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DHEA‐induced Voltage‐dependent Inhibition of I Ca,L Is Augmented by Cholesterol Depletion and Down‐regulated by GPCR Blockade in Aortic Smooth Muscle Cells
Author(s) -
Ochi Rikuo,
Chettimada Sukrutha,
Gupte Sachin A
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.1007.41
Subject(s) - endocrinology , medicine , depolarization , dehydroepiandrosterone , chemistry , cholesterol , patch clamp , membrane potential , biophysics , hormone , biology , receptor , biochemistry , androgen
Dehydroepiandrosterone (DHEA) is a steroid hormone synthesized from cholesterol and abundantly secreted as DHEA sulfate from the adrenal gland. DHEA produces relaxation of systemic and pulmonary arterial smooth muscles (ASM) and epiandrosterone, a metabolite of DHEA, causes voltage‐dependent inhibition (VDI) of I Ca,L in ventricular myocytes. Here, we characterized DHEA‐induced VDI of I Ca,L recorded with Ba 2+ as a charge carrier by whole cell clamp and studied underlying mechanism and modulation by signal transduction in ASM cells (ASMCs) from bovine coronary artery and A7r5 cells from rat aorta. DHEA decreased peak amplitude of I Ca,L rapidly, reversibly and dose‐dependently and accelerated time course of current decay decreasing the ratio of current amplitude at 500 ms (r 500 ) to peak amplitude and shifted steady‐state inactivation curve (f ∞ ‐V) to the left. DHEA‐induced inhibition of I Ca,L became prominent by depolarization of holding potential; e.g . at −30 mV, the inhibition was 29% at 10 μM and 89% at 100 μM. Blockade of GPCR by dialysis of GDP βS shifted both f ∞ ‐V and I–V relationships to the depolarizing direction, and decreased 10 μM‐DHEA‐induced VDI obtained at HP of −40 mV by 40%. Depletion of membrane cholesterol by methyl‐b‐cyclodextrin increased r 500 and shifted f ∞ ‐V to the right. Conversely, loading PEG‐cholesterol, a non‐ionic amphiphile, to the membrane decreased r 500 and shifted f ∞ ‐V to the left. In the cholesterol‐depleted cells, DHEA produced more potent decrease of r 500 and larger negative shift of f ∞ ‐V than in control. Therefore, DHEA‐induced VDI of I Ca,L in ASMCs is due, at least partly, to cholesterol‐like action of DHEA on Ca V 1.2 in the membrane lipid bilayer. GPCR‐mediated signaling regulates voltage‐dependence of basal I Ca,L and indirectly augments DHEA‐induced VDI of I Ca,L in ASMCs.