Diosgenin, a Plant-Derived Sapogenin, Stimulates Ca²⁺-Activated K⁺ Current in Human Cortical HCN-1A Neuronal Cells

Abstract

The effects of diosgenin (3β-hydroxy-5-spirostene), a plant-derived sapogenin, on ion currents in human cortical neurons (HCN-1A) were investigated. In the whole-cell configuration, diosgenin (0.3 - 30 μM) increased the amplitude of K⁺ outward current (I _K). Diosgenin-stimulated I _K was sensitive to inhibition by paxilline (1 μM), but not by apamin (200 nM) or glibenclamide (10 μM). In the cell-attached configuration, diosgenin applied to the bath increased the activity of large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels without altering single-channel conductance. Diosgenin enhanced BK_Ca-channel activity with an EC₅₀ value of 25 μM. However, in inside-out patches, diosgenin applied to the intracellular surface had no effect on BK_Ca-channel activity, while cilostazol or caffeic acid phenethyl ester increased it. As shown with the aid of intracellular Ca²⁺ measurements, diosgenin elevated intracellular Ca²⁺ in HCN-1A cells. Western blotting also revealed the presence of the α-subunit of BK_Ca channels in these cells. The sustained stimulation of I _K arises primarily from the diosgenin-induced Ca²⁺ influx across the cell membrane. The effect of diosgenin on these channels may affect the functional activity of cortical neurons.

Abbreviations

I _K:K⁺ outward current

I _K(Ca):Ca²⁺-activated K⁺ current

BK_Ca channel:Large-conductance Ca²⁺-activated K⁺ channel

CAPE:caffeic acid phenethyl ester

[Ca²⁺]_i:intracellular Ca²⁺ concentration

I/V relationship:current/voltage relationship

K_ATP channel:ATP-sensitive K⁺ channel

K_Ca channel:Ca²⁺-activated K⁺ channel

Diosgenin - Ca²⁺-activated K⁺ currents - HCN-1A cells

References

• 1 Chakravarti R N, Dash S N. Variable yields of diosgenin from Dioscorea yams.  Bull Calcutta Sch Trop Med. 1966;  14 45-7
• 2 Marker R E, Tsukamoto T, Turner D L. Sterols. C. Diosgenin.  J Am Chem Soc. 1940;  62 2525-32
• 3 Komesaroff P A, Black C V, Cable V, Sudhir K. Effects of wild yam extract on menopausal symptoms, lipids and sex hormones in healthy menopausal women.  Climacteric. 2001;  4 144-50
• 4 Liu M J, Wang Z, Ju Y, Wong R N, Wu Q Y. Diosgenin induces cell cycle arrest and apoptosis in human leukemia K562 cells with the disruption of Ca²⁺ homeostasis.  Cancer Chemother Pharmacol. 2005;  55 79-90
• 5 Corbiere C, Liagre B, Terro F, Beneytout J L. Induction of antiproliferative effect by diosgenin through activation of p53, release of apoptosis-inducing factor (AIF) and modulation of caspase-3 activity in different human cancer cells.  Cell Res. 2004;  14 188-96
• 6 Liagre B, Vergne-Salle P, Corbiere C, Charissoux J L, Beneytout J L. Diosgenin, a plant steroid, induces apoptosis in human rheumatoid arthritis synoviocytes with cyclooxygenase-2 overexpression.  Arthritis Res Ther. 2004;  6 R373-83
• 7 Wang S L, Cai B, Cui C B, Liu H W, Wu C F, Yao X S. Diosgenin-3-O-alpha-L-rhamnopyranosyl-(1→4)-beta-D-glucopyranoside obtained as a new anticancer agent from Dioscorea futschauensis induces apoptosis on human colon carcinoma HCT-15 cells via mitochondria-controlled apoptotic pathway.  J Asian Nat Prod Res. 2004;  6 115-25
• 8 Leger D Y, Liagre B, Corbiere C, Cook-Moreau J, Beneytout J L. Diosgenin induces cell cycle arrest and apoptosis in HEL cells with increase in intracellular calcium level, activation of cPLA2 and COX-2 overexpression.  Int J Oncol. 2004;  25 555-62
• 9 Raju J, Patlolla J M, Swamy M V, Rao C V. Diosgenin, a steroid saponin of Trigonella foenum graecum (Fenugreek), inhibits azoxymethane-induced aberrant crypt foci formation in F344 rats and induces apoptosis in HT-29 human colon cancer cells.  Cancer Epidemiol Biomarkers Prev. 2004;  13 1392-8
• 10 Hou R, Zhou Q L, Wang B X, Tashiro S, Onodera S, Ikejima T. Diosgenin induces apoptosis in HeLa cells via activation of caspase pathway.  Acta Pharmacol Sin. 2004;  25 1077-82
• 11 Corbiere C, Battu S, Liagre B, Cardot P J, Beneytout J L. SdFFF monitoring of cellular apoptosis induction by diosgenin and different inducers in the human 1547 osteosarcoma cell line.  J Chromatogr B Analyt Technol Biomed Life Sci. 2004;  808 255-62
• 12 Moalic S, Liagre B, Corbiere C, Bianchi A, Dauca M, Bordji K. et al . A plant steroid, diosgenin, induces apoptosis, cell cycle arrest and COX activity in osteosarcoma cells.  FEBS Lett. 2001;  506 225-30
• 13 Au A L, Kwok C C, Lee A T, Kwan Y W, Lee M M, Zhang R Z. et al . Activation of iberiotoxin-sensitive, Ca²⁺-activated K⁺ channels of porcine isolated left anterior descending coronary artery by diosgenin.  Eur J Pharmacol. 2004;  502 123-33
• 14 Stocker M, Pedarzani P. Differential distribution of three Ca²⁺-activated K⁺ channel subunits, SK1, SK2, and SK3, in the adult rat central nervous system.  Mol Cell Neurosci. 2000;  15 476-93
• 15 Kaczorowski G J, Garcia M L. Pharmacology of voltage-gated and calcium-activated potassium channels.  Curr Opin Chem Biol. 1999;  3 448-58
• 16 Butler A, Tsunoda S, McCobb DP,Wei A, Salkoff L. mSlo, a complex mouse gene encoding ‘‘maxi’’ calcium-activated potassium channels.  Science. 1993;  261 221-4
• 17 Knaus H G, Garcia-Calvo M, Kaczorowski G J, Garcia M L. Subunit composition of the high conductance calcium-activated potassium channel from smooth muscle, a representative of the mSlo and slowpoke family of potassium channels.  J Biol Chem. 1994;  269 3921-4
• 18 Wu S N. Large-conductance Ca²⁺-activated K⁺ channels: physiological role and pharmacology.  Curr Med Chem. 2003;  10 649-61
• 19 Huang C W, Huang C C, Huang M H, Wu S N, Hsieh Y J. Sodium cyanate-induced opening of calcium-activated potassium currents in hippocampal neuron-derived H19 - 7 cells.  Neurosci Lett. 2005;  377 110-4
• 20 Ronnett G V, Hester L D, Nye J S, Connors K, Snyder S H. Human cortical neuronal cell line: establishment from a patient with unilateral megalencephaly.  Science. 1990;  248 603-5
• 21 Wu S N, Li H F, Chiang H T. Stimulatory effects of δ-hexachlorocyclohexane on Ca²⁺-activated K⁺ currents in GH₃ lactotrophs.  Mol Pharmacol. 2000;  57 865-73
• 22 Zhang Y, Gao Y J, Zuo J, Lee R M, Janssen L J. Alteration of arterial smooth muscle potassium channel composition and BK_Ca current modulation in hypertension.  Eur J Pharmacol. 2005;  514 111-9
• 23 Grynkiewicz G, Poenie M, Tsien R Y. A new generation of Ca²⁺ indicators with greatly improved fluorescence properties.  J Biol Chem. 1985;  260 3440-50
• 24 Knaus H G, Schwarzer C, Koch R O, Eberhart A, Kaczorowski G J, Glossmann H. et al . Distribution of high-conductance Ca²⁺-activated K⁺ channels in rat brain: targeting to axons and nerve terminals.  J Neurosci. 1996;  16 955-63
• 25 Wu S N, Liu S I, Huang M H. Cilostazol, an inhibitor of type 3 phosphodiesterase, stimulates large-conductance, calcium-activated potassium channels in pituitary GH₃ cells and pheochromocytoma PC12 cells.  Endocrinology. 2004;  145 1175-84
• 26 Lin M W, Yang S R, Huang M H, Wu S N. Stimulatory actions of caffeic acid phenethyl ester, a known inhibitor of NF-κ activation, on Ca²⁺-activated K⁺ current in pituitary GH₃ cells.  J Biol Chem. 2004;  279 26 885-92
• 27 Chiang H T, Wu S N. Inhibition of large-conductance calcium-activated potassium channel by 2-methoxyestradiol in cultured vascular endothelial (HUV-EC-C) cells.  J Membr Biol. 2001;  182 203-12
• 28 Wu S N, Lin P H, Hsieh K S, Li Y C, Chiang H T. Behavior of nonselective cation channels and large-conductance Ca^{2 +}-activated K⁺ channels induced by dynamic changes in membrane stretch in cultured smooth muscle cells of human coronary artery.  J Cardiovasc Electrophysiol. 2003;  14 44-51
• 29 Sah P. Ca^{2 +}-activated K⁺ currents in neurons: types, physiological roles and modulation.  Trends Neurosci. 1996;  19 150-4
• 30 Kaczorowski G J, Knaus H G, Leonard R J, McManus O B, Arcia M L. High conductance calcium-activated potassium channels: structure, pharmacology and function.  J Bioenerg Biomembr. 1996;  28 255-67
• 31 Wu S N, Li H F, Jan C R, Shen A Y. Inhibition of Ca²⁺-activated K⁺ current by clotrimazole in rat anterior pituitary GH₃ cells.  Neuropharmacology. 1999;  38 979-89
• 32 Kunz L, Thalhammer A, Berg F D, Berg U, Duffy D M, Stouffer R L. et al . Ca²⁺-activated, large conductance K⁺ channel in the ovary: identification, characterization, and functional involvement in steroidogenesis.  J Clin Endocrinol Metab. 2002;  87 5566-74
• 33 Korovkina V P, Brainard A M, Ismail P, Schmidt T J, England S K. Estradiol binding to maxi-K channels induces their down-regulation via proteasomal degradation.  J Biol Chem. 2004;  279 1217-23
• 34 Dimitropoulou C, White R E, Ownby D R, Catravas J D. Estrogen reduces carbachol-induced constriction of asthmatic airways by stimulating large-conductance voltage and calcium-dependent potassium channels.  Am J Respir Cell Mol Biol. 2005;  32 239-47
• 35 Du W, Bautista J F, Yang H, Diez-Sampedro A, You S A, Wang L. et al . Calcium-sensitive potassium channelopathy in human epilepsy and paroxysmal movement disorder.  Nat Genet. 2005;  37 733-8