Does hypothyroidism augment sun-induced skin damage?

• Published in: Redox report : communications in free radical research Vol. 23; no. 1; pp. 180 - 187
• Main Authors: Bocheva, Georgeta, Valcheva-Traykova, Maria, Landzhov, Boycho
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 01.01.2018; Taylor & Francis Group
• Subjects: Animals; Chronic sun exposure; Free Radicals - metabolism; hypothyroidism; Hypothyroidism - complications; lipid peroxidation; Male; NADP - metabolism; oxidative skin damage; oxidative stress; Rats; Rats, Wistar; skin; Skin - metabolism; Skin - pathology; Skin - radiation effects; SSUV; Sunlight - adverse effects; xanthine oxidase in the skin; Chronic sun exposure; hypothyroidism; xanthine oxidase in the skin; SSUV; skin; oxidative skin damage; lipid peroxidation; oxidative stress
• ISSN: 1351-0002; 1743-2928
• DOI: 10.1080/13510002.2018.1494421

Objectives: We investigated the mutual effects of overt hypothyroidism and prolonged sunlight exposure on free radical accumulation and oxidative skin damage. Methods: Free radical accumulation was evaluated by monitoring the transformation of 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) into MTT-formazan. The pro-oxidant enzymes xanthine oxidase (XO) and NADPH-diaphorase were measured in the skin. XO activity was estimated based on the yield of uric acid, while NADPH-diaphorase reactivity was monitored histochemically as an indirect marker of nitric oxide synthase and nitric oxide activity. Cellular damage was determined by malondialdehyde formation, a marker for lipid peroxidation. Results: In the skin of both euthyroid and hypothyroid animals, solar simulated ultraviolet irradiance increased the activity of XO and the NADPHdiaphorase reactivity as a protective response to formation of free radicals, such as reactive oxygen or nitrogen species. These pro-oxidant enzymes diminished in hypothyroid rats. Accumulation of the same amount of free radicals led to similar peroxidation in both hypothyroid and irradiated euthyroid rats. Hypothyroid skin after UV-exposure showed even greater lipid peroxidation. Discussion: The hypothyroid state could be a risk factor for enhanced oxidative skin damage in chronic photo-exposed skin due to oxidative stress. The lipid peroxidation is one of the major pathways by which photo-oxidative stress promotes photocarcinogenesis and photo-aging.