Urinary biomarker of oxidative stress in patients with psoriasis vulgaris and atopic dermatitis

Background The involvement of oxidative stress in the pathogenesis of various skin disorders has been suggested for decades. However, few clinical studies have assessed oxidative stress in skin diseases. The easiest and least invasive method to assess oxidative stress in patients may be the measurement of oxidation products in urine. Objective This study aims to assess oxidative stress in psoriasis and atopic dermatitis patients. Methods Urine samples were collected from 29 psoriasis patients (25 males and 4 females), 21 atopic dermatitis patients (14 males and 7 females) and 20 healthy controls (16 males and 4 females). The severity and extent of psoriasis and atopic dermatitis was assessed by their area and severity index. We measured nitrate as a metabolite of nitric oxide, malondialdehyde as a major lipid oxidation product, and 8-hydroxydeoxyguanosine (8-OHdG) as a DNA oxidation marker. Results Urinary nitrate and 8-OHdG levels, but not malondialdehyde, were significantly higher in psoriasis patients than those in healthy controls. On the contrary, only urinary nitrate level was significantly higher in atopic dermatitis patients than those in healthy controls. The severity and extent of both psoriasis and atopic dermatitis significantly correlated with urinary nitrate level and malondialdehyde level, but it did not correlate with urinary 8-OHdG level. Conclusions Measurement of these three urinary oxidative products is non-invasive. Above all, measurement of urinary nitrate may be most useful in the clinical assessment of oxidative stress in both psoriasis and atopic dermatitis patients. There is a possibility that urinary 8-OHdG level may indicate the different pathogenesis between psoriasis and atopic dermatitis.