The role of TREM-1 in septic myocardial pyroptosis and septic cardiomyopathy in vitro and in vivo

Endothelial TREM-1 mediates sepsis-induced blood‒brain barrier disruption and cognitive impairment via the PI3K/Akt pathway

The blood‒brain barrier (BBB) is a critical selective interface between the central nervous system (CNS) and the blood circulation. BBB dysfunction plays an important role in the neurological damage caused by sepsis. However, the mechanisms underlying the disruption of the BBB during sepsis remain unclear. We established a human induced pluripotent stem cell (iPSC)-derived BBB model and reported that treating with sepsis patient serum leads to structural and functional disruption of the BBB. In a cecal ligation and puncture (CLP)-induced mouse model of sepsis, we also observed disruption of the BBB, inflammation in the brain, and impairments in cognition. In both models, we found that the expression of TREM-1 was significantly increased in endothelial cells. TREM-1 knockout specifically in endothelial cells alleviated BBB dysfunction and cognitive impairments. Further study revealed that TREM-1 affects the expression of genes involved in the PI3K/Akt signaling pathway. The protective effects of TREM-1 inhibition on the BBB and cognition were abrogated by PI3K inhibitors. Our findings suggest that endothelial TREM-1 induces sepsis-induced BBB disruption and cognitive impairments via the PI3K/Akt signaling pathway. Targeting endothelial TREM-1 or the PI3K/Akt signaling pathway may be a promising strategy to maintain BBB integrity and improve cognitive function in sepsis patients.

A short history of the atrial NLRP3 inflammasome and its distinct role in atrial fibrillation

Inflammasomes are multiprotein complexes of the innate immune system that mediate inflammatory responses to infection and to local and systemic stress and tissue injury. The principal function is to facilitate caspase-1 auto-activation and subsequently maturation and release of the effectors interleukin (IL)-1β and IL-18. The atrial-specific NLRP3 inflammasome is a unifying causal feature of atrial fibrillation (AF) development, progression and recurrence after ablation. Many AF-associated risk factors and co-morbidities converge mechanistically on the activation of this central inflammatory signaling platform. This review presents the historical conceptual development of a distinct atrial inflammasome and its potential causal involvement in AF. We follow the early observations linking systemic and local inflammation with AF, to the emergence of an atrial-intrinsic NLRP3 inflammasome operating within not just immune cells but also in resident atrial fibroblasts and cardiomyocytes. We outline the key developments in understanding how the atrial NLRP3 inflammasome and its effector IL-1β contribute causally to cellular and tissue-level arrhythmogenesis in different pathological settings, and outline candidate therapeutic concepts verified in preclinical models of atrial cardiomyopathy and AF.

Identification and Exploration of Pyroptosis-Related Genes in Macrophage Cells Reveal Necrotizing Enterocolitis Heterogeneity Through Single-Cell and Bulk-Sequencing

Necrotizing enterocolitis (NEC) is an acute intestine dysfunction intestinal disorder characterized by inflammation and cell death, including pyroptosis. Previous studies have implicated pyroptosis, particularly via NLRP3 inflammatory activation, and contribute to the development of NEC. However, the genetic and molecular mechanisms underlying pyroptosis in NEC pathogenesis and sequelae remain unclear. Our study aimed to identify the pyroptosis-related cell populations and genes and explore potential therapeutic targets. Single-cell RNA sequencing (scRNA-seq) data were analyzed to identify the cell populations related to NEC and pyroptosis. Weighted gene correlation network analysis (WGCNA) of bulk RNA-seq was performed to identify gene modules associate with pyroptosis. Cell-cell communication was employed to investigate intercellular signaling networks. Gene Set Enrichment Analysis (GSEA) was conducted to compare the pathways enriched in the high and low TREM1-expressing subgroups. Immunofluorescence staining was performed to detect the TREM1+CD163+ macrophages in the intestines. PCR and Western blot were performed to detect the expression of mRNA and proteins in the intestine tissues and cells. scRNA-seq analysis revealed increased macrophage abundance in NEC, with one macrophage cluster (cluster 4) exhibiting a markedly elevated pyroptosis score. WGCNA identified a gene module (MEbrown) that positively correlated with pyroptosis. Five genes (TREM1, TLN1, NOTCH2, MPZL1, and ADA) within this module were identified as potential diagnostic markers of pyroptosis. Furthermore, we identified a novel macrophage subpopulation, TREM1+CD163+, in NEC. Cell-cell communication analysis suggested that TREM1+CD163+ macrophages interact with other cells primarily through the NAMPT/ITGA5/ITGB1 and CCL3/CCR1 pathways. GSEA revealed a significant association between high TREM1 expression and pathways related to pyroptosis, cell proliferation, and inflammation. In vivo and in vitro experiments confirmed an increase in TREM1+CD163+ macrophages in NEC-affected intestines. TREM1 inhibition in THP-1 cells significantly reduced the expression of pro-inflammatory cytokines and pyroptosis-related genes and proteins. We identified the TREM1+CD163+ macrophage population that plays a crucial role in pyroptosis during NEC progression. Our findings elucidate the biological functions and molecular mechanisms of TREM1, demonstrating its upregulation in vivo and pro-pyroptosis effects in vitro. These insights advance our understanding of the role of pyroptosis in NEC pathogenesis and suggest TREM1 is a potential therapeutic target for NEC.

Identification of STAT3 and MYC as critical ferroptosis-related biomarkers in septic cardiomyopathy: a bioinformatics and experimental study

Ferroptosis is the well-known mechanism of septic cardiomyopathy (SCM). Bioinformatics analysis was employed to identify ferroptosis-related SCM differentially expressed genes (DEG). DEGs' functional enrichment was explored. Weighted gene co-expression network analysis (WGCNA) was employed to form gene clusters. The identified hub genes, signal transducer and activator of transcription 3 (STAT3) and myelocytomatosis (MYC) were further evaluated by generating receiver operator characteristic (ROC) curves and a nomogram prediction model. Additionally, survival rate, cardiac damage markers, and cardiac function and ferroptosis markers were evaluated in septic mouse model. STAT3 and MYC levels were measured in SCM heart tissue via immunohistochemical (IHC) staining, real-time polymerase chain reaction (qPCR) and western blot analysis. Analysis identified 225 DEGs and revealed 22 intersected genes. Of the 7 hub genes, STAT3 and MYC showed enrichment in septic heart tissue and a strong predicative ability based on AUC values. Cardiac damage, iron metabolism, and lipid peroxidation occurred in the SCM model. By experiments, STAT3 and MYC expression was increased in the SCM model. Impairment was reversed with a ferroptosis inhibitor, Fer-1. As conclusion, STAT3 and MYC are related with ferroptosis and may serve as potential SCM predictor indicators. KEY MESSAGES: Septic cardiomyopathy (SCM) often leads to high mortality in septic patients, and the diagnostic criteria still remains unclear. Ferroptosis as the pathogenic mechanism of SCM could help predict its progression and clinical outcomes. STAT3 and MYC are related with ferroptosis and may serve as potential SCM predictor biomarkers.