Histamine Receptor H4-expressing Macrophages Contribute to the Pathogenesis of Laser-induced Choroidal Neovascularization in Mice

Abstract

Purpose: This study aimed to examine the function of histamine receptor H4 (HRH4)-positive macrophages on laser-induced choroidal neovascularization (laser-CNV) in mice.

Methods: Laser photocoagulation was performed to induce laser-CNV and histamine was administered intravitreously in wild-type mice at day 0. Mice were sacrificed at day 7 and CNV volume was measured. Laser photocoagulation and intravitreous injection of HRH4 antagonist JNJ7777120 dissolved in dimethylsulfoxide (DMSO)/PBS were performed after intraperitoneal injection of clodronate liposome and CNV volume was then compared with that in mice injected with the control (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 administrated perorally and laser-CNV volume was compared with the control.

Results: Intravitreous injection of histamine did not affect laser-CNV volume. The laser-CNV injected with JNJ7777120 was not reduced compared with that injected with control in mice that had received clodronate liposome. Flow cytometry after laser-CNV induction revealed that the F4/80⁺CD11b⁺ macrophage population in the RPE/choroid complex of Hrh4^−/− mice was significantly smaller than that in wild-type mice. Oral administration of JNJ28307474 significantly reduced laser-CNV volume in wild-type mice.

Conclusions: Our results suggest that HRH4-positive macrophages have a ligand different from histamine. In laser-CNV, HRH4-positive macrophages were recruited to promote CNV generation, whereas oral administration of HRH4 antagonist successfully reduced laser-CNV.