Swelling-induced chloride currents in neuroblastoma cells are calcium dependent

Abstract

The effects of osmotic stress on chloride (CI-) currents in the human neuroblastoma cell line CHP-100 were evaluated. Following exposure to hypoosmotic solution, an increase in whole-cell CI- current was observed. This current was blocked by the CI- channel blocker 5-nitro-2- (3-phenylpropylamino)-benzoic acid (NPPB). In cells loaded with the CI- permeability marker 125I, exposure to hypoosmotic solution increased 125I efflux by 197 +/- 14% (n = 41, p < 0.05) over controls. This increase was sensitive to NPPB. Hypoosmotic stress also increased cytosolic calcium levels (Ca2+) in fura-2-loaded cells. Pretreatment with EGTA inhibited the increase in cytosolic Ca2+, 125I efflux, and whole-cell CI- current produced by hypoosmotic solution. Antagonists of N-, L-, and T-type Ca2+ channels did not alter stimulation in 125I efflux or cytosolic Ca2+ levels during osmotic stress. However, omega- conotoxin MVIIC, a P-type Ca2+ channel blocker, inhibited hypoosmotically activated whole-cell CI- currents and increases in cytosolic Ca2+. It is concluded that a Ca(2+)-dependent change in CI- permeability is activated in CHP-100 cells in response to osmotic stress.

Molecular and functional aspects of anionic channels activated during regulatory volume decrease in mammalian cells*

“…In isolated cardiac myocytes cell swelling inhibits isoproterenol-stimulated cAMP accumulation by a mechanism that involves G i proteins, while in S49 lymphoma cells hormone-stimulated cAMP accumulation is enhanced [120]. Under isotonic conditions, both the activation of PKA with extracellular 8Br-cAMP or intracellular cAMP [102,318] and inhibition by Rp-cAMPS, H-8 and PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] are without effect on the basal Cl -conductance [37, 113,154,199,202,276,304,320]. The activation of PKA prior to a hypotonic challenge, however, leads to a partial inhibition of RVDC [72, 113,199] whereas stimulation of PKA by 8Br-cAMP reduces RVDC only in multiple drug resistance transporter-1 (MDR1)-expressing cells but has no effect on the rate of RVDC activation.…”

“…8-Br-cAMP: 8-bromoadenosine 3′:,5′-cyclic monophosphate · 8-Br-cGMP: 8-bromoguanosine 3′,5′-cyclic monophosphate · cAMP: adenosine 3′:,5′-cyclic monophosphate · CDC: cinnamyl-3,4-hydroxy-α-cyanocinnamate · DCDPC: 2,5-dichlorodiphenylamine-2-carboxylic acid · di-BA-(5)-C4: bis-1,3-dibutylbarbituric acidpentamethine oxonol · DIDS: 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid · DIOA: diisooctyl adipate · DiPhPC: 1,2-diphytanoyl 3-phosphocholine · DISA: 3,5-diiodosalicylate · DNDS: dinitrostilbene disulphonic acid · DPC: diphenylamine-2-carboxylate · DRB: 5,6-dichloro-1-β-D-ribofuranosylbenose · GF 109203X: 3-[N-(dimethylamino)propyl-3-indolyl]-4-[3-indolyl] maleimide · GTP-γ-S: guanosine 5′-O-(3-thiotriphosphate) · H-7: 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine · H-8: N-2-(methylamino)ethyl-5-isoquinolinesulphonamide · H-89: N- [2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulphonamide · IAA: indanyloxyacetic acid 94 · Ins(1,4,5)P 3 : inositol 1,4,5-trisphosphate · Ins(1,4,5,6)P 4 : inositol 1,4,5,6-tetrakisphosphate · Ins(3,4,5,6)P 4 : inositol 3,4,5,6-tetrakisphosphate · Ins(1,3,4,5,6)P 5 : inositol 1,3,4,5,6-pentakisphosphate · KN-62: 1-(N,O-bis [5-isoquinolinesulphonyl]-N-methyltyrosyl)-4-phenylpiperazine · KT5926: (8R,9S,11S)-(-)-9-hydroxy-9-methoxycarbonyl-8-methyl-14-npropoxy-2,3,9,10-tetrahydro-8,11-epoxy,1H,8H,11H-2,7b, 11a-triazadibenzo[a,g]cycloocta[c,d,e]trinden-1-one · MK-447: 2-aminomethyl-4-t-butyl-6-iodophenol HCL · NDGA: nordihydroguaiaretic acid · NO: nitric oxide · NPPB: nitrophenylpropylamino benzoate · OAG: 1-oleoyl-2-acetyl-sn-glycerol · pBPB: p-bromophenacyl bromide · PDBu: phorbol 12,13-dibutyrate · PtdIns(4,5)P 2 : phosphatidylinositol 4,5 bisphosphate · PKI [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] : protein kinase A inhibitor peptide 5-24 · PMA: phorbol-12-myristate-13-acetate · PPADS: pyridoxal phosphate-6-azophenyl-2′,4′-disulphonic acid tetrasodium salt · PtdIns 3 P: phosphatidylinositol-3-phosphate · PtdIns(3,4)P 2 : phosphatidylinositol-3,4-bisphosphate ·…”

Intracellular Signalling Involved in Volume Regulatory Decrease

“…It is, however, possible that some of the LIP inhibitors block I Cl,vol directly [31]. In rat hepatocytes, LTD 4 activates both Ca 2+ -dependent and Ca 2+ -independent anion conductances, whereas direct application of 100 nM LTD 4 in neuroblastoma cells [61] or 5 nM LTD 4 in EATC [41,62] failed to elicit efflux/currents. An increased Cl --permeability has previously been described after addition of 100 nM LTD 4 to EATC [63], but since this concentration of LTD 4 is known to increase [Ca 2+ ] i in EATC [64], it is likely that this permeability increase represents activation of I Cl,Ca .…”

Osmotically Induced Conductance and Capacitance Changes in in vitro Perfused Rectal Gland Tubules of Squalus acanthias

“…These findings are probably causally related. An increase in [Ca 2+ ] i has been found in many types of cells (but not all) when exposed to low osmolality [1,2,5,17,29,31,34,39]. This increase in [Ca 2+ ] i has been ascribed mostly to enhanced influx of Ca 2+ .…”