AMP-Activated Protein Kinase α2 in Neutrophils Regulates Vascular Repair via Hypoxia-Inducible Factor-1α and a Network of Proteins Affecting Metabolism and Apoptosis

Mechanochemically Reprogrammed Interface Orchestrates Neutrophil Bactericidal Activity and Apoptosis for Preventing Implant-Associated Infection

The onset of implant-associated infection (IAI) triggers a cascade of immune responses, which are initially dominated by neutrophils. Bacterial aggregate formation and hypoxic microenvironment, which occur shortly after implantation, may be two major risk factors that impair neutrophil function and lead to IAI. Here, the implant surface with phytic acid-Zn2+ coordinated TiO2 nanopillar arrays (PA-Zn@TiNPs) and oxygen self-supporting CaO2 nanoparticles, named as CPZTs, is mechanochemically reprogrammed. The engineered CPZTs interface integrates multiple properties to inhibit the formation of nascent biofilm, encompassing antibacterial adhesion, mechanobactericidal effect, and chemobiocidal effect. Meanwhile, continuous oxygenation fuels the neutrophils with reactive oxygen species (ROS) for efficient bacterial elimination on the implant surface and inside the neutrophils. Furthermore, this surface modulation strategy accelerates neutrophil apoptosis and promotes M2 macrophage-mediated osteogenesis both in vitro and in a rat model of IAI. In conclusion, targeting neutrophils for immunomodulation is a practical and effective strategy to prevent IAI and promote bone-implant integration.

Role of the soluble epoxide hydrolase in keratinocyte proliferation and sensitivity of skin to inflammatory stimuli

The lipid content of skin plays a determinant role in its barrier function with a particularly important role attributed to linoleic acid and its derivatives. Here we explored the consequences of interfering with the soluble epoxide hydrolase (sEH) on skin homeostasis. sEH; which converts fatty acid epoxides generated by cytochrome P450 enzymes to their corresponding diols, was largely restricted to the epidermis which was enriched in sEH-generated diols. Global deletion of the sEH increased levels of epoxides, including the linoleic acid-derived epoxide; 12,13-epoxyoctadecenoic acid (12,13-EpOME), and increased basal keratinocyte proliferation. sEH deletion (sEH-/- mice) resulted in thicker differentiated spinous and corneocyte layers compared to wild-type mice, a hyperkeratosis phenotype that was reproduced in wild-type mice treated with a sEH inhibitor. sEH deletion made the skin sensitive to inflammation and sEH-/- mice developed thicker imiquimod-induced psoriasis plaques than the control group and were more prone to inflammation triggered by mechanical stress with pronounced infiltration and activation of neutrophils as well as vascular leak and increased 12,13-EpOME and leukotriene (LT) B4 levels. Topical treatment of LTB4 antagonist after stripping successfully inhibited inflammation and neutrophil infiltration both in wild type and sEH-/- skin. While 12,13-EpoME had no effect on the trans-endothelial migration of neutrophils, like LTB4, it effectively induced neutrophil adhesion and activation. These observations indicate that while the increased accumulation of neutrophils in sEH-deficient skin could be attributed to the increase in LTB4 levels, both 12,13-EpOME and LTB4 contribute to neutrophil activation. Our observations identify a protective role of the sEH in the skin and should be taken into account when designing future clinical trials with sEH inhibitors.

AMPK-HIF-1α signaling enhances glucose-derived de novo serine biosynthesis to promote glioblastoma growth

BACKGROUND

Cancer cells undergo cellular adaptation through metabolic reprogramming to sustain survival and rapid growth under various stress conditions. However, how brain tumors modulate their metabolic flexibility in the naturally serine/glycine (S/G)-deficient brain microenvironment remain unknown.

METHODS

We used a range of primary/stem-like and established glioblastoma (GBM) cell models in vitro and in vivo. To identify the regulatory mechanisms of S/G deprivation-induced metabolic flexibility, we employed high-throughput RNA-sequencing, transcriptomic analysis, metabolic flux analysis, metabolites analysis, chromatin immunoprecipitation (ChIP), luciferase reporter, nuclear fractionation, cycloheximide-chase, and glucose consumption. The clinical significances were analyzed in the genomic database (GSE4290) and in human GBM specimens.

RESULTS

The high-throughput RNA-sequencing and transcriptomic analysis demonstrate that the de novo serine synthesis pathway (SSP) and glycolysis are highly activated in GBM cells under S/G deprivation conditions. Mechanistically, S/G deprivation rapidly induces reactive oxygen species (ROS)-mediated AMP-activated protein kinase (AMPK) activation and AMPK-dependent hypoxia-inducible factor (HIF)-1α stabilization and transactivation. Activated HIF-1α in turn promotes the expression of SSP enzymes phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase 1 (PSAT1), and phosphoserine phosphatase (PSPH). In addition, the HIF-1α-induced expression of glycolytic genes (GLUT1, GLUT3, HK2, and PFKFB2) promotes glucose uptake, glycolysis, and glycolytic flux to fuel SSP, leading to elevated de novo serine and glycine biosynthesis, NADPH/NADP+ ratio, and the proliferation and survival of GBM cells. Analyses of human GBM specimens reveal that the levels of overexpressed PHGDH, PSAT1, and PSPH are positively correlated with levels of AMPK T172 phosphorylation and HIF-1α expression and the poor prognosis of GBM patients.

CONCLUSION

Our findings reveal that metabolic stress-enhanced glucose-derived de novo serine biosynthesis is a critical metabolic feature of GBM cells, and highlight the potential to target SSP for treating human GBM.

α-Ketoglutarate Attenuates Hyperlipidemia-Induced Endothelial Damage by Activating the Erk-Nrf2 Signaling Pathway to Inhibit Oxidative Stress and Mitochondrial Dysfunction

Aims: α-Ketoglutarate (AKG) is an intermediate of the tricarboxylic acid cycle and a key hub linking amino acid metabolism and glucose oxidation. Previous studies have shown that AKG improved cardiovascular diseases such as myocardial infarction and myocardial hypertrophy through antioxidant and lipid-lowering characteristics. However, its protective effect and mechanism on endothelial injury caused by hyperlipidemia have not been elucidated yet. In this study, we tested whether AKG possesses protective effects on hyperlipidemia-induced endothelial injury and studied the mechanism. Results: AKG administration both in vivo, and in vitro significantly suppressed the hyperlipidemia-induced endothelial damage, regulated ET-1 and nitric oxide levels, and reduced the inflammatory factor interleukin-6 and matrix metallopeptidase-1 by inhibiting oxidative stress and mitochondrial dysfunction. The protective effects were achieved by the mechanism of activating the Nrf2 phase II system through the ERK signaling pathway. Innovation: These results reveal the role of the AKG-ERK-Nrf2 signaling pathway in the prevention of hyperlipidemia-induced endothelial damage, and suggest that AKG, as a mitochondria-targeting nutrient, is a potential drug for the treatment of endothelial damage in hyperlipidemia. Conclusion: AKG ameliorated the hyperlipidemia-induced endothelial damage and inflammatory response by inhibiting oxidative stress and mitochondrial dysfunction. Antioxid. Redox Signal. 39, 777-793.

A transient increase of HIF-1α during the G1 phase (G1-HIF) ensures cell survival under nutritional stress

The family of hypoxia-inducible transcription factors (HIF) is activated to adapt cells to low oxygen conditions, but is also known to regulate some biological processes under normoxic conditions. Here we show that HIF-1α protein levels transiently increase during the G1 phase of the cell cycle (designated as G1-HIF) in an AMP-activated protein kinase (AMPK)-dependent manner. The transient elimination of G1-HIF by a degron system revealed its contribution to cell survival under unfavorable metabolic conditions. Indeed, G1-HIF plays a key role in the cell cycle-dependent expression of genes encoding metabolic regulators and the maintenance of mTOR activity under conditions of nutrient deprivation. Accordingly, transient elimination of G1-HIF led to a significant reduction in the concentration of key proteinogenic amino acids and carbohydrates. These data indicate that G1-HIF acts as a cell cycle-dependent surveillance factor that prevents the onset of starvation-induced apoptosis.

Human neutrophils ≠ murine neutrophils: Does it matter?

Human and murine neutrophils differ with respect to representation in blood, receptors, nuclear morphology, signaling pathways, granule proteins, NADPH oxidase regulation, magnitude of oxidant and hypochlorous acid production, and their repertoire of secreted molecules. These differences often matter and can undermine extrapolations from murine studies to clinical care, as illustrated by several failed therapeutic interventions based on mouse models. Likewise, coevolution of host and pathogen undercuts fidelity of murine models of neutrophil-predominant human infections. However, murine systems that accurately model the human condition can yield insights into human biology difficult to obtain otherwise. The challenge for investigators who employ murine systems is to distinguish models from pretenders and to know when the mouse provides biologically accurate insights. Testing with human neutrophils observations made in murine systems would provide a safeguard but is not always possible. At a minimum, studies that use exclusively murine neutrophils should have accurate titles supported by data and restrict conclusions to murine neutrophils and not encompass all neutrophils. For now, the integration of evidence from studies of neutrophil biology performed using valid murine models coupled with testing in vitro of human neutrophils combines the best of both approaches to elucidate the mysteries of human neutrophil biology.

Modulations in human neutrophil metabolome and S-glutathionylation of glycolytic pathway enzymes during the course of extracellular trap formation

Neutrophil extracellular trap formation (NETosis) has been irrefutably referred to as a distinct and unique form of active cell death with the purpose to counteract invading pathogens or augmenting the inflammatory cascade. Since the discovery, consistent efforts have been made to understand the various aspects of the initiation and sustenance of NETosis. In this study, using a global metabolomics approach during the phorbol 12-myristate 13-acetate (PMA) induced NETosis in human neutrophils, various metabolic pathways were found to be altered which includes intermediates related to, carbohydrate metabolism, and redox related metabolites, nucleic acid metabolism, and amino acids metabolism. Enrichment analysis of the metabolite sets highlighted the importance of the pentose phosphate pathway (PPP) and glutathione metabolism PMA-induced NETotic neutrophils. Further, analysis of the glutathyniolation status of neutrophil proteins by Matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) indicated six different glutathionylated proteins: among them, two metabolically important proteins were α-enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) with MALDI score 166 and 70 respectively. Other proteins were lactoferrin, β-actin, c-myc promoter-binding protein, and uracil DNA glycosylase with MALDI scores of 96, 167, 104, and 68 respectively. Besides, activation of signalling proteins involved in metabolic regulation is also correlated with NETosis. Altogether, a balance between reactive oxygen species-glutathione metabolism seems to regulate the activity of glycolytic enzymes such as GAPDH and α-enolase during PMA-induced NETosis in a time-dependent manner.

The Role of Hypoxia-Inducible Factor in the Mechanisms of Aging

Aging is accompanied by a reduction in the oxygen delivery to all organs and tissues and decrease in the oxygen partial pressure in them, resulting in the development of hypoxia. The lack of oxygen activates cell signaling pathway mediated by the hypoxia-inducible transcription factor (HIF), which exists in three isoforms - HIF-1, HIF-2, and HIF-3. HIF regulates expression of several thousand genes and is a potential target for the development of new drugs for the treatment of many diseases, including those associated with age. Human organism and organisms of laboratory animals differ in their tolerance to hypoxia and expression of HIF and HIF-dependent genes, which may contribute to the development of inflammatory, tumor, and cardiovascular diseases. Currently, the data on changes in the HIF expression with age are contradictory, which is mostly due to the fact that such studies are conducted in different age groups, cell types, and model organisms, as well as under different hypoxic conditions and mainly in vitro. Furthermore, the observed discrepancies can be due to the individual tolerance of the studied organisms to hypoxia, which is typically not taken into account. Therefore, the purpose of this review was to analyze the published data on the connection between the mechanisms of aging, basal tolerance to hypoxia, and changes in the level of HIF expression with age. Here, we summarized the data on the age-related changes in the hypoxia tolerance, HIF expression and the role of HIF in aging, which is associated with its involvement in the molecular pathways mediated by insulin and IGF-1 (IIS), sirtuins (SIRTs), and mTOR. HIF-1 interacts with many components of the IIS pathway, in particular with FOXO, the activation of which reduces production of reactive oxygen species (ROS) and increases hypoxia tolerance. Under hypoxic conditions, FOXO is activated via both HIF-dependent and HIF-independent pathways, which contributes to a decrease in the ROS levels. The activity of HIF-1 is regulated by all members of the sirtuin family, except SIRT5, while the mechanisms of SIRT interaction with HIF-2 and HIF-3 are poorly understood. The connection between HIF and mTOR and its inhibitor, AMPK, has been identified, but its exact mechanism has yet to be studied. Understanding the role of HIF and hypoxia in aging and pathogenesis of age-associated diseases is essential for the development of new approaches to the personalized therapy of these diseases, and requires further research.

Hypoxia-primed monocytes/macrophages enhance postinfarction myocardial repair

Background: Oxygen supplementation in myocardial infarction (MI) remains controversial. Inflammation is widely believed to play a central role in myocardial repair. A better understanding of these processes may lead to the design of novel strategies complementary to MI treatment. Methods: To investigate the role of hypoxia in inflammation and myocardial repair after acute MI, we placed MI mice in a tolerable mild hypoxia (10% O₂) chamber for 7 days and then transferred the mice to ambient air for another 3 weeks. Results: We found that the cumulative survival rate of the MI mice under hypoxia was significantly higher than that under oxygen supplementation. Hypoxia promoted postinfarction myocardial repair. Importantly, we found that hypoxia modulated the phenotypic transition of blood monocytes from pro-inflammatory to pro-reparative in a timely manner, leading to the subsequent discontinuation of inflammation in myocardial tissues and promotion of myocardial repair post-MI. Specifically, cultured bone marrow-derived macrophages (BMDMs) primed by hypoxia in vitro exhibited improved reparative capacities and differed from M₁ and M₂ macrophages through the AMPKα2 signaling pathway. The deletion of AMPKα2 in monocytes/macrophages prevented the phenotypic transition induced by hypoxia and could not promote myocardial repair after MI when transplanted into the myocardium. Conclusions: Taken together, our work demonstrates that hypoxia promotes postinfarction myocardial repair by modulating the blood monocyte/macrophage phenotypic transition from pro-inflammatory to pro-reparative in a timely manner through the AMPKα2 signaling pathway. Hypoxia priming might be an attractive translational strategy for MI treatment by amplifying immune cells during early inflammation and subsequent resolution and repair.

Tert-Butylhydroquinone alleviates insulin resistance and liver steatosis in diabetes

OBJECTIVES:

This work aimed to determine tert-Butylhydroquinone (TBHQ)'s effects on insulin resistance (IR) and liver steatosis in diabetic animals and to explore the underpinning mechanisms.

MATERIALS AND METHODS:

Male ApoE^-/-mice underwent streptozocin (STZ) administration while receiving a sucrose/fat-rich diet for type 2 diabetes mellitus (T2DM) establishment. This was followed by a 6-week TBHQ administration. Body weight, fasting (FBG) and postprandial (PBG) blood glucose amounts, and insulin concentrations were measured, and the oral glucose tolerance test (OGTT) was carried out. Hematoxylin and eosin (H and E) staining and immunoblot were carried out for assessing histology and protein amounts in the liver tissue samples. In addition, cultured HepG2 cells were administered HClO and insulin for IR induction, and immunoblot was carried out for protein evaluation. Finally, the cells were stained with the Hoechst dye for apoptosis evaluation.

RESULTS:

The model animals showed T2DM signs, and TBHQ decreased FBG, ameliorated glucose tolerance and reduced liver steatosis in these animals. In addition, TBHQ markedly upregulated AMPKα2, GLUT4 and GSK3 β, as well as phosphorylated PI3K and AKT in the liver of mice with T2DM. In agreement, TBHQ decreased HClO-and insulin-related IR in cells and suppressed apoptosis through AMPKα2/PI3K/AKT signaling.

CONCLUSIONS:

TBHQ alleviates IR and liver steatosis in a mouse model of T2DM likely through AMPKα2/PI3K/AKT signaling.

HMGB1-Mediated Activation of the Inflammatory-Reparative Response Following Myocardial Infarction

Different cell types belonging to the innate and adaptive immune system play mutually non-exclusive roles during the different phases of the inflammatory-reparative response that occurs following myocardial infarction. A timely and finely regulation of their action is fundamental for the process to properly proceed. The high-mobility group box 1 (HMGB1), a highly conserved nuclear protein that in the extracellular space can act as a damage-associated molecular pattern (DAMP) involved in a large variety of different processes, such as inflammation, migration, invasion, proliferation, differentiation, and tissue regeneration, has recently emerged as a possible regulator of the activity of different immune cell types in the distinct phases of the inflammatory reparative process. Moreover, by activating endogenous stem cells, inducing endothelial cells, and by modulating cardiac fibroblast activity, HMGB1 could represent a master regulator of the inflammatory and reparative responses following MI. In this review, we will provide an overview of cellular effectors involved in these processes and how HMGB1 intervenes in regulating each of them. Moreover, we will summarize HMGB1 roles in regulating other cell types that are involved in the different phases of the inflammatory-reparative response, discussing how its redox status could affect its activity.

Polyphosphate in Chronic Wound Healing: Restoration of Impaired Metabolic Energy State

Many pathological conditions are characterized by a deficiency of metabolic energy. A prominent example is nonhealing or difficult-to-heal chronic wounds. Because of their unique ability to serve as a source of metabolic energy, inorganic polyphosphates (polyP) offer the opportunity to develop novel strategies to treat such wounds. The basis is the generation of ATP from the polymer through the joint action of two extracellular or plasma membrane-bound enzymes alkaline phosphatase and adenylate kinase, which enable the transfer of energy-rich phosphate from polyP to AMP with the formation of ADP and finally ATP. Building on these findings, it was possible to develop novel regeneratively active materials for wound therapy, which have already been successfully evaluated in first studies on patients.

Therapeutic potential of Scutellaria baicalensis Georgi in lung cancer therapy

BACKGROUND

Globally, lung cancer is the leading cause of cancer associated mortalities. The current conventional chemotherapy remains the preferred treatment option for lung cancer, as surgical resection plays little role in the treatment of over 75% of lung cancer patients. Therefore, there is a need to develop novel potential therapeutic drugs or adjuvants with a high efficiency and safety against lung cancer. Scutellaria baicalensis Georgi, a common Chinese medicinal herb that has been in use for more than 2000 years, has recently been shown to possess significant activities against lung cancer. However, current research progress on pharmacological effects and relevant molecular mechanisms of S. baicalensis in lung cancer therapy have not been systematically summarized.

PURPOSE

This review aimed at elucidating on the anti-lung cancer mechanisms and antitumor efficacies of S. baicalensis as well as its active ingredients, and providing a valuable reference for further investigation in this field.

METHODS

We used "Scutellaria baicalensis" or the name of the compound in S. baicalensis, in combination with "lung cancer" as key words to systematically search for relevant literature from the Web of Science and PubMed databases. Publications that investigated molecular mechanisms were the only ones selected for analysis. The PRISMA guidelines were followed.

RESULTS

Fifty-four publications met the inclusion criteria for this study. Five anti-lung cancer mechanisms of S. baicalensis and its constituent components are discussed. These mechanisms include apoptosis induction, cell-cycle arrest, suppression of proliferation, blockade of invasion and metastasis, and overcoming drug-resistance. These compounds exhibited high antitumor efficacies and safety against lung cancer xenografts.

CONCLUSION

Studies should aim at elucidating on the anti-cancer mechanisms of S. baicalensis to achieve the ultimate goal of lung cancer therapy.

AMPK-mTOR Signaling and Cellular Adaptations in Hypoxia

Cellular energy is primarily provided by the oxidative degradation of nutrients coupled with mitochondrial respiration, in which oxygen participates in the mitochondrial electron transport chain to enable electron flow through the chain complex (I-IV), leading to ATP production. Therefore, oxygen supply is an indispensable chapter in intracellular bioenergetics. In mammals, oxygen is delivered by the bloodstream. Accordingly, the decrease in cellular oxygen level (hypoxia) is accompanied by nutrient starvation, thereby integrating hypoxic signaling and nutrient signaling at the cellular level. Importantly, hypoxia profoundly affects cellular metabolism and many relevant physiological reactions induce cellular adaptations of hypoxia-inducible gene expression, metabolism, reactive oxygen species, and autophagy. Here, we introduce the current knowledge of hypoxia signaling with two-well known cellular energy and nutrient sensing pathways, AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin complex 1 (mTORC1). Additionally, the molecular crosstalk between hypoxic signaling and AMPK/mTOR pathways in various hypoxic cellular adaptions is discussed.

Liraglutide via Activation of AMP-Activated Protein Kinase-Hypoxia Inducible Factor-1α-Heme Oxygenase-1 Signaling Promotes Wound Healing by Preventing Endothelial Dysfunction in Diabetic Mice

Background/Aims: Diabetic foot ulcers (DFUs) present a major challenge in clinical practice, and hyperglycemia-induced angiogenesis disturbance and endothelial dysfunction likely exacerbate DFUs. The long-acting glucagon-like peptide-1 (GLP-1) analog liraglutide (Lira) is a potential activator of AMP-activated protein kinase (AMPK) that appears to enhance endothelial function and have substantial pro-angiogenesis and antioxidant stress effects. Therefore, in this study, we aimed to investigate whether the protective role of Lira in diabetic wound healing acts against the mechanisms underlying hyperglycemia-induced endothelial dysfunction and angiogenesis disturbance. Methods: Accordingly, db/db mice were assessed after receiving subcutaneous Lira injections. We also cultured human umbilical vein endothelial cells (HUVECs) in either normal or high glucose (5.5 or 33 mM glucose, respectively) medium with or without Lira for 72 h. Results: An obvious inhibition of hyperglycemia-triggered endothelial dysfunction and angiogenesis disturbance was observed; follow by a promotion of diabetic wound healing under Lira treatment combined with restored hyperglycemia-impaired AMPK signaling pathway activity. AMPKα1/2 siRNA and Compound C (Cpd C), an inhibitor of AMPK, abolished both Lira-mediated endothelial protection and pro-angiogenesis action, as well as the diabetic wound healing promoted by Lira. Furthermore, hypoxia inducible factor-1α (Hif-1α; transcription factors of AMPK substrates) knockdown in HUVECs and db/db mice demonstrated that Lira activated AMPK to prevent hyperglycemia-triggered endothelial dysfunction and angiogenesis disturbance, with a subsequent promotion of diabetic wound healing that was Hif-1α-heme oxygenase-1 (HO-1) axis-dependent. Taken together, these findings reveal that the promotion of diabetic wound healing by Lira occurs via its AMPK-dependent endothelial protection and pro-angiogenic effects, which are regulated by the Hif-1α-HO-1 axis.

Deciphering the in vivo Dynamic Proteomics of Mesenchymal Stem Cells in Critical Limb Ischemia

Objective

Regenerative therapy using mesenchymal stem cells (MSC) is a promising therapeutic method for critical limb ischemia (CLI). To understand how the cells are involved in the regenerative process of limb ischemia locally, we proposed a metabolic protein labeling method to label cell proteomes in situ and then decipher the proteome dynamics of MSCs in ischemic hind limb.

Methods and Results

In this study, we overexpressed mutant methionyl-tRNA synthetase (MetRS), which could utilize azidonorleucine (ANL) instead of methionine (Met) during protein synthesis in MSCs. Fluorescent non-canonical amino-acid tagging (FUNCAT) was performed to detect the utilization of ANL in mutant MSCs. Mice with hindlimb ischemia (HLI) or Sham surgery were treated with MetRS^mut MSCs or PBS, followed by i.p. administration of ANL at days 0, 2 6, and 13 after surgery. FUNCAT was also performed in hindlimb tissue sections to demonstrate the incorporation of ANL in transplanted cells in situ. At days 1, 3, 7, and 14 after the surgery, laser doppler imaging were performed to detect the blood reperfusion of ischemic limbs. Ischemic tissues were also collected at these four time points for histological analysis including HE staining and vessel staining, and processed for click reaction based protein enrichment followed by mass spectrometry and bioinformatics analysis. The MetRS^mut MSCs showed strong green signal in cell culture and in HLI muscles as well, indicating efficient incorporation of ANL in nascent protein synthesis. By 14 days post-treatment, MSCs significantly increased blood reperfusion and vessel density, while reducing inflammation in HLI model compared to PBS. Proteins enriched by click reaction were distinctive in the HLI group vs. the Sham group. 34, 31, 49, and 26 proteins were significantly up-regulated whereas 28, 32, 62, and 27 proteins were significantly down-regulated in HLI vs. Sham at days 1, 3, 7, and 14, respectively. The differentially expressed proteins were more pronounced in the pathways of apoptosis and energy metabolism.

Conclusion

In conclusion, mutant MetRS allows efficient and specific identification of dynamic cell proteomics in situ, which reflect the functions and adaptive changes of MSCs that may be leveraged to understand and improve stem cell therapy in critical limb ischemia.

Neutrophil dysfunction in bronchiectasis: an emerging role for immunometabolism

Bronchiectasis is a heterogenous disease with multiple underlying causes. The pathophysiology is poorly understood but neutrophilic inflammation and dysfunctional killing of pathogens is believed to be key. There are, however, no licensed therapies for bronchiectasis that directly target neutrophilic inflammation. In this review, we discuss our current understanding of neutrophil dysfunction and therapeutic targeting in bronchiectasis. Immunometabolic reprogramming, a process through which inflammation changes inflammatory cell behaviour by altering intracellular metabolic pathways, is increasingly recognised across multiple inflammatory and autoimmune diseases. Here, we show evidence that much of the neutrophil dysfunction observed in bronchiectasis is consistent with immunometabolic reprogramming. Previous attempts at developing therapies targeting neutrophils have focused on reducing neutrophil numbers, resulting in increased frequency of infections. New approaches are needed and we propose that targeting metabolism could theoretically reverse neutrophil dysfunction and dysregulated inflammation. As an exemplar, 5' adenosine monophosphate (AMP)-activated protein kinase (AMPK) activation has already been shown to reverse phagocytic dysfunction and neutrophil extracellular trap (NET) formation in models of pulmonary disease. AMPK modulates multiple metabolic pathways, including glycolysis which is critical for energy generation in neutrophils. AMPK activators can reverse metabolic reprogramming and are already in clinical use and/or development. We propose the need for a new immunomodulatory approach, rather than an anti-inflammatory approach, to enhance bacterial clearance and reduce bronchiectasis disease severity.

Apelin/APJ-Manipulated CaMKK/AMPK/GSK3β Signaling Works as an Endogenous Counterinjury Mechanism in Promoting the Vitality of Random-Pattern Skin Flaps

A random-pattern skin flap plays an important role in the field of wound repair; the mechanisms that influence the survival of random-pattern skin flaps have been extensively studied but little attention has been paid to endogenous counterinjury substances and mechanism. Previous reports reveal that the apelin-APJ axis is an endogenous counterinjury mechanism that has considerable function in protecting against infection, inflammation, oxidative stress, necrosis, and apoptosis in various organs. As an in vivo study, our study proved that the apelin/APJ axis protected the skin flap by alleviating vascular oxidative stress and the apelin/APJ axis works as an antioxidant stress factor dependent on CaMKK/AMPK/GSK3β signaling. In addition, the apelin/APJ-manipulated CaMKK/AMPK/GSK3β-dependent mechanism improves HUVECs' resistance to oxygen and glucose deprivation/reperfusion (OGD/R), reduces ROS production and accumulation, maintained the normal mitochondrial membrane potential, and suppresses oxidative stress in vitro. Besides, activation of the apelin/APJ axis promotes vascular migration and angiogenesis under relative hypoxia condition through CaMKK/AMPK/GSK3β signaling. In a word, we provide new evidence that the apelin/APJ axis is an effective antioxidant and can significantly improve the vitality of random flaps, so it has potential be a promising clinical treatment.

Activation of AMPK under Hypoxia: Many Roads Leading to Rome

AMP-activated protein kinase (AMPK) is known as a pivotal cellular energy sensor, mediating the adaptation to low energy levels by deactivating anabolic processes and activating catabolic processes in order to restore the cellular ATP supply when the cellular AMP/ATP ratio is increased. Besides this well-known role, it has also been shown to exert protective effects under hypoxia. While an insufficient supply with oxygen might easily deplete cellular energy levels, i.e., ATP concentration, manifold other mechanisms have been suggested and are heavily disputed regarding the activation of AMPK under hypoxia independently from cellular AMP concentrations. However, an activation of AMPK preceding energy depletion could induce a timely adaptation reaction preventing more serious damage. A connection between AMPK and the master regulator of hypoxic adaptation via gene transcription, hypoxia-inducible factor (HIF), has also been taken into account, orchestrating their concerted protective action. This review will summarize the current knowledge on mechanisms of AMPK activation under hypoxia and its interrelationship with HIF.

Diabetic Cardiomyopathy: An Update of Mechanisms Contributing to This Clinical Entity

Heart failure and related morbidity and mortality are increasing at an alarming rate, in large part, because of increases in aging, obesity, and diabetes mellitus. The clinical outcomes associated with heart failure are considerably worse for patients with diabetes mellitus than for those without diabetes mellitus. In people with diabetes mellitus, the presence of myocardial dysfunction in the absence of overt clinical coronary artery disease, valvular disease, and other conventional cardiovascular risk factors, such as hypertension and dyslipidemia, has led to the descriptive terminology, diabetic cardiomyopathy. The prevalence of diabetic cardiomyopathy is increasing in parallel with the increase in diabetes mellitus. Diabetic cardiomyopathy is initially characterized by myocardial fibrosis, dysfunctional remodeling, and associated diastolic dysfunction, later by systolic dysfunction, and eventually by clinical heart failure. Impaired cardiac insulin metabolic signaling, mitochondrial dysfunction, increases in oxidative stress, reduced nitric oxide bioavailability, elevations in advanced glycation end products and collagen-based cardiomyocyte and extracellular matrix stiffness, impaired mitochondrial and cardiomyocyte calcium handling, inflammation, renin-angiotensin-aldosterone system activation, cardiac autonomic neuropathy, endoplasmic reticulum stress, microvascular dysfunction, and a myriad of cardiac metabolic abnormalities have all been implicated in the development and progression of diabetic cardiomyopathy. Molecular mechanisms linked to the underlying pathophysiological changes include abnormalities in AMP-activated protein kinase, peroxisome proliferator-activated receptors, O-linked N-acetylglucosamine, protein kinase C, microRNA, and exosome pathways. The aim of this review is to provide a contemporary view of these instigators of diabetic cardiomyopathy, as well as mechanistically based strategies for the prevention and treatment of diabetic cardiomyopathy.

Myeloid-Specific Deletion of the AMPKα2 Subunit Alters Monocyte Protein Expression and Atherogenesis

The AMP-activated protein kinase (AMPK) is an energy sensing kinase that is activated by a drop in cellular ATP levels. Although several studies have addressed the role of the AMPKα1 subunit in monocytes and macrophages, little is known about the α2 subunit. The aim of this study was to assess the consequences of AMPKα2 deletion on protein expression in monocytes/macrophages, as well as on atherogenesis. A proteomics approach was applied to bone marrow derived monocytes from wild-type mice versus mice specifically lacking AMPKα2 in myeloid cells (AMPKα2^∆MC mice). This revealed differentially expressed proteins, including methyltransferases. Indeed, AMPKα2 deletion in macrophages increased the ratio of S-adenosyl methionine to S-adenosyl homocysteine and increased global DNA cytosine methylation. Also, methylation of the vascular endothelial growth factor and matrix metalloproteinase-9 (MMP9) genes was increased in macrophages from AMPKα2^∆MC mice, and correlated with their decreased expression. To link these findings with an in vivo phenotype, AMPKα2^∆MC mice were crossed onto the ApoE^-/- background and fed a western diet. ApoExAMPKα2^∆MC mice developed smaller atherosclerotic plaques than their ApoExα2^fl/fl littermates, that contained fewer macrophages and less MMP9 than plaques from ApoExα2^fl/fl littermates. These results indicate that the AMPKα2 subunit in myeloid cells influences DNA methylation and thus protein expression and contributes to the development of atherosclerotic plaques.

Biological Roles of Neutrophil-Derived Granule Proteins and Cytokines

Neutrophils, the most abundant white blood cells in human circulation, entertain intense interactions with other leukocyte subsets, platelets, and stromal cells. Molecularly, such interactions are typically communicated through proteins generated during granulopoiesis, stored in granules, or produced on demand. Here, we provide an overview of the mammalian regulation of granule protein production in the bone marrow and the de novo synthesis of cytokines by neutrophils recruited to tissues. In addition, we discuss some of the known biological roles of these protein messengers, and how neutrophil-borne granule proteins and cytokines can synergize to modulate inflammation and tumor development. Decoding the neutrophil interactome is important for therapeutically neutralizing individual proteins to putatively dampen inflammation, or for delivering modified neutrophil-borne proteins to boost host defense.

Angiogenesis and vascular stability in eicosanoids and cancer

Angiogenesis and inflammation are hallmarks of cancer. Arachidonic acid and other polyunsaturated fatty acids (PUFAs) are primarily metabolized by three distinct enzymatic systems initiated by cyclooxygenases, lipoxygenases, and cytochrome P450 enzymes (CYP) to generate bioactive eicosanoids, including prostanoids, leukotrienes, hydroxyeicosatetraenoic acids, and epoxyeicosatrienoic acids. As some of the PUFA metabolites playing essential roles in inflammatory processes, these pathways have been widely studied as therapeutic targets of inflammation. Because of their anti-inflammatory effects, these pathways were also proposed as anti-cancer targets. However, although the eicosanoids were linked to endothelial cell proliferation and angiogenesis almost two decades ago, it is only recently PUFA metabolites, especially those generated by CYP enzymes and the soluble epoxide hydrolase (sEH), have been recognized as important signaling mediators in physiological and pathological angiogenesis. Despite the fact that tumor growth and invasion are heavily dependent on inner-tumor angiogenesis and influenced by vascular stability, the role played by PUFA metabolites in tumor angiogenesis and vessel integrity has been largely overlooked. This review highlights current knowledge on the function of PUFA metabolites generated by the CYP/sEH pathway in angiogenesis and vascular stability as well as their potential involvement in cancer development.

AMPK promotes survival and adipogenesis of ischemia-challenged ADSCs in an autophagy-dependent manner

Some studies have shown that transplanted fat tissues usually cannot survive for long if adipose-derived stem cells (ADSCs) are removed from the tissues in advance. It is more meaningful to explore the mechanism mediating survival and differentiation of ADSCs in the transplanted microenvironment. AMP-activated protein kinase (AMPK) has been shown to be one of the energy receptors that regulate many aspects of cellular metabolism. AMPK activation has been implicated in models of adult ischemic injury, but the mechanism and the regulating effects of AMPK on survival and adipogenesis of transplanted ADSCs are still little known. In this study, we simulated the transplanted microenvironment using oxygen-glucose deprivation (OGD) to test the survival and adipogenesis of ADSCs. We found that OGD treatment triggered significant apoptosis and promoted autophagy. Simultaneously, OGD hindered the differentiation of ADSCs into mature adipocytes. After inhibiting AMPK, the OGD-induced apoptosis rate increased but autophagy was inhibited. The adipogenesis level also decreased. To show that the effects of AMPK on apoptosis and adipogenesis were autophagy-dependent, we pre-inhibited or pre-promoted autophagy with siATG7 or rapamycin while blocking AMPK. We found that inhibiting or improving autophagy exacerbated or alleviated the role of AMPK prohibition in apoptosis and adipogenesis. Furthermore, we showed that AMPK inhibition significantly lowered ULK1 activity but promoted mTOR activity, so that to inhibit autophagy. Our study shows that AMPK plays a protective role in maintaining survival and adipogenesis of OGD-challenged ADSCs partly by positively regulating autophagy. AMPK positively regulates autophagy by inhibiting mTOR but promoting ULK1 activity in OGD condition.

Extracellular Vesicle-Mediated Immune Regulation of Tissue Remodeling and Angiogenesis After Myocardial Infarction

Myocardial ischemia-related disorders constitute a major health problem, being a leading cause of death in the world. Upon ischemia, tissue remodeling processes come into play, comprising a series of inter-dependent stages, including inflammation, cell proliferation and repair. Neovessel formation during late phases of remodeling provides oxygen supply, together with cellular and soluble components necessary for an efficient myocardial reconstruction. Immune system plays a central role in processes aimed at repairing ischemic myocardium, mainly in inflammatory and angiogenesis phases. In addition to cellular components and soluble mediators as chemokines and cytokines, the immune system acts in a paracrine fashion through small extracellular vesicles (EVs) release. These vesicular structures participate in multiple biological processes, and transmit information through bioactive cargoes from one cell to another. Cell therapy has been employed in an attempt to improve the outcome of these patients, through the promotion of tissue regeneration and angiogenesis. However, clinical trials have shown variable results, which put into question the actual applicability of cell-based therapies. Paracrine factors secreted by engrafted cells partially mediate tissue repair, and this knowledge has led to the hypothesis that small EVs may become a useful tool for cell-free myocardial infarction therapy. Current small EVs engineering strategies allow delivery of specific content to selected cell types, thus revealing the singular properties of these vesicles for myocardial ischemia treatment.

PRKAA1/AMPKα1-driven glycolysis in endothelial cells exposed to disturbed flow protects against atherosclerosis

Increased aerobic glycolysis in endothelial cells of atheroprone areas of blood vessels has been hypothesized to drive increased inflammation and lesion burden but direct links remain to be established. Here we show that endothelial cells exposed to disturbed flow in vivo and in vitro exhibit increased levels of protein kinase AMP-activated (PRKA)/AMP-activated protein kinases (AMPKs). Selective deletion of endothelial Prkaa1, coding for protein kinase AMP-activated catalytic subunit alpha1, reduces glycolysis, compromises endothelial cell proliferation, and accelerates the formation of atherosclerotic lesions in hyperlipidemic mice. Rescue of the impaired glycolysis in Prkaa1-deficient endothelial cells through Slc2a1 overexpression enhances endothelial cell viability and integrity of the endothelial cell barrier, and reverses susceptibility to atherosclerosis. In human endothelial cells, PRKAA1 is upregulated by disturbed flow, and silencing PRKAA1 reduces glycolysis and endothelial viability. Collectively, these results suggest that increased glycolysis in the endothelium of atheroprone arteries is a protective mechanism.

Overexpression of miR‑17‑5p protects against high glucose‑induced endothelial cell injury by targeting E2F1‑mediated suppression of autophagy and promotion of apoptosis

E2 promoter binding factor 1 (E2F1) has been reported to have an important regulatory role in cell survival during hyperglycemic conditions; however, the mechanisms remain to be fully elucidated. Bioinformatics analyses have suggested that microRNA (miR)‑17‑5p targets the 3'untranslated region (3'UTR) of E2F1. The aim of the present study was to characterize the protective effect of miR‑17‑5p/E2F1 on human umbilical vein endothelial cells (HUVECs) under high glucose (HG) conditions, to confirm the regulatory effect of miR‑17‑5p on E2F1/AMP‑activated protein kinase α2 (AMPKα2)‑mediated apoptosis and E2F1/mammalian target of rapamycin complex 1 (mTORC1)‑mediated autophagy. Bifluorescein experiments were performed to characterize the interaction between miR‑17‑5p and E2F1. The Cell Counting Kit‑8 assay, flow cytometry, immunofluorescence, and reverse transcription‑quantitative polymerase chain reaction and western blot analyses were used to detect cell viability, apoptosis, autophagy, and relative mRNA and protein expression, respectively. The results showed that HG induced the downregulation of miR‑17‑5p and upregulation of E2F1 during HUVEC injury. The downregulation of E2F1 inhibited HG‑induced HUVEC dysfunction by suppressing mTORC1‑mediated inhibition of autophagy and AMPKα2‑mediated promotion of apoptosis. The results suggested that inhibiting the expression of E2F1 protected against HG‑induced HUVEC injury via the activation of autophagy. The overexpression of miR‑17‑5p inhibited E2F1‑mediated HUVEC injury under HG conditions, which was reversed following transfection with an E2F1‑overexpression vector. The bifluorescein experiments showed that miR‑17‑5p targeted the 3'UTR of E2F1. Taken together, the results suggested that the expression of miR‑17‑5p inhibited HG‑induced endothelial cell injury by targeting E2F1.

VASP regulates leukocyte infiltration, polarization, and vascular repair after ischemia

In ischemic vascular diseases, leukocyte recruitment and polarization are crucial for revascularization and tissue repair. The study of Laban et al. provides evidence that VASP is a major regulator of leukocyte recruitment and polarization and vascular repair after ischemia. Mechanistically, the study supports a novel role of VASP in chemokine receptor trafficking.

In ischemic vascular diseases, leukocyte recruitment and polarization are crucial for revascularization and tissue repair. We investigated the role of vasodilator-stimulated phosphoprotein (VASP) in vascular repair. After hindlimb ischemia induction, blood flow recovery, angiogenesis, arteriogenesis, and leukocyte infiltration into ischemic muscles in VASP^−/− mice were accelerated. VASP deficiency also elevated the polarization of the macrophages through increased signal transducer and activator of transcription (STAT) signaling, which augmented the release of chemokines, cytokines, and growth factors to promote leukocyte recruitment and vascular repair. Importantly, VASP deletion in bone marrow–derived cells was sufficient to mimic the increased blood flow recovery of global VASP^−/− mice. In chemotaxis experiments, VASP^−/− neutrophils/monocytes were significantly more responsive to M1-related chemokines than wild-type controls. Mechanistically, VASP formed complexes with the chemokine receptor CCR2 and β-arrestin-2, and CCR2 receptor internalization was significantly reduced in VASP^−/− leukocytes. Our data indicate that VASP is a major regulator of leukocyte recruitment and polarization in postischemic revascularization and support a novel role of VASP in chemokine receptor trafficking.

Glucose transport across lagomorph jejunum epithelium is modulated by AMP-activated protein kinase under hypoxia

The gastrointestinal epithelium possesses adaptation mechanisms to cope with huge variations in blood flow and subsequently oxygenation. Since sufficient energy supply is crucial under hypoxic conditions, glucose uptake especially must be regulated by these adaptation mechanisms. Therefore, we investigated glucose transport under hypoxic conditions. Jejunal epithelia of rabbits were incubated in Ussing chambers under short-circuit current conditions. Hypoxia was simulated by gassing with 1% O₂ instead of 100% O₂. The activity of sodium-coupled glucose transporter-1 (SGLT-1) was assessed by measuring the increase of short circuit current ( I_sc) after the addition of 2 mM glucose to the mucosal buffer solution. We observed decreased activity of SGLT-1 after hypoxia compared with control conditions. To investigate underlying mechanisms, epithelia were exposed to agonists and antagonists of AMP-activated protein kinase (AMPK) before assessment of SGLT-1-mediated transport and the pAMPK/AMPK protein ratio. Preincubation with the antagonist restored SGLT-1 activity under hypoxic conditions to the level of control conditions, indicating an involvement of AMPK in the downregulation of SGLT-1 activity under hypoxia, which was confirmed in Western blot analysis of pAMPK/AMPK. Transepithelial flux studies using radioactively labeled glucose, ortho-methyl-glucose, fructose, and mannitol revealed no changes after hypoxic incubation. Therefore, we could exclude a decreased transepithelial glucose transport rate and increased paracellular conductance under hypoxia. In conclusion, our study hints at a decreased activity of SGLT-1 under hypoxic conditions in an AMPK-dependent manner. However, transepithelial transport of glucose is maintained. Therefore, we suggest other transport mechanisms, especially glucose transporter 1 and/or 2 to substitute SGLT-1 under hypoxia. NEW & NOTEWORTHY To our knowledge, this is the first approach to simulate hypoxia and study its effects in the jejunal epithelium using the Ussing chamber technique. We were able show that AMPK plays a role in the downregulation of SGLT-1 and that there seems to be an upregulation of other glucose transport mechanisms in the apical membrane of lagomorph jejunum epithelium under hypoxia, securing the epithelial energy supply and thus integrity.

Effect of a single bout of aerobic exercise on high-fat meal-induced inflammation

BACKGROUND AND AIMS

Chronic low-grade inflammation is involved in the development of metabolic disorders including atherosclerosis, type 2 diabetes (T2D) and metabolic syndrome. Aerobic exercise has been shown to be anti-inflammatory and attenuate postprandial blood lipids, however, the effect of exercise on postprandial inflammation remains unclear. The aim of this study was to determine the protective effect of a single bout of aerobic exercise against postprandial lipemia and peripheral blood mononuclear cell (PBMC) inflammation and to evaluate associations with changes in the energy-sensing enzyme, AMP-activated protein kinase (AMPK).

MATERIALS AND METHODS

Healthy male subjects (n=12, age=23±2, %Fat=19±2) reported to the laboratory following an overnight fast (12-14h) on two separate occasions for consumption of a high-fat meal (HFM). Participants completed an acute bout of aerobic exercise the afternoon prior to one of the HFM visits.

RESULTS AND CONCLUSION

Results indicate that the single bout of moderate aerobic exercise increased AMPK signaling in PBMCs, as shown by increased phosphorylated acetyl-CoA carboxylase (p-ACC). This may be due to decreases in the AMPK inhibitory kinases PKD and GSK3β. Additionally, prior moderate intensity exercise decreased postprandial lipemia (PPL) and some mediators of the inflammatory pathway, such as p-NF-κB. These findings that acute aerobic exercise improves AMPK and NF-κB signaling in human PBMCs contribute support to the anti-inflammatory roles of exercise.