Farnesol Blocks the L-Type Ca ²⁺ Channel by Targeting the α _1C Subunit

Abstract

Abstract-We recently demonstrated that farnesol, a 15-carbon isoprenoid, blocks L-type Ca 2ϩ channels in vascular smooth muscle cells. To elucidate farnesolЈs mechanism of action, we performed whole-cell and perforated-patch clamp experiments in rat aortic A7r5 cells and in Chinese hamster ovary (CHO) C9 cells expressing smooth muscle Ca 2ϩ channel ␣ 1C subunits. Farnesol dose-dependently and voltage-independently inhibited Ba 2ϩ currents in both A7r5 and CHOC9 cells, with similar half-maximal inhibitions at 2.6 and 4.3 mmol/L, respectively (PϭNS). In both cell lines, current inhibition by farnesol was prominent over the whole voltage range without changes in the current-voltage relationship peaks. Neither intracellular infusion of the stable GDP analogue guanosine-5Ј-O-(2-thiodiphosphate) (100 mmol/L) via the patch pipette nor strong conditioning membrane depolarization prevented the inhibitory effect of farnesol, which indicates G protein-independent inhibition of Ca 2ϩ channels. In an analysis of the steady-state inactivation curve for voltage dependence, farnesol induced a significant, negative shift (Ϸ10 mV) of the potential causing 50% channel inactivation in both cell lines (PϽ0.001). In contrast, the steepness factor characterizing the voltage sensitivity of the channels was unaffected. Unlike pharmacological Ca 2ϩ channel blockers, farnesol blocked Ca 2ϩ currents in the resting state: initial block was 63Ϯ8% in A7r5 cells and 50Ϯ9% in CHOC9 cells at a holding potential of Ϫ80 mV. We then gave 500 mg/kg body weight farnesol by gavage to Sabra hypertensive and normotensive rats and found that farnesol reduced blood pressure significantly in the hypertensive strain for at least 48 hours. We conclude that farnesol may represent an endogenous smooth muscle L-type Ca 2ϩ channel antagonist. Because farnesol is active in cells expressing only the pore-forming ␣ 1 subunit, the data further suggest that this subunit represents the molecular target for farnesol binding and principal action. Key Words: smooth muscle cells Ⅲ farnesol Ⅲ patch clamp Ⅲ calcium channel blockers Ⅲ L-class channels F arnesol is 1 of several nonsterol mevalonate derivatives in the cholesterol pathway. 1 Farnesol is derived from farnesyl pyrophosphate, a C 15 isoprenoid lipid implicated in the regulation of G protein activity. 2 Some studies suggest that farnesol participates in the control of cholesterol synthesis by increasing 3-hydroxy-3-methylglutaryl coenzyme A reductase degradation. 3,4 Others suggest that farnesol is implicated in the regulation of cell growth. 5 Roullet et al 6 recently showed that farnesol inhibited contraction in both human and animal arteries. This effect explained earlier reports of a mevalonate-dependent positive regulation of vascular tone. 7,8 These studies featured a series of experiments that showed that farnesol blunted the KCl-induced increase in intracellular Ca 2ϩ concentration in intact arteries and vascular smooth muscle cells (VSMCs) in culture. 9 The patch-clamp technique revealed that micromolar co...

Statins and Modulation of Oxidative Stress

“…Further studies by this group confirmed these observations in rat conduit arteries and in human resistance arteries (Roullet et al 1995). Farnesol was identified as a mevalonate derivative producing vasodilation and lowering blood pressure through the inhibition of smooth muscle cell calcium channels (Luft et al 1999;Roullet et al 1996Roullet et al , 1997aRoullet et al , 1997b. Defect of mevalonate cascade (decreased activity of mevalonylpyrophosphate decarboxylase) leading to decreased plasma cholesterol and nonsteroid isoprenoids is observed in SHR (Sawamura et al 1992), in which excessive vascular production of ROS leads to blood pressure elevation (Vaziri et al 2000).…”

“…Defect of mevalonate cascade (decreased activity of mevalonylpyrophosphate decarboxylase) leading to decreased plasma cholesterol and nonsteroid isoprenoids is observed in SHR (Sawamura et al 1992), in which excessive vascular production of ROS leads to blood pressure elevation (Vaziri et al 2000). Oral administration of mevalonate or farnesol normalized blood pressure in SHR (Luft et al 1999;Roullet et al 1993). Some studies demonstrated that UQ supplementation decreases blood pressure in hypertensive humans, and it is suggested that this effect is accounted for by its reducing effect on endothelial superoxide generation (McCarty 1999).…”

Squalene synthase inhibitors suppress triglyceride biosynthesis through the farnesol pathway in rat hepatocytes

“…Farnesol is produced from FPP by farnesyl pyrophosphatase (21). It exhibits a wide variety of biological activities, including cell growth inhibition (22,23), induction of apoptosis (24,25), and vascular tone regulation (26)(27)(28). In the lipid metabolism, farnesol accelerates the degradation of HMG-CoA reductase (29)(30)(31)(32).…”

Microbial Quorum-Sensing Molecules Induce Acrosome Loss and Cell Death in Human Spermatozoa

“…Interestingly, both the QS molecules 3-oxo-C 12 -HSL and farnesol have been linked before with a potential impact on intracellular calcium levels. Higher concentrations (100 M) of 3-oxo-C 12 -HSL were revealed to induce apoptosis in a detectable proportion of murine fibroblasts via an increase of intracellular calcium (31), and farnesol has been identified as a potent blocker of smooth muscle L-type calcium channels (20). In our experiments, concentrations of 1 to 5 M 3-oxo-C 12 -HSL were sufficient to induce the calcium-mediated acrosome reaction in a considerable proportion of sperm, an observation which supports the view that 3-oxo-C 12 -HSL likely acts as a true signal on human spermatozoa.…”