P300 Participates in Ionizing Radiation-Mediated Activation of Cathepsin L by Mutant p53.

Our previous studies have shown that cathepsin L (CTSL) is involved in the ability of tumors to resist ionizing radiation (IR), but the specific mechanisms responsible for this remain unknown. We report here that mutant p53 (mut-p53) is involved in IR-induced transcription of CTSL. We found that irradiation caused activation of CTSL in mut-p53 cell lines, whereas there was almost no activation in p53 wild-type cell lines. Additionally, luciferase reporter gene assay results demonstrated that IR induced the p53 binding region on the CTSL promoter. We further demonstrated that the expression of p300 and early growth response factor-1 (Egr-1) was upregulated in mut-p53 cell lines after IR treatment. Accordingly, the expression of Ac-H3, Ac-H4, AcH3K9 was upregulated after IR treatment in mut-p53 cell lines, whereas histone deacetylase (HDAC) 4 and HDAC6 were reciprocally decreased. Moreover, knockdown of either Egr-1 or p300 abolished the binding of mut-p53 to the promoter of CTSL. Chromatin immunoprecipitation assay results showed that the IR-activated transcription of CTSL was dependent on p300. To further delineate the clinical relevance of interactions between Egr-1/p300, mut-p53, and CTSL, we accessed primary tumor samples to evaluate the relationships between mut-p53, CTSL, and Egr-1/p300 ex vivo. The results support the notion that mut-p53 is correlated with CTSL transcription involving the Egr-1/p300 pathway. Taken together, the results of our study revealed that p300 is an important target in the process of IR-induced transcription of CTSL, which confirms that CTSL participates in mut-p53 gain-of-function. SIGNIFICANCE STATEMENT: Transcriptional activation of cathepsin L by ionizing radiation required the involvement of mutated p53 and Egr-1/p300. Interference with Egr-1 or p300 could inhibit the expression of cathepsin L induced by ionizing radiation. The transcriptional activation of cathepsin L by p300 may be mediated by p53 binding sites on the cathepsin L promoter.

Neuroprotective effects of olanzapine against rotenone-induced toxicity in PC12 cells.

Olanzapine is an antipsychotic drug used to treat patients with schizophrenia due to its lower incidence of extrapyramidal symptoms. Previous studies have shown that olanzapine activates AMP-activated protein kinase (AMPK), and induce autophagy in SH-SY5Y cell line. In this study, we investigated whether olanzapine protected against rotenone-induced neurotoxicity in PC12 cells. We showed that treatment with olanzapine increased the phosphorylation of AMPK in both dose- and time-dependent manners in PC12 cells. In addition, olanzapine activated autophagy and increased autophagic vacuoles. Furthermore, olanzapine pretreatment could protect PC12 cells from rotenone-induced apoptosis. Besides, olanzapine pretreatment could suppress the rotenone-induced depolarization of mitochondrial potential and thus protect the cells. Moreover, pretreatment with specific AMPK inhibitor compound C or with autophagy inhibitor 3-methyladenine impaired the protective effect of olanzapine on rotenone-treated PC12 cells. In summary, our results show for the first time that olanzapine ameliorates rotenone-induced injury by activating autophagy through AMPK pathway.

Cathepsin L induced PC-12 cell apoptosis via activation of B-Myb and regulation of cell cycle proteins.

Cathepsin L (CTSL), a cysteine protease, is responsible for the degradation of a variety of proteins. It is known to participate in neuronal apoptosis associated with abnormal cell cycle. However, the mechanisms underlying CTSL-induced cell apoptosis remain largely unclear. We reported here that rotenone caused an activation of CTSL expression in PC-12 cells, while knockdown of CTSL by small interfering RNAs or its inhibitor reduced the rotenone-induced cell cycle arrest and apoptosis. Moreover, elevation of CTSL and increased-apoptosis were accompanied by induction of B-Myb, a crucial cell cycle regulator. We found that B-Myb was increased in rotenone-treated PC-12 cells and knockdown of B-Myb ameliorated rotenone-stimulated cell apoptosis. Further analysis demonstrated that CTSL influenced the expression of B-Myb as suppression of CTSL activity led to a decreased B-Myb expression, whereas overexpression of CTSL resulted in B-Myb induction. Reduction of B-Myb in CTSL-overexpressing cells revealed that regulation of cell cycle-related proteins, including cyclin A and cyclin B1, through CTSL was mediated by the transcription factor B-Myb. In addition, we demonstrated that the B-Myb target, Bim, and its regulator, Egr-1, which was also associated with CTSL closely, were both involved in rotenone-induced apoptosis in PC-12 cells. Our data not only revealed the role of CTSL in rotenone-induced neuronal apoptosis, but also indicated the involvement of B-Myb in CTSL-related cell cycle regulation.

A miRNA-200c/cathepsin L feedback loop determines paclitaxel resistance in human lung cancer A549 cells in vitro through regulating epithelial-mesenchymal transition.

Cathepsin L (CTSL), a cysteine protease, is closely related to tumor occurrence, development, and metastasis, and possibly regulates cancer cell resistance to chemotherapy. miRNAs, especially the miR-200 family, have been implicated in drug-resistant tumors. In this study we explored the relationship of CTSL, miRNA-200c and drug resistance, and the potential regulatory mechanisms in human lung cancer A549 cells and A549/TAX cells in vitro. A549/TAX cells were paclitaxel-resistant A549 cells overexpressing CTSL and characterized by epithelial-mesenchymal transition (EMT). We showed that miRNA-200c and CTSL were reciprocally linked in a feedback loop in these cancer cells. Overexpression of miRNA-200c in A549/TAX cells decreased the expression of CTSL, and enhanced their sensitivity to paclitaxel and suppressed EMT, whereas knockdown of miRNA-200c in A549 cells significantly increased the expression of CTSL, and decreased their sensitivity to paclitaxel and induced EMT. Overexpression of CTSL in A549 cells significantly decreased the expression of miRNA-200c, and reduced their sensitivity to paclitaxel and induced EMT, but these effects were reversed by miRNA-200c, whereas knockdown of CTSL in A549/TAX cells attenuated paclitaxel resistance and remarkably inhibited EMT, but the inhibition of miRNA-200c could reverse these effects. Therefore, miRNA-200c may be involved in regulating paclitaxel resistance through CTSL-mediated EMT in A549 cells, and CTSL and miRNA-200c are reciprocally linked in a feedback loop.

Cathepsin L upregulation-induced EMT phenotype is associated with the acquisition of cisplatin or paclitaxel resistance in A549 cells.

AIM: Cathepsin L (CTSL), a lysosomal acid cysteine protease, is known to play important roles in tumor metastasis and chemotherapy resistance. In this study we investigated the molecular mechanisms underlying the regulation of chemoresistance by CTSL in human lung cancer cells. METHODS: Human lung cancer A549 cells, A549/PTX (paclitaxel-resistant) cells and A549/DDP (cisplatin-resistant) cells were tested. The resistance to cisplatin or paclitaxel was detected using MTT and the colony-formation assays. Actin remodeling was observed with FITC-Phalloidin fluorescent staining or immunofluorescence. A wound-healing assay or Transwell assay was used to assess the migration or invasion ability. The expression of CTSL and epithelial and mesenchymal markers was analyzed with Western blotting and immunofluorescence. The expression of EMT-associated transcription factors was measured with Western blotting or q-PCR. BALB/c nude mice were implanted subcutaneously with A549 cells overexpressing CTSL, and the mice were administered paclitaxel (10, 15 mg/kg, ip) every 3 d for 5 times. RESULTS: Cisplatin or paclitaxel treatment (10-80 ng/mL) induced CTSL expression in A549 cells. CTSL levels were much higher in A549/PTX and A549/DDP cells than in A549 cells. Silencing of CTSL reversed the chemoresistance in A549/DDP and A549/TAX cells, whereas overexpression of CTSL attenuated the sensitivity of A549 cells to cisplatin or paclitaxel. Furthermore, A549/DDP and A549/TAX cells underwent morphological and cytoskeletal changes with increased cell invasion and migration abilities, accompanied by decreased expression of epithelial markers (E-cadherin and cytokeratin-18) and increased expression of mesenchymal markers (N-cadherin and vimentin), as well as upregulation of EMT-associated transcription factors Snail, Slug, ZEB1 and ZEB2. Silencing of CTSL reversed EMT in A549/DDP and A549/TAX cells; In contrast, overexpression of CTSL induced EMT in A549 cells. In xenograft nude mouse model, the mice implanted with A549 cells overexpressing CTSL exhibited significantly reduced sensitivity to paclitaxel treatment, and increased expression of EMT-associated proteins and transcription factors in tumor tissues. CONCLUSION: Cisplatin and paclitaxel resistance is associated with CTSL upregulation-induced EMT in A549 cells. Thus, CTSL-mediated EMT may be exploited as a target to enhance the efficacy of cisplatin or paclitaxel against lung cancer and other types of malignancies.

Inhibition of cathepsin L sensitizes human glioma cells to ionizing radiation in vitro through NF-κB signaling pathway.

AIM: Cathepsin L, a lysosomal cysteine proteinase, is exclusively elevated in a variety of malignancies, including gliomas. In this study we investigated the relationship between cathepsin L and NF-κB, two radiation-responsive elements, in regulating the sensitivity of human glioma cells ionizing radiation (IR) in vitro. METHODS: Human glioma U251 cells were exposed to IR (10 Gy), and the expression of cathepsin L and NF-κB was measured using Western blotting. The nuclear translocation of NF-κB p65 and p50 was analyzed with immunofluorescence assays. Cell apoptosis was examined with clonogenic assays. NF-κB transcription and NF-κB-dependent cyclin D1 and ATM transactivation were monitored using luciferase reporter and ChIP assays, respectively. DNA damage repair was investigated using the comet assay. RESULTS: IR significantly increased expression of cathepsin L and NF-κB p65 and p50 in the cells. Furthermore, IR significantly increased the nuclear translocation of NF-κB, and NF-κB-dependent cyclin D1 and ATM transactivation in the cells. Knockdown of p65 did not change the expression of cathepsin L in IR-treated cells. Pretreatment with Z-FY-CHO (a selective cathepsin L inhibitor), or knockdown of cathepsin L significantly attenuated IR-induced nuclear translocation of NF-κB and cyclin D1 and ATM transactivation, and sensitized the cells to IR. Pretreatment with Z-FY-CHO, or knockdown of p65 also decreased IR-induced DNA damage repair and clonogenic cell survival, and sensitized the cells to IR. CONCLUSION: Cathepsin L acts as an upstream regulator of NF-κB activation in human glioma cells and contributes to their sensitivity to IR in vitro. Inhibition of cathepsin L can sensitize the cells to IR.

Cathepsin L suppression increases the radiosensitivity of human glioma U251 cells via G2/M cell cycle arrest and DNA damage.

AIM: Cathepsin L is a lysosomal cysteine protease that plays important roles in cancer tumorigenesis, proliferation and chemotherapy resistance. The aim of this study was to determine how cathepsin L regulated the radiosensitivity of human glioma cells in vitro. METHODS: Human glioma U251 cells (harboring the mutant type p53 gene) and U87 cells (harboring the wide type p53 gene) were irradiated with X-rays. The expression of cathepsin L was analyzed using Western blot and immunofluorescence assays. Cell survival and DNA damage were evaluated using clonogenic and comet assays, respectively. Flow cytometry was used to detect the cell cycle distribution. Apoptotic cells were observed using Hoechst 33258 staining and fluorescence microscopy. RESULTS: Irradiation significantly increased the cytoplasmic and nuclear levels of cathepsin L in U251 cells but not in U87 cells. Treatment with the specific cathepsin L inhibitor Z-FY-CHO (10 µmol/L) or transfection with cathepsin L shRNA significantly increased the radiosensitivity of U251 cells. Both suppression and knockdown of cathepsin L in U251 cells increased irradiation-induced DNA damage and G2/M phase cell cycle arrest. Both suppression and knockdown of cathepsin L in U251 cells also increased irradiation-induced apoptosis, as shown by the increased levels of Bax and decreased levels of Bcl-2. CONCLUSION: Cathepsin L is involved in modulation of radiosensitivity in human glioma U251 cells (harboring the mutant type p53 gene) in vitro.

The protective mechanism of schisandrin A in d-galactosamine-induced acute liver injury through activation of autophagy.

CONTEXT: The principal bioactive lignan of Schisandra chinensis fructus, commonly used for traditional Chinese medicine, is schisandrin A. Schisandrin A has been widely reported as being very effective for the treatment of liver disease. However, the mechanisms of its protective effects in liver remain unclear. OBJECTIVE: To explore the hepatoprotective mechanisms of schisandrin A. MATERIALS AND METHODS: d-Galactosamine (d-GalN)-induced liver injury in mice was used as a model. Schisandrin A was examined for its protective mechanisms using hematoxylin-eosin (HE) staining, enzyme-linked immunosorbent assay (ELISA), western blotting and real-time PCR (RT-PCR). RESULTS: Aspartate amino-transferase (AST) and alanine transaminase (ALT) levels in the schisandrin A group were significantly decreased (p < 0.01) compared with those in the d-GalN-treated group. HE results showed that the pathological changes in hepatic tissue seen in the d-GalN-treated were reduced in the schisandrin A/d-GalN-treated group, with the morphological characteristics being close to those of the control (untreated) group. Western blotting results showed that schisandrin A can activate autophagy flux and inhibit progression of apoptosis. The immune function of the schisandrin A-pretreated group was assayed by flow cytometry. It was found that the mechanism may involve activated autophagy flux, inhibited apoptosis, and improved immunity in response to liver damage. CONCLUSION: Our results show that the hepatoprotective mechanisms of schisandrin A may include activation of autophagy flux and inhibition of apoptosis. These results provide pharmacological evidence supporting its future clinical application.

Regulation of FSP1 myristoylation by NADPH: A novel mechanism for ferroptosis inhibition.

Excitotoxicity is a prevalent pathological event in neurodegenerative diseases. The involvement of ferroptosis in the pathogenesis of excitotoxicity remains elusive. Transcriptome analysis has revealed that cytoplasmic reduced nicotinamide adenine dinucleotide phosphate (NADPH) levels are associated with susceptibility to ferroptosis-inducing compounds. Here we show that exogenous NADPH, besides being reductant, interacts with N-myristoyltransferase 2 (NMT2) and upregulates the N-myristoylated ferroptosis suppressor protein 1 (FSP1). NADPH increases membrane-localized FSP1 and strengthens resistance to ferroptosis. Arg-291 of NMT2 is critical for the NADPH-NMT2-FSP1 axis-mediated suppression of ferroptosis. This study suggests that NMT2 plays a pivotal role by bridging NADPH levels and neuronal susceptibility to ferroptosis. We propose a mechanism by which the NADPH regulates N-myristoylation, which has important implications for ferroptosis and disease treatment.

NVP-BEZ235, a novel dual PI3K/mTOR inhibitor, enhances the radiosensitivity of human glioma stem cells in vitro.

AIM: NVP-BEZ235 is a novel dual PI3K/mTOR inhibitor and shows dramatic effects on gliomas. The aim of this study was to investigate the effects of NVP-BEZ235 on the radiosensitivity and autophagy of glioma stem cells (GSCs) in vitro. METHODS: Human GSCs (SU-2) were tested. The cell viability and survival from ionizing radiation (IR) were evaluated using MTT and clonogenic survival assay, respectively. Immunofluorescence assays were used to identify the formation of autophagosomes. The apoptotic cells were quantified with annexin V-FITC/PI staining and flow cytometry, and observed using Hoechst 33258 staining and fluorescence microscope. Western blot analysis was used to analyze the expression levels of proteins. Cell cycle status was determined by measuring DNA content after staining with PI. DNA repair in the cells was assessed using a comet assay. RESULTS: Treatment of SU-2 cells with NVP-BEZ235 (10-320 nmol/L) alone suppressed the cell growth in a concentration-dependent manner. A low concentration of NVP-BEZ235 (10 nmol/L) significantly increased the radiation sensitivity of SU-2 cells, which could be blocked by co-treatment with 3-MA (50 µmol/L). In NVP-BEZ235-treated SU-2 cells, more punctate patterns of microtubule-associated protein LC3 immunoreactivity was observed, and the level of membrane-bound LC3-II was significantly increased. A combination of IR with NVP-BEZ235 significantly increased the apoptosis of SU-2 cells, as shown in the increased levels of BID, Bax, and active caspase-3, and decreased level of Bcl-2. Furthermore, the combination of IR with NVP-BEZ235 led to G1 cell cycle arrest. Moreover, NVP-BEZ235 significantly attenuated the repair of IR-induced DNA damage as reflected by the tail length of the comet. CONCLUSION: NVP-BEZ235 increases the radiosensitivity of GSCs in vitro by activating autophagy that is associated with synergistic increase of apoptosis and cell-cycle arrest and decrease of DNA repair capacity.

TIGAR plays neuroprotective roles in KA-induced excitotoxicity through reducing neuroinflammation and improving mitochondrial function.

Excitotoxicity refers to the ability of excessive extracellular excitatory amino acids to damage neurons via receptor activation. It is a crucial pathogenetic process in neurodegenerative diseases. TP53 is confirmed to be involved in excitotoxicity. It is demonstrated that TP53 induced glycolysis and apoptotic regulator (TIGAR)-regulated metabolic pathway can protect against neuronal injury. However, the role of TIGAR in excitotoxicity and specific mechanisms is still unknown. In this study, an in vivo excitotoxicity model was constructed via stereotypical kainic acid (KA) injection into the striatum of mice. KA reduced TIGAR expression levels, neuroinflammatory responses and mitochondrial dysfunction. TIGAR overexpression could reverse KA-induced neuronal injury by reducing neuroinflammation and improving mitochondrial function, thereby exerting neuroprotective effects. Therefore, this study could provide a potential therapeutic target for neurodegenerative diseases.

Rapamycin induces differentiation of glioma stem/progenitor cells by activating autophagy.

Glioma stem/progenitor cells (GSPCs) are considered to be responsible for the initiation, propagation, and recurrence of gliomas. The factors determining their differentiation remain poorly defined. Accumulating evidences indicate that alterations in autophagy may influence cell fate during mammalian development and differentiation. Here, we investigated the role of autophagy in GSPC differentiation. SU-2 cells were treated with rapamycin, 3-methyladenine (3-MA) plus rapamycin, E64d plus rapamycin, or untreated as control. SU-2 cell xenografts in nude mice were treated with rapamycin or 3-MA plus rapamycin, or untreated as control. Western blotting and immunocytochemistry showed up-regulation of microtubule-associated protein light chain-3 (LC3)-II in rapamycin-treated cells. The neurosphere formation rate and the number of cells in each neurosphere were significantly lower in the rapamycin treatment group than in other groups. Real-time PCR and immunocytochemistry showed down-regulation of stem/progenitor cell markers and up-regulation of differentiation markers in rapamycin-treated cells. Transmission electron microscopy revealed autophagy activation in rapamycin-treated tumor cells in mice. Immunohistochemistry revealed decreased Nestin-positive cells and increased GFAP-positive cells in rapamycin-treated tumor sections. These results indicate that rapamycin induces differentiation of GSPCs by activating autophagy.

NADPH and Mito-Apocynin Treatment Protects Against KA-Induced Excitotoxic Injury Through Autophagy Pathway.

AIM: Previous research recognizes that NADPH can produce reduced glutathione (GSH) as a coenzyme and produce ROS as a substrate of NADPH oxidase (NOX). Besides, excessive activation of glutamate receptors results in mitochondrial impairment. The study aims at spelling out the effects of NADPH and Mito-apocynin, a NOX inhibitor which specifically targets the mitochondria, on the excitotoxicity induced by Kainic acid (KA) and its mechanism. METHODS: The in vivo neuronal excitotoxicity model was constructed by stereotypically injecting KA into the unilateral striatum of mice. Administrated NADPH (i.v, intravenous) 30 min prior and Mito-apocynin (i.g, intragastric) 1 day prior, respectively, then kept administrating daily until mice were sacrificed 14 days later. Nissl staining measured the lesion of striatum and survival status of neurons. Cylinder test of forelimb asymmetry and the adhesive removal test reflected the behavioral deficit caused by neural dysfunction. Determined Total superoxide dismutase (T-SOD), malondialdehyde (MDA), and GSH indicated oxidative stress. Western blot presented the expression levels of LC3-II/LC3-I, SQSTM1/p62, TIGAR, and NOX4. Assessed oxygen consumption rate using High-Resolution Respirometry. In vitro, the MitoSOX Indicator reflected superoxide released by neuron mitochondria. JC-1 and ATP assay Kit were used to detect mitochondrial membrane potential (MMP) and energy metabolism, respectively. RESULTS: In this study, we have successfully established excitotoxic model by KA in vivo and in vitro. KA induced decreased SOD activity and increased MDA concentration. KA cause the change of LC3-II/LC3-I, SQSTM1/p62, and TIGAR expression, indicating the autophagy activation. NADPH plays a protective role in vivo and in vitro. It reversed the KA-mediated changes in LC3, SQSTM1/p62, TIGAR, and NOX4 protein expression. Mito-apocynin inhibited KA-induced increases in mitochondrial NOX4 expression and activity. Compared with NADPH, the combination showed more significant neuroprotective effects, presenting more neurons survive and better motor function recovery. The combination also better inhibited the over-activated autophagy. In vitro, combination of NADPH and Mito-apocynin performed better in restoring mitochondria membrane potential. CONCLUSION: In summary, combined administration of NADPH and NOX inhibitors offers better neuroprotection by reducing NADPH as a NOX substrate to generate ROS. The combined use of NADPH and Mito-apocynin can better restore neurons and mitochondrial function through autophagy pathway.

NADPH protects against kainic acid-induced excitotoxicity via autophagy-lysosome pathway in rat striatum and primary cortical neurons.

PURPOSE: To investigate the effects and mechanisms of NADPH on Kainic acid (KA)-induced excitotoxicity. METHODS: KA, a non-N-methyl-d-aspartate glutamate receptor agonist, was exposed to adult SD rats via intrastriatal injection and rat primary cortical neurons to establish excitotoxic models in vivo and in vitro, respectively. To determine the effects of NADPH on KA-induced excitotoxicity, neuronal survival, neurologically behavioral score and oxidative stress were evaluated. To explore the mechanisms of neuroprotective effects of NADPH, the autophagy-lysosome pathway related proteins were detected. RESULTS: In vivo, NADPH (1 mg/kg or 2 mg/kg) diminished KA (2.5 nmol)-induced enlargement of lesion size in striatum, improved KA-induced dyskinesia and reversed KA-induced activation of glial cells. Nevertheless, the neuroprotective effect of NADPH was not significant under the condition of autophagy activation. NADPH (2 mg/kg) inhibited KA (2.5 nmol)-induced down-regulation of TP-53 induced glycolysis and apoptosis regulator (TIGAR) and p62, and up-regulation of the protein levels of LC3-II/LC3-I, Beclin-1 and Atg5. In vitro, the excitotoxic neuronal injury was induced after KA (50 µM, 100 µM or 200 µM) treatment as demonstrated by decreased cell viability. Moreover, KA (100 µM) increased the intracellular levels of calcium and reactive oxygen species (ROS) and declined the levels of the reduced form of glutathione (GSH). Pretreatment of NADPH (10 µM) effectively reversed these changes. Meanwhile NADPH (10 µM) inhibited KA (100 µM)-induced down-regulation of TIGAR and p62, and up-regulation of the ratio of LC3-II/LC3-I, Beclin-1, Atg5, active-cathepsin B and active-cathepsin D. CONCLUSIONS: Our data provide a possible mechanism that NADPH ameliorates KA-induced excitotoxicity by blocking the autophagy-lysosome pathway and up-regulating TIGAR along with its antioxidant properties.

p53 induction contributes to excitotoxic neuronal death in rat striatum through apoptotic and autophagic mechanisms.

The present study sought to investigate mechanisms by which p53 induction contributes to excitotoxic neuronal injury. Rats were intrastriatally administered the N-methyl-D-aspartate (NMDA) receptor agonist quinolinic acid (QA), the changes in the expression of p53 and its target genes involved in apoptosis and autophagy, including p53-upregulated modulator of apoptosis (PUMA), Bax, Bcl-2, damage-regulated autophagy modulator (DRAM) and other autophagic proteins including microtubule-associated protein 1 light chain 3 (LC3) and beclin 1 were assessed. The contribution of p53-mediated autophagy activation to apoptotic death of striatal neurons was assessed with co-administration of the nuclear factor-kappaB (NF-kappaB) inhibitor SN50, the p53 inhibitor Pifithrin-alpha (PFT-alpha) or the autophagy inhibitor 3-methyladenine (3-MA). The increased formation of autophagosomes and secondary lysosomes were observed with transmission electron microscope after excitotoxin exposure. QA induced increases in the expression of p53, PUMA, Bax and a decrease in Bcl-2. These changes were significantly attenuated by pre-treatment with SN50, PFT-alpha or 3-MA. SN50, PFT-alpha or 3-MA also reversed QA-induced upregulation of DRAM, the ratio of LC3-II/LC3-I and beclin 1 protein levels in the striatum. QA-induced internucleosomal DNA fragmentation and loss of striatal neurons were robustly inhibited by SN50, PFT-alpha or 3-MA. These results suggest that overstimulation of NMDA receptors can induce NF-kappaB-dependent expression of p53. p53 participates in excitotoxic neuronal death probably through both apoptotic and autophagic mechanisms.

Autophagic and apoptotic mechanisms of curcumin-induced death in K562 cells.

Curcumin (1), a natural polyphenolic compound, has shown strong antioxidant and anticancer activities. Several molecular mechanisms have been attributed to its inhibitory effects on a wide range of tumor cells. In this study, the response of the chronic myeloid leukemia cell line K562 cells to 1 is investigated. Curcumin inhibited the viability of K562 cells in a dose- and time-dependent manner. Furthermore, curcumin-induced cell death was associated with the formation of the apoptosome complex, the collapse of the mitochondrial membrane potential, and caspase-3 activation. Curcumin treatment also induced Bid cleavage and downregulated the expression of Bcl-2 protein. Surprisingly, even with these molecular features of apoptosis, we showed that 1 stimulated autophagy, which was evidenced by microtubule-associated protein light chain 3 (LC3) immunoreactivty. Curcumin also increased the protein levels of beclin 1 and membrane form LC3 (LC3-II). Autophagy inhibitor bafilomycin A1 and the pan-caspase inhibitor Z-VAD-fmk suppressed curcumin-induced K562 cell death. Overall, these results suggest that curcumin induces autophagic and apoptotic death of K562 cells. These findings suggest that both apoptotic and autophagic mechanisms contribute to the curcumin-induced K562 cell death.

Olanzapine induced autophagy through suppression of NF-κB activation in human glioma cells.

AIMS: Our laboratory previously reported that olanzapine treatment inhibited growth of glioma cell lines and hypothesized that autophagy may be involved in the proliferation inhibitory effects of olanzapine. However, the mechanisms of olanzapine-contributed autophagy activation are unclear. METHODS: The inhibitory effects of olanzapine on glioma cells were evaluated by CCK8 assay, Hoechst 33258 staining and annexin V-FITC/PI staining. Western blotting, nuclear separation techniques, and immunofluorescence assays were used to investigate the relationship between the inhibition of NF-κB and autophagy activation by olanzapine. RESULTS: In this work, we verified that olanzapine increased autophagic flux and autophagic vesicles. In addition, we confirmed that autophagy was related to NF-κB inhibition in cancer progression, especially with the nuclear translocation of p65. Furthermore, we demonstrated that autophagy induced by olanzapine could be impaired with TNFα cotreatment. We also found that olanzapine had an inhibitory effect on T98 cells with positive MGMT protein expression, which may involve the inhibition of MGMT through effects on NF-κB. CONCLUSIONS: Our findings identify a pathway by which olanzapine induces autophagy by depressing NF-κB in a glioma cell line, providing evidence which supports the use of olanzapine as a potential anticancer drug.

Effect of curcumin on the adhesion of platelets to brain microvascular endothelial cells in vitro.

AIM: To determine whether curcumin prevents the adhesion of platelets to brain microvascular endothelial cells (BMECs) cultured in vitro. METHODS: [3H]Adenine- labeled platelets were incubated with BMECs to investigate the role of curcumin in the adhesion of platelets to BMECs. The number of platelets adhering to the BMECs monolayer was determined by liquid scintillation spectroscopy. The thrombin-induced expression of platelets P-selectin, glycoprotein IIb (GPIIb), and glycoprotein IIIa (GPIIIa) on the cell surface, was measured by flow cytometry. P-selectin mRNA levels of BMECs were determined by RT-PCR. The TNF-alpha- induced expressions of P-selectin and E-selectin on the surface of BMECs were determined by Western blotting. RESULTS: The adhesion between thrombin-activated platelets and normal BMECs, and that of TNF-alpha-activated BMECs and normal platelets were significantly increased, and this increase could be inhibited by curcumin (30-240 micromol/L) in a concentration-dependant manner. The platelets activated with thrombin and BMECs stimulated by TNF-alpha demonstrated an upregulated expressions of P-selectin and E-selectin, and this increase, when pretreated with curcumin for 30 min, could be restrained dose dependently. Curcumin also inhibited the increase of the GPIIb/GPIIIa expression of thrombinactivated platelets in a concentration-dependent manner. CONCLUSION: Curcumin can inhibit the platelets to BMECs. This effect may be related to the decreased expressions of P-selectin, E-selectin, and GPIIb/GPIIIa on platelets and BMECs.

Bilobalide inhibits 6-OHDA-induced activation of NF-kappaB and loss of dopaminergic neurons in rat substantia nigra.

AIM: To investigate the effects of bilobalide on the activation of NF-kappaB, and apoptosis of dopaminergic neurons induced by 6-hydroxydopamine (6-OHDA). METHODS: A rat model of Parkinson's disease was produced with a unilateral infusion of 6-OHDA (8 mug) into the substantia nigra par compact. Bilobalide was administered 5, 10, and 20 mg/kg (ip) once a day for 7 d, starting 6 d prior to the 6- OHDA infusion. The rats were subjected to locomotor activity and rotational behavior testing 2 or 3 weeks after the 6-OHDA infusion. The expressions of tyrosine hydroxylase (TH) and NF-kappaB p65 were examined by immunofluorescence. The loss of dopaminergic neurons was detected by Nissl's staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was used to identify apoptosis. RESULTS: The behavioral changes due to 6-OHDA were significantly restored by bilobalide pretreatment. Bilobalide inhibited the 6-OHDA-induced loss of TH-positive neurons, decreased the activation of NF-kappaB, and protected dopaminergic neurons from apoptosis remarkably. CONCLUSION: NF-kappaB activation contributes to the 6-OHDA-induced loss of dopaminergic neurons, and the inhibition of the NF-kappaB pathway is likely to be involved in the neuroprotective effect of bilobalide.

LY294002 induces p53-dependent apoptosis of SGC7901 gastric cancer cells.

AIM: To study the effects of LY294002, an inhibitor of class I phosphatidylinositol 3-kinase (PI3K), on proliferation and apoptosis of SGC7901 gastric cancer cells. METHODS: The MTT assay was used to determine the cytotoxic effects of LY294002. Cell cycle distribution was analyzed using flow cytometry and apoptosis was assessed using flow cytometry analysis after staining DNA with propidium iodide. Mitochondrial membrane potential was measured using the fluorescent probe JC-1. Expression of p53 and PUMA was determined using real-time RT-PCR and Western blotting analysis. RESULTS: The viability of SGC7901 cells was significantly reduced by LY294002 treatment. Expression of p53 and PUMA was induced, and mitochondrial membrane potential collapsed after treatment with LY294002. LY294002 induced apoptotic cell death. CONCLUSION: Activation of the p53 pathway is involved in LY294002-induced SGC7901 cell death.