Eicosapentaenoic acid ethyl ester ameliorates atopic dermatitis-like symptoms in special diet-fed hairless mice, partly by restoring covalently bound ceramides in the stratum corneum.

Skin barrier dysfunction has a key role in the development of atopic dermatitis (AD). Covalently bound ceramides (Cer), which are essential lipids for permeability barrier homoeostasis, are reportedly decreased in the stratum corneum (SC) of AD patients. Hairless mice fed a special diet develop pruritic dermatitis resembling human AD. Our previous study found that oral administration of the n-3 polyunsaturated fatty acid α-linolenic acid ameliorated skin barrier dysfunction in AD mice with concomitant increase in serum eicosapentaenoic acid (EPA). In this study, we examined the effects of EPA ethyl ester (EPA-E) on diet-induced AD in hairless mice. Oral administration of EPA-E ameliorated skin barrier dysfunction and pruritus in AD mice. In the SC of AD mice, covalently bound Cer were markedly diminished. EPA-E administration restored the lack of bound Cer. Our findings imply the possible therapeutic clinical application of EPA-E in the treatment of human AD.

Deficiency of n-6 polyunsaturated fatty acids is mainly responsible for atopic dermatitis-like pruritic skin inflammation in special diet-fed hairless mice.

Hairless mice fed a special diet, HR-AD, develop atopic dermatitis (AD)-like skin inflammation with skin barrier defects and itch-related scratching; however, the ingredient(s) causing the dermatitis remains unclear. In this study, we examined whether deficiency of certain polyunsaturated fatty acids (PUFAs) is involved in HR-AD-induced AD. High-purity PUFAs were given to HR-AD-fed mice by dietary supplementation or gavage. Fatty acid levels in the serum and skin were determined by using gas chromatography-mass spectrometry. In serum from HR-AD-fed mice, linoleic acid (LA, 18:2n-6) and α-linolenic acid (ALA, 18:3n-3), as well as their metabolites, were markedly decreased. When mice were fed HR-AD supplemented with LA or ALA in an amount equal to that contained in a normal diet, the development of AD-like symptoms was completely prevented by supplementation with LA but not with ALA. Relatively high dose of ALA slightly alleviated skin barrier defects, but did neither itch-related scratching nor skin inflammation. On the other hand, gavage administration of LA metabolites, such as γ-linolenic acid and arachidonic acid (AA), significantly ameliorated established dermatitis without increasing LA in the serum and skin. Moreover, AA-induced amelioration of dermatitis was not affected by pharmacological blockade of 5-lipoxygenase (5-LOX) and cyclooxygenase (COX), suggesting no involvement of 5-LOX- or COX-mediated AA metabolites in the amelioration. In conclusion, our results indicate that deficiency of n-6 PUFAs is mainly responsible for AD-like symptoms by HR-AD feeding. Thus, this model could be useful for studying the pathomechanisms associated with deficiency of n-6 PUFAs in AD.