Induction of local angiotensin II-producing systems in stenotic aortic valves

https://doi.org/10.1016/j.jacc.2004.07.054Get rights and content
Under an Elsevier user license
open archive

Objectives

The purpose of this study was to investigate the expression of angiotensin II (Ang II)-producing enzyme systems in normal and stenotic aortic valves.

Background

Chronic inflammation and fibrosis are involved in the pathogenesis of aortic stenosis (AS), but the detailed molecular mechanisms of this atherosclerosis-like process remain obscure. Angiotensin II, a powerful mediator of inflammation and fibrosis, may participate in AS progression.

Methods

Stenotic aortic valves (n = 86) were obtained from patients undergoing valve replacement surgery, and control valves (n = 11) were obtained from patients undergoing cardiac transplantation. Angiotensin-converting enzyme (ACE) and mast cell (MC)-derived chymase were quantified by reverse-transcription polymerase chain reaction, autoradiography, and immunostaining. The MCs, macrophages, and T lymphocytes were detected by immunohistochemistry, and angiotensin II type 1 receptor (AT-1R) by autoradiography.

Results

Compared with control valves, stenotic aortic valves showed a significant increase in both messenger ribonucleic acid (mRNA) (p = 0.001) and protein (p < 0.001) expression of ACE, which colocalized with macrophages. Similarly, the expression of AT-1R protein and chymase mRNA and proteinwas upregulated (p < 0.001), and the number of MCs was six-fold higher in stenotic than in normal valves. The MCs were associated with the calcified areas, and—in contrast to control valves—showed an increased degree of degranulation, a prerequisite for chymase secretion and action.

Conclusions

Angiotensin-converting enzyme and chymase, two Ang II-forming enzymes, are locally expressed in aortic valves, and owing to infiltration of macrophages and MCs, are further upregulated in stenotic valves. These novel findings, implicating chronic inflammation and an increased expression of local Ang II-forming systems, suggest that therapeutic interventions aiming at inhibiting these processes may slow AS progression.

Abbreviations and acronyms

ACE
angiotensin-converting enzyme
Ang II
angiotensin II
AS
aortic stenosis
AT-1R
angiotensin II type 1 receptor
AT-2R
angiotensin II type 2 receptor
DNA
deoxyribonucleic acid
GAPDH
glyceraldehyde-3-phosphate dehydrogenase
LDL
low-density lipoprotein
MC
mast cell
mRNA
messenger ribonucleic acid
RT-PCR
reverse transcription-polymerase chain reaction

Cited by (0)

Supported by the Finnish Foundation for Cardiovascular Research, Helsinki, Finland (to Dr. Helke); the Sigrid Juselius Foundation, Helsinki, Finland; and the EVO research funds of Helsinki University Central Hospital.