Modulation of functionally active endothelin-converting enzyme by chronic neutral endopeptidase inhibition in experimental atherosclerosis.
BACKGROUND
Endothelin-converting enzyme-1 (ECE-1) processes big endothelin-1 (ET-1) to ET-1, a peptide implicated in atheroma formation. ECE-1 exists in 2 isoforms (ECE-1alpha and ECE-1beta), the result of alternative splicing of a common gene. Neutral endopeptidase (NEP) is a genetically distinct metallopeptidase that degrades the natriuretic peptides. These peptides mediate antiproliferative and vasodilating actions. We sought to demonstrate the distribution of the 2 ECE-1 isoforms in experimental atherosclerosis, to determine the effects of chronic NEP-I on plasma cGMP concentrations, vascular wall ECE-1 activity, and ET-1 concentration, and to correlate these actions with atheroma formation. Our hypothesis was that chronic NEP-I, in association with augmented cGMP, would inhibit ECE-1 conversion of big ET-1 to active ET-1, thus reducing tissue ET-1 concentrations and associated atheroma formation.


RESULTS
Cholesterol-fed New Zealand White rabbits (n=8, 1% cholesterol diet) and NEP-I-treated cholesterol-fed New Zealand White rabbits (n=8; candoxatril, 30 mg/kg per day, Pfizer) were euthanized after 8 weeks of feeding. ECE-1alpha and ECE-1beta immunoreactivity was present in the aortas of both groups. Compared with control values, plasma cGMP concentrations were increased (2.8+/-0.6 versus 8.4+/-1.2 pmol/mL, P<0.05), ECE-1 activity was attenuated (68+/-3% versus 32+/-8%, P<0. 05), aortic tissue ET-1 concentrations were reduced (4.6+/-0.5 versus 3.2+/-0.3 pg/mg protein, P<0.05), and atheroma formation was attenuated (62+/-6% versus 34+/-5%, P<0.01) by NEP-I.


CONCLUSIONS
These studies suggest that ECE-1 is present and functionally active in the vascular wall in atherosclerosis. Inhibition of ECE-1 by NEP-I represents a novel approach to interruption of the endothelin system in this cardiovascular disease state.
Grantham
J A
JA
Cardiorenal Research Laboratory, Division of Cardiovascular Diseases, Mayo Clinic, Rochester, MN 55905, USA. grantham.aaron@mayo.edu
Schirger
J A
JA
Wennberg
P W
PW
Sandberg
S
S
Heublein
D M
DM
Subkowski
T
T
Burnett
J C
JC
D000818:Animals; D001011:Aorta / Q000201:enzymology; D001161:Arteriosclerosis / Q000201:enzymology*; D016282:Aspartic Acid Endopeptidases / Q000032:analysis / Q000378:metabolism*; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D002908:Chronic Disease; D006152:Cyclic GMP / Q000378:metabolism; D004036:Diet, Atherogenic; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000378:metabolism; D000072396:Endothelin-Converting Enzymes; D016232:Endothelins / Q000378:metabolism; D066298:In Vitro Techniques; D007527:Isoenzymes / Q000032:analysis / Q000378:metabolism*; D008297:Male; D008666:Metalloendopeptidases; D015260:Neprilysin / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011498:Protein Precursors / Q000378:metabolism; D011817:Rabbits; D013997:Time Factors; D014661:Vasoconstriction / Q000502:physiology
D019332:Endothelin-1; D016232:Endothelins; D007527:Isoenzymes; D011498:Protein Precursors; D009320:Atrial Natriuretic Factor; D016282:Aspartic Acid Endopeptidases; D008666:Metalloendopeptidases; D015260:Neprilysin; D000072396:Endothelin-Converting Enzymes; D006152:Cyclic GMP