Antagonists of stretch-activated ion channels restore contractile function in hamster dilated cardiomyopathy

2004 ◽  
Vol 23 (8) ◽  
pp. 1003-1007 ◽  
Author(s):  
Alfred C. Nicolosi ◽  
Chiaki S. Kwok ◽  
Zeljko J. Bosnjak
Keyword(s):  
Ion Channels ◽  
Dilated Cardiomyopathy ◽  
Contractile Function ◽  
Stretch Activated Ion Channels

Stretch-activated ion channels contribute to membrane depolarization after eccentric contractions

2000 ◽  
Vol 88 (1) ◽  
pp. 91-101 ◽  
Author(s):  
Todd A. McBride ◽  
Bradley W. Stockert ◽  
Fredric A. Gorin ◽  
Richard C. Carlsen
Keyword(s):  
Ion Channels ◽  
Channel Blocker ◽  
Contractile Function ◽  
Muscle Fibers ◽  
Membrane Depolarization ◽  
Membrane Potentials ◽  
Eccentric Contractions ◽  
Multiple Exposures ◽  
Cation Conductance ◽  
Stretch Activated Ion Channels

We tested the hypothesis that eccentric contractions activate mechanosensitive or stretch-activated ion channels (SAC) in skeletal muscles, producing increased cation conductance. Resting membrane potentials and contractile function were measured in rat tibialis anterior muscles after single or multiple exposures to a series of eccentric contractions. Each exposure produced a significant and prolonged (>24 h) membrane depolarization in exercised muscle fibers. The magnitude and duration of the depolarization were related to the number of contractions. Membrane depolarization was due primarily to an increase in Na+ influx, because the estimated Na+-to-K+ permeability ratio was increased in exercised muscles and resting membrane potentials could be partially repolarized by substituting an impermeant cation for extracellular Na+ concentration. Neither the Na+/H+ antiport inhibitor amiloride nor the fast Na+ channel blocker TTX had a significant effect on the depolarization. In contrast, addition of either of two nonselective SAC inhibitors, streptomycin or Gd3+, produced significant membrane repolarization. The results suggest that muscle fibers experience prolonged depolarization after eccentric contractions due, principally, to the activation of Na+-selective SAC.

Increased coronary perfusion augments cardiac contractility in the rat through stretch-activated ion channels

2002 ◽  
Vol 282 (4) ◽  
pp. H1334-H1340 ◽  
Author(s):  
R. R. Lamberts ◽  
M. H. P. van Rijen ◽  
P. Sipkema ◽  
P. Fransen ◽  
S. U. Sys ◽  
...  
Keyword(s):  
Ion Channels ◽  
Perfusion Pressure ◽  
Cardiac Contractility ◽  
No Synthase ◽  
Coronary Perfusion ◽  
Channel Blockade ◽  
No Release ◽  
Sustained Increase ◽  
Stretch Activated Ion Channels

The role of stretch-activated ion channels (SACs) in coronary perfusion-induced increase in cardiac contractility was investigated in isolated isometrically contracting perfused papillary muscles from Wistar rats. A brief increase in perfusion pressure (3–4 s, perfusion pulse, n = 7), 10 repetitive perfusion pulses ( n = 4), or a sustained increase in perfusion pressure (150–200 s, perfusion step, n = 7) increase developed force by 2.7 ± 1.1, 7.7 ± 2.2, and 8.3 ± 2.5 mN/mm2 (means ± SE, P < 0.05), respectively. The increase in developed force after a perfusion pulse is transient, whereas developed force during a perfusion step remains increased by 5.1 ± 2.5 mN/mm2 ( P < 0.05) in the steady state. Inhibition of SACs by addition of gadolinium (10 μmol/l) or streptomycin (40 and 100 μmol/l) blunts the perfusion-induced increase in developed force. Incubation with 100 μmol/l N ω-nitro-l-arginine [nitric oxide (NO) synthase inhibition], 10 μmol/l sodium nitroprusside (NO donation) and 0.1 μmol/l verapamil (L-type Ca2+ channel blockade) are without effect on the perfusion-induced increase of developed force. We conclude that brief, repetitive, or sustained increases in coronary perfusion augment cardiac contractility through activation of stretch-activated ion channels, whereas endothelial NO release and L-type Ca2+channels are not involved.

Abstract 88: A Crucial Role of BAG3 in Preventing Dilated Cardiomyopathy

2017 ◽  
Vol 121 (suppl_1) ◽  
Author(s):  
Xi Fang ◽  
Julius Bogomolovas ◽  
Wei Zhang ◽  
Tongbin Wu ◽  
Canzhao Liu ◽  
...  
Keyword(s):  
Heart Failure ◽  
Dilated Cardiomyopathy ◽  
Protein Quality ◽  
Contractile Function ◽  
Metabolic Stress ◽  
Insoluble Fraction ◽  
Therapeutic Benefit ◽  
Loss Of Function ◽  
Specific Subset

Defective protein quality control (PQC) systems are implicated in multiple diseases, with molecular chaperones/co-chaperones being critical to PQC. Cardiomyocytes are constantly challenged by mechanical and metabolic stress, placing great demand on the PQC system. Mutations and downregulation of the co-chaperone protein B cl-2- a ssociated athano g ene 3 (BAG3) are associated with cardiac myopathy and heart failure, and a BAG3 E455K mutation leads to Dilated cardiomyopathy (DCM). However, the role of BAG3 in the heart and mechanisms by which the E455K mutation lead to DCM remained obscure. Here, we found that cardiac-specific BAG3 knockout (CKO) and cardiac-specific E455K BAG3 knockin mice developed DCM. Comparable phenotypes in the two mutants demonstrated that the E455K mutation resulted in loss-of-function, and experiments revealed that the E455K mutation disrupted interaction between BAG3 and HSP70. In both mutants, decreased levels of small heat shock proteins (sHSPs) were observed, and a specific subset of proteins required for metabolic and contractile function of cardiomyocytes was enriched in the insoluble fraction. Together, these observations suggested that interaction between BAG3 and HSP70 was essential for BAG3 to stabilize sHSPs and maintain cardiomyocyte protein homeostasis. Our results provide new insight into the pathogenesis of heart failure caused by defects in BAG3 pathways, suggesting that increasing protein levels of BAG3 may be of therapeutic benefit in heart failure.

scholarly journals Gating pore currents are defects in common with two Nav1.5 mutations in patients with mixed arrhythmias and dilated cardiomyopathy

2015 ◽  
Vol 145 (2) ◽  
pp. 93-106 ◽  
Author(s):  
Adrien Moreau ◽  
Pascal Gosselin-Badaroudine ◽  
Lucie Delemotte ◽  
Michael L. Klein ◽  
Mohamed Chahine
Keyword(s):  
Ion Channels ◽  
Dilated Cardiomyopathy ◽  
Patch Clamp Technique ◽  
Dynamic Simulations ◽  
Voltage Gated ◽  
Clinical Phenotypes ◽  
Pathological Mechanism ◽  
Cardiac Disorders ◽  
Voltage Gated Ion Channels ◽  
Gated Ion Channels

The gating pore current, also called omega current, consists of a cation leak through the typically nonconductive voltage-sensor domain (VSD) of voltage-gated ion channels. Although the study of gating pore currents has refined our knowledge of the structure and the function of voltage-gated ion channels, their implication in cardiac disorders has not been established. Two Nav1.5 mutations (R222Q and R225W) located in the VSD are associated with atypical clinical phenotypes involving complex arrhythmias and dilated cardiomyopathy. Using the patch-clamp technique, in silico mutagenesis, and molecular dynamic simulations, we tested the hypothesis that these two mutations may generate gating pore currents, potentially accounting for their clinical phenotypes. Our findings suggest that the gating pore current generated by the R222Q and R225W mutations could constitute the underlying pathological mechanism that links Nav1.5 VSD mutations with human cardiac arrhythmias and dilatation of cardiac chambers.

Gadolinium and mechanotransduction of rat aortic baroreceptors

1992 ◽  
Vol 262 (5) ◽  
pp. H1415-H1421 ◽  
Author(s):  
M. C. Andresen ◽  
M. Yang
Keyword(s):  
Ion Channels ◽  
Direct Effects ◽  
Cellular Mechanisms ◽  
Pressure Discharge ◽  
Ethanesulfonic Acid ◽  
Discharge Pressure ◽  
Aortic Baroreceptors ◽  
Stretch Activated Channels ◽  
Stretch Activated Ion Channels

The cellular mechanisms enabling baroreceptors to transduce wall distortion into axonal discharge are unknown but might involve stretch-activated ion channels. Gadolinium (Gd3+, 10 microM) blocks stretch-activated channels in several preparations. Here we tested Gd3+ effects on discharge responses of 15 single-fiber baroreceptors in vitro. We simultaneously measured discharge, pressure, and aortic diameter at Gd3+ concentrations from 0.001 to 400 microM. High levels of Gd3+ added to a bicarbonate-buffered perfusate (Krebs) slightly shifted the pressure-discharge relation (less than 4 mmHg, n = 3, P = 0.01) without affecting slope or discharge frequency at threshold. Gd3+ in Krebs variably altered the pressure-diameter relation. Because 500 microM Gd3+ produced visible precipitate in Krebs, we tested Gd3+ in a simpler perfusate using N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES). Gd3+ in HEPES (n = 10) induced minor, but statistically significant, average increases in threshold (less than +5-7%) and no changes in gain. However, prolonged HEPES exposure alone (n = 2) produced similar shifts. Electron microscopy verified that Gd3+ diffused from the lumen to reach extracellular locations near baroreceptor endings. We conclude that 1) HEPES perfusate alone reversibly depresses baroreceptor discharge and 2) Gd3+ has no direct effects on baroreceptors. Thus it appears that aortic baroreceptor mechanotransduction must utilize a different class of stretch-activated ion channels.

scholarly journals Cardiac-Specific Overexpression of Catalytically Inactive Corin Reduces Edema, Contractile Dysfunction, and Death in Mice with Dilated Cardiomyopathy

2019 ◽  
Vol 21 (1) ◽  
pp. 203 ◽  
Author(s):  
Ranjana Tripathi ◽  
Ryan D. Sullivan ◽  
Tai-Hwang M. Fan ◽  
Aiilyan K. Houng ◽  
Radhika M. Mehta ◽  
...  
Keyword(s):  
Dilated Cardiomyopathy ◽  
Serine Protease ◽  
Natriuretic Peptide ◽  
Genetic Model ◽  
Glycogen Synthase ◽  
Contractile Function ◽  
Free Water ◽  
Guanosine Monophosphate ◽  
Heart Weight ◽  
Lung Edema

Humans with dilated cardiomyopathy (DCM) and heart failure (HF) develop low levels of corin, a multi-domain, cardiac-selective serine protease involved in natriuretic peptide cleavage and sodium and water regulation. However, experimental restoration of corin levels markedly attenuates HF progression. To determine whether the beneficial effects of corin in HF require catalytic activity, we engineered cardiac overexpression of an enzymatically inactive corin transgene (corin-Tg(i)). On a wild-type (WT) background, corin-Tg(i) had no evident phenotypic effects. However, in a well-established genetic model of DCM, corin-Tg(i)/DCM mice had increased survival (p < 0.01 to 0.001) vs. littermate corin-WT/DCM controls. Pleural effusion (p < 0.01), lung edema (p < 0.05), systemic extracellular free water (p < 0.01), and heart weight were decreased (p < 0.01) in corin-Tg(i)/DCM vs. corin-WT/DCM mice. Cardiac ejection fraction and fractional shortening improved (p < 0.01), while ventricular dilation decreased (p < 0.0001) in corin-Tg(i)/DCM mice. Plasma atrial natriuretic peptide, cyclic guanosine monophosphate, and neprilysin were significantly decreased. Cardiac phosphorylated glycogen synthase kinase-3β (pSer9-GSK3β) levels were increased in corin(i)-Tg/DCM mice (p < 0.01). In summary, catalytically inactive corin-Tg(i) decreased fluid retention, improved contractile function, decreased HF biomarkers, and diminished cardiac GSK3β activity. Thus, the protective effects of cardiac corin on HF progression and survival in experimental DCM do not require the serine protease activity of the molecule.

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