Effects of the cyclin-dependent kinase inhibitor R-roscovitine on eosinophil survival and clearance.
BACKGROUND
Eosinophils are pro-inflammatory cells implicated in the pathogenesis of asthma and atopy. Apoptosis has been proposed as a potential mechanism underlying the resolution of eosinophilic inflammation and studies have indicated the ability of interventions that induce human eosinophil apoptosis to promote the resolution of eosinophilic inflammation. Recently, the cyclin-dependent kinase (CDK) inhibitor R-roscovitine was shown to enhance neutrophil apoptosis and promote the resolution of neutrophilic inflammation.


OBJECTIVE
The purpose of this study was to examine the expression of CDKs in human blood eosinophils, the effects of R-roscovitine on eosinophil survival in vitro and whether R-roscovitine could influence eosinophilic lung inflammation in vivo.


METHODS
Eosinophils were isolated from human peripheral blood and the effects of R-roscovitine on apoptosis, degranulation and phagocytic uptake examined in vitro. The effects of R-roscovitine on eosinophilic lung inflammation in vivo were also assessed using an ovalbumin mouse model.


RESULTS
Our data demonstrate that human eosinophils express five known targets for R-roscovitine: CDK1, -2, -5, -7 and -9. R-roscovitine induced eosinophil apoptosis in a time- and concentration-dependent manner but also accelerated transition to secondary necrosis as assessed by microscopy, flow cytometry and caspase activation. In addition, we show that R-roscovitine can override the anti-apoptotic signals of GM-CSF and IL-5. We report that the pro-apoptotic effect of R-roscovitine is associated with suppression of Mcl-1L expression and that this compound enhanced phagocytic clearance of eosinophils by macrophages. Finally, we show that R-roscovitine induces apoptosis in murine peripheral blood and spleen-derived eosinophils; despite this, R-roscovitine did not modulate the tissue and lumen eosinophilia characteristic of the ovalbumin mouse model of airway eosinophilia.


CONCLUSIONS
These data demonstrate that R-roscovitine is capable of inducing rapid apoptosis and secondary necrosis in eosinophils but does not affect the onset or improve the resolution of eosinophilic airway inflammation in vivo.
Division of Respiratory Medicine, Department of Medicine, University of Cambridge School of Clinical Medicine, Addenbrooke's and Papworth Hospitals, Cambridge, UK.
N
N
Farahi
L
L
Uller
J K
JK
Juss
A J
AJ
Langton
A S
AS
Cowburn
A
A
Gibson
M R
MR
Foster
S N
SN
Farrow
P
P
Marco-Casanova
A
A
Sobolewski
A M
AM
Condliffe
E R
ER
Chilvers
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000276:immunology; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000276:immunology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004804:Eosinophils / Q000166:cytology* / Q000187:drug effects* / Q000276:immunology; D005260:Female; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008807:Mice, Inbred BALB C; D010047:Ovalbumin; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology*; D000077546:Roscovitine; D013997:Time Factors
D047428:Protein Kinase Inhibitors; D011687:Purines; D000077546:Roscovitine; D010047:Ovalbumin; D018844:Cyclin-Dependent Kinases