The Histamine H4 Receptor: A Novel Target for Safe Anti-inflammatory Drugs?

Anti-inflammatory effect of a new piperazine derivative: (4-methylpiperazin-1-yl)(1-phenyl-1H-pyrazol-4-yl)methanone

AIMS

This study investigates the anti-nociceptive and anti-inflammatory effects of new piperazine compound (LQFM182) as well as the toxicity acute in vitro.

MAIN METHODS

To evaluate the anti-nociceptive activity, the acetic acid-induced abdominal writhing test, tail flick test and formalin-induced pain test were used. The anti-inflammatory activity was evaluated using the models of paw oedema and pleurisy induced by carrageenan and some inflammatory parameters were evaluated, including cell migration, myeloperoxidase enzyme activity and the levels of TNF-α and IL-1β cytokines in pleural exudate. The acute oral systemic toxicity of LQFM182 in mice was evaluated through the neutral red uptake (nru) assay.

KEY FINDINGS

LQFM182 (50, 100 or 200 mg/kg, p.o.) decreased the number of writhings induced by acetic acid in a dose-dependent manner, and an intermediate dose (100 mg/kg, p.o.) reduced the paw licking time of animals in the second phase of the formalin test. Furthermore, LQFM182 (100 mg/kg, p.o.) reduced oedema formation at all hours of the paw oedema induced by carrageenan test and in pleurisy test reduced cell migration from the reduction of polymorphonuclear cells, myeloperoxidase enzyme activity and the levels of pro-inflammatory cytokines IL-1β and TNF-α. Therefore, it was classified in GHS category 300 < LD₅₀ < 2000 mg/kg.

SIGNIFICANCE

Reduction of the TNF-α and IL-1β levels.

Suppression of Laser-Induced Choroidal Neovascularization by the Oral Medicine Targeting Histamine Receptor H4 in Mice

PURPOSE

This study aimed to examine relationship of histamine receptor H4 (HRH4) and the pathogenesis of laser-induced choroidal neovascularization (laser-CNV) and to determine whether oral administration of HRH4 antagonists suppressed laser-CNV in mice.

METHODS

Laser photocoagulation was performed in mice to induce the laser-CNV. Histamine was administered intravitreously, and CNV volume was measured. Laser photocoagulation and intravitreous injection of HRH4 antagonist JNJ7777120 were performed after intraperitoneal injection of clodronate liposome, which depletes circulating monocyte-derived macrophages; CNV volume was compared with that in mice injected with control (dimethyl sulfoxide [DMSO]/PBS). Three days after laser-CNV, the F4/80⁺CD11b⁺ macrophage population in retinal pigment epithelium (RPE)/choroid complex was quantified with flow cytometry in wild-type and Hrh4^-/- mice. The long-acting HRH4 antagonist JNJ28307474 was then administrated periorally, and the laser-CNV volume was compared with controls.

RESULTS

Intravitreous injection of histamine did not affect laser-CNV volume. The laser-CNV from the eye injected with JNJ7777120 was equivalent to that injected with the DMSO/PBS in mice that had intraperitoneally received clodronate liposome. Flow cytometry after laser-CNV induction revealed a smaller F4/80⁺CD11b⁺ macrophage population in the RPE/choroid complex of Hrh4^-/- mice than in wild-type mice. Oral administration of JNJ28307474 significantly reduced laser-CNV volume in wild-type mice.

CONCLUSIONS

Our results suggested that HRH4-positive macrophages played an important role in the pathogenesis of laser-CNV and that they require a different ligand from that of histamine. The oral administration of an HRH4 antagonist successfully reduced laser-CNV.

TRANSLATIONAL RELEVANCE

Our results indicate that drugs targeting HRH4 are potentially a novel oral treatment for age-related macular degeneration.