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Physiology (Bethesda, Md.) Jul 2013Stimulating antibodies against G-protein-coupled receptors, including the β1- and β2-adrenergic receptors, the α1-adrenergic receptor, and the angiotensin II AT1... (Review)
Review
Stimulating antibodies against G-protein-coupled receptors, including the β1- and β2-adrenergic receptors, the α1-adrenergic receptor, and the angiotensin II AT1 receptor, have been described, as well as activating antibodies directed at the platelet-derived growth factor receptor tyrosine kinase. Their existence and actions appear to be established. Lacking are mechanistic studies of receptor activation and translational studies to document receptor-stimulating antibodies as worthwhile therapeutic targets.
Topics: Amino Acid Sequence; Autoantibodies; Cardiovascular Diseases; Humans; Molecular Sequence Data; Receptor, Angiotensin, Type 1; Receptors, Adrenergic, beta; Translational Research, Biomedical
PubMed: 23817800
DOI: 10.1152/physiol.00014.2013 -
Theoretical Biology & Medical Modelling Jan 2006There have been indications that common Angiotensin Receptor Blockers (ARBs) may be exerting anti-inflammatory actions by directly modulating the immune system. We...
BACKGROUND
There have been indications that common Angiotensin Receptor Blockers (ARBs) may be exerting anti-inflammatory actions by directly modulating the immune system. We decided to use molecular modelling to rapidly assess which of the potential targets might justify the expense of detailed laboratory validation. We first studied the VDR nuclear receptor, which is activated by the secosteroid hormone 1,25-dihydroxyvitamin-D. This receptor mediates the expression of regulators as ubiquitous as GnRH (Gonadatrophin hormone releasing hormone) and the Parathyroid Hormone (PTH). Additionally we examined Peroxisome Proliferator-Activated Receptor Gamma (PPARgamma), which affects the function of phagocytic cells, and the C-CChemokine Receptor, type 2b, (CCR2b), which recruits monocytes to the site of inflammatory immune challenge.
RESULTS
Telmisartan was predicted to strongly antagonize (Ki asymptotically equal to 0.04 nmol) the VDR. The ARBs Olmesartan, Irbesartan and Valsartan (Ki asymptotically equal to10 nmol) are likely to be useful VDR antagonists at typical in-vivo concentrations. Candesartan (Ki asymptotically equal to 30 nmol) and Losartan (Ki asymptotically equal to 70 nmol) may also usefully inhibit the VDR. Telmisartan is a strong modulator of PPARgamma (Ki asymptotically equal to 0.3 nmol), while Losartan (Ki asymptotically equal to 3 nmol), Irbesartan (Ki asymptotically equal to 6 nmol), Olmesartan and Valsartan (Ki asymptotically equal to 12 nmol) also seem likely to have significant PPAR modulatory activity. Olmesartan and Irbesartan (Ki asymptotically equal to 9 nmol) additionally act as antagonists of a theoretical model of CCR2b. Initial validation of this CCR2b model was performed, and a proposed model for the Angiotensin II Type1 receptor (AT2R1) has been presented.
CONCLUSION
Molecular modeling has proven valuable to generate testable hypotheses concerning receptor/ligand binding and is an important tool in drug design. ARBs were designed to act as antagonists for AT2R1, and it was not surprising to discover their affinity for the structurally similar CCR2b. However, this study also found evidence that ARBs modulate the activation of two key nuclear receptors-VDR and PPARgamma. If our simulations are confirmed by experiment, it is possible that ARBs may become useful as potent anti-inflammatory agents, in addition to their current indication as cardiovascular drugs.
Topics: Amino Acid Sequence; Angiotensin II Type 1 Receptor Blockers; Angiotensin Receptor Antagonists; Binding Sites; Computer Simulation; Dose-Response Relationship, Drug; Gene Expression Regulation; Models, Molecular; PPAR gamma; Protein Binding; Protein Conformation; Receptors, Angiotensin; Receptors, CCR2; Receptors, Calcitriol; Receptors, Chemokine
PubMed: 16403216
DOI: 10.1186/1742-4682-3-1 -
Current Hypertension Reports Feb 2017Drugs targeting the renin-angiotensin system (RAS), namely angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are the most commonly... (Review)
Review
PURPOSE OF THE REVIEW
Drugs targeting the renin-angiotensin system (RAS), namely angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers, are the most commonly prescribed drugs for patients with or at risk for cardiovascular events. However, new treatment strategies aimed at mitigating the rise of the heart failure pandemic are warranted because clinical trials show that RAS blockers have limited benefits in halting disease progression. The main goal of this review is to put forward the concept of an intracrine RAS signaling through the novel angiotensin-(1-12)/chymase axis as the main source of deleterious angiotensin II (Ang II) in cardiac maladaptive remodeling leading to heart failure (HF).
RECENT FINDINGS
Expanding traditional knowledge, Ang II can be produced in tissues independently from the circulatory renin-angiotensin system. In the heart, angiotensin-(1-12) [Ang-(1-12)], a recently discovered derivative of angiotensinogen, is a precursor of Ang II, and chymase rather than ACE is the main enzyme contributing to the direct production of Ang II from Ang-(1-12). The Ang-(1-12)/chymase axis is an independent intracrine pathway accounting for the trophic, contractile, and pro-arrhythmic Ang II actions in the human heart. Ang-(1-12) expression and chymase activity have been found elevated in the left atrial appendage of heart disease subjects, suggesting a pivotal role of this axis in the progression of HF. Recent meta-analysis of large clinical trials on the use of ACE inhibitors and angiotensin receptor blockers in cardiovascular disease has demonstrated an imbalance between patients that significantly benefit from these therapeutic agents and those that remain at risk for heart disease progression. Looking to find an explanation, detailed investigation on the RAS has unveiled a previously unrecognized complexity of substrates and enzymes in tissues ultimately associated with the production of Ang II that may explain the shortcomings of ACE inhibition and angiotensin receptor blockade. Discovery of the Ang-(1-12)/chymase axis in human hearts, capable of producing Ang II independently from the circulatory RAS, has led to the notion that a tissue-delimited RAS signaling in an intracrine fashion may account for the deleterious effects of Ang II in the heart, contributing to the transition from maladaptive cardiac remodeling to heart failure. Targeting intracellular RAS signaling may improve current therapies aimed at reducing the burden of heart failure.
Topics: Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Angiotensinogen; Animals; Chymases; Heart Failure; Humans; Hypertension; Peptide Fragments; Receptors, Angiotensin; Renin-Angiotensin System
PubMed: 28233239
DOI: 10.1007/s11906-017-0708-3 -
Neurochemistry International Sep 2022We and others have previously shown that angiotensin II receptor type 2 receptor (AT2R) is upregulated in the contralesional hemisphere after stroke in normoglycemic...
We and others have previously shown that angiotensin II receptor type 2 receptor (AT2R) is upregulated in the contralesional hemisphere after stroke in normoglycemic Wistar rats. In this study, we examined the expression of AT2R in type 2 diabetic Goto-Kakizaki (GK) rats and control Wistars after stroke. We also tested the contribution of the contralesional AT2R in recovery after stroke through a specific knockdown of the AT2R in this hemisphere only. Two experiments were conducted. In the first experiment, GK rats were subjected to middle cerebral artery occlusion (MCAO) and treated with the angiotensin II receptor type 1 receptor (AT1R) blocker candesartan or saline at reperfusion. Stroke outcomes, as well as AT2R expression, were examined and compared to control Wistars at 24 h. In the second experiment, localized AT2R knockdown was achieved through intrastriatal injection of short hairpin RNA (shRNA) lentiviral particles or non-targeting control into the left-brain hemisphere of Wistar rats. After 14 days, rats were subjected to right MCAO and treated with the AT2R agonist, Compound 21 (C21), or saline for 7 days. Behavioral outcomes were assessed for up to 10 days. In the first experiment, stroke reduced the expression of AT2R in GK rats. Candesartan treatment failed to improve the neurobehavioral outcomes, preserve vascular integrity or reduce oxidative/nitrative stress or apoptotic markers at 24 h post stroke in these animals. In the second experiment, contralesional AT2R knockdown reduced the C21-mediated functional recovery after stroke. In conclusion, contralesional AT2R upregulation after stroke is blunted in diabetic rats which show reduced sensitivity to post-stroke candesartan treatment. Contralesional AT2R could be involved in C21-mediated functional recovery after stroke.
Topics: Animals; Diabetes Mellitus, Experimental; Imidazoles; Infarction, Middle Cerebral Artery; Rats; Rats, Wistar; Receptor, Angiotensin, Type 2; Stroke; Sulfonamides; Thiophenes
PubMed: 35688299
DOI: 10.1016/j.neuint.2022.105375 -
ESC Heart Failure Dec 2021This study aimed to compare the efficacy of angiotensin receptor-neprilysin inhibitor (ARNI) therapy with angiotensin converting enzyme inhibitor or angiotensin receptor...
AIMS
This study aimed to compare the efficacy of angiotensin receptor-neprilysin inhibitor (ARNI) therapy with angiotensin converting enzyme inhibitor or angiotensin receptor blocker (ACEI/ARB) therapy for cardiovascular outcomes in patients with acute myocardial infarction (AMI).
METHODS AND RESULTS
Data were collected from the Biobank of the First Affiliated Hospital of Xi'an Jiaotong University between January 2016 and December 2020. A total of 7556 AMI patients were screened for eligibility. Propensity score matching based on age, sex, blood pressure, kidney function, baseline left ventricular ejection fraction (LVEF), and cardiovascular medication were conducted, resulting in 291 patients with AMI being assigned to ARNI, ACEI, and ARB group, respectively. Patients receiving ARNI had significantly lower rates of the composite cardiovascular outcome than ACEI {hazard ratio [HR] 0.51, [95% confidence interval (CI), 0.27-0.95], P = 0.02}, and ARB users [HR 0.47, (95%CI, 0.24-0.90), P = 0.02]. Patients receiving ARNI showed lower rates of cardiovascular death than ACEI [HR 0.37, (95%CI, 0.18-0.79), P = 0.01] and ARB users [HR 0.41, (95%CI, 0.18-0.95), P = 0.04]. Subgroup analysis indicated that patients with LVEF no more than 40% tend to benefit more from ARNI as compared with ACEI [HR 0.30, (95%CI, 0.11-0.86), P = 0.01] or ARB [HR 0.21, (95%CI, 0.04-1.1), P = 0.05]. Patients aged no more than 60 years exhibited reduced composite endpoints [HR for ARNI vs. ARB: 0.11, (95%CI, 0.03-0.46), P = 0.002].
CONCLUSIONS
In patients with AMI, ARNI was superior to ACEI/ARB in reducing the long-term adverse cardiovascular outcomes. Subgroup analysis further indicates that ARNI is more likely to benefit patients with LVEF less than 40% and aged less than 60 years.
Topics: Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Humans; Middle Aged; Myocardial Infarction; Receptors, Angiotensin; Stroke Volume; Ventricular Function, Left
PubMed: 34664407
DOI: 10.1002/ehf2.13644 -
Internal and Emergency Medicine Aug 2020SARS-CoV-2 is characterized by a spike protein allowing viral binding to the angiotensin-converting enzyme (ACE)-2, which acts as a viral receptor and is expressed on...
The SARS-CoV-2 receptor, ACE-2, is expressed on many different cell types: implications for ACE-inhibitor- and angiotensin II receptor blocker-based cardiovascular therapies.
SARS-CoV-2 is characterized by a spike protein allowing viral binding to the angiotensin-converting enzyme (ACE)-2, which acts as a viral receptor and is expressed on the surface of several pulmonary and extra-pulmonary cell types, including cardiac, renal, intestinal and endothelial cells. There is evidence that also endothelial cells are infected by SARS-COV-2, with subsequent occurrence of systemic vasculitis, thromboembolism and disseminated intravascular coagulation. Those effects, together with the "cytokine storm" are involved in a worse prognosis. In clinical practice, angiotensin-converting enzyme inhibitors (ACE-Is) and angiotensin II receptor blockers (ARBs) are extensively used for the treatment of hypertension and other cardiovascular diseases. In in vivo studies, ACE-Is and ARBs seem to paradoxically increase ACE-2 expression, which could favour SARS-CoV-2 infection of host's cells and tissues. By contrast, in patients treated with ACE-Is and ARBs, ACE-2 shows a downregulation at the mRNA and protein levels in kidney and cardiac tissues. Yet, it has been claimed that both ARBs and ACE-Is could result potentially useful in the clinical course of SARS-CoV-2-infected patients. As detected in China and as the Italian epidemiological situation confirms, the most prevalent comorbidities in deceased patients with COVID-19 are hypertension, diabetes and cardiovascular diseases. Older COVID-19-affected patients with cardiovascular comorbidities exhibit a more severe clinical course and a worse prognosis, with many of them being also treated with ARBs or ACE-Is. Another confounding factor is cigarette smoking, which has been reported to increase ACE-2 expression in both experimental models and humans. Sex also plays a role, with chromosome X harbouring the gene coding for ACE-2, which is one of the possible explanations of why mortality in female patients is lower. Viral entry also depends on TMPRSS2 protease activity, an androgen dependent enzyme. Despite the relevance of experimental animal studies, to comprehensively address the question of the potential hazards or benefits of ACE-Is and ARBs on the clinical course of COVID-19-affected patients treated by these anti-hypertensive drugs, we will need randomized human studies. We claim the need of adequately powered, prospective studies aimed at answering the following questions of paramount importance for cardiovascular, internal and emergency medicine: Do ACE-Is and ARBs exert similar or different effects on infection or disease course? Are such effects dangerous, neutral or even useful in older, COVID-19-affected patients? Do they act on multiple cell types? Since ACE-Is and ARBs have different molecular targets, the clinical course of SARS-CoV-2 infection could be also different in patients treated by one or the other of these two drug classes. At present, insufficient detailed data from trials have been made available.
Topics: Angiotensin Receptor Antagonists; Angiotensin-Converting Enzyme Inhibitors; Betacoronavirus; COVID-19; Cardiovascular Diseases; Coronavirus Infections; Humans; Pandemics; Pneumonia, Viral; Receptors, Angiotensin; Receptors, Virus; Risk Factors; SARS-CoV-2
PubMed: 32430651
DOI: 10.1007/s11739-020-02364-6 -
International Journal of Molecular... Jul 2023In angiotensin II (Ang II)-dependent hypertension, Ang II activates angiotensin II type 1 receptors (AT1R) on renal vascular smooth muscle cells, leading to renal... (Review)
Review
In angiotensin II (Ang II)-dependent hypertension, Ang II activates angiotensin II type 1 receptors (AT1R) on renal vascular smooth muscle cells, leading to renal vasoconstriction with eventual glomerular and tubular injury and interstitial inflammation. While afferent arteriolar vasoconstriction is initiated by the increased intrarenal levels of Ang II activating AT1R, the progressive increases in arterial pressure stimulate the paracrine secretion of adenosine triphosphate (ATP), leading to the purinergic P2X receptor (P2XR)-mediated constriction of afferent arterioles. Thus, the afferent arteriolar tone is maintained by two powerful systems eliciting the co-existing activation of P2XR and AT1R. This raises the conundrum of how the AT1R and P2XR can both be responsible for most of the increased renal afferent vascular resistance existing in angiotensin-dependent hypertension. Its resolution implies that AT1R and P2XR share common receptor or post receptor signaling mechanisms which converge to maintain renal vasoconstriction in Ang II-dependent hypertension. In this review, we briefly discuss (1) the regulation of renal afferent arterioles in Ang II-dependent hypertension, (2) the interaction of AT1R and P2XR activation in regulating renal afferent arterioles in a setting of hypertension, (3) mechanisms regulating ATP release and effect of angiotensin II on ATP release, and (4) the possible intracellular pathways involved in AT1R and P2XR interactions. Emerging evidence supports the hypothesis that P2X1R, P2X7R, and AT1R actions converge at receptor or post-receptor signaling pathways but that P2XR exerts a dominant influence abrogating the actions of AT1R on renal afferent arterioles in Ang II-dependent hypertension. This finding raises clinical implications for the design of therapeutic interventions that will prevent the impairment of kidney function and subsequent tissue injury.
Topics: Humans; Adenosine Triphosphate; Angiotensin II; Arterioles; Hypertension; Kidney; Receptor, Angiotensin, Type 1; Receptors, Angiotensin; Receptors, Purinergic P2X
PubMed: 37511174
DOI: 10.3390/ijms241411413 -
Regulatory Peptides Nov 2009To clarify the relationship between Angiotensin II AT(1) and AT(2) receptors, we studied AT(1) receptor mRNA and binding expression in tissues from AT(2) receptor gene...
To clarify the relationship between Angiotensin II AT(1) and AT(2) receptors, we studied AT(1) receptor mRNA and binding expression in tissues from AT(2) receptor gene disrupted (AT(2)(-/-)) female mice, where AT(2) receptors are not expressed in vivo, using in situ hybridization and quantitative autoradiography. Wild type mice expressed AT(1A) receptor mRNA and AT(1) receptor binding in lung parenchyma, the spleen, predominantly in the red pulp, and in liver parenchyma. In wild type mice, lung AT(2) receptors were expressed in lung bronchial epithelium and smooth muscle, and were not present in the lung parenchyma, the spleen or the liver. This indicates that AT(1) and AT(2) receptors were not expressed in the same cells. In AT(2)(-/-) mice, we found higher AT(1A) receptor mRNA and AT(1) receptor binding in lung parenchyma and in the red pulp of the spleen, but not in the liver, when compared to littermate wild type controls. Our results suggest that impaired AT(2) receptor function upregulates AT(1) receptor transcription and expression in a tissue-specific manner and in cells not expressing AT(2) receptors. AT(1) upregulation explains the increased sensitivity to Angiotensin II characteristic of the AT(2)(-/-) phenotype, consistent with enhanced AT(1) receptor activation in a number of tissues.
Topics: Animals; Autoradiography; Base Sequence; DNA Primers; In Situ Hybridization; Lung; Mice; Mice, Inbred C57BL; Polymerase Chain Reaction; Protein Binding; RNA, Messenger; Receptor, Angiotensin, Type 1; Receptors, Angiotensin; Spleen
PubMed: 19766151
DOI: 10.1016/j.regpep.2009.09.004 -
Brazilian Journal of Medical and... Sep 2002Angiotensin II (Ang II) is a multifunctional hormone that influences the function of cardiovascular cells through a complex series of intracellular signaling events... (Review)
Review
Angiotensin II (Ang II) is a multifunctional hormone that influences the function of cardiovascular cells through a complex series of intracellular signaling events initiated by the interaction of Ang II with AT1 and AT2 receptors. AT1 receptor activation leads to cell growth, vascular contraction, inflammatory responses and salt and water retention, whereas AT2 receptors induce apoptosis, vasodilation and natriuresis. These effects are mediated via complex, interacting signaling pathways involving stimulation of PLC and Ca2+ mobilization; activation of PLD, PLA2, PKC, MAP kinases and NAD(P)H oxidase, and stimulation of gene transcription. In addition, Ang II activates many intracellular tyrosine kinases that play a role in growth signaling and inflammation, such as Src, Pyk2, p130Cas, FAK and JAK/STAT. These events may be direct or indirect via transactivation of tyrosine kinase receptors, including PDGFR, EGFR and IGFR. Ang II induces a multitude of actions in various tissues, and the signaling events following occupancy and activation of Ang receptors are tightly controlled and extremely complex. Alterations of these highly regulated signaling pathways may be pivotal in structural and functional abnormalities that underlie pathological processes in cardiovascular diseases such as cardiac hypertrophy, hypertension and atherosclerosis.
Topics: Angiotensin II; Cardiovascular Diseases; Humans; Mitogen-Activated Protein Kinases; Muscle, Smooth, Vascular; Protein-Tyrosine Kinases; Reactive Oxygen Species; Receptor Protein-Tyrosine Kinases; Receptor, Angiotensin, Type 1; Receptor, Angiotensin, Type 2; Receptors, Angiotensin; Signal Transduction
PubMed: 12219172
DOI: 10.1590/s0100-879x2002000900001 -
American Journal of Physiology. Heart... Dec 2001Angiotensin II (ANG II) is a pleiotropic vasoactive peptide that binds to two distinct receptors: the ANG II type 1 (AT(1)) and type 2 (AT(2)) receptors. Activation of... (Review)
Review
Angiotensin II (ANG II) is a pleiotropic vasoactive peptide that binds to two distinct receptors: the ANG II type 1 (AT(1)) and type 2 (AT(2)) receptors. Activation of the renin-angiotensin system (RAS) results in vascular hypertrophy, vasoconstriction, salt and water retention, and hypertension. These effects are mediated predominantly by AT(1) receptors. Paradoxically, other ANG II-mediated effects, including cell death, vasodilation, and natriuresis, are mediated by AT(2) receptor activation. Our understanding of ANG II signaling mechanisms remains incomplete. AT(1) receptor activation triggers a variety of intracellular systems, including tyrosine kinase-induced protein phosphorylation, production of arachidonic acid metabolites, alteration of reactive oxidant species activities, and fluxes in intracellular Ca(2+) concentrations. AT(2) receptor activation leads to stimulation of bradykinin, nitric oxide production, and prostaglandin metabolism, which are, in large part, opposite to the effects of the AT(1) receptor. The signaling pathways of ANG II receptor activation are a focus of intense investigative effort. We critically appraise the literature on the signaling mechanisms whereby AT(1) and AT(2) receptors elicit their respective actions. We also consider the recently reported interaction between ANG II and ceramide, a lipid second messenger that mediates cytokine receptor activation. Finally, we discuss the potential physiological cross talk that may be operative between the angiotensin receptor subtypes in relation to health and cardiovascular disease. This may be clinically relevant, inasmuch as inhibitors of the RAS are increasingly used in treatment of hypertension and coronary heart disease, where activation of the RAS is recognized.
Topics: Animals; Ceramides; Humans; Receptors, Angiotensin; Renin-Angiotensin System; Signal Transduction; Vascular Diseases
PubMed: 11709400
DOI: 10.1152/ajpheart.2001.281.6.H2337