2-Deoxy-D-glucose treatment of endothelial cells induces autophagy by reactive oxygen species-mediated activation of the AMP-activated protein kinase

Glycolytic PFKFB3 and Glycogenic UGP2 Axis Regulates Perfusion Recovery in Experimental Hind Limb Ischemia

BACKGROUND

Despite being in an oxygen-rich environment, endothelial cells (ECs) use anaerobic glycolysis (Warburg effect) as the primary metabolic pathway for cellular energy needs. PFKFB (6-phosphofructo-2-kinase/fructose-2,6-biphosphatase)-3 regulates a critical enzymatic checkpoint in glycolysis and has been shown to induce angiogenesis. This study builds on our efforts to determine the metabolic regulation of ischemic angiogenesis and perfusion recovery in the ischemic muscle.

METHODS

Hypoxia serum starvation (HSS) was used as an in vitro peripheral artery disease (PAD) model, and hind limb ischemia by femoral artery ligation and resection was used as a preclinical PAD model.

RESULTS

Despite increasing PFKFB3-dependent glycolysis, HSS significantly decreased the angiogenic capacity of ischemic ECs. Interestingly, inhibiting PFKFB3 significantly induced the angiogenic capacity of HSS-ECs. Since ischemia induced a significant in PFKFB3 levels in hind limb ischemia muscle versus nonischemic, we wanted to determine whether glucose bioavailability (rather than PFKFB3 expression) in the ischemic muscle is a limiting factor behind impaired angiogenesis. However, treating the ischemic muscle with intramuscular delivery of D-glucose or L-glucose (osmolar control) showed no significant differences in the perfusion recovery, indicating that glucose bioavailability is not a limiting factor to induce ischemic angiogenesis in experimental PAD. Unexpectedly, we found that shRNA-mediated PFKFB3 inhibition in the ischemic muscle resulted in an increased perfusion recovery and higher vascular density compared with control shRNA (consistent with the increased angiogenic capacity of PFKFB3 silenced HSS-ECs). Based on these data, we hypothesized that inhibiting HSS-induced PFKFB3 expression/levels in ischemic ECs activates alternative metabolic pathways that revascularize the ischemic muscle in experimental PAD. A comprehensive glucose metabolic gene qPCR arrays in PFKFB3 silenced HSS-ECs, and PFKFB3-knock-down ischemic muscle versus respective controls identified UGP2 (uridine diphosphate-glucose pyrophosphorylase 2), a regulator of protein glycosylation and glycogen synthesis, is induced upon PFKFB3 inhibition in vitro and in vivo. Antibody-mediated inhibition of UGP2 in the ischemic muscle significantly impaired perfusion recovery versus IgG control. Mechanistically, supplementing uridine diphosphate-glucose, a metabolite of UGP2 activity, significantly induced HSS-EC angiogenic capacity in vitro and enhanced perfusion recovery in vivo by increasing protein glycosylation (but not glycogen synthesis).

CONCLUSIONS

Our data present that inhibition of maladaptive PFKFB3-driven glycolysis in HSS-ECs is necessary to promote the UGP2-uridine diphosphate-glucose axis that enhances ischemic angiogenesis and perfusion recovery in experimental PAD.

No energy, no autophagy-Mechanisms and therapeutic implications of autophagic response energy requirements

Autophagy is a lysosome-mediated self-degradation process of central importance for cellular quality control. It also provides macromolecule building blocks and substrates for energy metabolism during nutrient or energy deficiency, which are the main stimuli for autophagy induction. However, like most biological processes, autophagy itself requires ATP, and there is an energy threshold for its initiation and execution. We here present the first comprehensive review of this often-overlooked aspect of autophagy research. The studies in which ATP deficiency suppressed autophagy in vitro and in vivo were classified according to the energy pathway involved (oxidative phosphorylation or glycolysis). A mechanistic insight was provided by pinpointing the critical ATP-consuming autophagic events, including transcription/translation/interaction of autophagy-related molecules, autophagosome formation/elongation, autophagosome fusion with the lysosome, and lysosome acidification. The significance of energy-dependent fine-tuning of autophagic response for preserving the cell homeostasis, and potential implications for the therapy of cancer, autoimmunity, metabolic disorders, and neurodegeneration are discussed.

Aerobic glycolysis of vascular endothelial cells: a novel perspective in cancer therapy

Vascular endothelial cells (ECs) are monolayers of cells arranged in the inner walls of blood vessels. Under normal physiological conditions, ECs play an essential role in angiogenesis, homeostasis and immune response. Emerging evidence suggests that abnormalities in EC metabolism, especially aerobic glycolysis, are associated with the initiation and progression of various diseases, including multiple cancers. In this review, we discuss the differences in aerobic glycolysis of vascular ECs under normal and pathological conditions, focusing on the recent research progress of aerobic glycolysis in tumor vascular ECs and potential strategies for cancer therapy.

Transcriptome analysis reveals organ-specific effects of 2-deoxyglucose treatment in healthy mice

OBJECTIVE

Glycolytic inhibition via 2-deoxy-D-glucose (2DG) has potential therapeutic benefits for a range of diseases, including cancer, epilepsy, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA), and COVID-19, but the systemic effects of 2DG on gene function across different tissues are unclear.

METHODS

This study analyzed the transcriptional profiles of nine tissues from C57BL/6J mice treated with 2DG to understand how it modulates pathways systemically. Principal component analysis (PCA), weighted gene co-network analysis (WGCNA), analysis of variance, and pathway analysis were all performed to identify modules altered by 2DG treatment.

RESULTS

PCA revealed that samples clustered predominantly by tissue, suggesting that 2DG affects each tissue uniquely. Unsupervised clustering and WGCNA revealed six distinct tissue-specific modules significantly affected by 2DG, each with unique key pathways and genes. 2DG predominantly affected mitochondrial metabolism in the heart, while in the small intestine, it affected immunological pathways.

CONCLUSIONS

These findings suggest that 2DG has a systemic impact that varies across organs, potentially affecting multiple pathways and functions. The study provides insights into the potential therapeutic benefits of 2DG across different diseases and highlights the importance of understanding its systemic effects for future research and clinical applications.

Nuclear DNA damage-triggered ATM-dependent AMPK activation regulates the mitochondrial radiation response

PURPOSE

AMP-activated protein kinase (AMPK) acts as a cellular energy sensor and is essential for controlling mitochondrial homeostasis. Here, we investigated the regulatory mechanisms involved in AMPK activation to elucidate how networks of intracellular signaling pathways respond to stress conditions.

MATERIALS AND METHODS

Inhibitors of ATM, DNA-PK, and AKT were tested in normal TIG-3 and MRC-5 human fibroblasts to determine which upstream kinases are responsible for AMPK activation. SV40 transformed-human ATM-deficient fibroblasts (AT5BIVA) and their ATM-complemented cells (i.e., AT5BIVA/ATMwt) were also used. Protein expression associated with AMPK signaling was examined by immunostaining and/or Western blotting.

RESULTS

Radiation-induced nuclear DNA damage activates ATM-dependent AMPK signaling pathways that regulate mitochondrial quality control. In contrast, hypoxia and glucose starvation caused ATP depletion and activated AMPK via a pathway independent of ATM. DNA-PK and AKT are not involved in AMPK-mediated mitochondrial signaling pathways.

CONCLUSION

Activation of the AMPK signaling pathway differs depending on the stimulus. Radiation activates AMPK through two pathways: depletion of ATP-mediated LKB1 signaling and nuclear DNA damage-induced ATM signaling. Nuclear DNA damage signaling to mitochondria therefore plays a pivotal role in determining the cell fates of irradiated cells.

Angiogenesis-on-a-chip coupled with single-cell RNA sequencing reveals spatially differential activations of autophagy along angiogenic sprouts

Several functions of autophagy associated with proliferation, differentiation, and migration of endothelial cells have been reported. Due to lack of models recapitulating angiogenic sprouting, functional heterogeneity of autophagy in endothelial cells along angiogenic sprouts remains elusive. Here, we apply an angiogenesis-on-a-chip to reconstruct 3D sprouts with clear endpoints. We perform single-cell RNA sequencing of sprouting endothelial cells from our chip to reveal high activation of autophagy in two endothelial cell populations- proliferating endothelial cells in sprout basements and stalk-like endothelial cells near sprout endpoints- and further the reciprocal expression pattern of autophagy-related genes between stalk- and tip-like endothelial cells near sprout endpoints, implying an association of autophagy with tip-stalk cell specification. Our results suggest a model describing spatially differential roles of autophagy: quality control of proliferating endothelial cells in sprout basements for sprout elongation and tip-stalk cell specification near sprout endpoints, which may change strategies for developing autophagy-based anti-angiogenic therapeutics.

Cadmium affects autophagy in the human intestinal cells Caco-2 through ROS-mediated ERK activation

Cadmium is a toxic metal that enters the food chain. Following oral ingestion, the intestinal epithelium has the capacity to accumulate high levels of this metal. We have previously shown that Cd induces ERK1/2 activation in differentiated but not proliferative human enterocytic-like Caco-2 cells. As autophagy is a dynamic process that plays a critical role in intestinal mucosa, we aimed the present study 1) to investigate the role of p-ERK1/2 in constitutive autophagy in proliferative Caco-2 cells and 2) to investigate whether Cd-induced activation of ERK1/2 modifies autophagic activity in postconfluent Caco-2 cell monolayers. Western blot analyses of ERK1/2 and autophagic markers (LC3, SQSTM1), and cellular staining with acridine orange showed that ERK1/2 and autophagic activities both decreased with time in culture. GFP-LC3 fluorescence was also associated with proliferative cells and the presence of a constitutive ERK1/2-dependent autophagic flux was demonstrated in proliferative but not in postconfluent cells. In the latter condition, serum and glucose deprivation triggered autophagy via a transient phosphorylation of ERK1/2, whereas Cd-modified autophagy via a ROS-dependent sustained activation of ERK1/2. Basal autophagy flux in proliferative cells and Cd-induced increases in autophagic markers in postconfluent cells both involved p-ERK1/2. Whether Cd blocks autophagic flux in older cell cultures remains to be clarified but our data suggest dual effects. Our results prompt further studies investigating the consequences that Cd-induced ERK1/2 activation and the related effect on autophagy may have on the intestinal cells, which may accumulate and trap high levels of Cd under some nutritional conditions.

Transcriptome Analysis Reveals Organ-Specific Effects of 2-Deoxyglucose Treatment in Healthy Mice

OBJECTIVE

Glycolytic inhibition via 2-deoxy-D-glucose (2DG) has potential therapeutic benefits for a range of diseases, including cancer, epilepsy, systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA), and COVID-19, but the systemic effects of 2DG on gene function across different tissues are unclear.

METHODS

This study analyzed the transcriptional profiles of nine tissues from C57BL/6J mice treated with 2DG to understand how it modulates pathways systemically. Principal component analysis (PCA), weighted gene co-network analysis (WGCNA), analysis of variance, and pathway analysis were all performed to identify modules altered by 2DG treatment.

RESULTS

PCA revealed that samples clustered predominantly by tissue, suggesting that 2DG affects each tissue uniquely. Unsupervised clustering and WGCNA revealed six distinct tissue-specific modules significantly affected by 2DG, each with unique key pathways and genes. 2DG predominantly affected mitochondrial metabolism in the heart, while in the small intestine, it affected immunological pathways.

CONCLUSIONS

These findings suggest that 2DG has a systemic impact that varies across organs, potentially affecting multiple pathways and functions. The study provides insights into the potential therapeutic benefits of 2DG across different diseases and highlights the importance of understanding its systemic effects for future research and clinical applications.

Autophagy activation attenuates the circadian clock oscillators in U2OS cells via the ATG5 pathway

The circadian clock and autophagy are essential biological mechanisms involved in regulating many physiological processes. Accumulating evidence has revealed that autophagic activity is regulated by the circadian clock system. However, whether autophagy regulates the circadian clock system remains unclear. In this study, rapamycin and AICAR, two classical activators of autophagy, were used to create autophagy activation models in BMAL1-dLuc U2OS cell line. The results showed that the mRNA expression of MAP1LC3B and ATG5 were significantly upregulated after autophagy activation, whereas the mRNA expression of circadian clock genes (BMAL1, PER2, REV-ERBα, and DBP) were significantly decreased. Consistent with these data, the relative ratio of LC3-II/LC3-I and the protein level of ATG5 were increased after rapamycin or AICAR treatment. In contrast, BMAL1 and REV-ERBα levels were decreased. Notably, the mRNA expression of circadian clock genes (BMAL1, PER2, REV-ERBα, and DBP) and autophagy-related genes (MAP1LC3B and ATG5) showed rhythmic expression patterns in both untreated and rapamycin/AICAR-treated U2OS cells. Moreover, the autophagy inhibitor 3-methyladenine partially reversed the inhibitory effects of autophagy on circadian clock genes expression and BMAL1-Luc oscillations. Another critical finding was that ATG5 knockout alleviates the inhibitory effect of rapamycin-mediated autophagy activation on the circadian clock oscillators in U2OS cells. Collectively, our data indicate that autophagy activation attenuates the circadian clock oscillators in U2OS cells via the ATG5 pathway.

Genetic impairment of succinate metabolism disrupts bioenergetic sensing in adrenal neuroendocrine cancer

Metabolic dysfunction mutations can impair energy sensing and cause cancer. Loss of function of the mitochondrial tricarboxylic acid (TCA) cycle enzyme subunit succinate dehydrogenase B (SDHB) results in various forms of cancer typified by pheochromocytoma (PC). Here we delineate a signaling cascade where the loss of SDHB induces the Warburg effect, triggers dysregulation of [Ca²⁺]_i, and aberrantly activates calpain and protein kinase Cdk5, through conversion of its cofactor from p35 to p25. Consequently, aberrant Cdk5 initiates a phospho-signaling cascade where GSK3 inhibition inactivates energy sensing by AMP kinase through dephosphorylation of the AMP kinase γ subunit, PRKAG2. Overexpression of p25-GFP in mouse adrenal chromaffin cells also elicits this phosphorylation signaling and causes PC. A potent Cdk5 inhibitor, MRT3-007, reverses this phospho-cascade, invoking a senescence-like phenotype. This therapeutic approach halted tumor progression in vivo. Thus, we reveal an important mechanistic feature of metabolic sensing and demonstrate that its dysregulation underlies tumor progression in PC and likely other cancers.

The combination of hydroxychloroquine and 2-deoxyglucose enhances apoptosis in breast cancer cells by blocking protective autophagy and sustaining endoplasmic reticulum stress

2-Deoxyglucose (2-DG) can be used in antitumour research by inhibiting glycolysis and promoting the endoplasmic reticulum stress (ERS) pathway, but its clinical application is restricted due to dose-limiting side effects and survival chance for cancer cells by protective autophagy. Therefore, our research explored whether the combination of hydroxychloroquine (HCQ), an FDA-approved autophagy inhibiting drug, and 2-DG is a promising therapeutic strategy. Here, we report that HCQ combined with 2-DG can further inhibit the viability and migration and induce apoptosis of breast tumour cells compared with other individual drugs. The combination of 2-DG and HCQ can significantly reduce transplanted tumour size and tumour cell metastasis of the lung and liver in vivo. At the cellular level, HCQ suppressed autolysosome formation and terminated the autophagy process induced by 2-DG-mediated ERS, resulting in the continuous accumulation of misfolded proteins in the endoplasmic reticulum, which generated sustained ERS through the PERK-eIF2α-ATF-4-CHOP axis and triggered the transformation from a survival process to cell death. Our research reinforced the research interest of metabolic disruptors in triple-negative breast cancer and emphasized the potential of the combination of 2-DG and HCQ as an anticancerous treatment.

Inhibiting nuclear factor erythroid 2 related factor 2-mediated autophagy in bovine mammary epithelial cells induces oxidative stress in response to exogenous fatty acids

Background

In early lactation, bovine mammary epithelial cells undergo serious metabolic challenges and oxidative stress both of which could be alleviated by activation of autophagy. Nuclear factor erythroid 2 related factor 2 (NFE2L2), a master regulator of cellular redox homeostasis, plays an important role in the regulation of autophagy and oxidative stress. Thus, the objective of this study was to investigate the role of NFE2L2-mediated autophagy on oxidative stress of bovine mammary epithelial cells in response to exogenous free fatty acids (FFA).

Results

Exogenous FFA induced linear and quadratic decreases in activities of glutathione peroxidase (GSH-Px), catalase (CAT), and superoxide dismutase (SOD), and increases in the contents of reactive oxygen species (ROS) and malondialdehyde (MDA). Protein abundance of LC3-phosphatidylethanolamine conjugate (LC3-II) and the number of autophagosomes and autolysosomes decreased in a dose-dependent manner, while protein abundance of p62 increased in cells challenged with FFA. Activation of autophagy via pre-treatment with Rap attenuated the FFA-induced ROS accumulation. Importantly, FFA inhibited protein abundance of NFE2L2 and the translocation of NFE2L2 into the nucleus. Knockdown of NFE2L2 by siRNA decreased protein abundance of LC3-II, while it increased protein abundance of p62. Furthermore, sulforaphane (SFN) pre-treatment attenuated the FFA-induced oxidative stress by activating NFE2L2-mediated autophagy.

Conclusions

The data suggested that NFE2L2-mediated autophagy is an important antioxidant mechanism in bovine mammary epithelial cells experiencing increased FFA loads.

Microbial metabolite butyrate promotes induction of IL-10+IgM+ plasma cells

The microbially-derived short-chain fatty acid butyrate is a central inhibitor of inflammatory innate and adaptive immune responses. Emerging evidence suggests that butyrate induces differentiation of IL-10-producing (IL-10+) regulatory B cells. However, the underlying mechanisms of butyrate-driven modulation of B cell differentiation are not fully defined. Given the dominant role of regulatory plasma cells (PCs) as the main source of anti-inflammatory cytokines including IL-10 and the observation that butyrate also induces the differentiation of PCs, we here investigated the effect of the microbial metabolite butyrate on the induction of regulatory IL-10+ PCs and underlying mechanisms. Here we show that butyrate induces the differentiation of IL-10+IgM+ PCs. Ex vivo, butyrate, but hardly propionate, another microbially-derived short-chain fatty acid, induced the differentiation of IL-10+IgM+ CD138high PCs from isolated splenic murine B cells. In vivo, administration of butyrate via drinking water or by daily intraperitoneal injection increased the number of IL-10+IgM+ CD138high PCs in the spleens of Ovalbumin (Ova)/complete Freund’s adjuvant-immunized mice. The induction of these regulatory PCs was associated with an increase of anti-Ova IgM, but a reduction of anti-Ova class-switched pathogenic IgG2b serum antibodies. Based on the knowledge that butyrate inhibits histone deacetylases (HDACs) thereby increasing histone acetylation, we identified here that HDAC3 inhibition was sufficient to induce PC differentiation and IL-10+ expression. Furthermore, reduced mitochondrial superoxide levels following butyrate treatment and HDAC3 inhibition were necessary for PC differentiation, but not IL-10 expression. In summary, the microbial metabolite butyrate promotes the differentiation of IgM+ PCs and their expression of IL-10. HDAC3 inhibition may be involved as an underlying pathway for both PC differentiation and IL-10 expression, while reduced mitochondrial superoxide levels are crucial only for PC differentiation. The induction of regulatory IL-10+IgM+ PCs and the inhibition of class switching to antigen-specific pathogenic IgG subclasses might represent important pathways of butyrate to limit inflammation.

The Yin and Yang dualistic features of autophagy in thermal burn wound healing

Burn healing should be regarded as a dynamic process consisting of two main, interrelated phases: (a) the inflammatory phase when neutrophils and monocytes infiltrate the injury site, through localized vasodilation and fluid extravasation, and (b) the proliferative-remodeling phase, which represents a key event in wound healing. In the skin, both canonical autophagy (induced by starvation, oxidative stress, and environmental aggressions) and non-canonical or selective autophagy have evolved to play a discrete, but, essential, “housekeeping” role, for homeostasis, immune tolerance, and survival. Experimental data supporting the pro-survival roles of autophagy, highlighting its Yang, luminous and positive feature of this complex but insufficient explored molecular pathway, have been reported. Autophagic cell death describes an “excessive” degradation of important cellular components that are necessary for normal cell function. This deadly molecular mechanism brings to light the darker, concealed, Yin feature of autophagy. Autophagy seems to perform dual, conflicting roles in the angiogenesis context, revealing once again, its Yin–Yang features. Autophagy with its Yin–Yang features remains the shadow player, able to decide quietly whether the cell survives or dies.

2-Deoxyglucose Glycolysis Inhibitor Augment Oncolytic Virotherapy to Induce Oxidative Stress and Apoptosis in Breast Cancer (Part Ⅲ)

One of the "hallmarks of cancer" is altered energy metabolism, which is increased glycolysis in cancer cells, the primary source of energy that uses this metabolic pathway to generate ATP. Oncolytic virotherapy with aerobic glycolysis inhibitor smart therapeutic approach to induce apoptosis in cancer cells. The current study aimed to use the 2-Deoxyglucose (2DG), a specific glycolysis inhibitor, to enhance the Newcastle disease virus (NDV). In this study, a mouse model of breast cancer allograft with mammary adenocarcinoma tumor cells (AN3) was used and treated with 2DG, NDV, and a combination of both. Anti-tumor efficacy and glycolysis analysis (hexokinase -1 (HK-1), pyruvate, and ATP) were determined. The induction of oxidative stress was investigated by reactive oxygen species (ROS) and total glutathione assay examination. Apoptosis induction was investigated using immunohistochemistry (cleaved Caspase-3) and histopathology. The result showed that combination therapy enhances anti-tumor efficacy (decrease in relative tumor volume and increase in tumor growth inhibition) of NDV against breast cancer. This effect was accompanied by a reduction in HK-1 concentration, pyruvate, and ATP (glycolysis products). Moreover, NDV+2DG therapy induces oxidative stress (decreases total glutathione and increases ROS). Immunohistochemistry and histopathological examination showed the apoptotic area in tumor tissues in treated groups. In conclusion, the present study found that the combination therapy could be considered as an effective cancer therapy through induction of glycolysis inhibition, oxidative stress, and apoptosis selectively in cancer cells.

Laminar Flow on Endothelial Cells Suppresses eNOS O-GlcNAcylation to Promote eNOS Activity

[Figure: see text].

Therapeutic Potential of Mitophagy-Inducing Microflora Metabolite, Urolithin A for Alzheimer's Disease

Mitochondrial dysfunction including deficits of mitophagy is seen in aging and neurodegenerative disorders including Alzheimer’s disease (AD). Apart from traditionally targeting amyloid beta (Aβ), the main culprit in AD brains, other approaches include investigating impaired mitochondrial pathways for potential therapeutic benefits against AD. Thus, a future therapy for AD may focus on novel candidates that enhance optimal mitochondrial integrity and turnover. Bioactive food components, known as nutraceuticals, may serve as such agents to combat AD. Urolithin A is an intestinal microbe-derived metabolite of a class of polyphenols, ellagitannins (ETs). Urolithin A is known to exert many health benefits. Its antioxidant, anti-inflammatory, anti-atherogenic, anti-Aβ, and pro-mitophagy properties are increasingly recognized. However, the underlying mechanisms of urolithin A in inducing mitophagy is poorly understood. This review discusses the mitophagy deficits in AD and examines potential molecular mechanisms of its activation. Moreover, the current knowledge of urolithin A is discussed, focusing on its neuroprotective properties and its potential to induce mitophagy. Specifically, this review proposes potential mechanisms by which urolithin A may activate and promote mitophagy.

Epigenetic Regulation of Autophagy in Cardiovascular Pathobiology

Cardiovascular diseases (CVDs) are the number one cause of debilitation and mortality worldwide, with a need for cost-effective therapeutics. Autophagy is a highly conserved catabolic recycling pathway triggered by various intra- or extracellular stimuli to play an essential role in development and pathologies, including CVDs. Accordingly, there is great interest in identifying mechanisms that govern autophagic regulation. Autophagic regulation is very complex and multifactorial that includes epigenetic pathways, such as histone modifications to regulate autophagy-related gene expression, decapping-associated mRNA degradation, microRNAs, and long non-coding RNAs; pathways are also known to play roles in CVDs. Molecular understanding of epigenetic-based pathways involved in autophagy and CVDs not only will enhance the understanding of CVDs, but may also provide novel therapeutic targets and biomarkers for CVDs.

Structural and functional remodeling of mitochondria as an adaptive response to energy deprivation

Cancer cells bioenergetics is more dependent on glycolysis than mitochondrial oxidative phosphorylation, a phenomenon known as the Warburg Effect. It has been proposed that inhibition of glycolysis may selectively affect cancer cells. However, the effects of glycolysis inhibition on mitochondrial function and structure in cancer cells are not completely understood. Here, we investigated the comparative effects of 2-deoxy-d-glucose (2-DG, a glucose analogue, which suppresses cellular glycolysis) on cellular bioenergetics in human colon cancer DLD-1 cells, smooth muscle cells, human umbilical vein endothelial cells and HL-1 cardiomyocytes. In all cells, 2-DG treatment resulted in significant ATP depletion, however, the cell viability remained unchanged. Also, we did not observe the synergistic effects of 2-DG with anticancer drugs doxorubicin and 5-fluorouracil. Instead, after 2-DG treatment and ATP depletion, mitochondrial respiration and membrane potential were significantly enhanced and mitochondrial morphology changed in the direction of more network organization. Analysis of protein expression demonstrated that 2-DG treatment induced an activation of AMPK (elevated pAMPK/AMPK ratio), increased mitochondrial fusion (mitofusins 1 and 2) and decreased fission (Drp1) proteins. In conclusion, this study suggests a strong link between respiratory function and structural organization of mitochondria in the cell. We propose that the functionality of the mitochondrial network is enhanced compared to disconnected mitochondria.

Endothelial response to glucose: dysfunction, metabolism, and transport

The endothelial cell response to glucose plays an important role in both health and disease. Endothelial glucose-induced dysfunction was first studied in diabetic animal models and in cells cultured in hyperglycemia. Four classical dysfunction pathways were identified, which were later shown to result from the common mechanism of mitochondrial superoxide overproduction. More recently, non-coding RNA, extracellular vesicles, and sodium-glucose cotransporter-2 inhibitors were shown to affect glucose-induced endothelial dysfunction. Endothelial cells also metabolize glucose for their own energetic needs. Research over the past decade highlighted how manipulation of endothelial glycolysis can be used to control angiogenesis and microvascular permeability in diseases such as cancer. Finally, endothelial cells transport glucose to the cells of the blood vessel wall and to the parenchymal tissue. Increasing evidence from the blood-brain barrier and peripheral vasculature suggests that endothelial cells regulate glucose transport through glucose transporters that move glucose from the apical to the basolateral side of the cell. Future studies of endothelial glucose response should begin to integrate dysfunction, metabolism and transport into experimental and computational approaches that also consider endothelial heterogeneity, metabolic diversity, and parenchymal tissue interactions.

The Intratumoral Heterogeneity of Cancer Metabolism

Cancer is one of the deadliest diseases in the world, causing over half a million deaths a year in the USA alone. Despite recent advances made in the field of cancer biology and the therapies that have been developed [1, 2], it is clear that more advances are necessary for us to classify cancer as curable. The logical question that arises is simple: Why, despite all the technologies and medical innovations of our time, has a complete cure eluded us? This chapter sheds light on one of cancer's most impactful attributes: its heterogeneity and, more specifically, the intratumoral heterogeneity of cancer metabolism. Simply put, what makes cancer one of the deadliest diseases is its ability to change and adapt. Cancer cells' rapid evolution, coupled with their irrepressible ability to divide, gives most of them the advantage over our immune systems. In this chapter, we delve into the complexities of this adaptability and the vital role that metabolism plays in the rise and progression of this heterogeneity.

The Relationship Between Reactive Oxygen Species and Endothelial Cell Metabolism

Cardiovascular disease (CVD) has been the leading cause of death for many decades, highlighting the importance of new research and treatments in the field. The role of hypoxia and subsequent free radical production [reactive oxygen species (ROS)] have become an area of particular interest in CVD. Interestingly, our laboratory and other laboratories have recently reported positive roles of subcellular ROS in modulating endothelial cell (EC) metabolism, proliferation, and angiogenesis. This bidirectional relationship between ROS and EC metabolism, as well as functional changes, continues to be an area of active research. Interestingly, ECs have been shown to rely on anaerobic processes for ATP generation, despite their direct access to oxygen. This paradox has proven to be beneficial as the major reliance on glycolysis produces ATP faster, preserves oxygen, and results in reduced ROS levels in contrast to oxidative phosphorylation. This review will address the relationship between ROS and carbohydrate, lipid, and nitrogen metabolism in ECs, and their effects on EC phenotype such as sprouting angiogenesis.

Regulation of autophagy, glucose uptake, and glycolysis under dengue virus infection

We previously reported that dengue virus (DENV)-induced autophagy plays a promoting role in viral replication and pathogenesis both in vitro and in vivo. Although it is known that DENV infection increases glycolysis, which promotes viral replication, the role of glucose metabolism together with autophagic activity in DENV replication remains unclear. In this study, we reveal that DENV2 infection increased autophagic activity, glucose uptake, protein levels of glucose transporter-1 (GLUT1), and glycolysis rate-limiting enzyme hexokinase-2 (HK2) in cells. Furthermore, the protein levels of LC3-II and HK2 were increased in the brain tissues of the DENV2-infected suckling mice. However, DENV2 infection decreased ATP level and showed no effect on mRNA expression of HK2 and phosphofructokinase, as well as lactate production, indicating that DENV2-regulated glycolytic flux occurs at the post-transcriptional level and is lactate pathway-independent. Moreover, amiodarone-induced autophagic activity, glucose uptake, HK2 level, and viral titer were reversed by the autophagy inhibitor spautin-1 or silencing of Atg5 gene expression. Intriguingly, blocking of glycolysis, HK2 protein level, and viral titer were accordingly decreased, but autophagic activity was increased, suggesting the existence of another regulation mechanism that influences the relationship between glycolysis and autophagy. This is the first report to reveal that DENV2-induced autophagy positively regulates glycolysis and viral replication in vitro and in vivo. Our findings open a new avenue wherein metabolic modulation could be used as a target for the treatment of DENV infection.

Increased mTOR and suppressed autophagic flux in the heart of a hypomorphic Pkd1 mouse model of autosomal dominant polycystic kidney disease

Cardiac hypertrophy is common in autosomal dominant polycystic kidney disease (ADPKD) patients. We found increased heart weight in Pkd1^RC/RC and Pkd2^WS25/+ mouse models of ADPKD. As there is a link between increased heart weight and mammalian target of rapamycin (mTOR), the aim of the study was to determine mTOR complex 1 and 2 signaling proteins in the heart in the Pkd1^RC/RC mouse model of PKD. In 70 day old Pkd1^RC/RC hearts, on immunoblot analysis, there was a large increase in p-AMPK^Thr172, a known autophagy inducer, and an increase in p-Akt^Ser473 and p-Akt^Thr308, but no increase in other mTORC1/2 proteins (p-S6^Ser240/244, p-mTOR^Ser2448). In 150 day old Pkd1^RC/RC hearts, there was an increase in mTORC1 (p-S6^Ser240/244) and mTOR-related proteins (p-Akt^Thr308, p-GSK3β^Ser9, p-AMPK^Thr172). As the mTOR pathway is the master regulator of autophagy, autophagy proteins were measured. There was an increase in p-Beclin-1 (BECN1), an autophagy regulator and activating molecule in Beclin-1-regulated autophagy (AMBRA1), a regulator of Beclin that play a role in autophagosome formation, an early stage of autophagy. There was a defect in the later stage of autophagy, the fusion of the autophagosome with the lysosome, known as autophagic flux, as evidenced by the lack of an increase in LC3-II, a marker of autophagosomes, with the lysosomal inhibitor bafilomycin, in both 70 day old and 150 day old hearts. To determine the role of autophagy in causing increased heart weight, Pkd1^RC/RC were treated with 2-deoxyglucose (2-DG) or Tat-Beclin1 peptide, agents known to induce autophagy. 2-DG treatment from 150 to 350 days of age, a time period when increased heart weight developed, did not reduce the increased heart weight. Unexpectedly, Tat-Beclin 1 peptide treatment from 70 to 120 days of age resulted in increased heart weight. In summary, there is suppressed autophagic flux in the heart at an early age in Pkd1^RC/RC mice. Increased mTOR signaling in older mice is associated suppressed autophagic flux. There was a large increase in p-AMPK^Thr172, a known autophagy inducer, in both young and old mice. 2-DG treatment did not impact increased heart weight and Tat-Beclin1 peptide increased heart weight.

A tRNA-derived fragment (tRF-3001b) aggravates the development of nonalcoholic fatty liver disease by inhibiting autophagy

AIM

Nonalcoholic fatty liver disease (NAFLD) is a growing health problem worldwide. Impaired autophagy has been linked to NAFLD pathogenesis. Whether transfer RNA (tRNA)-derived fragments (tRFs) regulate the progression of NAFLD via autophagy is not clear. Here, we aimed to identify autophagy- or adipogenesis-related tRFs and investigate their roles in NAFLD.

METHODS

Small RNA sequencing was performed on NAFLD and control mice, and candidate tRFs were validated using quantitative reverse transcription PCR (qRT-PCR). The role of a key tRF was investigated using Oil red O staining, western blotting, qRT-PCR and a luciferase reporter assay.

KEY FINDINGS

In NAFLD mice, the expression of p62 was increased and the ratio of LC3B-II/LC3-I was decreased compared to control mice. We identified nine differentially expressed tRFs, among which tRF-3001b was found to be significantly upregulated in NAFLD mice compared to the control liver tissues. Autophagy was decreased in FA （fatty acids)-induced LO2 cells, while silencing of tRF-3001b significantly abrogated the decrease in autophagy and increase in lipid formation. Moreover, chloroquine (CQ) dramatically abrogated the effect of tRF-3001b inhibition on lipid formation. Mechanistically, tRF-3001b targeted and inhibited the expression of the autophagy-related gene Prkaa1. In vivo, tRF-3001b silencing significantly improved pathology and decreased the levels of triglycerides and cholesterol in NAFLD mice, while CQ dramatically abrogated the effect of tRF-3001b deficiency.

SIGNIFICANCE

tRF-3001b may aggravate the development of NAFLD by inhibiting autophagy via targeting Prkaa1.

Cannabidiol Promotes Endothelial Cell Survival by Heme Oxygenase-1-Mediated Autophagy

Cannabidiol (CBD), a non-psychoactive cannabinoid, has been reported to mediate antioxidant, anti-inflammatory, and anti-angiogenic effects in endothelial cells. This study investigated the influence of CBD on the expression of heme oxygenase-1 (HO-1) and its functional role in regulating metabolic, autophagic, and apoptotic processes of human umbilical vein endothelial cells (HUVEC). Concentrations up to 10 µM CBD showed a concentration-dependent increase of HO-1 mRNA and protein and an increase of the HO-1-regulating transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2). CBD-induced HO-1 expression was not decreased by antagonists of cannabinoid-activated receptors (CB₁, CB₂, transient receptor potential vanilloid 1), but by the reactive oxygen species (ROS) scavenger N-acetyl-L-cysteine (NAC). The incubation of HUVEC with 6 µM CBD resulted in increased metabolic activity, while 10 µM CBD caused decreased metabolic activity and an induction of apoptosis, as demonstrated by enhanced caspase-3 cleavage. In addition, CBD triggered a concentration-dependent increase of the autophagy marker LC3A/B-II. Both CBD-induced LC3A/B-II levels and caspase-3 cleavage were reduced by NAC. The inhibition of autophagy by bafilomycin A₁ led to apoptosis induction by 6 µM CBD and a further increase of the proapoptotic effect of 10 µM CBD. On the other hand, the inhibition of HO-1 activity with tin protoporphyrin IX (SnPPIX) or knockdown of HO-1 expression by Nrf2 siRNA was associated with a decrease in CBD-mediated autophagy and apoptosis. In summary, our data show for the first time ROS-mediated HO-1 expression in endothelial cells as a mechanism by which CBD mediates protective autophagy, which at higher CBD concentrations, however, can no longer prevent cell death inducing apoptosis.

AMPK, Mitochondrial Function, and Cardiovascular Disease

Adenosine monophosphate-activated protein kinase (AMPK) is in charge of numerous catabolic and anabolic signaling pathways to sustain appropriate intracellular adenosine triphosphate levels in response to energetic and/or cellular stress. In addition to its conventional roles as an intracellular energy switch or fuel gauge, emerging research has shown that AMPK is also a redox sensor and modulator, playing pivotal roles in maintaining cardiovascular processes and inhibiting disease progression. Pharmacological reagents, including statins, metformin, berberine, polyphenol, and resveratrol, all of which are widely used therapeutics for cardiovascular disorders, appear to deliver their protective/therapeutic effects partially via AMPK signaling modulation. The functions of AMPK during health and disease are far from clear. Accumulating studies have demonstrated crosstalk between AMPK and mitochondria, such as AMPK regulation of mitochondrial homeostasis and mitochondrial dysfunction causing abnormal AMPK activity. In this review, we begin with the description of AMPK structure and regulation, and then focus on the recent advances toward understanding how mitochondrial dysfunction controls AMPK and how AMPK, as a central mediator of the cellular response to energetic stress, maintains mitochondrial homeostasis. Finally, we systemically review how dysfunctional AMPK contributes to the initiation and progression of cardiovascular diseases via the impact on mitochondrial function.

Dihydroartemisinin Inhibits the Proliferation of Leukemia Cells K562 by Suppressing PKM2 and GLUT1 Mediated Aerobic Glycolysis

BACKGROUND

Leukemia threatens so many lives around the world. Dihydroartemisinin (DHA), as a typical derivative of artemisinin (ART), can efficiently inhibit leukemia, but the controversial mechanisms are still controversial. Many reports showed that tumor cells acquire energy through the glycolysis pathway, pyruvate kinase M2 (PKM2) plays a crucial role in regulating glycolysis. However, it is unclear whether PKM2 or other key molecules are involved in DHA induced cytotoxicity in leukemia cells. Thus, this paper systematically investigated the anticancer effect and mechanism of DHA on human chronic myeloid leukemia K562 cells.

METHODS

In vitro, cytotoxicity was detected with CCK-8. Glucose uptake, lactate production and pyruvate kinase activity were investigated to evaluate the effect of DHA on K562 cells. To elucidate the cellular metabolism alterations induced by DHA, the extracellular acidification rate was assessed using Seahorse XF96 extracellular flux analyzer. Immunofluorescence, real-time PCR, and Western blotting were used to investigate the molecular mechanism.

RESULTS

We found that DHA prevented cell proliferation in K562 cells through inhibiting aerobic glycolysis. Lactate product and glucose uptake were inhibited after DHA treatment. Results showed that DHA modulates glucose uptake through downregulating glucose transporter 1 (GLUT1) in both gene and protein levels. The cytotoxicity of DHA on K562 cells was significantly reversed by PKM2 agonist DASA-58. Pyruvate kinase activity was significantly reduced after DHA treatment, decreased expression of PKM2 was confirmed in situ.

CONCLUSION

The present study implicated that DHA inhibits leukemia cell proliferation by regulating glycolysis and metabolism, which mediated by downregulating PKM2 and GLUT1 expression. Our finding might enrich the artemisinins' antitumor mechanisms.

Pharmacological management of vascular endothelial dysfunction in diabetes: TCM and western medicine compared based on biomarkers and biochemical parameters

Diabetes, a worldwide health concern while burdening significant populace of countries with time due to a hefty increase in both incidence and prevalence rates. Hyperglycemia has been buttressed both in clinical and experimental studies to modulate widespread molecular actions that effect macro and microvascular dysfunctions. Endothelial dysfunction, activation, inflammation, and endothelial barrier leakage are key factors contributing to vascular complications in diabetes, plus the development of diabetes-induced cardiovascular diseases. The recent increase in molecular, transcriptional, and clinical studies has brought a new scope to the understanding of molecular mechanisms and the therapeutic targets for endothelial dysfunction in diabetes. In this review, an attempt made to discuss up to date critical and emerging molecular signaling pathways involved in the pathophysiology of endothelial dysfunction and viable pharmacological management targets. Importantly, we exploit some Traditional Chinese Medicines (TCM)/TCM isolated bioactive compounds modulating effects on endothelial dysfunction in diabetes. Finally, clinical studies data on biomarkers and biochemical parameters involved in the assessment of the efficacy of treatment in vascular endothelial dysfunction in diabetes was compared between clinically used western hypoglycemic drugs and TCM formulas.

VEGF Triggers Transient Induction of Autophagy in Endothelial Cells via AMPKα1

AMP-activated protein kinase (AMPK) is activated by vascular endothelial growth factor (VEGF) in endothelial cells and it is significantly involved in VEGF-induced angiogenesis. This study investigates whether the VEGF/AMPK pathway regulates autophagy in endothelial cells and whether this is linked to its pro-angiogenic role. We show that VEGF leads to AMPKα1-dependent phosphorylation of Unc-51-like kinase 1 (ULK1) at its serine residue 556 and to the subsequent phosphorylation of the ULK1 substrate ATG14. This triggers initiation of autophagy as shown by phosphorylation of ATG16L1 and conjugation of the microtubule-associated protein light chain 3B, which indicates autophagosome formation; this is followed by increased autophagic flux measured in the presence of bafilomycin A1 and by reduced expression of the autophagy substrate p62. VEGF-induced autophagy is transient and probably terminated by mechanistic target of rapamycin (mTOR), which is activated by VEGF in a delayed manner. We show that functional autophagy is required for VEGF-induced angiogenesis and may have specific functions in addition to maintaining homeostasis. In line with this, inhibition of autophagy impaired VEGF-mediated formation of the Notch intracellular domain, a critical regulator of angiogenesis. Our study characterizes autophagy induction as a pro-angiogenic function of the VEGF/AMPK pathway and suggests that timely activation of autophagy-initiating pathways may help to initiate angiogenesis.

The Exacerbation of Aging and Oxidative Stress in the Epididymis of Sod1 Null Mice

There is growing evidence that the quality of spermatozoa decreases with age and that children of older fathers have a higher incidence of birth defects and genetic mutations. The free radical theory of aging proposes that changes with aging are due to the accumulation of damage induced by exposure to excess reactive oxygen species. We showed previously that absence of the superoxide dismutase 1 (Sod1) antioxidant gene results in impaired mechanisms of repairing DNA damage in the testis in young Sod1^−/− mice. In this study, we examined the effects of aging and the Sod^−/− mutation on mice epididymal histology and the expression of markers of oxidative damage. We found that both oxidative nucleic acid damage (via 8-hydroxyguanosine) and lipid peroxidation (via 4-hydroxynonenal) increased with age and in Sod1^−/− mice. These findings indicate that lack of SOD1 results in an exacerbation of the oxidative damage accumulation-related aging phenotype.

Autophagy as an emerging therapeutic target for age-related vascular pathologies

Introduction: The incidence of age-related vascular diseases such as arterial stiffness, hypertension and atherosclerosis, is rising dramatically and is substantially impacting healthcare systems. Mounting evidence suggests that there is an important role for autophagy in maintaining (cardio)vascular health. Impaired vascular autophagy has been linked to arterial aging and the initiation of vascular disease.Areas covered: The function and implications of autophagy in vascular smooth muscle cells and endothelial cells are discussed in healthy blood vessels and arterial disease. Furthermore, we discuss current treatment options for vascular disease and their links with autophagy. A literature search was conducted in PubMed up to October 2019.Expert opinion: Although the therapeutic potential of inducing autophagy in age-related vascular pathologies is considerable, several issues should be addressed before autophagy induction can be clinically used to treat vascular disease. These issues include uncertainty regarding the most effective drug target as well as the lack of potency and selectivity of autophagy inducing drugs. Moreover, drug tolerance or autophagy mediated cell death have been reported as possible adverse effects. Special attention is required for determining the cause of autophagy deficiency to optimize the treatment strategy.

Hydrogen-Rich Saline Inhibits Lipopolysaccharide-Induced Acute Lung Injury and Endothelial Dysfunction by Regulating Autophagy through mTOR/TFEB Signaling Pathway

Background

Hydrogen-rich saline (HRS) has strong anti-inflammatory, antioxidative stress, and antiapoptotic properties. The study focused on the protection of HRS on lipopolysaccharide (LPS)-induced acute lung injury (ALI) in rat models and the relationship with autophagic regulation and mTOR/TFEB signaling pathway. Material and Methods. The LPS-induced ALI rats' model was established. Pathohistological change in lung tissue was detected by hematoxylin-eosin staining. The inflammatory cytokines were examined by enzyme-linked immunosorbent assay (ELISA). The key apoptosis proteins and autophagy-relevant proteins were analyzed by western blotting. In vitro, HPMEC models of ALI were treated with LPS. The inflammatory cytokines were detected. Apoptosis rate was determined by flow cytometry. The autophagy and mTOR/TFEB signaling pathway-related proteins were detected by western blot and immunohistochemical staining.

Results

HRS attenuated LPS-induced ALI and apoptosis both in vivo and in vitro. HRS attenuated inflammatory response, inhibited apoptosis, induced and activated autophagy in LPS-induced ALI model, and downregulated mTOR/TFEB signaling pathway. The protection of HRS can be blocked by autophagy inhibitor. Moreover, mTOR activator reversed HRS protection and mTOR inhibitor enhanced HRS protection in LPS-induced model and HRS activated autophagy via mTOR/TFEB signaling pathway.

Conclusion

The results confirmed the protection of HRS in LPS-induced ALI by regulating apoptosis through inhibiting the mTOR/TFEB signaling pathway.

2-Deoxy-d-Glucose and Its Analogs: From Diagnostic to Therapeutic Agents

The ability of 2-deoxy-d-glucose (2-DG) to interfere with d-glucose metabolism demonstrates that nutrient and energy deprivation is an efficient tool to suppress cancer cell growth and survival. Acting as a d-glucose mimic, 2-DG inhibits glycolysis due to formation and intracellular accumulation of 2-deoxy-d-glucose-6-phosphate (2-DG6P), inhibiting the function of hexokinase and glucose-6-phosphate isomerase, and inducing cell death. In addition to glycolysis inhibition, other molecular processes are also affected by 2-DG. Attempts to improve 2-DG’s drug-like properties, its role as a potential adjuvant for other chemotherapeutics, and novel 2-DG analogs as promising new anticancer agents are discussed in this review.

Liraglutide Treatment Ameliorates Neurotoxicity Induced by Stable Silencing of Pin1

Post-translational modulation of peptidylprolyl isomerase Pin1 might link impaired glucose metabolism and neurodegeneration, being Pin1 effectors target for the glucagon-Like-Peptide1 analog liraglutide. We tested the hypotheses in Pin1 silenced cells (SH-SY5Y) treated with 2-deoxy-d-glucose (2DG) and methylglyoxal (MG), stressors causing altered glucose trafficking, glucotoxicity and protein glycation. Rescue by liraglutide was investigated. Pin1 silencing caused increased levels of reactive oxygen species, upregulated energy metabolism as suggested by raised levels of total ATP content and mRNA of SIRT1, PGC1α, NRF1; enhanced mitochondrial fission events as supported by raised protein expression of FIS1 and DRP1. 2DG and MG reduced significantly cell viability in all the cell lines. In Pin1 KD clones, 2DG exacerbated altered mitochondrial dynamics causing higher rate of fission events. Liraglutide influenced insulin signaling pathway (GSK3b/Akt); improved cell viability also in cells treated with 2DG; but it did not revert mitochondrial dysfunction in Pin1 KD model. In cells treated with MG, liraglutide enhanced cell viability, reduced ROS levels and cell death (AnnexinV/PI); and trended to reduce anti-apoptotic signals (BAX, BCL2, CASP3). Pin1 silencing mimics neuronal metabolic impairment of patients with impaired glucose metabolism and neurodegeneration. Liraglutide rescues to some extent cellular dysfunctions induced by Pin1 silencing.

Autophagy, cancer and angiogenesis: where is the link?

Background

Autophagy is a catabolic process for degradation of intracellular components. Damaged proteins and organelles are engulfed in double-membrane vesicles ultimately fused with lysosomes. These vesicles, known as phagophores, develop to form autophagosomes. Encapsulated components are degraded after autophagosomes and lysosomes are fused. Autophagy clears denatured proteins and damaged organelles to produce macromolecules further reused by cells. This process is vital to cell homeostasis under both physiologic and pathologic conditions.

Main body

While the role of autophagy in cancer is quite controversial, the majority of studies introduce it as an anti-tumorigenesis mechanism. There are evidences confirming this role of autophagy in cancer. Mutations and monoallelic deletions have been demonstrated in autophagy-related genes correlating with cancer promotion. Another pathway through which autophagy suppresses tumorigenesis is cell cycle. On the other hand, under hypoxia and starvation condition, tumors use angiogenesis to provide nutrients. Also, autophagy flux is highlighted in vessel cell biology and vasoactive substances secretion from endothelial cells. The matrix proteoglycans such as Decorin and Perlecan could also interfere with angiogenesis and autophagy signaling pathway in endothelial cells (ECs). It seems that the connection between autophagy and angiogenesis in the tumor microenvironment is very important in determining the fate of cancer cells.

Conclusion

Matrix glycoproteins can regulate autophagy and angiogenesis linkage in tumor microenvironment. Also, finding details of how autophagy and angiogenesis correlate in cancer will help adopt more effective therapeutic approaches.

Genetic background, epigenetic factors and dietary interventions which influence human longevity

Longevity is mainly conditioned by genetic, epigenetic and environmental factors. Different genetic modifications seem to be positively associated to longevity, including SNPs in SIRT1, APOE, FOXO3A, ACE, ATM, NOS1 and NOS2 gene. Epigenetic changes as DNA hyper- and hypo-methylation influence significantly human longevity by activating/deactivating different genes involved in physiological mechanisms. Several studies have confirmed that centenarians have a lower DNA methylation content compared to young subjects, which showed more homogeneously methylated DNA region. Also the up-regulation of miR-21 seems to be more associated with longevity in different populations of long-lived subjects, suggesting its role as potential epigenetic biomarkers. A non-pharmacological treatment that seems to contrast age-related diseases and promote longevity is represented by dietary intervention. It has been evaluated the effects of dietary restriction of both single nutrients or total calories to extend lifespan. However, in daily practice it is very difficult to guarantee adherence/compliance of the subjects to dietary restriction and at the same time avoid dangerous nutritional deficiencies. As consequence, the attention has focused on a variety of substances both drugs and natural compounds able to mime the beneficial effects of caloric restriction, including resveratrol, quercetin, rapamycin, metformin and 2-deoxy-D-glucose.

Respiratory chain inactivation links cartilage-mediated growth retardation to mitochondrial diseases

Children with mitochondrial diseases often present with slow growth and short stature, but the underlying mechanism remains unclear. In this study, Holzer et al. provide in vivo evidence that mitochondrial respiratory chain dysfunction induces cartilage degeneration coincident with altered metabolism, impaired extracellular matrix formation, and cell death at the cartilage–bone junction.

In childhood, skeletal growth is driven by transient expansion of cartilage in the growth plate. The common belief is that energy production in this hypoxic tissue mainly relies on anaerobic glycolysis and not on mitochondrial respiratory chain (RC) activity. However, children with mitochondrial diseases causing RC dysfunction often present with short stature, which indicates that RC activity may be essential for cartilage-mediated skeletal growth. To elucidate the role of the mitochondrial RC in cartilage growth and pathology, we generated mice with impaired RC function in cartilage. These mice develop normally until birth, but their later growth is retarded. A detailed molecular analysis revealed that metabolic signaling and extracellular matrix formation is disturbed and induces cell death at the cartilage–bone junction to cause a chondrodysplasia-like phenotype. Hence, the results demonstrate the overall importance of the metabolic switch from fetal glycolysis to postnatal RC activation in growth plate cartilage and explain why RC dysfunction can cause short stature in children with mitochondrial diseases.

A GBF1-Dependent Mechanism for Environmentally Responsive Regulation of ER-Golgi Transport

How can anterograde membrane trafficking be modulated by physiological cues? A screen of Golgi-associated proteins revealed that the ARF-GEF GBF1 can selectively modulate the ER-Golgi trafficking of prohaemostatic von Willebrand factor (VWF) and extracellular matrix (ECM) proteins in human endothelial cells and in mouse fibroblasts. The relationship between levels of GBF1 and the trafficking of VWF into forming secretory granules confirmed GBF1 is a limiting factor in this process. Further, GBF1 activation by AMPK couples its control of anterograde trafficking to physiological cues; levels of glucose control GBF1 activation in turn modulating VWF trafficking into secretory granules. GBF1 modulates both ER and TGN exit, the latter dramatically affecting the size of the VWF storage organelles, thereby influencing the hemostatic capacity of the endothelium. The role of AMPK as a central integrating element of cellular pathways with intra- and extra-cellular cues can now be extended to modulation of the anterograde secretory pathway.

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The Arf-GEF GBF1 modulates anterograde trafficking of VWF and ECM proteins

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Loss of GBF1 slows ER and TGN exit, producing swollen ER and giant WPBs

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Activation of GBF1 via AMPK reduces endothelial WPB size and secretion

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Metabolic change alters anterograde trafficking and cargo secretion via AMPK-GBF1

Immune Cell Metabolism in Tumor Microenvironment

Tumor microenvironment (TME) is composed of tumor cells, immune cells, cytokines, extracellular matrix, etc. The immune system and the metabolisms of glucose, lipids, amino acids, and nucleotides are integrated in the tumorigenesis and development. Cancer cells and immune cells show metabolic reprogramming in the TME, which intimately links immune cell functions and edits tumor immunology. Recent findings in immune cell metabolism hold the promising possibilities toward clinical therapeutics for treating cancer. This chapter introduces the updated understandings of metabolic reprogramming of immune cells in the TME and suggests new directions in manipulation of immune responses for cancer diagnosis and therapy.

Autophagy in Crotonaldehyde-Induced Endothelial Toxicity

Crotonaldehyde is an extremely toxic α,β-unsaturated aldehyde found in cigarette smoke, and it causes inflammation and vascular dysfunction. Autophagy has been reported to play a key role in the pathogenesis of vascular diseases. However, the precise mechanism underlying the role of acute exposure crotonaldehyde in vascular disease development remains unclear. In the present study, we aimed to investigate the effect of crotonaldehyde-induced autophagy in endothelial cells. Acute exposure to crotonaldehyde decreased cell viability and induced autophagy followed by cell death. In addition, inhibiting the autophagic flux markedly promoted the viability of endothelial cells exposed to high concentrations of crotonaldehyde. Crotonaldehyde activated the AMP-activated protein kinase (AMPK) and p38 mitogen-activated protein kinase (MAPK) pathways, and pretreatment with inhibitors specific to these kinases showed autophagy inhibition and partial improvement in cell viability. These data show that acute exposure to high concentrations of crotonaldehyde induces autophagy-mediated cell death. These results might be helpful to elucidate the mechanisms underlying crotonaldehyde toxicity in the vascular system and contribute to environmental risk assessment.

Glycolysis Is an Intrinsic Factor for Optimal Replication of a Norovirus

Viruses depend on the host cells they infect to provide the machinery and substrates for replication. Host cells are highly dynamic systems that can alter their intracellular environment and metabolic behavior, which may be helpful or inhibitory for an infecting virus. In this study, we show that macrophages, a target cell of murine norovirus (MNV), increase glycolysis upon viral infection, which is important for early steps in MNV infection. Human noroviruses (hNoV) are a major cause of gastroenteritis globally, causing enormous morbidity and economic burden. Currently, no effective antivirals or vaccines exist for hNoV, mainly due to the lack of high-efficiency in vitro culture models for their study. Thus, insights gained from the MNV model may reveal aspects of host cell metabolism that can be targeted for improving hNoV cell culture systems and for developing effective antiviral therapies.

The metabolic pathways of central carbon metabolism, glycolysis and oxidative phosphorylation (OXPHOS), are important host factors that determine the outcome of viral infections and can be manipulated by some viruses to favor infection. However, mechanisms of metabolic modulation and their effects on viral replication vary widely. Herein, we present the first metabolomics and energetic profiling of norovirus-infected cells, which revealed increases in glycolysis, OXPHOS, and the pentose phosphate pathway (PPP) during murine norovirus (MNV) infection. Inhibiting glycolysis with 2-deoxyglucose (2DG) in macrophages revealed that glycolysis is an important factor for optimal MNV infection, while inhibiting the PPP and OXPHOS showed a relatively minor impact of these pathways on MNV infection. 2DG affected an early stage in the viral life cycle after viral uptake and capsid uncoating, leading to decreased viral protein production and viral RNA. The requirement of glycolysis was specific for MNV (but not astrovirus) infection, independent of the type I interferon antiviral response, and unlikely to be due to a lack of host cell nucleotide synthesis. MNV infection increased activation of the protein kinase Akt, but not AMP-activated protein kinase (AMPK), two master regulators of cellular metabolism, implicating Akt signaling in upregulating host metabolism during norovirus infection. In conclusion, our findings suggest that the metabolic state of target cells is an intrinsic host factor that determines the extent of norovirus replication and implicates glycolysis as a virulence determinant. They further point to cellular metabolism as a novel therapeutic target for norovirus infections and improvements in current human norovirus culture systems.

The Biguanides Metformin and Buformin in Combination with 2-Deoxy-glucose or WZB-117 Inhibit the Viability of Highly Resistant Human Lung Cancer Cells

The biguanides metformin (MET) and to a lesser extent buformin (BUF) have recently been shown to exert anticancer effects. In particular, MET targets cancer stem cells (CSCs) in a variety of cancer types but these compounds have not been extensively tested for combination therapy. In this study, we investigated in vitro the anticancer activity of MET and BUF alone or in combination with 2-deoxy-D-glucose (2-DG) and WZB-117 (WZB), which are a glycolysis and a GLUT-1 inhibitor, respectively, in H460 human lung cancer cells growing under three different culture conditions with varying degrees of stemness: (1) routine culture conditions (RCCs), (2) floating lung tumorspheres (LTSs) that are enriched for stem-like cancer cells, and (3) adherent cells under prolonged periods (8-12 days) of serum starvation (PPSS). These cells are highly resistant to conventional anticancer drugs such as paclitaxel, hydroxyurea, and colchicine and display an increased level of stemness markers. As single agents, MET, BUF, 2-DG, and WZB-117 potently inhibited the viability of cells growing under RCCs. Both MET and BUF showed a strong synergistic effect when used in combination with 2-DG. A weak potentiation was observed when used with WZB-117. Under RCCs, H460 cells were more sensitive to MET and BUF and WZB-117 compared to nontumorigenic Beas-2B cells. While LTSs were less sensitive to each single drug, both MET and BUF in combination with 2-DG showed a strong synergistic effect and reduced cell viability to similar levels compared to the parental H460 cells. Adherent cells growing under PPSS were also less sensitive to each single drug, and MET and BUF showed a strong synergistic effect on cell viability in combination with 2-DG. Overall, our data demonstrates that the combination of BGs with either 2-DG or WZB-117 has “broad-spectrum” anticancer activities targeting cells growing under a variety of cell culture conditions with varying degrees of stemness. These properties may be useful to overcome the chemoresistance due to intratumoral heterogeneity found in lung cancer.

A Rise in ATP, ROS, and Mitochondrial Content upon Glucose Withdrawal Correlates with a Dysregulated Mitochondria Turnover Mediated by the Activation of the Protein Deacetylase SIRT1

Glucose withdrawal has been used as a model for the study of homeostatic defense mechanisms, especially for how cells cope with a shortage of nutrient supply by enhancing catabolism. However, detailed cellular responses to glucose withdrawal have been poorly studied, and are controversial. In this study, we determined how glucose withdrawal affects mitochondrial activity, and the quantity and the role of SIRT1 in these changes. The results of our study indicate a substantial increase in ATP production from mitochondria, through an elevation of mitochondrial biogenesis, mediated by SIRT1 activation that is driven by increased NAD⁺/NADH ratio. Moreover, mitochondria persisted in the cells as elongated forms, and apparently evaded mitophagic removal. This led to a steady increase in mitochondria content and the reactive oxygen species (ROS) generated from them, indicating failure in ATP and ROS homeostasis, due to a misbalance in SIRT1-mediated mitochondria turnover in conditions of glucose withdrawal. Our results suggest that SIRT1 activation alone cannot properly manage energy homeostasis under certain metabolic crisis conditions.

Autophagy promotes angiogenesis via AMPK/Akt/mTOR signaling during the recovery of heat-denatured endothelial cells

Our previous study demonstrated that angiogenesis increased during the recovery of heat-denatured endothelial cells. However, the mechanism is still unclear. This study aimed to investigate the relation of autophagy and angiogenesis during the recovery of heat-denatured endothelial cells. A rat deep partial-thickness burn model and heat-denatured human umbilical vein endothelial cells (HUVECs) model (52 °C for 35 s) were used. Autophagy increased significantly in the dermis and HUVECs in a time-dependent manner after heat denaturation and recovery for 2-5 days. Rapamycin-mediated autophagy enhanced the pro-angiogenic effect, evidenced by increased proliferation and migration of HUVECs, and formation of tube-like structures. Autophagy inhibition by 3-Methyladenine (3-MA) abolished the angiogenesis in heat-denatured HUVECs after recovery for 3-5 days. Moreover, heat denaturation augmented the phosphorylation of AMP-activated protein kinase (AMPK) but reduced the phosphorylation of Akt and mTOR in HUVECs. Furthermore, autophagy inhibition by antioxidant NAC, compound C or AMPK siRNA impaired cell proliferation, migration and tube formation heat-denatured HUVECs. At last, the in vivo experiments also showed that inhibition of autophagy by bafilomycin A1 could suppress angiogenesis and recovery of heat-denatured dermis.Taken together, we firstly revealed that autophagy promotes angiogenesis via AMPK/Akt/mTOR signaling during the recovery of heat-denatured endothelial cells and may provide a potential therapeutic target for the recovery of heat-denatured dermis.

Microgravity induces autophagy via mitochondrial dysfunction in human Hodgkin's lymphoma cells

Gravitational forces can impose physical stresses on the human body as it functions to maintain homeostasis. It has been reported that astronauts exposed to microgravity experience altered biological functions and many subsequent studies on the effects of microgravity have therefore been conducted. However, the anticancer mechanisms of simulated microgravity remain unclear. We previously showed that the proliferation of human Hodgkin's lymphoma (HL) cells was inhibited when these cells were cultured in time-averaged simulated microgravity (taSMG). In the present study, we investigated whether taSMG produced an anticancer effect. Exposure of human HL cells to taSMG for 2 days increased their reactive oxygen species (ROS) production and NADPH oxidase family gene expression, while mitochondrial mass, ATPase, ATP synthase, and intracellular ATP levels were decreased. Furthermore, human HL cells exposed to taSMG underwent autophagy via AMPK/Akt/mTOR and MAPK pathway modulation; such autophagy was inhibited by the ROS scavenger N-acetylcysteine (NAC). These results suggest an innovative therapeutic approach to HL that is markedly different from conventional chemotherapy and radiotherapy.

Glucosamine Extends the Lifespan of Caenorhabditis elegans via Autophagy Induction

Glucosamine (GlcN) is commonly used as a dietary supplement to promote cartilage health in humans. We previously reported that GlcN could induce autophagy in cultured mammalian cells. Autophagy is known to be involved in the prevention of various diseases and aging. Here, we showed that GlcN extended the lifespan of the nematode Caenorhabditis elegans by inducing autophagy. Autophagy induction by GlcN was demonstrated by western blotting for LGG-1 (an ortholog of mammalian LC3) and by detecting autophagosomal dots in seam cells by fluorescence microscopy. Lifespan assays revealed that GlcN-induced lifespan extension was achieved with at least 5 mM GlcN. A maximum lifespan extension of approximately 30 % was achieved with 20 mM GlcN (p<0.0001). GlcN-induced lifespan extension was not dependent on the longevity genes daf-16 and sir-2.1 but dependent on the autophagy-essential gene atg-18. Therefore, we suggest that oral administration of GlcN could help delay the aging process via autophagy induction.

Aggregation is impaired in starved platelets due to enhanced autophagy and cellular energy depletion

Platelet hyperactivity is the hallmark of thrombosis and hemostasis disorders including atherosclerosis, diabetes, stroke, arthritis, and cancer causing significant mortality and morbidity. Therefore, regulating platelet hyperactivity is an ever growing interest. Very recently, basal autophagic process has been demonstrated to be essential for normal functioning of platelets. However, autophagy can be elevated above basal level under conditions like starvation, and how platelets respond in these settings remains to be elucidative. Therefore, in this study we demonstrate a substantial autophagy induction (above basal level) by starvation, which decreases platelet aggregation responses to various agonists. The decreased aggregation in starved platelets was restored in combination with autophagy inhibitors (3-methyladenine and NH₄Cl) and acetate supplementation. Starved platelets also showed decreased calcium mobilization, granule release, and adhesive properties. Furthermore, ex vivo platelets obtained from starved rats showed increased autophagy markers and decreased aggregation responses to various agonists. Our results distinctly explain that enhanced autophagy and cellular energy depletion are the cause for decreased platelet activation and aggregation. The study emphasizes the cardinal role of starvation and autophagy in the management of diseases and disorders associated with platelet hyperactivity.

Cancer stem cells (CSCs): metabolic strategies for their identification and eradication

Phenotypic and functional heterogeneity is one of the most relevant features of cancer cells within different tumor types and is responsible for treatment failure. Cancer stem cells (CSCs) are a population of cells with stem cell-like properties that are considered to be the root cause of tumor heterogeneity, because of their ability to generate the full repertoire of cancer cell types. Moreover, CSCs have been invoked as the main drivers of metastatic dissemination and therapeutic resistance. As such, targeting CSCs may be a useful strategy to improve the effectiveness of classical anticancer therapies. Recently, metabolism has been considered as a relevant player in CSC biology, and indeed, oncogenic alterations trigger the metabolite-driven dissemination of CSCs. More interestingly, the action of metabolic pathways in CSC maintenance might not be merely a consequence of genomic alterations. Indeed, certain metabotypic phenotypes may play a causative role in maintaining the stem traits, acting as an orchestrator of stemness. Here, we review the current studies on the metabolic features of CSCs, focusing on the biochemical energy pathways involved in CSC maintenance and propagation. We provide a detailed overview of the plastic metabolic behavior of CSCs in response to microenvironment changes, genetic aberrations, and pharmacological stressors. In addition, we describe the potential of comprehensive metabolic approaches to identify and selectively eradicate CSCs, together with the possibility to 'force' CSCs within certain metabolic dependences, in order to effectively target such metabolic biochemical inflexibilities. Finally, we focus on targeting mitochondria to halt CSC dissemination and effectively eradicate cancer.