Confusion between protectin D1 (PD1) and its isomer protectin DX (PDX). An overview on the dihydroxy-docosatrienes described to date.

There is currently a growing interest in docosahexaenoic acid (DHA) oxygenated metabolites. Among them, protectin D1 (PD1), an endogenous dihydroxylated and non-cyclic docosatriene made through lipoxygenation and hydrolysis of an epoxide intermediate, shows appealing biological effects. However, with the present paper we wish to point out that results are sometimes assigned to PD1 while they are indeed related to its isomer protectin DX (PDX) made through double lipoxygenation only. These misleading conclusions urge us to review herein the structural/chemical and biological differences in the docosatrienes reported to date in the literature i.e. PD1, the related PD1n-3 DPA, AT-NPD1, maresin 1 (MaR1) and MaR1n-3 DPA, as well as their poxytrin analogs such as PDX, and some synthetic diastereoisomers. Hopefully, this will avoid further mistakes and confusion in the future.