Synthesis and cellular impact of diene-ruthenium(II) complexes: a new class of organoruthenium anticancer agents

Ruthenium(II)/Benzonitrile Complex Induces Cytotoxic Effect in Sarcoma-180 Cells by Caspase-Mediated and Tp53/p21-Mediated Apoptosis, with Moderate Brine Shrimp Toxicity

Ruthenium(II)/benzonitrile complexes have demonstrated promising anticancer properties. Considering that there are no specific therapies for treating sarcoma, we decided to evaluate the cytotoxic, genotoxic, and lethal effects of cis-[RuCl(BzCN)(phen)(dppb)]PF₆ (BzCN = benzonitrile; phen = 1,10-phenanthroline; dppb = 1,4-bis-(diphenylphosphino)butane), as well as the mechanism of cell death induction that occurs against murine sarcoma-180 tumor. Thus, MTT assay was applied to assess the ruthenium cytotoxicity, showing that the compound is a more potent inhibitor for the sarcoma-180 tumor cell viability than normal cells (lymphocytes). The comet assay indicated low genotoxic for normal cells. cis-[RuCl(BzCN)(phen)(dppb)]PF₆ also showed moderate lethality in Artemia salina. The complex induced cell cycle arrest in the G0/G1 phase in sarcoma-180 cells. In addition, the complex caused S180 cells to die by apoptosis by an increase in Annexin-V-positive cells and morphological changes typical of apoptotic cells. Additionally, cis-[RuCl(BzCN)(phen)(dppb)]PF₆ increased the gene expression of Bax, Casp3, and Tp53 in S180 cells. By using a western blot, we observed an increased protein level of TNF-R2, Bax, and p21. In conclusion, cis-[RuCl(BzCN)(phen)(dppb)]PF₆ is active and selective for sarcoma-180 cells, leading to cell cycle arrest at the G0/G1 and cell death through a caspases-mediated and Tp53/p21-mediated pathway.

Synthesis and biological assessment of a ruthenium(II) cyclopentadienyl complex in breast cancer cells and on the development of zebrafish embryos

Ruthenium-based complexes currently attract great attention as they hold promise to replace platinum-based drugs as a first line cancer treatment. Whereas ruthenium arene complexes are some of the most studied species for their potential anticancer properties, other types of ruthenium complexes have been overlooked for this purpose. Here, we report the synthesis and characterization of Ru(II) cyclopentadienyl (Cp), Ru(II) cyclooctadienyl (COD) and Ru(III) complexes bearing anastrozole or letrozole ligands, third-generation aromatase inhibitors currently used for the treatment of estrogen receptor positive (ER +) breast cancer. Among these complexes, Ru(II)Cp 2 was the only one that displayed a high stability in DMSO and in cell culture media and consequently, the only complex for which the in vitro and in vivo biological activities were investigated. Unlike anastrozole alone, complex 2 was considerably cytotoxic in vitro (IC50 values < 1 μM) in human ER + breast cancer (T47D and MCF7), triple negative breast cancer (TNBC) (MBA-MB-231), and in adrenocortical carcinoma (H295R) cells. Theoretical (docking simulation) and experimental (aromatase catalytic activity) studies suggested that an interaction between 2 and the aromatase enzyme was not likely to occur and that the bulkiness of the PPh3 ligands could be an important factor preventing the complex to reach the active site of the enzyme. Exposure of zebrafish embryos to complex 2 at concentrations around its in vitro cytotoxicity IC50 value (0.1-1 μM) did not lead to noticeable signs of toxicity over 96 h, making it a suitable candidate for further in vivo investigations. This study confirms the potential of Ru(II)Cp complexes for breast cancer therapy, more specifically against TNBCs that are usually not responsive to currently used chemotherapeutic agents.

Ru(II)/diphenylphosphine/pyridine-6-thiolate complexes induce S-180 cell apoptosis through intrinsic mitochondrial pathway involving inhibition of Bcl-2 and p53/Bax activation

The aim of this work was the synthesis, characterization, and cytotoxicity evaluation of three new Ru(II) complexes with a general formula [Ru(Spy)(bipy)(P-P)]PF₆ [Spy = pyridine-6-thiolate; bipy = 2,2'-bipyridine; P-P = 1,2-bis(diphenylphosphine)ethane (1); 1,3-bis(diphenylphosphine) propane (2); and 1,1'-bis(diphenylphosphino)ferrocene] (4). Complex (3) with the 1,4-bis(diphenylphosphine)butane ligand, already known from the literature, was also synthesized, to be better studied here. The cytotoxicities of the complexes toward two kinds of cancerous cells (K562 and S-180 cells) were evaluated and compared to normal cells (L-929 and PBMC) by MTT assay. The complex [Ru(Spy)(bipy)(dppb)]PF₆ (3) was selected to study both the cellular and molecular mechanisms underlying its promising anticancer action in S-180 cells. The results obtained from this study indicated that complex (3) induces cell cycle arrest in the G0/G1 phase in S-180 cells associated with a decrease in the number of cells in S phase. After 24 and 48 h of exposure to complex (3), the cell viability decreased when compared to the negative control. Complex (3) does not appear to be involved in the DNA damage, but induced changes in the mitochondrial membrane potential in S-180 cells. Furthermore, there was also an increase in the gene expression of Bax, Caspase 9, and Tp53. According to our results, complex (3) induces cell apoptosis through p53/Bax-dependent intrinsic pathway and suppresses the expression of active antiapoptotic Bcl-2 protein.

Recent developments in the nanostructured materials functionalized with ruthenium complexes for targeted drug delivery to tumors

In recent years, the field of metal-based drugs has been dominated by other existing precious metal drugs, and many researchers have focused their attention on the synthesis of various ruthenium (Ru) complexes due to their potential medical and pharmaceutical applications. The beneficial properties of Ru, which make it a highly promising therapeutic agent, include its variable oxidation states, low toxicity, high selectivity for diseased cells, ligand exchange properties, and the ability to mimic iron binding to biomolecules. In addition, Ru complexes have favorable adsorption properties, along with excellent photochemical and photophysical properties, which make them promising tools for photodynamic therapy. At present, nanostructured materials functionalized with Ru complexes have become an efficient way to administer Ru-based anticancer drugs for cancer treatment. In this review, the recent developments in the nanostructured materials functionalized with Ru complexes for targeted drug delivery to tumors are discussed. In addition, information on "traditional" (ie, non-nanostructured) Ru-based cancer therapies is included in a precise manner.

Novel binuclear μ-oxo diruthenium complexes combined with ibuprofen and ketoprofen: Interaction with relevant target biomolecules and anti-allergic potential

This work presents the synthesis and characterization of two novel binuclear ruthenium compounds of general formula [Ru2O(carb)2(py)6](PF6)2, where py=pyridine and carb are the non-steroidal anti-inflammatory drugs ibuprofen (1) and ketoprofen (2). Both complexes were characterized by ESI-MS/MS spectrometry. The fragmentation patterns, which confirm the proposed structures, are presented. Besides that, compounds 1 and 2 present the charge transfer transitions within 325-330nm; and the intra-core transitions around 585nm, which is the typical spectra profile for [Ru2O] analogues. This suggests the carboxylate bridge has little influence in their electronic structure. The effects of the diruthenium complexes on Ig-E mediated mast cell activation were evaluated by measuring the enzyme β-hexosaminidase released by mast cells stimulated by antigen. The inhibitory potential of the ketoprofen complex against mast cell stimulation suggests its promising application as a therapeutic agent for treating or preventing IgE-mediated allergic diseases. In addition, in vitro metabolism assays had shown that the ibuprofen complex is metabolized by the cytochrome P450 enzymes.

Toward white electroluminescence by ruthenium quinoxaline light emitting diodes

Exciplex transfer as a new approach to produce white electroluminescence in ruthenium quinoxaline light emitting diodes.

Iron(iii) and nickel(ii) complexes as potential anticancer agents: synthesis, physicochemical and structural properties, cytotoxic activity and DNA interactions

The iron complex 3 was cytotoxic at low concentrations in K562 cells and could damage the DNA, specifically the adenine base.

A TrxR inhibiting gold(I) NHC complex induces apoptosis through ASK1-p38-MAPK signaling in pancreatic cancer cells

Background

Cancer cells in the advanced stage show aberrant antioxidant capacity to detoxify excessive ROS resulting in the compensation for intrinsic oxidative stress and therapeutic resistance. PDAC is one of the most lethal cancers and often associated with a high accumulation of ROS. Recent studies identified gold(I) NHC complexes as potent TrxR inhibitors suppressing cell growth in a wide spectrum of human malignant cell lines at the low micromolar concentration. However, the mechanism of action is not completely elucidated yet.

Methods

To understand the biological function of gold(I) NHC complexes in PDAC, we used a recently published gold(I) NHC complex, MC3, and evaluated its anti-proliferative effect in four PDAC cell lines, determined by MTT and SRB assays. In further detailed analysis, we analyzed cellular ROS levels using the ROS indicator DHE and mitochondrial membrane potential indicated by the dye JC-1 in Panc1. We also analyzed cell cycle arrest and apoptosis by FACS. To elucidate the role of specific cell signaling pathways in MC3-induced cell death, co-incubation with ROS scavengers, a p38-MAPK inhibitor and siRNA mediated depletion of ASK1 were performed, and results were analyzed by immunoblotting, ELISA-microarrays, qRT-PCR and immunoprecipitation.

Results

Our data demonstrate that MC3 efficiently suppressed cell growth, and induced cell cycle arrest and apoptosis in pancreatic cancer cells, in particular in the gemcitabine-resistant cancer cells Panc1 and ASPC1. Treatment with MC3 resulted in a substantial alteration of the cellular redox homeostasis leading to increased ROS levels and a decrease in the mitochondrial membrane potential. ROS scavengers suppressed ROS formation and rescued cells from damage. On the molecular level, MC3 blocked the interaction of Trx with ASK1 and subsequently activated p38-associated signaling. Furthermore, inhibition of this pathway by using ASK1 siRNA or a p38 inhibitor clearly attenuated the effect of MC3 on cell proliferation in Panc1 and ASPC1.

Conclusions

Our results confirm that MC3 is a TrxR inhibitor and show MC3 induced apoptosis in gemcitabine-resistant PDACs. MC3 mediated cell death could be blocked by using anti-oxidants, ASK1 siRNA or p38 inhibitor suggesting that the Trx-ASK1-p38 signal cascade played an important role in gold(I) NHC complexes-mediated cellular damage.

Electronic supplementary material

The online version of this article (doi:10.1186/1476-4598-13-221) contains supplementary material, which is available to authorized users.

Molecular and cellular characterization of the biological effects of ruthenium(II) complexes incorporating 2-pyridyl-2-pyrimidine-4-carboxylic acid

A great majority of the Ru complexes currently studied in anticancer research exert their antiproliferative activity, at least partially, through ligand exchange. In recent years, however, coordinatively saturated and substitutionally inert polypyridyl Ru(II) compounds have emerged as potential anticancer drug candidates. In this work, we present the synthesis and detailed characterization of two novel inert Ru(II) complexes, namely, [Ru(bipy)(2)(Cpp-NH-Hex-COOH)](2+) (2) and [Ru(dppz)(2)(CppH)](2+) (3) (bipy = 2,2'-bipyridine; CppH = 2-(2'-pyridyl)pyrimidine-4-carboxylic acid; Cpp-NH-Hex-COOH = 6-(2-(pyridin-2-yl)pyrimidine-4-carboxamido)hexanoic acid; dppz = dipyrido[3,2-a:2',3'-c]phenazine). 3 is of particular interest as it was found to have IC(50) values comparable to cisplatin, a benchmark standard in the field, on three cancer cell lines and a better activity on one cisplatin-resistant cell line than cisplatin itself. The mechanism of action of 3 was then investigated in detail and it could be demonstrated that, although 3 binds to calf-thymus DNA by intercalation, the biological effects that it induces did not involve a nuclear DNA related mode of action. On the contrary, confocal microscopy colocalization studies in HeLa cells showed that 3 specifically targeted mitochondria. This was further correlated by ruthenium quantification using High-resolution atomic absorption spectrometry. Furthermore, as determined by two independent assays, 3 induced apoptosis at a relatively late stage of treatment. The generation of reactive oxygen species could be excluded as the cause of the observed cytotoxicity. It was demonstrated that the mitochondrial membrane potential in HeLa was impaired by 3 as early as 2 h after its introduction and even more with increasing time.