Oxidative-Damaged Mitochondria Activate GABARAPL1-Induced NLRP3 Inflammasomes in an Autophagic-Exosome Manner after Acute Myocardial Ischemia

Abstract

Objective

This study is aimed at identifying the potential diagnostic markers for circulating endothelial cells (CECs) for acute myocardial ischemia (AMI) and exploring the regulatory mechanisms of the selected biomarker in mitochondrial oxidative damage and vascular inflammation in AMI pathology.

Methods

Utilizing the Gene Expression Omnibus dataset GSE66360, we scanned for differentially expressed genes (DEGs) in 49 AMI patients and 50 healthy subjects. To discover possible biomarkers, LASSO regression and support vector machine recursive feature elimination examinations were conducted. Using the GSE60993 and GSE123342 datasets and AMI rat models, the expression levels and diagnostic accuracy of the biomarkers in AMI were thoroughly verified. CIBERSORT was employed to evaluate the compositional patterns of 22 distinct immunological cell percentages in AMI according to combined cohorts. The oxidative-damaged mitochondria were detected by confocal microscopy observation of MitoTracker, ROS-DCFH-DA, and mCherry-GFP-LC3B.

Results

In total, 122 genes were identified. The identified DEGs primarily contributed in arteriosclerosis, arteriosclerotic cardiovascular disorders, bacterial infectious disorder, coronary artery disease, and myocardial infarction. Nine features (NR4A2, GABARAPL1 (GEC1), CLEC4D, ITLN1, SNORD89, ZFP36, CH25H, CCR2, and EFEMP1) of the DEGs were shared by two algorithms, and GABARAPL1 (GEC1) was identified and verified as a diagnostic mitochondrial biomarker for AMI. Confocal results showed that there existed mitochondrial damage and oxidative stress in cardiac CMECs after AMI, and the blocked autophagy flux could be released by exosome burst in cardiac CMECs and blood CECs. Immune cell infiltration testing declared that elevated GEC1 expression in blood CECs was linked to the rise of monocytes and neutrophils. Functional tests revealed that high GEC1 expression in CMECs and CECs could activate the vascular inflammatory response by stimulating NLRP3 inflammasome production after AMI.

Conclusion

Oxidative-damaged mitochondria in cardiac CMECs activate GEC1-mediated autophagosomes but block autophagy flux after AMI. The exfoliated cardiac CMECs evolve into abnormal blood CECs, and the undegraded GEC1 autophagosomes produce a large number of NLRP3 inflammasomes by exosome burst, stimulating the increase in monocytes and neutrophils and ultimately triggering vascular inflammation after AMI. Therefore, GEC1 in blood CECs is a highly specific diagnostic mitochondrial biomarker for AMI.