Is there an association between angiotensin-converting enzyme gene variants and chronic nonproductive cough?

Pharmacogenetics of ACE inhibitor-induced angioedema and cough: a systematic review and meta-analysis

AIM

Angioedema and cough are the two most important adverse effects of ACE inhibitors (ACEIs). Evidence exists that ACEI-related angioedema/cough is partly genetically determined and several genes have been identified to play a role in the development of ACEI-related adverse effects.

MATERIALS & METHODS

This study was performed in order to evaluate the evidence of these genetic associations and ACEIs' adverse effects. After removing duplicates and critical appraisal, 19 studies were considered to be eligible to review; 14 articles about cough and five articles about angioedema. A separate meta-analysis was performed for the most studied ACE insertion/deletion polymorphism (rs4646994) and its association with cough.

RESULTS & CONCLUSION

One gene region (XPNPEP2) was associated with ACEI-induced angioedema in three studies. In our meta-analysis we did not find a significant association between the ACE insertion/deletion polymorphism and ACEI cough.

Use of ACE inhibitors and risk of community-acquired pneumonia: a review

BACKGROUND

The administration of angiotensin-converting enzyme (ACE) inhibitors has been suggested as an alternative strategy for lowering the risk of community-acquired pneumonia (CAP) in the elderly, especially in patients with neurological and cerebrovascular comorbidity.

METHODS

We critically examined the relevant data from studies regarding the impact of ACE inhibitors in lowering the risk of CAP and/or mortality due to CAP in the elderly. We searched PubMed, Cochrane Database, and references of initially retrieved articles, and http://clinicaltrials.gov for ongoing trials.

RESULTS

We identified 285 evaluable studies. Fourteen studies met the inclusion criteria and were evaluated further, of which seven were prospective studies, two randomized controlled trials, and five retrospective studies. Eight of ten studies including patients of Asian origin demonstrated a statistical significance in favor of ACE inhibitors. On the contrary, only one of five studies including patients of non-Asian origin demonstrated results in favor of ACE inhibitors.

CONCLUSION

The available data suggest that ACE inhibitors may contribute to the reduction of the risk of CAP. Nevertheless, clinical data are scarce and mainly comprise studies including patients of Asian origin. As there seem to be differences regarding the genetic polymorphism of ACE among patients of different origins, future studies are needed that incorporate relevant genetics data that may help clarify the role, if any, of ACE inhibitors in preventing CAP.

Association of genetic variations in neurokinin-2 receptor with enhanced cough sensitivity to capsaicin in chronic cough

BACKGROUND

Chronic cough is associated with increased sensitivity to inhaled capsaicin, and both tachykinins and their receptors play important roles in the cough reflex. However, associations between polymorphisms of the tachykinin receptor genes and cough sensitivity in patients with non-productive chronic cough have not been reported.

METHODS

Direct sequencing was used to identify single nucleotide polymorphisms (SNPs) in the genes for the neurokinin-1 and neurokinin-2 receptors (NK-1R and NK-2R, respectively). Informative non-synonymous SNPs were scored using the single base extension method for 312 patients with chronic cough and for 100 age matched healthy controls. The cough response to capsaicin was recorded for 312 patients with chronic cough, and the potential genetic association between cough sensitivity to capsaicin and the NK-1R and NK-2R genotypes was evaluated.

RESULTS

Two informative SNPs were identified in NK-2R (Gly231Glu and Arg375His), whereas no informative SNP was found in NK-1R. After adjusting for atopy, sex, age, and smoking, the prevalence of enhanced cough sensitivity to capsaicin was higher in the chronic cough patients with the 231Glu allele (p = 0.004; OR 1.69 (95% CI 1.18 to 2.42)) and the 231Glu_375Arg haplotype (p = 0.003; OR 1.71 (95% CI 1.20 to 2.24)). Moreover, the lowest capsaicin concentration to cause five consecutive coughs (C5) was significantly lower in patients with 231Glu (mean (SD) 44.1 (53.2) v 60.9 (55.8) microM/l, p = 0.04) and those with 231Glu_375Arg (43.2 (52.7) v 69.6 (52.0) microM/l, p = 0.03).

CONCLUSIONS

The results of this study suggest that NK-2R gene polymorphisms are involved in the enhanced cough sensitivity to capsaicin of patients with chronic cough.

Safety of capsaicin cough challenge testing

BACKGROUND

Capsaicin, the pungent extract of red peppers, has achieved widespread use in clinical research because it induces cough in a dose-dependent and reproducible manner. Although > 2 decades of experience has led investigators to consider capsaicin cough challenge testing a safe diagnostic modality, this issue has not been specifically addressed in the literature.

STUDY OBJECTIVES

To review the published experience with capsaicin inhalation challenge testing in terms of safety.

DESIGN

Literature review and personal communication with study authors.

SETTING

Academic medical center.

RESULTS

One hundred twenty-two published studies since 1984 described 4,833 subjects (4,374 adults, 459 children) undergoing capsaicin cough challenge, with no serious adverse events reported. Subjects included healthy volunteers as well as patients with asthma, COPD, pathologic cough, and other respiratory conditions. Minor complaints described in a small fraction of studies consisted mainly of transient throat irritation. Personal communication with the authors of > 90% of the studies confirmed an absence of any serious adverse events. Furthermore, these investigators have performed thousands of additional capsaicin challenge studies not reported in the literature, also without any associated serious adverse events.

CONCLUSIONS

A review of the 20-year clinical experience has failed to uncover a single serious adverse event associated with capsaicin cough challenge testing in humans. Given the need for better antitussive therapies, capsaicin represents a vital component of future scientific inquiry in the field of cough.

Insertion/deletion polymorphism of the ACE gene and adherence to ACE inhibitors

AIMS

We investigated whether the insertion/deletion (I/D) polymorphism of the ACE gene modified the adherence to ACE inhibitors as measured by the discontinuation of an ACE inhibitor, or addition of another antihypertensive drug.

METHODS

This was a cohort study among 239 subjects who started ACE inhibitor therapy. A Cox proportional hazard model was used to calculate relative risk (RR).

RESULTS

During follow-up there was no significant difference between subjects with the DD, ID or II genotype (DD vs II; RR = 1.17, 95%CI: 0.78, 1.77 and ID vs II; RR = 1.06, 95%CI: 0.73, 1.55) in adherence.

CONCLUSIONS

The I/D polymorphism of the ACE gene does not influence the adherence to ACE inhibitors.