Malassezia furfur induces the expression of beta-defensin-2 in human keratinocytes in a protein kinase C-dependent manner

Antimicrobial peptides of the beta-defensin family are expressed in all human epithelial tissues tested to date and have recently been the subject of vigorous investigation. Their localization and characteristics support the hypothesis that these peptides play a role in mucosal and skin defense. The lipophilic yeast Malassezia furfur is a saprophyte found in normal human cutaneous flora. Malassezia furfur is not only a saprophyte, but is also associated with several diseases such as Malassezia folliculitis, seborrheic dermatitis and some forms of atopic dermatitis, psoriasis and confluent and reticulate papillomatosis. Little is known about the mechanism by which M. furfur overcomes the natural barrier of the skin. To further define the role of the beta-defensins in the innate human skin immune response, we analyzed the mRNA expression of two human beta-defensins HBD-1 and HBD-2 in human keratinocytes treated with M. furfur. In addition, we looked into how M. furfur of TGF-beta1 and IL-10, cytokines that interfere with the development of protective cell immunity, regulate their expression. Finally, we examined the signal transduction mechanisms involved during M. furfur uptake. Cultured human keratinocytes were treated with M. furfur. The mRNA and protein expression were analyzed, respectively, by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blotting. Our data demonstrate that M. furfur does not modify HBD-1 expression, whereas it up-regulates, via protein kinase C (PKC), the expression of HBD-2, TGFbeta-1 and IL-10 48 h after treatment. Our results suggest that beta-defensins are integral components of innate host defenses. They play an essential part in the resistance of the human skin surfaces against M. furfur uptake and other microbial invasion.