AT1 Receptor Blockade Research Articles

Spinal AT1R contributes to neuroinflammation and neuropathic pain via NOX2-dependent redox signaling in microglia

Microglia-mediated neuroinflammation demonstrates a crucial act in the progression of neuropathic pain. Oxidative damage induced by reactive oxygen species (ROS) derived from NADPH oxidase (NOX) in microglia drives proinflammatory microglia activation. Recent evidence points to the central renin angiotensin system (RAS) is involved in oxidative stress and neuroinflammation, with the angiotensin converting enzyme/angiotensin II/angiotensin receptor-1 (ACE/Ang II/AT1R) axis promoting inflammation through increased ROS production, counteracted by the ACE2/Ang (1-7)/ Mas receptor (MasR) axis. While interventions targeting spinal AT1R have been shown to alleviate nociceptive hypersensitivity; yet the mechanisms remain elusive. Here, we discovered that spared nerve injury (SNI)-induced mechanical allodynia in rats were associated with M1-like microglia activation, oxidative stress and overactivity of ACE/Ang II/AT1R axis in the spinal cord. Increased AT1R and NOX2 expression were observed in activated dorsal horn microglia following SNI. Blockade of AT1R with losartan potassium (LOP) suppressed NOX2-mediated oxidative stress, and promoted a shift in microglia from the proinflammatory M1 phenotype to the anti-inflammatory M2 phenotype in LPS-treated BV-2 cells. Additionally, NOX2 overexpression triggered the activation of the high-mobility group box 1/ nuclear factor-kappa B (HMGB1/NF-κB) signaling pathway. Intrathecal administration of LOP effectively inhibited SNI-induced NOX2 overactivation in microglia and suppressed the HMGB1/NF-kB pathway, reducing oxidative stress and shifting the microglia polarization from M1 to M2 in the spinal cord, thereby attenuating neuroinflammation and pain hypersensitivity. Collectively, these findings underscore the neuroimmune-modulating effects of spinal AT1R in neuropathic pain, highlighting the regulation of redox homeostasis in microglia via a NOX2 dependent mechanism.

Therapeutic opportunities in targeting the protective arm of the renin-angiotensin system to improve insulin sensitivity: a mechanistic review.

In recent years, the knowledge of the physiological and pathophysiological roles of the renin-angiotensin system (RAS) in glucose metabolism has advanced significantly. It is now well-established that blockade of the angiotensin AT1 receptor (AT1R) improves insulin sensitivity. Activation of the AT2 receptor (AT2R) and the MAS receptor are significant contributors to this beneficial effect. Elevated availability of angiotensin (Ang) II) for interaction with the AT2R and increased Ang-(1-7) formation during AT1R blockade mediate these effects. The ongoing development of selective AT2R agonists, such as compound 21 and the novel Ang III peptidomimetics, has significantly advanced the exploration of the role of AT2R in metabolism and its potential as a therapeutic target. These agents show promise, particularly when RAS inhibition is contraindicated. Additionally, other RAS peptides, including Ang IV, des-Asp-Ang I, Ang-(1-9), and alamandine, hold therapeutic capability for addressing metabolic disturbances linked to type 2 diabetes. The possibility of AT2R heteromerization with either AT1R or MAS receptor offers an exciting area for future research, particularly concerning therapeutic strategies to improve glycemic control. This review focuses on therapeutic opportunities to improve insulin sensitivity, taking advantage of the protective arm of the RAS.

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

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

#185 The role of angiotensin 2 type 1 receptor and type 2 receptor after postischemic acute kidney injury in spontaneously hypertensive rats

Abstract Background and Aims Renal ischemia/reperfusion injury is a common cause of acute kidney injury (AKI), and hypertension might contribute to the increased incidence of AKI. AKI has a multifactorial causality, but the mechanism of pathogenesis and the development of this disease are still incompletely defined. The purpose of this study was to compare the effects of AT1R blockade and AT2R simulation on AKI development in spontaneously hypertensive rats (SHR). Method We used male 24 weeks old SHR. Animals were divided into following experimental groups: sham operated rats (SHAM); rats with induced postischemic AKI (AKI); a group which received AT1R antagonist Losartan (10 mg/kg b.w.)(AKI+LOS) and group which received AT2R agonist novokinin (0.3 mg/kg b.w.)(AKI+NOVO) in the moment of kidney reperfusion. AKI was induced by surgical removal of right kidney followed by atraumatic clamp occlusion of the left renal artery for 40 minutes. Hemodynamic and biochemical measurements were done 24 hours after reperfusion. Results Conclusion Our results confirm the dominant role of AT1R on AKI development, but AT2R stimulation failed to buffer deleterious effects of AT1R hyperactivity on renal vasoconstriction and glomerular filtration. However, the role of AT2R during AKI development in hypertension will be in focus in our further studies.

Losartan and metabolite EXP3179 activate endothelial function without lowering blood pressure in AT2 receptor KO mice

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

Effect of angiotensin II receptor blockade combined with a thiazide diuretic on plasma aldosterone escape in healthy subjects

Objective: The chronic administration of ARBs is associated with an incomplete ALDO suppression suggesting either a partial blockade of adrenal angiotensin AT1 receptors or a breakthrough phenomenon. We have investigated the adrenal response to exogenous Ang II in healthy subjects receiving an ARB alone or in association with a thiazide diuretic. Methods: Thirty subjects participated in this randomised, controlled, single-blind study. The effect of a 1 h infusion of Ang II (3 ng/kg/min) on plasma ALDO levels were investigated in each volunteer before and after a 1-week single-blind administration of either irbesartan 300 mg alone or in association with hydrochlorothiazide (HCTZ) 12.5 or 25 mg. After one week washout period, volunteers were switched to olmesartan 20mg/HCTZ 25 mg or valsartan 160/HCTZ 25 mg or losartan 100/HCTZ 25mg for another week. Results: Compared to pre-treatment values and to irbesartan alone, trough plasma ALDO values were higher in subjects receiving Irb300/12.5, and were significantly increased with Irb300/25 (to 4.9±1.8 and 7.5±1.2 ng/dl respectively, p&lt;0.05). In participants receiving Olm20/25, Vals160/25 and Los100/25, trough ALDO were also significantly elevated. Before any treatment, exogenous Ang II increased plasma ALDO acutely from 3.6±0.7 to 13.2±1.3 ng/dl. With Irb300, the ALDO response to Ang II was blunted by 50-60% independently of the presence of HCTZ (p&lt;0.05). The ALDO response to Ang II was also significantly blunted by about 50-60% with Olm20/25 and Vals160/25, but not with Los100/25. Conclusion: These results demonstrate that recommended doses of most ARBs only partially block the adrenal response to exogenous Ang II when associated with a thiazide diuretic. The ARB-thiazide association accentuates the aldosterone escape thus further justifying the use of mineralocorticoid antagonists in some clinical circumstances such as resistant hypertension or hypertension with severe end organ damage.

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.

Circulating Dipeptidyl Peptidase 3 Modulates Systemic and Renal Hemodynamics Through Cleavage of Angiotensin Peptides.

High circulating DPP3 (dipeptidyl peptidase 3) has been associated with poor prognosis in critically ill patients with circulatory failure. In such situation, DPP3 could play a pathological role, putatively via an excessive angiotensin peptides cleavage. Our objective was to investigate the hemodynamics changes induced by DPP3 in mice and the relation between the observed effects and renin-angiotensin system modulation. Ten-week-old male C57Bl/6J mice were subjected to intravenous injection of purified human DPP3 or an anti-DPP3 antibody (procizumab). Invasive blood pressure and renal blood flow were monitored throughout the experiments. Circulating angiotensin peptides and catecholamines were measured and receptor blocking experiment performed to investigate the underlying mechanisms. DPP3 administration significantly increased renal blood flow, while blood pressure was minimally affected. Conversely, procizumab led to significantly decreased renal blood flow. Angiotensin peptides measurement and an AT1R (angiotensin II receptor type 1) blockade experiment using valsartan demonstrated that the renovascular effect induced by DPP3 is due to reduced AT1R activation via decreased concentrations of circulating angiotensin II, III, and IV. Measurements of circulating catecholamines and an adrenergic receptor blockade by labetalol demonstrated a concomitant catecholamines release that explains blood pressure maintenance upon DPP3 administration. High circulating DPP3 increases renal blood flow due to reduced AT1R activation via decreased concentrations of circulating angiotensin peptides while blood pressure is maintained by concomitant endogenous catecholamines release.

Telmisartan Protects Mitochondrial Function, Gait, and Neuronal Apoptosis by Activating the Akt/GSK3β/PGC1α Pathway in an MPTP-Induced Mouse Model of Parkinson's Disease.

Mitochondrial dysfunction is one of the major hallmarks of Parkinson's disease (PD). Recently, angiotensin II type 1 and type 2 receptors (AT1R, AT2R) were reported to be present on the mitochondrial membrane. Both are crucial players in the brain renin-angiotensin system (RAS). Current evidence indicates that blockade of brain AT1R protects dopaminergic neurons in PD. Thus, the current study was aimed to explore the effects of Telmisartan (Tel), a selective AT1R blocker, on mitochondrial function and a mouse model by exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) [250 mg/kg body weight (10 divided i.p. injections, each 25 mg/kg body weight at 3.5 days interval) + Probenecid 250 mg/kg]. Gait function was assessed by beam walk, and mice were euthanized on the 35th day and their brain tissues isolated for Western blot analysis. Pretreatment with Tel significantly protected motor functions during the beam walk in MPTP-treated mice. Tel attenuated the increased levels of AT1R, α-syn, and inflammatory markers such as inducible nitric oxide synthase (iNOS) and ionized calcium-binding adaptor molecule 1 (IBA1) in MPTP-treated mice. In addition, Tel preserved the expression of AT2R, tyrosine hydroxylase (TH), p-Akt/Akt, and p-GSK3β (Ser-9)/GSK3β, as well as protecting mitofusin protein 1 (MFN1) and Peroxisome proliferator-activated receptor-gamma coactivator-α (PGC1α), a critical activator of mitochondrial biogenesis. These results indicate that Tel protects mitochondrial function and gait in a mouse model of PD by modulating the Akt/GSK3β/PGC1α pathway.

Effect of AT1 receptor blockade on cardiovascular outcome after cardiac arrest: an experimental study in rats

Angiotensin II receptor 1(AT1) antagonists are beneficial in focal ischemia/reperfusion (I/R). However, in cases of global I/R, such as cardiac arrest (CA), AT1 blocker's potential benefits are still unknown. Wistar male rats were allocated into four groups: Control group (CG)—animals submitted to CA by ventricular fibrillation induced by direct electrical stimulation for 3 min, and anoxia for 5 min; Group AT1 (GAT1)—animals subjected to CA and treated with 0.2 mg/kg of candesartan diluted in dimethylsulfoxide (DMSO) (0.1%); Vehicle Group (VG): animals subjected to CA and treated with 0.2 ml/kg of DMSO and Sham group (SG)—animals submitted to surgical interventions, without CA. Cardiopulmonary resuscitation consisted of group medications, chest compressions, ventilation, epinephrine (20 mcg/kg) and defibrillation. The animals were observed up to 4 h after spontaneous circulation (ROSC) return, and survival rates, hemodynamic variables, histopathology, and markers of tissue injury were analyzed. GAT1 group had a higher rate of ROSC (62.5% vs. 42.1%, p < 0.0001), survival (100% vs. 62.5%, p = 0.027), lower incidence of arrhythmia after 10 min of ROSC (10% vs. 62.5%, p = 0.000), and lower neuronal and cardiac injury scores on histology evaluation (p = 0.025 and p = 0.0052, respectively) than GC group. The groups did not differ regarding CA duration, number of adrenaline doses, or number of defibrillations. AT1 receptor blockade with candesartan yielded higher rates of ROSC and survival, in addition to neuronal and myocardial protection.

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.

Frequency-coded patterns of sympathetic vasomotor activity are differentially evoked by the paraventricular nucleus of the hypothalamus in the Goldblatt hypertension model.

The paraventricular nucleus of the hypothalamus (PVN) contains premotor neurons involved in the control of sympathetic vasomotor activity. It is known that the stimulation of specific areas of the PVN can lead to distinct response patterns at different target territories. The underlying mechanisms, however, are still unclear. Recent evidence from sympathetic nerve recording suggests that relevant information is coded in the power distribution of the signal along the frequency range. In the present study, we addressed the hypothesis that the PVN is capable of organizing specific spectral patterns of sympathetic vasomotor activation to distinct territories in both normal and hypertensive animals. To test it, we investigated the territorially differential changes in the frequency parameters of the renal and splanchnic sympathetic nerve activity (rSNA and sSNA, respectively), before and after disinhibition of the PVN by bicuculline microinjection. Subjects were control and Goldblatt rats, a sympathetic overactivity-characterized model of neurogenic hypertension (2K1C). Additionally, considering the importance of angiotensin II type 1 receptors (AT1) in the sympathetic responses triggered by bicuculline in the PVN, we also investigated the impact of angiotensin AT1 receptors blockade in the spectral features of the rSNA and sSNA activity. The results revealed that each nerve activity (renal and splanchnic) presents its own electrophysiological pattern of frequency-coded rhythm in each group (control, 2K1C, and 2K1C treated with AT1 antagonist losartan) in basal condition and after bicuculline microinjection, but with no significant differences regarding total power comparison among groups. Additionally, the losartan 2K1C treated group showed no decrease in the hypertensive response triggered by bicuculline when compared to the non-treated 2K1C group. However, their spectral patterns of sympathetic nerve activity were different from the other two groups (control and 2K1C), suggesting that the blockade of AT1 receptors does not totally recover the basal levels of neither the autonomic responses nor the electrophysiological patterns in Goldblatt rats, but act on their spectral frequency distribution. The results suggest that the differential responses evoked by the PVN were preferentially coded in frequency, but not in the global power of the vasomotor sympathetic responses, indicating that the PVN is able to independently control the frequency and the power of sympathetic discharges to different territories.

Novel AT2R agonist, β-Pro7Ang III, is cardio- and vaso-protective in diabetic spontaneously hypertensive rats

Stimulation of the angiotensin II type 2 receptor (AT2R) evokes protective effects in various cardiovascular diseases. Thus, this study aimed to investigate the effects of AT2R stimulation, with or without AT1R blockade, in a model of hypertension with concomitant type 1 diabetes mellitus (T1DM). Spontaneously hypertensive rats (SHRs) were given either citrate or a single dose of streptozotocin (STZ; 55 mg/kg, i.p.) to induce diabetes. After 4 weeks of diabetes, animals were administered either a vehicle (saline), AT2R agonist, β-Pro7Ang III (0.1 mg/kg/day via osmotic mini-pump), AT1R blocker, candesartan (2 mg/kg/day via drinking water), or a combination of both for a further 8 weeks. β-Pro7Ang III treatment had no effect on blood pressure, but attenuated the significant increase in cardiac interstitial collagen and protein expression of fibrotic and inflammatory markers, and superoxide levels that was evident in diabetic SHRs. These effects were not observed with candesartan, despite its blood pressure lowering effects. Although β-Pro7Ang III had no effect on aortic fibrosis, it significantly attenuated MCP-1 protein expression and superoxide levels when compared to both the non-diabetic and diabetic SHRs, to a similar extent as candesartan. In both the heart and vasculature, the effects of β-Pro7Ang III in combination with candesartan were similar to those of β-Pro7Ang III alone, and superior to candesartan alone. It was concluded that in hypertension with concomitant diabetes, AT2R stimulation with a novel ligand alone, or in combination with AT1R blockade, improved the cardiac and vascular structural changes that were strongly associated with inflammation and oxidative stress, independent of blood pressure regulation.

Inappropriate activation of the renin-angiotensin system improves cardiac tolerance to ischemia/reperfusion injury in rats with late angiotensin II-dependent hypertension.

The aim of the study was to clarify the role of the interplay between hypertension and the renin-angiotensin system (RAS) in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. We hypothesized that in the late phase of hypertension with already developed signs of end-organ damage, inappropriate RAS activation could impair cardiac tolerance to I/R injury. Experiments were performed in male Cyp1a1-Ren-2 transgenic rats with inducible hypertension. The early phase of ANG II-dependent hypertension was induced by 5days and the late phase by the 13days dietary indole-3-carbinol (I3C) administration. Noninduced rats served as controls. Echocardiography and pressure-volume analysis were performed, angiotensins' levels were measured and cardiac tolerance to ischemia/reperfusion injury was studied. The infarct size was significantly reduced (by 50%) in 13days I3C-induced hypertensive rats with marked cardiac hypertrophy, this reduction was abolished by losartan treatment. In the late phase of hypertension there are indications of a failing heart, mainly in reduced preload recruitable stroke work (PRSW), but only nonsignificant trends in worsening of some other parameters, showing that the myocardium is in a compensated phase. The influence of the RAS depends on the balance between the vasoconstrictive and the opposed vasodilatory axis. In the initial stage of hypertension, the vasodilatory axis of the RAS prevails, and with the development of hypertension the vasoconstrictive axis of the RAS becomes stronger. We observed a clear effect of AT1 receptor blockade on maximum pressure in left ventricle, cardiac hypertrophy and ANG II levels. In conclusion, we confirmed improved cardiac tolerance to I/R injury in hypertensive hypertrophied rats and showed that, in the late phase of hypertension, the myocardium is in a compensated phase.

Renal vascular responses to angiotensin II infusion in two kidneys-one clip hypertensive rats under partial ischemia/reperfusion with and without ischemia preconditioning: the roles of AT1R blockade and co-blockades of AT1R and MasR.

The renin-angiotensin system activation, partial ischemia/reperfusion (IR) injury, and hypertension contribute to the development of acute kidney injury. The study aims to look at the vascular responses of angiotensin II (Ang II) during Ang II type 1 receptor (AT1R) blockade (losartan) or co-blockades of AT1R and Mas receptor (A779) in two kidneys one clip (2K1C) hypertensive rats which subjected to partial IR injury with and without ischemia preconditioning (IPC). Thirty-three 2K1C male Wistar rats with systolic blood pressure ≥ 150 mmHg were divided into three groups of sham, IR, and IPC + IR divided into two sub-groups receiving losartan or losartan + A779. The IR group had 45 min partial kidney ischemia, while the IPC + IR group had two 5 min cycles of partial ischemia followed by 10 min of reperfusion and then 45 min of partial kidney ischemia followed by reperfusion. The sham group was subjected to similar surgical procedures except for IR or IPC. Ang II increased mean arterial pressure in all the groups, but there were no significant differences between the sub-groups. A significant difference was observed in the renal blood flow response to Ang II between two sub-groups of sham and IR groups treated with AT1R blockade alone or co-blockades of AT1R + A779. These findings demonstrated the significance of AT1R and Mas receptor following partial renal IR in the renal blood flow responses to Ang II in 2K1C hypertensive rats.

CHLOROGENIC ACID CAN INHIBIT CATECHOLAMINE SECRETION FROM THE ADRENAL MEDULLA

Objective: Chlorogenic acid (CGA) is one of the most available phenolic acid compounds in foods, such as coffee and tea, which is known to be the most effective agent in lowering blood pressure and helpful in treating hypertension-related disorders. Thus the present study was aimed to determine the characteristics of CGA on secretion of catecholamines (CA) in the perfused model of the rat adrenal medulla, and also to validify its mechanism of action. Design and method: he adrenal gland was isolated and perfused with Krebs-bicarbonate. CA was measured directly by using the fluorospectrophotometer. Results: CGA, administered into an adrenal vein for 90 min, reduced ACh -induced CA secretion in a dose- and time-dependent manner. CGA also time-dependently depressed the CA secretion induced by McN-A-343, DMPP, and angiotensin II . CGA itself failed to influence spontaneous CA secretion. Also, During the perfusion of CGA for 90 min, the CA secretory responses induced by high K+, veratridine, cyclopiazonic acid, Bay-K-8644 were suppressed. However, in the simultaneous presence of CGA and L-NAME, the CA secretory responses induced by ACh, Ang II, Bay-K-8644 and veratridine was restored nearly to the control level compared to those of the inhibitory effects of CGA-treatment alone. Virtually, the adrenal NO release was significantly enhanced by CGA-treatment. Also, in the coexistence of CGA and olmesartan, ACh-induced CA secretion was markedly reduced compared to that of olmesartan-treatment alone. Conclusions: Taken together, we present the first evidence that CGA suppresses the CA secretion induced by activation of cholinoceptors as well as AT1-receptors. This CGA-induced inhibitory effect seems to be exerted by reducing both the influx of Na+ and Ca2+ through their ionic channels into adrenomedullary chromaffin cells as well as by suppressing the Ca2+ release from the cytoplasmic calcium store, through the elevated NO release by the activation of NO synthase, which is associated to the blockade of neuronal cholinonoceptors and AT1-receptors. Based on these results, the ingestion of CGA may be helpful to alleviate or prevent the cardiovascular diseases, via reduction of adrenal CA secretion and consequent decreased CA level in circulation.

AT1R BLOCKADE PROMOTES TRANSFER OF HYPERTENSION BY RENAL CD11C+F4/80+ MACROPHAGES

Objective: The immune system participates in arterial hypertension (AHT) induced by Angiotensin II (AngII). dendritic cells (DCs)-CD11c+ and macrophages (Mo) are abundant in the kidney. However, new subpopulations of CD11c+ cells with Mo characteristics have been described, presenting an F4/80+ phenotype. Additionally, recent studies have shown a controversial role of the type 1 AngII receptor (AT1R) in CD11c+ cells. In this context, it is unknown whether Mo CD11c+-F4/80+ modifies their phenotype during AngII-induced inflammatory kidney damage, and whether this promotes AHT in an AT1R-dependent manner. The goal was evaluate whether renal Mo CD11c+-F4/80+ (rMo) modify their phenotype in AHT by AngII and determine whether their transfer to normotensive animals promotes AHT in an AT1R-dependent manner. Design and method: Male C57BI/6 mice (8 - 10 weeks, n = 6) were infused with AngII (490 ng/kg/min), AngII+Losartan (LOS; 20mg/kg/day, in drinking water), or vehicle for 14 -days. Systolic blood pressure (SBP) was measured by photoplestimography, DCs-CD11c+-F4/80- and rMo infiltrate were evaluated in cortex and medulla by flow cytometry. These cells were isolated and transferred to normotensive recipients, whose SBP was measured for 7-days (n = 3 - 5). Finally, the rMo were stimulated in vitro with AngII (100nM-24h) to analyze the abundance of mRNAs (Nox2, Sgk1, ENaC and AT1R; qRT-PCR). The data correspond to the mean ± standard deviation. Results: AngII increased SBP (AngII 134.7 ± 6.9 vs. Vehicle (Vh) 114.5 ± 7.8mmHg;p &lt; 0.001) and promoted DCs-CD11c+F4/80- (AngII = 45.6 ± 11.9% vs. Vh = 31.7 ± 6.7%; p &lt; 0.05) and Mo-CD11c+F4/80+ (AngII = 66.1 ± 8.4% vs. Vh = 55.6 ± 5.1%; p &lt; 0.05) infiltration in renal medulla, and that was prevented by LOS (p &lt; 0.05). We did not observe statistical differences in cortex. Interestingly, rMo transfer from AngII animals did not induce AHT in healthy recipient animals after 24h (Basal = 106.8 ± 2.3 vs.112.4 ± 4.9 mmHg;ns), compared to DCs-CD11c+-F4/80- (Basal = 110.0 ± 8.3 vs.132.0 ± 14.3mmHg;p &lt; 0.05). However, the rMo of AngII+LOS animals increased SBP healthy recipients with respect to their baseline (basal = 109 ± 5.6 vs. 123 ± 8.0mmHg;p &lt; 0.05). The rMo and DCs of hypertensive animals showed an increase in the abundance of AT1R (p &lt; 0.05) compared to vehicle rMo. Conclusions: Pharmacological blockade of AT1R in vivo would have a differential effect on rMo, transferring AHT to normotensive animals. These findings suggest that subpopulations of renal CD11c+ cells have a differential role in AHT.

Signaling crosstalk between Dipeptidyl Peptidase 4 and Angiotensin II-AT1R plays a role in proximal tubule NHE3 regulation and salt sensitive hypertension

Background: Salt sensitivity to hypertension occurs in 50-60% of all hypertensive patients and is more common in overweight/obese, females and aging population. In salt sensitive hypertension, the renin-angiotensin system (RAS) is known to play a major role and in particular, Angiotensin II (Ang II) regulation of the sodium hydrogen exchanger (NHE3) in the proximal tubule may mediate the pathophysiology. Dipeptidyl peptidase 4 (DPP4), an exopeptidase expressed abundantly on the brush border, binds to NHE3 and DPP4 inhibition reduces NHE3-mediated sodium reabsorption in proximal tubule cells. Interestingly, we observed both in vitro and in vivo that Ang II stimulates DPP4 activity. However, the mechanisms mediating the interplay between Ang II and DPP4 and its role in NHE3 regulation remain unknown. Therefore, we hypothesized that Ang II stimulation of DPP4 activity via crosstalk between AT1R and DPP4 may account for NHE3 modulation and, consequently, salt-sensitive hypertension. Methods: To address this hypothesis, we stimulated OK-AT1R (stable expressing rat AT1R) proximal tubule cells with Ang II (10 -8 to 10 -10 M), OKP cells with Ang II 10 -8 M and microperfused rat nephrons (Ang II 10 -10 M). In addition, sodium balance studies were conducted on DPP4-/- mice with high salt (1% sodium choride in drinking water) and low salt (0.02% in diet) Results: In OK-AT1R cells, we observed a dose-dependent increase in DPP4 activity, which was inhibited with AT1R blockade, and a battery of kinase inhibitors, including those for Src, PI3K, mTOR, S6K, ERK, and EGFR. Blockade with the DPP4 inhibitor MK-0626 not only suppressed DPP4 activity but partially suppressed Ang II-mediated signaling via EGFR, src, PI3K, mTOR and S6K. Further dissection of the pathways revealed that the blockade of src, which binds to both AT1R and DPP4, mimicked many of the effects of AT1R and DPP4 blockade. Mechanistically, blockade of motor proteins myosin II and myosin VI, which have been shown to redistribute with DPP4 and NHE3 along the microvilli microdomains, did not inhibit Ang II-induced DPP4 activity suggesting other mechanisms (phosphorylation) may underlie Ang II-DPP4 crosstalk in proximal tubule cells. Importantly, we found that DPP4 inhibition blocked Ang II-mediated stimulation of NHE3 activity (pHi) in vitro (OKP cells) and JHCO 3 - in vivo (rat nephrons). In addition, we observed that DPP4 gene-deleted mice lose more salt under both high and low salt ingestion and that DPP4 deficiency lowers BP under conditions of high salt, suggesting that DPP4 may regulate salt-sensitive hypertension. In conclusion, Ang II-AT1R and DPP4 likely crosstalk via binding to src and/or PI3-K, and inhibition of DPP4 suppresses Ang II-AT1R signaling and downstream effectors, including NHE3. Moreover, inhibition of signaling downstream of AT1R can suppress DPP4 activity, suggesting that AT1R and DPP4 act in concert but not via subcellular redistribution via motor proteins. The Sao Paulo Research Foundation - FAPESP (2021/14534-3), Sao Paulo, SP, Brazil to Flavia Martins and Dr. Adriana Girardi; NIH/NIDDK - K08 DK115886 to Dr. Ravi Nistala This is the full abstract presented at the American Physiology Summit 2023 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.

Expression of human sPRR in renal collecting duct cells increases blood pressure in female mice independently of its circulating levels

Elevated circulating sPRR has been associated with essential hypertension, obesity-related hypertension, heart failure and chronic kidney disease in humans. However, the exact contribution of tissue-specific human sPRR in blood pressure control remains to be investigated. Therefore, we evaluated the effect of human sPRR on circulating sPRR and blood pressure control when expressed in mouse kidney, adipose tissue or liver from both male and female mice.Human sPRR-Myc-tag transgenic mice were bred with mice expressing either Hoxb7/Cre, Adiponectin/Cre or Albumin/Cre to selectively express human sPRR (HsPRR) in the collecting duct of the kidney (Kid-HsPRR), adipose tissue (Adi-HsPRR) or liver (Liv-HsPRR), respectively. The presence of human sPRR-Myc-tag (28 KDa) was validated in each mouse model by detecting the presence of C-myc. HsPRR and control (WT) male and female mice were fed a control diet throughout the study (n=8-12/group). At 6 months, baseline and acute blood pressure responses were assessed by radio-telemetry.Tissue expression of sPRR increased in kidney-derived HsPRR (M: 1.0±0.2 vs. 1.6±0.3 AU, F: 1.0±0.1 vs. 1.7±0.2 AU p&lt;0.05), adipose-derived HsPRR (M: 1.0±0.3 vs. 4.7±1.5 AU, F: 1.0±0.2 vs. 3.2±1.4 AU p&lt;0.05) and liver-derived HsPRR mice (M: 1.0±0.2 vs. 9.7±0.8 AU, F: 1.0±0.1 vs. 8.7±0.9 AU p&lt;0.05) but only liver-derived HsPRR mice elevated circulating sPRR (M: 7.0±2.4 vs. 125.0±7.9 ng/ml, F: 2.2±0.4 vs. 93.9±13.4 ng/ml p&lt;0.05). Human sPRR increased blood pressure only in female mice expressing HsPRR in kidney (F: 111±2 vs. 121±4 mmHg p&lt;0.05). Also, only female mice expressing HsPRR in kidney displayed a blunted acute response to losartan injection (M: -30.1±3.3 vs. -22.1±3.7, F: -16.3±2.4 vs. 14.1±5.8 Δ mmHg p&lt;0.05) and Ang II-induced pressor response in acute (M: 28.9±5.1 vs. 47.6±4.4 mmHg p&lt;0.05, F: 35.2±7.2 vs. 26.9±7.5 mmHg) and chronic fashion (M: 33.9±3.6 vs. 30.7±5.0, F: 35.1±6.8 vs.17.6±3.2 Δ mmHg, p&lt;0.05).Overall, our data show that increased intrarenal human sPRR expression contributes to increase blood pressure in a sex-specific manner. Taken together, increased HsPRR in kidney is associated with hypertension and impaired response to AT1R blockade and AngII-induced pressor response suggesting a dysfunctional AT1R-mediated signaling that could be due to ligand competition. These studies were supported by grants from the American Heart Association (13SDG17230008), the National Institute of General Medical Sciences (P30 GM127211), the Center for Clinical and Translational Sciences (UL1TR000117) and the National Heart Lung and Blood Institute (R01HL142969-01) This is the full abstract presented at the American Physiology Summit 2023 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.

Telmisartan and losartan: The marked differences between their chemical and pharmacological properties may explain the difference in therapeutic efficacy in hospitalized patients with COVID‐19

Telmisartan and losartan: The marked differences between their chemical and pharmacological properties may explain the difference in therapeutic efficacy in hospitalized patients with COVID‐19