Role of pulmonary C fibers in adenosine-induced respiratory inhibition in anesthetized rats

1998 ◽  
Vol 84 (2) ◽  
pp. 417-424 ◽  
Author(s):  
Kevin Kwong ◽  
Ju-Lun Hong ◽  
Robert F. Morton ◽  
Lu-Yuan Lee
Keyword(s):  
Left Ventricular ◽  
Right Atrial ◽  
Dependent Manner ◽  
Sensory Afferents ◽  
C Fibers ◽  
Respiratory Inhibition ◽  
Anesthetized Rats ◽  
Long Latency ◽  
Therapeutic Doses

Kwong, Kevin, Ju-Lun Hong, Robert F. Morton, and Lu-Yuan Lee. Role of pulmonary C fibers in adenosine-induced respiratory inhibition in anesthetized rats. J. Appl. Physiol. 84(2): 417–424, 1998.—The clinical use of adenosine is commonly associated with pulmonary side effects, namely dyspnea, that suggest the possible involvement of bronchopulmonary sensory afferents. Our objective in this study was to characterize the effects of adenosine on breathing and to determine whether the vagal pulmonary afferents play a role in mediating these effects. We measured respiratory and cardiovascular changes in anesthetized, spontaneously breathing rats after bolus injections of adenosine at therapeutic doses. Right atrial injection of adenosine (0.04–0.6 mg/kg) elicits, in a dose-dependent manner, a pulmonary chemoreflex-like response consisting of a delayed apnea, bradycardia, and hypotension. In contrast, the classic capsaicin-elicited pulmonary chemoreflex occurs immediately after injection. Perineural capsaicin treatment of the cervical vagi blocked the adenosine-induced respiratory inhibition. Left ventricular administration of adenosine failed to elicit an apneic response. Pretreatment with the adenosine A1-receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine attenuated the adenosine-induced apnea. These results indicate that adenosine elicits a respiratory inhibition via stimulation of pulmonary C fibers and that activation of the A1-receptor is probably involved. It is unclear, however, what accounts for the exceedingly long latency in this response.

Alveolar hypercapnia augments pulmonary C-fiber responses to chemical stimulants: role of hydrogen ion

2002 ◽  
Vol 93 (1) ◽  
pp. 181-188 ◽  
Author(s):  
Qihai Gu ◽  
Lu-Yuan Lee
Keyword(s):  
Hydrogen Ion ◽  
Right Atrial ◽  
Mechanical Stimuli ◽  
Hydrogen Ions ◽  
Lung Inflation ◽  
C Fibers ◽  
Arterial Blood ◽  
Blood Ph ◽  
C Fiber

To determine whether the excitabilities of pulmonary C fibers to chemical and mechanical stimuli are altered by CO2-induced acidosis, single-unit pulmonary C-fiber activity was recorded in anesthetized, open-chest rats. Transient alveolar hypercapnia (HPC) was induced by administering CO2-enriched gas mixture (15% CO2, balance air) via the respirator inlet for 30 s, which rapidly lowered the arterial blood pH from a baseline of 7.40 ± 0.01 to 7.17 ± 0.02. Alveolar HPC markedly increased the responses of these C-fiber afferents to several chemical stimulants. For example, the C-fiber response to right atrial injection of the same dose of capsaicin (0.25–1.0 μg/kg) was significantly increased from 3.07 ± 0.70 impulses/s at control to 8.48 ± 1.52 impulses/s during HPC ( n = 27; P < 0.05), and this enhanced response returned to control within ∼10 min after termination of HPC. Similarly, alveolar HPC also induced significant increases in the C-fiber responses to right atrial injections of phenylbiguanide (4–8 μg/kg) and adenosine (0.2 mg/kg). In contrast, HPC did not change the response of pulmonary C fibers to lung inflation. Furthermore, the peak response of these C fibers to capsaicin during HPC was greatly attenuated when the HPC-induced acidosis was buffered by infusion of bicarbonate (1.36–1.82 mmol · kg−1 · min−1 for 35 s). In conclusion, alveolar HPC augments the responses of these afferents to various chemical stimulants, and this potentiating effect of CO2 is mediated through the action of hydrogen ions on the C-fiber sensory terminals.

scholarly journals Conditional MN1-TEL knock-in mice develop acute myeloid leukemia in conjunction with overexpression of HOXA9

Blood ◽  
2005 ◽  
Vol 106 (13) ◽  
pp. 4269-4277 ◽  
Author(s):  
Hiroyuki Kawagoe ◽  
Gerard C. Grosveld
Keyword(s):  
Acute Myeloid Leukemia ◽  
Myeloid Leukemia ◽  
Chromosomal Translocation ◽  
Lymphoid Cells ◽  
Dependent Manner ◽  
Myeloproliferative Disease ◽  
Long Latency ◽  
Acute Myeloid

The chromosomal translocation t(12; 22)(p13;q11) in human myeloid leukemia generates an MN1-TEL (meningioma 1-translocation-ETS-leukemia) fusion oncoprotein. This protein consists of N-terminal MN1 sequences, a transcriptional coactivator fused to C-terminal TEL sequences, an ETS (E26 transformation-specific) transcription factor. Enforced expression of MN1-TEL in multipotent hematopoietic progenitors in knock-in mice perturbed growth and differentiation of myeloid as well as lymphoid cells. Depending on obligatory secondary mutations, these mice developed T-cell lympholeukemia. Here we addressed the role of MN1-TEL in myeloid leukemogenesis using the same mouse model. Expression of MN1-TEL enhanced the growth of myeloid progenitors in an interleukin 3/stem cell factor (IL-3/SCF)–dependent manner in vitro whereas 10% of MN1-TEL–expressing mice developed altered myelopoiesis with severe anemia after long latency. Coexpression of MN1-TEL and IL-3, but not SCF, rapidly caused a fatal myeloproliferative disease rather than acute myeloid leukemia (AML). Because MN1-TEL+ AML patient cells overexpress HOXA9 (homeobox A9), we tested the effect of coexpression of MN1-TEL and HOXA9 in mice and found that 90% of MN1-TEL+/HOXA9+ mice developed AML much more rapidly than control HOXA9+ mice. Thus, the leukemogenic effect of MN1-TEL in our knock-in mice is pleiotropic, and the type of secondary mutation determines disease outcome.

scholarly journals Loss of Endothelial HIF-Prolyl hydroxylase 2 (PHD2) Induces Cardiac Hypertrophy and Fibrosis

2021 ◽  
Author(s):  
Zhiyu Dai ◽  
Jianding Cheng ◽  
Bin Liu ◽  
Dan Yi ◽  
Anlin Feng ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Cardiac Fibrosis ◽  
Left Ventricular ◽  
Dependent Manner ◽  
Adaptive Responses ◽  
Genetic Ablation ◽  
Pathological Cardiac Hypertrophy ◽  
And Function

Cardiac hypertrophy and fibrosis are common adaptive responses to injury and stress, eventually leading to heart failure. Hypoxia signaling is important to the (patho)physiological process of cardiac remodeling. However, the role of endothelial Prolyl-4 hydroxylase 2 (PHD2)/hypoxia inducible factors (HIFs) signaling in the pathogenesis of heart failure remains elusive. We observed a marked decrease of PHD2 expression in heart tissues and cardiovascular endothelial cells from patients with cardiomyopathy. Mice with Tie2-Cre-mediated deletion of Egln1 (encoding PHD2) or tamoxifen-induced endothelial Egln1 deletion exhibited left ventricular hypertrophy and cardiac fibrosis. Genetic ablation and pharmacological inhibition of Hif2a but not Hif1a in endothelial Egln1 deficient mice normalized cardiac size and function. The present studies define for the first time an unexpected role of endothelial PHD2 deficiency in inducing cardiac hypertrophy and fibrosis in a HIF-2α dependent manner. Targeting PHD2/HIF-2α signaling may represent a novel therapeutic approach for the treatment of pathological cardiac hypertrophy and failure.

Role of cardiac output in mediating arterial blood pressure oscillations

1996 ◽  
Vol 271 (3) ◽  
pp. R641-R646 ◽  
Author(s):  
D. S. O'Leary ◽  
D. J. Woodbury
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Low Frequency ◽  
Left Ventricular ◽  
Right Atrial ◽  
Total Power ◽  
Av Block ◽  
Arterial Blood ◽  
Low Frequency Oscillations

The objective of this study was to determine the role of cardiac output in mediating spontaneous fluctuations in mean arterial pressure (MAP) conscious dogs. Dogs were chronically instrumented to monitor MAP and cardiac output. Atrioventricular (AV) block was induced, and left ventricular and right atrial electrodes were implanted. After recovery, MAP was observed for 5 min under two conditions: 1) normal variation in heart rate and cardiac output via triggering the ventricular stimulator with each atrial depolarization (effectively reversing the AV block, AV-linked stimulation) and 2) computer control of ventricular rate to maintain cardiac output constant on a by-beat basis at the same level as observed during normal variations in heart rate and cardiac output. When cardiac output was held constant, large-amplitude, low-frequency oscillations in MAP were readily apparent. Spectral analysis by fast Fourier transform revealed that during constant cardiac output the power observed at low frequencies in the MAP spectrum represented 95.0 +/- 2.7% of the total power compared with 75.5 +/- 4.6% during normal variations in heart rate and cardiac output (P < 0.05). In addition, when cardiac output was held constant, the power observed at higher frequencies markedly decreased from 24.5 +/- 4.6% of total power during AV-linked stimulation to only 5.0 +/- 2.7% of total power during constant cardiac output (P < 0.05). We conclude that low-frequency oscillations in MAP are due to changes in peripheral resistance, whereas a significant amount of high-frequency changes in MAP stems from spontaneous changes in cardiac output.

Selected Contribution: Hypersensitivity of pulmonary C fibers induced by adenosine in anesthetized rats

2003 ◽  
Vol 95 (3) ◽  
pp. 1315-1324 ◽  
Author(s):  
Qihai Gu ◽  
Ting Ruan ◽  
Ju-Lun Hong ◽  
Nausherwan Burki ◽  
Lu-Yuan Lee
Keyword(s):  
Receptor Antagonist ◽  
Potential Role ◽  
Right Atrial ◽  
Adenosine Infusion ◽  
Lung Inflation ◽  
C Fibers ◽  
Baseline Activity ◽  
Tracheal Pressure ◽  
C Fiber

Compelling clinical evidence implicates the potential role of adenosine in development of airway hyperresponsiveness and suggests involvement of pulmonary sensory receptors. This study was carried out to determine the effect of a low dose of adenosine infusion on sensitivity of pulmonary C-fiber afferents in anesthetized open-chest rats. Infusion of adenosine (40 μg · kg-1 · min-1 iv for 90 s) mildly elevated baseline activity of pulmonary C fibers. However, during adenosine infusion, pulmonary C-fiber responses to chemical stimulants and lung inflation (30 cmH2O tracheal pressure) were markedly potentiated; e.g., the response to right atrial injection of capsaicin (0.25 or 0.5 μg/kg) was increased by more than fivefold (change in fiber activity = 2.64 ± 0.67 and 16.27 ± 3.11 impulses/s at control and during adenosine infusion, n = 13, P < 0.05), and this enhanced response returned to control in ∼10 min. The potentiating effect of adenosine infusion was completely blocked by pretreatment with 8-cyclopentyl-1,3-dipropylxanthine (100 μg/kg), a selective antagonist of the adenosine A1 receptor, but was not affected by 3,7-dimethyl-1-propargylxanthine (1 mg/kg), an A2-receptor antagonist, or 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(±)-dihydropyridine-3,5-dicarboxylate (2 mg/kg), an A3-receptor antagonist. This potentiating effect was also mimicked by N6-cyclopentyladenosine (0.25 μg·kg-1·min-1 for 90 s), a selective agonist of the adenosine A1 receptor. In conclusion, our results showed that infusion of adenosine significantly elevated the sensitivity of pulmonary C-fiber afferents in rat lungs and that this potentiating effect is likely mediated through activation of the adenosine A1 receptor.

Myocardial remodeling after discrete radiofrequency injury: effects of tissue inhibitor of matrix metalloproteinase-1 gene deletion

2004 ◽  
Vol 286 (4) ◽  
pp. H1242-H1247 ◽  
Author(s):  
Rupak Mukherjee ◽  
Andrea M. Parkhurst ◽  
Joseph T. Mingoia ◽  
Sarah E. Sweterlitsch ◽  
Jennifer S. Leiser ◽  
...  
Keyword(s):  
Gene Deletion ◽  
Left Ventricular ◽  
Time Dependent ◽  
Collagen Content ◽  
Dependent Manner ◽  
Myocardial Remodeling ◽  
Matrix Metalloproteinase 1 ◽  
Heart Mass ◽  
C 30

Discrete myocardial lesions created through the delivery of radiofrequency (RF) energy can expand; however, the mechanisms have not been established. Matrix metalloproteinases (MMPs) play an important role in myocardial remodeling, and MMP activity can be regulated by the tissue inhibitors of the metalloproteinases (TIMPs). This study examined the role of TIMP-1 in postinjury myocardial remodeling. Lesions were created on the left ventricular (LV) epicardium of wild-type (WT, 8–12 wk, 129SVE) and age-matched TIMP-1 gene-deficient ( timp-1–/–) mice through the delivery of RF current (80°C, 30 s). Heart mass, LV scar volumes, and collagen content were measured at 1 h and 3, 7, and 28 days postinjury ( n = 10 each). Age-matched, nonablated mice were used as reference controls ( n = 5). Heart mass indexed to tibial length increased in WT and timp-1–/– mice but was greater in the timp-1–/– mice by 7 days. Scar volumes increased in a time-dependent manner in both groups but were higher in the timp-1–/– mice than the WT mice at 7 days (1.48 ± 0.09 vs. 1.20 ± 0.11 mm3·mg–1·mm, P < 0.05) and remained higher at 28 days. In the remote myocardium, wall thickness was greater and relative collagen content was lower in the timp-1–/– mice at 28 days postinjury. Discrete myocardial RF lesions expand in a time-dependent manner associated with myocyte hypertrophy remote to the scar. Moreover, postinjury myocardial remodeling was more extensive with TIMP-1 gene deletion. Thus TIMP-1 either directly or through modulation of MMP activity may regulate myocardial remodeling following infliction of a discrete injury.

scholarly journals Loss of Endothelial Hypoxia Inducible Factor‐Prolyl Hydroxylase 2 Induces Cardiac Hypertrophy and Fibrosis

2021 ◽  
Author(s):  
Zhiyu Dai ◽  
Jianding Cheng ◽  
Bin Liu ◽  
Dan Yi ◽  
Anlin Feng ◽  
...  
Keyword(s):  
Heart Failure ◽  
Endothelial Cells ◽  
Left Ventricular Hypertrophy ◽  
Cardiac Hypertrophy ◽  
Ventricular Hypertrophy ◽  
Hypoxia Inducible Factor ◽  
Left Ventricular ◽  
Sequencing Analysis ◽  
Dependent Manner

Background Cardiac hypertrophy and fibrosis are common adaptive responses to injury and stress, eventually leading to heart failure. Hypoxia signaling is important to the (patho)physiological process of cardiac remodeling. However, the role of endothelial PHD2 (prolyl‐4 hydroxylase 2)/hypoxia inducible factor (HIF) signaling in the pathogenesis of cardiac hypertrophy and heart failure remains elusive. Methods and Results Mice with Egln1 Tie2Cre ( Tie2 ‐Cre‐mediated deletion of Egln1 [encoding PHD2]) exhibited left ventricular hypertrophy evident by increased thickness of anterior and posterior wall and left ventricular mass, as well as cardiac fibrosis. Tamoxifen‐induced endothelial Egln1 deletion in adult mice also induced left ventricular hypertrophy and fibrosis. Additionally, we observed a marked decrease of PHD2 expression in heart tissues and cardiovascular endothelial cells from patients with cardiomyopathy. Moreover, genetic ablation of Hif2a but not Hif1a in Egln1 Tie2Cre mice normalized cardiac size and function. RNA sequencing analysis also demonstrated HIF‐2α as a critical mediator of signaling related to cardiac hypertrophy and fibrosis. Pharmacological inhibition of HIF‐2α attenuated cardiac hypertrophy and fibrosis in Egln1 Tie2Cre mice. Conclusions The present study defines for the first time an unexpected role of endothelial PHD2 deficiency in inducing cardiac hypertrophy and fibrosis in an HIF‐2α–dependent manner. PHD2 was markedly decreased in cardiovascular endothelial cells in patients with cardiomyopathy. Thus, targeting PHD2/HIF‐2α signaling may represent a novel therapeutic approach for the treatment of pathological cardiac hypertrophy and failure.

Unravelling the impact of intrauterine growth restriction on heart development: insights into mitochondria and sexual dimorphism from a non-hominoid primate

2021 ◽  
Vol 135 (14) ◽  
pp. 1767-1772
Author(s):  
George W. Booz ◽  
Gaelle P. Massoud ◽  
Raffaele Altara ◽  
Fouad A. Zouein
Keyword(s):  
Heart Development ◽  
In Utero ◽  
Left Ventricular ◽  
Dependent Manner ◽  
Primate Model ◽  
Mitochondrial Ros ◽  
Mitochondrial Functions ◽  
Mitochondrial Transcripts ◽  
The Impact

Abstract Fetal exposure to an unfavorable intrauterine environment programs an individual to have a greater susceptibility later in life to non-communicable diseases, such as coronary heart disease, but the molecular processes are poorly understood. An article in Clinical Science recently reported novel details on the effects of maternal nutrient reduction (MNR) on fetal heart development using a primate model that is about 94% genetically similar to humans and is also mostly monotocous. MNR adversely impacted fetal left ventricular (LV) mitochondria in a sex-dependent fashion with a greater effect on male fetuses, although mitochondrial transcripts increased more so in females. Increased expression for several respiratory chain and adenosine triphosphate (ATP) synthase proteins were observed. However, fetal LV mitochondrial complex I and complex II/III activities were significantly decreased, likely contributing to a 73% decreased LV ATP content and increased LV lipid peroxidation. Moreover, MNR fetal LV mitochondria showed sparse and disarranged cristae. This study indicates that mitochondria are targets of the remodeling and imprinting processes in a sex-dependent manner. Mitochondrial ROS production and inadequate energy production add another layer of complexity. Altogether these observations raise the possibility that dysfunctional mitochondria in the fetus may contribute in turn to epigenetic memory of in utero stress in the adult. The role of mitoepigenetics and involvement of mitochondrial and genomic non-coding RNAs in mitochondrial functions and nuclei–mitochondria crosstalk with in utero stress awaits further investigation.

Ventricular tachyarrhythmias in rats with acute myocardial infarction involves activation of small-conductance Ca2+-activated K+ channels

2013 ◽  
Vol 304 (1) ◽  
pp. H118-H130 ◽  
Author(s):  
Le Gui ◽  
Zhiwei Bao ◽  
Yinyu Jia ◽  
Xiaotong Qin ◽  
Zixi (Jack) Cheng ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Channel Blocker ◽  
Left Ventricular ◽  
Dependent Manner ◽  
Ventricular Tachyarrhythmias ◽  
Sk Channels ◽  
Sk Channel ◽  
Small Conductance

In vitro experiments have shown that the upregulation of small-conductance Ca2+-activated K+ (SK) channels in ventricular epicardial myocytes is responsible for spontaneous ventricular fibrillation (VF) in failing ventricles. However, the role of SK channels in regulating VF has not yet been described in in vivo acute myocardial infarction (AMI) animals. The present study determined the role of SK channels in regulating spontaneous sustained ventricular tachycardia (SVT) and VF, the inducibility of ventricular tachyarrhythmias, and the effect of inhibition of SK channels on spontaneous SVT/VF and electrical ventricular instability in AMI rats. AMI was induced by ligation of the left anterior descending coronary artery in anesthetized rats. Spontaneous SVT/VF was analyzed, and programmed electrical stimulation was performed to evaluate the inducibility of ventricular tachyarrhythmias, ventricular effective refractory period (VERP), and VF threshold (VFT). In AMI, the duration and episodes of spontaneous SVT/VF were increased, and the inducibility of ventricular tachyarrhythmias was elevated. Pretreatment in the AMI group with the SK channel blocker apamin or UCL-1684 significantly reduced SVT/VF and inducibility of ventricular tachyarrhythmias ( P < 0.05). Various doses of apamin (7.5, 22.5, 37.5, and 75.0 μg/kg iv) inhibited SVT/VF and the inducibility of ventricular tachyarrhythmias in a dose-dependent manner. Notably, no effects were observed in sham-operated controls. Additionally, VERP was shortened in AMI animals. Pretreatment in AMI animals with the SK channel blocker significantly prolonged VERP ( P < 0.05). No effects were observed in sham-operated controls. Furthermore, VFT was reduced in AMI animals, and block of SK channels increased VFT in AMI animals, but, again, this was without effect in sham-operated controls. Finally, the monophasic action potential duration at 90% repolarization (MAPD90) was examined in the myocardial infarcted (MI) and nonmyocardial infarcted areas (NMI) of the left ventricular epicardium. Electrophysiology recordings showed that MAPD90 in the MI area was shortened in AMI animals, and pretreatment with SK channel blocker apamin or UCL-1684 significantly prolonged MAPD90 ( P < 0.05) in the MI area but was without effect in the NMI area or in sham-operated controls. We conclude that the activation of SK channels may underlie the mechanisms of spontaneous SVT/VF and suseptibility to ventricular tachyarrhythmias in AMI. Inhibition of SK channels normalized the shortening of MAPD90 in the MI area, which may contribute to the inhibitory effect on spontaneous SVT/VF and inducibility of ventricular tachyarrhythmias in AMI.

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