الفهرس 
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Abstract
Vitiligo is an idiopathic, acquired, circumscribed, hypomelanotic skin disorder, characterized by milky white patches of different sizes and shapes. It is due to the destruction of melanocytes resulting in the absence of pigment production of the skin and mucosal surfaces. The worldwide incidence of vitiligo is reported to be 0.1–2%.
Vitiligo is a complex multifactorial disease, different mechanisms of pathogenesis had been suggested including genetic, immunological, neural and environmental factors. Neither one mechanism can account for the pathogenesis of the disease, rather interlacement between these different factors in genetically susceptible individuals are proposed as a unifying approach to understand the pathogenesis of the disease. It’s a life-altering disease with a tremendous effect on the patient’s quality of life.
Oxidative stress had been implicated as a major contributor to the vitiligo pathogenesis, as the imbalance between ROS and the antioxidant defense mechanisms were widely observed among the vitiligo patients.
Total oxidant status (TOS) level was considered to be reflecting the global status of oxidative stress in the serum, as it determines the cumulative oxidative effects of various oxidant reagents generated in biological systems.
Human paraoxonase 1 (PON1) is a Ca2+ dependent esterase synthesized in the liver. PON1 is related to high density lipoprotein. PON1 has two main roles: detoxifying organophosphate compounds, such as paraoxon, and protecting low density lipoprotein by hydrolysis of lipid peroxides.Reduced serum PON1 activity has been reported to be associated with some diseases under oxidative stress and inflammation condition. Antioxidants have a protective role in the development of some autoimmune diseases like psoriasis, vitiligo, and alopecia areata.
Our study aimed to evaluate the serum level of PON1 in vitiligo patients and its relation to total oxidant status and disease activity. This study was done on 48 patients with vitiligo, 24 were considered as active cases while the other 24 were non-active cases. The patients recruited from the Outpatient Dermatology Clinic at Ain Shams University Hospitals. The study also included 48 age-and sex-matched healthy adults as a control group. The vitiligo activity and tensity were assessed by VIDA and VETI scores, respectively. The serum TOS and PON1 levels were assessed by using ELISA kits.
We excluded pregnant and lactating women, cases with segmental vitiligo, cases using topical treatment in the past month or using systemic treatment in the past three months prior to enrollment in the study, cases with other dermatological or systemic diseases which may affect PON1 or TOS levels.
Our study revealed a significant increase in serum total oxidant status (TOS) and decrease serum paraoxonase1 (PON1) levels in vitiligo patients compared to controls. We also found a significant negative correlation between oxidative stress levels expressed by TOS levels and the serum PON1 levels. The levels of TOS were significantly elevated in active vitiligo patients compared to the non-active cases, while the PON1 levels were much reduced in active compared to the non-active vitiligo patients.
The paraoxonase (PON) family encompasses powerful antioxidant enzymes and PON 1 is especially noted for its powerful antioxidant capabilities and had been regarded to be deficient in many diseases with oxidative stress pathogenic role. Our observation of the reduced levels of PON1 in vitiligo gives a further evidence for the defective antioxidant mechanisms in vitiligo patients making them more vulnerable to oxidative stress.
We also observed significantly reduced levels of PON1 in active compared to non-active cases of vitiligo and we noticed a significant negative correlation between PON1 and vitiligo activity reflected by VIDA score. This reflects the significant role of oxidative stress in the active progression of vitiligo and the fundamental role of oxidative stress as a leading factor in the pathogenesis of vitiligo.
To summarize, we found that PON1 which is a powerful antioxidant mechanism is defective in vitiligo cases, while the serum TOS levels are significantly elevated. This denotes the imbalance between oxidant/antioxidant compounds in vitiligo patients creating an oxidative stress state. The serum TOS levels are positively correlated to the disease activity, while PON1 levels are negatively correlated. So, we strongly believe that the deficient role of PON1 in vitiligo augments the oxidative stress state in vitiligo cases and this is maximized in patients with active vitiligo. So, supplements with antioxidants may help the vitiligo patients to compete the oxidative metabolites especially in the active progressive disease. This hypothesis has to be confirmed in further studies.