EFFECT OF ORALLY-ADMINISTERED ANTITHYROID THIOUREYLENES ON PCNA AND P53 EXPRESSION IN PSORIATIC LESIONS

Background. Antithyroid thioureylenes are effective agents in the oral and topical treatment of patients with chronic plaque psoriasis. Method. The effect of oral treatment with 6-n-propyl 2-thiouracil (propylthiouracil, PTU) and 2-mercapto 1-methyl imidazole (methimazole, MMI) on proliferating cell nuclear antigen (PCNA), and p53 protein expression was studied in patients with stable plaque psoriasis. Results. Following treatment with PTU and MMI, PCNA staining in psoriatic epidermis was significantly decreased. P53 was minimally expressed in untreated lesions, and treatment with PTU and MMI did not enhance p53 expression in the psoriatic lesions. Conclusions. Since PCNA is a marker of cellular proliferation and p53 inhibits cellular cycling, some of the beneficial effects of PTU and MMI in psoriasis may depend on the ability of the drugs to impair cellular turnover, perhaps by binding to the triiodothyronine (T-3) receptor. These effects may be in addition to the previously described effects of PTU and MMI as immune modulators and free radical scavengers.