Angiotensin II type 1 receptor blocker ameliorates uncoupled endothelial nitric oxide synthase in rats with experimental diabetic nephropathy.
BACKGROUND
Recent studies showed that angiotensin II type 1 receptor blocker (ARB) slows progression of chronic renal disease in patients with type 2 diabetes, regardless of changes in blood pressure. We showed that the imbalance of nitric oxide (NO) and reactive oxygen species (ROS) due to endothelial NO synthase (eNOS) uncoupling contributed to renal dysfunction in the diabetic nephropathy. The aim of this study was to determine the effects of ARB on uncoupled eNOS in rat diabetic nephropathy.


METHODS
Diabetes was induced in Sprague-Dawley rats with streptozotocin (65 mg/ kg body weight). After 6 weeks, rats were divided into saline (DM; n = 11) and ARB, losartan groups (DM+Los; n = 11). After 2-week treatment, glomerular ROS production was assessed by 2',7'-dichlorofluorescin diacetate (DCFH-DA)-derived chemiluminescence. Renal NO and ROS production were imaged by confocal laser microscopy after renal perfusion with DCFH-DA and diaminorhodamine-4M acetoxymethyl ester with L-arginine. The dimeric form of eNOS was measured by low-temperature sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Serum tetrahydrobiopterin (BH4) concentrations were determined by high-performance liquid chromatography. Protein and mRNA expression of GTP cyclohydrolase 1 (GTPCH1), key enzyme of BH4 synthesis, were examined.


RESULTS
Losartan attenuated glomerular ROS production in DM. Accelerated ROS production and diminished bioavailable NO caused by NOS uncoupling were noted in DM glomeruli. Losartan reversed the decreased GTPCH1 and decreased dimeric form of eNOS and glomerular NO production by increased BH4 bioavailability.


CONCLUSIONS
ARB improved the NOS uncoupling in diabetic nephropathy by increasing BH4 bioavailability.
Satoh
Minoru
M
Division of Nephrology, Department of Internal Medicine, Kawasaki Medical School, Kurashiki, Okayama 701-0192, Japan. msatoh@med.kawasaki-m.ac.jp
Fujimoto
Sohachi
S
Arakawa
Sayaka
S
Yada
Toyotaka
T
Namikoshi
Tamehachi
T
Haruna
Yoshisuke
Y
Horike
Hideyuki
H
Sasaki
Tamaki
T
Kashihara
Naoki
N
D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001483:Base Sequence; D001708:Biopterins / Q000031:analogs & derivatives / Q000097:blood; D017931:DNA Primers / Q000235:genetics; D003921:Diabetes Mellitus, Experimental / Q000150:complications / Q000188:drug therapy / Q000201:enzymology; D003928:Diabetic Nephropathies / Q000188:drug therapy* / Q000201:enzymology* / Q000503:physiopathology; D006136:GTP Cyclohydrolase / Q000235:genetics / Q000378:metabolism; D007678:Kidney Glomerulus / Q000378:metabolism; D019808:Losartan / Q000494:pharmacology*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017382:Reactive Oxygen Species / Q000378:metabolism
D047228:Angiotensin II Type 1 Receptor Blockers; D017931:DNA Primers; D012333:RNA, Messenger; D017382:Reactive Oxygen Species; D001708:Biopterins; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D006136:GTP Cyclohydrolase; C003402:sapropterin; D019808:Losartan