A-family anti-inflammatory cyclopentenone prostaglandins: A novel class of non-statin inhibitors of HMG-CoA reductase.

Disruption of the intracellular lipid balance leading to cholesterol accumulation is one of the features of cells that participate in the development of atherosclerotic lesions. Evidence form our laboratory indicates that anti-inflammatory cyclopentenone prostaglandins (cyPGs) of A- and J-family deviate lipid metabolism from the synthesis of cholesterol and cholesteryl esters to the synthesis of phospholipids in foam-cell macrophages. cyPGs possessing an α,ß-unsaturated cyclopentane ring are highly electrophilic substances able to promptly react with reactive cysteines of intracellular molecules through Michael addition. On the other hand, HMG-CoA reductase (HMGCR), the enzyme responsible for the rate-limiting step in cholesterol biosynthesis, presents critically reactive cysteines at the entry of catalytic domain, particularly Cys561, that could be target of cyPG inhibition. In the present study, we showed that cyPGs (but not other non-α,ß-unsaturated PGs) physically interact with HMGCR, in a dithiothreitol- and ß-mercaptoethanol-sensitive way, and block the activity of the catalytic subunit of the enzyme (IC50 for PGA2 = 0.17 µM). PGA2 inhibits HMGCR activity in cultured rat and human macrophages/macrophage-foam cells and leads to enhanced expression of HMGCR protein, as observed with statins. In cell culture models, PGA2 effectively inhibits the reductase at non-toxic doses (e.g., 1 µM) that block cell proliferation thus suggesting that part of the well-known antiproliferative effect of PGA2 may be due to its ability of blocking HMGCR activity, as cells cannot proliferate without a robust cholesterogenesis. Therefore, besides the powerfully anti-inflammatory and antiproliferative effects, the anticholesterogenic effects of PGA2 should be exploited in atherosclerosis therapeutics.

Development of Rifapentine-Loaded PLGA-Based Nanoparticles: In vitro Characterisation and in vivo Study in Mice.

BACKGROUND: Tuberculosis (TB) is a leading cause of death amongst infectious diseases. The poor response to antitubercular agents necessitates the long-term use of high drug doses, resulting in low patient compliance, which is the main reason for chemotherapy failure and contributes to the development of multidrug-resistant TB. Patient non-compliance has been a major obstacle in the successful management of TB. The aim of this work was to develop and characterise rifapentine (RPT)-loaded PLGA-based nanoparticles (NPs) for reducing dosing frequency. METHODS: RPT-loaded PLGA and PLGA-PEG NPs were prepared using premix membrane homogenisation combined with solvent evaporation method. The resulting NPs were characterised in terms of physicochemical characteristics, toxicity, cellular uptake and antitubercular activity. NPs were further evaluated for pharmacokinetic and biodistribution studies in mice. RESULTS: The resulting NPs showed suitable and safe physicochemical characteristics and could be taken up by macrophages. RPT-loaded NPs were more effective against Mycobacterium tuberculosis than free RPT. In vivo studies revealed that NPs could improve pharmacokinetic parameters, particularly for RPT/PLGA-PEG NPs. Moreover, both formulations had no toxicity to the organs of mice and could reduce hepatotoxicity. CONCLUSION: The application of PLGA-based NPs as sustained-release delivery vehicles for RPT could prolong drug release, modify pharmacokinetics, increase antitubercular activity and diminish toxicity, thereby allowing low dosage and frequency.

Twin-arginine signal peptide of Bacillus licheniformis GlmU efficiently mediated secretory expression of protein glutaminase

Background: Protein glutaminase specifically deamidates glutamine residue in protein and therefore significantly improves protein solubility and colloidal stability of protein solution. In order to improve its preparation efficiency, we exploited the possibility for its secretory expression mediated by twin-arginine translocation (Tat) pathway in Bacillus licheniformis. Results: The B. licheniformis genome-wide twin-arginine signal peptides were analyzed. Of which, eleven candidates were cloned for construction of expression vectors to mediate the expression of Chryseobacterium proteolyticum protein glutaminase (PGA). The signal peptide of GlmU was confirmed that it significantly mediated PGA secretion into media with the maximum activity of 0.16 U/ml in Bacillus subtilis WB600. A mutant GlmU-R, being replaced the third residue aspartic acid of GlmU twin-arginine signal peptide with arginine by site-directed mutagenesis, mediated the improved secretion of PGA with about 40% increased (0.23 U/ml). In B. licheniformis CBBD302, GlmU-R mediated PGA expression in active form with the maximum yield of 6.8 U/ml in a 25-l bioreactor. Conclusions: PGA can be produced and secreted efficiently in active form via Tat pathway of B. licheniformis, an alternative expression system for the industrial-scale production of PGA.

Astrocytes synthesize primary and cyclopentenone prostaglandins that are negative regulators of their proliferation.

Recently, the modulation of cellular inflammatory responses via endogenous regulators became a major focus of medically relevant investigations. Prostaglandins (PGs) are attractive regulatory molecules, but their synthesis and mechanisms of action in brain cells are still unclear. Astrocytes are involved in manifestation of neuropathology and their proliferation is an important part of astrogliosis, a cellular neuroinflammatory response. The aims of our study were to measure synthesis of PGs by astrocytes, and evaluate their influence on proliferation in combination with addition of inflammatory pathway inhibitors. With UPLC-MS/MS analysis we detected primary PGs (1410 ±â€¯36 pg/mg PGE2, 344 ±â€¯24 PGD2) and cyclopentenone PGs (cyPGs) (87 ±â€¯17 15d-PGJ2, 308 ±â€¯23 PGA2) in the extracellular medium after 24-h lipopolysaccharide (LPS) stimulation of astrocytes. PGs reduced astrocytic proliferation with the following order of potencies (measured as inhibition at 20 µM): most potent 15d-PGJ2 (90%) and PGA2 (80%), > PGD2 (40%) > 15d-PGA2 (20%) > PGE2 (5%), the least potent. However, PGF2α and 2-cyclopenten-1-one, and ciglitazone and rosiglitazone (synthetic agonists of PPARγ) had no effect. Combinations of cyPGs with SC-560 or NS-398 (specific anti-inflammatory inhibitors of cyclooxygenase-1 and -2, respectively) were not effective; while GW9662 (PPARγ antagonist) or MK-741 (inhibitor of multidrug resistance protein-1, MRP1, and CysLT1 receptors) amplified the inhibitory effect of PGA2 and 15d-PGJ2. Although concentrations of individual PGs and cyPGs are low, all of them, as well as primary PGs suppress proliferation. Thus, the effects are potentially additive, and activated PGs synthesis suppresses proliferation in astrocytes.

A-class prostaglandins: early findings and new perspectives for overcoming tumor chemoresistance.

The antiproliferative properties of cyclopentenone prostaglandins of the A-class have long been known. Considerable research has led to the elucidation of some of the mechanisms of action of these pleiotropic compounds. A-class prostaglandins or derived molecules (A-PG) may block the cell cycle, inhibit anti-apoptotic transcription factors, activate apoptotic cascades, induce a stress response and inhibit protein synthesis in a cell type-dependent manner. In addition, recent reports indicate that A-class PG may interact with various cellular detoxification systems and drug metabolizing enzymes used by cancer cells as mechanisms of chemoresistance. Some of these findings may open new perspectives for the development of strategies aimed at overcoming cancer resistance to widely used antitumor drugs. Here we outline the mechanisms of action for the antitumoral effects of PGA and related compounds, emphasizing those with impact on cellular defence systems which may contribute to cancer chemoresistance. The ability of A-PG to form covalent adducts with thiol groups in proteins and in glutathione is essential for their biological actions. Therefore, identification of the protein targets and elucidation of the interactions of A-PG with the glutathione biotransformation system will be critical for understanding the antitumoral effects of these compounds per se or through their ability to sensitize cancer cells towards other drugs.

A biotinylated analog of the anti-proliferative prostaglandin A1 allows assessment of PPAR-independent effects and identification of novel cellular targets for covalent modification.

The cyclopentenone prostaglandin (cyPG) PGA(1) displays potent anti-proliferative and anti-inflammatory effects. Therefore, PGA(1) derivatives are being studied as therapeutic agents. One major mechanism for cyPG action is the modification of protein cysteine residues, the nature of the modified proteins being highly dependent on the structure of the cyPG. Biotinylated cyPGs may aid in the proteomic identification of cyPG targets of therapeutic interest. However, for the identified targets to be relevant it is critical to assess whether biotinylated cyPGs retain the desired biological activity. Here we have explored the anti-inflammatory, anti-proliferative and cell stress-inducing effects of a biotinylated analog of PGA(1) (PGA(1)-biotinamide, PGA(1)-B), to establish its validity to identify cyPG-protein interactions of potential therapeutic interest. PGA(1) and PGA(1)-B displayed similar effects on cell viability, Hsp70 and heme oxygenase-1 induction and pro-inflammatory gene inhibition. Remarkably, PGA(1)-B did not activate PPAR. Therefore, this biotinylated analog can be useful to identify PPAR-independent effects of cyPGs. Protein modification and subcellular distribution of PGA(1)-B targets were cell-type-dependent. Through proteomic and biochemical approaches we have identified a novel set of PGA(1)-B targets including proteins involved in stress response, protein synthesis, cytoskeletal regulation and carbohydrate metabolism. Moreover, the modification of several of the targets identified could be reproduced in vitro. These results unveil novel interactions of PGA(1) that will contribute to delineate the mechanisms for the anti-proliferative and metabolic actions of this cyPG.

Effects of 15-deoxy-delta 12, 14-prostaglandin J2 on the expression of p53 in MCF-7 cells.

Cyclopentenone prostaglandins (cyPGs) exert diverse cellular functions, such as anti-inflammatory and cytoprotective effects, via multiple mechanisms. CyPGs, especially those of the A and J series, are characterized by the presence of a chemically reactive alpha,beta-unsaturated carbonyl group. 15-Deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), a representative cyPG of the J series, has been reported to directly inhibit the activity of redox-sensitive transcription factors, such as activator protein-1 and nuclear factor-kappaB. In the present study, we examined the effects of 15d-PGJ(2) on activation of p53 tumor suppressor in human breast cancer (MCF-7) cells. MCF-7 cells treated with 15d-PGJ(2) exhibited elevated p53 protein expression in time- and concentration-related manners, whereas prostaglandin A(2) (PGA(2)) and the nonprostaglandin derivative 2-cyclopenten-1-one exerted an effect to a lesser extent than did 15d-PGJ(2). In addition, MCF-7 cells exposed to 15d-PGJ(2) significantly accumulated p53 in both cytosolic and nuclear fractions. Despite the elevated levels of p53, its DNA-binding activity was reduced in 15d-PGJ(2)-treated MCF-7 cells. Moreover, isolated MCF-7 nuclear extracts directly treated with 15d-PGJ(2) exhibite diminished DNA-binding ability of p53, while the same concentration of PGA(2) or 2-cyclopenten-1-one was much less inhibitory. Thus, the electrophilic carbon center located in the alpha,beta-unsaturated carbonyl moiety of the cyclopentenone ring might be critical for the control of DNA-binding activity as well as cellular levels of p53 by 15d-PGJ(2).

Study of protein targets for covalent modification by the antitumoral and anti-inflammatory prostaglandin PGA1: focus on vimentin.

Prostaglandins with cyclopentenone structure (cyPG) display potent antiproliferative actions that have elicited their study as potential anticancer agents. Several natural and synthetic analogs of the cyPG prostaglandin A(1) (PGA(1)) have proven antitumoral efficacy in cancer cell lines and animal models. In addition, PGA(1) has been used as an inhibitor of transcription factor NF-kappaB-mediated processes, including inflammatory gene expression and viral replication. An important determinant for these effects is the ability of cyPG to form Michael adducts with free thiol groups. The chemical nature of this interaction implies that PGA(1) could covalently modify cysteine residues in a large number of cellular proteins potentially involved in its beneficial effects. However, only a few targets of PGA(1) have been identified. In previous work, we have observed that a biotinylated analog of PGA(1) that retains the cyclopentenone moiety (PGA(1)-B) binds to multiple targets in fibroblasts. Here, we have addressed the identification of these targets through a proteomic approach. Cell fractionation followed by avidin affinity chromatography yielded a fraction enriched in proteins modified by PGA(1)-B. Analysis of this fraction by SDS-PAGE and LC-MS/MS allowed the identification of the chaperone Hsp90, elongation and initiation factors for protein synthesis and cytoskeletal proteins including actin, tubulin and vimentin. Furthermore, we have characterized the modification of vimentin both in vitro and in intact cells. Our observations indicate that cysteine 328 is the main site for PGA(1) addition. These results may contribute to a better understanding of the mechanism of action of PGA(1) and the potential of cyPG-based therapeutic strategies.

Addition of electrophilic lipids to actin alters filament structure.

Pathophysiological processes associated with oxidative stress lead to the generation of reactive lipid species. Among them, lipids bearing unsaturated aldehyde or ketone moieties can form covalent adducts with cysteine residues and modulate protein function. Through proteomic techniques we have identified actin as a target for the addition of biotinylated analogs of the cyclopentenone prostaglandins 15-deoxy-Delta(12,14)-PGJ(2) (15d-PGJ(2)) and PGA(1) in NIH-3T3 fibroblasts. This modification could take place in vitro and mapped to the protein C-terminal end. Other electrophilic lipids, like the isoprostane 8-iso-PGA(1) and 4-hydroxy-2-nonenal, also bound to actin. The C-terminal region of actin is important for monomer-monomer interactions and polymerization. Electron microscopy showed that actin treated with 15d-PGJ(2) or 4-hydroxy-2-nonenal formed filaments which were less abundant and displayed shorter length and altered structure. Streptavidin-gold staining allowed mapping of biotinylated 15d-PGJ(2) at sites of filament disruption. These results shed light on the structural implications of actin modification by lipid electrophiles.

Induction of Fas clustering and apoptosis by coral prostanoid in human hormone-resistant prostate cancer cells.

Cyclopentenone prostaglandins (PGs) such as PGA1, PGA2 and delta12-PGJ2 have been shown to suppress tumor cell growth and to induce apoptosis in prostate cancer cells. Bromovulone III, which is isolated from the soft coral Clavularia viridis, is a cyclopentenone prostanoid. In this study, the anti-tumor activity as well as action mechanism of bromovulone III was identified in prostate cancer cells. Bromovulone III displayed anti-tumor activity of 30 to 100 times more effective than PGA1, PGA2 and delta12-PGJ2 in PC-3 cells. Several targets of caspases and Bcl-2 family of proteins were detected and the data demonstrated that bromovulone III induced the activation of caspase-8, -9 and -3, and Bid cleavage in which the caspase-8 activation occurred the first. Bromovulone III did not modify the protein levels of death receptors and ligands. Of note, the Fas clustering in PC-3 cells responsive to bromovulone III was observed by confocal immunofluorescence microscopy suggesting the involvement of Fas-mediated pathway. Bromovulone III also induced the cleavage of Mcl-1 in this study. The cleavage fragments (24, 19 and 17 kDa) may partly share the apoptotic insult. Although it has been suggested that Fas-mediated signaling may contribute to the caspase-8 activation induced by DNA-damaging agents; however, bromovulone III did not induce any DNA breakage, suggesting that bromovulone III-induced Fas/caspase-8-dependent signaling is not through the direct target on DNA damage. In summary, the data suggest that bromovulone III causes a rapid redistribution and clustering of Fas in PC-3 cells. Subsequently, the Fas event causes the activation and interaction of caspase-8/Bid/caspase-9 signaling cascades, and the activation of executor caspase-3.

Cyclopentenone isoprostanes are novel bioactive products of lipid oxidation which enhance neurodegeneration.

Oxidative stress and subsequent lipid peroxidation are involved in the pathogenesis of numerous neurodegenerative conditions, including stroke. Cyclopentenone isoprostanes (IsoPs) are novel electrophilic lipid peroxidation products formed under conditions of oxidative stress via the isoprostane pathway. These cyclopentenone IsoPs are isomeric to highly bioactive cyclopentenone prostaglandins, yet it has not been determined if these products are biologically active or are formed in the brain. Here we demonstrate that the major cyclopentenone IsoP isomer 15-A2t-IsoP potently induces apoptosis in neuronal cultures at submicromolar concentrations. We present a model in which 15-A2t-IsoP induced neuronal apoptosis involves initial depletion of glutathione and enhanced production of reactive oxygen species, followed by 12-lipoxygenase activation and phosphorylation of extracellular signal-regulated kinase 1/2 and the redox sensitive adaptor protein p66shc, which results in caspase-3 cleavage. 15-A2t-IsoP application also dramatically potentiates oxidative glutamate toxicity at concentrations as low as 100 nm, demonstrating the functional importance of these molecules in neurodegeneration. Finally, we employ novel mass spectrometric methods to show that cyclopentenone IsoPs are formed abundantly in brain tissue under conditions of oxidative stress. Together these findings suggest that cyclopentenone IsoPs may contribute to neuronal death caused by oxidative insults, and that their activity should perhaps be addressed when designing neuroprotective therapies.

Biochemistry of prostaglandins A.

This review considers modern concepts on the structural-functional properties and antiproliferative, antitumor, and antiviral effects of cyclopentenone prostaglandins A and mechanisms underlying their actions. Possible directions of pharmacological application of these compounds and their analogs are discussed.

Low expression of MRP1/GS-X pump ATPase in lymphocytes of Walker 256 tumour-bearing rats is associated with cyclopentenone prostaglandin accumulation and cancer immunodeficiency.

Immunosuppression is a life-threatening complication of late cancer stages. In this regard, overproduction in the host plasma of the anti-inflammatory cyclopentenone prostaglandins (CP-PGs), which are strongly antiproliferative at high concentrations, may impair immune function. In fact, lymphoid tissues of tumour-bearing rats accumulated large amounts of CP-PGs while the tumour tissue itself did not. Expression of the CP-PG-induced 72-kDa heat shock protein (hsp70) was elevated in lymphocytes from tumour-bearing animals related to controls. As the capacity for CP-PG uptake by lymphocytes is the same as tumour cells, we investigated whether the latter could overexpress the multidrug resistance-associated protein (MRP1/GS-X pump) which extrudes CP-PGs towards the extracellular space as glutathione S-conjugates. Walker 256 tumour cells extruded 15-fold more S-conjugates than lymphocytes from the same rats (p < 0.001). This did not appear to be related to deficiency in lymphocyte glutathione (GSH) metabolism, since the major GSH metabolic routes are consistent with CP-PG conjugation in lymphocytes. This was not the case, however, for the MRP1/GS-X pump activity in lymphocyte membranes (in pmol/min/mg protein: 3.1 +/- 1.7 from normal rats, 0.2 +/- 0.2 from tumour-bearing animals vs 64.3 +/- 7.0 in tumour cells) which was confirmed by Western blot analysis for MRP1 protein. Transfection of lymphocytes with MRP1 gene completely abolished CP-PG (0-40 microM) toxicity. Taken together, these findings suggest that CP-PG accumulation in lymphocytes may be, at least partially, responsible for cancer immunodeficiency. Clinical approaches for overexpressing MRP1/GS-X pump in lymphocytes could then play a role as a tool for the management of cancer therapeutics.

Solid-phase synthesis and biological activity of a combinatorial cross-conjugated dienone library.

The solid-phase synthesis of a combinatorial cross-conjugated dienone library based on the structure of clavulones and their biological activity are reported. Clavulones are a family of marine prostanoids, and are composed of a cross-conjugated dienone system bearing two alkyl side-chains. The cross-conjugated dienone system irreversibly reacted with two nucleophiles. Our strategy for the solid-phase synthesis of the cross-conjugated dienones involves the Sonogashira-coupling reaction of a solid-supported cyclopentenone 10 bearing an acetylene group, followed by aldol condensation with aldehydes. The diphenyl derivative 7 aA was prepared from the solid-supported cyclopentenone 10 in 56% total yield. Combinatorial synthesis of a small library using twelve halides and eight aldehydes resulted in the production of 74 desired compounds from 98 candidates, and were detected by their mass spectra. Antiproliferative effects of the crude compounds against HeLaS3 cells showed that eleven samples showed strong antitumor activity (IC50<0.05 microM). Further biological examination of four purified compounds by using five tumor cell lines (A549, HeLaS3, MCF7, TMF1, and P388) revealed strong cytotoxicity comparable to that of adriamycin.

Delta12-Prostaglandin J2 inhibits the ubiquitin hydrolase UCH-L1 and elicits ubiquitin-protein aggregation without proteasome inhibition.

To investigate molecular mechanisms linking inflammation with neurodegeneration, we treated neuronal cultures with prostaglandins (PGs), which are mediators of inflammation. PGA1, D2, J2, and Delta12-PGJ2, but not PGE2, reduced the viability and raised the levels of ubiquitinated proteins in the neuronal cells. PGJ2 and its metabolite, Delta12-PGJ2, were the most potent of the four neurotoxic PGs tested in inducing both effects. To address the mechanism by which these agents lead to the accumulation of ubiquitinated proteins, we tested their effects on neuronal ubiquitin hydrolases UCH-L1 and UCH-L3 as well as on proteasome activity. Notably, Delta12-PGJ2 inhibited the activities of UCH-L1 (K(i) approximately 3.5 microM) and UCH-L3 (K(i) approximately 8.1 microM) without affecting proteasome activity. Intracellular aggregates containing ubiquitinated proteins were detected in Delta12-PGJ2-treated cells, indicating that these aggregates can form independently of proteasome inhibition. In conclusion, impairment of ubiquitin hydrolase activity, such as triggered by Delta12-PGJ2, may be an important contributor to neurodegeneration associated with accumulation of ubiquitinated proteins and inflammation.

The cyclopentenone product of lipid peroxidation, 15-A2t-isoprostane, is efficiently metabolized by HepG2 cells via conjugation with glutathione.

Cyclopentenone isoprostanes (IsoPs), A(2)/J(2)-IsoPs, are one class of IsoPs formed via the free radical-initiated peroxidation of arachidonic acid. These compounds, which are structurally similar to cyclooxygenase-derived PGA(2) and PGJ(2), contain highly reactive alpha,beta-unsaturated carbonyl moieties. A(2)/J(2)-IsoPs are generated in vivo in humans esterified in glycerophospholipids. Unlike other classes of IsoPs, however, cyclopentenone IsoPs cannot be detected in the free form; we postulated that this might be due to their rapid adduction to various thiol-containing biomolecules via Michael addition. Recently, we reported that the A-ring IsoP, 15-A(2t)-IsoP, is efficiently conjugated with glutathione in vitro by certain human and rat glutathione transferases (GSTs), with the isozyme GSTA4-4 displaying the highest activity. Herein, we examined the metabolic disposition of 15-A(2t)-IsoP in HepG2 cells. We report that 15-A(2t)-IsoP is primarily metabolized by these cells via conjugation to glutathione. Within 6 h, approximately 60% of 15-A(2t)-IsoP added to HepG2 cells was present in the form of a water soluble conjugate(s). Structural characterization of the adduct(s) by liquid chromatography-tandem mass spectrometry revealed four major conjugates. These include the intact 15-A(2t)-IsoP-GSH conjugate, the GSH conjugate in which the carbonyl at C-9 of 15-A(2t)-IsoP is reduced, and the corresponding cysteine conjugates. These studies thus show that the primary pathway of metabolic disposition of endogenously derived cyclopentenone IsoPs occurs via conjugation with thiols.

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.

Localization of clavulones, prostanoids with antitumor activity, within the Okinawan soft coral Clavularia viridis (Alcyonacea, Clavulariidae): preparation of a high-purity Symbiodinium fraction using a protease and a detergent.

To investigate the localization of clavulones (CV), prostanoids with antitumor activity, in the Okinawan soft coral Clavularia viridis, we developed a method for the isolation of Symbiodinium cells from the coral, i.e., treatment of a coral homogenate with a protease, pronase E, and a detergent, Nonidet P-40. The conditions for the treatment were optimized by monitoring the morphology microscopically and the amount of chlorophyll in the Symbiodinium fraction (SymF) optically. To evaluate the purity of SymF and a Symbiodinium-free coral fraction (CorF), we analyzed them for proteins and lipids using cultivated Symbiodinium as a reference. TLC of lipids revealed that SymF contained a greater amount of glycolipids, whereas CorF comprised mostly phospholipids. SDS-PAGE of proteins in SymF and CorF revealed their distinct profiles. Thus, we could obtain each fraction with high purity; we reached the conclusion that CV and arachidonic acid, their possible precursor, are localized exclusively in the insoluble fraction of host coral cells.

The cyclopentenone product of lipid peroxidation, 15-A(2t)-isoprostane (8-isoprostaglandin A(2)), is efficiently conjugated with glutathione by human and rat glutathione transferase A4-4.

Glutathione transferases (GSTs) are a large family of enzymes that can be divided into different classes based on structure. There has been considerable interest in the ability of GSTs to conjugate and inactivate endogenously derived reactive lipid peroxidation products that contain alpha,beta-unsaturated carbonyl moieties such as 4-hydroxyalkenals. One enzyme with prominent activity toward these substrates is human GST A4-4. Recently, we described a novel series of compounds termed A(2)/J(2)-isoprostanes (IsoPs) that are formed endogenously in humans from the free radical-initiated peroxidation of arachidonic acid. These compounds contain alpha,beta-unsaturated carbonyl groups and have structures similar to cyclooxygenase-derived PGA(2) and PGJ(2). Because of their chemical reactivity, these compounds may mediate tissue injury associated with oxidant stress. Herein, we report that the A-ring IsoP 15-A(2t)-IsoP (8-iso-PGA(2)) is efficiently conjugated to glutathione (GSH) by human GST A4-4 with a k(cat)/K(m) value of >200 s(-)(1) mM(-)(1). The k(cat)/K(m) value for conjugation of 15-A(2t)-IsoP by the homologous rat GST A4-4 is >2000 s(-)(1) mM(-)(1). Similar high enzyme activities were observed when PGA(2) was used as a substrate. In contrast, the human GSTs A1-1, M1-1, M2-2, P1-1, and T1-1 and rat GST T2-2 did not significantly metabolize 15-A(2t)-IsoP. These studies have therefore defined a potentially important route by which cyclopentenone IsoPs are metabolized that may serve as a mechanism for the inactivation of these highly reactive compounds.

Enantioselective synthesis of 12-amino alkylidenecyclopentenone prostaglandins.

An enantioselective synthesis of new 12-amino alkylidenecyclopentenone prostaglandins is reported. The key step of the synthesis involved a [3.3] sigmatropic rearrangement of an asymmetric allylic cyanate to elaborate an asymmetric 5-amino-1,6-diene which was further transformed into cyclopentenone by successive ring-closing metathesis reaction catalyzed by the Grubbs reagent and one-pot oxidation. A palladium-catalyzed cross-coupling reaction on a 5-iodo-1,5-diene allowed the synthesis of prostanoids with variable Rw side chains. These new compounds exhibit high cytotoxic activities.