HMGB1 inhibits monocyte apoptosis induced by ABT-737 (A,C) or staurosporine (B,D), which is reversed when monocytes are pretreated with a blocking TLR4 antibody, as evaluated by Annexin V (A,B) and TMRE (C,D) stainings. (E) U0126, a specific MEK/ERK inhibitor, inhibits the effect of rHMGB1 on TMRE fluorescence in monocytes. (F) rHMGB1 (100 ng/ml) induces phosphorylation of ERK in monocytes, which does not occur when monocytes are pretreated with a blocking TLR4 antibody. Data are presented as mean ± SD for N≥4 and at least three separate experiments in all studies. * p<0.05, # p<0.05, ** p<0.01 (Student’s t test).