Evidence that PAR2-triggered prostaglandin E2 (PGE2) formation involves the ERK-cytosolic phospholipase A2-COX-1-microsomal PGE synthase-1 cascade in human lung epithelial cells

Increased expression of cPLA2 (cytosolic phospholipase A2) has been shown to be the cause of tumorigenesis of NSCLC (non-small-cell lung cancer). Our laboratory has previously demonstrated that oncogenic forms of Ras increase transcription of cPLA2 in normal lung epithelial cells and NSCLC lines through activation of the ERK (extracellular-signal-regulated kinase) and JNK (c-Jun N-terminal kinase) MAPK (mitogen-activated protein kinase) family. We have also defined a minimal region of the cPLA2 promoter that is critical for this induction. To identify potential transcription factors that bind to this region and regulate expression, a yeast one-hybrid screen was performed with a rat lung cDNA library. Multiple members of the Krüppel family were identified, with LKLF (lung Krüppel-like factor) being isolated a number of times. Overexpression of LKLF in lung epithelial cells or Drosophila SL-2 cells increased cPLA2 promoter activity. Conversely, expression of a dominant negative form of LKLF inhibited induction of cPLA2 promoter activity by oncogenic Ras in normal lung epithelial cells and NSCLC. By electrophoretic mobility-shift assay analysis, it was found that LKLF bound to a GC-rich region of the cPLA2 promoter located between −37 and −30 upstream from the transcription start site. Expression of siRNA (small interfering RNA) directed against LKLF inhibited basal expression of cPLA2 in lung epithelial cells and blocked induction by H-Ras. In NSCLC, siRNA against LKLF co-operated with siRNA against Sp1 (stimulatory protein 1) to inhibit cPLA2 promoter activity. Finally, recombinant LKLF was a substrate for ERKs. These results indicate that LKLF is an important regulator of cPLA2 expression and participates in the induction of this protein, which is critical for increased eicosanoid production associated with lung tumorigenesis.

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Curcumin Inhibits the Proteinase-Activated Receptor-2–Triggered Prostaglandin E2 Production by Suppressing Cyclooxygenase-2 Upregulation and Akt-Dependent Activation of Nuclear Factor-κB in Human Lung Epithelial Cells

Journal of Pharmacological Sciences ◽

10.1254/jphs.10126sc ◽

2010 ◽

Vol 114 (2) ◽

pp. 225-229 ◽

Cited By ~ 18

Author(s):

Kazumi Moriyuki ◽

Fumiko Sekiguchi ◽

Kaori Matsubara ◽

Hiroyuki Nishikawa ◽

Atsufumi Kawabata

Keyword(s):

Epithelial Cells ◽

Prostaglandin E2 ◽

Human Lung ◽

Nuclear Factor Κb ◽

Cyclooxygenase 2 ◽

Lung Epithelial Cells ◽

Nuclear Factor ◽

Lung Epithelial ◽

Human Lung Epithelial Cells

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TNF-α induces cytosolic phospholipase A2 expression via Jak2/PDGFR-dependent Elk-1/p300 activation in human lung epithelial cells

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.00320.2013 ◽

2014 ◽

Vol 306 (6) ◽

pp. L543-L551 ◽

Cited By ~ 8

Author(s):

Chuen-Mao Yang ◽

I-Ta Lee ◽

Pei-Ling Chi ◽

Shin-Ei Cheng ◽

Li-Der Hsiao ◽

...

Keyword(s):

Epithelial Cells ◽

Human Lung ◽

Growth Factor Receptor ◽

Lung Epithelial Cells ◽

Mapk Phosphorylation ◽

Cytosolic Phospholipase ◽

Tnf Α ◽

Lung Epithelial ◽

Phosphoinositide 3 Kinase ◽

Human Lung Epithelial Cells

Cytosolic phospholipase A2 (cPLA2) plays a pivotal role in mediating agonist-induced arachidonic acid release for prostaglandin (PG) synthesis during inflammation triggered by tumor necrosis factor-α (TNF-α). However, the mechanisms underlying TNF-α-induced cPLA2 expression in human lung epithelial cells (HPAEpiCs) were not completely understood. Here, we demonstrated that TNF-α induced cPLA2 mRNA and protein expression, promoter activity, and PGE2 secretion in HPAEpiCs. These responses induced by TNF-α were inhibited by pretreatment with the inhibitor of Jak2 (AG490), platelet-derived growth factor receptor (PDGFR) (AG1296), phosphoinositide 3 kinase (PI3K) (LY294002), or MEK1/2 (PD98059) and transfection with siRNA of Jak2, PDGFR, Akt, or p42. We showed that TNF-α markedly stimulated Jak2, PDGFR, Akt, and p42/p44 MAPK phosphorylation, which were attenuated by their respective inhibitors. Moreover, TNF-α stimulated Akt activation via a Jak2/PDGFR pathway in HPAEpiCs. In addition, TNF-α-induced p42/p44 MAPK phosphorylation was reduced by AG1296 or LY294002. On the other hand, TNF-α could induce Akt and p42/p44 MAPK translocation from the cytosol into the nucleus, which was inhibited by AG490, AG1296, or LY294002. Finally, we showed that TNF-α stimulated Elk-1 phosphorylation, which was reduced by LY294002 or PD98059. We also observed that TNF-α time dependently induced p300/Elk-1 and p300/Akt complex formation in HPAEpiCs, which was reduced by AG490, AG1296, or LY294002. The activity of cPLA2 protein upregulated by TNF-α was reflected on the PGE2 release, which was reduced by AG490, AG1296, LY294002 , or PD98059. Taken together, these results demonstrated that TNF-α-induced cPLA2 expression and PGE2 release were mediated through a Jak2/PDGFR/PI3K/Akt/p42/p44 MAPK/Elk-1 pathway in HPAEpiCs.

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