ALDH2 mutation results in excessive basal nitric oxide production and a delayed response to nitroglycerin

Abstract Background and purpose: Nitroglycerin tolerance is a common phenomenon in patients with coronary artery disease (CAD). Aldehyde dehydrogenase 2 (ALDH2) is the enzyme that metabolizes nitroglycerin to its active form nitric oxide (NO). Previous studies showed altered nitroglycerin in subjects with ALDH2 mutation, but the functional impact on endothelial cells is not fully understood. Methods: In the first step of in vitro experiments, we examined functional properties of induced pluripotent stem cell-derived CD144+ endothelial cells (iPSC-ECs) that expressed wildtype (WT) vs ALDH2+/− variant. In the second step of human studies, diameter of the left anterior descending (LAD) coronary artery was determined using angiography in 151 adult volunteers (111 with WT ALDH2, 32 with ALDH2+/− and 8 with ALDH2−/− genotype) prior to as well as after intracoronary injection of 200-μg nitroglycerin. Results: Briefly, the ALDH2+/− iPSC-ECs demonstrated impaired low-density lipoprotein (LDL) uptake, proliferation, migration, tube formation, oxidative stress resistance, and viability. In comparison to the WT control, the ALDH2+/− iPSC-ECs had elevated NO production under baseline conditions, but exhibited a delayed NO release after nitroglycerin treatment. Exposure to 10-μg/mL nitroglycerin for 2 h increased NO production in WT iPSC-ECs but 4-h exposure was required to stimulate NO production in the ALDH2+/− iPSC-ECs. In comparison to the WT control, the subjects carrying the ALDH2+/− variants had seemingly larger LAD coronary artery diameter (3.5 and 3.8 mm vs 3.4 mm in the WT control), but attenuated vasodilatory response to nitroglycerin (ALDH2MUT group vs the WT control, 7.1 ± 0.6% vs 10.1 ± 0.8%, P = 0.024). Conclusion: These findings indicated elevated NO production by endothelia cells under basal conditions but attenuated response to nitroglycerin upon ALDH2 mutation.