Inhibition of JNK aggravates the recovery of rat hearts after global ischemia: the role of mitochondrial JNK

Halicin: A New Horizon in Antibacterial Therapy against Veterinary Pathogens

It is crucial to discover novel antimicrobial drugs to combat resistance. This study investigated the antibacterial properties of halicin (SU3327), an AI-identified anti-diabetic drug, against 13 kinds of common clinical pathogens of animal origin, including multidrug-resistant strains. Employing minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assessments, halicin demonstrated a broad-spectrum antibacterial effect. Time-killing assays revealed its concentration-dependent bactericidal activity against Escherichia coli ATCC 25922 (E. coli ATCC 25922), Staphylococcus aureus ATCC 29213 (S. aureus ATCC 29213), and Actinobacillus pleuropneumoniae S6 (APP S6) after 4 h of treatment at concentrations above the MIC. Halicin exhibited longer post-antibiotic effects (PAEs) and sub-MIC effects (PA-SMEs) for E. coli 25922, S. aureus 29213, and APP S6 compared to ceftiofur and ciprofloxacin, the commonly used veterinary antimicrobial agents, indicating sustained antibacterial action. Additionally, the results of consecutive passaging experiments over 40 d at sub-inhibitory concentrations showed that bacteria exhibited difficulty in developing resistance to halicin. Toxicology studies confirmed that halicin exhibited low acute toxicity, being non-mutagenic, non-reproductive-toxic, and non-genotoxic. Blood biochemical results suggested that halicin has no significant impact on hematological parameters, liver function, and kidney function. Furthermore, halicin effectively treated respiratory A. pleuropneumoniae infections in murine models. These results underscore the potential of halicin as a new antibacterial agent with applications against clinically relevant pathogens in veterinary medicine.

Mitochondrial Kinase Signaling for Cardioprotection

Myocardial ischemia/reperfusion injury is reduced by cardioprotective adaptations such as local or remote ischemic conditioning. The cardioprotective stimuli activate signaling cascades, which converge on mitochondria and maintain the function of the organelles, which is critical for cell survival. The signaling cascades include not only extracellular molecules that activate sarcolemmal receptor-dependent or -independent protein kinases that signal at the plasma membrane or in the cytosol, but also involve kinases, which are located to or within mitochondria, phosphorylate mitochondrial target proteins, and thereby modify, e.g., respiration, the generation of reactive oxygen species, calcium handling, mitochondrial dynamics, mitophagy, or apoptosis. In the present review, we give a personal and opinionated overview of selected protein kinases, localized to/within myocardial mitochondria, and summarize the available data on their role in myocardial ischemia/reperfusion injury and protection from it. We highlight the regulation of mitochondrial function by these mitochondrial protein kinases.

Effect of IQ-1 on the Infarct Size and the Parameters of Cardiodynamic Indicators in the Acute Period after Myocardial Ischemia/Reperfusion in Rats

The effect of a new JNK inhibitor IQ-1 (11H-indeno[1,2-b]quinoxalin-11-one oxime) was studied in male Wistar rats in a model of acute myocardial ischemia/reperfusion. Area at risk and myocardial infarct zones were studied in two series of experiments: 16 h after a single dose of IQ-1 (25 mg/kg intraperitoneally during cardiac ischemia) and on day 5 after its course administration (25 mg/kg intraperitoneally during cardiac ischemia and daily over 4 days). On day 5 after ischemia/reperfusion, cardiodynamic indicators were also studied: systolic, end-diastolic, and minimum pressure in the left ventricle, stress-time index, as well as the maximum rates of pressure rise and fall in the left ventricle (+dP/dtmax and -dP/dtmax). In 16 h after ischemia/reperfusion, the infarct area in the control was 24±2% of the total area of the sections, while after administration of IQ-1 this parameter was 14±1% (p<0.05). On day 5, the infarct area in the control group was 25±1% of the total area of myocardial sections. A course of IQ-1 administration led to a significant reduction in the infarct area to 10±2% of the total area of myocardial slices. Course administration of IQ-1 led to improvement in contractile function and weakening of the diastolic dysfunction of the left ventricle: systolic pressure in the left ventricle increased by 20%, +dP/dtmax by 23%, voltage-time index by 12%, -dP/dtmax by 43%, and the minimum pressure in the left ventricle decreased by 3.4 times.

Cardioprotective Effects of a Selective c-Jun N-terminal Kinase Inhibitor in a Rat Model of Myocardial Infarction

Activation of c-Jun N-terminal kinases (JNKs) is involved in myocardial injury, left ventricular remodeling (LV), and heart failure (HF) after myocardial infarction (MI). The aim of this research was to evaluate the effects of a selective JNK inhibitor, 11H-indeno [1,2-b]quinoxalin-11-one oxime (IQ-1), on myocardial injury and acute myocardial ischemia/reperfusion (I/R) in adult male Wistar rats. Intraperitoneal administration of IQ-1 (25 mg/kg daily for 5 days) resulted in a significant decrease in myocardial infarct size on day 5 after MI. On day 60 after MI, a significant (2.6-fold) decrease in LV scar size, a 2.2-fold decrease in the size of the LV cavity, a 2.9-fold decrease in the area of mature connective tissue, and a 1.7-fold decrease in connective tissue in the interventricular septum were observed compared with the control group. The improved contractile function of the heart resulted in a significant (33%) increase in stroke size, a 40% increase in cardiac output, a 12% increase in LV systolic pressure, a 28% increase in the LV maximum rate of pressure rise, a 45% increase in the LV maximum rate of pressure drop, a 29% increase in the contractility index, a 14% increase in aortic pressure, a 2.7-fold decrease in LV end-diastolic pressure, and a 4.2-fold decrease in LV minimum pressure. We conclude that IQ-1 has cardioprotective activity and reduces the severity of HF after MI.

Synergism between the Synthetic Antibacterial and Antibiofilm Peptide (SAAP)-148 and Halicin

Recently, using a deep learning approach, the novel antibiotic halicin was discovered. We compared the antibacterial activities of two novel bactericidal antimicrobial agents, i.e., the synthetic antibacterial and antibiofilm peptide (SAAP)-148 with this antibiotic halicin. Results revealed that SAAP-148 was more effective than halicin in killing planktonic bacteria of antimicrobial-resistant (AMR) Escherichia coli, Acinetobacter baumannii and Staphylococcus aureus, especially in biologically relevant media, such as plasma and urine, and in 3D human infection models. Surprisingly, SAAP-148 and halicin were equally effective against these bacteria residing in immature and mature biofilms. As their modes of action differ, potential favorable interactions between SAAP-148 and halicin were investigated. For some specific strains of AMR E. coli and S. aureus synergism between these agents was observed, whereas for other strains, additive interactions were noted. These favorable interactions were confirmed for AMR E. coli in a 3D human bladder infection model and AMR S. aureus in a 3D human epidermal infection model. Together, combinations of these two novel antimicrobial agents hold promise as an innovative treatment for infections not effectively treatable with current antibiotics.

Maskrey T, Wipf P, Javadov S. Effects of Ferroptosis on the Metabolome in Cardiac Cells: The Role of Glutaminolysis

Ferroptosis is a novel iron-dependent regulated cell death mechanism that affects cell metabolism; however, a detailed metabolomic analysis of ferroptotic cells is not yet available. Here, we elucidated the metabolome of H9c2 cardioblasts by gas chromatography-mass spectrometry during ferroptosis induced by RSL3, a GPX4 inhibitor, in the presence of ferrostatin-1 (a ferroptosis inhibitor), XJB-5-131 (a mitochondrial-targeted ROS scavenger), or TSM-1005-44 (a newly developed cellular ROS scavenger). Results demonstrated that RSL3 decreased the levels of amino acids involved in glutathione synthesis more than two-fold. In contrast, saturated fatty acids levels were markedly increased in RSL3-challenged cells, with no effects on unsaturated fatty acids. RSL3 significantly altered the levels of mitochondrial tricarboxylic acid cycle intermediates; isocitrate and 2-oxoglutarate were found to increase, whereas succinate was significantly decreased in RSL3-challenged cells. Ferrostatin-1, XJB-5-131, and TSM-1005-44 prevented RSL3-induced cell death and conserved the metabolomic profile of the cells. Since 2-oxoglutarate is involved in the regulation of ferroptosis, particularly through glutamine metabolism, we further assessed the role of glutaminolysis in ferroptosis in H9c2 cardioblasts. Genetic silencing of GLS1, which encodes the K-type mitochondrial glutaminase (glutaminase C), protected against ferroptosis in the early stage. In conclusion, our study demonstrates that RSL3-induced ferroptosis impairs the metabolome of H9c2 cardioblasts.

Metabolic Remodeling and Implicated Calcium and Signal Transduction Pathways in the Pathogenesis of Heart Failure

The heart is an organ with high-energy demands in which the mitochondria are most abundant. They are considered the powerhouse of the cell and occupy a central role in cellular metabolism. The intermyofibrillar mitochondria constitute the majority of the three-mitochondrial subpopulations in the heart. They are also considered to be the most important in terms of their ability to participate in calcium and cellular signaling, which are critical for the regulation of mitochondrial function and adenosine triphosphate (ATP) production. This is because they are located in very close proximity with the endoplasmic reticulum (ER), and for the presence of tethering complexes enabling interorganelle crosstalk via calcium signaling. Calcium is an important second messenger that regulates mitochondrial function. It promotes ATP production and cellular survival under physiological changes in cardiac energetic demand. This is accomplished in concert with signaling pathways that regulate both calcium cycling and mitochondrial function. Perturbations in mitochondrial homeostasis and metabolic remodeling occupy a central role in the pathogenesis of heart failure. In this review we will discuss perturbations in ER-mitochondrial crosstalk and touch on important signaling pathways and molecular mechanisms involved in the dysregulation of calcium homeostasis and mitochondrial function in heart failure.

Hypoxic Jumbo Squid Activate Neuronal Apoptosis but Not MAPK or Antioxidant Enzymes during Oxidative Stress

AbstractThe limitations that hypoxia imparts on mitochondrial oxygen supply are circumvented by the activation of anaerobic metabolism and prosurvival mechanisms in hypoxia-tolerant animals. To deal with the hypoxia that jumbo squid (Dosidicus gigas) experience in the ocean's depth, they depress their metabolic rate by up to 52% relative to normoxic conditions. This is coupled with molecular reorganization to facilitate their daily descents into the ocean's oxygen minimum zone, where they face not only low oxygen levels but also higher pressures and colder frigid waters. Our current study explores the tissue-specific hypoxia responses of three central processes: (1) antioxidant enzymes responsible for defending against oxidative stress, (2) early apoptotic machinery that signals the activation of cell death, and (3) mitogen-activated protein kinases (MAPKs) that act as central regulators of numerous cellular processes. Luminex xMAP technology was used to assess protein levels and phosphorylation states under normoxic and hypoxic conditions in brains, branchial hearts, and mantle muscles. Hypoxic brains were found to activate apoptosis via upregulation of phospho-p38, phospho-p53, activated caspase 8, and activated caspase 9, whereas branchial hearts were the only tissue to show an increase in antioxidant enzyme levels. Hypoxic muscles seemed the least affected by hypoxia. Our results suggest that hypoxic squid do not undergo large dynamic changes in the phosphorylation states of key apoptotic and central MAPK factors, except for brains, suggesting that these mechanisms are involved in squid hypometabolic responses.

Mastering the Gram-negative bacterial barrier - Chemical approaches to increase bacterial bioavailability of antibiotics

To win the battle against resistant, pathogenic bacteria, novel classes of anti-infectives and targets are urgently needed. Bacterial uptake, distribution, metabolic and efflux pathways of antibiotics in Gram-negative bacteria determine what we here refer to as bacterial bioavailability. Understanding these mechanisms from a chemical perspective is essential for anti-infective activity and hence, drug discovery as well as drug delivery. A systematic and critical discussion of in bacterio, in vitro and in silico assays reveals that a sufficiently accurate holistic approach is still missing. We expect new findings based on Gram-negative bacterial bioavailability to guide future anti-infective research.

JNK signaling pathway in metabolic disorders: An emerging therapeutic target

Metabolic Syndrome is a multifactorial disease associated with increased risk of cardiovascular disorders, type 2 diabetes mellitus, fatty liver disease, etc. Various stress stimuli such as reactive oxygen species, endoplasmic reticulum stress, mitochondrial dysfunction, increased cytokines, or free fatty acids are known to aggravate progressive development of hyperglycemia and hyperlipidemia. Although the exact mechanism contributing to altered metabolism is unclear. Evidence suggests stress kinase role to be a crucial one in metabolic syndrome. Stress kinase, c-jun N-terminal kinase activation (JNK) is involved in various metabolic manifestations including obesity, insulin resistance, fatty liver disease as well as cardiometabolic disorders. It emerged as a foremost mediator in regulating metabolism in the liver, skeletal muscle, adipose tissue as well as pancreatic β cells. It has three isoforms each having a unique and tissue-specific role in altered metabolism. Current findings based on genetic manipulation or chemical inhibition studies identified JNK isoforms to play a central role in the regulation of whole-body metabolism, suggesting it to be a novel therapeutic target. Hence, it is imperative to elucidate its role in metabolic syndrome onset and progression. The purpose of this review is to elucidate in vitro and in vivo implications of JNK signaling along with the therapeutic strategy to inhibit specific isoform. Since metabolic syndrome is an array of diseases and complex pathway, carefully examining each tissue will be important for specific treatment strategies.

STAT3 Localizes in Mitochondria-Associated ER Membranes Instead of in Mitochondria

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor (TF) that regulates a variety of biological processes, including a key role in mediating mitochondrial metabolism. It has been shown that STAT3 performs this function by translocating in minute amounts into mitochondria and interacting with mitochondrial proteins and genome. However, whether STAT3 localizes in mitochondria is still up for debate. To decipher the role of mitochondrial STAT3 requires a detailed understanding of its cellular localization. Using Percoll density gradient centrifugation, we surprisingly found that STAT3 is not located in the mitochondrial fraction, but instead, in the mitochondria-associated endoplasmic reticulum membrane (MAM) fraction. This was confirmed by sub-diffraction image analysis of labeled mitochondria in embryonic astrocytes. Also, we find that other TFs that have been previously found to localize in mitochondria are also found instead in the MAM fraction. Our results suggest that STAT3 and other transcriptional factors are, contrary to prior studies, consolidated specifically at MAMs, and further efforts to understand mitochondrial STAT3 function must take into consideration this localization, as the associated functional consequences offer a different interpretation to the questions of STAT3 trafficking and signaling in the mitochondria.

JNK and cardiometabolic dysfunction

Cardiometabolic syndrome (CMS) describes the cluster of metabolic and cardiovascular diseases that are generally characterized by impaired glucose tolerance, intra-abdominal adiposity, dyslipidemia, and hypertension. CMS currently affects more than 25% of the world’s population and the rates of diseases are rapidly rising. These CMS conditions represent critical risk factors for cardiovascular diseases including atherosclerosis, heart failure, myocardial infarction, and peripheral artery disease (PAD). Therefore, it is imperative to elucidate the underlying signaling involved in disease onset and progression. The c-Jun N-terminal Kinases (JNKs) are a family of stress signaling kinases that have been recently indicated in CMS. The purpose of this review is to examine the in vivo implications of JNK as a potential therapeutic target for CMS. As the constellation of diseases associated with CMS are complex and involve multiple tissues and environmental triggers, carefully examining what is known about the JNK pathway will be important for specificity in treatment strategies.

Elucidating the contribution of ETC complexes I and II to the respirasome formation in cardiac mitochondria

Mitochondrial electron transport chain (ETC) plays a central role in ATP synthesis, and its dysfunction is associated with human diseases. Recent studies revealed that individual ETC complexes are assembled into supercomplexes. The main supercomplex, respirasome composed of complexes I, III, and IV has been suggested to improve electron channeling and control ROS production, maintain the structural integrity of ETC complexes and prevent protein aggregation in the inner mitochondrial membrane. However, many questions related to the structural organization of the respirasome, particularly, a possible role of complexes I and II in respirasome formation remain unclear. Here, we investigated whether genetic and pharmacological inhibition of complexes I and II affect respirasome assembly in cardioblast cells and isolated cardiac mitochondria. Pharmacological inhibition of the enzymatic activity of complexes I and II stimulated disruption of the respirasome. Likewise, knockdown of the complex I subunit NDUFA11 stimulated dissociation of respirasome and reduced the activity of complexes I, III, and IV. However, silencing of the membrane-anchored SDHC subunit of complex II had no effect on the respirasome assembly but reduced the activity of complexes II and IV. Downregulation of NDUFA11 or SDHC reduced ATP production and increased mitochondrial ROS production. Overall, these studies, for the first time, provide biochemical evidence that the complex I activity, and the NDUFA11 subunit are important for assembly and stability of the respirasome. The SDHC subunit of complex II is not involved in the respirasome however the complex may play a regulatory role in respirasome formation.

FAF1 mediates necrosis through JNK1-mediated mitochondrial dysfunction leading to retinal degeneration in the ganglion cell layer upon ischemic insult

BACKGROUND

Aberrant cell death induced by ischemic stress is implicated in the pathogenesis of ischemic diseases. Fas-associated factor 1 (FAF1) has been identified as a death-promoting protein. This study demonstrates that FAF1 functions in death signaling triggered by ischemic insult.

METHODS

The expression changes of FAF1 and phophorylated JNK1 were detected by Western blotting. Immunoprecipitation was employed to investigate protein-protein interaction. We determined the cell death using flow cytometry and lactate dehydrogenase release measurement. To validate the death-promoting role of FAF1 in the retina, we generated conditional retinal FAF1 knockout mice. We used hematoxylin and eosin staining to detect retinal cell death in retinal ganglion cell layer.

RESULTS

FAF1 was found to function upstream of c-Jun N-terminal kinase 1 (JNK1), followed by mitochondrial dysregulation and necrotic cell death processes upon ischemic insult. We investigated whether FAF1 is involved in the pathogenesis of ischemic diseases using a retinal ischemia model. Indeed, FAF1 potentiated necrosis through JNK1 activation upon ischemic stress in retinal cells demonstrating retinal ganglion-like character. Conditional FAF1 depletion attenuated JNK1 activation in the retinas of Dkk3-Cre;Faf1flox/flox mice and ameliorated death of retinal cells due to elevated intraocular pressure (IOP).

CONCLUSIONS

Our results show that FAF1 plays a key role in ischemic retinal damage and may be implicated in the pathogenesis of retinal ischemic disease.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

Remifentanil preconditioning confers cardioprotection via c-Jun NH2-terminal kinases and extracellular signal regulated kinases pathways in ex-vivo failing rat heart

Remifentanil preconditioning (RPC) exerts protection in normal hearts, but has not been investigated in heart failure. The aim of the present study was to evaluate the effect of RPC in a chronic failing rat heart model and the mechanisms involving mitogen-activated protein kinases (MAPK) and Bcl-2 protein family. The doxorubicin induced failing rat hearts were subjected to 30 min ischemia / 120 min reperfusion (IR) with or without RPC by using Langendorff apparatus. RPC was induced by three cycles of 5 min remifentanil / 5 min drug-free perfusion before IR, with three different concentrations: 25, 50 and 100 μg/l. An extracellular signal regulated kinases (ERK) inhibitor PD98059, p38MAPK inhibitor SB203580, c-Jun NH₂-terminal kinases (JNK) inhibitor SP600125 were perfused at 10 min before RPC. Infarct size, cardiac function and protein kinase activity were determined. RPC significantly reduced infarct size and the rise in lactate dehydrogenase (LDH) level caused by IR injury in failing heart. The JNK inhibitor SP600125 and ERK inhibitor PD98059 abolished the RPC mediated reduction effect on the infarct size and LDH activity after reperfusion. In addition, RPC increased the phosphorylation of JNK, ERK1/2 and the downstream GSK-3β, as well as the Bcl-2/Bax ratio, while, these changes were completely reversed by SP600125 and PD98059. And of note, SB203580 had no effect. In conclusion, our results suggested that the activation of JNK and ERK pathways, by leading to inhibition of GSK-3β and regulating Bcl-2 protein family, is a major mechanism that RPC confers cardioprotection in failing rat heart.

Simple kinetic model of mitochondrial swelling in cardiac cells

Mitochondria play an important role in both cell survival and cell death. In response to oxidative stress, they undergo opening of non-selective permeability transition pores (PTP) in the inner mitochondrial membrane. Sustained PTP opening triggers mitochondrial swelling due to increased colloidal osmotic pressure in the matrix accompanied by mitochondrial membrane depolarization and ATP hydrolysis. Mitochondrial swelling is the major factor leading to mitochondria-mediated cell death through both apoptosis and necrosis. Hence, precise estimation of the threshold parameters of the transition of reversible swelling to irreversible swelling is important for understanding the mechanisms of PTP-mediated cell death as well as for the development of new therapeutic approaches targeting the mitochondria under pathological conditions. In this study, we designed a simple kinetic model of the Ca²⁺ -induced mitochondrial swelling that describes the mechanisms of transition from reversible to irreversible swelling in cardiac mitochondria. Values of kinetic parameters calculated using parameter estimation techniques that fit experimental data of mitochondrial swelling with minimum average differences between the experimental data and model parameters. Overall, this study provides a kinetic model verified by data simulation and model fitting that adequately describes the dynamics of mitochondrial swelling.

Angiotensin II-preconditioning is associated with increased PKCε/PKCδ ratio and prosurvival kinases in mitochondria

Angiotensin II-preconditioning (APC) has been shown to reproduce the cardioprotective effects of ischaemic preconditioning (IPC), however, the molecular mechanisms mediating the effects of APC remain unknown. In this study, Langendorff-perfused rat hearts were subjected to IPC, APC or both (IPC/APC) followed by ischaemia-reperfusion (IR), to determine translocation of PKCε, PKCδ, Akt, Erk1/2, JNK, p38 MAPK and GSK-3β to mitochondria as an indicator of activation of the protein kinases. In agreement with previous observations, IPC, APC and IPC/APC increased the recovery of left ventricular developed pressure (LVDP), reduced infarct size (IS) and lactate dehydrogenase (LDH) release, compared to controls. These effects were associated with increased mitochondrial PKCε/PKCδ ratio, Akt, Erk1/2, JNK, and inhibition of permeability transition pore (mPTP) opening. Chelerythrine, a pan-PKC inhibitor, abolished the enhancements of PKCε but increased PKCδ expression, and inhibited Akt, Erk1/2, and JNK protein levels. The drug had no effect on the APC- and IPC/APC-induced cardioprotection as previously reported, but enhanced the post-ischaemic LVDP in controls. Losartan, an angiotensin II type 1 receptor (AT1-R) blocker, abolished the APC-stimulated increase of LVDP and reduced PKCε, Akt, Erk1/2, JNK, and p38. Both drugs reduced ischaemic contracture and LDH release, and abolished the inhibition of mPTP by the preconditioning. Chelerythrine also prevented the reduction of IS by APC and IPC/APC. These results suggest that the cardioprotection induced by APC and IPC/APC involves an AT1-R-dependent translocation of PKCε and survival kinases to the mitochondria leading to mPTP inhibition. In chelerythrine-treated hearts, however, alternate mechanisms appear to maintain cardiac function.

Association between ROS production, swelling and the respirasome integrity in cardiac mitochondria

Although mitochondrial Ca²⁺ overload and ROS production play a critical role in mitochondria-mediated cell death, a cause-effect relationship between them remains elusive. This study elucidated the crosstalk between mitochondrial swelling, ROS production, and electron transfer chain (ETC) supercomplexes in rat heart mitochondria in response to Ca²⁺ and tert-butyl hydroperoxide (TBH), a lipid-soluble organic peroxide. Results showed that ROS production induced by TBH was significantly increased in the presence of Ca²⁺ in a dose-dependent manner. TBH markedly inhibited the state 3 respiration rate with no effect on the mitochondrial swelling. Ca²⁺ exerted a slight effect on mitochondrial respiration that was greatly aggravated by TBH. Analysis of supercomplexes revealed a minor difference in the presence of TBH and/or Ca²⁺. However, incubation of mitochondria in the presence of high Ca²⁺ (1 mM) or inhibitors of ETC complexes (rotenone and antimycin A) induced disintegration of the main supercomplex, respirasome. Thus, PTP-dependent swelling of mitochondria solely depends on Ca²⁺ but not ROS. TBH has no effect on the respirasome while Ca²⁺ induces disintegration of the supercomplex only at a high concentration. Intactness of individual ETC complexes I and III is important for maintenance of the structural integrity of the respirasome.

Elucidating Mitochondrial Electron Transport Chain Supercomplexes in the Heart During Ischemia-Reperfusion

AIMS

Mitochondrial supercomplexes (SCs) are the large supramolecular assembly of individual electron transport chain (ETC) complexes that apparently provide highly efficient ATP synthesis and reduce electron leakage and reactive oxygen species (ROS) production. Oxidative stress during cardiac ischemia-reperfusion (IR) can result in degradation of SCs through oxidation of cardiolipin (CL). Also, IR induces calcium overload and enhances reactive oxygen species (mitROS) in mitochondria that result in the opening of the nonselective permeability transition pores (PTP). The opening of the PTP further compromises cellular energetics and increases mitROS ultimately leading to cell death. Here, we examined the role of PTP-induced mitROS in disintegration of SCs during cardiac IR. The relationship between mitochondrial PTP, ROS, and SCs was investigated using Langendorff-perfused rat hearts subjected to global ischemia (25 min) followed by short-time (5 min) or long-time (60 min) reperfusion in the presence or absence of the PTP inhibitor, sanglifehrin A (SfA), and the mitochondrial targeted ROS and electron scavenger, XJB-5-131. Also, the effects of CL deficiency on SC degradation, PTP, and mitROS were investigated in tafazzin knockdown (TazKD) mice.

RESULTS

Cardiac IR induced PTP opening and mitROS generation, inhibited by SfA. Percent distributions of SCs were significantly affected by IR, and the effects were dependent on the reperfusion time and reversed by SfA and XJB-5-131. TazKD mice demonstrated a 40% lower SC I + III+IV with reduced basal mitochondrial PTP, ROS, and ETC complex activity. Innovation and Conclusion: Sustained reperfusion after cardiac ischemia induces disintegration of mitochondrial SCs, and PTP-induced ROS presumably play a causal role in SC disassembly. Antioxid. Redox Signal. 27, 57-69.

The p21-activated kinase 1 (Pak1) signalling pathway in cardiac disease: from mechanistic study to therapeutic exploration

p21-activated kinase 1 (Pak1) is a member of the highly conserved family of serine/threonine protein kinases regulated by Ras-related small G-proteins, Cdc42/Rac1. It has been previously demonstrated to be involved in cardiac protection. Based on recent studies, this review provides an overview of the role of Pak1 in cardiac diseases including disrupted Ca²⁺ homoeostasis-related cardiac arrhythmias, adrenergic stress- and pressure overload-induced hypertrophy, and ischaemia/reperfusion injury. These findings demonstrate the important role of Pak1 mediated through the phosphorylation and transcriptional modification of hypertrophy and/or arrhythmia-related genes. This review also discusses the anti-arrhythmic and anti-hypertrophic, protective function of Pak1 and the beneficial effects of fingolimod (an FDA-approved sphingolipid drug), a Pak1 activator, and its ability to prevent arrhythmias and cardiac hypertrophy. These findings also highlight the therapeutic potential of Pak1 signalling in the treatment and prevention of cardiac diseases.

LINKED ARTICLES

This article is part of a themed section on Spotlight on Small Molecules in Cardiovascular Diseases. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.8/issuetoc.

High Sensitivity of SIRT3 Deficient Hearts to Ischemia-Reperfusion Is Associated with Mitochondrial Abnormalities

Aim: Sirtuins are NAD⁺-dependent deacetylases that regulate cell metabolism through protein acetylation/deacetylation, and SIRT3 is the major deacetylase among mitochondrial isoforms. Here, we elucidated the possible role of acetylation of cyclophilin D, a key regulator of the mitochondrial permeability transition pore (mPTP), in mitochondria-mediated cardiac dysfunction induced by ischemia-reperfusion (IR) in wild type (WT) and SIRT3 knockout (SIRT3^-/-) mice.

Materials and Methods: Isolated and Langendorff-mode perfused hearts of WT and SIRT3^-/- mice were subjected to 25-min global ischemia followed by 60-min of reperfusion in the presence or absence of the mPTP inhibitor, sanglifehrin A (SfA).

Results: Analysis of mitochondrial sirtuins demonstrated that SIRT3 deficiency upregulated SIRT4 with no effect on SIRT5 expression. Hearts of SIRT3^-/- mice exhibited significantly less recovery of cardiac function at the end of IR compared to WT mice. Intact (non-perfused) SIRT3^-/- hearts exhibited an increased rate of Ca²⁺-induced swelling in mitochondria as an indicator of mPTP opening. However, there was no difference in mPTP opening and cyclophilin D acetylation between WT and SIRT3^-/- hearts subjected to IR injury. Ca²⁺-stimulated H₂O₂ production was significantly higher in SIRT3^-/- mitochondria that was prevented by SfA. Superoxide dismutase activity was lower in SIRT3^-/- heart mitochondria subjected to IR which correlated with an increase in protein carbonylation. However, mitochondrial DNA integrity was not affected in SIRT3^-/- hearts after IR.

Conclusion: SIRT3 deficiency exacerbates cardiac dysfunction during post-ischemic recovery, and increases mPTP opening and ROS generation without oxidative damage to mitochondrial proteins and DNA.

JNK pathway signaling: a novel and smarter therapeutic targets for various biological diseases

JNK pathway regulates various physiological processes including inflammatory responses, cell differentiation, cell proliferation, cell death, cell survival and expression of proteins. Deregulation of JNK is linked with various diseases including neurodegenerative disease, autoimmune disease, diabetes, cancer, cardiac hypertrophy and asthma. Three distinct genes JNK1, JNK2 and JNK3 have been identified as regulator of JNK pathway. JNK1 and JNK2 have broad tissue distribution and play a potential role in insulin resistance, inflammation and cell signaling. JNK3 is predominantly found in the CNS neurons, making it an attractive target for neurodegenerative disorders. In this review, we summarize the evidence supporting JNK as a potent therapeutic target, and small molecules from various chemical classes as JNK inhibitors.

Cross-validation of item selection and scoring for the SF-12 Health Survey in nine countries: results from the IQOLA Project. International Quality of Life Assessment

Activated AMPK protects the heart from cardiac ischemia-reperfusion (IR) injury and is associated with inhibition of mitochondrial permeability transition pore (PTP) opening. On the other hand, pharmacological inhibition of the PTP reduces infarct size and improves cardiac function. However, it is unclear whether beneficial effects of AMPK are mediated through the PTP and, if they are not, whether simultaneous activation of AMPK and inhibition of the PTP exert synergistic protective effects against cardiac IR injury. Here, we examined the effects of the AMPK activator, A-769662 in combination with the PTP inhibitor, sanglifehrin A (SfA) on in vivo cardiac IR. Cardiac dysfunction following IR injury was associated with decreased activity of the mitochondrial electron transport chain (ETC) and increased mitochondrial ROS and PTP opening. Administration of A-769662 or SfA individually upon reperfusion improved cardiac function, reduced infarction size, and inhibited ROS production and PTP opening. However, simultaneous administration of SfA and A-769662 did not provide synergistic improvement of postischemic recovery of cardiac and mitochondrial function, though both compounds disrupted IR-induced interaction between PPARα and CyP-D. In conclusion, A-769662 or SfA prevents PPARα interaction with CyP-D, improving cardiac outcomes and increasing mitochondrial function, and simultaneous administration of the drugs does not provide synergistic effects.