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N Kawada

Publications and source records attributed to N Kawada.

At least 109 records · Page 6Linked to original sources
PubMed1994

Effect of adrenomedullin on hepatic pericytes (stellate cells) of the rat.

When hepatic stellate cells (Ito cells, fat-storing cells) were incubated with adrenomedullin, they underwent relaxation as monitored by the silicone-rubber membrane method; 43%, 65% and 87% of stellate cells relaxed 5, 10 and 20 min, respectively, after addition of 10(-6) M adrenomedullin. Adrenomedullin also triggered the dissociation of F-actin and induced transformation of stellate cells to dendritic cell-like structure. When incubated with 10(-6) M of adrenomedullin for 30 min, cellular levels of cAMP increased from the basal value of 10.2 +/- 1.4 to 107 +/- 2.8 pmol/2 x 10(5) cells without affecting cGMP levels. The reaction occurred dose-dependently and was inhibited by an antagonist of calcitonin gene-related peptide. Adrenomedullin had negligible effects on DNA and protein synthesis in proliferating stellate cells. Thus, adrenomedullin is a potent relaxing peptide to hepatic stellate cells and may contribute to the regulation of sinusoidal microcirculation.

Actins↗
PubMed1994

Nucleotide receptors in hepatic stellate cells of the rat.

When hepatic stellate cells were stimulated by UTP, ATP, or ADP, cellular levels of inositol phosphates significantly increased (UTP > ATP > ADP > 5'-O-(3-thiotriphosphate). Thirty min after incubation with 100 microM of UTP, ATP, or ADP, levels of inositol monophosphate increased to 1318 +/- 116, 616 +/- 87 and 591 +/- 234% of control levels, respectively, with concomitant increase in the production of inositol trisphosphate and bisphosphate. These nucleotides transiently increased the [Ca2+]i of fura-2-loaded stellate cells. Moreover, UTP, ATP, ADP and adenosine 5'-O-(3-thiotriphosphate) were able to induce contraction of stellate cells as detected using the silicone-rubber membrane method. These results suggested that hepatic stellate cells have nucleotide receptors which react predominantly with extracellular UTP and ATP and trigger the receptor-mediated contraction of the cells.

Animals↗
PubMed1993

The contraction of hepatic stellate (Ito) cells stimulated with vasoactive substances. Possible involvement of endothelin 1 and nitric oxide in the regulation of the sinusoidal tonus.

We have studied the contractility of liver sinusoidal stellate (Ito) cells stimulated with endothelin 1, nitric-oxide donors and eicosanoids. Contraction and relaxation of stellate cells were detected by the use of a silicone-rubber method that revealed the traction forces exerted by these cells. Endothelin 1 was a strong elicitor for stellate-cell contraction. 78, 55, 59 and 56% of stellate cells were contracted 2.5, 5, 10 and 20 min, respectively, after exposure to 10 nM endothelin 1. The effect of endothelin 1 was dose dependent and still detectable at an endothelin 1 concentration of 100 pM. Concomitantly, an endothelin-dependent formation of inositol phosphates was apparent; values of InsP, InsP2, and InsP3 were 881 +/- 99%, 1965 +/- 368%, and 791 +/- 120% of control, respectively, 20 min after addition of 10 nM endothelin 1. In addition, endothelin 1 caused a transient increase of [Ca2+]i in stellate cells from a basal value of 121 +/- 9 nM to maximal 1015 +/- 86 nM. These endothelin-1 effects were much stronger than those of the thromboxane-A2 analogue U46619 and of prostaglandin F2 alpha. In contrast, Iloprost, prostaglandin E2, and sodium nitroprusside promoted stellate-cell relaxation; for example, 82, 83 and 71% of stellate cells relaxed 5, 10, and 20 min, respectively, after addition of 500 microM sodium nitroprusside to contacted cells. Prostaglandin E2 and Iloprost led to elevation of cAMP levels in stellate cells from a basal value of 9.2 +/- 0.8 pmol/well to 55.1 +/- 8.0 and 122.2 +/- 12.2 pmol/well 10 min after addition of prostaglandin E2 (5 microM) and Iloprost (5 microM), respectively, in the presence of 3-isobutyl-1-methylxanthine (0.5 mM). However, sodium nitroprusside was a trigger for cGMP accumulation. Intracellular cGMP increased from a basal value of 0.9 +/- 0.07 pmol/well to 13.4 +/- 6.7 pmol/well 10 min after addition of 500 microM sodium nitroprusside into the medium. It is interesting that Iloprost and sodium nitroprusside also induced the disappearance of actin stress fibers in contracted cells; F-actin stress fibers became less numerous and de-aggregated; more than 90% of stellate cells were void of stress fibers after 10 microM Iloprost treatment for 30 min. Thus, endothelin 1, eicosanoids and sodium nitroprusside are able to modulate the contractility of stellate cells.(ABSTRACT TRUNCATED AT 400 WORDS)

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1993

Regulation of endothelin-1 action on the perfused rat liver.

Endothelin-1 (ET-1) was found to be a very potent stimulus for contraction and glycogenolysis in the perfused rat liver. At 1 nM it caused a dramatic increase in portal pressure of 22.1 +/- 2.7 cm water and enhanced the glucose output up to 3-fold. Extracellular Ca2+ and protein kinase C were involved in the signal transduction of ET-1. ET-1 action does not seem to be mediated by endogenous eicosanoids. The effects of ET-1 were significantly reduced in the presence of 1 microM Iloprost, a prostaglandin I2 analogue, or by 100 microM sin-1, a nitric oxide donor. In cultured hepatocytes, glycogenolysis was also stimulated by ET-1 although to an extent too small to explain the high glucose output found in the perfused liver.

Animals↗
PubMed1993

Network of cytokine and arachidonic acid cascade in acute hepatic failure.

When heat-killed Propionibacterium acnes (P. acnes) was intravenously injected into mice and 7 days later a small amount of lipopolysaccharide (LPS) endotoxin was administered, most of the mice died of massive liver necrosis. In this liver injury model, cytokines, immunomediators, and eicosanoids, inflammatory products, were produced by Kupffer cells and liver-infiltrated macrophages, which were thought to participate, directly or indirectly, in the induction of liver cell damage. Furthermore, these two networks seemed to regulate each other. Thus, this regulatory mechanism might play an important role in the induction of liver cell injury.

Animals↗
PubMed1993

[A study to predict the clinical efficacy of house dust mite immunotherapy in bronchial asthmatics].

To predict the clinical efficacy of house dust mite immunotherapy (IT), clinical factors before IT were analyzed in relation to clinical efficacy in bronchial asthmatics treated by standard IT method. In 111 asthmatics treated by IT, 88 cases (80%) obtained favorable results over a one-year period, while only 39% of asthmatics without IT showed clinical improvement (p < 0.05, chi 2 test). Factors including severity, skin test threshold, age, age at which IT was started, duration of asthma, onset of asthma, FEV1.0% and serum IgE levels before IT were analyzed. Severity showed the most significant influence on clinical efficacy (r = 0.412, p < 0.01). A study to determine whether some specific criteria could be used to predict the clinical efficacy of IT was then carried out. Using multivariate analysis with the factors above mentioned, the clinical efficacy ranging from deteriorated to good response could be expressed as a formula with a multi-regression coefficient of 0.56, p < 0.05. Moreover, the application of linear discriminating analysis gave an 80% true positive discriminating rate in 75 asthmatics. In both methods, severity seemed to be the most important factor, skin test threshold next and FEV1.0% third. The other factors were not significant. Hopefully, the use of this formula in clinical practice will improve the efficacy of IT, thus providing further therapeutic benefits to bronchial asthmatics.

Adult↗
PubMed1992

Eicosanoid-mediated contractility of hepatic stellate cells.

To approach experimentally the problem of contractility, stellate cells from rats were isolated and grown on a flexible silicone rubber substrate. Increases or decreases in the number of wrinkles of the silicone membrane beneath the cells that were easily observable by microscopy was employed as semi-quantitative measure of stellate cell motility. Contraction of stellate cells accompanied by diminution of cell body size was induced by U46619 (a thromboxane A2 analogue) and prostaglandin (PG) F2 alpha. Wrinkle formation became detectable 1.5 min after addition of 2 microM-U46619 and reached its maximum 10-15 min later. The effect of PGF2 alpha was not so striking, but lasted for a longer period of time. On the other hand, dibutyryl cyclic AMP, Iloprost (a PGI2 analogue) and PGE2 led to the disappearance or decrease in the number of wrinkles, indicating relaxation of contracted stellate cells. For instance, after addition of 2 microM-Iloprost, 47, 75 and 82% of contracted stellate cells had relaxed within 5, 10 and 20 min respectively. Moreover, dibutyryl cyclic AMP induced disappearance of alpha-smooth muscle actin stress fibres. This response became recognizable 10 min after addition of dibutyryl cyclic AMP; 40 min later, 97% of stellate cells were devoid of stress fibres. Thus stellate cells are able to undergo reversible contraction in primary culture, and the contraction of these cells may be mediated by eicosanoids that can be produced within the liver.

Animals↗
PubMed1992

Increased 5-lipoxygenase activity in massive hepatic cell necrosis in the rat correlates with neutrophil infiltration.

Rats were treated with heat-killed Propionibacterium acnes and subsequent injection of a small amount of lipopolysaccharide after 7 days. After 24 hr most of the rats died of massive liver cell necrosis. Nonparenchymal liver cells were isolated from this liver injury model and incubated with arachidonic acid. Reverse-phase high-pressure liquid chromatography detected the 5-lipoxygenase metabolites (leukotriene B4 and 5-hydroxy-arachidonic acid), whereas these compounds were produced in negligible amounts when the rats were treated with P. acnes only. Immunohistochemical studies with 5-lipoxygenase antiserum revealed that the injured livers contained a large number of positively stained round cells with segmented nuclei, which were rarely found in the livers treated with P. acnes only. These positively stained cells were histologically identified as neutrophils. The results suggested that the increased 5-lipoxygenase activity in the injured rat liver is attributable to the infiltrating neutrophils rather than to nonparenchymal hepatic cells.

Animals↗
PubMed1992

Arachidonate metabolism in D-galactosamine or carbon tetrachloride-induced acute and chronic liver injuries in rats.

Arachidonate metabolism was examined in rats with experimentally induced acute and chronic liver injuries. Acute liver injury was induced by a single administration of D-galactosamine (D-Galn) and lipopolysaccharide (LPS) or carbon tetrachloride (CCl4). Chronic liver injury was produced by several administrations of CCl4 for 5 weeks. Non-parenchymal liver cells from rats with D-Galn/LPS-induced acute liver injury produced prominently leukotriene B4 and 5-hydroxy-arachidonic acid which were hardly synthesized by the normal rat liver. No apparent changes were observed in the arachidonate metabolism of the non-parenchymal cells of the acute CCl4-injured liver. In chronic liver injury, the production of 6-ketoprostaglandin F1 alpha, a stable metabolite of prostaglandin I2, by the non-parenchymal cell fraction was significantly enhanced in contrast with the fixed amount of the other arachidonate metabolites. These results suggested the arachidonate metabolism by non-parenchymal liver cells might change according to the pathogenesis of the liver disease.

Acute Disease↗
PubMed1992

Possible induction of fatty acid cyclo-oxygenase in lipopolysaccharide-stimulated rat Kupffer cells.

In response to stimulation with lipopolysaccharide, isolated rat Kupffer cells released increased amounts of prostaglandin E2, prostaglandin D2, 6-keto-prostaglandin F1 alpha, and thromboxane B2. There was a lag of 2-6 hours before a significant release of these metabolites into the medium was detected. Nonstimulated Kupffer cells converted exogenous arachidonic acid to prostaglandins and thromboxane B2, and a major product was prostaglandin D2. Twenty-four hours after stimulation with lipopolysaccharide, Kupffer cells produced approximately 7 times more prostaglandin E2 and 2 times more prostaglandin D2, 6-keto-prostaglandin F1 alpha; and thromboxane B2 than nonstimulated cells. Western immunoblotting of microsomal proteins prepared from the stimulated rat Kupffer cells showed a 70-kilodalton component that was immunoreactive with a polyclonal anticyclo-oxygenase antibody. The intensity of the band increased with the time of the lipopolysaccharide stimulation. These results suggest that the accelerated arachidonate metabolism in lipopolysaccharide-stimulated rat Kupffer cells might be attributed to an induction of the cyclo-oxygenase enzyme.

6-Ketoprostaglandin F1 alpha↗
PubMed1992

Enhancement of prostaglandin E2 production by liver macrophages (Kupffer cells) after stimulation with biological response modifiers.

PGE2 production by liver macrophages (Kupffer cells) activated by biological response modifiers was examined. Kupffer cells obtained from a normal rat liver possessed cyclooxygenase activity and produced TXB2, PGD2, and PGE2 from (1-14C)arachidonic acid. The major product was PGD2. When Kupffer cells were incubated in the presence of lipo-polysaccharide (LPS), OK-432, or heat-killed Propionibacterium acnes for 24 h, the amount of arachidonate cyclooxygenase products increased and the major product changed from PGD2 to PGE2. When liver macrophages including Kupffer cells were prepared from rats after an injection of LPS, OK-432, or heat-killed P. acnes, it was noticed that the number of cells obtained and PGE2 production increased compared with those of normal rat. These results suggested that PGE2 production by rat liver was induced when they were treated with biological response modifiers.

Animals↗
PubMed1992

Calcium-dependent prostaglandin biosynthesis by lipopolysaccharide-stimulated rat Kupffer cells.

Isolated rat Kupffer cells produced and released prostaglandin (PG) E2, 6-keto-PGF1 alpha, and thromboxane B2 (TXB2) in response to lipopolysaccharide (LPS) stimulation. This elevation of PGE2, 6-keto-PGF1 alpha and TXB2 in the medium was not observed when cells were cultured in the absence of extracellular calcium or in the presence of an extracellular calcium chelator, EGTA. An intracellular calcium antagonist, TMB-8, also suppressed the production of PGE2, 6-keto-PGF1 alpha and TXB2 in a concentration-dependent manner. The intra-cellular calcium concentration of Kupffer cells elevated early after the addition of LPS determined by the use of fura-2 and a fluorescence microscopy. Moreover, calmodulin inhibitors, W-7 and W-13, apparently inhibited the production of PGF2, 6-keto-PGF1 alpha and TXB2. All these results suggest that LPS-induced PG production by stimulated rat Kupffer cells may be regulated by a calcium-calmodulin pathway.

6-Ketoprostaglandin F1 alpha↗