CircPRKCI-miR-545/589-E2F7 axis dysregulation mediates hydrogen peroxide-induced neuronal cell injury

Non-Coding RNAs Regulating Mitochondrial Functions and the Oxidative Stress Response as Putative Targets against Age-Related Macular Degeneration (AMD)

Age-related macular degeneration (AMD) is an ever-increasing, insidious disease which reduces the quality of life of millions of elderly people around the world. AMD is characterised by damage to the retinal pigment epithelium (RPE) in the macula region of the retina. The origins of this multi-factorial disease are complex and still not fully understood. Oxidative stress and mitochondrial imbalance in the RPE are believed to be important factors in the development of AMD. In this review, the regulation of the mitochondrial function and antioxidant stress response by non-coding RNAs (ncRNAs), newly emerged epigenetic factors, is discussed. These molecules include microRNAs, long non-coding RNAs, and circular non-coding RNAs. They act mainly as mRNA suppressors, controllers of other ncRNAs, or by interacting with proteins. We include here examples of these RNA molecules which affect various mitochondrial processes and antioxidant signaling of the cell. As a future prospect, the possibility to manipulate these ncRNAs to strengthen mitochondrial and antioxidant response functions is discussed. Non-coding RNAs could be used as potential diagnostic markers for AMD, and in the future, also as therapeutic targets, either by suppressing or increasing their expression. In addition to AMD, it is possible that non-coding RNAs could be regulators in other oxidative stress-related degenerative diseases.

Brain-protective mechanisms of autophagy associated circRNAs: Kick starting self-cleaning mode in brain cells via circRNAs as a potential therapeutic approach for neurodegenerative diseases

Altered autophagy is a hallmark of neurodegeneration but how autophagy is regulated in the brain and dysfunctional autophagy leads to neuronal death has remained cryptic. Being a key cellular waste-recycling and housekeeping system, autophagy is implicated in a range of brain disorders and altering autophagy flux could be an effective therapeutic strategy and has the potential for clinical applications down the road. Tight regulation of proteins and organelles in order to meet the needs of complex neuronal physiology suggests that there is distinct regulatory pattern of neuronal autophagy as compared to non-neuronal cells and nervous system might have its own separate regulator of autophagy. Evidence has shown that circRNAs participates in the biological processes of autophagosome assembly. The regulatory networks between circRNAs, autophagy, and neurodegeneration remains unknown and warrants further investigation. Understanding the interplay between autophagy, circRNAs and neurodegeneration requires a knowledge of the multiple steps and regulatory interactions involved in the autophagy pathway which might provide a valuable resource for the diagnosis and therapy of neurodegenerative diseases. In this review, we aimed to summarize the latest studies on the role of brain-protective mechanisms of autophagy associated circRNAs in neurodegenerative diseases (including Alzheimer's disease, Parkinson's disease, Huntington's disease, Spinal Muscular Atrophy, Amyotrophic Lateral Sclerosis, and Friedreich's ataxia) and how this knowledge can be leveraged for the development of novel therapeutics against them. Autophagy stimulation might be potential one-size-fits-all therapy for neurodegenerative disease as per considerable body of evidence, therefore future research on brain-protective mechanisms of autophagy associated circRNAs will illuminate an important feature of nervous system biology and will open the door to new approaches for treating neurodegenerative diseases.

Circular RNAs in Alzheimer's Disease: A New Perspective of Diagnostic and Therapeutic Targets

BACKGROUND

Circular RNAs (circRNAs), as covalently closed single-stranded noncoding RNA molecules, have been recently identified to involve in several biological processes, principally through targeting microRNAs. Among various neurodegenerative diseases (NDs), accumulating evidence has proposed key roles for circRNAs in the pathogenesis of Alzheimer's disease (AD); although the exact relationship between these RNA molecules and AD progression is not clear, they have been believed to mostly act as miRNA sponges or gene transcription modulators through correlating with multiple proteins, involved in the accumulation of Amyloid β (Aβ) peptides, as well as tau protein, as AD's pathological hallmark. More interestingly, circRNAs have also been reported to play diagnostic and therapeutic roles during AD progression.

OBJECTIVE

Literature review indicated that circRNAs could essentially contribute to the onset and development of AD. Thus, in the current review, the circRNAs' biogenesis and functions are addressed at first, and then the interplay between particular circRNAs and AD is comprehensively discussed. Eventually, the diagnostic and therapeutic significance of these noncoding RNAs is highlighted in brief.

RESULTS

A large number of circRNAs are expressed in the brain. Thereby, these RNA molecules are noticed as potential regulators of neural functions in healthy circumstances, as well as neurological disorders. Moreover, circRNAs have also been reported to have potential diagnostic and therapeutic capacities in relation to AD, the most prevalent ND.

CONCLUSION

CircRNAs have been shown to act as sponges for miRNAs, thereby regulating the function of related miRNAs, including oxidative stress, reduction of neuroinflammation, and the formation and metabolism of Aβ, all of which developed in AD. CircRNAs have also been proposed as biomarkers that have potential diagnostic capacities in AD. Despite these characteristics, the use of circRNAs as therapeutic targets and promising diagnostic biomarkers will require further investigation and characterization of the function of these RNA molecules in AD.

Insights into the multifaceted role of circular RNAs: implications for Parkinson's disease pathogenesis and diagnosis

Parkinson's disease (PD) is a complex, age-related, neurodegenerative disease whose etiology, pathology, and clinical manifestations remain incompletely understood. As a result, care focuses primarily on symptoms relief. Circular RNAs (circRNAs) are a large class of mostly noncoding RNAs that accumulate with aging in the brain and are increasingly shown to regulate all aspects of neuronal and glial development and function. They are generated by the spliceosome through the backsplicing of linear RNA. Although their biological role remains largely unknown, they have been shown to regulate transcription and splicing, act as decoys for microRNAs and RNA binding proteins, used as templates for translation, and serve as scaffolding platforms for signaling components. Considering that they are stable, diverse, and detectable in easily accessible biofluids, they are deemed promising biomarkers for diagnosing diseases. CircRNAs are differentially expressed in the brain of patients with PD, and growing evidence suggests that they regulate PD pathogenetic processes. Here, the biogenesis, expression, degradation, and detection of circRNAs, as well as their proposed functions, are reviewed. Thereafter, research linking circRNAs to PD-related processes, including aging, alpha-synuclein dysregulation, neuroinflammation, and oxidative stress is highlighted, followed by recent evidence for their use as prognostic and diagnostic biomarkers for PD.

Circ-Ctnnb1 regulates neuronal injury in spinal cord injury through Wnt/β-catenin signaling pathway

STUDY DESIGN

Spinal cord injury (SCI) rat model and cell model were established for in vivo and in vitro experiments. Functional assays were utilized to explore the role of the circRNAs derived from catenin beta 1 (mmu_circ_0001859, circ-Ctnnb1 herein) in regulating neuronal cell viability and apoptosis. Bioinformatics analysis and mechanism experiments were conducted to assess the underlying molecular mechanism of circ-Ctnnb1.

OBJECTIVE

We aimed to probe into the biological function of circ-Ctnnb1 in neuronal cells of SCI.

METHODS

The rat model of SCI and hypoxia-induced cell model were constructed to examine circ-Ctnnb1 expression in SCI through quantitative reverse transcription real-time polymerase chain reaction (RT-qPCR). Basso, Beattie and Bresnahan (BBB) score was utilized for evaluating the neurological function. Terminal-deoxynucleoitidyl Transferase Mediated Nick End labeling (TUNEL) assays were performed to assess the apoptosis of neuronal cells. RNase R and Actinomycin D (ActD) were used to treat cells to evaluate the stability of circ-Ctnnb1.

RESULTS

Circ-Ctnnb1 was highly expressed in SCI rat models and hypoxia-induced neuronal cells, and its deletion elevated the apoptosis rate of hypoxia-induced neuronal cells. Furthermore, circ-Ctnnb1 activated the Wnt/β-catenin signaling pathway via sponging mircoRNA-205-5p (miR-205-5p) to up-regulate Ctnnb1 and Wnt family member 2B (Wnt2b).

CONCLUSION

Circ-Ctnnb1 promotes SCI through regulating Wnt/β-catenin signaling via modulating the miR-205-5p/Ctnnb1/Wnt2b axis.

Circ-PRKCI Alleviates Lipopolysaccharide-induced Human Kidney 2 Cell Injury by Regulating miR-106b-5p/GAB1 Axis

ABSTRACT

Circular RNAs act as vital regulators in diverse diseases. However, the investigation of circular RNAs in sepsis-engendered acute kidney injury remains dismal. We aimed to explore the effects of circular RNA protein kinase C iota (circ-PRKCI) in lipopolysaccharide (LPS)-mediated HK2 cell injury. Sepsis in vitro model was established by LPS treatment. Quantitative real-time polymerase chain reaction assay was conducted for determining the levels of circ-PRKCI, microRNA-106b-5p (miR-106b-5p), and growth factor receptor binding 2-associated binding protein 1 (GAB1). Cell viability and apoptosis were evaluated using Cell Counting Kit-8 assay and flow cytometry analysis, respectively. The concentrations of interleukin-6, interleukin-1β, and tumor necrosis factor-α were measured with enzyme-linked immunosorbent assay kits. The levels of oxidative stress markers were determined using relevant commercial kits. Western blot assay was conducted for B-cell lymphoma-2 (Bcl-2), BCL2-Associated X (Bax), and GAB1 protein levels. Dual-luciferase reporter assay and RNA immunoprecipitation assay were used to verify the association between miR-106b-5p and circ-PRKCI or GAB1. We found the Circ-PRKCI level was decreased in sepsis patients and LPS-induced human kidney 2 (HK-2) cells. LPS exposure inhibited cell viability and facilitated apoptosis, inflammation, and oxidative stress in HK-2 cells. Circ-PRKCI overexpression abrogated the effects of LPS on cell apoptosis, inflammation, and oxidative stress in HK-2 cells. Furthermore, circ-PRKCI was identified as the sponge for miR-106b-5p to positively regulate GAB1 expression. Overexpression of circ-PRKCI relieved LPS-mediated HK-2 cell damage by sponging miR-106b-5p. MiR-106b-5p inhibition ameliorated the injury of HK-2 cells mediated by LPS, whereas GAB1 knockdown reversed the effect. Collectively, Circ-PRKCI overexpression attenuated LPS-induced HK-2 cell injury by regulating miR-106b-5p/GAB1 axis.

Circular RNAs in the Regulation of Oxidative Stress

Oxidative stress caused by an imbalance between the production and elimination of reactive metabolites and free radicals can lead to the development of a variety of diseases. Over the past years, with the development of science and technology, circular RNA (circRNA) has been found to be closely associated with oxidative stress, which plays an important role in the process of oxidative stress. Currently, the understanding of circRNAs in the mechanism of oxidative stress is limited. In this review, we described the relationship between oxidative stress and circRNAs, the circRNAs related to oxidative stress, and the role of circRNAs in promoting or inhibiting the occurrence and development of diseases associated with the oxidative stress system.

The Emerging Role of Circular RNAs in Alzheimer's Disease and Parkinson's Disease

Alzheimer’s disease (AD) and Parkinson’s disease (PD) are two neurodegenerative diseases (NDDs) commonly found in elderly patients that are difficult to diagnose and lack effective treatment. Currently, the available diagnostic methods for these two NDDs do not meet clinical diagnostic expectations. Circular RNAs (circRNAs) are a diverse group of endogenous non-coding RNAs (ncRNAs) found in eukaryotic cells. Emerging studies suggest that altered expression of circRNAs is involved in the pathological processes of NDDs. CircRNAs could also prove to be promising biomarkers for the early diagnosis of NDDs such as AD and PD. Growing evidence has improved our knowledge of the roles of circRNAs in NDDs, which may lead to new therapeutic approaches that target transcription for preventing neurodegeneration. In this review, we describe the formation mechanisms and functions of circRNAs as well as methods of validation. We also discuss the emerging role of circRNAs in the pathophysiology of AD and PD and their potential value as biomarkers and therapeutic targets for AD and PD in the future.

Circ_0003423 Alleviates ox-LDL-Induced Human Brain Microvascular Endothelial Cell Injury via the miR-589-5p/TET2 Network

Brain microvascular endothelial cells (BMECs) injury is one of the main causes of cerebrovascular diseases. Circular RNA (circRNA) has been found to be involved in the regulation of cerebrovascular diseases progression. However, the role and mechanism of circ_0003423 in cerebrovascular diseases is still unclear. In our study, oxidized low density lipoprotein (ox-LDL)-induced HBMEC-IM cells were used to construct cerebrovascular cell injury model in vitro. Quantitative real-time PCR was used to determine the expression levels of circ_0003423, miR-589-5p and Ten-eleven translocation 2 (TET2). The interactions between miR-589-5p and circ_0003423 or TET2 were confirmed by dual-luciferase reporter assay, RIP assay and RNA pull-down assay. Cell viability, angiogenesis and apoptosis were measured using cell counting kit 8 assay, tube formation assay and flow cytometry. Cell oxidative stress was evaluated by detecting the levels of reactive oxygen species and lactate dehydrogenase. The protein levels were examined by western blot analysis. Our results showed that circ_0003423 was a downregulated circRNA in ox-LDL-induced HBMEC-IM cells. In the terms of mechanism, circ_0003423 was found to be a sponge of miR-589-5p. Function analysis showed that circ_0003423 overexpression could relieve ox-LDL-induced HBMEC-IM cell injury, and this effect could be reversed by miR-589-5p mimic. In addition, TET2 was confirmed to be a target of miR-589-5p, and its overexpression could alleviate ox-LDL-induced HBMEC-IM cell injury. Moreover, the rescue experiments also confirmed that TET2 silencing could abolish the inhibition effect of anti-miR-589-5p on ox-LDL-induced HBMEC-IM cell injury. In summary, our data showed that circ_0003423 alleviated ox-LDL-induced HBMEC-IM cells injury through regulating the miR-589-5p/TET2 axis.

Circ_0091702 serves as a sponge of miR-545-3p to attenuate sepsis-related acute kidney injury by upregulating THBS2

Circular RNA (circRNA) has been shown to play an important function in the progression of human diseases, including sepsis with acute kidney injury (AKI). However, the role and mechanism of circ_0091702 in sepsis-induced AKI have yet to be confirmed. Lipopolysaccharide (LPS) was used to induce HK2 cells to construct AKI cell models in vitro. Quantitative real-time PCR was used to measure the expression of circ_0091702, inflammatory cytokines, microRNA (miR)-545-3p and thrombospondin 2 (THBS2). Cell counting kit 8 assay and flow cytometry were used to assess cell viability and apoptosis. Besides, the protein levels of apoptosis markers and THBS2 were evaluated by western blot analysis. In addition, the concentrations of inflammatory cytokines were detected by enzyme-linked immunosorbent assay (ELISA). Cell oxidative stress was determined by detecting the contents of oxidative stress markers. Dual-luciferase reporter assay and RIP assay were used to confirm the relationship between miR-545-3p and circ_0091702 or miR-545-3p and THBS2. Circ_0091702 was downregulated in septic AKI patients and LPS-induced HK2 cells. Circ_0091702 could attenuate LPS-induced HK2 cell injury, while its silencing had an opposite effect. In the terms of mechanism, circ_0091702 could act as a sponge of miR-545-3p, and miR-545-3p could directly target THBS2. Functional experiments revealed that miR-545-3p could reverse the alleviating effect of circ_0091702 on LPS-induced HK2 cell injury, and THBS2 knockdown also could overturn the suppressing effect of miR-545-3p inhibitor on LPS-induced HK2 cell injury. Additionally, we also suggested that circ_0091702 could sponge miR-545-3p to regulate THBS2 expression. In conclusion, our results showed that circ_0091702 could suppress LPS-induced HK2 cell injury via the miR-545-3p/THBS2 axis, indicating that circ_0091702 might be an important biomarker for relieving sepsis-related AKI.

Emerging Clues of Regulatory Roles of Circular RNAs through Modulating Oxidative Stress: Focus on Neurological and Vascular Diseases

Circular RNAs (circRNAs) are novel noncoding RNAs that play regulatory roles in gene expression. Dysregulation of circRNAs is associated with the development and progression of several diseases, such as diabetes mellitus, nervous system diseases, cardiovascular diseases, and cancer. CircRNAs functionally participate in cell physiological activities through various molecular mechanisms. However, these molecular mechanisms are unclear. Oxidative stress is an essential factor in the pathogenesis of various diseases, including neurological diseases. Emerging roles of circRNAs have been identified in different systems in response to oxidative stress. In this review, we summarize the current understanding of circRNA biogenesis, properties, expression profiles, and the clues indicating the regulatory roles of circRNAs through oxidative stress in various systems, especially the nervous system.

Identification of E2F transcription factor 7 as a novel potential biomarker for oral squamous cell carcinoma

BACKGROUND

As a tumor-accelerating transcriptional factor, E2F transcription factor 7 (E2F7) was up-regulated in many forms of cancers. Nevertheless, little has been reported about the impacts of E2F7 on oral squamous cell carcinoma (OSCC). Here, we aimed to probe whether E2F7 had influences on OSCC and its potential mechanism.

METHODS

The expression of E2F7 in OSCC tissues was analyzed using the data acquired from TCGA and ONCOMINE databases. E2F7 prognostic value in OSCC patients was analyzed utilizing TCGA database. The expression of E2F7 in OSCC cell lines was detected by qRT-PCR. Gain-and loss-function of E2F7 assays in TCA-83 and CAL27 cells were performed respectively to inquire the function of E2F7. Western blotting was applied to test the alternations of EMT-related markers.

RESULTS

In OSCC tissues, E2F7 was highly expressed. Besides, high expression of E2F7 predicted worse prognosis in OSCC patients. Moreover, E2F7 was over-expressed in TCA-83, HSC-4 and CAL27 (all OSCC cell lines) cells relative to that in HNOK (a normal cell line) cells. Gain-and loss-function assays displayed that deficiency of E2F7 suppresses CAL27 cell growth, migration, invasion and E2F7 high-expression resulted in inverse outcomes in TCA-83 cells. Finally, we found that silencing of E2F7 facilitated E-cadherin protein expression level and reduced N-cadherin, Vimentin and Snail protein levels in CAL27 cells, whilst E2F7 high-expression exhibited the opposite effects in TCA-83 cells.

CONCLUSIONS

These outcomes indicated that E2F7 performs a carcinogenic role in OSCC, which provides a theoretical basis for the therapeutic strategies of OSCC.

Effects of circular RNA Ttc3/miR-148a/Rcan2 axis on inflammation and oxidative stress in rats with acute kidney injury induced by sepsis

Aim Increasing evidence demonstrated circular RNAs (circRNAs) are involved in the development of various diseases, including sepsis-induced AKI. Although CIRC-Ttc3 has been proved to regulate cardiac function after myocardial infarction, its role in sepsis-induced AKI remains unclear.

MATERIALS AND METHODS

The AKI rat model was firstly induced by sepsis through cecal ligation puncture (CLP). Serum levels of creatinine, BUN, NGAL, TNF-α, IL-6, SOD, MDA and IL-1β were measured through appropriate kits. The pathological alteration and renal microvascular permeability in renal tissues were determined by HE staining and Evans Blue assays. Cell apoptosis was detected by TUNEL assay. The expression levels of CIRC-Ttc3, miR-148a, TNF-α, IL-1β and iNOS in rats' renal samples were tested by qRT-PCR or/and western blot. The binding ability between CIRC-Ttc3 and miR-148a was evaluated through luciferase reporter, RIP and RNA pull-down assays.

KEY FINDINGS

Kidney injury was found in CLP-treated rats. CIRC-Ttc3 expression was down-regulated, and upregulation of CIRC-Ttc3 improved inflammatory responses and oxidative stress in AKI rats. Mechanismly, CIRC-Ttc3 was confirmed to bind to and negatively regulate miR-148a. Further rescue assays revealed that overexpression of miR-148a rescued the improvement of CIRC-Ttc3 on sepsis-induced AKI. Then, it was illustrated that CIRC-Ttc3 regulated Rcan2 expression by binding to miR-148a. Finally, knockdown of Rcan2 reversed the effects of miR-148a inhibition on sepsis-induced AKI.

SIGNIFICANCE

CIRC-Ttc3 relieved inflammation and oxidative stress through regulating the miR-148a/Rcan2 axis in rats with AKI induced by sepsis. Therefore, CIRC-Ttc3 may be a potential therapeutic target for sepsis-induced AKI.

Circular RNAs in Toxicology

Circular RNAs (circRNAs) are a type of closed, long, non-coding RNAs, which have attracted significant attention in recent years. CircRNAs exhibit unique functions and are characterized by stable expression in various tissues across different species. Because the identification of circRNA in plant viroids in 1976, numerous studies have been conducted to elucidate its generation as well as expression under normal and disease conditions. The rapid development of research focused on the roles of circRNAs as biomarkers in diseases such as cancers has led to increased interests in evaluating the effects of toxicants on the human genetics from a toxicological perspective. Notably, increasing amounts of chemicals are generated in the environment; however, their toxic features and interactions with the human body, particularly from the epigenetic viewpoint, remain largely unknown. Considering the unique features of circRNAs as potential prognostic biomarkers as well as their roles in evaluating health risks following exposure to toxicants, the aim of this review was to assess the latest progress in the research concerning circRNA, to address the role of the circRNA-miRNA-mRNA axis in diseases and processes occurring after exposure to toxic compounds. Another goal was to identify the gaps in understanding the interactions between toxic compounds and circRNAs as potential biomarkers. The review presents general information about circRNA (ie, biogenesis and functions) and provides insights into newly discovered exosome-contained circRNA. The roles of circRNAs as potential biomarkers are also explored. A comprehensive review of the available literature on the role of circRNA in toxicological research (ie, chemical carcinogenesis, respiratory toxicology, neurotoxicology, and other unclassified toxicological categories) is included.

Identification of the Competing Endogenous RNA Networks in Oxidative Stress Injury of Melanocytes

Competing endogenous RNAs (ceRNAs), including long noncoding RNA (lncRNA), circular RNA (circRNA), pseudogenes, synthetic miRNA inhibitors, etc. are classes of RNAs that can compete and interact with each other within an organism. There are regions in these RNAs that can be bound by messenger-RNA-interfering complementary RNA (microRNA), called microRNA response elements (MREs). These RNAs compete with each other to combine complementary microRNAs and MREs to form ceRNA regulatory mechanisms and participate in the regulation of many biological processes. The oxidative stress injury of melanocytes is one of the crucial mechanisms of vitiligo. However, it is unclear whether the ceRNA regulation mechanism is involved in the oxidative stress injury of melanocytes. The purpose of this study is to explore the changes of messenger RNA (mRNA), lncRNAs, and circRNAs in melanocytes under oxidative stress and to identify the key ceRNA regulatory networks. Compared with the normal cells, the chip detection of ceRNA expression profile showed that the expression of 491 mRNAs, 865 lncRNAs, and 1161 circRNAs were altered more than fivefold during the oxidative stress injury of melanocytes. The oxidative stress-related genes (SOD2, PTGS2, DHFR, HMOX1, FOSL1, and PARP1), cell cycle-related genes (CDK1, CCNB1, CCNA2, OIP5, and MK167), and apoptosis-related gene (BIRC5) were identified in the formation of ceRNA regulation networks with lncRNAs and circRNAs, which shares the common MREs. Further verification found that LNCV6_120941_PI430048170 or hsa_circ_0048910 might regulate the expression of SOD2 by sponging hsa-miR-4755-3p, LNCV6_119109_PI430048170, or hsa_circ_0048909 might regulate the expression of HMOX1 by sponging hsa-miR-6721-5p in the oxidative stress injury of melanocytes. In conclusion, complex changes of the ceRNA regulatory network in the oxidative stress response of melanocytes are evident. Oxidative stress may mediate melanocyte injury through the ceRNA regulation mechanism and induce the pathogenesis of vitiligo.

Circular RNAs are a novel type of non-coding RNAs in ROS regulation, cardiovascular metabolic inflammations and cancers

Circular RNAs (circRNAs) are a novel class of endogenous non-coding RNAs characterized by a covalently closed-loop structure generated through a special type of alternative splicing termed back-splicing. Currently, an increasing body of evidence has demonstrated that 1) majority of circRNAs are evolutionarily conserved across species, stable, and resistant to RNase R degradation, and often exhibit cell-specific, and tissue-specific/developmental-stage-specific expression and can be largely independent of the expression levels of the linear host gene-encoded linear RNAs; 2) the biogenesis of circRNAs via back-splicing is different from the canonical splicing of linear RNAs; 3) circRNA biogenesis is regulated by specific cis-acting elements and trans-acting factors; 4) circRNAs regulate biological and pathological processes by sponging miRNAs, binding to RNA-binding protein (RBP), regulators of splicing and transcription, modifiers of parental gene expression, and regulators of protein translation or being translated into peptides in various diseases; 5) circRNAs have been identified for their enrichment and stability in exosomes and detected in body fluids such as human blood, saliva, and cerebrospinal fluids, suggesting that these exo-circRNAs have potential applications as disease biomarkers and novel therapeutic targets; 6) several circRNAs are regulated by oxidative stress and mediate reactive oxygen species (ROS) production as well as promote ROS-induced cellular death, cell apoptosis, and inflammation; 7) circRNAs have also emerged as important regulators in atherosclerotic cardiovascular disease, metabolic disease, and cancers; 8) the potential mechanisms of several circRNAs have been described in diseases, hinting at their potential applications as novel therapeutic targets. In this highlight, we summarized the current understandings of the biogenesis and functions of circRNAs and their roles in ROS regulation and vascular inflammation-associated with cardiovascular and metabolic disease. (Word count: 272).

Circular RNA PRKCI and microRNA-545 relate to sepsis risk, disease severity and 28-day mortality

This study aimed to explore the clinical values of circular RNA protein kinase C iota (circ-PRKCI) and its target microRNA-545 (miR-545) in sepsis patients. Plasma samples of 121 sepsis patients and 60 healthy controls (HCs) were collected, then circ-PRKCI and miR-545 expressions were detected using RT-qPCR. Sepsis patients' demographics, biochemical indexes, medical histories, infection information were recorded. Besides, comprehensive disease scores (APACHE II score and SOFA score) were assessed within 24 h after admission. According to the survival status, 28-day mortality was calculated. Decreased circ-PRKCI expression and increased miR-545 expression were observed in sepsis patients compared to HCs, both of which had close correlations with sepsis risk. Besides, circ-PRKCI was negatively correlated with miR-545 in sepsis patients and HCs, respectively. Circ-PRKCI was negatively correlated with serum creatinine, white blood cell, C-reactive protein, APACHE II score, SOFA score, but positively correlated with albumin, which also related to blood stream infection (as primary infection site) and anaerobes infection in sepsis patients. Whereas the miR-545 showed a roughly opposite tendency. Decreased circ-PRKCI and increased miR-545 expressions were discovered in deaths compared to survivors, and both of them had values for predicting 28-day mortality risk in sepsis patients, which were slightly lower than the predictive values of APACHE II score and SOFA score for predicting 28-day mortality risk. Multivariate logistic analyses displayed circ-PRKCI as an independent factor predicting decreased 28-day mortality risk. In conclusion, circ-PRCKI insufficiency and miR-545 sufficiency were related to sepsis risk, clinical disease severity and 28-day mortality risk.

CircPRKCI relieves lipopolysaccharide-induced HK2 cell injury by upregulating the expression of miR-545 target gene ZEB2

The aim of this study was to investigate the possible influences of circPRKCI abnormal expression on lipopolysaccharide (LPS)-induced HK2 cell injury and its mechanism. The circPRKCI level was identified in serum samples from patients with urosepsis and healthy subjects, as well as LPS-treated HK2 cells by qRT-PCR. Cell viability, apoptosis, expression of proteins associated with apoptosis, and expression of pro-inflammatory cytokines in LPS-treated HK2 cells were measured. Effects of circPRKCI abnormal expression on LPS-induced HK2 cell injury were then evaluated. Afterward, the binding miRNA of circPRKCI and target gene of miRNA were identified, and the involvements of NF-kB pathway signaling pathway with the effects of circPRKCI were finally studied. CircPRKCI was significantly down-regulated in serum samples from patients with urosepsis and LPS-treated HK2 cells. LPS-induced decrease of cell viability, increase of cell apoptosis, as well as elevated productions of tumor necrosis factor (TNF)-α, interleukins (IL)-1β, IL-6, and IL-8 in HK2 cells were attenuated by overexpressed circPRKCI. In addition, circPRKCI negatively regulated the expression of miR-545, and miR-545 up-regulation reversed the inhibiting effects of circPRKCI overexpression on LPS-induced HK2 cell injury. Moreover, zinc finger E-box-binding homeobox 2 (ZEB2) was identified as a target gene of miR-545, and ZEB2 overexpression partly reversed the effects of miR-545 up-regulation on LPS-induced HK2 cell injury. Furthermore, NF-kB pathway was revealed to be associated to the effects of circPRKCI on LPS-induced HK2 cell injury. This research indicated that the highly expressed circPRKCI relieved inflammatory injury induced by LPS in HK2 cells by suppressing miR-545/ZEBs and depressing the briskness of NF-kB pathway.

Circular RNA PRKCI promotes glioma cell progression by inhibiting microRNA-545

We here tested expression and potential functions of circular RNA PRKCI (circPRKCI) in human glioma. Our results show that circPRKCI is upregulated in human glioma tissues and glioma cells, correlating with downregulation of its potential target, microRNA-545 (miR-545). In A172 and primary human glioma cells, shRNA-mediated silencing of circPRKCI inhibited cancer cell growth, survival, proliferation, and migration. Conversely, ectopic circPRKCI overexpression promoted A172 cell progression. miR-545 is the primary target of circPRKCI in glioma cells. Forced overexpression of miR-545 mimicked circPRKCI shRNA-induced actions, inhibiting glioma cell survival and proliferation. In contrast, miR-545 inhibition, by a lentiviral antagomiR-545 construct, reversed circPRKCI shRNA-induced anti-A172 cell activity. Importantly, neither circPRKCI shRNA nor circPRKCI overexpression was effective in miR-545-knockout (Cas9 method) A172 cells. Importantly, the subcutaneous and orthotopic A172 xenograft growth was significantly inhibited by circPRKCI silencing. Collectively, circPRKCI promotes human glioma cell progression possibly by inhibiting miR-545. Targeting circPRKCI-miR-545 cascade could efficiently inhibit human glioma cells.