Atrial fibrillation (AF) and ischemic heart disease (IHD) represent the two most common clinical cardiac diseases, characterized by angina, arrhythmia, myocardial damage, and cardiac dysfunction, significantly contributing to cardiovascular morbidity and mortality and posing a heavy socio-economic burden on society worldwide. Current treatments of these two diseases are mainly symptomatic and lack efficacy. There is thus an urgent need to develop novel therapies based on the underlying pathophysiological mechanisms. Emerging evidence indicates that oxidative DNA damage might be a major underlying mechanism that promotes a variety of cardiac diseases, including AF and IHD. Antioxidants, nicotinamide adenine dinucleotide (NAD⁺) boosters, and enzymes involved in oxidative DNA repair processes have been shown to attenuate oxidative damage to DNA, making them potential therapeutic targets for AF and IHD. In this review, we first summarize the main molecular mechanisms responsible for oxidative DNA damage and repair both in nuclei and mitochondria, then describe the effects of oxidative DNA damage on the development of AF and IHD, and finally discuss potential targets for oxidative DNA repair-based therapeutic approaches for these two cardiac diseases.

PER2, a circadian clock gene, is associated with mammary gland development and lipid synthesis in rodents, partly via regulating peroxisome proliferator-activated receptor gamma (PPARG). Whether such a type of molecular link existed in bovines was unclear. We hypothesized that PER2 was associated with lipid metabolism and regulated cell cycles and apoptosis in bovine mammary epithelial cells (BMECs). To test this hypothesis, BMECs isolated from three mid-lactation (average 110 d postpartum) cows were used. The transient transfection of small interfering RNA (siRNA) was used to inhibit PER2 transcription in primary BMECs. The silencing of PER2 led to lower concentrations of cellular lipid droplets and triacylglycerol along with the downregulation of lipogenic-related genes such as ACACA, FASN, LPIN1, and SCD, suggesting an overall inhibition of lipogenesis and desaturation. The downregulation of PPARG and SREBF1 in response to PER2 silencing underscored the importance of circadian clock signaling and the transcriptional regulation of lipogenesis. Although the proliferation of BMECs was not influenced by PER2 silencing, the number of cells in the G2/GM phase was upregulated. PER2 silencing did not affect cell apoptosis. Overall, the data provided evidence that PER2 participated in the coordination of mammary lipid metabolism and was potentially a component of the control of lipid droplets and TAG synthesis in ruminant mammary cells. The present data suggested that such an effect could occur through direct effects on transcriptional regulators.

The core clock gene Period2 (PER2) is associated with mammary gland development and lipid synthesis in rodents and has recently been found to have a diurnal variation in the process of lactation, but has not yet been demonstrated in bovine mammary epithelial cells (BMECs). To explore the regulatory function of PER2 on milk fat synthesis in bovine mammary epithelial cells, we initially assessed the expression of clock genes and milk fat metabolism genes for 24 h using real-time quantitative PCR and fitted the data to a cosine function curve. Subsequently, we overexpressed the PER2 in BMECs using plasmid vector (pcDNA3.1-PER2), with empty vector pcDNA3.1-myc as the control. After transfecting BMECs for 48 h, we assessed the protein abundance related to milk fat synthesis by Western blot, the expression of genes coding for these proteins using real time-quantitative PCR, the production of triacylglycerol, and the fatty acid profile. The findings indicated that a total of nine clock genes (PER1/2, CRY1/2, REV-ERBα, BMAL1, NCOR1, NR2F2, FBXW11), seven fatty acid metabolism genes (CD36, ACSS2, ACACA, SCD, FADS1, DGAT1, ADFP), and six nuclear receptor-related genes (INSIG1, SCAP, SREBF1, C/EBP, PPARG, LXR) exhibited oscillation with a period close to 24 h in non-transfected BMECs (R² ≥ 0.7). Compared to the control group (transfected with empty pcDNA3.1-myc), the triglyceride content significantly increased in the PER2 overexpression group (p < 0.05). The lipogenic genes for fatty acid transport and triglyceride synthesis (ACACA, SCD, LPIN1, DGAT1, and SREBF1) were upregulated after PER2 overexpression, along with the upregulation of related protein abundance (p < 0.05). The contents and ratios of palmitic acid (C16:0), oleic acid (C18:1n9c), and trans-oleic acid (C18:1n9t) were significantly increased in the overexpression group (p < 0.05). Overall, the data supported that PER2 participated in the process of milk fat metabolism and is potentially involved in the de novo synthesis and desaturation of fatty acid in bovine mammary epithelial cells.

Atrial fibrillation (AF) is a growing cardiovascular epidemic lacking effective treatment. Reactive oxygen species are believed to contribute to AF pathophysiology, yet general antioxidants have limited effectiveness. Since mitochondria are abundant in the heart and a major ROS producer, mitochondrial oxidative stress (MitoOxS) could be a therapeutic target. To determine this, rat inducible immortalized atrial myocytes (iAMs) were tachypaced to mimic AF, followed by assessment of calcium transients, contractility, mitochondrial respiration and morphology, and ROS damage. Cells were pretreated with MitoTEMPO or Sul-238 to assess their protective effects. In Drosophila, heart wall contractions were analyzed to assess arrhythmogenesis after mitochondrial antioxidant pretreatment. Using the GAL4-UAS system, mitochondrial ROS levels and the effect of SOD1 or SOD2 knockdown or overexpression on arrhythmogenesis were evaluated. Tachypacing induced contractile dysfunction and arrhythmogenesis, mitochondrial impairment, and ROS damage in iAMs and increased mitochondrial ROS and arrhythmogenesis in Drosophila. Both MitoTEMPO and Sul-238 treatments prevented mitochondrial dysfunction and arrhythmogenesis in iAMs and rescued arrhythmia in Drosophila. Underscoring the potential to target MitoOxS specifically, SOD2 knockdown promoted arrhythmogenesis in iAMs and Drosophila, whereas SOD2 overexpression rescued tachypacing-induced arrhythmia. MitoOxS is thus a key driver of tachypacing-induced contractile dysfunction and arrhythmia. Mitochondria-targeted antioxidants, such as MitoTEMPO or Sul-238, represent promising therapeutic strategies for AF.

BACKGROUND: Long noncoding RNAs (lncRNA) have emerged as critical regulators in cardiovascular biology, influencing cardiac development, remodeling, and regeneration. Zeb2os (zeb2 opposite strand), a natural antisense transcript of the Zeb2 (zinc finger E-box-binding homeobox 2) gene, has been linked to these processes in various organs. Although ZEB2 promotes cardiac repair, the role of Zeb2os in these processes remains unclear. This study investigates the role of Zeb2os in modulating ZEB2 expression and cardiac remodeling after ischemic injury. METHODS: We used adeno-associated virus vectors to overexpress Zeb2os in mouse models of cardiac IR (ischemia/reperfusion) injury. RNA sequencing, immunofluorescence, and high-resolution respirometry were used to evaluate the effects of Zeb2os delivery on gene expression, ZEB2 reactivation, cardiomyocyte phenotype, scar composition, and mitochondrial function. Experiments in cultured cardiomyocytes under hypoxia further explored the regulatory dynamics between Zeb2os and Zeb2 . RESULTS: We identified Zeb2os as a hypoxia-responsive lncRNA that displays an inverse and oscillatory expression pattern with Zeb2 in both in vitro and in vivo models of cardiac injury. Functional experiments revealed that Zeb2os negatively regulates ZEB2 expression, impairing the cardiomyocyte dedifferentiation and metabolic remodeling necessary for effective repair. Adeno-associated virus-mediated delivery of Zeb2os resulted in preserved sarcomere structure, altered scar composition, reduced expression of regenerative genes, and diminished cardiac function following injury. In contrast, silencing of Zeb2os increased ZEB2 protein expression, suggesting a potential therapeutic strategy to enhance repair. Mechanistically, modulation of Zeb2os levels inversely regulated ZEB2 protein expression, whereas ZEB2 modulation did not affect Zeb2os levels, indicating a unidirectional regulatory axis between the 2 transcripts. CONCLUSIONS: Our findings identify Zeb2os as a stress-responsive inhibitor of ZEB2 reactivation that limits cardiomyocyte plasticity and hinders repair following ischemic injury. Given its specific activity under ischemic conditions, targeting Zeb2os may represent a novel therapeutic strategy to enhance endogenous cardiac regeneration.

Nicotinamide adenine dinucleotide and β-hydroxybutyrate restore mitochondrial function and metabolic balance, in part by preserving PINK1-Parkin-MFN2-mediated mitophagy. Silencing key mitophagy regulators abolishes these protective effects, identifying mitophagy as a central mechanism linking metabolic interventions to functional recovery and as a potential therapeutic target in atrial fibrillation-associated remodeling.