Cholesteryl ester hydroperoxides increase macrophage CD36 gene expression via PPARalpha.

Area of Science:

• Molecular biology
• Cardiovascular research
• Cell biology

Background:

• Macrophage uptake of oxidized low-density lipoprotein (LDL) is critical in atherosclerosis development.
• CD36 is a primary scavenger receptor mediating oxidized LDL internalization by macrophages.

Purpose of the Study:

• To investigate how copper-oxidized LDL and its components regulate CD36 expression in human macrophages.
• To elucidate the molecular pathways involved in CD36 gene regulation by oxidized LDL.

Main Methods:

• Treatment of differentiated human macrophages with copper-oxidized LDL and its derivatives.
• Quantitative analysis of CD36 mRNA levels.
• Reporter gene assays to assess promoter activity, specifically peroxisome-proliferator-activated-receptor responsive elements (PPRE).
• Electrophoretic mobility shift assays (EMSA) to study transcription factor binding.

Main Results:

• Oxidized cholesteryl ester hydroperoxides (CEOOH) significantly increased CD36 mRNA levels (2.5-fold).
• Both oxidized LDL and CEOOH treatments enhanced transcription from PPRE-containing promoters, mediated by PPARalpha or PPARgamma.
• EMSA confirmed increased binding of PPARalpha to the CD36 gene promoter PPRE following oxidized LDL or CEOOH treatment.

Conclusions:

• Oxidized cholesteryl ester hydroperoxides (CEOOH) within oxidized LDL are key drivers of increased CD36 gene expression.
• This upregulation occurs through a pathway involving the transcription factor PPARalpha.
• Findings highlight a specific mechanism contributing to the role of oxidized LDL in atherosclerosis pathogenesis.