scholarly journals Changes in excitability and ion channel expression in neurons of the major pelvic ganglion in female type II diabetic mice

2018 ◽  
Author(s):  
Michael Gray ◽  
Kawasi M. Lett ◽  
Virginia B. Garcia ◽  
Cindy W. Kyi ◽  
Kathleen A. Pennington ◽  
...  
Keyword(s):  
Action Potential ◽  
Ion Channel ◽  
Type Ii Diabetes ◽  
Neuronal Excitability ◽  
Type Ii ◽  
Pelvic Ganglion ◽  
Major Pelvic Ganglion ◽  
Non Linear ◽  
Channel Expression ◽  
Firing Properties

ABSTRACTBladder cystopathy is a common urological complication of diabetes, and has been associated with changes in parasympathetic ganglionic transmission and some measures of neuronal excitability in male mice. To determine whether type II diabetes also impacts excitability of parasympathetic ganglionic neurons in females, we investigated neuronal excitability and firing properties, as well as underlying ion channel expression, in major pelvic ganglion (MPG) neurons in control, 10-week, and 21-week db/db mice. Type II diabetes in Leprdb/db animals caused a non-linear change in excitability and firing properties of MPG neurons. At 10 weeks, cells exhibited increased excitability as demonstrated by an increased likelihood of firing multiple spikes upon depolarization, decreased rebound spike latency, and overall narrower action potential half-widths as a result of increased depolarization and repolarization slopes. Conversely, at 21 weeks MPG neurons of db/db mice reversed these changes, with spiking patterns and action-potential properties largely returning to control levels. These changes are associated with numerous time-specific changes in calcium, sodium, and potassium channel subunit mRNA levels. However, Principal Components Analysis of channel expression patterns revealed that the rectification of excitability is not simply a return to control levels, but rather a distinct ion channel expression profile in 21-week db/db neurons. These data indicate that type II diabetes can impact the excitability of post-ganglionic, parasympathetic bladder-innervating neurons of female mice, and suggest that the non-linear progression of these properties with diabetes may be the result of compensatory changes in channel expression that act to rectify disrupted firing patterns of db/db MPG neurons.

scholarly journals Changes in excitability and ion channel expression in neurons of the major pelvic ganglion in female type II diabetic mice

2019 ◽  
Vol 220 ◽  
pp. 102558
Author(s):  
Michael Gray ◽  
Kawasi M. Lett ◽  
Virginia B. Garcia ◽  
Cindy W. Kyi ◽  
Kathleen A. Pennington ◽  
...  
Keyword(s):  
Ion Channel ◽  
Type Ii ◽  
Diabetic Mice ◽  
Pelvic Ganglion ◽  
Female Type ◽  
Major Pelvic Ganglion ◽  
Channel Expression

scholarly journals Ion Channel and Structural Remodeling in Obesity-Mediated Atrial Fibrillation

2020 ◽  
Vol 13 (8) ◽  
Author(s):  
Mark D. McCauley ◽  
Liang Hong ◽  
Arvind Sridhar ◽  
Ambili Menon ◽  
Srikanth Perike ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Action Potential ◽  
Ion Channel ◽  
Sodium Channel ◽  
Action Potential Duration ◽  
Obese Mice ◽  
Atrial Fibrosis ◽  
Structural Remodeling ◽  
Cardiac Sodium Channel ◽  
Channel Expression

Background: Epidemiological studies have established obesity as an independent risk factor for atrial fibrillation (AF), but the underlying pathophysiological mechanisms remain unclear. Reduced cardiac sodium channel expression is a known causal mechanism in AF. We hypothesized that obesity decreases Nav1.5 expression via enhanced oxidative stress, thus reducing I Na , and enhancing susceptibility to AF. Methods: To elucidate the underlying electrophysiological mechanisms a diet-induced obese mouse model was used. Weight, blood pressure, glucose, F 2 -isoprostanes, NOX2 (NADPH oxidase 2), and PKC (protein kinase C) were measured in obese mice and compared with lean controls. Invasive electrophysiological, immunohistochemistry, Western blotting, and patch clamping of membrane potentials was performed to evaluate the molecular and electrophysiological phenotype of atrial myocytes. Results: Pacing-induced AF in 100% of diet-induced obese mice versus 25% in controls ( P <0.01) with increased AF burden. Cardiac sodium channel expression, I Na and atrial action potential duration were reduced and potassium channel expression (Kv1.5) and current ( I Kur ) and F 2 -isoprostanes, NOX2, and PKC-α/δ expression and atrial fibrosis were significantly increased in diet-induced obese mice as compared with controls. A mitochondrial antioxidant reduced AF burden, restored I Na , I Ca,L , I Kur , action potential duration, and reversed atrial fibrosis in diet-induced obese mice as compared with controls. Conclusions: Inducible AF in obese mice is mediated, in part, by a combined effect of sodium, potassium, and calcium channel remodeling and atrial fibrosis. Mitochondrial antioxidant therapy abrogated the ion channel and structural remodeling and reversed the obesity-induced AF burden. Our findings have important implications for the management of obesity-mediated AF in patients. Graphic Abstract: A graphic abstract is available for this article.

scholarly journals Inhibition of Histone Deacetylases Induces K+ Channel Remodeling and Action Potential Prolongation in HL-1 Atrial Cardiomyocytes

2018 ◽  
Vol 49 (1) ◽  
pp. 65-77 ◽  
Author(s):  
Patrick Lugenbiel ◽  
Katharina Govorov ◽  
Ann-Kathrin Rahm ◽  
Teresa Wieder ◽  
Dominik Gramlich ◽  
...  
Keyword(s):  
Action Potential ◽  
Ion Channel ◽  
Action Potential Duration ◽  
Histone Deacetylases ◽  
Trichostatin A ◽  
Class I ◽  
K Channel ◽  
Hdac Inhibition ◽  
Atrial Cardiomyocytes ◽  
Channel Expression

Background/Aims: Cardiac arrhythmias are triggered by environmental stimuli that may modulate expression of cardiac ion channels. Underlying epigenetic regulation of cardiac electrophysiology remains incompletely understood. Histone deacetylases (HDACs) control gene expression and cardiac integrity. We hypothesized that class I/II HDACs transcriptionally regulate ion channel expression and determine action potential duration (APD) in cardiac myocytes. Methods: Global class I/II HDAC inhibition was achieved by administration of trichostatin A (TSA). HDAC-mediated effects on K+ channel expression and electrophysiological function were evaluated in murine atrial cardiomyocytes (HL-1 cells) using real-time PCR, Western blot, and patch clamp analyses. Electrical tachypacing was employed to recapitulate arrhythmia-related effects on ion channel remodeling in the absence and presence of HDAC inhibition. Results: Global HDAC inhibition increased histone acetylation and prolonged APD90 in atrial cardiomyocytes compared to untreated control cells. Transcript levels of voltage-gated or inwardly rectifying K+ channels Kcnq1, Kcnj3 and Kcnj5 were significantly reduced, whereas Kcnk2, Kcnj2 and Kcnd3 mRNAs were upregulated. Ion channel remodeling was similarly observed at protein level. Short-term tachypacing did not induce significant transcriptional K+ channel remodeling. Conclusion: The present findings link class I/II HDAC activity to regulation of ion channel expression and action potential duration in atrial cardiomyocytes. Clinical implications for HDAC-based antiarrhythmic therapy and cardiac safety of HDAC inhibitors require further investigation.

scholarly journals Ion channel expression and electrophysiology of singular human (primary and induced pluripotent stem cell derived) cardiomyocytes

2021 ◽  
Author(s):  
Christina Schmid ◽  
Najah Abi-Gerges ◽  
Dietmar Zellner ◽  
Georg Rast
Keyword(s):  
Ion Channels ◽  
Action Potential ◽  
Ion Channel ◽  
Single Cell ◽  
Action Potential Duration ◽  
Drug Effects ◽  
Induced Pluripotent Stem Cell ◽  
Inward Current ◽  
Beat Rate ◽  
Channel Expression

SUMMARYHuman induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and primary human cardiomyocytes are used for in vitro cardiac safety testing. hiPSC-CMs have been associated with a vast heterogeneity regarding single-cell morphology, beating behavior and action potential duration, prompting a systematic analysis of single-cell characteristics. Previously published hiPSC-CM studies revealed action potentials with nodal-, atrial- or ventricular-like morphology, although ion channel expression of singular hiPSC-CMs is not fully understood. Other studies used single-cell RNA-sequencing, however, these studies did not extensively focus on expression patterns of cardiac ion channels or failed to detect ion channel transcripts. Thus, the current study used a single-cell patch-clamp-RT-qPCR approach to get insights into single-cell electrophysiology (capacitance, action potential duration at 90% of repolarization, upstroke velocity, spontaneous beat rate, and sodium-driven fast inward current) and ion channel expression (HCN4, CACNA1G, CACNA1D, KCNA5, KCNJ4, SCN5A, KCNJ2, CACNA1D, and KCNH2), the combination of both within individual cells, and their correlations in single cardiomyocytes. We used commercially available hiPSC-CMs (iCell cardiomyocytes, atrial and ventricular Pluricytes) and primary human adult atrial and ventricular cardiomyocytes. Recordings of electrophysiological parameters revealed differences between the cell groups and variation within the hiPSC-CMs groups as well as within primary ventricular cardiomyocytes. Expression analysis on mRNA level showed no-clear-cut discrimination between primary cardiac subtypes and revealed both similarities and differences between all cell groups. Higher expression of atrial-associated ion channels in primary atrial cardiomyocytes and atrial Pluricytes compared to their ventricular counterpart indicates a successful chamber-specific hiPSC differentiation. Interpretation of correlations between the single-cell parameters was challenging, as the total data set is complex, particularly for parameters depending on multiple processes, like the spontaneous beat rate. Yet, for example, expression of SCN5A correlated well with the fast inward current amplitude for all three hiPSC-CM groups. To further enhance our understanding of the physiology and composition of the investigated hiPSC-CMs, we compared beating and non-beating cells and assessed distributions of single-cell data. Investigating the single-cell phenotypes of hiPSC-CMs revealed a combination of attributes which may be interpreted as a mixture of traits of different adult cardiac cell types: (i) nodal-related pacemaking attributes are spontaneous generation of action potentials and high HCN4 expression; and (ii) non-nodal attributes: cells have a prominent INa-driven fast inward current, a fast upstroke velocity and a high expression of SCN5A. In conclusion, the combination of nodal- and non-nodal attributes in single hiPSC-CMs may hamper the interpretation of drug effects on complex electrophysiological parameters like beat rate and action potential duration. However, the proven expression of specific ion channels enables the evaluation of drug effects on ionic currents in a more realistic environment than in recombinant systems.

1019: Visualization of the Neurovascular Bundles and Major Pelvic Ganglion with Fluorescent Proteins after Penile Injection

2006 ◽  
Vol 175 (4S) ◽  
pp. 328-328 ◽  
Author(s):  
Hugo H. Davila ◽  
Maggie Mamcarz ◽  
Irving Nadelhaft ◽  
Raoul Salup ◽  
Jorge Lockhart ◽  
...  
Keyword(s):  
Fluorescent Proteins ◽  
Pelvic Ganglion ◽  
Major Pelvic Ganglion ◽  
Neurovascular Bundles
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