Elastase deposits in the kidney and urinary elastase excretion in patients with glomerulonephritis--evidence for neutrophil involvement in renal injury.

Objective: Elastase is a key proteolytic enzyme released during polymorphonuclear leukocyte degranulation. There are abundant data of elastase involvement in the development of injury in experimental models of glomerulonephritis (GN), but scant direct evidence of its involvement in human primary GN. The aims of this study were to determine the immunolocalization of elastase deposits in kidney biopsy specimens from patients with primary idiopathic GN, to attempt to correlate the distribution and intensity of deposits with urinary elastase excretion, and to determine clinical markers of renal injury in several types of primary idiopathic GN.

Material And Methods: The immunohistochemical localization and intensity of elastase deposits in kidney biopsies, the urinary excretion of leukocyte elastase, and proteinuria and serum creatinine levels were evaluated in 23 patients with primary GN and the associations between these factors were sought.

Results: Patients with crescentic proliferative GN had the highest intensity of elastase deposits. In this group of patients, elastase was present in the glomerular endothelium, as well as in the tubular epithelium and interstitium. Patients with a high intensity of elastase deposits within the glomerular endothelium and Bowman's capsule had significantly higher urinary excretion of elastase. Patients with interstitial, mesangial and perivascular elastase deposits had significantly higher serum creatinine than those without. Patients with elastase deposits in the glomerular endothelium and in the interstitium had insignificantly higher proteinuria than those without.

Conclusion: Our data provide morphological evidence of leukocyte elastase involvement in renal injury occurring in the course of primary idiopathic GN, in particular in the proliferative types.