TRAF3 Positively Regulates Host Innate Immune Resistance to Influenza A Virus Infection.

Tumor necrosis factor receptor-associated factor 3 (TRAF3) is one of the intracellular adaptor proteins for the innate immune response, which is involved in signaling regulation in various cellular processes, including the immune responses defending against invading pathogens. However, the defense mechanism of TRAF3 against influenza virus infection remains elusive. In this study, we found that TRAF3 could positively regulate innate antiviral response. Overexpression of TRAF3 significantly enhanced virus-induced IRF3 activation, IFN-ß production, and antiviral response, while TRAF3 knockdown promoted influenza A virus replication. Moreover, we clarified that inhibiting ubiquitinated degradation of TRAF3 was associated with anti-influenza effect, thereby facilitating antiviral immunity upon influenza A virus infection. We further demonstrated the key domains of TRAF3 involved in anti-influenza effect. Taken together, these results suggested that TRAF3 performs a vital role in host defense against influenza A virus infection by the type-I IFN signaling pathway. Our findings provide insights into the development of drugs to prevent TRAF3 degradation, which could be a novel therapeutic approach for treatment of influenza A virus infection.

Essential Oil-Rich Chinese Formula Luofushan-Baicao Oil Inhibits the Infection of Influenza A Virus through the Regulation of NF-κB P65 and IRF3 Activation.

BACKGROUND: Luofushan-Baicao Oil (LBO) is an essential oil-rich traditional Chinese medicine (TCM) formula that is commonly used to treat cold, cough, headache, sore throat, swelling, and pain. However, the anti-influenza activities of LBO and the underlying mechanism remain to be investigated. METHODS: The in vitro anti-influenza activity of LBO was tested with methyl thiazolyl tetrazolium (MTT) and plaque assays. The effects of LBO on the expressions of viral nucleoprotein and cytokines were evaluated. In the polyinosinic-polycytidylic acid- (Poly I: C-) induced inflammation model, the influences of LBO on the expression of cytokines and the activation of NF-κB P65 (P65) and interferon regulatory factor 3 (IRF3) were tested. After influenza A virus (IVA) infection, mice were administered with LBO for 5 days. The lung index, histopathologic change, the expression of viral protein, P65, and IRF3 in the lung tissue were measured. The levels of proinflammatory cytokines in serum were examined. RESULTS: In vitro, LBO could significantly inhibit the infection of IVA, decrease the formation of plaques, and reduce the expression of viral nucleoprotein and cytokines. LBO could also effectively downregulate the expression of interleukin-1ß (IL-1ß), interleukin-6 (IL-6), and interferon-ß and the activation of P65 and IRF3 in Poly I:C-treated cells. In the IVA-infected mice model, inhalation of LBO with atomizer could decrease the lung index, alleviate the pathological injury in the lung tissue, and reduce the serum levels of IL-1ß and IL-6. LBO could significantly downregulate the expression of viral protein (nucleoprotein, PB2, and matrix 2 ion channel) and the phosphorylation of P65 and IRF3 in the lungs of mice. CONCLUSION: The therapeutic effects of LBO on treating influenza might result from the regulation of the immune response of IVA infection. LBO can be developed as an alternative therapeutic agent for influenza prevention.

Identification of imidazo[4,5-c]pyridin-2-one derivatives as novel Src family kinase inhibitors against glioblastoma.

Glioblastoma multiforme (GBM) is the most common and malignant primary brain tumour in the central nervous system (CNS). As the ideal targets for GBM treatment, Src family kinases (SFKs) have attracted much attention. Herein, a new series of imidazo[4,5-c]pyridin-2-one derivatives were designed and synthesised as SFK inhibitors. Compounds 1d, 1e, 1q, 1s exhibited potential Src and Fyn kinase inhibition in the submicromolar range, of which were next tested for their antiproliferative potency on four GBM cell lines. Compound 1s showed effective activity against U87, U251, T98G, and U87-EGFRvIII GBM cell lines, comparable to that of lead compound PP2. Molecular dynamics (MDs) simulation revealed the possible binding patterns of the most active compound 1s in ATP binding site of SFKs. ADME prediction suggested that 1s accord with the criteria of CNS drugs. These results led us to identify a novel SFK inhibitor as candidate for GBM treatment.

Multiple modes of action of myricetin in influenza A virus infection.

Influenza A virus remains a major threat to public health worldwide after its first pandemic. Scientists keep searching novel anti-influenza drugs, of which natural products present to be an important source. Myricetin, a natural flavonol compound, which exists in many edible plants, which has a wide range of biological activities, but its anti-influenza A virus activity is ambiguous. This study aims to evaluate the anti-influenza activity of myricetin and elucidate its underlying mechanism. Our results demonstrated that myricetin could significantly inhibit influenza A virus replication, reduce viral polymerase activity via selective inhibition of viral PB2 subunit, and the production of inflammatory cytokines by inhibiting TLR3 signaling pathway. The binding affinity analysis and the result of molecular docking revealed that myricetin interacted with the PB2 cap-binding pocket of influenza A virus. The above results suggested myricetin could exhibit anti-influenza virus activity with low cytotoxicity as well, and myricetin had low toxicity in BALB/c mice in vivo. Results from this study highlighted myricetin could be considered as a promising anti-influenza virus agent with dual inhibition profile. Furthermore, the compound with similar structure would provide a new option for the development of novel inhibitors against influenza A virus.

Dihydromyricetin is a new inhibitor of influenza polymerase PB2 subunit and influenza-induced inflammation.

Development of new and effective anti-influenza drugs is critical for the treatment of influenza virus infection. The polymerase basic 2 (PB2) subunit as a core subunit of influenza A virus RNA polymerase complex is considered to be an attractive drug target for anti-influenza drug discovery. Dihydromyricetin, as a natural flavonoid, has a wide range of biological activities, but its anti-influenza A virus activity is ambiguous. Here, we found dihydromyricetin could inhibit the replication of a variety of influenza A virus strains. Mechanism studies demonstrated that dihydromyricetin reduced viral polymerase activity via selective inhibition of viral PB2 subunit, and decreased relative amounts of viral mRNA and genomic RNA during influenza A virus infection. The binding affinity and molecular docking analyses revealed that dihydromyricetin interacted with the PB2 cap-binding pocket, functioned as a cap-binding competitor. Interestingly, dihydromyricetin also reduced cellular immune injury by inhibiting TLR3 signaling pathway. Additionally, combination treatment of dihydromyricetin with zanamivir exerted a synergistic anti-influenza effect. Altogether, our experiments reveal the antiviral and anti-inflammatory activities of dihydromyricetin in vitro against influenza virus infection, which provides a new insight into the development of novel anti-influenza drugs.

Discovery of dihydropyrrolidones as novel inhibitors against influenza A virus.

More effective prophylactic and therapeutic strategies to combat influenza viruses are urgently required worldwide because the conventional anti-influenza drugs are facing drug resistance. Here, dihydropyrrolidones (DHPs), the products of an efficient multi-components reaction, were found to possess good activities against influenza A virus (IAV). Primary structure-activity relationship indicated that the activities of DHPs were greatly influenced by substituents and four of them had IC50 values lower than 10 µM (DHPs 5-2, 8, 14 and 19: IC50 = 3.11-9.23 µM). The activities against multiple IAV strains and mechanism of DHPs were further investigated by using 5-2 (IC50 = 3.11 µM). It was found that 5-2 possessed antiviral effects against all the investigated subtypes of IAVs with the IC50 values from 3.11 to 7.13 µM. Moreover, 5-2 showed very low cytotoxicity with CC50 > 400 µM. Results of mechanism study indicated that 5-2 could efficiently inhibit replication of IAV, up-regulate the expression of key antiviral cytokines IFN-ß and antiviral protein MxA, and suppress the production of the NDAPH oxidase NOX1 in MDCK cells. These results indicated that 5-2 could be used as a potential inhibitor against wide subtypes of IAVs.

Isocorilagin, isolated from Canarium album (Lour.) Raeusch, as a potent neuraminidase inhibitor against influenza A virus.

Canarium album (Lour.) Raeusch (C. album) as a normally medicinal and edible plant has been used widely in Asian countries and is considered a source of phytochemicals that are beneficial to human health. Here, we showed at the first time isocorilagin, a polyphenolic compound isolated from C. album, displayed antiviral activity against diverse strains of influenza A virus (IAV), including A/Puerto Rico/8/34 (H1N1), A/Aichi/2/68 (H3N2) and NA-H274Y (H1N1) with IC50 value of 9.19 ±â€¯1.99, 23.72 ±â€¯2.51 and 4.64 ±â€¯3.01 µM, respectively. Further mechanistic studies revealed that it clearly inhibited neuraminidase activity of IAV and directly influenced the virus release. The molecular docking studies presented isocorilagin could bind to the highly conserved residues in the active sites of NA, implying that isocorilagin may be effective against various influenza strains and not susceptible to produce drug resistance. Taken together, the results strongly suggest that isocorilagin has potential to be an effective, safe and affordable neuraminidase inhibitor against a diverse panel of IAV strains. More importantly, our work expands the biological activities of C. album extracts and provide a new option for the development of anti-influenza drug.