title: Farnesol inhibits L-type Ca2+ channels in vascular smooth muscle cells.
abstract: Earlier experiments with animal and human arteries have shown that farnesol, a natural 15-carbon (C15) isoprenoid, is an inhibitor of vasoconstriction (Roullet, J.-B., Xue, H., Chapman, J., McDougal, P., Roullet, C. M., and McCarron, D. A. (1996) J. Clin. Invest. 97, 2384-2390). We report here that farnesol reduced KCl- and norepinephrine-dependent cytosolic Ca2+ transients in fura-2-loaded intact arteries. An effect on Ca2+ signaling was also observed in cultured aortic smooth muscle cells (A10 cells). In these cells, farnesol reduced KCl-induced [Ca2+]i transients and mimicked the inhibitory effect of Ca2+-free medium on the [Ca2+]i response to both 12,13-phorbol myristate acetate, a protein kinase C activator, and thapsigargin, a specific endoplasmic reticulum ATPase inhibitor. Perforated patch-clamp experiments further showed in two vascular smooth muscle cell lines (A10 and A7r5), a reversible, dose-dependent inhibitory effect of farnesol on L-type Ca2+ currents (IC50 = 2.2 microM). Shorter (C10, geraniol) and longer (C20, geranylgeraniol) isoprenols were inactive. L-type Ca2+ channel blockade also occurred under tight (gigaohm) seal configuration using cell-attached, single-channel analysis, thus suggesting a possible action of farnesol from within the intracellular space. We finally demonstrated that farnesol did not affect Ca2+-sensitive pathways implicated in smooth muscle contraction, as tested with alpha-toxin permeabilized arteries. Altogether, our results indicate that farnesol is an inhibitor of vascular smooth muscle Ca2+ signaling with plasma membrane Ca2+ channel blocker properties. The data have implications for the endogenous and pharmacological regulation of vascular tone by farnesol or farnesol analogues.
authors.affiliation: Department of Nephrology, Hypertension and Clinical Pharmacology, Oregon Sciences Health University, Portland, Oregon 97201, USA. roulletj@ohsu.edu
authors.forename: J B
authors.initials: JB
authors.lastname: Roullet
authors.forename: U C
authors.initials: UC
authors.lastname: Luft
authors.forename: H
authors.initials: H
authors.lastname: Xue
authors.forename: J
authors.initials: J
authors.lastname: Chapman
authors.forename: R
authors.initials: R
authors.lastname: Bychkov
authors.forename: C M
authors.initials: CM
authors.lastname: Roullet
authors.forename: F C
authors.initials: FC
authors.lastname: Luft
authors.forename: H
authors.initials: H
authors.lastname: Haller
authors.forename: D A
authors.initials: DA
authors.lastname: McCarron
mesh_terms: D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D002478:Cells, Cultured; D004347:Drug Interactions; D005204:Farnesol / Q000494:pharmacology*; D066298:In Vitro Techniques; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D005204:Farnesol; D019284:Thapsigargin; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium