Role for Bcl-xL in delayed eosinophil apoptosis mediated by granulocyte-macrophage colony-stimulating factor and interleukin-5.
Eosinophils are potent inflammatory cells involved in allergic reactions. Inhibition of apoptosis of purified eosinophils by certain cytokines has been previously shown to be an important mechanism causing tissue eosinophilia. To elucidate the role of Bcl-2 family members in the inhibition of eosinophil apoptosis, we examined the expression of the known anti-apoptotic genes Bcl-2, Bcl-xL, and A1, as well as Bax and Bcl-xS, which promote apoptosis in other systems. We show herein that freshly isolated human eosinophils express significant amounts of Bcl-xL and Bax, but only little or no Bcl-2, Bcl-xS, or A1. As assessed by reverse transcription-polymerase chain reaction, immunoblotting, flow cytometry, and immunocytochemistry, we show that spontaneous eosinophil apoptosis is associated with a decrease in Bcl-xL mRNA and protein levels. In contrast, stimulation of the cells with granulocyte-macrophage colony-stimulating factor (GM-CSF) or interleukin-5 (IL-5) results in maintenance or upregulation of Bcl-xL mRNA and protein levels. Moreover, Bcl-2 protein is not induced by GM-CSF or IL-5 in purified eosinophils. Bcl-2 protein is also not expressed in tissue eosinophils as assessed by immunohistochemistry using two different eosinophilic tissue models. Furthermore, Bcl-xL antisense but not scrambled phosphorothioate oligodeoxynucleotides can partially block the cytokine-mediated rescue of apoptotic death in these cells. These data suggest that Bcl-xL acts as an anti-apoptotic molecule in eosinophils.
Dibbert
B
B
Swiss Institute of Allergy and Asthma Research (SIAF), University of Zurich, Davos, Switzerland.
Daigle
I
I
Braun
D
D
Schranz
C
C
Weber
M
M
Blaser
K
K
Zangemeister-Wittke
U
U
Akbar
A N
AN
Simon
H U
HU
D017209:Apoptosis / Q000187:drug effects; D002295:Carcinoma, Transitional Cell / Q000473:pathology; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics; D003876:Dermatitis, Atopic / Q000473:pathology; D004804:Eosinophils / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D018398:Homeodomain Proteins; D006801:Humans; D015848:Interleukin-5 / Q000494:pharmacology*; D015778:Minor Histocompatibility Antigens; D009298:Nasal Polyps / Q000473:pathology; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051818:Replication Protein C; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D001749:Urinary Bladder Neoplasms / Q000473:pathology; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494826:BAX protein, human; C096816:BCL2-related protein A1; C494811:BCL2L1 protein, human; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D015848:Interleukin-5; C096063:MATA1 protein, S cerevisiae; D015778:Minor Histocompatibility Antigens; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D051818:Replication Protein C