Chronic exposure of human bronchial epithelial cells to smoke extracts from indoor cooking leads to altered, enhanced gene expression compared to acute exposures

<bold>Introduction:</bold> Populations in low and middle-income countries are exposed to household air pollution due to reliance on combustion of solid biomass fuel for indoor cooking and heating, causing respiratory morbidity and mortality. Traditional cook stove (TCS) smoke extract collected in Nepal induces gene expression changes in human bronchial epithelial cells (HBECs) after acute exposure (24h). <bold>Aims:</bold> To assess the impact of chronic, repeated exposure of TCS, improved cookstove (ICS), and LPG cook stove smoke extracts on HBEC gene expression. <bold>Methods:</bold> HBECs were treated with smoke extracts for 6 hours a day, over 7 days. RNA was extracted and sequenced. Differential gene analysis was performed in R using limma. Pathway analysis was carried out using IPA (QIAGEN). <bold>Results:</bold> 2,156 genes were differentially expressed (5% FDR) after chronic TCS exposure, more than after acute TCS exposure (24 hours, 360 genes). Chronic induced genes were involved in oxidative phosphorylation (downregulation), and viral response and interferon signalling pathways (upregulated). Of the 360 DEGs caused by acute exposure, 102 of these were also differentially regulated after chronic exposure. These 102 genes were enriched in Aryl Hydrocarbon Receptor Signalling pathways. ICS induced 154 differentially expressed genes (DEGs) in contrast to zero after acute exposure. Of these, 90 genes were also differentially regulated after TCS exposure. <bold>Conclusion:</bold> Chronic TCS exposure produces a distinct and amplified HBEC transcriptomic response compared to acute exposure. Cleaner extracts (ICS) produce reduced but overlapping gene expression changes.