DNA repair Ku proteins in gastric cancer cells and pancreatic acinar cells

Ku70 and Ku80 participate in LPS-induced pro-inflammatory cytokines production in human macrophages and monocytes

In human macrophages and monocytes, lipopolysaccharide (LPS) induces nuclear factor kappa B (NFκB) activation and pro-inflammatory cytokines production. We tested the possible involvement of Ku70 and Ku80 in the process. In THP-1 macrophages and primary human peripheral blood mononuclear cells (PBMCs), shRNA-induced double knockdown of Ku70 and Ku80 potently inhibited LPS-induced production of pro-inflammatory cytokines (TNF-α, IL-1β and IL-6). Additionally, we developed CRISPR/Cas-9 gene-editing methods to knockout both Ku70 and Ku80 in THP-1 cells and PBMCs. Double knockout (DKO) largely inhibited LPS-induced pro-inflammatory cytokines production. Conversely, in THP-1 cells exogenous overexpression of both Ku70 and Ku80 enhanced the pro-inflammatory cytokines production by LPS. Ku70 and Ku80 co-immunoprecipitated with p65-p52 NFκB complex in the nuclei of LPS-treated THP-1 cells. Significantly, LPS-induced NFκB activation was inhibited by Ku70 plus Ku80 double knockdown or DKO. It was however enhanced with Ku70 and Ku80 overexpression. Together, Ku70 and Ku80 promote LPS-induced NFκB activation and pro-inflammatory response in THP-1 cells and human PBMCs.

Overexpression of miR-623 suppresses progression of hepatocellular carcinoma via regulating the PI3K/Akt signaling pathway by targeting XRCC5

It has been reported that miR-623 is deregulated in lung adenocarcinoma and inhibits tumor growth and invasion. However, it is unclear whether miR-623 has a role in the progression of hepatocellular carcinoma (HCC). Herein, we found that miR-623 was significantly downregulated in HCC, and that its expression was related to poor clinical outcomes of patients with HCC. Upregulation of miR-623 decreased cell proliferation, viability, migration, and invasion and further promoted apoptosis in 7721, Huh7, and Bel-7402 cells. Moreover, we also observed that miR-623 regulated the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt), Wnt/β-catenin, and extracellular regulated protein kinases/c-Jun N-terminal kinase (ERK/JNK) signaling pathways as well as the expression level of related proteins. Further, X-ray repair cross complementing 5 (XRCC5) was a direct target for miR-623, and the suppression of PI3K/Akt, Wnt/β-catenin, and ERK/JNK signaling pathways and cell proliferation and invasion abilities caused by miR-623 in HCC cells was significantly reversed by the upregulation of XRCC5. Collectively, our data suggested that miR-623 suppressed the progression of HCC by regulating the PI3K/Akt, Wnt/β-catenin, and ERK/JNK pathways by targeting XRCC5 in HCC in vitro, indicating that miR-623 may be a target for the therapy of HCC.

NF-κB signaling and crosstalk during carcinogenesis

Transcription factors (TFs) are proteins that control the transcription of genetic information from DNA to mRNA by binding to specific DNA sequences either on their own or with other proteins as a complex. TFs thus support or suppress the recruitment of the corresponding RNA polymerase. In general, TFs are classified by structure or function. The TF, Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), is expressed in all cell types and tissues. NF-κB signaling and crosstalk are involved in several steps of carcinogenesis including in sequences involving pathogenic stimulus, chronic inflammation, fibrosis, establishment of its remodeling to the precancerous niche (PCN) and transition of a normal cell to a cancer cell. Triggered by various inflammatory cytokines, NF-κB is activated along with other TFs with subsequent stimulation of cell proliferation and inhibition of apoptosis. The involvement of NF-κB in carcinogenesis provides an opportunity to develop anti-NF-κB therapies. The complexity of these interactions requires that we elucidate those aspects of NF-κB interactions that play a role in carcinogenesis, the sequence of events leading to cancer.

Clinical values of Ku80 upregulation in superficial esophageal squamous cell carcinoma

Ku80 is an important DNA repair protein. Here, this study sought to investigate clinical impacts of Ku80 expression for patients with superficial esophageal squamous cell carcinoma (ESCC). Immunohistochemical analysis of Ku80 expression was carried out in normal esophageal mucosa, squamous epithelial dysplasia, carcinoma in situ, and superficial ESCC. Its relationships with clinicopathological features and survival of superficial ESCC patients were further clarified. Lentivirus-mediated RNA interference was used to silence Ku80 gene in ECA109 and KYSE150 cells. Both quantitative real-time PCR and Western blot were employed to evaluate Ku80 levels. CCK-8 assay, clone formation assay, flow cytometry, and tumorigenesis experiment were performed to evaluate the malignant phenotype of ECA109 and KYSE150 cells. Increased Ku80 expression was observed in dysplastic esophageal mucosa and carcinoma in situ compared to normal esophageal mucosa (P < 0.001, P < 0.001). Ku80 expression was further increased in superficial ESCC in comparison with dysplastic esophageal mucosa and carcinoma in situ (P < 0.001, P = 0.034). In superficial ESCC, Ku80 overexpression was related to tumor differentiation (P = 0.017), T status (P = 0.011), nodal involvement (P = 0.005), TNM stage (P = 0.004), and postoperative recurrence (P = 0.008). Cox proportional hazards regression showed tumor differentiation, T status, nodal involvement, TNM stage, and Ku80 expression were both independent predictors of patients' overall survival and disease-free survival. Ku80 shRNA effectively reduced Ku80 expression, which significantly inhibited proliferation, clone formation, and induced apoptosis in ECA109 and KYSE150 cells. The tumor growth of xenografts was significantly reduced by Ku80 silencing in ECA109 and KYSE150 cells. Ku80 overexpression associates with unfavorable prognosis of superficial ESCC patients, and silencing of Ku80 could inhibit the malignant behavior of ESCC cells. We provide evidence that Ku80 has unrecognized roles in carcinogenesis and development of ESCC.

Studies of lncRNAs in DNA double strand break repair: what is new?

The ‘junk DNA’ that has haunted human genetics for a long time now turns out to hold enormous hidden treasures. As species had their genomes and transcriptomes sequenced, there are an overwhelming number of lncRNA transcripts being reported, however, less than 100 of them have been functionally characterized. DNA damage is recognized and quickly repaired by the cell, with increased expression of numerous genes involved in DNA repair. Most of the time the studies have focused only on proteins involved in these signaling pathways. However, recent studies have implied that lncRNAs can be broadly induced by DNA damage and regulate DNA repair processes by various mechanisms. In this paper, we focus on recent advances in the identification and functional characterization of novel lncRNAs participating in DNA double strand break repair.

Proteomic analysis of pancreatic cancer stem cells: Functional role of fatty acid synthesis and mevalonate pathways

Recently, we have shown that the secretome of pancreatic cancer stem cells (CSCs) is characterized by proteins that participate in cancer differentiation, invasion, and metastasis. However, the differentially expressed intracellular proteins that lead to the specific characteristics of pancreatic CSCs have not yet been identified, and as a consequence the deranged metabolic pathways are yet to be elucidated. To identify the modulated proteins of pancreatic CSCs, iTRAQ-based proteomic analysis was performed to compare the proteome of Panc1 CSCs and Panc1 parental cells, identifying 230 modulated proteins. Pathway analysis revealed activation of glycolysis, the pentose phosphate pathway, the pyruvate-malate cycle, and lipid metabolism as well as downregulation of the Krebs cycle, the splicesome and non-homologous end joining. These findings were supported by metabolomics and immunoblotting analysis. It was also found that inhibition of fatty acid synthase by cerulenin and of mevalonate pathways by atorvastatin have a greater anti-proliferative effect on cancer stem cells than parental cells. Taken together, these results clarify some important aspects of the metabolic network signature of pancreatic cancer stem cells, shedding light on key and novel therapeutic targets and suggesting that fatty acid synthesis and mevalonate pathways play a key role in ensuring their viability.

BIOLOGICAL SIGNIFICANCE

To better understand the altered metabolic pathways of pancreatic cancer stem cells (CSCs), a comprehensive proteomic analysis and metabolite profiling investigation of Panc1 and Panc1 CSCs were carried out. The findings obtained indicate that Panc1 CSCs are characterized by upregulation of glycolysis, pentose phosphate pathway, pyruvate-malate cycle, and lipid metabolism and by downregulation of Krebs cycle, spliceosome and non-homologous end joining. Moreover, fatty acid synthesis and mevalonate pathways are shown to play a critical contribution to the survival of pancreatic cancer stem cells. This study is helpful for broadening the knowledge of pancreatic cancer stem cells and could accelerate the development of novel therapeutic strategies.

Hsa-miR-623 suppresses tumor progression in human lung adenocarcinoma

Our previous study revealed that Ku80 was overexpressed in lung cancer tissues and hsa-miR-623 regulated the Ku80 expression; however, the detailed function of hsa-miR-623 in lung cancer was unclear. We identified that hsa-miR-623 bound to the 3'-UTR of Ku80 mRNA, thus significantly decreasing Ku80 expression in lung adenocarcinoma cells. Hsa-miR-623 was downregulated in lung adenocarcinoma tissues compared with corresponding non-tumorous tissues, and its expression was inversely correlated with Ku80 upregulation. Downregulation of hsa-miR-623 was associated with poor clinical outcomes of lung adenocarcinoma patients. Hsa-miR-623 suppressed lung adenocarcinoma cell proliferation, clonogenicity, migration and invasion in vitro. Hsa-miR-623 inhibited xenografts growth and metastasis of lung adenocarcinoma in vivo. Ku80 knockdown in lung adenocarcinoma cells suppressed tumor properties in vitro and in vivo similar to hsa-miR-623 overexpression. Further, hsa-miR-623 overexpression decreased matrix metalloproteinase-2 (MMP-2) and MMP-9 expression levels, with decreased ERK/JNK phosphorylation. Inhibition of hsa-miR-623 or overexpression of Ku80 promoted lung adenocarcinoma cell invasion, activated ERK/JNK phosphorylation and increased MMP-2/9 expressions, which could be reversed by ERK kinase inhibitor or JNK kinase inhibitor. In summary, our results showed that hsa-miR-623 was downregulated in lung adenocarcinoma and suppressed the invasion and metastasis targeting Ku80 through ERK/JNK inactivation mediated downregulation of MMP-2/9. These findings reveal that hsa-miR-623 may serve as an important therapeutic target in lung cancer therapy.

By downregulating Ku80, hsa-miR-526b suppresses non-small cell lung cancer

Ku80 is involved in DNA double-strand breaks (DSBs) repair. Ku80 is overexpressed in lung cancer tissues, yet, molecular mechanisms have not been examined. We identified that miRNA, hsa-miR-526b, is bound to the 3′-UTR of Ku80 mRNA, thus decreasing Ku80 expression in NSCLC cells. Hsa-miR-526b was downregulated in NSCLC tissues compared with corresponding non-tumorous tissues, and its expression was inversely correlated with Ku80 upregulation. Overexpression of Ku80 and downregulation of hsa-miR-526b were associated with poor clinical outcomes of NSCLC patients. Hsa-miR-526b suppressed NSCLC cell proliferation, clonogenicity, and induced cell cycle arrest and apoptosis. Hsa-miR-526b inhibited xenografts and orthotopic lung tumor growth. Further, Ku80 knockdown in NSCLC cells suppressed tumor properties in vitro and in vivo similar to hsa-miR-526b overexpression. In agreement, Ku80 restoration partially reversed cell cycle arrest and apoptosis induced by hsa-miR-526b in NSCLC cells in vitro and in vivo. In addition, hsa-miR-526b overexpression or Ku80 knockdown increased p53 and p21^CIP1/WAF1 expression. These findings reveal that hsa-miR-526b is a potential target in cancer therapy.

DNA-LCEB: a high-capacity and mutation-resistant DNA data-hiding approach by employing encryption, error correcting codes, and hybrid twofold and fourfold codon-based strategy for synonymous substitution in amino acids

Data-hiding in deoxyribonucleic acid (DNA) sequences can be used to develop an organic memory and to track parent genes in an offspring as well as in genetically modified organism. However, the main concerns regarding data-hiding in DNA sequences are the survival of organism and successful extraction of watermark from DNA. This implies that the organism should live and reproduce without any functional disorder even in the presence of the embedded data. Consequently, performing synonymous substitution in amino acids for watermarking becomes a primary option. In this regard, a hybrid watermark embedding strategy that employs synonymous substitution in both twofold and fourfold codons of amino acids is proposed. This work thus presents a high-capacity and mutation-resistant watermarking technique, DNA-LCEB, for hiding secret information in DNA of living organisms. By employing the different types of synonymous codons of amino acids, the data storage capacity has been significantly increased. It is further observed that the proposed DNA-LCEB employing a combination of synonymous substitution, lossless compression, encryption, and Bose-Chaudary-Hocquenghem coding is secure and performs better in terms of both capacity and robustness compared to existing DNA data-hiding schemes. The proposed DNA-LCEB is tested against different mutations, including silent, miss-sense, and non-sense mutations, and provides substantial improvement in terms of mutation detection/correction rate and bits per nucleotide. A web application for DNA-LCEB is available at http://111.68.99.218/DNA-LCEB.

Impact of the Ku complex on HIV-1 expression and latency

Ku, a cellular complex required for human cell survival and involved in double strand break DNA repair and multiple other cellular processes, may modulate retroviral multiplication, although the precise mechanism through which it acts is still controversial. Recently, Ku was identified as a possible anti-human immunodeficiency virus type 1 (HIV-1) target in human cells, in two global approaches. Here we investigated the role of Ku on the HIV-1 replication cycle by analyzing the expression level of a panel of non-replicative lentiviral vectors expressing the green fluorescent protein in human colorectal carcinoma HCT 116 cells, stably or transiently depleted of Ku. We found that in this cellular model the depletion of Ku did not affect the efficiency of (pre-)integrative steps but decreased the early HIV-1 expression by acting at the transcriptional level. This negative effect was specific of the HIV-1 promoter, required the obligatory step of viral DNA integration and was reversed by transient depletion of p53. We also provided evidence on a direct binding of Ku to HIV-1 LTR in transduced cells. Ku not only promotes the early transcription from the HIV-1 promoter, but also limits the constitution of viral latency. Moreover, in the presence of a normal level of Ku, HIV-1 expression was gradually lost over time, likely due to the counter-selection of HIV-1-expressing cells. On the contrary, the reactivation of transgene expression from HIV-1 by means of trichostatin A- or tumor necrosis factor α-administration was enhanced under condition of Ku haplodepletion, suggesting a phenomenon of provirus latency. These observations plead in favor of the hypothesis that Ku has an impact on HIV-1 expression and latency at early- and mid-time after integration.

Reduced glutathione: a radioprotector or a modulator of DNA-repair activity?

The tripeptide glutathione (GSH) is the most abundant intracellular nonprotein thiol, and it is involved in many cellular functions including redox-homeostatic buffering. Cellular radiosensitivity has been shown to be inversely correlated to the endogenous level of GSH. On the other hand, controversy is raised with respect to its role in the field of radioprotection since GSH failed to provide consistent protection in several cases. Reports have been published that DNA repair in cells has a dependence on GSH. Subsequently, S-glutathionylation (forming mixed disulfides with the protein-sulfhydryl groups), a potent mechanism for posttranslational regulation of a variety of regulatory and metabolic proteins when there is a change in the celluar redox status (lower GSH/GSSG ratio), has received increased attention over the last decade. GSH, as a single agent, is found to affect DNA damage and repair, redox regulation and multiple cell signaling pathways. Thus, seemingly, GSH does not only act as a radioprotector against DNA damage induced by X-rays through glutathionylation, it may also act as a modulator of the DNA-repair activity. Judging by the number of publications within the last six years, it is obvious that the field of protein glutathionylation impinges on many aspects of biology, from regulation of protein function to roles of cell cycle and apoptosis. Aberrant protein glutathionylation and its association with cancer and other diseases is an area of increasing interest.

Resveratrol induces gastric cancer cell apoptosis via reactive oxygen species, but independent of sirtuin1

The currently available chemotherapeutic regimens against gastric cancer are not very effective, leading to high recurrence and poor survival. Resveratrol is a naturally occurring polyphenol with potent apoptosis-inducing activity. However, the mechanism underlying its actions remains unknown. In the present study, human gastric adenocarcinoma SGC7901 cells were treated with resveratrol (0, 25, 50, 100 and 200 μmol/L) for 48 h, and cellular apoptosis DNA damage were determined. In certain experiments, cells were incubated with superoxide dismutase (100 U/mL), catalase (300 U/mL) or sirtinol (10 μmol/L) to determine the role of reactive oxygen species (ROS) and sirtuin1 in resveratrol-induced cellular apoptosis. Treatment with resveratrol (50-200 μmol/L) for 48 h significantly induced apoptosis and DNA damage in human gastric cancer SGC7901 cells. This was due to the increased generation of ROS following resveratrol treatment because incubation of cells with superoxide dismutase (100 U/mL) or catalase (300 U/mL) attenuated resveratrol-induced cellular apoptosis. Interestingly, treatment with resveratrol (25-200 μmol/L) did not affect the level and activity of sirtuin1, whereas the sirtuin1 inhibitor sirtinol (10 μmol/L) significantly reduced sirtuin1 activity. Furthermore, treatment with sirtinol (10 μmol/L) did not have any effect on apoptosis induced by resveratrol. These data provide evidence that resveratrol induces apoptosis via ROS, but independent of sirtuin1, in the human gastric cancer cell line SGC7901.

Ku80 functions as a tumor suppressor in hepatocellular carcinoma by inducing S-phase arrest through a p53-dependent pathway

Ku80 is a component of the protein complex called DNA-dependent protein kinase, which is involved in DNA double-strand break repair and multiple other functions. Previous studies revealed that Ku80 haplo-insufficient and poly (adenosine diphosphate-ribose) polymerase-null transgenic mice developed hepatocellular carcinoma (HCC) at a high frequency. The role of Ku80 has never been investigated in human HCC. Ku80 expressions in HCC and adjacent liver tissue were investigated by using immunohistochemical staining and western blot. Ku80 was transfected into a Ku80-deficient HCC cell line SMMC7721 cells, and the growth features of the Ku80-expressing cells and vector-transfected cells were studied both in vitro and in vivo. Cell cycle analysis and RNA interference were employed to investigate the mechanisms underlying the growth regulation associated with Ku80 expression. Ku80 was found frequently downregulated in HCC compared with adjacent liver tissue. Ku80 downregulation was significantly correlated with elevated hepatitis B virus-DNA load and severity of liver cirrhosis. Overexpression of Ku80 in SMMC7721 cells significantly suppressed cell proliferation in vitro and in vivo. Ku80 overexpression caused S-phase cell cycle arrest and was associated with upregulation of p53 and p21(CIP1/WAF1), and the inhibition of p53 or p21(CIP1/WAF1) expression by RNA interference overcame the growth suppression and S-phase arrest in the Ku80-expressing cells. A novel mechanism was revealed that Ku80 functions as a tumor suppressor in HCC by inducing S-phase arrest through a p53-dependent pathway.

Ku80 gene G-1401T promoter polymorphism and risk of gastric cancer

AIM: To evaluate the possible relationship between the Ku80 gene polymorphism and the risk of gastric cancer in China.

METHODS: In this hospital-based case-control study of gastric cancer in Jiangsu Province, China, we investigated the association of the Ku80 G-1401T (rs828907) polymorphism with gastric cancer risk. A total of 241 patients with gastric cancer and 273 age- and sex-matched control subjects were genotyped and analyzed by polymerase chain reaction-restriction fragment length polymorphism.

RESULTS: The frequencies of genotypes GG, GT and TT were 65.6%, 22.8% and 11.6% in gastric cancer cases, respectively, and 75.8%, 17.6% and 6.6% in controls, respectively. There were significant differences between gastric cancer and control groups in the distribution of their genotypes (P = 0.03) and allelic frequencies (P = 0.002) in the Ku80 promoter G-1401T polymorphism.

CONCLUSION: The T allele of Ku80 G-1401T may be associated with the development of gastric cancer.

Proteomic analysis of differentially expressed proteins in peripheral cholangiocarcinoma

Cholangiocarcinoma is an adenocarcinoma of the liver which has increased in incidence over the last thirty years to reach similar levels to other liver cancers. Diagnosis of this disease is usually late and prognosis is poor, therefore it is of great importance to identify novel candidate markers and potential early indicators of this disease as well as molecules that may be potential therapeutic targets. We have used a proteomic approach to identify differentially expressed proteins in peripheral cholangiocarcinoma cases and compared expression with paired non-tumoral liver tissue from the same patients. Two-dimensional fluorescence difference gel electrophoresis after labeling of the proteins with cyanines 3 and 5 was used to identify differentially expressed proteins. Overall, of the approximately 2,400 protein spots visualised in each gel, 172 protein spots showed significant differences in expression level between tumoral and non-tumoral tissue with p < 0.01. Of these, 100 spots corresponding to 138 different proteins were identified by mass spectrometry: 70 proteins were over-expressed whereas 68 proteins were under-expressed in tumoral samples compared to non-tumoral samples. Among the over-expressed proteins, immunohistochemistry studies confirmed an increased expression of 14-3-3 protein in tumoral cells while α-smooth muscle actin and periostin were shown to be overexpressed in the stromal myofibroblasts surrounding tumoral cells. α-Smooth muscle actin is a marker of myofibroblast differentiation and has been found to be a prognostic indicator in colon cancer while periostin may also have a role in cell adhesion, proliferation and migration and has been identified in other cancers. This underlines the role of stromal components in cancer progression and their interest for developing new diagnostic or therapeutic tools.

SCID dogs: similar transplant potential but distinct intra-uterine growth defects and premature replicative senescence compared with SCID mice

We have previously described DNA-dependent protein kinase (DNA-PKcs) mutations in horses and dogs that result in deficits in V(D)J recombination, DNA repair, and SCID. In this paper, we document substantial developmental growth defects in DNA-PKcs-deficient dogs that are not apparent in SCID mice. Fibroblast cell strains derived from either fetal or adult SCID dogs proliferate poorly in culture and undergo premature replicative senescence, somewhat reminiscent of cells derived from Ku-deficient mice. A limited number of animals have been immune reconstituted (by bone marrow transplantation) so that they can be maintained in a normal environment for long periods. Several of these animals have developed conditions associated with premature ageing at 2-3 years of age, roughly 20% of their expected lifespan. These conditions include intestinal malabsorption and primary neural cell neoplasia. These results suggest that DNA-PKcs deficiency is not tolerated equally in all species, perhaps providing insight into why DNA-PKcs deficiency has not been observed in humans. Finally, this study demonstrates the feasibility of maintaining SCID dogs for extended periods of time and documents their utility for bone marrow transplantation studies and as hosts for the propagation of xenografts. In sum, SCID dogs may present researchers with new possibilities for the development of animal models of human disease.

The ubiquitin-proteasome system in cancer, a major player in DNA repair. Part 2: transcriptional regulation

DNA repair is an indispensable part of a cell’s defence system against the devastating effects of DNA-damaging conditions. The regulation of this function is a really demanding situation, particularly when the stressing factors persist for a long time. In such cases, the depletion of existing DNA repair proteins has to be compensated by the induction of the analogous gene products. In addition, the arrest of transcription, which is another result of many DNA-damaging agents, needs to be overcome through regulation of transcription-specific DNA repair pathways. The involvement of the ubiquitin-proteasome system (UPS) in cancer- and chemotherapy-related DNA-damage repair relevant to the above transcriptional modification mechanisms are illustrated in this review. Furthermore, the contribution of UPS to the regulation of localization and accessibility of DNA repair proteins to chromatin, in response to cellular stress is discussed.

High fat feeding and dietary L-arginine supplementation differentially regulate gene expression in rat white adipose tissue

Dietary L-arginine (Arg) supplementation reduces white-fat gain in diet-induced obese rats but the underlying mechanisms are unknown. This study tested the hypothesis that Arg treatment affects expression of genes related to lipid metabolism in adipose tissue. Four-week-old male Sprague-Dawley rats were fed a low-fat (LF) or high-fat (HF) diet for 15 weeks. Thereafter, lean or obese rats continued to be fed their same respective diets and received drinking water containing 1.51% Arg-HCl or 2.55% L: -alanine (isonitrogenous control). After 12 weeks of Arg supplementation, rats were euthanized to obtain retroperitoneal adipose tissue for analyzing global changes in gene expression by microarray. The results were confirmed by RT-PCR analysis. HF feeding decreased mRNA levels for lipogenic enzymes, AMP-activated protein kinase, glucose transporters, heme oxygenase 3, glutathione synthetase, superoxide dismutase 3, peroxiredoxin 5, glutathione peroxidase 3, and stress-induced protein, while increasing expression of carboxypeptidase-A, peroxisome proliferator activated receptor (PPAR)-alpha, caspase 2, caveolin 3, and diacylglycerol kinase. In contrast, Arg supplementation reduced mRNA levels for fatty acid binding protein 1, glycogenin, protein phosphates 1B, caspases 1 and 2, and hepatic lipase, but increased expression of PPARgamma, heme oxygenase 3, glutathione synthetase, insulin-like growth factor II, sphingosine-1-phosphate receptor, and stress-induced protein. Biochemical analysis revealed oxidative stress in white adipose tissue of HF-fed rats, which was prevented by Arg supplementation. Collectively, these results indicate that HF diet and Arg supplementation differentially regulate gene expression to affect energy-substrate oxidation, redox state, fat accretion, and adipocyte differentiation in adipose tissue. Our findings provide a molecular mechanism to explain a beneficial effect of Arg on ameliorating diet-induced obesity in mammals.

Cerebral expression of DNA repair protein, Ku70, and its association with cell proliferation following cerebral hypoxia-ischemia in neonatal rats

We hypothesized that increased Ku70 expression could be involved in recovery following cerebral hypoxia-ischemia. We investigated the progression of cerebral alterations in Ku70 expression at different time points (24 h, 72 h, 1 week, 4 weeks and 8 weeks) after hypoxia-ischemia (right carotid artery occlusion plus 1.5h of hypoxia) in neonatal rats. To determine whether in addition to its known role of DNA repair, Ku70 was associated with cell death or cell proliferation we performed double staining for Ku70 and DNA fragmentation or bromodeoxyuridine, respectively. The results show that Ku70 expression was increased in the infarct core and peri-infarct regions at 24h following hypoxia-ischemia. The increased Ku70 expression was transient in the infarct core with a loss of Ku70 positive cells over days. In contrast, in the peri-infarct region the expression of Ku70 remained increased at chronic times 8 weeks following the insult. Cells positive for DNA fragmentation were not co-localized with cells positive for Ku70 after an insult. However, most of the cells positive for bromodeoxyuridine indicative of cell proliferation were positive for Ku70 in the peri-infarct region at 8 weeks after the insult. Considering the roles of Ku70 in DNA repair or inhibiting apoptosis and its co-localization within cells that had undergone proliferation, Ku70 may be considered a potential novel target to enhance recovery following hypoxia-ischemia.

Molecular mechanisms and clinical implications of reversible protein S-glutathionylation

Sulfhydryl chemistry plays a vital role in normal biology and in defense of cells against oxidants, free radicals, and electrophiles. Modification of critical cysteine residues is an important mechanism of signal transduction, and perturbation of thiol-disulfide homeostasis is an important consequence of many diseases. A prevalent form of cysteine modification is reversible formation of protein mixed disulfides (protein-SSG) with glutathione (GSH). The abundance of GSH in cells and the ready conversion of sulfenic acids and S-nitroso derivatives to S-glutathione mixed disulfides suggests that reversible S-glutathionylation may be a common feature of redox signal transduction and regulation of the activities of redox sensitive thiol-proteins. The glutaredoxin enzyme has served as a focal point and important tool for evolution of this regulatory mechanism, because it is a specific and efficient catalyst of protein-SSG deglutathionylation. However, mechanisms of control of intracellular Grx activity in response to various stimuli are not well understood, and delineation of specific mechanisms and enzyme(s) involved in formation of protein-SSG intermediates requires further attention. A large number of proteins have been identified as potentially regulated by reversible S-glutathionylation, but only a few studies have documented glutathionylation-dependent changes in activity of specific proteins in a physiological context. Oxidative stress is a hallmark of many diseases which may interrupt or divert normal redox signaling and perturb protein-thiol homeostasis. Examples involving changes in S-glutathionylation of specific proteins are discussed in the context of diabetes, cardiovascular and lung diseases, cancer, and neurodegenerative diseases.

ShRNA-mediated Ku80 gene silencing inhibits cell proliferation and sensitizes to gamma-radiation and mitomycin C-induced apoptosis in esophageal squamous cell carcinoma lines

To investigate the effects of Ku80 depletion on cell growth and sensitization to gamma-radiation and MMC-induced apoptosis in esophageal squamous cell carcinoma lines. Six human carcinoma cell lines (LNcaP, K562, MDA-MB-231, MCF-7, EC9706, and K150) and normal HEK293 cell line were examined for basal levels of Ku80 protein by western blotting analysis. The suppression of Ku80 expression was performed using vector-based shRNA in EC9706 cells. Cell proliferation was determined with MTT assay and colony formation assay and tumorigenicity in a xenograft model in vitro and in vivo. Sensitivity of EC9706 cells treated with shRNA vector to gamma-radiation and MMC was determined with colony formation assay and MTT assay. The cell cycle distribution was determined by Flow cytometry. Apoptosis induced by gamma-radiation and MMC was analyzed using GENMED-TUNEL FACS kit. Ku80 showed higher basal levels in six carcinoma cell lines than in HEK293. The suppression of Ku80 expression decreased cellular proliferation, colony formation and inhibited tumorigenicity in a xenograft model. Furthermore, it sensitized apoptosis of the cancer cells induced by gamma-radiation and MMC. Ku80 plays an important role not only in tumorigenesis but also in radiation resistance and chemotherapy resistance in esophageal cancer cells. Hence Ku80 may serve as a promising therapeutic target, particularly for recurrent esophageal tumors.