Vagal nerve modulation: A promising new therapeutic approach for cardiovascular diseases

Role of the autonomic nervous system in young, middle-aged, and older individuals with essential hypertension and sleep-related changes in neurocardiac regulation

Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep-wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep-wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30-79 years. They were stratified by age into young (< 40 years), middle-aged (40-59 years), and older (60-79 years) groups. Polysomnography and blood pressure data were recorded for 2 min before and during an hour-long nap. Autonomic function was assessed by measuring heart rate variability and blood pressure variability. Data were analyzed using t tests, correlation analyses, and two-way analysis of variance. During nonrapid eye movement (nREM), a main effect of age was observed on cardiac parasympathetic measures and baroreflex sensitivity (BRS), with the highest and lowest levels noted in the younger and older groups, respectively. The coefficients of the correlations between these measures and age were lower in patients with hypertension than in normotensive controls. The BRS of young patients with hypertension was similar to that of their middle-aged and older counterparts. However, cardiac sympathetic activity was significantly higher (p = 0.023) and BRS was significantly lower (p = 0.022) in the hypertension group than in the control group. During wakefulness, the results were similar although some of the above findings were absent. Autonomic imbalance, particularly impaired baroreflex, plays a more significant role in younger patients with hypertension. The nREM stage may be suitable for gaining insights into the relevant mechanisms.

Chronotropic Incompetence in Non-Hospitalized Patients with Post-COVID-19 Syndrome

Patients recovering from COVID-19 commonly report persistence of dyspnea, exertional fatigue, and difficulties in carrying out their daily activities. However, the nature of these symptoms is still unknown. The purpose of the study was to identify limiting causes of cardiopulmonary origin for the performance of physical exercise in post-COVID-19 condition that could explain the symptomatic persistence of dyspnea or fatigue-related symptoms. Thirty-two non-hospitalized patients with post-COVID-19 condition (i.e., still presenting a chronic symptomatic phase lasting >90 days since debut of symptoms that lasted for at least 2 months and cannot be explained by an alternative diagnosis) completed a clinical examination including echocardiography, submaximal and maximal cardiorespiratory fitness tests (Ekblom-Bak and Bruce’s protocols), and a battery of validated questionnaires about fatigue and exercise intolerance. Four participants (12.5%) reported an abnormal cardiac response to exercise during the submaximal test, which aroused suspicion of the presence of chronotropic incompetence. All of them were confirmed with a positive diagnosis maximal exercise test after cardiology screening, even with a comprehensive clinical examination, resting ECG, and echocardiogram, without other findings. No statistical differences were found in any physiological variables or questionnaire values, between patients with positive and negative diagnoses. Chronotropic incompetence and other autonomic disorders may appear in patients with mild forms of COVID-19 presentation and may persist in the long term, being responsible for exercise intolerance after resolution of acute infection. Clinicians should be aware that chronotropic incompetence and other autonomic disorders may be a complication of COVID-19 and should consider appropriate diagnostic and therapeutic interventions in these patients, especially when early exercise-related fatigability is reported.

Theophylline in Treatment of COVID-19 Induced Sinus Bradycardia

This is a retrospective case series of two patients with laboratory-confirmed coronavirus 2 (SARS-CoV-2) infection, presented to the University of Arkansas for Medical Sciences in January 2021. Medical records of these patients were reviewed using the EPIC electronic health record system. Clinical, laboratory, and treatment data were reviewed against periods of bradycardia in each patient. Both of the patients presented with dizziness and presyncope related to sinus bradycardia in which they received treatment with 1 mg of IV atropine and theophylline 200 mg orally. We share these two cases of theophylline treatment in COVID-19 induced sinus bradycardia. The first patient was a 39-year-old female, with a past medical history of polycystic ovarian syndrome, who presented to the emergency department with lightheadedness and dizziness. Two weeks prior to her presentation, she was tested positive for COVID-19 infection that was treated with azithromycin, dexamethasone and aspirin. Upon presentation, her ECG showed sinus bradycardia at a rate of 48 bpm. The second patient, a 21-year-old female with no significant past medical history, presented with presyncope. Three weeks prior to her presentation, she tested positive for COVID-19 infection that was treated symptomatically at her home. Upon presentation, her ECG showed junctional rhythm at a heart rate of 51 bpm.

Impact of Peripheral α7-Nicotinic Acetylcholine Receptors on Cardioprotective Effects of Donepezil in Chronic Heart Failure Rats

PURPOSE

Pharmacological modulation of parasympathetic activity with donepezil, an acetylcholinesterase inhibitor, improves the long-term survival of rats with chronic heart failure (CHF) after myocardial infarction (MI). However, its mechanism is not well understood. The α7-nicotinic acetylcholine receptor (α7-nAChR) reportedly plays an important role in the cholinergic anti-inflammatory pathway. The purpose of this study was to examine whether blockade of α7-nAChR, either centrally or peripherally, affects cardioprotection by donepezil during CHF.

METHODS

One-week post-MI, the surviving rats were implanted with an electrocardiogram or blood pressure transmitter to monitor hemodynamics continuously. Seven days after implantation, the MI rats (n = 74) were administered donepezil in drinking water or were untreated (UT). Donepezil-treated MI rats were randomly assigned to the following four groups: peripheral infusion of saline (SPDT) or an α7-nAChR antagonist methyllycaconitine (α7PDT), and brain infusion of saline (SBDT) or the α7-nAChR antagonist (α7BDT).

RESULTS

After the 4-week treatment, the role of α7-nAChR was evaluated using hemodynamic parameters, neurohumoral states, and histological and morphological assessment. Between the peripheral infusion groups, α7PDT (vs. SPDT) showed significantly increased heart weight and cardiac fibrosis, deteriorated hemodynamics, increased plasma neurohumoral and cytokine levels, and significantly decreased microvessel density (as assessed by anti-von Willebrand factor-positive cells). In contrast, between the brain infusion groups, α7BDT (vs. SBDT) showed no changes in either cardiac remodeling or hemodynamics.

CONCLUSION

Peripheral blockade of α7-nAChR significantly attenuated the cardioprotective effects of donepezil in CHF rats, whereas central blockade did not. This suggests that peripheral activation of α7-nAChR plays an important role in cholinergic pharmacotherapy for CHF.

Vagus Nerve Stimulation Attenuates Multiple Organ Dysfunction in Resuscitated Porcine Progressive Sepsis

OBJECTIVES

To investigate the potential benefits of vagus nerve stimulation in a clinically-relevant large animal model of progressive sepsis.

DESIGN

Prospective, controlled, randomized trial.

SETTING

University animal research laboratory.

SUBJECTS

Twenty-five domestic pigs were divided into three groups: 1) sepsis group (eight pigs), 2) sepsis + vagus nerve stimulation group (nine pigs), and 3) control sham group (eight pigs).

INTERVENTIONS

Sepsis was induced by cultivated autologous feces inoculation in anesthetized, mechanically ventilated, and surgically instrumented pigs and followed for 24 hours. Electrical stimulation of the cervical vagus nerve was initiated 6 hours after the induction of peritonitis and maintained throughout the experiment.

MEASUREMENTS AND MAIN RESULTS

Measurements of hemodynamics, electrocardiography, biochemistry, blood gases, cytokines, and blood cells were collected at baseline (just before peritonitis induction) and at the end of the in vivo experiment (24 hr after peritonitis induction). Subsequent in vitro analyses addressed cardiac contractility and calcium handling in isolated tissues and myocytes and analyzed mitochondrial function by ultrasensitive oxygraphy. Vagus nerve stimulation partially or completely prevented the development of hyperlactatemia, hyperdynamic circulation, cellular myocardial depression, shift in sympathovagal balance toward sympathetic dominance, and cardiac mitochondrial dysfunction, and reduced the number of activated monocytes. Sequential Organ Failure Assessment scores and vasopressor requirements significantly decreased after vagus nerve stimulation.

CONCLUSIONS

In a clinically-relevant large animal model of progressive sepsis, vagus nerve stimulation was associated with a number of beneficial effects that resulted in significantly attenuated multiple organ dysfunction and reduced vasopressor and fluid resuscitation requirements. This suggests that vagus nerve stimulation might provide a significant therapeutic potential that warrants further thorough investigation.

Vanillylmandelic acid protects against reperfusion injury in an experimental animal model of myocardial infarction

Vanillylmandelic acid, a catecholamine end-metabolite, has been shown to have several biological properties in previous studies, despite considered biologically inactive. We examined the potential effects of vanillylmandelic acid on the ischemic heart following myocardial infarction and reperfusion on a rat model. Thirty-four female Wistar rats were randomized into two groups, control and experimental. They were anesthetized and subjected to myocardial infarction through left anterior descending artery ligation. A previously studied dose of vanillylmandelic acid (10 mg/kg) was administered and the following parameters were studied during ischemia and reperfusion: a) mortality b) severity of ventricular tachyarrhythmias c) premature ventricular contractions and d) heart rate. Administration of vanillymandelic acid significantly reduced the severity of ventricular tachyarrhythmias and mortality rate during reperfusion, while it did not affect any other of the parameters studied. In conclusion, reperfusion injury was blunted through vanillylmandelic acid administration, which seems to be mediated by parasympathetic activation.

Effect of vagus nerve stimulation on tissue damage and function loss in a mouse myocardial ischemia-reperfusion model

OBJECTIVES

In cardiac ischemia, acute inflammatory responses further increase the detrimental effect on myocardial tissue. Since vagus nerve stimulation (VS) attenuates inflammatory responsiveness this study examines the effect of VS on myocardial damage development in a cardiac ischemia-reperfusion (IR) mouse model.

METHODS

54 male C57Bl/6j mice were subjected to an IR procedure with or without prior VS. The effects on inflammatory responsiveness, infarct size, cardiac function, neutrophils, lymphocytes and vascular endothelial growth factor (VEGF) in the infarcted myocardium were measured at 48 h after intervention. Group results were compared with unpaired Mann-Whitney or Kruskall-Wallis test.

RESULTS

A significant decrease in inflammatory responsiveness was not verified by decreased TNFα levels in blood from VS and IR treated mice. The percentage infarct size over area at risk was smaller in the group with VS + IR compared with IR (22.4 ± 10.2% vs 37.6 ± 9.0%, p = 0.003). The degree of the reduction in cardiac function was not different between the IR groups with or without VS and no group differences were found in amounts of neutrophils, CD3+ lymphocytes and VEGF in the reperfused mouse heart.

CONCLUSION

The present study does not provide clear evidence of a reducing role for VS on cardiac function loss. This could mean that VS has a less inhibiting effect on myocardial inflammation than may be expected from the literature.

Relationship between diabetes mellitus and heart rate variability in community-dwelling elders

BACKGROUND AND OBJECTIVE

Diabetes mellitus is one of the most common non-communicable diseases (NCDs) and may influence the autonomic nervous system. This study aims to analyze the autonomic control, through heart rate variability (HRV), from community-dwelling elders with (DM+) and without diabetes mellitus (DM-).

MATERIALS AND METHODS

This cross-sectional study, in which 205 elders (≥ 60 years old), from the urban area of Aiquara municipality gave their written consent to participate. HRV data was collected through a Polar RS800CX monitor with a 5-min initial record at rest, followed by the command to quickly stand up.

RESULTS

The mean age was 71 years (SD, 7.32). The population was mostly made up of women 121 (59%), with low or no schooling 123 (60%), and low income 166 (81%). HRV analysis in a frequency domain showed no difference when comparing the two groups of DM+ and DM-. Henceforth in a time domain, the rMSSD showed a median value of 16.09 (interquartile range, 9.91-30.68); pNN50 median of 0.79 (interquartile range, 0.00-6.62), with a statistical significance between the group of DM+ and DM-.

CONCLUSIONS

There is a difference between the studied groups principally in what concerns the time domain, which reflects the parasympathetic activity, suggesting that elders with diabetes mellitus may have a worse parasympathetic control.

Prospectively predicting PTSD status with heart rate reactivity and recovery in interpersonal violence survivors

The current study used heart rate (HR) reactivity to personalized trauma cues and HR recovery to predict later Posttraumatic Stress Disorder (PTSD) status in female interpersonal violence survivors. A scripted imagery paradigm was used to assess initial (M = 1 month posttrauma) HR reactivity during exposure to and recovery following idiographic trauma cues. In addition, follow-up PTSD status (M = 8 months posttrauma) was assessed with the Clinician Administered PTSD scale (CAPS). A logistic regression was used to predict PTSD status at the follow-up assessment with HR reactivity during exposure to a personalized trauma audio script and recovery periods at initial assessment entered hierarchically. Script HR reactivity alone did not significantly predict PTSD status. However, after adding HR recovery, the model was significant. Higher HR during recovery was significantly positively associated with PTSD-positive status while script HR reactivity remained a non-significant predictor. The model correctly classified 70% of cases with PTSD. A second logistic regression with initial CAPS severity as a covariate showed that HR recovery added predictive value beyond acute PTSD symptoms. These results suggest that HR recovery following trauma cue exposure is an important predictor of PTSD development.

Vagus nerve stimulation attenuates myocardial ischemia/reperfusion injury by inhibiting the expression of interleukin-17A

Interleukin (IL)-17A has an important role in myocardial ischemia/reperfusion (I/R) injury, and vagal stimulation (VS) has been demonstrated to exert cardioprotective effects. The present study aimed to investigate the effects of VS on a rat model of myocardial I/R injury, and detected an association between VS and IL-17A. Anesthetized rats underwent VS (2 msec; 10 Hz) or were treated with anti-IL-17A neutralized monoclonal antibodies (mAbs) (200 µg; iv), and subjected to ischemia for 30 min prior to 4 h reperfusion. The following parameters were measured: Infarct size; lactate dehydrogenase (LDH), creatine kinase (CK), malondialdehyde (MDA), superoxide dismutase (SOD) and caspase-3 activity levels; tumor necrosis factor (TNF)-α and IL-6 expression levels; and the percentage of terminal deoxynucleotidyl-transferase mediated dUTP nick-end labeling (TUNEL) positive cells. High mobility group box 1 protein (HMGB1) and IL-17A expression levels were assessed by immunoblotting. Following 4 h reperfusion, VS was able to significantly decrease the infarct size and the activity levels of LDH and CK (P<0.05). Furthermore, VS administration significantly suppressed the increased MDA and decreased SOD activity levels, and significantly reduced caspase-3 activity and the percentage of TUNEL-positive cells (P<0.05). Treatment with anti-IL-17A mAbs demonstrated the same effects as VS. Furthermore, VS was able to significantly inhibit the increased expression levels of TNF-α, IL-6, HMGB1 and IL-17A induced by I/R (P<0.05). The results of the present study suggested that VS may attenuate myocardial I/R injury by reducing the expression of inflammatory cytokines, oxidative stress and the apoptosis of cardiomyocytes. Furthermore, VS may induce cardioprotective effects, which may be associated with the inhibition of IL-17A expression.

Premature aging in chronic kidney disease and chronic obstructive pulmonary disease: similarities and differences

PURPOSE OF REVIEW

There is increasing clinical and pathophysiological evidence that a premature aging process is involved in the pathogenesis of systemic complications of many chronic organ diseases, which result in analogous phenotypes, including premature vascular aging, osteoporosis and muscle wasting. Novel developments from research into the aging process will, therefore, have relevance for understanding complications of organ diseases, such as chronic kidney disease and chronic obstructive pulmonary disease. The aim of the present article is to combine recent literature on aging mechanisms with evidence on the pathogenesis of systemic complications of these two chronic debilitating disorders.

RECENT FINDINGS

Recently, nine hallmarks of aging have been identified. In this review, we argue that all of these hallmarks are relevant for the pathogenesis of premature aging processes in chronic obstructive pulmonary disease and chronic kidney disease. Additionally, organ-specific alterations in proaging mechanisms, which reveal differences in phenotype against a generic background of premature aging, will be addressed. However, within patient populations who share a common diagnosis, clusters of patients with different phenotypes may be identified, which may show overlap with patients with other chronic diseases.

SUMMARY

An increased understanding of the premature aging process as well as its systemic consequences may pave the way for 'precision' intervention as well as shared treatment opportunities between chronic debilitating diseases of various causes.

Vagal nerve stimulation activates vagal afferent fibers that reduce cardiac efferent parasympathetic effects

Vagal nerve stimulation (VNS) has been shown to have antiarrhythmic effects, but many of these benefits were demonstrated in the setting of vagal nerve decentralization. The purpose of this study was to evaluate the role of afferent fiber activation during VNS on efferent control of cardiac hemodynamic and electrophysiological parameters. In 37 pigs a 56-electrode sock was placed over the ventricles to record local activation recovery intervals (ARIs), a surrogate of action potential duration. In 12 of 37 animals atropine was given systemically. Right and left VNS were performed under six conditions: both vagal trunks intact (n = 25), ipsilateral right (n = 11), ipsilateral left (n = 14), contralateral right (n = 7), contralateral left (n = 10), and bilateral (n = 25) vagal nerve transection (VNTx). Unilateral VNTx significantly affected heart rate, PR interval, Tau, and global ARIs. Right VNS after ipsilateral VNTx had augmented effects on hemodynamic parameters and increase in ARI, while subsequent bilateral VNTx did not significantly modify this effect (%change in ARI in intact condition 2.2 ± 0.9% vs. ipsilateral VNTx 5.3 ± 1.7% and bilateral VNTx 5.3 ± 0.8%, P < 0.05). Left VNS after left VNTx tended to increase its effects on hemodynamics and ARI response (P = 0.07), but only after bilateral VNTx did these changes reach significance (intact 1.1 ± 0.5% vs. ipsilateral VNTx 3.6 ± 0.7% and bilateral VNTx 6.6 ± 1.6%, P < 0.05 vs. intact). Contralateral VNTx did not modify VNS response. The effect of atropine on ventricular ARI was similar to bilateral VNTx. We found that VNS activates afferent fibers in the ipsilateral vagal nerve, which reflexively inhibit cardiac parasympathetic efferent electrophysiological and hemodynamic effects.

Reduction of Mitochondria–Endoplasmic Reticulum Interactions by Acetylcholine Protects Human Umbilical Vein Endothelial Cells From Hypoxia/Reoxygenation Injury

Objective—

We explored the role of endoplasmic reticulum (ER)–mitochondria Ca 2+ cross talk involving voltage-dependent anion channel-1 (VDAC1)/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex and mitofusin 2 in endothelial cells during hypoxia/reoxygenation (H/R), and investigated the protective effects of acetylcholine.

Approach and Results—

Acetylcholine treatment during reoxygenation prevented intracellular and mitochondrial Ca 2+ increases and alleviated ER Ca 2+ depletion during H/R in human umbilical vein endothelial cells. Consequently, acetylcholine enhanced mitochondrial membrane potential and inhibited proapoptotic cascades, thereby reducing cell death and preserving endothelial ultrastructure. This effect was likely mediated by the type-3 muscarinic acetylcholine receptor and the phosphatidylinositol 3-kinase/Akt pathway. In addition, interactions among members of the VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex were increased after H/R and were associated with mitochondrial Ca 2+ overload and cell death. Inhibition of the partner of the Ca 2+ channeling complex (VDAC1 siRNA) or a reduction in ER–mitochondria tethering (mitofusin 2 siRNA) prevented the increased protein interaction within the complex and reduced mitochondrial Ca 2+ accumulation and subsequent endothelial cell death after H/R. Intriguingly, acetylcholine could modulate ER–mitochondria Ca 2+ cross talk by inhibiting the VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex and mitofusin 2 expression. Phosphatidylinositol 3-kinase siRNA diminished acetylcholine-mediated inhibition of mitochondrial Ca 2+ overload and VDAC1/glucose-regulated protein 75/inositol 1,4,5-trisphosphate receptor 1 complex formation induced by H/R.

Conclusions—

Our data suggest that ER–mitochondria interplay plays an important role in reperfusion injury in the endothelium and may be a novel molecular target for endothelial protection. Acetylcholine attenuates both intracellular and mitochondrial Ca 2+ overload and protects endothelial cells from H/R injury, presumably by disrupting the ER–mitochondria interaction.

Assessment of brainstem function with auricular branch of vagus nerve stimulation in Parkinson's disease

Background

The efferent dorsal motor nucleus of the vagal nuclei complex may degenerate early in the course of Parkinson’s disease (PD), while efferent nucleus ambiguous, the principal source of parasympathetic vagal neurons innervating the heart, and afferent somatosensory nuclei remain intact.

Objective

To obtain neurophysiological evidence related to this pattern, we tested processing of afferent sensory information transmitted via the auricular branch of the vagus nerve (ABVN) which is known to be connected to autonomic regulation of cardiac rhythm.

Methods

In this cross-sectional observational study, we recorded (i) somatosensory evoked potentials (ABVN-SEP) and (ii) cutaneo-cardioautonomic response elicited by stimulation of the ABVN (modulation of heart-rate variability (HRV index; low frequency power, ln(LF), high frequency power, ln(HF); ln(LF/HF) ratio)) in 50 PD patients and 50 age and sex matched healthy controls. Additionally, auditory evoked potentials and trigeminal nerve SEP were assessed.

Results

Neither ABVN-SEP nor any of the other functional brainstem parameters differed between patients and controls. Although HRV index was decreased in PD patients, modulation of ln(LF/HF) by ABVN-stimulation, likely indicating cardiac parasympathetic activation, did not differ between both groups.

Conclusions

Findings do not point to prominent dysfunction of processing afferent information from ABVN and its connected parasympathetic cardiac pathway in PD. They are consistent with the known pattern of degeneration of the vagal nuclei complex of the brainstem.

Cardioprotection and anticholinesterases in patients with Alzheimer's disease: time for reappraisal

Background/Aim

Traditional risk factors, like impaired transmitral flow in diastolic filling [vortex formation time (VFT) as echocardiographic parameter], contribute to Alzheimer's disease (AD). Moreover, we observed that acetylcholinesterase inhibitors provide a significant cardioprotection. We assessed the pathogenetic role of VFT as early cardiovascular risk factor in 23 AD patients and 24 controls.

Results

The results showed no statistical difference between the two groups, but the VFT values were significantly lower in nontreated AD patients, and higher value were observed in AD patients treated with anticholinesterases.

Conclusions

The results support the beneficial effects of anticholinesterases on the cardiovascular system of AD patients. Thus, the transition to evidence-based medicine and an in vivo model of cardiomyocytes might strengthen these results.

Role of endothelial nitric oxide synthase and vagal activity in the endothelial protection of atorvastatin in ischemia/reperfusion injury

Vascular endothelial dysfunction plays a pivotal role in the development and maintenance of ischemia/reperfusion (I/R) injury. Statins, developed as lipid-lowering drugs, partially restore vagal activity and exhibit pleiotropic effects. This study was aimed at determining the effect of atorvastatin (ATV) on endothelial dysfunction in peripheral resistance arteries after I/R injury. After pretreatment with ATV (10 mg·kg·d) or its vehicle for 3 days, the superior mesenteric artery was occluded for 60 minutes and reperfusion for 90 minutes or the rats were anesthetized without being subjected to ischemia. In the ATV-treated I/R group, the increased contractions to KCl and 5-hydroxytryptamine induced by I/R were ameliorated, and attenuated endothelium-dependent relaxations to acetylcholine (ACh) were normalized. The restored relaxation to ACh was abolished by N-nitro-L-arginine methyl ester. ATV prevented the structural damage of vascular endothelial cells. Furthermore, the activities of phosphatidylinositol-3-kinase, Akt, and endothelial nitric oxide synthase were elevated in mesenteric arteries after ATV treatment. In addition, I/R-induced increment of endothelial cells apoptosis was also attenuated by ATV. Intriguingly, ATV also increased baroreflex sensitivity and serum ACh content after I/R. In conclusion, the endothelial protective effect of ATV in peripheral arteries is associated with the activated phosphatidylinositol-3-kinase/Akt/endothelial nitric oxide synthase pathway and restored vagal activity.

Low-amplitude, left vagus nerve stimulation significantly attenuates ventricular dysfunction and infarct size through prevention of mitochondrial dysfunction during acute ischemia-reperfusion injury

BACKGROUND

Right cervical vagus nerve stimulation (VNS) provides cardioprotective effects against acute ischemia-reperfusion injury in small animals. However, inconsistent findings have been reported.

OBJECTIVE

To determine whether low-amplitude, left cervical VNS applied either intermittently or continuously imparts cardioprotection against acute ischemia-reperfusion injury.

METHODS

Thirty-two isoflurane-anesthetized swine (25-30 kg) were randomized into 4 groups: control (sham operated, no VNS), continuous-VNS (C-VNS; 3.5 mA, 20 Hz), intermittent-VNS (I-VNS; continuously recurring cycles of 21-second ON, 30-second OFF), and I-VNS + atropine (1 mg/kg). Left cervical VNS was applied immediately after left anterior descending artery occlusion (60 minutes) and continued until the end of reperfusion (120 minutes). The ischemic and nonischemic myocardium was harvested for cardiac mitochondrial function assessment.

RESULTS

VNS significantly reduced infarct size, improved ventricular function, decreased ventricular fibrillation episodes, and attenuated cardiac mitochondrial reactive oxygen species production, depolarization, and swelling, compared with the control group. However, I-VNS produced the most profound cardioprotective effects, particularly infarct size reduction and decreased ventricular fibrillation episodes, compared to both I-VNS + atropine and C-VNS. These beneficial effects of VNS were abolished by atropine.

CONCLUSIONS

During ischemia-reperfusion injury, both C-VNS and I-VNS provide significant cardioprotective effects compared with I-VNS + atropine. These beneficial effects were abolished by muscarinic blockade, suggesting the importance of muscarinic receptor modulation during VNS. The protective effects of VNS could be due to its protection of mitochondrial function during ischemia-reperfusion.

Enalaprilat increases PPARβ/δ expression, without influence on PPARα and PPARγ, and modulate cardiac function in sub-acute model of daunorubicin-induced cardiomyopathy

Anthracycline therapy is limited by a cardiotoxicity that may eventually lead to chronic heart failure which is thought to be prevented by ACE inhibitors (ACEi). However, the protective effect of ACEi in early stages of this specific injury remains elusive. Activated nuclear transcription factors peroxisome proliferator-activated receptors (PPAR) regulate cellular metabolism, but their involvement in anthracycline cardiomyopathy has not been investigated yet. For this purpose, Wistar rats were administered with daunorubicin (i.p., 3 mg/kg, in 48 h intervals) or co-administered with daunorubicine and enalaprilat (i.p., 5 mg/kg in 12 h intervals). Control animals received vehicle. Left ventricular function was measured invasively under anesthesia. Cell-shortening was measured by videomicroscopy in isolated cardiomyocytes. Expression of PPARs mRNA in cardiac tissue was measured by Real-Time PCR. Although the hemodynamic parameters of daunorubicin-treated rats remained altered upon ACEi co-administration, ACEi normalized daunorubicin-induced QT prolongation. On cellular level, ACEi normalized altered basal and isoproterenol-stimulated cardiac cell shortening in daunorubicine-treated group. Moreover, anthracycline administration significantly up-regulated heart PPARα mRNA and its expression remained increased after ACEi co-administration. On the other hand, the expression of cardiac PPARβ/δ was not altered in anthracycline-treated animals, whereas co-administration of ACEi increased its expression. Conclusively, effect of ACEi can be already detected in sub-acute phase of anthracycline-induced cardiotoxicity. Altered expression of heart PPARs may suggest these nuclear receptors as a novel target in anthracycline cardiomyopathy.

Cardiovascular dysfunctions and sympathovagal imbalance in hypertension and prehypertension: physiological perspectives

Hypertension (HTN) and prehypertension (pre-HTN) have been identified as independent risk factors for adverse cardiovascular events. Recently, increased psychosocial stress and work stress have contributed to the increased prevalence of HTN and pre-HTN, in addition to the contribution of obesity, diabetes, poor food habits and physical inactivity. Irrespective of the etiology, sympathetic overactivity has been recognized as the main pathophysiologic mechanism in the genesis of HTN and pre-HTN. Sympathovagal imbalance owing to sympathetic overactivity and vagal withdrawal is reported to be the basis of many clinical disorders. However, the role played by vagal withdrawal has been under-reported. In this review, we have analyzed the pathophysiologic involvement of sympathovagal imbalance in the development of HTN and pre-HTN, and the link of sympathovagal imbalance to cardiovascular dysfunctions. We have emphasized that adaptation to a healthier lifestyle will help improve sympathovagal homeostasis and prevent the occurrence of HTN and pre-HTN.

Acoustically evoked immediate early gene expression in the pallium of female túngara frogs

In anurans, much is known about the role of the auditory midbrain in processing conspecific calls, but comparatively little is known about the role of the pallium. To address this deficiency, we investigated the induction of the immediate early gene egr-1 by natural mate chorus in the medial, dorsal, lateral, and ventral pallium of female túngara frogs. We found strong acoustically evoked egr-1 expression in the dorsal medial pallium (p < 0.01) and ventral pallium (p = 0.02), with a weaker effect in the lateral pallium (p = 0.05). In the ventral pallium, acoustically induced egr-1 expression was stronger in the anterior portion. Measures of movement and olfactory activity could not explain a significant portion of acoustically evoked pallial egr-1 expression. In contrast, egr-1 expression in the auditory midbrain covaried with egr-1 expression in the dorsal medial pallium and ventral pallium, suggesting that their activity was coupled with auditory activity. Taken together, these results suggest that the acoustically evoked egr-1 expression in the dorsal medial pallium and ventral pallium were a direct result of auditory stimulation. Furthermore, although both anatomical and electrophysiological evidence demonstrate that multiple modalities overlap in the frog pallium, our results show that a multimodal stimulus is not required to activate pallial neurons. Although the functional role of the frog pallium is not known, our results demonstrate that species-specific sounds activate spatially segregated and anatomically distinct areas of the frog pallium, inviting further investigation into the role of the frog pallium in acoustic communication.