Sodium thiosulfate, a reversible oxidation product of hydrogen sulfide, has vasodilating and anti-oxidative properties, making it an attractive agent to alleviate damaging effects of hypertension. In experimental settings, inhibition of nitric oxide synthase causes hypertension, renal dysfunction and damage. We hypothesized that thiosulfate would attenuate renal injury and improve renal function, hemodynamics and the efficiency of oxygen utilization for sodium reabsorption in hypertensive renal disease. Additionally, thiosulfate co-administration would further improve these variables when compared to inhibiting the renin-angiotensin system alone. Nitric oxide synthase was inhibited in Sprague Dawley rats by administering N-ω-nitro-L-arginine (L-NNA) in the food for three weeks. After one week, rats were split into two groups; without and with thiosulfate in the drinking water. In a parallel study, rats given N-ω-nitro-L-arginine and the angiotensin converting enzyme inhibitor lisinopril at a relatively low dose in their food were divided into two groups; without and with thiosulfate in the drinking water. Treatment with thiosulfate alleviated hypertension (mean 190 vs. 229 mmHg), lowered plasma urea (mean 11.3 vs. 20.0 mmol/L) and improved the terminal glomerular filtration rate (mean 503 vs. 260 μl/min/100 gbw), effective renal plasma flow (mean 919 vs. 514 μl/min/100 gbw) and oxygen utilization for sodium reabsorption (mean 14.3 vs. 8.6 μmol/μmol). Combining thiosulfate with lisinopril further lowered renal vascular resistance (mean 43 vs. 63 mmHg/ml/min/100 gbw) and prevented glomerulosclerosis. Thus, our results suggest that thiosulfate has therapeutic potential in hypertensive renal disease and might be of value when added to standard antihypertensive therapies.

Activation of the renin-angiotensin system may initiate chronic kidney disease. We hypothesised that renal hypoxia is a consequence of hemodynamic changes induced by angiotensin II and occurs prior to development of severe renal damage. Male Sprague-Dawley rats were infused continuously with angiotensin II (350 ng/kg/min) for 8 days. Mean arterial pressure (n = 5), cortical (n = 6) and medullary (n = 7) oxygenation (pO2) were continuously recorded by telemetry and renal tissue injury was scored. Angiotensin II increased arterial pressure gradually to 150 ± 18 mmHg. This was associated with transient reduction of oxygen levels in renal cortex (by 18 ± 2%) and medulla (by 17 ± 6%) at 10 ± 2 and 6 ± 1 hours, respectively after starting infusion. Thereafter oxygen levels normalised to pre-infusion levels and were maintained during the remainder of the infusion period. In rats receiving angiotensin II, adding losartan to drinking water (300 mg/L) only induced transient increase in renal oxygenation, despite normalisation of arterial pressure. In rats, renal hypoxia is only a transient phenomenon during initiation of angiotensin II-induced hypertension.

The pathological condition of chronic kidney disease may not be adequately recapitulated in immunocompromised mice due to the lack of T-cells, which are important for the development of hypertension and renal injury. We studied the role of the immune system in relation to salt-sensitive hypertension and renal injury in mice with subtotal nephrectomy (SNX).

Our understanding of the mechanisms underlying the role of hypoxia in the initiation and progression of renal disease remains rudimentary. We have developed a method that allows wireless measurement of renal tissue oxygen tension in unrestrained rats. This method provides stable and continuous measurements of cortical tissue oxygen tension (PO2) for more than 2 weeks and can reproducibly detect acute changes in cortical oxygenation. Exogenous angiotensin-II reduced renal cortical tissue PO2 more than equi-pressor doses of phenylephrine, probably because it reduced renal oxygen delivery more than did phenylephrine. Activation of the endogenous renin-angiotensin system in transgenic Cyp1a1Ren2 rats reduced cortical tissue PO2; in this model renal hypoxia precedes the development of structural pathology and can be reversed acutely by an angiotensin-II receptor type 1 antagonist. Angiotensin-II promotes renal hypoxia, which may in turn contribute to its pathological effects during development of chronic kidney disease.

Background Renal hypoxia, implicated as crucial factor in onset and progression of chronic kidney disease, may be attributed to reduced nitric oxide because nitric oxide dilates vasculature and inhibits mitochondrial oxygen consumption. We hypothesized that chronic nitric oxide synthase inhibition would induce renal hypoxia. Methods and Results Oxygen-sensitive electrodes, attached to telemeters, were implanted in either renal cortex (n=6) or medulla (n=7) in rats. After recovery and stabilization, baseline oxygenation ( pO 2) was recorded for 1 week. To inhibit nitric oxide synthase, N-ω-nitro-l-arginine (L-NNA; 40 mg/kg/day) was administered via drinking water for 2 weeks. A separate group (n=8), instrumented with blood pressure telemeters, followed the same protocol. L-NNA rapidly induced hypertension (165±6 versus 108±3 mm Hg; P<0.001) and proteinuria (79±12 versus 17±2 mg/day; P<0.001). Cortical pO 2, after initially dipping, returned to baseline and then increased. Medullary pO 2 decreased progressively (up to -19±6% versus baseline; P<0.05). After 14 days of L-NNA, amplitude of diurnal medullary pO 2 was decreased (3.7 [2.2-5.3] versus 7.9 [7.5-8.4]; P<0.01), whereas amplitudes of blood pressure and cortical pO 2 were unaltered. Terminal glomerular filtration rate (1374±74 versus 2098±122 μL/min), renal blood flow (5014±336 versus 9966±905 μL/min), and sodium reabsorption efficiency (13.0±0.8 versus 22.8±1.7 μmol/μmol) decreased (all P<0.001). Conclusions For the first time, we show temporal development of renal cortical and medullary oxygenation during chronic nitric oxide synthase inhibition in unrestrained conscious rats. Whereas cortical pO 2 shows transient changes, medullary pO 2 decreased progressively. Chronic L-NNA leads to decreased renal perfusion and sodium reabsorption efficiency, resulting in progressive medullary hypoxia, suggesting that juxtamedullary nephrons are potentially vulnerable to prolonged nitric oxide depletion.

A large animal model of (end-stage) kidney disease (ESKD) is needed for the preclinical testing of novel renal replacement therapies. This study aimed to create stable uremia via subtotal renal artery embolization in goats and induce a temporary further decline in kidney function by administration of gentamicin. Renal artery embolization was performed in five Dutch white goats by infusing polyvinyl alcohol particles in branches of the renal artery, aiming for the embolization of ~80% of one kidney and complete embolization of the contralateral kidney. Gentamicin was administered to temporarily further increase the plasma concentrations of uremic toxins. After initial acute kidney injury, urea and creatinine plasma concentrations stabilized 1.5 ± 0.7 months post-embolization and remained elevated (12 ± 1.4 vs. 5.6 ± 0.8 mmol/L and 174 ± 45 vs. 65 ± 5.6 µmol/L, resp.) during follow-up (16 ± 6 months). Gentamicin induced temporary acute-on-chronic kidney injury with a variable increase in plasma concentrations of small solutes (urea 29 ± 15 mmol/L, creatinine 841 ± 584 µmol/L, phosphate 2.2 ± 0.3 mmol/L and potassium 5.0 ± 0.6 mmol/L) and protein-bound uremic toxins representative of patients with ESKD. A uremic goat model characterized by stable moderate uremia was established via subtotal renal artery embolization with the induction of temporary severe acute-on-chronic kidney injury by the administration of gentamicin, allowing preclinical in vivo validation of novel renal replacement technologies.

The aging kidney exhibits a progressive decline in glomerular filtration rate, accompanied by inflammatory and oxidative damage. We hypothesized that accelerated, age-related progression of renal injury is ovarian hormones-dependant. To address this we used an established model of developmentally programmed accelerated renal aging in the rat, superimposed by ovariectomy to assess interactions between ovarian hormones and the aging process. Under our experimental conditions, we found that kidney function worsens with age, that is GFR reduces over 18 month analyzed time-course and this was worsened by fetal exposure to maternal low-protein diet and absence of estrogen. Reduction in GFR was followed by increases in albuminuria, proteinuria, inflammatory markers, and tissue carbonyls, all suggesting inflammatory response and oxidative stress. This was associated with changes in AGTR2 expression which was greater at 18 months of age compared to earlier time points, but in MLP offspring only. Our studies show an influence of ovarian hormones on programmed accelerated renal aging and the AGTR2 across the lifespan. The main findings are that ovariectomy is a risk factor for increased aging-related renal injury and that this and oxidative damage might be related to changes in AGTR2 expression.

Nitric oxide (NO) is known to depress ribosome biogenesis in vitro. In this study we analyzed the influence of exogenous NO on ribosome biogenesis in vivo using a proven antihypertensive model of perinatal NO administration in genetically hypertensive rats. Fawn-hooded hypertensive rat (FHH) dams were supplied with the NO-donor molsidomine in drinking water from 2 weeks before to 4 weeks after birth, and the kidneys were subsequently collected from 2 day, 2 week, and 9 to 10-month-old adult offspring. Although the NO-donor increased maternal NO metabolite excretion, the NO status of juvenile renal (and liver) tissue was unchanged as assayed by EPR spectroscopy of NO trapped with iron-dithiocarbamate complexes. Nevertheless, microarray analysis revealed marked differential up-regulation of renal ribosomal protein genes at 2 days and down-regulation at 2 weeks and in adult males. Such differential regulation of renal ribosomal protein genes was not observed in females. These changes were confirmed in males at 2 weeks by expression analysis of renal ribosomal protein L36a and by polysome profiling, which also revealed a down-regulation of ribosomes in females at that age. However, renal polysome profiles returned to normal in adults after early exposure to molsidomine. No direct effects of molsidomine were observed on cellular proliferation in kidneys at any age, and the changes induced by molsidomine in renal polysome profiles at 2 weeks were absent in the livers of the same rats. Our results suggest that the previously found prolonged antihypertensive effects of perinatal NO administration may be due to epigenetically programmed alterations in renal ribosome biogenesis during a critical fetal period of renal development, and provide a salient example of a drug-induced reduction of ribosome biogenesis that is accompanied by a beneficial long-term health effect in both males and females.

ACE inhibitor (ACE-I) treatment effectively inhibits proteinuria and ameliorates the course of various renal diseases. In experimental glomerulonephritis, however, angiotensin II (AngII) infusion has also been shown to be renoprotective. We evaluated the long-term (28 days) course of anti-Thy1 glomerulonephritis in animals with suppressed AngII formation by ACE-I treatment.

Treating spontaneously hypertensive rats (SHR) with L-arginine, taurine, and vitamins C and E (ATCE) during nephrogenesis (2 weeks before to 4 weeks after birth) persistently lowers blood pressure. Hypothetically, differential gene expression in kidney of SHR vs. normotensive Wistar-Kyoto rats (WKY) is partially corrected by maternal ATCE in SHR. Differential gene expression in 2-days, 2-weeks, and 48-week-old rats was studied using oligonucleotide chips. Transcription factor binding sites (TFBS) of differentially expressed genes were analyzed in silico. Differential gene expression varied between SHR+ATCE and SHR, suggesting both direct and indirect effects; but, few genes were modulated toward WKY level and there was little overlap between ages. TFBS analysis suggests less Elk-1-driven gene transcription in both WKY and SHR+ATCE vs. SHR at 2 days and 2 weeks. Concluding, in SHR, persistent antihypertensive effects of maternal ATCE are not primarily due to persistent corrective transcription. Less Elk-1-driven transcription at 2 days and 2 weeks may be involved.

Combined heart and renal failure is associated with high cardiovascular morbidity and mortality. Anti-oxidant and anti-inflammatory, non-hematopoietic effects of erythropoietin (EPO) treatment have been proposed. Monocytes may act as biosensors of the systemic environment. We hypothesized that monocyte transcriptomes of patients with cardiorenal syndrome (CRS) reflect the pathophysiology of the CRS and respond to short-term EPO treatment at a recommended dose for treatment of renal anemia.

Healthy bone marrow cell (BMC) infusion improves renal function and limits renal injury in a model of chronic kidney disease (CKD) in rats. However, BMCs derived from rats with CKD fail to retain beneficial effects, demonstrating limited therapeutic efficacy. Statins have been reported to improve cellular repair mechanisms.

This study aimed to investigate the acute renal effects of the glucagon-like peptide-1 receptor agonist (GLP-1RA) exenatide in type 2 diabetes patients.

To determine the effect of the dipeptidyl peptidase-4 inhibitor linagliptin on postprandial glomerular hyperfiltration compared with the sulphonylurea glimepiride in adults with type 2 diabetes (T2D).

Cell-based therapy is a promising strategy for treating chronic kidney disease (CKD) and is currently the focus of preclinical studies. We performed a systematic review and meta-analysis to evaluate the efficacy of cell-based therapy in preclinical (animal) studies of CKD, and determined factors affecting cell-based therapy efficacy in order to guide future clinical trials. In total, 71 articles met the inclusion criteria. Standardised mean differences (SMD) and 95% confidence intervals (CI) were calculated for outcome parameters including plasma urea, plasma creatinine, urinary protein, blood pressure, glomerular filtration rate, glomerulosclerosis and interstitial fibrosis. Sub-analysis for each outcome measure was performed for model-related factors (species, gender, model and timing of therapy) and cell-related factors (cell type, condition and origin, administration route and regime of therapy). Overall, meta-analysis showed that cell-based therapy reduced the development and progression of CKD. This was most prominent for urinary protein (SMD, 1.34; 95% CI, 1.00-1.68) and urea (1.09; 0.66-1.51), both P<0.001. Changes in plasma urea were associated with changes in both glomerulosclerosis and interstitial fibrosis. Sub-analysis showed that cell type (bone-marrow-derived progenitors and mesenchymal stromal cells being most effective) and administration route (intravenous or renal artery injection) were significant predictors of therapeutic efficacy. The timing of therapy in relation to clinical manifestation of disease, and cell origin and dose, were not associated with efficacy. Our meta-analysis confirms that cell-based therapies improve impaired renal function and morphology in preclinical models of CKD. Our analyses can be used to optimise experimental interventions and thus support both improved preclinical research and development of cell-based therapeutic interventions in a clinical setting.

Kidney transplantation (Tx) is considered the only definite treatment for end-stage kidney disease (ESKD) patients. The increasing prevalence of ESKD has necessitated the introduction of transplantation with kidneys from suboptimal donors. There is, however, still a lack of fundamental and longitudinal research on suboptimal kidney transplants. Specifically, there is a demand for accurate pre-Tx predictors of donor kidney function and injury to predict post-Tx outcome. In the present study, we combine rat models of chronic kidney disease (CKD) and renal Tx to dissect the effects of healthy and CKD renal grafts on healthy and CKD recipients. We show that renal function at 6 weeks post-Tx is exclusively determined by donor graft quality. Using cell tracking within enhanced green fluorescent protein-positive (eGFP+) recipients, we furthermore show that most inflammatory cells within the donor kidney originate from the donor. Oxidative and vascular extra-renal damage were, in contrast, determined by the recipient. Post- versus pre-Tx evaluation of grafts showed an increase in glomerular and peritubular capillary rarefaction in healthy but not CKD grafts within a CKD environment. Proliferation of glomerular endothelium was similar in all groups, and influx of eGFP+ recipient-derived cells occurred irrespective of graft or recipient status. Glomerular and peritubular capillary rarefaction, severity of inflammation and macrophage subtype data post-Tx were, however, determined by more complicated effects, warranting further study. Our experimental model could help to further distinguish graft from recipient environment effects, leading to new strategies to improve graft survival of suboptimal Tx kidneys.This article has an associated First Person interview with the first author of the paper.

While the presence of oxidative stress in chronic kidney disease (CKD) is well established, its relation to hypertensive renal hemodynamics remains unclear. We hypothesized that once CKD is established blood pressure and renal vascular resistance (RVR) no longer depend on reactive oxygen species. CKD was induced by bilateral ablation of 2/3 of each kidney. Compared to age-matched, sham-operated controls all ablated rats showed proteinuria, decreased glomerular filtration rate (GFR), more renal damage, higher mean arterial pressure (MAP), RVR and excretion of oxidative stress markers and hydrogen peroxide, while excretion of stable nitric oxide (NO) metabolites tended to decrease. We compared MAP, RVR, GFR and fractional excretion of sodium under baseline and during acute Tempol, PEG-catalase or vehicle infusion in rats with established CKD vs. controls. Tempol caused marked reduction in MAP in controls (96±5 vs.79±4 mmHg, P<0.05) but not in CKD (130±5 vs. 127±6 mmHg). PEG-catalase reduced MAP in both groups (controls: 102±2 vs. 94±4 mmHg, P<0.05; CKD: 118±4 vs. 110±4 mmHg, P<0.05), but did not normalize MAP in CKD rats. Tempol and PEG-catalase slightly decreased RVR in both groups. Fractional excretion of sodium was increased by both Tempol and PEG-catalase in both groups. PEG-catalase decreased TBARS excretion in both groups. In sum, although oxidative stress markers were increased, MAP and RVR did not depend more on oxidative stress in CKD than in controls. Therefore reactive oxygen species appear not to be important direct determinants of hypertensive renal hemodynamics in this model of established CKD.

Previously, we demonstrated increased Angiotensin II type I receptor expression in leukocytes from patients with untreated, but not in treated, essential hypertension (essential hypertension). We hypothesized that the Angiotensin II AT1 receptor is also increased in leukocytes from patients with chronic kidney disease, however and can still be corrected with combined anti-hypertensive treatment with renin-angiotensin system (RAS) blockers and statins. Blood pressure, cholesterol, renal function oxidative stress parameters, inflammation, and leukocyte Angiotensin II AT1 receptor mRNA expression were measured both on and (6 weeks) off treatment. Data were compared to data of 10 healthy control subjects. Untreated chronic kidney disease patients (n=20) had higher blood pressure, cholesterol and leukocyte Angiotensin II AT1 receptor mRNA expression, but no different ox-LDL, thiobarbituric acid reactive substances, paraoxonase activity or hs-CRP. OxLDL and Lipoprotein(a) were increased in untreated chronic kidney disease. Angiotensin II AT1 receptor expression inversely correlated with renal function (R(2)=0.15, P<0.03) and Lipoprotein(a) but not with the other parameters. Treatment with RAS blockers and statins normalized blood pressure and cholesterol, however it did not correct enhanced leukocyte Angiotensin II AT1 receptor expression. Leukocyte Angiotensin II AT1 receptor expression is inappropriately high in chronic kidney disease, correlates inversely with renal function and does not depend on antihypertensive and lipid-lowering treatment. The uremic environment seems to dominate over previously reported actions of high blood pressure and cholesterol to enhance leukocyte Angiotensin II AT1 receptor expression.

Cardiorenal syndrome type 2 is characterized by kidney failure as a consequence of heart failure that affects >50% of heart failure patients. Murine transverse aortic constriction (TAC) is a heart failure model, where pressure overload is induced on the heart without any systemic hypertension or its consequences. Whether renal function is altered in this model is debated, and if so, at which time post-TAC renal dysfunction starts to contribute to worsening of cardiac function. We therefore studied the effects of progressive heart failure development on kidney function in the absence of chronically elevated systemic blood pressure and renal perfusion pressure. C57BL/6J mice (N = 129) were exposed to TAC using a minimally invasive technique and followed from 3 to 70 days post-TAC. Cardiac function was determined with 3D ultrasound and showed a gradual decrease in stroke volume over time. Renal renin expression and plasma renin concentration increased with progressive heart failure, suggesting hypoperfusion of the kidney. In addition, plasma urea concentration, a surrogate marker for renal dysfunction, was increased post-TAC. However, no structural abnormalities in the kidney, nor albuminuria were present at any time-point post-TAC. Progressive heart failure is associated with increased renin expression, but only mildly affected renal function without inducing structural injury. In combination, these data suggest that heart failure alone does not contribute to kidney dysfunction in mice.

With increasing interest in home dialysis, there is a need for a translational uremic large animal model to evaluate technical innovations in peritoneal dialysis (PD). To this end, we developed a porcine model with kidney failure. Stable chronic kidney injury was induced by bilateral subtotal renal artery embolization. Before applying PD, temporary aggravation of uremia was induced by administration of gentamicin (10 mg/kg i.v. twice daily for 7 days), to obtain uremic solute levels within the range of those of dialysis patients. Peritoneal transport was assessed using a standard peritoneal permeability assessment (SPA). After embolization, urea and creatinine concentrations transiently increased from 1.6 ± 0.3 to 7.5 ± 1.2 mM and from 103 ± 14 to 338 ± 67 µM, respectively, followed by stabilization within 1-2 weeks to 2.5 ± 1.1 mM and 174 ± 28 µM, respectively. Gentamicin induced temporary acute-on-chronic kidney injury with peak urea and creatinine concentrations of 16.7 ± 5.3 mM and 932 ± 470 µM respectively. PD was successfully applied, although frequently complicated by peritonitis. SPA showed a low transport status (D/P creatinine at 4 h of 0.41 (0.36-0.53)) with a mass transfer area coefficient of 9.6 ± 3.1, 4.6 ± 2.6, 3.4 ± 2.3 mL/min for urea, creatinine, and phosphate respectively. In conclusion, this porcine model with on-demand aggravation of uremia is suitable for PD albeit with peritoneal transport characterized by a low transport status.