IL-4 Regulates Specific Arg-1+ Macrophage sFlt-1–Mediated Inhibition of Angiogenesis

Abstract

One of the main drivers for neovascularization in age-related macular degeneration is activation of innate immunity in the presence of macrophages. Here, we demonstrate that T helper cell type 2 cytokines and, in particular, IL-4 condition human and murine monocyte phenotype toward Arg-1(+), and their subsequent behavior limits angiogenesis by increasing soluble fms-like tyrosine kinase 1 (sFlt-1) gene expression. We document that T helper cell type 2 cytokine-conditioned murine macrophages neutralize vascular endothelial growth factor-mediated endothelial cell proliferation (human umbilical vein endothelial cell and choroidal vasculature) in a sFlt-1-dependent manner. We demonstrate that in vivo intravitreal administration of IL-4 attenuates laser-induced choroidal neovascularization (L-CNV) due to specific IL-4 conditioning of macrophages. IL-4 induces the expression of sFlt-1 by resident CD11b(+) retinal microglia and infiltrating myeloid cells but not from retinal pigment epithelium. IL-4-induced suppression of L-CNV is not prevented when sFlt-1 expression is attenuated in retinal pigment epithelium. IL-4-mediated suppression of L-CNV was abrogated in IL-4R-deficient mice and in bone marrow chimeras reconstituted with myeloid cells that had undergone lentiviral-mediated shRNA silencing of sFlt-1, demonstrating the critical role of this cell population. Together, these data establish how lL-4 directly drives macrophage sFlt-1 production expressing an Arg-1(+) phenotype and support the therapeutic potential of targeted IL-4 conditioning within the tissue to regulate disease conditions such as neovascular age-related macular degeneration.

Doyne lecture 2016: intraocular health and the many faces of inflammation

“…The latter can be perturbed through the augmentation of inhibitory CD200R signalling or through the administration of Th2 cytokines to either tonically suppress macrophage activation or drive anti-angiogenic function, respectively. 94,96,98 Thus our data and those from others 99,100 support the concept that interplay between macrophage and RPE within the subretinal space likely contributes to disease progression.…”

“…So when macrophages are alternatively activated via IL-4 they result in a sFlt-1-secreting M2 cell and this is seen in both mouse and man. 96 In man, macrophages associated with CNV or in specimens of AMD retina that are assessed using immunohistochemistry confirm the nature of VEGFexpressing CD68 + cells. 97 Finally, perturbing macrophage function can attenuate neovascularisation in experimental models.…”

Mechanistic Insights into the Anti-angiogenic Activity of Trypanosoma cruzi Protein 21 and its Potential Impact on the Onset of Chagasic Cardiomyopathy

“…We propose that P21 is continuously secreted to the extracellular space by intracellular amastigotes located in cardiac fibers that induces leukocyte recruitment to the site of inflammation and up-regulates IL-4 expression15. It is known that IL-4 induces macrophages to acquire alternative (M2) activation that is characterized by increased production of sFlt-1 (anti-angiogenic molecule)77. Moreover, we believe that P21 has the capacity to bind to CXCR4 + ECs from the heart.…”

Comprehensive analysis of mouse retinal mononuclear phagocytes

“…We have learned that Iba1 is not optimal for FACS as it requires a longer intracellular staining procedure and leads to more nonspecific signals. However, CD11b (OX42), a broadly expressed integrin marker of mononuclear phagocytes is suitable to determine relative numbers in either total retinal cell homogenates 32,35 or pre-sorted phagocyte populations 36 .…”