Effect of HO-1 inhibition on vascular cell viability by HbLDL. (A-B) Cells grown in 12- or 24-well dishes were incubated for 24 hours in the presence of increasing concentrations of different LDL preparations, washed, and replated. After 6 hours attached cells were counted and the replating efficiency was calculated as described in “Materials and methods.” Survival of RAECs (A) and MPHs (B) after treatments by HbLDL (♦), CuLDL (•), and HbLDL in the presence of 10 μM SnPPIX (▴). Data are presented as mean percent survival ± SD relative to the effect of nLDL treatment at the same concentration. Results are from at least 3 different experiments performed in triplicate. *P < .05; **P < .005. (C) Apoptotic cell number in MPHs after treatment with 200 μg/mL concentration of indicated LDLs. After treatment with LDLs, MPHs were stained with annexin V and propidium iodide and apoptotic cell number was measured using flow cytometry. *P < .05 compared with nLDL, #P < .01 compared with HbLDL.