Renal Nitric Oxide Production Research Articles

Malate reduced kidney injury molecule (KIM-1) expression and selectively upregulated the renal nitric oxide production in obstructive nephropathy

Malate, the tricarboxylic acid (TCA) cycle intermediary, upregulates renal nitric oxide (NO) signaling, and NO is renoprotective in nephropathy. This study explored the hypothesis that malate could increase renal NO and decrease renal injury and fibrotic markers in obstructive nephropathy. Kidney injury was induced in rats via unilateral surgical ligation of the ureter, there after, rats were treated with malate (600 mg/kg, p.o.) for ten days. Urine was collected on days 0, 4, 7 and 10. Urinary sodium excretion was also determined. Western blot and biochemical analyses were carried on the nephropathic kidneys. Malate reduced kidney injury molecule (KIM-1) expression in the renal cortex and medulla of nephropathic rats (p < 0.05). NO production was selectively increased in the medulla of nephropathic rats treated with malate (58.3 ± 1.3 vs 77.8 ± 4.4 µM/ng, p < 0.05). Superoxide dismutase and catalase activity increased in the kidney of malate-treated nephropathic rats (p < 0.05). Transforming growth factor (TGF-β), an index of fibrosis, increased in the cortex but not medulla of the malate-treated UUO group. There was a consistent increase in collagenase activity in the cortex, and a reduction in the medulla. Malate ameliorated the injury and inflammation but selectively reduced fibrosis in obstructive nephropathy (Fig. 6, Ref. 32). Text in PDF www.elis.sk Keywords: Malate, tricarboxylic acid cycle, nitric oxide, kidney injury molecule (KIM-1), obstructive nephropathy.

Underlying antihypertensive mechanism of egg white-derived peptide QIGLF using renal metabolomics analysis

The kidney is an important target organ in the treatment of hypertension, but the effect of peptide QIGLF with antihypertensive activity on kidneys remains unknown. In the work, we aimed to further understand the hypotensive effects of QIGLF in spontaneously hypertensive rats (SHRs) using widely targeted metabolomics technology to investigate the kidney metabolic profiling variations. After four weeks of oral administration, the results showed different renal metabolomics profiles between QIGLF and model groups. Besides, a total of 10 potential biomarkers were identified, that is, 3-hydroxybutanoate, 20-hydroxyeicosatetraenoic acid, 19(S)-hydroxyeicosatetraenoic acid, 15-oxoETE, L-ornithine, malonate, uridine, uridine 5′-monophosphate, argininosuccinic acid, and N-carbamoyl-L-aspartate. These metabolites might exhibit antihypertensive activity of QIGLF by regulating synthesis and degradation of ketone bodies, arachidonic acid metabolism, pyrimidine metabolism, and arginine biosynthesis. These findings suggest that QIGLF might alleviate hypertension by inhibiting renal inflammation, promoting natriuresis, and regulating renal nitric oxide production.

Pharmacological HIF-PHD inhibition reduces renovascular resistance and increases glomerular filtration by stimulating nitric oxide generation.

Hypoxia-inducible factors (HIFs) are O2 -sensitive transcription factors that regulate multiple biological processes which are essential for cellular adaptation to hypoxia. Small molecule inhibitors of HIF-prolyl hydroxylase domain (PHD) dioxygenases (HIF-PHIs) activate HIF-dependent transcriptional programs and have broad clinical potential. HIF-PHIs are currently in global late-stage clinical development for the treatment of anaemia associated with chronic kidney disease. Although the effects of hypoxia on renal haemodynamics and function have been studied in animal models and in humans living at high altitude, the effects of pharmacological HIF activation on renal haemodynamics, O2 metabolism and metabolic efficiency are not well understood. Using a cross-sectional study design, we investigated renal haemodynamics, O2 metabolism, gene expression and NO production in healthy rats treated with different doses of HIF-PHIs roxadustat or molidustat compared to vehicle control. Systemic administration of roxadustat or molidustat resulted in a dose-dependent reduction in renovascular resistance (RVR). This was associated with increased glomerular filtration rate (GFR), urine flow and tubular sodium transport rate (TNa ). Although both total O2 delivery and TNa were increased, more O2 was extracted per transported sodium in rats treated with high-doses of HIF-PHIs, suggesting a reduction in metabolic efficiency. Changes in RVR and GFR were associated with increased nitric oxide (NO) generation and substantially suppressed by pharmacological inhibition of NO synthesis. Our data provide mechanistic insights into dose-dependent effects of short-term pharmacological HIF activation on renal haemodynamics, glomerular filtration and O2 metabolism and identify NO as a major mediator of these effects.

Fructose‐induced salt‐sensitive hypertension increases aortic stiffness and induces changes in systemic and renal hemodynamics

When high fructose consumption is accompanied by high salt consumption, such as occurs in a typical Western diet, hypertension ensues and the exact mechanism still remains to be identified. Although it has been shown that at least part of the mechanism involves sodium retention by the small intestine and the proximal tubule of the kidney, and reduced renal nitric oxide production, the full spectrum of mechanisms of fructose‐induced salt‐sensitive hypertension and its impact on cardiovascular co‐morbidities remains unknown. The objective of this work was to delineate the longitudinal changes in systemic and renal hemodynamics as a consequence of fructose‐ and salt‐enriched diet. Our central hypothesis is that elevated fructose in the diet predisposes to salt‐sensitive hypertension and initiates changes in both renal and systemic hemodynamics. Previously we found that rats fed 20% fructose for one week develop salt sensitive hypertension within two weeks of high‐salt feeding (4% NaCl). In the present work, using echocardiography we found that fructose‐fed rats displayed increased stroke volume (190.1 ± 9.4 μL vs 145.7 ± 5.8 μL, p &lt; 0.05) and increased left ventricular mass index (1.03 ± 0.06 vs 0.75 ± 0.06), while relative wall thickness remained unchanged. These results are indicative of left ventricular remodeling consistent with eccentric hypertrophy. This is further corroborated by diastolic diameter (6.8 ± 0.2 mm vs 5.9 ± 0.3 mm). Fructose‐fed rats on a high salt (F+HS) diet showed signs of increased aortic stiffness, since the distention to vasodilator phenylephrine was reduced in the ascending aorta (7.1 ± 1.0% from baseline vs 18.2 ± 1.3% from baseline, p&lt;0.05) for the same increase in blood pressure, a result that was not observed in fructose fed rats that were on an normal salt diet (F+NS; 16.1± 2.9%, p &lt; 0.05 vs F+HS). The observed increase in stiffness in the ascending aorta of F+HS rats is likely due to an increase in collagen deposition compared to F+NS and control rats. Finally, we wanted to determine whether the changes in systemic hemodynamics and parameters of cardiac function were paralleled by changes in renal hemodynamics. We measured renal resistive index (RRI) using ultrasound and found that it was elevated in F+HS rats compared to F+NS and control rats. Taken together, these results point to the apparent role of dietary fructose in inducing salt‐sensitive hypertension that is accompanied by increased aortic stiffness and concomitant changes in systemic and renal hemodynamics.Support or Funding InformationVA Merit Award to N.F.R.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Previous Exercise Effects in Cisplatin-Induced Renal Lesions in Rats

Background/Aims: Physical training has beneficial effects on endothelial function and can influence the regeneration of the endothelial cell. We investigated the effect of physical training on cisplatin (CP)-induced acute kidney injury and assessed the impact of training on endothelial structure and function, and on the inflammatory processes in rats. Methods: We injected male Wistar rats subjected to previous physical training in treadmill running (trained, TR) or not (sedentary, SED) with CP (5 mg/kg) (TR+CP and SED+CP groups, respectively). Five days after the injections, blood and urine samples were collected to evaluate renal function and kidneys were harvested for morphological, immunohistochemical, enzyme-linked immunosorbent assay, and analysis of nitric oxide (NO) levels. Results: Rats treated with CP showed increased levels of plasma creatinine and sodium and potassium fractional excretion. These alterations were associated with increase in tubulointerstitial lesions and macrophage number, reduction of endothelial cells, and increased VEGF, vimentin, and α-smooth muscle actin expression in the outer renal medulla in the SED+CP group. We also found increased levels of renal IL-1β and increased excretion of monocyte chemoattractant protein-1 and transforming growth factor-β compared with controls. These changes were milder in trained rats, associated with increased levels of renal tissue NO, and increased expression of p-eNOS and stromal cell-derived factor-1α (a chemokine involved in kidney repair) in the kidneys of CP-injected trained rats. Conclusions: The protective effect of previous training in CP-treated rats was associated with reduced endothelial cell lesions and increased renal production of NO in trained rats.

Smooth Muscle PPARγ Mutation Causes Salt‐sensitive Hypertension

Systemic loss of peroxisome proliferator‐activated receptor‐γ (PPARγ) function causes hypertension, whereas its activation lowers blood pressure largely via PPARγ activity in the vasculature. We have recently shown that loss of PPARγ in smooth muscle cells increases mesenteric myogenic tone, promotes vascular remodeling, and predisposes to deoxycorticosterone acetate (DOCA)‐salt‐induced hypertension in mice. However, it is unclear whether these effects were attributable to altered salt sensitivity. In this study, we examined the role of smooth muscle PPARγ in regulating renal function and salt‐sensitivity. Transgenic mice expressing dominant negative PPARγ in smooth muscle cells (S‐P467L) and non‐transgenic littermates (NT) were fed normal chow diet (containing 0.3% salt) or a 4% salt diet for a total of 8 weeks and metabolic cage studies were performed at baseline, 3 weeks, 6 weeks, and at the end of the protocol. S‐P467L and NT mice had similar food intake, feces weight, and weight gain on high salt diet throughout the study. While 24‐hour water intake tripled in both strains (6.3 ± 0.21 mL S‐P467L vs. 5.9 ± 0.40 mL NT, n=7) when they were switched to high salt diet from normal chow, S‐P467L mice excreted 32% less urine in the third week (24‐hour urine 1.96 ± 0.13 mL S‐ P467L vs. 2.90 ± 0.17 mL NT, two‐way ANOVA p&lt;0.01). In order to assess renal function, mice were subjected to a bolus i.p. injection of normal saline equal to 10% of their body weight and the urine volume excreted in the subsequent 4 hours were plotted as a percentage of saline injected. We observed a marked decline in their capacity to excrete this volume challenge in S‐ P467L mice (28.2 ± 2.1% S‐P467L vs. 39.9 ± 5.1% NT, p&lt;0.05) in the third week of high salt diet. Because nitric oxide (NO) is known to regulate sodium and water balance, we determined daily renal NO production as indicated by 24‐hour urinary nitrate/nitrite. Three‐week dietary salt induced a 4‐fold increase in urinary NO metabolites in NT mice, but this was blunted in S‐P467L mice (2.82 ± 0.19 μmoL/24 hours S‐P467L vs. 4.42 ± 0.27 μmoL/24 hours NT, p&lt;0.01). In parallel with these renal phenotypes, S‐P467L mice developed marked elevation of blood pressure that peaked in the third week of high salt feeding (telemetry systolic pressure 136.4 ± 3.4 mmHg S‐P467L vs. 124.2 ± 2.4 mmHg NT, p&lt;0.01) and remained elevated throughout the study. At the end of 8 weeks, vascular function was assessed in freshly isolated carotid and basilar arteries, and flow cytometry analysis was performed in single cell suspensions of aorta and kidney tissues. S‐P467L mice, but not NT littermates, exhibited severe impairment of acetylcholine‐ and sodium nitroprusside‐induced vascular relaxation in the carotid and basilar arteries in response to high salt. CD45+ total leukocytes, CD3+ T cells, CD4+/CD8+ T cell subsets, and F4/80+ monocytes/macrophages were not altered in the aortas but were paradoxically reduced in the kidneys of S‐P467L mice in response to high salt. These data indicate that loss of PPARγ in smooth muscle cells predispose to impaired vascular relaxation, renal dysfunction, and salt‐sensitive hypertension. This study highlights the significance of vascular PPARγ in regulating systemic physiological responses.Support or Funding InformationNIH and AHA Grants

Evaluations of lipid peroxidation and inflammation in short‐term glycerol‐induced acute kidney injury in rats

Rhabdomyolysis is characterised by acute kidney injury (AKI) resulting from skeletal muscle injury. Lipid peroxidation-mediated oxidant injury and pro-inflammatory cytokine-mediated inflammatory response play critical roles in the pathogenesis of rhabdomyolysis-induced AKI. The present study aimed to investigate the short-term effects of both lipid peroxidation and inflammatory responses on rhabdomyolysis-induced AKI in a rat model of glycerol-induced rhabdomyolysis. Rhabdomyolysis was induced by the intramuscular injection of 50% glycerol in saline (10mL/kg) into the hind limbs of rats. Rats were killed 1 or 3hours after glycerol injection. Time-dependent increases in serum biochemical parameters, including blood urea nitrogen, creatinine, lactate dehydrogenase and creatine phosphokinase levels, were observed 1hour after glycerol injection. In kidneys, glycerol injection resulted in histopathological changes such as renal tubular injury and renal tubular myoglobin deposition. Levels of Nε-(hexanoyl)lysine-modified, 4-hydroxy-2-nonenal-modified, and nitrotyrosine-modified proteins in rat kidneys were unaltered at 1hour after glycerol injection, but increased significantly at 3hours. Increases in renal nitric oxide production and the expression levels of inducible nitric oxide synthase, interleukin-6 and tumour necrosis factor-α in the renal parenchyma were observed at 1hour after glycerol injection and plateaued at 3hours. Our findings suggest that the pro-inflammatory cytokine-mediated inflammatory response may cause rhabdomyolysis-induced AKI very shortly after glycerol injection, and lipid peroxidation-mediated oxidant injury may promote the development of these pathophysiological processes.

Hypergravity upregulates renal inducible nitric oxide synthase expression and nitric oxide production.

Exposure to hypergravity severely decreases renal blood flow, potentially causing renal dysfunction. Nitric oxide (NO), which is endogenously synthesized by inducible NO synthase (iNOS), plays an important role in the regulation of renal function. The purpose of this study was to examine the effect of hypergravity exposure on the production of NO in kidneys. To determine whether hypergravity induces renal hypoxia and alters renal iNOS expression and NO production, mice were exposed to short-term hypergravity at +3Gz for 1 h. The time course of iNOS mRNA expression, hypoxia-inducible factor (HIF)-1α expression, and NO production was examined. Renal HIF-1α levels were significantly elevated immediately after centrifugation, and this increase was sustained for 3 h post-exposure. iNOS mRNA levels were also significantly increased immediately after exposure and were maintained during the reoxygenation period. Immunohistochemical staining for iNOS revealed that the cortical tubular epithelium exhibited moderate to strong cytoplasmic iNOS immunoreactivity immediately after hypergravity exposure and during the reoxygenation period. The time course of NO production was similar to that of iNOS expression. Our results suggest that both hypoxia and reoxygenation might be involved in the upregulation of HIF-1α in the kidneys of mice exposed to hypergravity. Significant increases in renocortical iNOS expression immediately after centrifugation and during the reoxygenation period suggest that iNOS expression induced by hypergravity exposure might play a protective role against hypoxia/reoxygenation injury in the renal cortex. Further investigations are necessary to clarify the role of iNOS and NO in kidneys exposed to hypergravity.

Vitamin D3 pretreatment alleviates renal oxidative stress in lipopolysaccharide-induced acute kidney injury

Increasing evidence demonstrates that reactive oxygen species plays important roles in sepsis-induced acute kidney injury. This study investigated the effects of VitD3 pretreatment on renal oxidative stress in sepsis-induced acute kidney injury. Mice were intraperitoneally injected with lipopolysaccharide (LPS, 2.0mg/kg) to establish an animal model of sepsis-induced acute kidney injury. In VitD3+LPS group, mice were orally pretreated with three doses of VitD3 (25μg/kg) at 1, 24 and 48h before LPS injection. As expected, oral pretreatment with three daily recommended doses of VitD3 markedly elevated serum 25(OH)D concentration and efficiently activated renal VDR signaling. Interestingly, LPS-induced renal GSH depletion and lipid peroxidation were markedly alleviated in VitD3-pretreated mice. LPS-induced serum and renal nitric oxide (NO) production was obviously suppressed by VitD3 pretreatment. In addition, LPS-induced renal protein nitration, as determined by 3-nitrotyrosine residue, was obviously attenuated by VitD3 pretreatment. Further analysis showed that LPS-induced up-regulation of renal inducible nitric oxide synthase (inos) was repressed in VitD3-pretreated mice. LPS-induced up-regulation of renal p47phox and gp91phox, two NADPH oxidase subunits, were normalized by VitD3 pretreatment. In addition, LPS-induced down-regulation of renal superoxide dismutase (sod) 1 and sod2, two antioxidant enzyme genes, was reversed in VitD3-pretreated mice. Finally, LPS-induced tubular epithelial cell apoptosis, as determined by TUNEL, was alleviated by VitD3 pretreatment. Taken together, these results suggest that VitD3 pretreatment alleviates LPS-induced renal oxidative stress through regulating oxidant and antioxidant enzyme genes.

Renoprotective Effects of Fenofibrate via Modulation of LKB1/AMPK mRNA Expression and Endothelial Dysfunction in a Rat Model of Diabetic Nephropathy

This study was conducted to investigate whether the renoprotective effects of fenofibrate are mediated via attenuation of endothelial dysfunction and modulating the mRNA expression of adenosine monophosphate-activated protein kinase (AMPK) and its downstream kinase liver kinase B1 (LKB1) in rats with diabetic nephropathy (DN). Diabetes was induced by a single intraperitoneal injection of streptozotocin (55 mg kg^-1). Fenofibrate (100 mg kg^-1, p.o.) was given to diabetic rats daily for 12 weeks. Treatment with fenofibrate significantly improved the renal function as revealed by the significant reductions in urinary albumin excretion and serum levels of creatinine and urea, in addition to the significant increase in creatinine clearance compared with the diabetic control group. Hyperglycemia-induced oxidative damage was ameliorated by treatment with fenofibrate as indicated by the significantly increased levels of glutathione and catalase together with the significant decrease in lipid peroxidation. Administration of fenofibrate caused significant increases in renal nitric oxide (NO) production and mRNA expression of endothelial NO synthase (eNOS), AMPK and LKB1, reflecting improvement of endothelial function. Our results give further insights into the mechanisms underlying the protective role of fenofibrate in DN via modulation of AMPK, LKB1 and eNOS mRNA expression.

What level of sodium intake worsens renal outcomes?

What level of sodium intake worsens renal outcomes?

Melatonin therapy prevents programmed hypertension and nitric oxide deficiency in offspring exposed to maternal caloric restriction.

Nitric oxide (NO) deficiency is involved in the development of hypertension, a condition that can originate early in life. We examined whether NO deficiency contributed to programmed hypertension in offspring from mothers with calorie-restricted diets and whether melatonin therapy prevented this process. We examined 3-month-old male rat offspring from four maternal groups: untreated controls, 50% calorie-restricted (CR) rats, controls treated with melatonin (0.01% in drinking water), and CR rats treated with melatonin (CR + M). The effect of melatonin on nephrogenesis was analyzed using next-generation sequencing. The CR group developed hypertension associated with elevated plasma asymmetric dimethylarginine (ADMA, a nitric oxide synthase inhibitor), decreased L-arginine, decreased L-arginine-to-ADMA ratio (AAR), and decreased renal NO production. Maternal melatonin treatment prevented these effects. Melatonin prevented CR-induced renin and prorenin receptor expression. Renal angiotensin-converting enzyme 2 protein levels in the M and CR + M groups were also significantly increased by melatonin therapy. Maternal melatonin therapy had long-term epigenetic effects on global gene expression in the kidneys of offspring. Conclusively, we attributed these protective effects of melatonin on CR-induced programmed hypertension to the reduction of plasma ADMA, restoration of plasma AAR, increase of renal NO level, alteration of renin-angiotensin system, and epigenetic changes in numerous genes.

Abstract 535: Impaired Natriuresis and Increased Salt Sensitivity in Response to Acute Salt Load During Western Diet-intake: Role of Trpv1

Western diet (WD) intake increases morbidity of obesity, diabetes, and salt sensitive hypertension albeit mechanisms are largely unknown. We tested the hypothesis that the transient receptor potential vanilloid type 1 (TRPV1) channels are activated during WD intake to protect against salt-induced increases in blood pressure possibly via enhancing natriuresis. Wild-type (WT, C57BL/6) or gene-targeted TRPV1-null mutant (TRPV1 -/- ) mice were fed a normal (CON) or Western (WD) diet for 16-18 weeks. Mean arterial pressure (MAP), determined by radiotelemetry after acute sodium loading (NS, 0.9% NaCl) or vehicle (C) by gavage with or without treatment with Nω-nitro-l-arginine methyl ester ( L - NAME, 10mg/kg, ip. ) or a TRPV1 agonist, N-oleoyldopamine ( OLDA, 0.1mg/kg, ip ), was not different between two strains fed a CON diet. WT or TRPV1-/- mice fed a WD diet had increased MAP after NS, with a greater magnitude in TRPV1-/- mice (p&lt;0.05). OLDA decreased while L-NAME increased MAP in WT-WD-NS but not TRPV1-/-WD-NS mice (p&lt;0.05). The urinary nitrates plus nitrites excretion (UNOx, umol*4h urine/kg BW), an indicator of renal nitric oxide (NO) production, was increased in both strains fed a CON diet after NS (p&lt;0.05). OLDA further increased while L-NAME prevented NS-induced increases in UNOx in WT-CON-NS only or in both strains, respectively. TRPV1 ablation with WD intake decreased UNOx levels before NS and abolished NS-induced increment in UNOx (WT-WD-C: 0.3 ±0.06 vs. TRPV1-/-WD-C: 0.2 ±0.05; and WT-WD-NS: 0.7 ±0.1 vs. TRPV1-/-WD-NS: 0.3 ±0.1; p&lt;0.05). OLDA further increased while L-NAME prevented NS-induced increment in UNOx in WT-WD-NS mice only (p&lt;0.05). Urinary sodium excretion was increased in both strains fed a CON diet after NS (p&lt;0.05), which was unaffected by OLDA or L-NAME. UNa was increased in WT-WD-NS but not TRPV1-/-WD-NS after NS. OLDA further increased while L-NAME prevented NS-induced increases in UNa in WT-WD-NS only. Thus, TRPV1 ablation increases salt sensitivity during WD intake possibly via impaired NS-induced renal NO production and sodium excretion. Activation of TRPV1 with OLDA enhances renal NO production and sodium excretion, resulting in prevention of increased salt sensitivity during WD intake.

Role of iNOS and eNOS expression in a group of Egyptian diabetic and nondiabetic nephropathy patients

Abstract Introduction and aim Changes in renal nitric oxide (NO) production have been associated with glomerular hyperfiltration, vascular permeability, albuminuria, glomerulosclerosis, and tubulointerstitial fibrosis. This study aimed at detection of the role of both inducible nitric oxide synthases (iNOS) and endothelial nitric oxide synthases (eNOS) expression in diabetic and nondiabetic nephropathy patients. Methodology Renal biopsies and clinical data of 30 diabetic patients, 10 nondiabetic patients with renal impairment, and 10 control individuals were assessed for eNOS and iNOS expression. Results Both glomerular eNOS and iNOS expression levels were increased in diabetic nephropathy patients and this was associated with peripheral arterial occlusive disease. In nondiabetic patients, increased serum creatinine was found to be associated with increased iNOS and eNOS expression, and, together with the control group, they showed increased iNOS expression in tubular and interstitial cells. An association between cigarette smoking and increased expression of both iNOS and eNOS was detected in diabetic patients. Conclusion The presence of iNOS is associated with tubular damage resulting in renal failure. The upregulation of NO in diabetes mellitus type 2 may explain the endothelial dysfunction that is associated with almost all diabetic complications.

Ghrelin counteracts salt-induced hypertension via promoting diuresis and renal nitric oxide production in Dahl rats

Ghrelin is the endogenous ligand for the growth hormone-secretagogue receptor expressed in various tissues including the heart, blood vessels and kidney. This study sought to determine the effects of long-term treatment with ghrelin (10 nmol/kg, twice a day, intraperitoneally) on the hypertension induced by high salt (8.0% NaCl) diet in Dahl salt-sensitive hypertensive (DS) rats. Systolic blood pressure (SBP) was measured by a tail cuff method. During the treatment period for 3 weeks, high salt diet increased blood pressure compared to normal salt (0.3% NaCl) diet, and this hypertension was partly but significantly (P<0.01) attenuated by simultaneous treatment with ghrelin. Ghrelin significantly increased urine volume and tended to increase urine Na⁺ excretion. Furthermore, ghrelin increased urine nitric oxide (NO) excretion and tended to increase renal neuronal nitric oxide synthase (nNOS) mRNA expression. Ghrelin did not alter the plasma angiotensin II level and renin activity, nor urine catecholamine levels. Furthermore, ghrelin prevented the high salt-induced increases in heart thickness and plasma ANP mRNA expression. These results demonstrate that long-term ghrelin treatment counteracts salt-induced hypertension in DS rats primarily through diuretic action associated with increased renal NO production, thereby exerting cardio-protective effects.

Sexual Dimorphism in Development of Kidney Damage in Aging Fischer-344 Rats

Aging kidneys exhibit slowly developing injury and women are usually protected compared with men, in association with maintained renal nitric oxide. Our purpose was to test 2 hypotheses: (1) that aging intact Fischer-344 (F344) female rats exhibit less glomerular damage than similarly aged males, and (2) that loss of female ovarian hormones would lead to greater structural injury and dysregulation of the nitric oxide synthase (NOS) system in aging F344 rat kidneys. We compared renal injury in F344 rats in intact, ovariectomized, and ovariectomized with estrogen replaced young (6 month) and old (24 month) female rats with young and old intact male rats and measured renal protein abundance of NOS isoforms and oxidative stress. There was no difference in age-dependent glomerular damage between young or old intact male and female F344 rats, and neither ovariectomy nor estrogen replacement affected renal injury; however, tubulointerstitial injury was greater in old males than in old females. These data suggest that ovarian hormones do not influence these aspects of kidney aging in F344 rats and that the greater tubulointerstitial injury is caused by male sex. Old males had greater kidney cortex NOS3 abundance than females, and NOS1 abundance (alpha and beta isoforms) was increased in old males compared with both young males and old females. NOS abundance was preserved with age in intact females, ovariectomy did not reduce NOS1 or NOS3 protein abundance, and estrogen replacement did not uniformly elevate NOS proteins, suggesting that estrogens are not primary regulators of renal NOS abundance in this strain. Nicotinamide adenine dinucleotide phosphate oxidase-dependent superoxide production and nitrotyrosine immunoreactivity were increased in aging male rat kidneys compared with females, which could compromise renal nitric oxide production and/or bioavailability. The kidney damage expressed in aging F344 rats is fairly mild and is not related to loss of renal cortex NOS3 or NOS1 alpha.

Salt sensitivity of nitric oxide generation and blood pressure in mice with targeted knockout of the insulin receptor from the renal tubule

To elucidate the role of the insulin receptor (IR) on kidney nitric oxide generation and blood pressure (BP) control, we generated mice with targeted deletion of renal tubule IR using loxP recombination driven by a Ksp-cadherin promoter. Male knockout (KO) and wild-type (WT) littermates (~4 mo old) were transitioned through three 1-wk treatments: 1) low-NaCl diet (0.085%); 2) high-NaCl diet (HS; 5%); and 3) HS diet plus 3 mM tempol, a superoxide dismutase mimetic, in the drinking water. Mice were then switched to medium-NaCl (0.5%) diet for 5 days and kidneys harvested under pentobarbital anesthesia. Twenty-four-hour urinary nitrates plus nitrites were significantly higher in the WT mice under HS (2,067 ± 280 vs. 1,550 ± 230 nmol/day in WT and KO, respectively, P < 0.05). Tempol attenuated genotype differences in urinary nitrates plus nitrites. A rise in BP with HS was observed only in KO mice and not affected by tempol (mean arterial pressure, dark period, HS, 106 ± 5 vs. 119 ± 4 mmHg, for WT and KO, respectively, P < 0.05). Renal outer medullary protein levels of nitric oxide synthase (NOS) isoforms by Western blot (NOS1-3 and phosphorylated-S1177-NOS3) revealed significantly lower band density for NOS1 (130-kDa isoform) in the KO mice. A second study, when mice were euthanized under HS conditions, confirmed significantly lower NOS1 (130 kDa) in the KO, with an even more substantial (>50%) reduction of the 160-kDa NOS1 isoform. These studies suggest that the loss of renal IR signaling impairs renal nitric oxide production. This may be important in BP control, especially in insulin-resistant states, such as the metabolic syndrome.

Effects of hypercholesterolemia on contrast media-induced nephrotoxicity in rats

To explore the effects of short- and long-term dietary hypercholesterolemia on contrast media-induced nephrotoxicity in rats. The male Wistar rats were fed either a normal rodent diet or a high cholesterol diet. At the end of 2 and 8 weeks, 8 rats from each group received a tail vein injection of either Iohexol injection (groups NC and HC) or vehicle (groups N and H). Blood lipid, renal function, renal hemodynamics, renal and urinary prostaglandin E2 (PGE2) and thromboxane B2 (TXB2), renal nitric oxide and malondialdehyde (MDA) were determined at Day 1 following the administration of contrast media. The dosing of contrast media induced obviously increased serum creatinine compared with normal rats ((185 ± 28) vs (53 ± 3) µmol/L, P < 0.01) and severe renal tubular necrosis in rats with a high cholesterol diet for 8 weeks but did not in normal-diet rats or rats with a high cholesterol diet for 2 weeks. The renal and urinary levels of PGE2 and TXB2 increased significantly in rats of groups H and HC at the end of 8 weeks. The renal production of nitric oxide decreased while the concentration of MDA increased markedly in groups HC and H at the end of 8 weeks. Long-term hypercholesterolemia appears to be a risk factor of contrast media-induced acute renal failure. And it may be associated with the disorder of intrarenal prostaglandins and the abnormality of renal nitric oxide system as induced by lipid peroxidation.

Protection of curcumin against fructose-induced hyperuricaemia and renal endothelial dysfunction involves NO-mediated JAK–STAT signalling in rats

Increasing evidence has demonstrated that excess fructose consumption as a risk factor for metabolic syndrome causes hyperuricaemia and renal injury. Curcumin, a natural plant phenolic food additive, lowered serum urate, creatinine and blood urea nitrogen levels, and increased urinary urate and nitrate/nitrites levels, as well as renal nitric oxide (NO) production in fructose-fed rats. Moreover, curcumin regulated urate transport-related proteins and inhibited activation of the JAK2-STAT3 cascade and overexpression of SOCS3 and TGF-β1 in the kidneys of fructose-fed rats. These results suggested that the anti-hyperuricaemic and renal protective actions of curcumin might be the result of renal NO-mediated JAK2-STAT3 signalling and TGF-β1 normality, which ameliorated renal endothelial dysfunction to improve renal urate transporter system in this model. The present study may provide the evidence for the potential use of a functional food ingredient curcumin because of its action against hyperuricaemia and renal injury induced by high fructose intake.

Effects of Short- and Long-Term Hypercholesterolemia on Contrast-Induced Acute Kidney Injury

Background: Whether hypercholesterolemia is a risk factor for contrast-induced acute kidney injury (CI-AKI) remains unclear. In the present study, the effects of short- and long-term dietary hypercholesterolemia on contrast media-induced nephrotoxicity were evaluated. Methods: Rats were fed either a normal rodent diet (N) or high-cholesterol diet (H). At the end of 2 and 8 weeks, 8 rats from each diet group were given a tail vein injection of either iohexol (group NC and group HC) or vehicle (group N and group H). Blood lipids, renal function and renal hemodynamics were evaluated 1 day after contrast media administration. Renal and urinary prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) were detected by radioimmunoassay. Renal nitric oxide and malondialdehyde (MDA) were measured by the Griess reaction and thiobarbituric acid method, respectively. Results: Contrast media administration increased serum creatinine levels and induced severe renal tubular necrosis in rats fed the high-cholesterol diet for 8 weeks but not in rats fed the normal diet or high-cholesterol diet for 2 weeks. The renal and urinary PGE₂ and TXB₂ levels increased significantly in rats in group H and group HC at the end of 8 weeks. Renal nitric oxide production decreased, and MDA levels increased markedly in group HC and group H at the end of 8 weeks. Conclusions: We conclude that long-term hypercholesterolemia appeared to be a risk factor for CI-AKI, which might be associated with disorders in intrarenal prostaglandins and abnormalities in renal nitric oxide system induced by lipid peroxidation.