Drug-Metabolizing Enzymes in Human Keratinocytes and In Vitro Detection of Cytochrome P450-Mediated Phenolic Lamotrigine Metabolite

Drug-induced hypersensitivity reactions can manifest
as severe
cutaneous adverse reactions, with lamotrigine (LTG) being a known
elicitor in a subset of patients. While reactive metabolites are proposed
to play a role, the contribution of skin metabolism is not well established.
Here, we characterized drug-metabolizing enzymes and transporters
in primary human keratinocytes and assessed the LTG metabolism in
vitro. Using a combined transcriptomic and metabolomic approach, we
demonstrated that primary human keratinocytes show a limited drug-metabolizing
capacity. Although xenobiotic-metabolizing enzymes and drug transporters
(phases I-III) were expressed at the transcript level, key hepatic
cytochrome P450 enzymes (CYPs) were undetectable at both mRNA and
protein levels. Following LTG incubation, low levels of LTG-N2-glucuronide
were formed in keratinocytes as well as (reactive) metabolites, including
a glutathione (GSH) adduct and a putative phenolic LTG derivative,
in several in vitro assays. LTG-N2-sulfate formation could not be
achieved under aqueous conditions. Transcriptome profiling of keratinocytes
revealed no significant response to LTG, LTG-N2-oxide, or LTG+valproate,
whereas interferon-γ triggered a pronounced proinflammatory
gene expression signature. These findings provide new data of LTG
metabolism, highlighting a novel CYP-derived phenolic pathway linked
to GSH conjugation.