High-mobility group box-1 was released actively and involved in LPS induced depressive-like behavior.

Depression disorder is a common mental illness, of which the pathogenesis is not well understood. Studies suggest that immunity imbalance and up-regulation of pro-inflammatory cytokines may be associated with the pathogenesis of depression. High-mobility group box 1 protein (HMGB1) has gained much attention as an important player in innate immune responses and an modulating factor in several inflammatory diseases. Here we sought to explore the role of HMGB1 in the development of depression. Depression model was established with low dose of lipopolysaccharide (LPS) administration. Depressive behavior was reflected with increased immobility time in tail suspension test. Accompanying with depressive-like behavior, translocation of HMGB1 from nuclei to cytoplasm was observed by immunofluorescence assays. Meanwhile, no significant necrosis was observed evaluated by hematoxylin-eosin staining. These data indicated that HMGB1 was released actively in the central nervous system. In addition, treating the mice with human recombinant HMGB1 (rHMGB1) could induce the development of depressive-like behavior. Blockage of HMGB1 with GZA abrogated the depressive-like behavior induced by LPS or rHMGB1. These results implicated that HMGB1 was involved in LPS-induced depressive-like behavior.