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Abstract 319: Electronic Cigarettes Activate The Heat Shock Response In Vascular Smooth Muscle In Atherosclerosis


 Introduction:
 Electronic cigarettes pose a serious emerging risk for cardiovascular disease. Despite a significant association between exposure to e-cigarettes (e-cigs) and burden of coronary artery disease, the pathogenic mechanism is not well understood. The environment sensing transcription factor aryl-hydrocarbon receptor (Ahr) pathway has been implicated in tobacco-induced atherosclerosis but its role in e-cigarette exposure is not known.
 
 
 Methods:
 SMC-lineage tracing mice (WT, n=3) and SMC-specific Ahr knockout (KO, n=3) mice on a ApoE null hyperlipidemic background were put on high fat diet for 12 weeks and exposed to pod-based e-cigs (Juul) daily for 2 weeks in a whole body chamber (inExpose, Scireq) and compared to WT mice exposed to air (n=3). The aortic sinus was dissected and digested, FACS was performed to sort for live single cells, then single-cell RNA-Seq and ATAC-seq were performed on the 10X Genomics platform. Analyses were completed with Seurat and Signac tools.
 
 
 Results:
 There were total of 20102 cells included in the scRNA-Seq analysis (WT Control 5282, WT exposed to e-cig (WT-Ecig) 9425, and KO exposed to
 Juul
 (KO-Ecig) 5395). We found increased
 Cyp1b1
 expression in the modulated SMC population in the WT-Ecig group, suggesting activation of the Ahr pathway. The proportion of modulated SMC to quiescent SMC remained comparable following E-cig exposure in the WT mice. We identified a new cluster of SMC lineage cells that were enriched for markers of heat shock response, including
 Hspb1, Hsp90aa1
 , and
 Cryab
 . This subpopulation of SMC was nearly absent in the SMC-specific Ahr KO mice exposed to E-cigs. The scATAC-seq profiles showed enrichment for motifs of CCAAT/enhancer-binding proteins, and pathways of cytokine production, ECM organization, and cell migration in the clusters of heat shock response-activated SMC, as well as significant enrichment for Hsf2 motifs in open chromatin regions following E-cig exposure.
 
 
 Conclusion:
 Using single-cell genomics of atherosclerotic plaque from mice exposed to e-cigs, we identified the heat shock response pathway to be uniquely activated in the modulated SMC-lineage population, and that this process may be mediated by Ahr.
