A plausible involvement of plasmalemmal voltage-dependent anion channel 1 in the neurotoxicity of 15-deoxy-Δ12,14 -prostaglandin J2.

INTRODUCTION: 15-deoxy-Δ12,14 -prostaglandin J2 (15d-PGJ2 ) causes neuronal apoptosis independently of its nuclear receptor, peroxysome-proliferator activated receptor γ. Its membrane receptor, chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2), did not also mediate the neurotoxicity of 15d-PGJ2 . In the present study, we ascertained whether membrane targets beside CRTH2 were involved in the neurotoxicity of 15d-PGJ2 . METHODS: Neuronal membrane targets for 15d-PGJ2 were separated by two-dimensional electrophoresis, identified by proteomic approach. Their localizations were detected by microscopic immunofluorescence study. Cell viability and apoptosis was evaluated by MTT-reducing activity and caspase-3 activity, respectively. RESULTS: Voltage-dependent anion channel 1 (VDAC1) was identified as one of membrane targets for 15d-PGJ2 . Modification of VDAC1 with 15d-PGJ2 was detected by pull-down assay. VDAC1 was detected in the plasma membrane and localized on the neuronal cell surface. VDAC1 was partially colocalized with membrane targets for 15d-PGJ2 . The anti-VDAC antibody significantly attenuated the neurotoxicity of 15d-PGJ2 , accompanied by the suppression of the 15d-PGJ2 -stimulated caspase-3. CONCLUSION: These findings suggested that the plasmalemmal VDAC might be involved in the neurotoxicity of 15d-PGJ2 .

The Anti-Neuron-Specific Enolase Antibody Induced Neuronal Cell Death in a Novel Fashion.

Suppression of ubiquitin proteasome pathway (UPP) and stimulation of caspase-3 are involved in neurodegeneration. Can UPP activators and caspase-3 inhibitors ameliorate neurodegeneration? Here, we found a novel neuronal cell death accompanied with UPP activation and caspase-3 inhibition. Recently, plasmalemmal neuron-specific enolase (NSE) has been identified as one of membrane targets of 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). 15d-PGJ2 induces neuronal apoptosis via activating caspase-3 and inactivating UPP, whereas the anti-NSE antibody inactivated caspase-3, activated UPP, and caused neuronal cell death. The anti-NSE antibody activated caspase-1 (pyroptosis marker), but not condense chromatin (apoptosis marker). The anti-NSE antibody declined intracellular level of ATP, which is not altered in pyroptosis. The intracellular level of calcium is elevated in necrosis and pyroptosis, but its chelator did not ameliorate the neurotoxicity of anti-NSE. Thiol antioxidants such as N-acetyl cysteine and glutathione reduced the neurotoxicity of 15d-PGJ2 but enhanced that of the anti-NSE antibody. The anti-NSE antibody incorporated propidium iodide into neurons through the disrupted plasma membrane, which are not observed in ferroptosis and autophagic cell death. Thus, the anti-NSE antibody induced neuronal cell death in a novel fashion distinguished from necrosis, necroptosis, apoptosis, pyroptosis, ferroptosis, and autophagic cell death.

15-Deoxy-Δ12,14-prostaglandin J2 Inhibits Cell Migration on Renal Cell Carcinoma via Down-Regulation of Focal Adhesion Kinase Signaling.

Renal cell carcinoma (RCC) is one of the chemoresistant cancers. There is a pressing need to establish therapeutic approaches to prevent RCC proliferation and metastasis. The electrophilic 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) is an endogenous anti-cancerous agent. Treatment with high concentrations of 15d-PGJ2 is known to induce apoptosis of RCC cells, independent of the nuclear receptor, peroxisome proliferator-activated receptor-γ (PPARγ). In this study, we investigated the effects of 15d-PGJ2 on the metastatic properties of RCC Caki-2 cells. The metastatic potential of RCC was evaluated by measuring the migratory ability of Caki-2 cells. Although treatment with low concentrations of 15d-PGJ2 did not cause apoptosis, it did decrease the migration of Caki-2 cells in a concentration-dependent manner. PPARγ did not mediate the inhibitory effect of 15d-PGJ2 on the migration of Caki-2 cells. Treatment with a low concentration of 15d-PGJ2 resulted in disassembled focal adhesions and extensive filamentous actin reorganization. Furthermore, 15d-PGJ2 significantly reduced phosphorylation of focal adhesion kinase (FAK). In conclusion, 15d-PGJ2 attenuated the migratory ability of RCC, independent of PPARγ. Further, 15d-PGJ2 appeared to suppress cell migration via inactivation of FAK and subsequent disassembly of focal adhesion. Our present study highlights the therapeutic potential of 15d-PGJ2 for prevention of RCC metastasis.

4,4-Diisothiocyanatostilbene Disulfonic Acid Enhanced 15-Deoxy-Δ12,14-prostaglandin J2-Induced Neuronal Apoptosis.

4,4-Diisothiocyanatostilbene disulfonic acid (DIDS), an antagonist of anion channel including voltage-dependent anion channel (VDAC), acts as both neurotoxicant and neuroprotectant, resulting in the controversy. VDAC contributes to neuronal apoptosis and is a candidate target protein of 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2). Caspase-3 is activated during neuronal apoptosis caused by 15d-PGJ2. In the present study, we ascertained whether DIDS was neuroprotective or neurotoxic in the primary culture of rat cortical neurons. Neuronal cell viabilities were primarily evaluated by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H tetrazolium bromide (MTT) reduction assay. Plasma membrane integrity and apoptosis were detected by the staining of propidium iodide (PI) and Hoechst33342, respectively. Alternatively, apoptosis was also measured by caspase-3 assay kit. DIDS did not prevent neurons from undergoing the 15d-PGJ2-induced apoptosis. In contrast, DIDS caused neuronal cell death in a concentration-dependent manner by itself, confirming its neurotoxicity. The sublethal application of DIDS did not decrease MTT-reducing activity, increase caspase-3 activity, condense chromatin, allow PI to enter neuron and degenerate neuronal morphology significantly. Interestingly, DIDS enhanced the 15d-PGJ2-induced neuronal apoptosis markedly under the sublethal condition. To our knowledge, this is the first report of synergistic effects of DIDS on the neurotoxicity of 15d-PGJ2.

15-deoxy-Δ12, 14-prostaglandin J2 enhances anticancer activities independently of VHL status in renal cell carcinomas.

Renal cell carcinoma (RCC) is relatively resistant to chemotherapy and radiotherapy. Clear cell RCC (ccRCC) accounts for the majority of RCC, which have mutations or epigenetic silencing of the von Hippel-Lindau (VHL) gene. VHL-positive Caki-2 cells are killed by an endogenous anticancer substance, 15-deoxy-Δ12, 14-prostaglandin J2 (15d-PGJ2). The MTT reduction assay reflecting mitochondrial succinate dehydrogenase activity was employed for assessment of cell viability. We confirmed anticancer activities of camptothecin (topoisomerase I inhibitor), etoposide (topoisomerase II inhibitor), doxorubicin (topoisomerase II inhibitor) in VHL-positive Caki-2 cells. Combination of topoisomerase inhibitors with 15d-PGJ2 exhibited the synergistic effect in VHL-positive Caki-2 cells. However, 15d-PGJ2 did not increase cytotoxicities of topoisomerase inhibitors on VHL-negative 786-O cells. In addition, the 15d-PGJ2-enhanced antitumor activity of topoisomerase inhibitors was detected in neither VHL-positive nor VHL-negative RCC4 cells. Our finding indicated that 15d-PGJ2 enhanced the antitumor activity of topoisomerase inhibitors independently of VHL.

Pathophysiological Roles of Intracellular Proteases in Neuronal Development and Neurological Diseases.

Proteases are classified into six distinct classes (cysteine, serine, threonine, aspartic, glutamic, and metalloproteases) on the basis of catalytic mechanism. The cellular control of protein quality senses misfolded or damaged proteins principally by selective ubiquitin-proteasome pathway and non-selective autophagy-lysosome pathway. The two pathways do not only maintain cell homeostasis physiologically, but also mediate necrosis and apoptosis pathologically. Proteasomes are threonine proteases, whereas cathepsins are lysosomal aspartic proteases. Calpains are non-lysosomal cysteine proteases and calcium-dependent papain-like enzyme. Calpains and cathepsins are involved in the neuronal necrosis, which are accidental cell death. Necrosis is featured by the disruption of plasma membranes and lysosomes, the loss of ATP and ribosomes, the lysis of cell and nucleus, and the caspase-independent DNA fragmentation. On the other hand, caspases are cysteine endoproteases and mediate neuronal cell death such as apoptosis and pyroptosis, which are programmed cell death. In the central nervous system, necroptosis, ferroptosis and autophagic cell death are also classified into programmed cell death. Neuronal apoptosis is characterized by cell shrinkage, plasma membrane blebbing, karyorrhexis, chromatin condensation, and DNA fragmentation. Necroptosis and pyroptosis are necrotic and lytic forms of programmed cell death, respectively. Although autophagy is involved in cell survival, it fails to maintain cellular homeostasis, resulting in autophagic cell death. Ferroptosis is induced by reactive oxygen species in excitotoxicity of glutamate and ischemia-reperfusion. Apoptosis and pyroptosis are dependent on caspase-3 and caspase-1, respectively. Autophagic cell death and necroptosis are dependent on calpain and cathepsin, respectively, but independent of caspase. Although apoptosis has been defined by the absence of morphological features of necrosis, the two deaths are both parts of a continuum. The intracellular proteases do not only maintain cell homeostasis but also regulate neuronal maturation during the development of embryonic brain. Furthermore, neurodegenerative diseases are caused by the impairment of quality control mechanisms for a proper folding and function of protein.

Physiological and Pathological Roles of 15-Deoxy-Δ12,14-Prostaglandin J2 in the Central Nervous System and Neurological Diseases.

Prostaglandins (PGs) are divided into conventional PGs, e.g., PGD2, and cyclopentenone-type PGs, e.g., 15-deoxy-Δ12,14 prostaglandin J2 (15d-PGJ2). PGD2 is non-enzymatically metabolized to PGJ2, Δ12-PGJ2, and 15d-PGJ2. In the central nervous system, 15d-PGJ2 differentiates embryonic midbrain cells into dopaminergic neuronal cells via its nuclear peroxysome proliferator-activated receptor-γ (PPARγ). 15d-PGJ2 exerts conflict actions: proinflammatory and anti-inflammatory activities. In the brain, 15d-PGJ2 possesses opposite functions as a neuroprotectant at low concentrations and a neurotoxicant at high concentrations in the brain. PPARγ contributes to the neuroprotective effect of 15d-PGJ2 but not to the neurotoxic effect. Its membrane receptor, chemoattractant receptor-homologous molecule expressed on T-helper type 2 cells (CRTH2), is not also involved in the neurotoxicity of 15d-PGJ2. 15d-PGJ2 induces neuronal apoptosis via inactivating ubiquitin proteasome pathway and activating caspase cascade. Alternatively, 15d-PGJ2 downregulates phosphoinositide 3-kinase (PI3K)-Akt pathway and suppresses neurite outgrowth. 15d-PGJ2 possesses α,ß-unsaturated ketone moiety in its cyclopentenone ring and acts an endogenous electrophile. By the Michael addition reaction, 15d-PGJ2 is covalently bound to cellular nucleophiles, such as free cysteine residues of proteins that regulate intracellular signaling pathways. There are specific binding sites of [3H]15d-PGJ2 in the plasma membrane of cerebral cortices. Besides CRTH2, plasmalemmal glycolytic enzymes, respiratory chain enzymes, molecular chaperones, adaptor proteins and cytoskeletons are identified as membrane targets for 15d-PGJ2. In the present review, we provide evidences for pathophysiological roles of 15d-PGJ2 in the central nervous system and neurological diseases.

Synergistic effects of 15-deoxy Δ12,14-prostaglandin J2 on the anti-tumor activity of doxorubicin in renal cell carcinoma.

An endogenous anticancer agent, 15-deoxy -Δ12,14-prostaglandin J2 (15d-PGJ2) induces apoptosis in the chemoresistant renal cell carcinoma (RCC). Peroxisome proliferator-activated receptor-γ (PPARγ) is a nuclear receptor for 15d-PGJ2, and mediates the cytotoxicity of 15d-PGJ2 in many cancerous cells. However, 15d-PGJ2 induces apoptosis independently of PPARγ in human RCC cell line such as Caki-2. In the present study, we found that 15d-PGJ2 ameliorated the chemoresistance to one of anthracycline antibiotics, doxorubicin, in Caki-2 cells. Doxorubicin alone exhibited weak cytotoxicity at the concentrations effective for other cancer cells such as Hela cells. In addition, it did not activate caspase 3. However, the cytotoxicity of doxorubicin was increased remarkably and accompanied with the caspase- 3 activation in the presence of 15d-PGJ2. Doxorubicin alone damaged plasma membrane, and the combined application of 15d-PGJ2 with doxorubicin increased the membrane permeability slightly. PPARγ was involved in neither the anti-tumor activity nor the synergistic effect of 15d-PGJ2. 15d-PGJ2 induces apoptosis in Caki-2 cells via suppressing the phosphoinositide 3-kinase (PI3K)-Akt pathway. The effect of PI3K inhibitor on the cytotoxicity of doxorubicin was additive, but not synergistic. Although the PI3K inhibitor mimicked the cytotoxicity of 15d-PGJ2, it might not be involved in the synergism between 15d-PGJ2 and doxorubicin. In conclusion, 15d-PGJ2 enhanced the chemosensitivity of doxorubicin via the pathway independent of PPARγ and PI3K.

Anti-heat Shock 70 kDa Protein Antibody Induced Neuronal Cell Death.

Heat shock protein 70 (Hsp70) is not only a molecular chaperone in cytosol, but also presents in synaptic plasma membranes. To detect plasmalemmal Hsp70 (pl-Hsp70), neurons were immunostained with anti-Hsp70 antibody without permeabilization and fixation. Dotted immunofluorescent signals at neuronal cell bodies and neurites indicated the localization of Hsp70 on the neuronal cell surface. To target only pl-Hsp70, but not cytosolic Hsp70, the anti-Hsp70 antibody was applied without permeabilization in the primary culture of rat cortical neurons. The antibody induced neuronal cell death in a concentration-dependent manner. The anti-Hsp70 antibody activated ubiquitin-proteasome pathway, but inactivated caspase-3. A lag time was required for the neurotoxicity of anti-Hsp70 antibody. Hydrogen peroxide was increased in the anti-Hsp70 antibody-treated neurons during the lag time. Catalase suppressed the anti-Hsp70 antibody-reduced cell viability via the plausible inhibition of hydrogen peroxide generation. One of down-streams of hydrogen peroxide exposure is activation of the mitogen-activated protein kinase (MAPK) signaling cascade. The neurotoxicity of anti-Hsp70 antibody was partially ascribed to c-Jun N-terminal kinase among MAPKs. In conclusion, the anti-Hsp70 antibody targeted pl-Hsp70 on the neuronal cell surface and induced neuronal cell death without complement. Furthermore, hydrogen peroxide appeared to mediate the neuronal cell death, which was accompanied with the enhancement of the ubiquitin-proteasome pathway and the suppression of caspase in a different fashion from the known cell death.

15-Deoxy-Δ12,14-prostaglandin J2 induced neurotoxicity via suppressing phosphoinositide 3-kinase.

15-Deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) induces neuronal cell death via apoptosis independently of its receptors. 15d-PGJ2 inhibits growth factor-induced cell proliferation of primary astrocytes via down-regulating phosphoinositide 3-kinase (PI3K)-Akt pathway. Although 15d-PGJ2-reduced cell viability is accompanied with attenuation of the PI3K signaling in neuroblastoma, it has not been sufficiently clarified how 15d-PGJ2 induces cell death in primary neurons. Here, we found that 15d-PGJ2 exhibited neurotoxicity via inhibiting the PI3K signaling in the primary culture of rat cortical neurons. A PI3K inhibitor induced neuronal cell death regardless serum throughout maturation, confirming that PI3K is required for neuronal cell survival. The inhibitor disrupted neuronal cell bodies, shortened neurites thinly, damaged plasma membranes and activated caspase-3 similarly to 15d-PGJ2. Little additive or synergistic neurotoxicity was detected between 15d-PGJ2 and the PI3K inhibitor. A PI3K activator prevented neurons from undergoing the 15d-PGJ2-induced cell death in vitro. In vivo, the PI3K signaling is required for contextual memory retrieval, which was impaired by bilateral injection of 15d-PGJ2 into hippocampus. The activator suppressed the 15d-PGJ2-impaired memory retrieval significantly. In neurons as well as primary astrocytes and neuroblastomas, 15d-PGJ2 exhibited cytotoxicity via suppressing the PI3K-Akt pathway in vivo and in vitro.

Pathophysiological Roles of Cyclooxygenases and Prostaglandins in the Central Nervous System.

Cyclooxygenases (COXs) oxidize arachidonic acid to prostaglandin (PG) G2 and H2 followed by PG synthases that generates PGs and thromboxane (TX) A2. COXs are divided into COX-1 and COX-2. In the central nervous system, COX-1 is constitutively expressed in neurons, astrocytes, and microglial cells. COX-2 is upregulated in these cells under pathophysiological conditions. In hippocampal long-term potentiation, COX-2, PGE synthase, and PGE2 are induced in post-synaptic neurons. PGE2 acts pre-synaptic EP2 receptor, generates cAMP, stimulates protein kinase A, modulates voltage-dependent calcium channel, facilitates glutamatergic synaptic transmission, and potentiates long-term plasticity. PGD2, PGE2, and PGI2 exhibit neuroprotective effects via Gs-coupled DP1, EP2/EP4, and IP receptors, respectively. COX-2, PGD2, PGE2, PGF2α, and TXA2 are elevated in stroke. COX-2 inhibitors exhibit neuroprotective effects in vivo and in vitro models of stroke, Alzheimer's disease, Parkinson's disease, multiple sclerosis, amyotrophic lateral sclerosis, epilepsy, and schizophrenia, suggesting neurotoxicities of COX products. PGE2, PGF2α, and TXA2 can contribute to the neurodegeneration via EP1, FP, and TP receptors, respectively, which are coupled with Gq, stimulate phospholipase C and cleave phosphatidylinositol diphosphate to produce inositol triphosphate and diacylglycerol. Inositol triphosphate binds to inositol triphosphate receptor in endoplasmic reticulum, releases calcium, and results in increasing intracellular calcium concentrations. Diacylglycerol activates calcium-dependent protein kinases. PGE2 disrupts Ca(2+) homeostasis by impairing Na(+)-Ca(2+) exchange via EP1, resulting in the excess Ca(2+) accumulation. Neither PGE2, PGF2α, nor TXA2 causes neuronal cell death by itself, suggesting that they might enhance the ischemia-induced neurodegeneration. Alternatively, PGE2 is non-enzymatically dehydrated to a cyclopentenone PGA2, which induces neuronal cell death. Although PGD2 induces neuronal apoptosis after a lag time, neither DP1 nor DP2 is involved in the neurotoxicity. As well as PGE2, PGD2 is non-enzymatically dehydrated to a cyclopentenone 15-deoxy-Δ(12,14)-PGJ2, which induces neuronal apoptosis without a lag time. However, neurotoxicities of these cyclopentenones are independent of their receptors. The COX-2 inhibitor inhibits both the anchorage-dependent and anchorage-independent growth of glioma cell lines regardless of COX-2 expression, suggesting that some COX-2-independent mechanisms underlie the antineoplastic effect of the inhibitor. PGE2 attenuates this antineoplastic effect, suggesting that the predominant mechanism is COX-dependent. COX-2 or EP1 inhibitors show anti-neoplastic effects. Thus, our review presents evidences for pathophysiological roles of cyclooxygenases and prostaglandins in the central nervous system.

Localization of 14-3-3δ/ξ on the neuronal cell surface.

14-3-3 proteins are intracellularly expressed as ubiquitous adaptor proteins. Here, we found localization of 14-3-3δ/ξ on the neuronal cell surface. 14-3-3δ/ξ was identified as a membrane target for 15-deoxy-Δ(12,14)-prostaglandin J2 (15d-PGJ2). 15d-PGJ2 is a pathological mediator of neurodegenerative diseases including Alzheimer's disease (AD). A causative peptide for AD, amyloid ß, is one of binding partner of 14-3-3δ/ξ. Non-permeabilized neurons were used to avoid the intracellular effects of anti-14-3-3δ/ξ antibody in the present study. The plasmalemmal 14-3-3δ/ξ, but not the cytosolic one, was stimulated by its specific antibody, resulting in neuronal cell death. The neurotoxicity of anti-14-3-3δ/ξ antibody was suppressed by an antioxidant, catalase. Catalase prevented neurons from anti-14-3-3δ/ξ antibody-generating neurotoxic H2O2. The neuroprotective effect of catalase was also detected with the post-treatment of neurons after the application of anti-14-3-3δ/ξ antibody. Activation of mitogen-activated protein kinase signaling cascade is a down-stream consequence of H2O2 exposure. A c-Jun N-terminal kinase inhibitor suppressed anti-14-3-3δ/ξ antibody-induced neuronal cell death. To my knowledge, this is the first report that the antibody-stimulated plasmalemmal 14-3-3δ/ξ induced neuronal cell death. Furthermore, H2O2 and JNK contributed to the neurotoxicity of anti-14-3-3δ/ξ antibody as well as those of amyloid ß and 15d-PGJ2.

Hydrogen peroxide mediated the neurotoxicity of an antibody against plasmalemmal neuronspecific enolase in primary cortical neurons.

Neuron-specific enolase (NSE) is not only a glycolytic enzyme in the cytosol, but also localized in the synaptic plasma membrane. The plasmalemmal NSE is one of autoantigen targets in post-streptococcal autoimmune central nervous system disease. Although anti-neuronal antibodies in patients bind to a restricted group of NSE in cerebral cortex, it has not yet been clarified how the anti-NSE antibody have negative impacts on cortical neurons. Here, we found that NSE was also localized at neuronal cell bodies and neuritis on the neuronal cell surface in the primary culture of rat cortical neurons. The anti-NSE antibody induced neuronal cell death in a concentration-dependent manner. The neuronal cell death required a lag time and was not accompanied with caspase-3 activation and chromatin condensation. The anti-NSE antibody elevated a level of intracellular H2O2 prior to neuronal cell death. Catalase protected neurons from the anti-NSE antibody-induced H2O2 generation and cell death. The post-treatment of neurons with catalase after the application of the anti-NSE antibody exhibited neuroprotective effects as well as the co-treatment. The cascade of mitogen-activated protein kinase (MAPK) is one of signal transductions of H2O2. Among MAPK, a c-Jun N-terminal kinase partially contributed to the neurotoxicity of anti-NSE antibody. Thus, the anti-NSE antibody acted at the plasmalemmal NSE, produced H2O2, and caused neuronal cell death via non-apoptotic pathway in the cortical neurons.

Treatment of etoposide combined with 15-deoxy-Δ12,14-prostaglandin J2 exerted synergistic antitumor effects against renal cell carcinoma via peroxisome proliferator-activated receptor-γ-independent pathways.

Renal cell carcinoma (RCC) is characterized by diverse clinical manifestations, few early warning signs and a resistance to radiotherapy and chemotherapy. Although several clinical trials have investigated potential effective therapeutic strategies for RCC, the chemoresistance of RCC has not yet been overcome. An endogenous ligand for the peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2), was shown to induce apoptosis in RCC. The aim of the present study was to investigate the synergistic effects of carcinostatics on the antitumor activity of 15d-PGJ2 in the Caki-2 human RCC cell line with the MTT assay. Our results demonstrated that the topoisomerase-II inhibitor etoposide (VP-16) exhibited cytotoxic effects synergistically with 15d-PGJ2. Furthermore, the presence of the PPARγ antagonist GW9662 did not protect Caki-2 cells against 15d-PGJ2-induced cytotoxicity. Additionally, it was observed that the combined treatment of VP-16 and 15d-PGJ2 activated caspase-3 more efficiently compared to each treatment alone. Therefore, the combined treatment with 15d-PGJ2 and VP-16 exhibited synergistic antitumor activity independently of PPARγ.

The role of secretory phospholipase A2 in the central nervous system and neurological diseases.

Secretory phospholipase A2 (sPLA2s) are small secreted proteins (14-18 kDa) and require submillimolar levels of Ca(2+) for liberating arachidonic acid from cell membrane lipids. In addition to the enzymatic function, sPLA2 can exert various biological responses by binding to specific receptors. Physiologically, sPLA2s play important roles on the neurotransmission in the central nervous system and the neuritogenesis in the peripheral nervous system. Pathologically, sPLA2s are involved in the neurodegenerative diseases (e.g., Alzheimer's disease) and cerebrovascular diseases (e.g., stoke). The common pathology (e.g., neuronal apoptosis) of Alzheimer's disease and stroke coexists in the mixed dementia, suggesting common pathogenic mechanisms of the two neurological diseases. Among mammalian sPLA2s, sPLA2-IB and sPLA2-IIA induce neuronal apoptosis in rat cortical neurons. The excess influx of calcium into neurons via L-type voltage-dependent Ca(2+) channels mediates the two sPLA2-induced apoptosis. The elevated concentration of intracellular calcium activates PKC, MAPK and cytosolic PLA2. Moreover, it is linked with the production of reactive oxygen species and apoptosis through activation of the superoxide producing enzyme NADPH oxidase. NADPH oxidase is involved in the neurotoxicity of amyloid ß peptide, which impairs synaptic plasticity long before its deposition in the form of amyloid plaques of Alzheimer's disease. In turn, reactive oxygen species from NADPH oxidase can stimulate ERK1/2 phosphorylation and activation of cPLA2 and result in a release of arachidonic acid. sPLA2 is up-regulated in both Alzheimer's disease and cerebrovascular disease, suggesting the involvement of sPLA2 in the common pathogenic mechanisms of the two diseases. Thus, our review presents evidences for pathophysiological roles of sPLA2 in the central nervous system and neurological diseases.

15-Deoxy-Δ12,14-prostaglandin J2 enhanced the anti-tumor activity of camptothecin against renal cell carcinoma independently of topoisomerase-II and PPARγ pathways.

Renal cell carcinoma (RCC) is chemoresistant cancer. Although several clinical trials were conducted to explore effective medications, the chemoresistance of RCC has not yet been conquered. An endogenous ligand for peroxisome proliferator-activated receptor-γ (PPARγ), 15-deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)), induces apoptosis in RCC. Here, we examined synergistic effects of several carcinostatics on the anti-tumor activity of 15d-PGJ(2) in Caki-2 cell line by MTT assay. A topoisomerase-I inhibitor, camptothecin (CPT), exhibited synergistically toxicity with 15d-PGJ(2), but neither 5-fluorouracil nor cisplatin did. The combination of 15d-PGJ(2) and a topoisomerase-II inhibitor, doxorubicine, did not cause synergistic cell growth inhibition. The synergistic effect of topoisomerase-I and II inhibitors was not also detected. A PPARγ antagonist, GW9662, did not prevent Caki-2 from undergoing 15d-PGJ(2)-induced cytotoxicity. The treatment of CPT combined with 15d-PGJ(2) activated caspase-3 more than the separate treatment. These results suggest that 15d-PGJ(2) exhibited the anti-tumor activity synergistically with CPT independent of topoisomerase-II and PPARγ.