Phototoxicity, distribution and kinetics of association of UVA-activated chlorpromazine, 8-methoxypsoralen, and 4,6,4'-trimethylangelicin in Jurkat cells.

Extracorporeal phototherapy (ECP) is a therapeutic approach based on photobiological effects of 8-methoxypsoralen (8-MOP) on white blood cells isolated from the blood, exposed to UVA and then reinfused into the patient. 8-MOP is presently the only drug approved for clinical application of ECP; therefore, identification of other photosensitizers with better photochemical and pharmacokinetic properties might enhance the efficacy of this treatment modality. Among such alternative drugs are 4,6,4'-trimethylangelicin (TMA) and chlorpromazine (CPZ), which have previously been studied in an animal model for ECP. In this current study, cellular bioavailability of 8-MOP, TMA and CPZ was investigated in vitro, using low doses of UVA relevant for the clinical setting of ECP. Our fluorescence microscopy study revealed that 8-MOP and CPZ penetrated readily into the cells, where they accumulated with similar kinetics. No distinct fluorescence was observed in cells incubated with TMA. We found that the phototoxic efficiency of 8-MOP was an order of magnitude greater than that of CPZ, i.e., to obtain a similar reduction in survival of cells subjected to photosensitization by the drugs, the concentration of CPZ needed to be 10 times higher than that of 8-MOP. The photoactivated TMA exhibited the highest pro-apoptotic efficiency. A clear indication of photoinduced formation of reactive oxygen species and peroxidation of lipids was observed only in CPZ-sensitized cells, suggesting different mechanisms for phototoxicity mediated by CPZ and by the two furocoumarins.

Eicosapentaenoic acid, a n-3 polyunsaturated fatty acid differentially modulates TNF-alpha, IL-1alpha, IL-6 and PGE2 expression in UVB-irradiated human keratinocytes.

In response to UVB-irradiation keratinocytes release a variety of cytokines and prostaglandins, including tumor necrosis factor alpha (TNF-alpha), interleukin 1alpha (IL-1alpha), interleukin 6 (IL-6), and prostaglandin E2 (PGE2). n-3 Polyunsaturated fatty acids (PUFA), mainly present in fish oil, can modulate cytokine synthesis, as predominantly studied in macrophages. In order to investigate the immune modulating actions of n-3 PUFA on the UVB response in human skin, we investigated the effect of eicosapentaenoic acid (EPA), a n-3 PUFA and a precursor of eicosanoid biosynthesis, on UVB-modulated TNF-alpha, IL-1alpha, IL-6, and PGE2 expression in normal human keratinocytes (NHK). We show that cultured NHK can efficiently take up EPA. Basal TNF-alpha expression is very low in NHK. IL-1alpha on the contrary is significantly present in untreated cultured NHK. Upon UVB-irradiation (32 mJ per cm2) TNF-alpha mRNA expression and secretion is induced and IL-1alpha mRNA expression is reduced, although IL-1alpha secretion is induced. EPA treatment results in higher TNF-alpha and IL-1alpha expression, both in nonirradiated and UVB-irradiated keratinocytes. Moreover EPA and UVB appear to act synergistically to superinduce TNF-alpha expression. EPA treatment results also in lipid peroxidation and in decreased PGE2 and IL-6 secretion after UVB-irradiation. In contrast to EPA, oleic acid (monounsaturated fatty acid) and linoleic acid (n-6 PUFA) treatment did not result in higher TNF-alpha or IL-1alpha levels in nonirradiated or UVB-irradiated NHK, indicating that the observed effects are specific for EPA. In conclusion, these results show that EPA can differentially modulate UVB-induced cytokine and prostaglandin synthesis in NHK.