15-deoxy-Δ12, 14-prostaglandin J2 enhances anticancer activities independently of VHL status in renal cell carcinomas

Renal cell carcinoma (RCC) is relatively resistant to chemotherapy and radiotherapy. Clear cell RCC (ccRCC) accounts for the majority of RCC, which have mutations or epigenetic silencing of the von Hippel–Lindau (VHL) gene. VHL-positive Caki-2 cells are killed by an endogenous anticancer substance, 15-deoxy-Δ^{12, 14}-prostaglandin J₂ (15d-PGJ₂). The MTT reduction assay reflecting mitochondrial succinate dehydrogenase activity was employed for assessment of cell viability. We confirmed anticancer activities of camptothecin (topoisomerase I inhibitor), etoposide (topoisomerase II inhibitor), doxorubicin (topoisomerase II inhibitor) in VHL-positive Caki-2 cells. Combination of topoisomerase inhibitors with 15d-PGJ₂ exhibited the synergistic effect in VHL-positive Caki-2 cells. However, 15d-PGJ₂ did not increase cytotoxicities of topoisomerase inhibitors on VHL-negative 786-O cells. In addition, the 15d-PGJ₂-enhanced antitumor activity of topoisomerase inhibitors was detected in neither VHL-positive nor VHL-negative RCC4 cells. Our finding indicated that 15d-PGJ₂ enhanced the antitumor activity of topoisomerase inhibitors independently of VHL.     

15-Deoxy-Δ12,14-prostaglandin J2 enhanced the anti-tumor activity of camptothecin against renal cell carcinoma independently of topoisomerase-II and PPARγ pathways

Renal cell carcinoma (RCC) is chemoresistant cancer. Although several clinical trials were conducted to explore effective medications, the chemoresistance of RCC has not yet been conquered. An endogenous ligand for peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), induces apoptosis in RCC. Here, we examined synergistic effects of several carcinostatics on the anti-tumor activity of 15d-PGJ(2) in Caki-2 cell line by MTT assay. A topoisomerase-I inhibitor, camptothecin (CPT), exhibited synergistically toxicity with 15d-PGJ(2), but neither 5-fluorouracil nor cisplatin did. The combination of 15d-PGJ(2) and a topoisomerase-II inhibitor, doxorubicine, did not cause synergistic cell growth inhibition. The synergistic effect of topoisomerase-I and II inhibitors was not also detected. A PPARγ antagonist, GW9662, did not prevent Caki-2 from undergoing 15d-PGJ(2)-induced cytotoxicity. The treatment of CPT combined with 15d-PGJ(2) activated caspase-3 more than the separate treatment. These results suggest that 15d-PGJ(2) exhibited the anti-tumor activity synergistically with CPT independent of topoisomerase-II and PPARγ.     

Proteomic identification of protein targets for 15-deoxy-Δ(12,14)-prostaglandin J2 in neuronal plasma membrane

15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) is one of factors contributed to the neurotoxicity of amyloid β (Aβ), a causative protein of Alzheimer's disease. Type 2 receptor for prostaglandin D(2) (DP2) and peroxysome-proliferator activated receptorγ (PPARγ) are identified as the membrane receptor and the nuclear receptor for 15d-PGJ(2), respectively. Previously, we reported that the cytotoxicity of 15d-PGJ(2) was independent of DP2 and PPARγ, and suggested that 15d-PGJ(2) induced apoptosis through the novel specific binding sites of 15d-PGJ(2) different from DP2 and PPARγ. To relate the cytotoxicity of 15d-PGJ(2) to amyloidoses, we performed binding assay [(3)H]15d-PGJ(2) and specified targets for 15d-PGJ(2) associated with cytotoxicity. In the various cell lines, there was a close correlation between the susceptibilities to 15d-PGJ(2) and fibrillar Aβ. Specific binding sites of [(3)H]15d-PGJ(2) were detected in rat cortical neurons and human bronchial smooth muscle cells. When the binding assay was performed in subcellular fractions of neurons, the specific binding sites of [(3)H]15d-PGJ(2) were detected in plasma membrane, nuclear and cytosol, but not in microsome. A proteomic approach was used to identify protein targets for 15d-PGJ(2) in the plasma membrane. By using biotinylated 15d-PGJ(2), eleven proteins were identified as biotin-positive spots and classified into three different functional proteins: glycolytic enzymes (Enolase2, pyruvate kinase M1 (PKM1) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH)), molecular chaperones (heat shock protein 8 and T-complex protein 1 subunit α), cytoskeletal proteins (Actin β, F-actin-capping protein, Tubulin β and Internexin α). GAPDH, PKM1 and Tubulin β are Aβ-interacting proteins. Thus, the present study suggested that 15d-PGJ(2) plays an important role in amyloidoses not only in the central nervous system but also in the peripheral tissues.     

A PPAR-γ ligand, 15-deoxy-Δ12,14-prostaglandin J2, inhibited gastric mucosal injury induced by ischemia–reperfusion in rats

Abstract

Introduction: Recent studies have demonstrated the anti-inflammatory action of 15-deoxy-Δ12,14-prostaglandin J₂ (15d-PGJ₂), a derivative of the PGD₂ metabolic pathway. Acute inflammation, including neutrophil activation, plays a critical role in the pathogenesis of ischemia–reperfusion (I/R). The aim of the present study was to determine the effect of 15d-PGJ₂ on I/R-induced gastric mucosal injury in rats.

Methods: Gastric mucosal damage was induced in male Wistar rats by clamping the celiac artery for 30 min followed by reperfusion. 15d-PGJ₂ (0.01–1.0 mg/kg) was given to the rats intraperitoneally 1 h before the vascular clamping. The area of gastric mucosal erosions (erosion index) was measured. Thiobarbituric acid reactive substances (TBARS) and tissue-associated myeloperoxidase (MPO) activity were measured in the gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The expression of tumor necrosis factor-α (TNF-α) in gastric mucosa was measured by ELISA. In addition, to elucidate whether the protective effects of 15d-PGJ₂ are related to the activation of the PPAR-γ receptor, we also investigated the effects of a PPAR-γ antagonist, GW9662.

Results: After 60 min of reperfusion, the area of gastric erosion index had significantly increased from the mean basal levels. The increase in the erosion index was significantly inhibited by pretreatment with 15d-PGJ₂ in a dose-dependent manner. On the other hand, GW9662 reversed the protective effect of 15d-PGJ₂. The concentration of TBARS and MPO activity in the gastric mucosa were both significantly increased after I/R, and pretreatment with 15d-PGJ₂ significantly reduced these increases. The TNF-α content was significantly higher in the I/R group than in the sham-operated group. However, the increase in TNF-α was significantly inhibited by pretreatment with 15d-PGJ₂.

Conclusions: 15d-PGJ₂ significantly inhibited the severity of acute gastric mucosal injury induced by I/R in rats through PPAR-γ-dependent mechanisms. This effect may be due, in part, to a reduction in the infiltration of neutrophils into the gastric mucosa, possibly via the inhibition of inflammatory cytokine.     

15-Deoxy-Δ-prostaglandin J2 enhanced the anti-tumor activity of camptothecin against renal cell carcinoma independently of topoisomerase-II and PPARγ pathways

Renal cell carcinoma (RCC) is chemoresistant cancer. Although several clinical trials were conducted to explore effective medications, the chemoresistance of RCC has not yet been conquered. An endogenous ligand for peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂), induces apoptosis in RCC. Here, we examined synergistic effects of several carcinostatics on the anti-tumor activity of 15d-PGJ₂ in Caki-2 cell line by MTT assay. A topoisomerase-I inhibitor, camptothecin (CPT), exhibited synergistically toxicity with 15d-PGJ₂, but neither 5-fluorouracil nor cisplatin did. The combination of 15d-PGJ₂ and a topoisomerase-II inhibitor, doxorubicine, did not cause synergistic cell growth inhibition. The synergistic effect of topoisomerase-I and II inhibitors was not also detected. A PPARγ antagonist, GW9662, did not prevent Caki-2 from undergoing 15d-PGJ₂-induced cytotoxicity. The treatment of CPT combined with 15d-PGJ₂ activated caspase-3 more than the separate treatment. These results suggest that 15d-PGJ₂ exhibited the anti-tumor activity synergistically with CPT independent of topoisomerase-II and PPARγ.     

Synergistic effects of 15-deoxy Δ12,14-prostaglandin J2 on the anti-tumor activity of doxorubicin in renal cell carcinoma

An endogenous anticancer agent, 15-deoxy -Δ^12,14-prostaglandin J₂ (15d-PGJ₂) induces apoptosis in the chemoresistant renal cell carcinoma (RCC). Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor for 15d-PGJ₂, and mediates the cytotoxicity of 15d-PGJ₂ in many cancerous cells. However, 15d-PGJ₂ induces apoptosis independently of PPARγ in human RCC cell line such as Caki-2. In the present study, we found that 15d-PGJ₂ ameliorated the chemoresistance to one of anthracycline antibiotics, doxorubicin, in Caki-2 cells. Doxorubicin alone exhibited weak cytotoxicity at the concentrations effective for other cancer cells such as Hela cells. In addition, it did not activate caspase 3. However, the cytotoxicity of doxorubicin was increased remarkably and accompanied with the caspase- 3 activation in the presence of 15d-PGJ₂. Doxorubicin alone damaged plasma membrane, and the combined application of 15d-PGJ₂ with doxorubicin increased the membrane permeability slightly. PPARγ was involved in neither the anti-tumor activity nor the synergistic effect of 15d-PGJ₂. 15d-PGJ₂ induces apoptosis in Caki-2 cells via suppressing the phosphoinositide 3-kinase (PI3K)-Akt pathway. The effect of PI3K inhibitor on the cytotoxicity of doxorubicin was additive, but not synergistic. Although the PI3K inhibitor mimicked the cytotoxicity of 15d-PGJ₂, it might not be involved in the synergism between 15d-PGJ₂ and doxorubicin. In conclusion, 15d-PGJ₂ enhanced the chemosensitivity of doxorubicin via the pathway independent of PPARγ and PI3K.     

Phosphoinositide-dependent kinase 1–associated glycolysis is regulated by miR-409-3p in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most popular kidney cancer in adults. Metabolic shift toward aerobic glycolysis is a fundamental factor for ccRCC therapy. MicroRNAs (miRNAs) are thought to be important regulators in ccRCC development and progression. Phosphoinositide-dependent kinase 1 (PDK1) is required for metabolic activation; however, the role of PDK1-induced glycolytic metabolism regulated by miRNAs is unclear in ccRCC. So, the purpose of the current study is to elucidate the underlying mechanism in ccRCC cell metabolism mediated by PDK1. Our results revealed that miR-409-3p inhibited glycolysis by regulating PDK1 expression in ccRCC cells. We also found that miR-409-3p was regulated by hypoxia. Our results indicated that PDK1 facilitated ccRCC cell glycolysis, regulated by miR-409-3p in hypoxia.     

Observation of two modes of inhibition of human microsomal prostaglandin E synthase 1 by the cyclopentenone 15-deoxy-Δ(12,14)-prostaglandin J(2)

Microsomal prostaglandin E synthase 1 (MPGES1) is an enzyme that produces the pro-inflammatory molecule prostaglandin E(2) (PGE(2)). Effective inhibitors of MPGES1 are of considerable pharmacological interest for the selective control of pain, fever, and inflammation. The isoprostane, 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), a naturally occurring degradation product of prostaglandin D(2), is known to have anti-inflammatory properties. In this paper, we demonstrate that 15d-PGJ(2) can inhibit MPGES1 by covalent modification of residue C59 and by noncovalent inhibition through binding at the substrate (PGH(2)) binding site. The mechanism of inhibition is dissected by analysis of the native enzyme and the MPGES1 C59A mutant in the presence of glutathione (GSH) and glutathione sulfonate. The location of inhibitor adduction and noncovalent binding was determined by triple mass spectrometry sequencing and with backbone amide H/D exchange mass spectrometry. The kinetics, regiochemistry, and stereochemistry of the spontaneous reaction of GSH with 15d-PGJ(2) were determined. The question of whether the anti-inflammatory properties of 15d-PGJ(2) are due to inhibition of MPGES1 is discussed.     

Nonenzymatic free radical-catalyzed generation of 15-deoxy-Δ(12,14)-prostaglandin J₂-like compounds (deoxy-J₂-isoprostanes) in vivo

15-Deoxy-Δ^12,14-prostaglandin J₂ (15-d-PGJ₂) is a reactive cyclopentenone eicosanoid generated from the dehydration of cyclooxygenase-derived prostaglandin D₂ (PGD₂). This compound possesses an α,β-unsaturated carbonyl moiety that can readily adduct thiol-containing biomolecules such as glutathione and cysteine residues of proteins via the Michael addition. Due to its reactivity, 15-d-PGJ₂ is thought to modulate inflammatory and apoptotic processes and is believed to be an endogenous ligand for peroxisome proliferator-activated receptor-γ. However, the extent to which 15-d-PGJ₂ is formed in vivo and the mechanisms that regulate its formation are unknown. Previously, we have reported the formation of PGD₂ and PGJ₂-like compounds, termed D₂/J₂-isoprostanes (D₂/J₂-IsoPs), produced in vivo by the free radical-catalyzed peroxidation of arachidonic acid (AA). Based on these findings, we investigated whether 15-d-PGJ₂-like compounds are also formed via this nonenzymatic pathway. Here we report the generation of novel 15-d-PGJ₂-like compounds, termed deoxy-J₂-isoprostanes (deoxy-J₂-IsoPs), in vivo, via the nonenzymatic peroxidation of AA. Levels of deoxy-J₂-IsoPs increased 12-fold (6.4 ± 1.1 ng/g liver) in rats after oxidant insult by CCl₄ treatment, compared with basal levels (0.55 ± 0.21 ng/g liver). These compounds may have important bioactivities in vivo under conditions associated with oxidant stress.     

15-Deoxy-Δ12,14-prostaglandin J2 prevents oxidative injury by upregulating the expression of aldose reductase in vascular smooth muscle cells

Abstract

The omega-6 fatty acid derivative 15-Deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) is believed to play a role in cellular protection against oxidative stress in diverse cell systems. However, the cellular mechanisms by which protection is afforded by 15d-PGJ₂ are not fully elucidated in vascular smooth muscle cells (VSMCs). In this study, we report the finding that 15d-PGJ₂ elicited a time and concentration- dependent increase in aldose reductase (AR) expression. This induction was independent of the activation of peroxisome proliferator- activated receptor γ. Inhibition of phosphatidylinositol 3-kinase (PI3K) significantly suppressed the increase in expression and promoter activity of AR induced by 15d-PGJ₂. Luciferase reporter assays demonstrated that 15d-PGJ₂ targets the multiple stress response regions comprising the antioxidant response element in the promoter of the AR gene. 15d-PGJ₂-mediated induction of AR promoter activity was potentiated in the presence of nuclear factor-erythroid 2-related factor 2 (Nrf2), but not in cells expressing dominant negative Nrf2. Cells treated with 15d-PGJ₂ were resistant to oxidant-induced apoptotic cell death by inhibiting production of reactive oxygen species. These effects were significantly attenuated in the presence of an AR inhibitor or small interfering RNA against AR, indicating that AR plays a protective role against oxidative injury. Taken together, these findings demonstrate that activation of PI3K by 15d-PGJ₂ increases the expression of AR through Nrf2, and increased AR activity may function as an important cellular response against oxidative injury.     

15-Deoxy-Δ(12,14)-prostaglandin J(2) attenuates the biological activities of monocyte/macrophage cell lines

Monocytes/macrophages link the innate and adaptive immune systems, and in inflammatory disorders their activation leads to tissue damage. 15-Deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), a natural peroxisome proliferator-activated receptor gamma (PPARγ) ligand, has garnered much interest because it possesses anti-inflammatory properties in a number of experimental models. However, whether it regulates monocytes/macrophage pathophysiology is still unknown. This study was designed to examine the effects of 15d-PGJ(2) on the phagocytosis, proliferation and inflammatory cytokines generation in mouse monocyte/macrophage cell line RAW264.7 and J774A.1 cells upon lipopolysaccharide challenge. Our results showed that 15d-PGJ(2) inhibited the phagocytic activity and cell proliferation in a dose-dependent manner, and suppressed proinflammatory cytokines expression, such as tumor necrosis factor-α, transforming growth factor-β1, interleukin-6, and monocyte chemotactic protein-1. These effects were independent of PPARγ, because PPARγ agonist (troglitazone or ciglitazone) and PPARγ antagonist (GW9662) did not affect these activities mentioned above in cells. Treatment of 15d-PGJ(2) also did not modulate expression and distribution of PPARγ. However, these effects of 15d-PGJ(2) were abrogated by antioxidant N-acetylcysteine. Moreover, treatment of 15d-PGJ(2) induced a significant increase in reactive oxygen species production in RAW264.7 and J774A.1 cells. In conclusion, 15d-PGJ(2) attenuates the biological activities of mouse monocyte/macrophage cell line cells involving oxidative stress, independently of PPARγ. These data further underline the anti-inflammation potential of 15d-PGJ(2).     

15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) Induces Cell Death Through Caspase-independent Mechanism in A172 Human Glioma Cells

15-Deoxy-^Δ12,14-prostaglandin J₂ (15d-PGJ₂) is a naturally occurring cyclopentenone metabolite of prostaglandin D₂ (PGD₂) and is known as a specific potent ligand for the peroxisome proliferators activator receptor-γ (PPARγ). 15d-PGJ₂ inhibits cell growth and induces apoptosis in a number of different cancer cells. However, the underlying mechanism by which 15d-PGJ₂ induces cell death remains to be defined. The present study was undertaken to determine the effect of 15d-PGJ₂ on cell death in A172 human glioma cells. 15d-PGJ₂ caused reactive oxygen species (ROS) generation. 15d-PGJ₂-induced ROS production and cell death were prevented by the antioxidant N-acetylcysteine. Activation of mitogen-activated protein kinases (MAPK) was not observed in cells treated with 15d-PGJ₂ and inhibitors of MAPK subfamilies also were not effective in preventing 15d-PGJ₂-induced cell death. 15d-PGJ₂ treatment caused mitochondrial dysfunction, as evidenced by depolarization of mitochondrial membrane potential. 15d-PGJ₂ induced caspase activation at 24 h of treatment, but the 15d-PGJ₂-induced cell death was not prevented by caspase inhibitors. The antiapoptotic protein XIAP levels and release of apoptosis inducing factor (AIF) into the cytosol were not altered by 15d-PGJ₂ treatment. Taken together, these findings indicate that 15d-PGJ₂ triggers cell death through a caspase-independent mechanism and ROS production and disruption of mitochondrial membrane potential play an important role in the 15d-PGJ₂-induced cell death in A172 human glioma cells.     

Inhibition of mitochondrial division through covalent modification of Drp1 protein by 15 deoxy-Δ-prostaglandin J2

Arachidonic acid derived endogenous electrophile 15d-PGJ2 has gained much attention in recent years due to its potent anti-proliferative and anti-inflammatory actions mediated through thiol modification of cysteine residues in its target proteins. Here, we show that 15d-PGJ2 at 1 μM concentration converts normal mitochondria into large elongated and interconnected mitochondria through direct binding to mitochondrial fission protein Drp1 and partial inhibition of its GTPase activity. Mitochondrial elongation induced by 15d-PGJ2 is accompanied by increased assembly of Drp1 into large oligomeric complexes through plausible intermolecular interactions. The role of decreased GTPase activity of Drp1 in the formation of large oligomeric complexes is evident when Drp1 is incubated with a non-cleavable GTP analog, GTPγS or by a mutation that inactivated GTPase activity of Drp1 (K38A). The mutation of cysteine residue (Cys644) in the GTPase effector domain, a reported target for modification by reactive electrophiles, to alanine mimicked K38A mutation induced Drp1 oligomerization and mitochondrial elongation, suggesting the importance of cysteine in GED to regulate the GTPase activity and mitochondrial morphology. Interestingly, treatment of K38A and C644A mutants with 15d-PGJ2 resulted in super oligomerization of both mutant Drp1s indicating that 15d-PGJ2 may further stabilize Drp1 oligomers formed by loss of GTPase activity through covalent modification of middle domain cysteine residues. The present study documents for the first time the regulation of a mitochondrial fission activity by a prostaglandin, which will provide clues for understanding the pathological and physiological consequences of accumulation of reactive electrophiles during oxidative stress, inflammation and degeneration.     

15-Deoxy-Δ12,14-Prostaglandin J2 Inhibits Macrophage Colonization by Salmonella enterica Serovar Typhimurium

15-deoxy-Δ^12,14-prostaglandin J₂ (15d-PGJ₂) is an anti-inflammatory downstream product of the cyclooxygenase enzymes. It has been implicated to play a protective role in a variety of inflammatory mediated diseases, including rheumatoid arthritis, neural damage, and myocardial infarctions. Here we show that 15d-PGJ₂ also plays a role in Salmonella infection. Salmonella enterica Typhimurium is a Gram-negative facultative intracellular pathogen that is able to survive and replicate inside phagocytic immune cells, allowing for bacterial dissemination to systemic sites. Salmonella species cause a wide range of morbidity and mortality due to gastroenteritis and typhoid fever. Previously we have shown that in mouse models of typhoid fever, Salmonella infection causes a major perturbation in the prostaglandin pathway. Specifically, we saw that 15d-PGJ₂ production was significantly increased in both liver and feces. In this work we show that 15d-PGJ₂ production is also significantly increased in macrophages infected with Salmonella. Furthermore, we show that the addition of 15d-PGJ₂ to Salmonella infected RAW264.7, J774, and bone marrow derived macrophages is sufficient to significantly reduce bacterial colonization. We also show evidence that 15d-PGJ₂ is reducing bacterial uptake by macrophages. 15d-PGJ₂ reduces the inflammatory response of these infected macrophages, as evidenced by a reduction in the production of cytokines and reactive nitrogen species. The inflammatory response of the macrophage is important for full Salmonella virulence, as it can give the bacteria cues for virulence. The reduction in bacterial colonization is independent of the expression of Salmonella virulence genes SPI1 and SPI2, and is independent of the 15d-PGJ₂ ligand PPAR-γ. 15d-PGJ₂ also causes an increase in ERK1/2 phosphorylation in infected macrophages. In conclusion, we show here that 15d-PGJ₂ mediates the outcome of bacterial infection, a previously unidentified role for this prostaglandin.     

The glutathionylation of p65 modulates NF-κB activity in 15-deoxy-Δ¹²,¹⁴-prostaglandin J₂-treated endothelial cells

Protein glutathionylation is a posttranslational modification of cysteine residues with glutathione in response to mild oxidative stress. Because 15-deoxy-Δ12,14-prostaglandin J(2) (15d-PGJ(2)) is an electrophilic prostaglandin that can increase glutathione (GSH) levels and augment reactive oxygen species (ROS) production, we hypothesized that it induces NF-κB-p65 glutathionylation and would exert anti-inflammatory effects. Herein, we show that 15d-PGJ(2) suppresses the expression of ICAM-1 and NF-κB-p65 nuclear translocation. 15d-PGJ(2) upregulates the Nrf2-related glutathione synthase gene and thereby increases the GSH levels. Consistent with this, Nrf2 siRNA molecules abolish the inhibition of p65 nuclear translocation in 15d-PGJ(2)-induced endothelial cells (ECs). ECs treated with GSSG show increased thiol modifications of p65 and also a block in TNFα-induced p65 nuclear translocation and ICAM-1 expression, but not in IκBα degradation. However, the overexpression of glutaredoxin 1 was found to be accompanied by a modest increase in NF-κB activity. Furthermore, we found that multiple cysteine residues in p65 are responsible for glutathionylation. 15d-PGJ(2) was observed to induce p65 glutathionylation and is suppressed by a GSH synthesis inhibitor, buthionine sulfoximine, by catalase, and by Nrf2 siRNA molecules. Our results thus indicate that the GSH/ROS-dependent glutathionylation of p65 is likely to be responsible for 15d-PGJ(2)-mediated NF-κB inactivation and for the enhanced inhibitory effects of 15d-PGJ(2) on TNFα-treated ECs.