Abstract
N-3 docosapentaenoic acid–derived resolvin D5 (RvD5n-3 DPA) is diurnally regulated in peripheral blood and exerts tissue-protective actions during inflammatory arthritis. Here, using an orphan GPCR screening approach coupled with functional readouts, we investigated the receptor(s) involved in mediating the leukocyte-directed actions of RvD5n-3 DPA and identified GPR101 as the top candidate. RvD5n-3 DPA bound to GPR101 with high selectivity and stereospecificity, as demonstrated by a calculated KD of approximately 6.9 nM. In macrophages, GPR101 knockdown limited the ability of RvD5n-3 DPA to upregulate cyclic adenosine monophosphate, phagocytosis of bacteria, and efferocytosis. Inhibition of this receptor in mouse and human leukocytes abrogated the pro-resolving actions of RvD5n-3 DPA, including the regulation of bacterial phagocytosis in neutrophils. Knockdown of the receptor in vivo reversed the protective actions of RvD5n-3 DPA in limiting joint and gut inflammation during inflammatory arthritis. Administration of RvD5n-3 DPA during E. coli–initiated inflammation regulated neutrophil trafficking to the site of inflammation, increased bacterial phagocytosis by neutrophils and macrophages, and accelerated the resolution of infectious inflammation. These in vivo protective actions of RvD5n-3 DPA were limited when Gpr101 was knocked down. Together, our findings demonstrate a fundamental role for GPR101 in mediating the leukocyte-directed actions of RvD5n-3 DPA.
Highlights
Development of the inflammatory response was a fundamental step in the evolution of multicellular organisms, given that this mechanism is vital in warding off invading pathogens and in coordinating reparative and regenerative mechanisms [1, 2]
We recently uncovered a homeostatic role for RvD5n-3 DPA in regulating intestinal epithelial barrier function, where decreased levels of this mediator during inflammatory arthritis are linked with increased intestinal barrier permeability and joint inflammation [11]
In order to establish whether the biological actions of RvD5n-3 DPA were mediated by a GPCR, we screened a panel of orphan GPCRs to determine whether RvD5n-3 DPA showed agonistic activity toward these receptors, using 10 nM RvD5n-3 DPA and assessing increases in luminescence as a readout for receptor activation
Summary
Development of the inflammatory response was a fundamental step in the evolution of multicellular organisms, given that this mechanism is vital in warding off invading pathogens and in coordinating reparative and regenerative mechanisms [1, 2]. Recent studies demonstrate that in addition to arachidonic acid, eicosapentaenoic acid, and docosahexaenoic acid (DHA), n-3 docosapentaenoic acid (n-3 DPA) is a substrate for conversion to novel, structurally distinct bioactive mediators [9, 10] One of these novel mediators, n-3 DPA–derived resolvin D5 (RvD5n-3 DPA) (7S,17S-dihydroxy-8E,10Z,13Z,15E,19Z-docosapentaenoic acid), is diurnally regulated in human peripheral blood, and loss of its production, together with that of the related. We used an integrated approach to establish the identity of the GPCR that mediates the pro-resolving actions of RvD5n-3 DPA on leukocytes Results from these experiments identified GPR101 as a candidate receptor for RvD5n-3 DPA. Knockdown of Gpr101 in mice led to an abrogation of the protective actions of RvD5n-3 DPA in vivo by limiting its ability to regulate inflammatory arthritis and infectious inflammation
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