Lipoprotein-X reduces LDL atherogenicity in primary biliary cirrhosis by preventing LDL oxidation

Hypercholesterolemic human LDL contains oxidized subfractions that have atherogenic properties. Paradoxically, atherosclerosis incidence is low in patients with primary biliary cirrhosis (PBC), a disease characterized by marked increases in plasma LDL, including the LDL subfraction lipoprotein-X (Lp-X). To investigate the mechanisms underlying this paradox, we first examined the propensity to oxidation of unfractionated LDL isolated from PBC patients. After prolonged incubation with copper, PBC-LDL failed to increase the oxidation index or electrophoretic mobility noted in control LDL. An admixture of PBC-LDL or Lp-X with control LDL prevented oxidation of the latter in a dose-dependent manner. PBC-LDL was also noncompetitive against copper-oxidized LDL (oxLDL) for binding with a murine monoclonal anti-oxLDL antibody in a competitive ELISA. OxLDL exerts its proapoptotic and antiangiogenic effects in part by inhibiting fibroblast growth factor 2 (FGF2) expression. Preincubation of oxLDL with PBC-LDL, but not control LDL, attenuated the inhibitory effects of oxLDL on FGF2 expression in cultured bovine aortic endothelial cells (ECs). The antioxidant and prosurvival properties of PBC-LDL diminished after the patients underwent orthotopic liver transplantation.These results suggest that Lp-X reduces LDL atherogenicity by preventing LDL oxidation to protect EC integrity in the presence of hypercholesterolemia. They also suggest that altering LDL composition may be as important as reducing LDL concentration in preventing or treating atherosclerosis. Hypercholesterolemic human LDL contains oxidized subfractions that have atherogenic properties. Paradoxically, atherosclerosis incidence is low in patients with primary biliary cirrhosis (PBC), a disease characterized by marked increases in plasma LDL, including the LDL subfraction lipoprotein-X (Lp-X). To investigate the mechanisms underlying this paradox, we first examined the propensity to oxidation of unfractionated LDL isolated from PBC patients. After prolonged incubation with copper, PBC-LDL failed to increase the oxidation index or electrophoretic mobility noted in control LDL. An admixture of PBC-LDL or Lp-X with control LDL prevented oxidation of the latter in a dose-dependent manner. PBC-LDL was also noncompetitive against copper-oxidized LDL (oxLDL) for binding with a murine monoclonal anti-oxLDL antibody in a competitive ELISA. OxLDL exerts its proapoptotic and antiangiogenic effects in part by inhibiting fibroblast growth factor 2 (FGF2) expression. Preincubation of oxLDL with PBC-LDL, but not control LDL, attenuated the inhibitory effects of oxLDL on FGF2 expression in cultured bovine aortic endothelial cells (ECs). The antioxidant and prosurvival properties of PBC-LDL diminished after the patients underwent orthotopic liver transplantation. These results suggest that Lp-X reduces LDL atherogenicity by preventing LDL oxidation to protect EC integrity in the presence of hypercholesterolemia. They also suggest that altering LDL composition may be as important as reducing LDL concentration in preventing or treating atherosclerosis. Hypercholesterolemia increases atherosclerosis incidence in the general population but not in patients with primary biliary cirrhosis (PBC), a cholestatic liver disease often associated with marked increases in plasma LDL cholesterol (LDL-C) (1National Cholesterol Education ProgramThird report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III) final report.Circulation. 2002; 106: 3143-3421Crossref PubMed Scopus (11480) Google Scholar, 2Kaplan M.M. Primary biliary cirrhosis.N. Engl. J. Med. 1996; 335: 1570-1580Crossref PubMed Scopus (500) Google Scholar, 3Jahn C.E. Schaefer E.J. Taam L.A. Hoofnagle J.H. Lindgren F.T. Albers J.J. Jones E.A. Brewer H.B. Lipoprotein abnormalities in primary biliary cirrhosis: association with hepatic lipase inhibition as well as altered cholesterol esterification.Gastroenterology. 1985; 89: 1266-1278Abstract Full Text PDF PubMed Scopus (142) Google Scholar). Despite the highly increased cholesterol levels, prospective observation for a median of 7.4 years of 312 patients with PBC of various stages found no increased incidence of atherosclerotic death compared with age- and sex-matched controls (4Crippin J.S. Lindor K.D. Jorgensen R. Kottke B.A. Harrison J.M. Murtaugh P.A. Dickson E.R. Hypercholesterolemia and atherosclerosis in primary biliary cirrhosis: what is the risk?.Hepatology. 1992; 15: 858-862Crossref PubMed Scopus (123) Google Scholar). Factors that may account for this apparent paradox are not clearly defined. Lipoprotein-X (Lp-X), an LDL rich in phospholipid and nonesterified cholesterol but poor in cholesteryl ester, triglyceride, and protein, is characteristic of advanced PBC (3Jahn C.E. Schaefer E.J. Taam L.A. Hoofnagle J.H. Lindgren F.T. Albers J.J. Jones E.A. Brewer H.B. Lipoprotein abnormalities in primary biliary cirrhosis: association with hepatic lipase inhibition as well as altered cholesterol esterification.Gastroenterology. 1985; 89: 1266-1278Abstract Full Text PDF PubMed Scopus (142) Google Scholar). In all three isoforms, Lp-X1, Lp-X2, and Lp-X3, the particles are rich in phospholipids (65–67%) and cholesterol (23–27%) but poor in cholesteryl esters (0.5–2%), triglycerides (2–3%), and protein (3–7%), giving them a hydrated density similar to that of LDL (5Patsch J.R. Aune K.C. Gotto Jr., A.M. Morrisett J.D. Isolation, chemical characterization, and biophysical properties of three different abnormal lipoproteins: LP-X1, LP-X2, and LP-X3.J. Biol. Chem. 1997; 252: 2113-2120Abstract Full Text PDF Google Scholar). The lack of association between high LDL-C and atherosclerosis in PBC raises the question of the atherogenic properties of PBC-LDL and prompted us to investigate the physiological relevance of Lp-X in atherogenesis. The bioactivities of oxidized products of LDL may account for LDL atherogenicity (6Steinberg D. Witztum J.L. Is the oxidative modification hypothesis relevant to human atherosclerosis? Do the antioxidant trials conducted to date refute the hypothesis?.Circulation. 2002; 105: 2107-2111Crossref PubMed Scopus (462) Google Scholar). If PBC-LDL is resistant to oxidation, a lesser amount of such oxidized metabolites will be accumulated. Therefore, we first assessed the susceptibility of PBC-LDL to oxidation. Because PBC-LDL may contain a variable percentage of Lp-X, we also tested whether Lp-X renders LDL resistant to oxidants. Fibroblast growth factor 2 (FGF2), by functioning as an autocrine and paracrine agent, regulates the proliferation and apoptosis of vascular endothelial cells (ECs) by activating the phosphatidylinositol 3-kinase-protein kinase Akt pathway (7Raffioni S. Bradshaw R.A. Activation of phosphatidylinositol 3-kinase by epidermal growth factor, basic fibroblast growth factor, and nerve growth factor in PC12 pheochromocytoma cells.Proc. Natl. Acad. Sci. USA. 1992; 89: 9121-9125Crossref PubMed Scopus (119) Google Scholar, 8Chen C.H. Poucher S.M. Liu J. Henry P.D. Fibroblast growth factor 2: from laboratory evidence to clinical application.Curr. Vasc. Pharmacol. 2004; 2: 33-43Crossref PubMed Scopus (61) Google Scholar). Both copper-oxidized LDL (oxLDL) and hypercholesterolemic electronegative LDL inhibit proliferation and induce apoptosis in ECs in part by downregulating expression of the FGF2 gene (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar, 10Chen C.H. Jiang W. Via D.P. Luo S. Li T.R. Lee Y.T. Henry P.D. Oxidized low-density lipoproteins inhibit endothelial cell proliferation by suppressing basic fibroblast growth factor expression.Circulation. 2000; 101: 171-177Crossref PubMed Scopus (95) Google Scholar, 11Chang P.Y. Luo S. Jiang T. Lee Y.T. Lu S.C. Henry P.D. Chen C.H. Oxidized low-density lipoprotein down-regulates endothelial bFGF through a pertussis toxin-sensitive G-protein pathway: mediator role of platelet-activating factor-like phospholipids.Circulation. 2001; 104: 588-593Crossref PubMed Scopus (46) Google Scholar). Whether PBC-LDL regulates FGF2-mediated survival mechanisms depends on its effect on FGF2 expression. This important issue was also addressed in this study. EDTA was from Becton-Dickinson (Rutherford, NJ). The Superose 6HR 10/30 column was from Pharmacia LKB (Uppsala, Sweden). Enzymatic kits for cholesterol and triglyceride analyses were from E. Merck (Darmstadt, Germany). The Beckman Paragon system was from Beckman (Palo Alto, CA). DMEM was from Invitrogen (Carlsbad, CA). Nonidet P-40 was from Sigma (St. Louis, MO). LDL (d = 1.019–1.063 g/ml) was isolated by sequential ultracentrifugation from the plasma of six PBC patients after fasting (Table 1). To isolate Lp-X, PBC-LDL and LDL obtained from healthy, normolipidemic subjects were subjected to gel filtration chromatography using a Superose 6HR 10/30 column at 0.25 ml/min and collected in 0.5 ml fractions (12Franceschini G. Busnach G. Chiesa G. Sirtori C.R. Management of lipoprotein-X accumulation in severe cholestasis by semi-selective LDL-apheresis.Am. J. Med. 1991; 90: 633-638Abstract Full Text PDF PubMed Scopus (8) Google Scholar). OxLDL was prepared by incubating control LDL with 10 μM CuSO4 for 24 h as previously described (13Steinbrecher U.P. Parthasarathy S. Leake D.S. Witztum J.L. Steinberg D. Modification of low density lipoprotein by endothelial cells involves lipid peroxidation and degradation of low density lipoprotein phospholipids.Proc. Natl. Acad. Sci. USA. 1984; 81: 3883-3887Crossref PubMed Scopus (1419) Google Scholar). Protein in LDL preparations was estimated by the Lowry method (14Peterson G.L. A simplification of the protein assay method of Lowry et al. which is more generally applicable.Anal. Biochem. 1977; 83: 346-356Crossref PubMed Scopus (7154) Google Scholar), and thiobarbituric acid-reactive substances (TBARS) were assayed as a measure of oxidative lipid modification (13Steinbrecher U.P. Parthasarathy S. Leake D.S. Witztum J.L. Steinberg D. Modification of low density lipoprotein by endothelial cells involves lipid peroxidation and degradation of low density lipoprotein phospholipids.Proc. Natl. Acad. Sci. USA. 1984; 81: 3883-3887Crossref PubMed Scopus (1419) Google Scholar). Cholesterol and triglyceride concentrations in plasma and LDL preparations were determined enzymatically as previously described (15Lu S.C. Wu W.H. Lee C.A. Chou H.F. Lee H.R. Huang P.C. LDL of Taiwanese vegetarians are less oxidizable than those of omnivores.J. Nutr. 2000; 130: 1591-1596Crossref PubMed Scopus (43) Google Scholar).TABLE 1Characteristics and antioxidation index in six patients with primary biliary cirrhosisPatient No.AgeSexScheuer StageTotal CholesterolLDL CholesterolLipoprotein-X Content of LDLPlasma BilirubinAntioxidation Indexyearsmmol/lmmol/l%μmol/l147Female III34.131.790222.35+241Female III31.728.488201.85+334Female II29.327.16578.74+454Female not The antioxidation index was determined by the of a LDL to inhibit the mobility of control LDL on gel after h of = in a not The antioxidation index was determined by the of a LDL to inhibit the mobility of control LDL on gel after h of = The of LDL preparations was determined by electrophoretic mobility after to 10 μM CuSO4 at for h on using the Beckman Paragon system G. to oxidation of low-density PubMed Scopus Google Scholar). A competitive was using an monoclonal a from at the for and J. S. D. Oxidized LDL and LDL in patients with and PubMed Scopus Google Scholar). In oxLDL was as the was in the presence or of PBC-LDL, and control LDL. were for 2 h at After the were for h with against and The was as previously described J. S. D. Oxidized LDL and LDL in patients with and PubMed Scopus Google Scholar), and the was at Primary of bovine aortic endothelial cells were and as previously described C.H. Jr., J. Li Luo S. Gotto Jr., A.M. Henry P.D. effects of and oxidized LDL on endothelial growth in aortic role of basic fibroblast growth Vasc. Biol. 1997; PubMed Scopus Google Scholar). at in DMEM with and and 0.25 were to were three with and for h with control LDL oxLDL or PBC-LDL for 24 the of and FGF2 protein, cells were in well of cell FGF2 concentrations in cell prepared with Nonidet P-40 were by using a previously described C.H. Jr., J. Li Luo S. Gotto Jr., A.M. Henry P.D. effects of and oxidized LDL on endothelial growth in aortic role of basic fibroblast growth Vasc. Biol. 1997; PubMed Scopus Google Scholar), FGF2 concentrations were estimated at using FGF2 were determined by of the was in 10 of of murine for at was to described previously C.H. Jiang W. Via D.P. Luo S. Li T.R. Lee Y.T. Henry P.D. Oxidized low-density lipoproteins inhibit endothelial cell proliferation by suppressing basic fibroblast growth factor expression.Circulation. 2000; 101: 171-177Crossref PubMed Scopus (95) Google Scholar). The FGF2 were and an was with the and A of was on a and with were by The of the between was assessed by a for and by for of were are as the six PBC patients were three were and was The percentage of LDL as Lp-X increased with the of the disease and was as high as of LDL in the patients (Table 1). Because the of PBC-LDL depends on its of Lp-X we the properties of PBC-LDL obtained from the with the Lp-X The was a in for of and antibody of of of of cholesterol of and LDL-C of and liver results were with Despite marked and and were The of or A was of the LDL by Superose 6HR 10/30 column chromatography that of the LDL was for by Lp-X, as an in fractions compared with a in fractions for control LDL 1). of the patients a of or that were of the LDL to for to h failed to induce a in mobility on gel and LDL protein not In LDL isolated from a was the by 2 h concentration increased to at with the unfractionated LDL control LDL and prevented a in control LDL mobility The of inhibition in electrophoretic mobility by PBC-LDL well with the PBC-LDL to control LDL. in an admixture of PBC-LDL and control LDL at or a effect on the mobility after to for h To the antioxidant properties of the subfractions of PBC-LDL, electrophoretic mobility was assessed in the Lp-X and the LDL from the 2 h of the Lp-X was resistant to oxidation, LDL electrophoretic mobility to the of LDL oxidation resistant after admixture with an amount of Lp-X the of PBC-LDL to the electrophoretic mobility as an we found that such an on the of Lp-X (Table 1). In the PBC-LDL a marked antioxidant which was in PBC-LDL with plasma concentrations of a increased as Lp-X increased (Table was not in effect of LDL on LDL oxidation. and control unfractionated were at or as and with 10 μM CuSO4 for LDL oxidation was assessed by gel using PBC-LDL obtained from patients similar results to on the Lp-X of isolated Lp-X and LDL of a PBC Lp-X and LDL were with 10 μM CuSO4 for h as by gel of Lp-X and LDL fractions with 10 μM CuSO4 for h as The of LDL was also assessed by competitive using the anti-oxLDL monoclonal antibody LDL at more than concentrations failed to with oxLDL for binding The binding of LDL was to that of control LDL, an of survival was by and FGF2 expression in cultured Treatment of with oxLDL in FGF2 and cell control LDL PBC-LDL with for to 24 h failed to the FGF2 protein Preincubation of oxLDL with PBC-LDL attenuated FGF2 in a dose-dependent with control LDL not the inhibitory effect of oxLDL The FGF2 was also by oxLDL but not by Preincubation of oxLDL with PBC-LDL also attenuated FGF2 In with the in FGF2 oxLDL by PBC-LDL no Preincubation of oxLDL with PBC-LDL, but not control LDL, prevented the inhibitory effect of oxLDL not After the an orthotopic liver in cholesterol 2 to Lp-X and the LDL no antioxidant not In to LDL, which failed to induce a in mobility after oxidation LDL electrophoretic mobility to the of The was not different from that of control LDL. control LDL with LDL no attenuated the mobility of control LDL not Hypercholesterolemic human plasma contains atherogenic LDL subfractions that inhibit proliferation and increase apoptosis in ECs and induce (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar, C.Y. J.L. Chen Chen C.H. Pownall H.J. Isolation, characterization, and of subfractions of low-density Vasc. Biol. 2003; PubMed Scopus Google Scholar). the highly increased cholesterol and marked found in patients with PBC M.M. Primary biliary cirrhosis.N. Engl. J. Med. 1996; 335: 1570-1580Crossref PubMed Scopus (500) Google Scholar, 3Jahn C.E. Schaefer E.J. Taam L.A. Hoofnagle J.H. Lindgren F.T. Albers J.J. Jones E.A. Brewer H.B. Lipoprotein abnormalities in primary biliary cirrhosis: association with hepatic lipase inhibition as well as altered cholesterol esterification.Gastroenterology. 1985; 89: 1266-1278Abstract Full Text PDF PubMed Scopus (142) Google Scholar), the incidence of atherosclerotic not increase in patients (4Crippin J.S. Lindor K.D. Jorgensen R. Kottke B.A. Harrison J.M. Murtaugh P.A. Dickson E.R. Hypercholesterolemia and atherosclerosis in primary biliary cirrhosis: what is the risk?.Hepatology. 1992; 15: 858-862Crossref PubMed Scopus (123) Google Scholar). that LDL isolated from the plasma of PBC patients not normolipidemic LDL from oxidized but also prevented oxLDL from the survival in vascular The antioxidant effect of PBC-LDL on its Lp-X These may the LDL oxidation hypothesis for the of atherosclerosis. The atherogenic properties of LDL have to from oxidative modification of the lipoprotein (6Steinberg D. Witztum J.L. Is the oxidative modification hypothesis relevant to human atherosclerosis? Do the antioxidant trials conducted to date refute the hypothesis?.Circulation. 2002; 105: 2107-2111Crossref PubMed Scopus (462) Google Scholar, S. S. W. Chen Witztum J.L. LDL of oxidized LDL by and to atherosclerotic in Vasc. Biol. 2001; PubMed Scopus Google Scholar, S. G. in the oxidized of A role for and a Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, G.K. McIntyre T.M. factor and not is the oxidized phospholipid of high density lipoprotein Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). the incidence of is to the concentration of oxLDL by D. LDL as a of Med. PubMed Scopus Google Scholar, S.M. of high disease with oxidized LDL in the from the and Vasc. Biol. 2003; PubMed Scopus Google Scholar). LDL is a oxidized LDL that induce a of atherogenic effects in vascular ECs (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar, C.Y. J.L. Chen Chen C.H. Pownall H.J. Isolation, characterization, and of subfractions of low-density Vasc. Biol. 2003; PubMed Scopus Google Scholar, D. G. S. T. J. for and oxidation in to electronegative low density Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). Because electronegative LDL is more in hypercholesterolemic than normolipidemic human plasma (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar), hypercholesterolemic LDL have a susceptibility to oxidation than normolipidemic LDL. of to increase atherosclerosis incidence in PBC the question of whether PBC-LDL is resistant to oxidative including are important in the to the of PBC T. in primary biliary cirrhosis expression of and expression of 2002; Full Text Full Text PDF PubMed Scopus Google Scholar). In lipid peroxidation including plasma and and plasma are plasma such as are P.C. is a of primary biliary 2003; PubMed Scopus Google Scholar). to effects on the vascular have not In this severe biliary cirrhosis and of were not by or have the low atherosclerosis incidence in PBC to high plasma concentrations of and E.R. of lipoprotein particles in patients with primary biliary 1997; Full Text Full Text PDF PubMed Scopus Google and the observation that patients were M.M. Primary biliary cirrhosis.N. Engl. J. Med. 1996; 335: 1570-1580Crossref PubMed Scopus (500) Google Scholar). the of be disease in patients with LDL-C increased to the in PBC patients is well in patients of lipid or that PBC-LDL was resistant to oxidation, of the high of the preventing of the of the oxidizable are more the Lp-X isolated from PBC-LDL the from the resistant to oxidation. This may have to the of Lp-X than LDL for The of PBC-LDL to in the electrophoretic mobility of control LDL to the concentration These a for vascular in PBC than the and a physiological antioxidant in to inhibit LDL oxidation in J. R. and are for inhibiting plasma and low density lipoprotein lipid Biol. Chem. Full Text PDF PubMed Google Scholar). The increase in plasma with Lp-X may an role in LDL from oxidation in patients with the antioxidant effect of Lp-X in this was of was a lack of in Lp-X In this was as an for LDL oxidation. LDL oxidation is the of LDL oxidation in A of the of low density lipoprotein of lipid and Biochem. 2001; PubMed Scopus Google Scholar), and the are of physiological have that oxidized products of LDL by are similar to those in the presence of cells (13Steinbrecher U.P. Parthasarathy S. Leake D.S. Witztum J.L. Steinberg D. Modification of low density lipoprotein by endothelial cells involves lipid peroxidation and degradation of low density lipoprotein phospholipids.Proc. Natl. Acad. Sci. USA. 1984; 81: 3883-3887Crossref PubMed Scopus (1419) Google Scholar), and the properties of oxLDL are similar to those of atherogenic LDL isolated from hypercholesterolemic human plasma (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar, C.Y. J.L. Chen Chen C.H. Pownall H.J. Isolation, characterization, and of subfractions of low-density Vasc. Biol. 2003; PubMed Scopus Google Scholar). have to contain in that of lipid peroxidation and by the of human atherosclerotic J. 1992; PubMed Scopus Google Scholar). The role of as a in LDL oxidation may be by such as that inhibit LDL oxidation in S.M. of copper, but not by human low density lipoprotein for oxidative modification of Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, S.M. and on and oxidation of human low-density 1997; PubMed Scopus Google Scholar). In is that the antioxidant of Lp-X was by Lp-X its antioxidant unfractionated LDL was at and of Lp-X not FGF2 is a protein that exerts and effects by activating the phosphatidylinositol system and the (7Raffioni S. Bradshaw R.A. Activation of phosphatidylinositol 3-kinase by epidermal growth factor, basic fibroblast growth factor, and nerve growth factor in PC12 pheochromocytoma cells.Proc. Natl. Acad. Sci. USA. 1992; 89: 9121-9125Crossref PubMed Scopus (119) Google Scholar, 8Chen C.H. Poucher S.M. Liu J. Henry P.D. Fibroblast growth factor 2: from laboratory evidence to clinical application.Curr. Vasc. Pharmacol. 2004; 2: 33-43Crossref PubMed Scopus (61) Google Scholar). Both oxLDL and electronegative LDL FGF2 expression in to proliferation and increased apoptosis (9Chen C.H. Jiang T. Yang J.H. Jiang W. Lu J. Marathe G.K. Pownall H.J. Ballantyne C.M. McIntyre T.M. Henry P.D. Yang C.Y. Low-density lipoprotein in hypercholesterolemic human plasma induces vascular endothelial cell apoptosis by inhibiting fibroblast growth factor 2 transcription.Circulation. 2003; 107: 2102-2108Crossref PubMed Scopus (136) Google Scholar, 10Chen C.H. Jiang W. Via D.P. Luo S. Li T.R. Lee Y.T. Henry P.D. Oxidized low-density lipoproteins inhibit endothelial cell proliferation by suppressing basic fibroblast growth factor expression.Circulation. 2000; 101: 171-177Crossref PubMed Scopus (95) Google Scholar, 11Chang P.Y. Luo S. Jiang T. Lee Y.T. Lu S.C. Henry P.D. Chen C.H. Oxidized low-density lipoprotein down-regulates endothelial bFGF through a pertussis toxin-sensitive G-protein pathway: mediator role of platelet-activating factor-like phospholipids.Circulation. 2001; 104: 588-593Crossref PubMed Scopus (46) Google Scholar). In this PBC-LDL not inhibit FGF2 expression or in prevented the inhibitory effects of oxLDL on This be by of oxLDL after control LDL failed to effects after a similar These that PBC-LDL ECs in prevented the oxidation of LDL, as by of the part of LDL from the against oxidation. PBC-LDL attenuated the effects of LDL that oxidized on The is not at this Because platelet-activating factor or platelet-activating factor-like in oxLDL the bioactivities of the lipoprotein P.Y. Luo S. Jiang T. Lee Y.T. Lu S.C. Henry P.D. Chen C.H. Oxidized low-density lipoprotein down-regulates endothelial bFGF through a pertussis toxin-sensitive G-protein pathway: mediator role of platelet-activating factor-like phospholipids.Circulation. 2001; 104: 588-593Crossref PubMed Scopus (46) Google Scholar), is that PBC-LDL or Lp-X is rich in that in are to this The of the of the PBC LDL from oxidation after liver the antioxidant role of PBC-LDL to its Lp-X These results are not with the that the low incidence of atherosclerosis in PBC is a of increases in and In that PBC-LDL EC integrity by preventing LDL oxidation and the effects of LDL with of oxidative modification that may have in the is not at this the antioxidant effect of PBC-LDL be to its Lp-X The also suggest that the composition of LDL to resistant to may be as important as the plasma concentration of LDL in the or of atherosclerosis. This was by and from the National by and from National and by from the The are to for