Abstract 17126: Role of Aldehydes, Transient Receptor Potential Ankyrin 1, and Catecholamines in Electronic Cigarette-Induced Endothelial Dysfunction in Mice

Abstract

Although Electronic Nicotine Delivery Systems (ENDS)-derived aerosols induce endothelial dysfunction (ED), the mechanisms and constituents responsible for ED are unknown. Because ENDS use propylene glycol and vegetable glycerin (PG:VG) that thermally decompose into aldehydes, we hypothesized that acrolein and formaldehyde stimulate ED via the sensory transient receptor potential ankyrin-1 (TRPA1) receptor and the autonomic nervous system (ANS). To test this, female wild-type (WT) and TRPA1-null mice were exposed to either filtered air, PG:VG-derived aerosol, acrolein (AC; 1 ppm), or formaldehyde (FA, 5 ppm). Biomarkers of exposure (AC: 3HPMA; FA: 4TCA) and of harm (aortic ED; urinary catecholamines) were measured. The PG:VG and AC exposures significantly increased urinary 3HPMA levels; and the PG:VG and FA exposures significantly increased urinary 4TCA levels vs air controls. Both PG:VG and FA exposures (6h/d x 4d) in WT mice led to aortic ED (-64.6±3.8; –66.7±5.5 % ACh, respectively) vs air control (-81.5±1.5 % ACh); yet AC exposure did not induce ED (-76±2.9 % ACh). Exposures in TRPA1-null mice to PG:VG, AC, or FA did not lead to ED (-93.0±3.6; –82.8±3.1; -86.6±2.8 % ACh; respectively). As an index of ANS activation and a potential mediator of ED, urinary catecholamines (dopamine, DA; norepinephrine, NE; epinephrine, EPI; serotonin, 5HT) and metabolites were measured by UPLC-MS/MS in early (0-3h) and late (3-18h) post-exposure (PE) samples. In WT mice, PG:VG significantly increased early PE urine levels of NE (and two NE metabolites; +1.5-2.5x), DA metabolite (+1.5x), but not EPI nor 5HT; FA exposure increased DA (+3x), EPI (+2.5x), NE and NE metabolites (+1.2-2.5x), 5HT and 5HT metabolite (+2.5x) only in late PE; while AC exposure decreased early PE DA (-73%) and 5HT (-42%) levels. In TRPA1-null mice, PG:VG and AC exposures increased early PE levels of NE (+2x) and depressed EPI and 5HT levels (-40%); whereas FA exposure increased NE (+2x), EPI (+4x), and 5HT (+1.5) levels in late PE. Aldehydes induce ED through time-dependent mechanisms mediated in part by TRPA1 activation and ANS stimulation. These data indicate that ENDS use may increase cardiovascular disease risk via aldehydes generated by PG:VG independent of nicotine and flavorants.