ARB and Cardioprotection

An update of the molecular mechanisms underlying anthracycline induced cardiotoxicity

Anthracycline drugs mainly include doxorubicin, epirubicin, pirarubicin, and aclamycin, which are widely used to treat a variety of malignant tumors, such as breast cancer, gastrointestinal tumors, lymphoma, etc. With the accumulation of anthracycline drugs in the body, they can induce serious heart damage, limiting their clinical application. The mechanism by which anthracycline drugs cause cardiotoxicity is not yet clear. This review provides an overview of the different types of cardiac damage induced by anthracycline-class drugs and delves into the molecular mechanisms behind these injuries. Cardiac damage primarily involves alterations in myocardial cell function and pathological cell death, encompassing mitochondrial dysfunction, topoisomerase inhibition, disruptions in iron ion metabolism, myofibril degradation, and oxidative stress. Mechanisms of uptake and transport in anthracycline-induced cardiotoxicity are emphasized, as well as the role and breakthroughs of iPSC in cardiotoxicity studies. Selected novel cardioprotective therapies and mechanisms are updated. Mechanisms and protective strategies associated with anthracycline cardiotoxicity in animal experiments are examined, and the definition of drug damage in humans and animal models is discussed. Understanding these molecular mechanisms is of paramount importance in mitigating anthracycline-induced cardiac toxicity and guiding the development of safer approaches in cancer treatment.

Transcriptome and proteome analyses reveal that upregulation of GSTM2 by allisartan improves cardiac remodeling and dysfunction in hypertensive rats

Long-term hypertension can lead to hypertensive heart disease, which ultimately progresses to heart failure. As an angiotensin receptor blocker antihypertensive drug, allisartan can control blood pressure, and improve cardiac remodeling and cardiac dysfunction caused by hypertension. The aim of the present study was to investigate the protective effects of allisartan on the heart of spontaneously hypertensive rats (SHRs) and the underlying mechanisms. SHRs were used as an animal model of hypertensive heart disease and were treated with allisartan orally at a dose of 25 mg/kg/day. The blood pressure levels of the rats were continuously monitored, their body and heart weights were measured, and their cardiac structure and function were evaluated using echocardiography. Wheat germ agglutinin staining and Masson trichrome staining were employed to assess the morphology of the myocardial tissue. In addition, transcriptome and proteome analyses were performed using the Solexa/Illumina sequencing platform and tandem mass tag technology, respectively. Immunofluorescence co-localization was conducted to analyze Nrf2 nuclear translocation, and TUNEL was performed to detect the levels of cell apoptosis. The protein expression levels of pro-collagen I, collagen III, phosphorylated (p)-AKT, AKT, p-PI3K and PI3K, and the mRNA expression levels of Col1a1 and Col3a1 were determined by western blotting and reverse transcription-quantitative PCR, respectively. Allisartan lowered blood pressure, attenuated cardiac remodeling and improved cardiac function in SHRs. In addition, allisartan alleviated cardiomyocyte hypertrophy and cardiac fibrosis. Allisartan also significantly affected the 'pentose phosphate pathway', 'fatty acid elongation', 'valine, leucine and isoleucine degradation', 'glutathione metabolism', and 'amino sugar and nucleotide sugar metabolism' pathways in the hearts of SHRs, and upregulated the expression levels of GSTM2. Furthermore, allisartan activated the PI3K-AKT-Nrf2 signaling pathway and inhibited cardiomyocyte apoptosis. In conclusion, the present study demonstrated that allisartan can effectively control blood pressure in SHRs, and improves cardiac remodeling and cardiac dysfunction. Allisartan may also upregulate the expression levels of GSTM2 in the hearts of SHRs and significantly affect glutathione metabolism, as determined by transcriptome and proteome analyses. The cardioprotective effect of allisartan may be mediated through activation of the PI3K-AKT-Nrf2 signaling pathway, upregulation of GSTM2 expression and reduction of cardiomyocyte apoptosis in SHRs.

Myeloid Angiotensin II Type 1 Receptor Mediates Macrophage Polarization and Promotes Vascular Injury in DOCA/Salt Hypertensive Mice

Activation of the renin–angiotensin system has been implicated in hypertension. Angiotensin (Ang) II is a potent proinflammatory mediator. The present study investigated the role of myeloid angiotensin type 1 receptor (AT1R) in control of macrophage phenotype in vitro and vascular injury in deoxycorticosterone acetate (DOCA)/salt hypertension. In human THP-1/macrophages, Ang II increased mRNA expressions of M1 cytokines and decreased M2 cytokine expressions. Overexpression of AT1R further increased Ang II-induced expressions of M1 cytokines and decreased M2 cytokines. Silenced AT1R reversed Ang II-induced changes in M1 and M2 cytokines. Ang II upregulated hypoxia-inducible factor (HIF)1α, toll-like receptor (TLR)4, and the ratio of pIκB/IκB, which were prevented by silenced AT1R. Silenced HIF1α prevented Ang II activation of the TLR4/NFκB pathway. Furthermore, Ang II increased HIF1α via reactive oxygen species-dependent reduction in prolyl hydroxylase domain protein 2 (PHD2) expression. The expressions of AT1R and HIF1α and the ratio of pIκB/IκB were upregulated in the peritoneal macrophages of DOCA hypertensive mice, and the specific deletion of myeloid AT1R attenuated cardiac and vascular injury and vascular oxidative stress, reduced the recruitment of macrophages and M1 cytokine expressions, and improved endothelial function without significant reduction in blood pressure. Our results demonstrate that Ang II/AT1R controls the macrophage phenotype via stimulating the HIF1α/NFκB pathway, and specific myeloid AT1R KO improves endothelial function, vascular inflammation, and injury in salt-sensitive hypertension. The results support the notion that myeloid AT1R plays an important role in the regulation of the macrophage phenotype, and dysfunction of this receptor may promote vascular dysfunction and injury in salt-sensitive hypertension.

AT1 receptor blocker inhibits HMGB1 expression in pressure overload-induced acute cardiac dysfunction by suppressing the MAPK/NF-κB signaling pathway

BACKGROUND

High-mobility group box 1 (HMGB1) expression not only peaks during the early phase of pressure overload (PO), but also serves a role in the pathogenesis of PO-induced cardiac remodeling. Meanwhile, angiotensin II type 1 (AT1) receptor blockers reverse PO-induced cardiac remodeling and repress the secretion of inflammatory factors. However, whether AT1 receptor inhibitors decrease HMGB1 expression in the early stages of PO remains unknown.

MATERIALS AND METHODS

PO mouse models were established using transverse aortic constriction (TAC), in which losartan was administrated. Transthoracic echocardiography was performed 3 days after the operation, and serum and cardiac HMGB1 expression, as well as the expression levels of related proteins were measured.

RESULTS

PO-induced acute cardiac dysfunction was observed 3 days after TAC, and was subsequently slightly, but not significantly relieved by losartan. The expression levels of HMGB1, tumor necrosis factor-α and interleukin-6 in both the serum and myocardium were upregulated in response to TAC, while they were significantly reduced by losartan. Moreover, the phosphorylation of extracellular signal-regulated kinases, p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) in the myocardium were significantly increased under PO, and this was also prevented by losartan.

CONCLUSION

These data suggest that losartan may downregulate the expression of HMGB1 in acute cardiac dysfunction induced by PO by inhibiting the MAPKs/NF-κB signaling pathway, which indicates a novel beneficial role of AT1 receptor antagonists in ameliorating cardiac remodeling under PO.

Mechanisms of anthracycline-mediated cardiotoxicity and preventative strategies in women with breast cancer

While anthracyclines (ACs) are a class of chemotherapeutic agents that have improved the prognosis of many women with breast cancer, it is one of the most cardiotoxic agents used to treat cancer. Despite their reported dose-dependent cardiotoxicity, AC-based chemotherapy has become the mainstay of breast cancer therapy due to its efficacy. Elucidating the mechanisms of anthracycline-mediated cardiotoxicity and associated therapeutic interventions continue to be the main focus in the field of cardio-oncology. Herein, we summarized the current literature surrounding the mechanisms of anthracycline-induced cardiotoxicity, including the role of topoisomerase II inhibition, generation of reactive oxygen species, and elevations in free radicals. Furthermore, this review highlights the molecular mechanisms of potential cardioprotective interventions in this setting. The benefits of pharmaceuticals, including dexrazoxane, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, statins, and antioxidants in this setting, are reviewed. Finally, the mechanisms of emerging preventative interventions within this patient population including nutraceuticals and aerobic exercise are explored.

Pathological cardiac remodeling seen by the eyes of proteomics

Cardiac remodeling involves cellular and structural changes that occur as consequence of multifactorial events to maintain the homeostasis. The progression of pathological cardiac remodeling involves a transition from adaptive to maladaptive changes that eventually leads to impairment of ventricular function and heart failure. In this scenario, proteins are key elements that orchestrate molecular events as increased expression of fetal genes, neurohormonal and second messengers' activation, contractile dysfunction, rearrangement of the extracellular matrix and alterations in heart geometry. Mass spectrometry based-proteomics has emerged as a sound method to study protein dysregulation and identification of cardiac diseases biomarkers in plasma. In this review, we summarize the main findings related to large-scale proteome modulation of cardiac cells and extracellular matrix occurred during pathological cardiac remodeling. We describe the recent proteomic progresses in the selection of protein targets and introduce the renin-angiotensin system as an interesting target for the treatment of pathological cardiac remodeling.

Effect of medications after cardiac surgery on long-term outcomes in patients with cirrhosis

The aim of this study was to evaluate the effect of beta-blockers, angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) after cardiac surgery in the liver cirrhosis (LC) patients. We conducted a population-based cohort study using data from the Taiwanese National Health Insurance Research Database (NHIRD) from 2001 to 2013. The outcomes of interest included all-cause mortality, major adverse cardiac and cerebrovascular events (MACCE) and liver and renal outcomes. Among 1470 LC patients, 35.6% (n = 524) received beta-blockers and 33.4% (n = 491) were prescribed ACEIs and/or ARBs after cardiac surgery. The risk of negative liver outcomes was significantly lower in the ARB group compared with the ACEI group (9.6% vs 22.7%, hazard ratio [HR] 0.50, 95% confidence interval [CI] 0.31-0.83). Furthermore, the risk of MACCE (44.2% vs 54.7%, HR 0.79, 95% CI 0.65-0.96), all-cause mortality (35.3% vs 46.4%, HR 0.74, 95% CI 0.60-0.92), composite liver outcomes (9.6% vs 16.5%, HR 0.56, 95% CI 0.38-0.85) and hepatic encephalopathy (2.7% vs 5.7%, HR 0.45, 95% CI 0.21-0.94) were lower in the ARB group than the control group. Our study demonstrated that ARBs provide a greater protective effect than ACEIs in regard to long-term outcomes following cardiac surgery in patients with LC.

Neprilysin: A Potential Therapeutic Target of Arterial Hypertension?

Arterial hypertension is the most prevalent chronic disease in the adult population of developed countries and it constitutes a significant risk factor in the development of cardiovascular disease, contributing to the emergence of many comorbidities, among which heart failure excels, a clinical syndrome that nowadays represents a major health problem with uncountable hospitalizations and the indolent course of which progressively worsens until quality of life decreases and lastly death occurs prematurely. In the light of this growing menace, each day more efforts are invested in the field of cardiovascular pharmacology, searching for new therapeutic options that allow us to modulate the physiological systems that appear among these pathologies. Therefore, in the later years, the study of natriuretic peptides has become so relevant, which mediate beneficial effects at the cardiovascular level such as diuresis, natriuresis, and decreasing cardiac remodeling; their metabolism is mediated by neprilysin, a metalloproteinase, widely expressed in the human and capable of catalyzing many substrates. The modulation of these functions has been studied by decades, giving room to Sacubitril, the first neprilysin inhibitor, which in conjunction with an angiotensin receptor blocker has provided a high efficacy and tolerability among patients with heart failure, for whom it has already been approved and recommended. Nonetheless, in the matter of arterial hypertension, significant findings have arisen that demonstrate the potential role that it will play among the pharmacological alternatives in the upcoming years.

A Study of Morphological Changes in Renal Afferent Arterioles Induced by Angiotensin II Type 1 Receptor Blockers in Hypertensive Patients

BACKGROUND

Renin-angiotensin-aldosterone system blockers are known to reduce hypertrophy of vascular smooth muscle cells (SMCs) in hypertensive cases. However, we have reported marked proliferative changes of renal afferent arteriolar SMCs in rats induced by a long-term administration of angiotensin II type 1 receptor blockers (ARBs) and an angiotensin-converting enzyme inhibitor (ACEI). In this study, we examined the morphological changes of afferent arteriolar walls in human kidneys with or without ARBs/ACEIs.

METHODS

Forty-four wedge resections were taken from patients aged 45-74 years from 92 nephrectomized kidneys due to malignancy at Toho University Omori Medical Center between 2013 and 2016. They were divided into the following three groups: 18 hypertensive patients treated with antihypertensive agents including ARBs or ACEIs (the HTARB group), 6 hypertensive patients treated with calcium channel blockers without ARBs/ACEIs (the HTCCB group), and 20 normotensive patients (the normotensive group) as a control. Cases expecting vascular changes such as diabetes were excluded. In each case renal arterioles were measured as the ratio of inner/outer arteriolar diameter, and pathologists estimated morphological abnormal changes, scoring each specimen independently.

RESULTS

The ratio in the HTARB group was 0.39 ± 0.05 (mean ± SD), and was significantly the lowest among the three groups (0.46 ± 0.02 in the HTCCB, 0.53 ± 0.02 in the normotensive group; p = 0.0107 vs. HTCCB, p = 0.00001 vs. normotensive). The ratio in the three groups significantly correlated with the estimated glomerular filtration rate (r = 0.4915, p < 0.0007). The afferent arteriolar SMCs in the HTARB group frequently showed marked proliferative and irregular changes. The score of SMC abnormalities estimated regarding the proliferation, irregularity of the arrangement, and size in hilar afferent arteriolar SMCs was highest in the HTARB group and showed statistical significance (p = 0.0088, p = 0.00001, and p = 0.025 versus other two groups).

CONCLUSIONS

We consider that these morphological changes in arterioles are induced by ARBs/ACEIs. These changes could induce an important suppression of glomerular hyperfiltration and could lead to glomerular ischemia. However, the clinical consequences of these morphological changes in correlation with ARBs/ACEIs were not sufficiently clear and require further analysis. We should consider renal arteriolar morphological changes when using ARBs/ACEIs.

Genomic and rapid effects of aldosterone: what we know and do not know thus far

Aldosterone is the most known mineralocorticoid hormone synthesized by the adrenal cortex. The genomic pathway displayed by aldosterone is attributed to the mineralocorticoid receptor (MR) signaling. Even though the rapid effects displayed by aldosterone are long known, our knowledge regarding the receptor responsible for such event is still poor. It is intense that the debate whether the MR or another receptor-the "unknown receptor"-is the receptor responsible for the rapid effects of aldosterone. Recently, G protein-coupled estrogen receptor-1 (GPER-1) was elegantly shown to mediate some aldosterone-induced rapid effects in several tissues, a fact that strongly places GPER-1 as the unknown receptor. It has also been suggested that angiotensin receptor type 1 (AT1) also participates in the aldosterone-induced rapid effects. Despite this open question, the relevance of the beneficial effects of aldosterone is clear in the kidneys, colon, and CNS as aldosterone controls the important water reabsorption process; on the other hand, detrimental effects displayed by aldosterone have been reported in the cardiovascular system and in the kidneys. In this line, the MR antagonists are well-known drugs that display beneficial effects in patients with heart failure and hypertension; it has been proposed that MR antagonists could also play an important role in vascular disease, obesity, obesity-related hypertension, and metabolic syndrome. Taken altogether, our goal here was to (1) bring a historical perspective of both genomic and rapid effects of aldosterone in several tissues, and the receptors and signaling pathways involved in such processes; and (2) critically address the controversial points within the literature as regarding which receptor participates in the rapid pathway display by aldosterone.

Pathophysiology and therapeutic potential of cardiac fibrosis

Inflammatory and fibrotic responses to myocardial damage are essential for cardiac repair; however, these responses often result in extensive fibrotic remodeling with impaired systolic function. Recent reports have suggested that such acute phase responses provide a favorable environment for endogenous cardiac regeneration, which is mainly driven by the division of pre-existing cardiomyocytes (CMs). Existing CMs in mammals can re-acquire proliferative activity after substantial cardiac damage, and elements other than CMs in the physiological and/or pathological environment, such as hypoxia, angiogenesis, and the polarity of infiltrating macrophages, have been reported to regulate replication. Cardiac fibroblasts comprise the largest cell population in terms of cell number in the myocardium, and they play crucial roles in the proliferation and protection of CMs. The in vivo direct reprogramming of functional CMs has been investigated in cardiac regeneration. Currently, growth factors, transcription factors, microRNAs, and small molecules promoting the regeneration and protection of these CMs have also been actively researched. Here, we summarize and discuss current studies on the relationship between cardiac inflammation and fibrosis, and cardiac regeneration and protection, which would be useful for the development of therapeutic strategies to treat and prevent advanced heart failure.

Angiotensin Receptor Blockade Improves Cardiac Surgical Outcomes in Patients With Metabolic Syndrome

BACKGROUND

Perioperative use of angiotensin receptor blockers (ARBs) and angiotensin-converting enzyme inhibitors (ACEis) in patients undergoing cardiac operations remains controversial. The current practice of discontinuing renin-angiotensin-system inhibitors preoperatively may negate their beneficial effects in vulnerable populations, including patients with metabolic syndrome, who exhibit elevated renin-angiotensin system activity. We hypothesized that preoperative ARB use is associated with reduced incidence of postoperative complications, compared with ACEi or no drug, in patients with metabolic syndrome undergoing coronary artery bypass grafting.

METHODS

We used propensity matching to derive a cohort of 1,351 patients from 2,998 who underwent coronary artery bypass grafting based on preoperative use of ARBs, ACEis, or no renin-angiotensin-system inhibitors. Our primary end point was a composite of adverse events occurring within 30 days after the operation: new-onset atrial fibrillation/flutter, arrhythmia requiring cardioversion, perioperative myocardial infarction, acute renal failure, need for dialysis, cerebrovascular accidents, acute respiratory failure, or perioperative death.

RESULTS

At least one adverse event occurred in 524 (38.8%) of matched cohort patients (1,184 [39.6% of all patients]). Adjusting for European System for Cardiac Operative Risk Evaluation and metabolic syndrome in the matched cohort, preoperative use of ARBs was associated with a lower incidence of adverse events in patients with metabolic syndrome compared with preoperative use of no renin-angiotensin-system inhibitors (odds ratio, 0.43; 95% confidence interval, 0.19 to 0.99) or ACEis (odds ratio, 0.38; 95% confidence interval, 0.16 to 0.88).

CONCLUSIONS

Preoperative use of ARBs, but not ACEis, confers a benefit within 30 days after cardiac operations in patients with metabolic syndrome, suggesting potential efficacy differences of these drug classes in reducing cardiovascular morbidity and death in ambulatory vs surgical patients.

Inverse agonism: the classic concept of GPCRs revisited [Review]

In the classical two-state model, G protein-coupled receptors (GPCRs) are considered to exist in equilibrium between an active and an inactive conformation. Thus, even at the resting state, some subpopulation of GPCRs is in the active state, which underlies the basal activity of the GPCRs. In this review, we discuss inverse agonists, which are defined as GPCR ligands that shift the equilibrium toward the inactive state and thereby suppress the basal activity. Theoretically, if constitutive activation plays an essential role in the pathogenesis of a disease, only inverse agonists, and not neutral antagonists, can reverse this pathophysiological activation. Although many pharmacological examples of inverse agonism have been identified, its clinical importance is still unclear and debated. Thus, even though inverse agonism of angiotensin receptor blockers (ARBs) has been discussed for more than 10 years, its clinical relevance remains to be completely clarified.

[Irbesartan ameliorates cardiac inflammation in type 2 diabetic db/db mice]

OBJECTIVE

To investigate the protective effects of irbesartan against cardiac inflammation associated with diabetes and obesity in the db/db mouse model of type 2 diabetes and explore the underlying mechanisms.

METHODS

Twenty- four 10-week-old diabetic db/db mice were equally randomized into irbesartan treatment (50 mg/kg per day) group and model group, using 12 nondiabetic littermates (db/+) as the controls, The mice were treated with irbesartan or saline vehicle for 16 consecutive weeks, after which the heart pathology was observed and the heart weight, body weight, and serum levels of fasting blood glucose (FBG), total cholesterol(TC), and triglycerides(TG) were measured. The expression of nuclear factor-kappaB (NF-κB) p65 in the myocardium was assessed with immunohistochemistry, the protein levels of P-IκBα ,IκBα and β-actin were analyzed with Western blotting, and the pro-inflammatory cytokines IL-6 and TNF-α mRNA were detected using quantitative real-time PCR (qPCR).

RESULTS

Compared with db/+ mice, the saline-treated db/db mice developed obesity, hyperglycemia and hyperlipidemia (P<0.01). Histopathological examination of the heart tissue revealed inflammatory cell infiltration, increased myocardial interstitium and disorders of myocardial fiber arrangement. The diabetic mice showed increased P-IαBα and decreased IκBα protein levels, enhanced activity and expression of NF-κB in the hearts, and increased mRNA expression of IL-6 and TNF-α in the myocardium. These abnormalities were all associated with increased inflammatory response. Treatment with irbesartan improved the heart architecture and attenuated high glucose-induced inflammation in the diabetic mice.

CONCLUSION

Treatment with irbesartan attenuates cardiac inflammation in type 2 diabetic db/db mice, and this effect was probably associated with the suppression of cardiac angiotensin II and NF-κB signaling pathway.

Combined effects of aging and inflammation on renin-angiotensin system mediate mitochondrial dysfunction and phenotypic changes in cardiomyopathies

Although the effects of aging and inflammation on the health of the cardiac muscle are well documented, the combined effects of aging and chronic inflammation on cardiac muscle are largely unknown. The renin-angiotensin system (RAS) has been linked independently to both aging and inflammation, but is understudied in the context of their collective effect. Thus, we investigated localized cardiac angiotensin II type I and type II receptors (AT₁R, AT₂R), downstream effectors, and phenotypic outcomes using mouse models of the combination of aging and inflammation and compared it to a model of aging and a model of inflammation. We show molecular distinction in the combined effect of aging and inflammation as compared to each independently. The combination maintained an increased AT₁R:AT₂R and expression of Nox2 and exhibited the lowest activity of antioxidants. Despite signaling pathway differences, the combined effect shared phenotypic similarities with aging including oxidative damage, fibrosis, and hypertrophy. These phenotypic similarities have dubbed inflammatory conditions as premature aging, but they are, in fact, molecularly distinct. Moreover, treatment with an AT₁R blocker, losartan, selectively reversed the signaling changes and ameliorated adverse phenotypic effects in the combination of aging and inflammation as well as each independently.

Protective Role of Ramipril and Candesartan against Myocardial Ischemic Reperfusion Injury: A Biochemical and Transmission Electron Microscopical Study

The present study was designed to investigate the role of combined administration of Ramipril and Candesartan against in vitro myocardial ischemic reperfusion injury in rat. Male Wistar albino rats were divided into five groups (n = 6) and treated with saline (10 mL/kg), Ramipril (2 mg/kg), Candesartan (1 mg/kg), and the combination of both drugs, respectively 24 h before induction of global ischemia (5 min of stabilization, 9 min of global ischemia, and 12 min of reflow). Combination of Ramipril and Candesartan when compared to the monotherapy significantly increased the levels of superoxide dismutase, reduced glutathione, catalase, and nitric oxide and decreased the levels of thiobarbituric acid reactive substances. In addition, the superior protective role of combination of Ramipril and Candesartan on ischemia induced myocardial damage was further confirmed by well preserved myocardial tissue architecture in light microscopy and transmission electron microscopy analysis studies. The combination was proved to be effective in salvaging the myocardial tissue against ischemic reperfusion injury when compared to the monotherapy of individual drugs and further investigations on protective mechanism of drugs by increasing the nitric oxide level at molecular levels are needed.

Myocardial pathology induced by aldosterone is dependent on non-canonical activities of G protein-coupled receptor kinases

Hyper-aldosteronism is associated with myocardial dysfunction including induction of cardiac fibrosis and maladaptive hypertrophy. Mechanisms of these cardiotoxicities are not fully understood. Here we show that mineralocorticoid receptor (MR) activation by aldosterone leads to pathological myocardial signalling mediated by mitochondrial G protein-coupled receptor kinase 2 (GRK2) pro-death activity and GRK5 pro-hypertrophic action. Moreover, these MR-dependent GRK2 and GRK5 non-canonical activities appear to involve cross-talk with the angiotensin II type-1 receptor (AT1R). Most importantly, we show that ventricular dysfunction caused by chronic hyper-aldosteronism in vivo is completely prevented in cardiac Grk2 knockout mice (KO) and to a lesser extent in Grk5 KO mice. However, aldosterone-induced cardiac hypertrophy is totally prevented in Grk5 KO mice. We also show human data consistent with MR activation status in heart failure influencing GRK2 levels. Therefore, our study uncovers GRKs as targets for ameliorating pathological cardiac effects associated with high-aldosterone levels.

Differential Effects of β-Blockers, Angiotensin II Receptor Blockers, and a Novel AT2R Agonist NP-6A4 on Stress Response of Nutrient-Starved Cardiovascular Cells

In order to determine differences in cardiovascular cell response during nutrient stress to different cardiovascular protective drugs, we investigated cell responses of serum starved mouse cardiomyocyte HL-1 cells and primary cultures of human coronary artery vascular smooth muscles (hCAVSMCs) to treatment with β-blockers (atenolol, metoprolol, carvedilol, nebivolol, 3μM each), AT1R blocker losartan (1μM) and AT2R agonists (CGP42112A and novel agonist NP-6A4, 300nM each). Treatment with nebivolol, carvedilol, metoprolol and atenolol suppressed Cell Index (CI) of serum-starved HL-1 cells (≤17%, ≤8%, ≤15% and ≤15% respectively) as measured by the Xcelligence Real-Time Cell Analyzer (RTCA). Conversely, CI was increased by Ang II (≥9.6%), CGP42112A (≥14%), and NP-6A4 (≥25%) respectively and this effect was blocked by AT2R antagonist PD123319, but not by AT1R antagonist losartan. Thus, the CI signature for each drug could be unique. MTS cell proliferation assay showed that NP-6A4, but not other drugs, increased viability (≥20%) of HL-1 and hCAVSMCs. Wheat Germ Agglutinin (WGA) staining showed that nebivolol was most effective in reducing cell sizes of HL-1 and hCAVSMCs. Myeloid Cell Leukemia 1 (MCL-1) is a protein critical for cardiovascular cell survival and implicated in cell adhesion. β-blockers significantly suppressed and NP-6A4 increased MCL-1 expression in HL-1 and hCAVSMCs as determined by immunofluorescence. Thus, reduction in cell size and/or MCL-1 expression might underlie β-blocker-induced reduction in CI of HL-1. Conversely, increase in cell viability and MCL-1 expression by NP-6A4 through AT2R could have resulted in NP-6A4 mediated increase in CI of HL-1. These data show for the first time that activation of the AT2R-MCL-1 axis by NP-6A4 in nutrient-stressed mouse and human cardiovascular cells (mouse HL-1 cells and primary cultures of hCAVSMCs) might underlie improved survival of cells treated by NP-6A4 compared to other drugs tested in this study.

International Union of Basic and Clinical Pharmacology. XCIX. Angiotensin Receptors: Interpreters of Pathophysiological Angiotensinergic Stimuli [corrected]

The renin angiotensin system (RAS) produced hormone peptides regulate many vital body functions. Dysfunctional signaling by receptors for RAS peptides leads to pathologic states. Nearly half of humanity today would likely benefit from modern drugs targeting these receptors. The receptors for RAS peptides consist of three G-protein-coupled receptors—the angiotensin II type 1 receptor (AT1 receptor), the angiotensin II type 2 receptor (AT2 receptor), the MAS receptor—and a type II trans-membrane zinc protein—the candidate angiotensin IV receptor (AngIV binding site). The prorenin receptor is a relatively new contender for consideration, but is not included here because the role of prorenin receptor as an independent endocrine mediator is presently unclear. The full spectrum of biologic characteristics of these receptors is still evolving, but there is evidence establishing unique roles of each receptor in cardiovascular, hemodynamic, neurologic, renal, and endothelial functions, as well as in cell proliferation, survival, matrix-cell interaction, and inflammation. Therapeutic agents targeted to these receptors are either in active use in clinical intervention of major common diseases or under evaluation for repurposing in many other disorders. Broad-spectrum influence these receptors produce in complex pathophysiological context in our body highlights their role as precise interpreters of distinctive angiotensinergic peptide cues. This review article summarizes findings published in the last 15 years on the structure, pharmacology, signaling, physiology, and disease states related to angiotensin receptors. We also discuss the challenges the pharmacologist presently faces in formally accepting newer members as established angiotensin receptors and emphasize necessary future developments.

Angiotensin II receptor blockade promotes repair of skeletal muscle through down-regulation of aging-promoting C1q expression

Disruption of angiotensin II type 1 (AT₁) receptor prolonged life span in mice. Since aging-related decline in skeletal muscle function was retarded in Atgr1a^−/− mice, we examined the role of AT₁ receptor in muscle regeneration after injury. Administration of AT₁ receptor blocker irbesartan increased the size of regenerating myofibers, decreased fibrosis, and enhanced functional muscle recovery after cryoinjury. We recently reported that complement C1q, secreted by macrophages, activated Wnt/β-catenin signaling and promoted aging-related decline in regenerative capacity of skeletal muscle. Notably, irbesartan induced M2 polarization of macrophages, but reduced C1q expression in cryoinjured muscles and in cultured macrophage cells. Irbesartan inhibited up-regulation of Axin2, a downstream gene of Wnt/β-catenin pathway, in cryoinjured muscles. In addition, topical administration of C1q reversed beneficial effects of irbesartan on skeletal muscle regeneration after injury. These results suggest that AT₁ receptor blockade improves muscle repair and regeneration through down-regulation of the aging-promoting C1q-Wnt/β-catenin signaling pathway.

Angiotensin II type 1 receptor blockade suppresses light-induced neural damage in the mouse retina

Exposure to light contributes to the development and progression of retinal degenerative diseases. However, the mechanisms underlying light-induced tissue damage are not fully understood. Here, we examined the role of angiotensin II type 1 receptor (AT1R) signaling, which is part of the renin-angiotensin system, in light-induced retinal damage. Light-exposed Balb/c mice that were treated with the AT1R blockers (angiotensin II receptor blockers; ARBs) valsartan, losartan, and candesartan before and after the light exposure exhibited attenuated visual function impairment, compared to vehicle-treated mice. This effect was dose-dependent and observed across the ARB class of inhibitors. Further evaluation of valsartan showed that it suppressed a number of light-induced retinal effects, including thinning of the photoreceptor cell layer caused by apoptosis, shortening of the photoreceptor cell outer segment, and increased levels of reactive oxygen species (ROS). The role of ROS in retinal pathogenesis was investigated further using the antioxidant N-acetyl-l-cysteine (NAC). Treatment of light-exposed mice with NAC before the light exposure suppressed the visual function impairment and photoreceptor cell histological changes due to apoptosis. Moreover, treatment with valsartan or NAC suppressed the induction of c-fos (a component of the AP-1 transcription factor) and the upregulation of fasl (a proapoptotic molecule whose transcript is regulated downstream of AP-1). Our results suggest that AT1R signaling mediates light-induced apoptosis, by increasing the levels of ROS and proapoptotic molecules in the retina. Thus, AT1R blockade may represent a new therapeutic approach for preventing light-induced retinal neural tissue damage.

Designing of multi-targeted molecules using combination of molecular screening and in silico drug cardiotoxicity prediction approaches

We have previously investigated and reported a set of phenol- and indole-based derivatives at the binding pockets of carbonic anhydrase isoenzymes using in silico and in vitro analyses. In this study, we extended our analysis to explore multi-targeted molecules from this set of compounds. Thus, 26 ligands are screened at the binding sites of 229 proteins from 5 main enzyme family classes using molecular docking algorithms. Derived docking scores are compared with reported results of ligands at carbonic anhydrase I and II isoenzymes. Results showed potency of multi-targeted drugs of a few compounds from investigated ligand set. These promising ligands are then tested in silico for their cardiotoxicity risks. Results of this work can be used to improve the desired effects of these compounds by molecular engineering studies. In addition these results may lead to further investigation of studied molecules by medicinal chemists to explore different therapeutic aims.

The angiotensin receptor blocker and PPAR-γ agonist, telmisartan, delays inactivation of voltage-gated sodium channel in rat heart: novel mechanism of drug action

Telmisartan is an angiotensin II receptor blocker and partial peroxisome proliferator-activated receptor gamma agonist that modulates the renin-angiotensin-aldosterone system. It is used primarily to manage hypertension, diabetic nephropathy, and congestive heart failure. Recent studies have reported that myocardial infarction (MI) has occurred in telmisartan-treated patients. The purpose of the study was to investigate the specific conditions and underlying mechanisms that may result in telmisartan-induced MI. We evaluated the effect of telmisartan on whole hearts, cardiomyocytes, and cardiac sarcolemmal ion channels. Hearts of 8-week-old male Sprague-Dawley rats were perfused with 3, 10, 30, or 100 μM telmisartan or losartan or with normal Tyrode's solution (control) for 3 h. We found that telmisartan induced myocardial infarction, with an infarct size of 21 % of the total at 30 μM (P < 0.0001) and 63 % of the total area at 100 μM (P < 0.001). Telmisartan also induced cardiac dysfunction (e.g., decreased heart rate, diminished coronary flow, hypercontracture, and arrhythmia). Confocal microscopy demonstrated that 30 μM telmisartan significantly elevated the intracellular Ca(2+) level, leading to hypercontracture and cell death. Patch clamp analysis of isolated cardiomyocytes revealed that telmisartan induced Na(+) overload by slowing the inactivation of voltage-gated Na(+) current (I (Na)), activating the reverse mode of Na(+)-Ca(2+) exchanger activity, and causing Ca(2+) overload. Telmisartan significantly delayed the inactivation of the voltage-gated Na(+) channel, causing cytosolic Na(+) overload, prolonged action potential duration, and subsequent Ca(2+) overload. Above 30 μM, telmisartan may potentially cause cardiac cell death and MI.