15d-PGJ2 Research Articles

PPAR-gamma Agonists Inhibit Toll-Like Receptor Mediated Activation of Dendritic Cells Via the MAP Kinase and NF-kB Pathways.

Dendritic cells (DC) play an important role in initiating and maintaining of primary immune responses. However, little is known about the termination of once induced immunological responses. Cyclopentenone prostaglandins (15d-PGJ2, PGD2) are produced during the late phase of inflammation due to upregulation of COX2 and can lead to the resolution of an inflammation by activation of PPAR-gamma dependent and independent pathways. In this study we analyzed the effects of 15d-PGJ2 and the synthetic PPAR-gamma ligand troglitazone (TGZ) on the immunogenicity of monocyte derived DC upon stimulation with toll-like receptor (TLR) ligands. Activation of PPAR-gamma resulted in a reduced activation of DC via the TLR ligands 2, 3, 4 and 7 characterized by downregulation of CD83, adhesion and costimulatory molecules. Moreover, these cells secreted lower levels of cytokines and chemokines involved in T lymphocyte activation and recruitment including IL-12 and RANTES. In contrast to these results, MCP-1 production was increased due to the treatment with PPAR-gamma agonists. To determine the mechanisms by which PPAR-gamma regulates DC function we performed Western blot analyses and found that the inhibitory effects on TLR induced DC activation were mediated via inhibition of the NF-kB and MAP kinase pathways. Incubation of DC during the differentiation from monocytes with 15d-PGJ2 or TGZ resulted in downregulation of TLR ligands induced phosphorylation of ERK1 as well as reduced expression of nuclear localized members of the NF-kB family. No effect on the expression of MyD88, an adaptor molecule involved in the signal transduction of TLR, was observed. Our results demonstrate that inhibition of the MAP kinase and NF-kB pathways is critically involved in the regulation of TLR and PPAR-gamma mediated signaling in DC an represent a novel negative feed-back mechanism involved in the resolution of immunological responses.

Induction of reversible cysteine-targeted protein oxidation by an endogenous electrophile 15-deoxy-delta12,14-prostaglandin J2.

We have previously shown that a prostaglandin D(2) metabolite, 15-deoxy-delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), is the potent inducer of intracellular oxidative stress on human neuroblastoma SH-SY5Y cells [Kondo, M., Oya-Ito, T., Kumagai, T., Osawa, T., and Uchida, K. (2001) Cyclopentenone prostaglandins as potential inducers of intracellular oxidative stress. J. Biol. Chem. 276, 12076-12083.]. In the present study, to investigate the correlation between the redox regulation and the 15d-PGJ(2)-induced oxidative stress and to establish the cellular mechanism for protection against the endogenous electrophile, we analyzed S-oxidized proteins using biotinylated cysteine as a molecular probe. In addition, the reversible regulation of protein function by S-oxidation/thiolation was characterized in vitro. When human neuroblastoma SH-SY5Y cells were exposed to 15d-PGJ(2), followed by treatment with biotinylated cysteine, 26 proteins, including glycolytic enzymes, cytoskeletal proteins, redox enzymes, and stress proteins, were identified as substrates for reversible cysteine-targeted oxidation. To investigate the regulatory mechanism of protein function by S-oxidation/thiolation, the binding of a low molecular weight thiol (glutathione) to a glycolytic enzyme alpha-enolase was characterized. Treatment of alpha-enolase with the thiol oxidant diamide in the presence of glutathione in vitro resulted in the binding of glutathione to the protein and concomitant loss of the enzymatic activity, whereas the glutathiolation and inactivation of alpha-enolase were fully reversed by dithiothreitol. Mass spectrometric analysis of the tryptic fragments from native and oxidized alpha-enolase identified two cysteine residues, Cys-118 and Cys-388, as the S-oxidation sites, which may play a role in the regulation of the biological activities of the protein and may be regulated by a reversible S-oxidation/thiolation reaction. These results suggest that cysteine-targeted oxidation/thiolation plays a critical role in the regulation of protein function under conditions of electrophile-induced oxidative stress.

A Potential Role of 15-Deoxy-Δ12,14-prostaglandin J2 for Induction of Human Articular Chondrocyte Apoptosis in Arthritis

The cyclopentenone prostaglandin (PG) J2 is formed within the cyclopentenone ring of the endogenous prostaglandin PG D2 by a nonenzymatic reaction. The PG J family is involved in mediating various biological effects including the regulation of cell cycle progression and inflammatory responses. Here we demonstrate the potential role of 15-deoxy-Delta(12,14)-prostaglandin J2 (15d-PG J2) in human articular chondrocyte apoptosis. 15d-PG J2 was released by human articular chondrocytes and found in joint synovial fluids taken from osteoarthritis or rheumatoid arthritis patients. Proinflammatory cytokines such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) up-regulated chondrocyte release of 15d-PG J2. PG D2 synthase mRNA expression was up-regulated by IL-1beta, TNF-alpha, or nitric oxide. 15d-PG J2 induced apoptosis of chondrocytes from osteoarthritis or rheumatoid arthritis patients as well as control nonarthritic subjects in a time- and dose-dependent manner and in a peroxisome proliferator-activated receptor gamma-dependent manner. Peroxisome proliferator-activated receptor gamma expression was up-regulated by IL-1beta and TNF-alpha. Inhibition of NF-kappaB, and the activation of p38 MAPK were also found to be involved in 15d-PG J2-induced chondrocyte apoptosis. Such signal pathways led to the activation of the downstream pro-apoptotic molecule p53 and caspase cascades. Together, these results suggest that 15d-PGJ2 may play an important role in the pathogenesis of arthritic joint destruction via a regulation of chondrocyte apoptosis.

67 Assessment of treatment efficacy in preclinical drug testing using magnetic resonance imaging

Cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), which is generated from the dehydration of PGD2, is a natural ligand of peroxisome proliferator-activated receptor gamma (PPARγ) and a potential apoptotic mediator. The synthetic PPARγ ligands, troglitazone and ciglitazone, inhibit tumor progression in many cells by PPARγ activation, but the mechanism of 15d-PGJ2 is still unclear. In this study, GW9662, an antagonist of PPARγ, and quercetin, a natural antioxidant, were used to study the apoptotic mechanism of 15d-PGJ2 in A549 cells. Results showed that 15d-PGJ2 induced apoptosis, which was associated with the production of reactive oxygen species (ROS) and the decrease of GSH levels. Furthermore, quercetin reduced the activity of caspases in 15d-PGJ2-induced apoptotic processes. These results suggest that 15d-PGJ2 induces apoptosis in A549 cells mainly through the formation of ROS; it does not depend on PPARγ activation. Moreover, these findings support the use of quercetin and PPARγ agonists in non-small cell lung carcinoma.

15 d-prostaglandin J 2 reduces multiple organ failure caused by wall-fragment of Gram-positive and Gram-negative bacteria

Septic shock is still the major cause of death in surgical intensive care units. Both gram-positive (G+) and gram-negative (G−) bacteria have been isolated in the blood of a large portion of septic patients, and these polymicrobial infections often have a higher mortality than infections due to a single organism. Cell wall fragments from G+ and G− bacteria synergise to cause shock and multiple organ dysfunction in vivo (G+/G− shock). Male Wistar rats were anaesthetised and received a coadministration of wall fragments from G+ and G− bacteria, Staphilococcus aureus ( S. aureus) peptidoglycan [0.3 mg/kg, intravenously (i.v.)] and Escherichia coli ( E. coli) lipopolysaccharide (1 mg/kg, i.v.) or vehicle (saline, 1 ml/kg, i.v.). G+/G− shock for 6 h resulted in an increase in serum levels of creatinine (indicator of renal dysfunction), alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyl transferase (γ-GT), bilirubin (markers for hepatic injury and dysfunction) and creatine kinase (CK, an indicator of neuromuscular, skeletal muscle or cardiac injury). Pretreatment of rats with the peroxisome proliferator-activated receptor-γ (PPAR-γ) agonist 15 d-prostaglandin J 2 (0.3 mg/kg, i.v., 30 min prior to G+/G−) reduced the multiple organ injury/dysfunction caused by coadministration of peptidoglycan+lipopolysaccharide. The selective PPAR-γ antagonist GW9662 (2-Chloro-5-nitrobenzanilide) (1 mg/kg, i.v., given 45 min prior to G+/G−) abolished the protective effects of 15 d-prostaglandin J 2. 15 d- prostaglandin J 2 did not affect the biphasic fall in blood pressure or the increase in heart rate caused by administration of peptidoglycan+lipopolysaccharide. The mechanism(s) of the protective effect of this cyclopentenone prostaglandin are—at least in part—PPAR-γ dependent, as the protection afforded by 15 d-prostaglandin J 2 was reduced by the PPAR-γ antagonist GW9662. We propose that 15 d-prostaglandin J 2 or other ligands for PPAR-γ may be useful in the therapy of the organ injury associated with septic shock.

Protein thiol modification by 15-deoxy-Delta12,14-prostaglandin J2 addition in mesangial cells: role in the inhibition of pro-inflammatory genes.

The cyclopentenone prostaglandin and PPARgamma agonist 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) displays anti-inflammatory effects in several experimental models. Direct modification of protein thiols is arising as an important mechanism of cyclopentenone prostaglandin action. However, little is known about the extent or specificity of this process. Mesangial cells (MC) play a key role in glomerulonephritis. In this work, we have studied the selectivity of protein modification by 15d-PGJ(2) in MC, and the correlation with the modulation of several proinflammatory genes. MC incubation with biotinylated 15d-PGJ(2) results in the labeling of a distinct set of proteins as evidenced by two-dimensional electrophoresis. 15d-PGJ(2) binds to nuclear and cytosolic targets as detected by fluorescence microscopy and subcellular fractionation. The pattern of biotinylated 15d-PGJ(2)-modified polypeptides is readily distinguishable from that of total protein staining or labeling with biotinylated iodoacetamide. 15d-PGJ(2) addition requires the double bond in the cyclopentane ring. 9,10-Dihydro-15d-PGJ(2), a 15d-PGJ(2) analog that shows the same potency as peroxisome proliferator-activated receptor (PPAR) agonist in MC but lacks the cyclopentenone moiety, displays reduced ability to modify proteins and to block 15d-PGJ(2) binding. Micromolar concentrations of 15d-PGJ(2) inhibit cytokine-elicited levels of inducible nitricoxide synthase, cyclooxygenase-2, and intercellular adhesion molecule-1 in MC. In contrast, 9,10-dihydro-15d-PGJ(2) does not reproduce this inhibition. 15d-PGJ(2) effect is not blocked by the PPARgamma antagonist 2-chloro-5-nitro-N-phenylbenzamide (GW9662). Moreover, compounds possessing an alpha,beta-unsaturated carbonyl group, like 2-cyclopenten-1-one and 2-cyclohexen-1-one, reduce pro-inflammatory gene expression. These observations indicate that covalent modification of cellular thiols by 15d-PGJ(2) is a selective process that plays an important role in the inhibition of MC responses to pro-inflammatory stimuli.

Abrogation of IL-6-mediated JAK signalling by the cyclopentenone prostaglandin 15d-PGJ(2) in oral squamous carcinoma cells.

Cyclopentenone 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) exerts antineoplastic effects on various types of human cancer. We recently showed that treatment with 15d-PGJ2 induces apoptosis accompanied by downregulation of the oncogenic signal transducer and activator of transcription 3 (Stat3) signalling in human oral squamous cell carcinoma (SCC) cells. The current study examines the effects of 15d-PGJ2 on the epidermal growth factor receptor (EGFR) and Janus Kinase (JAK)-mediated signalling pathways. Inhibition of Stat3 by 15d-PGJ2 was abolished by exogenous stimulation with transforming growth factor alpha (TGF-α), but not interleukin 6 (IL-6), supporting a selective effect of 15d-PGJ2 on IL-6-mediated signalling. Importantly, 15d-PGJ2 selectively abrogated constitutive and IL-6-mediated JAK phosphorylation without affecting EGFR-activated levels. Moreover, the inhibitory effect of 15d-PGJ2 on JAK signalling required the reactive α,β-unsaturated carbon within the cyclopentenone ring. Targeting of JAK signalling using a specific JAK inhibitor also abolished Stat3 phosphorylation and resulted in apoptosis in oral SCC cells. Our findings provide the first evidence for 15d-PGJ2–mediated downregulation of constitutive and IL-6-induced JAK signalling in cancer and support that JAK inhibition and suppression of EGFR-independent Stat3 activation by 15d-PGJ2 represent a promising approach for induction of apoptosis in oral SCC cells.

Anti-apoptotic and pro-apoptotic effect of NEPP11 on manganese-induced apoptosis and JNK pathway activation in PC12 cells

Neurite outgrowth-promoting prostaglandins (NEPPs), cyclopentenone prostaglandin derivatives, are found to be neurotrophic. These small organic compounds promote neurite outgrowth of PC12 cells and dorsal root ganglion explants in the presence of nerve growth factor, and prevent neuronal cell death of HT22 cells and cortical neurons induced by various stimuli. In this study, we examined whether NEPP11 prevents manganese-induced apoptosis of PC12 cells. NEPP11 (5 μM) attenuated manganese-induced DNA fragmentation by approximately 50%. In addition, NEPP11 partially prevented manganese-induced c-Jun phosphorylation and c-Jun N-terminal kinase (JNK) phosphorylation determined by Western blotting. Inhibition of the JNK signaling pathway by NEPP11 appeared to be selective, because NEPP11 did not inhibit manganese-induced activation of p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinase1/2 (ERK1/2), MEK1/2 and p70 S6 kinase (p70S6K) in PC12 cells. In contrast, NEPP11 alone was toxic at higher concentrations (>10 μM) producing DNA fragmentation and activation of the JNK pathway. Molecular modifications of NEPP11 may strengthen its inhibitory effects on the JNK pathway while preventing its cytotoxicity, and thus may become a useful small molecule reagent for the treatment of manganese toxicity and other similar neurodegenerative processes.

Effect of prostaglandins on the regulation of tumor growth.

Prostaglandins (PGs) are involved in mediating or regulating many physiological as well as pathological processes. Important roles of PGs in the pathophysiology of carcinogenesis offer potentials of targeting PG synthesis and PG receptors in developing novel anti-cancer therapy. Although initial studies suggested direct growth inhibitory role of PGs from in vitro studies, it has been widely demonstrated that in general, PGs stimulate tumor growth. However, cyclopentenone PGs, especially 15d-PGJ2, which can activate peroxisome proliferator activated receptor (PPAR) gamma, exhibited anti-proliferative and proapoptotic effects on many types of cancer cells. But recent studies indicate that growth inhibitory effects of the cyclopentenone PGs might also be a nonspecific effect due to its highly reactive cyclopentenone ring. We have explored the published studies on PGs to specify its known regulatory roles on tumor growth with an objective of targeting the PGs or pathways activated by these lipids in treating cancers.

Inhibition of herpesvirus-induced HIV-1 replication by cyclopentenone prostaglandins: role of IkappaB kinase (IKK).

Herpes simplex virus (HSV) infections have been associated with reactivation of HIV-1 replication and increases of HIV-1-load in plasma of co-infected individuals. The present authors have previously reported that in epithelial cells HSV-1 induces the IkappaB-kinase (IKK) causing persistent activation of NF-kappaB, a critical regulator of HIV-1 replication. The present study was performed to investigate whether HSV-1-infection could induce IKK-mediated NF-kappaB activation and enhance HIV-1 expression in human T cells, and to analyze the effect of the IKK-inhibitor prostaglandin A1 (PGA1) and other prostanoids on the NF-kappaB-mediated HSV-HIV interaction. Induction of IKK and NF-kappaB activity was determined in lymphoblastoid Jurkat cells and HIV-1 chronically-infected H9 and ACH-2 cells by kinase assay and electrophoretic mobility shift assay, respectively. The effect of HSV-1 and different prostanoids on HIV-1 expression and replication was determined in Jurkat cells transfected with HIV-1-LTR-driven reporter genes, and in H9 and ACH-2 cells by p24-antigen level evaluation. The role of NF-kappaB in HSV-1-induced HIV-1 expression was investigated by using the IkappaBalpha dominant-negative IkappaBalpha-AA in co-transfection experiments. In human T lymphoblastoid cells HSV-1 potently induces IKK activity, causing a persistent induction of NF-kappaB. HSV-1-induced IKK and NF-kappaB function results in transactivation of HIV-1-LTR-regulated genes and induction of HIV-1 replication in chronically-infected T cells. The cyclopentenone PGA1 inhibits HSV-1-induced IKK and NF-kappaB activities, blocking HIV-1-LTR-driven expression and preventing HSV-1-induced HIV-1 replication in co-infected cells. The results indicate that IKK is a key factor in triggering HSV-1-induced HIV-1 transcription in chronically-infected cells and identify cyclopentenone prostanoids as potent inhibitors of HSV-1-induced HIV-1 reactivation.

Differential effects of serum constituents on apoptosis induced by the cyclopentenone prostaglandin 15-deoxy-Δ 12,14-prostaglandin J 2 in WISH epithelial cells

Cyclopentenone prostaglandins, Δ 12-PGJ 2 and 15d-PGJ 2, have potent anti-tumour and anti-inflammatory activities, and have been shown to induce apoptosis in amnion-derived WISH cells. In this study, we have investigated the protective effects of serum and its constituents (growth factors and albumin) on Δ 12-PGJ 2 and 15d-PGJ 2-induced apoptosis in WISH cells. Serum (0.5% w/v) was protective against both Δ 12-PGJ 2 and 15d-PGJ 2-induced apoptosis. This was not due to the presence of serum-derived growth factors (EGF, IGF-1 and IGF-2), since they had no significant effect on 15d-PGJ 2-induced cell death. In contrast, IGF-1 partially inhibited etoposide-induced apoptosis, confirming the presence of a functional IGF-1 receptor signalling system. Albumin was identified as the key survival factor in serum, since albumin and delipidated albumin exhibited the same level of protection from 15d-PGJ 2-induced apoptosis as serum itself. The potential for serum albumin to regulate the bioactivity of cyclopentenone PGs may be of considerable importance in pathological conditions where roles for cyclopentenone PGs have been identified.

15-Deoxy-Δ12,14-prostaglandin J2 Induces Heme Oxygenase-1 Gene Expression in a Reactive Oxygen Species-dependent Manner in Human Lymphocytes

15-Deoxy-delta(12,14)-prostaglandin J(2) (15dPGJ(2) has been recently proposed as a potent anti-inflammatory agent. However, the mechanisms by which 15dPGJ(2) mediates its therapeutic effects in vivo are unclear. We demonstrate that 15dPGJ(2) at micromolar (2.5-10 microm) concentrations induces the expression of heme oxygenase-1 (HO-1), an anti-inflammatory enzyme, at both mRNA and protein levels in human lymphocytes. In contrast, troglitazone and ciglitazone, two thiazolidinediones that mimic several effects of 15dPGJ(2) through their binding to the peroxisome proliferator-activated receptor (PPAR)-gamma, did not affect HO-1 expression, and the positive effect of 15dPGJ(2) on this process was mimicked instead by other cyclopentenone prostaglandins (PG), such as PGD(2) (the precursor of 15dPGJ(2)) and PGA(1) and PGA(2) which do not interact with PPAR-gamma. Also, 15dPGJ(2) enhanced the intracellular production of reactive oxygen species (ROS) and increased xanthine oxidase activity in vitro. Inhibition of intracellular ROS production by N-acetylcysteine, TEMPO, Me(2)SO, 1,10-phenanthroline, or allopurinol resulted in a decreased 15dPGJ(2)-dependent HO-1 expression in the cells. Furthermore, buthionine sulfoximine, an inhibitor of reduced glutathione synthesis, or Fe(2+)/Cu(2+) ions enhanced the positive effect of 15dPGJ(2) on HO-1 expression. On the other hand, the inhibition of phosphatidylinositol 3-kinase or p38 mitogen-activated protein kinase, or the blockade of transcription factor NF-kappaB activation, hindered 15dPGJ(2)-elicited HO-1 expression. Collectively, the present data suggest that 15dPGJ(2) anti-inflammatory actions at pharmacological concentrations involve the induction of HO-1 gene expression through mechanisms independent of PPAR-gamma activation and dependent on ROS produced via the xanthine/xanthine oxidase system and/or through Fenton reactions. Both phosphatidylinositol 3-kinase and p38 mitogen-activated protein kinase signaling pathways also appear implicated in modulation of HO-1 expression by 15dPGJ(2).

Differential effects of serum constituents on apoptosis induced by the cyclopentenone prostaglandin 15-deoxy-$Delta;12,14-prostaglandin J2 in WISH epithelial cells

<h2>Abstract</h2> Cyclopentenone prostaglandins, Δ¹²-PGJ₂ and 15d-PGJ₂, have potent anti-tumour and anti-inflammatory activities, and have been shown to induce apoptosis in amnion-derived WISH cells. In this study, we have investigated the protective effects of serum and its constituents (growth factors and albumin) on Δ¹²-PGJ₂ and 15d-PGJ₂-induced apoptosis in WISH cells. Serum (0.5% w/v) was protective against both Δ¹²-PGJ₂ and 15d-PGJ₂-induced apoptosis. This was not due to the presence of serum-derived growth factors (EGF, IGF-1 and IGF-2), since they had no significant effect on 15d-PGJ₂-induced cell death. In contrast, IGF-1 partially inhibited etoposide-induced apoptosis, confirming the presence of a functional IGF-1 receptor signalling system. Albumin was identified as the key survival factor in serum, since albumin and delipidated albumin exhibited the same level of protection from 15d-PGJ₂-induced apoptosis as serum itself. The potential for serum albumin to regulate the bioactivity of cyclopentenone PGs may be of considerable importance in pathological conditions where roles for cyclopentenone PGs have been identified.

Targeting of epidermal growth factor receptor by cyclopentenone prostaglandin 15-Deoxy-Δ 12,14-prostaglandin J 2 in human oral squamous carcinoma cells

Antineoplastic properties of cyclopentenone 15-deoxy-Δ 12,14-prostaglandin J 2 (15d-PGJ 2) involve peroxisome proliferator-activated receptor gamma (PPARγ) dependent and independent mechanisms. We recently reported that 15d-PGJ 2 inhibits cell growth and induces apoptosis in human oral squamous cell carcinoma (SCC) partly independent of PPARγ activation. Given the importance of epidermal growth factor receptor (EGFR) as a therapeutic target in head and neck SCC, we addressed the effects of 15d-PGJ 2 on EGFR expression. 15d-PGJ 2, but not other PPARγ ligands, abrogated EGFR protein expression in oral SCC cells. 15d-PGJ 2 also decreased EGFR mRNA, indicating downmodulation at the transcriptional level. Moreover, treatment with 9,10-dihydro-15d-PGJ 2, a 15d-PGJ 2 analog lacking the reactive carbonyl group, failed to effect EGFR expression. These findings provide evidence for EGFR downregulation in oral SCC cells through a novel anticancer effect of 15d-PGJ 2 that is attributed to the reactive cyclopentenone ring system.

500: Cyclopentenone Prostaglandin, 15-Deoxy-Δ12,14- PGJ2, Attenuates the Development of Cyclophosphamide Induced Cystitis in the Rat

You have accessJournal of UrologyDiscussed Poster, Sunday, May 9, 2004, 1:00 - 5:00 pm1 Apr 2004500: Cyclopentenone Prostaglandin, 15-Deoxy-Δ12,14- PGJ2, Attenuates the Development of Cyclophosphamide Induced Cystitis in the Rat Hiroshi Masuda, Kazunori Kihara, Michael B. Chancellor, and Naoki Yoshimura Hiroshi MasudaHiroshi Masuda More articles by this author , Kazunori KiharaKazunori Kihara More articles by this author , Michael B. ChancellorMichael B. Chancellor More articles by this author , and Naoki YoshimuraNaoki Yoshimura More articles by this author View All Author Informationhttps://doi.org/10.1016/S0022-5347(18)37762-0AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookLinked InTwitterEmail "500: Cyclopentenone Prostaglandin, 15-Deoxy-Δ12,14- PGJ2, Attenuates the Development of Cyclophosphamide Induced Cystitis in the Rat." The Journal of Urology, 171(4S), pp. 133–134 © 2016 by American Urological AssociationFiguresReferencesRelatedDetails Volume 171Issue 4SApril 2004Page: 133-134 Advertisement Copyright & Permissions© 2016 by American Urological AssociationMetricsAuthor Information Hiroshi Masuda More articles by this author Kazunori Kihara More articles by this author Michael B. Chancellor More articles by this author Naoki Yoshimura More articles by this author Expand All Advertisement PDF downloadLoading ...

Punaglandins, chlorinated prostaglandins, function as potent Michael receptors to inhibit ubiquitin isopeptidase activity.

Cyclopentenone prostaglandins exhibit unique antineoplastic activity and are potent growth inhibitors in a variety of cultured cells. Recently the dienone prostaglandin, Delta(12)-PGJ(2), was shown to preferentially inhibit ubiquitin isopeptidase activity of the proteasome pathway. It is theorized that isopeptidase inhibition and general cytotoxicity of prostaglandins depend on olefin-ketone conjugation, electrophilic accessibility, and the nucleophilic reactivity of the endocyclic beta-carbon. Delta(12)-PGJ(2), which contains a cross-conjugated alpha,beta-unsaturated ketone, was a potent inhibitor of isopeptidase activity, whereas PGA(1) and PGA(2) with simple alpha,beta-unsaturated pentenones were significantly less potent and PGB(1) with a sterically hindered alpha,beta-unsaturated ketone was inactive. To further investigate the proposed mechanism, punaglandins, which are highly functional cyclopentadienone and cyclopentenone prostaglandins chlorinated at the endocyclic alpha-carbon position, were isolated from the soft coral Telesto riisei. They were then assayed for inhibition of ubiquitin isopeptidase activity and antineoplastic effects. The punaglandins were shown to inhibit isopeptidase activity and exhibit antiproliferative effects more potently than A and J series prostaglandins. Also, the cross-conjugated dienone punaglandin was more potent than the simple enone punaglandin. The ubiquitin-proteasome pathway is a vital component of cellular metabolism and may be a suitable target for antineoplastic agents. These newly characterized proteasome inhibitors may represent a new chemical class of cancer therapeutics.

Stress protein activation by the cyclopentenone prostaglandin 15-deoxy-Δ12,14-prostaglandin J2 in human mesangial cells

The cyclopentenone prostaglandin 15-deoxy-delta12,14-prostaglandin J2 (15dPGJ2) affects mesangial proliferation, survival and production of proinflammatory proteins. During a survey of the mesangial cell proteome after treatment with 15dPGJ2, heat shock protein 70 (HSP70) was found to be the most conspicuously up-regulated protein, suggesting that stress proteins are key mediators or modulators of the effects of 15dPGJ2. Because cyclopentenone prostaglandins are highly reactive toward intracellular thiols, the role of intracellular thiol modification in the stress response to 15dPGJ2 was examined. Human mesangial cells were treated with 15dPGJ2 and intracellular thiol status was monitored by the fluorescent thiol probe monobromobimane (MBB). Specific intracellular thiol pools were manipulated by treating the cells with buthionine sulfoximine (BSO) to deplete glutathione (GSH), or phenylarsine oxide (PAO) to modify protein vicinal dithiols. Transcription pathways were examined with reporter gene or adenoviral constructs. 15dPGJ2 decreased mesangial GSH and other intracellular thiols, but depletion of GSH specifically with BSO did not induce HSP70. Thiol-replenishing reagents, which can restore modified protein thiols, attenuated 15dPGJ2-induced HSP70 levels. Furthermore, PAO mimicked the effects of 15dPGJ2 on HSP70. 15dPGJ2 also activated the stress-responsive transcription factor Nrf2, which requires thiol modification of its cytoplasmic inhibitor protein for transcriptional activity, and induced the Nrf2-dependent stress protein heme oxygenase-1 (HO-1). 15dPGJ2 activates a stress response in human mesangial cells by covalent modification of protein thiols through its unique cyclopentenone ring structure. This stress response may be beneficial in preventing renal cell injury or death during kidney inflammation or ischemia.

Cellular mechanisms of redox cell signalling: role of cysteine modification in controlling antioxidant defences in response to electrophilic lipid oxidation products.

The molecular mechanisms through which oxidized lipids and their electrophilic decomposition products mediate redox cell signalling is not well understood and may involve direct modification of signal-transduction proteins or the secondary production of reactive oxygen or nitrogen species in the cell. Critical in the adaptation of cells to oxidative stress, including exposure to subtoxic concentrations of oxidized lipids, is the transcriptional regulation of antioxidant enzymes, many of which are controlled by antioxidant-responsive elements (AREs), also known as electrophile-responsive elements. The central regulator of the ARE response is the transcription factor Nrf2 (NF-E2-related factor 2), which on stimulation dissociates from its cytoplasmic inhibitor Keap1, translocates to the nucleus and transactivates ARE-dependent genes. We hypothesized that electrophilic lipids are capable of activating ARE through thiol modification of Keap1 and we have tested this concept in an intact cell system using induction of glutathione synthesis by the cyclopentenone prostaglandin, 15-deoxy-Delta12,14-prostaglandin J2. On exposure to 15-deoxy-Delta12,14-prostaglandin J2, the dissociation of Nrf2 from Keap1 occurred and this was dependent on the modification of thiols in Keap1. This mechanism appears to encompass other electrophilic lipids, since 15-A(2t)-isoprostane and the lipid aldehyde 4-hydroxynonenal were also shown to modify Keap1 and activate ARE. We propose that activation of ARE through this mechanism will have a major impact on inflammatory situations such as atherosclerosis, in which both enzymic as well as non-enzymic formation of electrophilic lipid oxidation products are increased.

Glutathione S-transferases (GSTs) inhibit transcriptional activation by the peroxisomal proliferator-activated receptor gamma (PPAR gamma) ligand, 15-deoxy-delta 12,14prostaglandin J2 (15-d-PGJ2).

15-Deoxy-Delta(12,14)prostaglandin J(2) (15-d-PGJ(2)), a terminal metabolite of the J-series cyclopentenone prostaglandins, influences a variety of cellular processes including gene expression, differentiation, growth, and apoptosis. As a ligand of peroxisomal proliferator-activated receptor gamma (PPAR gamma), 15-d-PGJ(2) can transactivate PPAR gamma-responsive promoters. Previously, we showed that multidrug resistance proteins MRP1 and MRP3 attenuate cytotoxic and transactivating activities of 15-d-PGJ(2) in MCF7 breast cancer cells. Attenuation was glutathione-dependent and was associated with formation of the glutathione conjugate of 15-d-PGJ(2), 15-d-PGJ(2)-SG, and its active efflux by MRP. Here we have investigated whether the glutathione S-transferases (GST) can influence biological activities of 15-d-PGJ(2). MCF7 cells were stably transduced with human cytosolic GST isozymes M1a, A1, or P1a. These GSTs had no effect on 15-d-PGJ(2) cytotoxicity when expressed either alone or in combination with MRP1. However, expression of any of the three GSTs significantly inhibited 15-d-PGJ(2)-dependent transactivation of a PPAR gamma-responsive reporter gene. The degree of inhibition correlated with the level of GST expressed. Under physiologic conditions, the nonenzymatic rate of 15-d-PGJ(2) conjugation with glutathione was significant. Of the three GST isozymes, only GSTM1a-1a further stimulated the rate of 15-d-PGJ(2)-SG formation. Moreover, GSTM1a-1a rate enhancement was only a transient burst that was complete within 15 s. Hence, catalysis plays little, if any, role in GST inhibition of 15-d-PGJ(2)-dependent transactivation. In contrast, inhibition of transactivation was associated with strong GST/15-d-PGJ(2) interactions. Potent inhibition by 15-d-PGJ(2) and 15-d-PGJ(2)-SG of GST activity was observed with K(i) in the 0.15-2.0 microM range for the three GST isozymes, results suggesting avid associations between GST and 15-d-PGJ(2) or 15-d-PGJ(2)-SG. Electrospray ionization mass spectrometry (ESI/MS) studies revealed no stable adducts of GST and 15-d-PGJ(2) indicating that GST/15-d-PGJ(2) interactions are primarily noncovalent. These results are consistent with a mechanism of GST-mediated inhibition of transactivation in which GST binds 15-d-PGJ(2) and 15-d-PGJ(2)-SG thereby sequestering the ligands in the cytosol away from their nuclear target, PPAR gamma.

Inhibition of vesicular stomatitis virus replication by prostaglandin A1 in Aedes albopictus cells.

Cyclopentenone prostaglandins (PGs) exhibit antiviral activity against RNA and DNA viruses in mammalian cell lines, and this effect has been associated with the induction of a heat shock protein (hsp70). We investigated the effect of prostaglandin A1 (PGA1) on the replication of vesicular stomatitis virus (VSV) in Aedes albopictus (mosquito) cells. PGA1 was found to inhibit VSV replication dose dependently. Virus yield was reduced to 50% (3 microg PGA1/ml) and to 95% with 8 microg PGA1/ml. Even with the dramatic reduction of virus production observed in cells treated with PGA1, VSV-specific protein synthesis was unaltered. Treatment of cells with PGA1 (5 microg/ml) stimulated the synthesis of a polypeptide identified as a heat-shock protein (hsp) by immunoblot analysis. PGA1 induced hsp70 synthesis in uninfected cells. However, in VSV-infected cells the induction of hsp70 by PGA1 was reduced. This is the first report of antiviral effects of PGs affecting the replication of VSV in a mosquito cell line.