Zaprinast, a well‐known cyclic guanosine monophosphate‐specific phosphodiesterase inhibitor, is an agonist for GPR35

Abstract

We found that zaprinast, a well-known cyclic guanosine monophosphate-specific phosphodiesterase inhibitor, acted as an agonist for a G protein-coupled receptor, GPR35. In our intracellular calcium mobilization assay, zaprinast activated rat GPR35 strongly (geometric mean EC 50 value of 16 nM), whereas it activated human GPR35 moderately (geometric mean EC 50 value of 840 nM). We also demonstrated that GPR35 acted as a Ga i/o -and Ga 16 -coupled receptor for zaprinast when heterologously expressed in human embryonic kidney 293 (HEK 293) cells. These findings will facilitate the research on GPR35 and the drug discovery of the GPR35 modulators.

The Antiallergic Mast Cell Stabilizers Lodoxamide and Bufrolin as the First High and Equipotent Agonists of Human and Rat GPR35

“…Moreover, a number of other agonist ligands with antiasthma/antiallergenic pharmacology, including doxantrazole and pemirolast, although lacking a carboxyl function, clearly contain an acid bioisostere related to the triazole structure present in the standard GPR35 surrogate agonist zaprinast. These ligands, although also active at GPR35, displayed marked differences in potency between the rat and human orthologs, a feature previously noted for zaprinast (Taniguchi et al, 2006;Jenkins et al, 2010). The published literature indicates that certain GPR35 agonists such as pamoate (Jenkins et al, 2010), 4-{(Z)-[(2Z)-2-(2-fluorobenzylidene)-4-oxo-1,3-thiazolidin-5-ylidene]methyl}benzoic acid , and various 8-benzamidochromen-4-one-2-carboxylic acids (Funke et al, 2013) are highly selective for the human ortholog, whereas others such as pemirolast and amlexanox are highly selective for the rat ortholog.…”

“…4B). We and others have reported that many compounds first identified as ligands at human GPR35, including zaprinast, display markedly different potency and/or activity at rodent orthologs (Taniguchi et al, 2006;Jenkins et al, 2010Jenkins et al, , 2012Funke et al, 2013;Neetoo-Isseljee et al, 2013). We next examined the activity of a variety of mast cell stabilizers at the rat ortholog of GPR35 in the BRET-based b-arrestin-2 interaction assay.…”

“…Although GPR35 is indicated to be a receptor responsive to the endogenously produced tryptophan metabolite kynurenic acid (Wang et al, 2006), lack of convergence on this issue has resulted in a number of efforts to identify surrogate agonist ligands that might be used to help further define the roles of this receptor. Although a number of such ligands have been identified (Taniguchi et al, 2006;Jenkins et al, 2010;Zhao et al, 2010;Deng et al, 2012;Funke et al, 2013;Neetoo-Isseljee et al, 2013), many of these are either of modest potency and/or display markedly different potency at human and rodent orthologs of GPR35 (Jenkins et al, 2010;Funke et al, 2013;Neetoo-Isseljee et al, 2013). This has posed challenges both in efforts to define the orthosteric binding pocket of the receptor and to use rodents and cell lines derived from such animals to further explore the function of GPR35.…”

“…Zaprinast (Taniguchi et al, 2006;Jenkins et al, 2010Jenkins et al, , 2011 has become the standard surrogate agonist of GPR35 and, akin to zaprinast, a number of mast cell stabilizers also contain an acid bioisostere. Because zaprinast is an example of a ligand that displays marked variation in potency between rodent and human GPR35 (Taniguchi et al, 2006;Jenkins et al, 2010Jenkins et al, , 2011, this also encouraged us to also explore the contributions of a series of nonmaintained arginine residues within regions of the receptor species orthologs that are predicted to define the ligand binding pocket. Cross-species alterations of such residues provided novel insights into the binding pocket.…”

Antagonists of GPR35 Display High Species Ortholog Selectivity and Varying Modes of Action

“…For example, despite both kynurenic acid (Wang et al, 2006) and lysophosphatidic acid (Oka et al, 2010) being proposed as endogenous activators of GPR35, the synthetic ligand zaprinast has become the standard reference agonist. Zaprinast, however, is better appreciated as an inhibitor of cGMP phosphodiesterases (Taniguchi et al, 2006), and other recently reported GPR35 agonists are generally either very simple molecules with modest potency/ affinity and known activity at multiple other targets (Yang et al, 2010(Yang et al, , 2012Hu et al, 2012) or were identified via screens of libraries of known therapeutic ligands (Jenkins et al, 2010). As such, the identification of pamoate as a relatively potent GPR35 agonist (Jenkins et al, 2010;Zhao et al, 2010) potentially offers a more useful tool.…”