MED12 and BRD4 cooperate to sustain cancer growth upon loss of mediator kinase.

Mediator kinases (CDK8/19) are transcriptional regulators broadly implicated in cancer. Despite their central role in fine-tuning gene-expression programs, we find complete loss of CDK8/19 is tolerated in colorectal cancer (CRC) cells. Using orthogonal functional genomic and pharmacological screens, we identify BET protein inhibition as a distinct vulnerability in CDK8/19-depleted cells. Combined CDK8/19 and BET inhibition led to synergistic growth retardation in human and mouse models of CRC. Strikingly, depletion of CDK8/19 in these cells led to global repression of RNA polymerase II (Pol II) promoter occupancy and transcription. Concurrently, loss of Mediator kinase led to a profound increase in MED12 and BRD4 co-occupancy at enhancer elements and increased dependence on BET proteins for the transcriptional output of cell-essential genes. In total, this work demonstrates a synthetic lethal interaction between Mediator kinase and BET proteins and exposes a therapeutic vulnerability that can be targeted using combination therapies.

PFOS facilitates liver inflammation and steatosis: An involvement of NLRP3 inflammasome-mediated hepatocyte pyroptosis.

Perfluorooctane sulfonate (PFOS) is a fluorinated organic pollutant with substantial accumulation in mammalian liver tissues. However, the impact of chronic PFOS exposure on liver disease progression and the underlying molecular mechanisms remain elusive. Herein, we for the first time revealed that micromolar range of PFOS exposure initiates the activation of NLR pyrin domain containing 3 (NLRP3) inflammasome to drive hepatocyte pyroptosis. We showed that 5 mg/kg/day PFOS exposure may exacerbated liver inflammation and steatosis in high-fat diet (HFD)-fed mice with concurrently elevated expression of NLRP3 and caspase-1. PFOS exposure resulted in viability impairment and LDH release in BRL-3A rat liver cells. 25-100 µM concentrations of PFOS exposure activated the NLRP3 inflammasome, leading to consequent GSDMD cleavage, IL-1ß release and the initiation of pyroptosis in a dose-dependent manner, whereas treatment with 10 µM NLRP3 inhibitor MCC950 abrogated this effect. Moreover, pretreatment of 5 mM ROS scavenger N-acetyl-L-cysteine (NAC) ameliorated PFOS-induced NLRP3 inflammasome activation and pyroptosis. Collectively, our data highlight a pivotal role of pyroptotic death in PFOS-mediated liver inflammation and metabolic disorder.

Perfluorooctane sulfonate aggravates CCl4-induced hepatic fibrosis via HMGB1/TLR4/Smad signaling.

Perfluorooctane sulfonate (PFOS) is a widespread environmental pollutant and may cause a variety of adverse health effects. The hepatotoxicity of PFOS has attracted particular attention, given the fact that the liver has one of the highest PFOS accumulations among human tissues. In this study, we revealed that subchronic PFOS exposure may exacerbate carbon tetrachloride (CCl4 )-induced liver fibrosis in animal models. Administration with 1 mg/kg PFOS every other day for 56 days dramatically enhanced CCl4 -mediated liver injury and hepatic stellate cell (HSC) activation. Furthermore, PFOS exposure may promote the activation of high-mobility group box 1 (HMGB1)/toll-like receptor 4 (TLR4) signaling pathway through inducing the secretion of HMGB1 from hepatocytes. PFOS exposure induced the translocation of HMGB1 from the nucleus into the cytoplasm of hepatocytes and cultured BRL-3A cells at a starting concentration of 50 µM. This process is accompanied with concurrent flux of calcium, suggesting a link between calcium signaling and HMGB1 release following PFOS exposure. Finally, we showed that PFOS-exposed conditional medium (PFOS-CM) of hepatocytes may induce the translocation of Smad2/3 in HSCs in a TLR4-dependent manner. Taken together, subchronic PFOS exposure might play a pro-fibrotic role via a HMGB1/TLR4-dependent Smad signaling in HSCs. Our findings for the first time uncovered an involvement of PFOS exposure in liver fibrosis via HMGB1/TLR4/Smad signaling.

α7nAChR-mediated recruitment of PP1γ promotes TRAF6/NF-κB cascade to facilitate the progression of Hepatocellular Carcinoma.

The cholinergic signaling pathways have been recently implicated in the development of various human cancers. However, the underlying molecular mechanism remains largely unclear. In the present study, we reported that α7 nicotinic acetylcholine receptor (α7nAChR), an important member of nicotinic acetylcholine receptors, interacts with Protein Phosphatase-1γ (PP1γ) in human Hepatocellular Carcinoma (HCC) tissues. In addition, we found that α7nAChR facilitates the ubiquitination and activation of TRAF6 in a PP1γ-dependent manner in HCC cells. Furthermore, we showed that ligand-bounded α7nAChR induces the degradation of IκBα, leading to resultant phosphorylation and nuclear accumulation of NF-κB p65. Accordingly, acetylcholine triggers the expression of critical NF-κB target genes, such as Cyclin D1 and PCNA, as well as the proliferation of HCC cells in a PP1γ- and α7nAChR-dependent manner. Furthermore, we revealed that nicotine-triggered α7nAChR activation promotes oncosphere formation and in vivo tumor growth of HCC cells. Moreover, we showed that the protein levels of both α7nAChR and PP1γ are significantly upregulated in human HCC specimens compared with adjacent non-cancerous ones, and that upregulated expression of the two proteins predict significantly worsened prognosis in HCC patients. These findings together indicate that the cholinergic receptor α7nAChR exerts a facilitating role in HCC development through PP1γ-dependent TRAF6/NF-κB signaling.

Nrf2 Signaling Elicits a Neuroprotective Role Against PFOS-mediated Oxidative Damage and Apoptosis.

Perfluorooctanesulfonate (PFOS) may cause neurotoxicity through the initiation of oxidative stress. In the current study, we investigated the role of anti-oxidant nuclear factor erythroid 2-related factor 2 (Nrf2) pathway in PFOS-induced neurotoxicity. We found that human neuroblastoma SH-SY5Y cells exhibited significant apoptotic cell death following PFOS exposure, and this process was accompanied with apparent accumulation of reactive oxidative species (ROS). In addition, we revealed that PFOS exposure caused marked activation of Nrf2 pathway and the expression of Nrf2 transcription target heme oxygenase-1. We further found that pre-treatment with ROS scavenger N-acetyl-L-cysteine (NAC) dramatically ameliorated PFOS-induced ROS production and Nrf2 signaling. In keeping with these findings, western blot and Cell Counter Kit-8 analyses revealed that pre-incubation with NAC suppressed PFOS-induced expression of pro-apoptotic proteins and impairment of neuronal viability. Moreover, antagonizing Nrf2 pathway with Nrf2 inhibitor brusatol resulted in increased ROS production and enhanced PFOS-induced expression of apoptosis related proteins. Finally, we showed that PFOS exposure altered mitochondrial transmembrane potential and disrupted normal mitochondrial morphology in SH-SY5Y cells. Whereas treatment with NAC ameliorated PFOS-induced mitochondrial disorders, co-incubation with brusatol augmented PFOS-induced mitochondrial deficits, consequently contributing to neuronal apoptosis. These results manifest that Nrf2 pathway plays a protective role in PFOS-induced neurotoxicity, providing new insights into the prevention and treatment of PFOS-related toxicities.

Overexpression of Protein Phosphatase 1γ (PP1γ) Is Associated with Enhanced Cell Proliferation and Poor Prognosis in Hepatocellular Carcinoma.

BACKGROUND: Protein phosphatase 1γ (PP1γ), as a member of the protein phosphatase 1 family, may be involved in regulation of multiple cellular processes, such as mitosis, cell survival, and apoptosis. However, little is known about the underlying mechanisms by which PP1γ regulates hepatocellular carcinoma development. AIM: We investigated the expression profile of PP1γ in hepatocellular carcinoma (HCC) cell lines and human HCC specimens, as well as its potential prognostic significance in HCC. METHODS: PP1γ expression profile was detected in 94 HCC specimens using immunohistochemistry. PP1γ levels in HCC cells were downregulated by small interfering RNA (siRNA) transfection. Cell cycle progression and proliferation status of HCC cells and the effectiveness of doxorubicin were evaluated by flow cytometry and CCK-8 assay. The levels of PP1γ, CyclinD1, PCNA, Mdmx, p53, p21, and active caspase-3 were evaluated by Western blot analysis. RESULTS: PP1γ was upregulated in tumorous specimens, compared with adjacent nontumorous tissues. Univariate and multivariate survival analyses were conducted to determine the prognostic significance of PP1γ in HCC. The expression pattern of PP1γ was positively correlated with tumor size, histological grade, Ki-67 expression, and poor prognosis in HCC. In addition, depletion of PP1γ by siRNA could inhibit cell proliferation, resulted in G1 phase arrest, and attenuated resistance to doxorubicin in Huh7 cells. CONCLUSIONS: PP1γ is upregulated in HCC cell lines and HCC specimens, promotes cancer cell proliferation through regulation of p53, and may be a potential target for treatment of HCC.

PINK1 alleviates palmitate induced insulin resistance in HepG2 cells by suppressing ROS mediated MAPK pathways.

Oxidative stress is an important pathogenesis of insulin resistance (IR) and Type 2 diabetes mellitus (T2DM). Studies have shown that knockdown of PTEN-induced putative kinase 1 (PINK1) causes oxidative stress and mitophagy. In db/db mice, PINK1 protein level is down-regulated. However, little is known regarding the mechanism by which PINK1 modulates IR in response to reactive oxygen species (ROS) induced stress. In our study, PINK1 expression decreased during palmitate (PA) induced IR in HepG2 cells and the hepatic tissues of high fat diet (HFD) fed mice. Additionally, free fatty acids (FFAs) could increase ROS and suppress insulin signaling pathway, which was indicated by reduced phosphorylation of protein kinase B (AKT) and glycogen synthase kinase 3ß (GSK-3ß). In addition, insulin induced glucose uptake decreased and the expression of phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase), two key gluconeogenic enzymes, was up-regulated after PA treatment. Intriguingly, PINK1 overexpression could lead to opposite results. Moreover, PA induced hepatic IR through C-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) pathways, which were rescued by PINK1 overexpression. In summary, our results demonstrate that PINK1 promoted hepatic IR via JNK and ERK pathway in PA treated HepG2 cells, implying a novel molecular target for the therapy of diabetes.

RACK1 overexpression associates with pancreatic ductal adenocarcinoma growth and poor prognosis.

OBJECTIVES: The receptor for activated protein kinase C (RACK1) is a scaffold protein involved in multiple intracellular signal pathways. Previous studies have shown that RACK1 is associated with the progression of multiple cancer types, including hepatocellular carcinoma and gastric cancer. However, the role of RACK1 in human pancreatic ductal adenocarcinoma (PDAC) remains unclear. METHODS: In this study, the expression of RACK1 was evaluated by Western blot analysis in 8 paired fresh PDAC tissues and immunohistochemistry on 179 paraffin-embedded slices. Then, we used Fisher exact test to analyze the correlation between RACK1 expression and clinicopathological characteristics. Starvation and re-feeding assay was used to assess cell cycle. Western blot, CCK8, flow cytometry assays, and colony formation analyses demonstrated that RACK1 played an essential role in PDAC development. Annexin-V/PI apoptotic assay and western blot showed that RACK1 was involved in regulating the apoptosis of PDAC cells. RESULTS: RACK1 was highly expressed in PDAC tissues and cell lines and was significantly associated with multiple clinicopathological factors. Univariate and multivariate analyses showed that high RACK1 expression was identified to be an independent prognostic factor for PDAC patients' survival. In vitro, serum starvation-refeeding experiment suggested that RACK1 was upregulated in proliferating PDAC cells, together with the percentage of cells at the S phase, and was correlated with the expression of Cyclin D1. Moreover, Overexpression of RACK1 facilitated the proliferation and cell cycle progression of PDAC cells, while downregulation of RACK1 induced growth impairment, G1/S cell cycle arrest and apoptosis in PDAC cells. Silencing RACK1 decreased bcl-2 expression, increased cleaved caspase3 expression level and induced the apoptosis of PDAC cells. CONCLUSIONS: Our results suggest that RACK1 could play an important role in the tumorigenesis of PDAC and serve as a potential therapeutical target in PDAC treatment.

Autophagy potentially protects against 2,3,7,8-tetrachlorodibenzo-p-Dioxin induced apoptosis in SH-SY5Y cells.

The environmental toxicant TCDD may elicit cytotoxic effects by inducing reactive oxygen species (ROS) generation. Autophagy is one of the first lines of defense against oxidative stress damage. Herein, we investigated whether autophagy played a regulatory role in TCDD-induced neurotoxicity. Here, we showed that TCDD exposure caused marked autophagy in SH-SY5Y cells, whose dose range was close to that inducing apoptosis. Electron microscopic and Western blot analyses revealed that TCDD induced autophagy at a starting dose of approximate 100 nM. Interestingly, 100-200 nM TCDD exposure resulted in obviously decreased cell viability and evident apoptotic phenotype. Furthermore, the levels of pro-apoptotic molecules, Bax and cleaved-PARP, increased significantly, whereas Bcl2 declined after exposed to 100 nM TCDD. In addition, the apoptosis was verified using flow cytometrical analysis. These data strongly suggested that TCDD induced both autophagy and apoptosis at a similar dose range in SH-SY5Y cells. Interestingly, pretreatment with ROS scavenger, N-acetyl-cysteine (NAC), could effectively block both TCDD-induced apoptosis and autophagy. More surprisingly, inhibition of autophagy with 3-methyladenine (3MA), remarkably augmented TCDD-induced apoptosis. The findings implicated that the onset of autophagy might serve as a protective mechanism to ameliorate ROS-triggered cytotoxic effects in human SH-SY5Y neuronal cells under TCDD exposure. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1068-1079, 2016.

Zinc deficiency impairs the renewal of hippocampal neural stem cells in adult rats: involvement of FoxO3a activation and downstream p27(kip1) expression.

Zinc plays an important role in the development and maintenance of central neural system. Zinc deficiency has been known to alter normal brain function, whose molecular mechanism remains largely elusive. In the present study, we established a zinc deficiency-exposed rat model, and, using western blot and immunohistochemical analyses, found that the expression of FoxO3a and p27(kip1) was remarkably up-regulated in the rat brain hippocampus. Immunofluorescence assay showed that FOXO3a and p27(kip1) were significantly co-localized with nestin, the marker of neural stem cells (NSCs). Furthermore, we identified that the proportion of proliferating NSCs was markedly decreased in zinc-deficient rat hippocampaus. Using C17.2 neural stem cells, it was revealed that exposure to zinc chelator N,N,N',N'-tetrakis-(2-pyridylmethy) ethylenediamine induced the expression of FoxO3a and p27(kip1) , which coincided with reduced NSC proliferation. Furthermore, depletion of FoxO3a inhibited p27(kip1) expression and restored the growth of NSCs. On the basis of these data, we concluded that FoxO3a/p27(kip1) signaling might play a significant role in zinc deficiency-induced growth impairment of NSCs and consequent neurological disorders. We describe here that zinc deficiency induces the proliferative impairment of hippocampal neural stem cells partially through the activation of FOXO3a-p27 axis in rats. Neural progenitor cells exhibited significantly up-regulated expression of FOXO3a and p27 after zinc deficiency in vivo and in vitro. Depletion of FOXO3a ameliorates zinc deficiency-induced expression of p27 and growth impairment of neural stem cells. We provide novel insight into the mechanisms underlying zinc deficiency-induced neurological deficits.

TRAM1 protect HepG2 cells from palmitate induced insulin resistance through ER stress-JNK pathway.

Excess serum free fatty acids (FFAs) are fundamental to the pathogenesis of insulin resistance. Chronic endoplasmic reticulum (ER) stress is a major contributor to obesity-induced insulin resistance in the liver. With high-fat feeding (HFD), FFAs can activate chronic endoplasmic reticulum (ER) stress in target tissues, initiating negative crosstalk between FFAs and insulin signaling. However, the molecular link between insulin resistance and ER stress remains to be identified. We here reported that translocating chain-associated membrane protein 1 (TRAM1), an ER-resident membrane protein, was involved in the onset of insulin resistance in hepatocytes. TRAM1 was significantly up-regulated in insulin-resistant liver tissues and palmitate (PA)-treated HepG2 cells. In addition, we showed that depletion of TRAM1 led to hyperactivation of CHOP and GRP78, and the activation of downstream JNK pathway. Given the fact that the activation of ER stress played a facilitating role in insulin resistance, the phosphorylation of Akt and GSK-3ß was also analyzed. We found that depletion of TRAM1 markedly attenuated the phosphorylation of Akt and GSK-3ß in the cells. Moreover, application with JNK inhibitor SP600125 reversed the effect of TRAM1 interference on Akt phosphorylation. The accumulation of lipid droplets and expression of two key gluconeogenic enzymes, PEPCK and G6Pase, were also determined and found to display a similar tendency with the phosphorylation of Akt. Glucose uptake assay indicated that knocking down TRAM1 augmented PA-induced down-regulation of glucose uptake, and inhibition of JNK using SP600125 could block the effect of TRAM1 on glucose uptake. These data implicated that TRAM1 might protect HepG2 cells against PA-induced insulin resistance through alleviating ER stress.

Reactive oxygen species mediate nitric oxide production through ERK/JNK MAPK signaling in HAPI microglia after PFOS exposure.

Perfluorooctane sulfonate (PFOS), an emerging persistent contaminant that is commonly encountered during daily life, has been shown to exert toxic effects on the central nervous system (CNS). However, the molecular mechanisms underlying the neurotoxicity of PFOS remain largely unknown. It has been widely acknowledged that the inflammatory mediators released by hyper-activated microglia play vital roles in the pathogenesis of various neurological diseases. In the present study, we examined the impact of PFOS exposure on microglial activation and the release of proinflammatory mediators, including nitric oxide (NO) and reactive oxidative species (ROS). We found that PFOS exposure led to concentration-dependent NO and ROS production by rat HAPI microglia. We also discovered that there was rapid activation of the ERK/JNK MAPK signaling pathway in the HAPI microglia following PFOS treatment. Moreover, the PFOS-induced iNOS expression and NO production were attenuated after the inhibition of ERK or JNK MAPK by their corresponding inhibitors, PD98059 and SP600125. Interestingly, NAC, a ROS inhibitor, blocked iNOS expression, NO production, and activation of ERK and JNK MAPKs, which suggested that PFOS-mediated microglial NO production occurs via a ROS/ERK/JNK MAPK signaling pathway. Finally, by exposing SH-SY5Y cells to PFOS-treated microglia-conditioned medium, we demonstrated that NO was responsible for PFOS-mediated neuronal apoptosis.

High CHMP4B expression is associated with accelerated cell proliferation and resistance to doxorubicin in hepatocellular carcinoma.

Charged multivesicular body protein 4B (CHMP4B), a subunit of the endosomal sorting complex required for transport (ESCRT)-III complex, plays an important part in cytokinetic membrane abscission and the late stage of mitotic cell division. In this study, we explored the prognostic significance of CHMP4B in human hepatocellular carcinoma (HCC) and its impact on the physiology of HCC cells. Western blot and immunohistochemistrical analyses showed that CHMP4B was significantly upregulated in HCC tissues, compared with adjacent non-tumorous tissues. Meanwhile, clinicopathological analysis revealed that high CHMP4B expression was correlated with multiple clinicopathological variables, including AFP, cirrhosis, AJCC stage, Ki-67 expression, and poor prognosis. More importantly, univariate and multivariate survival analyses demonstrated that CHMP4B served as an independent prognostic factor for survival of HCC patients. Using HCC cell cultures, we found that the expression of CHMP4B was progressively upregulated after the release from serum starvation. To verify whether CHMP4B could regulate the proliferation of HCC cells, CHMP4B was knocked down through the transfection of CHMP4B-siRNA oligos. Flow cytometry and CCK-8 assays indicated that interference of CHMP4B led to cell cycle arrest and proliferative impairment of HCC cells. Additionally, depletion of CHMP4B expression could increase the sensitivity to doxorubicin in HepG2 and Huh7 cells. Taken together, our results implied that CHMP4B could be a promising prognostic biomarker as well as a potential therapeutic target of HCC.

High expression of ErbB3 binding protein 1 (EBP1) predicts poor prognosis of pancreatic ductal adenocarcinoma (PDAC).

Recent studies have identified that ErbB3 binding protein 1 (EBP1) is broadly expressed in various cancer tissues and critically involved in plenty of biological processes in this regard. However, the functional role of EBP1 in pancreatic ductal adenocarcinoma (PDAC) has never been elucidated. In this study, we found that EBP1 could serve as a prognostic biomarker of PDAC. Western blot analysis revealed that EBP1 was remarkably upregulated in PDAC tissues and cell lines. Using immunohistochemical analysis, we showed that the expression of EBP1 was correlated with tumor size (P = 0.004), histological differentiation (P = 0.041), and tumor node metastasis (TNM) stage (P = 0.000). Notably, Kaplan-Meier curve showed that high expression of EBP1 predicted significantly worsened prognosis of PDAC patients (P = 0.001). In addition, knockdown of EBP1 expression suppressed PDAC cell proliferation and retarded cell cycle progression. Furthermore, depletion of EBP1 induced the apoptosis of Panc-1 cells. Of great interest, we found that EBP1 interacted with anti-apoptotic protein, Bcl-xL, and promoted its accumulation. In summary, our results suggest that EBP1 is a novel prognostic indicator and potential therapeutic target of PDAC, shedding new insights into the important role of EBP1 in cancer development.

Critical Role of TAK1-Dependent Nuclear Factor-κB Signaling in 2,3,7,8-Tetrachlorodibenzo-p-dioxin-induced Astrocyte Activation and Subsequent Neuronal Death.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has been recently shown to elicit inflammatory response in a number of cell-types. However, whether TCDD could provoke inflammation in astrocytes, the most abundant glial cells in central nervous system (CNS), remains virtually unknown. In the present study, we showed that TCDD exposure could induce evident astrocyte activation both in vivo and in vitro. Further, we found that TGF-ß-activated kinase 1 (TAK1), a critical regulator of NF-κB signaling, was rapidly phosphorylated in the process of TCDD-induced reactive astroglia. Exposure to TCDD led to rapid TAK1 and NF-κB p65 phosphorylation, as well as IKBα degradation. Moreover, blockage of TAK1 using siRNA oligos or TAK1 inhibitor 5Z-7-oxozeaenol significantly attenuated TCDD-induced astrocyte activation as well as the release of TNF-α. Finally, we showed that the conditioned medium of TCDD-treated astrocytes promoted the apoptosis of PC12 neuronal cells, which could be blocked with the pre-treatment of TAK1 inhibitor. Taken together, these findings suggested that TCDD could promote the inflammatory activation of astrocytes through modulating TAK1-NF-κB cascade, implicating that reactive astrocytes might contribute to TCDD-induced adverse effects on CNS system.

NF45 overexpression is associated with poor prognosis and enhanced cell proliferation of pancreatic ductal adenocarcinoma.

NF45, also referred to as nuclear factor of activated T cells, has been reported to promote the progression of multiple cancer types. However, the expression and physiological significance of NF45 in pancreatic ductal adenocarcinoma (PDAC) remain largely elusive. In this study, we investigated the clinical relevance and potential role of NF45 expression in PDAC development. Western blot analysis revealed that NF45 was remarkably upregulated in PDAC tissues, compared with the adjacent non-tumorous ones. In addition, the expression of NF45 in 122 patients with PDAC was evaluated using immunohistochemistry. In this way, we found that NF45 was abundantly expressed in PDAC tissues, and the expression of NF45 was correlated with tumor size (p = 0.007), histological differentiation (p = 0.033), and TNM stage (p = 0.001). Importantly, patients with low levels of NF45 expression exhibited better postoperative prognosis as compared with those with high NF45 expression. Furthermore, using PDAC cell cultures, we found that interference of NF45 expression using siRNA oligos suppressed PDAC cell proliferation and retarded cell cycle progression. Moreover, depletion of NF45 impaired the levels of cellular cyclin E and proliferating cell nuclear antigen (PCNA). Conversely, overexpression of NF45 facilitated the cell growth and accelerated cell cycle progression. Our results establish NF45 as an important indicator of PDAC prognosis with potential utility as a therapeutic target in this lethal disease.

2, 3, 7, 8-Tetrachlorodibenzo-p-dioxin induces premature senescence of astrocytes via WNT/ß-catenin signaling and ROS production.

2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) is a ubiquitous environmental contaminant that could exert significant neurotoxicity in the human nervous system. Nevertheless, the molecular mechanism underlying TCDD-mediated neurotoxicity has not been clarified clearly. Herein, we investigated the potential role of TCDD in facilitating premature senescence in astrocytes and the underlying molecular mechanisms. Using the senescence-associated ß-galactosidase (SA-ß-Gal) assay, we demonstrated that TCDD exposure triggered significant premature senescence of astrocyte cells, which was accompanied by a marked activation of the Wingless and int (WNT)/ß-catenin signaling pathway. In addition, TCDD altered the expression of senescence marker proteins, such as p16, p21 and GFAP, which together have been reported to be upregulated in aging astrocytes, in both dose- and time-dependent manners. Further, TCDD led to cell-cycle arrest, F-actin reorganization and the accumulation of cellular reactive oxygen species (ROS). Moreover, the ROS scavenger N-acetylcysteine (NAC) markedly attenuated TCDD-induced ROS production, cellular oxidative damage and astrocyte senescence. Notably, the application of XAV939, an inhibitor of WNT/ß-catenin signaling pathway, ameliorated the effect of TCDD on cellular ß-catenin level, ROS production, cellular oxidative damage and premature senescence in astrocytes. In summary, our findings indicated that TCDD might induce astrocyte senescence via WNT/ß-catenin and ROS-dependent mechanisms.

The Role of PTP1B O-GlcNAcylation in Hepatic Insulin Resistance.

Protein tyrosine phosphatase 1B (PTP1B), which can directly dephosphorylate both the insulin receptor and insulin receptor substrate 1 (IRS-1), thereby terminating insulin signaling, reportedly plays an important role in insulin resistance. Accumulating evidence has demonstrated that O-GlcNAc modification regulates functions of several important components of insulin signal pathway. In this study, we identified that PTP1B is modified by O-GlcNAcylation at three O-GlcNAc sites (Ser104, Ser201, and Ser386). Palmitate acid (PA) impaired the insulin signaling, indicated by decreased phosphorylation of both serine/threonine-protein kinase B (Akt) and glycogen synthase kinase 3 beta (GSK3ß) following insulin administration, and upregulated PTP1B O-GlcNAcylation in HepG2 cells. Compared with the wild-type, intervention PTP1B O-GlcNAcylation by site-directed gene mutation inhibited PTP1B phosphatase activity, resulted in a higher level of phosphorylated Akt and GSK3ß, recovered insulin sensitivity, and improved lipid deposition in HepG2 cells. Taken together, our research showed that O-GlcNAcylation of PTP1B can influence insulin signal transduction by modulating its own phosphatase activity, which participates in the process of hepatic insulin resistance.

Nemo-like kinase (NLK) inhibits the progression of NSCLC via negatively modulating WNT signaling pathway.

Nemo-like kinase (NLK), an evolutionarily conserved serine/threonine kinase, is a critical regulator of various cancers. NLK expression was evaluated by Western blot in 8 paired fresh non-small-cell lung cancer (NSCLC) tissues and immunohistochemistry (IHC) on 83 paraffin-embedded slices. NLK was lowly expressed in NSCLC and significantly associated with NSCLC histological differentiation, clinical stage, lymph node status, and Ki-67. Multivariate analysis indicated that low NLK expression was an independent prognostic factor for NSCLC patients' low survival rate. In vitro, after the release of NSCLC cell line A549 from serum starvation, the expression of NLK was downregulated, whereas the cell-cycle-related proteins were upregulated. In addition, we used RNA interference to knock down NLK expression, then observed its effects on NSCLC's growth in vitro. Western blot analyses indicated that deletion of NLK was positively correlated with cell-cycle-related proteins. The present investigation demonstrated that suppression of NLK expression resulted in significant promotion of proliferation in NSCLC cells. And flow cytometry further indicated that loss of NLK promoted cell proliferation by facilitating S-phase and mitotic entry. Besides, the transcription activity of ß-catenin/TCF in A549 cells was remarkably enhanced when NLK was knocked down, which suggested that NLK participated in NSCLC cell proliferation via medulating Wnt signaling pathway. Based on these findings, we can provide a potential strategy for NSCLC therapy.

Downregulation of UBE2Q1 is associated with neuronal apoptosis in rat brain cortex following traumatic brain injury.

Aberrant functionality of the ubiquitin proteasome system (UPS) has been implicated in the pathology of various neurological disorders. Although it has been reported that the expressions of various UPS components were altered significantly following traumatic brain injury (TBI), detailed information on the subject remains largely unclear. In the study, using microarray assay, we identified a gene encoding ubiquitin-conjugating enzyme E2Q1 (UBE2Q1) that was significantly downregulated during TBI. Western blot and immunohistochemical analyses verified the reduced expression of UBE2Q1 in ipsilateral brain cortex adjacent to the lesion site compared with the contralateral and sham-operated ones. Double-immunofluorescence staining indicated that UBE2Q1 was expressed mainly in the nucleus of neurons, with a minority in astrocytes in normal cortex. In addition, we observed a remarkable reduction in the number of UBE2Q1-positive neurons following brain trauma. Furthermore, we showed that TBI resulted in a significant increase in the levels of p53, bax, p21 and active caspase 3 in brain cortex, which was correlated with decreased expression of UBE2Q1. We also found that knockdown of UBE2Q1 apparently increased the level of p53, whereas overexpressing UBE2Q1 attenuated cellular p53 level in PC12 neuronal cells. Accordingly, interference with UBE2Q1 augmented H2O2-induced apoptosis of PC12 cells. Taken together, our findings indicate that UBE2Q1 might play an important role in the neuropathological process of TBI through modulating p53 signaling.