phosphatidic acid (LPA) is a membrane-derived lysophospholipid with wide-ranging effects on multiple lung cells including airway epithelial and smooth muscle cells. LPA can augment migration and cytokine synthesis in lymphocytes, but its potential effects on Th2 cytokines have not been well studied. We examined the effects of physiological concentrations of LPA on IL-13 gene expression in human T cells. The Jurkat T cell line and human peripheral blood CD4ϩ T cells were incubated with LPA alone or with 1) pharmacological agonists of different signaling pathways, or 2) antibodies directed against the T cell receptor complex and costimulatory molecules. Luciferase-based reporter constructs driven by different lengths of the human IL-13 promoter were transfected by electroporation in Jurkat cells treated with and without LPA. The effects of LPA on IL-13 mRNA stability were examined using actinomycin D to halt ongoing transcription. Expression of mRNA encoding LPA 2 and LPP-1 increased with T cell activation. LPA augmented IL-13 secretion under conditions of submaximal T cell activation. This was observed using pharmacological agonists activating intracellular calcium-, PKC-, and cAMP-dependent signaling pathways, as well as antibodies directed against CD3 and CD28. LPA only slightly prolonged IL-13 mRNA half-life in submaximally stimulated Jurkat cells. In contrast, LPA significantly enhanced transcriptional activation of the IL-13 promoter via regulatory elements contained within proximal 312 bp. The effects of LPA on IL-13 promoter activation appeared to be distinct from those mediated by GATA-3. LPA can augment IL-13 gene expression in T cells, especially under conditions of submaximal activation.T lymphocytes; transcription factors; inflammation; lysophospholipids; transcriptional regulation LYSOPHOSPHATIDIC ACID (LPA) is a lysophospholipid with farreaching effects on different cell types ranging from platelet activation to enhancing cell proliferation. LPA binds to several members of a family of G protein-coupled receptors including LPA 1 , LPA 2 , and LPA 3 (formerly known as endothelial differentiation gene or Edg receptor-2, -4, and -7, respectively). A fourth LPA receptor related to the purinergic receptor family was recently identified (37). LPA is detectable in normal serum at a concentration in the micromolar range, where it is bound by both albumin and gelsolin (33). Major sources of LPA include platelets, epithelial cells, and certain tumor cells (24).LPA is generated by the action of both secretory phospholipase A 2 (via hydrolysis of phosphatidic acid) and lysophopholipase D (via cleavage of extracellular lysophosphatidylcholine) on membrane phospholipids, with the latter pathway representing a potential pathway of cell activation in cancer (14,34).Although most studies to date have examined the effects of LPA on structural tissue cells such as endothelium and epithelium, emerging data suggest that LPA and related lysosphingolipids [e.g., sphingosine-1-phosphate (S1P)] activate circulating leukocyte...

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