Metabolic Impact of Anticancer Drugs Pd2Spermine and Cisplatin on the Brain of Healthy Mice

Abstract

The new palladium agent Pd₂Spermine (Spm) has been reported to exhibit promising cytotoxic properties, while potentially circumventing the known disadvantages associated to cisplatin therapeutics, namely acquired resistance and high toxicity. This work presents a nuclear magnetic resonance (NMR) metabolomics study of brain extracts obtained from healthy mice, to assess the metabolic impacts of the new Pd₂Spm complex in comparison to that of cisplatin. The proton NMR spectra of both polar and nonpolar brain extracts were analyzed by multivariate and univariate statistics, unveiling several metabolite variations during the time course of exposition to each drug (1-48 h). The distinct time-course dependence of such changes revealed useful information on the drug-induced dynamics of metabolic disturbances and recovery periods, namely regarding amino acids, nucleotides, fatty acids, and membrane precursors and phospholipids. Putative biochemical explanations were proposed, based on existing pharmacokinetics data and previously reported metabolic responses elicited by the same metal complexes in the liver of the same animals. Generally, results suggest a more effective response of brain metabolism towards the possible detrimental effects of Pd₂Spm, with more rapid recovery back to metabolites' control levels and, thus, indicating that the palladium drug may exert a more beneficial role than cDDP in relation to brain toxicity.

Keywords: NMR; Pd2Spm; brain extracts; cisplatin; metabolomics; mice; palladium(II); platinum(II); spermine; toxicity.

Figure 1

Chemical structures of the (a) conventional Pt(II)-drug cisplatin and (b) novel complex Pd(II)-spermine (Pd₂Spm).

Figure 2

Average 500 MHz ¹H NMR spectra of (a) polar and (b) nonpolar extracts of brain from healthy BALB/c mice at 1 h post-injection with phosphate-buffered saline solution (control group). * Cutoff spectral regions corresponding to water (δ 4.54–5.10) and residual CDCl₃ and corresponding satellites (δ 7.00–7.50). Metabolite abbreviations: (a) 3-letter code used for amino acids; Ado, adenosine; ADP, adenosine diphosphate; AMP, adenosine monophosphate; ATP, adenosine triphosphate; Cho, choline; GABA, γ-aminobutyrate; GPC, glycerophosphocholine; GSH, glutathione (reduced); HX, hypoxanthine; IMP, inosine monophosphate; Ino, inosine; m-Ino, myo-Inositol; NAA, N-acetyl-aspartate; NAM, niacinamide; PC, phosphocholine; Suc, succinate; Tau, taurine. (b) FAs, fatty acids; MUFAs, monounsaturated fatty acids; PLs, phospholipids; PTC, phosphatidylcholine; PTE, phosphatidylethanolamine; PUFAs, polyunsaturated fatty acids; SM, sphingomyelin; TC, total cholesterol.

Figure 3

Score scatter plots of PLS-DA models for ¹H NMR spectra of polar (left) and nonpolar (right) extracts of BALB/c mice brain, considering (a) all time-course samples for all three groups (controls, black triangles, n = 14; cDDP-treated, blue diamonds, n = 15; Pd₂Spm-treated, red circles, n = 15), and (b) pairwise comparisons of cDDP-treated vs. controls, Pd₂Spm-treated vs. controls, and Pd₂Spm-treated vs. cDDP-treated. Post-injection time-points are specified for each sample. Validation parameters (R² and Q²) are indicated for each pairwise model, with Q² values > 0.5 highlighted in bold.

Figure 4

Heat map colored according to effect size of variations in the levels of polar metabolites, in the brain of healthy BALB/c mice, at 1, 12, and 48 h post-injection times either with cDDP or Pd₂Spm, compared to controls. Abbreviations: NAD⁺, nicotinamide adenine dinucleotides; d, doublet; t, triplet; other abbreviations as defined in the caption of Figure 2. ^† Tentative assignment. ^‡ Partial integration of resonance peak. * p-value < 5.0 × 10⁻²; ** p-value < 1.0 × 10⁻²; *** p-value < 1.0 × 10⁻³; **** p-value < 1.0 × 10⁻⁴ (asterisks correspond to comparison of each time point (for each drug) with controls).

Figure 5

Selected time-course trajectory plots for polar metabolites related to cDDP- (blue line) or Pd₂Spm-treated (red line) vs. controls (black line) mice brain tissue, comprising amino acids, choline derivatives, nucleotides/nucleosides and related compounds, organic acids, other compounds, and relevant unassigned resonances. Asterisks indicate the statistical significance of each drug compared only to controls at the indicated time point: * p-value < 5.0 × 10⁻²; ** p-value < 1.0 × 10⁻²; *** p-value < 1.0 × 10⁻³; **** p-value < 1.0 × 10⁻⁴.

Figure 6

Heat map colored according to effect size of variations in the levels of nonpolar metabolites, in the brain of healthy BALB/c mice, at 1, 12, and 48 h post-injection times either with cDDP or Pd₂Spm, compared to controls. Abbreviations: s, singlet; br, broad signal; other abbreviations as defined in Figure 2 and Figure 4. ^‡ Partial integration of resonance peak. * p-value < 5.0 × 10⁻²; ** p-value < 1.0 × 10⁻²; *** p-value < 1.0 × 10⁻³ (asterisks correspond to comparison of each time point (for each drug) with controls).

Figure 7

Selected time-course trajectory plots for nonpolar metabolites related to cDDP- (blue line) or Pd₂Spm-treated (red line) vs. controls (black line) mice brain, comprising cholesterol, fatty acids (FAs), phospholipids (PLs), fatty acids average chain length, unsaturation and polyunsaturation degrees, and relevant unassigned resonances. Average FA chain length is expressed in terms of the (CH₂)_n/CH₃ ratio, and average unsaturation and polyunsaturation degrees are expressed by the HC=CH/CH₃ and =CHCH₂CH=/CH₃ ratios, respectively. Asterisks indicate the statistical significance of each drug compared only to controls at the indicated time point: * p-value < 5.0 × 10⁻²; ** p-value < 1.0 × 10⁻²; *** p-value < 1.0 × 10⁻³.