Molecular and Functional Neuroscience in Immunity

Microglial and Macrophage Plasticity and Regional Cerebral Blood Flow in the Prenatal Brain and Gut Under Vagus Nerve Stimulation

An intricate relationship exists between the vagus nerve and systemic immune cell regulation, specifically during fetal development. Little is known about the connection between the vagus nerve and the brain's regional circulatory control. In this chapter, we present a methodology for studying the impact of vagus nerve signaling on these connections in the developing fetus using the sheep model for human fetal physiology. First, we present the protocol to study the connection between the vagus nerve physiology and the regional cerebral blood flow (rCBF). Next, we detail the protocol for measuring how vagal signaling alters microglial cell plasticity in gut and brain. In previous work, our team showed that vagotomy results in amplified redistribution of rCBF toward subcortical structures in the fetal brain. Conversely, efferent VNS reduces rCBF to cortical structures while afferent VNS diminishes the rise of rCBF to subcortical structures (independent of cortical rCBF) when compared to controls in the fetal brain. Additionally, our team showed that Iba-1 expression, a marker for microglial cellular signaling activation, rises in a dose-dependent relationship with systemic inflammatory activation in the setting of vagotomy. The findings support existing preclinical and clinical evidence in adult human physiology that vagotomy is neuroprotective for neurodegenerative diseases such as Parkinson's likely via a glial cell-mediated mechanism. Vagus nerve stimulation (VNS) has also been shown to alter rCBF patterns in adults with treatment-resistant depression, underscoring the importance of further investigation of the relationship between the vagus nerve and rCBF as early as in utero. Together, the body of evidence emphasizes that the vagal pathway is an important player in the programming of microglial cell phenotypes within the developing brain. Further study is needed to better understand the significance of these relationships for the development and treatment of early susceptibility to neuroinflammatory and neurodegenerative disorders in later life. Therefore, we present a methodology for assessing rCBF and morphometric features of microglial and macrophage cell activation to allow future teams to expand on the existing body of work and further examine these relationships at a cellular and systems' levels.

A Mechanistic Analysis of the Neural Modulation of the Inflammatory System Through Vagus Nerve Stimulation: A Systematic Review and Meta-analysis

OBJECTIVE

We aimed to conduct a systematic review and meta-analysis assessing the antiinflammatory effects of various VNS methods while exploring multiple antiinflammatory pathways.

MATERIALS AND METHODS

We included clinical trials that used electrical stimulation of the vagus nerve and assessed inflammatory markers up to October 2022. We excluded studies lacking control groups, those with combined interventions, or abstracts without full text. We adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and the Cochrane Handbook for Systematic Reviews. For each inflammatory marker, a random-effects meta-analysis using the inverse variance method was performed. Methods used include transcutaneous auricular VNS (taVNS), transcutaneous cervical VNS (tcVNS), invasive cervical VNS (iVNS), and electroacupuncture VNS (eaVNS). Main reported outcomes included tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-1ß, C-reactive protein (CRP), and IL-10. Risk of bias was evaluated using the Cochrane Collaboration Tool (RoB 2.0).

RESULTS

This review included 15 studies, involving 597 patients. No statistically significant general VNS effect was observed on TNF-α, IL-6, and IL-1ß. However, CRP, IL-10, and interferon (IFN)-γ were significantly modulated by VNS across all methods. Subgroup analysis revealed specific stimulation techniques producing significant results, such as taVNS effects in IL-1ß and IL-10, and iVNS in IL-6, whereas tcVNS and eaVNS did not convey significant pooled results individually. Cumulative exposure to VNS, higher risk of bias, study design, and pulse width were identified as effect size predictors in our meta-regression models.

CONCLUSIONS

Pooling all VNS techniques indicated the ability of VNS to modulate inflammatory markers such as CRP, IL-10, and IFN-γ. Individually, methods such as taVNS were effective in modulating IL-1ß and IL-10, whereas iVNS modulated IL-6. However, different VNS techniques should be separately analyzed in larger, homogeneous, and powerful studies to achieve a clearer and more consistent understanding of the effect of each VNS method on the inflammatory system.

Acute Effects of Slow-Paced Breathing on Measures of HRV in Hospitalized Patients With Bilateral COVID-19 Pneumonia: A Secondary Analysis of a Randomized Clinical Trial

OBJECTIVE

Slow-paced breathing (SPB) with prolonged exhalation is assumed to stimulate vagal reflexes, which is represented by increased heart rate variability (HRV) values. However, most trials were conducted in healthy participants. We sought to evaluate the feasibility of SPB in hospitalized patients with confirmed bilateral COVID-19 pneumonia with major respiratory impairment and to investigate if SPB shows acute increasing effects on HRV measures in these severely ill patients with distinctly reduced vagal tone.

METHODS

This single-center randomized controlled clinical trial enrolled 23 patients in the intervention (4-second inhalation, 6-second exhalation for 20 minutes 3× daily) and 23 patients in the control group (IG/CG). The effects of SPB on HRV were calculated using post-hoc likelihood ratio tests. Baseline HRV measures between the groups over time were compared using multilevel mixed-effect linear regression models with random slope including the covariates relevant comorbidities, COVID-19 medication, and age.

RESULTS

HRV values at baseline were significantly decreased in all patients. During SPB, HRV parameters increased significantly (ln(SDNN), ln(LF), ln(TP); all p < .001). Higher breathing rate at baseline correlated with lower LF during SPB (p < .045). IL-6 morning levels were associated with lower HRV measures (p < .001). Resting HRV measures as well as subjective health increased over hospitalization time with no differences between IG and CG (comparing random slope with random slope interaction models: all LR χ2(5) < 4.5; p > .48).

CONCLUSION

SPB is feasible and safe in patients with bilateral COVID-19 pneumonia and appears to be an effective self-performed intervention to acutely increase HRV measures. This observation was independent of comorbidities and comedication. Further trials should corroborate these findings and extend it to other severely ill populations.

REGISTRATION

German Clinical Trials Register under ID DRKS00023971 (https://drks.de/search/en/trial/DRKS00023971), with a Universal Trial Number (UTN) U1111-1263-8658.

Autonomic function and change in functional capacity in older adults: a longitudinal investigation

Functional capacity is an important objective health metric, and relies on the maintenance of physiological homeostasis. Autonomic nervous system is known to coordinates the maintenance of multi-organ homeostasis. The objective of this study was to examine the association of autonomic nervous system function with functional capacity in adults aged 55 years and older. A cohort of 542 adults (mean age of 70.1 years) received repeated measurements of heart rate variability, an autonomic nervous system function marker, and chair rise time, a functional capacity measure. Linear mixed models analysis showed that 1 SD lower powers in low-frequency range at baseline was associated with a 0.11 (95% CI 0.01-0.21) s/year faster increase in chair rise time during the follow-up, whereas 1 SD increase in powers in high-frequency range and 1 SD decrease in the ratio of powers in low-frequency range to powers in high-frequency range during the follow-up were associated with a 0.22 (95% CI 0.06-0.39) s and 0.17 (95% CI 0.01-0.33) s increase in chair rise time. In conclusion, autonomic nervous system function and its changes were longitudinally associated with changes in functional capacity in older adults.

The vagus nerve: An old but new player in brain-body communication

The vagus nerve is a crucial component of the parasympathetic nervous system, facilitating communication between the brain and various organs, including the ears, heart, lungs, pancreas, spleen, and gastrointestinal tract. The caudal nucleus of the solitary tract in the brainstem is the initial site regulated by the vagus nerve in brain-body communication, including the interactions with immune system. Increasing evidence suggests that the gut-brain axis, via the vagus nerve, may play a role in the development and progression of psychiatric, neurologic, and inflammation-related disorders. Population-based cohort studies indicate that truncal vagotomy may reduce the risk of neurological disorders such as Parkinson's disease and Alzheimer's disease, underscoring the vagus nerve's significance in these conditions. Given its role in the cholinergic anti-inflammatory pathway, α7 nicotinic acetylcholine receptors present a potential therapeutic target. Additionally, noninvasive transcutaneous auricular vagus nerve stimulation (taVNS) shows promise as a therapeutic tool for these disorders. This article provides a historical review of the vagus nerve and explores its role in brain-body communication. Finally, we discuss future directions, including the potential of noninvasive taVNS as a therapeutic approach.

The area postrema: a critical mediator of brain-body interactions

The dorsal vagal complex contains three structures: the area postrema, the nucleus tractus solitarii, and the dorsal motor nucleus of the vagus. These structures are tightly linked, both anatomically and functionally, and have important yet distinct roles in not only conveying peripheral bodily signals to the rest of the brain but in the generation of behavioral and physiological responses. Reports on the new discoveries in these structures were highlights of the symposium. In this outlook, we focus on the roles of the area postrema in mediating brain-body interactions and its potential utility as a therapeutic target, especially in cancer cachexia.

Microbiota-immune-brain interactions: A new vision in the understanding of periodontal health and disease

This review highlights the significance of interactions between the microbiota, immune system, nervous and hormonal systems, and the brain on periodontal health and disease. Microorganisms in the microbiota, immune cells, and neurons communicate via homeostatic nervous and hormonal systems, regulating vital body functions. By modulating pro-inflammatory and anti-inflammatory adaptive immune responses, these systems control the composition and number of microorganisms in the microbiota. The strength of these brain-controlled responses is genetically determined but is sensitive to early childhood stressors, which can permanently alter their responsiveness via epigenetic mechanisms, and to adult stressors, causing temporary changes. Clinical evidence and research with humans and animal models indicate that factors linked to severe periodontitis enhance the responsiveness of these homeostatic systems, leading to persistent hyperactivation. This weakens the immune defense against invasive symbiotic microorganisms (pathobionts) while strengthening the defense against non-invasive symbionts at the gingival margin. The result is an increased gingival tissue load of pathobionts, including Gram-negative bacteria, followed by an excessive innate immune response, which prevents infection but simultaneously destroys gingival and periodontal tissues. Thus, the balance between pro-inflammatory and anti-inflammatory adaptive immunity is crucial in controlling the microbiota, and the responsiveness of brain-controlled homeostatic systems determines periodontal health.

The protective effect of erythropoietin and its novel derived peptides in peripheral nerve injury

Peripheral nerve injury seriously endangers human life and health, but there is no clinical drug for the treatment of peripheral nerve injury, so it is imperative to develop drugs to promote the repair of peripheral nerve injury. Erythropoietin (EPO) not only has the traditional role of promoting erythropoiesis, but also has a tissue-protective effect. Over the past few decades, researchers have confirmed that EPO has neuroprotective effects. However, side effects caused by long-term use of EPO limited its clinical application. Therefore, EPO derivatives with low side effects have been explored. Among them, ARA290 has shown significant protective effects on the nervous system, but the biggest disadvantage of ARA290, its short half-life, limits its application. To address the short half-life issue, the researchers modified ARA290 with thioether cyclization to generate a thioether cyclized helical B peptide (CHBP). ARA290 and CHBP have promising applications as peptide drugs. The neuroprotective effects they exhibit have attracted continuous exploration of their mechanisms of action. This article will review the research on the role of EPO, ARA290 and CHBP in the nervous system around this developmental process, and provide a certain reference for the subsequent research.

Lung-innervating nociceptor sensory neurons promote pneumonic sepsis during carbapenem-resistant Klebsiella pneumoniae lung infection

Carbapenem-resistant Klebsiella pneumoniae (CRKP) causes Gram-negative lung infections and fatal pneumonic sepsis for which limited therapeutic options are available. The lungs are densely innervated by nociceptor sensory neurons that mediate breathing, cough, and bronchoconstriction. The role of nociceptors in defense against Gram-negative lung pathogens is unknown. Here, we found that lung-innervating nociceptors promote CRKP pneumonia and pneumonic sepsis. Ablation of nociceptors in mice increased lung CRKP clearance, suppressed trans-alveolar dissemination of CRKP, and protected mice from hypothermia and death. Furthermore, ablation of nociceptors enhanced the recruitment of neutrophils and Ly6Chi monocytes and cytokine induction. Depletion of Ly6Chi monocytes, but not of neutrophils, abrogated lung and extrapulmonary CRKP clearance in ablated mice, suggesting that Ly6Chi monocytes are a critical cellular population to regulate pneumonic sepsis. Further, neuropeptide calcitonin gene-related peptide suppressed the induction of reactive oxygen species in Ly6Chi monocytes and their CRKP-killing abilities. Targeting nociceptor signaling could be a therapeutic approach for treating multidrug-resistant Gram-negative infection and pneumonic sepsis.

Early brain neuroinflammatory and metabolic changes identified by dual tracer microPET imaging in mice with acute liver injury

Background

Acute liver injury (ALI) that progresses into acute liver failure (ALF) is a life-threatening condition with an increasing incidence and associated costs. Acetaminophen (N-acetyl-p-aminophenol, APAP) overdosing is among the leading causes of ALI and ALF in the Northern Hemisphere. Brain dysfunction defined as hepatic encephalopathy is one of the main diagnostic criteria for ALF. While neuroinflammation and brain metabolic alterations significantly contribute to hepatic encephalopathy, their evaluation at early stages of ALI remained challenging. To provide insights, we utilized post-mortem analysis and non-invasive brain micro positron emission tomography (microPET) imaging of mice with APAP-induced ALI.

Methods

Male C57BL/6 mice were treated with vehicle or APAP (600 mg/kg, i.p.). Serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), liver damage (using H&E staining), hepatic and serum IL-6 levels, and hippocampal IBA1 (using immunolabeling) were evaluated at 24h and 48h. Vehicle and APAP treated animals also underwent microPET imaging utilizing a dual tracer approach, including [11C]-peripheral benzodiazepine receptor ([11C]PBR28) to assess microglia/astrocyte activation and [18F]-fluoro-2-deoxy-2-D-glucose ([18F]FDG) to assess energy metabolism. Brain images were pre-processed and evaluated using conjunction and individual tracer uptake analysis.

Results

APAP-induced ALI and hepatic and systemic inflammation were detected at 24h and 48h by significantly elevated serum ALT and AST levels, hepatocellular damage, and increased hepatic and serum IL-6 levels. In parallel, increased microglial numbers, indicative for neuroinflammation were observed in the hippocampus of APAP-treated mice. MicroPET imaging revealed overlapping increases in [11C]PBR28 and [18F]FDG uptake in the hippocampus, thalamus, and habenular nucleus indicating microglial/astroglial activation and increased energy metabolism in APAP-treated mice (vs. vehicle-treated mice) at 24h. Similar significant increases were also found in the hypothalamus, thalamus, and cerebellum at 48h. The individual tracer uptake analyses (APAP vs vehicle) at 24h and 48h confirmed increases in these brain areas and indicated additional tracer- and region-specific effects including hippocampal alterations.

Conclusion

Peripheral manifestations of APAP-induced ALI in mice are associated with brain neuroinflammatory and metabolic alterations at relatively early stages of disease progression, which can be non-invasively evaluated using microPET imaging and conjunction analysis. These findings support further PET-based investigations of brain function in ALI/ALF that may inform timely therapeutic interventions.

Activation of nicotinic acetylcholine receptor α7 subunit limits Zika viral infection via promoting autophagy and ferroptosis

Vagus nerve regulates viral infection and inflammation via the alpha 7 nicotinic acetylcholine receptor (α7 nAChR); however, the role of α7 nAChR in ZIKA virus (ZIKV) infection, which can cause severe neurological diseases such as microcephaly and Guillain-Barré syndrome, remains unknown. Here, we first examined the role of α7 nAChR in ZIKV infection in vitro. A broad effect of α7 nAChR activation was identified in limiting ZIKV infection in multiple cell lines. Combined with transcriptomics analysis, we further demonstrated that α7 nAChR activation promoted autophagy and ferroptosis pathways to limit cellular ZIKV viral loads. Additionally, activation of α7 nAChR prevented ZIKV-induced p62 nucleus accumulation, which mediated an enhanced autophagy pathway. By regulating proteasome complex and an E3 ligase NEDD4, activation of α7 nAChR resulted in increased amount of cellular p62, which further enhanced the ferroptosis pathway to reduce ZIKV infection. Moreover, utilizing in vivo neonatal mouse models, we showed that α7 nAChR is essential in controlling the disease severity of ZIKV infection. Taken together, our findings identify an α7 nAChR-mediated effect that critically contributes to limiting ZIKV infection, and α7 nAChR activation offers a novel strategy for combating ZIKV infection and its complications.

Neuroimmune circuits in the plaque and bone marrow regulate atherosclerosis

Atherosclerosis remains the leading cause of death globally. Although its focal pathology is atheroma that develops in arterial walls, atherosclerosis is a systemic disease involving contributions by many organs and tissues. It is now established that the immune system causally contributes to all phases of atherosclerosis. Recent and emerging evidence positions the nervous system as a key modulator of inflammatory processes that underly atherosclerosis. This neuro-immune crosstalk, we are learning, is bidirectional, and immune regulated afferent signaling is becoming increasingly recognized in atherosclerosis. Here, we summarize data and concepts that link the immune and nervous systems in atherosclerosis by focusing on two important sites, the arterial vessel and the bone marrow.

Electrical stimulation of the dorsal motor nucleus of the vagus in male mice can regulate inflammation without affecting the heart rate

BACKGROUND

The vagus nerve plays an important role in neuroimmune interactions and in the regulation of inflammation. A major source of efferent vagus nerve fibers that contribute to the regulation of inflammation is the brainstem dorsal motor nucleus of the vagus (DMN), as recently shown using optogenetics. In contrast to optogenetics, electrical neuromodulation has broad therapeutic implications. However, the anti-inflammatory effectiveness of electrical stimulation of the DMN (eDMNS) and the possible heart rate (HR) alterations associated with this approach have not been investigated. Here, we examined the effects of eDMNS on HR and cytokine levels in mice administered with lipopolysaccharide (LPS, endotoxin) and in mice subjected to cecal ligation and puncture (CLP) sepsis.

METHODS

Anesthetized male 8-10-week-old C57BL/6 mice on a stereotaxic frame were subjected to eDMNS using a concentric bipolar electrode inserted into the left or right DMN or sham stimulation. eDMNS (500, 250 or 50 μA at 30 Hz, for 1 min) was performed and HR recorded. In endotoxemia experiments, sham or eDMNS utilizing 250 μA or 50 μA was performed for 5 mins and was followed by LPS (0.5 mg/kg) i.p. administration. eDMNS was also applied in mice with cervical unilateral vagotomy or sham operation. In CLP experiments sham or left eDMNS was performed immediately post CLP. Cytokines and corticosterone were analyzed 90 mins after LPS administration or 24 h after CLP. CLP survival was monitored for 14 days.

RESULTS

Either left or right eDMNS at 500 μA and 250 μA decreased HR, compared with baseline pre-stimulation. This effect was not observed at 50 μA. Left side eDMNS at 50 μA, compared with sham stimulation, significantly decreased serum and splenic levels of the pro-inflammatory cytokine TNF and increased serum levels of the anti-inflammatory cytokine IL-10 during endotoxemia. The anti-inflammatory effect of eDMNS was abrogated in mice with unilateral vagotomy and was not associated with serum corticosterone alterations. Right side eDMNS in endotoxemic mice suppressed serum TNF and increased serum IL-10 levels but had no effects on splenic cytokines. In mice with CLP, left side eDMNS suppressed serum IL-6, as well as splenic IL-6 and increased splenic IL-10 and significantly improved the survival rate of CLP mice.

CONCLUSIONS

For the first time we show that a regimen of eDMNS which does not cause bradycardia alleviates LPS-induced inflammation. These eDMNS anti-inflammatory effects require an intact vagus nerve and are not associated with corticosteroid alterations. eDMNS also decreases inflammation and improves survival in a model of polymicrobial sepsis. These findings are of interest for further studies exploring bioelectronic anti-inflammatory approaches targeting the brainstem DMN.

Investigations on the Ability of the Insular Cortex to Process Peripheral Immunosuppression

The brain and immune system communicate through complex bidirectional pathways, but the specificity by which the brain perceives or even remembers alterations in immune homeostasis is still poorly understood. Recent data revealed that immune-related information under peripheral inflammatory conditions, termed as "immunengram", were represented in specific neuronal ensembles in the insular cortex (IC). Chemogenetic reactivation of these neuronal ensembles was sufficient to retrieve the inflammatory stages, indicating that the brain can store and retrieve specific immune responses. Against this background, the current approach was designed to investigate the ability of the IC to process states of immunosuppression pharmacologically induced by the mechanistic target of rapamycin (mTOR) inhibitor rapamycin. We here show that the IC perceives the initial state of immunosuppression, reflected by increased deep-brain electroencephalography (EEG) activity during acute immunosuppressive drug treatment. Following an experienced period of immunosuppression, though, diminished splenic cytokine production as formerly induced by rapamycin could not be reinstated by nonspecific chemogenetic activation or inhibition of the IC. These findings suggest that the information of a past, or experienced status of pharmacologically induced immunosuppression is not represented in the IC. Together, the present work extends the view of immune-to-brain communication during the states of peripheral immunosuppression and foster the prominent role of the IC for interoception.

Effect of acetylcholinesterase inhibition on immune cells in the murine intestinal mucosa

The gastrointestinal tract (GI) is the largest immune organ whose function is controlled by a complex network of neurons from the enteric nervous system (ENS) as well as the sympathetic and parasympathetic system. Evolving evidence indicates that cross-communication between gut-innervating neurons and immune cells regulates many essential physiological functions including protection against mucosal infections. We previously demonstrated that following paraoxon treatment, 70 % of the mice were able to survive an oral infection with S. typhimurium, a virulent strain of Salmonella enterica serovar Typhimurium. The present study aims to investigate the effect that rivastigmine, a reversible AChE inhibitor used for the treatment of neurodegenerative diseases, has on the murine immune defenses of the intestinal mucosa. Our findings show that, similar to what is observed with paraoxon, administration of rivastigmine promoted the release of secretory granules from goblet and Paneth cells, resulting in increased mucin layer. Surprisingly, however, and unlike paraoxon, rivastigmine treatment did not affect overall mortality of infected mice. In order to investigate the mechanistic basis for the differential effects observed between paraoxon and rivastigmine, we used multi-color flowcytometric analysis to characterize the immune cell landscape in the intraepithelial (IE) and lamina propria (LP) compartments of intestinal mucosa. Our data indicate that treatment with paraoxon, but not rivastigmine, led to an increase of resident CD3+CD8+ T lymphocytes in the ileal mucosa (epithelium and lamina propria) and CD11b- CD11c+ dendritic cells in the LP. Our findings indicate the requirement for persistent cholinergic pathway engagement to effect a change in the cellular landscape of the mucosal tissue that is necessary for protection against lethal bacterial infections. Moreover, optimal protection requires a collaboration between innate and adaptive mucosal immune responses in the intestine.

Therapeutically Fine-Tuning Autonomic Nervous System to Treat Sepsis: A New Perspective on the Immunomodulatory Effects of Acupuncture

Recent studies have highlighted the immunomodulatory effects of acupuncture on sepsis and proposed novel non-pharmacological or bioelectronic approaches to managing inflammatory illnesses. Establishing rules for selectively activating sympathetic or vagal nerve-mediated anti-inflammatory pathways using acupuncture has valuable clinical applications. Over the years, studies have revealed the segmental modulatory role of acupuncture in regulating visceral function by targeting the autonomic nervous system (ANS). In this review, we aim to summarize recent findings on acupuncture in treating sepsis, focusing on the underlying ANS mechanism, as well as the rules of acupoint specificity, intensity, frequency, and other parameters utilized in these studies. Mechanistically, the immunomodulatory properties of the sympathetic nervous system have been highlighted. Furthermore, we explore the immunotherapeutic benefits of acupuncture in treating sepsis. A better understanding of the immunoregulatory mechanism of sympathetic nervous system may offer novel approaches for the development of therapeutics to treat or prevent a variety of inflammatory diseases.

Vagus nerve stimulation for cardiovascular diseases: Is there light at the end of the tunnel?

Autonomic dysfunction and chronic inflammation contribute to the pathogenesis and progression of several cardiovascular diseases (CVD), such as heart failure with preserved ejection fraction, atherosclerotic CVD, pulmonary arterial hypertension, and atrial fibrillation. The vagus nerve provides parasympathetic innervation to the heart, vessels, and lungs, and is also implicated in the neural control of inflammation through a neuroimmune pathway involving the spleen. Stimulation of the vagus nerve (VNS) can in principle restore autonomic balance and suppress inflammation, with potential therapeutic benefits in these diseases. Although VNS ameliorated CVD in several animal models, early human studies have demonstrated variable efficacy. The purpose of this review is to discuss the rationale behind the use of VNS in the treatment of CVD, to critically review animal and human studies of VNS in CVD, and to propose possible means to overcome the challenges in the clinical translation of VNS in CVD.

B cells modulate lung antiviral inflammatory responses via the neurotransmitter acetylcholine

The rapid onset of innate immune defenses is critical for early control of viral replication in an infected host, yet it can also lead to irreversible tissue damage, especially in the respiratory tract. Intricate regulatory mechanisms must exist that modulate inflammation, while controlling the infection. Here, B cells expressing choline acetyl transferase (ChAT), an enzyme required for production of the metabolite and neurotransmitter acetylcholine (ACh) are identified as such regulators of the immediate early response to influenza A virus. Lung tissue ChAT + B cells are shown to interact with a7 nicotinic Ach receptor-expressing lung interstitial macrophages in mice within 24h of infection to control their production of TNFa, shifting the balance towards reduced inflammation at the cost of enhanced viral replication. Thus, innate-stimulated B cells are key participants of an immediate-early regulatory cascade that controls lung tissue damage after viral infection.

Enteric neuropathy and the vagus nerve: Therapeutic implications

Enteric neuropathies are characterized by abnormalities of gut innervation, which includes the enteric nervous system, inducing severe gut dysmotility among other dysfunctions. Most of the gastrointestinal tract is innervated by the vagus nerve, the efferent branches of which have close interconnections with the enteric nervous system and whose afferents are distributed throughout the different layers of the digestive wall. The vagus nerve is a key element of the autonomic nervous system, involved in the stress response, at the interface of the microbiota-gut-brain axis, has anti-inflammatory and prokinetic properties, modulates intestinal permeability, and has a significant capacity of plasticity and regeneration. Targeting these properties of the vagus nerve, with vagus nerve stimulation (or non-stimulation/ pharmacological methods), could be of interest in the therapeutic management of enteric neuropathies.

Innervation of nociceptor neurons in the spleen promotes germinal center responses and humoral immunity

Peripheral sensory neurons widely innervate various tissues to continuously monitor and respond to environmental stimuli. Whether peripheral sensory neurons innervate the spleen and modulate splenic immune response remains poorly defined. Here, we demonstrate that nociceptive sensory nerve fibers extensively innervate the spleen along blood vessels and reach B cell zones. The spleen-innervating nociceptors predominantly originate from left T8-T13 dorsal root ganglia (DRGs), promoting the splenic germinal center (GC) response and humoral immunity. Nociceptors can be activated by antigen-induced accumulation of splenic prostaglandin E2 (PGE2) and then release calcitonin gene-related peptide (CGRP), which further promotes the splenic GC response at the early stage. Mechanistically, CGRP directly acts on B cells through its receptor CALCRL-RAMP1 via the cyclic AMP (cAMP) signaling pathway. Activating nociceptors by ingesting capsaicin enhances the splenic GC response and anti-influenza immunity. Collectively, our study establishes a specific DRG-spleen sensory neural connection that promotes humoral immunity, suggesting a promising approach for improving host defense by targeting the nociceptive nervous system.

Area postrema neurons mediate interleukin-6 function in cancer cachexia

Interleukin-6 (IL-6) has been long considered a key player in cancer cachexia. It is believed that sustained elevation of IL-6 production during cancer progression causes brain dysfunctions, which ultimately result in cachexia. However, how peripheral IL-6 influences the brain remains poorly understood. Here we show that neurons in the area postrema (AP), a circumventricular structure in the hindbrain, is a critical mediator of IL-6 function in cancer cachexia in male mice. We find that circulating IL-6 can rapidly enter the AP and activate neurons in the AP and its associated network. Peripheral tumor, known to increase circulating IL-6, leads to elevated IL-6 in the AP, and causes potentiated excitatory synaptic transmission onto AP neurons and AP network hyperactivity. Remarkably, neutralization of IL-6 in the brain of tumor-bearing mice with an anti-IL-6 antibody attenuates cachexia and the hyperactivity in the AP network, and markedly prolongs lifespan. Furthermore, suppression of Il6ra, the gene encoding IL-6 receptor, specifically in AP neurons with CRISPR/dCas9 interference achieves similar effects. Silencing Gfral-expressing AP neurons also attenuates cancer cachectic phenotypes and AP network hyperactivity. Our study identifies a central mechanism underlying the function of peripheral IL-6, which may serve as a target for treating cancer cachexia.

Disrupted autonomic pathways in spinal cord injury: Implications for the immune regulation

Spinal Cord Injury (SCI) disrupts critical autonomic pathways responsible for the regulation of the immune function. Consequently, individuals with SCI often exhibit a spectrum of immune dysfunctions ranging from the development of damaging pro-inflammatory responses to severe immunosuppression. Thus, it is imperative to gain a more comprehensive understanding of the extent and mechanisms through which SCI-induced autonomic dysfunction influences the immune response. In this review, we provide an overview of the anatomical organization and physiology of the autonomic nervous system (ANS), elucidating how SCI impacts its function, with a particular focus on lymphoid organs and immune activity. We highlight recent advances in understanding how intraspinal plasticity that follows SCI may contribute to aberrant autonomic activity in lymphoid organs. Additionally, we discuss how sympathetic mediators released by these neuron terminals affect immune cell function. Finally, we discuss emerging innovative technologies and potential clinical interventions targeting the ANS as a strategy to restore the normal regulation of the immune response in individuals with SCI.

A body-brain circuit that regulates body inflammatory responses

The body-brain axis is emerging as a principal conductor of organismal physiology. It senses and controls organ function1,2, metabolism3 and nutritional state4-6. Here we show that a peripheral immune insult strongly activates the body-brain axis to regulate immune responses. We demonstrate that pro-inflammatory and anti-inflammatory cytokines communicate with distinct populations of vagal neurons to inform the brain of an emerging inflammatory response. In turn, the brain tightly modulates the course of the peripheral immune response. Genetic silencing of this body-brain circuit produced unregulated and out-of-control inflammatory responses. By contrast, activating, rather than silencing, this circuit affords neural control of immune responses. We used single-cell RNA sequencing, combined with functional imaging, to identify the circuit components of this neuroimmune axis, and showed that its selective manipulation can effectively suppress the pro-inflammatory response while enhancing an anti-inflammatory state. The brain-evoked transformation of the course of an immune response offers new possibilities in the modulation of a wide range of immune disorders, from autoimmune diseases to cytokine storm and shock.

Neuroimmune modulation by tryptophan derivatives in neurological and inflammatory disorders

The nervous and immune systems are highly developed, and each performs specialized physiological functions. However, they work together, and their dysfunction is associated with various diseases. Specialized molecules, such as neurotransmitters, cytokines, and more general metabolites, are essential for the appropriate regulation of both systems. Tryptophan, an essential amino acid, is converted into functional molecules such as serotonin and kynurenine, both of which play important roles in the nervous and immune systems. The role of kynurenine metabolites in neurodegenerative and psychiatric diseases has recently received particular attention. Recently, we found that hyperactivity of the kynurenine pathway is a critical risk factor for septic shock. In this review, we first outline neuroimmune interactions and tryptophan derivatives and then summarized the changes in tryptophan metabolism in neurological disorders. Finally, we discuss the potential of tryptophan derivatives as therapeutic targets for neuroimmune disorders.

Updating functional brain units: Insights far beyond Luria

This paper reviews Luria's model of the three functional units of the brain. To meet this objective, several issues were reviewed: the theory of functional systems and the contributions of phylogenesis and embryogenesis to the brain's functional organization. This review revealed several facts. In the first place, the relationship/integration of basic homeostatic needs with complex forms of behavior. Secondly, the multi-scale hierarchical and distributed organization of the brain and interactions between cells and systems. Thirdly, the phylogenetic role of exaptation, especially in basal ganglia and cerebellum expansion. Finally, the tripartite embryogenetic organization of the brain: rhinic, limbic/paralimbic, and supralimbic zones. Obviously, these principles of brain organization are in contradiction with attempts to establish separate functional brain units. The proposed new model is made up of two large integrated complexes: a primordial-limbic complex (Luria's Unit I) and a telencephalic-cortical complex (Luria's Units II and III). As a result, five functional units were delineated: Unit I. Primordial or preferential (brainstem), for life-support, behavioral modulation, and waking regulation; Unit II. Limbic and paralimbic systems, for emotions and hedonic evaluation (danger and relevance detection and contribution to reward/motivational processing) and the creation of cognitive maps (contextual memory, navigation, and generativity [imagination]); Unit III. Telencephalic-cortical, for sensorimotor and cognitive processing (gnosis, praxis, language, calculation, etc.), semantic and episodic (contextual) memory processing, and multimodal conscious agency; Unit IV. Basal ganglia systems, for behavior selection and reinforcement (reward-oriented behavior); Unit V. Cerebellar systems, for the prediction/anticipation (orthometric supervision) of the outcome of an action. The proposed brain units are nothing more than abstractions within the brain's simultaneous and distributed physiological processes. As function transcends anatomy, the model necessarily involves transition and overlap between structures. Beyond the classic approaches, this review includes information on recent systemic perspectives on functional brain organization. The limitations of this review are discussed.

An Explainable Deep Learning Classifier of Bovine Mastitis Based on Whole-Genome Sequence Data-Circumventing the p >> n Problem

The serious drawback underlying the biological annotation of whole-genome sequence data is the p >> n problem, which means that the number of polymorphic variants (p) is much larger than the number of available phenotypic records (n). We propose a way to circumvent the problem by combining a LASSO logistic regression with deep learning to classify cows as susceptible or resistant to mastitis, based on single nucleotide polymorphism (SNP) genotypes. Among several architectures, the one with 204,642 SNPs was selected as the best. This architecture was composed of two layers with, respectively, 7 and 46 units per layer implementing respective drop-out rates of 0.210 and 0.358. The classification of the test data resulted in AUC = 0.750, accuracy = 0.650, sensitivity = 0.600, and specificity = 0.700. Significant SNPs were selected based on the SHapley Additive exPlanation (SHAP). As a final result, one GO term related to the biological process and thirteen GO terms related to molecular function were significantly enriched in the gene set that corresponded to the significant SNPs. Our findings revealed that the optimal approach can correctly predict susceptibility or resistance status for approximately 65% of cows. Genes marked by the most significant SNPs are related to the immune response and protein synthesis.

Vagus nerve stimulation modulates distinct acetylcholine receptors on B cells and limits the germinal center response

Acetylcholine is produced in the spleen in response to vagus nerve activation; however, the effects on antibody production have been largely unexplored. Here, we use a chronic vagus nerve stimulation (VNS) mouse model to study the effect of VNS on T-dependent B cell responses. We observed lower titers of high-affinity IgG and fewer antigen-specific germinal center (GC) B cells. GC B cells from chronic VNS mice exhibited altered mRNA and protein expression suggesting increased apoptosis and impaired plasma cell differentiation. Follicular dendritic cell (FDC) cluster dispersal and altered gene expression suggested poor function. The absence of acetylcholine-producing CD4+ T cells diminished these alterations. In vitro studies revealed that α7 and α9 nicotinic acetylcholine receptors (nAChRs) directly regulated B cell production of TNF, a cytokine crucial to FDC clustering. α4 nAChR inhibited coligation of CD19 to the B cell receptor, presumably decreasing B cell survival. Thus, VNS-induced GC impairment can be attributed to distinct effects of nAChRs on B cells.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

A novel neuroimmune modulation system for the treatment of rheumatoid arthritis

The vagus nerve has an anti-inflammatory effect through the inflammatory reflex, which inhibits the release of proinflammatory cytokines by macrophages. Recent pilot clinical trials, using implantable bioelectronic devices, have demonstrated the efficacy of vagus nerve stimulation in adult patients with rheumatoid arthritis and inflammatory bowel diseases as an alternative to drugs, which are not devoid of side effects and are costly. In this issue of Bioelectronic Medicine, Peterson et al. report the safety of novel implantable neuroimmune modulation device for treating rheumatoid arthritis (The RESET RA study), which I will discuss in this commentary.

Navigating the blurred path of mixed neuroimmune signaling

Evolution has created complex mechanisms to sense environmental danger and protect tissues, with the nervous and immune systems playing pivotal roles. These systems work together, coordinating local and systemic reflexes to restore homeostasis in response to tissue injury and infection. By sharing receptors and ligands, they influence the pathogenesis of various diseases. Recently, a less-explored aspect of neuroimmune communication has emerged: the release of neuropeptides from immune cells and cytokines/chemokines from sensory neurons. This article reviews evidence of this unique neuroimmune interplay and its impact on the development of allergy, inflammation, itch, and pain. We highlight the effects of this neuroimmune signaling on vital processes such as host defense, tissue repair, and inflammation resolution, providing avenues for exploration of the underlying mechanisms and therapeutic potential of this signaling.

Clinical safety and feasibility of a novel implantable neuroimmune modulation device for the treatment of rheumatoid arthritis: initial results from the randomized, double-blind, sham-controlled RESET-RA study

BACKGROUND

Rheumatoid arthritis (RA) is a chronic inflammatory autoimmune disease that causes persistent synovitis, bone damage, and progressive joint destruction. Neuroimmune modulation through electrical stimulation of the vagus nerve activates the inflammatory reflex and has been shown to inhibit the production and release of inflammatory cytokines and decrease clinical signs and symptoms in RA. The RESET-RA study was designed to determine the safety and efficacy of an active implantable device for treating RA.

METHODS

The RESET-RA study is a randomized, double-blind, sham-controlled, multi-center, two-stage pivotal trial that enrolled patients with moderate-to-severe RA who were incomplete responders or intolerant to at least one biologic or targeted synthetic disease-modifying anti-rheumatic drug. A neuroimmune modulation device (SetPoint Medical, Valencia, CA) was implanted on the left cervical vagus nerve within the carotid sheath in all patients. Following post-surgical clearance, patients were randomly assigned (1:1) to active stimulation or non-active (control) stimulation for 1 min once per day. A predefined blinded interim analysis was performed in patients enrolled in the study's initial stage (Stage 1) that included demographics, enrollment rates, device implantation rates, and safety of the surgical procedure, device, and stimulation over 12 weeks of treatment.

RESULTS

Sixty patients were implanted during Stage 1 of the study. All device implant procedures were completed without intraoperative complications, infections, or surgical revisions. No unanticipated adverse events were reported during the perioperative period and at the end of 12 weeks of follow-up. No study discontinuations were due to adverse events, and no serious adverse events were related to the device or stimulation. Two serious adverse events were related to the implantation procedure: vocal cord paresis and prolonged hoarseness. These were reported in two patients and are known complications of surgical implantation procedures with vagus nerve stimulation devices. The adverse event of vocal cord paresis resolved after vocal cord augmentation injections with filler and speech therapy. The prolonged hoarseness had improved with speech therapy, but mild hoarseness persists.

CONCLUSIONS

The surgical procedures for implantation of the novel neuroimmune modulation device for the treatment of RA were safe, and the device and its use were well tolerated.

TRIAL REGISTRATION

NCT04539964; August 31, 2020.

A multiscale inflammatory map: linking individual stress to societal dysfunction

As populations worldwide show increasing levels of stress, understanding emerging links among stress, inflammation, cognition, and behavior is vital to human and planetary health. We hypothesize that inflammation is a multiscale driver connecting stressors that affect individuals to large-scale societal dysfunction and, ultimately, to planetary-scale environmental impacts. We propose a 'central inflammation map' hypothesis to explain how the brain regulates inflammation and how inflammation impairs cognition, emotion, and action. According to our hypothesis, these interdependent inflammatory and neural processes, and the inter-individual transmission of environmental, infectious, and behavioral stressors - amplified via high-throughput digital global communications - can culminate in a multiscale, runaway, feed-forward process that could detrimentally affect human decision-making and behavior at scale, ultimately impairing the ability to address these same stressors. This perspective could provide non-intuitive explanations for behaviors and relationships among cells, organisms, and communities of organisms, potentially including population-level responses to stressors as diverse as global climate change, conflicts, and the COVID-19 pandemic. To illustrate our hypothesis and elucidate its mechanistic underpinnings, we present a mathematical model applicable to the individual and societal levels to test the links among stress, inflammation, control, and healing, including the implications of transmission, intervention (e.g., via lifestyle modification or medication), and resilience. Future research is needed to validate the model's assumptions, expand the factors/variables employed, and validate it against empirical benchmarks. Our model illustrates the need for multilayered, multiscale stress mitigation interventions, including lifestyle measures, precision therapeutics, and human ecosystem design. Our analysis shows the need for a coordinated, interdisciplinary, international research effort to understand the multiscale nature of stress. Doing so would inform the creation of interventions that improve individuals' lives and communities' resilience to stress and mitigate its adverse effects on the world.

Epigenetic regulation of microglia and neurons by proinflammatory signaling following adolescent intermittent ethanol (AIE) exposure and in human AUD

Adolescent alcohol drinking is linked to high rates of adult alcohol problems and alcohol use disorder (AUD). The Neurobiology of Alcohol Drinking in Adulthood (NADIA) consortium adolescent intermittent ethanol (AIE) models adolescent binge drinking, followed by abstinent maturation to adulthood to determine the persistent AIE changes in neurobiology and behavior. AIE increases adult alcohol drinking and preference, increases anxiety and reward seeking, and disrupts sleep and cognition, all risks for AUD. In addition, AIE induces changes in neuroimmune gene expression in neurons and glia that alter neurocircuitry and behavior. HMGB1 is a unique neuroimmune signal released from neurons and glia by ethanol that activates multiple proinflammatory receptors, including Toll-like receptors (TLRs), that spread proinflammatory gene induction. HMGB1 expression is increased by AIE in rat brain and in post-mortem human AUD brain, where it correlates with lifetime alcohol consumption. HMGB1 activation of TLR increase TLR expression. Human AUD brain and rat brain following AIE show increases in multiple TLRs. Brain regional differences in neurotransmitters and cell types impact ethanol responses and neuroimmune gene induction. Microglia are monocyte-like cells that provide trophic and synaptic functions, that ethanol proinflammatory signals sensitize or "prime" during repeated drinking cycles, impacting neurocircuitry. Neurocircuits are differently impacted dependent upon neuronal-glial signaling. Acetylcholine is an anti-inflammatory neurotransmitter. AIE increases HMGB1-TLR4 signaling in forebrain, reducing cholinergic neurons by silencing multiple cholinergic defining genes through upregulation of RE-1 silencing factor (REST), a transcription inhibitor known to regulate neuronal differentiation. HMGB1 REST induction reduces cholinergic neurons in basal forebrain and cholinergic innervation of hippocampus. Adult brain hippocampal neurogenesis is regulated by a neurogenic niche formed from multiple cells. In vivo AIE and in vitro studies find ethanol increases HMGB1-TLR4 signaling and other proinflammatory signaling as well as reducing trophic factors, NGF, and BDNF, coincident with loss of the cholinergic synapse marker vChAT. These changes in gene expression-transcriptomes result in reduced adult neurogenesis. Excitingly, HMGB1 antagonists, anti-inflammatories, and epigenetic modifiers like histone deacetylase inhibitors restore trophic the neurogenesis. These findings suggest anti-inflammatory and epigenetic drugs should be considered for AUD therapy and may provide long-lasting reversal of psychopathology.

Targeting monoamine oxidase A: a strategy for inhibiting tumor growth with both immune checkpoint inhibitors and immune modulators

Monoamine oxidase A (MAOA) is a membrane-bound mitochondrial enzyme present in almost all vertebrate tissues that catalyzes the degradation of biogenic and dietary-derived monoamines. MAOA is known for regulating neurotransmitter metabolism and has been implicated in antitumor immune responses. In this review, we retrospect that MAOA inhibits the activities of various types of tumor-associated immune cells (such as CD8+ T cells and tumor-associated macrophages) by regulating their intracellular monoamines and metabolites. Developing novel MAOA inhibitor drugs and exploring multidrug combination strategies may enhance the efficacy of immune governance. Thus, MAOA may act as a novel immune checkpoint or immunomodulator by influencing the efficacy and effectiveness of immunotherapy. In conclusion, MAOA is a promising immune target that merits further in-depth exploration in preclinical and clinical settings.

Noninvasive Vagus Nerve Stimulation in Postural Tachycardia Syndrome: A Randomized Clinical Trial

BACKGROUND

Low-level transcutaneous stimulation of the auricular branch of the vagus nerve at the tragus is antiarrhythmic and anti-inflammatory in animals and humans. Preliminary studies show that transcutaneous vagus nerve stimulation (tVNS) is beneficial in animal models of postural tachycardia syndrome (POTS).

OBJECTIVES

In this study the authors conducted a sham-controlled, double-blind, randomized clinical trial to examine the effect of tVNS on POTS over a 2-month period relative to sham stimulation.

METHODS

tVNS (20 Hz, 1 mA below discomfort threshold) was delivered using an ear clip attached to either the tragus (active; n = 12) or the ear lobe (sham; n = 14) for 1 hour daily over a 2-month period. Postural tachycardia was assessed during the baseline and 2-month visit. Heart rate variability based on 5-minute electrocardiogram, serum cytokines, and antiautonomic autoantibodies were measured at the respective time points.

RESULTS

Mean age was 34 ± 11 years (100% female; 81% Caucasian). Adherence to daily stimulation was 83% in the active arm and 86% in the sham arm (P > 0.05). Postural tachycardia was significantly less in the active arm compared with the sham arm at 2 months (mean postural increase in heart rate 17.6 ± 9.9 beats/min vs 31.7 ± 14.4 beats/min; P = 0.01). Antiadrenergic autoantibodies and inflammatory cytokines were lower in the active arm compared with the sham arm at 2 months (P < 0.05). Heart rate variability was better in the active arm. No device-related side effects were observed.

CONCLUSIONS

Our results support the emerging paradigm of noninvasive neuromodulation to treat POTS. Mechanistically, this effect appears to be related to reduction of antiautonomic autoantibodies and inflammatory cytokines, and improvement in autonomic tone. Further studies are warranted. (Autoimmune Basis for Postural Tachycardia Syndrome; NCT05043051).

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.

The gut-brain axis in Parkinson's disease

There is a bi-directional communication between the gut, including the microbiota, and the brain through the autonomic nervous system. Accumulating evidence has suggested a bidirectional link between gastrointestinal inflammation and neurodegeneration, in accordance with the concept of the gut-rain axis. An abnormal microbiota-gut-brain interaction contributes to the pathogeny of Parkinson's disease. This supports the hypothesis that Parkinson's disease originates in the gut to spread to the central nervous system, in particular through the vagus nerve. Targeting the gut-to-brain axis with vagus nerve stimulation, fecal microbiota transplantation, gut-selective antibiotics, as well as drugs targeting the leaky gut might be of interest in the management of Parkinson's disease.

Pharmacological anti-inflammatory treatment in children and adolescents with depressive symptoms: A systematic-review and meta-analysis

Growing evidence suggests an association between inflammatory processes and depressive disorders (DD). DD typically emerge during adolescence. Treatment effects of agents with anti-inflammatory properties in youth DD have not been systematically reviewed. Here, the existing evidence on the use of anti-inflammatory drugs (including polyunsaturated fatty acids, nonsteroidal anti-inflammatory drugs, cytokine inhibitors, statins, pioglitazone, corticosteroids, and minocycline or modafinil) in children and adolescents with DD was synthesized using meta-analysis. The PROSPERO preregistered search yielded 22 records meeting search criteria. Of these, data from 19 primary studies (n = 1366 subjects) were subjected to meta-analysis. A significant but small effect in favor of anti-inflammatory agents in reducing depressive symptoms in youth with DD was found (SMD = -0.29, 95 % CI = -0.514; -0.063, p = 0.01). Post-hoc analyzes of drug subclasses found a significant effect of omega-3 fatty acids in reducing depressive symptoms. Results underline the importance to consider inflammatory pathways in the supplemental treatment of youth with DD. Further research is warranted, to clarify if anti-inflammatory agents are only effective in a subpopulation of patients (inflammatory biotype of depression in youth) and/or to alleviate specific symptom domains of depression (e.g., cognitive symptoms).

Autonomic and cytokine mechanisms of acute electroacupuncture in a rodent model of functional dyspepsia

BACKGROUND

Cytokines have been presumed to play an important role in the pathophysiology of functional dyspepsia (FD). Electroacupuncture (EA) has been used for FD treatment; however, its mechanisms remain largely unknown. This study aimed to (1) compare the plasma levels of cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and IL-10, in "FD" rats with normal control rats; (2) investigate whether EA, using chronically implanted electrodes, could inhibit the release of these cytokines; and (3) explore the correlation of cytokine levels with plasma norepinephrine (NE) levels and gastric emptying (GE).

METHODS

A rodent model of FD was established via neonatal treatment with intragastric iodoacetamide. After 8 weeks, the rats were implanted with electrodes at acupoint ST36 for EA. The plasma levels of cytokines and NE were measured using enzyme-linked immunosorbent assay. We explored the correlations of cytokine levels with NE levels and GE.

KEY RESULTS

(i) "FD" rats demonstrated increased levels of TNF-α, IL-1β, and IL-6 (p < 0.05 each) compared with the control rats. (ii) EA significantly decreased the plasma levels of TNF-α, IL-1β, and IL-6 in "FD" rats (p < 0.05 each) compared with sham EA. (iii) The plasma levels of NE were positively correlated with those of IL-6 (r = 0.86, p < 0.05) and IL-1β (r = 0.81, p < 0.05), whereas NE levels and GE were negatively correlated with IL-10 levels (r = -0.870, p < 0.05 and r = -0.791, p < 0.05, respectively).

CONCLUSIONS

EA inhibits the release of proinflammatory cytokines probably via the suppression of sympathetic activity in "FD" rats.

Mechanism and application of β-adrenoceptor blockers in soft tissue wound healing

Soft tissue damage stimulates sympathetic nerves to release large amounts of catecholamine hormones which bind to β-adrenergic receptors (β-ARs) on the cell membrane surface. It activates the downstream effector molecules and impairs soft tissue wound healing. β-blockers specifically inhibit β-ARs activation in acute/chronic skin lesions and ulcerative hemangiomas. They also accelerate soft tissue wound healing by shortening the duration of inflammation, speeding keratinocyte migration and reepithelialization, promoting wound contraction and angiogenesis, and inhibiting bacterial virulence effects. In addition, β-blockers shorten wound healing periods in patients with severe thermal damage by reducing the hypermetabolic response. While β-blockers promote/inhibit corneal epithelial cell regeneration and restores limbal stem/progenitor cells function, it could well accelerate/delay corneal wound healing. Given these meaningful effects, a growing number of studies are focused on examining the efficacy and safety of β-blockers in soft tissue wound repair, including acute and chronic wounds, severe thermal damage, ulcerated infantile hemangioma, corneal wounds, and other soft tissue disorders. However, an intensive investigation on their acting mechanisms is imperatively needed. The purpose of this article is to summerize the roles of β-blockers in soft tissue wound healing and explore their clinical applications.

The role of neuroinflammation in the transition of acute to chronic pain and the opioid-induced hyperalgesia and tolerance

Current evidence suggests that activation of glial and immune cells leads to increased production of proinflammatory mediators, creating a neuroinflammatory state. Neuroinflammation has been proven to be a fundamental mechanism in the genesis of acute pain and its transition to neuropathic and chronic pain. A noxious event that stimulates peripheral afferent nerve fibers may also activate pronociceptive receptors situated at the dorsal root ganglion and dorsal horn of the spinal cord, as well as peripheral glial cells, setting off the so-called peripheral sensitization and spreading neuroinflammation to the brain. Once activated, microglia produce cytokines, chemokines, and neuropeptides that can increase the sensitivity and firing properties of second-order neurons, upregulating the signaling of nociceptive information to the cerebral cortex. This process, known as central sensitization, is crucial for chronification of acute pain. Immune-neuronal interactions are also implicated in the lesser-known complex regulatory relationship between pain and opioids. Current evidence suggests that activated immune and glial cells can alter neuronal function, induce, and maintain pathological pain, and disrupt the analgesic effects of opioid drugs by contributing to the development of tolerance and dependence, even causing paradoxical hyperalgesia. Such alterations may occur when the neuronal environment is impacted by trauma, inflammation, and immune-derived molecules, or when opioids induce proinflammatory glial activation. Hence, understanding these intricate interactions may help in managing pain signaling and opioid efficacy beyond the classical pharmacological approach.

Sensory nerves directly promote osteoclastogenesis by secreting peptidyl-prolyl cis-trans isomerase D (Cyp40)

Given afferent functions, sensory nerves have recently been found to exert efferent effects and directly alter organ physiology. Additionally, several studies have highlighted the indirect but crucial role of sensory nerves in the regulation of the physiological function of osteoclasts. Nonetheless, evidence regarding the direct sensory nerve efferent influence on osteoclasts is lacking. In the current study, we found that high levels of efferent signals were transported directly from the sensory nerves into osteoclasts. Furthermore, sensory hypersensitivity significantly increased osteoclastic bone resorption, and sensory neurons (SNs) directly promoted osteoclastogenesis in an in vitro coculture system. Moreover, we screened a novel neuropeptide, Cyp40, using an isobaric tag for relative and absolute quantitation (iTRAQ). We observed that Cyp40 is the efferent signal from sensory nerves, and it plays a critical role in osteoclastogenesis via the aryl hydrocarbon receptor (AhR)-Ras/Raf-p-Erk-NFATc1 pathway. These findings revealed a novel mechanism regarding the influence of sensory nerves on bone regulation, i.e., a direct promoting effect on osteoclastogenesis by the secretion of Cyp40. Therefore, inhibiting Cyp40 could serve as a strategy to improve bone quality in osteoporosis and promote bone repair after bone injury.

The Brain-Heart Axis: Neuroinflammatory Interactions in Cardiovascular Disease

PURPOSE OF REVIEW

The role of neuroimmune modulation and inflammation in cardiovascular disease has been historically underappreciated. Physiological connections between the heart and brain, termed the heart-brain axis (HBA), are bidirectional, occur through a complex network of autonomic nerves/hormones and cytokines, and play important roles in common disorders.

RECENT FINDINGS

At the molecular level, advances in the past two decades reveal complex crosstalk mediated by the sympathetic and parasympathetic nervous systems, the renin-angiotensin aldosterone and hypothalamus-pituitary axes, microRNA, and cytokines. Afferent pathways amplify proinflammatory signals via the hypothalamus and brainstem to the periphery, promoting neurogenic inflammation. At the organ level, while stress-mediated cardiomyopathy is the prototypical disorder of the HBA, cardiac dysfunction can result from a myriad of neurologic insults including stroke and spinal injury. Atrial fibrillation is not necessarily a causative factor for cardioembolic stroke, but a manifestation of an abnormal atrial substrate, which can lead to the development of stroke independent of AF. Central and peripheral neurogenic proinflammatory factors have major roles in the HBA, manifesting as complex bi-directional relationships in common conditions such as stroke, arrhythmia, and cardiomyopathy.

Bridging the Gap: Investigating the Link between Inflammasomes and Postoperative Cognitive Dysfunction

Postoperative cognitive dysfunction (POCD) is a cluster of cognitive problems that may arise after surgery. POCD symptoms include memory loss, focus inattention, and communication difficulties. Inflammasomes, intracellular multiprotein complexes that control inflammation, may have a significant role in the development of POCD. It has been postulated that the NLRP3 inflammasome promotes cognitive impairment by triggering the inflammatory response in the brain. Nevertheless, there are many gaps in the current literature to understand the underlying pathophysiological mechanisms and develop future therapy. This review article underlines the limits of our current knowledge about the NLRP3 (NOD-, LRR- and pyrin domain-containing protein 3) inflammasome and POCD. We first discuss inflammasomes and their types, structures, and functions, then summarize recent evidence of the NLRP3 inflammasome's involvement in POCD. Next, we propose a hypothesis that suggests the involvement of inflammasomes in multiple organs, including local surgical sites, blood circulation, and other peripheral organs, leading to systemic inflammation and subsequent neuronal dysfunction in the brain, resulting in POCD. Research directions are then discussed, including analyses of inflammasomes in more clinical POCD animal models and clinical trials, studies of inflammasome types that are involved in POCD, and investigations into whether inflammasomes occur at the surgical site, in circulating blood, and in peripheral organs. Finally, we discuss the potential benefits of using new technologies and approaches to study inflammasomes in POCD. A thorough investigation of inflammasomes in POCD might substantially affect clinical practice.

Inflammation and emotion regulation: a narrative review of evidence and mechanisms in emotion dysregulation disorders

Emotion dysregulation (ED) describes a difficulty with the modulation of which emotions are felt, as well as when and how these emotions are experienced or expressed. It is a focal overarching symptom in many severe and prevalent neuropsychiatric diseases, including bipolar disorders (BD), attention deficit/hyperactivity disorder (ADHD), and borderline personality disorder (BPD). In all these disorders, ED can manifest through symptoms of depression, anxiety, or affective lability. Considering the many symptomatic similarities between BD, ADHD, and BPD, a transdiagnostic approach is a promising lens of investigation. Mounting evidence supports the role of peripheral inflammatory markers and stress in the multifactorial aetiology and physiopathology of BD, ADHD, and BPD. Of note, neural circuits that regulate emotions appear particularly vulnerable to inflammatory insults and peripheral inflammation, which can impact the neuroimmune milieu of the central nervous system. Thus far, few studies have examined the link between ED and inflammation in BD, ADHD, and BPD. To our knowledge, no specific work has provided a critical comparison of the results from these disorders. To fill this gap in the literature, we review the known associations and mechanisms linking ED and inflammation in general, and clinically, in BD, ADHD, and BD. Our narrative review begins with an examination of the routes linking ED and inflammation, followed by a discussion of disorder-specific results accounting for methodological limitations and relevant confounding factors. Finally, we critically discuss both correspondences and discrepancies in the results and comment on potential vulnerability markers and promising therapeutic interventions.

Non-invasive vagus nerve stimulation: the future of inflammatory bowel disease treatment?

The vagus nerve regulates inflammation and cytokine release through the inflammatory reflex. Recent pilot clinical trials using implantable bioelectronic devices have demonstrated the efficacy of vagus nerve stimulation (VNS) in adult patients with inflammatory bowel diseases (IBD) as an alternative to drug treatments. However, the use of non-invasive VNS should be of interest in adults with IBD and even more in pediatric IBD. In this issue of Bioelectronic Medicine, Sahn et al. report that non-invasive transcutaneous auricular VNS attenuated signs and symptoms in a pediatric cohort with mild to moderate IBD thus opening new therapeutic avenues in the management of pediatric but also adult IBD patients.

Therapeutic Use of Low-Dose Local Anesthetics in Pain, Inflammation, and Other Clinical Conditions: A Systematic Scoping Review

The use of low-dose local anesthetics (LAs) has significantly transformed patient care by providing rapid and effective relief of pain and other clinical conditions while minimizing recovery time. This study aims to identify and describe the existing scientific evidence on the therapeutic use of low-dose LAs in various conditions and to identify gaps in the current literature in order to prioritize future research. This systematic scoping review adhered to the methodological guidelines outlined in the Arksey and O'Malley framework, which includes five distinct stages. Of the 129 studies included, 37.98% (n = 49) were clinical trials, 55.03% (n = 71) were observational studies, and 6.97% (n = 9) were systematic reviews. The most commonly reported indication for the use of low-dose LAs was chronic pain management (72.86%), followed by acute pain management (13.17%). Additionally, non-pain-related indications were also identified (13.95%). Overall, the administration of low-dose, short-acting LAs demonstrated favorable outcomes in terms of pain management and reduction in anxiety and depression scales, thereby having a positive impact on the patients' quality of life. This review represents the first systematic scoping review regarding the therapeutic role of LAs. To substantiate the reported positive effects on efficacy and safety, further rigorous research comprising larger, well-designed randomized controlled trials (RCTs) and long-term outcome monitoring is imperative.

Alpha-1 adrenergic signaling drives cardiac regeneration via extracellular matrix remodeling transcriptional program in zebrafish macrophages

The autonomic nervous system plays a pivotal role in cardiac repair. Here, we describe the mechanistic underpinning of adrenergic signaling in fibrotic and regenerative response of the heart to be dependent on immunomodulation. A pharmacological approach identified adrenergic receptor alpha-1 as a key regulator of macrophage phenotypic diversification following myocardial damage in zebrafish. Genetic manipulation and single-cell transcriptomics showed that the receptor signals activation of an "extracellular matrix remodeling" transcriptional program in a macrophage subset, which serves as a key regulator of matrix composition and turnover. Mechanistically, adrenergic receptor alpha-1-activated macrophages determine activation of collagen-12-expressing fibroblasts, a cellular determinant of cardiac regenerative niche, through midkine-mediated paracrine crosstalk, allowing lymphatic and blood vessel growth and cardiomyocyte proliferation at the lesion site. These findings identify the mechanism of adrenergic signaling in macrophage phenotypic and functional determination and highlight the potential of neural modulation for regulation of fibrosis and coordination of myocardial regenerative response.

Aging-related genes revealed Neuroinflammatory mechanisms in ischemic stroke by bioinformatics

Ischemic stroke (IS) is a leading cause of disability, morbidity, and mortality globally. Aging affects immune function and contributes to poor outcomes of IS in elderly individuals. However, little is known about how aging-related genes (ARGs) are involved in IS. In this study, the relationship between ARGs and IS immune microenvironment biomarkers was explored by bioinformatics. Two IS microarray datasets (GSE22255, GSE16561) from human blood samples were analyzed and 502 ARGs were identified, from which 29 differentially expressed ARGs were selected. Functional analysis revealed that 7 of these ARGs (IL1B, FOS, JUN, CXCL5, PTGS2, TNFAIP3 and TLR4) were involved in five top enriched pathways (IL-17 signaling pathway, TNF signaling pathway, Rheumatoid arthritis, NF-kappa B signaling pathway and Pertussis) related to immune responses and inflammation. Five hub DE-ARGs (IL2RB, FOS, IL7R, ALDH2 and BIRC2) were identified using machine learning algorithms, and their association with immune-related characteristics was confirmed by additional tests. Single-cell sequencing dataset GSE129788 was retrieved to analyze aging molecular-related features, which was in accordance with microarray datasets. Clustering analysis revealed two subtypes of IS, which were distinguished by their differential expression of genes related to the NF-kappa B signaling pathway. These findings highlight the importance of ARGs in regulating immune responses in IS and suggest potential prevention and treatment strategies as well as guidelines for future research.