title: Natural and synthetic flavonoid modulation of TRPC5 channels.
abstract: OBJECTIVE
  The TRPC5 proteins assemble to create calcium-permeable, non-selective, cationic channels. We sought novel modulators of these channels through studies of natural products.
  
  
  METHODS
  Intracellular calcium measurements and patch clamp recordings were made from cell lines. Compounds were generated by synthetic chemistry.
  
  
  RESULTS
  Through a screen of natural products used in traditional Chinese medicines, the flavonol galangin was identified as an inhibitor of lanthanide-evoked calcium entry in TRPC5 overexpressing HEK 293 cells (IC50 0.45 μM). Galangin also inhibited lanthanide-evoked TRPC5-mediated current in whole-cell and outside-out patch recordings. In differentiated 3T3-L1 cells, it inhibited constitutive and lanthanide-evoked calcium entry through endogenous TRPC5-containing channels. The related natural flavonols, kaempferol and quercetin were less potent inhibitors of TRPC5. Myricetin and luteolin lacked effect, and apigenin was a stimulator. Based on structure-activity relationship studies with natural and synthetic flavonols, we designed 3,5,7-trihydroxy-2-(2-bromophenyl)-4H-chromen-4-one (AM12), which inhibited lanthanide-evoked TRPC5 activity with an IC50 of 0.28 μM. AM12 also inhibited TRPC5 activity evoked by the agonist (-)-Englerin A and was effective in excised outside-out membrane patches, suggesting a relatively direct effect. It inhibited TRPC4 channels similarly, but its inhibitory effect on TRPC1-TRPC5 heteromeric channels was weaker.
  
  
  CONCLUSIONS
  The data suggest that galangin (a natural product from the ginger family) is a TRPC5 inhibitor and that other natural and synthetic flavonoids contain antagonist or agonist capabilities at TRPC5 and closely related channels depending on the substitution patterns of both the chromone core and the phenyl ring.
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Naylor
authors.affiliation: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Aisling
authors.initials: A
authors.lastname: Minard
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Hannah J
authors.initials: HJ
authors.lastname: Gaunt
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.|Clinical Physiology Department, Faculty of Medicine, Menoufiya University, Shibin Al Kawm, Egypt.
authors.forename: Mohamed S
authors.initials: MS
authors.lastname: Amer
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Lesley A
authors.initials: LA
authors.lastname: Wilson
authors.affiliation: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Marco
authors.initials: M
authors.lastname: Migliore
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Sin Y
authors.initials: SY
authors.lastname: Cheung
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Hussein N
authors.initials: HN
authors.lastname: Rubaiy
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Nicola M
authors.initials: NM
authors.lastname: Blythe
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Katie E
authors.initials: KE
authors.lastname: Musialowski
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Melanie J
authors.initials: MJ
authors.lastname: Ludlow
authors.affiliation: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: William D
authors.initials: WD
authors.lastname: Evans
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Ben L
authors.initials: BL
authors.lastname: Green
authors.affiliation: Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China.
authors.forename: Hongjun
authors.initials: H
authors.lastname: Yang
authors.affiliation: Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences, Beijing, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: You
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.affiliation: School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Colin W G
authors.initials: CW
authors.lastname: Fishwick
authors.affiliation: School of Pharmacy, Aichi-Gakuin University, Nagoya, 464-8650, Japan.
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Muraki
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Beech
authors.affiliation: School of Medicine, University of Leeds, Leeds, LS2 9JT, UK.|School of Chemistry, University of Leeds, Leeds, LS2 9JT, UK.
authors.forename: Robin S
authors.initials: RS
authors.lastname: Bon
mesh_terms: D041721:3T3-L1 Cells; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology*; D005682:Gadolinium / Q000494:pharmacology; D057809:HEK293 Cells; D006801:Humans; D007811:Lanthanum / Q000494:pharmacology; D051379:Mice; D050052:TRPC Cation Channels / Q000235:genetics / Q000502:physiology*
chemical_list: D005419:Flavonoids; D050052:TRPC Cation Channels; C491780:TRPC5 protein, human; D007811:Lanthanum; D005682:Gadolinium; D002118:Calcium