Menglong Wang

A potential relationship between gut microbes and atrial fibrillation: Trimethylamine N-oxide, a gut microbe-derived metabolite, facilitates the progression of atrial fibrillation

BACKGROUND Emerging evidence indicates gut microbes and their products could activate the autonomic nervous system (ANS), which plays important roles in the initiation and maintenance of atrial fibrillation (AF). Trimethylamine N-oxide (TMAO), a metabolite derived from gut microbes, is associated with cardiovascular diseases. The present study aimed to investigate the role of TMAO in the progression of AF. METHODS In part 1: TMAO or saline was locally injected into 4 major atrial ganglionated plexi (GP) to clarify its effect on cardiac ANS and AF inducibility in normal canines. In part 2: TMAO or saline was injected into 4 major atrial GP to test its effect on AF progression in a rapid atrial pacing (RAP)-induced AF model. RESULTS In part 1: Local injection of TMAO significantly increased anterior right GP (ARGP) function and neural activity, shortened ERP values. In part 2, compared with the control group, 6-hour RAP significantly shortened the ERP, widened the ∑WOV, enhanced the ARGP function and neural activity, increased the NGF and c-fos expression, and up-regulated the inflammatory cytokines. TMAO aggravated all of these changes by activating the proinflammatory p65 NF-κB signaling pathway. CONCLUSIONS TMAO could increase the instability of atrial electrophysiology in normal canines and aggravate the acute electrical remodeling in a RAP-induced AF model by exacerbating autonomic remodeling. The increased inflammatory cytokines in the GP due to the activation of p65 NF-κB signaling may contribute to these effects.

Blocking the Nav1.8 channel in the left stellate ganglion suppresses ventricular arrhythmia induced by acute ischemia in a canine model

Left stellate ganglion (LSG) hyperactivity promotes ischemia induced ventricular arrhythmia (VA). Blocking the Nav1.8 channel decreases neuron activity. Therefore, the present study aimed to investigate whether blocking the Nav1.8 channel with its specific blocker A-803467 in the LSG reduces sympathetic activity and exerts anti-arrhythmic effects. Forty canines were divided into dimethylsulfoxide (DMSO) group and 10 mM, 15 mM, and 20 mM A-803467 groups. A volume of 0.1 ml of A-803467 or DMSO was injected into the LSG. The ventricular electrophysiological parameters, LSG function were measured before and 30 min after the injection. VA was assessed for 60 min after ischemia and then LSG tissues were collected for molecular biological experiments. Compared with DMSO, concentration-dependent prolonged action potential duration and effective refractory period, decreased LSG function were identified after A-803467 treatment. Moreover, the severity of ischemia induced VA was decreased in A-803467 groups. Furthermore, decreased nerve growth factor, decreased c-fos and increased sympathetic neuron apoptosis were found in the LSG after A-803467 injection. In conclusion, blocking the Nav1.8 channel could significantly attenuate ischemia-induced VA, primarily by suppressing LSG activity.

Interleukin 22 Promotes Blood Pressure Elevation and Endothelial Dysfunction in Angiotensin II–Treated Mice

Background CD4+ T helper (Th) cells, including Th1, Th2, and Th17 cells, play critical roles in angiotensin II–induced hypertension. Th22 cells, a novel subset of Th cells, take part in cardiovascular diseases by producing IL‐22 (interleukin 22). This study aimed to investigate whether IL‐22 is involved in hypertension. Methods and Results Th22 cells and IL‐22 levels were detected in angiotensin II–infused mice, and the results showed that Th22 cells and IL‐22 levels significantly increased. To determine the effect of Th22/IL‐22 on blood pressure regulation, angiotensin II–infused mice were treated with recombinant mouse IL‐22, an anti–IL‐22 neutralizing monoclonal antibody, or control. Treatment with recombinant IL‐22 resulted in increased blood pressure, amplified inflammatory responses, and aggravated endothelial dysfunction, whereas the anti–IL‐22 neutralizing monoclonal antibody decreased blood pressure, reduced inflammatory responses, and attenuated endothelial dysfunction. To determine whether the STAT3 (signal transducer and activator of transcription 3) pathway mediates the effect of IL‐22 on blood pressure regulation, the special STAT3 pathway inhibitor S31‐201 was administered to mice treated with recombinant IL‐22. S31‐201 treatment significantly ameliorated the IL‐22 effects of increased blood pressure and endothelial dysfunction. In addition, serum IL‐22 levels were significantly increased in hypertensive patients compared with healthy persons. Correlation analysis showed a positive correlation between IL‐22 levels and blood pressure. Conclusions IL‐22 amplifies the inflammatory response, induces endothelial dysfunction and promotes blood pressure elevation in angiotensin II–induced hypertensive mice. The STAT3 pathway mediates the effect of IL‐22 on hypertension. Blocking IL‐22 may be a novel therapeutic strategy to prevent and treat hypertension.

Increased inflammation promotes ventricular arrhythmia through aggravating left stellate ganglion remodeling in a canine ischemia model

BACKGROUND Increased inflammation was found in the left stellate ganglion (LSG) in patients with malignant ventricular arrhythmia (VA). However, the role of inflammation in LSG remodeling is unknown. This study aimed to investigate whether exogenous interleukin-1β (IL-1β) could aggravate VA through regulating LSG remodeling. METHODS Twenty-four canines who received saline (Control, n=8), IL-1β injection into the LSG (n=8) or IL-1 receptor antagonist (IL-Ra) pre-injection plus IL-1β injection (n=8) were included. Ventricular electrophysiology parameters, heart rate variability (HRV), LSG activity were measured at different time points. VA was recorded for 60min after ischemia and then LSG tissues were collected for molecular detection. RESULTS Compared with the control group, IL-1β injection decreased the effective refractory period, action potential duration (APD)90 and increased the maximal slope of the restitution curve in normal hearts. Besides, the occurrence of VA was significantly increased in the IL-1β group. Additionally, IL-1β injection increased the sympathetic indices of HRV and LSG activity in normal and ischemic hearts. Mechanically, the mRNA expression of pro-inflammatory cytokines and protein expression of c-fos, nerve growth factor and neuropeptide Y in LSG were increased, whereas the expression of neuronal nitric oxide synthase was decreased in the IL-1β group. More importantly, all these effects induced by IL-1β were attenuated by IL-1Ra pre-injection. CONCLUSION Increased inflammation induced by IL-1β injection aggravates ischemia induced VA through regulating the neuronal remodeling of the LSG. Inflammation induced neuroplasticity may be a novel mechanism and therapeutic target for VA.

Noninvasive low-frequency electromagnetic stimulation of the left stellate ganglion reduces myocardial infarction-induced ventricular arrhythmia

Noninvasive magnetic stimulation has been widely used in autonomic disorders in the past few decades, but few studies has been done in cardiac diseases. Recently, studies showed that low-frequency electromagnetic field (LF-EMF) might suppress atrial fibrillation by mediating the cardiac autonomic nervous system. In the present study, the effect of LF-EMF stimulation of left stellate ganglion (LSG) on LSG neural activity and ventricular arrhythmia has been studied in an acute myocardium infarction canine model. It is shown that LF-EMF stimulation leads to a reduction both in the neural activity of LSG and in the incidence of ventricular arrhythmia. The obtained results suggested that inhibition of the LSG neural activity might be the causal of the reduction of ventricular arrhythmia since previous studies have shown that LSG hyperactivity may facilitate the incidence of ventricular arrhythmia. LF-EMF stimulation might be a novel noninvasive substitute for the existing implant device-based electrical stimulation or sympathectomy in the treatment of cardiac disorders.

Increased levels of interleukin-22 in thoracic aorta and plasma from patients with acute thoracic aortic dissection

BACKGROUND Interleukin (IL)-22 plays important roles in the development of arterial disease, including atherosclerosis and hypertension. However, the relationship between IL-22 and acute thoracic aortic dissection (TAD) remains unknown. METHODS Blood samples were collected from patients with chest pain who underwent computed tomography angiography of the thoracic aorta but had no known preoperative diagnosis of coronary artery disease, peripheral artery disease, arthritis, and/or membranous nephropathy. Patients were divided into non-AD (NAD) and TAD groups, and the plasma concentrations of IL-22, IL-6 and tumor necrosis factor (TNF)-α were measured. In addition, aortic tissue samples from acute TAD patients and normal donors were collected, and the expression levels of IL-22 and IL-22 receptor 1 (IL-22R1) were measured. RESULTS IL-22, IL-6 and TNF-α levels were significantly higher in acute TAD patients than in NAD patients (IL-22, NAD group: 27.0 (19.1, 38.6) pg/ml vs. TAD group: 32.9 (20.6, 58.3) pg/ml, p<0.0001). The correlation analysis showed that IL-22 levels were positively correlated with levels of IL-6, TNF-α, fasting glucose, blood pressure, white blood cells, C-reactive proteins and D-dimers. Binary logistic regression analyses showed that IL-22 was independently associated with the presence of acute TAD (OR 1.169, 95% CI 1.069 to 1.277; p=0.001). In addition, compared with aortic tissue of normal controls, TAD aortas showed increased expression of IL-22 and IL-22R1, especially in the torn section (IL-22, non-torn section: 2.8±0.5/HPF vs. torn section 2.8±0.5/HPF, p<0.001). Additionally, macrophage but not T lymphocyte infiltration was significantly increased in the torn section (Macrophage, non-torn section: 2.2±0.6/HPF vs. torn section 5.7±1.2/HPF, p<0.001; T lymphocyte, non-torn section: 2.7±0.9/HPF vs. torn section 2.4±0.5/HPF, p=0.28), as evidenced by increased positive staining for the macrophage marker CD68, as opposed to the T cell marker CD3. CONCLUSION IL-22 levels may correlate with the presence of acute TAD.

Increased interleukin-11 levels in thoracic aorta and plasma from patients with acute thoracic aortic dissection

BACKGROUND Interleukin (IL) 11 is closely related to tumor and hematological system diseases. Recent studies have demonstrated that IL-11 also participates in cardiovascular diseases, including ischemia-reperfusion mediated heart injury and acute myocardial infarction. This study aimed to investigate whether IL-11 is involved in acute thoracic aortic dissection (TAD). METHODS Aortic tissue samples from normal donors and acute TAD patients were collected, and the expression of IL-11 in all aortic tissue was analyzed. In addition, blood samples from patients with chest pain were collected and divided into a non-AD (NAD) group and a TAD group according to the results of computed tomography angiography of the thoracic aorta. The plasma IL-11, IL-17 and interferon (IFN) γ in all blood samples were measured. RESULTS Compared with aortic tissue of normal controls, IL-11 was significantly increased in aortic tissue of acute TAD patients, especially in the torn section. The IL-11 was derived from aorta macrophages in TAD. In addition, the plasma IL-11, IL-17 and IFN-γ were significantly higher in acute TAD patients than in NAD patients, and the correlation analysis showed that IL-11 levels were positively correlated with levels of IFN-γ, IL-17, glucose, systolic blood pressure, diastolic blood pressure, white blood cells, C-reactive proteins and D-dimers. Binary logistic regression analyses showed that elevated IL11 in patients who may have diagnostic value of TAD, but less that D-dimer. CONCLUSION IL-11 was increased in thoracic aorta and plasma of TAD patients and may be a promising biomarker for diagnosis in patients with TAD.

Atrial Fibrillation in Acute Obstructive Sleep Apnea: Autonomic Nervous Mechanism and Modulation

Background The mechanisms of atrial fibrillation (AF) induced by obstructive sleep apnea (OSA) are not completely understood. This study investigated the roles of the intrinsic and extrinsic cardiac autonomic nervous system in OSA‐induced AF and provided noninvasive autonomic nervous modulation for the suppression of OSA‐induced AF by using low‐level transcutaneous electrical stimulation (LL‐TS) of the auricular branch of the vagus nerve at the tragus. Methods and Results Eighteen dogs received tracheostomy under general anesthesia and were randomly divided into 3 groups: the OSA group (OSA was simulated via clamping of the endotracheal tube at end expiration for 1.5 minutes every 10 minutes, n=6), the LL‐TS + OSA group (simulated OSA plus LL‐TS, at 80% of the slowing sinus rate, n=6), and the control group (sham surgery without stimulation, n=6). The effective refractory period was significantly shortened after 1 hour of simulated OSA, and the window of vulnerability and plasma norepinephrine levels were both markedly increased in the OSA group. OSA dramatically increased the neural function and activity of the intrinsic and extrinsic cardiac autonomic nervous system, including the superior left ganglionated plexus, the left stellate ganglion, and the left renal sympathetic nerve. OSA also significantly upregulated the expression levels of c‐fos and nerve growth factor in the superior left ganglionated plexus and the left stellate ganglion. However, LL‐TS markedly improved these parameters. Conclusions These findings suggest that the intrinsic and extrinsic cardiac autonomic nervous system plays crucial roles in the acute stage of OSA‐induced AF. Noninvasive LL‐TS suppressed shortening of atrial refractoriness and autonomic remodeling, which prevented OSA‐induced AF.

The E23K variant of the Kir6.2 subunit of the ATP-sensitive potassium channel increases susceptibility to ventricular arrhythmia in response to ischemia in rats

BACKGROUND The E23K variant of the Kir6.2 subunit of the ATP-sensitive potassium (KATP) channel has been implicated in cardiac remodeling. However, the effects of E23K variant on ventricular electrophysiology and arrhythmogenesis remain unclear. METHODS Transgenic rats were generated to express human E23K-variant genomic DNA in the heart under the α-myosin heavy chain promoter. Electrophysiological parameters including electrocardiograph, ventricular action potential duration (APD), effective refractory period (ERP), electrical alternans and ventricle arrhythmia threshold were examined in wild type (WT) and transgenic rats. The KATP current in cardiomyocytes was recorded using whole-cell patch clamp techniques. RESULTS No differences in the electrophysiological parameters between the two groups were found at baseline. However, after acute ischemic stress, shortened QT intervals were further aggravated in the E23K-variant rats. Additionally, the E23K variant exacerbated the decrease of APD70, APD90 and ERP. The ventricular arrhythmia and alternans thresholds were significantly attenuated, and the duration of ventricular arrhythmia induced by electrical stimulation was significantly prolonged in the E23K-variant rats. More importantly, the KATP current in cardiomyocytes was significantly increased in the E23K-variant rats after ischemia. CONCLUSION The E23K variant of the KATP channel increased the susceptibility to ventricular arrhythmia under acute ischemia stress.

Recent Insights into the Biological Functions of Sestrins in Health and Disease

Sestrins (Sesns) have been identified as a family of highly conserved stress-inducible proteins that are strongly up-regulated by various stresses, including DNA damage, oxidative stress, and hypoxia. The Sesns play protective roles in most physiological and pathological conditions mainly through the regulation of oxidative stress, inflammation, autophagy, endoplasmic reticulum stress, and metabolic homeostasis. In this review, we discussed the possible regulators of Sesns expression, such as p53, forkhead box O, nuclear factor erythroid 2 like 2 (Nrf2), NH (2)-terminal kinase (JNK)/c-Jun pathway and hypoxia-inducible factor-1α (Hif-1α), and the downstream pathways regulated by the Sesns including AMP-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling, mitogen-activated protein kinases (MAPKs) signaling, Nrf2 signaling, NADPH oxidase signaling and transforming growth factor β (TGF-β) signaling in heart diseases, lung diseases, gastrointestinal tract diseases, liver and metabolism diseases, neurological diseases, kidney diseases and immunological diseases. This review aims to provide a comprehensive understanding the protective effects of Sesns.