Date of Award
Doctor of Philosophy (PhD)
Leslie C. Plhak
Jacqueline M. Stephens
Cyclooxygenase (COX) is the key enzyme in the biosynthesis of prostaglandins (PGs) known as pro-inflammatory mediators. COX has two isoforms: the constitutively expressed COX-1 and the mitogen-inducible COX-2. It has been demonstrated that COX-2 expression is selectively induced by lipopolysaccharide (LPS) treatment after several hours in rat alveolar macrophages (Lee et al., 1992; Chanmugam et al., 1995). The mitogen-activated protein kinases [MAPKs; extracellular signal-regulated kinases (ERKs), P38, and c-jun N-terminal kinases (JNKs)], nuclear factor kappa B (NF-kB), and Lyn kinase are known to be activated in the early stages (within minutes) of LPS signaling pathways. In the current study, the mechanism of COX-2 expression induced by LPS in RAW 264.7 macrophages was examined. To examine the involvement of MAPKs and NF-kB on COX-2 expression, RAW 264.7 cells were treated with LPS and known activators and inhibitors of MAPKs, NF-kB, or protein tyrosine kinases (PTKs). To examine the role of Lyn kinase on COX-2 expression, Phoenix ( F NX) cells, a packaging cell line, were transfected with Flag (epitope)-tagged lyn cDNAs in the retroviral vector pBPSTR1, and the infectious viral particles produced by transfected F NX cells were infected to NIH/3T3 cells, a murine fibroblast cell line. The activation of MAPKs by known activators was insufficient to induce COX2 expression. Partial inhibition of LPS-induced activation of MAPKs by PD98059 or SB203580 resulted in partial inhibition of COX-2 expression. Similarly, inhibition of LPS-induced activation of NF-kB by Z-LLF-CHO resulted in suppression of COX-2 expression. Both inhibition of LPS-induced activation of MAPKs and NF-kB by Radicicol or Herbimycin A resulted in suppression of COX-2 expression. Transfection data lead to an observation that high COX-2 expression and PGE 2 levels can be induced by overexpression of mutant Lyn in NIH/3T3 cells transfected with mutant lyn DNA. This study demonstrates that COX-2 expression induced by LPS in RAW 264.7 cells appears to be mediated via rapid activation of MAPKs and NF-kB in LPS signaling pathways.
Jang, Byeong Churl, "Studies on Cyclooxygenase-2 Expression in Lipopolysaccharide-Stimulated Macrophages." (1999). LSU Historical Dissertations and Theses. 6944.