HIF-1beta determines ABCA1 expression under hypoxia in human macrophages.

Area of Science:

• Cardiovascular Biology
• Cellular Metabolism
• Molecular Regulation

Background:

• Atherosclerosis involves lipid-laden macrophages in hypoxic lesions.
• Reverse cholesterol transport, crucial for preventing atherosclerosis, may be affected by hypoxia.
• ATP-binding cassette transporter A1 (ABCA1) is key in reverse cholesterol transport.

Purpose of the Study:

• To investigate the impact of hypoxia on ABCA1 regulation and cholesterol efflux in human macrophages.
• To elucidate the role of hypoxia-inducible factor 1 (HIF-1) in this process.

Main Methods:

• Studied ABCA1 promoter activity and expression in human macrophages under hypoxic conditions.
• Investigated the binding of HIF-1 to the ABCA1 promoter.
• Analyzed ABCA1-mediated cholesterol efflux.
• Correlated ABCA1 and HIF-1beta expression in macrophages from human atherosclerotic lesions and pre-eclamptic placentas.

Main Results:

• Hypoxia and active HIF-1alpha significantly increased ABCA1 expression in macrophages.
• HIF-1 directly binds to the ABCA1 promoter, enhancing its activity.
• ABCA1 expression strongly correlated with HIF-1beta levels (r: 0.95-0.91).
• Hypoxia-induced cholesterol efflux via ABCA1 was regulated by HIF-1beta.
• In vivo, ABCA1 levels in macrophages from atherosclerotic lesions correlated with HIF-1beta expression.

Conclusions:

• HIF-1beta availability dictates ABCA1 expression and cholesterol efflux in macrophages under hypoxic conditions.
• This HIF-1beta-mediated regulation of ABCA1 contributes to atherosclerotic lesion progression.
• The findings may explain interpersonal variability in atherosclerosis development.