Kidney stone disease.

Kidney stone disease is rapidly increasing with a strong relationship to metabolic syndrome. This review gives a brief overview of the current state and current treatment modalities. Increasing use of CT and ultrasound scans leads to increased diagnosis of asymptomatic kidney stones, which rarely require treatment. The trend in stone treatment goes towards endoscopic lithotripsy which together with ESWL enables a personalised approach. Obstructive stones with infection require urgent intervention to reduce mortality. Increased fluid intake, dietary changes as well as potassium citrate supplements are the most important elements in stone prevention in the common idiopathic stone disease.

Urinary proteome analysis in congenital bilateral hydronephrosis.

OBJECTIVE: A proteomics strategy was applied to map protein changes in urine after relief of congenital bilateral hydronephrosis to identify proteins correlated with the pathophysiological processes in congenital obstructive nephropathy as potential urinary biomarkers. MATERIAL AND METHODS: Urine samples from 10 infants with bilateral abnormal drainage from the kidneys were collected at the time of relief from obstruction, and after 2 and 4 weeks. Proteomics techniques were used on samples from three patients for identification of protein changes between the three time-points, and enzyme-linked immunosorbent assay (ELISA) was used on samples from all 10 patients for validation of five selected proteins. RESULTS: Mass spectrometry quantified 315 protein hits, out of which 33 proteins showed significantly changed urinary excretion between the time-points. Validation by ELISA showed high urinary excretion of fibrinogen, plasminogen, transthyretin and transferrin at the time of relief from obstruction, followed by a significant reduction. In contrast, Tamm-Horsfall protein exhibited the reverse pattern. CONCLUSION: Using a mass spectrometry-based proteomics approach, this study identified 33 proteins related to congenital bilateral hydronephrosis, and pinpointed a panel of five proteins consistently linked to this congenital kidney disorder as potential urinary biomarkers.

Disruption of cyclooxygenase-2 prevents downregulation of cortical AQP2 and AQP3 in response to bilateral ureteral obstruction in the mouse.

Bilateral ureteral obstruction (BUO) in rats is associated with increased cyclooxygenase type 2 (COX-2) expression, and selective COX-2 inhibition prevents downregulation of aquaporins (AQPs) in response to BUO. It was hypothesized that a murine model would display similar changes in renal COX-2 and AQPs upon BUO and that targeted disruption of COX-2 protects against BUO-induced suppression of collecting duct AQPs. COX-2(-/-) and wild-type littermates (C57BL/6) were employed to determine COX-1, -2, AQP2, and AQP3 protein abundances and localization after BUO. In a separate series, sham and BUO wild-type mice were treated with a selective COX-2 inhibitor, parecoxib. The COX-2 protein level increased in wild-type mice in response to BUO and was not detectable in COX-2(-/-). COX-1 protein abundance was increased in sham-operated and BUO mice. Total AQP2 and -3 mRNA and protein levels decreased significantly after BUO in the cortex+outer medulla (C+OM) and inner medulla (IM). The decrease in C+OM AQP2 and -3 levels was attenuated/prevented in COX-2(-/-) mice, whereas there was no change in the IM. In parallel, inhibition of COX-2 by parecoxib rescued C+OM AQP3 and IM AQP2 protein level in wild-type mice subjected to BUO. In summary, 1) In C57BL/6 mice, ureteral obstruction increases renal COX-2 expression in interstitial cells and lowers AQP2/-3 abundance and 2) inhibition of COX-2 activity by targeted disruption or pharmacological blockade attenuates obstruction-induced AQP downregulation. In conclusion, COX-2-derived prostaglandins contribute to downregulation of transcellular water transporters in the collecting duct and likely to postobstruction diureses in the mouse.

Age-related changes in expression in renal AQPs in response to congenital, partial, unilateral ureteral obstruction in rats.

Previously we demonstrated that neonatally induced partial unilateral ureteral obstruction (PUUO) in rats is associated with changes in the abundance of renal acid-base transporters that were paralleled by reduction in renal functions dependent on the severity and duration of obstruction. The aim of the present study was to identify whether changes in renal aquaporin abundance are age-dependent. Semiquantitative immunoblotting and immunohistochemistry were used to examine the changes in abundance of AQP1, AQP2, p-S256AQP2 (AQP2 phosphorylated at consensus site Ser(256)) and AQP3 in the kidneys of rats with neonatally induced PUUO within the first 48 h of life, and then monitored for 7 or 14 weeks. Protein abundance of AQP2 and AQP3 increased in both obstructed and non-obstructed kidneys 7 weeks after induction of neonatal PUUO (PUUO-7W). In contrast, AQP1 and AQP2 protein abundance in the obstructed kidney were reduced after 14 weeks of PUUO (PUUO-14W). Importantly, pS256-AQP2 protein abundance was reduced in obstructed kidneys of both PUUO-7W and PUUO-14W. Immunohistochemistry confirmed the persistent pS256-AQP2 downregulation in both PUUO-7W and PUUO-14W rats. The study shows that the protein abundance of AQP1, AQP2, and AQP3 in the obstructed kidney is increased in PUUO-7W, which may be a compensatory phenomenon and reduced in PUUO-14W rats suggesting a time-/age-dependent dysregulation in response to PUUO. pS256-AQP2 protein abundance is reduced consistent with obstruction-induced direct effects in the apical part of the collecting duct principal cells in response to PUUO.

Regulation of aquaporins and sodium transporter proteins in the solitary kidney in response to partial ureteral obstruction in neonatal rats.

Unilateral ureteral obstruction (UUO) impairs function of the obstructed kidney, and the contralateral nonobstructed kidney compensates depending on the degree and duration of UUO. This study aimed to determine the hemodynamic and molecular changes in the solitary kidney in response to partial ureteral obstruction (PUO) where any compensation from the contralateral kidney was eliminated so that all observed changes in the kidney tissue occurred in the kidney with PUO. Newborn rats were subjected to unilateral left nephrectomy (UNX) within the first 48 h of life and a subset of UNX rats was subjected to severe PUO of the right kidney at day 14. Renal blood flow and whole kidney volume were measured with MRI at week 10. The renal protein abundance of aquaporin 1 (AQP1), AQP2 and AQP3 as well as Na,K-ATPase, NaPi-2 (type 2 sodium-phosphate cotransporter) and NHE3 (type 3 sodium-proton exchanger) were examined by immunoblotting and immunocytochemistry. At 10 weeks of age, the protein abundance of AQP2, AQP3, Na,K-ATPase, NaPi-2 and NHE3 were increased in response to PUO. In contrast, AQP1 expression was markedly decreased compared to sham-operated rats. These findings were confirmed by immunohistochemistry. GFR, urine osmolality and urine sodium excretion were reduced and kidney weight increased in response to PUO. In conclusion, the present study demonstrated major changes in the protein abundance of renal AQP1, AQP2 and AQP3 and sodium transporters in the solitary PUO kidney. These changes were paralleled by decreased urinary sodium excretion and a significant reduction in urinary osmolality from the obstructed kidney, suggesting a functional association between the molecular changes and the ability of the obstructed kidney to handle sodium and water in this solitary kidney model.

Urinary tract obstruction induces transient accumulation of COX-2-derived prostanoids in kidney tissue.

Inhibitors of cyclooxygenase (COX)-2 prevent suppression of aquaporin-2 and reduce polyuria in the acute phase after release of bilateral ureteral obstruction (BUO). We hypothesized that BUO leads to COX-2-mediated local accumulation of prostanoids in inner medulla (IM) tissue. To test this, rats were subjected to BUO and treated with selective COX-1 or COX-2 inhibitors. Tissue was examined at 2, 6, 12, and 24 h after BUO. COX-2 protein abundance increased in IM 12 and 24 h after onset of BUO but did not change in cortex. COX-1 did not change at any time points in any region. A full profile of all five primary prostanoids was obtained by mass spectrometric determination of PGE(2), PGF(2alpha), 6-keto-PGF(1alpha), PGD(2), and thromboxane (Tx) B(2) concentrations in kidney cortex/outer medulla and IM fractions. IM concentration of PGE(2), 6-keto-PGF(1alpha), and PGF(2alpha) was increased at 6 h BUO, and PGE(2) and PGF(2alpha) increased further at 12 h BUO. TxB(2) increased after 12 h BUO. 6-keto-PGF(1alpha) remained significantly increased after 24 h BUO. The COX-2 inhibitor parecoxib lowered IM PGE(2,) TxB(2), 6-keto-PGF(1alpha), and PGF(2alpha) below vehicle-treated BUO and sham rats at 6, 12 and, 24 h BUO. The COX-1 inhibitor SC-560 lowered PGE(2), PGF(2alpha), and PGD(2) in IM compared with untreated 12 h BUO, but levels remained significantly above sham. In cortex tissue, PGE(2) and 6-keto-PGF(1alpha) concentrations were elevated at 6 h only. In conclusion, COX-2 activity contributes to the transient increase in prostacyclin metabolite 6-keto-PGF(1alpha) and TxB(2) concentration in the kidney IM, and COX-2 is the predominant isoform that is responsible for accumulation of PGE(2) and PGF(2alpha) with minor, but significant, contributions from COX-1. PGD(2) synthesis is mediated exclusively by COX-1. In BUO, therapeutic interventions aimed at the COX-prostanoid pathway should target primarily COX-2.

Oxygen tension correlates with regional blood flow in obstructed rat kidney.

As renal tissue oxygen tension (P(O(2))) is determined by the balance between oxygen supply and consumption, direct tissue P(O(2)) measurements are essential when evaluating the presence of hypoxia. The present study aimed at evaluating invasively and continuously the renal medullary and cortical tissue P(O(2)) by novel fibre-optic probes in rats subjected to acute unilateral ureteral obstruction (AUUO). In parallel, regional blood flow measurements were obtained by MRI to investigate the relationship between regional blood flow and tissue oxygen tension. The abundance of transport proteins was determined by immunoblotting. In the obstructed kidney, AUUO caused a prompt decrease in medullary tissue P(O(2)) to 60% of baseline level whereas cortical tissue P(O(2)) was unchanged. By contrast, tissue P(O(2)) slightly increased in the non-obstructed kidney. These changes developed during the first 30 min after AUUO and persisted for the 3 h observation period. Medullary blood flow declined 1.5-2 h after induction of AUUO to 61% of baseline level in the obstructed kidney. By contrast, cortical blood flow increased to 108% of baseline level in the non-obstructed kidney. Finally, the abundance of phosphorylated aquaporin 2 decreased significantly in the obstructed kidney medulla, but increased in the obstructed kidney cortex. The Na(+)/K(+)-ATPase abundance increased in the obstructed kidney medulla whereas the Na(+)/K(+)/2Cl(-) co-transporter abundance remained unchanged in the obstructed kidney. In conclusion, measurements of regional blood flow reflect tissue P(O(2)) changes during AUUO suggesting that reduced regional blood flow is a predictor of local hypoxia. Furthermore, the abundance of major transport protein is independent of tissue P(O(2)).

Age-dependent renal expression of acid-base transporters in neonatal ureter obstruction.

Congenital obstructive nephropathy accounts for a major proportion of renal insufficiency in infancy and childhood. In an earlier investigation we demonstrated that bilateral complete ureteral obstruction (BUO) in rats is associated with inadequate urinary acidification [Am J Physiol Renal Physiol. 295(2):F497-506, 2008]. The aim of the study reported here was to determine whether this defect is also associated with unilateral ureteral obstruction (UUO), which is clinically more common than BUO. The time-course of the changes in protein expression levels of major renal acid-base transporters was examined at 7 and 14 weeks in rats with neonatally induced partial unilateral ureteral obstruction (PUUO), which was performed within the first 48 h of life. We observed that protein expression of the renal acid-base transporters NHE3, NBC1, NBCn1, pendrin and Na(+)-K(+)-ATPase was increased in both obstructed and non-obstructed kidneys 7 weeks after the induction of neonatal PUUO. This was confirmed by immunocytochemistry. In contrast, 14 weeks after the induction of PUUO, there was a significant downregulation of the renal acid-base transporters NBC1, NBCn1 and Na(+)-K(+)-ATPase in the obstructed kidneys. These time/age-dependent changes in protein expression were associated with parallel changes in renal function resulting in urine acidification in response to exogenous acid loading. In conclusion, these results show that downregulation of protein expression is a time/age-dependent response to PUUO, which could contribute to the decreased net acid excretion and development of metabolic acidosis in neonatal rats with PUUO.

Verapamil attenuates renal tubular apoptosis in response to partial unilateral ureteral obstruction.

INTRODUCTION: Partial unilateral ureteral obstruction (PUUO) is the type of obstruction that is most often encountered in pediatric clinical practice. The majority of our knowledge on PUUO has been derived from experimental studies and the effects of PUUO on the kidney have still been a source of continual investigation. MATERIAL AND METHODS: In the present study, renal expression of p53, Fas and PCNA were examined in rabbits with long-term (4 weeks) partial obstruction. Additionally, the effect of calcium channel blocker on pronounced apoptotic changes were evaluated. RESULTS: Immunohistochemistry results revealed that PUUO for 4 weeks caused an upregulation of p53 to 55.2 +/- 2% and Fas to 30.1 +/- 1.1%, whereas verapamil challenge attenuated the expression of these two apoptotic markers (p53: 15.9 +/- 1.8%; Fas: 18.2 +/- 1.4%, p < 0.05). Importantly, PCNA activity was also increased in response to PUUO. However, verapamil treatment after onset of obstruction caused a markedly decrease in the expression of PCNA (42.9 +/- 10.8% vs. 9.6 +/- 2.1%, PUUO, PUUO + verapamil; respectively, p < 0.05). CONCLUSION: The expression of p53, Fas and PCNA molecules is associated with long-term partial ureteral obstruction, whereas verapamil seems to be a protective agent against apoptotic changes.

COX-2 activity transiently contributes to increased water and NaCl excretion in the polyuric phase after release of ureteral obstruction.

Release of bilateral ureteral obstruction (BUO) is associated with reduced expression of renal aquaporins (AQPs), polyuria, and impairment of urine-concentrating capacity. Recently, we demonstrated that 24 h of BUO is associated with increased cyclooxygenase (COX)-2 expression in the inner medulla (IM) and that selective COX-2 inhibition prevents downregulation of AQP2. In the present study, we tested the hypothesis that COX-2 activity increases in the postobstructive phase and that this increase in COX-2 activity contributes to polyuria and impaired urine-concentrating capacity. We examined the effect of the selective COX-2 inhibitor parecoxib (5 mg.kg(-1).day(-1) via osmotic minipumps) on renal functions and protein abundance of AQP2, AQP3, Na-K-2Cl cotransporter type 2 (NKCC2), and Na-K-ATPase 3 days after release of BUO. At 3 days after release of BUO, rats exhibited polyuria, dehydration and urine and IM tissue osmolality were decreased. There were inverse changes of COX-1 and COX-2 in the IM: COX-2 mRNA, protein, and activity increased, while COX-1 mRNA and protein decreased. Parecoxib reduced urine output 1 day after release of BUO, but sodium excretion and glomerular filtration rate were unchanged. Parecoxib normalized urinary PGE(2) and PGI(2) excretion and attenuated downregulation of AQP2 and AQP3, while phosphorylated AQP2 and NKCC2 remained suppressed. Parecoxib did not improve urine-concentrating capacity in response to 24 h of water deprivation. We conclude that decreased NKCC2 and collapse of the IM osmotic gradient, together with suppressed phosphorylated AQP2, are likely causes for the impaired urine-concentrating capacity and that COX-2 activity is not likely to mediate these changes in the chronic postobstructive phase after ureteral obstruction.

Candesartan prevents long-term impairment of renal function in response to neonatal partial unilateral ureteral obstruction.

Angiotensin II (ANG II) plays an important role in the development of obstructive nephropathy. Here, we examined the effects of the ANG II receptor type 1 (AT1R) blockade using candesartan on long-term renal molecular and functional changes in response to partial unilateral ureteral obstruction (PUUO). Newborn rats were subjected to severe PUUO or sham operation (Sham) within the first 48 h of life. Candesartan was provided in the drinking water (10 mg.kg(-1).day(-1)) from day 21 of life until 10 wk of age. Renal blood flow (RBF) was evaluated by MRI, glomerular filtration rate (GFR) was measured using the renal clearance of (51)Cr-EDTA, and the renal expression of Na-K-ATPase and the collecting duct water channel aquaporin-2 (AQP2) was examined by immunoblotting and immunocytochemistry. At 10 wk of age, PUUO significantly reduced RBF (0.8 +/- 0.1 vs. 1.6 +/- 0.1 ml.min(-1).100 g body wt(-1); P < 0.05) and GFR (37 +/- 16 vs. 448 +/- 111 microl.min(-1).100 g body wt(-1); P < 0.05) compared with Sham. Candesartan prevented the RBF reduction (PUUO+CAN: 1.6 +/- 0.2 vs. PUUO: 0.8 +/- 0.1 ml.min(-1).100 g body wt(-1); P < 0.05) and attenuated the GFR reduction (PUUO+CAN: 265 +/- 68 vs. PUUO: 37 +/- 16 microl.min(-1).100 g body wt(-1); P < 0.05). PUUO was also associated with a significant downregulation in the expression of Na-K-ATPase (75 +/- 12 vs. 100 +/- 5%, P < 0.05) and AQP2 (52 +/- 15 vs. 100 +/- 4%, P < 0.05), which were also prevented by candesartan (Na-K-ATPase: 103 +/- 8 vs. 100 +/- 5% and AQP2: 74 +/- 13 vs. 100 +/- 4%). These findings were confirmed by immunocytochemistry. Consistent with this, candesartan treatment partly prevented the reduction in solute free water reabsorption and attenuated fractional sodium excretion in rats with PUUO. In conclusion, candesartan prevents or attenuates the reduction in RBF, GFR and dysregulation of AQP2 and Na-K-ATPase in response to congenital PUUO in rats, suggesting that AT1R blockade may protect the neonatally obstructed kidney against development of obstructive nephropathy.