Signal Transduction for Proteinase-Activated Receptor-2-Triggered Prostaglandin E₂ Formation in Human Lung Epithelial Cells

Abstract

We investigated proteinase-activated receptor-2 (PAR 2 )-triggered signal transduction pathways causing increased prostaglandin E 2 (PGE 2 ) formation in human lung-derived A549 epithelial cells. The PAR 2 agonist, SLIGRL-NH 2 (Ser-Leu-Ile-Gly-Arg-Leu-amide), evoked immediate cytosolic Ca 2ϩ mobilization and delayed (0.5-3 h) PGE 2 formation. The PAR 2 -triggered PGE 2 formation was attenuated by inhibition of the following signal pathway enzymes: cyclooxygenases 1 and 2 (COX-1 and COX-2, respectively), cytosolic Ca 2ϩ -dependent phospholipase A 2 (cPLA 2 ), the mitogenactivated protein kinases (MAPKs), mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK)-extracellular signal-regulated kinase (ERK) and p38 MAPK, Src family tyrosine kinase, epidermal growth factor (EGF) receptor tyrosine kinase (EGFRK), and protein kinase C (PKC), but not by inhibition of matrix metalloproteinases. SLIGRL-NH 2 caused prompt (5 min) and transient ERK phosphorylation, blocked in part by inhibitors of PKC and tyrosine kinases but not by an EGFRK inhibitor. SLIGRL-NH 2 also evoked a relatively delayed (15 min) and persistent (30 min) phosphorylation of p38 MAPK, blocked by inhibitors of Src and EGFRK but not by inhibitors of COX-1 or COX-2. SLIGRL-NH 2 elicited a Src inhibitor-blocked prompt (5 min) and transient phosphorylation of the EGFRK. SLIGRL-NH 2 up-regulated COX-2 protein and/or mRNA levels that were blocked by inhibition of p38 MAPK, EGFRK, Src, and COX-2 but not MEK-ERK. SLIGRL-NH 2 also caused COX-1-dependent up-regulation of microsomal PGE synthase-1 (mPGES-1). We conclude that PAR 2 -triggered PGE 2 formation in A549 cells involves a coordinated up-regulation of COX-2 and mPGES-1 involving cPLA 2 , increased cytosolic Ca 2ϩ , PKC, Src, MEK-ERK, p38 MAPK, Src-mediated EGF receptor trans-activation, and also metabolic products of both COX-1 and COX-2.Proteinase-activated receptors (PARs), a family of G protein-coupled seven-trans-membrane domain receptors, consisting of PARs 1 to 4, are now known to mediate a variety of intracellular signaling and subsequent cellular events caused by specific extracellular proteinases (Hollenberg

Proteinase-Activated Receptor-2–Triggered Prostaglandin E2 Release, but Not Cyclooxygenase-2 Upregulation, Requires Activation of the Phosphatidylinositol 3–Kinase / Akt / Nuclear Factor-κB Pathway in Human Alveolar Epithelial Cells

“…Our signal transduction studies have shown that PAR2-triggered PGE 2 production involves formation of arachidonic acid via the MEK / ERK / cytosolic phospholipase A 2 (cPLA 2 ) pathway and upregulation of COX-2 via the Src / epidermal growth factor (EGF) receptor / p38 MAP kinase (p38MAPK) pathway in A549 cells (18,21). An independent study has also suggested possible involvement of the cAMP-response element-binding protein (CREB) pathway in the PAR2-mediated upregulation of COX-2 in the same cell line (22).…”

Serum-Free Medium Evokes Cyclooxygenase-2 Pathway in A549 Cells

“…Since the immediate product of the three types of COX catalyzed from AA was PGH 2 , the up-regulation of PGES expression is important in ensuring PGE 2 increase. PGES is an enzyme at the downstream of COX-2 pathway, and the expression of PGES often couples with that of COX-2 [12,13]. Based on the results in the present study, it could be deduced that, the up-regulation of COX-2 expression occurs first, and the up-regulation of PGES expression follows.…”

A small interfering RNA targeting proteinase‐activated receptor‐2 is effective in suppression of tumor growth in a Panc1 xenograft model

“…Factors related to the PAR-2 pathway are closely associated to inflammatory reactions and include prostaglandins, cytokines, growth factors and proteases, including matrix metalloprotease (MMP) and mast cell tryptase. [13][14][15][42][43][44] Activation of PAR-2 in various human cell lines upregulates COX-2 expression. [13][14][15] Nonsteroidal anti-inflammatory drugs, which can inhibit COX-2 activity, reduce the risks of several digestive diseases, including colon cancer.…”

“…[13][14][15][42][43][44] Activation of PAR-2 in various human cell lines upregulates COX-2 expression. [13][14][15] Nonsteroidal anti-inflammatory drugs, which can inhibit COX-2 activity, reduce the risks of several digestive diseases, including colon cancer. 45 Yip-Schneider et al 46 reported that COX-2 inhibitors suppress pancreatic cancer cell growth and may be an effective treatment for pancreatic cancer.…”

“…11,12 Signaling through PAR-2 is stimulated preferentially by trypsin and tryptase and can be activated independently by peptide SLIGKV as ligand, which is known to be related to cell activation and intracellular signaling pathways following ligand binding. 13,14 A PAR-2 agonist causes cytosolic Ca 21 mobilization and activates p44/42 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK) and p38 MAPK as well as the nuclear factor kappa B (NF-jB) pathway, [14][15][16] resulting in proliferation and upregulation of COX-2. In our previous study, trypsin and a PAR-2 agonist induced proliferation and enhanced cyclooxygenase-2 (COX-2) mRNA expression in 2 pancreatic cancer cell lines, T3M4 and BxPC3.…”