l-663536 and Respiratory-Distress-Syndrome

Neutrophil apoptosis is an important physiological process in the resolution of pulmonary inflammation. Previous studies have shown that eicosapentaenoic acid (EPA; 20:5n-3) increases the rate of apoptosis in a concentration- and time-dependent manner in HL-60 cells. However, it is not known if the EPA-induced apoptosis involves the lipoxygenase (LO) and cyclooxygenase (COX) enzymes or the downstream metabolic products of these enzymes. Thus, the objective of this study was to determine the effects of inhibitors LO and COX enzymes on apoptosis, viability, and necrosis in EPA-treated HL-60 cells.. Cells were incubated with 50 mum EPA in the presence of an enzyme inhibitor (1-10 microm) for 12 h. Compounds were used to inhibit COX 1 and 2 (ibuprofen), 5-, 12-, 15-LO (NDGA), 12-LO (baicalein), 5-LO (AA-861), and 5-LO activating protein (MK-886). Eicosanoid (0.001-1.0 mum) add-back experiments were also conducted; LTB(4) and 5-HETE with 5-LO inhibition and 12-HETE with 12-LO inhibition. Flow cytometry was used to assess apoptosis.. Inhibition of COX 1 and 2 had no effect on apoptosis. Inhibition of 5-LO and 12-LO significantly increased apoptosis in EPA-treated HL-60 cells. Addition of LTB(4) reduced apoptosis to levels significantly lower than in HL-60 cells treated with EPA alone; 5-HETE and 12-HETE also lowered apoptosis to control levels.. These data indicate that inhibition of LO, particularly 5-LO, increased apoptosis in EPA-treated HL-60 cells. Furthermore, this study demonstrated that the products of the LO enzymes, particularly LTB(4), are critical in the regulation of apoptosis in EPA-treated HL-60 cells.

Topics: Apoptosis; Arachidonate 12-Lipoxygenase; Arachidonate 15-Lipoxygenase; Arachidonate 5-Lipoxygenase; Cyclooxygenase Inhibitors; Eicosapentaenoic Acid; Enzyme Inhibitors; Fatty Acids, Unsaturated; Flavanones; Guaiacol; HL-60 Cells; Humans; Hydroxyeicosatetraenoic Acids; Ibuprofen; Indoles; Leukotriene B4; Lignans; Lipoxygenase Inhibitors; Neutrophils; Respiratory Distress Syndrome

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