Tamm-Horsfall protein: are serum levels a marker for urinary tract obstruction?

Uromodulin: from physiology to rare and complex kidney disorders

Uromodulin (also known as Tamm-Horsfall protein) is exclusively produced in the kidney and is the most abundant protein in normal urine. The function of uromodulin remains elusive, but the available data suggest that this protein might regulate salt transport, protect against urinary tract infection and kidney stones, and have roles in kidney injury and innate immunity. Interest in uromodulin was boosted by genetic studies that reported involvement of the UMOD gene, which encodes uromodulin, in a spectrum of rare and common kidney diseases. Rare mutations in UMOD cause autosomal dominant tubulointerstitial kidney disease (ADTKD), which leads to chronic kidney disease (CKD). Moreover, genome-wide association studies have identified common variants in UMOD that are strongly associated with risk of CKD and also with hypertension and kidney stones in the general population. These findings have opened up a new field of kidney research. In this Review we summarize biochemical, physiological, genetic and pathological insights into the roles of uromodulin; the mechanisms by which UMOD mutations cause ADTKD, and the association of common UMOD variants with complex disorders.

Urinary proteome analysis in congenital bilateral hydronephrosis

OBJECTIVE

A proteomics strategy was applied to map protein changes in urine after relief of congenital bilateral hydronephrosis to identify proteins correlated with the pathophysiological processes in congenital obstructive nephropathy as potential urinary biomarkers.

MATERIAL AND METHODS

Urine samples from 10 infants with bilateral abnormal drainage from the kidneys were collected at the time of relief from obstruction, and after 2 and 4 weeks. Proteomics techniques were used on samples from three patients for identification of protein changes between the three time-points, and enzyme-linked immunosorbent assay (ELISA) was used on samples from all 10 patients for validation of five selected proteins.

RESULTS

Mass spectrometry quantified 315 protein hits, out of which 33 proteins showed significantly changed urinary excretion between the time-points. Validation by ELISA showed high urinary excretion of fibrinogen, plasminogen, transthyretin and transferrin at the time of relief from obstruction, followed by a significant reduction. In contrast, Tamm-Horsfall protein exhibited the reverse pattern.

CONCLUSION

Using a mass spectrometry-based proteomics approach, this study identified 33 proteins related to congenital bilateral hydronephrosis, and pinpointed a panel of five proteins consistently linked to this congenital kidney disorder as potential urinary biomarkers.

Role of Tamm-Horsfall protein in the binding and in vivo phagocytosis of type 1 fimbriated Escherichia coli by mouse peritoneal macrophages

Tamm-Horsfall glycoprotein (THP) contains manno-oligosaccharides that are recognized by type 1 fimbriae (F1) of Escherichia coli. In the present study, we examined the in vivo phagocytic activity of mouse peritoneal macrophages after treatment of bacteria with THP. At low THP concentrations (12.5 microg/ml and 50 microg/ml) no significant difference was observed in the phagocytosis of E. coli F1+. However, at high THP concentrations (500 microg/ml and 1250 microg/ml) we obtained a reduction of bacterial phagocytosis by mouse peritoneal macrophages.

Serum levels of IgG antibodies against Tamm-Horsfall protein and urinary excretion of NAG and alpha-1-microglobulin as possible markers for tubular damage in patients with a continent ileal reservoir for urinary diversion

Serum IgG antibodies against Tamm-Horsfall protein and urinary excretion of NAG and alpha-1-microglobulin were measured in 26 patients with a Kock reservoir for continent urinary diversion or orthotopic bladder reconstruction in order to detect any signs of tubular damage. None of these markers for tubular damage was correlated to the postoperative observation time ranging between 2 and 16 years. No correlation was found between these markers and signs of renal scarring or upper urinary tract dilatation as judged from urographies. A positive correlation was demonstrated between NAG excretion and antibodies against Tamm-Horsfall protein. The annual reduction in GFR was increased in patients with elevated alpha-1-microglobulin excretion but not in patients with elevated titres of antibodies against Tamm-Horsfall protein or increased NAG excretion. Patients with previous or present reflux nipple problems had elevated excretion of alpha-1-microglobulin. Regular determinations of alpha-1-microglobulin excretion appear to be of value in the follow-up of these patients.