Increased HMGB1 serum levels and altered HMGB1 expression in patients with psoriasis vulgaris

High mobility group box-1 (HMGB1) has been implicated as a pro-inflammatory cytokine in the pathogenesis of various inflammatory and autoimmune diseases. However, information about HMGB1 in inflammatory skin diseases is unknown. Herein, we investigated the serum HMGB1 levels and tissue HMGB1 expression in patients with psoriasis vulgaris (PV) and atopic dermatitis (AD). Serum levels of HMGB1 in patients with PV and AD were detected by enzyme-linked immunosorbent assay (ELISA). The expression of HMGB1 in lesional skin was evaluated by immunohistochemistry and immunofluorescence. Protein levels of HMGB1 in the nuclear fraction and cytoplasmic fraction were determined by western blot. Serum levels of HMGB1 in patients with PV but not AD were significantly higher than those in nornal controls. Moreover, serum HMGB1 levels were correlated with the severity of PV according to PASI socres. Furthermore, by immunohistochemistry and immunofluorescence, we showed that the expression of HMGB1 in normal skin was almost completely restricted to the nucleus. However, abundant cytoplasmic expression of HMGB1 was observed in the epidermis in lesional skin of PV patients. In addition, western blot data indicated that HMGB1 expression was in the nucleus protein and was absent in the cytoplasm protein in control group. In contrast, HMGB1 expression in the cytoplasmic fraction was detectable in AD patients and more distinct in PV patients. Taken together, this study provides first observations on the association of HMGB1 with PV, and showed the elevated HMGB1 serum levels and altered HMGB1 distribution in lesional skin in patients with PV. We suggest that HMGB1 might be involved in the pathogenesis of PV.