Urine activity of cathepsin B, collagenase and urine excretion of TGF-beta 1 and fibronectin in membranous glomerulonephritis.

In 30% of cases nephrotic syndrome is caused by membranous glomerulonephritis (MG). Protein accumulation in glomeruli leads to progressive loss of kidney function and damage of structure in MG. The role of tissue proteolytic systems and growth factors in this process is not known. The purpose of the study was to estimate urine cathepsin B, collagenase activity and urine excretion of TGF-beta 1 and fibronectin in MG. Cathepsin B activity was greater in the urine of MG patients than in the control group (10.58 +/- 8.73 pmol AMC/mg creatinine per min-1 vs control 7.11 +/- 2.05 pmol AMC/mg creatinine per min-1; P < 0.05). Urine collagenase activity was higher in the group of patients than in the control group (8.59 +/- 4.26 pmol AMC/mg creatinine per min-1 vs control 3.84 +/- 2.09 pmol AMC/mg creatinine per min-1 P < 0.02). Urine excretion of fibronectin (45.60 ng/mg creatinine vs control 10.30 ng/mg creatinine; P < 0.04) and TGF-beta 1 levels in the urine were higher than in controls (283.55 +/- 248.13 pg/ml vs 36.11 +/- 48.01 pg/ml; P < 0.01). Results suggest glomerular overproduction of TGF-beta 1 and urinary leak of proteolytic enzymes (PE). This may result in decreased glomerular PE activity in MG and, with time, may lead to protein accumulation in renal glomeruli and to progressive loss of kidney function and damage of structures as the course of MG progresses. PE urine composition as well as ECM protein and cytokine urine excretion may allow noninvasive glomerulopathy course monitoring in humans in the future.