Background: Psoriasis is a systemic inflammatory disease with dramatic responses to TNF-α inhibitors. TNF-α is mainly produced by macrophages. However, how macrophage polarization contributes to psoriasis remains unknown.
Objective: We aimed to investigate the molecular mechanisms of macrophage polarization in psoriasis.
Methods: 8 patients with moderate to severe psoriasis (Male/Female: 4/4, average age: 47.9 years old) and 8 healthy controls (Male/Female: 4/4, average age: 49.3 years old) were recruited. Their peripheral CD14+ monocytes were isolated with magnetic beads and then were differentiated into macrophages. The differential macrophage polarization was compared among normal controls, psoriatic patients before and after TNF-α inhibitors. The U937 cells were used to investigate the mechanisms by which TNF-α altered the macrophage polarization.
Results: The ratio of M1 to M2a macrophage polarization was higher in psoriatic patients comparing with that in controls. The decreasing M1/M2a ratio was parallel to decreasing PASI severity score after adalimumab treatment. Consistently, TNF-α blockage decreased M1/M2a ratio in U937 cells. The induction of STAT1 and IRF-1 in polarized U937 M1 cells was inhibited by TNF-α inhibitor. However, STAT1 and/or IRF-1 interference could not resume M1 polarization. In skin, the increased M1 and M2 infiltration in lesions returned to baseline after successful treatment with TNF-α inhibitor.
Conclusions: Increased M1 polarization is associated with higher disease severity in psoriasis, resuming to baseline after successful treatment by TNF-α inhibitors. TNF-α blockage inhibits M1 polarization through STAT1- and IRF-1-independent pathways. Macrophage polarization may contribute to disease progression in psoriasis.
Keywords: IRF-1; Macrophage polarization; Psoriasis; STAT1; TNF-α inhibitor.
Copyright © 2018 Japanese Society for Investigative Dermatology. Published by Elsevier B.V. All rights reserved.