Protective role of nitric oxide in a model of thrombotic microangiopathy in rats.
Anew model of thrombotic microangiopathy (TMA) was previously developed, and it was demonstrated that endothelial nitric oxide (NO) synthase (NOS) is upregulated in glomeruli in this model. It was hypothesized that the synthesis of NO, a potent vasodilator and platelet inhibitory factor, is induced as a defense mechanism. The goal of this study was to clarify the role of NO in this model. Ex vivo experiments using Western blotting and functional assays demonstrated upregulation of endothelial NOS in isolated glomeruli from TMA rats. In in vivo experiments, five groups of rats were studied, including rats with TMA treated with vehicle, N(G)-nitro-L-arginine methyl ester (L-NAME) (a NOS inhibitor), or L-N(6)-(1-iminoethyl)lysine (L-NIL) (a specific inducible NOS inhibitor) and normal control rats treated with vehicle or L-NAME. Blood urea nitrogen levels, BP, urinary nitrate/nitrite excretion, and proteinuria were measured. Histologic assessments using periodic acid-Schiff staining and immunohistologic studies with markers for endothelium, platelets, fibrin, cell proliferation, and apoptosis were also performed. L-NAME inhibition of NO synthesis in rats with TMA resulted in more severe glomerular and tubulointerstitial injury, which was accompanied by thrombus formation and a marked loss of endothelial cells, with more apoptotic cells. These changes were associated with severe renal function deterioration. In contrast, these features were less pronounced in the vehicle- or L-NIL-treated rats with TMA and were absent in the control animals. In conclusion, inhibition of NO production in this model of TMA markedly exacerbated renal injury. The absence of effects with L-NIL treatment suggests a minor role for inducible NOS in this model. These results suggest that production of NO, most likely by endothelial cells, is an important protective mechanism in TMA.
Shao
Jing
J
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Miyata
Toshio
T
Department of Molecular Medicine, Tokai University School of Medicine, Kanagawa, Japan.
Yamada
Koei
K
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Hanafusa
Norio
N
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Wada
Takehiko
T
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Gordon
Katherine L
KL
Division of Nephrology, University of Washington Medical Center, Seattle, Washington.
Inagi
Reiko
R
Department of Molecular Medicine, Tokai University School of Medicine, Kanagawa, Japan.
Kurokawa
Kiyoshi
K
Department of Molecular Medicine, Tokai University School of Medicine, Kanagawa, Japan.
Fujita
Toshiro
T
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
Johnson
Richard J
RJ
Section of Nephrology, Baylor College of Medicine, Houston, Texas.
Nangaku
Masaomi
M
Division of Nephrology and Endocrinology, University of Tokyo School of Medicine, Tokyo, Japan.
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D015153:Blotting, Western; D002455:Cell Division / Q000187:drug effects; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007074:Immunoglobulin G / Q000276:immunology / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000503:physiopathology; D007678:Kidney Glomerulus / Q000276:immunology / Q000473:pathology; D008297:Male; D008833:Microcirculation / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009566:Nitrates / Q000652:urine; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors; D009573:Nitrites / Q000652:urine; D051381:Rats; D017208:Rats, Wistar; D012079:Renal Circulation / Q000187:drug effects; D012720:Severity of Illness Index; D013927:Thrombosis / Q000473:pathology* / Q000503:physiopathology
D004791:Enzyme Inhibitors; D007074:Immunoglobulin G; D009566:Nitrates; D009573:Nitrites; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester