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Simultaneous Study of the Recruitment of Monocyte Subpopulations Under Flow In Vitro
Published on: November 26, 2018
Staphylococcus aureus-derived extracellular vesicles induce monocyte recruitment by activating human dermal
Jihye Kim1, Bum-Ho Bin2, Eun-Jeong Choi2
1Skincare Research Division, R&D Unit, AmorePacific Corporation, Yongin-si, Gyeonggi-do, Korea.
Insights
Staphylococcus aureus extracellular vesicles (SEVs) activate human endothelial cells, increasing inflammatory responses and monocyte recruitment relevant to atopic dermatitis (AD). This research clarifies SEV
Area of Science:
- Immunology
- Dermatology
- Microbiology
Background:
- Atopic dermatitis (AD) involves significant immune cell infiltration in the skin.
- Colonization by Staphylococcus aureus and its extracellular vesicles (SEVs) is linked to AD pathogenesis.
- The precise molecular mechanisms of SEV-driven inflammation in AD are not fully understood.
Purpose of the Study:
- To investigate how SEVs mediate inflammatory responses in AD.
- To examine the effects of SEVs on human dermal microvascular endothelial cells (HDMECs).
Main Methods:
- HDMECs were treated with SEVs.
- Assessed expression of cell adhesion molecules and cytokines via RT-qPCR, Western blot, and cytokine arrays.
- Investigated SEV receptor and signaling pathways using gene knockdown and inhibitors.
- Performed monocyte recruitment assays on SEV-treated HDMECs.
Main Results:
- SEVs, unlike other bacterial EVs, activated HDMECs, upregulating adhesion molecules (E-selectin, VCAM1, ICAM1) and IL-6.
- SEV-induced HDMEC activation enhanced THP-1 monocyte recruitment.
- Activation depended on Toll-like receptor 4 and NF-κB signaling, with rapid induction within 1 hour.
- SEV effects were more potent than S. aureus extracts at equivalent protein concentrations.
Conclusions:
- SEVs act as proinflammatory factors contributing to immune cell infiltration in AD.
- SEVs efficiently induce endothelial cell activation and monocyte recruitment.
- Findings offer insights into mitigating S. aureus-driven AD onset, progression, and phenotypes.
Background:
Atopic dermatitis (AD) represents the most common inflammatory skin disorder in children showing massive infiltration of immune cells. The colonization of AD-afflicted skin by Staphylococcus aureus and S. aureus-derived extracellular vesicles (SEVs) has been associated with AD pathogenesis; however, the molecular mechanism underlying SEV-mediated inflammatory responses remains unclear.
Objective:
We investigated how SEVs can mediate inflammatory responses in AD pathogenesis by examining the effect of SEVs on human dermal microvascular endothelia cells (HDMECs).
Methods:
HDMECs were treated with SEVs, and the expression of cell adhesion molecules or cytokines was assessed using RT-qPCR, Western blot or cytokine array analyses. The receptor for SEVs and related signalling molecules in HDMECs were addressed and verified via gene knockdown or inhibitor experiments. The recruitment assay of human THP-1 monocytic cells on HDMECs was performed after SEV treatment in the presence or absence of the verified receptor or signalling molecule.
Results:
SEVs, but not other gram-positive bacteria-derived extracellular vesicles, directly activated HDMECs by increasing the expression of cell adhesion molecules (E-selectin, VCAM1 and ICAM1) and that of IL-6, the inflammatory cytokine; consequently, they enhanced the recruitment of THP-1 monocytic cells to HDMECs. The SEV-induced HDMEC activation was dependent on Toll-like receptor 4 and the NF-κB signalling pathway, which was rapidly activated within 1 hour post-treatment and followed by an upregulation of cell adhesion molecules and IL-6 at later time-points. Moreover, SEV-mediated HDMEC responses were more rapid and intense than those induced by the same protein concentrations of S. aureus extracts.
Conclusions & Clinical Relevance:
SEVs as proinflammatory factors could mediate immune cell infiltration in AD by efficiently inducing endothelial cell activation and monocyte recruitment, which may provide insights into alleviating the S. aureus-mediated onset or progression of AD and its phenotypes.
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