Kidney Of Hypertensive Rats Research Articles

Indoxyl Sulfate Downregulates Expression of Mas Receptor via OAT3/AhR/Stat3 Pathway in Proximal Tubular Cells

Renin-angiotensin system (RAS) plays a pivotal role in chronic kidney disease (CKD). Angiotensin converting enzyme-related carboxypeptidase 2 (ACE2)/angiotensin (Ang)-(1–7)/Mas receptor axis counteracts the deleterious actions of Ang II. ACE2 exerts its actions by cleaving Ang II into Ang-(1–7) which activates Mas receptor. This study aimed to determine if the expression of Mas receptor is altered in the kidneys of CKD rats, and if indoxyl sulfate (IS), a uremic toxin, affects the expression of Mas receptor in rat kidneys and cultured human proximal tubular cells (HK-2 cells). The expression of Mas receptor was examined in the kidneys of CKD and AST-120-treated CKD rats using immunohistochemistry. Further, the effects of IS on Mas receptor expression in the kidneys of normotensive and hypertensive rats were examined. The effects of IS on the expression of Mas receptor and phosphorylation of endothelial nitric oxide synthase (eNOS) in HK-2 cells were examined using immunoblotting. CKD rats showed reduced renal expression of Mas receptor, while AST-120 restored its expression. Administration of IS downregulated Mas receptor expression in the kidneys of normotensive and hypertensive rats. IS downregulated Mas receptor expression in HK-2 cells in a time- and dose-dependent manner. Knockdown of organic anion transporter 3 (OAT3), aryl hydrocarbon receptor (AhR), and signal transducer and activator of transcription 3 (Stat3) inhibited IS-induced downregulation of Mas receptor and phosphorylated eNOS. N-acetylcysteine, an antioxidant, also inhibited IS-induced downregulation of Mas receptor and phosphorylated eNOS. Ang-(1–7) attenuated IS-induced transforming growth factor-β1 (TGF-β1) expression.ConclusionMas receptor expression is reduced in the kidneys of CKD rats. IS downregulates renal expression of Mas receptor via OAT3/AhR/Stat3 pathway in proximal tubular cells. IS-induced downregulation of Mas receptor might be involved in upregulation of TGF-β1 in proximal tubular cells.

Effects of Yishen Pinggan Decoction on the urine microalbumin and the expression of ACE2, Ang II in the Spontaneously Hypertensive Rat Kidney

Objective To observe the effects of Yishen Decoction on blood pressure,and to observe the effects of Yishen Decoction on renin-angiotensin system (RAS) of spontaneously hypertensive rats (SHR).Methods Male spontaneously hypertensive rats (SHR) and normal Wistar-Kyoto rats(WKY) were studied at 10 weeks of age.SHR were randomly divided into model group (treated with distilled water),Yishen Pinggan group and lotensin group.And each group had eight rats.The WKY was used as the normal control group (treated with distilled water).They were continuously treated for 12 weeks.The blood pressure of rats was measured before experiment,6th week and 12th week after the experiment start.By the end of experiment on the 12th week,we detected the expression of ACE2,Ang Ⅱ in Serum and kidney on rat kidney,the results obtained by computer image analysis and statistical analysis.Results At 12 weekends,compared with model group we found that the blood pressure was significantly lower in TCM group and lotensin group (P ＜ 0.01),the ACE2 of serum in TCM group was significantly reduced (P ＜ 0.05) than in WKY rats and western medicine group,Ang Ⅱ then significantly increased (P ＜ 0.05),with no significant difference between the model group (P ＞ 0.05),while the expression in the kidney was different,the ACE2 of TCM group compared with the model group increased significantly (P ＜ 0.05),and with western and WKY group,showing no significant difference (P ＞ 0.05).Ang Ⅱ significantly reduced (P ＜ 0.05),no significant difference found with WKY group (P ＞ 0.05).Conclusion Yishen Decoction can decrease blood pressure so as to reduce kidney damage,its effect may be related to regulating the expression of the relevant local kidney RAS. Key words: Yishen Decoction; Hypertension; Renal Damage; RAS

Distinct protein signature of hypertension-induced damage in the renal proteome of the two-kidney, one-clip rat model.

Hypertensive nephrosclerosis is one of the most frequent causes of chronic kidney failure. Proteome analysis potentially improves the pathophysiological understanding and diagnostic precision of this disorder. In the present exploratory study, we investigated experimental nephrosclerosis in the two-kidney, one-clip (2K1C) hypertensive rat model. The renal cortex proteome from juxtamedullary cortex and outer cortex of 2K1C male Wistar-Hannover rats (n = 4) was compared with the sham-operated controls (n = 6), using mass spectrometry-based quantitative proteomics. We combined a high abundant plasma protein depletion strategy with an extended liquid chromatographic gradient to improve peptide and protein identification. Immunohistology was used for independent confirmation of abundance. We identified 1724 proteins, of which 1434 were quantified with at least two unique peptides. Comparative proteomics revealed 608 proteins, including the platelet-derived growth factor receptor-β signalling pathway, with different abundances between the non-clipped kidney of hypertensive 2K1C rats and the corresponding kidney of the normotensive controls (P < 0.05, absolute fold change ≥1.5). Among the most significantly altered proteins in the whole cortex were periostin, transgelin, and creatine kinase B-type. Relative abundance of periostin alone allowed clear classification of 2K1C and controls. Enrichment of periostin in 2K1C rats was verified by immunohistology, showing positivity especially around the fibrotic vessels. The proteome is altered in hypertension-induced kidney damage. We propose periostin, especially in combination with transgelin and creatine kinase B-type, as possible proteomic classifier to distinguish hypertensive nephrosclerosis from the normal tissue. This classifier needs to be further validated with respect to early diagnosis of fibrosis, prognosis, and its potential as a novel molecular target for pharmacological interventions.

Elevated expression of the Ephx2 mRNA in the kidney of hypertensive ISIAH rats

Epoxyeicosatrienoic acids (EETs) have antihypertensive properties and play a role in maintaining the renal microvascular function. EETs mediate vasodilation of rat preglomerular microvessels and activate ion channels. Ephx2 codes for a soluble epoxide hydrolase (sEH), which catalyzes EET degradation. The renal cortex and medulla were tested for Ephx2 mRNA level in ISIAH rats with hereditary stress-sensitive hypertension and in normotensive WAG rats at rest and in emotional stress. Ephx2 transcriptional activity in ISIAH rats was significantly higher than in WAG rats at rest and in stress by both microarray analysis and realtime PCR. The results implicated Ephx2 in controlling and modulating the vascular tone in the kidney in both hypertensive ISIAH and normotensive WAG rats.

Abstract 550: Large Blood Pressure Variability Aggravates Arteriolosclerosis and Ischemic Changes in the Kidney in Hypertensive Rats

Background: Increased blood pressure (BP) variability (BPV) is a characteristic feature of hypertensive patients. Large BPV aggravates hypertensive target organ damage, such as left ventricular hypertrophy, carotid atherosclerosis, and microalbuminuria. We have shown that angiotensin II (AngII)-mediated inflammation plays a role in the aggravation of hypertensive cardiac remodeling in spontaneously hypertensive rats (SHR) with large BPV. However, little was known regarding renal damages induced by large BPV. The aims of this study were to investigate pathological changes of the kidney and to examine whether candesartan would prevent the renal damages in SHR with large BPV. Methods and Results: A model of a combination of hypertension and large BPV was created by bilateral sino-aortic denervation (SAD) in SHR at 12 weeks old. SAD increased BPV without changes in mean BP. At 19 weeks old, SAD induced patchy cortical interstitial lesions associated with ischemic changes of glomeruli and tubules and interstitial fibrosis. The interlobular or afferent arterioles around ischemic lesions showed remarkable arteriolosclerotic changes characterized by vascular smooth muscle cell proliferation and extracellular matrix deposition, leading to the luminal narrowing and occlusion (Figure). Chronic treatment with a subdepressor dose of candesartan prevented not only arteriolosclerotic changes but also interstitial fibrosis and ischemic changes in SHR with SAD. Conclusion: Large BPV aggravates renal arteriolosclerosis, which results in the cortical ischemic changes and fibrosis in the kidney of hypertensive rats through angII-mediated mechanisms.

Abstract 501: Enhanced Expression of the Endocannabinoid 2-AG and CB-1 Receptor in the Kidney of the Diabetic Hypertensive Female Rat

The cannabinoids arachidonoylethanolamide (AEA) and 2-arachidonoylglycerol (2-AG) are endogenous ligands for the cannabinoid receptors including CB1 and CB2 subtypes. The endocannabinoid system (ECS) is typically associated with regulation of metabolic balance and appetite, although CB1 receptors (CB1R) may contribute to diabetic renal injury while CB2R are protective. The hypertensive mRen2.Lewis (mRen2) females have less renal injury than the males; however, diabetic female mRen2 lack this protection and show comparable indices of injury to the diabetic males. The present study addressed whether female and male diabetic mRen2 exhibit similar alterations in the renal ECS. Diabetes was induced with a single dose of streptozotocin (STZ at 65 mg/kg; ip). Cortical content of AEA and 2-AG was quantified by UPLC MS/MS. Receptor levels and the metabolizing enzymes for AEA (FAAH) and 2-AG (MAGL) were quantified by protein immunoblot. Basal 2-AG content was higher in male versus female mRen2, and significantly increased in both diabetic females and males (figure, n=6) while AEA was unchanged. Cortical Ang II correlated to 2-AG [p&lt;0.01; r = 0.89]. CB1R protein expression was higher in female diabetic mRen2 but unchanged in the males (figure, n=4). CB2R expression was lower in the male diabetics [p&lt;0.01; n=4], but not changed in females. MAGL expression was &gt;70% lower in female diabetics compared to controls [p&lt;0.05; n=4] while FAAH was not changed. Elements of the renal ECS are differentially regulated in the diabetic mRen2. Higher expression of both 2-AG and CB1R, but reduced MAGL (females) and CB2R (males) may contribute to the development and progression of renal injury in this model.

Abstract 559: Augmented Renal Levels of PDGFß And PDGFß Receptors in Cyp1a1-Ren2 Transgenic Rats With Angiotensin II-Dependent Malignant Hypertension

PDGF receptor antagonism with imatinib mesylate prevents the renal injury, proteinuria and augmented urinary ANG II excretion independent of changes in blood pressure that occur in Cyp1a1-Ren2 rats with ANG II-dependent malignant hypertension. These findings suggest that arterial pressure-dependent increases in PDGFβ protein levels and PDGFβ receptor activation contribute importantly to the marked renal functional and morphological derangements that occur in ANG II-dependent malignant hypertension. To address this issue, the present study was performed to determine the protein levels of PDGFβ and PDGFβ receptors in renal cortical and medullary tissue from kidneys of hypertensive Cyp1a1-Ren2 transgenic rats. Male Cyp1a1-Ren2 rats were fed a diet containing indole-3-carbinol (I3C; 0.3%) for 10 days to induce malignant hypertension (n=5) or a non-I3C containing diet (controls, n=6). Rats induced with I3C developed malignant hypertension and exhibited increases in PDGFβ protein levels in both the renal cortex (0.046±0.002 vs.0.026±0.003 AU, P&lt;0.05) and renal medulla (0.054±0.007 vs.0.026±0.003 AU, P&lt;0.05), and elevated PDGFβ receptor levels in both renal cortex (0.26±0.03 vs.0.12±0.02 AU, P&lt;0.05) and renal medulla (0.60±0.06 vs.0.21±0.02 AU, P&lt;0.05). In a separate group (n=5), rats were chronically treated with the PDGF receptor antagonist, imatinib mesylate, by oral gavage (60 mg/kg/d) starting 3 days before initiating I3C induction and maintained on imatinib for the 10 day duration of I3C administration. Chronic PDGF receptor blockade prevented the increase in PDGFβ protein levels in both renal cortical and medullary tissues (0.027±0.004 vs. 0.026±0.003 and 0.029±0.005 vs. 0.026±0.003 AU, respectively) but did not influence the elevated PDGFβ receptor levels in either renal cortex (0.23±0.02 vs. 0.26±0.02 AU) or renal medulla (0.46±0.03 vs.0.60±0.06 AU). These data demonstrate that both PDGFβ protein and PDGFβ receptor levels are elevated in both renal cortex and medulla in ANG II-dependent malignant hypertension. Such elevated levels may contribute to the renal injury and the increased urinary ANG II excretion in ANG II-dependent malignant hypertension.

Altered heart and kidney phospholipid fatty acid composition are associated with cardiac hypertrophy in hypertensive rats

ObjectiveWe examined the association of cardiac hypertrophy or fibrosis with the phospholipid fatty acid (FA) composition of heart and kidney in hypertensive rats. Design and methodsEight-week-old spontaneously hypertensive rats (SHRs) (n=8) and Wistar Kyoto rats (WKYs, n=8) as a normotensive control, were fed ad libitum for 6weeks with regular AIN-76 diet. Phospholipid FA compositions in the left ventricle and kidney were measured and histological analyses were performed. ResultsCompared with WKYs, SHRs had lower proportions of γ-linolenic acid, α-linolenic acid, eicosadienoic acid, eicosatrienoic acid, dihomo-γ-linoleic acid, docosadienoic acid and nervonic acid in heart, and stearic acid (SA), γ-linolenic acid, and eicosapentaenoic acid (EPA) in kidney. After adjusting for food intake, SHRs still maintained higher proportions of SA, and total saturated FAs in the heart and a lower proportion of eicosapentaenoic acid in the kidney. Additionally, compared with WKYs, SHRs showed larger cardiomyocyte diameters in the left ventricles, indicating cardiac hypertrophy and interstitial fibrosis. Cardiomyocyte diameters also positively correlated with cardiac SA (r=0.550, p<0.05) and negatively with kidney EPA (r=−0.575, p<0.05). ConclusionTissue FA compositions were associated with cardiac hypertrophy in a hypertensive setting, implicating the pathogenic role of tissue FAs in hypertension and related complications.

Proteomic analysis of outer and juxtamedullary cortex of non‐clipped kidneys in 2K1C hypertensive rats

Hypertensive damage in the non‐clipped kidney of two‐kidney, one‐clip (2K1C) rats is most pronounced in the juxtamedullary cortex (JMC), while the outer cortex (OC) is protected. In this study, 2K1C was induced with a 0.2mm silver clip in 6‐week‐old male Wistar rats that were sacrificed after 16‐weeks and compared to sham operated controls (19‐weeks). Differentially abundant proteins were identified in a hypothesis free manner using trypsin digested OC and JMC that was tagged with iTRAQ‐4plex, and analyzed on an Orbitrap Velos Pro liquid‐chromatography tandem mass spectrometer.2714 proteins were quantified (FDR &lt; 0.01). 269 proteins increased, and 127 decreased in abundance in 2K1C compared to control (fold change &gt;; 1.5). The number of differential abundant proteins was higher in JMC (338) than in OC (231). 51 of the differential abundant proteins overlapped with 565 differentially expressed genes from microarray gene expression data obtained previously in the same model.In conclusion, hypertensive kidney damage in the non‐clipped kidney of 2K1C is associated with large changes in the proteome, which are more pronounced in the JMC. Important proteins identified include Osteopontin, S100A4 and Decorin, which are known to play a role in fibrosis and tissue remodeling.This work was funded by Western Norway Regional Health Authority and the University of Bergen.

Effects of felodipine combined with puerarin on ACE2–Ang (1–7)–Mas axis in renovascular hypertensive rat

This study aimed to investigate the effect of combination of felodipine+puerarin on ACE2–Ang (1–7)–Mas axis, and to explore the protective effect of the combination against kidney in renovascular hypertensive rats. Goldblatt rats were randomly divided into 5 groups as follows: 4 groups which were treated with felodipine (Felo), puerarin (Pue), Felo+Pue, and Felo+captopril (Cap), respectively, and a control group of animals that were administrated with distilled water. Contents of Ang II and Ang (1–7) in renal tissues were determined by ELISA kit. The mRNA expression of ACE2/Mas and ACE/AT1 in kidneys was analyzed by RT-PCR. After 8weeks of treatment, compared with Goldblatt group, Felo+Pue reduced SBP, DBP and HR (p<0.01 or p<0.05), ameliorated renal interstitial fibrosis, decreased the level of Ang II and increased that of Ang (1–7), upregulated mRNA expression of ACE2 and Mas, decreased that of ACE and AT1, and downregulated protein expression of TGF-β1 in kidneys (p<0.01). Compared with Felo group, Felo+Pue decreased DBP and HR more markedly, attenuated fibrosis, decreased Ang II levels and increased those of Ang (1–7), upregulated mRNA expression of ACE2 in bilateral kidneys and that of Mas in ischemic kidney, downregulated that of ACE in bilateral kidneys and that of AT1 in ischemic kidney, and decreased expression of TGF-β1 protein significantly. In a word, a combination of Felo+Pue has a more efficient therapeutic effect on DBP and HR, and contributes to a better protection against renal interstitial fibrosis.

Ferulic Acid Improves Cardiovascular and Kidney Structure and Function in Hypertensive Rats

Ferulic acid is a simple phenolic acid commonly present in cereals. In this study, changes in heart and kidney structure and function were measured in young N(ω)-nitro-L-arginine methyl ester (L-NAME)-treated Wistar rats and 10-month-old spontaneously hypertensive rats (SHR) alone and after chronic treatment with ferulic acid (FA; 50 mg·kg⁻¹·d⁻¹; n = 6-10; *P < 0.05). Systolic blood pressures were increased after L-NAME treatment (control 125 ± 2 mm Hg, L-NAME 205 ± 6* mm Hg after 8 weeks) and in SHR (250 ± 2 mm Hg; WKY 149 ± 4 mm Hg). Hypertensive rats developed left ventricular hypertrophy, increased ventricular diastolic stiffness (κ; Wistar, 21.4 ± 1.6; L-NAME, 30.1 ± 0.9*; WKYs, 24.1 ± 0.9; SHR 29.5 ± 0.7) and fibrosis of heart and kidneys. Treatment with ferulic acid reduced systolic blood pressure (L-NAME + FA, 157 ± 4*; SHR + FA 214 ± 8* mm Hg), reduced left ventricular diastolic stiffness (L-NAME + FA, 25.2 ± 0.5*; SHR + FA 26.3 ± 0.5*) and attenuated inflammatory cell infiltration, ferric iron accumulation, and collagen deposition in left ventricles and kidneys. Ferulic acid improved both endothelium-dependent relaxation in isolated thoracic aortic rings and antioxidant status by increasing superoxide dismutase and catalase activity in the heart and kidneys. FA decreased plasma liver enzyme activities and plasma creatinine concentrations. Thus, FA improved the structure and function of the heart, blood vessels, liver, and kidneys in hypertensive rats.

Arterial damage precedes the development of interstitial damage in the nonclipped kidney of two-kidney, one-clip hypertensive rats

The progression of damage in the renal cortex has not been investigated in the nonclipped kidney of the two-kidney, one-clip model of renal hypertension. In other hypertensive models, damage has been found to progress from the juxtamedullary cortex (JMC) and outward, which has been attributed to early vascular effects. The present study investigated the relation between perivascular deposition of collagen and structural damage after 16 and 24 weeks of hypertension in the nonclipped kidney in rats. Periarterial collagen density in the kidney was significantly increased already 16 weeks after clipping, at that time tubulointerstitial damage was not evident. After 24 weeks of clipping, periarterial collagen was further increased, and tubulointerstitial damage had developed in the JMC, whereas the outer cortex was protected. Interstitial collagen was not significantly increased in any cortex part during the course of the experiment. Collagen type I a1 mRNA was increased in the JMC after 24 weeks, and α smooth muscle actin histochemistry and collagen type I a2 in-situ hybridization identified myofibroblasts around the arteries after 16 and 24 weeks as the major source of this increase. Fibrosis in the nonclipped kidney of renal hypertensive rats starts around the juxtamedullary resistance vessels and then progresses in the JMC, whereas the outer cortex is protected. This suggests that pressure-induced injury to the vasculature attracts or activates fibroblasts in the perivascular area, which may allow damage to progress by impairing vessel function.

Effects of Lipoic Acid in an Experimentally Induced Hypertensive and Diabetic Rat Model

In this study, experimental diabetes and nephrectomy have been applied separately and together in order to investigate the possible therapeutic effects of lipoic acid (LA) on hypertensive and diabetic rat kidneys. Wistar rats were divided into eight groups: control, diabetes mellitus (DM), 5/6 nephrectomy, DM + 5/6 nephrectomy, LA administration, DM + LA treated, 5/6 nephrectomy + LA treated, and DM + 5/6 nephrectomy + LA-treated groups, respectively. Renal damage was evaluated histomorphometrically, ultrastructurally, and biochemically. Our findings supported that diabetes and hypertension together increased the rate of renal injury, and LA had therapeutic effects on hypertensive and diabetic rat kidneys.

Beneficial effect of genistein on lowering blood pressure and kidney toxicity in fructose-fed hypertensive rats

The study evaluates the effects of genistein on blood pressure (BP) and ultrastructural changes in kidney of fructose-fed hypertensive rats. Male Wistar rats were fed a diet containing 60 % starch or 60 % fructose as the source of carbohydrate. After 15 d, rats in each dietary group were divided into two groups and were treated with either genistein (1 mg/kg per d) in dimethylsulfoxide (DMSO) or 30 % DMSO alone. BP, pressor mechanisms, protein kinase C-βII (PKC-βII) expression, endothelial NO synthase (eNOS) expression and renal ultrastructural changes were evaluated after 60 d. Fructose-fed rats displayed significant elevation in BP and heart rate. Significant increase in plasma angiotensin-converting enzyme (ACE) activity, alterations in renal lipid profile, nitrite and kallikrein activity, enhanced expression of membrane-associated PKC-βII and decreased expression of eNOS were observed in them. Histology and electron microscopic studies showed structural changes in the kidney. Genistein administration lowered BP, restored ACE, PKC-βII and eNOS expression and preserved renal ultrastructural integrity. These findings demonstrate that genistein has effects on eNOS activity in renal cells, leading to eNOS activation and NO synthesis. These effects could have been mediated by activation of PKC-βII. The observed benefits of genistein make it a promising candidate for therapy of diabetic kidney disease.

Abstract 240: Blood Pressure, Renal Function and Hemodynamic Responses to Systemic Ang1-7 in Rats Infused Chronically With Ang Ii: Does the Ang1-7 Natriuretic Effect Depend on Renal Hemodynamics?

Angiotensin II (AngII) is the primary effector of the renin-angiotensin system (RAS) eliciting hypertensinogenic effects. The final levels of AngII depend on AngII synthesis by angiotensin-converting enzyme (ACE) and its degradation to Ang1-7 by carboxypeptidase (ACE2) and to AngIII by aminopeptidase A. Ang 1-7 exerts natriuretic effects and counteracts some of the actions of increased AngII. The downregulation of ACE2 protein in the kidneys of hypertensive rats suggests that reduced Ang1-7 may play a role in the overall blood pressure, renal hemodynamic and excretory responses to chronic AngII infusion. In the present study, we examined the effects of systemic Ang1-7 infusions on blood pressure, renal hemodynamics and urinary excretion in male Sprague-Dawley rats subjected to chronic AngII infusion (80ng/min) for 14 days (N=8) and in control (N=6) rats. We examined if the natriuretic activity is associated with renal hemodynamic changes and if it is modified by RAS activation in the AngII infused rats. In surgically prepared rats, Ang1-7 was infused systemically at a dose of 110 fmol/min. Systemic Ang1-7 infusion increased MABP slightly at 60-120 min of infusion in both control and AngII infused rats (114±3 to 123±4 and 140±6 to 148 ±7 mmHg; p&lt;0.05). RBF significantly decreased in both control and AngII infused rats (7.5±0.9 to 6.4±1 and 9.5 ±1.3 to 8.4±1; p&lt;0.05). Ang1-7 infusion also decreased MBF in control rats, but not in AngII infused rats (124±22 to 113±19 PU, p&lt;0.05). Acute Ang1-7 infusion significantly increased urine flow predominantly in rats that received AngII infusion (5.2±0.4 to 15.6±3.5 μl/min; p&lt;0.05). Sodium excretion was enhanced in control rats (0.14±0.08 to 0.94±0.3 μmol/min; p&lt;0.05) as well as in those chronically infused with AngII (0.04±0.02 to 0.42±0.1; p&lt;0.05). These changes were observed despite the decreases in RBF and MBF. The results indicate that the decreased Ang1-7 levels observed in hypertensive rats chronically infused with AngII do not contribute to the alterations in renal hemodynamics. However, the natriuretic actions of Ang1-7 may exert opposing effects on tubular transport.

Apelin receptor expression in ischemic and non- ischemic kidneys and cardiovascular responses to apelin in chronic two‐kidney–one‐clip hypertension in rats

BackgroundChronic kidney diseases lead to severe cardiovascular consequences such as hypertension and cardiac failure. Apelin, along with its receptor APJ have been shown to involve in cardiovascular functions including blood pressure (BP) lowering effect and also a positive inotropic effect on failing hearts. Therefore we investigated the effect of apelin on BP and cardiac contractility in chronic two-kidney–one-clip (2K1C) hypertension, a kidney disease hypertension model. The changes in the level of apelin and some other hemodynamically effective hormones in serum and apelin receptor gene expression in nonischemic and ischemic kidneys were also assessed. Methods2K1C was produced by placing a Plexiglas clip around the left renal artery. 16weeks later, BP and cardiac indices of contractility were measured by power lab system. The mRNA and protein level of APJ were determined by RT-PCR and Western blot methods respectively. Results2K1C increased BP from 115/75mmHg in sham to 180/120mmHg in test group. Hypertensive rats had about ten times higher basal left ventricular end-diastolic pressure (LVEDP) (P<0.001) and higher basal LV systolic pressure (LVSP) (P<0.01). Apelin-13 (20μg/kg, iv) significantly decreased LVEDP and LVSP (P<0.001). Furthermore, apelin in 20μg/kg dose significantly decreased systolic (SBP) and diastolic (DBP) blood pressures in hypertensive rats. This reduction was persistent and prominent in 40μg/kg dose. 20μg/kg apelin increased +LVdp/dt max and −LV dp/dt max. However in the dose of 40μg/kg SBP, DBP, +LVdp/dt max and −LV dp/dt max greatly decreased. All of these effects were completely blocked by apelin antagonist F13A. 2K1C decreased serum apelin (P<0.05), did not change ang II and arginine-vasopressin levels, and slightly increased serum aldosterone. Apelin receptor mRNA and protein expression significantly decreased in both ischemic and non-ischemic kidneys. ConclusionOverall, chronic 2K1C rats showed hypertension and signs of cardiac failure. Apelin in medium doses induced antihypertensive and positive myocardial inotropic effects. Reduction of serum apelin and down regulation of apelin receptors in kidneys of hypertensive rats may play a role in pathophysiology of cardiovascular complications.

Impact of renal denervation on renalase expression in adult rats with spontaneous hypertension.

The aim of this study was to investigate the impact of renal denervation on the blood pressure, plasma renalase content and expression of renalase and tyrosine hydroxylase (TH) in the kidney of spontaneous hypertensive (SH) rats and to explore the mechanism of renal denervation involved in lowering blood pressure. SH rats (n=48) were randomly assigned to baseline, surgery (renal denervation), sham and control groups. WKY rats matched in age (n=12) served as the baseline control group. All rats were housed until they were 12 weeks old. The rats in the baseline group and the WKY group rats were sacrificed, and blood and kidney were collected for examination. In the renal denervation, sham and control groups, the blood pressure was continuously monitored. One and six weeks after renal denervation, 6 rats in each group were sacrificed, and blood and kidney were collected for examination. ELISA was employed to measure the plasma renalase, and western blot analysis was performed to detect the expression of TH and renalase in the kidney. Compared with the WKY rats, SH rats in the baseline group had significantly increased blood pressure and markedly elevated TH protein expression (P<0.05), but dramatically reduced plasma renalase content and protein expression of renalase in the kidney (P<0.05). One week after surgery, the mean arterial pressure and TH protein expression in the surgery group was lowered compared with the baseline group and dramatically reduced when compared with the sham and control groups (P<0.05). In the surgery group, renalase levels were markedly increased compared with the baseline, sham and control groups (P<0.05). Six weeks after renal denervation, the mean arterial pressure and TH levels in the surgery group were significantly increased while the renalase content and expression were markedly reduced compared with those at week 1, however, there were no marked differences among the surgery, sham and control groups (P>0.05). Moreover, no pronounced differences in the above variables were found between the sham and control groups at any timepoint (P>0.05). Renal denervation can lower blood pressure, which may be attributed to the suppression of sympathetic nerves, increase in plasma renalase content and renalase expression in the kidney.

Reduction of renal lipid content and proteinuria by a PPAR-γ agonist in a rat model of angiotensin II-induced hypertension

An excess of lipids may accumulate in the kidney in conditions such as diabetes and hypertension, and can potentially cause renal injury. We previously reported that an infusion of angiotensin II into a rat induced deposition of lipids in the renal tubular epithelial cells. Here we have examined the effect of pioglitazone, an agonist of the peroxisome proliferator-activated receptor-γ (PPAR-γ), on renal lipid accumulation and renal injury induced by angiotensin II infusion. Pioglitazone treatment (2.5mg/kg/day) reduced the amount of triglycerides in the kidney of the angiotensin II-induced hypertensive rat without significantly altering either blood pressure levels or mRNA expression of lipogenic genes in the kidney. In addition, pioglitazone, either alone or in conjunction with angiotensin II, increased the expression of phosphorylated, but not total, AMP-activated protein kinase (AMPK). Proteinuria and kidney weight in the angiotensin II-infused rat were significantly decreased by pioglitazone treatment. In addition, pioglitazone suppressed iron deposition and ferritin protein induction, but did not alter upregulated expression of the antioxidative molecule, heme oxygenase-1, in the kidney of the angiotensin II-infused rat. These findings suggested that pioglitazone suppressed the angiotensin II-induced increase in renal lipid content by inhibiting its proteinuric action, but not by direct alteration of the expression or activity of lipid metabolism-related genes. Reduction of lipotoxic renal damage may represent one of the renoprotective effects provided by pioglitazone in hypertension with activation of the renin–angiotensin system.

Activation of the Renal PI3K/Akt/mTOR Signaling Pathway in a DOCA-Salt Model of Hypertension

The present study investigated the changes that occurred in the mammalian target of rapamycin (mTOR) signaling pathway in the kidney as a result of deoxycorticosterone acetate (DOCA)-salt hypertension. Rats were implanted with DOCA strips (200 mg/kg) 1 week after unilateral nephrectomy and were then supplied with 0.9% saline to drink. Four weeks after DOCA implantation, systolic blood pressure (SBP) was measured by use of the tail-cuff method. The expression levels of phosphorylated phosphatidylinositol-3-kinase (PI3K), Akt, and mTOR, as well as the protein expression levels of ED-1 and cyclooxygenase-2 (COX-2), transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (SMA), caspase-3, Bax, and Bcl-2, were then examined in the kidney by semiquantitative immunoblotting. DOCA-salt hypertensive rats were found to have significantly increased SBP as well as an increased kidney weight-to-body weight ratio. Moreover, the phosphorylation of PI3K, Akt, and mTOR was increased in the kidney of DOCA-salt hypertensive rats compared with the control, as was the protein expression of ED-1, COX-2, TGF-β1, and α-SMA. The expression levels of caspase-3 and Bax were increased significantly, whereas Bcl-2 expression was decreased. In conclusion, the phosphorylation of PI3K/Akt/mTOR was increased in the kidney of DOCA-salt hypertensive rats.

Cryo-treatment of the renal nerve to the clipped kidney in 2K1C Hypertensive rats: Hemodynamic and neural responses

R renal denervation (DNX) is gaining increasing interest as a modality for treating resistant hypertension. The two-kidney one-clip (2K1C) hypertensive rat is a model of renovascular hypertension. In addition to activation of the reninangiotensinsystem, 2K1C rats display elevated sympathetic activity. Earlier work reported that surgical renal denervation (DNX) decreases mean arterial pressure (MAP) in this model. Since radiofrequency ablation may be problematic in atherosclerotic renal artery disease, we hypothesized that cryo-treatment of the renal nerve to the clipped kidney of 2K-1C rats would decrease MAP, decrease contralateral renal sympathetic nerve activity (RSNA), and improve baroreflex sensitivity. Male Sprague-Dawley rats had sham (SC) or right renal artery clipping (2K1C) and hemodynamic monitoring by telemetry. They were pair fed a 0.4% NaCl diet. Six weeks later,2K1C rats were stratified to moderate (MAP≥140 mmHg) or mild (MAP<140 mmHg) hypertension, instrumentedand underwent sham-DNX or cryo-DNX. All rats were studied in the conscious state. MAP decreased by 16±5 mmHg in the 2K1C cryo-DNXmoderate hypertension group (P<0.05). Cryo-DNX exerted only a small depressor effect in mildly hypertensive 2K1C rats. In the moderately hypertensive 2K1C cryo-DNX rats, contralateral RSNA decreased from 12.2±1.5 to 3.1±3.5 μV.s (P<0.05), a value no different from SC rats 3.3 μV.s. Baroreflex sensitivity of both heart rate and RSNA increased in the cryo-DNX 2K1C rats. Renal tissue norepinephrine decreased by 73% in the DNX kidney; renal tissue Ang II was not altered. Approaches using cryo-treatment to ablate renal nerves may provide an adjunctive therapeutic modality in resistant renovascular hypertension.