Selection and characterization of viruses resistant to the dual acting pyrimidinedione entry and non-nucleoside reverse transcriptase inhibitor IQP-0410

The 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT)-like compounds with homocyclic moieties at the N-1 of the pyrimidinedione, including the highly potent lead compound IQP-0410, inhibit HIV-1 at sub-nanomolar concentrations primarily through a typical non-nucleoside mechanism involving allosteric inhibition at the hydrophobic binding pocket of the HIV-1 RT. Like all NNRTIs, the pyrimidinediones have no activity against HIV-2 RT. The pyrimidinediones, however, also possess a second mode of action involving inhibition of virus entry at nanomolar concentrations which extends their range of action to include HIV-2. Entry inhibition occurs through recognition of a complex conformational binding site formed upon interaction of the virus with target cells, but does not involve direct inhibition of gp120-CD4 binding. In order to further explore the means by which the pyrimidinediones act, resistant strains of HIV-1 and HIV-2 were selected in cell culture and molecularly and biologically characterized. With HIV-1, three phases of resistance selection occurred which involve an initial appearance of single amino changes in the NNRTI binding pocket, followed by changes in the envelope glycoproteins gp120 and gp41, and subsequent multiple additional changes in the RT, resulting in high level resistance to IQP-0410. With HIV-2, resistance to entry inhibition was achieved with no resistance-engendering mutations detected in the HIV-2 RT. Detailed molecular and biological characterization of IQP-0410-resistant viruses was performed to define the resistance-engendering mutations present in the RT and envelope and to quantify cross-resistance to other HIV inhibitors.     

Antiviral evaluation of octadecyloxyethyl esters of (S)-3-hydroxy-2-(phosphonomethoxy)propyl nucleosides against herpesviruses and orthopoxviruses

Our previous studies showed that esterification of 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine (HPMPA) or 1-(S)-[3-hydroxy-2-(phosphonomethoxy)-propyl]cytosine (HPMPC) with alkoxyalkyl groups such as hexadecyloxypropyl (HDP) or octadecyloxyethyl (ODE) resulted in large increases in antiviral activity and oral bioavailability. The HDP and ODE esters of HPMPA were shown to be active in cells infected with human immunodeficiency virus, type 1 (HIV-1), while HPMPA itself was virtually inactive. To explore this approach in greater detail, we synthesized four new compounds in this series, the ODE esters of 9-(S)-[3-hydroxy-2-(phosphonomethoxy)-propyl]guanine (HPMPG), 1-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]thymine (HPMPT), 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-2,6-diaminopurine (HPMPDAP) and 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]-2-amino-6-cyclopropylaminopurine (HPMP-cPrDAP) and evaluated their antiviral activity against herpes simplex virus, type 1 (HSV-1), human cytomegalovirus (HCMV), and vaccinia, cowpox and ectromelia. Against HSV-1, subnanomolar EC₅₀ values were observed with ODE–HPMPA and ODE–HPMPC while ODE–HPMPG had intermediate antiviral activity with an EC₅₀ of 40 nM. In HFF cells infected with HCMV, the lowest EC₅₀ values were observed with ODE–HPMPC, 0.9 nM. ODE–HPMPA was highly active with an EC₅₀ of 3 nM, while ODE–HPMPG and ODE–HPMPDAP were also highly active with EC₅₀s of 22 and 77 nM, respectively. Against vaccinia and cowpox viruses, ODE–HPMPG and ODE–HPMPDAP were the most active and selective compounds with EC₅₀ values of 20–60 nM and selectivity index values of 600–3500. ODE–HPMPG was also active against ectromelia virus with an EC₅₀ value of 410 nM and a selectivity index value of 166. ODE–HPMPG and ODE–HPMPDAP are proposed for further preclinical evaluation as possible candidates for treatment of HSV, HCMV or orthopoxvirus diseases.     

The role of regulatory B cells (Bregs) in the Tregs-amplifying effect of Sirolimus

Sirolimus can significantly amplify regulatory T cells (Tregs) in vivo and in vitro, but the specific mechanism of this has not been well documented. The role of regulatory B cells (Bregs) in the Tregs-amplifying effect of Sirolimus was investigated in peripheral blood mononuclear cells (PBMCs) in vitro in this study. The results showed that the percentages of both CD19 + CD24 + CD38 + TGF-β1 + Bregs and CD19 + CD24 + CD38 + IL-10 + Bregs to B cells were elevated by Sirolimus in PBMCs including B cells. Sirolimus significantly enhances the cytokine production of transforming growth factor-β1 (TGF-β1) and interleukin-10 (IL-10) in PBMCs with B cells, and the enhancement significantly decreased in PBMCs without B cells. The percentage of CD4 + CD25 + Foxp3 + Tregs to T cells was also elevated by Sirolimus in PBMCs including B cells. The elevation of Tregs percentage decreased in PBMCs without B cells and recovered when additional TGF-β1 and IL-10 were added. The amplification of Tregs by Sirolimus was partially inhibited when either TGF-β1 or IL-10 was neutralized, and it even disappeared when these two cytokines were both neutralized. These results indicate that Sirolimus can amplify Bregs and Tregs in PBMCs in vitro, and Bregs may be the why Sirolimus amplifies Tregs.     

Clobenpropit,a histamine H3 receptor antagonist/inverse agonist,inhibits [3H]-dopamine uptake by human neuroblastoma SH-SY5Y cells and rat brain synaptosomes

Background

Clobenpropit, a potent antagonist/inverse agonist at the histamine H₃ receptor (H₃R), reduced the cytotoxic action of 6-hydroxydopamine (6-OHDA) in neuroblastoma SH-SY5Y cells transfected with the human H₃R. We therefore set out to study whether this effect involved a receptor-independent action on dopamine transport.

Antiviral effects of mifepristone on human immunodeficiency virus type-1 (HIV-1): Targeting Vpr and its cellular partner,the glucocorticoid receptor (GR)

The HIV-1 viral protein R, Vpr, increases virus replication in T cells and is necessary for the optimal infection of primary monocytes/macrophages and other non-dividing cells. Vpr interacts with the cellular glucocorticoid receptor (GR) and transactivates the HIV-1 LTR through glucocorticoid response element (GRE), an event that can be blocked by the GR antagonist, mifepristone. Results demonstrated that Vpr-induced transactivation of the HIV-1 LTR was inhibited by mifepristone in a dose-dependent manner by >60% at a 10 μM concentration. Infectivity assays using X4 and R5 viruses demonstrated antiviral effects on a dose-dependent regimen of mifepristone. The effects of mifepristone were also tested in latently infected cells that could be activated with extracellular Vpr protein and results indicated specific inhibition of virus reactivation in the presence of this antagonist.     

Exenatide modulates metalloproteinase expression in human cardiac smooth muscle cells via the inhibition of Akt signaling pathway

Background

Incretin analogue drugs, a FDA-approved treatment in diabetes, has been tested for its therapeutic properties as modulators of atherosclerosis. We investigated the effects of incretin drugs on the modulation of gene expression and protein levels of matrix metalloproteinases (MMPs) as well as their inhibitors ? tissue inhibitors of metalloproteinases (TIMPs) in coronary artery smooth muscle cells (hCASMC) in the context of atherosclerotic plaque formation and inflammation.

Regulation of RhoA/ROCK and sustained arterial contraction by low cytosolic Ca2 + levels during prolonged depolarization of arterial smooth muscle

The role of L-type Ca^2 + channels (LTCCs) and RhoA/Rho kinase (ROCK) on depolarization-induced sustained arterial contraction lasting several minutes is already known. However, in vivo, vascular smooth muscle cells can be depolarized for longer periods, inducing substantial inactivation of LTCCs and markedly reducing Ca^2 + influx into the myocytes. We have examined, in femoral arterial rings, the role of LTCCs and RhoA/ROCK during long-lasting depolarization. Our results reveal a new vasoreactive response after 20–30 min of depolarization in 2.5 mM external Ca^2 + that has not been identified previously with shorter stimuli. Prolonged depolarization-induced arterial contraction was permanently abolished when arterial rings were treated with 100 nM external Ca^2 + or 20 nM nifedipine. However, when Ca^2 + influx was restricted, applying ~ 7 μM external Ca^2 + solution or 3 nM nifedipine, vasorelaxation was transient, and isometric force slowly increased after 30 min and maintained its level until the end of the stimulus. Under these conditions, arterial contraction showed the same temporal course of RhoA activity and was sensitive to fasudil, nifedipine and cyclopiazonic acid. Ca^2 +-response curve in β-escin permeabilized arteries was also sensitive to ROCK inhibitors. Thus, although long-lasting depolarization inactivates LTCCs, the reduced Ca^2 + entry can induce a detectable arterial contraction via RhoA/ROCK activation.     

Susceptibility of avian influenza viruses of the N6 subtype to the neuraminidase inhibitor oseltamivir

Avian influenza viruses are a source of genetic material that can be transmitted to humans through direct introduction or reassortment. Although there is a wealth of information concerning global monitoring for antiviral resistance among human viruses of the N1 and N2 neuraminidase (NA) subtypes, information concerning avian viruses of these and other NA subtypes is limited. We undertook a surveillance study to investigate the antiviral susceptibility of avian influenza N6 NA viruses, the predominant subtype among wild waterfowl. We evaluated 73 viruses from North American ducks and shorebirds for susceptibility to the NA inhibitor oseltamivir in a fluorescence-based NA enzyme inhibition assay. Most (90%) had mean IC₅₀ values ranging from <0.01 to 5.0 nM; 10% were from 5.1 to 50.0 nM; and none were >50.0 nM. Susceptibility to oseltamivir remained stable among all isolates collected over approximately three decades (P ? 0.74). Two isolates with I222V NA substitution had moderately reduced susceptibility to oseltamivir in vitro (IC₅₀, 30.0 and 40.0 nM). One field sample was a mixed population containing an avian paramyxovirus (APMV) and H4N6 influenza virus, as revealed by electron microscopy and hemagglutination inhibition assays with a panel of anti-APMV antisera. This highlights the importance of awareness and careful examination of non-influenza pathogens in field samples from avian sources. This study showed that oseltamivir-resistant N6 NA avian influenza viruses are rare, and must be tested both phenotypically and genotypically to confirm resistance.     

Biarylmethoxy isonipecotanilides as potent and selective inhibitors of blood coagulation factor Xa

New chloro-substituted biarylmethoxyphenyl piperidine-4-carboxamides were synthesized and assayed in vitro as inhibitors of the blood coagulation enzymes factor Xa (fXa) and thrombin. An investigation of effects of the amidine and isopropyl groups attached at the piperidine nitrogen and 5-(halogenoaryl)isoxazol-3-yl groups as biaryl substituents led us to identify new compounds which proved to be selective fXa inhibitors, with inhibition constants in the low nanomolar range. The most potent compound 21e, that incorporates 2-Cl-thiophen-5-yl group as the P1 motif and 1-isopropylpiperidine P4 group, inhibited fXa with K_i value of 0.3 nM and very high selectivity over thrombin and some other tested serine proteases, achieving moderate levels of anticoagulant activity in the low micromolar range, as assessed by the prothrombin time clotting assay (PT₂ = 3.30 μM). Based on reliable docking simulations, molecular modeling provided a rationale for interpreting structure–activity relationships. The predicted binding modes highlighted the structural requirements for addressing the subsites S1 and S4 of the fXa enzyme.     

Characterisation of the roles of ABCB1, ABCC1, ABCC2 and ABCG2 in the transport and pharmacokinetics of actinomycin D in vitro and in vivo

Actinomycin D plays a key role in the successful treatment of Wilms tumour. However, associated liver toxicities remain a drawback to potentially curative treatment. We have used MDCKII cells over-expressing ABCB1, ABCC1, ABCC2 and ABCG2, alongside knockout mouse models to characterise actinomycin D transport and its impact on pharmacokinetics. Growth inhibition, intracellular accumulation and cellular efflux assays were utilised. A 59-fold difference in GI₅₀ was observed between MDCKII-WT and MDCKII-ABCB1 cells (12.7 nM vs. 745 nM, p < 0.0001). Reduced sensitivity was also seen in MDCKII-ABCC1 and ABCC2 cells (GI₅₀ 25.7 and 40.4 nM respectively, p < 0.0001). Lower intracellular accumulation of actinomycin D was observed in MDCKII-ABCB1 cells as compared to MDCKII-WT (0.98 nM vs. 0.1 nM, p < 0.0001), which was reversed upon ABCB1 inhibition. Lower accumulation was also seen in MDCKII-ABCC1 and ABCC2 cells. Actinomycin D efflux over 2 h was most pronounced in MDCKII-ABCB1 cells, with 5.5-fold lower intracellular levels compared to WT. In vivo studies showed that actinomycin D plasma concentrations were significantly higher in Abcb1a/1b^?/? as compared to WT mice following administration of 0.5 mg/kg actinomycin D (AUC_0–6 h 242 vs. 152 μg/L h respectively). While comparable actinomycin D concentrations were observed in the kidneys and livers of Abcb1a/1b^?/? and Abcc2^?/? mice, concentrations in the brain were significantly higher at 6 h following drug administration in Abcb1a/1b^?/? mice compared to WT. Results confirm actinomycin D as a substrate for ABCB1, ABCC1 and ABCC2, and indicate that Abcb1a/1b and Abcc2 can influence the in vivo disposition of actinomycin D. These data have implications for ongoing clinical pharmacology trials involving children treated with actinomycin D.     

Influence of anticancer agents on cell survival,proliferation, and CD4+CD25+Foxp3+ regulatory T cell-frequency in human peripheral-blood mononuclear cells activated by T cell-mitogen

Many anticancer agents currently used are considered to be cytotoxic not only to cancer cells but also to functional immune cells. To learn more about the immunosuppressive adverse influence of chemotherapeutic drugs in cancer chemotherapy, we examined the effects of arsenic trioxide, dacarbazine, 5-fluorouracil, and methotrexate on the survival, proliferation, cytokine production, and CD4⁺CD25⁺Foxp3⁺ regulatory T (Treg) cell-frequency in human peripheral blood mononuclear cells (PBMCs) activated by T cell mitogen in vitro. Arsenic trioxide, dacarbazine, and 5-fluorouracil increased trypan-blue stained (dead) cell rates and suppressed the mitogen-activated proliferation of PBMCs significantly at 1–100 μM (p < 0.05). Methotrexate also significantly increased the percentages of dead cells and suppressed the mitogen-activated PBMC-proliferation at concentrations of more than 0.05 μM (p < 0.01). Arsenic trioxide significantly inhibited the production of interferon γ, interleukin (IL)-4, -6, and -10 from the activated PBMCs at 5 μM (p < 0.05). In contrast, the anticancer agents significantly increased Treg cell-frequency in the activated PBMCs at concentrations of more than 0.1 μM for methotrexate, 5 μM for arsenic trioxide and 5-fluorouracil, and 50 μM for dacarbazine, respectively (p < 0.05). These agents did not significantly influence the production of transforming growth factor (TGF) β from the activated PBMCs at a concentration range of 0.05–50 μM. Our data suggest that the anticancer agents: arsenic trioxide, dacarbazine, 5-fluorouracil, and methotrexate attenuate T cell mediated immunity by not only inhibiting the proliferative response of T cells but by also increasing the frequency of Treg cells, which may result in the suppression of the effector T cell function.     

Influenza A virus replication is inhibited in IFN-λ2 and IFN-λ3 transfected or stimulated cells

Interferons lambda (IFN-λ) are the most recently defined members of the class III cytokine family. To investigate whether IFN-λ2 and IFN-λ3 displayed antiviral activity against influenza A virus (IAV), a number of cell lines induced with IFNs – as well as two established cell lines (A549-IFN-λ2 and A549-IFN-λ3) – were infected with IAV. Our results indicate that IFN-λ2 has statistically significant antiviral activity in A549-IFN-λ2 (P = 0.0028) although less so than IFN-λ3, which reduced viral titer to 10% (P < 0.0001). The reverse was observed for cells treated with IFNs, with IFN-λ2-treated A549 cells inhibiting IAV infection more efficiently than IFN-λ3-treated A549 cells. The antiviral effect on IFN-stimulated cells was most apparent on Vero cells (compared with MDCK and HeLa). Both IFNs significantly inhibited IAV replication and inhibition was observed in a dose-dependent manner, with an optimal IFN concentration of 20 ng/ml. IFN-λ2 was more potent than IFN-λ3 on Vero cells while IFN-λ3 appeared more efficient than IFN-λ2 on MDCK and HeLa cells.     

Induction of G2/M arrest,caspase activation and apoptosis by α-santonin derivatives in HL-60 cells

Sesquiterpene lactones (SLs) are natural products with a variety of biological activities. Previously, we demonstrated the cytotoxic effects of three new α-santonin derivatives on different tumor cell lines with low toxic effects upon peripheral human leukocytes. Here, we evaluated the mechanism of action triggered by these derivatives. HL-60 cell cycle determined after 24 h treatment revealed a significant inhibition on cell-cycle progression and leading to an increasing of cells in G₂/M [7.6% and 9.0% for compound 3% and 9.0% and 8.6% for compound 4 (1 and 2 μM, respectively)]. However, after 48 h exposure, all compounds caused G₂/M reduction and a significant DNA fragmentation. Compounds 2, 3 and 4 were able to induce apoptosis on leukemia cells, which was corroborated by phosphatidyserine externalization and activation of caspases-3 and -7 after 24 h exposure. None of the derivatives analyzed caused depolarization of mitochondrial membrane within 24 h of incubation, suggesting the involvement of the extrinsic apoptotic pathway in the death process. The antiproliferative action of these compounds is related to the DNA synthesis inhibition and cell cycle arrest, which probably lead to apoptosis activation. Therefore, these santonin derivatives are promising lead candidates for development of new cytotoxic agents.