The anti-apoptotic effect of leukotriene B4 in neutrophils: a role for phosphatidylinositol 3-kinase, extracellular signal-regulated kinase and Mcl-1.
The constitutive commitment of neutrophils to apoptosis is a key process for the control and resolution of inflammation and it can be delayed by various inflammatory mediators including leukotriene B4 (LTB4). The mechanisms by which LTB4 contributes to neutrophil survival are still unclear and the present work aims at identifying intracellular pathways underlying this effect. Inhibition of human neutrophil apoptosis by LTB4 was abrogated by the phosphatidylinositol 3-kinase (PI3-K) inhibitor wortmannin and by the specific MEK inhibitor PD98059. In contrast, inhibitors of p38 MAPK, Jak2/3 and Src did not hinder the anti-apoptotic effect of LTB4. We also investigated the effects of members of the Bcl-2 family as they play a crucial role in the regulation of programmed cell death. When neutrophils were incubated with LTB4 for 1 to 6 h, the mRNA levels of the anti-apoptotic protein Mcl-1 were upregulated approximately 2-fold, while those of the pro-apoptotic protein Bax were downregulated 3- to 4-fold, as determined by real-time PCR. Accordingly, Western blot analysis revealed that the expression of Mcl-1 was upregulated in presence of LTB4, while flow cytometric analysis revealed that Bax protein was downregulated. Furthermore, the modulatory effects of LTB4 on Mcl-1 and Bax proteins were abolished in the presence of either wortmannin or PD98059. Taken together, these results demonstrate the participation of PI3-K and MEK/ERK kinases, as well as regulatory apoptotic proteins such as Mcl-1 and Bax, in the anti-apoptotic effects of LTB4 in human neutrophils.
Pétrin
Darlaine
D
Immunology Division, Department of Pediatrics, Faculty of Medicine, Université de Sherbrooke, 3001, North 12th Avenue, Sherbrooke, Québec, Canada J1H 5N4.
Turcotte
Sylvie
S
Gilbert
Annie-Kim
AK
Rola-Pleszczynski
Marek
M
Stankova
Jana
J
D000730:Androstadienes / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000502:physiology*; D005419:Flavonoids / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D007975:Leukotriene B4 / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D009504:Neutrophils / Q000166:cytology / Q000187:drug effects*; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D012016:Reference Values; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013997:Time Factors; D000077191:Wortmannin; D051028:bcl-2-Associated X Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
D000730:Androstadienes; C494826:BAX protein, human; D005419:Flavonoids; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D007975:Leukotriene B4; D019869:Phosphatidylinositol 3-Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D000077191:Wortmannin