leukotriene-b4 and Necrosis

The staphylococcal bi-component leukotoxins constitute a family included in the super-family of the beta-sheet-structured pore-forming toxins. They may be produced by Staphylococcus aureus and by Staphylococcus intermedius and their target cells vary according to the molecules. The mode of action proceeds by the sequential binding of the class S proteins, then by that of the class F proteins at the surface of the membranes. Then, the activation of cellular calcium-channels precedes the pore formation which seems to be sensitive to several monovalent cations. The cell response is inflammatory and includes the neosynthesis as well as the secretion of leukotriene B4, interleukin -8, histamine. The injection of leukotoxins to rabbits generates cell chemotaxis , vasodilatation, and tissue necrosis. The association of the production of leukotoxins with clinical syndromes concerns several aspects of the pathology of S. aureus, and confers to these leukotoxins an important role of virulence factors.

Topics: Animals; Bacterial Proteins; Bacterial Toxins; Calcium Channels; Cations, Divalent; Cattle; Cell Membrane Permeability; Chemotaxis, Leukocyte; Cross Infection; Erythrocytes; Exotoxins; Female; Hemolysin Proteins; Histamine Release; Humans; Interleukin-8; Ion Transport; Leukocidins; Leukotriene B4; Male; Mastitis, Bovine; Models, Biological; Necrosis; Neutrophils; Rabbits; Staphylococcal Infections; Staphylococcus aureus; T-Lymphocytes; Vasodilation; Virulence; Vitreous Body

Both leukotrienes and neutrophils have been linked to plaque destabilization. Despite being evoked, the role of leukotriene B4 (LTB4) in neutrophil recruitment to plaques and the concomitant effects of these two actors on plaque stability remain to be proven. Since both actors are elicited during endotoxaemia, a condition associated with the risk of cardiovascular events, we investigated whether endotoxaemia promotes LTB4-mediated neutrophil infiltration in plaques and explored the roles of LTB4 and neutrophils in plaque destabilization.. Endotoxaemia induced by repeated peritoneal endotoxin injections at a non-lethal dose (1.5 mg/kg, 5 days) in chow-fed aged Apoe-/- mice (over 45 weeks old) resulted in neutrophil infiltration and activation in plaques. Subsequently to neutrophil invasion, plaques exhibited increased features of vulnerability: reduced collagen content, expanded necrotic cores, and thinned fibrous caps. These plaque features were reproduced by direct deposition of isolated neutrophils onto murine atheromatous carotid arteries in an in vivo assay. In endotoxemic mice, plaques produced increased amounts of LTB4. Genomic or pharmacological impairments of this production reduced neutrophil infiltration, collagenolysis, and apoptosis of smooth muscle cells in plaques of endotoxemic mice. Furthermore, conditioned media of human culprit plaques (CPs) contained more LTB4 than non-CPs and levels of LTB4 correlated to both neutrophil activation markers and endotoxin releases in CPs.. These results show that the increased neutrophil recruitment elicited by LTB4 contributes to increase features of plaque destabilization in endotoxemic contexts and point out LTB4 as a potential therapeutic target in atherosclerosis.

Topics: Animals; Aorta; Aortic Diseases; Arachidonate 5-Lipoxygenase; Atherosclerosis; Disease Models, Animal; Endotoxemia; Female; Fibrosis; Humans; Leukotriene B4; Lipopolysaccharides; Male; Mice, Inbred C57BL; Mice, Knockout, ApoE; Necrosis; Neutrophil Activation; Neutrophil Infiltration; Neutrophils; Paracrine Communication; Plaque, Atherosclerotic; Signal Transduction; Tissue Culture Techniques

Infection of humans with Mycobacterium tuberculosis (Mtb) results in diverse outcomes that range from acute disease to establishment of persistence and to even clearance of the pathogen. These different outcomes represent the combined result of host heterogeneity on the one hand, and virulence properties of the infecting strain of pathogen on the other. From the standpoint of the host, the balance between PGE2, LXA4 and LTB4 represents at least one of the factors that dictates the eventual pathophysiology. We therefore built an ODE model to describe the host-pathogen interaction and studied the local stability properties of the system, to obtain the parametric conditions that lead to different disease outcomes. We then modulated levels of the pro- and anti-inflammatory lipid mediators to better understand the convergence between host phenotype and factors that relate to virulence properties of the pathogen. Global sensitivity analysis, using the variance-based method of extended Fourier Amplitude Sensitivity Test (eFAST), revealed that disease severity was indeed defined by combined effects of phenotypic variability at the level of both host and pathogen. Interestingly here, [PGE2] was found to act as a switch between bacterial clearance and acute disease. Our mathematical model suggests that development of more effective treatments for tuberculosis will be contingent upon a better understanding of how the intrinsic variability at the level of both host and pathogen contribute to influence the nature of interactions between these two entities.

Topics: Apoptosis; Computer Simulation; Dinoprostone; Humans; Inflammation; Leukotriene B4; Lipoxins; Macrophages; Models, Theoretical; Mycobacterium Infections; Mycobacterium tuberculosis; Necrosis; Phenotype; Treatment Outcome; Virulence

Liver cell death by apoptosis and necrosis occurs upon the liver injury. Lipoxygenase pathway of arachidonic acid metabolism is known to regulate the viability and apoptosis in some cell types, but its role in hepatocyte cell death is not fully understood. We studied the influence of leukotrienes (LT) and lipoxygenase inhibitors on apoptosis and necrosis in rat hepatocyte primary culture by double staining with Hoechst 33342 and propidium iodide and electron microscopy. Treatment with general lipoxygenase inhibitor nordihydoguaiaretic acid and 5-lipoxygenase inhibitor caffeic acid (2. 10(-5) M) for 4 and 24 h induced hepatocyte apoptosis. LTB4 and LTC4 (10(-8) M) decreased the number of living cells and increased the number of necrotic cells. LTs exerted the same necrotic effect on hepatocytes, treated with lipoxygenase inhibitors. It is important that LTs decreased apoptosis induced by inhibitors treatment. These data suggest that lipoxygenase pathway of arachidonic acid metabolism is important regulator of hepatocytes viability and apoptosis The increase of lipoxygenase product formation, in particular LTs, may diminish apoptosis and increase necrosis in hepatocytes upon the liver injury.

Topics: Animals; Apoptosis; Cells, Cultured; Hepatocytes; Leukotriene B4; Leukotriene C4; Leukotrienes; Lipoxygenase Inhibitors; Male; Masoprocol; Necrosis; Rats; Rats, Wistar

Arachidonic acid (AA)-induced cytotoxicity was evaluated in leukocytes: the human leukemia cell lines HL-60, Jurkat and Raji and in rat lymphocytes. Such cytotoxicity was dose- and time-dependent. At concentrations below 5 microM, AA was not toxic; at 10-400 microM, AA induced apoptosis and at concentrations beyond 400 microM, necrosis. The minimum exposure time to trigger cell death was of around 1 h, but the effect was increased by longer exposure times until 6-24 h. Apoptosis was morphologically characterized by a decrease in cell and nuclear volume, chromatin condensation and DNA fragmentation and the presence of lipid bodies, without changes in organelle integrity. Biochemically, AA-induced apoptosis was associated with internucleosomal fragmentation and caspase activation, evaluated by PARP cleavage and the use of a caspase inhibitor. Necrosis was characterized by increased cell volume, presence of loose chromatin, appearance of vacuoles, loss of membrane integrity and of the definition of organelles. The apoptotic effect of AA was studied as to oxidative-reductive imbalance and the participation of eicosanoids. Apoptotic AA treatment was accompanied by an increase in the quantity of thiobarbituric acid reactive substances (TBARS), low-level chemiluminescence and in the glutathione disulfide/reduced glutathione ratio, indicating oxidative stress. The addition of tocopherol, ascorbate, prostaglandin E2 and lipoxygenase inhibitors delayed cell death, whereas the inhibition of cyclooxygenase promoted AA-induced cell death. Cell treatment with AA was accompanied by increased cellular production of LTB4. AA, therefore, is cytotoxic at physiological and supraphysiological concentrations, causing apoptosis and necrosis. Cell treatment with apoptotic concentrations of AA involves oxidative stress and changes in eicosanoid biosynthesis.

Topics: Animals; Antioxidants; Apoptosis; Arachidonic Acid; Caspases; Cell Nucleus; Cyclooxygenase Inhibitors; Cytotoxins; DNA Fragmentation; Dose-Response Relationship, Drug; Drug Administration Schedule; Eicosanoids; Glutathione Disulfide; HL-60 Cells; Humans; Jurkat Cells; Leukocytes; Leukotriene B4; Necrosis; Oxidative Stress; Poly (ADP-Ribose) Polymerase-1; Poly(ADP-ribose) Polymerases; Proteins; Rats; Thiobarbituric Acid Reactive Substances

Leukotriene B4 is a potent inflammatory mediator that is derived from the 5-lipoxygenase pathway of arachidonic acid metabolism and that has been implicated in the pathophysiology of polymorphonuclear leukocyte-dependent reperfusion injury in a variety of organ systems. The objectives of these investigations were to determine whether inhibition of leukotriene B4 attenuates postischemic polymorphonuclear leukocyte infiltration and subsequent injury in myocutaneous flaps. Anesthetized female Yorkshire pigs were randomized to receive normal saline (n = 8), the 5-lipoxygenase inhibitor diethylcarbamazine (n = 7), or the leukotriene B4 receptor antagonist SC-41930 (n = 7). All animals underwent 6 hours of rectus abdominis myocutaneous flap ischemia followed by 4 hours of reperfusion. In saline-treated controls, flap ischemia was associated with massive polymorphonuclear leukocyte infiltration at 1 and 4 hours of reperfusion (252 +/- 70 and 619 +/- 137 polymorphonuclear leukocytes per 25 high-power fields, respectively). Skeletal muscle neutrophil content was significantly attenuated by pretreatment with diethylcarbamazine (72 +/- 29 and 229 +/- 63 polymorphonuclear leukocytes per 25 high-power fields; p < 0.05) or SC-41930 (25 +/- 3 and 193 +/- 25 polymorphonuclear leukocytes per 25 high-power fields; p < 0.05). Wet-to-dry weight ratios of full-thickness flap biopsies were lower in the diethylcarbamazine and SC-41930 groups (2.98 +/- 0.15 and 2.90 +/- 0.26, respectively) than in the control group (4.13 +/- 0.23; p < 0.01), and mean muscle infarct size, as determined by nitroblue tetrazolium staining, diminished from 47.6 +/- 11.3 percent in controls to 25.1 +/- 6.5 percent in diethylcarbamazine-treated animals and 7.3 +/- 4.8 percent in SC41930-treated animals (p < 0.05). These data indicate that leukotriene B4 plays a critical role in mediating neutrophil-dependent injury in postischemic skeletal muscle flaps.

Topics: Animals; Benzopyrans; Diethylcarbamazine; Female; Inflammation Mediators; Leukotriene B4; Lipoxygenase Inhibitors; Muscle, Skeletal; Necrosis; Neutrophils; Receptors, Leukotriene B4; Reperfusion Injury; Surgical Flaps; Swine

An ideal form of cancer therapy is the harnessing of innate immunity to eradicate spontaneously arising clones of malignant cells. To date, attempts to develop effective immunotherapies have met with limited success. Prostaglandins and leukotrienes, collectively known as eicosanoids, are important mediators of immune and inflammatory responses. Harnessing these compounds could be a method to treat cancers. Eicosanoids are formed after cleavage of fatty acids from phospholipids by phospholipase enzymes. We have previously described, characterized and cloned a naturally occurring mammalian activator of phospholipase A2. Injection of a 24 amino acid peptide from this phospholipase A2 activating protein (PLAP), resulted in induction of an acute inflammatory response, and a concomitant regression of gliomas in rats. Administration of 500 micrograms of this protein resulted in a 50% decrease of the tumor mass within 72 h. Tumor regression coincided with a greater than twenty-fold increase in levels of prostaglandin E2(PGE2) and leukotriene B4(LTB4), and a marked infiltration of natural killer(NK) cells. These data suggest that activation of phospholipase A2 and modulation of the eicosanoid biosynthetic pathway may provide a novel therapeutic strategy for the successful treatment of malignant tumors of the nervous system.

Topics: Amino Acid Sequence; Animals; Cell Division; Dinoprostone; Dose-Response Relationship, Drug; Female; Glioma; Inflammation; Leukotriene B4; Molecular Sequence Data; Necrosis; Neoplasm Transplantation; Phospholipases A; Phospholipases A2; Proteins; Rats; Rats, Wistar; Staining and Labeling

Compound BW B70C, a selective 5-lipoxygenase inhibitor was tested for its ability to reduce inflammatory damage in an in vivo rabbit model of renal storage and transplantation. Kidneys were stored at 0-2 degrees C for 48 hr prior to autografting. In controls, renal vein LTB4 levels rose significantly after 30 min reperfusion but fell after 2 hr to baseline. TxB2 levels remained at baseline for the 6 hr measured. 6-k-PGF1 alpha levels rose significantly after 1 hr of reperfusion and remained elevated thereafter. Histology after 6 hr reperfusion showed moderate-to-severe cortical edema and mild congestion. Infused colloidal carbon was retained in the perivascular area in a narrow band at the corticomedullary junction, indicating a zone of vascular permeability. At 3 days after transplant, kidneys exhibited widespread tubular necrosis and calcification but little inflammation. Serum creatinine and urea peaked between days 3 and 5. 3/6 rabbits showed no symptoms of renal failure after 3 weeks. Pretreatment with BW B70C prevented the increase in LTB4 but had little effect on TxB2 and 6-k-PGF1 alpha levels. Histology showed no amelioration of cortical edema at 6 hr and congestion and hemorrhage were exacerbated. BW B70C had no effect on either colloidal carbon retention or distribution but did significantly reduce tubular necrosis and calcification at day 3. There was very little inflammatory infiltrate. BW B70C treatment did not improve the long-term viability of transplanted kidneys: 2/6 rabbits showed no symptoms of renal failure after 3 weeks. These data indicate that inhibition of LTB4 synthesis by BW B70C does not prevent the development of acute renal failure following 48 hr hypothermic storage and transplantation.

Topics: Acute Kidney Injury; Animals; Capillary Permeability; Creatinine; Disease Models, Animal; Eicosanoids; Enzyme-Linked Immunosorbent Assay; Female; Graft Rejection; Graft Survival; Hydroxylamines; Hydroxyurea; Kidney Transplantation; Kidney Tubules; Leukotriene B4; Lipoxygenase Inhibitors; Methylurea Compounds; Necrosis; Organ Preservation; Prostaglandins F; Rabbits; Thromboxane B2; Urea

Rats were treated with heat-killed Propionibacterium acnes and subsequent injection of a small amount of lipopolysaccharide after 7 days. After 24 hr most of the rats died of massive liver cell necrosis. Nonparenchymal liver cells were isolated from this liver injury model and incubated with arachidonic acid. Reverse-phase high-pressure liquid chromatography detected the 5-lipoxygenase metabolites (leukotriene B4 and 5-hydroxy-arachidonic acid), whereas these compounds were produced in negligible amounts when the rats were treated with P. acnes only. Immunohistochemical studies with 5-lipoxygenase antiserum revealed that the injured livers contained a large number of positively stained round cells with segmented nuclei, which were rarely found in the livers treated with P. acnes only. These positively stained cells were histologically identified as neutrophils. The results suggested that the increased 5-lipoxygenase activity in the injured rat liver is attributable to the infiltrating neutrophils rather than to nonparenchymal hepatic cells.

Topics: Animals; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Hydroxyeicosatetraenoic Acids; Immunohistochemistry; Leukotriene B4; Lipopolysaccharides; Liver; Male; Necrosis; Neutrophils; Propionibacterium acnes; Rats; Rats, Inbred Strains

1. PAF and LTs may be mediators of the acute gastrointestinal mucosal damage due to endotoxic shock. 2. LTs may be mediators of the acute gastrointestinal mucosal damage due to PAF administration. 3. LMW heparin and unfractionated heparin prevented the increase of LTs due to endotoxin and PAF administration.

Topics: Acute Disease; Animals; Benzoquinones; Dogs; Gastric Mucosa; Hemorrhage; Heparin; Heparin, Low-Molecular-Weight; Intestinal Mucosa; Leukotriene B4; Lipoxygenase Inhibitors; Necrosis; Phospholipid Ethers; Platelet Activating Factor; Shock, Septic

Recent evidence suggests that leucocytes may exert an important influence on microvessel flow during pathophysiologic conditions. This is particularly true in the case of coronary occlusive disorders. Diminution of coronary perfusion pressure favours trapping of the large, stiff leucocytes in capillaries. Perhaps more importantly, ischaemic changes in the endothelial lining of microvessels promote early sequestration of leucocytes within capillaries of ischaemic regions during underperfusion and, to a much greater degree, during reperfusion. If these trapped leucocytes are activated by the ischaemic environment, the mechanical plugging of microvessels can be significantly complicated by leucocyte release of a variety of materials affecting the function of blood vessels and myocytes. Leukotrienes are a potent group of inflammatory mediators released by activated leucocytes. A subgroup, the peptidoleukotrienes (C4, D4, and E4), has a profound vasoconstrictor influence on coronary microvessels. Members of this group can also cause platelet aggregation. Agents that block peptidoleukotriene synthesis, such as nafazatrom, have been reported to diminish the adverse effects of myocardial ischaemia. However, these agents often have non-specific actions that blur the interpretation of their anti-ischaemic efficacy. Our laboratory has made a number of observations that cast doubt--or at least stimulate further inquiry--on the role of peptidoleukotrienes on promotion of sustained microvessel constriction in ischaemic coronary beds. Most importantly, we found that continuous intracoronary administration of leukotriene C4 or D4 led initially to marked diminution of coronary flow and myocardial contractility. However, this was soon followed by a complete, dose-independent escape from these effects even though leukotrienes continued to be infused at a constant rate. The cause of this escape is unclear, but it may involve a specific product released when leukotrienes interact with platelets. In a second series of experiments, we found that the coronary constrictor efficacy of bolus leukotrienes (and also the stable thromboxane A2 analogue, U46619) was markedly reduced by concomitant myocardial ischaemia. Constrictor responses were rapidly restored with reperfusion, suggesting a transient metabolic blockade of constrictor responsiveness during myocardial ischaemia. Nevertheless, these data indicate that leukotrienes may not act simply as agents that exaggerate underperfusi

Topics: Animals; Coronary Circulation; Coronary Disease; Coronary Vessels; Leukocytes; Leukotriene B4; Leukotrienes; Myocardium; Necrosis; SRS-A; Swine; Vasoconstriction

Interleukin 1 (IL-1) may be a key mediator of inflammation and tissue damage in inflammatory bowel disease (IBD). In rabbits with immune complex-induced colitis, IL-1 alpha and beta mRNA levels were detectable at 4 h, peaked at 12 but were absent at 96 h after the induction of colitis. Colonic IL-1 tissue levels were measured by specific radioimmunoassays. IL-1 alpha was significantly elevated at 4 h (9.4 +/- 1.5 ng/g colon), progressively increased at 48 h (31 +/- 5.8 ng/g) and then decreased by 96 h (11.5 +/- 3.4 ng/g). IL-1 beta levels were 2.0 +/- 0.5 ng/g colon at 4 h, 5.0 +/- 1.6 ng/g at 48 h and undetectable by 96 h. By comparison, colonic levels of PGE2 and LTB4 were unchanged during the first 12 h and did not become elevated until 24 h. IL-1 alpha levels were highly correlated with inflammation (r = 0.885, P less than 0.0001), edema (r = 0.789, P less than 0.0001) and necrosis (r = 0.752, P less than 0.0005). Treatment with a specific IL-1 receptor antagonist (IL-1 ra) before and during the first 33 h after the administration of immune complexes markedly reduced inflammatory cell infiltration index (from 3.2 +/- 0.4 to 1.4 +/- 0.3, P less than 0.02), edema (from 2.2 +/- 0.4 to 0.6 +/- 0.3, P less than 0.01) and necrosis (from 43 +/- 10% to 6.6 +/- 3.2%, P less than 0.03) compared to vehicle-matched colitis animals. These studies demonstrate that (a) IL-1 gene expression and synthesis occur early in the course of immune complex-induced colitis; (b) are significantly elevated for 12 h before the appearance of PGE2 and LTB4; (c) tissue levels of IL-1 correlate with the degree of tissue inflammation and; (d) specific blockade of IL-1 receptors reduces the inflammatory responses associated with experimental colitis.

Topics: Antigen-Antibody Complex; Blotting, Northern; Colitis; Edema; Gene Expression; Interleukin-1; Leukotriene B4; Necrosis; Prostaglandins E; Receptors, Immunologic; Receptors, Interleukin-1; Time Factors

The role of increased prostaglandin production and the effects of exogenous prostaglandins on inflammation of colitis are not established. We administered intramuscular 16,16-dimethyl prostaglandin E2 (DiM-PGE2) and indomethacin to rabbits with formalin immune-complex colitis and measured leukotriene B4 (LTB4), prostaglandin E2 (PGE2) and severity of inflammation. DiM-PGE2 (100 micrograms/kg/BID) reduced LTB4 production (from 401 +/- 108 to 216 +/- 58 pg/ml) and infiltration of neutrophils, mucosal necrosis, inflammatory exudate and edema (all P less than 0.05). Other studies determined that parenteral DiM-PGE2 did not reduce the initial chemical damage induced by formalin, suggesting that cytoprotection of chemical insult was not the mechanism of suppressed inflammation in the immune colitis model. Indomethacin (10 mg/kg/d) reduced endogenous PGE2 by 80%, but did not reduce leukotriene production or inflammation. Exogenous prostaglandins cause a dose-dependent suppression of inflammation in experimental colitis, by a mechanism other than cytoprotection of chemical-induced mucosal injury.

Topics: Animals; Colitis; Colon; Dinoprostone; Dose-Response Relationship, Drug; Indomethacin; Leukotriene B4; Male; Necrosis; Prostaglandins E, Synthetic; Rabbits