proscillaridin and convallatoxin

Sodium taurocholate cotransporting polypeptide (NTCP) has been reported as a functional receptor for hepatitis B virus (HBV) infection. However, HBV could not efficiently infect HepG2 cells expressing NTCP (NTCP-HepG2 cells) under adherent monolayer-cell conditions. In this study, NTCP was mainly detected in the basolateral membrane region, but not the apical site, of monolayer NTCP-HepG2 cells. We hypothesized that non-adherent cell conditions of infection would enhance HBV infectivity. Non-adherent NTCP-HepG2 cells were prepared by treatment with trypsin and EDTA, which did not degrade NTCP in the membrane fraction. HBV successfully infected NTCP-HepG2 cells at a viral dose 10 times lower in non-adherent phase than in adherent phase. Efficient infection of non-adherent NTCP-HepG2 cells with blood-borne or cell-culture-derived HBV was observed and was remarkably impaired in the presence of the myristoylated preS1 peptide. HBV could also efficiently infect HepaRG cells under non-adherent cell conditions. We screened several compounds using our culture system and identified proscillaridin A as a potent anti-HBV agent with an IC50 value of 7.2 nM. In conclusion, non-adherent host cell conditions of infection augmented HBV infectivity in an NTCP-dependent manner, thus providing a novel strategy to identify anti-HBV drugs and investigate the mechanism of HBV infection.

Topics: Antiviral Agents; Bufanolides; Cell Adhesion; Digitoxin; Digoxin; Gene Expression; Hep G2 Cells; Hepatitis B virus; High-Throughput Screening Assays; Humans; Organic Anion Transporters, Sodium-Dependent; Phthalazines; Proscillaridin; Receptors, Virus; Simvastatin; Strophanthins; Symporters; Transgenes; Viral Envelope Proteins; Virus Internalization

Cardiac glycosides have been reported to exhibit cytotoxic activity against several different cancer types, but studies against colorectal cancer are lacking. In a screening procedure aimed at identifying natural products with activity against colon cancer, several cardiac glycosides were shown to be of interest, and five of these were further evaluated in different colorectal cancer cell lines and primary cells from patients. Convallatoxin (1), oleandrin (4), and proscillaridin A (5) were identified as the most potent compounds (submicromolar IC50 values), and digitoxin (2) and digoxin (3), which are used in cardiac disease, exhibited somewhat lower activity (IC50 values 0.27-4.1 microM). Selected cardiac glycosides were tested in combination with four clinically relevant cytotoxic drugs (5-fluorouracil, oxaliplatin, cisplatin, irinotecan). The combination of 2 and oxaliplatin exhibited synergism including the otherwise highly drug-resistant HT29 cell line. A ChemGPS-NP application comparing modes of action of anticancer drugs identified cardiac glycosides as a separate cluster. These findings demonstrate that such substances may exhibit significant activity against colorectal cancer cell lines, by mechanisms disparate from currently used anticancer drugs, but at concentrations generally considered not achievable in patient plasma.

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Camptothecin; Cardenolides; Colonic Neoplasms; Digitoxin; Digoxin; Drug Screening Assays, Antitumor; HT29 Cells; Humans; Irinotecan; NF-kappa B; Proscillaridin; Strophanthins

In the anaesthetized cat, SCOA ( Miroton ), a product which contains extracts from Scilla , Convallaria , Oleander and Adonis , displays not only its well-known positive inotropic effect but has also constrictor effects on veins when applied in intravenous doses of 21.5-100 GPU /kg ( GPU = guinea-pig units, i.e. cardiotoxic equivalents related to 1 g body weight of guinea-pigs). The latter effect differs in that it is somewhat more prolonged. With intraduodenal administration the doses required to achieve equal peak effects as with intravenous injection are about 4 times larger and this suggests a relatively good enteral availability in the cat. SCOA constricts not only veins but also arteries. However, this latter effect is comparatively small and occurs only after intraarterial infusion of high doses (9.1 and 91 GPU /min, respectively).--The cardiac glycosides contained in the drug product primarily account for its vasoactive qualities. The venous constrictor effect correlates with the guinea-pig units. In qualitative respects, the pure glycosides cymarin , convallatoxin , proscillaridin , and scillaren exert equal effects. There is, however, evidence that the correlation between the effect on veins and on the heart differs for the glycosides tested. Based on equal guinea-pig units, the adonis extract, for instance, acts on capacitance vessels about twice as much as scilla , oleander and convallaria extracts. Cymarin , too, has a stronger effect on veins than would be expected from its cardiotoxic effect. The action on arteries and veins are based on different mechanism.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Blood Vessels; Cardiac Glycosides; Cats; Cymarine; Dogs; Duodenum; Female; Glycosides; Hindlimb; In Vitro Techniques; Injections, Intravenous; Intubation, Gastrointestinal; Male; Myocardial Contraction; Plant Extracts; Proscillaridin; Regional Blood Flow; Strophanthins; Vascular Resistance