Summary
The cellular phospholipid, lysophosphatidic acid (LPA), released by activated platelets
and fibroblasts or, at high levels, from ovarian and cervical carcinomas is a powerful
serum mitogen that may modulate several signaling pathways in endothelial cells (EC).
Hence, LPA could function in a paracrine manner during EC-platelet interactions at
sites of vascular injury.
Here, we demonstrate activation of the transcription factor nuclear factor kappa B
(NF-κB) in EC following exposure to LPA. EC activation was further characterized by
increased levels of mRNA transcripts encoding E-selectin, Intercellular Adhesion Molecule-1,
Interleukin-8 and Monocyte Chemoattractant Protein-1. These effects were inhibited
by preincubating EC either in the presence of mepacrine (to block phospholipase A2) or of pertussis toxin (to increase ADP-ribosylation of Gi proteins). No inhibition was observed in the presence of putative LPA receptor antagonists
suramin or thrombospondin.
LPA induces a proinflammatory activation of endothelial cells that (i) involves Gi proteins; (ii) depends on phospholipase A2 activity; (iii) is associated with the activation of NF-κB and (iv) results in increased
expression of proinflammatory genes. We propose that LPA release by activated platelets
may directly modulate vascular inflammatory responses.
Abbreviations: EC, endothelial cells; LPA, lysophosphatidic acid; NF-κB, nuclear factor kappa B;
PA, phosphatidic acid; IL-8, interleukin-8; MCP-1, monocyte chemoattractant protein-1,
ICAM-1, intercellular adhesion molecule-1, vascular adhesion molecule-1; GAPDH, glycerol
aldehyde phosphate dehydrogenase; MAPK, mitogen activated kinase, MEK, MAPK kinase,
PAEC, porcine aortic EC.
Keywords
Lysophosphatidic acid - nuclear factor kappa B - transcription factor - inflammation
- endothelial cells - platelets - gene expression