Atlas of tissue renin-angiotensin-aldosterone system in human: A transcriptomic meta-analysis

Evaluation effect of alginate hydrogel containing losartan on wound healing and gene expression

Skin tissue engineering has become an increasingly popular alternative to conventional treatments for skin injuries. Hydrogels, owing to their advantages have become the ideal option for wound dressing, and they are extensively employed in a mixture of different drugs to accelerate wound healing. Sodium alginate is a readily available natural polymer with advantages such as bio-compatibility and a non-toxicological nature that is commonly used in hydrogel form for medical applications such as wound repair and drug delivery in skin regenerative medicine. Losartan is a medicine called angiotensin receptor blocker (ARB) that can prevent fibrosis by inhibiting AT1R (angiotensin II type 1 receptor). In this research, for the first time, three-dimensional scaffolds based on cross-linked alginate hydrogel with CaCl2 containing different concentrations of losartan for slow drug release and exudate absorption were prepared and characterized as wound dressing. Alginate hydrogel was mixed with 10, 1, 0.1, and 0.01 mg/mL of losartan, and their properties such as morphology, chemical structure, water uptake properties, biodegradability, stability assay, rheology, blood compatibility, and cellular response were evaluated. In addition, the therapeutic efficiency of the developed hydrogels was then assessed in an in vitro wound healing model and with a gene expression. The results revealed that the hydrogel produced was very porous (porosity of 47.37 ± 3.76 µm) with interconnected pores and biodegradable (weight loss percentage of 60.93 ± 4.51% over 14 days). All hydrogel formulations have stability under various conditions. The use of CaCl2 as a cross-linker led to an increase in the viscosity of alginate hydrogels. An in vitro cell growth study revealed that no cytotoxicity was observed at the suggested dosage of the hydrogel. Increases in Losartan dosage, however, caused hemolysis. In vivo study in adult male rats with a full-thickness model showed greater than 80% improvement of the primary wound region after 2 weeks of treatment with alginate hydrogel containing 0.1 mg/mL Losartan. RT-PCR and immunohistochemistry analysis showed a decrease in expression level of TGF-β1 and VEGF in treatment groups. Histological analysis demonstrated that the alginate hydrogel containing Losartan can be effective in wound repair by decreasing the size of the scar and tissue remodeling, as evidenced by future in vivo studies.

Steroid hormones in systemic sclerosis: associations with disease characteristics and modifications during scleroderma renal crisis

OBJECTIVE

The renin-angiotensin-aldosterone system (RAAS) and glucocorticoids (GCs) are involved in vascular remodeling and fibrosis but have not been extensively studied in systemic sclerosis (SSc). Our aim was to investigate the RAAS and GC hormones in SSc patients.

METHODS

Serum levels of renin (dosage and activity), aldosterone and its precursors (DOC, B, 18-OH-DOC, 18-OH-B), and GCs (cortisol, cortisone, 11-deoxycortisol, 18-OH-F) were assessed in 122 SSc patients and 52 healthy controls. After applying stringent inclusion criteria aimed at ensuring accurate hormone assessments (exclusion of interfering drugs, strict sampling conditions), we analysed RAAS hormones in 61 patients, and GCs in 96 patients. Hormone levels were compared between patients and controls; and associations with disease characteristics were assessed in patients.

RESULTS

Regarding RAAS hormones, SSc patients displayed significantly lower aldosterone levels (although within normal range), similar renin levels, and higher B levels than controls. Abnormal RAAS hormone levels were associated with a more severe SSc phenotype (lung and skin fibrosis, heart and pulmonary vascular involvements, inflammation). Regarding GC hormones, SSc patients had higher levels of cortisol, 11-desoxycortisol (precursor) and 18-OH-F (metabolite) but lower levels of cortisone (inactive counterpart) than controls. RAAS hormone levels were assessed in five SSc patients before and during scleroderma renal crisis (SRC): concentrations varied considerably between patients, but consistently included normal/increased aldosterone levels and elevated renin levels.

CONCLUSION

RAAS and GC hormones are abnormally produced in SSc patients, especially in patients with severe SSc and during SRC. This could suggest a participation of these hormonal systems in SSc pathogenesis.

Whole -genome survival analysis of 144 286 people from the UK Biobank identifies novel loci associated with blood pressure

This study utilized UK Biobank data from 144 286 participants and employed whole-genome sequencing (WGS) data and time-to-event data over a 12-year follow-up period to identify susceptibility in genetic variants associated with hypertension. Following genotype quality control, 6 319 822 single nucleotide polymorphisms underwent analysis, revealing 31 significant variant-level associations. Among these, 29 were novel - 15 in Fibrillin-2 ( FBN2 ) and 4 in Junctophilin-2 ( JPH2 ). Mendelian randomization utilizing two identified variants (rs17677724 and rs1014754) suggested that a genetically induced decrease in heart FBN2 expression and an increase in adrenal gland JPH2 expression were causally linked to hypertension. Phenome-wide association (PheWAS) analysis using the FinnGen dataset confirmed positive associations of rs17677724 and rs1014754 with hypertension, assessed across 2727 traits in 377 277 individuals. Lastly, rs1014754 positively associated with kallistatin, whereas rs17677724 negatively associated with renin in the Fenland study, suggesting a counterregulatory response to high blood pressure. This study, employing WGS data, identified novel genetic loci and potential therapeutic targets for hypertension.

Injectable, reversibly thermoresponsive captopril-laden hydrogel for the local treatment of sensory loss in diabetic neuropathy

A major and irreversible complication of diabetes is diabetic peripheral neuropathy (DPN), which can lead to significant disability and decreased quality of life. Prior work demonstrates the peptide hormone Angiotensin II (Ang II) is released locally in neuropathy and drives inflammation and impaired endoneurial blood flow. Therefore, we proposed that by utilizing a local thermoresponsive hydrogel injection, we could deliver inhibitors of angiotensin-converting enzyme (ACE) to suppress Ang II production and reduce nerve dysfunction in DPN through local drug release. The ACE inhibitor captopril was encapsulated into a micelle, which was then embedded into a reversibly thermoresponsive pluronics-based hydrogel matrix. Drug-free and captopril-loaded hydrogels demonstrated excellent product stability and sterility. Rheology testing confirmed sol properties with low viscosity at ambient temperature and increased viscosity and gelation at 37 °C. Captopril-loaded hydrogels significantly inhibited Ang II production in comparison to drug-free hydrogels. DPN mice treated with captopril-loaded hydrogels displayed normalized mechanical sensitivity and reduced inflammation, without side-effects associated with systemic exposure. Our data demonstrate the feasibility of repurposing ACE inhibitors as locally delivered anti-inflammatories for the treatment of sensory deficits in DPN. To the best of our knowledge, this is the first example of a locally delivered ACE inhibitor for the treatment of DPN.

Panax notoginseng saponin alleviates pulmonary fibrosis in rats by modulating the renin-angiotensin system

ETHNOPHARMACOLOGICAL RELEVANCE

Pulmonary fibrosis (PF) is a chronic, progressive, and often fatal interstitial lung disease. Traditional Chinese medicine formulations and their active ingredients have shown potential in the treatment of PF. Panax notoginseng saponin (PNS) is extracted from the widely used traditional Chinese medicinal herb Panax notoginseng (Burkill) F. H. Chen, exhibiting therapeutic effects in pulmonary diseases treatment.

AIM OF THE STUDY

This study aimed to investigate the effects and elucidate possible potential mechanisms of PNS on bleomycin (BLM)-induced PF in rats.

MATERIALS AND METHODS

PF was induced in rats by intratracheal administration of bleomycin (BLM, 5 mg/kg). After disease model induction, the rats were treated with PNS (50, 100, or 200 mg/kg per day) or pirfenidone (PFD, 50 mg/kg per day) for 28 days. Lung function, histopathological changes, collagen deposition, and E- and N-cadherin levels in lung tissue were evaluated. The mechanism of action of PNS was investigated using tandem mass tag-based quantitative proteomics analysis. Immunohistochemistry, enzyme-linked immunosorbent assay (ELISA), and Western blot analysis were performed to verify the proteomic results.

RESULTS

PNS treatment improved lung function, ameliorated the BLM-induced increase in the lung coefficient, attenuated the degree of alveolar inflammation and fibrosis, and reduced the elevated collagen level in PF rats. PNS treatment also down-regulated the expression of N-cadherin while up-regulating the expression of E-cadherin. Proteomic and bioinformatic analyses revealed that the renin-angiotensin system (RAS) was closely related to the therapeutic effect of PNS. Immunohistochemistry, Western blot, and ELISA results indicated that PNS exerted its anti-fibrotic effect via regulation of the balance between the angiotensin-converting enzyme (ACE)-angiotensin (Ang)II-AngII receptor type 1 (AT1R) and ACE2-Ang(1-7)-MasR axes.

CONCLUSIONS

PNS ameliorates BLM-induced PF in rats by modulating the RAS homeostasis, and is a new potential therapeutic agent for PF.

Lipotoxicity-Related Hematological Disorders in Obesity

Lipotoxicity can mediate endothelial dysfunction in obesity. Altered endothelial cell phenotype during the pathobiological course of the lipotoxicity may lead to hemostatic abnormalities, which is a hallmark of several hematological disorders. Impaired hemostasis could also be directly related to numerous metabolic diseases such as hypertension, diabetes, and atherosclerosis. On the other hand, the local hematopoietic bone marrow (BM) renin-angiotensin system (RAS) contributes to the development of atherosclerosis via acting on the lipotoxicity processes. Local BM RAS, principally an autocrine/paracrine/intracrine hematological system, is located at the crossroads of cellular regulation, molecular interactions, and lipotoxicity-mediated vascular endothelial dysfunction. The positive regulatory role of plasma LDL on AT1 receptor-mediated hematopoietic stem cell (HSC) differentiation and the production of pro-atherogenic monocytes have been described. LDL-regulated HSC function may explain in part hypercholesterolemia-induced inflammation as well as the anti-inflammatory and anti-atherosclerotic effects of AT1 receptor blockers. The role of local adipose tissue RAS is directly related to the pathogenesis of metabolic derangements in obesity. There may be a crosstalk between local BM RAS and local adipose tissue RAS at the genomics and transcriptomics levels. This chapter aims to review hematological alterations propagating the pathological influences of lipotoxicity on the vascular endothelium.

Catch your breath: The protective role of the angiotensin AT2 receptor for the treatment of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive interstitial lung disease whereby excessive deposition of extracellular matrix proteins (ECM) ultimately leads to respiratory failure. While there have been advances in pharmacotherapies for pulmonary fibrosis, IPF remains an incurable and irreversible disease. There remains an unmet clinical need for treatments that reverse fibrosis, or at the very least have a more tolerable side effect profile than currently available treatments. Transforming growth factor β1(TGFβ1) is considered the main driver of fibrosis in IPF. However, as our understanding of the role of the pulmonary renin-angiotensin system (PRAS) in the pathogenesis of IPF increases, it is becoming clear that targeting angiotensin receptors represents a potential novel treatment strategy for IPF - in particular, via activation of the anti-fibrotic angiotensin type 2 receptor (AT2R). This review describes the current understanding of the pathophysiology of IPF and the mediators implicated in its pathogenesis; focusing on TGFβ1, angiotensin II and related peptides in the PRAS and their contribution to fibrotic processes in the lung. Preclinical and clinical assessment of currently available AT2R agonists and the development of novel, highly selective ligands for this receptor will also be described, with a focus on compound 21, currently in clinical trials for IPF. Collectively, this review provides evidence of the potential of AT2R as a novel therapeutic target for IPF.

The contribution of the AT1 receptor to erythropoiesis

The renin-angiotensin system (RAS) comprises a broad set of functional peptides and receptors that play a role in cardiovascular homeostasis and contribute to cardiovascular pathologies. Angiotensin II (Ang II) is the most potent peptide hormone produced by the RAS due to its high abundance and its strong and pleiotropic impact on the cardiovascular system. Formation of Ang II takes place in the bloodstream and additionally in tissues in the so-called local RAS. Of the two Ang II receptors (AT1 and AT2) that Ang II binds to, AT1 is the most expressed throughout the mammalian body. AT1 expression is not restricted to cells of the cardiovascular system but in fact AT1 protein is found in nearly all organs, hence, Ang II takes part in several modulatory physiological processes one of which is erythropoiesis. In this review, we present multiple evidence supporting that Ang II modulates physiological and pathological erythropoiesis processes trough the AT1 receptor. Cumulative evidence indicates that Ang II by three distinct mechanisms influences erythropoiesis: 1) stimulation of renal erythropoietin synthesis; 2) direct action on bone marrow precursor cells; and 3) modulation of sympathetic nerve activity to the bone marrow. The text highlights clinical and preclinical evidence focusing on mechanistic studies using rodent models.

Renin-Angiotensin System: Updated Understanding and Role in Physiological and Pathophysiological States

The classical view of the renin-angiotensin system (RAS) is that of the circulating hormone pathway involved in salt and water homeostasis and blood pressure regulation. It is also involved in the pathogenesis of cardiac and renal disorders. This led to the creation of drugs blocking the actions of this classical pathway, which improved cardiac and renal outcomes. Our understanding of the RAS has significantly expanded with the discovery of new peptides involved in this complex pathway. Over the last two decades, a counter-regulatory or protective pathway has been discovered that opposes the effects of the classical pathway. Components of RAS are also implicated in the pathogenesis of obesity and its metabolic diseases. The continued discovery of newer molecules also provides novel therapeutic targets to improve disease outcomes. This article aims to provide an overview of an updated understanding of the RAS, its role in physiological and pathological processes, and potential novel therapeutic options from RAS for managing cardiorenal disorders, obesity, and related metabolic disorders.

An explorative epigenome-wide association study of plasma renin and aldosterone concentration in a Ghanaian population: the RODAM study

BACKGROUND

The epigenetic regulation of the renin-angiotensin-aldosterone system (RAAS) potentially plays a role in the pathophysiology underlying the high burden of hypertension in sub-Saharan Africans (SSA). Here we report the first epigenome-wide association study (EWAS) of plasma renin and aldosterone concentrations and the aldosterone-to-renin ratio (ARR).

METHODS

Epigenome-wide DNA methylation was measured using the Illumina 450K array on whole blood samples of 68 Ghanaians. Differentially methylated positions (DMPs) were assessed for plasma renin concentration, aldosterone, and ARR using linear regression models adjusted for age, sex, body mass index, diabetes mellitus, hypertension, and technical covariates. Additionally, we extracted methylation loci previously associated with hypertension, kidney function, or that were annotated to RAAS-related genes and associated these with renin and aldosterone concentration.

RESULTS

We identified one DMP for renin, ten DMPs for aldosterone, and one DMP associated with ARR. Top DMPs were annotated to the PTPRN2, SKIL, and KCNT1 genes, which have been reported in relation to cardiometabolic risk factors, atherosclerosis, and sodium-potassium handling. Moreover, EWAS loci previously associated with hypertension, kidney function, or RAAS-related genes were also associated with renin, aldosterone, and ARR.

CONCLUSION

In this first EWAS on RAAS hormones, we identified DMPs associated with renin, aldosterone, and ARR in a SSA population. These findings are a first step in understanding the role of DNA methylation in regulation of the RAAS in general and in a SSA population specifically. Replication and translational studies are needed to establish the role of these DMPs in the hypertension burden in SSA populations.

Renin Production by Juxtaglomerular Cell Tumors and Clear Cell Renal Cell Carcinoma and the Role of Angiotensin Signaling Inhibitors

OBJECTIVE

To profile juxtaglomerular cell tumors (JXG) and histologic mimics by analyzing renin expression; to identify non-JXG renin-producing tumors in The Cancer Genome Atlas (TCGA) data sets; and to define the prevalence of hypertension (HTN) and patient outcomes with angiotensin signaling inhibitor (ASI) use in tumors of interest.

PATIENTS AND METHODS

Thirteen JXGs and 10 glomus tumors (GTs), a histologic mimic, were evaluated for clinicopathologic features; TCGA data were analyzed to identify non-JXG renin-overexpressing tumors. An institutional registry was queried to determine the incidence of HTN, the use of ASIs in hypertensive patients, and the impact of ASIs on outcomes including progression-free survival (PFS) in a tumor type with high renin expression (clear cell renal cell carcinoma [CC-RCC] diagnosed between January 1, 2005, and December 31, 2012).

RESULTS

We found an association between renin production and HTN in JXG compared with GT. Analysis of TCGA data found that a subset of CC-RCCs overexpress renin relative to 29 other tumor types. Furthermore, analysis of our institutional registry revealed a high prevalence (64%) of HTN among 1203 patients treated with radical or partial nephrectomy for nonmetastatic CC-RCC. On multivariable Cox regression, patients with HTN treated with ASIs (34%) had improved PFS (hazard ratio, 0.76; 95% CI, 0.57 to 1.00; P=.05) compared with patients with HTN not treated with ASIs (30%).

CONCLUSION

The identification of renin expression in a subset of CC-RCC may provide a biologic rationale for the high prevalence of HTN and improved PFS with ASI use in hypertensive patients with nonmetastatic CC-RCC.

The Angiotensin AT2 Receptor: From a Binding Site to a Novel Therapeutic Target

Discovered more than 30 years ago, the angiotensin AT2 receptor (AT2R) has evolved from a binding site with unknown function to a firmly established major effector within the protective arm of the renin-angiotensin system (RAS) and a target for new drugs in development. The AT2R represents an endogenous protective mechanism that can be manipulated in the majority of preclinical models to alleviate lung, renal, cardiovascular, metabolic, cutaneous, and neural diseases as well as cancer. This article is a comprehensive review summarizing our current knowledge of the AT2R, from its discovery to its position within the RAS and its overall functions. This is followed by an in-depth look at the characteristics of the AT2R, including its structure, intracellular signaling, homo- and heterodimerization, and expression. AT2R-selective ligands, from endogenous peptides to synthetic peptides and nonpeptide molecules that are used as research tools, are discussed. Finally, we summarize the known physiological roles of the AT2R and its abundant protective effects in multiple experimental disease models and expound on AT2R ligands that are undergoing development for clinical use. The present review highlights the controversial aspects and gaps in our knowledge of this receptor and illuminates future perspectives for AT2R research. SIGNIFICANCE STATEMENT: The angiotensin AT2 receptor (AT2R) is now regarded as a fully functional and important component of the renin-angiotensin system, with the potential of exerting protective actions in a variety of diseases. This review provides an in-depth view of the AT2R, which has progressed from being an enigma to becoming a therapeutic target.

Hormone-Dependent Regulation of Renin and Effects on Prorenin Receptor Signaling in the Collecting Duct

The production of renin by the principal cells of the collecting duct has widened our understanding of the regulation of intrarenal angiotensin II (Ang II) generation and blood pressure. In the collecting duct, Ang II increases the synthesis and secretion of renin by mechanisms involving the activation of Ang II type 1 receptor (AT1R) via stimulation of the PKCα, Ca²⁺, and cAMP/PKA/CREB pathways. Additionally, paracrine mediators, including vasopressin (AVP), prostaglandins, bradykinin (BK), and atrial natriuretic peptide (ANP), regulate renin in principal cells. During Ang II-dependent hypertension, despite plasma renin activity suppression, renin and prorenin receptor (RPR) are upregulated in the collecting duct and promote de novo formation of intratubular Ang II. Furthermore, activation of PRR by its natural agonists, prorenin and renin, may contribute to the stimulation of profibrotic factors independent of Ang II. Thus, the interactions of RAS components with paracrine hormones within the collecting duct enable tubular compartmentalization of the RAS to orchestrate complex mechanisms that increase intrarenal Ang II, Na+ reabsorption, and blood pressure.

Local aldosterone synthesis in the large intestine of mouse: An ex vivo incubation study

Objective

To investigate the regulation of local aldosterone synthesis by physiological stimulants in the murine gut.

Methods

Male mice were fed for 14 days with normal, high (1.6%) or low (0.01%) sodium diets. Tissue liver receptor homolog-1 and aldosterone in the colon and caecum were detected using an enzyme-linked immunosorbent assay (ELISA). Released corticosterone and aldosterone in tissue incubation experiments after stimulation with angiotensin II (Ang II) and dibutyryl-cAMP (DBA; the second messenger of adrenocorticotropic hormone) were assayed using an ELISA. Tissue aldosterone synthase (CYP11B2) protein levels were measured using an ELISA and Western blots.

Results

In incubated colon tissues, aldosterone synthase levels were increased by a low-sodium diet; and by Ang II and DBA in the normal diet group. Release of aldosterone into the incubation buffer was increased from the colon by a low-sodium diet and decreased by a high-sodium diet in parallel with changes in aldosterone synthase levels. In mice fed a normal diet, colon incubation with both Ang II and DBA increased the release of aldosterone as well as its precursor corticosterone.

Conclusion

Local aldosterone synthesis in the large intestine is stimulated by a low-sodium diet, dibutyryl-cAMP and Ang II similar to the adrenal glands.

Can Previous Levels of Physical Activity Affect Risk Factors for Cardiorespiratory Diseases and Functional Capacity after COVID-19 Hospitalization? A Prospective Cohort Study

Purpose

To evaluate the influence of previous levels of physical activity on hemodynamic, vascular, ventilatory, and functional outcomes after coronavirus disease 2019 (COVID-19) hospitalization.

Methods

Sixty-three individuals with COVID-19 had their clinical status and previous levels (12 month) of physical activity (Baecke Questionnaire of Habitual Physical Activity) assessed at hospital admission. Individuals were then allocated to lower levels of physical activity (ACT_LOWER; N = 22), intermediate levels of physical activity (ACT_INTERMEDIATE; N = 22), or higher levels of physical activity (ACT_HIGHER; N = 19) groups, according to tertiles of physical activity. Resting hemodynamic (heart rate and brachial/central blood pressures) and vascular (carotid-femoral pulse wave velocity, augmentation index, and brachial artery flow-mediated dilation) variables, pulmonary function (spirometry), respiratory muscle strength (maximal respiratory pressures), and functional capacity (handgrip strength, five-time sit-to-stand, timed-up and go, and six-minute walking tests) were measured at 30 to 45 days after hospital discharge.

Results

ACT_LOWER showed lower levels (P < 0.05) of forced vital capacity, forced expiratory volume in the first second, maximal voluntary ventilation, and maximal expiratory pressure than ACT_HIGHER. ACT_LOWER also had lower (P = 0.023) walking distance (~21%,) and lower percentage of predicted walking distance (~20%) at six-minute walking test during follow-up than ACT_INTERMEDIATE. However, hemodynamic and vascular variables, handgrip strength, five-time sit-to-stand, and timed-up and go were not different among groups.

Conclusion

ACT_LOWER showed impaired ventilatory parameters and walking performance when compared with ACT_HIGHER and ACT_INTERMEDIATE, respectively. These results suggest that previous levels of physical activity may impact ventilatory and exercise capacity outcomes 30 to 45 days after COVID-19 hospitalization discharge.

Mapping the biogenesis of forward programmed megakaryocytes from induced pluripotent stem cells

Platelet deficiency, known as thrombocytopenia, can cause hemorrhage and is treated with platelet transfusions. We developed a system for the production of platelet precursor cells, megakaryocytes, from pluripotent stem cells. These cultures can be maintained for >100 days, implying culture renewal by megakaryocyte progenitors (MKPs). However, it is unclear whether the MKP state in vitro mirrors the state in vivo, and MKPs cannot be purified using conventional surface markers. We performed single-cell RNA sequencing throughout in vitro differentiation and mapped each state to its equivalent in vivo. This enabled the identification of five surface markers that reproducibly purify MKPs, allowing us insight into their transcriptional and epigenetic profiles. Last, we performed culture optimization, increasing MKP production. Together, this study has mapped parallels between the MKP states in vivo and in vitro and allowed the purification of MKPs, accelerating the progress of in vitro-derived transfusion products toward the clinic.

Renin angiotensin aldosterone system in pulmonary fibrosis: Pathogenesis to therapeutic possibilities

Pulmonary fibrosis is a devastating lung disease with multifactorial etiology characterized by alveolar injury, fibroblast proliferation and excessive deposition of extracellular matrix proteins, which progressively results in respiratory failure and death. Accumulating evidence from experimental and clinical studies supports a central role of the renin angiotensin aldosterone system (RAAS) in the pathogenesis and progression of idiopathic pulmonary fibrosis. Angiotensin II (Ang II), a key vasoactive peptide of the RAAS mediates pro-inflammatory and pro-fibrotic effects on the lungs, adversely affecting organ function. Recent years have witnessed seminal discoveries in the field of RAAS. Identification of new enzymes, peptides and receptors has led to the development of several novel concepts. Of particular interest is the establishment of a protective axis of the RAAS comprising of Angiotensin converting enzyme 2 (ACE2), Angiotensin-(1-7) [Ang-(1-7)], and the Mas receptor (the ACE2/Ang-(1-7)/Mas axis), and the discovery of a functional role for the Angiotensin type 2 (AT₂) receptor. Herein, we will review our current understanding of the role of RAAS in lung fibrogenesis, provide evidence on the anti-fibrotic actions of the newly recognized RAAS components (the ACE2/Ang-(1-7)/Mas axis and AT₂ receptor), discuss potential strategies and translational efforts to convert this new knowledge into effective therapeutics for PF.

Human Tissue Angiotensin Converting Enzyme (ACE) Activity Is Regulated by Genetic Polymorphisms, Posttranslational Modifications, Endogenous Inhibitors and Secretion in the Serum, Lungs and Heart

Objective: Inhibitors of the angiotensin converting enzyme (ACE) are the primarily chosen drugs to treat heart failure and hypertension. Moreover, an imbalance in tissue ACE/ACE2 activity is implicated in COVID-19. In the present study, we tested the relationships between circulating and tissue (lung and heart) ACE levels in men. Methods: Serum, lung (n = 91) and heart (n = 72) tissue samples were collected from Caucasian patients undergoing lung surgery or heart transplantation. ACE I/D genotype, ACE concentration and ACE activity were determined from serum and tissue samples. Clinical parameters were also recorded. Results: A protocol for ACE extraction was developed for tissue ACE measurements. Extraction of tissue-localized ACE was optimal in a 0.3% Triton-X-100 containing buffer, resulting in 260 ± 12% higher ACE activity over detergent-free conditions. SDS or higher Triton-X-100 concentrations inhibited the ACE activity. Serum ACE concentration correlated with ACE I/D genotype (II: 166 ± 143 ng/mL, n = 19, ID: 198 ± 113 ng/mL, n = 44 and DD: 258 ± 109 ng/mL, n = 28, p < 0.05) as expected. In contrast, ACE expression levels in the lung tissue were approximately the same irrespective of the ACE I/D genotype (II: 1423 ± 1276 ng/mg, ID: 1040 ± 712 ng/mg and DD: 930 ± 1273 ng/mg, p > 0.05) in the same patients (values are in median ± IQR). Moreover, no correlations were found between circulating and lung tissue ACE concentrations and activities (Spearman’s p > 0.05). In contrast, a significant correlation was identified between ACE activities in serum and heart tissues (Spearman’s Rho = 0.32, p < 0.01). Finally, ACE activities in lung and the serum were endogenously inhibited to similar degrees (i.e., to 69 ± 1% and 53 ± 2%, respectively). Conclusion: Our data suggest that circulating ACE activity correlates with left ventricular ACE, but not with lung ACE in human. More specifically, ACE activity is tightly coordinated by genotype-dependent expression, endogenous inhibition and secretion mechanisms.

Emerging importance of ACE2 in external stratified epithelial tissues

Angiotensin converting enzyme 2 (ACE2), a component of the renin-angiotensin system (RAS), has been identified as the receptor for the SARS-CoV-2. Several RAS components including ACE2 and its substrate Ang II are present in both eye and skin, two stratified squamous epithelial tissues that isolate organisms from external environment. Our recent findings in cornea and others in both skin and eye suggest contribution of this system, and specifically of ACE2 in variety of physiological and pathological responses of these organ systems. This review will focus on the role RAS system plays in both skin and cornea, and will specifically discuss our recent findings on ACE2 in corneal epithelial inflammation, as well as potential implications of ACE2 in patients with COVID-19.

Horizontal meta-analysis identifies common deregulated genes across AML subgroups providing a robust prognostic signature

Advances in transcriptomics have improved our understanding of leukemic development and helped to enhance the stratification of patients. The tendency of transcriptomic studies to combine AML samples, regardless of cytogenetic abnormalities, could lead to bias in differential gene expression analysis because of the differential representation of AML subgroups. Hence, we performed a horizontal meta-analysis that integrated transcriptomic data on AML from multiple studies, to enrich the less frequent cytogenetic subgroups and to uncover common genes involved in the development of AML and response to therapy. A total of 28 Affymetrix microarray data sets containing 3940 AML samples were downloaded from the Gene Expression Omnibus database. After stringent quality control, transcriptomic data on 1534 samples from 11 data sets, covering 10 AML cytogenetically defined subgroups, were retained and merged with the data on 198 healthy bone marrow samples. Differentially expressed genes between each cytogenetic subgroup and normal samples were extracted, enabling the unbiased identification of 330 commonly deregulated genes (CODEGs), which showed enriched profiles of myeloid differentiation, leukemic stem cell status, and relapse. Most of these genes were downregulated, in accordance with DNA hypermethylation. CODEGs were then used to create a prognostic score based on the weighted sum of expression of 22 core genes (CODEG22). The score was validated with microarray data of 5 independent cohorts and by quantitative real time-polymerase chain reaction in a cohort of 142 samples. CODEG22-based stratification of patients, globally and into subpopulations of cytologically healthy and elderly individuals, may complement the European LeukemiaNet classification, for a more accurate prediction of AML outcomes.

Maternal Angiotensin Increases Placental Leptin in Early Gestation via an Alternative Renin-Angiotensin System Pathway: Suggesting a Link to Preeclampsia

[Figure: see text].

Combination of Angiotensin (1-7) Agonists and Convalescent Plasma as a New Strategy to Overcome Angiotensin Converting Enzyme 2 (ACE2) Inhibition for the Treatment of COVID-19

Coronavirus disease-2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is currently the most concerning health problem worldwide. SARS-CoV-2 infects cells by binding to angiotensin-converting enzyme 2 (ACE2). It is believed that the differential response to SARS-CoV-2 is correlated with the differential expression of ACE2. Several reports proposed the use of ACE2 pharmacological inhibitors and ACE2 antibodies to block viral entry. However, ACE2 inhibition is associated with lung and cardiovascular pathology and would probably increase the pathogenesis of COVID-19. Therefore, utilizing ACE2 soluble analogs to block viral entry while rescuing ACE2 activity has been proposed. Despite their protective effects, such analogs can form a circulating reservoir of the virus, thus accelerating its spread in the body. Levels of ACE2 are reduced following viral infection, possibly due to increased viral entry and lysis of ACE2 positive cells. Downregulation of ACE2/Ang (1-7) axis is associated with Ang II upregulation. Of note, while Ang (1-7) exerts protective effects on the lung and cardiovasculature, Ang II elicits pro-inflammatory and pro-fibrotic detrimental effects by binding to the angiotensin type 1 receptor (AT1R). Indeed, AT1R blockers (ARBs) can alleviate the harmful effects associated with Ang II upregulation while increasing ACE2 expression and thus the risk of viral infection. Therefore, Ang (1-7) agonists seem to be a better treatment option. Another approach is the transfusion of convalescent plasma from recovered patients with deteriorated symptoms. Indeed, this appears to be promising due to the neutralizing capacity of anti-COVID-19 antibodies. In light of these considerations, we encourage the adoption of Ang (1-7) agonists and convalescent plasma conjugated therapy for the treatment of COVID-19 patients. This therapeutic regimen is expected to be a safer choice since it possesses the proven ability to neutralize the virus while ensuring lung and cardiovascular protection through modulation of the inflammatory response.

Angiotensin receptors and neuropathic pain

Growing evidence implicates the renin-angiotensin system (RAS) in multiple facets of neuropathic pain (NP). This narrative review focuses primarily on the major bioactive RAS peptide, Angiotensin II (Ang II), and its receptors, namely type 1 (AT1R) and type 2 (AT2R). Both receptors are involved in the development of NP and represent potential therapeutic targets. We first discuss the potential role of Ang II receptors in modulation of NP in the central nervous system. Ang II receptor expression is widespread in circuits associated with the perception and modulation of pain, but more studies are required to fully characterize receptor distribution, downstream signaling, and therapeutic potential of targeting the central nervous system RAS in NP. We then describe the peripheral neuronal and nonneuronal distribution of the RAS, and its contribution to NP. Other RAS modulators (such as Ang (1-7)) are briefly reviewed as well. AT1R antagonists are analgesic across different pain models, including NP. Several studies show neuronal protection and outgrowth downstream of AT2R activation, which may lead to the use of AT2R agonists in NP. However, blockade of AT2R results in analgesia. Furthermore, expression of the RAS in the immune system and a growing appreciation of neuroimmune crosstalk in NP add another layer of complexity and therapeutic potential of targeting this pathway. A growing number of human studies also hint at the analgesic potential of targeting Ang II signaling. Altogether, Ang II receptor signaling represents a promising, far-reaching, and novel strategy to treat NP.

Impact of cortisol on blood pressure and hypertension-mediated organ damage in hypertensive patients

OBJECTIVES

Patients with overt and subclinical Cushing's syndrome frequently develop hypertension, metabolism disorders, and atherosclerotic lesions. The aim of the present study was to test the association between cortisol and blood pressure (BP), organ damage, and metabolic parameters in hypertensive patients without hypercortisolism.

METHODS

After exclusion of patients treated with corticosteroids or with Cushing's syndrome, the cohort included 623 hypertensive patients (mean ± SD age 50.3 ± 15.4 years, 50.9% men, median 24-h BP 146/88 mmHg) with an extended work-up (lipid profile, hypertension-mediated organ damage). Cortisol secretion was assessed by plasma cortisol at 0800 and 1600 h, and by 24-h urinary free cortisol (24 h UFC) normalized if required to urine creatinine (UFC/U creat).

RESULTS

Plasma cortisol at 1600 h, 24 h-UFC, and UFC/U creat were significantly and positively correlated with daytime, night-time, and 24-h SBP; plasma cortisol at 0800 h was not associated with BP. The strongest correlations were observed in the subgroup of aged more than 50 years (correlation coefficients between 0.23 and 0.28). These correlations remained after adjustment on plasma aldosterone. Metabolic parameters were weakly associated with cortisol. Arterial stiffness (central pulse pressure and pulse wave velocity), plasma NT-proBNP, and microalbuminuria were significantly correlated with 24 h UFC, UFC/U creat, and plasma cortisol at 1600 h.

CONCLUSION

Cortisol influences weakly the level of BP independently from plasma aldosterone in hypertensive patients, particularly in older patients, and that there was weak association with HMOD. It may, therefore, be of interest to test specific treatments targeting cortisol excess in selected hypertensive patients.

Insights on SARS-CoV-2 Molecular Interactions With the Renin-Angiotensin System

The emergence of SARS-CoV-2/human/Wuhan/X1/2019, a virus belonging to the species Severe acute respiratory syndrome-related coronavirus, and the recognition of Coronavirus Disease 2019 (COVID-19) as a pandemic have highly increased the scientific research regarding the pathogenesis of COVID-19. The Renin Angiotensin System (RAS) seems to be involved in COVID-19 natural course, since studies suggest the membrane-bound Angiotensin-converting enzyme 2 (ACE2) works as SARS-CoV-2 cellular receptor. Besides the efforts of the scientific community to understand the virus' molecular interactions with human cells, few studies summarize what has been so far discovered about SARS-CoV-2 signaling mechanisms and its interactions with RAS molecules. This review aims to discuss possible SARS-CoV-2 intracellular signaling pathways, cell entry mechanism and the possible consequences of the interaction with RAS components, including Angiotensin II (Ang II), Angiotensin-(1-7) [Ang-(1-7)], Angiotensin-converting enzyme (ACE), ACE2, Angiotensin II receptor type-1 (AT1), and Mas Receptor. We also discuss ongoing clinical trials and treatment based on RAS cascade intervention. Data were obtained independently by the two authors who carried out a search in the PubMed, Embase, LILACS, Cochrane, Scopus, SciELO and the National Institute of Health databases using Medical Subject Heading terms as "SARS-CoV-2," "COVID-19," "Renin Angiotensin System," "ACE2," "Angiotensin II," "Angiotensin-(1-7)," and "AT1 receptor." Similarly to other members of Coronaviridae family, the molecular interactions between the pathogen and the membrane-bound ACE2 are based on the cleavage of the spike glycoprotein (S) in two subunits. Following the binding of the S1 receptor-binding domain (RBD) to ACE2, transmembrane protease/serine subfamily 2 (TMPRSS2) cleaves the S2 domain to facilitate membrane fusion. It is very likely that SARS-CoV-2 cell entry results in downregulation of membrane-bound ACE2, an enzyme that converts Ang II into Ang-(1-7). This mechanism can result in lung injury and vasoconstriction. In addition, Ang II activates pro-inflammatory cascades when binding to the AT1 Receptor. On the other hand, Ang-(1-7) promotes anti-inflammatory effects through its interactions with the Mas Receptor. These molecules might be possible therapeutic targets for treating COVID-19. Thus, the understanding of SARS-CoV-2 intracellular pathways and interactions with the RAS may clarify COVID-19 physiopathology and open perspectives for new treatments and strategies.

Covid-19: the renin-angiotensin system imbalance hypothesis

The emergency of SARS-CoV-2 in China started a novel challenge to the scientific community. As the virus turns pandemic, scientists try to map the cellular mechanisms and pathways of SARS-CoV-2 related to the pathogenesis of Coronavirus Disease 2019 (Covid-19). After transmembrane angiotensin-converting enzyme 2 (ACE2) has been found to be SARS-CoV-2 receptor, we hypothesized an immune-hematological mechanism for Covid-19 based on renin-angiotensin system (RAS) imbalance to explain clinical, laboratory and imaging findings on disease course. We believe that exaggerated activation of ACE/Angiotensin II (Ang II)/Angiotensin Type 1 (AT1) receptor RAS axis in line with reduction of ACE2/Angiotensin-(1-7)/Mas receptor may exert a pivotal role in the pathogenesis of Covid-19. In this perspective, we discuss potential mechanisms and evidence on this hypothesis.

Protective role of ACE2 and its downregulation in SARS-CoV-2 infection leading to Macrophage Activation Syndrome: Therapeutic implications

In light of the outbreak of the 2019 novel coronavirus disease (COVID-19), the international scientific community has joined forces to develop effective treatment strategies. The Angiotensin-Converting Enzyme (ACE) 2, is an essential receptor for cell fusion and engulfs the SARS coronavirus infections. ACE2 plays an important physiological role, practically in all the organs and systems. Also, ACE2 exerts protective functions in various models of pathologies with acute and chronic inflammation. While ACE2 downregulation by SARS-CoV-2 spike protein leads to an overactivation of Angiotensin (Ang) II/AT1R axis and the deleterious effects of Ang II may explain the multiorgan dysfunction seen in patients. Specifically, the role of Ang II leading to the appearance of Macrophage Activation Syndrome (MAS) and the cytokine storm in COVID-19 is discussed below. In this review, we summarized the latest research progress in the strategies of treatments that mainly focus on reducing the Ang II-induced deleterious effects rather than attenuating the virus replication.

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Protective role of ACE2 in the organs and system

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Downregulation of ACE2 expression by SARS-CoV-2 leads to Ang II-induced organ damage.

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The appearance of MAS in COVID-19 patient

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Suggested treatment to diminish the deleterious effect of Ang II or appearance of MAS

Peptidomic Analysis of Urine from Youths with Early Type 1 Diabetes Reveals Novel Bioactivity of Uromodulin Peptides In Vitro

Chronic hyperglycemia is known to disrupt the proteolytic milieu, initiating compensatory and maladaptive pathways in the diabetic kidney. Such changes in intrarenal proteolysis are captured by the urinary peptidome. To elucidate the early kidney response to chronic hyperglycemia, we conducted a peptidomic investigation into urines from otherwise healthy youths with type 1 diabetes and their non-diabetic peers using unbiased and targeted mass spectrometry-based techniques. This cross-sectional study included two separate cohorts for the discovery (n = 30) and internal validation (n = 30) of differential peptide excretion. Peptide bioactivity was predicted using PeptideRanker and subsequently verified in vitro Proteasix and the Nephroseq database were used to identify putative proteases responsible for peptide generation and examine their expression in diabetic nephropathy. A total of 6550 urinary peptides were identified in the discovery analysis. We further examined the subset of 162 peptides, which were quantified across all thirty samples. Of the 15 differentially excreted peptides (p < 0.05), seven derived from a C-terminal region (589SGSVIDQSRVLNLGPITRK607) of uromodulin, a kidney-specific protein. Increased excretion of five uromodulin peptides was replicated in the validation cohort using parallel reaction monitoring (p < 0.05). One of the validated peptides (SGSVIDQSRVLNLGPI) activated NFκB and AP-1 signaling, stimulated cytokine release, and enhanced neutrophil migration in vitro. In silico analyses highlighted several potential proteases such as hepsin, meprin A, and cathepsin B to be responsible for generating these peptides. In summary, we identified a urinary signature of uromodulin peptides associated with early type 1 diabetes before clinical manifestations of kidney disease and discovered novel bioactivity of uromodulin peptides in vitro Our present findings lay the groundwork for future studies to validate peptide excretion in larger and broader populations, to investigate the role of bioactive uromodulin peptides in high glucose conditions, and to examine proteases that cleave uromodulin.

tRNA‑derived small RNAs: A novel class of small RNAs in human hypertrophic scar fibroblasts

tRNA‑derived small RNAs (tsRNAs) have been shown to play regulatory roles in many physiological and pathological processes. However, their roles in hypertrophic scars remain unclear. The present study investigated differentially expressed tsRNAs in human hypertrophic scar fibroblasts and normal skin fibroblasts via high‑throughput sequencing. Several dysregulated tsRNAs were validated by reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, target prediction, coexpression networks and competing endogenous RNA (ceRNA) networks were evaluated to discover the principal functions of significantly differentially expressed tsRNAs. In total, 67 differentially expressed tsRNAs were detected, of which 27 were upregulated and 40 downregulated in hypertrophic scar fibroblasts. The GO analysis indicated that the dysregulated tsRNAs are associated with numerous biological functions, including 'nervous system development', 'cell adhesion', 'focal adhesion', 'protein binding', 'angiogenesis' and 'actin binding'. KEGG pathway analysis revealed that the most altered pathways include 'Ras signaling pathway', 'Rap1 signaling pathway' and 'cGMP‑PKG signaling pathway'. The target genes of the differentially expressed tsRNAs participate in several signaling pathways important for scar formation. The results of RT‑qPCR were consistent with those of sequencing. MicroRNA (miR)‑29b‑1‑5p was identified as a target of tsRNA‑23678 and was downregulated in hypertrophic scar fibroblasts, constituting a negative regulatory factor for scar formation. Furthermore, tsRNA‑23761 acted as a ceRNA and bound to miR‑3135b to regulate the expression of miR‑3135b targets, including angiotensin‑converting enzyme. Collectively, these findings reveal that tsRNAs are differentially expressed in human hypertrophic scar fibroblasts, and may contribute to the molecular mechanism and treatment of hypertrophic scars.

Pathobiological Interactions of Local Bone Marrow Renin-Angiotensin System and Central Nervous System in Systemic Arterial Hypertension

Circulating renin-angiotensin system (RAS) and local paracrin-autocrin-intracrin tissue-based RAS participate in numerous pathobiological events. Pro-inflammatory, pro-fibrotic, and pro-thrombotic consequences associated with local RAS activation have been detected at cellular and molecular level. Regenerative progenitor cell therapy in response to RAS modulating pharmacotherapy has emerged as an adjunct in the context of endothelial cell injury and regeneration to improve regeneration of the vascular endothelium. Local hematopoietic bone marrow (BM) RAS symbolizes the place of cross-interaction between vascular biology and cellular events from embryogenesis to definitive hematopoiesis underlying vascular atherosclerosis. The BM microenvironment also contains Mas receptors, which control the proliferative role of Ang 1-7 on hematopoietic stem cells. Ang 1-7 is produced from Ang-II or Ang-I with the help of ACE2. Various tissues and organs also have an effect on the RAS system. The leukocytes contain and synthesize immunoreactive angiotensinogen species capable of producing angiotensin in the basal state or after incubation with renin. The significance of RAS employment in atherosclerosis and hypertension was indicated by novel bidirectional Central Nervous System (CNS) RAS-BM RAS communications. Myeloid cells generated within the context of hematopoietic BM RAS are considered as the initiators and decision shapers in atherosclerosis. Macrophages in the atherosclerotic lesions contain angiotensin peptides by which RAS blockers inhibit monocyte activation and adherence. Furthermore, vascular biology in relation to inflammation and neoplasia is also affected by local tissue RAS. The purpose of this article is to outline interactions of circulating and local angiotensin systems, especially local bone marrow RAS, in the vascular pathobiological microenvironment of CNS.

Upregulation of Cortical Renin and Downregulation of Medullary (Pro)Renin Receptor in Unilateral Ureteral Obstruction

Chronic kidney disease (CKD) is characterized by renal dysfunction, which is a common feature of other major diseases, such as hypertension and diabetes. Unilateral ureteral obstruction (UUO) has been used as a model of CKD in experimental animals and consists of total obstruction of one kidney ureter. The UUO decreases renal blood flow, which promotes the synthesis of renin in the juxtaglomerular apparatus, the first step in renin–angiotensin system (RAS) cascade. RAS induces inflammation and remodeling, along with reduced renal function. However, it remains unknown whether intrarenal RAS (iRAS) is activated in early stages of CKD. Our objective was to characterize different iRAS components in the renal cortex and in the medulla in an early phase of UUO. Male C57BL/6 mice (8–12 weeks old) were subjected to UUO in the left kidney, or to sham surgery, and were euthanized after 7 days (n = 5/group). Renal function, renal inflammatory/remodeling processes, and iRAS expression were evaluated. UUO increased plasma creatinine, right renal hypertrophy (9.08 ± 0.31, P < 0.05 vs. Sham), and tubular dilatation in the left kidney cortex (42.42 ± 8.19µm, P < 0.05 vs. Sham). This correlated with the increased mRNA of IL-1β (1.73 ± 0.14, P < 0.01 vs. Sham, a pro-inflammatory cytokine) and TGF-β1 (1.76 ± 0.10, P < 0.001 vs. Sham, a pro-fibrotic marker). In the renal cortex of the left kidney, UUO increased the mRNA and protein levels of renin (in 35% and 28%, respectively, P < 0.05 vs. Sham). UUO decreased mRNA and protein levels for the (pro)renin receptor in the renal medulla (0.67 ± 0.036 and 0.88 ± 0.028, respectively, P < 0.05 vs. Sham). Our results suggest that modulation of iRAS components depends on renal localization and occurs in parallel with remodeling and pro-inflammatory/pro-fibrotic mechanisms.

Effects of angiotensin-II on brain endothelial cell permeability via PPARalpha regulation of para- and trans-cellular pathways

Angiotensin-II (Ang-II) is a key factor in hypertension, diabetes and aging, which are all primary risk factors for CNS disease. Furthermore, Ang-II may play under-appreciated roles in neurogenesis, angiogenesis and CNS remodeling. Therefore, any contemplated attempts for neurorestorative therapies in the CNS should consider the context of Ang-II signaling. Here, we investigate how Ang-II may regulate cerebral endothelial permeability, a key functional feature of the neurovascular unit. Exposure of human brain endothelial cell cultures to Ang-II increased its permeability to BSA-Alexa488 tracer. Immunocytochemistry and pulse-chase experiments suggested that both para-cellular as well as trans-cellular pathways were involved. Candesartan but not PD123319 blocked Ang-II permeability effects, suggesting that Ang-II effects may be mediated via type 1 receptor. Immunocytochemistry and western blots showed that Ang-II disrupted the membrane distributions of ZO-1 and VE-Cad, decreased total levels of JAM-A and Mfsd2a, and increased Cav1. These effects of Ang-II were accompanied by dephosphorylation of PPARalpha. Finally, Ang-II-induced increases in endothelial permeability were ameliorated by PPARalpha agonists. Taken together, these studies suggest that Ang-II may disrupt both para- and trans-cellular permeability in cerebral endothelium, and PPARalpha-related pathways may offer potential therapeutic targets for ameliorating these effects in cell-based regenerative medicine.

Potassium Intake Prevents the Induction of the Renin-Angiotensin System and Increases Medullary ACE2 and COX-2 in the Kidneys of Angiotensin II-Dependent Hypertensive Rats

In angiotensin II (Ang II)-dependent hypertensive rats there is an increased expression of proximal tubule angiotensinogen (AGT), collecting duct renin and angiotensin converting enzyme (ACE), which contributes to intratubular Ang II formation. Ang II acts on Ang II type 1 receptors promoting sodium retention and vasoconstriction. However concurrently, the ACE2-Ang-(1–7) axis and the expression of kallikrein and medullary prostaglandins counteract the effects of Ang II, promoting natriuresis and vasodilation. Human studies demonstrate that dietary potassium (K⁺) intake lowers blood pressure. In this report we evaluate the expression of AGT, ACE, medullary prorenin/renin, ACE2, kallikrein and cyclooxygenase-2 (COX-2) in Ang II-infused rats fed with high K⁺ diet (2%) for 14 days. Dietary K⁺ enhances diuresis in non-infused and in Ang II-infused rats. The rise in systolic blood pressure in Ang II-infused rats was attenuated by dietary K⁺. Ang II-infused rats showed increased renal protein levels of AGT, ACE and medullary prorenin and renin. This effect was attenuated in the Ang II + K⁺ group. Ang II infusion decreased ACE2 compared to the control group; however, K⁺ diet prevented this effect in the renal medulla. Furthermore, medullary COX-2 was dramatically induced by K⁺ diet in non-infused and in Ang II infused rats. Dietary K⁺ greatly increased kallikrein immunostaining in normotensive rats and in Ang II-hypertensive rats. These results indicate that a high K⁺ diet attenuates Ang II-dependent hypertension by preventing the induction of ACE, AGT and collecting duct renin and by enhancing medullary COX-2 and ACE2 protein expression in the kidney.

The Role of the Local Bone Marrow Renin-Angiotensin System in Multiple Myeloma

Objective:

Angiotensin II promotes growth and angiogenesis via type 1 receptors (AGTR1) in certain tumors. In this study, we examine the bone marrow AGTR1 expression in multiple myeloma (MM) and its relationship with the regulation of angiogenesis and prognostic factors.

Materials and Methods:

Bone marrow AGTR1 mRNA levels of 39 MM patients and 15 healthy controls were analyzed with quantitative RT-PCR. Immunohistochemical staining of the tissue vascular endothelial growth factor (VEGF), CD34, and factor VIIIrAg (fVIIIrAg) was used to assess bone marrow angiogenesis.

Results:

Bone marrow samples of the patients showed increased VEGF, fVIIIrAg, and CD34 staining and higher AGTR1 expression levels when compared to controls. Patients with severe-diffuse bone marrow infiltration showed higher bone marrow VEGF, fVIIIrAg, CD34, and AGTR1 mRNA levels when compared to other patients.

Conclusion:

AGTR1 expression was found positively correlated with plasma β2-microglobulin level and patients with increased AGTR1 expression showed increased bone marrow CD34 levels.

Losartan and isoproterenol promote alterations in the local renin-angiotensin system of rat salivary glands

Renin-angiotensin system (RAS) systemically or locally collaborates with tissue homeostasis, growth and development, which has been extensively studied for its pharmacological implications. This study was primarily aimed at finding and characterizing local RAS in rat parotid, sublingual and submandibular glands. It was also hypothesized that vasoactive drugs could affect the expression of RAS targets, as well as saliva flow and its composition. Therefore, another objective of this study was to compare the effects of losartan (angiotensin II receptor blocker) and isoproterenol (β-adrenergic receptor agonist). Forty-one Wistar rats were divided into three groups and administered a daily intraperitoneal dose of saline, losartan or isoproterenol solutions for one week. The following RAS targets were studied using qPCR: renin (REN), angiotensinogen (AGT), angiotensin converting enzyme (ACE), ACE-2, elastase-2 (ELA-2), AT1-a and MAS receptors, using RPL-13 as a reference gene. Morphology of glands was analyzed by immunohistochemistry using REN, ACE, ACE-2, AT1, AT2 and MAS antibodies. The volume and total protein content of saliva were measured. Our results revealed that ACE, ACE-2, AT1-a, AT2 and MAS receptors were expressed in all salivary gland samples, but REN and ELA-2 were absent. Losartan decreased mRNA expression of RAS targets in parotid (MAS) and submandibular glands (ACE and both AT receptors), without affecting morphological alterations, and significantly decreased saliva and total protein secretions. Isoproterenol treatment affected gene expression profiles in parotid (ACE, ACE-2, AT1-a, MAS, AGT), and submandibular (ACE, AT2, AGT) glands, thus promoting acinar hypertrophy in serous acini, without significant changes in salivary flow or total protein content. These drugs affected mainly acini, followed by duct systems and myoepithelial cells, whereas blood vessels were not affected. In conclusion, there is a local RAS in major rat salivary glands and losartan, an angiotensin II receptor blocker, affected not only the RAS-target gene expression but also decreased salivary flow and total protein content.

An Update on the Tissue Renin Angiotensin System and Its Role in Physiology and Pathology

In its classical view, the renin angiotensin system (RAS) was defined as an endocrinesystem involved in blood pressure regulation and body electrolyte balance. However, the emergingconcept of tissue RAS, along with the discovery of new RAS components, increased thephysiological and clinical relevance of the system. Indeed, RAS has been shown to be expressed invarious tissues where alterations in its expression were shown to be involved in multiple diseasesincluding atherosclerosis, cardiac hypertrophy, type 2 diabetes (T2D) and renal fibrosis. In thischapter, we describe the new components of RAS, their tissue-specific expression, and theiralterations under pathological conditions, which will help achieve more tissue- and conditionspecifictreatments.

An Update on the Tissue Renin Angiotensin System and Its Role in Physiology and Pathology

In its classical view, the renin angiotensin system (RAS) was defined as an endocrine system involved in blood pressure regulation and body electrolyte balance. However, the emerging concept of tissue RAS, along with the discovery of new RAS components, increased the physiological and clinical relevance of the system. Indeed, RAS has been shown to be expressed in various tissues where alterations in its expression were shown to be involved in multiple diseases including atherosclerosis, cardiac hypertrophy, type 2 diabetes (T2D) and renal fibrosis. In this chapter, we describe the new components of RAS, their tissue-specific expression, and their alterations under pathological conditions, which will help achieve more tissue- and condition-specific treatments.

Periarterial fat from two human vascular beds is not a source of aldosterone to promote vasoconstriction

Mouse adipocytes have been reported to release aldosterone and reduce endothelium-dependent relaxation. It is unknown whether perivascular adipose tissue (PVAT) releases aldosterone in humans. The present experiments were designed to test the hypothesis that human PVAT releases aldosterone and induces endothelial dysfunction. Vascular reactivity was assessed in human internal mammary and renal segmental arteries obtained at surgery. The arteries were prepared with/without PVAT, and changes in isometric tension were measured in response to the vasoconstrictor thromboxane prostanoid receptor agonist U46619 and the endothelium-dependent vasodilator acetylcholine. The effects of exogenous aldosterone and of mineralocorticoid receptor (MR) antagonist eplerenone were determined. Aldosterone concentrations were measured by ELISA in conditioned media incubated with human adipose tissue with/without angiotensin II stimulation. Presence of aldosterone synthase and MR mRNA was examined in perirenal, abdominal, and mammary PVAT by PCR. U46619 -induced tension and acetylcholine-induced relaxation were unaffected by exogenous and endogenous aldosterone (addition of aldosterone and MR blocker) in mammary and renal segmental arteries, both in the presence and absence of PVAT. Aldosterone release from incubated perivascular fat was not detectable. Aldosterone synthase expression was not consistently observed in human adipose tissues in contrast to that of MR. Thus, exogenous aldosterone does not affect vascular reactivity and endothelial function in ex vivo human arterial segments, and the tested human adipose tissues have no capacity to synthesize/release aldosterone. In perspective, physiologically relevant effects of aldosterone on vascular function in humans are caused by systemic aldosterone originating from the adrenal gland.

Comparison of Enalapril, Candesartan and Intralesional Triamcinolone in Reducing Hypertrophic Scar Development: An Experimental Study

BACKGROUND

The purpose of this study was to compare the effects of oral enalapril, an angiotensin-converting enzyme inhibitor (ACE-I), oral candesartan, an angiotensin receptor blocker (ARB), and intralesional corticosteroid treatments in reducing scar formation.

METHODS

Twenty male rabbits were divided into five study groups: A (sham), B (control), C (ACE-I), D (ARB) and E (intralesional corticosteroid). The rabbit ear hypertrophic scar model was used. The hypertrophic scars were photographed and analyzed with the program ImageJ quantitatively to determine the degree of collagen fibers. The scar elevation index (SEI) was calculated at the end of the 40th day. Tissue samples were stained with hematoxylin and eosin and Masson's trichrome and examined under light microscopy for the determination of fibroblast number, epithelization, vascularization, inflammation and fibrosis.

RESULTS

The SEI was the highest in the control group with the highest number of fibroblasts under the epithelium. In the steroid group, the SEI was significantly lower than both the ACE-I (p: 0.02) and ARB (p: 0.001) groups. The density of type 1 collagen fibers was the lowest in the control group, whereas type 3 collagen fibers were highest in that group. The ACE-I and ARB groups were similar regarding densities of type 1 and type 3 collagen fibers. The density of type 1 collagen fibers was the highest in the steroid group, whereas the density of type 3 collagen fibers was the lowest in that group.

CONCLUSIONS

Enalapril, candesartan and intralesional steroid therapies were all effective in reducing scar tissue development; however, enalapril and steroid groups revealed better results.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Acute Exposure to Cigarette Smoking Followed by Myocardial Infarction Aggravates Renal Damage in an In Vivo Mouse Model

Cigarette smoking (S) is a risk factor for progressive chronic kidney disease, renal dysfunction, and renal failure. In this study, the effect of smoking on kidney function was investigated in a mouse model of myocardial infarction (MI) using 4 groups: control (C), smoking (S), MI, and S+MI. Histological analysis of S+MI group showed alterations in kidney structure including swelling of the proximal convoluted tubules (PCTs), thinning of the epithelial lining, focal loss of the brush border of PCTs, and patchy glomerular retraction. Molecular analysis revealed that nephrin expression was significantly reduced in the S+MI group, whereas sodium-hydrogen exchanger-1 (NHE-1) was significantly increased, suggesting altered glomerular filtration and kidney functions. Moreover, S+MI group, but not S alone, showed a significant increase in the expression of connective tissue growth factor (CTGF) and fibrotic proteins fibronectin (FN) and α-smooth muscle actin (SMA), in comparison to controls, in addition to a significant increase in mRNA levels of IL-6 and TNF-α inflammatory markers. Finally, reactive oxygen species (ROS) production was significantly accentuated in S+MI group concomitant with a significant increase in NOX-4 protein levels. In conclusion, smoking aggravates murine acute renal damage caused by MI at the structural and molecular levels by exacerbating renal dysfunction.

Differential effects of Losartan and Atorvastatin in partial and full thickness burn wounds

Healing of burn wounds is often associated with scar formation due to excessive inflammation and delayed wound closure. To date, no effective treatment is available to prevent the fibrotic process. The Renin Angiotensin System (RAS) was shown to be involved in fibrosis in various organs. Statins (e.g. Atorvastatin), Angiotensin receptor antagonists (e.g. Losartan) and the combination of these drugs are able to reduce the local RAS activation, and reduced fibrosis in other organs. We investigated whether inhibition of the RAS could improve healing of burn wounds by treatment with Atorvastatin, Losartan or the combination of both drugs. Therefore, full and partial thickness burn wounds were inflicted on both flanks of Yorkshire pigs. Oral administration of Atorvastatin, Losartan or the combination was started at post-burn day 1 and continued for 28 days. Full thickness wounds were excised and transplanted with an autologous meshed split-thickness skin graft at post-burn day 14. Partial thickness wounds received conservative treatment. Atorvastatin treatment resulted in enhanced graft take and wound closure of the full thickness wounds, faster resolution of neutrophils compared to all treatments and reduced alpha-smooth muscle actin positive cells compared to control treatment. Treatment with Losartan and to a lesser extent the combination therapy resulted in diminished graft take, increased wound contraction and poorer scar outcome. In contrast, Losartan treatment in partial thickness wounds decreased the alpha-smooth muscle actin+ fibroblasts and contraction. In conclusion, we showed differential effects of Losartan and Atorvastatin in full and partial thickness wounds. The extensive graft loss seen in Losartan treated wounds is most likely responsible for the poor clinical outcome of these full thickness burn wounds. Therefore, Losartan treatment should not be started before transplantation in order to prevent graft loss. Atorvastatin seems to accelerate the healing process in full thickness wounds possibly by dampening the pro-inflammatory response.

Cellular distribution and interaction between extended renin-angiotensin-aldosterone system pathways in atheroma

The importance of the renin-angiotensin-aldosterone system (RAAS) in the development of atherosclerotic has been experimentally documented. In fact, RAAS components have been shown to be locally expressed in the arterial wall and to be differentially regulated during atherosclerotic lesion progression. RAAS transcripts and proteins were shown to be differentially expressed and to interact in the 3 main cells of atheroma: endothelial cells, vascular smooth muscle cells, and macrophages. This review describes the local expression and cellular distribution of extended RAAS components in the arterial wall and their differential regulation during atherosclerotic lesion development.

Transcriptomic Analysis Reveals Novel Transcription Factors Associated With Renin-Angiotensin-Aldosterone System in Human Atheroma

Despite the well-known role of the renin-angiotensin-aldosterone system (RAAS) in atheroma, its global local organization is poorly understood. In this study, we used transcriptomic meta-analysis to reveal the local transcriptional organization and regulation of 37 extended RAAS (extRAAS) genes in atheroma. Expression analysis and hierarchical clustering were done on extRAAS genes in 32 paired early and advanced atherosclerotic lesions. Contrary to receptor-coding transcripts, multiple angiotensin-metabolizing enzymes showed higher expression in advance, in comparison to early lesions. Interestingly, similar results were obtained from GEO data sets containing human (n=839) and mouse (n=18) atherosclerotic samples, but different from normal human (n=11) arterial tissues. The expression and coordination patterns were then used to construct transcriptional maps of extRAAS, displaying favored pathways in atheroma. Three coexpression modules (M1, M2, and M3) with >80% reproducibility across human atheroma data sets were identified. M1 and M3 contained angiotensin-metabolizing enzymes transcripts, whereas M2 contained proatherogenic receptor-coding transcripts. Interestingly, M1 and M2 were negatively correlated. A total of 21 transcription factors with enriched binding sites in the promoters of coordinated genes were extracted, among which IRF5, MAX, and ETV5 showed significant positive correlations with M1, but negative correlations with M2. However, ETS1 and SMAD1 transcripts were positively correlated to receptor-coding genes in M2. Despite sharing some similarities in extRAAS organization with kidney and adipose, atheroma showed specific correlations between extRAAS and transcription factors. In conclusion, our transcriptional map helps in designing more efficient treatments for atherosclerosis. In addition, the identified transcription factors provide a basis for the discovery of atheroma-specific modulators of extRAAS.

The kinetics of angiotensin-I metabolism in human carotid atheroma: An emerging role for angiotensin (1-7)

AIM

Local levels of angiotensin peptides depend on their rates of production and degradation, which induce proatherogenic or atheroprotective effects. Here, we reveal the kinetics of Angiotensin-I metabolism in paired early and advanced atherosclerotic lesions.

METHODS

Lesions were spiked with labeled Ang-I* and supernatants withdrawn after 0, 10, 20, 40 and 80min. The concentration of produced Ang-II*, Ang-III*, Ang-IV* and Ang-(1-7)* peptides were measured using multiple reaction monitoring mass spectrometry coupled to ultra-performance liquid chromatography, normalized to tissue weight and initial [Ang-I*].

RESULTS

Ang-(1-7)* was the major angiotensin peptide produced, showing increased levels in both tissue types, with 2-3 fold lower levels in advanced compared to early lesions. In contrast, Ang-II* was 2-3 fold higher in advanced compared to early lesions, showing a decrease between 0 and 40min then an increase at 80min in both tissue types. The levels of Ang-IV were stable in both tissue types across all time points. Finally, Ang-III was non-detectable in both lesions across all time points.

CONCLUSION

Our results suggest that progression of atherosclerosis depends on the increased levels of Ang-II along with the decreased levels of Ang-(1-7), which supports the use of Ang-(1-7) along with Angiotensin type-1 receptor (AT1R) blockers.