Hypercholesterolemia-induced erectile dysfunction: endothelial nitric oxide synthase (eNOS) uncoupling in the mouse penis by NAD(P)H oxidase.
BACKGROUND
Hypercholesterolemia induces erectile dysfunction (ED) mostly by increasing oxidative stress and impairing endothelial function in the penis, but the mechanisms regulating reactive oxygen species (ROS) production in the penis are not understood.


OBJECTIVE
We evaluated whether hypercholesterolemia activates nicotinamide adenine dinucleotide phosphate (NAD[P]H) oxidase in the penis, providing an initial source of ROS to induce endothelial nitric oxide synthase (eNOS) uncoupling and endothelial dysfunction resulting in ED.


METHODS
Low-density-lipoprotein receptor (LDLR)-null mice were fed Western diet for 4 weeks to induce early-stage hyperlipidemia. Wild type (WT) mice fed regular chow served as controls. Mice received NAD(P)H oxidase inhibitor apocynin (10 mM in drinking water) or vehicle. Erectile function was assessed in response to cavernous nerve electrical stimulation. Markers of endothelial function (phospho [P]-vasodilator-stimulated-protein [VASP]-Ser-239), oxidative stress (4-hydroxy-2-nonenal [HNE]), sources of ROS (eNOS uncoupling and NAD[P]H oxidase subunits p67(phox) , p47(phox) , and gp91(phox) ), P-eNOS-Ser-1177, and eNOS were measured by Western blot in penes.


METHODS
The main outcome measures are the molecular mechanisms of ROS generation and endothelial dysfunction in hypercholesterolemia-induced ED.


RESULTS
Erectile response was significantly (P<0.05) reduced in hypercholesterolemic LDLR-null mice compared with WT mice. Relative to WT mice, hypercholesterolemia increased (P<0.05) protein expressions of NAD(P)H oxidase subunits p67(phox) , p47(phox) and gp91(phox) , eNOS uncoupling, and 4-HNE-modified proteins, and reduced (P<0.05) P-VASP-Ser-239 expression in the penis. Apocynin treatment of LDLR-null mice preserved (P<0.05) maximal intracavernosal pressure, and reversed (P<0.05) the abnormalities in protein expressions of gp67(phox) and gp47(phox) , 4-HNE, P-VASP-Ser-239, and eNOS uncoupling in the penis. Apocynin treatment of WT mice did not affect any of these parameters. Protein expressions of P-eNOS-Ser-1177 and total eNOS were unaffected by hypercholesterolemia.


CONCLUSIONS
Activated NAD(P)H oxidase in the penis is an initial source of oxidative stress resulting in eNOS uncoupling, thus providing a mechanism of eNOS uncoupling and endothelial dysfunction in hypercholesterolemia-induced ED.
Musicki
Biljana
B
Department of Urology, Johns Hopkins University, Baltimore, MD 21287, USA. bmusicki@jhmi.edu
Liu
Tongyun
T
Lagoda
Gwen A
GA
Strong
Travis D
TD
Sezen
Sena F
SF
Johnson
Justin M
JM
Burnett
Arthur L
AL
D000098:Acetophenones / Q000494:pharmacology; D000447:Aldehydes / Q000378:metabolism; D000818:Animals; D015815:Cell Adhesion Molecules / Q000187:drug effects / Q000378:metabolism; D002791:Cholesterol, Dietary / Q000008:administration & dosage / Q000009:adverse effects; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007172:Erectile Dysfunction / Q000209:etiology / Q000378:metabolism*; D006937:Hypercholesterolemia / Q000150:complications*; D008297:Male; D051379:Mice; D008840:Microfilament Proteins / Q000187:drug effects / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III / Q000187:drug effects / Q000378:metabolism; D010413:Penis / Q000294:innervation / Q000378:metabolism*; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism; D017382:Reactive Oxygen Species; D000098662:Vasodilator-Stimulated Phosphoprotein
D000098:Acetophenones; D000447:Aldehydes; D015815:Cell Adhesion Molecules; D002791:Cholesterol, Dietary; D004791:Enzyme Inhibitors; D008840:Microfilament Proteins; D010750:Phosphoproteins; D017382:Reactive Oxygen Species; D000098662:Vasodilator-Stimulated Phosphoprotein; C056165:acetovanillone; D052250:Nitric Oxide Synthase Type III; C496315:Nos3 protein, mouse; D019255:NADPH Oxidases; C027576:4-hydroxy-2-nonenal