STUDIES OF PHOSPHOLIPASE A2 GENE EXPRESSION

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Cytosolic phospholipase A2 (cPLA2) is an arachidonate-specific phospholipase important in cellular production of eicosanoids. Cytokine activation of cPLA2 activity was studied in airway epithelial cells. It was found that the T lymphocyte cytokine Interferon-gamma caused arachidonic acid release from airway epithelial cells. Western blot analysis revealed an increase in cPLA2 in epithelial cells treated with Interferon-g for 4 to 24 hours. Assays for steady-state mRNA levels demonstrated increased cPLA2 mRNA levels over the same time. Transcriptional analysis demonstrated an increase in the transcription rate of cPLA2 mRNA in response to Interferon stimulation. Similarly, tumor necrosis factor (TNF) treatment of an airway epithelial cell line results in activation of arachidonic acid release. Western blots reveal increases in cPLA2 protein. Ribonuclease protection assay for cPLA2 mRNA reveals increases in steady-state message for 4 to 24 hours. Transcriptional assay reveals an increased rate of transcription of cPLA2 mRNA in response to TNF treatment. Interleukin-6 is capable of activating PLA2 activity in some inflammatory cells. Another cytokine that uses gp130 as a portion of its receptor is leukemia inhibitory factor (LIF). Western blot of an airway epithelial cell line revealed LIF receptor protein. LIF treatment of these cells results in increased arachidonic acid release. Western blot analysis of cellular cPLA2 protein reveals an increase in protein in response to LIF treatment. Ribonuclease protection assay for cPLA2 steady-state mRNA levels reveals an increase in cPLA2 message over 4 to 24 hours of treatment with LIF. Ongoing studies will assess the cytokine control of cPLA2 activity by gene expression and by post-translational mechanisms. An understanding of the mechanisms of cytokine activation of cPLA2 may allow for new therapeutic treatment of diseases of the airways. Two manuscripts have been published, and one manuscript has been prepared.