Influence of time and chloride ions on the interaction of cisplatin with human albumin in-vitro

Abstract

The interaction of cis-dichlorodiammineplatinum (II) (cisplatin) with human serum albumin (HSA), dissolved in phosphate buffer with or without sodium chloride (0.1 M) has been examined at pH 7.4 and mu = 0.154. Equal volumes of cisplatin and HSA solutions were incubated at 37 degrees C for various times and filterable platinum concentrations versus time measured by flameless atomic absorption spectrophotometry. Binding kinetics differed depending on the buffer solutions used and on the time elapsing between cisplatin dissolution and outset of incubation with HSA. Experimental data were fitted to a theoretical equation used to calculate the number of nucleophilic sites per HSA molecule. Titrations of the HSA sulphydryl group content before and after incubation with a cisplatin solution were made, from which it was shown that the lone SH-group of the HSA macromolecule is involved in cisplatin binding. We also studied HSA's sensitivity towards denaturing agents when it was complexed with cisplatin. This sensitivity was decreased upon cisplatin binding. Also, the binding capacities of HSA and the HSA-Pt(II) complex to both tryptophan and warfarin were compared to determine the possible influence of cisplatin upon the binding to HSA of other drugs; this influence was negligible.

Characterisation of Cisplatin Binding Sites in Human Serum Proteins Using Hyphenated Multidimensional Liquid Chromatography and ESI Tandem Mass Spectrometry

“…C34 does, indeed, also give the highest Xcorr value for the sequence 1(b) in Table 1 and the sequences 1(a) and 1(e) in Table 2. This assignment is also in agreement with previous studies, [13][14][15][16] which have established the free thiol group of C34 as a preferred cisplatin binding site in HSA.…”

“…coli system, which identified seventeen O-donor residues for a total of thirty-one characterised protein targets. [23] Previous studies of cisplatin binding to HSA [13][14][15][16] and other proteins [29][30][31] have emphasised the important role of the softer cysteine and methionine sulfur atoms as preferred targets, and our present investigation does, of course, confirm C34 and establish M329 and M548 as specific binding residues in HSA, and M256 in Trfe. O-donor atoms, however, are known to be kinetically preferred [32][33][34] as initial binding sites for cisplatin, and inspection of the 1 H, 15 N HSQC NMR spectrum taken for a cisplatin-HSA mixture (310 K, pH 6.4) after 2 h in the presence of added chloride (Figure 2 a in ref.…”

“…[10] The free SH group in C34 was identified as an important cisplatin binding site by Gronias and Pizzo, [13] who observed a 4-5-fold decrease in Pt coordination after carboxyamidomethylation of the thiol function. This residue was confirmed by Momburg et al, [14] and by the IR spectroscopic studies of Neault and Tajmir-Riahi, [15] who also provided evidence for the possible participation of HSA tyrosine residues in cisplatin binding. A detailed 1 H, 15 N HSQC NMR spectroscopy study by Sadler et al [16] established a probable methionyl k 2 S M ,N M chelate as the major HSA sulfur-binding site after incubation of a 1:1 cisplatin-protein mixture for 17 h at 310 K. Monofunctional adducts involving C34 and one or two other methionine residues were also observed.…”

Cisplatin Binding Sites on Human Albumin

“…Despite numerous studies of cisplatin-albumin binding during the last few decades (7,15,18,19,(33)(34)(35)(36)(37), the precise mechanism of interaction is still poorly understood. Gonias and Pizzo reported that carboxyamidomethylation of the SH group in bovine and human serum albumin resulted in a 4 -5-fold decrease in platinum binding and suggested formation of a single monodentate complex of cisplatin with the free sulfhydryl group (Cys-34) (7,33).…”

Drug sensitivity testing for clinical samples from oesophageal cancer using adhesive tumour cell culture system

“…These discrepancies may be caused by the differences in pharmacokinetics and pharmacodynamics between in vivo and in vitro condition. In particular, CDDP, which is thought to be a most potent agent in clinical chemotherapy, was reported to be inactivated by binding to human serum albumin (Momburo et al, 1987), and the instability in culture media was also investigated (Hiderbrand-Zanki and Kern, 1984). This is the reason why the in vitro AUC was much higher than in vivo AUC.…”