The various effects of fractionated oxidized low density lipoproteins on the growth of smooth muscle cells in culture

The effects of fractionated oxidized low density lipoproteins (oxidized LDL ) on the growth of vascular smooth muscle cells (VSMC) and their relationsh ip to the formation of lysophosphatidylcholine (lyso-PC) as well as the act ivation of protein kinase C (PKC) were studied, VSMC were isolated from por cine aorta by explant culture. LDL was isolated from porcine blood by seque ntial ultracentrifugation and oxidized LDL was obtained by incubating LDL w ith 5 mu M CuSO4 at 37 degrees C for various lengths of time. Our results s howed that LDL oxidized for 12 h and eluted from fast protein liquid chroma tography at 43 min inhibited the growth of VSMC, and that LDL oxidized for longer than 48 h and eluted at 48 min stimulated the growth of VSMC, The fo rmation of lyse-PC in the oxidized LDL correlated well with its stimulatory effect, suggesting that lyse-PC is responsible for the mitogenic effect of oxidized LDL. This stimulatory effect of oxidized LDL was inhibited by sta urosporine, a PKC inhibitor. Treatment with oxidized IDL increased the acti vity of membrane PKC, but it decreased that of cytosolic PKC, suggesting th e translocation of PKC from cytosol to the membrane in the presence of oxid ized LDL. These results suggested that the oxidized LDL-stimulated VSMC gro wth was mediated by the formation of lyse-PC and the activation of PKC.