Transcriptional regulation and structural organization of the human cytosolic phospholipase A(2) gene

Cytokines are established regulators of the arachidonic acid cascade in lun g cells. The levels of various arachidonic metabolites distinguish the norm al and pathogenic states of the human lung. Arachidonyl-selective cytosolic phospholipase A(2) (cPLA(2)) is ubiquitously present in human lung and is most likely the rate-limiting step in eicosanoid generation. We therefore s tudied the regulation of this pivotal gene in human lung fibroblasts and ep ithelial cells by proinflammatory cytokines. We demonstrate a dose- and tim e-dependent induction of human cPLA(2) mRNA by interleukin-1 beta, tumor ne crosis factor-alpha, and interferon-gamma as well as the abrogation of this induction by glucocorticoids. Nuclear runoff studies demonstrate that de n ovo transcription of the cPLA(2) gene is required for cytokine induction. W e have characterized the human cPLA(2) gene, which is encoded by 18 exons a nd spans in excess of 137 kb. Deletion analysis of a 3.4-kb fragment of the human promoter identified two regions responsible for basal expression of the cPLA(2) gene. Conversely a CA-dinucleotide repeat in the proximal promo ter appears to repress overall promoter activity. Understanding the molecul ar mechanisms associated with cytokine-dependent expression of the cPLA(2) gene should provide further insight into regulating the level of proinflamm atory mediators in pulmonary diseases.