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 Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 35  |  Issue : 1  |  Page : 54-59

Evaluation of serum interleukin-33 in nonsegmental vitiligo


1 Department of Dermatology and Andrology, Benha Faculty of medicine, Benha University, Benha, Egypt
2 Department of Clinical and Chemical Pathology, Benha Faculty of medicine, Benha University, Benha, Egypt
3 Department of Dermatology & Andrology, Basrah Faculty of Medicine, Basrah University, Basrah, Iraq

Date of Submission19-Mar-2017
Date of Acceptance04-May-2017
Date of Web Publication28-Feb-2018

Correspondence Address:
Alaa S Khudhair
Basrah Faculty of Medicine, Basrah University, Basrah, 13511
Iraq
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/bmfj.bmfj_59_17

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  Abstract 


Background Vitiligo is a common, acquired pigmentary disorder of unknown etiology, affecting up to 0.1–2% of the population worldwide. It is characterized by white macules and patches. Loss of melanocytes in vitiligo appears to occur through a combination of several mechanisms that act in concert. Interleukin (IL)-33 is a recently discovered cytokine and one of the newest members that belongs to the IL-1 superfamily of inflammatory cytokines, and is mainly expressed by different types of structural cells. IL-33 is considered an alarmin because of its release after necrosis or tissue damage.
Objective The aims of the present study were to evaluate serum levels of IL-33 in nonsegmental vitiligo patients and to examine its relationship with disease severity and vitiligo type.
Patients and methods This was a case–control study that included 40 vitiligo patients (group A) and 40 apparently healthy individuals as controls (group B), who were matched for age and sex, at the Dermatology and Andrology Clinic, Benha University Hospital. All participants were subjected to the following: detailed history taking, assessment of the rule of nine score and the Vitiligo Disease Activity score measuring the activity of vitiligo, tests to determine the distribution and morphology of the lesions, complete dermatological examination, and laboratory investigations including assessment of IL-33 using commercial enzyme-linked immunosorbent assay kits.
Results The majority of our sample included females. Serum IL-33 levels were significantly higher in patients affected by vitiligo as compared with controls. There was no statistically significant difference in serum levels of IL-33 among different types of vitiligo. There was no significant correlation between serum IL-33 levels and severity of vitiligo. A statistically significant negative correlation was found between serum levels of IL-33 and duration of vitiligo, and a statistically significant difference was found in serum levels of IL-33 between stable (negative) type and progressive vitiligo.
Conclusion Serum IL-33 levels in patients with vitiligo were significantly increased compared with controls. There was a positive correlation between serum IL-33 levels and disease activity, but there was no correlation with the clinical type of vitiligo. This explains a possible systemic role of IL-33 in the pathogenesis of vitiligo, and IL-33 serves as an alarmin in inducing melanocyte death in vitiligo skin. Inhibiting IL-33 activity might be a novel therapeutic strategy in the treatment of autoimmune inflammatory diseases such as vitiligo.

Keywords: autoimmune inflammatory disease, cytokine, interleukin-33, vitiligo


How to cite this article:
Ebrahim AA, Hamed AM, Ahmed ES, Khudhair AS. Evaluation of serum interleukin-33 in nonsegmental vitiligo. Benha Med J 2018;35:54-9

How to cite this URL:
Ebrahim AA, Hamed AM, Ahmed ES, Khudhair AS. Evaluation of serum interleukin-33 in nonsegmental vitiligo. Benha Med J [serial online] 2018 [cited 2018 Jul 22];35:54-9. Available from: http://www.bmfj.eg.net/text.asp?2018/35/1/54/226421




  Introduction Top


Vitiligo is defined as a specific, common, acquired dermatological disorder characterized by the presence of irregularly shaped, milky-white cutaneous macules and patches due to destruction or disappearance of melanocytes. About 0.1–2% of the world’s population is affected by this disease. It usually begins in childhood or adolescence, but it may occur at any age. Both sexes are equally affected. Multiple pathogenetic factors have been proposed to clarify the etiology of vitiligo, including the neural theory, genetic predisposition, and impaired antioxidative defense [1].

Loss of melanocytes in vitiligo appears to occur through a combination of several mechanisms that act in concert. Apoptotic death has been suggested in vitiligo. Cytokines such as interleukin (IL)-1, interferon γ, and tumor necrosis factor-α (TNF-α) are paracrine inhibitors of melanocytes and can initiate apoptosis [2].

IL-33 is a cytokine of the IL-1 family, which has been demonstrated to induce cytokine synthesis and mediate inflammatory responses through its receptor (also known as IL-1RL1 and ST2) [3].

IL-33 is expressed by fibroblasts, epithelial cells, endothelial cells, and activated macrophages [4].

IL-33 can be classified as an alarmin because it is released into the extracellular space following cell damage or tissue injury and acts as an endogenous danger signal by sending out warning signals to alert neighboring cells and tissues [5].

Mitsui et al. [6] investigated serum levels of IL-33 in psoriasis vulgaris, psoriatic arthritis, and pustular psoriasis, suggesting that serum IL-33 levels generally reflect increased inflammation in patients with psoriasis.

Savinko et al. [7] suggested that IL-33 expression increases in skin affected by atopic dermatitis compared with healthy skin.

Keratinocytes in vitiligo tend to undergo apoptosis. Therefore, Li et al. [8] suggested that IL-33 released by keratinocytes might play a role in the induction and augmentation of vitiligo. The aims of the present study were to evaluate serum levels of IL-33 in nonsegmental vitiligo patients and to examine the relationship with disease severity and vitiligo type.


  Patients and methods Top


Studied groups

All patients were selected from the Outpatients Clinic of Dermatology and the Andrology Clinic, Benha University Hospital. This was a case–control study including 40 vitiligo patients (group A) diagnosed clinically and 40 apparently healthy individuals who served as a control (group B) matched for age and sex

Inclusion criteria

  1. Patients with nonsegmental vitiligo.
  2. Patients not taking any treatment for vitiligo for at least 1 month.


Exclusion criteria

  1. Any skin disease other than vitiligo.
  2. Haemolyzed samples were discarded.
  3. Segmental vitiligo.



  Methods Top


All participants were subjected to the following:
  1. Full history taking including the following:
    1. Personal history: name, age, sex, residence, occupation, and special habits such as smoking.
    2. History of present illness: onset, course, duration of the disease, and precipitating factors such as psychic stress and trauma.
    3. Drug history: type and date of last treatment.
    4. Family history of vitiligo.
  2. General medical examination:
    • To detect signs of other systemic diseases and the presence of any exclusion criteria, a general medical examination was carried out.
  3. Local dermatological examination:
    • Patients were carefully examined for site, size, distribution, and clinical type of vitiligo. Extent and severity of vitiligo were evaluated according to the rule of nine and Vitiligo Disease Activity scores.
  4. Serological evaluation: 3-ml venous blood samples were collected under aseptic conditions. Samples were left at room temperature for 20 min for coagulation and then centrifuged for 10 min at 1300 rpm. Serum was separated from blood and subdivided in two aliquots and freezed at −40°C until analyses. IL-33 was measured using a double-antibody sandwich enzyme-linked immunosorbent assay.


Statistical analysis

Statistical presentation and analysis of the present study were carried out using mean values and their SDs as well as the χ2-test using SPSS V.20 (IBM Corporation, Chicago, USA). The accepted level of significance 0.05 (P<0.05 was considered significant). P-value less than or equal to 0.001 was considered highly significant. P-value more than 0.05 was considered nonsignificant.


  Results Top


[Table 1] shows that the mean age of patients in group A was 34.85±12.68 years, with a range of 16–60 years, whereas in group B the mean age was 36.25±9.94 years with a range of 20–55 years. The difference between the two groups was not significant.
Table 1 Comparison between patients and controls according to age

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[Table 2] shows that group A included 62.5% females and 37.5% males. Group B: 19 Females (47.5%), 21 males (52.5%). The total number being 40. No statistically significant difference between the two groups regarding sex was found.
Table 2 Comparison between patients and controls according to sex

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[Table 3] shows that the duration of vitiligo ranged from 0.5 to 12 years, with a mean of 4.34±2.90; the mean extent of involved body surface area (BSA) was 11.73±6.57% (range 2–26%).
Table 3 Clinical data of the studied patients

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[Table 4] shows that 47.5% of our patients had vitiligo vulgaris, 40% had the acrofacial type, and only 12.5% had the focal type.
Table 4 Distribution of the patient group according to the clinical types of vitiligo

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[Table 5] shows that 22.5% of our patients had a stable (inactive) course, whereas77.5% had the progressive (active) type − patients reported either worsening of already existing lesions or development of new lesions.
Table 5 Distribution of the patient group according to activity of disease

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[Table 6] shows that serum IL-33 levels were statistically significant in patients affected by vitiligo compared with controls (group A, mean=32.79±18.99 ng/ml and group B, mean=22.25±6.29 ng/ml) (P<0.001).
Table 6 Comparison between patients and controls according to serum levels of interleukin-33

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[Table 7] shows that no statistically significant correlation existed between serum levels of IL-33 and different types of vitiligo (P=0.340).
Table 7 Relationship between serum levels of interleukin-33 and clinical type of vitiligo

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[Table 8] shows that there is no significant correlation between serum IL-33 levels and extent of vitiligo; the mean BSA was 11.73±6.57 with a range of 2–26 (P=0.469).
Table 8 Correlation between interleukin-33 and BSA

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[Table 9] shows a statistically significant negative correlation between serum levels of IL-33 and duration of vitiligo (r=−0.401, P=0.011).
Table 9 Correlation between interleukin-33 and duration of vitiligo

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[Table 10] shows a statistically significant difference in serum levels of IL-33 between stable (negative) type and progressive type vitiligo (P=0.001).
Table 10 Correlation between interleukin-33 and vitiligo activity

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No significant correlations were found between sex, age, family history, smoking status, precipitated factors, and serum IL-33 levels.


  Discussion Top


Vitiligo is an acquired pigmentary disorder of unknown etiology, affecting ∼0.1–2% of the world’s population, without predilection for race or sex. It is characterized by white macules and patches, whose size increases over time, due to the loss of melanocytes. Vitiligo can appear at any time, and it significantly impairs patients’ quality-of-life [9].

Multiple pathogenetic factors have been proposed to clarify the etiology of vitiligo, including the neural theory, genetic predisposition, and impaired antioxidative defense [1].

In fact, growth factors produced by adjacent keratinocytes regulate the proliferation and differentiation of melanocytes [10].

The mechanism of melanocyte loss in vitiligo is possibly related to keratinocyte-derived cytokines that stimulate melanocytes such as basic fibroblast growth factor (bFGF) and stem cell factor (SCF) or to those that inhibit melanocytes such as IL-6 and TNF-α. SCF is an essential factor for melanocyte survival [8]. IL-33 is a new cytokine that belongs to the IL-1 family, and it is released in the extracellular space after cell necrosis or mechanical injury. Several immune cell types such as macrophages and dendritic cells express IL-33, as well as nonimmune cells such as endothelial cells, epithelial cells, and fibroblasts. It has been described as an alarmin, because IL-33 alerts the immune system of tissue damage (necrosis, trauma, and infection) [11] Recent studies have shown that IL-33 is secreted by psoriatic keratinocytes, and its expression level is raised in psoriatic lesions compared with healthy skin [6].

Given that keratinocytes express IL-33 in some skin diseases and that keratinocytes in vitiligo tend to undergo apoptosis, it has been suggested that IL-33 released by keratinocytes might play a role in the induction and augmentation of vitiligo [8].

The aim of this study was to assess the levels of IL-33 in patients with vitiligo. The study also aimed to determine whether there is a relationship between IL-33 levels and clinical type of vitiligo and activity of disease.

The present study demonstrated a predominance of females (62, 5%) over males (37.5%). This was in accordance with Jha [12], who found that the incidence of vitiligo was higher in females, and this may be attributed to the fact that females are more concerned by the disease and its distressing appearance than males, leading to an increased and earlier presentation of females to dermatology clinics. In addition, autoimmune diseases are more common in females [13].

With respect to age, there was no statistically significant difference between patient and control groups. These data reinforce that vitiligo is a disease that can occur at any age. This was in accordance with Sinani et al. [14], who reported no significant difference in age of onset between the two sexes.

Regarding the clinical distribution of the disease, vitiligo vulgaris was the most common (47.5%); this result is in agreement with Karadag et al. [15] and Dash et al. [16] who suggested that vitiligo vulgaris was the most common type.

According to the Vitiligo Disease Activity score (six-point scale), 22.5% patients had a stable course, whereas 77.5% patients had a progressive course. The course of vitiligo is often unpredictable. The natural course of the disease involved slow progression, but it may stabilize or exacerbate rapidly. Vitiligo spreads either by appearance of new depigmented macules or by centrifugal enlargement of pre-existing lesions or both [17].

According to the rule of nine scoring system, the mean values for BSA affected were 11.73±6.57 (range 2–26). This finding in contrast with the study of Shaker and El‐Tahlawi [18], who found that the mean values for BSA affected were 43.80±16.09, whereas Hartmann et al. [19] suggested that the mean percentage of depigmented skin area was 30.8±25.2%. There is no standardized method for measuring vitiligo lesions, and the lack of standardization is responsible for the high variability in vitiligo assessment. Therefore the rule of nine, VASI, and Wood’s lamp are likely the best available methods for assessing the degree of pigmentary lesions and measuring the extent and progression of vitiligo in the clinic and in clinical trials [20].

In the present study, serum IL-33 concentrations were statistically higher in patients with vitiligo than in controls. This finding was supported by Li et al. [8], who showed for the first time that IL-33 and ST2 expressions are increased in the skin, and they found that IL-33 is secreted by keratinocytes and is transferred from the nucleus to the cytoplasm in keratinocytes in patients with vitiligo and functions as an alarmin. It may induce melanocyte death by regulating cytokines in the cellular microenvironment.

This is in agreement with the study by Mitsui et al. [6], who showed increased serum IL-33 levels in patients with psoriasis. In addition, these results are also in agreement with the study by Tamagawa-Mineoka et al. [21], who found increased serum IL-33 levels in patients with Th-2-mediated atopic dermatitis.

Another study showed that serum IL-33 levels were greatly increased in patients with rheumatoid arthritis (RA), in both serum and synovial fluid, and IL-33 levels were higher than in those with osteoarthritis, probably due to the increased IL-33 release from human fibroblasts into the synovial fluid in patients with RA [22]. This shows that in all these autoimmune diseases increased levels of IL-33 are secreted by keratinocytes after tissue damage of ST2-expressing cells such as Th2 cells, mast cells, DCs, and eosinophils, and that IL-33 plays an important role mainly in Th2-driven diseases such as atopic dermatitis or Th1/Th17-driven autoimmune diseases such as psoriasis, RA and inflammatory bowel syndrome (IBD).

Regarding the clinical type of the disease, no significant difference was found in serum IL-33 levels in either types of vulgaris, acrofacial and focal types of vitiligo (P=0.340). This suggests that the clinical type of the disease has no influence on serum IL-33 levels.

In the present study, there was no statistically significant correlation between serum levels of IL-33 and extent of vitiligo (P=0.469). This finding is in contrast with the study by Vaccaro et al. [23], who reported a significant positive correlation between serum IL-33 levels and extent of vitiligo (P=0.05). This can be explained by the fact that all patients in their study reported worsening of already existent as well as the development of new lesions during the previous 3 months.

In the present study, a statistically significant negative correlation was found between serum IL-33 levels and disease duration (r=−0.401, P=0.011), adding more evidence to the importance of IL-33 in disease activity. This finding is in contrast with the study by El-Taweel et al. [24], who suggested that there is no significant correlation between serum IL-33 levels in both moderate and severe cases of psoriasis and duration of disease. This can explain the fact that some of our patients reported long durations of vitiligo with a stable course.

In the present study, there was a positive correlation between activity of vitiligo and IL-33 levels (P=0.001). This finding suggests that IL-33 is involved in the occurrence and development of vitiligo. This finding is in agreement with the study of Li et al. [8], who found that IL-33 may bind ST2 receptors on keratinocytes and stimulate TNF-α production. TNF-α is a paracrine inhibitor of melanocytes, resulting in the loss of pigmentation or loss of melanocytes, and its promoter polymorphisms correlate with disease progression; moreover, TNF-α stimulates IL-33 secretion, which subsequently stimulates TNF-α expression in an autocrine manner, and IL-33 serves as an alarmin in inducing melanocyte death in vitiligo skin. Such positive-feedback loops may be involved in the pathogenesis of vitiligo. Mitsui et al. [6] also studied psoriatic patients and suggested that serum IL-33 levels correlate with activity of disease through the interaction of IL-33 with serum levels of TNF-α, IL-6, vascular endothelial growth factor, and C-reactive protein. In addition, serum IL-33 levels were decreased by anti-TNF-α agents. In the study by Xu et al. [22], which was carried out on patients with RA, serum IL-33 levels correlated with disease severity in RA. The study by Pastorelli et al. [25] on patients with inflammatory bowel disease reported a positive correlation between activity of IBD and IL-33 levels. The study by Tamagawa-Mineoka et al. [21] found that IL-33 levels are correlated with severity of AD, IL-33 released from damaged skin may increase inflammation in AD, and that IL-33 may be a useful marker for monitoring the outcome of drug therapy for AD.


  Conclusion Top


Serum IL-33 levels in patients with vitiligo were significantly increased compared with healthy controls. There was a positive correlation between serum IL-33 levels with disease activity. IL-33 could be considered a reliable marker for increasing disease severity. This explains a possible systemic role of IL-33 in the pathogenesis of vitiligo, and IL-33 serves as an alarmin in inducing melanocyte death in vitiligo skin. Inhibiting IL-33 activity might be a novel therapeutic strategy in the treatment of autoimmune inflammatory disease such as vitiligo. These results might therefore partly explain the mechanism for TNF-α inhibitor efficacy in patients with vitiligo.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]



 

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