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A Ichikawa

Publications and source records attributed to A Ichikawa.

At least 73 records · Page 4Linked to original sources
PubMed1999

Roles of prostaglandin E receptors in mesangial cells under high-glucose conditions.

BACKGROUND: High glucose reportedly stimulates prostaglandin (PG) E2 production and DNA synthesis in mesangial cells (MCs). However, the pathophysiological significance of PGE2 in MCs has remained unclear. METHODS: The effects of prostanoids on [3H]-thymidine uptake and cAMP production in rat MCs cultured with 5.6 mM glucose, 25 mM glucose, or 5.6 mM glucose supplemented with 19.4 mM mannitol were examined. The gene expression of PGE2 receptor (EP) subtypes in MCs was analyzed with Northern blotting techniques. RESULTS: Northern blotting indicated EP1 and EP4 gene expression in MCs. EP1 agonists and PGE2 stimulated [3H]-thymidine uptake in MCs. EP1 antagonists dose dependently attenuated high-glucose-induced [3H]-thymidine uptake, which suggests EP1 involvement, by an increase in intracellular Ca2+, in DNA synthesis of MCs. On the other hand, forskolin, db-cAMP, and 11-deoxy-PGE1, an EP4/EP3/EP2 agonist, significantly decreased DNA synthesis in MCs. These inhibitory effects are thought to be mediated via EP4 as a result of an increase in cAMP synthesis. The effects via EP4 seem to be particularly important because PGE2-induced cAMP synthesis was significantly attenuated in the high-glucose group compared with the mannitol group, in which [3H]-thymidine uptake did not increase in spite of augmented PGE2 production. CONCLUSION: The increase in DNA synthesis in MCs under high-glucose conditions can be explained, at least in part, by the high-glucose-induced inhibition of cAMP production via EP4, which augments EP1 function in conjunction with the overproduction of PGE2.

1-Methyl-3-isobutylxanthine↗
PubMed1999

Posttreatment M-protein nadir level is a significant prognostic factor associated with survival in multiple myeloma. Nagoya Myeloma Cooperative Study Group.

In the present study 142 patients with myeloma (102 with IgG M-protein and 40 with IgA) treated with either VMCP (65 patients) or MMCP (77 patients) as remission induction therapy were retrospectively analyzed. Response to treatment was evaluated in terms of a more-than-50% fall of pretreatment M-protein and the posttreatment M-protein nadir. Though significantly more patients treated with MMCP achieved partial response (PR) as compared with those treated with VMCP (P=0.019) and though patients achieving PR showed a significantly longer survival than those with less responsiveness (P=0.0091), the difference in survival curves between the two treatment groups was not significant (P=0.1871). The difference in response between the treatment groups evaluated in terms of posttreatment nadir was not significant (P=0.507). Multivariate analysis identified posttreatment M-protein nadir as a significant prognostic factor associated with survival, along with 3 other factors: sex, performance status, and hemoglobin. The lack of difference between the survival curves for patients treated with the 2 regimens despite the significantly different response rates evaluated in terms of percent fall of pretreatment M-protein levels was considered to be due to the lack of a difference in the ability to induce a deep posttreatment nadir between the regimens. Posttreatment M-protein nadir is an important prognostic factor associated with survival and should be included in the evaluation of the efficacy of chemotherapy.

Aged↗
PubMed1999

[Molecular biology of prostaglandin receptor and L-histidine decarboxylase].

This review summarizes our studies on the molecular biology of prostaglandin (PG) receptors and L-histidine decarboxylase (HDC). Regarding PG receptors, we have cloned five basic PG receptors (DP, EP, FP, IP, TP) and four EP subtypes (EP1-EP4). The PG receptors are divided into three families related to signal transduction systems of the receptors; Gs-couple group (IP, DP, EP2 and EP4), Gq-couple group (TP, FP and EP1), and Gi-couple group (EP3 and its isoform). EP3 isoforms having different C-terminal peptides can couple to distinct G proteins (Gi, Gs, Gq). Tissue specific expression of EP subtype mRNAs was observed in various organs. The phenotypic changes of mice deficient in each receptor are; the abnormal labor in FP-deficient mice, the failure of febrile response in EP3-deficient mice, the abnormal closure of ductus arteriosus after birth in EP4-deficient mice, and the impaired inflammatory swelling and pain responses in IP-deficient mice. Regarding HDC, we have purified mouse HDC from mastocytoma cells, which is a dimer of 53 kDa subunit, and then cloned its cDNA. The size of a cDNA-deduced HDC is 74 kDa. In the rat mast cell line, the endogenous 74 kDa form of HDC was translated in the cytosol and then translocated to the ER, where it was post-translationally processed to the 53 kDa form. On the other hand, the cytosolic 74 kDa form was rapidly degraded by an ATP/ubiquitin-dependent proteasome system. The 74 kDa form without on N-terminal signal sequence is inserted into the ER membrane with a C-terminal segment.

Amino Acid Sequence↗
PubMed1999

[Preliminary evaluation of adjuvant chemotherapy against stage Ib or II gastric cancer].

The prognostic influence of post-operative adjuvant chemotherapy on stage I b or II gastric cancer was studied retrospectively. The immunohistochemical expressions of p53 protein and thymidine phosphorylase (TP) were also examined; the relations between these protein expressions and clinicopathological features along with the effect of adjuvant chemotherapy were also investigated. The 5-year survival rate of the patients who received adjuvant chemotherapy was 95.5%, which was better than that (89.8%) of those who did not, although the difference did not reach significance (p = 0.09). The venous invasion of tumor was slight frequently observed in p53 or TP positive cases than negative cases, respectively (p < 0.1), but no significant associations were found between the t-, n- or ly-factor, and p53 or TP expression. Moreover p53 and TP expression had no significant influence on post-operative survival. But, among the patients with p53- or TP-positive tumor, adjuvant chemotherapy conferred survival benefits, although the difference did not reach significance. The 5-year survival rate was 100% with adjuvant chemotherapy, 84.3% without chemotherapy in p53-positive patients (p = 0.137), 97.0% with adjuvant chemotherapy, and 90.8% without chemotherapy in TP-positive tumors (p = 0.326).

Administration, Oral↗
PubMed1998

Constitutively active Galpha12, Galpha13, and Galphaq induce Rho-dependent neurite retraction through different signaling pathways.

In neuronal cells, activation of a certain heterotrimeric G protein-coupled receptor causes neurite retraction and cell rounding via the small GTPase Rho. However, the specific heterotrimeric G proteins that mediate Rho-dependent neurite retraction and cell rounding have not yet been identified. Here we investigated the effects of expression of constitutively active Galpha subunits on the morphology of differentiated PC12 cells. Expression of GTPase-deficient Galpha12, Galpha13, and Galphaq, but not Galphai2, caused neurite retraction and cell rounding in differentiated PC12 cells. These morphological changes induced by Galpha12, Galpha13, and Galphaq were completely inhibited by C3 exoenzyme, which specifically ADP-ribosylates and inactivates Rho. The tyrosine kinase inhibitor tyrphostin A25 blocked the neurite retraction and cell rounding induced by Galpha13 and Galphaq. However, tyrphostin A25 failed to inhibit the Galpha12-induced neuronal morphological changes. On the other hand, inhibition of protein kinase C or elimination of extracellular Ca2+ blocked the neurite retraction and cell rounding induced by Galphaq, whereas the morphological effects of Galpha12 and Galpha13 did not require activation of protein kinase C and extracellular Ca2+. These results demonstrate that activation of Galpha12, Galpha13, and Galphaq induces Rho-dependent morphological changes in PC12 cells through different signaling pathways.

ADP Ribose Transferases↗
PubMed1998

Characterization of the LPS-stimulated expression of EP2 and EP4 prostaglandin E receptors in mouse macrophage-like cell line, J774.1.

The expression of prostaglandin (PG) E receptor subtypes were characterized in J774.1, a mouse macrophage-like cell line. EP2- and EP4-mRNAs were found to be expressed. The expression of EP2 mRNA increased by the addition of lipopolysaccharide (LPS) in a dose-dependent manner. EP2 mRNA rapidly increased by more than 5-fold of the control level at 1 h, and decreased after 4 h. EP4 mRNA increased by only 2-fold of the control at 2 h. Gamma interferon inhibited both basal and LPS-induced expression of EP2 mRNA but did not affect the expression level of EP4 mRNA. When tumor necrosis factor-alpha (TNF-alpha) accumulation was measured after the treatment ofthe cells with LPS for 90 min, PGE2 was found to inhibit this accumulation, but butaprost, an EP2-selective agonist, did not. When TNF-alpha release was measured after the treatment of the cells with LPS for 8 h, accumulation was inhibited by butaprost as well as PGE2. These results indicated that the inhibitory effects of PGE2 on TNF-alpha production are mediated by EP2 and EP4 in macrophages, and that expression regulation of EP2 and EP4 in macrophages is quite different.

Alprostadil↗
PubMed1998

Membrane targeting and binding of the 74-kDa form of mouse L-histidine decarboxylase via its carboxyl-terminal sequence.

The role of the C-terminal region of the 74-kDa form of L-histidine decarboxylase (HDC) in the targeting to the endoplasmic reticulum (ER) was investigated in COS-7 cells. The deletion of a 10-kDa segment (residues 578-662) of the C-terminal end of HDC, especially a 20 amino acid sequence (residues 588-607), abrogated the targeting to the ER. The C-terminal 10-kDa portion is sufficient to target the green fluorescent protein (GFP) to the ER. The 74-kDa form of HDC synthesized in an in vitro translation system post-translationally associated with the heterogeneous canine microsomal membranes. These results suggest that the C-terminal 10-kDa portion of HDC contains a signal necessary for HDC to be targeted to the ER membrane.

Animals↗
PubMed1998

Localization of a cyclopentenone prostaglandin to the endoplasmic reticulum and induction of BiP mRNA.

Cyclopentenone prostaglandins (PGs) are transported into cells and stimulate the expression of various stress genes, such as that coding for BiP (an ER luminal protein). To reveal the site of action of the PGs for the induction of stress-gene expression, we introduced a fluorescent probe, pyrene, into two types of PG analogue, GIF0010 (a cyclopentenone type) and GIF0037 (a cyclopentanone type) and examined their intracellular localization in normal rat kidney cells and their ability to induce the BiP gene expression. GIF0010 accumulated around the nuclei and coincided with BiP, a resident protein in the endoplasmic reticulum (ER) and markedly induced BiP gene expression. By contrast, GIF0037 and pyrene neither accumulated in the cell nor induced BiP gene expression. Thus the ER localization of GIF0010 and the induction of gene expression by GIF0010 are ascribed to the cyclopentenone structure. Treatment with cycloheximide inhibited both the accumulation of GIF0010 and the induction of the BiP mRNA, suggesting that the ER localization of the PG and subsequent gene expression require the nascent protein synthesis. These results demonstrate that the cyclopentenone PG is specifically accumulated in the ER, transducing a signal for BiP gene expression in the nuclei.

Animals↗
PubMed1998

Impaired febrile response in mice lacking the prostaglandin E receptor subtype EP3.

Fever, a hallmark of disease, is elicited by exogenous pyrogens, that is, cellular components, such as lipopolysaccharide (LPS), of infectious organisms, as well as by non-infectious inflammatory insults. Both stimulate the production of cytokines, such as interleukin (IL)-1beta, that act on the brain as endogenous pyrogens. Fever can be suppressed by aspirin-like anti-inflammatory drugs. As these drugs share the ability to inhibit prostaglandin biosynthesis, it is thought that a prostaglandin is important in fever generation. Prostaglandin E2 (PGE2) may be a neural mediator of fever, but this has been much debated. PGE2 acts by interacting with four subtypes of PGE receptor, the EP1, EP2, EP3 and EP4 receptors. Here we generate mice lacking each of these receptors by homologous recombination. Only mice lacking the EP3 receptor fail to show a febrile response to PGE2 and to either IL-1beta or LPS. Our results establish that PGE2 mediates fever generation in response to both exogenous and endogenous pyrogens by acting at the EP3 receptor.

Animals↗
PubMed1998

Patent ductus arteriosus and neonatal death in prostaglandin receptor EP4-deficient mice.

The physiological role of the prostaglandin E2 receptor EP4 subtype was investigated by generation of EP4-deficient-mice by gene targeting. Loss of the EP4 receptor was not lethal in utero, but most EP4 (-/-) neonates became pale and lethargic approximately 24 h after birth and died within 72 h. Less than 5% of the EP4 (-/-) mice survived and grew normally more than a year. Histological examination revealed that the ductus arteriosus in dead neonates remained open, while it was partially closed in the survivors. In situ hybridization study showed that EP4 mRNA was strongly expressed in the ductus. These results suggest that neonatal death is at least partly due to patent ductus arteriosus and that the EP4 receptor plays a role in regulation of the patency of this vessel. They also indicate that normal function of the EP4 receptor is essential in neonatal adaptation of the circulatory system.

Animals↗
PubMed1998

Intracellular localization of the 74- and 53-kDa forms of L-histidine decarboxylase in a rat basophilic/mast cell line, RBL-2H3.

To clarify the process of post-translational modification of L-histidine decarboxylase (HDC), we investigated the conversion of the 74-kDa form of HDC into the 53-kDa form in specialized organella of a rat basophilic/mast cell line (RBL-2H3). With treatment of streptolysin-O, RBL-2H3 cells released approximately 40% of HDC activity accompanied by over 90% of lactate dehydrogenase activity. Only the 74-kDa form of HDC was detected in the leaked fraction by SDS-polyacrylamide gel electrophoresis. The 74-kDa form in the homogenate of pulse-labeled cells was recovered in both the supernatant and particulate fractions, while the 53-kDa form was detected only in the particulate fraction containing marker proteins of microsomes, Golgi, and lysosomal granules. Confocal microscopic observation using double staining immunofluorescence with anti-GST fusion HDC antiserum showed that most of the HDC coexists with protein-disulfide isomerase, a typical marker of the luminal space of the ER. With treatment of digitonin, RBL-2H3 cells released only 74-kDa HDC. Trypsin digestion of digitonin-permeabilized cells resulted in the disappearance of the 74-kDa form but not the 53-kDa form. From these results, it is assumed that the 74-kDa form of HDC, synthesized in the cytosol, is translocated into the lumen of the ER, where it is converted to the 53-kDa form.

Animals↗
PubMed1998

Characterization of the gene for the mouse prostaglandin E receptor subtype EP2: tissue-specific initiation of transcription in the macrophage and the uterus.

Genomic DNA clones for the mouse prostaglandin (PG) E receptor subtype EP2 were isolated and characterized. The mouse EP2 gene is composed of 2 exons and 1 intron, and spans 16 kb. The intron which is approx. 12 kb in length is located at the end of the sixth transmembrane domain, as with other prostanoid receptor genes. Based on this structure, transcripts were analysed in endotoxin-treated macrophages and pseudopregnant uteri, in which abundant expression of EP2 mRNA was observed. Sequence analysis of cDNA clones from these origins and Northern hybridization of these RNAs revealed that the uterine EP2 mRNA (U-type) has a longer 5'-untranslated region than the macrophage EP2 transcript (M-type). The major transcription initiation sites for M-type and U-type EP2 are located 124 and 769 bp upstream of the translation start site, respectively. The M-type was expressed in various tissues, whereas the U-type was found only in the uterus. The 2 kb segment containing the immediate 5'-flanking and 5'-noncoding regions contain three consensus sequences for the NF-IL6 binding site, one consensus sequence for the NF-kappaB binding site, four AP-2 consensus sequences, one AP-4 consensus sequence, one potential cAMP response element, and one potential progesterone response element. These results suggest that EP2 gene expression in the macrophage and uterus is under the control of distinct mechanisms involving alternative promoters.

Amino Acid Sequence↗
PubMed1998

Cytoskeletal regulation of the signal transduction of prostaglandin EP4 receptor.

Prostaglandin (PG) EP4 receptor is coupled to Gs, stimulating adenylate cyclase. We tested whether cytoskeleton modulates the signal transduction of the EP4 receptor. A microtubule depolymerizing agent, colcemid, enhanced the PGE2-induced cAMP formation in the cloned EP4 receptor-expressing Chinese hamster ovary cells, but enhanced neither NaF plus AlCl3 nor forskolin-induced cAMP formation. Other microtubule depolymerizing agents, including colchicine, also induced the enhancement. These effects stemmed from the action of the agents on microtubules, because beta-lumicolchicine, an inactive isomer of colchicine, had no effect. In contrast, the microfilament depolymerizing agents did not affect the PGE2-induced cAMP formation but potentiated the enhancing effect of colcemid. This enhancement by colcemid was not due to the suppression of the desensitization of the EP4 receptor. The enhancing effect of colcemid was also observed in another Gs-coupled PGE receptor subtype, EP2 receptor. These results demonstrate that the state of microtubule assembly modulates the signal transduction of the EP4 receptor in concert with microfilament.

Adenylyl Cyclases↗
PubMed1998

p160 RhoA-binding kinase ROKalpha induces neurite retraction.

We previously reported that the activation of prostaglandin E receptor EP3 subtype caused neurite retraction via small GTPase Rho in the EP3B receptor-expressing PC12 cells (Katoh, H., Negishi, M., and Ichikawa, A. (1996) J. Biol. Chem. 271, 29780-29784). However, a potential downstream effector of Rho that induces neurite retraction was not identified. Here we examined the morphological effect of p160 RhoA-binding kinase ROKalpha, a target for RhoA recently identified, on the nerve growth factor-differentiated PC12 cells. Microinjection of the catalytic domain of ROKalpha rapidly induced neurite retraction similar to that induced by microinjection of a constitutively active Rho, RhoV14, whereas microinjection of the kinase-deficient catalytic domain of ROKalpha did not induce neurite retraction. This morphological change was observed even though C3 exoenzyme, which was known to inactivate Rho, had been preinjected. On the other hand, microinjection of the Rho-binding domain or the pleckstrin homology domain of ROKalpha inhibited the EP3 receptor-induced neurite retraction. These results demonstrate that ROKalpha induces neurite retraction acting downstream of Rho in neuronal cells.

Animals↗
PubMed1998

Female reproduction in mice lacking the prostaglandin F receptor. Roles of prostaglandin and oxytocin receptors in parturition.

Female mice lacking the receptor for prostaglandin F2 alpha (FP) do not deliver fetuses at term, although these can be successfully rescued by cesarean section. No induction of oxytocin receptor mRNA is found in the uterus of these mice, and they show no uterine contraction on intravenous administration of oxytocin. Furthermore, a decline in serum progesterone levels during the periparturition period is not observed in these animals. Ovariectomy at day 19 of pregnancy restored induction of the oxytocin receptor and caused successful delivery in these animals. These results indicate not only the essential role of luteolytic PGF 2 alpha action in natural parturition but also the importance of oxytocin receptor induction in this process.

Animals↗
PubMed1998

Asymmetries of benzodiazepine receptor binding potential in the inferior medial temporal lobe and cerebellum detected with 123I-iomazenil SPECT in comparison with 99mTc-HMPAO SPECT in patients with partial epilepsy.

We examined the relation between regional 123I-iomazenil (IMZ) parameters and cerebral blood flow (CBF) to evaluate the difference between the quantitative parameters of IMZ and the CBF in detecting epileptic abnormality. Seventeen patients with unilateral partial epilepsy were subjected to 99mTc-hexamethylpropylene amine oxime (HMPAO) SPECT, and early and delayed IMZ SPECT. Then we quantitatively obtained the blood-to-brain transfer constants (K1) and binding potentials (BP) for nine regions of interest, and the regional CBF was also by using the simple angiographic method. From our data, significant asymmetries of BP in the inferior medial temporal lobe and cerebellum were shown and may be related to a remote effect such as crossed cerebellar diaschisis. In conclusion, the asymmetry of BP with iomazenil SPECT was demonstrated in patients with unilateral epilepsy that was not detectable by HMPAO SPECT.

Adult↗