Implications of dietary oils and polyunsaturated fatty acids in the management of cutaneous disorders.

A major proinflammatory metabolite of arachidonic acid, leukotriene B4, is known to accumulate in the lesions of psoriasis. Most of this metabolite is biosynthesized by the polymorphonuclear cells that infiltrate into the psoriatic lesions. Epidermal 15-lipoxygenase, on the other hand, metabolizes arachidonic acid into 15-hydroxyeicosatetraenoic acid (15-20:4n-6), presumably serving as a negative feedback to inhibit the local generation of leukotriene B4. Eicosapentaenoic acid, a major polyunsaturated fatty acid in fish oil, and gamma-linolenic acid, a poly-unsaturated fatty acid in certain vegetable oils, are both metabolized by epidermal 15-lipoxygenase into 15-hydroxyeicosapentaenoic acid (15-OH-20:5n-3) and 15-hydroxyeicosatriaenoic acid (15-OH-20:3n-3), respectively. Both of these monohydroxy acids are potent in vitro inhibitors of leukotriene B4 generation. It seems reasonable, therefore, that adequate dietary supplementation with eicosapentaenoic acid or gamma-linolenic acid may offer a novel and nontoxic approach to suppressing cutaneous inflammatory disorders.