21-Benzylidene digoxin decreases proliferation by inhibiting the EGFR/ERK signaling pathway and induces apoptosis in HeLa cells

Inhibition of human cervical cancer development through p53-dependent pathways induced by the specified triple helical β-glucan

This study demonstrates that the purified β-glucan (LNT) with a triple helix and relatively narrow molecular weight distribution, extracted and purified from artificially cultured Lentinus edodes, showed a significant cervical cancer inhibition with little cytotoxicity against normal cells in vitro and in vivo. From the in vitro data, the potential mechanism of anti-cervical cancer was preliminarily revealed as follows: LNT was firstly recognized by the human cervical cancer cell line of Hela and induced cell proliferation inhibition through p21 and apoptosis via a mitochondrion-dependent pathway by targeting the tumor suppressor of p53, indicated by an increase in reactive oxygen species (ROS) generation and a loss of mitochondrial membrane potential (Δψm), in a significant dosage-dependent manner. Meanwhile, LNT repressed tumor growth with an inhibition ratio of 61.2 % and induced tumor cell apoptosis through endogenous MDM2/p53/Bax/mitochondrion signal pathway by up-regulating the expression of p53, Bax, Cyt. c, caspase 9, and caspase 3, as well as down-regulating Bcl-2, MDM2, and PARP1 levels in Hela cells-transplanted BALB/c nude mice. This study provides a scientific basis for the clinical treatment of cervical cancer with LNT as a potential drug candidate characterized by the triple helix and specified molecular weight with a relatively narrow distribution.

Targeting mTOR Signaling by Dietary Polysaccharides in Cancer Prevention: Advances and Challenges

Cancer is the most serious problem for public health. Traditional treatments often come with unavoidable side effects. Therefore, the therapeutic effects of natural products with wide sources and low toxicity are attracting more and more attention. Polysaccharides have been shown to have cancer-fighting potential, but the molecular mechanisms remain unclear. The mammalian target of rapamycin (mTOR) pathway has become an attractive target of antitumor therapy research in recent years. The regulation of mTOR pathway not only affects cell proliferation and growth but also has an important effect in tumor metabolism. Recent studies indicate that dietary polysaccharides play a vital role in cancer prevention and treatment by regulating mTOR pathway. Here, the progress in targeting mTOR signaling by dietary polysaccharides in cancer prevention and their molecular mechanisms are systemically summarized. It will promote the understanding of the anticancer effects of polysaccharides and provide reference to investigators of this cutting edge field.

Anticancer potential of cardiac glycosides and steroid-azole hybrids

Steriods are well-known scaffolds that have a widespread occurrence in different compounds characterized by extensive biological properties including anticancer activity. Structural modifications on steroids always generate potential lead compounds with superior bioactivity, and creation of steroid hybrids by combining steroid with other anticancer pharmacophores in one molecule, which can exert the anticancer activity through different mechanisms, is one of the most promising strategies to enhance efficiency, overcome drug resistance and reduce side effects. Sugars and azoles, can act on diverse receptors, proteins and enzymes in cancer cells, are pharmacologically significant scaffolds in the development of novel anticancer agents. Therefore, steroid-sugar hybrids cardiac glycosides and steroid-azole hybrids are privileged scaffolds for the discovery of novel anticancer candidates. This review emphasized on the development, the structure-activity relationship and the mechanism of action of cardiac glycosides and steroid-azole hybrids with potential application for fighting against various cancers including drug-resistant forms to facilitate further rational design of novel drug candidates covering articles published between 2015 and 2020.

Implications of Synthetic Modifications of the Cardiotonic Steroid Lactone Ring on Cytotoxicity

Na,K-ATPase (NKA) and cardiotonic steroids (CTS) have shown potent cytotoxic and anticancer effects. Here, we have synthesized a series of CTS digoxin derivatives (γ-benzylidene) with substitutions in the lactone ring and evaluated the cytotoxicity caused by digoxin derivatives in tumor and non-tumor cells lines, as well as their effects on NKA. The cytotoxicity assay was determined in HeLa, A549, and WI-26 VA4 after they were treated for 48 h with increased concentrations of CTS. The effects of CTS on NKA activity and immunoblotting of α1 and β1 isoforms were evaluated at IC₅₀ concentrations in A549 cell membrane. NKA activity from mouse brain cortex was also measured. The majority of CTS exhibited low cytotoxicity in tumor and non-tumor cells, presenting IC₅₀ values at micromolar concentrations, while digoxin showed cytotoxicity at nanomolar concentrations. BD-15 presented the lowest IC₅₀ value (8 µM) in A549 and reduced its NKA activity in 28%. In contrast, BD-7 was the compound that most inhibited NKA (56% inhibition) and presented high IC₅₀ value for A549. In mouse cortex, only BD-15 modulated the enzyme activity in a concentration-dependent inhibition curve. These results demonstrate that the cytotoxicity of these compounds is not related to NKA inhibition. The substitutions in the lactone ring of digoxin led to an increase in the cytotoxic concentration in tumor cells, which may not be interesting for cancer, but it has the advantage of increasing the therapeutic margin of these molecules when compared to classic CTS, and can be used safely in research for other diseases.

Inhibitory Effects of Digoxin and Digitoxin on Cell Growth in Human Ovarian Cancer Cell Line SKOV-3

Background:

Cardiac glycosides (CGs) possess a chemical structure similar to steroids, and are inhibitors of the sodium potassium pump. An anti-tumor effect of CGs in breast and prostate cancers has been reported, but the effect of CGs on ovarian cancer is still unclear.

Aims:

In this study, the effects of CGs on proliferation, cytotoxicity and cell cycle of ovarian cancer cell line (SKOV-3) have been investigated.

Procedure:

The cell proliferation and cytotoxicity were detected by MTT assay and LDH activity assay, respectively. CGs, at concentrations higher than IC50, decreased cell proliferation and showed increased cytotoxicity toward SKOV-3 cells. The colony-formation ability was reduced after treatment with digoxin and digitoxin for 10 days. Furthermore, we explored the effect of digoxin and digitoxin on the distribution of cell cycle by flow cytometry.

Results:

Results revealed that both digoxin and digitoxin led to cell cycle arrest in G₀/G₁ phase with 24 or 48 hours, but the arrest of G₀/G₁ phase was not observed at 72 hours. We evaluated the percentage of hypodiploid cell population as an index of the cellular fragments through flow cytometry. The data indicated that cellular fragments were significantly increased by treating with digitoxin at the concentrations of IC50 and 10⁻⁶ M for 72 hours.

Conclusion:

Taken together, these data suggest that CGs decreased cell proliferation and increased cytotoxicity through cell cycle arrest at the G₀/G₁ phase. CGs have anti-tumor effect in SKOV-3 cells and might be a potential therapeutic drug for ovarian cancer. Since this study is a preliminary investigation of CGs on SKOV-3 cells, more experiments might be performed in the future. Furthermore, more ovarian cancer cell lines might also be employed in the future studies to confirm the effect of CGs in ovarian cancer.

The γ-Benzylidene Digoxin Derivative BD-15 Increases the α3-Na, K-ATPase Activity in Rat Hippocampus and Prefrontal Cortex and no Change on Heart

Our study aimed to investigate the effects of the new cardiotonic steroid BD-15 (γ-benzylidene derivatives) in the behavioral parameters, oxidative stress and the Na, K-ATPase activity in the hippocampus, prefrontal cortex and heart from rats to verify the safety and possible utilization in brain disorders. For this study, groups of male Wistar rats were used after intraperitoneal injection of 20, 100 and 200 µg/Kg with BD-15. The groups were treated for three consecutive days and the control group received 0.9% saline. BD-15 did not alter behavior of rats treated with different doses. An increase in the specific α2,3-Na, K-ATPase activity was observed for all doses of BD-15 tested in the hippocampus. However, in the prefrontal cortex, only the dose of 100 µg/Kg increased the activity of all Na, K-ATPase isoforms. BD-15 did not cause alteration in the lipid peroxidation levels in the hippocampus, but in the prefrontal cortex, a decrease of lipid peroxidation (~ 25%) was observed. In the hippocampus, GSH levels increased with all doses tested, while in the prefrontal cortex no changes were found. Subsequently, when the effect of BD-15 on cardiac tissue was analyzed, no changes were observed in the tested parameters. BD-15 at a dosage of 100 µg/Kg proved to be promising because it is considered therapeutic for brain disorders, since it increases the activity of the α3-Na, K-ATPase in the hippocampus and prefrontal cortex, as well as decreasing the oxidative stress in these brain regions. In addition, this drug did not cause changes in the tissues of the heart and kidneys, preferentially demonstrating specificity for the brain.

Dehydrobufotenin extracted from the Amazonian toad Rhinella marina (Anura: Bufonidae) as a prototype molecule for the development of antiplasmodial drugs

Background:

The resistance against antimalarial drugs represents a global challenge in the fight and control of malaria. The Brazilian biodiversity can be an important tool for research and development of new medicinal products. In this context, toxinology is a multidisciplinary approach on the development of new drugs, including the isolation, purification, and evaluation of the pharmacological activities of natural toxins. The present study aimed to evaluate the cytotoxicity, as well as the antimalarial activity in silico and in vitro of four compounds isolated from Rhinella marina venom as potential oral drug prototypes.

Methods:

Four compounds were challenged against 35 target proteins from P. falciparum and screened to evaluate their physicochemical properties using docking assay in Brazilian Malaria Molecular Targets (BraMMT) software and in silico assay in OCTOPUS® software. The in vitro antimalarial activity of the compounds against the 3D7 Plasmodium falciparum clones were assessed using the SYBR Green I based assay (IC₅₀). For the cytotoxic tests, the LD₅₀ was determined in human pulmonary fibroblast cell line using the [3(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] (MTT) assay.

Results:

All compounds presented a ligand-receptor interaction with ten Plasmodium falciparum-related protein targets, as well as antimalarial activity against chloroquine resistant strain (IC₅₀ = 3.44 μM to 19.11 μM). Three of them (dehydrobufotenine, marinobufagin, and bufalin) showed adequate conditions for oral drug prototypes, with satisfactory prediction of absorption, permeability, and absence of toxicity. In the cell viability assay, only dehydrobufotenin was selective for the parasite.

Conclusions:

Dehydrobufotenin revealed to be a potential oral drug prototype presenting adequate antimalarial activity and absence of cytotoxicity, therefore should be subjected to further studies.

Cordyceps cicadae polysaccharides inhibit human cervical cancer hela cells proliferation via apoptosis and cell cycle arrest

The present study presented the extraction and purification of polysaccharides from artificially cultured Cordyceps cicadae and wild Cordyceps cicadae by pre-soaking ultrasonic water extraction. The effects of different concentrations of polysaccharides on proliferation and cytotoxicity of Hela cells were detected by MTT and LDH methods. The results showed that the proliferation of Hela cells was inhibited by polysaccharides treatment (25 μg/mL-1600 μg/mL). The results of flow cytometry further confirmed that polysaccharides blocked the cell cycle in the S phase and promoted apoptosis. RT-qPCR and Western Blot were used to study the mRNA and protein expression of genes related to cell cycle and apoptosis signaling pathway. The results showed that polysaccharides treatment inhibited the expression of Cyclin E, Cyclin A and CDK2 and up regulated the expression of P53. Further, activation of Caspase cascade reaction, up regulation of death receptor, and the ratio of pro-apoptotic factor/anti-apoptotic factors, thus caused the cell cycle arrest and induced the apoptosis. The above research results lay a foundation for extending the anti-cancer effects of natural plant resources with low toxicity and high efficiency.