Effect of oxidation of low-density lipoprotein on drug binding affinity studied by high performance frontal analysis-capillary electrophoresis

Abstract

The effect of oxidation of low-density lipoprotein (LDL) on the enantioselective drug binding affinity was investigated using high performance frontal analysis--capillary electrophoresis (HPFA-CE). Verapamil and nilvadipine enantiomers were used as the chiral model drugs. LDL was oxidized with copper sulfate for 0, 0.5, 1, 2, and 12 h at 37 degrees C. The HPFA-CE method enabled microdetermination of unbound drug concentrations in native and oxidized LDL solutions. It was found that the bindings between LDL and the model drugs were not enantioselective at any oxidation stage. The total binding affinity (nK) between LDL and verapamil enantiomers was increased by 3.3-, 4.6-, 7.0-, and 19-fold after 0.5, 1, 2, and 12 h oxidation, respectively, whereas the nK value between nilvadipine and LDLwas increased by 1.3-, 1.4-, 1.4-, and 1.7-fold in the same reaction times, respectively. These results indicate that the LDL oxidation enhances the drug binding affinity, and the affinity of verapamil is increased more sensitively than that of nilvadipine. The nK value of each model drug increased steeply after the first 2 h oxidation, followed by the gradual increase after the next 10 h oxidation. It is considered that the net increase in the negative charges and/or the formation of hydroperoxides in the first 2 h oxidation enhances the drug-LDL binding more significantly than the formation of aldehydes or Schiff bases in the following 10 h oxidation.

Evalution of capillary electrophoresis-frontal analysis for the study of low molecular weight drug-human serum albumin interactions

“…The authors concluded that CE-FA is the method of choice, being less laborious than HD and VP methods, simple, robust, and applicable to multiple equilibria [15]. In addition to albumin binding, the FA method has been used to study the interaction of low molecular weight compounds with plasma lipoproteins [23,29,[38][39][40][41], a 1 -acid glycoprotein [23,25,[42][43][44], simulated cord blood serum [26,30], human plasma [31], serum protein mixtures and human serum [23].…”

Capillary electrophoresis frontal analysis: Principles and applications for the study of drug‐plasma protein binding

“…Otherwise the free concentrations determined would be associated with an error. Experiments strongly indicate that low-molecular-weight ligand-HSA [34], drug-a 1 -acid glycoprotein (AGP) [48][49][50][51], and drug-lipoprotein [41] binding fulfil these requirements. The order of magnitude of the errors arising from not complying with the mobility restrictions has not been assessed.…”

Recent advances in the study of biomolecular interactions by capillary electrophoresis

“…The binding of propranolol enantiomers to HDL and LDL was not enantioselective; the total binding affinity of propranolol to LDL (4.01610 5 M 21 ) was 18-fold of that of propranolol-HDL binding (2.38610 4 M 21 ) [102]. In a study on the effect of oxidation of LDL on enantioselective drug binding [103], the binding was not enantioselective at any oxidation stage. Similar results were obtained in studies of enantiomers of nilvadipine interacting with LDL and HDL [104].…”