Cholinergic stimulation improves autonomic and hemodynamic profile during dynamic exercise in patients with heart failure

Effect of olfactory stimulation from aromatherapy on the autonomic nervous activity during aerobic exercises

Variations in the autonomic nervous system activity during exercise therapy in patients with cardiovascular diseases may lead to adverse events. Aromatherapy may reduce these adverse events by enhancing parasympathetic nervous activity (PNA). However, the effects of aromatherapy during exercise remain relatively unknown. This study aimed to evaluate the effect of aromatherapy on autonomic nervous activity during exercise and recovery. This randomized crossover study included 20 healthy men subjected to both aroma and placebo conditions which involved rest and moderate-intensity aerobic exercise on a cycle ergometer, followed by recovery. Blood pressure, heart rate variability indices, and SpO2 were measured during the rest, exercise, and recovery phases. Moreover, aroma preferences and emotional changes in response to the aroma were assessed. Under the placebo condition, high frequency (HF), root mean square of successive differences indices, and heart rate showed delayed recovery (P < 0.05). Furthermore, a moderate positive correlation was identified between aroma preference, pleasant emotions induced by aromatherapy, and the HF index (P < 0.05). These results indicate that aromatherapy facilitates the recovery of PNA after exercise. Furthermore, these effects were more pronounced among individuals who exhibited a stronger preference for and more positive emotions toward aromas.

Cholinesterase inhibitors associated with lower rate of mortality in dementia patients with heart failure: a nationwide propensity weighting study

PURPOSE

This study investigates the potential impact of cholinesterase inhibitors (ChEIs) on patients with heart failure (HF) and dementia. ChEIs are known to boost acetylcholine levels and benefit cognition in patients with dementia; however, their effect on patients with HF is uncertain. This study aimed to assess whether cardiovascular events and mortality among patients with HF and dementia are altered by ChEI therapy.

METHODS

Data from the National Health Insurance Research Database in Taiwan were retrospectively analyzed. Dementia patients diagnosed with HF were followed for 5 years until all-cause mortality, cardiovascular mortality, hospitalization for worsening HF, or the end of the study. Multivariable Cox models and inverse probability of treatment weighting (IPTW) were employed.

RESULTS

Out of 20,848 patients with dementia, 5138 had HF. Among them, 726 were ChEI users and 4412 were non-users. Based on IPTW, the ChEI users had significantly lower estimated risks of all-cause mortality [hazard ratio (HR) 0.43; 95% confidence interval (CI) 0.38-0.49, p < 0.001] and cardiovascular mortality (HR 0.41; 95% CI 0.33-0.53, p < 0.001) compared with the non-users, but there was no significant difference in hospitalization for worsening HF (HR 0.73; 95% CI 0.51-1.05, p = 0.091) after 5 years. The survival benefits of ChEIs were consistent across subgroups.

CONCLUSIONS

The results of this retrospective cohort study suggest that ChEIs may be beneficial in reducing all-cause and cardiovascular mortality in patients with dementia with HF. Further research is needed to validate these findings and explore the potential benefits of ChEIs in all patients with HF, including those without dementia.

Association Between Cholinesterase Inhibitors and New-Onset Heart Failure in Patients With Alzheimer's Disease: A Nationwide Propensity Score Matching Study

Background

Autonomic nervous dysfunction is a shared clinical feature in Alzheimer's disease (AD) and heart failure (HF). Cholinesterase inhibitors (ChEIs) are widely used autonomic modulators in patients with AD, but their primary preventive benefit on new-onset HF is still uncertain.

Objective

This study examined whether ChEIs have a primary preventive effect on new-onset HF in patients with AD.

Methods

This propensity score matching (PSM) study was conducted using data from the National Health Insurance Research Database of Taiwan for 1995 to 2017. Certificated patients with AD and without a history of HF were divided into ChEI (donepezil, rivastigmine, or galantamine) users or nonusers. The primary endpoint was new-onset HF, and the secondary endpoints were myocardial infarction and cardiovascular death after 10-year follow-up.

Results

After screening 16,042 patients, 7,411 patients were enrolled, of whom 668 were ChEI users and 1,336 were nonusers after 1:2 PSM. Compared with nonusers, ChEI users exhibited a significantly lower incidence of new-onset HF (HR 0.48; 95% CI 0.34–0.68, p < 0.001) and cardiovascular death (HR 0.55; 95% CI 0.37–0.82, p = 0.003) but not of myocardial infarction (HR 1.09; 95% CI 0.52–1.62, p = 0.821) after 10-year follow-up. The preventive benefit of ChEI use compared with Non-use (controls) was consistent across all exploratory subgroups without statistically significant treatment-by-subgroup interactions.

Conclusions

Prescription of ChEIs may provide a preventive benefit associated with lower incidence of new-onset HF in patients with AD after 10-year follow-up.

Benefits of pharmacological and electrical cholinergic stimulation in hypertension and heart failure

Systemic arterial hypertension and heart failure are cardiovascular diseases that affect millions of individuals worldwide. They are characterized by a change in the autonomic nervous system balance, highlighted by an increase in sympathetic activity associated with a decrease in parasympathetic activity. Most therapeutic approaches seek to treat these diseases by medications that attenuate sympathetic activity. However, there is a growing number of studies demonstrating that the improvement of parasympathetic function, by means of pharmacological or electrical stimulation, can be an effective tool for the treatment of these cardiovascular diseases. Therefore, this review aims to describe the advances reported by experimental and clinical studies that addressed the potential of cholinergic stimulation to prevent autonomic and cardiovascular imbalance in hypertension and heart failure. Overall, the published data reviewed demonstrate that the use of central or peripheral acetylcholinesterase inhibitors is efficient to improve the autonomic imbalance and hemodynamic changes observed in heart failure and hypertension. Of note, the baroreflex and the vagus nerve activation have been shown to be safe and effective approaches to be used as an alternative treatment for these cardiovascular diseases. In conclusion, pharmacological and electrical stimulation of the parasympathetic nervous system has the potential to be used as a therapeutic tool for the treatment of hypertension and heart failure, deserving to be more explored in the clinical setting.

Increased cholinergic activity under conditions of low estrogen leads to adverse cardiac remodeling

Cholinesterase inhibitors are used in postmenopausal women for the treatment of neurodegenerative diseases. Despite their widespread use in the clinical practice, little is known about the impact of augmented cholinergic signaling on cardiac function under reduced estrogen conditions. To address this gap, we subjected a genetically engineered murine model of systemic vesicular acetylcholine transporter overexpression (Chat-ChR2) to ovariectomy and evaluated cardiac parameters. Left-ventricular function was similar between Chat-ChR2 and wild-type (WT) mice. Following ovariectomy, WT mice showed signs of cardiac hypertrophy. Conversely, ovariectomized (OVX) Chat-ChR2 mice evolved to cardiac dilation and failure. Transcript levels for cardiac stress markers atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) were similarly upregulated in WT/OVX and Chat-ChR2/OVX mice. 17β-Estradiol (E2) treatment normalized cardiac parameters in Chat-ChR2/OVX to the Chat-ChR2/SHAM levels, providing a link between E2 status and the aggravated cardiac response in this model. To investigate the cellular basis underlying the cardiac alterations, ventricular myocytes were isolated and their cellular area and contractility were assessed. Myocytes from WT/OVX mice were wider than WT/SHAM, an indicative of concentric hypertrophy, but their fractional shortening was similar. Conversely, Chat-ChR2/OVX myocytes were elongated and presented contractile dysfunction. E2 treatment again prevented the structural and functional changes in Chat-ChR2/OVX myocytes. We conclude that hypercholinergic mice under reduced estrogen conditions do not develop concentric hypertrophy, a critical compensatory adaptation, evolving toward cardiac dilation and failure. This study emphasizes the importance of understanding the consequences of cholinesterase inhibition, used clinically to treat dementia, for cardiac function in postmenopausal women.

Pyridostigmine improves cardiac function and rhythmicity through RyR2 stabilization and inhibition of STIM1-mediated calcium entry in heart failure

Heart failure (HF) is characterized by asymmetrical autonomic balance. Treatments to restore parasympathetic activity in human heart failure trials have shown beneficial effects. However, mechanisms of parasympathetic-mediated improvement in cardiac function remain unclear. The present study examined the effects and underpinning mechanisms of chronic treatment with the cholinesterase inhibitor, pyridostigmine (PYR), in pressure overload HF induced by transverse aortic constriction (TAC) in mice. TAC mice exhibited characteristic adverse structural (left ventricular hypertrophy) and functional remodelling (reduced ejection fraction, altered myocyte calcium (Ca) handling, increased arrhythmogenesis) with enhanced predisposition to arrhythmogenic aberrant sarcoplasmic reticulum (SR) Ca release, cardiac ryanodine receptor (RyR2) hyper-phosphorylation and up-regulated store-operated Ca entry (SOCE). PYR treatment resulted in improved cardiac contractile performance and rhythmic activity relative to untreated TAC mice. Chronic PYR treatment inhibited altered intracellular Ca handling by alleviating aberrant Ca release and diminishing pathologically enhanced SOCE in TAC myocytes. At the molecular level, these PYR-induced changes in Ca handling were associated with reductions of pathologically enhanced phosphorylation of RyR2 serine-2814 and STIM1 expression in HF myocytes. These results suggest that chronic cholinergic augmentation alleviates HF via normalization of both canonical RyR2-mediated SR Ca release and non-canonical hypertrophic Ca signaling via STIM1-dependent SOCE.

The effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure: From cells to patient reports

Cardiovascular diseases remain a major cause of morbidity and mortality worldwide. Cardiovascular diseases such as acute myocardial infarction, ischaemia/reperfusion injury and heart failure are associated with cardiac autonomic imbalance characterized by sympathetic overactivity and parasympathetic withdrawal from the heart. Increased parasympathetic activity by electrical vagal nerve stimulation has been shown to provide beneficial effects in the case of cardiovascular diseases in both animals and patients by improving autonomic function, cardiac remodelling and mitochondrial function. However, clinical limitations for electrical vagal nerve stimulation exist because of its invasive nature, costly equipment and limited clinical validation. Therefore, novel therapeutic approaches which moderate parasympathetic activities could be beneficial for in the case of cardiovascular disease. Acetylcholinesterase inhibitors inhibit acetylcholinesterase and hence increase cholinergic transmission. Recent studies have reported that acetylcholinesterase inhibitors improve autonomic function and cardiac function in cardiovascular disease models. Despite its potential clinical benefits for cardiovascular disease patients, the role of acetylcholinesterase inhibitors in acute myocardial infarction and heart failure remediation remains unclear. This article comprehensively reviews the effects of acetylcholinesterase inhibitors on the heart in acute myocardial infarction and heart failure scenarios from in vitro and in vivo studies to clinical reports. The mechanisms involved are also discussed in this review.

The non-neuronal cholinergic system in the heart: A comprehensive review

The autonomic influences on the heart have a ying-yang nature, albeit oversimplified, the interplay between the sympathetic and parasympathetic system (known as the cholinergic system) is often complex and remain poorly understood. Recently, the heart has been recognized to consist of neuronal and non-neuronal cholinergic system (NNCS). The existence of cardiac NNCS has been confirmed by the presence of cholinergic markers in the cardiomyocytes, which are crucial for synthesis (choline acetyltransferase, ChAT), storage (vesicular acetylcholine transporter, VAChT), reuptake of choline for synthesis (high-affinity choline transporter, CHT1) and degradation (acetylcholinesterase, AChE) of acetylcholine (ACh). The non-neuronal ACh released from cardiomyocytes is believed to locally regulate some of the key physiological functions of the heart, such as regulation of heart rate, offsetting hypertrophic signals, maintenance of action potential propagation as well as modulation of cardiac energy metabolism via the muscarinic ACh receptor in an auto/paracrine manner. Apart from this, several studies have also provided evidence for the beneficial role of ACh released from cardiomyocytes against cardiovascular diseases such as sympathetic hyperactivity-induced cardiac remodeling and dysfunction as well as myocardial infarction, confirming the important role of NNCS in disease prevention. In this review, we aim to provide a fundamental overview of cardiac NNCS, and information about its physiological role, regulatory factors as well as its cardioprotective effects. Finally, we propose the different approaches to target cardiac NNCS as an adjunctive treatment to specifically address the withdrawal of neuronal cholinergic system in cardiovascular disease such as heart failure.

Effects of Heart Rate Reduction With Either Pyridostigmine or Ivabradine in Patients With Heart Failure: A Randomized, Double-Blind Study

Background:

Heart rate (HR) reduction with ivabradine has been proved to reduce hospitalization and death from heart failure (HF). We sought to investigate whether pyridostigmine would effectively reduce HR in patients with chronic HF as compared with ivabradine.

Methods:

Twenty-one patients with HF who were in sinus rhythm with a resting HR over 70 bpm, despite optimal medical treatment, were included in a randomized, double-blind study comparing pyridostigmine versus ivabradine. The initial dose of ivabradine was 5 mg twice daily to reach a target HR between 50 and 60 bpm and could be titrated to a maximum of 7.5 mg twice daily. Pyridostigmine was used in a fixed dose of 30 mg 3 times daily.

Results:

The baseline HR for ivabradine and pyridostigmine groups was 89.1 (13.5) and 80.1 (7.2) bpm, respectively ( P = .083). After 6 months of treatment, HR was significantly reduced to 64.8 (8.3) bpm in the ivabradine group ( P = .0014) and 63.6 (5.9) bpm in the pyridostigmine group ( P = .0001). The N-terminal pro-B-type natriuretic peptide was reduced in the ivabradine group (median: 1308.4 [interquartile range: 731-1896] vs 755.8 [134.5-1014] pg/mL; P = .027) and in the pyridostigmine group (132.8 [89.9-829] vs 100.7 [38-360] pg/mL; P = .002). Inflammatory markers interleukin-1, interleukin-6, and tumor necrosis factor were reduced in both groups. Exercise capacity was improved in both groups, with increments in volume of oxygen utilization ([Formula: see text]O2; ivabradine: 13.1 vs 15.6, P = .048; pyridostigmine: 13.3 vs 16.7, P = .032). Heart rate recovery in the first minute postexercise was improved with pyridostigmine (11.8 [3.9] vs 18 [6.5]; P = .046), but not with ivabradine (13.3 [6.9] vs 14.1 [8.2]; P = .70). No differences in either group were observed in the myocardial scintigraphy with 123-iodine-metaiodobenzylguanidine.

Conclusion:

Both drugs significantly reduced HR, with improvements in exercise capacity and in neurohormonal and inflammatory profiles.

Pyridostigmine protects against cardiomyopathy associated with adipose tissue browning and improvement of vagal activity in high-fat diet rats

Obesity, a major contributor to the development of cardiovascular diseases, is associated with an autonomic imbalance characterized by sympathetic hyperactivity and diminished vagal activity. Vagal activation plays important roles in weight loss and improvement of cardiac function. Pyridostigmine is a reversible acetylcholinesterase inhibitor, but whether it ameliorates cardiac lipid accumulation and cardiac remodeling in rats fed a high-fat diet has not been determined. This study investigated the effects of pyridostigmine on high-fat diet-induced cardiac dysfunction and explored the potential mechanisms. Rats were fed a normal or high-fat diet and treated with pyridostigmine. Vagal discharge was evaluated using the BL-420S system, and cardiac function by echocardiograms. Lipid deposition and cardiac remodeling were determined histologically. Lipid utility was assessed by qPCR. A high-fat diet led to a significant reduction in vagal discharge and lipid utility and a marked increase in lipid accumulation, cardiac remodeling, and cardiac dysfunction. Pyridostigmine improved vagal activity and lipid metabolism disorder and cardiac remodeling, accompanied by an improvement of cardiac function in high-fat diet-fed rats. An increase in the browning of white adipose tissue in pyridostigmine-treated rats was also observed and linked to the expression of UCP-1 and CIDEA. Additionally, pyridostigmine facilitated activation of brown adipose tissue via activation of the SIRT-1/AMPK/PGC-1α pathway. In conclusion, a high-fat diet resulted in cardiac lipid accumulation, cardiac remodeling, and a significant decrease in vagal discharge. Pyridostigmine ameliorated cardiomyopathy, an effect related to reduced cardiac lipid accumulation, and facilitated the browning of white adipose tissue while activating brown adipose tissue.

Long-term administration of pyridostigmine attenuates pressure overload-induced cardiac hypertrophy by inhibiting calcineurin signalling

Cardiac hypertrophy is associated with autonomic imbalance, characterized by enhanced sympathetic activity and withdrawal of parasympathetic control. Increased parasympathetic function improves ventricular performance. However, whether pyridostigmine, a reversible acetylcholinesterase inhibitor, can offset cardiac hypertrophy induced by pressure overload remains unclear. Hence, this study aimed to determine whether pyridostigmine can ameliorate pressure overload-induced cardiac hypertrophy and identify the underlying mechanisms. Rats were subjected to either sham or constriction of abdominal aorta surgery and treated with or without pyridostigmine for 8 weeks. Vagal activity and cardiac function were determined using PowerLab. Cardiac hypertrophy was evaluated using various histological stains. Protein markers for cardiac hypertrophy were quantitated by Western blot and immunoprecipitation. Pressure overload resulted in a marked reduction in vagal discharge and a profound increase in cardiac hypertrophy index and cardiac dysfunction. Pyridostigmine increased the acetylcholine levels by inhibiting acetylcholinesterase in rats with pressure overload. Pyridostigmine significantly attenuated cardiac hypertrophy based on reduction in left ventricular weight/body weight, suppression of the levels of atrial natriuretic peptide, brain natriuretic peptide and β-myosin heavy chain, and a reduction in cardiac fibrosis. These effects were accompanied by marked improvement of cardiac function. Additionally, pyridostigmine inhibited the CaN/NFAT3/GATA4 pathway and suppressed Orai1/STIM1 complex formation. In conclusion, pressure overload resulted in cardiac hypertrophy, cardiac dysfunction and a significant reduction in vagal discharge. Pyridostigmine attenuated cardiac hypertrophy and improved cardiac function, which was related to improved cholinergic transmission efficiency (decreased acetylcholinesterase and increased acetylcholine), inhibition of the CaN/NFAT3/GATA4 pathway and suppression of the interaction of Orai1/STIM1.

Cholinesterase inhibition reduces arrhythmias in asymptomatic Chagas disease

INTRODUCTION

Parasympathetic dysfunction may play a role in the genesis of arrhythmias in Chagas disease.

AIM

This study evaluates the acute effects of pyridostigmine (PYR), a reversible cholinesterase inhibitor, on the occurrence of arrhythmias in patients with Chagas cardiac disease.

METHOD

Following a double-blind, randomized, placebo-controlled, cross-over protocol, 17 patients (age 50±2 years) with Chagas cardiac disease type B underwent 24-hour Holter recordings after oral administration of either pyridostigmine bromide (45 mg, 3 times/day) or placebo (PLA).

RESULTS

Pyridostigmine reduced the 24-hours incidence (median [25%-75%]) of premature ventricular beats-PLA: 2998 (1920-4870), PYR: 2359 (940-3253), P=.044; ventricular couplets-PLA: 84 (15-159), PYR: 33 (6-94), P=.046. Although the total number of nonsustained ventricular tachycardia in the entire group was not different (P=.19) between PLA (1 [0-8]) and PYR (0 [0-4]), there were fewer episodes under PYR in 72% of the patients presenting this type of arrhythmia (P=.033).

CONCLUSION

Acute administration of pyridostigmine reduced the incidence of nonsustained ventricular arrhythmias in patients with Chagas cardiac disease. Further studies that address the use of pyridostigmine by patients with Chagas cardiac disease under a more prolonged follow-up are warranted.

Subacute pyridostigmine exposure increases heart rate recovery and cardiac parasympathetic tone in rats

Heart rate recovery (HRR) describes the rapid deceleration of heart rate after strenuous exercise and is an indicator of parasympathetic tone. A reduction in parasympathetic tone occurs in patients with congestive heart failure, resulting in prolonged HRR. Acetylcholinesterase inhibitors, such as pyridostigmine, can enhance parasympathetic tone by increasing cholinergic input to the heart. The objective of this study was to develop a rodent model of HRR to test the hypothesis that subacute pyridostigmine administration decreases cholinesterase activity and accelerates HRR in rats. Ten days after implantation of radiotelemetry transmitters, male Sprague Dawley rats were randomized to control (CTL) or treated (PYR; 0.14 mg/mL pyridostigmine in the drinking water, 29 days) groups. Rats were exercised on a treadmill to record HRR, and blood samples were collected on days 0, 7, 14, and 28 of pyridostigmine administration. Total cholinesterase and acetylcholinesterase (AChE) activity in plasma was decreased by 32%-43% and 57%-80%, respectively, in PYR rats on days 7-28, while plasma butyrylcholinesterase activity did not significantly change. AChE activity in red blood cells was markedly reduced by 64%-66%. HRR recorded 1 minute after exercise was higher in the PYR group on days 7, 14 and 28, and on day 7 when HRR was estimated at 3 and 5 minutes. Autonomic tone was evaluated pharmacologically using sequential administration of muscarinic (atropine) and adrenergic (propranolol) blockers. Parasympathetic tone was increased in PYR rats as compared with the CTL group. These data support the study hypothesis that subacute pyridostigmine administration enhances HRR by increasing cardiac parasympathetic tone.

Supervised exercise improves autonomic modulation in participants in cardiac rehabilitation programs

BACKGROUND AND OBJECTIVES

An attenuated heart rate recovery (HRR) response after exercise testing is a robust predictor of mortality. Regular exercise can enhance various physiological parameters. Studies indicate that participation in a cardiac rehabilitation program can improve heart rate recovery. The aim of this study was to analyze changes in functional capacity and autonomic modulation in patients following a cardiac rehabilitation program.

METHODS

Between 2009 and 2014, 248 individuals were assessed through exercise testing, at baseline and after six months of participation in a cardiac rehabilitation program. The exercise test was performed on a treadmill using a ramp protocol. The first minute of active recovery was standardized at a speed of 1.5 mph and slope of 2.5%. The degree of parasympathetic modulation was assessed by the difference between peak exercise heart rate and heart rate at one minute of recovery. The subjects were divided into two groups according to pre-training HRR (≤ 12 bpm and >12 bpm).

RESULTS

Exercise training resulted in a similar increase in metabolic equivalent values in both groups, but only the HRR ≤ 12 bpm group showed improvement after training (F=16.13; p<0.001), with a mean increase from 7.4 ± 3.69 bpm to 13.0 ± 9.74 bpm.

CONCLUSIONS

The cardiac rehabilitation program had a positive impact in a group that had both low functional capacity and reduced parasympathetic activity, producing a favorable effect on these recognized prognostic markers.

Neural control of circulation and exercise: a translational approach disclosing interactions between central command, arterial baroreflex, and muscle metaboreflex

The last 100 years witnessed a rapid and progressive development of the body of knowledge concerning the neural control of the cardiovascular system in health and disease. The understanding of the complexity and the relevance of the neuroregulatory system continues to evolve and as a result raises new questions. The purpose of this review is to articulate results from studies involving experimental models in animals as well as in humans concerning the interaction between the neural mechanisms mediating the hemodynamic responses during exercise. The review describes the arterial baroreflex, the pivotal mechanism controlling mean arterial blood pressure and its fluctuations along with the two main activation mechanisms to exercise: central command (parallel activation of central somatomotor and autonomic descending pathways) and the muscle metaboreflex, the metabolic component of exercise pressor reflex (feedback from ergoreceptors within contracting skeletal muscles). In addition, the role of the cardiopulmonary baroreceptors in modulating the resetting of arterial baroreflex is identified, and the mechanisms in the central nervous system involved with the resetting of baroreflex function during dynamic exercise are also described. Approaching a very relevant clinical condition, the review also presents the concept that the impaired arterial baroreflex function is an integral component of the metaboreflex-mediated exaggerated sympathetic tone in subjects with heart failure. This increased sympathetic activity has a major role in causing the depressed ventricular function observed during submaximal dynamic exercise in these patients. The potential contribution of a metaboreflex arising from respiratory muscles is also considered.

Autonomic cardiocirculatory control in mice with reduced expression of the vesicular acetylcholine transporter

In cardiovascular diseases, sympathetic tone has been comprehensively studied, whereas parasympathetic tone has received minor attention. The vesicular ACh transporter (VAChT) knockdown homozygous (VAChT KD(HOM)) mouse is a useful model for examining the cardiocirculatory sympathovagal balance. Therefore, we investigated whether cholinergic dysfunction caused by reduced VAChT expression could adversely impact hemodynamic parameter [arterial pressure (AP) and heart rate (HR)] daily oscillation, baroreflex sensitivity, hemodynamic variability, sympathovagal balance, and cardiovascular reactivity to restraint stress. Wild-type and VAChT KD(HOM) mice were anesthetized for telemetry transmitter implantation, and APs and HRs were recorded 10 days after surgical recovery. Changes in HR elicited by methylatropine and propranolol provided the indexes of sympathovagal tone. Cardiovascular reactivity in response to a restraint test was examined 24 h after continuous recordings of AP and HR. VAChT KD(HOM) mice exhibited reduced parasympathetic and elevated sympathetic tone. Daily oscillations of AP and HR as well as AP variability were similar between groups. Nevertheless, HR variability, patterns with two dissimilar variations from symbolic analysis, and baroreflex sensitivity were reduced in VAChT KD(HOM) mice. The change in mean AP due to restraint stress was greater in VAChT KD(HOM) mice, whereas the tachycardic response was not. These findings demonstrate that the cholinergic dysfunction present in the VAChT KD(HOM) mouse did not adversely impact basal hemodynamic parameters but promoted autonomic imbalance, an attenuation of baroreflex sensitivity, and a greater pressure response to restraint stress. These results provide a framework for understanding how autonomic imbalance impacts cardiovascular function.

Cholinergic activity as a new target in diseases of the heart

The autonomic nervous system is an important modulator of cardiac signaling in both health and disease. In fact, the significance of altered parasympathetic tone in cardiac disease has recently come to the forefront. Both neuronal and nonneuronal cholinergic signaling likely play a physiological role, since modulating acetylcholine (ACh) signaling from neurons or cardiomyocytes appears to have significant consequences in both health and disease. Notably, many of these effects are solely due to changes in cholinergic signaling, without altered sympathetic drive, which is known to have significant adverse effects in disease states. As such, it is likely that enhanced ACh-mediated signaling not only has direct positive effects on cardiomyocytes, but it also offsets the negative effects of hyperadrenergic tone. In this review, we discuss recent studies that implicate ACh as a major regulator of cardiac remodeling and provide support for the notion that enhancing cholinergic signaling in human patients with cardiac disease can reduce morbidity and mortality. These recent results support the idea of developing large clinical trials of strategies to increase cholinergic tone, either by stimulating the vagus or by increased availability of Ach, in heart failure.

Effects of cholinergic stimulation with pyridostigmine bromide on chronic chagasic cardiomyopathic mice

The aim of the present study was to assess the effects of an anticholinesterase agent, pyridostigmine bromide (Pyrido), on experimental chronic Chagas heart disease in mice. To this end, male C57BL/6J mice noninfected (control:Con) or chronically infected (5 months) with Trypanosoma cruzi (chagasic:Chg) were treated or not (NT) with Pyrido for one month. At the end of this period, electrocardiogram (ECG); cardiac autonomic function; heart histopathology; serum cytokines; and the presence of blood and tissue parasites by means of immunohistochemistry and PCR were assessed. In NT-Chg mice, significant changes in the electrocardiographic, autonomic, and cardiac histopathological profiles were observed confirming a chronic inflammatory response. Treatment with Pyrido in Chagasic mice caused a significant reduction of myocardial inflammatory infiltration, fibrosis, and hypertrophy, which was accompanied by a decrease in serum levels of IFNγ with no change in IL-10 levels, suggesting a shift of immune response toward an anti-inflammatory profile. Lower nondifferent numbers of parasite DNA copies were observed in both treated and nontreated chagasic mice. In conclusion, our findings confirm the marked neuroimmunomodulatory role played by the parasympathetic autonomic nervous system in the evolution of the inflammatory-immune response to T. cruzi during experimental chronic Chagas heart disease in mice.

Pyridostigmine restores cardiac autonomic balance after small myocardial infarction in mice

The effect of pyridostigmine (PYR) - an acetylcholinesterase inhibitor - on hemodynamics and cardiac autonomic control, was never studied in conscious myocardial infarcted mice. Telemetry transmitters were implanted into the carotid artery under isoflurane anesthesia. Seven to ten days after recovery from the surgery, basal arterial pressure and heart rate were recorded, while parasympathetic and sympathetic tone (ΔHR) was evaluated by means of methyl atropine and propranolol. After the basal hemodynamic recording the mice were subjected to left coronary artery ligation for producing myocardial infarction (MI), or sham operation, and implantation of minipumps filled with PYR or saline. Separate groups of anesthetized (isoflurane) mice previously (4 weeks) subjected to MI, or sham coronary artery ligation, were submitted to cardiac function examination. The mice exhibited an infarct length of approximately 12%, no change in arterial pressure and increased heart rate only in the 1st week after MI. Vagal tone decreased in the 1^st week, while the sympathetic tone was increased in the 1^st and 4^th week after MI. PYR prevented the increase in heart rate but did not affect the arterial pressure. Moreover, PYR prevented the increase in sympathetic tone throughout the 4 weeks. Concerning the parasympathetic tone, PYR not only impaired its attenuation in the 1^st week, but enhanced it in the 4^th week. MI decreased ejection fraction and increased diastolic and systolic volume. Therefore, the pharmacological increase of peripheral acetylcholine availability by means of PYR prevented tachycardia, increased parasympathetic and decreased sympathetic tone after MI in mice.

Optimal detection of cholinesterase activity in biological samples: modifications to the standard Ellman's assay

Ellman's assay is the most commonly used method to measure cholinesterase activity. It is cheap, fast, and reliable, but it has limitations when used for biological samples. The problems arise from 5,5-dithiobis(2-nitrobenzoic acid) (DTNB), which is unstable, interacts with free sulfhydryl groups in the sample, and may affect cholinesterase activity. We report that DTNB is more stable in 0.09 M Hepes with 0.05 M sodium phosphate buffer than in 0.1M sodium phosphate buffer, thereby notably reducing background. Using enzyme-linked immunosorbent assay (ELISA) to enrich tissue homogenates for cholinesterase while depleting the sample of sulfhydryl groups eliminates unwanted interactions with DTNB, making it possible to measure low cholinesterase activity in biological samples. To eliminate possible interference of DTNB with enzyme hydrolysis, we introduce a modification of the standard Ellman's assay. First, thioesters are hydrolyzed by cholinesterase to produce thiocholine in the absence of DTNB. Then, the reaction is stopped by a cholinesterase inhibitor and the produced thiocholine is revealed by DTNB and quantified at 412 nm. Indeed, this modification of Ellman's method increases butyrylcholinesterase activity by 20 to 25%. Moreover, high stability of thiocholine enables separation of the two reactions of the Ellman's method into two successive steps that may be convenient for some applications.

Increase in parasympathetic tone by pyridostigmine prevents ventricular dysfunction during the onset of heart failure

Heart failure (HF) is characterized by elevated sympathetic activity and reduced parasympathetic control of the heart. Experimental evidence suggests that the increase in parasympathetic function can be a therapeutic alternative to slow HF evolution. The parasympathetic neurotransmission can be improved by acetylcholinesterase inhibition. We investigated the long-term (4 wk) effects of the acetylcholinesterase inhibitor pyridostigmine on sympathovagal balance, cardiac remodeling, and cardiac function in the onset of HF following myocardial infarction. Myocardial infarction was elicited in adult male Wistar rats. After 4 wk of pyridostigmine administration, per os, methylatropine and propranolol were used to evaluate the cardiac sympathovagal balance. The tachycardic response caused by methylatropine was considered to be the vagal tone, whereas the bradycardic response caused by propranolol was considered to be the sympathetic tone. In conscious HF rats, pyridostigmine reduced the basal heart rate, increased vagal, and reduced sympathetic control of heart rate. Pyridostigmine reduced the myocyte diameter and collagen density of the surviving left ventricle. Pyridostigmine also increased vascular endothelial growth factor protein in the left ventricle, suggesting myocardial angiogenesis. Cardiac function was assessed by means of the pressure-volume conductance catheter system. HF rats treated with pyridostigmine exhibited a higher stroke volume, ejection fraction, cardiac output, and contractility of the left ventricle. It was demonstrated that the long-term administration of pyridostigmine started right after coronary artery ligation augmented cardiac vagal and reduced sympathetic tone, attenuating cardiac remodeling and left ventricular dysfunction during the progression of HF in rats.

Stability of relative oxygen pulse curve during repeated maximal cardiopulmonary testing in professional soccer players

During cardiopulmonary exercise testing (CPET), stroke volume can be indirectly assessed by O(2) pulse profile. However, for a valid interpretation, the stability of this variable over time should be known. The objective was to analyze the stability of the O(2) pulse curve relative to body mass in elite athletes. VO(2), heart rate (HR), and relative O(2) pulse were compared at every 10% of the running time in two maximal CPETs, from 2005 to 2010, of 49 soccer players. Maximal values of VO(2) (63.4 ± 0.9 vs 63.5 ± 0.9 mL O(2)•kg(-1)•min(-1)), HR (190 ± 1 vs188 ± 1 bpm) and relative O(2) pulse (32.9 ± 0.6 vs 32.6 ± 0.6 mL O(2)•beat(-1)•kg(-1)) were similar for the two CPETs (P > 0.05), while the final treadmill velocity increased from 18.5 ± 0.9 to 18.9 ± 1.0 km/h (P < 0.01). Relative O(2) pulse increased linearly and similarly in both evaluations (r(2) = 0.64 and 0.63) up to 90% of the running time. Between 90 and 100% of the running time, the values were less stable, with up to 50% of the players showing a tendency to a plateau in the relative O(2) pulse. In young healthy men in good to excellent aerobic condition, the morphology of the relative O(2) pulse curve is consistent up to close to the peak effort for a CPET repeated within a 1-year period. No increase in relative O(2)pulse at peak effort could represent a physiologic stroke volume limitation in these athletes.

Dysautonomia due to reduced cholinergic neurotransmission causes cardiac remodeling and heart failure

Overwhelming evidence supports the importance of the sympathetic nervous system in heart failure. In contrast, much less is known about the role of failing cholinergic neurotransmission in cardiac disease. By using a unique genetically modified mouse line with reduced expression of the vesicular acetylcholine transporter (VAChT) and consequently decreased release of acetylcholine, we investigated the consequences of altered cholinergic tone for cardiac function. M-mode echocardiography, hemodynamic experiments, analysis of isolated perfused hearts, and measurements of cardiomyocyte contraction indicated that VAChT mutant mice have decreased left ventricle function associated with altered calcium handling. Gene expression was analyzed by quantitative reverse transcriptase PCR and Western blotting, and the results indicated that VAChT mutant mice have profound cardiac remodeling and reactivation of the fetal gene program. This phenotype was attributable to reduced cholinergic tone, since administration of the cholinesterase inhibitor pyridostigmine for 2 weeks reversed the cardiac phenotype in mutant mice. Our findings provide direct evidence that decreased cholinergic neurotransmission and underlying autonomic imbalance cause plastic alterations that contribute to heart dysfunction.

Effect of the cholinesterase inhibitor donepezil on cardiac remodeling and autonomic balance in rats with heart failure

In an earlier study we demonstrated the beneficial effect of direct vagal electrical stimulation on cardiac remodeling and survival. In the study reported here, we attempted to reproduce the effect of vagal enhancement through the administration of an acetylcholinesterase inhibitor, donepezil. A rat model of heart failure following extensive healed myocardial infarction was used. Compared to their nontreated counterparts, rats given donepezil (5 mg/kg/day) in their drinking water had a smaller biventricular weight (3.40 +/- 0.13 vs. 3.02 +/- 0.21 g/kg body weight, P < 0.05), and maximal rate of rise (3256 +/- 955 vs. 3822 +/- 389 mmHg/s, P < 0.05) and the end-diastolic value (30.1 +/- 5.6 vs. 23.2 +/- 5.7 mmHg, P < 0.05) of left ventricular pressure were improved. Neurohumoral factors were suppressed in donepezil-treated rats (norepinephrine 1885 +/- 1423 vs. 316 +/- 248 pg/ml, P < 0.01; brain natriuretic peptide 457 +/- 68 vs. 362 +/- 80 ng/ml, P < 0.05), and the high-frequency component of heart rate variability showed a nocturnal increase. These findings indicated that donepezil reproduced the anti-remodeling effect of electrical vagal stimulation. Further studies are warranted to evaluate the clinical usefulness of donepezil in heart failure.