Suppression of W256 carcinosarcoma cell apoptosis by arachidonic acid and other polyunsaturated fatty acids

Comparison of the Effects of Monounsaturated Fatty Acids and Polyunsaturated Fatty Acids on Liver Lipid Disorders in Obese Mice

Obesity is a recognized epidemic worldwide, and the accumulation of excess free saturated fatty acids (SFAs) in cells induces cellular lipotoxic damage and increases the risk of a wide spectrum of metabolic diseases including type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD). Monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) have been reported to combat SFA-induced cellular damage. However, the comparative studies of the two types of unsaturated fatty acids (UFAs) are still limited. We investigated the effects of different MUFAs and PUFAs in the human hepatocyte line L-02 cells in vitro, and in high-fat-diet (HFD)-induced obese C57BL/6 mice in vivo. The results of the in vitro study showed that SFAs induced significant cellular lipotoxic damage, but the combination of MUFAs/PUFAs with SFAs significantly improved the impaired cell viability. Particularly, oleic acid (OA) was superior to eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and arachidonic acid (AA) in terms of its anti-apoptotic effect and inhibition of endoplasmic reticulum (ER) stress. In vivo, both olive-oil-enriched (HFD + OO) and fish-oil-enriched high-fat diets (HFD + FO) reduced hepatic steatosis and improved insulin sensitivity in obese mice. However, FO induced an abnormal increase in serum aspartate aminotransferase (AST) and an increase in the oxidative stress indicator Malondialdehyde (MDA). Liver-targeted lipidomic analysis showed that liver lipid metabolites under the two types of UFA dietary interventions differed from the HFD group, modulating the abundance of some lipid metabolites such as triglycerides (TGs) and glycerophospholipids. Furthermore, the FO diet significantly increased the abundance of the associated FA 20:5 long-chain lipid metabolites, whereas the OO diet regulated the unsaturation of all fatty acids in general and increased the abundance of FA 18:1 in the overall lipid metabolites, especially TGs, which may primarily contribute to the FO, and OO drove protection in NAFLD.

Arachidonic acid activates extrinsic apoptotic pathway to enhance tumoricidal action of bleomycin against IMR-32 cells

Bleomycin is a commonly used anti-cancer drug in the management of a variety of cancers. Previously, we showed that arachidonic acid (AA) augmented the growth inhibitory action of bleomycin on IMR-32 (human neuroblastoma cells) in vitro by enhancing oxidative stress. Despite these results, the exact molecular mechanism of cytotoxic action of bleomycin and its augmentation by AA is not known. Our current study revealed that a combination of bleomycin and AA significantly enhanced the expression of FAS gene, which is involved in programmed cell death (apoptosis) and caspases 3 and 8 compared to either bleomycin or AA alone implying that activation of extrinsic apoptotic pathway plays a major role in their (bleomycin + AA) tumoricidal action. It is interesting to note that AA by itself enhanced the expression of FAS and caspases 3 and 8 compared to control. Since caspases have a role in inflammation, cell proliferation, tumour suppression, cell differentiation, neural development and axon guidance and ageing, this may explain pleiotropic actions of AA and their metabolites.

Deletions linked to TP53 loss drive cancer through p53-independent mechanisms

Mutations disabling the TP53 tumour suppressor gene represent the most frequent events in human cancer and typically occur through a two-hit mechanism involving a missense mutation in one allele and a 'loss of heterozygosity' deletion encompassing the other. While TP53 missense mutations can also contribute gain-of-function activities that impact tumour progression, it remains unclear whether the deletion event, which frequently includes many genes, impacts tumorigenesis beyond TP53 loss alone. Here we show that somatic heterozygous deletion of mouse chromosome 11B3, a 4-megabase region syntenic to human 17p13.1, produces a greater effect on lymphoma and leukaemia development than Trp53 deletion. Mechanistically, the effect of 11B3 loss on tumorigenesis involves co-deleted genes such as Eif5a and Alox15b (also known as Alox8), the suppression of which cooperates with Trp53 loss to produce more aggressive disease. Our results imply that the selective advantage produced by human chromosome 17p deletion reflects the combined impact of TP53 loss and the reduced dosage of linked tumour suppressor genes.

Effect of polyunsaturated fatty acids on drug-sensitive and resistant tumor cells in vitro

Previous studies showed that γ-linolenic acid (GLA, 18: 3 ω-6), arachidonic acid (AA, 20:4 ω -6), eicosapentaenoic acid (EPA, 20: 5 ω -3) and docosahexaenoic acid (DHA, 22:6 ω -3) have selective tumoricidal action. In the present study, it was observed that dihomo-gamma-linolenic acid (DGLA) and AA, EPA and DHA have cytotoxic action on both vincristine-sensitive (KB-3-1) and resistant (KB-Ch^R-8-5) cancer cells in vitro that appeared to be a free-radical dependent process but not due to the formation of prostaglandins, leukotrienes and thromboxanes. Uptake of vincristine and fatty acids was higher while their efflux was lower in KB-3-1 cells compared with KB-Ch^R-8-5 cells, suggesting that drug resistant cells have an effective efflux pump. GLA, DGLA, AA, EPA and DHA enhanced the uptake and decreased efflux in both drug-sensitive and drug-resistant cells and augmented the susceptibility of tumor cells especially, of drug-resistant cells to the cytotoxic action of vincristine. These results suggest that certain polyunsaturated fatty acids have tumoricidal action and are capable of enhancing the cytotoxic action of anti-cancer drugs specifically, on drug-resistant cells by enhancing drug uptake and reducing its efflux. Thus, polyunsaturated fatty acids either by themselves or in combination with chemotherapeutic drugs have the potential as anti-cancer molecules.

Enhanced generation of megakaryocytes from umbilical cord blood-derived CD34(+) cells expanded in the presence of two nutraceuticals, docosahexanoic acid and arachidonic acid, as supplements to the cytokine-containing medium

BACKGROUND AIMS

Ex vivo generation of megakaryocytes (MK) from hematopoietic stem cells (HSC) is important for both basic research, to understand the mechanism of platelet biogenesis, and clinical infusions, for rapid platelet recovery in thrombocytopenic patients. We investigated the role of two nutraceuticals, docosahexanoic acid (DHA) and arachidonic acid (AA), in the in vitro generation of MK.

METHODS

Umbilical cord blood (UCB)-derived CD34+cells were cultured with stem cell factor (SCF) and thrombopoietin (TPO) in the presence (test) or absence (control) of the two additives. On day 10, MK and platelets generated were quantitated by morphologic, phenotypic and functional assays.

RESULTS

The cell yield of MK and platelet numbers were significantly higher in test compared with control cells. Phenotypic analyzes and gene expression profiles confirmed these findings. Functional properties, such as colony-forming unit (CFU)-MK formation, chemotaxis and platelet activation, were found to be enhanced in cells cultured with nutraceuticals. The engraftment potential of ex vivo-expanded cells was studied in NOD/SCID mice. Mice that received MK cultured in the presence of DHA/AA engrafted better. There was a reduction in apoptosis and total reactive oxygen species (ROS) levels in the CD41(+) compartment of the test compared with control sets. The data suggest that these compounds probably exert their beneficial effect by modulating apoptotic and redox pathways.

CONCLUSIONS

Use of nutraceuticals like DHA and AA may prove to be a useful strategy for efficient generation of MK and platelets from cord blood cells, for future use in clinics and basic research.

Antineoplastic effects of melatonin on a rare malignancy of mesenchymal origin: melatonin receptor-mediated inhibition of signal transduction, linoleic acid metabolism and growth in tissue-isolated human leiomyosarcoma xenografts

Melatonin provides a circadian signal that regulates linoleic acid (LA)-dependent tumor growth. In rodent and human cancer xenografts of epithelial origin in vivo, melatonin suppresses the growth-stimulatory effects of linoleic acid (LA) by blocking its uptake and metabolism to the mitogenic agent, 13-hydroxyoctadecadienoic acid (13-HODE). This study tested the hypothesis that both acute and long-term inhibitory effects of melatonin are exerted on LA transport and metabolism, and growth activity in tissue-isolated human leiomyosarcoma (LMS), a rare, mesenchymally-derived smooth muscle tissue sarcoma, via melatonin receptor-mediated inhibition of signal transduction activity. Melatonin added to the drinking water of female nude rats bearing tissue-isolated LMS xenografts and fed a 5% corn oil (CO) diet caused the rapid regression of these tumors (0.17 +/- 0.02 g/day) versus control xenografts that continued to grow at 0.22 +/- 0.03 g/day over a 10-day period. LMS perfused in situ for 150 min with arterial donor blood augmented with physiological nocturnal levels of melatonin showed a dose-dependent suppression of tumor cAMP production, LA uptake, 13-HODE release, extracellular signal-regulated kinase (ERK 1/2), mitogen activated protein kinase (MEK), Akt activation, and [(3)H]thymidine incorporation into DNA and DNA content. The inhibitory effects of melatonin were reversible and preventable with either melatonin receptor antagonist S20928, pertussis toxin, forskolin, or 8-Br-cAMP. These results demonstrate that, as observed in epithelially-derived cancers, a nocturnal physiological melatonin concentration acutely suppress the proliferative activity of mesenchymal human LMS xenografts while long-term treatment of established tumors with a pharmacological dose of melatonin induced tumor regression via a melatonin receptor-mediated signal transduction mechanism involving the inhibition of tumor LA uptake and metabolism.

New aspects of the role of hydroxyeicosatetraenoic acids in cell growth and cancer development

Lipoxygenase (LOX) pathway leads to the formation of leukotrienes and also catalyses the conversion of arachidonic acid (AA) to hydroperoxyeicosatetraenoic acids that are then reduced to hydroxyeicosatetraenoic acids (HETE) by glutathione peroxidase. There are four mammalian LOXs that produce 5-, 8-, 12- and 15-HETE, respectively. Cytochrome P-450 isozymes are also capable of metabolising AA to HETEs either by bis-allylic oxidation (lipoxygenase-like reaction) to generate 5-, 8-, 9-, 11-, 12- and 15-HETE; or by varpi/varpi-1 hydroxylation to yield 16-, 17-, 18-, 19- and 20-HETEs. It is now widely recognised that HETEs have important physiological and pathological functions that modulate ion transport, renal and pulmonary functions, vascular tone and reactivity, and inflammatory and growth responses. They can be released during the action of growth factors and cytokines, reaching physiological concentrations higher than that of prostanoids and modulating the functions of these factors. Their effects can occur through receptor or non-receptor mechanisms. Recent reviews have summarised the effects of HETEs in vascular homeostasis or lung and renal physiology. The present review focuses on the emerging effects of HETEs on cell signalling and physiological cell growth. It also discusses current observations regarding the role of HETEs in apoptosis, angiogenesis, the proliferation of cancer cells and metastasis, which constitute a potential area for successful therapeutic intervention.

Anti-Apoptotic Effects of Arachidonic Acid and Prostaglandin E2 in Pancreatic β-Cells

BACKGROUND/AIMS

The polyunsaturated fatty acid arachidonic acid (AA) has been implicated in beta-cell defence mechanisms and prostaglandin (PG) products of cyclooxygenase (COX) 2 action confer resistance to alloxan-induced apoptosis in insulin-secreting RIN cells. We have now investigated the anti-apoptotic effects of AA and its metabolite, PGE(2), in the MIN6 mouse insulin-secreting beta-cell line and mouse islets.

METHODS

Apoptosis was determined in MIN6 beta-cell and mouse islet extracts by measurement of capase-3 activity, and COX2 mRNA levels were quantified by real-time RT-PCR.

RESULTS

Exposure of MIN6 cells to AA (3.1-12.5 microM) caused concentration-dependent reductions in apoptosis, and similar results were obtained when endogenous AA levels were elevated in cytosolic phospholipase A(2)-overexpressing MIN6 cells. 25mM glucose caused both a significant up-regulation of MIN6 cell COX2 mRNA levels and a decrease in apoptosis. Inhibition of MIN6 cell COX2 activity with a selective inhibitor, NS-398 (10-100 microM), increased apoptosis and exogenous PGE(2) (0.2-5 microM) reduced NS-398-induced apoptosis in a concentration-dependent manner. The protective effects of AA and PGE(2) were also observed in primary mouse islets.

CONCLUSION

These data show that AA and its COX2-generated metabolite, PGE(2), can protect beta-cells from apoptosis.

Effects of dietary unsaturated fatty acids on oocyte quality and follicular development in lactating dairy cows in summer

Dietary sources of fatty acids were evaluated for their influence on oocyte quality and follicular development using 54 lactating cows in summer. Fat supplements were 1) sunflower oil (80% cis 18:1), 2) Ca salt of transoctadecenoic acids (57% trans 18:1), 3) Ca salt of vegetable oils (30% 18:2), and 4) linseed oil (56% 18:3 and 16% 18:2). Fats were fed at 1.35% of dietary dry matter beginning at 5 wk prior to expected calving date and at 1.5% (oils) and 1.75% (Ca salts) of dietary dry matter for 15 wk after parturition. Four days following a programmed induced ovulation, 5 transvaginal oocyte aspirations were performed 3 or 4 d apart. Three days after the last aspiration, PGF2alpha was injected, followed 3 d later by a GnRH injection and a timed artificial insemination (d 0) 16 to 20 h later. For the first 4 aspirations, oocytes grading 1 or 2 were used for in vitro embryo production. Total cell number and the proportion of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive blastomeres were analyzed at d 8. At the fifth aspiration, the occurrence of metaphase II, group II caspase activity, and TUNEL labeling were determined after oocyte maturation. A total of 1,011 oocytes were collected. The proportion of oocytes with high caspase activity was greater for grade 3 compared with grades 1 and 2 (37.5 vs. 1.54 and 1.61%). Feeding polyunsaturated fatty acids, as compared with monosaturated fatty acids, failed to affect oocyte quality, as demonstrated by subsequent embryo development. Cows fed 18:2- or 18:3-enriched diets had a larger preovulatory follicle at insemination and subsequent volume of the corpus luteum compared with those fed cis 18:1 or trans 18:1 diets (16.8, 16.2 vs. 15.0, 14.9 +/- 0.7 mm; 7,323, 8,208 vs. 6,033, 5,495 +/- 644 mm3, respectively). The previously documented benefits of polyunsaturated fatty acids on reproductive performance appear to reflect actions at alternative biological windows in lactating dairy cows.

Metabolic and morphological alterations induced by proteolysis-inducing factor from Walker tumour-bearing rats in C2C12 myotubes

BACKGROUND

Patients with advanced cancer suffer from cachexia, which is characterised by a marked weight loss, and is invariably associated with the presence of tumoral and humoral factors which are mainly responsible for the depletion of fat stores and muscular tissue.

METHODS

In this work, we used cytotoxicity and enzymatic assays and morphological analysis to examine the effects of a proteolysis-inducing factor (PIF)-like molecule purified from ascitic fluid of Walker tumour-bearing rats (WF), which has been suggested to be responsible for muscle atrophy, on cultured C2C12 muscle cells.

RESULTS

WF decreased the viability of C2C12 myotubes, especially at concentrations of 20-25 mug.mL-1. There was an increase in the content of the pro-oxidant malondialdehyde, and a decrease in antioxidant enzyme activity. Myotubes protein synthesis decreased and protein degradation increased together with an enhanced in the chymotrypsin-like enzyme activity, a measure of functional proteasome activity, after treatment with WF. Morphological alterations such as cell retraction and the presence of numerous cells in suspension were observed, particularly at high WF concentrations.

CONCLUSION

These results indicate that WF has similar effects to those of proteolysis-inducing factor, but is less potent than the latter. Further studies are required to determine the precise role of WF in this experimental model.

Stimulation of suicidal erythrocyte death by lipoxygenase inhibitor Bay-Y5884

The prostaglandin PGE(2), a metabolite of the cyclooxygenase pathway, activates Ca(2+)-permeable cation channels in erythrocyte cell membranes leading to entry of Ca(2+) with subsequent eryptosis, i.e. cell shrinkage, breakdown of phosphatidylserine (PS) asymmetry and membrane blebbing, all features typical for apoptosis in nucleated cells. PS exposing cells are recognized by macrophages, engulfed, degraded and thus cleared from circulating blood. The present study explored whether the specific lipoxygenase inhibitor Bay-Y5884 influences eryptosis. As determined by competitive ELISA, Bay-Y5884 (20 microM) enhanced the release of PGE(2) from human erythrocytes. According to whole-cell patch-clamp, Bay-Y5884 (20 microM) activated nonselective cation channels. The effect of Bay-Y5884 on cation channels was abolished by the cyclooxygenase inhibitor diclophenac (10 microM). Bay-Y5884 (30-40 microM) significantly increased erythrocyte free Ca(2+) concentration and PS exposure as analyzed in flow cytometry by Fluo3 fluorescence and annexin-V binding, respectively. PS exposure triggered by 20 microM (but not by 40 microM) Bay-Y5884 was blunted by cyclooxygenase inhibitors acetylsalicylic acid (50 microM) and diclophenac (10 microM). In conclusion, the lipoxygenase inhibitor Bay-Y5884 enhances erythrocyte PGE(2) formation with subsequent activation of non-selective cation channels, Ca(2+) entry and phospholipid scrambling.

The inhibition of lung colonization of B16-F10 melanoma cells in EFA-deficient animals is related to enhanced apoptosis and reduced angiogenesis

Previous studies conducted in our laboratory showed that the reproduction of spontaneous and experimental metastases was reduced in host animals deprived of essential fatty acids (EFA). In the present study, we have explored the possibility whether apoptosis, proliferation, and angiogenesis might be involved in the antimetastatic effect of EFA deficiency. To this aim, in pulmonary colonies developed from B16-F10 cells in EFA-deficient animals or in animals fed a 5% corn oil diet, we performed an immunohistochemical analysis of bcl-2/bax proteins, PCNA, and VEGF and von Willebrand Factor (vWF), typical markers of apoptosis, proliferation, and angiogenesis, respectively. Apoptosis was also evaluated by detecting DNA fragments in metastatic cells. We found that the reduction of pulmonary colonies grown in EFA-deficient animals was associated with a high expression of apoptotic activity as revealed by the presence of apoptotic nuclei and a high immunoreactivity for bax. Cell proliferation seemed not to be influenced by EFA deficiency in view of the observation that PCNA was highly expressed in pulmonary colonies of control as well as EFA-deficient animals. Pulmonary colonies developed in EFA- deficient animals showed a lower expression of VEGF and a decreased microvessel density, indicating that a reduced angiogenesis contributes to the antimetastatic effects of EFA deficiency. Our analysis of the results invokes the possibility that a relationship between angiogenesis and apoptosis may account for the diminution of the development of experimental metastases in the lungs of EFA-deficient animals.

Calcium ionophore-induced de-encryption of tissue factor in monocytes is associated with extensive cell death

INTRODUCTION

Cell surface tissue factor (TF) is normally encrypted, but can be activated by various cellular perturbations. Exposure of TF bearing cells to calcium ionophore has been reported to increase TF activity, de-encrypt TF, by phosphatidylserine (PS)-dependent and -independent mechanisms. Our aim has been to examine at the single cell level, if increased cell surface PS coincided with increased cell surface TF antigen, and cell death (necrosis, 7-AAD-intercalation), and relate this to monocyte- and microparticle (MP)-associated procoagulant activity.

MATERIALS AND METHODS

We exposed lipopolysaccharide-stimulated, human, elutriation-purified, cryopreserved TF bearing monocytes to increasing concentrations of calcium ionophore (A23187) and measured procoagulant activity in cells and supernatants. These measurements were compared with quantification of cell surface TF and PS (Annexin V) and of cell necrosis (7-AAD) by flow cytometry, and complemented by confocal microscopy.

RESULTS

We observed that calcium ionophore increased cellular and MP-associated TF activity, but not cell surface TF antigen. The discrepancy between TF activity and TF antigen coincided with a dose-dependent increase in the number of cells expressing PS. These cells were to a large extent necrotic and many of them also expressed TF.

CONCLUSIONS

We suggest such TF positive dying cells to contribute to the discordance between TF activity and TF expression. Calcium ionophore also increased MP-associated TF activity and release of MPs may be a way to disseminate procoagulant activity. Our findings emphasize the importance of adequately assessing cell death and taking into consideration its possible role in experiments with calcium ionophore.

Nordy, a synthetic lipoxygenase inhibitor, inhibits the expression of formylpeptide receptor and induces differentiation of malignant glioma cells

We recently found that formylpeptide receptor (FPR), a G-protein-coupled receptor that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine, is expressed by malignant human glioma cells and promotes tumor growth and angiogenesis. In this study, we examined the effect of Nordy, a novel chiral lipoxygenase inhibitor which was synthesized based on the structure of a natural nordihydroguaiaretic acid, on the expression of FPR by human glioblastoma cells. We found that FPR was expressed at the protein level by highly malignant human glioma cell lines U87 and BT325, and a rat glioma cell line C6. The expression level of FPR was correlated with the degree of the malignancy of tumor cells. The poorly differentiated glioma cell line U87 expressed the highest level of FPR. In U87 glioma cells, the expression of FPR was attenuated at the protein level by Nordy treatment for 48 (P<0.05). Nordy did not affect FPR mRNA expression in U87 cells. In addition, Nordy treatment seemed to promote glioma cell differentiation, as evidenced by their reduced expression of vimentin and increased expression of GFAP. Our results suggest that Nordy was capable of reducing the level of malignancy of glioma cells.

Overexpression of 15-lipoxygenase in the vascular endothelium is associated with increased thymic apoptosis in LDL receptor-deficient mice

BACKGROUND

15-Lipoxygenase (15-LO) is a nonheme iron-containing enzyme that catalyzes the peroxidation of fatty acids. Herein, we studied the effect of 15-LO overexpression in the vascular endothelium on thymocyte apoptosis by evaluating thymuses from low-density lipoprotein receptor-deficient (LDL-RD) mice and LDL-RD/15-LO mice. Thymuses were evaluated by immunohistochemistry and by TUNEL whereas in vitro studies were carried out by employing freshly isolated thymocytes from the respective mice and evaluation of apoptosis by propidium iodide and annexin V cytometry.

METHODS AND RESULTS

The apoptotic index in LDL-RD/15-LO mice was significantly higher than in the LDL-RD mice. In the thymic medulla the difference was smaller, although still significant. Freshly isolated thymus cells from LDL-RD/15-LO mice exhibited a higher rate of spontaneous cell death than controls. Incubation of thymus cells in the presence of the cell-permeable caspase-3 inhibitor DEVD-CMK resulted in a decrease in the frequency of apoptotic cells in LDL-RD/15-LO thymocytes, whereas no effect was evident in control thymocytes. The antioxidant N-acetylcysteine causes the increase in apoptosis in both groups.

CONCLUSION

LDL-RD/15-LO mice exhibit increased thymocyte apoptosis both in vivo and in vitro. These findings may suggest a role for 15-LO in the natural selection of thymocytes.

Sphingosine 1-Phosphate Protects Bovine Oocytes from Heat Shock During Maturation1

Sphingosine 1-phosphate (S1P) is a sphingolipid metabolite that can block apoptosis by counteracting the proapoptotic effects of ceramide. Experiments were performed to evaluate whether S1P blocks the disruption in oocyte developmental competence caused by heat shock. Cumulus-oocyte complexes (COCs) were placed in maturation medium and cultured at 38.5 or 41 degrees C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization, and embryonic development were performed at 38.5 degrees C. Heat shock during the first 12 h of maturation reduced cleavage rate, the number of oocytes developing to the blastocyst stage, and the percentage of cleaved embryo that subsequently developed to blastocysts. Addition of 50 nM S1P to maturation medium had no effect on oocytes matured at 38.5 degrees C but blocked effects of thermal stress on cleavage and subsequent development. The blastocysts formed at Day 8 did not differ between S1P and control groups in caspase activity, total cell number, or percentage of cells that were apoptotic. Blocking endogenous generation of S1P by addition of 50 nM N1N-dimethylsphingosine, a sphingosine kinase inhibitor, reduced or tended to reduce cleavage rate and blastocyst development regardless of whether maturation of COCs was at 38.5 or 41 degrees C. Results demonstrate that S1P protects oocytes from a physiologically relevant heat shock and affects oocyte maturation even in the absence of heat shock. The S1P-treated oocytes that survived heat shock and became blastocysts had a normal developmental potential as determined by caspase activity, total cell number, and percentage of apoptotic cells. Thus, modulation of developmental competence of oocytes using S1P may be a useful approach for enhancing fertility in situations where developmental competence of oocytes is compromised.

Effect of catechol derivatives on cell growth and lipoxygenase activity

Derivatives of salicylic acid have been synthesized as potential lipoxygenase inhibitors. Agents containing a phenolic dihydroxy moiety showed potent (IC(50)10(-6)-10(-7) M) inhibition of the growth of murine colonic tumour cells in vitro, and were effective inhibitors of 5-, 12- and 15-lipoxygenase in intact cells. The catechols were also potent inhibitors of rabbit reticulocyte 15-lipoxygenase (IC(50) approximately 1 microM).

Lack of influence of omega-3 fatty acid-enriched lipids on apoptosis and secondary necrosis of cultured human lymphocytes

OBJECTIVE

The anti-inflammatory properties of parenteral nutrition might be improved by enrichment with omega-3 polyunsaturated fatty acids (PUFAs), which are responsible for the enhanced release of metabolites derived from eicosapentaenoic acid. Under physiologic conditions, lymphocyte populations are regulated by cellular mechanisms such as apoptosis. In contrast to cell death by necrosis, apoptosis does not induce an inflammatory response that might injure the host.

METHODS

Apoptosis and necrosis of cultured human blood lymphocytes were investigated in vitro after incubation for 48 and 72 h with three lipid emulsions containing 50% medium-chain triacylglycerols. The lipid emulsions differed in the percentage of long-chain triacylglycerols, which were replaced in part by different amounts of omega-3 PUFA (8%, 20%, or 40%). Rates of apoptosis and necrosis of lymphocyte subpopulations were analyzed with a sensitive annexin V flow cytometric assay.

RESULTS

After 48 and 72 h of incubation, time- and dose-dependent increases of apoptosis and necrosis, respectively, were found in all lymphocyte subsets regardless of the percentage of omega-3 PUFAs.

CONCLUSIONS

Our results suggested that enrichment with omega-3 PUFAs in the tested lipid emulsions does not alter apoptosis and secondary necrosis of lymphocyte populations. Thus PUFAs may exert their functional effects through other mechanisms.

Saturated free fatty acids, palmitic acid and stearic acid, induce apoptosis by stimulation of ceramide generation in rat testicular Leydig cell

In men, obesity has generally been associated with reduced plasma testosterone levels and with elevation of the plasma free fatty acids (FFAs). In this study, we investigated the effects of saturated FFAs including palmitic acid (PA) and stearic acid (SA), and polyunsaturated FFA arachidonic acid (AA) on the survival of rat testicular Leydig cell cultured in vitro. PA and SA markedly suppressed Leydig cell survival in a time- and dose-dependent manner. In contrast, AA stimulated the cell proliferation at 5-10 times of physiological concentration. The suppressive effect of PA and SA on cell survival was caused by apoptosis evidenced by DNA ladder formation and Annexin V-EGFP/propidium iodide staining of the cells. The apoptotic effect of PA was possibly mediated by ceramide generation because it could be completely blocked by ceramide synthase inhibitor fumonisin B1 and exogenous ceramide itself could directly induce apoptosis in vitro. Surprisingly, the apoptosis induced by PA could be partly prevented by AA. These results indicate that PA and SA induce apoptosis in testicular Leydig cells by ceramide production and these apoptotic effects may be a possible mechanism for reproductive abnormalities in obese men, and AA can partly prevent the apoptotic effect induced by saturated FFA.

Increased cytosol Ca(2+) and type 1 programmed cell death in Bcl-2-positive U937 but not in Bcl-2-negative PC-3 and Panc-1 cells induced by the 5-lipoxygenase inhibitor MK 886

MK 886, an arachidonic acid-related analog which inhibits the enzyme, 5-lipoxygenase by an indirect mechanism involving the 5-lipoxygenase activating protein, rapidly increased U937 cytosol Ca(2+), much of which localized around the cell nuclei. Five-lipoxygenase activity was not directly involved since the direct redox-dependent 5-LPOx inhibitor, SC-41661A did not increase Ca(2+). U937 cells subsequently undergo classic type 1 programmed cell death. At least initially the ionized calcium originates from internal stores. Coincident with the rise in U937 ionized calcium, MK 886 rapidly increased reactive oxygen species and reduced mitochondrial membrane potential, as judged by several fluorescent probes. The Ca(2+) response of myeloid leukemia-derived HL-60 cells to MK 886 was similar and both cell lines express Bcl-2 protein. Bcl-2-negative Panc-1 and PC-3 cells did not respond to MK 886 with a Ca(2+) signal but did develop oxidative stress and a decline in mitochondrial membrane potential; these events are thought to contribute to the inhibition of cell proliferation and induction of a type 2 PCD. In addition to its marked inhibition of Bcl-2 mRNA synthesis, an interesting hypothesis is that MK 886, serving as a low molecular weight ligand, either by direct or indirect inhibition of U937 Bcl-2 protein function, possibly related to an ion channel activity, alters the distribution of intracellular, possibly nuclear Ca(2+), thereby promoting the development of type 1 programmed cell death.

Fatty acid oxidation and signaling in apoptosis

It is well established that fatty acid metabolites of cyclooxygenase, lipoxygenase (LOX), and cytochrome P450 are implicated in essential aspects of cellular signaling including the induction of programmed cell death. Here we review the roles of enzymatic and non-enzymatic products of polyunsaturated fatty acids in controlling cell growth and apoptosis. Also, the spontaneous oxidation of polyunsaturated fatty acids yields reactive aldehydes and other products of lipid peroxidation that are potentially toxic to cells and may also signal apoptosis. Significant conflicting data in terms of the role of LOX enzymes are highlighted, prompting a re-evaluation of the relationship between LOX and prostate cancer cell survival. We include new data showing that LNCaP, PC3, and Du145 cells express much lower levels of 5-LOX mRNA and protein compared with normal prostate epithelial cells (NHP2) and primary prostate carcinoma cells (TP1). Although the 5-LOX activating protein inhibitor MK886 killed these cells, another 5-LOX inhibitor AA861 hardly showed any effect. These observations suggest that 5-LOX is unlikely to be a prostate cancer cell survival factor, implying that the mechanisms by which LOX inhibitors induce apoptosis are more complex than expected. This review also suggests several mechanisms involving peroxisome proliferator activated receptor activation, BCL proteins, thiol regulation, and mitochondrial and kinase signaling by which cell death may be produced in response to changes in non-esterified and non-protein bound fatty acid levels. Overall, this review provides a context within which the effects of fatty acids and fatty acid oxidation products on signal transduction pathways, particularly those involved in apoptosis, can be considered in terms of their overall importance relative to the much better studied protein or peptide signaling factors.

Cytosolic phospholipase A(2) activity during the ongoing cell cycle

Cytosolic phospholipase A(2) (cPLA(2)) is of special interest because it selectively releases arachidonic acid from membrane phospholipids. Arachidonic acid has been implicated to play an important role in various cellular responses. Recently arachidonic acid release and prostaglandin synthesis have been shown to be cell cycle dependent and therefore the activity of cPLA(2) during the ongoing cell cycle was investigated, using the mitotic shake off method for cell synchronisation. cPLA(2) activity was high in mitotic cells and decreased rapidly in the early G1 phase. A strong increase in activity was measured following the G1/S transition in both neuroblastoma and Chinese hamster ovary cells. The changes in activity were not due to a difference in cPLA(2) expression but due to phosphorylation of cPLA(2). Phosphorylation of cPLA(2) occurs through MAPK since the use of a specific MAPK kinase inhibitor and serum depletion of synchronised cells inhibited cPLA(2) activity.

Lipoxygenases and their involvement in programmed cell death

Lipoxygenases are a family of enzymes which dioxygenate unsaturated fatty acids, thus initiating lipoperoxidation of membranes and the synthesis of signaling molecules. Consequently, they induce structural and metabolic changes in the cell in a number of pathophysiological conditions. Recently, a pro-apoptotic effect of lipoxygenase, and of the hydroperoxides produced thereof, has been reported in different cells and tissues, leading to cell death. Anti-apoptotic effects of lipoxygenases have also been reported; however, this has often been based on the use of enzyme inhibitors. Here we review the characteristics of the lipoxygenase family and its involvement in the initiation of oxidative stress-induced apoptosis. Finally, we discuss the role of lipoxygenase activation in apoptosis of animal and plant cells, suggesting a common signal transduction pathway in cell death conserved through evolution of both kingdoms.

Saturated FFAs, palmitic acid and stearic acid, induce apoptosis in human granulosa cells

Obesity is associated with insulin resistance and some reproductive abnormalities. Circulating FFAs are often elevated in obese subjects and are also closely linked to insulin resistance. In this study, we demonstrated that saturated FFAs, such as palmitic acid and stearic acid, markedly suppressed the granulosa cell survival in a time- and dose-dependent manner. Polyunsaturated FFA, arachidonic acid, had no effect on the cell survival, even at supraphysiological concentrations. The suppressive effect of saturated FFAs on cell survival was caused by apoptosis, as evidenced by DNA ladder formation and annexin V-EGFP/propidium iodide staining of the cells. The apoptotic effects of palmitic acid and stearic acid were unrelated to the increase of ceramide generation or nitric oxide production and were also completely blocked by Triacsin C, an inhibitor of acylcoenzyme A synthetase. In addition, acylcoenzyme A, pamitoylcoenzyme A, and stearylcoenzyme A markedly suppressed granulosa cell survival, whereas arachidonoylcoenzyme A had no such effect, and this finding was consistent with the effect of the respective FFA form. Surprisingly, arachidonic acid instead showed a protective effect on palmitic acid- and stearic acid-induced cell apoptosis. A Western blot analysis showed the apoptosis of the granulosa cells induced by palmitic acid to be accompanied by the down-regulation of an apoptosis inhibitor, Bcl-2, and the up-regulation of an apoptosis effector, Bax. These results indicate that saturated FFAs induce apoptosis in human granulosa cells caused by the metabolism of the respective acylcoenzyme A form, and the actual composition of circulating FFAs may thus play a critical role in the apoptotic events of human granulosa cells. These effects of FFAs on granulosa cell survival may be a possible mechanism for reproductive abnormalities, such as amenorrhea, which is frequently observed in obese women.

Inhibitors of arachidonic acid metabolism potentiate tumour necrosis factor-alpha-induced apoptosis in HL-60 cells

We investigated whether and how could various modulators of arachidonic acid metabolism affect apoptosis induced by tumour necrosis factor-alpha (TNF-alpha) in human myeloid leukaemia HL-60 cells. These included arachinonyltrifluoromethyl ketone (AACOCF3; cytosolic phospholipase A2 inhibitor), indomethacin (cyclooxygenase inhibitor), MK-886 (3-[1-(4-chlorobenzyl)-3-t-butyl-thio-5-isopropylindol-2-yl]-2,2-dimethyl propanoic acid; 5-lipoxygenase-activating protein inhibitor), nordihydroguaiaretic acid (general lipoxygenase inhibitor), and arachidonic acid itself. Incubation of HL-60 cells with nordihydroguaiaretic acid resulted in apoptosis and it was characterised by mitochondria membrane depolarisation, release of cytochrome c from mitochondria into cytosol and activation of caspase-3. Indomethacin and nordihydroguaiaretic acid synergistically potentiated TNF-alpha-induced apoptosis, while arachidonic acid, AACOCF3 and MK-886 did not modulate its effects. Furthermore, indomethacin potentiated apoptosis in cells treated with a differentiating agent, all-trans retinoic acid, which induces resistance to TNF-alpha. However, the observed effects were probably not associated either with the cyclooxygenase- or lipoxygenase-dependent activities of indomethacin and nordihydroguaiaretic acid, respectively. Since indomethacin may reportedly activate peroxisome proliferator-activated receptors (PPARs), the effects of specific ligands of PPARs on apoptosis were studied as well. It was found that selective PPARs ligands had no effects on TNF-alpha-induced apoptosis. The findings suggest that arachidonic acid metabolism does not play a key role in regulation of apoptosis induced by TNF-alpha in the present model. Nevertheless, our data raise the possibility that indomethacin could potentially be used to improve the treatment of human myeloid leukaemia.

Activation of the Phosphatidylinositol 3-Kinase-Akt/Protein Kinase B Signaling Pathway in Arachidonic Acid-stimulated Human Myeloid and Endothelial Cells

Although arachidonic acid has been demonstrated to stimulate a wide variety of cellular functions, the responsible mechanisms remain poorly defined. We now report that arachidonic acid stimulated the activity of class Ia phosphatidylinositol 3-kinase (PI3K) in human umbilical vein endothelial cells, HL60 cells, and human neutrophils. Pretreatment of endothelial cells with AG-1478, an inhibitor of the ErbB receptor family, resulted in the suppression of PI3K activation by arachidonic acid. The fatty acid enhanced the tyrosine phosphorylation of ErbB4 but not of ErbB2 or ErbB3. The ability of arachidonic acid to stimulate PI3K activity in neutrophils was suppressed by indomethacin and nordihydroguaiaretic acid, inhibitors of the cyclooxygenases and lipoxygenases, respectively, but not by 17-octadecynoic acid, an inhibitor of omega-hydroxylation of arachidonic acid by cytochrome P450 monooxygenases. Consistent with this, the activity of PI3K in neutrophils was stimulated by 5-hydroxyeicosatetraenoic acid. Arachidonic acid also transiently stimulated the phosphorylation of Akt on Thr-308 and Ser-473. Although PI3K was not required for the activation of the mitogen-activated protein kinases, ERK1, ERK2, and p38, in arachidonic acid-stimulated neutrophils, the fatty acid acted via PI3K to stimulate the respiratory burst. These results not only define a novel mechanism through which some of the actions of arachidonic acid are mediated but also demonstrate that, in addition to ErbB1 (epidermal growth factor receptor), ErbB4 can also be transactivated by a non-epidermal growth factor-like ligand.

HIV-1 coat glycoprotein gp120 induces apoptosis in rat brain neocortex by deranging the arachidonate cascade in favor of prostanoids

Human immunodeficiency virus type-1 coat glycoprotein gp 120 causes delayed programmed cell death (apoptosis) in rat brain neocortex. Here, we investigated the possible role of the arachidonate cascade and membrane peroxidation in this process. It is shown that gp 120 causes a rapid increase in the activity and expression of the arachidonate-metabolizing enzyme prostaglandin H synthase, paralleled by increased prostaglandin E(2) levels. The selective inhibitor of prostaglandin H synthase indomethacin inhibited enzyme activity, reduced prostaglandin E(2) content, and partially protected neocortex against gp 120-induced apoptosis. Conversely, the activity and expression of the arachidonate-metabolizing enzyme 5-lipoxygenase decreased upon gp 120 treatment, as well as the level of its product, leukotriene B(4). Treatment with gp 120 also reduced membrane lipid peroxidation, and this may be implicated in the execution of programmed cell death. These results suggest that early derangement of the arachidonate cascade in favor of prostanoids may be instrumental in the execution of delayed apoptosis in the brain neocortex of rats.

Activation of different lipoxygenase isozymes induces apoptosis in human erythroleukemia and neuroblastoma cells

We investigated the ability of different hydroperoxides generated by lipoxygenase isozymes to induce programmed cell death (PCD) in human cells. Erythroleukemia K562 and neuroblastoma CHP100 cells were used, because they showed high basal activity of lipoxygenase. The hydroperoxides generated by 5-, 12-, or 15-lipoxygenases from linoleate, linolenate, or arachidonate, and the corresponding hydroxides, were able to induce PCD in both cell types, in a concentration- and time-dependent manner. After 24 h, K562 and CHP100 cells showed 2.5- to 3.5-fold more apoptotic bodies than the untreated controls. PCD elicited by lipoxygenase products was independent of intracellular glutathione concentration, and did not require mRNA transcription or protein synthesis. On the other hand, lipoxygenase products evoked an immediate and sustained rise in cytoplasmic calcium (within seconds), followed by mitochondrial uncoupling (within hours). Unlike the hydro(pero)xides, the terminal products of the arachidonate cascade (i.e., leukotrienes, prostaglandins and thromboxane) were not cytotoxic.

The early phase of apoptosis in human neuroblastoma CHP100 cells is characterized by lipoxygenase-dependent ultraweak light emission

Human neuroblastoma CHP100 cells were forced into apoptosis (programmed cell death, PCD) or necrosis by treatment with calcium chloride or sodium nitroprusside (a nitric oxide donor), respectively. Cellular luminescence, a marker of membrane lipid peroxidation, was increased by calcium but not by nitroprusside, and reached a maximum of 4-fold the control value 2 hours after treatment. The increase in luminescence was paralleled by increased 5-lipoxygenase (up to 250% of the control value) and decreased catalase (down to 50%) activity within the same time window. Consistently, incubation of CHP100 cells with inhibitors of 5-lipoxygenase (5,8,11,14-eicosatetraynoic acid and MK886) reduced light emission and PCD, whereas inhibition of catalase by 3-amino-1, 2,4-triazole enhanced both processes. Treatment of CHP100 cells with retinoic acid or cisplatin, unrelated PCD inducers reported to activate the lipoxygenase pathway, also gave enhanced light emission parallel to PCD increase. Altogether, these results suggest that cellular luminescence is an early marker of apoptotic, but not necrotic, program(s) involving generation of hydrogen peroxide and activation of 5-lipoxygenase.

Induction of apoptosis and apoptotic mediators in Balb/C splenic lymphocytes by dietary n-3 and n-6 fatty acids

The present study was designed to investigate the effect of dietary n-6 and n-3 polyunsaturated fatty acids (PUFA) on anti-CD3 and anti-Fas antibody-induced apoptosis and its mediators in mouse spleen cells. Nutritionally adequate semipurified diets containing either 5% w/w corn oil (n-6 PUFA) or fish oil (n-3 PUFA) were fed to weanling female Balb/C mice, and 24 wk later mice were sacrificed. In n-3 PUFA-fed mice, serum and splenocyte lipid peroxides were increased by 20 and 28.3% respectively, compared to n-6 PUFA-fed mice. Further, serum vitamin E levels were decreased by 50% in the n-3 PUFA-fed group, whereas higher anti-Fas- and anti-CD3-induced apoptosis (65 and 66%) and necrosis (17 and 25%), compared to the n-6 PUFA-fed group, were found when measured with Annexin V and propidium iodide staining, respectively. In addition, decreased Bcl-2 and increased Fas-ligand (Fas-L) also were observed in the n-3 PUFA-fed group compared to the n-6 PUFA-fed group. No difference in the ratio of splenocyte subsets nor their Fas expression was observed between the n-3 PUFA-fed and n-6 PUFA-fed groups, whereas decreased proliferation of splenocytes was found in n-3 PUFA-fed mice compared to n-6 PUFA-fed mice. In conclusion, our results indicate that dietary n-3 PUFA induces higher apoptosis by increasing the generation of lipid peroxides and elevating Fas-L expression along with decreasing Bcl-2 expression. A reduced proliferative response of immune cells also was observed in n-3 PUFA-fed mice.

Health benefits of docosahexaenoic acid (DHA)

Docosahexaenoic acid (DHA) is essential for the growth and functional development of the brain in infants. DHA is also required for maintenance of normal brain function in adults. The inclusion of plentiful DHA in the diet improves learning ability, whereas deficiencies of DHA are associated with deficits in learning. DHA is taken up by the brain in preference to other fatty acids. The turnover of DHA in the brain is very fast, more so than is generally realized. The visual acuity of healthy, full-term, formula-fed infants is increased when their formula includes DHA. During the last 50 years, many infants have been fed formula diets lacking DHA and other omega-3 fatty acids. DHA deficiencies are associated with foetal alcohol syndrome, attention deficit hyperactivity disorder, cystic fibrosis, phenylketonuria, unipolar depression, aggressive hostility, and adrenoleukodystrophy. Decreases in DHA in the brain are associated with cognitive decline during aging and with onset of sporadic Alzheimer disease. The leading cause of death in western nations is cardiovascular disease. Epidemiological studies have shown a strong correlation between fish consumption and reduction in sudden death from myocardial infarction. The reduction is approximately 50% with 200 mg day(-1)of DHA from fish. DHA is the active component in fish. Not only does fish oil reduce triglycerides in the blood and decrease thrombosis, but it also prevents cardiac arrhythmias. The association of DHA deficiency with depression is the reason for the robust positive correlation between depression and myocardial infarction. Patients with cardiovascular disease or Type II diabetes are often advised to adopt a low-fat diet with a high proportion of carbohydrate. A study with women shows that this type of diet increases plasma triglycerides and the severity of Type II diabetes and coronary heart disease. DHA is present in fatty fish (salmon, tuna, mackerel) and mother's milk. DHA is present at low levels in meat and eggs, but is not usually present in infant formulas. EPA, another long-chain n-3 fatty acid, is also present in fatty fish. The shorter chain n-3 fatty acid, alpha-linolenic acid, is not converted very well to DHA in man. These longchain n-3 fatty acids (also known as omega-3 fatty acids) are now becoming available in some foods, especially infant formula and eggs in Europe and Japan. Fish oil decreases the proliferation of tumour cells, whereas arachidonic acid, a longchain n-6 fatty acid, increases their proliferation. These opposite effects are also seen with inflammation, particularly with rheumatoid arthritis, and with asthma. DHA has a positive effect on diseases such as hypertension, arthritis, atherosclerosis, depression, adult-onset diabetes mellitus, myocardial infarction, thrombosis, and some cancers.

Essential fatty acids, lipid peroxidation and apoptosis

Essential fatty acids (EFAs) and their metabolites, especially gamma-linolenic acid, arachidonic acid, eicosapentaenoic acid and decosahexaenoic acid are known to induce apoptotic death of tumour cells. But the exact mechanism by which these fatty acids are able to induce apoptosis is not clear. Recent studies suggest that these fatty acids are able to induce apoptosis in cells over expressing cytochrome P450 following depletion of cellular glutathione and inhibition of carnitine palmitoyl transferase I (CPTI) activity. On the other hand, BCL-2 prevented apoptosis induced by these long-chain fatty acids, where as n-3 fatty acids suppressed ras expression leading to suppression of development of overt neoplasia. Phosphorylation of BCL-2 inhibits its ability to interfere with apoptosis and enhances lipid peroxidation leading to the occurrence of apoptosis. Tumour cells treated with long-chain fatty acids show increase in lipid peroxidation process, depletion of antioxidants and phosphorylation of proteins. Based on these results, it is suggested that long-chain fatty acids induce apoptosis by enhancing lipid peroxidation, suppressing BCL-2 expression possibly by phosphorylation and augmentation of P450 activity. Thus, these long-chain fatty acids may, infact act at the level of gene/oncogene expression in producing their cytotoxic action on tumour cells.

Regulation of 12-lipoxygenase in rat intestinal epithelial cells during differentiation and apoptosis induced by sodium butyrate

We evaluated the expression and activity of rat 12-lipoxygenase (LO) in rat intestinal epithelial (RIE) cells during apoptosis and cell differentiation. Sodium butyrate (NaBT) treatment induced wild-type RIE (W-RIE) cells to undergo differentiation and apoptosis. Alkaline phosphatase (ALP) activity, a marker of cell differentiation, and DNA fragmentation, an index of apoptosis, were increased by NaBT treatment. Arachidonic acid was metabolized primarily to 12-hydroxyeicosatetraenoic acid (HETE) suggesting induction of 12-LO activity. In contrast, sense-RIE (S-RIE) cells engineered to overexpress COX-2 were resistant to apoptosis by treatment with 5 mM NaBT and NaBT did not induce 12-LO activity. The upregulation of 12-LO expression by NaBT in W-RIE cells was confirmed at both the transcriptional and translational level but 12-LO was undetectable in S-RIE cells following NaBT treatment. The expression of 12-LO mRNA in W-RIE cells occurs as early as 6 h after treatment and reaches maximum expression at 24 h following treatment. This inducible 12-LO was isolated by RT-PCR and identified as rat "leukocyte-type" 12-LO. The level of 12-LO expression in W-RIE cells was dependent on the concentration of NaBT and appears to reflect the extent of cell differentiation. NDGA, a lipoxygenase inhibitor, attenuated induction of ALP activity by NaBT treatment of W-RIE cells. These observations suggested that 12-LO is regulated by treatment with NaBT and is associated with cell differentiation in rat intestinal epithelial cells.

Dose-dependent inhibition of cell proliferation induced by lipid peroxidation products in rat hepatoma cells after enrichment with arachidonic acid

Polyunsaturated fatty acids (PUFA) are important constituents of membrane phospholipids, whose levels are decreased in some tumor cells. This deficiency may cause alterations in signal transduction and an interruption of normal cellular events. The enrichment of tumor cells with PUFA may stimulate or inhibit tumor growth, probably depending on the type of PUFA and the cellular concentration of aldehydes derived from restored lipid peroxidation. We examined the effect of several doses of prooxidant on the growth of hepatoma cells with different aldehyde dehydrogenase activities, enriched with arachidonic acid. Two doses of prooxidant were sufficient to reduce growth of hepatoma cells with low aldehyde dehydrogenase activity, whereas three doses were necessary for those with high enzyme activity. In both cases, lipid peroxidation products blocked the cells in the S phase.

Arachidonic acid induces differentiation of uterine stromal to decidual cells

Fatty acids have been involved in the proliferation and differentiation of numerous cells, as mediated via peroxisome proliferator-activated receptors (PPARs) or lipid metabolites (prostaglandins, diacylglycerol). In the present study, we have investigated the effect of arachidonic acid (AA), docosahexaenoic acid (DHA) and its precursor eicosapentaenoic acid (EPA) on the differentiation of a rat uterine stromal cell line, UIII. As markers of decidualization, we have investigated morphological changes, monitored by inverted light and scanning electron microscopy. The induction of 3 proteins, desmin, hsp-25 and prolactin, which are all considered to be markers of decidualization, were analyzed by immunocytochemistry or Western blotting. Addition of AA (30 microM) to the medium of cultured cells for 48h induced cell spreading and flattening. Cells became enlarged (x 2.5) and some of them were binucleated. Using scanning electron microscopy, we confirmed these morphological changes and showed that the enlargement of the cells was followed by numerous extracellular processes, leading to an increase in cell surface area and intercellular communications. Immunocytochemistry showed that this treatment also induced the expression of desmin, which seems to direct morphological changes, beginning as a perinuclear ring and extending to the cell membrane. The time course of desmin expression was studied by Western blotting. No desmin expression was present before 4h of AA treatment. Desmin induction was maximum at 24h of treatment and plateaued thereafter. DHA and EPA (30 microM), added to the medium, failed to induce any change. However, in cells previously differentiated with AA and expressing desmin, treatment with DHA or EPA (30microM) reversed partially the action of AA, EPA being the most effective. AA also induced hsp-25, though all cells did not express this protein. A prolactin (PRL)-like factor was induced by AA, as recognized by an antibody against pituitary rPRL, and migrated as the standard. Moreover, a fragment of 16 kDa was also revealed by this antibody, suggesting that the PRL-like factor cleaved, was similar to PRL and that the PRL-like factor could be identical to PRL. In conclusion, these results show that AA is able to specifically induce the decidualization of uterine stromal cells in vitro.

Effects of mutant p53 expression on human 15-lipoxygenase-promoter activity and murine 12/15-lipoxygenase gene expression: evidence that 15-lipoxygenase is a mutator gene

Human 15-lipoxygenase (h15-LO) is present on chromosome 17p13.3 in close proximity to the tumor-suppressor gene, p53. 15-LO is implicated in antiinflammation, membrane remodeling, and cancer development/metastasis. The murine BALB/c embryo fibroblast cell line, (10)1val, expresses p53 in mutant (mt) conformation when grown at 39 degrees C and in wild-type conformation when grown at 32 degrees C. Transfection of h15-LO promoter constructs (driving luciferase reporter) into (10)1val cells and into p53-deficient (10)1 cells resulted in a marked increase in h15-LO promoter activity in (10)1val cells at 39 degrees C, but not at 32 degrees C, or as compared with (10)1 cells. Transfection of h15-LO promoter deletion constructs, however, resulted in total loss of activity in both cell types at 32 degrees C and 39 degrees C. Cotransfection of (10)1 cells with h15-LO promoter (driving luciferase reporter) along with increasing levels of a mt p53 expression vector demonstrated dose-dependent capacity of mt p53 to induce 15-LO promoter activity. No effect was observed with wild-type p53. In contrast to h15-LO promoter activity, (10)1val cells had significantly lower levels of endogenous (murine) 12/15-LO (mouse analog of h15-LO) mRNA and protein when grown at 39 degrees C compared with cells grown at 32 degrees C. Our data support the hypothesis that loss of a tumor-suppressor gene (p53), or "gain-of-function activities" resulting from the expression of its mutant forms, regulates 15-LO promoter activity in man and in mouse, albeit in directionally opposite manners. The studies define a direct link between 15-LO activity and an established tumor-suppressor gene located in close chromosomal proximity.

Cyclic stretch induces both apoptosis and secretion in rat alveolar type II cells

We examined the effects of short-term cyclic stretch on both phosphatidylcholine (PC) secretion and apoptosis in primary cultures of rat alveolar type II cells. A 22% cyclic stretch (3 cycles/min) was applied to type II cells cultured on silastic membranes using a Flexercell strain unit. This induced, after a lag period of about 1 h, a small, but significant release of [3H]PC from prelabelled cells. In addition, stretch increased nuclear condensation, the generation of oligosomal DNA fragments and the activation of caspases. Similar responses were triggered by sorbitol-induced osmotic shock, but not by the secretagogue ATP. We conclude that stretch can induce both apoptosis and PC secretion in alveolar type II cells and propose that these diverse responses occur within the lung as a consequence of normal respiratory distortion of the alveolar epithelium.

Antioxidative and proapoptotic effects of riluzole on cultured cortical neurons

Riluzole is used clinically in patients with amyotrophic lateral sclerosis. As oxidative stress, in addition to excitotoxicity, may be a major mechanism of motoneuron degeneration in patients with amyotrophic lateral sclerosis, we examined whether riluzole protects against nonexcitotoxic oxidative injury. Probably reflecting its weak antiexcitotoxic effects, riluzole (1-30 microM) attenuated submaximal neuronal death induced by 24-h exposure to 30 microM kainate or NMDA, but not that by 100 microM NMDA, in cortical cultures. Riluzole also attenuated nonexcitotoxic oxidative injury induced by exposure to FeCl3 in the presence of MK-801 and CNQX. Consistent with its antioxidative effects, riluzole reduced Fe3+-induced lipid peroxidation, and inhibited cytosolic phospholipase A2. By contrast, riluzole did not attenuate neuronal apoptosis induced by staurosporine. Rather unexpectedly, 24-48-h exposure to 100-300 microM riluzole induced neuronal death accompanied by nuclear and DNA fragmentations, which was attenuated by caspase inhibitor carbobenzyloxy-Val-Ala-Asp-fluoromethyl ketone but not by protein synthesis inhibitor cycloheximide. The present study demonstrates that riluzole has direct antioxidative actions, perhaps in part by inhibiting phospholipase A2. However, in the same neurons, riluzole paradoxically induces neuronal apoptosis in a caspase-sensitive manner. Considering current clinical use of riluzole, further studies are warranted to investigate its potential cytolethal effects.

Modulation of antioxidant enzymes and apoptosis in mice by dietary lipids and treadmill exercise

The current experiments were designed to study the effect of dietary n-6 and n-3 polyunsaturated fatty acids on antioxidant enzyme activity and dexamethasone (DEX)-induced apoptosis in spleen cells of sedentary (Sed) and treadmill-exercised (Ex) ICR male mice. Two-month-old mice maintained on AIN 76 formula diet, supplemented with either 5% corn oil (CO) or 5% fish oil (FO) diets, were trained on a treadmill to run from 45 to 50 min 1 km/day, 6 days a week for 12 weeks. After 12 weeks of exercise, both Sed and Ex groups were sacrificed. Blood and various tissues, including spleen, were collected asceptically. Increased serum and spleen homogenate peroxide [malondialdehyde (MDA)] levels were observed in mice fed FO (n-3 PUFA) diets, compared to mice fed CO (n-6 PUFA). However, exercise did not alter MDA levels in either CO- or FO-fed mice. Feeding n-3 PUFA significantly increased superoxide dismutase (SOD), catalase, and glutathione peroxidase activity of spleen homogenates. Exercise also significantly increased SOD and peroxidase in CO-fed animals, whereas catalase, glutathione peroxidase, and glutathione transferase were higher in FO-fed mice, compared to the Sed group. Apoptosis and necrosis were quantitated in splenocytes incubated with or without 1 microM Dex in RPMI medium for 8 and 24 hr. Cells were stained with Annexin V and propidium iodide (PI) for apoptotic and necrotic cells. FO-fed mice showed higher apoptosis (64 vs 50%) and necrosis (40 vs 22%) in spleen cells than CO-fed mice. Cells from FO-fed mice, incubated in medium alone, showed increased apoptosis (112%) 24 hr after incubation, and necrosis (37 and 70%) at 8 and 24 hr of incubation, compared to CO-fed mice. In Ex group, apoptosis was increased in both CO- and FO-fed mice only at 24 hr after incubation. In summary, these results indicate that FO (n-3 PUFA-enriched) diets increase apoptosis and antioxidant enzyme activity in spleen cells, probably due to elevated lipid peroxides.

A relationship between 5-lipoxygenase-activating protein and bcl-xL expression in murine pro-B lymphocytic FL5.12 cells

Inhibitors of 5-lipoxygenase-activating protein (FLAP) have been found to induce apoptosis. The current study examined the expression of FLAP and bcl family proteins and the induction of apoptosis in interleukin-3-dependent control and bcl-xL-overexpressing FL5.12 cell lines after treatment with MK886, a specific FLAP inhibitor. FL5.12 cells contained a substantial amount of FLAP protein and mRNA but surprisingly had no measurable 5-lipoxygenase protein or 5-, 12-, or 15-lipoxygenase activity. The basal level of FLAP protein in cells overexpressing bcl-xL was 70% less than in controls. FLAP disappeared 4 h after withdrawal of interleukin-3 in bcl-xL cells but not in control cells, which underwent apoptosis. A dose- and time-response study revealed that 5 nmol of MK886/10(6) cells was sufficient to induce apoptosis both in control and bcl-xL cells, respectively, but to different degrees. bcl-xL and bcl-2 proteins, but not bax or FLAP, were decreased by 4 h after 5 nmol of MK886/10(6) cells in both cell lines, although the higher levels of bcl-xL in overexpressors took longer to disappear. This early loss of bcl-xL and bcl-2 was not attributable to generalized proteolysis, as shown by Coomassie Blue staining and by the maintenance of bax. Caspase-3 was activated 2 h after MK886 treatment in control cells but not in bcl-xL cells. Inhibition of caspase-3 decreased MK886-induced apoptosis by 50% in control cells. Inhibition of this caspase after MK886 treatment was unable to prevent the loss of bcl-xL in control cells but did provide partial protection for the loss of the transfected form, but not the endogenous form, in overexpressing cells. These data indicate that MK886 induces extensive apoptosis that is partially caspase-3 dependent and may be related to a rapid loss of bcl-xL. Although caspase-3 inhibitors had no effect on the loss of bcl-xL, other caspases or protease systems may still be involved. The absence of 5-lipoxygenase in cells containing FLAP, the lower level of FLAP in bcl-xL cells, the apoptosis-inducing activity of MK886, and the rapid loss of bcl-xL and bcl-2 proteins after treatment with MK886 strongly indicate that FLAP has activities unrelated to lipoxygenase and suggest a possible functional or regulatory link between these proteins, which share similar subcellular localizations.

BMD188, A novel hydroxamic acid compound, demonstrates potent anti-prostate cancer effects in vitro and in vivo by inducing apoptosis: requirements for mitochondria, reactive oxygen species, and proteases

A newly synthesized cyclic hydroxamic acid compound, BMD188 [cis-1-hydroxy-4-(1-naphthyl)-6-octylpiperidine-2-one], was found to induce the apoptotic death of cultured prostate cancer cells by activating caspase-3. Orally administered BMD188 significantly inhibited the primary growth of prostate cancer cells (Du145) orthotopically implanted into SCID mice. Mechanistic studies indicated that BMD188 did not alter the protein levels of several Bcl-2 family members. In contrast, the BMD188 effect required three essential factors: reactive oxygen species (ROS), the mitochondrial respiratory chain function, and proteases. First, the apoptosis-inducing effect of BMD188 could be blocked by ROS scavengers such as Desferal. Second, both BMD188-induced PARP cleavage as well as PC3 cell apoptosis could be dramatically inhibited by several complex-specific mitochondrial respiration blockers. The involvement of mitochondria was also supported by the observations that BMD188 dramatically altered the mitochondrial distribution and morphology without affecting the cellular ATP levels. Finally, the apoptosis-inducing effect of BMD188 in PC3 cells could be significantly inhibited by serine protease inhibitors (TPCK and TLCK) as well as by caspase inhibitors (zVAD-fmk and DEVD-CHO). Collectively, the present study suggests that BMD188 and its analogs may find clinical applications in the treatment of prostate cancer patients by inducing apoptotic death of prostate cancer cells.

Actin cleavage in various tumor cells is not a critical requirement for executing apoptosis

Actin is a major cytoskeletal protein which is involved in many physiological cellular functions such as motility, cell shape, and adhesion. Recently, actin has also been reported to be cleaved by apoptotic proteases (i.e., caspases) and this cleavage is thought to contribute to the apoptotic process. However, conflicting data also exists as to whether actin represents a true caspase substrate during apoptosis induction in vivo (i.e., inside the cells). In this study, we critically examined the actin cleavage patterns during apoptosis of several tumor cell lines derived from three different species (i.e., mouse, rat, and human). Our findings demonstrate that: 1) actin cleavage in vivo is not a common phenomenon since apoptosis caused by multiple inducers in most cell types examined occurs without evidence of actin degradation; and 2) in certain cell types (e.g., U937), spontaneous, actin cleavage is observed which is not prevented by various specific chemical/peptide inhibitors of proteases such as caspases or serine proteases although apoptosis per se is retarded by some of these inhibitors. Our results conclude that actin is not a critical substrate for apoptotic proteases in vivo during apoptosis.