Long noncoding RNAs in the pathogenesis of diabetic kidney disease: implications for novel therapeutic strategies

The role of lncRNAs in regulation of DKD and diabetes-related cancer

Diabetes mellitus often results in several complications, such as diabetic kidney disease (DKD) and end-stage renal diseases (ESRDs). Cancer patients often have the dysregulated glucose metabolism. Abnormal glucose metabolism can enhance the tumor malignant progression. Recently, lncRNAs have been reported to regulate the key proteins and signaling pathways in DKD development and progression and in cancer patients with diabetes. In this review article, we elaborate the evidence to support the function of lncRNAs in development of DKD and diabetes-associated cancer. Moreover, we envisage that lncRNAs could be diagnosis and prognosis biomarkers for DKD and cancer patients with diabetes. Furthermore, we delineated that targeting lncRNAs might be an alternative approach for treating DKD and cancer with dysregulated glucose metabolism.

lncRNA KCNQ1OT1 regulated high glucose-induced proliferation, oxidative stress, extracellular matrix accumulation, and inflammation by miR-147a/SOX6 in diabetic nephropathy (DN)

Long non-coding RNAs (lncRNAs) have been proved to play critical roles in diabetic nephropathy (DN). This study aimed to investigate the functions and underlying mechanism of potassium voltage-gated channel subfamily Q member 1 overlapping transcript 1 (KCNQ1OT1) in DN. Blood samples were obtained from 33 DN patients and 30 healthy volunteers. Kidney biopsies tissues of DN patients (n = 10) and patients with normal kidney morphology (n = 10) were collected. We found that KCNQ1OT1 was markedly overexpressed in the blood and kidney biopsies tissues of DN patients, as well as in high glucose (HG)-cultured human glomerular mesangial (HGMC) cells. Knockdown of KCNQ1OT1 suppressed proliferation, extracellular matrix (ECM) accumulation, inflammation, and oxidative stress in HG-treated HGMC cells in vitro. KCNQ1OT1 functioned as a sponge for microRNA-147a (miR-147a), and SRY-Box Transcription Factor 6 (SOX6) was directly targeted by miR-147a. Downregulation of miR-147a or upregulation of SOX6 partly overturned the prohibitive effects of KCNQ1OT1 knockdown or miR-147a overexpression on proliferation, ECM accumulation, inflammation, and oxidative stress in HG-treated HGMC cells. Altogether, KCNQ1OT1 mediated the proliferation, ECM accumulation, inflammation, and oxidative stress in HG-treated HGMC cells via miR-147a/SOX6 axis, which might be a novel target for DN therapy.

LncRNA NEAT1 accelerates the proliferation, oxidative stress, inflammation and fibrosis and suppresses the apoptosis via miR-423-5p/GLIPR2 axis in diabetic nephropathy

ABSTRACT

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes. The aim of our study was to investigate the potential mechanism in DN progression. SV40 MES13 cells were exposed to high concentration of glucose (HG: 30 mmol/L) for 48 h to establish DN cell model in vitro. Bioinformatic software StarBase was adopted to establish long non-coding RNA (lncRNA)-microRNA (miRNA)-messenger RNA (mRNA) axis. Dual-luciferase reporter assay, RNA immunoprecipitation (RIP) assay and RNA-pull down assay were performed to verify intermolecular interaction. LncRNA nuclear paraspeckle assembly transcript 1 (NEAT1) was overexpressed in the serum of DN patients. HG time-dependently up-regulated NEAT1 level, and HG promotes cell proliferation, oxidative stress, inflammation and fibrosis and suppressed cell apoptosis in SV40 MES13 cells partly via up-regulating NEAT1. NEAT1 functioned as a molecular sponge of miR-423-5p, and NEAT1 silencing-mediated effects were partly overturned by miR-423-5p interference in HG-induced SV40 MES13 cells. Glioma pathogenesis related-2 (GLIPR2) was a target of miR-423-5p. GLIPR2 overexpression in normal concentration of glucose (NG)-induced SV40 MES13 cells partly simulated HG-induced effects. GLIPR2 overexpression partly reversed NEAT1 interference-induced effects in HG-induced SV40 MES13 cells. LncRNA NEAT1 contributed to HG-induced DN progression via miR-423-5p/GLIPR2 axis in vitro. NEAT1/miR-423-5p/GLIPR2 axis might be potential target for DN treatment.

LncRNA KCNQ1OT1 promotes the development of diabetic nephropathy by regulating miR-93-5p/ROCK2 axis

BACKGROUND

Long non-coding RNAs (lncRNAs) have been reported to play vital roles in diabetic nephropathy (DN). The aim of this study was to explore the function of mechanism of lncRNA KCNQ1 opposite strand/antisense transcript 1 (KCNQ1OT1) in DN.

METHODS

DN cell models were established using high glucose (HG) treatment in human glomerular mesangial cells (HGMC) and human renal glomerular endothelial cells (HRGEC). The expression levels of KCNQ1OT1, microRNA-93-5p (miR-93-5p), and Rho associated coiled-coil containing protein kinase 2 (ROCK2) mRNA was detected by quantitative real-time polymerase chain reaction (qRT-PCR). Cell Counting Kit-8 (CCK-8) assay and flow cytometry were used to detect cell proliferation and apoptosis, respectively. ROCK2 and apoptosis/fibrosis-related protein levels were examined by western blot. The predicted interaction between miR-93-5p and KCNQ1OT1 or ROCK2 was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

KCNQ1OT1 was upregulated in DN patients and DN cell models. KCNQ1OT1 knockdown inhibited cell proliferation and fibrosis and induced apoptosis in DN cell models. MiR-93-5p was a direct target of KCNQ1OT1, and miR-93-5p inhibition restored the KCNQ1OT1 knockdown-mediated effects on cell proliferation, fibrosis and apoptosis in DN cell models. In addition, ROCK2 was identified as a target of miR-93-5p, and miR-93-5p overexpression suppressed cell proliferation and fibrosis and accelerated apoptosis by targeting ROCK2 in DN cell models. Moreover, KCNQ1OT1 regulated ROCK2 expression by binding to miR-93-5p.

CONCLUSION

KCNQ1OT1 knockdown inhibited cell proliferation and fibrosis and induced apoptosis in DN by regulating miR-93-5p/ROCK2 axis, providing potential value for the treatment of DN.

Long noncoding RNA MIAT inhibits the progression of diabetic nephropathy and the activation of NF-κB pathway in high glucose-treated renal tubular epithelial cells by the miR-182-5p/GPRC5A axis

Background

Diabetic nephropathy (DN) is a common diabetic complication. Long noncoding RNAs (lncRNAs) have been identified as essential regulators in DN progression. This study is devoted to the research of lncRNA-myocardial infarction-associated transcript (MIAT) in DN.

Methods

DN cell model was established by high glucose (HG) treatment for human renal tubular epithelial cells (HK-2). Cell viability and colonizing capacity were analyzed by Cell Counting Kit-8 (CCK-8) and colony formation assay. Apoptosis was assessed via caspase-3 detection and flow cytometry. Enzyme-linked immunosorbent assay (ELISA) was used for evaluating inflammation. The protein determination was completed using western blot. MIAT, microRNA-182-5p (miR-182-5p), and G protein-coupled receptor class C group 5 member A (GPRC5A) levels were all examined via reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Intergenic binding was verified using dual-luciferase reporter, RNA immunoprecipitation (RIP), and RNA pull-down assays.

Results

HG induced the inhibition of cell growth, but accelerated apoptosis and inflammation as well as the activation of nuclear factor kappa B (NF-κB) pathway. MIAT reestablishment prevented the HG-induced cell damages and NF-κB signal activation. Mechanistically, MIAT was proved as a miR-182-5p sponge and regulated the expression of GPRC5A that was a miR-182-5p target. The rescued experiments demonstrated that MIAT downregulation or miR-182-5p upregulation aggravated the HG-induced cell damages and activated the NF-κB pathway via the respective regulation of miR-182-5p or GPRC5A.

Conclusion

Taken together, MIAT functioned as an inhibitory factor in the pathogenesis to impede the development of DN and inactivate the NF-κB pathway via regulating the miR-182-5p/GPRC5A axis.

Long non-coding RNA CASC2 restrains high glucose-induced proliferation, inflammation and fibrosis in human glomerular mesangial cells through mediating miR-135a-5p/TIMP3 axis and JNK signaling

BACKGROUND

Diabetic nephropathy (DN) is a common complication of diabetes. Long non-coding RNA (lncRNA) cancer susceptibility candidate 2 (CASC2) is reported to exert a protective role in DN by a previous study. The working mechanism underlying the protective role of CASC2 in DN progression was further explored in this study.

METHODS

The expression of CASC2 and microRNA-135a-5p (miR-135a-5p) was determined by real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation ability was assessed by Cell Counting Kit-8 (CCK8) assay and 5-ethynyl-29-deoxyuridine (EDU) assay. Enzyme-linked immunosorbent assay (ELISA) was conducted to analyze the production of inflammatory cytokines in the supernatant. Western blot assay was performed to analyze protein expression. Dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay were performed to verify the target relationship between miR-135a-5p and CASC2 or tissue inhibitors of metalloproteinase 3 (TIMP3).

RESULTS

High glucose (HG) treatment reduced the expression of CASC2 in human glomerular mesangial cells (HMCs) in a time-dependent manner. CASC2 overexpression suppressed HG-induced proliferation, inflammation and fibrosis in HMCs. miR-135a-5p was validated as a target of CASC2, and CASC2 restrained HG-induced influences in HMCs partly by down-regulating miR-135a-5p. miR-135a-5p bound to the 3' untranslated region (3'UTR) of TIMP3, and CASC2 positively regulated TIMP3 expression by sponging miR-135a-5p in HMCs. miR-135a-5p silencing inhibited HG-induced effects in HMCs partly by up-regulating its target TIMP3. CASC2 overexpression suppressed HG-induced activation of Jun N-terminal Kinase (JNK) signaling partly through mediating miR-135a-5p/TIMP3 signaling.

CONCLUSIONS

In conclusion, CASC2 alleviated proliferation, inflammation and fibrosis in DN cell model by sponging miR-135a-5p to induce TIMP3 expression.

Overexpression of the Long Noncoding RNA HIF2PUT Inhibits Non-Small Cell Lung Cancer Cell Proliferation and Invasion Through HIF-2a Pathway

Objective: The role and molecular mechanism of long-chain noncoding RNAs (lncRNAs) in lung cancer remain to be elucidated. The aim of this study was to investigate the association between a long coding RNA hypoxia-inducible factor-2α (HIF-2α) promoter upstream transcript (HIF2PUT) and clinical characteristics of non-small cell lung cancer (NSCLC) and its regulatory role in NSCLC. Materials and Methods: The correlation between HIF2PUT expression and pathological features of NSCLC was analyzed in NSCLC patient samples. Real-time polymerase chain reaction and Western blot were used to detect genes' mRNA and protein expression, respectively. Cell proliferation assay, invasion, and transwell assay were performed to determine the effects of HIF2PUT on NSCLC cells. Results: lncRNA HIF2PUT was downregulated in NSCLC tissues and cell lines. The authors also indicated that HIF2PUT mainly expressed in cytoplasm and overexpression of HIF2PUT attenuates cell proliferation and invasion in NSCLC cells. Moreover, low expression of HIF2PUT was significantly related to TNM stage (p = 0.045) and histological type (p = 0.025). Furthermore, they found that HIF2PUT plays role in cell proliferation and invasion in NSCLC through regulating HIF-2a. Conclusion: Based on the study, the inhibitory role of HIF2PUT on NSCLC proliferation, invasion could be blocked by HIF-2a silencing. In summary, this study suggests that HIF2PUT and HIF-2a may play an important role in the regulation of NSCLC progression, which provides new insights for clinical treatment.

ATF4-dependent heme-oxygenase-1 attenuates diabetic nephropathy by inducing autophagy and inhibiting apoptosis in podocyte

AIM

Podocyte injury plays an important role in diabetic nephropathy (DN), yet the underlying molecular mechanisms of podocyte injury in DN is not clear. Here, we investigated the role of activating transcription factor 4 (ATF4) and HO-1 in DN-induced podocyte injury.

METHODS

Protein expression was measured by western blotting (WB) and immunofluorescence. Cellular apoptosis was quantified by flow cytometry. ATF4 siRNA knockdown and HO-1 overexpression in podocyte were employed to evaluate the role of ER stress in DN-induced apoptosis and autophagy response. Urinary protein levels, nephrin expression, serum creatinine and BUN were evaluated and glomerulosclerosis was quantified by Periodic Acid-Schiff staining.

RESULTS

Expression of ATF4 was increased in podocytes exposed to serum from DN mice. ATF4 knockdown enhanced DN-induced podocyte apoptosis. HO-1 overexpression reduced the decline of DN-induced podocyte autophagy and inhibited apoptosis and the beneficial effects of HO-1 overexpression in DN were blocked by ATF4 knockdown. The diabetic mice were significantly ameliorated by HO-1 agonist hemin treatment.

CONCLUSIONS

ATF4 induces autophagy by enhancing the expression of HO-1, and inhibits podocyte apoptosis in DN. Treatment with the HO-1 agonist reduced proteinuria, apoptosis, and enhanced autophagy response, and thus improved renal function in DN mice.

LncRNA TUG1 ameliorates diabetic nephropathy via inhibition of PU.1/RTN1 signaling pathway

Diabetic nephropathy (DN) is a leading cause of end-stage renal failure. The study aimed to investigate whether long noncoding RNA taurine-upregulated gene 1 (TUG1) can ameliorate the endoplasmic reticulum stress (ERS) and apoptosis of renal tubular epithelial cells in DN, and the underlying mechanism. The DN mouse model was established by streptozocin injection, and the human renal tubular epithelial cell line HK-2 was treated with high glucose (HG) to mimic DN in vitro. The molecular mechanism was explored through dual-luciferase activity assay, RNA pull-down assay, RNA immunoprecipitation (RIP), and chromatin immunoprecipitation (CHIP) assay. The expression of TUG1 was significantly decreased in the renal tubules of DN model mice. Overexpression of TUG1 reduced the levels of ERS markers and apoptosis markers by inhibiting reticulon-1 (RTN1) expression in HG-induced HK-2 cells. Furthermore, TUG1 down-regulated RTN1 expression by inhibiting the binding of transcription factor PU.1 to the RTN1 promoter, thereby reducing the levels of ERS markers and apoptosis markers. Meanwhile, TUG1-overexpression adenovirus plasmids injection significantly alleviated tubular lesions, and reduced RTN1 expression, ERS markers and apoptosis markers, whereas these results were reversed by injection of PU.1-overexpression adenovirus plasmids. TUG1 restrains the ERS and apoptosis of renal tubular epithelial cells and ameliorates DN through inhibition of transcription factor PU.1.

Epigenetic Landscape Analysis of the Long Non-Coding RNA and Messenger RNA in a Mouse Model of Corneal Alkali Burns

Purpose

Corneal alkali burns (CABs) are a common clinical ocular disease, presenting a poor prognosis. Although some long noncoding RNAs (lncRNAs) reportedly play a key role in epigenetic regulation associated with CABs, studies regarding the lncRNA signature in CABs remain rare and elusive.

Methods

A CAB model was established in C57BL/6J mice and profiling of lncRNA expressions was performed by RNA-Seq. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted to predicate the related pathological pathways and candidate genes. RT-qPCR was used to verify the expression pattern of lncRNAs and related mRNAs, both in vitro and in vivo. Data were statistically analyzed by GraphPad Prism version 6.0.

Results

In all, 4436 aberrantly expressed lncRNAs were identified in CAB mice when compared with control mice. In the top 13 aberrantly expressed lncRNAs, Bc037156 and 4930511E03Rik were confirmed as the most significantly altered lncRNAs. Pathway analysis revealed that mitogen-activated protein kinase (MAPK) signaling pathway was most enriched. Following 4930511E03Rik siRNA treated, Srgn, IL-1β and Cxcr2 were significant upregulated in corneal epithelial cells, corneal keratocytes, and bone marrow dendritic cells, with NaOH treatment. Moreover, after Bc037156 siRNA treated, expression levels of IL-1β and Srgn were significantly downregulated in the three cell lines.

Conclusions

Our study suggests that Bc037156 and 4930511E03Rik may be involved in inflammation, immune response, and neovascularization by regulating Srgn, IL-1β, and Cxcr2 expression after CAB. These candidate lncRNAs and mRNAs may be the potential targets for the treatment strategy of the alkali injured cornea.

LncRNA Meg3-mediated regulation of the Smad pathway in atRA-induced cleft palate

Palatal mesenchymal cell proliferation is essential to the process of palatogenesis, and the proliferation of mouse embryonic palate mesenchymal (MEPM) cells is impacted by both all-trans retinoic acid (atRA) and the TGF-β/Smad signaling pathway. The long non-coding RNA (lncRNA) MEG3 has been shown to activate TGF-β/Smad signaling and to thereby regulate cell proliferation, differentiation, and related processes. Herein, we found that atRA treatment (100 mg/kg) promoted Meg3 upregulation in MEPM cells, and that such upregulation was linked to the suppression of MEPM cell proliferation in the context of secondary palate fusion on gestational day (GD) 13 and 14. Moreover, the demethylation of specific CpG sites within the lncRNA Meg3 promoter was detected in atRA-treated MEPM cells, likely explaining the observed upregulation of this lncRNA. Smad signaling was also suppressed by atRA treatment in these cells, and RNA immunoprecipitation analyses revealed that Smad2 can directly interact with Meg3 in MEPM cells following atRA treatment. Therefore, we propose a model wherein Meg3 is involved in the suppression of MEPM cell proliferation, functioning at least in part via interacting with the Smad2 protein and thereby suppressing Smad signaling in the context of atRA-induced cleft palate.

Diabetic nephropathy alters circulating long noncoding RNA levels that normalize following simultaneous pancreas-kidney transplantation

Simultaneous pancreas-kidney transplantation (SPKT) replaces kidney function and restores endogenous insulin secretion in patients with diabetic nephropathy (DN). Here, we aimed to identify circulating long noncoding RNAs (lncRNAs) that are associated with DN and vascular injury in the context of SPKT. Based on a pilot study and a literature-based selection of vascular injury-related lncRNAs, we assessed 9 candidate lncRNAs in plasma samples of patients with diabetes mellitus with a kidney function >35 mL/min/1.73 m² (DM; n = 12), DN (n = 14), SPKT (n = 35), healthy controls (n = 15), and renal transplant recipients (KTx; n = 13). DN patients were also studied longitudinally before and 1, 6, and 12 months after SPKT. Of 9 selected lncRNAs, we found MALAT1, LIPCAR, and LNC-EPHA6 to be higher in DN compared with healthy controls. SPKT caused MALAT1, LIPCAR, and LNC-EPHA6 to normalize to levels of healthy controls, which was confirmed in the longitudinal study. In addition, we observed a strong association between MALAT1, LNC-EPHA6, and LIPCAR and vascular injury marker soluble thrombomodulin and a subset of angiogenic microRNAs (miR-27a, miR-130b, miR-152, and miR-340). We conclude that specific circulating lncRNAs associate with DN-related vascular injury and normalize after SPKT, suggesting that lncRNAs may provide a promising novel monitoring strategy for vascular integrity in the context of SPKT.

LINC00052 ameliorates acute kidney injury by sponging miR-532-3p and activating the Wnt signaling pathway

Acute kidney injury (AKI) is a complex renal disease. Long non-coding RNAs (lncRNAs) have frequently been associated with AKI. In the present study, we aimed to investigate the molecular mechanism(s) of LINC00052 in AKI. We found that LINC00052 expression was significantly decreased in AKI patient serum. In addition, in a hypoxic AKI cell model, LINC00052 expression was strongly elevated. In an I/R-triggered AKI rat model, the expression of TNF-α, IL-6 and IL-1β mRNA was strongly elevated. Moreover, we predicted miR-532-3p to be targeted by LINC00052 in AKI. Overexpression of LINC00052 increased hypoxia-induced inhibition of NRK-52E cell proliferation and reversed hypoxia-triggered apoptosis. Furthermore, we found that induction of TNF-α, IL-6 and IL-1β was repressed by overexpression of LINC00052. LINC00052 decreased hypoxia-induced ROS and MDA accumulation in vitro and increased SOD activity. Decreased levels of c-myc and cyclin D1 were observed in renal tissues of AKI rats. Lastly, Wnt/β-catenin signaling was inactivated in NRK-52E cells experiencing hypoxia, and LINC00052 upregulation reactivated Wnt/β-catenin signaling by sponging miR-532-3p. Taken together, these results suggest that LINC00052 ameliorates AKI by sponging miR-532-3p and activating Wnt signaling.

LncRNA CASC2 Alleviates the Progression of Diabetic Nephropathy by Regulating the miR-144/SOCS2 Signalling Axis

BACKGROUND

Diabetic nephropathy constitutes a large proportion of end-stage kidney failure in diabetic patients. However, the underlying molecular mechanisms remain unclear.

METHODS

Db/db diabetic mouse models and high glucose (HG)-induced human renal mesangial cells (HRMCs) were used as research models in vivo and in vitro. The expression of cancer susceptibility candidate 2 (CASC2) was quantified by qRT-PCR. The regulatory role of CASC2 in cell apoptosis, inflammatory factor release, and fibrosis was verified by flow cytometry, qRT-PCR, and Western blot assay, respectively. The bioinformatics prediction software DIANA and starBase v2.0 were used to predict the putative binding sites. The interactions among CASC2, miR-144, and SOCS2 were explored by the luciferase assay and Western bolt assay.

RESULTS

The expression of CASC2 in diabetic mouse models and HG-induced HRMCs was lower than that in the control (p < 0.05). Overexpression of CASC2 resulted in a decrease in the apoptosis rate, inflammatory factor release (TNF-α, IL-6, and IL-1β), expression of cleaved caspase-3, and fibrotic proteins (fibronectin, Col-IV, and TGF-β1) and an increase in Bcl-2 expression. Inhibition of CASC2 caused increased expression of miR-144. Furthermore, mechanistic investigations confirmed that activation of the miR-144/SOCS2 regulatory loop by overexpression of miR-144 reversed the in vitro effects of CASC2 on inhibiting cell apoptosis, inflammatory factor release, and fibrosis. In addition, simultaneous overexpression of miR-144 and SOCS2 further increased the inhibition of cell apoptosis, inflammatory factor release, and fibrosis by CASC2.

CONCLUSION

CASC2 could alleviate the degree and process of apoptosis, inflammation, and fibrosis in diabetic nephropathic models by regulating the miR-144/SOCS2 axis.

Increased long noncoding RNA maternally expressed gene 3 contributes to podocyte injury induced by high glucose through regulation of mitochondrial fission

Excessive mitochondrial fission plays a key role in podocyte injury in diabetic kidney disease (DKD), and long noncoding RNAs (lncRNAs) are important in the development and progression of DKD. However, lncRNA regulation of mitochondrial fission in podocytes is poorly understood. Here, we studied lncRNA maternally expressed gene 3 (Meg3) in mitochondrial fission in vivo and in vitro using human podocytes and Meg3 podocyte-specific knockdown mice. Expression of lncRNA Meg3 in STZ-induced diabetic mice was higher, and correlated with the number of podocytes. Excessive mitochondrial fission of podocytes and renal histopathological and physiological parameters were improved in podocyte-specific Meg3 knockdown diabetic mice. Elongated mitochondria with attenuated podocyte damage, as well as mitochondrial translocation of dynamin-related protein 1 (Drp1), were decreased in Meg3 knockout podocytes. By contrast, increased fragmented mitochondria, podocyte injury, and Drp1 expression and phosphorylation were observed in lncRNA Meg3-overexpressing podocytes. Treatment with Mdivi1 significantly blunted more fragmented mitochondria and reduced podocyte injury in lncRNA Meg3-overexpressing podocytes. Finally, fragmented mitochondria and Drp1 mitochondrial translocation induced by high glucose were reduced following treatment with Mdivi1. Our data show that expression of Meg3 in podocytes in both human cells and diabetic mice was higher, which regulates mitochondrial fission and contributes to podocyte injury through increased Drp1 and its translocation to mitochondria.

KCNQ1OT1/miR-18b/HMGA2 axis regulates high glucose-induced proliferation, oxidative stress, and extracellular matrix accumulation in mesangial cells

The dysregulated long noncoding RNAs (lncRNAs) are associated with the pathogenesis of diabetic nephropathy (DN). LncRNA potassium voltage-gated channel subfamily Q member 1 overlapping transcript 1 (KCNQ1OT1) plays an important role in diabetes, but the role and mechanism of KCNQ1OT1 in DN are largely unknown. Serum samples were collected from 30 DN patients and normal volunteers. High glucose (HG)-challenged human mesangial cells (HMCs) were used as a cell model of DN. KCNQ1OT1, microRNA-18b (miR-18b), and high mobility group protein A2 (HMGA2) abundances were examined via quantitative reverse transcription polymerase chain reaction or western blot. Cell proliferation was assessed via 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide. Oxidative stress was assessed via the levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and SOD2. Extracellular matrix (ECM) accumulation was investigated by the levels of fibronectin (FN), collagen I (Col I), and Col IV. The relationship between miR-18b and KCNQ1OT1 or HMGA2 was determined via dual-luciferase reporter analysis, RNA immunoprecipitation, and pull-down. KCNQ1OT1 expression was increased and miR-18b expression was decreased in DN patients and HG-challenged HMCs. miR-18b was targeted via KCNQ1OT1. Knockdown of KCNQ1OT1 weakened HG-caused proliferation, oxidative stress, and ECM accumulation of HMCs by increasing miR-18b. HMGA2 was targeted via miR-18b. miR-18b alleviated HG-induced cell proliferation, oxidative stress, and ECM accumulation by decreasing HMGA2. Silence of KCNQ1OT1 reduced HMGA2 expression via miR-18b. KCNQ1OT1 knockdown attenuated HG-induced proliferation, oxidative stress, and ECM accumulation of HMCs by regulating miR-18b/HMGA2 axis.

Emerging role of lncRNAs in renal fibrosis

Fibrosis is the final common pathological feature of a wide variety of chronic kidney disease (CKD). However, an understanding of the mechanisms underlying the development of renal fibrosis remains challenging and controversial. As the current focus of molecular research, noncoding RNAs (ncRNAs), mainly microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular noncoding RNAs (circRNAs), have powerful and abundant biological functions, which essentially makes them mediators of the physiological and pathological processes of various system diseases. The role of ncRNAs in renal fibrosis has also received great attention in recent years, but most research has mainly focused on miRNAs. In fact, although a large number of studies of lncRNAs have emerged recently, the role these molecules play in renal fibrosis haven't been fully understood till now. Thus, this review discusses the discovery of lncRNAs and their biological functions in different types of renal fibrosis, as well as the imminent applications of these findings in clinical use. Undoubtedly, in the future, further understanding of the function of all types of lncRNAs will reveal large breakthroughs in the treatment of renal fibrosis.

The effect of lncRNA-ARAP1-AS2/ARAP1 on high glucose-induced cytoskeleton rearrangement and epithelial-mesenchymal transition in human renal tubular epithelial cells

The epithelial-mesenchymal transition (EMT) plays an important role in diabetic renal fibrosis. The ARAP1 gene is located near risk alleles for Type 2 diabetes, and its function has been linked to cytoskeleton rearrangement, Golgi apparatus remodeling, and endocytic trafficking of membrane receptors. The role of ARAP1 and its antisense RNA, ARAP1-AS2, in the pathogenesis of diabetes is unclear. To clarify the roles of ARAP1 and its antisense RNA in diabetes and related complications, we examined if the expression of these transcripts changed under high glucose (HG) conditions. To do this, we examined transcript levels in HK-2 cells, and explored the roles of ARAP1 and ARAP1-AS2 in the EMT process in HK-2 cells. We found increased expression of ARAP1-AS2 and ARAP1 in HK-2 cells under HG condition, and observed that the overexpression of ARAP1-AS2 significantly increased the EMT process. In addition, HG upregulated Cdc42-GTP levels in HK-2 cells, and increased cytoskeleton rearrangement, cell viability, and migration. After knockdown of ARAP1, the level of Cdc42-GTP was decreased; cytoskeleton reorganization, cell viability, and migration processes were decreased; and EMT and expression of fibrosis marker protein. Overall, our results indicated that ARAP1-AS2/ARAP1 may participate in cytoskeleton rearrangement and EMT processes in HK-2 cells through increased Cdc42-GTP levels.

LncRNA SNHG16 induces proliferation and fibrogenesis via modulating miR-141-3p and CCND1 in diabetic nephropathy

LncRNAs are reported to participate in the progression of various diseases including diabetic nephropathy. Currently, we reported that SNHG16 was obviously upregulated in db/db mice and high glucose-treated mice mesangial cells. Then, functional experiments showed that SNHG16 silencing significantly inhibited proliferation of mice mesangial cells, which induced the apoptosis and triggered cell cycle arrest. Meanwhile, proliferation-related biomarkers PCNA and Cyclin D1 (CCND1) were greatly repressed. Furthermore, western blot analysis was conducted to test fibrogenesis-associated genes Fibronectin and α-SMA. Meanwhile, the increased protein expression levels of Fibronectin and α-SMA under high glucose conditions were reversed by loss of SNHG16. miR-141-3p has been reported to be involved in various diseases. Then, RNA immunoprecipitation assay revealed the relation between SNHG16 and miR-141-3p. Downregulation of SNHG16 was able to induce expression of miR-141-3p, which was obviously reduced in db/db diabetic nephropathy mice. In addition, CCND1 is a crucial cell cycle master in human diseases. CCND1 was speculated as the target of miR-141-3p and miR-141-3p inhibited CCND1 expression significantly. Meanwhile, we observed that loss of CCND1 greatly repressed mice mesangial cell proliferation and induced cell apoptosis. Taken these together, we revealed for the first time that SNHG16 induced proliferation and fibrogenesis via modulating miR-141-3p and CCND1 in diabetic nephropathy. SNHG16/miR-141-3p/CCND1 axis can suggest a pathological mechanism of progression of diabetic nephropathy.

LncRNA MALAT1 promoted high glucose-induced pyroptosis of renal tubular epithelial cell by sponging miR-30c targeting for NLRP3

Diabetic nephropathy (DN), characterized by the chronic loss of kidney function during diabetes, is a long-term kidney disease that affects millions of populations. However, the etiology of DN remains unclear. DN cell model was established by treating HK-2 cells with high glucose (HG) in vitro. Expression of metastasis-associated lung adenocarcinoma transcript-1 (MALAT1), miR-30c, nucleotide binding and oligomerization domain-like receptor protein 3 (NLRP3), caspase-1, IL-1β, and IL-18 in treated HK-2 cells were tested by quantitative polymerase chain reaction. HK-2 cell pyroptosis was assessed using flow cytometry analysis. Lactate dehydrogenase (LDH) activity was examined with a LDH assay kit. Correlation among MALAT1, miR-30c, and NLRP3 was examined via dual-luciferase reporter assay. Here, we revealed that MALAT1 was upregulated, but miR-30c was downregulated in HG-treated HK-2 cells, leading to upregulation of NLRP3 expression and cell pyroptosis. Knockdown of MALAT1 or overexpression of miR-30c protected HK-2 cells from HG-induced pyroptosis. Meanwhile, we found that MALAT1 promoted NLRP3 expression by sponging miR-30c through dual-luciferase reporter assay. Moreover, the co-transfection of sh-MALAT1 and miR-30c inhibitor could reverse the protective effects of the sh-MALAT1 on the HG-induced pyroptosis. These results confirmed that MALAT1 regulated HK-2 cell pyroptosis by inhibiting miR-30c targeting for NLRP3, contributing to a better understanding of DN pathogenesis and help to find out the effective treatment for DN.

Long noncoding RNA growth arrest-specific transcript 5 alleviates renal fibrosis in diabetic nephropathy by downregulating matrix metalloproteinase 9 through recruitment of enhancer of zeste homolog 2

Diabetic nephropathy (DN) is a frequently occurred microvascular complication associated with type I and type II diabetes mellitus. The participation of long noncoding RNAs (lncRNAs) in diabetes-related microvascular complications has been reported extensively. We attempted to unveil the possible regulatory mechanism of lncRNA growth arrest-specific transcript 5 (GAS5) and matrix metalloproteinase 9 (MMP9), an important inflammatory protein, in the progression of DN. A rat DN model was induced by streptozocin (STZ). The low expression of GAS5 and high expression of MMP9 in DN rats with DN was then determined by RT-qPCR and western blot analysis, and lentivirus-mediated GAS5 overexpression was shown to ameliorate STZ-induced renal interstitial fibrosis (RIF) and inflammatory reaction in the kidney of DN rats. Moreover, MMP9 was found to be upregulated in STZ-induced DN, while MMP9 silencing induced by lentivirus expressing shRNA against MMP9 reduced RIF and suppressed inflammation in the kidney of DN rats. RIP, RNA pull-down, and ChIP assays demonstrated that GAS5 downregulated MMP9 via recruiting enhancer of zeste homolog 2 (EZH2) in the promoter region of MMP9. Overall, our study reveals that GAS5 downregulates MMP9 expression through recruiting EZH2 to MMP9 promoter region and alleviates the progression of renal fibrosis in DN rats, which sheds new light on the therapeutic potential of GAS5-targeted therapies in combating that disease.

LNCRNA CDKN2B-AS1 regulates mesangial cell proliferation and extracellular matrix accumulation via miR-424-5p/HMGA2 axis

BACKGROUND

Previous study has demonstrated that long noncoding RNA cyclin-dependent kinase inhibitor 2B antisense RNA 1 (CDKN2B-AS1) was abnormally expressed in diabetic nephropathy (DN). However, the underlying mechanism that allows CDKN2B-AS1 in the progression of DN remains to be further elucidated.

METHODS

Peripheral blood cells of 24 diabetes patients with DN and 20 without DN were collected. Human glomerular mesangial cells (HGMC) were cultured in high glucose or low glucose medium. The expression levels of CDKN2B-AS1, microRNA (miR)-424-5p and high mobility group AT hook 2 (HMGA2) were detected by quantitative real-time polymerase chain reaction or western blot. The target association between miR-424-5p and CDKN2B-AS1 or HMGA2 was confirmed by dual-luciferase reporter and RNA immunoprecipitation assays. Cell proliferation, extracellular matrix (ECM) accumulation and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) and western blot, respectively.

RESULTS

CDKN2B-AS1 expression was up-regulated and miR-424-5p level was down-regulated in peripheral blood of DN patients and high glucose-treated HGMC cells. CDKN2B-AS1 was validated as a sponge of miR-424-5p. Silence of CDKN2B-AS1 repressed proliferation and ECM accumulation by increasing miR-424-5p. HMGA2 was a target of miR-424-5p and miR-424-5p overexpression inhibited proliferation, ECM accumulation and PI3K/AKT pathway by targeting HMGA2. Moreover, knockdown of CDKN2B-AS1 inhibited HMGA2 expression and PI3K/AKT pathway by increasing miR-424-5p.

CONCLUSION

Knockdown of CDKN2B-AS1 suppressed proliferation, ECM accumulation and PI3K/AKT signaling by increasing miR-424-5p and decreasing HMGA2 in high glucose-treated HMGC cells.

Non-Coding RNAs in IGF-1R Signaling Regulation: The Underlying Pathophysiological Link between Diabetes and Cancer

The intricate molecular network shared between diabetes mellitus (DM) and cancer has been broadly understood. DM has been associated with several hormone-dependent malignancies, including breast, pancreatic, and colorectal cancer (CRC). Insulin resistance, hyperglycemia, and inflammation are the main pathophysiological mechanisms linking DM to cancer. Non-coding RNAs (ncRNAs), particularly microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are widely appreciated as pervasive regulators of gene expression, governing the evolution of metabolic disorders, including DM and cancer. The ways ncRNAs affect the development of DM complicated with cancer have only started to be revealed in recent years. Insulin-like growth factor 1 receptor (IGF-1R) signaling is a master regulator of pathophysiological processes directing DM and cancer. In this review, we briefly summarize a number of well-known miRNAs and lncRNAs that regulate the IGF-1R in DM and cancer, respectively, and further discuss the potential underlying molecular pathogenesis of this disease association.

LncRNA GAS5 exacerbates renal tubular epithelial fibrosis by acting as a competing endogenous RNA of miR-96-5p

Renal fibrosis is at the core of various renal diseases, including diabetic kidney disease (DKD). Long noncoding RNAs (lncRNAs) are known players in the regulation of renal fibrosis. However, their expression and function in DKD still need to be elucidated. The purpose of this study was to assess how lncRNA GAS5 regulates fibrosis and its mechanism in TGF-β1-treated renal proximal tubular cell.In this study, the lncRNA GAS5 was upregulated in both TGF-β1-treated HK-2 cells and the kidneys of HDF/STZ mice. Knockdown of GAS5 relieved renal tubular epithelial fibrosis. This effect was mediated by the downregulation and functional inactivation of miR-96-5p. Furthermore, miR-96-5p was downregulated in DKD mice, and this downregulation attenuated the repression of FN1(fibronectin, FN) and led to its upregulation. The decrease in miR-96-5p was partially attributed to the miRNA-sponge action of GAS5.Our research demonstrates that knockdown of lncRNA GAS5 leads to antifibrosis by competitively binding miR-96-5p, which inhibits the expression of FN1. These results indicate that targeting lncRNA GAS5 may be a promising therapeutic strategy for preventing DKD.

NORAD affects the progression of diabetic nephropathy through targeting miR-520h to upregulate TLR4

To uncover the role of NORAD in the progression of diabetic nephropathy (DN) and the underlying mechanism. Relative levels of NORAD and TLR4 in db/m mice and db/db mice were tested. Meanwhile, their levels in glomerular mesangial cells undergoing high-level (H-MC group) or low-level (L-MC) glucose treatment were determined. Regulatory effects of NORAD and TLR4 on proliferative ability and apoptosis in SV40-MES-13 cells were assessed. The interaction in the regulatory loop NORAD/miR-520h/TLR4 was verified through dual-luciferase reporter gene assay, determination of subcellular distribution and RIP (RNA Immunoprecipitation) assay. At last, potential role of the regulatory loop NORAD/miR-520h/TLR4 in regulating DN was clarified. NORAD and TLR4 were upregulated in db/db mice and SV40-MES-13 cells in H-MC group. Overexpression of them promoted proliferative ability and inhibited apoptosis in SV40-MES-13 cells. MiR-520h was confirmed to bind NORAD and TLR4. NORAD, miR-520h and TLR4 were mainly distributed in cytoplasm, which were enriched in anti-Ago2. The regulatory loop NORAD/miR-520h/TLR4 has been demonstrated to promote the progression of DN. The regulatory loop NORAD/miR-520h/TLR4 promotes the proliferative ability and inhibits apoptosis in glomerular mesangial cells, thus aggravating the progression of DN.

DNA Methylome and Transcriptome Alterations in High Glucose-Induced Diabetic Nephropathy Cellular Model and Identification of Novel Targets for Treatment by Tanshinone IIA

Diabetic nephropathy (DN) is a diabetes complication that comes from overactivation of Renin-Angiotensin System, excessive pro-inflammatory factors, reactive oxygen species (ROS) overproduction, and potential epigenetic changes. Tanshinone IIA (TIIA), a diterpene quinone phytochemical, has been shown to possess powerful antioxidant, anti-inflammatory, epigenetics, and protective effects against different diseases including DN by inhibiting ROS induced by high glucose (HG). However, epigenomic and transcriptomic study of DN and the protective effect of TIIA are lacking. In this study, next-generation sequencing of RNA and DNA methylation profiles on the potential underlying mechanisms of a DN model in mouse kidney mesangial mes13 cells challenged with HG and treatment with TIIA were conducted. Bioinformatic analysis coupled with Ingenuity Pathway analysis of RNA-seq was performed, and 1780 genes from HG/LG and 1416 genes from TIIA/HG were significantly altered. Several pro-inflammatory pathways like leukotriene biosynthesis and eicosanoid signaling pathways were activated by HG stimulation, while TIIA treatment would enhance glutathione-mediated detoxification pathway to overcome the excess oxidative stress and inflammation triggered by HG. Combination analysis of RNA-seq and Methyl-seq data sets, DNA methylation, and RNA expression of a list of DN associated genes, Nmu, Fgl2, Glo, and Kcnip2, were found to be altered in HG-induced mes13 DN model, and TIIA treatment would effectively restore the alterations. Taken together, these findings provide novel insights into the understanding of how epigenetic/epigenomic modifications could affect the progression of DN and the potential preventive effect of TIIA in DN.

Association Between IL-6 Polymorphisms and Diabetic Nephropathy Risk: A Meta-analysis

BACKGROUND

The objective of this work was to evaluate the relevance of frequent interleukin-6 (IL-6) polymorphisms and diabetic nephropathy (DN) susceptibility by a systematic meta-analysis.

MATERIALS AND METHODS

The included studies related to the relationship between IL-6 and DN risk were searched from Pubmed, Embase and the Cochrane Library, and the Newcastle-Ottawa Scale was used to evaluate the study quality. A heterogeneity test was performed to determine the appropriate effect models based on the Q test and I² statistic. Odds ratios with 95% confidence intervals were used to determine the strength of associations. Afterwards, subgroup analysis was conducted to assess the effect of specific factors on the corresponding results. Additionally, publication bias and sensitivity analysis were also undertaken.

RESULTS

In total, 11 eligible articles were obtained. The meta-analysis revealed that the "C"allele of IL-6 rs1800795 was related to the decreased risk of DN (C versus G: P = 0.0471). The "G"allele of IL-6 rs1800796 was predominately associated with higher DN risks (GG versus CC: P = 0.0194; GG versus CC + GC: P = 0.0196). The "C"allele of IL-6 rs1800797 was implicated with higher prevalence of DN (C versus G: P = 0.0001; CC versus GG: P = 0.0003; CC versus GG + CG: P = 0.0227; CC + CG versus GG: P = 0.0001) while IL-6 rs2069837 and rs2069840 were not correlated with the susceptibility to DN.

CONCLUSIONS

This meta-analysis indicated that IL-6 rs1800795, rs1800796 and rs1800797 played important roles in DN development while IL-6 rs2069837 and rs2069840 might not be related to DN.

Long noncoding RNA: an emerging player in diabetes and diabetic kidney disease

Diabetic kidney disease (DKD) is among the most common complications of diabetes mellitus (DM), and remains the leading cause of end-stage renal diseases (ESRDs) in developed countries, with no definitive therapy yet available. It is imperative to decipher the exact mechanisms underlying DKD and identify novel therapeutic targets. Burgeoning evidence indicates that long non-coding RNAs (lncRNAs) are essential for diverse biological processes. However, their roles and the mechanisms of action remain to be defined in disease conditions like diabetes and DKD. The pathogenesis of DKD is twofold, so is the principle of treatments. As the underlying disease, diabetes per se is the root cause of DKD and thus a primary focus of therapy. Meanwhile, aberrant molecular signaling in kidney parenchymal cells and inflammatory cells may directly contribute to DKD. Evidence suggests that a number of lncRNAs are centrally involved in development and progression of DKD either via direct pathogenic roles or as indirect mediators of some nephropathic pathways, like TGF-β1, NF-κB, STAT3 and GSK-3β signaling. Some lncRNAs are thus likely to serve as biomarkers for early diagnosis or prognosis of DKD or as therapeutic targets for slowing progression or even inducing regression of established DKD. Here, we elaborated the latest evidence in support of lncRNAs as a key player in DKD. In an attempt to strengthen our understanding of the pathogenesis of DKD, and to envisage novel therapeutic strategies based on targeting lncRNAs, we also delineated the potential mechanisms of action as well as the efficacy of targeting lncRNA in preclinical models of DKD.

Roles of Identified Long Noncoding RNA in Diabetic Nephropathy

Diabetes mellitus is the leading chronic disease in the world, and diabetic nephropathy (DN) as one of its complications could increase the mortality. The development of DN is associated to abnormal hemodynamic factors like cytokine networks and the intervention of metabolic risk factors like blood pressure, blood glucose, and blood lipid. However, the pathogenesis of DN is still poorly understood. Although glucose-lowering drugs and insulins have significant effects on blood glucose, the fluctuation of blood glucose or other risk factors could continuously damage the kidney. Recent studies reported that the progression of DN is closely related to the expression of long noncoding RNA (lncRNA), which is important for the early diagnosis and targeted intervention of DN. In this review, we briefly summarize the published studies on the functions and potential mechanism of reported lncRNA in the regulation of DN.

LncRNA NEAT1 promotes extracellular matrix accumulation and epithelial-to-mesenchymal transition by targeting miR-27b-3p and ZEB1 in diabetic nephropathy

Diabetic nephropathy (DN) is a kind of microvascular complications of diabetes. Long noncoding RNAs (lnRNAs) can participate in the development of various diseases, including DN. However, the function of lncRNA NEAT1 is unclear. In our present study, we reported that NEAT1 was significantly increased in streptozotocin-induced DN rat models and high-glucose-induced mice mesangial cells. We observed that knockdown of NEAT1 greatly inhibited renal injury of DN rats. Meanwhile, downregulation of NEAT1-modulated extracellular matrix (ECM) proteins (ASK1, fibronectin, and TGF-β1) expression and epithelial-mesenchymal transition (EMT) proteins (E-cadherin and N-cadherin) in vitro. Previously, miR-27b-3p has been reported to be involved in diabetes. Here, miR-27b-3p was decreased in DN rats and high-glucose-induced mice mesangial cells. The direct correlation between NEAT1 and miR-27b-3p was validated using the dual-luciferase reporter assay and RNA immunoprecipitation experiments. In addition, zinc finger E-box binding homeobox 1 (ZEB1), which has been identified in the process of EMT clearly contributes to EMT progression. ZEB1 was predicted as a target of miR-27b-3p and overexpression of miR-27b-3p dramatically repressed ZEB1 expression. Therefore, our data implied the potential role of NEAT1 in the fibrogenesis and EMT in DN via targeting miR-27b-3p and ZEB1.

Long noncoding RNA NEAT1 accelerates the proliferation and fibrosis in diabetic nephropathy through activating Akt/mTOR signaling pathway

Accumulating evidence has indicated the significant roles of long noncoding RNAs (lncRNAs) in the pathophysiology of diabetic nephropathy (DN). LncRNA nuclear enriched abundant transcript 1 (NEAT1) has been reported to exert a key role in the progression of several diseases including diabetes. However, the role of NEAT1 in the regulation of DP progression remains barely known. Therefore, our study aimed to investigate the role of NEAT1 in a streptozotocin-induced diabetes model (DM) of rats and glucose-induced mouse mesangial cell models. Currently, we found that NEAT1 was greatly upregulated in DM rats and glucose-induced mice mesangial cells, in which a high activation of Akt/mTOR signaling was also observed. Then, it was shown that knockdown of NETA1 was able to reduce renal injury in DM rats obviously. In addition, cell counting kit-8 assay and 5-ethynyl-2'-deoxyuridine assay were carried out and we observed downregulation of NEAT1 significantly inhibited mesangial cell proliferation. Meanwhile, extracellular matrix proteins and messenger RNA (transforming growth factor β1, fibronectin, and collagen IV) expression was dramatically restrained by silencing of NEAT1 in the high glucose-induced mesangial cells. Finally, knockdown of NEAT1 greatly reduced the expression of the phosphorylation of Akt and mammalian target of rapamycin (mTOR) in vitro. These findings revealed that the decrease of NEAT1 repressed the proliferation and fibrosis in DN via activating the Akt/mTOR signaling pathway, which might represent a novel pathological mechanism of DN progression.