Myocardial Energy Stress, Autophagy Induction, and Cardiomyocyte Functional Responses

Surveying the Therapeutic Potentials of Isoliquiritigenin (ISL): A Comprehensive Review

Isoliquiritigenin (ISL), a major chalcone-type flavonoid produced predominantly from liquorice roots (Glycyrrhiza species), has exceptional therapeutic potential across a wide range of pharmacological activities. ISL has numerous benefits including antioxidant, anti-inflammatory, antidiabetic, cardioprotective, hepatoprotective, neuroprotective, and anticancer activities. This review gathers the pharmacological effects of ISL remarking into its mechanism of actions such as how it modulates oxidative stress, inflammatory pathways, glucose metabolism, and cancer growth, demonstrating its pharmacological versatility. The review emphasizes new advances in the field, allowing for more rational development and clinical use of ISL in medicine. However, further research is required to confirm the target-organ toxicity or side-effect investigations.

Caveolin-3: therapeutic target for diabetic myocardial ischemia/reperfusion injury

Myocardial ischemia/reperfusion (I/R) injury is a major global health problem with high rates of mortality and disability, which is more severe in patients with diabetes. Substantial researches have documented that diabetic myocardium are more susceptible to I/R injury, but many current intervention strategies against myocardial I/R injury have limited effectiveness in diabetic hearts. Caveolin-3 (Cav-3) is the signature protein of caveolae and serves as a signal integration and transduction platform in the plasma membrane of cardiomyocytes, which plays a vital role in myocardial functions, metabolism and protection of multiple conditioning strategies against I/R injury. Nevertheless, numerous studies have revealed that the expression of Cav-3 is impaired in diabetic hearts, which contributes to increased vulnerability of myocardium to I/R injury and resistance to protective conditioning strategies. In this review, we outline the basic structure and function of Cav-3, emphatically present the unique role of Cav-3 as a signal integration and transduction element in diabetic myocardial I/R injury and discuss its therapeutic perspective in strategies against myocardial I/R injury in diabetes.

Jellyfish stings-induced cardiac failure was ameliorated through AAG-mediated glycogen-driven ATP production

Jellyfish stings have become a common injury among fishermen and divers. Severe jellyfish stings could worsen cardiac function and even cause cardiac complications, ultimately leading to cardiac failure (CF). Currently, there are no effective drugs available. Single cell sequencing revealed alpha-1 acid glycoprotein (AAG), an energy regulatory protein targeting to glycogen, was highly expressed in jellyfish stings-induced CF patients. However, the mechanism remains elusive. It is postulated that AAG could increase glycogen metabolism, protecting against jellyfish stings-induced CF. AAG deletion exacerbated CF, while exogenous and endogenous AAG ameliorated CF. AAG also rescued the decline triggered by the AAG knockout (KO). Intriguingly, AAG improved cardiac function and metabolic adaptation by glycogen-driven ATP production, shifting mitochondrial/glycolytic ATP production towards glycolysis. Sorted by single-cell RNA sequencing and spatial transcription technology, CC-chemokine receptor 5 (CCR5) and Peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α) were differentially expressed. Mechanistically, CCR5 inhibitor MVC abolished AAG's protective effect and PGC-1α overexpression. Collectively, jellyfish stings-induced CF was ameliorated through AAG-mediated glycogen-driven ATP production, promoting glycolytic/mitochondrial metabolic switches to rely energetically primarily on glycolysis, which might serve as a therapeutic target of CF.

Role of glycogen in cardiac metabolic stress

Metabolic stress in the myocardium arises from a diverse array of acute and chronic pathophysiological contexts. Glycogen mishandling is a key feature of metabolic stress, while maladaptation in energy-stress situations confers functional deficits. Cardiac glycogen serves as a pivotal reserve for myocardial energy, which is classically described as an energy source and contributes to glucose homeostasis during hypoxia or ischemia. Despite extensive research activity, how glycogen metabolism affects cardiovascular disease remains unclear. In this review, we focus on its regulation across myocardial energy metabolism in response to stress, and its role in metabolism, immunity, and autophagy. We further summarize the cardiovascular-related drugs regulating glycogen metabolism. In this way, we provide current knowledge for the understanding of glycogen metabolism in the myocardium.

Fuzi Polysaccharide Isolated from Aconitum Carmichaeli Protects Against Liquid Nitrogen Cryopreservation-Induced Damage in Rat Abdominal Aorta by Enhancing Autophagy

BACKGROUND

To investigate the potential protective mechanisms of aconite polysaccharide (fuzi polysaccharide [FZPS-1]) during cryopreservation, with a particular emphasis on morphological changes in autophagy in rat abdominal aorta.

METHODS

Thirty-six male standard deviation rats were divided into the control group, the cryopreserved model group, and the FZPS-1 intervention group treated with different concentrations of FZPS-1. The structural changes of the abdominal aortic wall were assessed via Masson staining, while cytolysosomes were identified using transmission electron microscope (TEM). The expression of Beclin-1, microtubule-associated protein 1A/1B-light chain 3 (LC3)-II, and P62 was detected by immunohistochemistry and western blot separately. Bcl-2 and Bax messenger RNA (mRNA) expression was measured by RT-qPCR.

RESULTS

Compared with the control group, the abdominal aortic wall in the model group was severely damaged. Contrarily, FZPS-1 10 mg/mL and 20 mg/mL groups had relatively normal structure of the blood vessel wall, higher cytolysosome counts, and increased Beclin-1 and LC3-II expression compared with the model group (all P < 0.05); P62 expression also increased in the FZPS-1 20 mg/mL group (P < 0.05). Compared with the control group, the mRNA expression of Bcl-2 in the cryopreservation model group was reduced (P < 0.05), while Bax was increased (P < 0.05). Compared with the cryopreservation model group, the mRNA expression of Bcl-2 was upregulated, while Bax was downregulated in the farnesyl pyrophosphate synthase 10 mg/L group (P < 0.05).

CONCLUSION

During liquid nitrogen cryopreservation, autophagy is inhibited in the rat abdominal aorta, and the blood vessel wall structure is damaged. FZPS-1, as a cryoprotectant, can enhance autophagy and mitigate blood vessel wall damage in the rat abdominal aorta.

Overview of Panax ginseng and its active ingredients protective mechanism on cardiovascular diseases

ETHNIC PHARMACOLOGICAL RELEVANCE

Panax ginseng is a traditional Chinese herbal medicine used to treat cardiovascular diseases (CVDs), and it is still widely used to improve the clinical symptoms of various CVDs. However, there is currently a lack of summary and analysis on the mechanism of Panax ginseng exerts its cardiovascular protective effects. This article provides a review of in vivo and in vitro pharmacological studies on Panax ginseng and its active ingredients in reducing CVDs damage.

AIM OF THIS REVIEW

This review summarized the latest literature on Panax ginseng and its active ingredients in CVDs research, aiming to have a comprehensive and in-depth understanding of the cardiovascular protection mechanism of Panax ginseng, and to provide new ideas for the treatment of CVDs, as well as to optimize the clinical application of Panax ginseng.

METHODS

Enrichment of pathways and biological terms using the traditional Chinese medicine molecular mechanism bioinformatics analysis tool (BATMAN-TCM). The literature search is based on electronic databases such as PubMed, ScienceDirect, Scopus, CNKI, with a search period of 2002-2023. The search terms include Panax ginseng, Panax ginseng ingredients, ginsenosides, ginseng polysaccharides, ginseng glycoproteins, ginseng volatile oil, CVDs, heart, and cardiac.

RESULTS

132 articles were ultimately included in the review. The ingredients in Panax ginseng that manifested cardiovascular protective effects are mainly ginsenosides (especially ginsenoside Rb1). Ginsenosides protected against CVDs such as ischemic reperfusion injury, atherosclerosis and heart failure mainly through improving energy metabolism, inhibiting hyper-autophagy, antioxidant, anti-inflammatory and promoting secretion of exosomes.

CONCLUSION

Panax ginseng and its active ingredients have a particularly prominent effect on improving myocardial energy metabolism remodeling in protecting against CVDs. The AMPK and PPAR signaling pathways are the key targets through which Panax ginseng produces multiple mechanisms of cardiovascular protection. Extracellular vesicles and nanoparticles as carriers are potential delivery ways for optimizing the bioavailability of Panax ginseng and its active ingredients.

Energy metabolism: from physiological changes to targets in sepsis-induced cardiomyopathy

Sepsis is a systemic inflammatory response syndrome caused by a variety of dysregulated responses to host infection with life-threatening multi-organ dysfunction. Among the injuries or dysfunctions involved in the course of sepsis, cardiac injury and dysfunction often occur and are associated with the pathogenesis of hemodynamic disturbances, also defined as sepsis-induced cardiomyopathy (SIC). The process of myocardial metabolism is tightly regulated and adapts to various cardiac output demands. The heart is a metabolically flexible organ capable of utilizing all classes of energy substrates, including carbohydrates, lipids, amino acids, and ketone bodies, to produce ATP. The demand of cardiac cells for energy metabolism changes substantially in septic cardiomyopathy, with distinct etiological causes and different times. This review describes changes in cardiomyocyte energy metabolism under normal physiological conditions and some features of myocardial energy metabolism in septic cardiomyopathy and briefly outlines the role of the mitochondria as a center of energy metabolism in the septic myocardium, revealing that changes in energy metabolism can serve as a potential future therapy for infectious cardiomyopathy.

The study on the role of O-GlcNAcylation of SIRT3 in regulating mitochondrial oxidative stress during simulate myocardial ischemia-reperfusion

Myocardial ischemia-reperfusion injury (MIRI) is a significant complication following reperfusion therapy after myocardial infarction. Mitochondrial oxidative stress is a critical factor in MIRI, and Sirtuin 3 (SIRT3), as a major mitochondrial deacetylase, plays a key protective role, with its activity potentially regulated by O-GlcNAcylation. This study used the H9C2 cell line to establish a simulated ischemia/reperfusion (SI/R) model, we utilized co-immunoprecipitated to validate the relationship between O-GlcNAc transferase (OGT) and SIRT3, demonstrated SIRT3 O-GlcNAcylation sites through LC-MS/MS, and performed site mutations using CRISPR/Cas9 technology. The results were validated using immunoblotting. SIRT3 and superoxide dismutase 2 (SOD2) activities were detected using a fluorometric assay, while mitochondrial reactive oxygen species (MROS) levels and cellular apoptosis were assessed using immunofluorescence. We have identified an interaction between SIRT3 and OGT, where SIRT3 undergoes dynamic O-GlcNAcylation at the S190 site, facilitating SIRT3 deacetylase activity. During SI/R, elevated levels of O-GlcNAcylation activate SOD2 by promoting SIRT3 enzyme activity, thereby inhibiting excessive MROS production. This significantly mitigates the occurrence of malignant autophagy in myocardial cells during reperfusion, promoting their survival. Conversely, blocking SIRT3 O-GlcNAcylation at the S190 site exacerbates SI/R injury. We demonstrate that O-GlcNAcylation is a crucial post-translational modification (PTM) of SIRT3 during SI/R, shedding light on a promising mechanism for future therapeutic approaches.

Perfluoroalkyl sulfonate induces cardiomyocyte apoptosis via endoplasmic reticulum stress activation and autophagy flux inhibition

Perfluoroalkyl sulfonate (PFOS) is a commonly used chemical compound that often found in materials such as waterproofing agents, food packaging, and fire retardants. Known for its stability and persistence in the environment, PFOS can enter the human body through various pathways, including water and the food chain, raising concerns about its potential harm to human health. Previous studies have suggested a cardiac toxicity of PFOS, but the specific cellular mechanisms remained unclear. Here, by using AC16 cardiomyocyte as a model to investigate the molecular mechanisms potential the cardiac toxicity of PFOS. Our findings revealed that PFOS exposure reduced cell viability and induces apoptosis in human cardiomyocyte. Proteomic analysis and molecular biological techniques showed that the Endoplasmic Reticulum (ER) stress-related pathways were activated, while the cellular autophagy flux was inhibited in PFOS-exposed cells. Subsequently, we employed strategies such as autophagy activation and ER stress inhibition to alleviate the PFOS-induced apoptosis in AC16 cells. These results collectively suggest that PFOS-induced ER stress activation and autophagy flux inhibition contribute to cardiomyocyte apoptosis, providing new insights into the mechanisms of PFOS-induced cardiomyocyte toxicity.

Targeting NF-κB in Hepatic Ischemia-Reperfusion Alleviation: from Signaling Networks to Therapeutic Targeting

Hepatic ischemia-reperfusion injury (HIRI) is a major complication of liver trauma, resection, and transplantation that can lead to liver dysfunction and failure. Scholars have proposed a variety of liver protection methods aimed at reducing ischemia-reperfusion damage, but there is still a lack of effective treatment methods, which urgently needs to find new effective treatment methods for patients. Many studies have reported that signaling pathway plays a key role in HIRI pathological process and liver function recovery mechanism, among which nuclear transfer factor-κB (NF-κB) signaling pathway is one of the signal transduction closely related to disease. NF-κB pathway is closely related to HIRI pathologic process, and inhibition of this pathway can delay oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction. In addition, NF-κB can also interact with PI3K/Akt, MAPK, and Nrf2 signaling pathways to participate in HIRI regulation. Based on the role of NF-κB pathway in HIRI, it may be a potential target pathway for HIRI. This review emphasizes the role of inhibiting the NF-κB signaling pathway in oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction in HIRI, as well as the effects of related drugs or inhibitors targeting NF-κB on HIRI. The objective of this review is to elucidate the role and mechanism of NF-κB pathway in HIRI, emphasize the important role of NF-κB pathway in the prevention and treatment of HIRI, and provide a theoretical basis for the target NF-κB pathway as a therapy for HIRI.

Crosstalk among Reactive Oxygen Species, Autophagy and Metabolism in Myocardial Ischemia and Reperfusion Stages

Myocardial ischemia is the most common cardiovascular disease. Reperfusion, an important myocardial ischemia tool, causes unexpected and irreversible damage to cardiomyocytes, resulting in myocardial ischemia/reperfusion (MI/R) injury. Upon stress, especially oxidative stress induced by reactive oxygen species (ROS), autophagy, which degrades the intracellular energy storage to produce metabolites that are recycled into metabolic pathways to buffer metabolic stress, is initiated during myocardial ischemia and MI/R injury. Excellent cardioprotective effects of autophagy regulators against MI and MI/R have been reported. Reversing disordered cardiac metabolism induced by ROS also exhibits cardioprotective action in patients with myocardial ischemia. Herein, we review current knowledge on the crosstalk between ROS, cardiac autophagy, and metabolism in myocardial ischemia and MI/R. Finally, we discuss the possible regulators of autophagy and metabolism that can be exploited to harness the therapeutic potential of cardiac metabolism and autophagy in the diagnosis and treatment of myocardial ischemia and MI/R.

SIRT1 is a regulator of autophagy: Implications for the progression and treatment of myocardial ischemia-reperfusion

SIRT1 is a highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent histone deacetylase. It is involved in the regulation of various pathophysiological processes, including cell proliferation, survival, differentiation, autophagy, and oxidative stress. Therapeutic activation of SIRT1 protects the heart and cardiomyocytes from pathology-related stress, particularly myocardial ischemia/reperfusion (I/R). Autophagy is an important metabolic pathway for cell survival during energy or nutrient deficiency, hypoxia, or oxidative stress. Autophagy is a double-edged sword in myocardial I/R injury. The activation of autophagy during the ischemic phase removes excess metabolic waste and helps ensure cardiomyocyte survival, whereas excessive autophagy during reperfusion depletes the cellular components and leads to autophagic cell death. Increasing research on I/R injury has indicated that SIRT1 is involved in the process of autophagy and regulates myocardial I/R. SIRT1 regulates autophagy through various pathways, such as the deacetylation of FOXOs, ATGs, and LC3. Recent studies have confirmed that SIRT1-mediated autophagy plays different roles at different stages of myocardial I/R injury. By targeting the mechanism of SIRT1-mediated autophagy at different stages of I/R injury, new small-molecule drugs, miRNA activators, or blockers can be developed. For example, resveratrol, sevoflurane, quercetin, and melatonin in the ischemic stage, coptisine, curcumin, berberine, and some miRNAs during reperfusion, were involved in regulating the SIRT1-autophagy axis, exerting a cardioprotective effect. Here, we summarize the possible mechanisms of autophagy regulation by SIRT1 in myocardial I/R injury and the related molecular drug applications to identify strategies for treating myocardial I/R injury.

Broadening horizons: The role of ferroptosis in myocardial ischemia-reperfusion injury

Ferroptosis is a novel type of regulated cell death (RCD) discovered in recent years, where abnormal intracellular iron accumulation leads to the onset of lipid peroxidation, which further leads to the disruption of intracellular redox homeostasis and triggers cell death. Iron accumulation with lipid peroxidation is considered a hallmark of ferroptosis that distinguishes it from other RCDs. Myocardial ischemia-reperfusion injury (MIRI) is a process of increased myocardial cell injury that occurs during coronary reperfusion after myocardial ischemia and is associated with high post-infarction mortality. Multiple experiments have shown that ferroptosis plays an important role in MIRI pathophysiology. This review systematically summarized the latest research progress on the mechanisms of ferroptosis. Then we report the possible link between the occurrence of MIRI and ferroptosis in cardiomyocytes. Finally, we discuss and analyze the related drugs that target ferroptosis to attenuate MIRI and its action targets, and point out the shortcomings of the current state of relevant research and possible future research directions. It is hoped to provide a new avenue for improving the prognosis of the acute coronary syndrome.

Roles of pigment epithelium-derived factor in cardiomyocytes: implications for use as a cardioprotective therapeutic

OBJECTIVES

Cardiovascular diseases are the leading cause of death worldwide, with patients having limited options for treatment. Pigment epithelium-derived factor (PEDF) is an endogenous multifunctional protein with several mechanisms of action. Recently, PEDF has emerged as a potential cardioprotective agent in response to myocardial infarction. However, PEDF is also associated with pro-apoptotic effects, complicating its role in cardioprotection. This review summarises and compares knowledge of PEDF's activity in cardiomyocytes with other cell types and draws links between them. Following this, the review offers a novel perspective of PEDF's therapeutic potential and recommends future directions to understand the clinical potential of PEDF better.

KEY FINDINGS

PEDF's mechanisms as a pro-apoptotic and pro-survival protein are not well understood, despite PEDF's implication in several physiological and pathological activities. However, recent evidence suggests that PEDF may have significant cardioprotective properties mediated by key regulators dependent on cell type and context.

CONCLUSIONS

While PEDF's cardioprotective activity shares some key regulators with its apoptotic activity, cellular context and molecular features likely allow manipulation of PEDF's cellular activity, highlighting the importance of further investigation into its activities and its potential to be applied as a therapeutic to mitigate damage from a range of cardiac pathologies.

Co-exposure to arsenic and fluoride to explore the interactive effect on oxidative stress and autophagy in myocardial tissue and cell

Co-contamination of arsenic and fluoride is widely distributed in groundwater. However, little is known about the interactively influence of arsenic and fluoride, especially the combined mechanism in cardiotoxicity. Cellular and animal models exposure to arsenic and fluoride were established to assess the oxidative stress and autophagy mechanism of cardiotoxic damage using the factorial design, a widely used statistical method for assessing two factor interventions. In vivo, combined exposure to high arsenic (50 mg/L) and high fluoride (100 mg/L) induced myocardial injury. The damage is accompanied by accumulation of myocardial enzyme, mitochondrial disorder, and excessive oxidative stress. Further experiment identified that arsenic and fluoride induced the accumulation of autophagosome and increased expression level of autophagy related genes during the cardiotoxicity process. These findings were further demonstrated through the in vitro model of arsenic and fluoride-treated the H9c2 cells. Additionally, combined of arsenic-fluoride exposure possesses the interactively influence on oxidative stress and autophagy, contributing to the myocardial cell toxicity. In conclusion, our data suggest that oxidative stress and autophagy are involved in the process of cardiotoxic injury, and that these indicators showed interaction effect in response to the combined exposure of arsenic and fluoride.

Targeting Energy Protection as a Novel Strategy to Disclose Di'ao Xinxuekang against the Cardiotoxicity Caused by Doxorubicin

Doxorubicin (DOX) can induce myocardial energy metabolism disorder and further worsen heart failure. "Energy protection" is proposed as a new cardiac protection strategy. Previous studies have found that Di'ao Xinxuekang (DXXK) can improve doxorubicin-induced cardiotoxicity in mice by inhibiting ferroptosis. However, there are very few studies associating DXXK and energy protection. This study aims to explore the "energy protection" effect of DXXK on cardiotoxicity induced by DOX. A DOX-induced cardiotoxicity model established in rats and H9c2 cells are used to analyze the therapeutic effects of DXXK on serum indexes, cardiac function indexes and cardiac histopathology. The metabonomic methods were used to explore the potential mechanism of DXXK in treating DOX-induced cardiotoxicity. In addition, we also observed the mitochondrial- and autophagy-related indicators of myocardial cells and the mRNA expression level of the core target regulating energy-metabolism-related pathways. Our results indicated that DXXK can improve cardiac function, reduce myocardial enzymes and alleviate the histological damage of heart tissue caused by DOX. In addition, DXXK can improve mitochondrial damage induced by DOX and inhibit excessive autophagy. Metabonomics analysis showed that DOX can significantly affects the pathways related to energy metabolism of myocardial cells, which are involved in the therapeutic mechanism of DXXK. In conclusion, DXXK can treat DOX-induced cardiotoxicity through the AMPK-mediated energy protection pathway.

Protective Effect of Natural Medicinal Plants on Cardiomyocyte Injury in Heart Failure: Targeting the Dysregulation of Mitochondrial Homeostasis and Mitophagy

Heart failure occurs because of various cardiovascular pathologies, such as coronary artery disease or cardiorenal syndrome, eventually reaching end-stage disease. Various factors contribute to cardiac structural or functional changes that result in systolic or diastolic dysfunction. Several studies have confirmed that the key factor in heart failure progression is myocardial cell death, and mitophagy is the major mechanism regulating myocardial cell death in heart failure. The clinical mechanisms of heart failure are well understood in practice. However, the essential role of mitophagic regulation in heart failure has only recently received widespread attention. Receptor-mediated mitophagy is involved in various mitochondrial processes like oxidative stress injury, energy metabolism disorders, and calcium homeostasis, which are also the main causes of heart failure. Understanding of the diverse regulatory mechanisms in mitophagy and the complexity of its pathophysiology in heart failure remains incomplete. Related studies have found that various natural medicinal plants and active ingredients, such as flavonoids and saponins, can regulate mitophagy to a certain extent, improve myocardial function, and protect myocardial cells. This review comprehensively covers the relevant mechanisms of different types of mitophagy in regulating heart failure pathology and controlling mitochondrial adaptability to stress injury. Further, it explores the relationship between mitophagy and cardiac ejection dysfunction. Natural medicinal plant-targeted regulation strategies and scientific evidence on mitophagy were provided to elucidate current and potential strategies to apply mitophagy-targeted therapy for heart failure.

Sphingosine-1-phosphate in mitochondrial function and metabolic diseases

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite. The past decade has witnessed exponential growth in the field of S1P research, partly attributed to drugs targeting its receptors or kinases. Accumulating evidence indicates that changes in the S1P axis (i.e., S1P production, transport, and receptors) may modify metabolism and eventually mediate metabolic diseases. Dysfunction of the mitochondria on a master monitor of cellular metabolism is considered the leading cause of metabolic diseases, with aberrations typically induced by abnormal biogenesis, respiratory chain complex disorders, reactive oxygen species overproduction, calcium deposition, and mitophagy impairment. Accordingly, we discuss decades of investigation into changes in the S1P axis and how it controls mitochondrial function. Furthermore, we summarize recent scientific advances in disorders associated with the S1P axis and their involvement in the pathogenesis of metabolic diseases in humans, including type 2 diabetes mellitus and cardiovascular disease, from the perspective of mitochondrial function. Finally, we review potential challenges and prospects for S1P axis application to the regulation of mitochondrial function and metabolic diseases; these data may provide theoretical guidance for the treatment of metabolic diseases.

Glycogen-autophagy: Molecular machinery and cellular mechanisms of glycophagy

Autophagy is an essential cellular process involving degradation of superfluous or defective macromolecules and organelles as a form of homeostatic recycling. Initially proposed to be a “bulk” degradation pathway, a more nuanced appreciation of selective autophagy pathways has developed in the literature in recent years. As a glycogen-selective autophagy process, “glycophagy” is emerging as a key metabolic route of transport and delivery of glycolytic fuel substrate. Study of glycophagy is at an early stage. Enhanced understanding of this major noncanonical pathway of glycogen flux will provide important opportunities for new insights into cellular energy metabolism. In addition, glycogen metabolic mishandling is centrally involved in the pathophysiology of several metabolic diseases in a wide range of tissues, including the liver, skeletal muscle, cardiac muscle, and brain. Thus, advances in this exciting new field are of broad multidisciplinary interest relevant to many cell types and metabolic states. Here, we review the current evidence of glycophagy involvement in homeostatic cellular metabolic processes and of molecular mediators participating in glycophagy flux. We integrate information from a variety of settings including cell lines, primary cell culture systems, ex vivo tissue preparations, genetic disease models, and clinical glycogen disease states.

Pharmacological inhibition of arachidonate 12-lipoxygenase ameliorates myocardial ischemia-reperfusion injury in multiple species

Myocardial ischemia-reperfusion (MIR) injury is a major cause of adverse outcomes of revascularization after myocardial infarction. To identify the fundamental regulator of reperfusion injury, we performed metabolomics profiling in plasma of individuals before and after revascularization and identified a marked accumulation of arachidonate 12-lipoxygenase (ALOX12)-dependent 12-HETE following revascularization. The potent induction of 12-HETE proceeded by reperfusion was conserved in post-MIR in mice, pigs, and monkeys. While genetic inhibition of Alox12 protected mouse hearts from reperfusion injury and remodeling, Alox12 overexpression exacerbated MIR injury. Remarkably, pharmacological inhibition of ALOX12 significantly reduced cardiac injury in mice, pigs, and monkeys. Unexpectedly, ALOX12 promotes cardiomyocyte injury beyond its enzymatic activity and production of 12-HETE but also by its suppression of AMPK activity via a direct interaction with its upstream kinase TAK1. Taken together, our study demonstrates that ALOX12 is a novel AMPK upstream regulator in the post-MIR heart and that it represents a conserved therapeutic target for the treatment of myocardial reperfusion injury.

Uhrf1 regulates H3K9me2 modification of mTOR to inhibit the effect of autophagy in myocardial ischemia-reperfusion injury

The regulation of mTOR and the dimethylation of histone H3 on lysine 9 (H3K9me2) H3K9me2 by Uhrf1 and the mechanism of autophagy regulation in myocardial ischemia-reperfusion injury (MIRI) were studied in vivo and in vitro.

An in vitro I/R injury model was established using the primary mouse cardiomyocytes treated with H₂O₂. Subsequent analysis by qRT-PCR, western blot, and immunofluorescence indicated that overexpression of Uhrf1 significantly inhibited apoptosis of the H₂O₂-treated cardiomyocytes, reduced expression of apoptosis factors caspase-3 and Bax, and increased expression of apoptosis inhibitory factor Bcl-2. Furthermore, Uhrf1 was found to increase cardiomyocyte proliferation and promote the expression of mTOR, while the four expression peaks of H3K9me2 on the mTOR gene were inhibited by overexpression of Uhrf1. The expression of autophagy factors LC3, Beclin-1, and p-mTOR in Uhrf1-overexpressed cardiomyocytes was dramatically increased, and P62 expression was dramatically decreased. When an H3K9me2 inhibitor was added to the Uhrf1-knockdown cardiomyocytes, the expression of mTOR was increased, the expression of LC3, Beclin-1, and p-mTOR was decreased, and P62 expression was significantly increased.

In the present study, Uhrf1 exhibits a protective function in MIRI, reducing the apoptosis of cardiomyocytes while increasing their proliferation and viability.

Granulocyte-colony stimulating factor gene therapy as a novel therapeutics for stroke in a mouse model

Background

Global ischemia is the resulting effect of a cardiopulmonary arrest (CPA). Presently there is no effective treatment to address neurological deficits in patients who survived a CPA. Granulocyte-colony stimulating factor is a growth factor (G-CSF) with a plethora of beneficial effects, including neuroprotection. Clinical application of human G-CSF (hG-CSF) is limited due to its plasma half-life of 4 h. Therefore, novel approaches need to be investigated that would (1) enable prolonged manifestation of hG-CSF and (2) demonstrate G-CSF efficacy from studying the underlying protective mechanisms of hG-CSF. In our previous work, we used the self-complementary adeno-associated virus (stereotype2: scAAV2) as a vector to transfect the hG-CSF gene into the global ischemic brain of a mouse. As an extension of that work, we now seek to elucidate the protective mechanisms of hG-CSF gene therapy against endoplasmic reticulum induced stress, mitochondrial dynamics and autophagy in global ischemia.

Method

A single drop of either AAV-CMV-hG-CSF or AAV-CMV-GFP was dropped into the conjunctival sac of the Swiss Webster mouse’s left eye, 30–60 min after bilateral common artery occlusion (BCAO). The efficacy of the expressed hG-CSF gene product was analyzed by monitoring the expression levels of endoplasmic reticulum stress (ER), mitochondrial dynamics and autophagic proteins over 4- and 7-days post-BCAO in vulnerable brain regions including the striatum, overlying cortex (frontal brain regions) and the hippocampus (middle brain regions). Statistical analysis was performed using mostly One-Way Analysis of variance (ANOVA), except for behavioral analysis, which used Repeated Measures Two-Way ANOVA, post hoc analysis was performed using the Tukey test.

Results

Several biomarkers that facilitated cellular death, including CHOP and GRP78 (ER stress) DRP1 (mitochondrial dynamics) and Beclin 1, p62 and LC3-ll (autophagy) were significantly downregulated by hG-CSF gene transfer. hG-CSF gene therapy also significantly upregulated antiapoptotic Bcl2 while downregulating pro-apoptotic Bax. The beneficial effects of hG-CSF gene therapy resulted in an overall improvement in functional behavior.

Conclusion

Taken together, this study has substantiated the approach of sustaining the protein expression of hG-CSF by eye drop administration of the hG-CSF gene. In addition, the study has validated the efficacy of using hG-CSF gene therapy against endoplasmic reticulum induced stress, mitochondrial dynamics and autophagy in global ischemia.

Recent advances in understanding glucose transport and glucose disposal

Deficient glucose transport and glucose disposal are key pathologies leading to impaired glucose tolerance and risk of type 2 diabetes.  The cloning and identification of the family of facilitative glucose transporters have helped to identify that underlying mechanisms behind impaired glucose disposal, particularly in muscle and adipose tissue.  There is much more than just transporter protein concentration that is needed to regulate whole body glucose uptake and disposal.  The purpose of this review is to discuss recent findings in whole body glucose disposal.  We hypothesize that impaired glucose uptake and disposal is a consequence of mismatched energy input and energy output.  Decreasing the former while increasing the latter is key to normalizing glucose homeostasis.

Protective Role of mTOR in Liver Ischemia/Reperfusion Injury: Involvement of Inflammation and Autophagy

Liver ischemia/reperfusion (IR) injury is a common phenomenon after liver resection and transplantation, which often results in liver graft dysfunction such as delayed graft function and primary nonfunction. The mammalian target of rapamycin (mTOR) is an evolutionarily highly conserved serine/threonine protein kinase, which coordinates cell growth and metabolism through sensing environmental inputs under physiological or pathological conditions, involved in the pathophysiological process of IR injury. In this review, we mainly present current evidence of the beneficial role of mTOR in modulating inflammation and autophagy under liver IR to provide some evidence for the potential therapies for liver IR injury.

mTOR and Beclin1: Two key autophagy-related molecules and their roles in myocardial ischemia/reperfusion injury

Autophagy is the general term of lysosomal degradation of substances in cells, which is considered the key to maintaining the normal structure and function of the heart. It also has a correlation with several heart diseases, in particular, myocardial ischemia/reperfusion (I/R) injury. At the stage of myocardial ischemia, autophagy degrades nonfunctional cytoplasmic proteins providing the critical nutrients for the critical life activities, thereby suppressing cell apoptosis and necrosis. However, autophagy is likely to affect the heart negatively in the reperfusion stage. Mammalian target of rapamycin (mTOR) and Beclin1 are two vital autophagy-related molecules in myocardial I/R injury playing significant roles in different stages. In the ischemia stage, mTOR plays its roles through AMPK/mTOR and phosphoinositide 3-kinase/Akt/mTOR pathway, whereas Beclin1 plays its roles through its upregulation in the reperfusion stage. A possible interaction between mTOR and Beclin1 has been reported recently, and further studies need to be done to find the underlying interaction between the two molecules in myocardial I/R injury.