Proteinuria is preceded by decreased nitric oxide synthesis and prevented by a NO donor in cholesterol-fed rats.
BACKGROUND
Hypercholesterolemia decreases nitric oxide (NO) availability in the circulation and induces podocyte activation and renal injury in rats. It is unknown whether hypercholesterolemia decreases renal NO availability. To dissociate the injury-independent effect of hypercholesterolemia on renal NO availability from secondary effects of proteinuria, increasing concentrations of cholesterol were administered. To determine whether podocyte activation and renal injury were associated with NO deficiency, molsidomine, an exogenous NO donor, was administered to hypercholesterolemic rats.


METHODS
Female rats were fed 0, 0.5, 1, or 2% cholesterol for 24 weeks. Rats fed 2% cholesterol were also studied for two weeks. In addition rats fed 0 or 1% cholesterol received 120 mg molsidomine/L drinking water. Renal NO availability was determined by measuring renal NO synthesis and superoxide activity. Podocyte activation was monitored by desmin staining.


RESULTS
Hypercholesterolemia dose-dependently increased proteinuria. In the absence of proteinuria, hypercholesterolemia decreased renal NO synthesis (4.2 +/- 0.5 in 0.5% cholesterol vs. 6.8 +/- 0.6 pmol/min/mg protein in controls; P < 0.05). With the exception of neuronal nitric oxide synthase (nNOS), renal NOS protein mass remained unaffected. Renal superoxide activity was dose-dependently increased, thus further lowering renal NO availability. Podocyte injury was dose-dependently increased even in the absence of proteinuria (score, 40 +/- 4 in 0.5% cholesterol vs. 9 +/- 4 in controls; P < 0.05). After two weeks, hypercholesterolemia caused no proteinuria, but did cause some podocyte injury. Renal NOS activity was decreased, but glomerular endothelial NOS (eNOS) staining was unchanged. Molsidomine prevented proteinuria, podocyte activation, and all further renal injury.


CONCLUSIONS
Hypercholesterolemia decreases renal NO synthesis, and induces podocyte activation before proteinuria appears. Renal superoxide activity is increased once rats are proteinuric, further lowering renal NO availability. All of these changes can be prevented by a NO donor.
Attia
Diana M
DM
Department of Nephrology and Hypertension, Utrecht University Medical Center, Utrecht, The Netherlands.
Ni
Zhenmin N
ZN
Boer
Peter
P
Attia
Mahmoud A
MA
Goldschmeding
Roel
R
Koomans
Hein A
HA
Vaziri
Nosratola D
ND
Joles
Jaap A
JA
D000818:Animals; D001794:Blood Pressure; D001835:Body Weight; D002791:Cholesterol, Dietary / Q000494:pharmacology*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D015243:Cholesterol, VLDL / Q000097:blood; D005260:Female; D006937:Hypercholesterolemia / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D007678:Kidney Glomerulus / Q000201:enzymology / Q000473:pathology; D008981:Molsidomine / Q000494:pharmacology; D020030:Nitric Oxide Donors / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000096:biosynthesis / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D011507:Proteinuria / Q000188:drug therapy* / Q000378:metabolism* / Q000473:pathology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014665:Vasodilator Agents / Q000494:pharmacology
D002791:Cholesterol, Dietary; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D020030:Nitric Oxide Donors; D014665:Vasodilator Agents; D008981:Molsidomine; D019001:Nitric Oxide Synthase; D052248:Nitric Oxide Synthase Type I; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496322:Nos1 protein, rat; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat