Identification and Validation of Larixyl Acetate as a Potent TRPC6 Inhibitor.
Classical or canonical transient receptor potential 6 (TRPC6), a nonselective and Ca(2+)-permeable cation channel, mediates pathophysiological responses within pulmonary and renal diseases that are still poorly controlled by current medication. Thus, controlling TRPC6 activity may provide a promising and challenging pharmacological approach. Recently identified chemical entities have demonstrated that TRPC6 is pharmacologically targetable. However, isotype-selectivity with regard to its closest relative, TRPC3, is difficult to achieve. Reasoning that balsams, essential oils, or incense materials that are traditionally used for inhalation may contain biologic activities to block TRPC6 activity, we embarked on a natural compound strategy to identify new TRPC6-blocking chemical entities. Within several preparations of plant extracts, a strong TRPC6-inhibitory activity was found in conifer balsams. The biologic activity was associated with nonvolatile resins, but not with essential oils. Of various conifers, the larch balsam was unique in displaying a marked TRPC6-prevalent mode of action. By testing the main constituents of larch resin, we identified larixol and larixyl acetate as blockers of Ca(2+) entry and ionic currents through diacylglycerol- or receptor-activated recombinant TRPC6 channels, exhibiting approximately 12- and 5-fold selectivity compared with its closest relatives TRPC3 and TRPC7, respectively. No significant inhibition of more distantly related TRPV or TRPM channels was seen. The potent inhibition of recombinant TRPC6 by larixyl acetate (IC50 = 0.1-0.6 µM) was confirmed for native TRPC6-like [Ca(2+)]i signals in diacylglycerol-stimulated rat pulmonary artery smooth muscle cells. In isolated mouse lungs, larix-6-yl monoacetate (CAS 4608-49-5; larixyl acetate; 5 µM) prevented acute hypoxia-induced vasoconstriction. We conclude that larch-derived labdane-type diterpenes are TRPC6-selective inhibitors and may represent a starting point for pharmacological TRPC6 modulation within experimental therapies.
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.).
Nicole
N
Urban
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.).
Liming
L
Wang
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.).
Sandra
S
Kwiek
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.).
Jörg
J
Rademann
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.).
Wolfgang M
WM
Kuebler
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie, Universität Leipzig, Leipzig, Germany (N.U., M.S.); Institut für Pharmazie, Freie Universität Berlin, Berlin, Germany (S.K., J.R.); and The Keenan Research Centre of St. Michael's Hospital, Toronto, Canada (L.W., W.M.K.) michael.schaefer@medizin.uni-leipzig.de.
Michael
M
Schaefer
D000818:Animals; D002478:Cells, Cultured; D057809:HEK293 Cells; D006801:Humans; D028221:Larix; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D010936:Plant Extracts / Q000302:isolation & purification* / Q000494:pharmacology*; D010938:Plant Oils / Q000302:isolation & purification* / Q000494:pharmacology*; D051381:Rats; D050052:TRPC Cation Channels / Q000037:antagonists & inhibitors*; D000074287:TRPC6 Cation Channel
D010936:Plant Extracts; D010938:Plant Oils; D050052:TRPC Cation Channels; D000074287:TRPC6 Cation Channel; C117032:TRPC6 protein, human