Lysis

About: Lysis is a research topic. Over the lifetime, 6072 publications have been published within this topic receiving 216978 citations.

Role of oxygen-dependent mechanisms in antibody-induced lysis of tumor cells by activated macrophages*

Abstract: The alloantiserum-dependent lysis of TLX9 lymphoma cells by peritoneal cells from Bacille Calmette-Guerin (BCG)-treated mice was inhibited 62 percent by depletion of oxygen. This effect did not appear to be a result of interference with mitochondrial respiration because cyanide, azide, and dinitrophenol did not inhibit cytotoxicity. Preincubating the effector cells for 2 h without glucose, which markedly reduces their ability to release hydrogen peroxide, likewise suppressed antibody-dependent cytolysis by 62 percent. Lysis of sensitized lymphoma cells was virtually abolished by 6 mg/ml of thioglycollate broth, a concentration that also abrogated the detectable release of hydrogen peroxide and the lysis of lymphoma cells by BCG-activated macrophages in response to phorbol myristate acetate (PMA). This concentration of thioglycollate broth was not toxic to the effector cells, as judged by adherence to plastic, binding of opsonized erythrocytes, and phagocytosis of radiolabeled starch granules. Catalase, superoxide dismutase, horseradish peroxidase, mannitol, ethanol, benzoate, and diazabicyclooctane were without consistent effects. Cytochalasin B and dihydrocytochalasin B both markedly suppressed cytolysis, whether induced by antibody or by PMA (ID(50), 0.5 μg/ml). Cytoehalasin B was an equally potent suppressor of glucose uptake and PMA-induced hydrogen peroxide release by BCG-activated macrophages (ID(50), 0.5 μg/ml). However, dihydrocytochalasin B lacked these latter effects, which suggests that cytotoxicity required intact contractile elements. The extracellular lysis of antibody-coated lymphoma cells by BCG-activated macrophages appears to have a predominantly oxidative basis.

Physiologic relevance of the membrane attack complex inhibitory protein CD59 in human seminal plasma: CD59 is present on extracellular organelles (prostasomes), binds cell membranes, and inhibits complement-mediated lysis.

Abstract: We demonstrate here that CD59, an inhibitor of the membrane attack complex (MAC) of the complement system, is present in cell-free seminal plasma (SP) at a concentration of at least 20 micrograms/ml. Analyses by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, Western blotting, and Edman degradation indicated that this protein, SP CD59, was similar, if not identical, to CD59 isolated from erythrocyte (E) membranes (E CD59). Like purified E CD59, SP CD59 also possesses a glycosyl phosphatidyl inositol (GPI) anchor and incorporates into the membranes of heterologous cells where it inhibits lysis by the human MAC. This phenomenon could be demonstrated not only if cells were incubated with purified SP CD59 but also if unfractionated SP were used. Further, CD59 in unfractionated SP bound to washed spermatozoa, increasing their membrane content of the protein. The mechanism by which this protein retains its GPI anchor while apparently present in the fluid phase is of interest and was further investigated. Using the techniques of high-speed centrifugation, fast performance liquid chromatography fractionation, and electron microscopy, we found that all detectable SP CD59 was associated with vesicular extracellular organelles. These organelles, named "prostasomes," were previously known to be present in SP and to interact with spermatozoa, although their function was uncertain. Interaction of heterologous E with prostasomes rendered the cells more resistant to lysis by human MACs. We propose that these organelles represent a pool of CD59 from which protein lost from spermatozoa, perhaps as a result of low level complement attack or of normal membrane turnover, can be replenished.

Autolytic system of Staphylococcus simulans 22: influence of cationic peptides on activity of N-acetylmuramoyl-L-alanine amidase.

Abstract: Pep 5 and nisin are cationic peptide antibiotics which in addition to their membrane-disruptive action induce autolysis in staphylococci. To investigate the mechanism of lysis induction, the influence of the peptides on the activity of the N-acetylmuramoyl-L-alanine amidase of Staphylococcus simulans 22 was studied. In experiments with isolated cell walls at low ionic strength, the amidase activity was stimulated by the addition of Pep 5 and nisin, as well as by polylysine, streptomycin, and mono- and divalent cations. The concentrations necessary for activation depended on the nature of the cation and ranged from 5 microM for poly-L-lysine (n = 17) to 150 mM for Na+ at a cell wall concentration of 100 micrograms of cell walls per ml. No effect was observed if the cell walls were devoid of polyanionic constituents. Kinetic data suggested that the amidase bound to the teichoic and teichuronic acids of the cell wall and was thereby inhibited. Cationic molecules reversed this inhibition, most likely by displacing the enzyme from the polyanions. If the concentrations of the larger peptides were high in relation to cell wall concentration, the activation turned into inhibition, presumably by interfering with the access of the enzyme to its substrate. These experiments demonstrate that the activity of the amidase is modulated by basic peptides in vitro and help to explain how Pep 5 and nisin may cause lysis of treated cells.

Islet Cell DNA Is a Target of Inflammatory Attack by Nitric Oxide

Abstract: NO has been identified recently as the prime islet-toxic product of inflammatory macrophages. The adverse effects of IL-1 on isolated islets also have been reported to involve NO. We now show that exposure of an islet cell suspension to the NO donor nitroprusside or to activated macrophages leads to DNA strand breaks. Macrophages did not induce DNA damage in the presence of the NO synthase inhibitor NG-methyl-L-arginine. DNA strand breaks were demonstrated at the level of single cells by a modified nick-translation procedure and confirmed by analysis of DNA fragmentation by gel electrophoresis. DNA strand breaks occurred within 1 h and preceded islet cell lysis. DNA damage could not be prevented by inhibitors of endogenous endonucleases. We conclude that islet cell DNA is an early target of NO action.