Salinomycin Inhibits Influenza Virus Infection by Disrupting Endosomal Acidification and Viral Matrix Protein 2 Function.

Screening of chemical libraries with 2,000 synthetic compounds identified salinomycin as a hit against influenza A and B viruses, with 50% effective concentrations ranging from 0.4 to 4.3 µM in cells. This compound is a carboxylic polyether ionophore that exchanges monovalent ions for protons across lipid bilayer membranes. Monitoring the time course of viral infection showed that salinomycin blocked nuclear migration of viral nuclear protein (NP), the most abundant component of the viral ribonucleoprotein (vRNP) complex. It caused cytoplasmic accumulation of NP, particularly within perinuclear endosomes, during virus entry. This was primarily associated with failure to acidify the endosomal-lysosomal compartments. Similar to the case with amantadine (AMT), proton channel activity of viral matrix protein 2 (M2) was blocked by salinomycin. Using purified retroviral Gag-based virus-like particles (VLPs) with M2, it was proved that salinomycin directly affects the kinetics of a proton influx into the particles but in a manner different from that of AMT. Notably, oral administration of salinomycin together with the neuraminidase inhibitor oseltamivir phosphate (OSV-P) led to enhanced antiviral effect over that with either compound used alone in influenza A virus-infected mouse models. These results provide a new paradigm for developing antivirals and their combination therapy that control both host and viral factors.IMPORTANCE Influenza virus is a main cause of viral respiratory infection in humans as well as animals, occasionally with high mortality. Circulation of influenza viruses resistant to the matrix protein 2 (M2) inhibitor, amantadine, is highly prevalent. Moreover, the frequency of detection of viruses resistant to the neuraminidase inhibitors, including oseltamivir phosphate (OSV-P) or zanamivir, is also increasing. These issues highlight the need for discovery of new antiviral agents with different mechanisms. Salinomycin as the monovalent cation-proton antiporter exhibited consistent inhibitory effects against influenza A and B viruses. It plays multifunctional roles by blocking endosomal acidification and by inactivating the proton transport function of M2, the key steps for influenza virus uncoating. Notably, salinomycin resulted in marked therapeutic effects in influenza virus-infected mice when combined with OSV-P, suggesting that its chemical derivatives could be developed as an adjuvant antiviral therapy to treat influenza infections resistant or less sensitive to existing drugs.

In vitro screening of NADPH oxidase inhibitors and in vivo effects of L-leucinethiol on experimental autoimmune encephalomyelitis-induced mice.

Experimental autoimmune encephalomyelitis (EAE), a Th1 polarized demyelinating disease of the central nervous system, shares many pathological and clinical similarities with multiple sclerosis (MS). The objectives of this study were i) to evaluate the suppressive effects of L-leucinethiol (LeuSH), a metalloprotease inhibitor on EAE-induced mice and ii) to study the effects of LeuSH on matrix metalloproteinase-9 (MMP-9), NADPH oxidase and cytokines (IFN-γ, IL-5 and IL-10) in tissues and plasma of EAE mice as a measure of potential markers associated with EAE disease. C57BL/6 mice were immunized with myelin oligodendrocyte glycoprotein (MOG35-55) peptide in complete Freund's adjuvant to induce EAE. A significant difference was observed in body weights and clinical signs of LeuSH (8 mg/kg) administered EAE-induced mice compared to control mice. The findings of this study include alterations in the enzymatic expression of MMP-9, NADPH oxidase and cytokine levels in the brain, spinal cord, spleen, thymus and plasma of inhibitor-treated EAE mice as well as EAE-induced mice. The enzyme activities of NADPH oxidase were inhibited by LeuSH. From these results, it can be considered that LeuSH acts as one of the antigen candidates in ameliorating the clinical symptoms of EAE disease in mice.

Effects of ginsenosides, active ingredients of Panax ginseng, on development, growth, and life span of Caenorhabditis elegans.

The backbone structure of ginsenosides, active ingredients of Panax ginseng, is similar with that of sterol, especially cholesterol. Caenorhabditis elegans (C. elegans) is one of free living nematodes and is well-established animal model for biochemical and genetic studies. C. elegans cannot synthesize de novo cholesterol, although cholesterol is essential requirement for its growth and development. In the present study, we investigated the effects of ginseng total saponins (GTS) on the average brood size, growth, development, worm size, and life span of C. elegans in cholesterol-deprived and -fed medium. Cholesterol deprivation caused damages on normal growth, reproduction, and life span of worms throughout F1 to F3 generations. GTS supplement to cholesterol-deprived medium restored the growth, reproduction, and life span of worms as much as cholesterol alone-fed medium. GTS co-supplement to cholesterol-fed medium not only promoted worm reproduction but also induced bigger worms and faster growth than cholesterol-fed medium. In study to identify which ginsenosides are responsible for life span restoring effects of GTS, we found that ginsenoside Rc supplement not only restored life span of worms grown in cholesterol-deprived medium but also prolonged life span of worms grown in cholesterol-fed medium. Worms grown in medium supplemented with ginsenoside Rb(1) or Rc to cholesterol-deprived medium exhibited strong filipin staining, in which filipin forms tight and specific complexes with 3beta-hydroxy sterols. These results show a possibility that ginsenosides could be utilized by C. elegans as a sterol substitute and further indicate that ginsenoside Rc is the component of Panax ginseng that prolongs the life span of C. elegans.

Pharmacokinetics and bioequivalence of tiropramide in healthy volunteers.

Two formulations of tiropramide ((+/-)alpha-(benzoylamino)-4-[2-(diethylamino) ethoxy]-N,N-dipropyl-benzenepropanamide hydrochloride, CAS 55837-29-1), an antispasmodic agent, were orally administered to 16 healthy volunteers by the Latin cross-over design with the purpose of evaluating bioequivalence and pharmacokinetics of tiropramide. Tiropramide in human plasma was determined by a gas chromatography/nitrogen phosphorus detector. The detection limit of tiropramide was 5 ng/ml. Cmax values of test and reference formulations were 93.9 +/- 54.3 and 96.4 +/- 51.6 ng/ml, respectively. AUC0-->last and AUC0-->inf were 330.7 +/- 193.9 and 349.5 +/- 205.3 ng.h/ml, respectively, for the test formulation, 348.9 +/- 207.7 and 380.8 +/- 239.0 ng.h/ml, respectively, for the reference formulation. The terminal half-life was 2.34-2.61 h. Bioavailability differences for Cmax and AUC0-->last were -2.48% and -5.22%, respectively. Minimum detection differences were less than 20% for both Cmax and AUC0-->last. The 90% confidence limits of geometric mean values for logarithmically transformed Cmax and AUCs were within 0.8-1.25. Based on these results, the two formulations of tiropramide are considered to be bioequivalent.

Quantitative analysis of tiropramide in human blood by gas chromatography with nitrogen-phosphorus detector.

The analytical method of antispasmodic agent tiropramide ((+/-)alpha-(benzoylamino)-4-[2-(diethylamino)ethoxy]-N,N-dipropylbenzenepropanamide hydrochloride) was developed by gas chromatography/nitrogen-phosphorus detector (GC/NPD) in human plasma. Two kinds of tiropramide tablets were orally administered to volunteers by Latin square crossover design, and blood was withdrawn as designed schedule. The plasma of 1 mL was loaded on Sep-pak C18 cartridge and eluted with methanol after washing with 30% methanol. The residue dissolved in 100 microL of methanol after evaporation was analyzed by GC/NPD. Precision (CV%) of intra-day was located within 2.6% and accuracy was less than 9.7%. Inter-day precision was below 8.7% and accuracy was relatively good as less than 14%. Plasma samples obtained from human volunteers were analyzed for the determination of tiropramide concentration by using this method. The method was sensitive, rapid and suitable enough to be applied for pharmacokinetic and bioequivalence studies of tiropramide in human volunteers.