The potential of the essential fatty acid-deficient hairless rat as a psoriasis screening model for topical anti-proliferative drugs

Barrier abnormality due to ceramide deficiency leads to psoriasiform inflammation in a mouse model

It has been recognized that ceramides are decreased in the epidermis of patients with psoriasis and atopic dermatitis. Here, we generated Sptlc2 (serine palmitoyltransferase long-chain base subunit 2)-targeted mice (SPT-cKO mice), thereby knocking out serine palmitoyltransferase (SPT), the critical enzyme for ceramide biosynthesis, in keratinocytes. SPT-cKO mice showed decreased ceramide levels in the epidermis, which impaired water-holding capacity and barrier function. From 2 weeks of age, they developed skin lesions with histological aberrations including hyperkeratosis, acanthosis, loss of the granular layer, and inflammatory cell infiltrates. Epidermal Langerhans cells showed persistent activation and enhanced migration to lymph nodes. Skin lesions showed upregulation of psoriasis-associated genes, such as IL-17A, IL-17F, IL-22, S100A8, S100A9, and β-defensins. In the skin lesions and draining lymph nodes, there were increased numbers of γδ T cells that produced IL-17 (γδ-17 cells), most of which also produced IL-22, as do Th17 cells. Furthermore, IL-23-producing CD11c(+) cells were observed in the lesions. In vivo treatment of SPT-cKO mice with an anti-IL-12/23p40 antibody ameliorated the skin lesions and reduced the numbers of γδ-17 cells. Therefore, we conclude that a ceramide deficiency in the epidermis leads to psoriasis-like lesions in mice, probably mediated by IL-23-dependent IL-22-producing γδ-17 cells.

Decreased keratinocyte motility in skin wound on mice lacking the epidermal fatty acid binding protein gene

Fatty acids are shown to be important in various skin functions. Fatty acid binding protein (FABP) is postulated to serve as a lipid shuttle, solubilizing hydrophobic fatty acids and delivering them to the appropriate metabolic system. Among the FABP family proteins, epidermal-type FABP (E-FABP) is solely expressed in keratinocyte but its specific role in skin is not yet fully established. We found an elevated expression of E-FABP in regenerative keratinocytes of healing wounds. However, E-FABP null mice showed no marked differences compared to wild type mice in the process of wound closure, in vivo. On the other hand, in keratinocyte culture, E-FABP gene disruption decreased the cell motility, but did not affect the cell proliferation. E-FABP deletion may be compensated for in vivo by the microenvironment comprised of various cells such as fibroblasts and endothelial cells around the wound. Our analyses suggest that the E-FABP elevation may be necessary for the activation of cell motility within regenerative epidermis during wound healing.