Auricular Vagus Nerve Stimulation Attenuates Lipopolysaccharide-Induced Acute Lung Injury by Inhibiting Neutrophil Infiltration and Neutrophil Extracellular Traps Formation

A Narrative Review: The Role of NETs in Acute Respiratory Distress Syndrome/Acute Lung Injury

Nowadays, acute respiratory distress syndrome (ARDS) still has a high mortality rate, and the alleviation and treatment of ARDS remains a major research focus. There are various causes of ARDS, among which pneumonia and non-pulmonary sepsis are the most common. Trauma and blood transfusion can also cause ARDS. In ARDS, the aggregation and infiltration of neutrophils in the lungs have a great influence on the development of the disease. Neutrophils regulate inflammatory responses through various pathways, and the release of neutrophils through neutrophil extracellular traps (NETs) is considered to be one of the most important mechanisms. NETs are mainly composed of DNA, histones, and granuloproteins, all of which can mediate downstream signaling pathways that can activate inflammatory responses, generate immune clots, and cause damage to surrounding tissues. At the same time, the components of NETs can also promote the formation and release of NETs, thus forming a vicious cycle that continuously aggravates the progression of the disease. NETs are also associated with cytokine storms and immune balance. Since DNA is the main component of NETs, DNase I is considered a viable drug for removing NETs. Other therapeutic methods to inhibit the formation of NETs are also worthy of further exploration. This review discusses the formation and mechanism of NETs in ARDS. Understanding the association between NETs and ARDS may help to develop new perspectives on the treatment of ARDS.

Transcutaneous auricular vagus nerve stimulation reduces cytokine production in sepsis: An open double-blind, sham-controlled, pilot study

BACKGROUND

Studies have shown that vagus nerve-mediated inflammatory reflex could inhibit cytokine production and inflammation in sepsis animals.

OBJECTIVES

This study aimed to explore the efficacy of transcutaneous auricular vagus nerve stimulation (taVNS) on inflammation and disease severity of sepsis patients.

METHODS

A randomized, double-blind, sham-controlled pilot study was performed. Twenty sepsis patients were randomly assigned to receive taVNS or sham stimulation for five consecutive days. Stimulation effect was assessed with serum cytokine levels, Acute Physiology and Chronic Health Evaluation (APACHE) Ⅱ score, and Sequential Organ Failure Assessment (SOFA) score at baseline and on Day 3, Day 5, and Day 7.

RESULTS

TaVNS was well tolerated in the study population. Patients receiving taVNS experienced significant reductions in serum TNF-α and IL-1β levels and increases in IL-4 and IL-10 levels. SOFA scores decreased on Day 5 and Day 7 compared with baseline in the taVNS group. However, no changes were found in sham stimulation group. The changes of cytokine from Day 7 to Day 1 were greater with taVNS than sham stimulation. No differences in the APACHE Ⅱ score and SOFA score were observed between the two groups.

CONCLUSIONS

TaVNS resulted in significantly lower serum pro-inflammatory cytokines and higher serum anti-inflammatory cytokines in sepsis patients.

Activation of α7 nicotinic acetylcholine receptor retards the development of endometriosis

BACKGROUND

Women with endometriosis have been shown to have a reduced vagal tone as compared with controls and vagotomy promoted while vagus nerve stimulation (VNS) decelerated the progression of endometriosis in mice. Extensive research also has shown that the activation of the cholinergic anti-inflammatory pathway by VNS activates α7 nicotinic acetylcholine receptor (α7nAChR), potently reducing inflammation. Yet whether α7nAChR plays any role in endometriosis is unknown. We evaluated its expression in normal endometrium, ovarian and deep endometriotic lesions, and evaluated its role in the development of endometriosis.

METHODS

Immunohistochemistry analyses of α7nAChR in endometriotic lesions as well as control endometrium, and quantification of tissue fibrosis by Masson trichrome staining were performed. Mouse experiments were conducted to evaluate the impact of α7nAChR activation or suppression on lesional progression and possible therapeutic effect. Finally, in vitro experiments were conducted to evaluate the effect of activation of α7nAChR on epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT), smooth muscle metaplasia (SMM) and fibrogenesis in an endometriotic epithelial cell line and primary endometriotic stromal cells derived from ovarian endometrioma tissue samples.

RESULTS

Immunostaining of α7nAChR was significantly reduced in human endometriotic epithelial cells as compared with their counterpart in normal endometrium. Lesional α7nAChR staining levels correlated negatively with lesional fibrosis and the severity of dysmenorrhea. The α7nAChR agonist significantly impeded the development of endometriotic lesions in mouse models possibly through hindrance of EMT and FMT. It also demonstrated therapeutic effects in mice with induced deep endometriosis. Treatment of endometriotic epithelial and stromal cells with an α7nAChR agonist significantly abrogated platelet-induced EMT, FMT and SMM, and suppressed cellular contractility and collagen production.

CONCLUSIONS

α7nAChR is suppressed in endometriotic lesions, and its activation by pharmacological means can impede EMT, FMT, SMM, and fibrogenesis of endometriotic lesions. As such, α7nAChR can be rightfully viewed as a potential target for therapeutic invention.

TRIAL REGISTRATION

Not applicable.