Abstract
Purpose:
Effective therapies for treatment resistant neovascular age-related macular degeneration (nAMD) remain an unmet need. Beta-adrenergic receptor (AR) blockers can decrease laser-induced choroidal neovascularization (CNV) size in mice. We have shown that monocyte-derived macrophages (MDMs) and interleukin-6 (IL-6) are necessary for beta-AR blockers to inhibit CNV. However, the specific beta-AR and the mechanism of this pathway are not fully elucidated. We hypothesized that beta2-AR (Adrb2) signaling on MDMs increases IL-6 production and stimulates CNV.
Methods:
Previously published single-cell RNA-sequencing data was reanalyzed to determine which mononuclear phagocytes express beta-ARs. Adrb2flox/flox: Cx3cr1CreER/+ mice (Adrb2ΔMacs) or Adrb2flox/flox (Adrb2flox) controls were given tamoxifen injections at either four weeks before or at the time of laser-induced CNV to knockout Adrb2 in tissue resident or all macrophages, respectively. Mice underwent laser induced-CNV, and eyes were collected for choroidal wholemount immunofluorescence imaging to measure CNV area, multiparameter flow cytometry to analyze macrophage heterogeneity, and ELISAs to quantitate IL-6 levels.
Results:
Adrb2 was the predominantly expressed beta-AR and was found on microglia, macrophages, and monocytes. Adrb2 deletion in tissue resident macrophages had no effect upon CNV area. Adrb2 deletion in all macrophages decreased CNV area by 1.4-fold. Adrb2ΔMacs posterior eye cups demonstrated similar levels of pro-angiogenic CD11c+ macrophages compared to Adrb2flox controls, but Ly6CnegCD11cneg macrophages were significantly increased. IL-6 levels increased with laser in Adrb2flox controls, but IL-6 levels in Adrb2ΔMacs posterior eye cups were unchanged.
Conclusions:
Beta2-AR deletion in ocular-infiltrating macrophages decreases laser-induced CNV area. Beta2-AR expression regulates IL-6 expression in monocyte-derived macrophages.