Papel do fator de crescimento vascular endotelial na angiogênese e na retinopatia diabética

Effect of chronic exposure to fine particulate matter on cardiac tissue of NZBWF1 mice

Epidemiological and toxicological studies have shown that inhalation of particulate matter (PM) is associated with development of cardiovascular diseases. Long-term exposure to PM may increase the risk of cardiovascular events and reduce life expectancy. Systemic lupus erythematosus (SLE) is a chronic inflammatory disease, autoimmune in nature, that is characterized by the production of autoantibodies that affects several organs, including the heart. Air pollution - which can be caused by several different factors - may be one of the most important points both at the onset and the natural history of SLE. Therefore this study aims to investigate whether exposure to air pollution promotes increased inflammation and cardiac remodelling in animals predisposed to SLE. Female NZBWF1 mice were exposed to an environmental particle concentrator. Aspects related to cardiac remodelling, inflammation and apoptosis were analysed in the myocardium. Body weight gain, cardiac trophism by heart/body weight ratio, relative area of cardiomyocytes and the fibrotic area of cardiac tissue were evaluated during the exposure period. Animals exposed to PM2.5 showed increased area of cardiomyocytes, and area of fibrosis; in addition, we observed an increase in IL-1 and C3 in the cardiac tissue, demonstrating increased inflammation. We suggest that air pollution is capable of promoting cardiac remodelling and increased inflammation in animals predisposed to SLE.

A comparison between the therapeutic effects of Conbercept combined with panretinal photocoagulation and panretinal photocoagulation monotherapy for high-risk proliferative diabetic retinopathy

OBJECTIVE

To compare the therapeutic effects of the administration of intravitreal Conbercept (IVC) plus panretinal photocoagulation (PRP) to that of PRP monotherapy in patients with high-risk proliferative diabetic retinopathy (PDR).

METHODS

In this retrospective consecutive case series, we analyzed the data on high-risk PDR patients followed up for 12 months. Patients were divided into two groups: the IVC+PRP group and the PRP monotherapy group. Patients in the IVC+PRP group were initially administered 3 IVC injections and PRP, while patients in the PRP monotherapy group received PRP only. Depending on the grouping criteria, patients in both groups were administered either IVC+PRP or PRP only if the neovascularization (NV) did not regress. From the initiation to month 12 of treatment, we recorded and compared the data on the NV regression rate, improvement in best-corrected visual acuity (BCVA), laser spots, changes in central macular thickness (CMT), complications, and the need for vitrectomy for all patients.

RESULTS

In this study, 79 eyes of 58 patients in the IVC+PRP group and 86 eyes of 60 patients in the PRP monotherapy group were included. During the follow-up of 12 months, the number of eyes with complete regression, partial regression, and no regression or increase in NV were 56 (70.88%), 23 (29.12%), and 0 (0%) in the IVC+PRP group and 13 (15.12%), 50 (58.14%), and 23 (26.74%) in the PRP group (p < 0.001). The BCVA was significantly higher and CMT was lower in the patients of the IVC+PRP group than in the PRP monotherapy group at 3, 6, and 12 months of follow-up (p < 0.05). The mean number of laser spots was lower in the patients of the IVC+PRP group than in the PRP group (1,453 ± 87 spots vs. 2,267 ± 94 spots, p < 0.05). A significantly lower percentage of patients in the IVC+PRP group underwent vitrectomy than that in the PRP group (7 (8.86%) vs. 27 (31.40%), p < 0.001).

CONCLUSION

High-risk PDR patients treated with IVC + PRP showed a higher rate of NV regression, more effective improvement in the BCVA, and lower vitrectomy rate compared to those who were administered PRP monotherapy.

The effects of Bushen Yiqi Huoxue prescription and its disassembled prescriptions on a diabetic retinopathy model in Sprague Dawley rats

BACKGROUND

Diabetic retinopathy (DR) is one of the most serious complications in the late stages of diabetes, with a complex mechanism. As a complication affecting local lesions, few studies have compared differences of cytokine expression in the serum and retina. Owing to the specific value of traditional Chinese medicine (TCM) to complex diseases, TCM research has recently boomed in the prevention and treatment of diabetes. Bushen Yiqi Huoxue (BYH) prescription is a Chinese herbal compound that has been independently developed by our research group and has been proved to have a positive effect on DR; however, its specific mechanism and compatibility rule remain to be further explored.

OBJECTIVE

To construct a DR model of Sprague Dawley (SD) rats, simultaneously detect multiple factor expression in the serum and retina of rats, explore the effect of BYH prescription and its disassembled prescriptions on DR, and discuss the influence of various compatibility combinations.

METHODS

BYH prescription was disassembled into two new compatibilities in the absence of Rehmanniae Radix (Yiqi Huoxue prescription, YH prescription) or Ginseng Radix et Rhizoma (Bushen Huoxue prescription, BH prescription). Male SD rats were induced using streptozotocin + high-fat and high-sugar diet to establish DR models and were divided into groups, then the intragastric administration and sampling. The body weight and fasting blood glucose of rats were continuously recorded during feeding; pathophysiological status observation of the retina by haematoxylin and eosin (HE) staining; advanced glycation end products (AGEs) and haemoglobin A1c (HbA1c) level detection in the rat serum by enzyme-linked immunosorbent assay; and the Luminex technique was used to detect the ICAM-1, IL-1β, IL-6, TNF-α and vascular endothelial growth factor (VEGF) expression concentrations in the retinal tissue and serum.

RESULTS

The results of blood glucose, body weight and HE staining proved that the model was successfully constructed, and the three combinations could reduce the retinal injury in DR rats. Serum AGEs and HbA1c levels of the model group increased compared with the control group (CG). Compared with the DR model group, only AGEs decreased in the BYH group, while the AGEs and HbA1c levels were significantly inhibited in the YH and BH groups, showing a significant correlation between the expression of AGEs and HbA1c in the serum of DR rats. In the serum of rats, IL-1β, IL-6, TNF-α and VEGF concentrations in the DR model group increased, although no statistical difference was observed in the ICAM-1 data compared with the CG. Compared with the DR model group, the IL-1β, IL-6 and TNF-α expression decreased in the BYH group. Moreover, the IL-6 and TNF-α expression decreased in the YH group and only the IL-6 expression decreased in the BH group. In the retina tissue, the model group had higher ICAM-1, IL-1β, IL-6, TNF-α and VEGF levels than the CG. Compared with the DR model group, TNF-α in the BYH group rats decreased, and the ICAM-1, IL-6 and TNF-α concentrations decreased in the YH and BH groups. Furthermore, differences in the ICAM-1 and VEGF expression in the serum and retina existed.

CONCLUSION

BYH compound and its disassembled prescriptions could improve the DR model rats induced with streptozotocin + high-fat and high-sugar diet, respectively, by inhibiting chronic blood glucose, AGEs, or inflammation response. The expression level and location of each factor are different, confirming that the effect of TCM prescriptions is not the simple addition of each single drug or its chemical components, but the rationality of its internal compatibility combination. Further, ICAM-1 and VEGF have exactly different expression levels, suggesting more attention to be paid by other researchers or doctors in future studies.

Recent advances in intraocular and novel drug delivery systems for the treatment of diabetic retinopathy

Introduction: Diabetic retinopathy (DR) is associated with damage to the retinal blood vessels that lead eventually to vision loss. The existing treatments of DR are invasive, expensive, and cumbersome. To overcome challenges associated with existing therapies, various intraocular sustained release and novel drug delivery systems (NDDS) have been explored.Areas covered: The review discusses recently developed intraocular devices for sustained release of drugs as well as novel noninvasive drug delivery systems that have met a varying degree of success in local delivery of drugs to retinal circulation.Expert opinion: The intraocular devices have got very good success in providing sustained release of drugs in patients. The development of NDDS and their application through the ocular route has certainly provided an edge to treat DR over existing therapies such as anti-VEGF administration but their success rate is quite low. Moreover, most of them have proved to be effective only in animal models. In addition, the extent of targeting the drug to the retina still remains variable and unpredictable. The toxicity aspect of the NDDS has generally been neglected. In order to have successful commercialization of nanotechnology-based innovations well-designed clinical research studies need to be conducted to evaluate their clinical superiority over that of the existing formulations.

MicroRNA-15b Targets VEGF and Inhibits Angiogenesis in Proliferative Diabetic Retinopathy

BACKGROUND

Vascular endothelial growth factor (VEGF)-induced angiogenesis is a critical compensatory response to microvascular rarefaction in the diabetic retina that contributes to proliferative diabetic retinopathy (PDR). In this study, we sought to determine the role of specific micro ribonucleic acids (RNAs) (miRs) associated with VEGF in patients with PDR pathology.

METHODS

RNA sequencing was employed to detect differentially circulating miR associated with VEGF in patients with diabetes mellitus (DM), nonproliferative diabetic retinopathy (NPDR) and PDR. Quantitative real-time polymerase chain reaction was performed to measure the concentration of miR-15b in the serum of patients with DM (n = 115), NPDR (n = 47), or PDR (n = 76). The effects of miR-15b on DR and regulation of VEGF and endothelial cell function were also characterized.

RESULTS

We demonstrated that circulating miR-15b was directly associated with VEGF compared with other miRs in patients with PDR. We found a significant inverse relationship between low levels of miR-15b and high levels of VEGF in patients with PDR when compared with the DM or NPDR groups. We found that miR-15b regulates the expression of VEGF by targeting the 3'-untranslated regions to inhibit its transcription. Similarly, overexpression of miR-15b suppressed vascular abnormalities in vivo in diabetic GK rats, inhibiting endothelial tube formation and VEGF expression.

CONCLUSION

Circulating miR-15b is associated with PDR and may be targeted to regulate VEGF expression and angiogenesis.

Melatonin regulates the expression of inflammatory cytokines, VEGF and apoptosis in diabetic retinopathy in rats

The present study analyzed whether melatonin could mediate the expression of VEGF, IL-6 and TNF-α, as well as the apoptotic index in rats with diabetic retinopathy. Fifty Wistar albino rats were divided into the following groups: GC: rats without induction of diabetes by streptozotocin; GD: rats induced to diabetes by streptozotocin and treated with placebo; GDM: rats induced to diabetes by streptozotocin and after confirmation treated with melatonin at a dose of 10 mg/kg for 20 days; GDMS: rats induced to diabetes by streptozotocin and treated simultaneously with melatonin at a dosage of 10 mg/kg for 20 days; GDI: rats induced to diabetes by streptozotocin and after confirmation treated with insulin for 20 days. Diabetes was induced by intraperitoneal injections of streptozotocin (60 mg/kg), and insulin (5 U/day) was administered subcutaneously. For apoptosis TUNEL was used, while for the analysis of VEGF, IL-6 and TNF-α. The results showed that the groups that were treated with melatonin decreased the expression of cytokines and VEGF, in addition to apoptosis. Thus, it is concluded that melatonin can regulate the expression of these factors by improving the condition of the retina in diabetic retinopathy.

Suppression of pathological ocular neovascularization by a small molecule, SU1498

Selective inhibition of vascular endothelial growth factor receptor (VEGFR), particularly VEGFR-2, is an efficient method for the treatment of ocular neovascularization. SU1498 is a specific inhibitor of VEGFR-2. In this study, we investigated the role of SU1498 in ocular neovascularization. Administration of SU1498 did not show any cytotoxicity and tissue toxicity at the tested concentrations. Administration of SU1498 reduced the size and thickness of choroidal neovascularization and decreased the mean length and mean number of corneal neovascular vessels induced by alkali burn. Pretreatment of SU1498 significantly reduced the proliferation, migration, and tube formation ability of HUVECs. SU1498 played the anti-angiogenic role through the regulation of p38-MAPK signaling. Taken together, inhibition of VEGFR-2 by SU1498 provides a novel therapeutic approach for ocular neovascularization.

Intranasal delivery of VEGF enhances compensatory lung growth in mice

Vascular endothelial growth factor (VEGF) has previously been demonstrated to accelerate compensatory lung growth (CLG) in mice and may be a useful therapy for pulmonary hypoplasia. Systemic administration of VEGF can result in side effects such as hypotension and edema. The aim of this study was to explore nasal delivery as a route for intrapulmonary VEGF administration. Eight-week-old C57BL/6 male mice underwent left pneumonectomy, followed by daily nasal instillation of VEGF at 0.5 mg/kg or isovolumetric saline. Lung volume measurement, morphometric analysis, and protein expression studies were performed on lung tissues harvested on postoperative day (POD) 4. To understand the mechanism by which VEGF accelerates lung growth, proliferation of human bronchial epithelial cells (HBEC) was assessed in a co-culture model with lung microvascular endothelial cells (HMVEC-L) treated with and without VEGF (10 ng/mL). The assay was then repeated with a heparin-binding EGF-like growth factor (HB-EGF) neutralizing antibody ranging from 0.5-50 μg/mL. Compared to control mice, the VEGF-treated group displayed significantly higher lung volume (P = 0.001) and alveolar count (P = 0.005) on POD 4. VEGF treatment resulted in increased pulmonary expression of HB-EGF (P = 0.02). VEGF-treated HMVEC-L increased HBEC proliferation (P = 0.002) while the addition of an HB-EGF neutralizing antibody at 5 and 50 μg/mL abolished this effect (P = 0.01 and 0.002, respectively). These findings demonstrate that nasal delivery of VEGF enhanced CLG. These effects could be mediated by a paracrine mechanism through upregulation of HB-EGF, an epithelial cell mitogen.

Current Advances in Pharmacotherapy and Technology for Diabetic Retinopathy: A Systematic Review

Diabetic retinopathy (DR) is classically defined by its vascular lesions and damage in the neurons of the retina. The cellular and clinical elements of DR have many features of chronic inflammation. Understanding the individual cell-specific inflammatory changes in the retina may lead to novel therapeutic approaches to prevent vision loss. The systematic use of available pharmacotherapy has been reported as a useful adjunct tool to laser photocoagulation, a gold standard therapy for DR. Direct injections or intravitreal anti-inflammatory and antiangiogenesis agents are widely used pharmacotherapy to effectively treat DR and diabetic macular edema (DME). However, their effectiveness is short term, and the delivery system is often associated with adverse effects, such as cataract and increased intraocular pressure. Further, systemic agents (particularly hypoglycemic, hypolipidemic, and antihypertensive agents) and plants-based drugs have also provided promising treatment in the progression of DR. Recently, advancements in pluripotent stem cells technology enable restoration of retinal functionalities after transplantation of these cells into animals with retinal degeneration. This review paper summarizes the developments in the current and potential pharmacotherapy and therapeutic technology of DR. Literature search was done on online databases, PubMed, Google Scholar, clinitrials.gov, and browsing through individual ophthalmology journals and leading pharmaceutical company websites.

Role of microRNA-29a in the development of diabetic retinopathy by targeting AGT gene in a rat model

OBJECTIVES

This study intends to explore the role of microRNA-29a (miRNA-29a) in the development of diabetic retinopathy by targeting AGT gene in a rat model.

METHODS

Fifty-six DR rat models were established and divided into 7 groups (with 8 rats in each group): the model group, the miRNA-29a group, the miRNA-29a knockdown group, the negative control (NC) group, the AGT group, the miRNA-29a+AGT group, and the miRNA-29a knockdown+AGT group respectively, while 8 normal rats were selected as the normal group. The qRT-PCR was used to detect the expression of miRNA-29a and AGT mRNA. The AGT protein expression was measured using Western blotting. The ADPase histochemical staining was applied to detect retinal neo-vascular morphology. The number of retinal vascular endothelial cells was counted by H&E staining.

RESULTS

MiRNA-29a and AGT mRNA expressions were negatively correlated. Compared with rats in the normal group, the miRNA-29a expression in DR rats of each group decreased, but the AGT mRNA and protein expression increased; the vascular distribution was in disorder, and the new retinal vessels, vascular density, and endothelial nuclei all increased. Compared with the model group, miRNA-29a increased, and the AGT mRNA and protein expression decreased in the miRNA-29a group; additionally, the vascular density, tortuosity, and endothelial cell nuclei significantly decreased. The opposite trend was found in the miRNA-29a knockdown group, the miRNA-29a knockdown+AGT group, and the AGT group, particularly in the miRNA-29a knockdown+AGT group.

CONCLUSION

Overexpression of miRNA-29a could down-regulate AGT expression, thereby preventing the development of DR in a rat model.

MiR-20b targets AKT3 and modulates vascular endothelial growth factor-mediated changes in diabetic retinopathy

Diabetic retinopathy (DR) is the leading cause of new-onset blindness. The roles of microRNAs in diabetic retinopathy are largely unknown. The aim of this study is to investigate the role of miR-20b in DR. Transfection of miR-20b mimic in high glucose (HG)-treated human retinal endothelial cells (HRECs) increased miR-20b expression and decreased the expression level of VEGF mRNA, while transfection of miR-20b inhibitor in control HRECs reduced the miR-20b expression with a corresponding increase of VEGF mRNA. In vitro functional assay showed that transfection of miR-20b mimic prevented HG-induced increase in transendothelial permeability and tube formation in HRECs. Transfection of miR-20b inhibitor or treatment of VEGF increased transendothelial permeability and tube formation in control HRECs. Luciferase reported assay showed that AKT3 is a target of miR-20b. Transfection of miR-20b mimic prevented the up-regulation of AKT3 induced by HG without changing the protein levels of other isoforms of AKT, and silencing of AKT3 caused decrease of VEGF mRNA and protein levels as well as prevented HG-induced increase in transendothelial permeability and tube formation. Finally, we showed that miR-20b was down-regulated in the retina and retinal endothelial cells in diabetic rats, with a correlated up-regulation of VEGF and AKT3. Intravitreal injection of miR-20b mimic in the diabetic rat significantly increased the miR-20b expression and decreased the expression levels of AKT3 and VEGF in the retina tissues, and intravitreal delivery of AKT3 siRNA in the diabetic rat significantly decreased the expressions of AKT3 and VEGF. Collectively, miR-20b is important for the regulation of VEGF-mediated changes in HRECs and rat retinal tissues under hyperglycemic conditions possibly via targeting AKT3.

Nitric oxide in the normal kidney and in patients with diabetic nephropathy

Nitric oxide (NO) is a gas with biological and regulatory properties, produced from arginine by the way of nitric oxide synthases (NOS), and with a very short half-life (few seconds). A "coupled" NOS activity leads to NO generation, whereas its uncoupling produces the reactive oxygen species peroxynitrite (ONOO(-)). Uncoupling is usually due to inflammation, oxidative stress, decreased cofactor availability, or excessive NO production. Competitive inhibitors of NO production are post-translationally methylated arginine residues in proteins, which are constantly released into the circulation. NO availability is altered in many clinical conditions associated with vascular dysfunction, such as diabetes mellitus. The kidney plays an important role in body NO homeostasis. This article provides an overview of current literature, on NO production/availability, with a focus on diabetic nephropathy. In diabetes, NO availability is usually decreased (with exception of the early, hyper filtration phase of nephropathy in Type 1 diabetes), and it could constitute a factor of the generalized vasculopathy present in diabetic nephropathy. NO generation in Type 2 diabetes with nephropathy is inversely associated with the dimethyl-arginine concentrations, which are therefore important modulators of NO synthesis independently from the classic stimulatory pathways (such as the insulin effect). A disturbed NO metabolism is present in diabetes associated with nephropathy. Although modulation of NO production is not yet a common therapeutical strategy, a number of yet experimental compounds need to be tested as potential interventions to treat the vascular dysfunction and nephropathy in diabetes, as well as in other diseased states. Finally, in diabetic nephropathy NO deficiency may be associated to that of hydrogen sulfide, another interesting gaseous mediator which is increasingly investigated.

Nitric oxide system and diabetic nephropathy

About 30% of patients with type 2 diabetes mellitus develop clinically overt nephropathy. Hyperglycemia is necessary, but not sufficient, to cause the renal damage that leads to kidney failure. Diabetic nephropathy (DN) is a multifactorial disorder that results from interaction between environmental and genetic factors. In the present article we will review the role of the nitric oxide synthase (NOS) in the pathogenesis of DN.Nitric oxide (NO) is a short-lived gaseous lipophilic molecule produced in almost all tissues, and it has three distinct genes that encode three NOS isoforms: neuronal (nNOS), inducible (iNOS) and endothelial (eNOS).The correct function of the endothelium depends on NO, participating in hemostasis control, vascular tone regulation, proliferation of vascular smooth muscle cells and blood pressure homeostasis, among other features. In the kidney, NO plays many different roles, including control of renal and glomerular hemodynamics. The net effect of NO in the kidney is to promote natriuresis and diuresis, along with renal adaptation to dietary salt intake.The eNOS gene has been considered a potential candidate gene for DN susceptibility. Three polymorphisms have been extensively researched: G894T missense mutation (rs1799983), a 27-bp repeat in intron 4, and the T786C single nucleotide polymorphism (SNP) in the promoter (rs2070744). However, the potential link between eNOS gene variants and the induction and progression of DN yielded contradictory results in the literature.In conclusion, NOS seems to be involve in the development and progression of DN. Despite the discrepant results of many studies, the eNOS gene is also a good candidate gene for DN.

Decursin inhibited proliferation and angiogenesis of endothelial cells to suppress diabetic retinopathy via VEGFR2

Diabetes induces pathologic proliferation and angiogenesis in the retina that leads to catastrophic loss of vision. Decursin is a novel therapeutic that targets the vascular endothelial growth factor (VEGF) receptor (VEGFR) with putative anti-proliferative and anti-angiogenic activities. Thereby we utilized human retinal microvascular endothelial cells (HRMEC) and human umbilical vein endothelial cells (HUVEC) under conditions of excess glucose to explore dose-dependent responses of decursin on markers of migration, angiogenesis, and proliferation. Decursin dose-dependently inhibited tube formation, VEGFR-2 expression, along with relative metabolic activity and 5-bromo-2'-deoxy-uridine (BrdU) activity in both cell lines. We then correlated our findings to the streptozotocin-induced rat model of diabetes. Following three months of decursin treatment VEGFR-2 expression was significantly inhibited. Our data would suggest that decursin may be a potent anti-angiogenic and anti-proliferative agent targeting the VEGFR-2 signaling pathway, which significantly inhibits diabetic retinal neovascularization.

Effects of intravitreal injection of KH902, a vascular endothelial growth factor receptor decoy, on the retinas of streptozotocin-induced diabetic rats

AIMS

KH902 is a fusion protein that can bind vascular endothelial growth factor (VEGF) and placental growth factor (PlGF) through its binding ligand taken from the domains of VEGF receptor 1 and VEGF receptor 2 (VEGFR2). This study was to investigate the effects of intravitreal injection of KH902 on the retinas of streptozotocin-induced diabetic rats.

METHODS

Two weeks after induction of diabetes, the left eyes of diabetic rats in each group received an intravitreal injection of phosphate-buffered saline (PBS), Avastin or KH902 solution, respectively. Four weeks after intravitreal injection, retinal electrophysiological function and the integrity of inner blood retinal barrier (iBRB) were measured by electroretinogram and Evans blue perfusion. The protein levels of VEGF signal pathway were assayed by western blot. The expression and distribution of claudin-5 and occludin were analysed by double immunofluorescent staining under confocal microscope. The expression of VEGFR2 and PlGF was measured by immunohistochemistry.

RESULTS

Four weeks after intravitreal injection, KH902-treated rats had better retinal electrophysiological function, less retinal vessel leakage and lower levels of VEGFR2, PI3K, AKT, p-AKT, p-ERK and p-SRC than PBS or Avastin-treated rats. The distribution of claudin-5 and occludin in the retinal vessels of diabetic rats treated by KH902 was smoother and more uniform than those of diabetic rats treated by PBS or Avastin. The expression of PlGF and VEGFR2 in KH902-treated rats was decreased compared with those in PBS or Avastin-treated rats.

CONCLUSIONS

KH902 could improve retinal electrophysiological function and inhibit the breakdown of iBRB by inhibiting the expression of VEGFR2, PlGF and PI3K, and the activation of SRC, AKT and ERK.