Regulation of eosinophil apoptosis by nitric oxide: Role of c-Jun-N-terminal kinase and signal transducer and activator of transcription 5.
BACKGROUND
Reduced eosinophil apoptosis is considered to be a key mechanism for eosinophilia in allergic diseases such as asthma, rhinitis, and eczema.


OBJECTIVE
The aim of our study was to investigate the possible modulatory effect of nitric oxide (NO) in human eosinophils.


METHODS
Apoptosis in isolated eosinophils was assessed by relative DNA fragmentation assay, annexin-V binding, and morphologic analysis. The activation of c-Jun-N-terminal kinase (JNK) and signal transducer and activator of transcription 5 (STAT5) was assessed by immunoblot analysis.


RESULTS
The NO donor S-nitroso-N -acetylpenicillamine (SNAP) reversed the survival-prolonging effect of IL-5 by inducing apoptosis. This effect was blocked by the NO scavenger (2-(4-Carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3 oxide.potassium salt), indicating that reversal of IL-5-mediated eosinophil survival was due to NO. The effect of NO on IL-5-afforded cell survival was not mediated by cyclic guanosine 3': 5'-monophosphate (cGMP), because neither an inhibitor of guanylyl cyclase nor inhibitors of phosphodiesterases had any effect on SNAP-induced eosinophil apoptosis in IL-5-treated cells. SNAP induced a time-dependent increase in the activity of JNK, and an inhibitor peptide specific for JNK, L-JNKI1, completely reversed SNAP-induced apoptosis in IL-5-treated eosinophils. In contrast, SNAP did not inhibit IL-5-induced STAT5 activation. Inhibition of the activity of caspases by Z-Asp-CH(2)-DCB reversed the effect of SNAP, suggesting that NO promotes apoptosis in IL-5-treated human eosinophils in a caspase-dependent manner. However, this effect of NO was not mediated by means of activation of caspases 3, 8, or 9.


CONCLUSIONS
Our results suggest that exogenous NO reverses IL-5-mediated eosinophil survival by inducing apoptosis, and this is mediated by means of activation of JNK in a cGMP-independent manner.
Zhang
Xianzhi
X
Immunopharmacological Research Group, Medical School, University of Tampere, Finland.
Msc
Moilanen
Eeva
E
Lahti
Aleksi
A
Hämäläinen
Mari
M
Giembycz
Mark A
MA
Barnes
Peter J
PJ
Lindsay
Mark A
MA
Kankaanranta
Hannu
H
D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D006152:Cyclic GMP / Q000502:physiology; D004268:DNA-Binding Proteins / Q000502:physiology*; D004804:Eosinophils / Q000502:physiology*; D006801:Humans; D015848:Interleukin-5 / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases; D008894:Milk Proteins; D020928:Mitogen-Activated Protein Kinases / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis / Q000494:pharmacology*; D010396:Penicillamine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis; D050799:STAT5 Transcription Factor; D015534:Trans-Activators / Q000502:physiology*
D004268:DNA-Binding Proteins; D015848:Interleukin-5; D008894:Milk Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; C110881:S-nitro-N-acetylpenicillamine; D050799:STAT5 Transcription Factor; C494095:STAT5B protein, human; D015534:Trans-Activators; D009569:Nitric Oxide; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D010396:Penicillamine; D006152:Cyclic GMP