Structural determinants for calcium mobilization by prostaglandin E2 and prostaglandin F2α glyceryl esters in RAW 264.7 cells and H1819 cells

Abstract

2-Arachidonoylglycerol is oxygenated by cyclooxygenase-2 to form prostaglandin glyceryl esters. Previous work in this laboratory has suggested that PGE2-G activates a novel G protein-coupled receptor in a murine macrophage-like cell line, RAW 264.7. To probe the structural determinants for the putative receptor in RAW 264.7 cells, a panel of 10 analogs was tested for their ability to increase intracellular calcium. These analogs included PGE2- and PGF2α– ethanolamide, 4 PGE2 glyceryl ester analogs, and 4 PGF2α glyceryl ester analogs. The glyceryl ester analogs differed in the positioning of the hydroxyl groups in the glycerol moiety and the type of linker (ester, amide, or thioester) of the prostaglandin to the glycerol moiety. Compounds were also evaluated in a human non-small cell lung cancer cell line (H1819). The glycerol moiety was required for the calcium response. All glyceryl ester analogs but not ethanolamides caused a concentration-dependent increase in calcium levels in both RAW 264.7 and H1819 cells. An amide or ester linkage was preferable to a thioester linkage. The EC50 values did not significantly change when the positioning of the hydroxyls was varied. This calcium response induced by the glyceryl ester analogs appears to be independent of the putative hydrolysis products, PGE2 and PGF2α, and appears to represent a novel signaling pathway.

Identification of the Major Prostaglandin Glycerol Ester Hydrolase in Human Cancer Cells

“…COX-2 oxygenates 2-AG to form PG-Gs, which display effects that are frequently opposite those of endocannabinoids, e.g. hyperalgesia and neuroinflammation (13)(14)(15)(16)(17)(18)(19). However, complete elucidation of the effects of PG-Gs in vivo has been challenging due to their instability to enzymatic hydrolysis (20).…”

“…1). These lipids are of growing interest because they elicit a wide array of cellular responses, including activation of calcium mobilization, modulation of synaptic transmission, induction of hyperalgesia, exacerbation of neurotoxicity and neuroinflammation, and stimulation of anti-inflammatory effects upon lipopolysaccharide stimulation (13)(14)(15)(16)(17)(18)(19).…”

Prostaglandin E2-Glyceryl Ester: In Vivo Evidence for a Distinct Pharmacological Identity from Intraocular Pressure Studies

“…PGE 2 -glyceryl ester and its stable analogs PGE 2 -serinolamide and PGE 2 -propanediolamide were all found to be ocular hypotensive agents, which correlates with the in vitro activity of the compounds at the PGE 2 -glyceryl ester-sensitive receptor in RAW 264.7 and H1819 cells (Richie-Jannetta et al, 2010). This represents the first in vivo study designed to test pharmacological hypotheses concerning PGE 2 -glyceryl ester.…”

“…PGE 2 -glyceryl ester has been reported as a very potent, naturally occurring prostanoid (Nirodi et al, 2004;Hu et al, 2008). In vivo PGE 2 -glyceryl ester studies, to date, have largely been limited to studying neurology (Hu et al, 2008;Lindgren et al,2013;Valdeolivas et al, 2013;Shimizu et al, 2014), and a more detailed pharmacological analysis has been limited to comparing chemically stable analogs in cells (Richie-Jannetta et al, 2010). No confirmatory evidence for the unique pharmacology of PGE 2 -glyceryl ester has been reported, thus far, in isolated tissues or living animals.…”

“…These obstacles were overcome by replacement of the noncarbonyl O atom of the ester with NH to stabilize the ester by preventing both facile rearrangement (Rouzer and Marnett, 2011) and enzymatic hydrolysis. This resulted in two potent compounds, PGE 2 -serinolamide and PGE 2 -1(3)-propanediolamide, which have been reported as equipotent to PGE 2 -glycerol ester in RAW 264.7 and H1819 cells (Richie-Jannetta et al, 2010). Prior to ocular evaluations, these two amido-PGE 2 -glycerol ester analogs were subjected to detailed pharmacological analyses at human recombinant prostanoid receptors.…”