NG-nitro-L-[3H]arginine binding properties of neuronal nitric oxide synthase in rat brain

NG-Nitro-L-arginine (L-NNA), a derivative of L-arginine (L-Arg), is known as a pseudosubstrate and inhibitor for nitric oxide synthase (NOS). To clarify the regulatory mechanism of substrate-binding domain in neuronal NOS (nNOS), we examined the characteristics of NG-nitro-L-[3H]Arg (L-[3H]NNA) binding using the cytosolic fraction and purified nNOS from the rat cerebellum, in comparison with L-[14C]citrulline formation from L-[14C]Arg. The L-[3H]NNA binding was inhibited by L-NNA > NG-methyl-L-Arg > diphenyleneiodonium > L-Arg, but was not inhibited by L-citrulline and D-Arg. Thus, L-NNA seems to bind the substrate-binding domain in the nNOS with high affinity rather than L-Arg. Even in the absence of NADPH, tetrahydrobiopterin (BH4) and Ca2+, the L-[3H]NNA binding activity was observed in the cerebellar cytosol, although L-[14C]citrulline could not be produced from L-[14C]Arg. L-[3H]NNA binding was increased by BH4 alone and was markedly enhanced by NADPH plus BH4 (NADPH/BH4), but not by Ca2+/CaM. In contrast, L-[14C]citrulline was formed only in the presence of NADPH/BH4 and Ca2+. Similar results were obtained in purified nNOS. These results suggest that L-[3H]NNA seems to bind the substrate-binding domain in the nNOS but the binding affinity of L-Arg was lower than the affinity of L-NNA. Although the substrate binding is necessary to BH4 and NADPH, Ca2+/CaM are further necessary for the formation of NO and L-citrulline.

Possible involvement of ADP-ribosylation of particular enzymes in cell death induced by nitric oxide-donors in human neuroblastoma cells

To clarify the mechanisms of nitric oxide (NO)-induced cell death in human neuronal cells, we examined effects of NO donors such as sodium nitroprusside (SNP) and S-nitroso-N-acetylpenicillamine (SNAP) on activities of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and poly(ADP-ribose) polymerase (PARP) in human neuroblastoma cell line, SH-SY5Y. SNP-induced [32P]ADP-ribosylation of 113-kDa and 37-kDa proteins in SH-SY5Y cells. Treatment with PARP inhibitors such as 3-aminobenzamide and 1,5-isoquinolinediol partially prevented SNAP-induced cell death of SH-SY5Y. In purified GAPDH (37-kDa protein), SNP- and SNAP-induced enhancement of [32P]ADP-ribosylation, and inhibition of GAPDH activity. These results suggest that NO-induced cell death in human neuroblastoma SH-SY5Y cells possibly involves in covalent modifications such as ADP-ribosylation in PARP and GAPDH.

Cloning of the cDNA encoding rat Presenilin-1

We isolated rat presenilin-1 (PS-1; also called S182 previously) cDNA from total brain RNA by using a reverse transcription-polymerase chain reaction (RT-PCR) technique with primers homologous to the conserved sequences of human and mouse PS-1. Rat PS-1 cDNA encoded 468 amino acids (aa) and the deduced aa sequence was highly homologous to those of the human (88.4%) and mouse (92.7%). Northern blot analysis of the rat PS-1 cDNA revealed two mRNA species in rat neurotypic pheochromocytoma and glioma cell lines (PC-12 and C6, respectively) that migrated at rates corresponding to approximately 3.0 and 7.5 kb.

Characterization of hepatic-specific regulatory elements in the promoter region of the human cholesterol 7alpha-hydroxylase gene

Cholesterol 7alpha-hydroxylase is the rate-limiting enzyme in the degradation of cholesterol to bile salts and plays a central role in regulating cholesterol homeostasis. The mechanisms involved in the transcriptional control of the human gene are largely unknown. HepG2 cells represent an appropriate model system for the study of the regulation of the gene. To identify liver-specific DNA sequences in the promoter of the human CYP7 gene, we first examined the DNase I hypersensitivity in the 5'-region of the gene. An area of hypersensitivity was observed in the region from -50 to -200 of the human gene in nuclei from transcriptionally active HepG2 cells, but was absent in transcriptionally inactive HeLa cell nuclei or in free DNA. Various 5'-promoter deletion constructs were made and transfected into HepG2 cells. About 300 base pairs of upstream sequence are required for high level promoter activity of the human CYP7 gene in HepG2 cells. DNase I footprinting of the hypersensitive region revealed nine protected sequences. Gel retardation experiments demonstrated binding of HNF-3 to the segment from -80 to -70 and of hepatocyte nuclear factor HNF-4 (and ARP-1) to the segment from -148 to -127 of the human CYP7 promoter. Deletion of either of these sites depressed promoter activity in HepG2 cells. A third region from -313 to -285 is bound by members of the HNF-3 family and acts as an enhancer. Additionally, the segment from -197 to -173 binds a negative regulatory protein that is present in Chinese hamster ovary cell extracts and in HepG2 cell extracts. These experiments define the key control elements responsible for basal transcription of the human CYP7 gene in HepG2 cells.

Detection of cyclin D1 (bcl-1, PRAD1) overexpression by a simple competitive reverse transcription-polymerase chain reaction assay in t(11;14)(q13;q32)-bearing B-cell malignancies and/or mantle cell lymphoma

In mantle cell lymphoma, the t(11;14)(q13;q32) and its molecular counterpart, bcl-1 rearrangement, are consistent features and lead to cyclin D1 (bcl-1, PRAD1) proto-oncogene overexpression. In order to detect cyclin D1 overexpression, we developed a simple assay involving a reverse transcription followed by competitive polymerase chain reaction (PCR). A single upstream primer was derived from a homologous region between cyclin D1 and the other D-type cyclins, cyclins D2 and D3, while three downstream primers were specific to their respective D-type cyclins. Because the upstream primer was shared in PCR amplification of the three sequences, each PCR product served as a competitor and the quantification of the target was made by comparison of the intensity of the three products. With this assay we analyzed 45 hematopoietic cell lines and 40 clinical specimens. Cyclin D1 was rarely expressed in lymphoid cell lines except in t(11;14)(q13;q32)-bearing B-cell malignancies and/or mantle cell lymphoma, which expressed cyclin D1 predominantly. In myeloid cell lines, the levels of cyclin D1 expression varied and never exceeded the sum of cyclin D2 and D3 levels. Cyclin D3 was ubiquitously expressed while cyclins D1 and D2 were differentially used. The observations suggest that human cyclin D3 may play a fundamental role in hematopoiesis and that cyclins D1 and D2 may have different lineage- or differentiation-dependent functions. With this assay, small aliquots of clinical specimens such as 100 microL peripheral blood were enough to detect cyclin D1 overexpression without a well-controlled standard. The technique was validated as highly comparable with Northern analysis. This rapid and reliable detection of cyclin D1 overexpression may have practical clinical utility in the analysis and management of B-cell malignancies.

Studies on the response of nitroglycerin oral spray compared with sublingual tablets for angina pectoris patients with dry mouth. A multicenter trial

Nitroglycerin (glyceryl trinitrate, CAS 55-63-0, NTG) administered with an oral spray may be more effective in relieving anginal pain than sublingual tablets especially when the patient's mouth is dry. In this study, the effect of a NTG oral spray (Myocor Spray) on exercise-induced angina was compared with that of a sublingual tablet in relation to the oral dryness. In 17 patients with effort angina, graded bicycle exercise was performed twice at an interval of one week. Exercise was discontinued upon the onset of moderate anginal pain. Immediately after exercise, the oral dryness was evaluated by touching the tip of the tongue with a blotting paper for a moment. Then, 0.3 mg of NTG was administered by either a squirt of spray or a sublingual tablet in a randomized crossover fashion. Exercise results were reproducible between two exercise tests. According to the extent of the wet area of the blotting paper, the subjects were divided into two groups. In 7 patients of the wet group, the remission times of chest pain and ST segment depression were not significantly different by the formulation of NTG. In 10 patients of the dry group, however, both chest pain and ST depression more rapidly recovered with use of the oral spray (p < 0.05 and p < 0.05, respectively). These results strongly suggest that the NTG oral spray is superior to the sublingual tablet in relieving anginal attacks, when the oral wetness is decreased.

Identification of cytochrome P450 isoforms involved in citalopram N-demethylation by human liver microsomes

Studies to assess the enzyme kinetic behavior and to identify the cytochrome P450 (CYP) isoform(s) involved in the major metabolic pathway (N-demethylation) for citalopram (CIT), a selective serotonin reuptake inhibitor, were performed using human liver microsomes and cDNA-expressed human cytochrome P450 isoforms. The N-demethylation activities showed significant correlations with the alpha- and 4-hydroxylation activities of triazolam (r(s) = 0.818 and 0.851, respectively; P < .01) in 10 different human liver microsomes. Anti-CYP3A antibodies and ketoconazole strongly inhibited CIT N-demethylation. In addition, there was a significant correlation between CIT N-demethylation and (S)-mephenytoin 4'-hydroxylation (r(s) = 0.773, P < .05), although little inhibition was observed in the presence of anti-CYP2C antibodies or (S)-mephenytoin. cDNA-expressed CYP3A4 and CYP2C19 catalyzed CIT N-demethylation, whereas no appreciable activities were observed for CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6 and CYP2E1. The percentage contributions of CYP3A4 and CYP2C19 to the overall N-demethylation of CIT in human liver microsomes were estimated using a relative activity factor; respective values of 70% and 7% were calculated for microsomes obtained from livers from putative extensive metabolizers for (S)-mephenytoin 4'-hydroxylation. These results suggest that CYP3A4 is the major isoenzyme and CYP2C19 is the minor form involved in the major metabolic pathway for CIT in human liver microsomes.

Cloning, functional expression and tissue distribution of rabbit alpha 1d-adrenoceptor

We have cloned a cDNA encoding rabbit alpha 1d-adrenoceptor from the rabbit liver cDNA library. The deduced amino-acid sequence of this clone encodes a protein of 576 amino acids that shows strong sequence homology to previously cloned human, rat and mouse alpha 1d-adrenoceptors. The pharmacological radioligand binding properties of this clone expressed in COS-7 cells were similar to those of rat alpha 1d-adrenoceptors. Competitive RT/PCR assays revealed wide tissue distribution of the alpha 1d-adrenoceptor mRNA in rabbit, especially abundant in vas deferens, aorta, prostate and cerebral cortex.

Increase in the circulating level of hepatocyte growth factor in gastric cancer patients

We measured serum concentrations of hapatocyte growth factor (HGF) in patients with gastric cancer and compared these with the histological findings and conventional tumour markers, including CEA, CA19-9 and CA125, for evaluation of the significance of serum HGF levels as a tumour marker. The HGF levels were measured by an enzyme-linked immunosorbent assay (ELISA) system. The average levels of serum HGF in 89 healthy control subjects, 104 patients with primary gastric cancer and 15 patients with recurrent gastric cancer were 0.31 +/- 0.11 ng ml(1), 0.42 +/- 0.50 ng ml(-1) and 0.92 +/- 0.39 ng ml(-1) respectively. The average level in patients with recurrent disease was significantly higher than in healthy control subjects and in primary cancer patients (P< 0.001 and P< 0.003 respectively). Of 104 patients with primary gastric cancer, 35 (33.7%) showed an aberrant increase in the circulating level of HGF. The increased HGF levels were significantly associated with the degrees of histological tumour invasion and venous invasion. Of 15 patients with recurrent gastric cancer, 14 (93.3%) showed an aberrant increase. No correlation was found between serum HGF levels and CEA levels, CA19-9 levels and CA125 levels. However, the rate of the aberrant increase in HGF levels was significantly higher than that of any other tumour markers, including CEA, CA19-9 and CA125, in primary gastric cancer patients. In conclusion, the circulating levels of HGF were elevated in approximately one-third of patients with primary gastric cancer, particularly in those with high grades of histological tumour invasion and venous invasion, and frequently in patients with distant metastases, suggesting that HGF might play important roles in the tumour progression of gastric cancer. Furthermore, serum HGF levels may be of value as a tumour marker in patients with gastric cancer.

Cloning, functional expression and tissue distribution of rabbit alpha1a-adrenoceptor

A cDNA clone, which has an open reading frame of 1398 nucleotides encoding a 466-amino-acid peptide, has been isolated from rabbit liver cDNA library. Compared with the peptide sequence, it shows high homology to alpha1a adrenoceptors of human, bovine and rat. We expressed this clone in COS-7 and investigated the pharmacological properties, revealing similarity to those of human alpha1a adrenoceptors. Competitive RT/PCR has detected the mRNA in variety of rabbit tissues, especially abundantly in liver, vas deferens, brain, and aorta, but not in heart.

[Changes in the extent of mitral regurgitation during hemodialysis: color Doppler echocardiographic study]

The changes in the extent of mitral regurgitation (MR) during maintenance hemodialysis patients were studied in six patients with MR by color Doppler echocardiography. M-mode, two-dimensional and color Doppler echocardiography were performed before and every hour during hemodialysis. The severity of MR was evaluated by a semiquantitative grading system and maximal MR area. Hemodialysis removed 2.1 +/- 0.9/body fluid. Blood pressure and heart rate did not change systematically by hemodialysis. Left atrial, left ventricular end-diastolic and end-systolic dimensions were significantly decreased by hemodialysis (p < 0.05). Stroke volume and left ventricular wall stress were also significantly decreased (p < 0.01). MR area was significantly smaller at the end of hemodialysis compared to pre-hemodialysis (49.0 +/- 20.5 vs 171.0 +/- 49.2 mm2, p < 0.05). During hemodialysis, the extent of MR was continuously decreased. In two out of six patients, the MR jet disappeared. The extent of MR may depend on the fluid volume removed by hemodialysis because the MR area diminished more as more fluid was removed. No major disorders of the mitral complex were detected when the MR area was decreased rapidly to less than 60 mm2 in response to the removal of a small amount of fluid. The dry weight should be determined as the body weight when MR is as small as possible by color Doppler echocardiography.

Interleukin-2 (IL-2) upregulates BAG-1 gene expression through serine-rich region within IL-2 receptor beta c chain

BAG-1 is a Bci-2-binding protein which functions in protection from apoptotic cell death. Here we provide evidence for interleukin-2 (IL-2)-mediated upregulation of BAG-1 expression. In hematopoietic cell line BAF-B03 F7 cells, gene transfer mediated expression of the IL-2R beta c chain is sufficient to confer proliferation and cell survival responses to IL-2. In these IL-2R beta c-expressing cells, BAG-1 mRNA was dramatically induced by IL-2. The IL-2-mediated induction of BAG-1 expression required the activation of tyrosine kinase(s) and was sensitive to rapamycin as the induction of bcl-2 expression was. Analysis of the transfectants which express mutant IL-2R beta c chains or mutant Janus family protein tyrosine kinase Jak3 lacking the kinase domain showed that the IL-2-mediated BAG-1 gene expression required the serinerich region within the IL-2R beta c chain, but Jak3 activation was dispensable. The signaling pathway for BAG-1 gene expression thus highly resembles that for bcl-2 gene expression, strongly suggesting that their induction shares the same signaling pathway. In addition, deletion of the serine-rich region led to loss of IL-2-mediated protection from apoptotic cell death. Taken together, these studies demonstrate that the serine-rich region of the IL-2R beta c chain mediates the coordinated expression of bcl-2 and BAG-1 genes, thereby contributing to suppression of apoptosis.

Ocular hypotensive mechanism of intravitreally injected brain natriuretic peptide in rabbit

PURPOSE

To determine whether brain natriuretic peptide (BNP) affects intraocular pressure (IOP), aqueous humor dynamics, and cyclic guanosine monophosphate (cGMP) concentration in the aqueous humor of the rabbit eye.

METHODS

Twenty microliters of 10(-4) M and 10(-5) M (2 nmol, 0.2 nmol) BNP or atrial natriuretic peptide (ANP) were injected intravitreally into rabbit eyes, after which the IOP was measured using a pneumatonometer. Aqueous humor dynamics were studied at approximately 6 hours after the intravitreal injection of 2 nmol BNP. Aqueous humor flow was measured by fluorophotometry, and outflow facility was measured by the two-level constant pressure perfusion method, whereas uveoscleral outflow was measured by the fluorescein isothiocyanate-dextran perfusion method. The concentration of cGMP in the aqueous humor at 6 hours after injection of 2 or 0.2 nmol BNP also was measured by enzyme immunoassay.

RESULTS

Intravitreal administration of BNP or of ANP caused a decrease in IOP, with a maximum effect at approximately 6 hours after the injection. Total outflow facility in eyes treated with 2 nmol BNP increased by 29%, although the aqueous humor flow and uveoscleral outflow did not show significant changes. The concentration of cGMP in the aqueous humor increased significantly in BNP-treated eyes.

CONCLUSIONS

Intravitreal injection of BNP into rabbit eyes reduced IOP because of an increase in the outflow facility. Brain natriuretic peptide also increased the concentration of cGMP in the aqueous humor. It is probable that BNP-activated guanylate cyclase induced an upregulation of cGMP in the aqueous humor.

Mechanism of resistance to NO-induced neurotoxicity in cultured rat dopaminergic neurons

We previously reported that mesencephalic dopaminergic neurons are resistant to cytotoxicity induced by nitric oxide (NO). This study investigated the intracellular mechanism that protects dopaminergic neurons against NO toxicity in rat mesencephalic cultures. Peroxynitrite anion, an active metabolite of NO, caused significant cytotoxic effects against dopaminergic and nondopaminergic neurons, but NO caused cytotoxic effects restricted to nondopaminergic neurons. In addition, we studied the effects of ascorbate, an anti-oxidant, on NO-induced neurotoxicity against dopaminergic neurons and found that coadministration of ascorbate failed to affect resistance against NO-induced neurotoxicity. These findings suggest that the protecting mechanism from NO neurotoxicity in dopaminergic neurons is based on inhibition of conversion of NO to peroxynitrite anion, is independent of the NO redox state, and is possibly due to suppression of superoxide anion production. Furthermore, we investigated NO-induced neurotoxicity with or without pretreatment with sublethal doses of methylphenylpyridium ion (MPP+). Following pretreatment with 1 microM MPP+, which did not show significant cytotoxic effects against dopaminergic neurons, NO demonstrated significant cytotoxicity. Therefore, MPP+ may inhibit the protecting systems from NO neurotoxicity in dopaminergic neurons.

Regulation of IFN-alpha/beta genes: evidence for a dual function of the transcription factor complex ISGF3 in the production and action of IFN-alpha/beta

BACKGROUND

Efficient production of interferons (IFNs) in virally infected cells is an essential aspect of the host defence. The transcription factor complex ISGF3 (IFN-stimulated gene factor 3) was originally identified as a critical mediator of the IFN signal; it is formed upon IFN receptor (IFNR) stimulation and binds to ISREs (IFN-stimulated response elements) to activate IFN-inducible genes. It has recently been shown that the DNA binding component of ISGF3, p48 (ISGF3gamma) also binds to virus-inducible elements in the IFN-alpha/beta genes, suggesting a potential new role of p48 in IFN production.

RESULTS

Primary cells from mice with a targeted disruption of the p48 gene show severe defects in virus-induced IFN-alpha/beta gene expression. A similar defect was also observed in cells lacking type I IFNR or Stat1, further demonstrating the role of IFN signalling in the induction of these IFN genes. ISGF3 in fact binds to the virus-inducible elements within the IFN-alpha/beta promoters. We also provide evidence showing that these elements are additionally controlled by an unidentified factor(s) which presumably triggers the primary phase of IFN gene induction.

CONCLUSIONS

Our results demonstrate that the IFN signal transducing complex ISGF3 plays a crucial role in IFN production and suggest that ISGF3 may participate directly in the activation of IFN-alpha/beta promoters. This dual function of ISGF3 may insure the efficient operation of this cytokine system in the host defence.

In vivo induction of inducible nitric oxide synthase by microinjection with interferon-gamma and lipopolysaccharide in rat hippocampus

To clarify whether the inducible nitric oxide synthase (iNOS) protein can be induced in in vivo brain, we examined the influence of direct intrahippocampal injection with interferon-gamma (IFN-gamma) plus lipopolysaccharide (LPS) in the rat. In the area surrounding the microinjection site, NOS activity (NO2- accumulation) was enhanced 24 h after injection with IFN-gamma plus LPS. Although the level of 160-kDa nNOS protein was not changed, the 130-kDa iNOS protein was induced 12 h after the injection. On the other hand, iNOS mRNA could be detected at 6 and 12 h but not at 24 h. iNOS immunoreactivity was observed in CD11b-immunopositive microglia in close proximity to the injection site, but the immunoreactivity was not colocalized with glial fibrillary acidic protein-immunopositive astrocytes. Although CD11b-immunopositive microglia were of the ramified type even after injection with vehicle after 24 h, injection with IFN-gamma plus LPS caused numerous microglia to change to the ameboid type and to express major histocompatibility complex (MHC) class II antigens. In some of these ameboidal microglia, iNOS immunoreactivity was observed. These results suggest that intrahippocampal injection with IFN-gamma plus LPS induced iNOS mRNA after 6 h and iNOS protein after 12 h in some of the ameboidal microglia that expressed MHC class II antigens in in vivo rat brain.

Autocrine loop through cholecystokinin-B/gastrin receptors involved in growth of human leukemia cells

The cholecystokinin (CCK)-B/gastrin receptor binds two brain-gut hormones, CCK and gastrin, with high affinities. These peptides have a trophic effect on gastrointestinal cells expressing the receptor in vivo as well as in vitro. Recently, this receptor mRNA was reported to be expressed in immunocytes localized in the lamina propria of normal rat stomach mucosa. Here, we studied the receptor expression in human hematopoietic cells in order to determine whether they play a role in cell growth. The CCK-B/gastrin receptor mRNA was detectable in the polymorphonuclear (PMN) cells but not in the mononuclear cells of normal peripheral white blood cells by reverse transcription-polymerase chain reaction. The receptor transcript was, however, expressed in human leukemia cell lines (14 of 18 cell lines tested) derived from not only myeloid, but also T- and B- lymphoid lineages. The CCK-B/gastrin receptors on several leukemia cell lines were shown to be biologically active by demonstrating ligand-dependent cell proliferation in serum-deprived medium. Interestingly, a human CCK-B/gastrin receptor specific antagonist, YM022, but not its stereotype isoform, selectively inhibited the DNA synthesis of THP-1, MOLT-16, MOLT-14, and CCRF-CEM in the absence of exogenous peptide ligands. Further investigation revealed that these leukemia cell lines and normal PMN cells also expressed gastrin mRNA. These results suggest that growth of human leukemia cells is promoted by an autocrine mechanism through the CCK-B/gastrin receptors.

ONO-1078 antagonizes diarrhea-causing changes in ion transport and smooth muscle contraction induced by peptidoleukotrienes in rat and human colon in vitro

Leukotrienes play important roles in inflammatory bowel diseases. Previous studies have revealed the effects of peptidoleukotrienes on smooth muscle contraction and transmucosal ion transport, which may cause hyperactive bowel movement and the loss of electrolytes and water, i.e., diarrhea. The purpose of the present study was to evaluate the effects of the peptidoleukotrienes antagonist ONO-1078 and to assess its possible future clinical use. We examined the effects of ONO-1078 on peptidoleukotrienes-induced changes in electrolyte transport and muscle contraction in the rat colon, with the Ussing and Magnus techniques. Human biopsy specimens obtained at colonoscopy were also used for ion transport studies. Transmucosal ion transport in both rats and humans, and smooth muscle contractions in the rat colon, were induced by similar doses of peptidoleukotrienes at estimated interstitial concentrations (1 nM-100 nM). The time course of changes in short circuit current had two phases, a rapid and transient decrease and a subsequent transient increase, which seemed to be due mainly to Na+ and Cl-, respectively. Rat colon smooth muscle contracted transiently after the addition of peptidoleukotrienes. These effects of peptidoleukotrienes, which could be related to the diarrhea in inflammatory bowel diseases, were inhibited by ONO-1078. ONO-1078 is expected to be effective in clinical use against peptidoleukotrienes-related diarrhea in mild to moderate inflammatory bowel diseases.