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Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 307 records · Page 17Linked to original sources
PubMed1998

A novel insulin sensitizer acts as a coligand for peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and PPAR-gamma: effect of PPAR-alpha activation on abnormal lipid metabolism in liver of Zucker fatty rats.

We investigated the biological activity of a novel thiazolidinedione (TZD) derivative, KRP-297, and the molecular basis of this activity. When administered to obese Zucker fatty rats (obese rats) at 10 mg/kg for 2 weeks, KRP-297, unlike BRL-49,653, restored reduced lipid oxidation, that is, CO2 and ketone body production from [14C]palmitic acid, in the liver by 39% (P < 0.05) and 57% (P < 0.01), respectively. KRP-297 was also significantly more effective than BRL-49,653 in the inhibition of enhanced lipogenesis and triglyceride accumulation in the liver. To understand the molecular basis of the biological effects of KRP-297, we examined the effect on peroxisome proliferator-activated receptor (PPAR) isoforms, which may play key roles in lipid metabolism. Unlike classical TZD derivatives, KRP-297 activated both PPAR-alpha and PPAR-gamma, with median effective concentrations of 1.0 and 0.8 micromol/l, respectively. Moreover, radiolabeled [3H]KRP-297 bound directly to PPAR-alpha and PPAR-gamma with dissociation constants of 228 and 326 nmol/l, respectively. Concomitantly, KRP-297, but not BRL-49,653, increased the mRNA and the activity (1.5-fold [P < 0.01] and 1.8-fold [P < 0.05], respectively) of acyl-CoA oxidase, which has been reported to be regulated by PPAR-alpha, in the liver. By contrast, KRP-297 (P < 0.05) was less potent than BRL-49,653 (P < 0.01) in inducing the PPAR-gamma-regulated aP2 gene mRNA expression in the adipose tissues. These results suggest that PPAR-alpha agonism has a protective effect against abnormal lipid metabolism in liver of obese rats.

Acyl-CoA Oxidase↗
PubMed1998

Significant role of the increase in renin-angiotensin system in cardiac hypertrophy and renal glomerular sclerosis in double transgenic tsukuba hypertensive mice carrying both human renin and angiotensinogen genes.

Tsukuba hypertensive mice (THM) are a hypertensive model prepared by mating a transgenic mice with human renin gene and a transgenic mice with human angiotensinogen gene. In the present study, we examined effects of renin-angiotensin system (RAS) on cardiac hypertrophy and renal disorders using Tsukuba hypertensive mice. While THM showed an increase of about 30 mmHg in systolic pressure compared to C57BL/6 mice employed as normal control animals, the increase in blood pressure was not observed in the mice to which either gene was transferred. Urinary volume, water intake volume, urinary albumin excretion, heart to body weight ratio and renal glomerular sclerosis index increased significantly in THM, but none of these parameters showed a significant difference from the C57 mice when they were examined in mice to which either of the genes was transferred. In contrast, when lisinopril was administered to THM, all the parameters decreased significantly without lowering the systolic pressure. From these findings, it was demonstrated that RAS was playing a significant role in cardiac hypertrophy and renal disorders of THM and that lisinopril had inhibitory effects on cardiac hypertrophy and renal glomerular sclerosis by inhibiting RAS.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1998

Pathologic characterization of hypotensive C57BL/6J-agt: angiotensinogen-deficient C57BL/6J mice.

a fpreviously produced angiotensinogen-deficient mice, i.e. mice with deleted renin-angiotensin system (RAS), with a genetic background on C57BL/6J - C57BL/6J-agt (-/-) -, but no C57BL/6J-agt (-/-) which survived long enough to be weaned. In the present study, we attempted to prevent neonatal death and analyzed pathological development in C57BL/6J-agt (-/-). We indicate that mortality in C57BL/6J-agt (-/-) derived from C57BL/6J-agt (+/-) can be reduced by hypodermic saline injection in the 7 days following birth, that hydronephrosis developed by day 14 in association with polydiplasia and polyuria by day 30, and that chronic hypotension occurs. Hydronephrosis is less damaging to electrolyte resorption in younger mice, but not in adults. We also observed that C57BL/6J-agt (-/-) derived from C57BL/6J-agt (-/-) frequently develop fetal hydronephrosis and die of respiratory failure at birth. These results suggest that maternal RAS is associated with structural maturation of kidney and lung in late fetus and that postnatal RAS plays important roles in structural and functional maintenance of the kidneys.

Angiotensinogen↗
PubMed1998

Quantitative differences in telomerase activity among malignant, premalignant, and benign ovarian lesions.

Telomerase activation has been demonstrated in both cancers and some noncancerous lesions. However, few studies have determined levels of telomerase activity in these lesions. In the present study, using a recently developed stretch PCR assay, telomerase activity was quantitatively determined in a variety of ovarian lesions including 36 ovarian cancers, 5 ovarian low potential malignancy (LPM) lesions, 10 ovarian cysts, and 12 normal ovaries. Telomerase activity was normalized to control activity (100 units) in C33A cell line and given in relative units. Telomerase activity in ovarian cancer (51 +/- 7 units, mean +/- SE) was significantly higher than that in LPM lesions, ovarian cysts, and normal ovaries (7 +/- 3, 10 +/- 2, and 10 +/- 2 units, respectively; P < 0.001). Interestingly, all LPMs, ovarian cysts, and normal ovaries exhibited low telomerase activity less than 30 units, and no significant difference in level of telomerase activity was found among them. We also found a significant correlation between the level of telomerase activity and the clinical stage of ovarian cancer. Our quantitative telomerase assay thus clearly distinguished telomerase activity in ovarian cancers from that in LPM lesions and ovarian cysts. Significant levels of telomerase activation frequently occurred in cancer but rarely occurred in premalignant and benign lesions, suggesting that telomerase activation is a critical step in cancer development.

Female↗
PubMed1998

Rebamipide prevents indomethacin-induced gastric mucosal lesion formation by inhibiting activation of neutrophils in rats.

Since granulocyte elastase has been shown to be involved in the pathogenesis of gastric mucosal lesion formation induced by nonsteroidal antiinflammatory drugs, inhibition of granulocyte elastase release from neutrophils may be useful in the prevention of these lesions. The objective of this study was to determine whether rebamipide inhibits neutrophil activation in vivo and in vitro. Rebamipide and ONO-5046, a specific granulocyte elastase inhibitor, markedly inhibited indomethacin-induced mucosal injury in rats. Gastric myeloperoxidase activity was significantly increased 3 h after indomethacin administration. This increase was significantly inhibited by rebamipide and ONO-5046. Although cimetidine markedly prevented the indomethacin-induced mucosal lesion formation, it did not reduce the gastric myeloperoxidase activity. Rebamipide inhibited granulocyte elastase release from neutrophils in vitro by inhibiting the increase in intracellular Ca2+ level. Cimetidine did not inhibit granulocyte elastase release from neutrophils. Furthermore, the elevation of intracellular Ca2+ level was not inhibited by cimetidine. Therefore, unlike cimetidine, rebamipide may prevent indomethacin-induced mucosal injury by inhibiting neutrophil activation.

Alanine↗
PubMed1998

Salt-sensitive aortic aneurysm and rupture in hypertensive transgenic mice that overproduce angiotensin II.

We studied the effect of excessive salt intake on vascular lesion development in hypertensive transgenic mice that overproduce angiotensin II, ie, Tsukuba hypertensive mice (THM). At 6 weeks of age, THM and C57BL/6J (controls) were given either 1% sodium chloride ("salt-loaded") drinking water or tap water for 30 days. Salt-loaded THM, but not controls, suffered frequent thoracic or abdominal cavity hemorrhage. THM mortality after 7 days of salt loading was 23%; after 30 days of salt loading, it rose to 67%. Hemorrhaging occurred due to the development of aortic aneurysm and rupture at the aortic arch and aorta near the renal arteries. Vascular lesions progressed with structural degeneration of the aortic media. Electronmicroscopic analysis revealed that intact THM already exhibited vascular remodeling consisting of vascular smooth muscle cells (VSMCs) with developed organelles and an increased extracellular matrix. Salt-loaded THM suffered aggravated vascular hypertrophy and vascular structure destruction by plasma material invasion, necrosis of VSMCs possessing extremely swollen cytoplasm and abundant organelles, and interlamellar bleeding, resulting in aortic aneurysm and eventual rupture. Interestingly, blood pressure levels and heart rates in salt-loaded THM did not differ significantly from those of controls; plasma renin activity between drinking regimens was also comparable between the two groups. Drinking volume and the concentration of atrial natriuretic peptide (ANP) in plasma, however, were significantly higher in salt-loaded THM than in intact THM. In addition to aneurysm localization, the findings regarding drinking volume and plasma ANP suggest that aortic aneurysm and rupture in salt-loaded THM occurred as the result of an unknown mechanical stress, other than blood pressure, on the aortic wall. High salt ingestion is involved in the development of thoracic and abdominal aortic aneurysm in the presence of hypertension in the activated renin-angiotensin system. THM should therefore serve as a useful animal model for studying the pathogenesis of aortic aneurysm accompanied by hypertension.

Angiotensin II↗
PubMed1998

Effect of 4-[3,5-bis(trimethylsilyl)benzamido] benzoic acid (TAC-101) on the liver metastasis of colon 26-L5 carcinoma cells.

We found that oral administration of the benzoic acid derivative, TAC-101 ¿4-[3,5-bis(trimethylsilyl)benzamido] benzoic acid¿ significantly inhibited experimental liver metastasis of murine colon 26-L5 carcinoma cells, whereas all-trans-retinoic acid (ATRA) did not show any inhibitory effect. Treatment with more than 10 microM TAC-101 for 24 h showed direct cytotoxicity against tumor cells in vitro. In contrast, ATRA did not have any direct cytotoxicity. TAC-101 also inhibited the tumor cell invasion enhanced by TPA (12-O-tetradecanoylphorbol-13-acetate; AP-1 activator) in a concentration-dependent manner, whereas ATRA did not. Furthermore, zymographic analysis revealed that noncytotoxic concentrations (< 10 microM) of TAC-101 inhibited TPA-induced production of urokinase-type plasminogen activator (u-PA) and matrix metalloproteinase (MMP)-9 from tumor cells, which is considered to be associated with their invasive and metastatic potentials. These results suggest that such an inhibitory effect is partly due to the ability of TAC-101 to bind a retinoic acid receptor (RAR)-alpha and consequently inhibit metastasis-related gene transcription by interfering with AP-1/DNA binding, as we showed previously. On the other hand, TAC-101 also inhibited the production of MMP-2, which is not affected by TPA. Therefore, the antimetastatic effect of TAC-101 includes an alternative regulatory mechanism for MMP production. These results indicate that the in vivo antimetastatic effect of TAC-101 is partly due to the cytotoxicity against tumor cells, which may be caused by the induction of apoptosis, and inhibition of the production of invasion-associated proteolytic enzymes.

Animals↗
PubMed1998

Antiviral effects of 6-chloro-2',3'-dideoxyguanosine in rhesus monkeys acutely infected with simian immunodeficiency virus.

A lipophilic dideoxynucleoside analogue, 6-chloro-2',3'-dideoxyguanosine (6-Cl-ddG), was expected to be effective against AIDS-related dementia. In this study, we tested the effect of 6-Cl-ddG on simian immunodeficiency virus (SIVmac239) replication in vitro and on acute infection of six rhesus monkeys (Macaca mulatta) with SIVmac239. This compound inhibited SIV-induced cytopathic effect in CEM x 174 cells and SIV replication in vitro with an ED50 value of 2.5 microM. A dose of 25 mg/kg 6-Cl-ddG was administered to three monkeys every 8 h for 10 days and an untreated group of three monkeys was injected with the solvent without drug. Although 6-Cl-ddG was not detected in the plasma, the metabolite ddG was maintained at a concentration of more than 3 microM for 8 h after administration. In the cerebrospinal fluid, the ddG concentration was 2 microM at 2 h after administration. SIV antigen (p27) and antibody appearance in the plasma were delayed for 5-8 days compared with the mock-treated group. The occurrence of lymphadenopathy in treated monkeys was delayed for 6 days compared with the mock-treated group. Signs of 6-Cl-ddG toxicity were minimal after the treatment. The results of this study provide further evidence that 6-Cl-ddG may act as a potent anti-human immunodeficiency virus agent in vivo.

Animals↗
PubMed1997

Functional association between CBP and HNF4 in trans-activation.

CBP functions as a key transcriptional coactivator for a variety of transcription factors. We show here that the hepatocyte nuclear factor 4 (HNF4), a transcription factor in the nuclear receptor superfamily with no defined ligand, is cloned by yeast two-hybrid system using CBP as a bait. GST-pull down assay with nuclear extracts or in vitro translation products revealed that CBP and HNF4 interact with each other at the middle portion (aa 119-375) of HNF4 and two distinct regions (aa 271-451 and 1626-2259) of CBP, respectively, in the ligand-independent manner. Co-transfection experiments indicated that CBP is capable of activating HNF4 site-mediated transcription. These results suggested a functional association between CBP and HNF4 in trans-activation.

Animals↗
PubMed1997

Efficacy of 6-chloro-2',3'-dideoxyguanosine (6-Cl-ddG) on rhesus macaque monkeys chronically infected with simian immunodeficiency virus (SIVmac239).

To assess the therapeutic effects of 6-chloro-2',3'-dideoxyguanosine (6-Cl-ddG), a lipophilic dideoxynucleoside analogue, three rhesus macaques chronically infected with simian immunodeficiency virus (SIVmac239) were subcutaneously administered 25 mg/kg of the drug every 8 hours for 2 weeks. In two of three animals, the viral RNA in plasma and the cell-associated viral load from peripheral blood mononuclear cells were markedly decreased and the number of CD4+ and CD8+ lymphocytes were increased after 6-Cl-ddG administration. The decrease of the virus copies was associated with a reciprocal increase in the number of CD4+ lymphocytes. Additionally, a limiting dilution assay revealed a marked decrease in the lymph node cell-associated virus titer during the treatment. However, in the third monkey, the baseline of the number of CD4+ and CD8+ lymphocytes was higher than that of the other monkeys; these numbers changed very little during the treatment. In this monkey, the plasma SIV RNA level was decreased at the first week and was the same as the pretreatment level at the second week of the 6-Cl-ddG administration. In all three treated monkeys, the number of SIV RNA copies in the cerebrospinal fluid also tended to decrease during the 6-Cl-ddG treatment.

Animals↗
PubMed1997

Molecular variation of the human angiotensinogen core promoter element located between the TATA box and transcription initiation site affects its transcriptional activity.

Recent genetic studies indicate that several molecular variants discovered in angiotensinogen (AG), the precursor of vasoactive octapeptide angiotensin II, could potentially be responsible for inherited predisposition to human blood pressure variation. We have previously shown that a ubiquitously expressed nuclear factor, AGCF1, bound to AGCE1 (AG core promoter element 1 including the core nucleotides, CTCGTG, CTC-type) located between the TATA box and transcription initiation site (positions -25 to -1) is an authentic regulator of human AG transcription. In the present study, we showed that AGCF1 has biologically and immunologically similar properties to those of a helix-loop-helix nuclear factor USF1 and examined the effects of two other naturally occurring molecular variants (ATCGTG, ATC-type and ATTGTG, ATT-type) found in the AGCE1 position on the human AG transcriptional activity. Competitive gel-shift and transfection experiments demonstrated that the transcriptional activity for the CTC- and ATC-type promoters was 2.5 times higher than that for the ATT-type through the alteration of AGCF1-binding affinity. These results suggest the possible involvement of USF1 as a component in AGCF1 formation and the potential importance of AGCE1 variation in blood pressure regulation through human AG expression.

Angiotensinogen↗
PubMed1997

Lysophosphatidic acid inhibits epidermal-growth-factor-induced Stat1 signaling in human epidermoid carcinoma A431 cells.

Lysophosphatidic acid (LPA) is a lipid mediator which acts on its putative G protein-coupled receptor (GPCR). Recently, activation of signal transducers and activators of transcription (STATs) mediated by GPCR has been reported. In this study, we examined the effect of LPA on STAT activation using the electrophoretic mobility shift assays and the heterologous promoter analysis in human epidermoid carcinoma A431 cells. We found that LPA inhibited epidermal growth factor (EGF)-induced Stat1 activation in a concentration-dependent manner. Other phospholipase C (PLC)-coupled GPCR agonists, bradykinin and ATP, also inhibited Stat1 activation. This inhibitory effect of LPA was completely mimicked by an activator of protein kinase C (PKC), a PLC-downstream effector. These findings suggest that the inhibitory effect on EGF-induced Stat1 activation may be a general characteristic of PLC-coupled GPCRs and PKC pathway may be mainly associated with this inhibitory effect. This is the first evidence showing that GPCR agonists inhibit the Janus kinase-independent Stat1 activation induced by receptor tyrosine kinase.

Bradykinin↗
PubMed1997

Positioning of two alpha subunit carboxy-terminal domains of RNA polymerase at promoters by two transcription factors.

Interactions between the cAMP receptor protein (CRP) and the carboxy-terminal regulatory domain (CTD) of Escherichia coli RNA polymerase alpha subunit were analyzed at promoters carrying tandem DNA sites for CRP binding using a chemical nuclease covalently attached to alpha. Each CRP dimer was found to direct the positioning of one of the two alpha subunit CTDs. Thus, the function of RNA polymerase may be subject to regulation through protein-protein interactions between the two alpha subunits and two different species of transcription factors.

Amino Acid Substitution↗
PubMed1997

Repression and activation of promoter-bound RNA polymerase activity by Gal repressor.

By binding to the DNA site OE at position -60.5 in the gal operon, the GalR protein activates transcription from the P2 promoter located on the opposite face of DNA (position -5) and represses transcription from the P1 promoter located on the same face (position +1). GalR increases RNA polymerase binding at P2 and inhibits isomerization at P1 by forming a GalR-DNA-RNA polymerase ternary complex in each case. The specific effect of GalR at one promoter is independent of the presence of the other promoter. The enhancement or repression is also not the intrinsic property of a promoter; the regulation can be reversed by switching the angular orientation of the promoters relative to OE. Both enhancement and repression appear to require the same interaction between RNA polymerase alpha-subunit and GalR and/or the same interaction between RNA polymerase alpha-subunit and DNA in the ternary complexes. We have discussed how GalR might exert opposite effects in the steps involved in the formation of the open complex from free RNA polymerase and DNA.

Binding Sites↗
PubMed1997

Anti-apoptotic action of angiotensin fragments to neuronal cells from angiotensinogen knock-out mice.

The morphological analysis in a congenic line of angiotensinogen knock-out mice (AgKO) revealed the decreased density in granular layer cells of hippocampus and cerebellum, suggesting neuronal cells of AgKO susceptible to apoptotic cell death. This phenomenon was further studied by culture of the hippocampal neurons with decreased concentration of serum. AgKO neuronal cells, which showed apoptosis by lower concentration of the serum within several hours, however, survived much longer in the presence of angiotensin II (AII) and IV (AIV). This anti-apoptotic action was not interfered by AII receptor antagonists, CV11874 and PD123319. These results suggest that the renin-angiotensin system could play a critical role in central nervous system, preventing neuronal cells from apoptosis not only by AII but also AIV.

Angiotensin II↗