Photomutagenicity of chlorpromazine and its N-demethylated metabolites assessed by NGS

[EN] The human genome is constantly attacked by endogenous and exogenous agents (ultraviolet light, xenobiotics, reactive oxygen species), which can induce chemical transformations leading to DNA lesions. To combat DNA damage, cells have developed several repair mechanisms; however, if the repair is defective, DNA lesions lead to permanent mutations. Single-cell gel electrophoresis (COMET assay) is a sensitive and well-established technique for quantifying DNA damage in individual cells. Nevertheless, this tool lacks relationship with mutagenesis. Therefore, to identify errors that give rise to mutations it would be convenient to test an alternative known procedure, such as next generation sequencing (NGS). Thus, the present work aims to evaluate the photomutagenicity of neuroleptic drug chlorpromazine (CPZ), and its N-demethylated metabolites using COMET assay and to test NGS as an alternative method to assess photomutagenesis. In this context, upon exposure to UVA radiation, COMET assay reveals CPZ-photosensitized DNA damage partially repaired by cells. Conversely with this result, metabolites demethylchlorpromazine (DMCPZ) and didemethylchlorpromazine (DDMCPZ) promote extensive DNA-photodamage, hardly repaired under the same conditions. Parallel assessment of mutagenesis by NGS is consistent with these results with minor discrepancies for DDMCPZ. To our knowledge, this is the first example demonstrating the utility of NGS for evaluating drug-induced photomutagenicity.
This study was funded by the Carlos III Institute (ISCIII) of Health (Grants: PI15/00303, PI18/00540, PI16/01877, CPII16/00052, the Thematic Networks and Co-operative Research Centres: ARADyAL RD16/0006/0004 and RD16/0006/0030), IB16170, GR18145 from Junta de Extremadura, Spain, co-funded by European Regional Development Fund and Generalitat Valenciana Prometeo/2017/075. We would also like to thank M. Dolores Coloma for technical assistance in the preliminary experiments.