Angiotensin II Type 1 Receptor Research Articles

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.

Identification of a Locus Coeruleus-amygdala Angiotensinergic Circuit: Implications for Stress-related Cardiovascular Diseases

Background: The locus coeruleus (LC) is a significant noradrenergic nucleus in the brain sensitive to afferent interoceptive signals. It responds to behavioral challenges by increasing noradrenaline release through ascending projections to the hypothalamus, thalamus, cortex, and amygdala. The brain renin-angiotensin system (RAS) plays a role in stress-related cardiovascular diseases, and previous research has identified angiotensin II (Ang II) and its receptors in the LC. The current study aimed to gain a deeper understanding of the function of the Ang II type 1 receptor (AT1R) in the LC, particularly its involvement in transmitting interoceptive cardiovascular signals by regulating LC activity. Methods: Using AT1R-eGFP and AT1R-Cre mice combined with neuroanatomical tract-tracing, chemogenetic and behavioral approaches, we examined AT1R expressing neurons in the LC. Dual immunohistochemistry was used in AT1R-eGFP reporter mice to characterize LC-AT1R-eGFP+ cells by looking at the colocalization of noradrenergic neuron maker tyrosine hydroxylase (TH) and GFP. Cre-inducible tracing with AT1R-cre mice was applied for circuit anterograde analysis and in vivo chemogenetics were used for behavior testing and analysis. Results: The majority of AT1R-eGFP+ neurons (94%) in the LC were found to be co-localized with TH. By using anterograde labeling with cre-inducible GFP virus (AAV-DIO-GFP) in AT1R-Cre mice, it was revealed that the AT1R+ neurons in the LC predominantly project to the amygdala and extended amygdala regions. Only a few or no projections to other brain areas known to receive LC inputs were observed. Within the amygdala, the AT1R+ nerve terminals were specifically limited to the medial division of the central amygdala (CeM) and the basomedial amygdala (BMA). Subsequently, AT1R was deleted from LC by injecting Cre virus into AT1R-Flox mice. Although the general anxiety level remained unchanged, restraint stress-induced anxiety was attenuated following LC AT1R deletion as shown by increased open arm distance in the elevated plus maze (EPM) test (21.7±6.6mm AAV-GFP vs. 98.1±27.5mm AAV-Cre, p<0.05, n=10). Moreover, the study employed Cre-dependent inhibitory and excitatory designer receptors exclusively activated by designer drug (hM4Di and hM3Dq DREADD) with Clozapine-n-oxide (CNO) to selectively silence and activate the AT1R+ neurons in the LC. The inhibition of AT1R+ neurons decreased the baseline anxiety level in mice (36.6±8.6mm Saline vs. 153.4±38.9mm CNO, p<0.01, n=8, EPM open arm distance), while activation of AT1R+ neurons increased baseline anxiety level (963.1±223.1mm Saline vs. 408.5±92mm CNO, p<0.01, n=10, EPM open arm distance). Additionally, the acoustic startle response, which is associated with anxiety levels, was reduced after silencing the LC AT1R+ neurons (324±39.2mV Saline vs. 168.8±54.1mV CNO, p<0.05, n=8). Conclusion: These findings suggest that a specific group of angiotensinergic LC neurons sends projections to the amygdala, highlighting the potential significance of AT1R in mediating noradrenergic activation between the LC and amygdala. Future investigations will explore the response of LC AT1R+ neurons to stress-induced cardiovascular stimuli and afferent interoceptive LC inputs, which may offer novel insights, and new therapeutic direction for the link between stress disorders and cardiovascular disease risk. NIH 1R01HL137103-01A1. 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.

Local Activation of Angiotensin II Type 2 Receptors Improves Microvascular Endothelial Function in Healthy Women With a History Preeclampsia

Women who had preeclampsia (hxPE) have a >4-fold risk for developing cardiovascular disease (CVD) compared to women who had an uncomplicated pregnancy (hxHC). These women demonstrate attenuated vascular endothelium- and nitric oxide (NO)-dependent dilation, secondary to exaggerated angiotensin (ang) II-mediated constriction, following pregnancy but before the onset of CVD. Despite the known dysregulation of ang II-mediated responses postpartum, the role of vasodilatory ang II type 2 receptors (AT2R) in this dysfunction is unknown. We hypothesized that, compared to hxHC, hxPE would have reduced AT2R-mediated dilation and reduced AT2R expression in primary biopsied endothelial cells. We further hypothesized that endothelium- and NO-dependent dilation would be attenuated in hxPE, and that local AT2R activation would improve these responses in hxPE. Nine hxPE (34±7 years, 25±14 months postpartum) and 9 hxHC (35±3 years, 32±12 months postpartum) had 4 intradermal microdialysis fibers placed in the ventral forearm. Sites 1-2 received graded infusions of compound 21 (C21, AT2R agonist; 10−14-10−3mol/L) alone or with L-NAME (NO-synthase inhibitor; 15mM). Sites 3-4 received lactated Ringer’s (control) or 10−11M C21 and underwent a standard local heating (LH) protocol (42°C; 0.1°C·s−1) to assess endothelium-dependent dilation. After full expression of the LH response, 15mM L-NAME was perfused to assess NO-dependent dilation. Red cell flux was measured over each site with laser-Doppler flowmetry. Cutaneous vascular conductance was calculated (CVC=flux/mean arterial pressure) and normalized to maximum (%CVCmax; 28mM SNP+43°C). AT2R protein expression in biopsied venous endothelial cells (n=4/group) was quantified using immunofluorescence. AT2R-mediated dilation (31±8 vs. hxHC: 95±25%CVCmax, p=0.01) and the NO-dependent portion of this response (21±9 vs. hxHC: 64±23%, p=0.04) was reduced in hxPE. AT2R expression in biopsied endothelial cells was attenuated in hxPE (0.59±0.10 vs. hxHC: 0.79±0.07 arbitrary units; p=0.008). hxPE had attenuated endothelium- (79±7 vs. hxHC: 94±9%CVCmax, p<0.001) and NO-dependent dilation (55±11 vs. hxHC: 71±13%; p=0.01) responses to LH. Local AT2R activation augmented endothelium- (92±11%CVCmax vs. control; p=0.02) and NO-dependent (78±12% vs. control; p<0.001) dilation in hxPE but had no effect in hxHC (all p>0.05). These data suggest that reductions in AT2R-mediated dilation and expression contribute to attenuated endothelial function after preeclampsia. Furthermore, AT2R activation may improve endothelial function through NO-dependent mechanisms in women who have had preeclampsia before the onset of CVD. Internal Funds. 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.

Sex and tissue-specific downregulation of miR410-3p in a mouse model of cardiometabolic diseases

The brain Renin-Angiotensin System (RAS) plays a pivotal role in controlling cardiometabolic homeostasis, fluid balance, and other functions including inflammation. Previous studies have shown that more than a thousand microRNA (miRNA) families regulate RAS genes expression, and their dysregulation has been associated with HTN, cardiac ischemia, and aging. Recently, we observed that hypercaloric diet (HCD) programming resulted in differentially expressed miRNA in the hypothalamus of only the male progeny, including miR-410-3p which is thought to target angiotensin-II type 1 receptors (AT1R). Here, we aimed to investigate whether miR-410-3p regulate AT1R expression in a mouse model of cardiometabolic disease (CMD) exhibiting hypertension, diabetes and obesity. C57BI/6J mice (3-week-old, both sexes, n=10) were fed a HCD (D12492. 60 kcal% Fat, Research Diets, USA) while weight and fasting blood glucose levels were measured weekly to ensure the acquisition of metabolic syndrome. At 12 weeks of age, the mice were infused subcutaneously (osmotic pump model 1004, Alzet) with Ang-II (600 ng/kg/min/4 weeks). Gene expression of miR-410-3p (QRT-PCR) was reduced in the hypothalamus of CMD male mice (0.5 ±0.1 vs.1.0 ±0.1, p<0.05) but increased in females (1.6 ±0.4 vs.0.7 ±0.2, p<0.001), while both sexes showed a reduction in the heart (Males: 0.2 ±0.0 vs.1.7 ±0.3; Females: 0.23 ±0.0 vs. 3.2 ±0.3, p<0.01). AT1R protein expression (Capillary Western) was increased in the hypothalamus of CMD male (1.5 ±0.1 vs.1.0 ±0.2, p<0.05) mice but not in females (1.0 ±0.1 vs.1.2 ±0.1, P>0.05) while both sexes exhibited elevated levels in the heart (Males: 2.0 ±0.1 vs. 1.0 ±0.1; Females: 2.3 ±0.1 vs. 1.3 ±0.2, p<0.05). Binding specificity (luciferase assay) was further assessed between miR-410-3p and the 3’UTR of AT1R. Binding was decreased in presence of miR410-3p mimic (0.9 ±0.0 vs. 2.1 ±0.0; p<0.001) and enhanced by a miR410-3p inhibitor (2.5 ±0.1 vs. 2.1 ±0.0; p<0.01), confirming that AT1R is a direct target of miR410-3p. Together, our data suggest that in CMD downregulation of miR410-3p is associated with the upregulation of AT1R both in the hypothalamus and heart, notably in males. This positions miR410-3p as a possible new therapeutic strategy to control RAS overactivity in CMD. This work was supported in part by a research grant from the National Institutes of Health (HL163588). 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.

Upregulation of miR-361-3p Is Associated With Impaired AT2 Receptor Expression in Cardiometabolic Diseases

Cardiometabolic homeostasis has been shown to be regulated by the brain Renin-Angiotensin System (RAS), including via epigenetic mechanisms. MicroRNA (miRNA) regulation is one of the most common mechanisms controlling the expression of RAS genes and has previously been implicated in hypertension, cardiac ischemia, and aging. Recently, we observed that hypercaloric diet (HCD) programming resulted in differentially expressed miRNA in the hypothalamus of only the male progeny, including miR-361-3p which is thought to target angiotensin-II type 2 receptors (AT2R). Here, we aimed to investigate whether miR-361-3p regulate AT2R expression in a mouse model of cardiometabolic disease (CMD) exhibiting hypertension, diabetes and obesity. C57BI/6J mice (3-week-old, both sexes, n=10) were fed a HCD (D12492. 60 kcal% Fat, Research Diets, USA) while weight and fasting blood glucose levels were measured weekly to ensure the acquisition of metabolic syndrome. At 12 weeks of age, the mice were infused subcutaneously (osmotic pump model 1004, Alzet) with Ang-II (600 ng/kg/min/4 weeks). BP, food intake and glycemia were recorded weekly while intraperitoneal glucose (GTT), insulin (ITT) tolerance tests and body composition (EchoMRI) were assessed at the end of the study. Gene expression of miR-361-3p (QRT-PCR) was increased in the hypothalamus of CMD male mice (2.0 ±0.5 vs.1.2 ±0.2, p<0.05) but not in females (2.7 ±0.8 vs.2.5 ±0.4, P>0.05). However, both sexes showed an increase in the heart (Males: 2.0 ±0.5 vs.1.0 ±0.3; Females: 1.6 ±0.4 vs. 0.8 ±0.2, p<0.05) which was associated with decreased AT2R cardiac expression (Capillary Western) in CMD male (0.9 ±0.0 vs.1.0 ±0.0, p<0.05) and females (0.1 ±0.0 vs.0.6 ±0.1, p<0.001). Together, our data suggest that in CMD, upregulation of miR-361-3p is associated with the decrease of AT2R in the heart, possibly contributing to impaired cardiac function in this model. This positions inhibitors of miR-361-3p as a possible new therapeutic strategy to control RAS overactivity in CMD. This work was supported in part by a research grant from the National Institutes of Health (HL163588). 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.

Droplet-based microfluidic platform for detecting agonistic peptides that are self-secreted by yeast expressing a G-protein-coupled receptor

BackgroundSingle-cell droplet microfluidics is an important platform for high-throughput analyses and screening because it provides an independent and compartmentalized microenvironment for reaction or cultivation by coencapsulating individual cells with various molecules in monodisperse microdroplets. In combination with microbial biosensors, this technology becomes a potent tool for the screening of mutant strains. In this study, we demonstrated that a genetically engineered yeast strain that can fluorescently sense agonist ligands via the heterologous expression of a human G-protein-coupled receptor (GPCR) and concurrently secrete candidate peptides is highly compatible with single-cell droplet microfluidic technology for the high-throughput screening of new agonistically active peptides.ResultsThe water-in-oil microdroplets were generated using a flow-focusing microfluidic chip to encapsulate engineered yeast cells coexpressing a human GPCR [i.e., angiotensin II receptor type 1 (AGTR1)] and a secretory agonistic peptide [i.e., angiotensin II (Ang II)]. The single yeast cells cultured in the droplets were then observed under a microscope and analyzed using image processing incorporating machine learning techniques. The AGTR1-mediated signal transduction elicited by the self-secreted Ang II peptide was successfully detected via the expression of a fluorescent reporter in single-cell yeast droplet cultures. The system could also distinguish Ang II analog peptides with different agonistic activities. Notably, we further demonstrated that the microenvironment of the single-cell droplet culture enabled the detection of rarely existing positive (Ang II-secreting) yeast cells in the model mixed cell library, whereas the conventional batch-culture environment using a shake flask failed to do so. Thus, our approach provided compartmentalized microculture environments, which can prevent the diffusion, dilution, and cross-contamination of peptides secreted from individual single yeast cells for the easy identification of GPCR agonists.ConclusionsWe established a droplet-based microfluidic platform that integrated an engineered yeast biosensor strain that concurrently expressed GPCR and self-secreted the agonistic peptides. This offers individually isolated microenvironments that allow the culture of single yeast cells secreting these peptides and gaging their signaling activities, for the high-throughput screening of agonistic peptides. Our platform base on yeast GPCR biosensors and droplet microfluidics will be widely applicable to metabolic engineering, environmental engineering, and drug discovery.

Reduced cardiac antioxidant defenses mediate increased susceptibility to workload-induced myocardial injury in males with genetic cardiomyopathy

Ongoing cardiomyocyte injury is a major mechanism in the progression of heart failure, particularly in dystrophic hearts. Due to the poor regenerative capacity of the adult heart, cardiomyocyte death results in the permanent loss of functional myocardium. Understanding the factors contributing to myocyte injury is essential for the development of effective heart failure therapies. As a model of persistent cardiac injury, we examined mice lacking β-sarcoglycan (β-SG), a key component of the dystrophin glycoprotein complex (DGC). The loss of the sarcoglycan complex markedly compromises sarcolemmal integrity in this β-SG−/− model. Our studies aim to characterize the mechanisms underlying dramatic sex differences in susceptibility to cardiac injury in β-SG−/− mice. Male β-SG−/− hearts display significantly greater myocardial injury and death following isoproterenol-induced cardiac stress than female β-SG−/− hearts. This protection of females was independent of ovarian hormones. Male β-SG−/− hearts displayed increased susceptibility to exogenous oxidative stress and were significantly protected by angiotensin II type 1 receptor (AT1R) antagonism. Increasing general antioxidative defenses or increasing the levels of S-nitrosylation both provided protection to the hearts of β-SG−/− male mice. Here we demonstrate that increased susceptibility to oxidative damage leads to an AT1R-mediated amplification of workload-induced myocardial injury in male β-SG−/− mice. Improving oxidative defenses, specifically by increasing S-nitrosylation, provided protection to the male β-SG−/− heart from workload-induced injury. These studies describe a unique susceptibility of the male heart to injury and may contribute to the sex differences in other forms of cardiac injury.

The angiotensin II type 1 receptor mediates the induction of oxidative stress, apoptosis, and autophagy in HUVECs induced by angiotensin II

Angiotensin (Ang) II, which is the central effector of the renin-angiotensin system (RAS), is one of the principal mediators of vascular dysfunction in hypertension and cardiovascular diseases. Proper vascular function is mediated by oxidative stress, cell apoptosis, and autophagy. However, the underlying signaling pathways and the major RAS components involved in this process are still not fully understood. In the present study, the effect of Ang II on reactive oxygen species (ROS) production, apoptosis induction, and autophagy in human umbilical vein endothelial cells (HUVECs) was investigated. An Annexin V kit was used for the apoptosis analysis, and caspase-3/7 activities were measured with the Caspase-Glo 3/7 Assay Kit. ROS production was measured using a 2,7-dichlorodihydrofluorescein diacetate probe whereas detection of autophagy was performed using acridine orange staining. We found that Ang II increases oxidative stress via ROS production, cell apoptosis via caspase 3/7, and the mitochondrial membrane potential (MMP). Interestingly, losartan, being an antagonist of the angiotensin II type 1 receptor (AT1R), has demonstrated the ability to restore autophagy levels to that of the control group subsequent to its induction by Ang II. The latter can thus induce endothelial cell damage, through excessive oxidative stress and defective autophagy-related apoptosis, which can be inhibited by losartan. These findings reinforce the pivotal role played by the Ang II/AT1R axis in the pathogenesis of vascular damage and bolster our knowledge of the role played by ROS/autophagy-related apoptosis via AT1R in the pathogenesis of hypertension and vascular diseases.

Angiotensin II type-2 receptor signaling facilitates liver injury repair and regeneration via inactivation of Hippo pathway.

The angiotensin II type 2 receptor (AT2R) is a well-established component of the renin-angiotensin system and is known to counteract classical activation of this system and protect against organ damage. Pharmacological activation of the AT2R has significant therapeutic benefits, including vasodilation, natriuresis, anti-inflammatory activity, and improved insulin sensitivity. However, the precise biological functions of the AT2R in maintaining homeostasis in liver tissue remain largely unexplored. In this study, we found that the AT2R facilitates liver repair and regeneration following acute injury by deactivating Hippo signaling and that interleukin-6 transcriptionally upregulates expression of the AT2R in hepatocytes through STAT3 acting as a transcription activator binding to promoter regions of the AT2R. Subsequently, elevated AT2R levels activate downstream signaling via heterotrimeric G protein Gα12/13-coupled signals to induce Yap activity, thereby contributing to repair and regeneration processes in the liver. Conversely, a deficiency in the AT2R attenuates regeneration of the liver while increasing susceptibility to acetaminophen-induced liver injury. Administration of an AT2R agonist significantly enhances the repair and regeneration capacity of injured liver tissue. Our findings suggest that the AT2R acts as an upstream regulator in the Hippo pathway and is a potential target in the treatment of liver damage.

Chronic exercise improves renal AT1 and ETB receptor functions via modulating GRK4 expression in obese Zucker rats

ABSTRACT Background Physical activity has profound benefits on health, especially in patients with cardiovascular and metabolic disease. Exercise training can reduce oxidative stress, improve renal function, and thus lower blood pressure. However, the effect of exercise training on angiotensin II type 1 receptors (AT1R) and endothelin subtype B receptors (ETBR)-mediated diuresis and natriuresis in obese Zucker rats is unclear. Methods Lean and obese Zucker rats were exercised or placed on a nonmoving treadmill for 8 weeks. Blood pressure was measured by tail-cuff plethysmography, and functions of AT1R and ETBR in the kidney were measured by natriuresis, respectively. Results Our data showed that exercise training improved glucose and lipid metabolism, renal function and sodium excretion in obese Zucker rats, accompanied by decreased oxidative stress and GRK4 expression in obese Zucker rats. Moreover, exercise training reduced the Candesartan-induced an increase in diuresis and natriuresis and increased ETBR agonists (BQ3020)-mediated diuresis and natriuresis in obese Zucker rats, which were associated with decreased renal AT1R expression and ETBR phosphorylation levels. Conclusions The results demonstrate that exercise training lowers blood pressure via improving renal AT1R and ETBR function through modulating GRK4 expression in Obese Zucker Rats and provides potentially effective targets for obesity-related hypertension.

Combined vaccines against angiotensin II receptor type 1 and alpha 1D-adrenergic receptor for hypertension.

Compared with monotherapy, combination therapy with multiple antihypertensive drugs has demonstrated superior efficacy in the management of hypertension. The aim of this study was to explore the efficacy of multitarget combined vaccines in achieving simultaneous antihypertensive and target organ protection effects. Our team has developed ATRQβ-001 and ADRQβ-004 vaccines targeting Ang II type 1 receptor (AT1R) and α1D-adrenergic receptor (α1D-AR), respectively. In NG-nitroarginine methyl ester ( l -NAME) + abilities spontaneously hypertensive rats (SHRs) model, SHRs were simultaneously inoculated with ATRQβ-001 and ADRQβ-004 vaccines. Histological and biochemical analyses were performed to evaluate the antihypertensive effects and target organ protection of the ATRQβ-001 and ADRQβ-004 combined vaccines in comparison with those of the single vaccine. Both ATRQβ-001 and ADRQβ-004 vaccines induced robust antibody production, resulting in persistent high antibody titers in rats. Notably, the combined administration of both vaccines significantly decreased SBP in SHRs compared with treatment with a single vaccine, both before and after l -NAME administration. Furthermore, the combined vaccine regimen demonstrated superior efficacy in protecting against vascular remodeling, myocardial hypertrophy and fibrosis, and kidney injury in SHRs. Mechanistically, the combined vaccines exhibited significantly downregulated the expression of angiotensin II type 1 receptor (AT1R) and α1D-adrenergic receptor (α1D-AR). Importantly, no apparent immune-related adverse effects were observed in animals immunized with the combined vaccines. Preliminary findings from this investigation suggest that co-administration of the novel ATRQβ-001 and ADRQβ-004 vaccines holds potential as a groundbreaking therapeutic strategy for managing hypertension.

Bidirectional relation between dipeptidyl peptidase 4 and angiotensin II type I receptor signaling.

Cardiometabolic diseases are often associated with heightened levels of angiotensin II (Ang II), which accounts for the observed oxidative stress, inflammation, and fibrosis. Accumulating evidence indicates a parallel upregulation of dipeptidyl dipeptidase 4 (DPP4) activity in cardiometabolic diseases, with its inhibition shown to mitigate oxidative stress, inflammation, and fibrosis. These findings highlight an overlap between the pathophysiological mechanisms used by Ang II and DPP4. Recent evidence demonstrates that targeted inhibition of DPP4 prevents the rise in Ang II and its associated molecules in experimental models of cardiometabolic diseases. Similarly, inhibitors of the angiotensin I-converting enzyme (ACE) or Ang II type 1 receptor (AT1R) blockers downregulate DPP4 activity, establishing a bidirectional relationship between DPP4 and Ang II. Here, we discuss the current evidence supporting the cross talk between Ang II and DPP4, along with the potential mechanisms promoting this cross regulation. A comprehensive analysis of this bidirectional relationship across tissues will advance our understanding of how DPP4 and Ang II collectively promote the development and progression of cardiometabolic diseases.

A Review of Olmesartan-based Therapy in Targeting Effective Blood Pressure Control and Achieving Blood Pressure Goals.

For >3 decades now, angiotensin receptor blockers (ARB) have been used in the management of hypertension (HTN) and HTN-related cardiovascular (CV) diseases. Olmesartan medoxomil (OLM) is an angiotensin II type 1 (AT1) receptor antagonist (or blocker) that binds tightly to the AT1 receptor with long-lasting efficacy over the 24-hour period and safety demonstrated in several trials. It is well tolerated and effective in reducing blood pressure (BP) in mono and combination therapy with thiazide diuretics or calcium channel blockers across a wide range of patient subgroups. The effectiveness and safety of OLM-based combination therapies have good and tolerable profiles with high adherence in the fixed single-pill formulation. Consistent antihypertensive efficacy and good tolerability when used as monotherapy or as a combined therapy make OLM a valuable treatment option for adults with HTN. In this review, we discuss the important clinical implications of OLM as an optimal choice as monotherapy and combination therapy in managing patients with HTN.

Piper sarmentosum Roxb. Inhibits Angiotensin-Converting Enzyme Activity in Phorbol 12-Myristate-13-Acetate-Induced Endothelial Cells.

Angiotensin-converting enzyme (ACE) plays a crucial role in the pathogenesis of hypertension. Piper sarmentosum Roxb., an herb known for its antihypertensive effect, lacks a comprehensive understanding of the mechanism underlying its antihypertensive action. This study aimed to elucidate the antihypertensive mechanism of aqueous extract of P. sarmentosum leaves (AEPS) via its modulation of the ACE pathway in phorbol 12-myristate-13-acetate (PMA)-induced human umbilical vein endothelial cells (HUVECs). HUVECs were divided into five groups: control, treatment with 200 µg/mL AEPS, induction 200 nM PMA, concomitant treatment with 200 nM PMA and 200 µg/mL AEPS, and treatment with 200 nM PMA and 0.06 μM captopril. Subsequently, ACE mRNA expression, protein level and activity, angiotensin II (Ang II) levels, and angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) mRNA expression in HUVECs were determined. AEPS successfully inhibited ACE mRNA expression, protein and activity, and angiotensin II levels in PMA-induced HUVECs. Additionally, AT1R expression was downregulated, whereas AT2R expression was upregulated. In conclusion, AEPS reduces the levels of ACE mRNA, protein and activity, Ang II, and AT1R expression in PMA-induced HUVECs. Thus, AEPS has the potential to be developed as an ACE inhibitor in the future.

PPARγ Agonist Rosiglitazone and Antagonist GW9662: Antihypertensive Effects on Chronic Intermittent Hypoxia-Induced Hypertension in Rats.

The increased incidence of hypertension associated with obstructive sleep apnea (OSA) presents significant physical, psychological, and economic challenges. Peroxisome proliferator-activated receptor gamma (PPARγ) plays a role in both OSA and hypertension, yet the therapeutic potential of PPARγ agonists and antagonists for OSA-related hypertension remains unexplored. Therefore, we constructed a chronic intermittent hypoxia (CIH)-induced hypertension rat model that mimics the pathogenesis of OSA-related hypertension in humans. The model involved administering PPARγ agonist rosiglitazone (RSG), PPARγ antagonist GW9662, or normal saline, followed by regular monitoring of blood pressure and thoracic aorta analysis using staining and electron microscopy. Intriguingly, our results indicated that both RSG and GW9662 appeared to potently counteract CIH-induced hypertension. In silico study suggested that GW9662's antihypertensive effect might mediated through angiotensin II receptor type 1 (AGTR1). Our findings provide insights into the mechanisms of OSA-related hypertension and propose novel therapeutic targets.

The central renin–angiotensin system: A genetic pathway, functional decoding, and selective target engagement characterization in humans

Accumulating evidence suggests that the brain renin angiotensin system (RAS) plays a pivotal role in the regulation of cognition and behavior as well as in the neuropathology of neurological and mental disorders. The angiotensin II type 1 receptor (AT1R) mediates most functional and neuropathology-relevant actions associated with the central RAS. However, an overarching comprehension to guide translation and utilize the therapeutic potential of the central RAS in humans is currently lacking. We conducted a comprehensive characterization of the RAS using an innovative combination of transcriptomic gene expression mapping, image-based behavioral decoding, and pre-registered randomized controlled discovery-replication pharmacological resting-state functional magnetic resonance imaging (fMRI) trials (N = 132) with a selective AT1R antagonist. The AT1R exhibited a particular dense expression in a subcortical network encompassing the thalamus, striatum, and amygdalo-hippocampal formation. Behavioral decoding of the AT1R gene expression brain map showed an association with memory, stress, reward, and motivational processes. Transient pharmacological blockade of the AT1R further decreased neural activity in subcortical systems characterized by a high AT1R expression, while increasing functional connectivity in the cortico-basal ganglia-thalamo-cortical circuitry. Effects of AT1R blockade on the network level were specifically associated with the transcriptomic signatures of the dopaminergic, opioid, acetylcholine, and corticotropin-releasing hormone signaling systems. The robustness of the results was supported in an independent pharmacological fMRI trial. These findings present a biologically informed comprehensive characterization of the central AT1R pathways and their functional relevance on the neural and behavioral level in humans.

Angiotensin II Type 2 Receptor Agonism Alleviates Progressive Post-stroke Cognitive Impairment in Aged Spontaneously Hypertensive Rats.

Hypertension and aging are leading risk factors for stroke and vascular contributions to cognitive impairment and dementia (VCID). Most animal models fail to capture the complex interplay between these pathophysiological processes. In the current study, we examined the development of cognitive impairment in 18-month-old spontaneously hypertensive rats (SHR) before and following ischemic stroke. Sixty SHRs were housed for 18months with cognitive assessments every 6months and post-surgery. MRI scans were performed at baseline and throughout the study. On day 3 post-stroke, rats were randomized to receive either angiotensin II type 2 receptor (AT2R) agonist Compound 21 (C21) or plain water for 8weeks. SHRs demonstrated a progressive cognitive decline and significant MRI abnormalities before stroke. Perioperative mortality within 72h of stroke was low. Stroke resulted in significant acute brain swelling, chronic brain atrophy, and sustained sensorimotor and behavioral deficits. There was no evidence of anhedonia at week 8. C21 enhanced sensorimotor recovery and ischemic lesion resolution at week 8. SHRs represent a clinically relevant animal model to study aging and stroke-associated VCID. This study underscores the importance of translational disease modeling and provides evidence that modulation of the AT2R signaling via C21 may be a useful therapeutic option to improve sensorimotor and cognitive outcomes even in aged animals.

Utilizing venous occlusion plethysmography to assess vascular effects: A study with buloxibutid, an angiotensin II type 2 receptor agonist.

Buloxibutid (also known as C21) is a potent and selective angiotensin II type 2 receptor (AT2R) agonist, in development for oral treatment of fibrotic lung disease. This phase I, open-label, pharmacodynamic study investigated vascular effects of buloxibutid in five healthy male volunteers. Subjects were administered intra-arterial infusions of buloxibutid for 5 min in ascending doses of 3, 10, 30, 100, and 200 μg/min, infused sequentially in the forearm. Infusions of sodium nitroprusside (SNP) solution in doses of 0.8-3.2 μg/min were administered as a positive control. Forearm blood flow (FBF) was measured by venous occlusion plethysmography. Safety and tolerability of intra-arterial administrations of buloxibutid were evaluated. Following infusion of buloxibutid in doses of 3-200 μg/min, the range of increase in FBF was 27.8%, 17.2%, 37.0%, 28.5%, and 60.5%, compared to the respective baseline. The largest increase was observed in the highest dose group. Infusions of SNP as a positive control, increased FBF 230-320% compared to baseline. Three adverse events (AEs) of mild intensity, not related to buloxibutid or SNP, were reported for two subjects. Two of these AEs were related to study procedures. There were no clinically relevant changes in arterial blood pressure during the study period. Intra-arterial infusion of buloxibutid in low, ascending doses increased FBF, indicating that buloxibutid may be effective in conditions associated with endothelial dysfunction. Venous occlusion plethysmography was found to be a useful method to explore pharmacodynamic vascular effects of novel AT2R agonists, while avoiding systemic adverse effects.