High glucose promotes retinal endothelial cell migration through activation of Src, PI3K/Akt1/eNOS, and ERKs

Resilience to diabetic retinopathy

Chronic elevation of blood glucose at first causes relatively minor changes to the neural and vascular components of the retina. As the duration of hyperglycemia persists, the nature and extent of damage increases and becomes readily detectable. While this second, overt manifestation of diabetic retinopathy (DR) has been studied extensively, what prevents maximal damage from the very start of hyperglycemia remains largely unexplored. Recent studies indicate that diabetes (DM) engages mitochondria-based defense during the retinopathy-resistant phase, and thereby enables the retina to remain healthy in the face of hyperglycemia. Such resilience is transient, and its deterioration results in progressive accumulation of retinal damage. The concepts that co-emerge with these discoveries set the stage for novel intellectual and therapeutic opportunities within the DR field. Identification of biomarkers and mediators of protection from DM-mediated damage will enable development of resilience-based therapies that will indefinitely delay the onset of DR.

Lnc-216 regulates the miR-143-5p /MMP2 signaling axis aggravates retinal endothelial cell dysfunction

PURPOSE

Diabetic retinopathy (DR) is a serious retinal vascular disease that affects many individuals in their prime working years. The present research aimed at whether and how LOC681216 (LNC-216) is involved in retinal vascular dysfunction under diabetic conditions.

METHODS

Rat retinal microvascular endothelial cells (RRMECs) treated with high glucose (HG) were used for functional analysis. Gene expression analysis was conducted using the Clariom D Affymetrix platform. The wound healing, transwell, and vascular tube formation assays were used to identify the migration, invasion, and tube formation capability of RRMECs. The dual-luciferase reporter confirmed the binding interaction between miR-143-5p and LNC-216 or matrix metallopeptidase 2 (MMP2).

RESULTS

Lnc-216 was upregulated in RRMECs treated with HG. Lnc-216 knockdown markedly suppressed the tube formation, cell migration, and wound healing of cultured RRMECs under HG conditions. Mechanistically, Lnc-216 acted as a miR-143-5p sponge to affect the biological activity of miR-143-5p, which led to increased expression of matrix metallopeptidase 2 (MMP2).

CONCLUSIONS

Lnc-216 attenuates diabetic retinal vascular dysfunction through the miR-143-5p/MMP2 axis, providing a potential therapeutic strategy for DR.

Diabetes Modulates Iodothyronine Deiodinase 2 Expression in the Mouse Retina: A Role for Thyroid Hormone in the Pathogenesis of Diabetic Retinopathy

Purpose

Clinical investigations associate hypothyroidism with an increased risk for microvascular complications, yet the mechanism by which thyroid hormone regulates the development of diabetic retinopathy is not clearly understood. We investigated the role of iodothyronine deiodinase 2 (DIO2) in the pathogenesis of diabetic retinopathy.

Methods

Retinas from streptozotocin-induced diabetic and nondiabetic mice were evaluated by RNA sequencing, RT-PCR, and immunostaining. Media and cell lysates from mouse retinal microvascular endothelial cells and retinal astrocytes exposed to physiologic (5 mM) and high glucose (25 mM) containing media were assessed by liquid chromatography-tandem mass spectrometry to measure tetraiodothyronine (T4) and tri-iodothyronine (T3) concentrations and by Western blot analysis to determine the relationship of T4/T3 to oxidative stress and inflammatory mediators. Cell death was determined by Trypan Blue exclusion assay.

Results

At 12 weeks of diabetes duration, retinas from diabetic mice compared with nondiabetic mice demonstrated a significant decrease in Dio2 transcripts and Dio2 gene and protein (P < 0.05) expression. When cultured in the presence of high glucose, both mouse retinal astrocytes and microvascular endothelial cells demonstrated a significant reduction of DIO2 protein compared with cells cultured in physiologic glucose. High glucose inhibited generation of T3, leading to a significantly increased T4/T3 (P < 0.0079). Supplementation of cells with T3, but not T4, prevented the high glucose-induced rise in endothelial nitric oxide synthase, intercellular cell adhesion molecule 1, and endothelial cell death (P < 0.0079).

Conclusions

Decreased intraretinal T3 owing to diabetes-induced loss of DIO2 may lead to dysfunction and death of cells in the retina, thereby contributing to the pathogenesis of early diabetic retinopathy.

Subvacuum environment-enhanced cell migration promotes wound healing without increasing hypertrophic scars caused by excessive cell proliferation

Cell migration and proliferation are conducive to wound healing; however, regulating cell proliferation remains challenging, and excessive proliferation is an important cause of scar hyperplasia. Here, we aimed to explore how a subvacuum environment promotes wound epithelisation without affecting scar hyperplasia. Human immortalized keratinocyte cells and human skin fibroblasts were cultured under subvacuum conditions (1/10 atmospheric pressure), and changes in cell proliferation and migration, target protein content, calcium influx, and cytoskeleton and membrane fluidity were observed. Mechanical calcium (Ca2+ ) channel blockers were used to prevent Ca2+ influx for reverse validation. A rat wound model was used to elucidate the mechanism of the subvacuum dressing in promoting healing. The subvacuum environment was observed to promote cell migration without affecting cell proliferation; intracellular Ca2+ concentrations and PI3K, p-PI3K, AKT1, p-AKT 1 levels increased significantly. The cytoskeleton was depolymerized, pseudopodia were reduced or absent, and membrane fluidity increased. The use of Ca2+ channel blockers weakened or eliminated these changes. Animal experiments confirmed these phenomena and demonstrated that subvacuum dressings can effectively promote wound epithelisation. Our study demonstrates that the use of subvacuum dressings can enhance cell migration without affecting cell proliferation, promote wound healing, and decrease the probability of scar hyperplasia.

Endothelin-1 acutely increases nitric oxide production via the calcineurin mediated dephosphorylation of Caveolin-1

Endothelin (ET)-1 is an endothelial-derived peptide that exerts biphasic effects on nitric oxide (NO) levels in endothelial cells such that acute exposure stimulates-while sustained exposure attenuates-NO production. Although the mechanism involved in the decrease in NO generation has been identified but the signaling involved in the acute increase in NO is still unresolved. This was the focus of this study. Our data indicate that exposing pulmonary arterial endothelial cells (PAEC) to ET-1 led to an increase in NO for up to 30min after which levels declined. These effects were attenuated by ET receptor antagonists. The increase in NO correlated with significant increases in pp60Src activity and increases in eNOS phosphorylation at Tyr83 and Ser1177. The ET-1 mediated increase in phosphorylation and NO generation were attenuated by the over-expression of a pp60Src dominant negative mutant. The increase in pp60Src activity correlated with a reduction in the interaction of Caveolin-1 with pp60Src and the calcineurin-mediated dephosphorylation of caveolin-1 at three previously unidentified sites: Thr91, Thr93, and Thr95. The calcineurin inhibitor, Tacrolimus, attenuated the acute increase in pp60Src activity induced by ET-1 and a calcineurin siRNA attenuated the ET-1 mediated increase in eNOS phosphorylation at Tyr83 and Ser1177 as well as the increase in NO. By using a Caveolin-1 celluSpot peptide array, we identified a peptide targeting a sequence located between aa 41-56 as the pp60Src binding region. This peptide fused to the TAT sequence was found to decrease caveolin-pp60Src interaction, increased pp60Src activity, increased eNOS pSer1177 and NO levels in PAEC and induce vasodilation in isolated aortic rings in wildtype but not eNOS knockout mice. Together, our data identify a novel mechanism by which ET-1 acutely increases NO via a calcineurin-mediated dephosphorylation of caveolin-1 and the subsequent stimulation of pp60Src activity, leading to increases in phosphorylation of eNOS at Tyr83 and Ser1177.

Network pharmacology mechanism of Scutellarin to inhibit RGC pyroptosis in diabetic retinopathy

To investigate the effect of scutellarin (SCU) in diabetic retinopathy (DR) and explore the associated molecular network mechanism. The animal model of DR was established from diabetic mellitus (DM) rats by intraperitoneally injected streptozotocin (STZ) at dosage 55 mg/kg. Meanwhile, SCU was intraperitoneally administrated to protect retina from cell pyroptosis induced by DM, and cell pyroptosis was detected by using HE, Nissl staining, and immunofluorescence recognition. Moreover, the hub gene involving in pyroptosis in DR was screened by bioinformatics and network pharmacology, designated as Venny intersection screen, GO and KEGG analysis, PPI protein interaction, and molecular docking. Lastly, the expressional change of hub genes were validated with experimental detection. Cell pyroptosis of the DR, specifically in retina ganglion cells (RGC), was induced in DM rats; SCU administration results in significant inhibition in the cell pyroptosis in DR. Mechanically, 4084 genes related to DR were screened from GeneCards and OMIM databases, and 120 SCU therapeutic targets were obtained, by using GeneCards, TCMSP with Swiss Target Prediction databases. Moreover, 357 targets related to pyroptosis were found using GenenCards database, and Drug, disease and phenotypic targets were analyzed online using the Draw Venn Diagram website, and 12 cross targets were obtained. Through GO function and KEGG pathway enrichment analysis, 659 BP related items, 7 CC related items, 30 MF related items, and 70 signal pathways were screened out; Of these, eleven proteins screened from cross-target PPI network were subsequently docked with the SCU, and their expressions including caspase-1, IL-1β, IL-18, GSDMD and NLRP3 in RGC indicated by immunofluorescence, and the mRNA expression for caspase-1 in DR indicated by quantitative PCR, were successfully validated. SCU can effectively protect RGC pyroptosis in DR, and underlying mechanisms are involved in the inhibition of caspase-1, GSDMD, NLRP3, IL-1β and IL-18. Our findings therefore provide crucial evidence to support the clinic practice of SCU for the treatment of DR, and explained the underlying molecular network mechanism.

Identification of critical autophagy-related proteins in diabetic retinopathy: A multi-dimensional computational study

Diabetic retinopathy (DR) is a common consequence of diabetes mellitus and a primary cause of visual impairment in middle-aged and elderly individuals. DR is susceptible to cellular degradation facilitated by autophagy. In this study, we have employed a multi-layer relatedness (MLR) approach to uncover novel autophagy-related proteins involved in DR. The objective of MLR is to determine the relatedness of autophagic and DR proteins by incorporating both expression and prior-knowledge-based similarities. We constructed a prior knowledge-based network and identified the topologically significant novel disease-related candidate autophagic proteins (CAPs). Then, we evaluated their significance in a gene co-expression and a differentially-expressed gene (DEG) network. Finally, we investigated the proximity of CAPs to the known disease-related proteins. Leveraging this methodology, we identified three crucial autophagy-related proteins, TP53, HSAP90AA1, and PIK3R1, which can influence the DR interactome in various layers of heterogeneity of clinical manifestations. They are strongly related to multiple detrimental characteristics of DR, such as pericyte loss, angiogenesis, apoptosis, and endothelial cell migration, and hence may be used to prevent or delay the progression and development of DR. We evaluated one of the identified targets, TP53, in a cell-based model and found that its inhibition resulted in reduced angiogenesis in high glucose condition required to control DR.

Thioredoxin-Interacting Protein Inhibited Vascular Endothelial Cell-Induced HREC Angiogenesis Treatment of Diabetic Retinopathy

Diabetic retinopathy is the most common reason for blindness among employed adults worldwide. Hyperglycemia and the overaccumulation of vascular endothelial growth factor (VEGF) lead to diabetic retinopathy, pathological angiogenesis in diabetic retinopathy, and consequent visual impairment. Expression levels of thioredoxin-interacting protein (TXNIP) substantially increase in retinal endothelial cells in diabetic circumstances. The part of TXNIP in retinal angiogenesis combined with diabetes remains unclear. This study examined the effect of reduced TXNIP expression levels and determined how it affects diabetic retinal angiogenesis. Display of human retinal vascular endothelial cells (HRECs) to moderately high glucose (MHG) encouraged tube formation and cell migration, not cell proliferation. In response to MHG conditions, in HRECs, TXNIP knockdown inhibited the production of reactive oxygen species (ROS), cell migration, tube formation, and the Akt/mTOR activation pathway. In addition, gene silencing of TXNIP decreased the VEGF-triggered angiogenic response in HRECs by preventing activation of both VEGF receptor 2 and the downstream components of the Akt/mTOR pathway signaling. Furthermore, TXNIP knockout mice reduced VEGF-induced or VEGF- and MHG-triggered ex vivo retinal angiogenesis compared to wild-type mice. Finally, our findings revealed that TXNIP knockdown suppressed VEGF- and MHG-triggered angiogenic responses in HRECs and mouse retinas, indicating that TXNIP is a promising therapeutic window against the proliferation of diabetic patients' retinopathy.

Expression of Osteopontin and Integrin αvβ3 Receptor in Retina of Diabetic Guinea Pigs with High Myopia

INTRODUCTION

The study aimed to investigate the effect of high myopia on the expression of retinal osteopontin (OPN) and integrin αvβ3 receptor in guinea pigs and determine the relationship between high myopia and diabetic retinopathy (DR).

METHODS

Ninety-three-week-old male guinea pigs were randomly divided into four groups that included normal control group (NOR, n = 18), high myopia group (HM, n = 24), diabetes group (DR, n = 24), and diabetes with high myopia group (DR+HM, n = 24). HM was induced by form deprivation (FDHM) in the right eye. The DR group was injected with 5% streptozotocin 280 mg/kg intraperitoneally in the lower left abdomen of guinea pigs. The DRHM group was subjected to the same treatment as the HM and DR groups. Eighteen guinea pigs in each group were randomly selected to complete the experimental measurement. After enucleation of eyeballs, HE and immunohistochemical staining were performed to observe the retina morphology and count the positive rate of OPN and integrin αvβ3 receptor.

RESULTS

Diabetic retinal changes were found in group DR and HM+DR. The degree of retinal change in group HM+DR was less than that in group DR. In the DR group, the morphology of retinal tissue was loose, the number of cells decreased, retinal microaneurysms were increased, and a small amount of small artery embolism and venous thrombosis were observed. Although the retinal structure in the HM+DR group also became thinner, looser, and disordered, only a small number of microaneurysms were observed compared with the diabetic group. Immunohistochemical staining showed that the expression of OPN and integrin αvβ3 receptors in the diabetic groups (DR, HM+DR) was significantly higher than in the HM and NOR groups. The positive expression rates of OPN and integrin αvβ3 receptors in group HM+DR were significantly lower than those in group DR (p < 0.05).

CONCLUSION

The expression of OPN and integrin αvβ3 receptor in the retina of diabetic guinea pigs with high myopia was lower than that of diabetic models, which may be due to the influence of high myopia on neovascularization in DR.

Knockdown of lncRNA TUG1 alleviates diabetic retinal vascular dysfunction through regulating miR-524-5p/FGFR2

Long noncoding RNAs (LncRNAs) have been shown to play critical roles in the development of diabetic retinopathy (DR), which is often regarded as the most frequent cause of visual loss in the world. This study investigated the effect and mechanism of lncRNA taurine-upregulated gene 1 (TUG1) in DR. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed that TUG1 was upregulated in streptozotocin (STZ)-induced rat model of DR and human retinal microvascular endothelial cells (hRMECs) incubated with high glucose (HG). TUG1 suppression decreased the proliferation, migration, and angiogenesis of HG-induced hRMECs. TUG1 sponges miR-524-5p, which is downregulated in hyperglycemia. Additionally, the fibroblast growth factor receptor 2 (FGFR2) was verified as a miR-524-5p target gene and was overexpressed in HG-treated hRMECs. More notably, overexpression of FGFR2 has been shown to significantly reduce the impact of miR-524-5p overexpression. Additionally, TUG1 silencing ameliorates diabetes mellitus-induced retinal vascular impairment in vivo. Taken together, suppressing TUG1 impairs vascular function in diabetic retinas via controlling miR-524-5p and FGFR2, suggesting a possible therapy method for DR.

Osteopontin-induced vascular hyperpermeability through tight junction disruption in diabetic retina

Diabetic retinopathy is a major cause of blindness in developed countries, and is characterized by deterioration of barrier function causing vascular hyperpermeability and retinal edema. Vascular endothelial growth factor (VEGF) is a major mediator of diabetic macular edema. Although anti-VEGF drugs are the first-line treatment for diabetic macular edema, some cases are refractory to anti-VEGF therapy. Osteopontin (OPN) is a phosphoglycoprotein with diverse functions and expressed in various cells and tissues. Elevated OPN level has been implicated in diabetic retinopathy, but whether OPN is involved in hyperpermeability remains unclear. Using streptozotocin-induced diabetic mice (STZ mice) and human retinal endothelial cells (HRECs), we tested the hypothesis that up-regulated OPN causes tight junction disruption, leading to vascular hyperpermeability. The serum and retinal OPN concentrations were elevated in STZ mice compared to controls. Intravitreal injection of anti-OPN neutralizing antibody (anti-OPN Ab) suppressed vascular hyperpermeability and prevented decreases in claudin-5 and ZO-1 gene expression levels in the retina of STZ mice. Immunohistochemical staining of retinal vessels in STZ mice revealed claudin-5 immunoreactivity with punctate distribution and attenuated ZO-1 immunoreactivity, and these changes were prevented by anti-OPN Ab. Intravitreal injection of anti-OPN Ab did not change VEGF gene expression or protein concentration in retina of STZ mice. In an in vitro study, HRECs were exposed to normal glucose or high glucose with or without OPN for 48 h, and barrier function was evaluated by transendothelial electrical resistance and Evans blue permeation. Barrier function deteriorated under high glucose condition, and was further exacerbated by the addition of OPN. Immunofluorescence localization of claudin-5 and ZO-1 demonstrated punctate appearance with discontinuous junction in HRECs exposed to high glucose and OPN. There were no changes in VEGF and VEGF receptor-2 expression levels in HRECs by exposure to OPN. Our results suggest that OPN induces tight junction disruption and vascular hyperpermeability under diabetic conditions. Targeting OPN may be an effective approach to manage diabetic retinopathy.

Targeted P2X7/NLRP3 signaling pathway against inflammation, apoptosis, and pyroptosis of retinal endothelial cells in diabetic retinopathy

Retinal endothelial cells (RECs) are the primary target cells for diabetes-induced vascular damage. The P2X7/NLRP3 pathway plays an essential role in amplifying inflammation via an ATP feedback loop, promoting the inflammatory response, pyroptosis, and apoptosis of RECs in the early stages of diabetic retinopathy induced by hyperglycemia and inflammation. 3TC, a type of nucleoside reverse transcriptase inhibitor, is effective against inflammation, as it can targeting formation of the P2X7 large pore formation. Hence, our aim was to evaluated the anti-inflammatory effects and potential mechanisms of action of 3TC in vitro in retinal microvascular endothelial cells treated with high-glucose (HG) and lipopolysaccharide (LPS), as well as in vivo in the retinas of C57BL/6J male mice with streptozotocin-induced diabetes. The expression of inflammasome-related proteins P2X7 and NLRP3, and apoptosis in the retinas of 3TC-treated diabetic mice were compared to those of untreated diabetic mice. Furthermore, the anti-inflammatory, anti-apoptotic, and anti-pyroptotic effects of 3TC were evaluated in vitro in cultured mice retinal endothelial cells. Co-application of HG and LPS significantly increased the secretion of IL-6, IL-1β, and TNF-α, and ATP levels, whereas 3TC decreased cell inflammation, apoptosis, and pyroptosis. Inhibition of P2X7R and NLRP3 inflammasome activation decreased NLRP3 inflammasome-mediated injury. 3TC prevented cytokine and ATP release following co-application of HG and LPS/BzATP. Our findings provide new insights regarding the mechanisms of action of 3TC in diabetic environment-induced retinal injury, including apoptosis and pyroptosis.

Investigating the Mechanisms of Pollen Typhae in the Treatment of Diabetic Retinopathy Based on Network Pharmacology and Molecular Docking

OBJECTIVE

To explore the main bioactive compounds and investigate the underlying mechanism of Pollen Typhae (PT) against diabetic retinopathy (DR) by network pharmacology and molecular docking analysis.

METHODS

Bioactive ingredients and the target proteins of PT were obtained from TCMSP, and the related target genes were acquired from the SwissTargetPrediction database. The target genes of DR were obtained from GeneCards, TTD database, DisGeNET database, and DrugBank. The compound-target interaction network was established based on Cytoscape 3.7.2. The protein-protein interaction (PPI) network was constructed via STRING database and Cytoscape 3.7.2. Gene ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were visualized through DAVID database and Bioinformatics. Ingredient-gene-pathway network analysis was conducted to further screen the ingredients, target proteins, and pathways closely related to the biological mechanism on PT for DR, and molecular docking analysis was performed by SYBYL-X 2.1.1 software. Finally, the mechanism and underlying targets of PT in the treatment of DR were predicted.

RESULTS

A total of 8 compounds and 171 intersection targets were obtained based on the online network database. 7 main compounds were screened from compound-target network, and 53 targets including the top six key targets (PTGS2, AKT1, VEGFA, MAPK3, TNF, and EGFR) were further acquired from PPI analysis. The 53 key targets covered 80 signaling pathways, among which PI3K-Akt signaling pathway, focal adhesion, Rap1 signaling pathway, VEGF signaling pathway, and HIF-1 signaling pathway were closely connected with the biological mechanism involved in the alleviation of DR by PT. Ingredient-gene-pathway network shows that AKTI, EGFR, and VEGFA were core genes, kaempferol and isorhamnetin were pivotal ingredients, and VEGF signaling pathway and Rap1 signaling pathway were closely involved in anti-DR. The docking results indicated that five main compounds (arachidonic acid, isorhamnetin, quercetin, kaempferol, and (2R)-5,7-dihydroxy-2-(4-hydroxyphenyl)chroman-4-one) had good binding activity with EGFR and AKT1 targets.

CONCLUSION

The active ingredients in PT may regulate the levels of inflammatory factors, suppress the oxidative stress, and inhibit the proliferation, migration, and invasion of retinal pericytes by acting on PTGS2, AKT1, VEGFA, MAPK3, TNF, and EGFR targets through VEGF signaling pathway, PI3K-Akt signaling pathway, Rap1 signaling pathway, and HIF-1 signaling pathway to play a therapeutic role in diabetic retinopathy.

Retinal Protein O-GlcNAcylation and the Ocular Renin-angiotensin System: Signaling Cross-roads in Diabetic Retinopathy

It is well established that diabetes and its associated hyperglycemia negatively impact retinal function, yet we know little about the role played by augmented flux through the Hexosamine Biosynthetic Pathway (HBP). This offshoot of the glycolytic pathway produces UDP-Nacetyl- glucosamine, which serves as the substrate for post-translational O-linked modification of proteins in a process referred to as O-GlcNAcylation. HBP flux and subsequent protein O-GlcNAcylation serve as nutrient sensors, enabling cells to integrate metabolic information to appropriately modulate fundamental cellular processes including gene expression. Here we summarize the impact of diabetes on retinal physiology, highlighting recent studies that explore the role of O-GlcNAcylation- induced variation in mRNA translation in retinal dysfunction and the pathogenesis of Diabetic Retinopathy (DR). Augmented O-GlcNAcylation results in wide variation in the selection of mRNAs for translation, in part, due to O-GlcNAcylation of the translational repressor 4E-BP1. Recent studies demonstrate that 4E-BP1 plays a critical role in regulating O-GlcNAcylation-induced changes in the translation of the mRNAs encoding Vascular Endothelial Growth Factor (VEGF), a number of important mitochondrial proteins, and CD40, a key costimulatory molecule involved in diabetes-induced retinal inflammation. Remarkably, 4E-BP1/2 ablation delays the onset of diabetes- induced visual dysfunction in mice. Thus, pharmacological interventions to prevent the impact of O-GlcNAcylation on 4E-BP1 may represent promising therapeutics to address the development and progression of DR. In this regard, we discuss the potential interplay between retinal O-GlcNAcylation and the ocular renin-angiotensin system as a potential therapeutic target of future interventions.

Distinct Mechanisms of Human Retinal Endothelial Barrier Modulation In Vitro by Mediators of Diabetes and Uveitis

Ocular diseases such as diabetic retinopathy (DR) and uveitis are associated with injury to the blood–retinal barrier (BRB). Whereas high glucose (HG) and advanced glycation end products (AGE) contribute to DR, bacterial infections causing uveitis are triggered by endotoxins such as lipopolysaccharide (LPS). It is unclear how HG, AGE, and LPS affect human retinal endothelial cell (HREC) junctions. Moreover, tumor necrosis factor-α (TNFα) is elevated in both DR and ocular infections. In the current study, we determined the direct effects of HG, AGE, TNFα, and LPS on the expression and intracellular distribution of claudin-5, VE-cadherin, and β-catenin in HRECs and how these mediators affect Akt and P38 MAP kinase that have been implicated in ocular pathologies. In our results, whereas HG, AGE, and TNFα activated both Akt and P38 MAPK, LPS treatment suppressed Akt but increased P38 MAPK phosphorylation. Furthermore, while treatment with AGE and HG increased cell-junction protein expression in HRECs, LPS elicited a paradoxical effect. By contrast, when HG treatment increased HREC-barrier resistance, AGE and LPS stimulation compromised it, and TNFα had no effect. Together, our results demonstrated the differential effects of the mediators of diabetes and infection on HREC-barrier modulation leading to BRB injury.

Tasquinimod efficacy and S100A9 expression in glucose-treated HREC cells

PURPOSE

Diabetic retinopathy (DR) is one of the leading causes of blindness in working-aged people. Few studies were on the relationship between S100 Calcium Binding Protein A9 (S100A9) protein and DR, and none on endothelial cells induced by tasquinimod in high glucose. Therefore, we assessed the relationship between tasquinimod and S100A9 in DR.

METHODS

DR pathogenesis was simulated using high-glucose-induced human retinal endothelial cells (HRECs) to study the mRNA expression of s100a9, thrombospondin-1 (tsp-1), hypoxia-inducible factor 1-alpha (hif1-α), intercellular adhesion molecule 1 (icam-1), and vascular endothelial growth factor (vegf) after tasquinimod treatment. The protein expression of S100A9, TSP-1, extracellular signal-regulated kinase (ERK), ICAM-1 and VEGF was also analyzed.

RESULT

A total of 28 eyes of 26 patients were included in this experiment. A significantly higher expression of S100A9 as well as enhanced proliferation and mobility was observed in the high-glucose-treated HRECs compared with that in low-glucose-treated cells. However, these were significantly inhibited when treated with high glucose with 50 μM tasquinimod. The mRNA expression of tsp-1 was increased, whereas that of hif1-α, icam-1 and vegf was decreased after tasquinimod treatment. Western blot indicated the increased TSP-1 but decreased ERK, ICAM-1 and VEGF expression after treating with tasquinimod.

CONCLUSION

High glucose promoted the expression of s100a9, S100A9 protein in DR patients and HRECs. Tasquinimod inhibited the proliferation, migration and lumen formation of HRECs under a high glucose environment. Tasquinimod might play a vital role in inhibiting angiogenesis through inducing TSP-1 and inhibiting VEGF, ICAM-1 and ERK.

PHD2 attenuates high-glucose-induced blood retinal barrier breakdown in human retinal microvascular endothelial cells by regulating the Hif-1α/VEGF pathway

OBJECTIVE

Diabetic macular edema (DME) is one of the most frequent causes of severe vision loss. The pathogenesis of DME is still not fully understood; however, it is hypothesized to result from breakdown of the blood-retinal barrier (BRB) due to retinal inflammation by vascular endothelial growth factor (VEGF) secretion under hyperglycemic conditions. In this investigation, we discovered that Prolyl-4-hydroxylase 2 (PHD2), an upstream regulator of hypoxia-inducible factor 1 (HIF-1) modulates VEGF expression and thus preserves BRB function in the mouse retina.

MATERIALS AND METHODS

Primary human retinal microvascular endothelial cells (hRMECs) were cultured in human endothelial serum-free growth medium and exposed to hyperglycemia. Changes in cell viability were investigated by an MTT assay. BRB function in each group was revealed by a paracellular permeability assay and trans-endothelial electrical resistance (TEER). Morphological changes in the BRB were investigated by immunofluorescence staining of occludin and zonula occludens-1 (ZO-1). The mRNA and protein levels of the tight junction proteins, PHD2, HIF-1α, and VEGF were measured by reverse transcription-quantitative PCR (RT-qPCR), western blot analysis and ELISA.

RESULTS

Under hyperglycemic conditions, the viability of hRMECs was decreased, and PHD2 expression was downregulated, accompanied by increased paracellular permeability and decreased trans-endothelial electrical resistance. Additionally, HIF-1α and VEGF expression levels were increased, whereas the expression levels of tight junction proteins, including occludin and ZO-1, were decreased and BRB function was compromised. The PHD2 activator R59949 (diacylglycerol kinase inhibitor II), altered these pathological changes, and the PHD2 inhibitor dimethyloxalylglycine (DMOG) resulted in the opposite effects.

CONCLUSION

These results demonstrated that PHD2 inhibited HIF-1 activity by inhibiting HIF-1α expression in hRMECs under hyperglycemic conditions, which led to the downregulation of the expression of the angiogenic factor VEGF, and thus helped to maintain the functions of hRMECs. Therefore, it is reasonable to propose that PHD2 could be a potential novel target for the treatment of DME or other diseases with a similar pathogenesis.

Diabetic neovascularization defects in the retina are improved by genistein supplementation in the ovariectomized rat

Genistein seems to have a protective and therapeutic effect on conditions associated with neovascular growth in the retina. This study investigated the angiogenesis, antioxidant, and anti-inflammatory effect of genistein on the retinas in ovariectomized diabetic rats. In this study, 40 female albino Wistar rats were divided into four groups (n = 8 per group): sham, ovariectomized group (OVX), OVX + diabetes (OVX.D), and OVX.D + genistein (OVX.D.G). OVX induced by removal of bilateral ovaries and then high-fat diet (HFD) and a low dose of streptozotocin (STZ) (1 mg/kg; intraperitoneal (IP) injection) was used for diabetes induction (OVX.D) with 8 weeks of genistein treatment (OVX.D.G). At the end of 8 weeks, the retina was removed under anesthesia. The samples were used to measure extracellular signal-regulated kinase (ERK), matrix metalloproteinase 2 (MMP-2), vascular endothelial growth factor (VEGF), and nuclear factor NF-kappa-B (NF-κB) by western blotting and inflammatory factors ELISA and oxidative stress. Measurements of glutathione (GSH) and malondialdehyde (MDA) showed that OVX and especially OVX.D significantly decreased GSH and increased MDA level in the retina, but genistein reversed these effects in OVX.D.G groups. Also, OVX and OVX.D significantly increased VEGF, MMP-2, p-ERK, NF-κB, interleukin-1beta (IL-1β), and tumor necrosis factor alpha (TNFα) expression in the retina of OVX and OVX.D groups in comparison to the sham group (p < 0.05). However, a significant reduction of these proteins was observed in the genistein-treated group (p < 0.05). In conclusion, bilateral ovariectomy and subsequently estrogen deficiency caused the development of inflammation, neovascularization, and then retinopathy in STZ-induced diabetic ovariectomized rats. On the basis of the results, genistein administration may be a practical approach for improving symptoms and complications of ovariectomized diabetic retinopathy.

Synthetic dysmobility screen unveils an integrated STK40-YAP-MAPK system driving cell migration

Integrating signals is essential for cell survival, leading to the concept of synthetic lethality. However, how signaling is integrated to control cell migration remains unclear. By conducting a "two-hit" screen, we revealed the synergistic reduction of cell migration when serine-threonine kinase 40 (STK40) and mitogen-activated protein kinase (MAPK) were simultaneously suppressed. Single-cell analyses showed that STK40 knockdown reduced cell motility and coordination by strengthening focal adhesion (FA) complexes. Furthermore, STK40 knockdown reduced the stability of yes-associated protein (YAP) and subsequently decreased YAP transported into the nucleus, while MAPK inhibition further weakened YAP activities in the nucleus to disturb FA remodeling. Together, we unveiled an integrated STK40-YAP-MAPK system regulating cell migration and introduced "synthetic dysmobility" as a novel strategy to collaboratively control cell migration.

TPTEP1 suppresses high glucose-induced dysfunction in retinal vascular endothelial cells by interacting with STAT3 and targeting VEGFA

AIMS

Diabetic retinopathy (DR) is a vascular complication of diabetes mellitus that causes visual impairment and blindness. Long noncoding RNAs (lncRNAs) have been revealed to be involved in biological processes of several diseases including DR. We designed this study to investigate the specific role of TPTEP1 in DR.

METHODS

First, we mimicked diabetic conditions with high glucose (HG) stimulation of human retinal vascular endothelial cells (HRVECs) and measured TPTEP1 expression in HG-stimulated HRVECs using RT-qPCR analysis. Then, CCK-8, Transwell, and Matrigel tube formation assays as well as western blot analysis were performed to reveal the biological functions of TPTEP1 in HG-stimulated HRVECs. Subsequently, bioinformatics analysis, RNA pull down, luciferase reporter and ChIP assays as well as western blot analysis evaluated the relationship of TPTEP1, signal transducer and activator of transcription 3 (STAT3) and vascular endothelial growth factor A (VEGFA) in HG-stimulated HRVECs. Finally, to verify the regulation of the TPTEP1/STAT3/VEGFA axis in HG-stimulated HRVECs, rescue experiments were carried out in HG-stimulated HRVECs.

RESULTS

TPTEP1 presented a significant downregulation in HG-stimulated HRVECs. Additionally, TPTEP1 overexpression reduced viability, migration, and angiogenesis in HG-stimulated HRVECs. Moreover, TPTEP1 suppressed phosphorylation and nuclear translocation of STAT3, and thereby downregulated VEGFA mRNA and protein levels. Furthermore, TPTEP1 overexpression-mediated suppression of HG-induced dysfunction in HRVECs was countervailed by STAT3 upregulation or VEGFA upregulation.

CONCLUSIONS

TPTEP1 alleviated HG-induced dysfunction in HRVECs via interacting with STAT3 and targeting VEGFA.

Role of mTOR Complex 1 Signaling Pathway in the Pathogenesis of Diabetes Complications; A Mini Review

The mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine/threonine-protein kinase that senses and combines various environmental signals to regulate the growth and homeostasis of human cells. This signaling pathway synchronizes many critical cellular processes and is involved in an increasing number of pathological conditions such as diabetes, cancer, obesity, and metabolic syndrome. Here, we review different complications of diabetes that are associated with mTOR complex 1 imbalance. We further discuss pharmacological approaches to treat diabetes complications linked to mTOR deregulation.

Inhibition of hsa_circ_0002570 suppresses high-glucose-induced angiogenesis and inflammation in retinal microvascular endothelial cells through miR-1243/angiomotin axis

Diabetic retinopathy (DR) is the most severe microvascular complication of diabetes and a major cause of visual impairment and blindness. However, the treatment for DR is still limited. Our study aimed to explore the role of circular RNA_0002570 in DR. First, we predicted the potential microRNA and mRNA that could bind to circ_0002570 and identified the miR-1243 and angiomotin gene; then, we used RT-PCR and Western blot to measure their expression. Next, we evaluated the abilities of proliferation, migration, and angiogenesis in vitro in human retinal microvascular endothelial cells (hRMECs) by CCK-8, transwell assay, and tube formation assay, respectively. To analyze the relationship among miR-1243, circ_0002570, and angiomotin, RNA pull-down and luciferase assay were performed. Our results showed that, in DR patients and high-glucose-induced hRMECs, miR-1243, circ_0002570, and angiomotin were all abnormally expressed. MiR-1243 could directly and competitively bind to both circ_0002570 and angiomotin mRNA to inhibit their expression. Moreover, circ_0002570 suppressed the abilities of proliferation, migration, and angiogenesis in hRMECs induced by high glucose, which was dependent on miR-1243-angiomotin axis. Furthermore, circ_0002570 could upregulate angiomotin by targeting miR-1243 to mediate the dysfunction of hRMECs induced by high glucose. In conclusion, circ_0002570 might serve as a potential target for diagnosis and treatment for DR.

Identification of the aberrantly methylated differentially expressed genes in proliferative diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes. Proliferative DR (PDR) is a more advanced stage of DR, which can cause severe impaired vision and even blindness. However, the precise pathological mechanisms of PDR remain unknown. DNA methylation serves an important role in the initiation and progression of numerous types of disease including PDR. The purpose of this study was to identify the aberrantly methylated differentially expressed genes (DEGs) as potential therapeutic targets of PDR. The gene expression microarray dataset GSE60436 and the methylation profiling microarray dataset GSE57362 were used to determine the aberrantly methylated DEGs in PDR, utilizing normal retinas as controls and fibrovascular membranes (FVMs) in patients with PDR as PDR samples. The functional term and signaling pathway enrichment analysis of the selected genes were subsequently performed. In addition, protein-protein interaction (PPI) networks were constructed to determine the hub genes, and the network of transcriptional factor (TF) and target hub genes was also analyzed. In total, 132 hypomethylated genes were found to be upregulated, whereas 172 hypermethylated genes were discovered to be downregulated in PDR. The hypomethylated upregulated genes were found to be enriched in the pathways, such as "cell-substrate adhesion", "adherens junction", "cell adhesion molecule binding" and "extracellular matrix receptor interactions". Meanwhile, the hypermethylated downregulated genes were enriched in the pathways, such as "visual perception", "presynapse" and the "synaptic vesicle cycle". Based on the PPI analysis, a total of eight hub genes were identified: CTGF, SERPINH1, LOX, RBP3, OTX2, RPE65, OPN1SW and NRL. It was hypothesized that the aberrant methylation of these genes might be related to the possible pathophysiology of PDR. An important transcriptional factor, TFDP1, was discovered to share the closest interactions with the hub genes from the gene-TF network. In conclusion, the present study identified an association among DNA methylation and gene expression in PDR using bioinformatics analysis, and identified the hub genes which might be potential methylation-based diagnosis and treatment targets for PDR in the near future.

Ginsenoside Re Attenuates High Glucose-Induced RF/6A Injury via Regulating PI3K/AKT Inhibited HIF-1α/VEGF Signaling Pathway

Hyperglycaemia-induced retinal microvascular endothelial cell apoptosis is a critical and principle event in diabetic retinopathy (DR), which involves a series of complex processes such as mitochondrial dysfunction and oxidative stress. Ginsenoside Re (Re), a key ingredients of ginseng, is considered to have various pharmacologic functions, such as antioxidative, inhibition of inflammation and anti-apoptotic properties. However, the effects of Re in DR and the related mechanisms of endothelial cell injury induced by high glucose (HG) exposure remain unclear. The present study was designed to investigate and evaluate the ability of Re to ameliorate HG-induced retinal endothelial RF/6A cell injury and the potential mechanisms involved in the hypoxia-inducible factor-1-alpha (HIF-1α)/vascular endothelial growth factor (VEGF) signaling regulated by phosphoinositide 3-kinase (PI3K)/AKT pathway. Our results showed that preincubation with Re exerted cytoprotective effects by reversing the HG-induced decrease in RF/6A cell viability, downregulation of apoptosis rate and inhibition of oxidative-related enzymes, thereby reducing the excess intracellular reactive oxygen species (ROS) and HG-triggered RF/6A cell injury. In addition, Western blot analysis results showed ginsenoside Re significantly increased HIF-1α expression in the cytoplasm but decreased its expression in the nucleus, suggesting that it reduced the translocation of HIF-1α from the cytoplasm to the nucleus, and downregulated VEGF level. Moreover, this effect is involved in the activation of the PI3K/Akt pathway. LY294002, a PI3K inhibitor, was used to block the Akt pathway. Afterwards, the effects of Re on the regulation of apoptotic related proteins, VEGF and HIF-1α nuclear transcription was partially reversed. These findings suggested the exerting protective effects of ginsenoside Re were associated with regulating of PI3K/AKT and HIF-1α/VEGF signaling pathway, which indicates that ginsenoside Re may ameliorates HG-induced retinal angiogenesis and suggests the potential for the development of Re as a therapeutic for DR.

The Effect and Mechanism of TRPC1, 3, and 6 on the Proliferation, Migration, and Lumen Formation of Retinal Vascular Endothelial Cells Induced by High Glucose

OBJECTIVE

Transient receptor potential canonical (TRPC) channels are involved in neovascularization repairing after vascular injury in many tissues. However, whether TRPCs play a regulatory role in the development of diabetic retinopathy (DR) has rarely been reported. In the present study, we selected TRPC1, 3, and 6 to determine their roles and mechanism in human retina vascular endothelial cells (HREC) under high glucose (HG) conditions.

METHODS

HRECs were cultured in vitro under HG, hyper osmosis, and normal conditions. The expression of TRPC1, 3, and 6 in the cells at 24 and 48 h were detected by RT-polymerase chain reaction (PCR), Western blot and cell immunohistochemistry (IHC); In various concentrations, SKF96365 acted on HG cultured HRECs, the expression of vascular endothelial growth factor (VEGF) were detected by the same methods above; and the CCK-8, Transwell, cell scratch assay, and Matrigel assay were used to assess cell proliferation, migration, and lumen formation.

RESULTS

The RT-PCR, Western blot, and IHC results showed that TRPC1 expression was increased, and TRPC6 mRNA expression was increased under high-glucose conditions. SKF96365 acted on HG cultured HRECs that VEGF expression was significantly decreased. The CCK-8 assay, Transwell assay, cell scratch assay, and Matrigel assay showed that cell proliferation, migration, and lumen formation were downregulated by SKF96365.

CONCLUSION

HG can induce increased expression of TRPC1 and 6 in HRECs. Inhibition of the TRPC pathway not only can decrease VEGF expression but also can prevent proliferation, migration, and lumen formation of HRECs induced by HG. Inhibition of TRPC channels is expected to become a drug target for DR.

Osteopontin Upregulates Col IV Expression by Repressing miR-29a in Human Retinal Capillary Endothelial Cells

Abnormal synthesis of extracellular matrix (ECM), especially collagen type IV (Col IV), in human retinal capillary endothelial cells (HRCECs) and resultant basement membrane (BM) thickening is the most prominent and characteristic feature of early diabetic retinopathy (DR). Osteopontin (OPN) has been shown to play an important role in the pathogenesis of DR and specifically, found to be critically involved in diabetic nephropathy, as it can upregulate many factors, like collagen IV. However, the precise role of OPN in the pathogenesis of DR and the underlying mechanisms remain unclear. In this study, 51 differentially expressed microRNAs (miRNAs; 42 miRNAs upregulated and 9 miRNAs downregulated) were first identified in retina of streptozotocin (STZ)-induced diabetic mice with DR. Among these miRNAs, we identified miRNA (miR)-29a as a prominent miRNA that targeted and directly downregulated Col IV expression through database prediction and dual-luciferase reporter assay, which was further confirmed in HRCECs using miR-29a mimic, miR-29a inhibitor, and pre-miR-29a transfection. Furthermore, OPN upregulated Col IV expression via a miR-29a-repressed pathway in HRCECs. Taken together, these results provided a miR-29a-repressing mechanism through which OPN plays roles in abnormal synthesis of Col IV in HRCECs and resultant BM thickening, contributing to the pathogenesis of DR.

Thrombospondin-1: A Key Protein That Induces Fibrosis in Diabetic Complications

Fibrosis accompanies most common pathophysiological features of diabetes complications in different organs. It is characterized by an excessive accumulation of extracellular matrix (ECM) components, the response to which contributes to inevitable organ injury. The extracellular protein thrombospondin-1 (TSP-1), a kind of extracellular glycoprotein, is upregulated by the increased activity of some transcription factors and results in fibrosis by activating multiple pathways in diabetes. The results of studies from our team and other colleagues indicate that TSP-1 is associated with the pathological process leading to diabetic complications and is considered to be the most important factor in fibrosis. This review summarizes the molecular mechanism of increased TSP-1 induced by hyperglycemia and the role of TSP-1 in fibrosis during the development of diabetes complications.

Downregulation of circRNA DMNT3B contributes to diabetic retinal vascular dysfunction through targeting miR-20b-5p and BAMBI

Background

Diabetic retinopathy, a vascular complication of diabetes mellitus, is the leading cause of visual impairment and blindness. circRNAs act as competing endogenous RNA, sponging target miRNA and thus influencing mRNA expression in vascular diseases. We investigated whether and how circDNMT3B is involved in retinal vascular dysfunction under diabetic conditions.

Methods

qRT-PCR was performed to detect expression of circDNMT3B, miR-20b-5p, and BAMBI in retinal microvascular endothelial cells under diabetic conditions. Western blot, Cell Counting Kit-8, Transwell, Matrigel tube formation, and retinal trypsin digestion assays were conducted to explore the roles of circDNMT3B/miR-20b-5p/BAMBI in retinal vascular dysfunction. Bioinformatics analysis and luciferase reporter, siRNA, and overexpression assays were used to reveal the mechanisms of the circDNMT3B/miR-20b-5p/BAMBI interaction. Electroretinograms were used to evaluate visual function.

Findings

Upregulation of miR-20b-5p under diabetic conditions promoted proliferation, migration, and tube formation of human retinal microvascular endothelial cells (HRMECs), which was mediated by downregulated BAMBI. Under diabetic conditions, circDNMT3B, which acts as a sponge of miR-20b-5p, is downregulated. circDNMT3B overexpression reduced retinal acellular capillary number and alleviated visual damage in diabetic rats. Changes in expression of circDNMT3B and miR-20b-5p were confirmed in the proliferative fibrovascular membranes of patients with diabetic retinopathy.

Interpretation

Downregulation of circDNMT3B contributes to vascular dysfunction in diabetic retinas through regulating miR-20b-5p and BAMBI, providing a potential treatment strategy for diabetic retinopathy.

Funding

National Natural Science Foundation of China, National Key Basic Research Program of China, Shanghai Municipal Science and Technology Major Project, and ZJLab.

Activation of endothelial ras-related C3 botulinum toxin substrate 1 (Rac1) improves post-stroke recovery and angiogenesis via activating Pak1 in mice

BACKGROUND AND PURPOSE

Long-term disability after stroke is common yet the mechanisms of post-stroke recovery are far from clear. It has been suggested that Ras-related C3 botulinum toxin substrate 1 (Rac1) contributes to functional recovery after ischemic stroke in mice. As Rac1 activation plays diverse roles in multiple cell types after central nervous system (CNS) injury, we herein examined the functional role of endothelial Rac1 in post-stroke recovery and angiogenesis.

METHODS

Transient middle cerebral artery occlusion (MCAO) in mice and oxygen-glucose deprivation (OGD) in human brain endothelial cell line-5i (HEBC 5i) were performed to mimic ischemic stroke. Lentivirus vectors encoding Rac1 with GFP and endothelial promotor ENG were injected into the animal's brain after stroke to overexpress Rac1. After injection, stroke recovery was tested by multiple behavioral tests including novel object recognition, adhesive removal and single pellet reaching tests. Endothelial regeneration in the peri-infarct zone was detected by immunohistochemistry (IHC). In the vitro model, the effect of Rac1 and Pak1 inhibitors to cell proliferation and migration was examined by CCK-8 and wound healing assays after OGD. The cellular protein level of brain-derived neurotrophic factor (BDNF), phosphorylated cAMP response element-binding protein (CREB), extracellular signal-regulated kinase (ERK) 1/2 and mitogen-activated protein kinase kinase (MEK) 1/2 were detected by western blots.

RESULTS

Delayed overexpression of endothelial Rac1 after MCAO improved cognitive and sensorimotor recovery from day 14 to 21 after stroke, increased vascular density and the protein level of pericytes in the peri-infarct zone without altering tissue loss in mice. Consistently, inhibition of Rac1 prevented endothelial proliferation and migration after OGD. Pak1 inhibition exerted a similar effect on endothelial cells. However, co-incubation of Rac1 and Pak1 inhibitors with cells did not lead to additive effects when compared with either inhibitor alone. Moreover, individual inhibition of Rac1 or Pak1 suppressed OGD-induced activation of pro-regenerative molecules, including CREB, MEK1/2 and ERK1/2, as well as the production of BDNF in vitro. The level of these proteins did not further decrease if both Rac1 and Pak1 were simultaneously inhibited.

CONCLUSIONS

We conclude that activation of endothelial Rac1 improves functional recovery and angiogenesis after stroke, and this process is mediated by Pak1 signaling. This study provides novel insight for Rac1 in the mechanism of long-term stroke recovery.

[T-786C endothelial nitric oxide gene polymorphism and type 1 diabetic retinopathy in the Algerian population]

INTRODUCTION

Diabetic retinopathy (DR) results from interactions between genetic and environmental factors. We were interested in the endothelial nitric oxide gene (eNOS), given the involvement of this enzyme in functional alterations in the retinal microvasculature in diabetes. The goal of our study was to assess the association of T-786C endothelial nitric oxide synthase (eNOS) gene polymorphism with diabetic retinopathy in the Algerian population.

PATIENTS AND METHODS

Our study enrolled 110 patients with and without DR. All subjects were genotyped for the T786C eNOS polymorphism using the PCR-RFLP method. We also investigated the association between this polymorphism and certain clinical and laboratory characteristics of patients with DR.

RESULTS

A significant increase in the frequency of the CC genotype is noted in subjects without DR (P=0.03). We also report a significant increase in the frequencies of the TT+TC genotypes in individuals with DR (P=0.03). However, the association between the different genotypes and clinical or laboratory profiles in patients with DR reveals that the NO level is lower in subjects carrying the TT genotype (P=0.039).

CONCLUSION

Our preliminary results suggest that the CC genotype could confer protection from type 1 diabetic retinopathy in the Algerian population, while the T allele seems to confer susceptibility.

Time-lapse microscopy of oxidative stress demonstrates metabolic sensitivity of retinal pericytes under high glucose condition

Hyperglycemia affects retinal vascular cell function, promotes the development and progression of diabetic retinopathy and ultimately causes vision loss. Oxidative stress, reactive oxygen species (ROS) in excess, is a key biomarker for diabetic retinopathy. Using time-lapse fluorescence microscopy, ROS dynamics was monitored and the metabolic resistivity of retinal endothelial cells (REC) and pericytes (RPC) was compared under metabolic stress conditions including high glucose (HG). In the presence of a mitochondrial stressor, REC exhibited a significant increase in the rate of ROS production compared with RPC. Thus, under normal glucose (NG), REC may utilize oxidative metabolism as the bioenergetic source, while RPC metabolic activity is independent of mitochondrial respiration. In HG condition, the rate of ROS production in RPC was significantly higher, whereas this rate remained unchanged in REC. Thus, under HG condition RPC may preferentially utilize oxidative metabolism, which results in increased rate of ROS production. In contrast, REC use glycolysis as their major bioenergetic source for ATP production, and consequently HG minimally affects their ROS levels. These observations are consistent with our previous studies where we showed HG condition has minimal effect on apoptosis of REC, but results in increased rate of apoptosis in RPC. Collectively, our results suggest that REC and RPC exhibit different metabolic activity preferences under different glucose conditions. Thus, protection of RPC from oxidative stress may provide an early point of intervention in development and progression of diabetic retinopathy.

Fetoplacental endothelial exosomes modulate high d-glucose-induced endothelial dysfunction

INTRODUCTION

Gestational diabetes mellitus (GDM) is associated with fetoplacental endothelial dysfunction, which may be induced by hyperglycemia. We hypothesized that endothelial exosomes, which are extracellular nanovesicles affecting endothelial function, play a role in the high glucose (HG)-induced endothelial dysfunction.

METHODS

Exosomes were isolated from HUVECs incubated with basal glucose (5.5 mmol/L; HUVEC- BG; exo-BG) and from HUVECs incubated with HG for 24 h (25 mmol/L; HUVEC-HG; exo-HG) in exosome-free medium. Exosomes were isolated and characterized by ultracentrifugation, sucrose gradient, electron microscopy, nanotracking analysis and Western blotting. HUVEC-BG and HUVEC-HG were exposed to exo-BG and exo-HG in two different concentrations: 5 μg and 1 μg exosome protein/mL. The exosomal effect on endothelial cell function was determined by wound healing assay, expression of endothelial nitric oxide synthase (eNOS), human cationic amino acid transporter type 1 (hCAT-1), vascular endothelial growth factor (VEGF) and intracellular adhesion molecule type 1 (ICAM-1) by Western blotting, qPCR or flow cytometry.

RESULTS

HG increased the exosomal release from HUVECs, endothelial wound healing and expression of phosphorylated (P∼Ser¹¹⁷⁷)-eNOS, hCAT-1, VEGF and ICAM-1. Exo-HG also increased endothelial cell wound healing, P∼Ser¹¹⁷⁷-eNOS, hCAT-1 and ICAM-1 expression in HUVEC-BG. Exo-BG reverted the effect of HG on endothelial cell wound healing and hCAT-1 mRNA expression to normal values.

DISCUSSION

Our results show that HG may induce endothelial dysfunction in HUVECs and that exosomes from HUVEC-HG mimicked some of the effects of HG. This study contributes to the unraveling of the mechanism by which hyperglycemia affects the fetoplacental vasculature in GDM.

Identification of the functional pathways altered by placental cell exposure to high glucose: lessons from the transcript and metabolite interactome

The specific consequences of hyperglycaemia on placental metabolism and function are incompletely understood but likely contribute to poor pregnancy outcomes associated with diabetes mellitus (DM). This study aimed to identify the functional biochemical pathways perturbed by placental exposure to high glucose levels through integrative analysis of the trophoblast transcriptome and metabolome. The human trophoblast cell line, BeWo, was cultured in 5 or 25 mM glucose, as a model of the placenta in DM. Transcriptomic analysis using microarrays, demonstrated 5632 differentially expressed gene transcripts (≥± 1.3 fold change (FC)) following exposure to high glucose. These genes were used to generate interactome models of transcript response using BioGRID (non-inferred network: 2500 nodes (genes) and 10541 protein-protein interactions). Ultra performance-liquid chromatography-mass spectrometry (MS) and gas chromatography-MS analysis of intracellular extracts and culture medium were used to assess the response of metabolite profiles to high glucose concentration. The interactions of altered genes and metabolites were assessed using the MetScape interactome database, resulting in an integrated model of systemic transcriptome (2969 genes) and metabolome (41 metabolites) response within placental cells exposed to high glucose. The functional pathways which demonstrated significant change in response to high glucose included fatty acid β-oxidation, phospholipid metabolism and phosphatidylinositol phosphate signalling.

Glucose dilates renal afferent arterioles via glucose transporter-1

Glomerular hyperfiltration occurs during the early stage of diabetes. An acute glucose infusion increases glomerular filtration rate. The involvement of tubuloglomerular feedback response and direct effect of glucose on the afferent arterioles (Af-Arts) have been suggested. However, the signaling pathways to trigger Af-Art dilatation have not been fully identified. Therefore, in the present study we tested our hypothesis that an increase in glucose concentration enhances endothelial nitric oxide synthesis activity and dilates the Af-Arts via glucose transporter-1 (GLUT1) using isolated mouse Af-Arts with perfusion. We isolated and microperfused the Af-Arts from nondiabetic C57BL/6 mice. The Af-Arts were preconstricted with norepinephrine (1 µM). When we switched the d-glucose concentration from low (5 mM) to high (30 mM) in the perfusate, the preconstricted Af-Arts significantly dilated by 37.8 ± 7.1%, but L-glucose did not trigger the dilation. GLUT1 mRNA was identified in microdisserted Af-Arts measured by RT-PCR. Changes in nitric oxide (NO) production in Af-Art were also measured using fluorescent probe when ambient glucose concentration was increased. When the d-glucose concentration was switched from 5 to 30 mM, NO generation in Af-Art was significantly increased by 19.2 ± 6.2% (84.7 ± 4.1 to 101.0 ± 9.3 U/min). l-Glucose had no effect on the NO generation. The GLUT1-selective antagonist 4-[({[4-(1,1-Dimethylethyl)phenyl]sulfonyl}amino)methyl]- N-3-pyridinylbenzamide and the nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester blocked the high glucose-induced NO generation and vasodilation. In conclusion, we demonstrated that an increase in glucose concentration dilates the Af-Art by stimulation of the endothelium-derived NO production mediated by GLUT1.

Association of plasma osteopontin with diabetic retinopathy in Asians with type 2 diabetes

Purpose

Osteopontin (OPN) is a proinflammatory cytokine with diverse functions. Increased levels of OPN in vitreous fluid have been reported in patients with diabetic retinopathy (DR); however, studies on circulating OPN levels in DR are limited. We aim to examine the association of plasma OPN levels with the presence and severity of DR in a multiethnic cohort with type 2 diabetes mellitus (type 2 diabetes) in Singapore.

Methods

Plasma levels of OPN were measured using enzyme-linked immunosorbent assay. Digital color fundus photographs were assessed for DR. DR severity was categorized into non-proliferative DR (NPDR) and proliferative DR (PDR). Gradable fundus photographs and OPN measurements for 443 patients were used for analysis. A logistic regression model was used to evaluate the association of OPN with DR.

Results

DR was diagnosed in 174 (39.3%) patients, including 132 (75.9%) with NPDR and 42 (24.1%) with PDR. The median of OPN was higher in the patients with DR (64.7 [49.7-89.5] ng/ml) than in the patients without DR (51.7 [38.9-66.9] ng/ml; p<0.001). After adjustment for clinical and biochemical factors, a 1-unit increase in nature logarithm (ln)-transformed OPN was associated with the presence of DR (2.770 [1.599-3.800], p<0.001). The area under the curve (AUC) increased statistically significantly after the addition of OPN (0.805[0.763-0.846] versus 0.825 [0.785-0.865], p=0.011). In the severity analyses, the median of OPN was statistically significantly higher in the patients with PDR (76.8 [55.0-103.6] ng/ml) than in the patients with NPDR (61.7 [47.7-87.3] ng/ml; p=0.017). After adjustment, the 1-unit increase in lnOPN remained associated with NPDR (2.673 [1.519-4.704], p=0.001) and PDR (3.389 [1.254-9.226], p=0.017), respectively (p-trend=0.001).

Conclusions

Plasma OPN levels were associated with the presence and severity of DR in patients with type 2 diabetes, suggesting OPN may be useful as a potential biomarker for DR.

O-Linked β-N-acetylglucosamine (O-GlcNAc) modification: a new pathway to decode pathogenesis of diabetic retinopathy

The incidence of diabetes continues to rise among all ages and ethnic groups worldwide. Diabetic retinopathy (DR) is a complication of diabetes that affects the retinal neurovasculature causing serious vision problems, including blindness. Its pathogenesis and severity is directly linked to the chronic exposure to high glucose conditions. No treatments are currently available to stop the development and progression of DR. To develop new and effective therapeutic approaches, it is critical to better understand how hyperglycemia contributes to the pathogenesis of DR at the cellular and molecular levels. We propose alterations in O-GlcNAc modification of target proteins during diabetes contribute to the development and progression of DR. The O-GlcNAc modification is regulated through hexosamine biosynthetic pathway. We showed this pathway is differentially activated in various retinal vascular cells under high glucose conditions perhaps due to their selective metabolic activity. O-GlcNAc modification can alter protein stability, activity, interactions, and localization. By targeting the same amino acid residues (serine and threonine) as phosphorylation, O-GlcNAc modification can either compete or cooperate with phosphorylation. Here we will summarize the effects of hyperglycemia-induced O-GlcNAc modification on the retinal neurovasculature in a cell-specific manner, providing new insight into the role of O-GlcNAc modification in early loss of retinal pericytes and the pathogenesis of DR.

Negative Regulators of Angiogenesis, Ocular Vascular Homeostasis, and Pathogenesis and Treatment of Exudative AMD

Angiogenesis, the formation of new blood vessels from pre-existing capillaries, is very tightly regulated and normally does not occur except during developmental and reparative processes. This tight regulation is maintained by a balanced production of positive and negative regulators, and alterations under pathological conditions such as retinopathy of prematurity, diabetic retinopathy, and age-related macular degeneration can lead to growth of new and abnormal blood vessels. Although the role of proangiogenic factors such as vascular endothelial growth factor has been extensively studied, little is known about the roles of negative regulators of angiogenesis in the pathogenesis of these diseases. Here, we will discuss the role of thrombospondin-1 (TSP1), one of the first known endogenous inhibitors of angiogenesis, in ocular vascular homeostasis, and how its alterations may contribute to the pathogenesis of age-related macular degeneration and choroidal neovascularization. We will also discuss its potential utility as a therapeutic target for treatment of ocular diseases with a neovascular component.

Thioredoxin-interacting protein deficiency ameliorates diabetic retinal angiogenesis

Diabetic retinopathy is the leading cause of blindness among working-aged adults around the world. Hyperglycemia and intraocular vascular endothelial growth factor (VEGF) over-accumulation are essential for the progression of diabetic retinopathy, which eventually results in proliferative diabetic retinopathy, characterized by pathologic angiogenesis and impaired vision. Thioredoxin-interacting protein (TXNIP) was highly induced in retinal endothelial cells under diabetic conditions. However, the role of TXNIP in diabetes-associated retinal angiogenesis remains elusive. Here, we investigated whether the absence of TXNIP alters diabetes-associated retinal angiogenesis. Exposure of human retinal microvascular endothelial cells (HRMECs) to moderately high glucose (MHG) promoted cell migration and tube formation, but not proliferation. Knockdown of TXNIP suppressed moderately high glucose (MHG)-induced reactive oxygen species (ROS) generation, migration, tube formation and activation of Akt/mTOR pathway in HRMECs. Moreover, gene silencing of TXNIP inhibited VEGF-induced angiogenic response by blocking VEGFR2 and downstream signal pathway Akt/mTOR activation in HRMECs. Furthermore, TXNIP knockout inhibited VEGF or VEGF and MHG-induced retinal angiogenesis ex vivo compared with wild-type mice. In conclusion, our study demonstrated that TXNIP deficiency inhibited VEGF or/and MHG-induced angiogenic response in HRMECs and mice retinas and suggested TXNIP may be a potential therapy target for treating proliferative diabetic retinopathy.

LncRNA NONRATT021972 siRNA normalized the dysfunction of hepatic glucokinase through AKT signaling in T2DM rats

Hepatic glucokinase (GK) expression and activity are decreased in type 2 diabetes mellitus (T2DM), and glycogen synthase kinase-3 (GSK-3) inhibits the synthesis of GK. In hepatocytes, the activation of the protein kinase B (PKB/AKT) signaling pathway enhances GK expression and inhibits the phosphorylation of GSK-3β. The dysfunction of certain long noncoding RNAs (lncRNAs) has been associated with a variety of diseases.

AIMS

This study explored the effects of the lncRNA NONRATT021972 small interfering RNA (siRNA) on the dysfunction of hepatic GK through AKT signaling in T2DM rats.

METHODS

Livers from type 2 diabetic rats and hepatocytes cultured in high glucose and high fatty acid media were studied. The changes in expression of AKT, GK and GSK 3β were detected by western blotting or RT-PCR. The application of bioinformatics technology (CatRAPID) was used to identify the targets of NONRATT021972 RNA.

RESULTS

We found that lncRNA NONRATT021972 levels in the liver were increased in type 2 diabetic rats, and the increase was associated with an increase in the blood glucose levels. The NONRATT021972 siRNA enhanced phospho-AKT (p-AKT) levels, GK expression and hepatic glycogen synthesis. This siRNA also reduced phospho-glycogen synthase kinase-3β (p-GSK-3β) levels and hyperglycemia in T2DM rats, as well as in hepatocytes cultured in high glucose media with fatty acids. CatRAPID predicted that there was the interaction between NONRATT021972 and p-AKT.

CONCLUSIONS

LncRNA NONRATT021972 siRNA may have beneficial effects on T2DM.

Kaempferol inhibited VEGF and PGF expression and in vitro angiogenesis of HRECs under diabetic-like environment

Diabetic retinopathy (DR) is one of the common and specific microvascular complications of diabetes. This study aimed to investigate the anti-angiogenic effect of kaempferol and explore its underlying molecular mechanisms. The mRNA expression level of vascular endothelial growth factor (VEGF) and placenta growth factor (PGF) and the concentrations of secreted VEGF and PGF were measured by qTR-PCR and ELISA assay, respectively. Human retinal endothelial cells (HRECs) proliferation, migration, and sprouting were measured by CCK-8 and transwell, scratching wound, and tube formation assays, respectively. Protein levels were determined by western blot. High glucose (25 mM) increased the mRNA expression levels of VEGF and PGF as well as the concentrations of secreted VEGF and PGF in HRECs, which can be antagonized by kaempferol (25 µM). Kaempferol (5-25 µM) significantly suppressed cell proliferation, migration, migration distance and sprouting of HRECs under high glucose condition. The anti-angiogenic effect of kaempferol was mediated via downregulating the expression of PI3K and inhibiting the activation of Erk1/2, Src, and Akt1. This study indicates that kaempferol suppressed angiogenesis of HRECs via targeting VEGF and PGF to inhibit the activation of Src-Akt1-Erk1/2 signaling pathway. The results suggest that kaempferol may be a potential drug for better management of DR.

Autophagy in Diabetic Retinopathy

Autophagy is an important homeostatic cellular process encompassing a number of consecutive steps indispensable for degrading and recycling cytoplasmic materials. Basically autophagy is an adaptive response that under stressful conditions guarantees the physiological turnover of senescent and impaired organelles and, thus, controls cell fate by various cross-talk signals. Diabetic retinopathy (DR) is a serious microvascular complication of diabetes and accounts for 5% of all blindness. Although, various metabolic disorders have been linked with the onset of DR, due to the complex character of this multi-factorial disease, a connection between any particular defect and DR becomes speculative. Diabetes increases inflammation, advanced glycation end products (AGEs) and oxidative stress in the retina and its capillary cells. Particularly, a great number of evidences suggest a mutual connection between oxidative stress and other major metabolic abnormalities implicated in the development of DR. In addition, the intricate networks between autophagy and apoptosis establish the degree of cellular apoptosis and the progression of DR. Growing data underline the crucial role of reactive oxygen species (ROS) in the activation of autophagy. Depending on their delicate balance both redox signaling and autophagy, being detrimental or beneficial, retain opposing effects. The molecular mechanisms of autophagy are very complex and involve many signaling pathways cooperating at various steps. This review summarizes recent advances of the possible molecular mechanisms in autophagic process that are involved in pathophysiology of DR. In-depth analysis on the molecular mechanisms leading to autophagy in the retinal pigment epithelial (RPE) will be helpful to plan new therapies aimed at preventing or improving the progression of DR.

High glucose promotes the migration of retinal pigment epithelial cells through increased oxidative stress and PEDF expression

Defects in the outer blood-retinal barrier have significant impact on the pathogenesis of diabetic retinopathy and macular edema. However, the detailed mechanisms involved remain largely unknown. This is, in part, attributed to the lack of suitable animal and cell culture models, including those of mouse origin. We recently reported a method for the culture of retinal pigment epithelial (RPE) cells from wild-type and transgenic mice. The RPE cells are responsible for maintaining the integrity of the outer blood-retinal barrier whose dysfunction during diabetes has a significant impact on vision. Here we determined the impact of high glucose on the function of RPE cells. We showed that high glucose conditions resulted in enhanced migration and increased the level of oxidative stress in RPE cells, but minimally impacted their rate of proliferation and apoptosis. High glucose also minimally affected the cell-matrix and cell-cell interactions of RPE cells. However, the expression of integrins and extracellular matrix proteins including pigment epithelium-derived factor (PEDF) were altered under high glucose conditions. Incubation of RPE cells with the antioxidant N-acetylcysteine under high glucose conditions restored normal migration and PEDF expression. These cells also exhibited increased nuclear localization of the antioxidant transcription factor Nrf2 and ZO-1, reduced levels of β-catenin and phagocytic activity, and minimal effect on production of vascular endothelial growth factor, inflammatory cytokines, and Akt, MAPK, and Src signaling pathways. Thus high glucose conditions promote RPE cell migration through increased oxidative stress and expression of PEDF without a significant effect on the rate of proliferation and apoptosis.

Erythropoietin-activated mesenchymal stem cells promote healing ulcers by improving microenvironment

BACKGROUND

Mesenchymal stem cell (MSC) transplantation is an effective treatment therapy for ischemic ulcers. However, in high-glucose microenvironment, the original inflammation-inhibiting function of MSCs leads to turns into secreting large amounts of inflammatory mediators, such as tumor necrosis factor alpha, for example, which decreases their capacity and becomes poor quality stem cells over inflammation cells for diabetic foot ulcers repair in the healing of diabetic foot ulcers. Erythropoietin (EPO) is an anti-inflammatory, proangiogenic cytokine. It is unclear whether EPO-activated MSCs with biomaterials can promote the effective healing of diabetic foot ulcers.

METHODS

Cultivated MSCs in MSC-L, MSC-H, EPO-G, Akt-G, and mTOR-G, then separated the supernatant-conditioned medium of these groups to stimulate human umbilical vein endothelial cells on proliferation and migration experiments; a new type of biomaterial planted with the EPO-activated MSCs was applied to the diabetic foot ulcers of the C57 mice.

RESULTS

In vitro experiments showed that EPO could stimulate MSCs to secrete vascular endothelial growth factor in high-glucose microenvironment. More importantly, EPO could reduce the damage to MSCs by high-glucose microenvironment, promote their proliferation and migration functions, and inhibit the high-glucose-induced MSCs from secreting the inflammatory mediator tumor necrosis factor alpha. In vivo experiments showed greater angiogenesis in EPO-MSC group than in control group, ulcer healing in EPO-MSC group was significantly better than that in control group, and MSCs partially differentiated into endothelial cells. EPO-activated MSCs could inhibit the monocyte invasion of localized diabetic foot ulcers.

CONCLUSIONS

Our results indicate that EPO-activated MSCs can promote the effective healing of diabetic foot ulcers. The mechanism is that EPO can change stem cells from excessive inflammation into general inflammation and improved diabetic foot ulcers inflammatory microenvironment.

VEGF-B inhibits hyperglycemia- and Macugen-induced retinal apoptosis

Vascular endothelial growth factor B (VEGF-B) was discovered a long time ago. However, its role in hyperglycemia- and VEGF-A inhibition-induced retinal apoptosis remains unknown thus far. Yet, drugs that can block VEGF-B are being used to treat patients with diabetic retinopathy and other ocular neovascular diseases. It is therefore urgent to have a better understanding of the function of VEGF-B in these pathologies. Here, we report that both streptozotocin (STZ)-induced diabetes in rats and Macugen intravitreal injection in mice leads to retinal apoptosis in retinal ganglion cell and outer nuclear layers respectively. Importantly, VEGF-B treatment by intravitreal injection markedly reduced retinal apoptosis in both models. We further reveal that VEGF-B and its receptors, vascular endothelial growth factor 1 (VEGFR1) and neuropilin 1 (NP1), are abundantly expressed in rat retinae and choroids and are upregulated by high glucose with concomitant activation of Akt and Erk. These data highlight an important function of VEGF-B in protecting retinal cells from apoptosis induced by hyperglycemia and VEGF-A inhibition. VEGF-B may therefore have a therapeutic potential in treating various retinal degenerative diseases, and modulation of VEGF-B activity in the eye needs careful consideration.

c-Src tyrosine kinase mediates high glucose-induced endothelin-1 expression

Endothelin-1 (ET-1) plays an important role in the pathophysiology of diabetes-associated cardiovascular disorders. The molecular mechanisms leading to ET-1 upregulation in diabetes are not entirely defined. c-Src tyrosine kinase regulates important pathophysiological aspects of vascular response to insults. In this study, we aimed to elucidate whether high glucose-activated c-Src signaling plays a role in the regulation of ET-1 expression. Human endothelial cells EAhy926 (ECs) were exposed to normal or high levels of glucose for 24h. Male C57BL/6J mice were rendered diabetic with streptozotocin and then treated with a specific c-Src inhibitor (Src I1) or c-Src siRNA. Real-time PCR, Western blot, and ELISA, were used to investigate ET-1 regulation. The c-Src activity and expression were selectively downregulated by pharmacological inhibition and siRNA-mediated gene silencing, respectively. High glucose dose-dependently up-regulated c-Src phosphorylation and ET-1 gene and protein expression levels in human ECs. Chemical inhibition or silencing of c-Src significantly decreased the high-glucose augmented ET-1 expression in cultured ECs. In vivo studies showed significant elevations in the aortic ET-1 mRNA expression and plasma ET-1 concentration in diabetic mice compared to non-diabetic animals. Treatment with Src I1, as well as in vivo silencing of c-Src, significantly reduced the upregulated ET-1 expression in diabetic mice. These data provide new insights into the regulation of ET-1 expression in endothelial cells in diabetes. Pharmacological targeting of c-Src activity and/or expression may represent a potential therapeutic strategy to reduce ET-1 level and to counteract diabetes-induced deleterious vascular effects.

Lipid peroxidation is associated with poor control of type-2 diabetes mellitus

BACKGROUND

Hyperglycemia increases oxidative stress through the overproduction of reactive oxygen species, which results in an imbalance between free radicals and the antioxidant defense system of the cells. A positive correlation was reported between lipid peroxide levels and diabetic complication.

OBJECTIVES

The aim of the present study was to investigate the state of oxidative stress in controlled and uncontrolled diabetic patients.

METHODS

One hundred thirty nine participants were included in this study, grouped as: Group-I: Healthy Control group of non-diabetic normal subjects, Group-II: Controlled type-2 DM group of subjects with type-2 DM and HbA1c≤8% and Group-III: Uncontrolled type-2 DM group of subjects with type-2 DM and HbA1c>8%. Fasting blood glucose, 2h postprandial glucose, MDA and HbA1c were quantified. The association between diabetic control and lipid peroxidation (malondialdehyde) was evaluated.

RESULTS

The mean HbA1c increased significantly in uncontrolled type-2 DM subjects compared to controlled type-2 DM group. Lipid peroxidation as expressed in MDA was significantly increased in uncontrolled type-2 DM group compared to controlled type-2 DM, both groups show significant elevation in this parameter compared to healthy subjects. There is a significant positive correlation between MDA and HbA1c in the studied subjects.

CONCLUSION

The core problem during diabetes is poor glycemic control, which leads to protein glycation, lipid peroxidation, oxidative stress and finally varieties of complications. Periodic evaluation of lipid peroxidation products in diabetes mellitus is recommended as it could contribute to the early identification and management of oxidative stress.

Silencing Matrix Metalloproteinases 9 and 2 Inhibits Human Retinal Microvascular Endothelial Cell Invasion and Migration

PURPOSE

Proliferative retinal angiogenesis may severely impair the retina. Previous studies have indicated that matrix metalloproteinase (MMP)-2 and MMP-9 play important roles in the process of retinal angiogenesis. In this study, we suppressed MMP-2 and MMP-9 expression with RNA interference (RNAi) and then observed the inhibitory effects on the invasion and migration of human retinal microvascular endothelial cells (HRMECs).

METHODS

Small interfering RNAs against MMP-2 mRNA and MMP-9 mRNA were synthesized. After transfection, the MMP-2 and MMP-9 expression in HRMECs was examined by real-time polymerase chain reaction and Western blot analysis. Cell migration and invasion were measured with a migration assay and a scratch wound assay, respectively.

RESULTS

RNAi against MMP-2 and MMP-9 successfully inhibited the mRNA and protein expression of MMP-2 and MMP-9 in HRMECs. MMP-2 and MMP-9 knockdown could inhibit the invasion and migration of HRMECs.

CONCLUSIONS

These findings suggest that the RNAi approach towards MMP-2 and MMP-9 may be a potentially effective therapeutic method for the treatment of proliferative retinal angiogenesis.

c-MYC responds to glucose deprivation in a cell-type-dependent manner

Metabolic reprogramming supports cancer cells’ demands for rapid proliferation and growth. Previous work shows that oncogenes, such as MYC, hypoxia-inducible factor 1 (HIF1), have a central role in driving metabolic reprogramming. A lot of metabolic enzymes, which are deregulated in most cancer cells, are the targets of these oncogenes. However, whether metabolic change affects these oncogenes is still unclear. Here we show that glucose deprivation (GD) affects c-MYC protein levels in a cell-type-dependent manner regardless of P53 mutation status. GD dephosphorylates and then decreases c-MYC protein stability through PI3K signaling pathway in HeLa cells, but not in MDA-MB-231 cells. Role of c-MYC in sensitivity of GD also varies with cell types. c-MYC-mediated glutamine metabolism partially improves the sensitivity of GD in MDA-MB-231 cells. Our results reveal that the heterogeneity of cancer cells in response to metabolic stress should be considered in metabolic therapy for cancer.

Interaction of the EGF Receptor and the Hippo Pathway in the Diabetic Kidney

Activation of the EGF receptor (EGFR) or the Hippo signaling pathway can control cell proliferation, apoptosis, and differentiation, and the dysregulation of these pathways can contribute to tumorigenesis. Previous studies showed that activation of EGFR signaling in renal epithelial cells can exacerbate diabetic kidney injury. Moreover, EGFR has been implicated in regulating the Hippo signaling pathway in Drosophila; thus, we examined this potential interaction in mammalian diabetic kidney disease. Yes-associated protein (YAP) is a transcriptional regulator regulated by the Hippo signaling pathway. We found YAP protein expression and phosphorylation were upregulated in diabetic mouse renal proximal tubule epithelial cells, which were inhibited in diabetic proximal tubule EGFR-knockout mice (EGFR(ptKO)) or administration of an EGFR tyrosine kinase inhibitor erlotinib. Furthermore, activation of an EGFR-PI3K-Akt-CREB signaling pathway mediated YAP gene expression and YAP nuclear translocation and interaction with the TEA domain (TEAD) transcription factor complex, which led to upregulated expression of two TEAD-dependent genes, the connective tissue growth factor and amphiregulin genes. In a renal proximal tubule cell line, either pharmacologic or genetic inhibition of EGFR, Akt, or CREB blunted YAP expression in response to high-glucose treatment. Additionally, knocking down YAP expression by specific siRNA inhibited cell proliferation in response to high glucose or exogenous EGF. Therefore, these results link the Hippo pathway to EGFR-mediated renal epithelial injury in diabetes.