Abstract
Spleen tyrosine kinase (Syk) is an immunoregulatory tyrosine kinase that was identified originally in leukocytes. It is a key regulator of innate immunity as well as hematopoietic cell differentiation and proliferation. A role for Syk in regulating normal cellular functions in nonhematopoietic cells is increasingly recognized. We have shown previously robust Syk expression in airway epithelium, where it regulates the early inflammatory response to human rhinovirus (HRV) infections, and HRV cell entry by clathrin-mediated endocytosis. To test the hypothesis that Syk plays a role in modulating airway epithelial cell proliferation, migration, and production of vascular endothelial growth factor and interleukin-8, we studied the BEAS-2B human bronchial epithelial cell line and primary human airway epithelia from normal and asthmatic donors using Syk-specific pharmacologic inhibitors and small interfering RNA. Using an in vitro “wounding” model, we demonstrated significant impairment of “wound” closure after treatment with the Syk inhibitors N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine (R406) and 2-[7-(3,4-dimethoxyphenyl)-imidazo[1,2-c]pyrimidin-5-ylamino]-nicotinamide dihydrochloride (BAY61-3606), overexpression of the kinase-inactive SykK396R mutant, and Syk knockdown by small interfering RNA. HRV infection also impaired wound healing, an effect that was partly Syk-dependent because wound healing was impaired further when HRV infection occurred in the presence of Syk inhibition. Further investigation of potential regulatory mechanisms revealed that inhibition of Syk suppressed HRV-induced vascular endothelial growth factor expression while promoting the activation of caspase-3, a mediator of epithelial cell apoptosis. Together, these results indicate that Syk plays a role in promoting epithelial cell proliferation and migration, while mitigating the effects of apoptosis.
Footnotes
This work was supported by grants from the Canadian Institutes for Health [MOP 83388], Ontario Thoracic Society Grants in Aid, and the Canadian Foundation for Innovation.
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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The online version of this article (available at http://jpet.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- Syk
- spleen tyrosine kinase
- BEGM
- bronchial epithelial growth medium
- DMSO
- dimethyl sulfoxide
- EGF
- epidermal growth factor
- HRV
- human rhinovirus
- ICAM-1
- intercellular adhesion molecule-1
- IL
- interleukin
- PI3K
- phosphatidylinositol 3-kinase
- siRNA
- small interfering RNA
- TGF-β
- transforming growth factor-β
- VEGF
- vascular endothelial growth factor
- WT
- wild-type
- R406
- N4-(2,2-dimethyl-3-oxo-4H-pyrid[1,4]oxazin-6-yl)-5-fluoro-N2-(3,4,5-trimethoxyphenyl)-2,4-pyrimidinediamine
- BAY61-3606
- 2-[7-(3,4-dimethoxyphenyl)-imidazo[1,2-c]pyrimidin-5-ylamino]-nicotinamide dihydrochloride
- NVP-QAB-205
- N-[4-[6-(Cyclobutylamino)-9H-purin-2-ylamino]phenyl]-N-methylacetamide
- TCID
- tissue culture infective dose.
- Received July 27, 2011.
- Accepted October 21, 2011.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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