Macrophages, an essential component of immune system, play a critical role not only in inflammation but also in wound healing. There are two subtypes of macrophages, M1 macrophages which encourage inflammation and M2 macrophages which decrease inflammation and encourage tissue repair. Glycoprotein non-metastatic melanoma protein b (GPNMB) is a glycosylated transmembrane protein which is highly expressed in multiple cells, including macrophages. GPNMB is also reported to act as a negative regulator of macrophage inflammatory responses in Alzheimer diseases and Parkinson diseases. Previous study has also shown the presence of macrophages in vitiligo skin. However, the role of macrophage-derived GPNMB in vitiligo is still unknown. In this study, using skin tissues from healthy donors and vitiligo patients, the expression of CD163(a marker of M2 macrophages) and GPNMB were analyzed by double immunofluorescence staining. The results showed that more M2 macrophages existed in vitiligo skin, compared with healthy skin. Furthermore, increased expression of GPNMB was observed in M2 macrophages from skin of patients with vitiligo, compared with that from healthy skin. In in vitro study, recombinant GPNMB protected cultured melanocytes against oxidative stress, i.e. UV irradiation or chemical stimuli. These findings suggest that increased M2 macrophages and macrophages-derived GPNMB might be involved in the pathogenesis of vitiligo.

Increased Number of M2 Macrophages and High Expression of Macrophage-Derived Glycoprotein Non-Metastatic Melanoma Protein B in Vitiliginous Skin