Renal expression of endothelial and inducible nitric oxide synthase, and formation of peroxynitrite-modified proteins and reactive oxygen species in Wegener's granulomatosis

To investigate the role of nitric oxide (NO) in glomerular inflammation, th e expression of endothelial NO synthase (eNOS) and inducible NOS (iNOS) was studied in conjunction with inflammatory cell influx, H2O2 production, and the formation of nitrotyrosines in renal biopsies from patients with Wegen er's granulomatosis (WG), Renal cryostat sections from patients with WG (n = 15) were stained by immunohistochemistry for eNOS, iNOS, endothelial cell s (CD31), nitrotyrosines, polymorphonuclear cells (PMNs, CD15), and monocyt es/macrophages (CD14, CD68), Production of H2O2 was identified by enzyme cy tochemistry using diaminobenzidine. In control tissues, strong staining for eNOS was found in glomerular and interstitial tubular capillaries and cort ical vessels. A significant reduction in eNOS expression was found in WG bi opsies, which was associated with a reduction in CD31 expression. Expressio n of iNOS was found in infiltrating inflammatory cells, mainly located in t he interstitium, H2O2-producing cells were detected in glomeruli and were a bundantly present in the interstitium. Nitrotyrosine-positive cells, howeve r, were almost exclusively found in the interstitium, It is concluded that renal inflammation in WG is associated with the induction of iNOS in inflam matory cells and the formation of nitrotyrosines, Expression of eNOS in glo merular capillaries is lost, most likely due to endothelial cell damage. Th ese results suggest that decreased NO. production by endothelial cells, in conjunction with increased NO. production by iNOS-positive inflammatory cel ls, is involved in renal tissue injury in WG, Copyright (C) 2000 John Wiley & Sons, Ltd.