scholarly journals The Protective Effect of H2-Receptor Activation Against the Duration of Myocardial Hypoxia/Reoxygenation-Induced Ventricular Fibrillation in Sensitized Guinea-Pig Hearts

2005 ◽  
Vol 99 (4) ◽  
pp. 400-407 ◽  
Author(s):  
Naoki Imajo ◽  
Saori Matsui ◽  
Yumiko Yasui ◽  
Nobuaki Matsui ◽  
Nobuyuki Fukuishi ◽  
...  
Keyword(s):  
Ventricular Fibrillation ◽  
Guinea Pig ◽  
Protective Effect ◽  
Receptor Activation ◽  
H2 Receptor ◽  
Myocardial Hypoxia ◽  
Hypoxia Reoxygenation

Effect of Ado A1- and A2-receptor activation on ventricular fibrillation during hypoxia-reoxygenation

1994 ◽  
Vol 267 (4) ◽  
pp. H1447-H1454 ◽  
Author(s):  
L. Chi ◽  
G. S. Friedrichs ◽  
J. Y. Oh ◽  
A. L. Green ◽  
B. R. Lucchesi
Keyword(s):  
Ventricular Fibrillation ◽  
Action Potential ◽  
Action Potential Duration ◽  
Receptor Activation ◽  
Monophasic Action Potential ◽  
Perfused Heart ◽  
Receptor Stimulation ◽  
Myocardial Hypoxia ◽  
A1 Receptor ◽  
Hypoxia Reoxygenation

We examined the hypothesis that adenosine (Ado)-induced alterations in ventricular electrophysiology may contribute to arrhythmogenesis in a setting of myocardial hypoxia through activation of Ado A1 and A2 receptors in the rabbit isolated perfused heart. There was a 20% incidence of ventricular fibrillation (VF) in control hearts subjected to perfusion conditions of hypoxia and reoxygenation. The incidence of VF was increased to 50% in the presence of 1 microM Ado when hearts were exposed to hypoxia-reoxygenation. The incidence of VF was 20% when Ado was increased to 10 microM. Inhibition of the Ado A2 receptor with 3,7-dimethyl-l-propargylxanthine (DMPX; 10 microM) increased the incidence of VF to 100% when 10 microM Ado was added to the perfusion medium. The A1 antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 1 microM), attenuated (from 100% to 20%) VF induced by Ado + DMPX (10 microM each). The ventricular refractory period and monophasic action potential duration were determined in a separate group of hearts. Our findings indicate that 1) Ado A1-receptor stimulation facilitates VF by decreasing action potential duration and refractoriness in hearts subjected to hypoxia and reoxygenation and 2) the arrhythmogenic potential of Ado A1-receptor stimulation is modulated by simultaneous activation of the ventricular A2 Ado receptor.

scholarly journals Hydrogen Sulfide Attenuates Myocardial Hypoxia-Reoxygenation Injury by Inhibiting Autophagy via mTOR Activation

2015 ◽  
Vol 37 (6) ◽  
pp. 2444-2453 ◽  
Author(s):  
Jian Xiao ◽  
Xiaoyan Zhu ◽  
Bo Kang ◽  
Jibin Xu ◽  
Lihui Wu ◽  
...  
Keyword(s):  
Hydrogen Sulfide ◽  
Protective Effect ◽  
Cell Injury ◽  
Ischemia Reperfusion ◽  
Protective Role ◽  
Cell Vitality ◽  
Myocardial Hypoxia ◽  
Mtor Protein ◽  
Myocardial Ischemia Reperfusion ◽  
Hypoxia Reoxygenation

Background: Autophagy plays a significant role in myocardial ischemia reperfusion (IR) injury. Hydrogen sulfide (H2S) has been demonstrated to protect cardiomyocytes against IR injury, while whether it has anti-autophagy effect has not been known. The aim of this study was to investigate whether H2S regulates autophagy during IR injury and its possible mechanism. Methods and Results: The cardiomyocytes of neonatal rats were randomized into Con, hypoxia-reoxygenation (HR) and H2S protection groups. The severity of cell injury was evaluated by cell vitality (MTT) and lactate dehydrogenase (LDH) release assays, and autophagy level was evaluated by flow cytometry and the assessment of autophagy-related gene (Atg) expression, such as that of Beclin1 and LC3-II. In response to H2S, Beclin1 and LC3-II protein were found to be down-regulated and p-mTOR protein was found to be up-regulated, together with an increase in cell vitality and a decrease in LDH. Furthermore, to find out whether mTOR was involved in the protective effect of H2S, rapamycin, inhibiter of mTOR, was used with or without applying NaHS and HR. It was found that rapamycin attenuated the myocardiocyte protective effect of H2S. To demonstrate the effect of autophagy during HR injury, the cardiomyocytes were pre-treated with 3-MA, which is an autophagy inhibitor, cell injury was attenuated by 3-MA. Conclusions: H2S plays a myocardial protective role against IR injury by regulating autophagy via mTOR activation.

scholarly journals P2X2 receptors differentiate placodal vs. neural crest C-fiber phenotypes innervating guinea pig lungs and esophagus

2008 ◽  
Vol 295 (5) ◽  
pp. L858-L865 ◽  
Author(s):  
Kevin Kwong ◽  
Marian Kollarik ◽  
Christina Nassenstein ◽  
Fei Ru ◽  
Bradley J. Undem
Keyword(s):  
Guinea Pig ◽  
Neural Crest ◽  
Single Cell ◽  
Dorsal Root Ganglia ◽  
Dorsal Root ◽  
Receptor Activation ◽  
Rt Pcr ◽  
C Fibers ◽  
Embryonic Origin ◽  
Ganglion Neurons

The lungs and esophagus are innervated by sensory neurons with somata in the nodose, jugular, and dorsal root ganglion. These sensory ganglia are derived from embryonic placode (nodose) and neural crest tissues (jugular and dorsal root ganglia; DRG). We addressed the hypothesis that the neuron's embryonic origin (e.g., placode vs. neural crest) plays a greater role in determining particular aspects of its phenotype than the environment in which it innervates (e.g., lungs vs. esophagus). This hypothesis was tested using a combination of extracellular and patch-clamp electrophysiology and single-cell RT-PCR from guinea pig neurons. Nodose, but not jugular C-fibers innervating the lungs and esophagus, responded to α,β-methylene ATP with action potential discharge that was sensitive to the P2X3 (P2X2/3) selective receptor antagonist A-317491. The somata of lung- and esophagus-specific sensory fibers were identified using retrograde tracing with a fluorescent dye. Esophageal- and lung-traced neurons from placodal tissue (nodose neurons) responded similarly to α,β-methylene ATP (30 μM) with a large sustained inward current, whereas in neurons derived from neural crest tissue (jugular and DRG neurons), the same dose of α,β-methylene ATP resulted in only a transient rapidly inactivating current or no detectable current. It has been shown previously that only activation of P2X2/3 heteromeric receptors produce sustained currents, whereas homomeric P2X3 receptor activation produces a rapidly inactivating current. Consistent with this, single-cell RT-PCR analysis revealed that the nodose ganglion neurons innervating the lungs and esophagus expressed mRNA for P2X2 and P2X3 subunits, whereas the vast majority of jugular and dorsal root ganglia innervating these tissues expressed only P2X3 mRNA with little to no P2X2 mRNA expression. We conclude that the responsiveness of C-fibers innervating the lungs and esophagus to ATP and other purinergic agonists is determined more by their embryonic origin than by the environment of the tissue they ultimately innervate.

scholarly journals Two New Compounds From the Heartwood of Dalbergia melanoxylon and Their Protective Effect on Hypoxia/Reoxygenation Injury in H9c2

2021 ◽  
Vol 16 (1) ◽  
pp. 1934578X2098777
Author(s):  
Yang Liu ◽  
Ni Zhang ◽  
Jun-wei He ◽  
Lan-ying Chen ◽  
Li Yang ◽  
...  
Keyword(s):  
Superoxide Dismutase ◽  
Lactate Dehydrogenase ◽  
Protective Effect ◽  
Superoxide Dismutase Activity ◽  
Spectral Evidence ◽  
Reoxygenation Injury ◽  
Dalbergia Melanoxylon ◽  
New Compounds ◽  
Hypoxia Reoxygenation

A new neoflavonoid, named as (7 R)-(-)-3′,5-dihydroxy-4′,2,4-trimethoxy-dalbergiquinol (1) and a new phenanthrenedione, named as 3′,7-dihydroxy-3,6- dimethoxy-9-phenyl-1,4-phenanthrenedione (2), together with 4 known compounds, 5- O-methyldalbergiphenol (3), 3′,7-dihydroxy-4′,3,6-trimethoxy-9-phenyl-1,4-phenanthrenedione (4), (+)-obtusafuran (5), and melanoxin (6) were isolated from the heartwood of Dalbergia melanoxylon. Their structures were elucidated on the basis of chemical and spectral evidence, as well as by comparison with literature data. Moreover, compound 1 showed a protective effect on hypoxia/reoxygenation injury in H9c2 at 10.0 μM by decreasing lactate dehydrogenase and malondialdehyde activity and enhancing superoxide dismutase activity.

Protective effect of nicotinamide on neuronal cells under oxygen and glucose deprivation and hypoxia/reoxygenation

2004 ◽  
Vol 11 (4) ◽  
pp. 472-481 ◽  
Author(s):  
Chiung-Chyi Shen ◽  
Hsueh-Meei Huang ◽  
Hsiu-Chung Ou ◽  
Huan-Lian Chen ◽  
Wen-Chi Chen ◽  
...  
Keyword(s):  
Protective Effect ◽  
Neuronal Cells ◽  
Glucose Deprivation ◽  
Oxygen And Glucose Deprivation ◽  
Hypoxia Reoxygenation

Comparison of changes evoked by GABA (γ-aminobutyric acid) and anoxia in [K+]o, [Cl-]o, and [Na+]o in stratum pyramidale and stratum radiatum of the guinea pig hippocampus

2000 ◽  
Vol 78 (5) ◽  
pp. 378-391 ◽  
Author(s):  
G V Obrocea ◽  
M E Morris
Keyword(s):  
Guinea Pig ◽  
Extracellular Space ◽  
Hippocampal Slices ◽  
Brain Slices ◽  
Receptor Activation ◽  
Ion Concentration ◽  
Aminobutyric Acid ◽  
Stratum Radiatum ◽  
Bicuculline Methiodide ◽  
Stratum Pyramidale

Ion-selective microelectrode recordings were made to assess a possible contribution of extracellular γ-aminobutyric acid (GABA) accumulation to early responses evoked in the brain by anoxia and ischemia. Changes evoked by GABA or N2 in [K+]o, [Cl-]o, [Na+]o, and [TMA+]o were recorded in the cell body and dendritic regions of the stratum pyramidale (SP) and stratum radiatum (SR), respectively, of pyramidal neurons in CA1 of guinea pig hippocampal slices. Bath application of GABA (1-10 mM) for approximately 5 min evoked changes in [K+]o and [Cl-]o with respective EC50 levels of 3.8 and 4.1 mM in SP, and 4.7 and 5.6 mM in SR. In SP 5 mM GABA reversibly increased [K+]o and [Cl-]o and decreased [Na+]o; replacement of 95% O2 -5% CO2 by 95% N2 -5% CO2 for a similar period of time evoked changes which were for each ion in the same direction as those with GABA. In SR both GABA and N2 caused increases in [K+]o and decreases in [Cl-]o and [Na+]o. The reduction of extracellular space, estimated from levels of [TMA+]o during exposures to GABA and N2, was 5-6% and insufficient to cause the observed changes in ion concentration. Ion changes induced by GABA and N2 were reversibly attenuated by the GABAA receptor antagonist bicuculline methiodide (BMI, 100 µM). GABA-evoked changes in [K+]o in SP and SR and [Cl-]o in SP were depressed by >=90%, and of [Cl-]o in SR by 50%; N2-evoked changes in [K+]o in SP and SR were decreased by 70% and those of [Cl-]o by 50%. BMI blocked Δ [Na+]o with both GABA and N2 by 20-30%. It is concluded that during early anoxia: (i) accumulation of GABA and activation of GABAA receptors may contribute to the ion changes and play a significant role, and (ii) responses in the dendritic (SR) regions are greater than and (or) differ from those in the somal (SP) layers. A large component of the [K+]o increase may involve a GABA-evoked Ca2+-activated gk, secondary to [Ca2+]i increase. A major part of [Cl-]o changes may arise from GABA-induced gCl and glial efflux, with strong stimulation of active outward transport and anion exchange at SP, and inward Na+/K+/2Cl- co-transport at SR. Na+ influx is attributable mainly to Na+-dependent transmitter uptake, with only a small amount related to GABAA receptor activation. Although the release and (or) accumulation of GABA during anoxia might be viewed as potentially protectant, the ultimate role may more likely be an important contribution to toxicity and delayed neuronal death. Key words: brain slices, ion-selective microelectrodes, stratum pyramidale, stratum radiatum, bicuculline methiodide, extracellular space shrinkage.

scholarly journals Relevance of Hydrogen Bonds for the Histamine H2 Receptor-Ligand Interactions: A Lesson from Deuteration

Biomolecules ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 196 ◽  
Author(s):  
Mojca Kržan ◽  
Jan Keuschler ◽  
Janez Mavri ◽  
Robert Vianello
Keyword(s):  
Hydrogen Bonding ◽  
Active Sites ◽  
Density Functional ◽  
Receptor Activation ◽  
Histamine H2 Receptor ◽  
Therapeutic Practice ◽  
H2 Receptor ◽  
Ligand Interactions ◽  
Solvent Molecules ◽  
Near Future

We used a combination of density functional theory (DFT) calculations and the implicit quantization of the acidic N–H and O–H bonds to assess the effect of deuteration on the binding of agonists (2-methylhistamine and 4-methylhistamine) and antagonists (cimetidine and famotidine) to the histamine H2 receptor. The results show that deuteration significantly increases the affinity for 4-methylhistamine and reduces it for 2-methylhistamine, while leaving it unchanged for both antagonists, which is found in excellent agreement with experiments. The revealed trends are interpreted in the light of the altered strength of the hydrogen bonding upon deuteration, known as the Ubbelohde effect, which affects ligand interactions with both active sites residues and solvent molecules preceding the binding, thus providing strong evidence for the relevance of hydrogen bonding for this process. In addition, computations further underline an important role of the Tyr250 residue for the binding. The obtained insight is relevant for the therapy in the context of (per)deuterated drugs that are expected to enter therapeutic practice in the near future, while this approach may contribute towards understanding receptor activation and its discrimination between agonists and antagonists.

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