The role of lipoxygenases in the activation of macrophages by lipopolysaccharide.
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Animals↗
Biomedical subjects
U F Schade
Publications and source records attributed to U F Schade.
Increased 13-hydroxyoctadecadienoic acid content in lipopolysaccharide stimulated macrophages.
Endotoxin-stimulated mouse peritoneal macrophages were found to contain 13-hydroxyoctadecadienoic acid, which was released upon alkaline hydrolysis of the cells. Compared to untreated cells, incubation with LPS increased the content of 13-hydroxyoctadecadienoic acid in macrophage hydrolysates to about 8-fold. Analysis of the material on chiralphase HPLC revealed that it consisted prevalently of 13(S)-hydroxyoctadecadienoic acid. This indicates its enzymatic origine.
Animals↗
The effect of endotoxin on the lipoxygenase-mediated conversion of exogenous and endogenous arachidonic acid in mouse peritoneal macrophages.
The influence of lipopolysaccharide (LPS, endotoxin) or its lipid A component (bacterial and synthetic) on the synthesis of zymosan induced leukotriene C4, prostaglandin E2 and prostacyclin and on the conversion of exogenous arachidonic acid was studied in mouse peritoneal macrophages. It was found that following preincubation with LPS the amount of leukotriene C4 released during phagocytosis of zymosan was substantially decreased. The levels of prostaglandin E2 and prostacyclin, however, were the same in LPS-treated cells and controls. Likewise, pretreatment with LPS impaired the capacity to convert exogenously added arachidonic acid to mono- and di-HETE's. Lipid A (bacterial and synthetic) exhibited the same activity as LPS. LPS had no effect on macrophages of the endotoxin low responder mouse strain (C3H/HeJ). Several explanations could be possible for the observed LPS effect. The finding that low doses of alpha-tocopheryl acetate prevented the LPS-induced decrease of LTC4 synthesis indicates a protective role of this agent. We would, therefore, favour the idea that lipoxygenases undergo oxidative selfinactivation during LPS action.
Animals↗
Metabolism of exogenous arachidonic acid by mouse peritoneal macrophages.
On incubation of resident mouse peritoneal macrophages with arachidonic acid several hydroxyacyl derivatives detectable in cellular supernatants are formed. As main products monohydroxyarachidonic acids (monoHETE's) were identified. In addition, smaller amounts of dihydroxyarachidonic acids (diHETE's) were formed. A detailed analysis of cell culture supernatants by reversed phase HPLC, normal phase HPLC in combination with UV-spectroscopy and combined gas-chromatography/masspectrometry revealed the presence of 5-, 8-, 12- and 15- monoHETE's, two distinct 5,12-diHETE's, several 8,15-diHETE's and 14,15-diHETE. Among the 5,12-diHETE's, only small amounts of a compound with the characteristics of LTB4 were detected. Under the conditions employed, the cyclooxygenase products PGE2 and PGI2 (as 6-keto-PGF1 alpha) were only minor metabolites. In contrast, when macrophage cultures were stimulated with the phagocytic stimulus zymosan, PGI2, PGE2 and LTC4 were found as the major conversion products of arachidonic acid, whereas mono- and diHETE's were not formed in detectable amounts.
Animals↗
Involvement of lipoxygenases in the activation of mouse macrophages by endotoxin.
Preincubation with lipopolysaccharides stimulated the phagocytic capacity of mouse peritoneal macrophages. Treatment of cell cultures with inhibitors of lipoxygenases which affect this pathway specifically (diethylcarbamazine) or compounds which block lipoxygenases and cyclooxygenase (BW 755 C, eicosatetraynoic acid) inhibited the increase, while inhibitors of cyclooxygenase (indomethacin, aspirin) did not affect the LPS induced enhancement of the phagocytic capacity. It is, therefore, concluded that lipoxygenase products are required for the activation of macrophages by endotoxins.
Animals↗
Oxpentifylline in endotoxaemia.
Oxpentifylline (pentoxifylline), which is known to have pharmacological effects in animal models of respiratory distress syndrome, multiorgan failure, and shock, was tested in human beings after injection of endotoxin. Of ten healthy volunteers, nine met the inclusion criterion of a rise in body temperature of at least 1.0 degrees C after 100 ng endotoxin (Salmonella abortus equi) as a bolus injection. Serum levels of tumour necrosis factor alpha (TNF) and interleukin-6 (IL-6) were both significantly higher than baseline levels 2 h and 3 h after endotoxin injection. 3 weeks later the nine volunteers were again injected with 100 ng endotoxin and oxpentifylline (500 mg over 4 h) was also infused. There was no rise in TNF levels, though IL-6 levels rose in parallel with body temperature. These data suggest that oxpentifylline blocks the endotoxin-induced synthesis of TNF in man and, therefore, could possibly have beneficial effects in clinical endotoxaemia.
Adult↗
Ascorbic acid induces lipid peroxidation on neuroectodermal SK-N-LO cells with high endogenous ferritin content and loaded with MAb-ferritin immunoconjugates.
Neuroblasma-and other malignant cells often contain elevated amounts of iron-rich ferritin and H2O2 and may therefore be a potential target for pro-oxidative effects of ascorbic acid (AA), generating cytotoxic products e.g. by lipid peroxidation (LPO). The influence of H2O2 and iron, either in its free form or bound to ferritin, on AA induced LPO was first investigated using erythrocyte ghosts as a model system. Results of these experiments showed that AA induced LPO not only in the presence of free available iron but also in the presence of ferritin. Similarly, AA induced significant LPO in neuroectodermal SK-N-LO cells with elevated intracellular ferritin levels. These LPO promoting effects of ferritin in the presence of AA on SK-N-LO cells could also be observed using ferritin-immunoconjugates: for this purpose, ferritin was bound to human monoclonal antibodies (MAb-ferritin) recognizing ganglioside GD2 which is present in large quantities on cell surfaces of SK-N-LO and many neuroblastoma cells. We conclude that the pro-oxidative effects of AA could be exploited in the treatment of ferritin rich neuroblastoma in combination with chemotherapy or with MAb-ferritin immunoconjugates.
Antibodies, Monoclonal↗