P14 Developing a mass spectrometry imaging approach to investigate phototoxicity in HaCaT keratinocytes
Xiaoqi Ma, Aliye Bashak, Alexandra Kendall, Mark Farrar, Anna NicolaouAbstract
Introduction and aims
Phototoxicity reactions are adverse drug responses caused by exposure to ultraviolet (UV) radiation and are commonly attributed to reactions between drugs and/or their metabolites with UVA, leading to oxidative stress and damage to skin cells. However, the skin distribution of systemically taken photosensitizing drugs and drug–UVA reactions remains unclear. This project aims to develop a mass spectrometry imaging (MSI) approach to investigate the skin distribution of photosensitizing drugs and their metabolites in vitro.
Methods
HaCaT keratinocytes were treated with hydrochlorothiazide, naproxen, quinine and 8-methoxypsorolen, with or without UVA exposure. Cell viability was assessed using MTT assay. Fragmentation patterns of UVA-irradiated drugs were examined by electrospray ionization tandem mass spectrometry, and used to set up experimental conditions for matrix-assisted laser desorption ionization (MALDI) analysis of these drugs and their metabolites (using CHCA as a matrix). Following optimization, MALDI-MSI was applied to detect the prevalence of drug and metabolite-derived ions and generate spatial ion maps in treated HaCaT cultures.
Results
UVA exposure (5 J cm−2) combined with the tested drugs (at different concentrations) reduced HaCaT cell viability, indicating cellular damage. MALDI-MS analysis of drug solutions treated with UVA (5–50 J cm−2) enabled detection of ions corresponding to the molecular ion and photoproduct ions of the tested drugs, including hydrochlorothiazide m/z 261.985 [M+H-Cl]+; naproxen photoproduct and fragment m/z 201.082 [2A6MN+H]+ and m/z 186.096 [M+H-COOH]+; quinine fragments m/z 160.070, m/z 172.034 and m/z 307.172; and 8-MOP m/z 433.096 [dimer+H]+. These ions served as references to generate spatial maps of drug-derived species in HaCaT cultures.
Conclusions
Developing an MSI workflow to detect drugs and their photoproducts in HaCaT keratinocytes, is vital for translating MSI to skin biopsy sections to explore drug distribution in human skin, which will help elucidate mechanisms underlying drug-induced phototoxicity in order to develop novel preventive interventions.