l-663536 and Necrosis

Proinflammatory eicosanoids formed from arachidonic acid (AA) by lipoxygenase (LO) and cyclooxygenase (COX) pathways have been shown to inhibit apoptosis in certain cell types. This study determined whether inhibition of LO and COX increased apoptosis in AA-treated HL-60 cells in vitro.. HL-60 cells were incubated with 50 micromol/L AA and an enzyme inhibitor (1-10 micromol/L) for COX, LO, 12-LO, and 5-LO for 12 hours. Flow cytometry was used to assess viability, apoptosis, and necrosis. Apoptosis was further assessed using terminal dUTP nick end-labeling and DNA fragmentation.. The highest concentration of LO inhibitors, but not COX inhibitors, decreased viability and increased apoptosis and necrosis in the presence of exogenous AA.. These results suggest that disruption of the metabolism of AA by LO, in particular 5-LO, decreases cell survival and increases apoptosis. Thus, downstream metabolic processing of AA by LO but not COX plays a critical role in the regulation of HL-60 cell apoptosis.

Topics: Apoptosis; Arachidonate 5-Lipoxygenase; Benzoquinones; Cyclooxygenase Inhibitors; DNA Fragmentation; Fatty Acids, Unsaturated; Fish Oils; Flavanones; Flavonoids; Flow Cytometry; HL-60 Cells; Humans; Ibuprofen; In Situ Nick-End Labeling; Indoles; Inflammation; Lipoxygenase Inhibitors; Necrosis; Neutrophils; Prostaglandin-Endoperoxide Synthases; Respiratory Distress Syndrome

Human neuroblastoma CHP100 cells were forced into apoptosis (programmed cell death, PCD) or necrosis by treatment with calcium chloride or sodium nitroprusside (a nitric oxide donor), respectively. Cellular luminescence, a marker of membrane lipid peroxidation, was increased by calcium but not by nitroprusside, and reached a maximum of 4-fold the control value 2 hours after treatment. The increase in luminescence was paralleled by increased 5-lipoxygenase (up to 250% of the control value) and decreased catalase (down to 50%) activity within the same time window. Consistently, incubation of CHP100 cells with inhibitors of 5-lipoxygenase (5,8,11,14-eicosatetraynoic acid and MK886) reduced light emission and PCD, whereas inhibition of catalase by 3-amino-1, 2,4-triazole enhanced both processes. Treatment of CHP100 cells with retinoic acid or cisplatin, unrelated PCD inducers reported to activate the lipoxygenase pathway, also gave enhanced light emission parallel to PCD increase. Altogether, these results suggest that cellular luminescence is an early marker of apoptotic, but not necrotic, program(s) involving generation of hydrogen peroxide and activation of 5-lipoxygenase.

Topics: 5,8,11,14-Eicosatetraynoic Acid; Amitrole; Apoptosis; Arachidonate 5-Lipoxygenase; Catalase; Cisplatin; Enzyme Inhibitors; Humans; Hydrogen Peroxide; Indoles; Leukotrienes; Lipid Peroxidation; Lipoxygenase Inhibitors; Luminescent Measurements; Necrosis; Neuroblastoma; Tretinoin; Tumor Cells, Cultured

Topics: Animals; Benzeneacetamides; Cell Survival; Dermatologic Surgical Procedures; Female; Hydroxamic Acids; Indoles; Leukotriene Antagonists; Leukotrienes; Lipoxygenase Inhibitors; Necrosis; Rats; Rats, Sprague-Dawley; Skin; Surgical Flaps

Intragastric ethanol stimulates mucosal formation of leukotriene C4 in the rat stomach. The present study demonstrates that the increase in leukotriene C4 formation begins within 30 seconds and is maximal within 5 minutes, closely paralleled by the appearance of hemorrhagic lesions. Leukotriene C4 formation returns to prechallenge levels within 3 hours, although erosions still persist. Intragastric 0.2N NaOH, acidified 100 mmol/L taurocholate, 25% NaCl, or 0.6N HCl did not consistently increase leukotriene C4 formation despite severe mucosal injury. A number of sulfhydryl-containing or sulfhydryl-blocking agents as well as metals protected against mucosal damage and simultaneously prevented the stimulation of leukotriene C4 formation induced by ethanol. None of the agents increased and some virtually abolished mucosal formation of prostaglandin E2, indicating that gastroprotection can occur completely independently of the endogenous prostaglandin system. The leukotriene biosynthesis inhibitor MK-886 markedly suppressed gastric leukotriene C4 formation but did not protect against damage caused by ethanol, NaOH, NaCl, or acidified taurocholate. Oral indomethacin reduced the ex vivo formation of both prostaglandin E2 and, to a lesser extent, leukotriene C4 in the gastric mucosa, inducing a shift in the balance from protective prostaglandins to proulcerogenic leukotriene C4. Pretreatment with MK-886, however, did not significantly diminish indomethacin-induced lesions. These data suggest that leukotriene C4 is not the exclusive mediator of gastric injury caused by necrotizing agents or indomethacin. On the other hand, certain protective compounds exhibit a striking parallelism between protection and inhibition of ethanol-induced leukotriene C4 formation, suggesting that they may affect a target crucial for both mucosal injury and stimulation of 5-lipoxygenase.

Topics: Animals; Arachidonate 5-Lipoxygenase; Dinoprostone; Ethanol; Gastric Mucosa; Indoles; Indomethacin; Leukotriene Antagonists; Male; Necrosis; Rats; Rats, Inbred Strains; Sodium Chloride; Sodium Hydroxide; SRS-A; Stomach Ulcer; Taurocholic Acid