Local Renin-angiotensin-aldosterone System Research Articles

Dapagliflozin protects the kidney in a non-diabetic model of cardiorenal syndrome

Cardiorenal syndrome encompasses a spectrum of disorders involving heart and kidney dysfunction, and sharing common risk factors, such as hypertension and diabetes. Clinical studies have shown that patients with and without diabetes may benefit from using sodium-glucose cotransporter 2 inhibitors to reduce the risk of heart failure and ameliorate renal endpoints. Because the underlying mechanisms remain elusive, we investigated the effects of dapagliflozin on the progression of renal damage, using a model of non-diabetic cardiorenal disease. Dahl salt-sensitive rats were fed a high-salt diet for five weeks and then randomized to dapagliflozin or vehicle for the following six weeks. After treatment with dapagliflozin, renal function resulted ameliorated as shown by decrease of albuminuria and urine albumin-to-creatinine ratio. Functional benefit was accompanied by a decreased accumulation of extracellular matrix and a reduced number of sclerotic glomeruli. Dapagliflozin significantly reduced expression of inflammatory and endothelial activation markers such as NF-κB and e-selectin. Upregulation of pro-oxidant-releasing NADPH oxidases 2 and 4 as well as downregulation of antioxidant enzymes were also counteracted by drug treatment. Our findings also evidenced the modulation of both classic and non-classic renin-angiotensin-aldosterone system (RAAS), and effects of dapagliflozin on gene expression of ion channels/transporters involved in renal homeostasis. Thus, in a non-diabetic model of cardiorenal syndrome, dapagliflozin provides renal protection by modulating inflammatory response, endothelial activation, fibrosis, oxidative stress, local RAAS and ion channels.

Relationship Between Urinary Angiotensinogen and Mortality in Patients with Heart Failure with Reduced Ejection Fraction.

Activation of the reninangi otens in-aldosterone system has an important role in the pathophysiology of heart failure with reduced ejection fraction. While the effects of systemic reninangi otens in-aldosterone system activation on heart failure with reduced ejection fraction are well known, the impact of the local reninangi otens in-aldosterone system on heart failure with reduced ejection fraction is not fully understood because of limited clinical research. This study aimed to investigate the effect of urinary angiotensinogen level, an accepted indicator of local reninangi otens in-aldosterone system activation, on all-cause mortality in patients with heart failure with reduced ejection fraction. This retrospective, single-center study included 60 patients with baseline urinary angiotensinogen data and survival/mortality data at 4 years. Urinary angiotensinogen values were standardized to the urinary creatinine value measured from the same urine sample. The median urinary angio tensi nogen /urin ary creatinine value among all patients (114 μg/g) was used as a cutoff to divide the patients into 2 groups. Mortality data were obtained from the national registry systems or by telephone. Comparison of all-cause mortality in the 2 groups showed that 22 deaths (71%) occurred in the group with a urinary angio tensinogen/urinary creatinine ratio above the median and 10 deaths (35.5%) occurred in the group of patients with urinary angio tensinogen/urinary creatinine equal to or below the median value (P =.005). Our study suggests that urinary angiotensinogen can be used as a new biomarker in the prognosis and follow-up of heart failure patients.

Interaction of local and systemic renin angiotensin aldosteron system with COVID-19

Severe acute respiratory syndrome-Coronavirus-2 (SARS-CoV-2) passes into cells through binding the angiotensin-converting enzyme-2 (ACE-2). While many scientists worldwide are trying to understand the physiopathological mechanisms of the disease and its relationship with other diseases, they are trying to find drugs that can treat Coronavirus disease-2019 (COVID-19). It is reported that the incidence of COVID-19 increases in cardiovascular diseases and associated conditions such as diabetes mellitus and hypertension in studies. That is why a large number of scientists are now questioning the use of renin-angiotensin-aldosterone system (RAS) antagonists, angiotensin-2 (Ang-2) receptor antagonists (angiotensin receptor blockers), and ACEs in COVID-19 patients. When all these facts are considered together, their potential effects may be more significant. Some researchers stated that RAS inhibitors might amplify COVID-19 severity. Per the classical knowledge, ACE-2 regulates RAS by converting Ang-2 to angiotensin-(1-7), which has antioxidant, vasodilatory, anti-inflammatory, and protective effects on many cell types, especially cardiomyocytes and vascular cells. Local and systemic RAS components such as ACE-2, ACE, and Ang-2 and their interactions are pretty complex. However, numerous reported RAS substrates and enzymes are synthesized intracellularly in many cell types. This review highlights that the intracellular RAS may have prominent roles in developing potential treatment strategies for COVID-19.

Contribution of Gut Microbiota-Derived Uremic Toxins to the Cardiovascular System Mineralization.

Chronic kidney disease (CKD) affects more than 10% of the world population and leads to excess morbidity and mortality (with cardiovascular disease as a leading cause of death). Vascular calcification (VC) is a phenomenon of disseminated deposition of mineral content within the media layer of arteries preceded by phenotypic changes in vascular smooth muscle cells (VSMC) and/or accumulation of mineral content within the atherosclerotic lesions. Medial VC results in vascular stiffness and significantly contributes to increased cardio-vascular (CV) morbidity, whereas VC of plaques may rather increase their stability. Mineral and bone disorders of CKD (CKD-MBD) contribute to VC, which is further aggravated by accumulation of uremic toxins. Both CKD-MBD and uremic toxin accumulation affect not only patients with advanced CKD (glomerular filtration rate (GFR) less than 15 mL/min/1.72 m2, end-stage kidney disease) but also those on earlier stages of a disease. The key uremic toxins that contribute to VC, i.e., p-cresyl sulphate (PCS), indoxyl sulphate (IS) and trimethylamine-N-oxide (TMAO) originate from bacterial metabolism of gut microbiota. All mentioned toxins promote VC by several mechanisms, including: Transdifferentiation and apoptosis of VSMC, dysfunction of endothelial cells, oxidative stress, interaction with local renin–angiotensin–aldosterone system or miRNA profile modification. Several attractive methods of gut microbiota manipulations have been proposed in order to modify their metabolism and to limit vascular damage (and VC) triggered by uremic toxins. Unfortunately, to date no such method was demonstrated to be effective at the level of “hard” patient-oriented or even clinically relevant surrogate endpoints.

MO026TREATMENT WITH ACTIVE VITAMIN D DOES NOT IMPROVE LEFT VENTRICULAR HYPERTROPHY BUT FURTHER INCREASES FGF23 AND ACCELERATES CKD PROGRESSION IN CHILDREN

Abstract Background and Aims Elevated FGF23, activation of the renin-angiotensin-aldosterone system (RAAS), and vitamin D and Klotho deficiency promote left ventricular hypertrophy (LVH) and LV fibrosis in chronic kidney disease (CKD). Whether treatment with active vitamin D affects uremic cardiomyopathy and/or FGF23/Klotho system in CKD is unclear. Method 5/6 nephrectomized (5/6Nx) rats, as a well-established model of CKD, were dose-dependently treated with calcitriol for 10 weeks and the cardiac phenotype, including local RAAS activation, was investigated compared to untreated 5/6Nx and sham-operated rats. Additionally, 38 children with eGFR ≤ 30 ml/min/1.73 m2 selected from the Cardiovascular Comorbidity in Children with CKD (4C) study were enrolled in a case-control study. Nineteen children were started on active vitamin D treatment with either calcitriol or calcidiol (average dosage 0.4 μg/day), and 19 CKD children with non-active vitamin D treatment matched for age, eGFR, serum calcium, parathyroid hormone, and phosphate served as controls. LV mass index (LVMI), LVH prevalence (LVMI >95th percentile), intact (iFGF23) and C-terminal FGF23 (cFGF23), and soluble Klotho (sKlotho) were assessed at baseline and after nine months. Results In 5/6Nx rats, FGF23 synthesis in bone and heart was enhanced compared to sham-operated rats, and calcitriol further stimulated its expression in bone only. Renal Klotho expression was reduced in 5/6 rats and almost normalized after calcitriol treatment. 5/6Nx induced cardiomyocyte growth and LV fibrosis, and calcitriol treatment significantly ameliorated both. Cardiac RAAS genes, such as angiotensinogen, renin, angiotensin-converting-enzyme, and angiotensin II receptor type I, were significantly upregulated in 5/6Nx rats compared to sham-operated animals, and normalized by calcitriol treatment. In the 4C study cohort, median plasma cFGF23 and iFGF23 were significantly elevated in both groups, whereas sKlotho was not altered compared to healthy children. Forty-seven percent and 42% of active vitamin D-treated patients and controls, respectively, received blood pressure (BP) medications, however diastolic BP was slightly but significantly enhanced in both groups compared to healthy children. Mean LVMI and LVH prevalence of 47% in active vitamin D-treated patients and controls did not differ at baseline. After nine months, median cFGF23 and iFGF23 were significantly increased in active vitamin D-treated patients compared to controls. sKlotho levels were decreased in the active vitamin D-treated group compared to baseline but not in controls. A significant decline in median eGFR was observed in active vitamin D group but not in controls. Likewise, the median eGFR change during the observation period was higher in the active vitamin D group compared to controls. Median LVMI as well as frequency of LVH did not change significantly during vitamin D treatment, nor in controls. Consequently, final median LVMI as well as percentage of patients with LVH did not significantly differ between groups. Conclusion Calcitriol treatment in 5/6Nx rats improves cardiac hypertrophy and fibrosis, reduces uremia-induced cardiac RAAS gene expression, and improves renal Klotho expression. By contrast, treatment with active vitamin D does not decrease the prevalence of LVH in children with advanced CKD compared to matched controls. This may be due to further enhancement of FGF23 levels, faster progression of CKD associated with reduced Klotho in active vitamin D-treated patients and/or concomitant treatment with RAAS inhibitors. The latter may blunt the favorable effects of calcitriol on the activated RAAS.

The expression of the renin-angiotensin-aldosterone system in the skin and its effects on skin physiology and pathophysiology.

The local renin-angiotensin-aldosterone system (RAAS) is fully expressed in the human skin at the mRNA and protein level. Local RAAS is known to play a regulatory function in epidermal proliferation, wound healing, scarring, cutaneous heating adaptation, and aging. There are also some indications of its role in the regulation of hair growth and sebum secretion. Impaired wound healing, skin diseases associated with diabetes, cancer development, psoriasis, and scleroderma may be related to changes in skin RAAS activity. Extensive research has shown that RAAS-modulating drugs can affect the skin when applied orally or topically, creating new therapeutic approaches against dermatological diseases.

Inhibition of AT1 receptors by losartan affects myocardial slow force response in healthy but not in monocrotaline-treated young rats.

The slow force response (SFR) of a cardiac muscle to a sudden stretch is thought to be important in the regulatory adaptation of myocardial contraction. Autocrine-paracrine regulation pathways which involve angiotensin II are participating in this mechanism. On the other hand, renin-angiotensin-aldosterone system (RAS) is altered in hypertrophic or failing myocardium. We compared the effects of sudden stretch to SFR as well as to twitch and Ca2+ transient characteristics in rat myocardium with monocrotaline-induced heart failure with those in normal rat myocardium without and with inhibition of angiotensin II type-1 (AT1) receptors. Our findings indicate that the myocardium of rats with monocrotaline-induced right ventricular failure is deficient with activation of local RAS and therefore expresses blunted SFR, very similar to the depression of SFR observed in normal myocardium under inhibition of AT1 receptors. The "failing" myocardium does not further respond to the "putative" inhibition of AT1 receptors by losartan. In conclusion, SFR is related to autocrine-paracrine regulation of myocardial contraction in normal rat myocardium and that the involvement of RAS into stretch-induced modulation of contractility may be significantly altered in failing heart.

Abstract P311: Intracellular Renin Angiotensin Aldosterone System inMesangial Cells Under the Stimulus of Aldosterone

Mesangial cells (MCs) are a local target for aldosterone (aldo) action in the modulation of the renin angiotensin aldosterone system (RAAS).Its molecular mechanisms is far from clear, and are extremely important in understanding renal pathologies. We investigated if the effect of aldosterone stimulus in supra, physiological and sub physiological doses was able to modulate the intracrine human MCs RAAS. We performed viability assays, western blot, immunofluorescence, ACE and ACE2 activities. As a result, we have obtained that the ACE activity was increased after MCs treatment with aldosterone 1 and 10 nM when compared with 0.1nM after 72h. Previous cells treatment with spirolactone followed by aldo reduced ACE catalytic activity but not ACE2. ACE and ACE 2 expression increased after 72h of MCs treatment with aldo 10 nM. The immunofluorescence showed that ACE was overexpressed in MCs after 72h with 10nM aldosterone treatment being similar to control group, differing from the treatment with spirolactone + aldo stimulation that decreased ACE expression, internalized Angiotensin II and changed the AT1 receptor localization. The same treatment increased MAS receptor production in MCs after 72h of aldosterone treatment with 10, 1.0, 0.1 and 0.01nM , but not with spirolactone + aldo treatment that inhibited receptor synthesis. ACE2 was detected in cell nucleus with 24h of treatment with aldo and in cytoplasm after 72h, being reduced after the treatment with spirolactone+aldo. Ang 1-7 was localized at cell nucleus and in cytoplasm after treatment with aldo 24h and 72h, decreasing with spirolactone + aldo treatment. Immunofluorescence results demonstrated that MCs pre-treated with spironolactone decreased ACE, ACE2 and MAS receptor expression, and altered ANG II localization, suggesting that spironolactone acts on the mineralocorticoid receptor internalizing ANG II into the nucleus, probably by AT1 and AT2 receptors pathways. These results demonstrated that aldosterone can modulate the local RAAS in mesangial cells suggesting that its physiological concentrations are necessary for the feasibility of these cells while high doses are cytotoxic and altered the local system.

Impact of Blocking Renin Angiotensin Aldosterone Axis in Acute Kidney Injury

Acute Kidney injury (AKI) is a common health problem especially the dug induced AKI as a side or toxic effect during treatment of different medical disorders. Local Renin angiotensin aldosterone system (RAAS) has been described in addition to the systemic RAAS and it is activated by renal injury. The aim of the current study was to evaluate and compare the renoprotective effect of inhibiting RAAS by losartan versus captopril on drug induced AKI. 36 male albino rats constituted the animal model and have been divided into 6 groups (6 rats/group): control, AKI, AKI+losartan, AKI+captopril, losartan, captopril groups. Systolic blood pressure, glomerular filtration rate (GFR) have been measured. Serum samples were collected for measurement of urea, creatinine, cystatin-c , Monocyte Chemoattractant Protein-1 (MCP-1) , Intercellular Adhesion Molecule 1 (ICAM-1) and Neutrophil gelatinase-associated lipocalin (NGAL). Kidney tissues were removed for measurement of tissue Malondialdehyde (MDA) and renal expression of Megalin, and kidney injury molecule 1(KIM1). Both captopril and losartan attenuated drug induced AKI as revealed from the measured serum and tissue parameters. Captopril was superior to losartan on normalizing ICAM-1, megalin and KIM-1, however; losartan improved GFR more than captopril. Other measured parameters showed no significant difference in AKI groups treated with losartan and groups treated with captopril.

The Role of Renin Angiotensin Aldosterone System Genes in Diabetic Nephropathy.

The role of the renin angiotensin aldosterone system (RAAS) and the gene variants of its components in susceptibility to diabetic nephropathy (DN) have been investigated in numerous studies. The effects of some RAAS gene variants, including angiotensin converting enzyme (ACE), angiotensinogen (AGT) and angiotensin II type 1 receptor (AT1R), on the risk for DN have been studied more extensively, but there has been controversy. The reasons for controversy in this field could be attributed to the effect of ethnicity, gender, stage of diabetes complications, the presence of intrarenal RAAS, methodologic limitations of the association studies in multifactorial diseases, inadequate sample size, genetic heterogeneity, and the lack of studies that involved all RAAS genes and their interactions. This review looks at the current available information about the role of all RAAS gene variants in the pathogenesis of DN. Further, the concomitant study of both systemic and local RAAS, counter-regulators of ACE and ACE2, and also AT1R and angiotensin II type 2 receptor (AT2R) genes could help to elucidate the role of the genes of this system in the pathogenesis of DN.

The Effects of the Angiotensin Converting Enzyme Inhibitor Enalapril and the Angiotensin II Type 1 Receptor Blocker Losartan on Fracture Healing in Rats.

Angiotensin converting enzyme inhibitors (ACEI) and type I angiotensin receptor blockers (ARB) have been shown to exert significant effects on bone tissue via a local renin-angiotensin-aldosterone system (RAS). The aim of our study was to delineate their influences on fracture healing process. Sixty adult male Wistar Albino rats were divided into three groups. After undergoing surgical femoral fracture and fixation, the ACEI group received 10 mg/kg of Enalapril, the ARB group received 10 mg/kg of Losartan and the Control group did not receive any medication. Fracture healing was evaluated at second and fifth postoperative weeks by the Lane-Sandhu radiological staging system and by histological scoring system of Huoet al. ACE expression in fracture callus was studied by immunohistochemistry. Both ACEI and ARB groups showed less fibrous tissue in the fracture area at the second week, but the histologic score differences were significant only between Control and ARB groups. At the fifth week, however, both radiological and histological scores for the ACEI group were significantly higher than both ARB and Control groups, while the scores for ARB and Control groups were similar. The presence of ACE expression in fracture callus was also observed. ACEIs had significant positive effects on fracture repair. Losartan failed to display these stimulatory effects, which suggests that local RAS in bone tissue exerts its actions via alternative receptors or pathways than the AT1 receptor.

Pathophysiological role of oxidative stress in systolic and diastolic heart failure and its therapeutic implications.

Systolic and diastolic myocardial dysfunction has been demonstrated to be associated with an activation of the circulating and local renin-angiotensin-aldosterone system (RAAS), and with a subsequent inappropriately increased production of reactive oxygen species (ROS). While, at low concentrations, ROS modulate important physiological functions through changes in cellular signalling and gene expression, overproduction of ROS may adversely alter cardiac mechanics, leading to further worsening of systolic and diastolic function. In addition, vascular endothelial dysfunction due to uncoupling of the nitric oxide synthase, activation of vascular and phagocytic membrane oxidases or mitochondrial oxidative stress may lead to increased vascular stiffness, further compromising cardiac performance in afterload-dependent hearts. In the present review, we address the potential role of ROS in the pathophysiology of myocardial and vascular dysfunction in heart failure (HF) and their therapeutic targeting. We discuss possible mechanisms underlying the failure of antioxidant vitamins in improving patients' prognosis, the impact of angiotensin-converting enzyme inhibitors or AT1 receptor blockers on oxidative stress, and the mechanism of the benefit of combination of hydralazine/isosorbide dinitrate. Further, we provide evidence supporting the existence of differences in the pathophysiology of HF with preserved vs. reduced ejection fraction and whether targeting mitochondrial ROS might be a particularly interesting therapeutic option for patients with preserved ejection fraction.

8D.07

Abstract The implication of the renin-angiotensin-aldosterone system (RAAS) in atheroma development is well described. However, a complete view of the local RAAS in atheroma is still missing. In this study we aimed to reveal the organization of RAAS in atheroma at the transcriptomic level and identify the transcriptional regulators behind it. Extended RAAS (extRAAS) was defined as the set of 37 genes coding for classical and novel RAAS participants (Figure 1). Five microarray datasets containing overall 590 samples representing carotid and peripheral atheroma were downloaded from the GEO database. Correlation-based hierarchical clustering (R software) of extRAAS genes within each dataset allowed the identification of modules of co-expressed genes. Reproducible co-expression modules across datasets were then extracted. Transcription factors (TFs) having common binding sites (TFBSs) in the promoters of coordinated genes were identified using the Genomatix database tools and analyzed for their correlation with extRAAS genes in the microarray datasets. Expression data revealed the expressed extRAAS components and their relative abundance displaying the favored pathways in atheroma. Three co-expression modules with more than 80% reproducibility across datasets were extracted. Two of them (M1 and M2) contained genes coding for angiotensin metabolizing enzymes involved in different pathways: M1 included ACE, MME, RNPEP, and DPP3, in addition to 7 other genes; and M2 included CMA1, CTSG, and CPA3. The third module (M3) contained genes coding for receptors known to be implicated in atheroma (AGTR1, MR, GR, LNPEP, EGFR and GPER). M1 and M3 were negatively correlated in 3 of 5 datasets. We identified 19 TFs that have enriched TFBSs in the promoters of genes of M1, and two for M3, but none was found for M2. Among the extracted TFs, ELF1, MAX, and IRF5 showed significant positive correlations with peptidase-coding genes from M1 and negative correlations with receptors-coding genes from M3 (p

Local Angiotensin Pathways in Human Carotid Atheroma: Towards a Systems Biology Approach

We will summarize the data we have obtained in human carotid artery concerning the organization of an extended local renin angiotensin aldosterone system and its variations at different stages of atheroma. In a system view, we propose a model where concomitant increase in angiotensin and glucocorticoid signaling is induced and amplified in VSMC while vascular smooth muscle cells transdifferentiate toward a lipid storing phenotype.

Role of estrogen in diastolic dysfunction

The prevalence of left ventricular diastolic dysfunction (LVDD) sharply increases in women after menopause and may lead to heart failure. While evidence suggests that estrogens protect the premenopausal heart from hypertension and ventricular remodeling, the specific mechanisms involved remain elusive. Moreover, whether there is a protective role of estrogens against cardiovascular disease, and specifically LVDD, continues to be controversial. Clinical and basic science have implicated activation of the renin-angiotensin-aldosterone system (RAAS), linked to the loss of ovarian estrogens, in the pathogenesis of postmenopausal diastolic dysfunction. As a consequence of increased tissue ANG II and low estrogen, a maladaptive nitric oxide synthase (NOS) system produces ROS that contribute to female sex-specific hypertensive heart disease. Recent insights from rodent models that mimic the cardiac phenotype of an estrogen-insufficient or -deficient woman (e.g., premature ovarian failure or postmenopausal), including the ovariectomized congenic mRen2.Lewis female rat, provide evidence showing that estrogen modulates the tissue RAAS and NOS system and related intracellular signaling pathways, in part via the membrane G protein-coupled receptor 30 (GPR30; also called G protein-coupled estrogen receptor 1). Complementing the cardiovascular research in this field, the echocardiographic correlates of LVDD as well as inherent limitations to its use in preclinical rodent studies will be briefly presented. Understanding the roles of estrogen and GPR30, their interactions with the local RAAS and NOS system, and the relationship of each of these to LVDD is necessary to identify new therapeutic targets and alternative treatments for diastolic heart failure that achieve the cardiovascular benefits of estrogen replacement without its side effects and contraindications.

The Renin-Angiotensin-Aldosterone System in Podocytes

The renin-angiotensin-aldosterone system (RAAS) plays a critical role in kidney function and its inhibition reduces proteinuria and preserves kidney function in patients with chronic kidney disease. Recent studies have shown that podocytes generate many components of the RAAS and they express receptors of RAAS, including angiotensin II, mineralocorticoid, and prorenin receptors. Crucial functions of podocytes, such as contraction, apoptosis, autophagocytosis, and cytoskeletal organization, have been shown to be regulated by the angiotensin II type 1 receptors. An activation of the glomerular RAAS and protection from podocyte injury by RAAS inhibitors have been shown in many glomerular diseases. Exploring the interaction between the local RAAS and the signaling involved in RAAS activation in podocytes will lead to new therapeutic strategies of podocyte protection.

<b>３．ミネラルコルチコイド受容体拮抗薬</b>

Heart failure is currently the leading cause of death and disability across the globe. Although significant advances in pharmacological and mechanical treatments have improved the outcome of patients with heart failure, the prognosis in such patients remains poor. At present, the optimal pharmacological treatment of heart failure targets the suppression of neurohumoral activations such as the renin-angiotensin-aldosterone system (RAAS) and/or β-adrenergic receptor signaling, as well as regulation of hemodynamics. Large clinical trials in patients with heart failure, even in those with mild symptoms, have shown that mineralocorticoid receptor (MR) antagonists used in conjunction with the current standard of care improve morbidity and mortality. Increasing evidence supports the detrimental effects of aldosterone on the cardiovascular system, mainly via its MR-dependent action, in a variety of experimental models and clinical research. Of note, these unfavorable effects are more pronounced under high sodium or glucose conditions, as we and others have reported. Moreover, the pathological significance of not only systemic but also local RAAS has attracted growing attention. Furthermore, some reports have demonstrated that MR signaling can be activated without specific ligands such as aldosterone and corticosterone. Taken together, MR signaling cascades, in their high salt and/or glucose sensitive manner, play a pivotal role in the pathogenesis of heart failure. Therefore, the usefulness of MR antagonists and their indication should be more enhanced and extended, while diet control including salt restriction remains of paramount importance in the treatment of heart failure. (Jpn J Clin Pharmacol Ther 2012; 43(5): 317-322)

Altered Regulation of Renin-Angiotensin, Endothelin and Natriuretic Peptide Systems in Rat Kidney with Chronic Unilateral Ureteral Obstruction

Background: The present study was designed to investigate the role of the local renin-angiotensin-aldosterone system (RAAS), endothelin (ET) and the natriuretic peptide system (NPS) for the development of renal fibrosis and progressive renal disease in experimental unilateral ureteral obstructed (UUO) rats. Methods: Male Sprague-Dawley rats (180–200 g) were unilaterally obstructed by ligation of the proximal ureters for 14 days. Control rats were treated in the same way, except that no ligature was made. The mRNA expressions of local renin-angiotensin system, aldosterone synthase (CYP11B2), ET-1 and NPS was determined in the cortex by real-time polymerase chain reaction. Results: Following the unilateral ureteral obstruction, the mRNA expressions of angiotensin-converting enzyme 1, ET-1 and transforming growth factor-β₁ (TGF-β₁) were increased, while angiotensin-converting enzyme 2 was decreased in the obstructed kidney compared with the controls. Angiotensin II type 1 receptor was decreased and TGF-β₁ was not changed in contralateral kidney compared with the controls. Atrial natriuretic peptide, brain natriuretic peptide, and C-type natri- uretic peptide expressions were increased in UUO kidneys compared with the controls, while natriuretic peptide receptor-A was decreased in UUO kidneys. Conclusion: The local RAAS and ET-1 was upregulated which may play a role in the progressive renal fibrosis in obstructed kidneys in rats with UUO. The enhanced activity of NPS in UUO kidney may play a role to compensate against progressive renal fibrosis in chronic obstructive uropathy.

The role of the renin-angiotensin-aldosterone system in diabetes and its vascular complications

Clinical trials have demonstrated the benefit of blood pressure (BP) reduction in reducing the risk of cardiovascular and renal complications in patients with diabetes mellitus. Incorporation of agents that inhibit the renin-angiotensin-aldosterone system (RAAS) into antihypertensive regimens has been shown to provide reductions in renal and cardiovascular events that are mediated by both BP-dependent and -independent mechanisms. Recent studies exploring these potential mechanisms have demonstrated a direct role of angiotensin II (ATII) in the pathology of the vasculature and other sites of end-organ injury. In animal models of diabetes, inhibition of the RAAS with angiotensin-converting enzyme (ACE) inhibition or angiotensin type 1 (AT(1)) receptor blockade has been shown to prevent atherosclerosis, an effect that was independent of BP reduction. In addition to its direct effects on the vasculature, ATII also has direct detrimental effects on end organs, including the kidney and the heart, which lead to the development of proteinuria and left ventricular hypertrophy (LVH), respectively. Left ventricular hypertrophy has been shown to be predictive of cardiovascular and renal events, and the benefits of RAAS inhibition with angiotensin receptor blocker therapy are accompanied by a reduction in LVH. In addition to preventing the cardiovascular and renal complications of diabetes, the RAAS blockade has also been shown, in several large randomized clinical trials, to inhibit new onset of diabetes. Recent studies have revealed that many tissues, including pancreatic islets and adipose tissue, have a local RAAS. In the diabetic rat model (Zucker diabetic fatty rats), pancreatic islets exhibit an increased intraislet expression of ACE and AT(1) as well as increased intraislet fibrosis, apoptosis, and oxidative stress. The local RAAS also appears to play a role in the function of the adipocyte. Angiotensin II inhibits adipocyte differentiation, potentially decreasing the storage capacity of adipose tissue. The reduced capacity of adipose tissue to store fatty acids may cause their accumulation in other tissues, leading to insulin resistance and development of diabetes. Collectively, these studies demonstrate that ATII has direct effects on multiple tissues, and inhibition of ATII action in these tissues may be responsible for many of the clinical benefits observed with RAAS inhibition.

Effects of aldosterone on cardiac local rennin- angiotensin -aldosterone system: an important role of cardiac fibroblasts

Recent studies showed cardiac local renin-angiotensin-aldosterone system (RAAS) play a pivotal role in pathophysiology in heart, and spironolactone, which is aldosterone blockade has beneficial effects on prognosis of patients with heart failure. We sought to determine how aldosterone, which is distal component of RAAS, acts on cardiac local RAAS using cultured cardiac myocytes and fibroblasts, and whether spironolactone inhibits these effects. Cultured cardiocytes were prepared from 1- or 2-day-old neonatal Sprague-Dawley rats by digestion with collagenase and pancratin. Cardiac myocytes and fibroblasts were separated by Percoll method and cultivated. After starvation period, aldosterone was added to culture medium and later, total RNA was extracted from the cells. mRNAs of renin, angiotensiongen, and ACE were semiquantified by RT-PCR. Basal mRNA expressions of renin, angiotensinogen, and ACE were observed in both cadiac myocytes and fibroblasts. After 48 hours of aldosterone stimulation, ACE mRNA was significantly upregulated in cardiac fibroblasts, however, gene expressions of renin and angiotensinogen were unchanged in cardiac fibroblasts and none of these RAAS component was upregulated in cardiac myocytes. Moreover, spironolactone completely inhibited aldosterone-induced augmentation of ACE gene expression in cardiac fibroblasts.In conclusion, our data support an idea that cardiac local RAAS has positive feedback system, which mainly depends on cardiac fibroblasts, and clinical beneficial effects of spironolactone may be partly due to blockage of positive feedback circuit.