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Phototoxicity to diuretics and antidiabetics in the cultured keratinocyte cell line HaCaT: evaluation by clonogenic assay and single cell gel electrophoresis Comet assay)

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Potential phototoxicity has been described for a number of drugs and chemical substances. Psoralens, chlorpromazines and fluoroquinolones have been described as inducing photomutagenicity and photocarcinogenicity in vitro and in vivo. We wanted to investigate oral antidiabetics and diuretics for potential phototoxicity and possible DNA damage in the HaCaT cell line.


The oral antidiabetics tolbutamide, glibenclamide and glipizide, and the diuretics bendroflumethiazide, butizide, furosemide, hydrochlorothiazide and trichlormethiazide were dissolved in DMSO to final concentrations of 1 mM, 0.1 mM, and 0.01 mM, incubated together with the cells, and exposed to UVA1 (23 or 48 J/cm2). Cell survival was evaluated in a clonogenic assay and phototoxic DNA damage was investigated by single cell gel electrophoresis (comet assay). To investigate possible inhibiting effects of antioxidants, L-ascorbic acid and α-tocopherol were added at a final concentration of 1 mM 24 h before treatment with the drugs.


Bendroflumethiazide, furosemide, hydrochlorothiazide, trichlormethiazide and tolbutamide induced dose-dependent phototoxicity in the clonogenic assay. Cells incubated with bendroflumethiazide, tolbutamide and glibenclamide and irradiated with UVA1 demonstrated increased oxidative DNA damage, revealed as alkali-labile sites in the comet assay. Pretreatment with L-ascorbic acid or α-tocopherol suppressed the UVA-induced DNA damage in cells incubated with 1 mM bendroflumethiazide, furosemide, glibenclamide, glipizide, tolbutamide or trichloromethiazide.


Several oral antidiabetics and diuretics show phototoxic effects in the HaCaT cell line. Inhibiting effects of antioxidants point towards involvement of reactive oxygen species in phototoxic DNA damage, suggesting a link between the phototoxic and photocancerogenic potential of the sulfonamide-derived oral antidiabetic and diuretic drugs. Excessive exposure to UV light may be deleterious for patients treated with oral antidiabetic and diuretic drugs.

Keywords: Comet assay; DNA-damage; HaCa T cells; antidiabetics; diuretics; phototoxicity

Document Type: Original Article

Affiliations: Department of Dermatology, Bispebjerg Hospital, Copenhagen, Denmark

Publication date: 2002-04-01

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