Acetaldehyde in e‐cigarette aerosol and cigarette smoke exacerbate pulmonary microvascular endothelial dysfunction in ALDH2*2 mice

Abstract

Background Pulmonary endothelial dysfunction caused by the frequent exposure to cigarette smoke can lead to pulmonary artery hypertension (PAH). E-cigarette vapor, similar to cigarette smoke, contains the aldehydes including acetaldehyde. Further, ~560 million people carry an inactivating genetic variant in aldehyde dehydrogenase 2 (ALDH2), known as ALDH2*2, the primary enzyme responsible for metabolizing acetaldehyde. However, little is known how reactive acetaldehyde present in cigarette smoke and e-cigarette aerosol, when coupled with genetics, influence pulmonary vascular function. Hypothesis: Acetaldehyde in e-cigarette aerosol and cigarette smoke lead to pulmonary endothelial dysfunction that is exacerbated in mice carrying the ALDH2*2 variant. Methods: Primary cultures of pulmonary microvascular endothelial cells from wild type ALDH2 and ALDH2*2 male mice were used. Cultures were treated with acetaldehyde (1 μM for 1 hour) in the presence and absence of the ALDH2 activator, Alda-1 (20 μM). Intracellular ROS accumulation, reactive aldehyde-induced protein adducts, mitochondrial bioenergetics, and endothelial function by capillary tube formation were measured. ANOVA with Bonferroni correction was performed for multiple comparisons between groups. * P<0.05. Results: In ALDH2 and ALDH2*2 mice, no differences were noted in endothelial cell morphology and expression of CD31, an endothelial specific marker. However, when exposed to acetaldehyde, pulmonary microvascular endothelial cells from ALDH2*2 mice showed a 91.2±23.2% increase in 4-HNE-induced protein adducts, a 27.8±5.1% reduction in mitochondrial bioenergetics, a 11.1±1.6% decrease in cell viability, and an 70.4±17.2% exacerbation of endothelial dysfunction compared to wild type ALDH2 cells (p<0.05 for each assay, n=3 biological replicates). Pretreatment with Alda-1 partially reversed the oxidative stress and endothelial injury caused by acetaldehyde treatment. Conclusion: Acetaldehyde, the primary aldehyde present in e-cigarette aerosol which is also in cigarette smoke triggers pulmonary endothelial dysfunction particularly for rodents carrying an inactivating ALDH2 variant, ALDH2*2. This study provides a mechanism how e-cigarette vapor similar to cigarette smoke can trigger endothelial dysfunction that can over time potentially lead to the development of PAH.