Polycomb repressive complex 2 regulates MiR-200b in retinal endothelial cells: potential relevance in diabetic retinopathy

Genetic association of diabetic retinopathy with long noncoding RNA CDKN2B-AS1 gene polymorphism

AIM

We attempted to test the influences of cyclin dependent kinase inhibitor 2B antisense RNA 1 (CDKN2B-AS1) gene polymorphisms on the susceptibility to Diabetic retinopathy (DR).

METHODS

Five single-nucleotide polymorphisms (SNPs) of the CDKN2B-AS1 gene, rs564398, rs1333048, rs1537373, rs2151280, and rs8181047 were examined in 280 DR cases and 455 DR-free diabetic controls.

RESULTS

Among these loci tested, we demonstrated that diabetic carriers of at least one polymorphic allele (G) of rs2151280 (AG and GG; AOR, 1.613; 95% CI, 1.040-2.501; p = 0.033) are more susceptible to proliferative DR but not non-proliferative DR. This genetic association with the risk of developing proliferative DR was further strengthened in homozygotes for the polymorphic allele (G) of rs2151280 (GG; AOR, 2.194; 95% CI, 1.117-4.308; p = 0.023). We detected a significant association of the polymorphic allele (G) of rs2151280 with proliferative DR patients (OR, 1.503; 95% CI, 1.112-2.033; p = 0.008) but not with the entire DR or non-proliferative DR group. Moreover, as compared to those who do not possess the polymorphic allele of rs2151280 (AA), DR patients carrying at least one polymorphic allele of rs2151280 (AG + GG) exhibited a lower glomerular filtration rate and HDL cholesterol level, revealing a promotive role of rs2151280 in renal and cardiovascular complications of diabetes.

CONCLUSION

Taken together, our findings implicate an impact of CDKN2B-AS1 gene polymorphisms on the progression of DR.

The role of long noncoding RNAs in ocular angiogenesis and vascular oculopathy

BACKGROUND

Long noncoding RNAs (lncRNAs) are RNA transcripts over 200 nucleotides in length that do not code for proteins. Initially considered a genomic mystery, an increasing number of lncRNAs have been shown to have vital roles in physiological and pathological conditions by regulating gene expression through diverse mechanisms depending on their subcellular localization. Dysregulated angiogenesis is responsible for various vascular oculopathies, including diabetic retinopathy, retinopathy of prematurity, age-related macular degeneration, and corneal neovascularization. While anti-VEGF treatment is available, it is not curative, and long-term outcomes are suboptimal, and some patients are unresponsive. To better understand these diseases, researchers have investigated the role of lncRNAs in regulating angiogenesis and models of vascular oculopathies. This review summarizes recent research on lncRNAs in ocular angiogenesis, including the pro-angiogenic lncRNAs ANRIL, HOTAIR, HOTTIP, H19, IPW, MALAT1, MIAT, NEAT1, and TUG1, the anti-angiogenic lncRNAs MEG3 and PKNY, and the human/primate specific lncRNAs lncEGFL7OS, discussing their functions and mechanisms of action in vascular oculopathies.

Complementary Approaches to Retinal Health Focusing on Diabetic Retinopathy

Diabetes mellitus affects carbohydrate homeostasis but also influences fat and protein metabolism. Due to ophthalmic complications, it is a leading cause of blindness worldwide. The molecular pathology reveals that nuclear factor kappa B (NFκB) has a central role in the progression of diabetic retinopathy, sharing this signaling pathway with another major retinal disorder, glaucoma. Therefore, new therapeutic approaches can be elaborated to decelerate the ever-emerging "epidemics" of diabetic retinopathy and glaucoma targeting this critical node. In our review, we emphasize the role of an improvement of lifestyle in its prevention as well as the use of phytomedicals associated with evidence-based protocols. A balanced personalized therapy requires an integrative approach to be more successful for prevention and early treatment.

Non-coding RNA-mediated endothelial-to-mesenchymal transition in human diabetic cardiomyopathy, potential regulation by DNA methylation

AIMS

Diabetic cardiomyopathy (DCM) is a major complication of diabetes and a risk factor for cardiovascular disease. Endothelial dysfunction is central to DCM, and endothelial-to-mesenchymal transition (EndMT) is a key form of endothelial dysfunction in diabetes. EndMT in DCM has been well-studied in model systems and has been found to be epigenetically regulated by non-coding RNAs (ncRNAs). However, EndMT in DCM and its associated epigenetic changes need further characterization in human patients. It is also not known if ncRNAs are affected by changes in DNA methylation in DCM. This study aims to confirm in human hearts, the findings from animal and cell studies, and potentially provide novel insight into interactions between DNA methylation and ncRNAs in EndMT in DCM.

METHODS AND RESULTS

Heart tissues were collected from autopsy patients, fixed in formalin, and embedded in paraffin. Thin sections from paraffin-embedded tissues were used for histology and immunofluorescence analyses, where we confirmed that diabetic patients showed increased cardiac fibrosis that EndMT had occurred. Tissue curls from the paraffin-embedded tissues were used for RT-qPCR and methylation analyses. RT-qPCR quantitatively showed that EndMT occurs in the hearts of diabetics, and that EndMT in human hearts corresponded to changes in key ncRNAs. Methylation analysis showed that some of the EndMT-related ncRNAs were regulated by DNA promoter methylation, while others may be regulated through different epigenetic mechanisms.

CONCLUSIONS

We show that EndMT is a relevant pathological process in human hearts during DCM, and that its occurrence coincides with changes in relevant ncRNAs. We further find that interplay between DNA methylation and certain ncRNAs involved in the regulation of EndMT may contribute to the observed changes in ncRNA expression. These findings reinforce the role of EndMT in patients afflicted with DCM and underscore the complexities and importance of the interactions between different facets of epigenetic regulation.

Coordination of cross-talk between metabolism and epigenetic regulation by the SIN3 complex

Post-translational modifications of histone proteins control the expression of genes. Metabolites from central and one-carbon metabolism act as donor moieties to modify histones and regulate gene expression. Thus, histone modification and gene regulation are connected to the metabolite status of the cell. Histone modifiers, such as the SIN3 complex, regulate genes involved in proliferation and metabolism. The SIN3 complex contains a histone deacetylase and a histone demethylase, which regulate the chromatin landscape and gene expression. In this chapter, we review the cross-talk between metabolic pathways that produce donor moieties, and epigenetic complexes regulating proliferation and metabolic genes. This cross-talk between gene regulation and metabolism is tightly controlled, and disruption of this cross-talk leads to metabolic diseases. We discuss promising therapeutics that directly regulate histone modifiers, and can affect the metabolic status of the cell, alleviating some metabolic diseases.

The role of EZH2 in ocular diseases: a narrative review

EZH2, acting as a catalytic subunit of PRC2 to catalyze lysine 27 in histone H3, induces the suppression of gene expression. EZH2 can regulate cell proliferation and differentiation of retinal progenitors, which are required for physiological retinal development. Meanwhile, an abnormal level of EZH2 has been observed in ocular tumors and other pathological tissues. This review summarizes the current knowledge on EZH2 in retinal development and ocular diseases, including inherited retinal diseases, ocular tumors, corneal injury, cataract, glaucoma, diabetic retinopathy and age-related retinal degeneration. We highlight the potential of targeting EZH2 as a precision therapeutic target in ocular diseases.

Knockdown of Krüppel-Like Factor 9 Inhibits Aberrant Retinal Angiogenesis and Mitigates Proliferative Diabetic Retinopathy

Advanced proliferative diabetic retinopathy (PDR) characterized by aberrant retinal angiogenesis is a leading cause of retinal detachment and blindness. Krüppel-like factor 9 (KLF9), a member of the zinc-finger family of transcription factors, participates in the development of diabetic nephropathy and the promotion of angiogenesis of human umbilical vein endothelial cells. Therefore, we speculate that KLF9 may exert a crucial role in PDR. The current study revealed that KLF9 was highly expressed in the high glucose (HG)-treated human retinal microvascular endothelial cells (HRMECs) and the retinas of oxygen-induced retinopathy (OIR) rats. Knockdown of KLF9 inhibited the proliferation, migratory capability, invasiveness and tube formation of HG-treated HRMECs. Besides, knockdown of KLF9 decreased the expression of yes-associated protein 1 (YAP1) in HG-treated HRMECs. Dual-luciferase reporter assays confirmed that KLF9 transcriptionally upregulated YAP1 expression. Overexpression of YAP1 reversed the KLF9 silencing-induced repression of HRMEC proliferation and tube formation. Further in vivo evidence demonstrated that knockdown of KLF9 reduced the expression of Ki67, CD31 and vascular endothelial growth factor A (VEGFA) in the retinas of OIR rats. Collectively, KLF9 silencing might mitigate the progression of PDR by inhibiting angiogenesis via blocking YAP1 transcription.

Long non-coding RNAs in retinal neovascularization: current research and future directions

PURPOSE

Retinal neovascularization (RNV) is an intractable pathological hallmark of numerous ocular blinding diseases, including diabetic retinopathy, retinal vein occlusion, and retinopathy of prematurity. However, current therapeutic methods have potential side effects and limited efficacy. Thus, further studies on the pathogenesis of RNV-related disorders and novel therapeutic targets are critically required. Long non-coding RNAs (lncRNAs) have various functions and participate in almost all biological processes in living cells, such as translation, transcription, signal transduction, and cell cycle control. In addition, recent research has demonstrated critical modulatory roles of various lncRNAs in RNV. In this review, we summarize current knowledge about the expression and regulatory functions of lncRNAs related to the progression of pathological RNV.

METHODS

We searched databases such as PubMed and Web of Science to gather and review information from the published literature.

CONCLUSIONS

In general, lncRNA MEG3 attenuates RNV, thus protecting the retina from excessive and dysregulated angiogenesis under high glucose stress. In contrast, lncRNAs MALAT1, MIAT, ANRIL, HOTAIR, HOTTIP, and SNHG16, have been identified as causative molecules in the pathological progression of RNV. Comprehensive and in-depth studies of the roles of lncRNAs in RNV indicate that targeting lncRNAs may be an alternative therapeutic approach in the near future, enabling new options for attenuating RNV progression and treating RNV-related retinal diseases.

miRNAs as cornerstones in diabetic microvascular complications

Diabetes mellitus is usually accompanied by nephropathy, retinopathy, and neuropathy as microvascular complications. MicroRNAs (miRNAs) can affect the kidney, retina, and peripheral neurons through their implication in pathways involved in angiogenesis, inflammation, apoptosis, as well as fibrosis within these tissues and hence, play a crucial role in the pathogenesis of microvascular complications. In this review, the updated knowledge of the role of miRNAs in the pathogenesis of diabetic microvascular complications was summarized. PubMed Central was searched extensively to retrieve data from a wide range of reputable biomedical reports/articles published after the year 2000 to systematically collect and present a review of the key molecular pathways mediating the hyperglycemia-induced adverse effects on vascular tissues, particularly in persons with T2DM. In the present review, miR-126, miR-29b, and miR-125a are implicated in diabetes-induced microvascular complications, while miR-146a is found to be connected to all these complications. Also, vascular endothelial growth factors are noted to be the most impacted targets by miRNAs in all diabetic microvascular problems.

Potential epigenetic molecular regulatory networks in ocular neovascularization

Neovascularization is one of the many manifestations of ocular diseases, including corneal injury and vascular diseases of the retina and choroid. Although anti-VEGF drugs have been used to effectively treat neovascularization, long-term use of anti-angiogenic factors can cause a variety of neurological and developmental side effects. As a result, better drugs to treat ocular neovascularization are urgently required. There is mounting evidence that epigenetic regulation is important in ocular neovascularization. DNA methylation and histone modification, non-coding RNA, and mRNA modification are all examples of epigenetic mechanisms. In order to shed new light on epigenetic therapeutics in ocular neovascularization, this review focuses on recent advances in the epigenetic control of ocular neovascularization as well as discusses these new mechanisms.

LINC00963 silencing inhibits the proliferation and migration of high glucose-induced retinal endothelial cells via targeting miR-27b

The association between long intergenic non-protein-coding RNA 963 (LINC00963) and diabetes has not been fully elucidated. Therefore, the present study aimed to investigate the effect of the long non-coding RNA LINC00963 on diabetic retinopathy (DR), in order to provide a new therapeutic target for this condition. Human retinal capillary endothelial cells (HRECs) were induced with high concentrations of glucose to establish a DR model. The expression levels of LINC00963, cell viability, the protein expression levels of proliferating cell nuclear antigen (PCNA) and Ki67, and the migratory capacity of HRECs were determined using reverse transcription-quantitative PCR (RT-qPCR), Cell Counting Kit-8 assay, western blot analysis, and wound healing and Transwell assays, respectively. Furthermore, the Encyclopedia of RNA Interactomes database was used to predict the binding targets of LINC00963, and luciferase reporter assay was used to verify the direct binding of microRNA (miR)-27b to LINC00963. RT-qPCR was also utilized to measure the expression levels of miR-27b, PCNA and Ki67. The results demonstrated that LINC00963 silencing inhibited glucose-induced HREC proliferation and migration, and downregulated PCNA and Ki67 expression. Following transfection with miR-27b inhibitor, cell proliferation and migration were notably enhanced, and the protein expression levels of PCNA and Ki67 were increased. Taken together, the results of the present study suggested that the LINC00963/miR-27b axis may regulate the proliferation and migration of glucose-induced HRECs. Therefore, LINC00963 may be considered as a potential therapeutic target for DR.

MicroRNA-93-5p participates in type 2 diabetic retinopathy through targeting Sirt1

OBJECTIVE

To investigate the role of miR-93-5p in rats with type 2 diabetic retinopathy (DR) through targeting Sirt1.

METHODS

The targeting correlation between miR-93-5p and Sirt1 was validated by dual-luciferase reporter gene assay. Type 2 diabetes mellitus (T2DM) rat models were received intravitreal injection of antagomir NC (negative control), miR-93-5p antagomir, miR-93-5p agomir and/or recombinant Sirt1, followed by observation of pathological changes in retina via HE staining. Besides, retinal vascular permeability was determined by fluorescein isothiocyanate-bovine serum albumin (FITC-BSA), while the retinal vasculature was observed through retinal trypsin digestion. Expression of miR-93-5p and Sirt1 was measured by qRT-PCR and Western blotting, while the levels of VEGF, proinflammatory cytokines and anti-oxidative indicators were determined using corresponding kits.

RESULTS

MiR-93-5p could target Sirt1 as analyzed by the luciferase reporter gene assay. Rats in the T2DM group presented the up-regulation of miR-93-5p and down-regulation of Sirt1 in the retina, and miR-93-5p inhibition could up-regulate Sirt1 expression in the T2DM rats. Recombinant Sirt1 decreased retinal vascular permeability and acellular capillaries with improved pathological changes in retina from T2DM rats, which was abolished by miR-93-5p agomir. Moreover, miR-93-5p inhibition or Sirt1 overexpression decreased the levels of VEGF and proinflammatory cytokines while enhancing the activity of anti-oxidative indicators. However, indicators above had no significant differences between T2DM group and T2DM + agomir + Sirt1 group.

CONCLUSION

MiR-93-5p, via targeting Sirt1, could affect the vascular permeability and acellular capillaries and mitigate the inflammation and oxidative stress in the retinas, which may play a critical role in DR.

The Long Non-Coding RNA HOTAIR Is a Critical Epigenetic Mediator of Angiogenesis in Diabetic Retinopathy

Purpose

Diabetic retinopathy (DR) remains a pressing issue worldwide. Abnormal angiogenesis is a distinct vascular lesion in DR, and research has established that vascular endothelial growth factor A (VEGF-A) is a primary mediator of such changes. However, limitations in current anti-VEGF therapies suggest that our understanding of molecular networks underlying ocular angiogenesis remains far from complete. Based on our long non-coding RNA (lncRNA) array analyses, HOX antisense intergenic RNA (HOTAIR) was identified as one of the top upregulated lncRNAs in high glucose-cultured human retinal endothelial cells (HRECs). Given the well-documented roles of HOTAIR in cancer, no studies have examined the epigenetic implications of HOTAIR in DR, and we investigated such relationships herein.

Methods

We used HRECs exposed to various glucose concentrations and epigenetic modulators to examine HOTAIR, angiogenic, and DR-related molecular markers. Oxidative stress, angiogenesis, and mitochondrial dysfunction were assessed. Retinal tissues of diabetic rodents and the vitreous humor and serum of patients with proliferative DR were also investigated.

Results

Hyperglycemia significantly augmented HOTAIR expression in HRECs and promoted angiogenesis, oxidative damage, and mitochondrial aberrations. Similarly, vitreous humor and serum from proliferative DR patients and retinas from diabetic animals demonstrated increased HOTAIR expression compared to non-diabetic controls. HOTAIR knockdown protected against glucose-induced increases of angiogenic and diabetes-associated molecules in the retina. Mechanistically, we showed that HOTAIR exerts its capabilities by preventing oxidative stress and modulating epigenetic pathways involving histone methylation, histone acetylation, DNA methylation, and transcription factors.

Conclusions

Our findings suggest that HOTAIR is a critical lncRNA in the pathogenesis of DR and may potentially be important for diagnostic and therapeutic targeting.

Noncoding RNAs involved in DNA methylation and histone methylation, and acetylation in diabetic vascular complications

Diabetes is a metabolic disorder and its incidence is still increasing. Diabetic vascular complications cause major diabetic mobility and include accelerated atherosclerosis, nephropathy, retinopathy, and neuropathy. Hyperglycemia contributes to the pathogenesis of diabetic vascular complications via numerous mechanisms including the induction of oxidative stress, inflammation, metabolic alterations, and abnormal proliferation of EC and angiogenesis. In the past decade, epigenetic modifications have attracted more attention as they participate in the progression of diabetic vascular complications despite controlled glucose levels and regulate gene expression without altering the genomic sequence. DNA methylation and histone methylation, and acetylation are vital epigenetic modifications and their underlying mechanisms in diabetic vascular complication are still urgently needed to be investigated. Non-coding RNAs (nc RNAs) such as micro RNAs (miRNAs), long non-coding RNA (lncRNAs), and circular RNAs (circ RNAs) were found to exert transcriptional regulation in diabetic vascular complication. Although nc RNAs are not considered as epigenetic components, they are involved in epigenetic modifications. In this review, we summarized the investigations of non-coding RNAs involved in DNA methylation and histone methylation and acetylation. Their cross-talks might offer novel insights into the pathology of diabetic vascular complications.

The Impact of lncRNAs in Diabetes Mellitus: A Systematic Review and In Silico Analyses

Long non-coding RNAs (lncRNAs) are non-coding transcripts that have emerged as one of the largest and diverse RNA families that regulate gene expression. Accumulating evidence has suggested a number of lncRNAs are involved in diabetes mellitus (DM) pathogenesis. However, results about lncRNA expressions in DM patients are still inconclusive. Thus, we performed a systematic review of the literature on the subject followed by bioinformatics analyses to better understand which lncRNAs are dysregulated in DM and in which pathways they act. Pubmed, Embase, and Gene Expression Omnibus (GEO) repositories were searched to identify studies that investigated lncRNA expression in cases with DM and non-diabetic controls. LncRNAs consistently dysregulated in DM patients were submitted to bioinformatics analysis to retrieve their target genes and identify potentially affected signaling pathways under their regulation. Fifty-three eligible articles were included in this review after the application of the inclusion and exclusion criteria. Six hundred and thirty-eight lncRNAs were differentially expressed between cases and controls in at least one study. Among them, six lncRNAs were consistently dysregulated in patients with DM (Anril, Hotair, Malat1, Miat, Kcnq1ot1, and Meg3) compared to controls. Moreover, these six lncRNAs participate in several metabolism-related pathways, evidencing their importance in DM. This systematic review suggests six lncRNAs are dysregulated in DM, constituting potential biomarkers of this disease.

Luo Tong Formula Alleviates Diabetic Retinopathy in Rats Through Micro-200b Target

Aim: Diabetic retinopathy (DR) is a serious complication of diabetes (DM). Luo Tong formula (LTF) exerts protective effects against DR in rats, but its underlying mechanism remains unknown. Methods: Sprague-Dawley rats injected with streptozotocin (STZ) were used as an experimental diabetes model. LTF or calcium dobesilate (CaD) was administered to diabetic rats via gastric gavage. After the 12 weeks of treatment, blood and tissue samples were collected to determine serum glucose and retinal structure. Blood samples were collected for blood glucose and hemorheology analysis. Gene or protein expression levels were evaluated by immunohistochemistry, western blotting and/or quantitative real-time polymerase chain reaction (PCR). Results: DM rats exhibits significantly increased blood retinal-barrier (BRB) breakdown and VEGF/VEGFR expression in the retina, and decreased miR-200b and tight junction ZO-1/Occludin/ Claudin-5 genes expression, as well as Ang-1/Tie-2 expressions in the retina compared to normal control group. LTF treatment significantly moderated histological abnormalities in diabetic rats, independent of blood glucose level; improved some hemorrheological parameters; decreased the expressions of VEGF/VEGFR and BRB breakdown, significantly increased PEDF and tight junction proteins ZO-1/Occludin, as well as increased retinal miR-200b expression compared to non-treatment diabetic rats. Moreover, LTF prevented the reduction in Ang-1/Tie-2 expression. Conclusions: LTF treatment ameliorated DR through its repair vascular and attenuate vascular leakage. A mechanism involving miR-200b may contribute to benefit effects.

Roles of Epigenetic Modifications in the Differentiation and Function of Pancreatic β-Cells

Diabetes, a metabolic disease with multiple causes characterized by high blood sugar, has become a public health problem. Hyperglycaemia is caused by deficiencies in insulin secretion, impairment of insulin function, or both. The insulin secreted by pancreatic β cells is the only hormone in the body that lowers blood glucose levels and plays vital roles in maintaining glucose homeostasis. Therefore, investigation of the molecular mechanisms of pancreatic β cell differentiation and function is necessary to elucidate the processes involved in the onset of diabetes. Although numerous studies have shown that transcriptional regulation is essential for the differentiation and function of pancreatic β cells, increasing evidence indicates that epigenetic mechanisms participate in controlling the fate and regulation of these cells. Epigenetics involves heritable alterations in gene expression caused by DNA methylation, histone modification and non-coding RNA activity that does not result in DNA nucleotide sequence alterations. Recent research has revealed that a variety of epigenetic modifications play an important role in the development of diabetes. Here, we review the mechanisms by which epigenetic regulation affects β cell differentiation and function.

Histone methylation and vascular biology

The vasculature not only transports oxygenated blood, metabolites, and waste products but also serves as a conduit for hormonal communication between distant tissues. Therefore, it is important to maintain homeostasis within the vasculature. Recent studies have greatly expanded our understanding of the regulation of vasculature development and vascular-related diseases at the epigenetic level, including by protein posttranslational modifications, DNA methylation, and noncoding RNAs. Integrating epigenetic mechanisms into the pathophysiologic conceptualization of complex and multifactorial vascular-related diseases may provide promising therapeutic approaches. Several reviews have presented detailed discussions of epigenetic mechanisms not including histone methylation in vascular biology. In this review, we primarily discuss histone methylation in vascular development and maturity, and in vascular diseases.

Therapeutic potential of enhancer of zeste homolog 2 in autoimmune diseases

Introduction: Autoimmune diseases (ADs) are idiopathic and heterogeneous disorders with contentious pathophysiology. Great strides have been made in epigenetics and its involvement in ADs. Zeste homolog 2 (EZH2) has sparked extensive interest because of its pleiotropic roles in distinct pathologic contexts.Areas covered: This review summarizes the epigenetic functions and the biological significance of EZH2 in the etiology of rheumatoid arthritis (RA), systemic lupus erythematosus (SLE), type 1 diabetes (T1D), inflammatory bowel disease (IBD), multiple sclerosis (MS), and systemic sclerosis (SSc). A brief recapitulation of the therapeutic potential of EZH2 targeting is provided.Expert opinion: There are questions marks and controversies surrounding the feasibility and safety of EZH2 targeting; it is recommended in RA and SLE, but queried in T1D, IBD, MS, and SSc. Future work should focus on contrast studies, systematic analyses and preclinical studies with optimizing methodologies. Selective research studies conducted in a stage-dependent manner are necessary because of the relapsing-remitting clinical paradigms.

ANRIL and atherosclerosis

WHAT IS KNOWN AND OBJECTIVE

The 3.8-kb-long antisense non-coding RNA at the INK4 locus (ANRIL) is transcribed from the short arm of human chromosome 9 on P21 and is associated with malfunction of the vascular endothelium, vascular smooth muscle cell (VSMC) proliferation/migration/senescence/apoptosis, mononuclear cell adhesion and proliferation, glycolipid metabolism disorder and DNA damage. Hence, ANRIL plays an important role in atherogenesis. Moreover, genome-wide association studies (GWAS) have identified ANRIL as a biomarker that is closely related to coronary heart disease (CHD). The objective of this review was to discuss the pathological mechanism of ANRIL in atherosclerotic development and its significance as a predictor of cardiovascular disease.

METHODS

Review of the PubMed, EMBASE and Cochrane databases for articles demonstrating the roles of ANRIL in the development of atherosclerotic diseases.

RESULTS AND DISCUSSION

The abnormal expression of ANRIL is linked to vascular endothelium injury; the proliferation, migration, senescence and apoptosis of VSMCs; mononuclear cell adhesion and proliferation; glycolipid metabolism disorder; DNA damage; and competing endogenous RNAs. Moreover, ANRIL accelerates the progression of CHD by regulating its single nucleotide polymorphisms (SNPs).

WHAT IS NEW AND CONCLUSION

Considering that ANRIL accelerates atherosclerosis (AS) development and is a risk factor for CHD, it is reasonable for us to explore an efficacious ANRIL-based therapy for AS in CHD.

The Regulatory Roles of Non-coding RNAs in Angiogenesis and Neovascularization From an Epigenetic Perspective

Angiogenesis is a crucial process for organ morphogenesis and growth during development, and it is especially relevant during the repair of wounded tissue in adults. It is coordinated by an equilibrium of pro- and anti-angiogenic factors; nevertheless, when affected, it promotes several diseases. Lately, a growing body of evidence is indicating that non-coding RNAs (ncRNAs), such as miRNAs, circRNAs, and lncRNAs, play critical roles in angiogenesis. These ncRNAs can act in cis or trans and alter gene transcription by several mechanisms including epigenetic processes. In the following pages, we will discuss the functions of ncRNAs in the regulation of angiogenesis and neovascularization, both in normal and disease contexts, from an epigenetic perspective. Additionally, we will describe the contribution of Next-Generation Sequencing (NGS) techniques to the discovery and understanding of the role of ncRNAs in angiogenesis.

Targeting epigenetic modifications as a potential therapeutic option for diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment in adults of working age (20-65 years) in developed countries. The metabolic memory phenomena (persistent effect of a glycemic insult even after retrieved) associated with it has increased the risk of developing the complication even after the termination of the glycemic insult. Hence, the need for finding early diagnosis and treatment options has been of great concern. Epigenetic modifications which generally occur during the beginning stages of the disease are responsible for the metabolic memory effect. Therefore, the therapy based on the reversal of the associated epigenetic mechanism can bring new insight in the area of early diagnosis and treatment mechanism. This review discusses the diabetic retinopathy, its pathogenesis, current treatment options, need of finding novel treatment options, and different epigenetic alterations associated with DR. However, the main focus is emphasized on various epigenetic modifications particularly DNA methylation which are responsible for the initiation and progression of diabetic retinopathy and the use of different epigenetic inhibitors as a novel therapeutic option for DR.

Diabetic Retinopathy, lncRNAs, and Inflammation: A Dynamic, Interconnected Network

Diabetic retinopathy (DR) is reaching epidemic levels globally due to the increase in prevalence of diabetes mellitus (DM). DR also has detrimental effects to quality of life, as it is the leading cause of blindness in the working-age population and the most common cause of vision loss in individuals with DM. Over several decades, many studies have recognized the role of inflammation in the development and progression of DR; however, in recent years, accumulating evidence has also suggested that non-coding RNAs, especially long non-coding (lncRNAs), are aberrantly expressed in diabetes and may play a putative role in the development and progression of DR through the modulation of gene expression at the transcriptional, post-transcriptional, or epigenetic level. In this review, we will first highlight some of the key inflammatory mediators and transcription factors involved in DR, and we will then introduce the critical roles of lncRNAs in DR and inflammation. Following this, we will discuss the implications of lncRNAs in other epigenetic mechanisms that may also contribute to the progression of inflammation in DR.

Epigenetics and vascular diseases

Cardiovascular disease remains the number one cause of death and disability worldwide despite significant improvements in diagnosis, prevention, and early intervention efforts. There is an urgent need for improved understanding of cardiovascular processes responsible for disease development in order to develop more effective therapeutic strategies. Recent knowledge gleaned from the study of epigenetic mechanisms in the vasculature has uncovered new potential targets for intervention. Herein, we provide an overview of epigenetic mechanism, and review recent findings related to epigenetics in vascular diseases, highlighting classical epigenetic mechanism such as DNA methylation and histone modification as well as the newly discovered non-coding RNA mechanisms.

Increased Extracellular Matrix Protein Production in Chronic Diabetic Complications: Implications of Non-Coding RNAs

Management of chronic diabetic complications remains a major medical challenge worldwide. One of the characteristic features of all chronic diabetic complications is augmented production of extracellular matrix (ECM) proteins. Such ECM proteins are deposited in all tissues affected by chronic complications, ultimately causing organ damage and dysfunction. A contributing factor to this pathogenetic process is glucose-induced endothelial damage, which involves phenotypic transformation of endothelial cells (ECs). This phenotypic transition of ECs, from a quiescent state to an activated dysfunctional state, can be mediated through alterations in the synthesis of cellular proteins. In this review, we discussed the roles of non-coding RNAs, specifically microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), in such processes. We further outlined other epigenetic mechanisms regulating the biogenesis and/or function of non-coding RNAs. Overall, we believe that better understanding of such molecular processes may lead to the development of novel biomarkers and therapeutic strategies in the future.

Curcumin Analogs Reduce Stress and Inflammation Indices in Experimental Models of Diabetes

Chronic inflammation and oxidative stress lead to a multitude of adverse cellular responses in target organs of chronic diabetic complications. Curcumin, a highly investigated phytochemical, has been shown to exhibit both anti-inflammatory and antioxidant activities. However, the clinical application of curcumin has been greatly limited due to a poor pharmacokinetic profile. To overcome these limitations, we have generated analogs of curcumin to enhance bioavailability and offer a preferable pharmacokinetic profile. Here, we explored the effects of two mono-carbonyl curcumin analogs, L2H21 and L50H46, in alleviating indices of inflammation and oxidative stress in cell culture and mouse model of diabetic complications. Our results show that L2H21 and L50H46 normalize inflammatory mediators (IL-6 and TNF-α), extracellular matrix proteins (FN and COL4α1), vasoactive factors (VEGF and ET-1) and a key transcriptional coactivator (p300) in cultured human retinal microvascular endothelial cells (HRECs) and dermal-derived microvascular endothelial cells (HMVECs) challenged with high levels of glucose. These curcumin analogs also reduced glucose-induced oxidative DNA damage as evidenced by 8-OHdG labeling. We further show that treatment of streptozotocin-induced diabetic mice with curcumin analogs prevents cardiac and renal dysfunction. The preservation of target tissue function was associated with normalization of pro-inflammatory cytokines and matrix proteins. Collectively, our results show that L2H21 and L50H46 offer the anti-inflammatory and antioxidant activities as has been reported for curcumin, and may provide a clinically applicable therapeutic option for the treatment of diabetic complications.

Plasma levels of miR-29b and miR-200b in type 2 diabetic retinopathy

MicroRNAs (miRNAs/miRs) are involved in the pathogenesis of diabetes mellitus and its chronic complications, and their circulating levels have emerged as potential biomarkers for the development and progression of diabetes. However, few studies have examined the expression of miRNAs in diabetic retinopathy (DR) in humans. This case-control study aimed to investigate whether the plasma levels of miR-29b and miR-200b are associated with DR in 186 South Brazilians with type 2 diabetes (91 without DR, 46 with non-proliferative DR and 49 with proliferative DR). We also included 20 healthy blood donors to determine the miRNA expression in the general population. Plasma levels of miR-29b and miR-200b were quantified by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Proliferative DR was inversely associated with plasma levels of miR-29b (unadjusted OR = 0.694, 95% CI: 0.535-0.900, P = 0.006) and miR-200b (unadjusted OR = 0.797, 95% CI: 0.637-0.997, P = 0.047). However, these associations were lost after controlling for demographic and clinical covariates. In addition, patients with type 2 diabetes had lower miR-200b levels than blood donors. Our findings reinforce the importance of addressing the role of circulating miRNAs, including miR-29 and miR-200b, in DR.

ANRIL: A lncRNA at the CDKN2A/B Locus With Roles in Cancer and Metabolic Disease

The CDKN2A/B genomic locus is associated with risk of human cancers and metabolic disease. Although the locus contains several important protein-coding genes, studies suggest disease roles for a lesser-known antisense lncRNA encoded at this locus, called ANRIL. ANRIL is a complex gene containing at least 21 exons in simians, with many reported linear and circular isoforms. Like other genes, abundance of ANRIL is regulated by epigenetics, classic transcription regulation, splicing, and post-transcriptional influences such as RNA stability and microRNAs. Known molecular functions of ANRIL include in cis and in trans gene regulation through chromatin modification complexes, and influence over microRNA signaling networks. Polymorphisms at the ANRIL gene are linked to risk for many different cancers, as well as risk of atherosclerotic cardiovascular disease, bone mass, obesity and type 2 diabetes. A broad array of variable reported impacts of polymorphisms on ANRIL abundance, splicing and function suggests that ANRIL has cell-type and context-dependent regulation and actions. In cancer cells, ANRIL gain of function increases proliferation, metastasis, cell survival and epithelial-mesenchymal transformation, whereas ANRIL loss of function decreases tumor size and growth, invasion and metastasis, and increases apoptosis and senescence. In metabolic disease, polymorphisms at the ANRIL gene are linked to risk of type 2 diabetes, coronary artery disease, coronary artery calcium score, myocardial infarction, and stroke. Intriguingly, with the exception of one polymorphism in exon 2 of ANRIL, the single nucleotide polymorphisms (SNPs) associated with atherosclerosis and diabetes are non-overlapping. Evidence suggests that ANRIL gain of function increases atherosclerosis; in diabetes, a risk-SNP reduced the pancreatic beta cell proliferation index. Studies are limited by the uncertain relevance of rodent models to ANRIL studies, since most ANRIL exons do not exist in mouse. Diverse cell-type-dependent results suggest it is necessary to perform studies in the relevant primary human tissue for each disease. Much remains to be learned about the biology of ANRIL in human health and disease; this research area may lead to insight into disease mechanisms and therapeutic approaches.

Epigenetic control of gene regulation during development and disease: A view from the retina

Complex biological processes, such as organogenesis and homeostasis, are stringently regulated by genetic programs that are fine-tuned by epigenetic factors to establish cell fates and/or to respond to the microenvironment. Gene regulatory networks that guide cell differentiation and function are modulated and stabilized by modifications to DNA, RNA and proteins. In this review, we focus on two key epigenetic changes - DNA methylation and histone modifications - and discuss their contribution to retinal development, aging and disease, especially in the context of age-related macular degeneration (AMD) and diabetic retinopathy. We highlight less-studied roles of DNA methylation and provide the RNA expression profiles of epigenetic enzymes in human and mouse retina in comparison to other tissues. We also review computational tools and emergent technologies to profile, analyze and integrate epigenetic information. We suggest implementation of editing tools and single-cell technologies to trace and perturb the epigenome for delineating its role in transcriptional regulation. Finally, we present our thoughts on exciting avenues for exploring epigenome in retinal metabolism, disease modeling, and regeneration.

Endothelin-1 Regulation Is Entangled in a Complex Web of Epigenetic Mechanisms in Diabetes

Endothelial cells (ECs) are primary targets of glucose-induced tissue damage. As a result of hyperglycemia, endothelin-1 (ET-1) is upregulated in organs affected by chronic diabetic complications. The objective of the present study was to identify novel transcriptional mechanisms that influence ET-1 regulation in diabetes. We carried out the investigation in microvascular ECs using multiple approaches. ECs were incubated with 5 mM glucose (NG) or 25 mM glucose (HG) and analyses for DNA methylation, histone methylation, or long non-coding RNA- mediated regulation of ET-1 mRNA were then performed. DNA methylation array analyses demonstrated the presence of hypomethylation in the proximal promoter and 5’ UTR/first exon regions of EDN1 following HG culture. Further, globally blocking DNA methylation or histone methylation significantly increased ET-1 mRNA expressions in both NG and HG-treated HRECs. While, knocking down the pathogenetic lncRNAs ANRIL, MALAT1, and ZFAS1 subsequently prevented the glucose-induced upregulation of ET-1 transcripts. Based on our past and present findings, we present a novel paradigm that reveals a complex web of epigenetic mechanisms regulating glucose-induced transcription of ET-1. Improving our understanding of such processes may lead to better targeted therapies.

MALAT1: An Epigenetic Regulator of Inflammation in Diabetic Retinopathy

Despite possessing limited protein-coding potential, long non-coding RNAs (lncRNAs) have been implicated in a myriad of pathologic conditions. Most well documented in cancer, one prominent intergenic lncRNA known as MALAT1 is notorious for its role in impacting epigenetic mechanisms. In this study, we established a novel epigenetic paradigm for MALAT in diabetic retinopathy (DR) by employing siRNA-mediated MALAT1 knockdown in human retinal endothelial cells (HRECs), a Malat1 knockout animal model, vitreous humor from diabetic patients, pharmacological inhibitors for histone and DNA methylation, RNA immunoprecipitation, western blotting, and a unique DNA methylation array to determine glucose-related alterations in MALAT1. Our findings indicated that MALAT1 is capable of impacting the expressions of inflammatory transcripts through its association with components of the PRC2 complex in diabetes. Furthermore, the vitreous humors from diabetic patients revealed increased expressions of MALAT1, TNF-α, and IL-6. Intriguingly, our DNA methylation array demonstrated that transient high glucose exposure in HRECs does not contribute to significant methylation alterations at CpG sites across the MALAT1 gene. However, global inhibition of DNA methyltransferases induced significant increases in MALAT1 and associated inflammatory transcripts in HRECs. Our findings collectively demonstrate the importance of MALAT1 in inflammation and epigenetic regulation in DR.

LncRNAs: Proverbial Genomic "Junk" or Key Epigenetic Regulators During Cardiac Fibrosis in Diabetes?

Long non-coding RNAs (lncRNAs) are critical regulators in a multitude of biological processes. Recent evidences demonstrate potential pathogenetic implications of lncRNAs in diabetic cardiomyopathy (DCM); however, the majority of lncRNAs have not been comprehensively characterized. While the precise molecular mechanisms underlying the functions of lncRNAs remain to be deciphered in DCM, emerging data in other pathophysiological conditions suggests that lncRNAs can have versatile features such as genomic imprinting, acting as guides for certain histone-modifying complexes, serving as scaffolds for specific molecules, or acting as molecular sponges. In an effort to better understand these features of lncRNAs in the context of DCM, our review will first summarize some of the key molecular alterations that occur during fibrosis in the diabetic heart (extracellular proteins and endothelial-to-mesenchymal transitioning), followed by a review of the current knowledge on the crosstalk between lncRNAs and major epigenetic mechanisms (histone methylation, histone acetylation, DNA methylation, and microRNAs) within this fibrotic process.

MALAT1: A regulator of inflammatory cytokines in diabetic complications

OBJECTIVES AND DESIGN

In this study, we examined the role of MALAT1, a highly conserved nuclear long non-coding RNA molecule, in chronic diabetic complications affecting the heart and kidneys using both in vitro and in vivo models: human endothelial cell culture and a Malat1 knockout mice model.

RESULTS

Findings from our in vitro experiments demonstrated that MALAT1 was predominantly localized to nuclear speckles in endothelial cells and MALAT1 expression was significantly increased following incubation with high glucose in association with increased expression of inflammatory cytokines. As for our in vivo experiments, we used Malat1 knockout mice and wild-type controls with or without streptozotocin-induced diabetes over 2 months of follow-up, where all of our diabetic animals showed hyperglycaemia and polyuria. Examination of cardiac and renal tissues demonstrated altered MALAT1 RNA expression in wild-type diabetic animals. Such changes were associated with augmented production of downstream inflammatory molecules at the mRNA and protein levels. Diabetes-induced elevations of inflammatory markers were significantly decreased in Malat1 knockout diabetic animals. In addition to transcript and protein analyses, we examined functional changes in the heart and kidneys. Organ functions were affected in the wild-type diabetic mice but were rescued in Malat1 knockout mice.

CONCLUSIONS

Taken together, findings from this study will provide direct evidence and insight into the importance of MALAT1 in the pathogenesis of chronic diabetic complications involving the heart and kidneys.

Epigenetic modulation of vascular diseases: Assessing the evidence and exploring the opportunities

Vascular adaptations to either physiological or pathophysiological conditions commonly require gene expression modifications in the most represented cellular elements of the vessel wall, i.e. endothelial and smooth muscle cells. In addition to transcription factors, a number of mechanisms contribute to the regulation of gene expression in these cells including noncoding RNAs, histone and DNA modifications, collectively indicated as epigenetic modifications. Here, we summarize the state of art regarding the role of epigenetic changes in major vascular diseases, and discuss the potential diagnostic and therapeutic applications of epigenetic modulation in this context.

ANRIL regulates production of extracellular matrix proteins and vasoactive factors in diabetic complications

noncoding RNAs (lncRNAs) have gained widespread interest due to their prevailing presence in various diseases. lncRNA ANRIL (a. k. a. CDKN2B-AS1) is located on human chromosome 9 (p21.3) and transcribed in opposite direction to the INK4b-ARF-INK4a gene cluster. It has been identified as a highly susceptible region for diseases such as coronary artery diseases and type 2 diabetes. Here, we explored its regulatory role in diabetic nephropathy (DN) and diabetic cardiomyopathy (DCM) in association with epigenetic modifiers p300 and polycomb repressive complex 2 (PRC2) complex. We used an ANRIL-knockout (ANRILKO) mouse model for this study. The wild-type and ANRILKO animals with or without streptozotocin-induced diabetes were monitored for 2 min. At the end of the time point, urine and tissues were collected. The tissues were measured for fibronectin (FN), type IV collagen (Col1α4), and VEGF mRNA and protein expressions. Renal function was determined by the measurement of 24-h urine volume and albumin/creatinine ratio at euthanasia. Renal and cardiac structures were investigated using periodic acid-Schiff stain and/or immunohistochemical analysis. Elevated expressions of extracellular matrix (ECM) proteins were prevented in ANRILKO diabetic animals. Furthermore, ANRILKO had a protective effect on diabetic mouse kidneys, as evidenced by lowering of urine volume and urine albumin levels in comparison with the wild-type diabetic animals. These alterations regulated by ANRIL may be mediated by p300 and enhancer of zeste 2 (EZH2) of the PRC2 complex. Our study concludes that ANRIL regulates functional and structural alterations in the kidneys and hearts in diabetes through controlling the expressions of ECM proteins and VEGF.

Recombinant human maspin inhibits high glucose-induced oxidative stress and angiogenesis of human retinal microvascular endothelial cells via PI3K/AKT pathway

Maspin is known as a tumor suppressor and a potent angiogenesis inhibitor, however, its effects on proliferative diabetic retinopathy (PDR) have not been fully elucidated. This study aimed at evaluating the effects of maspin on high glucose-induced oxidative stress and angiogenesis in human retinal microvascular endothelial cells (HRMECs). Herein, HRMECs were treated with 0.25, 0.5, or 1 µM recombinant human maspin in the presence of 30 mM glucose, and their proliferation, tube formation, and oxidative stress responses were further detected. Our results revealed that maspin inhibited the high glucose-induced proliferation, migration, and tube formation of HRMECs. Maspin also decreased reactive oxygen species, nitric oxide level, and increased glutathione S-transferase activity in HRMECs. Meanwhile, maspin reduced the mRNA and protein levels of hypoxia-inducible factor-1α and vascular endothelial growth factor in high glucose-stimulated cells in a dose-dependent manner. Additionally, the high glucose-induced elevation of phosphorylated phosphoinositide-3-kinase (p-PI3K) and phosphorylated AKT was also suppressed by maspin. In summary, our data suggest that maspin inhibits high glucose-induced proliferation, oxidative stress, and angiogenesis of HRMECs at least by modulating the PI3K/AKT pathway. Maspin may be a potential therapeutic agent for the prevention and treatment of PDR.

Crosstalk Between Histone and DNA Methylation in Regulation of Retinal Matrix Metalloproteinase-9 in Diabetes

Purpose

Diabetes activates matrix metalloproteinase-9 (MMP-9), and MMP-9 via damaging retinal mitochondria, activates capillary cell apoptosis. MMP-9 promoter has binding sites for many transcription factors, and in diabetes its promoter undergoes epigenetic modifications, including histone modifications and DNA methylation. Enhancer of Zeste homolog 2 (Ezh2), which catalyzes dimethylation/trimethylation of histone 3 lysine 27 (H3K27me2 and me3), is also associated with DNA methylation. Our aim was to investigate link(s) between histone and DNA modifications in the regulation of MMP-9.

Methods

Using human retinal endothelial cells, and also retinal microvessels from diabetic rats, effect of hyperglycemia on H3K27me3, and recruitment of Ezh2 at the MMP-9 promoter were quantified by chromatin-immunoprecipitation technique. Role of H3K27 trimethylation in regulating DNA methylation-transcription of MMP-9 was determined by regulating Ezh2 by its specific siRNA and also a pharmacologic inhibitor.

Results

Hyperglycemia elevated H3K27me3 levels and the recruitment of Ezh2 at the MMP-9 promoter, and increased the enzyme activity of Ezh2. Inhibition of Ezh2 attenuated recruitment of both DNA methylating (Dnmt1) and hydroxymethylating (Tet2) enzymes and 5 hydroxymethyl cytosine at the same region of the MMP-9 promoter, and prevented increase in MMP-9 transcription and mitochondrial damage.

Conclusions

Activation of Ezh2 in diabetes, via trimethylation of H3K27, facilitates recruitment of the enzymes responsible for regulation of DNA methylation of the MMP-9 promoter, resulting in its transcriptional activation. Thus, a close crosstalk between H3K27 trimethylation and DNA methylation in diabetes plays a critical role in the maintenance of cellular epigenetic integrity of MMP-9.

Emerging Evidence of Epigenetic Modifications in Vascular Complication of Diabetes

Genes, dietary, and lifestyle factors have been shown to be important in the pathophysiology of diabetes and associated microvascular complications. Epigenetic modifications, such as DNA methylation, histone acetylation, and post-transcriptional RNA regulation, are being increasingly recognized as important mediators of the complex interplay between genes and the environment. Recent studies suggest that diabetes-induced dysregulation of epigenetic mechanisms resulting in altered gene expression in target cells can lead to diabetes-associated complications, such as diabetic cardiomyopathy, diabetic nephropathy, retinopathy, and so on, which are the major contributors to diabetes-associated morbidity and mortality. Thus, knowledge of dysregulated epigenetic pathways involved in diabetes can provide much needed new drug targets for these diseases. In this review, we constructed our search strategy to highlight the role of DNA methylation, modifications of histones and role of non-coding RNAs (microRNAs and long non-coding RNAs) in vascular complications of diabetes, including cardiomyopathy, nephropathy, and retinopathy.

Long Noncoding RNAs as Diagnostic and Therapeutic Targets in Type 2 Diabetes and Related Complications

Protein-coding genes represent only a small fraction of the human genome. In the past, the majority of the genomic sequence has been considered transcriptionally silent, but recent large-scale studies have uncovered an array of functionally significant elements, including non-protein-coding transcripts, within these noncoding regions of the human genome. Long noncoding RNAs (lncRNAs), a class of noncoding transcripts with lengths >200 nucleotides, are pervasively transcribed in the genome and function as signals, decoys, guides, or scaffolds to regulate gene expression. More than 200 diseases have been associated with dysregulated or dysfunctional lncRNAs, and new associations continue to accumulate in the literature. The role of lncRNAs in the pathogenesis of type 2 diabetes mellitus and related complications has only recently been recognized, but there is already evidence for their involvement in many of the pathophysiological mechanisms underlying the disease. In this review, we summarize the current knowledge of the functions and underlying mechanisms of lncRNA activity with a focus on type 2 diabetes mellitus and related renal and retinal complications of the disease. We also discuss the potential of lncRNAs to serve as therapeutic targets for drug development and diagnostic markers for clinical applications in the management of diabetes.

The impact of miR-26b on retinal pigment epithelium cells in rhegmatogenous retinal detachment model

Rhegmatogenous retinal detachment (RRD) is a type of blind eye disease that seriously affects the physical and mental health. The early pathological changes are closely related to the migration of retinal pigment epithelium (RPE) cells to the vitreous body. It was showed miR-26b plays an important role in regulating lens epithelial cell growth and proliferation. However, the expression and role of miR-26b in RPE from RRD is still unclear. Rabbit RRD model was established. RPE cells were isolated and cultivated. MiR-26b inhibitor was transfected to RPE cells from model group. MiR-26b expression was tested by Real-time PCR. RPE cell proliferation was evaluated by MTT assay. Ki-67 and PCNA expressions were detected by Western blot. Caspase 3 activity was measured by the kit. RPE cell invasion was determined by Transwell assay. MiR-26b significantly increased in RPE cells from model group. It obviously promoted RPE cell proliferation and invasion, suppressed Caspase 3 activity, and upregulated Ki-67 and PCNA expression compared with control (P < 0.05). MiR-26b inhibitor transfection markedly restrained RPE cell proliferation and invasion, enhanced Caspase 3 activity, and inhibited Ki-67 and PCNA levels compared with model group (P < 0.05). MiR-26b expression was upregulated in RRD. Downregulation of miR-26b can postpone the occurrence and development of RRD through inhibiting Ki-67 and PCNA, regulating cell apoptosis, and restraining RPE cell proliferation and invasion.

Effects of miRNA-200b on the development of diabetic retinopathy by targeting VEGFA gene

The present study explored the effect of miR-200b on the development of diabetic retinopathy (DR) by targeting vascular endothelial growth factor A (VEGFA) gene. The study populations consisted of 255 DR patients (case group) and 253 healthy people (control group), while the expressions of miR-200b and VEGFA mRNA were detected by quantitative real-time PCR (qRT-PCR). Bioinformatics software and dual-luciferase reporter assay were used to confirm VEGFA as a target gene of miR-200b Also, a total of 70 Wistar male rats were selected and randomly assigned into blank, normal control (NC), miR-200b mimics, miR-200b inhibitors, miR-200b inhibitors + silencing vascular endothelial growth factor A (siVEGFA), and siVEGFA groups (n=10/group) respectively. Streptozotocin (STZ)-induced rat models of DR were successfully established. VEGFA, transforming growth factor-β1 (TGF-β1), hepatocyte growth factor (HGF), and pigment epithelium-derived factor (PEDF) were detected using qRT-PCR and Western blotting. In comparison with the control group, the case group showed lower expression of miR-200b but higher expression of VEGFA mRNA. VEGFA was confirmed as a target gene of miR-200b Rats in the miR-200b mimics and siVEGFA groups exhibited higher expression of PEDF mRNA and protein but lower expressions of VEGFA, TGF-β1, HGF protein, and mRNA than the NC group. There was no remarkable difference in expressions of PEDF, VEGFA, TGF-β1, HGF protein, and mRNA between the miR-200b inhibitors + siVEGFA and NC groups. In conclusion, the present study demonstrated that miR-200b might alleviate DR development by down-regulating its target gene VEGFA.

MiR-126 overexpression inhibits high glucose-induced migration and tube formation of rhesus macaque choroid-retinal endothelial cells by obstructing VEGFA and PIK3R2

AIM

The aims of this study are to investigate the relative regulation between miR-126 and VEGF/PI3K/AKT signaling pathway in retinal vascular endothelial cells.

METHODS

Rhesus macaque choroid-retinal endothelial cell line (RF/6A) cells were cultured in high glucose to imitate the conditions occurring in DR. First, we detected the expression of miR-126, VEGFA and PIK3R2 in RF/6A cells on the condition of high glucose by q-PCR and western blot. Then, after addition of miR-126 mimics and miR-126 inhibitor, we investigated the function of miR-126 in RF/6A cells by scratch wound, Transwell migration and tube formation assays, and the effect of miR-126 on the expression of VEGFA, PIK3R2 and AKT. Moreover, bioinformatics analysis and luciferase array were used to confirm the direct or specific regulation of miR-126 to VEGFA or PIK3R2.

RESULTS

Here, first, we found that high glucose could induce the decrease of miR-126 and the increase of VEGFA and PIK3R2 in RF/6A. Then, by scratch wound, Transwell migration and tube formation assays, we found that miR-126 overexpression could inhibit the migration and sprouting of RF/6A cells induced by high glucose, while knockdown of miR-126 led to the opposite results. Moreover, overexpression of miR-126 inhibited the increased expression of VEGFA, PIK3R2, SDF-1α, VCAM-1, and SPRED1, and the activation of AKT1 induced by high glucose and miR-126 inhibitor caused the opposite results which were determined by q-PCR and western blot. In addition, by luciferase assay, we found that miR-126 could directly negatively regulate VEGFA and PIK3R2.

CONCLUSION

Our results suggest that miR-126 overexpression inhibits the migration and sprouting of RF/6A cells induced by high glucose which might possibly be by blocking VEGFA and PIK3R2 in the VEGF/PI3K/AKT signaling pathway.

miR-146a regulates glucose induced upregulation of inflammatory cytokines extracellular matrix proteins in the retina and kidney in diabetes

Hyperglycemic damage to the endothelial cells (ECs) leads to increased synthesis of inflammatory cytokines. We have previously shown miR-146a downregulation in ECs and in the tissues of diabetic mice. Here we investigated the role of miR-146a, in the production of specific inflammatory cytokines and extracellular matrix (ECM) proteins in retina and kidneys in diabetes. We generated an endothelial specific miR-146a overexpressing transgenic mice (TG). We investigated these mice and wild type (WT) controls with or without streptozotocin (STZ) induced diabetes. Retinal and renal cortical tissues from the mice were examined for mRNAs for specific inflammatory markers, (ECM) proteins and inflammation inducible transcription factor by real time RT-PCR. Corresponding proteins, where possible, were examined using immunofluorescence or ELISA. In parallel, we examined ECs following incubation with various levels of glucose with or without miR-146a mimic transfection. In the retina and kidneys of WT mice with diabetes, increased expression of inflammatory markers (IL-6, TNFα, IL1β) in association augmented expression of ECM proteins (collagen 1αIV, fibronectin) and NF κB-P65 were observed, compared to WT non-diabetic controls. These changes were prevented in diabetic miR-146a TG mice along with retinal and renal functional and structural changes. In vitro studies showed similar changes in the ECs exposed to high glucose. Such changes were corrected in the cells following miR-146a mimic transfection. Further analyses of renal cortical tissues showed diabetes induced significant upregulation of two regulators of NFκB, namely Interleukin-1 associated Kinase 1 and tumour necrosis factor receptor associated factor. Such changes were prevented in diabetic TG animals. These data indicate that augmented production of inflammatory cytokines and ECM proteins in the retina and kidneys in diabetes are regulated through endothelium derived miR-146a. Identification of such novel mechanisms may potentially lead to the development of novel therapies.

miRNAs: Nanomachines That Micromanage the Pathophysiology of Diabetes Mellitus

Diabetes mellitus (DM) refers to a combination of heterogeneous complex metabolic disorders that are associated with episodes of hyperglycemia and glucose intolerance occurring as a result of defects in insulin secretion, action, or both. The prevalence of DM is increasing at an alarming rate, and there exists a need to develop better therapeutics and prognostic markers for earlier detection and diagnosis. In this review, after giving a brief introduction of diabetes mellitus and microRNA (miRNA) biogenesis pathway, we first describe various in vitro and animal model systems that have been developed to study diabetes. Further, we elaborate on the significant roles played by miRNAs as regulators of gene expression in the context of development of diabetes and its secondary complications. The different approaches to quantify miRNAs and their potential to be used as therapeutic targets for alleviation of diabetes have also been discussed.