Role of pH in a nitric oxide-dependent increase in cytosolic Cl− in retinal amacrine cells

Nitric oxide (NO) synthase-expressing neurons are found throughout the vertebrate retina. Previous work by our laboratory has shown that NO can transiently convert inhibitory GABAergic synapses onto cultured retinal amacrine cells into excitatory synapses by releasing Cl− from an internal store in the postsynaptic cell. The mechanism underlying this Cl− release is currently unknown. Because transport of Cl− across internal membranes can be coupled to proton flux, we asked whether protons could be involved in the NO-dependent release of internal Cl−. Using pH imaging and whole cell voltage-clamp recording, we addressed the relationship between cytosolic pH and cytosolic Cl− in cultured retinal amacrine cells. We found that NO reliably produces a transient decrease in cytosolic pH. A physiological link between cytosolic pH and cytosolic Cl− was established by demonstrating that shifting cytosolic pH in the absence of NO altered cytosolic Cl− concentrations. Strong buffering of cytosolic pH limited the ability of NO to increase cytosolic Cl−, suggesting that cytosolic acidification is involved in generating the NO-dependent elevation in cytosolic Cl−. Furthermore, disruption of internal proton gradients also reduced the effects of NO on cytosolic Cl−. Taken together, these results suggest a cytosolic environment where proton and Cl− fluxes are coupled in a dynamic and physiologically meaningful way.

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Nitric Oxide Transiently Converts Synaptic Inhibition to Excitation in Retinal Amacrine Cells

Journal of Neurophysiology ◽

10.1152/jn.01317.2005 ◽

2006 ◽

Vol 95 (5) ◽

pp. 2866-2877 ◽

Cited By ~ 27

Author(s):

Brian Hoffpauir ◽

Emily McMains ◽

Evanna Gleason

Keyword(s):

Nitric Oxide ◽

Hippocampal Neurons ◽

Reversal Potential ◽

Amacrine Cells ◽

Cell Types ◽

Synaptic Function ◽

Positive Shift ◽

Gabaergic Synapses ◽

Multiple Cell

Nitric oxide (NO) is generated by multiple cell types in the vertebrate retina, including amacrine cells. We investigate the role of NO in the modulation of synaptic function using a culture system containing identified retinal amacrine cells. We find that moderate concentrations of NO alter GABAA receptor function to produce an enhancement of the GABA-gated current. Higher concentrations of NO also enhance GABA-gated currents, but this enhancement is primarily due to a substantial positive shift in the reversal potential of the current. Several pieces of evidence, including a similar effect on glycine-gated currents, indicate that the positive shift is due to an increase in cytosolic Cl−. This change in the chloride distribution is especially significant because it can invert the sign of GABA- and glycine-gated voltage responses. Furthermore, current- and voltage-clamp recordings from synaptic pairs of GABAergic amacrine cells demonstrate that NO transiently converts signaling at GABAergic synapses from inhibition to excitation. Persistence of the NO-induced shift in ECl− in the absence of extracellular Cl− indicates that the increase in cytosolic Cl− is due to release of Cl− from an internal store. An NO-dependent release of Cl− from an internal store is also demonstrated for rat hippocampal neurons indicating that this mechanism is not restricted to the avian retina. Thus signaling in the CNS can be fundamentally altered by an NO-dependent mobilization of an internal Cl− store.

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Dynamic measurement of cytosolic pH and [NO3−] uncovers the role of the vacuolar transporter AtCLCa in cytosolic pH homeostasis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2007580117 ◽

2020 ◽

Vol 117 (26) ◽

pp. 15343-15353 ◽

Cited By ~ 2

Author(s):

Elsa Demes ◽

Laetitia Besse ◽

Paloma Cubero-Font ◽

Béatrice Satiat-Jeunemaitre ◽

Sébastien Thomine ◽

...

Keyword(s):

Chloride Channel ◽

Loss Of Function ◽

Ion Transporters ◽

Ph Homeostasis ◽

Cytosolic Ph ◽

Cellular Processes ◽

Plasma Membrane Proton Pump ◽

Cytosolic Acidification

Ion transporters are key players of cellular processes. The mechanistic properties of ion transporters have been well elucidated by biophysical methods. Meanwhile, the understanding of their exact functions in cellular homeostasis is limited by the difficulty of monitoring their activity in vivo. The development of biosensors to track subtle changes in intracellular parameters provides invaluable tools to tackle this challenging issue. AtCLCa (Arabidopsis thalianaChloride Channel a) is a vacuolar NO3−/H+exchanger regulating stomata aperture inA.thaliana. Here, we used a genetically encoded biosensor, ClopHensor, reporting the dynamics of cytosolic anion concentration and pH to monitor the activity of AtCLCa in vivo inArabidopsisguard cells. We first found that ClopHensor is not only a Cl−but also, an NO3−sensor. We were then able to quantify the variations of NO3−and pH in the cytosol. Our data showed that AtCLCa activity modifies cytosolic pH and NO3−. In an AtCLCa loss of function mutant, the cytosolic acidification triggered by extracellular NO3−and the recovery of pH upon treatment with fusicoccin (a fungal toxin that activates the plasma membrane proton pump) are impaired, demonstrating that the transport activity of this vacuolar exchanger has a profound impact on cytosolic homeostasis. This opens a perspective on the function of intracellular transporters of the Chloride Channel (CLC) family in eukaryotes: not only controlling the intraorganelle lumen but also, actively modifying cytosolic conditions.

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Role of endothelial nitric oxide in control of peripheral vascular conductance during muscle metaboreflex activation

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00515.2016 ◽

2017 ◽

Vol 313 (1) ◽

pp. R29-R34

Author(s):

Danielle Senador ◽

Jasdeep Kaur ◽

Alberto Alvarez ◽

Hanna W. Hanna ◽

Abhinav C. Krishnan ◽

...

Keyword(s):

Nitric Oxide ◽

Cardiac Output ◽

Arterial Pressure ◽

Vascular Conductance ◽

Muscle Metaboreflex ◽

Peripheral Vasodilation ◽

Dependent Flow ◽

Flow Mediated Vasodilation ◽

The Relationship

The muscle metaboreflex is a powerful pressor reflex induced by the activation of chemically sensitive muscle afferents as a result of metabolite accumulation. During submaximal dynamic exercise, the rise in arterial pressure is primarily due to increases in cardiac output, since there is little systemic vasoconstriction. Indeed, in normal animals, we have often shown a small, but significant, peripheral vasodilation during metaboreflex activation, which is mediated, at least in part, by release of epinephrine and activation of vascular β2-receptors. We tested whether this vasodilation is in part due to increased release of nitric oxide caused by the rise in cardiac output eliciting endothelium-dependent flow-mediated vasodilation. The muscle metaboreflex was activated via graded reductions in hindlimb blood flow during mild exercise with and without nitric oxide synthesis blockade [ NG-nitro-l-arginine methyl ester (l-NAME); 5 mg/kg]. We assessed the role of increased cardiac output in mediating peripheral vasodilation via the slope of the relationship between the rise in nonischemic vascular conductance (conductance of all vascular beds excluding hindlimbs) vs. the rise in cardiac output. l-NAME increased mean arterial pressure at rest and during exercise. The metaboreflex-induced increases in mean arterial pressure were unaltered by l-NAME, whereas the increases in cardiac output and nonischemic vascular conductance were attenuated. However, the slope of the relationship between nonischemic vascular conductance and cardiac output was not affected by l-NAME, indicating that the rise in cardiac output did not elicit vasodilation via increased release of nitric oxide. Thus, although nitric oxide is intrinsic to the vascular tonus, endothelial-dependent flow-mediated vasodilation plays little role in the small peripheral vasodilation observed during muscle metaboreflex activation.

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Metabolic aspects of the relationship of asthma and obesity

Obesity and metabolism ◽

10.14341/omet9578 ◽

2019 ◽

Vol 15 (4) ◽

pp. 9-14 ◽

Cited By ~ 3

Author(s):

Oxana Y. Kytikova ◽

Marina V. Antonyuk ◽

Tatyana A. Gvozdenko ◽

Tatyana Р. Novgorodtseva

Keyword(s):

Nitric Oxide ◽

Insulin Resistance ◽

Metabolic Syndrome ◽

Common Mechanism ◽

The Metabolic Syndrome ◽

Duration Of Hospitalization ◽

Mechanisms Of Formation ◽

Relationship Of ◽

The Relationship

Asthma and obesity are serious medical and social world problems, and their combined course is characterized by a decrease in the quality of life, an increase in the frequency and duration of hospitalization. The present review summarizes the current views on the mechanisms of formation of asthma phenotype combined with obesity, role of leptin and adiponectin imbalance in the development of systemic inflammation in obesity in the pathophysiology of asthma, its interrelations with metabolic syndrome. We present data that shows that syndrome is closely related not only to the debut of asthma, but also to a decrease in its control. Along with obesity, the role of other components of metabolic syndrome, in particular insulin resistance, as a predictor of asthma development is considered. Insulin resistance may be the most likely factor in the relationship between asthma and obesity, independent of other components of the metabolic syndrome. Insulin resistance associated with obesity can lead to disruption of nitric oxide synthesis. We reveal common mechanism of metabolic disorders of nitric oxide and arginine in metabolic syndrome and asthma and show that insulin resistance treatment can be therapeutically useful in patients with asthma in combination with obesity.

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Pathogenetic significance of C774T single nucleotide polymorphism of the endothelial NO synthase gene in the development of metabolic syndrome

Biomeditsinskaya Khimiya ◽

10.18097/pbmc20166204447 ◽

2016 ◽

Vol 62 (4) ◽

pp. 447-452 ◽

Cited By ~ 1

Author(s):

N.S. Fattakhov ◽

M.A. Vasilenko ◽

D.A. Skuratovskaia ◽

D.I. Kulikov ◽

E.V. Kirienkova ◽

...

Keyword(s):

Nitric Oxide ◽

Metabolic Syndrome ◽

Single Nucleotide Polymorphism ◽

Serum Levels ◽

Nucleotide Polymorphism ◽

Single Nucleotide ◽

Nos3 Gene ◽

Kaliningrad Region ◽

The Relationship

The relationship between nitric oxide production and metabolic disorders and the role of endothelial nitric oxide synthase (eNOS or NOS3) in metabolic syndrome (MS) remain poorly understood and need deeper investigation. In this context the role of the NOS3 gene in pathogenesis of MS is of special interest. The aim of the study was to investigate association of NOS3 single nucleotide polymorphism C774T with risk of MS in the Slavic population of the Kaliningrad region and the relationship of this polymorphic variant with some parameters of endothelial dysfunction. The study included 128 patients (48 men and 80 women aged from 36 to 52 years) with MS. The control group consisted of 126 healthy volunteers (60 men and 66 women aged from 30 to 40 years). Genotyping was performed by real-time PCR. Serum nitrite levels were determined spectrophotometrically by the Griess method. Serum levels of endothelin-1 and eNOS were evaluated by ELISA. The study has shown association of T allele (OR=2.06; p=0.0004; CI: 1.38-3.08) and CT genotype (OR=1.97; p=0.014; CI: 1.14-3.40 ) C774T polymorphism of the NOS3 gene with risk of MS in the Slavic population of the Kaliningrad region. Allele C (OR=0.48; p=0.0004; CI: 0.32-0.72) and homozygous CC genotype (OR=0.41; p=0.001; CI: 0.24-0,69) C774T polymorphism of the NOS3 gene were associated with reduced risk of the development of MS. Significant differences in serum levels of eNOS and endothelin-1 depended on the CT and TT genotypes of C774T polymorphism of the NOS3 gene in MS.

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Inhibition of NHE protects reoxygenated cardiomyocytes independently of anoxic Ca2+ overload and acidosis

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.2000.279.5.h2143 ◽

2000 ◽

Vol 279 (5) ◽

pp. H2143-H2150 ◽

Cited By ~ 7

Author(s):

C. Schäfer ◽

Y. V. Ladilov ◽

M. Schäfer ◽

H. M. Piper

Keyword(s):

Intracellular Ph ◽

Cytosolic Ph ◽

Bicarbonate Buffer ◽

Rat Cardiomyocytes ◽

Hepes Buffer ◽

Adult Rat ◽

Reoxygenation Injury ◽

Sodium Binding ◽

Cytosolic Acidification

We investigated the question of whether inhibition of the Na+/H+ exchanger (NHE) during ischemia is protective due to reduction of cytosolic Ca2+ accumulation or enhanced acidosis in cardiomyocytes. Additionally, the role of the Na+-HCO3 − symporter (NBS) was investigated. Adult rat cardiomyocytes were exposed to simulated ischemia and reoxygenation. Cytosolic pH [2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF)], Ca2+ (fura 2), Na+ [sodium-binding benzolfuran isophthatlate (SBFI)], and cell length were measured. NHE was inhibited with 3 μmol/l HOE 642 or 1 μmol/l 5-( N-ethyl- N-isopropyl)-amiloride (EIPA), and NBS was inhibited with HEPES buffer. During anoxia in bicarbonate buffer, cells developed acidosis and intracellular Na and Ca (Nai and Cai, respectively) overload. During reoxygenation cells underwent hypercontracture (44.0 ± 4.1% of the preanoxic length). During anoxia in bicarbonate buffer, inhibition of NHE had no effect on changes in intracellular pH (pHi), Nai, and Cai, but it significantly reduced the reoxygenation-induced hypercontracture (HOE: 61.0 ± 1.4%, EIPA: 68.2 ± 1.8%). The sole inhibition of NBS during anoxia was not protective. We conclude that inhibition of NHE during anoxia protects cardiomyocytes against reoxygenation injury independently of cytosolic acidification and Cai overload.

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P-1274 - Possible pathophysiological role of the relationship between levels of nitric oxide and bilirubin in patients with schizophrenia

European Psychiatry ◽

10.1016/s0924-9338(12)75441-x ◽

2012 ◽

Vol 27 ◽

pp. 1

Author(s):

A. Memic ◽

A. Kucukalic ◽

L. Oruc ◽

J. Huskic ◽

L. Burnazovic ◽

...

Keyword(s):

Nitric Oxide ◽

Pathophysiological Role ◽

The Relationship

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Role of lysosomal and cytosolic pH in the regulation of macrophage lysosomal enzyme secretion

Biochemical Journal ◽

10.1042/bj2720407 ◽

1990 ◽

Vol 272 (2) ◽

pp. 407-414 ◽

Cited By ~ 54

Author(s):

H Tapper ◽

R Sundler

Keyword(s):

Intracellular Ph ◽

Fluorescent Probes ◽

Lysosomal Enzyme ◽

Enzyme Secretion ◽

Relative Role ◽

Ion Composition ◽

Cytosolic Ph ◽

Lysosomal Ph ◽

Cytosolic Acidification

Rapid and parallel secretion of lysosomal beta-N-acetylglucosaminidase and preloaded fluorescein-labelled dextran was initiated in macrophages by agents affecting intracellular pH (methylamine, chlorpromazine, and the ionophores monensin and nigericin). In order to evaluate the relative role of changes in lysosomal and cytosolic pH, these parameters were monitored by using pH-sensitive fluorescent probes [fluorescein-labelled dextran or 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein]. All agents except chlorpromazine caused large increases in lysosomal pH under conditions where they induced secretion. By varying extracellular pH and ion composition, the changes in lysosomal and cytosolic pH could be dissociated. Secretion was then found to be significantly modulated by changes in cytosolic pH, being enhanced by alkalinization and severely inhibited by cytosolic acidification. However, changes in cytosolic pH in the absence of stimulus were unable to initiate secretion. Dissociation of the effects on lysosomal and cytosolic pH was also achieved by combining stimuli with either nigericin or acetate. Further support for a role of intracellular pH in the control of lysosomal enzyme secretion was provided by experiments where bicarbonate was included in the medium. The present study demonstrates that an increase in lysosomal pH is sufficient to initiate lysosomal enzyme secretion in macrophages and provides evidence for a significant regulatory role of cytosolic pH.

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