Biomedical subjects

S Murota

Publications and source records attributed to S Murota.

At least 37 records · Page 2Linked to original sources

PubMed2000

Sera from patients with sepsis induce nitric oxide production in vascular smooth muscle cells.

BACKGROUND: Nitric oxide (NO) is an important physiological mediator of vascular tone and is involved in pathophysiology of septic shock. Although plasma nitrite is a stable end product of NO oxidation derived from endogenous NO, the plasma nitrite level is also easily affected by the intake of various foods, bacterial products and renal functional status. AIMS: We propose an excellent alternative assay technique for measuring endogenous NO production. METHODS: We measured the nitrite level in cultured vascular smooth muscle cells (SMC) treated with serum obtained from patients with sepsis (4 patients), by means of a chemiluminescence detector. RESULTS: The nitrite concentrations in such cells were significantly higher as compared to those in the cells treated with normal serum. Moreover, the increased nitrite levels in the SMC treated with the sera obtained from patients with sepsis were completely inhibited by L-nitroarginine (1 mmol/L), a nitric oxide synthase inhibitor. CONCLUSION: These data suggest that this assay method enable us to know the ability of endogenous NO production in each patient.

Aged↗

PubMed2000

Expression of adhesion molecules LFA-I and ICAM-I on osteoclast precursors during osteoclast differentiation and involvement of estrogen deficiency.

OBJECTIVES: Estrogen deficiency caused by the menopause or ovariectomy leads to stimulation of osteoclastogenesis. The adhesion molecules, leukocyte function-associated antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1), are necessary for osteoclast formation. In this study, the expression of LFA-1 and ICAM-1 on osteoclast precursors during osteoclast differentiation, and the involvement of ovariectomy in the expression, were investigated. METHODS: Spleen cells isolated from normal or ovariectomized (OVX) mice were co-cultured with TMS14, stromal cells derived from mouse bone marrow, in the absence or presence of 1 alpha,25-dihydroxyvitamin D3 (1 alpha,25(OH)2D3) for 7 days. On days 3, 5 and 7 of culture, the expression of LFA-1 and ICAM-1 on osteoclast precursors was quantitated using indirect immunofluorescence and confocal laser cytometry, and, on day 7, the number of formed osteoclasts was measured by tartrate-resistant acid phosphatase (TRAP) stain. RESULTS: The level of ICAM-1 expression on osteoclast precursors gradually increased with osteoclast differentiation, whereas that of LFA-1 did not change. A high level of ICAM-1 was observed on the integrin beta 3-positive mononuclear cells. On the osteoclast precursors isolated from OVX mice, both the level of ICAM-1 expression per cell and the number of cells showing a high expression of ICAM-1 significantly increased, with an increase in the number of osteoclast-like cells. However, the level of LFA-1 did not change. CONCLUSIONS: These results indicate that the expression level of ICAM-1, but not that of LFA-1, is involved in osteoclast differentiation. Estrogen deficiency results in an increase in ICAM-1 expression on osteoclast precursors, which may be one of the mechanisms underlying bone loss following the menopause or ovariectomy.

Acid Phosphatase↗

PubMed2000

Hydrogen peroxide induced apoptosis of endothelial cells concomitantly with cycloheximide.

We examined whether or not hydrogen peroxide induced apoptosis of vascular endothelial cells. Cultured vascular endothelial cells from bovine carotid arteries were used. Apoptosis was determined by a propidium iodide assay. Under serum free conditions, treatment of the endothelial cells with hydrogen peroxide (H2O2) for 6 hours induced cytotoxicity (51Cr release) in a dose-dependent manner (10 micromol/l-1 mmol/l). Under the condition containing 10% serum, H2O2 did not induce cytotoxicity even at the highest concentration (1 mmol/l). However, concomitant treatment of endothelial cells with cycloheximide at a dose of 10 microg/ml elicited endothelial cell apoptosis of by 15.6+/-1.7% at 6 hours after administration, even under the 10% serum condition. In addition, endothelial cell apoptosis due to H2O2 and cycloheximide was completely inhibited by zD-dcb (50 micromol/l), an inhibitor of caspase. 1 mmol/l of 4, 4-diisothiocyanatostilbene-2, 2-disulfonic acid (DIDS), which is a chloride bicarbonate exchanger blocker, partially inhibited the H2O2 and cycloheximide-induced endothelial cell apoptosis. On the other hand, cytotoxicity of endothelial cells due to H2O2 under serum free conditions was not inhibited by DIDS. These data suggested that hydrogen peroxide could induce endothelial cell apoptosis or cell membrane injury (51Cr release) in the presence or absence of an inhibitor of protein synthesis.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed1999

Induction of neuronal nitric oxide synthase by methylmercury in the cerebellum.

A free radical, nitric oxide (NO), besides being a messenger molecule in the brain, becomes a neurotoxin if overproduced. We recently reported that methylmercury (MeHg) induces neuronal NO synthase (nNOS) in Purkinje cells. In the present study, we examined the distribution and the mechanism of nNOS induction by MeHg. Subcutaneous administration of MeHg chloride to mice, 10 mg/kg/day for 9 days, increased calcium-dependent NOS activity to 60% more than the controls only in the cerebellum but not in other brain regions. The Western blots showed a comparable increase in nNOS protein in the cerebellum. A N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, did not block, but rather enhanced, the increase in the nNOS activity. Another NMDA antagonist, 3-(2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid (CPP), did not affect the nNOS activity. The Western blots of protein kinase C (PKC), which is an important cofactor regulating nNOS, did not change after the administration of MeHg. These results show that MeHg induces biologically active nNOS selectively in the cerebellum. The induction is independent of PKC and is not reduced by the blockade of the NMDA receptor.

Animals↗

PubMed1999

Neuronal nitric oxide synthase is resistant to ethanol.

To test for a possible role of nitric oxide (NO) in the neurotoxicity of ethanol, we studied the effects of ethanol on the neuronal NO synthase (nNOS) both in vitro and in vivo. Ethanol, up to 200 mM, did not change the NOS activity in the cerebellar homogenate or the production of NO by the cultured cerebellar granule cells. The number of NADPH diaphorase-positive cells in the culture did not change after the exposure to 200 mM ethanol in vitro. The NOS activity in the various brain regions of mice remained similar to the controls after the acute (3 g/kg) and the chronic (33 g/kg/day, 3.5 days) administration of ethanol. N(omega)-nitro-L-arginine, a NOS inhibitor, did not affect the ethanol-withdrawal behavior. These results indicate that nNOS is resistant to ethanol at clinically relevant concentrations and that ethanol affects the NO-operated system in the brain through a pathway other than that of nNOS.

Animals↗

PubMed1999

Interleukin-4 and interferon-gamma inhibit prostaglandin production by interleukin-1beta-stimulated human periodontal ligament fibroblasts.

The purpose of the present study was to investigate the involvement of cyclooxygease-1 (COX-1) and cyclooxygenase-2 (COX-2) in prostaglandin (PG) production by human periodontal ligament (PDL) fibroblasts stimulated with a proinflammatory cytokine, inerleukin-1beta (IL-1beta), and to examine the effect of interleukin-4 (IL-4), a Th2 cytokine, and interferon-gamma (IFN-gamma), a Th1 cytokine, on PG production by the cells. IL-1beta-stimulated PDL fibroblasts produced prostaglandin E2 (PGE2) in a time-dependent manner. Indomethacin, a non-selective COX-1/COX-2 inhibitor, and NS-398, a selective COX-2 inhibitor, completely inhibited PGE2 production by IL-1beta-stimulated cells. Northern blot analysis showed that COX-2 mRNA was detected in IL-1beta-stimulated PDL cells, although not detected in unstimulated cells, while expression of COX-1 mRNA was in the same extent in both the cells. Dexamethasone inhibited COX-2 mRNA expression, COX activity and PGE2 production in IL-1beta-stimulated cells. IL-4 and IFN-gamma suppressed PGE2 production by IL-1beta-stimulated PDL fibroblasts, but COX activity enhanced by IL-1beta treatment was significantly inhibited by IL-4, not by IFN-gamma. Northern blot analysis showed that IL-4 depressed COX-2 mRNA expression with no effect on COX-1 mRNA expression. On the other hand, IFN-gamma had no effect on expression of COX-1 and -2 mRNA. These data suggest that COX-2 is primarily responsible for PGE2 production by IL-1beta-stimulated human PDL fibroblasts and that IL-4 inhibited PGE2 production by IL-1beta-stimulated PDL fibroblasts through down-regulation of COX-2 expression, while IFN-gamma suppressed the PGE2 production with no effect on COX-2 expression.

Cells, Cultured↗

PubMed1999

Pretreatment with eicosapentaenoic acid prevented hypoxia/reoxygenation-induced abnormality in endothelial gap junctional intercellular communication through inhibiting the tyrosine kinase activity.

Eicosapentaenoic acid (EPA) may protect against atherosclerotic disease, and modulation of endothelium function is one possible mechanism. Hypoxia/reoxygenation (H/R) is a potential risk factor for the pathogenesis of atherosclerosis, and it causes endothelial dysfunction. To evaluate whether EPA may improve the endothelial dysfunction under the condition of H/R, we examined endothelial gap junctional intercellular communication (GJIC), which is said to be important for the endothelium to maintain its normal function. The results indicate that H/R induced a temporal reduction in GJIC after 2 h of reoxygenation in cultured human umbilical vein endothelial cells (HUVEC). This reduction in GJIC was not observed in cells pretreated with 3 microg/ml EPA for 2 days. The results of immunofluorescence show that 2 h reoxygenation caused an increased production of tyrosine-phosphorylated proteins, which was inhibited by EPA pretreatment. Immunoprecipitation demonstrated that tyrosine residues of connexin 43 (Cx43), an important gap junctional protein in HUVEC, were phosphorylated by H/R. However, pretreatment with EPA significantly suppressed this increased phosphorylation. The protective effect of EPA on the reduction in GJIC was also observed in cells treated with 1.5 mM vanadate, a tyrosine phosphatase inhibitor. These data suggest that EPA may ameliorate the H/R-induced GJIC abnormality via inhibition of the tyrosine kinase activation.

Cell Hypoxia↗

PubMed1999

Existence of endogenous inhibitor(s) of prostaglandin endoperoxide H synthase activities in murine NIH3T3 fibroblasts.

The production of prostaglandins (PGs) is regulated by several processes, i.e. arachidonic acid release, prostaglandin endoperoxide H synthase (PGHS) activity and its induction. In the present study, we investigated the possibility that inhibitor(s) of PGHS activities exist endogenously and regulate PG production. NIH3T3 cell, a cloned murine fibroblast, expressed PGHS-1 under unstimulated conditions and induced PGHS-2 protein under stimulation by serum. When PGHS activity was measured by individual intact cell assay, there was heterogeneity in PGHS activities in individual cells after serum treatment. We isolated and cultured many cloned cells which showed different PGHS activities after serum treatment. In these cells, however, there was no difference in the expression of PGHS-1 and PGHS-2 mRNA. The protein level of PGHS-1 and PGHS-2 was also not different in these cloned cells. The lysate obtained from the cells that showed lower PGHS activity after the serum treatment suppressed PGHS-1 activities of sheep seminal vesicle and PGHS-2 activity in purified ovine placenta. The suppression by this lysate was stronger than that by the lysate obtained from the cells which showed higher PGHS activity after the serum treatment. The production of the inhibitor(s) was up-regulated by the serum treatment and abolished by actinomycin D and cycloheximide during the serum treatment. From these results, we suggest that there is some endogenous inhibitor(s) of PGHS-1 and -2 activities in NIH3T3 cells, and that the inhibitor(s) is induced by serum.

3T3 Cells↗

PubMed1999

A possible involvement of ion transporter in tumor necrosis factor alpha and cycloheximide-induced apoptosis of endothelial cells.

We examined the tumor necrosis factor alpha (TNFalpha)-induced apoptosis of vascular endothelial cells from the standpoint of ion channels. Cultured vascular endothelial cells from bovine carotid artery were used. Apoptosis was determined by a propidium iodide assay. Treatment of the endothelial cells with TNFalpha and cycloheximide for 6 h induced nuclear fragmentation in a TNFalpha dose-dependent manner (1-10 ng/ml). Concomitant treatment of endothelial cells with TNFalpha at a dose of 10 ng/ml and cycloheximide at a dose of 10 microg/ml elicited endothelial cell apoptosis as high as 23.4+/-4.1% at 6 h after administration. However, 10 ng/ml TNFalpha alone elicited a little apoptosis at 6 h after its administration (% apoptosis=4.1+/-0.8%). Cycloheximide (10 microg/ml) did not induce apoptosis at all. Concomitant treatment of endothelial cells with 1 mmol/l of 4,4-diisothiocyanatostilbene-2,2-disulfonic acid, which is a chloride bicarbonate exchanger blocker, partially inhibited the TNFalpha and cycloheximide-induced endothelial cell apoptosis. On the other hand, endothelial cell apoptosis due to TNFalpha and cycloheximide was completely inhibited by benzyloxycarbonyl-Asp-CH2OC(O)-2,6-dichlorobenzene (50 micromol/l), an inhibitor of caspase. Moreover, pyrrolidine dithiocarbanate, an inhibitor of nuclear factor kappa B (NF-kappaB), also suppressed endothelial cell apoptosis induced by TNFalpha and cycloheximide completely. These findings suggest that the endothelial cell apoptosis induced by TNFalpha and cycloheximide is closely related to not only chloride ions, but also both NF-kappaB and caspase activation. That is to say, there is a possibility that chloride ions or bicarbonate (pH) may play an important role in signal transduction such as NF-kappaB and caspase activation in the apoptosis induced by TNFalpha and cycloheximide.

Animals↗

PubMed1999

Vitamin K2 (menatetrenone) induces iNOS in bovine vascular smooth muscle cells: no relationship between nitric oxide production and gamma-carboxylation.

It has been recently reported that vitamin K2 (menaquinone-4: menatetrenone, VK2) has an anti-atherogenic effect as well as the ability to produce clotting factors and improve osteoporosis. However, the mechanism by which VK2 acts on atherosclerosis is still unclear. In this paper, we investigated the effects of vitamin K and its side chain on NO production as an anti-atherogenic substance in a cultured vascular system. Treatment of bovine vascular smooth muscle cells (SMC) with VK2 (30 microM) caused a time-dependent (24-72 h) increase in the nitrite (NO2) level in the conditioned medium, but not in bovine vascular endothelial cells. Classical NOS inhibitor (L-nitro arginine) and iNOS-specific inhibitors completely blocked the increased nitrite level induced by VK2 treatment, but D-nitro arginine could not it. Immunostaining and Western blotting analysis showed that VK2 induced iNOS protein in the SMC. VK2 has a naphtoquinone nucleus, which is identical in menadione (VK3), and an unsaturated side chain, which is called geranylgeraniol (GGO). To determine whether the structure of VK2 was related to an increasing nitrite level, we investigated the nitrite level in conditioned medium treated with VK3 or GGO. Neither VK3 nor GGO treatment of SMC increased the nitrite level. In addition, warfarin, an inhibitor of VK2-dependent gamma-carboxylation, did not affect the increased nitrite level induced by VK2 in SMC. In conclusion, VK2 caused NO production through iNOS induction in bovine SMC, that was not related to the structure of VK2, naphtoquinone nucleus or its side chain, independently of gamma-carboxylation.

Animals↗

PubMed1998

NO is not involved in the simvastatin induced cell division and differentiation in PC12 cells.

Simvastatin, a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor has been reported to inhibit cell division and induce neurite-like outgrowth in PC12 cells [Sato-Suzuki, I. and Murota, S., Neurosci. Lett., 220 (1996) 21-24]. In the present paper, we examined whether the induced nitric oxide (NO) in the simvastatin-treated PC12 cells is involved in the growth arrest and differentiation as reported in nerve growth factor (NGF) treated PC12 cells. Treatment of PC12 cells with simvastatin caused peripherin formation and enhanced NO production just like NGF-treated PC12 cells. Different from NGF, however, NO synthase inhibitors could not affect the growth arrest and differentiation in simvastatin-treated PC12 cells. In conclusion, NO had nothing to do with cell division and differentiation in simvastatin-treated PC12 cells.

Animals↗

PubMed1998

Different substrate utilization between prostaglandin endoperoxide H synthase-1 and -2 in NIH3T3 fibroblasts.

Recent studies suggested that prostaglandin endoperoxide H synthase- and prostaglandin endoperoxide H synthase-2 (PGHS-1 and PGHS-2) utilize different pools of arachidonic acid for synthesizing prostanoids. Using cultured murine NIH3T3 fibroblasts, we investigated the mechanism for the different utilization of arachidonic acid between PGHS-1 and -2. Histofluorescence staining for PGHS activity in intact cells demonstrated that quiescent 3T3 cells expressed only PGHS-1 activity and serum-activated 3T3 cells pretreated with aspirin expressed only PGHS-2 activity. Endogenous arachidonic acid released by calcium ionophore A23187 was not converted by PGHS-1 but exclusively converted by PGHS-2. In the cell free system, the kinetics of PGHS-1 were not so much different from those of PGHS-2. However, in intact cells, arachidonic acid at concentrations lower than 2.5 microM was converted by PGHS-2 alone but not by PGHS-1. Our findings indicated that this small amount of arachidonic acid as released by some stimuli is converted exclusively by PGHS-2. Furthermore, treating the PGHS-2-expressing cells with sodium selenite or ebselen, reducing agents of intracellular peroxides, only decreased PGHS-2 activity. We speculate that only PGHS-2 has been activated by intracellular peroxides and subsequently, it can convert the arachidonic acid released endogenously.

3T3 Cells↗

PubMed1998

Arachidonic acid pretreatment enhances smooth muscle cell migration via increased Ca2+ influx.

It is well known that vascular smooth muscle cell (SMC) migration is an initial step in atheromatous plaque formation. In the present study, we investigated the effects of arachidonic acid (AA, 20:4 n-6) on bovine carotid artery SMC migration using the modified Boyden chamber technique. SMCs pretreated with 2.5 microg/ml of AA for 2 days, showed an enhanced migration response to fetal bovine serum. AA pretreatment (0.5-5.0 microg/ml) increased fetal bovine serum-induced SMC migration dose-dependently, and maximum stimulation was observed at a concentration of 2.5 microg/ml. However, AA pretreatment did not enhance fetal bovine serum-induced endothelial cell migration. Using lipid analysis, we found that AA was substantially incorporated into cellular phospholipids. When SMC migration was induced by platelet derived growth factor (PDGF)-BB, instead of serum, the stimulative effect of AA pretreatment was retained. SMCs pretreated with AA showed greater mobilization of intracellular Ca2+ in response to PDGF-BB than SMCs without AA pretreatment (controls). Nifedipine, a Ca2+ channel blocker, and glycoletherdiamine-tetraacetic acid (EGTA) had no effect on PDGF-induced migration of controls but both drugs reduced the enhanced PDGE-induced migration of AA-pretreated SMCs to the control level. Baicalein, an inhibitor of 12-lipoxygenase, reduced PDGF-BB-induced migration of both control and AA pretreated SMCs, however the AA-pretreated cells still showed enhanced migration compared to control cells. These findings suggest that AA accelerates SMC migration in the thickening of the intima during atheroma formation, via stimulation of extracellular Ca2+ influx.

Animals↗

PubMed1998

Expression of IL-6 receptor and GP130 in mouse bone marrow cells during osteoclast differentiation.

Interleukin-6 (IL-6) has been postulated as a possible mediator of bone loss after estrogen deficiency, and its signal is transduced via glycoprotein 130 (gp130) after binding IL-6 receptor (IL-6R) in the membrane of target cells. In this study, the expression of IL-6R and gp130 in bone marrow cells during osteoclast differentiation was investigated. Mouse bone marrow cells were isolated and cultured with or without 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3]. During the formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs), IL-6R and gp130 expression in the mononuclear cells, stromal cells, and TRAP-positive MNCs were quantitated, using a laser cytometer with a fluorescence confocal microscopy. With 1,25(OH)2D3 stimulus, the level of gp130 significantly increased, but that of IL-6R did not in the stromal cells. In contrast, the levels of both gp130 and IL-6R significantly increased in the mononuclear cells by the treatment with 1,25(OH)2D3. The high expression of both gp130 and IL-6R was observed in the TRAP-positive mononuclear cells. Moreover, both IL-6R and gp130 were expressed in the TRAP-positive MNCs and isolated murine osteoclasts. The treatment of TRAP-positive MNCs with IL-6 caused enhancement of the resorbing activity in a dose-dependent manner, and the effect was prevented by a neutralizing antibody against IL-6R. These data suggest that gp130 and IL-6R, as well as IL-6, are involved in the formation and activation of osteoclasts.

Acid Phosphatase↗

PubMed1998

Involvement of cholesterol in osteoclast-like cell formation via cellular fusion.

Osteoclasts, the bone resorbing cells, are formed from hematopoietic precursors via plasma membrane fusion. To investigate the possibility that cholesterol is involved in cellular fusion events, we examined the effects of the depletion of low density lipoproteins (LDL) and the effects of a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor on osteoclast-like cell formation. Tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells (MNCs), osteoclast-like cells, were formed as a result of the coculture of mouse spleen cells with mouse stromal cells TMS-14 in the presence of 1alpha, 25-dihydroxyvitamin D3 (1, 25 VD3). The depletion of LDL suppressed the formation of TRAP-positive MNCs, but the effect was abrogated by the addition of LDL. This inhibitory effect was not observed following the depletion of LDL in the early stages of the culture (day 0-3). The decrease in the number of TRAP-positive MNCs resulting from LDL depletion was accompanied by an increase in the number of TRAP-positive mononuclear cells. Furthermore, the formation of MNCs was also suppressed by the addition of simvastatin, an HMG-CoA reductase inhibitor. The inhibitory effect of simvastatin on the generation of TRAP-positive MNCs was dose and time dependent. However, treatment with simvastatin did not affect the increase in TRAP activities. These results suggest that cholesterol in the membranes of monocytes is involved in osteoclast-like cell formation via cellular membrane fusion events.

Acid Phosphatase↗

PubMed1998

A caspase inhibitor blocks ischaemia-induced delayed neuronal death in the gerbil.

Caspases play a critical role in the cell death machinery in various cell types. Here we investigated the involvement of caspases in the delayed neuronal death after transient global forebrain ischaemia in the gerbil. Intrahippocampal injection of benzyloxycarbonyl-Asp-CH2-dichlorobenzene (zD), an irreversible inhibitor of caspases, saved hippocampal CA1 neurones from chromatin condensation and DNA fragmentation at post-ischaemia day 4, and these neurones maintained normal morphology at day 8 post-insult. Intrahippocampal injection of interleukin-1beta (IL-1beta) after ischaemic insults did not influence the neuroprotective effect of zD, suggesting that the neuroprotective effect does not depend on the inhibition of mature IL-1beta production. Animals that received zD-injection showed significant improvement in step-through and step-down passive avoidance learning at post-ischaemia days 4 and 5, suggesting that neural functions were preserved in these animals. At post-ischaemia day 4, the cleavage of poly(ADP-ribose)polymerase was observed, and this cleavage was almost completely suppressed in zD-injected hippocampus, suggesting involvement of caspase-3 and caspase-3-like caspase in the delayed neuronal death. Our findings indicate that caspases play important roles in the delayed neuronal death after transient global forebrain ischaemia in the gerbil, and suggest that ischaemia-induced brain damage can be blocked by caspase inhibitors.

Animals↗

PubMed1998

Simvastatin, a potent HMG-CoA reductase inhibitor, inhibits the proliferation of human and bovine endothelial cells in vitro.

We investigated in vitro effect of simvastatin, a potent 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, on the proliferation of human and bovine endothelial cells (EC) compared to that of bovine smooth muscle cells (SMC). Cells were cultured in a medium supplemented with 10% normal serum (FBS). Simvastatin at concentrations ranging from 0.1 microg/ml to 10 microg/ml were used. In each kind of cells the proliferation was markedly reduced at 1 microg/ml of simvastatin (P<0.01) which was accompanied by morphological changes in the cell shape. We conclude that simvastatin inhibits the proliferation of not only the smooth muscle cells but also the endothelial cells.

Animals↗

PubMed1997

Cationic amino acid transporter-2 mRNA induction by tumor necrosis factor-alpha in vascular endothelial cells.

Nitric oxide (NO) synthesis may be coupled to the activity of the cellular L-arginine transporter, namely the cationic amino acid transporter. The present study examined tumor necrosis factor (TNF)-alpha-induced alterations in the gene expression of the cationic amino acid transporter (CAT) and NO production in human umbilical vein endothelial cells. In quiescent endothelial cells, CAT-1 mRNA expression, determined by reverse transcription-polymerase chain reaction, was dominant to that of CAT-2. TNF-alpha (10 ng/ml for 1-24 h) induced a time-dependent increase in CAT-2 but not CAT-1 expression. Moreover, TNF-alpha (1-30 ng/ml) treatment for 6 h induced a concentration-dependent increase in CAT-2 mRNA expression. The upregulation of CAT-2 expression by TNF-alpha was associated with enhanced nitrite accumulation in the culture medium (70% increase compared with vehicle-treated cells at 24 h). Thus, induction of the cationic amino acid transporter may constitute one mechanism for the TNF-alpha-induced NO production in human umbilical vein endothelial cells.

Amino Acid Transport Systems, Basic↗