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Oxidized LDL interacts strongly with dermatan sulfate proteoglycan
Wednesday 12 October 1994: Poster Abstracts Lipoproteins
scribed (Biochim Biophys Acta 1990; 1037: 48-57). Analysis of the LDL showed that light LDL (LDL-I; LDL-2) had higher levels of triglycerides while the protein concentration was greater in small dense LDL (LDL-5; LDL-6). LDL-3 and LDL-4 had intermediate lipid and protein content. For the cell-culture experiments the LDL subfractions LDL-1, LDL-3 and LDL-6 were incubated with human fibroblasts in which LDL receptors had previously been up-regulated. All LDL subfractions interacted with the cells in a concentration-dependent and saturable manner. The maximal capacities for binding, internalization and degradation, as well as the affinity to the receptors, were lowest for LDL 6 and highest for LDL-3. In competition studies, LDL-6 displaced total LDL less efficiently than LDL-1 or LDL-3. These data indicate that LDL-6 interacts with a lower affinity with fibroblast LDL receptors than other LDL subspecies. Therefore LDL-6 should remain longer in the circulation, making it more likely to undergo modification, which in turn may promote the development of atherosclerosis. The reduced ability of LDL-6 to interact with LDL receptors could be one reason for the atherogenicity of small dense LDL. + Preferential binding of small, dense LDL to human arterial proteoglycan Anber V, Griffin BA, Packard CJ, Shepherd J, Dept. of Path.
1
Biochem., Univ. of Glasgow, Royal Infirmary, Glasgow G4 OSF, UK
The association between a predominance of small, dense LDL and increased risk of coronary artery disease (CAD) may derive in part from differential binding of LDL subfractions to arterial wall proteoglycans (APO). The objective of this study was to determine whether a raised concentration of small, dense LDL (LDLIII, 1.044-1.064 g/ml) within total LDL increases the latter’s binding affinity for APG. Total LDL (1.019-1.063 g/ml) were isolated from the plasma of 16 CAD patients and their LDL subfraction profile was determined by density gradient centrifugation. Binding assays were performed using total LDL (0.1 mg!ml apo LDL) and a standard preparation of APG containing 2.5,~/ml chondroitin sulfate. The extent of APG-LDL complex formation was followed by absorbance after 30 min of incubation at 25°C (AU, absorbance unit at 600 nm). The extent of LDL-APG complex formation showed a positive association with the concentration of LDL-III within total LDL (r = 0.62, P < O.Ol), but a negative one with the concentration of the least dense LDL-I (r = -0.42, P < 0.02) and none with intermediate LDL-II. In addition the LDL-U-III ratio was negatively associated with APG binding (r=-O.58, P< 0.01). In terms of lipoprotein mass, the mean amount of complex formed per gram of LDL-I, LDL-II and LDLIII was 9.7AU, 2.6AU and 15.8AU respectively. In conclusion, the concentration of LDLIII within total LDL was shown to be the most significant determinant of LDLAPG complex formation. These findings demonstrate a potentially proatherogenic property of a raised LDL-III level and highlight the important role of APG as a sequestrant of small, dense LDL in the arterial intima-media. Oxidized LDL interacts strongly with dermatan sulfate proteoglycan Wasty F, Alavi MZ, Moore S, Dept. of Pathol., McGill Univ.,
1
Montreal, Canada
The interaction of proteoglycans and lipoproteins is widely regarded as an important underlying mechanism that facilitates lipid entrapment within atherosclerotic lesions. More recent reports suggest that some modification of LDL such as oxidation may augment its affinity for proteoglycans. Two major pmteoglycans implicated in atherogenesis are chondroitin sulfate-proteoglycan
217
(CS-PG) and dermatan sulfate-proteoglycan (DS-PG). We therefore asked whether oxidized LDL has a preferential affinity for CS-PG or DS-PG. Proteoglycans were extracted from human aortic tissues with a urea buffer, isolated by ion-exchange and gel-filtration chromatography. Plasma LDL was isolated by ultracentrifugation radiolabeled with lz51 and oxidized with Cu2+. The radiolabeled oxidized LDL was incubated with different amounts of CS-PG or DS-PG at 37°C in a low, physiological, or high ionic strength buffer containing Ca, Mg and 2% polyethylene glycol. Both CSPG and DS-PG showed a stronger affinity for oxidized LDL than for native LDL. The interaction at physiological, ionic strength required a minimum threshold of PG concentration. DS-PG consistently displayed stronger interaction with oxidized LDL than CS-PG. The result indicates that oxidized LDL interacts strongly with proteoglycans and shows a preferential affinity for DS-PG. The self-aggregation tendency of oxidized LDL added to its higher affinity for proteoglycans than native LDL may facilitate its accumulation in atherosclerotic lesions. Effect of postprandial state on lipids, apolipoproteins and lipoprotein particles in normal and hypertriglyceridemic subjects JRe DM, Alaupovic P, Gibson C, Huang M-m, Oklahoma Med.
1142
Res. Foundation. 825 NE 13th St., Oklahoma City, OK 73104, USA
The purpose of this study was to determine the effect of a typical American breakfast (1200 kcal with 40% calories from fat) on the postprandial (PP) levels of lipids, apolipoproteins and apo Bcontaining lipoprotein particles in normal subjects and patients with mild hypertriglyceridemia (HTG). In the PP plasma, TG concentradons were increased in all subjects, whereas a significant decrease in the apo C-III ratio was observed only in HTG patients. Among lipoprotein density subfractions, the major changes occurred only in d < 1.019 g/ml lipoproteins characterized by slight increases in the levels of TG and apolipoproteins B and CIII both in normal and HTG subjects. However, the measurement of cholesterol-rich LP-B and TG-rich LP-B, (the sum of LP-B:C, LP-B:C:E and LP-A-1I:B:C:D:E (LP-A-II:B,) particles) revealed that the elevated levels of LP-B,, but not LP-B, were the only statistically significant change in d < 1.019 g/ml lipoproteins in normal and HTG subjects. Furthermore, subfractionation of LP-B, showed a significant increase in the levels of LP-B:C and LPB:C:E (from 12.6 to 29.7 mg/dl) and a significant decrease in those of LP-A-II:Bc (from 11.3 to 5.3 mg/dl) in HTG subjects. In contrast, the increased level of LP-B, in normal subjects was due to an increase in LP-A-II:B, (from 1.2 to 8.8 mg/dl) rather than LP-B:C + LP-B:C:E. It has been shown previously that lipoprotein particles stimulated cholesterol accumulation in macrophages in the decreasing order LP-B:C + LP-B:C:E, LP-A-II:Bc and LPB (Karen et al Abstracts, Council on Arteriosclerosis, AHA 1992, p. 68). These results show that the PP state is characterized by marked changes in the concentration and composition of TG-rich lipoprotein subspecies, and that the postprandial has a greater atherogenic potential than the fasting state. Differential atherogenicity of complex apo B-containing lipoprotein particles Karen E, Koscec M, Corder C, Knight-Gibson C, Lee DM, Alaupovic P, Oklahoma Med. Rex Foundation, 825 NE 13th m
Street, Oklahoma City, OK 73104, USA
It is generally accepted that apolipoprotein (apo) B-containing lipoproteins (LP) are atherogenic. Studies from this and other laboratories have shown that these lipoproteins consist of chemi-
Atherosclerosis X, Montreal, October 1994
scribed (Biochim Biophys Acta 1990; 1037: 48-57). Analysis of the LDL showed that light LDL (LDL-I; LDL-2) had higher levels of triglycerides while the protein concentration was greater in small dense LDL (LDL-5; LDL-6). LDL-3 and LDL-4 had intermediate lipid and protein content. For the cell-culture experiments the LDL subfractions LDL-1, LDL-3 and LDL-6 were incubated with human fibroblasts in which LDL receptors had previously been up-regulated. All LDL subfractions interacted with the cells in a concentration-dependent and saturable manner. The maximal capacities for binding, internalization and degradation, as well as the affinity to the receptors, were lowest for LDL 6 and highest for LDL-3. In competition studies, LDL-6 displaced total LDL less efficiently than LDL-1 or LDL-3. These data indicate that LDL-6 interacts with a lower affinity with fibroblast LDL receptors than other LDL subspecies. Therefore LDL-6 should remain longer in the circulation, making it more likely to undergo modification, which in turn may promote the development of atherosclerosis. The reduced ability of LDL-6 to interact with LDL receptors could be one reason for the atherogenicity of small dense LDL. + Preferential binding of small, dense LDL to human arterial proteoglycan Anber V, Griffin BA, Packard CJ, Shepherd J, Dept. of Path.
1
Biochem., Univ. of Glasgow, Royal Infirmary, Glasgow G4 OSF, UK
The association between a predominance of small, dense LDL and increased risk of coronary artery disease (CAD) may derive in part from differential binding of LDL subfractions to arterial wall proteoglycans (APO). The objective of this study was to determine whether a raised concentration of small, dense LDL (LDLIII, 1.044-1.064 g/ml) within total LDL increases the latter’s binding affinity for APG. Total LDL (1.019-1.063 g/ml) were isolated from the plasma of 16 CAD patients and their LDL subfraction profile was determined by density gradient centrifugation. Binding assays were performed using total LDL (0.1 mg!ml apo LDL) and a standard preparation of APG containing 2.5,~/ml chondroitin sulfate. The extent of APG-LDL complex formation was followed by absorbance after 30 min of incubation at 25°C (AU, absorbance unit at 600 nm). The extent of LDL-APG complex formation showed a positive association with the concentration of LDL-III within total LDL (r = 0.62, P < O.Ol), but a negative one with the concentration of the least dense LDL-I (r = -0.42, P < 0.02) and none with intermediate LDL-II. In addition the LDL-U-III ratio was negatively associated with APG binding (r=-O.58, P< 0.01). In terms of lipoprotein mass, the mean amount of complex formed per gram of LDL-I, LDL-II and LDLIII was 9.7AU, 2.6AU and 15.8AU respectively. In conclusion, the concentration of LDLIII within total LDL was shown to be the most significant determinant of LDLAPG complex formation. These findings demonstrate a potentially proatherogenic property of a raised LDL-III level and highlight the important role of APG as a sequestrant of small, dense LDL in the arterial intima-media. Oxidized LDL interacts strongly with dermatan sulfate proteoglycan Wasty F, Alavi MZ, Moore S, Dept. of Pathol., McGill Univ.,
1
Montreal, Canada
The interaction of proteoglycans and lipoproteins is widely regarded as an important underlying mechanism that facilitates lipid entrapment within atherosclerotic lesions. More recent reports suggest that some modification of LDL such as oxidation may augment its affinity for proteoglycans. Two major pmteoglycans implicated in atherogenesis are chondroitin sulfate-proteoglycan
217
(CS-PG) and dermatan sulfate-proteoglycan (DS-PG). We therefore asked whether oxidized LDL has a preferential affinity for CS-PG or DS-PG. Proteoglycans were extracted from human aortic tissues with a urea buffer, isolated by ion-exchange and gel-filtration chromatography. Plasma LDL was isolated by ultracentrifugation radiolabeled with lz51 and oxidized with Cu2+. The radiolabeled oxidized LDL was incubated with different amounts of CS-PG or DS-PG at 37°C in a low, physiological, or high ionic strength buffer containing Ca, Mg and 2% polyethylene glycol. Both CSPG and DS-PG showed a stronger affinity for oxidized LDL than for native LDL. The interaction at physiological, ionic strength required a minimum threshold of PG concentration. DS-PG consistently displayed stronger interaction with oxidized LDL than CS-PG. The result indicates that oxidized LDL interacts strongly with proteoglycans and shows a preferential affinity for DS-PG. The self-aggregation tendency of oxidized LDL added to its higher affinity for proteoglycans than native LDL may facilitate its accumulation in atherosclerotic lesions. Effect of postprandial state on lipids, apolipoproteins and lipoprotein particles in normal and hypertriglyceridemic subjects JRe DM, Alaupovic P, Gibson C, Huang M-m, Oklahoma Med.
1142
Res. Foundation. 825 NE 13th St., Oklahoma City, OK 73104, USA
The purpose of this study was to determine the effect of a typical American breakfast (1200 kcal with 40% calories from fat) on the postprandial (PP) levels of lipids, apolipoproteins and apo Bcontaining lipoprotein particles in normal subjects and patients with mild hypertriglyceridemia (HTG). In the PP plasma, TG concentradons were increased in all subjects, whereas a significant decrease in the apo C-III ratio was observed only in HTG patients. Among lipoprotein density subfractions, the major changes occurred only in d < 1.019 g/ml lipoproteins characterized by slight increases in the levels of TG and apolipoproteins B and CIII both in normal and HTG subjects. However, the measurement of cholesterol-rich LP-B and TG-rich LP-B, (the sum of LP-B:C, LP-B:C:E and LP-A-1I:B:C:D:E (LP-A-II:B,) particles) revealed that the elevated levels of LP-B,, but not LP-B, were the only statistically significant change in d < 1.019 g/ml lipoproteins in normal and HTG subjects. Furthermore, subfractionation of LP-B, showed a significant increase in the levels of LP-B:C and LPB:C:E (from 12.6 to 29.7 mg/dl) and a significant decrease in those of LP-A-II:Bc (from 11.3 to 5.3 mg/dl) in HTG subjects. In contrast, the increased level of LP-B, in normal subjects was due to an increase in LP-A-II:B, (from 1.2 to 8.8 mg/dl) rather than LP-B:C + LP-B:C:E. It has been shown previously that lipoprotein particles stimulated cholesterol accumulation in macrophages in the decreasing order LP-B:C + LP-B:C:E, LP-A-II:Bc and LPB (Karen et al Abstracts, Council on Arteriosclerosis, AHA 1992, p. 68). These results show that the PP state is characterized by marked changes in the concentration and composition of TG-rich lipoprotein subspecies, and that the postprandial has a greater atherogenic potential than the fasting state. Differential atherogenicity of complex apo B-containing lipoprotein particles Karen E, Koscec M, Corder C, Knight-Gibson C, Lee DM, Alaupovic P, Oklahoma Med. Rex Foundation, 825 NE 13th m
Street, Oklahoma City, OK 73104, USA
It is generally accepted that apolipoprotein (apo) B-containing lipoproteins (LP) are atherogenic. Studies from this and other laboratories have shown that these lipoproteins consist of chemi-
Atherosclerosis X, Montreal, October 1994