Ruthenium red alleviates post-resuscitation myocardial dysfunction by upregulating mitophagy through inhibition of USP33 in a cardiac arrest rat model.

Cardiac arrest (CA) remains a leading cause of death, with suboptimal survival rates despite efforts involving cardiopulmonary resuscitation and advanced life-support technology. Post-resuscitation myocardial dysfunction (PRMD) is an important determinant of patient outcomes. Myocardial ischemia/reperfusion injury underlies this dysfunction. Previous reports have shown that ruthenium red (RR) has a protective effect against cardiac ischemia-reperfusion injury; however, its precise mechanism of action in PRMD remains unclear. This study investigated the effects of RR on PRMD and analyzed its underlying mechanisms. Ventricular fibrillation was induced in rats, which were then subjected to cardiopulmonary resuscitation to establish an experimental CA model. At the onset of return of spontaneous circulation, RR (2.5 mg/kg) was administered intraperitoneally. Our study showed that RR improved myocardial function and reduced the production of oxidative stress markers such as malondialdehyde (MDA), glutathione peroxidase (GSSG), and reactive oxygen species (ROS) production. RR also helped maintain mitochondrial structure and increased ATP and GTP levels. Additionally, RR effectively attenuated myocardial apoptosis. Furthermore, we observed downregulation of proteins closely related to mitophagy, including ubiquitin-specific protease 33 (USP33) and P62, whereas LC3B (microtubule-associated protein light chain 3B) was upregulated. The upregulation of mitophagy may play a critical role in reducing myocardial injury. These results demonstrate that RR may attenuate PRMD by promoting mitophagy through the inhibition of USP33. These effects are likely mediated through diverse mechanisms, including antioxidant activity, apoptosis suppression, and preservation of mitochondrial integrity and energy metabolism. Consequently, RR has emerged as a promising therapeutic approach for addressing post-resuscitation myocardial dysfunction.

The role of (18F)-fluoro-D-glucose positron emission tomography/computed tomography in the surveillance of abnormal myocardial energy metabolism and cardiac dysfunction in a rat model of cardiopulmonary resuscitation.

PURPOSE: To investigate the feasibility and usefulness of 2-deoxy-2-(18F)-fluoro-D-glucose positron emission tomography/computed tomography [(18F)-FDG PET/CT] as a novel examination in the surveillance of abnormal myocardial energy metabolism and cardiac dysfunction after cardiopulmonary resuscitation (CPR). METHODS: Thirteen male Sprague-Dawley rats were randomly divided into a sham group (n = 4), CPR group (n = 4), and trimetazidine (TMZ) + CPR group (n = 5). The expression levels of the myocardial injury marker cardiac troponin I (CTNI) in serum were tested at 6 hours after CPR or TMZ + CPR. The ejection fraction and fraction shortening were evaluated by echocardiography. (18F)-FDG PET/CT was used to measure the FDG uptake and the standardized uptake value (SUV) after CPR or TMZ + CPR for 6 hours. The intermediary carbohydrate metabolites of glycolysis including phosphoenolpyruvate, 3-phospho-D-glycerate, and the lactate/pyruvate ratio were detected through the multiple reaction monitoring approach. Simultaneously, the authors also tested the expression levels of the total adenosine triphosphate (ATP) and the key intermediate products of glucose ovidation as alpha ketoglutarate, citrate, and succinate in the myocardium. RESULTS: The authors found that the aerobic oxidation of glucose was reduced, and the anaerobic glycolysis was significantly enhanced in the myocardium in the early stage of CPR. Meanwhile, the myocardial injury marker CTNI was upregulated considerably (P = 0.014, P = 0.021), and the left ventricular function of the animal heart also markedly deteriorated with the downregulation of ATP after CPR. In contrast, myocardial injury and cardiac function were greatly improved with the increase of ATP in the CPR + TMZ group. In addition, aerobic glucose oxidation metabolites were significantly increased (P < 0.05) and anaerobic glycolysis metabolites were significantly decreased (P < 0.05) after CPR in the myocardium. Surprisingly, (18F)-FDG PET/CT could track the above changes by detecting the FDG uptake value and the SUV. CONCLUSION: Glucose metabolism is an essential factor for myocardial self-repair after CPR. (18F) FDG PET/CT, as a non-invasive technology, can monitor myocardial energy metabolism and cardiac function by tracking changes in glucose metabolism after CPR.

BAICALEIN RELIEVES BRAIN INJURY VIA INHIBITING FERROPTOSIS AND ENDOPLASMIC RETICULUM STRESS IN A RAT MODEL OF CARDIAC ARREST.

ABSTRACT: Background: Cardiac arrest (CA) is one of the leading causes of death worldwide. Endoplasmic reticulum (ER) stress and ferroptosis are proven pathological mechanisms implicated in neuronal damage. Baicalein, a ferroptosis Inhibitor, improved outcomes after traumatic brain injury. We aimed to explore the effects of baicalein on brain injury via ferroptosis and ER stress in a rat model of CA.Methods: Cardiac arrest models were established in Sprague-Dawley (SD) rats. The sham group (n = 6) was untreated with inducing ventricular fibrillation to cardiac arrest and cardiopulmonary resuscitation (CPR). Survival rats were randomly divided into five groups (n = 6). Ferroptosis inhibitor and ER stress agonist were administered separately and together in three groups. There was no drug intervention in the remaining group. The neurological deficit scores were recorded. Characteristics of ferroptosis were observed. And the associated protein of ferroptosis and ER stress were determined by Western blot. Cerebral ROS production was measured by using 2',7'-dichlorofluorescein diacetate as the oxidative fluorescent probe. Results: Baicalein treatment improved neurological outcomes and decreased neurocyte injuries compared with CPR group. The changes of ferroptosis, more specifically, iron content, glutathione peroxidase 4 (GPX4), reactive oxygen species (ROS), arachidonate 15-lipoxygenase (ALOX15) and mitochondrial characteristics, were observed in brain tissue after ROSC. ALOX15 was lower in baicalein group than in CPR group. The morphology and structure of mitochondria in baicalein group were better than in CPR group. The ER stress markers, glucose-regulated protein 78, activating Transcription Factor 4 and C/EBP homologous protein was lower in baicalein group compared with CPR group. ROS in tunicamycin group was higher than in CPR group. And ROS in baicalein +tunicamycin group was lower than in tunicamycin group. Conclusion: Ferroptosis and ER stress are both involved in brain injury after ROSC. Baicalein alleviates brain injury via suppressing the ferroptosis and ER stress, and reduces ROS partly through inhibiting ER stress. Baicalein is a potential drug to relieve brain injury after ROSC.