Abstract 13515: Complete Disruption of All Nitric Oxide Synthase Genes Causes Markedly Accelerated Renal Remodeling in Mice in Vivo
Background: Due to substantial interactions among 3 nitric oxide (NO) synthases (NOSs), the role of NO derived from all NOSs in renal remodeling is not completely understood. We addressed this issue in mice lacking all NOS genes.
Methods and Results: Renal injury was induced by unilateral ureteral obstruction (UUO) in wild-type (WT) and triply n/i/eNOS-KO mice (n=6–8). At days 3, 7, and 14 after UUO, histological changes of the obstructed kidneys were examined by hematoxylin-eosin and Masson-trichrome staining. In the obstructed kidneys of both WT and triply-KO mice, significant renal tubular apoptosis and interstitial fibrosis were noted (both P<0.05). However, the extent of renal tubular apoptosis (incidence of apoptosis: 23±2% vs. 11±1%) and the extent of interstitial fibrosis (area of fibrosis: 44±4% vs. 23±3%) were both markedly greater in the triply-KO than in the WT mice (both P<0.05). Furthermore, inflammatory macrophage infiltration (F4/80-immunoreactive cell counts: 24±5 vs. 12±7/field), TGF-β levels (53±10 vs. 32±11 ng/g, ELISA), and induction of epithelial mesenchymal transition (EMT) (α-smooth muscle actin-immunoreactive area: 29±4% vs. 13±2%) were also markedly enhanced in the obstructed kidneys of the triply-KO mice as compared with those of the WT mice (all P<0.05), suggesting the involvement of inflammation, TGF-β, and EMT. Importantly, the activity of angiotensin-converting enzyme was significantly higher in the obstructed kidneys of the triply-KO mice than in those of the WT mice (103±39 vs. 65±22 unit/ml, Kasahara method) (P<0.05), and long-term oral treatment with the angiotensin II type 1 [AT1] receptor blocker olmesartan (5 mg/kg/day, 14 days), but not with the equi-potent antihypertensive drug hydralazine (0.05 mg/ml, 14 days), significantly reversed all these renal abnormalities of the triply-KO mice (tubular apoptosis [7±3], interstitial fibrosis [21±3], macrophage infiltration [13±3], TGF-β [23±5], and EMT [16±3], all P<0.05).
Conclusions: These results provide the first evidence that complete disruption of all NOS genes causes markedly accelerated renal lesion formation in mice in vivo through the AT1 receptor pathway, demonstrating the critical role of the endogenous NOS system in preventing renal remodeling.
- © 2010 by American Heart Association, Inc.