circRNA_010383 Acts as a Sponge for miR-135a, and Its Downregulated Expression Contributes to Renal Fibrosis in Diabetic Nephropathy

RfxCas13d-mediated inhibition of Circ1647 alleviates renal fibrosis via PI3K/AKT signaling pathway

BACKGROUND

Circular RNAs (CircRNAs) have been shown to be involved in the development of chronic kidney disease (CKD). This study aimed to investigate the role of Circ1647 in renal fibrosis, which is a hallmark of CKD.

METHODS

In this study, we established a unilateral ureteral obstruction (UUO) model and delivered Circ1647 RfxCas13d knockdown plasmid into renal parenchymal cells via retrograde injection through the ureter followed by electroporation. After that, the pathological changes were determined by Hematoxylin and Eosin. Meanwhile, Immunohistochemistry, qRT-PCR and Western blot were conducted to assess the degree of fibrosis. In addition, overexpressing of Circ1647 in renal tubular epithelial cells (TCMK1) was performed to investigate the underlying mechanisms of Circ1647.

RESULTS

Our results displayed that electroporation-mediated knockdown of Circ1647 by RfxCas13d knockdown plasmid significantly inhibited renal fibrosis in UUO mice as evidenced by reduced expression of fibronectin and α-SMA (alpha-smooth muscle actin). Conversely, overexpression of Circ1647 in TCMK1 cells promoted the fibrosis. In terms of mechanism, Circ1647 may mediate the PI3K/AKT Signaling Pathway as demonstrated by the balance of the phosphorylation of PI3K and AKT in vivo and the aggravated phosphorylation of PI3K and AKT in vitro. These observations were corroborated by the effects of the PI3K inhibitor LY294002, which mitigated fibrosis post Circ1647 overexpression.

CONCLUSION

Our study suggests that Circ1647 plays a significant role in renal fibrosis by mediating the PI3K/AKT signaling pathway. RfxCas13d-mediated inhibition of Circ1647 may serve as a therapeutic target for renal fibrosis in CKD.

circCUL3 drives malignant progression of cervical cancer by activating autophagy through sponge miR-223-3p upregulation of ATG7

Circular RNA (circRNA) has emerged as a pivotal regulatory factor in cancer biology, yet its exact role in cervical cancer remains incompletely understood. In this study, we investigated the functional role of circCUL3 in cervical cancer and explored its potential as a therapeutic target. Functional gain and loss experiments were conducted in Hela and Siha cell lines to elucidate the biological functions of circCUL3 in cervical cancer. The results revealed that circCUL3 overexpression significantly enhanced cell viability, migration, and invasion while suppressing apoptosis, while circCUL3 knockout displayed the opposite effects. Mechanistically, we identified hsa-miR-223-3p as a target of circCUL3, with its expression being negatively regulated by circCUL3. Furthermore, we discovered that circCUL3 could sequester miR-223-3p, leading to the upregulation of ATG7 expression, and this was linked to the regulation of autophagy in cervical cancer cells. In vivo validation using a xenograft mouse model further supported our in vitro findings. Notably, we found that chloroquine (CQ), an autophagy inhibitor, restored miR-223-3p expression and counteracted the oncogenic effect of circCUL3 overexpression. In conclusion, circCUL3 potentially contributes to the malignant progression of cervical cancer by acting as a sponge for miR-223-3p, resulting in the upregulation of ATG7 and the activation of autophagy.

CircRAB11A act as miR-24-5p sponge promotes proliferation and resists apoptosis of chicken granulosa cell via EGFR/ERK1/2 and RAB11A/ PI3K/AKT pathways

Circular RNAs (circRNAs) are a class of endogenous non-coding RNAs that have been implicated in mediating granulosa cell (GC) proliferation and apoptosis. CircRAB11A was found to have a significantly higher expression in normal follicles compared to atrophic follicles. In this study, we determined that the knockdown of circRAB11A resulted in the inhibition of proliferation and promotion of apoptosis in GCs of chicken. Moreover, circRAB11A was found to act as a sponge for miR-24-5p, both member RAS oncogene family (RAB11A) and epidermal growth factor receptor (EGFR) were revealed to be targets of miR-24-5p through a dual-luciferase reporter assay. RAB11A or EGFR promoted proliferation and suppressed apoptosis in GCs through the phosphatidylinositol-kinase (PI3K)/AKT or extracellular signal-regulated kinase (ERK)1/2 pathway. These findings suggest that circRAB11A may function as a competing endogenous RNA (ceRNA) by targeting the miR-24-5p/RAB11A and miR-24-5p/EGFR axes and activating the ERK1/2 and PI3K/AKT pathways, offering a potential avenue for exploring the mechanism of follicle development.

Circ-0000953 deficiency exacerbates podocyte injury and autophagy disorder by targeting Mir665-3p-Atg4b in diabetic nephropathy

Circular RNAs (circRNAs) are special non-coding RNA (ncRNA) molecules that play a significant role in many diseases. However, the biogenesis and regulation of circRNAs in diabetic nephropathy (DN) are largely unknown. Here, we investigated the expression profile of circRNAs in kidney of DN mice through circular RNA sequencing (circRNA-seq). The renal biopsy samples of patients with DN had low circ -0,000,953 expression, which was significantly associated with renal function. Furthermore, loss-of-function and gain-of-function experiments were carried out to prove the role of circ -0,000,953 in DN. Podocyte conditional knockin (cKI) or systemic overexpression of circ -0,000,953 alleviated albuminuria and restored macroautophagy/autophagy in kidney of diabetic mice. However, circ -0,000,953 knockdown exacerbated albuminuria and podocyte injury. Mechanistically, we found circ -0,000,953 directly binds to Mir665-3p-Atg4b to perform its function. Silencing of Mir665-3p or overexpression of Atg4b recovered podocyte autophagy both in vitro and in vivo. To examine the cause of circ -0,000,953 downregulation in DN, bioinformatics prediction found that circ -0,000,953 sequence has a high possibility of containing an m6A methylation site. Additionally, METTL3 was proved to regulate the expression and methylation level of circ -0,000,953 through YTHDF2 (YTH N6-methyladenosine RNA binding protein 2). In conclusion, this study revealed that circ -0,000,953 regulates podocyte autophagy by targeting Mir665-3p-Atg4b in DN. Therefore, circ -0,000,953 is a potential biomarker for prevention and cure of DN.Abbreviation: CCL2/MCP-1: C-C motif chemokine ligand 2; ceRNA: competing endogenous RNA; circRNA: circular RNA; cKI: conditional knockin; cKO: conditional knockout; CRE: creatinine; DM: diabetes mellitus; DN: diabetic nephropathy; ESRD: end-stage renal disease; HG: high glucose; IF: immunofluorescence; MAP1LC3/LC3B: microtubule-associated protein 1 light chain 3 beta; MPC5: mouse podocyte clone 5; MTECs: mouse tubular epithelial cells; MTOR: mechanistic target of rapamycin kinase; NC: normal control; ncRNA: non-coding RNA; NPHS1: nephrosis 1, nephrin; NPHS2: nephrosis 2, podocin; PAS: periodic acid-Schiff; RELA/p65: v-rel reticuloendotheliosis viral oncogene homolog A (avian); SDs: slit diaphragm proteins; Seq: sequencing; STZ: streptozotocin; SV40: SV40-MES13-cells, mouse mesangial cell line; T1D: type 1 diabetes mellitus; T2D: type 2 diabetes mellitus; TEM: transmission electron microscopy; TNF/TNF-α: tumor necrosis factor; VECs: vascular endothelial cells; WT1: WT1 transcription factor; YTHDF2: YTH N6-methyladenosine RNA binding protein 2.

Current advances in circular RNA detection and investigation methods: Are we running in circles?

Circular RNAs (circRNAs), characterized by their closed-loop structure, have emerged as significant transcriptomic regulators, with roles spanning from microRNA sponging to modulation of gene expression and potential peptide coding. The discovery and functional analysis of circRNAs have been propelled by advancements in both experimental and bioinformatics tools, yet the field grapples with challenges related to their detection, isoform diversity, and accurate quantification. This review navigates through the evolution of circRNA research methodologies, from early detection techniques to current state-of-the-art approaches that offer comprehensive insights into circRNA biology. We examine the limitations of existing methods, particularly the difficulty in differentiating circRNA isoforms and distinguishing circRNAs from their linear counterparts. A critical evaluation of various bioinformatics tools and novel experimental strategies is presented, emphasizing the need for integrated approaches to enhance our understanding and interpretation of circRNA functions. Our insights underscore the dynamic and rapidly advancing nature of circRNA research, highlighting the ongoing development of analytical frameworks designed to address the complexity of circRNAs and facilitate the assessment of their clinical utility. As such, this comprehensive overview aims to catalyze further advancements in circRNA study, fostering a deeper understanding of their roles in cellular processes and potential implications in disease. This article is categorized under: RNA Methods > RNA Nanotechnology RNA Methods > RNA Analyses in Cells RNA Methods > RNA Analyses In Vitro and In Silico.

CircPRKD3/miR-6783-3p responds to mechanical force to facilitate the osteogenesis of stretched periodontal ligament stem cells

BACKGROUND

The mechanotransduction mechanisms by which cells regulate tissue remodeling are not fully deciphered. Circular RNAs (circRNAs) are crucial to various physiological processes, including cell cycle, differentiation, and polarization. However, the effects of mechanical force on circRNAs and the role of circRNAs in the mechanobiology of differentiation and remodeling in stretched periodontal ligament stem cells (PDLSCs) remain unclear. This article aims to explore the osteogenic function of mechanically sensitive circular RNA protein kinase D3 (circPRKD3) and elucidate its underlying mechanotransduction mechanism.

MATERIALS AND METHODS

PDLSCs were elongated with 8% stretch at 0.5 Hz for 24 h using the Flexcell® FX-6000™ Tension System. CircPRKD3 was knockdown or overexpressed with lentiviral constructs or plasmids. The downstream molecules of circPRKD3 were predicted by bioinformatics analysis. The osteogenic effect of related molecules was evaluated by quantitative real-time PCR (qRT-PCR) and western blot.

RESULTS

Mechanical force enhanced the osteogenesis of PDLSCs and increased the expression of circPRKD3. Knockdown of circPRKD3 hindered PDLSCs from osteogenesis under mechanical force, while overexpression of circPRKD3 promoted the early osteogenesis process of PDLSCs. With bioinformatics analysis and multiple software predictions, we identified hsa-miR-6783-3p could act as the sponge of circPRKD3 to indirectly regulate osteogenic differentiation of mechanically stimulated PDLSCs.

CONCLUSIONS

Our results first suggested that both circPRKD3 and hsa-miR-6783-3p could enhance osteogenesis of stretched PDLSCs. Furthermore, hsa-miR-6783-3p could sponge circPRKD3 to indirectly regulate RUNX2 during the periodontal tissue remodeling process in orthodontic treatment.

Calcium signalling and transport in the kidney

The kidney plays a pivotal role in regulating calcium levels within the body. Approximately 98% of the filtered calcium is reabsorbed in the nephron, and this process is tightly controlled to maintain calcium homeostasis, which is required to facilitate optimal bone mineralization, preserve serum calcium levels within a narrow range, and support intracellular signalling mechanisms. The maintenance of these functions is attributed to a delicate balance achieved by various calcium channels, transporters, and calcium-binding proteins in renal cells. Perturbation of this balance due to deficiency or dysfunction of calcium channels and calcium-binding proteins can lead to severe complications. For example, polycystic kidney disease is linked to aberrant calcium transport and signalling. Furthermore, dysregulation of calcium levels can promote the formation of kidney stones. This Review provides an updated description of the key aspects of calcium handling in the kidney, focusing on the function of various calcium channels and the physiological stimuli that control these channels or are communicated through them. A discussion of the role of calcium as an intracellular second messenger and the pathophysiology of renal calcium dysregulation, as well as a summary of gaps in knowledge and future prospects, are also included.

CircPRMT5 promotes progression of osteosarcoma by recruiting CNBP to regulate the translation and stability of CDK6 mRNA

Research has demonstrated that circular RNAs (circRNAs) exert critical functions in the occurrence and progression of numerous malignant tumors. CircPRMT5 was recently reported to be involved in the pathogenesis of cancers. However, the potential role of circPRMT5 in osteosarcoma needs further investigation. In present study, our results suggested that circPRMT5 was highly upregulated in osteosarcoma cells and mainly localizes in the cytoplasm. CircPRMT5 promoted the proliferation, migration and invasion capacities of osteosarcoma cells, and suppressed cell apoptosis. Knockdown of circPRMT5 exerted the opposite effects. Mechanically, circPRMT5 promoted the binding of CNBP to CDK6 mRNA, which enhanced the stability of CDK6 mRNA and facilitated its translation, thereby promoting the progression of osteosarcoma. Knockdown of CDK6 reversed the promoting effect of circPRMT5 on osteosarcoma cells. These findings suggest that circPRMT5 promotes osteosarcoma cell malignant activity by recruiting CNBP to regulate the translation and stability of CDK6 mRNA. Thus, circPRMT5 may represent a promising therapeutic target for osteosarcoma.

CircNUP54 promotes hepatocellular carcinoma progression via facilitating HuR cytoplasmic export and stabilizing BIRC3 mRNA

Circular RNAs (circRNAs) have been implicated in tumorigenesis and progression of various cancers. However, the underlying mechanisms of circRNAs in hepatocellular carcinoma (HCC) have not been fully elucidated. Herein, a new oncogenic circRNA, hsa_circ_0070039 (circNUP54), was identified to be significantly upregulated in HCC through circRNA sequencing. As verified in 68 HCC samples, circNUP54 overexpression was correlated with aggressive cancerous behaviors and poor outcomes. Moreover, the function experiments showed that knockdown of circNUP54 inhibited the malignant progression of HCC in vitro and in vivo, whereas overexpression of circNUP54 had the opposite role. Mechanistic investigations carried out by RNA pull-down, RNA immunoprecipitation, and immunofluorescence revealed that circNUP54 interacted with the RNA-binding protein Hu-antigen R (HuR) and promoted its cytoplasmic export. The cytoplasmic accumulation of HuR stabilized the downstream BIRC3 mRNA through its binding to the 3' UTR region. Consequently, the encoded protein of BIRC3, cellular inhibitor of apoptosis 2 (cIAP2), proceeded to activate the NF-κB signal pathway and ultimately contributed to HCC progression. In addition, depletion of BIRC3 rescued the pro-tumorigenic effect of circNUP54 on HCC cells. Overall, this study demonstrated that circNUP54 facilitates HCC progression via regulating the HuR/BIRC3/NF-κB axis, which may serve as a promising therapeutic target for HCC treatment.

MiR-205-5p-Mediated MAGI1 Inhibition Attenuates the Injury Induced by Diabetic Nephropathy

INTRODUCTION

Membrane-associated guanylate kinase with an inverted domain structure-1 (MAGI1) is dysregulated in diabetes; however, its role in diabetic nephropathy (DN) remains unclear. In this study, we determined the function and associated mechanisms of MAGI1 in DN.

METHODS

Serum samples from 28 patients with DN and 28 normal volunteers were collected. High-glucose (HG)-treated human renal mesangial cells (HRMCs) and streptozotocin-treated rats were used as cell and animal models of DN, respectively. MAGI1 mRNA expression was measured by quantitative reverse transcription polymerase chain reaction. An 5-Ethynyl-2'-deoxyuridine assay was used to assess cell proliferation, whereas Western blot analysis was performed to quantitate the levels of markers associated with proliferation, the extracellular matrix (ECM), and inflammation. These included collagens I, collagen IV, cyclin D1, AKT, phosphorylated-AKT (p-AKT), PI3K, and phosphorylated-PI3K (p-PI3K). The predicted binding of miR-205-5p with the MAGI1 3'UTR was verified using a luciferase assay.

RESULTS

MAGI1 expression was increased in serum samples from DN patients and in HRMCs treated with HG. MAGI1 knockdown attenuated excessive proliferation, ECM accumulation, and inflammation in HG-induced HRMCs as well as injury to DN rats. MiR-205-5p potentially interacted with the 3'UTR of MAGI1 and binding was verified using a dual-luciferase reporter assay. Moreover, miR-205-5p repression offset the inhibitory influence of MAGI1 knockdown on proliferation, collagen deposition, and inflammation in HG-treated HRMCs.

CONCLUSION

MAGI1 contributes to injury caused by DN. Furthermore, miR-205-5p binds to MAGI1 and suppresses MAGI1 function. These findings suggest that miR-205-5p-mediates MAGI1 inhibition, which represents a potential treatment for DN.

The Landscape of Biomimetic Nanovesicles in Brain Diseases

Brain diseases, such as brain tumors, neurodegenerative diseases, cerebrovascular diseases, and brain injuries, are caused by various pathophysiological changes, which pose a serious health threat. Brain disorders are often difficult to treat due to the presence of the blood-brain barrier (BBB). Biomimetic nanovesicles (BNVs), including endogenous extracellular vesicles (EVs) derived from various cells and artificial nanovesicles, possess the ability to penetrate the BBB and thus can be utilized for drug delivery to the brain. BNVs, especially endogenous EVs, are widely distributed in body fluids and usually carry various disease-related signal molecules such as proteins, RNA, and DNA, and may also be analyzed to understand the etiology and pathogenesis of brain diseases. This review covers the exhaustive classification and characterization of BNVs and pathophysiological roles involved in various brain diseases, and emphatically focuses on nanotechnology-integrated BNVs for brain disease theranostics, including various diagnosis strategies and precise therapeutic regulations (e.g., immunity regulation, disordered protein clearance, anti-neuroinflammation, neuroregeneration, angiogenesis, and the gut-brain axis regulation). The remaining challenges and future perspectives regarding the nanotechnology-integrated BNVs for the diagnosis and treatment of brain diseases are also discussed and outlined.

miR-135a Mediates Mitochondrial Oxidative Respiratory Function through SIRT1 to Regulate Atrial Fibrosis

INTRODUCTION

This study aimed to explore the function of miR-135a in the progress of atrial fibrosis and the mechanism of miR-135a/SIRT1 (sirtuin 1) in human cardiac fibroblasts and mouse cardiac fibroblasts (MCFs) mediating the regulation of atrial fibrosis by mitochondrial oxidative respiration function.

METHODS

Using Ang II (angiotensin II) to induce fibrosis in HCFs (human corneal fibroblasts) and MCF (Michigan Cancer Foundation, MCF) cells in vitro, the miRNA-seq results of previous studies were validated. Proliferative and invasive ability of HCFs and MCFs was detected by Cell Counting Kit-8 assay (CCK-8) and scratch experiment after overexpressing miR-135a in HCFs and MCF cells. Protein and mRNA expression was tested using Western blot and qPCR. The target of miR-135a was verified as SIRT1 by a luciferase reporter assay and the activities of the mitochondrial respiratory enzyme complexes I, II, III, and IV were determined colorimetrically. The activities of malondialdehyde, reactive oxygen species, and superoxide dismutase in cells were detected with enzyme-linked immunosorbent assay (ELISA).

RESULTS

miR-135a expression was elevated in HCFs and MCFs cells in the Ang II group than control group. Overexpression of miR-135a could promote the proliferation, migration, oxidative stress, as well as fibrosis of cardiac fibroblasts and suppresses mitochondrial activity. In addition, we found SIRT1 was a target gene of miR-135a. What is more, the findings showed miR-135a promoted fibrosis in HCFs and MCFs cells acting through regulation of SIRT1.

CONCLUSIONS

miR-135a mediates mitochondrial oxidative respiratory function through SIRT1 to regulate atrial fibrosis.

Hsa_circ_0001583 fuels bladder cancer metastasis by promoting staphylococcal nuclease and tudor domain containing 1-mediated MicroRNA decay

Muscle-invasive and metastatic bladder cancer indicates extra worse prognosis. Accumulating evidence roots for the prominent role of circular RNAs(circRNAs) in bladder cancer, while the mechanisms linking circRNAs and bladder cancer metastasis remain limitedly investigated. Here, we identified a significantly upregulated circRNA candidate, hsa_circ_0001583, from online datasets. Validated by qRT-PCR, PCR, sanger sequencing, actinomycin D and RNase R digestion experiments, hsa_circ_0001583 was proved to be a genuine circular RNA with higher expression levels in bladder cancer tissue. Through gain and loss of function experiments, hsa_circ_0001583 exhibited potent migration and invasion powers both in vitro and in vivo. The staphylococcal nuclease and Tudor domain containing 1 (SND1) was identified as an authentic binding partner for hsa_circ_0001583 through RNA pulldown and RIP experiments. Elevated levels of hsa_circ_0001583 could bind more to SND1 and protect the latter from degradation. Rescue experiments demonstrated that such interaction-induced increased in SND1 levels in bladder cancer cells enabled the protein to pump its endonuclease activity, leading to the degradation of tumor-suppressing MicroRNAs (miRNAs) including miR-126-3p, the suppressor of Disintegrin And Metalloproteinase Domain-Containing Protein 9 (ADAM9), ultimately driving cells into a highly migrative and invasive state. In summary, our study is the first to highlight the upregulation of hsa_circ_0001583 in bladder cancer and its role in downregulating miR-126-3p by binding to and stabilizing the SND1 protein, thereby promoting bladder cancer cell migration and invasion. This study adds hsa_circ_0001583 to the pool of bladder cancer metastasis biomarkers and therapeutic targets.

CircLARP1B promotes pyroptosis of high glucose-induced renal mesangial cells by regulating the miR-578/TLR4 axis

BACKGROUND

Diabetic nephropathy (DN) is a main cause of end-stage renal disease with high mortality. Circular RNAs (circRNAs) are associated with the pathogenesis of DN. This study aimed to explore the role of circLARP1B in DN.

METHODS

The levels of circLARP1B, miR-578, TLR4 in DN and high glucose (HG)-treated cells using quantitative real-time PCR. Their relationship was analyzed using dual-luciferase reporter assay. The biological behaviors were assessed by MTT assay, EDU assay, flow cytometry, ELISA, and western blot.

RESULTS

The results indicated that circLARP1B and TLR4 were highly expressed, and miR-578 was low expressed in patients with DN and HG-induced cells. Knockdown of circLARP1B promoted the proliferation and cell cycle, and inhibited pyroptosis and inflammation of HG-induced cells. CircLARP1B is a sponge of miR-578, which targets TLR4. Rescue experiments showed that inhibition of miR-578 reversed the effects of circLARP1B knockdown, while TLR4 reversed the effects of miR-578.

CONCLUSION

CircLARP1B/miR-578/TLR4 axis suppressed the proliferation, blocked cell cycle at the G0-G1 phase, promoted pyroptosis, and inflammatory factor release of renal mesangial cells induced by HG. The findings suggested that circLARP1B may be a target for the treatment of DN.

Circular RNAs: An emerging precise weapon for diabetic nephropathy diagnosis and therapy

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication associated with diabetes mellitus and represents a major cause of chronic kidney disease and renal failure. Current treatment strategies for DN primarily focus on symptom alleviation, lacking effective approaches to halt or reverse DN progression. Circular RNA (circRNA), characterized by a closed-loop structure, has emerged as a novel non-coding RNA regulator of gene expression, attributed to its conservation, stability, specificity, and multifunctionality. Dysregulation of circRNA expression is closely associated with DN progression, whereby circRNA impacts kidney cell injury by modulating cell cycle, differentiation, cell death, as well as influencing the release of inflammatory factors and stromal fibronectin expression. Consequently, circRNA is considered a predictive biomarker and a potential therapeutic target for DN. This review provides an overview of the latest research progress in the classification, functions, monitoring methods, and databases related to circRNA. The paper focuses on elucidating the impact and underlying mechanisms of circRNA on kidney cells under diabetic conditions, aiming to offer novel insights into the prevention, diagnosis, and treatment of DN.

CircRNA and ferroptosis in human disease: Insights for new treatments

Circular RNA (circRNA), classified as a type of non-coding RNA, has gained significant attention in the field of biology due to its distinctive ring structure and functional properties. Recent research has provided evidence that specific circRNAs have the ability to modulate disease progression through diverse mechanisms, one of which is by regulating cellular ferroptosis. Ferroptosis is a form of regulated cell death that is driven by iron dependency and lipid peroxidation, and extensive investigations have revealed a relationship between ferroptosis and disease development. In addition to evidence that both circRNAs and ferroptosis exert critical roles in disease progression, circRNAs have also been shown to actively mediate the process of ferroptosis. The relationship between circRNAs and ferroptosis therefore influences disease progression and offers novel targets for disease treatment. By directly or indirectly modulating the expression of circRNAs that regulate the expression of ferroptosis-related proteins, it may be possible to impact disease progression by promoting or inhibiting ferroptosis. Current research indicates such approaches may hold significant value in a wide variety of common diseases across physiological systems. This review comprehensively summarizes the findings of recent studies investigating the roles of circRNAs in the regulation of ferroptosis in various diseases.

Decrypting the circular RNAs does a favor for us: Understanding, diagnosing and treating diabetes mellitus and its complications

Circular RNAs (circRNAs), a novel type of single-stranded noncoding RNAs with a covalently closed loop structure, are generated in a circular conformation via non-canonical splicing or back-splicing events. Functionally, circRNAs have been elucidated to soak up microRNAs (miRNAs) and RNA binding proteins (RBPs), serve as protein scaffolds, maintain mRNA stability, and regulate gene transcription and translation. Notably, circRNAs are strongly implicated in the regulation of β-cell functions, insulin resistance, adipocyte functions, inflammation as well as oxidative stress via acting as miRNA sponges and RBP sponges. Basic and clinical studies have demonstrated that aberrant alterations of circRNAs expressions are strongly associated with the initiation and progression of diabetes mellitus (DM) and its complications. Here in this review, we present a summary of the biogenesis, transportation, degradation and functions of circRNAs, and highlight the recent findings on circRNAs and their action mechanisms in DM and its complications. Overall, this review should contribute greatly to our understanding of circRNAs in DM pathogenesis, offering insights into the further perspectives of circRNAs for DM diagnosis and therapy.

Circular RNA COL1A2 Mediates High Glucose-Induced Oxidative Stress and Pyroptosis by Regulating MiR-424-5p/SGK1 in Diabetic Nephropathy

Diabetic nephropathy (DN) represents a major diabetes-related complication, which could undermine renal function. CircCOL1A2 has been previously reported to show abnormal expression during DN. However, its functional role in the progression of DN, as well as the potential molecular mechanisms, remains unclear. The present work examined the expression of circCOL1A2 in the plasma of DN patients, and employed high glucose (HG)-challenged HK-2 cells as the in vitro cell model of hyperglycemia (HG)-induced DN. CircCOL1A2 was silenced using siRNA in HK-2 cells to clarify the functional engagement of circCOL1A2 in HG-induced DN. We examined the roles of circCOL1A2 in regulating oxidative stress by measuring reactive oxygen species (ROS), lipid peroxidation, and superoxide dismutase (SOD) levels. Besides, the effects of circCOL1A2 silencing on pyroptosis were investigated by RT-qPCR, western blot (WB), and ELISA assays. StarBase (version 2.0) was used to identify the downstream effector of circCOL1A2, and their interactions were further verified through dual-luciferase reporter analysis, RNA pull-down assays, and RNA immunoprecipitation (RIP) assay. CircCOL1A2 was highly expressed in DN patients and HG-induced HK-2 cells. Knocking down circCOL1A2 alleviated oxidative stress and pyroptosis upon HG treatment. In addition, we demonstrated that circCOL1A2 knockdown could promote miR-424-5p expression while inhibiting Serum/Glucocorticoid Regulated Kinase 1 (SGK1) level. Furthermore, miR-424-5p inhibitor or SGK1 overexpression impaired the effects of circCOL1A2 knockdown on HG-induced oxidative stress and pyroptosis. Hence, our results demonstrated that the circCOL1A2 mediates HG-exposed pyroptosis and oxidative stress through modulating miR-424-5p/SGK1 axis in diabetic nephropathy, indicating that silencing circCOL1A2 is a potential intervention strategy for DN management.

Circular RNA in Multiple Sclerosis: Pathogenicity and Potential Biomarker Development: A Systematic Review

Multiple sclerosis (MS) is a complex autoimmune disorder of the CNS that affects millions of people worldwide. The causes of the disease remain unknown despite extensive efforts to understand it. CircRNAs are a unique class of endogenous non-coding RNA that are abundant, stable, conserved, and specifically expressed molecules, making them a promising biomarker of diseases. This review investigates the role of circRNA in MS pathogenicity and their potential as a biomarker through a comprehensive literature search conducted in 8 scientific databases. The studies found that there are differentially expressed circRNAs in MS patients compared to healthy controls (HC), and this difference is even more pronounced in different MS subtypes. Enrichment of circRNAs in linkage disequilibrium (LD) blocks that harbor MS-associated SNPs suggests that these SNPs manipulate the levels of circRNAs in the surrounding area, contributing to disease pathogenicity. While circRNA shows promise as an indicator or biomarker for MS disease pathology, further research is needed to fully explore its potential and impact on human biology.

circRNA-miRNA-mRNA Deregulated Network in Ischemic Heart Failure Patients

Noncoding RNAs (ncRNAs), which include circular RNAs (circRNAs) and microRNAs (miRNAs), regulate the development of cardiovascular diseases (CVD). Notably, circRNAs can interact with miRNAs, influencing their specific mRNA targets' levels and shaping a competing endogenous RNAs (ceRNA) network. However, these interactions and their respective functions remain largely unexplored in ischemic heart failure (IHF). This study is aimed at identifying circRNA-centered ceRNA networks in non-end-stage IHF. Approximately 662 circRNA-miRNA-mRNA interactions were identified in the heart by combining state-of-the-art bioinformatics tools with experimental data. Importantly, KEGG terms of the enriched mRNA indicated CVD-related signaling pathways. A specific network centered on circBPTF was validated experimentally. The levels of let-7a-5p, miR-18a-3p, miR-146b-5p, and miR-196b-5p were enriched in circBPTF pull-down experiments, and circBPTF silencing inhibited the expression of HDAC9 and LRRC17, which are targets of miR-196b-5p. Furthermore, as suggested by the enriched pathway terms of the circBPTF ceRNA network, circBPTF inhibition elicited endothelial cell cycle arrest. circBPTF expression increased in endothelial cells exposed to hypoxia, and its upregulation was confirmed in cardiac samples of 36 end-stage IHF patients compared to healthy controls. In conclusion, circRNAs act as miRNA sponges, regulating the functions of multiple mRNA targets, thus providing a novel vision of HF pathogenesis and laying the theoretical foundation for further experimental studies.

CircTNPO1 promotes the tumorigenesis of osteosarcoma by sequestering miR-578 to upregulate WNT5A expression

As a type of non-coding RNAs, circular RNAs (circRNAs) have the ability to bind to miRNAs and regulate gene expression. Recent studies have shown that circRNAs are involved in certain pathological events. However, the expression and functional role of circTNPO1 in osteosarcoma (OS) are not yet clear. To investigate circRNAs that are differentially expressed in OS tissues and cells, circRNA microarray analysis combined with qRT-PCR was performed. The in-vitro and in-vivo functions of circTNPO1 were studied by knocking it down or overexpressing it. The binding and regulatory relationships between circTNPO1, miR-578, and WNT5A were evaluated using dual luciferase assays, RNA pull-down and rescue assays, as well as RNA immunoprecipitation (RIP). Furthermore, functional experiments were conducted to uncover the regulatory effect of the circTNPO1/miR-578/WNT5A pathway on OS progression. Cytoplasm was identified as the primary location of circTNPO1, which exhibited higher expression in OS tissues and cells compared to the corresponding controls. The overexpression of circTNPO1 was found to enhance malignant phenotypes in vitro and increase oncogenicity in vivo. Moreover, circTNPO1 was observed to sequester miR-578 in OS cells, resulting in the upregulation of WNT5A and promoting carcinoma progression. These findings indicate that circTNPO1 can contribute to the progression of OS through the miR-578/WNT5A axis. Therefore, targeting the circTNPO1/miR-578/WNT5A axis could be a promising therapeutic strategy for OS.

Identification of urinary extracellular vesicles differentially expressed RNAs in diabetic nephropathy via whole-transcriptome integrated analysis

BACKGROUND

Diabetic nephropathy (DN) is a common systemic microvascular complication of diabetes and a leading cause of chronic kidney disease worldwide. Urinary extracellular vesicles (uEVs), which are natural nanoscale vesicles that protect RNA from degradation, have the potential to serve as an invasive diagnostic biomarker for DN.

METHODS

We enrolled 24 participants, including twelve with renal biopsy-proven T2DN and twelve with T2DM, and isolated uEVs using ultracentrifugation. We performed microarrays for mRNAs, lncRNAs, and circRNAs in parallel, and Next-Generation Sequencing for miRNAs. Differentially expressed RNAs (DE-RNAs) were subjected to CIBERSORTx, ssGSEA analysis, GO enrichment, PPI network analysis, and construction of the lncRNA/circRNA-miRNA-mRNA regulatory network. Candidate genes and potential biomarker RNAs were validated using databases and machine learning models.

RESULTS

A total of 1684 mRNAs, 126 lncRNAs, 123 circRNAs and 66 miRNAs were found in uEVs in T2DN samples compared with T2DM. CIBERSORTx revealed the involvement of uEVs in immune activity and ssGSEA explored possible cell or tissue sources of uEVs. A ceRNA co-expression and regulation relationship network was constructed. Candidate genes MYO1C and SP100 mRNA were confirmed to be expressed in the kidney using Nephroseq database, scRNA-seq dataset, and Human Protein Atlas database. We further selected 2 circRNAs, 2 miRNAs, and 2 lncRNAs from WGCNAs and ceRNAs and demonstrated their efficacy as potential diagnostic biomarkers for T2DN using machine learning algorithms.

CONCLUSIONS

This study reported, for the first time, the whole-transcriptome genetic resources found in urine extracellular vesicles of T2DN patients. The results provide additional support for the possible interactions, and regulators between RNAs from uEVs themselves and as potential biomarkers in DN.

Hsa_circ_0003928 regulates the progression of diabetic nephropathy through miR-136-5p/PAQR3 axis

BACKGROUND

Diabetic nephropathy (DN) is one of the complications of diabetes and has a high mortality, but its specific pathogenesis is not clear. In recent years, researches on the mechanism of circRNAs in DN have been proved a lot, whereas the functional mechanism of circ_0003928 in DN remains open and it must be investigated to value its important role in DN prevention.

METHODS

HK-2 cells were treated with high glucose (HG), normal glucose (NG) or Mannitol. Cell counting kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays were performed to detect cell proliferation. Enzyme-linked immunosorbent assay (ELISA) was applied to analyze malondialdehyde (MDA) and superoxide dismutase 1 (SOD) levels. Flow cytometry and western blot were preformed to measure cell apoptosis. Real-time quantitative PCR (RT-qPCR) was used to test the levels of circ_0003928, miR-136-5p and progestin and adipoQ receptor family member 3 (PAQR3) mRNA. Western blot was executed to detect Bcl2 associated X (Bax), B cell leukemia/lymphoma 2 (Bcl2), smooth muscle (αSMA), apolipoprotein (C-IV) and PAQR3 levels. Luciferase reporter assay and RNA pull-down assay were used to analyze the target relationship between miR-136-5p and circ_0003928 or PAQR3.

RESULTS

Circ_0003928 and PAQR3 expression were up-regulated, whereas miR-136-5p was decreased in DN serum and HG-induced HK-2 cells. Circ_0003928 knockdown promoted cell proliferation, and inhibit cell apoptosis, oxidative stress, and fibrosis in HK-2 cells under HG condition. MiR-136-5p silencing overturned the protective effects of si-circ_0003928 on HG-induced HK-2 cells. MiR-136-5p was targeted by circ_0003928 and directly targeted PAQR3. Overexpression of PAQR3 counteracted the inhibitory functions of circ_0003928 knockdown or miR-136-5p overexpression on HG-induced HK-2 cell injury.

CONCLUSION

Circ_0003928 acted as a sponge of miR-136-5p to up-regulating PAQR3 expression, and then regulate the proliferation, oxidative stress, fibrosis and apoptosis in HG-induced HK-2 cells.

CircUBXN7 promotes macrophage infiltration and renal fibrosis associated with the IGF2BP2-dependent SP1 mRNA stability in diabetic kidney disease

Introduction

Inflammatory cell infiltration is a novel hallmark of diabetic kidney disease (DKD), in part, by activated macrophages. Macrophage-to-tubular epithelial cell communication may play an important role in renal fibrosis. Circular RNAs (circRNAs) have been reported in the pathogenesis of various human diseases involving macrophages activation, including DKD. However, the exact mechanism of circRNAs in macrophage infiltration and renal fibrosis of DKD remains obscure.

Methods

In our study, a novel circRNA circUBXN7 was identified in DKD patients using microarray. The function of circUBXN7 in vitro and in vivo was investigated by qRT-PCR, western blot, and immunofluorescence. Finally, a dual-luciferase reporter assay, ChIP, RNA pull-down, RNA immunoprecipitation and rescue experiments were performed to investigate the mechanism of circUBXN7.

Results

We demonstrated that the expression of circUBXN7 was significantly upregulated in the plasma of DKD patients and correlated with renal function, which might serve as an independent biomarker for DKD patients. According to investigations, ectopic expression of circUBXN7 promoted macrophage activation, EMT and fibrosis in vitro, and increased macrophage infiltration, EMT, fibrosis and proteinuria in vivo. Mechanistically, circUBXN7 was transcriptionally upregulated by transcription factor SP1 and could reciprocally promote SP1 mRNA stability and activation via directly binding to the m6A-reader IGF2BP2 in DKD.

Conclusion

CircUBXN7 is highly expressed in DKD patients may provide the potential biomarker and therapeutic target for DKD.

Multimodal roles of transient receptor potential channel activation in inducing pathological tissue scarification

Transient receptor potential (TRP) channels are a class of transmembrane proteins that can sense a variety of physical/chemical stimuli, participate in the pathological processes of various diseases and have attracted increasing attention from researchers. Recent studies have shown that some TRP channels are involved in the development of pathological scarification (PS) and directly participate in PS fibrosis and re-epithelialization or indirectly activate immune cells to release cytokines and neuropeptides, which is subdivided into immune inflammation, fibrosis, pruritus and mechanical forces increased. This review elaborates on the characteristics of TRP channels, the mechanism of PS and how TRP channels mediate the development of PS, summarizes the important role of TRP channels in the different pathogenesis of PS and proposes that therapeutic strategies targeting TRP will be important for the prevention and treatment of PS. TRP channels are expected to become new targets for PS, which will make further breakthroughs and provide potential pharmacological targets and directions for the in-depth study of PS.

A Novel Circ_Arf3/miR-452-5p/Mbnl1 Axis Regulates Proliferation and Expression of Fibrosis-Related Proteins of Mouse Mesangial Cells Under High Glucose

Background

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes that may lead to chronic renal failure and end-stage renal disease. Circular RNAs (circRNAs) play important roles in DN progression. However, the action of circRNA ADP ribosylation factor 3 (circ_Arf3) in high glucose (HG)-induced change is still unclear.

Methods

Mouse mesangial cells (MCs) were treated with 30 mM HG as a DN cell model in vitro. Quantitative real-time polymerase chain reaction (qRT-PCR) was employed to examine the expression levels of circ_Arf3, microRNA (miR)-452-5p and muscleblind like splicing regulator 1 (Mbnl1). The proliferation of HG-treated MCs was assessed using 5 Ethynyl 2' deoxyuridine (EdU) and cell counting kit-8 (CCK-8) assays, and the levels of proliferation and fibrosis-related proteins and Mbnl1 were detected by Western blot. Dual-luciferase reporter and RNA pull-down assays were utilized to determine the relationship between miR-452-5p and circ_Arf3 or Mbnl1.

Results

Our results discovered that circ_Arf3 and Mbnl1 were lowly expressed in HG-treated MCs, while miR-452-5p expression was up-regulated. Moreover, circ_Arf3 was mainly located in the cytoplasm and had a ring-like stable structure. Functional assays demonstrated that overexpression of circ_Arf3 prevented cell proliferation and fibrous formation in HG-treated MCs. Circ_Arf3 could sponge miR-452-5p, and the effect of circ_Arf3 overexpression was reversed by enhanced expression of miR-452-5p. Mbnl1 was a direct target of miR-452-5p. Knockdown of Mbnl1 abolished the suppressive effects of miR-452-5p inhibitor on proliferation and fibrosis-related protein expression in HG-treated MCs. Moreover, circ_Arf3 regulated Mbnl1 through miR-452-5p.

Conclusion

Overexpression of circ_Arf3 prevents cell proliferation and fibrous formation in HG-treated MCs by regulating the expression of Mbnl1 via miR-452-5p.

Emerging roles of circ_NRIP1 in tumor development and cancer therapy (Review)

Circular RNA (circRNA) is a class of endogenous non-coding RNA, a type of single-stranded covalently closed RNA molecule formed by alternative splicing of exons or introns. Previous studies have demonstrated that circRNA participates in modulating biological processes such as cell proliferation, differentiation and apoptosis, and plays key roles in tumor occurrence and development. CircRNA nuclear receptor interacting protein 1 (circ_NRIP1), a form of circRNA, is abnormally expressed in certain human tumor types. It is present at a higher abundance compared with cognate linear transcripts and can regulate malignant biological behaviors such as tumor proliferation, invasion and migration, revealing a currently unexplored frontier in cancer progression. The present review presents a pattern of circ_NRIP1 expression in various malignant tumor types and highlights its significance in cancer development, in addition to its potential as a disease indicator or future therapeutic agent.

Epigenetic modification in diabetic kidney disease

Diabetic kidney disease (DKD) is a common microangiopathy in diabetic patients and the main cause of death in diabetic patients. The main manifestations of DKD are proteinuria and decreased renal filtration capacity. The glomerular filtration rate and urinary albumin level are two of the most important hallmarks of the progression of DKD. The classical treatment of DKD is controlling blood glucose and blood pressure. However, the commonly used clinical therapeutic strategies and the existing biomarkers only partially slow the progression of DKD and roughly predict disease progression. Therefore, novel therapeutic methods, targets and biomarkers are urgently needed to meet clinical requirements. In recent years, increasing attention has been given to the role of epigenetic modification in the pathogenesis of DKD. Epigenetic variation mainly includes DNA methylation, histone modification and changes in the noncoding RNA expression profile, which are deeply involved in DKD-related inflammation, oxidative stress, hemodynamics, and the activation of abnormal signaling pathways. Since DKD is reversible at certain disease stages, it is valuable to identify abnormal epigenetic modifications as early diagnosis and treatment targets to prevent the progression of end-stage renal disease (ESRD). Because the current understanding of the epigenetic mechanism of DKD is not comprehensive, the purpose of this review is to summarize the role of epigenetic modification in the occurrence and development of DKD and evaluate the value of epigenetic therapies in DKD.

Tartary buckwheat flavonoids alleviates high-fat diet induced kidney fibrosis in mice by inhibiting MAPK and TGF-β1/Smad signaling pathway

Tartary buckwheat flavonoids (TBF) are active components extracted from Tartary buckwheat, which have abundant biological effects. According to this study, we investigated the effect of TBF on high-fat diet (HFD)-induced kidney fibrosis and its related mechanisms. In vivo, we established an HFD-induced kidney fibrosis model in mice and administered TBF. The results showed that TBF was able to alleviate kidney injury and inflammatory response. Subsequently, the mRNA levels between the HFD group and the TBF + HFD group were detected using RNA-seq assay. According to the gene set enrichment analysis (GSEA) and Kyoto Encyclopedia of Genes and Genomes (KEGG) results, the differential genes were enriched in lipid metabolism and mitogen-activated protein kinases(MAPK) signaling pathways. We examined the protein expression of lipid metabolism-related pathways and the level of lipid metabolism. The results showed that TBF significantly activated the adenosine monophosphate activated protein kinase/acetyl-CoA carboxylase (AMPK/ACC) pathway and effectively reduced kidney total cholesterol (TC), triglyceride (TG) and low-density lipoproteinc cholesterol (LDL-C) levels and increased high-density lipoprotein cholesterol (HDL-C) levels in mice. TBF also inhibited transforming growth factor-β1/Smad (TGF-β1/Smad) and MAPK signaling pathways, thus slowing down the kidney fibrosis process. In vitro, using palmitic acid (PA) to stimulate TCMK-1 cells, the in vivo results similarly demonstrated that TBF could alleviate kidney fibrosis in HFD mice by inhibiting TGF1/Smad signaling pathway and MAPK signaling pathway.

Extracellular Matrix and Protein Phosphorylation Dysregulation Related to Diabetes-Induced Erectile Dysfunction

Diabetes can cause erectile dysfunction (ED) in more than half of male patients. However, the mechanisms underlying diabetes-induced erectile dysfunction (DED) remain unknown. This study is aimed at systematically analyzing the cellular and molecular mechanisms leading to DED using bioinformatic analysis and providing molecular targets for predicting and treating DED. In total, we identified 800 DEGs in the DED samples compared with those in the control group. The 407 upregulated DEGs were mainly enriched in glucose and lipid metabolism-related pathways, and the 393 downregulated DEGs were primarily enriched in tissue development and structure. Dysregulated extracellular matrix genes (especially collagen and elastin) may be closely related to damage to the erectile function of the corpus cavernosum. Sixteen hub genes and 24 modules were detected with hub genes and MCODE analysis. The consensus sequence AAA (G/C) AAA was observed at the promoter sites of most genes that were enriched in the “posttranslational protein phosphorylation” pathway. These genes had abundant phosphorylation sites. Furthermore, 20 TFs targeting DEGs were identified using ChEA3 tool. In conclusion, our research comprehensively and systematically describes the molecular characteristics of DED and suggests that dysregulated extracellular matrix genes and protein phosphorylation may play critical roles in DED. Therefore, they may be potential markers for diagnosing and treating DED.

circSPECC1 Promotes Proliferation and Migration of LNCaP Prostate Cancer Cells by Affecting Their Epithelial-Mesenchymal Transition

Objective. To determine the effects of circSPECC1 (hsa_circ_0000745) on the proliferation and migration of LNCaP prostate cancer cells and to explore the potential molecular mechanism. Methods. Stable circSPECC1 shRNA-expressing and circSPECC1-overexpressing LNCaP cell lines were constructed, and relative gene expression levels were determined by RT-PCR. MTT and clonogenic assays were used to assess proliferative ability while a scratch test was used to analyze cell migration. Western blotting was used to determine protein expression levels. The effects of circSPECC1 on the proliferation of LNCaP prostate cancer cells were observed in vivo. Results. circSPECC1 was found to be derived from the SPECC1 (sperm antigen with calponin homology and coiled-coil domains 1) parent gene and to form a loop. Overexpression of circSPECC1 promoted the proliferation and migration of the LNCaP cells, whereas decreased expression of circSPECC1 inhibited these properties. Overexpression of circSPECC1 promoted the expression of MMP-2, MMP-9, VEGF, vimentin, and N-cad but downregulated the expression of E-cad. Decreased expression of circSPECC1 inhibited the expression of MMP-2, MMP-9, VEGF, vimentin, and N-cad but increased the expression of E-cad. Conclusion. circSPECC1 promotes cell proliferation and migration by affecting the epithelial-mesenchymal transition of LNCaP prostate cancer cells.

Circ ASAP2 decreased inflammation and ferroptosis in diabetic nephropathy through SOX2/SLC7A11 by miR-770-5p

AIMS

Diabetes nephropathy (DN) is one of the major complications in diabetes. With the improvement of people's living standards in China in recent years, the incidence of diabetes has become the main cause of end-stage renal disease. However, how and whether circ ASAP2 could mediate DN remain poorly understood. This study aimed to determine the function and its biological mechanism of circ ASAP2 on inflammation and ferroptosis of DN.

METHODS

C57BL/6 mice were fed with a high-fat diet and injected with streptozotocin. Human renal glomerular endothelial cells stimulated with 20 mmol/L D-glucose.

RESULTS

In mice model DN, circular ASAP2 expression level was down-regulated, and miR-770-5p expression level was up-regulated. Moreover, the inhibition of ASAP2 aggravated diabetic nephropathy in mice model. The inhibition of ASAP2 promoted inflammation and oxidative stress to aggravate renal injury in mice model. Circular ASAP2 was reducing inflammation and oxidative stress in vitro model. The inhibition of ASAP2 promoted ferroptosis in model of DN. CASAP2 suppressed miR-770-5p in DN. Additionally, miR-770-5p aggravated diabetic nephropathy in mice model. MiR-770-5p promoted inflammation and oxidative stress to aggravate renal injury in mice model. MiR-770-5p was increasing inflammation and oxidative stress in vitro model. Circular ASAP2 induced SLC7A11 expression in model of DN through SOX2 by miR-770-5p.

CONCLUSIONS

These results suggest that circ ASAP2 decreased inflammation and ferroptosis in DN through SOX2/SLC7A11 by miR-770-5p, which might serve as a target for improving the role of ferroptosis in DN.

YY1-induced upregulation of LncRNA-ARAP1-AS2 and ARAP1 promotes diabetic kidney fibrosis via aberrant glycolysis associated with EGFR/PKM2/HIF-1α pathway

Objectives: Dimeric pyruvate kinase (PK) M2 (PKM2) plays an important role in promoting the accumulation of hypoxia-inducible factor (HIF)-1α, mediating aberrant glycolysis and inducing fibrosis in diabetic kidney disease (DKD). The aim of this work was to dissect a novel regulatory mechanism of Yin and Yang 1 (YY1) on lncRNA-ARAP1-AS2/ARAP1 to regulate EGFR/PKM2/HIF-1α pathway and glycolysis in DKD. Materials and methods: We used adeno-associated virus (AAV)-ARAP1 shRNA to knocked down ARAP1 in diabetic mice and overexpressed or knocked down YY1, ARAP1-AS2 and ARAP1 expression in human glomerular mesangial cells. Gene levels were assessed by Western blotting, RT-qPCR, immunofluorescence staining and immunohistochemistry. Molecular interactions were determined by RNA pull-down, co-immunoprecipitation, ubiquitination assay and dual-luciferase reporter analysis. Results: YY1, ARAP1-AS2, ARAP1, HIF-1α, glycolysis and fibrosis genes expressions were upregulated and ARAP1 knockdown could inhibit dimeric PKM2 expression and partly restore tetrameric PKM2 formation, while downregulate HIF-1α accumulation and aberrant glycolysis and fibrosis in in-vivo and in-vitro DKD models. ARAP1 knockdown attenuates renal injury and renal dysfunction in diabetic mice. ARAP1 maintains EGFR overactivation in-vivo and in-vitro DKD models. Mechanistically, YY1 transcriptionally upregulates ARAP1-AS2 and indirectly regulates ARAP1 and subsequently promotes EGFR activation, HIF-1α accumulation and aberrant glycolysis and fibrosis. Conclusion: Our results first highlight the role of the novel regulatory mechanism of YY1 on ARAP1-AS2 and ARAP1 in promoting aberrant glycolysis and fibrosis by EGFR/PKM2/HIF-1α pathway in DKD and provide potential therapeutic strategies for DKD treatments.

Urinary exosomes derived circRNAs as biomarkers for chronic renal fibrosis

BACKGROUND

Chronic renal disease (CKD) is a common and irreversible loss of renal function. Renal fibrosis reflected the degree of renal dysfunction. However, the current biomarkers only characterize the renal function instead of indicating the fibrosis degree. The potential diagnostic value of urinary exosomes derived circRNAs for renal fibrosis needs to be further studied.

METHODS

Urine exosomes from 3 chronic kidney disease (CKD) patients without renal fibrosis and 3 renal fibrotic patients were collected and human circRNAs microarray analysis were performed to detect the circRNAs expression profile. 110 biopsy-proven CKD patients and 54 healthy controls were enrolled and urine exosomes derived RNA was isolated. The expression of hsa_circ_0036649 was measured and the correlation with renal function parameter and pathological indicators was performed. The receiver operating characteristic (ROC) curve for the diagnosis of renal fibrosis was calculated.

RESULTS

Human circRNAs microarray showed 365 circRNAs up expressed and 195 circRNAs down expressed in renal fibrotic patients compared to none fibrosis CKD patients. The expression of hsa_circ_0036649 was decreased in renal fibrotic patients according to RT-PCR and correlated with serum creatinine, blood urea nitrogen (BUN), estimated glomerular filtration rate and cystatin c. Further, the expression of hsa_circ_0036649 was correlated with the score of tubulointerstitial fibrosis (TIF) and the score of glomerular sclerosis. The ROC curve showed that hsa_circ_0036649 may predict renal fibrosis at a cut-off value of 0.597 with a sensitivity of 45.5% and specificity of 87.9%.

CONCLUSION

Expression of urinary exosomes derived hsa_circ_0036649 associated with the degree of renal fibrosis. Its potential role as a biomarker in CKD remained to be supported by further follow-up studies.Key MessagescircRNAs profile in urine exosomes in renal fibrosis patients was revealed.The expression of urine exosomes derived hsa_circ_0036649 was correlated to renal function and fibrosis degree.circRNAs derived from urinary exosomes may become a new research direction for biomarkers of renal fibrosis.

Circ_0007534 as new emerging target in cancer: Biological functions and molecular interactions

Circular RNA (circRNAs), an important member of the non-coding RNA (ncRNA) family, are widely expressed in a variety of biological cells. Owing to their stable structures, sequence conservations, and cell- or tissue-specific expressions, these RNA have become a popular subject of scientific research. With the development of sequencing methods, it has been revealed that circRNAs exert their biological function by sponging microRNAs (miRNAs), regulating transcription, or binding to proteins. Humans have historically been significantly impacted by various types of cancer. Studies have shown that circRNAs are abnormally expressed in various cancers and are involved in the occurrence and development of malignant tumors, such as tumor cell proliferation, migration, and invasion. As one of its star molecules, circ_0007534 is upregulated in colorectal, cervical, and pancreatic cancers; is closely related to the occurrence, development, and prognosis of tumors; and is expected to become a novel tumor marker and therapeutic target. This article briefly reviews the expression and mechanism of circ_0007534 in malignant tumors based on the domestic and foreign literature.

Expression profiles of tRNA‑derived fragments in high glucose‑treated tubular epithelial cells

Transfer RNA-derived fragments (tRFs), a novel class of small non-coding RNA produced by the cleavage of pre- and mature tRNAs, are involved in various diseases. Renal tubulointerstitial fibrosis is a common final pathway in diabetic nephropathy (DN) in which hyperglycemia-induced tubular extracellular matrix (ECM) accumulation serves a vital role. The present study aimed to detect and investigate the role of tRFs in the accumulation of tubular ECM. Differentially expressed tRFs were analysed with high-throughput sequencing in primary mouse tubular epithelial cells treated with high glucose (HG). The Gene Ontology (GO) was used to analyze the potential molecular functions of these differentially expressed tRFs, and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to analyze the associated signaling pathways involved in these differentially expressed tRFs. tRF-1:30-Gln-CTG-4 was overexpressed using tRF-1:30-Gln-CTG-4 mimic, followed by HG treatment. A total of 554 distinct tRFs were detected and 64 differentially expressed tRFs (fold change >2; P<0.05) were identified in tubular epithelial cells following high glucose (HG) treatment, among which 27 were upregulated and 37 were downregulated. Ten selected tRFs with the greatest difference (fold change >2; P<0.05) were verified to be consistent with small RNA-sequencing data, of which tRF-1:30-Gln-CTG-4 showed the most pronounced difference in expression and was significantly decreased in response to HG. GO analysis indicated that the differentially expressed tRFs were associated with 'cellular process', 'biological regulation' and 'metabolic process'. An analysis of the KEGG database suggested that these differentially expressed tRFs were involved in 'autophagy' and signaling pathways for 'forkhead box O', 'the mammalian target of rapamycin' and 'mitogen-activated protein kinase'. Finally, the overexpression of tRF-1:30-Gln-CTG-4 ameliorated HG-induced ECM accumulation in tubular epithelial cells. Therefore, the present study demonstrated that there may be a significant association between tRFs and HG-induced ECM accumulation in tubular epithelial cells; these differentially expressed tRFs warrant further study to explore the pathogenesis of DN.

Down-Regulation of circCOL1A2 Suppresses the Dysfunction of Diabetes-Related Retinal Microvascular Endothelial Cells via miR-646/FGF7 Axis

PURPOSE

Diabetic retinopathy (DR), the major complication of diabetes, is the leading cause of vision loss and blindness globally. Altered circular RNAs (circRNAs) expression has been found to be involved in DR process. Hence, this work aimed to explore the role and mechanism of circCOL1A2 in DR.

METHODS

Human retinal microvascular endothelial cells (RMECs) treated with high glucose (HG) were used for functional analysis. Levels of genes and proteins were detected using quantitative real-time polymerase chain reaction and western blotting. In vitro experiments were conducted by transwell, tube formation, CCK-8 assays and ELISA, respectively. The binding interaction between miR-646 and circCOL1A2 or FGF7 (Fibroblast Growth Factor 7) was confirmed using dual-luciferase reporter and RNA immunoprecipitation assays.

RESULTS

CircCOL1A2 was highly expressed in retinal tissues of DR patients and HG-induced RMECs. Then RMECs were exposed to HG treatment to mimic the diabetic conditions in vitro. Functionally, circCOL1A2 knockdown attenuated HG-evoked RMEC migration, proliferation, angiogenesis, blood-retina barrier (BRB) injury and inflammation. Mechanistically, circCOL1A2 functioned as a sponge for miR-646, and miR-646 directly targeted FGF7. Further rescue experiments showed that miR-646 inhibition abated the protective effects of circCOL1A2 knockdown on RMEC function under HG treatment. Besides that, miR-646 was decreased in HG-induced RMECs, re-expression of miR-646 reversed HG-evoked RMEC dysfunction, which was rescued by FGF7 overexpression.

CONCLUSION

CircCOL1A2 silencing can suppress HG-induced migration, proliferation, angiogenesis, BRB injury and inflammation in RMECs through miR-646/FGF7 axis, suggesting the potential involvement of circCOL1A2 in DR process.

Circular RNA circBNC2 inhibits epithelial cell G2-M arrest to prevent fibrotic maladaptive repair

The mechanisms underlying fibrogenic responses after injury are not well understood. Epithelial cell cycle arrest in G2/M after injury is a key checkpoint for determining wound-healing leading to either normal cell proliferation or fibrosis. Here, we identify a kidney- and liver-enriched circular RNA, circBNC2, which is abundantly expressed in normal renal tubular cells and hepatocytes but significantly downregulated after acute ischemic or toxic insult. Loss of circBNC2 is at least partially mediated by upregulation of DHX9. Gain- and loss-of-function studies, both in vitro and in vivo, demonstrate that circBNC2 acts as a negative regulator of cell G2/M arrest by encoding a protein that promotes formation of CDK1/cyclin B1 complexes. Restoring circBNC2 in experimentally-induced male mouse models of fibrotic kidney and liver, decreases G2/M arrested cell numbers with secretion of fibrotic factors, thereby mitigating extracellular matrix deposition and fibrosis. Decreased expression of circBNC2 and increased G2/M arrest of epithelial cells are recapitulated in human ischemic reperfusion injury (IRI)-induced chronic kidney disease and inflammation-induced liver fibrosis, highlighting the clinical relevance. These findings suggest that restoring circBNC2 might represent a potential strategy for therapeutic intervention in epithelial organ fibrosis.

Circular RNAs in diabetes and its complications: Current knowledge and future prospects

A novel class of non-coding RNA transcripts called circular RNAs (circRNAs) have been the subject of significant recent studies. Accumulating evidence points that circRNAs play an important role in the cellular processes, inflammatory expression, and immune responses through sponging miRNA, binding, or translating in proteins. Studies have found that circRNAs are involved in the physiologic and pathologic processes of diabetes. There has been an increased focus on the relevance of between abnormal circRNA expression and the development and progression of various types of diabetes and diabetes-related diseases. These circRNAs not only serve as promising diagnostic and prognostic molecular biomarkers, but also have important biological roles in islet cells, diabetes, and its complications. In addition, many circRNA signaling pathways have been found to regulate the occurrence and development of diabetes. Here we comprehensively review and discuss recent advances in our understanding of the physiologic function and regulatory mechanisms of circRNAs on pancreatic islet cells, different subtypes in diabetes, and diabetic complications.

circMTND5 Participates in Renal Mitochondrial Injury and Fibrosis by Sponging MIR6812 in Lupus Nephritis

Recent studies have focused on nuclear-encoded circular RNAs (circRNAs) in kidney diseases, but little is known about mitochondrial circRNAs. Differentially expressed circRNAs were analyzed by RNA deep sequencing from lupus nephritis (LN) biopsies and normal human kidneys. In LN renal biopsies, the most downregulated circRNA was circMTND5, which is encoded in the mitochondrial genome. We quantitated circMTND5 by qPCR and localized by fluorescence in situ hybridization (FISH). Mitochondrial abnormalities were identified by electron microscopy. The expression of mitochondrial genes was decreased, and the expression of profibrotic genes was increased on qPCR and immunostaining. RNA binding sites for MIR6812 and circMTND5 were predicted. MIR6812 expression was increased by FISH and qPCR. In HK-2 cells and its mitochondrial fraction, the role of circMTND5 sponging MIR6812 was assessed by their colocalization in mitochondria on FISH, RNA immunoprecipitation, and RNA pulldown coupled with luciferase reporter assay. circMTND5 knockdown upregulated MIR6812, decreased mitochondrial functional gene expression, and increased profibrotic gene expression. Overexpression of circMTND5 reversed these effects in hTGF-β stimulated HK-2 cells. Similar effects were observed in HK-2 cells with overexpression and with knockdown of MIR6812. We conclude that circMTND5 alleviates renal mitochondrial injury and kidney fibrosis by sponging MIR6812 in LN.

Neat1 promotes acute kidney injury to chronic kidney disease by facilitating tubular epithelial cells apoptosis via sequestering miR-129-5p

Acute kidney injury (AKI) is increasingly identified as a crucial risk factor for progression to CKD. However, the factors governing AKI to CKD progression remain largely unknown. By high-throughput RNA sequencing, we found that Neat1_2, a transcript variant of Neat1, was upregulated in 40-min ischemia/reperfusion injury (IRI), which resulted in the development of renal fibrotic lesions. The upregulation of Neat1_2 in hypoxia-treated TECs was attributed to p53 transcriptional regulation. Gain- and loss-of-function studies, both in vitro and in vivo, demonstrated that Neat1_2 promoted apoptosis of injured TECs induced by IRI and caused tubulointerstitial inflammation and fibrosis. Mechanistically, Neat1_2 shares miRNA response elements with FADD, CASP-8, and CASP-3. Neat1_2 competitively binds to miR-129-5p and prevents miR-129-5p from decreasing the levels of FADD, CASP-8, and CASP-3, and ultimately facilitates TEC apoptosis. Increased expression of Neat1_2 associated with kidney injury and TEC apoptosis was recapitulated in human AKI, highlighting its clinical relevance. These findings suggest that preventing TEC apoptosis by hindering Neat1_2 expression may be a potential therapeutic strategy for AKI to CKD progression.

CircRNA SCMH1 regulates the miR-200a-3p/ZEB1 signaling axis to promote diabetes-induced retinal epithelial-mesenchymal transition

Diabetic retinopathy (DR) is one of the common systemic complications of diabetes. Epithelial-mesenchymal transition (EMT) is required for DR progression. Previous studies have explored that circular RNAs (circRNAs) are crucial for DR development. Herein, we focused on the biological functions of circSCMH1 in DR. RT-qPCR determined the expression of circSCMH1, miR-200a-3p and ZEB1. EMT-related proteins were measured by Western blot. Gene combinations were validated by RIP and dual luciferase reporter assays. CCK-8, EdU, TUNEL staining and Transwell analysis were used to assess the cellular function. FISH analysis assessed the localization of circSCMH1 and miR-200a-3p. HE staining was used to detect retinal structures in a mouse DR model. High-glucose (HG) significantly increased circSCMH1 expression in ARPE-19 cells. Additionally, circSCMH1 silencing repressed proliferation, migration, and EMT in HG cells. Mechanistically, circSCMH1 positively regulated ZEB1 expression via targeting miR-200a-3p. Furthermore, circSCMH1 was observed to induce HG cell growth and EMT by regulating the miR-200a-3p/ZEB1 axis. Finally, we verified that downregulation of circSCMH1 or ZEB1 alleviated EMT in the retina of diabetic mice. These findings have implications for new therapeutic targets for DR.

Crosstalk between regulatory non-coding RNAs and oxidative stress in Parkinson’s disease

Parkinson’s disease is the second most common neurodegenerative disease after Alzheimer’s disease, which imposes an ever-increasing burden on society. Many studies have indicated that oxidative stress may play an important role in Parkinson’s disease through multiple processes related to dysfunction or loss of neurons. Besides, several subtypes of non-coding RNAs are found to be involved in this neurodegenerative disorder. However, the interplay between oxidative stress and regulatory non-coding RNAs in Parkinson’s disease remains to be clarified. In this article, we comprehensively survey and overview the role of regulatory ncRNAs in combination with oxidative stress in Parkinson’s disease. The interaction between them is also summarized. We aim to provide readers with a relatively novel insight into the pathogenesis of Parkinson’s disease, which would contribute to the development of pre-clinical diagnosis and treatment.

Circular RNAs in Acute Kidney Injury: Roles in Pathophysiology and Implications for Clinical Management

Acute kidney injury (AKI) is a common clinical condition, results in patient morbidity and mortality, and incurs considerable health care costs. Sepsis, ischaemia-reperfusion injury (IRI) and drug nephrotoxicity are the leading causes. Mounting evidence suggests that perturbations in circular RNAs (circRNAs) are observed in AKI of various aetiologies, and have pathogenic significance. Aberrant circRNA expressions can cause altered intracellular signalling, exaggerated oxidative stress, increased cellular apoptosis, excess inflammation, and tissue injury in AKI due to sepsis or IRI. While circRNAs are dysregulated in drug-induced AKI, their roles in pathogenesis are less well-characterised. CircRNAs also show potential for clinical application in diagnosis, prognostication, monitoring, and treatment. Prospective observational studies are needed to investigate the role of circRNAs in the clinical management of AKI, with special focus on the safety of therapeutic interventions targeting circRNAs and the avoidance of untoward off-target effects.

circRNA: Regulatory factors and potential therapeutic targets in inflammatory dermatoses

The skin is the largest organ of the human body and acts as the first line of defence against injury and infection. Skin diseases are among the most common health problems and are associated with a considerable burden that encompasses financial, physical and mental consequences for patients. Exploring the pathogenesis of skin diseases can provide insights into new treatment strategies. Inflammatory dermatoses account for a large proportion of dermatoses and have a great impact on the patients' body and quality of life. Therefore, it is important to study their pathogenesis and explore effective treatment. Circular RNAs (circRNAs) are a special type of RNA molecules that play important regulatory roles in several diseases and are involved in skin pathophysiological processes. This review summarizes the biogenesis, properties and functions of circRNAs as well as their roles in the pathogenesis of inflammatory dermatoses, including psoriasis, lupus erythematosus, atopic dermatitis, lichen planus and severe acne and their potential as therapeutic targets.

Construction of a Novel circRNA/miRNA/mRNA Regulatory Network to Explore the Potential Pathogenesis of Wilson’s Disease

Studies show that non-coding RNAs, especially microRNAs (miRNAs) and circular RNAs (circRNAs), and protein-coding genes are involved in the pathophysiology of multi-organ damage caused by Wilson’s disease (WD). However, circRNA expression profiles and their role in initiation and progression of WD kidney injury remain largely unclear at present. Here, we explored potential critical protein-coding genes, miRNAs, and circRNAs, as well as identify competitive endogenous RNAs (ceRNAs) in a WD mouse model by high-throughput sequencing. We investigated the expression profiles of circRNAs, miRNAs, and protein-coding genes, and identified 32 DEcircRs, 45 DEmiRs, and 1623 DEPs. Identified DEcircRs, DEmiRs, and DEPs were used to construct a ceRNA network, which consisted of 15 DEcircRNAs (four upregulated and 11 downregulated), 18 DEmiRNAs (14 upregulated and four downregulated), and 352 DEmRNAs (205 upregulated and 147 downregulated). Further experiments proved that mmu_circ_0001333 and mmu_circ_0000355 acted as sponges of miR-92b-5p, miR-107-3p, and miR-187-3p to regulate the expression of genes including Smad9, Mapk10, and Aldh3a2, which may participate in WD-related kidney injury. Taken together, this study identified the circRNA/miRNA/mRNA network involved in kidney failure in WD, which may serve as a potential biomarker for the pathogenesis of WD.

The Emerging Role of Non-Coding RNAs in Osteogenic Differentiation of Human Bone Marrow Mesenchymal Stem Cells

Autologous bone marrow-derived mesenchymal stem cells (BMSCs) are more easily available and frequently used for bone regeneration in clinics. Osteogenic differentiation of BMSCs involves complex regulatory networks affecting bone formation phenomena. Non-coding RNAs (ncRNAs) refer to RNAs that do not encode proteins, mainly including microRNAs, long non-coding RNAs, circular RNAs, piwi-interacting RNAs, transfer RNA-derived small RNAs, etc. Recent in vitro and in vivo studies had revealed the regulatory role of ncRNAs in osteogenic differentiation of BMSCs. NcRNAs had both stimulatory and inhibitory effects on osteogenic differentiation of BMSCs. During the physiological condition, osteo-stimulatory ncRNAs are upregulated and osteo-inhibitory ncRNAs are downregulated. The opposite effects might occur during bone degenerative disease conditions. Intracellular ncRNAs and ncRNAs from neighboring cells delivered via exosomes participate in the regulatory process of osteogenic differentiation of BMSCs. In this review, we summarize the recent advances in the regulatory role of ncRNAs on osteogenic differentiation of BMSCs during physiological and pathological conditions. We also discuss the prospects of the application of modulation of ncRNAs function in BMSCs to promote bone tissue regeneration in clinics.

Bioinformatics analysis of the potential regulatory mechanisms of renal fibrosis and the screening and identification of factors related to human renal fibrosis

Background

This paper aimed to identify the key genes and potential mechanisms of renal fibrosis, and provide methods of evaluation and new ideas for the early diagnosis and treatment of renal fibrosis.

Methods

The GSE102515 dataset was searched from the Gene Expression Omnibus (GEO) database was searched, the differential genes were screened out, and the down-regulated and up-regulated genes were identified. Enrichment analysis of differential genes in the development of renal fibrosis was carried out using the DAVID database, differential genes were analyzed using the STRING database, and Cytoscape software was used for visual processing.

Results

Eighteen up-regulated genes and ten down-regulated genes were screened. Differential genes are mainly involved in the integrin-mediated signaling pathway and mitotic sister chromatid binding, etc. We found that the molecular functions (MFs) of the differential genes are phospholipid binding and regulatory region DNA binding, etc. Moreover, the cellular components (CCs) of the differential genes are mainly related to low-density lipoprotein (LDL) particles and nuclei. Screening revealed that ADM, ARRB1, AVPR2, CCR1, MTNR1A, PTH, and S1PR2 were core genes in the interaction network of renal fibrosis risk-related proteins.

Conclusions

In this study, the differential genes in the occurrence of renal fibrosis were screened out via dataset analysis. It was found that ADM, ARRB1, AVPR2, CCR1, MTNR1A, PTH, and S1PR2 may be important participants in the development of renal fibrosis, which provides analytical support for the identification of valuable markers of renal fibrosis.

Research progress of endothelial-mesenchymal transition in diabetic kidney disease

Renal fibrosis is an important pathological feature of diabetic kidney disease (DKD), manifested as tubular interstitial fibrosis, tubular atrophy, glomerulosclerosis and damage to the normal structure of the kidney. Renal fibrosis can eventually develop into renal failure. A better understanding of renal fibrosis in DKD is needed due to clinical limitations of current anti‐fibrotic drugs in terms of effectiveness, cost‐effectiveness and side effects. Fibrosis is characterized by local excessive deposition of extracellular matrix, which is derived from activated myofibroblasts to increase its production or specific tissue inhibitors of metalloproteinases to reduce its degradation. In recent years, endothelial‐mesenchymal transition (EndMT) has gradually integrated into the pathogenesis of fibrosis. In animal models of diabetic kidney disease, it has been found that EndMT is involved in the formation of renal fibrosis and multiple signalling pathways such as TGF‐β signalling pathway, Wnt signalling pathway and non‐coding RNA network participate in the regulation of EndMT during fibrosis. Here, we mainly review EndMT regulation and targeted therapy of renal fibrosis in DKD.