Inhibition of miR-134 Protects Against Hydrogen Peroxide-Induced Apoptosis in Retinal Ganglion Cells

BDNF Modulation by microRNAs: An Update on the Experimental Evidence

MicroRNAs can interfere with protein function by suppressing their messenger RNA translation or the synthesis of its related factors. The function of brain-derived neurotrophic factor (BDNF) is essential to the proper formation and function of the nervous system and is seen to be regulated by many microRNAs. However, understanding how microRNAs influence BDNF actions within cells requires a wider comprehension of their integrative regulatory mechanisms. Aim: In this literature review, we have synthesized the evidence of microRNA regulation on BDNF in cells and tissues, and provided an analytical discussion about direct and indirect mechanisms that appeared to be involved in BDNF regulation by microRNAs. Methods: Searches were conducted on PubMed.gov using the terms "BDNF" AND "MicroRNA" and "brain-derived neurotrophic factor" AND "MicroRNA", updated on 1 September 2023. Papers without open access were requested from the authors. One hundred and seventy-one papers were included for review and discussion. Results and Discussion: The local regulation of BDNF by microRNAs involves a complex interaction between a series of microRNAs with target proteins that can either inhibit or enhance BDNF expression, at the core of cell metabolism. Therefore, understanding this homeostatic balance provides resources for the future development of vector-delivery-based therapies for the neuroprotective effects of BDNF.

The role of miRNA134 in pathogenesis and treatment of intractable epilepsy: a review article

MicroRNA-134 (miRNA134) has emerged as a critical regulator in the pathogenesis of epilepsy, particularly in intractable cases resistant to conventional therapies. This review explores the multifaceted roles of miRNA134 in epileptogenesis, focusing on its influence on dendritic spine morphology and synaptic plasticity. Through its interactions with proteins such as LIM kinase 1 (LIMK1), Pumilio 2 (PUM2), and Tubby-like protein 1 (TULP1), miRNA134 modulates various molecular pathways implicated in epilepsy development. Preclinical studies have shown pro-mising results in targeting miRNA134 for mitigating seizure activity, highlighting its potential as a therapeutic target. Furthermore, miRNA134 holds promise as a biomarker for epilepsy diagnosis and prognosis, offering opportunities for personalized treatment approaches. However, further research is warranted to elucidate the precise mechanisms underlying miRNA134's effects and to translate these findings into clinical applications.

Mbd2 deficiency alleviates retinal cell apoptosisvia the miR-345-5p/Atf1 axis in high glucoseinjury and streptozotocin-induced diabetic mice

DNA methylation is considered to play an important role in the development of diabetic retinopathy. Here, our goal was to investigate the precise role of methyl-CpG binding domain protein 2 (Mbd2) in the apoptosis of retinal ganglion cells (RGCs) in the early diabetic retina. Mbd2 was significantly upregulated after high glucose (HG) treatment and played a proapoptotic role in RGCs during HG-induced apoptosis. Combining ChIP and gene microarray datasets, the results showed that Mbd2 possessed potential binding sites for miR-345-5p, thereby elevating the expression levels of miR-345-5p via the enhancement of promoter demethylation. Activating transcription factor 1 (Atf1) played an anti-apoptotic role during the process of apoptosis in RGCs and acted as the target gene for miR-345-5p. Furthermore, the number of surviving RGCs in the diabetic retina was increased in Mbd2-knockout mice when compared with wild-type mice and the visual function became better accordingly. Collectively, our data demonstrated that the HG-induced overexpression of Mbd2 in the retina was partly responsible for the apoptosis of retinal neuronal cells through the miR-345-5p/Atf1 axis. Therefore, the targeting of Mbd2 might represent a novel therapeutic strategy for the treatment of neurodegeneration in the early diabetic retina.

MicroRNAs in the aqueous humor of patients with different types of glaucoma

Purpose

The aim of the study was to compare the frequency and the level of expression of selected miRNAs in the aqueous humor of patients with various types of glaucoma.

Methods

The studied group consisted of 42 patients with glaucoma: 19 with primary open-angle glaucoma (POAG), 14 with pseudoexfoliation glaucoma (PEXG), 9 with primary angle closure glaucoma (PACG), and the control group of 36 patients with senile cataract without glaucoma. The real-time polymerase chain reaction method was used to analyze the expression of miRNAs.

Results

There were no significant differences in the frequency and the level of miRNA expression between various types of glaucoma. There was a tendency for hsa-miR-6722-3p and hsa-miR-184 to be expressed more frequently in PEXG and hsa-miR-1260b in POAG. The expression levels of hsa-miR-1260b and hsa-miR-6515-3p were correlated with age in POAG. Target annotation and functional analyses showed that genes targeted by the most frequently expressed miRNAs (hsa-miR-1202, -1260b, -184, -187-5p, -6515-3p, -6722-3p, and hsa-mir-4634) are involved mainly in response to hypoxia, cardiovascular system development, and apoptosis.

Conclusion

Hsa-miR-1260b was the most abundantly expressed among studied miRNAs and may be a potential biomarker of clinical status in PEXG and PACG.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00417-021-05214-z.

Dendrobium nobile Lindl. polysaccharides reduce cerebral ischemia/reperfusion injury in mice by increasing myeloid cell leukemia 1 via the downregulation of miR-134

OBJECTIVE

The traditional Chinese medicine, Dendrobium nobile Lindl. polysaccharides (DNLP), reportedly has neuroprotective effects. However, its effects following ischemic stroke remain unclear. This study aimed to explore the role and mechanism of DNLP in experimental models of inflammation and apoptosis.

METHODS

Inflammation and apoptosis were induced by in vivo ischemia/reperfusion and by in vitro oxygen glucose deprivation/reperfusion (OGD/R). In the in vivo model, immediately after the induction of cerebral ischemia, 50, 100, and 200 mg/kg DNLP were injected intraperitoneally. We subsequently detected indicators of neuronal damage.

RESULTS

Treatment with Dendrobium nobile Lindl. polysaccharide significantly reduced cerebral ischemic injury. After in vivo and in vitro middle cerebral artery occlusion/reperfusion or OGD/R-induced hypoxia injury, miR-134 expression in neurons was significantly increased. Altering the expression of miR-134 induced changes in myeloid cell leukemia 1 (MCL-1), one of its target proteins. In addition, DNLP significantly downregulated the in vivo and in vitro expression of miR-134 after ischemic injury, and influenced inflammation and apoptotic proteins by altering the level of MCL-1 protein. DNLP also had a protective effect on neurons damaged by OGD/R, which could improve cell survival rates and inhibit lactate dehydrogenase release as well as apoptosis.

CONCLUSIONS

DNLP may protect the brain and neurons from hypoxic damage in mice with ischemic stroke by activating MCL-1 and downregulating miR-134, providing a new therapeutic target for ischemic stroke.

Retinal miRNA Functions in Health and Disease

The health and function of our visual system relies on accurate gene expression. While many genetic mutations are associated with visual impairment and blindness, we are just beginning to understand the complex interplay between gene regulation and retinal pathologies. MicroRNAs (miRNAs), a class of non-coding RNAs, are important regulators of gene expression that exert their function through post-transcriptional silencing of complementary mRNA targets. According to recent transcriptomic analyses, certain miRNA species are expressed in all retinal cell types, while others are cell type-specific. As miRNAs play important roles in homeostasis, cellular function, and survival of differentiated retinal cell types, their dysregulation is associated with retinal degenerative diseases. Thus, advancing our understanding of the genetic networks modulated by miRNAs is central to harnessing their potential as therapeutic agents to overcome visual impairment. In this review, we summarize the role of distinct miRNAs in specific retinal cell types, the current knowledge on their implication in inherited retinal disorders, and their potential as therapeutic agents.

Identification of pathogenic genes and transcription factors in glaucoma

Glaucoma is a group of eye diseases characterized by alterations in the contour of the optic nerve head, with corresponding visual field defects and progressive loss of retinal ganglion cells. The present study aimed to identify the key genes and upstream regulators in glaucoma. To screen the pathogenic genes involved in glaucoma, an integrated analysis was performed by using the microarray datasets in glaucoma derived from the Gene Expression Omnibus (GEO) database. The functional annotation and potential pathways of differentially expressed genes (DEGs) were additionally examined by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses. A glaucoma‑specific transcriptional regulatory network was constructed to identify crucial transcriptional factors that target the DEGs in glaucoma. From two GEO datasets, 1,935 DEGs (951 upregulated and 984 downregulated genes) between glaucoma and normal controls were identified. GO and KEGG analyses identified that 'eye development' [false discovery rate (FDR)=0.00415533] and 'visual perception' (FDR=0.00713283) were significantly enriched pathways for DEGs. The expression of lipocalin 2 (LCN2), monoamine oxidase A (MAOA), hemoglobin subunit β (HBB), paired box 6 (PAX6), fibronectin (FN1) and cAMP responsive element binding protein 1 (CREB1) were demonstrated to be involved in the pathogenesis of glaucoma. In conclusion, LCN2, MAOA, HBB, PAX6, FN1 and CREB1 may serve roles in glaucoma, regulated by PAX4, solute carrier family 22 member 1, hepatocyte nuclear factor 4 α and ELK1, ETS transcription factor. These data may contribute to the development of novel potential biomarkers, reveal the underlying pathogenesis and additionally identify novel therapeutic targets for glaucoma.

Silencing MicroRNA-134 Alleviates Hippocampal Damage and Occurrence of Spontaneous Seizures After Intraventricular Kainic Acid-Induced Status Epilepticus in Rats

Epilepsy is a disorder of abnormal brain activity typified by spontaneous and recurrent seizures. MicroRNAs (miRNAs) are short non-coding RNAs, critical for the post-transcriptional regulation of gene expression. MiRNA dysregulation has previously been implicated in the induction of epilepsy. In this study, we examined the effect of silencing miR-134 against status epilepticus (SE). Our results showed that level of miR-134 was significantly up-regulated in rat brain after Kainic acid (KA)-induced SE. TUNEL staining showed that silencing miR-134 alleviated seizure-induced neuronal apoptosis in the CA3 subfield of the hippocampus. Western blot showed that a miR-134 antagonist suppressed lesion-induced endoplasmic reticulum (ER) stress and apoptosis related expression of CHOP, Bim and Cytochrome C, while facilitated the expression of CREB at 24 h post KA-induced lesion in the hippocampus. Consistently, silencing miR-134 significantly diminished loss of CA3 pyramidal neurons using Nissl staining as well as reducing aberrant mossy fiber sprouting (MFS) in a rat epileptic model. In addition, the results of EEG and behavior analyses showed seizures were alleviated by miR-134 antagonist in our experimental models. These results suggest that silencing miR-134 modulates the epileptic phenotype by upregulating its target gene, CREB. This in turn attenuates oxidative and ER stress, inhibits apoptosis, and decreases MFS long term. This indicates that silencing miR-134 might be a promising intervention for the treatment of epilepsy.

miR-146a down-regulation alleviates H2O2-induced cytotoxicity of PC12 cells by regulating MCL1/JAK/STAT pathway : miR-146a down-regulation relieves H2O2-induced PC12 cells cytotoxicity by MCL1/JAK/STAT

Oxidative stress and miRNAs have been confirmed to play an important role in neurological diseases. The study aimed to explore the underlying effect and mechanisms of miR-146a in H₂O₂-induced injury of PC12 cells. Here, PC12 cells were stimulated with 200 μM of H₂O₂ to construct oxidative injury model. Cell injury was evaluated on the basis of the changes in cell viability, migration, invasion, apoptosis, and DNA damage. Results revealed that miR-146a expression was up-regulated in H₂O₂-induced PC12 cells. Functional analysis showed that down-regulation of miR-146a alleviated H₂O₂-induced cytotoxicity in PC12 cells. Dual-luciferase reporter and western blot assay verified that MCL1 was a direct target gene of miR-146a. Moreover, anti-miR-146a-mediated suppression on cell cytotoxicity was abated following MCL1 knockdown in H₂O₂-induced PC12 cells. Furthermore, MCL1 activated JAK/STAT signaling pathway and MCL1 overexpression attenuated H₂O₂-induced cytotoxicity in PC12 cells by JAK/STAT signaling pathway. In conclusion, this study suggested that suppression of miR-146a abated H₂O₂-induced cytotoxicity in PC12 cells via regulating MCL1/JAK/STAT pathway.

Dissecting microRNA dysregulation in age-related macular degeneration: new targets for eye gene therapy

MicroRNAs (miRNAs) are key regulators of gene expression in humans. Overexpression or depletion of individual miRNAs is associated with human disease. Current knowledge suggests that the retina is influenced by miRNAs and that dysregulation of miRNAs as well as alterations in components of the miRNA biogenesis machinery are involved in retinal diseases, including age-related macular degeneration (AMD). Furthermore, recent studies have indicated that the vitreous has a specific panel of circulating miRNAs and that this panel varies according to the specific pathological stress experienced by the retinal cells. MicroRNA (miRNA) profiling indicates subtype-specific miRNA profiles for late-stage AMD highlighting the importance of proper miRNA regulation in AMD. This review will describe the function of important miRNAs involved in inflammation, oxidative stress and pathological neovascularization, the key molecular mechanisms leading to AMD, and focus on dysregulated miRNAs as potential therapeutic targets in AMD.

MicroRNA-137 regulates hypoxia-induced retinal ganglion cell apoptosis through Notch1

The apoptosis of retinal ganglion cells (RGCs) is a hallmark of several optic neuropathies. MicroRNAs (miRNAs) are recently identified regulators of various biological processes. However, the role of miRNAs in regulating RGC apoptosis remains largely unknown. We herein aimed to demonstrate that miR-137 acts as a hypoxia-responsive gene in RGCs that is downregulated under hypoxic conditions. It was observed that overexpression of miR-137 markedly aggravated hypoxia-induced cell apoptosis, whereas inhibition of miR-137 effectively protected RGCs against hypoxia-induced apoptosis. Hypoxia induced Notch1 expression and signaling activation, while blocking Notch signaling significantly aggravated hypoxia-induced cell apoptosis. Further data revealed that the pro-survival Akt signaling pathway was involved in miR-137-Notch signaling pathway-mediated RGC protection. Knockdown of Notch significantly reversed the effect of anti‑miR-137 on RGC protection and Akt signaling activation. In addition, blocking Akt signaling also significantly abrogated the protective effect of anti-miR-137 on hypoxia-induced cell injury. Overall, the results of the present study demonstrated that miR-137 targets Notch1 expression, revealing a novel link between miR-137 and Notch signaling, and suggesting that a miR-137/Notch1 axis may serve as a potential molecular target for the treatment of hypoxia-induced retinal diseases.

Antagomirs Targeting MiroRNA-134 Attenuates Epilepsy in Rats through Regulation of Oxidative Stress, Mitochondrial Functions and Autophagy

The effects of the existing anti-epileptic drugs are unsatisfactory to almost one third of epileptic patients. MiR-134 antagomirs prevent pilocarpine-induced status epilepticus. In this study, a lithium chloride-pilocarpine-induced status epilepticus model was established and treated with intracerebroventricular injection of antagomirs targeting miR-134 (Ant-134). The Ant-134 treatment significantly improved the performance of rats in Morris water maze tests, inhibited mossy fiber sprouting in the dentate gyrus, and increased the survival neurons in the hippocampal CA1 region. Silencing of miR-134 remarkably decreased malonaldehyde and 4-hydroxynonenal levels and increased superoxide dismutase activity in the hippocampus. The Ant-134 treatment also significantly increased the production of ATP and the activities of mitochondrial respiratory enzyme complexes and significantly decreased the reactive oxygen species generation in the hippocampus compared with the status epilepticus rats. Finally, the Ant-134 treatment remarkably downregulated the hippocampal expressions of autophagy-associated proteins Atg5, beclin-1 and light chain 3B. In conclusion, Ant-134 attenuates epilepsy via inhibiting oxidative stress, improving mitochondrial functions and regulating autophagy in the hippocampus.

Transcriptome profiling of the rat retina after optic nerve transection

Glaucoma is a group of eye diseases characterized by alterations in the contour of the optic nerve head (ONH), with corresponding visual field defects and progressive loss of retinal ganglion cells (RGCs). This progressive RGC death is considered to originate in axonal injury caused by compression of the axon bundles in the ONH. However, the molecular pathomechanisms of axonal injury-induced RGC death are not yet well understood. Here, we used RNA sequencing (RNA-seq) to examine transcriptome changes in rat retinas 2 days after optic nerve transection (ONT), and then used computational techniques to predict the resulting alterations in the transcriptional regulatory network. RNA-seq revealed 267 differentially expressed genes after ONT, 218 of which were annotated and 49 unannotated. We also identified differentially expressed transcripts, including potentially novel isoforms. An in silico pathway analysis predicted that CREB1 was the most significant upstream regulator. Thus, this study identified genes and pathways that may be involved in the pathomechanisms of axonal injury. We believe that our data should serve as a valuable resource to understand the molecular processes that define axonal injury-driven RGC death and to discover novel therapeutic targets for glaucoma.

Cholinergic system and cell proliferation

The cholinergic system, comprising acetylcholine, the proteins responsible for acetylcholine synthesis and release, acetylcholine receptors and cholinesterases, is expressed by most human cell types. Acetylcholine is a neurotransmitter, but also a local signalling molecule which regulates basic cell functions, and cholinergic responses are involved in cell proliferation and apoptosis. So, activation of nicotinic and muscarinic receptors has a proliferative and anti-apoptotic effect in many cells. The content of choline acetyltransferase, acetylcholine receptors and cholinesterases is altered in many tumours, and cholinesterase content correlates with patient survival in some cancers. During apoptosis, acetylcholinesterase is induced and appears in the nuclei. Acetylcholinesterase participates in the regulation of cell proliferation and apoptosis through hydrolysis of acetylcholine and by other catalytic and non catalytic mechanisms, in a variant-specific manner. This review gathers information on the role of cholinergic system and specially acetylcholinesterase in cell proliferation and apoptosis.

MicroRNA-134 Contributes to Glucose-Induced Endothelial Cell Dysfunction and This Effect Can Be Reversed by Far-Infrared Irradiation

Diabetes mellitus (DM) is a metabolic disease that is increasing worldwide. Furthermore, it is associated with the deregulation of vascular-related functions, which can develop into major complications among DM patients. Endothelial colony forming cells (ECFCs) have the potential to bring about medical repairs because of their post-natal angiogenic activities; however, such activities are impaired by high glucose- (HG) and the DM-associated conditions. Far-infrared radiation (FIR) transfers energy as heat that is perceived by the thermoreceptors in human skin. Several studies have revealed that FIR improves vascular endothelial functioning and boost angiogenesis. FIR has been used as anti-inflammatory therapy and as a clinical treatment for peripheral circulation improvement. In addition to vascular repair, there is increasing evidence to show that FIR can be applied to a variety of diseases, including cardiovascular disorders, hypertension and arthritis. Yet mechanism of action of FIR and the biomarkers that indicate FIR effects remain unclear. MicroRNA-134 (miR-134-5p) was identified by small RNA sequencing as being increased in high glucose (HG) treated dfECFCs (HG-dfECFCs). Highly expressed miR-134 was also validated in dmECFCs by RT-qPCR and it is associated with impaired angiogenic activities of ECFCs. The functioning of ECFCs is improved by FIR treatment and this occurs via a reduction in the level of miR-134 and an increase in the NRIP1 transcript, a direct target of miR-134. Using a mouse ischemic hindlimb model, the recovery of impaired blood flow in the presence of HG-dfECFCs was improved by FIR pretreatment and this enhanced functionality was decreased when there was miR-134 overexpression in the FIR pretreated HG-dfECFCs. In conclusion, our results reveal that the deregulation of miR-134 is involved in angiogenic defects found in DM patients. FIR treatment improves the angiogenic activity of HG-dfECFCs and dmECFCs and FIR has potential as a treatment for DM. Detection of miR-134 expression in FIR-treated ECFCs should help us to explore further the effectiveness of FIR therapy.