Redox regulation of the glucocorticoid receptor

Redox regulation is currently considered as a mode of signal transduction for coordinated regulation of a variety of cellular processes. The transcriptional regulation of gene expression is also influenced by cellular redox state, most possibly through the oxido-reductive modification of transcription factors. The glucocorticoid receptor belongs to a nuclear receptor superfamily and acts as a ligand-dependent transcription factor. We demonstrate that the glucocorticoid receptor function is regulated via redox-dependent mechanisms at multiple levels. Moreover, it is suggested that redox regulation of the receptor function is one of dynamic cellular responses to environmental stimuli and plays an important role in orchestrated crosstalk between central and peripheral stress responses.

Signal transduction in hypoxic cells: inducible nuclear translocation and recruitment of the CBP/p300 coactivator by the hypoxia-inducible factor-1alpha

In response to decreased cellular oxygen concentrations the basic helix-loop-helix (bHLH)/PAS (Per, Arnt, Sim) hypoxia-inducible transcription factor, HIF-1alpha, mediates activation of networks of target genes involved in angiogenesis, erythropoiesis and glycolysis. Here we demonstrate that the mechanism of activation of HIF-1alpha is a multi-step process which includes hypoxia-dependent nuclear import and activation (derepression) of the transactivation domain, resulting in recruitment of the CREB-binding protein (CBP)/p300 coactivator. Inducible nuclear accumulation was shown to be dependent on a nuclear localization signal (NLS) within the C-terminal end of HIF-1alpha which also harbors the hypoxia-inducible transactivation domain. Nuclear import of HIF-1alpha was inhibited by either deletion or a single amino acid substitution within the NLS sequence motif and, within the context of the full-length protein, these mutations also resulted in inhibition of the transactivation activity of HIF-1alpha and recruitment of CBP. However, nuclear localization per se was not sufficient for transcriptional activation, since fusion of HIF-1alpha to the heterologous GAL4 DNA-binding domain generated a protein which showed constitutive nuclear localization but required hypoxic stimuli for function as a CBP-dependent transcription factor. Thus, hypoxia-inducible nuclear import and transactivation by recruitment of CBP can be functionally separated from one another and play critical roles in signal transduction by HIF-1alpha.

Analysis of oligosaccharide structures from the reducing end terminal by combining partial acid hydrolysis and a two-dimensional sugar map

A new sensitive and convenient method for the structural analysis of oligosaccharides was developed, in which partial acid hydrolysis was combined with two-dimensional sugar mapping of pyridylamino (PA)-oligosaccharides. A PA-oligosaccharide was partially hydrolyzed, the acid hydrolysis conditions being optimized so as to obtain various PA-oligosaccharide fragments with high yields from different types of PA-oligosaccharides. The acid hydrolyzates were then fractionated every 1 glucose unit by size-fractionation HPLC, and each fraction was analyzed by reversed-phase HPLC. The structure of each PA-oligosaccharide fragment was identified on a two-dimensional sugar map prepared with standard PA-sugar chains, after which the original PA-oligosaccharide was reconstructed from the reducing end terminal based on the obtained structures of the PA-oligosaccharide fragments. The method was successfully applied to resolving the structure of an N-linked sugar chain.

[A case of adenocarcinoma of the thymus]

We report an adenocarcinoma of the thymus in a 39-year-old male. The patient presented with chest pain, and the chest X-ray film and chest CT showed an abnormal mass in the mediastinum. A preoperative clinical diagnosis of invasive thymoma was suspected. The tumor was resected along with the pleura and pericardium. The pathological findings were compatible with those of adenocarcinoma of the thymus. Despite a thorough examination, no primary tumor could be found. An adenocarcinoma of the thymus is rare and to the authors knowledge there are few previous reports in the literature.

Cloning of a novel rat gene, DB83, that encodes a putative membrane protein

Using a partial cDNA sequence and a 5'-RACE technique, we isolated a novel cDNA from rat liver referred to as DB83. DB83 had four hydrophobic trans-membrane domains and one N-myristoylation site as well as multiple possible phosphorylation sites. The db83 gene was highly expressed in the liver and significantly in brain, lungs and kidneys. We suggest that DB83 is a tissue-specific putative membrane protein. p6

[Risk factors and prevention of acute coronary syndrome]

Acute coronary syndromes (ACS) such as unstable angina, myocardial infarction, or sudden ischemic death evolve from coronary thrombosis consequence of atherosclerotic plaque disruption. Plaque stabilization is an important therapeutic strategy in the prevention of ACS. Coronary risk factors include age, male sex, cigarette smoking, hypertension, dislipidemia, diabetes mellitus, insulin resistance and/or hyper insulinemia, obesity, sedentary lifestyle, stress, and the morning surge of sympathetic activity. New risk factors are emerging such as high homocystein, inflammation, and some kinds of infection. Control of blood pressure and cholesterol clearly reduce the risk of coronary events and mortality although the effects of antihypertensive therapy have been less than expected. The benefits of smoking cessation, moderate alcohol consumption, low-dose aspirin prophylaxis, estrogen-replacement therapy in postmenoposal women have also been shown.

Gene expression in hepatomas

Gene expression changes in accordance with cell growth, differentiation and carcinogenesis. To elucidate the molecular mechanisms for hepatocarcinogenesis as well as maintenance of normal hepatocytes, it is important to identify the genes that have altered expression with carcinogenesis. We established a new and efficient cDNA subtraction method via two cDNA populations. By using this method along with rat hepatomas made by the Solt-Farber protocol, we identified a number of genes, some of which are activated in hepatocellular carcinoma (HCC). These genes include ones which code for a transcription factor and a metabolic enzyme. One particular gene can be used as a tumour marker. Our method is beneficial for the isolation of a wide range of HCC-related genes in rats which, in turn, enables easy identification of their human counterparts. In this review, we describe details of our method and the isolated genes. We also briefly describe transcription factors in the liver.

Crystal structure of a GCN5-related N-acetyltransferase: Serratia marcescens aminoglycoside 3-N-acetyltransferase

The X-ray structure of a canonical GCN5-related N-acetyltransferase (GNAT), Serratia marcescens aminoglycoside 3-N-acetyltransferase, bound to coenzyme A (CoA) has been determined at 2.3 A resolution. The single domain alpha/beta protein resembles a cupped right hand wrapped around a cylinder and consists of a highly curved, six-stranded beta sheet of mixed polarity that is sandwiched between four alpha helices. The structure includes all four conserved GNAT motifs (C, D, A, and B) and represents the catalytic core of this large enzyme superfamily. Acetyl CoA recognition is mediated by a betaalpha structure derived from GNAT motif A, which presents an invariant Arg/Gln-X-X-Gly-X-Gly/Ala segment for hydrogen bonding with the cofactor. Motif B contributes acidic residues to the binding site for the positively charged antibiotic substrate.

Shear stress gradient over endothelial cells in a curved microchannel system

Our purpose was to test a scale model of the microcirculation by measuring the shear forces to which endothelial cells were exposed, and comparing this to computer simulations. In vitro experiments were performed to measure the 2-dimensional projected velocity profile along endothelial cell lined microchannels (D-shaped, 10-30 microns radius, n = 15), or in microchannels without endothelial cells (n = 18). Microchannels were perfused with fluorescently labeled microspheres (0.5 micron dia., < 1%) suspended in cell culture media. The velocity of individual microspheres was obtained off-line (videorecording), using an interactive software program; velocity was determined as the distance traveled in one video field (1/60 s). Mass balance was verified in the microchannels by comparing the microsphere velocities to the perfusion pump rate. In confluent endothelial cell lined microchannels, a velocity profile was obtained as microspheres passed an endothelial cell nucleus (identified by fluorescent dye), and again, for a paired region 100 microns away without nuclei (cytoplasm region). The velocity profile was significantly shifted and sharpened by the endothelial cell nucleus, as anticipated. Over the nucleus, data are consistent with a normal sized nucleus extending into the lumen, further confirming that this scale model can be used to determine the wall shear stress to which endothelial cells are exposed. Using the experimental bulk phase fluid parameters as boundary conditions, we used computational fluid dynamics (CFD) to predict the expected wall shear stress gradient along an endothelial cell lined D-shaped tube. The wall shear stress gradient over the nucleus was 2-fold greater in the radial versus axial directions, and was sensitive to lateral versus midline positioned nuclei.

Restoration of the glucocorticoid receptor function by the phosphodiester compound of vitamins C and E, EPC-K1 (L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-benzopyran-6-yl hydrogen phosphate] potassium salt), via a redox-dependent mechanism

We examined the effect of the novel antioxidant EPC-K1 (L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H -1-benzopyran-6-yl hydrogen phosphate] potassium salt) on glucocorticoid receptor function. We used cloned CHOpMTGR cells in which human glucocorticoid receptor cDNA was stably transfected and the glucocorticoid receptor was expressed at high levels. We recently suggested that glucocorticoid-mediated gene expression is modulated via the cellular redox state [Makino et al., J Clin Invest 98: 2469-2477, 1996]. In the present study, this issue was clearly evidenced by the finding that cellular treatment with H2O2 decreased the ligand binding and transcriptional activity of the glucocorticoid receptor, and we showed that these inhibitory effects of H2O2 were effectively titrated by the addition of EPC-K1. Moreover, DNA-binding activity of the bacterially expressed DNA-binding domain of the glucocorticoid receptor was repressed by the thiol-oxidizing reagent diamide; EPC-K1 also counteracted this repressive effect of diamide. Thus, the redox state was indicated to influence glucocorticoid receptor function at various steps, and EPC-K1 may be useful in restoring the cellular glucocorticoid-responsiveness in oxidative conditions.

A case of congenital familial short femur diagnosed prenatally

A fetus at 24 weeks of gestation had been suspected of congenital familial bilateral short femur. The Japanese mother, 41 years old and 139 cm in height presented with bilateral short femur herself. The mother had two affected aunts and one affected daughter in her family history. Ultrasound examination was given to the mother for the first time at 24 weeks of gestation and it revealed bilateral short femur of 30 mm in length on the right and 31 mm on the left femur of the fetus. Other examinations were entirely normal and the pregnancy resulted in a full-term spontaneous vaginal delivery to a male baby. Birth weight was 2,790 g and the 1 and 5 min Apgar scores were at 8 and 10. Diagnosis was confirmed by skeletal radiographs.

[Subjective well-being and self acceptance]

The purpose of the present study was to examine the relationship between subjective well-being and self acceptance, and to design a happiness self-writing program to increase self acceptance and subjective well-being of adolescents. In study 1, we examined the relationship between social interaction and self acceptance. In study 2, we created a happiness self-writing program in cognitive behavioral approach, and examined whether the program promoted self acceptance and subjective well-being. Results indicated that acceptance of self-openness, an aspect of self acceptance, was related to subjective well-being. The happiness self-writing program increased subjective well-being, but it was not found to have increased self acceptance. It was discussed why the program could promote subjective well-being, but not self acceptance.

A dynein light chain of sea urchin sperm flagella is a homolog of mouse Tctex 1, which is encoded by a gene of the t complex sterility locus

The outer-arm dynein of sea urchin sperm flagella contains six light chains with molecular masses of 23.2, 20.8, 12.3, 11.5, 10.4 and 9. 3kDa. We have cloned a cDNA for the 12.3kDa polypeptide (light chain 3) and found that this protein is highly homologous to mouse Tctex1, a protein encoded by a member of the multigene family in the t complex region that is involved in male sterility and the development of the germ cells. Tctex1 has recently been shown to be homologous to a light chain of cytoplasmic dynein. Therefore, the cytoplasmic dynein light chain has been implicated in the mechanism for the transmission ratio distortion (meiotic drive) that is characteristic of t haplotypes in mice. Our present finding, however, indicates that axonemal light chain 3 must be considered equally important.

TIP49, homologous to the bacterial DNA helicase RuvB, acts as an autoantigen in human

TATA-binding protein (TBP), a central component for transcriptional regulation, forms complexes with various transcription regulators. We have isolated a novel human cDNA for a 49-kD TBP-interacting protein (TIP49). The human TIP49 was highly homologous to bacterial RuvB proteins that function as a DNA helicase to promote branch migration of the Holliday junction. Immunofluorescence analysis using anti-TIP49 antibody showed a typical dot-shaped nuclear staining pattern, suggesting that TIP49 is included in a macromolecular structure in the nucleus and may participate in nuclear events such as transcription and recombination. Moreover, glycerol gradient analysis demonstrated that TIP49 is present in a macromolecular complex in nuclear extracts. Interestingly, we detected a high level of autoantibodies against TIP49 in sera of patients with autoimmune diseases such as polymyositis/dermatomyositis and autoimmune hepatitis. This indicates that the autoantibody against this protein is a new marker for particular connective tissue diseases. These findings provide further evidence that the macromolecular structures described above are targeted by an autoimmune mechanism. The anti-TIP49 antibodies can be useful probes for clinical diagnosis and for investigation of intranuclear structure.

Enhanced expression of a new class of liver-enriched b-Zip transcription factors, hepatocarcinogenesis-related transcription factor, in hepatocellular carcinomas of rats and humans

Rat hepatocarcinogenesis-related transcription factor (HTF) was earlier identified as a b-Zip transcription factor in chemically induced rat hepatocellular carcinoma (HCC) by cDNA subtraction, and its structure was found to be different from that of the conventional b-Zip proteins. We investigated htf gene expression in rat tissues by Northern analysis and found that HTF expression was ubiquitous but was enriched in the liver. HTF expression increased concomitantly with HCC development in rat liver, and the HTF-containing DNA-binding factor also increased. Stimulated HTF gene expression also was observed in rat regenerating livers. From the results of various assays, X-box-binding protein 1/Tax-response element binding factor 5 was suggested to be a human homologue of rat HTF. In humans, HTF gene expression was also abundant in the liver and was revealed to be specifically stimulated in HCCs, but not in other types of cancers. To our knowledge, HTF is the first example of a liver-enriched transcription factor that exhibits HCC-associated gene expression. Injection of anti-HTF antibody decreased the growth rate of cultured HCC cells. Consequently, HTF is thought to participate in hepatocyte growth as well as in hepatocarcinogenesis.

Direct involvement of the Y-box binding protein YB-1 in genotoxic stress-induced activation of the human multidrug resistance 1 gene

The human multidrug resistance 1 (MDR1) gene encoding P-glycoprotein is often overexpressed in various human tumors after chemotherapy. During treatment with various chemotherapeutic agents, the MDR1 gene is activated at the transcriptional level and/or amplified, resulting in overexpression. Our previous studies demonstrated that an inverted CCAAT box (Y-box) might be a critical cis-regulatory element regulating UV or drug-induced MDR1 gene expression. We have now established various cell lines from human head and neck cancer KB cells which were stably transfected with the chloramphenicol acetyltransferase (CAT) reporter gene driven by various MDR1 promoter deletion constructs. Transient transfection of antisense YB-1 expression constructs resulted in a decrease of both YB-1 protein levels and DNA binding activity to the inverted CCAAT box, as determined by Western blot and gel mobility shift assays. The limited expression and binding activity due to expression of antisense YB-1 constructs were also observed when cells were treated with UV. CAT activity of constructs containing the Y-box was enhanced after treatment with UV irradiation as well as genotoxic agents such as cisplatin and etoposide. Moreover, this activation was reduced by 50-80% by transfection of antisense YB-1 expression constructs. In contrast, transfection of antisense YB-1 expression constructs had no effect on CAT activity driven by MDR1 promoter constructs not containing the Y-box. These data indicate that YB-1 is directly involved in MDR1 gene activation in response to genotoxic stress.

Inhibition of NF-kappaB-dependent transcription of human immunodeficiency virus 1 promoter by a phosphodiester compound of vitamin C and vitamin E, EPC-K1

We investigated the effect of EPC-K1, which is a phosphodiester compound of vitamin E and vitamin C, on NF-kappaB activity in human cultured astrocytoma cells T98G. In TNFalpha-stimulated T98G cells, treatment with EPC-K1 inhibited both DNA binding activity and transactivation of NF-kappaB in a dose-dependent manner, and the suppressive effect of EPC-K1 was stronger than either that of vitamin E or vitamin C. Moreover, we showed that in TNFalpha-stimulated T98G cells treatment with EPC-K1 repressed NF-kappaB-dependent activation of the human immunodeficiency virus 1 promoter. In contrast, TNFalpha-induced activation of the human immunodeficiency virus 1 promoter was not completely inhibited by either treatment with vitamin E or vitamin C. We, thus, suggest that EPC-K1 is considered to be one of the inhibitory agents of NF-kappaB.

Novel endogenous 1,2,3,4-tetrahydroisoquinoline derivatives: uptake by dopamine transporter and activity to induce parkinsonism

We designed as candidate metabolites and synthesized two 1-benzyl-1,2,3,4-tetrahydroisoquinoline derivatives containing a dopamine moiety: 1-(3',4'-dihydroxybenzyl)-1,2,3,4-tetrahydroisoquinoline (3',4'DHBnTIQ) and 1-benzyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (6,7DHBnTIQ). Both were detected in mouse brain as endogenous amines by gas chromatography/mass spectrometry. 3',4'DHBnTIQ induced parkinsonism in mice when chronically administered intraperitoneally, whereas 6,7DHBnTIQ did not despite the structural similarity of the two compounds. This difference may be related to cellular uptake: In rat striatal synaptosomes, these compounds were intracellularly transported by the dopamine transporter with Km values of 6.14 and 7.82 microM and Vmax values of 214.3 and 112.2 pmol/min/mg of protein, respectively. Thus, endogenous 3',4'DHBnTIQ may be actively transported into dopaminergic neurons and accumulated there, contributing at least in part to the induction of idiopathic Parkinson's disease.

Primary non-Hodgkin's lymphoma of the lacrimal sac: a case report and a review of the literature

BACKGROUND

Primary non-Hodgkin's lymphoma of the lacrimal sac is extremely rare, with most reported cases representing secondary involvement of a systemic malignancy.

METHODS

The clinical record of a 70-year-old female who presented with epiphora and swelling of the lacrimal sac area is described. A review of the literature of patients with primary lacrimal sac lymphoma also is presented.

RESULTS

Computed tomography demonstrated a lacrimal sac mass involving the nasolacrimal canal. Histopathologic examination of a biopsy specimen revealed a diffuse large cell lymphoma. Using immunohistologic staining, the tumor was a B-cell type, similar to those described in the literature. The patient was treated with 50 gray of irradiation and chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone. The patient remained free of lymphoma 26 months after initial treatment. An ocular examination was unremarkable except for epiphora.

CONCLUSIONS

Radiotherapy and/or chemotherapy can treat localized lymphoma of the lacrimal sac successfully.

The role of N-terminal glycosylation in the human oxytocin receptor

The human oxytocin receptor includes three N-glycosylation sites in its extracellular N-terminal domain. We have established permanent cell-lines in which the gene for the human oxytocin receptor (OTR) has been introduced into HeLa cells. These cells differ by the disruption of one or more of the N-terminal N-glycosylation sites by site-directed mutagenesis of the transfected OTR constructs. The binding capacity of each transfectant, calculated per mg membrane protein, was 5-17 times higher than that of human term myometrium. The pharmacological characteristics of the transfected wild-type OTR are very similar to those of native myometrial OTR. The mutation of N-glycosylation sites (Asn-X-Ser/Thr), namely OTR-D8N15N26 (Asn8-->Asp8), -N8D15N26(Asn15-->Asp15), -N8D15D26(Asn15-->Asp15, Asn26-->Asp26) and -D8N15D26 (Asn8-->Asp8, Asn26-->Asp26) appear to affect neither their dissociation constant (Kd), nor the affinities for various oxytocin related ligands. As a high level of cell surface binding was retained for each clone, receptor trafficking appears to be normal. This suggests that the full glycosylation of OTR observed in vivo is not essential for its activity. These results indicate also that these cell lines may prove very useful for pharmacological screening of oxytocin related products.

Functional modulation of estrogen receptor by redox state with reference to thioredoxin as a mediator

Redox regulation of transcription factors has recently been demonstrated for AP-1, NF-kappaB, Sp-1 and glucocorticoid receptor in vitro and in vivo. The redox state in estrogen-dependent cells possibly influences the function of estrogen receptor (ER), and the regulation of the function of ER is essential for understanding of growth and differentiation of these cells, as well as promotion and progression of estrogen-associated cancer. In this paper, we first analyzed the effects of redox state on transcriptional activity of ER in terms of pS2 mRNA expression and transfection of ERE-CAT plasmid in human breast cancer cells. Addition of H2O2 at low concentrations lowered levels of pS2 mRNA and also down-regulated ERE-CAT activity, which was recovered by transfection of thioredoxin (TRX) expression vector. Next, the transfection of antisense TRX plasmid diminished ERE-CAT activity, and the activity was recovered by co-transfected sense TRX. Furthermore, specific DNA binding activity of recombinant ER was inhibited by sulfhydryl-modifying reagents and restored by the addition of recombinant TRX protein in electrophoretic mobility shift assay. These results in vitro and in vivo revealed that the transcription activity of ER is strongly influenced by its redox state, which is reversibly modulated by endogenous redox effector protein, TRX.

Enhancement of in vivo anti-influenza virus activity of 5,7,4'-trihydroxy-8-methoxyflavone by drug delivery system using hydroxypropyl cellulose

Enhancement of in vivo antiviral activity of 5,7,4'-trihydroxy-8-methoxyflavone (F36) against H3N2 subtype of influenza A virus by drug delivery system (DDS) with hydroxypropyl cellulose (HPC) was studied. Although in the absence of HPC F36 (0.5 mg/kg) showed no antiviral activity against mouse-adapted influenza virus A/Guizhou/54/89 (H3N2) in mice, when F36 solution containing HPC was administered intranasally 5 min after the virus inoculation, proliferation of the virus in both nasal and broncho-alveolar cavities was inhibited significantly. The relationship between concentration (0.2-0.5%) and deposition ratio of HPC was studied. When 10 microliters of fluorescein isothiocyanate (FITC)-conjugated HPC solution was administered intranasally to BALB/c mice, deposition ratio of HPC at 6 h after inoculation in nasal cavity was dependent on its concentration. The deposition ratio of HPC in broncho-alveolar cavity, however, was reversely dependent on its concentration. Anti-influenza virus activity of F36 in nasal and broncho-alveolar cavities was dependent both on the concentration and deposition ratio of HPC. HPC was most effective at 0.5% in nasal cavity and at 0.3% in broncho-alveolar cavity. These results indicate that DDS with HPC enhances the anti-influenza virus activity of F36 in vivo.

SUG1, a component of the 26 S proteasome, is an ATPase stimulated by specific RNAs

SUG1 is an integral component of the 26 S proteasome. Belonging to a novel putative ATPase family, it shares four conserved motifs characteristic of ATP-dependent DNA/RNA helicases. Recombinant rat SUG1 (rSUG1) produced in Escherichia coli was highly purified and characterized in terms of its biochemical properties. The rSUG1 exhibited a Mg2+-dependent ATPase activity. The Km for ATP and Vmax of rSUG1 were 35 microM and 7 pmol of ATP/min/microg of protein, respectively. Both ATPase activity to release [32P]monophosphate and [32P]ATP-labeling activity were coordinately affected by cold ATP severely, GTP and UTP moderately, and CTP little. Interestingly, the rSUG1 ATPase activity was stimulated by poly(U) and poly(C), but not by poly(A), poly(G), or by any forms of DNAs tested. A UV cross-linking assay also indicated poly(U)- and poly(C)-stimulated labeling of rSUG1 with [alpha-32P]ATP. Moreover, the ATPase activity was facilitated by cellular poly(A)+ RNA, but not by poly(A)- RNA. RNA transcribed in vitro from cDNA encoding a b-Zip protein could stimulate the ATPase activity. This is the first report to demonstrate a specific RNA requirement for ATPase with respect to the proteasomal ATPases. Our present work suggests that SUG1 can specifically interact with protein-coding RNA (mRNA) and play some roles in mRNA metabolism.