We hypothesized and investigated whether prenatal exposure to preeclampsia (PE) would simultaneously affect perinatal cardiovascular features and angiotensin system expressions. This prospective study was composed of mother-neonate dyads with (n = 49) and without maternal preeclampsia (n = 48) in a single tertiary medical center. The neonates exposed to PE had significantly larger relative sizes for the left and right coronary arteries and a higher cord plasma level of aminopeptidase-N, which positively correlated with the maternal diastolic blood pressures and determined the relative sizes of the left and right coronary arteries, whereas the encoding aminopeptidase-N (ANPEP) mRNA level in the PE cord blood leukocytes was significantly decreased, positively correlated with the neonatal systolic blood pressures (SBPs), and negatively correlated with the cord plasma-induced endothelial vascular cell adhesion molecule-1 mRNA levels. The PE cord plasma significantly induced higher endothelial mRNA levels of angiotensin II type 1 receptor (AT1R) and AT4R, whereas in the umbilical arteries, the protein expressions of AT2R and AT4R were significantly decreased in the PE group. The endothelial AT1R mRNA level positively determined the maternal SBPs, and the AT4R mRNA level positively determined the neonatal chamber size and cardiac output. In conclusion, PE may influence perinatal angiotensin system and cardiovascular manifestations of neonates across placentae. Intriguing correlations between these two warrant further mechanistic investigation.

The Renin-Angiotensin-Aldosterone System (RAAS) has been implicated in systemic and neurogenic hypertension. The infusion of RAAS inhibitors blunted arterial pressure and efficacy of use-dependent synaptic transmission in sympathetic ganglia. The current investigation aims to elucidate the impact of RAAS-mediated receptors on left ventricular cardiomyocytes and the role of the sarcolemma-bound carrier system in the heart of the hypertensive transgene model. A significant increase in mRNA and the protein expression for angiotensin II (AngII) receptor subtype-1 (AT1R) was observed in (mREN2)27 transgenic compared to the normotensive rodents. Concurrently, there was an upregulation in AT1R and a downregulation in the MAS1 proto-oncogene protein receptor as well as the AngII subtype-2 receptor in hypertensive rodents. There were modifications in the expressions of sarcolemma Na+-K+-ATPase, Na+-Ca2+ exchanger, and Sarcoendoplasmic Reticulum Calcium ATPase in the transgenic hypertensive model. These observations suggest chronic RAAS activation led to a shift in receptor balance favoring augmented cardiac contractility and disruption in calcium handling through modifications of membrane-bound carrier proteins and blood pressure. The study provides insight into mechanisms underlying RAAS-mediated cardiac dysfunction and highlights the potential value of targeting the protective arm of AngII in hypertension.

BACKGROUND: Astrocytes are the most abundant cell type of the central nervous system and are fundamentally involved in homeostasis, neuroprotection, and synaptic plasticity. This regulatory function of astrocytes on their neighboring cells in the healthy brain is subject of current research. In the ischemic brain we assume disease specific differences in astrocytic acting. The renin-angiotensin-aldosterone system regulates arterial blood pressure through endothelial cells and perivascular musculature. Moreover, astrocytes express angiotensin II type 1 and 2 receptors. However, their role in astrocytic function has not yet been fully elucidated. We hypothesized that the angiotensin II receptors impact astrocyte function as revealed in an in vitro system mimicking cerebral ischemia. Astrocytes derived from neonatal wistar rats were exposed to telmisartan (angiotensin II type 1 receptor-blocker) or PD123319 (angiotensin II type 2 receptor-blocker) under normal conditions (control) or deprivation from oxygen and glucose. Conditioned medium (CM) of astrocytes was harvested to elucidate astrocyte-mediated indirect effects on microglia and cortical neurons.
RESULTS: The blockade of angiotensin II type 1 receptor by telmisartan increased the survival of astrocytes during ischemic conditions in vitro without affecting their proliferation rate or disturbing their expression of S100A10, a marker of activation. The inhibition of the angiotensin II type 2 receptor pathway by PD123319 resulted in both increased expression of S100A10 and proliferation rate. The CM of telmisartan-treated astrocytes reduced the expression of pro-inflammatory mediators with simultaneous increase of anti-inflammatory markers in microglia. Increased neuronal activity was observed after treatment of neurons with CM of telmisartan- as well as PD123319-stimulated astrocytes.
CONCLUSIONS: Data show that angiotensin II receptors have functional relevance for astrocytes that differs in healthy and ischemic conditions and effects surrounding microglia and neuronal activity via secretory signals. Above that, this work emphasizes the strong interference of the different cells in the CNS and that targeting astrocytes might serve as a therapeutic strategy to influence the acting of glia-neuronal network in de- and regenerative context.

The stabilization of different active conformations of G protein-coupled receptors is thought to underlie the varying efficacies of biased and balanced agonists. Here, profiling the activation of signal transducers by angiotensin II type 1 receptor (AT1R) agonists revealed that the extent and kinetics of β-arrestin binding exhibited substantial ligand-dependent differences, which were lost when receptor internalization was inhibited. When AT1R endocytosis was prevented, even weak partial agonists of the β-arrestin pathway acted as full or near-full agonists, suggesting that receptor conformation did not exclusively determine β-arrestin recruitment. The ligand-dependent variance in β-arrestin translocation was much larger at endosomes than at the plasma membrane, showing that ligand efficacy in the β-arrestin pathway was spatiotemporally determined. Experimental investigations and mathematical modeling demonstrated how multiple factors concurrently shaped the effects of agonists on endosomal receptor-β-arrestin binding and thus determined the extent of functional selectivity. Ligand dissociation rate and G protein activity had particularly strong, internalization-dependent effects on the receptor-β-arrestin interaction. We also showed that endocytosis regulated the agonist efficacies of two other receptors with sustained β-arrestin binding: the V2 vasopressin receptor and a mutant β2-adrenergic receptor. In the absence of endocytosis, the agonist-dependent variance in β-arrestin2 binding was markedly diminished. Our results suggest that endocytosis determines the spatiotemporal bias in GPCR signaling and can aid in the development of more efficacious, functionally selective compounds.

We addressed the heteromerization of the epidermal growth factor receptor (EGFR) with G-protein coupled receptors (GPCR) on the basis of angiotensin-II-receptor-subtype-1(AT1R)-EGFR interaction as proof-of-concept and show its functional relevance during synergistic nuclear information transfer, beyond ligand-dependent EGFR transactivation. Following in silico modelling, we generated EGFR-interaction deficient AT1R-mutants and compared them to AT1R-wildtype. Receptor interaction was assessed by co-immunoprecipitation (CoIP), Förster resonance energy transfer (FRET) and fluorescence-lifetime imaging microscopy (FLIM). Changes in cell morphology, ERK1/2-phosphorylation (ppERK1/2), serum response factor (SRF)-activation and cFOS protein expression were determined by digital high content microscopy at the single cell level. FRET, FLIM and CoIP confirmed the physical interaction of AT1R-wildtype with EGFR that was strongly reduced for the AT1R-mutants. Responsiveness of cells transfected with AT1R-WT or -mutants to angiotensin II or EGF was similar regarding changes in cell circularity, ppERK1/2 (direct and by ligand-dependent EGFR-transactivation), cFOS-expression and SRF-activity. By contrast, the EGFR-AT1R-synergism regarding these parameters was completely absent for in the interaction-deficient AT1R mutants. The results show that AT1R-EGFR heteromerisation enables AT1R-EGFR-synergism on downstream gene expression regulation, modulating the intensity and the temporal pattern of nuclear AT1R/EGFR-information transfer. Furthermore, remote EGFR transactivation, via ligand release or cytosolic tyrosine kinases, is not sufficient for the complete synergistic control of gene expression.

Clinical treatment of acute myeloid leukemia (AML) largely relies on intensive chemotherapy. However, the application of chemotherapy is often hindered by cardiotoxicity. Patient sequence data revealed that angiotensin II receptor type 1 (AGTR1) is a shared target between AML and cardiovascular disease (CVD). We found that inhibiting AGTR1 sensitized AML to chemotherapy and protected the heart against chemotherapy-induced cardiotoxicity in a human AML cell-transplanted mouse model. These effects were regulated by the AGTR1-Notch1 axis in AML cells and cardiomyocytes from mice. In mouse cardiomyocytes, AGTR1 was hyperactivated by AML and chemotherapy. AML leukemogenesis increased the expression of the angiotensin-converting enzyme and led to increased production of angiotensin II, the ligand of AGTR1, in an MLL-AF9-driven AML mouse model. In this model, the AGTR1-Notch1 axis regulated a variety of genes involved with cell stemness and chemotherapy resistance. AML cell stemness was reduced after Agtr1a deletion in the mouse AML cell transplant model. Mechanistically, Agtr1a deletion decreased γ-secretase formation, which is required for transmembrane Notch1 cleavage and release of the Notch1 intracellular domain into the nucleus. Using multiomics, we identified AGTR1-Notch1 signaling downstream genes and found decreased binding between these gene sequences with Notch1 and chromatin enhancers, as well as increased binding with silencers. These findings describe an AML/CVD association that may be used to improve AML treatment.

The N-terminal portion of the octapeptide angiotensin II (DRVYIHPF; AngII), a vasopressor peptide that favorably binds to, and activates, AngII type 1 receptor (AT1R), has an important role in maintaining bioactive conformation. It involves all three charged groups, namely (i) the N-terminal amino group cation, (ii) the Asp sidechain anion and (iii) the Arg guanidino cation. Neutralization of any one of these three charged groups results in a substantial reduction (<5%) in bioactivity, implicating a specialized function for this cluster. In contrast, angiotensin A (ARVYIHPF; AngA) has reduced bioactivity at AT1R; however, replacement of Asp in AngII with sarcosine (N-methyl-glycine) not only restores bioactivity but increases the activity of agonist, antagonist, and inverse agonist analogues. A bend produced at the N-terminus by the introduction of the secondary amino acid sarcosine is thought to realign the functional groups that chaperone the C-terminal portion of AngII, allowing transfer of the negative charge originating at the C-terminus to be transferred to the Tyr hydroxyl-forming tyrosinate anion, which is required to activate the receptor and desensitizes the receptor (tachyphylaxis). Peptide (sarilesin) and nonpeptide (sartans) moieties, which are long-acting inverse agonists, appear to desensitize the receptor by a mechanism analogous to tachyphylaxis. Sartans/bisartans were found to bind to alpha adrenergic receptors resulting in structure-dependent desensitization or resensitization. These considerations have provided information on the mechanisms of receptor desensitization/tolerance and insights into possible avenues for treating addiction. In this regard sartans, which appear to cross the blood-brain barrier more readily than bisartans, are the preferred drug candidates.

As a result of the lack of modern techniques, the study of Tibetan medicine has been hindered in identifying bioactive compounds. Herein, we established a chromatographic approach using an immobilized angiotensin II type 1 receptor (AT1R) via a one-step method triggered by haloalkane dehalogenase. The bioactive compounds from Choerospondias axillaris (Guangzao) were screened and identified using the immobilized AT1R followed by MS. Frontal analysis (FA) and adsorption energy distribution (AED) were used to evaluate the association constants. Molecular docking was used to investigate the binding configurations, and the surface efficiency index, binding efficiency index, and ligand-lipophilicity efficiency (LLE) were calculated to assess the drug-like properties. The results identified naringenin, pinocembrin, and chrysin as the compounds that specifically bind to AT1R in Guangzao. FA and AED confirmed that there is only one type of binding site between these compounds and AT1R. The association constants were (2.40 ± 0.02) × 104 M-1 for naringenin (5.22 ± 0.26) × 104 M-1 for pinocembrin, and (4.27 ± 0.14) × 104 M-1 for chrysin, respectively. These compounds can bind with AT1R through the orthosteric binding pocket. Naringenin exhibited better LLE than pinocembrin and chrysin. These results confirmed the feasibility of using the immobilized AT1R column for screening and analyzing bioactive compounds in Tibetan medicines.

OBJECTIVE: Diabetic nephropathy (DN) is one of the complications of diabetes mellitus (DM). This study aimed to investigate the association between genetic polymorphisms, specifically AGTR1 (rs5186) and TGF-β1 (rs1800470), and the risk of developing Diabetic nephropathy (DN) in type 2 diabetes mellitus patients, compared to those without DN and healthy controls.
METHODS: A case-control study was conducted on 165 diabetic patients (59 with diabetic nephropathy (DN) and 54 without DN (DM)), and 52 healthy controls (HC). The genotyping was done using amplification refractory mutation system method (ARMS-PCR). Age, gender, and duration of diabetes were matched across groups. Clinical parameters including FBS, RBS, HbA1C, creatinine, urea, SBP, DBP, total cholesterol, triglycerides, LDL, and BMI were assessed.
RESULTS: Diabetic patients with nephropathy exhibited significantly higher levels of clinical parameters compared to those without nephropathy and healthy controls. The risk allele of AGTR1 , C (p <0.0001), and risk allele containing genotypes AC (p <0.0001) and CC (p - 0.0010) were significantly higher in DN patients compared to DM and HC groups. Similarly, the TGF-β1 risk allele C (p - 0.0001), and corresponding genotypes TC (p - 0.0038) and CC (p - 0.0027) were significantly associated with increased risk of diabetic nephropathy compared to DM and HC groups.
CONCLUSIONS: The data showed significant association of AGTR1 (rs5186) and TGF-β1 (rs1800470) polymorphism with an increased risk of diabetic nephropathy in type 2 diabetes mellitus patients. More investigation will be required to disseminate the results, while increasing the samples size and using whole genome sequencing.

BACKGROUND: We have documented profound release of nitric oxide (NO) and endothelium-derived hyperpolarization factor (EDHF) by angiotensin II (ANGII) receptor 1 (AT1) blocker (ARB) losartan and its unique metabolite EXP3179, a pleiotropic effect that may help rationalize the protective properties of ARBs. Since blood pressure (BP) lowering by ARBs likely require an ANGII-dependent switch from AT1 to ANGII receptor 2 (AT2) signaling, a receptor known to stimulate endothelial NO release, we investigated the contribution of AT1 and AT2 to losartan and EXP3179\'s endothelial function-activating properties.
METHODS: Two AT1 ligands were used in an attempt to block the AT1-dependent endothelium-enhancing effects of EXP3179. AT2-null mice were used to evaluate the acute ex vivo and chronic in vivo effects of EXP3179 (20μM) and losartan (0.6 g/l), respectively, on endothelial function, BP and aortic stiffness.
RESULTS: Ex vivo blockade of AT1 receptors did not attenuate EXP3179\'s effects on NO and EDHF-dependent endothelial function activation. We observed significant reductions in PE-induced contractility with EXP3179 in both WT and AT2 knockout (KO) aortic rings. In vivo, a 1-month chronic treatment with losartan did not affect pulse wave velocity (PWV) but decreased PE-induced contraction by 74.9 % in WT (p < 0.0001) and 47.3 % in AT2 KO (p < 0.05). Presence of AT2 was critical to losartan\'s BP lowering activity.
CONCLUSIONS: In contrast to BP lowering, the endothelial function-enhancing effects of losartan and EXP3179 are mostly independent of the classic ANGII/AT1/AT2 pathway, which sheds light on ARB pleiotropism.