A platinum(II) complex of liriodenine from traditional Chinese medicine (TCM): Cell cycle arrest, cell apoptosis induction and telomerase inhibition activity via G-quadruplex DNA stabilization

G-Quadruplex Structures as a "Switch" Regulate ATF4 Expression in Ferroptotic HepG2 Cells

G-quadruplex (G4) is a noncanonical structure folded in a widespread manner by guanine-rich tandem repeated sequences. As a key response factor, activating transcription factor 4 (ATF4) has dual functions in managing iron-dependent ferroptosis by regulating amino acid synthesis and antioxidant-related gene expression. In our study, the activity of ATF4 expression was elevated in HepG2 cells induced by erastin. Based on preliminary bioinformatics analyses, the G-tract region, named WT, had high potential to form G4, and it was found that PDS could markedly weaken the increase of ATF4 expression by reducing the sensitivity of HepG2 cells toward erastin. In circular dichroism spectra, WT oligonucleotides showed characteristic molar ellipticity at specific wavelengths of parallel G4 structures, while corresponding single-base mutants possessed a weaker ability to form G4, which were consistent with immunostaining results. In addition, endogenous G4 formed by the WT motif was significantly destroyed in HepG2 cells treated with erastin. After being transfected with WT oligonucleotides, the levels of ATF4 mRNA decreased significantly regardless of being treated with erastin or not. Meanwhile, mutations of G-tracts could advantageously impact the luciferase expression downstream of an ATF4 promoter in reporter assays, manifesting that the decrease of endogenous G4 in the ATF4 promoter was positively associated with the expression enhanced by erastin in HepG2 cells.

Rapid identification and pharmacokinetic studies of multiple active alkaloids in rat plasma through UPLC-Q-TOF-MS and UPLC-MS/MS after the oral administration of Zanthoxylum nitidum extract

Zanthoxylum nitidum (Roxb.) DC. (ZN) belongs to the genus Zanthoxylum of Rutaceae and has various chemical ingredients and pharmacologic effects. Alkaloids are its main active constituents responsible for diverse pharmacologic effects, such as anti-tumor, anti-bacterial, anti-inflammatory, and analgesic activities. The chemical and pharmacological effects of ZN are well reported, but the in vivo pharmacokinetic profiles of its main active alkaloids are poorly investigated. This study aims to elucidate the absorbed constituents and pharmacokinetic behavior of main active ingredients in rat plasma after the oral administration of ZN extract. The absorbed constituents in rat plasma were qualitatively analyzed using ultra-high-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS). Ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination and pharmacokinetic studies of dihydrochelerythrine (DHCHE), nitidine chloride (NIT), chelerythrine (CHE), sanguinarine (SAN), liriodenine (LIR), skimmianine (SKI), γ-fagarine (FAG), and dictamnine (DIC) in rat plasma. Eighteen prototypes and metabolites were identified according to exact mass, characteristic diagnostic fragment ions, and reference standards. The established UPLC-MS/MS quantitative method met the requirements of FDA for biological analysis methods. Method validation showed that this method has good linearity (r ≥ 0.9910), precision (RSD ≤ 18.63 %), accuracy (88.11 %-117.50 %), and stability. The limit of detection (LOD) could reach 1 ng/mL, and the limit of quantitation could reach 2 ng/mL. The plasma drug concentration of benzophenanthridine alkaloids, such as NIT, CHE, and DHCHE, were still low even after dose differences were deducted. For the furan quinoline alkaloids (such as SKI, FAG, and DIC), only SKI showed high plasma drug concentration, although SKI content comprised only approximately 1/6 of benzophenanthridine alkaloids. This study is the first to simultaneously determine the above-mentioned active alkaloids in rat plasma and would contribute to the comprehensive understanding of in vivo pharmacokinetic behavior on active alkaloids in ZN extract.

Anticancer Activity of Platinum (II) Complex with 2-Benzoylpyridine by Induction of DNA Damage, S-Phase Arrest, and Apoptosis

OBJECTIVE

To overcome the disadvantages of cisplatin, numerous platinum (Pt) complexes have been prepared. However, the anticancer activity and mechanism of Pt(II) complexed with 2-benzoylpyridine [Pt(II)- Bpy]: [PtCl2(DMSO)L] (DMSO = dimethyl sulfoxide, L = 2-benzoylpyridine) in cancer cells remain unknown.

METHODS

Pt(II)-Bpy was synthesized and characterized by spectrum analysis. Its anticancer activity and underlying mechanisms were demonstrated at the cellular, molecular, and in vivo levels.

RESULTS

Pt(II)-Bpy inhibited tumor cell growth, especially HepG2 human liver cancer cells, with a halfmaximal inhibitory concentration of 9.8±0.5μM, but with low toxicity in HL-7702 normal liver cells. Pt(II)- Bpy induced DNA damage, which was demonstrated through a marked increase in the expression of cleavedpoly (ADP ribose) polymerase (PARP) and gamma-H2A histone family member X and a decrease in PARP expression. The interaction of Pt(II)-Bpy with DNA at the molecular level was most likely through an intercalation mechanism, which might be evidence of DNA damage. Pt(II)-Bpy initiated cell cycle arrest at the S phase in HepG2 cells. It also caused severe loss of the mitochondrial membrane potential; a decrease in the expression of caspase-9 and caspase-3; an increase in reactive oxygen species levels; the release of cytochrome c and apoptotic protease activation factor; and the activation of caspase-9 and caspase-3 in HepG2 cells, which in turn resulted in apoptosis. Meanwhile, changes in p53 and related proteins were observed including the upregulation of p53, the phosphorylation of p53, p21, B-cell lymphoma-2-associated X protein, and NOXA; and the downregulation of B-cell lymphoma 2. Moreover, Pt(II)-Bpy displayed marked inhibitory effects on tumor growth in the HepG2 nude mouse model.

CONCLUSION

Pt(II)-Bpy is a potential candidate for cancer chemotherapy.

Raising the bar in anticancer therapy: recent advances in, and perspectives on, telomerase inhibitors

Telomerase is a ribonucleic reverse transcriptase enzyme that uses an integral RNA component as a template to add tandem telomeric DNA repeats, TTAGGG, at the 3' end of the chromosomes. 85-90% of human tumors and their derived cell lines predominantly express high levels of telomerase, therefore contributing to cancer cell development. However, in normal cells, telomerase activity is almost always absent except in germ cells and stem cells. This differential expression has been exploited to develop highly specific and potent cancer therapeutics. In this review, we outline recent advances in the development of telomerase inhibitors as anticancer agents.

Liriodenine enhances radiosensitivity in esophageal cancer ECA-109 cells by inducing apoptosis and G2/M arrest

At present, chemotherapy and radiotherapy represent the primary modalities of treatment for patients with unresectable esophageal squamous cell carcinoma (ESCC). However, the outcome of patients remains poor owing to radioresistance. The present study aimed to determine the radiosensitizing effect of liriodenine, an aporphine alkaloid derived from Enicosanthellum pulchrum, and investigating the underlying mechanisms in ESCC, using the esophageal cancer ECA-109 cell line. Cellular proliferation was evaluated using the Cell Counting kit-8 assay. Colony formation assay was performed to characterize the radiosensitive effects of liriodenine on ECA-109 cells, and flow cytometry was used to detect the percentage of cells undergoing apoptosis. An immunofluorescence assay was utilized to evaluate the DNA damage repair ability. Western blotting was used to assess the protein levels of caspase-3, B cell lymphoma-2 (Bcl-2) and Bcl-2-associated X (Bax). Liriodenine dose-dependently inhibited ECA-109 cell viability. The clonogenic survival assay demonstrated that liriodenine increased the radiosensitivity of ESCC cells, with a sensitization enhancement ratio of 1.11-1.69. The results of flow cytometry demonstrated that liriodenine induced apoptosis and G₂/M arrest. The immunofluorescence assay revealed that liriodenine delays DNA damage repair. The upregulation of Bax and Caspase-3, and the suppression of Bcl-2 confirmed that apoptosis was occurring. Liriodenine radiosensitizes ECA-109 cells by inducing apoptosis and G₂/M arrest. The findings of the present study indicated that liriodenine may represent an anticancer agent with promising potential for the treatment of ESCC.

Metal Complexes of Natural Product Like-compounds with Antitumor Activity

Cancer continues to be one of the major causes of death worldwide. Despite many advances in the understanding of this complex disease, new approaches are needed to improve the efficacy of current therapeutic treatments against aggressive tumors. Natural products are one of the most consistently successful sources of drug leads. In recent decades, research activity into the clinical potential of this class of compounds in cancer has increased. Furthermore, a highly promising field is the use of metals and their complexes in the design and development of metal-based drugs for the treatment of cancer. Metal complexes offer unique opportunities due to their ability to alter pharmacology, improving the efficacy and/or reducing the negative side effects of drug molecules. In addition, transition metals as copper, iron, and manganese, among others, can interact with active sites of enzymes, playing important roles in multiple biological processes. Thus, these complexes not only possess higher activities but also reach their targets more efficiently. This review article highlights recent advances on the emerging and expanding field of metal-based drugs. The emphasis is on new therapeutic strategies consisting of metal complexes with natural product like-compounds as a starting point for the rational design of new antitumor agents.

Rhodium (II) complex with 2-benzoylpyridine, a novel potential chemotherapeutic drug, induces cell cycle arrest and apoptosis in HepG2 cells

Rhodium (II) complex with 2-benzoylpyridine (Rh(L)₂Cl₂) is a new, synthetic, active metal-complex, which is produced by the reaction of 2-benzoylpyridine (L) with rhodium chloride hydrate (RhCl₃·nH₂O). The crystal structure was determined by X-ray diffraction which is mono-nuclear. In order to explore the biological properties of the novel complex, a series of studies were performed. The results showed that Rh(L)₂Cl₂ had the anti-tumor activity in HepG₂ and other cell lines and has been shown to induce G1 cell cycle arrest and apoptosis in HepG₂ cells. The anti-cancer effect of Rh(L)₂Cl₂ is regulated by increased expression of caspase-3 and PARP via the mitochondrial and the death receptor pathways. Bcl-2 family proteins might play an important role in the Rh(L)₂Cl₂-induced changes in these two pathways. Further studies indicated that Rh(L)₂Cl₂ increased the level of reactive oxygen species (ROS), but that Rh(L)₂Cl₂-induced apoptosis was ROS-independent. In conclusion, Rh(L)₂Cl₂ is a potential new anti-tumor drug, which induces HepG₂ cell death via the mitochondrial and death receptor pathways and has no obvious toxicity to normal liver cell.

Enhanced cytotoxicity by a benzothiazole-containing cisplatin derivative in breast cancer cells

A synergic acting cisplatin derivative, made via conjugating CJM126 with cisplatin, was synthesized and delivered using liposomes to inhibit tumor cells.

Preparation of 6/8/11-Amino/Chloro-Oxoisoaporphine and Group-10 Metal Complexes and Evaluation of Their in Vitro and in Vivo Antitumor Activity

A series of group-10 metal complexes 1–14 of oxoisoaporphine derivatives were designed and synthesized. 1–14 were more selectively cytotoxic to Hep-G2 cells comparing with normal liver cells. In vitro cytotoxicity results showed that complexes 1–6, 7, 8, 10 and 11, especially 3, were telomerase inhibitors targeting c-myc, telomeric, and bcl-2 G4s and triggered cell senescence and apoptosis; they also caused telomere/DNA damage and S phase arrest. In addition, 1–6 also caused mitochondrial dysfunction. Notably, 3 with 6-amino substituted ligand L^a exhibited less side effects than 6 with 8-amino substituted ligand L^b and cisplatin, but similar tumor growth inhibition efficacy in BEL-7402 xenograft model. Complex 3 has the potential to be developed as an effective anticancer agent.

Oxoisoaporphine as Potent Telomerase Inhibitor

Two compounds previously isolated from traditional Chinese medicine, Menispermum dauricum (DC), 6-hydroxyl-oxoisoaporphine (H-L^a), and 4,6-di(2-pyridinyl)benzo[h]isoindolo[4,5,6-de]quinolin-8(5H)-one (H-L^b), were known to have in vitro antitumor activity and to selectively bind human telomeric, c-myc, and bcl-2 G-quadruplexes (G4s). In this study, the binding properties of these two compounds to telomerase were investigated through molecular docking and telomeric repeat amplication protocol and silver staining assay (TRAP-silver staining assay). The binding energies bound to human telomerase RNA were calculated by molecular docking to be -6.43 and -9.76 kcal/mol for H-L^a and H-L^b, respectively. Compared with H-L^a, the ligand H-L^b more strongly inhibited telomerase activity in the SK-OV-3 cells model.

Novel FeII and CoII Complexes of Natural Product Tryptanthrin: Synthesis and Binding with G-Quadruplex DNA

Tryptanthrin is one of the most important members of indoloquinoline alkaloids. We obtained this alkaloid from Isatis. Two novel Fe^II and Co^II complexes of tryptanthrin were first synthesized. Single-crystal X-ray diffraction analyses show that these complexes display distorted four-coordinated tetrahedron geometry via two heterocyclic nitrogen and oxygen atoms from tryptanthrin ligand. Binding with G-quadruplex DNA properties revealed that both complexes were found to exhibit significant interaction with G-quadruplex DNA. This study may potentially serve as the basis of future rational design of metal-based drugs from natural products that target the G-quadruplex DNA.

Cobalt(ii) 8-hydroxyquinoline complexes: structure, cytotoxicity and action mechanism

Three cobalt(ii) complexes with 8-hydroxyquinoline derivatives as ligands were synthesized. They exhibited strong proliferation inhibition activity against T-24 cancer cells, which induced cancer cell apoptosis via intrinsic caspase-mitochondria pathways.

Dose-dependent cytotoxic effects of boldine in HepG-2 cells-telomerase inhibition and apoptosis induction

Plant metabolites are valuable sources of novel therapeutic compounds. In an anti-telomerase screening study of plant secondary metabolites, the aporphine alkaloid boldine (1,10-dimethoxy-2,9-dihydroxyaporphine) exhibited a dose and time dependent cytotoxicity against hepatocarcinoma HepG-2 cells. Here we focus on the modes and mechanisms of the growth-limiting effects of this compound. Telomerase activity and expression level of some related genes were estimated by real-time PCR. Modes of cell death also were examined by microscopic inspection, staining methods and by evaluating the expression level of some critically relevant genes. The growth inhibition was correlated with down-regulation of the catalytic subunit of telomerase (hTERT) gene (p < 0.01) and the corresponding reduction of telomerase activity in sub-cytotoxic concentrations of boldine (p < 0.002). However, various modes of cell death were stimulated, depending on the concentration of boldine. Very low concentrations of boldine over a few passages resulted in an accumulation of senescent cells so that HepG-2 cells lost their immortality. Moreover, boldine induced apoptosis concomitantly with increasing the expression of bax/bcl2 (p < 0.02) and p21 (p < 0.01) genes. Boldine might thus be an interesting candidate as a potential natural compound that suppresses telomerase activity in non-toxic concentrations.

Experimental and theoretical investigations of Michelia alba leaves extract as a green highly-effective corrosion inhibitor for different steel materials in acidic solution

Michelia alba leaves extract was first reported as a general highly-efficient inhibitor for acid corrosion of different steels.