title: Suppression of Virulence of Toxigenic Vibrio cholerae by Anethole through the Cyclic AMP (cAMP)-cAMP Receptor Protein Signaling System.
abstract: Use of natural compounds as antivirulence drugs could be an alternative therapeutic approach to modify the outcome of bacterial infections, particularly in view of growing resistance to available antimicrobials. Here, we show that sub-bactericidal concentration of anethole, a component of sweet fennel seed, could suppress virulence potential in O1 El Tor biotype strains of toxigenic Vibrio cholerae, the causative agent of the ongoing 7th cholera pandemic. The expression of cholera toxin (CT) and toxin coregulated pilus (TCP), the major virulence factors of V. cholerae, is controlled through a regulatory cascade involving activation of ToxT with synergistic coupling interaction of ToxR/ToxS with TcpP/TcpH. We present evidence that anethole inhibits in vitro expression of CT and TCP in a toxT-dependent but toxR/toxS-independent manner and through repression of tcpP/tcpH, by using bead-ELISA, western blotting and quantitative real-time RT-PCR assays. The cyclic AMP (cAMP)-cAMP receptor protein (CRP) is a well-studied global signaling system in bacterial pathogens, and this complex is known to suppress expression of tcpP/tcpH in V. cholerae. We find that anethole influences the virulence regulatory cascade by over-expressing cyaA and crp genes. Moreover, suppression of toxigenic V. cholerae-mediated fluid accumulation in ligated ileum of rabbit by anethole demonstrates its potentiality as an antivirulence drug candidate against the diseases caused by toxigenic V. cholerae. Taken altogether, these results revealing a mechanism of virulence inhibition in V. cholerae by the natural compound anethole, may have relevance in designing antivirulence compounds, particularly against multiple antibiotic resistant bacterial pathogens.
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: M Shamim Hasan
authors.initials: MS
authors.lastname: Zahid
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Sharda Prasad
authors.initials: SP
authors.lastname: Awasthi
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Asakura
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Shruti
authors.initials: S
authors.lastname: Chatterjee
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hinenoya
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Shah M
authors.initials: SM
authors.lastname: Faruque
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Osaka, Japan.
authors.forename: Shinji
authors.initials: S
authors.lastname: Yamasaki
mesh_terms: D000081248:Allylbenzene Derivatives; D000818:Animals; D000840:Anisoles / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D002772:Cholera Toxin / Q000235:genetics / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D002373:Cyclic AMP Receptor Protein / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D036781:Fimbriae Proteins / Q000378:metabolism; D007082:Ileum / Q000382:microbiology; D008565:Membrane Proteins / Q000378:metabolism; D011817:Rabbits; D015290:Second Messenger Systems; D014157:Transcription Factors / Q000378:metabolism; D014734:Vibrio cholerae / Q000187:drug effects* / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence / Q000187:drug effects
chemical_list: D000081248:Allylbenzene Derivatives; D000840:Anisoles; D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002373:Cyclic AMP Receptor Protein; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; C097244:TCPP protein, Vibrio cholerae; C099204:TcpH protein, Vibrio cholerae; D014157:Transcription Factors; C066719:toxR protein, bacteria; C066828:ToxS protein, Vibrio cholerae; D036781:Fimbriae Proteins; D002772:Cholera Toxin; D000242:Cyclic AMP; C006578:anethole