1
|
Chaiyarit S, Thongboonkerd V. Oxidized forms of uromodulin promote calcium oxalate crystallization and growth, but not aggregation. Int J Biol Macromol 2022; 214:542-553. [PMID: 35752338 DOI: 10.1016/j.ijbiomac.2022.06.132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2022] [Revised: 06/17/2022] [Accepted: 06/18/2022] [Indexed: 11/19/2022]
Abstract
Roles of an abundant human urinary protein, uromodulin (UMOD), in kidney stone disease were previously controversial. Recently, we have demonstrated that oxidative modification reverses overall modulatory activity of whole urinary proteins, from inhibition to promotion of calcium oxalate (CaOx) stone-forming processes. We thus hypothesized that oxidation is one of the factors causing those previously controversial UMOD data on stone modulation. Herein, we addressed effects of performic-induced oxidation on CaOx crystal modulatory activity of UMOD. Sequence analyses revealed two EGF-like calcium-binding domains (65th-107th and 108th-149th), two other calcium-binding motifs (65th-92nd and 108th-135th), and three oxalate-binding motifs (199th-207th, 361st-368th and 601st-609th) in UMOD molecule. Analysis of tandem mass spectrometric dataset of whole urinary proteins confirmed marked increases in oxidation, dioxidation and trioxidation of UMOD in the performic-modified urine samples. UMOD was then purified from the normal urine and underwent performic-induced oxidative modification, which was confirmed by Oxyblotting. The oxidized UMOD significantly promoted CaOx crystallization and crystal growth, whereas the unmodified native UMOD inhibited CaOx crystal growth. However, the oxidized UMOD did not affect CaOx crystal aggregation. Therefore, our data indicate that oxidized forms of UMOD promote CaOx crystallization and crystal growth, which are the important processes for CaOx kidney stone formation.
Collapse
Affiliation(s)
- Sakdithep Chaiyarit
- Medical Proteomics Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
| | - Visith Thongboonkerd
- Medical Proteomics Unit, Office for Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand.
| |
Collapse
|
2
|
Khan SR. Histological aspects of the "fixed-particle" model of stone formation: animal studies. Urolithiasis 2016; 45:75-87. [PMID: 27896391 DOI: 10.1007/s00240-016-0949-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2016] [Accepted: 11/22/2016] [Indexed: 01/25/2023]
Abstract
Crystallization by itself is not harmful as long as the crystals are not retained in the kidneys and are allowed to pass freely down the renal tubules to be excreted in the urine. A number of theories have been proposed, and studies performed, to determine the mechanisms involved in crystal retention within the kidneys. It has been suggested that urinary transit through the nephron is too fast for crystals to grow large enough to be retained. Thus, free particle mechanism alone cannot lead to stone formation, and there must be a mechanism for crystal fixation within the kidneys. Animal model studies suggest that crystal retention is possible through both the free- and fixed-particle mechanisms. Crystal-cell interaction leads to pathological changes which promote crystal attachment to either epithelial cells or their basement membrane. Alternatively, crystals aggregate and produce large enough particles to block the tubules particularly at sites, where urinary flow is affected because of changes in the luminal diameter of the tubule. Crystal deposits plugging the openings of the ducts of Bellini may be the result of such a phenomenon. Intratubular crystals translocating to renal interstitium may produce osteogenic changes in the epithelial or endothelial cells resulting in the formation of the Randall's plaques. Thus, fixation appears to be either through the formation of Randall's plugs, crystal plugs clogging the openings of the ducts of Bellini or sub-epithelial crystal deposits, and the Randall's plaques.
Collapse
Affiliation(s)
- Saeed R Khan
- Department of Pathology, Immunology and Laboratory Investigation, College of Medicine, University of Florida, Gainesville, FL, USA. .,Department of Urology, College of Medicine, University of Florida, Gainesville, FL, USA.
| |
Collapse
|
3
|
Mohamaden WI, Heng W, Huawei G, Meng X, Li J. Electron imaging of calcium oxalate crystals in beagle dogs’ urine. Int J Vet Sci Med 2014. [DOI: 10.1016/j.ijvsm.2014.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Affiliation(s)
- Walaa I. Mohamaden
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Wang Heng
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Guan Huawei
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Xia Meng
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| | - Jianji Li
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, 225009, China
| |
Collapse
|
4
|
Mohamaden W, Wang H, Guan H, Meng X, Li J. Immunohistochemical localization and mRNA quantification of osteopontin and Tamm-Horsfall protein in canine renal tissue after potassium oxalate injection. BMC Vet Res 2014; 10:70. [PMID: 24628885 PMCID: PMC3995431 DOI: 10.1186/1746-6148-10-70] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2013] [Accepted: 03/11/2014] [Indexed: 12/05/2022] Open
Abstract
Background Urinary macromolecules contribute to promoting or inhibiting crystal retention in renal tissue and stone formation. Osteopontin (OPN) and Tamm-Horsfall protein (THP) are the most important proteins involved in this process. Although these two proteins were discovered a long time ago, their role in setting kidney stone formation has not yet been fully investigated. We conducted a study to explore the role of OPN and THP in canine renal oxalosis. Ten dogs were carefully examined prior to the study. Six dogs were assigned to the treatment group and were injected intravenously with 0.5 M potassium oxalate (KOx). The other four dogs were assigned to a control group and were injected intravenously with 0.9% NaCl three times a day (tid) for 7 consecutive days. Then kidneys were harvested for pathological, immunohistochemical examination and OPN and THP mRNA expression levels were quantified by quantitative real-time PCR. Results Calcium oxalate crystals deposition was observed in both renal cortex and medulla. Immunohistochemistry examination revealed increased tissue expression of OPN in the renal tissue while THP was significantly decreased. OPN mRNA expression level significantly increased in treated dogs compared to that in the controls, while THP mRNA level significantly decreased. Conclusion Together, these results suggest that THP and OPN are both involved in the pathogenesis and response to oxalate exposure.
Collapse
Affiliation(s)
| | | | | | | | - Jianji Li
- Department of Clinical Veterinary Medicine, College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu 225009, China.
| |
Collapse
|
5
|
Roop-ngam P, Chaiyarit S, Pongsakul N, Thongboonkerd V. Isolation and characterizations of oxalate-binding proteins in the kidney. Biochem Biophys Res Commun 2012; 424:629-34. [DOI: 10.1016/j.bbrc.2012.07.015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2012] [Accepted: 07/06/2012] [Indexed: 01/06/2023]
|
6
|
Thurgood LA, Sørensen ES, Ryall RL. The effect of intracrystalline and surface-bound osteopontin on the degradation and dissolution of calcium oxalate dihydrate crystals in MDCKII cells. ACTA ACUST UNITED AC 2011; 40:1-15. [PMID: 21932131 DOI: 10.1007/s00240-011-0423-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2011] [Accepted: 08/22/2011] [Indexed: 01/12/2023]
Abstract
In vivo, urinary crystals are associated with proteins located within the mineral bulk as well as upon their surfaces. Proteins incarcerated within the mineral phase of retained crystals could act as a defence against urolithiasis by rendering them more vulnerable to destruction by intracellular and interstitial proteases. The aim of this study was to examine the effects of intracrystalline and surface-bound osteopontin (OPN) on the degradation and dissolution of urinary calcium oxalate dihydrate (COD) crystals in cultured Madin Darby canine kidney (MDCK) cells. [(14)C]-oxalate-labelled COD crystals with intracrystalline (IC), surface-bound (SB) and IC + SB OPN, were generated from ultrafiltered (UF) urine containing 0, 1 and 5 mg/L human milk OPN and incubated with MDCKII cells, using UF urine as the binding medium. Crystal size and degradation were assessed using field emission scanning electron microscopy (FESEM) and dissolution was quantified by the release of radioactivity into the culture medium. Crystal size decreased directly with OPN concentration. FESEM examination indicated that crystals covered with SB OPN were more resistant to cellular degradation than those containing IC OPN, whose degree of disruption appeared to be related to OPN concentration. Whether bound to the crystal surface or incarcerated within the mineral interior, OPN inhibited crystal dissolution in direct proportion to its concentration. Under physiological conditions OPN may routinely protect against stone formation by inhibiting the growth of COD crystals, which would encourage their excretion in urine and thereby perhaps partly explain why, compared with calcium oxalate monohydrate crystals, COD crystals are more prevalent in urine, but less common in kidney stones.
Collapse
Affiliation(s)
- Lauren A Thurgood
- Urology Unit, Department of Surgery, Flinders Medical Centre, Flinders University, Bedford Park, SA 5042, Australia
| | | | | |
Collapse
|
7
|
Thurgood LA, Sørensen ES, Ryall RL. The effect of intracrystalline and surface-bound osteopontin on the attachment of calcium oxalate dihydrate crystals to Madin-Darby canine kidney (MDCK) cells in ultrafiltered human urine. BJU Int 2011; 109:1100-9. [DOI: 10.1111/j.1464-410x.2011.10530.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
8
|
Wang T, Thurgood LA, Grover PK, Ryall RL. A comparison of the binding of urinary calcium oxalate monohydrate and dihydrate crystals to human kidney cells in urine. BJU Int 2011; 106:1768-74. [PMID: 20230382 DOI: 10.1111/j.1464-410x.2010.09258.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
OBJECTIVE To compare the binding kinetics of urinary calcium oxalate monohydrate (COM) and dihydrate (COD) crystals to human kidney (HK-2) cells in ultra-filtered (UF), and centrifuged and filtered (CF) human urine; and to quantify the binding of COM and COD crystals to cultured HK-2 cells in UF and CF urine samples collected from different individuals. MATERIALS AND METHODS Urine was collected from healthy subjects, pooled, centrifuged and filtered. (14) C-oxalate-labelled COM and COD crystals were precipitated from the urine by adding oxalate after adjustment of two aliquots of the urine to 2 and 8 mm Ca(2+), respectively. For the kinetic study, the crystals were incubated with HK-2 cells for up to 120 min in pooled CF urine adjusted to 2 and 8 mm Ca(2+). Identical experiments were also carried out in UF urine samples collected from the same individuals. For the quantitative study, the same radioactively labelled COM and COD crystals were incubated with HK-2 cells for 50 min in separate CF and UF urines collected from eight healthy individuals at the native Ca(2+) concentrations of the urines. Field emission electron microscopy and Fourier transform-infrared spectroscopy were used to confirm crystal morphology. RESULTS COM and COD crystals generally bound more strongly at 8 mm than at 2 mm Ca(2+). The kinetic binding curves of COM were smooth, while those of COD were consistently biphasic, suggesting that the two crystal types induce different cellular metabolic responses: HK-2 cells crystals appear to possess a transitory mechanism for detaching COD, but not COM crystals. In UF urine, COM binding was significantly greater than that of COD at 2 mm Ca(2+), but at 8 mm Ca(2+) the binding of COD was greater at early and late time points. COD also bound significantly more strongly at early time points in CF urine at both 2 and 8 mm Ca(2+). In both CF and UF urine, there was no difference between the binding affinity of urinary COM and COD crystals. CONCLUSION Binding of both COM and COD crystals to cultured human renal epithelial cells is influenced by urinary macromolecules and ambient Ca(2+) concentration. HK-2 cells appear to possess a mechanism for the rapid detachment of bound COD crystals, making it difficult to show any unambiguous overall difference between the binding affinity of COM and COD crystals.
Collapse
Affiliation(s)
- Tingting Wang
- Department of Surgery, Flinders Medical Centre, Flinders University, South Australia, Australia
| | | | | | | |
Collapse
|
9
|
Chutipongtanate S, Thongboonkerd V. Renal tubular cell membranes inhibit growth but promote aggregation of calcium oxalate monohydrate crystals. Chem Biol Interact 2010; 188:421-6. [DOI: 10.1016/j.cbi.2010.08.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2010] [Revised: 08/14/2010] [Accepted: 08/17/2010] [Indexed: 12/31/2022]
|
10
|
Li Y, McLaren MC, McMartin KE. Involvement of urinary proteins in the rat strain difference in sensitivity to ethylene glycol-induced renal toxicity. Am J Physiol Renal Physiol 2010; 299:F605-15. [DOI: 10.1152/ajprenal.00419.2009] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Ethylene glycol (EG) exposure is a common model for kidney stones, because animals accumulate calcium oxalate monohydrate (COM) in kidneys. Wistar rats are more sensitive to EG than Fischer 344 (F344) rats, with greater COM deposition in kidneys. The mechanisms by which COM accumulates differently among strains are poorly understood. Urinary proteins inhibit COM adhesion to renal cells, which could alter COM deposition in kidneys. We hypothesize that COM accumulates more in Wistar rat kidneys because of lower levels of inhibitory proteins in urine. Wistar and F344 rats were treated with 0.75% EG in drinking water for 8 wk. Twenty-four-hour urine was collected every 2 wk for analysis of urinary proteins. Similar studies were conducted for 2 wk using 2% hydroxyproline (HP) as an alternative oxalate source. Total urinary protein was higher in F344 than Wistar rats at all times. Tamm-Horsfall protein was not different between strains. Osteopontin (OPN) levels in Wistar urine and kidney tissue were higher and were further increased by EG treatment. This increase in OPN occurred before renal COM accumulation. Untreated F344 rats showed greater CD45 and ED-1 staining in kidneys than untreated Wistars; in contrast, EG treatment increased CD45 and ED-1 staining in Wistars more than in F344 rats, indicating macrophage infiltration. This increase occurred in parallel with the increase in OPN and before COM accumulation. Like EG, HP induced markedly greater oxalate concentrations in the plasma and urine of Wistar rats compared with F344 rats. These results suggest that OPN upregulation and macrophage infiltration do not completely protect against COM accumulation and may be a response to crystal retention. Because the two oxalate precursors, EG and HP, produced similar elevations of oxalate, the strain difference in COM accumulation may result more so from metabolic differences between strains than from differences in urinary proteins or inflammatory responses.
Collapse
Affiliation(s)
- Yan Li
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, Louisiana
| | - Marie C. McLaren
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, Louisiana
| | - Kenneth E. McMartin
- Department of Pharmacology, Toxicology, and Neuroscience, Louisiana State University Health Sciences Center, Shreveport, Louisiana
| |
Collapse
|
11
|
Thurgood LA, Cook AF, Sørensen ES, Ryall RL. Face-specific incorporation of osteopontin into urinary and inorganic calcium oxalate monohydrate and dihydrate crystals. ACTA ACUST UNITED AC 2010; 38:357-76. [DOI: 10.1007/s00240-010-0300-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2010] [Accepted: 07/01/2010] [Indexed: 10/19/2022]
|
12
|
Kaur T, Bijarnia RK, Singla SK, Tandon C. In vivo efficacy of Trachyspermum ammi anticalcifying protein in urolithiatic rat model. JOURNAL OF ETHNOPHARMACOLOGY 2009; 126:459-462. [PMID: 19781619 DOI: 10.1016/j.jep.2009.09.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2009] [Revised: 08/27/2009] [Accepted: 09/14/2009] [Indexed: 05/28/2023]
Abstract
ETHNOPHARMACOLOGICAL RELEVANCE Many medicinal plants have been employed during ages to treat urinary stones though the rationale behind their use is not well established. Recently, we have successfully purified an anticalcifying protein from the seeds of Trachyspermum ammi (L.) Sprague ex Turril (Umbelliferae) using oxalate depletion assay and deciphered its inhibitory activity against calcium oxalate crystal growth. AIM In this report, the antilithiatic activity of Trachyspermum ammi anticalcifying protein (TAP) was studied in urolithiatic rat model. METHODOLOGY Urolithiasis was induced by exposure of 0.4% ethylene glycol (EG) and 1.0% ammonium chloride (NH(4)Cl) for 9 days. The efficacy of TAP was studied in another group given same dose of EG and NH(4)Cl in addition to 2mg/kg body weight of TAP. Further, we evaluated ability of TAP to inhibit the attachment of calcium oxalate (CaO(x)) crystal in kidney tissue and studied the consequences of CaO(x) adhesion on renal functioning and tissue integrity. RESULTS The antilithiatic potential of TAP was confirmed by its ability to maintain renal functioning, reduce renal injury and decrease crystal excretion in urine and retention in renal tissues. CONCLUSIONS Thus, the present investigation suggests the potential of TAP in preventing calcium oxalate deposition and forms the basis for the development of antilithiatic drug interventions against urolithiasis.
Collapse
Affiliation(s)
- Tanzeer Kaur
- Department of Biotechnology and Bioinformatics, Jaypee University of Information Technology, Waknaghat 173215, Solan, India
| | | | | | | |
Collapse
|
13
|
Chen S, Gao X, Sun Y, Xu C, Wang L, Zhou T. Analysis of HK-2 cells exposed to oxalate and calcium oxalate crystals: proteomic insights into the molecular mechanisms of renal injury and stone formation. ACTA ACUST UNITED AC 2009; 38:7-15. [DOI: 10.1007/s00240-009-0226-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2009] [Accepted: 10/06/2009] [Indexed: 11/30/2022]
|
14
|
Grover PK, Thurgood LA, Wang T, Ryall RL. The effects of intracrystalline and surface-bound proteins on the attachment of calcium oxalate monohydrate crystals to renal cells in undiluted human urine. BJU Int 2009; 105:708-15. [PMID: 19694711 DOI: 10.1111/j.1464-410x.2009.08816.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To compare the binding to Madin-Darby canine kidney (MDCK)-II cells of: (i) inorganic calcium oxalate monohydrate (iCOM) crystals and COM crystals precipitated from urine containing different concentrations of protein; and (ii) urinary COM crystals containing intracrystalline and intracrystalline + surface-bound protein. MATERIALS AND METHODS Urinary COM crystals were generated in sieved (sCOM), centrifuged and filtered (cfCOM), and ultrafiltered (ufCOM) portions of a pooled human urine and their adhesion to MDCK-II cells was compared using six different ultrafiltered urine samples as the binding medium. Crystal matrix extract (CME) was prepared by demineralizing calcium oxalate crystals precipitated from human urine and used to prepare COM crystals with intracrystalline, and intracrystalline + surface-bound CME at protein concentrations of 0, 0.05, 0.1, 0.5 and 5.0 mg/L. The amount of protein associated with the crystals was qualitatively assessed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and Western blotting, using prothrombin fragment 1 (PTF1) as a marker. Protein concentration was determined in sieved, centrifuged and filtered, and ultrafiltered fractions of 10 additional urine samples. RESULTS The median crystal attachment in the six urine types decreased in the order iCOM > ufCOM > cfCOM = sCOM, in inverse proportion to the concentration of protein in the solution or urine from which they were precipitated. sCOM and cfCOM crystals bound approximately 23% less than iCOM crystals. The attachment of COM crystals generated in the presence of increasing concentrations of CME proteins was unaffected up to a concentration of 5 mg/L, but binding of crystals containing the same concentrations of intracrystalline + surface-bound proteins decreased proportionally at protein concentrations from 0 to 5.0 mg/L. CONCLUSION Inorganic COM crystals bind significantly more strongly to MDCK-II cells than urinary crystals precipitated from sieved, centrifuged and filtered, and ultrafiltered urine, and binding affinity is inversely related to the concentration of protein in the urine in which they are formed. While both intracrystalline and superficial CME proteins reduce the attachment of COM crystals to MDCK-II cells, those located on the crystal surface have a greater influence than those incarcerated within the mineral bulk. Future cell-crystal interaction studies should use urinary crystals and be performed in human urine.
Collapse
Affiliation(s)
- Phulwinder K Grover
- Urology Unit, Department of Surgery, School of Medicine, The Flinders University of South Australia, Bedford Park, South Australia, Australia.
| | | | | | | |
Collapse
|
15
|
Grover PK, Thurgood LA, Fleming DE, van Bronswijk W, Wang T, Ryall RL. Intracrystalline urinary proteins facilitate degradation and dissolution of calcium oxalate crystals in cultured renal cells. Am J Physiol Renal Physiol 2007; 294:F355-61. [PMID: 18077596 DOI: 10.1152/ajprenal.00529.2007] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have previously proposed that intracrystalline proteins would increase intracellular proteolytic disruption and dissolution of calcium oxalate (CaOx) crystals. Chauvet MC, Ryall RL. J Struct Biol 151: 12-17, 2005; Fleming DE, van Riessen A, Chauvet MC, Grover PK, Hunter B, van Bronswijk W, Ryall RL. J Bone Miner Res 18: 1282-1291, 2003; Ryall RL, Fleming DE, Doyle IR, Evans NA, Dean CJ, Marshall VR. J Struct Biol 134: 5-14, 2001. The aim of this investigation was to determine the effect of increasing concentrations of intracrystalline protein on the rate of CaOx crystal dissolution in Madin-Darby canine kidney (MDCKII) cells. Crystal matrix extract (CME) was isolated from urinary CaOx monohydrate (COM) crystals. Cold and [14C]oxalate-labeled COM crystals were precipitated from ultrafiltered urine containing 0-5 mg/l CME. Crystal surface area was estimated from scanning electron micrographs, and synchrotron X-ray diffraction was used to determine nonuniform strain and crystallite size. Radiolabeled crystals were added to MDCKII cells and crystal dissolution, expressed as radioactive label released into the medium, was measured. Increasing CME content did not significantly alter crystal surface area. However, nonuniform strain increased and crystallite size decreased in a dose-response manner, both reaching saturation at a CME concentration of 3 mg/ and demonstrating unequivocally the inclusion of increasing quantities of proteins in the crystals. This was confirmed by Western blotting. Crystal dissolution also followed saturation kinetics, increasing proportionally with final CME concentration and reaching a plateau at a concentration of approximately 2 mg/l. These findings were complemented by field emission scanning electron microscopy, which showed that crystal degradation also increased relative to CME concentration. Intracrystalline proteins enhance degradation and dissolution of CaOx crystals and thus may constitute a natural defense against urolithiasis. The findings have significant ramifications in biomineral metabolism and pathogenesis of renal stones.
Collapse
Affiliation(s)
- Phulwinder K Grover
- Urology Unit, Department of Surgery, School of Medicine, Flinders University, Bedford Park, South Australia, Australia.
| | | | | | | | | | | |
Collapse
|