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

Abstract 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 ( PUFA s) is involved in HR ‐ AD ‐induced AD . High‐purity PUFA s 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 PUFA s 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 PUFA s in AD .