The Influence of Metabolic Inhibitors, Antibiotics, and Microgravity on Intact Cell MALDI-TOF Mass Spectra of the Cyanobacterium Synechococcus Sp. UPOC S4.

The aim and novelty of this paper are found in assessing the influence of inhibitors and antibiotics on intact cell MALDI-TOF mass spectra of the cyanobacterium Synechococcus sp. UPOC S4 and to check the impact on reliability of identification. Defining the limits of this method is important for its use in biology and applied science. The compounds included inhibitors of respiration, glycolysis, citrate cycle, and proteosynthesis. They were used at 1-10 µM concentrations and different periods of up to 3 weeks. Cells were also grown without inhibitors in a microgravity because of expected strong effects. Mass spectra were evaluated using controls and interpreted in terms of differential peaks and their assignment to protein sequences by mass. Antibiotics, azide, and bromopyruvate had the greatest impact. The spectral patterns were markedly altered after a prolonged incubation at higher concentrations, which precluded identification in the database of reference spectra. The incubation in microgravity showed a similar effect. These differences were evident in dendrograms constructed from the spectral data. Enzyme inhibitors affected the spectra to a smaller extent. This study shows that only a long-term presence of antibiotics and strong metabolic inhibitors in the medium at 10-5 M concentrations hinders the correct identification of cyanobacteria by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF).

Terazosin Stimulates Pgk1 to Remedy Gastrointestinal Disorders.

Gastrointestinal disease is the most common health concern that occurs due to environmental, infectious, immunological, psychological, and genetic stress. Among them, the most frequent diseases are gastric ulcer (GU) and ulcerative colitis (UC). DSS-induced UC and ethanol-stimulated GU models resemble the pathophysiology of human gastrointestinal disease. The current study was designed to explore the anti-oxidation, anti-inflammation, anti-cell death properties of terazosin, an α-adrenergic receptor antagonist, in vivo and in vitro. Our results indicate that terazosin dramatically activates Pgk1, and upregulates glycose metabolism, evidenced by the enhanced ATP production and higher LDH enzymatic activity. Also, terazosin significantly enhances p-AKT expression and inhibits NF-κB p65 activation through abrogating the phosphorylation of IKBα, as well as lowers Caspase-1 and GSDMD expression. The findings in this study demonstrate that terazosin exhibits anti-inflammatory effects by downregulating NF-κB-GSDMD signal pathway, along with enhancing glycolysis for gastrointestinal disease treatment. Meanwhile, we also find terazosin ameliorates ethanol-induced gastric mucosal damage in mice. Collectively, as a clinical drug, terazosin should be translated into therapeutics for gastrointestinal disease soon.

Alteration of Intestinal Microbiota in 3-Deoxyglucosone-Induced Prediabetic Rats.

Our previous research suggests that 3-deoxyglucosone (3DG), formed in the caramelization course and Maillard reactions in food, is an independent factor for the development of prediabetes. Since the relationship between type 2 diabetes (T2D) and intestinal microbiota is moving from correlation to causality, we investigated the alterations in the composition and function of the intestinal microbiota in 3DG-induced prediabetic rats. Rats were given 50 mg/kg 3DG by intragastric administration for two weeks. Microbial profiling in faeces samples was determined through the 16S rRNA gene sequence. The glucagon-like peptide 2 (GLP-2) and lipopolysaccharide (LPS) levels in plasma and intestinal tissues were measured by ELISA and Limulus test, respectively. 3DG treatment did not significantly change the richness and evenness but affected the composition of intestinal microbiota. At the phylum level, 3DG treatment increased the abundance of nondominant bacteria Proteobacteria but did not cause the change of the dominant bacteria. Meanwhile, the abundance of the Prevotellaceae family and Parasutterela genus and the Alcaligencaeae family and Burkholderiales order and its attachment to the Betaproteobacteria class were overrepresented in the 3DG group. The bacteria of Candidatus Soleaferrea genus, Gelria genus, and Thermoanaerobacteraceae family and its attachment to Thermoanaerobacterales order were apparently more abundant in the control group. In addition, 45 KEGG pathways were altered after two-week intragastric administration of 3DG. Among these KEGG pathways, 13 KEGG pathways were involved in host metabolic function related to amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, and metabolism of terpenoids and polyketides. Moreover, the increased LPS levels and the decreased GLP-2 concentration in plasma and intestinal tissues were observed in 3DG-treated rats, together with the impaired fasting glucose and oral glucose tolerance. The alterations in composition and function of the intestinal microbiota were observed in 3DG-treated rats, which provides a possible mechanism linking exogenous 3DG intake to the development of prediabetes.

Cellular toxicity of the metabolic inhibitor 2-deoxyglucose and associated resistance mechanisms.

Most malignant cells display increased glucose absorption and metabolism compared to surrounding tissues. This well-described phenomenon results from a metabolic reprogramming occurring during transformation, that provides the building blocks and supports the high energetic cost of proliferation by increasing glycolysis. These features led to the idea that drugs targeting glycolysis might prove efficient in the context of cancer treatment. One of these drugs, 2-deoxyglucose (2-DG), is a synthetic glucose analog that can be imported into cells and interfere with glycolysis and ATP generation. Its preferential targeting to sites of cell proliferation is supported by the observation that a derived molecule, 2-fluoro-2-deoxyglucose (FDG) accumulates in tumors and is used for cancer imaging. Here, we review the toxicity mechanisms of this drug, from the early-described effects on glycolysis to its other cellular consequences, including inhibition of protein glycosylation and endoplasmic reticulum stress, and its interference with signaling pathways. Then, we summarize the current data on the use of 2-DG as an anti-cancer agent, especially in the context of combination therapies, as novel 2-DG-derived drugs are being developed. We also show how the use of 2-DG helped to decipher glucose-signaling pathways in yeast and favored their engineering for biotechnologies. Finally, we discuss the resistance strategies to this inhibitor that have been identified in the course of these studies and which may have important implications regarding a medical use of this drug.

Neuroprotection Effect of Astragaloside IV from 2-DG-Induced Endoplasmic Reticulum Stress.

OBJECTIVE: Astragaloside IV shows neuroprotective activity, but its mechanism remains unclear. To investigate whether astragaloside IV protects from endoplasmic reticulum stress (ERS), we focus on the regulation of glycogen synthase kinase-3ß (GSK-3ß) and mitochondrial permeability transition pore (mPTP) by astragaloside IV in neuronal cell PC12. METHODS AND RESULTS: PC12 cells treated with different concentrations of ERS inductor 2-deoxyglucose (2-DG) (25-500 µM) showed a significant increase of glucose-regulated protein 78 (GRP 78) and GRP 94 expressions and a decrease of tetramethylrhodamine ethyl ester (TMRE) fluorescence intensity and mitochondrial membrane potential (∆Ψm), with the peak effect seen at 50 µM, indicating that 2-DG induces ERS and the mPTP opening. Similarly, 50 µM of astragaloside IV increased the GSK-3ß phosphorylation at Ser9 most significantly. Next, we examined the neuroprotection of astragaloside IV by dividing the PC12 cells into control group, 2-DG treatment group, astragaloside IV plus 2-DG treatment group, and astragaloside IV only group. PC12 cells treated with 50 µM 2-DG for different time courses (0-36 hr) showed a significant increase of Cleaved-Caspase-3 with the peak at 6 hr. 2-DG significantly induced cell apoptosis and increased the green fluorescence intensity of Annexin V-FITC, and these effects were reversed by astragaloside IV. Such a result indicates that astragaloside IV protected neural cell survival from ERS. 2-DG treatment significantly increased the expressions of inositol-requiring ER-to-nucleus signal kinase 1 (IRE1), phosphor-protein kinase R-like ER kinase (p-PERK), but not affect the transcription factor 6 (ATF6) expression. 2-DG treatment significantly decreased the phosphorylation of GSK-3ß and significantly reduced the TMRE fluorescence intensity and ∆Ψm, following mPTP open. Astragaloside IV significantly inhibited the above effects caused by 2-DG, except the upregulation of ATF6 protein. Taken together, astragaloside IV significantly inhibited the ERS caused by 2-DG. CONCLUSION: Our data suggested that astragaloside IV protects PC12 cells from ERS by inactivation of GSK-3ß and preventing the mPTP opening. The GRP 78, GRP 94, IRE1, and PERK signaling pathways but not ATF6 are responsible for GSK-3ß inactivation and neuroprotection by astragaloside IV.

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.

Effect of Lactobacillus delbrueckii LAB4 on hepatic and pancreatic sympathetic nerve activity and blood glucose levels in rats.

Various lactobacilli have been suggested to exert beneficial effects in humans. In this study, we examined the effects of intraduodenal (ID) administration of heat-killed Lactobacillus delbrueckii LAB4 (LAB4) on activities of efferent sympathetic nerves innervating the liver and pancreas. Consequently, it was observed that ID administration of LAB4 significantly reduced either the efferent hepatic sympathetic nerve activity (hepatic-SNA) or pancreatic sympathetic nerve activity (pancreatic-SNA) in urethane-anaesthetised rats. Moreover, the effect of acute and chronic administration of LAB4 (1×109 cells/ml) on hyperglycaemia induced by intracranial injection of 2-deoxy-D-glucose (2DG) were examined in conscious rats. We found that LAB4 significantly inhibited 2DG-induced hyperglycaemia. These findings suggest that ID administration of heat-killed LAB4 might lower plasma glucose level via changes in the autonomic nervous system in rats.

Glycolytic Inhibitor 2-Deoxy-D-Glucose at Chronic Low Dose Mimics Calorie Restriction in Rats Through Mitohormetic Induction of Reactive Oxygen Species.

Caloric restriction mimetics (CRMs) provide an exciting antiaging intervention strategy. 2-Deoxy-D-glucose (2-DG), a glycolytic inhibitor, is known to work as a CRM at high doses; however, at chronic high dose it has been linked to increased mortality in rats. We have investigated chronic low-dose dietary administration of 2-DG on age-related stress protection in young and old male Wistar rats by evaluating age-dependent biomarkers in plasma and erythrocytes. Significant increase was observed in reactive oxygen species levels in 2-DG-treated rats (both young and old), concomitant with increase in activities of erythrocyte plasma membrane redox system (PMRS), catalase (CAT), and superoxide dismutase (SOD). 2-DG treatment also decreased plasma sialic acid and advanced glycation end products. We propose that 2-DG induces a mitohormetic response resulting in augmentation of defense mechanism(s) manifested by higher activity of PMRS, CAT, and SOD. Our findings provide evidence that at chronic low dose 2-DG could be a potential CRM.

Sestrin-Mediated Inhibition of Stress-Induced Intervertebral Disc Degradation Through the Enhancement of Autophagy.

BACKGROUND/AIMS: Intervertebral disc degeneration (IDD) is a pathological process that is the primary cause of low back pain and is potentially mediated by compromised stress defense. Sestrins (Sesn) promote cell survival under stress conditions and regulate AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) signaling. Here, we investigated the expression of Sesn in normal and degraded nucleus pulposus (NP) cells and its potential roles during IDD pathogenesis. METHODS: Sesn expression in normal and degraded NP cells was determined by quantitative polymerase chain reaction and immunoblotting and immunohistochemistry, respectively. Sesn function was investigated by using Sesn knockdown and overexpression techniques with analysis of extracellular matrix (ECM), cell apoptosis, autophagy, AMPK, and mTOR activation. RESULTS: In human cultured NP cells, Sesn expression was significantly decreased in degraded NP cells at both the RNA and protein levels. The expression of Sesn1, 2, and 3 increased after stimulation by 2-deoxyglucose (2-DG), an endoplasmic reticulum stress inducer. 2-DG could also increase cell apoptosis, promote extracellular matrix (ECM) degradation, and positively regulate autophagy in NP cells. Sesn knockdown by small interfering RNA increased NP cell apoptosis and ECM degradation under basal culture conditions and in the presence of 2DG. Conversely, Sesn overexpression mediated by plasmid transfection repressed IDD by enhancing autophagy, which was associated with changes in mTOR but not AMPK activation. CONCLUSIONS: Sesn expression is suppressed in degraded NP cells. In addition, Sesn inhibits stress-induced cell apoptosis and ECM degradation by enhancing autophagy, which is modulated though mTOR activity. Suppression of Sesn might therefore represent an important cellular dysfunction mechanism in the process of IDD.

2-Deoxy-D-glucose Restore Glucocorticoid Sensitivity in Acute Lymphoblastic Leukemia via Modification of N-Linked Glycosylation in an Oxygen Tension-Independent Manner.

In childhood acute lymphoblastic leukemia, treatment failure is associated with resistance to glucocorticoid agents. Resistance to this class of drugs represents one of the strongest indicators of poor clinical outcome. We show that leukemic cells, which are resistant to the glucocorticoid drug methylprednisolone, display a higher demand of glucose associated with a deregulation of metabolic pathways, in comparison to sensitive cells. Interestingly, a combinatorial treatment of glucocorticoid and the glucose analog 2-deoxy-D-glucose displayed a synergistic effect in methylprednisolone-resistant cells, in an oxygen tension-independent manner. Unlike solid tumors, where 2-deoxy-D-glucose promotes inhibition of glycolysis by hexokinase II exclusively under hypoxic conditions, we were able to show that the antileukemic effects of 2-deoxy-D-glucose are far more complex in leukemia. We demonstrate a hexokinase II-independent cell viability decrease and apoptosis induction of the glucose analog in leukemia. Additionally, due to the structural similarity of 2-deoxy-D-glucose with mannose, we could confirm that the mechanism by which 2-deoxy-D-glucose predominantly acts in leukemia is via modification in N-linked glycosylation, leading to endoplasmic reticulum stress and consequently induction of the unfolded protein response.

Nitrosative stress by peroxynitrite impairs ATP production in human spermatozoa.

The most toxic species in live systems include reactive nitrogen species such as peroxynitrite, which at high levels induces nitrosative stress. In human spermatozoa, the negative effect of peroxynitrite on motility and mitochondrial membrane potential was recently demonstrated, and the hypothesis of this work is that impairment of ATP production could be one cause of the effect on motility. Therefore, the aim here was to evaluate ATP production by both glycolysis and oxidative phosphorylation (OXPHOS) in spermatozoa exposed to peroxynitrite in vitro. Human spermatozoa were incubated with SIN-1, a molecule which generates peroxynitrite, and the ATP level was evaluated. Then, to inactivate glycolysis or OXPHOS, spermatozoa were incubated with pharmacological inhibitors of these pathways. Spermatozoa treated for inactivating one or the other pathway were exposed to SIN-1, and the ATP level was compared to the control without SIN-1 in each condition. The ATP level fell after peroxynitrite exposure. The ATP in spermatozoa treated for inactivating one or the other metabolic pathway and subsequently exposed to peroxynitrite was reduced compared with the control. These results show for the first time that an important mechanism by which peroxynitrite reduces sperm function is the inhibition of ATP production, affecting both glycolysis and OXPHOS.

2-Deoxy-d-Glucose (2-DG)-Induced Cardiac Toxicity in Rat: NT-proBNP and BNP as Potential Early Cardiac Safety Biomarkers.

2-Deoxy-d-glucose (2-DG) is being developed as a potential anticonvulsant and disease-modifying agent for patients with epilepsy; however, during preclinical development, cardiac toxicity has been encountered in rats. This study was performed to determine whether cardiac troponin (cTnI and cTnT), atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), N-terminal pro-brain natriuretic peptide (NT-proBNP), and/or creatine kinase (CK) could be useful as indicators of 2-DG cardiac toxicity. In addition, this study also investigated the association of cardiac histopathological changes with these biomarkers. F344 rats (4/sex/group/sacrifice point) were gavaged with either vehicle or 2-DG (50, 125, or 375 mg/kg twice daily; total daily dose of 100, 250, or 750 mg/kg/d) for 7, 14, 21, or 45 days followed by a 15-day recovery. Dose-dependent increases in NT-proBNP and BNP plasma concentrations were observed. Following recovery period, the NT-proBNP and BNP concentrations returned to baseline levels. There were no remarkable increases in CK, ANP, cTnI, or cTnT concentrations. There were no gross cardiac lesions observed at the necropsy. Microscopic findings of vacuolar degeneration and hypertrophy of the endothelial cells of the endocardium were present in the heart at doses of 250 and 750 mg/kg/d. Microscopic findings, in general, were associated with increases in NT-proBNP levels. Cardiac toxicity appeared to be reversible. In conclusion, NT-proBNP and BNP are potential early biomarkers for 2-DG-induced cardiac toxicity that can be useful to monitor 2-DG therapy in clinical trials.

Distribution and neurochemical characterization of neurons in the rat ventrolateral medulla activated by glucoprivation.

Hypoglycemia elicits physiological and behavioral responses which are mediated in part by neurons within the ventrolateral medulla (VLM). The present study describes the neurochemistry of neurons activated by glucoprivation (2-deoxy-D-glucose, 2DG), specifically those within regions containing the A1, caudal C1 (cC1) and rostral C1 (rC1) cell groups. 2DG induced c-Fos immunoreactivity throughout the VLM. Activated neurons expressing prepro-cocaine and amphetamine-regulated transcript (PPCART), neuropeptide Y (NPY), glutamic acid decarboxylase (GAD67) or prepro-enkephalin (PPE) mRNA and/or immunoreactivity (-ir) for tyrosine hydroxylase (TH) were identified. TH(+) neurons were recruited in a dose-dependent manner. At high doses of 2DG [400 mg/kg, (n = 6)], 76 ± 1.2 % of activated neurons were TH(+) representing 52 ± 1.3 % of the total TH population. Virtually all activated neurons in the A1 and cC1 regions but only 60 % in the rC1 region were TH(+). Within the A1 region, TH(+), TH(+)NPY(+) and TH(+)NPY(+)PPE(+) subpopulations were activated and likely regulate vasopressin, oxytocin, and corticotrophin releasing hormone (CRH) from the hypothalamus. Within the cC1 region, non-TH neurons, TH(+)NPY(+), TH(+)NPY(+)PPCART(+), and TH(+)NPY(+)PPE(+) subpopulations were activated, likely regulating autonomic hypothalamic neurons or CRH and thyrotropin releasing hormone secretion. Within the rC1 region, non-TH neurons (40 % of those activated) were predominantly PPE(+) and were recruited by higher 2DG doses. Of the TH(+) activated neurons in the rC1 region, many expressed PPCART and half expressed NPY. The activated spinally projecting population was almost entirely TH(+)PPCART(+) and is likely to regulate adrenaline and glucagon release. These data indicate that glucoprivation activates at least nine phenotypically distinct populations of neurons in the VLM.

The unfolded protein response mediates reversible tau phosphorylation induced by metabolic stress.

The unfolded protein response (UPR) is activated in neurodegenerative tauopathies such as Alzheimer's disease (AD) in close connection with early stages of tau pathology. Metabolic disturbances are strongly associated with increased risk for AD and are a potent inducer of the UPR. Here, we demonstrate that metabolic stress induces the phosphorylation of endogenous tau via activation of the UPR. Strikingly, upon restoration of the metabolic homeostasis, not only the levels of the UPR markers pPERK, pIRE1α and BiP, but also tau phosphorylation are reversed both in cell models as well as in torpor, a physiological hypometabolic model in vivo. Intervention in the UPR using the global UPR inhibitor TUDCA or a specific small-molecule inhibitor of the PERK signaling pathway, inhibits the metabolic stress-induced phosphorylation of tau. These data support a role for UPR-mediated tau phosphorylation as part of an adaptive response to metabolic stress. Failure to restore the metabolic homeostasis will lead to prolonged UPR activation and tau phosphorylation, and may thus contribute to AD pathogenesis. We demonstrate that the UPR is functionally involved in the early stages of tau pathology. Our data indicate that targeting of the UPR may be employed for early intervention in tau-related neurodegenerative diseases.

Structure- and concentration-specific assessment of the physiological reactivity of α-dicarbonyl glucose degradation products in peritoneal dialysis fluids.

In peritoneal dialysis (PD), glucose degradation products (GDPs), which are formed during heat sterilization of dialysis fluids, lead to structural and functional changes in the peritoneal membrane, which eventually result in the loss of its ultrafiltration capacity. To determine the molecular mechanisms behind these processes, the present study tested the influence of the six major α-dicarbonyl GDPs in PD fluids, namely, glyoxal, methylglyoxal, 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), and glucosone with respect to their potential to impair the enzymatic activity of RNase A as well as their effects on cell viability. For comprehensive risk assessment, the α-dicarbonyl GDPs were applied separately and in concentrations as present in conventional PD fluids. Thus, it was shown that after 5 days, glucosone impaired RNase A activity most distinctly (58% remaining activity, p < 0.001 compared to that of the control), followed by 3,4-DGE (62%, p < 0.001), 3-DGal (66%, p < 0.001), and 3-DG (76%, p < 0.01). Methylglyoxal and glyoxal caused weaker inactivation with significant effects only after 10 days of incubation (79%, 81%, p < 0.001). Profiling of the advanced glycation end products formed during the incubation of RNase A with methylglyoxal revealed predominant formation of the arginine modifications imidazolinone, CEA/dihydroxyimidazoline, and tetrahydropyrimidine at Arg10, Arg33, Arg39, and Arg85. Particularly, modification at Arg39 may severely affect the active site of the enzyme. Additionally, structure- and concentration-specific assessment of the cytotoxicity of the α-dicarbonyl GDPs was performed. Although present at very low concentration, the cytotoxic effect of PD fluids after 2 days of incubation was exclusively caused by 3,4-DGE (14% cell viability, p < 0.001). After 4 days of incubation, 3-DGal (13% cell viability, p < 0.001), 3-DG (24%, p < 0.001), and, to a lower extent, glyoxal and methylglyoxal (both 57%, p < 0.01) also reduced cell viability significantly. In conclusion, 3,4-DGE, 3-DGal, and glucosone appear to be the most relevant parameters for the biocompatibility of PD fluids.

Temperature increase exacerbates apoptotic neuronal death in chemically-induced ischemia.

It is well-established that hyperthermia increases neuronal death and worsens stroke outcome. However, little is known about the mechanisms of how hyperthermia is involved in this neuronal death process. In the present study, we examined how temperature increase exacerbates neuronal death using a model of chemical ischemia. Chemical ischemia was induced by treating SH-SY5Y neuroblastoma cells with sodium azide and deoxyglucose. Temperature increase was treated by placing the cells at 37°C (control) and 41°C (experimental). Cell survival was determined by trypan blue assay and ATP levels were measured with ATP assay kits. Protein expression was detected by western blot. Treatment with sodium azide resulted in cell death in a dose-responsive manner. Increased temperature worsened the ATP depletion and cell volume shrinkage. Temperature increase also enhanced ER stress as demonstrated by the elevated level of phospho-eIF2α and C/EBP homologous protein (CHOP). Inhibition of CHOP expression significantly decreased sodium azide-induced neuronal death. In addition, the increased temperature intensified the activation of caspase-3, an apoptotic effector protease, and inhibition of capspase-3 significantly reduced cell death. These findings support that temperature increase worsened the neuronal death by depleting intracellular ATP, inducing ER stress response and activating apoptotic signal transduction.

Sestrin2 integrates Akt and mTOR signaling to protect cells against energetic stress-induced death.

The phosphoinositide-3 kinase/Akt (PI3K/Akt) pathway has a central role in cancer cell metabolism and proliferation. More importantly, it is one of the cardinal pro-survival pathways mediating resistance to apoptosis. The role of Akt in response to an energetic stress is presently unclear. Here, we show that Sestrin2 (Sesn2), also known as Hi95, a p53 target gene that protects cells against oxidative and genotoxic stresses, participates in the protective role of Akt in response to an energetic stress induced by 2-deoxyglucose (2-DG). Sesn2 is upregulated in response to an energetic stress such as 2-DG and metformin, and mediates the inhibition of mammalian target of rapamycin (mTOR), the major cellular regulator of energy metabolism. The increase of Sesn2 is independent of p53 but requires the anti-apoptotic pathway, PI3K/Akt. Inhibition of Akt, as well as loss of Sesn2, sensitizes cells to 2-DG-induced apoptosis. In addition, the rescue of Sesn2 partially reverses the pro-apoptotic effects of 2-DG. In conclusion, we identify Sesn2 as a new energetic stress sensor, which appears to be protective against energetic stress-induced apoptosis that integrates the pro-survival function of Akt and the negative regulation of mTOR.

Glucose--a sweet way to die: metabolic switching modulates tumor cell death.

TRAIL, a putative anticancer cytokine, induces extrinsic cell death by activating the caspase cascade directly (Type I cells) via the death-inducing signaling complex (DISC) or indirectly (Type II cells) by caspase-8 cleavage of Bid and activation of the mitochondrial cell death pathway. Cancer cells are characterized by their dependence on aerobic glycolysis, which, although inefficient in terms of ATP production, facilitates tumor metabolism. Our studies show that TRAIL-induced cell death is significantly affected by the metabolic status of the cell. Inhibiting glycolysis with 2-deoxyglucose potentiates TRAIL-induced cell death, whereas glucose deprivation can paradoxically inhibit apoptosis. These conflicting responses to glycolysis inhibition are modulated by the balance between the Akt and AMPK pathways and their subsequent downstream regulation of mTORC1. This results in marked changes in protein translation, in which the equilibrium between anti- and pro-apoptotic Bcl-2 family member proteins is decided by their individual degradation rates. This regulates the mitochondrial cell death pathway and alters its sensitivity not only to TRAIL, but to ABT-737, a Bcl-2 inhibitor. Taken together, our studies show that the sensitivity of cancer cells to apoptosis can be modulated by targeting their unique metabolism in order to enhance sensitivity to apoptotic agents.

Adipose tissue and bone marrow-derived stem cells react similarly in an ischaemia-like microenvironment.

Mesenchymal stem cells (MSCs) from adipose tissue and bone marrow are promising cell sources for autologous cell therapy of nerve injuries, as demonstrated by their intrinsic neurotrophic potential. However, extensive death of transplanted cells limits their full benefits. This study investigated the effects of ischaemia (metabolically induced by sodium azide and 2-deoxyglucose) and serum-derived mitogens on the viability and functional profile of MSCs in vitro. MSCs were more susceptible to combined, rather than individual, blockade of glycolysis and oxidative phosphorylation. Apoptosis and autophagy were involved in ischaemia-induced cell death. Chemical ischaemia alone and serum withdrawal alone induced a similar amount of cell death, with significantly different intracellular ATP maintenance. Combined ischaemia and serum deprivation had additive effects on cell death. Expression of the extracellular matrix (ECM) molecules laminin and fibronectin was attenuated under ischaemia and independent of serum level; however, BDNF and NGF levels remained relatively constant. Strong upregulation of VEGF and to a lesser extent angiopoietin-1 was observed under ischaemia but not in serum withdrawal conditions. Importantly, this study demonstrated similar reactions of MSCs derived from adipose and bone marrow tissue, in ischaemia-like and mitogen-deprived microenvironments in terms of viability, cellular energetics, cell death mechanisms and expression levels of various growth-promoting molecules. Also, the results suggest that ischaemia has a larger impact on the ability of MSCs to survive transplantation than withdrawal of mitogens.

Enhancement of cytotoxic and pro-apoptotic effects of 2-aminophenoxazine-3-one on the rat hepatocellular carcinoma cell line dRLh-84, the human hepatocellular carcinoma cell line HepG2, and the rat normal hepatocellular cell line RLN-10 in combination with 2-deoxy-D-glucose.

The cytotoxic and pro-apoptotic effects of a single dose of 2-aminophenoxazine-3-one (Phx-3) or 2-deoxyglucose (2-DG) or of a combined dose of Phx-3 and 2-DG were studied in the rat hepatocellular carcinoma cell line dRLh-84, the human hepatocellular carcinoma cell line HepG2 and the rat normal hepatocellular cell line RLN-10. The number of viable cells decreased in a dose-dependent manner, when dRLh-84, HepG2 or RLN-10 cells were treated with 2-DG (0.5-20 mM) or Phx-3 (1-50 µM) alone at 37˚C for 48 h. When these cells were treated with 10 mM 2-DG and different concentrations of Phx-3, the number of viable cells decreased dose-dependently and in an additive manner for these agents. A single dose of 2 or 10 µM Phx-3 induced apoptotic morphology characterized by nuclear condensation and cell shrinkage in dRLh-84, HepG2 and RLN-10 cells, while a single dose of 10 mM 2-DG did not. When Phx-3 (2 or 10 µM) treatment was combined with 2-DG (10 mM) treatment in these three cell lines, the cells with apoptotic morphology increased extensively, which was confirmed by flow cytometric analysis. In addition, autophagic morphology characterized by cytosolic vacuole formation was significantly increased in the hepatocellular carcinoma cell lines dRLh-84 and HepG2 but not in the normal hepatocellular cell line RLN-10 after a single dose of Phx-3 or 2-DG or a combined dose of Phx-3 and 2-DG. Furthermore, when dRLh-84 and HepG2 cells were treated with Phx-3 alone or a combined dose of Phx-3 and 2-DG, depolarization of the mitochondria was extensive, but that of the normal cell line RLN-10 was not. These results may imply that the mechanism for the apoptosis of hepatocellular carcinoma cells caused by Phx-3 alone or a combined dose of Phx-3 and 2-DG differs from that of the normal cell line RLN-10. The present results demonstrate that Phx-3 alone may be beneficial for targeting liver cancer and that its anticancer activity may be enhanced by 2-DG. However, a combined dose of Phx-3 and 2-DG may exert adverse effects on normal liver cells, as evidenced by the cytotoxic and pro-apoptotic effects of the combined treatment in the rat normal hepatocellular cell line RLN-10.