In vitro long-term repeated exposure and exposure switching of a novel tobacco vapor product in a human organotypic culture of bronchial epithelial cells.

Introduction:
This article reports the results of an in vitro study examining the effects of repeated exposure and exposure switching of a novel tobacco vapor product (NTV) on human bronchial epithelial cells. The study compares the effects of NTV to those of cigarette smoke (CS) and fresh medium, and includes a 40-day exposure repetition of NTV. The key points of the study design and major findings are summarized below.

Key Points:

* The study used a 3D bronchial epithelial tissue culture model and exposed it to CS or NTV for up to 40 days.
* Tissue samples were also switched from CS exposure to NTV exposure or fresh medium after 20 days to mimic smoking cessation or switching to NTV.
* The study measured cytotoxicity, inflammatory mediator secretion, and transcriptomic alterations in the tissue samples.
* Repeated exposure to CS caused cumulative damage, as evidenced by increased aK activity, IL-8 secretion, and MMP-9 secretion, as well as perturbed biological pathways related to inflammation and xenobiotic metabolism.
* Intermediate switching from CS exposure to NTV exposure or fresh medium resulted in recovery from CS-induced damage, although there was a time-course difference.
* Repeated exposure to NTV produced negligible effects on the tissue samples.
* The study suggests that the use of NTV, including switching to NTV from cigarette smoking, has fewer effects on bronchial epithelial tissues than continuing smoking.

Main Message:
The main message of this study is that the use of NTV, including switching to NTV from cigarette smoking, has fewer effects on bronchial epithelial tissues than continuing smoking. The study provides evidence that intermediate switching from CS exposure to NTV exposure or fresh medium results in recovery from CS-induced damage, and that repeated exposure to NTV produces negligible effects on the tissue samples. These findings suggest that NTV may be a less harmful alternative to cigarette smoking, and support the potential for reduced risk compared to combustible cigarettes. however, further scientific evidence, including clinical and nonclinical studies, is necessary to elucidate the reduced risk potential of NTV.

Ito S, Matsumura K, Ishimori K, Ishikawa S. In vitro long-term repeated exposure and exposure switching of a novel tobacco vapor product in a human organotypic culture of bronchial epithelial cells. J appl Toxicol. 2020;40:1248-1258. doi:10.1002/jat.3982