An important role of α-hemolysin in extracellular vesicles on the development of atopic dermatitis induced by Staphylococcus aureus.

Sung-Wook Hong,Young-Koo Jee,Taek-Ki Min,Bok-Yang Pyun,Byung-Jae Lee,Yong Song Gho,Seong Gyu Jeon,Min-Hye Kim,Eun-Byul Choi,Yoon-Keun Kim,Ji-Hyun Kim,Malcolm James Horsburgh

doi:10.1371/journal.pone.0100499

Abstract

Skin barrier disruption and dermal inflammation are key phenotypes of atopic dermatitis (AD). Staphylococcus aureus secretes extracellular vesicles (EVs), which are involved in AD pathogenesis. Here, we evaluated the role of EVs-associated α-hemolysin derived from S. aureus in AD pathogenesis. α-hemolysin production from S. aureus was detected using western blot analyses. The cytotoxic activity of α-hemolysin on HaCaT keratinocytes was evaluated by measuring cell viability after treating cells with soluble and EVs-associated α-hemolysin. To determine the type of cell death, HaCaT keratinocytes were stained with annexin V and 7-AAD. The in vivo effects of α-hemolysin were evaluated by application of soluble and EV-associated α-hemolysin on the mouse skin. The present study showed that increased α-hemolysin was produced by S. aureus colonized on AD patients compared to healthy subjects. α-hemolysin production was also related to AD severity. In addition, EV-associated α-hemolysin was more cytotoxic to HaCaT keratinocytes than soluble α-hemolysin, and α-hemolysin-negative EVs did not induce keratinocyte death. EV-associated α-hemolysin induced necrosis, but soluble α-hemolysin induced apoptosis of keratinocytes. In vivo, skin barrier disruption and epidermal hyperplasia were induced by soluble and EV-associated α-hemolysin. However, AD-like dermal inflammation was only caused by EV-associated α-hemolysin. Moreover, neither skin barrier disruption nor AD-like skin inflammation was induced by α-hemolysin-negative EVs. Taken together, α-Hemolysin secreted from S. aureus, particularly the EV-associated form, induces both skin barrier disruption and AD-like skin inflammation, suggesting that EV-associated α-hemolysin is a novel diagnostic and therapeutic target for the control of AD.

Highlights

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is characterized by eczematous lesions with pruritus and xerosis [1]
When a-hemolysin production was measured in S. aureus culture media from 90 AD patients, 91% of S. aureus from AD patients were positive for ahemolysin compared to 33% of healthy controls (Fig. 1, B and Table 1)
In terms of a-hemolysin production according to AD severity, a-hemolysin production was significantly higher from S. aureus from the severe group compared to S. aureus from the mild and moderate groups (Fig. 1, C and Table 1)

Summary

Introduction

Atopic dermatitis (AD) is a chronic inflammatory skin disease that is characterized by eczematous lesions with pruritus and xerosis [1]. Abnormal skin barrier function induced by the death of keratinocytes is one of the major causes in the etiology of AD [2,3,4]. Skin lesions of AD patients show increased keratinocyte cell death induced by immunologic mediators [5,6,7]. S. aureus is closely related to AD because it colonizes the skin lesions of most AD patients and augments disease severity [9,10]. S. aureus produces staphylococcal enterotoxins that can induce excessive T-cell responses, as well as hemolysins, that cause cell death by forming heptameric membrane pores [8,11]. It has been reported that a-hemolysin can target keratinocytes and is related to AD disease severity [14,15]

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