Folic acid and its photoproducts, 6-formylpterin and pterin-6-carboxylic acid, as generators of reactive oxygen species in skin cells during UVA exposure.

Folic acid (FA) is the synthetic form of folate (vitamin B9), present in supplements and fortified foods. During ultraviolet (UV) radiation FA is degraded to 6-formylpterin (FPT) and pterin-6-carboxylic acid (PCA) which generate reactive oxygen species (ROS) and may be phototoxic. The aim of the present study was to investigate the production of ROS and phototoxicity of FA, FPT and PCA in skin cells during UVA exposure. The production of ROS and phototoxicity of FA, FPT and PCA were studied in the immortal human keratinocytes (HaCaT) and malignant skin cells (A431 and WM115) during UVA exposure. Increased ROS production and the photoinactivation of cells in vitro were observed during UVA exposure in the presence of FA, FPT and PCA. HPLC analysis revealed that 10 µM FA photodegradation was around 2.1 and 5.8-fold faster than that of 5 µM and 1 µM FA. Photodegradation of FA is concentration dependent, and even non-phototoxic doses of FA and its photoproducts, FPT and PCA, generate high levels of ROS in vitro. FA, FPT and PCA are phototoxic in vitro. The photodegradation of topical or unmetabolized FA during UV exposure via sunlight, sunbeds or phototherapy may lead to ROS production, to the cutaneous folate deficiency, skin photocarcinogenesis and other deleterious skin effects. Further studies are needed to confirm whether UV exposure can decrease cutaneous and serum folate levels in humans taking FA supplements or using cosmetic creams with FA.

Decrease in cytotoxicity of copper-based intrauterine devices (IUD) pretreated with 6-mercaptopurine and pterin as biocompatible corrosion inhibitors.

The copper intrauterine device (IUD) based its contraceptive action on the release of cupric ions from a copper wire. Immediately after the insertion, a burst release of copper ions occurs, which may be associated to a variety of side effects. 6-Mercaptopurine (6-MP) and pterin (PT) have been proposed as corrosion inhibitors to reduce this harmful release. Pretreatments with 1 × 10(-4) M 6-MP and 1 × 10(-4) M PT solutions with 1h and 3h immersion times were tested. Conventional electrochemical techniques, EDX and XPS analysis, and cytotoxicity assays with HeLa cell line were employed to investigate the corrosion behavior and biocompatibility of copper with and without treatments. Results showed that copper samples treated with PT and 6-MP solutions for 3 and 1 h, respectively, are more biocompatible than those without treatment. Besides, the treatment reduces the burst release effect of copper in simulated uterine solutions during the first week after the insertion. It was concluded that PT and 6-MP treatments are promising strategies able to reduce the side effects related to the "burst release" of copper-based IUD without altering the contraceptive action.

[Photosensitized DNA damage: mechanisms and clinical use].

On the basis of our recent investigations by a DNA sequencing technique, mechanisms of photoinduced DNA damage in the presence of various endogenous molecules are summarized with special reference to UV carcinogenesis. In particular, riboflavin and pterin derivatives have been shown to induce DNA damage, mainly 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG) formation, specifically at the 5' site of 5'-GG-3' sequences through electron transfer reaction. The involvement of 8-oxodG formation in ras mutation is discussed. In addition, recent works concerning the mechanism of photodynamic therapy and the properties of photoactivatable DNA-cleaving molecules are described.

Antifolates can potentiate topoisomerase II inhibitors in vitro and in vivo.

Antifolates have been shown to increase the DNA strand breaks produced by the topoisomerase inhibitor etoposide. PT523 is a potent new antifolate that cannot be polyglutamated. Human SCC-25 squamous carcinoma cells were exposed to methotrexate, trimetrexate or PT523 at a concentration of 5 microM for 24 h along with various concentrations of etoposide or novobiocin during the final 2 h. Isobologram analysis of the treatment combinations indicated that exposure of the cells to PT523/etoposide, methotrexate/etoposide, PT523/novobiocin, methotrexate/novobiocin and trimetrexate/novobiocin resulted in greater than additive cytotoxicity. DNA alkaline elution studies with the same drug combinations indicated that there were three- to four-fold increases in the radiation equivalent (rad equivalent) strand breaks in the cellular DNA with etoposide or novobiocin along with the antifolate compared with the topoisomerase II inhibitors alone. Tumor growth delay studies were carried out in the murine SCC VII squamous carcinoma. PT523 (0.5 mg/kg) and methotrexate (2 mg/kg) were administered by 7-day continuous infusion while trimetrexate (3.75 mg/kg) was administered intraperitoneally daily on days 7-9. Etoposide (10 mg/kg) and novobiocin (100 mg/kg) were administered intraperitoneally on alternate days (7, 9, 11). The combinations of PT523 with etoposide or novobiocin were significantly more effective than methotrexate and etoposide or novobiocin, producing tumor growth delays of 8.4 days and 6.9 days, respectively. Overall, the antifolate/topoisomerase II inhibitor treatment combinations produced tumor growth delays that were apparently additive to greater than additive.

New thiophene substituted 10-deazaaminopterins: synthesis and biological evaluation.

Analogues of 10-deazaaminopterin (10-DAM) and 4-amino-4-deoxy-10-deazapteroyl-gamma-methylene glutamic acid (MDAM) in which the benzene ring was replaced with a thiophene ring have been synthesized and evaluated for their antitumor activity. These analogues were N-([5-(2,4-diamino-6-pteridinyl)ethyl]-2-thenoyl)-L- glutamic acid (1) and N-([5-(2,4-diamino-6-pteridinyl)ethyl]-2-thenoyl)-gamma-meth ylene glutamic acid (2).