Author Correction: Bisphosphonate enhances TRAIL sensitivity to human osteosarcoma cells via death receptor 5 upregulation.

After publication of this article, the authors noticed an error in the figure section.

Modulation of the expression of sphingosine 1-phosphate 2 receptors regulates the differentiation of pre-adipocytes.

Sphingosine 1-phosphate (S1P) is a bioactive lipid mediator that regulates multiple signals through S1P receptors responsible for biological responses. In particular, the S1P2 receptor has distinct roles in the S1P­mediated differentiation of certain cell types. The present study was the first, to the best of our knowledge, to report the role of the S1P2 receptor in the adipocyte differentiation of 3T3­L1 pre­adipocytes. In order to investigate the influence of S1P2 receptors in the anti­adipogenic effects of S1P, S1P2 receptor silencing and overexpression of were used. S1P2 overexpression with adenoviral vectors inhibited adipogenesis and inhibited the expression of peroxisome proliferator­activated receptor γ (PPARγ), adiponectin and CCAAT/enhancer binding protein­α, which were upregulated following incubation in differentiation media. Furthermore, S1P completely lost its ability to impair adipogenic differentiation following silencing of S1P2. Silencing of the S1P2 receptor additionally blocked the downregulation of PPARγ protein and phospho­c­Jun N­terminal kinase protein induced by S1P treatment. In conclusion, the present study demonstrated that the S1P2 receptor is a key signaling molecule in the S1P­dependent inhibition of adipogenic differentiation and additionally suggested that selective targeting of S1P2 receptors may have clinical applications for the treatment of obesity.

Activation of S1P2 receptor, a possible mechanism of inhibition of adipogenic differentiation by sphingosine 1­phosphate.

Sphingosine 1­phosphate (S1P) belongs to a significant group of signaling sphingolipids and exerts most of its activity as a ligand of G­protein­coupled receptors. In our previous study, S1P demonstrated a novel biological activity with the anti­adipogenesis of 3T3­L1 preadipocytes. In the present study, we identified a possible mechanism of S1P­mediated anti­adipogenic effects, particularly in target pathways of the S1P receptors, including S1P1 and S1P2. The mRNA levels of S1P1 and S1P2 receptors were increased by MDI media treatment, whereas S1P treatment highly induced S1P2 but not S1P1 receptor protein in adipocytes. Triglyceride accumulation assay using an agonist and antagonist of S1P receptors revealed that S1P2 receptor was only involved in S1P­mediated anti­adipogenic effects. Furthermore, pharmacological inhibition of S1P2 signals completely retrieved S1P­mediated downregulation of the transcriptional levels of peroxisome proliferator­activated receptor γ, CCAAT/enhancer binding protein α and adiponectin, which are markers of adipogenic differentiation. This study demonstrated that S1P2 receptor signals may regulate the S1P­mediated anti­adipogenic differentiation and also identifies the S1P2 receptor as a possible mechanism of anti­adipogenic differentiation.

Sphingosine-1-phosphate inhibits the adipogenic differentiation of 3T3-L1 preadipocytes.

Sphingosine-1-phosphate (S1P) is a pluripotent lipid mediator that transmits signals through G-protein-coupled receptors to control diverse biological processes. The novel biological activity of S1P in the adipogenesis of 3T3-L1 preadipocytes was identified in the present study. S1P significantly decreased lipid accumulation in maturing preadipocytes in a dose­dependent manner. In order to understand the anti­adipogenic effects of S1P, preadipocytes were treated with S1P, and the change in the expression of several adipogenic transcription factors and enzymes was investigated using quantitative RT-PCR. S1P downregulated the transcriptional levels of the peroxisome proliferator-activated receptor γ, CCAAT/enhancer binding proteins and adiponectin, which are markers of adipogenic differentiation. The effects of S1P on the levels of mitogen­activated protein kinase (MAPK) signals in preadipocytes were also investigated. The activation of JNK and p38 were downregulated by S1P treatment in human preadipocytes. In conclusion, the results of this study suggest that S1P alters fat mass by directly affecting adipogenesis. This is mediated by the downregulation of adipogenic transcription factors and by inactivation of the JNK and p38 MAPK pathways. Thus, selective targeting of the S1P receptors and sphingosine kinases may have clinical applications for the treatment of obesity.

FTY720 protects neuronal cells from damage induced by human prion protein by inactivating the JNK pathway.

Prion diseases affect the central nervous system (CNS) in humans and animals, and are associated with the conversion of the cellular prion protein (PrPC) to the misfolded isoform (PrPSc). FTY720, an immune modulator and synthetic analogue of sphingosine-1-phosphate (S1P), activates S1P receptors and has been shown to be effective in experimental models of transplantation and autoimmunity, including multiple sclerosis. Whereas the immune modulatory functions of FTY720 have been extensively investigated, the other functions of FTY720 are not yet well understood. In this study, we investigated the effects of FTY720 phosphate (FTY720-p) on prion protein-mediated neuronal cell death, as well as its effects on intracellular apoptotic pathways. Treatment with FTY720-p protected neuronal cells from synthetic human prion protein peptide [PrP (106­126)]-mediated damage and prevented mitochondrial dysfunction by inhibiting the activation of c-jun N-terminal kinase. Moreover, FTY720-p prevented the PrP (106­126)-induced reduction in mitochondrial potential, the translocation of Bax to the mitochondria and the release of cytochrome c. To the best of our knowledge, this study is the first to demonstrate the effects of FTY720 on prion protein-mediated neurotoxicity and to suggest that FTY720 has therapeutic potential in prion diseases.

Autophagy induced by the class III histone deacetylase Sirt1 prevents prion peptide neurotoxicity.

Sirtuin 1 (Sirt1) is a class III histone deacetylase that mediates the protective effects of neurons in neurodegenerative disorders, including Alzheimer's and prion disease. However, the mechanism directly involved in neuroprotection is still poorly understood. Recent evidence has demonstrated that activating Sirt1 induces autophagy, and that activating autophagy protects neurons against neurodegenerative disorders by regulating mitochondrial homeostasis. Thus, we focused on the mechanism of the Sirt1-mediated neuroprotective effect that was associated with regulating mitochondrial homeostasis via autophagy. Adenoviral-mediated Sirt1 overexpression prevented prion protein (PrP)(106-126)-induced neurotoxicity via autophagy processing. Moreover, Sirt1-induced autophagy protected against the PrP(106-126)-mediated decrease in the mitochondrial membrane potential value. Additionally, Sirt1 overexpression decreased PrP(106-126)-induced Bax translocation to the mitochondria and cytochrome c release into the cytosol. Sirt1 knockdown using small interfering (si) RNAs induced downregulation of Sirt1 protein expression and sensitized neuron cells to PrP(106-126)-induced cell death and mitochondrial dysfunction. Knockdown of autophagy-related 5 (ATG5) using small interfering RNA decreased autophagy-related 5 and autophagy marker microtubule-associated protein 1 light chain 3-II protein levels and blocked the effect of a Sirt1 activator against PrP(106-126)-induced mitochondrial dysfunction and neurotoxicity. Taken together, this study is the first report demonstrating that autophagy induced by Sirt1 activation plays a pivotal role protecting against prion-induced neuron cell death and also suggests that regulating autophagy including which by Sirt1 activation may be a therapeutic target for neurodegenerative disorders including the prion disease.

Gingerol-induced hypoxia-inducible factor 1 alpha inhibits human prion peptide-mediated neurotoxicity.

Prion diseases are a family member of neurodegenerative disorders caused by the accumulation of misfolded-prion proteins (scrapie form of PrP, PrP(Sc)). The accumulation of PrP(Sc) in the brain leads to neurotoxicity by the induction of mitochondrial-apoptotic pathways. Recent studies implicated gingerol in protection against neurodegeneration. However, the basis of the neuroprotection in prion disease remains unclear. Thus, we investigated the influence of gingerol on prion peptide-induced neuronal damage. Gingerol blocked PrP(106-126)-mediated neurotoxicity by protecting mitochondrial function. Moreover, the protective effect of gingerol against PrP(106-126)-induced mitochondrial damage was associated with hypoxia-inducible factor 1 alpha (HIF-1α) expression. Gingerol-induced HIF-1α expression inhibited the PrP(106-126)-induced mitochondrial dysfunction. On the other hand, inhibition of gingerol-induced HIF-1 α expression attenuated the gingerol-mediated neuroprotective effect. Here, we demonstrate for the first time that treatment with gingerol prevents prion peptide-mediated neuronal cell death and that the neuroprotection is induced by HIF-1α-mediated signals. This study suggests that treatment with gingerol may provide a novel therapeutic strategy for prion-mediated neurotoxicity.

Sphingosine-1-phosphate inhibits interleukin-1ß-induced inflammation in human articular chondrocytes.

Sphingosine-1-phosphate (S1P) is a pluripotent lipid mediator that transmits signals through a family of G-protein-coupled receptors (GPCRs) to control diverse biological processes including inflammation and wound-healing. In this study, a novel biological activity of S1P in articular chondrocytes was identified. Human primary chondrocytes were cultured in a monolayer. Reverse transcription-polymerase chain reaction (RT-PCR) and western blotting were performed to detect genes and proteins involved in inflammation and cartilage degradation when human primary chondrocytes were stimulated by interleukin (IL)-1ß. Matrix metalloproteinase (MMP)-2 and MMP-9 activity was evaluated by gelatin zymography. Glycosaminoglycan (GAG) degradation was evaluated using the dimethylene blue method. Prostaglandin E2 (PGE2) was measured by enzyme-linked immunosorbent assay (ELISA). By using the S1P1 receptor agonist and antagonist, we discovered the key role played by S1P1 in the S1P-dependent inhibition of IL-1ß-induced inflammation in human chondrocytes. S1P dose-dependently inhibited IL-1ß-induced NF-κB p65, cyclooxygenase (COX)-2, MMP-1, MMP-3, MMP-13 and MMP-14 mRNA expression in human chondrocytes and IL-1ß-induced PGE2 synthesis and GAG degradation in human cartilage explants. W146, a known S1P1 receptor antagonist, inhibited the active form of NF-κB p65 and COX-2 expression induced by IL-1ß. The anti-inflammatory action of the S1P1 receptor agonist SEW2871 was similar to that of S1P. This study demonstrates that S1P has anti-inflammatory effects on chondrocytes via the S1P1 receptor. Our data suggest that targeting S1P and S1P1 may be a potential therapy for arthritis.

Sulforaphane induced adipolysis via hormone sensitive lipase activation, regulated by AMPK signaling pathway.

Sulforaphane, an aliphatic isothiocyanate derived from cruciferous vegetables, is known for its antidiabetic properties. The effects of sulforaphane on lipid metabolism in adipocytes are not clearly understood. Here, we investigated whether sulforaphane stimulates lipolysis. Mature adipocytes were incubated with sulforaphane for 24h and analyzed using a lipolysis assay which quantified glycerol released into the medium. We investigated gene expression of hormone-sensitive lipase (HSL), and levels of HSL phosphorylation and AMP-activated protein kinase on sulforaphane-mediated lipolysis in adipocytes. Sulforaphane promoted lipolysis and increased both HSL gene expression and HSL activation. Sulforaphane suppressed AMPK phosphorylation at Thr-172 in a dose-dependent manner, which was associated with a decrease in HSL phosphorylation at Ser-565, enhancing the phosphorylation of HSL Ser-563. Taken together, these results suggest that sulforaphane promotes lipolysis via hormone sensitive lipase activation mediated by decreasing AMPK signal activation in adipocytes.

Insulin-like growth factor-1 protects against prion peptide-induced cell death in neuronal cells via inhibition of Bax translocation.

Insulin-like growth factor-1 (IGF-1) is one of the most important components of bovine colostrum. It exhibits antiapoptotic and antioxidative activities. Prion diseases are neurodegenerative disorders caused by cell death through mitochondrial dysfunction and increasing generation of reactive oxygen species (ROS). This study examined the protective effect of IGF-1 on residues 106-126 of the cellular prion protein [PrP (106-126)]-mediated mitochondrial neurotoxicity and oxidative stress. In SH-SY5Y human neuronal cells, treatment with PrP (106-126) decreased the cell viability and IGF-1 pretreatment markedly blocked the PrP (106-126)-induced neuronal cell death. IGF-1 inhibited PrP (106-126)-induced intracellular ROS generation and mitochondrial oxidative stress. In addition, IGF-1 blocked the translocation of the Bax protein to the mitochondria induced by PrP (106-126). These results demonstrate that IGF-1 protects neuronal cells against PrP (106-126)-mediated neurotoxicity through an antioxidative effect and blockage of mitochondrial Bax translocation. The results also suggest that regulation of IGF-1 secretion may have a therapeutic potential in the management of mitochondrial dysfunction and oxidative stress-induced neurodegeneration.

Antiobesity activity of a sphingosine 1-phosphate analogue FTY720 observed in adipocytes and obese mouse model.

Higher levels of body fat are associated with an increased risk for development numerous adverse health conditions. FTY720 is an immune modulator and a synthetic analogue of sphingosine 1-phosphate (S1P), activated S1P receptors and is effective in experimental models of transplantation and autoimmunity. Whereas immune modulation by FTY720 has been extensively studied, other actions of FTY720 are not well understood. Here we describe a novel role of FTY720 in the prevention of obesity, involving the regulation of adipogenesis and lipolysis in vivo and in vitro. Male C57B/6J mice were fed a standard diet or a high fat diet (HFD) without or with FTY720 (0.04 mg/kg, twice a week) for 6 weeks. The HFD induced an accumulation of large adipocytes, down-regulation of phosphorylated AMP-activated protein kinase α (p-AMPKα) and Akt (p-Akt); down-regulation of hormone- sensitive lipase (HSL), adipose triglyceride lipase (ATGL) and perilipin mRNA as well as up-regulation of phosphorylated HSL (p-HSL, Ser563) and glycogen synthase kinase 3 α/ß (p-GSK3α/ß). All these effects were blunted by FTY720 treatment, which inhibited adipogenesis and promoted lipolysis. Also, FTY720 significantly decreased lipid accumulation in maturing preadipocytes. FTY720 down-regulated the transcriptional levels of the PPARγ, C/EBPα and adiponectin, which are markers of adipogenic differentiation. FTY720 significantly increased the release of glycerol and the expression of the HSL, ATGL and perilipin, which are regulators of lipolysis. These results show that FTY720 prevented obesity by modulating adipogenesis and lipolysis, and suggest that FTY720 is used for the treatment of obesity.

Autophagy induced by resveratrol prevents human prion protein-mediated neurotoxicity.

Our previous study revealed that resveratrol blocks prion protein peptide PrP(106-126)-induced neurotoxicity. However, the mechanism of resveratrol-mediated neuroprotection in prion diseases is not clear. Resveratrol initiates neuroprotective effects via the activation of autophagy, which protects organelles, cells, and organisms against misfolded protein-disorders, including Alzheimer's disease and Parkinson's disease via regulation of mitochondrial homeostasis. Thus, we focused on elucidating the mechanisms responsible for resveratrol-mediated neuroprotection related to mitochondrial homeostasis as a result of autophagy activation. Resveratrol prevented PrP(106-126)-induced neuronal cell death by activating autophagy. Moreover, resveratrol-induced autophagy prevented the PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. Our results indicate that treatment with resveratrol appears to protect against neurotoxicity caused by prion protein peptides and the neuroprotection is induced by resveratrol-mediated autophagy signals.

18ß-Glycyrrhetinic acid inhibits adipogenic differentiation and stimulates lipolysis.

18ß-Glycyrrhetinic acid (18ß-GA) obtained from the herb liquorice has various pharmacological properties including anti-inflammatory and anti-bacterial activities. However, potential biological anti-obesity activities are unclear. In this study, novel biological activities of 18ß-GA in the adipogenesis of 3T3-L1 preadipocytes and in lipolysis of differentiated adipocytes were identified. Mouse 3T3-L1 cells were used as an in vitro model of adipogenesis and lipolysis, using a mixture of insulin/dexamethasone/3-isobutyl-1-methylxanthine (IBMX) to induce differentiation. The amount of lipid droplet accumulation was determined by an AdipoRed assay. The expression of several adipogenic transcription factors and enzymes was investigated using real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blotting. 18ß-GA dose-dependently (1-40 µM) significantly decreased lipid accumulation in maturing preadipocytes. In 3T3-L1 preadipocytes, 10 µM of 18ß-GA down-regulated the transcriptional levels of the peroxisome proliferator-activated receptor γ, CCAAT/enhancer-binding protein α and adiponectin, which are markers of adipogenic differentiation via Akt phosphorylation. Also, in differentiated adipocytes, 18ß-GA increased the level of glycerol release and up-regulated the mRNA of hormone-sensitive lipase, adipose TG lipase and perilipin, as well as the phosphorylation of hormone-sensitive lipase at Serine 563. The results indicate that 18ß-GA alters fat mass by directly affecting adipogenesis in maturing preadipocytes and lipolysis in matured adipocytes. Thus, 18ß-GA may be useful for the treatment of obesity.

Melatonin-induced autophagy protects against human prion protein-mediated neurotoxicity.

  Melatonin has neuroprotective effects in the models of neurodegenerative disease including Alzheimer's and Parkinson's disease. Several studies have shown that melatonin prevents neurodegeneration by regulation of mitochondrial function. However, the protective action of melatonin has not been reported in prion disease. We investigated the influence of melatonin on prion-mediated neurotoxicity. Melatonin rescued neuronal cells from PrP(106-126)-induced neurotoxicity by prevention of mitochondrial dysfunction. Moreover, the protective effect of melatonin against mitochondrial dysfunction was related with autophagy activation. Melatonin-treated cells were dose-dependently increased in LC3-II, an autophagy marker. Melatonin-induced autophagy prevented a PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. On the other hand, downregulation of autophagy protein 5 with Atg5 siRNA or the autophagy blocker 3-methyladenine prevented the melatonin-mediated neuroprotective effects. This is the first report demonstrating that treatment with melatonin appears to protect against prion-mediated neurotoxicity and that the neuroprotection is induced by melatonin-mediated autophagy signals. The results of this study suggest that regulation of melatonin is a therapeutic strategy for prion peptide-induced apoptosis.

SIRT1, a histone deacetylase, regulates prion protein-induced neuronal cell death.

Prion diseases associated with the conversion of the cellular prion protein (PrP(C)) to the misfolded isoform (PrP(Sc)), affect the central nervous system (CNS) of humans and animals. Resveratrol, an activator of class III histone deacetylase SIRT1, is important in attenuating cellular injury and oxidative stress. The present study investigated the effects of SIRT1 activation on prion protein-mediated neuronal cell death and examined its possible signals in intracellular apoptotic pathways. Resveratrol treatment significantly increased both SIRT1 protein expression and SIRT1 activity and protected neuronal cells against PrP (106-126)-induced cell death. Resveratrol-mediated SIRT1 activation decreased the acetylation of p53 and p65 induced by prion protein and SIRT1 inhibitor. SIRT1 activation also inhibited PrP (106-126)-mediated p38 mitogen-activating protein kinase (MAPK) activation and caspase-3 cleavage, and increased the expression of anti-apoptotic Bcl-xL protein. Furthermore, SIRT1 overexpression by using adenoviral vector protected neuronal cells against PrP (106-126). These results indicate that resveratrol inhibits PrP (106-126)-induced neuronal cell death by regulating SIRT1 activity and SIRT-related signaling, and suggest that prion-related disease may be attenuated by SIRT1 activation or by intake of SIRT1-activating molecules.

Hypoxia-inducible factor-1 α regulates prion protein expression to protect against neuron cell damage.

The human prion protein fragment, PrP (106-126), may contain a majority of the pathological features associated with the infectious scrapie isoform of PrP, known as PrP(Sc). Based on our previous findings that hypoxia protects neuronal cells from PrP (106-126)-induced apoptosis and increases cellular prion protein (PrP(C)) expression, we hypothesized that hypoxia-related genes, including hypoxia-inducible factor-1 alpha (HIF-1α), may regulate PrP(C) expression and that these genes may be involved in prion-related neurodegenerative diseases. Hypoxic conditions are known to elicit cellular responses designed to improve cell survival through adaptive processes. Under normoxic conditions, a deferoxamine-mediated elevation of HIF-1α produced the same effect as hypoxia-inhibited neuron cell death. However, under hypoxic conditions, doxorubicin-suppressed HIF-1α attenuated the inhibitory effect on neuron cell death mediated by PrP (106-126). Knock-down of HIF-1α using lentiviral short hairpin (sh) RNA-induced downregulation of PrP(C) mRNA and protein expression under hypoxic conditions, and sensitized neuron cells to prion peptide-mediated cell death even in hypoxic conditions. In PrP(C) knockout hippocampal neuron cells, hypoxia increased the HIF-1α protein but the cells did not display the inhibitory effect of prion peptide-induced neuron cell death. Adenoviruses expressing the full length Prnp gene (Ad-Prnp) were utilized for overexpression of the Prnp gene in PrP(C) knockout hippocampal neuron cells. Adenoviral transfection of PrP(C) knockout cells with Prnp resulted in the inhibition of prion peptide-mediated cell death in these cells. This is the first report demonstrating that expression of normal PrP(C) is regulated by HIF-1α, and PrP(C) overexpression induced by hypoxia plays a pivotal role in hypoxic inhibition of prion peptide-induced neuron cell death. These results suggest that hypoxia-related genes, including HIF-1α, may be involved in the pathogenesis of prion-related diseases and as such may be a therapeutic target for prion-related neurodegenerative diseases.

Translocation of cellular prion protein to non-lipid rafts protects human prion-mediated neuronal damage.

Prions are the causative agents of transmissible spongiform encephalopathies, such as variant Creutzfeldt-Jakob disease in humans. Cellular prion proteins (PrPC) connect with cholesterol- and glycosphingolipid-rich lipid rafts through association of their glycosyl-phosphatidylinositol (GPI) anchor with saturated raft lipids and interaction of their N-terminal regions. Our previous study showed that cellular cholesterol enrichment prevented PrP(106-126)-induced neuronal death. We have now studied the influence of membrane cholesterol in PrP(106-126)-mediated neurotoxicity and identified membrane domains involved in this activity. We found that PrPC is normally distributed in lipid rafts, but high membrane cholesterol levels as a result of cholesterol treatment led to the translocation of PrPC from lipid rafts to non-lipid rafts. Moreover, cholesterol-mediated PrPC translocation protects PrP(106-126)-mediated apoptosis and p-38 activation and caspase-3 activation. In a mitochondrial functional assay including mitochondrial transmembrane potential, cholesterol treatment prevented the loss of mitochondrial potential, translocation of Bax and cytochrome c by prion protein fragment. Our results indicate that modulation of the PrPC location appears to protect against neuronal cell death caused by prion peptides. The results of this study suggest that regulation of membrane cholesterol affects the translocation of PrPC, which in turn regulates PrP(106-126)-induced mitochondrial dysfunction and neurotoxicity.

Roles of putative sodium-hydrogen antiporter (SHA) genes in S. coelicolor A3(2) culture with pH variation.

Culture pH change has some important roles in signal transduction and secondary metabolism. We have already reported that acidic pH shock enhanced actinorhodin production in Streptomyces coelicolor. Among many potential governing factors on pH variation, the putative Na(+)/H(+) antiporter (sha) genes in S. coelicolor have been investigated in this study to elucidate the association of the sha on pH variation and secondary metabolism. Through the transcriptional analysis and overexpression experiments on 8 sha genes, we observed that most of the sha expressions were promoted by pH shock, and in the opposite way the pH changes and actinorhodin production were enhanced by the overexpression of each sha. We also confirmed that sha8 especially has a main role in maintaining cell viability and pH homeostasis through Na(+) extrusion, in salt effect experiment under the alkaline medium condition by deleting sha8. Moreover, this gene was observed to have a function of pH recovery after pH variation such as the pH shock, being able to cause the sporulation. However, actinorhodin production was not induced by the only pH recovery. The sha8 gene could confer on the host cell the ability to recover pH to the neutral level after pH variation like a pH drop. Sporulation was closely associated with this pH recovery caused by the action of sha8, whereas actinorhodin production was not due to such pH variation patterns alone.

Inhibition of the ubiquitin-proteasome system sensitizes TRAIL-resistant prostate cancer cells by up-regulation of death receptor 5.

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a type II transmembrane cytokine and a potent inducer of apoptosis in cancer cells. However, some cancer cells, particularly prostate cancer cells, such as LNCaP cells, were found to be resistant to TRAIL. In the present study, we demonstrate that the proteasome inhibitor ALLN significantly enhanced TRAIL-induced apoptosis by up-regulating TRAIL/Apo2L death receptor 5 expression in LNCaP cells. LNCaP cells were exposed to ALLN for 3 h and treated with recombinant TRAIL protein. ALLN alone induced a 20% cell death after a 3­h treatment; however, pretreatment with ALLN induced death to more than 80% of cells after 3 h of TRAIL treatment. ALLN also enhanced the cell death of TRAIL-sensitive/resistant prostate cancer and other cancer cell lines. Western blotting results showed that the combination of ALLN and TRAIL increased the levels of activated caspase-8, -3 and DR-5 in LNCaP cells. Furthermore, we observed an increase in DR-5 expression following 3 h of treatment of ALLN alone. Taken together, our findings indicate that ALLN enhances TRAIL-induced apoptosis in LNCaP cells by up-regulating DR-5 expression. Thus, our results suggest that the combination of ALLN and TRAIL is a novel therapeutic strategy in TRAIL-resistant tumors.

Bee venom phospholipase A2 prevents prion peptide induced-cell death in neuronal cells.

Bee venom phospholipase A2 (bvPLA2) is a prototypic group III enzyme which consists of unique N-terminal and C-terminal domains and a central secretory PLA2 (sPLA2) domain. This sPLA2 domain is highly homologous with human group III sPLA2. Current evidence suggests that group III sPLA2 may affect some neuronal functions, such as neuritogenesis, neurotransmitter release and neuronal survival. The prion diseases are neurodegenerative disorders characterized by the conversion of the normal cellular prion (PrPC) to the misfolded isoform scrapie prion protein (PrPSc). PrPSc accumulation in the central nervous system (CNS) leads to neurotoxicity by inhibition of the PI3K/AKT pathway or activation of p38 mitogen-activated protein kinase (MAPK) pathways. In the present study, we found that bvPLA2 inhibited prion protein (PrP) fragment (106-126)-induced neuronal cell death. PrP(106-126)-mediated increase of p-p38 MAPK and cleaved caspases and decrease of p-AKT were blocked by bvPLA2 treatment. These results indicate that increasing PLA2, including the group III sPLA2 is key to regulating PrP(106-126)-mediated neurotoxicity. Taken together, the results of this study suggest that specific modulation of PLA2 appears to prevent neuronal cell death caused by prion peptides.