Phospholipase D Activation by Sphingosine 1-Phosphate Regulates Interleukin-8 Secretion in Human Bronchial Epithelial Cells

Abstract

Sphingosine 1-phosphate (S1P), a potent bioactive sphingolipid, has been implicated in many critical cellular events, including a regulatory role in the pathogenesis of airway inflammation. We investigated the participation of S1P as an inflammatory mediator by assessing interleukin-8 (IL-8) secretion and phospholipase D (PLD) activation in human bronchial epithelial cells (Beas-2B). S1P 1 , S1P 3 , S1P 4 , S1P 5 , and weak S1P 2 receptors were detected in Beas-2B and primary human bronchial epithelial cells. S1P stimulated a rapid activation of PLD, which was nearly abolished by pertussis toxin (PTX) treatment, consistent with S1P receptor/G i protein coupling. S1P also markedly induced Beas-2B secretion of IL-8, a powerful neutrophil chemoattractant and activator, in a PTX-sensitive manner. This S1P-mediated response was dependent on transcription as indicated by a strong induction of IL-8 promoter-mediated luciferase activity in transfected Beas-2B cells and a complete inhibition by actinomycin D. Beas-2B exposure to 1-butanol, which converts the PLD-generated phosphatidic acid (PA) to phosphatidylbutanol by a transphosphatidylation reaction, significantly attenuated the S1P-induced IL-8 secretion, indicating the involvement of PLD-derived PA in the signaling pathway. Inhibition of 12-O-tetradecanoyl-phorbol-13-acetatestimulated IL-8 production by 1-butanol further strengthened this observation. Blocking protein kinase C and Rho kinase also attenuated S1P-induced IL-8 secretion. Our data suggest that PLD-derived PA, protein kinase C, and Rho are important signaling components in S1P-mediated IL-8 secretion by human bronchial epithelial cells.

The immunomodulator FTY720 interferes with effector functions of human monocyte‐derived dendritic cells

“…As a biological, highly active lipid mediator, S1P has also been reported to play an important role in regulating cytokine production in different cell types [25,26]. In human DC, S1P has been considered to inhibit their capacity to induce Th1 responses [18].…”

Protein Kinase Cδ Mediates Lysophosphatidic Acid-induced NF-κB Activation and Interleukin-8 Secretion in Human Bronchial Epithelial Cells

“…The role of PKC in S1P-induced IL-8 production has been reported previously (21); however, little information is available on the PKC isoform(s) and downstream target(s) of PKC regulating IL-8 generation. The PKC family of serine/ threonine kinases includes three major types of isoenzymes.…”

“…LPA is a potent bioactive lipid that mediates several cellular responses such as proliferation, differentiation, suppression of apoptosis, tumor metastasis, and cytoskeletal reorganization (15,(21)(22)(23)(24)(25)(26)(27)(28). LPA mediates the broad range of cellular responses through the G-protein-coupled receptors LPA 1 /Edg-2, LPA 2 /Edg-4, and LPA 3 /Edg-7 (19).…”

“…HBEpCs-We have recently reported that the bioactive sphingolipid S1P stimulates IL-8 production in BEAS-2B bronchial epithelial cells (21). Extracellular LPA has been shown to be an immunological regulator by activating NF-B and increasing levels of mRNA transcripts encoding E-selectin, ICAM-1, IL-8, and MCP-1 (monocyte chemoattractant protein-1) in endothelial cells (17).…”

“…Studies in our laboratory have revealed that S1P stimulates significant production and secretion of IL-8 in a human bronchial epithelial cell line (BEAS-2B) (21) and that LPA is capable of transactivating platelet-derived growth factor receptor-␤ in HBEpCs (20). In guinea pigs, administration of exogenous LPA into the airway enhances the response to acetylcholine (22) and infiltration of neutrophils (23).…”