Cardioprotective effects of telmisartan against heart failure in rats induced by experimental autoimmune myocarditis through the modulation of angiotensin-converting enzyme-2/angiotensin 1-7/mas receptor axis

Molecular Insights Into SARS COV-2 Interaction With Cardiovascular Disease: Role of RAAS and MAPK Signaling

In December 2019, reports of viral pneumonia came out of Wuhan city in Hubei province in China. In early 2020, the causative agent was identified as a novel coronavirus (CoV) sharing some sequence similarity with SARS-CoV that caused the severe acute respiratory syndrome outbreak in 2002. The new virus, named SARS-CoV-2, is highly contagious and spread rapidly across the globe causing a pandemic of what became known as coronavirus infectious disease 2019 (COVID-19). Early observations indicated that cardiovascular disease (CVD) patients are at higher risk of progression to severe respiratory manifestations of COVID-19 including acute respiratory distress syndrome. Moreover, further observations demonstrated that SARS-CoV-2 infection can induce de novo cardiac and vascular damage in previously healthy individuals. Here, we offer an overview of the proposed molecular pathways shared by the pathogenesis of CVD and SARS-CoV infections in order to provide a mechanistic framework for the observed interrelation. We examine the crosstalk between the renin-angiotensin-aldosterone system and mitogen activated kinase pathways that potentially links cardiovascular predisposition and/or outcome to SARS-CoV-2 infection. Finally, we summarize the possible effect of currently available drugs with known cardiovascular benefit on these pathways and speculate on their potential utility in mitigating cardiovascular risk and morbidity in COVID-19 patients.

Interactions of coronaviruses with ACE2, angiotensin II, and RAS inhibitors-lessons from available evidence and insights into COVID-19

The rapid spread of a novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to an ongoing pandemic of coronavirus disease 2019 (COVID-19). Recently, angiotensin-converting enzyme 2 (ACE2) has been shown to be a functional receptor for SARS-CoV-2 to enter host target cells. Given that angiotensin receptor blockers (ARBs) and an ACE inhibitor (ACEI) upregulated ACE2 expression in animal studies, the concern might arise regarding whether ARBs and ACEIs would increase the morbidity and mortality of COVID-19. On the other hand, animal data suggested a potential protective effect of ARBs against COVID-19 pneumonia because an ARB prevented the aggravation of acute lung injury in mice infected with SARS-CoV, which is closely related to SARS-CoV-2. Importantly, however, there is no clinical or experimental evidence supporting that ARBs and ACEIs either augment the susceptibility to SARS-CoV-2 or aggravate the severity and outcomes of COVID-19 at present. Until further data are available, it is recommended that ARB and ACEI medications be continued for the treatment of patients with cardiovascular disease and hypertension, especially those at high risk, according to guideline-directed medical therapy based on the currently available evidence.

Olmesartan attenuates type 2 diabetes-associated liver injury: Cross-talk of AGE/RAGE/JNK, STAT3/SCOS3 and RAS signaling pathways

Olmesartan (OLM), an angiotensin receptor blocker, was tested against diabetes/insulin resistance (IR) models associated with renal/cardiovascular complications. Methods: we tested its potential role against diabetes-induced hepatic hitches using an IR/type2 diabetic (IR/D) model induced by high fat/high fructose diet for 7 weeks ​+ ​a single sub-diabetogenic dose of streptozotocin (35mg/kg; i.p). IR/D rats were orally treated with OLM (10 ​mg/kg), pioglitazone (PIO; 5 or 10 ​mg/kg) or their combinations for 4 consecutive weeks. OLM alone opposed the detrimental effects of IR/D; it significantly improved metabolic parameters, liver function, and abated hepatic oxidative stress, and inflammatory cytokine interleukin-6 (IL-6) and its upstream mediator nuclear factor kappa B. Consequently, OLM turned off the downstream cue p-Jak2/STAT3/SOCS3. Moreover, it suppressed the elevated AGE/RAGE/p-JNK pathway and increased the PPARγ/adiponectin cue to signify its anti-inflammatory and anti-oxidant capacity (GSH, MDA). Nevertheless, co-administration of OLM to PIO showed a synergistic improvement in all the aforementioned parameters in a dose dependent manner. Additionally, OLM with PIO₁₀ provoked a surge in hepatic PPARγ and adiponectin (5 and 6 folds) with a sharp decrease of about 85% in the NF-κB/IL-6/p-STAT3/SCOS3 pathway. These effects were confirmed by the histopathological study. In conclusion, OLM and its combination with PIO enhanced insulin sensitivity and guarded against hepatic complications associated with type 2 diabetes probably via modulating various inter-related pathways; namely, metabolic alteration, renin-angiotensin system, inflammatory trajectories, as well as oxidative stress. This study manifests the potential synergistic effects of OLM as an adjuvant therapy to the conventional antidiabetic therapies.

Telmisartan/17β-estradiol mitigated cognitive deficit in an ovariectomized rat model of Alzheimer's disease: Modulation of ACE1/ACE2 and AT1/AT2 ratio

AIMS

The higher incidence rate of Alzheimer's disease (AD) among women has led to explorations on the association between estrogen deficiency and AD. Also, usage of antihypertensive drugs has been suggested to reduce the incidence of AD in elderly hypertensive patients. Thus, this study aimed to investigate the effects of telmisartan and/or 17β-estradiol on a cognitively impaired ovariectomized rat model of AD.

MAIN METHODS

75 female Wistar rats were randomly allocated into five groups. One group was sham operated and the other four groups were subjected to ovariectomy, received D-galactose and either untreated or treated with telmisartan and/or 17β-estradiol for 6 weeks.

KEY FINDINGS

Ovariectomized rats showed cognitive impairment in Morris water maze and novel object recognition tests, increasing inflammatory biomarkers (tumor necrosis factor-α, and interleukin-1β), increasing AD biomarkers (amyloid beta1-42, and acetylcholine esterase), and over activation of classical arm of renin angiotensin system (RAS) (ACE1/Ang2/AT1) in hippocampi. Also, hippocampi histopathological examination revealed amyloid beta deposition. Whereas, administration of telmisartan and/or 17β-estradiol improved animals' behavior, alleviated histopathological alterations and reduced the level of inflammatory and AD biomarkers, modulated RAS activity favoring the novel neuroprotective arm (ACE2/Ang(1-7)/MasR).

SIGNIFICANCE

Our findings suggest that combined administration of both drugs has synergetic neuroprotective effects; supporting their potential application in AD treatment.

Cardiomyocyte-Specific Snrk Prevents Inflammation in the Heart

Background The SNRK (sucrose-nonfermenting-related kinase) enzyme is critical for cardiac function. However, the underlying cause for heart failure observed in Snrk cardiac conditional knockout mouse is unknown. Methods and Results Previously, 6-month adult mice knocked out for Snrk in cardiomyocytes (CMs) displayed left ventricular dysfunction. Here, 4-month adult mice, on angiotensin II (Ang II) infusion, show rapid decline in cardiac systolic function, which leads to heart failure and death in 2 weeks. These mice showed increased expression of nuclear factor κ light chain enhancer of activated B cells (NF-κB), inflammatory signaling proteins, proinflammatory proteins in the heart, and fibrosis. Interestingly, under Ang II infusion, mice knocked out for Snrk in endothelial cells did not show significant systolic or diastolic dysfunction. Although an NF-κB inflammation signaling pathway was increased in Snrk knockout endothelial cells, this did not lead to fibrosis or mortality. In hearts of adult mice knocked out for Snrk in CMs, we also observed NF-κB pathway activation in CMs, and an increased presence of Mac2+ macrophages was observed in basal and Ang II-infused states. In vitro analysis of Snrk knockdown HL-1 CMs revealed similar upregulation of the NF-κB signaling proteins and proinflammatory proteins that was exacerbated on Ang II treatment. The Ang II-induced NF-κB pathway-mediated proinflammatory effects were mediated in part through protein kinase B or AKT, wherein AKT inhibition restored the proinflammatory signaling protein levels to baseline in Snrk knockdown HL-1 CMs. Conclusions During heart failure, SNRK acts as a cardiomyocyte-specific repressor of cardiac inflammation and fibrosis.

Therapies to limit myocardial injury in animal models of myocarditis: a systematic review and meta-analysis

Current myocarditis guidelines do not advocate treatment to prevent myocardial injury and scar deposition in patients with myocarditis and normal left ventricular ejection fraction. We aimed to ascertain the utility of beta blockers, calcium channel blockers and antagonists of the renin–angiotensin system in ameliorating myocardial injury, scar formation and calcification in animal in vivo models of myocarditis. The project was prospectively registered with the PROSPERO database of systematic reviews (CRD42018089336). Primary outcomes (necrosis, fibrosis and calcification) were meta-analysed with random-effects modelling. 52 studies were systematically reviewed. Meta-analysis was performed compared with untreated controls. In each study, we identified all independent comparisons of treatment versus control groups. The pooled weighted mean difference (WMD) indicated treatment reduced necrosis by 16.9% (71 controlled analyses, 95% CI 13.2–20.7%; P < 0.001), however there was less evidence of an effect after accounting for publication bias. Treatment led to a 12.8% reduction in fibrosis (73 controlled analyses, 95% CI 7.6–18.0%; P < 0.001). After accounting for publication bias this was attenuated to 7.8% but remained significant. Treatment reduced calcification by 4.1% (28 controlled analyses, 95% CI 0.2–8.0%; P < 0.0395). We observed significant heterogeneity in effect size in all primary endpoints, which was predominantly driven by differences between drug categories. Beta blockers and angiotensin-converting enzyme (ACE) inhibitors were the only agents that were effective for both necrosis and fibrosis, while only ACE inhibitors had a significant effect on calcification. This study provides evidence for a role for ACE inhibitors and beta blockers to prevent myocardial injury and scar deposition in in vivo models of myocarditis. There is a need for further well-designed studies to assess the translational application of these treatments.

Telmisartan and captopril ameliorate pregabalin-induced heart failure in rats

Pregabalin (PRG) is highly effective in the treatment of epilepsy, neuropathic pain and anxiety disorders. Despite its potential benefits, PRG administration has been reported to induce or exacerbate heart failure (HF). It has been previously documented that overactivation of the renin angiotensin system (RAS) is involved in HF pathophysiological mechanism. The target of the current study was to examine the possible cardioprotective effect of telmisartan (Tel), an angiotensin II type 1 receptor (AT1R) blocker, compared with that of captopril (Cap), an angiotensin converting enzyme (ACE) inhibitor, in ameliorating PRG-induced HF in rats by assessing morphometric, echocardiographic and histopathological parameters. Furthermore, to investigate the role of RAS blockade by the two drugs in guarding against PRG-induced changes in cardiac angiotensin 1-7 (Ang 1-7) and angiotensin II (Ang II) levels, in addition to myocardial expression of ACE2, ACE, Mas receptor (MasR) and AT1R. Results showed that PRG administration induced morphometric, echocardiographic and histopathological deleterious alterations and significantly elevated cardiac Ang II, ACE and AT1R levels, while reduced Ang 1-7, ACE2 and MasR cardiac levels. Concurrent treatment with either Tel or Cap reversed PRG-induced morphometric, echocardiographic and histopathological abnormalities and revealed prominent protection against PRG-induced HF via downregulation of ACE/Ang II/AT1R and upregulation of ACE2/Ang 1-7/MasR axes. These are the first findings to demonstrate that the potential benefits of Tel and Cap are mediated by counteracting the altered balance between the RAS axes induced by PRG. Hence; Tel and Cap may attenuate PRG-induced HF partially through stimulation of ACE2/Ang 1-7/MasR pathway.

Angiotensin II Increases Endoplasmic Reticulum Stress in Adipose Tissue and Adipocytes

The Renin Angiotensin System (RAS), a key regulator of blood pressure has been linked to metabolic disorders. We have previously reported that adipose overexpression of angiotensinogen in mice (Agt-Tg) induces obesity, in part mediated by adipose tissue inflammation, through yet unidentified mechanisms. Hence, we hypothesize that adipose tissue enrichment of angiotensinogen leads to activation of inflammatory cascades and endoplasmic reticulum (ER) stress, thereby, contributing to obesity. We used wild type (Wt), Agt-Tg and Agt-knockout (KO) mice along with 3T3-L1 and human adipocytes treated with RAS, ER stress and inflammation inhibitors. ER stress and pro-inflammation markers were significantly higher in Agt-Tg compared to Wt mice and captopril significantly reduced their expression. Furthermore, in vitro treatment with Ang II significantly induced ER stress and inflammation, whereas angiotensin II receptor inhibitor, telmisartan reduced RAS effects. Moreover, miR-30 family had significantly lower expression in Agt-Tg group. MiR-708-5p and -143-3p were upregulated when RAS was overexpressed, and RAS antagonists reduced miR-143-3p and -708-5p in both mouse adipose tissue and adipocytes. Activation of RAS by Ang II treatment, increased inflammation and ER stress in adipocytes mainly via AT1 receptor, possibly mediated by miR-30 family, -708-5p and/or -143-3p. Hence, RAS and mediating microRNAs could be used as potential targets to reduce RAS induced obesity and related comorbid diseases.

Endoplasmic reticulum stress inhibition blunts the development of essential hypertension in the spontaneously hypertensive rat

Essential hypertension is the leading cause of premature death worldwide. However, hypertension’s cause remains uncertain. endoplasmic reticulum (ER) stress has recently been associated with hypertension, but it is unclear whether ER stress causes hypertension. To clarify this question, we examined if ER stress occurs in blood vessels before the development of hypertension and if ER stress inhibition would prevent hypertension development. We used the spontaneously hypertensive rat (SHR) as a model of human essential hypertension and the Wistar-Kyoto (WKY) rat as its normotensive control. Resistance arteries collected from young rats determined that ER stress was present in SHR vessels before the onset of hypertension. To assess the effect of ER stress inhibition on hypertension development, another subset of rats were treated with 4-phenylbutyric acid (4-PBA; 1 g·kg−1·day−1) for 8 wk from 5 wk of age. Blood pressure was measured via radiotelemetry and compared with untreated SHR and WKY rats. Mesenteric resistance arteries were collected and assessed for structural and functional changes associated with hypertension. Systolic and diastolic blood pressures were significantly lower in the 4-PBA-treated SHR groups than in untreated SHRs. Additionally, 4-PBA significantly decreased the media-to-lumen ratio and ER stress marker expression, improved vasodilatory response, and reduced contractile responses in resistance arteries from SHRs. Overall, ER stress inhibition blunted the development of hypertension in the SHR. These data add evidence to the hypothesis that a component of hypertension in the SHR is caused by ER stress.

NEW & NOTEWORTHY In this study, 4-phenylbutyric acid’s (4-PBA’s) molecular chaperone capability was used to inhibit endoplasmic reticulum (ER) stress in the small arteries of young spontaneously hypertensive rats (SHRs) and reduce their hypertension. These effects are likely mediated through 4-PBA's effects to reduce resistant artery contractility and increase nitric oxide-mediated endothelial vasodilation through a process preventing endothelial dysfunction. Overall, ER stress inhibition blunted the development of hypertension in this young SHR model. This suggests that a component of the increase in blood pressure found in SHRs is due to ER stress. However, it is important to note that inhibition of ER stress was not able to fully restore the blood pressure to normal, suggesting that a component of hypertension may not be due to ER stress. This study points to the inhibition of ER stress as an important new physiological pathway to lower blood pressure, where other known approaches may not achieve blood pressure-lowering targets.

Small molecule disruption of G protein βγ subunit signaling reprograms human macrophage phenotype and prevents autoimmune myocarditis in rats

The purpose of this study was to determine whether blocking of G protein βγ (Gβγ) signaling halts heart failure (HF) progression by macrophage phenotype manipulation. Cardiac Gβγ signaling plays a crucial role in HF pathogenesis. Previous data suggested that inhibiting Gβγ signaling reprograms T helper cell 1 (Th1) and Th2 cytokines, suggesting that Gβγ might be a useful drug target for treating HF. We investigated the efficacy of a small molecule Gβγ inhibitor, gallein, in a clinically relevant, experimental autoimmune myocarditis (EAM) model of HF as well as in human macrophage phenotypes in vitro. In the myocardium of HF patients, we observed that G protein coupled receptor kinase (GRK)2 levels were down-regulated compared with healthy controls. In rat EAM, treatment with gallein effectively improved survival and cardiac function, suppressed cardiac remodeling, and further attenuated myocardial protein expression of GRK2 as well as high mobility group box (HMGB)1 and its cascade signaling proteins. Furthermore, gallein effectively inhibited M1 polarization and promoted M2 polarization in vivo in the EAM heart and in vitro in human monocyte-derived macrophages. Taken together, these data suggest that the small molecule Gβγ inhibitor, gallein, could be an important pharmacologic therapy for HF as it can switch the phenotypic reprogramming from M1 to M2 phenotype in a rat model of EAM heart and in human macrophages.

Angiotensin-(1-7)/Mas receptor as an antinociceptive agent in cancer-induced bone pain

Many cancerous solid tumors metastasize to the bone and induce pain (cancer-induced bone pain [CIBP]). Cancer-induced bone pain is often severe because of enhanced inflammation, rapid bone degradation, and disease progression. Opioids are prescribed to manage this pain, but they may enhance bone loss and increase tumor proliferation, further compromising patient quality of life. Angiotensin-(1-7) (Ang-(1-7)) binds and activates the Mas receptor (MasR). Angiotensin-(1-7)/MasR activation modulates inflammatory signaling after acute tissue insult, yet no studies have investigated whether Ang-(1-7)/MasR play a role in CIBP. We hypothesized that Ang-(1-7) inhibits CIBP by targeting MasR in a murine model of breast CIBP. 66.1 breast cancer cells were implanted into the femur of BALB/cAnNHsd mice as a model of CIBP. Spontaneous and evoked pain behaviors were assessed before and after acute and chronic administration of Ang-(1-7). Tissues were collected from animals for ex vivo analyses of MasR expression, tumor burden, and bone integrity. Cancer inoculation increased spontaneous pain behaviors by day 7 that were significantly reduced after a single injection of Ang-(1-7) and after sustained administration. Preadministration of A-779 a selective MasR antagonist prevented this reduction, whereas pretreatment with the AT2 antagonist had no effect; an AT1 antagonist enhanced the antinociceptive activity of Ang-(1-7) in CIBP. Repeated Ang-(1-7) administration did not significantly change tumor burden or bone remodeling. Data here suggest that Ang-(1-7)/MasR activation significantly attenuates CIBP, while lacking many side effects seen with opioids. Thus, Ang-(1-7) may be an alternative therapeutic strategy for the nearly 90% of patients with advanced-stage cancer who experience excruciating pain.

Loss of angiotensin converting enzyme II (ACE2) accelerates the development of liver injury induced by thioacetamide

Angiotensin converting enzyme II (ACE2), an angiotensin converting enzyme (ACE) homologue that displays antagonist effects on ACE/angiotensin II (Ang II) axis in renin-angiotensin system (RAS), could play a protective role against liver damages. The purpose of this study is to investigate whether inflammation-mediated liver injury could be affected by ACE2 derived pathways in the RAS. Eight-weeks-old wild-type (WT; C57BL/6) and Ace2 KO (hemizygous Ace2^-/y) male mice were used to induce liver fibrosis by thioacetamide (TAA) administration (0, 100, and 200 mg/kg BW). The mice administrated with TAA could be successfully induced liver fibrosis in a TAA-dose dependent manner. Compared to WT mice, the results show that Ace2 KO mice have high sensitive, and developed more serious reaction of hepatic inflammation and fibrosis by TAA administration. The physiological and pathological examinations demonstrated higher serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) and alkaline phosphatase (ALP) levels, infiltration of white blood cells and fibrotic lesions within liver in the Ace2 KO mice. The severe liver damage of Ace2 KO mice were also confirmed by the evidence of higher expression of hepatic inflammation-related genes (IL-6 and Tnf) and fibrosis-related genes (Col1a1, Timp1 and Mmp9). Ace2 gene deficiency could lead to a severe inflammation and collagen remodeling in the liver administrated by TAA, and the responses lead the pathogenesis of liver fibrosis. Our studies provided the main messages and favorable study directions of relationship of Ace2 and liver disease.

AAV8-Mediated Angiotensin-Converting Enzyme 2 Gene Delivery Prevents Experimental Autoimmune Uveitis by Regulating MAPK, NF-κB and STAT3 Pathways

Renin angiotensin system (RAS) is a key hormonal system which regulates the cardiovascular function and is implicated in several autoimmune diseases. With the discovery of the angiotensin-converting enzyme 2 (ACE2), a protective axis of RAS namely ACE2/Ang-(1-7)/Mas that counteracts the deleterious ACE/AngII/AT1R axis has been established. This axis is emerging as a novel target to attenuate ocular inflammation. However, the underlying molecular mechanisms remain unclear. We investigated the hypothesis that enhancing the activity of the protective axis of RAS by subretinal delivery of an AAV8 (Y733F)-ACE2 vector would protect against the ocular inflammation in experimental autoimmune uveitis (EAU) mice through regulating the local immune responses. Our studies demonstrated that increased ACE2 expression exerts protective effects on inflammation in EAU mouse by modulating ocular immune responses, including the differentiation of Th1/Th17 cells and the polarization of M1/M2 macrophages; whereas the systemic immune responses appeared not affected. These effects were mediated by activating the Ang-(1-7)/Mas and inhibiting the MAPK, NF-κB and STAT3 signaling pathways. This proof-of-concept study suggests that activation of ocular ACE2/Ang-(1-7)/Mas axis with AAV gene transfer modulates local immune responses and may be a promising, long-lasting therapeutic strategy for refractory and recurrent uveitis, as well as other inflammatory eye diseases.

Angiotensin-converting enzyme 2 prevents lipopolysaccharide-induced rat acute lung injury via suppressing the ERK1/2 and NF-κB signaling pathways

Acute respiratory distress syndrome (ARDS) caused by severe sepsis remains a major challenge in intensive care medicine. ACE2 has been shown to protect against lung injury. However, the mechanisms of its protective effects on ARDS are largely unknown. Here, we report that ACE2 prevents LPS-induced ARDS by inhibiting MAPKs and NF-κB signaling pathway. Lentiviral packaged Ace2 cDNA or Ace2 shRNA was intratracheally administrated into the lungs of male SD rats. Two weeks after gene transfer, animals received LPS (7.5 mg/Kg) injection alone or in combination with Mas receptor antagonist A779 (10 μg/Kg) or ACE2 inhibitor MLN-4760 (1 mg/Kg) pretreatment. LPS-induced lung injury and inflammatory response were significantly prevented by ACE2 overexpression and deteriorated by Ace2 shRNA. A779 or MLN-4760 pretreatment abolished the protective effects of ACE2. Moreover, overexpression of ACE2 significantly reduced the Ang II/Ang-(1-7) ratio in BALF and up-regulated Mas mRNA expression in lung, which was reversed by A779. Importantly, the blockade of ACE2 on LPS-induced phosphorylation of ERK1/2, p38 and p50/p65 was also abolished by A779. Whereas, only the ERK1/2 inhibitor significantly attenuated lung injury in ACE2 overexpressing rats pretreated with A779. Our observation suggests that AEC2 attenuates LPS-induced ARDS via the Ang-(1-7)/Mas pathway by inhibiting ERK/NF-κB activation.

Telmisartan Ameliorates Nephropathy in Metabolic Syndrome by Reducing Leptin Release From Perirenal Adipose Tissue

Metabolic syndrome (MetS) is associated with nephropathy. Along with common risk factors such as hypertension and hyperglycemia, adipocytokines released from perirenal adipose tissue (PRAT) are implicated in the pathogenesis of MetS nephropathy. The study was designed to elucidate the adverse effects of PRAT-derived leptin on nephropathy and to determine whether the angiotensin II type 1 receptor antagonist telmisartan exerts a renoprotective effect by decreasing the PRAT-derived leptin level in the high-fat diet-induced MetS rat. In MetS rats, PRAT-derived leptin expression increased concomitant with dysfunction of adipogenesis, and the activities of the angiotensin II-angiotensin II type 1 receptor and the angiotensin-converting enzyme 2-angiotensin (1-7)-Mas receptor axes were imbalanced in PRAT. PRAT-derived leptin from MetS rats promoted proliferation of rat glomerular endothelial cells (GERs) by activating the p38 MAPK (mitogen-activated protein kinase) pathway, thereby contributing to the development of nephropathy. Long-term telmisartan treatment improved metabolic parameters and renal function, decreased the amount of PRAT, promoted adipogenesis, increased the expression of angiotensin-converting enzyme 2, restored balanced activities of the angiotensin II-AT1R and angiotensin-converting enzyme 2-angiotensin (1-7)-Mas axes, and exerted an indirect renoprotective effect on MetS rats by decreasing PRAT-derived leptin release. Our results demonstrate a novel link between nephropathy and PRAT in MetS and show that telmisartan confers an underlying protective effect on visceral adipose tissue and the kidney, suggesting that it has potential as a therapeutic agent for the treatment of MetS-associated nephropathy.

The effects of different angiotensin II type 1 receptor blockers on the regulation of the ACE-AngII-AT1 and ACE2-Ang(1-7)-Mas axes in pressure overload-induced cardiac remodeling in male mice

Angiotensin II (AngII) type 1 receptor blockers (ARBs) have been effectively used in hypertension and cardiac remodeling. However, the differences among them are still unclear. We designed this study to examine and compare the effects of several ARBs widely used in clinics, including Olmesartan, Candesartan, Telmisartan, Losartan, Valsartan and Irbesartan, on the ACE-AngII-AT1 axis and the ACE2-Ang(1-7)-Mas axis during the development of cardiac remodeling after pressure overload. Although all of the six ARBs, attenuated the development of cardiac hypertrophy and heart failure induced by transverse aortic constriction (TAC) for 2 or 4weeks in the wild-type mice evaluated by echocardiography and hemodynamic measurements, the degree of attenuation by Olmesartan, Candesartan and Losartan tended to be larger than that of the other three drugs tested. Additionally, the degree of downregulation of the ACE-AngII-AT1 axis and upregulation of the ACE2-Ang(1-7)-Mas axis was higher in response to Olmesartan, Candesartan and Losartan administration in vivo and in vitro. Moreover, in angiotensinogen-knockdown mice, TAC-induced cardiac hypertrophy and heart failure were inhibited by Olmesartan, Candesartan and Losartan but not by Telmisartan, Valsartan and Irbesartan administration. Furthermore, only Olmesartan and Candesartan could downregulate the ACE-AngII-AT1 axis and upregulate the ACE2-Ang(1-7)-Mas axis in vitro. Our data suggest that Olmesartan, Candesartan and Losartan could effectively inhibit pressure overload-induced cardiac remodeling even when with knockdown of Ang II, possibly through upregulation of the expression of the ACE2-Ang(1-7)-Mas axis and downregulation of the expression of the ACE-AngII-AT1 axis. In contrast, Telmisartan, Valsartan and Irbesartan only played a role in the presence of AngII, and Losartan had no effect in the presence of AngII in vitro.

Angiotensin II type 1 receptor antagonists in animal models of vascular, cardiac, metabolic and renal disease

We have reviewed the effects of angiotensin II type 1 receptor antagonists (ARBs) in various animal models of hypertension, atherosclerosis, cardiac function, hypertrophy and fibrosis, glucose and lipid metabolism, and renal function and morphology. Those of azilsartan and telmisartan have been included comprehensively whereas those of other ARBs have been included systematically but without intention of completeness. ARBs as a class lower blood pressure in established hypertension and prevent hypertension development in all applicable animal models except those with a markedly suppressed renin-angiotensin system; blood pressure lowering even persists for a considerable time after discontinuation of treatment. This translates into a reduced mortality, particularly in models exhibiting marked hypertension. The retrieved data on vascular, cardiac and renal function and morphology as well as on glucose and lipid metabolism are discussed to address three main questions: 1. Can ARB effects on blood vessels, heart, kidney and metabolic function be explained by blood pressure lowering alone or are they additionally directly related to blockade of the renin-angiotensin system? 2. Are they shared by other inhibitors of the renin-angiotensin system, e.g. angiotensin converting enzyme inhibitors? 3. Are some effects specific for one or more compounds within the ARB class? Taken together these data profile ARBs as a drug class with unique properties that have beneficial effects far beyond those on blood pressure reduction and, in some cases distinct from those of angiotensin converting enzyme inhibitors. The clinical relevance of angiotensin receptor-independent effects of some ARBs remains to be determined.

ACE inhibition, ACE2 and angiotensin-(1-7) axis in kidney and cardiac inflammation and fibrosis

The Renin Angiotensin System (RAS) is a pivotal physiological regulator of heart and kidney homeostasis, but also plays an important role in the pathophysiology of heart and kidney diseases. Recently, new components of the RAS have been discovered, including angiotensin converting enzyme 2 (ACE2), Angiotensin(Ang)-(1-7), Mas receptor, Ang-(1-9) and Alamandine. These new components of RAS are formed by the hydrolysis of Ang I and Ang II and, in general, counteract the effects of Ang II. In experimental models of heart and renal diseases, Ang-(1-7), Ang-(1-9) and Alamandine produced vasodilation, inhibition of cell growth, anti-thrombotic, anti-inflammatory and anti-fibrotic effects. Recent pharmacological strategies have been proposed to potentiate the effects or to enhance the formation of Ang-(1-7) and Ang-(1-9), including ACE2 activators, Ang-(1-7) in hydroxypropyl β-cyclodextrin, cyclized form of Ang-(1-7) and nonpeptide synthetic Mas receptor agonists. Here, we review the role and effects of ACE2, ACE2 activators, Ang-(1-7) and synthetic Mas receptor agonists in the control of inflammation and fibrosis in cardiovascular and renal diseases and as counter-regulators of the ACE-Ang II-AT1 axis. We briefly comment on the therapeutic potential of the novel members of RAS, Ang-(1-9) and alamandine, and the interactions between classical RAS inhibitors and new players in heart and kidney diseases.

Myofibroblast secretome and its auto-/paracrine signaling

Myofibroblasts (myoFb) are phenotypically transformed, contractile fibroblast-like cells expressing α-smooth muscle actin microfilaments. They are integral to collagen fibrillogenesis with scar tissue formation at sites of repair irrespective of the etiologic origins of injury or tissue involved. MyoFb can persist long after healing is complete, where their ongoing turnover of collagen accounts for a progressive structural remodeling of an organ (a.k.a. fibrosis, sclerosis or cirrhosis). Such persistent metabolic activity is derived from a secretome consisting of requisite components in the de novo generation of angiotensin (Ang) II. Autocrine and paracrine signaling induced by tissue AngII is expressed via AT1 receptor ligand binding to respectively promote: i) regulation of myoFb collagen synthesis via the fibrogenic cytokine TGF-β1-Smad pathway; and ii) dedifferentiation and protein degradation of atrophic myocytes immobilized and ensnared by fibrillar collagen at sites of scarring. Several cardioprotective strategies in the prevention of fibrosis and involving myofibroblasts are considered. They include: inducing myoFb apoptosis through inactivation of antiapoptotic proteins; AT1 receptor antagonist to interfere with auto-/paracrine myoFb signaling or to induce counterregulatory expression of ACE2; and attacking the AngII-AT1R-TGF-β1-Smad pathway by antibody or the use of triplex-forming oligonucleotides.

Alternative Roles of STAT3 and MAPK Signaling Pathways in the MMPs Activation and Progression of Lung Injury Induced by Cigarette Smoke Exposure in ACE2 Knockout Mice

Inflammation-mediated abnormalities in the renin-angiotensin system (RAS) and expression of matrix metalloproteinases (MMPs) are implicated in the pathogenesis of lung injury. Angiotensin converting enzyme II (ACE2), an angiotensin converting enzyme (ACE) homologue that displays antagonist effects on ACE/angiotensin II (Ang II) axis, could also play a protective role against lung diseases. However, the relationship between ACE2 and MMPs activation in lung injury is still largely unclear. The purpose of this study is to investigate whether MMPs activity could be affected by ACE2 and which ACE2 derived signaling pathways could be also involved via using a mouse model with lung injury induced by cigarette smoke (CS) exposure for 1 to 3 weeks. Wild-type (WT; C57BL/6) and ACE2 KO mice (ACE2^-/-) were utilized to study CS-induced lung injury. Increases in the resting respiratory rate (RRR), pulmonary immunokines, leukocyte infiltration and bronchial hyperplasia were observed in the CS-exposed mice. Compared to WT mice, more serious physiopathological changes were found in ACE2^-/- mice in the first week of CS exposure. CS exposure increased pulmonary ACE and ACE2 activities in WT mice, and significantly increased ACE in ACE2^-/- mice. Furthermore, the activity of pulmonary MMPs was decreased in CS-exposed WT mice, whereas this activity was increased in ACE2^-/- mice. CS exposure increased the pulmonary p-p38, p-JNK and p-ERK1/2 level in all mice. In ACE2^-/- mice, a significant increase p-STAT3 signaling was detected; however, no effect was observed on the p-STAT3 level in WT mice. Our results support the hypothesis that ACE2 deficiency influences MMPs activation and STAT3 phosphorylation signaling to promote more pulmonary inflammation in the development of lung injury.

Methods for Testing Immunological Factors

Hypersensitivity reactions can be elicited by various factors: either immunologically induced, i.e., allergic reactions to natural or synthetic compounds mediated by IgE, or non-immunologically induced, i.e., activation of mediator release from cells through direct contact, without the induction of, or the mediation through immune responses. Mediators responsible for hypersensitivity reactions are released from mast cells. An important preformed mediator of allergic reactions found in these cells is histamine. Specific allergens or the calcium ionophore 48/80 induce release of histamine from mast cells. The histamine concentration can be determined with the o-phthalaldehyde reaction.

Effects of telmisartan and linagliptin when used in combination on blood pressure and oxidative stress in rats with 2-kidney-1-clip hypertension

OBJECTIVE

To investigate the effects of linagliptin alone and in combination with the angiotensin II receptor blocker (ARB), telmisartan on blood pressure (BP), kidney function, heart morphology and oxidative stress in rats with renovascular hypertension.

METHODS

Fifty-seven male Wistar rats underwent unilateral surgical stenosis of the renal artery [2-kidney-1-clip (2k1c) method]. Animals were randomly divided into four treatment groups (n = 14-18 per group) receiving: telmisartan (10 mg/kg per day in drinking water), linagliptin (89 ppm in chow), combination (linagliptin 89 ppm + telmisartan 10 mg/kg per day) or placebo. An additional group of 12 rats underwent sham surgery. BP was measured one week after surgery. Hypertensive animals entered a 16-week dosing period. BP was measured 2, 4, 8, 12 and 16 weeks after the initiation of treatment. Blood and urine were tested for assessment of kidney function and oxidative stress 6, 10, 14 and 18 weeks after surgery. Blood and urine sampling and organ harvesting were finally performed.

RESULTS

Renal stenosis caused an increase in mean ± SD systolic BP as compared with the sham group (157.7 ± 29.3 vs. 106.2 ± 20.5 mmHg, respectively; P < 0.001). Telmisartan alone and in combination with linagliptin, normalized SBP (111.1 ± 24.3 mmHg and 100.4 ± 13.9 mmHg, respectively; P < 0.001 vs. placebo). Telmisartan alone and in combination with linagliptin significantly prevented cardiac hypertrophy, measured by heart weight and myocyte diameter. Renal function measured by cystatin C was not affected by 2k1c surgery. Telmisartan significantly increased plasma concentration of cystatin C. 2k1c surgery initiated fibrosis in both kidneys. Telmisartan promoted further fibrotic changes in the clipped kidney, as measured by protein expression of Col1a1 and histology for interstitial fibrosis and glomerulosclerosis. In non-clipped kidneys, telmisartan demonstrated antifibrotic properties, reducing Col1a1 protein expression. Plasma levels of oxidized low-density lipoprotein were higher in the placebo-treated 2k1c rats as compared to sham-operated animals. The increase was abolished by linagliptin alone (P = 0.03 vs. placebo) and in combination with telmisartan (P = 0.02 vs. placebo). Combination therapy also significantly reduced plasma concentration of carbonyl proteins (P = 0.04 vs. placebo).

CONCLUSION

Inhibition of type 4 dipeptidyl peptidase with linagliptin did not counter BP-lowering effects of ARB in 2k1c rats. Linagliptin reduced lipid and protein oxidation in 2k1c rats, and this effect was BP-independent.

Mas receptor deficiency exacerbates lipopolysaccharide-induced cerebral and systemic inflammation in mice

Beyond the classical actions of the renin-angiotensin system on the regulation of cardiovascular homeostasis, several studies have shown its involvement in acute and chronic inflammation. The G protein-coupled receptor Mas is a functional binding site for the angiotensin-(1-7); however, its role in the immune system has not been fully elucidated. In this study, we evaluated the effect of genetic deletion of Mas receptor in lipopolysaccharide (LPS)-induced systemic and cerebral inflammation in mice. Inflammatory response was triggered in Mas deficient (Mas(-/-)) and C57BL/6 wild-type (WT) mice (8-12 weeks-old) by intraperitoneal injection of LPS (5 mg/kg). Mas(-/-) mice presented more intense hypothermia compared to WT mice 24 h after LPS injection. Systemically, the bone marrow of Mas(-/-) mice contained a lower number of neutrophils and monocytes 3 h and 24 h after LPS injection, respectively. The plasma levels of inflammatory mediators KC, MCP-1 and IL-10 were higher in Mas(-/-) mice 24 h after LPS injection in comparison to WT. In the brain, Mas(-/-) animals had a significant increase in the number of adherent leukocytes to the brain microvasculature compared to WT mice, as well as, increased number of monocytes and neutrophils recruited to the pia-mater. The elevated number of adherent leukocytes on brain microvasculature in Mas(-/-) mice was associated with increased expression of CD11b - the alpha-subunit of the Mac-1 integrin - in bone marrow neutrophils 3h after LPS injection, and with increased brain levels of chemoattractants KC, MIP-2 and MCP-1, 24 h later. In conclusion, we demonstrated that Mas receptor deficiency results in exacerbated inflammation in LPS-challenged mice, which suggest a potential role for the Mas receptor as a regulator of systemic and brain inflammatory response induced by LPS.

Angiotensin-converting enzyme 2/angiotensin-(1-7)/Mas axis prevents lipopolysaccharide-induced apoptosis of pulmonary microvascular endothelial cells by inhibiting JNK/NF-κB pathways

ACE2 and Ang–(1–7) have important roles in preventing acute lung injury. However, it is not clear whether upregulation of the ACE2/Ang–(1–7)/Mas axis prevents LPS–induced injury in pulmonary microvascular endothelial cells (PMVECs) by inhibiting the MAPKs/NF–κB pathways. Primary cultured rat PMVECs were transduced with lentiviral–borne Ace2 or shRNA–Ace2, and then treated or not with Mas receptor blocker (A779) before exposure to LPS. LPS stimulation resulted in the higher levels of AngII, Ang–(1–7), cytokine secretion, and apoptosis rates, and the lower ACE2/ACE ratio. Ace2 reversed the ACE2/ACE imbalance and increased Ang–(1–7) levels, thus reducing LPS–induced apoptosis and inflammation, while inhibition of Ace2 reversed all these effects. A779 abolished these protective effects of Ace2. LPS treatment was associated with activation of the ERK, p38, JNK, and NF–κB pathways, which were aggravated by A779. Pretreatment with A779 prevented the Ace2–induced blockade of p38, JNK, and NF–κB phosphorylation. However, only JNK inhibitor markedly reduced apoptosis and cytokine secretion in PMVECs with Ace2 deletion and A779 pretreatment. These results suggest that the ACE2/Ang–(1–7)/Mas axis has a crucial role in preventing LPS–induced apoptosis and inflammation of PMVECs, by inhibiting the JNK/NF–κB pathways.

Angiotensin-(1-7): A Novel Peptide to Treat Hypertension and Nephropathy in Diabetes?

The renin-angiotensin system (RAS) plays a pivotal role in mammalian homeostasis physiology. The RAS can be delineated into a classical RAS (the pressor arm) including angiotensinogen (Agt), renin, angiotensin-converting enzyme (ACE), angiotensin II (Ang II) and angiotensin type 1 receptor (AT1R), and a counterbalancing novel RAS (the depressor arm) including Agt, renin, angiotensin-converting enzyme-2 (ACE-2), angiotensin-(1-7) (Ang 1-7) and Ang 1-7 receptor (or Mas receptor (MasR)). Hyperglycemia (diabetes) induces severe tissue oxidative stress, which stimulates the pressor arm of the renal RAS axis and leads to an increase in ACE/ACE-2 ratio, with excessive formation of Ang II. There is a growing body of evidence for beneficial effects of the depressor arm of RAS (ACE-2/Ang 1-7/MasR) axis in diabetes, hypertension and several other diseased conditions. Evidence from in vitro, in vivo and clinical studies reflects anti-oxidant, anti-fibrotic, and anti-inflammatory properties of Ang 1-7. Most of the currently available therapies only target suppression of the pressor arm of RAS with angiotensin receptor blockers (ARBs) and ACE inhibitors (ACEi). However, it is time to consider simultaneous activation of the depressor arm for more effective outcomes. This review summarizes the recent updates on the protective role of Ang 1-7 in hypertension and kidney injury in diabetes, as well as the possible underlying mechanism(s) of Ang 1-7 action, suggesting that the ACE-2/Ang 1-7/MasR axis can be developed as a therapeutic target for the treatment of diabetes-induced hypertension and renal damage.

Protective effects of angiotensin-(1-7) administrated with an angiotensin-receptor blocker in a rat model of chronic kidney disease

AIM

Angiotensin-(1-7) (Ang-(1-7)) opposes angiotensin-II-induced cell growth, matrix accumulation and fibrosis in cardiac tissue. However, the role of Ang-(1-7) in the pathogenesis of renal fibrosis is uncertain. This study observed the effects of Ang-(1-7), on its own or in combination with losartan, an angiotensin-receptor blocker, on five-sixths nephrectomized rats.

METHODS

Male Sprague-Dawley rats underwent five-sixths nephrectomy, and then were either untreated, treated with Ang-(1-7), treated with losartan, or treated with a combination therapy of Ang-(1-7) and losartan. After 8 weeks, renal function was assessed by measuring systolic blood pressure, serum creatinine and proteinuria. The effect of nephrectomy on the renin-angiotensin system was examined by measuring plasma levels of Ang-II and Ang-(1-7). The extent of glomerulosclerosis and tubulointerstitial fibrosis was assessed by periodic acid-Schiff staining and Masson-trichrome staining. The expression of plasminogen activator inhibitor-1, fibronectin and angiopoietins-Tie-2 was investigated by immunohistochemistry and western blot.

RESULTS

In the groups of treated rats, serum creatinine, proteinuria and markers of glomerulosclerosis, such as fibronectin and plasminogen activator inhibitor-1, were ameliorated compared with the untreated, nephrectomized rats. Plasma Ang-(1-7) levels were elevated in all treatment groups, but the plasma Ang-II levels were reduced in the Ang-(1-7)-treated group and the combination therapy group. The ratio of Ang-1/Ang-2 was increased in the combination therapy group compared with two other treatment groups.

CONCLUSION

Ang-(1-7) ameliorated the renal injury of nephrectomized rats. The combination of Ang-(1-7) treatment alongside losartan exerted a superior effect to that of Ang-(1-7) alone on regression of glomerulosclerosis.

PI3K/AKT signaling pathway plays a role in enhancement of eNOS activity by recombinant human angiotensin converting enzyme 2 in human umbilical vein endothelial cells

The aim of this study was to investigate the effect of PI3K/AKT signaling pathway in the activity of recombinant human angiotensin converting enzyme 2 (rhACE2) promoted the activity of endothelial nitric oxide synthase (eNOS). The human umbilical vein endothelial cells (HUVEC) were cultured in vitro. Then treated with Ang II (1×10(-6) mol/L) for 24 h. The rhACE2 (100 μmol/L) was added and incubated for 5, 10, 15, 30, 60 min respectively which was based on Ang II intervention. The effect of rhACE2 on phosphorylation eNOS level was also observed in the presence of LY294002 (10 μmol/L) (PI3K/AKT inhibitors). Griess reagent method was applied to measure NO contents in cell culture supernatant, RT-PCR to detect the expression of eNOSmRNA in HUVEC, and Western blot to detect the expression of eNOS and phosphorylated eNOS. In Ang II intervention group, NO contents were significantly lower than control group (P < 0.05). Through rhACE2 treatment, the NO contents in cell culture medium and the expression level of phosphorylated eNOS were significantly higher than in Ang II intervention group (P < 0.05), but eNOSmRNA and non-phosphorylated eNOS protein expression level showed no significant difference (P > 0.05). After HUVEC was intervened by PI3K/AKT pathway inhibitor LY294002, the expression level of phosphorylated eNOS was significantly lower than that in the rhACE2 30 min treatment group (P < 0.05). rhACE2 may reduce the activity of Ang II inhibited endothelial cell eNOS, which can be blocked by PI3K/AKT pathway inhibitor LY294002, suggesting PI3K/AKT signaling pathway plays an important role in rhACE2's promotion of the activity of endothelial cell eNOS.

ACE2, angiotensin-(1-7) and Mas receptor axis in inflammation and fibrosis

Recent advances have improved our understanding of the renin-angiotensin system (RAS). These have included the recognition that angiotensin (Ang)-(1-7) is a biologically active product of the RAS cascade. The identification of the ACE homologue ACE2, which forms Ang-(1-7) from Ang II, and the GPCR Mas as an Ang-(1-7) receptor have provided the necessary biochemical and molecular background and tools to study the biological significance of Ang-(1-7). Most available evidence supports a counter-regulatory role for Ang-(1-7) by opposing many actions of Ang II on AT₁ receptors, especially vasoconstriction and proliferation. Many studies have now shown that Ang-(1-7) by acting via Mas receptor exerts inhibitory effects on inflammation and on vascular and cellular growth mechanisms. Ang-(1-7) has also been shown to reduce key signalling pathways and molecules thought to be relevant for fibrogenesis. Here, we review recent findings related to the function of the ACE2/Ang-(1-7)/Mas axis and focus on the role of this axis in modifying processes associated with acute and chronic inflammation, including leukocyte influx, fibrogenesis and proliferation of certain cell types. More attention will be given to the involvement of the ACE2/Ang-(1-7)/Mas axis in the context of renal disease because of the known relevance of the RAS for the function of this organ and for the regulation of kidney inflammation and fibrosis. Taken together, this knowledge may help in paving the way for the development of novel treatments for chronic inflammatory and renal diseases.

Autocrine and paracrine function of Angiotensin 1-7 in tissue repair during hypertension

BACKGROUND

Angiotensin-converting enzyme 2 (ACE2) cleaves angiotensin (Ang) II to generate Ang1-7, which mediates cellular actions through Mas receptors (MasR). Hypertension is accompanied by high or low circulating AngII levels and cardiac/renal injury. The purpose of this study is to explore (i) whether circulating AngII affects ACE2/MasR expressions in the hypertensive heart and kidney; and (ii) whether Ang1-7 regulates cardiac repair/remodeling responses through MasR during hypertension.

METHODS

In the first portion of the study, rats received either an AngII infusion (400ng/kg/min) for 4 weeks, leading to hypertension with high circulating AngII, or an aldosterone (ALDO, 0.75 μg/h) infusion for 4 weeks, leading to hypertension with low/normal circulating AngII. Cardiac and renal ACE2/MasR expressions were examined. We found that cardiac ACE2 was increased and MasR attenuated in both AngII and ALDO groups. However, renal ACE2 and MasR remained unchanged in both AngII- and ALDO-treated animals.

RESULTS

In the second portion, rats received AngII infusion with/without MasR antagonist (A779, 1mg/kg/day) for 4 weeks. The roles of MasR blockade in cardiac inflammation, fibrosis, apoptosis, and ventricular function were examined. Chronic AngII infusion caused scattered cardiac injuries, and A779 cotreatment exacerbated cardiac injury, resulting in aggravated inflammatory, fibrogenic, and apoptotic responses compared with the AngII group. Cardiac function, however, was unaltered in the AngII and A779 groups.

CONCLUSIONS

ACE2 and MasR expressions in the hypertensive heart and kidney are not regulated by circulating AngII levels. Ang1-7 is involved in multiple repair responses, suggesting that therapeutic strategies aimed at administering Ang1-7 hold potential for the management of cardiac remodeling.

Angiotensin-converting enzyme 2 (ACE2) activator diminazene aceturate ameliorates endotoxin-induced uveitis in mice

PURPOSE

Uveitis is a common cause of vision loss. The renin angiotensin system (RAS), which plays a vital role in cardiovascular system, is a potent mediator of inflammation and has been implicated in the pathogenesis of uveitis. A newly identified axis of RAS, ACE2/Ang-(1-7)/Mas, has emerged as a novel target because it counteracts the deleterious effect of angiotensin II. The purpose of this study was to investigate the effect of endogenous ACE2 activation in preventing endotoxin-induced uveitis (EIU) in mice.

METHODS

ACE2 activator diminazene aceturate (DIZE) was administered both systemically and locally. For systemic administration, female BALB/c mice received intraperitoneal injection of DIZE (60 mg/kg body weight [BW]) for 2 days prior to lipopolysaccharide (LPS) intravitreal injection (125 ng) to induce uveitis. For local study, DIZE was given at 0.5, 0.1, and 0 mg/mL as eyedrops six times per day for 2 days before LPS injection. The anterior segment of the mice was examined at 12, 24, 48, and 72 hours after LPS injection, and clinical scores were determined at the same time. Morphology and infiltrating inflammatory cells were evaluated after 24 hours. The mRNA levels of inflammatory cytokines were analyzed by real-time RT-PCR. ACE2 activity was determined using a self-quenching fluorescent substrate.

RESULTS

At 24 hours, the clinical score of mice treated with DIZE systemically was significantly lower (mean, ∼1.75) than the saline vehicle group (mean, ∼4) (P < 0.001). Histological examination showed 63.4% reduction of infiltrating inflammatory cells in the anterior segment and 57.4% reduction in the posterior segment of DIZE-treated eyes. The number of CD45(+) inflammatory cells in the vitreous of the DIZE-treated group was decreased (43.3%) compared to the vehicle group (P < 0.01). The mRNA levels of inflammatory cytokines were significantly reduced in the DIZE-treated group (P < 0.01, P < 0.001). The number of infiltrating inflammatory cells was also significantly reduced in eyes that received topical administration of DIZE: 73.8% reduction in the 0.5 mg/mL group and 51.7% reduction in the 0.1mg/mL group compared to the control group. DIZE treatment resulted in significantly increased ACE2 activity in the retina (P < 0.001).

CONCLUSIONS

Endogenous ACE2 activation by DIZE has a preventive effect on LPS-induced ocular inflammation in the EIU mouse model. These results support the notions that RAS plays a role in modulating ocular immune response and that enhancing ACE2 provides a novel therapeutic strategy for uveitis.

Telmisartan attenuates colon inflammation, oxidative perturbations and apoptosis in a rat model of experimental inflammatory bowel disease

Accumulating evidence has indicated the implication of angiotensin II in the pathogenesis of inflammatory bowel diseases (IBD) via its proinflammatory features. Telmisartan (TLM) is an angiotensin II receptor antagonist with marked anti-inflammatory and antioxidant actions that mediated its cardio-, reno- and hepatoprotective actions. However, its impact on IBD has not been previously explored. Thus, we aimed to investigate the potential alleviating effects of TLM in tri-nitrobenezene sulphonic acid (TNBS)-induced colitis in rats. Pretreatment with TLM (10 mg/kg p.o.) attenuated the severity of colitis as evidenced by decrease of disease activity index (DAI), colon weight/length ratio, macroscopic damage, histopathological findings and leukocyte migration. TLM suppressed the inflammatory response via attenuation of tumor necrosis factor-α (TNF-α), prostaglandin E₂ (PGE₂) and myeloperoxidase (MPO) activity as a marker of neutrophil infiltration besides restoration of interleukin-10 (IL-10). TLM also suppressed mRNA and protein expression of nuclear factor kappa B (NF-κB) p65 and mRNA of cyclo-oxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) proinflammatory genes with concomitant upregulation of PPAR-γ. The alleviation of TLM to colon injury was also associated with inhibition of oxidative stress as evidenced by suppression of lipid peroxides and nitric oxide (NO) besides boosting glutathione (GSH), total anti-oxidant capacity (TAC) and the activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). With respect to apoptosis, TLM downregulated the increased mRNA, protein expression and activity of caspase-3. It also suppressed the elevation of cytochrome c and Bax mRNA besides the upregulation of Bcl-2. Together, these findings highlight evidences for the beneficial effects of TLM in IBD which are mediated through modulation of colonic inflammation, oxidative stress and apoptosis.

ACE2: angiotensin II/angiotensin-(1-7) balance in cardiac and renal injury

Our current recognition of the renin-angiotensin system is more convoluted than originally thought due to the discovery of multiple novel enzymes, peptides, and receptors inherent in this interactive biochemical cascade. Over the last decade, angiotensin-converting enzyme 2 (ACE2) has emerged as a key player in the pathophysiology of hypertension and cardiovascular and renal disease due to its pivotal role in metabolizing vasoconstrictive/hypertrophic/proliferative angiotensin II into favorable angiotensin-(1-7). This review addresses the considerable advancement in research on the role of tissue ACE2 in the development and progression of hypertension and cardiac and renal injury. We summarize the results from recent clinical and experimental studies suggesting that serum or urine soluble ACE2 may serve as a novel biomarker or independent risk factor relevant for diagnosis and prognosis of cardiorenal disease. We also review recent proceedings on novel therapeutic approaches to enhance ACE2/angiotensin-(1-7) axis.

Mechanisms of the anti-inflammatory actions of the angiotensin type 1 receptor antagonist losartan in experimental models of arthritis

Angiotensin (Ang) II and its AT1 receptors have been implicated in the pathogenesis of rheumatoid arthritis. Activation of the counter-regulatory Ang-(1-7)-Mas receptor axis may contribute to some of the effects of AT₁ receptor blockers (ARBs). In this study, we have used losartan, an ARB, to investigate the role of and the mechanisms by which AT₁ receptors participated in two experimental models of arthritis: antigen-induced arthritis (AIA) in mice and adjuvant-induced arthritis (AdIA) in rats. Treatment with losartan decreased neutrophil recruitment, hypernociception and the production of TNF-α, IL-1β and chemokine (C-X-C motif) ligand 1 in mice subjected to AIA. Histopathological analysis showed significant reduction of tissue injury and inflammation and decreased proteoglycan loss. In addition to decreasing cytokine production, losartan directly reduced leukocyte rolling and adhesion. Anti-inflammatory effects of losartan were not associated to Mas receptor activation and/or Ang-(1-7) production. Anti-inflammatory effects were reproduced in rats subjected to AdIA. This study shows that ARBs have potent anti-inflammatory effects in animal models of arthritis. Mechanistically, reduction of leukocyte accumulation and of joint damage was associated with local inhibition of cytokine production and direct inhibition of leukocyte-endothelium interactions. The anti-inflammatory actions of losartan were accompanied by functional improvement of the joint, as seen by reduced joint hypernociception. These findings support the use of ARBs for the treatment of human arthritis and provide potential mechanisms for the anti-inflammatory actions of these compounds.

Beneficial effects of the activation of the angiotensin-(1-7) MAS receptor in a murine model of adriamycin-induced nephropathy

Angiotensin-(1–7) [Ang-(1–7)] is a biologically active heptapeptide that may counterbalance the physiological actions of angiotensin II (Ang II) within the renin-angiotensin system (RAS). Here, we evaluated whether activation of the Mas receptor with the oral agonist, AVE 0991, would have renoprotective effects in a model of adriamycin (ADR)-induced nephropathy. We also evaluated whether the Mas receptor contributed for the protective effects of treatment with AT₁ receptor blockers. ADR (10 mg/kg) induced significant renal injury and dysfunction that was maximal at day 14 after injection. Treatment with the Mas receptor agonist AVE 0991 improved renal function parameters, reduced urinary protein loss and attenuated histological changes. Renoprotection was associated with reduction in urinary levels of TGF-β. Similar renoprotection was observed after treatment with the AT₁ receptor antagonist, Losartan. AT₁ and Mas receptor mRNA levels dropped after ADR administration and treatment with losartan reestablished the expression of Mas receptor and increased the expression of ACE2. ADR-induced nephropathy was similar in wild type (Mas^+/+) and Mas knockout (Mas^−/−) mice, suggesting there was no endogenous role for Mas receptor activation. However, treatment with Losartan was able to reduce renal injury only in Mas^+/+, but not in Mas^−/− mice. Therefore, these findings suggest that exogenous activation of the Mas receptor protects from ADR-induced nephropathy and contributes to the beneficial effects of AT₁ receptor blockade. Medications which target specifically the ACE2/Ang-(1–7)/Mas axis may offer new therapeutic opportunities to treat human nephropathies.

Myofibroblast-mediated mechanisms of pathological remodelling of the heart

The syncytium of cardiomyocytes in the heart is tethered within a matrix composed principally of type I fibrillar collagen. The matrix has diverse mechanical functions that ensure the optimal contractile efficiency of this muscular pump. In the diseased heart, cardiomyocytes are lost to necrotic cell death, and phenotypically transformed fibroblast-like cells-termed 'myofibroblasts'-are activated to initiate a 'reparative' fibrosis. The structural integrity of the myocardium is preserved by this scar tissue, although at the expense of its remodelled architecture, which has increased tissue stiffness and propensity to arrhythmias. A persisting population of activated myofibroblasts turns this fibrous tissue into a living 'secretome' that generates angiotensin II and its type 1 receptor, and fibrogenic growth factors (such as transforming growth factor-β), all of which collectively act as a signal-transducer-effector signalling pathway to type I collagen synthesis and, therefore, fibrosis. Persistent myofibroblasts, and the resultant fibrous tissue they produce, cause progressive adverse myocardial remodelling, a pathological hallmark of the failing heart irrespective of its etiologic origin. Herein, we review relevant cellular, subcellular, and molecular mechanisms integral to cardiac fibrosis and consequent remodelling of atria and ventricles with a heterogeneity in cardiomyocyte size. Signalling pathways that antagonize collagen fibrillogenesis provide novel strategies for cardioprotection.

Telmisartan attenuates hepatic fibrosis in bile duct-ligated rats

AIM

To evaluate the antifibrotic effect of telmisartan, an angiotensin II receptor blocker, in bile duct-ligated rats.

METHODS

Adult Sprague-Dawley rats were allocated to 3 groups: sham-operated rats, model rats underwent common bile duct ligation (BDL), and BDL rats treated with telmisartan (8 mg/kg, po, for 4 weeks). The animals were sacrificed on d 29, and liver histology was examined, the Knodell and Ishak scores were assigned, and the expression of angiotensin-converting enzyme (ACE) and ACE2 was evaluated with immunohistochemical staining. The mRNAs and proteins associated with liver fibrosis were evaluated using RTQ-PCR and Western blot, respectively.

RESULTS

The mean fibrosis score of BDL rats treated with telmisartan was significantly lower than that of the model rats (1.66±0.87 vs 2.13±0.35, P=0.015). However, there was no significant difference in inflammation between the two groups, both of which showed moderate inflammation. Histologically, treatment with telmisartan significantly ameliorated BDL-caused the hepatic fibrosis. Treatment with telmisartan significantly upregulated the mRNA levels of ACE2 and MAS, and decreased the mRNA levels of ACE, angiotensin II type 1 receptor (AT1-R), collagen type III, and transforming growth factor β1 (TGF-β1). Moreover, treatment with telmisartan significantly increased the expression levels of ACE2 and MAS proteins, and inhibited the expression levels of ACE and AT1-R protein.

CONCLUSION

Telmisartan attenuates liver fibrosis in bile duct-ligated rats via increasing ACE2 expression level.

Anti-oxidized low-density lipoprotein antibodies in chronic heart failure

Oxidative stress may play a significant role in the pathogenesis of heart failure (HF). Antibodies to oxidized low-density lipoprotein (oxLDL Abs) reflect an immune response to LDL over a prolonged period and may represent long-term oxidative stress in HF. The oxLDL plasma level is a useful predictor of mortality in HF patients, and measurement of the oxLDL Abs level may allow better management of those patients. Antibodies to oxLDL also significantly correlate with the New York Heart Association score. Hypercholesterolemia, smoking, hypertension, and obesity are risk factors for atherosclerotic coronary heart disease (CHD) leading to HF, but these factors account for only one-half of all cases, and understanding of the pathologic process underlying HF remains incomplete. Nutrients with antioxidant properties can reduce the susceptibility of LDL to oxidation. Antioxidant therapy may be an adjunct to lipid-lowering, angiotensin converting enzyme inhibition and metformin (in diabetes) therapy for the greatest impact on CHD and HF. Observational data suggest a protective effect of antioxidant supplementation on the incidence of HD. This review summarizes the data on oxLDL Abs as a predictor of morbidity and mortality in HF patients.

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.

Therapeutic targeting of the angiotensin-converting enzyme 2/Angiotensin-(1-7)/Mas cascade in the renin-angiotensin system: a patent review

INTRODUCTION

The renin-angiotensin system (RAS) is a main therapeutic target for cardiovascular diseases. Within the last two decades, novel components of the RAS have been discovered, opening new opportunities to interfere with its activity. Angiotensin(Ang)-(1-7) is synthesized by angiotensin-converting enzyme 2 (ACE2), and interacts with the G-protein-coupled receptor Mas. The axis formed by ACE2/Ang-(1-7)/Mas represents an endogenous counter regulatory pathway within the RAS.

AREAS COVERED

In this review, the authors discuss patents and recent initiatives to develop therapeutic strategies based on the ACE2/Ang-(1-7)/Mas axis.

EXPERT OPINION

Many publications and patents support a strategy to interfere with the activity of the RAS by stimulating its counter-regulatory axis mainly in two different ways: i) To increase the activity of ACE2, which will impact the system by increasing the inactivation of Ang II and the production of Ang-(1-7); ii) To stimulate Mas, taking advantage of nanostructured formulations of the natural peptide or analogues of Ang-(1-7). Although the preclinical studies are compelling, the possible impact of these novel therapeutic tools for the treatment of cardiometabolic diseases will only be known after completion of the ongoing clinical studies.