Shuwen Wu

Synthesis and antiviral activities of novel gossypol derivatives.

In this study, a series of novel gossypol derivatives were synthesized and screened in vitro for their anti-HIV-1 and anti-H(5)N(1) activities, respectively. Replacing the aldehyde groups of gossypol with some amino acids not only reduced the cytotoxicity but also enhanced the activities against HIV-1 and H(5)N(1). Compounds 13-17 showed more potent activities against HIV-1 and H(5)N(1) than the other gossypol derivatives. Meanwhile, these compounds also exhibited more potent activities against H(5)N(1) than 1-adamantylamine. The absence of the COONa group in gossypol derivatives resulted in a loss of anti-HIV-1 activity, suggesting that this group might play an important role in mediating the antiviral activity. Time-of-addition assays indicated that compounds 13-17 had the similar mechanism of anti-HIV-1 action with T20. Molecular modeling analysis demonstrated that compounds 13-17 could fit inside the gp41 hydrophobic pocket through hydrogen bonding network, hydrophobic contacts and strong electrostatic interactions.

Enantioselective inhibition of reverse transcriptase (RT) of HIV-1 by non-racemic indole-based trifluoropropanoates developed by asymmetric catalysis using recyclable organocatalysts.

Herein, we report the development of efficient inhibitors of reverse transcriptase (RT) of HIV-1 based on indole-alkyl trifluoropyruvate derivatives by a TZM-bl cell assay. The inhibitory activities of the two enantiomers and the corresponding racemic mixture have been compared. TZM-bl cells exhibited strong enantioselective discrimination for the (R)-configuration, among these indole derivatives, the most active compound R-12, with a 5-NO2 substituent, gave the best result when tested in the TZM-bl cells on HIV virus type HIV-1IIIB, with an EC50 value of 0.019 μM, CC50 value of 210.697 μM and SI (selectivity index, CC50/EC50) value of 11,089, respectively. The cell test showed that, in most cases, the R-enantiomer was superior to the Rac-mixture, which was better than the corresponding S-enantiomer. The results indicated that the R-enantiomer is the most favorable configuration as an efficient HIV-1 inhibitor. Molecular modeling studies suggested a structural basis for the enantioselectivity of RT towards this class of molecules.

Amino acid derivatives of the (−) enantiomer of gossypol are effective fusion inhibitors of human immunodeficiency virus type 1

T20 and maraviroc are the only two currently available entry inhibitors that have shown efficacy in treating HIV-1-infected individuals who have failed to respond to first-line antiretroviral drugs. Gossypol is a polyphenolic aldehyde extracted from cotton plants. By modifying the (-) enantiomer of gossypol with a series of small molecules, we have found that neutral amino acids with aliphatic group derivatives of (-) gossypol show the strongest inhibitory activity and the lowest cytotoxicity in vitro among all the derivatives tested. Additionally, the selectivity index of the (-) gossypol-neutral amino acid conjugates is increased 100-fold when compared with (-) gossypol alone. It is widely accepted that gossypol and gossypol derivatives inhibit HIV-1 replication by targeting reverse transcriptase. However, from the results of our time-of-addition assay, HIV-1-mediated cell fusion assay and VSV-G pseudotyped virus assay, we demonstrate that the alanine-(-) gossypol derivative ((-)G-Ala) is an effective HIV-1 entry inhibitor. Further mechanistic analysis revealed that (-)G-Ala neither blocks gp120-CD4 binding nor interacts with the HIV-1 co-receptor CXCR4. Results from sandwich ELISA, native-PAGE and circular dichroism (CD) show that (-)G-Ala inhibits the cell fusion-activated gp41 core domain. Moreover, (-)G-Ala binds to the HIV-5-Helix protein and blocking D-peptide (PIE7) binding to the hydrophobic pocket on the surface of the gp41 internal trimeric coiled-coil domain. The contraceptive properties of (-) gossypol and amino acid derivatives of (-) gossypol are also discussed. Collectively, our results indicate that (-)G-Ala may bind to the gp41 hydrophobic pocket and block the formation of the cell fusion-activated gp41 core to inhibit HIV-1-mediated membrane fusion and subsequent viral entry.

Synthesis and anti-H5N1 activity of chiral gossypol derivatives and its analogs implicated by a viral entry blocking mechanism

A series of chiral gossypol derivatives and its analogs were synthesized and tested in vitro for their anti-H5N1 activity. Interestingly, (+)-gossypol derivatives and its analogs were more active against H5N1 than the corresponding (-)-gossypol derivatives and its analogs. Through a simple chemical modification with amino acids, less active chiral gossypol could be converted into more active derivatives, and most of chiral gossypol derivatives were more potent against H5N1 than 1-adamantylamine. With regard to the mechanism of action, chiral gossypol derivatives and its analogs might impair the virus entry step of cell infection, likely targeting to HA2 protein.

DYRK2 Negatively Regulates Type I Interferon Induction by Promoting TBK1 Degradation via Ser527 Phosphorylation.

Viral infection activates the transcription factors NF-κB and IRF3, which contribute to the induction of type I interferons (IFNs) and cellular antiviral responses. Protein kinases play a critical role in various signaling pathways by phosphorylating their substrates. Here, we identified dual-specificity tyrosine-(Y)-phosphorylation-regulated kinase 2 (DYRK2) as a negative regulator of virus-triggered type I IFN induction. DYRK2 inhibited the virus-triggered induction of type I IFNs and promoted the K48-linked ubiquitination and degradation of TANK-binding kinase 1 (TBK1) in a kinase-activity-dependent manner. We further found that DYRK2 phosphorylated Ser527 of TBK1, which is essential for the recruitment of NLRP4 and for the E3 ubiquitin ligase DTX4 to degrade TBK1. These findings suggest that DYRK2 negatively regulates virus-triggered signaling by targeting TBK1 for phosphorylation and priming it for degradation, and these data provide new insights into the molecular mechanisms that dictate the cellular antiviral response.

Halolactones are Potent HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors

Herein, we report the discovery of halolactone derivatives as efficient non-nucleoside reverse transcriptase inhibitors (NNRTIs) and the study of their structure–activity relationships (SARs). Among the various halolactone derivatives, 5-exo lactone 3-(chloro(2-chlorophenyl)-methyl)isobenzofuran-1(3H)-one 13a showed excellent potency against WT HIV-1 in the reverse transcriptase gene with a low EC50 value of 0.45 μM. In most of the cases, the property and the position of the substituents had a definite effect on the activities of anti-HIV-1 activity. In contrast, the 6-endo lactones (isochroman-1-ones) had inferior inhibitory activities against HIV-1. This work offered a structurally simple scaffold (isobenzofuran-1(3H)-one) for the development of novel anti-HIV drugs.

Identification and Structure–Activity Relationships of Diarylhydrazides as Novel Potent and Selective Human Enterovirus Inhibitors

Enterovirus 71 (EV71) plays an important role in hand-foot-and-mouth disease. In this study, a series of diarylhydrazide analogues was synthesized, and the systematic exploration of SAR led to potent enterovirus inhibitors, of which compound 15 exhibits significant improvements in inhibition potency with an EC50 value of 0.02 μM against EV71. It is very interesting that this class of diarylhydrazides exhibits activities against a series of human enteroviruses at the picomolar level, including EV71 and Coxsackieviruses B1 (CVB1), CVB2, CVB3, CVB4, CVB5, and CVB6 (EC50 as low as 0.5 nM). Compared with the reference antienterovirus drug 1 (enviroxime) and known inhibitor 5 (WIN 51711), the four highly selective compounds 15, 27, 41 and 47 inhibited EV71 replication with EC50 values of 0.17-0.02 μM and SI values in a range of 978.4-12338. A preliminary mechanistic study indicated that VP1 might be the target site for this type of compound.

Isocyanides as Influenza A Virus Subtype H5N1 Wild-Type M2 Channel Inhibitors

Basic bulky amines such as amantadine are well‐characterized M2 channel blockers, useful for treating influenza. Herein we report our surprising findings that charge‐neutral, bulky isocyanides exhibit activities similar to—or even higher than—that of amantadine. We also demonstrate that these isocyanides have potent growth inhibitory activity against the H5N1 virus. The −NH2 to −N≡C group replacement within current anti‐influenza drugs was found to give compounds with high activities at low‐micromolar concentrations. For example, a tenfold improvement in potency was observed for 1‐isocyanoadamantane (27), with an EC50 value of 0.487 μm against amantadine‐sensitive H5N1 virus as determined by both MTT and plaque‐reduction assays, without showing cytotoxicity. Furthermore, the isocyanide analogues synthesized in this study did not inhibit the V27A or S31N mutant M2 ion channels, according to electrophysiology experiments, and did not exhibit activity against amantadine‐resistant virus strains.

Design, synthesis and biological evaluation of small molecular polyphenols as entry inhibitors against H5N1

To find novel compounds against H5N1, three series of known or novel small molecular polyphenols were synthesized and tested in vitro for anti-H5N1 activity. In addition, the preliminary structure-antiviral activity relationships were elaborated. The results showed that some small molecular polyphenols had better anti-H5N1 activity, and could serve as novel virus entry inhibitors against H5N1, likely targeting to HA2 protein. Noticeably, compound 4a showed the strongest activity against H5N1 among these compounds, and the molecular modeling analysis also suggested that this compound might target to HA2 protein. Therefore, compound 4a is well qualified to serve as a lead compound or scaffold for the further development of H5N1 entry inhibitor.

Heat shock cognate 71 (HSC71) regulates cellular antiviral response by impairing formation of VISA aggregates

In response to viral infection, RIG-I-like RNA helicases detect viral RNA and signal through the mitochondrial adapter protein VISA. VISA activation leads to rapid activation of transcription factors IRF3 and NF-κB, which collaborate to induce transcription of type I interferon (IFN) genes and cellular antiviral response. It has been demonstrated that VISA is activated by forming prion-like aggregates. However, how this process is regulated remains unknown. Here we show that overexpression of HSC71 resulted in potent inhibition of virus-triggered transcription of IFNB1 gene and cellular antiviral response. Consistently, knockdown of HSC71 had opposite effects. HSC71 interacted with VISA, and negatively regulated virus-triggered VISA aggregation. These findings suggest that HSC71 functions as a check against VISA-mediated antiviral response.