Docosahexaenoic acid (DHA), a major ω-3 polyunsaturated fatty acid (PUFA) found in fish oil is the source of protectins (PDs), one of the specialized proresolving mediators (SPMs) that show potent anti-inflammatory and pro-resolving actions (Molfino et al. 2017, Balas & Durand 2016). The switch from synthesis of pro-inflammatory eicosanoids, such as the prostaglandins and the thromboxanes, to the pro-resolving lipoxins, resolvins and protectins, occurs via induction of the 15-lipoxygenase enzyme.
Protectin, identified as (N)PD1 (N signifies neuroprotectin when produced in neural tissues) is derived from DHA through the actions of 15-lipoxygenase then enzymatic hydrolysis. Aspirin can also trigger the formation of epimeric protectin (AT-PD1) (Serhan et al. 2015). An additional protectin (DX) is formed through the sequential actions of two lipoxygenase reactions. The biosynthesis of these protectins is described here (Balas & Durand 2016, Balas et al. 2014, Serhan et al. 2014, Serhan et al. 2015).