Assessing phototoxic drug properties of hydrochlorothiazide using human skin biopsies

The diuretic drug hydrochlorothiazide (HCT) is associated with an increased risk of non-melanoma skin cancer upon UV exposure. The underlying cellular and molecular mechanisms behind this association remain elusive. Herein, a human skin model to assess the photocarcinogenic effects of HCT is established. Skin biopsies collected from human body donors are treated with HCT and irradiated with 300 mJ/cm² low dose UVA or UVB or with 5 J/cm² high dose UVA. In HCT-treated biopsies but not in control, low dose UVA irradiation results in activation and nuclear translocation of the tumor-suppressor protein p53 accompanied by an upregulated gene expression of p53-negative regulator MDM2. High dose UVA additionally provokes DNA damage and initiation of pro-inflammatory gene expression. In contrast, UVB induces pronounced DNA damage, p53 protein activation, gene expression of MDM2 and inflammatory marker genes in both HCT-treated biopsies and untreated control. In summary, in HCT-treated skin biopsies, activation of the p53-MDM2 axis, induction of DNA damage, and inflammatory response depends on UVA-dosage and may influence skin carcinogenesis over time. This human model eliminates the need for animal testing and mitigates species difference, offering a valuable tool for future drug development and safety testing.