The efficacy of the ACE (angiotensin-converting enzyme) inhibitor perindopril in coronary artery disease [EUROPA (European trial on reduction of cardiac events with perindopril in stable coronary artery disease) study] is associated with the rs12050217 A/G single nucleotide polymorphism in the B 1 receptor (bradykinin type 1 receptor) gene. To investigate the underlying mechanism, we examined the effect of this polymorphism on B 1 -receptor-mediated coronary artery dilation and peripheral blood mononuclear cell activation. Vasorelaxant responses of human coronary microarteries from subjects without coronary disease to des-Arg 9 -bradykinin and to bradykinin were studied in organ bath experiments. Des-Arg 9 -bradykinin responses were endothelium-dependent and exclusively mediated by B 1 receptors, whereas responses to bradykinin were induced through B 2 receptors (bradykinin type 2 receptors). The presence of the G allele reduced the response to 3×10 −8 mol/l des-Arg 9 -bradykinin by 29% [AA ( n =13) compared with AG/GG ( n =8); P <0.03], and tended to lower concentration-related responses ( P =0.065) to this agonist, whereas the responses to bradykinin were unaffected by the rs12050217 genotype. In freshly obtained human mononuclear cells 1 μmol/l des-Arg 9 -bradykinin increased expression of the pro-inflammatory factors CXCL5 (CXC chemokine ligand 5) and IL6 (interleukin-6). These responses were not affected by genotype and exclusively occurred in blood cells from women, correlating (in the case of CXCL5 ) with their plasma 17β-oestradiol levels ( r 2 =0.32, P =0.02; n =17). IL-1β (interleukin-1β) increased CXCL5 and IL6 expression in both genders, and this response was not associated with 17β-oestradiol levels. The gender difference in responses to B 1 receptor stimulation in blood mononuclear cells implies possible gender differences in the response to ACE inhibitor therapy, which needs to be studied more comprehensively. The observed decrease in coronary vasodilator response might contribute to the impaired treatment response to perindopril of G allele carriers found in the EUROPA study.

The effect of previous nitrate therapy on vascular responses to endothelin-1 (ET-1) and NO was investigated in human internal mammary artery (IMA) in vitro. Cumulative concentration–response curves to ET-1 were constructed in rings of IMA and the data grouped into IMA from patients given nitrates prior to the bypass graft operation (nitrate group) and IMA from patients who were not prescribed nitrates (control group). No significant differences were observed between the two groups, either in EC 50 value [ P >0.05; 3.5nM (2.4–5.3nM; 95% confidence interval) and 4.8 (2.2–10nM), nitrate and control groups respectively] or E max ( P >0.05; 78±7.5% and 85±9.5%, nitrate and control group respectively). No significant differences in concentration–response curves to the NO-donor diethylamine NONOate (DEA/NO) in rings of IMA pre-constricted with 10nM ET-1 were observed between control and nitrate groups [ P >0.05; EC 50 values 0.59 (0.21–1.7) µ M and 0.17 (0.03–0.87) µ M; E max 110±5.7% and 112±4.5%, nitrate and control groups respectively]. Concentration–response curves to DEA/NO constructed in normal coronary artery were not significantly different from those in coronary artery obtained from patients with ischaemic heart disease (IHD) [ P >0.05; E max 124±11% and 138±20%; EC 50 0.08 (0.02–0.30) µ M and 0.23 (0.02–24) µ M, normal and IHD respectively]. These data indicate that nitrate therapy does not induce long-term changes in the ET signalling pathway. Furthermore, the tolerance to nitrate therapy is likely to be because of impaired bio-transformation of the drug rather than reduced sensitivity of the media to NO. The similar responses to DEA/NO in normal and atherosclerotic coronary artery suggests that the reduced vasodilator responses in IHD is because of a dysfunctional endothelium and is not mediated by changes in the NO signalling pathway of the smooth muscle.