Evaluation of Selective Competitive Binding of Basic Drugs to .ALPHA.1-Acid Glycoprotein Variants

Abstract

The binding of drugs to proteins is an important determinant of their efficacy and/or side-effects in clinical use. Many basic drugs bind mainly to a 1 -acid glycoprotein (AGP), an acute phase reactant, in plasma, but the plasma level of AGP varies greatly in various diseases. It is increased by inflammatory reaction, injury, and surgery, [1][2][3] but decreased by liver cancer, hepatitis and nephritic syndrome. [4][5][6] We have shown that there is a good correlation between the unbound fraction (f u ) of ropivacaine and AGP concentration after surgery. 3)Recently, it has been reported that human AGP exists as a heterogeneous population of three genetic variants of ORM1 F 1 and ORM1 S derived from the AGP-A gene and ORM2 A derived from the AGP-B/BЈ genes in the plasma of most individuals. 7,8) The variants can be identified by isoelectric focusing assay 9) and separated by chromatography on an immobilized copper(II) affinity adsorbent. 10,11) Fitos et al. demonstrated that the two main forms (the F 1 S and A variants) have different drug binding properties by means of circular dichroism (CD) spectroscopy using dicumarol and acridine orange as probes.12) It has been clarified that some drugs bind selectively to different AGP variants: for example, dipyridamole binds selectively to the F 1 S variant, and disopyramide to the A variant, whereas lidocaine binds to both the F 1 S and A variants. [13][14][15][16] However, there are few reports regarding the effects of drug-drug interaction arising from selective binding to AGP variants on the f u values of basic drugs. In this study, we evaluated the selective competitive binding of basic drugs to the F 1 S and A variants isolated from native human AGP. MATERIALS AND METHODS Materials Anapeine injection® (ropivacaine hydrochloride) and Xylocaine injection ® (lidocaine hydrochloride) were purchased from AstraZeneca Co., Ltd. (Osaka, Japan). Persantin injection ® (dipyridamole) was purchased from Boehringer Ingelheim Co., Ltd. (Tokyo, Japan). Vasolan injection ® (verapamil hydrochloride) was purchased from Eisai Co., Ltd. (Tokyo, Japan). Rythmodan P injection ® (disopyramide phosphate) was purchased from Chugai Pharmaceutical Co., Ltd. (Tokyo, Japan). Nifejipine and amlodipine besilate were purchased from Wako Pure Chemicals Co., Ltd. (Osaka, Japan). Herbesser injection ® (diltiazem hydrochloride) was purchased from Tanabe Co., Ltd. (Tokyo, Japan). Carvedilol was purchased from LKT Laboratories, Inc. (MN, U.S.A.). Native human a 1 -acid glycoprotein (total AGP) was purchased from Sigma-Aldrich Co., Ltd. (MO, U.S.A.). 3,3Ј-Methylene-bis(4-hydroxycoumarin)(dicumarol), acridine orange hemi(zinc chloride) salt and mepivacaine were purchased from Sigma-Aldrich Co., Ltd. Other chemicals were of reagent grade.Drug Assays Concentrations of ropivacaine, lidocaine and disopyramide were determined by GC-MS (Model GC-17 system Class 5000, Shimadzu, Kyoto, Japan). The assay for these drugs was carried out by using the procedure described for ropivacaine by Yokogawa et al. 3)Aliquots...

Drug‐binding energetics of human α‐1‐acid glycoprotein assessed by isothermal titration calorimetry and molecular docking simulations

“…The imidazole free fractions were found to contain the F1*S variant(s), whereas the A variant eluted later during the imidazole gradient. The fractions were desalted by ultrafiltration, and purity was accessed by isoelectric focusing as previously described (Eap and Baumann, ; Ishizaki et al ., ).…”

“…The fractions were desalted by ultrafiltration, and purity was accessed by isoelectric focusing as previously described (Eap and Baumann, 1988;Ishizaki et al, 2010).…”

“…Comparably, the narrower ligand-binding pocket of the A variant only displays two lobes, the main central hydrophobic lobe I is present, with a smaller flanking lobe II structure (Nishi et al, 2011). Investigations into the drug-binding selectivity of the individual variants revealed that the A variant displays a stricter drug-binding selectivity and an overall higher drug-binding affinity (Eap et al, 1988a(Eap et al, , 1988b(Eap et al, , 1990Hervé et al, 1993bHervé et al, , 1996Hervé et al, 1998;Matsumoto et al, 2002;Nakagawa et al, 2003;Taheri et al, 2003;Nishi et al, 2009;Ishizaki et al, 2010). In contrast, the F1*S variant generally displayed a broader drug-binding selectivity, with an overall lower drug-binding affinity (Eap et al, 1988a(Eap et al, , 1988b(Eap et al, , 1990Hervé et al, 1993bHervé et al, , 1996Hervé et al, 1998;Matsumoto et al, 2002;Nakagawa et al, 2003;Taheri et al, 2003;Nishi et al, 2009;Ishizaki et al, 2010).…”

Acute-Phase Proteins: Alpha -1- Acid Glycoprotein

“…[30,31] Concerning the binding of various basic drugs to the F(1)S and A genetic variants of alpha(1)-acid glycoprotein, it was found that , the higher the affinity of basic drugs for AGP, the more they inhibit the binding of other basic drugs, and further, the inhibitory potency depends on the selectivity of binding to the AGP variants. [32] During specific circular dichroism (CD) probes, dicumarol and acridine orange were found to specifically bind to the F1-S and A variants, respectively. Dicumarol binding to the F1-S variant produced induced Cotton effects originating from the favored chiral conformation of the bound label.…”

Characterization of binding mode of imatinib to human α1-acid glycoprotein

“…The genetic variant composition of individuals, however, shows large variability [9]. The F1*S and A genetic variants were found to have different ligand binding characteristics [10][11][12][13][14]. The exact tertiary structure of AGP has been reported only recently, determining the X-ray structures of the recombinant unglycosylated F1 [15] and A [16] variants.…”