Effect of Pretreatment with the NADPH Oxidase Inhibitor Apocynin on the Therapeutic Efficacy of Human Placenta-Derived Mesenchymal Stem Cells in Intracerebral Hemorrhage.

Several studies have demonstrated the beneficial effect of mesenchymal stem cells (MSCs) on intracerebral hemorrhage (ICH). Enhancement of the therapeutic efficacy of MSCs in ICH is necessary, considering the diseases high association with mortality and morbidity. Various preconditioning methods to enhance the beneficial properties of MSCs have been introduced. We suggested apocynin, a well-known nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, as a novel preconditioning regimen to enhance the therapeutic efficacy of MSCs in ICH. Rat ICH models were made using bacterial collagenase. 24 h after ICH induction, the rats were randomly divided into apocynin-preconditioned MSC-treated (Apo-MSC), naïve MSC-treated and control groups. Hematoma volume, brain edema, and degenerating neuron count were compared at 48 h after the ICH induction. The expression of tight junction proteins (occludin, zona occludens [ZO]-1) were also compared. Hematoma size, hemispheric enlargement and degenerating neuron count were significantly lower in the Apo-MSC group than in the naïve MSC group (p = 0.004, 0.013 and 0.043, respectively), while the expression of occludin was higher (p = 0.024). Apocynin treatment enhances the therapeutic efficacy of MSCs in ICH in the acute stage, through the improvement of the beneficial properties of MSCs, such as neuroprotection and the reinforcement of endovascular integrity of cerebral vasculature.

High-throughput drug screening using the Ebola virus transcription- and replication-competent virus-like particle system.

The massive epidemic of Ebola virus disease (EVD) in West Africa, followed in recent months by two outbreaks in the Democratic Republic of the Congo, underline the importance of this severe disease. Because Ebola virus (EBOV) must be manipulated under biosafety level 4 (BSL4) containment, the discovery and development of virus-specific therapies have been hampered. Recently, a transient transfection-based transcription- and replication competent virus-like particle (trVLP) system was described, enabling modeling of the entire EBOV life cycle under BSL2 conditions. Using this system, we optimized the condition for bulk co-transfection of multiple plasmids, developed a luciferase reporter-based assay in 384-well microtiter plates, and performed a high-throughput screening (HTS) campaign of an 8,354-compound collection consisting of U.S. Food & Drug Administration (FDA) -approved drugs, bioactives, kinase inhibitors, and natural products in duplicates. The HTS achieved a good signal-to-background ratio with a low percent coefficient of variation resulting in Z' = 0.7, and data points were reproducible with R2 = 0.89, indicative of a robust assay. After applying stringent hit selection criteria of ≥70% EBOV trVLP inhibition and ≥70% cell viability, 381 hits were selected targeting early, entry, and replication steps and 49 hits targeting late, maturation, and secretion steps in the viral life cycle. Of the total 430 hits, 220 were confirmed by dose-response analysis in the primary HTS assay. They were subsequently triaged by time-of-addition assays, then clustered and ranked according to their chemical structures, biological functions, therapeutic index, and maximum inhibition. Several novel drugs have been identified to very efficiently inhibit EBOV. Interestingly, most showed pharmacological activity in treatments for central nervous system-related diseases. We developed and screened an HTS assay using the novel EBOV trVLP system. Newly identified inhibitors are useful tools to study the poorly understood EBOV life cycle. In addition, they also provide opportunities to either repurpose FDA-approved drugs or develop novel viral interventions to combat EVD.

Human Placenta-Derived Mesenchymal Stem Cells Reduce Mortality and Hematoma Size in a Rat Intracerebral Hemorrhage Model in an Acute Phase.

Intracerebral hemorrhage (ICH) is a critical disease, highly associated with mortality and morbidity. Several studies have demonstrated the beneficial effect of mesenchymal stem cells (MSCs) on ICH, mostly focused on their mid-to-long-term effect. Acute hematoma expansion is one of the most important prognostic factors of ICH. We hypothesized that MSCs would decrease mortality and hematoma size in acute ICH, based on the findings of a few recent researches reporting their effect on blood-brain barrier and endothelial integrity. Rat ICH models were made using bacterial collagenase. One hour after ICH induction, the rats were randomly divided into MSC-treated and control groups. Mortality, hematoma volume, ventricular enlargement, brain edema, and degenerating neuron count were compared at 24 hours after ICH induction. Expression of tight junction proteins (ZO-1, occludin) and coagulation factor VII mRNA was also compared. Mortality rate (50% versus 8.3%), hematoma size, ventricular size, hemispheric enlargement, and degenerating neuron count were significantly lower in the MSC-treated group (p = 0.034, 0.038, 0.001, 0.022, and <0.001, resp.), while the expression of ZO-1 and occludin was higher (p = 0.007 and 0.012). Administration of MSCs may prevent hematoma expansion in the hyperacute stage of ICH and decrease acute mortality by enhancing the endothelial integrity of cerebral vasculature.

Abl Tyrosine Kinase Regulates Hepatitis C Virus Entry.

Abl is a central regulator of multiple cellular processes controlling actin dynamics, proliferation, and differentiation. Here, we showed that knockdown of Abl impaired hepatitis C virus (HCV) propagation. Treatment of Abl tyrosine kinase-specific inhibitor, imatinib and dasatinib, also significantly decreased HCV RNA and protein levels in HCV-infected cells. We showed that both imatinib and dasatinib selectively inhibited HCV infection at the entry step of HCV life cycle, suggesting that Abl kinase activity may be necessary for HCV entry. Using HCV pseudoparticle infection assays, we verified that Abl is required for viral entry. By employing transferrin uptake and immunofluorescence assays, we further demonstrated that Abl was involved in HCV entry at a clathrin-mediated endocytosis step. These data suggest that Abl may represent a novel host factor for HCV entry.

In Silico Design and Experimental Validation of siRNAs Targeting Conserved Regions of Multiple Hepatitis C Virus Genotypes.

RNA interference (RNAi) is a post-transcriptional gene silencing mechanism that mediates the sequence-specific degradation of targeted RNA and thus provides a tremendous opportunity for development of oligonucleotide-based drugs. Here, we report on the design and validation of small interfering RNAs (siRNAs) targeting highly conserved regions of the hepatitis C virus (HCV) genome. To aim for therapeutic applications by optimizing the RNAi efficacy and reducing potential side effects, we considered different factors such as target RNA variations, thermodynamics and accessibility of the siRNA and target RNA, and off-target effects. This aim was achieved using an in silico design and selection protocol complemented by an automated MysiRNA-Designer pipeline. The protocol included the design and filtration of siRNAs targeting highly conserved and accessible regions within the HCV internal ribosome entry site, and adjacent core sequences of the viral genome with high-ranking efficacy scores. Off-target analysis excluded siRNAs with potential binding to human mRNAs. Under this strict selection process, two siRNAs (HCV353 and HCV258) were selected based on their predicted high specificity and potency. These siRNAs were tested for antiviral efficacy in HCV genotype 1 and 2 replicon cell lines. Both in silico-designed siRNAs efficiently inhibited HCV RNA replication, even at low concentrations and for short exposure times (24h); they also exceeded the antiviral potencies of reference siRNAs targeting HCV. Furthermore, HCV353 and HCV258 siRNAs also inhibited replication of patient-derived HCV genotype 4 isolates in infected Huh-7 cells. Prolonged treatment of HCV replicon cells with HCV353 did not result in the appearance of escape mutant viruses. Taken together, these results reveal the accuracy and strength of our integrated siRNA design and selection protocols. These protocols could be used to design highly potent and specific RNAi-based therapeutic oligonucleotide interventions.

Pim Kinase Interacts with Nonstructural 5A Protein and Regulates Hepatitis C Virus Entry.

UNLABELLED: The life cycle of hepatitis C virus (HCV) is highly dependent on host cellular proteins for virus propagation. In order to identify the cellular factors involved in HCV propagation, we performed protein microarray assay using the HCV nonstructural 5A (NS5A) protein as a probe. Of ∼ 9,000 human cellular proteins immobilized in a microarray, approximately 90 cellular proteins were identified as NS5A interactors. Of these candidates, Pim1, a member of serine/threonine kinase family composed of three different isoforms (Pim1, Pim2, and Pim3), was selected for further study. Pim kinases share a consensus sequence which overlaps with kinase activity. Pim kinase activity has been implicated in tumorigenesis. In the present study, we verified the physical interaction between NS5A and Pim1 by both in vitro pulldown and coimmunoprecipitation assays. Pim1 interacted with NS5A through amino acid residues 141 to 180 of Pim1. We demonstrated that protein stability of Pim1 was increased by NS5A protein and this increase was mediated by protein interplay. Small interfering RNA (siRNA)-mediated knockdown or pharmacological inhibition of Pim kinase abrogated HCV propagation. By employing HCV pseudoparticle entry and single-cycle HCV infection assays, we further demonstrated that Pim kinase was involved in HCV entry at a postbinding step. These data suggest that Pim kinase may represent a new host factor for HCV entry. IMPORTANCE: Pim1 is an oncogenic serine/threonine kinase. HCV NS5A protein physically interacts with Pim1 and contributes to Pim1 protein stability. Since Pim1 protein expression level is upregulated in many cancers, NS5A-mediated protein stability may be associated with HCV pathogenesis. Either gene silencing or chemical inhibition of Pim kinase abrogated HCV propagation in HCV-infected cells. We further showed that Pim kinase was specifically required at an early entry step of the HCV life cycle. Thus, we have identified Pim kinase not only as an HCV cell entry factor but also as a new anti-HCV therapeutic target.

Saponin inhibits hepatitis C virus propagation by up-regulating suppressor of cytokine signaling 2.

Saponins are a group of naturally occurring plant glycosides which possess a wide range of pharmacological properties, including anti-tumorigenic and antiviral activities. To investigate whether saponin has anti-hepatitis C virus (HCV) activity, we examined the effect of saponin on HCV replication. HCV replication was efficiently inhibited at a concentration of 10 µg/ml of saponin in cell culture grown HCV (HCVcc)-infected cells. Inhibitory effect of saponin on HCV replication was verified by quantitative real-time PCR, reporter assay, and immunoblot analysis. In addition, saponin potentiated IFN-α-induced anti-HCV activity. Moreover, saponin exerted antiviral activity even in IFN-α resistant mutant HCVcc-infected cells. To investigate how cellular genes were regulated by saponin, we performed microarray analysis using HCVcc-infected cells. We demonstrated that suppressor of cytokine signaling 2 (SOCS2) protein level was distinctively increased by saponin, which in turn resulted in inhibition of HCV replication. We further showed that silencing of SOCS2 resurrected HCV replication and overexpression of SOCS2 suppressed HCV replication. These data imply that saponin inhibits HCV replication via SOCS2 signaling pathway. These findings suggest that saponin may be a potent therapeutic agent for HCV patients.