Atrial natriuretic peptide reduces vascular leakage and choroidal neovascularization

Vasoactive peptides as biomarkers for the prediction of retinopathy of prematurity

BACKGROUND

Retinopathy of prematurity (ROP) is a major complication in preterm infants. We assessed if plasma levels of midregional pro-atrial natriuretic peptide (MR-proANP) and C-terminal pro-endothelin-1 (CT-proET1) serve as early markers for subsequent ROP development in preterm infants <32 weeks gestation.

METHODS

Prospective, two-centre, observational cohort study. MR-proANP and CT-proET1 were measured on day seven of life. Associations with ROP ≥ stage II were investigated by univariable and multivariable logistic regression models.

RESULTS

We included 224 infants born at median (IQR) 29.6 (27.1-30.8) weeks gestation and birth weight of 1160 (860-1435) g. Nineteen patients developed ROP ≥ stage II. MR-proANP and CT-proET1 levels were higher in these infants (median (IQR) 864 (659-1564) pmol/L and 348 (300-382) pmol/L, respectively) compared to infants without ROP (median (IQR) 299 (210-502) pmol/L and 196 (156-268) pmol/L, respectively; both P < 0.001). MR-proANP and CT-proET1 levels were significantly associated with ROP ≥ stage II in univariable logistic regression models and after adjusting for co-factors, including gestational age and birth weight z-score.

CONCLUSIONS

MR-proANP and CT-proET1 measured on day seven of life are strongly associated with ROP ≥ stage II in very preterm infants and might improve early prediction of ROP in the future.

IMPACT

Plasma levels of midregional pro-atrial natriuretic peptide and C-terminal pro-endothelin-1 measured on day seven of life in very preterm infants show a strong association with development of retinopathy of prematurity ≥ stage II. Both biomarkers have the potential to improve early prediction of retinopathy of prematurity. Vasoactive peptides might allow to reduce the proportion of screened infants substantially.

New retinoblastoma (RB) drug delivery approaches: anti-tumor effect of atrial natriuretic peptide (ANP)-conjugated hyaluronic-acid-coated gold nanoparticles for intraocular treatment of chemoresistant RB

Intraocular drug delivery is a promising approach for treatment of ocular diseases. Chemotherapeutic drugs used in retinoblastoma (RB) treatment often lead to side effects and drug resistances. Therefore, new adjuvant therapies are needed to treat chemoresistant RBs. Biocompatible gold nanoparticles (GNPs) have unique antiangiogenic properties and can inhibit cancer progression. The combination of gold and low-molecular-weight hyaluronan (HA) enhances the stability of GNPs and promotes the distribution across ocular barriers. Attached to HA-GNPs, the atrial natriuretic peptide (ANP), which diminishes neovascularization in the eye, is a promising new therapeutic agent for RB treatment. In the study presented, we established ANP-coupled HA-GNPs and investigated their effect on the tumor formation potential of chemoresistant RB cells in an in ovo chicken chorioallantoic membrane model and an orthotopic in vivo RB rat eye model. Treatment of etoposide-resistant RB cells with ANP-HA-GNPs in ovo resulted in significantly reduced tumor growth and angiogenesis compared with controls. The antitumorigenic effect could be verified in the rat eye model, including a noninvasive application form via eye drops. Our data suggest that ANP-HA-GNPs represent a new minimally invasive, adjuvant treatment option for RB.

Tocilizumab attenuates choroidal neovascularization by regulating macrophage polarization through the IL-6R/STAT3/VEGF pathway

Globally, age-related macular degeneration (AMD) is the leading cause of irreversible visual impairment. Up to 80% of severe vision loss is caused by AMD, which is characterized by the development of choroidal neovascularization (CNV). Uncertainty exists regarding the precise pathophysiological mechanisms of CNV. It has been suggested that the interleukin (IL) IL-6/IL-6R signaling pathway is crucial in the progression of CNV. Tocilizumab (TCZ), a monoclonal antibody, binds to soluble and membrane-bound IL-6R and competitively inhibits IL-6 downstream signaling. Previous research has demonstrated that TCZ promotes several roles related to inflammation and neovascularization. However, the effects of TCZ on CNV and the underlying mechanism are still unknown. This study found that TCZ administration decreased the area and leakage of CNV lesions in the mice model of laser-induced CNV. Additionally, results demonstrated that TCZ promotes the expression of iNOS, CCL-3, CCL-5, TNF-α and inhibits the expression of Arg-1, IL-10, YM-1 and CD206. Furthermore, TCZ treatment inhibited the signal transducer and activator of transcription (STAT) STAT3/vascular endothelial growth factor (VEGF) pathway, which was activated after CNV formation. Colivelin, a STAT3 agonist, reversed the inhibitory effects of TCZ on CNV formation and macrophage polarization. In a mouse model of laser-induced CNV, our findings demonstrated that TCZ attenuated CNV formation and inhibited the leakage of CNV lesions by regulating macrophage polarization via inhibiting the STAT3/VEGF axis. TCZ is the potential therapeutic strategy for CNV.

Honokiol Attenuates Choroidal Neovascularization by Inhibiting the Hypoxia-Inducible Factor-α/Vascular Endothelial Growth Factor Axis via Nuclear Transcription Factor-Kappa B Activation

PURPOSE

Honokiol is a lignan isolated from Magnolia officinalis and exhibits anti-angiogenic properties. This study was conducted to investigate the role of honokiol in choroidal neovascularization.

METHODS

C57BL/6 mice were treated with honokiol at 10-20 mg/kg by daily intraperitoneal injection from day 1 to 6 after laser photocoagulation. ARPE-19 cells were cultured under hypoxic conditions with or without the presence of honokiol. After laser photocoagulation and honokiol treatment, hematoxylin and eosin staining, immunofluorescence and fundus fluorescein angiography were used to analyze the effect of honokiol on choroidal neovascularization formation. Quantitative real-time PCR, western blot, enzyme-linked immunosorbent assay, immunofluorescence, luciferase assay, and chromatin immunoprecipitation were performed to explore the mechanism of honokiol in the pathological process of choroidal neovascularization. Finally, the role of honokiol on the human choroidal vascular endothelial cells was detected by using 5-ethynyl-20-deoxyuridine assay, Transwell and Tube formation assays.

RESULTS

The results of hematoxylin and eosin staining and immunofluorescence suggested that honokiol reduced the thickness, length, and area of choroidal neovascularization lesions in laser-induced choroidal neovascularization mouse model. Fundus fluorescein angiography showed that choroidal neovascularization leakage was reduced in honokiol group and the concentration of 20 mg/kg showed better effects. Mechanism studies have shown that honokiol exerted inhibitory effects on choroidal neovascularization by inactivating hypoxia-inducible factor-1α/vascular endothelial growth factor axis through the nuclear transcription factor-kappa B signaling pathway. The same results were obtained in ARPE-19 cells under hypoxic conditions. Furthermore, the conditional medium of retinal pigmented epithelial cells promoted the proliferation, migration, and tube formation of human choroidal vascular endothelial cells, while honokiol reversed these.

CONCLUSION

We demonstrated that honokiol attenuated choroidal neovascularization formation by inactivating the hypoxia-inducible factor-1α/vascular endothelial growth factor axis through nuclear transcription factor-kappa B signaling pathway.

LncRNA MALAT1 knockdown inhibits the development of choroidal neovascularization

In the pathogenesis of age-related macular degeneration, long non-coding RNAs have become important regulators. This study aimed to investigate the role of metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) in the progression of choroidal neovascularization (CNV) and the underlying mechanisms. The in vivo and in vitro model of CNV was established using laser-induced mouse CNV model and human choroidal vascular endothelial cells (HCVECs) exposed to hypoxia respectively. We explore the role of MALAT1 in the pathogenesis of CNV by using the small interference RNA both in vivo and in vitro. MALAT1 expression was found to be upregulated in the retinal pigment epithelial-choroidal complexes. MALAT1 knockdown inhibited CNV development and leakage in vivo and decreased HCVECs proliferation, migration, and tube formation in vitro. MALAT1 performed the task as a miR-17-5p sponge to regulate the expression of vascular endothelial growth factor A (VEGFA) and E26 transformation specific-1 (ETS1). This study provides a new perspective on the pathogenesis of CNV and suggests that the axis MALAT/miR-17-5p/VEGFA or ETS1 may be an effective therapeutic target for CNV.

A draft genome of Drung cattle reveals clues to its chromosomal fusion and environmental adaptation

Drung cattle (Bos frontalis) have 58 chromosomes, differing from the Bos taurus 2n = 60 karyotype. To date, its origin and evolution history have not been proven conclusively, and the mechanisms of chromosome fusion and environmental adaptation have not been clearly elucidated. Here, we assembled a high integrity and good contiguity genome of Drung cattle with 13.7-fold contig N50 and 4.1-fold scaffold N50 improvements over the recently published Indian mithun assembly, respectively. Speciation time estimation and phylogenetic analysis showed that Drung cattle diverged from Bos taurus into an independent evolutionary clade. Sequence evidence of centromere regions provides clues to the breakpoints in BTA2 and BTA28 centromere satellites. We furthermore integrated a circulation and contraction-related biological process involving 43 evolutionary genes that participated in pathways associated with the evolution of the cardiovascular system. These findings may have important implications for understanding the molecular mechanisms of chromosome fusion, alpine valleys adaptability and cardiovascular function.

Glipizide Combined with ANP Suppresses Breast Cancer Growth and Metastasis by Inhibiting Angiogenesis through VEGF/VEGFR2 Signaling

BACKGROUND

Breast cancer is one of the most common cancers worldwide among women, and angiogenesis has an important effect on its growth and metastasis. Glipizide, which is a widely used drug for type 2 diabetes mellitus, has been reported to inhibit tumor growth and metastasis by upregulating the expression of natriuretic peptide receptor A (NPRA). Atrial natriuretic peptide (ANP), the receptor of NPRA, plays an important role in angiogenesis. The purpose of this study was to explore the effect of glipizide combined with ANP on breast cancer growth and metastasis.

METHODS

To investigate the effect of glipizide combined with ANP on breast cancer, glipizide, ANP or glipizide combined with ANP was intraperitoneally injected into MMTV-PyMT mice. To explore whether the anticancer efficacy of glipizide combined with ANP was correlated with angiogenesis, a tube formation assay was performed.

RESULTS

Glipizide combined with ANP was found to inhibit breast cancer growth and metastasis in MMTV-PyMT mice, which spontaneously develop breast cancer. Furthermore, the inhibitory effect of ANP combined with glipizide was better than that of glipizide alone. ANP combined with glipizide significantly inhibited tube formation of human umbilical vein endothelial cells (HUVECs) by suppressing vascular endothelial growth factor (VEGF)/VEGFR2 (vascular endothelial growth factor receptor 2) signaling.

CONCLUSIONS

These results demonstrate that glipizide combined with ANP has a greater potential than glipizide alone to be repurposed as effective agents for the treatment of breast cancer by targeting tumor-induced angiogenesis.

Angiotensin Receptor Blocker and Neprilysin Inhibitor Suppresses Cardiac Dysfunction by Accelerating Myocardial Angiogenesis in Apolipoprotein E-Knockout Mice Fed a High-Fat Diet

Materials and Methods

Male apolipoprotein E-knockout mice fed a high-fat diet were divided into control (CTL), valsartan (30 mg/kg) (VAL), sacubitril (30 mg/kg) (SAC), and valsartan plus sacubitril (30 mg/kg each) (VAL/SAC) groups after 4 weeks of prefeeding and were subsequently treated for 12 weeks.

Results

The VAL/SAC group exhibited significantly higher serum brain natriuretic peptide levels; more subtle changes in left ventricular systolic diameter, fractional shortening, and ejection fraction, and significantly higher expression levels of natriuretic peptide precursor B and markers of angiogenesis, including clusters of differentiation 34, vascular endothelial growth factor A, and monocyte chemotactic protein 1, than the CTL group.

Conclusions

Valsartan plus sacubitril preserved left ventricular systolic function in apolipoprotein E-knockout mice fed a high-fat diet. This result suggests that myocardial angiogenic factors induced by ARNI might provide cardioprotective effects.

Molecular Dambusters: What Is Behind Hyperpermeability in Bradykinin-Mediated Angioedema?

In the last few decades, a substantial body of evidence underlined the pivotal role of bradykinin in certain types of angioedema. The formation and breakdown of bradykinin has been studied thoroughly; however, numerous questions remained open regarding the triggering, course, and termination of angioedema attacks. Recently, it became clear that vascular endothelial cells have an integrative role in the regulation of vessel permeability. Apart from bradykinin, a great number of factors of different origin, structure, and mechanism of action are capable of modifying the integrity of vascular endothelium, and thus, may participate in the regulation of angioedema formation. Our aim in this review is to describe the most important permeability factors and the molecular mechanisms how they act on endothelial cells. Based on endothelial cell function, we also attempt to explain some of the challenging findings regarding bradykinin-mediated angioedema, where the function of bradykinin itself cannot account for the pathophysiology. By deciphering the complex scenario of vascular permeability regulation and edema formation, we may gain better scientific tools to be able to predict and treat not only bradykinin-mediated but other types of angioedema as well.

A Good Way to Reduce Screening for Retinopathy of Prematurity: Development of the ROP Model in a China Preterm Population

Importance: Retinopathy of prematurity (ROP) is a preventable cause of blindness in children. Without treatment, more than 45% of eyes may suffer permanent vision loss. Current ROP screening guidelines, which include a range of birth weights (BWs) and gestational ages (GAs), may require screening many low-risk preemies who might develop severe ROP. Method: All high-risk infants in the neonatal intensive care unit (NICU) of the First Affiliated Hospital of Zhengzhou University from 2017 to 2021 were included in this retrospective cohort study. Each of the 27 candidate risk factors was evaluated in univariate analysis and adjusted for known risk factors (i.e., GA and BW). The significant results were analyzed in a backward selection multivariate logistic regression model. Receiver operating characteristic (ROC) curves and a nomogram were drawn. Results: The study included 2,040 infants who underwent ROP screening. The weight gain rate [OR, 2.65; 95% confidence interval (CI), 1.49-1.21 ≤ 12 g/d vs. > 18 g/d; P = 0.001], blood transfusion (OR, 2.03; 95% CI, 1.14-3.64; P = 0.017), invasive mechanical ventilation (OR, 1.74; 95% CI, 1.15-2.66; P = 0.009) and N-terminal segment of pro-B-type natriuretic peptide (NT-proBNP) ≥ 25,000 ng/L (OR, 1.51; 95% CI, 1.00-2.28; P = 0.048) were four new statistically independent risk factors in addition to GA and BW. The area under the curve (AUC) of the final multivariate model was 0.90 (95% CI, 0.88-0.92; P < 0.001). Conclusions and Relevance: These findings add to our understanding of ROP screening because they include all eligible infants rather than only high-risk infants, as in previous studies. Under the control of BW and GA, low weight gain rate, increased number of blood transfusion, invasive mechanical ventilation and NT-proBNP ≥ 25,000 ng/L were "new" statistically independent risk factors for ROP. The ROP risk can be calculated manually or represented by a nomogram for clinical use.

Melatonin attenuates choroidal neovascularization by regulating macrophage/microglia polarization via inhibition of RhoA/ROCK signaling pathway

Choroidal neovascularization (CNV) is an important characteristic of advanced wet age-related macular degeneration (AMD) and leads to severe visual impairment among elderly patients. Previous studies have demonstrated that melatonin induces several biological effects related to antioxidation, anti-inflammation, and anti-angiogenesis. However, the role of melatonin in CNV, and its underlying mechanisms, has not been investigated thus far. In this study, we found that melatonin administration significantly reduced the scale and volume of CNV lesions, suppressed vascular leakage, and inhibited the capacity of vascular proliferation in the laser-induced mouse CNV model. Additionally, the results also show that the melatonin-treated retinal microglia in the laser-induced mice exhibited enhanced expression of M1-type markers, such as iNOS, CCL-3, CCL-5, and TNF-α, as well as decreased production of M2-type markers, such as Arg-1, Fizz-1, IL-10, YM-1, and CD206, indicating that melatonin switched the macrophage/microglia polarization from pro-angiogenic M2 phenotype to anti-angiogenic M1 phenotype. Furthermore, the RhoA/ROCK signaling pathway was activated during CNV formation, yet was suppressed after an intraperitoneal injection of melatonin. In conclusion, melatonin attenuated CNV, reduced vascular leakage, and inhibited vascular proliferation by switching the macrophage/microglia polarization from M2 phenotype to M1 phenotype via inhibition of RhoA/ROCK signaling pathway in CNV. This suggests that melatonin could be a novel agent for the treatment of AMD.

Aucuba japonica extract inhibits retinal neovascularization in a mouse model of oxygen-induced retinopathy, with its bioactive components preventing VEGF-induced retinal vascular hyperpermeability

Neovascularization in the retina is common pathophysiology of diabetic retinal microvasculopathy and exudative macular degeneration. Our study assessed the inhibitory activity of an ethanol-based extract of Aucuba japonica (AJE) on abnormal angiogenesis in the retina with a hyperoxia-induced neovascular retinopathy model. The inhibitory effects of aucubin, quercetin, and kaempferol, bioactive compounds, from A. japonica, on retinal vascular hyperpermeability were also examined. On the 7th postnatal day (P7), the C57BL/6 pups were exposed to a hyperoxic environment with 75% oxygen to develop the experimental angiogenesis in retinas. On the 12th postnatal day (P12), the pups were then returned to the normal atmospheric pressure of oxygen. From P12 to P16, the administration was intraperitoneal. The dose per day was 250 mg per kg weight. Retinal neovascularization was measured with retinal flat mounts prepared on P17. We also measured the vascular leakage mediated by the vascular endothelial growth factor (VEGF) in retinas. Mice treated with AJE had markedly smaller neovascular lesions, in comparison with vehicle-administered mice. AJE downregulated the expression of both VEGF protein and mRNA. In addition, aucubin, quercetin, and kaempferol ameliorated VEGF-induced retinal vascular leakage. The results of our study suggest that AJE is a potent antiangiogenic substance. AJE could also serve as a therapeutic agent for abnormal growth of vessels in the retina in patients with ischemic retinopathy. The bioactive compounds of AJE may be responsible for its antiangiogenic abilities.

Dual Angiotensin Receptor and Neprilysin Inhibitor Ameliorates Portal Hypertension in Portal Hypertensive Rats

BACKGROUND

Portal hypertension is characterized by exaggerated activation of the renin-angiotensin-aldosterone axis. Natriuretic peptide system plays a counter-regulatory role, which is modulated by neprilysin. LCZ696 (sacubitril/valsartan) is a dual angiotensin receptor and neprilysin inhibitor. This study evaluated the effect of LCZ696 on portal hypertensive rats.

METHODS

Portal hypertension was induced by partial portal vein ligation (PVL) in rats. LCZ696, valsartan (angiotensin receptor blocker), or normal saline (control) was administered in PVL rats for 10 days. Then, hemodynamic and biochemistry data were obtained. The hepatic histology and protein expressions were surveyed. On the parallel groups, the portal-systemic shunting degrees were determined.

RESULTS

LCZ696 and valsartan reduced mean arterial pressure and systemic vascular resistance. LCZ696, but not valsartan, reduced portal pressure in portal hypertensive rats (control vs. valsartan vs. LCZ696: 15.4 ± 1.6 vs. 14.0 ± 2.3 vs. 12.0 ± 2.0 mmHg, control vs. LCZ696: P < 0.05). LCZ696 and valsartan improved liver biochemistry data and reduced intrahepatic Cluster of Differentiation 68 (CD68)-stained macrophages infiltration. Hepatic endothelin-1 (ET-1) protein expression was downregulated by LCZ696. The portal-systemic shunting was not affected by LCZ696 and valsartan.

CONCLUSION

LCZ696 and valsartan reduced mean arterial pressure through peripheral vasodilation. Furthermore, LCZ696 significantly reduced portal pressure in PVL rats via hepatic ET-1 downregulation.

Natriuretic Peptides Attenuate Retinal Pathological Neovascularization Via Cyclic Guanosine Monophosphate Signaling in Pericytes and Astrocytes

OBJECTIVE

In proliferative retinopathies, complications derived from neovascularization cause blindness. During early disease, pericyte's apoptosis contributes to endothelial dysfunction and leakage. Hypoxia then drives VEGF (vascular endothelial growth factor) secretion and pathological neoangiogenesis. Cardiac ANP (atrial natriuretic peptide) contributes to systemic microcirculatory homeostasis. ANP is also formed in the retina, with unclear functions. Here, we characterized whether endogenously formed ANP regulates retinal (neo)angiogenesis. Approach and Results: Retinal vascular development and ischemia-driven neovascularization were studied in mice with global deletion of GC-A (guanylyl cyclase-A), the cGMP (cyclic guanosine monophosphate)-forming ANP receptor. Mice with a floxed GC-A gene were interbred with Tie2-Cre, GFAP-Cre, or PDGF-Rβ-Cre^ERT2 lines to dissect the endothelial, astrocyte versus pericyte-mediated actions of ANP in vivo. In neonates with global GC-A deletion (KO), vascular development was mildly delayed. Moreover, such KO mice showed augmented vascular regression and exacerbated ischemia-driven neovascularization in the model of oxygen-induced retinopathy. Notably, absence of GC-A in endothelial cells did not impact retinal vascular development or pathological neovascularization. In vitro ANP/GC-A/cGMP signaling, via activation of cGMP-dependent protein kinase I, inhibited hypoxia-driven astrocyte's VEGF secretion and TGF-β (transforming growth factor beta)-induced pericyte apoptosis. In neonates lacking ANP/GC-A signaling in astrocytes, vascular development and hyperoxia-driven vascular regression were unaltered; ischemia-induced neovascularization was modestly increased. Remarkably, inactivation of GC-A in pericytes retarded physiological retinal vascularization and markedly enhanced cell apoptosis, vascular regression, and subsequent neovascularization in oxygen-induced retinopathy.

CONCLUSIONS

Protective pericyte effects of the ANP/GC-A/cGMP pathway counterregulate the initiation and progression of experimental proliferative retinopathy. Our observations indicate augmentation of endogenous pericyte ANP signaling as target for treatment of retinopathies associated with neovascularization.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

A Critical Analysis of the Available In Vitro and Ex Vivo Methods to Study Retinal Angiogenesis

Angiogenesis is a biological process with a central role in retinal diseases. The choice of the ideal method to study angiogenesis, particularly in the retina, remains a problem. Angiogenesis can be assessed through in vitro and in vivo studies. In spite of inherent limitations, in vitro studies are faster, easier to perform and quantify, and typically less expensive and allow the study of isolated angiogenesis steps. We performed a systematic review of PubMed searching for original articles that applied in vitro or ex vivo angiogenic retinal assays until May 2017, presenting the available assays and discussing their applicability, advantages, and disadvantages. Most of the studies evaluated migration, proliferation, and tube formation of endothelial cells in response to inhibitory or stimulatory compounds. Other aspects of angiogenesis were studied by assessing cell permeability, adhesion, or apoptosis, as well as by implementing organotypic models of the retina. Emphasis is placed on how the methods are applied and how they can contribute to retinal angiogenesis comprehension. We also discuss how to choose the best cell culture to implement these methods. When applied together, in vitro and ex vivo studies constitute a powerful tool to improve retinal angiogenesis knowledge. This review provides support for researchers to better select the most suitable protocols in this field.

Beneficial Effects of Combined AT1 Receptor/Neprilysin Inhibition (ARNI) Versus AT1 Receptor Blockade Alone in the Diabetic Eye

Purpose

Dysfunction of the renin-angiotensin system (RAS) contributes to pathogenesis of diabetic retinopathy (DR). Yet RAS blockers have only limited beneficial effects on progression of DR in clinical trials. The natriuretic peptide system offsets RAS, so that enhancing the activity of this system on top of RAS blockade might be beneficial. Neprilysin has an important role in the degradation of natriuretic peptides. Therefore, we hypothesize that dual angiotensin receptor-neprilysin inhibition (ARNI) may outperform angiotensin receptor blocker (ARB) in protection against DR. We tested this hypothesis in streptozotocin-induced diabetic transgenic (mRen2)27 rats.

Methods

Adult male diabetic (mRen2)27 rats were followed for 5 or 12 weeks. Treatment with vehicle, irbesartan (ARB), or ARB combined with the neprilysin inhibitor thiorphan (irbesartan+thiorphan [ARNI]) occurred during the final 3 weeks. Retinal cell death, gliosis, and capillary loss were evaluated. Real-time polymerase chain reaction (RT-PCR) analyses were performed to quantify the retinal level of inflammatory cell markers.

Results

Both ARB- and ARNI-treated groups showed similarly reduced retinal apoptotic cell death, gliosis, and capillary loss compared to the vehicle-treated group in the 5-week study. Treatment with ARNI reduced the expression of inflammatory markers more than ARB treatment in the 5-week study. In the 12-week study, ARNI treatment showed significantly more reduction in apoptotic cell death (51% vs. 25% reduction), and capillary loss (68% vs. 43% reduction) than ARB treatment.

Conclusions

Treatment with ARNI provides better protection against DR in diabetic (mRen2)27 transgenic rats, compared to ARB alone. This approach may be a promising treatment option for patients with DR.

Transcriptome analysis reveals a role for the endothelial ANP-GC-A signaling in interfering with pre-metastatic niche formation by solid cancers

Cancer establishes a microenvironment called the pre-metastatic niche in distant organs where disseminated cancer cells can efficiently metastasize. Pre-metastatic niche formation requires various genetic factors. Previous studies suggest that inhibiting a single niche-factor is insufficient to completely block pre-metastatic niche formation especially in human patients. Here we show that the atrial natriuretic peptide (ANP), an endogenous hormone produced by the heart, inhibits pre-metastatic niche formation and metastasis of murine solid cancer models when pharmacologically supplied in vivo. On the basis of a wealth of comprehensive RNA-seq data, we demonstrated that ANP globally suppressed expression of cancer-induced genes including known niche-factors in the lung. The lungs of mice overexpressing GC-A, a receptor for ANP in endothelial cells, were conferred resistance against pre-metastatic niche formation. Importantly, neither ANP administration nor GC-A overexpression had a detrimental effect on lung gene expression in a cancer-free condition. The current study establishes endothelial ANP-GC-A signaling as a therapeutic target to control the pre-metastatic niche.

Atrial natriuretic peptide in cardiovascular biology and disease (NPPA)

Atrial natriuretic peptide (ANP) is a cardiac hormone that regulates salt-water balance and blood pressure by promoting renal sodium and water excretion and stimulating vasodilation. ANP also has an anti-hypertrophic function in the heart, which is independent of its systemic blood pressure-lowering effect. In mice, ANP deficiency causes salt-sensitive hypertension and cardiac hypertrophy. Recent studies have shown that ANP plays an important role in regulating vascular remodeling and energy metabolism. Variants in the human NPPA gene, encoding the ANP precursor, are associated with hypertension, stroke, coronary artery disease, heart failure (HF) and obesity. ANP and related peptides are used as biomarkers for heart disease. Recombinant proteins and small molecules that enhance the ANP pathway have been developed to treat patients with HF. In this review, we discuss the role of ANP in cardiovascular biology and disease.

Glipizide suppresses embryonic vasculogenesis and angiogenesis through targeting natriuretic peptide receptor A

Glipizide, a second-generation sulfonylurea, has been widely used for the treatment of type 2 diabetes. However, it is controversial whether or not glipizide would affect angiogenesis or vasculogenesis. In the present study, we used early chick embryo model to investigate the effect of glipizide on angiogenesis and vasculogenesis, which are the two major processes for embryonic vasculature formation as well as tumor neovascularization. We found that Glipizide suppressed both angiogenesis in yolk-sac membrane (YSM) and blood island formation during developmental vasculogenesis. Glipizide did not affect either the process of epithelial to mesenchymal transition (EMT) or mesoderm cell migration. In addition, it did not interfere with separation of smooth muscle cell progenitors from hemangioblasts. Moreover, natriuretic peptide receptor A (NPRA) has been identified as the putative target for glipizide׳s inhibitory effect on vasculogenesis. When NPRA was overexpressed or activated, blood island formation was reduced. NPRA signaling may play a crucial role in the effect of glipizide on vasculogenesis during early embryonic development.

ROCK-isoform-specific polarization of macrophages associated with age-related macular degeneration

Age is a major risk factor in age-related macular degeneration (AMD), but the underlying cause is unknown. We find increased Rho-associated kinase (ROCK) signaling and M2 characteristics in eyes of aged mice, revealing immune changes in aging. ROCK isoforms determine macrophage polarization into M1 and M2 subtypes. M2-like macrophages accumulated in AMD, but not in normal eyes, suggesting that these macrophages may be linked to macular degeneration. M2 macrophages injected into the mouse eye exacerbated choroidal neovascular lesions, while M1 macrophages ameliorated them, supporting a causal role for macrophage subtypes in AMD. Selective ROCK2 inhibition with a small molecule decreased M2-like macrophages and choroidal neovascularization. ROCK2 inhibition upregulated M1 markers without affecting macrophage recruitment, underlining the plasticity of these macrophages. These results reveal age-induced innate immune imbalance as underlying AMD pathogenesis. Targeting macrophage plasticity opens up new possibilities for more effective AMD treatment.

Longitudinal changes in maternal corin and mid-regional proatrial natriuretic peptide in women at risk of pre-eclampsia

OBJECTIVE

Corin, an atrial natriuretic peptide-converting enzyme, has been found to promote trophoblast invasion and spiral artery remodeling. Yet, elevated maternal plasma atrial natriuretic peptide (ANP) and corin levels have been reported in pregnancies complicated by pre-eclampsia (PE). The aim of this study was to investigate longitudinal changes in maternal plasma levels of corin and mid-regional proatrial natriuretic peptide (MR-PANP) in pregnancies that develop PE and gestational hypertension (GH).

METHODS

This was a nested case-control study drawn from a larger prospective longitudinal study in singleton pregnancies identified as being at high risk for PE by screening at 11 + 0 to 13 + 6 weeks' gestation. Blood samples were taken every 4 weeks until delivery. Values were compared in pregnancies that developed preterm PE (requiring delivery before 37 weeks' gestation), term PE, GH and those that remained normotensive.

RESULTS

A total of 471 samples were analyzed from 122 women, including 85 that remained normotensive, 12 that developed GH, 13 term PE and 12 preterm PE. In the normotensive group, log10 corin levels were associated with gestational age (P < 0.01), whereas log10 MR-PANP levels were not. In the preterm-PE group, compared with the normotensive group, corin was significantly lower until 20 weeks' gestation (P = 0.001). In the GH and term-PE groups, corin did not differ significantly from the normotensive group (P = 0.637 and P = 0.161, respectively). Compared with the normotensive group, MR-PANP levels were significantly higher in the pregnancies that developed preterm PE and GH (P = 0.046 and P = 0.019, respectively), but not term PE (P = 0.467).

CONCLUSION

Maternal-plasma corin and MR-PANP could potentially be useful biomarkers for the prediction of preterm PE.

RNA-seq and high-definition mass spectrometry reveal the complex and divergent venoms of two rear-fanged colubrid snakes

Background

Largely because of their direct, negative impacts on human health, the venoms of front-fanged snakes of the families Viperidae and Elapidae have been extensively characterized proteomically, transcriptomically, and pharmacologically. However, relatively little is known about the molecular complexity and evolution of the venoms of rear-fanged colubrid snakes, which are, with a few notable exceptions, regarded as harmless to humans. Many of these snakes have venoms with major effects on their preferred prey, and their venoms are probably as critical to their survival as those of front-fanged elapids and viperids.

Results

We sequenced the venom-gland transcriptomes from a specimen of Hypsiglena (Desert Night Snake; family Colubridae, subfamily Dipsadinae) and of Boiga irregularis (Brown Treesnake; family Colubridae, subfamily Colubrinae) and verified the transcriptomic results proteomically by means of high-definition mass spectrometry. We identified nearly 3,000 nontoxin genes for each species. For B. irregularis, we found 108 putative toxin transcripts in 46 clusters with <1% nucleotide divergence, and for Hypsiglena we identified 79 toxin sequences that were grouped into 33 clusters. Comparisons of the venoms revealed divergent venom types, with Hypsiglena possessing a viper-like venom dominated by metalloproteinases, and B. irregularis having a more elapid-like venom, consisting primarily of three-finger toxins.

Conclusions

Despite the difficulty of procuring venom from rear-fanged species, we were able to complete all analyses from a single specimen of each species without pooling venom samples or glands, demonstrating the power of high-definition transcriptomic and proteomic approaches. We found a high level of divergence in the venom types of two colubrids. These two venoms reflected the hemorrhagic/neurotoxic venom dichotomy that broadly characterizes the difference in venom strategies between elapids and viperids.

Senescent retinal pigment epithelial cells are more sensitive to vascular endothelial growth factor: implications for "wet" age-related macular degeneration

PURPOSE

Senescence of the retinal pigment epithelial (RPE) cell layer has been implicated in the occurrence of age-related macular degeneration (AMD). The present study examines whether the ability of vascular endothelial growth factor (VEGF) to decrease the barrier function of RPE cells is enhanced in senescent RPE cells, which could contribute to the pathology of "wet" AMD.

METHODS

Low or high population doubling level (PDL) range ARPE-19 human RPE cells were cultured in 6-well plates on membrane-containing inserts. After 2 weeks, the cells were treated with either VEGF or its vehicle and their transepithelial electrical resistance (TEER) was measured. One week later, the cells were stained for senescence-associated β-galactosidase (SABG) activity.

RESULTS

VEGF was significantly more effective in reducing the TEER of the high PDL ARPE-19 cell layers than the low PDL layers (25% decrease vs. 6% decrease; t-test, P=0.0013). The low PDL cell layers had a modest uniform level of SABG staining. In contrast, the high PDL layers displayed darker and more mottled SABG staining indicative of the presence of senescent cells.

CONCLUSIONS

The present results show that the ability of VEGF to reduce the barrier function of RPE cell layers is greater in high PDL layers, which display signs of senescence, than in low PDL layers. Senescence-induced changes in the responsiveness of RPE cell layers to VEGF could contribute to the pathology of AMD. Agents that strengthen the barrier properties of RPE cells or reduce their responsiveness to VEGF could be effective in treating "wet" AMD.

Hypoxic conditions stimulate the release of B-type natriuretic peptide from human retinal pigment epithelium cell culture

PURPOSE

A-type peptide, a natriuretic peptide belonging to the natriuretic peptide family, has been shown to be increased in the vitreous of patients suffering from diabetic retinopathy and that human retina has a well-developed natriuretic peptide system. The stimulus to which the synthesis of natriuretic peptides responded in these patients has, however, remained unknown. As the natriuretic peptides have recently been shown to respond to hypoxic conditions, the genes of both A-type and B-type have a hypoxia-response element (HRE) in their promoter sequence, we therefore hypothesized that hypoxia in the human retinal pigment epithelium will increase the secretion of NT-proBNP, the most common natriuretic peptide monitored in clinical medicine.

METHODS

We used cultured human retinal pigment epithelium cell line (ARPE-19) which was exposed either to normoxia or to hypoxia for 2 hr, 4 hr, 6 hr and 24 hr. NT-proBNP was measured with enzyme immunoassay, VEGF with ELISA and HIF-1α with Western blotting.

RESULTS

Hypoxia induced VEGF 165 release in culture medium and HIF-1α expression in cultured ARPE-19 cells. Time-dependent NT-proBNP release was detected when the ARPE-19 cells were cultured under normoxia. When hypoxia was induced, a statistically significant increase in NT-proBNP release was demonstrated in the culture medium.

CONCLUSIONS

Hypoxic conditions increase the release of a natriuretic peptide from retinal pigment epithelium (RPE) cells. The secretion of VEGF was also enhanced. The responses were associated with the up-regulation of the HIF-1α transcription factor. These results explain the previous findings from patients with diabetes, which also suggest that hypoxia is a ubiquitous stimulus for the secretion of natriuretic peptides in human body.

Role of corin and atrial natriuretic peptide in preeclampsia

In pregnancy, uterine spiral artery remodeling is an adaptive morphological change at the maternal and fetal interface, which is critical for dilating the artery and promoting blood flow to the fetus. Incompletely remodeled spiral arteries have been recognized as a common pathological feature in preeclamptic patients. To date, the molecular mechanism that controls spiral artery remodeling is not well defined. Corin is a transmembrane serine protease discovered in the heart, where it converts pro-atrial natriuretic peptide (pro-ANP) to active ANP, a cardiac hormone that regulates salt-water balance and blood pressure. Recent studies show that corin is up-regulated in the decidua of the pregnant uterus, suggesting a potential role of corin in pregnancy. In mice lacking corin or ANP, high blood pressure and proteinuria were found at late gestational stages. Histological analysis indicated delayed trophoblast invasion and impaired spiral artery remodeling in the uterus. In humans, CORIN gene mutations were identified in patients with preeclampsia. In this review, we discuss the function of corin and ANP in regulating blood pressure and their potential role in preeclampsia.

C-type natriuretic peptide protects the retinal pigment epithelium against advanced glycation end product-induced barrier dysfunction

In diabetic retinopathy, vision loss is usually secondary to macular edema, which is thought to depend on the functional integrity of the blood-retina barrier. The levels of advanced glycation end products in the vitreous correlate with the progression of diabetic retinopathy. Natriuretic peptides (NP) are expressed in the eye and their receptors are present in the retinal pigment epithelium (RPE). Here, we investigated the effect of glycated-albumin (Glyc-alb), an advanced glycation end product model, on RPE-barrier function and the ability of NP to suppress this response. Transepithelial electrical resistance (TEER) measurements were used to assess the barrier function of ARPE-19 and human fetal RPE (hfRPE) monolayers. The monolayers were treated with 0.1-100 μg/ml Glyc-alb in the absence or presence of 1 pM to 100 nM apical atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), or C-type natriuretic peptide (CNP). Glyc-alb induced a significant reduction in TEER within 2 hours. This response was concentration-dependent (EC(50)= 2.3 μg/ml) with a maximal reduction of 40 ± 2% for ARPE-19 and 27 ± 7% for hfRPE at 100 μg/ml 6 hours post-treatment. One hour pretreatment with ANP, BNP, or CNP blocked the reduction in TEER induced by Glyc-alb (100 μg/ml). The suppression of the Glyc-alb response by NP was dependent on the generation of cyclic guanosine monophosphate and exhibited a rank order of agonist potency consistent with the activation of natriuretic-peptide-receptor-2 (NPR2) subtype (CNP >> BNP ≥ ANP). Our data demonstrate that Glyc-alb is effective in reducing RPE-barrier function, and this response is suppressed by NP. Moreover, these studies support the idea that NPR2 agonists can be potential candidates for treating retinal edema in diabetic patients.

Endothelial actions of atrial and B-type natriuretic peptides

The cardiac hormone atrial natriuretic peptide (ANP) is critically involved in the maintenance of arterial blood pressure and intravascular volume homeostasis. Its cGMP-producing GC-A receptor is densely expressed in the microvascular endothelium of the lung and systemic circulation, but the functional relevance is controversial. Some studies reported that ANP stimulates endothelial cell permeability, whereas others described that the peptide attenuates endothelial barrier dysfunction provoked by inflammatory agents such as thrombin or histamine. Many studies in vitro addressed the effects of ANP on endothelial proliferation and migration. Again, both pro- and anti-angiogenic properties were described. To unravel the role of the endothelial actions of ANP in vivo, we inactivated the murine GC-A gene selectively in endothelial cells by homologous loxP/Cre-mediated recombination. Our studies in these mice indicate that ANP, via endothelial GC-A, increases endothelial albumin permeability in the microcirculation of the skin and skeletal muscle. This effect is critically involved in the endocrine hypovolaemic, hypotensive actions of the cardiac hormone. On the other hand the homologous GC-A-activating B-type NP (BNP), which is produced by cardiac myocytes and many other cell types in response to stressors such as hypoxia, possibly exerts more paracrine than endocrine actions. For instance, within the ischaemic skeletal muscle BNP released from activated satellite cells can improve the regeneration of neighbouring endothelia. This review will focus on recent advancements in our understanding of endothelial NP/GC-A signalling in the pulmonary versus systemic circulation. It will discuss possible mechanisms accounting for the discrepant observations made for the endothelial actions of this hormone-receptor system and distinguish between (patho)physiological and pharmacological actions. Lastly it will emphasize the potential therapeutical implications derived from the actions of NPs on endothelial permeability and regeneration.

Human retinal pigment epithelium cells as functional models for the RPE in vivo

PURPOSE

The two most commonly used in vitro models of the retinal pigment epithelium (RPE) are fetal human RPE (fhRPE) and ARPE-19 cells; however, studies of their barrier properties have produced contradictory results. To compare their utility as RPE models, their morphologic and functional characteristics were analyzed.

METHODS

Monolayers of both cell types were grown on permeable membrane filters. Barrier function and cellular morphology were assessed by transepithelial resistance (TER) measurements and immunohistochemistry. Protein expression was evaluated by immunoblotting and ELISA assays, and retinoid metabolism characterized by HPLC.

RESULTS

Both cultures developed tight junctions. However, only the fhRPE cells were pigmented, uniform in size and shape, expressed high levels of RPE markers, metabolized all-trans retinal, and developed high TER (>400 Ωcm(2)). The net secretion of pigment-epithelium-derived factor (PEDF) was directed apically in both cultures, but fhRPE cells exhibited secretion rates a thousand-fold greater than in ARPE-19 cells. The net secretion of vascular endothelial growth factor (VEGF) was significantly higher in fhRPE cultures and the direction of this secretion was basolateral; while net secretion was apical in ARPE-19 cells. In fresh media, VEGF-E reduced TER in both cultures; however, in conditioned media fhRPE cells did not respond to VEGF-E administration, but retreatment of the conditioned media with anti-PEDF antibodies allowed fhRPE cells to fully respond to VEGF-E.

CONCLUSIONS

Properties of fhRPE cells align with a functionally normal RPE in vivo, while ARPE-19 cells resemble a pathologic or aged RPE. These results suggest a utility for both cell types in understanding distinct, particular aspects of RPE function.

Urinary N-terminal B-type natriuretic peptide predicts severe retinopathy of prematurity

OBJECTIVE

The goal of this study was to evaluate urinary N-terminal fragment of B-type natriuretic peptide concentrations, normalized to creatinine (UNBCR), to predict morbidities at discharge in preterm infants.

METHODS

UNBCR were determined in urine collected on day of life (DOL) 2, 7, 14, and 28 in 136 preterm infants <1500 g birth weight, 22 of whom developed bronchopulmonary dysplasia (BPD), defined as oxygen supplementation at 36 weeks' gestational age) and 11 infants developed severe retinopathy (ROP), defined as stage 3 or stage ≥ 2 requiring surgery).

RESULTS

UNBCR on DOL 7, 14, and 28 was elevated in infants who developed BPD or ROP compared with controls (P ≤ .001). On multiple regression analysis including birth weight and gestational age, ROP but not BPD remained independently associated with UNBCR on DOL 14 and 28. Areas under receiver operating characteristic curves for UNBCR on DOL 14 and 28 to predict ROP were 0.938 (0.027) and 0.954 (0.021), respectively. UNBCR DOL 14 and 28 thresholds exceeded by all infants with severe ROP (100% sensitivity, 100% negative predictive value) had a specificity of 66% and 85%, respectively.

CONCLUSIONS

UNBCR might hold promise to reduce unnecessary eye examinations by timely and accurate identification of infants at risk of severe ROP.

Cloning and sequence analysis of an Ophiophagus hannah cDNA encoding a precursor of two natriuretic peptide domains

The king cobra (Ophiophagus hannah) is the largest venomous snake. Despite the components are mainly neurotoxins, the venom contains several proteins affecting blood system. Natriuretic peptide (NP), one of the important components of snake venoms, could cause local vasodilatation and a promoted capillary permeability facilitating a rapid diffusion of other toxins into the prey tissues. Due to the low abundance, it is hard to purify the snake venom NPs. The cDNA cloning of the NPs become a useful approach. In this study, a 957 bp natriuretic peptide-encoding cDNA clone was isolated from an O. hannah venom gland cDNA library. The open-reading frame of the cDNA encodes a 210-amino acid residues precursor protein named Oh-NP. Oh-NP has a typical signal peptide sequence of 26 amino acid residues. Surprisingly, Oh-NP has two typical NP domains which consist of the typical sequence of 17-residue loop of CFGXXDRIGC, so it is an unusual NP precursor. These two NP domains share high amino acid sequence identity. In addition, there are two homologous peptides of unknown function within the Oh-NP precursor. To our knowledge, Oh-NP is the first protein precursor containing two NP domains. It might belong to another subclass of snake venom NPs.

A novel natriuretic peptide from the cobra venom

Natriuretic peptides (NPs) play crucial roles in human physiology and pathophysiology through natriuresis, dieresis and vasorelaxation. NPs are also one of the important components of snake venoms. However, the low abundance in snake venom hampered the investigation. Here, a novel natriuretic peptide named Na-NP was purified from the cobra Naja atra venom. Na-NP consists of 45 amino acid residues and its molecular weight is 4618.5 Da. A full-length cDNA encoding Na-NP was obtained from the cDNA library constructed from the venom gland. The open reading frame of cloned Na-NP was composed of 498bp and coded for a 165-amino acid residue protein precursor. The nucleotide and deduced protein sequences of Na-NP were remarkably conserved with other elapid NPs while significant different from the viperid NPs. Na-NP showed weak activity to relax the aortic rings precontracted with phenylephrine. Meanwhile, Na-NP showed cGMP-promotion activity against primary cultured rabbit endocardial endothelial cells, but had no effect on human platelet aggregation. In conclusion, this is the first report of a natriuretic peptide from the cobra N. atra venom. Na-NP might be served as a useful tool for the study of human NPs and the development of novel therapeutic drugs.