Aortic eNOS expression and phosphorylation in Apo-E knockout mice: differing effects of rapamycin and simvastatin.
BACKGROUND
The inhibition of nitric oxide (NO) by hypercholesterolemia may be mediated, in part, by interactions with caveolin-1 (Cav-1). Because of the facilitatory effects of statins on endothelial function and the adverse effects of rapamycin (RAPA) on plasma lipids, we compared the effects of simvastatin (SMV) and RAPA on endothelial NO synthase (eNOS) and Cav-1 protein expression and phosphorylation in the aortas of apolipoprotein E (Apo-E) knockout (-/-) mice.


METHODS
Apo-E -/- mice (n = 38) fed a high-cholesterol diet were given SMV (100 mg/kg/day po), RAPA (3 mg/kg/day ip), or no treatment for 10 weeks. Blood was drawn for serum lipid analysis, and protein was extracted for Western immunoblotting. Selected aortic specimens from 2 animals in each group were examined by histology and immunohistochemistry. The data are expressed as the mean +/- SEM and compared by the Student t test and ANOVA. Significance was established as P < .05.


RESULTS
Lipid levels at 10 weeks were similar in the 3 groups except for higher triglyceride levels in RAPA-treated animals. eNOS expression was highest in RAPA-treated mice, but the p-eNOS to eNOS protein expression ratio was significantly greater in the SMV treatment group compared to both RAPA and controls (P < .05). Both Cav-1 and p-Cav-1 expression was significantly lower in the SMV-treated animals (P < .05) compared to mice treated with RAPA.


CONCLUSIONS
Although eNOS expression was greatest in the RAPA-treated mice, the expression of p-eNOS was similar in the RAPA- and SMV-treated animals. The increase in eNOS induced by RAPA and the inverse relationship between p-eNOS and Cav-1 protein expression observed with SMV treatment suggest different mechanisms for the regulation of aortic eNOS expression in Apo-E mice by these 2 agents.
Department of Surgery, University of Texas Medical Branch at Galveston, TX 77555, USA.
Joseph J
JJ
Naoum
Shu
S
Zhang
Kenneth J
KJ
Woodside
Wei
W
Song
Qian
Q
Guo
Ligia M
LM
Belalcazar
Glenn C
GC
Hunter
D000818:Animals; D001011:Aorta / Q000201:enzymology*; D001057:Apolipoproteins E / Q000502:physiology*; D051242:Caveolin 1; D022461:Caveolins / Q000032:analysis; D002784:Cholesterol / Q000097:blood; D042783:Endothelial Cells / Q000502:physiology; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D010766:Phosphorylation; D019821:Simvastatin / Q000494:pharmacology*; D020123:Sirolimus / Q000494:pharmacology*
D001057:Apolipoproteins E; C495541:Cav1 protein, mouse; D051242:Caveolin 1; D022461:Caveolins; D002784:Cholesterol; D019821:Simvastatin; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D020123:Sirolimus