Bis(triazinyl)pyridine complexes of Pt(II) and Pd(II): studies of the nucleophilic substitution reactions, DNA/HSA interactions, molecular docking and biological activity

New Pd(II)-pincer type complexes as potential antitumor drugs: synthesis, nucleophilic substitution reactions, DNA/HSA interaction, molecular docking study and cytotoxic activity

Two new complexes of Pd(II), [Pd(L1)Cl]Cl (Pd1) and [Pd(L2)Cl]Cl (Pd2), (where L1 = N2,N6-bis(5-methylthiazol-2-yl)pyridine-2,6-dicarboxamide and L2 = N2,N6-di(benzo[d]thiazol-2-yl)pyridine-2.6-dicarboxamide) were synthesized. Characterization of the complexes was performed using elemental analysis, IR, 1H NMR spectroscopy and MALDI-TOF mass spectrometry. The nucleophilic substitution reactions of complexes with L-Methionine (L-Met), L-Cysteine (L-Cys) and guanosine-5'-monophosphate (5'-GMP) were studied by stopped-flow method at physiological conditions (pH = 7.2 and 37 °C). Complex Pd1 was more reactive than Pd2 in all studied reactions, while the order of reactivity of the selected ligands was: L-Met > L-Cys > 5'-GMP. The interaction of complexes with calf thymus-DNA (CT-DNA) was studied by Uv-Vis absorption and fluorescence emission spectroscopy. Competitive binding studies with intercalative agent ethidium bromide (EB) and minor groove binder Hoechst 33258 were performed as well. Both complexes interacted with DNA through intercalation and minor groove binding, where the latter was preferred. Additionally, the interaction of Pd1 and Pd2 complexes with human serum albumin (HSA) was studied employing fluorescence quenching spectroscopy. The results indicate a moderate binding affinity of complexes, with slightly stronger binding of the Pd1. Fluorescence competition experiments with site-markers (eosin Y and ibuprofen) for HSA were used to locate the binding site of Pd1 to the HSA. Additionally, the interaction with DNA and HSA was studied by molecular docking and the revealed results were in good agreement with the experimentally obtained ones. Pd1 complex exhibited cytotoxicity toward human (HCT116) and mouse cell lines (CT26) of colorectal cancer, mouse (4T1) and human (MDA-MB468) breast cancer lines and non-cancerous mouse mesenchymal stem cells (mMSC). In addition, Pd1 complex demonstrated significant selectivity towards cancer cells over non-cancerous mMSC, indicating a high potential to eliminate malignant cells without affecting normal cells. It induced apoptosis in CT26 cells, effectively arrested the cell cycle in the S phase, and selectively down-regulated cyclin D and cyclin E. Moreover, it can alter the expression of cell cycle regulators by increasing p21 and decreasing p-AKT. These findings confirm its ability to disrupt key tumor cell survival signals and suggest that the Pd1 complex is a potent candidate for effective cancer treatment.

Therapeutic and Toxic Effects of Valproic Acid Metabolites

Valproic acid (VPA) and its salts are psychotropic drugs that are widely used in neurological diseases (epilepsy, neuropathic pain, migraine, etc.) and psychiatric disorders (schizophrenia, bipolar affective disorder, addiction diseases, etc.). In addition, the indications for the appointment of valproate have been expanding in recent years in connection with the study of new mechanisms of action of therapeutic and toxic metabolites of VPA in the human body. Thus, VPA is considered a component of disease-modifying therapy for multiple tumors, neurodegenerative diseases (Huntington's disease, Parkinson's disease, Duchenne progressive dystrophy, etc.), and human immunodeficiency syndrome. The metabolism of VPA is complex and continues to be studied. Known pathways of VPA metabolism include: β-oxidation in the tricarboxylic acid cycle (acetylation); oxidation with the participation of cytochrome P-450 isoenzymes (P-oxidation); and glucuronidation. The complex metabolism of VPA explains the diversity of its active and inactive metabolites, which have therapeutic, neutral, or toxic effects. It is known that some active metabolites of VPA may have a stronger clinical effect than VPA itself. These reasons explain the relevance of this narrative review, which summarizes the results of studies of blood (serum, plasma) and urinary metabolites of VPA from the standpoint of the pharmacogenomics and pharmacometabolomics. In addition, a new personalized approach to assessing the cumulative risk of developing VPA-induced adverse reactions is presented and ways for their correction are proposed depending on the patient's pharmacogenetic profile and the level of therapeutic and toxic VPA metabolites in the human body fluids (blood, urine).