Expression and functional properties of canine, rat, and murine histamine H4 receptors in Sf9 insect cells

Abstract

The histamine H₄ receptor (H₄R) is expressed on cells of the immune system including eosinophils, dendritic cells, and T cells and plays an important role in the pathogenesis of bronchial asthma, atopic dermatitis, and pruritus. Analysis of the H₄R in these diseases depends on the use of animal models. However, there are substantial pharmacological differences between various H₄R species orthologs. The purpose of this study was to analyze the pharmacological properties of canine, rat, and murine H₄R in comparison to human H₄R expressed in Sf9 insect cells. Only hH₄R and cH₄R exhibited a sufficiently high [³H]histamine affinity for radioligand binding studies. Generally, cH₄R exhibited lower ligand-affinities than hH₄R. Similarly, in high-affinity GTPase studies, ligands were more potent at hH₄R than at other H₄R species orthologs. Unlike the other H₄R species orthologs, hH₄R exhibited high agonist-independent (constitutive) activity. Most strikingly, the prototypical H₄R antagonist (1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine) (JNJ7777120) exhibited partial agonistic activity at cH₄R, rH₄R, and mH₄R, whereas at hH₄R, JNJ7777120 was a partial inverse agonist. H₄R agonists from the class of N ( G )-acylated imidazolylpropylguanidines and cyanoguanidines exhibited substantial differences in terms of affinity, potency, and efficacy among H₄R species orthologs, too. The species-dependent pharmacological profiles are not due to the highly variable amino acid sequence position 341. Finally, H₄R species orthologs differ from each other in terms of regulation by NaCl. Collectively, there are profound pharmacological differences between H₄R species orthologs. Most importantly, caution must be exerted when interpreting pharmacological effects of "the prototypical H₄R antagonist" JNJ7777120 as H₄R antagonism.

Histamine H4-Receptors Inhibit Mast Cell Renin Release in Ischemia/Reperfusion via Protein Kinase Cε-Dependent Aldehyde Dehydrogenase Type-2 Activation

“…That constitutive activity plays an important role in this case is proven by our previous findings with H 3 Rs, which are located on sympathetic nerve endings in the heart, where they inhibit NE release in I/R (Imamura et al, 1994). Unlike H 4 Rs, H 3 Rs have a very high constitutive activity (Schnell et al, 2011). Indeed, we had found that when hearts from H 3 R-deleted mice were exposed to I/R, NE release was greatly enhanced (Koyama et al, 2003), which substantiates the functional relevance of receptor constitutive activity.…”

“…Given the anti-RAS role of H 4 Rs, one might have expected renin and NE release and arrhythmia to be enhanced when H 4 Rs were pharmacologically blocked or deleted. An explanation of why this did not occur is probably found in the very low constitutive activity of H 4 Rs in the mouse (Schnell et al, 2011). That constitutive activity plays an important role in this case is proven by our previous findings with H 3 Rs, which are located on sympathetic nerve endings in the heart, where they inhibit NE release in I/R (Imamura et al, 1994).…”

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

“…Observations of marked variation in the pharmacology of species orthologs of GPCRs are well known but are of particular relevance in the early stages of receptor characterization. For example, the differences in ligand affinity at the orthologs of the histamine H4 receptor (Liu et al, 2001) even led to suggestions that there might be other receptors for histamine and further detailed pharmacological characterization of various orthologs of this receptor (Lim et al, 2010;Schnell et al, 2011), and the development of early-generation ␤ 3 -adrenoceptor selective agonists was severely compromised by, at that time unappreciated, ortholog selectivity (de Souza and Burkey, 2001;Arch, 2008).…”

International Union of Basic and Clinical Pharmacology. XCVIII. Histamine Receptors

“…Partial sequences of other species orthologs have been identified but not published. Species differences in pharmacology (ligand binding and signaling efficacy) are profound, also depending on readout systems (Nordemann et al, 2013), and several molecular features for the observed species differences have been elucidated (Liu et al, 2001b;Lim et al, 2008Lim et al, , 2010Schnell et al, 2011).Whereas proximal readout systems such as [ ]GTPS binding assays show pronounced differences between species orthologs, more distal reporter gene assays revealed less pronounced differences. Species splice isoforms have yet to be reported.…”

“…However, the pharmacology of H 4 receptor ligands is not clear cut and well understood and therefore care must be taken when interpreting the results from any single ligand. For example, Schnell et al (2011) reconstituted H 4 receptor species orthologs from human, rat, mouse, and canine with the G protein heterotrimer G i a 2 b 1 g 2 plus the regulator of G protein signaling RGS19 in Sf9 insect cell membranes and measured high-affinity steady-state GTPase activity as a parameter for receptor activation. At all four H 4 receptor species orthologs, histamine acted as full agonist.…”