Effect of PTU on IL-12 and IL-10 in Psoriasis
December 2003 | Volume 2 | Issue 6 | Original Article | 645 | Copyright © December 2003
Alan N. Elias, MD; Vandana S. Nanda, MD and Ronald J. Barr, MD
Propylthiouracil (PTU), an antithyroid thioureylene with immunomodulatory properties, has been shown to be effective in the therapy
of patients with plaque psoriasis. The mechanism of action of antithyroid thioureylenes in psoriasis remains unknown.
Propylthiouracil is a commonly used agent in the treatment of patients with Graves’ hyperthyroidism, a condition associated with elevated
levels of interleukin-12 (IL-12), which fall significantly after propylthiouracil treatment. IL-12 is believed to play a pivotal role in
the development of psoriasis. Production of IL-12 is modulated by the anti-inflammatory cytokine IL-10. The effect of PTU on IL-
12 and IL-10 levels was, therefore, studied in twelve patients with plaque psoriasis. Treatment with 300 mg of PTU daily in divided
doses for three months produced significant improvement of the PASI and histological scores in the patients. Serum IL-12 concentrations
were undetectable at baseline and did not change with treatment. IL-10 concentrations were 1.39 ± 1.49 pg /ml (mean ± SD)
at baseline, and showed no significant change after 2 weeks (1.63 ± 1.61 pg /ml and 12 weeks 1.15 ± 1.58 pg /ml of treatment with PTU.
The data suggest that the clinical improvement with patients with psoriasis treated with PTU is not due to a fall in circulating IL-12
or a rise in IL-10 concentrations. Although the drug may have effects on lesional production of these cytokines this is not reflected
in the circulating levels. It is speculated that the beneficial effect is likely mediated by an inhibitory effect on keratinocyte proliferation
or promotion of apoptosis in these proliferated keratinocytes.