Swelling-activated efflux of taurine and other organic osmolytes in endothelial cells

1997 ◽  
Vol 273 (1) ◽  
pp. C214-C222 ◽  
Author(s):  
V. G. Manolopoulos ◽  
T. Voets ◽  
P. E. Declercq ◽  
G. Droogmans ◽  
B. Nilius
Keyword(s):  
Endothelial Cells ◽  
Anion Channel ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Organic Osmolytes ◽  
Dependent Manner ◽  
Anion Channels ◽  
Whole Cell Patch Clamp ◽  
Osmolyte Efflux ◽  
Dose Dependent

We used a combined biochemical, pharmacological, and electrophysiological approach to study the effects of hyposmotic swelling on organic osmolyte efflux in endothelial cells (EC). In [3H]taurine-loaded monolayers of calf pulmonary artery EC (CPAEC), hyposmolality activated time- and dose-dependent effluxes of [3H]taurine. Swelling-activated [3H]taurine efflux (Jtau swell)in CPAEC was inhibited by the anion channel blockers tamoxifen, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), fenamates, and also quinine (in a pH-dependent manner), ATP, and the phospholipase A2 inhibitor 4-bromophenacyl bromide. In contrast, Jtau swell was partly or totally insensitive to bumetanide, forskolin, phorbol 12-myristate 13-acetate, and staurosporine. Swelling also activated myo-[3H]inositol efflux that was blocked by tamoxifen, NPPB, DIDS, and niflumic acid. Moreover, the cellular content of taurine and other amino acids was significantly reduced in osmotically activated CPAEC. Finally, in whole cell patch-clamp experiments, taurine, glycine, aspartate, and glutamate exhibited significant permeability for swelling-activated anion channels. In conclusion, hyposmotic swelling activates efflux of taurine and other organic osmolytes in EC. In addition, our results suggest that anion channels may provide a pathway for swelling-activated efflux of organic osmolytes in EC.

Anion channels influence ECC by modulating L-type Ca2+ channel in ventricular myocytes

2002 ◽  
Vol 93 (5) ◽  
pp. 1660-1668 ◽  
Author(s):  
Shi-Sheng Zhou ◽  
Zhan Gao ◽  
Ling Dong ◽  
Yan-Feng Ding ◽  
Xiao-Dong Zhang ◽  
...  
Keyword(s):  
Ventricular Myocytes ◽  
Anion Channel ◽  
Niflumic Acid ◽  
Cardiac Contraction ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Anion Channels ◽  
Cell Shortening ◽  
Fluorescence Measurements ◽  
Intracellular Ca

Anion channels are extensively expressed in the heart, but their roles in cardiac excitation-contraction coupling (ECC) are poorly understood. We, therefore, investigated the effects of anion channels on cardiac ventricular ECC. Edge detection, fura 2 fluorescence measurements, and whole cell patch-clamp techniques were used to measure cell shortening, the intracellular Ca2+ transient, and the L-type Ca2+ current ( I Ca,L) in single rat ventricular myocytes. The anion channel blockers 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) and niflumic acid reversibly inhibited the Ca2+ transients and cell shortening in a dose-dependent manner. Comparable results were observed when the majority of the extracellular Cl− was replaced with the relatively impermeant anions glutamate (Glt−) and aspartate (Asp−). NPPB and niflumic acid or the Cl− substitutes did not affect the resting intracellular Ca2+ concentration but significantly inhibited I Ca,L. In contrast, replacement of extracellular Cl− with the permeant anions NO[Formula: see text], SCN−, and Br− supported the ECC and I Ca,L, which were still sensitive to blockade by NPPB. Exposure of cardiac ventricular myocytes to a hypotonic bath solution enhanced the amplitude of cell shortening and supported I Ca,L, whereas hypertonic stress depressed the contraction and I Ca,L. Moreover, cardiac contraction was completely abolished by NPPB (50 μM) under hypotonic conditions. It is concluded that a swelling-activated anion channel may be involved in the regulation of cardiac ECC through modulating L-type Ca2+ channel activity.

More than just a pressure relief valve: physiological roles of volume-regulated LRRC8 anion channels

2019 ◽  
Vol 400 (11) ◽  
pp. 1481-1496 ◽  
Author(s):  
Lingye Chen ◽  
Benjamin König ◽  
Tianbao Liu ◽  
Sumaira Pervaiz ◽  
Yasmin S. Razzaque ◽  
...  
Keyword(s):  
Volume Regulation ◽  
Regulatory Volume Decrease ◽  
Anion Channel ◽  
Therapy Resistance ◽  
Cell Swelling ◽  
Organic Osmolytes ◽  
Anion Channels ◽  
Relief Valve ◽  
Wide Range ◽  
And Migration

Abstract The volume-regulated anion channel (VRAC) is a key player in the volume regulation of vertebrate cells. This ubiquitously expressed channel opens upon osmotic cell swelling and potentially other cues and releases chloride and organic osmolytes, which contributes to regulatory volume decrease (RVD). A plethora of studies have proposed a wide range of physiological roles for VRAC beyond volume regulation including cell proliferation, differentiation and migration, apoptosis, intercellular communication by direct release of signaling molecules and by supporting the exocytosis of insulin. VRAC was additionally implicated in pathological states such as cancer therapy resistance and excitotoxicity under ischemic conditions. Following extensive investigations, 5 years ago leucine-rich repeat-containing family 8 (LRRC8) heteromers containing LRRC8A were identified as the pore-forming components of VRAC. Since then, molecular biological approaches have allowed further insight into the biophysical properties and structure of VRAC. Heterologous expression, siRNA-mediated downregulation and genome editing in cells, as well as the use of animal models have enabled the assessment of the proposed physiological roles, together with the identification of new functions including spermatogenesis and the uptake of antibiotics and platinum-based cancer drugs. This review discusses the recent molecular biological insights into the physiology of VRAC in relation to its previously proposed roles.

scholarly journals Biochemical and biological activity of arginine deiminase from Streptococcus pyogenes M22

2016 ◽  
Vol 94 (2) ◽  
pp. 129-137 ◽  
Author(s):  
Eleonora A. Starikova ◽  
Alexey V. Sokolov ◽  
Anna Yu. Vlasenko ◽  
Larisa A. Burova ◽  
Irina S. Freidlin ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
Endothelial Cells ◽  
Streptococcus Pyogenes ◽  
Group A Streptococcus ◽  
Bacterial Pathogen ◽  
Arginine Deiminase ◽  
Dependent Manner ◽  
Group A ◽  
Micro Organisms ◽  
Dose Dependent

Streptococcus pyogenes (group A Streptococcus; GAS) is an important gram-positive extracellular bacterial pathogen responsible for a number of suppurative infections. This micro-organism has developed complex virulence mechanisms to avoid the host’s defenses. We have previously reported that SDSC from GAS type M22 causes endothelial-cell dysfunction, and inhibits cell adhesion, migration, metabolism, and proliferation in a dose-dependent manner, without affecting cell viability. This work aimed to isolate and characterize a component from GAS type M22 supernatant that suppresses the proliferation of endothelial cells (EA.hy926). In the process of isolating a protein possessing antiproliferative activity we identified arginine deiminase (AD). Further study showed that this enzyme is most active at pH 6.8. Calculating Km and Vmax gave the values of 0.67 mmol·L–1 and 42 s−1, respectively. A distinctive feature of AD purified from GAS type M22 is that its optimum activity and the maximal rate of the catalytic process is close to neutral pH by comparison with enzymes from other micro-organisms. AD from GAS type M22 suppressed the proliferative activity of endothelial cells in a dose-dependent mode. At the same time, in the presence of AD, the proportion of cells in G0/G1 phase increased. When l-Arg was added at increasing concentrations to the culture medium containing AD (3 μg·mL–1), the enzyme’s capacity to inhibit cell proliferation became partially depressed. The proportion of cells in phases S/G2 increased concomitantly, although the cells did not fully recover their proliferation activity. This suggests that AD from GAS type M22 has potential for the suppression of excessive cell proliferation.

scholarly journals Phenanthrene impacts zebrafish cardiomyocyte excitability by inhibiting IKr and shortening action potential duration

2021 ◽  
Vol 153 (2) ◽  
Author(s):  
Shiva N. Kompella ◽  
Fabien Brette ◽  
Jules C. Hancox ◽  
Holly A. Shiels
Keyword(s):  
Air Pollution ◽  
Action Potential ◽  
Action Potential Duration ◽  
Cardiac Electrophysiology ◽  
Resting Membrane Potential ◽  
Dependent Manner ◽  
Polyaromatic Hydrocarbon ◽  
Premature Ventricular Contractions ◽  
Whole Cell Patch Clamp ◽  
Dose Dependent

Air pollution is an environmental hazard that is associated with cardiovascular dysfunction. Phenanthrene is a three-ringed polyaromatic hydrocarbon that is a significant component of air pollution and crude oil and has been shown to cause cardiac dysfunction in marine fishes. We investigated the cardiotoxic effects of phenanthrene in zebrafish (Danio rerio), an animal model relevant to human cardiac electrophysiology, using whole-cell patch-clamp of ventricular cardiomyocytes. First, we show that phenanthrene significantly shortened action potential duration without altering resting membrane potential or upstroke velocity (dV/dt). L-type Ca2+ current was significantly decreased by phenanthrene, consistent with the decrease in action potential duration. Phenanthrene blocked the hERG orthologue (zfERG) native current, IKr, and accelerated IKr deactivation kinetics in a dose-dependent manner. Furthermore, we show that phenanthrene significantly inhibits the protective IKr current envelope, elicited by a paired ventricular AP-like command waveform protocol. Phenanthrene had no effect on other IK. These findings demonstrate that exposure to phenanthrene shortens action potential duration, which may reduce refractoriness and increase susceptibility to certain arrhythmia triggers, such as premature ventricular contractions. These data also reveal a previously unrecognized mechanism of polyaromatic hydrocarbon cardiotoxicity on zfERG by accelerating deactivation and decreasing IKr protective current.

Calcium dependence of the thrombin-induced increase in endothelial albumin permeability

1989 ◽  
Vol 66 (3) ◽  
pp. 1471-1476 ◽  
Author(s):  
H. Lum ◽  
P. J. Del Vecchio ◽  
A. S. Schneider ◽  
M. S. Goligorsky ◽  
A. B. Malik
Keyword(s):  
Endothelial Cells ◽  
Endothelial Permeability ◽  
Base Line ◽  
Dependent Manner ◽  
Extracellular Medium ◽  
Influx Rate ◽  
Before And After ◽  
Dependent Inhibition ◽  
Permeability Increase ◽  
Dose Dependent

We examined whether the increase in endothelial albumin permeability induced by alpha-thrombin is dependent on extracellular Ca2+ influx. Permeability of 125I-albumin across confluent monolayers of cultured bovine pulmonary artery endothelial cells was measured before and after the addition of 0.1 microM alpha-thrombin. In the presence of normal extracellular Ca2+ concentration ([Ca2+]o, 1000 microM), alpha-thrombin produced a 175 +/- 10% increase in 125I-albumin permeability. At lower [Ca2+]o (100, 10, 1, or less than 1 microM), alpha-thrombin caused a 140% increase in permeability (P less than 0.005). LaCl3 (1 mM), which competes for Ca2+ entry, blunted 38% of the increase in permeability. Preloading endothelial monolayers with quin2 to buffer cytosolic Ca2+ (Cai2+) produced a dose-dependent inhibition of the increase in 125I-albumin permeability. Preincubation with nifedipine or verapamil was ineffective in reducing the thrombin-induced permeability increase. A 60 mM K+ isosmotic solution did not alter base-line endothelial permeability. alpha-Thrombin increased [Ca2+]i in a dose-dependent manner and the 45Ca2+ influx rate. Extracellular medium containing 60 mM K+ did not increase 45Ca2+ influx, and nifedipine did not block the rise in 45Ca2+ influx caused by alpha-thrombin. Ca2+ flux into endothelial cells induced by alpha-thrombin does not occur through voltage-sensitive channels but may involve receptor-operated channels. In conclusion, the increase in endothelial albumin permeability caused by alpha-thrombin is dependent on Ca2+ influx and intracellular Ca2+ mobilization.

PMA-activated neutrophils decrease ectoenzyme activities in rabbit aortic endothelial cells in culture

1992 ◽  
Vol 263 (6) ◽  
pp. L657-L663
Author(s):  
X. Chen ◽  
M. Tzanela ◽  
M. K. Baumgartner ◽  
J. R. McCormick ◽  
J. D. Catravas
Keyword(s):  
Endothelial Cells ◽  
Dependent Manner ◽  
Concentration Dependent Manner ◽  
Aortic Endothelial Cells ◽  
Endothelial Monolayers ◽  
Activated Neutrophils ◽  
Ace Activity ◽  
Dose Dependent Decrease ◽  
Dose Dependent ◽  
Aortic Endothelial

We have studied the effects of phorbol 12-myristate 13-acetate (PMA)-activated neutrophils [polymorphonuclear leukocytes (PMN)] on endothelial ectoenzyme [angiotensin-converting enzyme (ACE) and 5'-nucleotidase (NCT)] activities in cultured rabbit aortic endothelial cells (EC) with the use of [3H]benzoyl-Phe-Ala-Pro and 14C-labeled AMP as substrates, respectively, under first-order reaction conditions. PMA (1–1,000 ng/ml) or PMN alone had no effect on ACE activity. When PMA was incubated together with PMN (PMN/EC = 1.25:1 or 2.5 x 10(5) neutrophils/ml) for 4 h in Earle's salts, a PMA dose-dependent decrease in ACE activity was observed. Threshold PMA concentration was 2 ng/ml. At 8 ng PMA/ml, ACE activity was totally abolished, without any evidence of cytotoxicity, as inferred from release of 51Cr from prelabeled EC. The decrease in ACE activity was also dependent on PMN concentration and was detectable at PMN/EC values as low as 1.25:10 (0.25 x 10(5) PMN/ml). Inhibition of ACE occurred as early as 1 h after incubation (PMA 10 ng/ml, PMN/EC = 1.25:1). PMA alone caused a small but significant increase in NCT activity, whereas PMA coincubation with PMN produced a significant decrease in NCT activity (20–29%), which was PMA and PMN concentration independent. PMA increased PMN adherence to endothelial monolayers in a concentration-dependent manner. Pretreating PMN with monoclonal antibody 60.3 (raised against the adhesion glycoprotein CD18) or placing a 2-microns filter between PMN and EC, protected the decrease in ACE activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Electrophysiological properties of cultured outer medullary collecting duct cells

1992 ◽  
Vol 263 (6) ◽  
pp. F1004-F1010 ◽  
Author(s):  
C. A. Pappas ◽  
B. M. Koeppen
Keyword(s):  
Collecting Duct ◽  
Extracellular Fluid ◽  
Outward Current ◽  
Membrane Voltage ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Dependent Manner ◽  
Whole Cell ◽  
Electrophysiological Properties ◽  
Medullary Collecting Duct

Whole cell patch-clamp techniques were used to characterize the electrophysiological properties of cells from the inner stripe portion of the rabbit outer medullary collecting duct (OMCDi) grown in primary culture. With pipette and bathing solutions mimicking intracellular and extracellular fluid, the resting membrane voltage was -30 to -40 mV. The whole cell conductance exhibited slight outward rectification, and at the resting membrane voltage the cell conductance averaged 2.58 +/- 0.49 nS (n = 17). The major conductive ion species was Cl-. The Cl- conductance was also found to have a significant permeability to HCO3- and was inhibited by the Cl(-)-channel blockers diphenylamine carboxylic acid and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid. A small K+ conductance was also present, but no Na+ conductance was detected. Current generated by the H(+)-adenosinetriphosphatase (H(+)-ATPase) was quantitated. This current was dependent on the presence of ATP in the pipette. Dicyclohexylcarbodiimide, N-ethylmaleimide, and bafilomycin A1, inhibitors of the vacuolar H(+)-ATPase, also reduced this outward current in an ATP-dependent manner. The inhibitor-sensitive component of the outward current, a measure of the current generated by the H(+)-ATPase, was in the range of 35-100 pA/cell.

Anion channel blockers inhibit swelling-activated anion, cation, and nonelectrolyte transport in HeLa cells

1996 ◽  
Vol 271 (2) ◽  
pp. C579-C588 ◽  
Author(s):  
J. A. Hall ◽  
J. Kirk ◽  
J. R. Potts ◽  
C. Rae ◽  
K. Kirk
Keyword(s):  
Hela Cells ◽  
Anion Channel ◽  
Cell Swelling ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Influx Rate ◽  
Cation Permeability ◽  
Transport Component ◽  
Selective Channel ◽  
Substrate Concentrations

The effect of osmotic cell swelling on the permeability of HeLa cells to a range of structurally unrelated solutes including taurine, sorbitol, thymidine, choline, and K+ (96Rb+) was investigated. For each solute tested, reduction in the osmolality of the medium from 300 to 200 mosmol/kgH2O caused a significant increase in the unidirectional influx rate. In each case, the osmotically activated transport component was nonsaturable up to external substrate concentrations of 50 mM. Inhibitors of the swelling-activated anion channel of HeLa cells [quinine, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, niflumate, 1,9-dideoxyforskolin, 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB), and tamoxifen] blocked the osmotically activated influx of each of the different substrates tested, as well as the osmotically activated efflux of taurine and I-. Tamoxifen and NPPB were similarly effective at blocking the osmotically activated efflux of 96Rb+. The simplest of several hypotheses consistent with the data is that the osmotically activated transport of the different solutes tested here is via a swelling-activated anion-selective channel that has a significant cation permeability and a minimum pore diameter of 8-9 A.

Characterization of a swelling-induced chloride conductance in cultured rat epididymal cells

1993 ◽  
Vol 265 (4) ◽  
pp. C997-C1005 ◽  
Author(s):  
H. C. Chan ◽  
W. O. Fu ◽  
Y. W. Chung ◽  
S. J. Huang ◽  
T. S. Zhou ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Disulfonic Acid ◽  
Channel Blockers ◽  
Induced Current ◽  
Whole Cell ◽  
Cyclic Monophosphate ◽  
Whole Cell Patch Clamp ◽  
Current Activation ◽  
Ethanesulfonic Acid ◽  
Cl Conductance

Swelling-induced Cl- conductance in cultured rat epididymal cells was characterized using whole cell patch-clamp techniques. Activation of whole cell current with an outwardly rectifying current-potential relationship was observed in cells exposed to hyposmotic solutions. This current was determined, from the observed current-reversal potentials at different Cl- concentrations, to be Cl- selective. The anion selectivity sequence of the swelling-induced Cl- conductance was I- approximately NO3- approximately Br- > Cl- > 2-(N-morpholino)ethanesulfonic acid. The swelling-induced Cl- conductance was reversibly inhibited by different Cl- channel blockers. Unlike diphenylamine-2-carboxylate or 5-nitro-2-(3-phenylpropylamino)-benzoate, which showed voltage-independent blockade, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid showed a marked voltage-dependent blockade of the volume-sensitive Cl- current, with a greater effect at depolarizing voltages. The swelling-induced Cl- conductance appeared to be different from the Ca(2+)- or adenosine 3',5'-cyclic monophosphate-activated Cl- conductances on the basis of the following observations: 1) swelling-induced current activation was seen even in the presence of kinase inhibitor (H-8) or absence of external free Ca2+, and 2) further increase in current activation could be produced by swelling after Ca(2+)- or adenosine 3',5'-cyclic monophosphate-induced current activation. The swelling-induced Cl- conductance may be involved in regulating epithelial cell volume as well as serving other important epididymal functions such as facilitating transepithelial secretion of organic compounds.

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