Monocyte-derived macrophages are necessary for beta-adrenergic receptor-driven choroidal neovascularization inhibition

Abstract

PURPOSE: Beta-adrenergic receptor (AR) antagonists, like propranolol, inhibit angiogenesis in multiple ocular conditions through an unknown mechanism. We previously showed that propranolol reduces choroidal neovascularization (CNV) by decreasing interleukin-6 levels. Since macrophages are one of the central producers of interleukin-6, we examined whether macrophages are required for propranolol-driven inhibition of choroidal angiogenesis. METHODS: We tested the anti-angiogenic properties of propranolol in the choroidal sprouting assay and the laser-induced CNV model. Bone marrow-derived monocytes (BMDMs) were added to the choroidal sprouting assay and Ccr2-/- mice were subjected to laser-induced CNV. Multi-parameter flow cytometry was performed to characterize the ocular mononuclear phagocyte populations after laser injury and during propranolol treatment. RESULTS: Propranolol reduced choroidal angiogenesis by 41% (P < 0.001) in the choroidal sprouting assay. Similarly, propranolol decreased laser-induced CNV by 50% (P < 0.05) in female mice, with no change in males. BMDMs increased choroidal sprouting by 146% (P < 0.0001), and this effect was ablated by propranolol. Beta-AR inhibition had no effect upon laser-induced CNV area in female Ccr2-/- mice. MHCII+ and MHCII- macrophages increased 20-fold following laser treatment in wildtype mice as compared to untreated mice, and this effect was completely attenuated in lasered Ccr2-/- mice. Moreover, propranolol increased the numbers of MHCII+ and MHCII- macrophages by 1.9 (P ¼ 0.07) and 3.1 (P < 0.05) fold in lasered female mice with no change in macrophage numbers in males. CONCLUSIONS: Our data suggest that propranolol inhibits angiogenesis through recruitment of monocyte-derived macrophages in female mice only. These data show the anti-angiogenic nature of beta-AR blocker-recruited monocyte-derived macrophages in CNV.