A novel circular RNA (hsa_circ_0059930)-mediated miRNA-mRNA axis in the lipopolysaccharide-induced acute lung injury model of MRC-5 cells

Development of biomimetic co-culture and tri-culture models to mimic the complex structure of the alveolar-capillary barrier

Alveoli are the functional area of respiratory system where the gaseous exchanges take place at level of the alveolar-capillary barrier. The development of safe and effective therapeutic approaches for treating lung disease is currently limited due to the lack of realistic preclinical models for their testing and validation. In this work, tissue engineering approaches were exploited to develop a biomimetic platform that provide an appropriate mimicking of the extracellular environment and the multicellular architecture of human alveoli. Here, we propose the implementation of two biomimetic in vitro models to reproduce the features of the main anatomic portions of the physiological alveolar-capillary barrier. First, a co-culture barrier model was obtained by integrating an electrospun polycaprolactone-gelatin (PCL-Gel) membrane in a modified transwell insert (PCL-Gel TW) to mimic the alveolar basement membrane (coded as thin model). Alveolar epithelial (A549) and lung microvascular endothelial (HULEC-5a) cells were cultured on the apical and basolateral side of the PCL-Gel membrane, respectively, under physiologic air-liquid interface (ALI) conditions for 7 days. The ALI condition promoted the expression of type I and type II alveolar epithelial cell markers and the secretion of mucus in A549 cells. Increased cell viability and barrier properties in co-cultures of A549 and HULEC-5a compared to mono-cultures revealed the effectiveness of the model to reproduce in vitro physiological-relevant features of the alveolar-capillary barrier. The second portion of the alveolar-capillary barrier was developed implementing a tri-culture model (coded as thick model) including a type I collagen (COLL) hydrogel formulated to host lung fibroblasts (MRC-5). The thick barrier model was implemented by seeding HULEC-5a on the basolateral side of PCL-Gel TW and then pouring sequentially MRC-5-laden COLL hydrogel and A549 cells on the apical side of the electrospun membrane. The thick model was maintained up to 7 days at ALI and immunofluorescence staining of tight and adherent junctions demonstrated the formation of a tight barrier. Lastly, the ability of models to emulate pathological inflammatory conditions was validated by exposing the apical compartment of the PCL-Gel TW to lipopolysaccharide (LPS). The damage of A549 tight junctions, the increase of barrier permeability and IL-6 pro-inflammatory cytokine release was observed after 48 h exposure to LPS.

CircRNA itchy E3 ubiquitin protein ligase improves mitochondrial dysfunction in sepsis-induced acute kidney injury by targeting microRNA-214-3p/ATP-binding cassette A1 axis

BACKGROUND

Circular RNAs (circRNAs) are promising biomarkers and therapeutic targets for acute kidney injury (AKI). In this study, we investigated the mechanism by which circRNA itchy E3 ubiquitin protein ligase (circ-ITCH) regulates sepsis-induced AKI.

METHODS

A sepsis-induced AKI mouse model was created using LPS induction and circ-ITCH overexpression. Circ-ITCH levels were confirmed via RT-qPCR. Kidney tissue changes were examined through various stains and TUNEL. Enzyme-linked immunosorbent assay (ELISA) gauged oxidative stress and inflammation. Mitochondrial features were studied with electron microscopy. RT-qPCR and western blotting assessed mitochondrial function parameters. Using starBase, binding sites between circ-ITCH and miR-214-3p, as well as miR-214-3p and ABCA1, were predicted. Regulatory connections were proven by dual-luciferase assay, RT-qPCR, and western blotting.

RESULTS

Circ-ITCH expression was downregulated in LPS-induced sepsis mice. Overexpression of circ-ITCH ameliorates indicators of renal function (serum creatinine [SCr], blood urea nitrogen [BUN], neutrophil gelatinase-associated lipocalin [NGAL], and kidney injury molecule-1 [Kim-1]), reduces renal cell apoptosis, mitigates oxidative stress markers (reactive oxygen species [ROS] and malondialdehyde [MDA]), and diminishes inflammatory markers (interleukin [IL]-1β, IL-6, and tumor necrosis factor [TNF-α]). Moreover, circ-ITCH overexpression alleviated mitochondrial damage and dysfunction. Furthermore, circ-ITCH acts as a sponge for miR-214-3p, thereby upregulating ABCA1 expression. In addition, the miR-214-3p inhibitor repressed oxidative stress, inflammation, and mitochondrial dysfunction, which was reversed by circ-ITCH knockdown. Further cellular analysis in HK-2 cells supported these findings, highlighting the protective role of circ-ITCH against sepsis-induced AKI, particularly through the miR-214-3p/ABCA1 axis.

CONCLUSION

The novel circ-ITCH/miR-214-3p/ABCA1 pathway plays an essential role in the regulation of oxidative stress and mitochondrial dysfunction in sepsis-induced AKI.

Upregulated miR-194-5p suppresses retinal microvascular endothelial cell dysfunction and mitigates the symptoms of hypertensive retinopathy in mice by targeting SOX17 and VEGF signaling

BACKGROUND

Hypertensive retinopathy (HR) is a retinal disease that may lead to vision loss and blindness. Sex-determining region Y (SRY)-box (SOX) family transcription factors have been reported to be involved in HR development. In this study, the role and upstream mechanism of SRY-box transcription factor 17 (SOX17) in HR pathogenesis were investigated.

METHODS

SOX17 and miR-194-5p levels in Angiotensin II (Ang II)-stimulated human retinal microvascular endothelial cells (HRMECs) and retinas of mice were detected by RT-qPCR. SOX17 protein level as well as levels of tight junction proteins and vascular endothelial growth factor (VEGF) signaling-associated proteins were quantified by western blotting. Tube formation assays were performed to evaluate angiogenesis in HRMECs. The structure of mouse retinal tissues was observed by H&E staining. The interaction between miR-194-5p and SOX17 was confirmed by a luciferase reporter assay.

RESULTS

SOX17 was upregulated in HRMECs treated with Ang II. SOX17 knockdown inhibited angiogenesis in Ang II-stimulated HRMECs and increased tight junction protein levels. Mechanically, SOX17 was targeted by miR-194-5p. Moreover, miR-194-5p upregulation restrained angiogenesis and increased tight junction protein levels in Ang II-treated HRMECs, and the effect was reversed by SOX17 overexpression. MiR-194-5p elevation inactivated VEGF signaling via targeting SOX17. miR-194-5p alleviated pathological symptoms of HR in Ang II-treated mice, and its expression was negatively correlated with SOX17 expression in the retinas of model mice.

CONCLUSIONS

MiR-194-5p upregulation suppressed Ang II-stimulated HRMEC dysfunction and mitigates the symptoms of HR in mice by regulating the SOX17/VEGF signaling.

Research progress on circular RNA vaccines

Owing to the success of linear mRNA coronavirus disease 2019 (COVID-19) vaccines, biopharmaceutical companies and research teams worldwide have attempted to develop more stable circular RNA (circRNA) vaccines and have achieved some preliminary results. This review aims to summarize key findings and important progress made in circRNA research, the in vivo metabolism and biological functions of circRNAs, and research progress and production process of circRNA vaccines. Further, considerations regarding the quality control of circRNA vaccines are highlighted herein, and the main challenges and problem-solving strategies in circRNA vaccine development and quality control are outlined to provide a reference for circRNA vaccine-related research.

Circular RNAs in organ injury: recent development

Circular ribonucleic acids (circRNAs) are a class of long non-coding RNA that were once regarded as non-functional transcription byproducts. However, recent studies suggested that circRNAs may exhibit important regulatory roles in many critical biological pathways and disease pathologies. These studies have identified significantly differential expression profiles of circRNAs upon changes in physiological and pathological conditions of eukaryotic cells. Importantly, a substantial number of studies have suggested that circRNAs may play critical roles in organ injuries. This review aims to provide a summary of recent studies on circRNAs in organ injuries with respect to (1) changes in circRNAs expression patterns, (2) main mechanism axi(e)s, (3) therapeutic implications and (4) future study prospective. With the increasing attention to this research area and the advancement in high-throughput nucleic acid sequencing techniques, our knowledge of circRNAs may bring fruitful outcomes from basic and clinical research.

Circ_0093887 regulated ox-LDL induced human aortic endothelial cells viability, apoptosis, and inflammation through modulating miR-758-3p/BAMBI axis in atherosclerosis

BACKGROUND: Compelling evidence demonstrated that circular RNAs (circRNAs) were involved in the progression of atherosclerosis (AS). However, the role of circ_0093887 in the progression of AS is unclear. The purpose of this study was to explore the role and mechanism of circ_0093887 in oxidized-low density lipoprotein (ox-LDL)-induced human aortic endothelial cells (HAECs). METHODS: HAECs were stimulated by ox-LDL to simulate AS-like injury in vitro. Circ_0093887, microRNA-758-3p (miR-758-3p), and BMP And Activin Membrane-Bound Inhibitor (BAMBI) levels were detected by quantitative real-time polymerase chain reaction (qRT-PCR). PCNA, Bax, Bcl-2, and BAMBI protein levels were detected by western blot. Cell viability and apoptosis were examined by Cell Counting Kit-8 (CCK-8) assay and flow cytometry. Tube formation assay was used to assess tube formation. The levels of inflammatory factors TNF-α and IL-1β were detected by corresponding ELISA kits. The relationship between miR-758-3p and circ_0093887 or BAMBI was tested via dual-luciferase reporter analysis and RNA immunoprecipitation. Oxidative stress related indexes (ROS and MDA) were detected by corresponding kits. RESULTS: The expression levels of circ_0093887 and BAMBI were prominently downregulated in ox-LDL-induced HAECs compared with control, whereas the expression of miR-758-3p was upregulated. Overexpression of circ_0093887 promoted HAECs viability and tube formation, and restrained cell apoptosis in ox-LDL-induced HAECs compared with untreated HAECs. Mechanistically, circ_0093887 regulated the expression of BAMBI through miR-758-3p. Further experiments showed that upregulation of miR-758-3p reversed changes in cell function induced by circ_0093887. In addition, reduced BAMBI salvaged miR-758-3p knockdown mediated effects on cell function. CONCLUSION: Circ_0093887 demonstrated its diagnostic and therapeutic value in AS by promoting the role of the miR-758-3p/BAMBI axis in the ox-LDL-induced endothelial injury of HAECs.

Circular RNA ITCH: An Emerging Multifunctional Regulator

In the last decade, numerous circRNAs were discovered by virtue of the RNA-Seq technique. With the deepening of experimental research, circRNAs have brought to light the key biological functions and progression of human diseases. CircRNA ITCH has been demonstrated to be a tumor suppressor in numerous cancers, and recently it was found to play an important role in bone diseases, diabetes mellitus, and cardiovascular diseases. However, the functions of circ-ITCH have not been completely understood. In this review, we comprehensively provide a conceptual framework to elucidate circ-ITCH biological functions of cell proliferation, apoptosis and differentiation, and the pathological mechanisms of inflammation, drug resistance/toxicity, and tumorigenesis. Finally, we summarize its clinical applications in various diseases. This research aimed at clarifying the role of circ-ITCH, which could be a promising therapeutic target.

Long non-coding RNA growth arrest specific 5 is downregulated in sepsis-ALI and inhibits apoptosis by up-regulating miR-146a

Long non-coding RNA (lncRNA) growth arrest specific 5 (GAS5) and microRNA (miR)-146a both have inhibitory effects on LPS-induced inflammation, suggesting the crosstalk between them. In this study, the expression of GAS5 and miR-146a in patients with sepsis-induced acute lung injury (sepsis-ALI), sepsis patients without obvious complications (sepsis) and healthy controls were studied by RT-qPCR. The role of GAS5 in the expression and methylation of miR-146a in human bronchial epithelial cells (HBEpCs) were studied by RT-qPCR and methylation-specific PCR (MSP), respectively. Cell apoptosis was analyzed by flow cytometry. We found that GAS5 and miR-146a were downregulated in sepsis-ALI and the expression of these two were correlated. LPS induced the downregulation of GAS5 and miR-146a in HBEpCs. In HBEpCs, overexpression of GAS5 increased the expression levels of miR-146a and reduced the methylation of miR-146a gene. Under lipopolysaccharide (LPS) treatment, overexpression of GAS5 and miR-146a decreased the apoptotic rate of HBEpCs. Moreover, the combined overexpression of GAS5 and miR-146a showed stronger effects. Therefore, GAS5 is downregulated in sepsis-ALI and inhibits cell apoptosis by up-regulating the expression of miR-146a.

Circ_nuclear factor I X (circNfix) attenuates pressure overload-induced cardiac hypertrophy via regulating miR-145-5p/ATF3 axis

Cardiac hypertrophy can cause heart failure. However, the mechanisms underlying the progression of cardiac hypertrophy remain unclear. Emerging evidence suggests that circular RNAs (circRNAs) play a critical role in cardiac hypertrophy. However, the association between circ_nuclear factor I X (circNfix) and cardiac hypertrophy remain largely unknown. Therefore, the aim of the present study was to explore the role of circNfix in cardiac hypertrophy. In order to detect the function of circNfix in cardiac hypertrophy, cardiomyocytes were stimulated with angiotensin II (Ang II) to mimic the pathogenesis of the disease. In addition, pressure overload-induced cardiac hypertrophy in a mouse model was established using transverse aortic constriction (TAC) surgery. The mechanism via which circNfix regulated cardiac hypertrophy was investigated using RNA pull-down and luciferase reporter assays, and fluorescence in situ hybridization (FISH). circNfix was downregulated in Ang II-treated cardiomyocytes. Similarly, circNfix expression was markedly downregulated in mice following TAC surgery. In addition, circNfix overexpression significantly prevented the progression of cardiac hypertrophy in TAC-treated mice. Luciferase activity and RNA pull-down assays indicated that circNfix could indirectly target activating transcription factor 3 (ATF3) by binding with microRNA (miR)-145-5p in cardiomyocytes. miR-145-5p overexpression or ATF3 knockdown could reverse the effects of circNfix in Ang II-treated mouse cardiomyocytes. circNfix attenuated pressure overload-induced cardiac hypertrophy by regulating the miR-145-5p/ATF3 axis. Therefore, circNfix may serve as a molecular target for cardiac hypertrophy treatment.

Upregulated expression of long non-coding RNA MEG3 serves as a prognostic biomarker in severe pneumonia children and its regulatory mechanism

Severe pneumonia is a high-mortality disorder in children. The expression and underlying effects of lncRNA maternally expressed 3 (MEG3) were detected. The relationships between MEG3 and other parameters were reported by Pearson correlation. The prognostic importance of MEG3 was assessed by Kaplan-Meier (K-M) curve and COX analysis and its diagnostic potential was uncovered by the receiver operating characteristic (ROC) curve. Luciferase activity assay was performed to demonstrate the target gene of MEG3. Elevated expression of MEG3 and reduced microRNA-29 c (miR-29 c) were evaluated in severe pneumonia children, and a negative relationship between MEG3 and miR-29 c was propounded. MEG3 might function as an independent prognostic indicator. The diagnostic efficiency of MEG3 was also indicated for severe pneumonia children. In MRC-5 cell models and MH-S cell models, lipopolysaccharide (LPS) contributed to the increased expression of MEG3. Interference of MEG3 restricted the upregulation of MEG3 triggered by LPS. Silenced MEG3 protected MRC-5 and MH-S cells against damages managed by LPS on cell apoptosis, viability, and inflammation. MiR-29 c was a ceRNA of MEG3 and the absence of MEG3 abrogated the decreased expression of miR-29 c caused by LPS. Overall, the increased expression of MEG3 and the reduced levels of miR-29 c were identified in severe pneumonia. Prognostic and diagnostic significances of MEG3 provided a novel perspective for severe pneumonia. Disruption of MEG3 alleviated cell injury and inflammation as characterized by high LPS by binding miR-29 c.

A novel fusion circular RNA F-circBA1 derived from the BCR-ABL fusion gene displayed an oncogenic role in chronic myeloid leukemia cells

The BCR-ABL fusion gene plays a crucial role in the leukemogenesis of chronic myeloid leukemia (CML). The BCR-ABL oncoprotein encoded by this fusion gene has been extensively studied. However, research on whether BCR-ABL also affects circular RNAs (circRNAs) is limited. This study aimed to explore the new fusion circRNAs produced by BCR-ABL and their role in CML cells. In this study, we identified a novel fusion circRNA, named F-circBA1, originating from BCR-ABL in K562 and K562/G01 cells using quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Sanger sequencing. qRT-PCR of the nuclear RNA and cytoplasmic RNA were separated, indicating that F-circBA1 was mainly localized in the cytoplasm. Cell counting kit-8 assay and flow cytometry showed that F-circBA1 knockdown by shRNA prevented the proliferation of K562 and K562/G01 cells, and the cell cycle was arrested at G2/M. Mechanically, dual-luciferase reporter assay and western blotting assay showed that F-circBA1 sponged miR-148-3p and F-circBA1 silencing decreased CDC25B expression in vitro. Furthermore, the results of the murine leukemogenesis model showed that F-circBA1 knockdown suppressed leukemogenesis in vivo. Besides, we found the existence of F-circBA1 in some patients with BCR-ABL-positive CML. In conclusion, these results demonstrate the presence of F-circBA1 and its oncogenic role in CML cells.

Targeting the miR-6734-3p/ZEB2 axis hampers development of non-small cell lung cancer (NSCLC) and increases susceptibility of cancer cells to cisplatin treatment

The unclear pathogenesis mechanisms and resistance of cancer cells to chemical drugs serious limits the development of effective treatment strategies for non-small cell lung cancer (NSCLC). In this study, we managed to investigate this issue, and identify potential cancer associated biomarkers for NSCLC diagnosis, prognosis and treatment. This study found that miR-6734-3p was downregulated in both NSCLC clinical specimens (tissues and serum) and cells, compared to the normal tissues and cells. Next, upregulation of miR-6734-3p inhibited cancer formation and progression in NSCLC cells in vitro and in vivo. Conversely, miR-6734-3p ablation had opposite effects and facilitated NSCLC development. In addition, miR-6734-3p bound to the 3ʹ untranslated region (3ʹUTR) of zinc finger E-box binding homeobox 2 (ZEB2) mRNA to suppress its expressions in NSCLC cells. Interestingly, the inhibiting effects of miR-6734-3p overexpression on NSCLC progression were abrogated by upregulating ZEB2. Furthermore, both upregulated miR-6734-3p and silencing of ZEB2 increased cisplatin-sensitivity in cisplatin-resistant NSCLC (CR-NSCLC) cells. Taken together, miR-6734-3p played an anti-tumor role to hinder cancer development and enhanced the cytotoxic effects of cisplatin treatment on NSCLC cells by downregulating ZEB2.