The Tyrosine Kinase Pyk2 Mediates Lipopolysaccharide-Induced IL-8 Expression in Human Endothelial Cells

Department of Pathology, Ohio State University Medical Center, Columbus, OH 43210, USA.
The Journal of Immunology (Impact Factor: 4.92). 05/2008; 180(8):5636-44. DOI: 10.4049/jimmunol.180.8.5636
Source: PubMed


Secretion of proinflammatory cytokines by LPS activated endothelial cells contributes substantially to the pathogenesis of sepsis. However, the mechanism involved in this process is not well understood. In the present study, we determined the role of a nonreceptor proline-rich tyrosine kinase, Pyk2, in LPS-induced IL-8 (CXCL8) production in endothelial cells. First, we observed a marked activation of Pyk2 in response to LPS. Furthermore, inhibition of Pyk2 activity in these cells by transduction with the catalytically inactive Pyk2 mutant, transfection with Pyk2-specific small interfering RNA, or treatment with Tyrphostin A9 significantly blocked LPS-induced IL-8 production. The supernatants of LPS-stimulated cells exhibiting attenuated Pyk2 activity blocked transendothelial neutrophil migration in comparison to the supernatants of LPS-treated controls, thus confirming the inhibition of functional IL-8 production. Investigations into the molecular mechanism of this pathway revealed that LPS activates Pyk2 leading to IL-8 production through the TLR4. In addition, we identified the p38 MAPK pathway to be a critical step downstream of Pyk2 during LPS-induced IL-8 production. Taken together, these results demonstrate a novel role for Pyk2 in LPS-induced IL-8 production in endothelial cells.

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Available from: Magali Cucchiarini
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    • "PLC activation is required for the signal transduction events leading to inflammatory responses [16], [37]. In LPS-stimulated macrophages and human endothelial cells, proinflammatory cytokine secretion and expression are dependent on Src kinase [38], [39], [40]. Therefore, the role of Src kinase in immune response is rapidly emerging. "
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    • "This may be explained by the negative feedback mechanism since TAT-Pyk2-CT treated and LPS challenged mice has less neutrophils in the lung. Anand AR et al. found that inhibition of Pyk2 activity in endothelial cells in vitro by transfection with the catalytically inactive C-terminal Pyk2 significantly blocked LPS-induced IL-8 production [34]. The inability of Pyk2 inhibition to affect IL-8 homolog secretion in mouse BAL in our study may suggest that lung resident cells (such as airway epithelial cells and alveolar macrophages) other than endothelial cells may be at least in part responsible for the secretion of IL-8 homologs found in the BAL. "
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    • "There is much evidence that central to the recognition of LPS expression in endothelial cells is a family of transmembrane proteins known as Toll-like receptors (TLRs).24–26 Most effector cells of the immune responses, especially the innate immune system, such as monocytes and endothelial cells express TLR2 and TLR4.27 When LPS binds to TLR4, multiple intracellular signaling pathways are activated, including transcription factor, NF-κB, pathway as well as MAPK.28 "
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