Immunohistochemical expression of AQP-3 in vitiligo: a new potential guide for disease activity

Is vitiligo associated with systemic aquaporin-3 deficiency?

Introduction

Recent studies on pathomechanisms of vitiligo have focused on the abnormality of keratinocytes that affect the melanocytes. Aquaporin-3 (AQP3) was implicated as a mechanism for keratinocyte apoptosis owing to the relationship between the PI3K/AKT pathway and the E-cadherin-catenin complex.

Aim

Based on this evidence, we undertook a cross-sectional study to assess the skin and blood AQP-3 levels in patients with non-segmental vitiligo in comparison to controls and to correlate these levels with malondialdehyde (MDA) levels and total antioxidant status (TAS) in the skin and blood of patients with non-segmental vitiligo and also with their disease activity.

Material and methods

Thirty-six patients with non-segmental vitiligo and 36 controls were included in this study. AQP3, TAS and MDA levels were assayed both in skin as well as in circulation.

Results

We observed that skin and plasma aquaporin and TAS were lowered and MDA levels were increased in patients with non-segmental vitiligo as compared to controls. There was a significant negative correlation of skin and plasma aquaporin levels with disease activity. We also observed the local and systemic AQP3 deficiency to correlate with the local and systemic oxidative stress in vitiligo.

Conclusions

Our results demonstrate a systemic and local AQP3 deficiency in vitiligo correlating with the disease severity and oxidative stress which might have therapeutic implications.

Indirect Proton MR Imaging and Kinetic Analysis of 17O-Labeled Water Tracer in the Brain

Purpose:

The feasibility of steady-state sequences for ¹⁷O imaging was evaluated based on a kinetic analysis of the brain parenchyma and cerebrospinal fluid (CSF).

Materials and Methods:

The institutional review board approved this prospective study with written informed consent. Dynamic 2D or 3D steady-state sequences were performed in five and nine participants, respectively, with different parameters using a 3T scanner. During two consecutive dynamic scans, saline was intravenously administered for control purposes in the first scan, and 20% ¹⁷O-labeled water (1 mL/Kg) was administered in the second scan. Signal changes relative to the baseline were calculated, and kinetic analyses of the curves were conducted for all voxels. Region of interest analysis was performed in the brain parenchyma, choroid plexus, and CSF spaces.

Results:

Average signal drops were significantly larger in the ¹⁷O group than in the controls for most of the imaging parameters. Different kinetic parameters were observed between the brain parenchyma and CSF spaces. Average and maximum signal drops were significantly larger in the CSF spaces and choroid plexus than in the brain parenchyma. Bolus arrival, time to peak, and the first moment of dynamic curves of ¹⁷O in the CSF space were delayed compared to that in the brain parenchyma. Significant differences between the ventricle and subarachnoid space were also noted.

Conclusion:

Steady-state sequences are feasible for indirect ¹⁷O imaging with reasonable temporal resolution; this result is potentially important for the analysis of water kinetics and aquaporin function for several disorders.

Aquaporin 3 and E-Cadherin Expression in Perilesional Vitiligo Skin

INTRODUCTION

Vitiligo is a common dermatologic disorder with debated aetiology. Most studies focused on role of melanocytes and few investigated the role of keratinocytes in pathogenesis of the disease.

AIM

To investigate the keratinocyte adhesion in perilesional vitiligo skin through the immunolocalization of Aquaporin-3 (AQP3) and E-cadherin.

SETTING AND DESIGN

Sixty five subjects were selected. These included 40 cases with vitiligo and 25 age and gender-matched healthy subjects as a control group.

MATERIALS AND METHODS

Skin biopsies were taken from perilesional skin of cases and from site-matched areas of control subjects. The expression of AQP3 and E-cadherin was evaluated by immunohistochemical techniques.

STATISTICAL ANALYSIS

Results were statistically analysed using IBM personal computer and the statistical package SPSS version 11. Fisher-exact and Chi-square tests were used to study the association between two qualitative variables. Mann-Whitney test was used for comparison between quantitative variables not normally distributed. Spearman's correlation coefficient was used to assess correlation between two quantitative variables. The p≤0.05 was considered significant.

RESULTS

Regarding AQP3 expression, strong intensity, diffuse distribution, higher percent of expression and higher H-score (p<0.001 for all) were significantly associated with control skin compared with perilesional skin in follicular and inter-follicular epidermis. Regarding E-cadherin expression, moderate intensity, higher percent of expression and higher H- score (p<0.001 for all) were significantly associated with control skin compared with perilesional skin in follicular and inter-follicular epidermis. No significant association was found between E-cadherin and AQP3 H-scores or percent of expression and clinical data of selected cases. No significant correlation was detected between E-cadherin and AQP3 H-scores or percent of expression and age of cases, disease duration or Vitiligo Disease Activity (VIDA) score.

CONCLUSION

The following sequence of events can be suggested for vitiligo pathogenesis, based on findings in perilesional skin: AQP3 is downregulated by a primary unknown factor and this will lead to down regulation of its downstream molecules, mainly phosphatidylinositol 3-kinase, E-cadherin and catenins, which is followed by defective keratinocyte adhesion and decreased release of keratinocyte-derived growth factors. Subsequently a secondary event, physical trauma, oxidative stress or autoantibodies, may lead to exfoliation of keratinocytes and pigmented cells.