Differential expression of urinary inter-alpha-trypsin inhibitor trimers and dimers in normal compared to active calcium oxalate stone forming men

Regulation of macromolecular modulators of urinary stone formation by reactive oxygen species: transcriptional study in an animal model of hyperoxaluria

We used an unbiased approach of gene expression profiling to determine differential gene expression of all the macromolecular modulators (MMs) considered to be involved in stone formation, in hyperoxaluric rats, with and without treatment with the NADPH oxidase inhibitor apocynin. Male rats were fed rat chow or chow supplemented with 5% wt/wt hydroxy-l-proline (HLP) with or without apocynin-supplemented water. After 28 days, rats were euthanized and their kidneys explanted. Total RNA was isolated and microarray analysis was conducted using the Illumina bead array reader. Gene ontology analysis and the pathway analyses of the genes were done using Database for Annotation, Visualization of Integrated Discovery enrichment analysis tool. Quantitative RT-PCR of selected genes was carried out to verify the microarray results. Expression of selected gene products was confirmed using immunohistochemistry. Administration of HLP led to crystal deposition. Genes encoding for fibronectin, CD 44, fetuin B, osteopontin, and matrix-gla protein were upregulated while those encoding for heavy chains of inter-alpha-inhibitor 1, 3, and 4, calgranulin B, prothrombin, and Tamm-Horsfall protein were downregulated. HLP-fed rats receiving apocynin had a significant reversal in gene expression profiles: those that were upregulated came down while those that were downregulated stepped up. Apocynin treatment resulted in near complete absence of crystals. Clearly, there are two types of MMs; one is downregulated while the other is upregulated during hyperoxaluria and crystal deposition. Apparently gene and protein expressions of known macromolecular modulators of CaOx crystallization are likely regulated by ROS produced in part through the activation of NADPH oxidase.

Bikunin and α1-microglobulin/bikunin precursor (AMBP) gene mutational screening in patients with kidney stones: a case-control study

OBJECTIVE

Bikunin is an inhibitor of kidney stone formation synthesized in the liver together with α(1)-microglobulin from the α(1)-microglobulin/bikunin precursor (AMBP) gene. The aim of this study was to investigate the possible association between bikunin/AMBP gene polymorphisms and urinary stone formation.

MATERIAL AND METHODS

To analyse the DNA, blood samples were taken from 75 kidney stone formers who had a familial stone history, 35 sporadic stone formers and 101 healthy individuals. Four exons of bikunin gene and five parts of the promoter region of the AMBP gene were screened using single-strand conformation polymorphism and nucleotide sequence analysis.

RESULTS

The Init-2 region of the promoter of AMBP gene had polymorphisms at positions -218 and -189 nt giving three different genotypes having 1,3, 2,4 and 1,2,3,4 alleles with frequencies of 17.06%, 60.19% and 22.75%, respectively, in all groups. Therefore, the Init-2 region appears to be polymorphic. As a result, the 1,3 allele has -218G and -189T complying with the reference database sequence, the 2,4 allele has -218G and T-189C substitution and the allele 1,2,3,4 genotype has substitutions at positions G-218C and T-189C.

CONCLUSIONS

There were no significant differences in allele distribution between patients and controls. These common alleles exist in the Turkish population independent of stone formation. These results are the first to demonstrate the existence of bikunin and AMBP promoter polymorphism. Although the Init-2 region of the AMBP gene is the binding site for various transcription factors, the results showed no association between these observed genotypes and stone-forming phenotypes.

Structure and function of inter-alpha-trypsin inhibitor heavy chains

Inter-alpha-trypsin inhibitor family proteins are mainly detected in plasma and urine and comprise the common light chain bikunin and at least 6 closely related heavy chains. The bikunin moiety exhibits protease inhibitory activity and has been studied extensively; however, the heavy chains have been largely overlooked. Recent studies clearly indicate that the heavy chain moieties have important biological functions either in association with or independent of bikunin. Because the heavy chains comprise the main part of the protein structure of this family, it is important to understand their functions. This review summarizes the domain structural features of heavy chains, the heavy chain-interacting molecules identified thus far, and the association of heavy chains with diseases to encourage the discovery of novel heavy chains-interacting molecules and to gain a deeper insight into their functions.

Renal inter-alpha-trypsin inhibitor heavy chain 3 increases in calcium oxalate stone-forming patients

Inter-alpha-trypsin inhibitor heavy-chain proteins bind to the protease inhibitor bikunin and to hyaluronan, stabilizes extracellular matrix in various tissues, and also inhibits calcium oxalate crystallization in vitro. In both normal and stone-forming patients, we found heavy chain 3 and hyaluronan in the interstitial matrix of the kidney. Osteopontin was found in the collecting duct, thin loop of Henle, and urothelial cells. In stone formers, heavy chain 3 was also present in collecting duct, thin loop, and interstitial cells. Heavy chain 3 and osteopontin colocalized in plaque matrix and urothelial cells. Within individual plaque spherules, heavy chain 3 was found in the matrix layer while osteopontin was located along the crystal-matrix interface. Bikunin was present only in the collecting duct apical membranes and the loop cell cytoplasm of stone formers colocalizing with osteopontin and heavy chain 3. Widespread heavy chain 3 was only present in stone formers, whereas osteopontin was similarly expressed in normal and stone-forming subjects except for its localization in plaques of the stone formers. This is consistent with studies linking inter-alpha-trypsin inhibitor components to human stone disease, although their role is still unclear. Heavy chain 3 may also play a role in stabilizing hyaluronan in the renal interstitial matrix.

Urine protein markers distinguish stone-forming from non-stone-forming relatives of calcium stone formers

We have investigated urine protein inhibitors of calcium oxalate crystallization to determine whether variations in these proteins are associated with kidney stone disease and whether protein measurements improve the identification of stone formers compared with conventional risk factors (RF). Using Western blotting, we studied variations in the electrophoretic mobility patterns and relative abundances of crystallization-inhibitory proteins in urine from 50 stone-forming (SF) and 50 non-stone-forming (NS) first-degree relatives of calcium SF patients, matched by gender and age. Standard urine chemistry stone risk measurements were also made. Multivariate discriminant analysis was used to test the association of these proteins with nephrolithiasis. Differences in form and abundance of several urine proteins including inter-alpha-trypsin inhibitor (ITI), prothrombin fragment 1 (PF1), CD59, and calgranulin B (calB) were found to be associated with stone formation. By multivariate discriminant analysis, measurements of forms of PF1, ITI, and calB in men and ITI and CD59 in women, classified 84% of men and 76% of women correctly by stone status. In contrast, standard urine chemistry RF identified only 70% of men correctly and failed to distinguish female SF from NS. Thus a small subset of protein measurements distinguished SF from NS far better than conventional RF in a population of relatives of calcium SF, illustrating the significant association of these proteins with stone disease. Variations in these proteins may serve as markers of stone disease activity or vulnerability to recurrence and may provide new insights into mechanisms of stone formation.

Kidney stone disease

About 5% of American women and 12% of men will develop a kidney stone at some time in their life, and prevalence has been rising in both sexes. Approximately 80% of stones are composed of calcium oxalate (CaOx) and calcium phosphate (CaP); 10% of struvite (magnesium ammonium phosphate produced during infection with bacteria that possess the enzyme urease), 9% of uric acid (UA); and the remaining 1% are composed of cystine or ammonium acid urate or are diagnosed as drug-related stones. Stones ultimately arise because of an unwanted phase change of these substances from liquid to solid state. Here we focus on the mechanisms of pathogenesis involved in CaOx, CaP, UA, and cystine stone formation, including recent developments in our understanding of related changes in human kidney tissue and of underlying genetic causes, in addition to current therapeutics.

A simple procedure for isolating microgram quantities of biologically active bikunin from human urine

OBJECTIVE

To report a simple, relatively rapid protocol to isolate biologically active bikunin from human urine using ion-exchange-trypsin affinity chromatography. Bikunin is a protease inhibitor which has been shown to play a role in various processes, including inhibition of calcium oxalate crystallization, the regulation of proliferation and modulation of carcinogenesis. The unavailability of the purified protein has hampered studies on bikunin's expanding role in these processes.

MATERIALS AND METHODS

Female human urine was dialysed (15 kDa threshold) and crudely fractionated with a double-saturated ammonium sulphate precipitation. The first precipitation was with 35% saturated ammonium sulphate, and the supernatant was harvested, and the second with 90% saturated ammonium sulphate, and the precipitate collected. The protein mixture was then passed over Sepharose SP-fast-flow cation exchange and Sepharose Q-fast-flow anion exchange columns connected in series. The final purification was with a trypsin-affinity column which selectively bound bikunin.

RESULTS

This procedure could recover 1 microg of bikunin per 2 mL of urine, and the final product was essentially free of contaminating inter-alpha-trypsin inhibitor heavy chains or bikunin-heavy chain conjugates. Product purity was confirmed by two-dimensional polyacrylamide gel electrophoresis combined with silver staining or Western blot. All isolations contained the 17 kDa minimally glycoslyated/sulphated form of bikunin and the 28 kDa form of bikunin. Some preparations also contained 33-48 kDa forms of bikunin. The protein cores of all three proteins were confirmed to be bikunin by mass spectrometry and Western blot. Harvested bikunin retained its trypsin inhibitory activity (L-benzoylarginine-p-nitroanilide assay). Preparations containing the 33-45 kDa form had two to three times more trypsin inhibitory activity than preparations without this band.

CONCLUSIONS

This novel ion exchange-trypsin affinity chromatography protocol uses only two chromatographic steps. The product consists of three isomers of biologically active bikunin, free of contaminating heavy chains or bikunin-heavy chain conjugates. The ready availability of purified bikunin should facilitate future studies of bikunin's emerging role in urolithiasis, proliferation and carcinogenesis.

Levels of urinary inter-alpha-trypsin inhibitor trimer as a function of age and sex-hormone status in males and females not forming stones

OBJECTIVES

To determine if levels of inter-alpha-trypsin inhibitor (I alpha TI)-trimer differ in normal individuals based on age, gender or hormonal status, as the regulation of calcium oxalate (CaOx) crystallization inhibitors, e.g. by sex steroids, could be a mechanism contributing to the differences in CaOx urolithiasis between the sexes.

SUBJECTS AND METHODS

Voided urine samples were collected from normal males and females. In Experiment 1 samples were grouped by gender and age, i.e. paediatric (PED) < or = 10 years, male (M) 21, female (F) 14; young adult (YGAD) 20-30 years, M 23, F 18; adults (AD), 35-50 year, M 25, F 13; adults aged > or = 60 years (> 60), M 24, F 16 (totals, M 93, F 61). In Experiment 2 samples were grouped by gender, age and hormonal status, i.e. PED, M 24, F 17; AD, M 24, F 22; > 60 and not on hormonal therapy, M 23, F 30; M > 60 and on androgen deprivation therapy (ANDEP) 18; and F > 60 on oestrogen supplementation, F+EST, 18 (total M 89, F 85). Levels of urinary I alpha TI-trimer were determined by immunoblotting and enhanced chemiluminescence, and relative densities of the bands determined.

RESULTS

In both experiments the relative levels of I alpha TI-trimer were 2-7 times higher in M-PED than in all other groups of males (P < or = 0.007). Among adult males, I alpha TI-trimer levels were similar in all groups, including ANDEP (P > or = 0.9). There were no differences in the relative levels of I alpha TI-trimer among any of the groups of females, regardless of age or hormonal status (P > or = 0.7).

CONCLUSIONS

In males a decrease in I alpha TI-trimer was associated with the onset of adulthood and entry into the 'stone-forming years'. Females did not show this decrease, and neither sex showed an increase in I alpha TI-trimer in the > 60 group, when the incidence of CaOx urolithiasis is supposedly declining. While changes in urinary I alpha TI-trimer levels in males may reflect maturational changes in the kidney, overall these data do not support the hypothesis that the age-related changes in the incidence of urolithiasis are paralleled by changes in the expression I alpha TI-trimer. Additionally, the sex steroids do not appear to acutely regulate the expression of I alpha TI-trimer in adults, making differences in I alpha TI-trimer levels unlikely to be the reason for the disparity in the incidence of CaOx urolithiasis between the sexes.

Expression of proteins that inhibit calcium oxalate crystallization in vitro in the urine of normal and stone-forming individuals

The factors precipitating clinically active calcium oxalate (CaOx) urolithiasis are not known. This study examined the relationships between urinary proteins that inhibit CaOx crystallization in vitro and the incidence of CaOx urolithiasis. The first hypothesis is that levels of urinary CaOx crystallization inhibitors differ between clinically active stone formers (SFs) and normal individuals. The second hypothesis is that lower levels of urinary CaOx crystallization inhibitors contribute to the two- to threefold greater incidence of CaOx urolithiasis in males compared with females. These hypotheses were derived from previous observations on the expression of urinary inter-alpha-trypsin inhibitor trimer (IalphaTI-trimer) in normal and stone-forming individuals. The proteins of void urine samples from normal volunteers (24 males, 19 females) and CaOx-SFs (26 males, 16 females) were resolved by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Immunoreactive IalphaTI-trimer, osteopontin, and prothrombin were detected by immunoblot plus enhanced chemiluminescence; the relative densities of the bands were then determined. With the exception of IalphaTI-trimer (P: </= 0.026, approximately twofold), there was no difference in the relative densities of CaOx crystallization inhibitors in the urine of normal and CaOx stone-forming individuals. Thus, there does not appear to be a generalized increase or decrease in levels of CaOx crystallization inhibitory proteins between normal and CaOx stone-forming individuals. The relative density of IalphaTI-trimer was approximately threefold greater in females than in males (P: </= 0.001). Differences in the relative densities of the other CaOx crystallization inhibitors were small and of questionable physiological importance. These data do not support the hypothesis that males have a greater incidence of CaOx urolithiasis because of a generalized decrease in urinary CaOx crystallization inhibitory protein levels.

Changing concepts in the aetiology of renal stones

In the past two decades an increasing number of nephrolithiasis-related urinary proteins have been identified. This paper focuses on two of them, namely prothrombin fragment 1 and bikunin, members of the prothrombin and inter-alpha-trypsin inhibitor families of proteins, respectively. Besides their role as inhibitors of crystallization, these proteins are also involved in inflammation-mediated tissue repair. This is the basis for the concept that the response of renal tissue to injury might play an important role in the aetiology of kidney stones.

Identification of hyaluronan as a crystal-binding molecule at the surface of migrating and proliferating MDCK cells

BACKGROUND

The adherence of calcium oxalate crystals to the renal tubule epithelium is considered a critical event in the pathophysiology of calcium nephrolithiasis. Calcium oxalate monohydrate (COM) crystals cannot adhere to the surface of a functional Madin-Darby canine kidney (MDCK) monolayer, but they bind avidly to the surface of proliferating and migrating cells.

METHODS

To identify crystal-binding molecules (CBMs) at the surface of crystal-attracting cells, we applied metabolic labeling protocols in combination with differential enzymatic digestion and gel filtration, which was compared with [14C]COM crystal binding and confirmed by confocal microscopy.

RESULTS

The indication that hyaluronan [hyaluronic acid (HA)] might act as a CBM in subconfluent cultures came from studies with glycosaminoglycan (GAG)-degrading enzymes. Subsequently, metabolic-labeling studies revealed that hyaluronidase cleaved significantly more radiolabeled glycoconjugates from crystal-attracting cells than from cells without affinity for crystals. During wound repair, crystal binding could be prevented by pretreating the healing cultures with hyaluronate lyase, an enzyme that specifically hydrolyzes HA. Binding to immobilized HA provided evidence that COM crystals physically can become associated with this polysaccharide. Finally, confocal microscopy demonstrated that fluorescently labeled HA binding protein (HABP) adhered to the surface of proliferating cells in subconfluent cultures as well as to cells involved in closing a wound, but not to cells in confluent monolayers.

CONCLUSIONS

These results identify HA as binding molecule for COM crystals at the surface of migrating and proliferating MDCK cells.

Mannan-binding lectin (MBL)-associated plasma protein present in human urine inhibits calcium oxalate crystal growth

Mannan-binding lectin (MBL)-associated plasma protein (MAp19) is an alternatively spliced form of MBL-associated serine protease-2, a component of a complement activation cascade. We observed that MAp19 is excreted in human urine. Interestingly, the amount of MAp19 was higher in urine of renal cell carcinoma patients than healthy people. Pretreatment of urine dialysate with 50 mM EDTA increased the recovery of MAp19, suggesting that MAp19 is a calcium-binding protein. The recombinant MAp19 showed a strong inhibition of calcium oxalate crystal growth in vitro in a concentration-dependent manner. Thus, we conclude that MAp19 plays a role in the inhibition of calcium oxalate renal stone formation.

A new human prostate carcinoma cell line, 22Rv1

A cell line has been derived from a human prostatic carcinoma xenograft, CWR22R. This represents one of very few available cell lines representative of this disease. The cell line is derived from a xenograft that was serially propagated in mice after castration-induced regression and relapse of the parental, androgen-dependent CWR22 xenograft. Flow cytometric and cytogenetic analysis showed that this cell line represents one hyper DNA-diploid stem line with two clonal, evolved cytogenetic sublines. The basic karyotype is close to that of the grandparent xenograft, CWR22, and is relatively simple with 50 chromosomes. In nude mice, the line forms tumors with morphology similar to that of the xenografts, and like the parental CWR22 and CWR22R xenografts, this cell line expresses prostate specific antigen. Growth is weakly stimulated by dihydroxytestosterone and lysates are immunoreactive with androgen receptor antibody by Western blot analysis. Growth is stimulated by epidermal growth factor but is not inhibited by transforming growth factor-beta1.

Temporal changes in mRNA expression for bikunin in the kidneys of rats during calcium oxalate nephrolithiasis

Inter-alpha-inhibitor and other bikunin-containing proteins are synthesized in relatively large quantities by the liver. These proteins function as Kunitz-type serine protease inhibitors and appear capable of inhibiting calcium oxalate (CaOx) crystallization in vitro. Preliminary studies have shown that renal tubular epithelial cells synthesize bikunin in response to CaOx challenge. To examine this response in vivo, a sensitive reverse transcription-quantitative competitive template-PCR was developed to detect and quantify poly(A)+ -tailed bikunin mRNA expression in kidney tissue from normal rats and rats developing CaOx nephrolithiasis after challenge with ethylene glycol. Bikunin mRNA expression in rat liver tissue was assessed as a positive control. The expression of bikunin mRNA in liver did not differ significantly between normal control rats and experimental rats with induced hyperoxaluria and renal CaOx crystallization. In contrast, there were significant temporal increases in the levels of bikunin mRNA expression in rat kidneys during CaOx nephrolithiasis after challenge with ethylene glycol. Urinary excretion of bikunin-containing proteins seemed to increase concomitantly. These findings indicate an association between the induction of hyperoxaluria/CaOx nephrolithiasis and the expression of the bikunin gene in rat kidneys.