Identification of intracellular proteins and signaling pathways in human endothelial cells regulated by angiotensin-(1-7)

Identification of key pathways and genes in vestibular schwannoma using bioinformatics analysis

The aim of the present study is to identify novel promising marks and targets of diagnosis, therapy and prognosis for patients with vestibular schwannoma at the molecular level. The gene expression profiles of GSE54934, GSE39645 and GSE56597 datasets were obtained respectively from the Gene Expression Omnibus database. The differentially expressed genes (DEGs) were identified by comparing between gene expression profiles of the vestibular schwannoma tissues and normal tissues. Subsequently, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis and protein-protein interaction (PPI) network analysis were performed. The function and pathway enrichment analysis were performed for DEGs with DAVID. Reverse transcription-quantitative PCR were conducted to confirm the expression of BCL2, AGT, IL6 and ITGA2 in human Schwann cells and vestibular schwannoma cells. A total of 4,025, 1,1291 and 1,513 DEGs were identified from GSE54934, GSE56597 and GSE39645 datasets, respectively. GO and KEGG analysis showed that the mutual upregulated genes were mainly enriched in cell division, mitotic nuclear division, and transition of mitotic cell cycle, whilst mutual downregulated genes were enriched in chemical synaptic transmission, neurotransmitter transport, and synaptic vesicle membrane. Subsequently, 20 genes, including BCL2, AGT, IL6 and ITGA2 were selected as hub genes with high degrees after PPI network analysis. The significant differential expression of those genes were detected among vestibular schwannoma tissues compared with normal nerve tissues. In conclusion, BCL2, AGT, IL6 and ITGA2 are significantly higher expressed in vestibular schwannoma tissues compared with human Schwann tissues. The DEGs identified in the present study provide novel targets for the diagnosis and treatment of vestibular schwannoma.

Oestrogen-mediated upregulation of the Mas receptor contributes to sex differences in acute lung injury and lung vascular barrier regulation

Epidemiological data from the SARS-CoV-2 outbreak suggest sex differences in mortality and vulnerability; however, sex-dependent incidence of acute respiratory distress syndrome (ARDS) remains controversial and the sex-dependent mechanisms of endothelial barrier regulation are unknown. In premenopausal women, increased signalling of angiotensin (Ang)(1-7) via the Mas receptor has been linked to lower cardiovascular risk. Since stimulation of the Ang(1-7)/Mas axis protects the endothelial barrier in acute lung injury (ALI), we hypothesised that increased Ang(1-7)/Mas signalling may protect females over males in ALI/ARDS.Clinical data were collected from Charité inpatients (Berlin) and sex differences in ALI were assessed in wild-type (WT) and Mas-receptor deficient (Mas^-/- ) mice. Endothelial permeability was assessed as weight change in isolated lungs and as transendothelial electrical resistance (TEER) in vitroIn 734 090 Charité inpatients (2005-2016), ARDS had a higher incidence in men as compared to women. In murine ALI, male WT mice had more lung oedema, protein leaks and histological evidence of injury than female WT mice. Lung weight change in response to platelet-activating factor (PAF) was more pronounced in male WT and female Mas^-/- mice than in female WT mice, whereas Mas-receptor expression was higher in female WT lungs. Ovariectomy attenuated protection in female WT mice and reduced Mas-receptor expression. Oestrogen increased Mas-receptor expression and attenuated endothelial leakage in response to thrombin in vitro This effect was alleviated by Mas-receptor blockade.Improved lung endothelial barrier function protects female mice from ALI-induced lung oedema. This effect is partially mediated via enhanced Ang(1-7)/Mas signalling as a result of oestrogen-dependent Mas expression.

The angiotensin-(1-7)/Mas receptor axis protects from endothelial cell senescence via klotho and Nrf2 activation

Endothelial cell senescence is a hallmark of vascular aging that predisposes to vascular disease. We aimed to explore the capacity of the renin–angiotensin system (RAS) heptapeptide angiotensin (Ang)‐(1‐7) to counteract human endothelial cell senescence and to identify intracellular pathways mediating its potential protective action. In human umbilical vein endothelial cell (HUVEC) cultures, Ang II promoted cell senescence, as revealed by the enhancement in senescence‐associated galactosidase (SA‐β‐gal+) positive staining, total and telomeric DNA damage, adhesion molecule expression, and human mononuclear adhesion to HUVEC monolayers. By activating the G protein‐coupled receptor Mas, Ang‐(1‐7) inhibited the pro‐senescence action of Ang II, but also of a non‐RAS stressor such as the cytokine IL‐1β. Moreover, Ang‐(1‐7) enhanced endothelial klotho levels, while klotho silencing resulted in the loss of the anti‐senescence action of the heptapeptide. Indeed, both Ang‐(1‐7) and recombinant klotho activated the cytoprotective Nrf2/heme oxygenase‐1 (HO‐1) pathway. The HO‐1 inhibitor tin protoporphyrin IX prevented the anti‐senescence action evoked by Ang‐(1‐7) or recombinant klotho. Overall, the present study identifies Ang‐(1‐7) as an anti‐senescence peptide displaying its protective action beyond the RAS by consecutively activating klotho and Nrf2/HO‐1. Ang‐(1‐7) mimetic drugs may thus prove useful to prevent endothelial cell senescence and its related vascular complications.

Endoglin is a conserved regulator of vasculogenesis in zebrafish - implications for hereditary haemorrhagic telangiectasia

Hereditary haemorrhagic telangiectasia (HHT) is a progressive vascular disease with high mortality and prevalence. There is no effective treatment of HHT due to the lack of comprehensive knowledge of its underlying pathological mechanisms. The majority of HHT1 patients carry endoglin (ENG) mutations. Here, we used Danio rerio (zebrafish) as an in vivo model to investigate the effects of endoglin knockdown on vascular development. According to phylogenetic analyses and amino acid sequence similarity analyses, we confirmed that endoglin is conserved in vertebrates and descended from a single common ancestor. Endoglin is highly expressed in the vasculature beginning at the segmentation period in zebrafish. Upon endoglin knockdown by morpholinos, we observed disruption in the intersegmental vessels (ISVs) and decreased expression of several vascular markers. RNA sequencing (RNA-Seq) results implied that the BMP-binding endothelial regulator (bmper) is a gene affected by endoglin knockdown. Rescue experiments demonstrated that overexpression of bmper significantly increased the number of endothelial cells (ECs) and reduced the defects at ISVs in zebrafish. Moreover, there was enhanced tube formation in ENG mutant ECs derived from a HHT patient after human recombinant BMPER (hrBMPER) stimulation. Taken together, our results suggest that bmper, a potential downstream gene of ENG, could be targeted to improve vascular integrity in HHT.

Angiotensin II triggers autophagy and apoptosis in PC12 cell line: An in vitro Alzheimer's disease model

OBJECTIVE

The activation of renin angiotensin system is involved in multiple pathological processes. Growing evidence reveal that Angiotensin II (Ang II) contributes to the pathogenesis of Alzheimer disease (AD). However, the underlying mechanisms are still not fully understood.

METHODS

In this study, the effect of Ang II on Aβ_1-42 induced neurotoxicity was evaluated in PC12 cells. Apoptosis was examined by flow cytometry analysis and caspase-3 activity assay. Autophagy-related markers were also measured in each group.

RESULTS

The results indicated that Ang II activated autophagy and triggered apoptosis in PC12 cells in a dose-dependent manner, as demonstrated byincreased LC3 II/I ratio and decreased p62 expression. Moreover, inhibition of autophagy by 3-methyladenine markedly attenuated the apoptosis caused by Ang II. In addition, an AT1R antagonist losartan, rather than the AT2R antagonist PD123319, completely reversed the Ang II induced autophagic activation and subsequent cell apoptosis.

CONCLUSIONS

Taken together, our study strengthen the crucial function of Ang II/AT1R axis in the pathogenesis of AD in vitro. These findings have deepened our understanding on the role of Ang II in the pathogenesis of AD and support the use of AT1R antagonists for the treatment of this devastating neurodegenerative disease.

The pro-inflammatory signalling regulator Stat4 promotes vasculogenesis of great vessels derived from endothelial precursors

Vasculogenic defects of great vessels (GVs) are a major cause of congenital cardiovascular diseases. However, genetic regulators of endothelial precursors in GV vasculogenesis remain largely unknown. Here we show that Stat4, a transcription factor known for its regulatory role of pro-inflammatory signalling, promotes GV vasculogenesis in zebrafish. We find stat4 transcripts highly enriched in nkx2.5⁺ endothelial precursors in the pharynx and demonstrate that genetic ablation of stat4 causes stenosis of pharyngeal arch arteries (PAAs) by suppressing PAAs 3–6 angioblast development. We further show that stat4 is a downstream target of nkx2.5 and that it autonomously promotes proliferation of endothelial precursors of the mesoderm. Mechanistically, stat4 regulates the emerging PAA angioblasts by inhibiting the expression of hdac3 and counteracting the effect of stat1a. Altogether, our study establishes a role for Stat4 in zebrafish great vessel development, and suggests that Stat4 may serve as a therapeutic target for GV defects.

Stat4 is a transcription factor known to regulate pro-inflammatory signalling. Here, Meng et al. show that Stat4 is not only regulating inflammation but it is also crucial for great vessels development and endothelial precursor proliferation in zebrafish, by inhibiting the expression of hdac3 and counteracting the effect of Stat1a.

Mechanisms of Mas1 Receptor-Mediated Signaling in the Vascular Endothelium

OBJECTIVE

Angiotensin II (AngII) has been shown to regulate angiogenesis and at high pathophysiological doses to cause vasoconstriction through the AngII receptor type 1. Angiotensin 1 to 7 (Ang-(1-7)) acting through the Mas1 receptor can act antagonistically to high pathophysiological levels of AngII by inducing vasodilation, whereas the effects of Ang-(1-7) signaling on angiogenesis are less defined. To complicate the matter, there is growing evidence that a subpressor dose of AngII produces phenotypes similar to Ang-(1-7).

APPROACH AND RESULTS

This study shows that low-dose Ang-(1-7), acting through the Mas1 receptor, promotes angiogenesis and vasodilation similar to a low, subpressor dose of AngII acting through AngII receptor type 1. In addition, we show through in vitro tube formation that Ang-(1-7) augments the angiogenic response in rat microvascular endothelial cells. Using proteomic and genomic analyses, downstream components of Mas1 receptor signaling were identified, including Rho family of GTPases, phosphatidylinositol 3-kinase, protein kinase D1, mitogen-activated protein kinase, and extracellular signal-related kinase signaling. Further experimental antagonism of extracellular signal-related kinases 1/2 and p38 mitogen-activated protein kinase signaling inhibited endothelial tube formation and vasodilation when stimulated with equimolar, low doses of either AngII or Ang-(1-7).

CONCLUSIONS

These results significantly expand the known Ang-(1-7)/Mas1 receptor signaling pathway and demonstrate an important distinction between the pathological effects of elevated and suppressed AngII compared with the beneficial effects of AngII normalization and Ang-(1-7) administration. The observed convergence of Ang-(1-7)/Mas1 and AngII/AngII receptor type 1 signaling at low ligand concentrations suggests a nuanced regulation in vasculature. These data also reinforce the importance of mitogen-activated protein kinase/extracellular signal-related kinase signaling in maintaining vascular function.

Further intracellular proteins and signaling pathways regulated by angiotensin-(1-7) in human endothelial cells

In 2016, Meinert et al. (doi: 10.1016/j.jprot.2015.09.020) published the first 25 proteins in a protein array regulated in Human Umbilical Vein Endothelial Cells (HUVEC) by the heptapeptide angiotensin (Ang)-(1–7) and the first 10 intracellular signaling cascades at different time points. This supporting data article shows further proteins and pathways stimulated by Ang-(1–7) in human endothelial cells at time points of 1 h, 3 h, 6 h, and 9 h. HUVECs were stimulated with Ang-(1–7), and regulated proteins were identified via antibody microarray. Bioinformatics software IPA was used for association of regulated proteins to metabolic pathways.

G-Protein-Coupled Receptor MrgD Is a Receptor for Angiotensin-(1-7) Involving Adenylyl Cyclase, cAMP, and Phosphokinase A

Angiotensin (Ang)-(1-7) has cardiovascular protective effects and is the opponent of the often detrimental Ang II within the renin-angiotensin system. Although it is well accepted that the G-protein-coupled receptor Mas is a receptor for the heptapeptide, the lack in knowing initial signaling molecules stimulated by Ang-(1-7) prevented definitive characterization of ligand/receptor pharmacology as well as identification of further hypothesized receptors for the heptapeptide. The study aimed to identify a second messenger stimulated by Ang-(1-7) allowing confirmation as well as discovery of the heptapeptide's receptors. Ang-(1-7) elevates cAMP concentration in primary cells, such as endothelial or mesangial cells. Using cAMP as readout in receptor-transfected human embryonic kidney (HEK293) cells, we provided pharmacological proof that Mas is a functional receptor for Ang-(1-7). Moreover, we identified the G-protein-coupled receptor MrgD as a second receptor for Ang-(1-7). Consequently, the heptapeptide failed to increase cAMP concentration in primary mesangial cells with genetic deficiency in both Mas and MrgD Mice deficient in MrgD showed an impaired hemodynamic response after Ang-(1-7) administration. Furthermore, we excluded the Ang II type 2 receptor as a receptor for the heptapeptide but discovered that the Ang II type 2 blocker PD123319 can also block Mas and MrgD receptors. Our results lead to an expansion and partial revision of the renin-angiotensin system, by identifying a second receptor for Ang-(1-7), by excluding Ang II type 2 as a receptor for the heptapeptide, and by enforcing the revisit of such publications which concluded Ang II type 2 function by only using PD123319.