Usefulness of α7 nicotinic receptor messenger RNA levels in peripheral blood mononuclear cells as a marker for cholinergic antiinflammatory pathway activity in septic patients: results of a pilot study

Cholinergic signaling via the α7 nicotinic acetylcholine receptor regulates the migration of monocyte-derived macrophages during acute inflammation

BACKGROUND

The involvement of the autonomic nervous system in the regulation of inflammation is an emerging concept with significant potential for clinical applications. Recent studies demonstrate that stimulating the vagus nerve activates the cholinergic anti-inflammatory pathway that inhibits pro-inflammatory cytokines and controls inflammation. The α7 nicotinic acetylcholine receptor (α7nAChR) on macrophages plays a key role in mediating cholinergic anti-inflammatory effects through a downstream intracellular mechanism involving inhibition of NF-κB signaling, which results in suppression of pro-inflammatory cytokine production. However, the role of the α7nAChR in the regulation of other aspects of the immune response, including the recruitment of monocytes/macrophages to the site of inflammation remained poorly understood.

RESULTS

We observed an increased mortality in α7nAChR-deficient mice (compared with wild-type controls) in mice with endotoxemia, which was paralleled with a significant reduction in the number of monocyte-derived macrophages in the lungs. Corroborating these results, fluorescently labeled α7nAChR-deficient monocytes adoptively transferred to WT mice showed significantly diminished recruitment to the inflamed tissue. α7nAChR deficiency did not affect monocyte 2D transmigration across an endothelial monolayer, but it significantly decreased the migration of macrophages in a 3D fibrin matrix. In vitro analysis of major adhesive receptors (L-selectin, β1 and β2 integrins) and chemokine receptors (CCR2 and CCR5) revealed reduced expression of integrin αM and αX on α7nAChR-deficient macrophages. Decreased expression of αMβ2 was confirmed on fluorescently labeled, adoptively transferred α7nAChR-deficient macrophages in the lungs of endotoxemic mice, indicating a potential mechanism for α7nAChR-mediated migration.

CONCLUSIONS

We demonstrate a novel role for the α7nAChR in mediating macrophage recruitment to inflamed tissue, which indicates an important new aspect of the cholinergic regulation of immune responses and inflammation.

Heart rate variability as a marker and predictor of inflammation, nosocomial infection, and sepsis - A systematic review

PURPOSE

The autonomic nervous system interacts with the immune system via the inflammatory response. Heart rate variability (HRV), a marker of autonomic activity, is associated with inflammation, and nosocomial infections/sepsis, and has clinical implications for the monitoring of at-risk patients. Due to the vagal tone's influence on anti-inflammatory immune response, this association may predominately be reflected by vagally-mediated HRV indices. However, HRV's predictive significance on inflammation/infection remains unclear.

METHODS

843 studies examining the associations/prognostic value of HRV indices on inflammation, and nosocomial infection/sepsis were screened in this systematic review. According to inclusion and exclusion criteria, 68 associative studies and 14 prediction studies were included.

RESULTS

HRV and pro-inflammatory state were consistently associated in healthy subjects and patient groups. Pro-inflammatory state was related to reduced total power HRV including vagally- and non-vagally-mediated HRV indices. Similar, compared to controls, HRV reductions were observed during nosocomial infections/sepsis. Only limited evidence supports the predictive value of HRV in the development of nosocomial infections/sepsis. Reduced very low frequency power HRV showed the highest predictive value in adults, even with different clinical conditions. In neonates, an increased heart rate characteristic score, combining reduced total power HRV, decreased complexity, and vagally-dominated asymmetry, predicted sepsis.

CONCLUSIONS

Pro-inflammatory state is related to an overall reduction in HRV rather than a singular reduction in vagally-mediated HRV indices, reflecting the complex autonomic-regulatory changes occurring during inflammation. The potential benefit of using continuous HRV monitoring for detecting nosocomial infection-related states, and the implications for clinical outcome, need further clarification.

Nicotinic acetylcholine receptors: Therapeutic targets for novel ligands to treat pain and inflammation

Nicotinic acetylcholine receptors (nAChRs) have been historically defined as ligand-gated ion channels and function as such in the central and peripheral nervous systems. Recently, however, non-ionic signaling mechanisms via nAChRs have been demonstrated in immune cells. Furthermore, the signaling pathways where nAChRs are expressed can be activated by endogenous ligands other than the canonical agonists acetylcholine and choline. In this review, we discuss the involvement of a subset of nAChRs containing α7, α9, and/or α10 subunits in the modulation of pain and inflammation via the cholinergic anti-inflammatory pathway. Additionally, we review the most recent advances in the development of novel ligands and their potential as therapeutics.

Association of the Cholinergic Anti-Inflammatory Pathway Activity with Proinflammatory Factors and Prognosis of Patients with Acute Respiratory Distress Syndrome

Objective

The cholinergic anti-inflammatory pathway (CAP) has been shown to modulate cytokine release by activating alpha-7 nicotinic acetylcholine receptors (α7nAChR) in monocytes/macrophages. However, their association with proinflammatory factors and prognosis in patients with acute respiratory distress syndrome (ARDS) has not been clarified. Here, we explored the correlation between CAP activity, proinflammatory factors, and the prognosis of ARDS patients.

Methods

The data of patients with ARDS (n = 65; underwent treatment) and healthy individuals (the control group; n = 65; underwent routine physical examination) at the Chongqing People's Hospital were investigated. Based on the survival status, ARDS patients were divided into a death ARDS group (n = 22) and a survival ARDS group (n = 43), and based on the diagnostic criteria of ARDS, the patients were also divided into a severe ARDS group (n = 30) and a mild-to-moderate ARDS group (n = 35). The levels of acetylcholine (ACh), acetylcholinesterase (AChE), and α7nAChR mRNA in peripheral blood monocytes were assessed. The levels of TNF-α and IL-6 in peripheral serum and peripheral monocytes were detected by ELISA and Western blot tests. The association between α7nAChR and inflammatory factors and prognosis was analyzed. The receiver-operating characteristic (ROC) curve was used to evaluate the reliability of CAP-related factors in predicting the survival status of ARDS patients.

Results

Compared with the control group, the levels of ACh, AChE, and α7nAChR mRNA of the ARDS group were significantly decreased. And, the ACh, AChE, and α7nAChR mRNA levels in the death/severe ARDS group were significantly lower than in the survival/mild-to-moderate ARDS group. However, the levels of TNF-α and IL-6 were significantly higher in the severe/death ARDS group. Furthermore, we observed that CAP-related factors were negatively correlated with the levels of IL-6 and TNF-α in peripheral serum in the ARDS group. The ROC curve showed that CAP-related factors were reliable markers for predicting the survival status of ARDS patients.

Conclusion

The related factors of the cholinergic anti-inflammatory pathway were significantly decreased in patients with ARDS, suggesting the ACh, AChE, and α7nAChR levels as potential indicators to evaluate the severity and prognosis status of ARDS patients.

Sepsis Mortality Prediction Using Wearable Monitoring in Low-Middle Income Countries

Sepsis is associated with high mortality—particularly in low–middle income countries (LMICs). Critical care management of sepsis is challenging in LMICs due to the lack of care providers and the high cost of bedside monitors. Recent advances in wearable sensor technology and machine learning (ML) models in healthcare promise to deliver new ways of digital monitoring integrated with automated decision systems to reduce the mortality risk in sepsis. In this study, firstly, we aim to assess the feasibility of using wearable sensors instead of traditional bedside monitors in the sepsis care management of hospital admitted patients, and secondly, to introduce automated prediction models for the mortality prediction of sepsis patients. To this end, we continuously monitored 50 sepsis patients for nearly 24 h after their admission to the Hospital for Tropical Diseases in Vietnam. We then compared the performance and interpretability of state-of-the-art ML models for the task of mortality prediction of sepsis using the heart rate variability (HRV) signal from wearable sensors and vital signs from bedside monitors. Our results show that all ML models trained on wearable data outperformed ML models trained on data gathered from the bedside monitors for the task of mortality prediction with the highest performance (area under the precision recall curve = 0.83) achieved using time-varying features of HRV and recurrent neural networks. Our results demonstrate that the integration of automated ML prediction models with wearable technology is well suited for helping clinicians who manage sepsis patients in LMICs to reduce the mortality risk of sepsis.

Polymorphisms in alpha 7 nicotinic acetylcholine receptor gene, CHRNA7, and its partially duplicated gene, CHRFAM7A, associate with increased inflammatory response in human peripheral mononuclear cells

The vagus nerve can, via the alpha 7 nicotinic acetylcholine receptor (α7nAChR), regulate inflammation. The gene coding for the α7nAChR, CHRNA7, can be partially duplicated, that is, CHRFAM7A, which is reported to impair the anti-inflammatory effect mediated via the α7nAChR. Several single nucleotide polymorphisms (SNPs) have been described in both CHRNA7 and CHRFAM7A, however, the functional role of these SNPs for immune responses remains to be investigated. In the current study, we set out to investigate whether genetic variants of CHRNA7 and CHRFAM7A can influence immune responses. By investigating data available from the Swedish SciLifeLab SCAPIS Wellness Profiling (S3WP) study, in combination with droplet digital PCR and freshly isolated PBMCs from the S3WP participants, challenged with lipopolysaccharide (LPS), we show that CHRNA7 and CHRFAM7A are expressed in human PBMCs, with approximately four times higher expression of CHRFAM7A compared with CHRNA7. One SNP in CHRFAM7A, rs34007223, is positively associated with hsCRP in healthy individuals. Furthermore, gene ontology (GO)-terms analysis of plasma proteins associated with gene expression of CHRNA7 and CHRFAM7A demonstrated an involvement for these genes in immune responses. This was further supported by in vitro data showing that several SNPs in both CHRNA7 and CHRFAM7A are significantly associated with cytokine response. In conclusion, genetic variants of CHRNA7 and CHRFAM7A alters cytokine responses. Furthermore, given that CHRFAM7A SNP rs34007223 is associated with inflammatory marker hsCRP in healthy individuals suggests that CHRFAM7A may have a more pronounced role in regulating inflammatory processes in humans than previously been recognized.

The Human-Restricted Isoform of the α7 nAChR, CHRFAM7A: A Double-Edged Sword in Neurological and Inflammatory Disorders

CHRFAM7A is a relatively recent and exclusively human gene arising from the partial duplication of exons 5 to 10 of the α7 neuronal nicotinic acetylcholine receptor subunit (α7 nAChR) encoding gene, CHRNA7. CHRNA7 is related to several disorders that involve cognitive deficits, including neuropsychiatric, neurodegenerative, and inflammatory disorders. In extra-neuronal tissues, α7nAChR plays an important role in proliferation, differentiation, migration, adhesion, cell contact, apoptosis, angiogenesis, and tumor progression, as well as in the modulation of the inflammatory response through the “cholinergic anti-inflammatory pathway”. CHRFAM7A translates the dupα7 protein in a multitude of cell lines and heterologous systems, while maintaining processing and trafficking that are very similar to the full-length form. It does not form functional ion channel receptors alone. In the presence of CHRNA7 gene products, dupα7 can assemble and form heteromeric receptors that, in order to be functional, should include at least two α7 subunits to form the agonist binding site. When incorporated into the receptor, in vitro and in vivo data showed that dupα7 negatively modulated α7 activity, probably due to a reduction in the number of ACh binding sites. Very recent data in the literature report that the presence of the duplicated gene may be responsible for the translational gap in several human diseases. Here, we will review the studies that have been conducted on CHRFAM7A in different pathologies, with the intent of providing evidence regarding when and how the expression of this duplicated gene may be beneficial or detrimental in the pathogenesis, and eventually in the therapeutic response, to CHRNA7-related neurological and non-neurological diseases.

Effects of Exercise Training on the Autonomic Nervous System with a Focus on Anti-Inflammatory and Antioxidants Effects

Studies show that the autonomic nervous system (ANS) has an important impact on health in general. In response to environmental demands, homeostatic processes are often compromised, therefore determining an increase in the sympathetic nervous system (SNS)’s functions and a decrease in the parasympathetic nervous system (PNS)’s functions. In modern societies, chronic stress associated with an unhealthy lifestyle contributes to ANS dysfunction. In this review, we provide a brief introduction to the ANS network, its connections to the HPA axis and its stress responses and give an overview of the critical implications of ANS in health and disease—focused specifically on the immune system, cardiovascular, oxidative stress and metabolic dysregulation. The hypothalamic–pituitary–adrenal axis (HPA), the SNS and more recently the PNS have been identified as regulating the immune system. The HPA axis and PNS have anti-inflammatory effects and the SNS has been shown to have both pro- and anti-inflammatory effects. The positive impact of physical exercise (PE) is well known and has been studied by many researchers, but its negative impact has been less studied. Depending on the type, duration and individual characteristics of the person doing the exercise (age, gender, disease status, etc.), PE can be considered a physiological stressor. The negative impact of PE seems to be connected with the oxidative stress induced by effort.

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.

The human-specific duplicated α7 gene inhibits the ancestral α7, negatively regulating nicotinic acetylcholine receptor-mediated transmitter release

Gene duplication generates new functions and traits, enabling evolution. Human-specific duplicated genes in particular are primary sources of innovation during our evolution although they have very few known functions. Here we examine the brain function of one of these genes (CHRFAM7A) and its product (dupα7 subunit). This gene results from a partial duplication of the ancestral CHRNA7 gene encoding the α7 subunit that forms the homopentameric α7 nicotinic acetylcholine receptor (α7-nAChR). The functions of α7-nAChR in the brain are well defined, including the modulation of synaptic transmission and plasticity underlying normal attention, cognition, learning, and memory processes. However, the role of the dupα7 subunit remains unexplored at the neuronal level. Here, we characterize that role by combining immunoblotting, quantitative RT-PCR and FRET techniques with functional assays of α7-nAChR activity using human neuroblastoma SH-SY5Y cell variants with different dupα7 expression levels. Our findings reveal a physical interaction between dupα7 and α7 subunits in fluorescent protein-tagged dupα7/α7 transfected cells that negatively affects normal α7-nAChR activity. Specifically, in both single cells and cell populations, the [Ca²⁺]_i signal and the exocytotic response induced by selective stimulation of α7-nAChR were either significantly inhibited by stable dupα7 overexpression or augmented after silencing dupα7 gene expression with specific siRNAs. These findings identify a new role for the dupα7 subunit as a negative regulator of α7-nAChR-mediated control of exocytotic neurotransmitter release. If this effect is excessive, it would result in an impaired synaptic transmission that could underlie the neurocognitive and neuropsychiatric disorders associated with α7-nAChR dysfunction.

Nicotinic Acetylcholine Receptor Involvement in Inflammatory Bowel Disease and Interactions with Gut Microbiota

The gut-brain axis describes a complex interplay between the central nervous system and organs of the gastrointestinal tract. Sensory neurons of dorsal root and nodose ganglia, neurons of the autonomic nervous system, and immune cells collect and relay information about the status of the gut to the brain. A critical component in this bi-directional communication system is the vagus nerve which is essential for coordinating the immune system’s response to the activities of commensal bacteria in the gut and to pathogenic strains and their toxins. Local control of gut function is provided by networks of neurons in the enteric nervous system also called the ‘gut-brain’. One element common to all of these gut-brain systems is the expression of nicotinic acetylcholine receptors. These ligand-gated ion channels serve myriad roles in the gut-brain axis including mediating fast synaptic transmission between autonomic pre- and postganglionic neurons, modulation of neurotransmitter release from peripheral sensory and enteric neurons, and modulation of cytokine release from immune cells. Here we review the role of nicotinic receptors in the gut-brain axis with a focus on the interplay of these receptors with the gut microbiome and their involvement in dysregulation of gut function and inflammatory bowel diseases.

Disruption of the cholinergic anti-inflammatory response by R5-tropic HIV-1 protein gp120JRFL

Despite current pharmacological intervention strategies, patients with HIV still suffer from chronic inflammation. The nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the nervous and immune systems. In macrophages, activation of alpha7-nAChR (α7-nAChR) controls inflammatory processes through the cholinergic anti-inflammatory response (CAR). Given that this innate immune response controls inflammation and α7-nAChR plays a critical role in the regulation of systemic inflammation, we investigated the effects of an R5-tropic HIV soluble component, gp120JRFL, on the CAR functioning. We previously demonstrated that X4-tropic HIV-1 gp120IIIB disrupts the CAR as well as inducing upregulation of the α7-nAChR in vitro in monocyte-derived macrophages (MDMs), which correlates with the upregulation observed in monocytes, T-lymphocytes, and MDMs recovered from HIV-infected people. We demonstrate here using imaging and molecular assays that the R5-tropic HIV-1 glycoprotein gp120JRFL upregulates the α7-nAChR in MDMs dependent on CD4 and/or CCR5 activation. This upregulation was also dependent on MEK1 since its inhibition attenuates the upregulation of α7-nAChR induced by gp120JRFL and was concomitant with an increase in basal calcium levels, which did not result in apoptosis. Moreover, the CAR was determined to be disrupted, since α7-nAChR activation in MDMs did not reduce the production of the proinflammatory cytokines IL-6, GRO-α, or I-309. Furthermore, a partial antagonist of α7-nAChR, bupropion, rescued IL-6 but not GRO-α or I-309 production. Together, these results demonstrate that gp120JRFL disrupts the CAR in MDMs. Other medications targeting the α7-nAChR need to be tested to reactivate the CAR to ameliorate inflammation in HIV-infected subjects.

The role of the cholinergic anti-inflammatory pathway in septic cardiomyopathy

Septic cardiomyopathy (SCM)is common in septic patients and results in cardiovascular failure. The pathogenesis of SCM is complicated, and patients with SCM have high mortality because current treatment methods are limited. The cholinergic anti-inflammatory pathway (CAP) modulates inflammatory responses through vagus nerve stimulation that leads to the release of acetylcholine (ACh), which binds to the alpha7 nicotinic acetylcholine receptor (α7nAChR). Moreover, α7nAChR activation by its agonists at the tissue level inhibits inflammatory mediators and regulates the function of immune cells in sepsis. Therefore, the α7nAChR can maintain balance of the inflammatory-immune response in sepsis. CAP has been elucidated as a critical regulator of anti-inflammation in many diseases, including rheumatoid arthritis, inflammatory boweldisease and SCM. Additionally, some clinical and preclinical trials show therapeutic potential via regulating CAP. There are excellent studies regarding the beneficial role of CAP activation, especially α7nAChR, in experimental SCM. This review aims to discuss the CAP in attenuating inflammation and the potential role of α7nAChR activation in regulating immune and reducing inflammation in SCM.

Sympathetic function and markers of inflammation in well-controlled HIV

PURPOSE

HIV-associated autonomic neuropathy (HIV-AN) is common and may be associated with both sympathetic and parasympathetic dysfunction. Sympathetic nervous system (SNS) dysfunction occurs on a continuum of hyper-to hypo-adrenergic function, and may be a mediator between psychological stress and chronic inflammation. We sought to describe patterns of SNS dysfunction in people living with HIV, and to determine whether SNS dysfunction is associated with markers of systemic inflammation (focusing on IL-6 and TNF-α) and pain and anxiety.

METHODS

Forty-seven people with well-controlled HIV and without confounding medical conditions or medications completed the Medical Outcomes Survey (MOS-HIV), quantification of a panel of 41 plasma cytokines/chemokines, and a standardized, non-invasive autonomic reflex screen (ARS). Adrenergic baroreflex sensitivity (BRSA) was calculated from the ARS as a measure of SNS function.

RESULTS

Pain (46%) and anxiety (52%) were commonly reported on the MOS-HIV. BRSA was reduced in 30% of participants and elevated in 9% with the latter occurring only in participants with normal to mild HIV-AN. BRSA was significantly associated with IL-6, but not with TNF-α, pain or anxiety. Exploratory analyses also revealed positive associations of BRSA with numerous other cytokines with no significant inverse associations.

CONCLUSION

Higher BRSA, indicative of a more hyperadrenergic state, can be part of the spectrum of early HIV-AN, and may be associated with elevations in multiple cytokines including IL-6. These associations do not appear to be driven by stressors such as pain or anxiety.

Tragus Nerve Stimulation Suppresses Post-Infarction Ventricular Arrhythmia by Modulating Autonomic Activity and Heterogeneities of Cardiac Receptor Distribution

Background

Imbalanced cardiac autonomic control and cardiac receptors redistribution contribute to the arrhythmogenic substrate under the myocardial infarction (MI) condition. Stimulating the auricular branch of vagus nerve (AB-VNS) has been proven to reduce post-infarction ventricular arrhythmia (VAs), but its potential mechanisms were largely unknown.

This study aimed to investigate whether long-term intermittent low-intensity AB-VNS could produce a protective effect on modulating autonomic activities and abnormal redistribution of autonomic nerve efferent receptors in a MI canine model.

Material/Methods

Twelve healthy beagle dogs underwent ligation of the left anterior descending coronary artery to establish a MI model and were randomized into 2 groups: an AB-VNS group, (AB-VNS for 4 weeks) and a control group (sham stimulation for 4 weeks). Dynamic electrocardiogram recording, neural recording, catecholamine concentration, and histological studies were conducted subsequently.

Results

Compared to the control group, the AB-VNS group had significantly suppressed post-infarction VAs, reduced low frequency (LF) power and increased high frequency (HF) power. In the AB-VNS group, with the progression of reduced cardiac sympathetic activities and augmented cardiac parasympathetic activities, the catecholamine concentration in heart tissue declined in the peripheral infarction area and right ventricle (RV); tyrosine hydroxylase (TH)-positive neurons decreased in the inferior cardiac sympathetic nerve, and choline acetyltransferase (ChAT)-positive neurons increased in the cervical vagus nerve. Expression of TrkA and P75NGFR were reduced in the peripheral MI (peri-MI) and non-MI area with AB-VNS. The mRNA expression of adrenergic and nicotinic receptors (β₁-AR, β₃-AR, and CHRNA7) significantly declined in the peri-MI and non-MI area of the AB-VNS group.

Conclusions

Chronic intermittent low-intensity AB-VNS effectively suppressed post-infarction VAs by potentially rebalancing extracardiac intrathoracic autonomic activities, reducing excessive cardiac sympathetic denervation, and attenuating the heterogeneities of cardiac efferent nerve receptors distribution.

Beyond neurotransmission: acetylcholine in immunity and inflammation

Acetylcholine (ACh) is best known as a neurotransmitter and was the first such molecule identified. ACh signalling in the neuronal cholinergic system has long been known to regulate numerous biological processes (reviewed by Beckmann and Lips). In actuality, ACh is a ubiquitous signalling molecule that is produced by numerous non-neuronal cell types and even by some single-celled organisms. Within multicellular organisms, a non-neuronal cholinergic system that includes the immune system functions in parallel with the neuronal cholinergic system. Several immune cell types both respond to ACh signals and can directly produce ACh. Recent work from our laboratory has demonstrated that the capacity to produce ACh is an intrinsic property of T cells responding to viral infection, and that this ability to produce ACh is dependent upon IL-21 signalling to the T cells. Furthermore, during infection this immune-derived ACh is necessary for the T cells to migrate into infected tissues. In this review, we will discuss the various sources of ACh that are relevant during immune responses and describe how ACh acts on immune cells to influence their functions. We will also address the clinical implications of this fascinating aspect of immunity, focusing on ACh's role in the migration of T cells during infection and cancer.

GTS-21 ameliorates polymicrobial sepsis-induced hepatic injury by modulating autophagy through α7nAchRs in mice

BACKGROUND

Previous studies showed that GTS-21, a selective alpha 7 nAchR agonist, can trigger anti-inflammatory effects and improve the survival of septic animals. However, whether GTS-21 affects autophagy responses remains unclear. Here, we tested the hypothesis that GTS-21 ameliorates sepsis-induced hepatic injury by modulating autophagy in mice.

METHOD

C57BL/6 male mice were randomly separated and categorized into four groups: the sham group, and CLP group subjected to caecal ligation and puncture (CLP, a model of polymicrobial sepsis). The CLP + GTS-21 group was administered GTS-21 immediately after CLP challenge. α-Bungarotoxin (an alpha 7 nAchR antagonist) was injected before CLP was performed, and then, after CLP challenge, GTS-21 was administered to α-BGT + CLP + GTS-21 group. The hepatic tissue and blood samples were harvested 6 h after the operation.

RESULTS

CLP challenge increased TNF-α and IL-6 production, and hepatic enzyme alanine aminotransferase and aspartate transaminase levels. CLP also elevated the expression of hepatic LC3-II, sequestosome-1/p62, Atg7 and Atg5. The administration of GTS-21 inhibited pro-inflammatory cytokine production and hepatic enzymatic marker expression, promoted the expression of LC3-II, Atg7, Atg5, and decreased the expression of p62, which could be reversed by α-BGT treatment.

CONCLUSION

Our findings suggested that α7nAchR is involved in diminishing hepatic damage by inhibiting inflammatory responses and improving autophagy in mice with polymicrobial sepsis.

Sepsis-associated encephalopathy: a vicious cycle of immunosuppression

Sepsis-associated encephalopathy (SAE) is commonly complicated by septic conditions, and is responsible for increased mortality and poor outcomes in septic patients. Uncontrolled neuroinflammation and ischemic injury are major contributors to brain dysfunction, which arises from intractable immune malfunction and the collapse of neuroendocrine immune networks, such as the cholinergic anti-inflammatory pathway, hypothalamic-pituitary-adrenal axis, and sympathetic nervous system. Dysfunction in these neuromodulatory mechanisms compromised by SAE jeopardizes systemic immune responses, including those of neutrophils, macrophages/monocytes, dendritic cells, and T lymphocytes, which ultimately results in a vicious cycle between brain injury and a progressively aberrant immune response. Deep insight into the crosstalk between SAE and peripheral immunity is of great importance in extending the knowledge of the pathogenesis and development of sepsis-induced immunosuppression, as well as in exploring its effective remedies.

A Personalized Signature and Chronotherapy-Based Platform for Improving the Efficacy of Sepsis Treatment

Sepsis remains a major therapeutic challenge and is associated with a high rate of morbidity and mortality. It is a dynamic condition in which multiple parameters change over time, rendering it difficult to overcome the various injurious responses, which worsen the prognosis in these patients. The prognosis of sepsis is associated with a disbalance of compensatory responses to infectious triggers, part of which can be deleterious. Marked inter- and intra-patient variability characterizes the mechanisms that underlie sepsis progression and determine the response to therapy. In this paper, we review some of the data on the use of chronopharmacological approaches for the treatment of patients with sepsis and discuss the role of the autonomic nervous system in the mechanisms associated with immune response and chronotherapy in these patients. We describe the implementation of an individualized platform that is based on the personalized autonomic nervous system, immune, and chronobiology-derived parameters for generating a patient-tailored therapeutic regimen. The notion of overcoming the deleterious compensatory response in a highly dynamic system in sepsis is presented to ensure an improved response to current therapies.

Dexmedetomidine-mediated protection against septic liver injury depends on TLR4/MyD88/NF-κB signaling downregulation partly via cholinergic anti-inflammatory mechanisms

BACKGROUND

Uncontrolled inflammatory responses exacerbate the pathogenesis of septic acute liver injury (ALI), posing a lethal threat to the host. Dexmedetomidine (DEX) has been reported to possess protective properties in inflammatory conditions. This study aimed to investigate whether DEX pretreatment exhibits hepatoprotection against ALI induced by lipopolysaccharide (LPS) in rats and determine its possible molecular mechanism.

METHODS

Septic ALI was induced by intravenous injection of LPS. The rats received DEX intraperitoneally 30 min before LPS administration. α-Bungarotoxin (α-BGT), a specific α7 nicotinic acetylcholine receptor (α7nAChR) antagonist, was administered intraperitoneally 1 h before LPS exposure. The role of the vagus nerve was verified by performing unilateral cervical vagotomy or sham surgery before sepsis.

RESULTS

The expression of α7nAChR, toll-like receptor 4 (TLR4), high mobility group box 1 (HMGB1), and cleaved caspase-3 increased, peaking 24 h during sepsis. DEX enhanced α7nAChR activation and reduced TLR4 expression upon challenge with LPS. DEX significantly prevented LPS-induced ALI, which was associated with increased survival, the mitigation of pathological changes, the attenuation of inflammatory cytokine expression and apoptosis, and the downregulation of TLR4/MyD88/NF-κB pathway. Moreover, the hepatoprotective effect of DEX was abolished by α-BGT. Further investigation established that vagotomy, compared to sham surgery, triggered more severe pathogenic manifestations and higher proinflammatory cytokine levels. The inhibitory effects of DEX were shown in sham-operated rats but not in vagotomized rats.

CONCLUSIONS

Our data highlight the pivotal function of α7nAChR and intact vagus nerves in protecting against LPS-induced ALI through inhibiting the TLR4/MyD88/NF-κB signaling pathway upon pretreatment with DEX.

Downregulation of α7 nicotinic acetylcholine receptors in peripheral blood monocytes is associated with enhanced inflammation in preeclampsia

Background

Preeclampsia is associated with chronic inflammation. The cholinergic anti-inflammatory pathway regulates systemic inflammation through activating α7 nicotinic acetylcholine receptors (α7nAChR) expressed in monocytes/macrophages. This study aimed to investigate the role of α7nAChR in peripheral blood monocytes in preeclampsia.

Methods

Peripheral blood monocytes were isolated from 30 nonpregnant (NP), 32 normotensive pregnant (NT), and 35 preeclamptic (PE) women.

Results

We found that both protein and mRNA expression levels of α7nAChR in monocytes from the PE women were significantly lower than those of the NP and NT women (both p < 0.01). α7nAChR protein expression levels in monocytes were negatively correlated with levels of systolic blood pressure (r = − 0.40, p = 0.04), proteinuria (r = − 0.54, p < 0.01), tumor necrosis factor-alpha (TNF-α, r = − 0.42, p = 0.01), and interleukin (IL)-1β (r = − 0.56, p < 0.01), while positively correlated with IL-10 levels (r = 0.43, p = 0.01) in the PE women. Both baseline and lipopolysaccharides (LPS)-induced increase of TNF-α, IL-1β, and IL-6 levels from monocytes were higher in the PE group than the NP and NT groups (all p < 0.01), but IL-10 levels in the PE group was lower than that of the NP and NT groups (p < 0.01). In addition, the NF-κB activity in monocytes from the PE women was higher than the NP and NT women (p < 0.01). Importantly, activation of α7nAChR with its agonist PNU-282987 inhibited NF-κB, decreased TNF-α, IL-1β, and IL-6 release, and increased IL-10 release in monocytes from the PE women (all p < 0.01).

Conclusion

In conclusion, these findings suggest that downregulation of α7nAChR may be associated with the development of preeclampsia through increasing pro-inflammatory and decreasing anti-inflammatory cytokine release via the NF-κB pathway.

Anti-tumoral activity of the human-specific duplicated form of α7-nicotinic receptor subunit in tobacco-induced lung cancer progression

OBJECTIVES

Tobacco smoking is strongly correlated with the onset and progression of non-small cell lung cancer (NSCLC). By activating α7 nicotinic acetylcholine receptors (α7-nAChRs) in these tumors nicotine and its tobacco-derived nitrosamine, NNK, contribute to these oncogenic processes. Here, we investigated whether the human-specific duplicated form of the α7-nAChR subunit (dupα7) behaves as an endogenous negative regulator of α7-nAChR-mediated tumorigenic activity induced by tobacco in NSCLC cells, similarly to its influence on other α7-nAChR-controlled functions in non-tumor cells.

METHODS

Two human NSCLC cell lines, lung adenocarcinoma (A549) and squamous cell carcinoma of the lung (SK-MES-1), both wild-type or with stable overexpression of dupα7 (A549^dupα7 or SK-MES-1^dupα7), were used to investigate in vitro anti-tumor activity of dupα7 on nicotine- or NNK-induced tumor progression. For this purpose, migration, proliferation or epithelial-mesenchymal transition (EMT) were examined. The anti-tumor effect of dupα7 on nicotine-promoted tumor growth, proliferation or angiogenesis was also assessed in vivo in an athymic mouse model implanted with A549^dupα7 or A549 xenografts.

RESULTS

Overexpression of dupα7 in both cell lines almost completely suppresses the in vitro tumor-promoting effects induced by nicotine (1 μM) or NNK (100 nM) in wild-type cells. Furthermore, in mice receiving nicotine, A549^dupα7 xenografts show: (i) a significant reduction of tumor growth, and (ii) decreased expression of cell markers for proliferation (Ki67) or angiogenesis (VEGF) compared to A549 xenografts.

CONCLUSION

Our study demonstrates, for the first time, the in vitro and in vivo anti-tumor capacity of dupα7 to block the α7-nAChR-mediated tumorigenic effects of tobacco in NSCLC, suggesting that up-regulation of dupα7 expression in these tumors could offer a potential new therapeutic target in smoking-related cancers.

Heart rate variability as predictor of mortality in sepsis: A systematic review

BACKGROUND

Autonomic dysregulation is one of the recognized pathophysiological mechanisms in sepsis, generating the hypothesis that heart rate variability (HRV) can be used to predict mortality in sepsis.

METHODS

This was a systematic review of studies evaluating HRV as a predictor of death in patients with sepsis. The search was performed by independent researchers in PubMed, LILACS and Cochrane, including papers in English, Portuguese or Spanish, indexed until August 20th, 2017 with at least 10 patients. Study quality was assessed by Newcastle-Ottawa Scale. To analyze the results, we divided the articles between those who measured HRV for short-term recordings (≤ 1 hour), and those who did long-term recordings (≥ 24 hours).

RESULTS

Nine studies were included with a total of 536 patients. All of them were observational studies. Studies quality varied from 4 to 7 stars in Newcastle-Ottawa Scale. The mortality rate in the studies ranged from 8 to 61%. Seven studies performed HRV analysis in short-term recordings. With the exception of one study that did not explain which group had the lowest results, all other studies showed reduction of several HRV parameters in the non-survivors in relation to the surviving septic patients. SDNN (Standard deviation of the Normal to Normal interval), TP (Total Power), VLF (Very Low Frequency Power), LF (Low Frequency Power), LF/HF (Low Frequency Power / High Frequency Power), nLF (Normalized Low Frequency Power), α1/α2 (short-term and long-term fractal scaling coefficients from DFA) and r-MSSD (Square root of the squared mean of the difference of successive NN-intervals) of the non-survivor group were reduced in relation to the survivors in at least one study. Two studies found that SDNN is associated with mortality in sepsis, even after adjusting for possible confounding factors. Three studies performed HRV analysis using long-term recordings. Only one of these studies found difference between surviving and non-surviving groups, and even so, in only one HRV parameter: LogHF.

CONCLUSIONS

Several HRV parameters are reduced in nonsurviving septic patients in short-term recording. Two studies have found that SDNN is associated with mortality in sepsis, even after adjusting for possible confounding factors.

Interaction of the α7-nicotinic subunit with its human-specific duplicated dupα7 isoform in mammalian cells: Relevance in human inflammatory responses

The α7 nicotinic receptor subunit and its partially duplicated human-specific dupα7 isoform are coexpressed in neuronal and non-neuronal cells. In these cells, α7 subunits form homopentameric α7 nicotinic acetylcholine receptors (α7-nAChRs) implicated in numerous pathologies. In immune cells, α7-nAChRs are essential for vagal control of inflammatory response in sepsis. Recent studies show that the dupα7 subunit is a dominant-negative regulator of α7-nAChR activity in Xenopus oocytes. However, its biological significance in mammalian cells, particularly immune cells, remains unexplored, as the duplicated form is indistinguishable from the original subunit in standard tests. Here, using immunocytochemistry, confocal microscopy, coimmunoprecipitation, FRET, flow cytometry, and ELISA, we addressed this challenge in GH4C1 rat pituitary cells and RAW264.7 murine macrophages transfected with epitope- and fluorescent protein-tagged α7 or dupα7. We used quantitative RT-PCR of dupα7 gene expression levels in peripheral blood mononuclear cells (PBMCs) from patients with sepsis to analyze its relationship with PBMC α7 mRNA levels and with serum concentrations of inflammatory markers. We found that a physical interaction between dupα7 and α7 subunits in both cell lines generates heteromeric nAChRs that remain mainly trapped in the endoplasmic reticulum. The dupα7 sequestration of α7 subunits reduced membrane expression of functional α7-nAChRs, attenuating their anti-inflammatory capacity in lipopolysaccharide-stimulated macrophages. Moreover, the PBMC's dupα7 levels correlated inversely with their α7 levels and directly with the magnitude of the patients' inflammatory state. These results indicate that dupα7 probably reduces human vagal anti-inflammatory responses and suggest its involvement in other α7-nAChR-mediated pathophysiological processes.

Activation of the monocytic α7 nicotinic acetylcholine receptor modulates oxidative stress and inflammation-associated development of coronary artery spasm via a p38 MAP-kinase signaling-dependent pathway

OBJECTIVE

Smoking and high-sensitivity C-reactive protein (hs-CRP) are risk factors for coronary artery spasm (CAS), which is characterized by the increased interleukin-6 (IL-6) level and monocyte counts; however, limited data are available regarding the role of cigarette-embedded nicotine in the modulation of monocytic inflammatory activity in CAS.

APPROACH

We investigated and elucidated the putative roles and associations of nicotine, monocytic IL-6, α7 nicotinic acetylcholine receptor (α7-nAChR), and CRP in CAS development.

RESULTS

We demonstrated that a significantly increased α7-nAChR (p = 0.001) and IL-6 (p = 0.0036) messenger RNA (mRNA) expression in the serum of patients with CAS. Serum hs-CRP levels exhibited a strong positive correlation with the monocytic mRNA expression of α7-nAChR (r = 0.71, p < 0.001) and IL-6 (r = 0.49, p = 0.006). The α7-nAChR and IL-6 expression levels of the CAS group were also positively correlated (r = 0.63, p < 0.001). Compared with the untreated controls, THP-1 cells and patient-derived monocytes treated with different concentrations of CRP displayed significantly increased expression levels of α7-nAChR mRNA and protein (p = 0.0054), in a dose-dependent manner. We also demonstrated that compared with the IL-6 expression elicited by CRP alone (p = 0.0489), the CRP-induced rise in monocytic IL-6 mRNA and protein expression in the presence of nicotine (p = 0.0002), is mediated by α7-nAChR activation and the deregulation of the human p38 mitogen-activated protein kinases (MAPK) signaling pathway.

CONCLUSIONS

Our data demonstrate that the elevated monocytic IL-6 and α7-nAChR mRNA and protein expression levels are associated with the interaction between nicotine and CRP positively modulates CAS development. Our study suggests the potential role of α7-nAChR mRNA and/or protein expression as a diagnostic biomarker for CAS.

New Insights on Neuronal Nicotinic Acetylcholine Receptors as Targets for Pain and Inflammation: A Focus on α7 nAChRs

BACKGROUND

Nicotine and nicotinic acetylcholine receptors (nAChRs) have been explored for the past three decades as targets for pain control. The aim of this review is to introduce readers particularly to α7 nAChRs in a perspective of pain and its modulation.

METHODS

Developments for α7 nAChR modulators and recent animal studies related to pain are reviewed.

RESULTS

Accumulating evidences suggest that selective ligands for α7 nAChRs hold promise in the treatment of chronic pain conditions as they lack many of side effects associated with other nicotinic receptor types.

CONCLUSION

This review provides the reader recent insights on α7 nAChRs from structure and function to the latest findings on the pharmacology and therapeutic targeting of these receptors for the treatment of pain and inflammation.

Nicotinic acetylcholine receptors in neuropathic and inflammatory pain

Nicotinic acetylcholine receptors (nAChRs) are actively being investigated as therapeutic targets for the treatment of pain and inflammation, but despite more than 30 years of research, there are currently no FDA-approved analgesics that are specific for these receptors. Much of the initial research effort focused on the α4β2 nAChR subtype, but more recently, additional subtypes have been identified as promising new leads and include α6β4, α7, and α9-containing nAChRs. This Review will focus on the distribution of these nAChRs in the cell types involved in neuropathic pain and inflammation and the activity of currently available nicotinic ligands.

Expression patterns for nicotinic acetylcholine receptor subunit genes in smoking-related lung cancers

Cigarette smoking is associated with increased risk for all histologic types of lung cancer, but why the strength of this association is stronger for squamous cell carcinoma than adenocarcinoma of the lung (SQC-L, ADC-L) is not fully understood. Because nicotine and tobacco-specific nitrosamines contribute to carcinogenesis by activating nicotinic acetylcholine receptors (nAChRs) on lung tumors and epithelial cells, we investigated whether differential expression of nAChR subtypes in these tumors could explain their different association with smoking. Expression of nAChR subunit genes in paired tumor and non-tumor lung specimens from 40 SQC-L and 38 ADC-L patients was analyzed by quantitative PCR. Compared to normal lung, both tumors share: i) transcriptional dysregulation of CHRNA3/CHRNA5/CHRNB4 (α3, α5, β4 subunits) at the chromosomal locus that predisposes to lung cancer; and ii) decreased expression of CHRFAM7A (dupα7 subunit); this last subunit negatively modulates α7-nAChR activity in oocytes. In contrast, CHRNA7 (α7 subunit) expression was increased in SQC-L, particularly in smokers and non-survivors, while CHRNA4 (α4 subunit) expression was decreased in ADC-L. Thus, over-representation of cancer-stimulating α7-nAChR in SQC-L, also potentiated by smoking, and under-representation of cancer-inhibiting α4β2-nAChR in ADC-L could explain the different tobacco influences on the tumorigenic process in each cancer type.

The Protective Effect of Alpha 7 Nicotinic Acetylcholine Receptor Activation on Critical Illness and Its Mechanism

Critical illnesses and injuries are recognized as major threats to human health, and they are usually accompanied by uncontrolled inflammation and dysfunction of immune response. The alpha 7 nicotinic acetylcholine receptor (α7nAchR), which is a primary receptor of cholinergic anti-inflammatory pathway (CAP), exhibits great benefits for critical ill conditions. It is composed of 5 identical α7 subunits that form a central pore with high permeability for calcium. This putative structure is closely associated with its functional states. Activated α7nAChR exhibits extensive anti-inflammatory and immune modulatory reactions, including lowered pro-inflammatory cytokines levels, decreased expressions of chemokines as well as adhesion molecules, and altered differentiation and activation of immune cells, which are important in maintaining immune homeostasis. Well understanding of the effects and mechanisms of α7nAChR will be of great value in exploring effective targets for treating critical diseases.

Therapeutic potential and limitations of cholinergic anti-inflammatory pathway in sepsis

Sepsis is one of the main causes of mortality in hospitalized patients. Despite the recent technical advances and the development of novel generation of antibiotics, severe sepsis remains a major clinical and scientific challenge in modern medicine. Unsuccessful efforts have been dedicated to the search of therapeutic options to treat the deleterious inflammatory components of sepsis. Recent findings on neuronal networks controlling immunity raised expectations for novel therapeutic strategies to promote the regulation of sterile inflammation, such as autoimmune diseases. Interesting studies have dissected the anatomical constituents of the so-called "cholinergic anti-inflammatory pathway", suggesting that electrical vagus nerve stimulation and pharmacological activation of beta-2 adrenergic and alpha-7 nicotinic receptors could be alternative strategies for improving inflammatory conditions. However, the literature on infectious diseases, such as sepsis, is still controversial and, therefore, the real therapeutic potential of this neuroimmune pathway is not well defined. In this review, we will discuss the beneficial and detrimental effects of neural manipulation in sepsis, which depend on the multiple variables of the immune system and the nature of the infection. These observations suggest future critical studies to validate the clinical implications of vagal parasympathetic signaling in sepsis treatment.

Vagal Modulation of the Inflammatory Response in Sepsis

The vagus nerve can sense peripheral inflammation and transmit action potentials from the periphery to the brainstem. Vagal afferent signaling is integrated in the brainstem, and efferent vagus nerves carry outbound signals that terminate in spleen and other organs. Stimulation of efferent vagus nerve leads to the release of acetylcholine in these organs. In turn, acetylcholine interacts with members of the nicotinic acetylcholine receptor (nAChR) family, particularly with the alpha7 nicotinic acetylcholine receptor (α7nAChR), which is expressed by macrophages and other cytokine-producing cells. Ultimately, the production of proinflammatory cytokines is markedly inhibited. This neuroimmune communication is termed "the inflammatory reflex". The uncontrolled inflammation as a result from sepsis can lead to multiple organ failure, and even death. Experimental data show that regulation of the inflammatory reflex appears to be a useful interventional strategy for septic response. Herein, we review recent advances in the understanding of the inflammatory reflex and discuss potential therapeutics that vagal modulation of the immune system for the treatment of severe sepsis and septic shock.

Inhibited Expression of α4β2 Nicotinic Acetylcholine Receptor in Blood Leukocytes of Chinese Patients with Vascular Dementia and in Blood Leukocytes as Well as the Hippocampus of Brain from Ischemic Rats

Our present aim was to investigate whether changes in the expression of α₄β₂ nicotinic acetylcholine receptor (nAChR) in patients with vascular dementia (VaD) and ischemic rats are related to cognitive scores. Blood leukocytes for 59 Chinese patients with VaD (diagnosed on the basis of clinical guidelines) and 31 cases as age-matched controls were examined, and the animal model established employing Pulsinelli's four-vessel occlusion. The levels of α₄ and β₂ subunit mRNA in leukocytes and the hippocampus were analyzed by real-time PCR, and the protein level in the hippocampus by Western blotting. The mini-mental state examination was utilized to characterize the intellectual capacity of the patients with reference to the DSM IV diagnosis and Hachinski Ischemic Scale score, and the Morris Water Maze test to assess the ability of learning and memory of the rats. In patients, the level of α₄ mRNA, but not β₂, in blood leukocytes was clearly lowered, which was significantly correlated to their clinical cognitive test scores. Smoking exerted no impact on the level of α₄ mRNA in the present study. In the blood leukocytes and the hippocampus of the brains of the ischemic rats, the levels of both α₄ and β₂ mRNA were lowered, and the proteins of these subunits in the hippocampus were decreased. The changes of α₄ and β₂ mRNA in blood leukocytes, and their protein levels in the hippocampus were significantly correlated with impaired learning and memory. These findings indicate that alterations in expression of the α₄β₂ subtype of nAChR may be involved in the molecular mechanism(s) underlying the cognitive deficit associated with VaD.

Non-Neuronal Acetylcholine: The Missing Link Between Sepsis, Cancer, and Delirium?

The interaction between living organisms and the environment requires a balancing act between genomic and epigenomic forces. Inflammation and cellular proliferation are kept in check by the genes, which code for their components and the microRNAs, which are capable of silencing the transcription of these genes. Acetylcholine (ACh) may play a unique role in the maintenance of this equilibrium, as the epigenomic inhibition of the gene coding for nicotinic receptors, and disinhibits the gene causing anergia in immune cells. We hypothesize that age-induced ACh deficiency is the result of an epigenomic dysfunction of microRNA-6775 (miR-6775), which silences the transcription of CHRNA7 gene [coding for alpha 7 nicotinic cholinergic receptors (nAChRs)]. When silenced, this gene induces decreased expression of alpha 7 nAChRs, which may predispose elderly individuals to inflammation, neuroinflammation, and delirium. We hypothesize further that miR-6775-induced hypocholinergia augments the expression of RNF 128, the gene related to anergy in lymphocytes (GRAIL). This gene favors regulatory T cells (Tregs), promoters of immunologic tolerance, which may predispose to both cancer and sepsis-induced immunosuppression.