Explore PMI Science, where innovation meets harm reduction. Learn about our scientists, smoke-free research, and commitment to transparency in research.
PMI offers smoke-free alternatives with the potential to reduce the risk of harm for adult smokers who do not quit. Learn about harm reduction, the role of nicotine, and the regulation of smoke-free products.
Discover PMI's rigorous scientific approach to smoke-free products and product assessment. Dive into our research results, peer-reviewed publications, independent research, and expert reports.
PMI believes that offering a range of smoke-free alternatives is essential to ensure individual smokers are able to find a smoke-free product that they can fully switch to.
Explore the latest insights and stay informed about upcoming events and conference presentations from PMI scientists.
Ask a question or send us feedback. We're happy to answer.
Explore PMI Science, where innovation meets harm reduction. Learn about our scientists, smoke-free research, and commitment to transparency in research.
PMI offers smoke-free alternatives with the potential to reduce the risk of harm for adult smokers who do not quit. Learn about harm reduction, the role of nicotine, and the regulation of smoke-free products.
Discover PMI's rigorous scientific approach to smoke-free products and product assessment. Dive into our research results, peer-reviewed publications, independent research, and expert reports.
PMI believes that offering a range of smoke-free alternatives is essential to ensure individual smokers are able to find a smoke-free product that they can fully switch to.
Explore the latest insights and stay informed about upcoming events and conference presentations from PMI scientists.
Ask a question or send us feedback. We're happy to answer.
PMI
The Neutral Red Assay is probably the most widely used assay for the assessment of cytotoxicity in the context of tobacco product testing.
Neutral red is a dye that is taken up by a specific type of mouse embryo cells (BALB/c 3T3 cells) where it accumulates in the lysosomes / endosomes. We can test the cytotoxicity of a compound by applying the dye to cells, washing away any that remains on their exterior and then measuring the amount of dye that is extracted from within the cells’ lysosomes. The more dye that is recovered from a cell, the less cytotoxic the substance that the cell was exposed to.
Neutral Red Assay to assess Reduced-Risk Products
The Neutral Red Uptake (NRU) in vitro cytotoxicity assay developed by Borenfreund and coworkers[1] has been widely used and accepted as a screening method to determine the cytotoxicity of compounds[2]. The test is known to be responsive to both the total particulate matter (TPM) and the gas-vapour phase (GVP) of cigarette smoke[3] and it can discriminate between different cigarette tobacco types[4]. Cytotoxicity is determined in the NRU assay according to the INVITTOX protocol No. 3a.
We have recently carried out studies to compare the relative cytotoxicity of the TPM and GVP from our Reduced-Risk Product Platform 1 with the TPM and GVP from 3R4F[5].
Cytotoxicity substantially decreased compared to 3R4F.
Note: these data alone do not imply or represent a claim of reduced exposure or reduced risk.
The results show that for both the TPM and GVP, cytotoxicity was significantly lower in the cells exposed to Platform 1 than 3R4F. Further, there was little difference in the cytotoxicity potential between menthol and regular versions of Platform 1.
References:
[1] Borenfreund, E and JA Puerner. Toxicity determined in vitro by morphological alterations and neutral red absorption. Toxicol Lett, 1985. 24(2-3): p. 119-24. Available online at: https://www.sciencedirect.com/science/article/abs/pii/0378427485900463
[2] National Institute of Health. Report of the international workshop on in vitro methods for assessing acute systemic toxicity. 2001. Available online at: https://ntp.niehs.nih.gov/iccvam/docs/acutetox_docs/finalrpt/finalall0801.pdf
[3] Tewes, FJ, et al. Toxicological evaluation of an electrically heated cigarette. Part 3: Genotoxicity and cytotoxicity of mainstream smoke. J Appl Toxicol, 2003. 23(5): p. 341-8. Available online at: https://analyticalsciencejournals.onlinelibrary.wiley.com/doi/10.1002/jat.925
[4] Bombick, DW, K Putnam, and DJ Doolittle. Comparative cytotoxicity studies of smoke condensates from different types of cigarettes and tobaccos. Toxicol In Vitro, 1998. 12(3): p. 241-9. Available online at: https://www.sciencedirect.com/science/article/abs/pii/S0887233397001197
[5] Philip Morris International. Investor day presentation. 26 June 2014. Available online at: https://www.pmi.com/resources/docs/default-source/pmi-investor-day-archives-2016/2014-day-1/2014-06-26-rrps_investor_day_slides_-website_final-(2).pdf?sfvrsn=b4e092b5_4
PMIScience.com is operated by Philip Morris International for the purpose of publishing and disseminating scientific information about Philip Morris International’s efforts in support of its smoke-free product portfolio. This site is a global site for use by scientists, the public health and regulatory communities, and other stakeholders with an interest in tobacco policy. The purpose of this site is not advertising or marketing, nor is it directed at any specific market. It is not intended for use by consumers. New tobacco products sold in the United States are subject to FDA regulation; therefore the content of this site is not intended to make, and nor should it be construed as making, any product related claims in the United States without proper FDA authorization.
Reduced Risk Products ("RRPs”) is the term we use to refer to products that present, are likely to present, or have the potential to present less risk of harm to smokers who switch to these products versus continuing smoking. PMI has a range of RRPs in various stages of development, scientific assessment and commercialization. All of our RRPs are smoke-free products that deliver nicotine with far lower quantities of harmful and potentially harmful constituents than found in cigarette smoke.