Toll-like receptor 4 activation modulates pericardium-myocardium interactions in lipopolysaccharide-induced atrial arrhythmogenesis

Evaluation of Toll-like Receptor 4 (TLR4) Involvement in Human Atrial Fibrillation: A Computational Study

In the present study, we have explored the involvement of Toll-like Receptor 4 (TLR4) in atrial fibrillation (AF), by using a meta-analysis of publicly available human transcriptomic data. The meta-analysis revealed 565 upregulated and 267 downregulated differentially expressed genes associated with AF. Pathway enrichment analysis highlighted a significant overrepresentation in immune-related pathways for the upregulated genes. A significant overlap between AF differentially expressed genes and TLR4-modulated genes was also identified, suggesting the potential role of TLR4 in AF-related transcriptional changes. Additionally, the analysis of other Toll-like receptors (TLRs) revealed a significant association with TLR2 and TLR3 in AF-related gene expression patterns. The examination of MYD88 and TICAM1, genes associated with TLR4 signalling pathways, indicated a significant yet nonspecific enrichment of AF differentially expressed genes. In summary, this study offers novel insights into the molecular aspects of AF, suggesting a pathophysiological role of TLR4 and other TLRs. By targeting these specific receptors, new treatments might be designed to better manage AF, offering hope for improved outcomes in affected patients.

Association of lipopolysaccharide with new-onset atrial fibrillation in ST-segment elevation myocardial infarction

Background

Lipopolysaccharide (LPS) is related to various cardiovascular diseases. However, the relationship between LPS and new-onset atrial fibrillation (NOAF) after ST-segment elevation myocardial infarction (STEMI) has yet to be elucidated. This study aimed to evaluate the impact of LPS on NOAF in STEMI patients.

Methods

This was a single-center retrospective observational study including 806 patients diagnosed with STEMI. LPS levels were determined using a commercial ELISA kit. NOAF was characterized by postadmission AF with the absence of any prior history of AF.

Results

A total of 806 participants were enrolled, with 752 individuals in the non-AF group (93.3%) and 54 individuals in the AF group (6.7%). Multivariable analysis showed that LPS (OR = 1.047; 95% CI: 1.029-1.065, P < 0.001) was an independent risk marker for NOAF. The analysis of the ROC demonstrated that LPS had an AUC of 0.717 in predicting NOAF. When LPS was added to the conventional model, the ability of the risk model to discriminate and reclassify NOAF was improved significantly (IDI 0.053, P = 0.001; NRI 0.510, P < 0.001).

Conclusion

Elevated LPS is associated with an increased risk of NOAF in STEMI patients. The integration of LPS can improve the ability to predict NOAF in STEMI patients.

Chemotaxis-guided Self-propelled Macrophage Motor for Targeted Treatment of Acute Pneumonia

Immune cells exhibit great potential as carriers of nanomedicine, attributed to their high tolerance to internalized nanomaterials and targeted accumulation in inflammatory tissues. However, the premature efflux of internalized nanomedicine during systemic delivery and slow infiltration into inflammatory tissues have limited their translational applications. Herein, a motorized cell platform as a nanomedicine carrier for highly efficient accumulation and infiltration in the inflammatory lungs and effective treatment of acute pneumonia are reported. β-Cyclodextrin and adamantane respectively modified manganese dioxide nanoparticles are intracellularly self-assembled into large aggregates mediated via host-guest interactions, to effectively inhibit the efflux of nanoparticles, catalytically consume/deplete H₂ O₂ to alleviate inflammation, and generate O₂ to propel macrophage movement for rapid tissue infiltration. With curcumin loaded into MnO₂ nanoparticles, macrophages carry the intracellular nano-assemblies rapidly into the inflammatory lungs via chemotaxis-guided, self-propelled movement, for effective treatment of acute pneumonia via immunoregulation induced by curcumin and the aggregates.

Inflammatory signalling in atrial cardiomyocytes: a novel unifying principle in atrial fibrillation pathophysiology

Inflammation has been implicated in atrial fibrillation (AF), a very common and clinically significant cardiac rhythm disturbance, but its precise role remains poorly understood. Work performed over the past 5 years suggests that atrial cardiomyocytes have inflammatory signalling machinery - in particular, components of the NLRP3 (NACHT-, LRR- and pyrin domain-containing 3) inflammasome - that is activated in animal models and patients with AF. Furthermore, work in animal models suggests that NLRP3 inflammasome activation in atrial cardiomyocytes might be a sufficient and necessary condition for AF occurrence. In this Review, we evaluate the evidence for the role and pathophysiological significance of cardiomyocyte NLRP3 signalling in AF. We first summarize the evidence for a role of inflammation in AF and review the biochemical properties of the NLRP3 inflammasome, as defined primarily in studies of classic inflammation. We then briefly consider the broader evidence for a role of inflammatory signalling in heart disease, particularly conditions that predispose individuals to develop AF. We provide a detailed discussion of the available information about atrial cardiomyocyte NLRP3 inflammasome signalling in AF and related conditions and evaluate the possibility that similar signalling might be important in non-myocyte cardiac cells. We then review the evidence on the role of active resolution of inflammation and its potential importance in suppressing AF-related inflammatory signalling. Finally, we consider the therapeutic potential and broader implications of this new knowledge and highlight crucial questions to be addressed in future research.

Sodium–glucose cotransporter-2 inhibitor alleviated atrial remodeling in STZ-induced diabetic rats by targeting TLR4 pathway

Purpose

The mechanism of sodium–glucose cotransporter-2 inhibitor (SGLT-2i) reducing the incidence of atrial fibrillation remains unclear. We hypothesize that sodium–glucose cotransporter-2 inhibitor alleviated atrial remodeling in STZ-induced diabetic rats by targeting TLR4 pathway.

Methods

A total of 42 rats were randomly assigned into three groups: control group (CON group); diabetes group (DM group): diabetes mellitus rats were established by 65 mg/kg streptozotocin (STZ) intraperitoneal injection; and diabetes + dapagliflozin group (DM + DAPA group): diabetic rats were given DAPA gavage administration (DAPA 2mg/kg/d for 4 weeks by gavage administration), 14 rats in each group. Epicardial multiple-lead recording and intracardiac electrophysiology studies were performed to investigate the electrical remodeling in the heart and the atrial fibrillation inducibility in each group. Western blot analysis and real-time PCR were used to determine the protein and mRNA expression of toll-like receptor 4 (TLR4), interleukin receptor-associated kinase 1 (IRAK1), tumor necrosis factor receptor-associated factor 6 (TRAF6), nuclear factor-kappa B (NF-κB), and type I collagen (collagen I).

Results

Compared with rats in CON group, rats in DM group showed marked myocardial fibrosis, ectopic pacing excitement, reduced conduction velocity, decreased cardiac function. TLR4/IRAK1/TRAF6/NF-κB, collagen I proteins expressions and incidence of atrial fibrillation (27.3%) were increased in DM group. Parts of these changes were reversed by treatment of DAPA. Incidence of atrial fibrillation was decreased in DM + DAPA group (2.8%).

Conclusions

SGLT-2i dapagliflozin may prevent diabetic rats' atrial remodeling and reduce the inducibility of atrial fibrillation partly by targeting TLR4/IRAK1/TRAF6/NF-κB inflammatory pathway.

Circulating Lipopolysaccharides and Impaired Antioxidant Status in Patients With Atrial Fibrillation. Data From the ATHERO-AF Study

Objectives: Atrial fibrillation (AF) is characterized by an oxidative imbalance, which is associated with an increased risk of cardiovascular events (CVEs). It is unclear whether low grade endotoxemia may contribute to the impaired antioxidant status in AF patients. We investigated the relationship between circulating lipopolysaccharides (LPS) and antioxidant status in AF patients.

Patients and Methods:Post-hoc analysis from the ongoing prospective observational cohort ATHERO-AF study including 907 patients. Antioxidant status was evaluated by the activity of glutathione peroxidase 3 (GPx3) and superoxide dismutase (SOD). Patients were divided into two groups to evaluate the risk of CVEs: (1) LPS below median and GPx3 above median (n = 254); (2) LPS above median and GPx3 below median (n = 263).

Results: The mean age was 73.5 ± 8.3 years, and 43.1% were women. Median LPS and GPx3 were 50.0 pg/ml [interquartile range (IQR) 15–108] and 20.0 U/ml (IQR 10.0–34.0), respectively. Patients of Groups 2 were older, with a higher prevalence of heart failure. LPS above the median was associated with reduced GPx3 [Odds Ratio for LPS 1.752, 95% Confidence Interval (CI) 1.344–2.285, p < 0.001] and SOD (OR 0.525, 95%CI 0.403–0.683) activity after adjustment for CHA₂DS₂VASc score. In a mean follow-up of 54.0 ± 36.8 months, 118 CVEs occurred, 42 in Group 1 and 76 in Group 2 (Log-Rank test p = 0.001). At multivariable Cox regression analysis, Group 2 was associated with a higher risk of CVEs [Hazard Ratio (HR) 1.644, 95%CI 1.117–2,421, p = 0.012], along with age ≥ 75 years (HR 2.035, 95%CI 1.394–2.972, p < 0.001), diabetes (HR 1.927, 95%CI 1.280–2.900, p = 0.002), and previous cerebrovascular disease (HR 1.895, 95%CI 1.251–2.870, p = 0.003) and previous cardiovascular disease (HR 1.708, 95%CI 1.149–2.538, p = 0.008).

Conclusions: Our study indicates that circulating LPS may contribute to impaired antioxidant status in patients with AF. Patients with coincidentally high LPS and reduced GPx3 activity showed the highest risk of CVEs.