Conditional knock out of N-WASP in keratinocytes causes skin barrier defects and atopic dermatitis-like inflammation

Pazhanichamy Kalailingam,Jeremy Soon Kiat Chan,Thirumaran Thanabalu,Hui Bing Tan,Ming Keat Sng,Neeraj Jain,Nguan Soon Tan

doi:10.1038/s41598-017-07125-8

Abstract

Neural-Wiskott Aldrich Syndrome Protein (N-WASP) is expressed ubiquitously and regulates actin cytoskeleton remodeling. In order to characterize the role of N-WASP in epidermal homeostasis and cutaneous biology, we generated conditional N-WASP knockout mouse using CK14-cre (cytokeratin 14) to ablate expression of N-WASP in keratinocytes. N-WASPK14KO (N-WASPfl/fl; CK14-Cre) mice were born following Mendelian genetics suggesting that N-WASP expression in keratinocytes is not essential during embryogenesis. N-WASPK14KO mice exhibited stunted growth, alopecia, dry and wrinkled skin. The dry skin in N-WASPK14KO mice is probably due to increased transepidermal water loss (TEWL) caused by barrier function defects as revealed by dye penetration assay. N-WASPK14KO mice developed spontaneous inflammation in the neck and face 10 weeks after birth. Histological staining revealed thickening of the epidermis, abnormal cornified layer and extensive infiltration of immune cells (mast cells, eosinophils and T-lymphocytes) in N-WASPK14KO mice skin compared to control mice. N-WASPK14KO mice had higher serum levels of IL-1α, TNF-α, IL-6 and IL-17 compared to control mice. Thus our results suggest that conditional N-WASP knockout in keratinocytes leads to compromised skin barrier, higher infiltration of immune cells and hyperproliferation of keratinocytes due to increased production of cytokines highlighting the importance of N-WASP in maintaining the skin homeostasis.

Highlights

Actin cytoskeleton remodeling and actin polymerization play critical roles in cell motility, cell growth, phagocytosis, cell polarity and other physiological processes[1]
These results suggest that Neural-Wiskott Aldrich Syndrome Protein (N-WASP) knockout is highly specific to epidermal keratinocytes
Monocytes and macrophages stimulate the secretion of keratinocyte chemoattractants (KC, IL-8) in skin lesions which function as chemoattractants for neutrophil accumulation[42]. These results suggest that IL-1α and TNF-α are the proinflammatory cytokines increased in cutaneous inflammation in N-WASPK14KO mice which subsequently activate immune cells to produce IL-6, IL-17 and chemokines (G-CSF, Eotaxin and KC) leading to a systemic immune response against skin lesion

Summary

Introduction

Actin cytoskeleton remodeling and actin polymerization play critical roles in cell motility, cell growth, phagocytosis, cell polarity and other physiological processes[1]. N-WASP plays a critical role in the maintenance of the epithelial junctional actin cytoskeleton through a non-canonical post-nucleation pathway[18]. A defective skin barrier leads to excessive water loss and allows pathogens or allergens to penetrate into the epidermis, causing the subsequent dysregulated release of proinflammatory cytokines and chemokines[25]. Both Th-1 and Th-2 cell responses are critical for the pathogenesis of atopic dermatitis as they produce cytokines which regulate the inflammatory response in AD26. The N-WASPK14KO mice displayed many characteristics of atopic dermatitis, including compromised skin barrier, abnormal cornification and spontaneous inflammation around the face and neck associated with increased infiltration of immune cells and hair loss. Our results suggest that N-WASP plays a critical in post-natal skin homeostasis

Methods

Results

Conclusion