Kidney Of 2K1C Rats Research Articles

Garcinia dulcis Extract Alleviates Inflammation in Kidney and Liver of the 2-Kidney-1-Clip Hypertensive rat.

Garcinia dulcis (GD) extract possesses anti-hypertensive property that are poorly characterized. This study aimed to investigate an anti-inflammatory effect of GD flower extract in the 2-kidney-1-clip (2K1C) hypertensive compared to sham operative (SO) rat. Male Wistar rats were divided into 2 groups; the 2K1C group in which a silver clip was placed around renal artery to induce hypertension, and the SO normotensive group. Four weeks later, each group of rats were further divided into 2 subgroups, each subgroup was orally gavaged of either corn oil (vehicle) or 50 mg/kg BW GD extract daily for 4 weeks. The malondialdehyde (MDA) levels in serum, liver, and kidney were determined. Hematoxylin and eosin staining was carried out for histological examination, Periodic acid - Schiff staining for glomerular injury, Masson's trichrome staining for renal fibrosis, and immunohistochemistry for either tumor necrosis factor alpha (TNF-α) or endothelial nitric oxide synthase (eNOS) investigation. Taken together, our results demonstrated that GD flower extract decreased the MDA level in both serum and liver and kidney tissue and suppressed the expression of TNF-α in both liver and kidney of 2K1C hypertensive rats. Mesangial cell proliferation, expansion of mesangial matrix, widening Bowman's capsule space, congestion of glomerular capillary and vessel, cloudy swelling of renal tubular epithelial cell, and renal fibrosis were observed in the kidneys of 2K1C rats. Therefore, we concluded that GD flower extract can alleviate liver and kidney inflammation in which partially attenuates the glomerular injury in the 2K1C rat.

Crataeva nurvala Bark (Capparidaceae) Extract Modulates Oxidative Stress-Related Gene Expression, Restores Antioxidant Enzymes, and Prevents Oxidative Stress in the Kidney and Heart of 2K1C Rats.

Crataeva nurvala is a medicinal plant, which contains a wide range of polyphenolic and bioactive compounds. The aim of the study was to evaluate the renal-protective activity of Crataeva nurvala in two-kidney, one-clip (2K1C) rats. In this study, the ethanol extract of Crataeva nurvala bark at a dose of 100 mg/kg was orally used to treat 2K1C rats for four weeks. At the end of the experiment, all rats were sacrificed and tissue samples were collected for further biochemical and histological assessments. This investigation showed that Crataeva nurvala treatment prevented the kidney dysfunction in 2K1C rats. Uric acid and creatinine concentration and CK-MB activities increased in 2K1C rats which were normalized by Crataeva nurvala. 2K1C rats also showed increased oxidative stress, depicted by the elevated level of MDA, NO, and APOP in plasma and tissues. Oxidative stress parameters declined in 2K1C rats by the treatment of Crataeva nurvala. These results could be attributed to the restoration of antioxidant enzyme activities such as catalase and SOD. Crataeva nurvala extracts also upregulated antioxidant gene expression in the kidneys of 2K1C rats. Moreover, several anti-inflammatory genes were suppressed by Crataeva nurvala treatment in 2K1C rats. Furthermore, fibrosis and collagen deposition in the kidneys were also lowered by the treatment of the Crataeva nurvala extract. The experimental data suggest that the Crataeva nurvala extract protected renal damage and oxidative stress, probably by restoring antioxidant enzymes activities in 2K1C rats.

Polyphenolic compounds of amla prevent oxidative stress and fibrosis in the kidney and heart of 2K1C rats.

Amla (Emblica officinalis Gaertn.) is a natural source of antioxidants and possesses valuable medicinal properties. However, the protective effect of amla in the kidney of two‐kidneys‐one‐clip (2K1C) rats has not been explained sufficiently. This study was performed to evaluate the renoprotective effect of amla fruit powder (2.5% W/W) supplementation in kidneys of 2K1C rats. 2K1C rats increased the remnant kidney wet weight and also increased plasma creatinine and uric acid concentration compared to the control. Amla supplementation ameliorates elevated creatinine and uric acid concentration in plasma of 2K1C rats. Various oxidative stress indicators such as malondialdehyde, nitric oxide (NO), and advanced protein oxidation product (APOP) were also increased in plasma, heart, and kidney tissues in 2K1C rats that were also significantly brought down to normal level by amla supplementation. Moreover, the inflammatory cells entry and fibrosis in the 2K1C rat's tissues were prevented by amla supplementation. These research results suggest that amla may restore plasma antioxidant capacities and prevents oxidative stress, inflammation, and fibrosis in 2K1C rats. Taken these results as a base, clinical supplementation of dried amla powder in diet or juice to the CKD patients would be beneficial.

Vaccarin alleviates hypertension and nephropathy in renovascular hypertensive rats

The kidney is an important organ in the regulation of blood pressure, and it is also one of the primary target organs of hypertension. Kidney damage in response to hypertension eventually leads to renal insufficiency. The authors previously demonstrated that vaccarin exhibits a protective role in endothelial injury. However, the effects of vaccarin on the two-kidney, one clip (2K1C) renovascular hypertension model and subsequent kidney injury have yet to be fully elucidated. The present study was designed to investigate the roles and mechanisms of vaccarin in attenuating hypertension and whether vaccarin had beneficial effects on kidney injury. The 2K1C rats had greater fibrosis, apoptosis, reactive oxygen species production, inflammation, angiotensin II (Ang II) and angiotensin type 1 (AT1) receptors in the right kidney compared with normotensive rats, which were alleviated by a high dose of vaccarin and captopril. Vaccarin treatment attenuated hypertension, reduced fibrosis markers, NADPH oxidase (NOX)-2, NOX-4, 3-nitrotyrosine, tumor necrosis factor-α, interleukin 1β (IL-1β), and IL-6 protein levels and altered pro-apoptotic protein levels including caspase-3, anti-apoptosis protein B cell lymphoma (Bcl)-2 and Bcl-2 associated X, apoptosis regulator in the right kidney of 2K1C rats. These findings suggest that the protective effects of vaccarin on the right kidney in renovascular hypertension are possibly due to downregulation of fibrosis, inflammatory molecules, oxidative stress, Ang II, and AT1 receptor levels.

Sequential activation of the intrarenal renin-angiotensin system in the progression of hypertensive nephropathy in Goldblatt rats.

The intrarenal renin-angiotensin system (RAS) has an important role in generating and maintaining hypertension in two-kidney, one-clip (2K1C) rats. This study evaluated how various intrarenal RAS components contributed to hypertension not only in the maintenance period (5w; 5 wk after operation) but also earlier (2w; 2 wk after operation). We inserted a 2.5-mm clip into the left renal artery of Sprague-Dawley rats and euthanized them at 2w and 5w following the operation. Systolic blood pressure increased within 1 wk after the operation, and left ventricular hypertrophy occurred in 2K1C rats. At 2w, juxtaglomerular apparatus (JGA) and collecting duct (CD) renin increased in clipped kidney (CK) of 2K1C rats. The tubular angiotensin I-converting enzyme (ACE) was not changed, but peritubular ACE2 decreased in nonclipped kidney (NCK) and CK of 2K1C rats. At 5w, ACE and CD renin were enhanced, and ACE2 was still lessened in both kidneys of 2K1C rats. However, plasma renin activity (PRA) was not different from that in sham rats. In proximal tubules of CK, the ANG II type 1 receptor (AT1R) was not suppressed, but the Mas receptor (MasR) was reduced; thus the AT1R/MasR ratio was elevated. Although hypoxic change in CK could not be excluded, the JGA renin of CK and CD renin in both kidneys was highly expressed independent of time. Peritubular ACE2 changed in the earlier period, and uninhibited AT1R in proximal tubules of CK was presented in the maintenance period. In 2K1C rats, attenuated ACE2 seems to contribute to initiating hypertension while upregulated ACE in combination with unsuppressed AT1R may have a key role in maintaining hypertension.

Downregulation of alpha7 nicotinic acetylcholine receptor in two-kidney one-clip hypertensive rats

BackgroundInflammation processes are important participants in the pathophysiology of hypertension and cardiovascular diseases. The role of the alpha7 nicotinic acetylcholine receptor (α7nAChR) in inflammation has recently been identified. Our previous study has demonstrated that the α7nAChR-mediated cholinergic anti-inflammatory pathway is impaired systemically in the genetic model of hypertension. In this work, we investigated the changes of α7nAChR expression in a model of secondary hypertension.MethodsThe 2-kidney 1-clip (2K1C) hypertensive rat model was used. Blood pressure, vagus nerve function, serum tumor necrosis factor-α (TNF-α) and both the mRNA and protein levels of α7nAChR in tissues from heart, kidney and aorta were measured at 4, 8 and 20 weeks after surgery.ResultsCompared with age-matched control, it was found that vagus nerve function was significantly decreased in 2K1C rats with the development of hypertension. Serum levels of TNF-α were greater in 2K1C rats than in age-matched control at 4, 8 and 20 weeks. α7nAChR mRNA in the heart was not altered in 2K1C rats. In the kidney of 2K1C rats, α7nAChR expression was significantly decreased at 8 and 20 weeks, but markedly increased at 4 weeks. α7nAChR mRNA was less in aorta of 2K1C rats than in age-matched control at 4, 8 and 20 weeks. These findings were confirmed at the protein levels of α7nAChR.ConclusionsOur results suggested that secondary hypertension may induce α7nAChR downregulation, and the decreased expression of α7nAChR may contribute to inflammation in 2K1C hypertension.

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.

Reciprocal changes in renal ACE/ANG II and ACE2/ANG 1–7 are associated with enhanced collecting duct renin in Goldblatt hypertensive rats

Alterations in the balance between ANG II/ACE and ANG 1-7/ACE2 in ANG II-dependent hypertension could reduce the generation of ANG 1-7 and contribute further to increased intrarenal ANG II. Upregulation of collecting duct (CD) renin may lead to increased ANG II formation during ANG II-dependent hypertension, thus contributing to this imbalance. We measured ANG I, ANG II, and ANG 1-7 contents, angiotensin-converting enzyme (ACE) and ACE2 gene expression, and renin activity in the renal cortex and medulla in the clipped kidneys (CK) and nonclipped kidneys (NCK) of 2K1C rats. After 3 wk of unilateral renal clipping, systolic blood pressure and plasma renin activity increased in 2K1C rats (n = 11) compared with sham rats (n = 9). Renal medullary angiotensin peptide levels were increased in 2K1C rats [ANG I: (CK = 171 ± 4; NCK = 251 ± 8 vs. sham = 55 ± 3 pg/g protein; P < 0.05); ANG II: (CK = 558 ± 79; NCK = 328 ± 18 vs. sham = 94 ± 7 pg/g protein; P < 0.001)]; and ANG 1-7 levels decreased (CK = 18 ± 2; NCK = 19 ± 2 pg/g vs. sham = 63 ± 10 pg/g; P < 0.001). In renal medullas of both kidneys of 2K1C rats, ACE mRNA levels and activity increased but ACE2 decreased. In further studies, we compared renal ACE and ACE2 mRNA levels and their activities from chronic ANG II-infused (n = 6) and sham-operated rats (n = 5). Although the ACE mRNA levels did not differ between ANG II rats and sham rats, the ANG II rats exhibited greater ACE activity and reduced ACE2 mRNA levels and activity. Renal medullary renin activity was similar in the CK and NCK of 2K1C rats but higher compared with sham. Thus, the differential regulation of ACE and ACE2 along with the upregulation of CD renin in both the CK and NCK in 2K1C hypertensive rats indicates that they are independent of perfusion pressure and contribute to the altered content of intrarenal ANG II and ANG 1-7.

Effects of chronic antioxidant treatment on AT‐1 receptor, NAD(P)H oxidase subunits and main antioxidant enzymes gene expression in the kidneys of 2K‐1C rats

Previous studies showed that chronic treatment with an antioxidant: vitamin C (vC) improves hypertension and sympathetic vasomotor hyperactivity in an Ang II‐dependent model of renovascular arterial hypertension. To test the hypothesis that oxidative stress is associated with NAD(P)H oxidase activation by Ang II, gene expressions of AT‐1 receptor (AT1R), NAD(P)H oxidase subunits (p47phox and gp91phox) and main antioxidant enzymes were evaluated in the renal cortex of 2 kidney‐1 clip model (2K1C, 6 weeks after clipping) rats before and after vC (150mg/kg/day). Gene expression of AT1R was elevated (51%) in the clipped kidney (CK) and reduced (47%) in the nonclipped kidney (NK) of 2K1C group. vC reduced AT1R expression only in the CK (31%). Elevated gene expression of p47phox and gp91phox was observed only in the CK of 2K‐1C group (184% and 132%, respectively) and vC produced no changes in these expressions. Gene expression of catalase was reduced in the CK (70%) and NK (83%) of 2K1C rats. vC increased gene expression of glutathione peroxidase (GPx) in the CK (185%) and NK (212%) of 2K1C. The present study suggests that renal oxidative stress may be related to elevated AT1R and NAD(P)H oxidase subunits gene expression in the CK of 2K1C rats and vitC treatment may produce beneficial effects by AT1R downregulation in the CK and increase in GPx gene expression in the kidneys of 2K1C rats.Supported by FAPESP (07/56925‐1)

Chronic Antioxidant Treatment Improves Arterial Renovascular Hypertension and Oxidative Stress Markers in the Kidney in Wistar Rats

Sympathetic vasomotor hyperactivity and baroreflex dysfunction are involved in the development and maintenance of renovascular arterial hypertension. We hypothesized that angiotensin (Ang) II-dependent oxidative stress contributes to the pathophysiology of the two-kidney, one-clip (2K-1C) model. The mean arterial pressure (MAP), baroreflex, and renal sympathetic nerve activity (rSNA) were evaluated after chronic administration of an antioxidant, vitamin C (vitC 150 mg/kg/day) in male Wistar 2K-1C rats. Additionally, the mRNA levels of Ang II subtype 1 receptor (AT(1)R), NAD(P)H oxidase subunits (p47phox and gp91phox), and major antioxidant enzymes were evaluated in the renal cortex. After vitC treatment, the MAP (170 +/- 4 vs. 133 +/- 6 mm Hg; P < 0.05) and rSNA (161 +/- 5 vs. 118 +/- 12 spikes/s; P < 0.05) were significantly reduced only in the 2K-1C group. VitC improved the baroreflex control of heart rate (HR) and rSNA. The expression of AT(1)R, p47phox, and gp91phox was elevated (51, 184, and 132%, respectively) in the clipped kidney of 2K-1C group. VitC downregulated AT(1)R in the clipped kidney (31%). Catalase (CAT) expression was reduced in clipped (70%) and nonclipped (83%) kidneys of 2K-1C rats. VitC treatment augmented the expression of glutathione peroxidase (GPx) in both clipped (185%) and nonclipped (212%) kidneys of the 2K-1C group. The present study suggests a role for oxidative stress in the cardiovascular and sympathetic alterations in renovascular hypertension, associated with changes in the expression of AT(1)R, NAD(P)H oxidase subunits, and antioxidant enzymes in the kidney.

Does Handle Region Peptide Provide Benefits in Chronic Kidney Disease?

Discovery of (pro)renin receptor uncovered a novel function of renin/prorenin as the receptor ligands in addition to enzyme and its precursor. Binding of renin and prorenin to the (pro)renin receptor activate two major signaling pathways: the locally generatedangiotensin II-dependent pathway as a result of the enzymatic activation of renin/prorenin, and the angiotensin II-independent (pro)renin receptor mediated intracellular pathway, involving hypertrophic, hyperplasic, and profibrotic signals. A specific blocker of the receptor was discovered through identification of amino acid sequence of prorenin pro-segment which binds to the receptor and leads to non-proteolytic alteration of prorenin to its active form. A peptide which contains this sequence was found to block the binding of prorenin to its receptor. Its continuous infusion in animal models of diabetes and low-renin hypertension significantly inhibited the development and progression of nephropathy, but (pro)renin receptor blockade was not effective on the clipped kidney of 2K1C rats or rat models of high-renin hypertension. Since renin is still active without a (pro)renin receptor, (pro)renin receptor blockade provides a maximum benefit under low-renin conditions. Thus, (pro)renin receptor blockade can be a effective therapeutic approach for chronic kidney disease with low renin levels in the plasma.

Renal vascular L‐arginine metabolism, NO release and contraction in Angiotensin II hypertensive rats

The effect of Angiotensin II (AngII) hypertension on L‐arginine metabolising enzymes and AngII induced vascular contraction and nitric oxide release was investigated because we found increased expressions in vessels from both kidneys of 2K1C rats and increased nitric oxide release from the non‐clipped kidney. Four groups of rats were infused with 80 ng/min AngII or saline for 14 days, and/or given 60 mg/kg/day Losartan. Gene expression was studied in isolated preglomerular vessels by RTPCR. Arteriolar contraction was studied using 10−10, 10−9, 10−8 and 10−7 mol/L of AngII and 10−4 mol/L L‐NAME in vessels isolated using the agar infusion/enzyme digestion method. Expressions of eNOS , caveolin‐1 and Arginase‐2 were not changed by AngII infusion. CAT‐1 (0.38±0.07 to 0.73±0.12, P&lt;0.05), CAT‐2 (1.14±0.29 to 2.74±0.48), DDAH‐2 (1.09±0.27 to 2.3±0.46) and Arginase‐1 (1.08±0.17 to 1.82±0.22) were increased in AngII infused rats and normalised by Losartan. Losartan reduced the expression of eNOS (0.97±0.26 to 0.37±0.11 in controls; 0.8±0.16 to 0.36±0.1 in AngII infused rats) and caveolin‐1 (2.49±0.59 to 0.82±0.24 in controls and 2.59±0.61 to 1.1±0.25 in AngII infused rats). AngII induced contraction was enhaced in the AngII infused animals (47±15 % vs. 7±5 % at 10−10 mol/L AngII). Contraction at 10−10 mol/L AngII was enhaced by L‐NAME in AngII infused rats (96±4 %). In conclusion, Losartan affects eNOS and caveolin‐1 expression through an AT1 receptor independent pathway. CAT‐1, CAT‐2, DDAH‐2 and Arginase‐1 expressions in renal resistance vessels are regulated through the AT1 receptor, which may be of direct importance for nitric oxide synthesis and the regulation of renal blood flow as can be seen by the buffering effect of NO on the contraction of isolated arterioles in the vessels from AngII infused animals. The study was funded by Helsevest, Norway.

Collecting Duct Renin Is Upregulated in Both Kidneys of 2-Kidney, 1-Clip Goldblatt Hypertensive Rats

Renin in collecting duct cells is upregulated in chronic angiotensin II-infused rats via angiotensin II type 1 receptors. To determine whether stimulation of collecting duct renin is a blood pressure-dependent effect; changes in collecting duct renin and associated parameters were assessed in both kidneys of 2-kidney, 1-clip Goldblatt hypertensive (2K1C) rats. Renal medullary tissues were used to avoid the contribution of renin from juxtaglomerular cells. Systolic blood pressure increased to 184+/-9 mm Hg in 2K1C rats (n=19) compared with sham rats (121+/-6 mm Hg; n=12). Although renin immunoreactivity markedly decreased in juxtaglomerular cells of nonclipped kidneys (NCK: 0.2+/-0.0 versus 1.0+/-0.0 relative ratio) and was augmented in clipped kidneys (CK: 1.7+/-1.0 versus 1.0+/-0.0 relative ratio), its immunoreactivity increased in cortical and medullary collecting ducts of both kidneys of 2K1C rats (CK: 2.8+/-1.0 cortex; 2.1+/-1.0 medulla; NCK: 4.6+/-2.0 cortex, 3.2+/-1.0 medulla versus 1.0+/-0.0 in sham kidneys). Renal medullary tissues of 2K1C rats showed greater levels of renin protein (CK: 1.4+/-0.2; NCK: 1.5+/-0.3), renin mRNA (CK: 5.8+/-2.0; NCK: 4.9+/-2.0), angiotensin I (CK: 120+/-18 pg/g; NCK: 129+/-13 pg/g versus sham: 67+/-6 pg/g), angiotensin II (CK: 150+/-32 pg/g; NCK: 123+/-21 pg/g versus sham: 91+/-12 pg/g; P<0.05), and renin activity (CK: 8.6 microg of angiotensin I per microgram of protein; NCK: 8.3 microg of angiotensin I per microgram of protein; sham: 3.4 microg of angiotensin I per microgram of protein) than sham rats. These data indicate that enhanced collecting duct renin in 2K1C rats occurs independently of blood pressure. Upregulation of distal tubular renin helps to explain how sustained intrarenal angiotensin II formation occurs even during juxtaglomerular renin suppression, thus allowing maintained effects on tubular sodium reabsorption that contribute to the hypertension.

Glomerular B2-kinin-binding sites in two-kidney, one-clip hypertensive rats

To extend our recent observations of the possible downregulation of glomerular B2-kinin-binding sites, we investigated density (Bmax) of bradykinin (BK)-binding sites in glomerular membranes of both the clipped (C) and nonclipped (NC) kidneys of two-kidney, one-clip (2K-1C) Goldblatt hypertensive rats, in relation to tissue kallikrein activity and glomerular three-dimensional structure. Compared with the Bmax of sham-operated (SO) kidney (31.8 +/- 7 fmol/mg protein), a significant increase in Bmax was observed in glomeruli of both kidneys in hypertensive rats, the Bmax being higher in glomeruli of NC than in C kidneys (98 +/- 11 vs. 59 +/- 12 fmol/mg protein). NC kidney compensatory hypertrophy was expressed by an increase in glomerular diameter, surface area, and volume. When expressed per unit of area or volume, Bmax in NC kidneys remained significantly higher than in both C and SO kidneys. Increased Bmax in both kidneys of 2K-1C rats was associated with a decreased intrarenal level of kallikrein. We also examined prostaglandin (PG) E2 release by isolated glomeruli from SO, C, and NC kidneys as a possible biological effect induced by BK. Whereas C kidney released more PGE2 than NC kidney under basal conditions, addition of BK (10 nM) induced greater PGE2 production in NC kidney consistent with the difference in Bmax between C and NC kidneys. These results suggest a possible downregulation of glomerular B2-binding sites by bradykinin, which may explain the difference between SO and C kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)