Increased expression of involucrin in people with psoriasis

[Fred]

This study looks at the use of Propylthiouracil (PTU), an anti-thyroid thioureylene as a treatment for psoriasis.

*Propylthiouracil (PTU) or 6-n-propylthiouracil[1] (PROP) is a thiouracil-derived drug used to treat hyperthyroidism (including Graves' disease) by decreasing the amount of thyroid hormone produced by the thyroid gland. Its notable side effects include a risk of agranulocytosis and aplastic anemia. On 3 June 2009, the FDA published an alert "notifying healthcare professionals of the risk of serious liver injury, including liver failure and death, with the use of propylthiouracil." As a result, propylthiouracil is no longer recommended in non-pregnant adults and in children as the front line antithyroid medication.

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Background:
Propylthiouracil (PTU), an anti-thyroid thioureylene, has been shown to be effective in chronic plaque psoriasis. Involucrin is a precursor protein that is upregulated in psoriasis.

Objectives:
This study evaluated the expression of involucrin in the epidermis of skin in psoriatic plaques before and after treatment with PTU.

Methods:
This was an open-label, prospective study in which 25 psoriasis patients underwent skin biopsies prior to treatment with oral PTU 100 mg three times per day for 12 weeks. Patients were assessed at 2, 6, and 12 weeks. Skin biopsies were repeated at the same sites at 12 weeks. Pre- and post-treatment specimens were subjected to immunohistochemical staining and real-time polymerase chain reaction for involucrin.

Results:
Mean ± standard deviation (SD) scores on the Psoriasis Area and Severity Index reduced significantly from 17.86 ± 9.9 at baseline to 4.63 ± 4.1 at week 12 (P < 0.001). Histomorphometric analysis revealed marked decreases in numbers of positively stained cells and intensity of staining. Staining became localized to the upper granular layers after therapy. Immunohistochemical scoring for involucrin reduced from a mean ± SD of 9.00 ± 0.67 at baseline to 3.90 ± 0.88 at week 12 (P < 0.0001).

Conclusions:
In psoriasis, there is increased expression of involucrin, which leads to abnormal keratinocyte differentiation and hence to the formation of psoriatic plaques. The therapeutic effect of PTU in psoriasis may be attributable to the downregulation of involucrin. Larger trials should further elucidate the mechanism and therapeutic potential of PTU in psoriasis.

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*Involucrin is a protein component of human skin and in humans is encoded by the IVL gene. In binding the protein loricrin, involucrin contributes to the formation of a cell envelope that protects corneocytes in the skin.