Nitric Oxide Prevents Aortic Neointimal Hyperplasia by Controlling Macrophage Polarization

Abstract

Objective— Nitric oxide synthase 3 (NOS3) prevents neointima hyperplasia by still unknown mechanisms. To demonstrate the significance of endothelial nitric oxide in the polarization of infiltrated macrophages through the expression of matrix metalloproteinase (MMP)-13 in neointima formation. Approach and Results— After aortic endothelial denudation, NOS3 null mice show elevated neointima formation, detecting increased mobilization of LSK (lineage-negative [Lin]-stem-cell antigen 1 [SCA1]+KIT+) progenitor cells, and high ratios of M1 (proinflammatory) to M2 (resolving) macrophages, accompanied by high expression of interleukin-5, interleukin-6, MCP-1 (monocyte chemoattractant protein), VEGF (vascular endothelial growth factor), GM-CSF (granulocyte-macrophage colony stimulating factor), interleukin-1β, and interferon-γ. In conditional c-Myc knockout mice, in which M2 polarization is defective, denuded aortas showed extensive wall thickening as well. Conditioned medium from NOS3-deficient endothelium induced extensive repolarization of M2 macrophages to an M1 phenotype, and vascular smooth muscle cells proliferated and migrated faster in conditioned medium from M1 macrophages. Among the different proteins participating in cell migration, MMP-13 was preferentially expressed by M1 macrophages. M1-mediated vascular smooth muscle cell migration was inhibited when macrophages were isolated from MMP-13–deficient mice, whereas exogenous administration of MMP-13 to vascular smooth muscle cell fully restored migration. Excess vessel wall thickening in mice lacking NOS3 was partially reversed by simultaneous deletion of MMP-13, indicating that NOS3 prevents neointimal hyperplasia by preventing MMP-13 activity. An excess of M1-polarized macrophages that coexpress MMP-13 was also detected in human carotid samples from endarterectomized patients. Conclusions— These findings indicate that at least M1 macrophage-mediated expression of MMP-13 in NOS3 null mice induces neointima formation after vascular injury, suggesting that MMP-13 may represent a new promising target in vascular disease.

Novel Multifunctional Nanomatrix Reduces Inflammation in Dynamic Conditions in Vitro and Dilates Arteries ex Vivo

“…These results underline the protective effects of NO against inflammatory responses, reaffirming previous studies’ findings. 26–28 …”

Deletion of Hyaluronan Synthase 3 Inhibits Neointimal Hyperplasia in Mice

“…Importantly, IL-13-primed macrophages are characterized by a more anti-inflammatory M2 phenotype and suppress pro-inflammatory type 1 macrophages 23 which in turn have been shown to substantially promote neointima formation via promotion of VSMC proliferation and migration. 24 In contrast, GM-CSF is thought to promote inflammation so that both, pro- and primarily anti-inflammatory cytokines seem to be induced in Has3 -deficiency and the net outcome remains unknown. Taken together, reduced inflammation is unlikely the mechanism underlying reduced neointimal hyperplasia in Has3 -deficient mice.…”

Redox Control of Vascular Function

“…84,85 Indeed, the regulation of intimal proliferation through downregulation of M1-macrophage markers like matrix metalloproteinase (MMP)-13, is a major function of NO. 86 Novel research using cross-transplanted eNOS knockout chimeras to investigate the role of eNOS in circulating blood cells established that hematopoetic cells are an important source of circulating NO within the blood. 87 A specific role for erythrocyte eNOS seems to be important for the regulation of nitrite homeostasis and systemic blood pressure.…”