An Important Role of α-Hemolysin in Extracellular Vesicles on the Development of Atopic Dermatitis Induced by Staphylococcus aureus

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.

Staphylococcus aureus impairs the airway epithelial barrier in vitro

“…Our data shows that the 13565, 14458, and 25923 strains carry several hemolysin genes and enterotoxin A (13565) or enterotoxin B (14458) genes. Strain 14458, a known enterotoxin B and hemolysin A–producing reference strain, and strain 25923, a biofilm‐forming reference strain, showed no effects significantly different to controls. The 13565 strain that severely compromised the TJ structure in our study is known to produce enterotoxin A and hemolysin B .…”

The Role of the Skin Microbiome in Atopic Dermatitis

“…It has been proposed that Th2 cytokines can also increase α-toxin-induced keratinocyte toxicity [62]. Murine models with subcutaneous injections of α-toxin display increased inflammation at the site of injection [63]. Although high concentrations of α-toxin are toxic to host cells, low concentration can also stimulate keratinocyte cytokine production leading to increased inflammation as well [64].…”

“…S. epidermidis has also been shown in both murine and keratinocyte models to have a protective role through the amplification of endogenous AMPs [80,81]. Finally, there is evidence that S. epidermidis can prevent S. aureus biofilm formation in the nasal cavities as well as produce its own AMPs to prevent SAgs (SEA/B, TSST-1) Non-specific APC-mediated T cell activation, keratinocyte cytokine production [56][57][58][59] α-Toxin Keratinocyte lysis and TNF-α production [60][61][62][63][64] δ-Toxin Mast cell degranulation and inflammation [65] V8 and ETA/B DSG-1 cleavage leading to both increased desquamation and skin inflammation [66][67][68] Protein A Keratinocyte TNF-α production [64] PSM Keratinocyte inflammation [69] SAg superantigen, SEA and SEB enterotoxins A and B, TSST-1 toxin shock syndrome toxin 1, ETA and ETB exfoliative toxins A and B, PSM phenol-soluble modulins other pathogens from colonizing the skin [37,82]. Therefore, increased S. epidermidis colonization in AD skin may represent a way for the skin to naturally prevent increased S. aureus colonization in AD.…”

A Metagenomic Analysis Provides a Culture-Independent Pathogen Detection for Atopic Dermatitis

“…Most importantly, EVs can be purified from body fluids, including plasma and urine, thereby providing an excellent tool to probe the effect of bacterial infection on a systemic level 16. We also previously reported that S. aureus -derived EVs induced AD-like inflammation in the skin and were causally related to the pathogenesis of AD 1718…”