SR-BI and signal transduction induced by HDL in EPCs. (A) Bar graph showing the number of migrated EPCs in modified Boyden chambers. After 7 days of culture, bone marrow EPCs isolated from control mice or AdA-I–treated C57BL/6 mice with SR-BI+/+ or SR-BI−/− bone marrow were seeded in the upper chamber. The lower chamber was supplemented with either HDL (100 μg/mL) or an equivalent amount of bovine serum albumin and the number of migrated cells per microscopy field was quantified after 5 hours (n = 4 for each group). (B) Bar graph showing the number of migrated EPCs in modified Boyden chambers. After 7 days of culture, EPCs isolated from chimeric SR-BI+/+ C57BL/6 mice (n = 6) were seeded in the upper chamber. The lower chamber was supplemented with either bovine serum albumin (100 μg/mL) or HDL (100 μg/mL). To inhibit ERK signaling and NO synthase activity, experiments were performed in the presence of U0126 (10 μM) and LNMA (2 mM), respectively. The number of migrated cells per microscopy field was quantified after 5 hours (n = 6 for each group). (C) p-ERK/ERK ratio determined by Western blot. After 7 days of culture, bone marrow EPCs isolated from SR-BI+/+ or SR-BI−/− mice were exposed to either bovine serum albumin (100 μg/mL) or HDL (100 μg/mL) for 2.5 minutes (n = 4 for each group). (D) NO production in cultured bone marrow EPCs. After 7 days of culture, bone marrow EPCs isolated from SR-BI+/+ or SR-BI−/− mice were exposed to either bovine serum albumin (100 μg/mL) or HDL (100 μg/mL) for 24 hours, and NO production (nanomoles per milligram of protein) was measured (n = 5 for each group). (E) NO production in cultured EPCs. After 7 days of culture, EPCs isolated from chimeric SR-BI+/+ C57BL/6 mice (n = 4) were exposed to either bovine serum albumin (100 μg/mL) or HDL (100 μg/mL). To inhibit ERK signaling, experiments were performed in the presence of U0126 (10 μM). NO production (nanomoles per milligram of protein) was determined (n = 4 for each group). (F) NO production in the bone marrow at day 35 after transfer with Adnull or saline (Controls) or AdA-I in C57BL/6 mice with SR-BI+/+ (n = 8 for each group) or SR-BI−/− bone marrow (n = 18 for each group). Data are mean plus or minus SEM.