Suppression of mitochondrial NADP(+)-dependent isocitrate dehydrogenase activity enhances curcumin-induced apoptosis in HCT116 cells

Tangshen formula targets the gut microbiota to treat non-alcoholic fatty liver disease in HFD mice: A 16S rRNA and non-targeted metabolomics analyses

BACKGROUND

Tangshen formula (TSF) has an ameliorative effect on hepatic lipid metabolism in non-alcoholic fatty liver disease (NAFLD), but the role played by the gut microbiota in this process is unknown.

METHOD

We conducted three batches of experiments to explore the role played by the gut microbiota: TSF administration, antibiotic treatment, and fecal microbial transplantation. NAFLD mice were induced with a high-fat diet to investigate the ameliorative effects of TSF on NAFLD features and intestinal barrier function. 16S rRNA sequencing and serum untargeted metabolomics were performed to further investigate the modulatory effects of TSF on the gut microbiota and metabolic dysregulation in the body.

RESULTS

TSF ameliorated insulin resistance, hypercholesterolemia, lipid metabolism disorders, inflammation, and impairment of intestinal barrier function. 16S rRNA sequencing analysis revealed that TSF regulated the composition of the gut microbiota and increased the abundance of beneficial bacteria. Antibiotic treatment and fecal microbiota transplantation confirmed the importance of the gut microbiota in the treatment of NAFLD with TSF. Subsequently, untargeted metabolomics identified 172 differential metabolites due to the treatment of TSF. Functional predictions suggest that metabolisms of choline, glycerophospholipid, linoleic acid, alpha-linolenic acid, and arachidonic acid are the key metabolic pathways by which TSF ameliorates NAFLD and this may be influenced by the gut microbiota.

CONCLUSION

TSF treats the NAFLD phenotype by remodeling the gut microbiota and improving metabolic profile, suggesting that TSF is a functional gut microbial and metabolic modulator for the treatment of NAFLD.

Reductive Stress, Bioactive Compounds, Redox-Active Metals, and Dormant Tumor Cell Biology to Develop Redox-Based Tools for the Treatment of Cancer

Significance: Cancer is related to redox biology from many points of view, such as initiation and promotion, metabolism and growth, invasion and metastasis, vascularization, or through the interaction with the immune system. In addition, this extremely complex relationship depends on the redox homeostasis of each cellular compartment, which might be used to fight cancer. Recent Advances: New ways of modulating specific and little explored aspects of redox biology have been revealed, as well as new delivery methods or uses of previously known treatments against cancer. Here, we review the latest experimental evidence regarding redox biology in cancer treatment and analyze its potential impact in the development of improved and more effective antineoplastic therapies. Critical Issues: A critical issue that deserves particular attention is the understanding that both extremes of redox biology (i.e., oxidative stress [OS] and reductive stress) might be useful or harmful in relation to cancer prevention and treatment. Future Directions: Additional research is needed to understand how to selectively induce reductive or OS adequately to avoid cancer proliferation or to induce cancer cell death.

Mechanism of Apoptosis Induced by Curcumin in Colorectal Cancer

Colorectal cancer (CRC) is among the top three cancer with higher incident and mortality rate worldwide. It is estimated that about over than 1.1 million of death and 2.2 million new cases by the year 2030. The current treatment modalities with the usage of chemo drugs such as FOLFOX and FOLFIRI, surgery and radiotherapy, which are usually accompanied with major side effects, are rarely cured along with poor survival rate and at higher recurrence outcome. This trigger the needs of exploring new natural compounds with anti-cancer properties which possess fewer side effects. Curcumin, a common spice used in ancient medicine was found to induce apoptosis by targeting various molecules and signaling pathways involved in CRC. Disruption of the homeostatic balance between cell proliferation and apoptosis could be one of the promoting factors in colorectal cancer progression. In this review, we describe the current knowledge of apoptosis regulation by curcumin in CRC with regard to molecular targets and associated signaling pathways.

A pilot study of the effect of phospholipid curcumin on serum metabolomic profile in patients with non-alcoholic fatty liver disease: a randomized, double-blind, placebo-controlled trial

BACKGROUND/OBJECTIVES

Curcumin, a natural polyphenol compound in the spice turmeric, has been found to have potent anti-oxidative and anti-inflammatory activity. Curcumin may treat non-alcoholic fatty liver disease (NAFLD) through its beneficial effects on biomarkers of oxidative stress (OS) and inflammation, which are considered as two feature of this disease. However, the effects of curcumin on NAFLD have been remained poorly understood. This investigation evaluated the effects of administrating curcumin on metabolic status in NAFLD patients.

SUBJECTS/METHODS

Fifty-eight NAFLD patients participated in a randomized, double-blind, placebo-controlled parallel design of study. The subjects were allocated randomly into two groups, which either received 250 mg phospholipid curcumin or placebo, one capsule per day for a period of 8 weeks. Fasting blood samples were taken from each subject at the start and end of the study period. Subsequently, metabolomics analysis was performed for serum samples using NMR.

RESULTS

Compared with the placebo, supplementing phospholipid curcumin resulted in significant decreases in serum including 3- methyl-2-oxovaleric acid, 3-hydroxyisobutyrate, kynurenine, succinate, citrate, α-ketoglutarate, methylamine, trimethylamine, hippurate, indoxyl sulfate, chenodeoxycholic acid, taurocholic acid, and lithocholic acid. This profile of metabolic biomarkers could distinguish effectively NAFLD subjects who were treated with curcumin and placebo groups, achieving value of 0.99 for an area under receiver operating characteristic curve (AUC).

CONCLUSIONS

Characterizing the serum metabolic profile of the patients with NAFLD at the end of the intervention using NMR-based metabolomics method indicated that the targets of curcumin treatment included some amino acids, TCA cycle, bile acids, and gut microbiota.

IDH2 knockdown sensitizes tumor cells to emodin cytotoxicity in vitro and in vivo

Although reactive oxygen species (ROS) work as second messengers at sublethal concentrations, higher levels of ROS can kill cancer cells. Since cellular ROS levels are determined by a balance between ROS generation and removal, the combination of ROS generators, and the depletion of reducing substances greatly enhance ROS levels. Emodin (1,3,8-trihydroxy-6-methyl anthraquinone), a natural anthraquinone derivative from the root and rhizome of numerous plants, is a ROS generator that induces apoptosis in cancer cells. The major enzyme to generate mitochondrial NADPH is the mitochondrial isoenzyme of NADP⁺-dependent isocitrate dehydrogenase (IDH2). In this report, we demonstrate that IDH2 knockdown effectively enhances emodin-induced apoptosis of mouse melanoma B16F10 cells through the regulation of ROS generation. Our findings suggest that suppression of IDH2 activity results in perturbation of the cellular redox balance and, ultimately, exacerbate emodin-induced apoptotic cell death in B16F10 cells. Our results strongly support a therapeutic strategy in the management of cancer that alters the intracellular redox status by the combination of a ROS generator and the suppression of antioxidant enzyme activity.

D-2-Hydroxyglutarate does not mimic all the IDH mutation effects, in particular the reduced etoposide-triggered apoptosis mediated by an alteration in mitochondrial NADH

Somatic mutations in isocitrate dehydrogenase (IDH)-1 and -2 have recently been described in glioma. This mutation leads to a neomorphic enzymatic activity as the conversion of isocitrate to alpha ketoglutarate (αKG) is replaced by the conversion of αKG to D-2-hydroxyglutarate (D-2HG) with NADPH oxidation. It has been suggested that this oncometabolite D-2HG via inhibition of αKG-dioxygenases is involved in multiple functions such as epigenetic modifications or hypoxia responses. The present study is aimed at deciphering how the mutant IDH can affect cancer pathogenesis, in particular with respect to its associated oncometabolite D-2HG. We show that the overexpression of mutant IDH in glioma cells or treatment with D-2HG triggered an increase in cell proliferation. However, although mutant IDH reduced cell sensitivity to the apoptotic inducer etoposide, D-2HG exhibited no effect on apoptosis. Instead, we found that the apoptotic effect was mediated through the mitochondrial NADH pool reduction and could be inhibited by oxamate. These data show that besides D-2HG production, mutant IDH affects other crucial metabolite pools. These observations lead to a better understanding of the biology of IDH mutations in gliomas and their response to therapy.

Proteomic investigation of the sinulariolide-treated melanoma cells A375: effects on the cell apoptosis through mitochondrial-related pathway and activation of caspase cascade

Sinulariolide is an active compound isolated from the cultured soft coral Sinularia flexibilis. In this study, we investigated the effects of sinulariolide on A375 melanoma cell growth and protein expression. Sinulariolide suppressed the proliferation and migration of melanoma cells in a concentration-dependent manner and was found to induce both early and late apoptosis by flow cytometric analysis. Comparative proteomic analysis was conducted to investigate the effects of sinulariolide at the molecular level by comparison between the protein profiles of melanoma cells treated with sinulariolide and those without treatment. Two-dimensional gel electrophoresis (2-DE) master maps of control and treated A375 cells were generated by analysis with PDQuest software. Comparison between these maps showed up- and downregulation of 21 proteins, seven of which were upregulated and 14 were downregulated. The proteomics studies described here identify some proteins that are involved in mitochondrial dysfunction and apoptosis-associated proteins, including heat shock protein 60, heat shock protein beta-1, ubiquinol cytochrome c reductase complex core protein 1, isocitrate dehydrogenase (NAD) subunit alpha (down-regulated), and prohibitin (up-regulated), in A375 melanoma cells exposed to sinulariolide. Sinulariolide-induced apoptosis is relevant to mitochondrial-mediated apoptosis via caspase-dependent pathways, elucidated by the loss of mitochondrial membrane potential, release of cytochrome c, and activation of Bax, Bad and caspase-3/-9, as well as suppression of p-Bad, Bcl-xL and Bcl-2. Taken together, our results show that sinulariolide-induced apoptosis might be related to activation of the caspase cascade and mitochondria dysfunction pathways. Our results suggest that sinulariolide merits further evaluation as a chemotherapeutic agent for human melanoma.

Natural compounds as regulators of the cancer cell metabolism

Even though altered metabolism is an "old" physiological mechanism, only recently its targeting became a therapeutically interesting strategy and by now it is considered an emerging hallmark of cancer. Nevertheless, a very poor number of compounds are under investigation as potential modulators of cell metabolism. Candidate agents should display selectivity of action towards cancer cells without side effects. This ideal favorable profile would perfectly overlap the requisites of new anticancer therapies and chemopreventive strategies as well. Nature represents a still largely unexplored source of bioactive molecules with a therapeutic potential. Many of these compounds have already been characterized for their multiple anticancer activities. Many of them are absorbed with the diet and therefore possess a known profile in terms of tolerability and bioavailability compared to newly synthetized chemical compounds. The discovery of important cross-talks between mediators of the most therapeutically targeted aberrancies in cancer (i.e., cell proliferation, survival, and migration) and the metabolic machinery allows to predict the possibility that many anticancer activities ascribed to a number of natural compounds may be due, in part, to their ability of modulating metabolic pathways. In this review, we attempt an overview of what is currently known about the potential of natural compounds as modulators of cancer cell metabolism.

Prevention and Treatment of Colorectal Cancer by Natural Agents From Mother Nature

Colorectal cancer (CRC) is the third most commonly diagnosed cancer in the United States after cancers of the lung and the breast/prostate. While the incidence of CRC in the United States is among the highest in the world (approximately 52/100,000), its incidence in countries in India is among the lowest (approximately 7/100,000), suggesting that lifestyle factors may play a role in development of the disease. Whereas obesity, excessive alcohol consumption, a high-calorie diet, and a lack of physical activity promote this cancer, evidence indicates that foods containing folates, selenium, Vitamin D, dietary fiber, garlic, milk, calcium, spices, vegetables, and fruits are protective against CRC in humans. Numerous agents from "mother nature" (also called "nutraceuticals,") that have potential to both prevent and treat CRC have been identified. The most significant discoveries relate to compounds such as cardamonin, celastrol, curcumin, deguelin, diosgenin, thymoquinone, tocotrienol, ursolic acid, and zerumbone. Unlike pharmaceutical drugs, these agents modulate multiple targets, including transcription factors, growth factors, tumor cell survival factors, inflammatory pathways, and invasion and angiogenesis linked closely to CRC. We describe the potential of these dietary agents to suppress the growth of human CRC cells in culture and to inhibit tumor growth in animal models. We also describe clinical trials in which these agents have been tested for efficacy in humans. Because of their safety and affordability, these nutraceuticals provide a novel opportunity for treatment of CRC, an "old age" disease with an "age old" solution.

Lupine embryo axes under salinity stress. II. Mitochondrial proteome response

Germination is the first step of plant growth in plant life cycle. An embryonic radicle protruding the seed coat is the first part of plant which has direct contact with external environment including salt-affected soil. In embryo axes, mitochondria are the main energy producer. To understand better salinity impact on mitochondria functioning, this study was focused on the effect of NaCl stress onto mitochondria proteome. Mitochondria were isolated from yellow lupine (Lupine luteus L. 'Mister') embryo axes cultured in vitro for 12 h with 250 and 500 mM NaCl. Two-dimensional gel electrophoresis of mitochondrial proteins isolated from NaCl-treated axes demonstrated significant changes in proteins abundances as a response to salinity treatment. Twenty-one spots showing significant changes in protein expression profiles both under 250 and 500 mM NaCl treatment were selected for tandem mass spectrometry identification. This approach revealed proteins associated with different metabolic processes that represent enzymes of tricarboxylic acid cycle, mitochondrial electron transport chain, enzymes and proteins involved in mitochondria biogenesis and stresses response. Among proteins involved in mitochondria biogenesis, mitochondrial import inner membrane translocase, subunit Tim17/22, mitochondrial-processing peptidase subunit alpha-1, mitochondrial elongation factor Tu and chaperonins CPN60 were revealed. Finally, formate dehydrogenase 1 was found to accumulate in lupine embryo axes mitochondria under salinity. The functions of identified proteins are discussed in relation to salinity stress response, including salinity-induced PCD.

Dysregulation of glutathione homeostasis in neurodegenerative diseases

Dysregulation of glutathione homeostasis and alterations in glutathione-dependent enzyme activities are increasingly implicated in the induction and progression of neurodegenerative diseases, including Alzheimer’s, Parkinson’s and Huntington’s diseases, amyotrophic lateral sclerosis, and Friedreich’s ataxia. In this review background is provided on the steady-state synthesis, regulation, and transport of glutathione, with primary focus on the brain. A brief overview is presented on the distinct but vital roles of glutathione in cellular maintenance and survival, and on the functions of key glutathione-dependent enzymes. Major contributors to initiation and progression of neurodegenerative diseases are considered, including oxidative stress, protein misfolding, and protein aggregation. In each case examples of key regulatory mechanisms are identified that are sensitive to changes in glutathione redox status and/or in the activities of glutathione-dependent enzymes. Mechanisms of dysregulation of glutathione and/or glutathione-dependent enzymes are discussed that are implicated in pathogenesis of each neurodegenerative disease. Limitations in information or interpretation are identified, and possible avenues for further research are described with an aim to elucidating novel targets for therapeutic interventions. The pros and cons of administration of N-acetylcysteine or glutathione as therapeutic agents for neurodegenerative diseases, as well as the potential utility of serum glutathione as a biomarker, are critically evaluated.

The Role of Mitochondrial NADPH-Dependent Isocitrate Dehydrogenase in Cancer Cells

Isocitrate dehydrogenase 2 (IDH2) is located in the mitochondrial matrix. IDH2 acts in the forward Krebs cycle as an NADP⁺-consuming enzyme, providing NADPH for maintenance of the reduced glutathione and peroxiredoxin systems and for self-maintenance by reactivation of cystine-inactivated IDH2 by glutaredoxin 2. In highly respiring cells, the resulting NAD⁺ accumulation then induces sirtuin-3-mediated activating IDH2 deacetylation, thus increasing its protective function. Reductive carboxylation of 2-oxoglutarate by IDH2 (in the reverse Krebs cycle direction), which consumes NADPH, may follow glutaminolysis of glutamine to 2-oxoglutarate in cancer cells. When the reverse aconitase reaction and citrate efflux are added, this overall “anoxic” glutaminolysis mode may help highly malignant tumors survive aglycemia during hypoxia. Intermittent glycolysis would hypothetically be required to provide ATP. When oxidative phosphorylation is dormant, this mode causes substantial oxidative stress. Arg172 mutants of human IDH2—frequently found with similar mutants of cytosolic IDH1 in grade 2 and 3 gliomas, secondary glioblastomas, and acute myeloid leukemia—catalyze reductive carboxylation of 2-oxoglutarate and reduction to D-2-hydroxyglutarate, which strengthens the neoplastic phenotype by competitive inhibition of histone demethylation and 5-methylcytosine hydroxylation, leading to genome-wide histone and DNA methylation alternations. D-2-hydroxyglutarate also interferes with proline hydroxylation and thus may stabilize hypoxia-induced factor α.

Isocitrate dehydrogenase mutations in gliomas: mechanisms, biomarkers and therapeutic target

PURPOSE OF REVIEW

Isocitrate dehydrogenases, IDH1 and IDH2, decarboxylate isocitrate to α-ketoglutarate (α-KG) and reduce NADP to NADPH. Point mutations of IDH1 and IDH2 have been discovered in gliomas. IDH mutations cause loss of native enzymatic activities and confer novel activity of converting α-KG to 2-hydroxyglutarate (2-HG). The mechanisms of IDH mutations in gliomagenesis, and their value as diagnostic, prognostic marker and therapeutic target have been extensively studied. This review is to summarize the findings of these studies.

RECENT FINDINGS

Crystal structural studies revealed conformation changes in mutant IDHs, which may explain the gain of function by mutant IDHs. The product of mutant IDHs, 2-HG, is an inhibitor of α-KG-dependent dioxygenases, which may cause genome-wide epigenetic changes in human gliomas. IDH mutations are a favorable prognostic factor for human glioma and can be used as biomarker for differential diagnosis and subclassification rather than predictor of response to treatment. Preliminary data suggested that inhibiting production of the substrate of mutant IDH enzymes caused slow-down of glioma cell growth.

SUMMARY

As valuable diagnostic and prognostic markers of human gliomas, there is still a lack of knowledge on biological functions of mutant IDHs, making targeting IDHs in glioma both difficult and unsecured.

An investigation into the cytotoxic effects of 13-acetoxysarcocrassolide from the soft coral Sarcophyton crassocaule on bladder cancer cells

Active compounds from natural products have been widely studied. The anti-tumor effects of 13-acetoxysarcocrassolide isolated from Formosan soft coral Sarcophyton crassocaule on bladder cancer cells were examined in this study. An MTT assay showed that 13-acetoxysarcocrassolide was cytotoxic to bladder female transitional cancer (BFTC) cells. We determined that the BFTC cells underwent cell death through apoptosis by flow cytometry. Due to the highly-migratory nature of the BFTC cells, the ability of 13-acetoxysarcocrassolide to stop their migration was assessed by a wound healing assay. To determine which proteins were affected in the BFTC cells upon treatment, a comparative proteomic analysis was performed. By LC-MS/MS analysis, we identified that 19 proteins were up-regulated and eight were down-regulated. Seven of the proteins were confirmed by western blotting analysis. This study reveals clues to the potential mechanism of the cytotoxic effects of 13-acetoxysarcocrassolide on BFTC cells. Moreover, it suggests that PPT1 and hnRNP F could be new biomarkers for bladder cancer. The results of this study are also helpful for the diagnosis, progression monitoring and therapeutic strategies of transitional cell tumors.