The histamine H4 receptor antagonist JNJ7777120 induces increases in the histamine content of the rat conjunctiva

Objectives:: Although the H4 receptor localisation in the eye is unresolved, this study aimed to investigate the effects of the H4 receptor antagonist JNJ7777120 in a model of experimental conjunctivitis. Methods:: JNJ7777120, at 0.005-1 mmol/l, was instilled into the lower conjunctival fornix of normal and compound 48/80 (C48/80)-challenged eyes of male Wistar rats, in the absence or presence of 40 mg/ml disodium cromoglycate (DSCG). Conjunctival histamine content was quantified 20 min post-challenge. Statistical analyses were performed by ANOVA. Results:: JNJ7777120 increased dose-dependently (r = 0.784, p < 0.001) the conjunctival histamine content. In the C48/80-challenged eye no effect of the antagonist was observed. Co-administration of JNJ7777120 with DSCG resulted in a biphasic action of JNJ7777120, implying a competitive action of the two agents. Conclusions:: These data suggest a functionality of the H4 receptor in the rat eye and address questions on the localization and the role of the receptor in ocular inflammation. © 2009 Birkhäuser Verlag, Basel

The histamine H4 receptor as a new therapeutic target for inflammation

Following the sequencing of the human genome, data-mining efforts have revealed the existence of a new histamine receptor that is expressed at high levels in mast cells and leukocytes. The histamine

Evaluation of histamine H1-, H2-, and H3-receptor ligands at the human histamine H4 receptor: identification of 4-methylhistamine as the first potent and selective H4 receptor agonist

The histamine

Cloning and pharmacological characterization of the dog histamine H4 receptor

The histamine

The histamine H4 receptor is a potent inhibitor of adhesion-dependent degranulation in human neutrophils

The histamine H4 receptor regulates the inflammatory response. However, it is not known whether this receptor has a functional role in human neutrophils. We found that fMLP (1 μM), but not histamine (0.1–1 μM), induced Mac-1-dependent adhesion, polarization, and degranulation (release of lactoferrin). A pretreatment of neutrophils with histamine (0.001–1 μM) or JNJ 28610244 (0.1–10 μM), a specific H4 receptor agonist, led to inhibition of degranulation. Total inhibition of degranulation was obtained with 0.1 μM histamine and 10 μM JNJ 28610244. Furthermore, such inhibition by histamine of degranulation was reversed by JNJ 7777120 and JNJ 28307474, two selective H4 receptor antagonists. However, neither histamine nor the H4 receptor agonist JNJ 28610244 prevented fMLP-induced, Mac-1-dependent adhesion, indicating that the H4 receptor may block signals emanating from Mac-1-controlling degranulation. Likewise, engagement of the H4 receptor by the selective agonist JNJ 28610244 blocked Mac-1-dependent activation of p38 MAPK, the kinase that controls neutrophil degranulation. We also show expression of the H4 receptor at the mRNA level in ultrapure human neutrophils and myeloid leukemia PLB-985 cells. We concluded that engagement of this receptor by selective H4 receptor agonists may represent a good, therapeutic approach to accelerate resolution of inflammation