Effect of hypercholesterolemia on expression and function of vascular soluble guanylyl cyclase.
BACKGROUND
Vasorelaxation to endothelial NO is mediated by activation of soluble guanylyl cyclase (sGC) and impaired by hypercholesterolemia in animals and humans. We investigated whether hypercholesterolemia impacts expression and function of sGC.


RESULTS
White New Zealand rabbits (n=10 per group) received a standard diet for 16 weeks (SD16) (n=20) or 32 weeks (SD32) and a cholesterol diet (7.5 g/kg) for 16 weeks (CD16) (n=20) or 32 weeks (CD32), respectively. Another group received cholesterol diet for 16 weeks followed by standard diet for 16 weeks (CD/SD). Aortic expression of the alpha1-subunit of sGC (sGC-alpha1) and beta1-subunit of sGC (sGC-beta1) was assessed by Western blot. Function was measured by aortic relaxation to S-Nitroso-N-acetyl-D, L-penicillamine (SNAP) and sGC activity in aortic cytosols. Hypercholesterolemia induced an upregulation of sGC-beta1 in CD16 (3.5+/-0.4-fold, P<0.001 versus SD16) and CD32 (4.0+/-0.4-fold, P<0.001 versus SD32). A similar increase was found for sGC-alpha1. In striking contrast, basal and NO-stimulated sGC activities in aortic cytosols of CD16 were only slightly enhanced (1.4-fold, P<0.05). Furthermore, the vasodilator potency of SNAP (EC50 in -logM) was 10-fold lower in CD16 (6.76a+/-0.09) than in SD16 (7.66+/-0.14, P<0.01). The increase of sGC expression was completely reversible, as indicated by comparable sGC-beta1 amounts in SD32 and CD/SD (1.2+/-0.1-fold, P>0.05). Immunohistochemical analysis suggests that a great portion of the overexpressed sGC is located in intimal lesions. Additional experiments showed that increased vascular superoxide production induced by 6-anilino-5,8-quinolinedione (LY85385) reduces sGC-activity but increases sGC-expression.


CONCLUSIONS
These results suggest that hypercholesterolemia induces a reversible overexpression of a dysfunctional vascular sGC, which may contribute to the pathogenesis of atherosclerosis.
Laber
Ute
U
Institut für Pharmakologie und Klinische Pharmakologie, Heinrich-Heine-Universität, Düsseldorf, Germany.
Kober
Thorsten
T
Schmitz
Verena
V
Schrammel
Astrid
A
Meyer
Wilfried
W
Mayer
Bernd
B
Weber
Martina
M
Kojda
Georg
G
D000634:Aminoquinolines / Q000494:pharmacology; D000818:Animals; D001011:Aorta / Q000187:drug effects / Q000473:pathology / Q000503:physiopathology*; D001161:Arteriosclerosis / Q000209:etiology / Q000473:pathology / Q000503:physiopathology; D002784:Cholesterol / Q000097:blood; D004036:Diet, Atherogenic; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006162:Guanylate Cyclase; D006937:Hypercholesterolemia / Q000201:enzymology* / Q000473:pathology; D066298:In Vitro Techniques; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015398:Signal Transduction; D000071756:Soluble Guanylyl Cyclase; D017539:Tunica Intima / Q000378:metabolism / Q000473:pathology; D015854:Up-Regulation; D014664:Vasodilation / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology
D000634:Aminoquinolines; D004791:Enzyme Inhibitors; D020030:Nitric Oxide Donors; D018160:Receptors, Cytoplasmic and Nuclear; D014665:Vasodilator Agents; D009569:Nitric Oxide; C041715:6-anilino-5,8-quinolinedione; D002784:Cholesterol; D006162:Guanylate Cyclase; D000071756:Soluble Guanylyl Cyclase