Structural Factors Affecting Binding of Platinum Anticancer Agents with Phospholipids: Influence of Charge and Phosphate Clamp Formation

Abstract

We report a detailed NMR and DFT study of the interaction of polynuclear platinum anticancer agents (PPCs) with negatively charged phospholipids as a mechanism for their cellular uptake. The reactions of fully N-labelled [{trans-PtCl(NH ) } (μ-trans-Pt(NH ) {NH (CH ) NH } )] ( N-1, 1,0,1/t,t,t) and the dinuclear [{trans-PtCl(NH ) } {μ-H N(CH ) NH }] ( N-2, 1,1/t,t) with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-phosphate (DHPA) were studied at 298 K, pH ≈5.4, by [ H, N] HSQC 2D NMR spectroscopy. Both N-1 and N-2 form an initial mono-adduct in which the DHPA is coordinated via the phosphate O atom. For the dinuclear N-2, coordination of a second DHPA, in two different orientations, leads to two conformers of the bifunctional adduct. For N-1, coordination of the second DHPA allows the central {PtN } coordination unit to bind electrostatically to two additional DHPA molecules via phosphate clamp interactions, in an extended network. For both 1,0,1/t,t,t (1) and 1,1/t,t (2), equilibrium conditions are obtained more slowly (>35 h) than in the presence of phosphate (12 h) and in each case the rate constant for the first step of DHPA binding (k ) is about 8 times higher than that for phosphate, whereas the rate constants for the reverse reactions are quite similar. Reaction of N-1 with the sodium salt of 1,2-dihexanoyl-sn-glycero-3-[phosphatidyl-l-serine] (DHPS) showed only minor adduct formation via coordination to the N-donor atom of the phosphoserine group.

Influence of geometric isomerism on the binding of platinum anticancer agents with phospholipids

“…For both adducts, coordination of the DHPA molecule by the phosphate O atom places the cis-NH 3 in a similar hydrogen bonded environment to that previously reported for the Pt-NH 3 groups in 1,1/t,t, 10 and this peak (δ 3.86/−65.3, labelled C m ) is similarly deshielded in both 1 H (∆δ = 0.10) and 15 N (∆δ = 0.7) dimensions with respect to the parent chlorido species. The Pt−NH 2 group (δ 4.56/−43.5), which is similarly cis to the coordinated DHPA molecule, exhibits a similar deshielding with respect to the parent chlorido complex ( 1 H ∆δ = 0.07, 15 N ∆δ = 0.7).…”

“…The Pt−NH 2 group (δ 4.56/−43.5), which is similarly cis to the coordinated DHPA molecule, exhibits a similar deshielding with respect to the parent chlorido complex ( 1 H ∆δ = 0.07, 15 N ∆δ = 0.7). The trans-NH 3 group (δ 4.21/−83.6) is noticeably shielded in the 1 H dimension (∆δ −0.08) with respect to the parent chlorido complex, whereas in the case of 1,1/t,t the 1 H shifts for the analogous Pt-NH 2 protons were almost identical in species A and C. 10 By observing the change in intensity of trans-NH 3 peak for the unbound {PtN 3 Cl} group (C m' Fig. 1) the mono-DHPA adduct (1,1/c,c-MF-1) reached a maximum intensity after about 9 h, and then decreased so that it represents only 2% of the total Pt species at equilibrium Bifunctional adduct formation.…”

“…9 We have studied also the interaction of these PPCs with 1,2-dihexanoyl-sn-glycero-3-phosphate (DHPA), a shorter, water-soluble model for the phospholipid DPPA (Chart 1). 10 These latter studies showed that the monofunctional DHPA adduct of 1,1/t,t coordinated to a second DHPA molecule in two different orientations, leading to formation of two conformers of the bifunctional adduct. Triplatin, which contains a charged {PtN 4 } 2+ central linker, is capable of forming higher order structures through "phosphate clamp" interactions with two molecules of DHPA.…”

“…The kinetics of 1,1/c,c-DHPA binding are also compared with previous studies on simple phosphate binding and with those reported for the binding of 1,0,1/t,t,t and 1,1/t,t with DHPA. 10 The work highlights how the interplay of modern experimental ([ 1 H, 15 N] NMR spectroscopy) and theoretical (DFT modelling) techniques allows prediction of interactions of platinum anticancer complexes with relevant biological targets by extrapolating studies with simple model systems.…”

Phosphorus-containing amino acids with a P–C bond in the side chain or a P–O, P–S or P–N bond: from synthesis to applications

“…In addition, recent studies have reported the interactions of such negatively charged phospholipids with polynuclear platinum anticancer agents to facilitate cellular uptake. 100 The synthesis of hexadecylphosphono-(L)-serine 333 was reported by Brachwitz et al The transesterication reaction was carried out by stirring a mixture of hexadecyl phosphonocholine 332 and excess (L)-serine, at a ratio of 1 : 100, with phospholipase D, which is known to convert phosphatidylcholine into phosphatidylserine (Scheme 77). 101 Aer treatment, the crude substance was puried via chromatography on cellulose to furnish the phosphonoserine 333 with 28% yield.…”