Hydroxycitric acid prevents hyperoxaluric-induced nephrolithiasis and oxidative stress via activation of the Nrf2/Keap1 signaling pathway

Nephrolithiasis is a common and frequently-occurring disease in the urinary system with high recurrence. The present study aimed to explore the protective effect and underlying mechanism of hydroxycitric acid (HCA) in hyperoxaluria-induced nephrolithiasis in vitro and in vivo. Crystal deposition and pathophysiological injury in rat models of glyoxylate-induced nephrolithiasis were examined using H&E staining. Cell models of nephrolithiasis were established by oxalate-treated renal tubular epithelial cells. The levels of oxidative stress indexes were determined by ELISA kits. Cell proliferation in vivo and in vitro was evaluated using a cell counting kit-8 (CCK-8) assay and Ki-67 cell proliferation detection kit. Cell apoptosis was measured by flow cytometry and TUNEL staining. The protein levels were examined by western blotting. Our results showed that HCA administration significantly reduced crystal deposition and kidney injury induced by glyoxylate. HCA also alleviated oxidative stress via upregulating the antioxidant enzyme activities of superoxide dismutase (SOD) and catalase (CAT) and reducing the malondialdehyde (MDA) content. Moreover, HCA treatment promoted cell proliferation and inhibited apoptosis of renal tubular epithelial cells exposed to hyperoxaluria. Of note, Nrf2 activator dimethyl fumarate (DMF) exerted the same beneficial effects as HCA in nephrolithiasis. Mechanistically, HCA prevented crystal deposition and oxidative stress induced by hyperoxaluria through targeting the Nrf2/Keap1 antioxidant defense pathway, while knockdown of Nrf2 significantly abrogated these effects. Taken together, HCA exhibited antioxidation and anti-apoptosis activities in nephrolithiasis induced by hyperoxaluria via activating Nrf2/Keap1 pathway, suggesting that it may be an effective therapeutic agent for the prevention and treatment of nephrolithiasis.

Acetate attenuates hyperoxaluria-induced kidney injury by inhibiting macrophage infiltration via the miR-493-3p/MIF axis

Hyperoxaluria is well known to cause renal injury and end-stage kidney disease. Previous studies suggested that acetate treatment may improve the renal function in hyperoxaluria rat model. However, its underlying mechanisms remain largely unknown. Using an ethylene glycol (EG)-induced hyperoxaluria rat model, we find the oral administration of 5% acetate reduced the elevated serum creatinine, urea, and protected against hyperoxaluria-induced renal injury and fibrosis with less infiltrated macrophages in the kidney. Treatment of acetate in renal tubular epithelial cells in vitro decrease the macrophages recruitment which might have reduced the oxalate-induced renal tubular cells injury. Mechanism dissection suggests that acetate enhanced acetylation of Histone H3 in renal tubular cells and promoted expression of miR-493-3p by increasing H3K9 and H3K27 acetylation at its promoter region. The miR-493-3p can suppress the expression of macrophage migration inhibitory factor (MIF), thus inhibiting the macrophages recruitment and reduced oxalate-induced renal tubular cells injury. Importantly, results from the in vivo rat model also demonstrate that the effects of acetate against renal injury were weakened after blocking the miR-493-3p by antagomir treatment. Together, these results suggest that acetate treatment ameliorates the hyperoxaluria-induced renal injury via inhibiting macrophages infiltration with change of the miR-493-3p/MIF signals. Acetate could be a new therapeutic approach for the treatment of oxalate nephropathy.

Successfully treated bronchopulmonary oxalosis caused by Aspergillus tubingensis in a non-neutropenic patient: A case report and review of the literature

Pulmonary oxalosis can be fatal, and Aspergillus tubingensis is commonly resistant to azoles in Japan. We report a case of bronchopulmonary oxalosis caused by A. tubingensis in a non-neutropenic patient who was successfully treated with voriconazole monotherapy. The susceptibility of the isolates to voriconazole and the effective elimination of contagious necrotic tissue by expectoration seemed to be two major factors contributing to the patient's survival. According to the literature review, pulmonary oxalosis is associated with a high mortality rate over a short term. An exploration of detailed information about the genomic characteristics and drug susceptibility of Aspergillus isolates is important for the development of treatment strategies for this life-threatening disease.

Nedosiran Dramatically Reduces Serum Oxalate in Dialysis-Dependent Primary Hyperoxaluria 1: A Compassionate Use Case Report

Primary hyperoxaluria 1 (PH1) is a devastating condition involving recurrent urolithiasis, early end-stage renal disease and multisystemic deposition of calcium oxalate crystals. Treatment options for PH1 are limited, inevitably requiring transplantation, usually combined kidney and liver transplant. Here we report successful compassionate use of Nedosiran, an RNA interference targeting lactate dehydrogenase, in an index patient. Monthly Nedosiran injections led to dramatically decreased plasma oxalate levels, decreased frequency of weekly hemodialysis sessions from 6 to 3, and deferral of combined kidney and liver transplant. Nedosiran represents a novel and impactful potential therapeutic for PH1 patients with end-stage renal disease.

Protective Effects of Quercetin on Oxidative Stress-Induced Tubular Epithelial Damage in the Experimental Rat Hyperoxaluria Model

Background and Objectives: The most common kidney stones are calcium stones and calcium oxalate (CaOx) stones are the most common type of calcium stones. Hyperoxaluria is an essential risk factor for the formation of these stones. Quercetin is a polyphenol with antioxidant, anti-inflammatory, and many other physiological effects. The aim of this study was to investigate the protective effect of quercetin in hyperoxaluria-induced nephrolithiasis. Materials and Methods: Male Wistar-Albino rats weighing 250–300 g (n = 24) were randomized into three groups: Control (n = 8), ethylene glycol (EG) (n = 8), and EG + quercetin (n = 8). One percent EG-water solution was given to all rats except for the control group as drinking water for five weeks. Quercetin-water solution was given to the EG + quercetin group by oral gavage at a dose of 10 mg/kg/day. Malondialdehyde (MDA), catalase (CAT), urea, calcium, and oxalate levels were analyzed in blood and urine samples. Histopathological assessments and immunohistochemical analyses for oxidative stress and inflammation indicators p38 mitogen-activated protein kinase (p38-MAPK) and nuclear factor kappa B (NF-kB) were performed on renal tissues. Results: The MDA levels were significantly lower in the quercetin-treated group than in the EG-treated group (p = 0.001). Although CAT levels were higher in the quercetin-treated group than the EG-administered group, they were not significantly different between these groups. The expression of p38 MAPK was significantly less in the quercetin-treated group than the EG group (p < 0.004). There was no statistically significant difference between the quercetin and EG groups in terms of NF-kB expression. Conclusions: We conclude that hyperoxaluria activated the signaling pathways, which facilitate the oxidative processes leading to oxalate stone formation in the kidneys. Our findings indicated that quercetin reduced damage due to hyperoxaluria. These results imply that quercetin can be considered a therapeutic agent for decreasing oxalate stone formation, especially in patients with recurrent stones due to hyperoxaluria.

ALLN-177, oral enzyme therapy for hyperoxaluria

Purpose

To evaluate the potential of ALLN-177, an orally administered, oxalate-specific enzyme therapy to reduce urine oxalate (UOx) excretion in patients with secondary hyperoxaluria.

Methods

Sixteen male and female subjects with both hyperoxaluria and a kidney stone history were enrolled in an open-label study. Subjects continued their usual diets and therapies. During a 3-day baseline period, two 24-h (24-h) urines were collected, followed by a 4-day treatment period with ALLN-177 (7,500 units/meal, 3 × day) when three 24-h urines were collected. The primary endpoint was the change in mean 24-h UOx from baseline. Safety assessments and 24-h dietary recalls were performed throughout.

Results

The study enrolled 5 subjects with enteric hyperoxaluria and 11 with idiopathic hyperoxaluria. ALLN-177 was well tolerated. Overall mean (SD) UOx decreased from 77.7 (55.9) at baseline to 63.7 (40.1) mg/24 h while on ALLN-177 therapy, with the mean reduction of 14 mg/24 h, (95% CI − 23.71, − 4.13). The calcium oxalate-relative urinary supersaturation ratio in the overall population decreased from a mean of 11.3 (5.7) to 8.8 (3.8) (− 2.8; 95% CI − 4.9, − 0.79). This difference was driven by oxalate reduction alone, but not any other urinary parameters. Mean daily dietary oxalate, calcium, and fluid intake recorded by frequent diet recall did not differ by study periods.

Conclusion

ALLN-177 reduced 24-h UOx excretion, and was well tolerated. The results of this pilot study provided justification for further investigation of ALLN-177 in patients with secondary hyperoxaluria.

Trial registration: Clinicaltrials.gov NCT02289755.

A Double-Blind, Placebo Controlled, Randomized Phase 1 Cross-Over Study with ALLN-177, an Orally Administered Oxalate Degrading Enzyme

BACKGROUND

Hyperoxaluria may result from increased endogenous production or overabsorption of dietary oxalate in the gastrointestinal tract leading to nephrolithiasis and, in some, to oxalate nephropathy and chronic kidney disease. ALLN-177 is an oral formulation of a recombinant, oxalate specific, microbial enzyme oxalate decarboxylase intended to treat secondary hyperoxaluria by degrading dietary oxalate in the gastrointestinal tract, thereby reducing its absorption and subsequent excretion in the urine.

METHODS

This double-blind, placebo controlled, randomized, cross-over, phase 1 study of ALLN-177 evaluated the tolerability of ALLN-177 and its effect on urinary oxalate excretion in 30 healthy volunteers with hyperoxaluria induced by ingestion of a high oxalate, low calcium (HOLC) diet. The primary end point was the difference in the mean 24-hour urinary oxalate excretion during the ALLN-177 treatment period compared with the placebo treatment period.

RESULTS

The daily urinary oxalate excretion increased in the study population from 27.2 ± 9.5 mg/day during screening to 80.8 ± 24.1 mg/day (mean ± SD) on the HOLC diet before introducing ALLN-177 or placebo therapy for 7 days. Compared to placebo, ALLN-177 treatment reduced urinary oxalate by 11.6 ± 2.7 mg/day, p = 0.0002 (least squares mean ± SD).

CONCLUSIONS

In healthy volunteers, with diet-induced hyperoxaluria treatment with ALLN-177, when compared to placebo, significantly reduced urinary oxalate excretion by degrading dietary oxalate in the gastrointestinal tract and thereby reducing its absorption. ALLN-177 may represent a new approach for managing secondary hyperoxaluria and its complications.

Polyacrylic acid attenuates ethylene glycol induced hyperoxaluric damage and prevents crystal aggregation in vitro and in vivo

The study explores calcium oxalate crystal inhibiting characteristic of polyacrylic acid (pAA), an anionic polymer in in vitro and in vivo. Animals were divided into 5 groups where group 1 served as control, group 2 were made hyperoxaluric by supplementing with Ethylene glycol (EG) 0.75% (v/v) for 30 days. Group 3, 4 & 5 were also given with EG and treated simultaneously with 2.5, 5 & 10 mg of pAA/kg of body weight, respectively. Urine, serum and tissue analyses along with histological studies were performed at the end of the 30 days study. In vitro crystallization was significantly inhibited by pAA and further it was supported by particle size analyses, XRD and FT-IR studies. Toxicological analyses showed that pAA was safe to use in animals at concentrations below 100 mg/kg BW. In vivo anti-urolithic study showed significant improvement in urinary lithogenic factors (calcium, oxalate, phosphate, citrate & magnesium) and renal function parameters (creatinine, urea and protein). Tissue analyses on anti-oxidant enzyme activity and lipid peroxides showed maintenance of tissue antioxidant status in the pAA supplemented rats and histological studies demonstrated the nephroprotection offered by pAA and were concurrent to the biochemical analyses. Supplementation of pAA not only reduces the crystal aggregation but also regulates the expression and localization of crystal inhibiting proteins and gene expression of inflammatory cytokines in experimental animals. In summary, pAA is a potent anti-urolithic agent in rats and we can propose that 10 mg/kg body weight is the effective dosage of pAA and this concentration can be used for further studies.

The most potent antilithiatic agent ameliorating renal dysfunction and oxidative stress from Bergenia ligulata rhizome

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizome of Bergenia ligulata is referred by the Ayurvedic system for the treatment of kidney stone since decades and a few, in vitro and in vivo studies also support it. To identify the main phytochemical constituent(s) responsible for antilithiatic activity of its rhizome.

MATERIALS AND METHODS

In order to identify the most potent antilithiatic metabolite, the crude extract of rhizome was fractionated using in vitro Calcium oxalate (CaOx) crystal growth inhibitory activity guided fractionation followed by its characterization via LC-MS, FTIR and NMR. Further, the antioxidant potential of purified molecule was assessed using in vitro assays (FRAP and H2O2 scavenging). In vivo activity of the metabolite was evaluated in hyperoxaluric rats given 0.4% ethylene glycol (EG) and 1.0% ammonium chloride (NH4Cl) for 9 days.

RESULTS

Activity guided fractionation led to the isolation of most potent antilithiatic metabolite from the rhizome of Bergenia ligulata and spectroscopic analysis revealed it as bergenin. Bergenin showed reducing ability and H2O2 scavenging activity comparable with commercially available anitioxidant, α-tocopherol. At a dose of 10mg/kg body weight of the treated rat, it protected against deleterious effects of lithogenic treatment including weight loss, impaired renal function and oxidative stress, manifested as increased malondialdehyde, reduced redox ratio and decreased antioxidant enzyme activities in the kidneys of hyperoxaluric rats. The creatinine clearance and kidney damage were more improved by bergenin as compared to crude extract of rhizome.

CONCLUSIONS

Since, bergenin maintained oxidant/antioxidant balance in hyperoxaluric rats, thus mechanistic insight of its antilithiatic activity was attributed to the antioxidant capability of bergenin. The results of the present study provide significant evidence that bergenin is an active component present in the rhizome of Bergenia ligulata for managing CaOx calculi.

Novel effect of the inhibitor of mitochondrial cyclophilin D activation, N-methyl-4-isoleucine cyclosporin, on renal calcium crystallization

OBJECTIVES

To experimentally evaluate the clinical application of N-methyl-4-isoleucine cyclosporin, a novel selective inhibitor of cyclophilin D activation.

METHODS

In vitro, cultured renal tubular cells were exposed to calcium oxalate monohydrate crystals and treated with N-methyl-4-isoleucine cyclosporin. The mitochondrial membrane was stained with tetramethylrhodamine ethyl ester perchlorate and observed. In vivo, Sprague-Dawley rats were divided into four groups: a control group, an ethylene glycol group (administration of ethylene glycol to induce renal calcium crystallization), a N-methyl-4-isoleucine cyclosporin group (administration of N-methyl-4-isoleucine cyclosporin) and an ethylene glycol + N-methyl-4-isoleucine cyclosporin group (administration of ethylene glycol and N-methyl-4-isoleucine cyclosporin). Renal calcium crystallization was evaluated using Pizzolato staining. Oxidative stress was evaluated using superoxide dismutase and 8-hydroxy-deoxyguanosine. Mitochondria within renal tubular cells were observed by transmission electron microscopy. Cell apoptosis was evaluated using cleaved caspase-3.

RESULTS

In vitro, calcium oxalate monohydrate crystals induced depolarization of the mitochondrial membrane potential, which was remarkably prevented by N-methyl-4-isoleucine cyclosporin. In vivo, ethylene glycol administration induced renal calcium crystallization, oxidative stress, mitochondrial collapse and cell apoptosis in rats, which were significantly prevented by N-methyl-4-isoleucine cyclosporin.

CONCLUSIONS

Herein we first report a new treatment agent determining renal calcium crystallization through cyclophilin D activation.

Therapeutic effect of inulin on enteric hyperoxaluria in rats

OBJECTIVE

To observe the therapeutic effect of inulin on enteric hyperoxaluria in rats.

METHODS

In experimental A, 24 healthy male Sprague-Dawley rats received an oxalate-free diet on day 1, a high-oxalate diet (oxalate, 74.82 mg/100 g feed stuffs) on days 2 and 3, and plus 2 g inulin to each rat on day 3. The 24-hour urinary volume, concentrations of urinary oxalate and urine creatinine were measured, and 24-hour urinary oxalate excretion was calculated. In experimental B, 24 healthy male Sprague-Dawley rats were equally randomized into control group and inulin group, Each rat received a high oxalate diet (oxalate, 74.82 mg/100 g feedstuffs), and plus 2 g inulin in inulin group. The 24-hour urinary oxalate excretion was calculated in both two groups.

RESULTS

In experimental A, the 24-hour urinary oxalate excretion varied with time (F=11.481, P=0.035). The 24-hour urinary oxalate excretion significantly increased on day 2 compared with that on day 1 (P=0.026) and day 3 (P=0.037); it significantly increased on day 3 compared with day 1 (P=0.004). In experimental B, the 24-hour urinary oxalate excretion significantly decreased in inulin group compared with the control (P=0.011).

CONCLUSION

Inulin may have potential therapeutic effect on enteric hyperoxaluria in rats.

[The treatment of patients with broncho-pulmonary pathology and concomitant disturbances of oxalic acid metabolism]

This work was aimed at estimating the role of special therapy of patients with bronchial asthma, COPD and hyperoxaluria designed to restrict the delivery or eliminate excess of oxalates and producing well apparent beneficial effect confirmed by the disappearance or decrease of clinical and functional manifestations of obstruction, reduction of requirements for broncholytic and anti-inflammatory agents.

Aqueous extract of Boerhaavia diffusa root ameliorates ethylene glycol-induced hyperoxaluric oxidative stress and renal injury in rat kidney

INTRODUCTION

Boerhaavia diffusa Linn. (Nyctaginaceae) is widely used in traditional Indian medicines against renal afflictions including calcium oxalate (CaOx) urolithiasis and is known for antioxidant activity.

OBJECTIVE

The present study was designed to investigate the ameliorating effect of aqueous extract of B. diffusa roots (BDE) in hyperoxaluric oxidative stress and renal cell injury.

MATERIAL AND METHODS

In vitro antioxidant activity of BDE was estimated in terms of total phenolic content and 1,1-diphenyl-2-picryl hydrazyl free radical scavenging activity. Wistar albino rats were given 0.75% v/v ethylene glycol in drinking water to induce chronic hyperoxaluria and simultaneously BDE was given to nephrolithiasic treated rats at the dose of 100 and 200 mg/kg b.w. orally for 28 days. Urinary volume, oxalate, serum creatinine, blood urea nitrogen (BUN), malondialdehyde (MDA) and antioxidant enzyme (SOD, CAT, GST, GPx) were evaluated.

RESULTS AND DISCUSSION

BDE extract was found to posses a high total phenolic content and exhibited significant free radicals scavenging activity. Oxalate excretion significantly increased in hyperoxaluric animals as compared to control which was protected in BDE-treated animals. BDE treatment significantly reduced level of MDA and improved the activity of antioxidant enzymes followed by reduction in BUN and serum creatinine. In addition, BDE reduced the number of CaOx monohydrate crystals in the urine. Histological analysis depicted that BDE treatment inhibited deposition of CaOx crystal and renal cell damage.

CONCLUSION

The present study reveals that antioxidant activity of BDE significantly protects against hyperoxaluric oxidative stress and renal cell injury in urolithiasis.

The Interaction between female sex hormone receptors and osteopontin in a rat hyperoxaluric model

It is well known that the incidence of urinary stones is higher in men than women. Although it is believed that the lower incidence of urinary stones in women is due to a protective effect of estrogen, the mechanisms remain unclear. To clarify the relation between female sex hormones and stone matrix protein, we examined the interaction of estrogen receptor-α (ERα), estrogen receptor-related receptor-α (ERRα), and stone matrix protein osteopontin (OPN) in a rat hyperoxaluric model and in primary cultured rat kidney cells. Adult female Wistar rats were divided into 6 groups. Groups 1 and 4 consisted of normal females, Groups 2 and 5 consisted of ovariectomized females, and Groups 3 and 6 consisted of ovariectomized females receiving female sex hormone supplements. Groups 1-3 were administered distilled water, while groups 4-6 were administered 0.5% ethyleneglycol (EG). Moreover, rat kidney primary cultured cells were examined after treatment with female sex hormones under various conditions. The expressions of ERα, ERRα and OPN-mRNA in whole kidney and primary cultured cells were examined using Real-Time PCR. The expressions of OPN and ERRα-mRNA were suppressed by ovariectomy. Supplementation with female sex hormones increased the expression of OPN and ERRα-mRNA. In contrast, the expression of ERα-mRNA was increased by ovariectomy and suppressed by supplementation with female sex hormones. The results of the mRNA expression in primary cultured cells matched those in the hyperoxaluric model rats. Although the reason for the difference in expression between ERα and ERRα-mRNA is unclear, estrogen may regulates OPN expression through ERα and/or ERRα, either independently or in combination. Moreover, the decrease of OPN induced by removal of estrogen may increase urinary stones in postmenopausal women.

Reversal of Hyperoxaluria-Induced Alteration in Rat Liver by Administration ofN-Acetylcysteine

The current work was designed to study the potential of N-acetylcysteine (NAC) in modulating hyperoxaluric manifestations induced by acute oxalate dose in rat liver. Hyperoxaluric conditions were induced by giving a single dose of sodium oxalate (70 mg/kg body weight) in one group, and in the other group, hyperoxaluric rats were administered NAC (200 mg/kg body weight) after 30 min of the oxalate dose. After 12 h of the above treatment, blood was taken from the orbital sinus for testing serum oxalate, and animals were sacrificed. To exploit the potential of NAC, various oxidative stress parameters [lipid peroxidation (LP) and activity of antioxidant enzymes], lipid content, and histologic analysis of rat liver were performed. The increased level of LP and activities of superoxide dismutase and catalase in hyperoxaluric rats were restored after NAC treatment. Not only the decreased amount of total lipids and phospholipids but also the increased ratio of cholesterol/phospholipid (showing decreased membrane fluidity) in hyperoxaluric rats were balanced by NAC treatment. Further restored histologic changes of liver tissue confirmed the protective antioxidant effects of the given drug. Thus, N-acetylcysteine being an extraneous antioxidant showed curative properties toward hyperoxaluric manifestations in liver.

Antiurolithic effect of lupeol and lupeol linoleate in experimental hyperoxaluria

The present study was undertaken to explore the efficiency of the pentacyclic triterpene lupeol (1) and its ester derivative, lupeol linoleate (2), in experimental hyperoxaluria. Hyperoxaluria was induced in male Wistar rats with 0.75% ethylene glycol (EG) in drinking water for 28 days. Hyperoxaluric animals were supplemented orally with 1 and 2 (50 mg/kg body wt/day) throughout the experimental period of 28 days. The renal enzymes were assayed as markers of renal tissue integrity. The redox status and oxalate metabolism in animals under oxalate overloading was also assessed. Microscopic analysis was done to investigate the abnormalities associated with oxalate exposure in renal tissues. Increase in oxidative milieu in hyperoxaluria was evident by increased lipid peroxidation (LPO) and decreased enzymic and nonenzymic antioxidants. Decrease in the activities of renal enzymes exemplified the damage induced by oxalate, which correlated positively with increased LPO and increased oxalate synthesis. Renal microscopic analysis further emphasized the oxalate-induced damage. These abnormal biochemical and histological aberrations were attenuated with test compound treatment, with 2 more effective than 1. From the present study, it can be concluded that 1 and 2 may serve as candidates for alleviating oxalate toxicity.

Hyperoxaluria is reduced and nephrocalcinosis prevented with an oxalate-degrading enzyme in mice with hyperoxaluria

BACKGROUND/AIMS

Hyperoxaluria is a major risk factor for recurrent urolithiasis and nephrocalcinosis. We tested an oral therapy with a crystalline, cross-linked formulation of oxalate-decarboxylase (OxDc-CLEC) on the reduction of urinary oxalate and decrease in the severity of kidney injury in two models: AGT1 knockout mice (AGT1KO) in which hyperoxaluria is the result of an Agxt gene deficiency, and in AGT1KO mice challenged with ethylene glycol (EG).

METHODS

Four different doses of OxDc-CLEC mixed with the food, or placebo were given to AGT1KO mice (200 mg/day, n = 7) for 16 days and to EG-AGT1KO mice (5, 25, and 80 mg, n = 11) for 32 days.

RESULTS

Oral therapy with 200 mg OxDc-CLEC reduced both urinary (44%) and fecal oxalate (72%) in AGT1KO mice when compared to controls. Similarly, in EG-AGT1KO mice, each of the three doses of OxDc-CLEC produced a 30-50% reduction in hyperoxaluria. A sustained urinary oxalate reduction of 40% or more in the 80 mg group led to 100% animal survival and complete prevention of nephrocalcinosis and urolithiasis.

CONCLUSION

These data suggest that oral therapy with OxDc-CLEC may reduce hyperoxaluria, prevent calcium oxalate nephrocalcinosis and urolithiasis, and can represent a realistic option for the treatment of human hyperoxaluria, independent of cause.

Effect of sulphated polysaccharides on erythrocyte changes due to oxidative and nitrosative stress in experimental hyperoxaluria

Kidney stones are known to haunt humanity for centuries and increase in oxalate is a predominant risk factor for stone formation. The present study was initiated with a notion to study the oxidative and nitrosative stress on erythrocytes under oxalate stress and the putative role of sulphated polysaccharides. Hyperoxaluria was induced in two groups by the administration of 0.75% ethylene glycol in drinking water for 28 days and one of them was treated with sulphated polysaccharides from Fucus vesiculosus from the 8th day to the end of the experimental period of 28 days at a dose of 5 mg/kg body weight subcutaneously. Control and drug control (sulphated polysaccharides alone) were also included in the study. Glycolic and glyoxylic acid levels of urine were analyzed as an index of hyperoxaluria. The plasma enzymic markers of cellular integrity, redox status of red blood cells, osmotic fragility, and (14)C-oxalate binding were investigated. Urine and plasma nitric oxide metabolites, expression of inducible nitric oxide synthase protein, and mRNA were assessed in kidney to evaluate the nitrosative stress. Increased levels of glycolic and glyoxylic acid in urine indicated the prevalence of hyperoxaluria in ethylene glycol-administered groups. Plasma aspartate and alanine transaminase were not altered, but alkaline phosphatase and lactate dehydrogenase of hyperoxaluric group were increased indicating tissue damage. Activities of antioxidant enzymes were decreased, whereas erythrocyte membrane lipid peroxidation was increased in hyperoxaluric rats. Moreover, an altered fragility with an increase in oxalate binding activity was observed in hyperoxaluric group. Increase in nitric oxide metabolites levels in urine and plasma along with an increase in expression of inducible nitric oxide synthase protein and mRNA in kidney were observed in hyperoxaluric rats. Administration of sulphated polysaccharides to hyperoxaluric rats averted the abnormal increase in urinary glycolic and glyoxylic acid levels and enzyme activities, decreased lipid peroxidation, and increased the activities of antioxidant enzymes. Furthermore, increased nitrosative stress accompanying hyperoxaluria was also normalized on sulphated polysaccharides treatment. To conclude, sulphated polysaccharide administration was able to maintain the integrity of erythrocyte membrane and decrease the damage to erythrocytes in hyperoxaluria.

Drug delivery to peroxisomes: employing unique trafficking mechanisms to target protein therapeutics

Peroxisomes are multifunctional organelles of all human cells, responsible for a variety of essential biochemical and metabolic processes including alpha- and beta-oxidation of specific fatty acids, plasmalogen biosynthesis and glyoxylate detoxification. Inborn errors of biogenesis or in the ability to synthesize or properly traffic specific enzymes to peroxisomes result in devastating human disease. The organelle has also emerged as a contributor to cellular oxidative stress through its ability to generate hydrogen peroxide. Unlike most other organelles, the peroxisome's import apparatus will accommodate fully folded, oligomeric and co-factor-bound substrates. The strategies outlined here are designed to take advantage of this unique mechanism to target protein therapeutics. Emphasis is also placed on how to deliver these bioactive molecules into cells to engage the peroxisomal protein import machine. The critical antioxidant enzyme catalase has been successfully delivered and targeted by many of the approaches detailed herein; these examples will be discussed.

Physico-chemical alterations of urine in experimental hyperoxaluria: a biochemical approach with fucoidan

Urinary supersaturation-induced crystal formation has been attributed as one of the key factor for the pathogenesis/progression of lithogenesis. This study was aimed at investigating whether fucoidan, a naturally occurring sulfated glycosaminoglycan, could ameliorate the biochemical changes in urine induced by stone formation. Two groups of male albino Wistar rats (120+/-20 g) received 0.75% ethylene glycol (EG) for 28 days to induce hyperoxaluria, and one of them received sulfated polysaccharides (fucoidan from Fucus vesiculosus, 5 mg kg(-1), s.c.), commencing from the 8(th) day of the experimental period. One group was maintained as normal control group and another group served as drug control, which received sulfated polysaccharides. The urine collected from all the groups was analysed for changes in pH, volume, oxalate, calcium, phosphorus, uric acid, magnesium, citric acid and glycosaminoglycans. Urinary crystals were analysed with a light microscope. Renal tissues were studied under polarized light for deposition of crystals and also analysed for their oxalate and calcium content. The changes in extracellular matrix on crystal deposition were also evaluated. The urinary pH and volume were altered in rats treated with EG along with an increase in weight of the kidney. Further, administration of EG to rats increased the supersaturation of urine by escalating the levels of the stone-forming constituents, such as oxalate, calcium, phosphorus and uric acid, which was completely restored by fucoidan treatment. The decrease in the inhibitors, like citrate, magnesium and glycosaminoglycans, in urine was prevented by the co-treatment with fucoidan. In hyperoxaluric rats, there was an increased excretion of calcium oxalate monohydrate crystals in urine along with crystal deposition in renal tissues; this was prevented by fucoidan treatment. Fucoidan administration reversed even the tissue levels of calcium and oxalate. The increased accumulation of collagen and expression of transforming growth factor-beta(1) in hyperoxaluria was normalized on fucoidan administration. These results suggest that the physico-chemical alterations in urine produced during hyperoxaluria can be reversed by fucoidan administration.

Hyperoxaluria in women with vulvar vestibulitis syndrome

OBJECTIVE

To determine whether evaluation and treatment of hyperoxaluria in vulvar vestibulitis syndrome (VVS) is justified.

STUDY DESIGN

Forty women (mean age, 24.5 years; range, 18-35) diagnosed with VVS at a sex therapy clinic participated. Diagnosis of VVS relied upon Friedrich's criteria: (1) severe vulvar vestibular pain upon touch or attempted vaginal entry, (2) tenderness to pressure localized within the vulvar vestibule, and (3) physical findings confined to vulvar erythema of various degrees. Oxalate was measured in 24-hour urine samples. Women with hyperoxaluria (urine oxalate >50 mg/24 h) were placed on a low-oxalate diet and oral calcium citrate as single therapy and reevaluated 3 months later.

RESULTS

Hyperoxaluria was diagnosed in 7 women (17.5%), of whom 1 demonstrated an objective improvement and could have pain-free vaginal intercourse following treatment, yielding a 2.5% benefit from the evaluation and treatment of hyperoxaluria.

CONCLUSION

There is no justification for evaluation and treatment of hyperoxaluria in women with VVS due to its low yield and economic burden.

Hyperoxaluria-induced oxidative stress and antioxidants for renal protection

Renal cellular exposure to oxalate (Ox) and/or CaOx crystals leads to the production of reactive oxygen species (ROS), development of oxidative stress followed by injury and inflammation. Renal injury and inflammation appear to play a significant role in stone formation. ROS are produced from many sources and involve a variety of signaling pathways. Tissue culture and animal model studies show that treatments with anti-oxidants and free radical scavengers reduce Ox/CaOx crystal induced injuries. In addition, CaOx crystal deposition in kidneys is significantly reduced by treatments with antioxidants and free radical scavengers, indicating their efficacy. These results point towards a great potential for the therapeutic application of antioxidants and free radical scavengers to reduce stone recurrence particularly after shock wave lithotripsy, which is itself known to generate ROS and cause renal damage.

Oral L-arginine supplementation ameliorates urinary risk factors and kinetic modulation of Tamm-Horsfall glycoprotein in experimental hyperoxaluric rats

BACKGROUND

Oral supplementation of l-arginine (l-arg) is found to be beneficial in many kidney disorders. We determined whether l-arg supplementation safeguards the renal epithelial cell damage induced by hyperoxaluria with excretion of urinary marker enzymes and lithogenic salts with special reference to Tamm-Horsfall glycoprotein (THP).

METHODS

Hyperoxaluria was induced by 0.75% ethylene glycol (EG) in drinking water. l-Arg was co-supplemented at the dose of 1.25 g/kg b.w. orally for 28 days. At the end of experimental period, 24-h urine samples were collected in all the experimental groups. Isolation and purification of THP was carried in rat urine and were subjected to spectrophotometric crystallization assay and calcium-(14)C-oxalate binding studies. Determination of the lithogenic risk factors like calcium, oxalate, phosphorus, citrate, and marker enzymes such as lactate dehydrogenase (LDH) and gamma-glutamyltransferase (gamma-GT) were carried out in the collected urine sample.

RESULTS

Urinary excretion of calcium and oxalate was significantly increased in EG-treated rats. In l-arg supplemented hyperoxaluric rats, these concentrations were significantly (p<0.001) decreased when compared to that of hyperoxaluric rats, and were moderately elevated from that of control rats. The activities of urinary marker enzymes, both LDH and gamma-GT were 2-fold increased in EG-treated rats, when compared to control rats, but these values were maintained near normal in l-arg supplemented EG-treated rats. Citrate excretion was enhanced in the l-arg co-supplemented hyperoxaluric rats. In spectrophotometric crystallization assay system, l-arg supplemented rat THP showed inhibition in nucleation and aggregation phases, whereas EG-treated rat THP showed promotion of both calcium oxalate nucleation and aggregation phases. In calcium-(14)C-oxalate binding assay, THP derived from hyperoxaluric rats exhibited 2-fold increase (p<0.001) in the Ca*Ox binding when compared to control and l-arg supplemented animals.

CONCLUSIONS

l-Arg could act as a potent antilithic agent, by increasing the level of citrate in the hyperoxaluria-induced rats and decreasing calcium oxalate binding to the THP. l-Arg also effectively prevents the deposition of calcium oxalate crystals by curtailing the renal epithelial damage and protein oxidation as evidenced by the normal activities of urinary marker enzymes in l-arg supplemented hyperoxaluric rats.

Counteraction of oxalate induced nitrosative stress by supplementation of l-arginine, a potent antilithic agent

BACKGROUND

Our understanding of nitrosative stress in the process of urolithiasis is far from complete. Earlier studies carried out in our laboratory demonstrate the presence of nitrated THP in stone formers, l-arginine (l-arg) a precursor of nitric oxide (NO), attenuates the endothelial dysfunction caused by reactive nitrogen species. We investigated the role of l-arg in ethylene glycol (EG)-induced urolithic rat model and observed its antilithic and antioxidative properties.

METHODS

Hyperoxaluria was induced using 0.75% EG in drinking water. l-arg [1.25 g/kg body weight] was given orally for a period of 28 days.

RESULTS

EG-treated rats showed significant loss in body weight and increase in the activities of oxalate synthesizing enzymes such as glycollic acid oxidase in liver. Lactate dehydrogenase activity in liver and kidney was increased. The activity of the free radical producing enzyme xanthine oxidase, tissue oxalate and calcium levels were significantly increased in EG-treated rats. Depletion in the antioxidant enzymes, membrane bound ATPases and thiol status was observed in these rats. l-arg co-supplementation to EG-treated rats maintained the activities of the oxalate synthesizing enzymes and free radical producing enzymes with in the normal range. Tissue oxalate and calcium levels were also maintained near normal in l-arg treated hyperoxaluric rats. l-arg, by its cytoprotective effect, maintained the thiol status, thereby preserving the activities of the membrane bound ATPases and preventing proteinuria and subsequent weight loss in EG-treated rats.

CONCLUSION

l-arg feeding prevents the retention of calcium oxalate crystals in hyperoxaluric rats by way of protecting the renal cells from oxidative injury and also by providing a second line of defense through the normalization of the oxalate metabolism. It reduces the risk of stone formation, by curtailing free radicals and hyperoxaluria as both of them have to work in close association to form stones.

Diagnostic and therapeutic approaches in patients with secondary hyperoxaluria

Secondary hyperoxaluria is due either to increased intestinal oxalate absorption or to excessive dietary oxalate intake. Certain intestinal diseases like short bowel syndrome, chronic inflammatory bowel disease or cystic fibrosis and other malabsorption syndromes are known to increase the risk of secondary hyperoxaluria. Although the urinary oxalate excretion is usually lower than in primary hyperoxaluria, it may still lead to significant morbidity by recurrent urolithiasis or progressive nephrocalcinosis. A clear distinction between primary and secondary hyperoxalurias is important. As correct classification may be difficult, appropriate diagnostic tools are needed to delineate the metabolic background as a basis for optimal treatment. We developed an individual approach for the evaluation of patients with suspected secondary hyperoxaluria. First, 24 h urines are examined repeatedly for lithogenic (e.g. calcium, oxalate, uric acid) and stone-inhibitory (e.g. citrate, magnesium) substances, and the patients are asked to fill in a dietary survey form. Urinary saturation is calculated using the computer based program EQUIL2, and the BONN-Risk-index is determined. The measurement of plasma oxalate and of urinary glycolate helps to distinguish between primary and secondary hyperoxalurias. If secondary hyperoxaluria is suspected, the stool is examined for Oxalobacter formigenes, an intestinal oxalate degrading bacterium, as lack or absence may lead to increased intestinal oxalate absorption. The last diagnostic step is to study the intestinal oxalate absorption using [13C2]oxalate. Depending on the results, various therapeutic options are available: 1) a diet low in oxalate, but normal or high in calcium, 2) a high fluid intake (>1.5 L/m2/d), 3) medications to increase the urinary solubility, 4) specific therapeutic measures in patients with malabsorption syndromes, depending on the underlying pathology, and 5) intestinal recolonization of Oxalobacter formigenes or the treatment with other oxalate degrading bacteria.

[The results of conservative treatment of oxalate urolithiasis in children]

Hyperoxaluria is defined as urinary oxalate excretion exceeding 0.45 mmol/1.73 m2/day and accounts for 15% of recurrent urolithiasis. There have been only a few reports on the prevalence and treatment of oxalate urolithiasis in children.

THE AIM

Of the study was to assess the efficacy and safety of the protocol of intensive and combined treatment of hyperoxaluria in children.

MATERIAL AND METHODS

Seventeen children at the mean age of 11.5 +/- 4.5 years with positive history of urolithiasis and diagnosis of hyperoxaluria were studied. In this group hyperoxaluria was an isolated defect in 9 of 17 children, but in 3/17 it was accompanied by hyperuricosuria, in 5/17 by hypomagnesuria and in 1 case by hypercalciuria. During the 12-month period the children were intensively hydrated and received a low-oxalate diet and supplemental therapy with vitamin B6, magnesium, citrates and lactic acid bacteria preparations.

RESULTS

In all but one child oxaluria decreased below 0.45 mmol/1.73 m2/day (decrease by 45%). No new stone formation was seen during the observation period. In all patients abdominal pain and haematuria subsided.

CONCLUSIONS

We conclude that the intensive, complex, conservative treatment of hyperoxaluria in children is effective and safe. It allows to decrease hyperoxaluria and prevent the recurrence of urolithiasis.

Conjugated bile acid replacement therapy reduces urinary oxalate excretion in short bowel syndrome

BACKGROUND

Patients with short bowel syndrome (SBS) have steatorrhea, in part because of bile acid malabsorption that causes decreased bile acid secretion into the duodenum and consequent fat maldigestion. In SBS patients with colon in continuity, luminal calcium forms calcium fatty acid soaps rather than precipitating as insoluble calcium oxalate. Soluble oxalate is hyperabsorbed by the colon leading to hyperoxaluria and an increased risk for renal calcium oxalate stones and deposits. The authors hypothesized that oral ingestion of conjugated bile acids would increase fat absorption and thereby decrease calcium fatty acid soap formation and oxalate hyperabsorption.

METHODS

The effect of conjugated bile acid replacement therapy (9 g/d) on fecal fat excretion and urine oxalate excretion was measured in an appropriate patient, utilizing the metabolic balance technique. The effects of chronic bile acid replacement therapy on oxalate excretion and nutritional status also were measured in a 3-month outpatient study.

RESULTS

Natural conjugated bile acid replacement therapy reduced fecal fat excretion from 119 to 79 g/d (Delta40 g/d), and urinary oxalate excretion from 87 to 64 mg/d (966 to 710 micromol/d; Delta23 mg/d). Cholylsarcosine, a synthetic conjugated bile acid, had similar but less powerful effects. During a 3-month outpatient trial of natural conjugated bile acids (9 g/d), urine oxalate decreased to normal levels (27 mg/d) in association with weight gain, decreased hunger, and decreased hyperphagia.

CONCLUSION

Conjugated bile acid replacement therapy reduced fecal fat excretion, reduced urinary oxalate excretion, and improved nutritional status in a patient with SBS with colon in continuity, hyperoxaluria, and oxalate nephrolithiasis.

The preventive effect of sodium pentosan polysulfate against renal stone formation in hyperoxaluric rats

Sodium pentosan polysulfate (SPP), a semi-synthetic glycosaminoglycan, was administered to rats with hyperoxaluria, induced by a vitamin B6 deficient diet, as a model of calcium oxalate stone formation. We studied the preventive effects of SPP on stone formation as well as its inhibitory effects on stone growth by autoradiography and radioluminography after intravenous injection of (14)C-oxalate. The rats were divided into non-treated and SPP-treated groups. The non-treated rats were divided into three groups: one group was fed a regular diet, while the other two groups were fed a vitamin B6 deficient diet for 2 and 4 weeks, respectively. The SPP-treated rats were divided into two groups: one group was intravenously injected with SPP from the start of the vitamin B6 deficient diet for a total of 4 weeks and the other group was injected with the same amount of SPP after 2 weeks of the diet for 2 weeks. (14)C-oxalate renal macroautoradiograms were prepared, and calcium oxalate deposits in the renal tissues were compared between the non-treated and SPP-treated groups. The preventive effects on calcium oxalate stone formation were clearly observed in the group injected with SPP for 4 weeks. Even in the other SPP-treated group, in which the administration of SPP was started at 2 weeks after the start of the diet when calcium oxalate stone formation was already observed, the size of the calcium oxalate deposits observed after 4 weeks was smaller than that in the non-treated group fed a vitamin B6 deficient diet for 4 weeks. In conclusion, our results show that SPP has not only preventive effects on calcium oxalate stone formation but also growth inhibitory effects on stones in hyperoxaluric rats.

Evaluation of the effect of triterpenes on urinary risk factors of stone formation in pyridoxine deficient hyperoxaluric rats

Investigations were carried out to evaluate the efficacy of the pentacyclic triterpene, lupeol and its ester, lupeol linoleate, against calcium oxalate urolithiasis in rats. Administration of a pyridoxine deficient diet containing 3% glycollic acid for 21 days led to increased excretion of stone forming constituents such as calcium, oxalate and uric acid. Crystal deposition and subsequent renal tubular damage resulted in increased excretion of the tubular enzymes alkaline phosphatase, lactate dehydrogenase, gamma glutamyl transferase, beta glucuronidase and N-acetyl glucosaminidase along with reduced fibrinolytic enzymes. A reduction in the urinary inhibitory factors magnesium and glycosaminoglycans was also observed. Treatment with lupeol and lupeol linoleate reduced the extent of tubular damage as evidenced from reduced enzymuria and minimized the excretion of stone forming constituents.

Mitigation of free radical toxicity in hyperoxaluric condition by a novel derivative eicosapentaenoate-lipoate

Lipoic acid (LA) and eicosapentaenoic acid (EPA) have been shown to ameliorate the changes associated with hyperoxaluria. This prompted us to study the effect of EPA-LA, a new derivative, in experimental urolithiatic condition. Foreign body implantation method followed by supplementation of ammonium oxalate was adopted to induce stone formation in the bladder. Significant depletion in the antioxidant status was observed in the kidney and bladder of stone-forming animals, associated with increased lipid peroxidation. The present observations provide supporting evidence to the hypothesis that free radicals might be involved in causing toxicity in hyperoxaluric condition. The three drugs, namely LA, EPA and EPA-LA had reversed the above changes, but the effect was more pronounced in EPA-LA-treated stone formers. These features highlight the beneficial effect of EPA-LA wherein the potency of two drugs has been combined. The practical outcome of these findings is that the cellular antioxidant defence can be increased by the supplementation of lipoate and its derivative EPA-LA.

Attenuation of oxalate-induced nephrotoxicity by eicosapentaenoate-lipoate (EPA-LA) derivative in experimental rat model

Hyperoxaluria is one of the major risk factors for the formation of urinary calcium oxalate stones. Calcium oxalate crystals and their deposition have been implicated in inducing renal tubular damage. Lipoic acid (LA) and eicosapentaenoic acid (EPA) have been shown to ameliorate the changes associated with hyperoxaluria. This prompted us to investigate the nephroprotectant role of EPA-LA, a new derivative, in vivo in hyperoxaluric rats. Elevation in the levels of calcium, oxalate and phosphorus, the stone-forming constituents, were observed in calculogenic rats as a manifestation of crystal deposition. Tubular damage to the renal tissue was assessed byassaying the excretion of marker enzymes in the urine. Damage to the tubules was indicated by increased excretion of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (gamma-GT), beta-Glucuronidase (beta-GLU) and N-Acetyl beta-D glucosaminidase (NAG). Fibrinolytic activity was found to be reduced. Administration of EPA, LA and EPA-LA reduced the tubular damage and decreased the markers of crystal deposition markedly, which was substantiated by the reduction in weight of bladder stone formed. Our results highlight that EPA-LA is the most effective drug in inhibiting stone formation and mitigating renal damage caused by oxalate toxicity, thus confirming it as a nephroprotectant. Further work in this direction is warranted to establish the therapeutic effectiveness of this new derivative.

Protective role of enalapril for chronic tubulointerstitial lesions of hyperoxaluria

PURPOSE

Hyperoxaluria is a recognized cause of tubulointerstitial lesions and it may contribute to chronic renal failure. In previous studies we demonstrated that enalapril was effective against the progression of tubulointerstitial lesions in a 4-week hyperoxaluria rat model. We evaluated whether the action of enalapril on the tubulointerstitial lesions produced by hyperoxaluria persisted for a long period.

MATERIALS AND METHODS

Two-month-old male Sprague-Dawley rats were divided into 4 groups of 12 each, including 1--control animals given tap water, 2--animals with hyperoxaluria, 3--animals with hyperoxaluria plus enalapril, 4--animals with enalapril. Hyperoxaluria in groups 2 and 3 rats was induced by administering 1% ethylene glycol, a precursor for oxalates, in the tap water continuously throughout the whole study. Meanwhile, groups 3 and 4 received 20 mg./l. enalapril in the drinking water. At the end of the study renal tubulointerstitial lesions were evaluated by immunostaining using monoclonal antibodies against macrophage infiltrates (ED1), tubulointerstitial alpha-smooth muscle actin and transforming growth factor-beta1. The lesions were quantified by semiquantitative scores. Creatinine clearance and urinary albumin excretion were also determined.

RESULTS

There was no difference in urine oxalate excretion in groups 2 and 3. Group 3 rats treated with enalapril showed fewer tubulointerstitial lesions than nontreated group 2 rats, as indicated by the mean scores plus or minus standard error of mean for inflammatory infiltrate (2.16 +/- 0.2 versus 0.83 +/- 0.16), tubular atrophy (2 +/- 0.27 versus 0.66 +/- 0.14), interstitial fibrosis (2.5 +/- 0.15 versus 0.5 +/- 0.1), glomerular ED1 (1.75 +/- 0.25 versus 0.16 +/- 0.11), interstitial ED1 (2.33 +/- 0.18 versus 0.58 +/- 0.10) tubular transforming growth factor-beta1 (2.09 +/- 0.08 versus 0.91 +/- 0.14), interstitial transforming growth factor-beta 1 (2.33 +/- 0.22 versus 0.66 +/- 0.12), tubulointerstitial alpha-smooth muscle actin (2.91 +/- 0.22 versus 0.83 +/- 0.16), lower urinary albumin excretion (35.5 +/- 2.7 mg. daily versus 10.9 +/- 1) and higher creatinine clearance (2.29 +/- 0.04 ml. per minute versus 2.54 +/- 0.03, all p <0.05).

CONCLUSIONS

Based on our results we believe that enalapril would provide a beneficial effect against chronic tubulointerstitial lesions caused by oxalates.

Effect of A. lanata leaf extract and Vediuppu chunnam on the urinary risk factors of calcium oxalate urolithiasis during experimental hyperoxaluria

Urolithiasis is one of the third most common afflictions found in humans. The efficacy of the two Siddha drugs, Aerva lanata and Vediuppu chunnam as antilithic agents using a urolithic rat model were tested in this study. Hyperoxaluria was induced in rats using 0.75% ethylene glycol in drinking water. Aerva lanata(3.0 mg kg(-1)body weight) and Vediuppu chunnam (3.5 mg kg(-1)body weight) were given orally for 28 days. Urinary risk factors of urolithiasis were monitored at the end of 7th, 14th, 21st and 28th days. Urinary volume was increased in hyperoxaluric as well as drug-treated rats. Increased urinary excretion of calcium, oxalate, uric acid, phosphorus and protein in hyperoxaluric rats was brought down significantly by the administration of A. lanata or Vediuppu chunnam. Decreased magnesium excretion in hyperoxaluric rats was normalized by drug treatment. The drug increases the urine volume, thereby reducing the solubility product with respect to calcium oxalate and other crystallizing salts such as uric acid, which may induce epitaxial deposition of calcium oxalate. Drug alone treated rats did not show any adverse effects. Combination therapy was found to be more effective and this indigenous medicine can be used successfully as an antilithic agent.

Oral calcium supplement decreases urinary oxalate excretion in patients with enteric hyperoxaluria

We studied the effect of oral calcium supplementation in patients with enteric hyperoxaluria. Three patients with renal stone events following ileal resection were given oral calcium supplement. One of the three patients was put on a low-fat diet. The treatment reduced urinary oxalate excretion to the normal range. Subsequently, 2 patients reduced the dose of calcium supplementation at their own discretion and consequently developed renal stones again together with hyperoxaluria. Based on these observations, we believe that an adequate dose of calcium can normalize urinary oxalate excretion.

Enalapril prevents tubulointerstitial lesions by hyperoxaluria

Hyperoxaluria is a recognized cause of tubulointerstitial lesions, and this could contribute to development of hypertension and chronic renal failure. Enalapril has been effective against the progression of tubulointerstitial lesions in various animal models. The aim of the present study was to evaluate the usefulness of enalapril on the tubulointerstitial damage produced by oxalates. Two-month-old male Sprague-Dawley rats were separated into 4 groups, control with tap water (G1), hyperoxaluric (G2), hyperoxaluric+enalapril (G3), enalapril (G4), for 4 weeks. G2 and G3 rats were given 1% ethyleneglycol (ETG, precursor for oxalates), and G3 and G4 rats were given enalapril 20 mg/L in drinking water. At the end of the study, we evaluated renal tubulointerstitial lesions by a semiquantitative score. Urine albumin excretion, serum and urine nitric oxide production, tubulointerstitial immunostaining by alpha-smooth muscle actin, transforming growth factor-beta1, and collagen type III were measured. Rats belonging to the hyperoxaluric group treated with enalapril (G3) showed fewer tubulointerstitial lesions (1.3+/-0.2 versus 3+/-0.2; P<0.01), lower urine albumin excretion (8+/-2 mg/d versus 25+/-2 mg/d; P<0.01), less percentage of alpha-smooth muscle actin in renal interstitium (2+/-0.4% versus 13.5+/-2.4%; P<0.01), less percentage of transforming growth factor-beta1 in tubulointerstitial area (3.3+/-1% versus 13.3+/-2. 1%; P<0.01), less percentage of collagen type III interstitial deposition (0.7+/-0.5% versus 7+/-2.6%; P<0.01), and increased NO production in serum as well as urine (both P<0.01), when compared with the hyperoxaluric group not treated with enalapril (G2). Considering these data, we believe that enalapril, by several mechanisms of action, could provide an important benefit in the prevention of inflammatory response, transforming growth factor-beta1 tubulointerstitial production, collagen type III interstitial deposition, and finally, the progressive tubulointerstitial fibrosis caused by oxalates.

Effect of cyclosporin A on tissue lipid peroxidation and membrane bound phosphatases in hyperoxaluric rat and the protection by vitamin E pretreatment

The effect of cyclosporin A, a highly effective immunosuppressant, was investigated on hyperoxaluric rats with and without vitamin E pretreatment. Hyperoxaluria was induced by oral feeding of 3% ammonium oxalate in water for 3 days. Cyclosporin A (50 mg/kg body wt.) was administered for 3 days. Pretreatment with vitamin E (50 mg/100 g body wt., once a week for 3 weeks) was carried out before the administration of cyclosporin A and ammonium oxalate. Nonenzymatic ascorbate-induced lipid peroxidation was increased to 1.55-fold in either cyclosporin A-administered or hyperoxaluric rat kidney and liver when compared to control. The lipid peroxidation was further elevated to 1.9-fold when both cyclosporin A and ammonium oxalate were coadministered. The activities of renal and hepatic ATPase, glucose-6-phosphatase as well as the concentrations of thiols were decreased significantly (p < 0.001) when cyclosporin A was administered under hyperoxaluric condition. On pretreatment with vitamin E the cyclosporin A-induced biochemical changes observed in the presence of hyperoxaluria were abolished.

Effect of lupeol, a pentacyclic triterpene, on urinary enzymes in hyperoxaluric rats

Investigations were undertaken to study the role of lupeol, a pentacyclic triterpene from Crataeva nurvala stem bark, in calcium oxalate experimental rat urolithiasis. A 2% solution of ammonium oxalate was administered by gastric intubation for inducing hyperoxaluric condition in adult male rats of Wistar strain. The duration of treatment was for 15 days. This resulted in increased urinary excretion of oxalate associated with reduction in citrate and glycosaminoglycans. The urinary marker enzymes which indicate renal tissue damage namely--lactate dehydrogenase, inorganic pyrophosphatase, alkaline phosphatase, gamma glutamyl transferase, beta-glucuronidase and N-acetyl beta-D glucosaminidase were found to be elevated. Lupeol administration (25 mg/kg body weight/day) reduced significantly the renal excretion of oxalate. It also reduced the extent of renal tubular damage as evidenced from the decreased levels of the above enzymes in urine. Such a reduction is likely to be beneficial in minimizing the deposition of stone-forming constituents in the kidney which provides antilithic effect.

Controlling influence of phosphocitrate in vitro and in vivo on calcium oxalate crystal formation and growth

Calcium oxalate (CaOx) crystallization in the presence of phosphocitrate (PC) was studied by both in vitro and in vivo techniques. Crystals of the monohydrate (COM) and the dihydrate (COD) forms were generated under controlled conditions in a silica gel matrix. Our data indicated only COD crystals formed when PC was present, inferring that the COD to COM transformation was being impeded. COD crystals were smaller in size than controls and there was evidence of interpenetral twinning. An in vivo study using a rat bladder implant model noted similar findings. Scanning electron microscopy (SEM) revealed that implants recovered from PC treated rats had primarily COD crystals deposited, whereas both the surface and inner layers of encrusted implants from normal rats contained predominantly COM crystals. Infrared (IR) analysis confirmed the visual findings indicating quantitatively that there was a higher proportion of COD present on the implants recovered from the treated rats than in the controls. It is concluded that although total CaOx crystallization cannot be eliminated by PC, its action could assist in reducing the harmful nature of such crystallites in the urine.

Results of long-term treatment with orthophosphate and pyridoxine in patients with primary hyperoxaluria

BACKGROUND

The prognosis for patients with primary hyperoxaluria has been ominous, with the expectation of renal failure, poor results with transplantation, and early death.

METHODS

We studied the long-term effects of orthophosphate and pyridoxine therapy in 25 patients with primary hyperoxaluria who were treated for an average of 10 years (range, 0.3 to 26). Their mean age at the start of treatment was 12 years (median, 6; range, 0.5 to 32). We also studied the effect of orthophosphate and pyridoxine on urinary supersaturation with calcium oxalate, crystal inhibition using a seeded growth system, and crystal formation using scanning electron microscopy in 12 patients during three-day stays in the clinical research center.

RESULTS

The mean (+/- SD) glomerular filtration rate at the start of treatment was 91 +/- 26 ml per minute per 1.73 m2. The median decline in glomerular filtration rates was 1.4 ml per minute per 1.73 m2 of body-surface area per year. The actuarial survival free of end-stage renal disease was 96, 89, 74, and 74 percent of 5, 10, 15, and 20 years, respectively. Treatment with orthophosphate and pyridoxine reduced urinary supersaturation with calcium oxalate from 8.3 +/- 3.0 to 2.1 +/- 1.7 kJ per mole at 38 degrees C (P < 0.001), increased the inhibition of calcium oxalate formation from 63 +/- 11 to 108 +/- 10 inhibitor units per 24 hours (P < 0.001), and improved the crystalluria score from 2.6 +/- 0.3 to 0.6 +/- 0.1 (P < 0.001).

CONCLUSIONS

Treatment of patients with primary hyperoxaluria with orthophosphate and pyridoxine decreases urinary calcium oxalate crystallization and appears to preserve renal function.

A "chemical" concept for the therapy of glyoxylate-induced oxalurias (1)

Glyoxylic acid is the toxic principle of acquired and inherited oxalurias. A "chemical", not enzyme-mediated detoxication concept for the trapping of this aldehyde is described, based on a spontaneous formation of alkaloid-type heterocycles by reaction with biogenic amines or amino acids. 5,5-Dimethylthiazolidine-2(R,S)-4(S)-dicarboxylic acid, prepared by the condensation of D(-)-penicillamine with glyoxylic acid, was found to be formed quickly in vitro, to be stable in vivo and of good physiological compatibility. Renal elimination of the unchanged thiazolidine occurs mainly within 24 h, after administration of its calcium salt to NMRI-mice. Recovery up to 85% of the applied dose was quantitatively monitored by HPLC after derivatization to the corresponding fluorescent dansyl compound, which was unequivocally identified by MS analysis after isolation from mice urine.

Calcium citrate for vulvar vestibulitis. A case report

A woman had suffered from vulvar vestibulitis (vulvodynia) for four years. Pain from the disorder had disrupted her ability to function at work and home as well as sexually. An initial full range of treatments, including multiple operations, had produced no relief. Examination of the urine for evidence of excess oxalate, which has been shown to cause epithelial reactions similar to those found in vulvodynia, showed periodic hyperoxaluria and pH elevations related to the symptoms. Calcium citrate was given to modify the oxalate crystalluria. The symptoms were significantly reduced in three months, and the patient was pain free after one year. She was able to resume normal work, family, sexual and recreational activities. Withdrawal of the calcium citrate resulted in a return of the symptoms; reinstitution alleviated them. These findings suggest that further study of individualized metabolic factors that may underlie vulvodynia is warranted.

The inhibition of metabolic oxalate production by sulfhydryl compounds

A number of sulfhydryl compounds were shown to inhibit CO2 and oxalate formation from glyoxylate by rat liver homogenates and hepatocytes. The most significant inhibition occurred with cysteine and this inhibition was concentration-dependent. In rats made hyperoxaluric by administering ethylene glycol in their drinking water, daily intraperitoneal injections of cysteine caused a rapid and marked decrease in urinary oxalate excretion which was maintained over the duration of the treatment (28 days). Over this time period, the level of urinary oxalate excretion in these ethylene glycol-treated rats was reduced to that of the controls. It is postulated that the decrease is due to the formation of a cysteine-glyoxylate adduct, 2-carboxy-4-thiazolidine carboxylate, which prevents glyoxylate being further oxidized to oxalate. Cysteine or similar sulphydryl compounds may therefore have potential as therapeutic agents in the prevention of renal stones.

Metabolism of pyridoxine in mild metabolic hyperoxaluria and primary hyperoxaluria (type 1)

Plasma pyridoxine metabolites in plasma and 4-pyridoxic acid excretions in urine were measured in normal subjects, in 7 patients with type-1 hyperoxaluria and in 8 patients with mild metabolic hyperoxaluria, while receiving various doses of pyridoxine. Compliance with ingestion of pyridoxine was verified by measuring urinary 4-pyridoxic acid. In the normal subjects the maximum level of pyridoxal phosphate was obtained after only 10 mg/day of pyridoxine. The patients were divided into nonresponders, good responders and poor responders to pyridoxine according to the fall in urinary oxalate and glycollate excretions. In patients taking pyridoxine, the plasma pyridoxal phosphate levels were as for normal subjects in primary hyperoxaluria, lower than for normal subjects in mild metabolic hyperoxaluria (p less than 0.01), and in the latter group lower in partial responders than in good responders (p = 0.04). Hence in mild metabolic hyperoxaluria there may be difficulty in converting pyridoxine to pyridoxal phosphate.

Effects of oral pyridoxine upon plasma and 24-hour urinary oxalate levels in normal subjects and stone formers with idiopathic hypercalciuria

The effect of pyridoxine hydrochloride, 200 mg/day (0.97 mmol/day) for 3 weeks, upon plasma and urinary oxalate has been determined in ten normal subjects and seven patients with idiopathic hypercalciuria while both groups were on low-oxalate diets. Patients had higher basal urinary oxalate levels than normal subjects. In normal subjects pyridoxine administration decreased plasma oxalate levels and raised urinary oxalate. The patients showed no change in either plasma or urinary oxalate.