AT1R Receptor Research Articles

Unraveling the relationship between the renin-angiotensin system and endometrial cancer: a comprehensive review.

Endometrial cancer (EC), the most common adenocarcinoma, represents 90% of uterine cancer in women with an increased incidence of occurrence attributed to age, obesity, hypertension, and hypoestrogenism. Being the most common gynecological malignancy in women, it shows a relation with the activation of different components of the renin-angiotensin system (RAS), which is predominantly involved in maintaining blood pressure, salt, water, and aldosterone secretion, thereby playing a significant role in the etiology of hypertension. The components of the RAS, i.e., ACE-I, ACE-II, AT1R, AT2R, and Pro(renin) receptor, are widely expressed in both glandular and stromal cells of the endometrium, with varying levels throughout the different phases of the menstrual cycle. This causes the endometrial RAS to implicate angiogenesis, neovascularization, and cell proliferation. Thus, dysfunctioning of the endometrial RAS could predispose the growth and spread of EC. Interestingly, the increased expression of AngII, AGTR1, and AGTR2 showed advancement in the stages and progression of EC via the prorenin/ATP6AP2 and AngII/AGTR1 pathway. Therefore, this review corresponds to unraveling the relationship between the progression and development of endometrial cancer with the dysfunction in the expression of various components associated with RAS in maintaining blood pressure.

Dissecting aortic aneurysm in Marfan syndrome is associated with losartan-sensitive transcriptomic modulation of aortic cells.

To improve our limited understanding of the pathogenesis of thoracic aortic aneurysm (TAA) that leads to acute aortic dissection, single-cell RNA sequencing (scRNA-seq) was employed to profile disease-relevant transcriptomic changes of aortic cell populations in a well-characterized mouse model of the most commonly diagnosed form of Marfan syndrome (MFS). As result, 2 discrete subpopulations of aortic cells (SMC3 and EC4) were identified only in the aorta of Fbn1mgR/mgR mice. SMC3 cells highly express genes related to extracellular matrix formation and nitric oxide signaling, whereas the EC4 transcriptional profile is enriched in smooth muscle cell (SMC), fibroblast, and immune cell-related genes. Trajectory analysis predicted close phenotypic modulation between SMC3 and EC4, which were therefore analyzed together as a discrete MFS-modulated (MFSmod) subpopulation. In situ hybridization of diagnostic transcripts located MFSmod cells at the intima of Fbn1mgR/mgR aortas. Reference-based data set integration revealed transcriptomic similarity between MFSmod- and SMC-derived cell clusters modulated in human TAA. Consistent with the angiotensin II type I receptor (At1r) contribution to TAA development, MFSmod cells were absent in the aorta of Fbn1mgR/mgR mice treated with the At1r antagonist losartan. Altogether, our findings indicate that a discrete dynamic alteration of aortic cell identity is associated with dissecting TAA in MFS mice and increased risk of aortic dissection in MFS patients.

Structural insights into angiotensin receptor signaling modulation by balanced and biased agonists.

The peptide hormone angiotensin II regulates blood pressure mainly through the type 1 angiotensin II receptor AT1 R and its downstream signaling proteins Gq and β-arrestin. AT1 R blockers, clinically used as antihypertensive drugs, inhibit both signaling pathways, whereas AT1 R β-arrestin-biased agonists have shown great potential for the treatment of acute heart failure. Here, we present a cryo-electron microscopy (cryo-EM) structure of the human AT1 R in complex with a balanced agonist, Sar1 -AngII, and Gq protein at 2.9 Å resolution. This structure, together with extensive functional assays and computational modeling, reveals the molecular mechanisms for AT1 R signaling modulation and suggests that a major hydrogen bond network (MHN) inside the receptor serves as a key regulator of AT1 R signal transduction from the ligand-binding pocket to both Gq and β-arrestin pathways. Specifically, we found that the MHN mutations N1113.35 A and N2947.45 A induce biased signaling to Gq and β-arrestin, respectively. These insights should facilitate AT1 R structure-based drug discovery for the treatment of cardiovascular diseases.

The effect of daidzein on renal injury in ovariectomized rats: interaction of angiotensin receptors and long non-coding RNAs H19, GAS5, MIAT, and Rian.

Renin-angiotensin system (RAS) is prominently associated with renal pathophysiology in postmenopausal women. Long non-coding RNAs (lncRNAs) H19, GAS5, MIAT, and Rian have been linked to the pathogenesis of renal injury. This study aimed to evaluate the beneficial effects of daidzein on unilateral ureteral obstruction (UUO) induced-renal injury in ovariectomized (OVX) rats through interaction with angiotensin AT1, Mas receptors, and lncRNAs. 84 female rats were ovariectomized (OVX) two weeks before performing obstruction of the left kidney ureter (UUO). The animals were then randomly divided into four main groups (n=21): Sham+DMSO, UUO+DMSO, UUO+17β-Estradiol (E2) (positive control), and UUO+daidzein. Each main group comprised three subgroups (n=7) and were treated with saline, A779 (MasR antagonist), or losartan (AT1R antagonist) for 15 days. On day 16, the animals were euthanized, and the left kidneys were harvested for histopathology and lncRNAs expression assays. UUO significantly increased kidney tissue damage score (KTDS) in the UUO rats, increased the expression of H19 and MIAT, and decreased the expression of GAS5 and Rian. Daidzein alone and in co-treatment with losartan or A779 reversed these effects. Daidzein with 1 mg/kg dose was more effective than E2. Daidzein alone and in co-treatment with A779 and losartan improved renal injury in UUO rats and recovered dysregulated expression of UUO-related lncRNAs through modulating MasR and AT1R receptors, associating with modulation of the expression of lncRNAs. Daidzein could be considered a renoprotective phytoestrogen substitute for E2 therapy in postmenopausal women suffering from renal diseases.

Increased Arterial Responsiveness to Angiotensin II in Mice Conceived by Assisted Reproductive Technologies.

Since the first report in 1978, the number of individuals conceived by Assisted Reproductive Technologies (ART) has grown incessantly. In parallel, with the recent emergence of possible underlying mechanisms of ART-induced epigenetic changes in the renin-angiotensin system, the cardiovascular repercussions of ART in mice and human offspring (including arterial hypertension, vascular dysfunction, and cardiac remodeling) have become increasingly recognized. Here, we hypothesized that ART may increase arterial responsiveness to angiotensin II (ANG II) by epigenetically modifying the expression of its receptors. To test this hypothesis, we assessed the vasoconstrictor responsiveness to ANG II in isolated aortas from ART and control mice. We also examined ANG II receptor (ATR) type 1 and 2 expression and the promoter methylation of the At1aR, At1bR and At2R genes. We found that the vasoconstrictor response to ANG II was markedly increased in ART mice compared to controls. This exaggerated vasoconstrictor responsiveness in ART mice correlated with a significant increase in the ANG II receptor (ATR) type 1 to ATR type 2 protein expression ratio in the aorta; this was mainly driven by an increase in AT1R expression, and by hypomethylation of two CpG sites located in the At1bR gene promoter leading to increased transcription of the gene. We conclude that in mice, ART increase the vasoconstrictor response to ANG II in the aorta by epigenetically causing an imbalance between the expression of vasoconstrictor (AT1R) and vasodilator (AT2R) ANG II receptors. Unbalanced expression of AT1R and AT2R receptors seems to be a novel mechanism contributing to ART-induced arterial hypertension in mice.

Low-dose rapamycin prevents Ang-II-induced toxicity in Leydig cells and testicular dysfunction in hypertensive SHR model.

Hypertension is a common chronic cardiovascular disease reported among both men and women. Hypertension in males affects the testis and reproduction function; however, the pathogenesis is poorly understood. Rapamycin has been reported to have a variety of beneficial pharmacological effects; however, high-doses rapamycin does have side effects such as immunosuppression. The present study investigates whether low-dose rapamycin can reduce the damage caused by hypertension to the testis of spontaneously hypertensive rats (SHRs) and further examines molecular mechanism of low-dose rapamycin in preventing testicular toxicity induced by angiotensin II (Ang II). Low rapamycin dose restores the testicle size, histological alterations, 3β-hydroxysteroid dehydrogenase (3β-HSD) expression, and prevents apoptosis in SHR rats. Ang II downregulates angiotensin-converting enzyme-2 (ACE2) expression through AT1R, p-ERK, and MAS receptor in LC-540 Leydig cells in a dose-dependent manner. Low doses of rapamycin effectively upregulate steroidogenic enzymes, steroidogenic acute regulatory protein and 3β-HSD expression in Leydig cells. Rapamycin upregulates ACE2 expression through p-PKAc and p-PI3k in Ang II-treated cells. Further, rapamycin curbs mitochondrial superoxide generation and depleted mitochondrial membrane potential induced by Ang II through activation of Nrf2-mediated Gpx4 and superoxide dismutase 2 expression. Our results revealed the involvement of ACE2, AT1R, AT2R, PKAc, and oxidative stress in Ang-II-induced testicular toxicity, suggesting low-dose rapamycin could be a potential therapeutic candidate to attenuate testicular toxicity.

Selective blockade of AT1R and B1R modulates the expression of ACE2 ubiquitination partners

Angiotensin Converting Enzyme 2 (ACE2) is an important compensatory enzyme in the renin‐angiotensin system (RAS), converting Angiotensin (Ang)‐II to Ang‐(1‐7). We previously reported that Ang‐II mediates ACE2 internalization through its type 1 receptor (AT1R), followed by ubiquitination and degradation in lysosomes. We recently identified UBR1 and BRCC36, as potential ubiquitinase and deubiquitinase, respectively, modulating ACE2 expression in hypertensive conditions. Here, we aimed to evaluate the role of bradykinin B1R receptor in Ang‐II‐mediated ACE2 internalization and the enzyme’s ubiquitination partners in hypertension.C57BI/6J mice (3‐month‐old, n=3/group) were divided into 3 groups: control (Ctrl), B1R antagonist SSR240612 (SSR), AT1R antagonist Losartan (Los). Mice were implanted with blood pressure (BP) probes (telemetry) and upon recovery, baseline BP was recorded for 24 hours. Mice were then implanted subcutaneously with an osmotic pump containing Ang‐II (490 ng/Kg/min/4 weeks) or saline. BP was recorded weekly, for 4 weeks. After 2weeks of Ang‐II infusion, the mice were implanted with an additional osmotic pump containing Losartan (30 mg/Kg/min) or SSR240612 (10 mg/Kg/min) for 2 weeks. Animals were sacrificed and the heart was isolated from all groups and protein expression for UBR1, BRCC36 and ACE2 was assessed using capillary western. Clinical relevance was further assessed in human heart left ventricle tissues of normal and hypertensive donors.Ang‐II infusion induced a significant increase in mean BP in Ctrl group (159.2±1.5 vs. 100.6±0.5 mmHg; one‐way ANOVA, **P<0.001) after 4 weeks of infusion. This was significantly attenuated with blockade of B1R or AT1R (SSR: 98.8±0.6; Los: 99.6±0.8 mmHg; n=3: one‐way ANOVA, **P<0.001). Capillary western with mouse heart tissue confirmed that Ang‐II‐induced a significant 2‐fold increase (*P<0.05) in UBR1 expression and the SSR240612 treatment contributed to a significant 4‐fold increase (**P<0.001). However, losartan had no effect. BRCC36 expression in Ang‐II, losartan and SSR240612 treated group was significantly decreased by 2‐3‐fold (*P<0.05). However, Ang‐II induced decrease in ACE2 levels was significantly attenuated by losartan and SSR240612 (**P<0.001), indicating both B1R and AT1R receptors contribute to ACE2 internalization and degradation. In human’s, the UBR1 expression was 2 folds (*P<0.05) higher in hypertensive CA male and AA female and BRCC36 expression showed 2 folds decrease (*P<0.05) in CA hypertensive females. However, ACE2 expression showed 3 folds decrease in hypertensive CA males, indicating elevated levels of UBR1 mediated ACE2 ubiquitination and degradation in hypertensive conditions.Our data show that Ang‐II‐mediated hypertension was attenuated with inhibition of both AT1R and B1R receptor, while B1R contributed to upregulation of UBR1 and both AT1R and B1R contributes to downregulation of BRCC36. Therefore, inhibition of both AT1R and B1R modulates the expression of ACE2 ubiquitination partners and also inhibits ACE2 internalization and degradation. Therefore, developing a treatments strategy and simultaneously targeting AT1R, B1R, UBR1 and BRCC36, involved in the regulation of ACE2 expression may be effective for the treatment of cardiovascular disorders.

Prediction of COVID-19 manipulation by selective ACE inhibitory compounds of Potentilla reptant root: In silico study and ADMET profile.

In the novel SARS-CoV-2 (COVID-19) as a global emergency event, the main reason of the cardiac injury from COVID-19 is angiotensin-converting enzyme 2 (ACE2) targeting in SARS-CoV-2 infection. The inhibition of ACE2 induces an increase in the angiotensin II (Ang II) and the angiotensin II receptor type 1 (AT1R) leading to impaired cardiac function or cardiac inflammatory responses. The ethyl acetate fraction of Potentilla reptans L. root can rescue heart dysfunction, oxidative stress, cardiac arrhythmias and apoptosis. Therefore, isolated components of P. reptans evaluated to identify natural anti-SARS-CoV-2 agents via molecular docking.In silico molecular docking study were carried out using the Auto Dock software on the isolated compounds of Potentilla reptans root. The protein targets of selective ACE and others obtained from Protein Data Bank (PDB). The best binding pose between amino acid residues involved in active site of the targets and compounds was discovered via molecular docking. Furthermore, ADMET properties of the compounds were evaluated.The triterpenoids of P. reptans showed more ACE inhibitory potential than catechin in both domains. They were selective on the nACE domain, especially compound 5. Also, the compound 5 & 6 had the highest binding affinity toward active site of nACE, cACE, AT1R, ACE2, and TNF-α receptors. Meanwhile, compound 3 showed more activity to inhibit TXA2. Drug likeness and ADMET analysis showed that the compounds passed the criteria of drug likeness and Lipinski rules. The current study depicted that P. reptans root showed cardioprotective effect in COVID-19 infection and manipulation of angiotensin II-induced side effects.

Effects of angiotensin peptides on colonic motility in rats.

Renin-angiotensin system (RAS) is involved in the pathophysiology of colonic inflammation. The aim of this study was to investigate whether small angiotensins (Angs) peptides play a role in the regulation of colonic motility and their roles are modulated in colitis. Experimental colitis was induced by an intake of 5% dextran sulfate sodium (DSS) dissolved in tap water for 7 days in Sprague-Dawley rats. After sacrifice, plasma hormone concentrations and messenger RNAs (mRNAs) for RAS were measured. Functional analysis of colonic motility in response to Angs peptides was performed using Taenia coli. DSS-treated colon showed an increased necrosis with massive infiltration of inflammatory cells. The mRNA level of colonic angiotensin II receptor type 2 (AT2R) in DSS-treated rats was higher than that in control rats whereas the mRNA levels of angiotensin II converting enzyme (ACE), ACE2, AT1R, AT4R, and Mars receptor were not different from those in control rats. Ang III, Ang IV, and Ang-(1-9) (1, 3 μM) increased the frequency of basal colonic motility. Ang-(1-7) did not cause any significant changes in frequency and amplitude of basal motility. The order of potency for an increased frequency of basal motility seems to be Ang II>>Ang IV>Ang III=Ang-(1-9). The increased frequency of basal motility by Ang-(1-9) but not Ang IV was significantly enhanced in DSS-treated rat colon. In conclusion, these data suggest that small Angs peptides are partly involved in the pathophysiological regulation of colonic motility in experimental colitis.

Angiotensin-(1-7) as a Potential Therapeutic Strategy for Delayed Cerebral Ischemia in Subarachnoid Hemorrhage.

Aneurysmal subarachnoid hemorrhage (SAH) is a substantial cause of mortality and morbidity worldwide. Moreover, survivors after the initial bleeding are often subject to secondary brain injuries and delayed cerebral ischemia, further increasing the risk of a poor outcome. In recent years, the renin–angiotensin system (RAS) has been proposed as a target pathway for therapeutic interventions after brain injury. The RAS is a complex system of biochemical reactions critical for several systemic functions, namely, inflammation, vascular tone, endothelial activation, water balance, fibrosis, and apoptosis. The RAS system is classically divided into a pro-inflammatory axis, mediated by angiotensin (Ang)-II and its specific receptor AT1R, and a counterbalancing system, presented in humans as Ang-(1–7) and its receptor, MasR. Experimental data suggest that upregulation of the Ang-(1–7)/MasR axis might be neuroprotective in numerous pathological conditions, namely, ischemic stroke, cognitive disorders, Parkinson’s disease, and depression. In the presence of SAH, Ang-(1–7)/MasR neuroprotective and modulating properties could help reduce brain damage by acting on neuroinflammation, and through direct vascular and anti-thrombotic effects. Here we review the role of RAS in brain ischemia, with specific focus on SAH and the therapeutic potential of Ang-(1–7).

Autoantibodies Targeting AT1- and ETA-Receptors Link Endothelial Proliferation and Coagulation via Ets-1 Transcription Factor.

Scleroderma renal crisis (SRC) is an acute life-threatening manifestation of systemic sclerosis (SSc) caused by obliterative vasculopathy and thrombotic microangiopathy. Evidence suggests a pathogenic role of immunoglobulin G (IgG) targeting G-protein coupled receptors (GPCR). We therefore dissected SRC-associated vascular obliteration and investigated the specific effects of patient-derived IgG directed against angiotensin II type 1 (AT1R) and endothelin-1 type A receptors (ETAR) on downstream signaling events and endothelial cell proliferation. SRC-IgG triggered endothelial cell proliferation via activation of the mitogen-activated protein kinase (MAPK) pathway and subsequent activation of the E26 transformation-specific-1 transcription factor (Ets-1). Either AT1R or ETAR receptor inhibitors/shRNA abrogated endothelial proliferation, confirming receptor activation and Ets-1 signaling involvement. Binding of Ets-1 to the tissue factor (TF) promoter exclusively induced TF. In addition, TF inhibition prevented endothelial cell proliferation. Thus, our data revealed a thus far unknown link between SRC-IgG-induced intracellular signaling, endothelial cell proliferation and active coagulation in the context of obliterative vasculopathy and SRC. Patients’ autoantibodies and their molecular effectors represent new therapeutic targets to address severe vascular complications in SSc.

Synergy of epidermal growth factor (EGFR) and angiotensin II (AT1R) receptor determines composition and temporal pattern of transcriptome variation

The tyrosine kinase receptor EGFR and the G-protein-coupled receptor AT1R induce essential cellular responses, in part via receptor crosstalk with an unknown role in nuclear information transfer and transcription regulation. We investigated whether this crosstalk results in linear, EGFR-mediated nuclear signalling or in parallel, synergistic information transfer leading to qualitative and temporal variations, relevant for gene expression and environment interaction. AT1R and EGFR synergistically activate SRF via the ERK1/2-TCF and actin-MRTF pathways. Synergism, comprised of switch-like and graded single cell response, converges on the transcription factors AP1 and EGR, resulting in synergistic transcriptome alterations, in qualitative (over-additive number of genes), quantitative (over-additive expression changes of individual genes) and temporal (more late onset and prolonged expressed genes) terms. Gene ontology and IPA® pathway analysis indicate prolonged cell stress (e.g. hypoxia-like) and dysregulated vascular biology. Synergism occurs during separate but simultaneous activation of both receptors and during AT1R-induced EGFR transactivation. EGFR and AT1R synergistically regulate gene expression in qualitative, quantitative and temporal terms with (patho)physiological relevance, extending the importance of EGFR-AT1R crosstalk beyond cytoplasmic signalling.

Shedding Light on the Pharmacological Interactions between μ-Opioid Analgesics and Angiotensin Receptor Modulators: A New Option for Treating Chronic Pain.

The current protocols for neuropathic pain management include µ-opioid receptor (MOR) analgesics alongside other drugs; however, there is debate on the effectiveness of opioids. Nevertheless, dose escalation is required to maintain their analgesia, which, in turn, contributes to a further increase in opioid side effects. Finding novel approaches to effectively control chronic pain, particularly neuropathic pain, is a great challenge clinically. Literature data related to pain transmission reveal that angiotensin and its receptors (the AT1R, AT2R, and MAS receptors) could affect the nociception both in the periphery and CNS. The MOR and angiotensin receptors or drugs interacting with these receptors have been independently investigated in relation to analgesia. However, the interaction between the MOR and angiotensin receptors has not been excessively studied in chronic pain, particularly neuropathy. This review aims to shed light on existing literature information in relation to the analgesic action of AT1R and AT2R or MASR ligands in neuropathic pain conditions. Finally, based on literature data, we can hypothesize that combining MOR agonists with AT1R or AT2R antagonists might improve analgesia.

Identification of oligopeptides from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) non structural protein 8 (NSP8) and their similarities with type 1 angiotensin II receptor key sites

Coronavirus disease 2019 is associated with clinical symptoms including severe inflammatory syndrome and a higher expression of angiotensin II. As a pro-inflammatory mediator, the physiologic effects of angiotensin II are mediated by a G-protein coupled receptor, termed AT1R. Following binding, AT1R initiates the process of signal desensitization necessary to maintain cellular homeostasis. At the cellular level, this function occurs via the G protein-dependent signaling and the phosphorylation. We describe amino acids similarities between SARS COV-2 nonstructural protein (NSP8) which is associated with intracellular membranes and AT1R key sites. Since abnormal activation of AT1R receptor leads to a number of physiological disorders, we hypothesize that SARS COV-2 might further interfere with the angiotensin II receptor functions.

The Embryonic Chick Femur Organotypic Model as a Tool to Analyze the Angiotensin II Axis on Bone Tissue

Activation of renin–angiotensin system (RAS) plays a role in bone deterioration associated with bone metabolic disorders, via increased Angiotensin II (AngII) targeting Angiotensin II type 1 receptor/Angiotensin II type 2 receptor (AT1R/AT2R). Despite the wide data availability, the RAS role remains controversial. This study analyzes the feasibility of using the embryonic chick femur organotypic model to address AngII/AT1R/AT2R axis in bone, which is an application not yet considered. Embryonic day-11 femurs were cultured ex vivo for 11 days in three settings: basal conditions, exposure to AngII, and modulation of AngII effects by prior receptor blockade, i.e., AT1R, AT2R, and AT1R + AT2R. Tissue response was evaluated by combining µCT and histological analysis. Basal-cultured femurs expressed components of RAS, namely ACE, AT1R, AT2R, and MasR (qPCR analysis). Bone formation occurred in the diaphyseal region in all conditions. In basal-cultured femurs, AT1R blocking increased Bone Surface/Bone Volume (BS/BV), whereas Bone Volume/Tissue Volume (BV/TV) decreased with AT2R or AT1R + AT2R blockade. Exposure to AngII greatly decreased BV/TV compared to basal conditions. Receptor blockade prior to AngII addition prevented this effect, i.e., AT1R blockade induced BV/TV, whereas blocking AT2R caused lower BV/TV increase but greater BS/BV; AT1R + AT2R blockade also improved BV/TV. Concluding, the embryonic chick femur model was sensitive to three relevant RAS research setups, proving its usefulness to address AngII/AT1R/AT2R axis in bone both in basal and activated conditions.

Using conformational constraints at position 6 of Angiotensin II to generate compounds with enhanced AT2R selectivity and proteolytic stability

The Renin-Angiotensin System (RAS) plays a crucial role in numerous pathological conditions. Two of the critical RAS players, the angiotensin receptors AT1R and AT2R, possess differential functional profiles, although they share high sequence similarity. Although the main focus has been placed on AT1R, several epidemiological studies have evidenced that activation of AT2R could operate as a multimodal therapeutic target for different diseases. Thus, the development of selective AT2R ligands could have a high clinical potential for different therapeutic directions. Furthermore, they could serve as a powerful tool to interrogate the molecular mechanisms that are mediated by AT2R. Based on our recently established high affinity and AT2R selective compound [Y]6-AII we developed several analogues through modifying aminoacids located at positions 6 and 7 with various conformationally constrained analogues to enhance both the selectivity and stability. We report the development of high-affinity AT2R binders, which displayed high selectivity for AT2R versus AT1R. Furthermore, all analogues presented enhanced stability in human plasma with respect to the parent hormone Angiotensin II as also [Y]6-AII.

Angiotensin II and Angiotensin‐(1‐7) Modulate Mitochondrial Respiration in Mouse Mesenchymal Stromal Cells

Mesenchymal stromal cells (MSCs) constitute bone marrow niches that support homing and quiescence of hematopoietic stem cells via paracrine functions. MSCs have the potential of differentiating into a variety of cell types and therefore have therapeutic potential in regenerative medicine. Mitochondria modulates cellular functions including paracrine functions by which MSCs modulate quiescence and differentiation of stem cells. Previous studies have provided evidence for the expression of renin-angiotensin system in MSCs. The current study evaluated the effects of Angiotensin II (Ang II) and Angiotensin-(1-7) (Ang-(1-7)) on mitochondrial respiration in mouse bone marrow MSCs. Study was carried out in cultured MSCs, passage eight or nine, and mitochondrial respiration was evaluated by using Seahorse (XFp). Expression of ACE, ACE2, AT1R, AT2R and Mas receptor were evaluated by real-time PCR and western blotting. Oxygen consumption rate (OCR) was determined by carrying out mito-stress test. For measuring OCR in real-time, the mito-stress test was carried out, which involved use of different pharmacological agents that modulate mitochondrial electron transport chain such as oligomycin (2µm), FCCP (0.5µm), rotenone/ antimycin A (0.5µm) to determine ATP-linked respiration, maximal respiration, non-mitochondrial respiration, respectively, after recording basal respiration. PCR detected mRNA transcripts of ACE, AT1R, AT2R, and Mas, but not ACE2. Mito-stress test showed dose-dependent (0.1nm, 1nm, 10nm) increase in basal, ATP-linked, maximal, and nonmitochondrial respiration by Ang-(1-7) and effects at 10nm concentration were significant (P<0.05, n=5) compared to the untreated cells (Figure 1). All these changes were blocked by A-779 (1µm). All of the mitochondrial respiratory parameters were significantly (P<0.05, n=5) decreased when only A-779 was present compared to untreated cells. Ang II (100nm) did not alter OCR in MSCs in mito-stress test (Figure 1). Proton leak was not changed by any treatments. Intriguingly, treatment with PD123391 (1µm) significantly increased basal respiration and maximal respiration compared to untreated cells (P<0.05). These effects were not observed when cells were treated with Ang II along with PD123391. Along similar lines, losartan (10µm) significantly increased the basal respiration compared to untreated MSCs (P<0.05), and this change was not observed in the presence of Ang II. This preliminary study shows that mitochondrial oxygen consumption in MSCs is differentially modulated by angiotensin peptides. Further investigations are needed to address the significance of mitochondrial modulation in the regenerative functions of MSCs by angiotensins.

Sex Differences in the Renal Vascular Responses of AT1 and Mas Receptors in Two-Kidney-One-Clip Hypertension.

Background The prevalence and severity of hypertension, as well as the activity of the systemic and local renin angiotensin systems (RASs), are gender related, with more symptoms in males than in females. However, the underlying mechanisms are not well understood. In this study, we investigated sex differences in renal vascular responses to angiotensin II (Ang II) administration with and without Ang II type 1 and Mas receptor (AT1R and MasR) antagonists (losartan and A779) in the 2K1C rat model of renovascular hypertension. Methods Male and female 2K1C rats were divided into 8 experimental groups (4 of each sex) treated with vehicle, losartan, A779, or A779+losartan. Responses of mean arterial pressure (MAP), renal blood flow (RBF), and renal vascular resistance (RVR) to Ang II were determined. Results In both sexes, the basal MAP, RBF, and RVR were not significantly different between the four groups during the control period. The Ang II administration decreased RBF and increased RVR in a dose-related manner in both sexes pretreated with vehicle or A779 (Pdose < 0.0001), but in vehicle pretreated groups, RBF and RVR responses were different between male and female rats (Pgroup < 0.05). AT1R blockade increased RBF and decreased RVR responses to Ang II, and no difference between the sexes was detected. Coblockades of AT1R and MasR receptors increased RBF response to Ang II significantly in males alone but not in females (Pgroup=0.04). Conclusion The impact of Ang II on RBF and RVR responses seems to be gender related with a greater effect on males, and this sex difference abolishes by Mas receptor blockade. However, the paradoxical role of dual losartan and A779 may provide the different receptor interaction in RAS between male and female rats.

Effects of carotid baroreceptor stimulation on aortic remodeling in obese rats

Background and aimOur previous study found carotid baroreceptor stimulation (CBS) reduces body weight and white adipose tissue (WAT) weight, restores abnormal secretion of adipocytokines and inflammation factors, decreases systolic blood pressure (SBP) by inhibiting activation of sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in obese rats. In this study, we explore effects of CBS on aortic remodeling in obese rats. Methods and resultsRats were fed high-fat diet (HFD) for 16 weeks to induce obesity and underwent either CBS device implantation and stimulation or sham operation at 8 weeks. BP and body weight were measured weekly. RAS activity of WAT, histological, biochemical and functional profiles of aortas were detected after 16 weeks. CBS effectively decreased BP in obese rats, downregulated mRNA expression of angiotensinogen (AGT) and renin in WAT, concentrations of AGT, renin, angiotensin II (Ang II), protein levels of Ang II receptor 1 (AT1R) and Ang II receptor 2 (AT2R) in WAT were declined. CBS inhibited reactive oxygen species (ROS) generation, inflammatory response and endoplasmic reticulum (ER) stress in aortas of obese rats, restrained vascular wall thickening and vascular smooth muscle cells (VSMCs) phenotypic switching, increased nitric oxide (NO) synthesis, promoted endothelium-dependent vasodilatation by decreasing protein expression of AT1R and leptin receptor (LepR), increasing protein expression of adiponectin receptor 1 (AdipoR1) in aortic VSMCs. ConclusionCBS reduced BP and reversed aortic remodeling in obese rats, the underlying mechanism might be related to the suppressed SNS activity, restored adipocytokine secretion and restrained RAS activity of WAT.

To Curb the Progression of Fatal COVID-19 Course-Dream or Reality.

Purpose of ReviewTo analyze the impact of sodium retention states on the course of COVID-19 and propose possible interventions to curb disease progression.Recent FindingsNumerous data confirm a positive association of non-communicable diseases, aging, and other sodium-retaining states, including iatrogenic ones, with more severe sometimes fatal clinical course of COVID-19. Reasons for this effect could include increased angiotensin signaling via the AT1R receptor. The endothelial glycocalyx also plays an important role in infection, leading to a vicious cycle of inflammation and tissue sodium retention when damaged. RAS inhibitors may help restore glycocalyx function and prevent severe organ damage. Anticoagulants, especially heparin, may also have therapeutic applications due to antithrombotic, anti-inflammatory, glycocalyx-repairing, and antialdosteronic properties. The ambiguous influence of some diuretics on sodium balance was also discussed.SummaryAbnormal sodium storage and increased angiotensin-converting enzyme activity are related to the severity of COVID-19. Inducing sodium removal and reducing intake might improve outcomes.