Is there an association between angiotensin-converting enzyme gene variants and chronic nonproductive cough?
BACKGROUND
It is unclear why some patients develop a chronic nonproductive cough. Angiotensin-converting enzyme (ACE) inactivates tussive peptides in the airways such as bradykinin and tachykinins. An insertion/deletion polymorphism in the ACE gene accounts for variation in ACE levels, and patients with the II genotype have lowest serum ACE levels compared with ID and DD genotypes. We hypothesized that the II genotype would be associated with increased risk of developing a chronic cough.


METHODS
We recruited 47 patients (33 women), referred for evaluation of cough (median cough duration, 24 months; range, 2 to 240 months). Cough patients were evaluated using a comprehensive diagnostic protocol, and cough reflex sensitivity was measured using a capsaicin inhalation challenge. ACE genotyping was performed on DNA samples from patients using the polymerase chain reaction followed by agarose gel electrophoresis. ACE genotypes in patients with chronic cough were compared with those in 199 healthy control subjects. Serum ACE levels were determined using a colorimetric assay.


RESULTS
Genotype frequencies for the ACE gene were similar between patients and control subjects. There was no correlation between capsaicin sensitivity and ACE genotypes or serum ACE levels.


CONCLUSIONS
Susceptibility to develop chronic cough is not associated with ACE genotype.
McGarvey
L P
LP
Department of Respiratory Medicine, Belfast City Hospital, Northern Ireland. lpamcgarvey@hotmail.com
Savage
D A
DA
Feeney
S A
SA
Heaney
L G
LG
Ennis
M
M
MacMahon
J
J
Maxwell
A P
AP
D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D002211:Capsaicin / Q000627:therapeutic use; D002908:Chronic Disease; D003371:Cough / Q000188:drug therapy / Q000201:enzymology* / Q000235:genetics; D004247:DNA / Q000032:analysis*; D004587:Electrophoresis, Agar Gel; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000097:blood / Q000235:genetics*; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic
D004247:DNA; D007703:Peptidyl-Dipeptidase A; D002211:Capsaicin