Angiotensin II Type 1 Receptor Research Articles

Association of ACE and AGTR1 variants with retinopathy of prematurity: a case-control study and meta-analysis.

Retinopathy of prematurity (ROP) is a major cause of childhood blindness worldwide, linked to gene variants in the renin-angiotensin-aldosterone system, including angiotensin-converting enzyme (ACE) and angiotensin II receptor type 1 (AGTR1). This study aims to evaluate the association between ACE insertion/deletion (I/D) and AGTR1 rs5186A > C variants with the occurrence and progression of ROP in a Polish cohort. A total of 377 premature infants were enrolled in the study. The ACE variant was evaluated using PCR, and AGTR1 was assessed using TaqMan probes. Clinical characteristics, including risk factors and comorbidities, were documented. A meta-analysis of the effects of the studied variants on ROP was also conducted. The AGTR1 rs5186C allele was significantly associated with both the progression of ROP and treatment outcomes. Homozygotes exhibited a 2.47-fold increased risk of developing proliferative ROP and a 4.82-fold increased risk of treatment failure. The impact of this allele increased at low birth weight. A meta-analysis, including 191 cases and 1661 controls, indicated an overall risk of 1.7 (95%CI 1.02-2.84) for the recessive effect of the rs5186C allele. The ACE variant did not show a significant association with ROP in our population; however, a meta-analysis of 996 cases and 2787 controls suggested a recessive effect of the insertion allele (an odds ratio of 1.21 (95%CI 1.00-1.60)). These results indicate that gain-of-function AGTR1 variants may play a crucial role in the development of ROP, potentially by promoting angiogenesis and pro-inflammatory effects. Screening for these variants could facilitate the development of personalized risk assessment and treatment strategies for ROP.

Phosphorylation patterns in the AT1R C-terminal tail specify distinct downstream signaling pathways.

Different ligands stabilize specific conformations of the angiotensin II type 1 receptor (AT1R) that direct distinct signaling cascades mediated by heterotrimeric G proteins or β-arrestin. These different active conformations are thought to engage distinct intracellular transducers because of differential phosphorylation patterns in the receptor C-terminal tail (the "barcode" hypothesis). Here, we identified the AT1R barcodes for the endogenous agonist AngII, which stimulates both G protein activation and β-arrestin recruitment, and for a synthetic biased agonist that only stimulates β-arrestin recruitment. The endogenous and β-arrestin-biased agonists induced two different ensembles of phosphorylation sites along the C-terminal tail. The phosphorylation of eight serine and threonine residues in the proximal and middle portions of the tail was required for full β-arrestin functionality, whereas phosphorylation of the serine and threonine residues in the distal portion of the tail had little influence on β-arrestin function. Similarly, molecular dynamics simulations showed that the proximal and middle clusters of phosphorylated residues were critical for stable β-arrestin-receptor interactions. These findings demonstrate that ligands that stabilize different receptor conformations induce different phosphorylation clusters in the C-terminal tail as barcodes to evoke distinct receptor-transducer engagement, receptor trafficking, and signaling.

Abstract We110: Novel allosteric ligand designed to prevent Autoantibody targeting the Angiotensin Type 1 Receptor (AT1R) in cardiovascular diseases (CVD)

Background: The clinical data suggest an association of autoantibodies (AAb) targeting angiotensin II type1 receptor (AT1R) and outcomes in heart failure (HF) and preeclampsia. Notably, patient’s risk increases 2 to 4-fold for heart diseases and hypertension. Although AT1R blockers (ARBs) have emerged as a key component in the therapeutic arsenal against CVD, we believe that rather than completely blocking AT1R signaling, maintaining a balanced signaling is crucial for cardiovascular homeostasis. Therefore, we posit that reducing AT1R overactivation and blocking AAb-mediated activation could benefit cardiac health and attenuate the progression of CVD. In our previous study (PMID:36440576), we identified small molecules capable of inhibiting AAb-induced AT1R signaling. Leveraging these observations, we have developed a novel AT1R allosteric ligand that inhibits autoantibody binding to AT1R while still retaining normal AT1R signaling. Methods: Using computational and medicinal chemistry approaches, we designed a series of novel AT1R ligands and obtained compounds with >98% purity through chemical synthesis. Monoclonal antibodies mimicking AT1R-AAb have been generated. Serum samples from dilated cardiomyopathy (DCM) and preeclampsia (PE) patient cohorts were collected and presence of AT1R-AAb was determined using ELISA and epitope-peptide competition studies. Pharmacological characterization of compounds was performed using calcium mobilization, 125I -AngII binding, ex vivo vasoconstriction, and ELISA assays. Results: We identified an AT1R allosteric compound that reduced AngII-mediated calcium signaling with a 5-fold shift in EC 50 . The IC 50 was determined to be 18 µM. It reduces the AngII-mediated vasoconstriction while blocking both monoclonal and patient-derived autoantibody binding with an IC 50 of 5 µM. Conclusion: We have identified a novel AT1R allosteric ligand with negative allosteric modulator (NAM) properties, which has the potential to block autoantibodies and could serve as a new generation of ARBs. Uniquely, it retains beneficial AT1R signaling without competing with AngII, and its allosteric ligand property can be tailored to achieve optimal AT1R signaling.

Screening and analysis of the targeted compounds in Choerospondias axillaris extract by receptor chromatographic column with immobilized angiotensin II type 1 receptor.

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.

Renin-Angiotensin System Genes Polymorphisms in Patients With COVID-19 and Its Relation to Severe Cases of SARS-CoV-2 Infection.

Different variants of single nucleotide polymorphisms (SNPs) of angiotensinogen (AGT), angiotensin-converting enzyme type 1 (ACE1), and angiotensin II receptors type 1 (AGTR1) and 2 (AGTR2) genes determine different susceptibility to cardiovascular disease (CVD) and hypertension, which can be considered as risk factors for fatal outcomes among coronavirus disease 2019 (COVID-19) patients. The objective of our study was to assess the relation between the frequency of SNPs of the renin-angiotensin system (RAS) components, and the severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. The cross-sectional study included 100 patients with a laboratory-confirmed diagnosis of COVID-19 admitted to the hospital. Criteria for severe COVID-19 included respiratory rate (RR) > 30/min, blood oxygen saturation (SpO2) ≤ 93%, signs of unstable hemodynamics with systolic blood pressure (SBP) < 90 and/or diastolic blood pressure (DBP) < 60 mm Hg. All patients were identified with alleles and genotypes of the polymorphic markers rs4762 of the AGT gene, rs1799752 of the ACE1 gene, rs5186 of the AGTR1 gene and rs1403543 of the AGTR2 gene using the polymerase chain reaction method in human DNA preparations on real-time CFX96C1000 Touch, Bio-Rad equipment (Syntol, Russia). Statistical analysis was performed in R v.4.2. Patients were divided into groups with severe (n = 44) and moderate COVID-19 (n = 56). For ACE1 rs1799752, a significant deviation from the population distribution was detected in both studied subgroups. A higher frequency of the C allele SNP rs5186 AGTR1 gene was detected in the group with severe disease. More frequent A/A genotype of SNP rs1403543 AGTR2 was detected among females with severe COVID-19. Haplotype analysis revealed more common DCG haplotype among patients with severe COVID-19. The odds ratio for severe COVID-19 in the presence of the DCG haplotype was 3.996 (95% confidential interval: 1.080 -14.791, P < 0.05). Our data suggest that the SNP genes of the RAS components, may allow to identify groups of patients predisposed to a more severe course of COVID-19.

Valsartan as a prophylactic treatment against breast cancer development and niche activation: What molecular sequels follow chronic AT-1R blockade?

AimsTransactivation of insulin-growth-factor-receptor (IGF-1R) by angiotensin-II-type-1-receptor (AT-1R) was only demonstrated in vascular-smooth-muscle cells and has never been tested in breast-cancer (BC). This investigation addressed the impact of chronic AT-1R blockade by valsartan (Val) on possible concurrent AT-1R/IGF-1R signaling inhibition, regressing BC-tumor-microenvironment (TME) cellular components activation, and hindering BC development. Main methodsThe effect of different Val doses (10, 20, 40 & 80 mg/kg/day for 490 days) was tested on dimethylbenz(a)anthracene (DMBA)-induced progesterone-promoted-BC in rats. The influence on intratumoral/circulating angiotensin-II (ANG-II) levels and AT-1R/Mas-R immunofluorescent-expression were assessed. The potential AT-1R/IGF-1R crosstalk within TME-BC-stem-cells (BCSCs) and cancer-associated-fibroblasts (CAFs) was evaluated by fluorescently marking these cells and locating the immunofluorescently-stained AT-1R/IGF-1R in them using confocal-laser-microscopy and further quantified by flow cytometry. In addition, the molecular alterations following blocking AT-1R were inspected including determining Src; crucial for IGF-1R transactivation by AT-1R, Notch-1; IGF-IR transcriptional-regulator, and PI3K/Akt &IL-6/STAT expression. Further, the suppression of CSCs' capabilities to maintain pluripotency, stemness features, epithelial-to-mesenchymal-transition (EMT), and angiogenesis was evaluated by assessing NANOG gene, aldehyde-dehydrogenase (ALDH), N-cadherin and vascular-endothelial-growth-factor (VEGF), respectively. Furthermore, the proliferative marker; Ki-67, was detected by immunostaining, and tumors were histologically graded using Elston-Ellis-modified-Scarff-Bloom-Richardson method. Key findingsProphylactic Val significantly reduced tumor size, prolonged latency, reduced tumor histopathologic grade, decreased circulating/intratumoral-ANG-II levels, increased Mas-R, and decreased AT1R expression. AT-1R/IGF-1R were co-expressed with a high correlation coefficient on CAFs/BCSCs. Moreover, Val significantly attenuated IGF-1R transactivation and transcriptional regulation via Src and Notch-1 genes' downregulation and reduced Src/IGF-IR-associated PI3K/Akt and IL-6/STAT3 signaling. Further, Val significantly decreased intratumoral NANOG, ALDH, N-cadherin, VEGF, and Ki-67 levels. SignificanceChronic Val administration carries a potential for repurposing as adjuvant or conjunct therapy for patients at high risk for BC.

Association between ACE (rs4343 and rs1799752), AGTR1 (rs5186), and PAI-1 (rs2227631) polymorphisms in the host and the severity of Covid-19 infection

Objective It is necessary to identify appropriate clinical, biochemical, epidemiological and genetic biomarkers to elucidate the underlying mechanisms of the coronavirus disease-2019 (COVID-19) disease. The study focused on not only the link between disease severity (non-intense unit care (non-ICU) versus intensive unit care (ICU) and genetic susceptibility in COVID-19 patients but also the connection between comorbidity and genetic susceptibility affecting the severity of COVID-19. Subject and methods One hundred and sixty-two COVID-19 patients treated in the non-ICU and ICU in Kayseri City Hospital were included. All volunteers underwent a physical examination and biochemical evaluation. Angiotensin-converting enzyme (ACE p.T776T G > A(rs4343) and g.16471_16472delinsALU (also referred to as I/D polymorphism; rs1799752), angiotensin II receptor type-1 (AGTR1) c.*86A > C (also referred to as A1166C; rs5186), and plasminogen activator inhibitor-1 (PAI-1-844 G > A (rs2227631) polymorphisms were analysed as well. Results To have ACE “ID” genotype did not change the severity of the disease (OR: 0.92, 95% CI: 0.41–2.1, p = 0.84), but decreased the mortality risk 2.9-fold (OR: 2.9, 95% CI: 1.1–7.0, p = 0.03). In PAI-1-844 G > A, having the “AA” genotype in the “A” recessive model increased the risk of the diabetes mellitus (DM) 2.3-fold (OR: 2.3 95%, CI: 1.16–4.66, p = 0.018). In the “G” recessive model, to have the GG genotype increased the risk of chronic kidney disease (CKD) 4.8-fold (OR:4.8, 95% CI: 1.5–15.5, p = 0.008). “GG” genotype in the DM group had a higher fibrinogen level compared to those with the “AG” genotype (AG:4847.2 mg/L (1704.3) versus GG:6444.67 mg/L (1861.62) p = 0.019) and “AA” genotype in the CKD group had lower platelet levels and those with “GG” had higher platelet levels (AA:149 µL (18–159) versus GG: 228 µL (146–357) p = 0.022). Conclusion This study was shown that genetic predispositions that causes comorbidities were also likely to affect the prognosis of COVID-19.

Activation AMPK in Hypothalamic Paraventricular Nucleus Improves Renovascular Hypertension Through ERK1/2-NF-κB Pathway.

Hypertension is a globally prevalent disease, but the pathogenesis remains largely unclear. AMP-activated protein kinase (AMPK) is a nutrition-sensitive signal of cellular energy metabolism, which has a certain influence on the development of hypertension. Previously, we found a down-regulation of the phosphorylated (p-) form of AMPK, and the up-regulation of the angiotensin II type 1 receptor (AT1-R) and that of p-ERK1/2 in the hypothalamic paraventricular nucleus (PVN) of hypertensive rats. However, the exact mechanism underlying the relationship between AMPK and AT1-R in the PVN during hypertension remains unclear. Thus, we hypothesized that AMPK modulates AT1-R through the ERK1/2-NF-κB pathway in the PVN, thereby inhibiting sympathetic nerve activity and improving hypertension. To examine this hypothesis, we employed a renovascular hypertensive animal model developed via two-kidney, one-clip (2K1C) and sham-operated (SHAM). Artificial cerebrospinal fluid (aCSF), used as vehicle, or 5-amino-1-β-D-ribofuranosyl-imidazole-4-carboxamide (AICAR, an AMPK activator, 60μg/day) was microinjected bilaterally in the PVN of these rats for 4weeks. In 2K1C rats, there an increase in systolic blood pressure (SBP) and circulating norepinephrine (NE). Also, the hypertensive rats had lowered expression of p-AMPK and p-AMPK/AMPK, elevated expression of p-ERK1/2, p-ERK1/2/ERK1/2 and AT1-R, increased NF-κB p65 activity in the PVN compared with the levels of these biomarkers in SHAM rats. Four weeks of bilateral PVN injection of AMPK activator AICAR, attenuated the NE level and SBP, increased the expression of p-AMPK and p-AMPK/AMPK, lessened the NF-κB p65 activity, decreased the expression of p-ERK1/2, p-ERK1/2/ERK1/2 and AT1-R in the PVN of 2K1C rats. Data from this study imply that the activation of AMPK within the PVN suppressed AT1-R expression through inhibiting the ERK1/2-NF-κB pathway, decreased the activity of the sympathetic nervous system, improved hypertension.

Association of Perinatal Cardiovascular Features with Angiotensin System Expressions in Maternal Preeclampsia.

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.

Losartan Treatment Reduces Esophageal Eosinophilic Inflammation in a Subset of Eosinophilic Esophagitis

BackgroundEosinophilic esophagitis (EoE) is a chronic, food antigen-driven esophageal disorder. Connective tissue disorders (CTDs) and esophageal connective tissue alterations are associated with EoE, therefore angiotensin II type 1 receptor (AT1R) blockade with losartan, an accepted CTD treatment, is a potential EoE treatment. ObjectiveWe evaluated losartan’s effects on esophageal pathology, symptoms, and safety in patients with EoE with and without a CTD in an open-label, non-placebo controlled multi-site study. MethodsFifteen participants, 5-23 years old, with EoE underwent treatment with a per-protocol titrated doses of losartan in an open-label, 16-week pilot trial. Losartan was added to standard-of-care therapy and 14 patients completed the study. Eosinophil counts served as the primary endpoint, while EoE Histology Scoring System (EoEHSS), Endoscopic Reference Scores (EREFS), EoE Diagnostic Panel (EDP), and patient-reported outcomes (PROs) were also assessed. ResultsEsophageal eosinophilia was not reduced following losartan. The peak eosinophil count was not reduced for the proximal (median (IQR): -3 (-22 to 3), p = 0.49) and distal esophagus (median (IQR): -18 (-39 to -1), p = 0.23). There were no differences in losartan response in EoE with or without CTD (n = 7 and 8, respectively). Regardless, a small subset of 4 participants resolved esophageal eosinophilia with concomitant reduction in EoEHSS and EREFS scores. Across all subjects, the Pediatric EoE Symptom Score and Pediatric Quality of Life Inventory EoE Module and EDP improved following losartan (p < 0.05). ConclusionLosartan treatment associated with improved PRO scores and EDP biomarkers albeit without reducing esophageal eosinophilia overall. A subset of patients demonstrated improved histopathological and endoscopic features which could not be tied to a specific feature which could predict response to treatment.

Acupuncture modulation of the ACE/Ang II/AT1R and ACE2/Ang(1-7)/MasR pathways in the rostral ventrolateral medulla reduces sympathetic output and prevents cardiac injury caused by SHR hypertension.

Acupuncture can reduce blood pressure, heart rate (HR), and ameliorate cardiac damage by modulating the excitability of the sympathetic nervous system, but the exact mechanism of this effect remains unclear. This study investigated the potential mechanisms of acupuncture in the treatment of cardiac damage in hypertension. Spontaneously hypertensive rats (SHR) were used as the hypertension model with Wistar-Kyoto rats as the control. Manual acupuncture, electroacupuncture, and metoprolol were used as interventions. Systolic and diastolic blood pressure (SBP, DBP) plus HR were monitored with cardiac structure determined using Masson staining. Angiotensin II (Ang II) and norepinephrine in myocardium were detected with ELISA as was Ang(1-7) and gamma aminobutyric acid (GABA) in the rostral ventrolateral medulla (RVLM). Expression of mRNA for collagen type I (Col-I), Col-III, actin α1 (ACTA1), and thrombospondin 4 (THBS4) in myocardium was detected using real-time PCR. Expression of angiotensin converting enzyme (ACE), Ang II, angiotensin II type 1 receptor (AT1R), ACE2, and Mas receptor (MasR) proteins in RVLM was monitored using western blot. After manual acupuncture and electroacupuncture treatment, SHRs showed decreased SBP, DBP and HR, reduced myocardial damage. There was decreased expression of the ACE/Ang II/AT1R axis, and increased expression of the ACE2/Ang(1-7)/MasR axis within the RVLM. GABA levels were increased within the RVLM and norepinephrine levels were decreased in myocardial tissue. Metoprolol was more effective than either manual acupuncture or electroacupuncture. Acupuncture directed against hypertensive cardiac damage may be associated with regulation of ACE/Ang II/AT1R and the ACE2/Ang(1-7)/MasR pathway within the RLVM to reduce cardiac sympathetic excitability.

G protein-coupled receptor endocytosis generates spatiotemporal bias in β-arrestin signaling.

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.

Inhibiting AGTR1 reduces AML burden and protects the heart from cardiotoxicity in mouse models.

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 role of angiotensin II type 1 receptor pathway in cerebral ischemia‒reperfusion injury: Implications for the neuroprotective effect of ARBs

AbstractCerebral ischemia–reperfusion (I/R) injury is a crucial factor that impacts the prognosis of recanalization therapy for acute ischemic stroke (AIS). It has been found that the brain renin–angiotensin system, especially the angiotensin II type 1 receptor (AT1R) pathway, plays a significant role in cerebral I/R injury. This pathway is involved in processes such as oxidative stress, neuroinflammation, apoptosis, and it affects cerebrovascular autoregulation and the maintenance of blood–brain barrier. AT1R blocker (ARB), widely used as an antihypertensive agent, has demonstrated stroke prevention capabilities in numerous prospective studies, independent of its antihypertensive characteristics. Studies focusing on neurological diseases like Alzheimer's disease, Parkinson's disease, and cognitive impairment have confirmed that ARBs exhibit neuroprotective effects and aid in improving neurological functions. Preclinical studies have shown that ARBs can reduce infarct volume and brain edema, inhibit multiple signaling pathways associated with I/R injury, restore energy levels in damaged brain regions, and rescue the penumbra by promoting neovascularization in cerebral I/R models. These findings suggest that ARBs have potential to become a novel category of neuroprotecting agents for clinical treatment of AIS. Therefore, this review primarily provides a theoretical foundation and practical evidence for the future clinical utilization of ARBs as neuroprotective agents following reperfusion therapy for AIS. It outlines the role of cerebral I/R injury through the AT1R pathway and highlights the research progress made on ARBs in I/R models.

Structural Features Influencing the Bioactive Conformation of Angiotensin II and Angiotensin A: Relationship between Receptor Desensitization, Addiction, and the Blood-Brain Barrier.

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.

#2123 Ageing, renal function and frailty: analysis of the FRASNET study

Abstract Background and Aims Frailty is a common geriatric syndrome of significant public health importance. The kidney is one of the organs that progressively loses function with aging leading a decrease of glomerular filtration rate (GFR). In elderly the definition of eGFR threshold for the diagnosis of CKD is debated. FRASNET study aims of identify the role of kidney function (glomerular and tubular involvement) in determining frailty among not community-dwelling elderly adults, also depending on the genetics of each single subject. Method The FRASNET study was a cross-sectional multicentre observational cohort study involving healthy. The exclusion criteria were: i) severe cognitive impairment, ii) severe health problems. They have been characterised for BP, GFR, sodium intake (Kawasaki formula), cognitive status, quality of life, anamnestic factors, health and socio-economic status. Frailty was determined according to modified Fried index by the presence of three conditions among reduced grip strength, reduced gait speed, low physical activity, self-reported exhaustion. We considered the number of drugs as an index of comorbidity. Genotyping of 20 targeted single nucleotide polymorphisms (SNPs) selected on renal and hypertension was performed. ANOVA and conditional inference tree analysis have been carried out. Results 1183 individuals were included in the study sample. Median age was 72 [IQ 69-77]. 328 (27.7%) subjects were robust, 445 (37.6%) pre-frail, 410 (34.7%) frail. Frailty increases with age, especially after 75 years (from 28.9% to 75.7%). The overall mean GFR was 71.8 ± 16.5 ml/min/1.73 m2. Estimated 24 h urinary sodium excretion was 194.5 mEq/24 h with median fractional excretion of sodium (FeNa) 0.75%. In 31.9% of sample FeNa was greater than 1%. Only 3% of subjects reported CKD. Moreover, 21.1% presented eGFR ≤ 60 and the prevalence of CKD increases according to age from 12.3% to 70.3%. CKD prevalence increases in linear manner across frailty classes from 20% in robust to 47.6% in frail. Conditional inference tree analysis confirmed the role of age, comorbidity and GFR in determining frailty. In oldest subjects (&amp;gt;75 years old), the eGFR level most strongly associated with frailty was below 53 (ml/min/1.73 m2) (Fig. 1). No differences in sodium excretion were observed according to frailty classes. Moreover, we observed an increase of FeNa according to age and frailty classes form 0.71% (median (IQR 0.567)) to 0.79% (median (IQR 0.690)). In frail group exaggerated FeNa (&amp;gt;1%) is more frequent than in robust and pre-frail subjects (Chi-squared p = 0.021). Even after the introduction of these variables in inferential trees the new proposed cut-off for GFR (53) is a main determinant of frailty in oldest (Fig. 2). The eGFR parameter resulted associated with two genetic variants in RAAS system, rs5051 in the angiotensinogen gene (AGT) and rs2131127 in the angiotensin II receptor type 1 (AGTR1). The rs4293393 in uromodulin gene (UMOD) was confirmed associated with eGFR value. Conclusion The present study is part of the complex debate on the relationship among renal function, aging and frailty. We can therefore conclude that glomerular filtration (eGFR below 50 and not the presence of CKD) must be considered among the factors that influence frailty. Our study also showed a deterioration of tubular function in frail subject that can be expression of structural changes due to nephroangiosclerosis.

#1166 ACTION3 pivotal Phase 3 &amp; open-label extension study assessing DMX-200 in adult &amp; paediatric patients with focal segmental glomerulosclerosis (FSGS)

Abstract Background and Aims Focal segmental glomerulosclerosis (FSGS) is a major cause of glomerular disease that affects both adults and children. FSGS can rapidly progress to end-stage kidney disease. Lack of safe and effective treatment represents a significant unmet need for patients with FSGS. Development of treatments has been hampered by complexities including the rare nature of the disease, varying drivers of pathogenesis, and the evolving diagnostic and clinical trial designs, necessitating innovative research approaches. DMX-200 (repagermanium) is a C-C motif chemokine receptor 2 (CCR2) pathway inhibitor. Activation of the angiotensin II type 1 receptor (AT1R) and CCR2 have been independently implicated in the pathogenesis and progression of FSGS. These receptors form a functional complex so inhibition of both receptors may provide an efficient approach to FSGS treatment. In vivo data shows co-administration of DMX-200 and the angiotensin receptor blocker (ARB) irbesartan demonstrated a synergistic reduction in proteinuria, macrophage infiltration, and podocyte loss compared with vehicle or either antagonist alone. A subsequent Phase 2a cross-over study (NCT03649152) in N = 8 patients with biopsy-proven primary FSGS showed that the combination of DMX-200 and irbesartan (compared to placebo) was well tolerated with most patients experiencing a reduction in proteinuria. Based on these data, the global Phase 3 study (ACTION3) was initiated to confirm the proteinuria lowering effects of DMX-200 and assess effects on eGFR decline. ACTION3 is a randomised, placebo-controlled, double-blind, long-duration study of FSGS patients and on completion will provide a resource for the wider nephrology community and advocacy groups on the natural history of FSGS patients and the effects of a CCR2-inhibitor on the background of an ARB. Here we present the baseline data from the first 90 patients enrolled in ACTION3 at 12th January 2024. Method The ACTION3 (NCT05183646) study is a pivotal Phase 3, multicentre study of the efficacy and safety of DMX-200, 120 mg twice daily compared with placebo in adult patients with biopsy-proven FSGS receiving maximal tolerated ARB, with persistent proteinuria &amp;gt;1.5g/ day and eGFR &amp;gt;25 ml/min/1.73 m2. The study plans to enroll approximately 286 patients with primary FSGS, genetic FSGS and FSGS of undetermined cause with the primary objective of evaluating the efficacy of DMX-200 in percent change in 24-hour urine PCR and eGFR slope. The initial 104-week randomized period will be extended in a 2-year open label extension study. A futility analysis by an Independent Data Monitoring Committee following the first 72 patients completing 35 weeks of treatment confirm that continuation of the study is non-futile. Results The study is actively recruiting at 71 sites in 11 countries listed in Table 1. Demographic data of randomised patients is listed in Table 2. Patients are predominantly male (65%), with an average age of 46.6 yrs. and mean eGFR 56.3 ± 27.6 (ml/min/1.73 m2). The study is expanding recruitment into additional countries in the Asia Pacific, Europe, and Latin American regions. Further, the study protocol has sought and received regulatory approval to enroll adolescent patients aged 12-18 in Argentina, Mexico, UK and the US. Conclusion DMX-200 (repagermanium) has shown encouraging signs of safety and efficacy in combination with an ARB for the treatment of FSGS. The contributing countries and baseline characteristics of the patients enrolled in ACTION3 are similar to the populations studied in other recent FSGS trials. No clinically significant safety concerns have been observed in patients enrolled to date in the ACTION3 Phase 3 study.

Pyridostigmine attenuates hypertension by inhibiting activation of the renin-angiotensin system in the hypothalamic paraventricular nucleus.

Activation of the renin-angiotensin system (RAS) triggers oxidative stress and an inflammatory response in the hypothalamic paraventricular nucleus (PVN), in turn increasing the sympathetic hyperactivity that is a major cause of hypertension. Pyridostigmine has cardioprotective effects by suppressing the RAS of myocardial tissue. However, whether pyridostigmine attenuates hypertension by inhibiting the RAS of the PVN remains unclear. We thus investigated the effect and mechanism of pyridostigmine on two-kidney one-clip (2K1C)-induced hypertension. 2K1C rats received pyridostigmine, or not, for 8weeks. Cardiovascular function, hemodynamic parameters, and autonomic activity were measured. The PVN levels of pro-/anti-inflammatory cytokines, oxidative stress, and RAS signaling molecules were evaluated. Our results showed that hypertension was accompanied by cardiovascular dysfunction and an autonomic imbalance characterized by enhanced sympathetic but diminished vagal activity. The PVN levels of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), reactive oxygen species (ROS), NOX-2, and malondialdehyde (MDA) increased; those of IL-10 and superoxide dismutase (SOD) decreased. Moreover, the RAS signaling pathway was activated, as evidenced by increased levels of the angiotensin-converting enzyme (ACE), angiotensin II (Ang II), and the Ang II type 1 receptor (AT1R) and a decreased AT2R level. Pyridostigmine lowered blood pressure and improved cardiovascular function, associated with restoration of the autonomic balance. Meanwhile, pyridostigmine decreased PVN IL-6, TNF-α, ROS, NOX-2, and MDA levels and increased IL-10 and SOD levels. Additionally, pyridostigmine suppressed PVN ACE, Ang II, and AT1R levels and increased AT2R expression. Pyridostigmine attenuated hypertension by inhibiting PVN oxidative stress and inflammation induced by the RAS.

Non-HLA angiotensin-type-1 receptor autoantibodies mediate the long-term loss of grafted neurons in Parkinson’s disease models

BackgroundClinical trials have provided evidence that transplants of dopaminergic precursors, which may be replaced by new in vitro stem cell sources, can integrate into the host tissue, and alleviate motor symptoms in Parkinson´s disease (PD). In some patients, deterioration of graft function occurred several months after observing a graft-derived functional improvement. Rejection of peripheral organs was initially related to HLA-specific antibodies. However, the role of non-HLA antibodies is now considered also relevant for rejection. Angiotensin-II type-1 receptor autoantibodies (AT1-AA) act as agonists of the AT1 receptors. AT1-AA are the non-HLA antibodies most widely associated with graft dysfunction or rejection after transplantation of different solid organs and hematopoietic stem cells. However, it is not known about the presence and possible functional effects of AT1-AA in dopaminergic grafts, and the effects of treatment with AT1 receptor blockers (ARBs) such as candesartan on graft survival.MethodsIn a 6-hydroxydopamine PD rat model, we studied the short-term (10 days)- and long-term (3 months) effects of chronic treatment with the ARB candesartan on survival of grafted dopaminergic neurons and microglial graft infiltration, as well as the effects of dopaminergic denervation and grafting on serum and CSF AT1-AA levels. The expression of AT1 receptors in grafted neurons was determined by laser capture microdissection.ResultsAt the early period post-grafting, the number of grafted dopaminergic neurons that survived was not significantly different between treated and untreated hosts (i.e., control rats and rats treated with candesartan), probably because, just after grafting, other deleterious factors are predominant for dopaminergic cell death, such as mechanical trauma, lack of growth factors/nutrients and ischemia. However, several months post-grafting, we observed a significantly higher number of surviving dopaminergic neurons and a higher density of striatal dopaminergic terminals in the candesartan-treated group. For several months, grafted rats showed blood and cerebrospinal fluid levels of AT1-AA higher than normal controls, and also higher AT1-AA levels than non-grafted parkinsonian rats.ConclusionsThe results suggest the use of ARBs such as candesartan in PD patients, particularly before and after dopaminergic grafts, and the need to monitor AT1-AA levels in PD patients, particularly in those candidates for dopaminergic grafting.

Investigation of Strategies to Block Downstream Effectors of AT1R-Mediated Signalling to Prevent Aneurysm Formation in Marfan Syndrome.

Cardiovascular outcome in Marfan syndrome (MFS) patients most prominently depends on aortic aneurysm progression with subsequent aortic dissection. Angiotensin II receptor blockers (ARBs) prevent aneurysm formation in MFS mouse models. In patients, ARBs only slow down aortic dilation. Downstream signalling from the angiotensin II type 1 receptor (AT1R) is mediated by G proteins and β-arrestin recruitment. AT1R also interacts with the monocyte chemoattractant protein-1 (MCP-1) receptor, resulting in inflammation. In this study, we explore the targeting of β-arrestin signalling in MFS mice by administering TRV027. Furthermore, because high doses of the ARB losartan, which has been proven beneficial in MFS, cannot be achieved in humans, we investigate a potential additive effect by combining lower concentrations of losartan (25 mg/kg/day and 5 mg/kg/day) with barbadin, a β-arrestin blocker, and DMX20, a C-C chemokine receptor type 2 (CCR2) blocker. A high dose of losartan (50 mg/kg/day) slowed down aneurysm progression compared to untreated MFS mice (1.73 ± 0.12 vs. 1.96 ± 0.08 mm, p = 0.0033). TRV027, the combination of barbadin with losartan (25 mg/kg/day), and DMX-200 (90 mg/kg/day) with a low dose of losartan (5 mg/kg/day) did not show a significant beneficial effect. Our results confirm that while losartan effectively halts aneurysm formation in Fbn1C1041G/+ MFS mice, neither TRV027 alone nor any of the other compounds combined with lower doses of losartan demonstrate a notable impact on aneurysm advancement. It appears that complete blockade of AT1R function, achieved by administrating a high dosage of losartan, may be necessary for inhibiting aneurysm progression in MFS.