Renal Acid Research Articles

Adaptive Mechanisms of Renal Bile Acid Transporters in a Rat Model of Carbon Tetrachloride-Induced Liver Cirrhosis.

Background: Acute kidney injury (AKI) is common in advanced liver cirrhosis, a consequence of reduced kidney perfusion due to splanchnic arterial vasodilation and intrarenal vasoconstriction. It clinically manifests as hepatorenal syndrome type 1, type 2, or as acute tubular necrosis. Beyond hemodynamic factors, an additional mechanism may be hypothesized to explain the renal dysfunction during liver cirrhosis. Recent evidence suggest that such mechanisms may be closely related to obstructive jaundice. Methods: Given the not completely elucidated role of bile acids in kidney tissue damage, this study developed a rat model of AKI with liver cirrhosis induction by carbon tetrachloride (CCl4) inhalation for 12 weeks. Histological analyses of renal and liver biopsies were performed at sacrifice. Organic anion tubular transporter distribution and apoptosis in kidney cells were analyzed by immunohistochemistry. Circulating and urinary markers of inflammation and tubular injury were assayed in 21 treated rats over time (1, 2, 4, 8, and 12 weeks of CCl4 administration) and 5 controls. Results: No renal histopathological alterations were found at sacrifice. Comparing treated rats with controls, organic anion transporters were differentially expressed and localized. High serum bile acid values were detected in cirrhotic animals, while caspase-3 staining was negative in both groups. Increased levels of serum inflammatory and urinary tubular injury biomarkers were observed during cirrhosis progression, with a peak after 4 and 8 weeks of treatment. Conclusions: These findings suggest possible adaptive tubular mechanisms for bile acid transporters in response to cirrhosis-induced AKI.

Effects of a novel hepatitis B antiviral drug in renal organic acid transporters

Effects of a novel hepatitis B antiviral drug in renal organic acid transporters

Molecular characterization of Gyps africanus (African white-backed vulture) organic anion transporter 1 and 2 expressed in the kidney.

Gyps species have been previously shown to be highly sensitive to the toxic effects of diclofenac, when present in their food sources as drug residues following use as a veterinary medicine. Vultures exposed to diclofenac soon become depressed and die with signs of severe visceral gout and renal damage on necropsy. The molecular mechanism behind toxicity and renal excretion of uric acid is still poorly understood. With the clinical pictures suggesting renal uric acid excretion as the target site for toxicity, as a first step the following study was undertaken to determine the uric acid excretory pathways present in the African white-backed vulture (Gyps africanus) (AWB), one of the species susceptible to toxicity. Using transcriptome analysis, immunohistochemistry and functional predictions, we demonstrated that AWB makes use of the organic anion transporter 2 (OAT2) for their uric acid excretion. RT-qPCR analysis subsequently demonstrated relatively similar expression of the OAT2 transporter in the vulture and chicken. Lastly docking analysis, predicted that the non-steroidal drugs induce their toxicity through an allosteric binding.

ACUTE KIDNEY INJURY (AKI) PADA KEHAMILAN

Acute Kidney Injury (AKI) in pregnancy remains a cause for fetomaternal morbidity and mortality, particularly in developing countries. Hypertensive complications of pregnancy (preeclampsia/eclampsia, HELLP syndrome) remains the leading cause of AKI in pregnancy. A set of systemic and renal physiological adaptive mechanisms occur during a normal gestation that will cause several changes in laboratory parameters of renal function, electrolytes, fluid and acid – base balance. Diagnosis of AKI in pregnancy is based on the serum creatinine increase and reduction of urine output. Management of AKI in pregnancy requires a multidisciplinary approach between nephrologists and obstetricians for optimizing care for both mother and child. In approaching AKI in pregnant woman, emphasis should be placed on making early and accurate diagnosis to allow prompt intervention and to facilitate recovery from AKI.

Indications of Liver and Kidney Functions in Non-Insulin Dependent Diabetic Patients

This study aimed at the investigation of abnormal liver and renal functions by biochemical manifestations of underlying metabolic abnormalities in relation to hyperglycemia in non-insulin-dependent diabetic patients. The study comprised 118 diabetic patients (56 males, 62 females) and 60 age-matched healthy non-diabetic controls (30 males, 30 females). All subjects were tested for serum levels of liver enzymatic indicators, which include aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP), as well as non enzymatic parameters, including total bilirubin and total proteins.Also, serum levels of renal function markers, including microalbumin, creatinine, urea, and uric acid were measured.
 The findings of this study stated that serum ALT, AST, and ALP levels were significantly higher in diabetic males and females with both age ranges (40-59 & 60-80 years). Serum total bilirubin level showed a significant decrease in diabetic males and females of both age groups. However, total proteins level showed a significant increase in diabetic males and females of both age groups. The results also showed that the level of microalbumin in urine as well as those of creatinine, urea, and uric acid in the serum were significantly higher in diabetic males and females. The present study concludes that there is a bidirectional relationship of enzymatic and non enzymatic liver and renal functions markers with the hyperglycemic status in Type 2 diabetes mellitus.

Role of endoplasmic reticulum stress in renal damage after myocardial infarction.

Myocardial infarction (MI) is associated with renal alterations resulting in poor outcomes in patients with MI. Renal fibrosis is a potent predictor of progression in patients and is often accompanied by inflammation and oxidative stress; however, the mechanisms involved in these alterations are not well established. Endoplasmic reticulum (ER) plays a central role in protein processing and folding. An accumulation of unfolded proteins leads to ER dysfunction, termed ER stress. Since the kidney is the organ with highest protein synthesis fractional rate, we herein investigated the effects of MI on ER stress at renal level, as well as the possible role of ER stress on renal alterations after MI. Patients and MI male Wistar rats showed an increase in the kidney injury marker neutrophil gelatinase-associated lipocalin (NGAL) at circulating level or renal level respectively. Four weeks post-MI rats presented renal fibrosis, oxidative stress and inflammation accompanied by ER stress activation characterized by enhanced immunoglobin binding protein (BiP), protein disulfide-isomerase A6 (PDIA6) and activating transcription factor 6-alpha (ATF6α) protein levels. In renal fibroblasts, palmitic acid (PA; 50-200 µM) and angiotensin II (Ang II; 10-8 to 10-6M) promoted extracellular matrix, superoxide anion production and inflammatory markers up-regulation. The presence of the ER stress inhibitor, 4-phenylbutyric acid (4-PBA; 4 µM), was able to prevent all of these modifications in renal cells. Therefore, the data show that ER stress mediates the deleterious effects of PA and Ang II in renal cells and support the potential role of ER stress on renal alterations associated with MI.

The Association between Urinary Glucose and Renal Uric Acid Excretion in Non-diabetic Patients with Stage 1-2 Chronic Kidney Disease

ABSTRACT Aims: To test the hypothesis that in non-diabetic patients with early-stage chronic kidney disease (CKD), the renal excretion of urate and glucose transportation are coupled and interconnected. Methods: A cross-sectional study of 255 non-diabetic participants with stage 1–2 CKD recruited from our department was conducted. Spearman’s correlation and multiple linear regression analyses were used to study the correlation between urinary glucose and renal uric acid excretion. ANOVA was used to compare urinary uric acid excretion among three tertiles of urinary glucose (UG; UG1: UG<0.24 mmol/24 h/1.73 m2, UG2: 0.24 mmol/24 h/1.73 m2≤ UG≤0.55 mmol/24 h/1.73 m2, and UG3: UG>0.55 mmol/24 h/1.73 m2), the fractional excretion of glucose (FEG; FEG1: FEG<0.04%, FEG2: 0.04%≤FEG≤0.09%, and FEG3: FEG>0.09%) and the excretion of glucose per volume of glomerular filtration (EgGF; EgGF1: EgGF<1.95 μmol/L, EgGF2: 1.95 μmol/L≤ EgGF≤3.99 μmol/L, and EgGF3: EgGF>3.99 μmol/L). Results: According to the multiple linear regression analysis, FEG and EgGF were positively correlated with the excretion of uric acid per volume of glomerular filtration (EurGF) after adjusting for confounding factors. The EurGF levels in the highest tertiles of UG, FEG and EgGF were higher than those in the lowest tertiles of UG, FEG and EgGF. Conclusion: Urinary glucose excretion is closely related to renal excretion of uric acid in non-diabetic patients with stage 1–2 CKD.

Efficacy of different urinary uric acid indicators in patients with chronic kidney disease

BackgroundMounting studies have shown that hyperuricemia is related to kidney diseases through multiple ways. However, the application of urinary uric acid indicators in patients with reduced renal function is not clear. In this study, we aim to determine the effects of renal function on various indicators reflecting uric acid levels in patients with chronic kidney disease (CKD).MethodsAnthropometric and biochemical examinations were performed in 625 patients with CKD recruited from Dept of Nephrology of Huadong hospital affiliated to Fudan University. Multiple regression analyses were used to study correlations of the estimated glomerular filtration rate (eGFR) with serum uric acid (SUA) and renal handling of uric acid. For further study, smooth curve plots and threshold effect analyses were applied to clarify associations between renal function and uric acid levels.ResultsThe nonlinear relationships were observed between eGFR and urinary uric acid indicators. The obvious inflection points were observed in smooth curve fitting of eGFR and fractional excretion of uric acid (FEur), excretion of uric acid per volume of glomerular filtration (EurGF). In subsequent analyses where levels of eGFR< 15 mL/min/1.73m2 were dichotomized (CKD5a/CKD5b), patients in the CKD5a showed higher levels of FEur and EurGF while lower levels of urinary uric acid excretion (UUA), clearance of uric acid (Cur) and glomerular filtration load of uric acid (FLur) compared with CKD5b group (all P < 0.05). And there was no significant difference of SUA levels between two groups. On the other hand, when eGFR< 109.9 ml/min/1.73 m2 and 89.1 ml/min/1.73 m2, the resultant curves exhibited approximately linear associations of eGFR with Cur and FLur respectively.ConclusionFEur and EurGF showed significantly compensatory increases with decreased renal function. And extra-renal uric acid excretion may play a compensatory role in patients with severe renal impairment to maintain SUA levels. Moreover, Cur and FLur may be more reliable indicators of classification for hyperuricemia in CKD patients.

P0169DYSFUNCTION OF ABCG2, URATE TRANSPORTER, IS RELATED WITH UROLITHIASIS

Abstract Background and Aims Urolithiasis is one of the rapidly increasing diseases in developed countries. It has been reported that urolithiasis is related with lifestyles, diet, obesity, climate and chronic diseases including hyperuricemia, diabetes mellitus, metabolic syndrome, chronic kidney disease et cetera. Among them, hyperuricemia is the leading cause of urolithiasis. ATP–binding cassette subfamily G member 2 (ABCG2), urate transporter, excretes uric acid in the kidney and the intestinal tract and ABCG2 dysfunction increases a risk of hyperuricemia. In this study, we investigated the estimated ABCG2 function by common two dysfunctional variants, Q126X (rs72552713) and Q141K (rs2231142), in patients with urolithiasis, and we evaluated the relation between urolithiasis and ABCG2 dysfunction. Method One hundred and ninety-seven urolithiasis patients without gout (150 males and 47 females) were enrolled. Q126X totally abolishes ABCG2 function, while Q141K reduces its function by about 50%. Since these two SNPs do not link each other and two SNPs do not exist on same chromosome, these two are regarded as independent risks. Namely, based on the genotype of Q126X and Q141K, it can be divided into three categories: a full functional group, a 75% functional group and a ≦50% functional group. Serum uric acid levels and amount of urinary uric acid were measured. Renal uric acid handling of the patients was classified into renal uric acid underexcretion type or renal uric acid overload type based on uric acid clearance and amount of urinary uric acid. Stone composition was analysed, if it had been possible. Results ABCG2 function of the patients was evaluated as follows: 82 patients, ABCG2 full function (41.6%); 78 patients, 75% function (39.6%); 37 patients, ≦50% function (18.8%). 155 patients were classified into renal uric acid underexcretion type, 13 patients were classified into renal uric acid overload type and 2 patients were classified into normal type (27 patients have not had 24-hour urine biochemical test). Stone composition analysis was performed for 136 patients; calcium oxalate stone was identified in 107 patients and uric acid stone in 29 patients. In this study, 58.4 % of the patients with urolithiasis had some ABCG2 dysfunction as against 49.8 % of the healthy individuals previously reported (p=0.0246). In addition, the ratio of subjects with urolithiasis having 50% or less of ABCG2 function was higher than healthy individuals significantly (OR=1.773, p=0.007). The high ratio of ABCG2 dysfunctional patients with urolithiasis suggested that ABCG2 dysfunction is a risk factor for urolithiasis. In the patients with urolithiasis, renal uric acid underexcretion type accounted for about 90% of the patients. This means that this type accelerated urolithiasis as well as hyperuricosuria. Conclusion ABCG2 dysfunction and renal uric acid underexcretion type were suggested to be a risk factor for urolithiasis.

P0964EFFECTS OF XANTHINE OXIDASE INHIBITORS AND DAPAGLIFLOZIN ON RENAL GLUCOSE AND URATE TRANSPORTERS IN METABOLIC SYNDROME

Abstract Background and Aims Metabolic syndrome consists of several medical conditions that collectively predict the risk for cardiovascular disease. Hyperglycemia and hyperuricemia are the major disorders of metabolic syndrome. Kidney reabsorbs almost all filtrated glucose by active transport at normal concentrations of plasma glucose via members of the sodium glucose transport (SGLT) family. Besides, the kidney plays a pivotal role in handling uric acid homeostasis. Uric acid is mainly controlled by urate transporter (UAT), urate anion exchanger 1 (URAT1) and glucose transporter 9 (GLUT9). The aims of the study were to determine the alteration of renal glucose and uric acid transporters in animals with metabolic syndrome after treatment of xanthine oxidase inhibitors and SGLT2 inhibitor. Method Sprague-Dawley rats were fed with normal chow (Control) or high fructose diet (60%) for totally 6 months. For those animals fed with high fructose diet for 3 months, they were divided into 4 groups including high fructose diet without treatment (FR), treatment with allopurinol (150 mg/L in drinking water), with febuxostat (30 mg/L in drinking water) or with dapagliflozin (1mg/kg/day intraperitoneal injection). Blood, urine and blood pressure were collected and measured at the end of study. Gene and protein expression of renal glucose and uric acid transporters were determined by reverse transcriptase polymerase chain reaction. The changes of transporters were then confirmed by immunohistochemical staining. Results High-fructose diet induced higher levels of fasting glucose, insulin resistance index, uric acid, triglyceride and blood pressure in FR group (all p &amp;lt;0.05 vs. control). Treatment of allopurinol, febuxostat and dapagliflozin reduced body weight significantly. Fasting glucose, insulin resistance index and hyperuricemia were improved in all drug treatment groups (all p &amp;lt;0.05). In the kidney, high fructose diet significantly upregulated SGLT1, SGLT2 and GLUT2 but downregulated GLUT1 expression. Urate transporters, including GLUT9, UAT and URAT1 were also increased (p &amp;lt;0.05). The improvement of insulin resistance by xanthine oxidase inhibitors was associated with suppression of renal SGLT1, SGLT2 and GLUT2 expression. Dapagliflozin alleviated hyperuricemia and induced uricosuria without affecting serum xanthine oxidase activity. Compared to FR, dapagliflozin significantly inhibited fructose-induced overexpression of GLUT9, UAT and URAT1 in the kidney. Conclusion Long term high fructose diet induced metabolic syndrome in rats. Treatment of xanthine oxidase inhibitors and dapagliflozin ameliorated components of metabolic syndrome. Both allopurinol and febuxostat improved insulin resistance in association with suppression of renal SGLT1, SGLT2 and GLUT2 expression. Although dapagliflozin and xanthine oxidase inhibitors reduced uric acid in different mechanisms, they shared a similar molecular changes in the kidney by downregulating GLUT9, UAT and URAT1 expression.

Acute Uterine Torsion Mimicking Tumor Lysis Syndrome

Background: Non-gravid uterine torsion is rare and mostly diagnosed at surgery. This report describes a patient with a large abdominal mass, critical illness, and tumor lysis syndrome. Case: A female presented with acute abdominal pain. Physical exam showed a large abdominal mass and abdominal rigidity. Serial laboratory tests showed a drop in hemoglobin level, progressive renal failure and serum uric acid and phosphate concentrations compatible with tumor lysis syndrome. Computed tomography showed a 30 cm mass filling the pelvis and abdomen. At an emergency exploratory laparotomy, a 360 degrees torsion of the uterus was found. An uneventful total hysterectomy was done. After surgery renal function restored. Conclusion: Uterine torsion is rare and can be potentially life threatening when presenting as tumor lysis syndrome

Ameliorative Effects of Annona muricata (Graviola) and Fullerene C60 Against Toxicity Induced by Carboplatin in Male Albino Rats

This study was designed to demonstrate the ameliorating effects Annona muricata (Graviola)plant extract and fullerene C60 on hematological and biochemical disorder alteration induced by intraperitoneal (i.p.) injection of carboplatin (CRP) on male rats. Five groups of adult male rats we established (n=10). Group1: animals were administered normal saline i.p. (10 ml/kg b.wt) for 40 days and served as a normal group. Group 2: rats were injected i.p. with a single dose of CRP (80 mg/kg b.wt), then received a saline solution for the remaining 40 days and served as a control group. Group 3: animals were oral administration of Annona muricata leaves extract at a dose of 200 mg/kg/day for 40 consecutive days after 24 hours of i.p. injected with a single dose of CRP (80 mg/kg b.wt.). Group 4: animals weretreated orally by fullerene C60 (4 mg/ kg b.wt.) daily for 40 daysafter 24 hours of i.p. injected a single dose of CRP (80 mg/kg b.wt.). Group 5: each rat in this group was daily oral administration of Annona muricata leaves extract at a dose of (200 mg/kg b.wt.)+ fullerene C60 (4 mg/ kg b. wt.) for 40 days after 24 hours of injected a single dose of CRP. Results obtained revealed that CRP administration in the control group (gp. 2) significantly reduced the levels of red blood cells (RBCs), haemoglobin (Hb), blood Platelets (PLTs) and PCV value, with a marked reduction in white blood cells (WBCs). Additionally, there is an elevation in serum ALT, AST, ALP, total bilirubin, creatinine and urea associated with a reduction in albumin, total protein, and uric acid. In addition, hepatic and renal thiobarbituric acid reactive substances (TBARS) levels were significantly increased by CRP administration while levels of endogenous antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) were reduced. This study confirmed the risk of increased oxidative stress, hepatotoxicity and nephrotoxicity due to CRP administration. In addition, Annona muricata leaves extractand fullerene C60, clarifiedmodulatory role against the cellular damage produced by free radical-induced by CRP.

Metabolic consequences of cystinuria

BackgroundCystinuria is an inherited disorder of renal amino acid transport that causes recurrent nephrolithiasis and significant morbidity in humans. It has an incidence of 1 in 7000 worldwide making it one of the most common genetic disorders in man. We phenotypically characterized a mouse model of cystinuria type A resultant from knockout of Slc3a1.MethodsKnockout of Slc3a1 at RNA and protein levels was evaluated using real-time quantitative PCR and immunofluorescence. Slc3a1 knockout mice were placed on normal or breeder chow diets and evaluated for cystine stone formation over time suing x-ray analysis, and the development of kidney injury by measuring injury biomarkers. Kidney injury was also evaluated via histologic analysis. Amino acid levels were measured in the blood of mice using high performance liquid chromatography. Liver glutathione levels were measured using a luminescent-based assay.ResultsWe confirmed knockout of Slc3a1 at the RNA level, while Slc7a9 RNA representing the co-transporter was preserved. As expected, we observed bladder stone formation in Slc3a1−/− mice. Male Slc3a1−/− mice exhibited lower weights compared to Slc3a1+/+. Slc3a1−/− mice on a regular diet demonstrated elevated blood urea nitrogen (BUN) without elevation of serum creatinine. However, placing the knockout animals on a breeder chow diet, containing a higher cystine concentration, resulted in the development of elevation of both BUN and creatinine indicative of more severe chronic kidney disease. Histological examination revealed that these dietary effects resulted in worsened kidney tubular obstruction and interstitial inflammation as well as worsened bladder inflammation. Cystine is a precursor for the antioxidant molecule glutathione, so we evaluated glutathione levels in the livers of Slc3a1−/− mice. We found significantly lowered levels of both reduced and total glutathione in the knockout animals.ConclusionsOur results suggest that that diet can affect the development and progression of chronic kidney disease in an animal model of cystinuria, which may have important implications for patients with this disease. Additionally, reduced glutathione may predispose those with cystinuria to injury caused by oxidative stress.Word count: 327.

2089-P: Regional Renal Hemodynamics and Fatty Acid Uptake: Effects of Obesity and Weight Loss

Objective: Changes of obesity on renal perfusion and metabolism are poorly understood. Our aims were to evaluate whether obesity increases renal regional hemodynamics and metabolism in vivo, and to determine the effects of weight loss. Methods: 23 morbidly obese and 15 age- and sex-matched nonobese controls were recruited. Renal perfusion and fatty acid uptake (FAU) were measured using PET-CT scanning and [15O]- H2O and [18F]fluoro-6-thia-heptadecanoic acid ([18F]THA), respectively. Kidney volumes and radiodensity were measured by CT and cardiac output by MRI. Intraglomerular pressure (Pglo) was estimated by Gomez formula. Obese subjects were re-studied six months after bariatric surgery. Results: As compared to controls, obese subjects had larger renal volume (340[118] vs. 256[63] ml, median[interquartile range]) and lower renal radiodensity (15.3[13.1] vs. 31.5[9.8] units, p≤0.05 for both), suggesting accumulation of water and/or lipid. Both cardiac output and glomerular filtration rate (eGFR) were increased by ∼25% in the obese. While there were no differences in total renal perfusion between the two groups, Pglo was higher in the obese (61±5 mmHg vs. 55±3 of controls, p&amp;lt;0.001). In both groups, regional blood flow was 50% higher in the cortex than medulla; in either region, FAU was higher in the obese (6.3±1.8 vs. 4.1±1.5 µmol.min-1.100g-1, and 7.5±2.2 vs. 4.6±2.1, both p≤0.05), mostly as a consequence of higher plasma FFA levels. Post-surgery (weight loss = 26±8 kg), renal volume, GFR, and Pglo all decreased and renal radiodensity increased to levels similar to controls. On the contrary, cortical and medullary FAU was not normalized. Conclusions: In obesity, renal hemodynamics are indicative of an incomplete protection against hyperperfusion and renal fatty acid uptake is increased, driven by higher substrate availability. Surgically-induced major weight loss reverses the hemodynamic but not the metabolic changes. Disclosure E. Rebelos: None. P. Dadson: None. V. Oikonen: None. H. Iida: None. J.C. Hannukainen: None. P. Iozzo: None. E. Ferrannini: None. P. Nuutila: Research Support; Self; AstraZeneca. Funding Academy of Finland; University of Turku; Turku University Hospital

Uric acid transporters BCRP and MRP4 involved in chickens uric acid excretion

BackgroundBreast cancer resistance protein (BCRP) and multidrug resistance protein 4 (MRP4) are involved in uric acid excretion in humans and mice. Despite evidence suggesting that renal proximal tubular epithelial cells participate in uric acid excretion in chickens, the roles of BCRP and MRP4 therein remain unclear. This study evaluated the relationship between BCRP and MRP4 expression and renal function in chickens.ResultsSixty laying hens were randomly divided into four treatment groups: a control group (NC) fed a basal diet; a sulfonamide-treated group (SD) fed the basal diet and supplemented with sulfamonomethoxine sodium via drinking water (8 mg/L); a fish meal group (FM) fed the basal diet supplemented with 16% fishmeal; and a uric acid injection group (IU) fed the basal diet and intraperitoneally injected with uric acid (250 mg/kg body weight). The results showed that serum uric acid, creatinine, and blood urea nitrogen levels were significantly higher in the SD and IU, but not FM, than in the NC groups. Renal tubular epithelial cells in the SD and IU groups were damaged. Liver BCRP and MRP4 mRNA and protein levels were significantly decreased in the SD and IU groups, but slightly increased in the FM group. In the SD group, BCRP and MRP4 were significantly increased in the ileum and slightly increased in the kidney. In the FM group, BCRP and MRP4 were significantly increased in the kidney and slightly increased in the ileum. In the IU group, BCRP and MRP4 were significantly increased in the kidney and ileum. BCRP and MRP4 expression in the jejunum was not affected by the treatments.ConclusionTogether, these results demonstrate that BCRP and MRP4 are involved in renal and intestinal uric acid excretion in chickens and that BCRP is positively related to MRP4 expression. Further, impairment of renal function results in an increase in serum uric acid as well as a compensatory increase in BCRP and MRP4 in the ileum; however, under normal renal function, renal BCRP and MRP4 are the main regulators of uric acid excretion.

Neprilysin colocalizes with the V‐ATPase in kidney A‐type intercalated cells: possible role in urinary acidification

Intercalated cells (IC) in kidney collecting ducts are essential for acid‐base homeostasis. A proteomic analysis of these cells after purification by FACS revealed unexpectedly that they express high levels of neprilysin, a neutral protease, previously reported to be located in the brush border of proximal tubule cells. Therefore, we re‐examined the distribution of neprilysin in the kidney by immunohistochemistry and western blot analysis. Using anti‐neprilysin antibodies and two collecting duct markers: anti‐AQP2 antibody (principal cells) and anti‐A1 subunit v‐ATPase subunit (intercalated cells), we found that neprilysin was detectable not only in the proximal tubule, but also in ICs (but not principal cells) in all regions of the collecting duct. A similar distribution of neprilysin was seen in both mouse and rat kidneys. We then used an anti‐pendrin antibody to identify B‐type ICs in cortical collecting ducts. Only 35% of IC‐B population express neprilysin. Western blot analysis using an antibody against neprilysin showed that both cortical and medullary membrane preparations expressed neprilysin, and that female mice express more neprilysin than males in the cortex. However, this sex difference is not present in the medullary preparation, and we, therefore, attribute it mainly to a difference in proximal tubule expression. A similar result was observed in the kidneys of knockout mice that lack the IC‐specific B1 subunit of the V‐ATPase. In order to study the potential role of neprilysin in renal physiology, we treated male mice for 3 days with thiorphan, a selective neprilysin inhibitor. We measured a slight reduction of urine osmolality 1851 ± 160 to 1357 ± 240 (p=0.12) and an increase in urine volume 0.86 ± 0.21 to 1.48 ± 0.50, p= 0.23). In contrast, the change in urine pH was significant, increasing from 6.6 ± 0.1 to 6.9 ± 0.1, (n=3, p= 0.029) with the inhibitor, suggesting a role of neprilysin in acid excretion, possibly via IC function and V‐ATPase activity. In summary, we found that neprilysin is highly expressed in A‐ICs, where it colocalizes with the V‐ATPase. Its expression is higher in female mice, and it may have an as yet undetermined role in renal acid excretion.Support or Funding InformationThis work was supported by National Institutes of Health (NIH) grant DK096586 (D. Brown). The Zeiss LMS 800 confocal system in the Program in Membrane Biology (PMB) Microscopy Core was purchased using an NIH Shared Instrumentation Grant S10 RR031563‐01 (DB).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

A renoprotective role of chitosan against lithium-induced renal toxicity in rats

BackgroundLithium (Li) is considered as the first therapeutic line for treatment of bipolar affective disorders and manic-depressive illness. Renal toxicity can be categorized as the most common undesirable side effect of Li therapy. Therefore, the present study aimed to reveal efficiency of chitosan (CS) as a natural chelator against renal toxicity induced as a result of Li injection. During current experiment, the renal functions (urea, creatinine, blood urea nitrogen (BUN), uric acid and total protein) were determined in serum samples. The urinary excretion of N-acetyl-β-D-glucosaminidase (NAG) was assayed through measuring its level in urine samples. Moreover, markers of the oxidative stress (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH) and lipid peroxidation product (LPO)) were assessed in renal tissues. In addition, histopathological and ultrastructural examinations were carried out in that tissue.ResultsIt was found that Li injection caused significant (P < 0.05) elevation in serum urea, creatinin and BUN levels associated with decline in uric acid and T. protein. Moreover, Li increased the urinary excretion of NAG significantly (P < 0.05). Administration of CS orally restored levels of these measurements to normalcy in CS pre-treated group through lowering urea, creatinin, BNU levels and urinary excretion of NAG with enhancing uric acid and T. protein levels.On the other hand, it was found that Li caused significant (P < 0.05) elevation in the LPO level associated with decline in activity of the antioxidant system in the renal tissues. Likewise, it caused severe alterations in the renal levels at histopathological and ultrastructural levels. The treatment with CS reduced the renal LPO associated with stimulating the antioxidant system through increasing levels of SOD, CAT, GPx and GSH in addition to its beneficial role against the histopathological abnormalities.ConclusionsThe CS exhibited promising role in the protection against the oxidative stress and renal toxicity induced as a result of Li injection.

Lithagogue effects of Pyrrosia lingua from Guizhou province on experimental renal calculus in rats

To screen the active fractions with lithagogue effects of Pyrrosia lingua from Guizhou province and preliminarily investigate its mechanism. The rats were fed with 1% ethylene glycol and 2% ammonium chloride to establish the nephrolithiasis models, which were used to evaluate thelithagogue effects of different polar fractions of P. lingua from Guizhou province. The level of urinary calcium and oxalic acid in urine, renal calcium, oxalic acid, superoxide dismutase (SOD), catalase(CAT) and malondialdehyde (MDA) in renal tissues,as well as crystalline deposit and lithogenesis in renal tissues and the levels of creatinine(Cr) and blood urea nitrogen (BUN) in the serum were detected. The effective compounds were inferred from the analysis of active fractions extract based on LC-MS technology. Petroleum ether fraction and dichloromethane fraction of P. lingua from Guizhou province can reduce renal oxalic acid and renal calcium concentration, increase urinary oxalic acid and urine calcium, with significant inhibitory effect on the formation of renal calculus in rats, significantly increase SOD and CAT activities in renal tissues, and significantly reduce MDA levels. LC-MS analysis showed that the caffeine, citric acid and tartaric acid among the compounds from petroleum ether fraction and dichloromethane fraction had lithagogue effects. Both the petroleum ether fraction and dichloromethane fraction of P. lingua from Guizhou province showed good effect on prevention and treatment of calculus in middle dose groups, and the mechanism may be associated with antioxidation, reducing calcium oxalate crystal deposition, and promoting calcium oxalatecrystal release, in addition, caffeine, citric acid and tartaric acid had lithagogue effects.

Sequential Treatment Reduces the Acute Phases of Adverse Effect of Zoledronic Acid in First Time Users

Objective: To investigate whether sequential regimen such as traditional anti-reabsorption medications followed by zoledronic acid could reduce the side effects after initiation of zoledronic acid in postmenopausal osteoporosis patients. Methods: A total of 156 postmenopausal osteoporosis patients who presented at our osteoporosis outpatient clinic were enrolled in this study. They were randomly divided into four groups: the control group, alendronate group, calcitonin group, and raloxifene group. All participants were treated with Caltrate 600 mg per day and calcitriol 0.25 ug per day as a baseline treatment, followed by administrating 5 mg/100 mL of zoledronic acid intravenously for one single time three months afterwards. During the abovementioned course of three months, the alendronate group received 70 mg of alendronate sodium orally once a week, the calcitonin group received nasal spray form of salmon calcitonin 10iu daily, the raloxifene group received 60mg of raloxifene orally daily, and the control group received nothing but only the baseline treatment. We tested parameters such as β-cross, blood calcium level, renal function both pre and post zoledronic acid treatment. We also documented those side effects that typically occurred within one week of treatment initiation, which included the proportion, severity, onset time, and duration of the fever, demand for pain medication, severity of bone and joint pain, flu-like symptoms, arrhythmia, blood calcium level, and kidney function impairment. We also evaluated how willing the patients were to receive a second dose of zoledronic acid. Then we did comparative analysis between control group and sequential group. Results: The side effects such as fever, bone and joint pain, flu-like symptoms after zoledronic acid treatment in alendronate group and calcitonin group were all significantly lower than that in control group, while raloxifene group showed no significant difference compared to that in the control group. The proportions of patients who needed NSAIDs in the alendronate group and the calcitonin group were significantly lower than that in control group. However, the raloxifene group showed no significant difference in the NSAIDs demand from that of the control group. The percentages of patients who consented to a second dose of zoledronate therapy in the alendronate, calcitonin and raloxifene groups were significantly higher than that in the control group. Conclusions: Sequential treatment with alendronate sodium or calcitonin can significantly reduce the side effects such as fever, bone/joint pain, flu-like symptoms caused by first-time zoledronic acid therapy. Raloxifene sequential treatment does not seem to have decreased or increased the side effects of zoledronic acid treatment. Also, sequential treatment can improve the patient compliance with a second dose of zoledronic acid.

Antireflux surgery does not change ongoing renal functional deterioration

Aim Treatment modalities of vesicoureteral reflux (VUR) consist of antimicrobial prophylaxis and antireflux surgery. In this study, we aimed to determine if antireflux surgery changes the course of renal functional deterioration in children with VUR and urinary tract infections (UTI). Methods Medical files of patients with VUR diagnosed during evaluation for UTI were evaluated retrospectively for gender, age, follow-up period, and renal ultrasonography (US) and serial 99mTc-dimercaptosuccinic acid (99mTc-DMSA) scintigraphy findings. Estimated glomerular filtration rate and urinary protein levels were determined at the initial and last visits, and before the operation in children who had antireflux surgery. The patients were divided into two groups as solely medically treated (Group 1) and both medically and surgically treated (Group 2). Group 2 was further divided as those with stable renal function (Group 2a) and with progressive renal injury (Group 2b). Results There were 140 patients (77 female; mean age 51.6 ± 51.9 months). Group 1 and Group 2 included 82 and 58 patients, respectively. In Group 2, the number of patients with the abnormal US, DMSA scintigraphy, and renal function was higher than in Group 1. Recurrent UTI rate was similar, but progressive scarring was more prominent in the antireflux surgery group. In Group 2, 31 patients had a stable renal function (Group 2a) while 27 had progressive deterioration of renal functions (Group 2b). These subgroups were not different with respect to the rate of high-grade VUR, the presence of a renal scar in DMSA, and UTI recurrence. However, the bilateral renal scar was more common in Group 2b. Conclusion Antireflux surgery does not change the course of ongoing renal injury and renal functional deterioration.