Roles of SEA-expressing Staphylococcus aureus, isolated from an atopic dermatitis patient, on expressions of human β-defensin-2 and inflammatory cytokines in HaCaT cells

Atopic dermatitis (AD) shows an increased susceptibility to Staphylococcus aureus infection partly due to decreased expression of human β-defensin-2 (HBD-2). Interestingly, it was reported that the nasal carrier S. aureus down-regulates the expression of HBD-2 and -3, thereby the carrier strains of S. aureus retain an advantage to epithelial colonization and infection. In this study, we tried to isolate and characterize S. aureus from an AD patient, with recurrent oozing on his face. We studied the increased expression of inflammatory cytokines, such as IL-1β, -6, -8, and TNF-α in S. aureus treated-HaCaT cells, which are mediated by secreting superantigens (SAgs), structural component, or both. In addition, we investigated whether the SAgs from S. aureus can down-regulate the expression of HBD-2 in HaCaT cells making favorable conditions for colonization on skin. Our data showed that the isolated S. aureus has the exotoxin gene, sea exotoxin. The SEA producing-S. aureus induced the expression of IL-1β, -6, -8 cytokines, and TNF-α in HaCaT cells. The expression of HBD-2 was increased in S. aureus-treated HaCaT cells. Furthermore IL-8 was also induced by the structure component of S. aureus. Taken together, the SEA producing S. aureus induced the up-regulation of pro-inflammatory cytokines as well as HBD-2, thereby resulting in induction of the persistent eczematous skin lesions in AD. Thus, our data may give insight into understanding the pathogenesis by which S. aureus induces and aggravates eczematous skin lesions in AD.