Ninjurin1: a potential adhesion molecule and its role in inflammation and tissue remodeling

Nerve injury induced protein 1, Ninj1 (Ninjurin1) is a cell surface protein that is induced by nerve injury and promotes axonal growth in the peripheral nervous system. However, the function of Ninj1 in the vascular system and central nervous system (CNS) is incompletely understood. Here we review recent studies that have shed further light on the role and regulation of Ninj1 in vascular remodeling and inflammation. Increasing evidence suggests that Ninj1 mediates cell communication and enhances the entry, migration, and activity of leukocytes such as monocytes and macrophages in developmental processes and inflammatory responses. Moreover, our recent studies show that Ninj1 regulates close interaction between leukocytes and vascular endothelial cells in vascular remodeling and inflamed CNS. Additionally, Ninj1 enhances the apoptosis-inducing activity of leukocytes and is cleaved by MMPs, resulting in loss of adhesion during tissue remodeling. The collective data described here show that Ninj1 is required for the entry, adhesion, activation, and movement of leukocytes during tissue remodeling and might be a potential therapeutic target to regulate the adhesion and trafficking of leukocytes in inflammation and leukocyte-mediated diseases such as multiple sclerosis, diabetic retinopathy, and neuropathy.