Circular RNA circPHKA2 Relieves OGD-Induced Human Brain Microvascular Endothelial Cell Injuries through Competitively Binding miR-574-5p to Modulate SOD2

CircRNA and Stroke: New Insight of Potential Biomarkers and Therapeutic Targets

Stroke, the second-largest cause of death and the leading cause of disability globally, presents significant challenges in terms of prognosis and treatment. Identifying reliable prognosis biomarkers and treatment targets is crucial to address these challenges. Circular RNA (circRNA) has emerged as a promising research biomarkers and therapeutic targets because of its tissue specificity and conservation. However, the potential role of circRNA in stroke prognosis and treatment remains largely unexplored. This review briefly elucidate the mechanism underlying circRNA's involvement in stroke pathophysiology. Additionally, this review summarizes the impact of circRNA on different forms of strokes, including ischemic stroke and hemorrhagic stroke. And, this article discusses the positive effects of circRNA on promoting cerebrovascular repair and regeneration, maintaining the integrity of the blood-brain barrier (BBB), and reducing neuronal injury and immune inflammatory response. In conclusion, the significance of circRNA as a potential prognostic biomarker and a viable therapeutic target was underscored.

Circular RNAs: Promising Treatment Targets and Biomarkers of Ischemic Stroke

Ischemic stroke is one of the most significant causes of morbidity and mortality worldwide. However, there is a dearth of effective drugs and treatment methods for ischemic stroke. Significant numbers of circular RNAs (circRNAs) exhibit abnormal expression following ischemic stroke and are considered potential therapeutic targets. CircRNAs have emerged as promising biomarkers due to their stable expression in peripheral blood and their potential significance in ischemic stroke diagnosis and prognosis. This review provides a summary of 31 circRNAs involved in the pathophysiological processes of apoptosis, autophagy, inflammation, oxidative stress, and angiogenesis following ischemic stroke. Furthermore, we discuss the mechanisms of action of said circRNAs and their potential clinical applications. Ultimately, circRNAs exhibit promise as both therapeutic targets and biomarkers for ischemic stroke.

Exploring the Multifaceted Biologically Relevant Roles of circRNAs: From Regulation, Translation to Biomarkers

CircRNAs are a category of regulatory RNAs that have garnered significant attention in the field of regulatory RNA research due to their structural stability and tissue-specific expression. Their circular configuration, formed via back-splicing, results in a covalently closed structure that exhibits greater resistance to exonucleases compared to linear RNAs. The distinctive regulation of circRNAs is closely associated with several physiological processes, as well as the advancement of pathophysiological processes in several human diseases. Despite a good understanding of the biogenesis of circular RNA, details of their biological roles are still being explored. With the steady rise in the number of investigations being carried out regarding the involvement of circRNAs in various regulatory pathways, understanding the biological and clinical relevance of circRNA-mediated regulation has become challenging. Given the vast landscape of circRNA research in the development of the heart and vasculature, we evaluated cardiovascular system research as a model to critically review the state-of-the-art understanding of the biologically relevant functions of circRNAs. We conclude the review with a discussion of the limitations of current functional studies and provide potential solutions by which these limitations can be addressed to identify and validate the meaningful and impactful functions of circRNAs in different physiological processes and diseases.

LncRNAs and CircRNAs as Strategies against Pathological Conditions Caused by a Hypoxic/Anoxic State

Brain damage can be induced by oxygen deprivation. It is known that hypoxic or anoxic conditions can lead to changes in the expression levels of non-coding RNAs (ncRNAs), which, in turn, can be related to Central Nervous System (CNS) injuries. Therefore, it could be useful to investigate the involvement of non-coding RNAs (ncRNAs), as well as the underlying mechanisms which are able to modulate them in brain damage induced by hypoxic or anoxic conditions. In this review, we focused on recent research that associates these conditions with long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). The results of this review demonstrate that the expression of both lncRNAs and circRNAs can be influenced by oxygen deprivation conditions and so they can contribute to inducing damage or providing neuroprotection by affecting specific molecular pathways. Furthermore, several experimental studies have shown that ncRNA activity can be regulated by compounds, thus also modifying their transcriptomic profile and their effects on CNS damages induced by hypoxic/anoxic events.

hsa_circ_0000264 promotes tumor progression via the hsa-let-7b-5p/HMGA2 axis in head and neck squamous cell carcinoma

OBJECTIVE

Circular RNAs (CircRNAs) are involved in various tumors. However, their role in head and neck squamous cell carcinoma (HNSCC) is unknown. CircRNA sequencing data showed that hsa_circ_0000264 is significantly upregulated in HNSCC tissues. In this study, we aimed to investigate the role of hsa_circ_0000264 in HNSCC and elucidate its underlying regulation mechanism.

MATERIALS AND METHODS

RNase R treatment was performed to confirm the loop structure of hsa_circ_0000264. Fluorescence in situ hybridization was performed to show the subcellular localization of hsa_circ_0000264. We then performed wound healing assay, Transwell assay, Western blot, and in vivo experiments to determine the effect of alterations in hsa_circ_0000264 expression. We performed RNA pull-down and dual luciferase reporter assay to identify and confirm the binding sites in RNAs.

RESULTS

hsa_circ_0000264 was upregulated in HNSCC tissues and cells, and its loop structure was confirmed. Knockdown of hsa_circ_0000264 inhibited the migration, invasion, and epithelial-to-mesenchymal transition of HNSCC cells in vivo and in vitro. Mechanistically, hsa_circ_000026 upregulation can upregulate the expression of high mobility group AT-hook 2 (HMGA2) by sponging hsa-let-7b-5p, which in turn promotes HNSCC progression.

CONCLUSION

Our results showed that hsa_circ_0000264 promotes HNSCC progression via the hsa-let-7b-5p/HMGA2 axis, and hsa_circ_0000264 can serve as a potential target for HNSCC treatment.

CircPDS5B Reduction Improves Angiogenesis Following Ischemic Stroke by Regulating MicroRNA-223-3p/NOTCH2 Axis

Background and Objectives

Ischemic stroke (IS) is responsible for major causes of global death and disability, for which promoting angiogenesis is a promising therapeutic strategy. This study analyzed circular RNA PDS5B (circPDS5B) and its related mechanisms in angiogenesis in IS.

Methods

In the permanent middle cerebral artery occlusion (pMCAO) mouse model, circPDS5B, microRNA (miR)-223-3p, and NOTCH2 levels were checked. By testing neurologic function, neuronal apoptosis, and expression of angiogenesis-related proteins in pMCAO mice, the protective effects of circPDS5B knockdown were probed. In human brain microvascular endothelial cells (HBMECs) under oxygen-glucose deprivation (OGD) conditions, the effects of circPDS5B, miR-223-3p, and NOTCH2 on angiogenesis were studied by measuring cellular activities.

Results

The increase of circPDS5B and NOTCH2 expression and the decrease of miR-223-3p expression were examined in pMCAO mice. Reducing circPDS5B expression indicated protection against neurologic dysfunction, apoptosis, and angiogenesis impairment. For circPDS5B-depleted or miR-223-3p-restored HBMECs under OGD treatment, angiogenesis was promoted. MiR-223-3p inhibition-associated reduction of angiogenesis could be counteracted by knocking down NOTCH2. CircPDS5B depletion-induced angiogenesis in OGD-conditioned HBMECs was repressed after overexpressing NOTCH2.

Discussion

In IS, the expression of circPDS5B was upregulated, and miR-223-3p inhibited HBMECs activity and promoted NOTCH2 expression, thus promoting IS. CircPDS5B reduction improves angiogenesis following ischemic stroke by regulating microRNA-223-3p/NOTCH2 axis.

The Role of Circular RNAs in Ischemic Stroke

Ischemic stroke (IS), a devastating condition characterized by intracranial artery stenosis and middle cerebral artery occlusion leading to insufficient oxygen supply to the brain, is a major cause of death and physical disability worldwide. Recent research has demonstrated the critical role of circular RNAs (circRNAs), a class of covalently enclosed noncoding RNAs that are widespread in eukaryotic cells, in regulating various physiological and pathophysiological cellular processes, including cell apoptosis, autophagy, synaptic plasticity, and neuroinflammation. In the past few years, circRNAs have attracted extensive attention in the field of IS research. This review summarizes the current understanding of the mechanisms underlying the involvement of circRNAs in IS development. A better understanding of circRNA-mediated pathogenic mechanisms in IS may pave the way for translating circRNA research into clinical practice, ultimately improving the clinical outcomes of IS patients.

Circ_0000566 contributes oxygen-glucose deprivation and reoxygenation (OGD/R)-induced human brain microvascular endothelial cell injury via regulating miR-18a-5p/ACVR2B axis

Circular RNAs (circRNAs) exert regulatory roles in cerebrovascular disease. Human brain microvascular endothelial cells (HBMECs) participated in brain vascular dysfunction in ischemic stroke. Herein, the functions of circ_0000566 in oxygen-glucose deprivation and reoxygenation (OGD/R)-induced HBMECs were investigated. The expression of circ_0000566, miR-18a-5p, and Activin receptor type 2B (ACVR2B) was measured via quantitative real-time PCR (qRT-PCR). Cell Counting Kit-8 (CCK-8) and flow cytometry assays were utilized to detect cell viability and cell apoptosis. Western blot assay was employed to measure the levels of apoptotic-related proteins and ACVR2B. The secretion of IL-1β, IL-6, and TNF-α was detected via corresponding kits. The relationship between miR-18a-5p and circ_0000566 or ACVR2B was examined via dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay. Circ_0000566 and ACVR2B were highly expressed, while miR-18a-5p was down-regulated in OGD/R-treated HBMECs. OGD/R treatment promoted HBMECs apoptosis and inflammation and suppressed cell viability, which could be attenuated by silencing of circ_0000566. Circ_0000566 acted as a miR-18a-5p sponge to contribute to OGD/R-induced HBMECs injury. ACVR2B served as a direct target of miR-18a-5p, and ACVR2B overexpression might abolish the inhibitory role of miR-18a-5p on OGD/R-treated HBMEC injury. Circ_0000566 sponged miR-18a-5p to regulate OGD/R-induced HBMECs injury via regulating ACVR2B expression.

Circular RNAs in Ischemic Stroke: Biological Role and Experimental Models

Ischemic stroke is among the leading causes of morbidity, disability, and mortality worldwide. Despite the recent progress in the management of acute ischemic stroke, timely intervention still represents a challenge. Hence, strategies to counteract ischemic brain injury during and around the acute event are still lacking, also due to the limited knowledge of the underlying mechanisms. Despite the increasing understanding of the complex pathophysiology underlying ischemic brain injury, some relevant pieces of information are still required, particularly regarding the fine modulation of biological processes. In this context, there is emerging evidence that the modulation of circular RNAs, a class of highly conserved non-coding RNA with a closed-loop structure, are involved in pathophysiological processes behind ischemic stroke, unveiling a number of potential therapeutic targets and possible clinical biomarkers. This paper aims to provide a comprehensive overview of experimental studies on the role of circular RNAs in ischemic stroke.

New insights into circRNA and its mechanisms in angiogenesis regulation in ischemic stroke: a biomarker and therapeutic target

Ischemic stroke accounts for about 71% of strokes worldwide. Due to limited recommended therapeutics for ischemic stroke, more attention is focused on angiogenesis in ischemic stroke. Not long after ischemic stroke, angiogenesis arises and is vital for the prognosis. Various pro-angiogenic, anti-angiogenic factors and their downstream pathways engage in angiogenesis regulation. CircRNAs are differentially expressed after ischemic stroke. Up to now, circRNAs have been found to exert many functions in regulating apoptosis, autophagy, proliferation, and differentiation of neurons and neural stem cells mainly as miRNAs sponges or proteins decoy. Thus, many circRNAs are considered promising biomarkers or therapeutic targets for ischemic stroke. Besides, circRNAs participate in the modulation of endothelial-mesenchymal transition and blood-brain barrier maintenance. Moreover, circRNAs play significant roles in endothelial dysfunction concerning inflammation responses, apoptosis, proliferation, and migration. They correlate with many angiogenesis-related signaling pathways and genes via the circRNA/miRNA/mRNA network. Novel insights into circRNAs significance in angiogenesis regulation in ischemic stroke could be provided for further researches on the clinical application of circRNAs in ischemic stroke.

The regulatory roles of circular RNAs via autophagy in ischemic stroke

Ischemic stroke (IS) is a severe disease with a high disability, recurrence, and mortality rates. Autophagy, a highly conserved process that degrades damaged or aging organelles and excess cellular components to maintain homeostasis, is activated during IS. It influences the blood–brain barrier integrity and regulates apoptosis. Circular RNAs (circRNAs) are novel non-coding RNAs involved in IS-induced autophagy and participate in various pathological processes following IS. In addition, they play a role in autophagy regulation. This review summarizes current evidence on the roles of autophagy and circRNA in IS and the potential mechanisms by which circRNAs regulate autophagy to influence IS injury. This review serves as a basis for the clinical application of circRNAs as novel biomarkers and therapeutic targets in the future.

Pathophysiology of Ischemic Stroke: Noncoding RNA Role in Oxidative Stress

Stroke is a neurological disease that causes significant disability and death worldwide. Ischemic stroke accounts for 75% of all strokes. The pathophysiological processes underlying ischemic stroke include oxidative stress, the toxicity of excitatory amino acids, ion disorder, enhanced apoptosis, and inflammation. Noncoding RNAs (ncRNAs) may have a vital role in regulating the pathophysiological processes of ischemic stroke, as confirmed by the altered expression of ncRNAs in blood samples from acute ischemic stroke patients, animal models, and oxygen-glucose-deprived (OGD) cell models. Due to specific changes in expression, ncRNAs can potentially be biomarkers for the diagnosis, treatment, and prognosis of ischemic stroke. As an important brain cell component, glial cells mediate the occurrence and progression of oxidative stress after ischemic stroke, and ncRNAs are an irreplaceable part of this mechanism. This review highlights the impact of ncRNAs in the oxidative stress process of ischemic stroke. It focuses on specific ncRNAs that underlie the pathophysiology of ischemic stroke and have potential as diagnostic biomarkers and therapeutic targets.

Advances of circRNA-miRNA-mRNA regulatory network in cerebral ischemia/reperfusion injury

Ischemic stroke (IS) is the most common type of stroke, and its pathophysiological process is more complex. In recent years, the key regulatory roles of non-coding RNA (miRNA, circRNA) and mRNA in the development of IS have attracted more attention. In the process of cerebral ischemia/reperfusion injury, circRNA can regulate nerves, blood vessels and immune system through miRNA/mRNA axis, so as to affect the neurovascular unit of IS. The combination of these noncoding RNAs and mRNAs can be used as non-invasive biomarkers and therapeutic tools for IS diagnosis, prognosis and brain injury. Therefore, it is very important to study the potential molecular mechanism, activation pathway and treatment methods of circRNA/miRNA/mRNA network in IS. This review will focus on the latest progress of circRNA/miRNA/mRNA regulatory network, we have also included some circRNAs, which does not mediate through a miRNA, so we also include circRNA -mRNA network. And explore the application prospect of these RNAs as potential therapeutic targets in the prevention and treatment of IS.

Long noncoding RNA LINC01426 promotes the progression of lung adenocarcinoma via regulating miRNA-125a-5p/ casein kinase 2 alpha 1 axis

Although long noncoding RNAs (lncRNAs) in lung adenocarcinoma (LUAD) have been increasingly studied, LINC01426 has not been fully investigated in LUAD. The GEPIA database revealed that LINC01426 was upregulated in LUAD tissues. In our study, we further verified the significantly high expression of LINC01426 in LUAD tissues and cell lines. We also analyzed the LINC01426 expression level and LUAD clinical features and found that high LINC01426 expression was associated with tumor diameter; tumor, node, and metastases (TNM) staging; lymph node metastasis (LNM); and overall survival (OS) rate of LUAD patients. In vitro experiments revealed that suppression of LINC01426 could repress the proliferation, migration and invasion of LUAD cells. Then, the bioinformatic analysis revealed that there were binding domains between miR-125a-5p and the 3′-UTR of LINC01426. As revealed by dual-luciferase reporter gene experiment and RNA Binding Protein Immunoprecipitation (RIP) assay, miR-125a-5p could bind to LINC01426. Additionally, the results of qRT-PCR and Pearson’s analysis respectively revealed that miR-125a-5p was slightly expressed in LUAD and its expression was negatively correlated with LINC01426. Moreover, casein kinase 2 alpha 1 (CSNK2A1) was predicted to bind to miR-125a-5p. CSNK2A1 expression was remarkably high in LUAD tissues, negatively associated with miR-125a-5p, and positively correlated with LINC01426. Subsequently, our results showed that CSNK2A1 enhanced the malignant progression of LUAD cells. Overall, our study revealed that LINC01426 might regulate the malignant phenotype of LUAD via the miR-125a-5p/CSNK2A1 axis.

LINC00467 facilitates the proliferation, migration and invasion of glioma via promoting the expression of inositol hexakisphosphate kinase 2 by binding to miR-339-3p

Our previous studies indicate that long noncoding RNA (lncRNA) LINC00467 can act as an oncogene to participate in the malignant progression of glioma, but the underlying molecular mechanism remains to be studied further. This study aimed to explore the biological role of the LINC00467/miR-339-3p/ inositol hexakisphosphate kinase 2 (IP6K2) regulatory axis in glioma. The Cancer Genome Atlas (TCGA), Oncomine databases and reverse transcription‑quantitative PCR (RT‑qPCR) were used to analyze IP6K2 expression in glioma. RT-PCR, EdU and transwell assays were conducted to observe the effect of IP6K2 on glioma cell proliferation, migration and invasion. Using bioinformatics analysis, RT-PCR, and dual luciferase reporter gene assay, the potential role of the LINC00467/miR-339-3p/IP6K2 regulatory axis in glioma was verified. The results showed that IP6K2 was up-regulated in glioma tissues and cell lines. Moreover, the expression level of IP6K2 was correlated with the clinical features of glioma patients. In vitro and in vivo experiments indicated that IP6K2 overexpression could promote the proliferation, migration, and invasion of glioma cells. Further bioinformatics analysis and in vitro assays revealed that LINC00467 could promote IP6K2 expression by binding to miR-339-3p and promote the malignant progression of glioma. Overall, LINC00467 could upregulate IP6K2 by binding to miR-339-3p and promote the proliferation, migration, and invasion of glioma cells. The LINC00467/miR-339-3p/IP6K2 regulatory axis might be a potential therapeutic target for glioma.