�@Although our skin is in permanent contact with various pathogens, the number and composition of the cutaneous microflora remain constant under physiologic conditions, and the skin is usually free of signs of infection. This is due to both the physical barrier of the skin and its production of antimicrobial proteins (AMPs) forming an innate epithelial chemical shield. Among these AMPs, we have been studying various cellular activities of human b-defensins (hBDs), cathelicidin LL-37, dermcidin, and psoriasin etc, which are mainly generated by epithelial cells and highly expressed in several skin disorders.
�@Apart from their microbicidal functions, aforementioned AMPs possess multiple roles as mediators of inflammation and/or infection with the effects on epithelial, immune and inflammatory cells. Some of these AMPs indeed chemoattract mast cells, and activate this cell population to release inflammatory mediators such as histamine, prostaglandins and cytokines/chemokines via different specific receptors, and are able to modulate passive cutaneous anaphylaxis. Moreover, these AMPs induce the chemotaxis of neutrophils, monocytes, T cells and dendritic cells, and stimulate keratinocytes to produce various cytokines/chemokines (See Figure). Our recent study has shown that these AMPs may also participate in wound healing through their induction of keratinocyte chemotaxis and cell proliferation. Interestingly, Skin-derived AMPs synergize to enhance not only microbicidal, but also their cellular activities.
�@Thus, understanding the actions of naturally occurring antimicrobial peptides in skin provides further insight into the mechanism of innate cutaneous disease control, and yields novel therapeutic approaches to the treatment of skin disorders.
(François Niyonsaba, July. 06, 2009)