Modulation of integrins and filaggrin expression by Propionibacterium acnes extracts on keratinocytes

Propionibacterium acnes plays an important role in the pathogenesis of acne and it is established that this bacteria is involved in the induction and maintenance of the inflammatory phase of acne. The aim of our work was to determine if P. acnes extracts could modulate integrins and filaggrin in vitro expression by keratinocytes. Integrins and filaggrin expression was examined using immunohistochemistry technique both on Normal Human Epiderminal Keratinocytes (NHEK) and on deep-frozen sections of normal human skin explants incubated with three different P. acnes extracts. In addition, the expression of filaggrin was investigated on biopsies of acne lesions and by western-blot associated with its precursor profilaggrin. We demonstrated that P. acnes extracts induced beta 1 integrin expression significantly on both proliferating keratinocytes and differentiated keratinocytes. In addition, P. acnes induced alpha 3, alpha 6s and alpha V beta 6 integrin expression and filaggrin expression on differentiated keratinocytes. Finally P. acnes extracts increased filaggrin expression by suprabasal layer of epidermis of explants. Western-blot confirmed that total amount of filaggrin was increased. These results indicate that P. acnes extracts are directly able to modulate the differentiation of keratinocytes suggesting that this bacteria play a role not only in the development of inflammatory acne lesions but also in the formation of the microcomedo.