Alterations in the transcriptome of human primary bronchial epithelial cells exposed to emissions from a heated tobacco product.

INTRODUCTION

IQOS is a Heated Tobacco Product marketed as reduced-risk alternative to cigarettes. This is based on limited industry-independent toxicological evidence.

METHODS

Cigarette Smoke Extract (CSE) and IQOS extract (IQOSE) were generated by puffing mainstream emissions in PBS. Nicotine levels were quantified via liquid chromatography-mass spectrometry (LC-MS). Subsequently, undifferentiated Primary human Bronchial Epithelial Cells (PBECs) from three donors were exposed (24 h) to 1 %CSE, 1 %IQOSE, 3 %IQOSE (v/v), or nicotine concentrations (1.5, 6 or 18 μg/mL), representative of the levels present in the extracts. Transcriptomic alterations were assessed via RNA sequencing, and specific mRNA alterations were validated at the protein level by Western blot.

RESULTS

IQOSE contained about 4-fold more nicotine than CSE. Nicotine did not significantly affect PBECs transcriptome. Substantial differences in the amount of differentially expressed genes (DEGs) were observed in response to CSE and IQOSE between donors. However, in all donors, 3 %IQOSE exposure downregulated pathways involved in cell cycle progress. In addition, both mRNA and protein levels of molecules controlling autophagy and mitophagy increased in response to IQOSE in one donor, and the disease Chronic Obstructive Pulmonary Disease (COPD) was enriched in cells from two donors upon exposure to CSE or IQOSE. In the most responsive donor, pathways associated with ER-stress and DNA replication were deregulated.

CONCLUSIONS

Despite significant inter-donor variability, IQOSE induced specific gene signatures associated with pathways known to be involved in (smoking-related) lung diseases in all donors. Collectively, these findings provide novel insights into the molecular toxicity of IQOS mainstream emissions in human bronchial epithelial cells.