Biomedical subjects
Publications and source records attributed to U Karck.
Thecomas are considered to be benign ovarian tumours. Whether there are malignant thecomas, is a subject of controversy in literature. This contribution describes a case of recurrent thecoma with a clinically malignant course and histological signs of malignant dedifferentiation. The particular diagnostic and therapeutic consequences of this rare disease are discussed with emphasis on the need for radical surgical intervention.
Kupffer cells are the main producers of tumor necrosis factor-alpha (TNF; cachectin) and eicosanoids in the liver exposed to lipopolysaccharide (endotoxin; LPS). A very rapid but transient release of TNF is followed by a slow, steady synthesis of prostaglandin E2 (PGE2). TNF itself is able to provoke eicosanoid synthesis in Kupffer cells; the rate and pattern of prostaglandin production are similar to those observed after treatment with LPS. Anti-TNF antibodies completely neutralize TNF action on Kupffer cells, thus ruling out any participation of contaminating LPS. LPS stimulation of PGE2 production in Kupffer cells is reduced by the antiserum to 50%, indicating an involvement of TNF in the stimulatory action of LPS. On the other hand, PGE2, a potent inhibitor of LPS-elicited TNF release, is able to suppress LPS- but not TNF-stimulated eicosanoid synthesis in rat Kupffer cells. In addition to this autocrine circuit, extrahepatic factors participate in the regulation of Kupffer cell activation: glucocorticoids not only inhibit TNF or prostaglandin production, they also reverse the LPS-specific changes in the prostaglandin pattern of Kupffer cells. LPS, TNF or cycloheximide when given alone in the concentration range applied in this study do not affect the viability of rat Kupffer cells. However, the combinations of cycloheximide and either LPS or TNF cause rapid death of the cultured cells. The cytolytic potential of either combination cannot be alleviated by treatment with glucocorticoids.
Macrophages (Mphi) and Mphi-depleted (nonadherent) nonparenchymal cells (NPC) of the liver were examined for their cytotoxic potential against tumor cells, production of tumor necrosis factor (TNF), and release of prostaglandins (PG) following stimulation by lipopolysaccharide (LPS), interferon-gamma (IFN gamma), and zymosan. Resident murine liver macrophages had no natural cytotoxicity for the TNF-resistant target cell line P815. Activation of these cells was only obtained by a combination of IFN gamma and LPS. Inflammatory murine macrophages were in a primed stage and could be activated by LPS alone in the absence of IFN gamma. Rat resident macrophages resembled functionally the inflammatory macrophages of the mouse liver rather than the resident macrophages. They displayed natural cytotoxicity against all targets tested and were further activated by LPS in the absence of IFN gamma. Similar results were obtained with respect to macrophage-depleted nonadherent NPC: Mouse NPC had a low level of NK activity against Yac-1 cells. Treatment with pyran copolymer resulted in a strong increase of cytotoxicity against Yac-1; furthermore, a TNF-dependent killing of Wehi 164 and TNF-independent cytotoxicity against P815 cells were now acquired. In the rat NPC prepared from unstimulated animals expressed high levels of natural cytotoxicity against all targets. No major differences could be observed between inflammatory Mphi and Kupffer cells of rat and mouse liver with regard to TNF production and TNF-dependent killing of Wehi 164 tumor cells. The same was true for the spectrum of secreted prostanoids. Upon activation of all cell populations a marked shift toward the production of PGE2 occurred. Experiments involving the cyclooxygenase inhibitor indomethacin showed enhanced TNF-dependent tumor cell killing by nonactivated Mphi in the absence of prostanoid production.
Evidence is presented that upon stimulation with endotoxin (lipopolysaccharide, LPS), Kupffer cells, the body's largest pool of sessile macrophages, synthesize and liberate a factor whose immunological, cytotoxic and chemical properties are those described for tumor necrosis factor (TNF)-alpha. Hepatocytes and sinusoidal endothelial cells do not produce detectable amounts of this protein. Ten nanograms of LPS per ml medium are sufficient to stimulate a substantial release of this mediator. Recombinant interferon-gamma (rIFN gamma) per se is a poor inducer of TNF release. Costimulation with endotoxin and rIFN gamma shows only a slight increment in the release of this cytotoxic factor, relative to LPS alone. Exposure of Kupffer cells to the Ca2+ ionophore A23187 or to elicitors of the oxidative burst and superoxide production, e.g. zymosan or phorbol 12-myristate 13-acetate, stimulates only a fraction (20%) of the TNF release seen after endotoxin challenge. Prostaglandin E2, the synthesis of which is strongly enhanced after challenge of rat Kupffer cells with LPS, suppresses the release of TNF by these cells. This autoregulatory mechanism may explain the kinetics of TNF production by stimulated Kupffer cells. Dexamethasone is another important mediator capable of reducing the LPS-elicited TNF formation. An effect of the glucocorticoid hormone can still be provoked if it is added simultaneously with or shortly after LPS. This rapid action requires a mechanism that is different from the time-consuming one leading to the inhibition of prostaglandin synthesis in Kupffer cells.
Tumor necrosis factor (TNF) has been shown to mediate lipopolysaccharide-induced neutrophil adhesion to liver sinusoidal endothelium in vivo. Female NMRI mice received either 5 micrograms lipopolysaccharide (R595) per animal alone (model A) or together with 116 mumol D-galactosamine (model B). One hour after injection, TNF activity in the serum was detectable to an equal extent in both models. Neutrophils in the liver, which had been identified by chloroacetate esterase staining of liver sections and quantitated by light microscopy, started to increase at 1 h and were elevated 10-fold above baseline at 6 h after application in (A) and (B). If 0.5 micrograms TNF instead of lipopolysaccharide was injected alone (model C) or together with D-galactosamine (model D), neutrophil influx into the liver was comparable to that observed in (A) or (B). Alanine aminotransferase activity in the serum was nearly normal in (A) and (C) 6 h after injection, while it reached levels up to 50-fold above baseline in models (B) and (D). This reflects the well-known D-galactosamine sensitization against lipopolysaccharide or TNF. Furthermore, degranulation of a large number of intrasinusoidal neutrophils could be observed 9 h after lipopolysaccharide-galactosamine injection. The administration of 116 mumol D-galactosamine per animal alone led neither to a measurable TNF activity in the serum nor to an increase in alanine aminotransferase activity or number of liver neutrophils. If the animals had received 50 microliter turpentine subcutaneously 24 h prior to lipopolysaccharide, TNF or D-galactosamine injection, the induced acute-phase reaction suppressed the increase of liver neutrophils in all models. Acute-phase reaction also prevented neutrophil degranulation and the rise of alanine aminotransferase in (B) to a great extent, while serum TNF activity was only minimally affected. It is concluded that TNF mediates neutrophil adhesion to the sinusoidal endothelium in vivo and that acute-phase reactants prevent lipopolysaccharide- or TNF-induced neutrophil influx into the liver.
The release of the prostaglandins E2 and D2, induced by zymosan and phorbol ester in cultured rat Kupffer cells, was found to depend on the extracellular concentration of Na+. Eicosanoid formation following the administration of the Ca2+ ionophore A23187 or of arachidonic acid, however, did not require the presence of sodium ions in the medium. A half-maximal rate of prostaglandin release by zymosan-treated Kupffer cells was obtained between 4 mM and 5 mM Na+; and a Na+ concentration of greater than or equal to 30 mM was required to maximally stimulate prostaglandin E2 and D2 formation in the cultured liver macrophages. In contrast, the superoxide production following the administration of zymosan or of phorbol ester was quite independent of extracellular Na+. The zymosan and phorbol-ester-stimulated release of prostaglandins E2 and D2 was inhibited by amiloride. Artificial intracellular alkalization enhanced the prostanoid production of unstimulated and of zymosan-stimulated cells whereas artificial intracellular acidification inhibited the zymosan-elicited prostaglandin synthesis. In contrast, the superoxide formation was independent of the pH changes. The data presented here suggest that the prostaglandin production elicited by zymosan or phorbol ester in cultured rat Kupffer cells requires an activated Na+/H+ exchange.
Supernatants of endotoxin-activated monocytes have been shown to stimulate human neutrophil adherence to rat liver sinusoidal endothelial cells 3-4-fold. Evidence will be presented that tumor necrosis factor (TNF) is responsible for this phenomenon: (a) in high-performance gel filtration of supernatants of lipopolysaccharide-activated monocytes, neutrophil adhesion-inducing activity coeluted with TNF activity measured in the L929 cell-lysing assay at 25-45 kDa; (b) anti-TNF antibody treatment of supernatants of activated macrophages abolished their adhesion-inducing activity; (c) human recombinant TNF alpha stimulated neutrophil adhesion to sinusoidal endothelial cells in a dose-dependent manner. In addition, polymyxine B sulfate, which was capable of neutralizing direct effects of lipopolysaccharide on neutrophil adhesion, could abolish neither the neutrophil-adhesion-inducing activity of the supernatants of endotoxin-activated monocytes nor the effect of human recombinant TNF itself. The neutrophil-adhesion-inducing activity was due both to a direct activation of neutrophils and to an influence of the sinusoidal endothelium itself by TNF: pretreatment of sinusoidal endothelial cells with TNF followed by thorough washing resulted in an increased neutrophil attachment. Protein synthesis by endothelial cells was not required. However, incubation of sinusoidal endothelium with TNF followed by anti-TNF antibody treatment abrogated the increased neutrophil adhesion. This suggests that TNF bound to sinusoidal endothelial cell surfaces was responsible for neutrophil adhesion. It is concluded that TNF by increasing granulocyte sticking to the endothelial lining of the liver sinusoids may play a significant role in endotoxin-induced inflammation of the liver as it is found in the septic state.