Angiotensin II Infusion–Induced Inflammation, Monocytic Fibroblast Precursor Infiltration, and Cardiac Fibrosis are Pressure Dependent

Angiotensin II promotes intramural hematoma of aorta in juvenile mice at early stage

OBJECTIVES

Intramural hematoma (IMH) is a serious aortic condition characterized by the presence of a contained hematoma within the aortic media. However, the animal model with a high incidence of IMH was lacking, and the specific pathological characteristics of IMH have not been thoroughly characterized.

METHODS AND RESULTS

We conducted an experimental study using 4-week-old male, 4-week-old female, and 8-week-old male C57BL/6J mice. These mice were subjected to angiotensin II infusion at a rate of 1000 ng/kg/min for a period of 4 days. In situ imaging was performed, and aorta was harvested and serially sectioned. Histological staining and immunostaining techniques were employed, and the subcellular structure was examined using transmission electron microscopy. Our findings revealed that 4-week-old male mice exhibited a higher susceptibility to angiotensin II-induced IMH, characterized by more circumferential appearances and larger affected areas. Furthermore, IMH was more likely to occur in the upper segment of the descending aorta rather than the lower segment. Within the IMH, older fibrinous thrombus was predominantly observed near the adventitia, while younger red thrombus was more prevalent near the lumen. Additionally, platelet activation and degranulation were observed, along with fibrin cross-linking and thrombus organization, indicating a potential relationship between platelet activation and the progression of IMH.

CONCLUSION

Our study demonstrated that angiotensin II infusion promoted the development of IMH during the early stages, especially in juvenile mice. Furthermore, the presence of platelet activation and thrombus organization suggested their potential involvement in the progression of IMH.

Heart remodelling affects ECG in rat DOCA/salt model

Myocardial remodelling involves structural and functional changes in the heart, potentially leading to heart failure. The deoxycorticosterone acetate (DOCA)/salt model is a widely used experimental approach to study hypertension-induced cardiac remodelling. It allows to investigate the mechanisms underlying myocardial fibrosis and hypertrophy, which are key contributors to impaired cardiac function. In this study, myocardial remodelling in rat deoxycorticosterone acetate/salt model was examined over a three-week period. The experiment involved 11 male Sprague-Dawley rats, divided into two groups: fibrosis (n=6) and control (n=5). Myocardial remodelling was induced in the fibrosis group through unilateral nephrectomy, deoxyco-rticosterone acetate administration, and increased salt intake. The results revealed significant structural changes, including increased left ventricular wall thickness, myocardial fractional volume, and development of myocardial fibrosis. Despite these changes, left ventricular ejection fraction was preserved and even increased. ECG analysis showed significant prolongation of the PR interval and widening of the QRS complex in the fibrosis group, indicating disrupted atrioventricular and ventricular conduction, likely due to fibrosis and hypertrophy. Correlation analysis suggested a potential relationship between QRS duration and myocardial hypertrophy, although no significant correlations were found among other ECG parameters and structural changes detected by MRI. The study highlights the advantage of the DOCA/salt model in exploring the impact of myocardial remodelling on electrophysiological properties. Notably, this study is among the first to show that early myocardial remodelling in this model is accompanied by distinct electrophysiological changes, suggesting that advanced methods combined with established animal models can open new opportunities for research in this field. Key words Myocardial fibrosis, Remodelling, Animal model, DOCA-salt, Magnetic resonance imaging.

Role of platelet factor 4 in arteriovenous fistula maturation failure: What do we know so far?

The rate of arteriovenous fistula (AVF) maturation failure remains unacceptably high despite continuous efforts on technique improvement and careful pre-surgery planning. In fact, half of all newly created AVFs are unable to be used for hemodialysis (HD) without a salvage procedure. While vascular stenosis in the venous limb of the access is the culprit, the underlying factors leading to vascular narrowing and AVF maturation failure are yet to be determined. We have recently demonstrated that AVF non-maturation is associated with post-operative medial fibrosis and fibrotic stenosis, and post-operative intimal hyperplasia (IH) exacerbates the situation. Multiple pathological processes and signaling pathways are underlying the stenotic remodeling of the AVF. Our group has recently indicated that a pro-inflammatory cytokine platelet factor 4 (PF4/CXCL4) is upregulated in veins that fail to mature after AVF creation. Platelet factor 4 is a fibrosis marker and can be detected in vascular stenosis tissue, suggesting that it may contribute to AVF maturation failure through stimulation of fibrosis and development of fibrotic stenosis. Here, we present an overview of the how PF4-mediated fibrosis determines AVF maturation failure.

SGK1 is necessary to FoxO3a negative regulation, oxidative stress and cardiac fibroblast activation induced by TGF-β1

Cardiac fibroblasts (CFs) activation is a common response to most pathological conditions affecting the heart, characterized by increased cellular secretory capacity and increased expression of fibrotic markers, such as collagen I and smooth muscle actin type alpha (α-SMA). Fibrotic activation of CFs induces the increase in tissue protein content, with the consequent tissue stiffness, diastolic dysfunction, and heart failure. Therefore, the search for new mechanisms of CFs activation is important to find novel treatments for cardiac diseases characterized by fibrosis. In this regard, TGF-β1, a cytokine with proinflammatory and fibrotic properties, is crucial in the CFs activation and the development of fibrotic diseases, whereas its molecular targets are not completely known. Serum and glucocorticoid-regulated kinase (SGK1) is a protein involved in various pathophysiological phenomena, especially cardiac and renal diseases that curse with fibrosis. Additionally, SGK1 phosphorylates and regulates the activity and expression of several targets, highlighting FoxO3a for its role in the regulation of oxidative stress and CFs activation induced by TGF-β1. However, the regulation of SGK1 by TGF-β1 and its role in CFs activation have not been studied. In this work, we evaluate the role of SGK1 in CFs isolated from neonatal Sprague-Dawley rats. The participation of SGK1 in the fibrotic activation of CFs induced by TGF-β1 was analyzed, using an inhibitor or siRNA of SGK1. In addition, the role of SGK1 on the regulation of FoxO3a and oxidative stress induced by TGF-β1 was analyzed. Our results indicate that TGF-β1 increased both the activity and expression of SGK1 in CFs, requiring the activation of MAPKs, ERK1/2, p38 and JNK, while inhibition and silencing of SGK1 prevented TGF-β1-induced fibrotic activation of CFs. In addition, SGK1 inhibition prevented FoxO3a inactivation and expression reduction, catalase and SOD2 expression decrease, and the increase of oxidative stress induced by TGF-β1. Taken together, our results position SGK1 as an important regulator of CFs activation driven by TGF-β1, at least in part, through the regulation of FoxO3a and oxidative stress.

How Effective Is a Late-Onset Antihypertensive Treatment? Studies with Captopril as Monotherapy and in Combination with Nifedipine in Old Spontaneously Hypertensive Rats

Background: A major problem in the treatment of human hypertension is the late diagnosis of hypertension and, hence, the delayed start of treatment. Very often, hypertension has existed for a long time and cardiac damage has already developed. Therefore, we tested whether late-onset antihypertensive treatment is effective in lowering blood pressure (BP) and in reducing or even preventing left ventricular hypertrophy and fibrosis. Methods: Twenty-one male 60-week-old spontaneously hypertensive rats (SHR) were included. Fourteen rats received oral treatment with captopril (CAP) either as monotherapy or combined with nifedipine (CAP + NIF) over 22 weeks. Seven untreated SHR served as controls. We examined the therapeutic effects on BP, heart weight and histological and biochemical markers of left ventricular remodeling and fibrosis. Results: At 82 weeks of age, BP was reduced in the CAP and CAP + NIF groups by 44 and 51 mmHg, respectively (p < 0.001), but not in untreated controls. Despite the late therapy start, cardiac hypertrophy and fibrosis were attenuated compared to controls. Both treatments reduced heart weight by 1.2 mg/g (25%, p = 0.001) and collagens I and III by 66% and 60%, respectively (p < 0.001), thus proving nearly equivalent cardioprotective efficacy. Conclusion: These data clearly emphasize the benefit of antihypertensive treatment in reducing BP and mitigating the development of cardiac damage even when treatment is started late in life.

Immunosuppression by Mycophenolate Mofetil Mitigates Intrarenal Angiotensinogen Augmentation in Angiotensin II-Dependent Hypertension

Augmentation of intrarenal angiotensinogen (AGT) leads to further formation of intrarenal angiotensin II (Ang II) and the development of hypertensive kidney injury. Recent studies demonstrated that macrophages and the enhanced production of pro-inflammatory cytokines can be crucial mediators of renal AGT augmentation in hypertension. Accordingly, this study investigated the effects of immunosuppression by mycophenolate mofetil (MMF) on intrarenal AGT augmentation. Ang II (80 ng/min) was infused with or without daily administration of MMF (50 mg/kg) to Sprague-Dawley rats for 2 weeks. Mean arterial pressure (MAP) in Ang II infused rats was slightly higher (169.7 ± 6.1 mmHg) than the Ang II + MMF group (154.7 ± 2.0 mmHg), but was not statistically different from the Ang II + MMF group. MMF treatment suppressed Ang II-induced renal macrophages and IL-6 elevation. Augmentation of urinary AGT by Ang II infusion was attenuated by MMF treatment (control: 89.3 ± 25.2, Ang II: 1194 ± 305.1, and Ang II + MMF: 389 ± 192.0 ng/day). The augmentation of urinary AGT by Ang II infusion was observed before the onset of proteinuria. Elevated intrarenal AGT mRNA and protein levels in Ang II infused rats were also normalized by the MMF treatment (AGT mRNA, Ang II: 2.5 ± 0.2 and Ang II + MMF: 1.5 ± 0.1, ratio to control). Ang II-induced proteinuria, mesangial expansion and renal tubulointerstitial fibrosis were attenuated by MMF. Furthermore, MMF treatment attenuated the augmentation of intrarenal NLRP3 mRNA, a component of inflammasome. These results indicate that stimulated cytokine production in macrophages contributes to intrarenal AGT augmentation in Ang II-dependent hypertension, which leads to the development of kidney injury.

Regression from pathological hypertrophy in mice is sexually dimorphic and stimulus-specific

Pathological cardiac hypertrophy is associated with increased morbidity and mortality. Understanding the mechanisms whereby pathological cardiac growth can be reversed could have therapeutic value. Here, we show that pathways leading to regression of pathological cardiac hypertrophy are strongly dependent on the hypertrophic trigger and are significantly modified by sex. Two pathological stimuli causing hypertrophy via distinct pathways were administered to male and female mice: Angiotensin II [Ang II] or Isoproterenol [Iso]. Stimuli were removed after 7 days of treatment, and left ventricles (LV) were studied at 1, 4, and 7 days. Ang II-treated Females did not show regression after stimulus removal. Iso-treated males showed rapid LV hypertrophy regression. Somewhat surprisingly, RNAseq analysis at day 1 after removal of triggers revealed only 45 differentially regulated genes in common among all groups, demonstrating distinct responses. Ingenuity Pathway Analysis predicted strong downregulation of the TGFβ1 pathway in all groups except for Ang II-treated females. Consistently, we found significant downregulation of Smad signaling after stimulus removal including in Ang II-treated females. Additionally, the ERK1/2 pathway was significantly reduced in the groups showing regression. Finally, protein degradation pathways were significantly activated only in Iso-treated males 1 day after stimulus removal. Our data indicate that TGFβ1 downregulation may play a role in the regression of pathological cardiac hypertrophy via downregulation of the ERK1/2 pathway and activation of autophagy and proteasome activity in Iso-treated males. This work highlights that the reversal of pathological hypertrophy does not utilize universal signaling pathways and that sex potently modifies this process.

Mechanical communication in fibrosis progression

Mechanical hallmarks of fibrotic microenvironments are both outcomes and causes of fibrosis progression. Understanding how cells sense and transmit mechanical cues in the interplay with extracellular matrix (ECM) and hemodynamic forces is a significant challenge. Recent advances highlight the evolvement of intracellular mechanotransduction pathways responding to ECM remodeling and abnormal hemodynamics (i.e., low and disturbed shear stress, pathological stretch, and increased pressure), which are prevalent biomechanical characteristics of fibrosis in multiple organs (e.g., liver, lung, and heart). Here, we envisage the mechanical communication in cell-ECM, cell-hemodynamics and cell-ECM-cell crosstalk (namely paratensile signaling) during fibrosis expansion. We also provide a comprehensive overview of in vitro and in silico engineering systems for disease modeling that will aid the identification and prediction of mechano-based therapeutic targets to ameliorate fibrosis progression.

Sex Differences in Molecular Mechanisms of Cardiovascular Aging

Cardiovascular disease (CVD) is still the leading cause of illness and death in the Western world. Cardiovascular aging is a progressive modification occurring in cardiac and vascular morphology and physiology where increased endothelial dysfunction and arterial stiffness are observed, generally accompanied by increased systolic blood pressure and augmented pulse pressure. The effects of biological sex on cardiovascular pathophysiology have long been known. The incidence of hypertension is higher in men, and it increases in postmenopausal women. Premenopausal women are protected from CVD compared with age-matched men and this protective effect is lost with menopause, suggesting that sex-hormones influence blood pressure regulation. In parallel, the heart progressively remodels over the course of life and the pattern of cardiac remodeling also differs between the sexes. Lower autonomic tone, reduced baroreceptor response, and greater vascular function are observed in premenopausal women than men of similar age. However, postmenopausal women have stiffer arteries than their male counterparts. The biological mechanisms responsible for sex-related differences observed in cardiovascular aging are being unraveled over the last several decades. This review focuses on molecular mechanisms underlying the sex-differences of CVD in aging.

Elevated circulating fibrocyte levels in hemodialysis-dependent end-stage renal disease patients

INTRODUCTION

Numerous studies have demonstrated that end-stage renal disease (ESRD) patients undergoing hemodialysis (HD) have high myocardial fibrosis (MF) levels. Circulating fibrocytes are bone marrow-derived circulating mesenchymal progenitors, and new evidence suggests a vital role for fibrocytes in the development of MF. This study aimed to investigate whether fibrocyte levels are elevated in patients undergoing HD and its influence factors.

METHODS

We carried out a flow cytometry analysis to measure the proportion of peripheral blood circulating fibrocytes in a cohort of 126 healthy control individuals and 161 subjects with HD. Cardiac function and morphology were assessed by electrocardiogram and transthoracic echocardiogram.

FINDINGS

Compared to healthy controls, individuals with ESRD had significantly higher levels of circulating fibrocytes. There was a strong correlation between the frequency of fragmented QRS (fQRS) and circulating fibrocytes in HD patients. Furthermore, higher fibrocytes correlated to increasing age, dialysis age, left ventricular mass index (LVMI), left ventricular ejection fraction (LVEF), and hypertension complication. On multivariate analysis, the dialysis age [odds ratio (OR) 1.011, 95% confidence interval (CI) 1.003-1.019, p = 0.006], LVMI (OR 1.012, 95% CI 1.002-1.022, p = 0.016), hypertension (OR 4.303, 95% CI 1.129-16.406, p = 0.033), and fQRS (OR 2.439, 95% CI 1.049-5.262, p = 0.038) were significant independent predictors of fibrocytes percentage.

DISCUSSION

We concluded that bone marrow-derived circulating fibrocytes were significantly increased in ESRD patients with HD compared with controls. Our data suggested that these cells might play essential roles during MF in HD patients.

Pinoresinol diglucoside (PDG) attenuates cardiac hypertrophy via AKT/mTOR/NF-κB signaling in pressure overload-induced rats

ETHNOPHARMACOLOGICAL RELEVANCE

Pinoresinol diglucoside (PDG), the active compound extracted from Eucommia ulmoides, Styrax sp. and Forsythia suspensa, plays the roles in regulating hypertension, inflammation and oxidative stress.

AIMS

Considering that hypertension and inflammation has been proved to contribute to cardiac remodeling, we tested the effects of PDG on cardiac hypertrophy (CM).

METHODS

Male Sprague Dawley (SD) rats were used to construct hypertrophic rats by partial abdominal aortic constriction (AAC)-surgery. PDG solution (2 mg/ml) was used to treat AAC-induced rats by intraperitoneal injection at low dose (L-PDG, 2.5 mg/kg per day), medium dose (M-PDG, 5 mg/kg per day), and high dose (H-PDG, 7.5 mg/kg per day) for 3 weeks post AAC-surgery. CM was evaluated by the ratio of left ventricular weight to body weight ratio (LVW/BW), left ventricular wall thickness by H&E staining, and collagen content deposit by Masson's staining. Further, isoproterenol (ISO) and phenylephrine (PE) were used to produce cellular models of CM in neonatal rat ventricular cardiomyocytes (NRVMs). PDG pre-treated NRVMs 2 h at low dose (L-PDG, 2.5 μg/ml), medium dose (M-PDG, 5 μg/ml), and high dose (H-PDG, 7.5 μg/ml) for 24 h with or without PE- and ISO-stimulation. CM was evaluated by the expressions of hypertrophic biomarkers. Next, the hypertrophic biomarkers and pro-inflammatory cytokines were measured using quantitative real-time PCR (qRT-PCR), the expressions of protein kinase B (AKT)/mammalian target of rapamycin (mTOR)/transcription factor nuclear factor-kappa B (NF-kB) signaling pathway were determined by Western blotting.

RESULTS

PDG treatment prevented cardiac histomorphology damages, decreased upregulations of hypertrophic biomarkers, and prevented fibrosis and inflammation after pressure overload resulting from AAC-surgery. Consistently, PDG remarkably inhibited the changes of cardiomyocyte hypertrophic biomarkers and inflammatory responses in cellular models of CM. Interestingly, PDG administration inhibited the activation of AKT/mTOR/NF-kB signaling pathway both in vivo and in vitro.

CONCLUSIONS

PDG prevents AAC-induced CM in vivo, PE- and ISO-induced CM in vitro. The AKT/mTOR/NF-kB signaling pathway could be the potential therapeutic target involved in the protection of PDG. These findings provide novel evidence that PDG might be a promising therapeutic strategy for CM.

Preclinical rodent models of cardiac fibrosis

Cardiac fibrosis (scarring), characterised by an increased deposition of extracellular matrix (ECM) proteins, is a hallmark of most types of cardiovascular disease and plays an essential role in heart failure progression. Inhibition of cardiac fibrosis could improve outcomes in patients with cardiovascular diseases and particularly heart failure. However, pharmacological treatment of the ECM build-up is still lacking. In this context, preclinical models of heart disease are important tools for understanding the complex pathogenesis involved in the development of cardiac fibrosis which in turn could identify new therapeutic targets and the facilitation of antifibrotic drug discovery. Many preclinical models have been used to study cardiac fibrosis and each model provides mechanistic insights into the many factors that contribute to cardiac fibrosis. This review discusses the most frequently used rodent models of cardiac fibrosis and also provides context for the use of particular models of heart failure.

Kidney and hypertension in older adults

Individuals over 65years are the fastest expanding population throughout the world, due to the increase in human life expectancy. This growing geriatric population, with increasingly associated chronic diseases, has relevant medical, social, and economic impact. Aging is characterized by progressive structural and functional changes in the kidney and in the cardiovascular system, leading to decline in renal function and hypertension. The purpose of this review is to describe the aging-related renal changes and blood pressure regulation during the aging process, their impact with regards to morbidity and mortality in these patients, and to summarize the most appropriate therapeutic approaches in these situations based on the particularities of this population group.

A Potential Role of the Renin-Angiotensin-System for Disturbances of Respiratory Chemosensitivity in Acute Respiratory Distress Syndrome and Severe Acute Respiratory Syndrome

Acute respiratory distress syndrome (ARDS) represents an acute diffuse inflammation of the lungs triggered by different causes, uniformly leading to a noncardiogenic pulmonary edema with inhomogeneous densities in lung X-ray and lung CT scan and acute hypoxemia. Edema formation results in "heavy" lungs, inducing loss of compliance and the need to spend more energy to "move" the lungs. Consequently, an ARDS patient, as long as the patient is breathing spontaneously, has an increased respiratory drive to ensure adequate oxygenation and CO2 removal. One would expect that, once the blood gases get back to "physiological" values, the respiratory drive would normalize and the breathing effort return to its initial status. However, in many ARDS patients, this is not the case; their respiratory drive appears to be upregulated and fully or at least partially detached from the blood gas status. Strikingly, similar alteration of the respiratory drive can be seen in patients suffering from SARS, especially SARS-Covid-19. We hypothesize that alterations of the renin-angiotensin-system (RAS) related to the pathophysiology of ARDS and SARS are involved in this dysregulation of chemosensitive control of breathing.

Fibrosis in Chronic Kidney Disease: Pathogenesis and Consequences

Fibrosis is a process characterized by an excessive accumulation of the extracellular matrix as a response to different types of tissue injuries, which leads to organ dysfunction. The process can be initiated by multiple and different stimuli and pathogenic factors which trigger the cascade of reparation converging in molecular signals responsible of initiating and driving fibrosis. Though fibrosis can play a defensive role, in several circumstances at a certain stage, it can progressively become an uncontrolled irreversible and self-maintained process, named pathological fibrosis. Several systems, molecules and responses involved in the pathogenesis of the pathological fibrosis of chronic kidney disease (CKD) will be discussed in this review, putting special attention on inflammation, renin-angiotensin system (RAS), parathyroid hormone (PTH), fibroblast growth factor 23 (FGF23), Klotho, microRNAs (miRs), and the vitamin D hormonal system. All of them are key factors of the core and regulatory pathways which drive fibrosis, having a great negative kidney and cardiac impact in CKD.

ADAM17-Mediated Shedding of Inflammatory Cytokines in Hypertension

The increase of Angiontesin-II (Ang-II), one of the key peptides of the renin-angiotensin system (RAS), and its binding to the Ang-II type 1 receptor (AT1R) during hypertension is a crucial mechanism leading to AD\AM17 activation. Among the reported membrane anchored proteins cleaved by ADAM17, immunological cytokines (TNF-α, IFN-γ, TGF-β, IL-4, IL-10, IL-13, IL-6, FKN) are the major class of substrates, modulation of which triggers inflammation. The rise in ADAM17 levels has both central and peripheral implications in inflammation-mediated hypertension. This narrative review provides an overview of the role of ADAM17, with a special focus on its cellular regulation on neuronal and peripheral inflammation-mediated hypertension. Finally, it highlights the importance of ADAM17 with regards to the biology of inflammatory cytokines and their roles in hypertension.

Targeting the renin-angiotensin-aldosterone system in fibrosis

Fibrosis is characterized by excessive deposition of extracellular matrix components such as collagen in tissues or organs. Fibrosis can develop in the heart, kidneys, liver, skin or any other body organ in response to injury or maladaptive reparative processes, reducing overall function and leading eventually to organ failure. A variety of cellular and molecular signaling mechanisms are involved in the pathogenesis of fibrosis. The renin-angiotensin-aldosterone system (RAAS) interacts with the potent Transforming Growth Factor β (TGFβ) pro-fibrotic pathway to mediate fibrosis in many cell and tissue types. RAAS consists of both classical and alternative pathways, which act to potentiate or antagonize fibrotic signaling mechanisms, respectively. This review provides an overview of recent literature describing the roles of RAAS in the pathogenesis of fibrosis, particularly in the liver, heart, kidney and skin, and with a focus on RAAS interactions with TGFβ signaling. Targeting RAAS to combat fibrosis represents a promising therapeutic approach, particularly given the lack of strategies for treating fibrosis as its own entity, thus animal and clinical studies to examine the impact of natural and synthetic substances to alter RAAS signaling as a means to treat fibrosis are reviewed as well.

KCa3.1 Channels Promote Cardiac Fibrosis Through Mediating Inflammation and Differentiation of Monocytes Into Myofibroblasts in Angiotensin II -Treated Rats

Background Cardiac fibrosis is a core pathological process associated with heart failure. The recruitment and differentiation of primitive fibroblast precursor cells of bone marrow origin play a critical role in pathological interstitial cardiac fibrosis. The K_{C a}3.1 channels are expressed in both ventricular fibroblasts and circulating mononuclear cells in rats and are upregulated by angiotensin II . We hypothesized that K_{C a}3.1 channels mediate the inflammatory microenvironment in the heart, promoting the infiltrated bone marrow-derived circulating mononuclear cells to differentiate into myofibroblasts, leading to myocardial fibrosis. Methods and Results We established a cardiac fibrosis model in rats by infusing angiotensin II to evaluate the impact of the specific K_{C a}3.1 channel blocker TRAM -34 on cardiac fibrosis. At the same time, mouse CD 4⁺ T cells and rat circulating mononuclear cells were separated to investigate the underlying mechanism of the TRAM -34 anti-cardiac fibrosis effect. TRAM -34 significantly attenuated cardiac fibrosis and the inflammatory reaction and reduced the number of fibroblast precursor cells and myofibroblasts. Inhibition of K_{C a}3.1 channels suppressed angiotensin II -stimulated expression and secretion of interleukin-4 and interleukin-13 in CD 4⁺ T cells and interleukin-4- or interleukin-13-induced differentiation of monocytes into fibrocytes. Conclusions K_{C a}3.1 channels facilitate myocardial inflammation and the differentiation of bone marrow-derived monocytes into myofibroblasts in cardiac fibrosis caused by angiotensin II infusion.

Chronic Kidney Disease as a Risk Factor for Heart Failure With Preserved Ejection Fraction: A Focus on Microcirculatory Factors and Therapeutic Targets

Heart failure (HF) and chronic kidney disease (CKD) co-exist, and it is estimated that about 50% of HF patients suffer from CKD. Although studies have been performed on the association between CKD and HF with reduced ejection fraction (HFrEF), less is known about the link between CKD and heart failure with preserved ejection fraction (HFpEF). Approximately, 50% of all patients with HF suffer from HFpEF, and this percentage is projected to rise in the coming years. Therapies for HFrEF are long established and considered quite successful. In contrast, clinical trials for treatment of HFpEF have all shown negative or disputable results. This is likely due to the multifactorial character and the lack of pathophysiological knowledge of HFpEF. The typical co-existence of HFpEF and CKD is partially due to common underlying comorbidities, such as hypertension, dyslipidemia and diabetes. Macrovascular changes accompanying CKD, such as hypertension and arterial stiffening, have been described to contribute to HFpEF development. Furthermore, several renal factors have a direct impact on the heart and/or coronary microvasculature and may underlie the association between CKD and HFpEF. These factors include: (1) activation of the renin-angiotensin-aldosterone system, (2) anemia, (3) hypercalcemia, hyperphosphatemia and increased levels of FGF-23, and (4) uremic toxins. This review critically discusses the above factors, focusing on their potential contribution to coronary dysfunction, left ventricular stiffening, and delayed left ventricular relaxation. We further summarize the directions of novel treatment options for HFpEF based on the contribution of these renal drivers.

Targeting Early Atherosclerosis: A Focus on Oxidative Stress and Inflammation

Atherosclerosis is a chronic vascular inflammatory disease associated to oxidative stress and endothelial dysfunction. Oxidation of low-density lipoprotein (LDL) cholesterol is one of the key factors for the development of atherosclerosis. Nonoxidized LDL have a low affinity for macrophages, so they are not themselves a risk factor. However, lowering LDL levels is a common clinical practice to reduce oxidation and the risk of major events in patients with cardiovascular diseases (CVD). Atherosclerosis starts with dysfunctional changes in the endothelium induced by disturbed shear stress which can lead to endothelial and platelet activation, adhesion of monocytes on the activated endothelium, and differentiation into proinflammatory macrophages, which increase the uptake of oxidized LDL (oxLDL) and turn into foam cells, exacerbating the inflammatory signalling. The atherosclerotic process is accelerated by a myriad of factors, such as the release of inflammatory chemokines and cytokines, the generation of reactive oxygen species (ROS), growth factors, and the proliferation of vascular smooth muscle cells. Inflammation and immunity are key factors for the development and complications of atherosclerosis, and therefore, the whole atherosclerotic process is a target for diagnosis and treatment. In this review, we focus on early stages of the disease and we address both biomarkers and therapeutic approaches currently available and under research.

Promising Directions in Atherosclerosis Treatment Based on Epigenetic Regulation Using MicroRNAs and Long Noncoding RNAs

Atherosclerosis is one of the leading causes of mortality from cardiovascular disease (CVD) and is a chronic inflammatory disease of the middle and large arteries caused by a disruption of lipid metabolism. Noncoding RNA (ncRNA), including microRNA (miRNA), small interfering RNA (siRNA) and long noncoding RNA (lncRNA), was investigated for the treatment of atherosclerosis. Regulation of the expression of noncoding RNA targets the constituent element of the pathogenesis of atherosclerosis. Currently, miRNA therapy commonly employs miRNA antagonists and mimic compounds. In this review, attention is focused on approaches to correcting molecular disorders based on the genetic regulation of the transcription of key genes responsible for the development of atherosclerosis. Promising technologies were considered for the treatment of atherosclerosis, and examples are given for technologies that have been shown to be effective in clinical trials.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

The renin-angiotensin-aldosterone system plays crucial roles in cardiovascular physiology and pathophysiology. However, many of the signaling mechanisms have been unclear. The angiotensin II (ANG II) type 1 receptor (AT₁R) is believed to mediate most functions of ANG II in the system. AT₁R utilizes various signal transduction cascades causing hypertension, cardiovascular remodeling, and end organ damage. Moreover, functional cross-talk between AT₁R signaling pathways and other signaling pathways have been recognized. Accumulating evidence reveals the complexity of ANG II signal transduction in pathophysiology of the vasculature, heart, kidney, and brain, as well as several pathophysiological features, including inflammation, metabolic dysfunction, and aging. In this review, we provide a comprehensive update of the ANG II receptor signaling events and their functional significances for potential translation into therapeutic strategies. AT₁R remains central to the system in mediating physiological and pathophysiological functions of ANG II, and participation of specific signaling pathways becomes much clearer. There are still certain limitations and many controversies, and several noteworthy new concepts require further support. However, it is expected that rigorous translational research of the ANG II signaling pathways including those in large animals and humans will contribute to establishing effective new therapies against various diseases.

Inflammation as a Regulator of the Renin-Angiotensin System and Blood Pressure

PURPOSE OF REVIEW

Mechanisms facilitating progression of hypertension via cross stimulation of the renin-angiotensin system (RAS) and inflammation have been proposed. Accordingly, we review and update evidence for regulation of RAS components by pro-inflammatory factors.

RECENT FINDINGS

Angiotensin II (Ang II), which is produced by RAS, induces vasoconstriction and consequent blood pressure elevation. In addition to this direct action, chronically elevated Ang II stimulates several pathophysiological mechanisms including generation of oxidative stress, stimulation of the nervous system, alterations in renal hemodynamics, and activation of the immune system. In particular, an activated immune system has been shown to contribute to the development of hypertension. Recent studies have demonstrated that immune cell-derived pro-inflammatory cytokines regulate RAS components, further accelerating systemic and local Ang II formation. Specifically, regulation of angiotensinogen (AGT) production by pro-inflammatory cytokines in the liver and kidney is proposed as a key mechanism underlying the progression of Ang II-dependent hypertension.

High salt intake shifts the mechanisms of flow-induced dilation in the middle cerebral arteries of Sprague-Dawley rats

The goal of the present study was to examine the effect of 1 wk of high salt (HS) intake and the role of oxidative stress in changing the mechanisms of flow-induced dilation (FID) in isolated pressurized middle cerebral arteries of male Sprague-Dawley rats ( n = 15–16 rats/group). Reduced FID in the HS group was restored by intake of the superoxide scavenger tempol (HS + tempol in vivo group). The nitric oxide (NO) synthase inhibitor Nω-nitro-l-arginine methyl ester, cyclooxygenase inhibitor indomethacin, and selective inhibitor of microsomal cytochrome P-450 epoxidase activity N-(methylsulfonyl)-2-(2-propynyloxy)-benzenehexanamide significantly reduced FID in the low salt diet-fed group, whereas FID in the HS group was mediated by NO only. Cyclooxygenase-2 mRNA (but not protein) expression was decreased in the HS and HS + tempol in vivo groups. Hypoxia-inducible factor-1α and VEGF protein levels were increased in the HS group but decreased in the HS + tempol in vivo group. Assessment by direct fluorescence of middle cerebral arteries under flow revealed significantly reduced vascular NO levels and increased superoxide/reactive oxygen species levels in the HS group. These results suggest that HS intake impairs FID and changes FID mechanisms to entirely NO dependent, in contrast to the low-salt diet-fed group, where FID is NO, prostanoid, and epoxyeicosatrienoic acid dependent. These changes were accompanied by increased lipid peroxidation products in the plasma of HS diet-fed rats, increased vascular superoxide/reactive oxygen species levels, and decreased NO levels, together with increased expression of hypoxia-inducible factor-1α and VEGF.

NEW & NOTEWORTHY High-salt (HS) diet changes the mechanisms of flow-induced dilation in rat middle cerebral arteries from a combination of nitric oxide-, prostanoid-, and epoxyeicosatrienoic acid-dependent mechanisms to, albeit reduced, a solely nitric oxide-dependent dilation. In vivo reactive oxygen species scavenging restores flow-induced dilation in HS diet-fed rats and ameliorates HS-induced increases in the transcription factor hypoxia-inducible factor-1α and expression of its downstream target genes.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

Acute Cardiac Complications in Critical Brain Disease

Acute cardiac complications in critical brain disease should be understood as a clinical condition representing an intense brain-heart crosstalk and might mimic ischemic heart disease. Two main entities (neurogenic stunned myocardium [NSM] and stress cardiomyopathy) have been better characterized in the neurocritically ill patients and they portend worse clinical outcomes in these cases. The pathophysiology of NSM remains elusive. However, significant progress has been made on the early identification of neurocardiac compromise following acute critical brain disease. Effective prevention and treatment interventions are yet to be determined.

TRPM7 regulates angiotensin II-induced sinoatrial node fibrosis in sick sinus syndrome rats by mediating Smad signaling

Sinoatrial node fibrosis is involved in the pathogenesis of sinus sick syndrome (SSS). Transient receptor potential (TRP) subfamily M member 7 (TRPM7) is implicated in cardiac fibrosis. However, the mechanisms underlying the regulation of sinoatrial node (SAN) fibrosis in SSS by TRPM7 remain unknown. The aim of this study was to investigate the role of angiotensin II (Ang II)/TRPM7/Smad pathway in the SAN fibrosis in rats with SSS. The rat SSS model was established with sodium hydroxide pinpoint pressing permeation. Forty-eight rats were randomly divided into six groups: normal control (ctrl), sham operation (sham), postoperative 1-, 2-, 3-, and 4-week SSS, respectively. The tissue explant culture method was used to culture cardiac fibroblasts (CFs) from rat SAN tissues. TRPM7 siRNA or encoding plasmids were used to knock down or overexpress TRPM7. Collagen (Col) distribution in SAN and atria was assessed using PASM–Masson staining. Ang II, Col I, and Col III levels in serum and tissues or in CFs were determined by ELISA. TRPM7, smad2 and p-smad2 levels were evaluated by real-time PCR, and/or western blot and immunohistochemistry. SAN and atria in rats of the SSS groups had more fibers and higher levels of Ang II, Col I and III than the sham rats. Similar findings were obtained for TRPM7 and pSmad2 expression. In vitro, Ang II promoted CFs collagen synthesis in a dose-dependent manner, and potentiated TRPM7 and p-Smad2 expression. TRPM7 depletion inhibited Ang II-induced p-Smad2 expression and collagen synthesis in CFs, whereas increased TRPM7 expression did the opposite. SAN fibrosis is regulated by the Ang II/TRPM7/Smad pathway in SSS, indicating that TRPM7 is a potential target for SAN fibrosis therapy in SSS.

Differential effect of angiotensin II and blood pressure on hippocampal inflammation in mice

Background

Angiotensin II (Ang II), a peptide hormone involved in the development of hypertension, causes systemic and cerebral inflammation, affecting brain regions important for blood pressure control. The cause-and-effect relationship between hypertension and inflammation is two-way, but the role of blood pressure in the induction of cerebral inflammation is less clear. The vulnerability of specific brain regions, particularly those important for memory, is also of interest.

Methods

We used molecular biology approaches, immunohistochemistry, and electron microscopy to examine the interdependence between the hypertensive and pro-inflammatory effects of Ang II. We examined the effect of blood pressure by administering a subpressive (200 ng/kg/min) or a pressive Ang II dose (1000 or 1900 ng/kg/min) with and without hydralazine (150 mg/L) for 1 week and used phenylephrine to increase blood pressure independently of the renin-angiotensin system.

Results

Ang II increased ionized calcium-binding adaptor molecule 1 (Iba-1) levels (marker of microgliosis) in the whole brain and in the hippocampus in a dose-dependent manner. Pressive Ang II induced specific changes in microglial morphology, indicating differences in functional phenotype. An increase in hippocampal glial fibrillary acidic protein (GFAP) was seen in mice receiving pressive Ang II, while no induction of cerebral gliosis was observed after 7 days of subpressive Ang II infusion. Although phenylephrine led to increased astrogliosis, it did not affect Iba-1 expression. Pressive Ang II stimulated TNF-α production in the hippocampus, and daily treatment with hydralazine prevented this increase. Hydralazine also reduced GFAP and Iba-1 levels. With longer perfusion (14 days), subpressive Ang II led to some but not all the inflammatory changes detected with the pressive doses, mainly an increase in CD68 and Iba-1 but not of GFAP or TNF-α.

Conclusions

Blood pressure and Ang II differentially contribute to hippocampal inflammation in mice. Control of blood pressure and Ang II levels should prevent or reduce brain inflammation and therefore brain dysfunctions associated with hypertension.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1090-z) contains supplementary material, which is available to authorized users.

2-Methoxyestradiol protects against pressure overload-induced left ventricular hypertrophy

Numerous experimental studies have supported the evidence that 2-methoxyestradiol (2 ME) is a biologically active metabolite that mediates multiple effects on the cardiovascular system, largely independent of the estrogen receptor. 2 ME is a major cytochrome P450 1B1 (CYP1B1) metabolite and has been reported to have vasoprotective and anti-inflammatory actions. However, whether 2 ME would prevent cardiac hypertrophy induced by abdominal aortic constriction (AAC) has not been investigated yet. Therefore, the overall objectives of the present study were to elucidate the potential antihypertrophic effect of 2 ME and explore the mechanism(s) involved. Our results showed that 2 ME significantly inhibited AAC-induced left ventricular hypertrophy using echocardiography. The antihypertrophic effect of 2 ME was associated with a significant inhibition of CYP1B1 and mid-chain hydroxyeicosatetraenoic acids. Based on proteomics data, the protective effect of 2 ME is linked to the induction of antioxidant and anti-inflammatory proteins in addition to the modulation of proteins involved in myocardial energy metabolism. In vitro, 2 ME has shown a direct antihypertrophic effect through mitogen-activated protein kinases- and nuclear factor-κB-dependent mechanisms. The present work shows a strong evidence that 2 ME protects against left ventricular hypertrophy. Our data suggest the potential of repurposing 2 ME as a selective CYP1B1 inhibitor for the treatment of heart failure.

Angiotensin II, hypertension and angiotensin II receptor antagonism: Roles in the behavioural and brain pathology of a mouse model of Alzheimer's disease

Elevated angiotensin II causes hypertension and contributes to Alzheimer's disease by affecting cerebral blood flow. Angiotensin II receptor blockers may provide candidates to reduce (vascular) risk factors for Alzheimer's disease. We studied effects of two months of angiotensin II-induced hypertension on systolic blood pressure, and treatment with the angiotensin II receptor blockers, eprosartan mesylate, after one month of induced hypertension in wild-type C57bl/6j and AβPPswe/PS1ΔE9 (AβPP/PS1/Alzheimer's disease) mice. AβPP/PS1 showed higher systolic blood pressure than wild-type. Subsequent eprosartan mesylate treatment restored this elevated systolic blood pressure in all mice. Functional connectivity was decreased in angiotensin II-infused Alzheimer's disease and wild-type mice, and only 12 months of Alzheimer's disease mice showed impaired cerebral blood flow. Only angiotensin II-infused Alzheimer's disease mice exhibited decreased spatial learning in the Morris water maze. Altogether, angiotensin II-induced hypertension not only exacerbated Alzheimer's disease-like pathological changes such as impairment of cerebral blood flow, functional connectivity, and cognition only in Alzheimer's disease model mice, but it also induced decreased functional connectivity in wild-type mice. However, we could not detect hypertension-induced overexpression of Aβ nor increased neuroinflammation. Our findings suggest a link between midlife hypertension, decreased cerebral hemodynamics and connectivity in an Alzheimer's disease mouse model. Eprosartan mesylate treatment restored and beneficially affected cerebral blood flow and connectivity. This model could be used to investigate prevention/treatment strategies in early Alzheimer's disease.

Drug Treatment of Hypertension: Focus on Vascular Health

Hypertension, the most common preventable risk factor for cardiovascular disease and death, is a growing health burden. Serious cardiovascular complications result from target organ damage including cerebrovascular disease, heart failure, ischaemic heart disease and renal failure. While many systems contribute to blood pressure (BP) elevation, the vascular system is particularly important because vascular dysfunction is a cause and consequence of hypertension. Hypertension is characterised by a vascular phenotype of endothelial dysfunction, arterial remodelling, vascular inflammation and increased stiffness. Antihypertensive drugs that influence vascular changes associated with high BP have greater efficacy for reducing cardiovascular risk than drugs that reduce BP, but have little or no effect on the adverse vascular phenotype. Angiotensin converting enzyme ACE inhibitors (ACEIs) and angiotensin II receptor blockers (ARBs) improve endothelial function and prevent vascular remodelling. Calcium channel blockers also improve endothelial function, although to a lesser extent than ACEIs and ARBs. Mineralocorticoid receptor blockers improve endothelial function and reduce arterial stiffness, and have recently become more established as antihypertensive drugs. Lifestyle factors are essential in preventing the adverse vascular changes associated with high BP and reducing associated cardiovascular risk. Clinicians and scientists should incorporate these factors into treatment decisions for patients with high BP, as well as in the development of new antihypertensive drugs that promote vascular health.

Role of Circulating Fibrocytes in Cardiac Fibrosis

OBJECTIVE

It is revealed that circulating fibrocytes are elevated in patients/animals with cardiac fibrosis, and this review aims to provide an introduction to circulating fibrocytes and their role in cardiac fibrosis.

DATA SOURCES

This review is based on the data from 1994 to present obtained from PubMed. The search terms were "circulating fibrocytes " and "cardiac fibrosis ".

STUDY SELECTION

Articles and critical reviews, which are related to circulating fibrocytes and cardiac fibrosis, were selected.

RESULTS

Circulating fibrocytes, which are derived from hematopoietic stem cells, represent a subset of peripheral blood mononuclear cells exhibiting mixed morphological and molecular characteristics of hematopoietic and mesenchymal cells (CD34+/CD45+/collagen I+). They can produce extracellular matrix and many cytokines. It is shown that circulating fibrocytes participate in many fibrotic diseases, including cardiac fibrosis. Evidence accumulated in recent years shows that aging individuals and patients with hypertension, heart failure, coronary heart disease, and atrial fibrillation have more circulating fibrocytes in peripheral blood and/or heart tissue, and this elevation of circulating fibrocytes is correlated with the degree of fibrosis in the hearts.

CONCLUSIONS

Circulating fibrocytes are effector cells in cardiac fibrosis.

Tanshinone IIA Inhibits β-Catenin Nuclear Translocation and IGF-2R Activation via Estrogen Receptors to Suppress Angiotensin II-Induced H9c2 Cardiomyoblast Cell Apoptosis

Cardiomyopathy involves changes in the myocardial ultra-structure, hypertrophy, apoptosis, fibrosis and inflammation. Angiotensin II (AngII) stimulates the expression of insulin like-growth factors (IGF-2) and IGF-2 receptor (IGF-2R) in H9c2 cardiomyoblasts and subsequently leads to apoptosis. Estrogen receptors protect cardiomyocytes from apoptosis and fibrosis. Tanshinone IIA (TSN), a main active ingredient from Danshen, has been shown to protect cardiomyocytes from death caused by different stress signals. Estrogen receptor α (ER) is required for the rapid activation of the IGF-1R signaling cascade. This study aimed to investigate whether TSN protected H9c2 cardiomyocytes from AngII-induced activation of IGF-2R pathway and hypertrophy via ERs. We found that AngII caused the reduction in IGF-1R phosphorylation and the elevation of β-catenin and IGF-2R levels. This was reversed by increasing doses of TSN and of caspase-3 and ERK1/2 phosphorylation mediated by ERs. The phytoestrogen significantly attenuated AngII-induced apoptosis and suppressed the subsequent cardiac remodeling effect. Therefore, TSN reduced the AngII-induced activation of β-catenin and IGF-2R pathways, apoptosis and cardiac remodeling via ERs in H9c2 cardiomyoblasts.

Multiple comparison procedure and modeling: a versatile tool for evaluating dose-response relationships in veterinary pharmacology - a case study with furosemide

Congestive heart failure (CHF) is a leading cause of mortality with an increasing prevalence in human and canine populations. While furosemide is a loop diuretic prescribed for the majority of CHF patients to reduce fluid retention, it also activates the renin-angiotensin aldosterone system (RAAS) which further contributes to the accelerated progression of heart failure. Our objective was to quantify the effect of furosemide on diuresis, renin activity (RA), and aldosterone (AL) in dogs, using a combined multiple comparisons and model-based approach (MCP-Mod). Twenty-four healthy beagle dogs were allocated to four treatment groups (saline vs. furosemide 1, 2, and 4 mg/kg i.m., q12 h for 5 days). Data from RA and AL values at furosemide trough concentrations, as well as 24-h Diuresis, were analyzed using the MCP-Mod procedure. A combination of E_max models adequately described the dose-response relationships of furosemide for the various endpoints. The dose-response curves of RA and AL were found to be well in agreement, with an apparent shallower slope compared with 24-h Diuresis. The research presented herein constitutes the first application of MCP-Mod in Veterinary Medicine. Our data show that furosemide produces a submaximal effect on diuresis at doses lower than those identified to activate the circulating RAAS.

Angiotensin II AT1 receptor alters ACE2 activity, eNOS expression and CD44-hyaluronan interaction in rats with hypertension and myocardial fibrosis

AIM

This study tested the hypothesis that angiotensin II (Ang II) AT1 receptor is involved in development of hypertension and cardiac fibrosis via modifying ACE2 activity, eNOS expression and CD44-hyaluronan interaction.

MAIN METHODS

Male Sprague-Dawley rats were subjected to Ang II infusion (500ng/kg/min) using osmotic minipumps up to 4weeks and the AT1 receptor blocker, telmisartan was administered by gastric gavage (10mg/kg/day) during Ang II infusion.

KEY FINDINGS

Our results indicated that Ang II enhances AT1 receptor, downregulates AT2 receptor, ACE2 activity and eNOS expression, and increases CD44 expression and hyaluronidase activity, an enzyme for hyaluronan degradation. Further analyses revealed that Ang II increases blood pressure and augments vascular/interstitial fibrosis. Comparison of the Ang II group, treatment with telmisartan significantly increased ACE2 activity and eNOS expression in the intracardiac vessels and intermyocardium. These changes occurred in coincidence with decreased blood pressure. Furthermore, the locally-expressed AT1 receptor was downregulated, as evidenced by an increased ratio of the AT2 over AT1 receptor (1.4±0.4% vs. 0.4±0.1% in Ang II group, P<0.05). Along with these modulations, telmisartan inhibited membrane CD44 expression and hyaluronidase activity, decreased populations of macrophages and myofibroblasts, and reduced expression of TGFβ1 and Smads. Collagen I synthesis and tissue fibrosis were attenuated as demonstrated by the less extensive collagen-rich area.

SIGNIFICANCE

These results suggest that the AT1 receptor is involved in development of hypertension and cardiac fibrosis. Selective activating ACE2/eNOS and inhibiting CD44/HA interaction might be considered as the therapeutic targets for attenuating Ang II induced deleterious cardiovascular effects.

Vascular Fibrosis in Aging and Hypertension: Molecular Mechanisms and Clinical Implications

Aging is the primary risk factor underlying hypertension and incident cardiovascular disease. With aging, the vasculature undergoes structural and functional changes characterized by endothelial dysfunction, wall thickening, reduced distensibility, and arterial stiffening. Vascular stiffness results from fibrosis and extracellular matrix (ECM) remodelling, processes that are associated with aging and are amplified by hypertension. Some recently characterized molecular mechanisms underlying these processes include increased expression and activation of matrix metalloproteinases, activation of transforming growth factor-β1/SMAD signalling, upregulation of galectin-3, and activation of proinflammatory and profibrotic signalling pathways. These events can be induced by vasoactive agents, such as angiotensin II, endothelin-1, and aldosterone, which are increased in the vasculature during aging and hypertension. Complex interplay between the “aging process” and prohypertensive factors results in accelerated vascular remodelling and fibrosis and increased arterial stiffness, which is typically observed in hypertension. Because the vascular phenotype in a young hypertensive individual resembles that of an elderly otherwise healthy individual, the notion of “early” or “premature” vascular aging is now often used to describe hypertension-associated vascular disease. We review the vascular phenotype in aging and hypertension, focusing on arterial stiffness and vascular remodelling. We also highlight the clinical implications of these processes and discuss some novel molecular mechanisms of fibrosis and ECM reorganization.

Persistent phenotypic shift in cardiac fibroblasts: impact of transient renin angiotensin system inhibition

Fibrotic cardiac remodeling ultimately leads to heart failure - a debilitating and costly condition. Select antihypertensive agents have been effective in reducing or slowing the development of cardiac fibrosis. Moreover, some experimental studies have shown that the reduction in fibrosis induced by these agents persists long after stopping treatment. What has not been as well investigated is whether this transient treatment results in a protection against future fibrotic cardiac remodeling. In the present review, previously published studies are re-examined to assess whether the relative percent increase in collagen deposition over an off-treatment period is attenuated, relative to control, following transient antihypertensive treatment in young or adult rats. Present findings suggest that transient inhibition of the renin angiotensin system (RAS) not only produces a sustained reduction in cardiac fibrosis, but also results in a degree of protection against future collagen deposition. In addition, prior transient RAS inhibition appears to alter the cardiac fibroblast phenotype such that these cells show a muted response to myocardial injury - namely reduced proliferation, chemokine release, and collagen deposition. This review puts forth several potential mechanisms underlying this long-term cardiac protection that is afforded by transient RAS inhibition. Specifically, fibroblast phenotypic change, cardiac fibroblast apoptosis, sustained suppression of the RAS, persistent reduction in left ventricular hypertrophy, and persistent reduction in arterial pressure are each discussed. Identifying the mechanisms ultimately responsible for this change in cardiac fibroblast response to injury, hypertension, and aging may reveal novel targets for therapy.

Attenuation of myocardial fibrosis with curcumin is mediated by modulating expression of angiotensin II AT1/AT2 receptors and ACE2 in rats

Curcumin is known to improve cardiac function by balancing degradation and synthesis of collagens after myocardial infarction. This study tested the hypothesis that inhibition of myocardial fibrosis by curcumin is associated with modulating expression of angiotensin II (Ang II) receptors and angiotensin-converting enzyme 2 (ACE2). Male Sprague Dawley rats were subjected to Ang II infusion (500 ng/kg/min) using osmotic minipumps for 2 and 4 weeks, respectively, and curcumin (150 mg/kg/day) was fed by gastric gavage during Ang II infusion. Compared to the animals with Ang II infusion, curcumin significantly decreased the mean arterial blood pressure during the course of the observation. The protein level of the Ang II type 1 (AT1) receptor was reduced, and the Ang II type 2 (AT2) receptor was up-regulated, evidenced by an increased ratio of the AT2 receptor over the AT1 receptor in the curcumin group (1.2±0.02%) vs in the Ang II group (0.7±0.03%, P<0.05). These changes were coincident with less locally expressed AT1 receptor and enhanced AT2 receptor in the intracardiac vessels and intermyocardium. Along with these modulations, curcumin significantly decreased the populations of macrophages and alpha smooth muscle actin-expressing myofibroblasts, which were accompanied by reduced expression of transforming growth factor beta 1 and phosphorylated-Smad2/3. Collagen I synthesis was inhibited, and tissue fibrosis was attenuated, as demonstrated by less extensive collagen-rich fibrosis. Furthermore, curcumin increased protein level of ACE2 and enhanced its expression in the intermyocardium relative to the Ang II group. These results suggest that curcumin could be considered as an add-on therapeutic agent in the treatment of fibrosis-derived heart failure patient who is intolerant of ACE inhibitor therapy.

Baicalein attenuates angiotensin II-induced cardiac remodeling via inhibition of AKT/mTOR, ERK1/2, NF-κB, and calcineurin signaling pathways in mice

BACKGROUND

Baicalein, a specific lipoxygenase (LOX) inhibitor, has anti-inflammatory and antioxidant effects. However, the functional role of baicalein in angiotensin II (Ang II)-induced hypertension and cardiac remodeling remains unclear. Here we investigated the effect of baicalein on cardiac hypertrophy and fibrosis and the underlying mechanism.

METHODS

Wild-type (WT) mice were injected with Ang II (1,200ng/kg/min) alone or together with 12/15-LOX inhibitor baicalein (25mg/kg) for 14 days. Histological examinations were performed on heart sections with hematoxylin and eosin, Masson's trichrome, wheat germ agglutinin staining, and immunohistochemistry. The messenger RNA (mRNA) expression of cytokines and protein levels were detected by real-time polymerase chain reaction (PCR) and western blot analysis respectively.

RESULTS

Ang II infusion significantly increased blood pressure but decreased cardiac contractile function reflected by fractional shortening% and ejection fraction% compared with saline-treated mice. Moreover, Ang II infusion resulted in marked cardiac hypertrophy and fibrosis, promoted accumulation of macrophages and T cells, the expression of proinflammatory cytokines and malondialdehyde (MDA) production. However, these actions were markedly reversed by administration of baicalein in mice. Mechanistically, the protective effects of baicalein were associated with the inhibition of inflammation, oxidative stress, and multiple signaling pathways (AKT/mTOR, ERK1/2, nuclear factor-κB (NF-κB), and calcineurin) in the Ang II-treated mice.

CONCLUSIONS

This study demonstrates that baicalein can significantly ameliorate Ang II-induced hypertension and cardiac remodeling, and may be a novel therapeutic drug for prevention of hypertensive heart diseases.

Vasculopathy-associated hyperangiotensinemia mobilizes haematopoietic stem cells/progenitors through endothelial AT₂R and cytoskeletal dysregulation

Patients in organ failure of vascular origin have increased circulating hematopoietic stem cells and progenitors (HSC/P). Plasma levels of angiotensin II (Ang-II), are commonly increased in vasculopathies. Hyperangiotensinemia results in activation of a very distinct Ang-II receptor set, Rho-family GTPase members, and actin in bone marrow endothelial cells (BMEC) and HSC/P, which results in decreased membrane integrin activation in both BMEC and HSC/P, and in HSC/P de-adhesion and mobilization. The Ang-II effect can be reversed pharmacologically and genetically by inhibiting Ang-II production or signaling through BMEC AT2R, HSCP AT₁R/AT₂R or HSC/P RhoA, but not by interfering with other vascular tone mediators. Hyperangiotensinemia and high counts of circulating HSC/P seen in sickle cell disease (SCD) as a result of vascular damage, is significantly decreased by Ang-II inhibitors. Our data define for the first time the role of Ang-II HSC/P traffic regulation and redefine the hematopoietic consequences of anti-angiotensin therapy in SCD.

Inhibition of platelet activation by clopidogrel prevents hypertension-induced cardiac inflammation and fibrosis

Purpose

Platelets are essential for primary hemostasis; however, platelet activation also plays an important proinflammatory role. Inflammation promotes the development of cardiac fibrosis and heart failure induced by hypertension. In this study, we aimed to determine whether inhibiting platelet activation using clopidogrel could inhibit hypertension-induced cardiac inflammation and fibrosis.

Methods

Using a mouse model of angiotensin II (Ang II) infusion (1,500 ng/[kg·min] for 7 days), we determined the role of platelet activation in Ang II infusion-induced cardiac inflammation and fibrosis using a P2Y₁₂ receptor inhibitor, clopidogrel (50 mg/[kg·day]).

Results

CD41 staining showed that platelets accumulated in Ang II-infused hearts. Clopidogrel treatment inhibited Ang II infusion-induced accumulation of α-SMA⁺ myofibroblasts and cardiac fibrosis (4.17 ± 1.26 vs. 1.46 ± 0.81, p < 0.05). Infiltration of inflammatory cells, including Mac-2⁺ macrophages and CD45⁺Ly6G⁺ neutrophils (30.38 ± 4.12 vs. 18.7 ± 2.38, p < 0.05), into Ang II-infused hearts was also suppressed by platelet inhibition. Real-time PCR and immunohistochemical staining showed that platelet inhibition significantly decreased the expression of interleukin-1β and transforming growth factor-β. Acute injection of Ang II or PE stimulated platelet activation and platelet-leukocyte conjugation, which were abolished by clopidogrel treatment.

Conclusion

Thus, inhibition of platelet activation by clopidogrel prevents cardiac inflammation and fibrosis in response to Ang II. Taken together, our results indicate Ang II infusion-induced hypertension stimulated platelet activation and platelet-leukocyte conjugation, which initiated inflammatory responses that contributed to cardiac fibrosis.

Adiponectin suppresses angiotensin II-induced inflammation and cardiac fibrosis through activation of macrophage autophagy

Previous studies have indicated that adiponectin (APN) protects against cardiac remodeling, but the underlying mechanism remains unclear. The present study aimed to elucidate how APN regulates inflammatory responses and cardiac fibrosis in response to angiotensin II (Ang II). Male APN knockout (APN KO) mice and wild-type (WT) C57BL/6 littermates were sc infused with Ang II at 750 ng/kg per minute. Seven days after Ang II infusion, both APN KO and WT mice developed equally high blood pressure levels. However, APN KO mice developed more severe cardiac fibrosis and inflammation compared with WT mice. This finding was demonstrated by the up-regulation of collagen I, α-smooth muscle actin, IL-1β, and TNF-α and increased macrophage infiltration in APN KO mice. Moreover, there were substantially fewer microtubule-associated protein 1 light chain 3-positive autophagosomes in macrophages in the hearts of Ang II-infused APN KO mice. Additional in vitro studies also revealed that globular APN treatment induced autophagy, inhibited Ang II-induced nuclear factor-κB activity, and enhanced the expression of antiinflammatory cytokines, including IL-10, macrophage galactose N-acetyl-galactosamine specific lectin 2, found in inflammatory zone 1, and type-1 arginase in macrophages. In contrast, APN-induced autophagy and antiinflammatory cytokine expression was diminished in Atg5-knockdown macrophages or by Compound C, an inhibitor of adenosine 5'-monophosphate-activated protein kinase. Our study indicates that APN activates macrophage autophagy through the adenosine 5'-monophosphate-activated protein kinase pathway and suppresses Ang II-induced inflammatory responses, thereby reducing the extent of cardiac fibrosis.