Sensitive UHPLC-MS/MS quantification method for 4β- and 4α-hydroxycholesterol in plasma for accurate CYP3A...

Area of Science:

• Biochemistry
• Analytical Chemistry
• Clinical Chemistry

Background:

• 4β-hydroxycholesterol (4β-OHC) is a biomarker for Cytochrome P450 (CYP)3A activity.
• 4β-OHC levels can be elevated by cholesterol autooxidation, independent of CYP3A activity.
• 4α-hydroxycholesterol (4α-OHC), a stereoisomer, reflects cholesterol autooxidation, not CYP3A activity.

Purpose of the Study:

• To develop and validate a sensitive method for simultaneous quantification of 4β-OHC and 4α-OHC in human plasma.
• To differentiate CYP3A activity from cholesterol autooxidation markers.

Main Methods:

• Ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS).
• Plasma sample preparation involving saponification, liquid-liquid extraction, and picolinic acid derivatization.
• Quantification using electrospray ionization and monitoring specific ion signals.

Main Results:

• The validated assay demonstrated a lower limit of quantification of 0.5 ng/ml for both analytes.
• High recovery rates (88.2–114.9%) and acceptable matrix effects (86.2–117.6%) were achieved.
• The method successfully measured 4β-OHC and 4α-OHC in plasma from healthy volunteers and chronic kidney disease patients.

Conclusions:

• A novel, sensitive, and validated UHPLC-MS/MS method for simultaneous 4β-OHC and 4α-OHC quantification in human plasma was established.
• This method can distinguish between CYP3A-mediated 4β-OHC formation and cholesterol autooxidation.
• The assay holds potential for accurate in vivo assessment of CYP3A activity and cholesterol oxidation status.