Regulation of apoptosis in eicosapentaenoic acid-treated HL-60 cells.
BACKGROUND
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Gillis
Robert C
RC
Department of Surgery, Division of Trauma and Critical Care, Graduate School of Medicine, University of Tennessee Medical Center, Knoxville, Tennessee 37920. USA.
Daley
Brian J
BJ
Enderson
Blaine L
BL
Kestler
Daniel P
DP
Karlstad
Michael D
MD
D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism; D001093:Arachidonate 15-Lipoxygenase / Q000378:metabolism; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D015118:Eicosapentaenoic Acid; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology*; D044950:Flavanones / Q000494:pharmacology; D006139:Guaiacol / Q000031:analogs & derivatives / Q000494:pharmacology; D018922:HL-60 Cells; D006801:Humans; D006893:Hydroxyeicosatetraenoic Acids / Q000494:pharmacology; D007052:Ibuprofen / Q000494:pharmacology; D007211:Indoles / Q000494:pharmacology; D007975:Leukotriene B4 / Q000494:pharmacology; D017705:Lignans / Q000494:pharmacology; D016859:Lipoxygenase Inhibitors / Q000494:pharmacology; D009504:Neutrophils / Q000473:pathology; D012128:Respiratory Distress Syndrome / Q000378:metabolism / Q000473:pathology; D002722:Chlorobenzenes
D001092:Arachidonate 12-Lipoxygenase; D001093:Arachidonate 15-Lipoxygenase; D001094:Arachidonate 5-Lipoxygenase; D016861:Cyclooxygenase Inhibitors; D015118:Eicosapentaenoic Acid; D004791:Enzyme Inhibitors; D005231:Fatty Acids, Unsaturated; D044950:Flavanones; D006139:Guaiacol; D006893:Hydroxyeicosatetraenoic Acids; D007052:Ibuprofen; D007211:Indoles; D007975:Leukotriene B4; D017705:Lignans; D016859:Lipoxygenase Inhibitors; C060893:MK-886; D002722:Chlorobenzenes; C015816:dihydroguaiaretic acid; C022022:5-hydroxy-6,8,11,14-eicosatetraenoic acid; C006680:baicalein