Abstract
ABSTRACTObjectives: 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.
Highlights
IntroductionHypothyroidism has a significant effect on many organs [1,2,3,4,5] and could lead to an increased level of oxidative stress (OS) [1,6,7,8,9,10]
Hypothyroidism has a significant effect on many organs [1,2,3,4,5] and could lead to an increased level of oxidative stress (OS) [1,6,7,8,9,10].It was published in a rodent model that the body mass, the mass of organs and their total protein content were significantly lowered in hypothyroid state than euthyroid one
In the hypothyroid state, was found a slight decrease in the activity of xanthine oxidase (XO) and MTT-formazan formation in the skin, whereas solar-simulated ultraviolet radiation (SSUV) exposure in euthyroid rats increased the content of UA and MTT-formazan, compared to the control group (C)
Summary
Hypothyroidism has a significant effect on many organs [1,2,3,4,5] and could lead to an increased level of oxidative stress (OS) [1,6,7,8,9,10]. It was published in a rodent model that the body mass, the mass of organs and their total protein content were significantly lowered in hypothyroid state than euthyroid one. The progression of subclinical to overt hypothyroidism is characterized by significantly decreased nitrite and nitrate levels, these allowing the use of serum nitric oxide (NO) level as an indicator for introduction and dosage of levothyroxine replacement therapy in patients with subclinical hypothyroidism [2]
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