A potential role for sterol 27-hydroxylase in atherogenesis.

Abstract

OBJECTIVE:

27-hydroxycholesterol is the product of the mitochondrial cytochrome P450 sterol 27-hydroxylase, a key enzyme in cholesterol metabolism present in most tissues of the body. 27-hydroxycholesterol increases in abundance with progression of human atherosclerotic lesions, therefore the aim of this study was to determine the pattern of sterol 27-hydroxylase gene expression in normal and diseased arteries and to identify the cell types responsible for its expression.

METHODS:

Reverse transcription-polymerase chain reaction (RT-PCR) analysis and in situ hybridisation, utilising a sterol 27-hydroxylase cDNA probe, and immunohistochemistry, utilising an antibody to sterol 27-hydroxylase, together with an antibody to smooth muscle cell alpha-actin and an antibody to CD68, a marker for macrophages, were used to study expression of 27-hydroxylase in arterial specimens. In addition, RT-PCR was used to study expression of 27-hydroxylase in cultured macrophages and smooth muscle cells.

RESULTS:

Semi-quantitative RT-PCR analysis of normal and atherosclerotic human aortas showed that 27-hydroxylase is constitutively expressed in the normal artery wall, and is substantially up-regulated in atherosclerosis. RT-PCR analysis of 27-hydroxylase expression in vitro demonstrated that macrophages constitutively express high levels throughout their differentiation in culture whilst de-differentiated vascular smooth muscle cells express very low levels. In situ hybridisation revealed that in normal artery and fatty streaks, expression of mRNA for 27-hydroxylase was low in the media, but higher in intimal smooth muscle cells. The macrophages of fatty streaks expressed low or undetectable levels of 27-hydroxylase. However in advanced lesions the highest expression of 27-hydroxylase was detectable in macrophages. Immunohistochemistry demonstrated that high levels of 27-hydroxylase protein occurred in macrophages near the shoulder region of plaques, at the edge of the lipid core.

CONCLUSIONS:

27-hydroxylase may constitute a protective mechanism for removing cholesterol from macrophages and smooth muscle cells. Genetic heterogeneity resulting in differences in sterol 27-hydroxylase activity between individuals may affect their ability to deal with accumulated cholesterol in the arterial intima, and hence their relative degree of predisposition to atherosclerosis.

• Authors: C M Shanahan, K L Carpenter, N R Cary
• Journal: Atherosclerosis (Atherosclerosis) Vol. 154 Issue 2 Pg. 269-76 (Feb 01 2001) ISSN: 0021-9150 [Print] Ireland
• PMID: 11166758 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Actins
• Antibodies
• Antigens, CD
• Antigens, Differentiation, Myelomonocytic
• Biomarkers
• CD68 antigen, human
• DNA Probes
• DNA, Complementary
• Hydroxycholesterols
• RNA, Messenger
• 27-hydroxycholesterol
• Cytochrome P-450 Enzyme System
• Steroid Hydroxylases
• CYP27A1 protein, human
• Cholestanetriol 26-Monooxygenase

Topics

• Actins (immunology, metabolism)
• Adolescent
• Adult
• Aged
• Antibodies (analysis)
• Antigens, CD (immunology)
• Antigens, Differentiation, Myelomonocytic (immunology)
• Aorta (enzymology, pathology)
• Arteriosclerosis (enzymology, pathology)
• Biomarkers
• Cells, Cultured
• Child
• Child, Preschool
• Cholestanetriol 26-Monooxygenase
• Coronary Vessels (enzymology, pathology)
• Cytochrome P-450 Enzyme System (genetics, immunology, metabolism)
• DNA Probes (chemistry)
• DNA, Complementary (analysis)
• Female
• Gene Expression
• Humans
• Hydroxycholesterols (metabolism)
• In Situ Hybridization
• Macrophages (enzymology, immunology)
• Male
• Middle Aged
• Muscle, Smooth, Vascular (enzymology, pathology)
• RNA, Messenger (genetics, metabolism)
• Reverse Transcriptase Polymerase Chain Reaction
• Steroid Hydroxylases (genetics, immunology, metabolism)
• Tunica Intima (enzymology, pathology)