The Relationship between Tissue Thioredoxin Reductase Activity and the Psoriasis Area and Severity Index

Psoriasis is an autoimmune disease. The important role of oxidative stress in the pathogenesis of psoriasis had been investigated in different studies. Thioredoxin reductase (TrxR) is a selenocysteine-containing enzyme which is involved in the protection of cells against oxidative stress. Here, we investigated the TrxR activity in skin lesions of psoriatic patients and the possible correlation between this activity and the severity of the disease that was scored based on the Psoriasis Area and Severity Index (PASI).TrxR activity was determined using TrxR colorimetric method based on the reduction of 5,5'-dithiobis-(2-nitrobenzoic acid) to 5-thio-2-nitrobenzoic acid by TrxR using nicotinamide adenine dinucleotide phosphate in 20 psoriatic patients (11 men and 9 women) aged 38.9 ± 12.6 years. For evaluating the disease severity, PASI score system (mild [PASI <10], moderate [PASI 10-20], or severe [PASI >20]) was utilized that was based on three factors including thickness, erythema, and scaling of lesions.Our results revealed that the TrxR activity between different groups of psoriatic patients (according to the PASI score) was statistically significant and it was higher in psoriatic patients with mild disease (correlation coefficient = -0.85).These results further strengthen the association between psoriasis and oxidative stress. The increased level of TrxR could be due to the protective effect of this enzyme against the inflammatory process and oxidative stress. Moreover, TrxR could be used as a novel marker for evaluating psoriasis severity.