Specific oxylipins enhance vertebrate hematopoiesis via the receptor GPR132

Abstract

Epoxyeicosatrienoic acids (EETs) are lipid-derived signaling molecules with cardioprotective and vasodilatory actions. We recently showed that 11,12-EET enhances hematopoietic induction and engraftment in mice and zebrafish. EETs are known to signal via G protein-coupled receptors, with evidence supporting the existence of a specific high-affinity receptor. Identification of a hematopoietic-specific EET receptor would enable genetic interrogation of EET signaling pathways, and perhaps clinical use of this molecule. We developed a bioinformatic approach to identify an EET receptor based on the expression of G protein-coupled receptors in cell lines with differential responses to EETs. We found 10 candidate EET receptors that are expressed in three EET-responsive cell lines, but not expressed in an EET-unresponsive line. Of these, only recombinant GPR132 showed EET-responsiveness in vitro, using a luminescence-based β-arrestin recruitment assay. Knockdown of zebrafish prevented EET-induced hematopoiesis, and marrow from GPR132 knockout mice showed decreased long-term engraftment capability. In contrast to high-affinity EET receptors, GPR132 is reported to respond to additional hydroxy-fatty acids in vitro, and we found that these same hydroxy-fatty acids enhance hematopoiesis in the zebrafish. We conducted structure-activity relationship analyses using both cell culture and zebrafish assays on diverse medium-chain fatty acids. Certain oxygenated, unsaturated free fatty acids showed high activation of GPR132, whereas unoxygenated or saturated fatty acids had lower activity. Absence of the carbon-1 position carboxylic acid prevented activity, suggesting that this moiety is required for receptor activation. GPR132 responds to a select panel of oxygenated polyunsaturated fatty acids to enhance both embryonic and adult hematopoiesis.

Distribution of Free and Esterified Oxylipins in Cream, Cell, and Skim Fractions of Human Milk

“…release and reesterification) of free oxylipins (Otoki et al, 2020). Free oxylipins are more bioactive than esterified oxylipins (Lahvic et al, 2018;Obinata et al, 2005), consistent with studies showing that they act as signaling molecules (Hennebelle et al, 2019). Thus, understanding their localization and proportional distribution relative to esterified pools in human milk would inform on how milk serves as a signaling system in infants.…”

Linoleic acid‐derived metabolites constitute the majority of oxylipins in the rat pup brain and stimulate axonal growth in primary rat cortical neuron‐glia co‐cultures in a sex‐dependent manner

“…This is because receptors for both compounds within neuron‐glia are not known. Recent studies have characterized GPR132 (also known as G2A) as a receptor for various FFAs and oxylipins, but it is not known to be selective for LA or 13‐HODE (Obinata et al ; Lahvic et al ). Identifying the receptor for LA and 13‐HODE in brain could help determine the molecular pathways and mechanisms underlying their sex‐specific effects on neuronal morphogenesis.…”

The Lipid Receptor G2A (GPR132) Mediates Macrophage Migration in Nerve Injury-Induced Neuropathic Pain

“…We observed that the linoleic acid metabolites 9- and 13-HODE were increased at the injured nerves in wild-type mice 7 days after the SNI surgery ( Figure 1 C,E), both of which are endogenous agonists of G2A ( Figure 1 B). Moreover, we could detect a strong increase of the lipid 12,13-epoxyoctadecenoic acid (EpOME) in the injured ipsilateral site of the nerve, which was recently identified as weak G2A agonist ( Figure 1 G) [ 43 ]. In contrast, G2A-deficient mice did not show any difference between the treated (ipsilateral) and untreated sites (contralateral) regarding the different lipid concentrations ( Figure 1 D,F,H,J).…”