Prostaglandin D(2) and J(2) induce apoptosis in human leukemia cells via activation of the caspase 3 cascade and production of reactive oxygen species

The presence of prostaglandins (PGs) has been demonstrated in the processes of carcinogenesis and inflammation. In the present study, we found that 12-o-tetradecanoylphorbol 13-acetate (TPA) induced cyclooxygenase 2 (COX-2), but not COX-1, protein expression in HL-60 cells, and the addition of arachidonic acid (AA) in the presence or absence of TPA significantly reduced the viability of HL-60 cells, an effect that was blocked by adding the COX inhibitors, NS398 and aspirin. The AA metabolites, PGD(2) and PGJ(2), but not PGE(2) or PGF(2alpha), reduced the viability of the human HL60 and Jurkat leukemia cells according to the MTT assay and LDH release assay. Apoptotic characteristics including DNA fragmentation, apoptotic bodies, and hypodiploid cells were observed in PGD(2)- and PGJ(2)-treated leukemia cells. A dose- and time-dependent induction of caspase 3 protein procession, and PARP and D4-GDI protein cleavage with activation of caspase 3, but not caspase 1, enzyme activity was detected in HL-60 cells treated with PGD(2) or PGJ(2). Additionally, DNA ladders induced by PGD(2) and PGJ(2) were significantly inhibited by the caspase 3 peptidyl inhibitor, Ac-DEVD-FMK, but not by the caspase 1 peptidyl inhibitor, Ac-YVAD-FMK, in accordance with the blocking of caspase 3, PARP, and D4-GDI protein procession. An increase in intracellular peroxide levels by PGD(2) and PGJ(2) was identified by the DCHF-DA assay, and anti-oxidant N-acetyl cysteine (NAC), mannitol (MAN), and tiron significantly inhibited cell death induced by PGD(2) and PGJ(2) by reducing reactive oxygen species (ROS) production. The PGJ(2) metabolites, 15-deoxy-Delta(12,14)-PGJ(2) and Delta(12)-PGJ(2), exhibited effective apoptosis-inducing activity in HL-60 cells through ROS production via activation of the caspase 3 cascade. The proliferator-activated receptor-gamma (PPAR-gamma) agonists, rosiglitazone (RO), troglitazone (TR), and ciglitazone (CI), induced apoptosis in cells which was blocked by the addition of the PPAR-gamma antagonists, GW9662 and BADGE, via blocking of caspase 3 and PARP cleavage. However, neither GW9662 nor BADGE showed any protective effect on PGD(2)- and PGJ(2)-induced apoptosis. A differential apoptotic effect of PGs through ROS production, followed by activation of the caspase 3 cascade, was demonstrated.     

Stimulation of NGF expression and secretion in 3T3-L1 adipocytes by prostaglandins PGD2, PGJ2, and Delta12-PGJ2

Nerve growth factor (NGF) has recently been shown to be secreted from white adipocytes, its production being strongly stimulated by the proinflammatory cytokine tumor necrosis factor-alpha. In this study, we have examined whether a series of prostaglandins and other inflammation-related factors also stimulate NGF expression and secretion by adipocytes, using 3T3-L1 cells. Although interleukin (IL)-1beta, IL-10, and IL-18 each induced a small decrease in NGF mRNA level in 3T3-L1 adipocytes, there was no significant effect of these cytokines on NGF secretion. A small reduction in NGF expression and/or secretion was also observed with adiponectin and prostaglandins PGE(2), PGF(2alpha), and PGI(2). In marked contrast, prostaglandin PGD(2) induced a major, dose-dependent increase (up to 20- to 40-fold) in NGF expression and secretion. The PGD(2) metabolites, PGJ(2) and Delta(12)-PGJ(2), also induced major increases (up to 30-fold) in NGF production. A further metabolite of PGJ(2), 15-deoxy-Delta(12,14)-PGJ(2), a peroxisome proliferator-activated receptor-gamma agonist, led paradoxically to a small increase in NGF mRNA level but a fall in NGF secretion. Both PGD(2) and PGJ(2) induced significant increases in NGF gene expression by 4 h after their addition. It is concluded that PGD(2) and the J series prostaglandins, PGJ(2) and Delta(12)-PGJ(2), can play a significant role in the regulation of NGF production by white adipocytes. These results provide support for the view that NGF is an important inflammatory response protein, as well as a target-derived neurotrophin, in white adipose tissue.     

Novel binding sites of 15-deoxy-Delta12,14-prostaglandin J2 in plasma membranes from primary rat cortical neurons

15-Deoxy-Delta12,14-prostaglandin J2 (15d-Delta12,14-PGJ2) is an endogenous ligand for a nuclear peroxysome proliferator activated receptor-gamma (PPAR). We found novel binding sites of 15d-Delta12,14-PGJ2 in the neuronal plasma membranes of the cerebral cortex. The binding sites of [3H]15d-Delta12,14-PGJ2 were displaced by 15d-Delta12,14-PGJ2 with a half-maximal concentration of 1.6 microM. PGD2 and its metabolites also inhibited the binding of [3H]15d-Delta12,14-PGJ2. Affinities for the novel binding sites were 15d-Delta12,14-PGJ2 > Delta12-PGJ2 > PGJ2 > PGD2. Other eicosanoids and PPAR agonists did not alter the binding of [3H]15d-Delta12,14-PGJ2. In primary cultures of rat cortical neurons, we examined the pathophysiologic roles of the novel binding sites. 15d-Delta12,14-PGJ2 triggered neuronal cell death in a concentration-dependent manner, with a half-maximal concentration of 1.1 microM. The neurotoxic potency of PGD2 and its metabolites was also 15d-Delta12,14-PGJ2 > Delta12-PGJ2 > PGJ2 > PGD2. The morphologic and ultrastructural characteristics of 15d-Delta12,14-PGJ2-induced neuronal cell death were apoptotic, as evidenced by condensed chromatin and fragmented DNA. On the other hand, we detected little neurotoxicity of other eicosanoids and PPAR agonists. In conclusion, we demonstrated that novel binding sites of 15d-Delta12,14-PGJ2 exist in the plasma membrane. The present study suggests that the novel binding sites might be involved in 15d-Delta12,14-PGJ2-induced neuronal apoptosis.     

Cyclopentenone prostaglandins as potential inducers of intracellular oxidative stress

In the present study, we find that cyclopentenone prostaglandins (PGs) of the J(2) series, naturally occurring derivatives of PGD(2), are potential inducers of intracellular oxidative stress that mediates cell degeneration. Based on an extensive screening of diverse chemical agents on induction of intracellular production of reactive oxygen species (ROS), we found that the cyclopentenone PGs, such as PGA(2), PGJ(2), Delta(12)-PGJ(2), and 15-deoxy-Delta(12,14)-PGJ(2), showed the most potent pro-oxidant effect on SH-SY5Y human neuroblastoma cells. As the intracellular events that mediate the PG cytotoxicity, we observed (i) the cellular redox alteration represented by depletion of antioxidant defenses, such as glutathione and glutathione peroxidase; (ii) a transient decrease in the mitochondrial membrane potential (Deltapsi); (iii) the production of protein-bound lipid peroxidation products, such as acrolein and 4-hydroxy-2-nonenal; and (iv) the accumulation of ubiquitinated proteins. These events correlated well with the reduction in cell viability. In addition, the thiol compound, N-acetylcysteine, could significantly inhibit the PG-induced ROS production, thereby preventing cytotoxicity, suggesting that the redox alteration is closely related to the pro-oxidant effect of cyclopentenone PGs. More strikingly, the lipid peroxidation end products, acrolein and 4-hydroxy-2-nonenal, detected in the PG-treated cells potently induced the ROS production, which was accompanied by the accumulation of ubiquitinated proteins and cell death, suggesting that the membrane lipid peroxidation products may represent one of the causative factors that potentiate the cytotoxic effect of cyclopentenone PGs by accelerating intracellular oxidative stress. These data suggest that the intracellular oxidative stress, represented by ROS production/lipid peroxidation and redox alteration, may underlie the well documented biological effects, such as antiproliferative and antitumor activities, of cyclopentenone PGs.     

Prostaglandin D2 and its metabolites induce caspase-dependent granulocyte apoptosis that is mediated via inhibition of I kappa B alpha degradation using a peroxisome proliferator-activated receptor-gamma-independent mechanism

Many inflammatory mediators retard granulocyte apoptosis. Most natural PGs studied herein (e.g., PGE(2), PGA(2), PGA(1), PGF(2 alpha)) either delayed apoptosis or had no effect, whereas PGD(2) and its metabolite PGJ(2) selectively induced eosinophil, but not neutrophil apoptosis. This novel proapoptotic effect does not appear to be mediated via classical PG receptor ligation or by elevation of intracellular cAMP or Ca(2+). Intriguingly, the sequential metabolites Delta(12)PGJ(2) and 15-deoxy-Delta(12,) Delta(14)-PGJ(2) (15dPGJ(2)) induced caspase-dependent apoptosis in both granulocytes, an effect that did not involve de novo protein synthesis. Despite the fact that Delta(12)PGJ(2) and 15dPGJ(2) are peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activators, apoptosis was not mimicked by synthetic PPAR-gamma and PPAR-alpha ligands or blocked by an irreversible PPAR-gamma antagonist. Furthermore, Delta(12)PGJ(2) and 15dPGJ(2) inhibited LPS-induced I kappa B alpha degradation and subsequent inhibition of neutrophil apoptosis, suggesting that apoptosis is mediated via PPAR-gamma-independent inhibition of NF-kappa B activation. In addition, we show that TNF-alpha-mediated loss of cytoplasmic I kappa B alpha in eosinophils is inhibited by 15dPGJ(2) in a concentration-dependent manner. The selective induction of eosinophil apoptosis by PGD(2) and PGJ(2) may help define novel therapeutic pathways in diseases in which it would be desirable to specifically remove eosinophils but retain neutrophils for antibacterial host defense. The powerful proapoptotic effects of Delta(12)PGJ(2) and 15dPGJ(2) in both granulocyte types suggest that these natural products control the longevity of key inflammatory cells and may be relevant to understanding the control and resolution of inflammation.     

Group IB secretory phospholipase A2 induces neuronal cell death via apoptosis

Group IB secretory phospholipase A2 (sPLA2-IB) mediates cell proliferation, cell migration, hormone release and eicosanoid production via its receptor in peripheral tissues. In the CNS, high-affinity binding sites of sPLA2-IB have been documented. However, it remains obscure whether sPLA2-IB causes biologic or pathologic response in the CNS. To this end, we examined effects of sPLA2-IB on neuronal survival in primary cultures of rat cortical neurons. sPLA2-IB induced neuronal cell death in a concentration-dependent manner. This death was a delayed response requiring a latent time for 6 h; sPLA2-IB-induced neuronal cell death was accompanied with apoptotic blebbing, condensed chromatin, and fragmented DNA, exhibiting apoptotic features. Before cell death, sPLA2-IB liberated arachidonic acid (AA) and generated prostaglandin D2 (PGD2) from neurons. PGD2 and its metabolite, Delta12-PGJ2, exhibited neurotoxicity. Inhibitors of sPLA2 and cyclooxygenase-2 (COX-2) significantly suppressed not only AA release, but also PGD2 generation. These inhibitors significantly prevented neurons from sPLA2-IB-induced neuronal cell death. In conclusion, we demonstrate a novel biological response, apoptosis, of sPLA2-IB in the CNS. Furthermore, the present study suggests that PGD2 metabolites, especially Delta12-PGJ2, might mediate sPLA2-IB-induced apoptosis.     

Old yellow enzymes, highly homologous FMN oxidoreductases with modulating roles in oxidative stress and programmed cell death in yeast

In a genetic screen to identify modifiers of Bax-dependent lethality in yeast, the C terminus of OYE2 was isolated based on its capacity to restore sensitivity to a Bax-resistant yeast mutant strain. Overexpression of full-length OYE2 suppresses Bax lethality in yeast, lowers endogenous reactive oxygen species (ROS), increases resistance to H(2)O(2)-induced programmed cell death (PCD), and significantly lowers ROS levels generated by organic prooxidants. Reciprocally, Delta oye2 yeast strains are sensitive to prooxidant-induced PCD. Overexpression and knock-out analysis indicate these OYE2 antioxidant activities are opposed by OYE3, a highly homologous heterodimerizing protein, which functions as a prooxidant promoting H(2)O(2)-induced PCD in wild type yeast. To exert its effect OYE3 requires the presence of OYE2. Deletion of the 12 C-terminal amino acids and catalytic inactivation of OYE2 by a Y197F mutation enhance significantly survival upon H(2)O(2)-induced PCD in wild type cells, but accelerate PCD in Delta oye3 cells, implicating the oye2p-oye3p heterodimer for promoting cell death upon oxidative stress. Unexpectedly, a strain with a double knock-out of these genes (Delta oye2 oye3) is highly resistant to H(2)O(2)-induced PCD, exhibits increased respiratory capacity, and undergoes less cell death during the adaptive response in chronological aging. Simultaneous deletion of OYE2 and other antioxidant genes hyperinduces endogenous levels of ROS, promoting H(2)O(2)-induced cell death: in Delta oye2 glr1 yeast high levels of oxidized glutathione elicited gross morphological aberrations involving the actin cytoskeleton and defects in organelle partitioning. Altering the ratio of reduced to oxidized glutathione by exogenous addition of GSH fully reversed these alterations. Based on this work, OYE proteins are firmly placed in the signaling network connecting ROS generation, PCD modulation, and cytoskeletal dynamics in yeast.     

15-Deoxy-Delta(12,14)-prostaglandin J(2), a ligand for peroxisome proliferator-activated receptor-gamma, induces apoptosis in JEG3 choriocarcinoma cells.

Apoptosis has been described in placental (trophoblast) tissues during both normal and abnormal pregnancies. We have studied the effects of the cyclopentenone prostaglandins (PGs) on trophoblast cell death using JEG3 choriocarcinoma cells. PGJ(2), Delta(12)PGJ(2), and 15-deoxy-Delta(12,14)-PGJ(2) (15dPGJ(2)) (10 microM) significantly reduced mitochondrial activity (MTT assay) over 16 h by 17.4 +/- 4.7%, 28 +/- 9.3%, and 62.5 +/- 2.8%, respectively (mean +/- sem), while PGA(2) and PGD(2) had no effect. The synthetic PPAR-gamma ligand ciglitizone (12.5 microM) had a potency similar to 15dPGJ(2) (69 +/- 3% reduction). Morphological examination of cultures treated with PGJ(2) and its derivatives revealed the presence of numerous cells with dense, pyknotic nuclei, a hallmark of apoptosis. FACS analysis revealed an abundance (approximately 40%) of apoptotic cells after 16-h treatment with 15dPGJ(2) (10 microM). The caspase inhibitor ZVAD-fmk (5 microM) significantly diminished the apoptotic effects of Delta(12)PGJ(2) and 15dPGJ(2). JEG3 cells expressed PPAR-gamma mRNA by Northern analysis. These novel findings imply a role for PPAR-gamma ligands in various processes associated with pregnancy and parturition.     

Prostaglandin J2 and its metabolites promote neurite outgrowth induced by nerve growth factor in PC12 cells

Although A- and J-type prostaglandins (PG's) arrest the cell cycle at the G1 phase in vitro and suppress tumor growth in vivo, their effects on neuronal cells have not so far been clarified. Here, we found promotion of neurite outgrowth as a novel biological function of PGJ's. In PC12h cells, PGJ's (PGJ2, Delta12-PGJ2 and 15-deoxy-Delta12,14-PGJ2) promoted neurite outgrowth in the presence of nerve growth factor (NGF), whereas they themselves did not show such a promotion. The potency of promoting neurite outgrowth was PGJ2 < Delta12-PGJ2 < 15-deoxy-Delta12,14-PGJ2. However, troglitazone, an activator of peroxisome proliferator-activated receptorgamma (PPARgamma), and other PG's including PGA1, PGA2 and PGD2 did not promote neurite outgrowth. These results suggest that PGJ's promote neurite outgrowth independently of PPARgamma activation.     

Preconditioning of human smooth muscle cells via cyclopentenone prostaglandins protects against toxic effects of oxidized low-density lipoprotein

Human vascular smooth muscle cells (SMC) exhibit upregulation of inducible heat shock protein 70 (Hsp70), upon exposure to oxidized low-density lipoproteins (LDL(ox)). The presence of Hsp70 is thought to protect the cell against the toxic effects of the modified lipoprotein. In order to test this hypothesis, Hsp70 in SMC was upregulated by exposure to Delta(12) prostaglandin J(2) (Delta(12)PGJ(2)) before cells were exposed to LDL(ox). Hsp70 levels were measured after exposure to Delta(12)PGJ(2) and before exposure to LDL(ox). Cell protection was monitored after LDL(ox) exposure by determination of cell toxicity measured by cell lactate dehydrogenase (LDH) release into the medium. Cells treated with Delta(12)PGJ(2) exhibited a 23-fold increase in Hsp70 levels and 56% lower LDH activity release after exposure to LDL(ox) when compared to cells that were not pretreated with Delta(12)PGJ(2). In addition, cells pretreated with prostaglandins that did not induce Hsp70 did not exhibit increased tolerance against the toxic effects of LDL(ox). The results support a protective role for Hsp70 against the toxic effects of LDL(ox) and hint at the potential for the use of small molecules for the prevention of deleterious effects of LDL(ox) through heat shock protein upregulation.     

Liquid chromatographic-mass spectrometric determination of cyclooxygenase metabolites of arachidonic acid in cultured cells

A liquid chromatographic-electrospray ionization-mass spectrometric (LC-ESI-MS) technique was developed to simultaneously determine the cyclooxygenase metabolites of arachidonic acid (6-keto-PGF(1alpha), PGD(2), PGE(2), PGF(2alpha), and PGJ(2)) produced by cultured cells. Samples were separated on a C(18) column with water-acetonitrile mobile phase, ionized by electrospray, and detected in the positive mode. Selected ion monitoring (SIM) of m/z 353, 335, 335, 319, and 317 were used for quantifying 6-keto-PGF(1alpha), PGD(2), PGE(2), PGF(2alpha), and PGJ(2), respectively. Prostaglandins were detected at concentrations as low as 1 pg (S/N=3) on the column. The method was used to determine the production of PGs from bovine coronary artery endothelial cells (ECs) and human prostate cancer cells (PC-3) with different degree of invasiveness. Bradykinin (10(-6) M) stimulated a marked increase in the production of 6-keto-PGF(1alpha), PGE(2), and PGF(2alpha) and a small increase of PGD(2) by ECs. 6-Keto-PGF(1alpha) was the major metabolite in these cells. The production of PGE(2) was threefold higher and PGD(2) was twofold higher in PC-3-S (invasive) cells than in PC-3-U (non-invasive) cells.     

Cell death of barley aleurone protoplasts is mediated by reactive oxygen species

The barley aleurone layer is a terminally differentiated secretory tissue whose activity is hormonally controlled. The plant hormone gibberellic acid (GA) stimulates the secretion of hydrolytic enzymes and triggers the onset of programmed cell death (PCD). Abscisic acid (ABA) antagonizes the effects of GA and inhibits enzyme secretion and PCD. Reactive oxygen species (ROS) are key players in many types of PCD, and data presented here implicate ROS in hormonally regulated death of barley aleurone cells. Incubation of aleurone layers or protoplasts in H(2)O(2)-containing media results in death of GA-treated but not ABA-treated aleurone cells. Cells that are programmed to die are therefore less able to withstand ROS than cells that are programmed to remain alive. Illumination of barley aleurone protoplasts with blue or UV-A light results in a rapid increase in intracellular H(2)O(2) production. GA-treated protoplasts die rapidly in response to this increase in intracellular H(2)O(2) production, but ABA-treated protoplasts do not die. The rate of light-induced death could be slowed by antioxidants, and incubating protoplasts in the dark with the antioxidant butylated hydroxy toluene reduces the rate of hormonally induced death. Taken together, these data demonstrate that GA-treated aleurone protoplasts are less able than ABA-treated protoplasts to tolerate internally generated or exogenously applied H(2)O(2), and strongly suggest that ROS are components of the hormonally regulated cell death pathway in barley aleurone cells.     

15-deoxy-delta12,14-prostaglandin J2-induced apoptosis in amnion-like WISH cells.

Apoptosis at the site of rupture has been proposed to play a role in premature rupture of the fetal membranes, a condition associated with increased risk of neonatal sepsis and preterm birth. We investigated the ability of peroxisome proliferator-activated receptor (PPAR)-gamma ligands 15-deoxy-delta12,14PGJ2 (15d-PGJ2), delta12PGJ2, ciglitizone and rosiglitazone to induce apoptosis in the amnion-like WISH cell line. 15d-PGJ2 (10 microM) induced morphological characteristics of apoptosis within 2 h, with biochemical indices (caspase activation and substrate cleavage) following shortly after; maximum cell death (approximately 60%) was observed by 16 h, with an EC50) of approximately 7 microM 15d-PGJ2. Delta12-PGJ2 also induced apoptosis but was less potent and acted at a much slower rate. While ciglitizone also induced apoptosis, rosiglitazone had no effect on cell viability. The mechanism of induction of apoptosis by 15d-PGJ2 and delta12PGJ2, which may be independent of PPAR-gamma activation, requires further elucidation.     

Regulation of mitochondrial NAD pool via NAD+ transporter 2 is essential for matrix NADH homeostasis and ROS production in Arabidopsis

Reactive oxygen species(ROS) play a crucial role in numerous biological processes in plants, including development, responses to environmental stimuli, and programmed cell death(PCD). Deficiency in MOSAIC DEATH 1(MOD1), a plastid-localized enoyl-ACP reductase essential for de novo fatty acid biosynthesis in Arabidopsis thaliana, leads to the increased malate export from chloroplasts to mitochondria, and the subsequent accumulation of mitochondria-generated ROS and PCD. In this study, we report the identification and characterization of a mod1 suppressor, som592. SOM592 encodes mitochondrion-localized NAD~+ transporter 2(NDT2). We show that the mitochondrial NAD pool is elevated in the mod1 mutant. The som592 mutation fully suppressed mitochondrial NADH hyper-accumulation, ROS production, and PCD in the mod1 mutant, indicating a causal relationship between mitochondrial NAD accumulation and ROS/PCD phenotypes. We also show that in wild-type plants, the mitochondrial NAD+uptake is involved in the regulation of ROS production in response to continuous photoperiod. Elevation of the alternative respiration pathway can suppress ROS accumulation and PCD in mod1, but leads to growth restriction. These findings uncover a regulatory mechanism for mitochondrial ROS production via NADH homeostasis in Arabidopsis thaliana that is likely important for growth regulation in response to altered photoperiod.     

Implication of reactive oxygen species and mitochondrial dysfunction in the early stages of plant programmed cell death induced by ultraviolet-C overexposure

Recent studies have suggested that ultraviolet-C (UV-C) overexposure induces programmed cell death (PCD) in Arabidopsis thaliana (L.) Heynh, and this process includes participation of caspase-like proteases, DNA laddering as well as fragmentation of the nucleus. To investigate possible early signal events, we used microscopic observations to monitor in vivo the behaviour of mitochondria, as well as the production and localization of reactive oxygen species (ROS) during protoplast PCD induced by UV-C. A quick burst of ROS was detected when the protoplasts were kept in continuous light after UV-C exposure, which was restricted in chloroplasts and the adjacent mitochondria. Pre-incubation with ascorbic acid (AsA, antioxidant molecule) or 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea (DCMU, an inhibitor of photosynthetic electron transport) decreased the ROS production and partially protected protoplasts from PCD. A mitochondrial transmembrane potential (MTP) loss occurred prior to cell death; thereafter, the mitochondria irregularly clumped around chloroplasts or aggregated in other places within the cytoplasm, and the movement of mitochondria was concomitantly blocked. Pre-treatment with an inhibitor of mitochondrial permeability transition pores (MPTP), cyclosporine (CsA), effectively retarded the decrease of MTP and reduced the percentage of protoplasts undergoing PCD after UV-C overexposure. Our results suggest that the MTP loss and the changes in distribution and mobility of mitochondria, as well as the production of ROS play important roles during UV-induced plant PCD, which is in good accordance with what has been reported in many types of apoptotic cell death, both in animals and plants. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Regulation of heme oxygenase expression by cyclopentenone prostaglandins

Prostaglandins (PGs) originate from the degradation of membranar arachidonic acid by cyclooxygenases (COX-1 and COX-2). The prostaglandin actions in the nervous system are multiple and have been suggested to play a significant role in neurodegenerative disorders. Some PGs have been reported to be toxic and, interestingly, the cyclopentenone PGs have been reported to be cytoprotective at low concentration and could play a significant role in neuronal plasticity. They have been shown to be protective against oxidative stress injury; however, the cellular mechanisms of protection afforded by these PGs are still unclear. It is postulated that the cascade leading to neuronal cell death in acute and chronic neurodegenerative conditions, such as cerebral ischemia and Alzheimer's disease, would be mediated by free radical damage. We tested the hypothesis that the neuroprotective action of cyclopentanone could be caused partially by an induction of heme oxygenase 1 (HO-1). We and others have previously reported that modulation of HO total activity may well have direct physiological implications in stroke and in Alzheimer's disease. HO acts as an antioxidant enzyme by degrading heme into iron, carbon monoxide, and biliverdin that is rapidly converted into bilirubin. Using mouse primary neuronal cultures, we demonstrated that PGs of the J series induce HO-1 in a dose-dependent manner (0, 0.5, 5, 10, 20, and 50 micro g/ml) and that PGJ(2) and dPGJ(2) were more potent than PGA(2), dPGA(2), PGD(2), and PGE(2). No significant effects were observed for HO-2 and actin expression. In regard to HO-3 expression found in rat, with its protein deducted sequence highly homologous to HO-2, no detection was observed in HO-2(-/-) mice, suggesting that HO-3 protein would not be present in mouse brain. We are proposing that several of the protective effects of PGJ(2) could be mediated through beneficial actions of heme degradation and its metabolites. The design of new mimetics based on the cyclopentenone structure could be very useful as neuroprotective agents and be tested in animal models of stroke and Alzheimer's disease.