA were reduced in the ischemic brain following a rat cerebral I/R injury and in the cultured rat cortical neurons after oxygen-glucose deprivation (OGD), an in vitro model of ischemic injury. We found that the decreased levels of transporter protein monocarboxylate transporter-1 (MCT1) were responsible for the OGD-induced reduction of PPA. Supplementing PPA reduced ischemia-induced neuronal death after I/R. Moreover, our results revealed that the neuroprotective effect of PPA is mediated through downregulation of phosphatase PTEN and subsequent upregulation of Lon protease 1 (LONP1). We demonstrated that direct-current stimulation (DCS) increased MCT1 expression and PPA level in OGD-insulted neurons, while tDCS decreased the brain infarct volume in the MCAO rats via increasing the levels of MCT1 expression and PPA. This study supports a potential application of tDCS in ischemic stroke.

Monocarboxylate Transporter 1 May Benefit Cerebral Ischemia via Facilitating Lactate Transport From Glial Cells to Neurons

Monocarboxylate transporter 1 (MCT1) is expressed in glial cells and some populations of neurons. MCT1 facilitates astrocytes or oligodendrocytes (OLs) in the energy supplement of neurons, which is crucial for maintaining the neuronal activity and axonal function. It is suggested that MCT1 upregulation in cerebral ischemia is protective to ischemia/reperfusion (I/R) injury. Otherwise, its underlying mechanism has not been clearly discussed. In this review, it provides a novel insight that MCT1 may protect brain from I/R injury via facilitating lactate transport from glial cells (such as, astrocytes and OLs) to neurons. It extensively discusses (1) the structure and localization of MCT1; (2) the regulation of MCT1 in lactate transport among astrocytes, OLs, and neurons; and (3) the regulation of MCT1 in the cellular response of lactate accumulation under ischemic attack. At last, this review concludes that MCT1, in cerebral ischemia, may improve lactate transport from glial cells to neurons, which subsequently alleviates cellular damage induced by lactate accumulation (mostly in glial cells), and meets the energy metabolism of neurons.

Bone marrow mesenchymal stem cells-derived exosomal microRNA-124-3p attenuates hypoxic-ischemic brain damage through depressing tumor necrosis factor receptor associated factor 6 in newborn rats

Mesenchymal stem cells (MSCs)-derived exosomes (Exo) are beneficial in the use of brain damages. Restrictively, the mechanism of Exo expressing miR-124-3p in hypoxic-ischemic brain damage (HIBD) is not completely comprehended. Thereupon, this work was put forward to reveal the action of bone marrow MSCs-derived Exo (BMSCs-Exo) expressing miR-124-3p in the illness. BMSCs were isolated and transfected with miR-124-3p agomir. Then, BMSCs-Exo were extracted and identified. The newborn HIBD rats were injected with miR-124-3p-modified BMSCs-Exo or tumor necrosis factor receptor associated factor 6 (TRAF6)-related vectors. Next, neurological functions, neuron pathological and structural damages, oxidative stress and neuronal apoptosis were observed. miR-124-3p and TRAF6 expression was tested, along with their targeting relationship. miR-124-3p was down-regulated, and TRAF6 was up-regulated in newborn HIBD rats. miR-124-3p targeted TRAF6. BMSCs-Exo improved neurological functions, alleviated neuron pathological and structural damages, suppressed oxidative stress and reduced neuronal apoptosis in newborn HIBD rats, whereas BMSCs-Exo-mediated effects were enhanced by restoring miR-124-3p. Silencing TRAF6 attenuated HIBD in newborn rats, but overexpression of TRAF6 reversed the protective role of miR-124-3p-overexpressing BMSCs-Exo. This work makes it comprehensive that up-regulated exosomal miR-124-3p ameliorates HIBD in newborn rats by targeting TRAF6, which replenishes the potential agents for curing HIBD.

Lactate Supply from Astrocytes to Neurons and its Role in Ischemic Stroke-induced Neurodegeneration

Glucose transported to the brain is metabolized to lactate in astrocytes and supplied to neuronal cells via a monocarboxylic acid transporter (MCT). Lactate is used in neuronal cells for various functions, including learning and memory formation. Furthermore, lactate can block stroke-induced neurodegeneration. We aimed to clarify the effect of astrocyte-produced lactate on stroke-induced neurodegeneration. Previously published in vivo and in vitro animal and cell studies, respectively, were searched in PubMed, ScienceDirect, and Web of Science. Under physiological conditions, lactate production and release by astrocytes are regulated by changes in lactate dehydrogenase (LDH) and MCT expression. Moreover, considering stroke, lactate production and supply are regulated through hypoxia-inducible factor (HIF)-1α expression, especially with hypoxic stimulation, which may promote neuronal apoptosis; contrastingly, neuronal survival may be promoted via HIF-1α. Stroke stimulation could prevent neurodegeneration through the strong enhancement of lactate production, as well as upregulation of MCT4 expression to accelerate lactate supply. However, studies using astrocytes derived from animal stroke models revealed significantly reduced lactate production and MCT expression. These findings suggest that the lack of lactate supply may strongly contribute to hypoxia-induced neurodegeneration. Furthermore, diminished lactate supply from astrocytes could facilitate stroke-induced neurodegeneration. Therefore, astrocyte-derived lactate may contribute to stroke prevention.

Loss of monocarboxylate transporter 1 aggravates white matter injury after experimental subarachnoid hemorrhage in rats

Monocarboxylic acid transporter 1 (MCT1) maintains axonal function by transferring lactic acid from oligodendrocytes to axons. Subarachnoid hemorrhage (SAH) induces white matter injury, but the involvement of MCT1 is unclear. In this study, the SAH model of adult male Sprague-Dawley rats was used to explore the role of MCT1 in white matter injury after SAH. At 48 h after SAH, oligodendrocyte MCT1 was significantly reduced, and the exogenous overexpression of MCT1 significantly improved white matter integrity and long-term cognitive function. Motor training after SAH significantly increased the number of ITPR2⁺SOX10⁺ oligodendrocytes and upregulated the level of MCT1, which was positively correlated with the behavioral ability of rats. In addition, miR-29b and miR-124 levels were significantly increased in SAH rats compared with non-SAH rats. Further intervention experiments showed that miR-29b and miR-124 could negatively regulate the level of MCT1. This study confirmed that the loss of MCT1 may be one of the mechanisms of white matter damage after SAH and may be caused by the negative regulation of miR-29b and miR-124. MCT1 may be involved in the neurological improvement of rehabilitation training after SAH.

MicroRNAs as Potential Orchestrators of Alzheimer's Disease-Related Pathologies: Insights on Current Status and Future Possibilities

Alzheimer's disease (AD) is a progressive and deleterious neurodegenerative disease, strongly affecting the cognitive functions and memory of seniors worldwide. Around 58% of the affected patients live in low and middle-income countries, with estimates of increasing deaths caused by AD in the coming decade. AD is a multifactor pathology. Mitochondrial function declines in AD brain and is currently emerging as a hallmark of this disease. It has been considered as one of the intracellular processes severely compromised in AD. Many mitochondrial parameters decline already during aging; mitochondrial efficiency for energy production, reactive oxygen species (ROS) metabolism and the de novo synthesis of pyrimidines, to reach an extensive functional failure, concomitant with the onset of neurodegenerative conditions. Besides its impact on cognitive functions, AD is characterized by loss of synapses, extracellular amyloid plaques composed of the amyloid-β peptide (Aβ), and intracellular aggregates of hyperphosphorylated Tau protein, accompanied by drastic sleep disorders, sensory function alterations and pain sensitization. Unfortunately, till date, effective management of AD-related disorders and early, non-invasive AD diagnostic markers are yet to be found. MicroRNAs (miRNAs) are small non-coding nucleic acids that regulate key signaling pathway(s) in various disease conditions. About 70% of experimentally detectable miRNAs are expressed in the brain where they regulate neurite outgrowth, dendritic spine morphology, and synaptic plasticity. Increasing studies suggest that miRNAs are intimately involved in synaptic function and specific signals during memory formation. This has been the pivotal key for considering miRNAs crucial molecules to be studied in AD. MicroRNAs dysfunctions are increasingly acknowledged as a pivotal contributor in AD via deregulating genes involved in AD pathogenesis. Moreover, miRNAs have been proved to control pain sensitization processes and regulate circadian clock system that affects the sleep process. Interestingly, the differential expression of miRNA panels implies their emerging potential as diagnostic AD biomarkers. In this review, we will present an updated analysis of miRNAs role in regulating signaling processes that are involved in AD-related pathologies. We will discuss the current challenges against wider use of miRNAs and the future promising capabilities of miRNAs as diagnostic and therapeutic means for better management of AD.

Synchrotron Radiation-Based FTIR Microspectroscopic Imaging of Traumatically Injured Mouse Brain Tissue Slices

Traumatic brain injury (TBI) is a health problem of global concern because of its serious adverse effects on public health and social economy. A technique that can be used to precisely detect TBI is highly demanded. Here, we report on a synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopic imaging technique that can be exploited to identify TBI-induced injury by examining model mouse brain tissue slices. The samples were first examined by conventional histopathological techniques including hematoxylin and eosin (H&E) staining and 2,3,5-triphenyltetrazolium chloride staining and then spectroscopically imaged by SR-FTIR. SR-FTIR results show that the contents of protein and nucleic acid in the injured region are lower than their counterparts in the normal region. The injured and normal regions can be unambiguously distinguished from each other by the principle component analysis of the SR-FTIR spectral data corresponding to protein or nucleic acid. The images built from the spectral data of protein or nucleic acid clearly present the injured region of the brain tissue, which is in good agreement with the H&E staining image and optical image of the sample. Given the label-free and fingerprint features, the demonstrated method suggests potential application of SR-FTIR spectroscopic mapping for the digital and intelligent diagnosis of TBI by providing spatial and chemical information of the sample simultaneously.

miR‑124‑3p regulates angiogenesis in peripheral arterial disease by targeting STAT3

Peripheral arterial disease (PAD) is the third leading cause of cardiovascular morbidity worldwide, after coronary artery disease and stroke. As endogenous regulators of gene expression, microRNAs (miRs) are implicated in the development and progression of various diseases, including types of cancer, autoimmune diseases and heart diseases. In the present study, the role of miR-124-3p in PAD was investigated. The reverse transcription-quantitative PCR results indicated that the expression levels of miR-124-3p were significantly increased in the ischemic tissue of the hindlimb ischemia (HLI) model and in hypoxic human umbilical vein endothelial cells compared with the corresponding control groups. Proliferation, wound healing and tube formation assays demonstrated the inhibition of miR-124-3p on angiogenesis in vitro and the HLI model indicated the same function of miR-124-3p in vivo. A dual-luciferase reporter revealed STAT3 as the target of miR-124-3p. The expression levels of miR-124-3p in human blood were negatively correlated with ankle-brachial index, which is an index for the evaluation of the severity of PAD. Collectively, the present study indicated that miR-124-3p was a critical regulator of angiogenesis in PAD, and a potential diagnostic, prognostic and therapeutic target for PAD.