Catechol-O-methyltransferase activity in psoriasis patients treated with psoralen plus ultraviolet A therapy

Catechol-O-methyltransferase (COMT) activity is increased in patients with mild/moderate psoriasis. Narrowband ultraviolet B (nbUVB) phototherapy decreases COMT activity. However, the effect of psoralen plus ultraviolet A (PUVA) on this enzyme activity is unknown, and it remains to be clarified if the nbUVB-induced effect in COMT activity is related to clinical response. The aim of this study is to evaluate COMT activity in moderate/severe psoriasis and assess whether PUVA therapy modifies this activity.

An observational study was conducted on 18 patients with moderate/severe psoriasis and 13 matched controls. Patients were treated with PUVA twice weekly during 6 weeks, and they were evaluated for Psoriasis Area and Severity Index (PASI) and COMT activity before photochemotherapy, at the end of it and 4 weeks after stopping.

Before PUVA therapy, S(soluble)-COMT activity was significantly (P < 0.05) higher in psoriasis patients than in controls. After photochemotherapy, no significant differences were found in S-COMT activity at all end points. Photochemotherapy significantly decreased PASI but COMT activity values remained higher than those of control population.

Psoriasis patients with moderate/severe disease present higher S-COMT activity than controls. Although a good clinical response was observed, PUVA therapy does not change S-COMT activity. This differential COMT effect of PUVA and nbUVB suggests a wavelength-specific regulation.