Serine 202 regulates the nuclear translocation of constitutive active/androstane receptor.

The constitutive active receptor (CAR) in mouse primary hepatocytes undergoes okadaic acid (OA)-sensitive nuclear translocation after activation by xenobiotics such as phenobarbital (PB) and 1,4 bis[2-(3,5-dichloropyridyloxy)]benzene (TCPOBOP). We have now mimicked this TCPOBOP-dependent and OA-sensitive translocation of mouse CAR (mCAR) in HepG2 cells and have demonstrated that protein phosphatase 2A regulates this nuclear translocation. Site-directed mutagenesis analysis of various Ser and Thr residues delineated the translocation activity to Ser-202. Mutation of Ser-202 to Asp (S202D) prevented mCAR translocation into the nucleus of TCPOBOP-treated HepG2 cells. In addition, in the livers of Car-/- mice, the YFP-tagged S202D mutant did not translocate into the nucleus after PB treatment. To examine whether Ser-202 can be phosphorylated, flag-tagged wild-type mCAR or flag-tagged S202A mutant was expressed in HepG2 cells and subjected to Western blot analysis using an antibody specific to a peptide containing phospho-Ser-202. A high molecular weight phosphorylated form of CAR was detected only with the wild-type mCAR. These results are consistent with the conclusion that the dephosphorylation of Ser-202 is a required step that regulates the xenobiotic-dependent nuclear translocation of mCAR.

[Disseminated bone marrow metastases from gastric cancer: detection and monitoring the effectiveness of chemotherapy by bone marrow scintigraphy].

Disseminated bone marrow metastasis of cancer is a critical condition, frequently complicated by disseminated intravascular coagulation (DIC). A 32-year-old man with gastric cancer was diagnosed as having disseminated bone marrow metastases. Bone scintigraphy demonstrated many abnormal radionuclide accumulations in the whole body. Bone marrow aspiration revealed cancer cells. Bone marrow scintigraphy with 111In-Cl3 demonstrated central marrow failure and peripheral expansion. The remission of DIC was observed after sequential methotrexate and 5-FU therapy, then uptake of radionuclide in the central bone marrow was remarkably improved by bone marrow scan. After thirteen anti-cancer chemotherapies, recurrence of DIC was suspected because of the reduction of blood platelet count. Nevertheless, repeated bone marrow scan still demonstrated the central bone marrow clearly. The patient discharged from our hospital without the recurrence of DIC. We considered bone marrow scintigraphy is useful in the detection of disseminated bone marrow metastases of cancer and monitoring the effectiveness of chemotherapy.

Reductive ring opening of o-nitrobenzylidene acetals of monosaccharides: synthesis and photolysis of some photolabile sugars.

[figure: see text] A 6-O-o-nitrobenzyl methylglucoside and methylmannoside were synthesized by reacting 4,6-O-o-nitrobenzylidene acetals with triethylsilane and boron trifluoride etherate. A 2,6-di-O-o-nitrobenzyl and a 3,6-di-O-o-nitrobenzyl methylmannoside were obtained from a 2,3:4,6-di-O-o-nitrobenzylidene methylmannoside by the same method. The photolabile sugars obtained were deprotected by irradiation at 350 nm to afford methylglycosides.

Significance of clinical risk factors of cystic periventricular leukomalacia in infants with different birthweights.

UNLABELLED: Fifteen appropriate-for-date premature low-birthweight infants with cystic periventricular leukomalacia (PVL) were studied. The infants were stratified into three birthweight groups: less than 1000 g, 1000 g and greater but less than 1500 g, and 1500 g or greater. Reported and new risk factors for PVL were compared with control patients for all patients and each birthweight group. Hypocarbia was significantly related to cystic PVL, especially in infants with birthweight 1000 g or greater (p < 0.03). Sensitivity to hypocarbia might be decreased in infants with birthweight less than 1000 g due to therapy or prematurity. In the group with birthweight less than 1000 g, the proportion of cystic PVL infants on continuous intra-arterial blood-pressure monitoring tended to be lower than the controls, with an almost significant difference (p = 0.05). The duration of tocolysis was significantly longer in the cystic PVL infants than in the controls when the birthweight was greater than 1500 g (p < 0.04). For some risk factors, a significant difference or a tendency of difference was demonstrated only after stratifying the birthweight. For others, the difference became insignificant after stratification. Assessing risk factors after stratifying by birthweight or degree of prematurity is therefore useful. CONCLUSION: The results suggest that hypocarbia should be avoided to prevent cystic PVL, especially in infants with birthweight of 1000 g or greater, continuous intra-arterial blood-pressure monitoring may be important in infants with birthweight less than 1000 g, and fetal status should be monitored carefully when the duration of tocolysis is prolonged, especially in infants with birthweight of 1500 g or more.

The phenobarbital response enhancer module in the human bilirubin UDP-glucuronosyltransferase UGT1A1 gene and regulation by the nuclear receptor CAR.

The UDP-glucuronosyltransferase, UGT1A1, is the critical enzyme responsible for detoxification of the potentially neurotoxic bilirubin by conjugating it with glucuronic acid. For decades, phenobarbital (PB) treatment for hyperbilirubinemia has been known to increase expression of the UGT1A1 gene in liver. We have now delineated the PB response activity to a 290-bp distal enhancer sequence (-3483/-3194) of the UGT1A1 gene. The enhancer contains 3 putative nuclear receptor motifs, and it was activated by the nuclear orphan receptor, human constitutive active receptor (hCAR), in cotransfected HepG2 cells. Bacterially expressed hCAR, acting as a heterodimer with in vitro-translated retinoid X receptor (RXRalpha), only bound to 1 of the 3 NR motifs, named gtNR1 in a gel-shift assay. Consistently, mutations of the gtNR1 site significantly decreased the activation by hCAR of the 290-bp DNA in transfection assays. Moreover, the 290-bp DNA was effectively activated in mouse primary hepatocytes in response to PB, offering an excellent clinical test for the examination of the responsiveness of the UGT1A1 to PB in the human population, particularly individuals with hyperbilirubinemia.

Mechanism of induction of cytochrome p450 enzymes by the proestrogenic endocrine disruptor pesticide-methoxychlor: interactions of methoxychlor metabolites with the constitutive androstane receptor system.

Methoxychlor, a structural analog of the DDT pesticide, was previously shown to induce rat hepatic CYP2B and -3A mRNAs and the corresponding proteins [J Biochem Mol Toxicol 1998;12:315-323], Additionally, methoxychlor was found to activate the constitutive androstane receptor (CAR) system and induce CYP2B6 (J Biol Chem 1999;274:6043-6046), suggesting a mechanism for methoxychlor-mediated cytochrome P450 (P450) 2B induction. However, it has not been established whether CAR activation and P450 induction was due to methoxychlor per se and/or due to its metabolites. Also, a possible link between the estrogenic potency of methoxychlor metabolites and CAR activation or P450 induction was not investigated. The current study explores the ability of methoxychlor and its metabolites to activate CAR and whether their potency of CAR activation correlates with their respective estrogenicity. Methoxychlor and its metabolites [mono-OH-M [1,1,1-trichloro-2 (4-hydroxyphenyl)-2'-(4-methoxyphenyl)ethane]; bis-OH-M [1,1,1-trichloro-2,2'-bis(4-hydroxyphenyl)ethane]; ring-OH-M [1,1,1-trichloro-2(4-methoxyphenyl)-2'-(3-hydroxy-4-methoxyphenyl)ethane]; and tris-OH-M [1,1,1-trichloro-2(4-hydroxyphenyl)-2'-(3,4-dihydroxyphenyl)ethane]] were found to be potent activators of CAR. Dose response curves indicated that tris-OH-M is a more potent CAR activator than methoxychlor, mono-OH-M, and bis-OH-M. Since tris-OH-M is a much weaker estrogen receptor-alpha agonist than mono-OH-M and bis-OH-M, it seems that estrogenicity is not a significant factor in CAR activation. These findings indicate that alteration of methoxychlor-benzene rings, i.e., generation of phenolic constituents, does not appreciably alter CAR activation and suggest that a common structural motif in the methoxychlor class of compounds controls CAR activation. Studies are needed to identify the structural motif necessary for CAR activation and CYP2B induction.

The peptide near the C terminus regulates receptor CAR nuclear translocation induced by xenochemicals in mouse liver.

In response to phenobarbital (PB) and other PB-type inducers, the nuclear receptor CAR translocates to the mouse liver nucleus (T. Kawamoto et al., Mol. Cell. Biol. 19:6318-6322, 1999). To define the translocation mechanism, fluorescent protein-tagged human CAR (hCAR) was expressed in the mouse livers using the in situ DNA injection and gene delivery systems. As in the wild-type hCAR, the truncated receptor lacking the C-terminal 10 residues (i.e., AF2 domain) translocated to the nucleus, indicating that the PB-inducible translocation is AF2 independent. Deletion of the 30 C-terminal residues abolished the receptor translocation, and subsequent site-directed mutagenesis delineated the PB-inducible translocation activity of the receptor to the peptide L313GLL316AEL319. Ala mutations of Leu313, Leu316, or Leu319 abrogated the translocation of CAR in the livers, while those of Leu312 or Leu315 did not affect the nuclear translocation. The leucine-rich peptide dictates the nuclear translocation of hCAR in response to various PB-type inducers and appears to be conserved in the mouse and rat receptors.

Phenobarbital response elements of cytochrome P450 genes and nuclear receptors.

Phenobarbital (PB) response elements are composed of various nuclear receptor (NR)-binding sites. A 51-bp distal element PB-responsive enhancer module (PBREM) conserved in the PB-inducible CYP2B genes contains two NR-binding direct repeat (DR)-4 motifs. Responding to PB exposure in liver, the NR constitutive active receptor (CAR) translocates to the nucleus, forms a dimer with the retinoid X receptor (RXR), and activates PBREM via binding to DR-4 motifs. For CYP3A genes, a common NR site [DR-3 or everted repeat (ER)-6] is present in proximal promoter regions. In addition, the distal element called the xenobiotic responsive module (XREM) is found in human CYP3A4 genes, which contain both DR-3 and ER-6 motifs. Pregnane X receptor (PXR) could bind to all of these sites and, upon PB induction, a PXR:RXR heterodimer could transactivate XREM. These response elements and NRs are functionally versatile, and capable of responding to distinct but overlapping groups of xenochemicals.

Nuclear receptor CAR as a regulatory factor for the sexually dimorphic induction of CYB2B1 gene by phenobarbital in rat livers.

The nuclear receptor constitutive active receptor (CAR) translocates into liver nuclei after phenobarbital (PB) treatment, and activates the conserved enhancer called the PB-response element module (PBREM) found in CYP2B genes. We have examined whether CAR regulates the dimorphic induction by PB of the CYP2B1 gene in Wistar Kyoto (WKY) rats. Northern blot analysis showed that PB induced CYP2B1 mRNA in male WKY rats but not female rats. An in situ injected PBREM-luciferase reporter gene was activated by PB only in the male livers. Western blot analysis revealed extremely low levels of CAR in the cytosols of female livers compared with male counterparts. CAR was accumulated in the liver nucleus of male rats in response to PB treatment, whereas the receptor was barely detectable in the liver nuclei of PB-induced females. These sexually dimorphic responses of PBREM and CAR to PB treatment were not observed with Fisher 344 rats, in which CYP2B1 mRNA was induced in both sexes. Thus, these results indicate that CAR is a regulatory factor that leads to the sexual dimorphic induction of CYP2B1 gene in WKY rats.

Phenobarbital-responsive nuclear translocation of the receptor CAR in induction of the CYP2B gene.

The constitutively active receptor (CAR) transactivates a distal enhancer called the phenobarbital (PB)-responsive enhancer module (PBREM) found in PB-inducible CYP2B genes. CAR dramatically increases its binding to PBREM in livers of PB-treated mice. We have investigated the cellular mechanism of PB-induced increase of CAR binding. Western blot analyses of mouse livers revealed an extensive nuclear accumulation of CAR following PB treatment. Nuclear contents of CAR perfectly correlate with an increase of CAR binding to PBREM. PB-elicited nuclear accumulation of CAR appears to be a general step regulating the induction of CYP2B genes, since treatments with other PB-type inducers result in the same nuclear accumulation of CAR. Both immunoprecipitation and immunohistochemistry studies show cytoplasmic localization of CAR in the livers of nontreated mice, indicating that CAR translocates into nuclei following PB treatment. Nuclear translocation of CAR also occurs in mouse primary hepatocytes but not in hepatocytes treated with the protein phosphatase inhibitor okadaic acid. Thus, the CAR-mediated transactivation of PBREM in vivo becomes PB responsive through an okadaic acid-sensitive nuclear translocation process.

Developmental action of estrogen receptor-alpha feminizes the growth hormone-Stat5b pathway and expression of Cyp2a4 and Cyp2d9 genes in mouse liver.

We have studied the roles of estrogen receptor-alpha (ERalpha) and the Stat5b form of STAT (signal transducers and activators of transcription) in sex-specific expression of Cyp2a4 (steroid 15alpha-hydroxylase) and Cyp2d9 (steroid 16alpha-hydroxylase) genes using ERalpha-deficient mice. ERalpha deficiency resulted in the repression of the female-specific Cyp2a4 and expression of the male-specific Cyp2d9 genes, respectively in females. In ERalpha-deficient males, the Cyp2d9 gene continued to be expressed. Nuclear localization of Stat5b occurs in both sexes of ERalpha-deficient mice, although it is normally observed in only wild-type males. Nuclear localization of Stat5b correlates with the repression of Cyp2a4 and expression of Cyp2d9, respectively. Because Stat5b was not detectable in liver nuclear extracts prepared from hypophysectomized ERalpha-deficient females, the regulation by ERalpha appeared to be mediated through a pituitary hormone (i.e., growth hormone). Thus, ERalpha appears to play a key role in the mechanism that inhibits nuclear localization of Stat5b in female mice, leading to feminization of a ERalpha-GH-Stat5b pathway and Cyp expression. Defaulting to this ERalpha-dependent mechanism results in localization of Stat5b to nuclei, which masculinizes the expression of Cyp genes in male mice.

Cross-Cultural Differences in Choice Behavior and Use of Decision Aids: A Comparison of Japan and the United States.

A controlled laboratory study was conducted to investigate the effect of cultural differences on decision strategy. Participants from two cultures (Japan and the United States) completed multi-attribute preferential choice tasks with and without use of computerized decision aids. The results indicate that Japanese participants were less likely to invoke compensatory decision processes, which involve conflict-confronting assessment of trade-offs among attributes. This behavior is consistent with some cultural differences described in extant literature. The results call into question the generalizability across cultures of descriptive decision theories, which come largely from the West, and suggest the need for descriptive theories that incorporate cultural factors. Copyright 1999 Academic Press.

Crystal structure of the sulfotransferase domain of human heparan sulfate N-deacetylase/ N-sulfotransferase 1.

Heparan sulfate N-deacetylase/N-sulfotransferase (HSNST) catalyzes the first and obligatory step in the biosynthesis of heparan sulfates and heparin. The crystal structure of the sulfotransferase domain (NST1) of human HSNST-1 has been determined at 2.3-A resolution in a binary complex with 3'-phosphoadenosine 5'-phosphate (PAP). NST1 is approximately spherical with an open cleft, and consists of a single alpha/beta fold with a central five-stranded parallel beta-sheet and a three-stranded anti-parallel beta-sheet bearing an interstrand disulfide bond. The structural regions alpha1, alpha6, beta1, beta7, 5'-phosphosulfate binding loop (between beta1 and alpha1), and a random coil (between beta8 and alpha13) constitute the PAP binding site of NST1. The alpha6 and random coil (between beta2 and alpha2), which form an open cleft near the 5'-phosphate of the PAP molecule, may provide interactions for substrate binding. The conserved residue Lys-614 is in position to form a hydrogen bond with the bridge oxygen of the 5'-phosphate.

The repressed nuclear receptor CAR responds to phenobarbital in activating the human CYP2B6 gene.

The endogenous CYP2B6 gene becomes phenobarbital (PB) inducible in androstenol-treated HepG2 cells either transiently or stably transfected with a nuclear receptor CAR expression vector. The PB induction mediated by CAR is regulated by a conserved 51-base pair element called PB-responsive enhancer module (PBREM) that has now been located between -1733 and -1683 bp in the gene's 5'-flanking region. An in vitro translated CAR acting as a retinoid X receptor alpha heterodimer binds directly to the two nuclear receptor sites NR1 and NR2 within PBREM. In a stably transfected HepG2 cell line, both PBREM and NR1 are activated by PB and PB-type compounds such as chlorinated pesticides, polychlorinated biphenyls and chlorpromazine. In addition to PBREM, CAR also transactivates the steroid/rifampicin-response element of the human CYP3A4 gene in HepG2 cells. Thus, activation of the repressed nuclear receptor CAR appears to be a versatile mediator that regulates PB induction of the CYP2B and other genes.

A role of Lys614 in the sulfotransferase activity of human heparan sulfate N-deacetylase/N-sulfotransferase.

An active sulfotransferase (ST, residues 558-882) domain of the human heparan sulfate N-deacetylase/N-sulfotransferase (hHSNST) has been identified by aligning the amino acid sequence of hHSNST to that of mouse estrogen sulfotransferase (EST). The bacterially expressed ST domain transfers the 5'-sulfuryl group of 3'-phosphoadenosine-5'-phosphosulfate (PAPS) to only deacetylated heparin with an efficiency similar to that previously reported for the purified rat HSNST. Moreover, the K(m,PAPS) (2.1 microM) of the ST domain is also similar to that of the rat enzyme. Lys48 is a key residue in mEST catalysis. The residue corresponding to Lys48 is conserved in all known heparan sulfate sulfotransferases (Lys614 in the ST domain of hHSNST). Mutation of Lys614 to Ala abolishes N-sulfotransferase activity, indicating an important catalytic role of Lys614 in the ST domain. Crystals of the ST domain have been grown (orthorhombic space group P2(1)2(1)2) with diffraction to 2.5 A resolution.

The nuclear orphan receptor CAR-retinoid X receptor heterodimer activates the phenobarbital-responsive enhancer module of the CYP2B gene.

PBREM, the phenobarbital-responsive enhancer module of the cytochrome P-450 Cyp2b10 gene, contains two potential nuclear receptor binding sites, NR1 and NR2. Consistent with the finding that anti-retinoid X receptor (RXR) could supershift the NR1-nuclear protein complex, DNA affinity chromatography with NR1 oligonucleotides enriched the nuclear orphan receptor RXR from the hepatic nuclear extracts of phenobarbital-treated mice. In addition to RXR, the nuclear orphan receptor CAR was present in the same enriched fraction. In the phenobarbital-treated mice, the binding of both CAR and RXR was rapidly increased before the induction of CYP2B10 mRNA. In vitro-translated CAR bound to NR1, but only in the presence of similarly prepared RXR. PBREM was synergistically activated by transfection of CAR and RXR in HepG2 and HEK293 cells when the NR1 site was functional. A CAR-RXR heterodimer has thus been characterized as a trans-acting factor for the phenobarbital-inducible Cyp2b10 gene.

Left lobe recurrent hepatocellular carcinoma treated with lipiodol-TAE via the left internal mammary artery.

A multinodular hepatocellular carcinoma (HCC) was treated with seven transarterial interventions via the hepatic artery over a 2-year, 5-month period before the eighth angiography showed a recurrent HCC in the anterior portion of the left hepatic lobe. The left internal mammary artery (IMA) was feeding the tumor. This was successfully treated with Lipiodol-transcatheter arterial embolization using a coaxial system via a branch of the left IMA. No complications resulted from the procedure. The left IMA should be considered as a possible feeding artery to an HCC occurring in the anterior portion of the left hepatic lobe.