The Conversion of Rapid TCCD Nongenomic Signals to Persistent Inflammatory Effects via Select Protein Kinases in MCF10A Cells

Abstract

Previously we found that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induces rapid inflammatory cellular responses in MCF10A mammary epithelial cells through a distinct nongenomic pathway by activating cytosolic phospholipase A2 and Src kinase within 30 min. In the current study we investigated how such an initial, seemingly transient signaling induced by TCDD is subsequently converted into more stable long-term messages. We found that TCDD causes prolonged activation of the binding activity of nuclear proteins to the oligonucleotide probes representing consensus activator protein 1 and CCAAT enhancer binding protein response element sequences, followed by later induction of some diagnostic marker including cyclooxgenase-2, matrix metalloproteinase-2, colony stimulating factor-1, and cytochrome P450 19 (or aromatase). Blocking the early steps of the nongenomic pathway inhibits this action of TCDD. It was also found that Src kinase is mainly responsible for the increase of binding activity to the activator protein 1 probe, and another kinase, protein kinase A (PKA), is accountable for most of the increase of binding activity to the CCAAT enhancer binding protein probe. The induction of those diagnostic markers is also affected by 4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3,4-d]pyrimidine (a Src kinase inhibitor) or H89 (a PKA inhibitor). These results indicate that Src kinase and PKA act as the second messengers in propagating the initial nongenomic signaling of TCDD.