Inhibition of spleen tyrosine kinase prevents mast cell activation and airway hyperresponsiveness.
BACKGROUND
Spleen tyrosine kinase (Syk) is important for Fc and B-cell receptor-mediated signaling.


OBJECTIVE
To determine the activity of a specific Syk inhibitor (R406) on mast cell activation in vitro and on the development of allergen-induced airway hyperresponsiveness (AHR) and inflammation in vivo.


METHODS
AHR and inflammation were induced after 10 d of allergen (ovalbumin [OVA]) exposure exclusively via the airways and in the absence of adjuvant. This approach was previously established to be IgE, FcepsilonRI, and mast cell dependent. Alternatively, mice were passively sensitized with OVA-specific IgE, followed by limited airway challenge. In vitro, the inhibitor was added to cultures of IgE-sensitized bone marrow-derived mast cells (BMMCs) before cross-linking with allergen.


RESULTS
The inhibitor prevented OVA-induced degranulation of passively IgE-sensitized murine BMMCs and inhibited the production of interleukin (IL)-13, tumor necrosis factor alpha, IL-2, and IL-6 in these sensitized BMMCs. When administered in vivo, R406 inhibited AHR, which developed in BALB/c mice exposed to aerosolized 1% OVA for 10 consecutive d (20 min/d), as well as pulmonary eosinophilia and goblet cell metaplasia. A similar inhibition of AHR was demonstrated in mice passively sensitized with OVA-specific IgE and exposed to limited airway challenge.


CONCLUSIONS
This study delineates a functional role for Syk in the development of mast cell- and IgE-mediated AHR and airway inflammation, and these results indicate that inhibition of Syk may be a target in the treatment of allergic asthma.
Matsubara
Shigeki
S
Department of Pediatrics, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
Li
Guiming
G
Takeda
Katsuyuki
K
Loader
Joan E
JE
Pine
Polly
P
Masuda
Esteban S
ES
Miyahara
Nobuaki
N
Miyahara
Satoko
S
Lucas
Joseph J
JJ
Dakhama
Azzeddine
A
Gelfand
Erwin W
EW
D000818:Animals; D001402:B-Lymphocytes / Q000276:immunology; D016535:Bronchial Hyperreactivity / Q000276:immunology*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D005260:Female; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors* / Q000276:immunology; D008407:Mast Cells / Q000187:drug effects / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors* / Q000276:immunology; D011961:Receptors, Fc / Q000276:immunology; D015398:Signal Transduction; D000072377:Syk Kinase
D047908:Intracellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; D011961:Receptors, Fc; D011505:Protein-Tyrosine Kinases; D000072377:Syk Kinase; C000606897:Syk protein, mouse