Electrical stimulation of the splenic nerve bundle ameliorates dextran sulfate sodium-induced colitis in mice

Multi-Organ Denervation: The Past, Present and Future

The sympathetic division of the autonomic nervous system plays a crucial role in maintaining homeostasis, but its overactivity is implicated in various pathological conditions, including hypertension, hyperglycaemia, heart failure, and rheumatoid arthritis. Traditional pharmacotherapies often face limitations such as side effects and poor patient adherence, thus prompting the exploration of device-based multi-organ denervation as a therapeutic strategy. Crucially, this procedure can potentially offer therapeutic benefits throughout the 24 h circadian cycle, described as an "always-on" effect independent of medication compliance and pharmacokinetics. In this comprehensive review, we evaluate the evidence behind targeted multi-organ sympathetic denervation by considering the anatomy and function of the autonomic nervous system, examining the evidence linking sympathetic nervous system overactivity to various cardiometabolic and inflammatory conditions and exploring denervation studies within the literature. So far, renal denervation, developed in 2010, has shown promise in reducing blood pressure and may have broader applications for conditions including arrhythmias, glucose metabolism disorders, heart failure, chronic kidney disease and obstructive sleep apnoea. We review the existing literature surrounding the denervation of other organ systems including the hepatic and splenic arteries, as well as the pulmonary artery and carotid body, which may provide additional physiological benefits and enhance therapeutic effects if carried out simultaneously. Furthermore, we highlight the challenges and future directions for implementing multi-organ sympathetic ablation, emphasising the need for further clinical trials to establish optimal procedural technique, efficacy and safety.

Effects of psychological stress on inflammatory bowel disease via affecting the microbiota-gut-brain axis

ABSTRACT

Inflammatory bowel disease (IBD) is an idiopathic intestinal inflammatory condition with chronic and relapsing manifestations and is characterized by a disturbance in the interplay between the intestinal microbiota, the gut, and the brain. The microbiota-gut-brain axis involves interactions among the nervous system, the neuroendocrine system, the gut microbiota, and the host immune system. Increasing published data indicate that psychological stress exacerbates the severity of IBD due to its negative effects on the microbiota-gut-brain axis, including alterations in the stress response of the hypothalamic-pituitary-adrenal (HPA) axis, the balance between the sympathetic nervous system and vagus nerves, the homeostasis of the intestinal flora and metabolites, and normal intestinal immunity and permeability. Although the current evidence is insufficient, psychotropic agents, psychotherapies, and interventions targeting the microbiota-gut-brain axis show the potential to improve symptoms and quality of life in IBD patients. Therefore, further studies that translate recent findings into therapeutic approaches that improve both physical and psychological well-being are needed.

Downregulation of CCR2 reduces ventricular remodeling after myocardial infarction by splenic nerve neuromodulation in acute and chronic rat models

OBJECTIVES

Pathological remodeling after myocardial infarction (MI) confers the development of heart failure. Our prior research has indicated that splenic nerve neuromodulation mitigates myocardial ischemia-reperfusion injury (IRI) by reducing levels of proinflammatory factors. This study aims to explore the potential therapeutic benefits of splenic nerve neuromodulation in MI and the underlying mechanism.

METHODS

Splenic nerve neuromodulation was performed through electrical splenic nerve stimulation (SpNS). In the acute myocardial IRI model, post-mortem analyses encompassed RNA sequencing and a range of molecular biology techniques, with the application of CCR2 antagonists (RS-504393) to inhibit the CCR2. In the chronic MI model, rats underwent echocardiographic assessment four weeks post-MI, after which tissues were harvested.

RESULTS

In the acute IRI model, the negative regulation of chemokines production pathway was enriched by RNA-seq, and SpNS reduced the levels of CCR2, CCL2, and CCL7. The administration of RS-504393 decreased cardiomyocyte apoptosis, reduced myocardial damage, and lowered proinflammatory cytokines levels following myocardial IRI. Additionally, SpNS was shown to inhibit oxidative stress, proinflammatory cytokine levels, and cardiac collagen deposition, as observed four weeks post-MI. SpNS also restrained sympathetic nerve remodeling and improved left ventricular function, in part by downregulating CCR2 in the chronic MI model.

CONCLUSIONS

SpNS demonstrated significant improvements in cardiac function, reductions of cardiac remodeling and inhibitions of excessive sympathetic activation in the chronic MI model by downregulation of CCR2. Our study provides novel evidence that splenic nerve neuromodulation may serve as a potential therapeutic intervention in MI patients.

A History of Psycho-Neuro-Endocrine Immune Interactions in Rheumatic Diseases

BACKGROUND

All active scientists stand on the shoulders of giants and many other more anonymous scientists, and this is not different in our field of psycho-neuro-endocrine immunology in rheumatic diseases. Too often, the modern world of publishing forgets about the collective enterprise of scientists. Some journals advise the authors to present only literature from the last decade, and it has become a natural attitude of many scientists to present only the latest publications. In order to work against this general unempirical behavior, neuroimmunomodulation devotes the 30th anniversary issue to the history of medical science in psycho-neuro-endocrine immunology.

SUMMARY

Keywords were derived from the psycho-neuro-endocrine immunology research field very well known to the authors (R.H.S. has collected a list of keywords since 1994). We screened PubMed, the Cochran Library of Medicine, Embase, Scopus database, and the ORCID database to find relevant historical literature. The Snowballing procedure helped find related work. According to the historical appearance of discoveries in the field, the order of presentation follows the subsequent scheme: (1) the sensory nervous system, (2) the sympathetic nervous system, (3) the vagus nerve, (4) steroid hormones (glucocorticoids, androgens, progesterone, estrogens, and the vitamin D hormone), (5) afferent pathways involved in fatigue, anxiety, insomnia, and depression (includes pathophysiology), and (6) evolutionary medicine and energy regulation - an umbrella theory.

KEY MESSAGES

A brief history on psycho-neuro-endocrine immunology cannot address all relevant aspects of the field. The authors are aware of this shortcoming. The reader must see this review as a viewpoint through the biased eyes of the authors. Nevertheless, the text gives an overview of the history in psycho-neuro-endocrine immunology of rheumatic diseases.

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.

Sympathetic activity regulates epithelial proliferation and wound healing via adrenergic receptor α2A

Innervation of the intestinal mucosa by the sympathetic nervous system is well described but the effects of adrenergic receptor stimulation on the intestinal epithelium remain equivocal. We therefore investigated the effect of sympathetic neuronal activation on intestinal cells in mouse models and organoid cultures, to identify the molecular routes involved. Using publicly available single-cell RNA sequencing datasets we show that the α2A isoform is the most abundant adrenergic receptor in small intestinal epithelial cells. Stimulation of this receptor with norepinephrine or a synthetic specific α2A receptor agonist promotes epithelial proliferation and stem cell function, while reducing differentiation in vivo and in intestinal organoids. In an anastomotic healing mouse model, adrenergic receptor α2A stimulation resulted in improved anastomotic healing, while surgical sympathectomy augmented anastomotic leak. Furthermore, stimulation of this receptor led to profound changes in the microbial composition, likely because of altered epithelial antimicrobial peptide secretion. Thus, we established that adrenergic receptor α2A is the molecular delegate of intestinal epithelial sympathetic activity controlling epithelial proliferation, differentiation, and host defense. Therefore, this receptor could serve as a newly identified molecular target to improve mucosal healing in intestinal inflammation and wounding.

Voltammetry in the spleen assesses real-time immunomodulatory norepinephrine release elicited by autonomic neurostimulation

BACKGROUND

The noradrenergic innervation of the spleen is implicated in the autonomic control of inflammation and has been the target of neurostimulation therapies for inflammatory diseases. However, there is no real-time marker of its successful activation, which hinders the development of anti-inflammatory neurostimulation therapies and mechanistic studies in anti-inflammatory neural circuits.

METHODS

In mice, we performed fast-scan cyclic voltammetry (FSCV) in the spleen during intravenous injections of norepinephrine (NE), and during stimulation of the vagus, splanchnic, or splenic nerves. We defined the stimulus-elicited charge generated at the oxidation potential for NE (~ 0.88 V) as the "NE voltammetry signal" and quantified the dependence of the signal on NE dose and intensity of neurostimulation. We correlated the NE voltammetry signal with the anti-inflammatory effect of splenic nerve stimulation (SpNS) in a model of lipopolysaccharide- (LPS) induced endotoxemia, quantified as suppression of TNF release.

RESULTS

The NE voltammetry signal is proportional to the estimated peak NE blood concentration, with 0.1 μg/mL detection threshold. In response to SpNS, the signal increases within seconds, returns to baseline minutes later, and is blocked by interventions that deplete NE or inhibit NE release. The signal is elicited by efferent, but not afferent, electrical or optogenetic vagus nerve stimulation, and by splanchnic nerve stimulation. The magnitude of the signal during SpNS is inversely correlated with subsequent TNF suppression in endotoxemia and explains 40% of the variance in TNF measurements.

CONCLUSIONS

FSCV in the spleen provides a marker for real-time monitoring of anti-inflammatory activation of the splenic innervation during autonomic stimulation.

Acute Inhibition of Inflammation Mediated by Sympathetic Nerves: The Inflammatory Reflex

In this review, we will try to convince the readers that the immune system is controlled by an endogenous neural reflex, termed inflammatory reflex, that inhibits the acute immune response during the course of a systemic immune challenge. We will analyse here the contribution of different sympathetic nerves as possible efferent arms of the inflammatory reflex. We will discuss the evidence that demonstrates that neither the splenic sympathetic nerves nor the hepatic sympathetic nerves are necessary for the endogenous neural reflex inhibition of inflammation. We will discuss the contribution of the adrenal glands to the reflex control of inflammation, noting that the neurally mediated release of catecholamines in the systemic circulation is responsible for the enhancement of the anti-inflammatory cytokine interleukin 10 (IL-10) but not of the inhibition of the pro-inflammatory cytokine tumour necrosis factor α (TNF). We will conclude by reviewing the evidence that demonstrates that the splanchnic anti-inflammatory pathway, composed by preganglionic and postganglionic sympathetic splanchnic fibres with different target organs, including the spleen and the adrenal glands, is the efferent arm of the inflammatory reflex. During the course of a systemic immune challenge, the splanchnic anti-inflammatory pathway is endogenously activated to inhibit the TNF and enhance the IL-10 response, independently, presumably acting on separate populations of leukocytes.

Chronic Effects of the Sympathetic Nervous System in Inflammatory Models

The immune system is embedded in a network of regulatory systems to keep homeostasis in case of an immunologic challenge. Neuroendocrine immunologic research has revealed several aspects of these interactions over the past decades, e.g., between the autonomic nervous system and the immune system. This review will focus on evidence revealing the role of the sympathetic nervous system (SNS) in chronic inflammation, like colitis, multiple sclerosis, systemic sclerosis, lupus erythematodes, and arthritis with a focus on animal models supported by human data. A theory of the contribution of the SNS in chronic inflammation will be presented that spans these disease entities. One major finding is the biphasic nature of the sympathetic contribution to inflammation, with proinflammatory effects until the point of disease outbreak and mainly anti-inflammatory influence thereafter. Since sympathetic nerve fibers are lost from sites of inflammation during inflammation, local cells and immune cells achieve the capability to endogenously produce catecholamines to fine-tune the inflammatory response independent of brain control. On a systemic level, it has been shown across models that the SNS is activated in inflammation as opposed to the parasympathetic nervous system. Permanent overactivity of the SNS contributes to many of the known disease sequelae. One goal of neuroendocrine immune research is defining new therapeutic targets. In this respect, it will be discussed that at least in arthritis, it might be beneficial to support β-adrenergic and inhibit α-adrenergic activity besides restoring autonomic balance. Overall, in the clinical setting, we now need controlled interventional studies to successfully translate the theoretical knowledge into benefits for patients.