Angiotensin II Type 1 Receptor Research Articles

Angiotensin II Type 2 Receptor (AT2R) Modulates CD4+ T Cells into Regulatory T Cells (Tregs) in Kidney Ischemia-Reperfusion Injury in Rats: Role of PP2A

Angiotensin II Type 2 Receptor (AT2R) Modulates CD4+ T Cells into Regulatory T Cells (Tregs) in Kidney Ischemia-Reperfusion Injury in Rats: Role of PP2A

Targeting Angiotensinogen With N-Acetylgalactosamine-Conjugated Small Interfering RNA to Reduce Blood Pressure.

Blood pressure management involves antihypertensive therapies blocking the renin-angiotensin system (RAS). Yet, it might be inadequate due to poor patient adherence or the so-called RAS escape phenomenon, elicited by the compensatory renin elevation upon RAS blockade. Recently, evidence points toward targeting hepatic AGT (angiotensinogen) as a novel approach to block the RAS pathway that could circumvent the RAS escape phenomenon. Removing AGT, from which all angiotensins originate, should prevent further angiotensin generation, even when renin rises. Furthermore, by making use of a trivalent N-acetylgalactosamine ligand-conjugated small interfering RNA that specifically targets the degradation of hepatocyte-produced mRNAs in a highly potent and specific manner, it may be possible in the future to manage hypertension with therapy that is administered 1 to 2× per year, thereby supporting medication adherence. This review summarizes all current findings on AGT small interfering RNA in preclinical models, making a comparison versus classical RAS blockade with either ACE (angiotensin-converting enzyme) inhibitors or AT1 (angiotensin II type 1) receptor antagonists and AGT suppression with antisense oligonucleotides. It ends with discussing the first-in-human study with AGT small interfering RNA.

Angiotensin II type 2 receptor-mediated dilation is greater in the cutaneous microvasculature of premenopausal women compared with men.

Differential activation of the renin-angiotensin system (RAS) likely contributes to sex differences in cardiovascular outcomes in premenopausal women compared with age-matched men. Women demonstrate reduced activation of the vasoconstrictor angiotensin II type 1 receptors (AT1R) compared with men, and evidence suggests that women also likely have increased sensitivity of the vasodilatory angiotensin II type 2 receptors (AT2R). However, few in vivo studies have directly examined sex differences in AT2R-mediated dilation, or the balance between AT1R- and AT2R-mediated vascular responses in humans. Using the cutaneous microcirculation as a model, we hypothesized that AT2R-mediated dilation would be greater in premenopausal women compared with men, and that AT1R-blockade would augment AT2R-mediated dilation to a greater extent in men than in women. Twelve healthy women (22 ± 3 yr) and 12 men (23 ± 5 yr) had two intradermal microdialysis fibers placed in the ventral forearm for graded infusions of compound 21 (AT2R agonist; 10-12 to 10-8 M) in a control fiber site and a site treated with 43 µM losartan (AT1R antagonist). Red blood cell flux was measured continuously by laser-Doppler flowmetry, and cutaneous vascular conductance [CVC = flux/mean arterial pressure (MAP)] was normalized to maximum [%max; 28 mM sodium nitroprusside (SNP) + 43 °C]. Women had greater AT2R-mediated dilation compared with men (women: 25 ± 4 vs. men: 15 ± 2%max, P = 0.03). Local AT1R inhibition increased AT2R-mediated dilation in men (losartan: 26 ± 4 vs. control: 15 ± 2%max, P < 0.001) but had no effect in women (losartan: 27 ± 6 vs. control: 25 ± 4%max, P > 0.05). These data suggest that premenopausal women have a greater AT2R-mediated vasodilation response than men, and that AT1R activation inhibits AT2R-mediated dilation in men, but not in women.NEW & NOTEWORTHY Premenopausal women have greater protection against cardiovascular disease than age-matched men. However, the role of vasoconstrictor angiotensin II type 1 receptors (AT1R) and vasodilatory angiotensin II type 2 receptors (AT2R) in mediating these sex differences is unclear. Here, we demonstrate that women have greater AT2R-mediated vasodilation than men and that AT1R negates AT2R-mediated dilation in men, but not in women.

THU596 Heteromerization Of The Angiotensin II Type 1 Receptor And The Bradykinin Type 2 Receptor

Abstract Disclosure: E.K. Johnstone: Grant Recipient; Self; Australian Research Council. K.D. Pfleger: Grant Recipient; Self; Australian Research Council. Stock Owner; Self; Dimerix Bioscience Pty Ltd. Background: Receptor heteromerization is the phenomenon whereby two different receptors form a functional complex that attains unique pharmacological properties. Consequently, receptor heteromers can be considered novel drug targets, with the potential to achieve greater therapeutic selectivity and specificity. In a landmark study, the first receptor heteromer to be associated with a disease was the heteromer that forms between the angiotensin II type 1 (AT1) receptor and the bradykinin type 2 (B2) receptor (1). The AT1-B2 heteromer reportedly led to increased angiotensin II signalling, which was implicated in the angiotensin II hypersensitivity involved in pre-eclampsia. However, the validity of this study was questioned by a collaboration of several groups who were unable to find any evidence for a physical or a function interaction between the two receptors (2). As a consequence of these conflicting studies, the existence of the AT1-B2 receptor heteromer has remained controversial. Aim: Investigation of evidence for heteromerization of the AT1 receptor and the B2 receptor. Methods: AT1 receptor and B2 receptor pharmacology and potential heteromerization was investigated in HEK293FT cells using various bioluminescence resonance energy transfer (BRET)-proximity based assays, as well as Dimerix’s Receptor-Heteromer Investigation Technology (Receptor-HIT) (3). Receptor-HIT enables the investigation of receptor heteromers through their specific ligand-induced proximity to interacting proteins. BRET assays, including in the Receptor-HIT configuration, allow real time, live cell monitoring of proximity between biomolecules of interest. Results: Using the Receptor-HIT assay, we confirmed the existence of the AT1-B2 receptor heteromer in HEK293FT cells. We found that the heteromer was able to recruit various GPCR interacting proteins, such as G proteins and arrestin in a bradykinin-dependent manner. Additionally, the heteromer also internalised and trafficked through the cell upon treatment with bradykinin. The close proximity of the two receptors was confirmed using a variation of the Receptor-HIT assay, which monitors receptor-ligand binding rather than protein-protein interactions. Discussion: Our study supports the existence of the AT1-B2 receptor heteromer and identifies various pharmacological properties of the complex. Further studies are required to relate these molecular properties to physiological consequences of heteromerization. (1)AbdAlla et al. Nat Med2001, 7 (9), 1003 1009.(2)Hansen et al. J Biol Chem2009;284(3):1831 1839.(3)Johnstone et al. Biochem Soc T. 2021;49:1555–65. Presentation: Thursday, June 15, 2023

AT1 receptors modulate ethanol-induced loss of anticontractile effect of perivascular adipose tissue

Ethanol consumption activates renin-angiotensin-aldosterone system (RAAS), which plays a major role in the pro-contractile and hypertensive effects linked to ethanol. We hypothesized that ethanol consumption induces loss of the anticontractile effect of perivascular adipose tissue (PVAT)through RAAS-mediated mechanisms. We examined the contribution of angiotensin II type 1 receptors (AT1R) to ethanol-induced PVAT dysfunction. With this purpose, male Wistar Hannover rats were treated with ethanol 20 % (in volume ratio) and/or losartan (antagonist of AT1R; 10 mg/kg/day, gavage) for 9 weeks. Losartan prevented the increase in blood pressure and the loss of the anticontractile effect of PVAT induced by ethanol consumption. PVAT dysfunction occurred after 3 and 9 weeks of treatment with ethanol in an endothelium-dependent manner. Blockade of AT1R prevented ethanol-induced reduction of adiponectin levels in PVAT from ethanol-treated rats. Functional assays revealed that ethanol impaired the anticontractile effect of PVAT-derived angiotensin (1–7) and endothelial nitric oxide (NO). In conclusion, AT1R are implicated in ethanol-induced loss of the anticontractile effect of PVAT. In PVAT, AT1R activation decreases the production of adiponectin, a PVAT-derived factor that promotes vasorelaxation in an endothelium-dependent manner. In the endothelium, AT1R favors the production of superoxide (O2•-) leading to a reduction in NO bioavailability. These responses impair the vasodilator action induced by PVAT-derived angiotensin (1–7), which occurs via Mas receptors located in endothelial cells. Ethanol-induced PVAT dysfunction favors vascular hypercontractility, a response that could contribute to the hypertensive state associated with ethanol consumption.

Prognosis of Midkine and AT1R expression in resectable head and neck squamous cell carcinoma

BackgroundResearch studies have demonstrated that Midkine (MDK) can influence the expression and activity of Renin-angiotensin system (RAS) components. Angiotensin II is involved in tumor growth and angiogenesis in different cancers. We previously observed Angiotensin II receptor blockers (ARBs) improve the survival rates of patients with oral cancers. These findings have prompted us to investigate whether MDK can influence the RAS pathway, mainly through its association with angiotensin II type 1 receptor (AT1R), which contributes to the observed poor prognosis in head and neck squamous cell carcinoma (HNSCC) patients.MethodsMDK and AT1R expressions were examined in 150 HNSCC patients post-operation by immunohistochemical staining between 1 January 2010 and 31 December 2016. We tested the over-expression and silencing of MDK to evaluate the AT1R expression and functional biological assays in HNSCC cell lines HSC-3 and SAS.ResultsPositive expression of MDK is correlated with positive AT1R expression. MDK predicted poor NSCC patients’ survival. Silencing MDK could suppress AT1R and pAKT expression and reduce the growth, migration, and invasion of HNSCC cells. ARB also inhibits MDK stimulating HNSCC cell proliferation. Overexpression of MDK could upregulate AT1R and pAKT.ConclusionsMDK is an independent prognostic factor of HNSCC post-operation, and AT1R regulates HNSCC cell growth, invasion, and migration. Positive MDK and AT1R expressions are highly correlated. Mechanistically, the interaction between MDK and AT1R is crucial for MDK-mediated cell viability, and inhibiting AT1R can effectively counteract or abolish these effects. Furthermore, MDK exerts a regulatory role in the expression of AT1R, as well as in the growth and motility of HNSCC cells. These findings highlight the involvement of the interaction between MDK, AT1R, and the pAkt signaling pathways in HNSCC cell viability growth.

Sequence-directed concentration of G protein-coupled receptors in COPII vesicles

G protein-coupled receptors (GPCRs) constitute the largest superfamily of plasma membrane signaling proteins. However, virtually nothing is known about their recruitment to COPII vesicles for forward delivery after synthesis in the endoplasmic reticulum (ER). Here, we demonstrate that some GPCRs are highly concentrated at ER exit sites (ERES) before COPII budding. Angiotensin II type 2 receptor (AT2R) and CXCR4 concentration are directed by a di-acidic motif and a 9-residue domain, respectively, and these motifs also control receptor ER-Golgi traffic. We further show that AT2R interacts with Sar1 GTPase and that distinct GPCRs have different ER-Golgi transport rates via COPII which is independent of their concentration at ERES. Collectively, these data demonstrate that GPCRs can be actively captured by COPII via specific motifs and direct interaction with COPII components that in turn affects their export dynamics, and provide important insights into COPII targeting and forward trafficking of nascent GPCRs.

Phloretin as an add-on therapy to losartan attenuates diabetes-induced AKI in rats: A potential therapeutic approach targeting TLR4-induced inflammation

AimTargeting Toll-like receptor 4 (TLR4) and Angiotensin II type 1 receptor (AT1R) could provide renoprotection during acute kidney injury (AKI) mainly by regulating inflammation, oxidative stress, mitochondrial dysfunction, and apoptosis. Phloretin (TLR4 inhibitor) as an add-on therapy to losartan (AT1R inhibitor) could provide more therapeutic benefits against AKI under diabetic condition. We aimed to study the effect of phloretin as an add-on therapy to losartan against AKI under diabetic condition. Main methodsTo mimic diabetic AKI condition, bilateral ischemia-reperfusion injury (BIRI) was done in diabetic male Wistar rats, and sodium azide treatment was given to high glucose NRK52E cells to mimic hypoxia-reperfusion injury. In diabetic rats, phloretin (50 mg/kg/per os (p.o.)) and losartan (10 mg/kg/p.o.) treatment was given for 4 days and 1 h prior to surgery while in NRK52E cells, both drugs (phloretin 50 μM and losartan 10 μM) were given 24 h prior to the hypoxia condition. The in vivo and in vitro samples were further used for different experiments. Key findingsTreatment with phloretin and losartan decreased diabetic and AKI biomarkers such as plasma creatinine, blood urea nitrogen (BUN), and kidney injury molecular 1 (KIM1). Moreover, a combination of phloretin and losartan significantly preserved ΔΨm and kidney morphology potentially by inhibiting TLR4-associated inflammation and AT1R-associated mitochondrial dysfunction, thereby oxidative stress. SignificanceCombination therapy of phloretin and losartan was more effective than monotherapies. Both drugs target TLR4/MyD88/NF-κB pathway and reduce inflammation and mitochondrial dysfunction in AKI under diabetic condition.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) drives angiotensin II-induced vascular remodeling through regulating mitochondrial fragmentation

BackgroundDNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a novel instigator for mitochondrial dysfunction, and plays an important role in the pathogenesis of cardiovascular diseases. However, the role and mechanism of DNA-PKcs in angiotensin II (Ang II)-induced vascular remodeling remains obscure. MethodsRat aortic smooth muscle cells (SMC) and VSMC-specific DNA-PKcs knockout (DNA-PKcsΔVSMC) mice were employed to examine the role of DNA-PKcs in vascular remodeling and the underlying mechanisms. Blood pressure of mice was monitored using the tail-cuff and telemetry methods. The role of DNA-PKcs in vascular function was evaluated using vascular relaxation assessment. ResultsIn the tunica media of remodeled mouse thoracic aortas, and renal arteries from hypertensive patients, elevated DNA-PKcs expression was observed along with its cytoplasmic translocation from nucleus, suggesting a role for DNA-PKcs in vascular remodeling. We then infused wild-type (DNA-PKcsfl/fl) and DNA-PKcsΔVSMC mice with Ang II for 14 days to establish vascular remodeling, and demonstrated that DNA-PKcsΔVSMC mice displayed attenuated vascular remodeling through inhibition of dedifferentiation of VSMCs. Moreover, deletion of DNA-PKcs in VSMCs alleviated Ang II-induced vasodilation dysfunction and hypertension. Mechanistic investigations denoted that Ang II-evoked rises in cytoplasmic DNA-PKcs interacted with dynamin-related protein 1 (Drp1) at its TQ motif to phosphorylate Drp1S616, subsequently promoting mitochondrial fragmentation and dysfunction, as well as reactive oxygen species (ROS) production. Treatment of irbesartan, an Ang II type 1 receptor (AT1R) blocker, downregulated DNA-PKcs expression in VSMCs and aortic tissues following Ang II administration. ConclusionOur data revealed that cytoplasmic DNA-PKcs in VSMCs accelerated Ang II-induced vascular remodeling by interacting with Drp1 at its TQ motif and phosphorylating Drp1S616 to provoke mitochondrial fragmentation. Maneuvers targeting DNA-PKcs might be a valuable therapeutic option for the treatment of vascular remodeling and hypertension.

Astrocytic AT1R deficiency ameliorates Aβ-induced cognitive deficits and synaptotoxicity through β-arrestin2 signaling.

Alzheimer's disease (AD) seriously influences human health, and there is no effective treatment to prevent or cure AD. Recent studies have shown that angiotensin II type 1 receptor (AT1R) blockers significantly reduce the prevalence of AD, while the precise role and mechanism of AT1R in AD remain obscure. In this study, for the first time, we identified that astrocytic but not neuronal AT1R levels were significantly increased in AD model rats and found that astrocyte-specific knockout of AT1R significantly ameliorated amyloid β (Aβ)-induced cognitive deficits and synaptotoxicity. Pretreating astrocytes with an AT1R blocker also alleviated Aβ-induced synaptotoxicity in the coculture system of hippocampal neurons and astrocytes. Moreover, AT1R could directly bind to Aβ1-42 and activate the astrocytic β-arrestin2 pathway in a biased manner, and biased inhibition of the astrocytic AT1R/β-arrestin2 pathway relieved Aβ-induced neurotoxicity. Furthermore, we demonstrated that astrocytic AT1R/β-arrestin2 pathway-mediated synaptotoxicity was associated with the aggregation of autophagosomes, which triggered the disordered degradation of Aβ. Our findings reveal a novel molecular mechanism of astrocytic AT1R in Aβ-induced neurodegeneration and might contribute to establishing new targets for AD prevention and therapy.

Drug therapy targeting angiotensin II type 1 receptors in brain against frequent urination

The production of angiotensin II (Ang II) in the brain plays important roles as neurotransmitter and neuropeptide. Central Ang II is involved in regulating various physiological processes, such as blood pressure and water homeostasis, via Ang II type 1 (AT1) receptors. We have demonstrated that Ang II induces frequent urination via AT1 receptors in the brain even at doses that does not seem to affect the blood pressure in animal experiment. Intracerebroventricular administration of Ang II was also found to reduce the bladder capacity without affecting the maximum voiding pressure, post voiding residual urine volume or voiding efficiency. Additionally, the activation of AT1 receptor downstream signal pathway (phospholipase C/protein kinase C/NADPH oxidase/superoxide anion) and suppression of GABAergic nervous system in the brain are involved in the mechanism underlying the central Ang II-inducted frequent urination. AT1 receptor blockers (ARBs) have been widely used to treat hypertension. We demonstrated that peripherally administered ARBs telmisartan, which can penetrate blood-brain barrier, exerted an inhibitory effect on central Ang II-inducted frequent urination. We present the possible drug therapy targeting AT1 receptors in the brain against frequent urination on the results obtained from our recent research work.

Abstract 055: Estrogen And Smooth Muscle Cell Estrogen Receptor Alpha Modulate Arterial Stiffness

Background: Arterial stiffness increases with age and contributes to cardiovascular disease. Although sex differences in arterial stiffness are clinically observed, the underlying mechanisms are unknown. Specifically, the role of estrogen (E2) and estrogen receptor alpha (ERα) in sex-dependent differences in arterial stiffness have not been defined. We hypothesize that E2 and ERα contribute to sex differences in arterial stiffness. Methods/Results: We measured aortic pulse wave velocity, an index of arterial stiffness, at 3, 12, and 18 months old, in male and female mice. Arterial stiffness increased in males at 12 and 18m but was delayed until 18m in females (p&lt;0.05). Circulating E2 decreased with age in females (p&lt;0.05), suggesting a link between estrogens and arterial stiffness. In young female mice, arterial stiffness increased with ovariectomy (OVX) versus sham surgery but was restored in OVX mice plus E2 pellet (p&lt;0.05). Aortic gene expression for the vasoprotective angiotensin II type 2 receptor (AT2R) decreased with OVX versus sham and was restored in OVX mice plus E2 pellet (p&lt;0.05). These data suggest a link between arterial stiffness, E2, and AT2R. We therefore created novel SMC-specific ERα knockout (SMC-ERα-KO) mice to assess the role of SMC-ERα in sex differences in arterial stiffness. Differences in arterial stiffness with age persist in ERα-intact mice, but 18m SMC-ERα-KO males and females exhibited less stiffness vs. age-matched ERα-intact littermates (p&lt;0.05). Trends persist in repeat PWV measures at 12 and 16-18m in individual males and females. Blood pressure (via telemetry) did not differ between 18m intact and KO males or females (p=0.73). In young ERα-intact females, OVX increased stiffness and decreased aortic AT2R expression, while OVX had no effect in SMC-ERα-KO females (all p&lt;0.05), supporting a role for E2 and SMC-ERα in arterial stiffness. Conclusion: These data suggest that estrogen contributes to sex differences in arterial stiffness and that with advancing age, SMC-ERα is unliganded due to the loss of estrogen and contributes to arterial stiffness in females, potentially via alterations in vascular AT2R function. These results also suggest a detrimental role for SMC-ERα in aging-associated arterial stiffness in males.

Abstract P209: Six Weeks Oral Losartan Treatment Improves Endothelium-dependent Dilation In Normotensive Women With A History Of Preeclampsia

Women with a history of preeclampsia have a 4-fold increased risk of cardiovascular disease compared to women who had a healthy pregnancy. These women demonstrate microvascular endothelial dysfunction, mediated by reduced nitric oxide (NO)-dependent dilation and increased sensitivity to angiotensin II. We hypothesized that systemic angiotensin II type 1 receptor (AT 1 R) inhibition would improve endothelium- and NO-dependent dilation in the microvasculature of women with a history of preeclampsia. Seven normotensive (seated SBP 118±6; DBP 78±6 mmHg) women (33±6 years of age, 11±7 months postpartum) with a history of preeclampsia participated in a double-blind placebo-controlled crossover study. Following 6 weeks of placebo and losartan treatment (50 mg/day), participants wore a 24-hour blood pressure monitor and completed 1 study visit in which 2 intradermal microdialysis fibers were placed in the skin of the ventral forearm for graded infusions of acetylcholine (ACh, 10 -7 -10 2 mM) or ACh + 15 mM N G nitro L-arginine methyl ester (L-NAME; NO synthase inhibitor) to assess endothelium- and NO-dependent dilation, respectively. Red blood cell flux was measured over each microdialysis site by laser-Doppler flowmetry. Cutaneous vascular conductance was calculated (CVC=Doppler flux/mean arterial pressure) and normalized to maximum (%max; 28 mM SNP + 43°C). Systemic losartan treatment augmented endothelium-dependent (losartan: 96±4 vs placebo: 70±14%max; P &lt;0.001) and NO-dependent (losartan: 35±14 vs placebo: 23±8%; P &lt;0.001) dilation. There was no effect of treatment on 24-hour systolic blood pressure (losartan: 117±4 vs placebo: 117±8 mmHg), diastolic blood pressure (losartan: 72±5 vs placebo: 71±5 mmHg) or mean arterial pressure (losartan: 92±4 vs placebo: 92±6 mmHg; all P&gt;0.05 ). Losartan treatment increased endothelium-dependent vasodilation via NO-mediated pathways in the absence of changes in blood pressure in women with a history of preeclampsia. These data suggest that systemic AT 1 R inhibition may be a viable therapeutic approach to treat persistent microvascular dysfunction in otherwise healthy women who have had preeclampsia.

Abstract P170: Beta-arrestin-2 Sustains Experience-dependent Plasticity Of Sodium Ingestive Behavior

Elevated sodium (Na) intake is a risk factor for hypertension. Na “appetite” is defined by the persistence of Na consumption despite adverse conditions and is commonly assessed through ingestion of aversive NaCl solutions. β-arrestins interact with many G Protein-Coupled Receptors (GPCR), including the Angiotensin II Type 1 Receptor (AT 1 R). β-arrestins play roles in many physiological processes including regulation of cardiovascular function, sensory processing, and energy metabolism. Recent work published by our group concluded that β-arrestin-2 deficient (Arrb2 KO ) mice exhibited increased ingestion of NaCl solutions even in the absence of physiological need. Thus, we hypothesize that β-arrestin-2 plays a role in experience-based Na seeking behavior and elevated NaCl consumption. To explore this question, mice were first presented with a 2-bottle choice of water and 0.15 NaCl.; then exposed to aversive 0.3 M NaCl exclusively for 24h; followed by the same 2-bottle choice as at baseline. Usually, this manipulation would yield a reduction in preference for previously preferred concentrations of NaCl, demonstrating experience-based plasticity of NaCl preference. At baseline, male Arrb2 KO mice exhibited the expected increase in preference for 0.15 M NaCl vs water (control n=14, 34±5%; Arrb2 KO n=10, 55±7%, p&lt;0.01). Following 24h hypertonic (0.3 M) saline exposure, both groups displayed a decrease in 0.15 M NaCl solution intake and preference (days 1+2 after exposure: 10±2% vs 21±4%, p&lt;0.01 vs baseline within each group, and p=0.15 between groups). While control mice maintained this significant suppression of preference for 0.15 M NaCl beyond one week after 24h 0.3 M NaCl exposure (e.g., days 7+8 after exposure: controls 22±3% p=0.01 vs baseline), preference of Arrb2 KO mice for 0.15 M NaCl returned to baseline levels within days (e.g., days 7+8 Arrb2 KO 45±9%, p=0.08 vs baseline, and p&lt;0.01 vs control). This supports the idea that Arrb2 is implicated in Na ingestive behaviors, potentially influencing memory maintenance and retrieval. Future studies aim to characterize the role of Arrb2 downstream of the AT 1 R within specific brain regions in Na consummatory behaviors.

Angiotensin II modulates THP-1-like macrophage phenotype and inflammatory signatures via angiotensin II type 1 receptor.

Angiotensin II (Ang II) is a major component of the renin-angiotensin or renin-angiotensin-aldosterone system, which is the main element found to be involved in cardiopathology. Recently, long-term metabolomics studies have linked high levels of angiotensin plasma to inflammatory conditions such as coronary heart disease, obesity, and type 2 diabetes. Monocyte/macrophage cellular function and phenotype orchestrate the inflammatory response in various pathological conditions, most notably cardiometabolic disease. An activation of the Ang II system is usually associated with inflammation and cardiovascular disease; however, the direct effect on monocyte/macrophages has still not been well elucidated. Herein, we have evaluated the cellular effects of Ang II on THP-1-derived macrophages. Ang II stimulated the expression of markers involved in monocyte/macrophage cell differentiation (e.g., CD116), as well as adhesion, cell-cell interaction, chemotaxis, and phagocytosis (CD15, CD44, CD33, and CD49F). Yet, Ang II increased the expression of proinflammatory markers (HLA-DR, TNF-α, CD64, CD11c, and CD38) and decreased CD206 (mannose receptor), an M2 marker. Moreover, Ang II induced cytosolic calcium overload, increased reactive oxygen species, and arrested cells in the G1 phase. Most of these effects were induced via the angiotensin II type 1 receptor (AT1R). Collectively, our results provide new evidence in support of the effect of Ang II in inflammation associated with cardiometabolic diseases.

Association of angiotensin-converting enzyme (ACE) I/D variation with biochemical parameters and oxidative stress markers in systemic lupus erythematosus patients in west of Iran.

We aimed to study insertion/deletion (I/D) variation (rs4646994) of ACE gene in a group of SLE patients in west of Iran and its possible relationship with oxidative stress. Genotypes and allele frequencies related to ACE (I/D) variation were determined in 108 SLE patients and 110 gender and age-matched healthy controls using PCR. Neopterin, malondialdehyde (MDA), and serum lipid concentrations were determined by HPLC and enzyme assay respectively. The overall distribution of ACE I/D genotypes in SLE patients was different from that of the control group (P = 0.005). DD genotype compared to ID genotype increased the risk of SLE (OR = 2.57, 95% CI 1.4-4.8, P = 0.003). ID genotype compared to the II genotype decreased the risk of disease (OR = 0.45, 95% CI 0.2-0.99, p = 0.042). SLE patients with DD, ID, and II genotypes had lower paraoxonase (PON) activity and higher serum levels of MDA and neopterin versus control patients. We also detected a significant protective effect against SLE in presence of ACE I alleles and lack of angiotensin II receptor, type 1 (AGTR1) A1166C (NCBI reference SNP id: rs5186), C alleles in this study (OR = 0.31, 95% CI 0.14-0.68, P = 0.002). Carriers of the DD genotype of ACE gene with higher serum concentrations of neopterin and MDA, and lower PON activity had a high risk to develop SLE, while ID genotype decreased the risk of disease development by 2.22 times compared to II genotype.

Antibodies against angiotensin II receptor type 1 and endothelin A receptor are increased in COVID-19 patients.

Increased titers of autoantibodies targeting the G-protein-coupled receptors angiotensin II type 1 receptor (AT1R) and endotelin-1 type A receptor (ETAR) are associated with severe coronavirus disease 2019 (COVID-19) infection. The aim of this study was to determine whether 1) these antibodies are specifically related to COVID-19 disease pathogenesis or increased during any severe respiratory illness, 2) if they are formed during illness, and 3) if they correlate with inflammatory markers or long-term symptoms. Antibodies against AT1R, ETAR, and antinuclear antibodies (ANAs) were measured in n=40 prospectively enrolled COVID-19 patients and n=207 COVID-19 patients included in a biobank. Clinical and laboratory findings were prospectively and retrospectively assessed in both cohorts, and results were combined for analysis. The presence of auto-antibodies against AT1R or ETAR in peripheral blood was compared between hospitalized patients with COVID-19 and controls (n=39). Additionally, AT1R and ETAR titers were compared between patients with an unfavorable disease course, defined as intensive care admission and/or death during hospital admission (n=121), to those with a favorable disease course (n=126). A subset of intubated patients with severe COVID-19 were compared to intubated patients with acute respiratory distress syndrome (ARDS) due to any other cause. Significantly increased AT1R and ETAR antibody titers were found in COVID-19 patients compared to controls, while titers were equal between favorable and unfavorable COVID-19 disease course groups. On ICU, intubated patients with COVID-19 had significantly increased AT1R and ETAR titers compared to patients with ARDS due to any other cause. The titers did not correlate with baseline inflammatory markers during admission or with diffusion capacity, cognitive impairment, or fatigue measured at 3 months follow-up. In patients hospitalized for COVID-19, antibodies against AT1R and ETAR are increased compared to controls and patients with ARDS due to other causes than COVID-19. The baseline antibody titers do not correlate with inflammatory markers or long-term symptoms in this study.

Unraveling allostery within the angiotensin II type 1 receptor for Gαq and β-arrestin coupling.

G protein-coupled receptors engage both G proteins and β-arrestins, and their coupling can be biased by ligands and mutations. Here, to resolve structural elements and mechanisms underlying effector coupling to the angiotensin II (AngII) type 1 receptor (AT1R), we combined alanine scanning mutagenesis of the entire sequence of the receptor with pharmacological profiling of Gαq and β-arrestin engagement to mutant receptors and molecular dynamics simulations. We showed that Gαq coupling to AT1R involved a large number of residues spread across the receptor, whereas fewer structural regions of the receptor contributed to β-arrestin coupling regulation. Residue stretches in transmembrane domain 4 conferred β-arrestin bias and represented an important structural element in AT1R for functional selectivity. Furthermore, we identified allosteric small-molecule binding sites that were enclosed by communities of residues that produced biased signaling when mutated. Last, we showed that allosteric communication within AT1R emanating from the Gαq coupling site spread beyond the orthosteric AngII-binding site and across different regions of the receptor, including currently unresolved structural regions. Our findings reveal structural elements and mechanisms within AT1R that bias Gαq and β-arrestin coupling and that could be harnessed to design biased receptors for research purposes and to develop allosteric modulators.

Telmisartan inhibits microglia-induced neurotoxic A1 astrocyte conversion via PPARγ-mediated NF-κB/p65 degradation

Astrocytes are crucially involved in neuroinflammation. Activated astrocytes exhibit at least two phenotypes, A1 (neurotoxic) and A2 (neuroprotective). The A1 phenotype is the major reactive astrocyte phenotype involved in aging and neurodegenerative diseases. Telmisartan, which is an antihypertensive agent, is a promising neuroprotective agent. This study aimed to investigate the effects of telmisartan on the phenotype of reactive astrocytes. Astrocytes were activated by culturing with the conditioned medium derived from lipopolysaccharide-stimulated microglia. This conditioned medium induced early, transient A2 astrocyte conversion (within 24 h) and late, sustained A1 conversion (beginning at 24 h and lasting up to 7 days), with a concomitant increase in the production of pro-inflammatory cytokines (interleukin [IL]-1β, tumor necrosis factor [TNF]α, and IL-6) and phosphorylation of nuclear factor-κB (NF-κB)/p65. Telmisartan treatment promoted and inhibited A2 and A1 conversion, respectively. Telmisartan reduced total and phosphorylated p65 protein levels. Losartan, a specific angiotensin II type-1 receptor (AT1R) blocker, did not influence the reactive state of astrocytes. Additionally, AT1R activation by angiotensin II did not induce the expression of pro-inflammatory cytokines and A1/A2 markers, indicating that the AT1R signaling pathway is not involved in the astrocyte-mediated inflammatory response. A peroxisome proliferator-activated receptor γ (PPARγ) antagonist reversed the effects of telmisartan. Moreover, telmisartan-induced p65 downregulation was reversed by the proteasome inhibitor MG132. These results indicate that telmisartan suppresses activated microglia-induced neurotoxic A1 astrocyte conversion through p65 degradation. Our findings contribute towards the elucidation of the anti-inflammatory activity of telmisartan in brain disorders.

Membrane mediated mechanical stimuli produces distinct active-like states in the AT1 receptor

The Angiotensin II Type 1 (AT1) receptor is one of the most widely studied GPCRs within the context of biased signaling. While the AT1 receptor is activated by agonists such as the peptide AngII, it can also be activated by mechanical stimuli such as membrane stretch or shear in the absence of a ligand. Despite the importance of mechanical activation of the AT1 receptor in biological processes such as vasoconstriction, little is known about the structural changes induced by external physical stimuli mediated by the surrounding lipid membrane. Here, we present a systematic simulation study that characterizes the activation of the AT1 receptor under various membrane environments and mechanical stimuli. We show that stability of the active state is highly sensitive to membrane thickness and tension. Structural comparison of membrane-mediated vs. agonist-induced activation shows that the AT1 receptor has distinct active conformations. This is supported by multi-microsecond free energy calculations that show unique landscapes for the inactive and various active states. Our modeling results provide structural insights into the mechanical activation of the AT1 receptor and how it may produce different functional outcomes within the framework of biased agonism.