Highly sensitive reversed-phase high-performance liquid chromatography assay for the detection of Tamm-Horsfall protein in human urine.

BACKGROUND: Tamm-Horsfall protein (also known as uromodulin) is the most abundant urinary protein in healthy individuals. Since initially characterized by Tamm and Horsfall, the amount of urinary excretion and structural mutations of Tamm-Horsfall protein is associated with kidney diseases. However, currently available assays for Tamm-Horsfall protein, which are mainly enzyme-linked immunosorbent assay-based, suffer from poor reproducibility and might give false negative results. METHODS: We developed a novel, quantitative assay for Tamm-Horsfall protein using reversed-phase high-performance liquid chromatography. A precipitation pretreatment avoided urine matrix interference and excessive sample dilution. High-performance liquid chromatography optimization based on polarity allowed excellent separation of Tamm-Horsfall protein from other major urine components. RESULTS: Our method exhibited high precision (based on the relative standard deviations of intraday [≤2.77%] and interday [≤5.35%] repetitions). The Tamm-Horsfall protein recovery rate was 100.0-104.2%. The mean Tamm-Horsfall protein concentration in 25 healthy individuals was 31.6 ± 18.8 mg/g creatinine. There was a strong correlation between data obtained by high-performance liquid chromatography and enzyme-linked immunosorbent assay (r = 0.906), but enzyme-linked immunosorbent assay values tended to be lower than high-performance liquid chromatography values at low Tamm-Horsfall protein concentrations. CONCLUSIONS: The high sensitivity and reproducibility of our Tamm-Horsfall protein assay will reduce the number of false negative results of the sample compared with enzyme-linked immunosorbent assay. Moreover, our method is superior to other high-performance liquid chromatography methods, and a simple protocol will facilitate further research on the physiological role of Tamm-Horsfall protein.

Immunomodulatory properties of Tamm-Horsfall glycoprotein (THP) and uromodulin.

BACKGROUND: Tamm-Horsfall glycoprotein (THP) and uromodulin are the most abundant glycoproteins in non-pregnant women's/men's and pregnant women's urine, respectively. However, the bioactivities of these glycoproteins are still unclear. OBJECTIVE: To evaluate the immunomodulatory properties of THP and uromodulin on human peripheral blood mononuclear cells (PBMC) METHODS: THP and uromodulin isolated with diatomaceous earth filtration were subjected to several bioassays, such as MTS viability assay, immunophenotyping and cytokine analysis. RESULTS: MTS viability assay and immunophenotyping analysis showed that uromodulin has greater inhibitory activities in suppressing PBMC viability and the percentage of CD4⁺ T helper cells and CD8⁺ cytotoxic T cells, compared to that of THP. In cytokine analysis, THP tended to induce pro-inflammatory cytokines such as IL-1ß, TNF and Th1 cytokine IFN-γ; while uromodulin only induced IL-1ß and suppressed both Th1 cytokine IFN-γ and Th2 cytokine IL-10. CONCLUSION: These results demonstrate that uromodulin has greater immunosuppressive activities and lower inductive property in relation to activation of immune cells, which provides a more tolerant environment for the developing fetus.

Isolation of urinary extracellular vesicles from Tamm- Horsfall protein-depleted urine and their application in the development of a lectin-exosome-binding assay.

Urine is a readily available source of relatively large quantities of extracellular vesicles (EVs). However, the isolation of urinary EVs (uEVs) is complicated by the presence of Tamm-Horsfall protein (THP), which polymerizes and co-precipitates as a contaminant. This may make glycan analysis of uEVs difficult since THP is heavily glycosylated. To facilitate glycosylation analysis and address the need for elimination of non-uEV glycans, we present a modification of the uEV isolation procedure and use the isolated uEVs in the development of a lectin-exosome binding assay. Salt precipitation was employed to remove THP under conditions originally described for its separation from urine, followed by differential centrifugation. The quality of the isolated uEVs was examined by electron microscopy, SDS-PAGE, and immunoblotting. The uEVs were subsequently immobilized on solid phase and probed with labeled plant lectins using the lectin-exosome binding assay. Our results indicate that the isolated uEVs had preserved structural integrity and reacted with labeled plant lectins in a selective, carbohydrate-dependent manner. The basic lectin binding pattern of uEVs obtained by our method can be used as a reference for assessing the composition of their surface glycans in different physiological and pathological conditions.

Surface glycosylation profiles of urine extracellular vesicles.

Urinary extracellular vesicles (uEVs) are released by cells throughout the nephron and contain biomolecules from their cells of origin. Although uEV-associated proteins and RNA have been studied in detail, little information exists regarding uEV glycosylation characteristics. Surface glycosylation profiling by flow cytometry and lectin microarray was applied to uEVs enriched from urine of healthy adults by ultracentrifugation and centrifugal filtration. The carbohydrate specificity of lectin microarray profiles was confirmed by competitive sugar inhibition and carbohydrate-specific enzyme hydrolysis. Glycosylation profiles of uEVs and purified Tamm Horsfall protein were compared. In both flow cytometry and lectin microarray assays, uEVs demonstrated surface binding, at low to moderate intensities, of a broad range of lectins whether prepared by ultracentrifugation or centrifugal filtration. In general, ultracentrifugation-prepared uEVs demonstrated higher lectin binding intensities than centrifugal filtration-prepared uEVs consistent with lesser amounts of co-purified non-vesicular proteins. The surface glycosylation profiles of uEVs showed little inter-individual variation and were distinct from those of Tamm Horsfall protein, which bound a limited number of lectins. In a pilot study, lectin microarray was used to compare uEVs from individuals with autosomal dominant polycystic kidney disease to those of age-matched controls. The lectin microarray profiles of polycystic kidney disease and healthy uEVs showed differences in binding intensity of 6/43 lectins. Our results reveal a complex surface glycosylation profile of uEVs that is accessible to lectin-based analysis following multiple uEV enrichment techniques, is distinct from co-purified Tamm Horsfall protein and may demonstrate disease-specific modifications.

Purification of exosome-like vesicles from urine.

Urinary exosome-like vesicles (ELVs), 20-200nm membrane-bound particles shed by renal epithelium, have been shown to interact with the primary cilia of distant epithelial cells of the nephron. These ELVs are emerging as an important source of protein, mRNA, and miRNA biomarkers to monitor renal disease. However, purification of ELVs is compromised by the presence of large amounts of the urinary protein Tamm-Horsfall Protein (THP). THP molecules oligomerize into long, double-helical strands several microns long. These linear assemblies form a three-dimensional gel which traps and sequesters ELVs in any centrifugation-based protocol. Here, we present a purification protocol that separates ELVs from THP and divides urinary ELVs into three distinct populations.