TNF-α-Induced Cyclooxygenase-2 Expression in Human Lung Epithelial Cells: Involvement of the Phospholipase C-γ2, Protein Kinase C-α, Tyrosine Kinase, NF-κB-Inducing Kinase, and I-κB Kinase 1/2 Pathway

Abstract

TNF-α induced a dose- and time-dependent increase in cyclooxygenase-2 (COX-2) expression and PGE2 formation in human NCI-H292 epithelial cells. Immunofluorescence staining demonstrated that COX-2 was expressed in cytosol and nuclear envelope. Tyrosine kinase inhibitors (genistein or herbimycin) or phosphoinositide-specific phospholipase C inhibitor (U73122) blocked TNF-α-induced COX-2 expression. TNF-α also stimulated phosphatidylinositol hydrolysis and protein kinase C (PKC) activity, and both were abolished by genistein or U73122. The PKC inhibitor, staurosporine, also inhibited TNF-α-induced response. The 12-O-tetradecanoylphorbol 13-acetate (TPA), a PKC activator, also stimulated COX-2 expression, this effect being inhibited by genistein or herbimycin. NF-κB DNA-protein binding and COX-2 promoter activity were enhanced by TNF-α, and these effects were inhibited by genistein, U73122, staurosporine, or pyrolidine dithiocarbamate. TPA stimulated both NF-κB DNA-protein binding and COX-2 promoter activity, these effects being inhibited by genistein, herbimycin, or pyrolidine dithiocarbamate. The TNF-α-induced, but not the TPA-induced, COX-2 promoter activity was inhibited by phospholipase C-γ2 mutants, and the COX-2 promoter activity induced by either agent was attenuated by dominant-negative mutants of PKC-α, NF-κB-inducing kinase, or I-κB (inhibitory protein that dissociates from NF-κB) kinase (IKK)1 or 2. IKK activity was stimulated by both TNF-α and TPA, and these effects were inhibited by staurosporine or herbimycin. These results suggest that, in NCI-H292 epithelial cells, TNF-α might activate phospholipase C-γ2 via an upstream tyrosine kinase to induce activation of PKC-α and protein tyrosine kinase, resulting in the activation of NF-κB-inducing kinase and IKK1/2, and NF-κB in the COX-2 promoter, then initiation of COX-2 expression and PGE2 release.

Induction of cyclooxygenase-2 expression by allergens in lymphocytes from allergic patients

“…The decrease in allergen-induced COX-2 mRNA levels promoted by SB203580 suggests that the p38 MAPK pathway may modulate the transcription and/or stabilisation of the COX-2 gene, as previously reported [6]. The relevance of the NF-jB binding sites in the COX-2 promoter is well established in macrophages [39], tumour cells [12] and epithelial cells [13], stimulated by LPS, IL-1b and TNF-a, respectively. Moreover, NF-jB plays a pivotal role in allergy [15], and an activation of NF-jB has been found in mononuclear cells of patients with atopic asthma [32].…”

“…MAPK activities have also been associated with allergic inflammation [8,9]. The transcriptional activation of COX-2 is mediated by the binding of transcription factors to regulatory elements in the COX-2 promoter, such as nuclear factor of activated T cells (NF-AT) [10,11] or NF-jB [12,13]. Available data also reveals an important role of NF-AT and NF-jB in allergic asthma [14,15].…”

Upregulation of cyclooxygenase-2 is accompanied by increased expression of nuclear factor-κB and IκB kinase-α in human colorectal cancer epithelial cells

“…NF-kB can induce the expression of numerous target genes, including COX-2. In model systems, overexpression of the COX-2 protein caused by hypoxia in human umbilical vein endothelial cells and by IL-1 in rheumatoid synoviocytes has been shown to be mediated by NF-kB (Schmedtje et al, 1997;Chen et al, 2000). Furthermore, there are two NF-kB consensus sites present in the promoter region of the human COX-2 gene (Tazawa et al, 1994), these being the NF-kB-3 0 site (À223/À214) and the NF-kB-5 0 site (À447/À438), indicating that NF-kB may be involved in COX-2 induction (Bowie and O'Neill, 2000).…”

“…Cyclooxygenases (COX) are intracellular proteins that catalyse the rate-limiting step in the synthesis of prostaglandins (PGs), a potent group of autocrine and paracrine lipid mediators (Mitchell et al, 1995;Smith et al, 1996;Chen et al, 2000) that are implicated in many normal cellular and pathophysiological processes (Mitchell et al, 1995;Portanova et al, 1996;Smith et al, 1996;Chen et al, 2000). Two forms of COX have been identified to date: the constitutively expressed form COX-1, and the inducible form COX-2.…”

Diet, reproductive factors and lung cancer risk among Chinese women in Singapore: Evidence for a protective effect of soy in nonsmokers

“…30 More recently, it has been shown to inhibit the induction of COX-2 expression in human pulmonary epithelial cells. 51,52 Each of these properties may contribute to the overall protective effect of these compounds. In addition, if circulating estrogens play a role in the development of lung cancer and these tumors remain responsive to their effects, the potential implications for prevention and for therapeutic interventions are many.…”