Prolylcarboxypeptidase Mitigates Myocardial Ischemia/Reperfusion Injury by Stabilizing Mitophagy

HMGB1-RAGE axis contributes to myocardial ischemia/reperfusion injury via regulation of cardiomyocyte autophagy and apoptosis in diabetic mice

Patients with acute myocardial infarction complicated with diabetes are more likely to develop myocardial ischemia/reperfusion (I/R) injury (MI/RI) during reperfusion therapy. Both HMGB1 and RAGE play important roles in MI/RI. However, the specific mechanisms of HMGB1 associated with RAGE are not fully clarified in diabetic MI/RI. This study aimed to investigate whether the HMGB1-RAGE axis induces diabetic MI/RI via regulating autophagy and apoptosis. A db/db mouse model of MI/RI was established, where anti-HMGB1 antibody and RAGE inhibitor (FPS-ZM1) were respectively injected after 10 min of reperfusion. The results showed that treatment with anti-HMGB1 significantly reduced the infarct size, serum LDH, and CK-MB level. Similar situations also occurred in mice administrated with FPS-ZM1, though the HMGB1 level was unchanged. Then, we found that treatment with anti-HMGB1 or FPS-ZM1 performed the same effects in suppressing the autophagy and apoptosis, as reflected by the results of lower LAMP2 and LC3B levels, increased Bcl-2 level, reduced BAX and caspase-3 levels. Moreover, the Pink1/Parkin levels were also inhibited at the same time. Collectively, this study indicates that the HMGB1-RAGE axis aggravated diabetic MI/RI via apoptosis and Pink1/Parkin mediated autophagy pathways, and inhibition of HMGB1 or RAGE contributes to alleviating those adverse situations.

Contribution and therapeutic value of mitophagy in cerebral ischemia-reperfusion injury after cardiac arrest

Cardiopulmonary resuscitation and related life support technologies have improved substantially in recent years; however, mortality and disability rates from cardiac arrest (CA) remain high and are closely associated with the high incidence of cerebral ischemia-reperfusion injury (CIRI), which is explained by a "double-hit" model (i.e., resulting from both ischemia and reperfusion). Mitochondria are important power plants in the cell and participate in various biochemical processes, such as cell differentiation and signaling in eukaryotes. Various mitochondrial processes, including energy metabolism, calcium homeostasis, free radical production, and apoptosis, are involved in several important stages of the progression and development of CIRI. Mitophagy is a key mechanism of the endogenous removal of damaged mitochondria to maintain organelle function and is a critical target for CIRI treatment after CA. Mitophagy also plays an essential role in attenuating ischemia-reperfusion in other organs, particularly during post-cardiac arrest myocardial dysfunction. Regulation of mitophagy may influence necroptosis (a programmed cell death pathway), which is the main endpoint of organ ischemia-reperfusion injury. In this review, we summarize the main signaling pathways related to mitophagy and their associated regulatory proteins. New therapeutic methods and drugs targeting mitophagy in ischemia-reperfusion animal models are also discussed. In-depth studies of the mechanisms underlying the regulation of mitophagy will enhance our understanding of the damage and repair processes in CIRI after CA, thereby contributing to the development of new therapeutic strategies.

Bradykinin-(1-9) mitigates autophagy through upregulating PI3K/Akt in rats with myocardial infarction

The cardioprotective mechanisms of bradykinin-(1-9) in myocardial infarction were unclear. We investigated the effect of bradykinin-(1-9) on cardiac function, fibrosis, and autophagy induced by myocardial infarction and identified the mechanisms involved. To investigate the cardioprotective effect of bradykinin-(1-9), various doses of bradykinin-(1-9), its B2 receptor blocker HOE140, or their combination were administered to rats via subcutaneous osmotic minipump implantation before myocardial infarction. After 2 days, myocardial infarction was induced by ligation of the left anterior descending coronary artery. After 2 weeks, echocardiographic measurements and euthanasia were performed. Bradykinin-(1-9) treatment attenuated left ventricular dysfunction, fibrosis, and autophagy in rats with myocardial infarction, which was partially reversed by HOE140 administration. Moreover, the downregulatory effect of bradykinin-(1-9) on autophagy was partially reversed by combination with the PI3K inhibitor LY294002. Thus, bradykinin-(1-9) inhibits myocardial infarction-induced cardiomyocyte autophagy by upregulating the PI3K/Akt pathway.

The roles of the mitophagy inducer Danqi pill in heart failure: A new therapeutic target to preserve energy metabolism

BACKGROUND

Mitophagy can regulate mitochondrial homeostasis, preserve energy metabolism and cardiomyocytes survival effectively to restrain the development of heart failure (HF). Danqi Pill (DQP), composed of the dry roots of Salvia miltiorrhiza Bunge and Panax notoginseng, is included in the 2015 national pharmacopeia and effective in the clinical treatment of coronary heart diseases. Our previous studies have approved that DQP exerted remarkable cardioprotective effects on HF. However, the effect and mechanism of DQP on mitophagy have not been proved yet.

HYPOTHESIS/PURPOSE

We aim to explore whether DQP regulates mitophagy to protect against HF and to elucidate the in-depth mechanism.

STUDY DESIGN

The HF rat model for evaluating DQP's efficacy was established with left anterior descending coronary artery ligation. The oxygen-glucose deprivation-reperfusion-induced cardiomyocyte model was conducted to clarify the potential mechanism of DQP.

METHODS

The mitochondria-targeted fluorescent protein Keima (mt-Keima) was applied for detecting mitophagy flux. Co-immunofluorescence and co-immunoprecipitation were performed to detect protein co-localization. Flow cytometry for JC-1 and Annexin-FITC/PI staining was utilized for assessing mitochondrial activity and function.

RESULTS

In vivo, medium dose of DQP (1.5 g/kg) notably improved cardiac function and inhibited cardiac apoptosis in HF rats. Co-immunofluorescent staining of LC3B and TOM20 showed that DQP restored mitophagy. Further co-immunoprecipitation demonstrated that DQP increased the co-localization of FUNDC1 with either ULK1 or PGAM5. In vitro, DQP markedly protected mitochondrial membrane potential damage, reduced cardiomyocytes apoptosis, decreased the level of mitochondrial ROS, and increased the ATP level. Parallel with the in vitro results, DQP increased the interaction of FUNDC1 and LC3B, while knockdown of FUNDC1 diminished the interaction. Besides, Mt-Keima signaling detection further confirmed that DQP significantly promoted mitophagy. Intriguingly, knockdown of ULK1 or PGAM5 separately weakened rather than eliminated these effects of DQP on FUNDC1-mediated mitophagy, mitochondrial homeostasis and energy metabolism.

CONCLUSION

Our results demonstrated that DQP protected against HF by improving FUNDC1-mediated mitophagy to perverse energy metabolism through the coordinated regulation of ULK1 and PGAM5.

Serum Metal Ion-Induced Cross-Linking of Photoelectrochemical Peptides and Circulating Proteins for Evaluating Cardiac Ischemia/Reperfusion

Patients having experienced the ischemia-reperfusion process are particularly vulnerable to subsequent heart attacks because this process can induce myocardial fibrosis, hallmarked by the release of reactive oxygen species and some proteases, such as cathepsin G, into the circulating blood. If these risk indicators can be monitored from the peripheral serum, early diagnosis and intervention may become a reality. For this purpose, we have designed an assay of free copper ions and cathepsin G in serum using only synthetic small molecules as the biosensing elements. No antibodies are needed to recognize the target protein, and no enzymes are needed to generate and amplify the biosensing signal. In this design, a short peptide can target-specifically recognize protease, while the copper ion in the serum can stimulate the photoelectrochemical activity of the probe, resulting in cross-linking of the serum proteins in a target protein-specific manner. Using this method, serum cathepsin G and free copper ion are found to be significantly elevated in the blood samples collected from patients with acute myocardial infarction and successful percutaneous coronary intervention in comparison with healthy controls, indicating a higher risk of subsequent myocardial injury and cardiovascular events. These results may point to the possible application of the proposed assay to evaluate the severity and prognosis of cardiac ischemia/reperfusion in the near future.

Advances in Cardiotoxicity Induced by Altered Mitochondrial Dynamics and Mitophagy

Mitochondria are the most abundant organelles in cardiac cells, and are essential to maintain the normal cardiac function, which requires mitochondrial dynamics and mitophagy to ensure the stability of mitochondrial quantity and quality. When mitochondria are affected by continuous injury factors, the balance between mitochondrial dynamics and mitophagy is broken. Aging and damaged mitochondria cannot be completely removed in cardiac cells, resulting in energy supply disorder and accumulation of toxic substances in cardiac cells, resulting in cardiac damage and cardiotoxicity. This paper summarizes the specific underlying mechanisms by which various adverse factors interfere with mitochondrial dynamics and mitophagy to produce cardiotoxicity and emphasizes the crucial role of oxidative stress in mitophagy. This review aims to provide fresh ideas for the prevention and treatment of cardiotoxicity induced by altered mitochondrial dynamics and mitophagy.

[Platelet-rich plasma alleviates myocardial ischemia-reperfusion injury in rats]

OBJECTIVE

To investigate the protective effect of platelet-rich plasma (PRP) against acute myocardial ischemiareperfusion (IR) injury and the possible mechanism.

OBJECTIVE

Aortic blood samples were collected from 10 SD rats to prepare PRP, in which the concentrations of platelet-derived growth factor-BB (PDGF-BB) and transforming growth factor-β1 (TGF-β1) were measured. Cell models of IR injury were established in primary cultures of neonatal SD rat cardiomyocytes by exposing the cells to 3 h of hypoxia. The cells were then reoxygenated and co-cultured with 1%, 5%, 10%, and 20% volume of PRP for 12 h, and the changes in cell viability was assessed. Immunofluorescence staining of the cardiomyocytes was performed, and the cellular expression of AMPK and its phosphorylation level were detected. The effects of PRP on the proliferation and migration of rat aortic endothelial cells (RAOECs) were examined. In a SD rat model of myocardial IR injury, 100 μL of PRP (n= 20) or normal saline (n=20) was injected at 4 sites around the ligation site immediately after cardiac reperfusion. One day after the injection, 6 rats were selected from each group for TTC staining of the myocardial tissues and measurement of troponin Ⅰ content. One week later, the cardiac function of the remaining rats was assessed by echocardiography, and HE staining of the myocardial tissues was performed. The effect of PRP treatment for 24 h on polarization of M1 and M2 macrophages was also examined by flow cytometry in RAW264.7 cells after hypoxic exposure for 3 h.

OBJECTIVE

The concentrations of PDGF-BB and TGF-β1 were significantly higher in PRP than in whole blood. Addition of 1% volume of PRP significantly reduced death of the cardiomyocytes following reoxygenation, and this effect was closely related with the activation of AMPK. Treatment with PRP obviously promoted the proliferation and migration of RAOECs. In rat models of acute myocardial IR injury, injections of PRP significantly reduced the infarct size and troponin Ⅰ concentration as compared with saline injection (P < 0.001). One week after PRP injection, the rats showed significantly improved cardiac function with a lowered level of inflammatory response in comparison with the rats with saline injection. In RAW264.7 cells with hypoxic exposure, treatment with PRP obviously decreased the number of M1 macrophages and increase the number of M2 macrophages.

OBJECTIVE

PRP can improve acute myocardial IR injury in rats by phosphorylating AMPK and regulating macrophage polarization, which produces a protective immunomodulatory effect on the ischemic myocardial tissues.