Psoralen and ultraviolet A effects on epidermal ornithine decarboxylase induction and DNA synthesis in the hairless mouse.

8-Methoxypsoralen (8-MOP), 3-carbethoxypsoralen (3-CP), and 5-methoxypsoralen (5-MOP), with and without ultraviolet A (UVA), were compared as inducers of epidermal ornithine decarboxylase (ODC) and modulators of epidermal DNA synthesis in vivo in female Skh:hairless-1 albino mice. Both 8- and 5-MOP plus UVA induced epidermal ODC. Peak ODC activity was induced 24 hours after treatment, and ODC activity was still elevated at 48 hours. These same treatments also suppressed epidermal DNA synthesis 4 hours after treatment, as measured by tritiated thymidine incorporation. The psoralen 3-CP, which lacks the DNA monoadducts, failed to induce epidermal ODC either alone or with UVA and stimulated rather than suppressed incorporation of the tritiated thymidine.

Inhibition of ultraviolet-B skin carcinogenesis by all-trans-retinoic acid regimens that inhibit ornithine decarboxylase induction.

There is a correlation between the ability to induce the polyamine-biosynthetic enzyme ornithine decarboxylase (ODC) and the tumor-promoting ability of various carcinogens in mouse epidermis. Some agents which inhibit skin carcinogenesis also inhibit ODC induction. In this study, all-trans-retinoic acid (RA) regimens that inhibited the induction of epidermal ODC by ultraviolet-B (UVB) were tested for their ability to inhibit UVB skin carcinogenesis. Hairless mice were irradiated once daily with UVB for 20 days, receiving a total dose of UVB (17.1 kJ/sq m). Topical RA was applied immediately (RA, one dose) or applied 0, 1, 2, 3, and 4 hr (RA, five doses) after each irradiance. The mice were maintained for 52 weeks and then sacrificed. Groups treated with RA tended to have fewer mice with tumors, fewer tumors per mouse, smaller tumor diameters, and slower growing tumors than did appropriate irradiated control groups. RA given five times was more effective than was RA given one time at inhibiting UVB skin carcinogenesis. These results show that RA treatments that inhibit epidermal ODC induction may be effective in reducing the carcinogenicity of UVB.

Epidermal polyamine profiles after multiple exposures to ultraviolet radiation.

In experimental studies of u.v.-skin-carcinogenesis u.v.-radiation is usually given in discrete amounts over a protracted period of time. Epidermal polyamine profiles were investigated in hairless mice after single and multiple exposures to ultraviolet-B (u.v.B). Hairless mice were irradiated with u.v.B from FS40 sunlamps and sacrificed after 1, 5, 10 or 20 days of daily irradiation with 0.9 kJ/sq m u.v.B at 6, 24 or 48 h after the final irradiation. Epidermis was analyzed for ornithine decarboxylase (ODC) activity, and for its putrescine, spermidine and spermine content. Skin biopsies were examined for histological changes. As previously reported epidermal ODC activity was induced 6 h after one irradiation with u.v.B and reached a maximum activity at approximately 24 h. In contrast after 5, 10 or 20 daily irradiations with u.v.B the epidermal ODC activity was maximal at approximately 6 h after the final irradiation and by 24 h had returned towards control levels. The magnitude of the ODC activity measured 6 h after irradiation increased with the number of irradiations. A similar pattern was seen with epidermal putrescine levels where a marked shift from a peak at approximately 24 h after one irradiation with u.v.B to a peak at approximately 6 h after 20 days of irradiation with u.v.B occurred. Spermidine levels increased as the number of u.v.B exposures was increased and spermine levels tended to decrease. The spermidine/spermine ratio increased most rapidly during the first 5 exposures, and remained elevated through to 20 days of daily irradiation. Chronic irradiation with u.v.B results in rapid induction of ODC activity and putrescine accumulation in the epidermis, events also elevated by chemical or viral transformation.

New coal tar extract and coal tar shampoos. Evaluation by epidermal cell DNA synthesis suppression assay.

Coal tar therapy has been used for many years in the treatment of scaling skin diseases, including psoriasis and eczema. Previous studies of the potential effectiveness of tar have utilized phototoxic erythema assays with long-wave ultraviolet light (UV-A). However, in clinical use, coal tar is rarely used with UV-A, particularly for scalp disease. Therefore, we investigated a nonphototoxic approach to evaluate different coal tar products. Coal tar was found to suppress epidermal cell DNA synthesis in the hairless mouse model, and this is the basis for the assay presented. Using the epidermal cell DNA synthesis suppression assay, we observed that crude coal tar and a new extract of crude coal tar were equally effective and that a concentration gradient effect was achieved. In addition, four commercial coal tar shampoos assayed varied greatly in their ability to suppress epidermal cell DNA synthesis. One shampoo was washed after ten minutes and no significant alteration of suppressive effect was seen.

Effect of isonicotinic acid hydrazide on the intratumor injection of BCG.

Rats with established subcutaneous tumors were treated by repeated intratumor injections of BCG over a 5-week period. Isonicotinic acid hydrazide (INH) was given to some rats to determine if this drug decreased the effect of BCG on local tumor growth. INH alone had no effect on either survival or tumor volume. Rats treated with either BCG or BCG and INH had prolonged survivals and smaller tumor volumes than did controls rats. In these experiments, INH did not decrease the effect of BCG on local tumor growth. However, the intratumor injection of BCG in rats receiving INH systematically was associated with better survival and smaller tumor volumes compared to the intratumor injection of BCG alone.