Nitric oxide mediates Kupffer cell-induced reduction of mitochondrial energization in hepatoma cells: a comparison with oxidative burst.

The metabolic changes in rat hepatoma cell line, AH70 cells, after coculturing with Kupffer cells were visualized using a silicon-intensified target camera and subsequent processing with a computer-assisted digital imaging processor. In cocultured tumor cells, nonactivated Kupffer cells reduced mitochondrial energization as indicated by the decrease in the fluorescence intensity of rhodamine 123 (Rh123) and induced lipid peroxidation as shown by the dichlorofluorescein (DCF) activation. The reduction in Rh123 could be eliminated by addition of an analogue of L-arginine (NG-monomethyl-L-arginine), suggesting the involvement of nitric oxide (NO.) in the decrease in mitochondrial energization. Superoxide dismutase did not inhibit the reduction in Rh123 but significantly inhibited DCF activation. These findings indicate that the latter reaction was mediated by superoxide anion. Two h after the cells were cocultured, propidium iodide-positive, severely injured tumor cells significantly increased in number. This increase was significantly attenuated by addition of NG-monomethyl-L-arginine but not by superoxide dismutase, suggesting that NO. may be greatly involved in Kupffer cell-mediated injury of AH70 cells. In another set of experiments, the culture medium of Kupffer cells caused no significant alteration of Rh123, DCF, and propidium iodide-associated fluorescences in AH70 cells. In addition, ultrastructural observation revealed that the membrane-to-membrane attachment between Kupffer cells and tumor cells occurred within 30 min after coculturing. These results suggest that Kupffer cell-derived NO. release, triggered by the close contact with tumor cells, may induce damage to tumor cells via inhibition of mitochondrial energization.

CD18/ICAM-1-dependent nitric oxide production of Kupffer cells as a cause of mitochondrial dysfunction in hepatoma cells: influence of chronic alcohol feeding.

The present study was designed to monitor the process for hepatoma cell injury induced by Kupffer cells. The non-activated Kupffer cells isolated from male Wistar rats reduced the mitochondrial membrane potential in the cocultured AH70 cells, which was indicated by the decreased rhodamine 123 (Rh123) fluorescence. Increased level of nitrite and nitrate in the medium and induction of iNOS in Kupffer cells were observed after coculture with AH70 cells. Incubation with either NG-monomethyl-L-arginine or aminoguanidine attenuated the increased nitric oxide (NO) production of Kupffer cells and the decreased Rh123 fluorescence of AH70 cells. Fluo-3, a calcium-sensitive probe, fluorescence in Kupffer cells increased after coculture with AH70 cells. Addition of TMB-8, a calcium inhibitor, or monoclonal antibody directed against ICAM-1 or CD18 prevented the increases in fluo-3 fluorescence and NO production of Kupffer cells and Kupffer cell-induced mitochondrial dysfunction in AH70 cells, suggesting the involvement of calcium mobilization and CD18/ICAM-1. It is therefore suggested that the Kupffer cell-mediated mitochondrial dysfunction of hepatoma cells largely depends on NO production by iNOS, and that the NO production by Kupffer cells is triggered by CD18/ICAM-1-dependent interaction with hepatoma cells and subsequent calcium mobilization. In other series of experiments, male Wistar rats fed ethanol for 4 weeks were used. The NO production and calcium mobilization of Kupffer cells and reduction of the mitochondrial membrane potential in cocultured hepatoma cells were diminished in the case of Kupffer cells isolated from chronically ethanol-fed rats, while CD18 and ICAM-1 expression was still observed. Thus, the present study further suggests that NO-dependent anti-hepatoma cell activity of Kupffer cells is suppressed in chronically ethanol-fed animals.

Indomethacin potentiates endotoxin-induced blood flow reduction and histological injury in rat gastric mucosa.

1. The effect of the intravenous administration of lipopolysaccharide from Salmonella typhosa endotoxin on arterial blood pressure (BP), gastric mucosal blood flow (GMBF) and gastric damage was studied in anaesthetized rats. The effect of the inhibition of endogenous prostaglandin generation by indomethacin on these parameters was also investigated in this model of endotoxin shock. 2. A similar and dose-dependent percentage of reduction in BP and GMBF was observed 5 min after a bolus injection of 20 or 30 mg kg-1 endotoxin. A transient recovery in GMBF at 15 min was observed followed by a second fall at 30 min, at a time when BP was slowly increasing. 3. Pretreatment with indomethacin (5 mg kg-1, s.c.) one hour before the administration of 30 mg kg-1 endotoxin, significantly augmented the reduction in GMBF without affecting the reduction in BP. 4. The gastric damage, assessed histologically, was similar and confined to the superficial mucosa 30 min after the administration of 20 or 30 mg kg-1 endotoxin. The histologically-assessed damage was significantly greater in indomethacin pretreated rats injected with 30 mg kg-1 endotoxin. 5. These findings suggest that endogenous prostaglandin generation plays a protective role in endotoxin-induced gastric mucosal microcirculatory disturbances and mucosal damage.

Autoradiographic demonstration of gastrin binding sites in rat gastric mucosa.

The location of 125I-iodotyrosyl gastrin I binding sites in rat gastric mucosa was studied. Peptide specificity was demonstrated by competitive binding studies through the addition of a large dose of cold human gastrin I or cholecystokinin-octapeptide. Autoradiography of the stomach tissue was carried out by freeze-drying, embedding in Epon, wet-sectioning with ethylene glycol, and dry-mounting the emulsion film by means of the wire-loop method to prevent loss of the labeled substance. Specific binding sites for gastrin were found on parietal and chief cells, whereas few binding sites were seen on the surface mucous or mucous neck cells. Binding sites on the parietal cells were dispersed in the cytoplasm, while those on the chief cells were found near the basal plasma membrane.

Effects of omeprazole and pirenzepine on enterochromaffin-like cells and parietal cells in rat stomach.

PURPOSE: The purpose of this study was to investigate the mechanism of the regulation of histamine synthesis in enterochromaffin-like cells, chemically and structurally, by treatment with omeprazole and pirenzepine. METHODS: The ultrastructures of enterochromaffin-like cells and parietal cells were examined in rats treated with oral omeprazole (20 mg/kg) or intraperitoneal pirenzepine (1 mg/kg) administration. Serum gastrin concentrations, mRNA levels of H+-K+-ATPase and histidine decarboxylase, and the fundic concentrations of somatostatin and histamine were determined. RESULTS: Pirenzepine treatment suppressed omeprazole-induced increases in serum gastrin levels and mRNA levels of H+-K+-ATPase and histidine decarboxylase. Pirenzepine also decreased omeprazole-induced increases of histamine concentration in fundic mucosa. Pirenzepine elevated somatostatin mRNA level, previously decreased by omeprazole treatment, in fundic mucosa. In the cytoplasm of enterochromaffin-like cells, omeprazole markedly reduced the numbers of vesicles and granules, but significantly increased their diameters, whereas pirenzepine treatment changed neither of these features. The densities and diameters of both vesicles and granules produced by treatment with omeprazole and pirenzepine were between those produced by treatment with omeprazole alone and pirenzepine alone. CONCLUSIONS: Omeprazole-induced hypergastrinemia and pirenzepine-induced somatostatin synthesis play important roles not only in histamine synthesis but also in ultrastructural changes in enterochromaffin-like cells.

A case of erythropoietic protoporphyria with liver cirrhosis suggesting a therapeutic value of supplementation with alpha-tocopherol.

Erythropoietic protoporphyria (EPP) was diagnosed in a 27-year-old man based on a typical clinical history, and a marked increase in erythrocyte and fecal protoporphyrin concentrations. Although liver disease is not a common feature in EPP, he had slight liver dysfunction. A percutaneous liver biopsy was performed and it showed minimal hepatocellular damage and many reddish brown pigment deposits in hepatocytes, Kupffer cells, portal histiocytes, bile canaliculi and small biliary radicles. Electron microscopic findings confirmed that these deposits were composed of protoporphyrin crystals. Liver biochemistry remained well for >2 years, but deteriorated rapidly and second liver biopsy obtained 28 months after the first biopsy revealed the development of liver cirrhosis. We treated the patient with intravenous administration of dl-a-tocopherol acetate (vitamin E; 500 IU/body/day). Following the administration of vitamin E, the concentration of protoporphyrin in erythrocytes decreased significantly and the liver function tests were improved. Sixteen weeks later he showed the full clinical and biochemical recovery suggesting that vitamin E supplementation might be useful in treating patients with EPP who developed liver damage.

Alterations in gastric mucosal microvascular endothelium in a stressed condition--relevance to gastric ulcerogenesis.

The present paper describes the morphological and functional alterations of the gastric mucosal microvascular endothelium under restraint-stressed condition. On the basis of the direct cholinergic innervation of capillaries and non-muscular venules in the gastric mucosa, these endothelial changes would be caused by the stress-induced overstimulation of the cholinergic nerves and modified by the degranulation of mast cells, contributing to the stress-induced ulcer formation as schematically illustrated in Fig. 10.