Analytical Interference in Chemiluminescence Assay-Measured Angiotensin I, Angiotensin II, Aldosterone, and Renin.

BACKGROUND: The interference can be a significant source of laboratory errors with the potential to cause immunoassay results to drift. Therefore, we evaluated the interference in various endogenous and exogenous substances on immunoassay for angiotensin I (Ang I), angiotensin II (Ang II), aldosterone, and renin in vitro. METHODS: Ten endogenous and eight exogenous substances were evaluated at supraphysiologic or supratherapeutic plasma levels using the screening study to identify potential interfering substances. Subsequently, potential interfering substances were further tested within maximum pathological or therapeutic plasma concentration ranges using the dose-response study to determine whether the interference has a significant bias. According to preset acceptance criteria, the interference in potential interfering substances for Ang I, Ang II, and renin and aldosterone assays was determined. RESULTS: Six potential interfering substances for Ang I immunoassays were identified, namely valsartan, nifedipine, spironolactone, cholesterol, hemoglobin, and triglyceride. Meanwhile, ethanol, nifedipine, spironolactone, heparin sodium, warfarin, hemoglobin, uric acid, cholesterol, and triglyceride appeared to have potential interference in the Ang II assay. Three identified as possible interferents for aldosterone immunoassays were glucose, valsartan, and spironolactone. Moreover, warfarin, valsartan, spironolactone, uric acid, cholesterol, bilirubin unconjugated, triglyceride, and hemoglobin were potential interfering substances for renin immunoassays. However, only spironolactone of these potential interfering substances exceeded preset mean bias limits (less than ±10.0%) in aldosterone immunoassays. CONCLUSION: Exogenous spironolactone caused clinically significant interference in aldosterone immunoassays. Moreover, the interference in other substances was acceptable in Ang I, Ang II, and renin and aldosterone immunoassays.

Circulating angiotensin-(1-7) is decreased in patients with isolated nocturnal hypertension.

Isolated nocturnal hypertension (INHT), defined as nighttime elevated blood pressure (BP) with normal daytime BP assessed by ambulatory BP monitoring, is associated with higher cardiovascular morbidity and mortality. We hypothesized that an alteration in the circulating renin-angiotensin system (RAS) contributes to INHT development. We examined circulating levels of angiotensin (Ang) (1-7) and Ang II and ACE2 activity in 26 patients that met the INHT criteria, out of 50 that were referred for BP evaluation (62% women, 45 ±â€Š16 years old). Those with INHT were older, had a higher BMI, lower circulating Ang-(1-7) (P = 0.002) and Ang II levels (P = 0.02) and no change in ACE2 activity compared to those normotensives. Nighttime DBP was significantly correlated with Ang-(1-7) and Ang II levels. Logistic regression showed significant association in Ang-(1-7) and Ang II levels with INHT. Our study reveals differences in circulating RAS in individuals with INHT.

The prognostic importance of the angiotensin II/angiotensin-(1-7) ratio in patients with SARS-CoV-2 infection.

BACKGROUND: Information about angiotensin II (Ang II), angiotensin-converting enzyme 2 (ACE2), and Ang-(1-7) levels in patients with COVID-19 is scarce. OBJECTIVE: To characterize the Ang II-ACE2-Ang-(1-7) axis in patients with SARS-CoV-2 infection to understand its role in pathogenesis and prognosis. METHODS: Patients greater than 18 years diagnosed with COVID-19, based on clinical findings and positive RT-PCR test, who required hospitalization and treatment were included. We compared Ang II, aldosterone, Ang-(1-7), and Ang-(1-9) concentrations and ACE2 concentration and activity between COVID-19 patients and historic controls. We compared baseline demographics, laboratory results (enzyme, peptide, and inflammatory marker levels), and outcome (patients who survived versus those who died). RESULTS: Serum from 74 patients [age: 58 (48-67.2) years; 68% men] with moderate (20%) or severe (80%) COVID-19 were analyzed. During 13 (10-21) days of hospitalization, 25 patients died from COVID-19 and 49 patients survived. Compared with controls, Ang II concentration was higher and Ang-(1-7) concentration was lower, despite significantly higher ACE2 activity in patients. Ang II concentration was higher and Ang-(1-7) concentration was lower in patients who died. The Ang II/Ang-(1-7) ratio was significantly higher in patients who died. In multivariate analysis, Ang II/Ang-(1-7) ratio greater than 3.45 (OR = 5.87) and lymphocyte count ⩽0.65 × 103/µl (OR = 8.43) were independent predictors of mortality from COVID-19. CONCLUSION: In patients with severe SARS-CoV-2 infection, imbalance in the Ang II-ACE2-Ang-(1-7) axis may reflect deleterious effects of Ang II and may indicate a worse outcome.

Dysregulation of ACE (Angiotensin-Converting Enzyme)-2 and Renin-Angiotensin Peptides in SARS-CoV-2 Mediated Mortality and End-Organ Injuries.

ACE (angiotensin-converting enzyme)-2 as the target for SARS-CoV-2 also negatively regulates the renin-angiotensin system. Pathological activation of ADAM17 (A disintegrin and metalloproteinase-17) may potentiate inflammation and diminish ACE2-mediated tissue protection through proteolytic shedding, contributing to SARS-CoV-2 pathogenesis. We aim to examine plasma soluble ACE2 and angiotensin profiles in relation to outcomes by enrolling consecutive patients admitted for COVID-19 with baseline blood collection at admission and repeated sampling at 7 days. The primary outcome was 90-day mortality, and secondary outcomes were the incidence of end-organ injuries. Overall, 242 patients were included, the median age was 63 (52-74) years, 155 (64.0%) were men, and 57 (23.6%) patients reached the primary end point. Baseline soluble ACE2 was elevated in COVID-19 but was not associated with disease severity or mortality. In contrast, an upward trajectory of soluble ACE2 at repeat sampling was independently associated with an elevated risk of mortality and incidence of acute myocardial injury and circulatory shock. Similarly, an increase in soluble tumor necrosis factor receptor levels was also associated with adverse outcomes. Plasma Ang I, Ang 1-7 (angiotensin 1-7) levels, and the Ang 1-7/Ang II (angiotensin II) ratio were elevated during SARS-CoV-2 infection related to downregulation of ACE activity at baseline. Moreover, patients having an upward trajectory of soluble ACE2 were characterized by an imbalance in the Ang 1-7/Ang II ratio. The observed dysregulation of ACE2 and angiotensin peptides with disease progression suggest a potential role of ADAM17 inhibition and enhancing the beneficial Ang 1-7/Mas axis to improve outcomes against SARS-CoV-2 infection.

Angiotensin-(1-7)/Mas receptor modulates anti-inflammatory effects of exercise training in a model of chronic allergic lung inflammation.

AIMS: Exercise training increases circulating and tissue levels of angiotensin-(1-7) [Ang-(1-7)], which was shown to attenuate inflammation and fibrosis in different diseases. Here, we evaluated whether Ang-(1-7)/Mas receptor is involved in the beneficial effects of aerobic training in a chronic model of asthma. MATERIAL AND METHODS: BALB/c mice were subjected to a protocol of asthma induced by ovalbumin sensitization (OVA; 4 i.p. injections) and OVA challenge (3 times/week for 4 weeks). Simultaneously to the challenge period, part of the animals was continuously treated with Mas receptor antagonist (A779, 1 µg/h; for 28 days) and trained in a treadmill (TRE; 60% of the maximal capacity, 1 h/day, 5 days/week during 4 weeks). PGC1-α mRNA expression (qRT-PCR), plasma IgE and lung cytokines (ELISA), inflammatory cells infiltration (enzymatic activity assay) and airway remodeling (by histology) were evaluated. KEY FINDINGS: Blocking the Mas receptor with A779 increased IgE and IL-13 levels and prevented the reduction in extracellular matrix deposition in airways in OVA-TRE mice. Mas receptor blockade prevented the reduction of myeloperoxidase activity, as well as, prevented exercise-induced IL-10 increase. These data show that activation of Ang-(1-7)/Mas receptor pathway is involved in the anti-inflammatory and anti-fibrotic effects of aerobic training in an experimental model of chronic asthma. SIGNIFICANCE: Our results support exercise training as a non-pharmacological tool to defeat lung remodeling induced by chronic pulmonary inflammation. Further, our result also supports development of new therapy based on Ang-(1-7) or Mas agonists as important tool for asthma treatment in those patients that cannot perform aerobic training.

Expression of ACE2, Soluble ACE2, Angiotensin I, Angiotensin II and Angiotensin-(1-7) Is Modulated in COVID-19 Patients.

The etiological agent of COVID-19 SARS-CoV-2, is primarily a pulmonary-tropic coronavirus. Infection of alveolar pneumocytes by SARS-CoV-2 requires virus binding to the angiotensin I converting enzyme 2 (ACE2) monocarboxypeptidase. ACE2, present on the surface of many cell types, is known to be a regulator of blood pressure homeostasis through its ability to catalyze the proteolysis of Angiotensin II (Ang II) into Angiotensin-(1-7) [Ang-(1-7)]. We therefore hypothesized that SARS-CoV-2 could trigger variations of ACE2 expression and Ang II plasma concentration in SARS-CoV-2-infected patients. We report here, that circulating blood cells from COVID-19 patients express less ACE2 mRNA than cells from healthy volunteers. At the level of circulating cells, this ACE2 gene dysregulation mainly affects the monocytes, which also show a lower expression of membrane ACE2 protein. Moreover, soluble ACE2 (sACE2) plasma concentrations are lower in prolonged viral shedders than in healthy controls, while the concentration of sACE2 returns to normal levels in short viral shedders. In the plasma of prolonged viral shedders, we also found higher concentrations of Ang II and angiotensin I (Ang I). On the other hand, the plasma levels of Ang-(1-7) remains almost stable in prolonged viral shedders but seems insufficient to prevent the adverse effects of Ang II accumulation. Altogether, these data evidence that the SARS-CoV-2 may affect the expression of blood pressure regulators with possible harmful consequences on COVID-19 outcome.

A pilot study to assess the circulating renin-angiotensin system in COVID-19 acute respiratory failure.

The renin-angiotensin system (RAS) is fundamental to COVID-19 pathobiology, due to the interaction between the SARS-CoV-2 virus and the angiotensin-converting enzyme 2 (ACE2) coreceptor for cellular entry. The prevailing hypothesis is that SARS-CoV-2-ACE2 interactions lead to an imbalance of the RAS, favoring proinflammatory angiotensin II (ANG II)-related signaling at the expense of the anti-inflammatory ANG-(1-7)-mediated alternative pathway. Indeed, multiple clinical trials targeting this pathway in COVID-19 are underway. Therefore, precise measurement of circulating RAS components is critical to understand the interplay of the RAS on COVID-19 outcomes. Multiple challenges exist in measuring the RAS in COVID-19, including improper patient controls, ex vivo degradation and low concentrations of angiotensins, and unvalidated laboratory assays. Here, we conducted a prospective pilot study to enroll 33 patients with moderate and severe COVID-19 and physiologically matched COVID-19-negative controls to quantify the circulating RAS. Our enrollment strategy led to physiological matching of COVID-19-negative and COVID-19-positive moderate hypoxic respiratory failure cohorts, in contrast to the severe COVID-19 cohort, which had increased severity of illness, prolonged intensive care unit (ICU) stay, and increased mortality. Circulating ANG II and ANG-(1-7) levels were measured in the low picomolar (pM) range. We found no significant differences in circulating RAS peptides or peptidases between these three cohorts. The combined moderate and severe COVID-19-positive cohorts demonstrated a mild reduction in ACE activity compared with COVID-19-negative controls (2.2 ± 0.9 × 105 vs. 2.9 ± 0.8 × 105 RFU/mL, P = 0.03). These methods may be useful in designing larger studies to physiologically match patients and quantify the RAS in COVID-19 RAS augmenting clinical trials.

Improved pharmacokinetics and bone tissue accumulation of Angiotensin-(1-7) peptide through bisphosphonate conjugation.

The renin-angiotensin system (RAS) has a central role in renal and cardiovascular homeostasis. Angiotensin-(1-7) (Ang1-7), one of the RAS active peptides, exerts beneficial effects through different mechanisms. These biological actions suggest that Ang1-7 is an effective therapeutic agent for treating various diseases associated with activated RAS. However, its short half-life and poor pharmacokinetics restrict its therapeutic utility. Our laboratory has successfully synthesized and characterized an Ang1-7 conjugate (Ang Conj.) with a prolonged half-life and improved pharmacokinetics profile. The Ang Conj. has been prepared by PEGylation of Ang1-7 and conjugation with a bisphosphonate using solid-phase peptide synthesis and characterized by HPLC and mass spectrometer. The compound's stability has been tested in different storage conditions. The bone binding capacity was evaluated using a hydroxyapatite assay. Pharmacokinetic and tissue distribution studies were performed using iodinated peptides in rats. Ang Conj. was synthesized with > 90% purity. Bone mineral affinity testing showed Ang Conj. exhibited significantly higher bone mineral affinity than Ang1-7. The Ang Conj. remained stable for more than a month using all tested storage conditions. The Ang Conj. demonstrated higher affinity to bone, a longer half-life, and better bioavailability when compared with the native peptide. These results support that conjugation of Ang1-7 with bisphosphonate enables it to utilize bone as a reservoir for the sustained delivery of Ang1-7 to maintain therapeutic plasma levels. High chemical stability and about five to tenfold prolongation of Ang Conj. plasma half-life after administrations into rats proves the effectiveness of our approach.

Myocardial Angiotensin Metabolism in End-Stage Heart Failure.

BACKGROUND: The myocardium exhibits an adaptive tissue-specific renin-angiotensin system (RAS), and local dysbalance may circumvent the desired effects of pharmacologic RAS inhibition, a mainstay of heart failure with reduced ejection fraction (HFrEF) therapy. OBJECTIVES: This study sought to investigate human myocardial tissue RAS regulation of the failing heart in the light of current therapy. METHODS: Fifty-two end-stage HFrEF patients undergoing heart transplantation (no RAS inhibitor: n = 9; angiotensin-converting enzyme [ACE] inhibitor: n = 28; angiotensin receptor blocker [ARB]: n = 8; angiotensin receptor neprilysin-inhibitor [ARNi]: n = 7) were enrolled. Myocardial angiotensin metabolites and enzymatic activities involved in the metabolism of the key angiotensin peptides angiotensin 1-8 (AngII) and Ang1-7 were determined in left ventricular samples by mass spectrometry. Circulating angiotensin concentrations were assessed for a subgroup of patients. RESULTS: AngII and Ang2-8 (AngIII) were the dominant peptides in the failing heart, while other metabolites, especially Ang1-7, were below the detection limit. Patients receiving an ARB component (i.e., ARB or ARNi) had significantly higher levels of cardiac AngII and AngIII (AngII: 242 [interquartile range (IQR): 145.7 to 409.9] fmol/g vs 63.0 [IQR: 19.9 to 124.1] fmol/g; p < 0.001; and AngIII: 87.4 [IQR: 46.5 to 165.3] fmol/g vs 23.0 [IQR: <5.0 to 59.3] fmol/g; p = 0.002). Myocardial AngII concentrations were strongly related to circulating AngII levels. Myocardial RAS enzyme regulation was independent from the class of RAS inhibitor used, particularly, a comparable myocardial neprilysin activity was observed for patients with or without ARNi. Tissue chymase, but not ACE, is the main enzyme for cardiac AngII generation, whereas AngII is metabolized to Ang1-7 by prolyl carboxypeptidase but not to ACE2. There was no trace of cardiac ACE2 activity. CONCLUSIONS: The failing heart contains considerable levels of classical RAS metabolites, whereas AngIII might be an unrecognized mediator of detrimental effects on cardiovascular structure. The results underline the importance of pharmacologic interventions reducing circulating AngII actions, yet offer room for cardiac tissue-specific RAS drugs aiming to limit myocardial AngII/AngIII peptide accumulation and actions.

Amplifying effect of chronic lisinopril therapy on diastolic function and the angiotensin-(1-7) Axis by the G1 agonist in ovariectomized spontaneously hypertensive rats.

G protein-coupled estrogen receptor (GPER) activation by G1 attenuates diastolic dysfunction from estrogen loss, which may be partly due to suppression of angiotensin II pathological actions. We aimed to determine the independent effects of 8 weeks of G1 (100 µg/kg/d, subcutaneous pellet), ACE-inhibition (ACEi; lisinopril 10 mg/kg, drinking water), or combination therapy versus vehicle in the ovariectomized (OVX) spontaneously hypertensive rat (SHR) on cardiac function and morphometrics (echocardiography), serum equilibrium of angiotensins (mass spectroscopy) and cardiac components of the RAS (Western blotting). G1 alone and when combined with ACEi enhanced myocardial relaxation (é: 30 and 17%) and diastolic wall strain (DWS: 76 and 68%) while reducing relative wall thickness (RWT: 20 and 33%) and filling pressures (E/é: 30 and 37%). Cardiac expression levels of Mas receptor (Mas-R) and ACE2 also increased in the presence of G1. Strong antihypertensive effects of lisinopril monotherapy were associated with reductions in RWT, collagen deposition and E/é without overtly altering é or DWS. Chronic ACEi also increased cardiac levels of Mas-R and AT1-R and tilted the circulating RAS toward the formation of Ang-(1-7), which was amplified in the presence of G1. In vitro studies further revealed that an inhibitor to prolyl endopeptidase (PEP), but not to neprilysin, significantly reduced serum Ang-(1-7) levels in G1-treated rats, suggesting that G1 might be increasing Ang-(1-7) formation via PEP. We conclude that activating GPER with G1 augments components of the cardiac RAS and improves diastolic function without lowering blood pressure, and that lisinopril-induced blood pressure control and cardiac alterations in OVX SHR are permissive in facilitating G1 to augment Ang-(1-7) in serum, thereby strengthening its cardioprotective benefits.

Renin-angiotensin-aldosterone system peptide profiles in patients with COVID-19.

OBJECTIVE: While evidence on the interface between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and the renin-angiotensin-aldosterone-system (RAAS) is accumulating, clinical data on RAAS peptide alteration among coronavirus disease-19 (COVID-19) patients is missing. DESIGN AND METHODS: In this exploratory study, we prospectively included adult patients (aged ≥ 18 years) admitted between February 26 and April 30, 2020 to a tertiary care hospital in Switzerland. We assessed the association of an underlying SARS-CoV-2 infection and equilibrium serum levels of RAAS peptides in hospitalized COVID-19 patients 1:1 propensity-score matched with patients suffering from SARS-CoV-2-negative respiratory infections. Subgroup analyses involved stratification for taking RAAS inhibitors. RESULTS: COVID-19 patients had about 50% lower equilibrium serum RAAS peptide levels as compared with matched controls (angiotensin I: 31.6 vs 66.8 pmol/L, -52.7% (95%CI: -68.5% to -36.9%); angiotensin II: 37.7 vs 92.5 pmol/L, -59.2% (95%CI: -72.1% to -46.3%); angiotensin (1-5): 3.3 vs 6.6 pmol/L, -49.7% (95%CI: -59.2% to -40.2%); angiotensin (1-7): 4.8 vs 7.6 pmol/L, -64.9% (95%CI: -84.5% to -45.3%)). While the plasma renin activity was lower in COVID-19 patients (88.6 vs 207.9 pmol/L, -58.5% (95%CI: -71.4% to -45.6%)), there was no difference of angiotensin-converting enzyme (ACE) and ACE2 plasma activity between the groups. Subgroup analyses revealed a pronounced RAAS peptide profile depression in COVID-19 patients among those not on RAAS inhibitors. CONCLUSIONS: As compared with SARS-CoV-2-negative patients, we found a downregulated RAAS in presence of a SARS-CoV-2 infection. Whether the lower levels of the protective angiotensin (1-5) and (1-7) are linked to adverse outcomes in COVID-19 warrants further investigation.

The renin-angiotensin-system and left ventricular mass in young adults: the African-PREDICT study.

PURPOSE: Raised blood pressure, with the renin-angiotensin system (RAS) as a central regulatory component, is one of the most important contributors to early development of left ventricular hypertrophy. Factors such as increased age, sex, black ethnicity and a low socio-economic status also contribute to left ventricular remodelling. To better understand early contributors to left ventricular mass, we investigated the relationship between left ventricular mass index (LVMi) and the components of the RAS in young healthy adults while considering ethnicity, sex and socio-economic status. MATERIALS AND METHODS: Black and white women and men (N = 1186) between the ages of 20-30 years were included. By using standard echocardiography, we determined LVMi. Ultra-pressure-liquid chromatography tandem-mass spectrometry (LC-MS/MS) was used to measure the RAS-fingerprint®. RESULTS: Components of the RAS such as plasma renin activity (PRA-S), angiotensin I (Ang I), angiotensin II (Ang II) and aldosterone were suppressed in the black compared to the white group (all p < 0.001). No associations between LVMi and the RAS were evident in the total, black or white groups. With additional grouping according to sex and socio-economic status, inverse associations between LVMi and PRA-S (ß= -0.168;  p = 0.017), Ang I (ß= -0.155; p = 0.028) and Ang II (ß= -0.172; p = 0.015) were found only in low socio-economic black women. CONCLUSION: Despite a suppressed RAS in the black compared to the white group, components of the RAS were not associated with LVMi in this young cohort. The low socio-economic black women of this study population may be vulnerable to future RAS-related increases in left ventricular mass.

Stable Plasma Sample Storage in Acetonitrile for Angiotensin and Aldosterone Analysis.

BACKGROUND: Angiotensin I, II (AI, AII) and aldosterone are unstable in plasma specimens at room temperature, making it difficult for collect samples for remote regions in centralized and collaborative studies. Here we introduce a stable storage method which do not require cold conditions.. METHODS: Acetonitrile was added to the plasma to 60%, and then the supernatants were kept at 4°C and room temperature for 0, 1, 2, 3, 10 and 30 days. AI, AII and aldosterone were extracted and analyzed by chemiluminescence immunoassays. RESULTS: AI, AII and aldosterone were well retained in the supernatant under this method. The intra- and inter-day CVs of this method were all below 10%. The levels of AI, AII and aldosterone by this method remained stable for 30 days at room temperature. CONCLUSION: Addition of 60% acetonitrile in the plasma provides a stable storage method for clinical AI, AII and aldosterone.

Altered Serum Levels of Renin-Angiotensin System Markers in Migraine.

OBJECTIVE: To compare the serum levels of renin-angiotensin system (RAS) components between patients with migraine and healthy controls, and to evaluate whether these levels are associated with migraine severity. We hypothesized that migraine would be associated with the activation of the inflammatory arm of the RAS, possibly leading to increased levels of angiotensin (Ang) II. BACKGROUND: Recent studies have proposed the use of drugs that interfere with RAS, a hormonal system primarily implicated in blood pressure regulation, as a prophylactic strategy for migraine. However, no previous studies have directly assessed RAS components in migraine. METHODS: This was a cross-sectional study involving 30 patients with episodic migraine who were in the interictal period and 20 healthy controls. This study was conducted at Hospital das Clínicas (Universidade Federal de Minas Gerais, Belo Horizonte, Brazil) outpatient clinic. Headache severity was evaluated using the Headache Impact Test, version 6 (HIT-6) and the Migraine Disability Test (MIDAS) questionnaires. Given that migraine is comorbid with mood disorders, depressive and anxious symptoms were evaluated using the Beck Anxiety and Depression Inventories (BDI and BAI), respectively. Clinical and demographic data were also collected. Serum levels of angiotensin-converting enzyme (ACE), ACE2, Ang II, and Ang (1-7) were measured by enzyme-linked immunosorbent assay. RESULTS: Patients with migraine and controls were comparable in age, body mass index, blood pressure, and depressive and anxious symptoms. Patients with migraine showed lower levels of ACE [85.2 (66.8, 101.2) vs 65.5 (54.2, 77.5); P = .005] and lower ACE/ACE2 ratio [4.3 (3.4, 5.2) vs 3.5 (2.9, 4.1); P = .032] than controls. Conversely, patients with migraine had higher levels of Ang II [309.7 ± 147.4 vs 605.4 ± 200.4; difference: -287.1 (95% CI: -391.4--182.8), P < .001] and Ang (1-7) [214.4 ± 155.8 vs 397.9 ± 217.9; difference: -184.6 (95% CI: -296.7--72.6), P = .001] than controls. There were no correlations between RAS serum markers and migraine severity scores (HIT and MIDAS) or depressive and anxious symptoms (BDI and BAI) (P > .05). CONCLUSIONS: Altogether, our results suggest the participation of RAS in migraine pathophysiology, but not in its severity.

Ambient fine particulate matter induced the elevation of blood pressure through ACE2/Ang(1-7) pathway: The evidence from urine metabolites.

BACKGROUND: Exposure to ambient fine particulate matter (PM2.5) is associated with various adverse health outcomes. Although several mechanisms have been proposed including oxidative stress and inflammatory responses, the exact mechanism is still unknown. Few studies have investigated the mechanism linking PM2.5 and blood pressure (BP). In this study, we measured urinary metabolites and BP -related renin-angiotensin-aldosterone system (RAAS) to investigate the associations between ambient PM2.5 exposure and BP in healthy C57BL/6 mice. METHODS: The C57BL/6 mice were exposed to ambient concentrated PM2.5 or filtered air (FA) for 16 weeks. Systolic BP and diastolic BP were measured by noninvasive BP system. The urine metabolites were quantified using the untargeted metabolomics approach. The expression of RAAS-related proteins angiotensin-converting enzyme (ACE)2, angiotensin (Ang) II, Ang (1-7) and aldosterone (ALD) were measured using Western blot and ELISA kits. RESULTS: The metabolomics analysis demonstrated that PM2.5 exposure induced significant changes of some metabolites in urine, including stress hormones, amino acids, fatty acids, and lipids. Furthermore, there was an elevation of BP, increase of serous Ang II and ALD, along with the decrease of ACE2 and Ang (1-7) in kidney in the PM2.5-exposed mice compared with FA-exposed mice. CONCLUSIONS: The results demonstrated that PM2.5 exposure-induced BP elevation might be associated with RAAS activation. Meanwhile, PM2.5 exposure-induced changes of stress hormone and lipid metabolism might mediate the activation of RAAS. The results suggested that the systemic stress hormone and lipid metabolism was associated with the development of hypertension.

Alteration and association between serum ACE2/ angiotensin(1-7)/Mas axis and oxidative stress in chronic kidney disease: A pilot study.

Activation of the renin angiotensin system and renal oxidative stress (OS) are critical contributors in the progression of chronic kidney disease(CKD). Recent studies have confirmed that the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas(ACE2/Ang(1-7)/Mas) axis, the important components of renin angiotensin system, protected kidneys against damage by antagonizing angiotensin II and attenuating OS in rats with several nephropathy models, but its effect needs to be further evaluated in clinic. In this study, we aimed to detected serum ACE2/Ang (1-7)/Mas axis, OS conditions and described its clinical associations in patients with CKD at different stages.A total of 48 patients with CKD and 6 healthy controls (CT) were enrolled, and serum angiotensin converting enzyme (ACE), ACE2, Ang (1-7), 8-hydroxy-2'-deoxyguanosine (8-OHdG) were determined by ELISA. Serum extracellular glutathione peroxidase(eGSH-Px) activity and renal functions were determined by the biochemical method.Serum ACE and ACE2 levels in CKD stages 3 to 5 and serum Ang(1-7) levels in CKD stages 4 to 5 without Ang II receptor blockers treatment significantly increased compared to those in the CT group. However, ACE2 was decreased and Ang(1-7) level increased in early CKD stage with Ang II receptor blockers treatment. Higher serum 8-OHdG levels and lower eGSH-Px activity were noted in CKD stages 4 to 5. Serum 8-OHdG level was correlated with serum ACE2, Ang(1-7) expression. Estimated glomerular filtration rate (eGFR) was correlated with serum ACE, ACE2, Ang(1-7), 8-OHdG, Hcy levels and serum eGSH-Px activity. Multiple-regression analysis eGFR was predicted by ACE, Hcy, eGSH-Px, and also can be predicted by ACE2, Ang(1-7), Hcy in CT subgroup.The ACE2/Ang(1-7)/Mas axis is associated with OS, and both them were associated with eGFR in the progression of CKD. Activation of ACE2/Ang(1-7)/Mas axis may have renoprotective effect and can be a potential therapeutic target in patients with early CKD stages.

Improvement in Angiotensin 1-7 precedes and correlates with improvement in Arterial stiffness and endothelial function following Renin-Angiotensin system inhibition in type 2 diabetes with newly diagnosed hypertension.

BACKGROUND AND AIM: Studies in cell cultures and animal models have revealed the possible pathophysiological factors associated with vascular endothelial dysfunction. However, the same in human subjects has not been clearly established. The current study uses a novel approach to identify the factors associated with endothelial function and arterial function by altering these vascular parameters using Angiotensin-Converting-Enzyme (ACE) inhibition. METHODS: Diabetic patients with newly diagnosed hypertension (n = 60) were recruited for the study. Flow-mediated-dilation (FMD), carotid-femoral (cf), carotid-radial (cr) Pulse-wave-velocity (PWV), Augmentation-Index, Carotid-Intima-Media-Thickness (CIMT), serum levels of Renin, Angiotensin II (AngII), Angiotensin-Converting-Enzyme2 (ACE2), Angiotensin1-7 (Ang1-7), E-selectin, Vascular-Cell-Adhesion-Molecule-1 (VCAM-1), Highly-sensitive-C-Reactive-Protein (hsCRP) and Interleukin-10 were measured at baseline (V1), after 1 week (V2) and 3 months (V3) of ACE inhibition in patients of diabetes with newly diagnosed hypertension. The amplitude of change after 1 week (V2-V1) and 3 months (V3-V1) for the clinical and various parameters were correlated with the change in endothelial function and arterial stiffness. RESULTS: Carotid radial-PWVV2-V1 (p = 0.001) and Ang1-7V2-V1 (p = 0.01) emerged as independent predictors of FMDV2-V1. ReninV2-V1 and VCAM-1V2-V1 independently predicted E-selectinV2-V1 [(p = 0.01) and (p = 0.001), respectively]. ACE 2V2-V1 was the only independent predictor of cf-PWVV2-V1. The same parameters remained as independent predictors of the respective vascular factors after 3 months of ACE inhibition. CONCLUSION: The study highlights the role of AngII/Ang1-7 balance in alteration of endothelial function and central arterial stiffness in humans in addition to identifying the interrelationship between the renin-angiotensin-aldosterone-system components and clinically ascertainable parameters.