BackgroundAquaporins (AQPs) are a family of water transporting proteins present in many mammalian epithelial and endothelial cell types. Among the AQPs, AQP3 is known to be a water/glycerol transporter expressed in human skin.ObjectiveThe relationship between the expression level of AQP3 and transpidermal water loss (TEWL) in the lesional and peri-lesional skin of psoriasis-affected patients, and skin hydration in the lesional and peri-lesional skin of psoriasis patients, was investigated.MethodsThe expression of AQP3 in psoriasis-affected and healthy control skin was determined using immunohistochemical and immunofluroscence staining. TEWL and skin hydration were measured using a Tewameter® TM210 (Courage & Khazaka, Cologne, Germany) and a Corneometer® CM 820 (Courage & Khazaka), respectively.ResultsAQP3 was mainly expressed in the plasma membrane of stratum corneum and the stratum spinosum in normal epidermis. Unlike the normal epidermis, AQP3 showed decreased expression in the lesional and peri-lesional epidermis of psoriasis. TEWL was increased, and skin hydration was decreased, in the lesional and peri-lesional skin of psoriasis patients, compared with the healthy control sample.ConclusionAlthough various factors contribute to reduced skin hydration in the lesional and peri-lesional skin of psoriasis, AQP3 appears to be a key factor in the skin dehydration of psoriasis-affected skin.

Ceramide is an important constituent of stratum corneum lipids, which act as both physical barriers and signal modulators. We synthesized several ceramide derivatives and investigated their effects on keratinocyte differentiation. RT-PCR and Western blotting showed that the novel synthetic ceramide derivatives K6PC-4 (N-ethanol-2-hexyl-3-hydroxy-decanamide), K6PC-5, (N-ethanol-3-oxo-2-tetradecyl/hexadecyl-octadecanamide/eicosanamide)and K6PC-9 [N-(1,3-dihydroxypropyl)-2-hexyl-3-oxo-decanamide] markedly increased keratin 1 and involucrin expression in normal human epidermal keratinocytes cultured in vitro. These ceramide derivatives elicited a rapid transient increase in intracellular calcium levels, which were measured using laser scanning confocal microscopy. In addition, K6PC-4, K6PC-5, and K6PC-9 stimulated the phosphorylation of p42/44 extracellular signal-regulated kinase and c-Jun N-terminal kinase. In a reconstituted epidermis model, K6PC-4, K6PC-5, and K6PC-9 significantly increased keratin 1 expression in the suprabasal layer. These results indicate that these novel synthetic ceramide derivatives have the potential to promote keratinocyte differentiation, suggesting that the lipid molecules are applicable for treating skin diseases involving abnormal keratinocyte differentia-

Sphingosylphosphorylcholine (SPC) is a bioactive sphingolipid metabolite that can enhance wound healing. In an effort to find downstream effectors of SPC, we performed microarray analysis and found that the expression of the gene for connective tissue growth factor (CTGF) was significantly affected in human skin fibroblasts cultured in vitro. Northern blot analysis showed that SPC markedly induced CTGF mRNA expression in a dose-and time-dependent manner. Consistent with this result, Western blot analysis also showed that SPC significantly induced the CTGF production. Pretreatment with cycloheximide did not prevent the CTGF induction by SPC, indicating that SPC stimulates CTGF mRNA expression without the increased synthesis of a regulatory protein. Inhibition by pretreatment with Y27632, but not by PD98059 (a mitogen-activated protein kinase 1/2 inhibitor) and LY294002 (a phosphatidylinositol 3-kinase inhibitor), indicated that r-kinase pathway was involved in SPC-induced CTGF expression. Together, these results reveal the potential importance of CTGF induction as a downstream event in SPC-induced cellular responses.

No abstract

In a search for the wound healing accelerators, we found that tetraacetyl-phytosphingosine (TAPS), a sphingolipid metabolite produced by phytosphingosine acetylation, has significant inhibitory potential on healing of rabbit ear wound. As angiogenesis is fundamental to proper wound healing, we examined the effect of TAPS on angiogenesis using human umbilical vein endothelial cells cultured in vitro. TAPS markedly decreased vascular endothelial growth factor (VEGF)-induced chemotactic migration and capillary-like tube formation. Recognizing its inhibitory potential on angiogenesis, we further investigated the action mechanism of TAPS. TAPS significantly inhibited VEGF-induced proteolytic enzyme production, including matrix metalloproteinase-2, urokinase-type plasminogen activator and plasminogen activator inhibitor-1. TAPS also suppressed VEGF-induced phosphorylation of p42/44 extracellular signal-regulated kinase and c-Jun N-terminal kinase. In addition, TAPS abolished VEGF-induced intracellular calcium increase, measured using laser scanning confocal microscopy. Together, these results suggest that TAPS exerts its inhibitory action on angiogenesis through the inhibition of mitogen-activated protein kinase activation and intracellular calcium increase, thereby affecting the process of wound healing negatively.