The cathepsin L/V inhibitor SID attenuated l‐Hcy‐induced endothelial inflammation in HUVECs. (A) HUVECs were incubated separately with either 2.0 mM l‐Hcy, 30 μM SID or l‐Hcy + SID for 24 h; the cathepsin V activity of a cell protein extract was analysed. (B) The HUVECs described in (A) were subsequently co‐cultured with THP‐1 cells for 30 min; next, the supernatants and unbound THP‐1 cells were discarded, and adherent THP‐1 cells were counted. (C) The HUVECs were seeded into the bottom chambers of transwell plates overnight and treated with l‐Hcy and SID as described in (A); neutrophils were added to the top chambers and allowed to migrate for 2 h before the number of neutrophils in the bottom wells were counted. (D, E) The mRNA levels and supernatant levels of IL‐6, IL‐8 and TNF‐α were determined separately by real‐time PCR and ELISA. The data shown are the mean ± SD of five independent experiments. *
P < 0.05.