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Eur J Dermatol. 2013 Jan-Feb;23(1):49-52. doi: 10.1684/ejd.2012.1912.

Catechol-O-methyltransferase activity is higher in psoriasis patients and is down-regulated by narrowband ultraviolet B treatment.

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Department of Pharmacology, Therapeutics, University of Porto Porto, Portugal.



Narrowband ultraviolet B (nbUVB) phototherapy is widely used in psoriasis treatment. UVB irradiation decreases catechol-O-methyltransferase (COMT) activity in human keratinocytes and melanoma cells. COMT activity is higher in psoriatic lesions than in normal skin but the effect of nbUVB on COMT activity in psoriasis patients is unknown.


To evaluate COMT activity in patients with psoriasis and determine whether nbUVB modifies this activity.


An open observational study was conducted with 20 psoriasis patients and 15 healthy volunteers. Patients were treated with nbUVB thrice weekly during six weeks and evaluated at baseline, three and six weeks after phototherapy and four weeks after stopping. In each evaluation body mass index (BMI), Psoriasis Area and Severity Index (PASI) and Dermatology Life Quality Index (DLQI) were calculated and blood samples for erythrocytes soluble (S-) COMT activity assessment were taken.


Before phototherapy (baseline), using a single concentration of substrate adreneline (1,000 μM), S-COMT activity levels (pmol/mg protein/h) were significantly higher in psoriasis patients than in controls. After nbUVB treatment, S-COMT activity significantly decreased. This decrease correlated positively with baseline activity. Four weeks after stopping phototherapy, S-COMT activity returned to baseline levels. After phototherapy, PASI score improved significantly but no correlation to baseline S-COMT values or decrease in S-COMT activity was found.


This study shows that baseline S-COMT activity is higher in psoriasis patients than in controls and that this activity is significantly decreased by nbUVB treatment for psoriasis. This decrease is more evident in patients with higher baseline S-COMT activity.


Narrowband ultraviolet B; catechol-O-methyltransferase (COMT); psoriasis

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