The present study was performed to clarify the effects of high mobility group box-1 protein (HMGB1), a recently described late-acting pro-inflammatory cytokine, on apoptosis of macrophages. Treatment with HMGB1 (0.01, 0.1, 1, 10 microg/ml for 24 h, or 10 microg/ml for 6, 12, 24, 48 h) resulted in a dose- and time-dependent induction of apoptosis in mice macrophages, peaked at 24 h after 10 microg/ml HMGB1 stimulation. HMGB1 treatment enhanced the receptor for advanced glycation end products (RAGE) expression and caspase-3 activation in macrophages. Blockage of RAGE and caspase-3 activation could significantly reduce apoptosis of macrophages induced by HMGB1. The activity of NF-kappaB/p65 in macrophages was decreased after HMGB1 treatment. These results suggested that HMGB1-induced apoptosis of macrophages in a dose- and time-dependent manner. RAGE, together with caspase-3 activation and inhibition of NF-kappaB signaling pathways, might be involved in the pathogenesis of macrophage apoptosis induced by HMGB1.