Comparative Photoaffinity Profiling of Omega‑3 Signaling Lipid Probes Reveals Prostaglandin Reductase 1 as a Metabolic Hub in Human Macrophages

The fish oil constituent
docosahexaenoic acid (DHA, 22:6
n-3) is
a signaling lipid with anti-inflammatory properties. The molecular
mechanisms underlying the biological effect of DHA are poorly understood.
Here, we report the design, synthesis, and application of a complementary
pair of bio-orthogonal, photoreactive probes based on the polyunsaturated
scaffold DHA and its oxidative metabolite 17-hydroxydocosahexaenoic
acid (17-HDHA). In these probes, an alkyne serves as a handle to introduce
a fluorescent reporter group or a biotin-affinity tag via copper(I)-catalyzed
azide-alkyne cycloaddition. This pair of chemical probes was used
to map specific targets of the omega-3 signaling lipids in primary
human macrophages. Prostaglandin reductase 1 (PTGR1) was identified
as an interaction partner that metabolizes 17-oxo-DHA, an oxidative
metabolite of 17-HDHA. 17-oxo-DHA reduced the formation of pro-inflammatory
lipids 5-HETE and LTB4 in human macrophages and neutrophils. Our results
demonstrate the potential of comparative photoaffinity protein profiling
for the discovery of metabolic enzymes of bioactive lipids and highlight
the power of chemical proteomics to uncover new biological insights.