Osteopontin knockdown in the kidneys of hyperoxaluric rats leads to reduction in renal calcium oxalate crystal deposition.

Osteopontin (OPN) expression is increased in kidneys of rats with ethylene glycol (EG) induced hyperoxaluria and calcium oxalate (CaOx) nephrolithiasis. The aim of this study is to clarify the effect of OPN knockdown by in vivo transfection of OPN siRNA on deposition of CaOx crystals in the kidneys. Hyperoxaluria was induced in 6-week-old male Sprague-Dawley rats by administering 1.5% EG in drinking water for 2 weeks. Four groups of six rats each were studied: Group A, untreated animals (tap water); Group B, administering 1.5% EG; Group C, 1.5% EG with in vivo transfection of OPN siRNA; Group D, 1.5% EG with in vivo transfection of negative control siRNA. OPN siRNA transfections were performed on day 1 and 8 by renal sub-capsular injection. Rats were killed at day 15 and kidneys were removed. Extent of crystal deposition was determined by measuring renal calcium concentrations and counting renal crystal deposits. OPN siRNA transfection resulted in significant reduction in expression of OPN mRNA as well as protein in group C compared to group B. Reduction in OPN expression was associated with significant decrease in crystal deposition in group C compared to group B. Specific suppression of OPN mRNA expression in kidneys of hyperoxaluric rats leads to a decrease in OPN production and simultaneously inhibits renal crystal deposition.

Effects of the Rho kinase inhibitor, hydroxyfasudil, on bladder dysfunction and inflammation in rats with HCl-induced cystitis.

OBJECTIVE: To evaluate the effect of the Rho kinase inhibitor, hydroxyfasudil, on bladder function in a rat model of HCl-induced chemical cystitis, and to elucidate the possible mechanisms associated with its therapeutic effect. METHODS: Female Sprague-Dawley rats with HCl-induced cystitis were given hydroxyfasudil (10 mg/kg, i.p.) for 7 days. Treatment efficacy was determined by comparing bladder function and histopathology to sham and untreated control rats. Bladder function was determined by cystometric analysis. Rho kinase activity was determined by quantitative reverse transcription polymerase chain reaction and signal inhibition of downstream Ras homolog member A/Rho kinase signaling molecules by western blot and immunohistochemistry. RESULTS: Treatment with hydroxyfasudil significantly improved bladder intercontraction intervals. Rats treated with hydroxyfasudil also showed a significant reduction of histopathological features associated with cystitis. Western blot and immunohistochemistry findings showed that hydroxyfasudil inhibited downstream molecules of Rho kinase that ameliorated changes associated with HCl-induced chemical cystitis, such as inflammatory cell recruitment and smooth muscle cell proliferation. CONCLUSION: The findings from the present study suggest a promising therapeutic role for hydroxyfasudil in bladder inflammation associated with cystitis.

Clinical utility of the prostate cancer gene 3 (PCA3) urine assay in Japanese men undergoing prostate biopsy.

UNLABELLED: WHAT'S KNOWN ON THE SUBJECT? AND WHAT DOES THE STUDY ADD?: It is known that a prostate cancer gene 3 (PCA3) urine assay is superior to serum PSA level or PSA-related indices for predicting a positive biopsy result in European and US men. This is the first report on PCA3 in a large cohort of Japanese men. The diagnostic value of the PCA3 score in Japanese men was similar to those reported in European and US men. The study concludes that a combination of PSA density and PCA3 score may be useful for selecting patients who could avoid an unnecessary biopsy. OBJECTIVE: To examine the diagnostic performance of the prostate cancer gene 3 (PCA3) score for prostate cancer in Japanese men undergoing prostate biopsy. PATIENTS AND METHODS: This Japanese, multicentre study included 647 Asian men who underwent extended prostate biopsy with elevated prostate-specific antigen (PSA) and/or abnormal digital rectal examination (DRE). Urine samples were collected after DRE. The PCA3 score was determined using a PROGENSA PCA3 assay and correlated with biopsy outcome. Its diagnostic accuracy was compared with that of serum PSA level, prostate volume (PV), PSA density (PSAD), and free/total PSA ratio (f/t PSA). RESULTS: A total of 633 urine samples were successfully analysed (the informative rate was 98%). Median PSA was 7.6 ng/mL. Biopsy revealed cancer in 264 men (41.7%). The PCA3 score for men with prostate cancer was significantly higher than that for men with negative biopsies (median PCA3 score: 49 vs. 18; P < 0.001). The rate of positive biopsy was 16.0% in men with a PCA3 score of <20 and 60.6% in those with a PCA3 score of ≥50. Using a PCA3 score threshold of 35, sensitivity and specificity were 66.5 and 71.6%, respectively. The area under the curve of the PCA3 score was significantly higher than that of the f/t PSA in men with PSA 4-10 ng/mL (0.742 vs 0.647; P < 0.05). In men with PSAD < 0.15 and PCA3 < 20, only three (4.2%) out of 72 men had prostate cancer. CONCLUSIONS: The PCA3 score was significantly superior to f/t PSA in predicting a positive biopsy result for prostate cancer in Japanese men with PSA 4-10 ng/mL. The combination of PSAD and PCA3 score may be useful for selecting patients who could avoid an unnecessary biopsy.

[Vital relationship between osteopontin and urolothiasis].

Urological rediscovery of osteopontin (OPN) in 1992 has opened a new era in the understanding of mechanisms in development of urolithiasis over the two decades. OPN had the multiple functions, and it was difficult to understand the overall role. It has been understood that OPN is a promoting agent for urolithiasis development in the issue as a result of a lot of experiments. And it became clear that OPN having received the control of free radicals from NADPH oxidase and angiotensin II . The clinical application that uses OPN antibody and/or ARB for preventing urolithiasis is expected. I describe the vital role of OPN in development of urolithiasis in this paragraph.

[Multifunctional character of osteopontin and strategy for clinical applications].

Osteopontin (OPN) is the major constituent of calcium-containing urinary stones and is involved in the inhibition of nucleation and aggregation of calcium oxalate (CaOx) crystals, promotion of the adherence of CaOx crystals to cultured renal epithelial cells, and regulation of inflammatory cells as chemokine. OPN has different effects (inhibitor and promoter) at each stage of stone formation in vitro and these multifunctional actions of OPN have not been fully elucidated. We developed a modified crystal method using collagen granules (CG) and immobilized OPN. OPN had strong inhibitory activity on the aggregation/growth of CaOx crystals, but the inhibitory activity decreased by use of OPN-immobilized CG. OPN is also a critical promoter of adherence for CaOx crystals to cultured renal epithelial cells in an in vitro experimental system. We examined the effect of OPN in vivo, by OPN siRNA transfection in rats. Hydrodynamic intravenous and renal subcapsular injections with lipofection were performed on days 1 and 8. The calcium concentration in the kidney was significantly lower and the frequency of CaOx crystal deposits in the tubules was lower in the OPN siRNA transfection group (drinking 1.5% ethylene glycol (EG)), than in the EG drinking group (sham operation) at day 15. We examined the effect of candesartan, an angiotensin II (Ang II) type 1 receptor blockers (ARB) in hyperoxaluric rats. ARB reduced crystal formation and calcium concentrations in the whole kidney. Hyperoxaluria leads to CaOx crystallization and the development of tubulointerstitial lesions in the kidney. AngII mediates OPN synthesis, which is involved in both macrophage recruitment and CaOx crystallization. OPN synthesis and production increased with hyperoxaluria but to a lesser extent in ARB-treated hyperoxaluric rats. These results show that oxalate can activate the renal renin-angiotensin system and that oxalate-induced upregulation of OPN is in part mediated via the renal renin-angiotensin system.

Superoxide from NADPH oxidase as second messenger for the expression of osteopontin and monocyte chemoattractant protein-1 in renal epithelial cells exposed to calcium oxalate crystals.

OBJECTIVE To test the hypothesis that exposure of a renal epithelial cell line, NRK52E, to calcium oxalate monohydrate crystals (COM) would up-regulate NADPH oxidase subunit p47(phox), enhance superoxide production and increase monocyte chemoattractant protein-1 (MCP-1) and osteopontin mRNA levels. MATERIALS AND METHODS Confluent cultures of NRK52E cells were exposed to COM (66.7 microg/cm(2)) with or with no pretreatment with diphenileneiodium chloride (DPI, 10 x 10(-6)m) an inhibitor for NADPH oxidase, under serum-free conditions. The conditioned medium was collected and total cellular RNA isolated from the cells, and subjected to enzyme-linked immunosorbent assay and real-time polymerase chain reaction (PCR). Production of reactive oxygen species (ROS) was estimated by dihydroethidium (DHE) staining using a fluorescence microscope. Immunohistochemistry and real-time PCR were used to analyse p47(phox) in NRK52E cells. RESULTS In COM treated NRK52E cells there was enhanced expression of p47(phox) and production of superoxide. COM-induced production of MCP-1 and osteopontin was significantly reduced after treatment with DPI. CONCLUSIONS While the generation of a lot of ROS might play a major role in tissue injury or death, the regulated generation of low concentration of ROS, possibly by NADPH oxidase, may represent a second messenger system for generation of COM-induced MCP-1 and osteopontin production in the renal tubules.

Oxalate ions and calcium oxalate crystal-induced up-regulation of osteopontin and monocyte chemoattractant protein-1 in renal fibroblasts.

OBJECTIVE: To examine the responses of renal fibroblasts to high oxalate (Ox) and calcium Ox (CaOx) crystals, as the latter are found in the renal interstitium of patients with primary or enteric hyperoxaluria, and in animals with experimental CaOx nephrolithiasis, and are associated with tubulointerstitial inflammation (TI). TI might begin with the production of chemoattractants by the renal epithelial cells exposed to high Ox and/or CaOx crystals; as Ox levels are also high in the renal interstitium and crystal deposition in nephrolithiasis might start in the interstitium, we hypothesized that renal fibroblasts might also be involved in the development of TI. MATERIALS AND METHODS: We exposed renal fibroblast cells of line NRK 49F in vitro to Ox ions (500 micromol/L) or CaOx monohydrate crystals (67 microg/cm(2)). We assessed the production of osteopontin and monocyte chemoattractant protein-1 (MCP-1), and expression of their mRNA, in the cells. We also determined the cellular malondialdehyde content as a marker of reactive oxygen species (ROS)-induced lipid peroxidation, and Trypan blue staining and the release of lactate dehydrogenase as markers of injury. RESULTS: Similar to renal epithelial cells, renal fibroblasts were stimulated by exposure to Ox and CaOx crystals. They showed signs of injury and ROS-induced lipid peroxidation. The mRNA expression and production of osteopontin and MCP-1 increased significantly. CONCLUSIONS: These results indicate that fibroblasts respond to high Ox and CaOx crystals by up-regulating specific pathways producing pro-inflammatory conditions. Migration of monocytes/macrophages to sites of interstitial crystal deposits can lead to localized interstitial inflammation and fibrosis.

[Evaluation of the crystal inhibitory effect of angiotensin II type I receptor blocker in etylene glycol treated rat kidney].

PURPOSE: We examined whether there would be any inhibitive effect to the crystal formation in ethylene glycol treated rat kidney by angiotensin II type I receptor blocker (candesartan). METHODS: We divided 10-weeks-old male Sprague-Dawley rats into 4 groups. In these groups, rats were given tap water (group A), 1.0% ethylene glycol (group B), 1.0% ethylene glycol and 20 microg/ml candesartan (group C), 20 microg/ml candesartan (group D) for 4 weeks. Immunohistochemical studies of a renal tissue was performed by ED1 antibody and the osteopontin antibody, the transcription of renin, angiotensin converting enzyme, angiotensin II and osteopontin mRNA in whole kidney was determined using real time PCR and malondialdehyde level was measured. Renal tissue was evaluated using H.E. stain for counting the calcium deposit in the renal tubules. Calcium concentrations in whole kidney were measured with an atomic absorption spectrophotometer. RESULTS: Although there is no significant difference urinary oxalate and calcium levels compared with group B and C, group C showed fewer the numbers of calcium deposit in the tubules and decreased the amount of calcium contained in the whole kidney, ED1 positive cells, osteopontine mRNA expression and malondialdehyde level. CONCLUSION: These results suggest that candesartan inhibited superfluously induced osteopontin in the whole kidney by ethylene glycol and crystal formation was also related decreased.

Analysis of bone mineral density in urolithiasis patients.

BACKGROUND: The association between hypercalciuria and bone mineral density (BMD) has been already recognized. The aim of the present study is to relate BMD to age and sex and to evaluate the calcium metabolism and hypercalciuria-defined dietary or non-dietary category in patients with urolithiasis. METHODS: The BMI of the L2-L4 lumbar vertebrae was measured in 310 renal stone patients (191 men and 119 women). Percent age matched score (%AMS), which is the percent ratio of measured BMD to the mean BMD of age-matched control subjects, was utilized for the appraisal of BMD. Low BMD groups were defined by lower than 90% of %AMS. RESULTS: Low BMD was observed in 27.7% of urinary stone patients, which was not a significant difference to that of control subjects (23.5%) who were measured in the health examination. In male patients with urolithiasis, the frequency of patients in whom BMD had been apt to decrease since youth was high, but there was not a proven significant difference among the three age groups (20-39 years old, 40-59 years old and 60 years old or older). In contrast, for female stone patients, the frequency of low BMD markedly increased in patients aged 40 years or older, when menopause occurs. Furthermore, in female stone patients with hypercalciuria, the frequency of reduced BMD reached more than 40%. When the cause was non-dietary hypercalciuria (classified mainly on the daily amount of urinary calcium excretion after ingestion of calculus test diet), the frequency of reduced BMD reached 65% (P < 0.01). CONCLUSIONS: In case female stone patients with non-dietary hypercalciuria become menopausal, not only the risk of recurrent lithiasis increases, but the possibility of developing osteopenia in the future also increases. Appropriate treatments for prophylactic effects on urolithiasis or osteopenia should be considered, as judged from BMD, diet, sex, urinary calcium excretion and other factors synthetically.

Diphenyleneiodium (DPI) reduces oxalate ion- and calcium oxalate monohydrate and brushite crystal-induced upregulation of MCP-1 in NRK 52E cells.

BACKGROUND: Our earlier studies have demonstrated upregulation of monocyte chemoattractant protein-1 (MCP-1) in NRK52E rat renal epithelial cells by exposure to oxalate (Ox) ions and crystals of calcium oxalate monohydrate (COM) or the brushite (Br) form of calcium phosphate. The upregulation was mediated by reactive oxygen species (ROS). This study was performed to investigate whether NADPH oxidase is involved in ROS production. METHODS: Confluent cultures of NRK52E cells were exposed to Ox ions or COM and Br crystals. They were exposed for 1, 3, 6, 12, 24 and 48 h for isolation of MCP-1 mRNA and 24 h for enzyme-linked immunosorbent assay (ELISA) to determine the secretion of protein into the culture medium. We also investigated the effect of free radical scavenger, catalase, and the NADPH oxidase inhibitor diphenyleneiodium (DPI) chloride, on the Ox- and crystal-induced expression of MCP-1 mRNA and protein. The transcription of MCP-1 mRNA in the cells was determined using real-time polymerase chain reaction. Hydrogen peroxide and 8-isoprostane were measured to investigate the involvement of ROS. RESULTS: Exposure of NRK52E cells to Ox ions as well as the crystals resulted in increased expression of MCP-1 mRNA and production of the chemoattractant. Treatment with catalase reduced the Ox- and crystal-induced expression of both MCP-1 mRNA and protein. DPI reduced the crystal-induced gene expression and protein production but not Ox-induced gene expression and protein production. CONCLUSIONS: Exposure to Ox ions, and COM and Br crystals stimulates a ROS-mediated increase in MCP-1 mRNA expression and protein production. Reduction in ROS production, lipid peroxidation, low-density lipoprotein release, and inducible MCP-1 gene and protein in the presence of DPI indicates an involvement of NADPH oxidase in the production of ROS.

Long-term outcome of the endoscopic correction of vesico-ureteric reflux: a comparison of injected substances.

OBJECTIVE: To summarize the long-term outcome of endoscopic surgery to correct vesico-ureteric reflux (VUR) using different injected substances, i.e. autologous blood, hyaluronan/dextranomer copolymer (HDC), PTFE and glutaraldehyde cross-linked bovine dermal (GAX) collagen. PATIENTS AND METHODS: Treatment results on 270 ureters of 185 patients followed for >5 years (mean 8.5) were summarized according to the injected substances. The substances were injected into the 6 o'clock position of the ureteric orifice endoscopically. "Success" was defined as the absence of VUR for >5 years after a single injection. RESULTS: The treatment was successful in two of 24 patients (8%) with autologous blood, 17 of 32 (53%) with HDC, 108 of 171 (63%) with PTFE and 24 of 43 (56%) with GAX collagen. The success rate was lower in patients with higher grades of VUR. CONCLUSIONS: Autologous blood is unsuitable for clinical application because of its poor durability. We will no longer use PTFE because its safety is not well established. The overall success rates of endoscopic surgery with GAX collagen and HDC were insufficient compared with surgical reimplantation, but it is advantageous that this procedure is less invasive and can be repeated. The cure rate could be improved by excluding high-grade VUR from the indications for endoscopic surgery.

Effect of angiotensin II receptor blockage on osteopontin expression and calcium oxalate crystal deposition in rat kidneys.

Hyperoxaluria leads to calcium oxalate (CaOx) crystallization and development of tubulointerstitial lesions in the kidneys. Treatment of hyperoxaluric rats with angiotensin II (Ang II) type I receptor blocker (ARB) reduces lesion formation. Because Ang II mediates osteopontin (OPN) synthesis, which is involved in both macrophage recruitment and CaOx crystallization, it was hypothesized that ARB acts via OPN. Hyperoxaluria was induced in 10-wk-old male Sprague-Dawley rats, and they were treated with ARB candesartan. At the end of 4 wk, kidneys were examined for crystal deposits, ED-1-positive cells, and expression of OPN mRNA. PCR was used to quantify OPN, renin, and angiotensin-converting enzyme (ACE) mRNA in kidneys. RIA was used to determine renal, plasma, and urinary OPN; plasma renin; Ang II and ACE; and renal Ang II. For evaluating oxidative stress, malondialdehyde was measured. Urinary calcium, oxalate, creatinine, and albumin were also determined. Despite similar urinary calcium and oxalate levels, kidneys of hyperoxaluric rats on candesartan had fewer CaOx crystals, fewer ED-1-positive cells, reduced OPN expression, and reduced malondialdehyde than hyperoxaluric rats. Urinary albumin excretion and serum creatinine levels improved significantly on candesartan treatment. mRNA for OPN, renin, and ACE were significantly elevated in hyperoxaluric rats. OPN synthesis and production increased with hyperoxaluria but to a lesser extent in candesartan-treated hyperoxaluric rats. These results show for the first time that oxalate can activate the renal renin-angiotensin system and that oxalate-induced upregulation of OPN is in part mediated via renal renin-angiotensin system.

The role of osteopontin on calcium oxalate crystal formation.

OBJECTIVE: We evaluated whether osteopontin (OPN) and other proteins with the RGD sequence as in OPN (RGD family proteins) that are present in renal tubular cells (fibronectin [FN], Tamm-Horsfall glycoprotein [THP], vitronectin [VN], and laminin [LN]) inhibit the aggregation and growth of calcium oxalate (CaOx) crystals by a novel seed crystal method using collagen granules (CG) with and without OPN adhered on the surface. We also evaluated the effect of solid phase OPN, FN and THP in which the relationship between their proteins and CaOx crystallization was reported. Moreover, the state and time-course changes in CaOx crystals adhered to CG were observed under scanning electron microscopy (SEM). METHODS: The inhibitory activity (IA) on the aggregation and growth of CaOx crystals was measured in vitro by the conventional seed crystal method using isotopes. In this study, the following nine samples were used: OPN alone; FN alone; THP alone; VN alone; LN alone; CG alone; and CG with OPN, FN, or THP adhered on the surface (OPN/FN/THP-immobilized CG). In addition, the state and time-course changes in CaOx crystals adhered to CG were evaluated by SEM. RESULTS: Using the conventional seed crystal method, the following values of IA were obtained: 91.7% (37.5 micro g/ml) for OPN, 5.0% (100 micro g/ml) for FN, 2.0% (100 micro g/ml) for THP, 3.0% (100 micro g/ml) for VN, and 1.0% (100 micro g/ml) for LN. However, the value of IA obtained by our seed crystal method using CG was 92.1% (180cm(2)/5ml PBS) when CG alone was used. Although the value of IA was decreased by 33.6% when OPN-immobilized CG was used, it did not significantly change when FN/THP-immobilized CG was used. When CG alone was used, the evaluation of CaOx crystallization by SEM demonstrated mild adherence and aggregation of CaOx crystal suspension (seed crystals) on the CG surface, although newly formed crystals only slightly adhered to the CG surface. When OPN-immobilized CG was used, marked adherence and aggregation of seed crystals were observed, in addition to the relatively increased adherence of newly formed crystals. When FN/THP-immobilized CG was used, newly formed crystals only slightly adhered to the CG surface, although the degree of seed crystal adherence and aggregation did not significantly change. CONCLUSIONS: These findings suggest that the immobilization of OPN to the CG surface enhances the adherence and aggregation of seed crystals, as well as enhancing the adherence of newly formed crystals, resulting in decreased IA of CG (overall promotion of crystal deposition). Therefore, the results of this study clarified that OPN enhances the formation and aggregation of CaOx crystals in this experimental system.

Increased expression of monocyte chemoattractant protein-1 (MCP-1) by renal epithelial cells in culture on exposure to calcium oxalate, phosphate and uric acid crystals.

BACKGROUND: During the development of non-infectious kidney stones, crystals form and deposit in the kidneys and become surrounded by monocytes/macrophages (M/M). We have proposed that in response to crystal exposure renal epithelial cells produce chemokines, which attract the M/M to the sites of crystal deposition. We investigated the expression of monocyte chemoattractant protein-1 (MCP-1) mRNA and protein by NRK52E rat renal tubular epithelial cells exposed to calcium oxalate (CaOx), brushite (Br, a calcium phosphate) and uric acid (UA) crystals. METHODS: Confluent cultures of NRK52E cells were exposed to CaOx, Br or UA at a concentration of 250 micro g/ml (66.7 micro g/cm(2)). They were exposed for 1, 3, 6, 12, 24 and 48 h for isolation of mRNA and 24 h for ELISA to determine the secretion of protein into the culture medium. Since cells are known to produce free radicals on exposure to CaOx crystals we also investigated the effect of free radical scavenger catalase on the crystal induced expression of MCP-1 mRNA and protein. RESULTS: Exposure of NRK52E cells to the crystals resulted in increased expression of MCP-1 mRNA and production of the chemoattractant. CaOx crystals were most provocative while UA the least. Treatment with catalase had a negative effect on the increased expression of both MCP-1 mRNA and protein, which indicates the involvement of free radicals in up-regulation of MCP-1 production. CONCLUSION: Exposure to both CaOx and calcium phosphate crystals stimulates increased production of MCP-1. Free radicals appear to be involved in this up-regulation. Results indicate that MCP-1, which is often associated with localized inflammation, may be one of the chemokine mediators associated with the deposition of various urinary crystals in the kidneys during kidney stone formation. Because of the small number of experiments performed here, results must be confirmed by more extensive studies with larger sample size.

Oxalate ions and calcium oxalate crystals stimulate MCP-1 expression by renal epithelial cells.

BACKGROUND: Crystals of calcium oxalate monohydrate (COM) and excess oxalate ions (OX) stimulate an array of responses inducing localized injury and inflammation in the kidneys. These inflammatory responses are key regulators of development of nephrolithiasis. We propose that monocyte chemoattractant protein-1 (MCP-1), a chemokine with potent chemotactic activity for monocytes/macrophages, is a mediator of local inflammatory responses to COM and OX-induced injury. To test this hypothesis, the effects of COM and OX on the expression of MCP-1 mRNA and protein by NRK52E rat renal tubular cells were investigated. METHODS: Confluent cultures of NRK52E cells were exposed to COM (33 to 267 microg/cm2) or OX (125 to 1000 micromol/L, estimated free oxalate levels of 65.8 to 540 micromol/L) and catalase (400 or 2000 U/mL), a free radical scavenger that protects the cells against detrimental effects of COM and OX, for 1 to 48 hours under serum free conditions. The conditioned media were collected and total cellular RNA isolated from the cells and subjected to enzyme-linked immunosorbent assay (ELISA) and semiquantitative polymerase chain reaction (PCR) to determine the expression of MCP-1 protein and mRNA, respectively. RESULTS: NRK52E cells express MCP-1 mRNA and protein, and the level of their expression significantly increases following treatments with COM and OX in a time and concentration dependent manner. MCP-1 mRNA expression and protein production increased more significantly after exposure to COM than to OX. These responses were significantly reduced following treatments with catalase (2000 U/mL). CONCLUSIONS: NRK52E cells express MCP-1 mRNA and protein, and their levels are altered following COM and OX exposure. Since catalase treatment reduced MCP-1 expression, free radicals may be involved in the up-regulation of MCP-1 production by the epithelial cells. The results suggest that elevated expression of MCP-1, which is often associated with local inflammatory response, may mediate similar reactions including attraction of macrophages seen around the interstitial crystals during the early stages of nephrolithiasis.