Lipocalin-2 exacerbates psoriasiform skin inflammation by augmenting T-helper 17 response

Lipocalin-2 (LCN2) is an antimicrobial protein and adipokine associated with insulin resistance, obesity and atherosclerotic disease. Psoriasis is a T-helper (Th)1/Th17-mediated, chronic inflammatory dermatosis related to metabolic syndromes and serum LCN2 levels are elevated in psoriatic patients. We examined the in vivo effects of LCN2 on topical imiquimod (IMQ)-induced psoriasiform skin in BALB/c mice and in vitro on human keratinocytes (KC). Clinically, i.p. injected LCN2 exacerbated erythema and scaling in IMQ-treated murine skin compared with phosphate-buffered saline injection alone, and it augmented interleukin (IL)-17A, IL-17F, IL-22, IL-23p19, IL-12p40, CCL20, tumor necrosis factor-α, chemokine (C-X-C motif) ligand (CXCL)1, CXCL2, DEFB4, DEFB14, LCN2 and S100A7 mRNA levels of IMQ-treated murine skin while it did not increase the mRNA levels of interferon-γ, IL-12p35 or CXCL10. LCN2 in synergy with IL-17 increased mRNA levels of CCL20, LCN2 and DEFB4A but not of CXCL10 in human KC in vitro. These results suggest that LCN2 enhances the expression of Th17 cytokines/chemokines and antimicrobial peptides in murine IMQ-treated psoriatic skin and KC. LCN2 may potentiate the development of psoriasis via the enhancement of Th17- and antimicrobial peptide-mediated inflammation.