Platinum(II)-oxalato complexes of seliciclib (CYC202) derivatives show different cellular effects and lesser adverse effects in mouse lymphoma model than cisplatin Abstract This work presents a deeper pharmacological evaluation of two formerly prepared and characterized, and highly in vitro cytotoxic platinum(II) oxalato complexes [Pt(ox)(L1)2] (1) and [Pt(ox)(L2)2] (2), containing the derivatives of cyclin-dependent kinase inhibitor (CDKi) seliciclib ((R)-roscovitine, CYC202) coordinating as N-donor carrier ligands, i.e., 2-(1-ethyl-2-hydroxyethylamino)-N6-(4-methoxybenzyl)-9-isopropyladenine (L1) and 2-chloro-N6-(2,4-dimethoxybenzyl)-9-isopropyladenine (L2). The positive results of in vitro cytotoxicity screening on human cancer cell lines (HeLa, HOS, A2780, A2780R, G361 and MCF7 with IC50 at low micromolar levels) published previously, motivated us to perform extended preclinical in vitro experiments to reveal the mechanisms associated with the induction of cancer cell death. In addition, the in vivo antitumor activity was evaluated using the mouse lymphocytic leukaemia L1210 model. The obtained results revealed that complex 1 exceeds the antitumor effect of cisplatin (as for the extension of life-span of mice) and shows far less adverse effects as compared to reference drug cisplatin. The in vitro and ex vivo studies of cellular effects and molecular mechanisms of cell death induction showed that the mechanism of action of complex 1 is essentially different from that of cisplatin. The obtained results showed a possible way how to obtain antitumor active platinum(II) oxalato complexes with better therapeutic profile than contemporary used platinum-based therapeutics.

Predominant cleavage of proteins N-terminal to serines and threonines using scandium(III) triflate Abstract Proteolytic digestion prior to LC–MS analysis is a key step for the identification of proteins. Digestion of proteins is typically performed with trypsin, but certain proteins or important protein sequence regions might be missed using this endoproteinase. Only few alternative endoproteinases are available and chemical cleavage of proteins is rarely used. Recently, it has been reported that some metal complexes can act as artificial proteases. In particular, the Lewis acid scandium(III) triflate has been shown to catalyze the cleavage of peptide bonds to serine and threonine residues. Therefore, we investigated if this compound can also be used for the cleavage of proteins. For this purpose, several single proteins, the 20S immune-proteasome (17 proteins), and the Universal Proteomics Standard UPS1 (48 proteins) were analyzed by MALDI–MS and/or LC–MS. A high cleavage specificity N-terminal to serine and threonine residues was observed, but also additional peptides with deviating cleavage specificity were found. Scandium(III) triflate can be a useful tool in protein analysis as no other reagent has been reported yet which showed cleavage specificity within proteins to serines and threonines. Graphic abstract

Copper, dityrosine cross-links and amyloid-β aggregation Abstract Copper is involved in Alzheimer’s disease (AD) where it appears to affect the aggregation of amyloid-β (Aβ) and to catalyze the production of reactive oxygen species (ROS). Oxidative stress apparently produces Aβ dimers that are covalently linked through two tyrosine residues. Such dityrosine cross-links are considered as potential markers of the disease and seem to be implicated in the pathological disorder. In the present study, pure o,o′-dityrosine (diY) was prepared enzymatically (with horseradish peroxidase; HRP), which was subsequently used to construct calibration lines aimed at quantifying nanomolar amounts of diY in reaction mixtures by fluorescence spectroscopy. Hence, diY concentrations down to 67 nM could be determined, which allowed to find that ca. 3% of dityrosine-bridged dimers of Aβ(1–40) were produced after 3 days at 37 °C in the presence of copper and dihydrogen peroxide. These cross-linked dimers in the presence of copper(II) ions completely inhibit the typical aggregation of Aβ, since β sheets could not be detected applying the usual Thioflavin T (ThT) method. Furthermore, the use of a potent Cu(II) chelator, such as the ATCUN tripeptide, l-histidyl-l-alanyl-l-histidine (HAH), efficiently prevented the copper-mediated generation of ROS and the associated dityrosine-bridged Aβ dimers, suggesting that such metal chelators may find future applications in the field of anti-AD drug design.

Cytotoxic platinum(II) complexes derived from saccharinate and phosphine ligands: synthesis, structures, DNA cleavage, and oxidative stress-induced apoptosis Abstract A series of the structurally related platinum(II) saccharinate (sac) complexes with alkylphenylphosphines, namely cis-[Pt(sac)2(PPh2Me)2]·DMSO (1), cis-[Pt(sac)2(PPhMe2)2] (2), cis-[Pt(sac)2(PPh2Et)2] (3), and cis-[Pt(sac)2(PPhEt2)2]·2DMSO (4), were synthesized and fully characterized; their structures were determined by X-ray crystallography. All the complexes were investigated for their anticancer potentials on three human cancer cells including A549 (lung), MCF-7 (breast), and HCT116 (colon) in addition to a noncancerous human bronchial epithelial cells (BEAS-2B). Specifically, 1 and 3 showed significant cytotoxic effects against MCF-7 and HCT116 cell lines in comparison to cisplatin, and were considered as the most potent ones in the series. The cytotoxic complexes were found to cleave DNA efficiently. In addition, the binding interactions of the complexes with DNA were confirmed by enzyme inhibition and molecular docking studies. Complexes 1 and 3 were capable of inducing apoptosis and arrested the cell cycle at the DNA synthesis (S) phase in MCF-7 cells. Furthermore, 1 and 3 caused the excessive generation of reactive oxygen species (ROS), leading to mitochondrial dysfunction and double-strand DNA breaks.

Anticancer activity, DNA binding and cell mechanistic studies of estrogen-functionalised Cu(II) complexes Abstract Four estrogen-functionalised copper complexes were synthesised and investigated as electrochemical active DNA binding and cleavage agents. These complexes strategically contain a biocompatible metal centre [Cu(II)], a planar aromatic ligand as DNA intercalative agent and an estradiol-derivative moiety which acts as delivery vector to target estrogen-receptor-positive (ER+) cancer cells. Cytotoxic activity was studied over a panel of estrogen-receptor-positive (ER+) and negative (ER−) human cancer cell lines by means of both 2D and 3D cell viability studies. The complexes showed high in vitro intercalative interaction with nuclear DNA and demonstrated to be strong DNA cleaving agents. This series of Cu compounds are potent anticancer agents with low and sub-micromolar IC50 values and the cellular uptake follows the lipophilicity order meaning that the internalisation mainly happened via passive diffusion. Finally, the estrogen-complexes are involved in the cellular redox stress by stimulating the production of ROS (reactive oxygen species). Graphic abstract

Investigation of combined photodynamic and radiotherapy effects of gallium phthalocyanine chloride on MCF-7 breast cancer cells Abstract In this study, we evaluated the effect of gallium phthalocyanine chloride (GaPcCl) as a radio- and photosensitizer on MCF-7 breast cancer cell line. We incubated cells with GaPcCl in different concentrations (from 3.125 to 100 μg/ml). Then cells in separate groups were exposed to different light doses (1.8 and 2.8 J/cm2) at wavelength of 660 nm and 2-Gy X-ray ionizing radiation, alone and in combination. Finally, cell survival and apoptosis were determined by MTT assay and flow cytometry, respectively. The results showed that the deactivated GaPcCl at concentration of 100 µg/ml reduces the cell viability up to 15%. While, photoactivated GaPcCl (100 µg/ml) at light dose of 2.8 J/cm2 significantly decreases cell viability up to 55.3%. Although MTT assay demonstrated that GaPcCl is not act as a radiosensitizer, flow cytometry showed significant increase in cell apoptosis when GaPcCl was exposed to 2 Gy X-ray. Using of GaPcCl-PDT (photodynamic therapy) integration with X-ray substantially increased cell death in comparison to the absence of X-ray. Furthermore, flow cytometry displayed a significant increase in apoptosis cells (especially late apoptosis) in this combination therapy. Our result proved that GaPcCl is an effective photosensitizer in MCF-7 human breast cancer cell line. The combination of GaPcCl-PDT and radiotherapy can be an efficient treatment against cancer. This approach needs further investigations on animal models for human purposes. Graphic abstract

Redox active metals in neurodegenerative diseases Abstract Copper (Cu) and iron (Fe) are redox active metals essential for the regulation of cellular pathways that are fundamental for brain function, including neurotransmitter synthesis and release, neurotransmission, and protein turnover. Cu and Fe are tightly regulated by sophisticated homeostatic systems that tune the levels and localization of these redox active metals. The regulation of Cu and Fe necessitates their coordination to small organic molecules and metal chaperone proteins that restrict their reactions to specific protein centres, where Cu and Fe cycle between reduced (Fe2+, Cu+) and oxidised states (Fe3+, Cu2+). Perturbation of this regulation is evident in the brain affected by neurodegeneration. Here we review the evidence that links Cu and Fe dyshomeostasis to neurodegeneration as well as the promising preclinical and clinical studies reporting pharmacological intervention to remedy Cu and Fe abnormalities in the treatment of Alzheimer’s disease (AD), Parkinson’s disease (PD) and Amyotrophic lateral sclerosis (ALS).

Apoptosis induction in lung and prostate cancer cells through silver nanoparticles synthesized from Pinus roxburghii bioactive fraction Abstract The current study was carried out to synthesize silver nanoparticles (AgNPs) via bioactive fraction of Pinus roxburghii needles using a simple, cost-effective, and eco-friendly green chemistry method. As butanol fraction of P. roxburghii exhibited maximum anticancer activity on lung adenocarcinomas (A549) as compared to other fractions therefore, butanol fraction was used to synthesize silver nanoparticles (PNb–AgNPs). The characterization studies by UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and selected area electron diffraction (SAED) confirmed the synthesis of the nanoparticles. The field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM) analysis showed the spherical structure of nanoparticles with an average diameter of approximately 80 nm. Interestingly, PNb–AgNPs exhibited significant cytotoxicity towards both A549 and prostatic small cell carcinomas (PC-3) with IC50 values of 11.28 ± 1.28 μg/ml and 56.27 ± 1.17 μg/ml, respectively, while lacking toxicity against normal human breast epithelial cells (fR2) and human peripheral blood lymphocytes (PBL). Further, enhanced reactive oxygen species generation, mitochondrial depolarization, apoptotic cell population (sub-G1) and DNA fragmentation observed in cancer cells were treated with PNb–AgNPs. Apoptosis was demonstrated by caspase-3 and PARP-1 activation in PNb–AgNPs-pretreated cancer cells. These results strongly suggest that PNb–AgNPs are capable of inducing cancer cell death and could act as a therapeutic nanoformulation for cancer. Graphic abstract

Bioinspired oxidation of oximes to nitric oxide with dioxygen by a nonheme iron(II) complex Abstract The ability of two iron(II) complexes, [(TpPh2)FeII(benzilate)] (1) and [(TpPh2)(FeII)2(NPP)3] (2) (TpPh2 = hydrotris(3,5-diphenylpyrazol-1-yl)borate, NPP-H = α-isonitrosopropiophenone), of a monoanionic facial N3 ligand in the O2-dependent oxidation of oximes is reported. The mononuclear complex 1 reacts with dioxygen to decarboxylate the iron-coordinated benzilate. The oximate-bridged dinuclear complex (2), which contains a high-spin (TpPh2)FeII unit and a low-spin iron(II)–oximate unit, activates dioxygen at the high-spin iron(II) center. Both the complexes exhibit the oxidative transformation of oximes to the corresponding carbonyl compounds with the incorporation of one oxygen atom from dioxygen. In the oxidation process, the oxime units are converted to nitric oxide (NO) or nitroxyl (HNO). The iron(II)–benzilate complex (1) reacts with oximes to afford HNO, whereas the iron(II)–oximate complex (2) generates NO. The results described here suggest that the oxidative transformation of oximes to NO/HNO follows different pathways depending upon the nature of co-ligand/reductant. Graphic abstract

Novel pyridinecarboxaldehyde thiosemicarbazone conjugated magnetite nanoparticulates (MNPs) promote apoptosis in human lung cancer A549 cells Abstract The present study highlights the apoptotic activity of magnetic Fe3O4 nanoparticulates functionalized by glutamic acid and 2-pyridinecarboxaldehyde thiosemicarbazone (PTSC) toward human lung epithelial carcinoma A549 cell line. To this aim, the Fe3O4 nanoparticulates were prepared using co-precipitation method. Then, the glutamic acid and Fe3O4 nanoparticulates were conjugated to each other. The product was further functionalized with bio-reactive PTSC moiety. In addition, the synthesized Fe3O4@Glu/PTSC nanoparticulates were characterized by physico-chemical techniques including scanning electron microscope (SEM), energy dispersive X-ray (EDX), X-ray diffraction (XRD), Fourier-transform infrared (FT–IR) spectroscopy and zeta potential analysis. The effects of in vitro cell viability in Fe3O4@Glu/PTSC nanoparticulate indicated the anti-proliferative properties in a dose-dependent manner (IC50 = 135.6 µM/mL). The high selectivity for tumor cells and far below of activity in HEK293 non-tumorigenic cells is considered as an important feature for this complex (SI, 3.48). Based on the results, PTSC failed to reveal any activity against A549 cells alone. However, Fe3O4 nanoparticulates had some effects in inhibiting the growth of lung cancer cell. Furthermore, Bax and Bcl-2 gene expressions were quantified by real-time PCR method. The expression of Bax increased 1.62-fold, while the expression of Bcl-2 decreased 0.76-fold at 135.6 µM/mL concentration of Fe3O4@Glu/PTSC compared to untreated A549 cells. Furthermore, the Fe3O4@Glu/PTSC nanoparticulate-inducing apoptosis properties were evaluated by Hoechst 33258 staining, Caspase-3 activation assay and Annexin V/propidium iodide staining. The results of the present study suggest that Fe3O4@Glu/PTSC nanoparticulates exhibit effective anti-cancer activity against lung cancer cells.