Angiotensin Type 1 Receptor Research Articles

7454 Angiotensin AT1 Receptor Type 1 (AT1) Autoantibodies In Patients with Primary Aldosteronism

Abstract Disclosure: J.K. Waraich: None. G. Kline: None. M.Y. Choi: None. R.J. Sigal: None. C. Caughlin: None. S.J. Przybojewski: None. A. Leung: None. Background: Primary aldosteronism (PA) is a condition characterized by excessive aldosterone secretion, and accounts for at least 10% - 20% of all cases of hypertension. Determination of PA subtype (i.e., unilateral vs. bilateral aldosterone hypersecretion) is clinically important to inform targeted treatment. We hypothesized that pathogenesis of PA is immune-mediated and autoantibodies to angiotensin receptor type 1 (AT1) may determine PA subtype. Aims: The aim of this study was to examine whether AT1 autoantibodies predict PA subtype. Methods: We conducted a cross-sectional study of patients with PA who were referred for adrenal vein sampling (AVS) for subtyping. AT1 autoantibody titres were measured using an enzyme-linked immunosorbent assay. AT1 antibodies were defined as present when the titre was >17 U/mL, negative if <10 U/mL, and indeterminate if between 10-17 U/mL. AVS was used as a gold standard to determine lateralization and PA . The frequency of positive AT1 autoantibodies was determined according to PA subtype and clinical predictors of lateralization. Baseline patient characteristics were reported as means (and standard deviations) for normally distributed variables, and medians (and interquartile ranges) for non-normally distributed variables. Fisher’s exact test was performed for categorical variables and Kruskal-Wallis test for continuous variables. Results: 54 patients had successful cannulation of both adrenal veins (mean age, 52.7 years; 46.3% male; mean body mass index, 31.2 kg/m2). AT1 antibodies were detected in 14 (25.9%) of the patients, absent in 32 (59.3%), and indeterminate in 8 (14.8%). Among the 25 patients with unilateral PA, 8 (32.0%) had positive AT1 antibodies, 15 (60.0%) negative, and 2 (8.0%) indeterminate. Similarly, among the 29 patients with bilateral PA, 6 (20.7%) had positive AT1 antibodies, 17 (58.6%) negative, and 6 (20.7%) indeterminate. There was no significant association detected between AT1 antibody status and lateralization (p=0.39). There were no associations between AT1 autoantibody status and any of the clinical factors traditionally predictive of PA, including sex (p=0.94), older age (p=0.76), hypokalemia (p=0.91), higher estimated glomerular filtration rate (p=0.46), or magnitude of aldosterone-to-renin ratio elevation (p=0.58). There was also no association between AT1 titres and these factors. Conclusion: AT1 autoantibodies are common in patients with PA; over a quarter of patients who underwent AVS in our study. Although they were not predictive of PA subtype, these results may still suggest that PA is immune-mediated. Future studies comparing AT1 autoantibodies in PA to other controls are underway. Presentation: 6/1/2024

Candesartan restores blood-brain barrier dysfunction, mitigates aberrant gene expression, and extends lifespan in a knockin mouse model of epileptogenesis.

Blockade of Angiotensin type 1 receptor (AT1R) has potential therapeutic utility in the treatment of numerous detrimental consequences of epileptogenesis, including oxidative stress, neuroinflammation, and blood-brain barrier (BBB) dysfunction. We have recently shown that many of these pathological processes play a critical role in seizure onset and propagation in the Scn8a-N1768D mouse model. Here we investigate the efficacy and potential mechanism(s) of action of candesartan (CND), an FDA-approved angiotensin receptor blocker (ARB) indicated for hypertension, in improving outcomes in this model of pediatric epilepsy. We compared length of lifespan, seizure frequency, and BBB permeability in juvenile (D/D) and adult (D/+) mice treated with CND at times after seizure onset. We performed RNAseq on hippocampal tissue to quantify differences in genome-wide patterns of transcript abundance and inferred beneficial and detrimental effects of canonical pathways identified by enrichment methods in untreated and treated mice. Our results demonstrate that treatment with CND gives rise to increased survival, longer periods of seizure freedom, and diminished BBB permeability. CND treatment also partially reversed or 'normalized' disease-induced genome-wide gene expression profiles associated with inhibition of NF-κB, TNFα, IL-6, and TGF-β signaling in juvenile and adult mice. Pathway analyses reveal that efficacy of CND is due to its known dual mechanism of action as both an AT1R antagonist and a PPARγ agonist. The robust effectiveness of CND across ages, sexes and mouse strains is a positive indication for its translation to humans and its suitability of use for clinical trials in children with SCN8A epilepsy.

The Role of Local Angiotensin II/Angiotensin Type 1 Receptor in Endometriosis: A Potential Target for New Treatment Approaches.

Endometriosis is a chronic inflammatory disorder described by the presence of functional endometrial-like tissues at extra-uterine locations that are related to chronic pelvic pain and infertility. Multiple molecular mechanisms, including inflammation, reactive oxygen species (ROS) generation, fibrotic reactions, and angiogenesis, are involved in the pathogenesis of endometriosis; however, the exact cause of this disorder still remains a matter of discussion. Recently, it has been shown that the local renin-angiotensin system (RAS) has been expressed in different tissues, like the gynecological tract, and alterations in its expression are associated with multiple pathological conditions like endometriosis. Angiotensin II (Ang II), as a main peptide of the RAS through angiotensin type 1 receptor (AT1R), upregulates signal transduction pathways such as nuclear factor kappa B (NF-κB), mitogen activation protein kinase (MAPK), and transforming growth factor beta (TGF-β) to promote inflammation, oxidative stress, and fibrogenesis. Angiotensin receptor blockers (ARBs) control high blood pressure, which is increased by excessive AT1R activity. Recently, it has been recognized that ARBs have tissue protective effects because of their anti-inflammatory and antifibrotic effects. In this review, we focused on the role of local Ang II/AT1R axis activity in endometriosis pathogenesis and justified the use of ARB agents as a potential therapeutic strategy to improve endometriosis.

Abstract Tu063: Acute sleep deprivation induces cardiac remodeling via activation of AT1R/ERK/GSK-3β signaling

Background: Sleep deprivation (SD) has an adverse effect on cardiovascular system. However, whether acute SD contributes to the morphological and functional changes of the heart remains unclear. Approach and Results: The modified multiple platform method (MMPM) was used to establish the SD model in Sprague-Dawley rats. Acute SD significantly enhanced cardiac ejection fraction and fractional shortening in rats as observed by echocardiography. The elevated ratio of heart weight to body weight (HW/BW) and enlarged cross-section area of cardiomyocytes by WGA staining were detected in SD groups (3, 7,10 days). The upregulation of ANP and BNP was also detected by western blotting. Masson-trichrome staining showed significant fibrosis in the SD groups, which was confirmed by western blotting of the fibrosis markers α-SMA and collagen 1. Furthermore, SD increased the level of angiotensin II (Ang II) and angiotensin type 1 receptor (AT1R) in the heart tissue of SD groups accompanied by the activation of the ERK/GSK-3β pathway. Administration of valsartan and benazepril dramatically ameliorated SD-induced cardiac fibrosis and hypertrophy by downregulating Ang II/AT1R and phosphor-ERK/GSK-3β levels. Conclusion: Our results indicated that cardiac remodeling was induced by the acute and short duration of SD, in which the AT1R/ ERK/GSK3β signal pathway was involved. Our study demonstrates a novel complementary phenomenon induced by SD and provides detailed evidence for the risk of SD on the cardiovascular system.

The Effect of Angiotensin II Type 1 Receptor Antagonist on Age-Related Differences in Renal Vascular Responses to Angiotensin II in Male and Female Rats.

Advancing age could influence renin angiotensin system components, especially angiotensin type 1 receptor (AT1R). This study examined the effect of AT1R antagonist, losartan, on age-related differences in renal vascular responses to angiotensin II in male and female rats. Forty-eight anesthetized male and female rats (8-12 and 24-28 weeks age ranges) were subjected to catheterize. Then, the responses of mean arterial pressure (MAP), renal perfusion pressure (RPP), renal blood flow (RBF), and renal vascular resistance (RVR) to angiotensin II with or without losartan were determined and evaluated. There were not significant differences in the basal values of MAP, RPP, RBF, and RVR in males. However, it was observed significant difference in RVR in females (P < 0.05). The blockade of AT1R attenuated basal MAP and RPP in all the groups (P < 0.05). The infusion of losartan altered basal RVR and RBF values in female groups (P < 0.05). Moreover, losartan eliminated vasoconstrictor responses to angiotensin II in female groups (P < 0.05). Also, losartan induced significant vascular responses to angiotensin II in male groups (P < 0.05). Losartan could maintain RBF changes in response to angiotensin II in both 8-12- and 24-28-week females. Losartan enhanced the RBF response to angiotensin II in 8-12-week males, but not in 24-28-week males. It seems that females (not males) in various age ranges are resistance against RBF changes by acutely increased angiotensin II.

Exploring the Molecular Underpinnings of Skin Regeneration and Wound Healing: The Role of Renin Angiotensin.

The aim of this study is to review the role of renin-angiotensin in skin regeneration and wound healing with a focus on molecular mechanisms. Angiotensin receptor type 1 (AT1R) are abundant in the wounded area, and thus, lead to the activation of ERK, STAT1, and STAT3 which can lead to epidermal self-renewal. The expression of Renin Angiotensin System (RAS) components was significantly lower in wounds caused by burning, rather than intact skin, noting that RAS is involved in the re-epithelialization of skin. ERK, STAT and STAT3 are the targets of Ang II, indicating that RAS active components are involved in fibroblast, stem cells and keratinocyte migration. The effect of inhibiting the RAS on wound healing is context-dependent. On one hand, it is suggested that inhibiting RAS during this phase may slow down wound healing speed. On the other hand, studies have shown that RAS inhibition in this phase can lead to α-SMA activation, ultimately accelerating the wound healing process. Most of the investigations indicate that the inhibition of RAS with Angiotensin Receptor Blockers (ARBs) and Angiotensin Converting Enzyme (ACE) plays a significant role in tissue remodeling in the last phase of wound healing. It has been shown that the inhibition of RAS can inhibit scar formation and fibrosis through the downregulation of inflammatory and fibrogenic agents, such as TGF-β, SMAD2/3, and TAK1, PDGF-BB, and HSP47. To sum up, that local administration of RAS regulators might lead to less scar formation and inflammation in the last phase of wound closure.

Sex-Dependent Effects of Angiotensin Type 2 Receptor–Expressing Medial Prefrontal Cortex Interneurons in Fear Extinction Learning

BackgroundThe renin-angiotensin system has been identified as a potential therapeutic target for posttraumatic stress disorder, although its mechanisms are not well understood. Brain angiotensin type 2 receptors (AT2Rs) are a subtype of angiotensin II receptors located in stress and anxiety-related regions, including the medial prefrontal cortex (mPFC), but their function and mechanism in the mPFC remain unexplored. Therefore, we used a combination of imaging, cre/lox, and behavioral methods to investigate mPFC-AT2R–expressing neurons in fear and stess related behavior. MethodsTo characterize mPFC-AT2R–expressing neurons in the mPFC, AT2R-Cre/tdTomato male and female mice were used for immunohistochemistry. mPFC brain sections were stained with glutamatergic or interneuron markers, and density of AT2R+ cells and colocalization with each marker were quantified. To assess fear-related behaviors in AT2R-flox mice, we selectively deleted AT2R from mPFC neurons using a Cre-expressing adeno-associated virus. Mice then underwent Pavlovian auditory fear conditioning, elevated plus maze, and open field testing. ResultsImmunohistochemistry results revealed that AT2R was densely expressed throughout the mPFC and primarily expressed in somatostatin interneurons in a sex-dependent manner. Following fear conditioning, mPFC-AT2R Cre-lox deletion impaired extinction and increased exploratory behavior in female but not male mice, while locomotion was unaltered by mPFC-AT2R deletion in both sexes. ConclusionsThese results identify mPFC-AT2R+ neurons as a novel subgroup of somatostatin interneurons and reveal their role in regulating fear learning in a sex-dependent manner, potentially offering insights into novel therapeutic targets for posttraumatic stress disorder.

Angiotensin II Type 2 Receptor Inhibits M1 Polarization and Apoptosis of Alveolar Macrophage and Protects Against Mechanical Ventilation-Induced Lung Injury.

Angiotensin II (Ang II) is associated with macrophage polarization and apoptosis, but the role of the angiotensin type 2 receptor (AT2R) in these processes remains controversial. However, the effect of AT2Rs on alveolar macrophages and mechanical ventilation-induced lung injury has not been determined.Mechanical ventilation-induced lung injury in Sprague‒Dawley (SD) rats and LPS-stimulated rat alveolar macrophages (NR8383) were used to determine the effects of AT2Rs, selective AT2R agonists and selective AT1Rs or AT2R antagonists. Macrophage polarization, apoptosis, and related signaling pathways were assessed via western blotting, QPCR and flow cytometry.AT2R expression was decreased in LPS-stimulated rat alveolar macrophages (NR8383). Administration of the AT2R agonist CGP-42112 was associated with an increase in AT2R expression and M2 polarization, but no effect was observed upon administration of the AT2R antagonist PD123319 or the AT1R antagonist valsartan. In mechanical ventilation-induced lung injury in Sprague‒Dawley (SD) rats, the administration of the AT2R agonist C21 was associated with attenuation of the pathological damage score, lung wet/dry weight, cell count and protein content in BALF. C21 can significantly reduce proinflammatory factor TNF-α, IL-1β levels, increase anti-inflammatory factor IL-4, IL-10 levels in BALF, compared with the model group (p < 0.01). Similarly, compared with those at the same time points, the M1/M2 ratios in alveolar macrophages and apoptosis in peritoneal macrophages at 4h, 6h and 8h in the mechanical ventilation models were lower after C21 administration.These findings indicated that the expression of AT2Rs in alveolar macrophages mediates M1 macrophage polarization and apoptosis and that AT2Rs play a protective role in mediating mechanical ventilation-induced lung injury.

Sex-Dependent Effects of Angiotensin Type 2 Receptor Expressing Medial Prefrontal Cortex (mPFC) Interneurons in Fear Extinction Learning

Background: The renin-angiotensin system (RAS) has been identified as a potential therapeutic target for PTSD, though its mechanisms are not well understood. Brain angiotensin type 2 receptors (AT2Rs) are a subtype of angiotensin II receptors located in stress and anxiety-related regions, including the medial prefrontal cortex (mPFC). Their function and mechanism in the mPFC, however, remain unexplored. We therefore used a combination of neuroanatomical, chemogenetic, and behavioral methods to investigate mPFC-AT2R-expressing neuron involvement in fear learning. Methods: To characterize mPFC-AT2R-expressing neurons in the mPFC, AT2R-Cre/td-Tomato male and female brains were perfused and used for immunohistochemistry. Brain sections were stained with glutamatergic or interneuron markers, and density of AT2R+ cells and colocalization with each marker was quantified. To assess fear-related behaviors in AT2R-flox mice, we selectively deleted AT2R from mPFC neurons using an AAV-Cre or GFP virus. Mice then underwent Pavlovian auditory fear conditioning and anxiety-like and locomotor behavior testing using open field (OF) and elevated plus maze (EPM) tests. Results: IHC revealed that AT2R is expressed throughout the mPFC in males ( 208.6±48.8 cells/mm2) and females ( 139.0±59.8 cells/mm2) and has low co-expression on glutamatergic neurons ( TBR1 co-staining, males: 7.1%±1.8%; females: 13.2%±4.2%). Of the interneuron markers tested, AT2R is primarily expressed on somatostatin interneurons, and has higher colocalization in the mPFC of females than males ( males: 16.5%±1.2%, females: 31.8%±4.2%, p=0.02). Following fear conditioning and extinction, mPFC-AT2R deletion impaired extinction in female ( p=0.03) but not male ( p=0.76) mice. Locomotion in the OF was unaltered by mPFC-AT2R deletion in males or females ( total distance travelled; males: GFP 44.11m±5.92m, Cre 56.00m±10.29m, p=0.35; females: GFP 42.86m±4.85m, Cre 42.39m±4.97m, p=0.95), while AT2R-deleted females had increased exploratory behavior in the EPM ( open arm entries; males: GFP 12.38±1.02, Cre 13.22±1.54, p=0.66; females: GFP 12.50±0.96, Cre 20.00±2.81, p=0.02). Conclusion: These results lend support for mPFC-AT2R+ neurons as a novel somatostatin subgroup that influences fear extinction in a sex-dependent manner. This furthers underscores the role of mPFC in top-down regulation and a unique role for peptidergic (ie., angiotensin) mPFC regulation of fear and sex differences, and increases the understanding of circuitry and function of the brain RAS in disordered fear learning. This may lead to improved therapeutic treatments for PTSD. This research and PJM was supported by NIH1R01HL137103-01A1 and the American Heart Association 15CSA24340001. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

β-Arrestin2 Deficiency in the Subfornical Organ Alters Fluid Intake and Blood Pressure Regulation

The activation of the angiotensin type 1 receptor (AT1R) in the brain through canonical Gαq-mediated signaling results in dipsogenic and pressor responses to angiotensin II (ANG). Non-canonical or β-arrestin-mediated signaling of AT1R activation is hypothesized to counterbalance maladaptive G protein signaling during disease. Recently, we found that global genetic deletion of β-arrestin2 ( Arrb2) resulted in higher 0.15 M saline intake at baseline and an exacerbated increase in blood pressure (BP) in response to deoxycorticosterone acetate-salt treatment, suggesting a protective role for ARRB2 during hypertension. We hypothesized that ARRB2 activation specifically within the subfornical organ (SFO) contributes to fluid intake and BP regulation. Male and female Arrb2FLOX mice received intracerebroventricular (ICV) injection of adeno-associated virus (AAV)-CRE to induce deletion of Arrb2 from the SFO. Infection with ICV AAV-CRE primarily targeted the SFO with few off-targets. Mice receiving ICV-AAV-Cre-GFP are denoted Arrb2SFO-KO, and littermate controls receiving ICV-AAV-GFP are denoted Arrb2WT. First, fluid intake was evaluated using the two-bottle choice paradigm, where mice were presented with two bottles, one containing water and one containing 0.15M NaCl. At baseline, Arrb2SFO-KO mice exhibited a significant increase in saline intake compared to controls ( Arrb2WT=1.7±0.9 and Arrb2SFO-KO 3.0±1.4 mL/day p&lt;0.05; n=13 and 18, respectively). This resulted in a saline preference, meaning mice preferred saline over water by more than 50% by volume. Second, we challenged the animals to water- and sodium-depleted conditions to elevate levels of endogenous ANG. After 18h of water and sodium depletion, mice were subjected to the same two-bottle choice paradigm and fluid intake was recorded for 4 hours. Preliminarily, we found Arrb2SFO-KO mice to exhibit higher 0.15M saline intake in both water replete and depleted conditions ( Arrb2WT=0.39±0.13 vs. Arrb2SFO-KO=0.82±0.80 mL/day; n=7-17 p=0.15 and Arrb2WT=1.66±0.95 vs. Arrb2SFO-KO=1.93±1.07 mL/day; n=9-12 p=0.55). BP was evaluated in response to ICV-ANG infusion (1 μg in 5 min) in awake animals. Arrb2SFO-KO mice had higher BP within the first 15 minutes in response to ICV-ANG infusion ( Arrb2WT=1566±85 vs. Arrb2SFO-KO=1726±61 mmHg*min; n=11 p&lt;0.05). Collectively, selective Arrb2 deletion in the SFO increased saline intake and exacerbated the pressor response to ICV-ANG. Overall, these data indicate that ARRB2 in the SFO is protective against sodium ingestion and increases in BP. Stimulation of the AT1R/β-arrestin axis in the brain may represent a novel strategy to treat hypertension. AHA to NMM, NIH to CDS and JLG. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The role of the brain renin-angiotensin system in Parkinson´s disease.

The renin-angiotensin system (RAS) was classically considered a circulating hormonal system that regulates blood pressure. However, different tissues and organs, including the brain, have a local paracrine RAS. Mutual regulation between the dopaminergic system and RAS has been observed in several tissues. Dysregulation of these interactions leads to renal and cardiovascular diseases, as well as progression of dopaminergic neuron degeneration in a major brain center of dopamine/angiotensin interaction such as the nigrostriatal system. A decrease in the dopaminergic function induces upregulation of the angiotensin type-1 (AT1) receptor activity, leading to recovery of dopamine levels. However, AT1 receptor overactivity in dopaminergic neurons and microglial cells upregulates the cellular NADPH-oxidase-superoxide axis and Ca2+ release, which mediate several key events in oxidative stress, neuroinflammation, and α-synuclein aggregation, involved in Parkinson's disease (PD) pathogenesis. An intraneuronal antioxidative/anti-inflammatory RAS counteracts the effects of the pro-oxidative AT1 receptor overactivity. Consistent with this, an imbalance in RAS activity towards the pro-oxidative/pro-inflammatory AT1 receptor axis has been observed in the substantia nigra and striatum of several animal models of high vulnerability to dopaminergic degeneration. Interestingly, autoantibodies against angiotensin-converting enzyme 2 and AT1 receptors are increased in PD models and PD patients and contribute to blood-brain barrier (BBB) dysregulation and nigrostriatal pro-inflammatory RAS upregulation. Therapeutic strategies addressed to the modulation of brain RAS, by AT1 receptor blockers (ARBs) and/or activation of the antioxidative axis (AT2, Mas receptors), may be neuroprotective for individuals with a high risk of developing PD or in prodromal stages of PD to reduce progression of the disease.

Adipose tissue plasticity mediated by the counterregulatory axis of the renin-angiotensin system: Role of Mas and MrgD receptors.

The renin-angiotensin system (RAS) is an endocrine system composed of two main axes: the classical and the counterregulatory, very often displaying opposing effects. The classical axis, primarily mediated by angiotensin receptors type 1 (AT1R), is linked to obesity-associated metabolic effects. On the other hand, the counterregulatory axis appears to exert antiobesity effects through the activation of two receptors, the G protein-coupled receptor (MasR) and Mas-related receptor type D (MrgD). The local RAS in adipose organ has prompted extensive research into white adipose tissue and brown adipose tissue (BAT), with a key role in regulating the cellular and metabolic plasticity of these tissues. The MasR activation favors the brown plasticity signature in the adipose organ by improve the thermogenesis, adipogenesis, and lipolysis, decrease the inflammatory state, and overall energy homeostasis. The MrgD metabolic effects are related to the maintenance of BAT functionality, but the signaling remains unexplored. This review provides a summary of RAS counterregulatory actions triggered by Mas and MrgD receptors on adipose tissue plasticity. Focus on the effects related to the morphology and function of adipose tissue, especially from animal studies, will be given targeting new avenues for treatment of obesity-associated metabolic effects.

Indoxyl sulphate-initiated activation of cardiac fibroblasts is modulated by aryl hydrocarbon receptor and nuclear factor-erythroid-2-related factor 2.

In the last decade, extensive attention has been paid to the uremic toxin indoxyl sulphate (IS) as an inducer of cardiac fibroblast (cFib) activation and cardiac fibrosis in chronic kidney disease. At cellular level, IS engages aryl hydrocarbon receptor (AhR) and regulates many biological functions. We analysed how AhR inhibition by CH-223191 (CH) and overexpression of non-functional (dominant negative, DN) nuclear factor-erythroid-2-related factor 2 (NRF2), a transcription factor recruited by AhR, modulate the response of neonatal mouse (nm) cFib to IS. We also evaluated nm-cardiomyocytes after incubation with the conditioned medium (CM) of IS±CH-treated nm-cFib. IS induced activation, collagen synthesis, TLR4 and-downstream-MCP-1, and the genes encoding angiotensinogen, angiotensin-converting enzyme, angiotensin type 1 receptor (AT1r) and neprilysin (Nepr) in nm-cFib. CH antagonized IS-initiated nm-cFib activation, but did not affect or even magnified the other features. IS promoted NRF2 nuclear translocation and expression the NRF2 target Nqo1. Both pre-incubation with CH and transfection of DN-NRF2 resulted in loss of NRF2 nuclear localization. Moreover, DN-NRF2 overexpression led to greater TLR4 and MCP-1 levels following exposure to IS. The CM of IS-primed nm-cFib and to a larger extent the CM of IS+CH-treated nm-cFib upregulated AT1r, Nepr and TNFα and myostatin genes in nm-cardiomyocytes. Hence, IS triggers pro-inflammatory activation of nm-cFib partly via AhR, and AhR-NRF2 counteract it. Strategies other than AhR inhibition are needed to target IS detrimental actions on cardiac cells.

Autoantibodies Targeting G-Protein-Coupled Receptors: Pathogenetic, Clinical and Therapeutic Implications in Systemic Sclerosis.

Systemic sclerosis (SSc) is a multifaceted connective tissue disease whose aetiology remains largely unknown. Autoimmunity is thought to play a pivotal role in the development of the disease, but the direct pathogenic role of SSc-specific autoantibodies remains to be established. The recent discovery of functional antibodies targeting G-protein-coupled receptors (GPCRs), whose presence has been demonstrated in different autoimmune conditions, has shed some light on SSc pathogenesis. These antibodies bind to GPCRs expressed on immune and non-immune cells as their endogenous ligands, exerting either a stimulatory or inhibitory effect on corresponding intracellular pathways. Growing evidence suggests that, in SSc, the presence of anti-GPCRs antibodies correlates with specific clinical manifestations. Autoantibodies targeting endothelin receptor type A (ETAR) and angiotensin type 1 receptor (AT1R) are associated with severe vasculopathic SSc-related manifestations, while anti-C-X-C motif chemokine receptors (CXCR) antibodies seem to be predictive of interstitial lung involvement; anti-muscarinic-3 acetylcholine receptor (M3R) antibodies have been found in patients with severe gastrointestinal involvement and anti-protease-activated receptor 1 (PAR1) antibodies have been detected in patients experiencing scleroderma renal crisis. This review aims to clarify the potential pathogenetic significance of GPCR-targeting autoantibodies in SSc, focusing on their associations with the different clinical manifestations of scleroderma. An extensive examination of functional autoimmunity targeting GPCRs might provide valuable insights into the underlying pathogenetic mechanisms of SSc, thus enabling the development of novel therapeutic strategies tailored to target GPCR-mediated pathways.

Novel Insights into the Cardioprotective Effects of the Peptides of the Counter-Regulatory Renin-Angiotensin System.

Currently, cardiovascular diseases are a major contributor to morbidity and mortality worldwide, having a significant negative impact on both the economy and public health. The renin-angiotensin system contributes to a high spectrum of cardiovascular disorders and is essential for maintaining normal cardiovascular homeostasis. Overactivation of the classical renin-angiotensin system is one of the most important pathophysiological mechanisms in the progression of cardiovascular diseases. The counter-regulatory renin-angiotensin system is an alternate pathway which favors the synthesis of different peptides, including Angiotensin-(1-7), Angiotensin-(1-9), and Alamandine. These peptides, via the angiotensin type 2 receptor (AT2R), MasR, and MrgD, initiate multiple downstream signaling pathways that culminate in the activation of various cardioprotective mechanisms, such as decreased cardiac fibrosis, decreased myocardial hypertrophy, vasodilation, decreased blood pressure, natriuresis, and nitric oxide synthesis. These cardioprotective effects position them as therapeutic alternatives for reducing the progression of cardiovascular diseases. This review aims to show the latest findings on the cardioprotective effects of the main peptides of the counter-regulatory renin-angiotensin system.

A chromatographic method for determining the interaction between a drug and two target proteins by fabricating a dual-heterogeneous surface

Characterization of the drug-target interactions is pivotal throughout the whole procedure of drug development. Most of the current assays, particularly, chromatographic methods lack the capacity to reveal drug adsorption on the muti-target surface. To this end, we derived a reliable and workable mathematical equation for revealing drug bindings to dual targets on the heterogeneous surface starting from the mass balance equation. The derivatization relied on the correlation of drug injection amounts with their retention factors. Experimental validation was performed by determining the binding parameters of three canonical drugs on a heterogeneous surface, which was fabricated by fusing angiotensin receptor type I and type II receptors (AT1R and AT2R) at the terminuses of circularly permuted HaloTag (cpHaloTag) and immobilizing the whole fusion protein onto 6-bromohexanoic acid modified silica gel. We proved that immobilized AT1R-cpHalo-AT2R maintained the original ligand- and antibody-binding activities of the two receptors in three weeks. The association constants of valsartan, candesartan, and telmisartan to AT1R were (6.26±0.14) × 105, (9.66±0.71) × 105, and (3.17±0.03) × 105 L/mol. In the same column, their association constants to AT2R were (1.25±0.04) × 104, (2.30±0.08) × 104, and (8.51±0.06) × 103 L/mol. The patterns of the association constants to AT1R/AT2R (candesartan>valsartan>telmisartan) were in good line with the data by performing nonlinear chromatography on control columns containing immobilized AT1R or AT2R alone. This provided proof of the fact that the derivatization allowed the determination of drug bindings on the heterogeneous surface with the utilization of a single series of injections and linear regression. We reasoned that is simple enough to model the bindings of drug adsorption on commercially available adsorbents in fundamental or industrial fields, thus having the potential to become a universal method for analyzing the bindings of a drug to the heterogeneous surface containing multiple targets.

Unlocking the protective potential of the angiotensin type 2 receptor (AT2R) in acute lung injury and age-related pulmonary dysfunction

Despite its known importance in the cardiovascular system, the specific role and impact of the angiotensin type 2 receptor (AT2R) in lung physiology and pathophysiology remain largely elusive. In this study, we highlight the distinct and specialized lung-specific roles of AT2R, primarily localized to an alveolar fibroblast subpopulation, in contrast to the angiotensin type 1 receptor (AT1R), which is almost exclusively expressed in lung pericytes. Evidence from our research demonstrates that the disruption of AT2R (AT2R-/y), is associated with a surge in oxidative stress and impaired lung permeability, which were further intensified by Hyperoxic Acute Lung Injury (HALI). With aging, AT2R-/y mice show an increase in oxidative stress, premature enlargement of airspaces, as well as increased mortality when exposed to hyperoxia as compared to age-matched WT mice. Our investigation into Losartan, an AT1R blocker, suggests that its primary HALI lung-protective effects are channeled through AT2R, as its protective benefits are absent in AT2R-/y mice. Importantly, a non-peptide AT2R agonist, Compound 21 (C21), successfully reverses lung oxidative stress and TGFβ activation in wild-type (WT) mice exposed to HALI. These findings suggest a possible paradigm shift in the therapeutic approach for lung injury and age-associated pulmonary dysfunction, from targeting AT1R with angiotensin receptor blockers (ARBs) towards boosting the protective function of AT2R.

Mechanistic insights into the therapeutic potential of Angiotensin type 2 receptors (AT2R) in shaping behavior of astrocytes and microglia during hypertensive state

AbstractBackgroundAstrocytes are the major glial cell type in the central nervous system (CNS) and play a critical role in the pathogenesis of neuroinflammatory and neurodegenerative diseases. In particular, astrocytic activation during neuroinflammatory conditions perpetuates the inflammatory response and brain damage and neurodegeneration. Conversely, Angiotensin type 2 receptor (AT2R) activation is known to promote neuroprotection.MethodTherefore, the present study evaluated the role of AT2R in astrocytic activation in vitro in primary astrocytes and in vivo in hypertensive rats.ResultHere, we demonstrated that Ang II‐induced astrogliosis in primary astrocytes as apparent from increased expression of GFAP and iNOS, ROS generation, inflammatory imbalance and mitochondrial dysfunction in the primary astrocytes. On the contrary, AT2R activation by CGP42112A (CGP) abrogated Ang II induced astrocytic activation by inhibition of ROS production, mitochondrial dysfunction and inflammatory imbalance. However, this anti‐inflammatory action of AT2R activation by CGP was reversed by AT2R antagonist, PD123319 in both in vitro and in vivo conditions. Mechanistically, we found that AT2R via protein phosphatase‐2A (PP2A) activation abrogated the Ang II induced NFкB activation, ROS generation and consequent pro‐inflammatory activation of astrocytes. Importantly, PP2A antagonist, okadaic acid, reversed the anti‐inflammatory action of CGP to the comparable level as that by AT2R antagonist PD123319.ConclusionThus, the present study suggests that AT2R by the activation of PP2A abrogates the NFкB inflammatory signalling and inflammatory activation of astrocytes. Therefore, the therapeutic strategies targeting AT2R might be advantageous for neuroinflammatory or degenerative diseases perpetuated by astrocytic activation.

Restoring Angiotensin Type 2 Receptor Function Reverses PFOS-Induced Vascular Hyper-Reactivity and Hypertension in Pregnancy.

Perfluorooctane sulfonic acid (PFOS) exposure during pregnancy induces hypertension with decreased vasodilatory angiotensin type-2 receptor (AT2R) expression and impaired vascular reactivity and fetal weights. We hypothesized that AT2R activation restores the AT1R/AT2R balance and reverses gestational hypertension by improving vascular mechanisms. Pregnant Sprague-Dawley rats were exposed to PFOS through drinking water (50 μg/mL) from gestation day (GD) 4-20. Controls received drinking water with no detectable PFOS. Control and PFOS-exposed rats were treated with AT2R agonist Compound 21 (C21; 0.3 mg/kg/day, SC) from GD 15-20. In PFOS dams, blood pressure was higher, blood flow in the uterine artery was reduced, and C21 reversed these to control levels. C21 mitigated the heightened contraction response to Ang II and enhanced endothelium-dependent vasorelaxation in uterine arteries of PFOS dams. The observed vascular effects of C21 were correlated with reduced AT1R levels and increased AT2R and eNOS protein levels. C21 also increased plasma bradykinin production in PFOS dams and attenuated the fetoplacental growth restriction. These data suggest that C21 improves the PFOS-induced maternal vascular dysfunction and blood flow to the fetoplacental unit, providing preclinical evidence to support that AT2R activation may be an important target for preventing or treating PFOS-induced adverse maternal and fetal outcomes.

Decoding Angiotensin Receptors: TOMAHAQ-Based Detection and Quantification of Angiotensin Type-1 and Type-2 Receptors.

Background The renin-angiotensin system plays a crucial role in human physiology, and its main hormone, angiotensin, activates 2 G-protein-coupled receptors, the angiotensin type-1 and type-2 receptors, in almost every organ. However, controversy exists about the location, distribution, and expression levels of these receptors. Concerns have been raised over the low sensitivity, low specificity, and large variability between lots of commercially available antibodies for angiotensin type-1 and type-2 receptors, which makes it difficult to reconciliate results of different studies. Here, we describe the first non-antibody-based sensitive and specific targeted quantitative mass spectrometry assay for angiotensin receptors. Methods and Results Using a technique that allows targeted analysis of multiple peptides across multiple samples in a single mass spectrometry analysis, known as TOMAHAQ (triggered by offset, multiplexed, accurate mass, high resolution, and absolute quantification), we have identified and validated specific human tryptic peptides that permit identification and quantification of angiotensin type-1 and type-2 receptors in biological samples. Several peptide sequences are conserved in rodents, making these mass spectrometry assays amenable to both preclinical and clinical studies. We have used this method to quantify angiotensin type-1 and type-2 receptors in postmortem frontal cortex samples of older adults (n=28) with Alzheimer dementia. We correlated levels of angiotensin receptors to biomarkers classically linked to renin-angiotensin system activation, including oxidative stress, inflammation, amyloid-β load, and paired helical filament-tau tangle burden. Conclusions These robust high-throughput assays will not only catalyze novel mechanistic studies in the angiotensin research field but may also help to identify patients with an unbalanced angiotensin receptor distribution who would benefit from angiotensin receptor blocker treatment.