TIGAR Has a Dual Role in Cancer Cell Survival through Regulating Apoptosis and Autophagy

TIGAR relieves PCOS by inhibiting granulosa cell apoptosis and oxidative stress through activating Nrf2

This study aimed to elucidate the role of TP53-induced glycolysis and apoptosis regulator (TIGAR) in polycystic ovary syndrome (PCOS). A rat model PCOS was constructed by subcutaneous injection with dehydroepiandrosterone (DHEA). Follicular atresia and reduced granular cells (GCs) in ovaries suggested successful modeling. The low expression of TIGAR was observed in ovarian tissue of PCOS rat. To explore the role of TIGAR in PCOS, lentivirus carrying the TIGAR were used to up-regulate TIGAR expression. TIGAR overexpression reduced the DHEA-induced increase of ovarian weight, the levels of estradiol (E2), and the ratio of luteinizing hormone/follicle-stimulating hormone (LH/FSH) in the serum, as well as improved the morphology of the follicle, especially increased the thickness of the GC layer, which attributed to the inhibition of apoptosis by TIGAR. In addition, high expression of TIGAR inhibited oxidative stress in ovaries of PCOS rat, as evidenced by decreased level of malondialdehyde (MDA), and reactive oxygen species (ROS), and enhanced activity of glutathione peroxidase (GPX) and superoxide dismutase (SOD). Mechanically, Nrf2/OH-1 signal pathway was activated by TIGAR. The effect of TIGAR on PCOS were verified in the primary rat GCs treated with dihydrotestosterone, but also the rescue experiment was performed. Downregulation of Nrf2 reversed the effects of TIGAR, indicating that TIGAR suppressed oxidative stress and GC apoptosis by activating Nrf2/OH-1 pathway in PCOS. Finally, non-targeted metabolomics revealed that TIGAR might affect the energy metabolic pathway, thereby altering the metabolic profile of primary rat GCs. This study provided new insights into the prevention and treatment of PCOS.

TIGAR coordinates senescence-associated secretory phenotype via lysosome repositioning and α-tubulin deacetylation

TP53-induced glycolysis and apoptosis regulator (TIGAR) regulates redox homeostasis and provides the intermediates necessary for cell growth by reducing the glycolytic rate. During cellular senescence, cells undergo metabolic rewiring towards the glycolytic pathway, along with the development of the senescence-associated secretory phenotype (SASP), also known as the secretome. We observed that TIGAR expression increased during replicative senescence following the in vitro expansion of human mesenchymal stromal cells (MSCs) and that TIGAR knockout (KO) decreased SASP factors and triggered premature senescence with decelerated progression. Additionally, TIGAR KO impaired flexible lysosomal movement to the perinuclear region and decreased the autophagic flux of MSCs. Research on the mechanism of lysosomal movement revealed that, while native senescent MSCs presented low levels of Ac-α-tubulin (lysine 40) and increased sirtuin 2 (SIRT2) activity compared with those in growing cells, TIGAR KO-MSCs maintained Ac-α-tubulin levels and exhibited decreased SIRT2 activity despite being in a senescent state. The overexpression of SIRT2 reduced Ac-α-tubulin as a protein target of SIRT2 and induced the positioning of lysosomes at the perinuclear region, restoring the cytokine secretion of TIGAR KO-MSCs. Furthermore, TIGAR expression was positively correlated with SIRT2 activity, indicating that TIGAR affects SIRT2 activity partly by modulating the NAD+ level. Thus, our study demonstrated that TIGAR provides a foundation that translates the regulation of energy metabolism into lysosome positioning, affecting the secretome for senescence development. Considering the functional value of the cell-secretome in aging-related diseases, these findings suggest the feasibility of TIGAR for the regulation of secretory phenotypes.

TIGAR exacerbates obesity by triggering LRRK2-mediated defects in macroautophagy and chaperone-mediated autophagy in adipocytes

Obesity is one of the most common metabolic diseases around the world, which is distinguished by the abnormal buildup of triglycerides within adipose cells. Recent research has revealed that autophagy regulates lipid mobilization to maintain energy balance. TIGAR (Trp53 induced glycolysis regulatory phosphatase) has been identified as a glycolysis inhibitor, whether it plays a role in the metabolism of lipids is unknown. Here, we found that TIGAR transgenic (TIGAR+/+) mice exhibited increased fat mass and trended to obesity phenotype. Non-target metabolomics showed that TIGAR caused the dysregulation of the metabolism profile. The quantitative transcriptome sequencing identified an increased levels of LRRK2 and RAB7B in the adipose tissue of TIGAR+/+ mice. It was confirmed in vitro that TIGAR overexpression increased the levels of LRRK2 by inhibiting polyubiquitination degradation, thereby suppressing macroautophagy and chaperone-mediated autophagy (CMA) while increasing lipid accumulation which were reversed by the LRRK2 inhibitor DNL201. Furthermore, TIGAR drove LRRK2 to interact with RAB7B for suppressing lysosomal degradation of lipid droplets, while the increased lipid droplets in adipocytes were blocked by the RAB7B inhibitor ML282. Additionally, fat-specific TIGAR knockdown of TIGAR+/+ mice alleviated the symptoms of obesity, and adipose tissues-targeting superiority DNL201 nano-emulsion counteracted the obesity phenotype in TIGAR+/+ mice. In summary, the current results indicated that TIGAR performed a vital function in the lipid metabolism through LRRK2-mediated negative regulation of macroautophagy and CMA in adipocyte. The findings suggest that TIGAR has the potential to serve as a viable therapeutic target for treating obesity and its associated metabolic dysfunction.

Berberine and berberine nanoformulations in cancer therapy: Focusing on lung cancer

Lung cancer is the second most prevalent cancer and ranks first in cancer-related death worldwide. Due to the resistance development to conventional cancer therapy strategies, including chemotherapy, radiotherapy, targeted therapy, and immunotherapy, various natural products and their extracts have been revealed as alternatives. Berberine (BBR), which is present in the stem, root, and bark of various trees, could exert anticancer activities by regulating tumor cell proliferation, apoptosis, autophagy, metastasis, angiogenesis, and immune responses via modulating several signaling pathways within the tumor microenvironment. Due to its poor water solubility, poor pharmacokinetics/bioavailability profile, and extensive p-glycoprotein-dependent efflux, BBR application in (pre) clinical studies is restricted. To overcome these limitations, BBR can be encapsulated in nanoparticle (NP)-based drug delivery systems, as monotherapy or combinational therapy, and improve BBR therapeutic efficacy. Nanoformulations also facilitate the selective delivery of BBR into lung cancer cells. In addition to the anticancer activities of BBR, especially in lung cancer, here we reviewed the BBR nanoformulations, including polymeric NPs, metal-based NPs, carbon nanostructures, and others, in the treatment of lung cancer.

TIGAR protects against adenine-induced ferroptosis in human proximal tubular epithelial cells by activating the mTOR/S6KP70 axis

TP53-induced glycolysis and apoptosis regulator (TIGAR) acts as a switch for nephropathy, but its underlying mechanism is still unclear. The purpose of this study was to explore the potential biological significance and underlying mechanism of TIGAR in modulating adenine-induced ferroptosis in human proximal tubular epithelial (HK-2) cells. HK-2 cells under- or overexpressing TIGAR were challenged with adenine to induce ferroptosis. The levels of reactive oxygen species (ROS), iron, malondialdehyde (MDA), and glutathione (GSH) were assayed. Expression of ferroptosis-associated solute carrier family seven-member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) at the level of mRNA and protein were measured by quantitative real-time-PCR and western blotting. The phosphorylation levels of proteins in the mTOR/S6KP70 pathway were determined by western blotting. Adenine overload triggered ferroptosis in HK-2 cells, as evidenced by reduced levels of GSH, SLC7A11, and GPX4, and increased levels of iron, MDA, and ROS. TIGAR overexpression repressed adenine-induced ferroptosis and induced mTOR/S6KP70 signaling. Inhibitors of mTOR and S6KP70 weakened the ability of TIGAR to inhibit adenine-induced ferroptosis. TIGAR inhibits adenine-induced ferroptosis in human proximal tubular epithelial cells by activating the mTOR/S6KP70 signaling pathway. Therefore, activating the TIGAR/mTOR/S6KP70 axis may be a treatment for crystal nephropathies.

JMJD5 inhibits lung cancer progression by regulating glucose metabolism through the p53/TIGAR pathway

Metabolic reprogramming is considered one of the main driving forces for tumor progression, providing energy and substrates of biosynthesis to support rapid neoplastic proliferation. Particularly, the tumor suppressor protein p53 was shown to revert the Warburg effect and play complex roles in regulating glucose metabolism. Jumonji C domain-containing protein 5 (JMJD5) has previously been reported as a negative regulator of p53. However, the role of JMJD5 in p53-mediated metabolic reprogramming remains elusive. Here, we discovered that knockdown of JMJD5 significantly enhances TIGAR expression in p53 wild-type non-small cell lung cancer (NSCLC) cells, which could further suppress glycolysis and promote the pentose phosphate pathway. Besides, JMJD5 knockdown promotes the NSCLC cell proliferation in vitro and xenograft tumor growth in vivo, while silencing TIGAR can abolish this effect. Low JMJD5 expression levels are associated with elevated TIGAR levels and correlates with poor prognosis in lung cancer patients. Taken together, our findings suggest that JMJD5 is a key regulator of tumor glucose metabolism by targeting the p53/TIGAR metabolic pathway.

TIGAR Protects Cochlear Hair Cells against Teicoplanin-Induced Damage

Teicoplanin is a glycopeptide antibiotic used to treat severe staphylococcal infections. It has been claimed that teicoplanin possesses ototoxic potential, although its toxic effects on cochlear hair cells (HCs) remain unknown. The TP53-induced glycolysis and apoptosis regulator (TIGAR) plays a crucial role in promoting cell survival. Prior research has demonstrated that TIGAR protects spiral ganglion neurons against cisplatin damage. However, the significance of TIGAR in damage to mammalian HCs has not yet been investigated. In this study, firstly, we discovered that teicoplanin caused dose-dependent cell death in vitro in both HEI-OC1 cells and cochlear HCs. Next, we discovered that HCs and HEI-OC1 cells treated with teicoplanin exhibited a dramatically decrease in TIGAR expression. To investigate the involvement of TIGAR in inner ear injury caused by teicoplanin, the expression of TIGAR was either upregulated via recombinant adenovirus or downregulated by shRNA in HEI-OC1 cells. Overexpression of TIGAR increased cell viability, decreased apoptosis, and decreased intracellular reactive oxygen species (ROS) level, whereas downregulation of TIGAR decreased cell viability, exacerbated apoptosis, and elevated ROS level following teicoplanin injury. Finally, antioxidant therapy with N-acetyl-L-cysteine decreased ROS level, prevented cell death, and restored p38/phosphorylation-p38 expression levels in HEI-OC1 cells injured by teicoplanin. This study demonstrates that TIGAR may be a promising novel target for the prevention of teicoplanin-induced ototoxicity.

NetCellMatch: Multiscale Network-Based Matching of Cancer Cell Lines to Patients Using Graphical Wavelets

Cancer cell lines serve as model in vitro systems for investigating therapeutic interventions. Recent advances in high-throughput genomic profiling have enabled the systematic comparison between cell lines and patient tumor samples. The highly interconnected nature of biological data, however, presents a challenge when mapping patient tumors to cell lines. Standard clustering methods can be particularly susceptible to the high level of noise present in these datasets and only output clusters at one unknown scale of the data. In light of these challenges, we present NetCellMatch, a robust framework for network-based matching of cell lines to patient tumors. NetCellMatch first constructs a global network across all cell line-patient samples using their genomic similarity. Then, a multi-scale community detection algorithm integrates information across topologically meaningful (clustering) scales to obtain Network-Based Matching Scores (NBMS). NBMS are measures of cluster robustness which map patient tumors to cell lines. We use NBMS to determine representative "avatar" cell lines for subgroups of patients. We apply NetCellMatch to reverse-phase protein array data obtained from The Cancer Genome Atlas for patients and the MD Anderson Cell Line Project for cell lines. Along with avatar cell line identification, we evaluate connectivity patterns for breast, lung, and colon cancer and explore the proteomic profiles of avatars and their corresponding top matching patients. Our results demonstrate our framework's ability to identify both patient-cell line matches and potential proteomic drivers of similarity. Our methods are general and can be easily adapted to other'omic datasets.

The role of TIGAR in nervous system diseases

TP53-induced glycolysis and apoptosis regulator (TIGAR) mainly regulates pentose phosphate pathway by inhibiting glycolysis, so as to synthesize ribose required by DNA, promote DNA damage repair and cell proliferation, maintain cell homeostasis and avoid body injury. Its physiological functions include anti-oxidative stress, reducing inflammation, maintaining mitochondrial function, inhibiting apoptosis, reducing autophagy etc. This paper reviews the research of TIGAR in neurological diseases, including stroke, Parkinson’s disease (PD), Alzheimer’s disease (AD), seizures and brain tumors, aiming to provide reference for the development of new therapeutic targets.

Tracking footprints of artificial and natural selection signatures in breeding and non-breeding cats

Stray non-breeding cats (stray) represent the largest heterogeneous cat population subject to natural selection, while populations of the Siamese (SIAM) and Oriental Shorthair (OSH) breeds developed through intensive artificial selection for aesthetic traits. Runs of homozygosity (ROH) and demographic measures are useful tools to discover chromosomal regions of recent selection and to characterize genetic diversity in domestic cat populations. To achieve this, we genotyped 150 stray and 26 household non-breeding cats (household) on the Illumina feline 63 K SNP BeadChip and compared them to SIAM and OSH. The 50% decay value of squared correlation coefficients (r²) in stray (0.23), household (0.25), OSH (0.24) and SIAM (0.25) corresponded to a mean marker distance of 1.12 Kb, 4.55 Kb, 62.50 Kb and 175.07 Kb, respectively. The effective population size (N_e) decreased in the current generation to 55 in stray, 11 in household, 9 in OSH and 7 in SIAM. In the recent generation, the increase in inbreeding per generation (ΔF) reached its maximum values of 0.0090, 0.0443, 0.0561 and 0.0710 in stray, household, OSH and SIAM, respectively. The genomic inbreeding coefficient (F_ROH) based on ROH was calculated for three length categories. The F_ROH was between 0.014 (F_ROH60) and 0.020 (F_ROH5) for stray, between 0.018 (F_ROH60) and 0.024 (F_ROH5) for household, between 0.048 (F_ROH60) and 0.069 (F_ROH5) for OSH and between 0.053 (F_ROH60) and 0.073 (F_ROH5) for SIAM. We identified nine unique selective regions for stray through genome-wide analyses for regions with reduced heterozygosity based on F_ST statistics. Genes in these regions have previously been associated with reproduction (BUB1B), motor/neurological behavior (GPHN, GABRB3), cold-induced thermogenesis (DIO2, TSHR), immune system development (TSHR), viral carcinogenesis (GTF2A1), host immune response against bacteria, viruses, chemoattractant and cancer cells (PLCB2, BAHD1, TIGAR), and lifespan and aging (BUB1B, FGF23). In addition, we identified twelve unique selective regions for OSH containing candidate genes for a wide range of coat colors and patterns (ADAMTS20, KITLG, TYR, TYRO3-a MITF regulator, GPNMB, FGF7, RAB38) as well as congenital heart defects (PDE4D, PKP2) and gastrointestinal disorders (NLGN1, ALDH1B1). Genes in stray that represent unique selective events indicate, at least in part, natural selection for environmental adaptation and resistance to infectious disease, and should be the subject of future research. Stray cats represent an important genetic resource and have the potential to become a research model for disease resistance and longevity, which is why we recommend preserving semen before neutering.

MiR-652-5p elevated glycolysis level by targeting TIGAR in T-cell acute lymphoblastic leukemia

The effect of glycolysis remains largely elusive in acute T lymphoblastic leukemia (T-ALL). Increasing evidence has indicated that the dysregulation of miRNAs is involved in glycolysis, by targeting the genes coding glycolysis rate-limiting enzymes. In our previous studies, we found that overexpression of the ARRB1-derived miR-223 sponge repressed T-ALL progress and reduced the expression of miR-652-5p. However, little is known about miR-652-5p on T-ALL. Here, we showed that impaired miR-652-5p expression inhibited growth, promoted apoptosis of T-ALL cells in vitro and prolonged overall survival (OS) in vivo. Based on the GO enrichment of miR-652-5p target genes, we uncovered that impaired miR-652-5p decreased glycolysis, including reduced the lactate, pyruvate, ATP level and the total extracellular acidification rate (ECAR), elevated oxygen consumption rate (OCR) in T-ALL cell lines. Mechanically, miR-652-5p targeted the 3ʹUTR of Tigar mRNA and inhibited its expression. Furthermore, the alteration of glycosis level was attributed to Tigar overexpression, consistent with the effect of impaired miR-652-5p. Additionally, Tigar suppressed the expression of PFKFB3, a glycolysis rate-limiting enzyme, in vivo and in vitro. Taken together, our results demonstrate that impaired miR-652-5p/Tigar axis could repress glycolysis, thus to slow growth of T-ALL cells, which support miR-652-5p as a novel potential drug target for T-ALL therapeutics.

STING1 in sepsis: Mechanisms, functions, and implications

Sepsis is a life-threatening clinical syndrome and one of the most challenging health problems in the world. Pathologically, sepsis and septic shock are caused by a dysregulated host immune response to infection, which can eventually lead to multiple organ failure and even death. As an adaptor transporter between the endoplasmic reticulum and Golgi apparatus, stimulator of interferon response cGAMP interactor 1 (STING1, also known as STING or TMEM173) has been found to play a vital role at the intersection of innate immunity, inflammation, autophagy, and cell death in response to invading microbial pathogens or endogenous host damage. There is ample evidence that impaired STING1, through its immune and non-immune functions, is involved in the pathological process of sepsis. In this review, we discuss the regulation and function of the STING1 pathway in sepsis and highlight it as a suitable drug target for the treatment of lethal infection.

HACE1-mediated NRF2 activation causes enhanced malignant phenotypes and decreased radiosensitivity of glioma cells

HACE1, an E3 ubiquitin-protein ligase, is frequently inactivated and has been evidenced as a putative tumor suppressor in different types of cancer. However, its role in glioma remains elusive. Here, we observed increased expression of HACE1 in gliomas related to control subjects, and found a strong correlation of high HACE1 expression with poor prognosis in patients with WHO grade III and IV as well as low-grade glioma (LGG) patients receiving radiotherapy. HACE1 knockdown obviously suppressed malignant behaviors of glioma cells, while ectopic expression of HACE1 enhanced cell growth in vitro and in vivo. Further studies revealed that HACE1 enhanced protein stability of nuclear factor erythroid 2-related factor 2 (NRF2) by competitively binding to NRF2 with another E3 ligase KEAP1. Besides, HACE1 also promoted internal ribosome entry site (IRES)-mediated mRNA translation of NRF2. These effects did not depend on its E3 ligase activity. Finally, we demonstrated that HACE1 dramatically reduced cellular ROS levels by activating NRF2, thereby decreasing the response of glioma cells to radiation. Altogether, our data demonstrate that HACE1 causes enhanced malignant phenotypes and decreased radiosensitivity of glioma cells by activating NRF2, and indicate that it may act as the role of prognostic factor and potential therapeutic target in glioma.

Structure, regulation, and biological functions of TIGAR and its role in diseases

TIGAR (TP53-induced glycolysis and apoptosis regulator) is the downstream target gene of p53, contains a functional sequence similar to 6-phosphofructose kinase/fructose-2, 6-bisphosphatase (PFKFB) bisphosphatase domain. TIGAR is mainly located in the cytoplasm; in response to stress, TIGAR is translocated to nucleus and organelles, including mitochondria and endoplasmic reticulum to regulate cell function. P53 family members (p53, p63, and p73), some transcription factors (SP1 and CREB), and noncoding miRNAs (miR-144, miR-885-5p, and miR-101) regulate the transcription of TIGAR. TIGAR mainly functions as fructose-2,6-bisphosphatase to hydrolyze fructose-1,6-diphosphate and fructose-2,6-diphosphate to inhibit glycolysis. TIGAR in turn facilitates pentose phosphate pathway flux to produce nicotinamide adenine dinucleotide phosphate (NADPH) and ribose, thereby promoting DNA repair, and reducing intracellular reactive oxygen species. TIGAR thus maintains energy metabolism balance, regulates autophagy and stem cell differentiation, and promotes cell survival. Meanwhile, TIGAR also has a nonenzymatic function and can interact with retinoblastoma protein, protein kinase B, nuclear factor-kappa B, hexokinase 2, and ATP5A1 to mediate cell cycle arrest, inflammatory response, and mitochondrial protection. TIGAR might be a potential target for the prevention and treatment of cardiovascular and neurological diseases, as well as cancers.

Plant Polyphenols for Aging Health: Implication from Their Autophagy Modulating Properties in Age-Associated Diseases

Polyphenols are a family of naturally occurring organic compounds, majorly present in fruits, vegetables, and cereals, characterised by multiple phenol units, including flavonoids, tannic acid, and ellagitannin. Some well-known polyphenols include resveratrol, quercetin, curcumin, epigallocatechin gallate, catechin, hesperetin, cyanidin, procyanidin, caffeic acid, and genistein. They can modulate different pathways inside the host, thereby inducing various health benefits. Autophagy is a conserved process that maintains cellular homeostasis by clearing the damaged cellular components and balancing cellular survival and overall health. Polyphenols could maintain autophagic equilibrium, thereby providing various health benefits in mediating neuroprotection and exhibiting anticancer and antidiabetic properties. They could limit brain damage by dismantling misfolded proteins and dysfunctional mitochondria, thereby activating autophagy and eliciting neuroprotection. An anticarcinogenic mechanism is stimulated by modulating canonical and non-canonical signalling pathways. Polyphenols could also decrease insulin resistance and inhibit loss of pancreatic islet β-cell mass and function from inducing antidiabetic activity. Polyphenols are usually included in the diet and may not cause significant side effects that could be effectively used to prevent and treat major diseases and ailments.

Autophagy and Ubiquitination as Two Major Players in Colorectal Cancer: A Review on Recent Patents

BACKGROUND

As one of the most commonly diagnosed cancers among men and women, Colorectal Cancer (CRC) leads to high rates of morbidity and mortality across the globe. Recent anti- CRC therapies are now targeting specific signaling pathways involved in colorectal carcinogenesis. Ubiquitin Proteasome System (UPS) and autophagy are two main protein quality control systems, which play major roles in the carcinogenesis of colorectal cancer. A balanced function of these two pathways is necessary for the regulation of cell proliferation and cell death.

OBJECTIVE

In this systematic review, we discuss the available evidence regarding the roles of autophagy and ubiquitination in progression and inhibition of CRC.

METHODS

The search terms "colorectal cancer" or "colon cancer" or "colorectal carcinoma" or "colon carcinoma" in combination with "ubiquitin proteasome" and "autophagy" were searched in PubMed, Web of Science, and Scopus databases, and also Google Patents (https://patents.google .com) from January 2000 to Feb 2020.

RESULTS

The most important factors involved in UPS and autophagy have been investigated. There are many important factors involved in UPS and autophagy but this systematic review shows the studies that have mostly focused on the role of ATG, 20s proteasome and mTOR in CRC, and the more important factors such as ATG8, FIP200, and TIGAR factors that are effective in the regulation of autophagy in CRC cells have not been yet investigated.

CONCLUSION

The most important factors involved in UPS and autophagy such as ATG, 20s proteasome and mTOR, ATG8, FIP200, and TIGAR can be considered in drug therapy for controlling or activating autophagy.

TP53-Induced Glycolysis and Apoptosis Regulator (TIGAR) Is Upregulated in Lymphocytes Stimulated with Concanavalin A

The glycolytic modulator TP53-Inducible Glycolysis and Apoptosis Regulator (TIGAR) is overexpressed in several types of cancer and has a role in metabolic rewiring during tumor development. However, little is known about the role of this enzyme in proliferative tissues under physiological conditions. In the current work, we analysed the role of TIGAR in primary human lymphocytes stimulated with the mitotic agent Concanavalin A (ConA). We found that TIGAR expression was induced in stimulated lymphocytes through the PI3K/AKT pathway, since Akti-1/2 and LY294002 inhibitors prevented the upregulation of TIGAR in response to ConA. In addition, suppression of TIGAR expression by siRNA decreased the levels of the proliferative marker PCNA and increased cellular ROS levels. In this model, TIGAR was found to support the activity of glucose 6-phosphate dehydrogenase (G6PDH), the first enzyme of the pentose phosphate pathway (PPP), since the inhibition of TIGAR reduced G6PDH activity and increased autophagy. In conclusion, we demonstrate here that TIGAR is upregulated in stimulated human lymphocytes through the PI3K/AKT signaling pathway, which contributes to the redirection of the carbon flux to the PPP.

In silico identification of potential inhibitor for TP53-induced glycolysis and apoptosis regulator in head and neck squamous cell carcinoma

Head and neck squamous cell carcinoma (HNSCC) is the six most common cancer globally and most common cancer in men in India. The metabolic regulation is highly altered and is considered as a hall mark of HNSCC. TP53-induced glycolysis and apoptosis regulator (TIGAR) plays very important role in the development and progression of HNSCC. The aim of our study is to identify a novel FDA approved anticancer inhibitor against mutated TP53-induced glycolysis and apoptosis regulator (TIGAR) through drug repurposing approach. A library of 105 FDA approved anticancer compounds were screened using molecular docking approach against TIGAR (PDB: 3DCY) both Wild-Type (WT) and mutated (Mut). Specific mutations in TIGAR were identified using cBioPortal, a cancer genomics database and mutated structure was modelled using SWISS-MODEL. Out of 510 sequenced cases/patients samples, 17(3%) patients showed alteration in TIGAR [TIGAR^WT and TIGAR^{Mut (R88W)}]. The virtual drug screening showed 45 drugs out of 105 high binding affinity with TIGAR, Trabectedin showed highest binding affinity with both TIGAR^WT (- 13.3 kcal/mol) as well as TIGAR^{Mut (R88W)} (- 13.8 kcal/mol). The molecular docking studies were validated using molecular dynamics simulation (MD Simulation) of protein-ligand complex of TIGAR and Trabectedin for 100 ns. The MD Simulation of Trabectedin complex showed more stable with TIGAR^{Mut (R88W)} compared to TIGAR^WT. Moreover, the string analysis revealed that metabolic-related genes, HK2, PFKFB1, PFKM, PFKP, PFKL, FBP1 are closely associated with TIGAR in HNSCC. Our findings suggest that Trabectedin can be proposed as an inhibitor for [TIGAR^{Mut (R88W)}] which can be used to target metabolic signalings in HNSCC. However, further investigation and in vitro and in vivo validation our findings required to understand the molecular mechanisms of regulation of Trabectedin in HNSCC.

Decitabine Downregulates TIGAR to Induce Apoptosis and Autophagy in Myeloid Leukemia Cells

Decitabine (DAC) is a well-known DNA methyltransferase inhibitor, which has been widely used for the treatment of acute myeloid leukemia (AML). However, in addition to hypomethylation, DAC in AML is also involved in cell metabolism, apoptosis, and immunity. The TP53-induced glycolysis and apoptosis regulator (TIGAR) functions to inhabit glycolysis and protect cancer cells from reactive oxygen species- (ROS-) associated apoptosis. Our previous study revealed that TIGAR is highly expressed in myeloid leukemia cell lines and AML primary cells and associated with poor prognosis in adult patients with cytogenetically normal AML. In the present study, it was found that in a time- and concentration-dependent manner, DAC downregulates the TIGAR expression, induces ROS production, and promotes apoptosis in HL-60 and K562 cells. However, blocking the glycolytic pathway partially reversed the combined effects of DAC and TIGAR knockdown on apoptosis, ROS production, and cell cycle arrest, indicating that DAC induced apoptosis through the glycolytic pathway. Furthermore, TIGAR also has a negative impact on autophagy, while DAC treatment upregulates autophagy-related proteins LC3, Beclin-1, ATG3, and ATG-5, downregulates p62, and promotes the formation of autophagosomes, indicating that DAC may activate autophagy by downregulating TIGAR. Taken together, DAC plays an unmethylated role in inducing apoptosis and activating autophagy in myeloid leukemia by downregulating TIGAR.

Research advances of intracellular mechanisms underlying gemcitabine resistance in pancreatic cancer

Pancreatic cancer is one of the most deadly malignant tumors that endanger human health, and pancreatic ductal adenocarcinoma (PDAC) is the most common histological type. Due to the lack of specific clinical symptoms, physical signs, and effective screening biomarkers for early stage PDAC, only 15%-20% of patients are qualified for surgical resection. Consequently, gemcitabine (GEM)-based monotherapy or combination therapy is still the most important or even the only treatment option. However, the overall response rate of PDAC to GEM is less than 20%, and GEM resistance is one of the most important factors affecting the efficacy of chemotherapy. At present, the mechanism of GEM resistance has not been clarified, which may involve congenital and acquired regulation. The heterogeneity of PDAC further increases its complexity. However, regulation of intracellular signaling pathways is the ultimate event to induce GEM resistance. This article will review the recent advances in research of GEM metabolism and regulation of signaling pathways in PDAC cells, and discuss potential GEM chemosensitization strategies, in order to improve the effective rate of chemotherapy and the outcome.

Challenges and Therapeutic Opportunities of Autophagy in Cancer Therapy

Simple Summary

Autophagy is a physiological process characterized by the degradation of the cell components through lysosomes due to stimuli/stress. In this study, we review the challenges and therapeutic opportunities that autophagy presents in the treatment of cancer. We discussed the results of several studies that evaluated autophagy as a therapeutic strategy in cancer, both through the modulation of therapeutic resistance and the death of cancer cells. Moreover, we discussed the role of autophagy in the biology of cancer stem cells and the inhibition of this process as a strategy to overcome resistance and progression of cancer stem cells.

Abstract

Autophagy is a physiological cellular process that is crucial for development and can occurs in response to nutrient deprivation or metabolic disorders. Interestingly, autophagy plays a dual role in cancer cells—while in some situations, it has a cytoprotective effect that causes chemotherapy resistance, in others, it has a cytotoxic effect in which some compounds induce autophagy-mediated cell death. In this review, we summarize strategies aimed at autophagy for the treatment of cancer, including studies of drugs that can modulate autophagy-mediated resistance, and/or drugs that cause autophagy-mediated cancer cell death. In addition, the role of autophagy in the biology of cancer stem cells has also been discussed.

Small molecules regulating reactive oxygen species homeostasis for cancer therapy

Elevated intracellular reactive oxygen species (ROS) and antioxidant defense systems have been recognized as one of the hallmarks of cancer cells. Compared with normal cells, cancer cells exhibit increased ROS to maintain their malignant phenotypes and are more dependent on the "redox adaptation" mechanism. Thus, there are two apparently contradictory but virtually complementary therapeutic strategies for the regulation of ROS to prevent or treat cancer. The first strategy, that is, chemoprevention, is to prevent or reduce intracellular ROS either by suppressing ROS production pathways or by employing antioxidants to enhance ROS clearance, which protects normal cells from malignant transformation and inhibits the early stage of tumorigenesis. The second strategy is the ROS-mediated anticancer therapy, which stimulates intracellular ROS to a toxicity threshold to activate ROS-induced cell death pathways. Therefore, targeting the regulation of intracellular ROS-related pathways by small-molecule candidates is considered to be a promising treatment for tumors. We herein first briefly introduce the source and regulation of ROS, and then focus on small molecules that regulate ROS-related pathways and show efficacy in cancer therapy from the perspective of pharmacophores. Finally, we discuss several challenges in developing cancer therapeutic agents based on ROS regulation and propose the direction of future development.

TIGAR reduces smooth muscle cell autophagy to prevent pulmonary hypertension

Yamanaka R, Hoshino A, Fukai K, Urata R, Minami Y, Honda S, Fushimura Y, Hato D, Iwai-Kanai E, Matoba S. TIGAR reduces smooth muscle cell autophagy to prevent pulmonary hypertension. Am J Physiol Heart Circ Physiol 319: H1087-H1096, 2020. First published September 18, 2020; doi:10.1152/ajpheart.00314.2020.-Pulmonary arterial hypertension (PAH) is a refractory disease. Its prognosis remains poor; hence, establishment of novel therapeutic targets is urgent. TP53-induced glycolysis and apoptosis regulator (TIGAR) is a downstream target of p53 and exhibits functions inhibiting autophagy and reactive oxygen species (ROS). Recently, p53 was shown to suppress PAH progression. Because inhibition of autophagy and ROS is known to improve PAH, we examined the effect of TIGAR on PAH progression. We compared pulmonary hypertension (PH) development between TIGAR-deficient knockout (KO) and wild-type (WT) mice using a hypoxia-induced PH model. Human pulmonary artery smooth muscle cells (PASMCs) were used for in vitro experiments with small interfering RNA (siRNA) to investigate the possible molecular mechanisms. From the analysis of right ventricular pressure, right ventricular weight, and mortality rate, we concluded that the hypoxia-induced PH development was remarkably higher in TIGAR KO than in WT mice. Pathological investigation revealed that medial thickening of the pulmonary arterioles and cell proliferation were increased in TIGAR KO mice. Autophagy and ROS activity were also increased in TIGAR KO mice. TIGAR knockdown by siRNA increased cell proliferation and migration, exacerbated autophagy, and increased ROS generation during hypoxia. Autophagy inhibition by chloroquine and ROS inhibition by N-acetylcysteine attenuated the proliferation and migration of PASMCs caused by TIGAR knockdown and hypoxia exposure. TIGAR suppressed the proliferation and migration of PASMCs via inhibiting autophagy and ROS and, therefore, improved hypoxia-induced PH. Thus, TIGAR might be a promising therapeutic target for PAH.NEW & NOTEWORTHY Pulmonary arterial hypertension is a refractory disease. TP53-induced glycolysis and apoptosis regulator (TIGAR) is a downstream target of p53 and exhibits functions inhibiting autophagy and reactive oxygen species (ROS). By using TIGAR-deficient knockout mice and human pulmonary artery smooth muscle cells, we found that TIGAR suppressed the proliferation and migration of PASMCs via inhibiting autophagy and ROS and, therefore, improved hypoxia-induced PH. TIGAR will be a promising therapeutic target for PAH.

Synthetic mRNA nanoparticle-mediated restoration of p53 tumor suppressor sensitizes p53-deficient cancers to mTOR inhibition

Loss of function in tumor suppressor genes is commonly associated with the onset/progression of cancer and treatment resistance. The p53 tumor suppressor gene, a master regulator of diverse cellular pathways, is frequently altered in various cancers, for example, in ~36% of hepatocellular carcinomas (HCCs) and ~68% of non-small cell lung cancers (NSCLCs). Current methods for restoration of p53 expression, including small molecules and DNA therapies, have yielded progressive success, but each has formidable drawbacks. Here, a redox-responsive nanoparticle (NP) platform is engineered for effective delivery of p53-encoding synthetic messenger RNA (mRNA). We demonstrate that the synthetic p53-mRNA NPs markedly delay the growth of p53-null HCC and NSCLC cells by inducing cell cycle arrest and apoptosis. We also reveal that p53 restoration markedly improves the sensitivity of these tumor cells to everolimus, a mammalian target of rapamycin (mTOR) inhibitor that failed to show clinical benefits in advanced HCC and NSCLC. Moreover, cotargeting of tumor-suppressing p53 and tumorigenic mTOR signaling pathways results in marked antitumor effects in vitro and in multiple animal models of HCC and NSCLC. Our findings indicate that restoration of tumor suppressors by the synthetic mRNA NP delivery strategy could be combined together with other therapies for potent combinatorial cancer treatment.

The Role of Pi, Glutamine and the Essential Amino Acids in Modulating the Metabolism in Diabetes and Cancer

Purpose

Re-examine the current metabolic models.

Methods

Review of literature and gene networks.

Results

Insulin activates Pi uptake, glutamine metabolism to stabilise lipid membranes. Tissue turnover maintains the metabolic health. Current model of intermediary metabolism (IM) suggests glucose is the source of energy, and anaplerotic entry of fatty acids and amino acids into mitochondria increases the oxidative capacity of the TCA cycle to produce the energy (ATP). The reduced cofactors, NADH and FADH2, have different roles in regulating the oxidation of nutrients, membrane potentials and biosynthesis. Trans-hydrogenation of NADH to NADPH activates the biosynthesis. FADH2 sustains the membrane potential during the cell transformations. Glycolytic enzymes assume the non-canonical moonlighting functions, enter the nucleus to remodel the genetic programmes to affect the tissue turnover for efficient use of nutrients. Glycosylation of the CD98 (4F2HC) stabilises the nutrient transporters and regulates the entry of cysteine, glutamine and BCAA into the cells. A reciprocal relationship between the leucine and glutamine entry into cells regulates the cholesterol and fatty acid synthesis and homeostasis in cells. Insulin promotes the Pi transport from the blood to tissues, activates the mitochondrial respiratory activity, and glutamine metabolism, which activates the synthesis of cholesterol and the de novo fatty acids for reorganising and stabilising the lipid membranes for nutrient transport and signal transduction in response to fluctuations in the microenvironmental cues. Fatty acids provide the lipid metabolites, activate the second messengers and protein kinases. Insulin resistance suppresses the lipid raft formation and the mitotic slippage activates the fibrosis and slow death pathways.

NADPH protects against kainic acid-induced excitotoxicity via autophagy-lysosome pathway in rat striatum and primary cortical neurons

PURPOSE

To investigate the effects and mechanisms of NADPH on Kainic acid (KA)-induced excitotoxicity.

METHODS

KA, a non-N-methyl-d-aspartate glutamate receptor agonist, was exposed to adult SD rats via intrastriatal injection and rat primary cortical neurons to establish excitotoxic models in vivo and in vitro, respectively. To determine the effects of NADPH on KA-induced excitotoxicity, neuronal survival, neurologically behavioral score and oxidative stress were evaluated. To explore the mechanisms of neuroprotective effects of NADPH, the autophagy-lysosome pathway related proteins were detected.

RESULTS

In vivo, NADPH (1 mg/kg or 2 mg/kg) diminished KA (2.5 nmol)-induced enlargement of lesion size in striatum, improved KA-induced dyskinesia and reversed KA-induced activation of glial cells. Nevertheless, the neuroprotective effect of NADPH was not significant under the condition of autophagy activation. NADPH (2 mg/kg) inhibited KA (2.5 nmol)-induced down-regulation of TP-53 induced glycolysis and apoptosis regulator (TIGAR) and p62, and up-regulation of the protein levels of LC3-II/LC3-I, Beclin-1 and Atg5. In vitro, the excitotoxic neuronal injury was induced after KA (50 μM, 100 μM or 200 μM) treatment as demonstrated by decreased cell viability. Moreover, KA (100 μM) increased the intracellular levels of calcium and reactive oxygen species (ROS) and declined the levels of the reduced form of glutathione (GSH). Pretreatment of NADPH (10 μM) effectively reversed these changes. Meanwhile NADPH (10 μM) inhibited KA (100 μM)-induced down-regulation of TIGAR and p62, and up-regulation of the ratio of LC3-II/LC3-I, Beclin-1, Atg5, active-cathepsin B and active-cathepsin D.

CONCLUSIONS

Our data provide a possible mechanism that NADPH ameliorates KA-induced excitotoxicity by blocking the autophagy-lysosome pathway and up-regulating TIGAR along with its antioxidant properties.

TIGAR Promotes Tumorigenesis and Protects Tumor Cells From Oxidative and Metabolic Stresses in Gastric Cancer

Cancer cells adopt glycolysis to facilitate the generation of biosynthetic substrates demanded by cell proliferation and growth, and to adapt to stress conditions such as excessive reactive oxygen species (ROS) accumulation. TIGAR (TP53-induced glycolysis and apoptosis regulator) is a fructose-2,6-bisphosphatase that is regulated by p53. TIGAR functions to inhibit glycolysis and promote antioxidative activities, which assists the generation of NADPH to maintain the levels of GSH and thus reduces intracellular ROS. However, the functions of TIGAR in gastric cancer (GC) remain unclear. TIGAR expression levels were detected by immunoblotting and immunohistochemistry in gastric cancer samples, along with four established cell lines of GC. The functions of TIGAR were determined by utilizing shRNA-mediated knockdown experiments. The NADPH/NADP⁺ ratio, ROS, mitochondrial ATP production, and phosphorus oxygen ratios were determined in TIGAR-depleted cells. Xenograft experiment was conducted with BALB/c nude mice. TIGAR was up-regulated compared with corresponding non-cancerous tissues in primary GCs. TIGAR knockdown significantly reduced cell proliferation and increased apoptosis. TIGAR protected cancer cells from oxidative stress-caused damages, but also glycolysis defects. TIGAR also increased the production of NADPH in gastric cancer cells. TIGAR knockdown led to increased ROS production, elevated mitochondrial ATP production, and phosphorus oxygen ratios. The prognosis of high TIGAR expression patients was significantly poorer than those with low TIGAR expression. Taken together, TIGAR exhibits oncogenic features in GC, which can be evaluated as a target for intervention in the treatment of GC.

TIGAR Attenuates High Glucose-Induced Neuronal Apoptosis via an Autophagy Pathway

Hyperglycemia-induced neuronal apoptosis is one of the important reasons for diabetic neuropathy. Long-time exposure to high glucose accelerates many aberrant glucose metabolic pathways and eventually leads to neuronal injury. However, the underlying mechanisms of metabolic alterations remain unknown. TP53-inducible glycolysis and apoptosis regulator (TIGAR) is an endogenous inhibitor of glycolysis and increases the flux of pentose phosphate pathway (PPP) by regulating glucose 6-phosphate dehydrogenase (G6PD). TIGAR is highly expressed in neurons, but its role in hyperglycemia-induced neuronal injury is still unclear. In this study, we observed that TIGAR and G6PD are decreased in the hippocampus of streptozotocin (STZ)-induced diabetic mice. Correspondingly, in cultured primary neurons and Neuro-2a cell line, stimulation with high glucose induced significant neuronal apoptosis and down-regulation of TIGAR expression. Overexpression of TIGAR reduced the number of TUNEL-positive neurons and prevented the activation of Caspase-3 in cultured neurons. Furthermore, enhancing the expression of TIGAR rescued high glucose-induced autophagy impairment and the decrease of G6PD. Nitric oxide synthase 1 (NOS1), a negative regulator of autophagy, is also inhibited by overexpression of TIGAR. Inhibition of autophagy abolished the protective effect of TIGAR in neuronal apoptosis in Neuro-2a. Importantly, overexpression of TIGAR in the hippocampus ameliorated STZ-induced cognitive impairment in mice. Therefore, our data demonstrated that TIGAR may have an anti-apoptosis effect via up-regulation of autophagy in diabetic neuropathy.

Metronomic photodynamic therapy with 5-aminolevulinic acid induces apoptosis and autophagy in human SW837 colorectal cancer cells

Metronomic photodynamic therapy (mPDT) has emerged as an attractive treatment for the selective destruction of tumor cells by induction of apoptosis. Here, we compared the effects of mPDT and acute photodynamic therapy (aPDT) on human SW837 colorectal cancer (CRC) cells. CRC cells were subjected to mPDT using various exposure durations, concentrations of 5-aminolevulinic acid (ALA), fluence rates and energy densities. The effects were compared with those induced by aPDT. We found that apoptosis and autophagy were earlier induced to a greater extent by mPDT than by the same dose applied as aPDT. The survival rates for mPDT vs. aPDT were 35.2%, 32.4%,27.6%,31.6% vs. 85.7%, 71.1%, 67.8%, 42.1% after 3, 6, 12, and 24 h PDT, respectively. For the same time points, the apoptotic rates for mPDT vs. aPDT were 43.2%, 47.3%, 54.7%, and 50.3% vs. 14.6%, 17.6%, 27.1%, and 53.2%, respectively. mPDT induced a peak rate of autophagy of 20.0% at 3 h, whereas aPDT induced two smaller peaks at 3 h (14.1%) and 12 h (15.8%). Advanced autophagosomes were more abundant in mPDT- than aPDT-treated cells and appeared earlier after mPDT (3 h) than after aPDT (3-12 h). Western Bloting results showed that the ratio of LC3B-II/β - actin at 3 h was higher (1.04 times) after mPDT than aPDT. Collectively, these datas indicated that ALA-mPDT was more effective than the same dose of ALA-aPDT at inducing SW837 CRC cell death via apoptosis and autophagy. Thus, mPDT may be a superior choice than aPDT for the treatment of human CRC.

TIGAR impedes compression-induced intervertebral disc degeneration by suppressing nucleus pulposus cell apoptosis and autophagy

To investigate whether TP53-induced glycolysis and apoptosis regulator (TIGAR) participates in compression-induced intervertebral disc (IVD) degeneration, and to determine the regulatory effect of TIGAR on nucleus pulposus (NP) cell autophagy and apoptosis following compression-induced injuries. IVD tissues were collected from human patients undergoing surgery (n = 20) and skeletally mature Sprague-Dawley rats (n = 15). Initially, the effect of compression on the expression of TIGAR was evaluated with in vivo and in vitro models. In addition, TIGAR was silenced to investigate the regulatory effect of TIGAR on compression-induced intracellular reactive oxygen species (ROS) levels, autophagy, and apoptosis in rat NP cells. Furthermore, the P53 inhibitor pifithrin-α (PFTα) and SP1 inhibitor mithramycin A were employed to detect expression level changes of TIGAR and autophagy-associated target molecules. TIGAR expression of NP cells increased gradually in human degenerative IVDs and in rat NP cells under compression both in vivo and in vitro. TIGAR knockdown enhanced compression-induced intracellular ROS generation and the NADPH/NADP⁺ and GSH/GSSG ratios. Moreover, TIGAR knockdown amplified the compression-induced caspase-3 activation and the apoptosis rate of rat NP cells. Likewise, knockdown of TIGAR significantly accelerated LC3B expression and autophagosome formation in rat NP cells during compression-induced injuries. The results also established that mithramycin A could inhibit TIGAR expression and autophagy levels in NP cells under compression conditions, while PFTα had no similar effect. Our data demonstrated that TIGAR acted as an important endogenous negative regulator of ROS levels, which might inhibit compression-induced apoptosis and autophagy through SP1-dependent mechanisms.

TIGAR promotes growth, survival and metastasis through oxidation resistance and AKT activation in glioblastoma

Glioblastoma has a poor prognosis and is one of the most lethal types of cancer in the world. TP53 induced glycolysis regulatory phosphatase (TIGAR) is upregulated in various types of cancer. Therefore, the present study investigated the role of TIGAR in glioblastoma. TIGAR expression was measured in glioma samples and cell lines using immunohistochemistry and western blotting. Reduced nicotinamide adenine dinucleotide phosphate (NADPH), glutathione, malondialdehyde and intracellular reactive oxygen species levels were detected to measure oxidative stress in U-87MG cells following short hairpin RNA (shRNA)-mediated knockdown of TIGAR. Cell viability was determined using an MTT assay for TIGAR-overexpression vector- and TIGAR-shRNA-transfected U-87MG cells. Apoptosis was assessed to evaluate whether TIGAR knockdown sensitized cells to the antitumor effects of temozolomide (TMZ). Migration, invasion and epithelial-mesenchymal transition (EMT) were further assessed using Transwell and western blotting assays. A co-immunoprecipitation assay was used to detect the interaction between TIGAR and protein kinase B (AKT). The results of the present study revealed that TIGAR was positively associated with poor survival and was upregulated in glioblastoma. TIGAR knockdown significantly increased oxidative stress, decreased cell proliferation and exacerbated TMZ-induced apoptosis in U-87MG cells. Additionally, TIGAR knockdown decreased migration, invasion and EMT, and treatment of TIGAR-shRNA-transfected cells with NADPH had no effect on metastasis. In addition, TIGAR promoted AKT activation and bound to AKT. In conclusion, the present study demonstrated that TIGAR may promote glioblastoma growth and progression through oxidation resistance and AKT activation.

The roles of glucose metabolic reprogramming in chemo- and radio-resistance

Reprogramming of cancer metabolism is a newly recognized hallmark of malignancy. The aberrant glucose metabolism is associated with dramatically increased bioenergetics, biosynthetic, and redox demands, which is vital to maintain rapid cell proliferation, tumor progression, and resistance to chemotherapy and radiation. When the glucose metabolism of cancer is rewiring, the characters of cancer will also occur corresponding changes to regulate the chemo- and radio-resistance of cancer. The procedure is involved in the alteration of many activities, such as the aberrant DNA repairing, enhanced autophagy, oxygen-deficient environment, and increasing exosomes secretions, etc. Targeting altered metabolic pathways related with the glucose metabolism has become a promising anti-cancer strategy. This review summarizes recent progress in our understanding of glucose metabolism in chemo- and radio-resistance malignancy, and highlights potential molecular targets and their inhibitors for cancer treatment.

Wnt Signaling Activates TP53-Induced Glycolysis and Apoptosis Regulator and Protects Against Cisplatin-Induced Spiral Ganglion Neuron Damage in the Mouse Cochlea

AIMS

Cisplatin can damage spiral ganglion neurons (SGNs) and cause sensorineural hearing loss. Wnt activation protects against neomycin-induced hair cell damage in the mouse cochlea, but the role of Wnt signaling in protecting SGNs from cisplatin treatment has not yet been elucidated. This study was designed to investigate the neuroprotective effects of Wnt signaling against cisplatin-induced SGN damage.

RESULTS

First, we found that Wnt signaling was activated in SGNs after cisplatin treatment. Next, we discovered that overexpression (OE) of Wnt signaling in SGNs reduced cisplatin-induced SGN loss by inhibiting caspase-associated apoptosis, thus preventing the loss of SGN function after cisplatin treatment. In contrast, inhibition of Wnt signaling increased apoptosis, made SGNs more vulnerable to cisplatin treatment, and exacerbated hearing loss. TP53-induced glycolysis and apoptosis regulator (TIGAR), which scavenges intracellular reactive oxygen species (ROS), was upregulated in SGNs in response to cisplatin administration. Wnt/β-catenin activation increased TIGAR expression and reduced ROS level, while inhibition of Wnt/β-catenin in SGNs reduced TIGAR expression and increased the ROS level. Moreover, OE of TIGAR reduced ROS and decreased caspase 3 expression, as well as increased the survival of SGNs in Wnt-inhibited SGNs. Finally, antioxidant treatment rescued the more severe SGN loss induced by β-catenin deficiency after cisplatin treatment. Innovation and Conclusion: This study is the first to indicate that Wnt signaling activates TIGAR and protects SGNs against cisplatin-induced damage through the inhibition of oxidative stress and apoptosis in SGNs, and this might offer novel therapeutic targets for the prevention of SGN injury. Antioxid. Redox Signal. 00, 000-000.

Potent effects of dioscin against hepatocellular carcinoma through regulating TP53-induced glycolysis and apoptosis regulator (TIGAR)-mediated apoptosis, autophagy, and DNA damage

BACKGROUND AND PURPOSE

Dioscin shows potent effects against cancers. We aimed to elucidate its pharmacological effects and mechanisms of action on hepatocellular carcinoma (HCC) in vivo and in vitro.

EXPERIMENTAL APPROACH

Effects of dioscin were investigated in SMMC7721 and HepG2 cells, diethylnitrosamine-induced primary liver cancer in rats, and cell xenografts in nude mice. Isobaric tags for relative and absolution quantitation (iTRAQ)-based proteomics was used to find dioscin's targets and investigate its mechanism.

KEY RESULTS

In SMMC7721 and HepG2 cells dioscin markedly inhibited cell proliferation and migration, induced apoptosis, autophagy, and DNA damage. It inhibited DEN-induced primary liver cancer in rats, markedly changed body weights and restored levels of α fetoprotein, alanine transaminase, aspartate transaminase, γ-glutamyltransferase, alkaline phosphatase, and Ki67. It also inhibited growth of xenografts in mice. In SMMC7721 cells, 191 differentially expressed proteins were found after dioscin, based on iTRAQ-based assay. TP53-inducible glycolysis and apoptosis regulator (TIGAR) was identified as being significantly down-regulated by dioscin. Dioscin induced cell apoptosis, autophagy, and DNA damage via increasing expression levels of p53, cleaved PARP, Bax, cleaved caspase-3/9, Beclin-1, and LC3 and suppressing those of Bcl-2, p-Akt, p-mammalian target of rapamycin (mTOR), CDK5, p-ataxia telangiectasia-mutated gene (ATM). The transfection of TIGAR siRNA into SMMC7721 cells and xenografts in nude mice further confirmed that the potent activity of dioscin against HCC is evoked by adjusting TIGAR-mediated inhibition of p53, Akt/mTOR, and CDK5/ATM pathways.

CONCLUSIONS AND IMPLICATIONS

The data suggest that dioscin has potential as a therapeutic, and TIGAR as a drug target for treating HCC.

Knockdown of the TP53-Induced Glycolysis and Apoptosis Regulator (TIGAR) Sensitizes Glioma Cells to Hypoxia, Irradiation and Temozolomide

The TP53-induced glycolysis and apoptosis regulator (TIGAR) has been shown to decrease glycolysis, to activate the pentose phosphate pathway, and to provide protection against oxidative damage. Hypoxic regions are considered characteristic of glioblastoma and linked with resistance to current treatment strategies. Here, we established that LNT-229 glioma cell lines stably expressed shRNA constructs targeting TIGAR, and exposed them to hypoxia, irradiation and temozolomide. The disruption of TIGAR enhanced levels of reactive oxygen species and cell death under hypoxic conditions, as well as the effectiveness of irradiation and temozolomide. In addition, TIGAR was upregulated by HIF-1α. As a component of a complex network, TIGAR contributes to the metabolic adjustments that arise from either spontaneous or therapy-induced changes in tumor microenvironment.

The emerging role of stimulator of interferons genes signaling in sepsis: Inflammation, autophagy, and cell death

Stimulator of interferons genes (STING) is an adaptor protein that plays a critical role in the secretion of type I interferons and pro-inflammatory cytokines in response to cytosolic nucleic acid. Recent research indicates the involvement of the STING pathway in uncontrolled inflammation, sepsis, and shock. STING signaling is significantly up-regulated in human sepsis, and STING agonists are suggested to contribute to the pathogenesis of sepsis and shock. Nevertheless, little is known about the consequences of activated STING-mediated signaling during sepsis. It has been shown that aberrant activation of the STING-dependent way can result in increased inflammation, type I interferons responses, and cell death (including apoptosis, necroptosis, and pyroptosis). In addition, autophagy modulation has been demonstrated to protect against multiple organs injuries in animal sepsis model. However, impaired autophagy may contribute to the aberrant activation of STING signaling, leading to uncontrolled inflammation and cell death. Here we present a comprehensive review of recent advances in the understanding of STING signaling, focusing on the regulatory mechanisms and the roles of this pathway in sepsis.

TIGAR knockdown enhanced the anticancer effect of aescin via regulating autophagy and apoptosis in colorectal cancer cells

Our previous study showed that TP53-induced glycolysis and apoptosis regulator (TIGAR) regulated ROS, autophagy, and apoptosis in response to hypoxia and chemotherapeutic drugs. Aescin, a triterpene saponin, exerts anticancer effects and increases ROS levels. The ROS is a key upstream signaling to activate autophagy. Whether there is a crosstalk between TIGAR and aescin in regulating ROS, autophagy, and apoptosis is unknown. In this study, we found that aescin inhibited cell viability and colony formation, and induced DNA damage, cell cycle arrest, and apoptosis in cancer cell lines HCT-116 and HCT-8 cells. Concurrently, aescin increased the expression of TIGAR, ROS levels, and autophagy activation. Knockdown of TIGAR enhanced the anticancer effects of aescin in vitro and in vivo, whereas overexpression of TIGAR or replenishing TIGAR downstream products, NADPH and ribose, attenuated aescin-induced apoptosis. Furthermore, aescin-induced ROS elevation and autophagy activation were further strengthened by TIGAR knockdown in HCT-116 cells. However, autophagy inhibition by knockdown of autophagy-related gene ATG5 or 3-methyladenine (3-MA) exaggerated aescin-induced apoptosis when TIGAR was knocked down. In conclusion, TIGAR plays a dual role in determining cancer cell fate via inhibiting both apoptosis and autophagy in response to aescin, which indicated that inhibition of TIGAR and/or autophagy may be a junctional therapeutic target in treatment of cancers with aescin.

Prognostic value of TIGAR and LC3B protein expression in nasopharyngeal carcinoma

Purpose

Autophagy, the process responsible for degrading cytoplasmic organelles to sustain cellular metabolism, has been associated with cancer initiation and progression. As TP53-induced glycolysis and apoptosis regulator (TIGAR) is among the important genes that can regulate autophagy, we aimed to investigate the correlation between the expression levels of TIGAR and the autophagy-related protein microtubule-associated protein 1 light chain 3 (LC3B), as well as their association with clinical outcomes, in nasopharyngeal carcinoma (NPC) patients.

Methods

We detected the expressions of TIGAR and LC3B in 182 NPC tissue samples via immunohistochemical staining.

Results

A significant correlation between TIGAR and LC3B expressions was identified (P=0.045). Moreover, survival analysis showed that TIGAR− or LC3B+ expression was associated with improved overall survival, local regional failure-free survival, distant failure-free survival, and failure-free survival rates, compared with TIGAR+ or LC3B− expression, respectively. Meanwhile, when combining TIGAR with LC3B expression in terms of prognostic value, patients with TIGAR+/LC3B− expression were significantly disadvantaged with regard to overall survival, local regional failure-free survival, distant failure-free survival, and failure-free survival compared with other groups based on the log-rank test and Cox regression analyses (all P<0.05).

Conclusion

TIGAR and LC3B may be novel biomarkers for predicting the prognosis of NPC patients and could be utilized as potential targets for future therapeutics aimed at treating NPC patients.

Aescin-induced reactive oxygen species play a pro-survival role in human cancer cells via ATM/AMPK/ULK1-mediated autophagy

Aescin, a natural mixture of triterpene saponins, has been reported to exert anticancer effect. Recent studies show that aescin increases intracellular reactive oxygen species (ROS) levels. However, whether the increased ROS play a role in the anticancer action of aescin remains to be explored. In this study, we demonstrated that aescin (20-80 μg/mL) dose-dependently induced apoptosis and activated mammalian target of rapamycin (mTOR)-independent autophagy in human hepatocellular carcinoma HepG2 cells and colon carcinoma HCT 116 cells. The activation of autophagy favored cancer cell survival in response to aescin, as suppression of autophagy with ATG5 siRNAs or 3-methyladenine (3-MA), a selective inhibitor of autophagy, promoted aescin-induced apoptosis in vitro, and significantly enhanced the anticancer effect of aescin in vivo. Meanwhile, aescin dose-dependently elevated intracellular ROS levels and activated Ataxia-telangiectasia mutated kinase/AMP-activated protein kinase/UNC-51-like kinase-1 (ATM/AMPK/ULK1) pathway. The ROS and ATM/AMPK/ULK1 pathway were upstream modulators of the aescin-induced autophagy, as N-acetyl-L-cysteine (NAC) or ATM kinase inhibitor (KU-55933) remarkably suppressed aescin-induced autophagy and consequently promoted aescin-induced apoptosis, whereas overexpression of ATG5 partly attenuated NAC-induced enhancement in aescin-induced apoptosis. In conclusion, this study provides new insights into the roles of aescin-mediated oxidative stress and autophagy in cancer cell survival. Our results suggest that combined administration of the antioxidants or autophagic inhibitors with aescin might be a potential strategy to enhance the anticancer effect of aescin.

The diverse role of TIGAR in cellular homeostasis and cancer

TP53-induced glycolysis and apoptosis regulator (TIGAR) is a p53 target protein that plays critical roles in glycolysis and redox balance. Accumulating evidence shows that TIGAR is highly expressed in cancer. TIGAR redirects glycolysis and promotes carcinoma growth by providing metabolic intermediates and reductive power derived from pentose phosphate pathway (PPP). The expression of TIGAR in cancer is positively associated with chemotherapy resistance, suggesting that TIGAR could be a novel therapeutic target. In this review, we briefly presented the function of TIGAR in metabolic homeostasis in normal and cancer cells. Finally, we discussed the future directions of TIGAR research in cancer.

Reduced nicotinamide adenine dinucleotide phosphate inhibits rat platelet aggregation and p38 phosphorylation

Previous studies found that reduced nicotinamide adenine dinucleotide phosphate (NADPH) protected neurons against ischemia/reperfusion-induced injury. In addition to ROS reduction and ATP increment, preliminary data suggested that NADPH inhibited ADP and thrombin-induced platelet aggregation. As the effect of NADPH on platelet function was not reported by other investigators, the actions of NADPH on platelet function and mechanisms of actions were investigated in the present study. In vitro studies, the effects of different concentrations of NADPH on platelet aggregation induced by ADP (10 μM), thrombin (0.05 U/mL) or AA (50 μM) were determined. The results showed that NADPH could inhibit platelet aggregation induced by ADP, thrombin or AA in a concentration dependent manner. When the inhibitory effects of NAD⁺, NADH, NADP⁺ and NADPH on platelet aggregation were compared, NADPH demonstrated the relatively best effect on platelet aggregation. In vivo studies, the effects of NADPH on platelet aggregation, tail bleeding time, coagulation response and ferric chloride-induced thrombosis were determined in mice or rats. The maximum aggregation rate of platelets of rats injected with NADPH (5 mg/kg) was lower than platelets from control rats. NADPH transiently prolonged tail bleeding time in mice at 30 min after the injection of NADPH (7.5 mg/kg), while aspirin (15 mg/kg) significantly prolonged the tail bleeding time in mice at all time points examined. NADPH (5 mg/kg), as well as aspirin (10 mg/kg), had no effect on coagulation response in rats. Using a FeCl₃-induced abdominal aorta injury thrombosis model, administration of NADPH (5 mg/kg) significantly delayed the onset of vessel occlusion, while aspirin (10 mg/kg) almost completely prevented the vessel occlusion. With microscopic examination the thrombi in injured vessel sections of rats received NADPH were much smaller and less dense than that of rats received vehicle treatment. ADP induced an increase in phosphorylation of p38 and the effect was markedly inhibited by the p38 inhibitor SB203580. Similarly, NADPH also inhibited ADP-induced phosphorylation of p38. Similar to NADPH, SB203580 robustly inhibited ADP- and thrombin-induced platelet aggregation. In addition, NADPH also reduced ADP-induced increases in ROS in platelets. The current results demonstrated that NADPH inhibited platelet aggregation, oxidative stress and p38 phosphorylation, suggesting that NADPH might be a novel compound for management of high risk of cardiovascular disease.

Loss of TIGAR Induces Oxidative Stress and Meiotic Defects in Oocytes from Obese Mice

Maternal obesity has been reported to impair oocyte quality in mice, however, the underlying mechanisms remain unclear. In the present study, by conducting a comparative proteomic analysis, we identified a reduced expression of TIGAR (TP53-induced glycolysis and apoptosis regulator) protein in ovulated oocytes from high-fat diet (HFD)-fed mice. Specific depletion of TIGAR in mouse oocytes results in the marked elevation of reactive oxygen species (ROS) levels and the failure of meiotic apparatus assembly. Importantly, forced expression of TIGAR in HFD oocytes not only attenuates ROS production, but also partly prevents spindle disorganization and chromosome misalignment during meiosis. Meantime, we noted that TIGAR knockdown in oocytes induces a strong activation of autophagy, whereas overexpression of TIGAR significantly reduces the LC3 accumulation in HFD oocytes. By anti-oxidant treatment, we further demonstrated that such an autophagic response is dependent on the TIGAR-controlled ROS production. In summary, our data indicate a role for TIGAR in modulating redox homeostasis during oocyte maturation, and uncover that loss of TIGAR is a critical pathway mediating the effects of maternal obesity on oocyte quality.

p53 and metabolism: from mechanism to therapeutics

The tumor cell changes itself and its microenvironment to adapt to different situations, including action of drugs and other agents targeting tumor control. Therefore, metabolism plays an important role in the activation of survival mechanisms to keep the cell proliferative potential. The Warburg effect directs the cellular metabolism towards an aerobic glycolytic pathway, despite the fact that it generates less adenosine triphosphate than oxidative phosphorylation; because it creates the building blocks necessary for cell proliferation. The transcription factor p53 is the master tumor suppressor; it binds to more than 4,000 sites in the genome and regulates the expression of more than 500 genes. Among these genes are important regulators of metabolism, affecting glucose, lipids and amino acids metabolism, oxidative phosphorylation, reactive oxygen species (ROS) generation and growth factors signaling. Wild-type and mutant p53 may have opposing effects in the expression of these metabolic genes. Therefore, depending on the p53 status of the cell, drugs that target metabolism may have different outcomes and metabolism may modulate drug resistance. Conversely, induction of p53 expression may regulate differently the tumor cell metabolism, inducing senescence, autophagy and apoptosis, which are dependent on the regulation of the PI3K/AKT/mTOR pathway and/or ROS induction. The interplay between p53 and metabolism is essential in the decision of cell fate and for cancer therapeutics.

Protective Effect of Nicotinamide Adenine Dinucleotide Phosphate on Renal Ischemia-Reperfusion Injury

BACKGROUND/AIMS

Renal ischemia-reperfusion injury (IRI) is a common consequence of acute kidney injury. Nicotinamide adenine dinucleotide phosphate (NADPH), which is derived from the pentose phosphate pathway, is essential for the proper functioning of essential redox and antioxidant defense systems. Previous studies have indicated that NADPH is responsible for protecting the brain from ischemic injury. The goal of this study was to analyze the protective function of NADPH in renal IRI.

METHODS

The IRI animal model was generated through a midline laparotomy surgery that clamped both sides of the renal pedicles for 40 min to induce renal ischemia. The in vitro model was generated by removing oxygen and glucose from human kidney epithelial cells (HK-2 cells), followed by reoxygenation to imitate IRI. Renal function and histopathological changes were observed and evaluated. Additionally, malondialdehyde and glutathione levels were determined in renal tissue homogenate as indicators of oxidative stress. ROS production in cells was determined by DHE staining. Protein biomarker expression was evaluated by western blot, apoptosis was analyzed by TUNEL staining, and p65 nuclear translocation was visualized by immunofluorescence.

RESULTS

Our data indicated that NADPH safeguarded the kidneys from histological and functional damage, and significantly reduce cell injury along with preventing potential increases in blood urea nitrogen and creatinine levels. Furthermore, we observed that NADPH increased glutathione levels, while reducing levels of malondialdehyde and reactive oxygen species. Additionally, our results suggested that NADPH treatment may alleviate IRI-induced apoptosis and inflammation.

CONCLUSION

NADPH treatment may protect against renal IRI and should be further developed as a new treatment for acute kidney injury.

Role of multifaceted regulators in cancer glucose metabolism and their clinical significance

Aberrant glucose metabolism, "aerobic glycolysis" or "Warburg effect", is a hallmark of human cancers. There is a cluster of "multifaceted regulators", which plays a pivotal role in the regulation of glucose metabolism. They can not only modulate the activities of specific enzymes, but also act as transcriptional activators to regulate the expression of metabolism related genes. Additionally, they can crosstalk with other key factors involved in glucose metabolism and work together to initiate multiple oncogenic processes. These "multifaceted regulators", especially p53, HIF-1, TIGAR and microRNA, will be focused in this review. And we will comprehensively illustrate their regulatory effects on cancer glucose metabolism, and further elaborate on their clinical significance. In-depth elucidation the role of "multifaceted regulators" in cancer glucose metabolism will provide us novel insights in cancer research field and offer promising therapeutic targets for anti-cancer therapies.

Melatonin ameliorates hypoglycemic stress-induced brain endothelial tight junction injury by inhibiting protein nitration of TP53-induced glycolysis and apoptosis regulator

Severe hypoglycemia has a detrimental impact on the cerebrovasculature, but the molecular events that lead to the disruption of the integrity of the tight junctions remain unclear. Here, we report that the microvessel integrity was dramatically compromised (59.41% of wild-type mice) in TP53-induced glycolysis and apoptosis regulator (TIGAR) transgenic mice stressed by hypoglycemia. Melatonin, a potent antioxidant, protects against hypoglycemic stress-induced brain endothelial tight junction injury in the dosage of 400 nmol/L in vitro. FRET (fluorescence resonance energy transfer) imaging data of endothelial cells stressed by low glucose revealed that TIGAR couples with calmodulin to promote TIGAR tyrosine nitration. A tyrosine 92 mutation interferes with the TIGAR-dependent NADPH generation (55.60% decreased) and abolishes its protective effect on tight junctions in human brain microvascular endothelial cells. We further demonstrate that the low-glucose-induced disruption of occludin and Caludin5 as well as activation of autophagy was abrogated by melatonin-mediated blockade of nitrosative stress in vitro. Collectively, we provide information on the detailed molecular mechanisms for the protective actions of melatonin on brain endothelial tight junctions and suggest that this indole has translational potential for severe hypoglycemia-induced neurovascular damage.

Reciprocal role of SIRT6 and Hexokinase 2 in the regulation of autophagy driven monocyte differentiation

Emerging evidences suggest the impact of autophagy on differentiation but the underlying molecular links between metabolic restructuring and autophagy during monocyte differentiation remain elusive. An increase in PPARγ, HK2 and SIRT6 expression was observed upon PMA induced monocyte differentiation. While PPARγ positively regulated HK2 and SIRT6 expression, the latter served as a negative regulator of HK2. Changes in expression of these metabolic modelers were accompanied by decreased glucose uptake and increase in Chibby, a potent antagonist of β-catenin/Wnt pathway. Knockdown of Chibby abrogated PMA induced differentiation. While inhibition of HK2 either by Lonidamine or siRNA further elevated PMA induced Chibby, mitochondrial ROS, TIGAR and LC3II levels; siRNA mediated knock-down of SIRT6 exhibited contradictory effects as compared to HK2. Notably, inhibition of autophagy increased HK2, diminished Chibby level and CD33 expression. In addition, PMA induced expression of cytoskeletal architectural proteins, CXCR4, phagocytosis, acquisition of macrophage phenotypes and release of pro-inflammatory mediators was found to be HK2 dependent. Collectively, our findings highlight the previously unknown reciprocal influence of SIRT6 and HK2 in regulating autophagy driven monocyte differentiation.

Transcription factor EB is involved in autophagy-mediated chemoresistance to doxorubicin in human cancer cells

Transcription factor EB (TFEB) is a master regulator of autophagy activity and lysosomal biogenesis, but its role in autophagy-mediated cell survival and chemotherapy resistance is not completely understood. In this study, we explored whether TFEB played an important role in autophagy-mediated chemotherapy resistance in human cancer LoVo and HeLa cells in vitro. Treatment of human colon cancer LoVo cells with doxorubicin (0.5 μmol/L) induced autophagy activation and nuclear translocation of TFEB, which resulted from inactivation of the mTOR pathway. In both LoVo and HeLa cells, overexpression of TFEB enhanced doxorubicin-induced autophagy activation and significantly decreased doxorubicin-induced cell death, whereas knockdown of TFEB with small interfering RNA blocked doxorubicin-induced autophagy and significantly enhanced the cytotoxicity of doxorubicin. In LoVo cells, autophagy inhibition by 3-methyladenine (3-MA) or knockdown of autophagy-related gene Atg5 increased cell death in response to doxorubicin, and abolished TFEB overexpression-induced chemotherapy resistance, suggesting that the inhibition of autophagy made cancer cells more sensitive to doxorubicin. The results demonstrate that TFEB-mediated autophagy activation decreases the sensitivity of cancer cells to doxorubicin.