E-Cigarette Use, Cigarette Smoking, and Sex Are Associated With Nasal Microbiome Dysbiosis.

Introduction: Previous research suggests that e-cigarettes can alter immune function, including in the nasal mucosa, in unique ways. The respiratory microbiome plays a key role in respiratory host defense, but the effects of e-cigarettes on the respiratory or nasal microbiome, are not well understood.

Aims and methods: Using 16S rRNA gene sequencing on nasal samples from adult e-cigarette users, smokers, and nonsmokers, we determined that e-cigarette use and cigarette smoking are associated with differential respiratory microbiome dysbiosis and substantial sex-dependent differences in the nasal microbiome, particularly in e-cigarette users.

Results: Staphylococcus aureus, a common respiratory pathogen, was more abundant in both e-cigarette users and smokers in comparison with nonsmokers, while Lactobacillus iners, often considered a protective species, was more abundant in smokers but less abundant in e-cigarette users in comparison with nonsmokers. In addition, we identified significant dysbiosis of the nasal microbiome between e-cigarette users and smokers with high versus low serum cotinine levels, an indicator of tobacco product use and toxicant exposure. We also analyzed nasal lavage fluid for immune mediators associated with host × microbiota interactions.

Conclusions: Our analysis identified disruption of immune mediators in the nose of e-cigarette users and smokers, which is indicative of disrupted respiratory mucosal immune responses. Taken together, our data identified unique, sex-dependent host immune dysfunction associated with e-cigarette use in the nasal mucosa. More broadly, our data highlight the need for continued inclusion and careful consideration of sex as an important variable in the context of toxicant exposures.

Implications: This is the first study investigating the effects of e-cigarette use and sex on the nasal microbiome, which is considered an important gatekeeper for protecting the lower respiratory tract from pathogens. We found significant sex, exposure group, and serum cotinine level-associated differences in the composition of the nasal microbiome, demonstrating the importance of considering sex in future nasal microbiome studies and warranting further investigation of the mechanisms by which e-cigarette use dysregulates nasal immune homeostasis.