85-kDa Cytosolic Phospholipase A2 Mediates Peroxisome Proliferator-activated Receptor γ Activation in Human Lung Epithelial Cells

Abstract

The 85-kDa cytosolic phospholipase A 2 (cPLA 2 ) plays an important role in the control of arachidonic acid metabolism. This study was designed to investigate the possible contributions of cPLA 2 and group IIA secretory phospholipase A 2 (sPLA 2 ) in the regulation of peroxisome proliferator-activated receptor (PPAR)-mediated gene transcription in human airway epithelial cells. Primary normal human bronchial epithelial cells and human lung epithelial cell lines BEAS 2B, A549, and NCI-H292 all express PPAR␥ and -␤. Overexpression of cPLA 2 in BEAS 2B cells and primary bronchial epithelial cells resulted in a significant increase of PPAR␥-mediated reporter activity. In contrast, overexpression of group IIA sPLA 2 had no effect on PPAR␥ activation. The PPAR␥ activity in A549 cells was significantly inhibited by the cPLA 2 inhibitor arachidonyltrifluoromethyl ketone but not by the sPLA 2 inhibitor LY311727 and the iPLA 2 inhibitor HELSS. Activation of cPLA 2 by the calcium ionophore, A23187, induced a dose-dependent increase of PPAR activity in normal human bronchial epithelial cells and in the A549 cells. Electrophoretic mobility shift assays show that the binding between PPAR isolated from A549 cells and peroxisome proliferator response element (PPRE) is enhanced by A23187 but partially blocked by the cPLA 2 inhibitors arachidonyltrifluoromethyl ketone and methyl arachidonyl fluorophosphate. Finally, NS 398, a COX-2 inhibitor, partially blocked the A23187 effect on PPAR activity and binding to the PPRE suggesting involvement of COX-2 metabolites in PPRE activation. The above results demonstrate a novel function of cPLA 2 in the control of PPAR␥ activation in human lung epithelial cells.

15-deoxy-Δ12,14-prostaglandin J2 up-regulates death receptor 5 gene expression in HCT116 cells: involvement of reactive oxygen species and C/EBP homologous transcription factor gene transcription

“…As reported, 15dPGJ 2 is an endogenous activator of PPAR-g; however, PPAR-g activation cannot account for all of the actions of 15dPGJ 2 (35,36). Herein, we produced some evidence to prove this suggestion.…”

Thioredoxin-mediated Negative Autoregulation of Peroxisome Proliferator-activated Receptor α Transcriptional Activity

“…The A549 cells transiently cotransfected with the luciferase reporter [(PPRE) 3 -TKLuc], PPAR␣ vector, and pcDNA3-based Trx or its mutant were used as model system because A549 cells are more sensitive to "nude Trx" than other cell types (see Figure 5B) and lack endogenous PPAR␣ (Pawliczak et al, 2002). As expected, cotransfection of the wild-type Trx markedly inhibited both constitutive and ligand-stimulated PPAR␣ activity, whereas the redox-inactive mutant Trx(C32/35S), in which the Cys32 and Cys35 was mutated to serine, completely lost its inhibitory effect.…”

Peroxisome Proliferator‐Activated Receptors: Potential Therapeutic Targets in Lung Disease?

“…Calcium-dependent nuclear translocation of cytosolic phospholipase A 2 (PLA 2 ) leads to the generation of PPAR ligands in the nucleus, where they can directly activate nuclear PPAR. 27 Similarly, liver fatty acid-binding protein (L-FABP) is important for the transport of fatty acids and other PPAR ligands to the nucleus. 6 Conversely, albumin binds 15-D 12,14 -PGJ 2 , and may limit its availability.…”

“…6,13 PPARb/d is also expressed in primary airway epithelial cells, and to a lesser extent in epithelial cell lines. 27 PPARg2 is the predominant form in epithelial cell lines (A549, BEAS-2B, and NCI-H292), whereas PPARg1 is the major variant in primary type II cells. 27 Of relevance to the pulmonary immune/inflammatory response, PPARg is also expressed in endothelial 25,[28][29][30][31][32][33] and smooth muscle cells 13,26,34,35 of the pulmonary vasculature, and in leukocytes (neutrophils, eosinophils, and mast cells).…”

“…27 PPARg2 is the predominant form in epithelial cell lines (A549, BEAS-2B, and NCI-H292), whereas PPARg1 is the major variant in primary type II cells. 27 Of relevance to the pulmonary immune/inflammatory response, PPARg is also expressed in endothelial 25,[28][29][30][31][32][33] and smooth muscle cells 13,26,34,35 of the pulmonary vasculature, and in leukocytes (neutrophils, eosinophils, and mast cells). 25,36,37 The widespread distribution of PPARs in the airway, along with their many physiological roles, suggests that they may play important roles in both lung health and disease.…”