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HDL-apoA-I exchange: rapid detection and association with atherosclerosis.

Borja MS, Zhao L, Hammerson B, Tang C, Yang R, Carson N, Fernando G, Liu X, Budamagunta MS, Genest J, Shearer GC, Duclos F, Oda MN - PLoS ONE (2013)

Bottom Line: Chemical modification of apoA-I also impairs its ability to exchange on and off HDL, a critical process in reverse cholesterol transport.In this study, we developed a method using electron paramagnetic resonance spectroscopy (EPR) to quantify HDL-apoA-I exchange.Using this approach, we measured the degree of HDL-apoA-I exchange for HDL isolated from rabbits fed a high fat, high cholesterol diet, as well as human subjects with acute coronary syndrome and metabolic syndrome.

View Article: PubMed Central - PubMed

Affiliation: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.

ABSTRACT
High density lipoprotein (HDL) cholesterol levels are associated with decreased risk of cardiovascular disease, but not all HDL are functionally equivalent. A primary determinant of HDL functional status is the conformational adaptability of its main protein component, apoA-I, an exchangeable apolipoprotein. Chemical modification of apoA-I, as may occur under conditions of inflammation or diabetes, can severely impair HDL function and is associated with the presence of cardiovascular disease. Chemical modification of apoA-I also impairs its ability to exchange on and off HDL, a critical process in reverse cholesterol transport. In this study, we developed a method using electron paramagnetic resonance spectroscopy (EPR) to quantify HDL-apoA-I exchange. Using this approach, we measured the degree of HDL-apoA-I exchange for HDL isolated from rabbits fed a high fat, high cholesterol diet, as well as human subjects with acute coronary syndrome and metabolic syndrome. We observed that HDL-apoA-I exchange was markedly reduced when atherosclerosis was present, or when the subject carries at least one risk factor of cardiovascular disease. These results show that HDL-apoA-I exchange is a clinically relevant measure of HDL function pertinent to cardiovascular disease.

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Related in: MedlinePlus

Oxidation of HDL by myeloperoxidase inhibits HDL-ApoA-I exchange.Human HDL from healthy, fasted volunteers (n = 3) was incubated at 37°C with increasing concentrations of H2O2 in the presence (open squares) or absence (closed circles) of 50 nM MPO. Reactions were performed at a constant apoA-I concentration of 10 mg/dL. Following oxidation, HAE was analyzed by EPR as described in materials and methods. Statistically significant differences are indicated (*P<0.05 and **P<0.01). Two-tailed Student's t-tests were performed on each pair of samples at their respective concentration.
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pone-0071541-g003: Oxidation of HDL by myeloperoxidase inhibits HDL-ApoA-I exchange.Human HDL from healthy, fasted volunteers (n = 3) was incubated at 37°C with increasing concentrations of H2O2 in the presence (open squares) or absence (closed circles) of 50 nM MPO. Reactions were performed at a constant apoA-I concentration of 10 mg/dL. Following oxidation, HAE was analyzed by EPR as described in materials and methods. Statistically significant differences are indicated (*P<0.05 and **P<0.01). Two-tailed Student's t-tests were performed on each pair of samples at their respective concentration.

Mentions: Previously, we observed that oxidation of lipid-free apoA-I by MPO reduces the rate of HAE with reconstituted HDL [25], concomitant with diminished cholesterol efflux capacity [44], [45]. To determine if impairment of HAE by MPO oxidation could be detected by EPR, we exposed purified human HDL to MPO-H2O2 or H2O2 alone for 30 minutes at 37°C. ApoA-I concentration was kept constant at 10 mg/dL across samples. Concentrations of MPO and H2O2 were in the physiological to pathological range [52], and HAE was measured by EPR, as described above. While samples incubated with H2O2 alone showed only minor loss of HAE, samples exposed to the MPO-H2O2 system had significant declines in HAE in a dose-dependent manner (Figure 3), consistent with results from the fluorescence-based HAE assay [25], and with ABCA1-dependent cholesterol efflux in previous studies [53], [62]. Thus, the EPR-based approach is sufficiently sensitive to detect chemically-induced changes in HDL with physiologically relevant concentrations of MPO and H2O2.


HDL-apoA-I exchange: rapid detection and association with atherosclerosis.

Borja MS, Zhao L, Hammerson B, Tang C, Yang R, Carson N, Fernando G, Liu X, Budamagunta MS, Genest J, Shearer GC, Duclos F, Oda MN - PLoS ONE (2013)

Oxidation of HDL by myeloperoxidase inhibits HDL-ApoA-I exchange.Human HDL from healthy, fasted volunteers (n = 3) was incubated at 37°C with increasing concentrations of H2O2 in the presence (open squares) or absence (closed circles) of 50 nM MPO. Reactions were performed at a constant apoA-I concentration of 10 mg/dL. Following oxidation, HAE was analyzed by EPR as described in materials and methods. Statistically significant differences are indicated (*P<0.05 and **P<0.01). Two-tailed Student's t-tests were performed on each pair of samples at their respective concentration.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3756009&req=5

pone-0071541-g003: Oxidation of HDL by myeloperoxidase inhibits HDL-ApoA-I exchange.Human HDL from healthy, fasted volunteers (n = 3) was incubated at 37°C with increasing concentrations of H2O2 in the presence (open squares) or absence (closed circles) of 50 nM MPO. Reactions were performed at a constant apoA-I concentration of 10 mg/dL. Following oxidation, HAE was analyzed by EPR as described in materials and methods. Statistically significant differences are indicated (*P<0.05 and **P<0.01). Two-tailed Student's t-tests were performed on each pair of samples at their respective concentration.
Mentions: Previously, we observed that oxidation of lipid-free apoA-I by MPO reduces the rate of HAE with reconstituted HDL [25], concomitant with diminished cholesterol efflux capacity [44], [45]. To determine if impairment of HAE by MPO oxidation could be detected by EPR, we exposed purified human HDL to MPO-H2O2 or H2O2 alone for 30 minutes at 37°C. ApoA-I concentration was kept constant at 10 mg/dL across samples. Concentrations of MPO and H2O2 were in the physiological to pathological range [52], and HAE was measured by EPR, as described above. While samples incubated with H2O2 alone showed only minor loss of HAE, samples exposed to the MPO-H2O2 system had significant declines in HAE in a dose-dependent manner (Figure 3), consistent with results from the fluorescence-based HAE assay [25], and with ABCA1-dependent cholesterol efflux in previous studies [53], [62]. Thus, the EPR-based approach is sufficiently sensitive to detect chemically-induced changes in HDL with physiologically relevant concentrations of MPO and H2O2.

Bottom Line: Chemical modification of apoA-I also impairs its ability to exchange on and off HDL, a critical process in reverse cholesterol transport.In this study, we developed a method using electron paramagnetic resonance spectroscopy (EPR) to quantify HDL-apoA-I exchange.Using this approach, we measured the degree of HDL-apoA-I exchange for HDL isolated from rabbits fed a high fat, high cholesterol diet, as well as human subjects with acute coronary syndrome and metabolic syndrome.

View Article: PubMed Central - PubMed

Affiliation: Children's Hospital Oakland Research Institute, Oakland, California, United States of America.

ABSTRACT
High density lipoprotein (HDL) cholesterol levels are associated with decreased risk of cardiovascular disease, but not all HDL are functionally equivalent. A primary determinant of HDL functional status is the conformational adaptability of its main protein component, apoA-I, an exchangeable apolipoprotein. Chemical modification of apoA-I, as may occur under conditions of inflammation or diabetes, can severely impair HDL function and is associated with the presence of cardiovascular disease. Chemical modification of apoA-I also impairs its ability to exchange on and off HDL, a critical process in reverse cholesterol transport. In this study, we developed a method using electron paramagnetic resonance spectroscopy (EPR) to quantify HDL-apoA-I exchange. Using this approach, we measured the degree of HDL-apoA-I exchange for HDL isolated from rabbits fed a high fat, high cholesterol diet, as well as human subjects with acute coronary syndrome and metabolic syndrome. We observed that HDL-apoA-I exchange was markedly reduced when atherosclerosis was present, or when the subject carries at least one risk factor of cardiovascular disease. These results show that HDL-apoA-I exchange is a clinically relevant measure of HDL function pertinent to cardiovascular disease.

Show MeSH
Related in: MedlinePlus