Medium-mediated effects increase cell killing in a human keratinocyte cell line exposed to solar-simulated radiation

Abstract

Purpose: The objective of this study was to investigate whether cell culture medium is a biologically relevant exposure medium that can be employed in non-ionising photobiological investigations.

Methods: The effect of solar-simulated irradiation on cell culture medium and its ability to elicit cell death was studied. The role of reactive oxygen species (ROS), cell secreted factors, and the contribution of individual components of the medium were investigated.

Results: Cell death was found to be primarily mediated through the formation of ROS via riboflavin photosensitisation and degradation in the cell culture medium. Phenol red was found to significantly reduce the cell killing ability of riboflavin. Exposures in riboflavin-free medium resulted in significantly increased cell survival compared to identical exposures in riboflavin containing medium.

Conclusions: This study has shown that solar radiation toxicity is augmented by cell culture medium due to the presence of riboflavin. Results suggest that exposures performed in phenol red-free medium may serve to increase phototoxic effects if riboflavin is present. Riboflavin-free media is recommended for solar radiation investigations to eliminate concerns regarding riboflavin photosensitisation and nutrient deprivation.

Keywords:

• solar UV
• medium mediated
• photosensitiser
• reactive oxygen species
• riboflavin
• phenol red

Acknowledgements

The authors would like to thank Prof. Hugh J. Byrne, Focas Research Institute, DIT, for his expert advice on the spectroscopic results. This research was funded by the Department of Education and Science, Ireland (Technological Sector Research Strand I).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.