Diabetes-induced extracellular matrix protein expression is mediated by transcription coactivator p300

Role of transcriptional cofactors in cardiovascular diseases

Cardiovascular disease is a main cause of mortality in the world and the highest incidence of all diseases. However, the mechanism of the pathogenesis of cardiovascular disease is still unclear, and we need to continue to explore its mechanism of action. The occurrence and development of cardiovascular disease is significantly associated with genetic abnormalities, and gene expression is affected by transcriptional regulation. In this complex process, the protein-protein interaction promotes the RNA polymerase II to the initiation site. And in this process of transcriptional regulation, transcriptional cofactors are responsible for passing cues from enhancers to promoters and promoting the binding of RNA polymerases to promoters, so transcription cofactors playing a key role in gene expression regulation. There is growing evidence that transcriptional cofactors play a critical role in cardiovascular disease. Transcriptional cofactors can promote or inhibit transcription by affecting the function of transcription factors. It can affect the initiation and elongation process of transcription by forming complexes with transcription factors, which are important for the stabilization of DNA rings. It can also act as a protein that interacts with other proteins to affect the expression of other genes. Therefore, the aim of this overview is to summarize the effect of some transcriptional cofactors such as BRD4, EP300, MED1, EZH2, YAP, SIRT6 in cardiovascular disease and to provide a promising therapeutic strategy for the treatment of cardiovascular disease.

miR-132-3p and KLF7 as novel regulators of aortic stiffening-associated EndMT in type 2 diabetes mellitus

BACKGROUND

The prevalence of diabetes mellitus has risen considerably and currently affects more than 422 million people worldwide. Cardiovascular diseases including myocardial infarction and heart failure represent the major cause of death in type 2 diabetes (T2D). Diabetes patients exhibit accelerated aortic stiffening which is an independent predictor of cardiovascular disease and mortality. We recently showed that aortic stiffness precedes hypertension in a mouse model of diabetes (db/db mice), making aortic stiffness an early contributor to cardiovascular disease development. Elucidating how aortic stiffening develops is a pressing need in order to halt the pathophysiological process at an early time point.

METHODS

To assess EndMT occurrence, we performed co-immunofluorescence staining of an endothelial marker (CD31) with mesenchymal markers (α-SMA/S100A4) in aortic sections from db/db mice. Moreover, we performed qRT-PCR to analyze mRNA expression of EndMT transcription factors in aortic sections of db/db mice and diabetic patients. To identify the underlying mechanism by which EndMT contributes to aortic stiffening, we used aortas from db/db mice and diabetic patients in combination with high glucose-treated human umbilical vein endothelial cells (HUVECs) as an in vitro model of diabetes-associated EndMT.

RESULTS

We demonstrate robust CD31/α-SMA and CD31/S100A4 co-localization in aortic sections of db/db mice which was almost absent in control mice. Moreover, we demonstrate a significant upregulation of EndMT transcription factors in aortic sections of db/db mice and diabetic patients. As underlying regulator, we identified miR-132-3p as the most significantly downregulated miR in the micronome of db/db mice and high glucose-treated HUVECs. Indeed, miR-132-3p was also significantly downregulated in aortic tissue from diabetic patients. We identified Kruppel-like factor 7 (KLF7) as a target of miR-132-3p and show a significant upregulation of KLF7 in aortic sections of db/db mice and diabetic patients as well as in high glucose-treated HUVECs. We further demonstrate that miR-132-3p overexpression and KLF7 downregulation ameliorates EndMT in high glucose-treated HUVECs.

CONCLUSIONS

We demonstrate for the first time that EndMT contributes to aortic stiffening in T2D. We identified miR-132-3p and KLF7 as novel EndMT regulators in this context. Altogether, this gives us new insights in the development of aortic stiffening in T2D.

Epigenetics and Degenerative Retinal Diseases: Prospects for New Therapeutic Approaches

ABSTRACT

There is growing evidence that retinal degenerative diseases are accompanied by epigenetic changes in both deoxyribonucleic acid methylation and histone modification. Even in the monogenic disease retinitis pigmentosa, there is a cascade of changes in gene expression that correlate with epigenetic changes, suggesting that many of the symptoms, and degenerative changes, may be a result of epigenetic changes downstream from the genetic mutation. This is supported by data from studies of diabetic retinopathy and macular degeneration, 2 diseases where it has been difficult to define a single causative change. Initial studies with modifiers of deoxyribonucleic acid methylation suggest that they can provide therapeutic benefit. A number of drugs are available to inhibit specific epigenetic histone modifier enzymes, and these offer the possibility of new therapeutic approaches to retinal disease. Systemic treatment with inhibitors of histone demethylases and histone deacetylases have arrested rod degeneration in rodent models of retinitis pigmentosa. Some evidence has suggested that similar treatments may provide benefits for patients with diabetic retinopathy. Because differentiation of retinal stem cells is regulated in part by epigenetic mechanisms, it may also be possible to direct stem cell differentiation pathways through the use of selective epigenetic modifiers. This is predicted to provide a valuable avenue to accelerate the introduction of regenerative approaches to retinal disease. Epigenetic modifiers are poised to become a powerful new approach to treat retinal degenerative diseases.

EndMT Regulation by Small RNAs in Diabetes-Associated Fibrotic Conditions: Potential Link With Oxidative Stress

Diabetes-associated complications, such as retinopathy, nephropathy, cardiomyopathy, and atherosclerosis, the main consequences of long-term hyperglycemia, often lead to organ dysfunction, disability, and increased mortality. A common denominator of these complications is the myofibroblast-driven excessive deposition of extracellular matrix proteins. Although fibroblast appears to be the primary source of myofibroblasts, other cells, including endothelial cells, can generate myofibroblasts through a process known as endothelial to mesenchymal transition (EndMT). During EndMT, endothelial cells lose their typical phenotype to acquire mesenchymal features, characterized by the development of invasive and migratory abilities as well as the expression of typical mesenchymal products such as α-smooth muscle actin and type I collagen. EndMT is involved in many chronic and fibrotic diseases and appears to be regulated by complex molecular mechanisms and different signaling pathways. Recent evidence suggests that small RNAs, in particular microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are crucial mediators of EndMT. Furthermore, EndMT and miRNAs are both affected by oxidative stress, another key player in the pathophysiology of diabetic fibrotic complications. In this review, we provide an overview of the primary redox signals underpinning the diabetic-associated fibrotic process. Then, we discuss the current knowledge on the role of small RNAs in the regulation of EndMT in diabetic retinopathy, nephropathy, cardiomyopathy, and atherosclerosis and highlight potential links between oxidative stress and the dyad small RNAs-EndMT in driving these pathological states.

Novel use of a chemically modified siRNA for robust and sustainable in vivo gene silencing in the retina

Despite efficient and specific in vitro knockdown, more reliable and convenient methods for in vivo knockdown of target genes remain to be developed particularly for retinal research. Using commercially available and chemically modified siRNA so-called Accell siRNA, we established a novel in vivo gene silencing approach in the rat retina. siRNA designed for knockdown of the house keeping gene Gapdh or four retinal cell type-specific genes (Nefl, Pvalb, Rho and Opn1sw) was injected into the vitreous body, and their retinal mRNA levels were quantified using real-time PCR. Intravitreal injection of siRNA for Gapdh resulted in approximately 40–70% reduction in its retinal mRNA levels, which lasted throughout a 9-day study period. Furthermore, all the selected retinal specific genes were efficiently down-regulated by 60–90% following intravitreal injection, suggesting injected siRNA penetrated into major retinal cell types. These findings were consistent with uniform distribution of a fluorescence-labeled siRNA injected into the vitreous body. Interestingly, gene silencing of Grin1, a core subunit of NMDA receptor, was accompanied by significant prevention from NMDA-induced retinal ganglion cell death. Thus, we provide single intravitreal injection of Accell siRNA as a versatile technique for robust and sustainable in vivo retinal gene silencing to characterize their biological functions under physiological and pathophysiological conditions.

Early Programming of Adult Systemic Essential Hypertension

Cardiovascular diseases are being included in the study of developmental origins of health and disease (DOHaD) and essential systemic hypertension has also been added to this field. Epigenetic modifications are one of the main mechanisms leading to early programming of disease. Different environmental factors occurring during critical windows in the early stages of life may leave epigenetic cues, which may be involved in the programming of hypertension when individuals reach adulthood. Such environmental factors include pre-term birth, low weight at birth, altered programming of different organs such as the blood vessels and the kidney, and living in disadvantageous conditions in the programming of hypertension. Mechanisms behind these factors that impact on the programming include undernutrition, oxidative stress, inflammation, emotional stress, and changes in the microbiota. These factors and their underlying causes acting at the vascular level will be discussed in this paper. We also explore the establishment of epigenetic cues that may lead to hypertension at the vascular level such as DNA methylation, histone modifications (methylation and acetylation), and the role of microRNAs in the endothelial cells and blood vessel smooth muscle which participate in hypertension. Since epigenetic changes are reversible, the knowledge of this type of markers could be useful in the field of prevention, diagnosis or epigenetic drugs as a therapeutic approach to hypertension.

Can Epigenetics of Endothelial Dysfunction Represent the Key to Precision Medicine in Type 2 Diabetes Mellitus?

In both developing and industrialized Countries, the growing prevalence of Type 2 Diabetes Mellitus (T2DM) and the severity of its related complications make T2DM one of the most challenging metabolic diseases worldwide. The close relationship between genetic and environmental factors suggests that eating habits and unhealthy lifestyles may significantly affect metabolic pathways, resulting in dynamic modifications of chromatin-associated proteins and homeostatic transcriptional responses involved in the progression of T2DM. Epigenetic mechanisms may be implicated in the complex processes linking environmental factors to genetic predisposition to metabolic disturbances, leading to obesity and type 2 diabetes mellitus (T2DM). Endothelial dysfunction represents an earlier marker and an important player in the development of this disease. Dysregulation of the endothelial ability to produce and release vasoactive mediators is recognized as the initial feature of impaired vascular activity under obesity and other insulin resistance conditions and undoubtedly concurs to the accelerated progression of atherosclerotic lesions and overall cardiovascular risk in T2DM patients. This review aims to summarize the most current knowledge regarding the involvement of epigenetic changes associated with endothelial dysfunction in T2DM, in order to identify potential targets that might contribute to pursuing “precision medicine” in the context of diabetic illness.

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.

Endothelin-1 traps potently reduce pathologic markers back to basal levels in an in vitro model of diabetes

Background

Diabetes mellitus is a group of metabolic disorders in which there are high blood glucose levels over a prolonged period. Diabetes is one of many diseases associated with pathologically elevated levels of endothelin (ET)-1. We have recently proposed the development of ET-traps, which are an antibody - based fusion protein that potently bind and sequester pathologically elevated levels of endothelin-1.

Methods

We constructed ET-traps that were found to be very potent binders to ET-1, with a K_D of 32.5ρM. We then treated human retinal microvascular endothelial cells (HRMECs), which are an in vitro model of glucose induced cellular damage, with 10 nM ET-1 or high glucose levels (25 mM).

Results

In this study, we investigated the effects of our ET-trap constructs on the expression levels of both collagen 4α1 and fibronectin, which are both important pathologic markers in diabetes. Treating HRMECs with 10 nM ET-1 or 25 mM glucose significantly induces the expression of the ECM proteins fibronectin and collagen 4α1, as is found in chronic diabetic complications; Incubation of the cells with the ET-traps significantly prevented the increased expression of fibronectin and collagen 4α1 back to basal levels. This was found with both mRNA and protein expression levels of the two ECM proteins.

Conclusion

Our results provide the first evidence of the efficacy of ET-traps in reducing pathologic markers in an in vitro model (of diabetes). Further research is warranted to determine the efficacy of ET-traps as a therapeutic tool for diabetes, which is a major public health burden around the world.

Histones and heart failure in diabetes

Although heart failure is now accepted as being a major long-term complication of diabetes, many of the recent advances in our understanding of the pathobiology of diabetes complications have come about through the study of more traditional microvascular or macrovascular diseases. This has been the case, for example, in the evolving field of the epigenetics of diabetes complications and, in particular, the post-translational modification of histone proteins. However, histone modifications also occur in human heart failure and their perturbation also occurs in diabetic hearts. Here, we review the principal histone modifications and their enzymatic writers and erasers that have been studied to date; we discuss what is currently known about their roles in heart failure and in the diabetic heart; we draw on lessons learned from the studies of microvascular and macrovascular complications; and we speculate that therapeutically manipulating histone modifications may alter the natural history of heart failure in diabetes.

Endothelial cell regulation through epigenetic mechanisms: Depicting parallels and its clinical application within an intra-islet microenvironment

The intra-islet endothelial cells (ECs), the building blocks of islet microvasculature, govern a number of cellular and pathophysiological processes associated with the pancreatic tissue. These cells are key to the angiogenic process and essential for islet revascularization after transplantation. Understanding fundamental mechanisms by which ECs regulate the angiogenic process is important as these cells maintain and regulate the intra-islet environment facilitated by a complex signaling crosstalk with the surrounding endocrine cells. In recent years, many studies have demonstrated the impact of epigenetic regulation on islet cell development and function. This review will present an overview of the reports involving endothelial epigenetic mechanisms particularly focusing on histone modifications which have been identified to play a critical role in governing EC functions by modifying the chromatin structure. A better understanding of epigenetic mechanisms by which these cells regulate gene expression and function to orchestrate cellular physiology and pathology is likely to offer improved insights on the functioning and regulation of an intra-islet endothelial microvascular environment.

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.

Melatonin levels in human diabetic dental pulp tissue and its effects on dental pulp cells under hyperglycaemic conditions

AIM

To investigate melatonin (MEL) levels in human dental pulp tissue (hDP) in type 2 diabetic (T2D) participants and the underlying molecular mechanisms of its effects in human dental pulp cells (hDPCs) under hyperglycaemia.

METHODOLOGY

The study included 16 healthy and 16 T2D participants who underwent vital pulp extirpation for hDP and four healthy participants undergoing third molar extraction for hDPCs analyses. MTT and NRU were used as tests for cytotoxicity. The pulp tissue levels of MEL, inducible NO synthase (iNOS) and superoxide dismutase (SOD) activity, as well as iNOS, histone acetyltransferase p300 (p300) and SOD activity levels in hDPCs incubated with MEL (0.1 and 1.0 mmol L^-1 ) under normoglycaemia and hyperglycaemia were measured by enzyme-linked immunosorbent assay. Comparisons between the two groups were made by unpaired t-tests or Mann-Whitney test whilst the chi-square test was used for dichotomous variables. To compare more groups, the Kruskal-Wallis test with Dunn's multiple comparison was used, whilst Spearman correlation was used to assess association between two variables.

RESULTS

Melatonin was decreased (124.30 ± 21.6 vs. 240.0 ± 19.1 pg mL^-1 , P < 0.01), whilst iNOS levels increased (0.92 ± 0.08 vs. 0.32 ± 0.09 ng mL^-1 , P < 0.01) in hDP from T2D compared to nondiabetic participants. In hDPCs, MEL (0.1 and 1.0 mmol L^-1 ) had no cytotoxicity. Incubation with 1.0 mmol L^-1 of MEL (24 h) decreased hyperglycaemia-induced increases of iNOS (0.34 ± 0.01 ng mL^-1 vs. 0.40 ± 0.01 ng mL^-1 , P < 0.01) and p300 (11.59 ± 0.58 ng mL^-1 vs. 16.12 ± 0.39 ng mL^-1 , P < 0.01), and also, increased SOD activity (87.11 ± 3.10% vs. 68.56 ± 3.77%, P < 0.01) to the levels comparable to the normoglycaemic; iNOS and p300 protein expression levels showed strong positive correlation under hyperglycaemia (Spearman r = 0.8242, P < 0.001).

CONCLUSION

Type 2 diabetic participants had decreased MEL in hDP. At pharmacological concentrations, MEL is not cytotoxic for hDPCs and normalizes iNOS and SOD activity levels in hyperglyceamic hDPCs suggesting its antioxidant and protective effects in human dental pulp tissue under hyperglycaemia.

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.

Impaired Antiviral Stress Granule and IFN-β Enhanceosome Formation Enhances Susceptibility to Influenza Infection in Chronic Obstructive Pulmonary Disease Epithelium

Chronic obstructive pulmonary disease (COPD) is a serious lung disease that progressively worsens lung function. Those affected are highly susceptible to influenza virus infections that result in exacerbations with exaggerated symptoms with increased mortality. The mechanisms underpinning this increased susceptibility to infection in COPD are unclear. In this study, we show that primary bronchial epithelial cells (pBECs) from subjects with COPD have impaired induction of type I IFN (IFN-β) and lead to heightened viral replication after influenza viral infection. COPD pBECs have reduced protein levels of protein kinase (PK) R and decreased formation of PKR-mediated antiviral stress granules, which are critical in initiating type I IFN inductions. In addition, reduced protein expression of p300 resulted in decreased activation of IFN regulatory factor 3 and subsequent formation of IFN-β enhanceosome in COPD pBECs. The decreased p300 induction was the result of enhanced levels of microRNA (miR)-132. Ectopic expression of PKR or miR-132 antagomiR alone failed to restore IFN-β induction, whereas cotreatment increased antiviral stress granule formation, induction of p300, and IFN-β in COPD pBECs. This study reveals that decreased induction of both PKR and p300 proteins contribute to impaired induction of IFN-β in COPD pBECs upon influenza infection.

Computational analyses of type 2 diabetes-associated loci identified by genome-wide association studies

BACKGROUND

Genome-wide association studies (GWAS) of type 2 diabetes (T2D) have discovered a number of loci that contribute to susceptibility to the disease. Future challenges include elucidation of functional mechanisms through which these GWAS-identified loci modulate T2D disease risk. The aim of the present study was to comprehensively characterize T2D associated single nucleotide polymorphisms (SNPs) and genes through computational approaches.

METHODS

Computational biology approaches used in the present study included comparative genomic analyses and functional annotation using GWAS3D and RegulomeDB, investigation of the effects of T2D-associated SNPs on miRNA binding and protein phosphorylation, and gene ontology, pathway enrichment, protein-protein interaction (PPI) networks and functional module analysis of T2D-associated genes from previously published GWAS.

RESULTS

Computational analysis identified a number of T2D GWAS-associated SNPs that were located at protein binding sites, including CCCTC-binding factor (CTCF), E1A binding protein p300 (EP300), hepatocyte nuclear factor 4alpha (HNF4A), transcription factor 7 like 2 (TCF7L2), forkhead box A1 (FOXA1) and A2 (FOXA2), and potentially affected the binding of miRNAs and protein phosphorylation. Pathway enrichment analysis confirmed two well-known maturity onset diabetes of the young and T2D pathways, whereas PPI network analysis identified highly interconnected "hub" genes, such as TCF7L2, melatonin receptor 1B (MTNR1B), and solute carrier family 30 (zinc transporter), member 8 (SLC30A8), that created two tight subnetworks.

CONCLUSIONS

The results provide objectives and clues for future experimental studies and further insights into the molecular pathogenesis of T2D.

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.

Curcumin as potential therapeutic natural product: a nanobiotechnological perspective

OBJECTIVES

Nanotechnology-based drug delivery systems can resolve the poor bioavailability issue allied with curcumin. The therapeutic potential of curcumin can be enhanced by making nanocomposite preparation of curcumin with metal oxide nanoparticles, poly lactic-co-glycolic acid (PLGA) nanoparticles and solid lipid nanoparticles that increases its bioavailability in the tissue.

KEY FINDINGS

Curcumin has manifold therapeutic effects which include antidiabetic, antihypertensive, anticancer, anti-inflammatory and antimicrobial properties. Curcumin can inhibit diabetes, heavy metal and stress-induced hypertension with its antioxidant, chelating and inhibitory effects on the pathways that lead to hypertension. Curcumin is an anticancer agent that can prevent abnormal cell proliferation. Nanocurcumin is an improved form of curcumin with enhanced therapeutic properties due to improved delivery to the diseased tissue, better internalization and reduced systemic elimination.

SUMMARY

Curcumin has multiple pharmacologic effects, but its poor bioavailability reduces its therapeutic effects. By conjugating curcumin to metal oxide nanoparticles or encapsulation in lipid nanoparticles, dendrimers, nanogels and polymeric nanoparticles, the water solubility and bioavailability of curcumin can be improved and thus increase its pharmacological effectiveness.

miR-200b Mediates Endothelial-to-Mesenchymal Transition in Diabetic Cardiomyopathy

Hyperglycemia-induced endothelial injury is a key pathogenetic factor in diabetic cardiomyopathy. Endothelial injury may lead to a phenotypic change (i.e., endothelial-to-mesenchymal transition [EndMT]), causing cardiac fibrosis. Epigenetic mechanisms, through specific microRNA, may regulate such a process. We investigated the mechanisms for such changes in cardiac microvascular endothelial cells and in the heart of genetically engineered mice with chemically induced diabetes. Cardiac tissues and isolated mouse heart endothelial cells (MHECs) from animals with or without endothelial-specific overexpression of miR-200b, with or without streptozotocin-induced diabetes, were examined at the mRNA and protein levels for endothelial and mesenchymal markers. Expression of miR-200b and its targets was quantified. Cardiac functions and structures were analyzed. In the hearts of wild-type diabetic mice, EndMT was observed, which was prevented in the miR-200b transgenic diabetic mice. Expression of specific markers such as vascular endothelial growth factor, zinc finger E-box-binding homeobox, transforming growth factor-β1, and p300 were increased in the hearts of diabetic mice and were prevented following miR-200b overexpression. MHECs showed similar changes. miR-200b overexpression also prevented diabetes-induced cardiac functional and structural changes. These data indicate that glucose-induced EndMT in vivo and in vitro in the hearts of diabetic mice is possibly mediated by miR-200b and p300.

Histone Acetylation and Its Modifiers in the Pathogenesis of Diabetic Nephropathy

Diabetic nephropathy (DN) remains a leading cause of mortality worldwide despite advances in its prevention and management. A comprehensive understanding of factors contributing to DN is required to develop more effective therapeutic options. It is becoming more evident that histone acetylation (HAc), as one of the epigenetic mechanisms, is thought to be associated with the etiology of diabetic vascular complications such as diabetic retinopathy (DR), diabetic cardiomyopathy (DCM), and DN. Histone acetylases (HATs) and histone deacetylases (HDACs) are the well-known regulators of reversible acetylation in the amino-terminal domains of histone and nonhistone proteins. In DN, however, the roles of histone acetylation (HAc) and these enzymes are still controversial. Some new evidence has revealed that HATs and HDACs inhibitors are renoprotective in cellular and animal models of DN, while, on the other hand, upregulation of HAc has been implicated in the pathogenesis of DN. In this review, we focus on the recent advances on the roles of HAc and their covalent enzymes in the development and progression of DN in certain cellular processes including fibrosis, inflammation, hypertrophy, and oxidative stress and discuss how targeting these enzymes and their inhibitors can ultimately lead to the therapeutic approaches for treating DN.

Data interpretation: deciphering the biological function of Type 2 diabetes associated risk loci

AIMS

Type 2 diabetes (T2D) is a complex multifactorial disorder with more than 40 loci associated with disease susceptibility. Most of these genome-wide significant loci reside in noncoding regions, it is important to decipher the potential regulatory function of these variants and to differentiate between true and tag signals. Nowadays, databases are being developed to study and predict the function of these associated variants, and RegulomeDB is one such database.

METHODS

We used RegulomeDB to analyze the potential function of the associated variants reported in five genome-wide association studies (GWAS) of T2D.

RESULTS

We investigated the 1,567 single nucleotide polymorphisms (SNPs) with 989 SNPs with a score of 1-6. Of those 989 SNPs, only 64 returned with RegulomeDB score <3 (evidence of regulatory function), and only four of these were GWAS significant SNPs (THADA/rs10203174, score = 1b; UBE2E2/rs7612463, score = 2a; ARAP1/rs1552224 and TP53INP1/rs8996852, score = 2b). But only 63 % of the annotated SNPs showed regulatory function that is an important limitation of the RegulomeDB as this database only provides information of few regulatory elements.

CONCLUSION

This study further supports that some of the noncoding GWAS variants are the true associations and not the tag ones. This study also proves the utility and importance of the RegulomeDB and other such databases. Although it is an extensive database of regulatory elements but has certain limitation due to utilization of only few types of regulatory elements and pathways.

SIRT1 reduction causes renal and retinal injury in diabetes through endothelin 1 and transforming growth factor β1

In diabetes, hyperglycaemia causes up-regulation of endothelin 1 (ET-1) and transforming growth factor beta 1 (TGF-β1). Previously we showed glucose reduces sirtuin1 (SIRT1), a class III histone deacetylase. Here, we investigated the regulatory role of SIRT1 on ET-1 and TGF-β1 expression. Human microvascular endothelial cells were examined following incubation with 25 mmol/l glucose (HG) and 5 mmol/l glucose (NG) with or without SIRT1 or histone acetylase p300 overexpression or knockdown. mRNA expressions of ET-1, TGF-β1, SIRT1, p300 and collagen 1α(I) were examined. SIRT1 enzyme activity, ET-1 and TGF-β1 protein levels were measured. Histone acetylation and endothelial permeability were further investigated. Similar analyses were performed in the kidneys and retinas of SIRT1 overexpressing transgenic mice with or without streptozotocin induced diabetes. Renal functions were evaluated. In the endothelial cells (ECs), HG caused increased permeability and escalated production of ET-1, TGF-β1, collagen Iα(I). These cells also showed increased p300 expression, histone acetylation and reduced SIRT1 levels. These changes were rectified in the ECs following p300 silencing or by SIRT1 overexpression, whereas SIRT1 knockdown or p300 overexpression in NG mimicked the effects of HG. High ET-1 and TGF-β1 levels were seen in the kidneys and retinas of diabetic mice along with micro-albuminuria and increased fibronectin protein (marker of glucose-induced cell injury) levels. Interestingly, these detrimental changes were blunted in SIRT1 overexpressing transgenic mice with diabetes. This study showed a novel SIRT1 mediated protection against renal and retinal injury in diabetes, regulated through p300, ET-1 and TGF-β1.

Epigenetic mechanisms in diabetic complications and metabolic memory

The incidence of diabetes and its associated micro- and macrovascular complications is greatly increasing worldwide. The most prevalent vascular complications of both type 1 and type 2 diabetes include nephropathy, retinopathy, neuropathy and cardiovascular diseases. Evidence suggests that both genetic and environmental factors are involved in these pathologies. Clinical trials have underscored the beneficial effects of intensive glycaemic control for preventing the progression of complications. Accumulating evidence suggests a key role for epigenetic mechanisms such as DNA methylation, histone post-translational modifications in chromatin, and non-coding RNAs in the complex interplay between genes and the environment. Factors associated with the pathology of diabetic complications, including hyperglycaemia, growth factors, oxidant stress and inflammatory factors can lead to dysregulation of these epigenetic mechanisms to alter the expression of pathological genes in target cells such as endothelial, vascular smooth muscle, retinal and cardiac cells, without changes in the underlying DNA sequence. Furthermore, long-term persistence of these alterations to the epigenome may be a key mechanism underlying the phenomenon of 'metabolic memory' and sustained vascular dysfunction despite attainment of glycaemic control. Current therapies for most diabetic complications have not been fully efficacious, and hence a study of epigenetic mechanisms that may be involved is clearly warranted as they can not only shed novel new insights into the pathology of diabetic complications, but also lead to the identification of much needed new drug targets. In this review, we highlight the emerging role of epigenetics and epigenomics in the vascular complications of diabetes and metabolic memory.

Human genetics of diabetic nephropathy

Diabetic vascular complications (DVCs) affecting several important organ systems of human body such as cardiovascular system contribute a major public health problem. Genetic factors contribute to the risk of diabetic nephropathy (DN). Genetics variants, structural variants (copy number variation) and epigenetic changes play important roles in the development of DN. Apart from nucleus genome, mitochondrial DNA (mtDNA) plays critical roles in regulation of development of DN. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. This review focused on the current knowledge of the genetic and epigenetic basis of DN. Ultimately, identification of genes or genetic loci, structural variants and epigenetic changes contributed to risk or protection of DN will benefit uncovering the complex mechanism underlying DN, with crucial implications for the development of personalized medicine to diabetes mellitus and its complications.

Epigenetic regulation of endothelial-cell-mediated vascular repair

Maintenance of vascular integrity is essential for the prevention of vascular disease and for recovery following cardiovascular, cerebrovascular and peripheral vascular events including limb ischemia, heart attack and stroke. Endothelial stem/progenitor cells have recently gained considerable interest due to their potential use in stem cell therapies to mediate revascularization after ischemic injury. Therefore, there is an urgent need to understand fundamental mechanisms regulating vascular repair in specific cell types to develop new beneficial therapeutic interventions. In this review, we highlight recent studies demonstrating that epigenetic mechanisms (including post-translational modifications of DNA and histones as well as non-coding RNA-mediated processes) play essential roles in the regulation of endothelial stem/progenitor cell functions through modifying chromatin structure. Furthermore, we discuss the potential of using small molecules that modulate the activities of epigenetic enzymes to enhance the vascular repair function of endothelial cells and offer insight on potential strategies that may accelerate clinical applications.

Human genetics of diabetic retinopathy

There is evidence demonstrating that genetic factors contribute to the risk of diabetic retinopathy (DR). Genetics variants, structural variants (copy number variation, CNV) and epigenetic changes play important roles in the development of DR. Genetic linkage and association studies have uncovered a number of genetic loci and common genetic variants susceptibility to DR. CNV and interactions of gene by environment have also been detected by association analysis. Apart from nucleus genome, mitochondrial DNA plays critical roles in regulation of development of DR. Epigenetic studies have indicated epigenetic changes in chromatin affecting gene transcription in response to environmental stimuli, which provided a large body of evidence of regulating development of diabetes mellitus. Identification of genetic variants and epigenetic changes contributed to risk or protection of DR will benefit uncovering the complex mechanism underlying DR. This review focused on the current knowledge of the genetic and epigenetic basis of DR.

Novel curcumin analog C66 prevents diabetic nephropathy via JNK pathway with the involvement of p300/CBP-mediated histone acetylation

Glomerulosclerosis and interstitial fibrosis represent the key events in development of diabetic nephropathy (DN), with connective tissue growth factor (CTGF), plasminogen activator inhibitor-1 (PAI-1) and fibronectin 1 (FN-1) playing important roles in these pathogenic processes. To investigate whether the plant metabolite curcumin, which exerts epigenetic modulatory properties when applied as a pharmacological agent, may prevent DN via inhibition of the JNK pathway and epigenetic histone acetylation, diabetic and age-matched non-diabetic control mice were administered a 3-month course of curcumin analogue (C66), c-Jun N-terminal kinase inhibitor (JNKi, sp600125), or vehicle alone. At treatment end, half of the mice were sacrificed for analysis and the other half were maintained without treatment for an additional 3 months. Renal JNK phosphorylation was found to be significantly increased in the vehicle-treated diabetic mice, but not the C66- and JNKi-treated diabetic mice, at both the 3-month and 6-month time points. C66 and JNKi treatment also significantly prevented diabetes-induced renal fibrosis and dysfunction. Diabetes-related increases in histone acetylation, histone acetyl transferases' (HATs) activity, and the p300/CBP HAT expression were also significantly attenuated by C66 or JNKi treatment. Chromatin immunoprecipitation assays showed that C66 and JNKi treatments decreased H3-lysine9/14-acetylation (H3K9/14Ac) level and p300/CBP occupancy at the CTGF, PAI-1 and FN-1 gene promoters. Thus, C66 may significantly and persistently prevent renal injury and dysfunction in diabetic mice via down-regulation of diabetes-related JNK activation and consequent suppression of the diabetes-related increases in HAT activity, p300/CBP expression, and histone acetylation.

Reprint of: miRNA-1 regulates endothelin-1 in diabetes

AIMS

MicroRNAs (miRNAs) play important roles in several biological processes. In this study, we investigated the role of miR-1, an endothelin-1 (ET-1) targeting miRNA, in endothelial cells (ECs) and tissues of diabetic animals. ET-1 is known to be of pathogenetic significance in several chronic diabetic complications.

MAIN METHODS

PCR array was used to identify alterations of miRNA expression in ECs exposed to glucose. miR-1 expression was validated by TaqMan real-time PCR assay. Human retinal ECs (HRECs) and human umbilical vein ECs (HUVECs) exposed to various glucose levels with or without miR-1 mimic transfection, and tissues from streptozotocin-induced diabetic animals after two months of follow-up, were examined for miR-1 expression, as well as ET-1 and fibronectin (FN) mRNA and protein levels.

KEY FINDINGS

Array analyses showed glucose-induced alterations of 125 miRNAs (out of 381) in ECs exposed to 25 mM glucose compared to 5 mM glucose. Fifty-one miRNAs were upregulated and 74 were downregulated. 25 mM glucose decreased miR-1 expression and increased ET-1 mRNA and protein levels. miR-1 mimic transfection prevented HG-induced ET-1 upregulation. Furthermore, glucose induced upregulation of FN, which is mediated partly by ET-1, was also prevented by such transfection. Diabetic animals showed decreased miR-1 expression in the retina, heart and kidneys. In parallel, ET-1 mRNA expressions were increased in these tissues of diabetic animals, in association with upregulation of FN.

SIGNIFICANCE

These results indicate a novel glucose-induced mechanism of tissue damage, in which miR-1 regulates ET-1 expressions in diabetes. Identifying such mechanisms may lead to RNA based treatment for diabetic complications.

P300-dependent STAT3 acetylation is necessary for angiotensin II-induced pro-fibrotic responses in renal tubular epithelial cells

AIM

To explore the signal transducer and activator of transcription 3 (STAT3) signaling pathway, especially STAT3 acetylation, in angiotensin II (Ang II)-induced pro-fibrotic responses in renal tubular epithelial cells.

METHODS

Rat renal tubular epithelial cell line (NRK-52E) was used. STAT3 acetylation and phosphorylation, as well as the expression of fibronectin, collagen IV and transforming growth factor-β1 (TGF-β1) were examined using Western blotting. The level and localization of STAT3 phosphorylation on Tyr705 were detected with fluorescence immunocytochemistry. The cells were transfected with a plasmid vector carrying p300 gene or siRNA targeting p300 to regulate p300 expression.

RESULTS

Overexpression of p300 significantly increased STAT3 acetylation on Lys685, STAT3 phosphorylation on Tyr705, and the expression of TGF-β1, collagen IV and fibronectin in the cells. Treatment of the cells with Ang II (1 μmol/L) significantly increased STAT3 phosphorylation on Tyr705 through JAK2 activation, and dose-dependently increased the expression of fibronectin, collagen IV and TGF-β1. Pretreatment with curcumin, an inhibitor of JAK2 and p300, blocked Ang II-induced effects. Knockdown of p300 significantly decreased STAT3 acetylation on Lys685, and abolished Ang II-stimulated STAT3 phosphorylation on Tyr705, whereas pretreatment of the cells with C646, a selective inhibitor of p300, inhibited Ang II-induced STAT3 nuclear translocation and the expression of TGF-β1, collagen IV and fibronectin. Pretreatment of the cells with AG490, a JAK2 inhibitor, markedly inhibited Ang II-induced STAT3 phosphorylation on Tyr705 and fibronectin expression.

CONCLUSION

p300-dependent STAT3 acetylation is necessary for Ang II-induced STAT3 phosphorylation and the consequent pro-fibrotic responses in renal tubular epithelial cells in vitro.

Preventive effects of benfotiamine in chronic diabetic complications

Aims/Introduction:  In diabetes, increased oxidative stress as a result of damage to the electron transport chain can lead to tissue injury through upregulation of multiple vasoactive factors and extracellular matrix proteins. Benfotiamine, a lipid soluble thiamine derivative, through reducing mitochondrial superoxide production, blocks multiple pathways leading to tissue damage in hyperglycemia. We investigated if treatment with benfotiamine can prevent diabetes‐induced production of vasoactive factors and extracellular matrix proteins, and whether such effects are tissue‐specific. We also examined whether effects of benfotiamine are mediated through a nuclear mechanism.

Materials and Methods:  Retinal, renal and cardiac tissues from the streptozotocin‐induced diabetic rats were examined after 4 months of follow up. mRNA levels were quantified using real‐time RT‐PCR. Protein levels were quantified using western blot and ELISA. Cellular expressions of 8‐Hydroxy‐2′‐deoxyguanosine, a marker of nuclear DNA damage and Phospho‐H2AX were also examined.

Results:  Diabetic animals showed hyperglycemia, glucosuria, increased urinary albumin/creatine ratio and loss of bodyweight. In the kidneys, heart and retina, diabetes caused increased production of endothelin‐1, transforming growth factor‐β1, vascular endothelial growth factor and augmented extracellular matrix proteins (collagen, fibronectin [FN] and its splice variant extradomain B containing FN), along with evidence of structural alterations, characteristic of diabetes‐induced tissue damage. Such changes were prevented by benfotiamine. Furthermore, benfotiamine prevented diabetes‐induced oxidative DNA damage and upregulation of p300, a histone acetylator and a transcription coactivator.

Conclusions:  Data from the present study suggest that benfotiamine is effective in preventing tissue damage in diabetes and at the transcriptional level such effects are mediated through prevention of p300 upregulation. (J Diabetes Invest, doi: 10.1111/j.2040‐1124.2010.00077.x, 2010)

High glucose induces Smad activation via the transcriptional coregulator p300 and contributes to cardiac fibrosis and hypertrophy

BACKGROUND

Despite advances in the treatment of heart failure, mortality remains high, particularly in individuals with diabetes. Activated transforming growth factor beta (TGF-β) contributes to the pathogenesis of the fibrotic interstitium observed in diabetic cardiomyopathy. We hypothesized that high glucose enhances the activity of the transcriptional co-activator p300, leading to the activation of TGF-β via acetylation of Smad2; and that by inhibiting p300, TGF-β activity will be reduced and heart failure prevented in a clinically relevant animal model of diabetic cardiomyopathy.

METHODS

p300 activity was assessed in H9c2 cardiomyoblasts under normal glucose (5.6 mmol/L-NG) and high glucose (25 mmol/L-HG) conditions. 3H-proline incorporation in cardiac fibroblasts was also assessed as a marker of collagen synthesis. The role of p300 activity in modifying TGF-β activity was investigated with a known p300 inhibitor, curcumin or p300 siRNA in vitro, and the functional effects of p300 inhibition were assessed using curcumin in a hemodynamically validated model of diabetic cardiomyopathy - the diabetic TG m(Ren-2)27 rat.

RESULTS

In vitro, H9c2 cells exposed to HG demonstrated increased p300 activity, Smad2 acetylation and increased TGF-β activity as assessed by Smad7 induction (all p < 0.05 c/w NG). Furthermore, HG induced 3H-proline incorporation as a marker of collagen synthesis (p < 0.05 c/w NG). p300 inhibition, using either siRNA or curcumin reduced p300 activity, Smad acetylation and TGF-β activity (all p < 0.05 c/w vehicle or scrambled siRNA). Furthermore, curcumin therapy reduced 3H-proline incorporation in HG and TGF-β stimulated fibroblasts (p < 0.05 c/w NG). To determine the functional significance of p300 inhibition, diabetic Ren-2 rats were randomized to receive curcumin or vehicle for 6 weeks. Curcumin treatment reduced cardiac hypertrophy, improved diastolic function and reduced extracellular matrix production, without affecting glycemic control, along with a reduction in TGF-β activity as assessed by Smad7 activation (all p < 0.05 c/w vehicle treated diabetic animals).

CONCLUSIONS

These findings suggest that high glucose increases the activity of the transcriptional co-regulator p300, which increases TGF-β activity via Smad2 acetylation. Modulation of p300 may be a novel strategy to treat diabetes induced heart failure.

miR-195 regulates SIRT1-mediated changes in diabetic retinopathy

AIMS/HYPOTHESIS

Endothelial cell (EC) damage is a key mechanism causing retinal microvascular injury in diabetes. Several microRNAs (miRNAs) have been found to regulate sirtuin 1 (SIRT1, which is involved in regulation of the cell cycle, survival and metabolism) in various tissues and disease states, but no studies have been conducted on the role of miRNA in regulation of SIRT1 in diabetic retinopathy. Here we investigated the effect of miRNA-195 (miR-195), a SIRT1-targeting miRNA, on the development of diabetes-induced changes in ECs and retina.

METHODS

The level of miR-195 was measured in human retinal and dermal microvascular ECs (HRECs, HMECs) following exposure to 25 mmol/l glucose (high glucose, HG) and 5 mmol/l glucose (normal glucose, NG). SIRT1 and fibronectin levels were examined following transfection with miR-195 mimic or antagomir or forced expression of SIRT1. Retinal tissues from diabetic rats were similarly studied following intravitreal injection of an miR-195 antagomir or mimic. In situ hybridisation was used to localise retinal miR-195.

RESULTS

HG caused increased miR-195 levels and decreased SIRT1 expression (compared with NG) in both HRECs and HMECs. Transfection with miR-195 antagomir and forced expression of SIRT1 prevented such changes, whereas transfection with miR-195 mimic produced HG-like effects. A luciferase assay confirmed the binding of miR-195 to the 3' untranslated region of SIRT1. miR-195 expression was upregulated in retinas of diabetic rats and intravitreal injection of miR-195 antagomir ameliorated levels of SIRT1.

CONCLUSIONS/INTERPRETATION

These studies identified a novel mechanism whereby miR-195 regulates SIRT1-mediated tissue damage in diabetic retinopathy.

Illustrating the interplay between the extracellular matrix and microRNAs

The discovery of cell surface receptors that bind to extracellular matrix (ECM) components marked a new era in biological research. Since then there has been an increasing appreciation of the importance of studying cells in the context of their extracellular environment. Cell behaviour is profoundly affected by the ECM, whose synthesis and turnover must be finely balanced in order to maintain normal function and prevent disease. In the last decade, microRNAs (miRNAs) have emerged as key regulators of ECM gene expression. As new technologies for the identification and validation of miRNA targets continue to be developed, a growing body of data supporting the role of miRNAs in regulating the ECM biology has arisen from a variety of cell and animal models along with clinical studies. However, more recent findings suggest an intriguing interplay between the ECM and miRNAs: not only can miRNAs control the composition of the ECM, but also the ECM can affect the expression of specific miRNAs. Here we discuss how miRNAs contribute to the synthesis, maintenance and remodelling of the ECM during development and disease. Furthermore, we bring to light evidence that points to a role for the ECM in regulating miRNA expression and function.

Identification of key nodes of type 2 diabetes mellitus protein interactome and study of their interactions with phloridzin

Network biology-inspired approaches could be used effectively in probing regulatory processes by which small molecules intervene with disease mechanisms. The present study aims at identification of key targets of type 2 diabetes mellitus (T2DM) by network analysis of the underlying protein interactome, and probing for mechanisms by which phloridzin could be critical at altering the disease phenotype. Towards this goal, we constructed a protein-protein interaction network associated with T2DM, starting from candidate genes and systems-level interactions data available. The relevance of the network constructed was verified with the help of gene ontology, node deletion, and biological essentiality studies. Using a network analysis method, MAPK1, EP300, and SMAD2 were identified as the most central proteins of potential therapeutic value. Phloridzin, a known antidiabetic agent, potentially interacts with proteins central to T2DM mechanisms. The structural understanding of interaction of phloridzin with these proteins of relevance to T2DM could provide better insight into its regulatory mechanisms and help in developing better therapeutic agents. The molecular docking results suggest that phloridzin is potentially involved in making critical interactions with MAPK1. These results could further be validated by experimental studies and could be used to design therapeutic agents for T2DM intervention.

Protein nitration promotes inducible nitric oxide synthase transcription mediated by NF-κB in high glucose-stimulated human lens epithelial cells

Although an important event in hyperglycaemia-induced oxidative stress is the nuclear factor-kappa b (NF-κB)-activated inducible nitric oxide synthase (iNOS) expression, the underlying mechanism is not fully characterized. Peroxynitrite, formed from NO and superoxide, can induce multiple proteins nitration, even including NF-κB and iNOS, to alter their functions. In this study, we found high glucose caused conspicuous nitration of nuclear NF-κB p65 and its co-activator p300 in human lens epithelial cells. The nitration of NF-κB and p300 promoted their co-localization and binding to ensure the activation of the iNOS gene transcription. Moreover, nearly all predicted NF-κB binding sites in the human iNOS gene promoter were responsive to high glucose stimulation, might for a synergistic role. While, only the NF-κB binding site -5212 showed significant alterations by high glucose and peroxynitrite stimulations, indicating it a more important role in the protein nitration promoted iNOS gene transcription. Our results demonstrated that protein nitration can promote the NF-κB-activated iNOS gene transcription in human lens epithelial cells by high glucose stimulation.

Signaling mechanisms of a water soluble curcumin derivative in experimental type 1 diabetes with cardiomyopathy

BACKGROUND

Curcumin exhibits anti-diabetic activities, induces heme-oxygenase-1 (HO-1) and is an inhibitor of transcriptional co-activator p300. A novel water soluble curcumin derivative (NCD) has been developed to overcome low invivo bioavailability of curcumin. We evaluated the effect of the NCD on signaling mechanisms involved in cardiomyocyte hypertrophy and studied whether its action is mediated via inducible HO-1.

MATERIALS AND METHODS

Rats were divided into controls, controls receiving NCD, diabetic, diabetic receiving NCD, diabetic receiving pure curcumin, diabetic receiving HO inhibitor, zinc protoporphyrin IX (ZnPP IX) and diabetic receiving NCD and ZnPP IX. NCD and curcumin were given orally. After 45 days, cardiac physiologic parameters, plasma glucose, insulin, glycated hemoglobin (GHb), HO-1 gene expression and HO activity in pancreas and cardiac tissues were assessed. Gene expression of p300, atrial natriuretic peptide (ANP) and myocyte enhancer factor 2 (MEF2A and MEF2C) were studied.

RESULTS

NCD and curcumin decreased plasma glucose, GHb and increased insulin levels significantly in diabetic rats. This action may be partially mediated by induction of HO-1 gene. HO-1 gene expression and HO activity were significantly increased in diabetic heart and pancreas. Diabetes upregulated the expression of ANP, MEF2A, MEF2C and p300. NCD and curcumin prevented diabetes-induced upregulation of these parameters and improved left ventricular function. The effect of the NCD was better than the same dose of curcumin.

Oxidative-stress-induced epigenetic changes in chronic diabetic complications

Oxidative stress plays an important role in the development and progression of chronic diabetic complications. Diabetes causes mitochondrial superoxide overproduction in the endothelial cells of both large and small vessels. This increased superoxide production causes the activation of several signal pathways involved in the pathogenesis of chronic complications. In particular, endothelial cells are major targets of glucose-induced oxidative damage in the target organs. Oxidative stress activates cellular signaling pathways and transcription factors in endothelial cells including protein kinase C (PKC), c-Jun-N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), forkhead box O (FOXO), and nuclear factor kappa-B (NF-κB). Oxidative stress also causes DNA damage and activates DNA nucleotide excision repair enzymes including the excision repair cross complimenting 1(ERCC1), ERCC4, and poly(ADP-ribose) polymerase (PARP). Augmented production of histone acetyltransferase p300, and alterations of histone deacetylases, including class III deacetylases sirtuins, are also involved in this process. Recent research has found that small noncoding RNAs, like microRNA, are a new kind of regulator associated with chronic diabetic complications. There are extensive and complicated interactions and among these molecules. The purpose of this review is to demonstrate the role of oxidative stress in the development of diabetic complications in relation to epigenetic changes such as acetylation and microRNA alterations.

P300 regulates the human RLIP76 promoter activity and gene expression

A 76-kDa Ral-interacting protein (RLIP76) has been implicated in the pathogenesis of cancer and diabetes. It is often over expressed in human malignant cell lines and human tumor samples and has been associated with metastasis and chemoresistance. RLIP76 homozygous knockout mice exhibit increased insulin sensitivity, hypoglycemia, and hypolipidemia, and resist cancer development. Little is known about the mechanism by which the expression of RLIP76 is regulated. In the present study, we functionally characterized the RLIP76 promoter using deletion mapping and mutational analysis to investigate the regulation of RLIP76 transcription. We have identified the promoter regions important for RLIP76 transcription, including a strong cis-activating element in the proximal promoter containing overlapping consensus cMYB and cETS binding sites. Transcription factor cMYB and the coactivator p300 associated with RLIP76 gene promoter as shown by CHIP assay. Knockdown of p300 in HEK293 cells reduced the activity of the promoter fragment containing wild type cMYB/cETS binding site in comparison to that with deleted or mutated cMYB/cETS binding site. Knockdown of p300 also decreased the RLIP76 expression as indicated by immunoblotting, immunocytochemistry and flow cytometry analysis. Thus, we report for the first time that p300 associates with the RLIP76 promoter via an overlapping cMYB and cETS binding site and regulates RLIP76 promoter activity and its expression.

High glucose induced alteration of SIRTs in endothelial cells causes rapid aging in a p300 and FOXO regulated pathway

In diabetes, some of the cellular changes are similar to aging. We hypothesized that hyperglycemia accelerates aging-like changes in the endothelial cells (ECs) and tissues leading to structural and functional damage. We investigated glucose-induced aging in 3 types of ECs using senescence associated β-gal (SA β-gal) staining and cell morphology. Alterations of sirtuins (SIRTs) and their downstream mediator FOXO and oxidative stress were investigated. Relationship of such alteration with histone acetylase (HAT) p300 was examined. Similar examinations were performed in tissues of diabetic animals. ECs in high glucose (HG) showed evidence of early senescence as demonstrated by increased SA β-gal positivity and reduced replicative capacities. These alterations were pronounced in microvascular ECs. They developed an irregular and hypertrophic phenotype. Such changes were associated with decreased SIRT (1–7) mRNA expressions. We also found that p300 and SIRT1 regulate each other in such process, as silencing one led to increase of the others’ expression. Furthermore, HG caused reduction in FOXO1’s DNA binding ability and antioxidant target gene expressions. Chemically induced increased SIRT1 activity and p300 knockdown corrected these abnormalities slowing aging-like changes. Diabetic animals showed increased cellular senescence in renal glomerulus and retinal blood vessels along with reduced SIRT1 mRNA expressions in these tissues. Data from this study demonstrated that hyperglycemia accelerates aging-like process in the vascular ECs and such process is mediated via downregulation of SIRT1, causing reduction of mitochondrial antioxidant enzyme in a p300 and FOXO1 mediated pathway.

Is there an epigenetic component underlying the resistance of triple-negative breast cancers to parp inhibitors?

Poly(ADP-ribose) polymerase (Parp) is an enzyme responsible for catalyzing post-translational modifications through the addition of poly(ADP-ribose) chains (known as PARylation). Modification by PARylation modulates numerous cellular processes including transcription, chromatin remodeling, apoptosis, and DNA damage repair. In particular, the role of Parp activation in response to DNA damage has been intensely studied. Tumors bearing mutations of the breast cancer susceptibility genes, Brca1/2, are prone to DNA breakages whose restoration into functional double-strand DNA is Parp dependent. This concept has been exploited therapeutically in Brca mutated breast and ovarian tumors, where acute sensitivity to Parp inhibitors is observed. Based on in vitro and clinical studies it remains unclear to what extent Parp inhibitors can be utilized beyond treating Brca mutated tumors. This review will focus on the often overlooked roles of PARylation in chromatin remodeling, epigenetics, and transcription to explain why some cancers may be unresponsive to Parp inhibition. We predict that understanding the impact of PARylation on gene expression will lead to alternative approaches to manipulate the Parp pathway for therapeutic benefit.