Up-regulation of circRNA_0068481 promotes right ventricular hypertrophy in PAH patients via regulating miR-646/miR-570/miR-885

Circular RNA in Cardiovascular Diseases: Biogenesis, Function and Application

Cardiovascular diseases pose a significant public health challenge globally, necessitating the development of effective treatments to mitigate the risk of cardiovascular diseases. Recently, circular RNAs (circRNAs), a novel class of non-coding RNAs, have been recognized for their role in cardiovascular disease. Aberrant expression of circRNAs is closely linked with changes in various cellular and pathophysiological processes within the cardiovascular system, including metabolism, proliferation, stress response, and cell death. Functionally, circRNAs serve multiple roles, such as acting as a microRNA sponge, providing scaffolds for proteins, and participating in protein translation. Owing to their unique properties, circRNAs may represent a promising biomarker for predicting disease progression and a potential target for cardiovascular drug development. This review comprehensively examines the properties, biogenesis, and potential mechanisms of circRNAs, enhancing understanding of their role in the pathophysiological processes impacting cardiovascular disease. Furthermore, the prospective clinical applications of circRNAs in the diagnosis, prognosis, and treatment of cardiovascular disease are addressed.

Sodium butyrate alleviates right ventricular hypertrophy in pulmonary arterial hypertension by inhibiting H19 and affecting the activation of let-7g-5p/IGF1 receptor/ERK

Pulmonary arterial hypertension (PAH) is a complex and fatal cardio-pulmonary vascular disease. Decompensated right ventricular hypertrophy (RVH) caused by cardiomyocyte hypertrophy often leads to fatal heart failure, the leading cause of mortality among patients. Sodium butyrate (SB), a compound known to reduce cardiac hypertrophy, was examined for its potential effect and the underlying mechanism of SB on PAH-RVH. The in vivo study showed that SB alleviated RVH and cardiac dysfunction, as well as improved life span and survival rate in MCT-PAH rats. The in vivo and in vitro experiments showed that SB could attenuate cardiomyocyte hypertrophy by reversing the expressions of H19, let-7g-5p, insulin-like growth factor 1 receptor (IGF1 receptor), and pERK. H19 inhibition restored the level of let-7g-5p and prevented the overexpression of IGF1 receptor and pERK in hypertrophic cardiomyocytes. In addition, dual luciferase assay revealed that H19 demonstrated significant binding with let-7g-5p, acting as its endogenous RNA. Briefly, SB attenuated PAH-RVH by inhibiting the H19 overexpression, restoring the level of let-7g-5p, and hindering IGF1 receptor/ERK activation.

Posttranscriptional Regulation by Proteins and Noncoding RNAs

Posttranscriptional regulation comprises those mechanisms occurring after the initial copy of the DNA sequence is transcribed into an intermediate RNA molecule (i.e., messenger RNA) until such a molecule is used as a template to generate a protein. A subset of these posttranscriptional regulatory mechanisms essentially are destined to process the immature mRNA toward its mature form, conferring the adequate mRNA stability, providing the means for pertinent introns excision, and controlling mRNA turnover rate and quality control check. An additional layer of complexity is added in certain cases, since discrete nucleotide modifications in the mature RNA molecule are added by RNA editing, a process that provides large mature mRNA diversity. Moreover, a number of posttranscriptional regulatory mechanisms occur in a cell- and tissue-specific manner, such as alternative splicing and noncoding RNA-mediated regulation. In this chapter, we will briefly summarize current state-of-the-art knowledge of general posttranscriptional mechanisms, while major emphases will be devoted to those tissue-specific posttranscriptional modifications that impact on cardiac development and congenital heart disease.

Circ_0068481 Affects the Human Pulmonary Artery Smooth Muscle Cells' Progression by miR-361-3p/KLF5 Axis

BACKGROUND

Uncontrolled proliferation of pulmonary artery smooth muscle cells (PASMCs) contributes to the pathogenesis of pulmonary arterial hypertension (PAH). In this work, we defined the precise part of circ_0068481 in PASMC proliferation and migration induced by hypoxia. We hypothesized that circ_0068481 enhanced hypoxia-induced PASMC proliferation, invasion, and migration through the microRNA (miR)-361-3p/Krüppel-like factor 5 (KLF5) pathway.

METHODS

Human PASMCs (hPASMCs) were exposed to hypoxic (3% O2) conditions. Circ_0068481, miR-361-3p, and KLF5 levels were gauged by qRT-PCR and western blot. Cell viability, proliferation, invasion, and migration were detected by XTT, EdU incorporation, transwell, and wound-healing assays, respectively. Dual-luciferase reporter, RNA immunoprecipitation, and RNA pull-down assays were performed to confirm the direct relationship between miR-361-3p and circ_0068481 or KLF5.

RESULTS

Circ_0068481 expression was increased in the serum of PAH patients and hypoxia-induced hPASMCs. Downregulation of circ_0068481 attenuated hypoxia-induced promotion in hPASMC proliferation, invasion, and migration. Circ_0068481 directly targeted miR-361-3p, and miR-361-3p downregulation reversed the inhibitory effects of circ_0068481 silencing on hypoxia-induced hPASMC proliferation, invasion, and migration. KLF5 was a direct miR-361-3p target, and miR-361-3p upregulation mitigated hypoxia-induced hPASMC proliferation, invasion, and migration by inhibiting KLF5 expression. Moreover, circ_0068481-induced KLF5 expression by binding to miR-361-3p in hypoxic hPASMCs.

CONCLUSIONS

Circ_0068481 knockdown ameliorated hypoxia-induced hPASMC proliferation, invasion, and migration at least in part through the miR-361-3p/KLF5 axis.

MicroRNAs and their regulators: Potential therapeutic targets in pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a complex and progressive disease characterized by pulmonary arterial remodeling. Despite that current combination therapy has shown improvement in morbidity and mortality, a better deciphering of the underlying pathological mechanisms and novel therapeutic targets is urgently needed to combat PAH. MicroRNA, the critical element in post-transcription mechanisms, mediates cellular functions mainly by tuning downstream target gene expression. Meanwhile, upstream regulators can regulate miRNAs in synthesis, transcription, and function. In vivo and in vitro studies have suggested that miRNAs and their regulators are involved in PAH. However, the miRNA-related regulatory mechanisms governing pulmonary vascular remodeling and right ventricular dysfunction remain elusive. Hence, this review summarized the controversial roles of miRNAs in PAH pathogenesis, focused on different miRNA-upstream regulators, including transcription factors, regulatory networks, and environmental stimuli, and finally proposed the prospects and challenges for the therapeutic application of miRNAs and their regulators in PAH treatment.

Right Ventricle and Epigenetics: A Systematic Review

There is an increasing recognition of the crucial role of the right ventricle (RV) in determining the functional status and prognosis in multiple conditions. In the past decade, the epigenetic regulation (DNA methylation, histone modification, and non-coding RNAs) of gene expression has been raised as a critical determinant of RV development, RV physiological function, and RV pathological dysfunction. We thus aimed to perform an up-to-date review of the literature, gathering knowledge on the epigenetic modifications associated with RV function/dysfunction. Therefore, we conducted a systematic review of studies assessing the contribution of epigenetic modifications to RV development and/or the progression of RV dysfunction regardless of the causal pathology. English literature published on PubMed, between the inception of the study and 1 January 2023, was evaluated. Two authors independently evaluated whether studies met eligibility criteria before study results were extracted. Amongst the 817 studies screened, 109 studies were included in this review, including 69 that used human samples (e.g., RV myocardium, blood). While 37 proposed an epigenetic-based therapeutic intervention to improve RV function, none involved a clinical trial and 70 are descriptive. Surprisingly, we observed a substantial discrepancy between studies investigating the expression (up or down) and/or the contribution of the same epigenetic modifications on RV function or development. This exhaustive review of the literature summarizes the relevant epigenetic studies focusing on RV in human or preclinical setting.

circ-BPTF serves as a miR-486-5p sponge to regulate CEMIP and promotes hypoxic pulmonary arterial smooth muscle cell proliferation in COPD

Hypoxia plays a crucial role in pulmonary vascular remodelling at the early stage of chronic obstructive pulmonary disease (COPD). Circle RNA (circRNA) has been identified to play a critical role in multiple diseases. However, the role of circRNAs in pulmonary vascular remodelling in COPD remains unclear. In this study, we aim to investigate the role of circRNAs in pulmonary arterial smooth muscle cell proliferation and pulmonary vascular remodelling in COPD. COPD patients show lower partial pressure of arterial oxygen and pulmonary arterial remodeling as compared with controls. circRNA microarray and real-time PCR analyses show significantly higher level of circ-BPTF and lower miR-486-5p level in the pulmonary arteries of COPD patients as compared with controls. Hypoxia suppresses miR-486-5p expression but promotes expressions of circ-BPTF and cell migration inducing protein (CEMIP) in human pulmonary arterial smooth muscle cells (PASMCs) in vitro. Loss- and gain-of-function experiments show that circ-BPTF promotes PASMC proliferation in vitro. Moreover, luciferase reporter assay results indicate that circ-BPTF regulates PASMC proliferation by acting as an miR-486-5p sponge. CEMIP is identified as a candidate target gene of miR-486-5p by luciferase reporter assay. Overall, our study shows that circ-BPTF serves as a miR-486-5p sponge to regulate CEMIP and promote hypoxic PASMC proliferation in pulmonary vascular remodelling in COPD.

The role of circular RNAs in pulmonary hypertension

Circular RNAs (circRNAs) are endogenous, covalently circularised, non-protein-coding RNAs generated from back-splicing. Most circRNAs are very stable, highly conserved, and expressed in a tissue-, cell- and developmental stage-specific manner. circRNAs play a significant role in various biological processes, such as regulation of gene expression and protein translation via sponging of microRNAs and binding with RNA-binding proteins. circRNAs have become a topic of great interest in research due to their close link with the development of various diseases. Their high stability, conservation and abundance in body fluids make them promising biomarkers for many diseases. A growing body of evidence suggests that aberrant expression of circRNAs and their targets plays a crucial role in pulmonary vascular remodelling and pulmonary arterial hypertension (group 1) as well as other forms (groups 3 and 4) of pulmonary hypertension (PH). Here we discuss the roles and molecular mechanisms of circRNAs in the pathogenesis of pulmonary vascular remodelling and PH. We also highlight the therapeutic and biomarker potential of circRNAs in PH.

Integration of RNA molecules data with prior-knowledge driven Joint Deep Semi-Negative Matrix Factorization for heart failure study

Heart failure (HF) is the main manifestation of cardiovascular disease. Recent studies have shown that various RNA molecules and their complex connections play an essential role in HF’s pathogenesis and pathological progression. This paper aims to mine key RNA molecules associated with HF. We proposed a Prior-knowledge Driven Joint Deep Semi-Negative Matrix Factorization (PD-JDSNMF) model that uses a hierarchical nonlinear feature extraction method that integrates three types of data: mRNA, lncRNA, and miRNA. The PPI information is added to the model as prior knowledge, and the Laplacian constraint is used to help the model resist the noise in the genetic data. We used the PD-JDSNMF algorithm to identify significant co-expression modules. The elements in the module are then subjected to bioinformatics analysis and algorithm performance analysis. The results show that the PD-JDSNMF algorithm can robustly select biomarkers associated with HF. Finally, we built a heart failure diagnostic model based on multiple classifiers and using the Top 13 genes in the significant module, the AUC of the internal test set was up to 0.8714, and the AUC of the external validation set was up to 0.8329, which further confirmed the effectiveness of the PD-JDSNMF algorithm.

The Landscape of Noncoding RNA in Pulmonary Hypertension

The transcriptome of pulmonary hypertension (PH) is complex and highly genetically heterogeneous, with noncoding RNA transcripts playing crucial roles. The majority of RNAs in the noncoding transcriptome are long noncoding RNAs (lncRNAs) with less circular RNAs (circRNAs), which are two characteristics gaining increasing attention in the forefront of RNA research field. These noncoding transcripts (especially lncRNAs and circRNAs) exert important regulatory functions in PH and emerge as potential disease biomarkers and therapeutic targets. Recent technological advancements have established great momentum for discovery and functional characterization of ncRNAs, which include broad transcriptome sequencing such as bulk RNA-sequence, single-cell and spatial transcriptomics, and RNA-protein/RNA interactions. In this review, we summarize the current research on the classification, biogenesis, and the biological functions and molecular mechanisms of these noncoding RNAs (ncRNAs) involved in the pulmonary vascular remodeling in PH. Furthermore, we highlight the utility and challenges of using these ncRNAs as biomarkers and therapeutics in PH.

CircFBXW7 inhibits the tumorigenesis of T-cell acute lymphoblastic leukemia through modulating miR-494-3p/SOX1 axis

T-cell acute lymphoblastic leukemia (T-ALL) is a type of leukemia with high malignant behaviors, which seriously threatens the health of people. It has been reported that circFBXW7 is downregulated in lymphoblastic leukemia. Nevertheless, the exact role of circFBXW7 in T-ALL remains elusive. MTT assay was used to assess the cell viability. Cell apoptosis was assessed by flow cytometry. In addition, mRNA expressions were assessed by RT-qPCR, and a western blot was applied to investigate the protein levels. Meanwhile, the correlation among circFBXW7, miR-494-3p, and SOX1 was explored by RNA pull-down and dual-luciferase reporter assays. Furthermore, a xenograft mice model was conducted to verify the function of circFBXW7 in T-ALL in vivo. CircFBXW7 was significantly downregulated in T-ALL, of which overexpression inhibited the cell viability and induced the apoptosis of Jurkat cells. Moreover, miR-494-3p was identified to be a functional downstream effector to be involved in circFBXW7-mediated T-ALL cell proliferation. Besides, SOX1 was a direct target of miR-494-3p, and the impact of miR-494-3p mimics on T-ALL cell growth was inhibited in the presence of SOX1 overexpression. Furthermore, overexpression of circFBXW7 dramatically inhibited T-ALL tumor growth. In summary, circFBXW7 attenuated the tumorigenesis of T-ALL through the mediation of the miR-494-3p/SOX1 axis, which might be novel targets for T-ALL treatment.

Circular RNA Sirtuin1 represses pulmonary artery smooth muscle cell proliferation, migration and autophagy to ameliorate pulmonary hypertension via targeting microRNA-145-5p/protein kinase-B3 axis

Recently, several studies have been clarified that circular RNA (circRNA) was a vital regulatory gene of pulmonary hypertension (PH). Nevertheless, the action of circRNA in PH was not yet explored. This study was to figure out the biological function and potential molecular mechanism of circSirtuin1 (SIRT1) in PH. Construction of the PH rat model and hypoxia pulmonary artery smooth muscle cells (PASMC) model was performed, and test of circSIRT1/microRNA (miR)-145-5p/protein kinase-B3 (Akt3) was conducted. The influence of the circSIRT1/miR-145-5p/Akt3 axis on the histopathology, hemodynamics with autophagy of the pulmonary artery in rats was examined. Additionally, the impact of circSIRT1/miR-145-5p/Akt3 on the proliferation, migration and apoptosis with autophagy of PASMC under hypoxic environment was also determined. The targeting of circSIRT1/miR-145-5p/Akt3 was testified. The results manifested that circSIRT1 and Akt3 were elevated in PH, while miR-145-5p was declined. Knockdown of circSIRT1 ameliorated rat PH, suppressed PASMC proliferation, migration with autophagy in hypoxic environment. CircSIRT1 competitively combined with miR-145-5p to mediate Akt3. To sum up, circSIRT1/miR-145-5p/Akt3 was supposed to perform as a prospective molecular target for the treatment of PH.

Circular RNAs in pulmonary hypertension: Emerging biological concepts and potential mechanism

Circular RNAs (circRNAs) are endogenous RNAs with a covalently closed single-stranded transcript. They are a novel class of genomic regulators that are linked to many important development and disease processes and are being pursued as clinical and therapeutic targets. Using the most powerful RNA sequencing and bioinformatics techniques, a large number of circRNAs have been identified and further functional studies have been performed. It is known that circRNAs act as potential biomarkers, sponges for microRNAs (miRNAs) and RNA-binding proteins (RBPs), and regulators of mRNA transcription. They also participate in the translation of peptides or proteins. Many types of circRNAs are dysregulated in plasma or lung tissues, and they may be involved in regulating the proliferation and apoptosis of pulmonary artery endothelial cells (PAECs) and pulmonary artery smooth muscle cells (PASMCs), leading to pulmonary vascular remodeling in pulmonary hypertension (PH). One possible mechanism is that circRNAs can regulate the function of PAECs and PASMCs by acting as miRNA sponge. However, other potential mechanisms of action of circRNAs are still being actively explored in PH. This paper presents a systematic review of the biogenesis, biological characterization, relevant underlying functions, and future perspectives for studies of circRNAs in the pathogenesis of PH.

circ‑Grm1 promotes pulmonary artery smooth muscle cell proliferation and migration via suppression of GRM1 expression by FUS

Pulmonary arterial hypertension is a progressive and fatal disease. Recent studies suggest that circular RNA (circRNAs/circs) can regulate various biological processes, including cell proliferation. Therefore, it is possible that circRNA may have important roles in pulmonary artery smooth muscle cell proliferation in hypoxic pulmonary hypertension (HPH). The aim of the present study was to determine the role and mechanism of circRNA‑glutamate metabotropic receptor 1 (circ‑Grm1; mmu_circ_0001907) in pulmonary artery smooth muscle cell (PASMC) proliferation and migration in HPH. High‑throughput transcriptome sequencing was used to screen circRNAs and targeted genes involved in HPH. Cell Counting Kit‑8 (CCK‑8), 5‑ethynyl‑2‑deoxyuridine and wound healing assays were employed to assess cell viability and migration. Reverse transcription‑quantitative PCR and western blotting were used to detect target gene expression in different groups. Bioinformatical approaches were used to predict the interaction probabilities of circ‑Grm1 and Grm1 with FUS RNA binding protein (FUS). The interactions of circ‑Grm1, Grm1 and FUS were evaluated using RNA silencing and RNA immunoprecipitation assays. The results demonstrated that circ‑Grm1 was upregulated in hypoxic PASMCs. Further experiments revealed that the knockdown of circ‑Grm1 could suppress the proliferation and migration of hypoxic PASMCs. Transcriptome sequencing revealed that Grm1 could be the target gene of circ‑Grm1. It was found that circ‑Grm1 could competitively bind to FUS and consequently downregulate Grm1. Moreover, Grm1 could inhibit the function of circ‑Grm1 by promoting the proliferative and migratory abilities of hypoxic PASMCs. The results also demonstrated that circ‑Grm1 influenced the biological functions of PASMCs via the Rap1/ERK pathway by regulating Grm1. Overall, the current results suggested that circ‑Grm1 was associated with HPH and promoted the proliferation and migration of PASMCs via suppression of Grm1 expression through FUS.

Up-regulation of circRNA_0068481 promotes right ventricular hypertrophy in PAH patients via regulating miR-646/miR-570/miR-885

CircRNA‐0068481 and several miRNAs are important in the pathogenesis of right ventricular hypertrophy (VH), while the inhibition of eye absent transcriptional coactivator and phosphatase 3 (EYA3) was proved to reverse vascular remodelling in rats. In this study, we tried to study the diagnostic value and mechanistic role of circRNA_0068481 in the diagnosis of RVH in PAH patients. qPCR was done to measure circRNA‐0068481, miR‐646, miR‐750, miR‐885 and EYA3 mRNA expression. Luciferase assay was done to explore the regulatory relationship between circRNA‐0068481/EYA3 and the miRNAs. Western blot was done to measure EYA3 expression in AC16 cells. The expression of circRNA‐0068481, miR‐646 and miR‐570 showed a considerable capability to diagnose RVH in PAH patients. The luciferase activity of circRNA‐0068481 was remarkably suppressed by miR‐646, miR‐570 or miR‐885. The luciferase signal of EYA3 was also inhibited by miR‐646, miR‐570 and miR‐885. Up‐regulation of circRNA‐0068481 expression in AC16 significantly decreased miR‐646, miR‐570 and miR‐885 expression, and up‐regulated EYA3 expression, whereas circRNA‐0068481 down‐regulation significantly increased miR‐646, miR‐570 and miR‐885 expression, and repressed EYA3 expression. CircRNA_0068481 sponged several miRNAs including miR‐646, miR‐570 and miR‐885. These miRNAs were all found to target the expression of EYA3 mRNA, which is involved in the onset of right ventricular hypertrophy. Therefore, it can be concluded that the up‐regulation of circRNA_0068481 can predict the diagnosis of right ventricular hypertrophy in pulmonary arterial hypertension patients.