Effect of APC on the HMGB1- and LPS-mediated expression of pattern recognition receptors on HUVECs and the proteolytic cleavage of HMGB1 by PC-gla/MeizoTh. (A) Confluent HUVECs were incubated with HMGB1 (1 μg/mL for 16 hours) with or without pretreating cells with protein C (100nM), APC (100nM), MeizoTh (2nM), and PC-gla/MeizoTh (2nM) for 3 hours as described in “Methods.” The expression of TLR2 (white bars), TLR4 (gray bars), and RAGE (black bars) on HUVECs was measured by a cell-based ELISA as described in “Methods.” (B) The same as panel A except that, instead of HMGB1, LPS (100 ng/mL for 4 hours) was used to stimulate HUVECs. All results are shown as means ± SDs of 5 different experiments. **P < .01 compared with HMGB1 in panel A and LPS in panel B.