Genomics-based deconvolution of multiplexed transcriptional responses to wood smoke particles defines rapid AHR signaling dynamics.

Abstract

Heterogeneity of respirable particulates and compounds complicates understanding transcriptional responses to air pollution. Here, we address this problem through applying precision nuclear run-on sequencing (PRO-seq) to measure nascent transcription and the assay for transposase-accessible chromatin using sequencing (ATAC-seq) to airway epithelial cells after wood smoke particle (WSP) exposure. We used transcription factor enrichment analysis to agnostically identify temporally distinct roles for the TCF/SRF family, the aryl hydrocarbon receptor (AHR), and NFkB in regulating transcriptional changes induced by WSP. Transcription of canonical targets of the AHR, such as CYP1A1 and AHRR, was robustly increased after just 30 minutes of WSP exposure, and we discovered novel AHR-regulated pathways and targets including the DNA methyltransferase, DNMT3L. Transcription of these genes and associated enhancers rapidly returned to near baseline by 120 minutes. The kinetics of AHR- and NFkB-regulated responses to WSP were distinguishable based on the timing of both transcriptional responses and chromatin remodeling, with induction of several cytokines implicated in maintaining NFkB responses through 120 minutes of exposure. In aggregate, our data establish a direct and primary role for AHR in mediating airway epithelial responses to WSP and identify crosstalk between AHR and NFkB signaling in controlling pro-inflammatory gene expression. This work also defines an integrated genomics-based strategy for deconvoluting multiplexed transcriptional responses to heterogeneous environmental exposures.