Mitochondrial Quality Control in Cardiac-Conditioning Strategies against Ischemia-Reperfusion Injury

Is There a Mitochondrial Protection via Remote Ischemic Conditioning in Settings of Anticancer Therapy Cardiotoxicity?

PURPOSE OF REVIEW

To provide an overview of (a) protective effects on mitochondria induced by remote ischemic conditioning (RIC) and (b) mitochondrial damage caused by anticancer therapy. We then discuss the available results of studies on mitochondrial protection via RIC in anticancer therapy-induced cardiotoxicity.

RECENT FINDINGS

In three experimental studies in healthy mice and pigs, there was a RIC-mediated protection against anthracycline-induced cardiotoxicity and there was some evidence of improved mitochondrial function with RIC. The RIC-mediated protection was not confirmed in the two available studies in cancer patients. In adult cancer patients, RIC was associated with an adverse outcome. There are no data on mitochondrial function in cancer patients. Studies in tumor-bearing animals are needed to determine whether RIC does not interfere with the anticancer properties of the drugs and whether RIC actually improves mitochondrial function, ultimately resulting in improved cardiac function.

Rhein alleviates myocardial ischemic injury by inhibiting mitochondrial division, activating mitochondrial autophagy and suppressing myocardial cell apoptosis through the Drp1/Pink1/Parkin pathway

BACKGROUND

Rhein, which has antioxidant and anti-inflammatory response properties, is a beneficial treatment for different pathologies. However, the mechanism by which rhein protects against myocardial ischemic injury is poorly understood.

METHODS AND RESULTS

To establish an acute myocardial infarction (AMI) rat model, we performed left anterior descending (LAD) ligation. Sprague‒Dawley rats were randomly divided into four groups: sham, AMI, AMI + rhein (AMI + R), and AMI + mitochondrial fission inhibitor (AMI + M). The extent of myocardial injury was evaluated by TTC staining, serum myocardial injury markers, and HE and Masson staining. Cardiac mitochondria ultrastructure was visualized by transmission electron microscopy. TUNEL assay and flow cytometry analysis were used to estimate cell apoptosis. Protein expression levels were measured by Western blotting. In vitro, the efficacy of rhein was assessed in H9c2 cells under hypoxic condition. Our results revealed that rats with AMI exhibited increased infarct size and indicators of myocardial damage, along with activation of Drp1-dependent mitochondrial fission, decreased mitophagy and increased apoptosis rates. However, pretreatment with rhein significantly reversed these effects and demonstrated similar efficacy to Mdivi-1. Furthermore, rhein pretreatment protected against myocardial ischemic injury by inhibiting mitochondrial fission, as evidenced by decreased Drp1 expression. It also enhanced mitophagy, as indicated by increased expression of Beclin1, Pink1 and Parkin, an increased LC3-II/LC3-I ratio and increased formation of autolysosomes. Additionally, rhein pretreatment mitigated apoptosis in AMI. These results were also confirmed in vitro in H9c2 cells.

CONCLUSION

Our results demonstrate that rhein pretreatment exerts cardioprotective effects against myocardial ischemic injury via the Drp1/Pink1/Parkin pathway.

Increased Ca2 + transport across the mitochondria-associated membranes by Mfn2 inhibiting endoplasmic reticulum stress in ischemia/reperfusion kidney injury

Renal ischemia/reperfusion (I/R) injury, which leads to acute kidney injury (AKI), is a major cause of morbidity and mortality in a variety of clinical situations. This study aimed to investigate the protective role of Mfn2 during renal I/R injury. Overexpression of Mfn2 in NRK-52E rat renal tubular epithelial cells and rats, then we constructed hypoxia reoxygenation (H/R) cells and I/R rat model. Apoptosis, ROS, ATP, Ca2+ levels in cells and rats, as well as renal tissue and functional injury in rats were detected respectively. Endoplasmic reticulum (ER) stress was further examined in cells and rats. The morphological changes of mitochondria-associated ER membranes (MAMs) were also detected. Mfn2 expression is reduced in H/R-treated NRK-52E cells and renal tissue of I/R rats. At the cellular level, overexpression of Mfn2 promoted cell proliferation, inhibited cell apoptosis, attenuated mitochondrial damage and Ca2+ overload, and ER stress. In addition, Mfn2 also restored the MAMs structure. In vivo experiments found that overexpression of Mfn2 could improve renal function and alleviate tissue injury. Concomitant with elevated Mfn2 expression in the kidney, reduced renal cell apoptosis, restored mitochondrial function, and reduced calcium overload. Finally, ER stress in rat kidney tissue was alleviated after overexpression of Mfn2. These results reveal that Mfn2 contributes to ER stress, mitochondrial function, and cell death in I/R injury, which provides a novel therapeutic target for AKI.

The additive effects of nicotinamide mononucleotide and melatonin on mitochondrial biogenesis and fission/fusion, autophagy, and microRNA-499 in the aged rat heart with reperfusion injury

The prognosis of myocardial ischemia/reperfusion (I/R) injury is poor in elderly patients. Aging increases the susceptibility of the heart to cell death from I/R injury and prevents the optimal effectiveness of cardioprotective modalities. Since the interaction of aging with cardioprotection is multifactorial, combination therapy may overcome the above-mentioned burden through correcting various components of the injury. Here, we explored the effects of nicotinamide mononucleotide (NMN)/melatonin combination therapy on mitochondrial biogenesis and fission/fusion, autophagy, and microRNA-499 in the aged rat heart with reperfusion injury. Ex vivo model of myocardial I/R injury was established by coronary occlusion and re-opening in 30 aged male Wistar rats (400-450 g, 22-24 months old). NMN (100 mg/kg/48 h, intraperitoneally) was administered over 28 days before I/R, and melatonin (50 µM) was added to the perfusion solution at early reperfusion. CK-MB release and expression of mitochondrial biogenesis genes and proteins, mitochondrial fission/fusion proteins, autophagy genes, and microRNA-499 were assessed. NMN/melatonin combination therapy concomitantly decreased CK-MB release in aged reperfused hearts (P < .001). It also upregulated SIRT1/PGC-1α/Nrf1/TFAM profiles at both gene and protein levels, Mfn2 protein, and microRNA-499 expression, and downregulated Drp1 protein and Beclin1, LC3, and p62 genes (P < .05 to P < .001). The effect of combination therapy was greater than individual ones. Co-application of NMN/melatonin within the setting of I/R injury in the aged rat heart induced noticeable cardioprotection through modulation of a coordinated network including microRNA-499 expression along with mitochondrial biogenesis associated with SIRT1/PGC-1α/Nrf1/TFAM profiles, mitochondrial fission/fusion, and autophagy, therefore, appears to prevent the burden of myocardial I/R injury in elderly patients.

Inhibitors of NLRP3 Inflammasome in Ischemic Heart Disease: Focus on Functional and Redox Aspects

Myocardial ischemia-reperfusion injury (MIRI) is caused by several mechanisms, including the production of reactive oxygen species (ROS), altered cellular osmolarity, and inflammatory response. Calcium overload, altered oxygen levels, and mitochondrial ROS are also involved in these MIRI processes, resulting in the irreversible opening of the mitochondrial permeability transition pore (mPTP). These mechanisms and processes are associated with NLRP3 inflammasome priming and activation, which can also induce cell death by pyroptosis through the up-regulation of the caspase-1 pathway and IL-18 release. In addition, endothelial dysfunction, both in the presence and absence of MIRI, is also accompanied by altered oxygen levels, decreased nitric oxide production, and ROS overproduction, resulting in the expression of adhesion molecules and leukocyte infiltration in which the NLRP3 inflammasome plays a central role, thus contributing, through endothelial dysfunction, to the alteration of coronary flow, typical of ischemic heart disease. Given the intricate interrelationship between ROS and NLRP3, ROS inhibitors can reduce NLRP3 inflammasome activation, while NLRP3 inhibitors can reduce oxidative stress and inflammation. NLRP3 inhibitors have been intensively studied as anti-inflammatory agents in basic cardiovascular sciences. In this review, we analyze the interrelation between ROS and NLRP3 in ischemic heart disease and the effects of some NLRP3 inhibitors as possible therapeutic agents in this disease condition. All compounds considered in this review need larger studies to confirm their appropriate use in clinical scenarios as anti-ischemic drugs.

Myocardial ischemia-reperfusion injury; Molecular mechanisms and prevention

Cardiovascular diseases are one of the leading causes of mortality in developed countries. Among cardiovascular disorders, myocardial infarction remains a life-threatening problem predisposing to the development and progression of ischemic heart failure. Ischemia/reperfusion (I/R) injury is a critical cause of myocardial injury. In recent decades, many efforts have been made to find the molecular and cellular mechanisms underlying the development of myocardial I/R injury and post-ischemic remodeling. Some of these mechanisms are mitochondrial dysfunction, metabolic alterations, inflammation, high production of ROS, and autophagy deregulation. Despite continuous efforts, myocardial I/R injury remains a major challenge in medical treatments of thrombolytic therapy, heart disease, primary percutaneous coronary intervention, and coronary arterial bypass grafting. The development of effective therapeutic strategies to reduce or prevent myocardial I/R injury is of great clinical significance.

Mitoprotective effect of mesenchymal stem cells-derived conditioned medium in myocardial reperfusion injury of aged rats: role of SIRT-1/PGC-1α/NRF-2 network

BACKGROUND

The aged myocardium experiences various forms of stress that cause reduction of its tolerance to injury induced by ischemia/reperfusion (I/R). Developing effective cardioprotective modalities to prevent the amplification of I/R injury during aging is under focus of investigation. Mesenchymal stem cells (MSCs) have the ability to regenerate infarcted myocardium mostly by producing multiple secretory factors. This study aimed to explore the mechanisms of mitoprotection by MSCs-conditioned medium (CM) in myocardial I/R injury of aged rats.

METHODS

Male Wistar rats (n = 72, 400-450 g, 22-24 months old) were randomized into groups with/without I/R and/or MSCs-CM treatment. To establish myocardial I/R injury, the method of LAD occlusion and re-opening was employed. MSCs-CM was administered intramyocardially (150 μl) at the onset of reperfusion in recipient group. After 24 h reperfusion, myocardial infarct size, LDH level, mitochondrial functional endpoints, expression of mitochondrial biogenesis-associated genes, and the levels of pro-inflammatory cytokines were evaluated. After 28 days reperfusion, echocardiographic assessment of cardiac function was performed.

RESULTS

MSCs-CM treatment improved myocardial function and decreased infarct size and LDH level in aged I/R rats (P < .05 to P < .001). It also decreased mitochondrial ROS formation, enhanced mitochondrial membrane potential and ATP content, upregulated mitochondrial biogenesis-related genes including SIRT-1, PGC-1α, and NRF-2, and lessened TNF-α, IL-1β, and IL-6 levels (P < .05 to P < .01).

CONCLUSIONS

MSCs-CM treatment attenuated myocardial I/R injury in aged rats, in part by improving mitochondrial function and biogenesis and restraining inflammatory reaction. the upregulation of SIRT-1/PGC-1α/NRF-2 profiles is a possible target for the mitoprotective effects of MSCs-CM following I/R injury during aging.

Mitochondrial Function and Signaling to Regulate Cellular Life

Mitochondria are essential organelles found in nearly all eukaryotic cells, responsible for producing the energy that drives cellular processes [...].

Modulation of Inula racemosa Hook Extract on Cardioprotection by Ischemic Preconditioning in Hyperlipidaemic Rats

Objectives

Hyperlipidemia (HL) is a major cause of ischemic heart diseases. The size-limiting effect of ischemic preconditioning (IPC), a cardioprotective phenomenon, is reduced in HL, possibly because of the opening of the mitochondrial permeability transition pore (MPTP). The objective of this study is to see what effect pretreatment with Inula racemosa Hook root extract (IrA) had on IPC-mediated cardioprotection on HL Wistar rat hearts. An isolated rat heart was mounted on the Langendorff heart array, and then ischemia reperfusion (I/R) and IPC cycles were performed. Atractyloside (Atr) is an MPTP opener.

Methods

The animals were divided into ten groups, each consisting of six rats (n = 6), to investigate the modulation of I. racemosa Hook extract on cardioprotection by IPC in HL hearts Sham control, I/R Control, IPC control, I/R + HL, I/R + IrA + HL, IPC + HL, IPC + NS + HL, IPC + IrA+ HL, IPC + Atr + oxidative stress, mitochondrial function, integrity, and hemodynamic parameters are evaluated for each group.

Results

The present experimental data show that pretreatment with IrA reduced the LDH, CK-MB, size of myocardial infarction, content of cardiac collagen, and ventricular fibrillation in all groups of HL rat hearts. This pretreatment also reduced the oxidative stress and mitochondrial dysfunction. Inhibition of MPTP opening by Atr diminished the effect of IrA on IPC-mediated cardioprotection in HL rats.

Conclusion

The study findings indicate that pretreatment with IrA e restores IPC-mediated cardioprotection in HL rats by inhibiting the MPTP opening.

Aging of Vascular System Is a Complex Process: The Cornerstone Mechanisms

Aging is one of the most intriguing processes of human ontogenesis. It is associated with the development of a wide variety of diseases affecting all organs and their systems. The victory over aging is the most desired goal of scientists; however, it is hardly achievable in the foreseeable future due to the complexity and ambiguity of the process itself. All body systems age, lose their performance, and structural disorders accumulate. The cardiovascular system is no exception. And it is cardiovascular diseases that occupy a leading position as a cause of death, especially among the elderly. The aging of the cardiovascular system is well described from a mechanical point of view. Moreover, it is known that at the cellular level, a huge number of mechanisms are involved in this process, from mitochondrial dysfunction to inflammation. It is on these mechanisms, as well as the potential for taking control of the aging of the cardiovascular system, that we focused on in this review.

A Selective Inhibitor of Cardiac Troponin I Phosphorylation by Delta Protein Kinase C (δPKC) as a Treatment for Ischemia-Reperfusion Injury

Myocardial infarction is the leading cause of cardiovascular mortality, with myocardial injury occurring during ischemia and subsequent reperfusion (IR). We previously showed that the inhibition of protein kinase C delta (δPKC) with a pan-inhibitor (δV1-1) mitigates myocardial injury and improves mitochondrial function in animal models of IR, and in humans with acute myocardial infarction, when treated at the time of opening of the occluded blood vessel, at reperfusion. Cardiac troponin I (cTnI), a key sarcomeric protein in cardiomyocyte contraction, is phosphorylated by δPKC during reperfusion. Here, we describe a rationally-designed, selective, high-affinity, eight amino acid peptide that inhibits cTnI's interaction with, and phosphorylation by, δPKC (ψTnI), and prevents tissue injury in a Langendorff model of myocardial infarction, ex vivo. Unexpectedly, we also found that this treatment attenuates IR-induced mitochondrial dysfunction. These data suggest that δPKC phosphorylation of cTnI is critical in IR injury, and that a cTnI/δPKC interaction inhibitor should be considered as a therapeutic target to reduce cardiac injury after myocardial infarction.

The effect of adaptation to hypoxia on cardiac tolerance to ischemia/reperfusion

The acute myocardial infarction (AMI) and sudden cardiac death (SCD), both associated with acute cardiac ischemia, are one of the leading causes of adult death in economically developed countries. The development of new approaches for the treatment and prevention of AMI and SCD remains the highest priority for medicine. A study on the cardiovascular effects of chronic hypoxia (CH) may contribute to the development of these methods. Chronic hypoxia exerts both positive and adverse effects. The positive effects are the infarct-reducing, vasoprotective, and antiarrhythmic effects, which can lead to the improvement of cardiac contractility in reperfusion. The adverse effects are pulmonary hypertension and right ventricular hypertrophy. This review presents a comprehensive overview of how CH enhances cardiac tolerance to ischemia/reperfusion. It is an in-depth analysis of the published data on the underlying mechanisms, which can lead to future development of the cardioprotective effect of CH. A better understanding of the CH-activated protective signaling pathways may contribute to new therapeutic approaches in an increase of cardiac tolerance to ischemia/reperfusion.