Cholesterol efflux analyses using stable isotopes and mass spectrometry.

Area of Science:

• Biochemistry
• Cardiovascular Biology
• Analytical Chemistry

Background:

• Cholesterol efflux from macrophages and vascular walls initiates reverse cholesterol transport, crucial for cardiovascular health.
• Accurate measurement of cholesterol efflux is vital for understanding and treating cardiovascular diseases.

Purpose of the Study:

• To develop and validate a mass spectrometry-based assay for quantifying cholesterol efflux.
• To compare the performance of this new assay using deuterated cholesterol ([d(7)]cholesterol) against traditional radiolabeled tracers.

Main Methods:

• Utilized a triple-quadrupole electrospray ionization-MS instrument in direct infusion mode.
• Employed product ion scanning and neutral loss (NL) scanning to detect cholesterol and cholesteryl esters (CE).
• Substituted [d(7)]cholesterol for [(3)H]cholesterol in standard efflux assay conditions.

Main Results:

• The mass spectrometry assay successfully measured cellular and medium cholesterol content.
• Intracellular [d(7)]cholesterol mass was twofold greater than unlabeled cholesterol post-loading.
• Cholesterol efflux to apolipoprotein A-I and HDL was comparable between [d(7)]cholesterol and [(3)H]cholesterol tracers.

Conclusions:

• The developed mass spectrometry assay provides a robust method for assessing cholesterol efflux.
• This technique offers enhanced molecular detail compared to traditional methods.
• It enables the assessment of unlabeled cholesterol efflux to various acceptors, including apolipoprotein A-I.