Doxorubicin (DOX)‐induced cardiotoxicity (DoIC) is a major side effect for cancer patients. Recently, ferroptosis, triggered by iron overload, is demonstrated to play a role in DoIC. How iron homeostasis is dysregulated in DoIC remains to be elucidated. Here, the authors demonstrate that DOX challenge exhibits reduced contractile function and induction of ferroptosis‐related phenotype in cardiomyocytes, evidenced by iron overload, lipid peroxide accumulation, and mitochondrial dysfunction. Compared to Ferric ammonium citrate (FAC) induced secondary iron overload, DOX‐challenged cardiomyocytes show a dysfunction of iron homeostasis, with decreased cytoplasmic and mitochondrial iron–sulfur (FeS) cluster‐mediated aconitase activity and abnormal expression of iron homeostasis–related proteins. Mechanistically, mass spectrometry analysis identified DOX‐treatment induces p53‐dependent degradation of Parkinsonism associated deglycase (Park7) which results in iron homeostasis dysregulation. Park7 counteracts iron overload by regulating iron regulatory protein family transcription while blocking mitochondrial iron uptake. Knockout of p53 or overexpression of Park7 in cardiomyocytes remarkably restores the activity of FeS cluster and iron homeostasis, inhibits ferroptosis, and rescues cardiac function in DOX treated animals. These results demonstrate that the iron homeostasis plays a key role in DoIC ferroptosis. Targeting of the newly identified p53–Park7 signaling axis may provide a new approach to prevent DoIC.

Extrachromosomal circular DNAs (eccDNAs) are commonly found in various tumors and play a critical role in promoting oncogenesis. However, little is known about the characteristics and nature of eccDNAs in human heart failure. The aim of this study was to comprehensively analyze eccDNAs in human heart failure caused by dilated cardiomyopathy (DCM) and explore their potential functions. Circle-Seq and RNA-Seq were performed in cardiac tissue samples obtained from patients with DCM and healthy controls to identify eccDNAs and corresponding genes. Inward PCR, outward PCR and Sanger sequencing were conducted to validate the circular structure of eccDNAs. Bioinformatics was employed to probe the transcriptional activity of eccDNAs and their potential roles in the development of DCM. Ligase assisted minicircle accumulation strategy was used to synthesize a 500 bp circular DNA with a random sequence. EccDNAs originated from all chromosomes, with the majority being less than 1 kb in size and about half containing genes or gene fragments. They were derived from specific repeat elements and primarily mapped to 5′UTR, 3′UTR, and CpG islands. Gene-rich chromosomes 17 and 19 exhibited higher eccDNA enrichment. Sequence motifs flanking eccDNA junction sites displayed frequent nucleotide repeats. The circular structure of eccDNAs were confirmed. Integration of Circle-Seq and RNA-Seq data identified that large eccDNAs can be directly transcribed in non-dividing cardiomyocytes, indicating their potential roles in gene expression. Small circular DNA elicited a stronger cytokine response than linear DNA with the same sequence. Our work provided a detailed profiling of eccDNAs in both healthy and DCM hearts and demonstrated the potential functions of both large and small eccDNAs. These findings enhance the comprehension of the role of eccDNAs in cardiac pathophysiology and establish a theoretical foundation for future investigations on eccDNAs in DCM.

A lacunar infarction (LACI) can cause damage to the surrounding brain tissue and place an individual at greater risk for future major stroke. LACI is associated with hypertension and hypertension is associated with left atrial enlargement. It is important to identify a high-risk patient who is more vulnerable to suffering a LACI in hypertensive group. So, we studied whether left atrium size is an independent risk predictor for LACI in hypertensive patients. We performed cross-sectional analysis of 365 patients with hypertension at Shanghai Ninth People's Hospital from January 2016 to January 2017. The results showed that left atrial diameter(LAD), left atrial volume (LAV) and the ratio of left atrial diameter to left ventricular diameter (LAD/LVD) were significantly associated with LACI in hypertensive patients. Based on the ROC curve analysis, the area under the ROC curve (AUC) of LAV used to predict LACI was 0.737 (95% CI: 0.686 - 0.788), and the AUC of LAD/LVD was 0.784 (95% CI: 0.737 - 0.830). The optimal cut-off value for LAV was 30.14, and the sensitivity and specificity were 72% and 63%, respectively. The optimal cut-off value for LAD/LVD was 0.757, and the sensitivity and specificity were 77% and 70%, respectively. LAV or LAD/LVD played an important role in LACI with hypertension and could be an independent risk factor in hypertensive patients.

Extrachromosomal circular DNAs (eccDNAs) are well-established drivers of tumorigenesis, yet their landscape and functional significance in human heart failure (HF) remain largely unknown. Using Tn5 transposase-based sequencing, we comprehensively profiled plasma eccDNAs from healthy controls and HF patients with myocardial ischemia (MI-HF) or non-myocardial ischemia (NMI-HF). Bioinformatics was employed to probe their chromosomal origins, genomic features, and potential roles in the development of HF. Circular structures of candidate eccDNAs were validated by inward and outward PCR followed by Sanger sequencing. Their clinical prognostic value was assessed by Kaplan-Meier and Cox regression analyses in a patient cohort. Most plasma eccDNAs were shorter than 1 kb and originated from all chromosomes, with selective enrichment from specific genomic regions including 5' UTRs, CpG islands, and Alu elements. Characteristic nucleotide repeats were identified at eccDNA junction sites. The circular structure of eccDNAs was confirmed. Furthermore, we discovered that the eccDNA ENPP1^{circle exon 25} was specifically detected in MI-HF patients. Its presence was significantly associated with a higher incidence of major adverse cardiac events (MACEs), and it served as an independent prognostic biomarker in multivariate analysis. This study delineates the first detailed landscape of plasma eccDNAs in HF and reveals their potential as noninvasive biomarkers for risk stratification. Our findings lay a crucial foundation for future research into eccDNA biology and their translational applications in cardiovascular disease.