Effect of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility on uric acid metabolism and urinary neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in rats with hyperuricemia.

OBJECTIVE: To explore the effects of Rhizoma Polygoni Cuspidati and Ramulus Cinnamomi compatibility (PR) on uric acid metabolism and the expression of urinary neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) in rats with hyperuricemia. METHODS: Seventy male Sprague Dawley (SD) rats were randomly divided into 7 groups with 10 rats per group, including the normal group, model group, allopurinol group, benzbromarone group and PR groups at 3 doses (3.5, 7, 14 g/kg). Except the normal group, rats of the other groups were intragastrically administered 100 mg/kg hypoxanthine and 250 mg/kg ethambutol, and subcutaneously injected with 200 mg/kg potassium oxonate. All rats were continuously modeled for 17 days, and gavaged with corresponding drugs. The rats of the normal and model groups were gavaged with saline, once a day, for 2 weeks. The levels of serum uric acid (SUA), blood urea nitrogen (BUN) and creatinine (Cr) were determined. In addition, the contents of NGAL and KIM-1 in urine and the mRNA and protein expressions of xanthine oxidase (XOD) in liver of hyperuricemia rats were measured by reverse transcription polymerase chain reaction (RT-PCR) and Western blot, respectively. Moreover, the pathological changes of kidney were analyzed by hematoxylin and eosin (HE) stain method. RESULTS: Compared with the normal group, the levels of SUA, BUN, NGAL and KIM-1 and the expressions of hepatic XOD mRNA and protein in the hyperuricemia rats were increased signifificantly (P<0.01). PR signifificantly decreased the levels of SUA, BUN, NGAL and KIM-1 and down-regulated the mRNA and protein expressions of hepatic XOD (P<0.05 or P<0.01). In addition, the pathological changes of kidney were signifificantly suppressed by oral administration of PR. CONCLUSIONS: PR ameliorated uric acid metabolism and protected renal function, the underlying mechanism was mediated by decreasing the levels of SUA, BUN, NGAL and KIM-1, inhibiting the expression of hepatic XOD and ameliorating the pathological change of kidney.

Potential renoprotective effects of piceatannol in ameliorating the early-stage nephropathy associated with obesity in obese Zucker rats.

Obesity-associated nephropathy is considered to be a leading cause of end-stage renal disease. Resveratrol supplementation represents a promising therapy to attenuate kidney injury, but the poor solubility and limited bioavailability of this polyphenol limits its use in dietary intervention. Piceatannol, a resveratrol analogue, has been suggested as a better option. In this study, we aimed to provide evidence of a preventive action of piceatannol in very early stages of obesity-associated nephropathy. Thirty obese Zucker rats were divided into three experimental groups: one control and two groups orally treated for 6 weeks with 15 and 45 mg piceatannol/kg body weight/day. Enzyme-linked immunosorbent assays (ELISA) were used to determine renal and urinary kidney injury molecule-1 (Kim-1), renal fibrosis markers (transforming growth factor ß1 and fibronectin) and renal sirtuin-1 protein. Oxidative stress was assessed in the kidney by measuring lipid peroxidation and nitrosative stress (thiobarbituric acid reactive substrates and 3-nitrotyrosine levels, respectively) together with the activity of the antioxidant enzyme superoxide dismutase. Renal fatty acids profile analysis was performed by thin-layer and gas chromatography. Piceatannol-treated rats displayed lower levels of urinary and renal Kim-1. Renal fibrosis biomarkers and lipid peroxidation exhibited a tendency to decrease in the piceatannol-treated groups. Piceatannol treatment did not modify superoxide dismutase activity or sirtuin-1 protein levels, while it seemed to increase the levels of polyunsaturated and omega-6 polyunsaturated fatty acids in the kidneys. Our findings suggest a mild renoprotective effect of piceatannol in obese Zucker rats and the need of intervention at early stages of renal damage.

Effects of valproic acid and dexamethasone administration on early bio-markers and gene expression profile in acute kidney ischemia-reperfusion injury in the rat.

Renal ischemia-reperfusion (IR) causes acute kidney injury (AKI) with high mortality and morbidity. The objective of this investigation was to ameliorate kidney IR injury and identify novel biomarkers for kidney injury and repair. Under general anesthesia, left renal ischemia was induced in Wister rats by occluding renal artery for 45 minutes, followed by reperfusion and right nephrectomy. Thirty minutes prior to ischemia, rats (n = 8/group) received Valproic Acid (150 mg/kg; VPA), Dexamethasone (3 mg/kg; Dex) or Vehicle (saline) intraperitoneally. Animals were sacrificed at 3, 24 or 120 h post-IR. Plasma creatinine (mg/dL) at 24 h was reduced (P<0.05) in VPA (2.7±1.8) and Dex (2.3±1.2) compared to Vehicle (3.8±0.5) group. At 3 h, urine albumin (mg/mL) was higher in Vehicle (1.47±0.10), VPA (0.84±0.62) and Dex (1.04±0.73) compared to naïve (uninjured/untreated control) (0.14±0.26) group. At 24 h post-IR urine lipocalin-2 (µg/mL) was higher (P<0.05) in VPA, Dex and Vehicle groups (9.61-11.36) compared to naïve group (0.67±0.29); also, kidney injury molecule-1 (KIM-1; ng/mL) was higher (P<0.05) in VPA, Dex and Vehicle groups (13.7-18.7) compared to naïve group (1.7±1.9). Histopathology demonstrated reduced (P<0.05) ischemic injury in the renal cortex in VPA (Grade 1.6±1.5) compared to Vehicle (Grade 2.9±1.1). Inflammatory cytokines IL1ß and IL6 were downregulated and anti-apoptotic molecule BCL2 was upregulated in VPA group. Furthermore, kidney DNA microarray demonstrated reduced injury, stress, and apoptosis related gene expression in the VPA administered rats. VPA appears to ameliorate kidney IR injury via reduced inflammatory cytokine, apoptosis/stress related gene expression, and improved regeneration. KIM-1, lipocalin-2 and albumin appear to be promising early urine biomarkers for the diagnosis of AKI.

Evaluation of cadmium-induced nephrotoxicity using urinary metabolomic profiles in sprague-dawley male rats.

The aim of this study was to investigate urinary metabolomic profiles associated with cadmium (Cd)-induced nephrotoxicity and their potential mechanisms. Metabolomic profiles were measured by high-resolution (1)H-nuclear magnetic resonance (NMR) spectroscopy in the urine of rats after oral exposure to CdCl2 (1, 5, or 25 mg/kg) for 6 wk. The spectral data were further analyzed by a multivariate analysis to identify specific urinary metabolites. Urinary excretion levels of protein biomarkers were also measured and CdCl2 accumulated dose-dependently in the kidney. High-dose (25 mg/kg) CdCl2 exposure significantly increased serum blood urea nitrogen (BUN), but serum creatinine (sCr) levels were unchanged. High-dose CdCl2 (25 mg/kg) exposure also significantly elevated protein-based urinary biomarkers including osteopontin, monocyte chemoattractant protein-1 (MCP-1), kidney injury molecules-1 (Kim-1), and selenium-binding protein 1 (SBP1) in rat urine. Under these conditions, six urinary metabolites (citrate, serine, 3-hydroxyisovalerate, 4-hydroxyphenyllactate, dimethylamine, and betaine) were involved in mitochondrial energy metabolism. In addition, a few number of amino acids such as glycine, glutamate, tyrosine, proline, or phenylalanine and carbohydrate (glucose) were altered in urine after CdCl2 exposure. In particular, the metabolites involved in the glutathione biosynthesis pathway, including cysteine, serine, methionine, and glutamate, were markedly decreased compared to the control. Thus, these metabolites are potential biomarkers for detection of Cd-induced nephrotoxicity. Our results further indicate that redox metabolomics pathways may be associated with Cd-mediated chronic kidney injury. These findings provide a biochemical pathway for better understanding of cellular mechanism underlying Cd-induced renal injury in humans.

Effects of Schizolobium parahyba extract on experimental Bothrops venom-induced acute kidney injury.

BACKGROUND: Venom-induced acute kidney injury (AKI) is a frequent complication of Bothrops snakebite with relevant morbidity and mortality. The aim of this study was to assess the effects of Schizolobium parahyba (SP) extract, a natural medicine with presumed anti-Bothrops venom effects, in an experimental model of Bothrops jararaca venom (BV)-induced AKI. METHODOLOGY: Groups of 8 to 10 rats received infusions of 0.9% saline (control, C), SP 2 mg/kg, BV 0.25 mg/kg and BV immediately followed by SP (treatment, T) in the doses already described. After the respective infusions, animals were assessed for their glomerular filtration rate (GFR, inulin clearance), renal blood flow (RBF, Doppler), blood pressure (BP, intra-arterial transducer), renal vascular resistance (RVR), urinary osmolality (UO, freezing point), urinary neutrophil gelatinase-associated lipocalin (NGAL, enzyme-linked immunosorbent assay [ELISA]), lactate dehydrogenase (LDH, kinetic method), hematocrit (Hct, microhematocrit), fibrinogen (Fi, Klauss modified) and blinded renal histology (acute tubular necrosis score). PRINCIPAL FINDINGS: BV caused significant decreases in GFR, RBF, UO, HcT and Fi; significant increases in RVR, NGAL and LDH; and acute tubular necrosis. SP did not prevent these changes; instead, it caused a significant decrease in GFR when used alone. CONCLUSION: SP administered simultaneously with BV, in an approximate 10∶1 concentration, did not prevent BV-induced AKI, hemolysis and fibrinogen consumption. SP used alone caused a decrease in GFR.

Ligustrazine attenuates elevated levels of indoxyl sulfate, kidney injury molecule-1 and clusterin in rats exposed to cadmium.

In this study, we aimed at evaluating the effect of ligustrazine, a major constituent of Ligusticum wallichii from traditional Chinese medicine, on Cd-induced changes in nephrotoxicity indices. Rats were divided into four experimental groups: control; ligustrazine; Cd and ligustrazine+Cd. Cd treated alone group showed significant decreases (P<0.05) in body weight, renal levels of superoxide dismutase (SOD) and glutathione reductase (GR); and significant increases (P<0.05) in urine volume (24h), pH values, serum blood urea nitrogen (BUN), serum uric acid, kidney malondialdehyde (MDA), urinary total protein, urinary glucose, urinary lactate dehydrogenase (LDH) and urinary alkaline phosphatase (ALP). Apart from indoxyl sulfate (a uremic toxin), two newly accepted nephrotoxicity biomarkers including kidney injury molecule-1 (kim-1) and clusterin were also found to be increased. Nonetheless, all these effects induced by Cd were reversed upon treatment by ligustrazine although it failed in decreasing the concentrations of Cd in kidney and urine. Histopathological studies in Cd-treated rats exhibited renal tubule damage, which was also ameliorated by ligustrazine pretreatment. These results suggest that ligustrazine exhibits protective effects on Cd-induced nephrotoxicity. Additionally, this study also demonstrates Cd exposure induces elevated levels of indoxyl sulfate in serum and kidney, and clusterin in urine.

Astragaloside IV prevents acute kidney injury in two rodent models by inhibiting oxidative stress and apoptosis pathways.

Oxidative stress and apoptosis play key role in the pathogenesis of acute kidney injury (AKI). We hypothesize that Astragaloside IV(AS-IV) prevents AKI through inhibiting oxidative stress and apoptosis. The rats were divided into sham control, saline-,vehicle-, or AS-IV-treated groups. AS-IV (20 mg/kg) was orally administered once daily to the rats for 7 consecutive days before terminating the experiments. In ischemia-induced AKI model, experimental rats were subjected to bilateral clamping of the renal arteries for 45 min, followed by reperfusion for 24 h. In contrast-induced AKI model, iopamidol (2.9 g iodine/kg) was administered intravenously into the rats. Renal function, histopathology, oxidative stress and apoptosis were evaluated in these models. Pretreatment with AS-IV significantly decreased blood urea nitrogen, serum creatinine, cystatin C and neutrophil gelatinase-associated lipocalin levels, as well as urinary kidney injury molecule-1 level and tubular injury. AS-IV also reduced oxidative stress and tubular cell apoptosis. The p38 mitogen-activated protein kinase phosphorylation and caspase-3 activity were elevated in kidney tissues from AKI rats, accompanied by an increase in Bax expression and a decrease in Bcl-2 expression at mRNA and protein levels. These changes were prevented by AS-IV pretreatment. Therefore, AS-IV can be developed as a novel therapeutic approach to prevent AKI through targeting inhibition of oxidative stress and apoptosis pathways.

Effects of deferasirox on renal function and renal epithelial cell death.

Iron-chelating therapy results in a significant improvement in the life expectancy of patients with transfusional iron overload. However, alterations of renal function have been observed in some patients undergoing chelation therapy. In the present study we evaluated the effect of treatment with deferasirox iron chelator on the renal function in normal Wistar rats and in mouse and human cultured tubular cell lines. Results indicate that deferasirox given daily via intraperitoneal route for 7 days induced: (1) an increased urinary protein, albumin and glucose excretion, (2) tubular necrosis/apoptosis, (3) and increased tubular damage markers, in spite of normal glomerular function. Moreover, in vitro studies revealed that: (1) mouse MCT cultures resulted more susceptible to the antiproliferative/cytotoxic effect of deferasirox, mainly at 24h after treatment, than human HK-2 cultures, (2) MCT cell content of damage molecules increased after 24h of iron chelator treatment with slight changes in their excretion into the culture medium and (3) MCT cultures showed a significant evidence of apoptotic cell death through an increased expression and activation of caspase-3 and marked DNA fragmentation. In conclusion, this renal side effect of deferasirox-chelating therapy seems to be based on direct toxic effects of deferasirox on renal tubular cells.

Desferrithiocin analogue iron chelators: iron clearing efficiency, tissue distribution, and renal toxicity.

The current solution to iron-mediated damage in transfusional iron overload disorders is decorporation of excess unmanaged metal, chelation therapy. The clinical development of the tridentate chelator deferitrin (1, Table 1) was halted due to nephrotoxicity. It was then shown by replacing the 4'-(HO) of 1 with a 3,6,9-trioxadecyloxy group, the nephrotoxicity could be ameliorated. Further structure-activity relationship studies have established that the length and the position of the polyether backbone controlled: (1) the ligand's iron clearing efficiency (ICE), (2) chelator tissue distribution, (3) biliary ferrokinetics, and (4) tissue iron reduction. The current investigation compares the ICE and tissue distribution of a series of (S)-4,5-dihydro-2-[2-hydroxy-4-(polyether)phenyl]-4-methyl-4-thiazolecarboxylic acids (Table 1, 3-5) and the (S)-4,5-dihydro-2-[2-hydroxy-3-(polyether)phenyl]-4-methyl-4-thiazolecarboxylic acids (Table 1, 8-10). The three most effective polyether analogues, in terms of performance ratio (PR), defined as mean ICE(primate)/ICE(rodent), are 3 (PR 1.1), 8, (PR 1.5), and 9, now in human trials, (PR 2.2). At the onset of the clinical trial on 9, no data were available for ligand 3 or 8. This is unfortunate, as 3 has many advantages over 9, e.g., the ICE of 3 in rats is 2.5-fold greater than that of 9 and analogue 3 achieves very high levels in the liver, pancreas, and heart, the organs most affected by iron overload. Finally, the impact of 3 on the urinary excretion of kidney injury molecule-1 (Kim-1), an early diagnostic biomarker for monitoring acute kidney toxicity, has been carried out in rats; no evidence of nephrotoxicity was found. Overall, the results suggest that 3 would be a far superior clinical candidate to 9.

Kidney injury molecule-1 outperforms traditional biomarkers of kidney injury in preclinical biomarker qualification studies.

Kidney toxicity accounts both for the failure of many drug candidates as well as considerable patient morbidity. Whereas histopathology remains the gold standard for nephrotoxicity in animal systems, serum creatinine (SCr) and blood urea nitrogen (BUN) are the primary options for monitoring kidney dysfunction in humans. The transmembrane tubular protein kidney injury molecule-1 (Kim-1) was previously reported to be markedly induced in response to renal injury. Owing to the poor sensitivity and specificity of SCr and BUN, we used rat toxicology studies to compare the diagnostic performance of urinary Kim-1 to BUN, SCr and urinary N-acetyl-beta-D-glucosaminidase (NAG) as predictors of kidney tubular damage scored by histopathology. Kim-1 outperforms SCr, BUN and urinary NAG in multiple rat models of kidney injury. Urinary Kim-1 measurements may facilitate sensitive, specific and accurate prediction of human nephrotoxicity in preclinical drug screens. This should enable early identification and elimination of compounds that are potentially nephrotoxic.