6-(Ar)Alkylamino-Substituted Uracil Derivatives: Lipid Mimetics with Potent Activity at the Orphan G Protein-Coupled Receptor 84 (GPR84)

Abstract

GPR84, a Gi protein-coupled receptor that is activated by medium-chain (hydroxy)fatty acids, appears to play an important role in inflammation, immunity, and cancer. Recently, 6-octylaminouracil (4) has been reported to act as an agonist at GPR84. Here, we describe the synthesis of 69 derivatives and analogs of 4, 66 of which represent new compounds. They were evaluated in (a) cyclic adenosine monophosphate accumulation and (b) β-arrestin assays in human GPR84-expressing cells. Potent nonbiased as well as G protein-biased agonists were developed, e.g., 6-hexylamino-2,4(1H,3H)-pyrimidinedione (20, PSB-1584, EC50 5.0 nM (a), 3.2 nM (b), bias factor: 0) and 6-((p-chloro- and p-bromo-phenylethyl)amino)-2,4(1H,3H)-pyrimidinedione (47, PSB-16434, EC50 7.1 nM (a), 520 nM (b), bias factor: 1.9 = 79-fold Gi pathway-selective; 48, PSB-17365, EC50 2.5 nM (a), 100 nM (b), bias factor 1.3 = 20-fold selective), which were selective versus other free fatty acid-activated receptors. Compounds 20 and 48 were found to be metabolically stable upon incubation with human liver microsomes. A pharmacophore model was created on the basis of structurally diverse lipidlike GPR84 agonists.

Cyclopropane-Containing Fatty Acids from the Marine Bacterium Labrenzia sp. 011 with Antimicrobial and GPR84 Activity

“…cAMP assays were performed as previously described [ 24 ]. CHO cells overexpressing the human GPR84 were stimulated with forskolin (10 μM) in the absence (control) or presence of test compound for 15 min.…”

“…β-arrestin assays were performed as previously described [ 24 ]. Briefly, CHO cells expressing the human GPR84 with a β-galactosidase fragment and β-arrestin containing the complementary fragment of the enzyme were incubated with a series of compound dilutions (in DMSO, final DMSO concentration: 1%) for 90 min before adding the detection reagent (DiscoverX ® , Fremont, CA, USA).…”

“…Therefore, 1 and 2 were tested against a range of bacteria and fungi including P. crassostreae . Moreover, medium-chain fatty acids are considered as the most potent agonists of the orphan G-protein coupled receptor (GPCR) GPR84 [ 24 ]. GPR84 is a protein highly expressed on immune cells, e.g., inflammatory macrophages and microglia, and was suggested to be involved in immune defense [ 25 ], and may thus be a promising drug target for a variety of inflammatory diseases including Alzheimer’s disease, neuropathic pain, reflux esophagitis, and inflammatory bowel disease [ 26 ].…”

20 Years an Orphan: Is GPR84 a Plausible Medium-Chain Fatty Acid-Sensing Receptor?

“…This is an exciting avenue to exploit for potential therapeutics (Kenakin, 2018), and the chemokine receptors are examples of immune-expressed GPCRs with multiple endogenous biased ligands (Rajagopal et al, 2013). Synthetic biased agonists at GPR84 have been identified (Pillaiyar et al, 2017(Pillaiyar et al, , 2018Moghaddam et al, 2018), and recent work by Lucy et al (2019) has shown that G-protein-biased DL-175 has a diminished chemoattractant effect on human myeloid cells, while maintaining levels of phagocytosis enhancement.…”

Metabolite Sensing GPCRs: Promising Therapeutic Targets for Cancer Treatment?

“…MCFAs, with a chain length of 9-14 carbons, bind GPR84 receptor [58]. It is predominantly expressed in immune system-related tissues and cells, such as bone marrow, spleen, lung, lymph nodes and brain microglia, and adipose tissue [59]. It is suggested that GPR84 is a proinflammatory receptor [60] and it could play a role in linking fatty acid metabolism and immune responses [61].…”