an inter-laboratory in vitro assessment of cigarettes and next generation nicotine delivery products.

Introduction:
This article presents the results of a collaborative study between two laboratories, one in the UK and one in Japan, evaluating the oxidative stress responses of lung epithelial cells exposed to cigarette smoke and next generation nicotine delivery products (NGPs) using four in vitro assays. The study aimed to assess whether consistent results could be obtained without major protocol alignment activities.

Key points:

* The study used four in vitro assays to evaluate oxidative stress responses in lung epithelial cells exposed to cigarette smoke and NGPs.
* The test matrices (TPM/aCM) were standardized, but the assays were conducted in different cell types without protocol alignment.
* The 3R4F cigarette smoke TPM induced concentration-dependent responses in all assays, while the NGPs were mostly negative.
* Slight differences were observed in the response to cigarette smoke between laboratories, possibly due to cell-specific sensitivity and protocol differences.
* The results demonstrate that consistent cigarette smoke responses can be obtained between laboratories without major harmonization efforts.
* The study represents a starting point for a harmonization journey that could yield positive results for in vitro NGP testing in a pragmatic and time-efficient manner.
* The authors suggest that further investigations should include the assessment of more highly concentrated NGP aCM preparations, whole aerosol exposures, or aerosol aqueous extracts (aqE).

Main message:
The study demonstrates that consistent results can be obtained between laboratories without major protocol alignment activities, providing a starting point for a harmonization journey in in vitro NGP testing. The results highlight the importance of considering cell-specific sensitivity and protocol differences when interpreting the results of in vitro assays. The authors suggest further investigations to optimize the assessment of NGPs using in vitro assays. Overall, the study provides valuable insights into the potential of in vitro assays for the assessment of NGPs and highlights the need for further research to optimize these methods.

Ito S, Taylor M, Mori S, et al. an inter-laboratory in vitro assessment of cigarettes and next generation nicotine delivery products. Toxicology letters. 2019;315:14-22. doi:10.1016/j.toxlet.2019.08.004