Vagal stimulation mimics preconditioning and postconditioning of ischemic myocardium in mice by activating different protection mechanisms

Vago-splenic signal transduction of cardioprotection in humans

BACKGROUND AND AIMS

The spleen serves as an important relay organ that releases cardioprotective factor(s) upon vagal activation during remote ischaemic conditioning (RIC) in rats and pigs. The translation of these findings to humans was attempted.

METHODS

Remote ischaemic conditioning or electrical auricular tragus stimulation (ATS) were performed in 10 healthy young volunteers, 10 volunteers with splenectomy, and 20 matched controls. Venous blood samples were taken before and after RIC/ATS or placebo, and a plasma dialysate was infused into isolated perfused rat hearts subjected to global ischaemia/reperfusion.

RESULTS

Neither left nor right RIC or ATS altered heart rate and heart rate variability in the study cohorts. With the plasma dialysate prepared before RIC or ATS, respectively, infarct size (% ventricular mass) in the recipient rat heart was 36 ± 6% (left RIC), 34 ± 3% (right RIC) or 31 ± 5% (left ATS), 35 ± 5% (right ATS), and decreased with the plasma dialysate from healthy volunteers after RIC or ATS to 20 ± 4% (left RIC), 23 ± 6% (right RIC) or to 19 ± 4% (left ATS), 26 ± 9% (right ATS); infarct size was still reduced with plasma dialysate 4 days after ATS and 9 days after RIC. In a subgroup of six healthy volunteers, such infarct size reduction was abrogated by intravenous atropine. Infarct size reduction by RIC or ATS was also abrogated in 10 volunteers with splenectomy, but not in their 20 matched controls.

CONCLUSIONS

In humans, vagal innervation and the spleen as a relay organ are decisive for the cardioprotective signal transduction of RIC and ATS.

The protective role of vagus nerve stimulation in ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) encompasses the damage resulting from the restoration of blood supply following tissue ischemia. This phenomenon commonly occurs in clinical scenarios such as hemorrhagic shock, severe trauma, organ transplantation, and thrombolytic therapy. Despite its prevalence, existing treatments exhibit limited efficacy against IRI. Vagus nerve stimulation (VNS) is a widely utilized technique for modulating the autonomic nervous system. Numerous studies have demonstrated that VNS significantly reduces IRI in various organs, including the heart, brain, and liver. This article reviews the pathological processes during IRI and summarizes the role and possible mechanisms of VNS in IRI of different organs. Furthermore, this review addresses the current challenges of VNS clinical applications, providing a novel perspective on IRI treatment.

Neuroadaptive Biochemical Mechanisms of Remote Ischemic Conditioning

This review summarizes the currently known biochemical neuroadaptive mechanisms of remote ischemic conditioning. In particular, it focuses on the significance of the pro-adaptive effects of remote ischemic conditioning which allow for the prevention of the neurological and cognitive impairments associated with hippocampal dysregulation after brain damage. The neuroimmunohumoral pathway transmitting a conditioning stimulus, as well as the molecular basis of the early and delayed phases of neuroprotection, including anti-apoptotic, anti-oxidant, and anti-inflammatory components, are also outlined. Based on the close interplay between the effects of ischemia, especially those mediated by interaction of hypoxia-inducible factors (HIFs) and steroid hormones, the involvement of the hypothalamic-pituitary-adrenocortical system in remote ischemic conditioning is also discussed.

Cooling Down Inflammation in the Cardiovascular System via the Nicotinic Acetylcholine Receptor

ABSTRACT

Inflammation is a major player in many cardiovascular diseases including hypertension, atherosclerosis, myocardial infarction, and heart failure. In many individuals, these conditions coexist and mutually exacerbate each other's progression. The pathophysiology of these diseases entails the active involvement of both innate and adaptive immune cells. Immune cells that possess the α7 subunit of the nicotinic acetylcholine receptor on their surface have the potential to be targeted through both pharmacological and electrical stimulation of the cholinergic system. The cholinergic system regulates the inflammatory response to various stressors in different organ systems by systematically suppressing spleen-derived monocytes and chemokines and locally improving immune cell function. Research on the cardiovascular system has demonstrated the potential for atheroma plaque stabilization and regression as favorable outcomes. Smaller infarct size and reduced fibrosis have been associated with improved cardiac function and a decrease in adverse cardiac remodeling. Furthermore, enhanced electrical stability of the myocardium can lead to a reduction in the incidence of ventricular tachyarrhythmia. In addition, improving mitochondrial dysfunction and decreasing oxidative stress can result in less myocardial tissue damage caused by reperfusion injury. Restoring baroreflex activity and reduction in renal damage can promote blood pressure regulation and help counteract hypertension. Thus, the present review highlights the potential of nicotinic acetylcholine receptor activation as a natural approach to alleviate the adverse consequences of inflammation in the cardiovascular system.

Unpacking the multimodal, multi-scale data of the fast and slow lanes of the cardiac vagus through computational modelling

NEW FINDINGS

What is the topic of this review? The vagus nerve is a crucial regulator of cardiovascular homeostasis, and its activity is linked to heart health. Vagal activity originates from two brainstem nuclei: the nucleus ambiguus (fast lane) and the dorsal motor nucleus of the vagus (slow lane), nicknamed for the time scales that they require to transmit signals. What advances does it highlight? Computational models are powerful tools for organizing multi-scale, multimodal data on the fast and slow lanes in a physiologically meaningful way. A strategy is laid out for how these models can guide experiments aimed at harnessing the cardiovascular health benefits of differential activation of the fast and slow lanes.

ABSTRACT

The vagus nerve is a key mediator of brain-heart signaling, and its activity is necessary for cardiovascular health. Vagal outflow stems from the nucleus ambiguus, responsible primarily for fast, beat-to-beat regulation of heart rate and rhythm, and the dorsal motor nucleus of the vagus, responsible primarily for slow regulation of ventricular contractility. Due to the high-dimensional and multimodal nature of the anatomical, molecular and physiological data on neural regulation of cardiac function, data-derived mechanistic insights have proven elusive. Elucidating insights has been complicated further by the broad distribution of the data across heart, brain and peripheral nervous system circuits. Here we lay out an integrative framework based on computational modelling for combining these disparate and multi-scale data on the two vagal control lanes of the cardiovascular system. Newly available molecular-scale data, particularly single-cell transcriptomic analyses, have augmented our understanding of the heterogeneous neuronal states underlying vagally mediated fast and slow regulation of cardiac physiology. Cellular-scale computational models built from these data sets represent building blocks that can be combined using anatomical and neural circuit connectivity, neuronal electrophysiology, and organ/organismal-scale physiology data to create multi-system, multi-scale models that enable in silico exploration of the fast versus slow lane vagal stimulation. The insights from the computational modelling and analyses will guide new experimental questions on the mechanisms regulating the fast and slow lanes of the cardiac vagus toward exploiting targeted vagal neuromodulatory activity to promote cardiovascular health.

Neuroimmune nexus in the pathophysiology and therapy of inflammatory disorders: role of α7 nicotinic acetylcholine receptors

The α7-nicotinic acetylcholine receptor (α7nAChR) is a key protein in the cholinergic anti-inflammatory pathway (CAP) that links the nervous and immune systems. Initially, the pathway was discovered based on the observation that vagal nerve stimulation (VNS) reduced the systemic inflammatory response in septic animals. Subsequent studies form a foundation for the leading hypothesis about the central role of the spleen in CAP activation. VNS evokes noradrenergic stimulation of ACh release from T cells in the spleen, which in turn activates α7nAChRs on the surface of macrophages. α7nAChR-mediated signaling in macrophages reduces inflammatory cytokine secretion and modifies apoptosis, proliferation, and macrophage polarization, eventually reducing the systemic inflammatory response. A protective role of the CAP has been demonstrated in preclinical studies for multiple diseases including sepsis, metabolic disease, cardiovascular diseases, arthritis, Crohn's disease, ulcerative colitis, endometriosis, and potentially COVID-19, sparking interest in using bioelectronic and pharmacological approaches to target α7nAChRs for treating inflammatory conditions in patients. Despite a keen interest, many aspects of the cholinergic pathway are still unknown. α7nAChRs are expressed on many other subsets of immune cells that can affect the development of inflammation differently. There are also other sources of ACh that modify immune cell functions. How the interplay of ACh and α7nAChR on different cells and in various tissues contributes to the anti-inflammatory responses requires additional study. This review provides an update on basic and translational studies of the CAP in inflammatory diseases, the relevant pharmacology of α7nAChR-activated drugs and raises some questions that require further investigation.

Glial cell activity in cardiovascular diseases and risk of acute myocardial infarction

Growing evidence indicates that the pathophysiological link between the brain and heart underlies cardiovascular diseases, specifically acute myocardial infarction (AMI). Astrocytes are the most abundant glial cells in the central nervous system and provide support/protection for neurons. Astrocytes and peripheral glial cells are emerging as key modulators of the brain-heart axis in AMI, by affecting sympathetic nervous system activity (centrally and peripherally). This review, therefore, aimed to gain an improved understanding of glial cell activity and AMI risk. This includes discussions on the potential role of contributing factors in AMI risk, i.e., autonomic nervous system dysfunction, glial-neurotrophic and ischemic risk markers [glial cell line-derived neurotrophic factor (GDNF), astrocytic S100 calcium-binding protein B (S100B), silent myocardial ischemia, and cardiac troponin T (cTnT)]. Consideration of glial cell activity and related contributing factors in certain brain-heart disorders, namely, blood-brain barrier dysfunction, myocardial ischemia, and chronic psychological stress, may improve our understanding regarding the pathological role that glial dysfunction can play in the development/onset of AMI. Here, findings demonstrated perturbations in glial cell activity and contributing factors (especially sympathetic activity). Moreover, emerging AMI risk included sympathovagal imbalance, low GDNF levels reflecting prothrombic risk, hypertension, and increased ischemia due to perfusion deficits (indicated by S100B and cTnT levels). Such perturbations impacted blood-barrier function and perfusion that were exacerbated during psychological stress. Thus, greater insights and consideration regarding such biomarkers may help drive future studies investigating brain-heart axis pathologies to gain a deeper understanding of astrocytic glial cell contributions and unlock potential novel therapies for AMI.

Chronic exposure to polluted urban air aggravates myocardial infarction by impaired cardiac mitochondrial function and dynamics

Air pollution exposure positively correlates with increased cardiovascular morbidity and mortality rates, mainly due to myocardial infarction (MI). Herein, we aimed to study the metabolic mechanisms underlying this association, focusing on the evaluation of cardiac mitochondrial function and dynamics, together with its impact over MI progression. An initial time course study was performed in BALB/c mice breathing filtered air (FA) or urban air (UA) in whole-body exposure chambers located in Buenos Aires City downtown for up to 16 weeks (n = 8 per group and time point). After 12 weeks, lung inflammatory cell recruitment was evident in UA-exposed mice. Interestingly, impaired redox metabolism, characterized by decreased lung SOD activity and increased GSSG levels and NOX activity, precede local inflammation in this group. At this selected time point, additional mice were exposed to FA or UA (n = 12 per group) and alveolar macrophage PM uptake and nitric oxide (NO) production was observed in UA-exposed mice, together with increased pro-inflammatory cytokine levels (TNF-α and IL-6) in BAL and plasma. Consequently, impaired heart tissue oxygen metabolism and altered mitochondrial ultrastructure and function were observed in UA-exposed mice after 12 weeks, characterized by decreased active state respiration and ATP production rates, and enhanced mitochondrial H₂O₂ production. Moreover, disturbed cardiac mitochondrial dynamics was detected in this group. This scenario led to a significant increase in the area of infarcted tissue following myocardial ischemia reperfusion injury in vivo, from 43 ± 3% of the area at risk in mice breathing FA to 66 ± 4% in UA-exposed mice (n = 6 per group, p < 0.01), together with a sustained increase in LVEDP during myocardial reperfusion. Taken together, our data unravel cardiac mitochondrial mechanisms that contribute to the understanding of the adverse health effects of urban air pollution exposure, and ultimately highlight the importance of considering environmental factors in the development of cardiovascular diseases.

Chronic Limb Remote Ischemic Conditioning may have an Antihypertensive Effect in Patients with Hypertension

Hypertension is the leading preventable risk factor for all-cause morbidity and mortality worldwide. Despite antihypertensive medications have been available for decades, a big challenge we are facing is to increase the blood pressure (BP) control rate among the population. Therefore, it is necessary to search for new antihypertensive means to reduce the burden of disease caused by hypertension. Limb remote ischemic conditioning (LRIC) can trigger endogenous protective effects through transient and repeated ischemia on the limb to protect specific organs and tissues including the brain, heart, and kidney. The mechanisms of LRIC involve the regulation of the autonomic nervous system, releasing humoral factors, improvement of vascular endothelial function, and modulation of immune/inflammatory responses. These underlying mechanisms of LRIC may restrain the pathogenesis of hypertension through multiple pathways theoretically, leading to a potential decline in BP. Several existing studies have explored the impact of LRIC on BP, however, controversial findings were reported. To explore the potential antihypertensive effect of LRIC and the underlying mechanisms, we systematically reviewed the relevant articles to provide an insight into the novel therapy of hypertension.

Interactions between remote ischemic conditioning and post-stroke sleep regulation

Sleep disturbances are common in patients with stroke, and sleep quality has a critical role in the onset and outcome of stroke. Poor sleep exacerbates neurological injury, impedes nerve regeneration, and elicits serious complications. Thus, exploring a therapy suitable for patients with stroke and sleep disturbances is imperative. As a multi-targeted nonpharmacological intervention, remote ischemic conditioning can reduce the ischemic size of the brain, improve the functional outcome of stroke, and increase sleep duration. Preclinical/clinical evidence showed that this method can inhibit the inflammatory response, mediate the signal transductions of adenosine, activate the efferents of the vagal nerve, and reset the circadian clocks, all of which are involved in sleep regulation. In particular, cytokines tumor necrosis factor α (TNFα) and adenosine are sleep factors, and electrical vagal nerve stimulation can improve insomnia. On the basis of the common mechanisms of remote ischemic conditioning and sleep regulation, a causal relationship was proposed between remote ischemic conditioning and post-stroke sleep quality.

Cholinergic modulation of the immune system - A novel therapeutic target for myocardial inflammation

The immune system and the nervous system depend on each other for their fine tuning and working, thus cooperating to maintain physiological homeostasis and prevent infections. The cholinergic system regulates the mobilization, differentiation, secretion, and antigen presentation of adaptive and innate immune cells mainly through α7 nicotinic acetylcholine receptors (α7nAChRs). The neuro-immune interactions are established and maintained by the following mechanisms: colocalization of immune and neuronal cells at defined anatomical sites, expression of the non-neuronal cholinergic system by immune cells, and the acetylcholine receptor-mediated activation of intracellular signaling pathways. Based on these immunological mechanisms, the protective effects of cholinergic system in animal models of diseases were summarized in this paper, such as myocardial infarction/ischemia-reperfusion, viral myocarditis, and endotoxin-induced myocardial damage. In addition to maintaining hemodynamic stability and improving the energy metabolism of the heart, both non-neuronal acetylcholine and neuronal acetylcholine in the heart can alleviate myocardial inflammation and remodeling to exert a significant cardioprotective effect. The new findings on the role of cholinergic agonists and vagus nerve stimulation in immune regulation are updated, so as to develop improved approaches to treat inflammatory heart disease.

A Step further-The Role of Trigeminocardiac Reflex in Therapeutic Implications: Hypothesis, Evidence, and Experimental Models

The trigeminocardiac reflex (TCR) is a well-recognized brainstem reflex that represents a unique interaction between the brain and the heart through the Vth and Xth cranial nerves and brainstem nuclei. The TCR has mainly been reported as an intraoperative phenomenon causing cardiovascular changes during skull-base surgeries. However, it is now appreciated that the TCR is implicated during non-neurosurgical procedures and in nonsurgical conditions, and its complex reflex pathways have been explored as potential therapeutic options in various neurological and cardiovascular diseases. This narrative review presents an in-depth overview of hypothetical and experimental models of the TCR phenomenon in relation to the Vth and Xth cranial nerves. In addition, primitive interactions between these 2 cranial nerves and their significance are highlighted. Finally, therapeutic models of the complex interactions of the TCR and areas for further research will be considered.

Effect of Electroacupuncture at Zusanli (ST36) on Sepsis Induced by Cecal Ligation Puncture and Its Relevance to Spleen

Background

Acupuncture at Zusanli (ST36), Quchi (LI11), and Tianshu (ST25) is commonly used in septic patients by traditional Chinese physicians. The protective effect of acupuncture at ST36 on the intestinal barrier is associated with Cholinergic Anti-Inflammatory Pathway (CAIP). However, its detailed mechanism and whether acupuncture at LI11 and ST25 have similar effects to ST36 remain unclear.

Aim

To explore the effects of electroacupuncture (EA) at ST36, LI11, and ST25 on septic rats and investigate the role of the spleen in the treatment of EA at ST36.

Methods

A septic rat model caused by cecal ligation and puncture (CLP) and a postsplenectomy (SPX) CLP rat model were established. Rats were divided into nine groups depending on different treatments. Serum levels of TNF-α, IL-10, D-lactic acidosis (D-LA), double amine oxidase (DAO), and T-lymphocyte subgroup level in intestinal lymph nodes were compared.

Results

EA could not improve the 2-day survival of CLP rats. For CLP rats, EA at ST36 and LI11 significantly decreased the levels of TNF-α, IL-10, DAO, and D-LA in serum and normalized intestinal T-cell immunity. For SPX CLP rats, EA at ST36 failed to reduce serum concentrations of TNF-α, IL-10, and D-LA but increased the values of CD3⁺CD4⁺/CD3⁺CD8⁺ cells and Treg/Th17 cells.

Conclusions

EA at ST36 and LI11, respectively, could alleviate inflammation reaction, protect the intestinal barrier, and maintain intestinal T-cell function in septic rats. Spleen participated in the protective effect of EA at ST36 in sepsis.

Targeting myocardial ischaemic injury in the absence of reperfusion

Sudden myocardial ischaemia causes an acute coronary syndrome. In the case of ST-elevation myocardial infarction (STEMI), this is usually caused by the acute rupture of atherosclerotic plaque and obstruction of a coronary artery. Timely restoration of blood flow can reduce infarct size, but ischaemic regions of myocardium remain in up to two-thirds of patients due to microvascular obstruction (MVO). Experimentally, cardioprotective strategies can limit infarct size, but these are primarily intended to target reperfusion injury. Here, we address the question of whether it is possible to specifically prevent ischaemic injury, for example in models of chronic coronary artery occlusion. Two main types of intervention are identified: those that preserve ATP levels by reducing myocardial oxygen consumption, (e.g. hypothermia; cardiac unloading; a reduction in heart rate or contractility; or ischaemic preconditioning), and those that increase myocardial oxygen/blood supply (e.g. collateral vessel dilation). An important consideration in these studies is the method used to assess infarct size, which is not straightforward in the absence of reperfusion. After several hours, most of the ischaemic area is likely to become infarcted, unless it is supplied by pre-formed collateral vessels. Therefore, therapies that stimulate the formation of new collaterals can potentially limit injury during subsequent exposure to ischaemia. After a prolonged period of ischaemia, the heart undergoes a remodelling process. Interventions, such as those targeting inflammation, may prevent adverse remodelling. Finally, harnessing of the endogenous process of myocardial regeneration has the potential to restore cardiomyocytes lost during infarction.

Mediation of Cardiac Macrophage Activity via Auricular Vagal Nerve Stimulation Ameliorates Cardiac Ischemia/Reperfusion Injury

Background

Myocardial infarction (MI) reperfusion therapy causes paradoxical cardiac complications. Following restoration of blood flow to infarcted regions, a multitude of inflammatory cells are recruited to the site of injury for tissue repair. Continual progression of cardiac inflammatory responses does, however, lead to adverse cardiac remodeling, inevitably causing heart failure.

Main Body

Increasing evidence of the cardioprotective effects of both invasive and non-invasive vagal nerve stimulation (VNS) suggests that these may be feasible methods to treat myocardial ischemia/reperfusion injury via anti-inflammatory regulation. The mechanisms through which auricular VNS controls inflammation are yet to be explored. In this review, we discuss the potential of autonomic nervous system modulation, particularly via the parasympathetic branch, in ameliorating MI. Novel insights are provided about the activation of the cholinergic anti-inflammatory pathway on cardiac macrophages. Acetylcholine binding to the α7 nicotinic acetylcholine receptor (α7nAChR) expressed on macrophages polarizes the pro-inflammatory into anti-inflammatory subtypes. Activation of the α7nAChR stimulates the signal transducer and activator of transcription 3 (STAT3) signaling pathway. This inhibits the secretion of pro-inflammatory cytokines, limiting ischemic injury in the myocardium and initiating efficient reparative mechanisms. We highlight recent developments in the controversial auricular vagal neuro-circuitry and how they may relate to activation of the cholinergic anti-inflammatory pathway.

Conclusion

Emerging published data suggest that auricular VNS is an inexpensive healthcare modality, mediating the dynamic balance between pro- and anti-inflammatory responses in cardiac macrophages and ameliorating cardiac ischemia/reperfusion injury.

Cardiac innervation in acute myocardial ischaemia/reperfusion injury and cardioprotection

Acute myocardial infarction (AMI) and the heart failure (HF) that often complicates this condition, are among the leading causes of death and disability worldwide. To reduce myocardial infarct (MI) size and prevent heart failure, novel therapies are required to protect the heart against the detrimental effects of acute ischaemia/reperfusion injury (IRI). In this regard, targeting cardiac innervation may provide a novel therapeutic strategy for cardioprotection. A number of cardiac neural pathways mediate the beneficial effects of cardioprotective strategies such as ischaemic preconditioning and remote ischaemic conditioning, and nerve stimulation may therefore provide a novel therapeutic strategy for cardioprotection. In this article, we provide an overview of cardiac innervation and its impact on acute myocardial IRI, the role of extrinsic and intrinsic cardiac neural pathways in cardioprotection, and highlight peripheral and central nerve stimulation as a cardioprotective strategy with therapeutic potential for reducing MI size and preventing HF following AMI. This article is part of a Cardiovascular Research Spotlight Issue entitled 'Cardioprotection Beyond the Cardiomyocyte', and emerged as part of the discussions of the European Union (EU)-CARDIOPROTECTION Cooperation in Science and Technology (COST) Action, CA16225.

Crosstalk between GSK-3β-actuated molecular cascades and myocardial physiology

The finding of "glycogen synthase kinase-3" (GSK-3) was initially identified as a protein kinase that phosphorylate and inhibited glycogen synthase. However, it was soon discovered that GSK-3 also has significant impact in regulation of truly astonishing number of critical intracellular signaling pathways ranging from regulation of cell growth, neurology, heart failure, diabetes, aging, inflammation, and cancer. Recent studies have validated the feasibility of targeting GSK-3 for its vital therapeutic potential to maintain normal myocardial homeostasis, conversely, its loss is incompatible with life as it can abrupt cell cycle and endorse fatal cardiomyopathy. The current study focuses on its expanding therapeutic action in myocardial tissue, concentrating primarily on its role in diabetes-associated cardiac complication, apoptosis and metabolism, heart failure, cardiac hypertrophy, and myocardial infarction. The current report also includes the finding of our previous investigation that has shown the impact of GSK-3β inhibitor against diabetes-associated myocardial injury and experimentally induced myocardial infarction. We have also discussed some recent identified GSK-3β inhibitors for their cardio-protective potential. The crosstalk of various underlying mechanisms that highlight the significant role of GSK-3β in myocardial pathophysiology have been discussed in the present report. For these literatures, we will rely profoundly on our previous studies and those of others to reconcile some of the deceptive contradictions in the literature.

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 signaling interplay of GSK-3β in myocardial disorders

Glycogen synthase kinase-3 (GSK-3) regulates numerous signaling transductions and pathological states, from cell growth, inflammation, apoptosis, and heart failure to cancer. Recent studies have validated the feasibility of targeting GSK-3β for its therapeutic potential to maintain myocardial homeostasis. Herein, we review the multifactorial roles of GSK-3β in cardiac abnormalities, focusing primarily on recent investigations into myocardial survival. In addition, we discuss the cardioprotective potential of divergent GSK-3β inhibitors. Finally, we also highlight crosstalk between the various mechanisms underlying abnormal myocardial functions in which GSK-3β is involved.

α7nAChR Deletion Aggravates Myocardial Infarction and Enhances Systemic Inflammatory Reaction via mTOR-Signaling-Related Autophagy

Alpha7 nicotinic acetylcholine receptor (α7nAChR) has been previously reported to play an alleviative role in myocardial infarction (MI). In this study, we investigated its specific mechanism. α7nAChR^-/- mice and its control (α7nAChR^+/+) were used for the study of α7nAChR. Left anterior descending coronary artery occlusion was conducted for the creation of mice MI model and lipopolysaccharide (LPS) was used as inflammatory stressor in murine peritoneal macrophages. Triphenyltetrazolium chloride (TTC) staining and echocardiography was used for the detection of infarct size and cardiac function, respectively. Western blot was conducted for the testing of autophagy-related proteins and enzyme-linked immunosorbent assay (ELISA) and real-time polymerase chain reaction (RT-PCR) was used for the testing of proinflammatory cytokines. Rapamycin was used for the induction of autophagy through inhibiting mammalian target of rapamycin (mTOR)-related signaling. We found that knocking out α7nAChR enhanced the cardiac infarct size and damaged cardiac function in MI. α7nAChR deficiency increased the levels of several proinflammatory cytokines in serum and spleen from MI mice as well as murine macrophages under inflammatory stress. α7nAChR deletion decreased the level of autophagy in spleen from MI mice and macrophages under inflammatory stress. Rapamycin alleviated the cardiac function and systemic inflammatory reaction in MI mice as well as inflammatory reaction in macrophages under inflammatory stress, which was attenuated by knocking out α7nAChR. Our current study investigated the mechanism of α7nAChR-mediated cardio-protective and anti-inflammatory effect related to mTOR-related autophagy, which might provide a novel insight in the treatment of MI.

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.

Inhibition of glycogen synthase kinase-3β is involved in cardioprotection by α7nAChR agonist and limb remote ischemic postconditionings

The present study was designed to determine whether glycogen synthase kinase-3β (GSK-3β) was involved in the cardioprotection by α7 nicotinic acetylcholine receptor (α7nAChR) agonist and limb remote ischemic postconditionings. Forty male Sprague-Dawley rats were randomly divided equally into control (C), α7nAChR agonist postconditioning (P), limb remote ischemic postconditioning (L), combined α7nAChR agonist and limb remote ischemic postconditioning (P+L) groups. At the end of experiment, serum cTnI, creatine kinase-MB (CK-MB), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), high mobility group protein (HMGB1) and interleukin-10 (IL-10) levels were measured; infarct size (IS), myocardial expressions of GSK-3β, p-GSK-3β (Ser9), nuclear factor-κB (NF-κB) and p-NF-κB (Ser536) in the ischemic area were assessed. The results showed that compared with group C, IS, serum cTnI and CK-MB levels obviously decreased in groups P, L and P+L. Compared with groups P and L, IS, serum cTnI and CK-MB levels significantly decreased in group P+L. Compared with group C, serum TNF-α, IL-6 and HMGB1 levels, and myocardial expression of p-NF-κBp65 (Ser536) evidently decreased, and myocardial expression of p-GSK-3β (Ser9) obviously increased in groups P, L and P+L. Compared with group P, serum TNF-α, IL-6 and HMGB1 levels and myocardial expression of p-NF-κBp65 (Ser536) significantly increased, and myocardial expression of p-GSK-3β (Ser9) evidently decreased in group L. Compared with group L, serum TNF-α, IL-6, HMGB1 levels, and myocardial expression of p-NF-κBp65 (Ser536) significantly decreased, and myocardial expression of p-GSK-3β (Ser9) obviously increased in group P+L. In conclusion, our findings indicate that inhibition of GSK-3β to decrease NF-κB transcription is one of cardioprotective mechanisms of α7nAChR agonist and limb remote ischemic postconditionings by anti-inflammation, but improved cardioprotection by combined two interventions is not completely attributable to an enhanced anti-inflammatory mechanism.

Revisiting the Cardioprotective Effects of Acetylcholine Receptor Activation against Myocardial Ischemia/Reperfusion Injury

Acute myocardial infarction (AMI) is the most common cause of acute myocardial injury and its most clinically significant form. The most effective treatment for AMI is to restore an adequate coronary blood flow to the ischemic myocardium as quickly as possible. However, reperfusion of an ischemic region can induce cardiomyocyte death, a phenomenon termed “myocardial ischemia/reperfusion (I/R) injury”. Disruption of cardiac parasympathetic (vagal) activity is a common hallmark of a variety of cardiovascular diseases including AMI. Experimental studies have shown that increased vagal activity exerts cardioprotective effects against myocardial I/R injury. In addition, acetylcholine (ACh), the principle cardiac vagal neurotransmitter, has been shown to replicate the cardioprotective effects of cardiac ischemic conditioning. Moreover, studies have shown that cardiomyocytes can synthesize and secrete ACh, which gives further evidence concerning the importance of the non-neuronal cholinergic signaling cascades. This suggests that the activation of ACh receptors is involved in cardioprotection against myocardial I/R injury. There are two types of ACh receptors (AChRs), namely muscarinic and nicotinic receptors (mAChRs and nAChRs, respectively). However, the effects of AChRs activation in cardioprotection during myocardial I/R are still not fully understood. In this review, we summarize the evidence suggesting the association between AChRs activation with both electrical and pharmacological interventions and the cardioprotection during myocardial I/R, as well as outline potential mechanisms underlying these cardioprotective effects.

Neural mechanisms in remote ischaemic conditioning in the heart and brain: mechanistic and translational aspects

Remote ischaemic conditioning (RIC) is a promising method of cardioprotection, with numerous clinical studies having demonstrated its ability to reduce myocardial infarct size and improve prognosis. On the other hand, there are several clinical trials, in particular those conducted in the setting of elective cardiac surgery, that have failed to show any benefit of RIC. These contradictory data indicate that there is insufficient understanding of the mechanisms underlying RIC. RIC is now known to signal indiscriminately, protecting not only the heart, but also other organs. In particular, experimental studies have demonstrated that it is able to reduce infarct size in an acute ischaemic stroke model. However, the mechanisms underlying RIC-induced neuroprotection are even less well understood than for cardioprotection. The existence of bidirectional feedback interactions between the heart and the brain suggests that the mechanisms of RIC-induced neuroprotection and cardioprotection should be studied as a whole. This review, therefore, addresses the topic of the neural component of the RIC mechanism.