Inhibition of oxidized LDL aggregation with the calcium channel blocker amlodipine: role of electrostatic interactions


      Atherogenic low-density lipoproteins (LDL) are characterized by elevations in cholesterol content and increased electronegativity, factors that contribute to aggregation and foam cell formation. This study was designed to test the effect of the positively charged calcium channel blocker (CCB) amlodipine on the aggregation properties of oxidized LDL lipids. Large unilamellar vesicles (LUVs) (100 nm diameter) labeled with a non-exchangeable marker [3H]cholesteryl hexadecyl ether were prepared with lipids extracted from human LDL following oxidation. The LUVs were shown to bind, in a reversible fashion, to charged diethylaminoethyl Sephadex columns. The addition of amlodipine inhibited binding of the oxidized LDL lipids in a dose-dependent fashion with an IC50 in the nanomolar range as a result of its high lipophilicity and positively charged amino group (pKa of 9.02). The activity of amlodipine was reproduced in model membranes that contained fixed amounts of charged phospholipid (glycerophospholipid) in a concentration-dependent manner. By contrast, drugs lacking a formal positive charge, including CCBs (felodipine, nifedipine, diltiazem, verapamil) and an angiotensin-converting enzyme-inhibitor (ramiprilate) had no effect on the column binding of the modified, electronegative lipids. These effects of amlodipine on LDL lipid aggregation and electrostatic properties may represent a novel antiatherosclerotic mechanism of action.



      LDL, low-density lipoproteins (), CCBs, calcium channel blockers (), ACE, angiotensin-converting enzyme (), POPG, 1-palmitoyl-2-oleoyl-phosphatidylglycerol (), POPC, 1-palmitoyl-2-oleoyl-phosphatidylcholine (), CHE, cholesteryl hexadecyl ether (), DEAE, diethylaminoethyl (), HPLC, high-performance liquid chromatography (), LUV, large unilamellar vesicle ()
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