Inhibition of JNK mitochondrial localization and signaling is protective against ischemia/reperfusion injury in rats

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.

Mitochondrial P-JNK target, SAB (SH3BP5), in regulation of cell death

Cell death occurs in various circumstances, such as homeostasis, stress response, and defense, via specific pathways and mechanisms that are regulated by specific activator-induced signal transductions. Among them, Jun N-terminal kinases (JNKs) participate in various aspects, and the recent discovery of JNKs and mitochondrial protein SAB interaction in signal regulation of cell death completes our understanding of the mechanism of sustained activation of JNK (P-JNK), which leads to triggering of the machinery of cell death. This understanding will lead the investigators to discover the modulators facilitating or preventing cell death for therapeutic application in acute or chronic diseases and cancer. We discuss here the mechanism and modulators of the JNK-SAB-ROS activation loop, which is the core component of mitochondria-dependent cell death, specifically apoptosis and mitochondrial permeability transition (MPT)-driven necrosis, and which may also contribute to cell death mechanisms of ferroptosis and pyroptosis. The discussion here is based on the results and evidence discovered from liver disease models, but the JNK-SAB-ROS activation loop to sustain JNK activation is universally applicable to various disease models where mitochondria and reactive oxygen species contribute to the mechanism of disease.

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.

Advances in the study of exosomes in cardiovascular diseases

BACKGROUND

Cardiovascular disease (CVD) has been the leading cause of death worldwide for many years. In recent years, exosomes have gained extensive attention in the cardiovascular system due to their excellent biocompatibility. Studies have extensively researched miRNAs in exosomes and found that they play critical roles in various physiological and pathological processes in the cardiovascular system. These processes include promoting or inhibiting inflammatory responses, promoting angiogenesis, participating in cell proliferation and migration, and promoting pathological progression such as fibrosis.

AIM OF REVIEW

This systematic review examines the role of exosomes in various cardiovascular diseases such as atherosclerosis, myocardial infarction, ischemia-reperfusion injury, heart failure and cardiomyopathy. It also presents the latest treatment and prevention methods utilizing exosomes. The study aims to provide new insights and approaches for preventing and treating cardiovascular diseases by exploring the relationship between exosomes and these conditions. Furthermore, the review emphasizes the potential clinical use of exosomes as biomarkers for diagnosing cardiovascular diseases.

KEY SCIENTIFIC CONCEPTS OF REVIEW

Exosomes are nanoscale vesicles surrounded by lipid bilayers that are secreted by most cells in the body. They are heterogeneous, varying in size and composition, with a diameter typically ranging from 40 to 160 nm. Exosomes serve as a means of information communication between cells, carrying various biologically active substances, including lipids, proteins, and small RNAs such as miRNAs and lncRNAs. As a result, they participate in both physiological and pathological processes within the body.

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.

Adaptor protein HIP-55-mediated signalosome protects against ferroptosis in myocardial infarction

Ischemic heart disease is a leading cause of death worldwide. Myocardial infarction (MI) results in cardiac damage due to cell death and insufficient cardiomyocyte self-renewal. Ferroptosis, a novel type of cell death, has recently been shown as a key cause of cardiomyocyte death after MI. However, the complicated regulation mechanisms involved in ferroptosis, especially how ferroptosis is integrated into classical cell survival/death pathways, are still unclear. Here, we discovered that HIP-55, a novel adaptor protein, acts as a hub protein for the integration of the ferroptosis mechanism into the classical AKT cell survival and MAP4K1 cell death pathways for MI injury. The expression of HIP-55 is induced in MI. Genetic deletion of HIP-55 increased cardiomyocyte ferroptosis and MI injury, whereas cardiac-specific overexpression of HIP-55 significantly alleviated cardiomyocyte ferroptosis and MI injury. Mechanistically, HIP-55 was identified as a new AKT substrate. AKT phosphorylates HIP-55 at S269/T291 sites and further HIP-55 directs AKT signaling to negatively regulate the MAP4K1 pathway against MI injury in a site-specific manner. S269A/T291A-mutated HIP-55 (HIP-55AA), which is defective in AKT phosphorylation and significantly decreases the interaction between HIP-55 and MAP4K1, failed to inhibit the MAP4K1/GPX4 ferroptosis pathway. In line with this mechanism, cardiac-specific overexpression of HIP-55WT mice, but not cardiac-specific overexpression of HIP-55AA mice, protected cardiomyocytes against MI-induced ferroptosis and cardiac injury in vivo. These findings suggest that HIP-55 rewired the classical AKT (cell survival) and MAPK (cell death) pathways into ferroptosis mechanism in MI injury. HIP-55 may be a new therapeutic target for myocardial damage.

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.

MKK4 Knockdown Plays a Protective Role in Hemorrhagic Shock-Induced Liver Injury through the JNK Pathway

Hemorrhagic shock (HS) triggers tissue hypoxia and organ failure during severe blood loss, and the liver is sensitive to HS. Mitogen-activated protein kinase kinase 4 (MKK4) activates the c-Jun NH2-terminal kinase (JNK) pathway, and its expression is upregulated in the serum of HS patients and mouse livers at 1 h post-HS. However, the function of MKK4 in HS-induced liver injury is unclear. The role of MKK4 was investigated in vivo using rat models of HS. Before HS, lentivirus harboring shRNA against MKK4 was injected into rats via the tail vein to knock down MKK4 expression. HS was induced by bloodletting via intubation of the femoral artery followed by resuscitation. The results showed that MKK4 knockdown reduced HS-induced apoptosis in the liver by decreasing Bax expression and the cleavage of caspase 3 and promoting Bcl-2 expression. Moreover, the generation of intracellular reactive oxygen species (ROS) and malondialdehyde (MDA) in the liver was promoted, while superoxide dismutase (SOD) activity was inhibited by HS. However, the effect of HS on oxidative stress was abrogated by MKK4 knockdown. Furthermore, MKK4 knockdown restored MMP and complex I and complex III activities and promoted ATP production, suggesting that HS-induced mitochondrial dysfunction in the liver was ameliorated by MKK4 knockdown. The inhibitory effect of MKK4 knockdown on the phosphorylation and activation of the JNK/c-Jun pathway was confirmed. Overall, MKK4 knockdown may suppress oxidative stress and subsequent apoptosis and improve mitochondrial function in the liver upon HS by inhibiting the JNK pathway. The MKK4/JNK axis was shown to be a therapeutic target for HS-induced liver injury in this study.

Mechanism and Therapeutic Targets of c-Jun-N-Terminal Kinases Activation in Nonalcoholic Fatty Liver Disease

Non-alcoholic fatty liver (NAFL) is the most common chronic liver disease. Activation of mitogen-activated kinases (MAPK) cascade, which leads to c-Jun N-terminal kinase (JNK) activation occurs in the liver in response to the nutritional and metabolic stress. The aberrant activation of MAPKs, especially c-Jun-N-terminal kinases (JNKs), leads to unwanted genetic and epi-genetic modifications in addition to the metabolic stress adaptation in hepatocytes. A mechanism of sustained P-JNK activation was identified in acute and chronic liver diseases, suggesting an important role of aberrant JNK activation in NASH. Therefore, modulation of JNK activation, rather than targeting JNK protein levels, is a plausible therapeutic application for the treatment of chronic liver disease.

Selective inhibition of JNK located on mitochondria protects against mitochondrial dysfunction and cell death caused by endoplasmic reticulum stress in mice with LPS‑induced ALI/ARDS

Few pharmacological interventions are able to improve the mortality rate of acute lung injury and acute respiratory distress syndrome (ALI/ARDS). The aim of this research was to elucidate whether endoplasmic reticulum (ER) stress and c-Jun-N-terminal kinase (JNK)-mitochondria pathways serve important roles in ALI/ARDS and to determine whether the key component Sab is a potential treatment target. The current study investigated the activation of ER stress and the JNK pathway, the content of JNK located on the mitochondria during ER stress and lipopolysaccharide (LPS)-induced ALI/ARDS by western blot analysis. The treatment effects of Tat-Sab_KIM1, a selective inhibitor of JNK located on mitochondria were explored by multiple methods including histopathological evaluation, lung cell apoptosis tested by TUNEL assay, mitochondrial membrane permeability and survival analysis. The results verified that ER stress was enhanced during LPS-induced ALI/ARDS and could induce activation of the JNK pathway and JNK-mitochondrial localization as well as mitochondrial dysfunction and cell death. Tat-Sab_KIM1 alleviated LPS injection-induced lung injury and improved mouse survival rates by specifically inhibiting JNK localization to mitochondria and mito-JNK signal activation without affecting cytosolic/nuclear JNK activation. The protective effect of Tat-Sab_KIM1 against ALI/ARDS was partly caused by inhibition of the excessive activation of mitochondria-mediated apoptosis and autophagy. These results showed the important role of Sab as a treatment target of ALI/ARDS and the potential treatment effect of Tat-Sab_KIM1. In conclusion, abnormal activation of the JNK-mitochondrial pathway could significantly disrupt the normal physiological function of lung cells, resulting in the occurrence of ALI/ARDS and selective inhibit of JNK located on mitochondria by Tat-Sab_KIM1 had a protective effect against the mitochondrial dysfunction and cell death caused by endoplasmic reticulum stress in mice with LPS-induced ALI/ARDS.

Mechanisms of Cardiorenal Protection With SGLT2 Inhibitors in Patients With T2DM Based on Network Pharmacology

Purpose

Sodium-glucose cotransporter 2 (SGLT2) inhibitors have cardiorenal protective effects regardless of whether they are combined with type 2 diabetes mellitus, but their specific pharmacological mechanisms remain undetermined.

Materials and Methods

We used databases to obtain information on the disease targets of “Chronic Kidney Disease,” “Heart Failure,” and “Type 2 Diabetes Mellitus” as well as the targets of SGLT2 inhibitors. After screening the common targets, we used Cytoscape 3.8.2 software to construct SGLT2 inhibitors' regulatory network and protein-protein interaction network. The clusterProfiler R package was used to perform gene ontology functional analysis and Kyoto encyclopedia of genes and genomes pathway enrichment analyses on the target genes. Molecular docking was utilized to verify the relationship between SGLT2 inhibitors and core targets.

Results

Seven different SGLT2 inhibitors were found to have cardiorenal protective effects on 146 targets. The main mechanisms of action may be associated with lipid and atherosclerosis, MAPK signaling pathway, Rap1 signaling pathway, endocrine resistance, fluid shear stress, atherosclerosis, TNF signaling pathway, relaxin signaling pathway, neurotrophin signaling pathway, and AGEs-RAGE signaling pathway in diabetic complications were related. Docking of SGLT2 inhibitors with key targets such as GAPDH, MAPK3, MMP9, MAPK1, and NRAS revealed that these compounds bind to proteins spontaneously.

Conclusion

Based on pharmacological networks, this study elucidates the potential mechanisms of action of SGLT2 inhibitors from a systemic and holistic perspective. These key targets and pathways will provide new ideas for future studies on the pharmacological mechanisms of cardiorenal protection by SGLT2 inhibitors.

Oxidative Stress and Redox-Dependent Signaling in Prostate Cancer

Tumor emergence and progression is complicated by the dual role of reactive oxygen species (ROS). Low concentrations of ROS are essential for many intracellular metabolic processes and cell proliferation, while excessive ROS generation disrupts the mechanisms of cancer suppression, leading to the cell damage and death. A long-term imbalance in the ROS/antioxidant ratio and upregulation of the ROS generation due to the reduced efficacy of the antioxidant defense system cause chronic oxidative stress resulting in the damage of proteins, lipid, and DNA molecules and cancer development. Numerous data demonstrate that prostate cancer (the most common cancer in males) is associated with the development of oxidative stress. However, the reasons for the emergence of prostate cancer, as well as changes in the redox signaling and cellular redox homeostasis in this disease, are still poorly understood. The review examines the role of prooxidant and antioxidant enzyme systems, the imbalance in their activity leading to the oxidative stress development, changes in the key components of redox signaling, and the role of microRNAs in the modulation of redox status of cancer cells in prostate cancer.

Cardioprotective Function of Green Rooibos (Aspalathus linearis) Extract Supplementation in Ex Vivo Ischemic Prediabetic Rat Hearts

Diabetic patients develop ischemic heart disease and strokes more readily. Following an ischemic event, restoration of blood flow increases oxidative stress resulting in myocardial damage, termed ischemia/reperfusion injury. Aspalathus linearis (rooibos), rich in the antioxidant phenolic compound aspalathin, has been implicated as cardioprotective against ischemia/reperfusion injury with undefined mechanism in control rats. Primarily, the therapeutic potential of Afriplex green rooibos extract to prevent ischemia/reperfusion injury in cardiovascular disease-compromised rats was investigated. Additionally, Afriplex Green rooibos extract's cardioprotective signaling on metabolic markers and stress markers was determined using western blotting. Three hundred male Wistar rats received either 16-wk standard diet or high-caloric diet. During the final 6 wk, half received 60 mg/kg/day Afriplex green rooibos extract, containing 12.48% aspalathin. High-caloric diet increased body weight, body fat, fasting serum triglycerides, and homeostatic model assessment of insulin resistance - indicative of prediabetes. High-caloric diet rats had increased heart mass, infarct size, and decreased heart function. Afriplex green rooibos extract treatment for 6 wk lowered pre-ischemic heart rate, reduced infarct size, and improved heart function pre- and post-ischemia, without significantly affecting biometric parameters. Stabilized high-caloric diet hearts had decreased insulin independence via adenosine monophosphate activated kinase and increased inflammation (p38 mitogen-activated protein kinase), whereas Afriplex green rooibos extract treatment decreased insulin dependence (protein kinase B) and conferred anti-inflammatory effect. After 20 min ischemia, high-caloric diet hearts had upregulated ataxia-telangiectasia mutated kinase decreased insulin independence, and downregulated insulin dependence and glycogen synthase kinase 3 β inhibition. In contrast, Afriplex green rooibos extract supplementation downregulated insulin independence and inhibited extracellular signal-regulated kinase 1 and 2. During reperfusion, all protective signaling was decreased in high-caloric diet, while Afriplex green rooibos extract supplementation reduced oxidative stress (c-Jun N-terminal kinases 1 and 2) and inflammation. Taken together, Afriplex green rooibos extract supplementation for 6 wk preconditioned cardiovascular disease-compromised rat hearts against ischemia/reperfusion injury by lowering inflammation, oxidative stress, and heart rate.

TBC1Domain Family Member 25 deficiency aggravates cerebral ischemia-reperfusion injury via TAK1-JNK/p38 pathway

TBC1Domain Family Member 25 (TBC1D25) is a protein that contains a TBC/RAB-GTPase activating protein (GAP) domain, which was shown to participate in autophagy in previous studies. However, the role of TBC1D25 in cerebral ischemia-reperfusion (I/R) injury remains unknown. In this study, we found that the mRNA and protein expression levels of TBC1D25 decreased in mouse brain after I/R injury and primary cortical neurons treated with oxygen and glucose deprivation/reoxygenation (OGD/R). Then TBC1D25 knockout (KO) mice were applied to demonstrate that TBC1D25 ablation aggravated cerebral I/R-induced neuronal loss and infarct size. In addition, neuronal apoptosis and inflammation were significantly potentiated in the TBC1D25-KO group. In in vitro OGD/R model, TBC1D25 knockdown can attenuate neuronal cell viability and aggravate the process of inflammation and apoptosis. Conversely, over-expression of TBC1D25 in primary neurons ameliorated the aforementioned processes. Mechanistically, RNA-sequencing (RNA-seq) analysis revealed mitogen-activated protein kinase (MAPK) signaling pathway was the most significant pathway that contributed to TBC1D25-mediated brain I/R injury process. Through experimental verification, TBC1D25 deficiency increased the phosphorylation of the transforming growth factor-β-activated kinase 1 (TAK1)-c-Jun N-terminal kinase (JNK)/p38 axis in neurons during the brain I/R injury. Furthermore, we found that TAK1 blockade abrogated the apoptosis and inflammatory response produced by TBC1D25 knockdown in vitro. In conclusion, this study is the first to demonstrate the functional significance of TBC1D25 in the pathophysiology of brain I/R injury, and the protective mechanism of TBC1D25 is dependent on the TAK1-JNK/p38 pathway.

Sex Differences in Nonalcoholic Fatty Liver Disease: Estrogen Influence on the Liver-Adipose Tissue Crosstalk

Significance: Nonalcoholic fatty liver disease (NAFLD) is a hepatic and systemic disorder with a complex multifactorial pathogenesis. Owing to the rising incidence of obesity and diabetes mellitus, the prevalence of NAFLD and its impact on global health care are expected to increase in the future. Differences in NAFLD exist between males and females, and among females depending on their reproductive status. Clinical and preclinical data show that females in the fertile age are more protected against NAFLD, and studies in postmenopausal women and ovariectomized animal models support a protective role for estrogens. Recent Advances: An efficient crosstalk between the liver and adipose tissue is necessary to regulate lipid and glucose metabolism, protecting the liver from steatosis and insulin resistance contributing to NALFD. New advances in the knowledge of sexual dimorphism in liver and adipose tissue are providing interesting clues about the sex differences in NAFLD pathogenesis that could inspire new therapeutic strategies. Critical Issues: Sex hormones influence key master regulators of lipid metabolism and oxidative stress in liver and adipose tissue. All these sex-biased metabolic adjustments shape the crosstalk between liver and adipose tissue, contributing to the higher protection of females to NAFLD. Future Directions: The development of novel drugs based on the protective action of estrogens, but without its feminizing or undesired side effects, might provide new therapeutic strategies for the management of NAFLD. Antioxid. Redox Signal. 35, 753-774.

Exendin-4 inhibits high glucose-induced oxidative stress in retinal pigment epithelial cells by modulating the expression and activation of p66Shc

PURPOSE

Activation of p⁶⁶Sch, an adaptor protein, is associated with oxidative stress and apoptosis and has been implicated in the pathogenesis of diabetes-induced retinal pigment epithelial cell damage and diabetic retinopathy. Exendin-4 is a glucagon-like protein that protects against diabetic retinopathy, but the mechanism of action is not well understood. This study aimed to investigate whether Exendin-4 could protect against high glucose-induced oxidative stress and apoptosis in the adult human retinal pigment epithelial-19 cell line by modulating levels and activation of p⁶⁶Shc and to study the underlying mechanisms.

MATERIALS AND METHODS

Adult human retinal pigment epithelial-19 cells were cultured under low (5 µM) or high glucose (100 µM) conditions in the presence or absence of Exendin-4 and with or without pre-incubation with Exendin-9-39, a glucagon-like peptide-1 receptor antagonist.

RESULTS

In a dose-dependent manner, Exendin-4 inhibited high glucose-induced cell death and decreased levels of reactive oxygen species, lactate dehydrogenase release, and single single-stranded DNA. At the most effective concentration (100 µM), Exendin-4 reduced mitochondrial levels of phospho-p⁶⁶Shc (Ser³⁶), cytoplasmic levels of cleaved caspase-3 and cytochrome-c, and NADPH oxidase levels in high glucose-treated cells. It also increased levels of glutathione and magnesium superoxide dismutase and protein levels of magnesium superoxide dismutase but downregulated total protein levels of protein kinase-β and p⁶⁶Shc and inhibited c-Jun N-terminal kinase phosphorylation in both low- and high glucose-treated cells. All these Exendin-4 effects, however, were inhibited by Exendin-9-39.

CONCLUSIONS

Exendin-4 protects against high glucose-induced adult human retinal pigment epithelial-19 cell damage by increasing antioxidants, downregulating NADPH, and inhibiting mitochondria-mediated apoptosis, effects that are associated with the inhibition of c-Jun N-terminal kinase and downregulation of protein kinase-β and p⁶⁶Shc.

Selective inhibition of JNK mitochondrial location is protective against seawater inhalation‑induced ALI/ARDS

Localization of phosphorylated (p)‑JNK to the mitochondria can lead to functional mitochondrial disorder, resulting in a decrease in energy supply and membrane potential, as well as an increase in reactive oxygen species production and apoptosis. JNK is involved in the occurrence of acute lung injury (ALI), and activation of the JNK pathway is one of the crucial factors resulting in injury. The aim of the present study was to investigate whether the JNK‑mitochondria (mitoJNK) location participated in the occurrence of ALI and acute respiratory distress syndrome (ALI/ARDS). The present study examined the activation of the JNK pathway, the content of JNK located on the mitochondria and the treatment effects of a cell‑permeable peptide Tat‑SabKIM1, which can selectively inhibit the location of JNK on mitochondria. The expression levels of proteins were detected by western blot analysis. Lung injuries were evaluated by histological examination, wet‑to‑dry weight ratios, and H2O2 and malondialdehyde concentrations in the lung tissues. Lung cells apoptosis was evaluated using TUNEL assay. The results demonstrated that JNK was phosphorylated and activated during seawater inhalation‑induced ALI/ARDS, not only in the routine JNK pathway but also in the mitoJNK pathway. It was also found that Tat‑SabKIM1 could specifically inhibit JNK localization to mitochondria and the activation of mitoJNK signaling. Furthermore, Tat‑SabKIM1 could inhibit Bcl‑2‑regulated autophagy and mitochondria‑mediated apoptosis. In conclusion, mitoJNK localization disrupted the normal physiological functions of the mitochondria during ALI/ARDS, and selective inhibition of JNK and mitochondrial SH3BP5 (also known as Sab) binding with Tat‑SabKIM1 can block deterioration from ALI/ARDS.

Mitochondrial abnormalities: a hub in metabolic syndrome-related cardiac dysfunction caused by oxidative stress

Metabolic syndrome (MetS) refers to a group of cardiovascular risk elements comprising insulin resistance, obesity, dyslipidemia, increased glucose intolerance, and increased blood pressure. Individually, all the MetS components can lead to cardiac dysfunction, while their combination generates additional risks of morbidity and mortality. Growing evidence suggests that oxidative stress, a dominant event in cellular damage and impairment, plays an indispensable role in cardiac dysfunction in MetS. Oxidative stress can not only disrupt mitochondrial activity through inducing oxidative damage to mitochondrial DNA, RNA, lipids, and proteins but can also impair cardiomyocyte contractile function via mitochondria-related oxidative modifications of proteins central to excitation-contraction coupling. Furthermore, excessive reactive oxygen species (ROS) generation can lead to the activation of several mitochondria apoptotic signaling pathways, release of cytochrome c, and eventual induction of myocardial apoptosis. This review will focus on such processes of mitochondrial abnormalities in oxidative stress induced cardiac dysfunction in MetS.

Mitochondrial Kinases and the Role of Mitochondrial Protein Phosphorylation in Health and Disease

The major role of mitochondria is to provide cells with energy, but no less important are their roles in responding to various stress factors and the metabolic changes and pathological processes that might occur inside and outside the cells. The post-translational modification of proteins is a fast and efficient way for cells to adapt to ever changing conditions. Phosphorylation is a post-translational modification that signals these changes and propagates these signals throughout the whole cell, but it also changes the structure, function and interaction of individual proteins. In this review, we summarize the influence of kinases, the proteins responsible for phosphorylation, on mitochondrial biogenesis under various cellular conditions. We focus on their role in keeping mitochondria fully functional in healthy cells and also on the changes in mitochondrial structure and function that occur in pathological processes arising from the phosphorylation of mitochondrial proteins.

Clinically Precedented Protein Kinases: Rationale for Their Use in Neurodegenerative Disease

Kinases are an intensively studied drug target class in current pharmacological research as evidenced by the large number of kinase inhibitors being assessed in clinical trials. Kinase-targeted therapies have potential for treatment of a broad array of indications including central nervous system (CNS) disorders. In addition to the many variables which contribute to identification of a successful therapeutic molecule, drug discovery for CNS-related disorders also requires significant consideration of access to the target organ and specifically crossing the blood-brain barrier (BBB). To date, only a small number of kinase inhibitors have been reported that are specifically designed to be BBB permeable, which nonetheless demonstrates the potential for success. This review considers the potential for kinase inhibitors in the context of unmet medical need for neurodegenerative disease. A subset of kinases that have been the focus of clinical investigations over a 10-year period have been identified and discussed individually. For each kinase target, the data underpinning the validity of each in the context of neurodegenerative disease is critically evaluated. Selected molecules for each kinase are identified with information on modality, binding site and CNS penetrance, if known. Current clinical development in neurodegenerative disease are summarized. Collectively, the review indicates that kinase targets with sufficient rationale warrant careful design approaches with an emphasis on improving brain penetrance and selectivity.

Exendin-4 protects the hearts of rats from ischaemia/reperfusion injury by boosting antioxidant levels and inhibition of JNK/p66 Shc/NADPH axis

Exendin-4, a glucagon-like peptide-1 receptor agonist, was shown to protect against cardiac ischaemia/reperfusion (I/R) injury by suppressing oxidative stress. p66 Shc, a pro-oxidant and an apoptotic protein, is activated in the infarcted left ventricles (LVs) after induction of I/R. This study investigated if the cardiac protective effect of Exendin-4 against I/R injury in rats involves inhibition of p66 Shc and to determine the underlying mechanisms behind this. Adult male rats (n = 12/group) were divided into four groups as a sham, a sham + Exendin-4, an I/R, and an I/R + Exendin-4. Exendin-4 was administered to rats 7 days before the induction of I/R. Ischaemia was induced by ligating the left anterior descending (LAD) coronary artery for 40 minutes followed by reperfusion for 10 minutes. The infarct myocardium was used for further analysis. Exendin-4 significantly reduced infarct area (by 62%), preserved LV function and lowered serum levels of LDH and CK-MB in I/R-induced rats. Also, it significantly reduced LV levels of ROS and MDA and protein levels of cytochrome-c and cleaved caspase-3 but significantly increased levels of glutathione (GSH) and manganese superoxide dismutase (MnSOD) in LVs of I/R rats indicating antioxidant and anti-apoptotic effects. Furthermore, it inhibited JNK and p66 Shc activation and downregulated protein levels of p66 Shc and NADPH oxidase with no effect on protein levels/activity of p53 and PKCβII. Of note, Exendin-4 also increased GSH and MnSOD in LVs of control rats. In conclusion, Exendin-4 cardioprotective effect in I/R hearts is mediated mainly by antioxidant effect and inhibition of JNK/P66 Shc/NADPH oxidase.

Rigosertib-Activated JNK1/2 Eliminate Tumor Cells through p66Shc Activation

Rigosertib, via reactive oxygen species (ROS), stimulates cJun N-terminal kinases 1/2 (JNK1/2), which inactivate RAS/RAF signaling and thereby inhibit growth and survival of tumor cells. JNK1/2 are not only regulated by ROS—they in turn can also control ROS production. The prooxidant and cell death function of p66Shc requires phosphorylation by JNK1/2. Here, we provide evidence that establishes p66Shc, an oxidoreductase, as a JNK1/2 effector downstream of Rigosertib-induced ROS production, DNA damage, and cell death. This may provide a common pathway for suppression of tumor cell growth by Rigosertib.

microRNA-195 attenuates neuronal apoptosis in rats with ischemic stroke through inhibiting KLF5-mediated activation of the JNK signaling pathway

BACKGROUND

Accumulating evidence has implicated the regulation of microRNAs (miRs) in ischemia stroke. The current study aimed to elucidate the role of microRNA-195 (miR-195) in neuronal apoptosis and brain plasticity in rats with ischemic stroke via the JNK signaling pathway/KLF5 axis.

METHODS

Ischemic stroke rat models were established by middle cerebral artery occlusion (MCAO), and oxygen deprivation (OGD) models were constructed in rat neuronal cells, followed by gain- or loss-of-function of miR-195 and/or KLF5 in rats and cells. Infarct volume, neuronal loss and ultrastructure, the expression of GAP-43, SYP and KLF5 protein as well as cell apoptosis were determined in the rats. Caspase-3 activity as well as the expression of miR-195, KLF5, GAP-43, SYP, JNK, phosphorylated JNK, Bax and Bcl-2 was measured in the cells.

RESULTS

The infarct size, expression of GAP-43 and SYP protein and apoptotic cells were increased in the miR-195^-/- MCAO rats, while reductions were detected in the miR-195 mimic MCAO and KLF5^-/- MCAO rats. Bcl-2 expression was increased, Bax and Caspase-3 expression as well as the ratio of phosphorylated JNK/JNK was decreased in response to miR-195 overexpression or KLF5 knockdown. Interestingly, the silencing of KLF5 reversed the effects exerted by the miR-195 inhibitor on the expression of Bcl-2, phosphorylated JNK/JNK, Bax and Caspase-3.

CONCLUSIONS

Collectively, our study unraveled that miR-195 could down-regulate KLF5 and block the JNK signaling pathway, ultimately inhibiting neuronal apoptosis in rats with ischemic stroke.

Oligomannuronate prevents mitochondrial dysfunction induced by IAPP in RINm5F islet cells by inhibition of JNK activation and cell apoptosis

Background

Oligomannuronates (OM) are natural products from alginate that is frequently used as food supplement. The aim of this study was to investigate the in vitro protective effects of OM on RINm5F cells against human Islet amyloid polypeptide (IAPP) induced mitochondrial dysfunction, as well as the underlying mechanisms.

Methods

In the present study, we obtained several kinds of OM with different molecular masses, and then we used RINm5F cells as a model to elucidate the involvement of JNK signal pathway in hIAPP-induced mitochondrial dysfunction in pancreatic beta cells, and the protective effects of OM are associated with its ability to attenuate the mitochondrial dysfunction.

Results

Our results demonstrated that human IAPP induced mitochondrial dysfunction, as evidence by loss of ΔΨm and ATP content, and decrease in oxygen consumption and complex activities, was accompanied by JNK activation, changes in the expressions of Bcl-2 and Bax proteins, release of cytochrome c (Cyto-c) and apoptosis inducing factor (AIF) from mitochondria into cytosol. Interestingly, the human IAPP induced damage in RINm5F cells were effectively restored by co-treatment of OM. Moreover, JNK activation was required for the OM mediated changes in RINm5F cells.

Conclusions

OM prevented mitochondrial dysfunction induced by human IAPP in RINm5F islet cells through JNK dependent signaling pathways.

Discovery of 1-Pyrimidinyl-2-Aryl-4,6-Dihydropyrrolo [3,4-d]Imidazole-5(1H)-Carboxamide as a Novel JNK Inhibitor

We designed and synthesized 1-pyrimidinyl-2-aryl-4, 6-dihydropyrrolo [3,4-d] imidazole-5(1H)-carboxamide derivatives as selective inhibitors of c-Jun-N-terminal Kinase 3 (JNK3), a target for the treatment of neurodegenerative diseases. Based on the compounds found in previous studies, a novel scaffold was designed to improve pharmacokinetic characters and activity, and compound 18a, (R)-1-(2-((1-(cyclopropanecarbonyl)pyrrolidin-3-yl)amino)pyrimidin-4-yl)-2-(3,4-dichlorophenyl)-4,6-dihydro pyrrolo [3,4-d]imidazole-5(1H)-carboxamide, showed the highest IC₅₀ value of 2.69 nM. Kinase profiling results also showed high selectivity for JNK3 among 38 kinases, having mild activity against JNK2, RIPK3, and GSK3β, which also known to involve in neuronal apoptosis.

trans-Fatty acids facilitate DNA damage-induced apoptosis through the mitochondrial JNK-Sab-ROS positive feedback loop

trans-Fatty acids (TFAs) are unsaturated fatty acids that contain one or more carbon-carbon double bonds in trans configuration. Epidemiological evidence has linked TFA consumption with various disorders, including cardiovascular diseases. However, the underlying pathological mechanisms are largely unknown. Here, we show a novel toxic mechanism of TFAs triggered by DNA damage. We found that elaidic acid (EA) and linoelaidic acid, major TFAs produced during industrial food manufacturing (so-called as industrial TFAs), but not their corresponding cis isomers, facilitated apoptosis induced by doxorubicin. Consistently, EA enhanced UV-induced embryonic lethality in C. elegans worms. The pro-apoptotic action of EA was blocked by knocking down Sab, a c-Jun N-terminal kinase (JNK)-interacting protein localizing at mitochondrial outer membrane, which mediates mutual amplification of mitochondrial reactive oxygen species (ROS) generation and JNK activation. EA enhanced doxorubicin-induced mitochondrial ROS generation and JNK activation, both of which were suppressed by Sab knockdown and pharmacological inhibition of either mitochondrial ROS generation, JNK, or Src-homology 2 domain-containing protein tyrosine phosphatase 1 (SHP1) as a Sab-associated protein. These results demonstrate that in response to DNA damage, TFAs drive the mitochondrial JNK-Sab-ROS positive feedback loop and ultimately apoptosis, which may provide insight into the common pathogenetic mechanisms of diverse TFA-related disorders.

Crucial role of NLRP3 inflammasome in a murine model of Kawasaki disease

Kawasaki disease (KD) is a systemic febrile syndrome during childhood that is characterized by coronary arteritis. The etiopathogenesis of KD remains to be elucidated. NLRP3 inflammasome is a large multiprotein complex that plays a key role in IL-1β-driven sterile inflammatory diseases. In the present study, we investigated the role of NLRP3 inflammasome in a murine model of KD induced by Candida albicans water-soluble fraction (CAWS) and found that NLRP3 inflammasome is required for the development of CAWS-induced vasculitis. CAWS administration induced IL-1β production, caspase-1 activation, leukocyte infiltration, and fibrotic changes in the aortic root and coronary arteries, which were significantly inhibited by a deficiency of IL-1β, NLRP3, and ASC. In vitro experiments showed that among cardiac resident cells, macrophages, but not endothelial cells or fibroblasts, expressed Dectin-2, but did not produce IL-1β in response to CAWS. In contrast, CAWS induced caspase-1 activation and IL-1β production in bone marrow-derived dendritic cells (BMDCs), which were inhibited by a specific caspase-1 inhibitor and a deficiency of NLRP3, ASC, and caspase-1. CAWS induced NLRP3 and pro-IL-1β expression through a Dectin-2/Syk/JNK/NF-κB pathway, and caspase-1 activation and cleavage of pro-IL-1β through Dectin-2/Syk/JNK-mediated mitochondrial ROS generation, indicating that CAWS induces the priming and activation of NLRP3 inflammasome in BMDCs. These findings provide new insights into the pathogenesis of KD vasculitis, and suggest that NLRP3 inflammasome may be a potential therapeutic target for KD.

Phosphoregulation on mitochondria: Integration of cell and organelle responses

Mitochondria are highly integrated organelles that are crucial to cell adaptation and mitigating adverse physiology. Recent studies demonstrate that fundamental signal transduction pathways incorporate mitochondrial substrates into their biological programs. Reversible phosphorylation is emerging as a useful mechanism to modulate mitochondrial function in accordance with cellular changes. Critical serine/threonine protein kinases, such as the c-Jun N-terminal kinase (JNK), protein kinase A (PKA), PTEN-induced kinase-1 (PINK1), and AMP-dependent protein kinase (AMPK), readily translocate to the outer mitochondrial membrane (OMM), the interface of mitochondria-cell communication. OMM protein kinases phosphorylate diverse mitochondrial substrates that have discrete effects on organelle dynamics, protein import, respiratory complex activity, antioxidant capacity, and apoptosis. OMM phosphorylation events can be tempered through the actions of local protein phosphatases, such as mitogen-activated protein kinase phosphatase-1 (MKP-1) and protein phosphatase 2A (PP2A), to regulate the extent and duration of signaling. The central mediators of OMM signal transduction are the scaffold proteins because the relative abundance of these accessory proteins determines the magnitude and duration of a signaling event on the mitochondrial surface, which dictates the biological outcome of a local signal transduction pathway. The concentrations of scaffold proteins, such as A-kinase anchoring proteins (AKAPs) and Sab (or SH3 binding protein 5-SH3BP5), have been shown to influence neuronal survival and vulnerability, respectively, in models of Parkinson's disease (PD), highlighting the importance of OMM signaling to health and disease. Despite recent progress, much remains to be discovered concerning the mechanisms of OMM signaling. Nonetheless, enhancing beneficial OMM signaling events and inhibiting detrimental protein-protein interactions on the mitochondrial surface may represent highly selective approaches to restore mitochondrial health and homeostasis and mitigate organelle dysfunction in conditions such as PD.

N-n-Butyl Haloperidol Iodide Ameliorates Oxidative Stress in Mitochondria Induced by Hypoxia/Reoxygenation through the Mitochondrial c-Jun N-Terminal Kinase/Sab/Src/Reactive Oxygen Species Pathway in H9c2 Cells

Both c-Jun N-terminal kinase (JNK) and reactive oxygen species (ROS) play important roles in myocardial ischemia/reperfusion (I/R) injury. Our previous studies suggest that N-n-butyl haloperidol iodide (F₂) exerts cardioprotection by reducing ROS production and JNK activation caused by I/R. In this study, we hypothesized that there is a JNK/Sab/Src/ROS pathway in the mitochondria in H9c2 cells following hypoxia/reoxygenation (H/R) that induces oxidative stress in the mitochondria and that F₂ exerts mitochondrial protective effects during H/R injury by modulating this pathway. The results showed that H/R induced higher-level ROS in the cytoplasm on the one hand and JNK activation and translocation to the mitochondria by colocalization with Sab on the other. Moreover, H/R resulted in mitochondrial Src dephosphorylation, and subsequently, oxidative stress evidenced by the increase in ROS generation and oxidized cardiolipin in the mitochondrial membranes and by the decrease in mitochondrial superoxide dismutase activity and membrane potential. Furthermore, treatment with a JNK inhibitor or Sab small interfering RNA inhibited the mitochondrial translocation of p-JNK, decreased colocalization of p-JNK and Sab on the mitochondria, and reduced Src dephosphorylation and mitochondrial oxidative stress during H/R. In addition, Src dephosphorylation by inhibitor PP2 increased mitochondrial ROS production. F₂, like inhibitors of the JNK/Sab/Src/ROS pathway, downregulated the H/R-induced mitochondrial translocation of p-JNK and the colocalization of p-JNK and Sab on the mitochondria, increased Src phosphorylation, and alleviated the above-mentioned mitochondrial oxidative stress. In conclusion, F₂ could ameliorate H/R-associated oxidative stress in mitochondria in H9c2 cells through the mitochondrial JNK/Sab/Src/ROS pathway.

The Regulation of JNK Signaling Pathways in Cell Death through the Interplay with Mitochondrial SAB and Upstream Post-Translational Effects

c-Jun-N-terminal kinase (JNK) activity plays a critical role in modulating cell death, which depends on the level and duration of JNK activation. The kinase cascade from MAPkinase kinase kinase (MAP3K) to MAPkinase kinase (MAP2K) to MAPKinase (MAPK) can be regulated by a number of direct and indirect post-transcriptional modifications, including acetylation, ubiquitination, phosphorylation, and their reversals. Recently, a JNK-mitochondrial SH3-domain binding protein 5 (SH3BP5/SAB)-ROS activation loop has been elucidated, which is required to sustain JNK activity. Importantly, the level of SAB expression in the outer membrane of mitochondria is a major determinant of the set-point for sustained JNK activation. SAB is a docking protein and substrate for JNK, leading to an intramitochondrial signal transduction pathway, which impairs electron transport and promotes reactive oxygen species (ROS) release to sustain the MAPK cascade.

Post-reperfusion hydrogen gas treatment ameliorates ischemia reperfusion injury in rat livers from donors after cardiac death: a preliminary study

BACKGROUND AND PURPOSE

We reported previously that hydrogen gas (H₂) reduced hepatic ischemia and reperfusion injury (IRI) after prolonged cold storage (CS) of livers retrieved from heart-beating donors. The present study was designed to assess whether H₂ reduced hepatic IRI during donation of a cardiac death (DCD) graft with subsequent CS.

METHODS

Rat livers were harvested after 30-min cardiac arrest and stored for 4 h in University of Wisconsin solution. The graft was reperfused with oxygenated buffer, with or without H₂ (H₂ or NT groups, respectively), at 37° for 90 min on isolated perfused rat liver apparatus.

RESULTS

In the NT group, liver enzyme leakage, apoptosis, necrosis, energy depletion, redox status, impaired microcirculation, and bile production were indicative of severe IRI, whereas in the H₂ group these impairments were significantly suppressed. The phosphorylation of cytoplasmic MKK4 and JNK were enhanced in the NT group and suppressed in the H₂ group. NFkB-p65 and c-Fos in the nucleus were unexpectedly unchanged by IRI regardless of H₂ treatment, indicating the absence of inflammation in this model.

CONCLUSION

H₂ was observed to ameliorate IRI in the DCD liver by maintaining microcirculation, mitochondrial functions, and redox status, as well as suppressing the cytoplasmic MKK4-JNK-mediated cellular death pathway.

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.

New insights into the role and mechanism of c-Jun-N-terminal kinase signaling in the pathobiology of liver diseases

The c-Jun-N-terminal-kinase (JNK) family is highly conserved across species such as Drosophila, C. elegans, zebrafish and mammals, and plays a central role in hepatic physiologic and pathophysiologic responses. These responses range from cell death to cell proliferation and carcinogenesis, as well as metabolism and survival, depending on the specific context and duration of activation of the JNK signaling pathway. Recently, several investigators identified the key molecules in the JNK activation loop which include apoptosis signal-regulating kinase (ASK1) and SH3-domain binding protein 5 (Sab) and their involvement in acute or chronic liver disease models. Thus, regulating JNK activation through modulating the JNK activation loop may represent an important new strategy in the prevention and treatment of acute and chronic liver diseases. In this review, we will discuss the molecular pathophysiology of the JNK activation loop and its role in the pathogenesis of liver diseases. (Hepatology 2018;67:2013-2024).

Inhibition of autophagy by berberine enhances the survival of H9C2 myocytes following hypoxia

Hypoxia may induce apoptosis and autophagy to promote cardiomyocyte injury. The present study investigated the effect of berberine, a natural extract of Rhizoma Coptidis, on hypoxia‑induced autophagy and apoptosis in the H9c2 rat myocardial cell line. Expression levels of apoptosis and autophagy markers were upregulated in H9c2 myocytes during hypoxia and cell viability was reduced. However, berberine significantly reduced hypoxia‑induced autophagy in H9c2 myocytes, as demonstrated by the ratio of microtubule‑associated proteins 1A/1B light chain 3 I/II and the expression levels of B‑cell lymphoma 2 (Bcl‑2)/adenovirus E1B 19 kDa protein‑interacting protein 3, and promoted cell viability. In addition, expression levels of the Bcl‑2 anti‑apoptotic protein were significantly downregulated, and expression levels of pro‑apoptotic proteins Bcl‑2‑associated X protein and cleaved caspase‑3 were upregulated during hypoxia injury in cardiac myocytes. This was reversed by treatment with berberine or the autophagy inhibitor 3‑methyladenine, whereas the autophagy agonist rapamycin had the opposite effects, suggesting that berberine reduces myocyte cell death via inhibition of autophagy and apoptosis during hypoxia. In addition, Compound C, a 5' adenosine monophosphate‑activated protein kinase (AMPK) inhibitor, reduced apoptosis and autophagy in hypoxic myocytes, suggesting that the activation of the AMPK signaling pathway may be involved in this process. These findings suggested that berberine protects cells from hypoxia‑induced apoptosis via inhibition of autophagy and suppression of AMPK activation. Therefore, berberine may be a potential therapeutic agent for the treatment of patients with cardiac myocyte injury and ischemia.

Sab mediates mitochondrial dysfunction involved in imatinib mesylate-induced cardiotoxicity

Imatinib mesylate is an effective treatment for chronic myelogenous leukemia and gastrointestinal stromal tumors. Although imatinib mesylate is highly tolerable, it has been implicated in severe congestive heart failure in mouse models and patients. A hallmark of imatinib mesylate-induced cardiotoxicity is mitochondrial dysfunction. The mitochondrial scaffold Sab has been implicated in facilitating signaling responsible for mitochondrial dysfunction in a c-Jun N-terminal Kinase (JNK)-dependent manner. We examined the impact of Sab-mediated signaling on imatinib mesylate cardiotoxicity in H9c2 rat cardiomyocyte-like cells. Silencing Sab increased the LD₅₀ of imatinib mesylate 4-fold in H9c2 cells. Disrupting Sab-mediated signaling prevented imatinib mesylate-induced apoptosis as well. Knockdown of Sab or inhibition with a small peptide prevented oxidative stress, which was indicated by decreased reactive oxygen species production, lipid peroxidation, and protein carbonylation. Further, inhibition of Sab-related signaling partially rescued deficits in mitochondrial respiration, ATP production, and membrane potential in imatinib mesylate-treated H9c2 cells. Conversely, over-expression of Sab in H9c2 cells increased the cardiotoxicity of imatinib mesylate in vitro decreasing the LD₅₀ over 4-fold. Sab expression was induced in H9c2 cells following cardiovascular-like stress in an AP-1 dependent manner. These data demonstrate that imatinib mesylate influences mitochondrial signaling leading to mitochondrial dysfunction and cardiotoxicity.

Novel Insights into the PKCβ-dependent Regulation of the Oxidoreductase p66Shc

Dysfunctional mitochondria contribute to the development of many diseases and pathological conditions through the excessive production of reactive oxygen species (ROS), and, where studied, ablation of p66Shc (p66) was beneficial. p66 translocates to the mitochondria and oxidizes cytochrome c to yield H₂O₂, which in turn initiates cell death. PKCβ-mediated phosphorylation of serine 36 in p66 has been implicated as a key regulatory step preceding mitochondrial translocation, ROS production, and cell death, and PKCβ thus may provide a target for therapeutic intervention. We performed a reassessment of PKCβ regulation of the oxidoreductase activity of p66. Although our experiments did not substantiate Ser³⁶ phosphorylation by PKCβ, they instead provided evidence for Ser¹³⁹ and Ser²¹³ as PKCβ phosphorylation sites regulating the pro-oxidant and pro-apoptotic function of p66. Mutation of another predicted PKCβ phosphorylation site also located in the phosphotyrosine binding domain, threonine 206, had no phenotype. Intriguingly, p66 with Thr²⁰⁶ and Ser²¹³ mutated to glutamic acid showed a gain-of-function phenotype with significantly increased ROS production and cell death induction. Taken together, these data argue for a complex mechanism of PKCβ-dependent regulation of p66 activation involving Ser¹³⁹ and a motif surrounding Ser²¹³.

JNK/PI3K/Akt signaling pathway is involved in myocardial ischemia/reperfusion injury in diabetic rats: effects of salvianolic acid A intervention

Recent studies have demonstrated that diabetes impairs the phosphatidylinositol 3-kinase/Akt (PI3K/Akt) pathway, while insulin resistance syndrome has been associated with alterations of this pathway in diabetic rats after ischemia/reperfusion (I/R), and activation of C-jun N-terminal kinase (JNK) is involved. The present study was designed to investigate whether inhibiting JNK activity would partially restore the PI3K/Akt signaling pathway and protect against myocardial I/R injury in diabetic rats, and to explore the effect of intervention with salvianolic acid A (Sal A). The inhibitor of JNK (SP600125) and Sal A were used in type 2 diabetic (T2D) rats, outcome measures included heart hemodynamic data, myocardial infarct size, the release of lactate dehydrogenase (LDH), SERCA2a activity, cardiomyocyte apotosis, expression levels of Bcl-2, Bax and cleaved caspase-3, and the phosphorylation status of Akt and JNK. The p-Akt levels were increased after myocardial I/R in non-diabetic rats, while there was no change in diabetic rats. Pretreatment with the SP600125 and Sal A decreased the p-JNK levels and increased the p-Akt levels in diabetic rats with I/R, and heart hemodynamic data improved, infarct size and LDH release decreased, SERCA2a activity increased, Bax and cleaved caspase-3 expression levels decreased, and the expression of Bcl-2 and the Bcl-2/Bax ratio increased. Our results suggest that the JNK/PI3K/Akt signaling pathway is involved in myocardial I/R injury in diabetic rats and Sal A exerts an anti-apoptotic effect and improves cardiac function following I/R injury through the JNK/PI3K/Akt signaling pathway in this model.

c-Jun N-terminal kinase mediates mouse liver injury through a novel Sab (SH3BP5)-dependent pathway leading to inactivation of intramitochondrial Src

Sustained c-Jun N-terminal kinase (JNK) activation has been implicated in many models of cell death and tissue injury. Phosphorylated JNK (p-JNK) interacts with the mitochondrial outer membrane SH3 homology associated BTK binding protein (Sab, or SH3BP5). Using knockdown or liver-specific deletion of Sab, we aimed to elucidate the consequences of this interaction on mitochondrial function in isolated mitochondria and liver injury models in vivo. Respiration in isolated mitochondria was directly inhibited by p-JNK + adenosine triphosphate. Knockdown or liver-specific knockout of Sab abrogated this effect and markedly inhibited sustained JNK activation and liver injury from acetaminophen or tumor necrosis factor/galactosamine. We then elucidated an intramitochondrial pathway in which interaction of JNK and Sab on the outside of the mitochondria released protein tyrosine phosphatase, nonreceptor type 6 (SHP1, or PTPN6) from Sab in the inside of the mitochondrial outer membrane, leading to its activation and transfer to the inner membrane, where it dephosphorylates P-Y419Src (active), which required a platform protein, docking protein 4 (DOK4), on the inner membrane. Knockdown of mitochondrial DOK4 or SHP1 inhibited the inactivation of mitochondrial p-Src and the effect of p-JNK on mitochondria.

CONCLUSIONS

The binding to and phosphorylation of Sab by p-JNK on the outer mitochondrial membrane leads to SHP1-dependent and DOK4-dependent inactivation of p-Src on the inner membrane; inactivation of mitochondrial Src inhibits electron transport and increases reactive oxygen species release, which sustains JNK activation and promotes cell death and organ injury. (Hepatology 2016;63:1987-2003).

Lazaroid U83836E protects the heart against ischemia reperfusion injury via inhibition of oxidative stress and activation of PKC

Oxidative stress has been demonstrated to be important during myocardial ischemia/reperfusion injury (MIRI). The lazaroid U83836E, which combines the amino functionalities of the 21‑aminosteroids with the antioxidant ring portion of vitamin E, is a reactive oxygen species scavenger. The aim of the current study was to investigate the effect of U83836E on MIRI and its mechanisms of action. Rat hearts were subjected to 30 min ligation of the left anterior descending coronary artery, followed by 2 h reperfusion. The results demonstrated that at 5 mg/kg, U83836E markedly protected cardiac function in ischemia/reperfusion rat models, decreased the malondialdehyde content and creatinine kinase activity, while increasing superoxide dismutase and glutathione peroxidase activity. Additionally, U83836E significantly decreased the histological damage to the myocardium, reduced the area of myocardial infarction in the left ventricle and modified the mitochondrial dysfunction. Furthermore, U83836E enhanced the translocation of protein kinase Cε (PKCε) from the cytoplasm to the membrane. However, the cardioprotective effects of U83836E were reduced in the presence of the PKC inhibitor, chelerythrine (1 mg/kg). Therefore, the results of the present study suggest that U83836E has a potent protective effect against MIRI in rat models through the direct anti‑oxidative stress mechanisms and the activation of PKC signaling.

cJun N-terminal kinase (JNK) phosphorylation of serine 36 is critical for p66Shc activation

p66Shc-dependent ROS production contributes to many pathologies including ischemia/reperfusion injury (IRI) during solid organ transplantation. Inhibiting p66Shc activation may provide a novel therapeutic approach to prevent damage, which is poorly managed by antioxidants in vivo. Previous work suggested that pro-oxidant and a pro-apoptotic function of p66Shc required mitochondrial import, which depended on serine 36 phosphorylation. PKCß has been proposed as S36 kinase but cJun N-terminal kinases (JNKs) may also phosphorylate this residue. To simulate the early stages of ischemia/reperfusion (IR) we either used H2O2 treatment or hypoxia/reoxygenation (HR). As during reperfusion in vivo, we observed increased JNK and p38 activity in mouse embryonic fibroblasts (MEFs) and HL-1 cardiomyocytes along with significantly increased p66ShcS36 phosphorylation, ROS production and cell damage. Application of specific inhibitors caused a pronounced decrease in p66ShcS36 phosphorylation only in the case of JNK1/2. Moreover, S36 phosphorylation of recombinant p66Shc by JNK1 but not PKCß was demonstrated. We further confirmed JNK1/2-dependent regulation of p66ShcS36 phosphorylation, ROS production and cell death using JNK1/2 deficient MEFs. Finally, the low ROS phenotype of JNK1/2 knockout MEFs was reversed by the phosphomimetic p66ShcS36E mutant. Inhibiting JNK1/2-regulated p66Shc activation may thus provide a therapeutic approach for the prevention of oxidative damage.

The NADase-Negative Variant of the Streptococcus pyogenes Toxin NAD⁺ Glycohydrolase Induces JNK1-Mediated Programmed Cellular Necrosis

Virulence factors are often multifunctional and contribute to pathogenesis through synergistic mechanisms. For the human pathogen Streptococcus pyogenes, two factors that act synergistically are the S. pyogenes NAD(+) glycohydrolase (SPN) and streptolysin O (SLO). Through distinct mechanisms, SLO forms pores in host cell membranes and translocates SPN into the host cell cytosol. Two natural variants of SPN exist, one that exhibits NADase activity and one that lacks this function, and both versions are translocated and act in concert with SLO to cause an accelerated death response in epithelial cells. While NADase(+) SPN is known to trigger a metabolic form of necrosis through the depletion of NAD(+), the mechanism by which NADase(-) SPN induces cell death was unknown. In the studies described here, we examined the pathway of NADase(-) cell death through analysis of activation patterns of mitogen-activated protein kinases (MAPKs). S. pyogenes infection resulted in activation of members of three MAPK subfamilies (p38, ERK, and JNK). However, only JNK was activated in an SLO-specific manner. NADase(-) SPN induced necrosis in HeLa epithelial cells associated with depolarization of mitochondrial membranes, activation of NF-κB, and the generation of reactive oxygen species. Remarkably, RNA interference (RNAi) silencing of JNK protected cells from NADase(-)-SPN-mediated necrosis, suggesting that NADase(-) SPN triggers a form of programmed necrosis dependent on JNK signaling. Taken together, these data demonstrate that SPN acts with SLO to elicit necrosis through two different mechanisms depending on its NADase activity, i.e., metabolic (NADase(+)) or programmed (NADase(-)), leading to distinct inflammatory profiles.

IMPORTANCE

Many bacterial pathogens produce toxins that alter how infected host cells interact with the immune system. For Streptococcus pyogenes, two toxins, a NAD(+) glycohydrolase (SPN) and streptolysin O (SLO), act in combination to cause infected cells to die. However, there are two natural forms of SPN, and these variants cause dying cells to produce different types of signaling molecules. The NADase(+) form of SPN kills cells by depleting reserves of NAD(+) and cellular energy. The other form of SPN lacks this activity (NADase(-)); thus, the mechanism by which this variant induces toxicity was unknown. Here, we show that infected cells recognize NADase(-) SPN through a specific signaling molecule called JNK, which causes these cells to undergo a form of cellular suicide known as programmed necrosis. This helps us to understand how different forms of toxins alter host cell signaling to help S. pyogenes cause different types of diseases.

AMPK is critical for mitochondrial function during reperfusion after myocardial ischemia

AMP-activated kinase (AMPK) is a stress responsive kinase that regulates cellular metabolism and protects against cardiomyocyte injury during ischemia-reperfusion (IR). Mitochondria play an important role in cell survival, but the specific actions of activated AMPK in maintaining mitochondrial integrity and function during reperfusion are unknown. Thus, we assessed the consequences of AMPK inactivation on heart mitochondrial function during reperfusion. Mouse hearts expressing wild type (WT) or kinase-dead (KD) AMPK were studied. Mitochondria isolated from KD hearts during reperfusion had intact membrane integrity, but demonstrated reduced oxidative capacity, increased hydrogen peroxide production and decreased resistance to mitochondrial permeability transition pore opening compared to WT. KD hearts showed increased activation of the mitogen activated protein kinase kinase 4 (MKK4) and downstream c-Jun terminal kinase (JNK) and greater necrosis during reperfusion after coronary occlusion. Transgenic expression of mitochondrial catalase (MCAT) prevented the excessive cardiac JNK activation and attenuated the increased myocardial necrosis observed during reperfusion in KD mice. Inhibition of JNK increased the resistance of KD hearts to mPTP opening, contractile dysfunction and necrosis during IR. Thus, intrinsic activation of AMPK is critical to prevent excess mitochondrial reactive oxygen production and consequent JNK signaling during reperfusion, thereby protecting against mPTP opening, irreversible mitochondrial damage and myocardial injury.

Diet-induced obesity promotes altered remodeling and exacerbated cardiac hypertrophy following pressure overload

Heart failure (HF) is the end stage of cardiovascular disease, in which hypertrophic remodeling no longer meets cardiac output demand. Established animal models of HF have provided insights into disease pathogenesis. However, these models are developed on dissimilar metabolic backgrounds from humans – patients with HF are frequently overweight or obese, whereas animal models of HF are typically lean. Thus, we aimed to develop and investigate model for cardiac hypertrophy and failure that also recapitulates the cardiometabolic state of HF in humans. We subjected mice with established diet-induced obesity (DIO) to cardiac pressure overload provoked by transverse aortic constriction (TAC). Briefly, we fed WT male mice a normal chow or high-fat diet for 10 weeks prior to sham/TAC procedures and until surgical follow-up. We then analyzed cardiac hypertrophy, mechanical function, and electrophysiology at 5–6 weeks after surgery. In DIO mice with TAC, hypertrophy and systolic dysfunction were exacerbated relative to chow TAC animals, which showed minimal remodeling with our moderate constriction intensity. Normalized heart weight was 55.8% greater and fractional shortening was 30.9% less in DIO TAC compared with chow TAC hearts. However, electrophysiologic properties were surprisingly similar between DIO sham and TAC animals. To examine molecular pathways activated by DIO and TAC, we screened prohypertrophic signaling cascades, and the exacerbated remodeling was associated with early activation of the c-Jun-N-terminal kinase (JNK1/2) signaling pathway. Thus, DIO aggravates the progression of hypertrophy and HF caused by pressure overload, which is associated with JNK1/2 signaling, and cardiometabolic state can significantly modify HF pathogenesis.

Improvement of liver injury and survival by JNK2 and iNOS deficiency in liver transplants from cardiac death mice

BACKGROUND & AIMS

Inclusion of liver grafts from cardiac death donors (CDD) would increase the availability of donor livers but is hampered by a higher risk of primary non-function. Here, we seek to determine mechanisms that contribute to primary non-function of liver grafts from CDD with the goal to develop strategies for improved function and outcome, focusing on c-Jun-N-terminal kinase (JNK) activation and mitochondrial depolarization, two known mediators of graft failure.

METHODS

Livers explanted from wild-type, inducible nitric oxide synthase knockout (iNOS(-/-)), JNK1(-/-) or JNK2(-/-) mice after 45-min aorta clamping were implanted into wild-type recipients. Mitochondrial depolarization was detected by intravital confocal microscopy in living recipients.

RESULTS

After transplantation of wild-type CDD livers, graft iNOS expression and 3-nitrotyrosine adducts increased, but hepatic endothelial NOS expression was unchanged. Graft injury and dysfunction were substantially higher in CDD grafts than in non-CDD grafts. iNOS deficiency and inhibition attenuated injury and improved function and survival of CDD grafts. JNK1/2 and apoptosis signal-regulating kinase-1 activation increased markedly in wild-type CDD grafts, which was blunted by iNOS deficiency. JNK inhibition and JNK2 deficiency, but not JNK1 deficiency, decreased injury and improved function and survival of CDD grafts. Mitochondrial depolarization and binding of phospho-JNK2 to Sab, a mitochondrial protein linked to the mitochondrial permeability transition, were higher in CDD than in non-CDD grafts. iNOS deficiency, JNK inhibition and JNK2 deficiency all decreased mitochondrial depolarization and blunted ATP depletion in CDD grafts. JNK inhibition and deficiency did not decrease 3-nitrotyrosine adducts in CDD grafts.

CONCLUSION

The iNOS-JNK2-Sab pathway promotes CDD graft failure via increased mitochondrial depolarization, and is an attractive target to improve liver function and survival in CDD liver transplantation recipients.

Protection of rat intestinal epithelial cells from ischemia/reperfusion injury by (D-Ala2, D-Leu5)-enkephalin through inhibition of the MKK7-JNK signaling pathway

Previous studies have demonstrated that (D‑Ala2, D‑Leu5)‑enkephalin (DADLE) protects rats from hepatic ischemia/reperfusion (I/R) injury. In the present study, DADLE was also observed to alleviate IR‑induced intestinal epithelial cell injury in rats by inhibiting mitogen‑activated protein kinase kinase 7 (MKK7)‑c‑Jun N‑terminal kinase (JNK) pathway signaling. To investigate the protective effect of DADLE on hypoxia/reoxygenation injury in rat intestinal epithelial cells, rat intestinal epithelial cells were treated with different concentrations of DADLE, following which the cell survival rate was determined using a tetrazolium (MTT) colorimetric assay, and apoptosis was determined using flow cytometry. To confirm whether the protective effect of DADLE was due to its effect on MKK7‑JNK signaling, the phosphorylation levels of MKK7 and JNK were analyzed using western blot analysis following treatment with different concentrations of DADLE. The results demonstrated that, following treatment with DADLE, the survival rate of the rat intestinal cells subjected to I/R‑induced injury increased significantly and the apoptotic rate decreased in a concentration‑dependent manner. In addition, the levels of phosphorylated MKK7 and JNK decreased in a concentration‑dependent manner following treatment with DADLE. Silencing the gene expression of MKK7 using small interfering RNA prior to DADLE treatment resulted in a reduction in the protective effects of DADLE on the rat intestinal epithelial cells subjected to I/R injury. Collectively, the results of the present study demonstrated that the protective effects of DADLE in I/R injury in rat intestinal cells occurred through inhibition of the MKK7‑JNK pathway.

Sub-chronic administration of LY294002 sensitizes cervical cancer cells to chemotherapy by enhancing mitochondrial JNK signaling

Chemo-sensitization is used to improve the efficacy of chemotherapeutic agents against cancers, and understanding the precise molecular mechanisms of chemo-sensitization could lead to safer and more effective approaches to treat cancer. We have previously demonstrated that mitochondrial c-Jun N-terminal Kinase (JNK) signaling is a critical component of cell death. Mitochondrial JNK signaling is coordinated on the scaffold protein Sab. In this work, we developed a sub-chronic chemo-sensitization model by exposing HeLa cells to low-dose (2 μM) LY294002. We found that this treatment increased Sab expression on mitochondria, an effect not observed in acute exposures. To examine the role of Sab in chemo-sensitization, we ectopically expressed and silenced Sab in HeLa cells. We found that elevating Sab levels in HeLa cells increased the efficacy of chemotherapeutic agents, paclitaxel and cisplatin, while silencing Sab decreased the sensitivity of cells towards these agents. The effect of Sab-mediated signaling appeared to be dependent upon mitogen dependent protein kinases (MAPKs) as ablation of Sab's MAPK-binding motifs prevented chemo-sensitization. These results suggest that mitochondrial JNK signaling is an adaptable signaling pathway that can be enhanced or restored in cancer cells to improve therapeutic efficacy.

Serum- and Glucocorticoid-Inducible Kinase 1 Confers Protection in Cell-Based and in In Vivo Neurotoxin Models via the c-Jun N-Terminal Kinase Signaling Pathway

Serum glucocorticoid kinase 1 (SGK1) has been shown to be protective in models of Parkinson's disease, but the details by which it confers benefit is unknown. The current study was designed to investigate the details by which SGK1 confers neuroprotection. To do this we employed a cellular neurodegeneration model to investigate c-Jun N-terminal kinase (JNK) signaling and endoplasmic reticulum (ER) stress induced by 6-hydroxydopamine. SGK1-expressing adenovirus was created and used to overexpress SGK1 in SH-SY5Y cells, and dexamethasone was used to increase endogenous expression of SGK1. Oxidative stress, mitochondrial dysfunction, and cell death were monitored to test the protective effect of SGK1. To investigate the effect of SGK1 overexpression in vivo, SGK1-expressing adenovirus was injected into the striatum of mice treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, and protection of dopaminergic neurons was quantitatively assessed by tyrosine hydroxylase immunohistochemistry. SGK1 overexpression was found to decrease reactive oxygen species generation, alleviate mitochondrial dysfunction, and rescue cell death in vitro and in vivo by inactivating mitogen-activated protein kinase kinase 4 (MKK4), JNK, and glycogen synthase kinase 3β (GSK3β) and thereby decreasing ER and oxidative stress. These results suggest that therapeutic strategies for activation of SGK1 may have the potential to be neuroprotective by deactivating the JNK and GSK3β pathways.

Structural basis and biological consequences for JNK2/3 isoform selective aminopyrazoles

Three JNK isoforms, JNK1, JNK2, and JNK3 have been reported and unique biological function has been ascribed to each. It is unknown if selective inhibition of these isoforms would confer therapeutic or safety benefit. To probe JNK isoform function we designed JNK2/3 inhibitors that have >30-fold selectivity over JNK1. Utilizing site-directed mutagenesis and x-ray crystallography we identified L144 in JNK3 as a key residue for selectivity. To test whether JNK2/3 selective inhibitors protect human dopaminergic neurons against neurotoxin-induced mitochondrial dysfunction, we monitored reactive oxygen species (ROS) generation and mitochondrial membrane potential (MMP). The results showed that JNK2/3 selective inhibitors protected against 6-hydroxydopamine-induced ROS generation and MMP depolarization. These results suggest that it was possible to develop JNK2/3 selective inhibitors and that residues in hydrophobic pocket I were responsible for selectivity. Moreover, the findings also suggest that inhibition of JNK2/3 likely contributed to protecting mitochondrial function and prevented ultimate cell death.