A functional XPNPEP2 promoter haplotype leads to reduced plasma aminopeptidase P and increased risk of ACE inhibitor-induced angioedema.

Angiotensin I-converting enzyme inhibitors (ACEi) are widely used antihypertensive agents that are associated with a potentially life-threatening reaction, ACEi-angioedema. Impaired metabolism of bradykinin and des-Arg(9) -bradykinin by aminopeptidase P (APP) is a key contributor to ACEi-angioedema. This study aimed to characterize the genetic regulation of the XPNPEP2 gene and identify the genetic factors contributing to variance in plasma APP activity and ACEi-angioedema. Additive genetic factors accounted for 47.3% of variance in plasma APP activity in healthy individuals. Nested deletion analysis identified the minimal promoter (-338 bp to -147 bp) and an enhancer region (-2,502 bp to -2,238 bp). Three polymorphisms (c.-2399C>A, c.-1612G>T, and c.-393G>A) were significantly associated with plasma APP activity. Haplotype ATG was significantly associated with reduced reporter gene activity and with reduced plasma APP activity. The c.-2399C>A polymorphism was located in an enhancer region and was predicted to differentially bind hepatic nuclear factor 4 (HNF4). Over expression of HNF4 increased the activation of haplotype ATG compared with haplotype CGG. In a case control study of subjects with a history of ACEi-angioedema, haplotype ATG was significantly associated with ACEi-angioedema (OR 4.87 [1.78-13.35] P = 0.002). The ATG haplotype is functional and contributes to ACEi-angioedema through a reduction in APP.