title: Differential antiviral and anti-inflammatory mechanisms of the flavonoids biochanin A and baicalein in H5N1 influenza A virus-infected cells.
abstract: From a panel of 22 flavonoids, we identified six compounds (apigenin, baicalein, biochanin A, kaempferol, luteolin, naringenin) that inhibited influenza A nucleoprotein production in human lung epithelial (A549) cells infected with the highly pathogenic avian influenza H5N1 virus strain A/Thailand/Kan-1/04 in non-toxic concentrations. Baicalein (IC(50): 18.79±1.17μM, selectivity index 5.82) and biochanin A (IC(50) 8.92±1.87μM, selectivity index 5.60) were selected for further experiments. Both compounds reduced H5N1 infectious titres (baicalein 40μM: 29-fold reduction, biochanin A 40μM: 55-fold reduction after infection at MOI 0.01), virus-induced caspase 3 cleavage, nuclear export of viral RNP complexes, and enhanced the effects of the neuraminidase inhibitor zanamivir. Biochanin A and baicalein also inhibited the replication of the H5N1 strain A/Vietnam/1203/04. Time of addition experiments indicated that both compounds interfere with H5N1 replication after the adsorption period. Further mechanistic investigations revealed clear differences between these two flavonoids. Only baicalein interfered with the viral neuraminidase activity (39±7% inhibition at 100μM, the maximum concentration tested). In contrast to baicalein, biochanin A affected cellular signalling pathways resulting in reduced virus-induced activation of AKT, ERK 1/2, and NF-kB. Moreover, biochanin A inhibited the virus-induced production of IL-6, IL-8, and IP-10 while baicalein inhibited IL-6 and IL-8 production without affecting IP-10 levels. In primary human monocyte-derived macrophages, only baicalein but not biochanin A impaired H5N1 virus replication. Both flavonoids interfered with the H5N1-induced production of IL-6, IP-10, and TNF-α but not of IL-8 in macrophages. These findings indicate that closely related flavonoids can exert anti-H5N1 effects by different molecular mechanisms.
authors.affiliation: Institute for Medical Virology, Clinics of the Goethe-University, Frankfurt am Main, Germany. spatchima@yahoo.com
authors.forename: Patchima
authors.initials: P
authors.lastname: Sithisarn
authors.forename: Martin
authors.initials: M
authors.lastname: Michaelis
authors.forename: Manfred
authors.initials: M
authors.lastname: Schubert-Zsilavecz
authors.forename: Jindrich
authors.initials: J
authors.lastname: Cinatl
mesh_terms: D000893:Anti-Inflammatory Agents / Q000494:pharmacology*; D000998:Antiviral Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D016207:Cytokines / Q000037:antagonists & inhibitors; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D004847:Epithelial Cells / Q000821:virology; D044950:Flavanones / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology*; D006801:Humans; D053124:Influenza A Virus, H5N1 Subtype / Q000187:drug effects* / Q000502:physiology; D020128:Inhibitory Concentration 50; D008264:Macrophages / Q000821:virology; D008826:Microbial Sensitivity Tests; D015398:Signal Transduction / Q000187:drug effects; D019562:Viral Load; D014779:Virus Replication / Q000187:drug effects*; D053243:Zanamivir / Q000494:pharmacology
chemical_list: D000893:Anti-Inflammatory Agents; D000998:Antiviral Agents; D016207:Cytokines; D044950:Flavanones; D005419:Flavonoids; C006680:baicalein; D019833:Genistein; D053243:Zanamivir; C004541:biochanin A