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Biomedical subjects

I Kurose

Publications and source records attributed to I Kurose.

At least 55 records · Page 3Linked to original sources
PubMed1996

Ethanol-induced oxidative stress in the liver.

Oxygen stress is well recognized to be a key step in the pathogenesis of ethanol-associated liver injury. Ethanol administration induces an increase in lipid peroxidation either by enhancing the production of oxygen-reactive species and/or by decreasing the level of endogenous antioxidants. Numerous experimental studies have emphasized the role of the ethanol-inducible cytochrome P-450 in the microsomes, as well as the molybdo-flavoenzymes xanthine oxidase in the cytosol. This review shows the putative role of ethanol-induced disturbances in iron metabolism in relation to iron as a prooxidant factor. Ethanol administration also affects the mitochondrial free radical generation. Although many previous studies suggest a role for active oxygens in ethanol-induced mitochondrial dysfunction in hepatocytes, the detailed mechanism of ethanol-induced oxidative stress on mitochondria remains to be clarified further. Studies of our laboratory using a confocal laser scanning microscopic system strongly suggest that active oxidants produced during ethanol metabolism modulate mitochondrial energy synthesis in isolated and cultured hepatocytes. In addition, our investigations implicate endogenous glutathione-glutathione peroxidase system and catalase as important antioxidants and cytoprotective machinery in the hepatocyte mitochondria exposed to ethanol. The fluorographic investigations using the confocal laser scanning microscopy may be useful to extend our knowledge and provide a new view about ethanol-associated oxidative stress and metabolic changes in hepatocytes.

Animals↗
PubMed1996

Microvascular dysfunction induced by nonsteroidal anti-inflammatory drugs: role of leukocytes.

The objectives of this study were to determine whether 1) the leukocyte-endothelial cell adhesion observed in venules exposed to nonsteroidal anti-inflammatory drugs (NSAIDs) is accompanied by enhanced albumin extravasation, and 2) leukocytes mediate this endothelial cell barrier dysfunction. Intravital video microscopy was used to monitor leukocyte-endothelial cell adhesion and the leakage of fluorescein isothiocyanate-labeled albumin in rat mesenteric venules exposed to either indomethacin or aspirin. Both NSAIDs induced the recruitment of adherent and emigrated leukocytes with temporally related increases in albumin leakage. Agents that effectively decreased or prevented the NSAID-induced leukocyte adherence/emigration (leukotriene B4 receptor antagonist or adhesion molecule-specific monoclonal antibodies) also blocked the corresponding albumin leakage response. These findings indicate that adherent and/or emigrating leukocytes mediate the early endothelial cell barrier dysfunction elicited by NSAIDs.

Animals↗
PubMed1996

Endotoxin stimulates lymphocyte-endothelial interactions in rat intestinal Peyer's patches and villus mucosa.

Although lymphocyte-endothelial cell interactions represent a key step in controlling the recruitment of lymphocytes into gut-associated tissues, its dynamic process in microvessels of lymphoid (Peyer's patches) and nonlymphoid (villus) regions of the small bowel remains poorly understood. We monitored the migration of fluorescence-labeled T lymphocytes into normal and lipopolysaccharide (LPS)-inflamed rat intestinal microvessels using intravital microscopy. In Peyer's patches, T lymphocytes selectively adhered to postcapillary venules, although such selectivity was not observed in submucosal venules of villi. T lymphocytes exhibited rolling behavior followed by firm adhesion in microvessels of both the Peyer's patches and the villi, with both types of adhesive interaction being mediated by alpha 4-integrins. The enhanced rolling and adherence of lymphocytes observed in Peyer's patches and submucosal venules of villi of LPS-treated rats were preceded by a reduction in shear rate and were mediated largely by alpha 4-integrins and partly by beta 2-integrins. In capillaries of intestinal mucosa, lymphocyte adherence occurred without rolling and was independent of alpha 4-integrins. LPS also significantly increased adherence of lymphocytes to villus capillaries, which was not mediated by either alpha 4- or beta 2-integrin. These observations demonstrate significant heterogeneity of lymphocyte-endothelial cell interactions within different regions of the intestinal mucosa.

Animals↗
PubMed1996

Roles of ET-1 in endotoxin-induced microcirculatory disturbance in rat small intestine.

The major objective of this study was to investigate whether endothelin-1 (ET-1) plays a significant role in endotoxin-induced microcirculatory disturbances of the intestinal mucosa. Submucosal microvessels of the rat ileum were observed by intravital microscopy with a high-speed video camera system. Preceding the apparent intestinal mucosal damage, red blood cell (RBC) velocity was significantly decreased 30 min after endotoxin treatment in both arterioles and venules. The number of leukocytes sticking to submucosal venules was significantly increased at 30 min. BQ-123, an ETA-receptor antagonist, significantly attenuated the decrease in RBC velocity and also prevented an increase in leukocyte sticking as well as the subsequent mucosal damage induced by endotoxin. The ET-1 concentrations began to be elevated in plasma at 15 min and in the mucosa at 30 min and subsequently further increased in a time-dependent manner. A significant decrease in calcium-dependent nitric oxide synthase activity and significant increases in the concentration of platelet-activating factor (PAF) were demonstrated in the intestinal mucosa after endotoxin treatment. BQ-123 also significantly attenuated these changes. We concluded that the increased ET-1 production in intestinal mucosa induced by endotoxin stimulation could lead to leukocyte sticking and decreased RBC velocity in the intestinal microcirculatory beds via ETA receptors, which are closely related to increased production of PAF and decreased synthesis of constitutive nitric oxide.

Animals↗
PubMed1996

Oxidative stress during platelet-activating factor-induced microvascular dysfunction.

OBJECTIVE: To assess the potential contribution of hydrogen peroxide (H2O2) to the leukocyte-endothelial cell adhesion and increased microvascular permeability (to fluorescein isothiocyanate [FITC]-albumin) observed in rat mesenteric venules exposed to platelet-activating factor (PAF). METHODS: The production of oxidants derived from H2O2 in mesenteric tissue was monitored using the H2O2-sensitive fluorochrome, dihydrorhodamine 123 (DHR). PAF elicited a rapid increase in both the albumin extravasation and oxidation of DHR, which was followed by an increased adherence and emigration of leukocytes in postcapillary venules. RESULTS: The PAF-induced oxidation of DHR, leukocyte-endothelial cells interactions, and albumin leakage were attenuated by treatment with either catalase or dimethylthiourea. Treatment with monoclonal antibody directed against either CD11b/CD18 on leukocytes or ICAM-1 on endothelial cells attenuated the PAF-induced oxidative stress, albumin leakage, and leukocyte-endothelial cell adhesion. CONCLUSIONS: These findings indicate that most of the oxidants generated in mesenteric tissue exposed to PAF results from the accumulation of activated leukocytes.

Animals↗
PubMed1996

Ethanol-induced apoptosis and oxidative stress in hepatocytes.

This short review focuses on ethanol-induced oxidative stress and hepatocyte apoptosis. Apoptosis is increasingly recognized as a fundamental biological process that impacts on an early development, maturation, and acquisition of disease states of multicellular organisms. Although the occurrence of apoptosis has been identified for many decades, relatively recent acceptance of this principle is evidenced by remarkable increases in special conferences and presentations on this topic as well as its rapidly expanding volume of scientific literature. Oxidative stress is well recognized to be a key step in the pathogenesis of ethanol-associated liver injury. Ethanol administration induces an increase in lipid peroxidation either by enhancing the production of oxygen reactive species and/or by decreasing the level of endogenous antioxidants. Studies in our laboratory using a confocal laser scanning microscopic system strongly suggest that agents which inhibit ethanol-induced oxidative stress effectively attenuate hepatocyte death, i.e., apoptosis and necrosis. In addition, our investigations demonstrated that inhibitors of intracellular antioxidants exaggerate ethanol-associated hepatocyte apoptosis. Although the detailed mechanism still remains unknown, it is conceivable that an oxidant-dependent mechanism is largely involved in the process for ethanol-induced hepatocyte apoptosis.

Animals↗
PubMed1996

Ethanol-induced leukocyte adherence and albumin leakage in rat mesenteric venules: role of CD18/intercellular adhesion molecule-1.

The adherence and emigration of leukocytes have been implicated as a rate-limiting step in the microvascular disturbance in a variety of pathogenic events. The objective of the present study was to investigate leukocyte-endothelial cell adhesion and endothelial barrier function in rat mesenteric microvessels exposed to ethanol, which is known to cause inflammation and injury in various organs. Mesentery of male Wistar rats was used for intravital microscopic observations. Leukocyte adherence and albumin leakage were monitored in single postcapillary venules using the intravital fluorescence microscope. Superfusion of 50 mM ethanol elicited the leukocyte adherence and albumin leakage within 60 min. Pretreatment with a monoclonal antibody directed against either CD18 or intercellular adhesion molecule-1 (ICAM-1) significantly prevented the ethanol-induced increase in leukocyte adherence and decrease in barrier function of endothelium. These results suggest that ethanol-induced leukocyte adherence is mediated by CD18 on leukocytes and ICAM-1 on endothelial cells. The present study further supports that CD18/ ICAM-1-dependent leukocyte-endothelial adhesive interactions lead to macromolecular leakage in the postcapillary venules exposed to ethanol.

Animals↗
PubMed1996

Chronic ethanol consumption enhances endotoxin induced hepatic sinusoidal leukocyte adhesion.

In alcoholic liver disease, endotoxin has been postulated to play an important role in its pathogenesis. Endotoxin is known to lead to impediment of hepatic microcirculation, including the adhesion of leukocytes to sinusoidal endothelial cells. In this study, the effect of chronic ethanol consumption on the leukocyte adhesion elicited by endotoxin was examined. Male Wistar rats were pair-fed with a liquid diet containing ethanol or an isocaloric control diet for 6 weeks. The liver of anesthetized rats were placed on the nonfluorescent cover-glass for observation by an intravital inverted microscope equipped with a silicon intensified target camera. The red blood cell (RBC) velocity in hepatic sinusoids was measured by an off-line temporal correlation velocimeter (Capiflow, Sweden) after intravenous injection of fluorescein isothiocyanate-labeled rat RBC. RBC velocity in sinusoids was more severely disturbed in ethanol fed rats than in controls. Leukocytes were stained by the intravenous injection of carboxyfluorescein succinimidyl ester for a fluorographic observation of leukocyte adhesion. After lipopolysaccharide injection, the number of adherent leukocytes was significantly greater in ethanol-fed rats than in controls. Plasma tumor necrosis factor-alpha levels were also higher in ethanol-fed rats than in controls. These results suggest that chronic ethanol consumption aggravates endotoxin induced leukocytes adhesion that may result in hepatic microcirculatory disturbances. Leukocyte adhesion to the sinusoidal wall may be associated with increased in tumor necrosis factor-alpha levels.

Animals↗
PubMed1995

Spatial heterogeneity of mucosal blood flow during ischemia-reperfusion injury of rat stomach investigated by laser Doppler perfusion imaging.

Spatial alterations in blood flow during the development of mucosal injury induced by ischemia-reperfusion in rats were determined with a two-dimensional laser Doppler tissue perfusion imager. The rats were anesthetized with pentobarbital, and the stomach was exteriorized on a stage; the mucosa was then sequentially scanned. The mucosa was constantly superfused with 0.1 N HCl in physiological saline. Systemic arterial pressure was continuously monitored and blood was stepwisely withdrawn from the femoral artery by 20-mmHg stage and then maintained at 20 mmHg for 20 min. The shed blood was reinfused and the stomach was removed 30 min later. Under control conditions, the average perfusion of the forestomach was usually greater than that in the glandular stomach. When systemic blood pressure was stepwisely decreased, the extent of decrease in the mucosal blood perfusion unit was always greater than that in systemic blood pressure, but mucosal perfusion appeared to be uniformly decreased throughout the stomach. Ten min after reperfusion, a hypoperfused area began to appear in the corpus near the greater curvature, and this area subsequently increased. The area of ulcer formation corresponded with the hypoperfused area in the gastric mucosa 30 min after reperfusion. Pretreatment with CV-6209, a platelet-activating factor antagonist, significantly attenuated the hypoperfusion induced by reperfusion and also prevented gastric mucosal damage. Our results suggest that hypoperfusion in the mucosal microcirculation is indeed an important factor contributing to the localized occurrence of gastric mucosal lesions and that the laser Doppler perfusion imager is useful for the detection of local hypoperfused areas in the gastric mucosa.

Analysis of Variance↗
PubMed1995

Wound healing of acetic acid-induced gastric ulcer in rats and the effects of cimetidine and calcitonin, with special reference to prolylhydroxylase and collagenase enzyme activity.

The healing of acetic acid-induced gastric ulcer in rats and the effects of cimetidine and calcitonin were investigated with reference to the enzyme activity of both prolylhydroxylase and collagenase as related to histological findings. The rats were observed by endoscopy on the 3rd day after the subserosal injection of acetic acid; rats with ulcers were divided into three groups: non-treated, and cimetidine- and calcitonin-treated. The latter two groups were treated for 7 days. Prolylhydroxylase activity in active ulcers in the non-treated group was slightly higher on the 3rd day and significantly higher on the 10th day than the activity in control rats that had received subserosal injections of physiological saline solution on the respective days. In non-treated rats, the healed ulcer on the 10th day showed lower prolylhydroxylase activity than that in the active ulcer on the same day. Cimetidine did not affect prolylhydroxylase activity, but, with calcitonin, there was higher prolylhydroxylase activity in the healed than in the active ulcer, although the difference was not significant. Interstitial collagenase showed the highest activity on the 3rd day and decreased on the 10th day in non-treated rats. Collagenase activity was higher in the cimetidine-treated group, than that in the non-treated group, and numerous peroxidase-positive granulocytes were seen in the mucosa and submucosa. Calcitonin did not affect collagenase activity. The participation of both enzymes is indispensable in the healing process and the effects of anti-ulcer agents on these enzymes must be considered.

Acetates↗
PubMed1995

Oxidative stress in gastric mucosal injury: role of platelet-activating factor-activated granulocytes.

Temporal and spatial changes due to oxidative stress in the rat gastric mucosa were visualized and quantified during the process of mucosal hemorrhagic change. The fluorescence associated with dichlorofluorescein (DCF), a hydroperoxide-sensitive fluorochrome, increased 30 min after repeated electrical stimuli to the gastric artery. The increase in the fluorescence was enhanced in the area between two adjacent collecting venules. The content of platelet-activating factor (PAF), the activity of myeloperoxidase (MPO) in the gastric mucosa, the area of mucosal lesions, and the luminol-dependent chemiluminescence activity in zymosan-treated blood samples, obtained from the gastric vein, were measured and found to increase significantly 30 min after the stimuli. The intravenous injection of CV-6209, a PAF antagonist, 5 min prior to the stimuli significantly inhibited the DCF activation, the increases in PAF level and MPO activity, the mucosal hemorrhagic change, and the elevation in chemiluminescence activity. In addition, continuous infusion of superoxide dismutase also inhibited all these changes, except for chemiluminescence activity. These results suggest that oxygen radicals derived from PAF-activated granulocytes induce oxidative stress, and that oxidative changes are actually implicated in the pathogenesis of gastric mucosal injury.

Animals↗
PubMed1995

Intravital demonstration of sequential migration process of lymphocyte subpopulations in rat Peyer's patches.

BACKGROUND & AIMS: Although recirculation of lymphocytes through Peyer's patches is important for specific immune defense, the intraorgan migration of lymphocyte subpopulations has not been clearly understood. The aim of this study was to compare the spatial distributions of labeled lymphocytes among various subpopulations in rat Peyer's patches. METHODS: Lymphocytes collected from intestinal lymph were separated into CD4+, CD8+, and T and B cells, labeled with a fluorochrome carboxyfluorescein diacetate succinimidyl ester, and injected into the jugular vein. Peyer's patches of recipient rats were observed by intravital fluorescence microscopy. RESULTS: No significant difference was found in the percentage of lymphocytes in transit or in the rolling velocity among different subpopulations. Lymphocytes sticking to the venules increased in number at 10-20 minutes, with preferential adherence of CD4+ cells to venules of 25-50 microns and preferential adherence of B cells to the venules of a wider size range. After 30 minutes, extravasated lymphocytes moved into the interstitium. B cells migrated from venules more quickly than CD4+ cells. CD8+ cells showed an intermediate pattern between CD4+ and B cells in sticking and migratory behaviors. Subsequently, CD4+ and CD8 cells preferentially appeared in parafollicular microlymphatics. CONCLUSIONS: Significant differences were observed among lymphocyte subpopulations in terms of spatial distribution of lymphocytes sticking to venules, migration into the interstitium, and their lymphatic transport.

Animals↗
PubMed1995

Rat Kupffer cell-derived nitric oxide modulates induction of lymphokine-activated killer cell.

BACKGROUND & AIMS: Nitric oxide is now recognized to regulate immune responses and cell viability in various organs. The present study was designed to clarify whether NO released from Kupffer cells modulates the lymphokine-activated killer (LAK) activity of interleukin 2 (IL-2)-treated splenocytes. METHODS: Splenocytes and Kupffer cells were isolated from male Wistar rats and cocultured for 48 hours in the presence of lipopolysaccharide (1 microgram/mL). The splenocyte LAK activity and expression of IL-2 receptor were determined. RESULTS: Kupffer cells with lipopolysaccharide reduced the IL-2 receptor expression and LAK activity of splenocytes. The addition of either NG-monomethyl-L-arginine, an inhibitor of NO synthesis, or aminoguanidine, an inhibitor of inducible NO synthase, to the medium reversed the suppression of IL-2 receptor expression and LAK activity by lipopolysaccharide-stimulated Kupffer cells. 8-bromoguanosine 3',5'-cyclic monophosphate and NO donors decreased the splenocyte LAK activity and IL-2 receptor expression. Treatment with lipopolysaccharide increased the inducible NO synthase activity as well as the nitrite and nitrate levels in the culture medium of Kupffer cells but not in splenocytes. CONCLUSIONS: The results of this study suggest that NO produced by the inducible NO synthase of Kupffer cells in response to lipopolysaccharide modulates the IL-2 receptor expression and LAK activity of splenocytes.

Analysis of Variance↗
PubMed1995

Nitric oxide mediates mitochondrial dysfunction in hepatoma cells induced by non-activated Kupffer cells: evidence implicating ICAM-1-dependent process.

The metabolic changes in a rat hepatoma cell line, AH70 cells, after co-culture with rat Kupffer cells (KC) were visualized and analysed using a fluorescence microscope equipped with a silicon intensified target camera and a laser scanning confocal microscopic system. Kupffer cells were isolated from male Wistar rats, and cultured without any stimuli. The non-activated KC reduced the mitochondrial energization in the cocultured AH70 cells within 2 h, which was indicated by decreased rhodamine 123 (Rh123) fluorescence. Either NG-monomethyl-L-arginine or dexamethasone significantly attenuated the KC-induced mitochondrial dysfunction in AH70 cells, suggesting the involvement of nitric oxide (NO) derived from inducible-type nitric oxide synthase (iNOS). Administration of monoclonal antibody (mAb) directed against rat ICAM-1 also prevented the decrease in Rh123 fluorescence. Electron microscopy revealed that the membrane-to-membrane attachment between KC and AH70 cells occurred within 2 h. A laser scanning confocal microscopic observation using mAb against ICAM-1 presented that the ICAM-1 expression on AH70 cells and KC increased after the co-culture. It is therefore concluded that the KC-mediated mitochondrial dysfunction of hepatoma cells largely depends on NO production by iNOS. Furthermore, the present study supports a scenario that the NO production and release from KC is triggered by the close contact with hepatoma cells through adhesion molecules such as ICAM-1.

Animals↗
PubMed1995

Effects of an endogenous inhibitor of nitric oxide synthesis on postcapillary venules.

The objective of this study was to determine whether an inhibitor of nitric oxide (NO) synthase (NG,NG'-dimethyl-L-arginine; L-DMA) that is produced by vascular endothelium elicits the inflammatory responses induced by synthetic analogues of L-arginine such as NG-nitro-L-arginine methyl ester (L-NAME). Leukocyte adherence and emigration, leukocyte-platelet aggregation, and albumin leakage were monitored in rat mesenteric venules exposed to different concentrations of either L-DMA or L-NAME. Increases in leukocyte adherence (7- to 9-fold) and emigration (3- to 5-fold), platelet-leukocyte aggregation, mast cell degranulation, and an enhanced albumin leakage (30-50%) were observed within 30 min after exposing the microvascular bed to either inhibitor; however, leukocyte emigration and albumin leakage responded more intensely to L-NAME than to L-DMA. The microvascular alterations and mast cell degranulation were attenuated by addition of L-arginine to the superfusate. These results suggest that the L-DMA is capable of eliciting an inflammatory response at concentrations detected in plasma under certain pathological conditions.

Amino Acid Oxidoreductases↗
PubMed1995

Microvascular responses to inhibition of nitric oxide production. Role of active oxidants.

The objective of this study was to assess the potential contribution of hydrogen peroxide (H2O2) to the leukocyte-endothelial cell adhesion and increased microvascular permeability observed in rat mesenteric venules after inhibition of nitric oxide synthesis with NG-nitro-L-arginine methyl ester (L-NAME). Leukocyte adherence and emigration and leakage of fluorescein isothiocyanate-labeled albumin were monitored in postcapillary venules before and after exposure of the tissue to L-NAME. H2O2 production in mesenteric tissue was monitored by using dihydrorhodamine 123 (DHR), the H2O2-sensitive fluorochrome. L-NAME elicited a rapid increase in both the rate of albumin extravasation and oxidation of DHR, which was followed by an increased adherence and emigration of leukocytes in postcapillary venules. Treatment with either catalase or dimethylthiourea attenuated the L-NAME-induced oxidative stress, albumin leakage, and leukocyte-endothelial cell adhesion. Oxidation of DHR was enhanced in animals treated with either 3-amino-1,2,4-triazole (ATZ), an inhibitor of endogenous catalase, or a combination of ATZ and maleic acid diethyl ester, which depletes intracellular glutathione. Animals receiving a CD11/CD18-specific antibody to prevent leukocyte adhesion/emigration exhibited a reduced oxidation of DHR in response to L-NAME. These findings indicate that most of the H2O2 (and secondarily derived oxidants) generated in mesenteric tissue exposed to an inhibitor of nitric oxide production is due to accumulation of activated leukocytes.

Amino Acid Oxidoreductases↗
PubMed1995

Active oxygen species generation by circulating leukocytes and gastric submucosal microcirculatory disturbances in the early period after thermal injury.

The purpose of the present study was to determine the pattern of microcirculatory disturbance to investigate the causes of gastric mucosal blood flow depression in the early period after thermal injury. Male Wistar rats were anesthetized and a 30% full skin-thickness dorsal burn was inflicted. Active oxygen species (AOS) generated by circulating leukocytes were measured by chemiluminescence. Contraction of arterioles and venules was observed by intravital microscopy, and rolling or sticking of leukocytes in venules was counted using fluorescence microscopy. AOS generation by circulating leukocytes was diminished and arteriolar contraction and increases in rolling or sticking leukocytes in venules were observed 15 min after thermal injury. Decreased AOS generation by circulating leukocytes, contractions of arterioles, and increased rolling or sticking of leukocytes in venules was observed in the early period after thermal injury. Arteriolar contraction may explain decreases in mucosal blood flow. Moreover, decreased AOS generation by circulating leukocytes does not obviate the potential participation of leukocytes in microcirculatory disturbances, because rolling or sticking leukocytes were increased significantly 15 min after thermal injury.

Animals↗