PTTG's C-terminal PXXP motifs modulate critical cellular processes in vitro

Human pituitary tumor-transforming gene (PTTG), known also as securin, is a multifunctional protein implicated in the control of mitosis and the pathogenesis of thyroid, colon, oesophageal and other tumour types. Critical to PTTG function is a C-terminal double PXXP motif, forming a putative SH3-interacting domain and housing the gene's sole reported phosphorylation site. The exact role of phosphorylation and PXXP structure in the modulation of PTTG action in vitro remains poorly understood. We therefore examined the mitotic, transformation, proliferation and transactivation function of the C-terminal PXXP motifs of human PTTG. Live-cell imaging studies using an EGFP-PTTG construct indicated that PTTG's regulation of mitosis is retained regardless of phosphorylation status. Colony-formation assays demonstrated that phosphorylation of PTTG may act as a potent inhibitor of cell transformation. In proliferation assays, NIH-3T3 cells stable transfected and overexpressing mutations preventing PTTG phosphorylation (Phos-) showed significantly increased [3H]thymidine incorporation compared with WT, whereas mutants mimicking constitutive phosphorylation of PTTG (Phos+) exhibited reduced cell proliferation. We demonstrated that PTTG transactivation of FGF-2 in primary thyroid and PTTG-null cell lines was not affected by PTTG phosphorylation but was prevented by a mutant disrupting the PXXP motifs (SH3-). Taken together, our data suggest that PXXP structure and phosphorylation are likely to exert independent and critical influences upon PTTG's diverse actions in vitro.

The lifetime of CFC substitutes studied by a network trained with chaotic mapping modified genetic algorithm and DFT calculations

The hydrohaloalkanes have attracted much attention as potential substitutes of chlorofluorocarbons (CFCs) that deplete the ozone layer and lead to great high global warming. Having a short atmospheric lifetime is very important for the potential substitutes that may also induce ozone depletion and yield high global warming gases to be put in use. Quantitative structure-activity relationship (QSAR) studies were presented for their lifetimes aided by the quantum chemistry parameters including net charges, Mulliken overlaps, E(HOMO) and E(LUMO) based on the density functional theory (DFT) at B3PW91 level, and the C-H bond dissociation energy based on AM1 calculations. Outstanding features of the logistic mapping, a simple chaotic system, especially the inherent ability to search the space of interest exhaustively have been utilized. The chaotic mapping aided genetic algorithm artificial neural network training scheme (CGANN) showed better performance than the conventional genetic algorithm ANN training when the structure of the data set was not favorable. The lifetimes of HFCs and HCs appeared to be greatly dependent on their energies of the highest occupied molecular orbitals. The perference of the RMSRE comparing to RMSE as objective function of ANN training was better for the samples of interest with relatively short lifetimes. C(2)H(6) and C(3)H(8) as potential green substitutes of CFCs present relatively short lifetimes.

Characterization of the eicosapentaenoic acid biosynthesis gene cluster from Shewanella sp. strain SCRC-2738

The 38 kb eicosapentaenoic acid (EPA) biosynthesis gene cluster of Shewanella sp. strain SCRC-2738 was cloned into the cosmid vector (pEPA). A 27 kb nucleotide sequence of the XhoI to SpeI region of pEPA showed EPA production (6.3%) in E. coli JM109. Among the nine open reading frames (ORFs) in this sequence, only five (ORFs 2 and 5-8) were essential for EPA production. High levels of production (16%-22%) were found in E. coli JM109 transformed with a multicopy pNEB vector carrying only the five essential ORFs and in that transformed with a pNEB vector that integrated ORFs 3, 5, 6, 7 and 8, and vector pSTV28 that integrated the ORF2 encoding phosphopantetheinyl transferase (PPTase). Thus, production of EPA appears to be regulated by the presence of all the biosynthesis gene products and by the ratio of PPTase to the other gene products. The temperature -EPA production relationship in E. coli strain DH5alpha varied between constructs, suggesting that it is controlled not only by EPA biosynthesis enzymes but also by other factors in vivo. There was a strict upper temperature limit for EPA biosynthesis: no EPA was synthesized at 30 degrees C in E. coli transformants carrying any gene construct for EPA biosynthesis.

Identification of systemically expanded activated T cell clones in MRL/lpr and NZB/W F1 lupus model mice

CD4(+) T lymphocytes play an important role in the pathogenesis of systemic lupus erythematosus (SLE). To characterize the clonal expansion of CD4(+) T cells in murine lupus models, we analysed the T cell clonality in various organs of young and nephritic MRL/lpr and NZB/W F1 mice using reverse transcription-polymerase chain reaction (RT-PCR) and subsequent single-strand conformation polymorphism (SSCP) analysis. We demonstrated that some identical T cell clonotypes expanded and accumulated in different organs (the bilateral kidneys, brain, lung and intestine) in nephritic diseased mice, and that a number of these identical clonotypes were CD4(+) T cells. In contrast, young mice exhibited little accumulation of common clones in different organs. The T cell receptor (TCR) V beta usage of these identical clonotypes was limited to V beta 2, 6, 8.1, 10, 16 and 18 in MRL/lpr mice and to V beta 6 and 7 in NZB/W F1 mice. Furthermore, some conserved amino acid motifs such as I, D or E and G were observed in CDR3 loops of TCR beta chains from these identical CD4(+) clonotypes. The existence of systemically expanding CD4(+) T cell clones in the central nervous system (CNS) suggests the involvement of the systemic autoimmunity in CNS lesions of lupus. FACS-sorted CD4(+)CD69(+) cells from the kidney displayed expanded clonotypes identical to those obtained from the whole kidney and other organs from the same individual. These findings suggest that activated and clonally expanded CD4(+) T cells accumulate in different tissues of nephritic lupus mice, and these clonotypes might recognize restricted T cell epitopes on autoantigens involved in specific immune responses of SLE, thus playing a pathogenic role in these lupus mice.

Dose ranging pharmacokinetic trial of high-dose alicaforsen (intercellular adhesion molecule-1 antisense oligodeoxynucleotide) (ISIS 2302) in active Crohn's disease

BACKGROUND AND AIMS

To evaluate the safety, pharmacokinetics and clinical efficacy of the intercellular adhesion molecule-1 antisense phosphorothioate oligonucleotide alicaforsen (ISIS 2302) at 250-350 mg in Crohn's disease.

METHODS

: Patients (> 50 kg) with active Crohn's disease (Crohn's disease activity index > or = 220) were assigned by gender, randomly, to two alicaforsen treatment groups: 300 or 350 mg, infused intravenously three times a week for 4 weeks. All patients weighing 36-50 kg received 250 mg of alicaforsen. Background aminosalicylates, antibiotics, immunosuppressives and corticosteroids were permitted, but tumour necrosis factor-alphainhibitors were prohibited. The primary end-point was clinical remission (Crohn's disease activity index < or = 150).

RESULTS

Twenty-two patients were enrolled with a mean baseline Crohn's disease activity index of 304. Steroids were used by 27%, 5-aminosalicylic acid by 68% and immunosuppressives by 27%; 23% had previously received infliximab. Five subjects withdrew after one to three infusions for infusion-related symptoms. Nine patients (41%) experienced clinical remission. Fifty-three per cent of the evaluable subjects receiving more than three infusions experienced remission (18% at week 8; 29% at week 12). The overall response, using a minimum decrease of 70 in the Crohn's disease activity index, was 41-47% for the evaluable group, at weeks 8 and 12. The median duration of remission was 14 weeks. Plasma pharmacokinetic results showed overlapping levels (Cmax, AUC) for the three doses. The infusion-related reaction profile consisted of fever, chills, headache, nausea, emesis or arthralgias, typically occurring 2-4 h after completion of the first infusion. Reactions were less frequent in patients receiving background corticosteroids. The 2-4-h transient post-infusion partial thromboplastin time prolongation values, a class effect of phosphorothioate oligonucleotides, were 18, 21 and 23 s for 250, 300 and 350 mg, respectively.

CONCLUSIONS

Alicaforsen (ISIS 2302), at fixed doses of 300 and 350 mg, achieved the desired drug exposure and may be an effective therapy for Crohn's disease. Infusion-related reactions were observed less frequently in patients on corticosteroids, and with decreasing frequency with continued treatment.

Proteasome inhibitors induce apoptosis in growth hormone- and prolactin-secreting rat pituitary tumor cells

Proteasome inhibitors induce apoptosis in some malignant cells, and we show here that these inhibitors induce apoptosis in rat pituitary MMQ and GH3 tumor cells but not in normal pituitary cells. Three proteasome inhibitors, PSI, MG-132, and lactacystin, but not the calpain inhibitor, ALLM, dose- and time-dependently caused apoptosis in these cells, and 10 microM PSI caused apoptosis in 70% of MMQ cells and in 25% of GH3 cells within 24 h. A lower PSI dose (10 nM) inhibited GH3 cell growth without causing significant apoptosis or affecting prolactin secretion. Primary rat pituitary cells were resistant to both PSI and MG-132 and did not undergo apoptosis. In MMQ cells, DNA synthesis was slowed (approximately 30%) after 6 h of 10 microM PSI treatment and a partial cell cycle block at G2/M was evident after 8 h. Colorimetric caspase substrate assay and Western blotting of caspase substrates showed that caspases 2 and 3 are activated by PSI while caspases 6 and 8 remained inactive. A broad-range caspase inhibitor, caspase inhibitor III, prevented apoptosis induced by PSI. The results show that proteasome inhibitors induce apoptosis in rat pituitary tumor cells by specific caspase activation. This novel group of drugs may potentially be used in treatment of aggressive pituitary tumors, especially as their action appears relative for tumor cells.

Double blind, placebo controlled trial of the remission inducing and steroid sparing properties of an ICAM-1 antisense oligodeoxynucleotide, alicaforsen (ISIS 2302), in active steroid dependent Crohn's disease

BACKGROUND AND AIMS

To evaluate the safety and efficacy of the intercellular adhesion molecule 1 (ICAM-1) antisense phosphorothioate oligonucleotide alicaforsen (ISIS 2302) in Crohn's disease.

METHODS

Active (Crohn's disease activity index (CDAI) 200-350), steroid dependent (prednisone 10-40 mg) Crohn's patients were randomised into three treatment groups: placebo versus ISIS 2302 (2 mg/kg intravenously three times a week) for two or four weeks. Patients were treated in months 1 and 3, with steroid withdrawal attempted by week 10. The primary end point (steroid free remission) was a CDAI <150 off steroids at the end of week 14.

RESULTS

A total of 299 patients were enrolled, with a mean baseline CDAI of 276 and steroid dose of 23 mg/day. Rates of steroid free remission were equivalent for the two and four week ISIS 2302 groups (20.2% and 21.2%) and the placebo group (18.8%). At week 14, steroid withdrawal was successful in more ISIS 2302 patients compared with placebo treated patients (78% v 64%; p=0.032). Steroid free remission was highly correlated with exposure (p=0.0064). Other clinical responses were correlated with exposure, with significant results versus placebo being observed in the highest area under the curve subgroup. CDAI scores decreased by 136 (112) at week 14 versus 52 (107) for placebo (p=0.027) and inflammatory bowel disease score questionnaire improved by 43 (31) versus 15 (36) for placebo (p=0.027).

CONCLUSIONS

Although the primary outcomes failed to demonstrate efficacy, pharmacodynamic modelling suggests that alicaforsen (ISIS 2302) may be an effective therapy for steroid dependent Crohn's disease.

Reversible structural transition in epitaxial manganite film

A reversible structural transition of an epitaxial La(2/3)Sr(1/3)MnO3 film deposited on a LaAlO3 substrate has been investigated by means of in situ high-resolution transmission electron microscopy and electron diffraction, combined with image and diffraction calculations. We observe that the crystallographic symmetry of the film can be lowered via electron beam irradiation, leading to a rhombohedral-monoclinic transition. This transition can be attributed to the cooperating effect of the mismatch stress and the irradiation-induced thermal stress.

Phase II trial of irofulven (6-hydroxymethylacylfulvene) for patients with advanced renal cell carcinoma

The aim of this study was to determine the antitumor activity of irofulven (6-hydroxymethylacylfulvene) in patients with advanced renal cell carcinoma (RCC). Eligible patients had advanced renal cell carcinoma with bidimensionally measurable disease, a Karnofsky performance status of at least 70, life expectancy of greater than three months, no prior treatment with chemotherapy, and no evidence of brain metastases. Irofulven was administered at a dose of 11 mg/m2 by 5-min intravenous infusion, on 5 consecutive days. Cycles were repeated every 28 days. Thirteen patients were enrolled in this study and 12 were evaluable for response. Of the twelve evaluable patients, no major responses were achieved. Eight patients had stable disease as best response. Toxicity included myelosuppression and gastrointestinal side effects. At the dose and schedule used in this trial, irofulven did not produce clinical response in RCC.

[Study of quinolones resistance in Escherichia coli, Staphylococcus aureus and Pseudomonas areuginosa]

OBJECTIVE

To investigate the factors of quinolone-resistance mediating in Escherichia coli(E. coli), Staphylococcus aureus (S. aureus) and Pseudomonas areuginosa(P. areuginosa) and examine the characteristic changes and quinolones resistance of these bacteria after exposing them to quinolones, dye-materials, and ultraviolet respectively.

METHODS

The agar plate inoculating on surface and tube broth two-fold dilution methods were adopted.

RESULTS

Quinolone-resistance was mainly mediated by repeated exposure of the bacteria to low level concentration of quinolone. No quinolone-resistance was found after exposure of the bacteria to ultra-violet and dye materials such as Ethidium bromide and Acry-orange. Among the three kinds of bacteria, E. coli tended to have stable high level of quinolone- resistance(MICs > or = 256 mg/L). S. aureus acquired mediate level of quinolone-resistance(MICs < or = 32 mg/L). P. aeruginosa acquired a high but not stable level(MICs > or = 256 mg/L) of resistance. These bacteria were cultured in the concentration of 1/2 x MIC, 1 x MIC, 2 x MIC, 4 x MIC, 5 x MIC ciprofloxacin, and were compared with those cultured in the same concentration of sparfloxacin and cefotaxime. After being affected by ciprofloxacin, the E. coli underwent apparent morphologic changes, such as becoming wider(2-3 times), longer(10-30 times), thread-like, and fewer in number. These changes were consistent with the increase of quinolone concentrations. The morphologic changes in P. aeruginosa and S. aureus were not so obvious as those in E. coli. Sparfloxacin and cefotaxime mainly led to the decrease in the numbers of bacteria. When the concentration of Sparfloxacin and cefotaxime were 4 x MICs, the changes of P. aeruginosa and S. aureus were less obvious.

CONCLUSION

The bacteria's quinolone-resistance is mainly induced by the quinolone itself. The quinolone-resistance is more likely occur in E. coli than in P. aeruginosa and S. aureus. After exposure of the bacteria to ciprofloxacin, E. coli might have most apparent morphologic changes and occurrence resistance.

[Expression and significance of serum soluble tumor necrosis factor receptor-I in patients with head and neck neoplasm]

OBJECTIVE

To investigate the expression and significance of serum soluble tumor necrosis factor receptor-I (sTNFR-I) in patients with head and neck neoplasms.

METHOD

The study was undertaken to detect serum sTNFR-I levels in 160 head neck cancer patients (including 12 cases of malignant lymphoma, 62 nasopharyngeal cancer, 56 laryngeal cancer, 22 hypopharyngeal cancer, 3 maxillary cancer and 5 thyrophyma), using Sandwich enzyme-linked immuno-sorbent assay.

RESULTS

The sTNFR-I levels were significantly higher in patients with carcinoma than those of healthy controls (P < 0.01). The sTNFR-I levels of malignant lymphoma and nasopharyngeal carcinoma were the highest among patients with head and neck neoplasm. The correlations between the serum sTNFR-I levels and the stages of head and neck neoplasms and other laboratory parameters were also analyzed and discussed.

CONCLUSION

The serum sTNFR-I levels may reflect the human immunity function, therefore it can be used as a helpful indicator to evaluate the therapeutic effect and monitor the relapses and metastasis of cancer.

Association of HIF-1alpha expression and cell apoptosis after traumatic brain injury in the rat

OBJECTIVE

To explore the expression of hypoxia inducible factor-1alpha (HIF-1alpha) and the correlation between HIF-1alpha and apoptosis after traumatic brain injury.

METHODS

Using experimental traumatic brain injury in the rats, the expression of HIF-1alpha was studied by immunohistochemistry in cerebral tissue, apoptotic cell death was evaluated with TUNEL (transferase-mediated X-dUTP nick end labeling), and double-labeled immunohistochemistry and TUNEL methods were used to investigate the relationship between HIF-1alpha and apoptosis.

RESULTS

There was remarkable difference in the expression of H IF-1alpha between the experimental groups and the control groups (P<0.01), in the experimental groups, the expression of HIF-1alpha at 48 hours was highest; the evidence of apoptotic cell death after experimental traumatic brain injury was found by TUNEL; the apoptotic percentage increased or decreased according to the changes of the positive expression of HIF-1alpha (r=0.99).

CONCLUSIONS

The results suggest that secondary brain ischemia plays a crucial role in apoptotic cell death after traumatic brain injury; HIF-1alpha can prompt apoptotic cell death after experimental traumatic brain injury.

Mice lacking pituitary tumor transforming gene show testicular and splenic hypoplasia, thymic hyperplasia, thrombocytopenia, aberrant cell cycle progression, and premature centromere division

Tumorigenic pituitary tumor transforming gene (PTTG) is a mammalian homolog of Xenopus securin that inhibits chromatid separation, is overexpressed in many human tumor types, and mediates transcriptional activation. Loss of yeast securin Pds1p or Drosophila securin pimples is lethal. Here we show that mice lacking PTTG (PTTG -/-) are, surprisingly, viable and fertile; but they have testicular and splenic hypoplasia, thymic hyperplasia, and thrombocytopenia. PTTG -/- mouse embryo fibroblasts exhibited aberrant cell cycle progression with prolonged G2-M phase and binucleated and multinucleated nuclei with increased aneuploidy. PTTG -/- mouse embryo fibroblast metaphases contained quadriradial, triradial, and chromosome breaks, as well as premature centromere division. The results show that PTTG functions to maintain chromosome stability, cell cycle progression, and appropriate cell division. Moreover, mammalian sister chromatid separation, an important transition in the cell cycle, is likely regulated by mechanisms in addition to securin.

Drug properties of second-generation antisense oligonucleotides: how do they measure up to their predecessors?

Antisense technology has progressed beyond the point of using only phosphorothioate oligodeoxynucleotides as therapeutic agents to looking at antisense molecules that contain additional chemical modifications as the next generation of therapeutic agents. These modifications are intended to improve the overall therapeutic properties by increasing potency, optimizing pharmacokinetic properties and improving the safety profile. This review will focus on the non-clinical pharmacokinetic and safety properties of 2'-O-methoxyethyl-modified oligonucleotides. Implications on the convenience and safe use of these compounds as therapeutic agents will be discussed.

Polymorphisms of 5,10-methylenetetrahydrofolate reductase and risk of gastric cancer in a Chinese population: a case-control study

Low dietary folate intake has been associated with increased risk of gastric cancer. The 5,10-methylenetetrahydrofolate reductase (MTHFR) involved in folate metabolism has 2 variants, C677T and A1298C, that result in decreased MTHFR activity and lower plasma folate levels. Therefore, we hypothesized that these 2 variants play a role in gastric carcinogenesis. We tested this hypothesis in a Chinese population-based case-control study of 187 histopathologically confirmed gastric cancer cases and 166 healthy controls frequency-matched by age (+/-5 years), gender and residential area. The 677TT genotype was associated with increased risk for gastric cancer [adjusted odds ratio (OR) = 1.87, 95% confidence interval (CI) = 1.00-3.48] compared to the 677CC genotype. This association was more pronounced for gastric cardia cancer (adjusted OR = 2.47, 95% CI = 1.14-5.32). However, no evidence was found for risk associated with the MTHFR A1298C polymorphism. Our findings support the hypothesis that MTHFR C677T variants contribute to gastric carcinogenesis, particularly in gastric cardia. Larger studies incorporating dietary folate intake and serum levels are needed to confirm our findings.

Polymorphisms of 5,10-methylenetetrahydrofolate reductase and risk of gastric cancer in a Chinese population: a case-control study

Low dietary folate intake has been associated with increased risk of gastric cancer. The 5,10-methylenetetrahydrofolate reductase (MTHFR) involved in folate metabolism has 2 variants, C677T and A1298C, that result in decreased MTHFR activity and lower plasma folate levels. Therefore, we hypothesized that these 2 variants play a role in gastric carcinogenesis. We tested this hypothesis in a Chinese population-based case-control study of 187 histopathologically confirmed gastric cancer cases and 166 healthy controls frequency-matched by age (+/-5 years), gender and residential area. The 677TT genotype was associated with increased risk for gastric cancer [adjusted odds ratio (OR) = 1.87, 95% confidence interval (CI) = 1.00-3.48] compared to the 677CC genotype. This association was more pronounced for gastric cardia cancer (adjusted OR = 2.47, 95% CI = 1.14-5.32). However, no evidence was found for risk associated with the MTHFR A1298C polymorphism. Our findings support the hypothesis that MTHFR C677T variants contribute to gastric carcinogenesis, particularly in gastric cardia. Larger studies incorporating dietary folate intake and serum levels are needed to confirm our findings.

Polymorphisms of 5,10-methylenetetrahydrofolate reductase and risk of gastric cancer in a Chinese population: a case-control study

Low dietary folate intake has been associated with increased risk of gastric cancer. The 5,10-methylenetetrahydrofolate reductase (MTHFR) involved in folate metabolism has 2 variants, C677T and A1298C, that result in decreased MTHFR activity and lower plasma folate levels. Therefore, we hypothesized that these 2 variants play a role in gastric carcinogenesis. We tested this hypothesis in a Chinese population-based case-control study of 187 histopathologically confirmed gastric cancer cases and 166 healthy controls frequency-matched by age (+/-5 years), gender and residential area. The 677TT genotype was associated with increased risk for gastric cancer [adjusted odds ratio (OR) = 1.87, 95% confidence interval (CI) = 1.00-3.48] compared to the 677CC genotype. This association was more pronounced for gastric cardia cancer (adjusted OR = 2.47, 95% CI = 1.14-5.32). However, no evidence was found for risk associated with the MTHFR A1298C polymorphism. Our findings support the hypothesis that MTHFR C677T variants contribute to gastric carcinogenesis, particularly in gastric cardia. Larger studies incorporating dietary folate intake and serum levels are needed to confirm our findings.

Signal transduction events elicited by cancer prevention compounds

Many chemopreventive agents have been shown to modulate gene expression including induction of phase II detoxifying enzymes, such as glutathione S-transferases (GST) and quinone reductases (QR). Induction of phase II enzymes in general leads to protection of cells/tissues against exogenous and/or endogenous carcinogenic intermediates. The antioxidant or electrophile response element (ARE/EpRE) found at the 5'-flanking region of these phase II genes may play important role in mediating their induction by xenobiotics including chemopreventive agents. Members of the basic leucine zipper (bZIP) transcription factor, Nrf2 which heterodimerizes with Maf G/K, are found to bind to the ARE, and transcriptionally-activated ARE. Recently, we showed that the mitogen-activated protein kinases (MAPK) were activated by phase II gene inducers such as phenolic antioxidant butylated hydroxyanisol (BHA) and isothiocyanate sulforaphane (SUL), and involved in the transcription activation of ARE-mediated reporter gene. Transfection studies with wild-type and dominant negative mutants of Nrf2 and MAPK showed synergistic response during co-transfection as well as to phase II gene inducers. However, increasing the concentrations of these compounds such as BHA, the activities of cell death signaling molecules, caspases, were stimulated and resulted in apoptotic cell death. At these concentrations, BHA stimulated loss of mitochondrial membrane potential, cytochrome c release, and activation of caspase 3, 8 and 9 preceding apoptosis. Further increase in concentrations led to rapid cell necrosis. A model is proposed for BHA and SUL, in that at low concentrations, these potential chemopreventive agents may modulate MAPK pathway leading to transcription activation of Nrf2 and ARE with subsequent induction of cellular defensive enzymes including phase II detoxifying enzymes as well as other defensive genes, which may protect the cells against cellular injury, which is a homeostatic response. At higher concentrations, these agents may activate the caspase pathways, leading to apoptosis, a potential beneficial effect if occurs at preneoplastic/neoplastic tissues, but a potential cytotoxic response if occurs in normal tissues. On the other hand, some phenolic compounds such as resveratrol inhibits TPA- or UV-induced AP-1-mediated activity through the inhibition of c-Src non-receptor tyrosine kinase and MAPK pathways. It is possible that in proliferating or stimulated cells, these chemopreventive compounds may block proliferation by inhibiting these signaling kinases, whereas in non-proliferating or quiescent cells, some of these compounds may activate these signaling kinases leading to gene expression of cellular defensive enzymes such as phase II detoxifying enzymes. The studies of these and other signaling pathways may yield insights into the development of potential chemopreventive compounds.

[Effects of selenium on hepatocellular protooncogene c-myc, c-fos and c-jun expression induced by cadmium in rats]

OBJECTIVES

This study was conducted to explore effects of selenium on hepatocellular protooncogene c-myc, c-fos and c-jun expression induced by cadmium in rats.

METHOD

Both cadmium and selenium were given to rats by i.p. and there were 5 SD rats in each group. Protooncogene c-myc, c-fos and c-jun expression in rat liver cells was measured with Northern Dot Hybridization.

RESULTS

The results showed that cadmium chloride at doses of 5, 10 or 20 mumol/kg, significantly induced proto-oncogene c-myc, c-fos and c-jun expression, and when sodium selenite at the dose of 5 mumol/kg was given at the time, the effect of cadmium chloride on hepatocellular protooncogene c-myc, c-fos and c-jun expression was inhibited.

CONCLUSION

Selenium at certain doses could inhibit hepatocellular protooncogene c-myc, c-fos and c-jun expression induced by cadmium in rats.

Activation of MAPK by TRH requires clathrin-dependent endocytosis and PKC but not receptor interaction with beta-arrestin or receptor endocytosis

To determine whether the interaction of the TRH receptor with beta-arrestin is necessary for TRH activation of MAPK, cells expressing either intact or truncated, internalization-defective TRH receptors were transfected with a beta-arrestin-green fluorescent protein conjugate. In cells expressing the wild-type pituitary TRH receptor, TRH caused translocation of the beta-arrestin-green fluorescent protein conjugate from the cytosol to the plasma membrane within 30 sec. After 5 min, the beta-arrestin-green fluorescent protein conjugate was visible in vesicles, where it colocalized with rhodamine-labeled TRH. In hypertonic sucrose, the beta-arrestin-green fluorescent protein conjugate translocated to the plasma membrane after TRH addition but did not internalize. In cells expressing the truncated TRH receptor, TRH did not cause translocation of the beta-arrestin-green fluorescent protein conjugate. TRH activated MAPK strongly in cells expressing intact or truncated TRH receptors, indicating that the receptor does not need to bind beta-arrestin or internalize. MAPK activation by TRH, epidermal growth factor, and phorbol ester was strongly inhibited by hypertonic sucrose and concanavalin A, which block movement of proteins into coated pits and coated pit assembly. Hypertonic sucrose did not affect MAPK activation in cells overexpressing MAPK kinase 1. Dominant negative dynamin, which blocks conversion of coated pits to vesicles, also reduced receptor internalization and TRH activation of MAPK. TRH activation of MAPK required PKC but was insensitive to pertussis toxin and did not require ras, epidermal growth factor receptor kinase, or PI3K. These results show that the TRH receptor itself does not need to bind beta-arrestin or undergo sequestration to activate MAPK but that the endocytic pathway must be intact.

Induction of xenobiotic enzymes by the MAP kinase pathway and the antioxidant or electrophile response element (ARE/EpRE)

Cellular responses to xenobiotic-induced stress can signal proliferation, differentiation, homeostasis, apoptosis, or necrosis. To better understand the underlying molecular mechanisms after exposure to xenobiotics or drugs, we studied the signal transduction pathways, the mitogen-activated protein kinase (MAPK), and the basic leucine zipper transcription factor Nrf2, activated by different agents in the induction of Phase II drug metabolizing enzymes (DMEs). The MAPKs, characterized as proline-directed serine/threonine kinases, are essential components of signaling pathways that convert various extracellular signals into intracellular responses through serial phosphorylation cascades. Once activated, MAPKs can phosphorylate many transcription factors, such as c-Jun, ATF-2, and ultimately lead to changes in gene expression. Two classes of Phase II gene inducers, which are also cancer chemopreventive agents, were studied: (1) the phenolic antioxidants, namely butylated hydroxyanisole (BHA) and its active de-methylated metabolite t-butylhydroquinone (tBHQ), and phenolic flavonoids such as green tea polyphenols (GTP) and (-)-epigallocatechin-3-gallate (EGCG); and (2) the naturally occurring isothiocyanates, namely phenethyl isothiocyanate (PEITC), and sulforaphane. BHA and tBHQ are both well-known phenolic antioxidants used as food preservatives, and strongly activate c-Jun N-terminal kinase 1 (JNK1), extracellular signal-regulated protein kinase 2 (ERK2), or p38, in a time- and dose-dependent fashion. Free radical scavengers N-acetyl-L-cysteine (NAC), or glutathione (GSH), inhibited ERK2 activation and, to a much lesser extent, JNK1 activation by BHA/tBHQ, implicating the role of oxidative stress. Under conditions where MAPKs were activated, BHA or GTP also activated ARE/EpRE (antioxidant/electrophile response element), with the induction of Phase II genes such as NQO. Transfection studies with various cDNAs encoding wild-type or dominant-negative mutants of MAPKs and/or transcription factor Nrf2, substantially modulated ARE-mediated luciferase reporter activity in the presence or absence of phenolic compounds. Other phytochemicals including PEITC, and sulforaphane, also differentially regulated the activities of MAPKs, Nrf2, and ARE-mediated luciferase reporter gene activity and Phase II enzyme induction. A model is proposed where these xenobiotics (BHA, tBHQ, GTP, EGCG, PEITC, sulforaphane) activate the MAPK pathway via an electrophilic-mediated stress response, leading to the transcription activation of Nrf2/Maf heterodimers on ARE/EpRE enhancers, with the subsequent induction of cellular defense/detoxifying genes including Phase II DMEs, which may protect the cells against toxic environmental insults and thereby enhance cell survival. The studies of these signaling pathways may yield insights into the fate of cells upon exposure to xenobiotics.

Inhibition of egg hatching success and larvae survival of the scallop, Chlamys farreri, associated with exposure to cells and cell fragments of the dinoflagellate Alexandrium tamarense

We report an apparently novel toxic effect of the dinoflagellate Alexandrium tamarense, manifested by inhibition of the egg hatching success of the scallop, Chlamys farreri. The hatching rate of C. farreri approached only 30% of controls when its fertilised eggs were exposed for 36h to A. tamarense cells or cellular fragments at a concentration of 100 cells/ml, and the hatching rate was just 5% after exposure to A. tamarense of 500 cells/ml. Similar exposures of the fertilised scallop eggs to two other algal species, the diatom Phaeodactylum tricornutum and the raphidophyte Heterosigma carterae, resulted in no such toxicity or inhibitory effects. Likewise, exposure of eggs to standard STX toxin, as well as to A. tamarense cell contents (supernant of re-suspended algal cells following ultrasonication and centrifugation), did not elicit this inhibitory response. However, exposure of the scallop eggs to cell cultures, intact algal cells, or cell fragments of A. tamarense produced marked toxicity. The alga also influenced larvae at early D-shape stage of scallop. The survival rates began to decrease significantly after exposed for 6 days at concentration of 3000 cells/ml and above; no larvae could survive after 14-day exposure to A. tamarense at 10,000 cells/ml or 20-day at 5000 cells/ml. The results indicated the production of novel substances from A. tamarense which can cause adverse effects on egg hatching and survival of the scallop larvae. The experiment also found that the developmental stages before blastula was the developmental period most sensitive to the A. tamarense toxin(s) and the alga at early exponential stage had the strongest effect on egg hatching comparing with other growth phases. The adverse effect of A. tamarense on early development of scallops may cause decline of shellfish population and may have further impact on marine ecosystem.

[Imaging diagnosis of intestinal tuberculosis]

OBJECTIVE

To assess significance and limitation of CT and radiological gastrointestinal examination in the diagnosis of the intestinal tuberculosis.

METHODS

22 cases of intestinal tuberculosis proven pathologically were analyzed. CT scans and radiological examination were performed (barium meal examination in 18 cases, intestinal or colonic double contrast examination in 10 cases and hypotonic duodenography in 3 cases).

RESULTS

Sensitivity and specificity of diagnosing the intestinal tuberculosis with CT were inferior than that with radiological examination. Lesions in small intestine (not including ileocecal region) were not easily identified by CT scan. However, CT scan was more preferable in identifying abdominal tuberculosis other than intestinal tuberculosis, especially typical tuberculous lymphadenopathy. Intestinal radiological examination was of great significance for the assessment of the status of intestinal tuberculosis by demonstrating mucosal alterations, morphologic appearance of ulcer, bowel deformation, and the involvement of lesion and fissures.

CONCLUSIONS

Gastrointestinal radiological examination and CT scans possess their diagnostic value, but have limitation in diagnosis of intestinal tuberculosis. CT scans combined with gastrointestinal radiological examination further improve the accuracy of diagnosis.