Abnormal glycosylation of Tamm‐Horsfall protein in patients with interstitial cystitis

Abstract

To confirm abnormal glycosylation of Tamm-Horsfall protein (THP) in patients with interstitial cystitis (IC). The sialic acid content of THP, a critical component of its biological activity, is reduced in patients with IC. N-glycan shows reduced levels of high molecular weight tri- and tetra-antennary sialylated oligosaccharides. These results are supported by quantitative monosaccharide analysis of neutral and amino sugars in patients vs control subjects. THP was isolated from urine samples of 23 patients with IC and 24 control subjects by salt precipitation. The sialic acid contents were measured using 1,2-diamino-4,5-methylene dioxybenzene-high performance liquid chromatography analysis. For N-glycan profiling, purified THP was treated with peptide:N-glycosidase F to release N-glycans. The purified N-glycans were labelled with 2-aminobenzamide and were profiled by high-pH anion exchange chromatography (HPAEC) with fluorescence detection. The neutral and amino sugars were determined by HPAEC with pulsed amperometric detection. The total sialic acid in patients was half of that in controls. There was a pattern of reduced level of high molecular weight sialylated oligosaccharide in 17 of 23 patients vs four of 24 controls. The total neutral and amino sugars showed a approximately 30% reduction in patients. The mean (sem) for the controls was 133.79 (6.51) vs 94.76 (6.67) nmol/200 microg of THP for patients (P < 0.001). THP in patients with IC has reduced sialylation and overall glycosylation, and by inference, THP has a role in the pathophysiology of IC.