Cardiac glycosides from Streblus asper with potential antiviral activity.

Ten undescribed cardiac glycosides, strasperosides A-J, together with twelve known analogues, were isolated from Streblus asper Lour. Their structures were elucidated on the basis of spectroscopic analysis, electronic circular dichroism data, and chemical methods. These cardiac glycosides showed diversity in steroid skeleton and sugar moiety. Strasperosides A and B are a pair of unusual stereoisomers featuring different orientation of the lactone motif. Ten cardiac glycosides demonstrated potent antiviral effects on HSV-1 in vitro with the IC50 values from 0.19 ± 0.08 to 1.03 ± 0.25 µM and the therapeutic indices from 66.61 ± 5.08 to 326.75 ± 11.75.

Pitsubcosides A-L, highly esterified eudesmane sesquiterpenoid glycosides with antibacterial activity from Pittosporum subulisepalum and their mechanism.

BACKGROUND: Plants from the genus Pittosporum are traditionally used as antibacterial, antifungal and antiviral agents. A bioassay evaluation of the extract of Pittosporum subulisepalum revealed antibacterial activity. This study focused on the discovery of the antibacterial metabolism in P. subulisepalum, as well as the modes of action of its active components. RESULTS: A chemical investigation of an ethyl acetate (EtOAc) extract of the aerial parts of P. subulisepalum led to the isolation of 12 previously undescribed eudesmane sesquiterpenoid glycoside esters (ESGEs), pitsubcosides A-L (1-12). Their structures were elucidated by extensive spectroscopic analysis, including one- and two-dimensional NMR, high-resolution electrospray ionization mass spectrometry, electronic circular dichroism spectra and single-crystal X-ray crystallography analysis or by comparing with authentic samples. The new ESGEs were characterized by their highly esterified glycoside moieties. Among them, compounds 1-3, 5 and 8 showed a moderate inhibitory effect against Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Bacillus cereus, Bacillus subtilis, Pseudomonas syringae pv. actinidiae (Psa) and Erwinia carotovora with minimum inhibitory concentrations (MICs) ranging from 3.13 to 100 µm. Among them, compounds 3 and 5 showed remarkable antibacterial activity against S. aureus and Psa with MIC values of 6.25 and 3.13 µm, respectively. Live bacterial mass and the biofilms of S. aureus and Psa were quantified using methyl tetrazolium and crystal violet assays. Fluorescence microscopy and scanning electron microscopy experiments revealed an antibacterial mechanism of cell membrane architectural disruption. CONCLUSION: The results suggest that ESGEs possess great potential for the development of antibacterial agents to control plant pathogens. © 2023 Society of Chemical Industry.

Quantification of plant cardenolides by HPLC, measurement of Na+/K+-ATPase inhibition activity, and characterization of target enzymes.

The biosynthesis of cardiac glycosides, broadly classified as cardenolides and bufadienolides, has evolved repeatedly among flowering plants. Individual species can produce dozens or even hundreds of structurally distinct cardiac glycosides. Although all cardiac glycosides exhibit biological activity by inhibiting the function of the essential Na+/K+-ATPase in animal cells, they differ in their level of inhibitory activity. For within- and between-species comparisons of cardiac glycosides to address ecological and evolutionary questions, it is necessary to not only quantify their relative abundance, but also their effectiveness in inhibiting the activity of different animal Na+/K+-ATPases. Here we describe protocols for characterizing the amount and toxicity of cardenolides from plant samples and the degree of insect Na+/K+-ATPase tolerance to inhibition: (1) an HPLC-based assay to quantify the abundance of individual cardenolides in plant extracts, (2) an assay to quantify inhibition of Na+/K+-ATPase activity by plant extracts, and (3) extraction of insect Na+/K+-ATPases for inhibition assays.

Evidence for Cardiac Glycosides in Foliage of Colorado Potato Beetle-Resistant Solanum okadae.

Leptinotarsa decemlineata, the Colorado potato beetle (CPB), is a herbivore that primarily feeds on Solanum foliage and is a global pest of the potato agricultural industry. Potato breeding through cross-hybridization with CPB-resistant wild relatives is used for genetic improvement. The wild species Solanum okadae was demonstrated to deter CPB feeding in choice and no choice feeding assays. Liquid chromatography-mass spectrometry (LC-MS) was used for comparative metabolite profiling between S. okadae and CPB-susceptible domesticated potato variety, Solanum tuberosum cv. Shepody. Major foliar metabolites detected were steroidal glycoalkaloids (SGAs) with tomatine and dehydrotomatine produced in S. okadae and solanine and chaconine in S. tuberosum cv. Shepody. Cardiac glycosides were also detected in the foliar metabolite profile of S. okadae but not S. tuberosum cv. Shepody. This class of plant compounds have known insecticidal activity through inhibition of animal Na+/K+ ATPase. Thin-layer chromatography (TLC) separation of foliar extracts also provided evidence for cardiac glycosides in S. okadae. Cardiac glycosides are known inhibitors of Na+/K+ ATPase, and foliar extracts from S. okadae (OKA15), but not S. tuberosum cv. Shepody, were able to inhibit the Na+/K+ ATPase of CPB. These findings suggest a novel mechanism of plant resistance against CPB involving production of cardiac glycosides in S. okadae.

Periplocin and cardiac glycosides suppress the unfolded protein response.

The unfolded protein response (UPR) controls protein homeostasis through transcriptional and translational regulation. However, dysregulated UPR signaling has been associated with the pathogenesis of many human diseases. Therefore, the compounds modulating UPR may provide molecular insights for these pathologies in the context of UPR. Here, we screened small-molecule compounds that suppress UPR, using a library of Myanmar wild plant extracts. The screening system to track X-box binding protein 1 (XBP1) splicing activity revealed that the ethanol extract of the Periploca calophylla stem inhibited the inositol-requiring enzyme 1 (IRE1)-XBP1 pathway. We isolated and identified periplocin as a potent inhibitor of the IRE1-XBP1 axis. Periplocin also suppressed other UPR axes, protein kinase R-like endoplasmic reticulum kinase (PERK), and activating transcription factor 6 (ATF6). Examining the structure-activity relationship of periplocin revealed that cardiac glycosides also inhibited UPR. Moreover, periplocin suppressed the constitutive activation of XBP1 and exerted cytotoxic effects in the human multiple myeloma cell lines, AMO1 and RPMI8226. These results reveal a novel suppressive effect of periplocin or the other cardiac glycosides on UPR regulation, suggesting that these compounds will contribute to our understanding of the pathological or physiological importance of UPR.

Malayoside, a cardenolide glycoside extracted from Antiaris toxicaria Lesch, induces apoptosis in human non-small lung cancer cells via MAPK-Nur77 signaling pathway.

Lung cancer is the leading cause of cancer deaths in the world. Non-small cell lung cancer (NSCLC), with poor prognosis and resistance to chemoradiotherapy, is the most common histological type of lung cancer. Therefore, it is necessary to develop new and more effective treatment strategy for NSCLC. Nur77, an orphan member of the nuclear receptor superfamily, induces apoptosis in cancer cells including NSCLC cells, by high expression and translocation to mitochondria. Small molecules trigger expression and mitochondrial localization of Nur77 may be an ideal anti-cancer drug candidate. Here, we report malayoside, a cardiac glycoside in the extract of Antiaris toxicaria Lesch., had different sensitivities to NSCLC cells. Malayoside induced apoptosis in NCI-H460 cells. Meanwhile, malayoside induced Nur77 expression and mitochondrial localization, and its induction of apoptosis was Nur77-dependent. To investigate the molecular mechanism of malayoside inducing Nur77 and apoptosis, we found that malayoside activated MAPK signaling pathway, including both ERK and p38 phosphorylation. The suppression of MAPK signaling activation inhibited the expression of Nur77 and apoptosis induced by malayoside. Our studies in nude mice showed that malayside potently inhibited the growth of tumor cells in vivo. Furthermore, the anti-cancer effect of malayosidwas in vivo was also related to the elevated expression of Nur77, p-ERK, and p-p38 proteins. Our results suggest that malayoside possesses an anti-NSCLC activity in vitro and in vivo mainly via activation of MAPK-Nur77 signaling pathway, indicating that malayoside is a promising chemotherapeutic candidate for NSCLC.

Implications for glycosylated compounds and their anti-cancer effects.

Glycosylated compounds are major secondary metabolites of plants, which have various therapeutic effects on human diseases, by acting as anti-cancer, antioxidant, and anti-inflammatory agents. Glycosylation increases stability, bioactivity, and solubility of compounds and improves their pharmacological properties. Two well-known examples of glycosylated compounds include cardiac and flavonoid, the anti-tumor activities of which have been emphasized by several studies. However, little is known about their role in the treatment or prevention of cancer. In this review, recent studies on anti-tumor properties of cardiac and flavonoid glycosides, and their mechanisms of action, have been investigated. More specifically, this review is aimed at focusing on the multifactorial properties of cardiac and flavonoid compounds as well as their correlation with signaling pathways in the treatment of cancer.

Modulatory properties of cardiac and quercetin glycosides from Dacryodes edulis seeds during L-NAME-induced vascular perturbation.

Background Numerous food wastes have been identified to possess potent bioactive compounds used for the treatment of several diseases. Therefore this study evaluated the potentials of cardiac and quercetin glycosides extracted from Dacryodes edulis seeds to reverse vascular and endothelial damage (VAED). Methods The glycoside composition of the seeds was extracted using standard methods and characterized by gas chromatography. We then recruited rats with L-NAME-induced VAED based on confirmatory biomarkers cardiac troponin (CnT), cellular adhesion molecule (VCAM-1), lipoprotein associated phospholipase A2 (Lp-PLA2), RAAS, VWF, endothelin, eNOx, and homocysteine. Only rats that showed total alterations of all biomarkers were recruited into the respective experimental groups and treated with either metaprolol succinate (met.su) + losartan or glycoside extracts of D. edulis seeds (NPSG). Results Chromatographic isolation of glycosides in the seed showed predominance of artemetin (1.59 mg/100 g), amygdalin (3.68 mg/100 g), digitoxin (19.21 mg/100 g), digoxin (27.23 mg/100 g), avicularin (133.59 mg/100 g), and hyperoside (481.76 mg/100 g). We observed decreased water intake and higher heart beats under vascular damage as the experiment progressed up to the fourth week. The met.su + losartan and H.D NPSG proved effective in restoring troponin, but both doses of NPSG normalized the VCAM-1 and RAAS activities excluding aldosterone and Lp-PLA2. Among the endothelial dysfunction biomarkers, H.D NPSG produced equivalent effects to met.su + losartan towards restoring the eNOx and VWF activities, but showed higher potency in normalizing the endothelin and Hcy levels. Conclusions We thus propose that the synergistic effect of the isolated glycosides from D. edulis shown in our study proved potent enough at high doses in treatment of vascular and endothelial dysfunction.

Cytotoxic and non-cytotoxic cardiac glycosides isolated from the combined flowers, leaves, and twigs of Streblus asper.

A new non-cytotoxic [(+)-17ß-hydroxystrebloside (1)] and two known cytotoxic [(+)-3'-de-O-methylkamaloside (2) and (+)-strebloside (3)] cardiac glycosides were isolated and identified from the combined flowers, leaves, and twigs of Streblus asper collected in Vietnam, with the absolute configuration of 1 established from analysis of its ECD and NMR spectroscopic data and confirmed by computational ECD calculations. A new 14,21-epoxycardanolide (3a) was synthesized from 3 that was treated with base. A preliminary structure-activity relationship study indicated that the C-14 hydroxy group and the C-17 lactone unit and the established conformation are important for the mediation of the cytotoxicity of 3. Molecular docking profiles showed that the cytotoxic 3 and its non-cytotoxic analogue 1 bind differentially to Na+/K+-ATPase. Compound 3 docks deeply in the Na+/K+-ATPase pocket with a sole pose, and its C-10 formyl and C-5, C-14, and C-4' hydroxy groups may form hydrogen bonds with the side-chains of Glu111, Glu117, Thr797, and Arg880 of Na+/K+-ATPase, respectively. However, 1 fits the cation binding sites with at least three different poses, which all depotentiate the binding between 1 and Na+/K+-ATPase. Thus, 3 was found to inhibit Na+/K+-ATPase, but 1 did not. In addition, the cytotoxic and Na+/K+-ATPase inhibitory 3 did not affect glucose uptake in human lung cancer cells, against which it showed potent activity, indicating that this cardiac glycoside mediates its cytotoxicity by targeting Na+/K+-ATPase but not by interacting with glucose transporters.

Combinatorial screening of a panel of FDA-approved drugs identifies several candidates with anti-Ebola activities.

Ebola virus (EBOV), pathogen of Ebola hemorrhagic fever (EHF), is an enveloped filamental RNA virus. Recently, the EHF crisis occurred in the Democratic Republic of the Congo again highlights the urgency for its clinical treatments. However, no Food and Drug Administration (FDA)-approved therapeutics are currently available. Drug repurposing screening is a time- and cost-effective approach for identifying anti-EBOV therapeutics. Here, by combinatorial screening using pseudovirion and minigenome replicon systems we have identified several FDA-approved drugs with significant anti-EBOV activities. These potential candidates include azithromycin, clomiphene, chloroquine, digitoxin, epigallocatechin-gallate, fluvastatin, tetrandrine and tamoxifen. Mechanistic studies revealed that fluvastatin inhibited EBOV pseudovirion entry by blocking the pathway of mevalonate biosynthesis, while the inhibitory effect of azithromycin on EBOV maybe due to its intrinsic cationic amphiphilic structure altering the homeostasis of later endosomal vesicle similar as tamoxifen. Moreover, based on structure and pathway analyses, the anti-EBOV activity has been extended to other family members of statins, such as simvastatin, and multiple other cardiac glycoside drugs, some of which exhibited even stronger activities. More importantly, in searching for drug interaction, we found various synergy between several anti-EBOV drug combinations, showing substantial and powerful synergistic against EBOV infection. In conclusion, our work illustrates a successful and productive approach to identify new mechanisms and targets for treating EBOV infection by combinatorial screening of FDA-approved drugs.

Characterization, quantitation, similarity evaluation and combination with Na+,K+-ATPase of cardiac glycosides from Streblus asper.

Streblus asper Lour. (Moraceae) is a medicinal plant in Asian countries including India and Thailand, possessing activities of anti-tumor, anti-allergy, anti-parasitic and anti-bacterial. In this paper, characterization, quantitation and similarity evaluation of cardiac glycosides in different parts of S. asper were investigated by HPLC-Q-TOF-MS and chemometric methods. Then, the inhibition of Na+,K+-ATPase activity by the compounds isolated from S. asper was measured. Meanwhile, enzyme kinetics and molecular docking were determined to exhibit the combination modes between cardiac glycosides and Na+,K+-ATPase. As a result, twenty peaks of cardiac glycosides were assigned. Strophanthidin-3-O-α-l-rhamnopyranosyl-(1 → 4)-6-deoxy-ß-d-allopyranoside (1), glucostrebloside (2), strebloside (4) and mansonin (8) with a significant activity of inhibiting Na+,K+-ATPase (IC50 7.55-13.60 µM) were chosen for the determination of enzyme kinetics, exhibiting anticompetitive inhibitory characteristics towards Na+,K+-ATPase. Compound 4 could reasonably bind to the active sites of Na+,K+-ATPase, proved by molecular docking. Furthermore, the contents of the major compounds in four different parts of S. asper were extremely different, analyzed by chemometric methods, similarity analysis and principle compounds analysis. All these findings indicated that the contents of major compounds in different parts of S. asper were extremely different with a significant activity of inhibiting Na+,K+-ATPase, providing a reference for determination of effective part and administered dosage. The combination modes between cardiac glycosides and Na+,K+-ATPase were also revealed by enzyme kinetics and molecular docking, which provided a basis for further study of pharmacological activity.

Molluscicidal activity of cardiac glycosides isolated from Adenium obesum.

BACKGROUND: Terrestrial mollusks are one of most important agricultural pests worldwide. Natural phytochemicals have an extended history as a source of pesticides. This study was planned to isolate molluscicidal active compounds from the stems of Adenium obesum. RESULTS: The benzene-soluble fraction of the hydroethanolic extract displayed the most potent molluscicidal activity against Monacha obstructa among different solvent fractions with a median lethal dose (LD50 ) of 4.91 µg g-1 body weight (bw). The bioactivity-guided chemical exploration of the benzene-soluble fraction led to the isolation of two known cardiac glycosides, cerberin and neriifolin which showed significant molluscicidal activity with LD50 values of 5.39 and 4.3 µg g-1 bw, respectively. CONCLUSION: Isolation of the cardiac glycoside neriifolin from A. obesum and the molluscicidal activity of cerberin and neriifolin against terrestrial snails are reported for the first time. © 2019 Society of Chemical Industry.

Identification and screening of cardiac glycosides in Streptocaulon griffithii using an integrated data mining strategy based on high resolution mass spectrometry.

The present study was designed to develop a practical strategy to tackle the problem of lacking standard compounds and limited references for identifying structure-related compounds in Streptocaulon griffithii Hook. f., especially those in trace concentrations, with a focus on antitumor activity. The cardiac glycosides (CGs)-enriched part was determined using in vitro bioactive assays in three cancer cell lines and then isolated using macroporous resins. The MS and MS/MS data were acquired using a high performance liquid chromatography coupled with hybrid quadrupole-time of flight (HPLC-Q-TOF-MS) system. To acquire data of trace compound in the extract, a multiple segment program was applied to modify the HPLC-Q-TOF-MS method. A mass defect filter (MDF) approach was employed to make a primary MS data filtration. Utilizing a MATLAB program, the redundant peaks obtained by imprecise MDF template calculated with limited references were excluded by fragment ion classification, which was based on the ion occurrence number in the MDF-filtered total ion chromatograms (TIC). Additionally, the complete cleavage pathways of CG aglycones were proposed to assist the structural identification of 29 common fragment ions (CFIs, ion occurrence number ≥ 5) and diagnostic fragment ions (DFIs, ion occurrence number < 5). As a result, 30 CGs were filtered out from the MDF results, among which 23 were identified. This newly developed strategy may provide a rapid and effective tool for identifying structure-related compounds in herbal medicines.

Phytochemical analysis and antimicrobial activity of some medicinal plants against selected pathogenic microorganisms.

The aim of the present study is to investigate the antimicrobial potency of leaves from various extracts of Capparis zeylanica, Streblus asper and Tribulus terrestris were evaluated. In addition, this is the first report on MIC, MBC/MFC antimicrobial activities of above mentioned plants and also identify the phytochemical, functional groups by GC-MS and FT-IR respectively. Soxhlet extraction method was used for preparation of different extracts viz., aqueous, petroleum ether, ethyl acetate and methanol. The extracts were examined against Staphylococcus epidermidis, Enterococcus faecallis, Salmonella paratyphi, Shigella dysenteriae, Candida albicans and Mycobacterium tuberculosis by agar well diffusion method, and Minimum Inhibitory Concentratioon (MIC), Minimum Bactericidal/Fungicidal Concentration (MBC/MFC) values were determined through micro dilution method. Phytochemical analysis of compounds was carried out by GC-MS analysis and functional groups were identified by FT-IR. Based on the outcome of our results, Ethyl acetate extract Showed significant antimicrobial activity against the tested pathogens especially, for C. albicans (40 mm) followed by ethyl acetate of S. asper against S. paratyphi (38 mm). While, the least inhibition was observed with aqueous extract of T. terrestris against S. paratyphi (10 mm). The MIC ranged from 3.21 mg/ml to 50 mg/ml and MBC/MFC 6.25 mg/ml to 50 mg/ml was recorded. Ethyl acetate extracts of almost all samples showed better activity than other extracts in inhibition growth of pathogens. Phytochemical analysis exhibited the presence of Steroids, tannins and cardiac glycosides were found only in ethyl acetate extract of C. zeylanica. Functional group of leaf extract was confirmed by FT-IR spectrum and GC-MS analysis of the ethyl acetate extract revealed the presence of 20 compounds. The results revealed that ethyl acetate extract of C. zeylanica leaves has potential activity than the other extracts as well as standard drugs (Gentamycin and Ketocozole). Hence, this plant may be recommended for further studies in isolation of active compounds and related pharmacological activities.

Cytotoxicity and chromosomal aberrations induced by methanolic extract of Cuscuta reflexa and its pure compounds on meristematic cells of Allium species.

Cuscuta reflexa (Convolvulaceae), is commonly known as amarbel or akashbel. In Bangladesh and Nepal some of the tribes use C. reflexa against edema, body ache, cancer, skin infections and liver disorders. Despite its traditional uses there is no information regarding genotoxic effects of either the plant extract or its pure compounds. Methanolic extract of C. reflexa (MECR) and pure compounds derived from it namely, odoroside H, neritaloside, and strospeside, were evaluated in Allium cepa L. and A. sativum L. for their effects on root growth, root apical meristem mitotic index (MI) , and chromosomal aberrations (CAs). In this study, we adopted a new method of calculating percent change in root length. MECR caused a concentration- and time- dependent inhibition in root length at 100 - 10000µg/ml in A. cepa root. It was accompanied by a subsequent decline in MI which is an indicative of its cytotoxic effect. On the contrary, at low concentrations a significant rise in root length was noticeable. In A. sativum, MECR also reduced the root length having IC50 values ~8 x and 4.3 x lower than A. cepa. A variety of CAs were evident in both Allium systems after treatment with MECR, odoroside H and neritaloside. Thus in MECR, cardenolides glycosides, i.e. odoroside H and neritaloside could be accountable for its genotoxicity.

Production of the Cytotoxic Cardenolide Glucoevatromonoside by Semisynthesis and Biotransformation of Evatromonoside by a Digitalis lanata Cell Culture.

Recent studies demonstrate that cardiac glycosides, known to inhibit Na+/K+-ATPase in humans, have increased susceptibility to cancer cells that can be used in tumor therapy. One of the most promising candidates identified so far is glucoevatromonoside, which can be isolated from the endangered species Digitalis mariana ssp. heywoodii. Due to its complex structure, glucoevatromonoside cannot be obtained economically by total chemical synthesis. Here we describe two methods for glucoevatromonoside production, both using evatromonoside obtained by chemical degradation of digitoxin as the precursor. 1) Catalyst-controlled, regioselective glycosylation of evatromonoside to glucoevatromonoside using 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide as the sugar donor and 2-aminoethyldiphenylborinate as the catalyst resulted in an overall 30 % yield. 2) Biotransformation of evatromonoside using Digitalis lanata plant cell suspension cultures was less efficient and resulted only in overall 18 % pure product. Structural proof of products has been provided by extensive NMR data. Glucoevatromonoside and its non-natural 1-3 linked isomer neo-glucoevatromonoside obtained by semisynthesis were evaluated against renal cell carcinoma and prostate cancer cell lines.

Anticancer potential of Thevetia peruviana fruit methanolic extract.

BACKGROUND: Thevetia peruviana (Pers.) K. Schum or Cascabela peruviana (L.) Lippold (commonly known as ayoyote, codo de fraile, lucky nut, or yellow oleander), native to Mexico and Central America, is a medicinal plant used traditionally to cure diseases like ulcers, scabies, hemorrhoids and dissolve tumors. The purpose of this study was to evaluate the cytotoxic, antiproliferative and apoptotic activity of methanolic extract of T. peruviana fruits on human cancer cell lines. METHODS: The cytotoxic activity of T. peruviana methanolic extract was carried out on human breast, colorectal, prostate and lung cancer cell lines and non-tumorigenic control cells (fibroblast and Vero), using the MTT assay. For proliferation and motility, clonogenic and wound-healing assays were performed. Morphological alterations were monitored by trypan blue exclusion, as well as DNA fragmentation and AO/EB double staining was performed to evaluate apoptosis. The extract was separated using flash chromatography, and the resulting fractions were evaluated on colorectal cancer cells for their cytotoxic activity. The active fractions were further analyzed through mass spectrometry. RESULTS: The T. peruviana methanolic extract exhibited cytotoxic activity on four human cancer cell lines: prostate, breast, colorectal and lung, with values of IC50 1.91 ± 0.76, 5.78 ± 2.12, 6.30 ± 4.45 and 12.04 ± 3.43 µg/mL, respectively. The extract caused a significant reduction of cell motility and colony formation on all evaluated cancer cell lines. In addition, morphological examination displayed cell size reduction, membrane blebbing and detachment of cells, compared to non-treated cancer cell lines. The T. peruviana extract induced apoptotic cell death, which was confirmed by DNA fragmentation and AO/EB double staining. Fractions 4 and 5 showed the most effective cytotoxic activity and their MS analysis revealed the presence of the secondary metabolites: thevetiaflavone and cardiac glycosides. CONCLUSION: T. peruviana extract has potential as natural anti-cancer product with critical effects in the proliferation, motility, and adhesion of human breast and colorectal cancer cells, and apoptosis induction in human prostate and lung cancer cell lines, with minimal effects on non-tumorigenic cell lines.

A Drug Screen using Human iPSC-Derived Hepatocyte-like Cells Reveals Cardiac Glycosides as a Potential Treatment for Hypercholesterolemia.

Efforts to identify pharmaceuticals to treat heritable metabolic liver diseases have been hampered by the lack of models. However, cells with hepatocyte characteristics can be produced from induced pluripotent stem cells (iPSCs). Here, we have used hepatocyte-like cells generated from homozygous familial hypercholesterolemia (hoFH) iPSCs to identify drugs that can potentially be repurposed to lower serum LDL-C. We found that cardiac glycosides reduce the production of apolipoprotein B (apoB) from human hepatocytes in culture and the serum of avatar mice harboring humanized livers. The drugs act by increasing the turnover of apoB protein. Analyses of patient medical records revealed that the treatment of patients with cardiac glycosides reduced serum LDL-C levels. These studies highlight the effectiveness of using iPSCs to screen for potential treatments for inborn errors of hepatic metabolism and suggest that cardiac glycosides could provide an approach for reducing hepatocyte production of apoB and treating hypercholesterolemia.

Na⁺i,K⁺i-Dependent and -Independent Signaling Triggered by Cardiotonic Steroids: Facts and Artifacts.

Na⁺,K⁺-ATPase is the only known receptor of cardiotonic steroids (CTS) whose interaction with catalytic α-subunits leads to inhibition of this enzyme. As predicted, CTS affect numerous cellular functions related to the maintenance of the transmembrane gradient of monovalent cations, such as electrical membrane potential, cell volume, transepithelial movement of salt and osmotically-obliged water, symport of Na⁺ with inorganic phosphate, glucose, amino acids, nucleotides, etc. During the last two decades, it was shown that side-by-side with these canonical Na⁺i/K⁺i-dependent cellular responses, long-term exposure to CTS affects transcription, translation, tight junction, cell adhesion and exhibits tissue-specific impact on cell survival and death. It was also shown that CTS trigger diverse signaling cascades via conformational transitions of the Na⁺,K⁺-ATPase α-subunit that, in turn, results in the activation of membrane-associated non-receptor tyrosine kinase Src, phosphatidylinositol 3-kinase and the inositol 1,4,5-triphosphate receptor. These findings allowed researchers to propose that endogenous CTS might be considered as a novel class of steroid hormones. We focus our review on the analysis of the relative impact Na⁺i,K⁺i-mediated and -independent pathways in cellular responses evoked by CTS.

New Knowledge About Old Drugs: The Anti-Inflammatory Properties of Cardiac Glycosides.

In the 19th century, cardio-active steroid glycosides, shortly cardiac glycosides, were scientifically established as drugs against heart failure. Their in vivo, cellular, and molecular actions as well as their predominant target, Na+-K+-ATPase, have been comprehensively investigated in the 20th century and the discovery of endogenous cardiac glycosides has fostered this research field. In the last years, however, results from clinical trials and meta-analyses have questioned their therapeutic value due to efficacy and safety issues. This has led to a considerable decline of their usage. Beyond the cardiovascular system, cardiac glycosides have been increasingly recognized as antitumor compounds and Na+-K+-ATPase has evolved into a promising drug target in oncology. A wealth of review articles exists that intensively discuss these topics. Surprisingly, the anti-inflammatory actions of cardiac glycosides, which were discovered in the 1960s, have so far hardly been perceived and have not yet been summarized. This review provides an overview of the in vivo and in vitro actions of cardiac glycosides on inflammatory processes and of the signaling mechanisms responsible for these effects: cardiac glycosides have been found to decrease inflammatory symptoms in different animal models of acute and chronic inflammation. Regarding the underlying mechanisms most research has focused on leukocytes. In these cells, cardiac glycosides primarily inhibit cell proliferation and the secretion of proinflammatory cytokines.