Secretogranin III: a diabetic retinopathy-selective angiogenic factor

Optimal Humanized Scg3-Neutralizing Antibodies for Anti-Angiogenic Therapy of Diabetic Retinopathy

Secretogranin III (Scg3) is a diabetic retinopathy (DR)-restricted angiogenic factor identified in preclinical studies as a target for DR therapy. Previously, our group generated and characterized ML49.3, an anti-Scg3 monoclonal antibody (mAb) which we then converted into an EBP2 humanized antibody Fab fragment (hFab) with potential for clinical application. We also generated anti-Scg3 mT4 mAb and related EBP3 hFab. In this study, to identify the preferred hFab for DR therapy, we compared all four antibodies for binding, neutralizing and therapeutic activities in vitro and in vivo. Octet binding kinetics analyses revealed that ML49.3 mAb, EBP2 hFab, mT4 mAb and EBP3 hFab have Scg3-binding affinities of 35, 8.7, 0.859 and 0.116 nM, respectively. Both anti-Scg3 EBP2 and EBP3 hFabs significantly inhibited Scg3-induced proliferation and migration of human umbilical vein endothelial cells in vitro, and alleviated DR vascular leakage and choroidal neovascularization with high efficacy. Paired assays in DR mice revealed that intravitreally injected EBP3 hFab is 26.4% and 10.3% more effective than EBP2 hFab and aflibercept, respectively, for ameliorating DR leakage. In conclusion, this study confirms the markedly improved binding affinities of hFabs compared to mAbs and further identifies EBP3 hFab as the preferred antibody to develop for anti-Scg3 therapy.

Genipin relieves diabetic retinopathy by down-regulation of advanced glycation end products via the mitochondrial metabolism related signaling pathway

BACKGROUND

Glycation is an important step in aging and oxidative stress, which can lead to endothelial dysfunction and cause severe damage to the eyes or kidneys of diabetics. Inhibition of the formation of advanced glycation end products (AGEs) and their cell toxicity can be a useful therapeutic strategy in the prevention of diabetic retinopathy (DR). Gardenia jasminoides Ellis (GJE) fruit is a selective inhibitor of AGEs. Genipin is an active compound of GJE fruit, which can be employed to treat diabetes.

AIM

To confirm the effect of genipin, a vital component of GJE fruit, in preventing human retinal microvascular endothelial cells (hRMECs) from AGEs damage in DR, to investigate the effect of genipin in the down-regulation of AGEs expression, and to explore the role of the CHGA/UCP2/glucose transporter 1 (GLUT1) signal pathway in this process.

METHODS

In vitro, cell viability was tested to determine the effects of different doses of glucose and genipin in hRMECs. Cell Counting Kit-8 (CCK-8), colony formation assay, flow cytometry, immunofluorescence, wound healing assay, transwell assay, and tube-forming assay were used to detect the effect of genipin on hRMECs cultured in high glucose conditions. In vivo, streptozotocin (STZ) induced mice were used, and genipin was administered by intraocular injection (IOI). To explore the effect and mechanism of genipin in diabetic-induced retinal dysfunction, reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-d-glucose (2-NBDG) assays were performed to explore energy metabolism and oxidative stress damage in high glucose-induced hRMECs and STZ mouse retinas. Immunofluorescence and Western blot were used to investigate the expression of inflammatory cytokines [vascular endothelial growth factor (VEGF), SCG3, tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1β, IL-18, and nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing 3 (NLRP3)]. The protein expression of the receptor of AGEs (RAGE) and the mitochondria-related signal molecules CHGA, GLUT1, and UCP2 in high glucose-induced hRMECs and STZ mouse retinas were measured and compared with the genipin-treated group.

RESULTS

The results of CCK-8 and colony formation assay showed that genipin promoted cell viability in high glucose (30 mmol/L D-Glucose)-induced hRMECs, especially at a 0.4 μmol/L dose for 7 d. Flow cytometry results showed that high glucose can increase apoptosis rate by 30%, and genipin alleviated cell apoptosis in AGEs-induced hRMECs. A high glucose environment promoted ATP, ROS, MMP, and 2-NBDG levels, while genipin inhibited these phenotypic abnormalities in AGEs-induced hRMECs. Furthermore, genipin remarkably reduced the levels of the pro-inflammatory cytokines TNF-α, IL-1β, IL-18, and NLRP3 and impeded the expression of VEGF and SCG3 in AGEs-damaged hRMECs. These results showed that genipin can reverse high glucose induced damage with regard to cell proliferation and apoptosis in vitro, while reducing energy metabolism, oxidative stress, and inflammatory injury caused by high glucose. In addition, ROS levels and glucose uptake levels were higher in the retina from the untreated eye than in the genipin-treated eye of STZ mice. The expression of inflammatory cytokines and pathway protein in the untreated eye compared with the genipin-treated eye was significantly increased, as measured by Western blot. These results showed that IOI of genipin reduced the expression of CHGA, UCP2, and GLUT1, maintained the retinal structure, and decreased ROS, glucose uptake, and inflammation levels in vivo. In addition, we found that SCG3 expression might have a higher sensitivity in DR than VEGF as a diagnostic marker at the protein level.

CONCLUSION

Our study suggested that genipin ameliorates AGEs-induced hRMECs proliferation, apoptosis, energy metabolism, oxidative stress, and inflammatory injury, partially via the CHGA/UCP2/GLUT1 pathway. Control of advanced glycation by IOI of genipin may represent a strategy to prevent severe retinopathy and vision loss.

Retinal Cell Damage in Diabetic Retinopathy

Diabetic retinopathy (DR), the most common microvascular complication that occurs in diabetes mellitus (DM), is the leading cause of vision loss in working-age adults. The prevalence of diabetic retinopathy is approximately 30% of the diabetic population and untreated DR can eventually cause blindness. For decades, diabetic retinopathy was considered a microvascular complication and clinically staged by its vascular manifestations. In recent years, emerging evidence has shown that diabetic retinopathy causes early neuronal dysfunction and neurodegeneration that may precede vascular pathology and affect retinal neurons as well as glial cells. This knowledge leads to new therapeutic strategies aiming to prevent dysfunction of retinal neurons at the early stage of DR. Early detection and timely treatment to protect retinal neurons are critical to preventing visual loss in DR. This review provides an overview of DR and the structural and functional changes associated with DR, and discusses neuronal degeneration during diabetic retinopathy, the mechanisms underlying retinal neurodegeneration and microvascular complications, and perspectives on current and future clinic therapies.

Fluorescence Angiography with Dual Fluorescence for the Early Detection and Longitudinal Quantitation of Vascular Leakage in Retinopathy

BACKGROUND

Diabetic retinopathy (DR) afflicts more than 93 million people worldwide and is a leading cause of vision loss in working adults. While DR therapies are available, early DR development may go undetected without treatment due to the lack of sufficiently sensitive tools. Therefore, early detection is critically important to enable efficient treatment before progression to vision-threatening complications. A major clinical manifestation of early DR is retinal vascular leakage that may progress from diffuse to more localized focal leakage, leading to increased retinal thickness and diabetic macular edema (DME). In preclinical research, a hallmark of DR in mouse models is diffuse retinal leakage without increased thickness or DME, which limits the utility of optical coherence tomography and fluorescein angiography (FA) for early detection. The Evans blue assay detects diffuse leakage but requires euthanasia, which precludes longitudinal studies in the same animals.

METHODS

We developed a new modality of ratiometric fluorescence angiography with dual fluorescence (FA-DF) to reliably detect and longitudinally quantify diffuse retinal vascular leakage in mouse models of induced and spontaneous DR.

RESULTS

These studies demonstrated the feasibility and sensitivity of FA-DF in detecting and quantifying retinal vascular leakage in the same mice over time during DR progression in association with chronic hyperglycemia and age.

CONCLUSIONS

These proof-of-concept studies demonstrated the promise of FA-DF as a minimally invasive method to quantify DR leakage in preclinical mouse models longitudinally.

Inhibitory effect of anti-Scg3 on corneal neovascularization: a preliminary study

BACKGROUND

Corneal neovascularization (CNV) is an important disease that causes blindness. Secretogranin III (Scg3) has emerged as a new influencing factor of neovascularization. This study analyzed the Scg3 antibody's inhibitory effect on CNV and and explored its preliminary mechanism.

METHODS

Human umbilical vein endothelial cells (HUVECs) were treated with Scg3 and anti-Scg3. Cell proliferation, wound healing migration and tube formation assays were performed. Healthy adult New Zealand rabbits were randomly selected to be alkali burned and establish the corneal neovascularization (CNV) model. The rabbits were randomly divided into 3 groups (the high concentration group, low concentration group and control group). Different doses of anti-Scg3 and PBS were administered to the rabbits. Clinical examinations, immunostaining, quantitative real-time polymerase chain reaction (qPCR) and western blotting analyses were performed postoperatively.

RESULTS

In the in vitro study, the Scg3 antibody mixture inhibited Scg3-induced endothelial cell proliferation and angiogenesis. In the in vivo study, significant CNV was observed in the control group. Confocal microscopy also revealed considerable active neovascularization in the control group. There was no obvious CNV growth in the high concentration group. Additionally, CD31, LYVE1 and CD45 expression was significantly inhibited after treatment with a high concentration of Scg3 antibody. The qPCR and western blotting analyses revealed that the levels of ERK in the low concentration group and high concentration group were higher than those in the control group at 7 days and 14 days. The levels of VEGF in the control group were significantly increased compared with those in the high concentration group. In all three groups, the levels of Akt were not significantly different at any time point.

CONCLUSION

The expression of Scg3 could affect the growth of HUVECs in vitro. Treatment with a high concentration (0.5 µg/mL) of Scg3 antibody reduced the inflammatory response and inhibited the growth of corneal neovascularization after corneal alkali burn injury in rabbits. The MEK/ERK pathway might play an important role in the inhibitory effect of anti-Scg3.

The pathophysiological mechanisms underlying diabetic retinopathy

Diabetic retinopathy (DR) is the most common complication of diabetes mellitus (DM), which can lead to visual impairment and even blindness in severe cases. DR is generally considered to be a microvascular disease but its pathogenesis is still unclear. A large body of evidence shows that the development of DR is not determined by a single factor but rather by multiple related mechanisms that lead to different degrees of retinal damage in DR patients. Therefore, this article briefly reviews the pathophysiological changes in DR, and discusses the occurrence and development of DR resulting from different factors such as oxidative stress, inflammation, neovascularization, neurodegeneration, the neurovascular unit, and gut microbiota, to provide a theoretical reference for the development of new DR treatment strategies.

Angiogenic footprints in diabetic retinopathy: opportunities for drug development

Diabetic retinopathy is one of the withering disorders that has been making the lives of patients miserable. Arising as a result of chronic high blood sugar levels in diabetes patients, retinopathy has become a major reason causing permanent blindness, retinal detachment, vitreous humor, rage, or glaucoma among patients. Angiogenesis being the major culprit behind the development of this condition is the growth of new blood vessels from the earlier ones existing. The abnormal growth and poor development of blood vessels also lead to aggravation of the conditions, with vascular endothelial growth factor (VEGF) playing a major role in the process. Various anti-angiogenic therapies or anti-VEGF therapies are being explored for the treatment of this condition. 4 widely explored drugs being-Bevacizumab, pegaptanib sodium, ranibizumab, and aflibercept. The review article tries to summarize studies illustrating the efficacy of these drugs in the treatment of diabetic retinopathy along with some of the herbal therapeutic paradigms displaying anti-angiogenic action that is being used to treat this condition.

COVID-19 and alcohol use disorder: putative differential gene expression patterns that might be associated with neurological complications

BACKGROUND

Several lines of evidence suggest that SARS-CoV-2 invasion of the central nervous system leads to meningitis and encephalopathy syndromes. Additionally, chronic alcoholics were found to be at a higher risk of developing mental health problems and serious neurological manifestations, if exposed to SARS-CoV-2 infection.

METHODS

Herein, we studied RNA seq data from alcoholics' brain tissue and COVID-19 patient's brain tissue to identify the common differentially expressed genes.

RESULTS

Overlap analysis depicted the expression of seven genes (GHRL, SLN, VGF, IL1RL1, NPTX2, PDYN, and RPRML) that were significantly upregulated in both groups. Along with these, protein-protein interaction analysis revealed 10 other key molecules with strong interactions with the aforementioned genes.

CONCLUSIONS

Taken together with the functional effect of these genes, we suggest a strong molecular link between COVID-19-induced severities and neurological impairment in patients suffering from alcohol abuse disorder. These findings emphasize the importance of identifying chronic alcoholism as a risk factor for developing cognitive and memory impairment in COVID-19 patients.

Neurovascular abnormalities in retinopathy of prematurity and emerging therapies

Blood vessels in the developing retina are formed in concert with neural growth, resulting in functional neurovascular network. Disruption of the neurovascular coordination contributes to the pathogenesis of retinopathy of prematurity (ROP), a potentially blinding retinal neovascular disease in preterm infants that currently lacks an approved drug therapy in the USA. Despite vasculopathy as predominant clinical manifestations, an increasing number of studies revealed complex neurovascular interplays among neurons, glial cells and blood vessels during ROP. Coordinated expression of glia-derived vascular endothelial growth factor (VEGF) in spatio-temporal gradients is pivotal to the formation of well-organized vascular plexuses in the healthy retina, whereas uncoordinated VEGF expression triggers pathological angiogenesis with disorganized vascular tufts in ROP. In contrast with VEGF driving both pathological and physiological angiogenesis, neuron-derived angiogenic factor secretogranin III (Scg3) stringently regulates ROP but not healthy retinal vessels in animal models. Anti-VEGF and anti-Scg3 therapies confer similar high efficacies to alleviate ROP in preclinical studies but are distinct in their disease selectivity and safety. This review discusses neurovascular communication among retinal blood vessels, neurons and glial cells during retinal development and ROP pathogenesis and summarizes the current and emerging therapies to address unmet clinical needs for the disease.

Secretogranin III stringently regulates pathological but not physiological angiogenesis in oxygen-induced retinopathy

Conventional angiogenic factors, such as vascular endothelial growth factor (VEGF), regulate both pathological and physiological angiogenesis indiscriminately, and their inhibitors may elicit adverse side effects. Secretogranin III (Scg3) was recently reported to be a diabetes-restricted VEGF-independent angiogenic factor, but the disease selectivity of Scg3 in retinopathy of prematurity (ROP), a retinal disease in preterm infants with concurrent pathological and physiological angiogenesis, was not defined. Here, using oxygen-induced retinopathy (OIR) mice, a surrogate model of ROP, we quantified an exclusive binding of Scg3 to diseased versus healthy developing neovessels that contrasted sharply with the ubiquitous binding of VEGF. Functional immunohistochemistry visualized Scg3 binding exclusively to disease-related disorganized retinal neovessels and neovascular tufts, whereas VEGF bound to both disorganized and well-organized neovessels. Homozygous deletion of the Scg3 gene showed undetectable effects on physiological retinal neovascularization but markedly reduced the severity of OIR-induced pathological angiogenesis. Furthermore, anti-Scg3 humanized antibody Fab (hFab) inhibited pathological angiogenesis with similar efficacy to anti-VEGF aflibercept. Aflibercept dose-dependently blocked physiological angiogenesis in neonatal retinas, whereas anti-Scg3 hFab was without adverse effects at any dose and supported a therapeutic window at least 10X wider than that of aflibercept. Therefore, Scg3 stringently regulates pathological but not physiological angiogenesis, and anti-Scg3 hFab satisfies essential criteria for development as a safe and effective disease-targeted anti-angiogenic therapy for ROP.

Selectively targeting disease-restricted secretogranin III to alleviate choroidal neovascularization

Choroidal neovascularization (CNV), a leading cause of blindness in the elderly, is routinely treated with vascular endothelial growth factor (VEGF) inhibitors that have limited efficacy and potentially adverse side effects. An unmet clinical need is to develop novel therapies against other angiogenic factors for alternative or combination treatment to improve efficacy and safety. We recently described secretogranin III (Scg3) as a disease-selective angiogenic factor, causally linked to diabetic retinopathy and acting independently of the VEGF pathway. An important question is whether such a disease-selective Scg3 pathway contributes to other states of pathological angiogenesis beyond diabetic retinopathy. By applying a novel in vivo endothelial ligand binding assay, we found that the binding of Scg3 to CNV vessels in live mice was markedly increased over background binding to healthy choriocapillaris and blocked by an Scg3-neutralizing antibody, whereas VEGF showed no such differential binding. Intravitreal injection of anti-Scg3 humanized antibody Fab (hFab) inhibited Matrigel-induced CNV with similar efficacy to the anti-VEGF drug aflibercept. Importantly, a combination of anti-Scg3 hFab and aflibercept synergistically alleviated CNV. Homozygous deletion of the Scg3 gene markedly reduced CNV severity and abolished the therapeutic activity of anti-Scg3 hFab, but not aflibercept, suggesting a role for Scg3 in VEGF-independent CNV pathogenesis and therapy. Our work demonstrates the stringent disease selectivity of Scg3 binding and positions anti-Scg3 hFab as a next-generation disease-targeted anti-angiogenic therapy for CNV.

Macrophage Heterogeneity in the Intestinal Cells of Salmon: Hints From Transcriptomic and Imaging Data

The intestine has many types of cells that are present mostly in the epithelium and lamina propria. The importance of the intestinal cells for the mammalian mucosal immune system is well-established. However, there is no in-depth information about many of the intestinal cells in teleosts. In our previous study, we reported that adherent intestinal cells (AIC) predominantly express macrophage-related genes. To gather further evidence that AIC include macrophage-like cells, we compared their phagocytic activity and morphology with those of adherent head kidney cells (AKC), previously characterized as macrophage-like cells. We also compared equally abundant as well as differentially expressed mRNAs and miRNAs between AIC and AKC. AIC had lower phagocytic activity and were larger and more circular than macrophage-like AKC. RNA-Seq data revealed that there were 18309 mRNAs, with 59 miRNAs that were equally abundant between AIC and AKC. Integrative analysis of the mRNA and miRNA transcriptomes revealed macrophage heterogeneity in both AIC and AKC. In addition, analysis of AIC and AKC transcriptomes revealed functional characteristics of mucosal and systemic macrophages. Five pairs with significant negative correlations between miRNA and mRNAs were linked to macrophages and epithelial cells and their interaction could be pointing to macrophage activation and differentiation. The potential macrophage markers suggested in this study should be investigated under different immune conditions to understand the exact macrophage phenotypes.

Neurovascular Unit: A New Target for Treating Early Stages of Diabetic Retinopathy

The concept of diabetic retinopathy as a microvascular disease has evolved and is now considered a more complex diabetic complication in which neurovascular unit impairment plays an essential role and, therefore, can be considered as a main therapeutic target in the early stages of the disease. However, neurodegeneration is not always the apparent primary event in the natural story of diabetic retinopathy, and a phenotyping characterization is recommendable to identify those patients in whom neuroprotective treatment might be of benefit. In recent years, a myriad of treatments based on neuroprotection have been tested in experimental models, but more interestingly, there are drugs with a dual activity (neuroprotective and vasculotropic). In this review, the recent evidence concerning the therapeutic approaches targeting neurovascular unit impairment will be presented, along with a critical review of the scientific gaps and problems which remain to be overcome before our knowledge can be transferred to clinical practice.

Role and function of granin proteins in diabetes mellitus

The granin glycoprotein family consists of nine acidic proteins; chromogranin A (CgA), chromogranin B (CgB), and secretogranin II–VIII. They are produced by a wide range of neuronal, neuroendocrine, and endocrine cells throughout the human body. Their major intracellular function is to sort peptides and proteins into secretory granules, but their cleavage products also take part in the extracellular regulation of diverse biological processes. The contribution of granins to carbohydrate metabolism and diabetes mellitus is a recent research area. CgA is associated with glucose homeostasis and the progression of type 1 diabetes. WE-14, CgA_10-19, and CgA_43-52 are peptide derivates of CgA, and act as CD4⁺ or CD8⁺ autoantigens in type 1 diabetes, whereas pancreastatin (PST) and catestatin have regulatory effects in carbohydrate metabolism. Furthermore, PST is related to gestational and type 2 diabetes. CgB has a crucial role in physiological insulin secretion. Secretogranins II and III have angiogenic activity in diabetic retinopathy (DR), and are novel targets in recent DR studies. Ongoing studies are beginning to investigate the potential use of granin derivatives as drugs to treat diabetes based on the divergent relationships between granins and different types of diabetes.

Neurovascular regulation in diabetic retinopathy and emerging therapies

Diabetic retinopathy (DR) is the leading cause of vision loss in working adults in developed countries. The disease traditionally classified as a microvascular complication of diabetes is now widely recognized as a neurovascular disorder resulting from disruption of the retinal neurovascular unit (NVU). The NVU comprising retinal neurons, glia and vascular cells coordinately regulates blood flow, vascular density and permeability to maintain homeostasis. Disturbance of the NVU during DR can lead to vision-threatening clinical manifestations. A limited number of signaling pathways have been identified for intercellular communication within the NVU, including vascular endothelial growth factor (VEGF), the master switch for angiogenesis. VEGF inhibitors are now widely used to treat DR, but their limited efficacy implies that other signaling molecules are involved in the pathogenesis of DR. By applying a novel screening technology called comparative ligandomics, we recently discovered secretogranin III (Scg3) as a unique DR-selective angiogenic and vascular leakage factor with therapeutic potential for DR. This review proposes neuron-derived Scg3 as the first diabetes-selective neurovascular regulator and discusses important features of Scg3 inhibition for next-generation disease-targeted anti-angiogenic therapies of DR.

Expression Pattern of the LacZ Reporter in Secretogranin III Gene-trapped Mice

Secretogranin III (SgIII) is a granin protein involved in secretory granule formation in peptide-hormone-producing endocrine cells. In this study, we analyzed the expression of the LacZ reporter in the SgIII knockout mice produced by gene trapping (SgIII-gtKO) for the purpose of comprehensively clarifying the expression patterns of SgIII at the cell and tissue levels. In the endocrine tissues of SgIII-gtKO mice, LacZ expression was observed in the pituitary gland, adrenal medulla, and pancreatic islets, where SgIII expression has been canonically revealed. LacZ expression was extensively observed in brain regions, especially in the cerebral cortex, hippocampus, hypothalamic nuclei, cerebellum, and spinal cord. In peripheral nervous tissues, LacZ expression was observed in the retina, optic nerve, and trigeminal ganglion. LacZ expression was particularly prominent in astrocytes, in addition to neurons and ependymal cells. In the cerebellum, at least four cell types expressed SgIII under basal conditions. The expression of SgIII in the glioma cell lines C6 and RGC-6 was enhanced by excitatory glutamate treatment. It also became clear that the expression level of SgIII varied among neuron and astrocyte subtypes. These results suggest that SgIII is involved in glial cell function, in addition to neuroendocrine functions, in the nervous system.

The changing features of serum adropin, copeptin, neprilysin and chitotriosidase which are associated with vascular endothelial function in type 2 diabetic retinopathy patients

AIMS

Adropin (AD), copeptin (CP), neprilysin (NEP) and chitotriosidase (CHIT1) have been associated with the regulation of vascular endothelial function. In this work, we analyzed the plasma concentrations of cytokines (AD, CP, NEP and CHIT1) in type 2 diabetic patients with or without retinopathy (DR) to predict the risk of DR for diabetic patients.

METHOD

A total of 392 patients diagnosed as type 2 diabetes mellitus (T2DM) and 120 healthy volunteers as a control group were enrolled in this study. T2DM patients were divided into three groups: diabetes without retinopathy (NDR, n = 174) group, non-proliferative diabetic retinopathy (NPDR, n = 118) group and proliferative diabetic retinopathy (PDR, n = 100) group. The serum AD, CP, NEP and CHIT1 levels of subjects were detected by enzyme-linked immunosorbent assay (ELISA).

RESULTS

We reported a significant decrease in AD and a significant increase in CP, NEP and CHIT1 in NDR as well as DR patients when compared with controls (p < 0.05), the lower level of AD and significantly higher levels of CP, NEP and CHIT1 were seen in DR patients compared to NDR group (p < 0.05), at the same time, we observed the lowest level of AD and the highest levels of CP, NEP and CHIT1 in the PDR group. Logistic regression analysis showed that AD was a protective factor for DR, conversely, CP, NEP and CHIT1 were the independent risk factors (p < 0.05). Moreover, receiver operating characteristic curve analyses indicated that CP had greater diagnosis capacity with an AUC (the areas under the ROC curve) of 0.901 than AD, NEP, CHIT1 for DR patients.

CONCLUSION

The decreased AD level and the elevated CP, NEP and CHIT1 levels involved in vascular endothelial function may be evidence facilitating the presence of DR. Thereby they can be explored to use as promising non-invasive biomarkers for prediction of DR severity, distinguishing DR from diabetic patients.

Neutrophil extracellular traps: The core player in vascular complications of diabetes mellitus

Diabetes mellitus (DM) is the most important metabolic disease with major threat for public health and increased risk of premature death. The prevalence of DM steadily rises in developing and developed countries achieving the epidemic level. Manifestation and progression of DM corresponds to developing vasculopathies, such as retinopathy, micro- and macro angiopathies, which negatively influence on clinical outcomes and quality-of-life. Although there are remarkable differences in the prevalence of vasculopathy in various types of DM, hyperglycemia and lipotoxicity are discussed as a major factors contributing to vascular complications partly through inducing neutrophil extracellular trap (NET). The NET or NETosis is unique form of cell death, which is an important core component of innate immune system. The review is dedicated the role of NET as a link between endothelium, inflammation and thrombosis that is crucial for development of DM-induced vasculopathy. It has suggested that NET formation could be not just a target for the DM care, but also a biomarker for stratification of DM patients at higher risk of vascular complications.

Spatiotemporal Regulation of Tumor Angiogenesis by Circulating Chromogranin A Cleavage and Neuropilin-1 Engagement

The unbalanced production of pro- and antiangiogenic factors in tumors can lead to aberrant vasculature morphology, angiogenesis, and disease progression. In this study, we report that disease progression in various murine models of solid tumors is associated with increased cleavage of full-length chromogranin A (CgA), a circulating vasoregulatory neurosecretory protein. Cleavage of CgA led to the exposure of the highly conserved PGPQLR site, which corresponds to residues 368-373 of human CgA_1-373, a fragment that has proangiogenic activity. Antibodies against this site, unable to bind full-length CgA, inhibited angiogenesis and reduced tumor perfusion and growth. The PGPQLR sequence of the fragment, but not of the precursor, bound the VEGF-binding site of neuropilin-1; the C-terminal arginine (R₃₇₃) of the sequence was crucial for binding. The proangiogenic activity of the CgA_1-373 was blocked by anti-neuropilin-1 antibodies as well as by nicotinic acetylcholine receptor antagonists, suggesting that these receptors, in addition to neuropilin-1, play a role in the proangiogenic activity of CgA_1-373. The R₃₇₃ residue was enzymatically removed in plasma, causing loss of neuropilin-1 binding and gain of antiangiogenic activity. These results suggest that cleavage of the R₃₇₃R₃₇₄ site of circulating human CgA in tumors and the subsequent removal of R₃₇₃ in the blood represent an important "on/off" switch for the spatiotemporal regulation of tumor angiogenesis and may serve as a novel therapeutic target. SIGNIFICANCE: This work reveals that the interaction between fragmented chromogranin A and neuropilin-1 is required for tumor growth and represents a novel potential therapeutic target.

Secretogranin III as a novel target for the therapy of choroidal neovascularization

Wet age-related macular degeneration (AMD) with choroidal neovascularization (CNV) is a leading cause of vision loss in the elderly. The advent of anti-vascular endothelial growth factor (VEGF) drugs represents a major breakthrough in wet AMD therapy but with limited efficacy to improve visual acuity. Secretogranin III (Scg3, SgIII) was recently discovered as a novel angiogenic factor with VEGF-independent mechanisms. Scg3-neutralizing monoclonal antibody (mAb) was reported to alleviate pathological retinal neovascularization in oxygen-induced retinopathy mice and retinal vascular leakage in diabetic mice with high efficacy and disease selectivity. Herein we investigated whether Scg3 is a novel angiogenic target for CNV therapy in mouse models. We found that anti-Scg3 ML49.3 mAb inhibited Scg3-induced proliferation and Src phosphorylation in human retinal microvascular endothelial cells. Intravitreal injection of Scg3-neutralizing polyclonal antibodies (pAb) or mAb significantly attenuated laser-induced CNV leakage, CNV 3D volume, lesion area and vessel density. Furthermore, subcutaneous administration of Scg3-neutralizing pAb or mAb significantly prevented Matrigel-induced CNV. The efficacy of anti-Scg3 pAb or mAb was comparable to VEGF inhibitor aflibercept. These findings suggest that Scg3 plays an important role in CNV pathogenesis and that anti-Scg3 mAb efficiently ameliorates laser- or Matrigel-induced CNV.

Secretogranin III promotes angiogenesis through MEK/ERK signaling pathway

Secretogranin III (Scg3) was recently discovered as the first highly diabetic retinopathy-associated angiogenic factor, and its neutralizing antibody alleviated the disease with high efficacy in diabetic mice. Investigation of its molecular mechanisms will facilitate the translation of this novel therapy. Scg3 was reported to induce the phosphorylation of mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK). Here we characterized the importance of MEK/ERK activation to Scg3 angiogenic activity. Our results showed that MEK inhibitor PD98059 blocked Scg3-induced proliferation of human umbilical vein endothelial cells (HUVECs). This finding was corroborated by PD98059 inhibition of HUVEC migration and tube formation. Furthermore, ERK inhibitor SCH772984 also suppressed Scg3-induced proliferation and migration of HUVECs. Taken together, these findings suggest that MEK-ERK pathway plays an important role in Scg3-induced angiogenesis.