Phosphatidylinositol 3-kinase/Akt signaling mediates interleukin-6 protection against p53-induced apoptosis in M1 myeloid leukemic cells

Anti-Inflammatory Effect of Simonsinol on Lipopolysaccharide Stimulated RAW264.7 Cells through Inactivation of NF-κB Signaling Pathway

Simonsinol is a natural sesqui-neolignan firstly isolated from the bark of Illicium simonsii. In this study, the anti-inflammatory activity of simonsinol was investigated with a lipopolysaccharide (LPS)-stimulated murine macrophages RAW264.7 cells model. The results demonstrated that simonsinol could antagonize the effect of LPS on morphological changes of RAW264.7 cells, and decrease the production of nitric oxide (NO), tumor necrosis factor α (TNF-α), and interleukin 6 (IL-6) in LPS-stimulated RAW264.7 cells, as determined by Griess assay and enzyme-linked immunosorbent assay (ELISA). Furthermore, simonsinol could downregulate transcription of inducible nitric oxide synthase (iNOS), TNF-α, and IL-6 as measured by reverse transcription polymerase chain reaction (RT-PCR), and inhibit phosphorylation of the alpha inhibitor of NF-κB (IκBα) as assayed by Western blot. In conclusion, these data demonstrate that simonsinol could inhibit inflammation response in LPS-stimulated RAW264.7 cells through the inactivation of the nuclear transcription factor kappa-B (NF-κB) signaling pathway.

Role of TLR4-Mediated PI3K/AKT/GSK-3β Signaling Pathway in Apoptosis of Rat Hepatocytes

We investigated the mechanism of the Toll-like receptor 4- (TLR4-) mediated PI3K/AKT/GSK-3β signaling pathway in rat hepatocytes apoptosis induced by LPS. The cultured rat hepatocytes were treated with LPS alone or first pretreated with TLR4 inhibitor, AKT inhibitor, and GSK-3β inhibitor, respectively, and then stimulated with the same dose of LPS. Cell viability, cell apoptotic rate, and apoptosis morphology were assessed; the level of P-AKT^Ser473, P-GSK-3β^Ser9, and active Caspase-3 and the ratio of Bax/Bcl-2 were evaluated. The results indicated that cell viability decreased, while cell apoptotic rate increased with time after LPS stimulation. The expression of P-AKT^Ser473 and P-GSK-3β^Ser9 in the LPS group decreased compared with the control, while the level of active Caspase-3 and the ratio of Bax/Bcl-2 were significantly increased. These effects were attenuated by pretreatment with CLI-095. In addition, the apoptotic ratio decreased after pretreatment with LiCl but increased following pretreatment with LY294002. The expression of P-AKT^Ser473 further decreased following pretreatment with LY294002 and the expression of P-GSK-3β^Ser9 increased following pretreatment with LiCl. Moreover, pretreatment with CLI-095 weakened LPS-induced nuclear translocation of GSK-3β. Our findings suggest that the TLR4-mediated PI3K/AKT/GSK-3β signaling pathway is present in rat hepatocytes and participates in apoptosis of BRL-3A cells.

Poor antibody validation is a challenge in biomedical research: a case study for detection of c-FLIP

Successful translation of findings derived from preclinical studies into effective therapies is critical in biomedical research. Lack of robustness and reproducibility of the preclinical data, due to insufficient number of repeats, inadequate cell-based and mouse models contribute to the poor success rate. Antibodies are widely used in preclinical research, notably to determine the expression of potential therapeutic targets in tissues of interest, including tumors, but also to identify disease and/or treatment response biomarkers. We sought to determine whether the current antibody characterization standards in preclinical research are sufficient to ensure reliability of the data found in peer-reviewed publications. To address this issue, we used detection of the protein c-FLIP, a major factor of resistance to apoptosis, as a proof of concept. Accurate detection of endogenous c-FLIP levels in the preclinical settings is imperative since it is considered as a potential theranostic biomarker. Several sources of c-FLIP antibodies validated by their manufacturer and recommended for western blotting were therefore rigorously tested. We found a wide divergence in immune recognition properties. While these antibodies have been used in many publications, our results show that several of them failed to detect endogenous c-FLIP protein by Western blotting. Our results suggest that antibody validation standards are inadequate, and that systematic use of genetic knockdowns and/or knockouts to establish proof of specificity is critical, even for antibodies previously used in the scientific literature. Because antibodies are fundamental tools in both preclinical and clinical research, ensuring their specificity is crucial.

Dysfunction of the TP53 tumor suppressor gene in lymphoid malignancies

Mutations of the TP53 gene and dysregulation of the TP53 pathway are important in the pathogenesis of many human cancers, including lymphomas. Tumor suppression by p53 occurs via both transcription-dependent activities in the nucleus by which p53 regulates transcription of genes involved in cell cycle, DNA repair, apoptosis, signaling, transcription, and metabolism; and transcription-independent activities that induces apoptosis and autophagy in the cytoplasm. In lymphoid malignancies, the frequency of TP53 deletions and mutations is lower than in other types of cancer. Nonetheless, the status of TP53 is an independent prognostic factor in most lymphoma types. Dysfunction of TP53 with wild-type coding sequence can result from deregulated gene expression, stability, and activity of p53. To overcome TP53 pathway inactivation, therapeutic delivery of wild-type p53, activation of mutant p53, inhibition of MDM2-mediated degradation of p53, and activation of p53-dependent and -independent apoptotic pathways have been explored experimentally and in clinical trials. We review the mechanisms of TP53 dysfunction, recent advances implicated in lymphomagenesis, and therapeutic approaches to overcoming p53 inactivation.

Apoptotic signaling by c-MYC

c-MYC has a pivotal function in growth control, differentiation and apoptosis, and its abnormal expression is associated with many tumors. Overexpression of c-MYC sensitizes cells to apoptosis by a variety of stimuli. The decision of a cell to undergo apoptosis and how this apoptotic response is regulated by c-MYC depends on the specific cell type and the physiological status of the cell. Multiple cooperating molecular pathways of cell survival and apoptosis determine whether a cell lives or dies, and understanding how c-MYC interfaces with these pathways to influence the survival of cells is important to understand normal and abnormal development, tumor initiation and progression, and response of tumors to different treatment regimens. This article will provide an overview of the function of the tumor suppressor gene product p53 in the c-MYC-mediated apoptotic response and how c-MYC amplifies the intrinsic mitochondrial pathway and triggers and/or amplifies the death receptor pathways. Finally, a model for how deregulated c-MYC prematurely triggers the normal apoptotic response associated with terminal myeloid differentiation while also blocking the differentiation program is presented.

The apoptotic effect of nanosilver is mediated by a ROS- and JNK-dependent mechanism involving the mitochondrial pathway in NIH3T3 cells

Nanomaterials and nanoparticles have received considerable attention recently because of their unique properties and diverse biotechnology and life sciences applications. Nanosilver products, which have well-known antimicrobial properties, have been used extensively in a range of medical settings. Despite the widespread use of nanosilver products, relatively few studies have been undertaken to determine the biological effects of nanosilver exposure. The purpose of this study was to evaluate the toxicity of nanosilver and to elucidate possible molecular mechanisms underlying the biological effects of nanosilver. Here, we show that nanosilver is cytotoxic, inducing apoptosis in NIH3T3 fibroblast cells. Treatment with nanosilver induced the release of cytochrome c into the cytosol and translocation of Bax to mitochondria, indicating that nanosilver-mediated apoptosis is mitochondria-dependent. Nanosilver-induced apoptosis was associated with the generation of reactive oxygen species (ROS) and JNK activation, and inhibition of either ROS or JNK attenuated nanosilver-induced apoptosis. In nanosilver-resistant HCT116 cells, up-regulation of the anti-apoptotic proteins, Bcl-2 appeared to be associated with a diminished apoptotic response. Taken together, our results provide the first evidence for a molecular mechanism of nanosilver cytotoxicity, showing that nanosilver acts through ROS and JNK to induce apoptosis via the mitochondrial pathway.