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M Nakashima

Publications and source records attributed to M Nakashima.

At least 73 records · Page 4Linked to original sources
PubMed2000

Modifying effects of carotenoids on superoxide and nitric oxide generation from stimulated leukocytes.

Excessive and prolonged generation of superoxide (O2-) and nitric oxide (NO) from inflammatory leukocytes is associated with several lifestyle-related diseases, including cancer. In the present study, we screened 19 natural carotenoids for their modifying effects on O2- and NO generation from differentiated human promyelocytic HL-60 cells and mouse macrophage RAW 264.7 cells, respectively. Of the carotenoids tested, halocynthiaxanthin, isolated from oysters, showed the highest suppressive effect on the generation of both free radicals. The inhibitory potencies of certain carotenoids on radical generation markedly exceeded that of beta-carotene. In addition, some important structural moieties regulating radical generation suppression are discussed.

Animals↗
PubMed2000

Expression of pituitary-tumour transforming gene in colorectal tumours.

BACKGROUND: Basic fibroblast growth factor promotes angiogenesis and mitogenesis in colon carcinomas. Pituitary-tumour transforming gene (PTTG1) causes in-vitro and in-vivo transformation, regulates secretion of basic fibroblast growth factor, and inhibits chromatid separation. Most normal tissues show little or no PTTG1 expression but cancer cells express the gene abundantly. We postulated that PTTG1 expression in colorectal tumours is related to tumour invasiveness. METHODS: PTTG1 gene and protein expression were assessed in 68 colorectal tumours and compared with invasive characteristics, such as lymph-node invasion, evidence of metastases, tumour vessel density, and expression of basic fibroblast growth factor. PTTG1 expression is given in terms of the fold-increase over that in normal-adjacent colorectal tissue. FINDINGS: PTTG1 was overexpressed in all of 48 colon carcinomas (median fold-increase 2.2 [IQR 1.8-3.3]) and in 19 of 20 colonic polyps (2.2 [1.6-3.1]) compared with normal colonic tissue. Invasion of surrounding lymph nodes was associated with higher PTTG1 expression than in carcinomas limited to the bowel wall (3.4 [2.1-5.9] vs 1.9 [1.7-2.4], p=0.007), and higher PTTG1 expression was seen in more vascular than in less vascular tumours (2.6 [1.9-5.1] vs 1.9 [1.8-2.5], p=0.04). INTERPRETATION: Increased tumour PTTG1 expression may be a marker of invasive colorectal carcinoma and could represent a new therapeutic target.

Colorectal Neoplasms↗
PubMed2000

Study on complex formation between recombinant human thrombomodulin fragment and thrombin using surface plasmon resonance.

Human thrombomodulin (hTM) is a newly described endothelial cell associated protein that functions as a potent natural anticoagulant by converting thrombin from a procoagulant protease to an anticoagulant. The affinity constant of recombinant human soluble TM (rhs-TM) and a peptide containing active site of hTM fragment (f-hTM) with thrombin were determined using the surface plasmon resonance. The interaction of f-hTM with thrombin could be analyzed by a simple model, whereas the association and the dissociation steps of rhs-TM with thrombin consisted of at least two kinds of interaction phases. The dissociation constant for complex (K(D)) of f-hTM and thrombin was determined to be 205 nM, which was more than twice as high as that of rhs-TM (6.7 and 75 nM). The lower affinity of f-hTM was not due to the slow association rate but to the rapid dissociation rate. It comes clear that f-hTM interacts with thrombin rapidly.

Humans↗
PubMed2000

The clinical significance of tumor-associated antigen RCAS1 expression in the normal, hyperplastic, and malignant uterine endometrium.

OBJECTIVE: A tumor-associated antigen, RCAS1, is recognized by 22-1-1 monoclonal antibody. It was found in carcinomas derived from the uterus and ovary and was especially strongly expressed in invasive cancers. A previous investigation showed the RCAS1 expression to be correlated with a poor prognosis in uterine cervical adenocarcinoma. In this study, we examined whether the expression of RCAS1 is associated with the progression of the uterine endometrial neoplasms. METHODS: The expression of RCAS1 was evaluated by an immunohistochemical analysis. The tissue specimens used in this study included 46 cases of normal uterine endometrium, 40 cases of hyperplasia, and 121 cases of adenocarcinoma. The relationship between RCAS1 expression and several clinicopathological variables (clinical stage, histology, grade, myometrial invasion, lymph-vascular space invasion, and lymph node metastasis) was also assessed in endometrial adenocarcinoma. RESULTS: RCAS1 was positive in 26% of the normal uterine endometrium specimens (12 of 46 total cases), in 32% of the hyperplasia specimens (13 of 40 total cases), and in 68% of the adenocarcinoma specimens (83 of 121 total cases). As a result, the expression of RCAS1 was statistically higher in adenocarcinoma than in the normal and hyperplastic endometrium (P < 0.0001). RCAS1 was statistically detected more frequently in grade 3 than in grade 1 or 2 (P < 0.05); however, there was no correlation between the antigen expression and the clinical stage, myometrial invasion, lymph-vascular space invasion, or lymph node metastasis. CONCLUSION: RCAS1 expression might thus be associated with the malignant transformation and poor differentiation observed in uterine endometrial adenocarcinoma.

Adenocarcinoma↗
PubMed2000

Molecular analysis of mechanisms regulating drug sensitivity and the development of new chemotherapy strategies for genitourinary carcinomas.

The emergence of drug-resistant tumors during treatment remains one of the major obstacles in cancer chemotherapy. Overexpression of P-glycoprotein encoded by the multidrug resistance 1 (MDR1) gene or multidrug resistance-associated protein (MRP) (or both) and decreased expression of DNA topoisomerase II are responsible for expression of the multidrug resistance (MDR) phenotype. The expression of P-glycoprotein is also often observed in untreated cancers showing spontaneous MDR, such as renal cell carcinoma. Regarding cisplatin resistance, decreased cisplatin accumulation, an increase in cisplatin detoxification by glutathione-related enzymes or metallothionein (or both), and increased repair of DNA damage are all considered to play an important role. The combination of reversal agents targeting such drug resistance markers may be a way to improve the outcome of chemotherapy. Regarding the presently available reversal agents, however, clinically relevant chemosensitizing doses cannot be given to humans without inducing significant toxicity. The development of new agents that reverse drug resistance without causing significant toxicity and their clinical application based on the mechanisms regulating drug sensitivity may therefore be a potentially effective new treatment strategy for genitourinary carcinomas.

Drug Resistance, Multiple↗
PubMed2000

An anterograde and retrograde tract-tracing study on the projections from the thalamic gustatory area in the rat: distribution of neurons projecting to the insular cortex and amygdaloid complex.

Projections from the thalamic gustatory nucleus, i.e. the parvicellular part of the posteromedial ventral thalamic nucleus (VPMpc) to the forebrain regions were studied in the rat by the tract-tracing methods with anterograde tracer (biotinylated dextran amine, BDA) and anterograde/retrograde tracer (wheat-germ agglutinin-horseradish peroxidase, WGA-HRP). After BDA injection into the VPMpc, terminal labeling was observed in the insular cortex, amygdaloid complex, and fundus striati. The terminal labeling in the amygdaloid complex was distributed in dorsolateral area of the rostral part of the lateral amygdaloid nucleus and the rostral part of the lateral subdivision of the central amygdaloid nucleus. The terminal labeling in the central amygdaloid nucleus extended to the fundus striati. The retrograde tracing study with WGA-HRP revealed that the projection fibers from the VPMpc to the amygdaloid complex originated from the medial part of the VPMpc and also from the thalamic area medial to the VPMpc. In the rats injected with Fluoro-Gold and WGA-HRP, respectively into the insular cortex and amygdaloid complex, no double-labeled neuronal cell bodies were found in the VPMpc, although neurons labeled singly with Fluoro-Gold were intermingled with those singly labeled with WGA-HRP in the medial part of the VPMpc. The results indicated that VPMpc neurons projecting to the amygdaloid complex constituted a population different from VPMpc neurons projecting to the insular cortex.

Amygdala↗
PubMed2000

Effect of estrogen replacement on temporomandibular joint remodeling in ovariectomized rats.

PURPOSE: The investigation was performed to elucidate the effect of estrogen on the temporomandibular joint (TMJ) and to evaluate the therapeutic effect of 17beta-estradiol replacement in growing rats. MATERIALS AND METHODS: Thirty 4-week-old female albino Wistar rats were divided into 3 groups. Ten rats were ovariectomized followed by intramuscular administration of 17beta-estradiol for hormone replacement (OVX + E2), 10 were sham operated (CTL), and 10 were ovariectomized without hormone replacement (OVX). Five rats from each group were killed at 1 and 2 weeks postoperatively, and the serum estrogen was determined to verify the adequacy of replacement. The temporomandibular joints of the age-matched sham-operated control and ovariectomized groups were histomorphometrically evaluated at the same periods. RESULTS: In OVX animals, the thickness of the articular soft tissue was increased by a concomitant increase of the transitional and cartilage zones in the anterior and posterior portions at 1 and 2 weeks postoperatively. However, the bone volume was decreased in the anterior and posterior portions at 2 weeks after the surgery and the condyle was flattened. Replacement with 17beta-estradiol restored most of the histomorphometric parameters. The thickness of articular soft tissue was increased in the anterior portion by an increase in the cartilage zone in the OVX + E2 group at 2 weeks postoperatively. Increase of bone volume was found at 2 weeks after hormone replacement with a corresponding increased osteoid surface and decreased quiescent surface in the central portion at 1 week postoperatively. A flattened condyle was still noted at 2 weeks postoperatively in the OVX + E2 animals despite the hormone replacement. CONCLUSIONS: Estrogen in a physiologic concentration may play an important role in TMJ remodeling. Progesterone may be indispensable for remodeling, particularly contributing to morphogenesis.

Animals↗
PubMed2000

Overexpression of Ets-1 transcription factor in angiosarcoma of the skin.

Angiosarcoma of the skin is a rare malignant tumor which is slow-growing but highly aggressive and often recurs following surgery and/or radiation therapy, finally metastasizing to the regional lymph nodes. The ets-1 protooncogene is shown to be transcribed in endothelial cells during angiogenesis in granulation tissue and in malignant cells during tumor invasion. Furthermore, it can regulate the expression of metalloproteinase genes such as collagenase-1 (MMP-1), stromelysin (MMP-3) and urokinase-type plasminogen activator (uPA). In this study we investigated the ets-1 and MMP-1 expression in 7 angiosarcomas of the skin, compared with 7 hemangiomas and 7 granuloma pyogenicums of the skin, which are well known as benign vascular diseases. The ets-1 and MMP-1 mRNAs and their proteins were overexpressed in all angiosarcomas tested, and the localization of MMP-1 expression corresponded to that of ets-1. On the other hand, they were weakly or not at all expressed in hemangiomas and granuloma pyogenicums. These results suggest that the constitutive overexpression of ets-1 might be closely related with the malignant progression of angiosarcoma, possibly through the up-regulation of the transcription of MMP-1.

Adult↗
PubMed2000

Antimutagens in gaiyou (Artemisia argyi levl. et vant.).

Antimutagens from gaiyou (Artemisia argyi Levl. et Vant., Compositae) were examined. The methanol extract prepared from aerial parts of this plant strongly reduced the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2), when Salmonella typhimurium TA98 was used in the presence of the rat liver microsomal fraction. The antimutagens were purified chromatographically while monitoring the antimutagenic activity against Trp-P-2 with a modified Ames test employing a plate method. This purification resulted in the isolation of four strong antimutagens, 5,7-dihydroxy-6,3',4'-trimethoxyflavone (eupatilin), 5, 7,4'-trihydroxy-6,3'-dimethoxyflavone (jaceosidin), 5,7, 4'-trihydroxyflavone (apigenin) and 5,7, 4'-trihydroxy-3'-methoxyflavone (chrysoeriol) from the methanol extract. These antimutagenic flavones exhibited strong antimutagenic activity against not only Trp-P-2 but also against other heterocyclic amines, such as 3-amino-1,4-dimethyl-5H-pyrido[4, 3-b]indole (Trp-P-1), 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (MeIQ), 2-amino-3, 8-dimethylimidazo[4,5-f]quinoxaline (MeIQx) and 2-amino-3-methyl-9H-pyrido[2,3-b]indole (MeA(alpha)C) in S. typhimurium TA98. In contrast, they did not exhibit antimutagenic activity against benzo[a]pyrene (B[a]P), 4-nitroquinoline-1-oxide (4-NQO), 2-aminofluorene (2-AF), 2-nitrofluorene (2-NF) or furylfuramide (AF-2) in S. typhimurium TA98, or B[a]P, 4-NQO, 2-NF, AF-2, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or sodium azide (SA) in Salmonella typhimurium TA100, whereas they decreased the mutagenicity caused by aflatoxin B(1) (AFB(1)) and 2-aminoanthracene (2-AA) in both of these tester strains. Regarding the structure-activity relationship, the tested flavones had distinct differences in the intensities of their antimutagenic activities according to the differences of their substitution patterns. Namely, the intensity of antimutagenic activities against Trp-P-2 decreased in the order of: 5,7,3',4'-tetrasubstituted flavones (IC(50): <0.1 mmol/plate), 5,7,4'-trisubstituted flavones (IC(50): 0.120-0.260 mmol/plate), 5,6,7,3',4'-pentasubstituted flavones (IC(50): 0.440-0. 772 mmol/plate). The four isolated flavones were also studied regarding their antimutagenic mechanisms with preincubation methods of the modified Ames test and emission spectroscopic analysis. The results suggested that all isolated flavones were desmutagens which directly inactivated Trp-P-2 or inhibited its metabolic activation.

Antimutagenic Agents↗
PubMed2000

Expression of matrix metalloproteinase-1 in human colorectal carcinoma.

Matrix metalloproteinases are considered to play an important role in tumor invasion and metastasis. To elucidate the involvement of MMP-1 in human colorectal carcinoma, we performed immunohistochemical analysis on tissues from 20 colorectal adenomas and 142 colorectal adenocarcinomas, including 27 intramucosal carcinomas and 115 invasive carcinomas. MMP-1 was not expressed in any of the 20 cases of colorectal adenoma examined. In contrast, 108 of 142 cases (76.1%) with colorectal adenocarcinoma showed immunoreactivity for MMP-1 in the carcinoma cells themselves. Expression of MMP-1 was also identified in stromal cells around the carcinoma. We investigated the relationship between pathological features in colorectal carcinoma and MMP-1 immunoreactivity of the tumor cells. MMP-1 expression was less frequent in intramucosal carcinomas and weaker than that in invasive carcinomas (P < .0001). Among the 115 cases of invasive carcinomas, MMP-1 immunoreactivity was significantly correlated with the depth grading of tumor invasion (P < .05), tumor growth pattern (P < .05), the presence of lymphatic invasion (P < .05), venous invasion (P < .05), neural invasion (P < .05), lymph node metastasis (P < .005), hepatic metastasis (P < .05), and increasing stages of Dukes' classification (P < .05). In situ hybridization, using an MMP-1 oligonucleotide probe, confirmed the presence of MMP-1 mRNA in colorectal carcinoma cells themselves. Expression of MMP-1 mRNA was detected by the reverse transcription polymerase chain reaction method in cultured human colorectal carcinoma cell lines and colon carcinoma tissue obtained at surgery. These findings suggest that the expression of MMP-1 is one of the important factors related to tumor invasion and metastasis in colorectal carcinoma.

Adenocarcinoma↗
PubMed2000

A double-blind, placebo-controlled steroid-sparing study with budesonide Turbuhaler in Japanese oral steroid-dependent asthma patients. Japanese Pulmicort Turbuhaler study group.

OBJECTIVE: The aim of this study was to evaluate the oral steroid-sparing capacity of budesonide Turbuhaler. METHODOLOGY: One hundred and thirteen oral steroid-dependent patients were treated for 6 months with placebo or budesonide 800 microg or 1600 microg daily. Every second week the oral steroid dose was reduced if asthma control permitted. RESULTS: The reductions in oral steroid doses were 9, 35 and 60% in the placebo and budesonide 800 microg and 1600 microg groups, respectively. Oral steroid treatment could be discontinued in 4% (placebo), 15% (800 microg) and 23% (1600 microg). Mean peak expiratory flow values increased by 21 and 24 L/min in the budesonide groups but decreased by 6 L/min in the placebo group. Asthma attack, activity and sleep scores remained unchanged showing maintained efficacy. Plasma cortisol levels increased and an adrenocorticotropic hormone test showed improved adrenocortical response in both budesonide groups, indicating improved safety. Adverse drug reactions were infrequent and mild in all study groups. CONCLUSION: Budesonide Turbuhaler, 800 microg and 1600 microg daily, resulted in a significant reduction in oral steroid usage in steroid-dependent patients. The effect was achieved with maintained asthma control together with improvements in lung and adrenal functions.

Administration, Inhalation↗
PubMed2000

A double-blind, placebo-controlled dose-response study with budesonide Turbuhaler in Japanese asthma patients. Japanese Pulmicort Turbuhaler study group.

OBJECTIVE: The aim of this study was to investigate the dose-response for inhaled budesonide via Turbuhaler in Japanese patients with mild to moderate asthma. METHODOLOGY: Inhaled budesonide 100 microg, 200 microg, 400 microg or placebo was administered twice daily via Turbuhaler for 6 weeks, to 267 adult Japanese patients (mean age 51 years) with mild-to-moderate, non-steroid-dependent bronchial asthma, in a double-blind, placebo-controlled, randomized, parallel group study. The patients had to be symptomatic for more than 3 days/week and have an average morning peak expiratory flow (PEF) 50-80% of predicted normal value. RESULTS: The response to budesonide was rapid, all treatments showing a significant improvement in morning PEF after 1 week (P<0.05). During week 6, mean improvements of 15, 45, 53 and 71 L/min were observed for the placebo, 200 microg, 400 microg and 800 microg budesonide groups, respectively. Compared with placebo all improvements in the budesonide groups were statistically significant and a significant dose-response was demonstrated (P<0.001). The difference between the 200 microg and 800 microg doses was significant. Also, for several secondary efficacy variables (e.g. evening PEF, symptom score, treatment score, daily activity score and sleep score) significant dose-responses were shown. Other variables included the investigators' assessments of improvement and usefulness. They also showed statistically significant dose-response relationships and confirmed the rapid onset of action. Budesonide was well tolerated at all tested doses, with a low incidence of adverse events, all of which were minor in severity. CONCLUSIONS: Budesonide Turbuhaler in the doses 100 microg to 400 microg twice daily was effective, well tolerated and showed a rapid onset of action in patients with mild-to-moderate asthma. Dose-response was demonstrated for several variables of clinical efficacy.

Administration, Inhalation↗
PubMed2000

The action of sevoflurane on vascular smooth muscle of isolated mesenteric resistance arteries (part 2): mechanisms of endothelium-independent vasorelaxation.

BACKGROUND: The precise mechanisms behind the direct inhibitory action of sevoflurane on vascular smooth muscle have not been fully elucidated. METHODS: Endothelium-denuded smooth muscle strips were prepared from rat small mesenteric arteries. Isometric force and intracellular Ca2+ concentration ([Ca2+]i) were measured simultaneously in the fura-2-loaded strips. In another series of experiments, only isometric force was measured in the beta-escin-membrane-permeabilized strips. RESULTS: Sevoflurane (3-5%) inhibited the increases in both the [Ca2+]i and the force induced by either norepinephrine (0.5-10 microm) or 40 mm K+. Sevoflurane still inhibited the increase in [Ca2+]i induced by norepinephrine after depletion of intracellular Ca2+ stores with ionomycin, although it little influenced the increase in [Ca2+]i induced by norepinephrine after treatment with verapamil. In the fura-2-loaded membrane-intact muscle, sevoflurane caused a rightward shift of Ca2+-force relation during force development to stepwise increment of extracellular Ca2+ concentration during 40-mm K+ depolarization in either the presence or the absence of norepinephrine. In contrast, sevoflurane did not influence Ca2+-activated contraction in the beta-escin-permeabilized muscle, in which alpha-adrenergic receptor coupling was not retained. CONCLUSIONS: The inhibitory effects of sevoflurane on both norepinephrine- and potassium chloride (KCl)-induced contractions are caused by reduction of [Ca2+]i in vascular smooth muscle and inhibition of the myofilament Ca2+ sensitivity. The [Ca2+]i-reducing effect of sevoflurane observed in both the norepinephrine- and the K+-stimulated muscle is mainly caused by inhibition of voltage-gated Ca2+ influx. The inhibitory effect of sevoflurane on Ca2+ activation of contractile proteins seems to be mediated by the cell membrane or by some diffusible substances that are lost in the beta-escin-permeabilized cells.

Actin Cytoskeleton↗
PubMed2000

Antitumor activity of dextran derivatives immobilizing platinum complex (II).

The in vivo antitumor activity and toxicity of a newly synthesized polymeric prodrug of cisplatin was investigated and also compared with plain cisplatin. The prodrug included a dicarboxymethyl-dextran conjugate of cisplatin (DCM-Dex/CDDP). DCM-Dex/CDDP was i.v. injected in mice bearing s.c. Colon 26 mouse colon cancer cells. The tissue distribution of platinum was thereafter determined by flameless atomic absorption spectrophotometry. The platinic concentration of the organs showed a high rate of retention at 24 h after injection in the DCM-Dex/CDDP-treated mice. No biochemical or hematologically adverse effects were observed. In addition, DCM-Dex/CDDP showed a significantly higher antitumor activity than cisplatin alone. These results indicate that DCM-Dex/CDDP may therefore be a potentially effective cancer chemotherapy.

Animals↗
PubMed2000

Transforming growth factor-alpha induces the differentiation of sarcomatoid cholangiocarcinoma cells.

A sarcomatoid cholangiocarcinoma cell line, ETK-1, was established from a patient. Phenotypically, the cells corresponded to immature biliary epithelial cells. Because a small number of ETK-1 cells appeared to differentiate spontaneously along a biliary epithelial lineage in continuous culture, we examined the factors that initiate and/or promote the differentiation of the cells. Transforming growth factor-alpha (TGFalpha) induced significant changes in ETK-1 cells. After stimulation with the factor, ETK-1 cells displayed morphologic transformation at a much higher frequency, with the appearance of many large cells with intracytoplasmic vacuoles, and the production of mucinous substances. These morphologically transformed cells were phenotypically similar to well-differentiated adenocarcinoma cells. The expression pattern of integrins after TGFalpha treatment also supported the maturation of the ETK-1 cells. The antibody against the receptor of TGFalpha inhibited these changes by TGFalpha. Moreover, the proliferation rate of ETK-1 cells was suppressed by TGFalpha. Our data suggest that TGFalpha can act as a differentiation factor along a biliary epithelial lineage.

Bile Duct Neoplasms↗
PubMed2000

Immunohistochemical localisation of protein tyrosine kinase receptors Tie-1 and Tie-2 in synovial tissue of rheumatoid arthritis: correlation with angiogenesis and synovial proliferation.

OBJECTIVE: To investigate the involvement of Tie-1 and Tie-2, receptor tyrosine kinases required for angiogenesis, in synovial proliferation and angiogenesis of rheumatoid arthritis (RA). METHODS: Synovial tissues from 10 patients with RA and three control subjects were analysed by double immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: Expression of Tie-1 and Tie-2 was seen in all synovia, but predominantly in papillary projected portions. In synovial lining cells, Tie-2 was expressed mainly in the basal layer and frequently colocalised with vimentin and proliferating cell nuclear antigen (PCNA), whereas Tie-1 was also expressed in the superficial layer. In stromal cells, Tie-2 immunoreactivity was restricted to vimentin positive fibroblast-but not macrophage derived cells, whereas Tie-1 expression was not dependent on the phenotype. Tie receptors were also highly expressed in the endothelium and surrounding pericytes of capillaries scattered over the papillary proliferated synovium without notable difference in the expression of the two receptors. Furthermore, Tie positive vessels often overexpressed PCNA. In normal synovia, expression of Tie receptors was restricted to the capillary endothelium. RT-PCR confirmed the expression of Tie-1 and Tie-2 in RA synovial tissues and also in the cultured synoviocytes. CONCLUSION: The results suggest the possible involvement of overexpressed Tie-1 and Tie-2 in synovial lining and stromal cells in the pathophysiology of RA synovitis, probably through distinct mechanisms. Furthermore, expression of Tie receptors in actively growing vasculature may reflect the direct involvement of these receptors in angiogenesis and subsequent vascularisation.

Adult↗
PubMed2000

Hydrogen peroxide is an endothelium-derived hyperpolarizing factor in mice.

The endothelium plays an important role in maintaining vascular homeostasis by synthesizing and releasing several endothelium-derived relaxing factors, such as prostacyclin, nitric oxide (NO), and the previously unidentified endothelium-derived hyperpolarizing factor (EDHF). In this study, we examined our hypothesis that hydrogen peroxide (H(2)O(2)) derived from endothelial NO synthase (eNOS) is an EDHF. EDHF-mediated relaxation and hyperpolarization in response to acetylcholine (ACh) were markedly attenuated in small mesenteric arteries from eNOS knockout (eNOS-KO) mice. In the eNOS-KO mice, vasodilating and hyperpolarizing responses of vascular smooth muscle per se were fairly well preserved, as was the increase in intracellular calcium in endothelial cells in response to ACh. Antihypertensive treatment with hydralazine failed to improve the EDHF-mediated relaxation. Catalase, which dismutates H(2)O(2) to form water and oxygen, inhibited EDHF-mediated relaxation and hyperpolarization, but it did not affect endothelium-independent relaxation following treatment with the K(+) channel opener levcromakalim. Exogenous H(2)O(2) elicited similar relaxation and hyperpolarization in endothelium-stripped arteries. Finally, laser confocal microscopic examination with peroxide-sensitive fluorescence dye demonstrated that the endothelium produced H(2)O(2) upon stimulation by ACh and that the H(2)O(2) production was markedly reduced in eNOS-KO mice. These results indicate that H(2)O(2) is an EDHF in mouse small mesenteric arteries and that eNOS is a major source of the reactive oxygen species.

Acetylcholine↗