Rapamycin modulates the eNOS vs. shear stress relationship.
OBJECTIVE
Studies in animals and patients indicate that rapamycin affects vasodilatation differently in outer and inner curvatures of blood vessels. We evaluated in this study whether rapamycin affects endothelial nitric oxide synthase (eNOS) responsiveness to shear stress under normo- and hypercholesteraemic conditions to explain these findings.


RESULTS
Shear stress levels were varied over a large range of values in carotid arteries of transgenic mice expressing human eNOS fused to enhanced green fluorescence protein. The mice were divided into control, low-dose rapamycin (3 microg/kg/day), and high-dose rapamycin (3 mg/kg/day) groups and into normocholesteraemic and hypercholesteraemic (ApoE-/- on high cholesterol diet for 3-4 weeks) groups. The effect of rapamycin treatment on eNOS was evaluated by quantification of eNOS expression and of intracellular protein levels by en face confocal microscopy. A sigmoid curve fit was used to described these data. The efficacy of treatment was confirmed by measurement of rapamycin serum levels (2.0 +/- 0.5 ng/mL), and of p27kip1 expression in vascular tissue (increased by 2.4 +/- 0.5-fold). In control carotid arteries, eNOS expression increased by 1.8 +/- 0.3-fold in response to rapamycin. In the treated vessels, rapamycin reduced maximal eNOS expression at high shear stress levels (>5 Pa) in a dose-dependent way and shifted the sigmoid curve to the right. Hypercholesteraemia had a tendency to increase the leftward shift and the reduction in maximal eNOS expression (P = 0.07).


CONCLUSIONS
Rapamycin is associated with high eNOS in low shear regions, i.e. in atherogenic regions, protecting these regions against atherosclerosis, and is associated with a reduction of eNOS at high shear stress affecting vasomotion in these regions.
Cheng
Caroline
C
Department of Cardiology, Thoraxcenter, Erasmus University Medical Center, Rotterdam, The Netherlands.
Tempel
Dennie
D
Oostlander
Angela
A
Helderman
Frank
F
Gijsen
Frank
F
Wentzel
Jolanda
J
van Haperen
Rien
R
Haitsma
David B
DB
Serruys
Patrick W
PW
van der Steen
Anton F W
AF
de Crom
Rini
R
Krams
Rob
R
D000818:Animals; D001057:Apolipoproteins E / Q000235:genetics / Q000378:metabolism; D002317:Cardiovascular Agents / Q000097:blood / Q000494:pharmacology*; D002339:Carotid Arteries / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology; D002340:Carotid Artery Diseases / Q000201:enzymology / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology; D005260:Female; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D006937:Hypercholesterolemia / Q000150:complications / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D011673:Pulsatile Flow; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020123:Sirolimus / Q000097:blood / Q000494:pharmacology*; D013314:Stress, Mechanical
D001057:Apolipoproteins E; D002317:Cardiovascular Agents; C493961:Cdkn1b protein, mouse; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; C496314:NOS3 protein, human; D052250:Nitric Oxide Synthase Type III; D020123:Sirolimus