The innate immune system of human skin contains antimicrobial peptides(AMPs) known as cathelicidins(LL-37) and human beta-defensins(hBD)-2. These peptides immediately respond to intruded microbes for prevention of further invasion. In normal skin these peptides are negligible, but they are accumulated in the skin affected by inflammatory diseases such as psoriasis. Although atopic dermatitis(AD) is recurrent inflammatory skin disease, it has been known that the expressions of AMPs in AD are decreased compared to that of psoriasis.

Current research was to identify the expressions of AMPs according to changes transepidermal water loss(TEWL) levels in AD.

The involved and uninvolved sites of patients diagnosed as having AD were evaluated using TEWL. And the expression of LL-37 and hBD-2 in skin biopsies specimens from involved and uninvolved site of these patients were determined by RT-PCR, Western blotting and immunohistochemical staining(IHC).

The TEWL levels increased in both uninvolved and involved sites, more increased in involved sites. It implicated that permeability barrier function was more disrupted in involved sites of atopic dermatitis. In RT-PCR, the expression levels of hBD-2 and LL-37 mRNA were down-regulated in both uninvolved and involved sites, more decreased in involved sites. In Western blotting of hBD-2 and LL-37 proteins, the levels of hBD-2, LL-37 protein expressions of uninvolved sites were determined to be more intense than those observed in the involved sites. These findings were also confirmed by IHC.

Our results demonstrate that expression of antimicrobial peptides downregulated according to increasing TEWL levels in atopic dermatitis lesions. Therefore, this deficiency may account for the susceptibility of patients with atopic dermatitis to skin infection, also implicate that localized skin barrier disruption play a role for decreased the expression of AMPs.