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

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

Quercetin prophylaxis protects the kidneys by modulating the renin-angiotensin-aldosterone axis under acute hypobaric hypoxic stress.

The study presented here aims at assessing the effects of hypobaric hypoxia on RAAS pathway and its components along with mitigation of anomalies with quercetin prophylaxis. One hour prior to hypobaric hypoxia exposure, male SD rats were orally supplemented with quercetin (50 mg/kg BW) and acetazolamide (50 mg/kg BW) and exposed them to 25,000 ft. (7,620 m) in a simulated environmental chamber for 12 h at 25 ± 2 °C. Different biochemical parameters like renin activity, aldosterone, angiotensin I, ACE 2 were determined in plasma. As a conventional response to low oxygen conditions, oxidative stress parameters (ROS and MDA) were elevated along with suppressed antioxidant system (GPx and catalase) in plasma of rats. Quercetin prophylaxis significantly down regulated the hypoxia induced oxidative stress by reducing plasma ROS & MDA levels with efficient enhancement of antioxidants (GPx and Catalase). Further, hypoxia mediated regulation of renin and ACE 2 proves the outstanding efficacy of quercetin in repudiating altercations in RAAS cascade due to hypobaric hypoxia. Furthermore, differential protein expression of HIF-1α, NFκB, IL-18 and endothelin-1 analyzed by western blotting approves the biochemical outcomes and showed that quercetin significantly aids in the reduction of inflammation under hypoxia. Studies conducted with Surface Plasmon Resonance demonstrated a binding among quercetin and ACE 2 that indicates that this flavonoid might regulate RAAS pathway via ACE 2. Henceforth, the study promotes the prophylaxis of quercetin for the better adaptability under hypobaric hypoxic conditions via modulating the RAAS pathway.

The role of telomerase reverse transcriptase in the mitochondrial protective functions of Angiotensin-(1-7) in diabetic CD34+ cells.

Angiotensin (Ang)-(1-7) stimulates vasoprotective functions of diabetic (DB) CD34+ hematopoietic stem/progenitor cells partly by decreasing reactive oxygen species (ROS), increasing nitric oxide (NO) levels and decreasing TGFß1 secretion. Telomerase reverse transcriptase (TERT) translocates to mitochondria and regulates ROS generation. Alternative splicing of TERT results in variants α-, ß- and α-ß-TERT, which may oppose functions of full-length (FL) TERT. This study tested if the protective functions of Ang-(1-7) or TGFß1-silencing are mediated by mitoTERT and that diabetes decreases FL-TERT expression by inducing splicing. CD34+ cells were isolated from the peripheral blood mononuclear cells of nondiabetic (ND, n = 68) or DB (n = 74) subjects. NO and mitoROS levels were evaluated by flow cytometry. TERT splice variants and mitoDNA-lesions were characterized by qPCR. TRAP assay was used for telomerase activity. Decoy peptide was used to block mitochondrial translocation (mitoXTERT). TERT inhibitor or mitoXTERT prevented the effects of Ang-(1-7) on NO or mitoROS levels in DB-CD34+ cells. FL-TERT expression and telomerase activity were lower and mitoDNA-lesions were higher in DB cells compared to ND and were reversed by Ang-(1-7) or TGFß1-silencing. The prevalence of TERT splice variants, with predominant ß-TERT expression, was higher and the expression of FL-TERT was lower in DB cells (n = 25) compared to ND (n = 30). Ang-(1-7) or TGFß1-silencing decreased TERT-splicing and increased FL-TERT. Blocking of ß-splicing increased FL-TERT and protected mitoDNA in DB-cells. The findings suggest that diabetes induces TERT-splicing in CD34+ cells and that ß-TERT splice variant largely contributes to the mitoDNA oxidative damage.

Angiotensin I and II Stimulate Cell Invasion of SARS-CoV-2: Potential Mechanism via Inhibition of ACE2 Arm of RAS.

Angiotensin-converting enzyme 2 (ACE2), one of the key enzymes of the renin-angiotensin system (RAS), plays an important role in SARS-CoV-2 infection by functioning as a virus receptor. Angiotensin peptides Ang I and Ang II, the substrates of ACE2, can modulate the binding of SARS-CoV-2 Spike protein to the ACE2 receptor. In the present work, we found that co incubation of HEK-ACE2 and Vero E6 cells with the SARS-CoV-2 Spike pseudovirus (PVP) resulted in stimulation of the virus entry at low and high micromolar concentrations of Ang I and Ang II, respectively. The potency of Ang I and Ang II stimulation of virus entry corresponds to their binding affinity to ACE2 catalytic pocket with 10 times higher efficiency of Ang II. The Ang II induced mild increase of PVP infectivity at 20 microM; while at 100 microM the increase (129.74+/-3.99 %) was highly significant (p<0.001). Since the angiotensin peptides act in HEK ACE2 cells without the involvement of angiotensin type I receptors, we hypothesize that there is a steric interaction between the catalytic pocket of the ACE2 enzyme and the SARS-CoV-2 S1 binding domain. Oversaturation of the ACE2 with their angiotensin substrate might result in increased binding and entry of the SARS-CoV-2. In addition, the analysis of angiotensin peptides metabolism showed decreased ACE2 and increased ACE activity upon SARS-CoV-2 action. These effects should be taken into consideration in COVID-19 patients suffering from comorbidities such as the over-activated renin-angiotensin system as a mechanism potentially influencing the SARS-CoV-2 invasion into recipient cells.

Alternative Renin-Angiotensin System.

The renin-angiotensin system is the most important peptide hormone system in the regulation of cardiovascular homeostasis. Its classical arm consists of the enzymes, renin, and angiotensin-converting enzyme, generating angiotensin II from angiotensinogen, which activates its AT1 receptor, thereby increasing blood pressure, retaining salt and water, and inducing cardiovascular hypertrophy and fibrosis. However, angiotensin II can also activate a second receptor, the AT2 receptor. Moreover, the removal of the C-terminal phenylalanine from angiotensin II by ACE2 (angiotensin-converting enzyme 2) yields angiotensin-(1-7), and this peptide interacts with its receptor Mas. When the aminoterminal Asp of angiotensin-(1-7) is decarboxylated, alamandine is generated, which activates the Mas-related G-protein-coupled receptor D, MrgD (Mas-related G-protein-coupled receptor type D). Since Mas, MrgD, and the AT2 receptor have opposing effects to the classical AT1 receptor, they and the enzymes and peptides activating them are called the alternative or protective arm of the renin-angiotensin system. This review will cover the historical aspects and the current standing of this recent addition to the biology of the renin-angiotensin system.

Glycyrrhizic acid restores the downregulated hepatic ACE2 signaling in the attenuation of mouse steatohepatitis.

Glycyrrhizic acid (GA), one of the major active components derived from licorice root, exerts liver-protecting activity. Its molecular mechanisms of action, however, remain not completely understood. The angiotensin (Ang) converting enzyme (ACE) 2/Ang-(1-7)/Mas axis, regulated by ACE2 through converting Ang II into Ang-(1-7) to activate Mas receptor, counteracts the pro-inflammatory and pro-steatotic effects of the ACE/Ang II/Ang II receptor type 1 (AT1) axis. Here, it was found that pretreatment with GA suppressed LPS/D-galactosamine-induced serum hyperactivities of alanine aminotransferase and aspartate aminotransferase, hepatomegaly, pathological changes, and over-accumulation of triglycerides and fatty droplets in the liver of mice. GA also diminished LPS/free fatty acid-induced inflammation and steatosis in cultured hepatocytes. Mechanistically, GA restored hepatic protein hypoexpression of ACE2 and Mas receptor, and the decrease in hepatic Ang-(1-7) content. Hepatic overexpression of angiotensin II and AT1 was also suppressed. However, GA did not alter hepatic protein expression of renin and ACE. In addition, GA inhibited hepatic protein over-phosphorylation of the p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, extracellular signal-regulated kinase, and nuclear factor κB at Ser536. Hepatic overexpression of tumor necrosis factor α, interleukin 6, interleukin 1ß, sterol regulatory element-binding protein 1c, and fatty acid synthase was also inhibited. GA-elicited recovery of ACE2 and Mas protein hypoexpression was further confirmed in the hepatocyte. Thus, the present results demonstrate that GA restores the downregulated hepatic ACE2-mediated anti-inflammatory and anti-steatotic signaling in the amelioration of steatohepatitis. We suggest that GA may protect the liver from injury by regulating the hepatic ACE2-mediated signaling.

Evaluation of different isotope dilution mass spectrometry strategies for the characterization of naturally abundant and isotopically labelled peptide standards.

Natural abundance and isotopically labelled tryptic peptides are routinely employed as standards in quantitative proteomics. The certification of the peptide content is usually carried out by amino acid analysis using isotope dilution mass spectrometry (IDMS) after the acid hydrolysis of the peptide. For the validation and traceability of the amino acid analysis procedure, expensive certified peptides must be employed. In this work we evaluate different IDMS alternatives which will reduce the amount of certified peptide required for validation of the amino acid analysis procedure. In this context, the characterization of both natural and isotopically labelled synthetic angiotensin I peptides was carried out. First, we applied a fast procedure for peptide hydrolysis based on microwave-assisted digestion and employed two certified peptide reference materials SRM 998 angiotensin I and CRM 6901-b C-peptide for validation of the hydrolysis procedure. The amino acids proline, leucine, isoleucine, valine, tyrosine, arginine and phenylalanine were evaluated for their suitability for peptide certification by IDMS by both liquid chromatography with tandem mass spectrometry (LC-MS/MS) and gas chromatography with mass spectrometry (GC)-MS/MS. Then, natural angiotensin I and 13C1-labelled angiotensin I were synthesized in-house and purified by preparative liquid chromatography. The concentration of the 13C1-labelled angiotensin I peptide was established by reverse IDMS in its native form using SRM 998 angiotensin I as reference. The concentration of the natural synthesized peptide was determined by IDMS both using the 13C1-labelled peptide in its native form and by amino acid analysis showing comparable results. Finally, the synthetic naturally abundant angiotensin I peptide was employed as "in-house" standard for the validation of subsequent peptide characterization procedures. Therefore, the novelty of this work relies on, first, the development of a faster hydrolysis procedure assisted by focused microwaves, providing complete hydrolysis in 150 min, and secondly, a validation strategy combining GC-MS and LC-MS/MS that allowed us to certify the purity of an in-house-synthesized peptide standard that can be employed as quality control in further experiments.

Targeting PI3K/p-Akt/eNOS, Nrf2/HO-1, and NF-κB/p53 signaling pathways by angiotensin 1-7 protects against liver injury induced by ischemia-reperfusion in rats.

The liver is an important organ, and hepatic ischemia-reperfusion (IR) injury is a frequent pathophysiological process that can cause significant morbidity and mortality. Thus, our study aimed to investigate the effect of targeting PI3K/p-Akt/eNOS (phosphoinositide 3-kinase/phospho-protein kinase B/endothelial nitric oxide synthase), Nrf2/HO-1 (nuclear factor-erythroid 2-related factor-2/heme oxygenase-1), and NF-κB/p53 (nuclear factor-κB/tumor protein 53) signaling pathways by using angiotensin (1-7) [ang-(1-7)] against hepatic injury induced by IR. Thirty-two male rats were included in sham group, ang-(1-7)-treated group, hepatic IR group, and hepatic IR group treated with ang-(1-7). The levels of hepatic ang-(1-7), angiotensin II (Ang II), angiotensin-converting enzyme 2 (ACE2), HO-1, malondialdehyde (MDA), PI3K, and p-Akt were assessed. The expressions of eNOS and B-cell leukemia/lymphoma-2 (BCL-2) in the liver were determined. Histological assessment and immunohistochemical expression of NF-κB, p53, and Nrf2 were carried out. The levels of reduced glutathione (GSH), aspartate aminotransferase (AST), alanine aminotransferase (ALT), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in serum were estimated. Results showed that administration of ang-(1-7) to hepatic IR rats led to significant amelioration of hepatic damage through a histological evaluation that was associated with significant upregulation of the expressions of PI3K/p-Akt/eNOS and Nrf2/HO-1 with downregulation of NF-κB/p53 signaling pathways. In conclusion, PI3K/p-Akt/eNOS and Nrf2/HO-1 signaling pathways are involved in the protective effects of ang-(1-7) against hepatic damage induced by IR. Therefore, ang-(1-7) can be used to prevent hepatic IR, which occurs in certain conditions such as liver transplantation, hemorrhagic shock, and severe infection.

Angiotensin II constricts mouse iliac arteries: possible mechanism for aortic aneurysms.

Abdominal aortic aneurysms (AAA) result from maladaptive remodeling of the vascular wall and reduces structural integrity. Angiotensin II (AngII) infusion has become a standard laboratory model for studying AAA initiation and progression. We determined the different vasoactive responses of various mouse arteries to Ang II. Ex vivo isometric tension analysis was conducted on 18-week-old male C57BL/6 mice (n = 4) brachiocephalic arteries (BC), iliac arteries (IL), and abdominal (AA) and thoracic aorta (TA). Arterial rings were mounted between organ hooks, gently stretched and an AngII dose response was performed. Rings were placed in 4% paraformaldehyde for immunohistochemistry analysis to quantify peptide expression of angiotensin type 1 (AT1R) and 2 receptors (AT2R) in the endothelium, media, and adventitia. Results from this study demonstrated vasoconstriction responses in IL were significantly higher at all AngII doses when compared to BC, and TA and AA responses (maximum constriction-IL: 68.64 ± 5.47% vs. BC: 1.96 ± 1.00%; TA: 3.13 ± 0.16% and AA: 2.75 ± 1.77%, p < 0.0001). Expression of AT1R was highest in the endothelium of IL (p < 0.05) and in the media and (p < 0.05) adventitia (p < 0.05) of AA. In contrast, AT2R expression was highest in endothelium (p < 0.05), media (p < 0.01, p < 0.05) and adventitia of TA. These results suggest that mouse arteries display different vasoactive responses to AngII, and the exaggerated response in IL arteries may play a role during AAA development.

Development and validation of an LC-MS/MS method for the simultaneous quantitation of angiotensin (1-7), (1-8), (1-9) and (1-10) in human plasma.

Cardiovascular diseases have cast a significant negative impact on the lives of millions worldwide. Over the years, extensive efforts have been dedicated to enhancing diagnostic and prognostic tools for these diseases. A growing body of evidence indicates that the angiotensin convertase enzyme (ACE) and the angiotensin convertase enzyme 2 (ACE2), and angiotensin peptide levels could hold a pivotal role in assisting clinicians with the management of cardiovascular conditions, notably hypertension and heart failure. However, despite the considerable body of knowledge in this domain, a void remains in the field of analytical methodologies for these molecules. In this study, we present a fully validated LC-MS/MS method for the precise quantitation of plasma angiotensin (1-7), (1-8), (1-9), and (1-10), following the guidelines set by the Clinical and Laboratory Standards Institute (CLSI). Our method not only enables the accurate quantification of angiotensin peptides but also provides a means to assess ACE and ACE2 activity. Remarkably, our method achieved a Lower Limit of Measurement Interval (LLMI) as low as 5 pg/mL. This has enabled the detection of angiotensin (1-7), (1-8), (1-9) and (1-10) and the accurate quantitation of angiotensin (1-7), (1-8) and (1-10) in all analyzed groups, including healthy controls, patients with high blood pressure, and patients with chronic kidney disease. To our knowledge, our method represents the most sensitive approach allowing for simultaneous quantitation of these four angiotensin peptides. A distinct advantage of our method, when compared to immunoassays, is its high sensitivity combined with comprehensive chromatographic separation of all currently known angiotensin peptides. This combination translates to an exceptional level of selectivity, underscoring the value and potential of our methodology in advancing cardiovascular disease research.

Effects of oral HPΒCD-angiotensin-(1-7) supplementation on recreational mountain bike athletes: a crossover study.

BACKGROUND: Supplementation with Angiotensin-(1-7) [(Ang-1-7)] has received considerable attention due to its possible ergogenic effects on physical performance. The effects of a single dose of Ang-(1-7) on the performance of mountain bike (MTB) athletes during progressive load tests performed until the onset of voluntary fatigue have previously been demonstrated. This study tested the effects of Ang-(1-7) in two different exercise protocols with different metabolic demands: aerobic (time trial) and anaerobic (repeated sprint). METHODS: Twenty one male recreational athletes were given capsules containing an oral formulation of HPßCD-Ang-(1-7) (0.8 mg) and HPßCD-placebo (only HPßCD) over a 7-day interval; a double-blind randomized crossover design was used. Physical performance was examined using two protocols: a 20-km cycling time trial or 4 × 30-s repeated all-out sprints on a leg cycle ergometer. Data were collected before and after physical tests to assess fatigue parameters, and included lactate levels, and muscle activation during the sprint protocol as evaluated by electromyography (EMG); cardiovascular parameters: diastolic and systolic blood pressure and heart rate; and performance parameters, time to complete (time trial), maximum power and mean power (repeated sprint). RESULTS: Supplementation with an oral formulation of HPßCD-Ang-(1-7) reduced basal plasma lactate levels and promoted the maintenance of plasma glucose levels after repeated sprints. Supplementation with HPßCD-Ang-(1-7) also increased baseline plasma nitrite levels and reduced resting diastolic blood pressure in a time trial protocol. HPßCD-Ang-(1-7) had no effect on the time trial or repeat sprint performance, or on the EMG recordings of the vastus lateralis and vastus medialis. CONCLUSIONS: Supplementation with HPßCD-Ang-(1-7) did not improve physical performance in time trial or in repeated sprints; however, it promoted the maintenance of plasma glucose and lactate levels after the sprint protocol and at rest, respectively. In addition, HPßCD-Ang-(1-7) also increased resting plasma nitrite levels and reduced diastolic blood pressure in the time trial protocol. TRIAL REGISTRATION: RBR-2nbmpbc, registered January 6th, 2023. The study was prospectively registered.

Regulation of vascular angiotensin II type 1 and type 2 receptor and angiotensin-(1-7)/MasR signaling in normal and hypertensive pregnancy.

Normal pregnancy (Norm-Preg) is associated with a slight reduction in blood pressure (BP) and decreased BP response to vasoconstrictor stimuli such as angiotensin II (Ang II), although the renin-angiotensin-aldosterone system (RAAS) is upregulated. Preeclampsia (PE) is a complication of pregnancy manifested as hypertension-in-pregnancy (HTN-Preg), and dysregulation of angiotensin biosynthesis and signaling have been implicated. Ang II activates vascular Ang II type-1 receptor (AT1R) and Ang II type-2 receptor (AT2R), while angiotensin-(1-7) promotes Ang-(1-7)/MasR signaling. The role of AT1R in vasoconstriction and the activated cellular mechanisms are well-characterized. The sensitivity of vascular AT1R to Ang II and consequent activation of vasoconstrictor mechanisms decrease during Norm-Preg, but dramatically increase in HTN-Preg. Placental ischemia in late pregnancy could also initiate the release of AT1R agonistic autoantibodies (AT1AA) with significant impact on endothelial dysfunction and activation of contraction pathways in vascular smooth muscle including [Ca2+]c and protein kinase C. On the other hand, the role of AT2R and Ang-(1-7)/MasR in vascular relaxation, particularly during Norm-Preg and PE, is less clear. During Norm-Preg, increases in the expression/activity of vascular AT2R and Ang-(1-7)/MasR promote the production of endothelium-derived relaxing factors such as nitric oxide (NO), prostacyclin and endothelium-derived hyperpolarizing factor leading to generalized vasodilation. Aortic segments of Preg rats show prominent endothelial AT2R staining and increased relaxation and NO production in response to AT2R agonist CGP42112A, and treatment with AT2R antagonist PD123319 enhances phenylephrine-induced contraction. Decreased vascular AT2R and Ang-(1-7)/MasR expression and receptor-mediated mechanisms of vascular relaxation have been suggested in HTN-Preg animal models, but their role in human PE needs further testing. Changes in angiotensin-converting enzyme-2 (ACE2) have been observed in COVID-19 patients, and whether ACE2 influences the course of COVID-19 viral infection/immunity in Norm-Preg and PE is an intriguing area for research.

Angiotensin 1-7 exerts antioxidant effects, suppresses Mammalian Target of Rapamycin (mTOR) signaling, and inhibits apoptosis in renal proximal tubular cells.

Oxidative stress is one of the crucial pathogenic factors involved in the progression of renal injury. Angiotensin (ANG) 1-7, a bioactive heptapeptide of the renin-angiotensin-aldosterone system is known to exert antioxidant and nephroprotective effects. However, the cellular mechanism involved in the beneficial effect of ANG 1-7 is not clear. Here, we assessed ANG 1-7's effect on H2O2-mediated oxidative damage in the human proximal tubular (HK2) cells and the underlying mechanisms. HK2 cells were incubated with H2O2 (500 µM, 4 h) pre-treated with and without ANG 1-7 (100 nM, 24 h), and reactive oxygen species (ROS) generation, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, apoptosis and mammalian target of rapamycin (mTOR) signaling were determined H2O2 induced an increase in oxidative and ER stress together with loss of mitochondrial membrane potential, decreased ATP levels, and induced apoptosis in HK2 cells. Moreover, H2O2 treatment resulted in the activation of mTOR complexes (mTORC1 and mTORC2) in these cells. ANG 1-7 significantly attenuated H2O2-induced ROS generation, ER stress and apoptosis, and also improved mitochondrial function. Additionally, pre-treatment of ANG 1-7 inhibited the H2O2-mediated mTOR activation. These effects of ANG 1-7 were blocked by co-treatment with the Mas receptor (MasR) inhibitor, A779. Furthermore, transfection of HK2 cells with Mas receptor siRNA also abolished the inhibitory effect of ANG 1-7 on mTOR activities. In conclusion, ANG 1-7 via MasR mitigates oxidative stress, suppresses mTOR signaling, and protects HK2 cells from ER stress, mitochondrial dysfunction, and apoptosis, suggesting ANG 1-7-MasR renoprotective effects.

Angiotensin-(1-7) plays an important role in regulating spermatogenesis in Trachemys scripta elegans under salinity stress.

Elevation in water salinity can threaten the spermatogenesis and fertility of freshwater animals. The role of the renin-angiotensin system (RAS) in regulating spermatogenesis has attracted considerable attention. Our previous study found that red-eared sliders (Trachemys scripta elegans), could survive in 10 PSU water for over 1 year. To understand the chronic impact of salinity on testicular spermatogenesis and underlying mechanisms, male T. s. elegans were subjected to treatment with water of 5 PSU and 10 PSU for a year, and spermatogenesis and regulation of the RAS signal pathway was assessed. Results showed induced inflammation in the testes of T. s. elegans in the 10 PSU group, as evidenced by a decrease in the number of testicular germ cells from 1586 to 943. Compared with the control group, the levels of proinflammatory genes, including TNF-α, IL-12A and IL-6 were elevated 3.1, 0.3, and 1.4 times, respectively, in animals exposed to 10 PSU water. Testicular antiapoptotic processes of T. s. elegans might involve the vasoactive peptide angiotensin-(1-7) in the RAS, as its level was significantly increased from 220.2 ng ml-1 in controls to 419.2 ng ml-1 in the 10 PSU group. As expected, specific inhibitor (A-779) for the Ang-(1-7) acceptor effectively prevented the salinity-induced upregulation of genes encoding anti-inflammatory and antiapoptotic factors (TGF-ß1, Bcl-6) in the testis of the 10 PSU animals, whereas it promoted the upregulation of proinflammatory and proapoptotic factors (TNF-α, IL-12A, IL-6, Bax and caspase-3). Our data indicated that Ang-(1-7) attenuates the effect of salinity on inflammation and apoptosis of the testis in T. s. elegans. A new perspective to prevent salinity-induced testis dysfunction is provided.

Chymase-independent vascular Ang-(1-12)/Ang II pathway and TXA2 generation are involved in endothelial dysfunction in the murine model of heart failure.

The angiotensin (Ang)-(1-12)/Ang II pathway contributes to cardiac pathology. However, its involvement in the development of peripheral endothelial dysfunction associated with heart failure (HF) remains unknown. Therefore, this study aimed to characterise the effect of exogenous Ang-(1-12) and its conversion to Ang II on endothelial function using the murine model of HF (Tgαq*44 mice), focusing on the role of chymase and vascular-derived thromboxane A2 (TXA2). Ex vivo myographic assessments of isolated aorta showed impaired endothelium-dependent vasodilation in late-stage HF in 12-month-old Tgαq*44 mice. However, endothelium-dependent vasodilation was fully preserved in the early stage of HF in 4-month-old Tgαq*44 mice and 4- and 12-month-old FVB control mice. Ang-(1-12) impaired endothelium-dependent vasodilation in 4- and 12-month-old Tgαq*44 mice, that was associated with increased Ang II production. The chymase inhibitor chymostatin did not inhibit this response. Interestingly, TXA2 production reflected by TXB2 measurement was upregulated in response to Ang-(1-12) and Ang II in aortic rings isolated from 12-month-old Tgαq*44 mice but not from 4-month-old Tgαq*44 mice or age-matched FVB mice. Furthermore, in vivo magnetic resonance imaging showed that Ang-(1-12) impaired endothelium-dependent vasodilation in the aorta of Tgαq*44 mice and FVB mice. However, this response was inhibited by angiotensin I converting enzyme (ACE) inhibitor; perindopril, angiotensin II receptor type 1 (AT1) antagonist; losartan and TXA2 receptor (TP) antagonist-picotamide in 12-month-old-Tgαq*44 mice only. In conclusion, the chymase-independent vascular Ang-(1-12)/Ang II pathway and subsequent TXA2 overactivity contribute to systemic endothelial dysfunction in the late stage of HF in Tgαq*44 mice. Therefore, the vascular TXA2 receptor represents a pharmacotherapeutic target to improve peripheral endothelial dysfunction in chronic HF.

Angiotensin-Converting Enzyme 2 (ACE2) Signaling in Pulmonary Arterial Hypertension: Underpinning Mechanisms and Potential Targeting Strategies.

Pulmonary arterial hypertension (PAH) is a debilitating progressive disease characterized by excessive pulmonary vasoconstriction and abnormal vascular remodeling processes that lead to right-ventricular heart failure and, ultimately, death. Although our understanding of its pathophysiology has advanced and several treatment modalities are currently available for the management of PAH patients, none are curative and the prognosis remains poor. Therefore, further research is required to decipher the molecular mechanisms associated with PAH. Angiotensin-converting enzyme 2 (ACE2) plays an important role through its vasoprotective functions in cardiopulmonary homeostasis, and accumulating preclinical and clinical evidence shows that the upregulation of the ACE2/Angiotensin-(1-7)/MAS1 proto-oncogene, G protein-coupled receptor (Mas 1 receptor) signaling axis is implicated in the pathophysiology of PAH. Herein, we highlight the molecular mechanisms of ACE2 signaling in PAH and discuss its potential as a therapeutic target.

Genetically engineered Lactobacillus paracasei rescues colonic angiotensin converting enzyme 2 (ACE2) and attenuates hypertension in female Ace2 knock out rats.

Engineered gut microbiota represents a new frontier in medicine, in part serving as a vehicle for the delivery of therapeutic biologics to treat a range of host conditions. The gut microbiota plays a significant role in blood pressure regulation; thus, manipulation of gut microbiota is a promising avenue for hypertension treatment. In this study, we tested the potential of Lactobacillus paracasei, genetically engineered to produce and deliver human angiotensin converting enzyme 2 (Lacto-hACE2), to regulate blood pressure in a rat model of hypertension with genetic ablation of endogenous Ace2 (Ace2-/- and Ace2-/y). Our findings reveal a sex-specific reduction in blood pressure in female (Ace2-/-) but not male (Ace2-/y) rats following colonization with the Lacto-hACE2. This beneficial effect of lowering blood pressure was aligned with a specific reduction in colonic angiotensin II, but not renal angiotensin II, suggesting the importance of colonic Ace2 in the regulation of blood pressure. We conclude that this approach of targeting the colon with engineered bacteria for delivery of ACE2 represents a promising new paradigm in the development of antihypertensive therapeutics.

Atomistic Molecular Insights into Angiotensin-(1-7) Interpeptide Interactions.

Angiotensin-(1-7) is an endogenous peptide known for its vasoprotective, antioxidant, and anti-inflammatory effects, making it a promising therapeutic candidate for various clinical conditions. However, the peptide exhibits pH-dependent physical instability in aqueous solutions, and a comprehensive atomistic study elucidating this behavior and its implications is currently lacking. Therefore, we performed all-atom molecular dynamics simulations to investigate the early formation of angiotensin-(1-7) oligomeric aggregates under different conditions: acidic and neutral pH-like conditions, physiological and high ionic strength, and high and low peptide concentrations. Our results are as follows: (1) under acidic pH-like conditions, angiotensin-(1-7) showed minimal clustering, (2) under neutral pH-like conditions, the peptides aggregated into a single cluster, consistent with the reported physical instability, and (3) increasing salt concentration under acidic pH-like conditions resulted in aggregation similar to that observed under neutral pH-like conditions. These results suggest that a combination of salt concentration and pH conditions can modulate angiotensin-(1-7) aggregation. Our protocol (molecular dynamics + cluster analysis + amino acid interaction map analysis) is general and could be applied to other peptides to study interpeptide interaction mechanisms.

G-protein-coupled receptor MAS deletion produces a preeclampsia-like phenotype in FVB/N mice.

BACKGROUND: An unbalance in the renin-angiotensin (Ang) system (RAS) between the Ang II/AT1 and Ang-(1-7)/Mas axis appears to be involved in preeclampsia (PE), in which a reduction in Ang-(1-7) was observed. Here, we tested whether the reduction in the activity of the Ang-(1-7)/Mas axis could be a contributing factor for the development of PE, using Mas-deficient (Mas-/-) mice. METHODS AND RESULTS: Cardiovascular parameters were evaluated by telemetry before, during pregnancy and 4 days postpartum in 20-week-old Mas-/- and wild-type (WT) female mice. Mas-/- mice presented reduced arterial blood pressure (BP) at baseline (91.3 ± 0.8 in Mas-/- vs. 94.0 ± 0.9 mmHg in WT, Diastolic, P<0.05). However, after the 13th day of gestation, BP in Mas-/- mice started to increase, time-dependently, and at day 19 of pregnancy, these animals presented a higher BP in comparison with WT group (90.5 ± 0.7 in Mas-/- vs. 80.3 ± 3.5 mmHg in WT, Diastolic D19, P<0.0001). Moreover, pregnant Mas-/- mice presented fetal growth restriction, increase in urinary protein excretion as compared with nonpregnant Mas-/-, oliguria, increase in cytokines, endothelial dysfunction and reduced ACE, AT1R, ACE2, ET-1A, and eNOS placental mRNA, similar to some of the clinical manifestations found in the development of PE. CONCLUSIONS: These results show that Mas-deletion produces a PE-like state in FVB/N mice.

Nonatherosclerotic Renovascular Hypertension.

Renovascular hypertension (RVH) is a secondary form of high blood pressure resulting from impaired blood flow to the kidneys with subsequent activation of the renin-angiotensin-aldosterone system. Often, this occurs due to abnormally small, narrowed, or blocked blood vessels supplying one or both kidneys (ie: renal artery occlusive disease) and is correctable. Juxtaglomerular cells release renin in response to decreased pressure, which in turn catalyzes the cleavage of circulating angiotensinogen synthesized by the liver to the decapeptide angiotensin I. Angiotensin-converting enzyme then cleaves angiotensin I to form the octapeptide angiotensin II, a potent vasopressor and the primary effector of renin-induced hypertension. The effects of angiotensin II are mediated by signaling downstream of its receptors. Angiotensin receptor type 1 is a G-protein-coupled receptor that activates vasoconstrictor and mitogenic signaling pathways resulting in peripheral arteriolar vasoconstriction and increased renal tubular reabsorption of sodium and water which promotes intravascular volume expansion. Angiotensin II stimulates the adrenal cortical release of aldosterone, which promotes renal tubular sodium reabsorption, resulting in volume expansion. Angiotensin II acts on glial cells and regions of the brain responsible for blood pressure regulation increasing renal sympathetic activation. Angiotensin II simulates the release of vasopressin from the pituitary which stimulates thirst and water reabsorption from the kidney to expand the intravascular volume and cause peripheral vasoconstriction (increased sympathetic tone). All of these mechanisms coalesce to increase arterial pressure by way of arteriolar constriction, enhanced cardiac output, and the retention of sodium and water.