Alterations in epidermal polyamine levels and DNA synthesis following topical treatment with chrysarobin in SENCAR mice

A single topical application of chrysarobin (220 nmol) to SENCAR mouse skin produced alterations in epidermal polyamine levels distinctly different from that following a single topical treatment with 3.4 nmol of 12-O-tetradecanoylphorbol-13-acetate (TPA). Putrescine and spermidine levels were elevated prior to the induction of epidermal ornithine decarboxylase. In this regard, putrescine levels were elevated at 6 and 24 h after a single application of chrysarobin. In addition, putrescine levels were elevated with a second major peak at 64 h after chrysarobin which coincided with elevated epidermal ornithine decarboxylase activity. Spermidine levels were substantially elevated from 24 to 96 h (peak at 60 h) after a single treatment. TPA treatment produced peak elevations in epidermal putrescine levels at 6 h and epidermal spermidine levels at 24 h after a single treatment. Epidermal spermine levels were dramatically depressed following treatment with chrysarobin (peak depression of approximately 60% below control at 24 h), but only slightly altered following treatment with TPA. The time courses for changes in epidermal DNA synthesis in mouse skin following single treatments with 3.4 nmol of TPA or 220 nmol of chrysarobin also showed considerable differences. TPA treatment produced several waves of DNA synthesis at approximately 18 and 48 h after treatment, while chrysarobin produced a single broad peak at 72 h after treatment. Treatment with chrysarobin was also associated with an initial, dramatic inhibition in epidermal DNA synthesis (to 23% of the control value) which was much more extensive than that elicited by TPA. Inhibition of epidermal DNA synthesis following treatment with chrysarobin was observed within a few hours after treatment and remained depressed until approximately 36 h after treatment. Following treatment with both chrysarobin and TPA, higher levels of epidermal DNA synthesis correlated closely with higher molar ratios of spermidine/spermine, indicating a strong relationship between epidermal spermidine levels and epidermal cell proliferation induced by both promoters. The data suggest that TPA and chrysarobin bring about initial changes in epidermal polyamines by distinct mechanisms; however, both compounds ultimately lead to a dramatic stimulation of epidermal DNA synthesis. These data further support our working hypothesis that anthrones promote skin tumors by an initial mechanism different from that of the phorbol esters.