NOTCH1 modulates activity of DNA-PKcs

Quercetin inhibits necroptosis in cardiomyocytes after ischemia-reperfusion via DNA-PKcs-SIRT5-orchestrated mitochondrial quality control

We investigated the mechanism by which quercetin preserves mitochondrial quality control (MQC) in cardiomyocytes subjected to ischemia-reperfusion stress. An enzyme-linked immunosorbent assay was employed in the in vivo experiments to assess myocardial injury markers, measure the transcript levels of SIRT5/DNAPK-cs/MLKL during various time intervals of ischemia-reperfusion, and observe structural changes in cardiomyocytes using transmission electron microscopy. In in vitro investigations, adenovirus transfection was employed to establish a gene-modified model of DNA-PKcs, and primary cardiomyocytes were obtained from a mouse model with modified SIRT5 gene. Reverse transcription polymerase chain reaction, laser confocal microscopy, immunofluorescence localization, JC-1 fluorescence assay, Seahorse energy analysis, and various other assays were applied to corroborate the regulatory influence of quercetin on the MQC network in cardiomyocytes after ischemia-reperfusion. In vitro experiments demonstrated that ischemia-reperfusion injury caused changes in the structure of the myocardium. It was seen that quercetin had a beneficial effect on the myocardial tissue, providing protection. As the ischemia-reperfusion process continued, the levels of DNA-PKcs/SIRT5/MLKL transcripts were also found to change. In vitro investigations revealed that quercetin mitigated cardiomyocyte injury caused by mitochondrial oxidative stress through DNA-PKcs, and regulated mitophagy and mitochondrial kinetics to sustain optimal mitochondrial energy metabolism levels. Quercetin, through SIRT5 desuccinylation, modulated the stability of DNA-PKcs, and together they regulated the "mitophagy-unfolded protein response." This preserved the integrity of mitochondrial membrane and genome, mitochondrial dynamics, and mitochondrial energy metabolism. Quercetin may operate synergistically to oversee the regulation of mitophagy and the unfolded protein response through DNA-PKcs-SIRT5 interaction.

Notch1 Protects against Ischemic-Reperfusion Injury by Suppressing PTEN-Pink1-Mediated Mitochondrial Dysfunction and Mitophagy

BACKGROUND

Myocardial ischemia/reperfusion injury is associated with adverse cardiovascular outcomes after acute myocardial infarction. However, the molecular mechanism of ischemia/reperfusion injury remains unclear. Mitochondria dysfunction is a participant in and regulator of myocardial ischemia-reperfusion injury. However, the molecular mechanisms involved in this process are not yet fully understood. We previously reported that Notch1 can reduce mitochondrial lysis, reduce myocardial infarct size, and inhibit ventricular remodeling. Herein, we explore the role of the downstream target Notch1 in mitochondrial regulation.

METHODS

This study constructs an ischemic/reperfusion injury rat model and a hypoxia/reoxygenation cell model. The expression of PTEN is detected by real-time PCR, Western blot, and immunofluorescence staining. Cell viability is analyzed with CCK-8. Apoptosis level is detected via the TUNEL assay, and mitochondrial fission/fusion is analyzed with MitoTracker Green staining. Cardiac troponin I (cTnI), lactate dehydrogenase (LDH), superoxide dismutase (SOD), and CK levels of creatine kinase-MB (CK) are measured with ELISA kits.

RESULTS

We found that PETN-Pink1-Parkin signaling is inhibited by Notch1 I/R in injured neonatal cardiomyocytes and hearts, i.e., via the inhibition of mitochondrial dysfunction and fragmentation. With the recure of PTEN or Pink1, the protective effect of Notch1 was largely diminished.

CONCLUSION

These results suggest that N1ICD acts protectively against ischemic reperfusion injury by suppressing PTEN-Pink1-mediated mitochondrial dysfunction and fragmentation.