5-Lipoxygenase in monocytes emerges as a therapeutic target for intimal hyperplasia in a murine wire-injured femoral artery

Given the importance of leukotrienes in vascular inflammation induced by local tissue injury, this study investigated the role for 5-lipoxygenase (5-LO) in monocytes in the development of intimal hyperplasia. As a mechanistic study, the importance of monocyte 5-LO in monocyte-macrophage differentiation with subsequent infiltration in neointima was evaluated. In a mouse model of wire-injured femoral artery, intimal hyperplasia started as early as 2 wks after injury, and luminal area and blood flow were reduced due to increased neointima formation. Time-dependent increases in macrophage infiltration were observed in neointima and showed a positive relationship with neointima volume. In 5-LO-deficient (KO) mice or wild-type (WT) mice treated with an inhibitor of 5-LO activating protein (MK886, 1 and 10 mg/kg), intimal hyperplasia and macrophage infiltration into neointima were reduced, but monocyte adhesion to injured luminal surface was not inhibited, which suggested 5-LO participates in monocyte-macrophage differentiation. In an in vitro study, monocyte-macrophage differentiation was found to be increased by high mobility group box 1 protein (HMGB1), but this effect was attenuated in cells isolated from 5-LO-KO mice. Furthermore, macrophage infiltration and intimal hyperplasia were more prominent in 5-LO-KO mice transplanted with monocytes from WT mice than in 5-LO-KO mice transplanted with monocytes from 5-LO-KO mice. Taken together, it was suggested that 5-LO in monocytes played a pivotal role in monocyte-macrophage differentiation and subsequent infiltration of macrophage in neointima, leading to vascular remodeling after vascular injury.