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Nicotine Downregulates the Compensatory Angiotensin-Converting Enzyme 2/Angiotensin Type 2 Receptor of the Renin–Angiotensin System

ABSTRACT: Rationale: Smoking is a major risk factor for the development of cardiovascular and pulmonary diseases. The importance of the renin–angiotensin system in the development of cardiovascular and pulmonary disease is well established. Angiotensin-II, by means of its type 1 receptor (angiotensin type 1 receptor, AT1R), promotes increased sympathetic activity, salt and water reabsorption, vasoconstriction, inflammation, and aldosterone and vasopressin release, contributing to tissue fibrosis, endothelium dysfunction, and hypertension. Angiotensin-converting enzyme 2 cleaves angiotensin-II into the vasodilator peptide, angiotensin-(1–7), hence playing a pivotal role in the angiotensin-converting enzyme 2/angiotensin-(1–7) compensatory axis of the renin–angiotensin system. Angiotensin type 2 receptor (AT2R), another receptor for angiotensin-II, opposes the deleterious effects of AT1R activation, and angiotensin-converting enzyme 2–formed angiotensin-(1–7) has been shown to activate AT2R. Objectives: The goal of the present study was to examine how nicotine, the addictive component of cigarette smoke, alters the homeostasis of the renin–angiotensin system. Methods: Quantitative real-time polymerase chain reaction was performed to examine the expression of the components of the renin–angiotensin system after cigarette smoke exposure or direct nicotine inhalation. Radio telemetry was used for continuous blood pressure recording in conscious, unrestrained mice. Results: Our study showed that cigarette smoke or direct nicotine inhalation inhibits the expression of angiotensin-converting enzyme 2/AT2R in multiple organs and cell types. In the lung, cigarette smoke (6 cigarettes/d, 12 wk) inhibited the expression of both angiotensin-converting enzyme 2 and AT2R. In cardiac fibroblasts, nicotine exposure resulted in near complete suppression of angiotensin-converting enzyme 2 and AT2R. In the brain, nicotine vapor inhalation inhibited angiotensin-converting enzyme 2 expression in the hypothalamus, a region involved in central regulation of cardiopulmonary function. In addition, cultured Neuro2A cells exposed to nicotine showed a dose-dependent reduction of enzymatic activity of angiotensin-converting enzyme 2. Functionally, mice exposed to nicotine vapor (12 h/d, 4 wk) exhibited significantly increased mean arterial blood pressure, which was more pronounced during the night active cycle (mean?±?SE, 124?±?0.6 mm Hg in nicotine vapor–exposed mice vs. 107?±?0.4 mm Hg in air control mice; P

SUBMITTER: Yue X

PROVIDER: S-EPMC5955030 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Project description:ACE2 (angiotensin-converting enzyme 2) has a multiplicity of physiological roles that revolve around its trivalent function: a negative regulator of the renin-angiotensin system, facilitator of amino acid transport, and the severe acute respiratory syndrome-coronavirus (SARS-CoV) and SARS-CoV-2 receptor. ACE2 is widely expressed, including, in the lungs, cardiovascular system, gut, kidneys, central nervous system, and adipose tissue. ACE2 has recently been identified as the SARS-CoV-2 receptor, the infective agent responsible for coronavirus disease 2019, providing a critical link between immunity, inflammation, ACE2, and cardiovascular disease. Although sharing a close evolutionary relationship with SARS-CoV, the receptor-binding domain of SARS-CoV-2 differs in several key amino acid residues, allowing for stronger binding affinity with the human ACE2 receptor, which may account for the greater pathogenicity of SARS-CoV-2. The loss of ACE2 function following binding by SARS-CoV-2 is driven by endocytosis and activation of proteolytic cleavage and processing. The ACE2 system is a critical protective pathway against heart failure with reduced and preserved ejection fraction including, myocardial infarction and hypertension, and against lung disease and diabetes mellitus. The control of gut dysbiosis and vascular permeability by ACE2 has emerged as an essential mechanism of pulmonary hypertension and diabetic cardiovascular complications. Recombinant ACE2, gene-delivery of Ace2, Ang 1-7 analogs, and Mas receptor agonists enhance ACE2 action and serve as potential therapies for disease conditions associated with an activated renin-angiotensin system. rhACE2 (recombinant human ACE2) has completed clinical trials and efficiently lowered or increased plasma angiotensin II and angiotensin 1-7 levels, respectively. Our review summarizes the progress over the past 20 years, highlighting the critical role of ACE2 as the novel SARS-CoV-2 receptor and as the negative regulator of the renin-angiotensin system, together with implications for the coronavirus disease 2019 pandemic and associated cardiovascular diseases.

Project description:BackgroundRenin inhibitors (RIs) reduce blood pressure more than placebo, with the magnitude of this effect thought to be similar to that for angiotensin converting enzyme (ACE) inhibitors. However, a drug's efficacy in lowering blood pressure cannot be considered as a definitive indicator of its effectiveness in reducing mortality and morbidity. The effectiveness and safety of RIs compared to ACE inhibitors in treating hypertension is unknown.ObjectivesTo evaluate the benefits and harms of renin inhibitors compared to ACE inhibitors in people with primary hypertension.Search methodsThe Cochrane Hypertension Group Information Specialist searched the following databases for randomized controlled trials up to August 2020: the Cochrane Hypertension Specialized Register, the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (from 1946), Embase (from 1974), the World Health Organization International Clinical Trials Registry Platform, and ClinicalTrials.gov. We also contacted authors of relevant papers about further published and unpublished work. The searches had no language restrictions.Selection criteriaWe included randomized, active-controlled, double-blinded studies (RCTs) with at least four weeks follow-up in people with primary hypertension, which compared renin inhibitors with ACE inhibitors and reported morbidity, mortality, adverse events or blood pressure outcomes. We excluded people with proven secondary hypertension.Data collection and analysisTwo review authors independently selected the included trials, evaluated the risks of bias and entered the data for analysis.Main resultsWe include 11 RCTs involving 13,627 participants, with a mean baseline age from 51.5 to 74.2 years. Follow-up duration ranged from four weeks to 36.6 months. There was no difference between RIs and ACE inhibitors for the outcomes: all-cause mortality: risk ratio (RR) 1.05, 95% confidence interval (CI) 0.93 to 1.18; 5 RCTs, 5962 participants; low-certainty evidence; total myocardial infarction: RR 0.86, 95% CI 0.22 to 3.39; 2 RCTs, 957 participants; very low-certainty evidence; adverse events: RR 0.98, 95% CI 0.93 to 1.03; 10 RTCs, 6007 participants; moderate-certainty evidence; serious adverse events: RR 1.21, 95% CI 0.89 to 1.64; 10 RTCs, 6007 participants; low-certainty evidence; and withdrawal due to adverse effects: RR 0.85, 95% CI 0.68 to 1.06; 10 RTCs, 6008 participants; low-certainty evidence. No data were available for total cardiovascular events, heart failure, stroke, end-stage renal disease or change in heart rate. Low-certainty evidence suggested that RIs reduced systolic blood pressure: mean difference (MD) -1.72, 95% CI -2.47 to -0.97; 9 RCTs, 5001 participants; and diastolic blood pressure: MD -1.18, 95% CI -1.65 to -0.72; 9 RCTs, 5001 participants, to a greater extent than ACE inhibitors, but we judged this to be more likely due to bias than a true effect. AUTHORS' CONCLUSIONS: For the treatment of hypertension, we have low certainty that renin inhibitors (RI) and angiotensin converting enzyme (ACE) inhibitors do not differ for all-cause mortality and myocardial infarction. We have low to moderate certainty that they do not differ for adverse events. Small reductions in blood pressure with renin inhibitors compared to ACE inhibitors are of low certainty. More independent, large, long-term trials are needed to compare RIs with ACE inhibitors, particularly assessing morbidity and mortality outcomes, but also on blood pressure-lowering effect.

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Nicotine Downregulates the Compensatory Angiotensin-Converting Enzyme 2/Angiotensin Type 2 Receptor of the Renin–Angiotensin System

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