Rikke Langkilde - Contribution of preurine protease activity to hypertension, diabetic nephropathy and loss of kidney function

Diabetic nephropathy is a common complication that affects 10-30 % of diabetic patients and is characterized by albuminuria, hypertension and kidney tissue changes. Hypertension is known as a leading risk factor for heart disease, death and disability worldwide making it a great health burden. One of the strongest predictors of a poor outcome in diabetes and cardiovascular disease is the degree of renal damage as measured by aberrant loss of plasma albumin into urine.

The project explores a new finding by the applicant that may explain causally the coupling between albuminuria, hypertension and poor kidney outcome in diabetes. The epithelial sodium channel (ENaC) located in the collecting duct of the kidney is one of the central effectors involved in regulation of salt and water homeostasis in the organism. We have found that aberrant glomerular filtration of plasma proteases, i.e. plasmin, prostasin and urokinase in diabetes patients, confers to preurine the ability to activate ENaC in renal collecting ducts by cleaving the ectodomain of the channel and thus lead to impaired sodium excretion and hypertension.

The study is divided in 3 hypothesis driven substudies with the following research questions:

1. Urinary, epitheliallyderived nanovesicles (“exosomes”) are a noninvasive surrogate marker for apical collecting duct epithelial transport protein abundance and proteolysis.
   
   
2. A quantitative urine plasmin activity assay reveals increased urine plasmin activity in albuminuria and predicts a poor outcome in diabetes.
   
   
3. A 43aminoacid peptide from the ENaC ectodomain is released into urine by aberrant presence of plasmin and yields a measure of intrarenal ENaC activity with predictive power.

The experiments are designed to explore human samples and the techniques are established including monoclonal ENaC antibodies developed and characterized by the applicant. The project is conducted in collaboration with departments of

Urology and Nephrology and may lead to methodological biomarker and pharmacological target development relevant for the large patient segments with albuminuria and hypertension, including diabetic patients, where nephropathy is a common complication.