Endoplasmic reticulum stress (ER-stress) by 2-deoxy-D-glucose (2DG) reduces cyclooxygenase-2 (COX-2) expression and N-glycosylation and induces a loss of COX-2 activity via a Src kinase-dependent pathway in rabbit articular chondrocytes

Novel insight on IRE1 in the regulation of chondrocyte dedifferentiation through ER stress independent pathway

Inositol-requiring enzyme-1 (IRE1) is the master regulator of the unfolded protein response pathway, associated with the endoplasmic reticulum (ER) in sensing and regulating cell stress. The activity of IRE1 is highly explored and well-characterized in cancer and other cells. However, the IRE1 molecular mechanism in chondrocytes is poorly understood. The present study explored the effect of IRE1 on chondrocytes regarding its chondrogenic gene expression and its correlation with different cellular pathways and cell behavior. Chondrocytes transfected with the cDNA of IRE1 reduced the expression of type II collagen, disrupting chondrocyte differentiation as confirmed by western blotting and immunofluorescence. Upon siRNA treatment, the influence of IRE1 on chondrocyte differentiation is restored by reviving the normal expression of type II collagen. Different molecular pathways were explored to investigate the role of IRE1 in causing chondrocyte dedifferentiation. However, we found no significant correlation, as IRE1 induces dedifferentiation through independent pathways. In response to various endoplasmic reticulum (ER) agonists (2-deoxy-D-glucose), and ER stress antagonists (tauroursodeoxycholic acid and salubrinal), IRE1 overexpression did not affect GRP78/94, as implicated in the pathogenesis of ER stress. Moreover, when IRE1 overexpression was correlated with the inflammation pathway, nuclear factor-kappa B (NFκB), IRE1 substantially increased the expression of p50 while decreasing the expression of nuclear factor kappa light polypeptide alpha (IκBα). These results suggest that IRE1 induces dedifferentiation in chondrocytes by modulating inflammatory pathways that cause dedifferentiation by disrupting type II collagen expression.

Cross-talk between bioactive lipid mediators and the unfolded protein response in ischemic stroke

Ischemic cerebral stroke is a severe medical condition that affects about 15 million people every year and is the second leading cause of death and disability globally. Ischemic stroke results in neuronal cell death and neurological impairment. Current therapies may not adequately address the deleterious metabolic changes and may increase neurological damage. Oxygen and nutrient depletion along with the tissue damage result in endoplasmic reticulum (ER) stress, including the Unfolded Protein Response (UPR), and neuroinflammation in the affected area and cause cell death in the lesion core. The spatio-temporal production of lipid mediators, either pro-inflammatory or pro-resolving, decides the course and outcome of stroke. The modulation of the UPR as well as the resolution of inflammation promotes post-stroke cellular viability and neuroprotection. However, studies about the interplay between the UPR and bioactive lipid mediators remain elusive and this review gives insights about the crosstalk between lipid mediators and the UPR in ischemic stroke. Overall, the treatment of ischemic stroke is often inadequate due to lack of effective drugs, thus, this review will provide novel therapeutical strategies that could promote the functional recovery from ischemic stroke.

Glycolytic enzyme PKM2 regulates cell senescence but not inflammation in the process of osteoarthritis

Chondrocyte senescence is an important mechanism underlying osteoarthritis in the senile population and is characterized by reduced expressions of the extracellular matrix proteins. The involvement of glycolysis and the tricarboxylic acid cycle in the development of osteoarthritis is inclusive. The present study aims to investigate the role of the glycolytic enzyme M2 isoform of pyruvate kinase (PKM2) in chondrocytes in senescence and inflammation. Primary chondrocytes are isolated from the knee joints of neonatal mice. Small interfering RNAs (siRNAs) against PKM2 are transfected using lipofectamine. RNA sequencing is conducted in primary chondrocytes with the PKM2 gene deleted. Cell apoptosis, autophagy, reactive oxygen species measurement, and senescent conditions are examined. The glycolytic rate in cells is measured by Seahorse examination. Interleukin 1-β (IL-1β) increases the protein expressions of matrix metallopeptidases (MMP)13 and PKM2 and reduces the protein expression of collagen type II (COL2A1) in primary chondrocytes. Silencing of PKM2 alters the protein expressions of MMP13, PKM2, and COL2A1 in the same pattern in quiescent and stimulated chondrocytes. RNA sequencing analysis reveals that PKM2 silencing reduces senescent biomarker p16 INK4a expression. Compared with low-passage chondrocytes, high-passage chondrocytes exhibit increased expression of p16 INK4a and reduced expression of COL2A1. Silencing of PKM2 reduces SA-β-Gal signals and increases COL2A1 expression in high-passage chondrocytes. Seahorse assay reveals that PKM2 deletion favors the tricarboxylic acid cycle in mitochondria in low- but not in high-passage chondrocytes. In summary, the glycolytic enzyme PMK2 modulates chondrocyte senescence but does not participate in the regulation of inflammation.

Osteoarthritic chondrocytes undergo a glycolysis-related metabolic switch upon exposure to IL-1b or TNF

BACKGROUND

Osteoarthritis is an age-related disease that currently faces a lack of symptomatic treatment. Inflammation, which is mainly sustained by pro-inflammatory cytokines such as IL-1b, TNF, and IL-6, plays an important role in osteoarthritis progression. In this context, pro-inflammatory cytokines are widely used to mimic the inflammatory component of osteoarthritis in vitro. However, the therapeutic failures of clinical trials evaluating anti-cytokines drugs highlight the lack of overall understanding of the effects of these cytokines on chondrocytes.

METHODS

Here, we generated a comprehensive transcriptomic and proteomic dataset of osteoarthritic chondrocytes treated with these cytokines to describe their pro-inflammatory signature and compare it to the transcriptome of non-osteoarthritic chondrocytes. Then, the dysregulations highlighted at the molecular level were functionally confirmed by real-time cellular metabolic assays.

RESULTS

We identified dysregulation of metabolic-related genes in osteoarthritic chondrocytes but not in non-osteoarthritic chondrocytes. A metabolic shift, toward increased glycolysis at the expense of mitochondrial respiration, was specifically confirmed in osteoarthritic chondrocytes treated with IL-1b or TNF.

CONCLUSION

These data show a strong and specific association between inflammation and metabolism in osteoarthritic chondrocytes, which was not found in non-osteoarthritic chondrocytes. This indicates that the link between inflammation and metabolic dysregulation may be exacerbated during chondrocyte damage in osteoarthritis. Video Abstract.

Multitranscript analysis reveals an effect of 2-deoxy-d-glucose on gene expression linked to unfolded protein response and integrated stress response in primary human monocytes and monocyte-derived macrophages

BACKGROUND

Glycolytic inhibitor 2-deoxy-d-glucose (2-DG) binds to hexokinase in a non-competitive manner and phosphoglucose isomerase in a competitive manner, blocking the initial steps of the glycolytic pathway. Although 2-DG stimulates endoplasmic reticulum (ER) stress, activating the unfolded protein response to restore protein homeostasis, it is unclear which ER stress-related genes are modulated in response to 2-DG treatment in human primary cells. Here, we aimed to determine whether the treatment of monocytes and monocyte-derived macrophages (MDMs) with 2-DG leads to a transcriptional profile specific to ER stress.

METHODS

We performed bioinformatics analysis to identify differentially expressed genes (DEGs) in previously reported RNA-seq datasets of 2-DG treated cells. RT-qPCR was performed to verify the sequencing data on cultured MDMs.

RESULTS

A total of 95 common DEGs were found by transcriptional analysis of monocytes and MDMs treated with 2-DG. Among these, 74 were up-regulated and 21 were down-regulated. Multitranscript analysis showed that DEGs are linked to integrated stress response (GRP78/BiP, PERK, ATF4, CHOP, GADD34, IRE1α, XBP1, SESN2, ASNS, PHGDH), hexosamine biosynthetic pathway (GFAT1, GNA1, PGM3, UAP1), and mannose metabolism (GMPPA and GMPPB).

CONCLUSIONS

Results reveal that 2-DG triggers a gene expression program that might be involved in restoring protein homeostasis in primary cells.

GENERAL SIGNIFICANCE

2-DG is known to inhibit glycolysis and induce ER stress; however, its effect on gene expression in primary cells is not well understood. This work shows that 2-DG is a stress inducer shifting the metabolic state of monocytes and macrophages.

Multifaceted role of ferroptosis in cardiovascular disease

Ferroptosis is a newly identified form of non-apoptotic cell death characterised primarily by iron-dependent lipid peroxidation. It differs morphologically, biochemically, and genetically from other forms of cell death, such as apoptosis, autophagy, and necrosis. Although the molecular mechanism underlying ferroptosis remains unclear, multiple biological processes, such as iron metabolism, lipid peroxides, and systems, such as the glutathione system and the tetrahydrobiopterin/coenzyme Q10 system, appear to be involved. While the contribution of ferroptotic mechanisms to human diseases is not clear, recent studies have identified a number of ferroptosis-related genes. Cardiovascular diseases are the main cause of death globally. In this review, we outline the progress regarding the emerging role of ferroptosis in the pathogenesis of cardiac pathophysiological conditions and the association of ferroptosis with cardiomyopathy, myocardial ischemia-reperfusion injury, heart failure, and atherosclerosis. We further summarise newly discovered ferroptotic targets for the development of therapies for cardiovascular diseases. Finally, we discuss the current challenges and future research directions in cardiovascular disease treatments.

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.

Targeted inhibition of STAT3 induces immunogenic cell death of hepatocellular carcinoma cells via glycolysis

In hepatocellular carcinoma (HCC), the signal transducer and activator of transcription 3 (STAT3) is present in an overactive state that is closely related to tumour development and immune escape. STAT3 inhibition reshapes the tumour immune microenvironment, but the underlying mechanisms have not been fully clarified. We found that STAT3 inhibition could induce immunogenic cell death (ICD) of HCC cells via translocation of the “eat me” molecule calreticulin to the cell surface and a significant reduction in the expression of the “don’t eat me” molecule leucocyte surface antigen CD47. STAT3 inhibition promoted dendritic cell (DC) activation and enhanced the recognition and phagocytosis of HCC cells by macrophages. Furthermore, STAT3 inhibition prevented the expression of key glycolytic enzymes, facilitating the induction of ICD in HCC. Interestingly, STAT3 directly regulated the transcription of CD47 and solute carrier family 2 member 1 (SLC2A1; also known as GLUT1). In subcutaneous and orthotopic transplantation mouse tumour models, the STAT3 inhibitor napabucasin prevented tumour growth and induced the expression of calreticulin and the protein disulfide isomerase family A member 3 (PDIA3; also known as ERp57) but suppressed that of CD47 and GLUT1. Meanwhile, the amount of tumour‐infiltrated DCs and macrophages increased, along with the expression of costimulatory molecules. More CD4⁺ and CD8⁺ T cells accumulated in tumour tissues, and CD8⁺ T cells had lower expression of checkpoint molecules such as lymphocyte activation gene 3 protein (LAG‐3) and programmed cell death protein 1 (PD‐1). Significantly, the antitumour immune memory response was induced by treatment targeting STAT3. These findings provide a new mechanism for targeting STAT3‐induced ICD in HCC, and confirms STAT3 as a potential target for the treatment of HCC via reshaping the tumour immune microenvironment.

PALMD regulates aortic valve calcification via altered glycolysis and NF-κB-mediated inflammation

Recent genome-wide association and transcriptome-wide association studies have identified an association between the PALMD locus, encoding palmdelphin, a protein involved in myoblast differentiation, and calcific aortic valve disease (CAVD). Nevertheless, the function and underlying mechanisms of PALMD in CAVD remain unclear. We herein investigated whether and how PALMD affects the pathogenesis of CAVD using clinical samples from CAVD patients and a human valve interstitial cell (hVIC) in vitro calcification model. We showed that PALMD was upregulated in calcified regions of human aortic valves and calcified hVICs. Furthermore, silencing of PALMD reduced hVIC in vitro calcification, osteogenic differentiation, and apoptosis, whereas overexpression of PALMD had the opposite effect. RNA-Seq of PALMD-depleted hVICs revealed that silencing of PALMD reduced glycolysis and nuclear factor-κB (NF-κB)–mediated inflammation in hVICs and attenuated tumor necrosis factor α–induced monocyte adhesion to hVICs. Having established the role of PALMD in hVIC glycolysis, we examined whether glycolysis itself could regulate hVIC osteogenic differentiation and inflammation. Intriguingly, the inhibition of PFKFB3-mediated glycolysis significantly attenuated osteogenic differentiation and inflammation of hVICs. However, silencing of PFKFB3 inhibited PALMD-induced hVIC inflammation, but not osteogenic differentiation. Finally, we showed that the overexpression of PALMD enhanced hVIC osteogenic differentiation and inflammation, as opposed to glycolysis, through the activation of NF-κB. The present study demonstrates that the genome-wide association– and transcriptome-wide association–identified CAVD risk gene PALMD may promote CAVD development through regulation of glycolysis and NF-κB–mediated inflammation. We propose that targeting PALMD-mediated glycolysis may represent a novel therapeutic strategy for treating CAVD.

Glycolytic inhibitor 2-deoxy-d-glucose attenuates SARS-CoV-2 multiplication in host cells and weakens the infective potential of progeny virions

Aims

Virus-infected host cells switch their metabolism to a more glycolytic phenotype, required for new virion synthesis and packaging. Therefore, we investigated the effect and mechanistic action of glycolytic inhibitor 2-Deoxy-d-glucose (2-DG) on virus multiplication in host cells following SARS-CoV-2 infection.

Main methods

SARS-CoV-2 induced change in glycolysis was examined in Vero E6 cells. Effect of 2-DG on virus multiplication was evaluated by RT-PCR (N and RdRp genes) analysis, protein expression analysis of Nucleocapsid (N) and Spike (S) proteins and visual indication of cytopathy effect (CPE), The mass spectrometry analysis was performed to examine the 2-DG induced change in glycosylation status of receptor binding domain (RBD) in SARS-CoV-2 spike protein.

Key findings

We observed SARS-COV-2 infection induced increased glucose influx and glycolysis, resulting in selectively high accumulation of the fluorescent glucose analog, 2-NBDG in Vero E6 cells. 2-DG inhibited glycolysis, reduced virus multiplication and alleviated cells from virus-induced cytopathic effect (CPE) in SARS-CoV-2 infected cells. The progeny virions produced from 2-DG treated cells were found unglycosylated at crucial N-glycosites (N331 and N343) of the receptor-binding domain (RBD) in the spike protein, resulting in production of defective progeny virions with compromised infective potential.

Significance

The mechanistic study revealed that the inhibition of SARS-COV-2 multiplication is attributed to 2-DG induced glycolysis inhibition and possibly un-glycosylation of the spike protein, also. Therefore, based on its previous human trials in different types of Cancer and Herpes patients, it could be a potential molecule to study in COVID-19 patients.

The beneficial effect of salubrinal on neuroinflammation and neuronal loss in intranigral LPS-induced hemi-Parkinson disease model in rats

OBJECTIVE

Endoplasmic reticulum stress (ERS) and neuroinflammation are triggers for neurodegenerative disorders. Salubrinal is a selective inhibitor of protein phosphatase 1 (PP1) complex involving dephosphorylation of phosphorylated eukaryotic initiation factor-2α (eIF2α), the key crucial pathway in the ERS. Therefore, this study assessed the effects of inhibition of the ERS with salubrinal in the intranigral hemi-Parkinson disease (PD) model.

MATERIALS AND METHODS

Animals were treated with salubrinal for one week after the PD model was created by intranigral lipopolysaccharide (LPS) administration. Apomorphine-induced rotation, rotarod, cylinder, and pole tests were performed to evaluate behavioral changes. Proinflammatory cytokines and the expression level of the dual specificity protein phosphatase 2 (DUSP2), PP1, and p-eIF2α were evaluated. Nigral expression of inducible nitric oxide synthase (iNOS), nuclear factor kappaB (Nf-κB), and cyclooxygenase (COX)-2 was determined. Finally, tyrosine hydroxylase and caspase-3/ caspase-9 expressions were assessed by immunohistochemistry.

RESULTS

Salubrinal reduced the motor impairments and dopamine-related behavioral deficiencies caused by the LPS. Salubrinal attenuated the LPS-induced increased levels of interleukin (IL)-1β, IL-6, tumor necrosis factor-α, and salubrinal rescued the loss of TH expression and dopamine levels and prevented the caspase-3/9 increase in the substantial nigra (SN). LPS potently increased iNOS, Nf-κB, and COX-2 expression, but this effect was reduced after salubrinal treatment. Additionally, salubrinal attenuated the LPS-induced PP1 and DUSP2 increase.

CONCLUSION

Our results reveal that salubrinal is attenuating several inflammatory mediators and thereby decreased the inflammatory effects of LPS in the neurons of the SN. Together this results in increased cellular survival and maintained integrity of SN. Taken together our data show the beneficial effects of inhibition of ERS to restrict neuroinflammatory progression and neuronal loss in a PD model.

Autophagy and organelle homeostasis in cancer

Beginning with the earliest studies of autophagy in cancer, there have been indications that autophagy can both promote and inhibit cancer growth and progression; autophagy regulation of organelle homeostasis is similarly complicated. In this review we discuss pro- and antitumor effects of organelle-targeted autophagy and how this contributes to several hallmarks of cancer, such as evading cell death, genomic instability, and altered metabolism. Typically, the removal of damaged or dysfunctional organelles prevents tumor development but can also aid in proliferation or drug resistance in established tumors. By better understanding how organelle-specific autophagy takes place and can be manipulated, it may be possible to go beyond the brute-force approach of trying to manipulate all autophagy in order to improve therapeutic targeting of this process in cancer.

Impact of impaired glucose metabolism on responses to a psychophysical stressor: modulation by ketamine

RATIONALE

There is evidence that hypoglycemia, a metabolic stressor, can negatively impact mood and motivation, and can interact with other stressors to potentiate their effects on behavior and physiology.

OBJECTIVES/METHODS

The current study in male Sprague-Dawley rats explored the interaction between impaired glucose metabolism induced by 0, 200, or 300 mg/kg 2-deoxy-D-glucose (2-DG) and a psychophysical stressor induced by forced swimming stress (FSS; 6 sessions, 10 min/session). The endpoints of interest were blood glucose levels, progressive behavioral immobility, and saccharin preference (2-bottle choice test). Furthermore, it was investigated whether pre-treatment with 0, 10, or 20 mg/kg ketamine could modify the interaction between 2-DG and FSS on these endpoints.

RESULTS

It was found that 2-DG increased blood glucose levels equally in all experimental groups, accelerated the immobile response to FSS, and suppressed saccharin preference 1 week following termination of stress exposure. As well, pre-treatment with ketamine blocked the effects of combined 2-DG and FSS on immobility and saccharin preference without affecting blood glucose levels and produced an anti-immobility effect that was observed during a drug-free test swim 1 week following administration.

CONCLUSIONS

Overall, these findings demonstrate that impaired glucose metabolism can potentiate the effects of a psychophysical stressor, and that this interaction can be modulated pharmacologically by ketamine.

Neutrophils Fuel Effective Immune Responses through Gluconeogenesis and Glycogenesis

Neutrophils can function and survive in injured and infected tissues, where oxygen and metabolic substrates are limited. Using radioactive flux assays and LC-MS tracing with U-¹³C glucose, glutamine, and pyruvate, we observe that neutrophils require the generation of intracellular glycogen stores by gluconeogenesis and glycogenesis for effective survival and bacterial killing. These metabolic adaptations are dynamic, with net increases in glycogen stores observed following LPS challenge or altitude-induced hypoxia. Neutrophils from patients with chronic obstructive pulmonary disease have reduced glycogen cycling, resulting in impaired function. Metabolic specialization of neutrophils may therefore underpin disease pathology and allow selective therapeutic targeting.

The role of antibody expression and their association with bladder cancer recurrence: a single-centre prospective clinical-pilot study in 35 patients

BACKGROUND

Bladder cancer (BC) is the 10th most common cancer in the UK, with about 10,000 new cases annually. About 75-85% of BC are non-muscle invasive (NMIBC), which is associated with high recurrence and progression rates (50-60% within 7-10 years). There are no routine biomarkers currently available for identifying BC patients at increased risk of developing recurrence. The focus of this research study was to evaluate antibody expression in BC patients and their association with cancer recurrence.

METHODS

35 patients scheduled for TURBT were recruited after written informed consent. Ethical approval for the project was granted via IRAS (REC4: 14/WA/0033). Following surgical procedure, tissues were preserved in 10% buffered formalin and processed within 24 h in FFPE blocks. 7 sections (4 µm each) were cut from each block and stained for CD31, Human epidermal growth factor receptor-2 (HER-2), S100P, Cyclooxygenase-2 (COX-2), VEGFR-3 thrombomodulin and CEACAM-1 using immunohistochemistry. Clinical outcome measures (obtained via cystoscopy) were monitored for up to 6 months following surgical procedure.

RESULTS

There was significantly increased expression of CD31 (p < 0.001), HER-2 (p = 0.032), S100P (p < 0.001), COX-2 (p < 0.001), VEGFR-3 (p < 0.001) and decreased expression of thrombomodulin (p = 0.010) and CEACAM-1 (p < 0.001) in bladder tumours compared to normal bladder tissues. HER-2 expression was also significantly associated with cancer grade (p = 0.003), especially between grade 1 and grade 2 (p = 0.002) and between grade 1 and grade 3 (p = 0.004). There was also a significant association between cancer stage and HER-2 expression (p < 0.001). Although recurrence was significantly associated with cancer grade, there was no association with antibody expression.

CONCLUSION

Findings from the present study may indicate an alternative approach in the monitoring and management of patients with BC. It is proposed that by allowing urological surgeons access to laboratory markers such as HER-2, Thrombomodulin and CD31 (biomarker profile), potentially, in the future, these biomarkers may be used in addition to, or in combination with, currently used scoring systems to predict cancer recurrence. However, verification and validation of these biomarkers are needed using larger cohorts.

Gallotannin attenuates 2‑deoxy‑D‑glucose‑induced dedifferentiation and endoplasmic reticulum stress through inhibition of inositol‑requiring enzyme 1 downstream p38 kinase pathway in chondrocytes

Gallotannin (GT) is a class of polyphenols with antioxidant, anticancer, and antiviral activities. 2‑Deoxy‑D‑glucose (2DG), a glucose‑derived molecule, can inhibit glucose metabolism and induce endoplasmic reticulum (ER) stress. GT in primary‑cultured chondrocytes enhances expression of type II collagen, an indicator of differentiation, and cyclooxygenase‑2 (COX‑2), which mediates inflammatory reactions. In contrast, 2DG reduces type II collagen and COX‑2 expression while driving ER‑stress‑induced unglycosylation. In the present study, it was investigated whether GT could attenuate 2DG‑induced dedifferentiation and ER‑stress. Following treatment with GT and 2DG, chondrocytes were assessed using western blotting, RT‑PCR, immunofluorescence, and alcian blue staining. GT restored type II collagen expression that was reduced by 2DG, inhibited ER‑stress‑induced COX‑2 unglycosylation, and induced COX‑2 expression. The expression of a glucose‑regulated protein, GRP78, which is an indicator of reduced ER‑stress, was decreased. To link the GT signaling pathway with pathways that inhibit 2DG‑induced dedifferentiation and ER‑stress, inhibitors were treated in chondrocytes. The results revealed that, among the different signaling pathways triggered by ER‑stress, the p38 kinase pathway was involved in the inositol‑requiring enzyme 1 (IRE1) downstream signaling pathway. Following inhibition of the IRE1 pathway, type II collagen expression was increased and COX‑2 expression was decreased. In addition, after examining the splicing of X‑box binding protein 1 (XBP‑1) which is dependent on IRE1 activation induced by ER‑stress, it was revealed that GT inhibited the increase of XBP‑1s after splicing due to 2DG‑induced ER stress. GT in chondrocytes inhibited 2DG‑induced dedifferentiation and ER‑stress‑induced COX‑2 unglycosylation while regulating differentiation and inflammation via the ER‑stress‑induced p38 kinase pathway downstream from the IRE1 pathway.

Profiling of key brain nuclei involved in CNS control of stress and glucose homeostasis

Previous work have shown several key brain nuclei involved in acute psychological stress and glucose homeostasis. Acute stress influences glucose metabolism via released stress hormones by activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Little is known about the brain nuclei which response to peripheral glucose alteration are either abundant with glucosesensing neurons or the activations are secondary to stress. Here we profile and compare the brain nuclei that response to stress and glucose homeostasis in mouse models of acute restraint stress, glucose and 2-DG injections respectively. Our present work provide a comprehensive depiction on key brain nuclei involved in CNS control of stress and glucose homeostasis, which gives clue for functional identification of brain nuclei that regulate glucose homeostasis under stress.

The Human Cytomegalovirus UL38 protein drives mTOR-independent metabolic flux reprogramming by inhibiting TSC2

Human Cytomegalovirus (HCMV) infection induces several metabolic activities that are essential for viral replication. Despite the important role that this metabolic modulation plays during infection, the viral mechanisms involved are largely unclear. We find that the HCMV UL38 protein is responsible for many aspects of HCMV-mediated metabolic activation, with UL38 being necessary and sufficient to drive glycolytic activation and induce the catabolism of specific amino acids. UL38's metabolic reprogramming role is dependent on its interaction with TSC2, a tumor suppressor that inhibits mTOR signaling. Further, shRNA-mediated knockdown of TSC2 recapitulates the metabolic phenotypes associated with UL38 expression. Notably, we find that in many cases the metabolic flux activation associated with UL38 expression is largely independent of mTOR activity, as broad spectrum mTOR inhibition does not impact UL38-mediated induction of glycolysis, glutamine consumption, or the secretion of proline or alanine. In contrast, the induction of metabolite concentrations observed with UL38 expression are largely dependent on active mTOR. Collectively, our results indicate that the HCMV UL38 protein induces a pro-viral metabolic environment via inhibition of TSC2.

Simvastatin prevents articular chondrocyte dedifferentiation induced by nitric oxide by inhibiting the expression of matrix metalloproteinases 1 and 13

IMPACT STATEMENT

Dedifferentiation of chondrocytes is the main character of cartilage degradation. Therefore the understanding of chondrocytes dedifferentiation is essential for arthritis therapy. However, the molecular mechanism of cartilage destroy is mostly unknown. In this work we show that simvastatin (SVT) inhibits dedifferentiation by nitric oxide by blocking the expression of matrix metalloproteinases 1 and 13. These effects of SVT on dedifferentiation suggest that SVT may be used as a drug for the cure of arthritis.

Cross-talk between signal transduction and metabolism in B cells

Mounting evidence demonstrates that specific metabolic adaptations are needed to support B cell development and differentiation and to enable B cells to thrive in different environments. Mitogen induced activation of intracellular signaling pathways triggers nutrient uptake and metabolic remodeling to meet the cells' current needs. Reciprocally, changes in the metabolic composition of the environment, or in intracellular metabolite levels, can modulate signal transduction and thus shape cell fate and function. In summary, signal transduction and metabolic pathways operate within an integrated network to cooperatively define cellular outcomes.

ER stress mediated regulation of miR23a confer Hela cells better adaptability to utilize glycolytic pathway

Cancer cells exhibit increased dependency on aerobic glycolysis, a phenomenon referred as the "Warburg effect" and therefore, blocking glycolysis by using non-metabolizable analogues of glucose, like 2-Deoxy glucose (2-DG), has been proposed to be of huge therapeutic importance. One of the major drawbacks of using 2-DG as a chemotherapeutic agent is that it can induce ER stress. ER stress is a hall mark in many solid tumors and the unfolded protein response (UPR) associated with it initiates many survival mechanisms in cancer cells. In the present study, we report a novel survival mechanism associated with ER stress, by which the cancer cells become more adapted to aerobic glycolysis. When ER stress was induced in Hela cells by treating them with 2-DG or Thapsigargin (TG) the expression and activity of LDH was significantly up regulated, conferring the cells a greater glycolytic potential. A simultaneous decrease was observed in the expression of miR-23a, which was predicted in silico to have target site on the 3'UTR of LDH A and B mRNAs. miRNA over expression studies and mRNA degradation assays suggest that miR-23a could target LDH A and LDH B mRNAs. Further on the basis of our results and previous scientific reports, we propose that "c-Myc," which is over expressed during ER stress, repress the expression of miR-23a, which in turn regulates the expression of its target genes viz., LDH A and LDH B, thereby making the cells more competent to survive in tumor microenvironment, which requires efficient use of aerobic glycolysis.

PEP-1-glutaredoxin-1 induces dedifferentiation of rabbit articular chondrocytes by the endoplasmic reticulum stress-dependent ERK-1/2 pathway and the endoplasmic reticulum stress-independent p38 kinase and PI-3 kinase pathways

Glutaredoxin-1 (GRX-1), belonging to the oxidoreductase family, is a component of the endogenous antioxidant defense system. In this study, we evaluated the effects of PEP-1-GRX-1 in rabbit articular chondrocytes. We found that PEP-1-GRX-1 causes a loss of the differentiated chondrocyte phenotype. PEP-1-GRX-1-treated cells exhibited decreases in type II collagen expression and sulfated-proteoglycan synthesis in a dose- and time-dependent manner. PEP-1-GRX-1 causes endoplasmic reticulum (ER)-stress, as evidenced by increases in ER stress marker proteins, i.e., glucose-regulated protein (GRP) 78, GRP 94, and phospho-eukaryotic initiation factor 2 (eIF2) α. These effects were inhibited by ER stress inhibitors. PEP-1-GRX-1 increased the phosphorylation of Akt, extracellular signal-regulated kinase (ERK)-1/2, and p38. Inhibition of ERK-1/2 by PD98059 prevented PEP-1-GRX-1-induced dedifferentiation and inhibited ER stress. The blockage of PI-3K/Akt or p38 kinase with SB203580 and LY294002 accelerated PEP-1-GRX-1-induced dedifferentiation, but did not have any effect on PEP-GRX-1-induced ER stress. Our results indicate that the ERK-1/2 pathway mediates chondrocyte dedifferentiation by PEP-GRX-1-induced ER stress. The PI-3K and p38 kinase pathways regulate PEP-1-GRX-1-induced chondrocyte dedifferentiation by an ER stress-independent pathway.

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.

Endoplasmic Reticulum Stress Sensor IRE1α Enhances IL-23 Expression by Human Dendritic Cells

Human monocyte-derived dendritic cells (DCs) exposed to pathogen-associated molecular patterns (PAMPs) undergo bioenergetic changes that influence the immune response. We found that stimulation with PAMPs enhanced glycolysis in DCs, whereas oxidative phosphorylation remained unaltered. Glucose starvation and the hexokinase inhibitor 2-deoxy-d-glucose (2-DG) modulated cytokine expression in stimulated DCs. Strikingly, IL23A was markedly induced upon 2-DG treatment, but not during glucose deprivation. Since 2-DG can also rapidly inhibit protein N-glycosylation, we postulated that this compound could induce IL-23 in DCs via activation of the endoplasmic reticulum (ER) stress response. Indeed, stimulation of DCs with PAMPs in the presence of 2-DG robustly activated inositol-requiring protein 1α (IRE1α) signaling and to a lesser extent the PERK arm of the unfolded protein response. Additional ER stressors such as tunicamycin and thapsigargin also promoted IL-23 expression by PAMP-stimulated DCs. Pharmacological, biochemical, and genetic analyses using conditional knockout mice revealed that IL-23 induction in ER stressed DCs stimulated with PAMPs was IRE1α/X-box binding protein 1-dependent upon zymosan stimulation. Interestingly, we further evidenced PERK-mediated and CAAT/enhancer-binding protein β-dependent trans-activation of IL23A upon lipopolysaccharide treatment. Our findings uncover that the ER stress response can potently modulate cytokine expression in PAMP-stimulated human DCs.

Menopause-induced uterine epithelium atrophy results from arachidonic acid/prostaglandin E2 axis inhibition-mediated autophagic cell death

Women experience menopause later in life. Menopause is characterized by dramatically decreased circulating estrogen level secondary to loss of ovarian function and atrophic state of genital organs. However, the molecular mechanisms for this process are not fully understood. In this study, we aimed to investigate the potential molecular mechanisms that underlie menopause-induced uterine endometrial atrophy. Our data showed that autophagy was activated in the uterine epithelial cells of both ovariectomized rats and peri-menopausal females. Endoplasmic reticulum (ER) stress occurred even prior to autophagy induction. Integrated bioinformatics analysis revealed that ER stress induced downstream decreased release of arachidonic acid (AA) and downregulation of AA/prostaglandin E2 (PGE2) axis, which led to Akt/mTOR signaling pathway inactivation. Consequently, autophagosomes were recruited and LC3-dependent autophagy was induced in uterine epithelial cells. Treatment with exogenous E2, PGE2, salubrinal or RNAi-mediated silencing of key autophagy genes could effectively counteract estrogen depletion-induced autophagy. Collectively, autophagy is a critical regulator of the uterine epithelium that accounts for endometrial atrophy after menopause.

A Novel Agent Enhances the Chemotherapeutic Efficacy of Doxorubicin in MCF-7 Breast Cancer Cells

We have previously demonstrated that DT-010, a novel conjugate of danshensu (DSS) and tetramethylpyrazine (TMP), displays anti-tumor effects in breast cancer cells both in vitro and in vivo. In the present study, we investigated whether DT-010 enhances the chemotherapeutic effect of doxorubicin (Dox) in MCF-7 breast cancer cells and exerts concurrent cardioprotective benefit at the same time. Our findings showed that DT-010 was more potent than TMP, DSS, or their combination in potentiating Dox-induced toxicity in MCF-7 cells. Co-treatment with DT-010 and Dox increased apoptosis in MCF-7 cells relative to Dox alone. Further study indicated that glycolytic capacity, glycolytic reserve and lactate level of MCF-7 cells were significantly inhibited after DT-010 treatment. DT-010 also increased the expression of the pro-survival protein GRP78, which was inhibited by co-treatment with Dox. Both endoplasmic reticulum stress inhibitor 4-PBA and knockdown of the expression of GRP78 protein potentiated DT-010-mediated apoptosis in MCF-7 cells. Moreover, DT-010 inhibited Dox-induced cardiotoxicity in H9c2 myoblasts. In conclusion, DT-010 and Dox confer synergistic anti-tumor effect in MCF-7 breast cancer cells through downregulation of the glycolytic pathway and inhibition of the expression of GRP78. Meanwhile, DT-010 also protects against Dox-induced cardiotoxicity.

2-Deoxy Glucose Modulates Expression and Biological Activity of VEGF in a SIRT-1 Dependent Mechanism

Reprogramming of energy metabolism particularly switching over of cells to aerobic glycolysis leading to accumulation of lactate is a hallmark of cancer. Lactate can induce angiogenesis, an important process underlying tumor growth and metastasis. VEGF is one of the most important cytokines which regulate this process and the present study was designed to examine if blocking glycolytic pathway in tumor cells can affect its angiogenic potency with respect to VEGF. For this, the expression and biological activity of VEGF synthesized and secreted by tumor derived cell lines in the presence or absence of 2-deoxy glucose (2-DG), an inhibitor of glycolysis was determined. The results suggested that inhibition of glycolysis using sub-lethal doses of 2-DG down-regulated the expression of VEGF and also significantly reduced its biological activity. Further mechanistic studies revealed that the down regulation of VEGF gene expression by 2-DG was due to an increase in SIRT-1 activity and the reduced biological activity was found to be due to an increase in the PAR modification of VEGF. Activity of SIRT-1 and PAR modification of VEGF in turn, was found to be correlated to the cellular NAD⁺ levels. The results presented here therefore suggest that treatment of cancer cells with 2-DG can significantly reduce its overall angiogenic potency through transcriptional and post-translational mechanisms. J. Cell. Biochem. 118: 252-262, 2017. © 2016 Wiley Periodicals, Inc.

Warburg metabolism in tumor-conditioned macrophages promotes metastasis in human pancreatic ductal adenocarcinoma

Patients with pancreatic ductal adenocarcinoma (PDAC) face a clinically intractable disease with poor survival rates, attributed to exceptionally high levels of metastasis. Epithelial-to-mesenchymal transition (EMT) is pronounced at inflammatory foci within the tumor; however, the immunological mechanisms promoting tumor dissemination remain unclear. It is well established that tumors exhibit the Warburg effect, a preferential use of glycolysis for energy production, even in the presence of oxygen, to support rapid growth. We hypothesized that the metabolic pathways utilized by tumor-infiltrating macrophages are altered in PDAC, conferring a pro-metastatic phenotype. We generated tumor-conditioned macrophages in vitro, in which human peripheral blood monocytes were cultured with conditioned media generated from normal pancreatic or PDAC cell lines to obtain steady-state and tumor-associated macrophages (TAMs), respectively. Compared with steady-state macrophages, TAMs promoted vascular network formation, augmented extravasation of tumor cells out of blood vessels, and induced higher levels of EMT. TAMs exhibited a pronounced glycolytic signature in a metabolic flux assay, corresponding with elevated glycolytic gene transcript levels. Inhibiting glycolysis in TAMs with a competitive inhibitor to Hexokinase II (HK2), 2-deoxyglucose (2DG), was sufficient to disrupt this pro-metastatic phenotype, reversing the observed increases in TAM-supported angiogenesis, extravasation, and EMT. Our results indicate a key role for metabolic reprogramming of tumor-infiltrating macrophages in PDAC metastasis, and highlight the therapeutic potential of using pharmacologics to modulate these metabolic pathways.

The effects of low-frequency ultrasound and microbubbles on rabbit hepatic tumors

High-intensity focused ultrasound in combination with microbubbles (MBs) is able to inhibit the growth of VX2 rabbit liver tumors in vivo and prolong the survival time of the animals. In this study, we attempt to investigate the feasibility of VX2 tumor growth inhibition using low-frequency ultrasound (US)-mediated MB disruption. Forty-eight New Zealand rabbits with hepatic VX2 tumors were divided into four groups: control, MBs group, low-frequency US group, and US + MB group. The parameters of the US were 20 kHz, 2 W/cm², 40% duty cycle, 5 min, and once every other day for 2 weeks. At the end of the therapy experiment, 24 rabbits were euthanized, and the cancers were collected and cut into five sections for histological examination, immunohistochemistry, laser confocal microscopy, western blotting assays, and transmission electron microscopy (TEM). Another 24 rabbits were saved, and overall survival time was recorded. The tumor volumes in control, MB, US, and US + MB groups were 6.36 ± 0.58, 5.68 ± 0.42, 5.29 ± 0.26, and 2.04 ± 0.14 cm³, respectively (US + MB versus the other three groups, P < 0.01). Tumor cells manifested coagulation necrosis with internal calcification. Hematoxylin and eosin (H–E) staining revealed interstitial hemorrhage and intravascular thrombosis. The intensity of cyclooxygenase-2 (COX-2), and vascular endothelial growth factor (VEGF) in the US + MB group in the immunohistochemical staining, laser confocal microscopy, and western blotting assays was lower than that of the other three groups (P < 0.05). TEM of the US + MB group revealed vascular endothelial cell wall rupture, widened endothelial cell gaps, interstitial erythrocyte leakage, and microvascular thrombosis, while intact vascular endothelial cells and normal erythrocytes in the tumor vessels were observed in control, MB, and US groups. Rabbits treated with US + MB had a significantly longer overall survival than those in the other three groups (χ2 = 9.328, P = 0.0242). VX2 tumor growth could be inhibited by cavitation induced using low-frequency US and MB.

Endoplasmic reticulum stress signaling in mammalian oocytes and embryos: life in balance

Mammalian oocytes and embryos are exquisitely sensitive to a wide range of insults related to physical stress, chemical exposure, and exposures to adverse maternal nutrition or health status. Although cells manifest specific responses to various stressors, many of these stressors intersect at the endoplasmic reticulum (ER), where disruptions in protein folding and production of reactive oxygen species initiate downstream signaling events. These signals modulate mRNA translation and gene transcription, leading to recovery, activation of autophagy, or with severe and prolonged stress, apoptosis. ER stress signaling has recently come to the fore as a major contributor to embryo demise. Accordingly, agents that modulate or inhibit ER stress signaling have yielded beneficial effects on embryo survival and long-term developmental potential. We review here the mechanisms of ER stress signaling, their connections to mammalian oocytes and embryos, and the promising indications that interventions in this pathway may provide new opportunities for improving mammalian reproduction and health.

2-Deoxy-D-glucose targeting of glucose metabolism in cancer cells as a potential therapy

Cancer cells are characterized by altered glucose metabolism known as the Warburg effect in which aerobic glycolysis is increased. Glucose is converted to lactate even under sufficient oxygen tension. Interfering with this process may be a potential effective strategy to cause cancer cell death because these cells rely heavily on glucose metabolism for survival and proliferation. 2-Deoxy-D-glucose (2DG), a glucose analog, targets glucose metabolism to deplete cancer cells of energy. In addition, 2DG increases oxidative stress, inhibits N-linked glycosylation, and induces autophagy. It can efficiently slow cell growth and potently facilitate apoptosis in specific cancer cells. Although 2DG itself has limited therapeutic effect in many types of cancers, it may be combined with other therapeutic agents or radiotherapy to exhibit a synergistic anticancer effect. In this review, we describe the Warburg effect and discuss 2DG and its underlying mechanisms and potential application for cancer treatment.

ATP increases within the lumen of the endoplasmic reticulum upon intracellular Ca2+ release

Multiple functions of the endoplasmic reticulum (ER) essentially depend on ATP within this organelle. However, little is known about ER ATP dynamics and the regulation of ER ATP import. Here we describe real-time recordings of ER ATP fluxes in single cells using an ER-targeted, genetically encoded ATP sensor. In vitro experiments prove that the ATP sensor is both Ca(2+) and redox insensitive, which makes it possible to monitor Ca(2+)-coupled ER ATP dynamics specifically. The approach uncovers a cell type-specific regulation of ER ATP homeostasis in different cell types. Moreover, we show that intracellular Ca(2+) release is coupled to an increase of ATP within the ER. The Ca(2+)-coupled ER ATP increase is independent of the mode of Ca(2+) mobilization and controlled by the rate of ATP biosynthesis. Furthermore, the energy stress sensor, AMP-activated protein kinase, is essential for the ATP increase that occurs in response to Ca(2+) depletion of the organelle. Our data highlight a novel Ca(2+)-controlled process that supplies the ER with additional energy upon cell stimulation.

Effects of low-frequency ultrasound and microbubbles on angiogenesis-associated proteins in subcutaneous tumors of nude mice

It has been shown that 1 and 3 MHz low-intensity ultrasound was able to affect the fragile and leaky angiogenic blood vessels in a tumor. However, the biological effects of 21 kHz low-intensity ultrasound on tumors remain unclear. The aim of the present study was to explore the effects of 21 kHz ultrasound with microbubbles on the regulation of vascular endothelial growth factor (VEGF), cyclooxygenase-2 (COX-2) and apoptosis in subcutaneous prostate tumors in nude mice. The study included three parts, each with 20 tumor-bearing nude mice. Twenty nude mice were divided into four groups: control (sham treatment), microbubble ultrasound contrast agent (UCA), low-frequency ultrasound (US) and US+UCA groups. The UCA used was a microbubble contrast agent (SonoVue). The parameter of ultrasound: 21 kHz, an intensity of 26 mW/cm2, 40% duty cycle (on 2 sec, off 3 sec), 3 min, once every other day for 2 weeks. In the first study, all subcutaneous tumors were examined by contrast-enhanced ultrasonography (CEUS) at the initiation and completion of the experiments. Peak intensity (PI), time to peak intensity (TTP) and area under the curve (AUC) on the time intensity curve (TIC) were analyzed. In the second study, the intensity of VEGF and COX-2 protein expression in the vascular endothelium and cytoplasm was evaluated using immunohistochemistry and laser confocal microscopy. In the third study, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling (TUNEL) assay was used for the evaluation of cell apoptosis in tumor tissues. The tumor cells and vasculature were examined by transmission electron microscopy (TEM). Only in the US+UCA group, PI and AUC decreased. The intensity of COX-2 and VEGF in the US+UCA group in immunohistochemical staining and laser confocal microscopy was lower compared to that of the other three groups. More cell apoptosis was found in the US+UCA group compared to the other 3 groups. In the control, UCA and US groups, the tumors had intact vascular endothelium and vessel lumens in TEM. However, lumen occlusion of vessels was observed in the US+UCA group. Twenty-one kHz low-intensity ultrasound with microbubbles may have anti-angiogenic effects on subcutaneous tumors in nude mice.

Laforin prevents stress-induced polyglucosan body formation and Lafora disease progression in neurons

Glycogen, the largest cytosolic macromolecule, is soluble because of intricate construction generating perfect hydrophilic-surfaced spheres. Little is known about neuronal glycogen function and metabolism, though progress is accruing through the neurodegenerative epilepsy Lafora disease (LD) proteins laforin and malin. Neurons in LD exhibit Lafora bodies (LBs), large accumulations of malconstructed insoluble glycogen (polyglucosans). We demonstrated that the laforin-malin complex reduces LBs and protects neuronal cells against endoplasmic reticulum stress-induced apoptosis. We now show that stress induces polyglucosan formation in normal neurons in culture and in the brain. This is mediated by increased glucose-6-phosphate allosterically hyperactivating muscle glycogen synthase (GS1) and is followed by activation of the glycogen digesting enzyme glycogen phosphorylase. In the absence of laforin, stress-induced polyglucosans are undigested and accumulate into massive LBs, and in laforin-deficient mice, stress drastically accelerates LB accumulation and LD. The mechanism through which laforin-malin mediates polyglucosan degradation remains unclear but involves GS1 dephosphorylation by laforin. Our work uncovers the presence of rapid polyglucosan metabolism as part of the normal physiology of neuroprotection. We propose that deficiency in the degradative phase of this metabolism, leading to LB accumulation and resultant seizure predisposition and neurodegeneration, underlies LD.

D-Glucose and D-mannose-based metabolic probes. Part 3: Synthesis of specifically deuterated D-glucose, D-mannose, and 2-deoxy-D-glucose

Altered carbohydrate metabolism in cancer cells was first noted by Otto Warburg more than 80 years ago. Upregulation of genes controlling the glycolytic pathway under normoxia, known as the Warburg effect, clearly differentiates malignant from non-malignant cells. The resurgence of interest in cancer metabolism aims at a better understanding of the metabolic differences between malignant and non-malignant cells and the creation of novel therapeutic and diagnostic agents exploiting these differences. Modified d-glucose and d-mannose analogs were shown to interfere with the metabolism of their respective monosaccharide parent molecules and are potentially clinically useful anticancer and diagnostic agents. One such agent, 2-deoxy-d-glucose (2-DG), has been extensively studied in vitro and in vivo and also clinically evaluated. Studies clearly indicate that 2-DG has a pleiotropic mechanism of action. In addition to effectively inhibiting glycolysis, 2-DG has also been shown to affect protein glycosylation. In order to better understand its molecular mechanism of action, we have designed and synthesized deuterated molecular probes to study 2-DG interference with d-glucose and d-mannose metabolism using mass spectrometry. We present here the synthesis of all desired probes: 2-deutero-d-glucose, 2-deutero-d-mannose, 6-deutero-d-glucose, 6-deutero-d-mannose, and 2-deutero-2-deoxy-d-glucose as well as their complete chemical characterization.

Protein phosphorylation on tyrosine restores expression and glycosylation of cyclooxygenase-2 by 2-deoxy-D-glucose-caused endoplasmic reticulum stress in rabbit articular chondrocyte

2-deoxy-D-glucose(2DG)-caused endoplasmic reticulum (ER) stress inhibits protein phosphorylation at tyrosine residues. However, the accurate regulatory mechanisms, which determine the inflammatory response of chondrocytes to ER stress via protein tyrosine phosphorylation, have not been systematically evaluated. Thus, in this study, we examined whether protein phosphorylation at tyrosine residues can modulate the expression and glycosylation of COX-2, which is reduced by 2DG-induced ER stress. We observed that protein tyrosine phosphatase (PTP) inhibitors, sodium orthovanadate (SOV), and phenylarsine oxide (PAO) significantly decreased expression of ER stress inducible proteins, glucose-regulated protein 94 (GRP94), and CCAAT/enhancer-binding-protein- related gene (GADD153), which was induced by 2DG. In addition, we demonstrated that SOV and PAO noticeably restored the expression and glycosylation of COX-2 after treatment with 2DG. These results suggest that protein phosphorylation of tyrosine residues plays an important role in the regulation of expression and glycosylation during 2DG-induced ER stress in rabbit articular chondrocytes.

Transcriptional and translational regulation of COX-2 expression by cadmium in C6 glioma cells

High exposure to cadmium is a risk factor for many neuronal diseases. Overexpression of cyclooxygenase (COX)-2 is linked to many neuroinflammatory and neoplastic diseases. We, herein, investigated the effect of cadmium on the expression of COX-2 in C6 rat glioma cells. Treatment with cadmium sulfate (cadmium) increased the expression of COX-2 mRNA. Remarkably, cadmium treatment further increased expression of not only the N-glycosylated COX-2 protein of 72 kDa but also the unglycosylated COX-2 of 66 kDa, as assessed by the unglycosylated COX-2 induced by tunicamycin or glucosamine, known inhibitors of COX-2 N-glycosylation. Of note, when translation was blocked in the presence of cycloheximide (CHX), levels of both N-glycosylated and unglycosylated COX-2 proteins induced by cadmium rapidly declined but the decline was prevented by MG132, a 26S proteasomal inhibitor. However, in the absence of CHX, cadmium induced and maintained expression of the unglycosylated COX-2 proteins. Pharmacological inhibition studies importantly demonstrated that the cadmium-mediated COX-2 transcriptional upregulation in C6 cells was not shown by exogenous glutathione (GSH) supplementation or treatment with inhibitors of extracellular signal-regulated protein kinase-1/2 (ERK-1/2), p38 MAPK and c-Jun N-terminal protein kinase-1/2 (JNK-1/2), respectively. Expression of COX-2 was not noted in C6 cells exposed to other heavy metals (cobalt or manganese). These results demonstrate that cadmium specifically induces expression of COX-2 through both transcriptional and co-translational (N-glycosylation) regulation in C6 cells in which the cadmium-induced COX-2 transcriptional upregulation is closely related to oxidative stress-dependent activation of the family of MAPKs and the cadmium-induced expression of both N-glycosylated and unglycosylated COX-2 proteins is proteasome- and translation-dependent.