Aurintricarboxylic acid inhibits influenza virus neuraminidase

Magnesium enhances aurintricarboxylic acid's inhibitory action on the plasma membrane Ca2+-ATPase

Our research aimed to elucidate the mechanism by which aurintricarboxylic acid (ATA) inhibits plasma membrane Ca2+-ATPase (PMCA), a crucial enzyme responsible for calcium transport. Given the pivotal role of PMCA in cellular calcium homeostasis, understanding how it is inhibited by ATA holds significant implications for potentially regulating physiopathological cellular processes in which this pump is involved. Our experimental findings revealed that ATA employs multiple modes of action to inhibit PMCA activity, which are influenced by ATP but also by the presence of calcium and magnesium ions. Specifically, magnesium appears to enhance this inhibitory effect. Our experimental and in-silico results suggest that, unlike those reported in other proteins, ATA complexed with magnesium (ATA·Mg) is the molecule that inhibits PMCA. In summary, our study presents a novel perspective and establishes a solid foundation for future research efforts aimed at the development of new pharmacological molecules both for PMCA and other proteins.

Natural Product-Derived Phytochemicals for Influenza A Virus (H1N1) Prevention and Treatment

Influenza A (H1N1) viruses are prone to antigenic mutations and are more variable than other influenza viruses. Therefore, they have caused continuous harm to human public health since the pandemic in 2009 and in recent times. Influenza A (H1N1) can be prevented and treated in various ways, such as direct inhibition of the virus and regulation of human immunity. Among antiviral drugs, the use of natural products in treating influenza has a long history, and natural medicine has been widely considered the focus of development programs for new, safe anti-influenza drugs. In this paper, we focus on influenza A (H1N1) and summarize the natural product-derived phytochemicals for influenza A virus (H1N1) prevention and treatment, including marine natural products, flavonoids, alkaloids, terpenoids and their derivatives, phenols and their derivatives, polysaccharides, and derivatives of natural products for prevention and treatment of influenza A (H1N1) virus. We further discuss the toxicity and antiviral mechanism against influenza A (H1N1) as well as the druggability of natural products. We hope that this review will facilitate the study of the role of natural products against influenza A (H1N1) activity and provide a promising alternative for further anti-influenza A drug development.

Inhibition Effects and Mechanisms of Marine Compound Mycophenolic Acid Methyl Ester against Influenza A Virus

Influenza A virus (IAV) can cause infection and illness in a wide range of animals, including humans, poultry, and swine, and cause annual epidemics, resulting in thousands of deaths and millions of hospitalizations all over the world. Thus, there is an urgent need to develop novel anti-IAV drugs with high efficiency and low toxicity. In this study, the anti-IAV activity of a marine-derived compound mycophenolic acid methyl ester (MAE) was intensively investigated both in vitro and in vivo. The results showed that MAE inhibited the replication of different influenza A virus strains in vitro with low cytotoxicity. MAE can mainly block some steps of IAV infection post adsorption. MAE may also inhibit viral replication through activating the cellular Akt-mTOR-S6K pathway. Importantly, oral treatment of MAE can significantly ameliorate pneumonia symptoms and reduce pulmonary viral titers, as well as improving the survival rate of mice, and this was superior to the effect of oseltamivir. In summary, the marine compound MAE possesses anti-IAV effects both in vitro and in vivo, which merits further studies for its development into a novel anti-IAV drug in the future.

Antiviral and cytotoxic indole diterpenoids from the antarctic sponge-derived fungus Aspergillus candidus HDN15-152

One new indole diterpenoid, ascandinine T (1), and three known analogues (2-4) were isolated from an Antarctic sponge-derived fungus Aspergillus candidus HDN15-152. The structures, including absolute configurations, were established based on NMR, HRESIMS, and electronic circular dichroism (ECD) calculations. All isolated compounds were tested for antiviral and anticancer activity. Compound 4 displayed antiviral activity against influenza A virus (IAV) of A/PR/8/34(H1N1) strain with an IC50 value of 39.2 μM, while compound 2 showed cytotoxicity against NCI-H446, NCI-H446/EP and L-02 cells with IC50 values ranging from 9.77 to 13.91 μM.

Identification and characterization of aurintricarboxylic acid as a potential inhibitor of SARS-CoV-2 PLpro

As the global health crisis due to evolution of mutations in SARS-CoV-2 continues, it is important to develop several effective antivirals to control the disease. Targeting papain-like protease (PLpro) of SARS-CoV-2 for drug development is a promising strategy due to its dual role in promoting viral replication and dysregulating host immune responses. Here, we screened a library of compounds to find potential inhibitors of PLpro. We find aurintricarboxylic acid (ATA) inhibits PLpro with K_i and IC₅₀ values of 16 μM and 30 μM, respectively. The binding of ATA to PLpro was further characterized using isothermal titration calorimetry, differential scanning fluorimetry, dynamic light scattering and circular dichroism spectrometry. In vitro assays showed the antiviral potential of ATA with IC₅₀ of 50 μM. In vivo efficacy was studied in Syrian hamsters and the results are being discussed.

Drug Repurposing for Therapeutic Discovery against Human Metapneumovirus Infection

Human metapneumovirus (HMPV) is recognized as an important cause of pneumonia in infants, in the elderly, and in immunocompromised individuals worldwide. The absence of an antiviral treatment or vaccine strategy against HMPV infection creates a high burden on the global health care system. Drug repurposing has become increasingly attractive for the treatment of emerging and endemic diseases as it requires less research and development costs than traditional drug discovery. In this study, we developed an in vitro medium-throughput screening assay that allows for the identification of novel anti-HMPV drugs candidates. Out of ~2,400 compounds, we identified 11 candidates with a dose-dependent inhibitory activity against HMPV infection. Additionally, we further described the mode of action of five anti-HMPV candidates with low in vitro cytotoxicity. Two entry inhibitors, Evans Blue and aurintricarboxylic acid, and three post-entry inhibitors, mycophenolic acid, mycophenolate mofetil, and 2,3,4-trihydroxybenzaldehyde, were identified. Among them, the mycophenolic acid series displayed the highest levels of inhibition, due to the blockade of intracellular guanosine synthesis. Importantly, MPA has significant potential for drug repurposing as inhibitory levels are achieved below the approved human oral dose. Our drug-repurposing strategy proved to be useful for the rapid discovery of novel hit candidates to treat HMPV infection and provide promising novel templates for drug design.

Small Molecule Receptor Binding Inhibitors with In Vivo Efficacy against Botulinum Neurotoxin Serotypes A and E

Botulinum neurotoxins (BoNTs) are the most poisonous substances in nature. Currently, the only therapy for botulism is antitoxin. This therapy suffers from several limitations and hence new therapeutic strategies are desired. One of the limitations in discovering BoNT inhibitors is the absence of an in vitro assay that correlates with toxin neutralization in vivo. In this work, a high-throughput screening assay for receptor-binding inhibitors against BoNT/A was developed. The assay is composed of two chimeric proteins: a receptor-simulating protein, consisting of the fourth luminal loop of synaptic vesicle protein 2C fused to glutathione-S-transferase, and a toxin-simulating protein, consisting of the receptor-binding domain of BoNT/A fused to beta-galactosidase. The assay was applied to screen the LOPAC1280 compound library. Seven selected compounds were evaluated in mice exposed to a lethal dose of BoNT/A. The compound aurintricarboxylic acid (ATA) conferred 92% protection, whereas significant delayed time to death (p < 0.005) was observed for three additional compounds. Remarkably, ATA was also fully protective in mice challenged with a lethal dose of BoNT/E, which also uses the SV2 receptor. This study demonstrates that receptor-binding inhibitors have the potential to serve as next generation therapeutics for botulism, and therefore the assay developed may facilitate discovery of new anti-BoNT countermeasures.

Identification of SARS-CoV-2 Receptor Binding Inhibitors by In Vitro Screening of Drug Libraries

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is responsible for the coronavirus disease 2019 (COVID-19) global pandemic. The first step of viral infection is cell attachment, which is mediated by the binding of the SARS-CoV-2 receptor binding domain (RBD), part of the virus spike protein, to human angiotensin-converting enzyme 2 (ACE2). Therefore, drug repurposing to discover RBD-ACE2 binding inhibitors may provide a rapid and safe approach for COVID-19 therapy. Here, we describe the development of an in vitro RBD-ACE2 binding assay and its application to identify inhibitors of the interaction of the SARS-CoV-2 RBD to ACE2 by the high-throughput screening of two compound libraries (LOPAC^®1280 and DiscoveryProbeTM). Three compounds, heparin sodium, aurintricarboxylic acid (ATA), and ellagic acid, were found to exert an effective binding inhibition, with IC50 values ranging from 0.6 to 5.5 µg/mL. A plaque reduction assay in Vero E6 cells infected with a SARS-CoV-2 surrogate virus confirmed the inhibition efficacy of heparin sodium and ATA. Molecular docking analysis located potential binding sites of these compounds in the RBD. In light of these findings, the screening system described herein can be applied to other drug libraries to discover potent SARS-CoV-2 inhibitors.

An effective human uracil-DNA glycosylase inhibitor targets the open pre-catalytic active site conformation

Human uracil DNA-glycosylase (UDG) is the prototypic and first identified DNA glycosylase with a vital role in removing deaminated cytosine and incorporated uracil and 5-fluorouracil (5-FU) from DNA. UDG depletion sensitizes cells to high APOBEC3B deaminase and to pemetrexed (PEM) and floxuridine (5-FdU), which are toxic to tumor cells through incorporation of uracil and 5-FU into DNA. To identify small-molecule UDG inhibitors for pre-clinical evaluation, we optimized biochemical screening of a selected diversity collection of >3,000 small-molecules. We found aurintricarboxylic acid (ATA) as an inhibitor of purified UDG at an initial calculated IC₅₀ < 100 nM. Subsequent enzymatic assays confirmed effective ATA inhibition but with an IC₅₀ of 700 nM and showed direct binding to the human UDG with a K_D of <700 nM. ATA displays preferential, dose-dependent binding to purified human UDG compared to human 8-oxoguanine DNA glycosylase. ATA did not bind uracil-containing DNA at these concentrations. Yet, combined crystal structure and in silico docking results unveil ATA interactions with the DNA binding channel and uracil-binding pocket in an open, destabilized UDG conformation. Biologically relevant ATA inhibition of UDG was measured in cell lysates from human DLD1 colon cancer cells and in MCF-7 breast cancer cells using a host cell reactivation assay. Collective findings provide proof-of-principle for development of an ATA-based chemotype and “door stopper” strategy targeting inhibitor binding to a destabilized, open pre-catalytic glycosylase conformation that prevents active site closing for functional DNA binding and nucleotide flipping needed to excise altered bases in DNA.

Inhibition of Orbivirus Replication by Aurintricarboxylic Acid

Bluetongue virus (BTV) and African horse sickness virus (AHSV) are vector-borne viruses belonging to the Orbivirus genus, which are transmitted between hosts primarily by biting midges of the genus Culicoides. With recent BTV and AHSV outbreaks causing epidemics and important economy losses, there is a pressing need for efficacious drugs to treat and control the spread of these infections. The polyanionic aromatic compound aurintricarboxylic acid (ATA) has been shown to have a broad-spectrum antiviral activity. Here, we evaluated ATA as a potential antiviral compound against Orbivirus infections in both mammalian and insect cells. Notably, ATA was able to prevent the replication of BTV and AHSV in both cell types in a time- and concentration-dependent manner. In addition, we evaluated the effect of ATA in vivo using a mouse model of infection. ATA did not protect mice against a lethal challenge with BTV or AHSV, most probably due to the in vivo effect of ATA on immune system regulation. Overall, these results demonstrate that ATA has inhibitory activity against Orbivirus replication in vitro, but further in vivo analysis will be required before considering it as a potential therapy for future clinical evaluation.

Discovery of M Protease Inhibitors Encoded by SARS-CoV-2

The coronavirus (CoV) disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome CoV-2 (SARS-CoV-2) is a health threat worldwide. Viral main protease (M^pro, also called 3C-like protease [3CL^pro]) is a therapeutic target for drug discovery. Herein, we report that GC376, a broad-spectrum inhibitor targeting M^pro in the picornavirus-like supercluster, is a potent inhibitor for the M^pro encoded by SARS-CoV-2, with a half-maximum inhibitory concentration (IC₅₀) of 26.4 ± 1.1 nM. In this study, we also show that GC376 inhibits SARS-CoV-2 replication with a half-maximum effective concentration (EC₅₀) of 0.91 ± 0.03 μM. Only a small portion of SARS-CoV-2 M^pro was covalently modified in the excess of GC376 as evaluated by mass spectrometry analysis, indicating that improved inhibitors are needed. Subsequently, molecular docking analysis revealed that the recognition and binding groups of GC376 within the active site of SARS-CoV-2 M^pro provide important new information for the optimization of GC376. Given that sufficient safety and efficacy data are available for GC376 as an investigational veterinary drug, expedited development of GC376, or its optimized analogues, for treatment of SARS-CoV-2 infection in human is recommended.

A sulfated glucuronorhamnan from the green seaweed Monostroma nitidum: Characteristics of its structure and antiviral activity

A water-soluble polysaccharide from Monostroma nitidum, designated MWS, was isolated using water extraction, anion-exchange and size-exclusion chromatography. MWS was a sulfated glucuronorhamnan consisting of →3)-α-l-Rhap-(1→, →4)-β-d-GlcpA-(1→ and →2)-α-l-Rhap-(1→ units. Sulfate ester groups located at C-4/C-2 of →3)-α-l-Rhap-(1→ and C-4/C-3 of →2)-α-l-Rhap-(1→ units. In in vitro tests, it was proved that MWS possessed broad spectrum against different viruses, especially for enterovirus 71 (EV71) with nearly no toxicity in relation to cell lines used. MWS may largely inhibit EV71 infection before or during viral adsorption through binding to virus particles and block some early steps of virus life cycle by down-regulating host phosphoinositide 3-kinase /protein kinase B signaling pathway. Intramuscular injection of MWS markedly reduced viral titers in EV71-infected mice. The data demonstrated that MWS could have great promising to become an antiviral drug for prevention and therapy of EV71 infection.

Identification of aurintricarboxylic acid as a potent allosteric antagonist of P2X1 and P2X3 receptors

The homotrimeric P2X3 receptor, one of the seven members of the ATP-gated P2X receptor family, plays a crucial role in sensory neurotransmission. P2X3 receptor antagonists have been identified as promising drugs to treat chronic cough and are suggested to offer pain relief in chronic pain such as neuropathic pain. Here, we analysed whether compounds affect P2X3 receptor activity by high-throughput screening of the Spectrum Collection of 2000 approved drugs, natural products and bioactive substances. We identified aurintricarboxylic acid (ATA) as a nanomolar-potency antagonist of P2X3 receptor-mediated responses. Two-electrode voltage clamp electrophysiology-based concentration-response analysis and selectivity profiling revealed that ATA strongly inhibits the rP2X1 and rP2X3 receptors (with IC₅₀ values of 8.6 nM and 72.9 nM, respectively) and more weakly inhibits P2X2/3, P2X2, P2X4 or P2X7 receptors (IC₅₀ values of 0.76 μM, 22 μM, 763 μM or 118 μM, respectively). Patch-clamp analysis of mouse DRG neurons revealed that ATA inhibited native P2X3 and P2X2/3 receptors to a similar extent than rat P2X3 and P2X2/3 receptors expressed in Xenopus oocytes. In a radioligand binding assay, up to 30 μM ATA did not compete with [³H]-ATP for rP2X3 receptor binding, indicating a non-competitive mechanism of action. Molecular docking studies, site-directed mutagenesis and concentration-response analysis revealed that ATA binds to the negative allosteric site of the hP2X3 receptor. In summary, ATA as a drug-like pharmacological tool compound is a nanomolar-potency, allosteric antagonist with selectivity towards αβ-methylene-ATP-sensitive P2X1 and P2X3 receptors.

Azaphilones from the Marine Sponge-Derived Fungus Penicillium sclerotiorum OUCMDZ-3839

Four new azaphilones, sclerotiorins A-D (1-4), as well as the dimeric sclerotiorin E (5) of which we first determined its absolute configuration, and 12 known analogues (5-16) were isolated from the fermentation broth of Penicillium sclerotiorum OUCMDZ-3839 associated with a marine sponge Paratetilla sp.. The new structures, including absolute configurations, were elucidated by spectroscopic analyses, optical rotation, ECD spectra, X-ray single-crystal diffraction, and chemical transformations. Compounds 11 and 14 displayed significant inhibitory activity against α-glycosidase, with IC₅₀ values of 17.3 and 166.1 μM, respectively. In addition, compounds 5, 7, 10, 12-14, and 16 showed moderate bioactivity against H1N1 virus.

Potent Inhibition of Zika Virus Replication by Aurintricarboxylic Acid

Zika virus (ZIKV) is one of the recently emerging vector-borne viruses in humans and is responsible for severe congenital abnormalities such as microcephaly in the Western Hemisphere. Currently, only a few vaccine candidates and therapeutic drugs are being developed for the treatment of ZIKV infections, and as of yet none are commercially available. The polyanionic aromatic compound aurintricarboxylic acid (ATA) has been shown to have a broad-spectrum antimicrobial and antiviral activity. In this study, we evaluated ATA as a potential antiviral drug against ZIKV replication. The antiviral activity of ATA against ZIKV replication in vitro showed median inhibitory concentrations (IC₅₀) of 13.87 ± 1.09 μM and 33.33 ± 1.13 μM in Vero and A549 cells, respectively; without showing any cytotoxic effect in both cell lines (median cytotoxic concentration (CC₅₀) > 1,000 μM). Moreover, ATA protected both cell types from ZIKV-induced cytopathic effect (CPE) and apoptosis in a time- and concentration-dependent manner. In addition, pre-treatment of Vero cells with ATA for up to 72 h also resulted in effective suppression of ZIKV replication with similar IC₅₀. Importantly, the inhibitory effect of ATA on ZIKV infection was effective against strains of the African and Asian/American lineages, indicating that this inhibitory effect was not strain dependent. Overall, these results demonstrate that ATA has potent inhibitory activity against ZIKV replication and may be considered as a potential anti-ZIKV therapy for future clinical evaluation.

Spirostaphylotrichin X from a Marine-Derived Fungus as an Anti-influenza Agent Targeting RNA Polymerase PB2

A new spirocyclic γ-lactam, named spirostaphylotrichin X (1), and three related known spirostaphylotrichins (2-4) were isolated from the marine-derived fungus Cochliobolus lunatus SCSIO41401. Their structures were determined by spectroscopic analyses. Spirostaphylotrichin X (1) displayed obvious inhibitory activities against multiple influenza virus strains, with IC₅₀ values from 1.2 to 5.5 μM. Investigation of the mechanism showed that 1 inhibited viral polymerase activity and interfered with the production of progeny viral RNA. Homogeneous time-resolved fluorescence, surface plasmon resonance assays, and a molecular docking study revealed that 1 could inhibit polymerase PB2 protein activity by binding to the highly conserved region of the cap-binding domain of PB2. These results suggest that 1 inhibits the replication of influenza A virus by interfering with the activity of PB2 protein and that 1 represents a new type of potential lead compound for the development of anti-influenza therapeutics.

Antiviral activity against enterovirus 71 of sulfated rhamnan isolated from the green alga Monostroma latissimum

Polysaccharide from Monostroma latissimum PML is a sulfated rhamnan, which consists of →3)-α-L-Rhap-(1→ and →2)-α-L-Rhap-(1→ residues with partial branches and sulfate groups at C-2 of →3)-α-L-Rhap-(1→ and/or C-3 of →2)-α-L-Rhap-(1→. The anti-enterovirus 71 (EV71) activity in vitro of PML was assessed by cytopathic effect inhibition and plaque reduction assays, and the results showed that PML was non-cytotoxic and significantly inhibited EV71 infection. The mechanism analysis of anti-EV71 activity demonstrated that PML largely inhibited viral replication before or during viral adsorption, mainly by targeting the capsid protein VP1. PML may also inhibit some early steps of infection after viral adsorption by modulating signaling through the epidermal growth factor receptor (EGFR)/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt) pathway. Moreover, PML markedly improved survival and decreased viral titers in EV71-infected mice. The investigation revealed that PML has potential as a novel anti-EV71 agent targeting the viral capsid protein as well as cellular EGFR/PI3K/Akt pathway.

Overexpression of a type III PKS gene affording novel violapyrones with enhanced anti-influenza A virus activity

BACKGROUND

Type III polyketide synthases (PKSs) are simple homodimer ketosynthases that distribute across plants, fungi, and bacteria, catalyzing formation of pyrone- and resorcinol-types aromatic polyketides with various bioactivities. The broad substrate promiscuity displayed by type III PKSs makes them wonderful candidates for expanding chemical diversity of polyketides.

RESULTS

Violapyrone B (VLP B, 10), an α-pyrone compound produced by deepsea-derived Streptomyces somaliensis SCSIO ZH66, is encoded by a type III PKS VioA. We overexpressed VioA in three different hosts, including Streptomyces coelicolor M1146, Streptomyces sanyensis FMA as well as the native producer S. somaliensis SCSIO ZH66, leading to accumulation of different violapyrone compounds. Among them, S. coelicolor M1146 served as the host producing the most abundant violapyrones, from which five new (2-4, 7 and 12) and nine known (1, 5, 6, 8-11, 13 and 14) compounds were identified. Anti-influenza A (H1N1) virus activity of these compounds was then evaluated using ribavirin as a positive control (IC₅₀ = 112.9 μM), revealing that compounds 11-14 showed considerable activity with IC₅₀ values of 112.7, 26.9, 106.7 and 28.8 μM, respectively, which are significantly improved as compared to that of VLP B (10) (IC₅₀ > 200 μM). The productions of 10 and 13 were increased by adding P450 inhibitor metyrapone. In addition, site-directed mutagenesis experiment led to demonstration of the residue S242 to be essential for the activity of VioA.

CONCLUSIONS

Biological background of the expression hosts is an important factor impacting on the encoding products of type III PKSs. By using S. coelicolor M1146 as cell factory, we were able to generate fourteen VLPs compounds. Anti-H1N1 activity assay suggested that the lipophilic nature of the alkyl chains of VLPs plays an important role for the activity, providing valuable guidance for further structural optimization of VLPs.

San Wu Huangqin Decoction, a Chinese Herbal Formula, Inhibits Influenza a/PR/8/34 (H1N1) Virus Infection In Vitro and In Vivo

The San Wu Huangqin Decoction (SWHD), a traditional Chinese medicine formula, is used to treat colds caused by exposure to wind-pathogen, hyperpyrexia, infectious diseases and cancer; moreover, it is used for detoxification. The individual herbs of SWHD, such as Sophora flavescens and Scutellaria baicalensis, exhibit a wide spectrum of antiviral, anti-inflammatory, antibacterial, anticancer and other properties. The Chinese compound formula of SWHD is composed of S. flavescens, S. baicalensis and Rehmannia glutinosa. However, the effect of SWHD on the influenza virus (IFV) and its mechanism remain unknown. The aim of this study was to evaluate, for the first time, whether SWHD could be used to treat influenza. Results showed that SWHD could effectively inhibit influenza A/PR/8/34 (H1N1) virus at different stages of viral replication (confirmed through antiviral effect assay, penetration assay, attachment assay and internalization assay) in vitro. It could reduce the infection of the virus in a dose- and time-dependent manner, as confirmed by observing the cell cytopathic effect and calculating the cell viability (p < 0.05). SWHD demonstrated better antiviral activity than oseltamivir in the evaluation of antiviral prophylaxis on influenza (p < 0.05). The antiviral activity of SWHD may be related to its regulation ability on the immune system. Western blot, real-time polymerase chain reaction and indirect immunofluorescence assay showed that the expression of the four target viral proteins of the IFV (namely, haemagglutinin (HA), neuraminidase (NA), nucleoprotein (NP) and matrix-2 (M2)) reduced significantly (p < 0.05). Moreover, SWHD (23.40 and 11.70 g/kg) significantly alleviated the clinical signs, reduced the mortality and increased the survival time of infected mice (p < 0.05). The lung index, virus titres, pathological changes in lung tissues and the expression of key proteins of the IFV in mice also decreased (p < 0.05). In conclusion, SWHD possessed anti-influenza activity. This work provided a new view of complementary therapy and drug discovery for clinical treatment.

Varilactones and wortmannilactones produced by Penicillium variabile cultured with histone deacetylase inhibitor

Seven polyketides, including four new ones named as varilactones A-B (1-2) and wortmannilactones M-N (3-4), as well as three biogenetically related known wortmannilactones E, F and H (5-7), were isolated from the fungus Penicillium variabile HXQ-H-1, cultivated in potato-based medium with the histone deacetylase inhibitor suberoylanilide hydroxamic acid (SAHA). Their structures (1-7) were established by analysis of NMR and MS data, and the absolute configuration of oxabicyclo[2.2.1]heptane unit was deduced from ¹H-NMR analyses on MPA esters after chemical reduction reaction. Among them, varilactones A and B (1 and 2), features a novel skeleton with a triene unit linking an oxabicyclo[2.2.1]heptane and an oxabicyclo[3.3.0]octane rings.

Identification of neuraminidase inhibitors against dual H274Y/I222R mutant strains

Influenza is an annual seasonal epidemic that has continually drawn public attentions, due to the potential death toll and drug resistance. Neuraminidase, which is essential for the spread of influenza virus, has been regarded as a valid target for the treatment of influenza infection. Although neuraminidase drugs have been developed, they are susceptible to drug-resistant mutations in the sialic-binding site. In this study, we established computational models (site-moiety maps) of H1N1 and H5N1 to determine properties of the 150-cavity, which is adjacent to the drug-binding site. The models reveal that hydrogen-bonding interactions with residues R118, D151, and R156 and van der Waals interactions with residues Q136, D151, and T439 are important for identifying 150-cavitiy inhibitors. Based on the models, we discovered three new inhibitors with IC₅₀ values <10 μM that occupies both the 150-cavity and sialic sites. The experimental results identified inhibitors with similar activities against both wild-type and dual H274Y/I222R mutant neuraminidases and showed little cytotoxic effects. Furthermore, we identified three new inhibitors situated at the sialic-binding site with inhibitory effects for normal neuraminidase, but lowered effects for mutant strains. The results suggest that the new inhibitors can be used as a starting point to combat drug-resistant strains.

Anti-influenza A Virus Activity of Dendrobine and Its Mechanism of Action

Dendrobine, a major component of Dendrobium nobile, increasingly draws attention for its wide applications in health care. Here we explore potential effects of dendrobine against influenza A virus and elucidate the underlying mechanism. Our results indicated that dendrobine possessed antiviral activity against influenza A viruses, including A/FM-1/1/47 (H1N1), A/Puerto Rico/8/34 H274Y (H1N1), and A/Aichi/2/68 (H3N2) with IC₅₀ values of 3.39 ± 0.32, 2.16 ± 0.91, 5.32 ± 1.68 μg/mL, respectively. Mechanism studies revealed that dendrobine inhibited early steps in the viral replication cycle. Notably, dendrobine could bind to the highly conserved region of viral nucleoprotein (NP), subsequently restraining nuclear export of viral NP and its oligomerization. In conclusion, dendrobine shows potential to be developed as a promising agent to treat influenza virus infection. More importantly, the results provide invaluable information for the full application of the Traditional Chinese Medicine named "Shi Hu".

Inhibition effects of novel polyketide compound PPQ-B against influenza A virus replication by interfering with the cellular EGFR pathway

Development of anti-influenza A virus (IAV) drugs with novel targets and low toxicity is critical for preparedness against influenza outbreaks. In the current study, our results indicated that the novel polyketide compound purpurquinone B (PPQ-B) derived from acid-tolerant fungus Penicillium purpurogenum strain JS03-21 suppressed the replication of IAV in vitro with low toxicity, and may block some stages after virus adsorption. PPQ-B could inhibit H1N1 (A/Puerto Rico/8/34; PR8), H1N1 (A/California/04/2009; Cal09) and H3N2 (A/swine/Minnesota/02719/2009) virus replication in vitro, suggesting that PPQ-B possesses broad-spectrum anti-IAV activities. PPQ-B's antiviral activity may be largely related to its inhibition of some steps that occur 0-4 h after adsorption. Oral administration of PPQ-B could decrease pulmonary viral titers and improve survival rate in IAV infected mice. PPQ-B also significantly decreased the production of inflammatory factors TNF-α, IL-6, RANTES and KC in IAV infected lungs and A549 cells, suggesting that PPQ-B may also attenuate the inflammatory responses caused by IAV infection. PPQ-B may down-regulate the NF-κB and MAPK pathways to inhibit both virus replication and inflammatory responses. In summary, PPQ-B has the potential to be developed into a novel anti-IAV drug targeting host EGFR pathway in the future.

Antiviral activities of compounds from aerial parts of Salvia plebeia R. Br

ETHNOPHARMACOLOGICAL RELEVANCE

Salvia plebeia R. Br. is an edible plant widely spread in many countries. It has been used as a traditional medicine to treat common cold, flu, cough, hepatitis, hemorrhoids, etc. The purpose of the study is to explicate antiviral compounds responsible for its traditional use for the common cold or flu.

MATERIALS AND METHODS

The methanolic extract of the aerial parts of S. plebeia was extracted with CHCl₃, EtOAc, and n-BuOH, successively. The EtOAc and CHCl₃ fractions were subjected to a successive of chromatographic method, which led to the isolation of fourteen compounds. Inhibition activities of the isolated compounds were evaluated against influenza A (H1N1) neuraminidase.

RESULTS

Chemical investigation of the methanolic extracts of S. plebeia resulted in the isolation of two novel benzoylated monoterpene glycosides, named as plebeiosides A (1) and B (2), together with twelve known compounds including four flavonoids (4-5, 7, 10), two sesquiterpenoids (8, 12), four phenolics (9-10, 13-14), a steroid (6), and a triterpenoid (3). Their chemical structures were elucidated based on spectroscopic data and absolute stereochemistries of 1 and 2 were determined by comparison of optical rotations of their hydrolysates with literature values. Compounds 5, 7, 9, and 11 exhibited potent enzymatic inhibition against H1N1 neuraminidase (IC₅₀ values ranging from 11.18±1.73 to 19.83±2.28μM). Furthermore, two flavonoids (5 and 7) and one rosmarinic acid methyl ester (9) reduced cytopathic effects of the H1N1 virus during replication.

CONCLUSIONS

The antiviral activities of the flavonoids and phenolics isolated from the extracts of S. plebeia supported the traditional application of this medicine on common cold or flu. In this study, benzoylated monoterpene glycosides were first found to exist in this species. Moreover, the present study suggested potential of three compounds (5, 7, and 9) to be new lead structures for the development of new neuraminidase inhibitors in the future.

Identification of Inhibitors for the DEDDh Family of Exonucleases and a Unique Inhibition Mechanism by Crystal Structure Analysis of CRN-4 Bound with 2-Morpholin-4-ylethanesulfonate (MES)

The DEDDh family of exonucleases plays essential roles in DNA and RNA metabolism in all kingdoms of life. Several viral and human DEDDh exonucleases can serve as antiviral drug targets due to their critical roles in virus replication. Here using RNase T and CRN-4 as the model systems, we identify potential inhibitors for DEDDh exonucleases. We further show that two of the inhibitors, ATA and PV6R, indeed inhibit the exonuclease activity of the viral protein NP exonuclease of Lassa fever virus in vitro. Moreover, we determine the crystal structure of CRN-4 in complex with MES that reveals a unique inhibition mechanism by inducing the general base His179 to shift out of the active site. Our results not only provide the structural basis for the inhibition mechanism but also suggest potential lead inhibitors for the DEDDh exonucleases that may pave the way for designing nuclease inhibitors for biochemical and biomedical applications.

The inhibitory effect of 7,7″-dimethoxyagastisflavone on the metastasis of melanoma cells via the suppression of F-actin polymerization

7,7″-Dimethoxyagastisflavone (DMGF), a biflavonoid isolated from Taxus × media cv. Hicksii, induces apoptotic and autophagic cell death. However, whether DMGF suppresses tumor metastasis is unclear. The aim of this study was to investigate the anti-metastatic activities of DMGF on the metastatic processes of melanoma cells in vivo and in vitro. A transwell assay showed that DMGF could effectively attenuate the motility of B16F10 cells, and the results of real-time PCR revealed that DMGF also suppressed the expressions of matrix metalloproteinase-2 (MMP-2). Moreover, DMGF did not influence tube formation but inhibited the migration of endothelial cells. Furthermore, animal models were used to monitor the effects of DMGF on tumor metastasis, and all models showed that DMGF significantly suppressed the metastatic behaviors of B16F10 cells, including intravasation, colonization, and invasion of the lymphatic duct. In addition, DMGF could also reduce the densities of the blood vessels in the tumor area in vivo. Further investigation of the molecular mechanisms of anti-metastatic activity revealed that DMGF can down-regulate the levels of key modulators of the Cdc42/Rac1 pathway to interfere in F-actin polymerization and suppress the formation of lamellipodia by reducing the phosphorylation of CREB. These data suggested that DMGF presents anti-metastatic activities in B16F10 melanoma cells. Here, we demonstrated that DMGF can inhibit the metastasis of highly invasive melanoma cancer cells through the down-regulation of F-actin polymerization. Considering these findings, DMGF may be further developed to serve as a chemoprevention drug for patients with metastatic melanoma.

Austalides S-U, New Meroterpenoids from the Sponge-Derived Fungus Aspergillus aureolatus HDN14-107

Three new meroterpenoids, named austalides S-U (1–3), were isolated from the culture of a sponge-derived fungus Aspergillus aureolatus HDN14-107, together with eleven known austalides derivates (4–14). Their structures, including absolute configurations, were assigned on the basis of NMR, MS data, and TDDFT ECD calculations. Compound 1 is the first case of austalides with the terpene ring fused to the chroman ring in trans configuration. Compounds 3 and 5 exhibited activities against influenza virus A (H1N1), with IC₅₀ values of 90 and 99 μM, respectively.

Synthesis and Anti-Influenza A Virus Activity of 6'-amino-6'-deoxy-glucoglycerolipids Analogs

A series of aminoglucoglycerolipids derivatives had been synthesized, including 6'-acylamido-glucoglycerolipids 1a-1f and corresponding 2'-acylamido-glucoglycerolipids 2a-2c bearing different fatty acids, glucosyl diglycerides 3a-3e bearing different functional groups at C-6' and ether-linked glucoglycerolipids 4a-4c with double-tailed alkyl alcohol. The anti-influenza A virus (IAV) activity was evaluated by the cytopathic effects (CPE) inhibition assay. The results indicated that the integral structure of the aminoglycoglycerolipid was essential for the inhibition of IAV in MDCK cells. Furthermore, oral administration of compound 1d was able to significantly improve survival and decrease pulmonary viral titers in IAV-infected mice, which suggested that compound 1d merited further investigation as a novel anti-IAV candidate in the future.

The significance of naturally occurring neuraminidase quasispecies of H5N1 avian influenza virus on resistance to oseltamivir: a point of concern

Viral adaptability and survival arise due to the presence of quasispecies populations that are able to escape the immune response or produce drug-resistant variants. However, the presence of H5N1 virus with natural mutations acquired without any drug selection pressure poses a great threat. Cloacal samples collected from the 2004-2005 epidemics in Thailand from Asian open-billed storks revealed one major and several minor quasispecies populations with mutations on the oseltamivir (OTV)-binding site of the neuraminidase gene (NA) without prior exposure to a drug. Therefore, this study investigated the binding between the NA-containing novel mutations and OTV drug using molecular dynamic simulations and plaque inhibition assay. The results revealed that the mutant populations, S236F mutant, S236F/C278Y mutant, A250V/V266A/P271H/G285S mutant and C278Y mutant, had a lower binding affinity with OTV as compared with the WT virus due to rearrangement of amino acid residues and increased flexibility in the 150-loop. This result was further emphasized through the IC50 values obtained for the major population and WT virus, 104.74 nM and 18.30 nM, respectively. Taken together, these data suggest that H5N1 viruses isolated from wild birds have already acquired OTV-resistant point mutations without any exposure to a drug.

Mangrove rare actinobacteria: taxonomy, natural compound, and discovery of bioactivity

Actinobacteria are one of the most important and efficient groups of natural metabolite producers. The genus Streptomyces have been recognized as prolific producers of useful natural compounds as they produced more than half of the naturally-occurring antibiotics isolated to-date and continue as the primary source of new bioactive compounds. Lately, Streptomyces groups isolated from different environments produced the same types of compound, possibly due to frequent genetic exchanges between species. As a result, there is a dramatic increase in demand to look for new compounds which have pharmacological properties from another group of Actinobacteria, known as rare actinobacteria; which is isolated from special environments such as mangrove. Recently, mangrove ecosystem is becoming a hot spot for studies of bioactivities and the discovery of natural products. Many novel compounds discovered from the novel rare actinobacteria have been proven as potential new drugs in medical and pharmaceutical industries such as antibiotics, antimicrobials, antibacterials, anticancer, and antifungals. This review article highlights the latest studies on the discovery of natural compounds from the novel mangrove rare actinobacteria and provides insight on the impact of these findings.

Dicarabrol, a new dimeric sesquiterpene from Carpesium abrotanoides L

A new dimeric sesquiterpene, dicarabrol (1), together with three known sesquiterpenes, carabrol (2), 11(13)-dehydroivaxillin (3), and 2-desoxy-4-epi-pulchellin (4), were isolated from the whole plant of Carpesium abrotanoides L. Their structures were elucidated on the basis of spectroscopic analysis, and single crystal X-ray diffraction analysis. Compound 1 possessed a dimeric sesquiterpene core featured with a cyclopentane ring connecting two sesquiterpene lactone units rarely discovered in nature. Dicarabrol (1), as well as three known sesquiterpenes (2-4), had potent in vitro cytotoxicities against the K562, MCF-7, Hela, DU145, U937, H1975, SGC-7901, A549, MOLT-4, and HL60 cell lines with IC50 values ranging from 0.10 to 46.7 μM, while they showed significant antiviral (H1N1 and H3N2) activities. Furthermore, compounds 1, 3 and 4 displayed significant antimycobacterial activity (IC50 3.7, 6.0, and 7.6 μM, respectively).

The Flavonoid Isoliquiritigenin Reduces Lung Inflammation and Mouse Morbidity during Influenza Virus Infection

The host response to influenza virus infection is characterized by an acute lung inflammatory response in which intense inflammatory cell recruitment, hypercytokinemia, and a high level of oxidative stress are present. The sum of these events contributes to the virus-induced lung damage that leads to high a level of morbidity and mortality in susceptible infected patients. In this context, we identified compounds that can simultaneously reduce the excessive inflammatory response and the viral replication as a strategy to treat influenza virus infection. We investigated the anti-inflammatory and antiviral potential activities of isoliquiritigenin (ILG). Interestingly, we demonstrated that ILG is a potent inhibitor of influenza virus replication in human bronchial epithelial cells (50% effective concentration [EC50] = 24.7 μM). In addition, our results showed that this molecule inhibits the expression of inflammatory cytokines induced after the infection of cells with influenza virus. We demonstrated that the anti-inflammatory activity of ILG in the context of influenza virus infection is dependent on the activation of the peroxisome proliferator-activated receptor gamma pathway. Interestingly, ILG phosphate (ILG-p)-treated mice displayed decreased lung inflammation as depicted by reduced cytokine gene expression and inflammatory cell recruitment. We also demonstrated that influenza virus-specific CD8(+) effector T cell recruitment was reduced up to 60% in the lungs of mice treated with ILG-p (10 mg/kg) compared to that in saline-treated mice. Finally, we showed that administration of ILG-p reduced lung viral titers and morbidity of mice infected with the PR8/H1N1 virus.

Methylene Salicylicacidyl Hexamer (MSH) Has DNAse Activity

Salicylic acid and formaldehyde form heterogenous methyl/methylene salicylicacidyl oligomers and polymers in presence of sulfuric acid (H2SO4) and sodium nitrite (NaNO2). One of the oligomers as aurintricarboxylic acid (ATA), methelene bridged salicylic acid trimer, has been identified and explored in biochemical research, which is a potent inhibitor of many biological processes. A very few reports are also available on dimer, trimer, and tetramer of methelene bridged salicylic acids from same reaction mixture. Herein, we report the isolation and biochemical screening of partial purified low-molecular component as methylene salicylicacidyl hexamer (MSH) from the above reaction mixture. The interaction of methylene salicylicacidyl oligomer with DNA was studied by agarose and polyacrylamide gel electrophoresis, which suggest that methylene salicylicacidyl oligomer has DNAse activity. So far, no such significant reports are available on low-molecular oligomer of methelene bridged salicylic acids. In further, we also attempted to investigate the nature of nuclease activity, which clearly indicates DNA exonuclease type of activity. Further studies are needed to establish the mechanism of actions.

The combination effects of licl and the active leflunomide metabolite, A771726, on viral-induced interleukin 6 production and EV-A71 replication

Enterovirus 71 (EV-A71) is a neurotropic virus that can cause severe complications involving the central nervous system. No effective antiviral therapeutics are available for treating EV-A71 infection and drug discovery efforts are rarely focused to target this disease. Thus, the main goal of this study was to discover existing drugs with novel indications that may effectively inhibit EV-A71 replication and the inflammatory cytokines elevation. In this study, we showed that LiCl, a GSK3β inhibitor, effectively suppressed EV-A71 replication, apoptosis and inflammatory cytokines production (Interleukin 6, Interleukin-1β) in infected cells. Furthermore, LiCl and an immunomodular agent were shown to strongly synergize with each other in suppressing EV-A71 replication. The results highlighted potential new treatment regimens in suppressing sequelae caused by EV-A71 replication.

Anomeric selectivity and influenza A virus inhibition study on methoxylated analogues of Pentagalloylglucose

Anomeric selectivity in galloylation of D-glucose and D-mannose with carboxylic acid was explored under steglich conditions. Base catalyst 4-dimethylaminopyridine favored the formation of alpha-anomers, while adding an acid and carbodiimide favored the formation of beta-anomers. Steric hindrance between α,β-unsaturated acid and C-2 OH stereochemistry (adjacent carbon to anomeric) influenced anomeric selectivity for both D-glucose and D-mannose. The influenza A virus inhibition activities of the synthesized compounds were evaluated in Madin-Darby canine kidney cell line using the cytopathic effect inhibition assay. All the synthetic methoxylated analogues showed more considerable activity against influenza A virus than their corresponding acids, which indicated the sugar core as key functionality for anti-viral activity. The activities of trimethoxy-cinnamic acid Pentagalloylglucose analogues, 3α, 3β, 4α, and 4β (IC50, 109.1 μM, 134.4 μM, 119.5 μM, 111.1 μM, respectively) were better than those of trimethoxy-benzoic acid Pentagalloylglucose analogues, 1-αβ and 2α, 2β (IC50, 209.8 μM, 132.9 μM, 161.2 μM, respectively), which suggested that the double bond in cinnamic acid Pentagalloylglucose analogues makes the major contribution for influenza A virus inhibitory activity. Notably, several anomeric mixtures showed better activities than pure alpha or beta anomer and were almost two times more effective than Ribavirin, a clinically used anti-viral drug.

Screening and identification of inhibitors against influenza A virus from a US drug collection of 1280 drugs

Infection with influenza A virus is still a global concern since it causes significant mortality, morbidity and economic loss. New burst pandemics and rapid emergence of drug-resistance strains in recent years call for novel antiviral therapies. One promising way to overcome this problem is searching new inhibitors among thousands of drugs approved in the clinic for the treatment of different diseases or approved to be safe by clinical trials. In the present work, a collection of 1280 compounds, most of which have been clinically used in human or animal, were screened for anti-influenza activity and 41 hits (SI>4.0) were obtained. Next the 18 hit compounds with SI >10.0 were tested for antiviral activity against 7 other influenza virus strains in canine-originated MDCK cells, 9 compounds exhibited broad antiviral spectrum. The antiviral effects of the 9 compounds were also confirmed in human-originated A549 cells and chicken-originated DF1 cells, by infectious virus yield reduction assay and indirect immunofluorescent assay. Results from the time of addition assay showed that the 9 candidates impaired different stages of influenza virus life cycle, indicating they are novel inhibitors with different mechanisms compared with the existing M2 ion-channel blockers or neuraminidase (NA) inhibitors. Taken together, our findings provide 9 novel drug candidates for the treatment of influenza virus infection. Further mechanism of action study of these inhibitors may lead to the discovery of new anti-influenza targets and structure-activity relationship (SAR) study can be initiated to improve the efficacy of these new classes of influenza inhibitors.

Sorbicatechols A and B, antiviral sorbicillinoids from the marine-derived fungus Penicillium chrysogenum PJX-17

Two novel sorbicillinoids combining a bicyclo[2.2.2]octane with a 2-methoxyphenol moiety, named sorbicatechols A (1) and B (2), were isolated from the culture of the marine sediment-derived fungus Penicillium chrysogenum PJX-17, together with the known protocatechuic acid methyl ester and caffeic acid methyl ester (3). Their structures, including absolute configurations, were assigned by analysis of NMR, MS data, and TDDFT ECD calculations. Compounds 1 and 2 exhibited activities against influenza virus A (H1N1), with IC50 values of 85 and 113 μ M, respectively.

Purpurides B and C, two new sesquiterpene esters from the aciduric fungus Penicillium purpurogenum JS03-21

Purpurides B and C (1 and 2, resp.), two new sesquiterpene alcohol esters generated from a drimane-type sesquiterpenoid lactone and an amino acid, together with two known analogs, berkedrimane B (3) and purpuride (4), were isolated from the aciduric fungus Penicillium purpurogenum JS03-21. Their structures were elucidated by spectroscopic analysis, X-ray single-crystal diffraction, and application of Marfey's method. Compounds 1-4 showed modest antifungal activities against Candida albicans with MIC values in the range of 1.2-3.3 μM. Compounds 1 and 2 showed moderate antimicrobial activities against Enterobacter aerogenes and Pseudomonas aeruginosa with MIC values in the range of 1.2-2.6 μM.

Alkaloids from the mangrove-derived actinomycete Jishengella endophytica 161111

A new alkaloid, 2-(furan-2-yl)-6-(2S,3S,4-trihydroxybutyl)pyrazine (1), along with 12 known compounds, 2-(furan-2-yl)-5-(2S,3S,4-trihydroxybutyl)pyrazine (2), (S)-4-isobutyl-3-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-6-carbaldehyde (3), (S)-4-isopropyl-3-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-6-carbaldehyde (4), (4S)-4-(2-methylbutyl)-3-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-6-carbaldehyde (5), (S)-4-benzyl-3-oxo-3,4-dihydro-1H-pyrrolo[2,1-c][1,4]oxazine-6-carbaldehyde (6), flazin (7), perlolyrine (8), 1-hydroxy-β-carboline (9), lumichrome (10), 1H-indole-3-carboxaldehyde (11), 2-hydroxy-1-(1H-indol-3-yl)ethanone (12), and 5-(methoxymethyl)-1H-pyrrole-2-carbaldehyde (13), were isolated and identified from the fermentation broth of an endophytic actinomycetes, Jishengella endophytica 161111. The new structure 1 and the absolute configurations of 2–6 were determined by spectroscopic methods, J-based configuration analysis (JBCA) method, lactone sector rule, and electronic circular dichroism (ECD) calculations. Compounds 8–11 were active against the influenza A virus subtype H1N1 with IC₅₀ and selectivity index (SI) values of 38.3(±1.2)/25.0(±3.6)/39.7(±5.6)/45.9(±2.1) μg/mL and 3.0/16.1/3.1/11.4, respectively. The IC₅₀ and SI values of positive control, ribavirin, were 23.1(±1.7) μg/mL and 32.2, respectively. The results showed that compound 9 could be a promising new hit for anti-H1N1 drugs. The absolute configurations of 2–5, ¹³C nuclear magnetic resonance (NMR) data and the specific rotations of 3–6 were also reported here for the first time.

Moiety-linkage map reveals selective nonbisphosphonate inhibitors of human geranylgeranyl diphosphate synthase

Bisphosphonates are potent inhibitors of farnesyl pyrophosphate synthase (FPPS) and geranylgeranyl diphosphate synthase (GGPPS). Current bisphosphonate drugs (e.g., Fosamax and Zometa) are highly efficacious in the treatment of bone diseases such as osteoporosis, Paget's disease, and tumor-induced osteolysis, but they are often less potent in blood and soft-tissue due to their phosphate moieties. The discovery of nonbisphosphonate inhibitors of FPPS and/or GGPPS for the treatment of bone diseases and cancers is, therefore, a current goal. Here, we propose a moiety-linkage-based method, combining a site-moiety map with chemical structure rules (CSRs), to discover nonbisphosphonate inhibitors from thousands of commercially available compounds and known crystal structures. Our moiety-linkage map reveals the binding mechanisms and inhibitory efficacies of 51 human GGPPS (hGGPPS) inhibitors. To the best of our knowledge, we are the first team to discover two novel selective nonbisphosphonate inhibitors, which bind to the inhibitory site of hGGPPS, using CSRs and site-moiety maps. These two compounds can be considered as a novel lead for the potent inhibitors of hGGPPS for the treatment of cancers and mevalonate-pathway diseases. Moreover, based on our moiety-linkage map, we identified two key residues of hGGPPS, K202, and K212, which play an important role for the inhibitory effect of zoledronate (IC50 = 3.4 μM and 2.4 μM, respectively). This result suggests that our method can discover specific hGGPPS inhibitors across multiple prenyltransferases. These results show that the compounds that highly fit our moiety-linkage map often inhibit hGGPPS activity and induce tumor cell apoptosis. We believe that our method is useful for discovering potential inhibitors and binding mechanisms for pharmaceutical targets.

Synthesis and antiviral evaluation of 6'-acylamido-6'-deoxy-α-D-mannoglycerolipids

Eight new aminomannoglycerolipids (2a-h) with linear, branched, or aromatic acyl chains were synthesized and evaluated for their anti-influenza A virus (IAV) activity. By comparing six mannosyl donors with different protecting and leaving groups, the critical glycosylation reaction employed mannosyl trichloroacetimidate with 2-O-benzoyl protecting group as the donor to give the glycoside with absolute α-anomeric selectivity. The bioactivity results showed that the branched compound 2g could effectively inhibit IAV multiplication in MDCK cells with IC50 69.9μM.

Development and characterization of a novel fluorescent indicator protein PMCA4-GCaMP2 in cardiomyocytes

Isoform 4 of the plasma membrane calcium/calmodulin dependent ATPase (PMCA4) has recently emerged as an important regulator of several key pathophysiological processes in the heart, such as contractility and hypertrophy. However, direct monitoring of PMCA4 activity and assessment of calcium dynamics in its vicinity in cardiomyocytes are difficult due to the lack of molecular tools. In this study, we developed novel calcium fluorescent indicators by fusing the GCaMP2 calcium sensor to the N-terminus of PMCA4 to generate the PMCA4-GCaMP2 fusion molecule. We also identified a novel specific inhibitor of PMCA4, which might be useful for studying the role of this molecule in cardiomyocytes and other cell types. Using an adenoviral system we successfully expressed PMCA4-GCaMP2 in both neonatal and adult rat cardiomyocytes. This fusion molecule was correctly targeted to the plasma membrane and co-localised with caveolin-3. It could monitor signal oscillations in electrically stimulated cardiomyocytes. The PMCA4-GCaMP2 generated a higher signal amplitude and faster signal decay rate compared to a mutant inactive PMCA4(mut)GCaMP2 fusion protein, in electrically stimulated neonatal and adult rat cardiomyocytes. A small molecule library screen enabled us to identify a novel selective inhibitor for PMCA4, which we found to reduce signal amplitude of PMCA4-GCaMP2 and prolong the time of signal decay (Tau) to a level comparable with the signal generated by PMCA4(mut)GCaMP2. In addition, PMCA4-GCaMP2 but not the mutant form produced an enhanced signal in response to β-adrenergic stimulation. Together, the PMCA4-GCaMP2 and PMCA4(mut)GCaMP2 demonstrate calcium dynamics in the vicinity of the pump under active or inactive conditions, respectively. In summary, the PMCA4-GCaMP2 together with the novel specific inhibitor provides new means with which to monitor calcium dynamics in the vicinity of a calcium transporter in cardiomyocytes and may become a useful tool to further study the biological functions of PMCA4. In addition, similar approaches could be useful for studying the activity of other calcium transporters during excitation-contraction coupling in the heart.