circ_0003204 Regulates Cell Growth, Oxidative Stress, and Inflammation in ox-LDL-Induced Vascular Endothelial Cells via Regulating miR-942-5p/HDAC9 Axis

Circ_0026218 ameliorates oxidized low-density lipoprotein-induced vascular endothelial cell dysfunction by regulating miR-188-3p/TLR4/NF-κB pathway

BACKGROUND

Circular RNAs (circRNAs) have shown important regulatory roles in cardiovascular diseases, including atherosclerosis (AS). However, the role and mechanism of circ_0026218 in AS remain unclear.

METHODS

The cell model of AS in vitro was established by stimulating human umbilical vein endothelial cells (HUVECs) with oxidized low-density lipoprotein (ox-LDL). In addition, circ_0026218, microRNA-188-3p (miR-188-3p), and toll-like receptor 4 (TLR4) expression was determined via real-time quantitative polymerase chain reaction (RT-qPCR) in serum samples from AS patients and healthy volunteers. Cell proliferation was assessed using Cell Counting Kit-8 (CCK-8) assay and 5-ethynyl-2'-deoxyuridine (EdU) assay. Cell apoptosis was measured using flow cytometry. The inflammatory response was assessed using enzyme-linked immunosorbent assay (ELISA). Oxidative stress level was assessed using corresponding kits. Nitric oxide (NO) level was examined using NO detection assay. The interaction between miR-188-3p and circ_0026218 or TLR4 was determined via dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays. Exosomes were observed using transmission electron microscopy (TEM). The size distribution of exosomes was analyzed using nanoparticle tracking analysis (NTA).

RESULTS

Ox-LDL treatment caused HUVEC dysfunction by inhibiting cell proliferation and promoting apoptosis, inflammation, and oxidative stress. Circ_0026218 was upregulated in AS serum samples and ox-LDL-treated HUVECs. Knockdown of circ_0026218 attenuated ox-LDL-induced dysfunction in HUVECs. MiR-188-3p acted as a target of circ_0026218, and miR-188-3p downregulation reversed the suppression role of circ_0026218 knockdown on ox-LDL-induced HUVEC disorder. TLR4 was a target of miR-188-3p, and miR-188-3p overexpression alleviated ox-LDL-induced dysfunction in HUVECs by targeting TLR4. Circ_0026218 could deregulate the TLR4/NF-κB pathway by sponging the miR-188-3p. Importantly, circ_0026218 was overexpressed in exosomes from ox-LDL-treated HUVECs and could be delivered via exosomes.

CONCLUSION

Circ_0026218 knockdown attenuated ox-LDL-induced dysfunction in HUVECs via regulating miR-188-3p/TLR4/NF-κB pathway.

Circular RNAs: Regulators of endothelial cell dysfunction in atherosclerosis

Endothelial cell (EC) dysfunction is associated with atherosclerosis. Circular RNAs (circRNAs) are covalently closed loops formed by back-splicing, are highly expressed in a tissue-specific or cell-specific manner, and regulate ECs mainly through miRNAs (mircoRNAs) or protein sponges. This review describes the regulatory mechanisms and physiological functions of circRNAs, as well as the differential expression of circRNAs in aberrant ECs. This review focuses on their roles in inflammation, proliferation, migration, angiogenesis, apoptosis, senescence, and autophagy in ECs from the perspective of signaling pathways, such as nuclear factor κB (NF-κB), nucleotide-binding domain, leucine-rich-repeat family, pyrin-domain-containing 3 (NLRP3)/caspase-1, Janus kinase/signal transducer and activator of transcription (JAK/STAT), and phosphoinositide-3 kinase/protein kinase B (PI3K/Akt). Finally, we address the issues and recent advances in circRNAs as well as circRNA-mediated regulation of ECs to improve our understanding of the molecular mechanisms underlying the progression of atherosclerosis and provide a reference for studies on circRNAs that regulate EC dysfunction and thus affect atherosclerosis.

PRMT5 knockdown enhances cell viability and suppresses cell apoptosis, oxidative stress, inflammation and endothelial dysfunction in ox-LDL-induced vascular endothelial cells via interacting with PDCD4

Atherosclerosis (AS) is an important pathological basis of cardiovascular disease (CVD). The development of AS commences with endothelial dysfunction due to vascular endothelial cell injury. It is well documented that protein arginine methyltransferase 5 (PRMT5) is highly related to cardiovascular events. BioGRID database analysis indicates that PRMT5 may interact with programmed cell death 4 (PDCD4), which is reported to be involved in AS progression. This present research was formulated to elucidate the biological roles of PRMT5/PDCD4 in vascular endothelial cell injury during AS. In this current work, HUVECs were stimulated with 100 mg/L ox-LDL for 48 h to construct an in vitro AS model. Expression levels of PRMT5 and PDCD4 were analyzed by performing RT-qPCR and western blot. The viability and apoptosis of HUVECs were determined using CCK-8, flow cytometry and western blot assays. The status of oxidative stress and inflammation was assessed via commercial detection kits and ELISA assay, respectively. Besides, biomarkers of endothelial dysfunction were detected via commercial detection kit and western blot assay. In addition, the interacting relationship between PRMT5 and PDCD4 was verified by Co-IP assay. Highly expressed PRMT5 was observed in ox-LDL-stimulated HUVECs. Knockdown of PRMT5 enhanced the viability and inhibited the apoptosis of ox-LDL-induced HUVECs as well as alleviated ox-LDL-triggered oxidative stress, inflammation and endothelial dysfunction in HUVECs. PRMT5 interacted and bound with PDCD4. Furthermore, the enhancing effect on cell viability as well as the suppressing effects on cell apoptosis, oxidative stress, inflammation and endothelial dysfunction of PRMT5 knockdown in ox-LDL-induced HUVECs were partially abolished upon up-regulation of PDCD4. To conclude, down-regulation of PRMT5 might exert protective effects against vascular endothelial cell injury during AS by suppressing PDCD4 expression.

Circular RNAs Variously Participate in Coronary Atherogenesis

Over the past decade, numerous studies have shown that circular RNAs (circRNAs) play a significant role in coronary artery atherogenesis and other cardiovascular diseases. They belong to the class of non-coding RNAs and arise as a result of non-canonical splicing of premature RNA, which results in the formation of closed single-stranded circRNA molecules that lack 5'-end caps and 3'-end poly(A) tails. circRNAs have broad post-transcriptional regulatory activity. Acting as a sponge for miRNAs, circRNAs compete with mRNAs for binding to miRNAs, acting as competing endogenous RNAs. Numerous circRNAs are involved in the circRNA-miRNA-mRNA regulatory axes associated with the pathogenesis of cardiomyopathy, chronic heart failure, hypertension, atherosclerosis, and coronary artery disease. Recent studies have shown that сirc_0001445, circ_0000345, circ_0093887, сircSmoc1-2, and circ_0003423 are involved in the pathogenesis of coronary artery disease (CAD) with an atheroprotective effect, while circ_0002984, circ_0029589, circ_0124644, circ_0091822, and circ_0050486 possess a proatherogenic effect. With their high resistance to endonucleases, circRNAs are promising diagnostic biomarkers and therapeutic targets. This review aims to provide updated information on the involvement of atherogenesis-related circRNAs in the pathogenesis of CAD. We also discuss the main modern approaches to detecting and studying circRNA-miRNA-mRNA interactions, as well as the prospects for using circRNAs as biomarkers and therapeutic targets for the treatment of cardiovascular diseases.

Atherosclerosis-associated endothelial dysfunction is promoted by miR-199a-5p/SIRT1 axis regulated by circHIF1ɑ

BACKGROUND AND AIMS

Atherosclerosis (AS) is a chronic inflammatory disease that damages the arterial wall as a result of hyperlipidemia and causes endothelial cell dysfunction, which increases the risk of atherothrombotic events. Multiple pathological conditions have shown ectopic miR-199a-5p levels to cause endothelial injury, but its role in the AS competitive endogenous RNA (CeRNA) network is still unknown.

METHODS AND RESULTS

The high-fat diet (HFD) apoE-/- mouse model was constructed in vivo, and ECs were cultured under ox-LDL treatment to induce EC injury in vitro. Immunohistochemistry and immunofluorescence staining were used to assess the effect of miR-199a-5p on the macrophage, SMC, collagen content, and endothelial coverage in the artery wall of mouse model. miR-199a-5p level was validated to be overexpression in the aorta tissue of HFD apoE-/- mice and in the ox-LDL-treated ECs, and even in the plasma EVs of the patients with cerebral AS. Silencing of miR-199a-5p significantly attenuated atherosclerotic progress in HFD apoE-/- mice, and the gain/loss-of-function assay indicated that miR-199a-5p overexpression aggravated ox-LDL-induced disabilities of endothelial proliferation, motility, and neovascularization based on cell counting kit-8 assay, transwell assay and matrigel assay. Mechanistically, miR-199a-5p prevented EC activation by activating the FOXO signaling pathway by targeting SIRT1. Additionally, circular RNA (circRNA) circHIF1ɑ was identified as having a low expression in the ox-LDL-treated EC and mediated SIRT1 expression via sponging miR-199a-5p to rescue ox-LDL-induced EC injury.

CONCLUSIONS

Our study demonstrated the vital role of miR-199a-5p/SIRT1 axis regulated by circHIF1ɑ in AS pathogenesis and provided novel effective targets for AS treatment.

Circ_0090231 knockdown protects vascular smooth muscle cells from ox-LDL-induced proliferation, migration and invasion via miR-942-5p/PPM1B axis during atherosclerosis

Atherosclerosis (AS) is a dominant pathological basis of cardiovascular disease. Circular RNAs (circRNAs) have been proposed to have crucial functions in regulating pathological progressions of AS. Hence, the aim of this study was to investigate the potential function of circ_0090231 in AS progression. Oxidized low densitylipoprotein (ox-LDL)-challenged vascular smooth muscle cells (VSMCs) were used for in vitro functional analysis. Levels of genes and proteins were measured by qRT-PCR and Western blot. The proliferation, migration and invasion were assessed using cell counting kit-8, 5-ethynyl-2'-deoxyuridine, and transwell assays. The interaction between miR-942-5p and circ_0090231 or PPM1B (Protein Phosphatase, Mg²⁺/Mn²⁺ Dependent 1B) was evaluated by dual-luciferase reporter and pull-down assays. Circ_0090231 is a stable circRNA, and was increased in the serum of AS patients and ox-LDL-challenged VSMCs. Functionally, silencing of circ_0090231 could reverse ox-LDL-induced proliferation, migration and invasion in VSMCs. Mechanistically, circ_0090231 directly targeted miR-942-5p, and PPM1B was a target of miR-942-5p. Besides, circ_0090231 sequestered miR-942-5p to release PPM1B expression, suggesting the circ_0090231/miR-942-5p/PPM1B axis. Further rescue experiments showed that miR-942-5p inhibition or ectopic overexpression of PPM1B dramatically attenuated the suppressing influences of circ_0090231 knockdown on VSMC proliferative, migratory and invasive abilities under ox-LDL treatment. Silencing of circ_0090231 could reverse ox-LDL-induced proliferation, migration and invasion in VSMCs via miR-942-5p/PPM1B axis, providing a theoretical basis for elucidating the mechanism of AS process.

Circular RNA as Therapeutic Targets in Atherosclerosis: Are We Running in Circles?

Much attention has been paid lately to harnessing the diagnostic and therapeutic potential of non-coding circular ribonucleic acids (circRNAs) and micro-RNAs (miRNAs) for the prevention and treatment of cardiovascular diseases. The genetic environment that contributes to atherosclerosis pathophysiology is immensely complex. Any potential therapeutic application of circRNAs must be assessed for risks, benefits, and off-target effects in both the short and long term. A search of the online PubMed database for publications related to circRNA and atherosclerosis from 2016 to 2022 was conducted. These studies were reviewed for their design, including methods for developing atherosclerosis and the effects of the corresponding atherosclerotic environment on circRNA expression. Investigated mechanisms were recorded, including associated miRNA, genes, and ultimate effects on cell mechanics, and inflammatory markers. The most investigated circRNAs were then further analyzed for redundant, disparate, and/or contradictory findings. Many disparate, opposing, and contradictory effects were observed across experiments. These include levels of the expression of a particular circRNA in atherosclerotic environments, attempted ascertainment of the in toto effects of circRNA or miRNA silencing on atherosclerosis progression, and off-target, cell-specific, and disease-specific effects. The high potential for detrimental and unpredictable off-target effects downstream of circRNA manipulation will likely render the practice of therapeutic targeting of circRNA or miRNA molecules not only complicated but perilous.

CircRnas in atherosclerosis, with special emphasis on the spongy effect of circRnas on miRnas

Atherosclerosis (AS) is a chronic inflammatory disease, which leads to atherosclerotic rupture, lumen stenosis and thrombosis, and often endangers life. Circular RNAs (circRNAs) are a special class of non-coding RNA molecules, whose abnormal expression has been proved to be closely related to human diseases, including AS. Both the abnormal regulation of circRNAs and the sponging effect on miRNAs would lead to changes in gene expression in the form of epigenetic modification, ultimately leading to the formation of AS. CircRNAs can be used as peripheral blood markers of AS, and play an important regulatory role in the proliferation, migration, inflammation and apoptosis of vascular smooth muscle cells, endothelial cells and macrophage, which are key cells for the development of AS. The in-depth understanding of circRNAs in AS not only provides a new method for the diagnosis of AS, but also provides a new idea for the treatment of AS.

circ_0014736 induces GPR4 to regulate the biological behaviors of human placental trophoblast cells through miR-942-5p in preeclampsia

Previous studies have indicated that the development of preeclampsia (PE) involves the regulation of circular RNA (circRNA). However, the role of hsa_circ_0014736 (circ_0014736) in PE remains unknown. Thus, the study proposes to reveal the function of circ_0014736 in the pathogenesis of PE and the underlying mechanism. The results showed that circ_0014736 and GPR4 expression were significantly upregulated, while miR-942-5p expression was downregulated in PE placenta tissues when compared with normal placenta tissues. circ_0014736 knockdown promoted the proliferation, migration, and invasion of placenta trophoblast cells (HTR-8/SVneo) and inhibited apoptosis; however, circ_0014736 overexpression had the opposite effects. circ_0014736 functioned as a sponge for miR-942-5p and regulated HTR-8/SVneo cell processes by interacting with miR-942-5p. Additionally, GPR4, a target gene of miR-942-5p, was involved in miR-942-5p-mediated actions in HTR-8/SVneo cells. Moreover, circ_0014736 stimulated GPR4 production through miR-942-5p. Collectively, circ_0014736 inhibited HTR-8/SVneo cell proliferation, migration, and invasion and induced cell apoptosis through the miR-942-5p/GPR4 axis, providing a possible target for the treatment of PE.

The role of class IIa histone deacetylases in regulating endothelial function

Vascular endothelial cells (ECs) are monolayer cells located in the inner layer of the blood vessel. Endothelial function is crucial in maintaining local and systemic homeostasis and is precisely regulated by sophisticated signaling pathways and epigenetic regulation. Endothelial dysfunctions are the main factors for the pathophysiological process of cardiovascular and cerebrovascular diseases like atherosclerosis, hypertension, and stroke. In these pathologic processes, histone deacetylases (HDACs) involve in epigenetic regulation by removing acetyl groups from lysine residues of histones and regulating downstream gene expression. Among all HDACs, Class IIa HDACs (HDAC4, 5, 7, 9) contain only an N-terminal regulatory domain, exert limited HDAC activity, and present tissue-specific gene regulation. Here, we discuss and summarize the current understanding of this distinct subfamily of HDACs in endothelial cell functions (such as angiogenesis and immune response) with their molecular underpinnings. Furthermore, we also present new thoughts for further investigation of HDAC inhibitors as a potential treatment in several vascular diseases.

Circ_0004104 participates in the regulation of ox-LDL-induced endothelial cells injury via miR-942-5p/ROCK2 axis

BACKGROUND

Cardiovascular disease was the most common disease among the elderly with high morbidity and mortality. Circ_0004104 was demonstrated to be involved in the regulation of atherosclerosis.

METHODS

Quantitative real-time polymerase chain reaction was employed to measure the expression of circ_0004104, miR-942-5p and Rho associated coiled-coil containing protein kinase 2 (ROCK2). Cell proliferation was tested by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. Cell apoptosis was measured by flow cytometry, and tube formation assay was used to detect the angiogenesis ability of cells. Western blot assay was performed to assess protein levels. Enzyme‑linked immunosorbent assay was used to detect the release of IL-1β and TNF-α. The relationship between miR-942-5p and circ_0004104 or ROCK2 was identified by dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay, and RNA pull-down assay.

RESULTS

Oxidized low-density lipoprotein (ox-LDL) inhibited the proliferation of human umbilical vein endothelial cells (HUVECs) and promoted apoptosis in a dose-dependent manner. Circ_0004104 was increased in serum of atherosclerosis patients and ox-LDL-treated HUVECs, and silence of circ_0004104 promoted the proliferation of ox-LDL-exposed HUVECs and inhibited cell apoptosis. MiR-942-5p downregulation reversed si-circ_0004104-mediated influences in HUVECs upon ox-LDL exposure. ROCK2 was the target of miR-942-5p and circ_0004104 regulated the expression of ROCK2 through sponging miR-942-5p. ROCK2 abated the influences of miR-942-5p in ox-LDL-stimulated HUVECs. Circ_0004104 was increased in the exosomes derived from ox-LDL-exposed HUVECs, and the expression of circ_0004104 was promoted in HUVECs after stimulation with ox-LDL-treated HUVECs cells-derived exosomes.

CONCLUSION

Circ_0004104 downregulation receded ox-LDL-induced injury in HUVECs through miR-942-5p and ROCK2.

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.

Circ_HECW2 regulates ox-LDL-induced dysfunction of cardiovascular endothelial cells by miR-942-5p/TLR4 axis

BACKGROUND

Coronary artery disease (CAD) is a common coronary artery disease. The functional mechanism of circular RNA (circRNA) HECT, C2 and WW domain containing E3 ubiquitin protein ligase 2 (circ_HECW2, hsa_circ_0057583) in ox-LDL-treated human cardiac microvascular endothelial cells (hCMECs) is still unclear.

METHODS

Expression levels of circ_HECW2, microRNA (miR)-942-5p, and toll-like receptor 4 (TLR4) were analyzed by quantitative real-time PCR (qRT-PCR) and western blot assays. Cell proliferation and apoptosis were analyzed by 5-ethynyl-2'-deoxyuridine (EdU) assay, cell counting kit-8 (CCK8) assay, and flow cytometry, respectively. Tube formation assay was performed to analyze the angiogenesis of cells. Luciferase reporter and RNA pull-down assays were performed to analyze the target relationship among circ_HECW2, miR-942-5p and TLR4.

RESULTS

Circ_HECW2 and TLR4 expression levels were up-regulated and miR-942-5p expression was decreased in the serum of CAD patients and oxidized low-density lipoprotein (ox-LDL)-induced hCMECs. Knockdown of circ_HECW2 enhanced cell proliferation and inhibited cell apoptosis in ox-LDL-treated hCMECs. MiR-942-5p was the target of circ_HECW2 and directly targeted TLR4. Moreover, the effect of circ_HECW2 knockdown could be weakened by anti-miR-942-5p, and TLR4 could restore the function of miR-942-5p on cell damage of ox-LDL-induced hCMECs.

CONCLUSION

Circ_HECW2 could regulate ox-LDL-induced cardiovascular endothelial cell dysfunction through targeting miR-942-5p/TLR4 axis.

The mechanisms of glycolipid metabolism disorder on vascular injury in type 2 diabetes

Patients with diabetes have severe vascular complications, such as diabetic nephropathy, diabetic retinopathy, cardiovascular disease, and neuropathy. Devastating vascular complications lead to increased mortality, blindness, kidney failure, and decreased overall quality of life in people with type 2 diabetes (T2D). Glycolipid metabolism disorder plays a vital role in the vascular complications of T2D. However, the specific mechanism of action remains to be elucidated. In T2D patients, vascular damage begins to develop before insulin resistance and clinical diagnosis. Endothelial dysregulation is a significant cause of vascular complications and the early event of vascular injury. Hyperglycemia and hyperlipidemia can trigger inflammation and oxidative stress, which impair endothelial function. Furthermore, during the pathogenesis of T2D, epigenetic modifications are aberrant and activate various biological processes, resulting in endothelial dysregulation. In the present review, we provide an overview and discussion of the roles of hyperglycemia- and hyperlipidemia-induced endothelial dysfunction, inflammatory response, oxidative stress, and epigenetic modification in the pathogenesis of T2D. Understanding the connections of glucotoxicity and lipotoxicity with vascular injury may reveal a novel potential therapeutic target for diabetic vascular complications.

Construction of circRNA-Mediated Immune-Related ceRNA Network and Identification of Circulating circRNAs as Diagnostic Biomarkers in Acute Ischemic Stroke

Background and Purpose

Accumulating evidence suggests that circular RNAs (circRNAs) are involved in immune and inflammatory processes after acute ischemic stroke (AIS). However, the roles of circRNA-mediated competing endogenous RNA (ceRNA) in modulating immune inflammation of AIS have not yet been determined. This study aimed to construct a circRNA-mediated immune-related ceRNA network and identify novel circRNAs in AIS.

Methods

Microarray data were downloaded from the GEO database and further analysed by R software. Then, we constructed a circRNA-mediated ceRNA network based on interaction information from the bioinformatics database. A topological property analysis of the ceRNA network was conducted to screen novel circRNAs. Finally, we further applied quantitative real-time polymerase chain reaction (qRT-PCR) to two independent sets.

Results

We constructed an AIS immune-related ceRNA (AISIRC) network containing immune-related genes (IRGs), miRNAs, and circRNAs. Additionally, we extracted the subnetwork from the AISIRC network and screened six immune-related circRNAs. After identification and validation, we finally confirmed that plasma levels of circPTP4A2 and circTLK2 were significantly increased in AIS patients compared with both healthy control subjects (HCs) and transient ischemic attack (TIA) patients. Logistic regression and receiver-operating characteristic (ROC) curve analyses demonstrated that these two circRNAs may function as predictive and discriminative biomarkers for AIS. We also confirmed that plasma levels of circPTP4A2 were elevated in TIA patients compared with HCs and might be an independent risk factor for predicting TIA. Longitudinal analysis of circRNA expression up to 90 days after AIS indicated that the ability of circPTP4A2 and circTLK2 to monitor AIS dynamics was highly desirable.

Conclusion

In summary, the circRNA-mediated immune-related ceRNA network was successfully constructed, and two circulating circRNAs (circPTP4A2 and circTLK2) improved sensitivity for the diagnosis of AIS and could be considered diagnostic biomarkers.

CircRNA-miRNA interactions in atherogenesis

Atherosclerosis is the major cause of coronary artery disease (CAD) which includes unstable angina, myocardial infarction, and heart failure. The onset of atherogenesis, a process of atherosclerotic lesion formation in the intima of arteries, is driven by lipid accumulation, a vicious cycle of reactive oxygen species (ROS)-induced oxidative stress and inflammatory reactions leading to endothelial cell (EC) dysfunction, vascular smooth muscle cell (VSMC) activation, and foam cell formation which further fuel plaque formation and destabilization. In recent years, there is a surge in the number of publications reporting the involvement of circular RNAs (circRNAs) in the pathogenesis of cardiovascular diseases, cancers, and metabolic syndromes. These studies have advanced our understanding on the biological functions of circRNAs. One of the most common mechanism of action of circRNAs reported is the sponging of microRNAs (miRNAs) by binding to the miRNAs response element (MRE), thereby indirectly increases the transcription of their target messenger RNAs (mRNAs). Individual networks of circRNA-miRNA-mRNA associated with atherogenesis have been extensively reported, however, there is a need to connect these findings for a complete overview. This review aims to provide an update on atherogenesis-related circRNAs and analyze the circRNA-miRNA-mRNA interactions in atherogenesis. The atherogenic mechanisms and clinical relevance of each atherogenesis-related circRNA were systematically discussed for better understanding of the knowledge gap in this area.

Circ_0003204 knockdown protects endothelial cells against oxidized low-density lipoprotein-induced injuries by targeting the miR-491-5p-ICAM1 pathway

Emerging evidence indicates that circular RNA (circRNA) is implicated in the development of atherosclerosis (AS). This study investigated the effect of circ_0003204 on endothelial cell function and explored the functional mechanism of circ_0003204 in AS progression. AS cell models were constructed by treating human umbilical vein endothelial cells (HUVEC) with oxidized low-density lipoprotein (ox-LDL). The expression of circ_0003204 was detected by quantitative real-time PCR (qPCR). The releases of pro-inflammatory factors were determined by ELISA. Cell viability was checked by CCK-8 assay. Cell apoptosis was monitored by flow cytometry assay. The ability of angiogenesis was assessed by tube formation assay. The protein levels of cell development- and apoptosis-related markers were measured by western blot. The binding relationship between miR-491-5p and circ_0003204 or intercellular adhesion molecule 1 (ICAM1) was verified by dual-luciferase reporter assay or RIP assay. The expression of circ_0003204 was strengthened in ox-LDL-treated HUVECs. Circ_0003204 knockdown inhibited ox-LDL-induced inflammation and cell apoptosis, and promoted ox-LDL-depleted cell viability and tube formation ability in HUVECs. MiR-491-5p was a target of circ_0003204, and miR-491-5p directly bound to ICAM1 3'UTR. Accordingly, circ_0003204 positively regulated ICAM1 expression by targeting miR-491-5p. Rescue experiments presented that miR-491-5p inhibition reversed the effects of circ_0003204 knockdown, and ICAM1 overexpression abolished the effects of miR-491-5p restoration. Circ_0003204 knockdown protects HUVECs against ox-LDL-induced injuries by targeting the miR-491-5p-ICAM1 pathway, hinting that circ_0003204 inhibition might prevent AS development.

miR-942-5p prevents sepsis-induced acute lung injury via targeting TRIM37

MicroRNAs (miRNAs) have been demonstrated to play pivotal roles in the pathogenesis of sepsis-induced acute lung injury (ALI). In this work, we aimed to clarify the potential role and the underlying mechanism of miR-942-5p in a lipopolysaccharide (LPS)-induced A549 cell injury model. The cell injury was evaluated by CCK-8 assay, flow cytometry and enzyme-linked immunosorbent assay (ELISA). The expression levels of miR-942-5p and tripartite motif-containing protein 37 (TRIM37) were measured by real-time PCR and Western blot, and their association was then validated by bioinformatics, luciferase reporter assay and RNA pull-down assay. We found that the expression of miR-942-5p was decreased in LPS-treated A549 cells. Furthermore, LPS treatment suppressed A549 cell viability, promoted apoptosis and increased the levels of inflammatory cytokines. Conversely, overexpression of miR-942-5p increased cell viability, reduced apoptosis and alleviated inflammatory cytokine secretion in the presence of LPS. Moreover, miR-942-5p directly targeted TRIM37 by binding to the 3'-UTR of TRIM37 mRNA. Upregulation of TRIM37 effectively reversed the anti-apoptotic and anti-inflammatory effects of miR-942-5p in LPS-induced A549 cells. Our findings suggested that miR-942-5p protected against LPS-induced cell injury through inhibiting apoptosis and inflammation in A549 cells by negatively regulating TRIM37.