Oxidation of methionine residues to methionine sulfoxides does not decrease potential antiatherogenic properties of...

Area of Science:

• Lipid metabolism and cardiovascular disease research.
• Biochemistry and structural biology of lipoproteins.
• Oxidative stress and its biological consequences.

Background:

• High density lipoproteins (HDL) possess antiatherogenic properties.
• Oxidation of apolipoprotein A-I (apoA-I), a key HDL component, can occur.
• Specific methionine residues in apoA-I are hypothesized to be crucial for HDL function.

Purpose of the Study:

• To identify oxidized methionine residues in apoA-I (+32).
• To investigate the impact of apoA-I oxidation on its secondary structure, lipid affinity, and cholesterol efflux capacity.
• To assess the effect of oxidized apoA-I on reconstituted HDL's interaction with LCAT and CETP.

Main Methods:

• Amino acid sequencing and mass spectrometry to identify Met(O) residues.
• Circular dichroism to assess secondary structure.
• Lipid-binding assays using phospholipid vesicles.
• Macrophage assays for cholesterol and phospholipid efflux.
• Enzyme assays for LCAT activity and CETP-mediated dissociation.

Main Results:

• Methionine residues Met(86) and Met(112) were identified as oxidized to Met sulfoxides (Met(O)) in apoA-I(+32).
• Selective oxidation did not alter apoA-I secondary structure or LCAT affinity.
• Oxidized apoA-I showed increased affinity for lipids and enhanced cholesterol efflux from macrophages.
• Cholesteryl ester transfer protein dissociated more readily from reconstituted HDL containing oxidized apoA-I.

Conclusions:

• Selective oxidation of Met residues in apoA-I enhances its antiatherogenic activities.
• Oxidized apoA-I demonstrates improved lipid removal from macrophages.
• HDL's role in detoxifying lipid hydroperoxides may contribute to its antiatherogenic potential.