Tetsu Sasaoki

Enhancement of hepatic macrophages in septic rats and their inhibitory effect on hepatocyte function

In the present study, the function of hepatic macrophages and the modulation of hepatocytes by sepsis-elicited hepatic macrophages were investigated in rats with induced sepsis. The functional state of hepatic macrophages was determined by the following indicators: phagocytic index, protein-synthesizing capacity, and superoxide (O2-) producing capacity. These indices of changes in hepatic macrophages were much higher in rats with sepsis than in healthy controls. Moreover, the activated hepatic macrophages had some biological properties which were different from those of the resident Kupffer cells. It was found that protein synthesis by cultured hepatocytes was inhibited in the co-culture system of hepatocytes and sepsis-elicited hepatic macrophages, and that the supernatant of hepatic macrophages from rats with sepsis also reduced the protein-synthesizing capacity of cultured hepatocytes. Thus, activated hepatic macrophages may play a role in inducing hepatic dysfunction in sepsis.

Depressed function of Kupffer cells in rats with CCl4-induced liver cirrhosis.

SummaryIn the present study, the Kupffer cell function of rats with CCl4-induced liver cirrhosis was tested by analyzing the changes in the host defense system. In rats without liver cirrhosis injected with CCl4 for 3 weeks concomitant with the high opsonic activity the endocytic index was significantly increased. Rats treated for 9 and 13 weeks developed cirrhosis, and their endocytic indices were not increased despite the rise in their opsonic activity. Particularly, the endocytic index of 13-week-treated rats with advanced liver cirrhosis was significantly lower than that of the other groups. The organic distribution of 51Cr-endotoxin injected intravenously exhibited characteristic changes in 9-week- and 13-week-treated rats: decreased hepatic uptake and increased splenic uptake. In contrast, pulmonary uptake was increased in all CCl4-treated rats. The superoxide production by Kupffer cells from 13-week-treated rats was greatly reduced, accompanied by the decreased superoxide dismutase activity of liver homogenate. Thus, results of this study suggest that Kupffer cell dysfunction is one of the main factors affecting host defenses in liver cirrhosis.

The three different phases of reticuloendothelial system phagocytic function in rats with liver injury

In the present study, reticuloendothelial system (RES) phagocytic function of rats with partial hepatectomy or experimentally induced liver cirrhosis was investigated by determining the phagocytic index, the opsonic index, and uptake rate in liver, spleen, and lung of a 51Cr-labeled endotoxin-injected rat. In both the partially hepatectomized and the cirrhotic rats, all three indicators varied markedly according to the elapsed period since liver injury. The changes in RES phagocytic function were classified into three different phases: compromised, compensatory, and enhanced. The compromised phase, consisting of a decrease in the phagocytic index, was observed during the first 24 hr after 67% hepatectomy and in advanced liver cirrhosis. This represented the failure of RES phagocytic function. The compensatory phase, in which the phagocytic index was maintained at nearly normal levels mainly by a compensatory enhancement in the opsonic index, was seen during the first to second postoperative day and in moderate liver cirrhosis. The enhanced phase, with a high phagocytic index, was observed from Day 4 to approximately Day 14 after surgery, and in the cases of mild liver damage. In the compromised and compensatory phases, the liver uptake rate was significantly decreased compared with the control. However, the uptake in the spleen and lung were markedly increased. In conclusion, the phagocytic function of the RES was significantly affected to a degree which changed with the extent of liver damage.

Hepatic macrophage malfunction in rats with obstructive jaundice and its biological significance

The present study was designed to investigate the pathophysiology of obstructive jaundice by analyzing the function of hepatic macrophages and their role in immune responses and homeostasis in rats. The phagocytic index, determined by the rate of disappearance of 51Cr-endotoxin from the peripheral blood after intravenous injection, was increased in obstructive jaundice 2 weeks after bile duct ligation. The superoxide production of isolated hepatic macrophages and peripheral blood monocytes, measured by the superoxide dismutase inhibitable ferricytochrome c reduction method, was increased. Prostaglandin E2 release, measured by RIA, was markedly increased in rats with obstructive jaundice, but there was no significant difference in interleukin-1 release between jaundiced and control rats. The flow-cytometric analysis of surface molecules of hepatic macrophages showed decreased expression of interleukin-2 receptor in rats with obstructive jaundice. Thus, the functions of hepatic macrophages in rats with obstructive jaundice were impaired. This malfunction may disturb the immunoregulatory network and metabolism, although the exact implications of the altered function of hepatic macrophages have not yet been clarified.

Enhancement and hepatocyte-modulating effect of chemical mediators and monokines produced by hepatic macrophages in rats with induced sepsis.

SummaryWe investigated the production of chemical mediators by hepatic macrophages from rats with sepsis and the modulation of hepatocyte function by these hepatic macrophages. The chemical mediators we measured were superoxide (O2−), TNF, IL-1, and PGE2. Production of these mediators by hepatic macrophages from rats with sepsis was significantly increased. Furthermore, protein synthesis by cultured hepatocytes was inhibited in a co-culture system of hepatocytes and hepatic macrophages from rats with sepsis, and it was even inhibited by the supernatant of cultured hepatic macrophages from septic rats. These results demonstrate that hepatic macrophages are activated in sepsis and may play a role in inducing hepatic dysfunction in sepsis.

Chemical mediator release and surface marker expression of hepatic macrophages in rats with CCl4-induced liver cirrhosis

The present study was performed to analyze possible functional alterations of hepatic macrophages (HM phi) in rats with carbon tetrachloride (CCl4)-induced liver cirrhosis. HM phi from rats injected with CCl4 for 13 weeks and cultured for 24 hours released less than normal amounts of prostaglandin E2 (PGE2) and tumor necrosis factor (TNF) and very large amounts of interleukin-1 (IL-1). In rats injected with CCl4 for 9 weeks, only PGE2 production was reduced. Interleukin-2 receptor (IL-2R), Ia antigen and asialo GM1 antigen expressions on HM phi from both the 9- and 13-week groups were significantly decreased. IL-2R and Ia antigen expressions showed larger decreases in the 13-week group. Thus, it is concluded that HM phi derived from CCl4-induced cirrhotic livers show a functional alteration in the release of cytokines (except for IL-1) and a decrease in surface marker expression, as cirrhosis advances. These results should provide a basis for further investigation into the host-compromised status in the presence of liver cirrhosis.

Enhancement of rat hepatic macrophages by treatment with interleukin-2 and streptococcal preparation OK432, with reference to antitumor activity, soluble factor production and Ia expression

SummaryThe effect of biological response modifiers, such as interleukin-2 (IL-2) and streptococcal preparation OK432, on the functions of hepatic macrophages was investigated. The macrophages, even with no exogenous stimulation, produced superoxide anion (O2-) and tumor necrosis factor (TNF), displayed cytotoxicity against K562 cells and cytostasis against P815 cells and expressed immune-region-associated antigen (Ia). IL-2 administered in vitro or in vivo enhanced O2- production by hepatic macrophages and the intravenous injection of OK432 also enhanced O2- production. Furthermore, IL-2 added to the culture medium of hepatic macrophages isolated from OK432-injected rats augmented O2- production even more. The TNF production and Ia expression of the macrophages were also increased by the intravenous injection of OK432. As with O2- production, the cytotoxicity of the cells was enhanced by OK432 injection or by IL-2 added to the culture medium and the combination of OK432 and IL-2 augmented their cytotoxicity even more. Thus, the present study suggested that IL-2 and OK432 induce the augmentation of the antitumor activity of hepatic macrophages, partly as a result of the increase in production of O2- and TNF and Ia expression.

Effects of Cholecystokinin and Carbachol on Membrane Fluidity in Pancreatic Acini

The effects of pancreatic secretagogues on the membrane fluidity of pancreatic acini were investigated using 1-[4-(trimethylammonium)phenyl]-6-phenyl-1,3,5-hexatriene iodide as a probe. Two kinds of pancreatic secretagogues, one category of which induces acute pancreatitis (cholecystokinin and carbachol) and another which does not induce acute pancreatitis (bombesin, CCK-JMV-180, and secretin), as well as lecithin were used to investigate the effect of changes in membrane fluidity of acini. Our study revealed that the membrane fluidity of the pancreatic acini was unaffected by a physiological dose (10−11 M) of cholecystokinin. However, stimulation with a supramaximal dose of cholecystokinin (10−8 M) increased membrane fluidity markedly within 20 min. Membrane fluidity increased dose-dependently with increasing CCK stimulation. A supramaximal dose of cholecystokinin also induced bleb formation and increased LDH release. These phenomena were blocked by simultaneous incubation with CR1505 (Loxiglumide), a potent antagonist of peripheral cholecystokinin receptors. A supramaximal dose of carbachol (10−3 M) also induced increases in the membrane fluidity. Pancreatic secretagogues that do not induce acute pancreatitis did not induce alterations in membrane fluidity. Lecithin increased both membrane fluidity and LDH release. These observations suggest that this increase in membrane fluidity of the pancreatic acini may be related to membrane alteration and to functional damage of the acini. These observation can serve as a window to detect the development of acute pancreatitis at an early stage.