SIRT1 promotes proliferation and inhibits apoptosis of human malignant glioma cell lines

Role of SIRT1-mediated mitochondrial and Akt pathways in glioblastoma cell death induced by Cotinus coggygria flavonoid nanoliposomes

Flavonoids, the major polyphenol components in Cotinus coggygria (CC), have been found to show an anticancer effect in our previous study; however, the exact mechanisms of inducing human glioblastoma (GBM) cell death remain to be resolved. In this study, a novel polyvinylpyrrolidone K-30/sodium dodecyl sulfate and polyethyleneglycol-coated liposome loaded with CC flavonoids (CCFs) was developed to enhance solubility and the antibrain tumor effect, and the molecular mechanism regarding how CCF nanoliposomes (CCF-NLs) induce apoptotic cell death in vitro was investigated. DBTRG-05MG GBM cell lines treated with CCF-NLs showed potential antiproliferative effects. Regarding the underlying mechanisms of inducing apoptosis in DBTRG-05MG GBM cells, CCF-NLs were shown to downregulate the expression of antiapoptotic B-cell lymphoma/leukemia 2 (Bcl-2), an apoptosis-related protein family member, but the expression of proapoptotic Bcl-2-associated X protein was enhanced compared with that in controls. CCF-NLs also inhibited the activity of caspase-3 and -9, which is the initiator caspase of the extrinsic and intrinsic apoptotic pathways. Blockade of caspase activation consistently induced apoptosis and inhibited growth in CCF-NL-treated DBTRG-05MG cells. This study further investigated the role of the Akt pathway in the apoptotic cell death by CCF-NLs, showing that CCF-NLs deactivated Akt. Specifically, CCF-NLs downregulated the expression of p-Akt and SIRT1 as well as the level of phosphorylated p53. Together, these results indicated SIRT1/p53-mediated cell death was induced by CCF-NLs, but not by extracellular signal-regulated kinase, in DBTRG-05MG cells. Overall, this study suggested caspase-dependent activation of both the intrinsic and extrinsic signaling pathways, probably through blockade of the SIRT1/p53-mediated mitochondrial and Akt pathways to exert the proapoptotic effect of CCF-NLs in DBTRG-05MG GBM cells.

NiO nanoparticles induce apoptosis through repressing SIRT1 in human bronchial epithelial cells

With application of nano-sized nickel-containing particles (Nano-Ni) expanding, the health concerns about their adverse effects on the pulmonary system are increasing. However, the mechanisms for the pulmonary toxicity of these materials remain unclear. In the present study, we focused on the impacts of NiO nanoparticles (NiONPs) on sirtuin1 (SIRT1), a NAD-dependent deacetylase, and investigated whether SIRT1 was involved in NiONPs-induced apoptosis. Although the NiONPs tended to agglomerate in fluid medium, they still entered into the human bronchial epithelial cells (BEAS-2B) and released Ni(2+) inside the cells. NiONPs at doses of 5, 10, and 20μg/cm(2) inhibited the cell viability. NiONPs' produced cytotoxicity was demonstrated through an apoptotic process, indicated by increased numbers of Annexin V positive cells and caspase-3 activation. The expression of SIRT1 was markedly down-regulated by the NiONPs, accompanied by the hyperacetylation of p53 (tumor protein 53) and overexpression of Bax (Bcl-2-associated X protein). However, overexpression of SIRT1 through resveratrol treatment or transfection clearly attenuated the NiONPs-induced apoptosis and activation of p53 and Bax. Our results suggest that the repression of SIRT1 may underlie the NiONPs-induced apoptosis via p53 hyperacetylation and subsequent Bax activation. Because SIRT1 participates in multiple biologic processes by deacetylation of dozens of substrates, this knowledge of the impact of NiONPs on SIRT1 may lead to an improved understanding of the toxic mechanisms of Nano-Ni and provide a molecular target to antagonize Nano-Ni toxicity.

Gene expression mapping of histone deacetylases and co-factors, and correlation with survival time and 1H-HRMAS metabolomic profile in human gliomas

Primary brain tumors are presently classified based on imaging and histopathological techniques, which remains unsatisfaying. We profiled here by quantitative real time PCR (qRT-PCR) the transcripts of eighteen histone deacetylases (HDACs) and a subset of transcriptional co-factors in non-tumoral brain samples from 15 patients operated for epilepsia and in brain tumor samples from 50 patients diagnosed with grade II oligodendrogliomas (ODII, n = 9), grade III oligodendrogliomas (ODIII, n = 22) and glioblastomas (GL, n = 19). Co-factor transcripts were significantly different in tumors as compared to non-tumoral samples and distinguished different molecular subgroups of brain tumors, regardless of tumor grade. Among all patients studied, the expression of HDAC1 and HDAC3 was inversely correlated with survival, whereas the expression of HDAC4, HDAC5, HDAC6, HDAC11 and SIRT1 was significantly and positively correlated with survival time of patients with gliomas. ¹H-HRMAS technology revealed metabolomically distinct groups according to the expression of HDAC1, HDAC4 and SIRT1, suggesting that these genes may play an important role in regulating brain tumorigenesis and cancer progression. Our study hence identified different molecular fingerprints for subgroups of histopathologically similar brain tumors that may enable the prediction of outcome based on the expression level of co-factor genes and could allow customization of treatment.

PTEN

The importance of PTEN in cellular function is underscored by the frequency of its deregulation in cancer. PTEN tumor-suppressor activity depends largely on its lipid phosphatase activity, which opposes PI3K/AKT activation. As such, PTEN regulates many cellular processes, including proliferation, survival, energy metabolism, cellular architecture, and motility. More than a decade of research has expanded our knowledge about how PTEN is controlled at the transcriptional level as well as by numerous posttranscriptional modifications that regulate its enzymatic activity, protein stability, and cellular location. Although the role of PTEN in cancers has long been appreciated, it is also emerging as an important factor in other diseases, such as diabetes and autism spectrum disorders. Our understanding of PTEN function and regulation will hopefully translate into improved prognosis and treatment for patients suffering from these ailments.

Roles of SIRT1 in granulosa cell apoptosis during the process of follicular atresia in porcine ovary

Ovarian follicular atresia is characterized by granulosa cell apoptosis, however, the exact mechanism is still unclear. Sirtuin 1 (SIRT1) is a NAD(+)-dependent deacetylase, which is associated with apoptosis in several of cell types, but its exact role in ovarian granulosa cell apoptosis is not clearly defined. In present study, we identified the involvement of SIRT1 in the process of follicle degeneration, which is known as "follicular atresia", both from in vivo models and cell culture data. The results of immunohistochemistry showed that SIRT1 was widely detected in non-apoptotic granulosa cells of follicles, but significantly decreased during the process of granulosa cell apoptosis. Quantitative real-time PCR and Western blot analysis showed that the expression levels of SIRT1 mRNA and protein were increased (P<0.05) during follicular atresia. In order to provide more evidences elucidating the roles of SIRT1 during the process of follicular atresia, granulosa cells were cultured in vitro with resveratrol which acts as a potent activator of SIRT1. Results showed that resveratrol caused a dose-dependent increase in both SIRT1 mRNA and protein levels. Meanwhile, apoptotic rate of granulosa cell was increased (P<0.01) in a dose-dependent manner. Additionally, resveratrol significantly increased the expression levels of Caspase-3 (P<0.01) and Bax mRNA (P<0.01), while Bcl-2 mRNA level was significantly decreased (P<0.01). Thus, our results suggest that SIRT1 may play important roles in the regulation of granulosa cell apoptosis during follicular atresia in porcine ovary.

SIRT1 is required for oncogenic transformation of neural stem cells and for the survival of "cancer cells with neural stemness" in a p53-dependent manner

BACKGROUND

Cancer stemness, observed in several types of glioma stem cells (GSCs), has been demonstrated to be an important barrier for efficient cancer therapy. We have previously reported that cancerous neural stem cells (F3.Ras.CNSCs), derived from immortalized human neural stem cells by a single oncogenic stimulation, form glial tumors in vivo.

METHOD

We searched for a commonly expressed stress modulator in both F3.Ras.CNSCs and GSCs and identified silent mating type information regulation 2, homolog (SIRT1) as a key factor in maintaining cancer stemness.

RESULT

We demonstrate that the expression of SIRT1, expressed in "cancer cells with neural stemness," is critical not only for the maintenance of stem cells, but also for oncogenic transformation. Interestingly, SIRT1 is essential for the survival and tumorigenicity of F3.Ras.CNSCs and GSCs but not for the U87 glioma cell line.

CONCLUSION

These results indicate that expression of SIRT1 in cancer cells with neural stemness plays an important role in suppressing p53-dependent tumor surveillance, the abrogation of which may be responsible not only for inducing oncogenic transformation but also for retaining the neural cancer stemness of the cells, suggesting that SIRT1 may be a putative therapeutic target in GSCs.

Theobromine, the primary methylxanthine found in Theobroma cacao, prevents malignant glioblastoma proliferation by negatively regulating phosphodiesterase-4, extracellular signal-regulated kinase, Akt/mammalian target of rapamycin kinase, and nuclear factor-kappa B

Theobromine, a caffeine derivative, is the primary methylxanthine produced by Theobroma cacao. We previously showed that methylxanthines, including caffeine and theophylline, have antitumor and antiinflammatory effects, which are in part mediated by their inhibition of phosphodiesterase (PDE). A member of the PDE family, PDE4, is widely expressed in and promotes the growth of glioblastoma, the most common type of brain tumor. The purpose of this study was to determine whether theobromine could exert growth inhibitory effects on U87-MG, a cell line derived from human malignant glioma. We show that theobromine treatment elevates intracellular cAMP levels and increases the activity of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase, whereas it attenuates p44/42 extracellular signal-regulated kinase activity and the Akt/mammalian target of rapamycin kinase and nuclear factor-kappa B signal pathways. It also inhibits cell proliferation. These results suggest that foods and beverages containing cocoa bean extracts, including theobromine, might be extremely effective in preventing human glioblastoma.

RETRACTED: Role of mammalian sirtuin 1 (SIRT1) in lipids metabolism and cell proliferation of goose primary hepatocytes

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Authors. It has come to the attention of the corresponding author that there are two errors in Section 3.1 of the Results section titled “Effect of overfeeding on gene expression and enzyme activity of several genes in liver”. The first error is that the article contains the wrong number of overfeeding days. The second error is that there are incorrect correlations between liver weight, lipids content in live and plasma metabolic substrates because of the wrong overfeeding days. The authors take responsibility for them and apologize to the readership of Molecular and Cellular Endocrinology.

Neutrophil and macrophage apoptosis in bronchoalveolar lavage fluid from healthy horses and horses with recurrent airway obstruction (RAO)

BACKGROUND

Dysregulation of apoptosis has been implicated in a range of diseases including tumors, neurodegenerative and autoimmune diseases, as well as allergic asthma and chronic obstructive pulmonary disease (COPD) in humans. Although it has a different pathophysiology, delayed apoptosis of various inflammatory cells may play a pivotal role in the development of recurrent airway obstruction (RAO) in horses. Reduction of inflammatory cell apoptosis or a dysregulation of this process could lead to chronic inflammation and tissue injury. Therefore, the aim of this study was to investigate the rate of apoptosis and necrosis of neutrophils and macrophages in bronchoalveolar lavage fluid obtained from seven horses suffering from RAO (study group) and seven control horses.

RESULTS

We demonstrated that neutrophil/macrophage apoptosis is altered in RAO-affected horses compared with the control group in the BAL fluid. We found a significant difference between the median percentage of early and late apoptosis of neutrophils between the study and control group of horses. Moreover, we found a positive correlation between the rate of apoptosis and the median percentage of macrophages in RAO-affected horses.

CONCLUSION

The findings suggest that apoptosis dysregulation may play a significant role in the pathogenesis of RAO. However, further studies are needed to clarify the role of altered apoptosis in the course of equine recurrent airway obstruction.

Redox regulation of tumor suppressor PTEN in cancer and aging (Review)

Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) has been shown to act as a tumor suppressor whose function includes important roles in regulating oxidative stress, indicating a potential role in oxidative damage-associated cancer. Accumulating evidence has revealed that PTEN also acts as a pivotal determinant of cell fate, regarding senescence and apoptosis, which is mediated by intracellular reactive oxygen species (ROS) generation. Cells are continuously exposed to ROS, which represent mutagens and are thought to be a major contributor to cancer and the aging process. Therefore, cellular ROS sensing and metabolism are firmly regulated by a variety of proteins involved in the redox mechanism. In this review, PTEN and the roles of oxidative stress in phosphoinositide-3 kinase/AKT signaling are summarized with a focus on the links between the pathways and ROS in cancer and aging.