ROS-mediated p38alpha MAPK activation and ERK inactivation responsible for upregulation of Fas and FasL and autocrine Fas-mediated cell death in Taiwan cobra phospholipase A(2)-treated U937 cells

Effectiveness of Albumin-Fused Thioredoxin against 6-Hydroxydopamine-Induced Neurotoxicity In Vitro

Parkinson's disease (PD) is a neurodegenerative disorder caused by oxidative stress-dependent loss of dopaminergic neurons in the substantia nigra and elevated microglial inflammatory responses. Recent studies show that cell loss also occurs in the hypothalamus in PD. However, effective treatments for the disorder are lacking. Thioredoxin is the major protein disulfide reductase in vivo. We previously synthesized an albumin-thioredoxin fusion protein (Alb-Trx), which has a longer plasma half-life than thioredoxin, and reported its effectiveness in the treatment of respiratory and renal diseases. Moreover, we reported that the fusion protein inhibits trace metal-dependent cell death in cerebrovascular dementia. Here, we investigated the effectiveness of Alb-Trx against 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in vitro. Alb-Trx significantly inhibited 6-OHDA-induced neuronal cell death and the integrated stress response. Alb-Trx also markedly inhibited 6-OHDA-induced reactive oxygen species (ROS) production, at a concentration similar to that inhibiting cell death. Exposure to 6-OHDA perturbed the mitogen-activated protein kinase pathway, with increased phosphorylated Jun N-terminal kinase and decreased phosphorylated extracellular signal-regulated kinase levels. Alb-Trx pretreatment ameliorated these changes. Furthermore, Alb-Trx suppressed 6-OHDA-induced neuroinflammatory responses by inhibiting NF-κB activation. These findings suggest that Alb-Trx reduces neuronal cell death and neuroinflammatory responses by ameliorating ROS-mediated disruptions in intracellular signaling pathways. Thus, Alb-Trx may have potential as a novel therapeutic agent for PD.

Naja atra Cardiotoxin 1 Induces the FasL/Fas Death Pathway in Human Leukemia Cells

This study aimed to investigate the mechanistic pathway of Naja atra (Taiwan cobra) cardiotoxin 1 (CTX1)-induced death of leukemia cell lines U937 and HL-60. CTX1 increased cytoplasmic Ca²⁺ and reactive oxygen species (ROS) production, leading to the death of U937 cells. It was found that Ca²⁺-induced NOX4 upregulation promoted ROS-mediated p38 MAPK phosphorylation, which consequently induced c-Jun and ATF-2 phosphorylation. Using siRNA knockdown, activated c-Jun and ATF-2 were demonstrated to regulate the expression of Fas and FasL, respectively. Suppression of Ca²⁺-mediated NOX4 expression or ROS-mediated p38 MAPK activation increased the survival of U937 cells exposed to CTX1. FADD depletion abolished CTX1-induced cell death, caspase-8 activation, and t-Bid production, supporting the correlation between the Fas death pathway and CTX1-mediated cytotoxicity. Among the tested N. atra CTX isotoxins, only CTX1 induced Fas and FasL expression. Chemical modification studies revealed that intact Met residues were essential for the activity of CTX1 to upregulate Fas and FasL expression. Taken together, the data in this study indicate that CTX1 induces c-Jun-mediated Fas and ATF-2-mediated FasL transcription by the Ca²⁺/NOX4/ROS/p38 MAPK axis, thereby activating the Fas death pathway in U937 cells. Furthermore, CTX1 activates Fas/FasL death signaling in the leukemia cell line HL-60.

A new risk score based on twelve hepatocellular carcinoma-specific gene expression can predict the patients' prognosis

A large panel of molecular biomarkers have been identified to predict the prognosis of hepatocellular carcinoma (HCC), yet with limited clinical application due to difficult extrapolation. We here generated a genetic risk score system comprised of 12 HCC-specific genes to better predict the prognosis of HCC patients. Four genomics profiling datasets (GSE5851, GSE28691, GSE15765 and GSE14323) were searched to seek HCC-specific genes by comparisons between cancer samples and normal liver tissues and between different subtypes of hepatic neoplasms. Univariate survival analysis screened HCC-specific genes associated with overall survival (OS) in the training dataset for next-step risk model construction. The prognostic value of the constructed HCC risk score system was then validated in the TCGA dataset. Stratified analysis indicated this scoring system showed better performance in elderly male patients with HBV infection and preoperative lower levels of creatinine, alpha-fetoprotein and platelet and higher level of albumin. Functional annotation of this risk model in high-risk patients revealed that pathways associated with cell cycle, cell migration and inflammation were significantly enriched. In summary, our constructed HCC-specific gene risk model demonstrated robustness and potentiality in predicting the prognosis of HCC patients, especially among elderly male patients with HBV infection and relatively better general conditions.

Selenium deficiency impaired structural integrity of the head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella)

This study focused on the effects of dietary selenium deficiency on structural integrity of the head kidney, spleen and skin in young grass carp (Ctenopharyngodon idella). A total of 540 healthy grass carp (mean weight 226.48 ± 0.68 g) were randomly divided into six groups and fed six separate diets with graded dietary levels of selenium (0.025-1.049 mg/kg diet) for 80 days. Results showed that selenium deficiency (1) caused oxidative damage in part by reducing the activities of antioxidant enzymes (such as SOD, CAT, GPx, GST and GR) and glutathione (GSH) content, down-regulating the transcript abundances of antioxidant enzymes (except GSTp1) partly related to Kelch-like-ECH-associated protein 1a (Keap1a)/NF-E2-related factor 2 (Nrf2) signalling; (2) aggravated apoptosis in part by up-regulating the mRNA levels of caspase-2, -3, -7, -8 and -9, which were partially related to p38MAPK/FasL/caspase-8 signalling and JNK/(BAX, Bcl-2, Mcl-1b, IAP)/(Apaf1, caspase-9) signalling; (3) damaged the tight junctions in part by down-regulating the mRNA levels of ZO-1 (except spleen), ZO-2 (except spleen), claudin-c, -f, -7, -11 and claudin-15, and up-regulating the mRNA levels of claudin-12, which were partially related to myosin light chain kinase (MLCK) signalling. Interesting, selenium deficiency failed to affect the expression of GSTp1, Keap1a, occludin, claudin-b, claudin-3c, ZO-1 (spleen only) and ZO-2 (spleen only) in the head kidney, spleen and skin of grass carp. Finally, based on the activities of glutathione peroxidase (GPx) and reactive oxygen species (ROS) content in the head kidney, spleen and skin, the dietary selenium requirements for young grass carp were estimated to be 0.558-0.588 mg/kg diet.

Novel proteasome inhibitor delanzomib sensitizes cervical cancer cells to doxorubicin-induced apoptosis via stabilizing tumor suppressor proteins in the p53 pathway

Cervical cancer, the third most commonly occurring cancer, is the second leading cause of cancer related mortality among women. Aberrant ubiquitination and proteasome activity, both human papillomavirus and tumor derived, have been shown to contribute to tumor angiogenesis, proliferation, and invasion in many cancers, including cervical cancer. Thus, small molecule proteasome inhibitors are a potential and strategic treatment option for cervical cancer. In this study, novel proteasome inhibitor delanzomib (CEP-18770) exhibited potent pro-apoptotic and cytotoxic effects on a panel of cervical cancer cell lines by blocking proteasomal activity. Delanzomib also significantly sensitized cervical cancer cells to treatment of doxorubicin (Dox), a traditional chemotherapeutic agent. Furthermore, proteasome inhibition revealed stabilization of p53 and p53 transcriptional targets and induction of p38/JNK phosphorylation. Additionally, delanzomib worked synergistically with Dox to further upregulate p53 and its downstream targets and enhanced Dox-induced p38 phosphorylation. Our study strongly supports the 26S proteasome as a potential therapeutic target in cervical cancer and proteasome inhibition by delanzomib may be a potential treatment strategy for cervical cancer patients.

The p38 MAPK inhibitor BIRB796 enhances the antitumor effects of VX680 in cervical cancer

VX680 is a potent and selective inhibitor that targets the Aurora kinase family. The p38 mitogen-activated protein kinase (MAPK) regulates a large number of cellular pathways and plays an important role in the regulation of cell survival and apoptosis. This study aimed to evaluate the effect of VX680 on cervical cancer cells and investigate whether the effects on apoptosis are enhanced by the ablation of p38 MAPK activation. The results suggested that VX680 inhibited the proliferation of cervical cancer cells by causing G2/M phase arrest and endoreduplication and that the apoptotic effect was attenuated by the activation of p38 MAPK. However, the addition of BIRB796, which is an important p38 MAPK inhibitor, effectively eliminated the expression of p-p38 and hence significantly enhanced the cell death induced by VX680 in vitro. Further study demonstrated that BIRB796 cooperated with VX680 to suppress cervical cancer cell growth in a mouse xenograft model. Taken together, our results demonstrated that VX680 induced cell cycle arrest and endoreduplication in human cervical cancer cells. Combined treatment with VX680 and BIRB796 synergistically inhibited tumor growth both in vitro and in vivo. Dual blockade of Aurora kinases and p38 MAPK is therefore a promising strategy for cervical cancer treatment.

Aloin promotes A549 cell apoptosis via the reactive oxygen species‑mitogen activated protein kinase signaling pathway and p53 phosphorylation

Aloin has the potential to be a novel anticancer agent in cancer therapies. However, the detailed anticancer effect of Aloin remains to be fully elucidated. The present study analyzed the p53‑dependent mechanisms in response to Aloin treatment. Using the p53‑proficient A549 cells, an Aloin‑induced apoptotic cell model was established, which was used to evaluate the potential underlying molecular mechanisms. The results demonstrated that 200, 300 and 400 µM Aloin induced intrinsic cell apoptosis, which was further confirmed by disruption of the mitochondrial membrane potential, elevation of cytosolic Ca2+ levels, and activation of B‑cell lymphoma 2 (Bcl‑2) homologous antagonist killer, Bcl‑2 X‑associated protein, p53 upregulated modulator of apoptosis and phorbol‑12‑myristate‑13‑acetate‑induced protein 1. Aloin‑induced apoptosis was also accompanied by the induction of p53 phosphorylation on Serine (Ser)15, Threonine 18, Ser20 and Ser392; however, there were no significant differences in the expression of p53 and mouse double minute 2 homolog. Aloin‑induced apoptosis was reactive oxygen species (ROS)‑ and c‑Jun/p38‑dependent, as specific inhibitors for ROS, phosphorylated (p)‑c‑Jun and p‑p38 may attenuate Aloin‑induced A549 cell proliferating inhibition. In conclusion, these results suggested that Aloin may induce apoptosis in A549 cells via the ROS‑mitogen activated protein kinase signaling pathway, with p53 phosphorylation. These results implicate Aloin as a potential therapeutic agent for the treatment of lung cancer.

Pseudomonas Quinolone Signal Induces Oxidative Stress and Inhibits Heme Oxygenase-1 Expression in Lung Epithelial Cells

Pseudomonasaeruginosa causes lung infections in patients with cystic fibrosis (CF). The Pseudomonas quinolone signal (PQS) compound is a secreted P. aeruginosa virulence factor that contributes to the pathogenicity of P. aeruginosa We were able to detect PQS in sputum samples from CF patients infected with P. aeruginosa but not in samples from uninfected patients. We then tested the hypothesis that PQS induces oxidative stress in host cells by determining the ability of PQS to induce the production of reactive oxygen species (ROS) in lung epithelial cells (A549 and primary normal human bronchial epithelial [NHBE]) cells and macrophages (J774A.1 and THP-1). ROS production induced by PQS was detected with fluorescent probes (dichlorodihydrofluorescein diacetate, dihydroethidium, and MitoSOX Red) in conjunction with confocal microscopy and flow cytometry. PQS induced ROS production in lung epithelial (A549 and NHBE) cells and macrophages (J774A.1 and THP-1 cells). NHBE cells were sensitive to PQS concentrations as low as 500 ng/ml. PQS significantly induced early apoptosis (P < 0.05, n = 6) in lung epithelial cells, as measured by annexin/propidium iodide detection by flow cytometry. However, no change in apoptosis upon PQS treatment was seen in J774A.1 cells. Heme oxygenase-1 (HO-1) protein is an antioxidant enzyme usually induced by oxidative stress. Interestingly, incubation with PQS significantly reduced HO-1 and NrF2 expression in A549 and NHBE cells but increased HO-1 expression in J774A.1 cells (P < 0.05, n = 3), as determined by immunoblotting and densitometry. These PQS effects on host cells could play an important role in the pathogenicity of P. aeruginosa infections.

Acetoacetate induces hepatocytes apoptosis by the ROS-mediated MAPKs pathway in ketotic cows

Dairy cows with ketosis are characterized by oxidative stress, hepatic damage, and hyperketonemia. Acetoacetate (AA) is the main component of ketone bodies in ketotic cows, and is associated with the above pathological process. However, the potential mechanism was not illuminated. Therefore, the aim of this study was to investigate the mechanism of AA-induced hepatic oxidative damage in ketotic cows. Compared with healthy cows, ketotic cows exhibited severe oxidative stress and hepatic damage. Moreover, the extent of hepatic damage and oxidative stress had a positive relationship with the AA levels. In vitro, AA treatment increased reactive oxygen species (ROS) content and further induced oxidative stress and apoptosis of bovine hepatocytes. In this process, AA treatment increased the phosphorylation levels of JNK and p38MAPK and decreased the phosphorylation level of ERK, which could increase p53 and inhibit nuclear factor E2-related factor 2 (Nrf2) expression, nuclear localization, and DNA-binding affinity, thereby inducing the overexpression of pro-apoptotic molecules Bax, Caspase 3, Caspase 9, PARP and inhibition of anti-apoptotic molecule Bcl-2. Antioxidant N-acetylcysteine (NAC) treatment or interference of MAPKs pathway could attenuate the hepatocytes apoptosis induced by AA. Collectively, these results indicate that AA triggers hepatocytes apoptosis via the ROS-mediated MAPKs pathway in ketotic cows.

Geldanamycin, an inhibitor of Hsp90, increases paclitaxel-mediated toxicity in ovarian cancer cells through sustained activation of the p38/H2AX axis

Paclitaxel is a mitotic inhibitor used in ovarian cancer chemotherapy. Unfortunately, due to the rapid genetic and epigenetic changes in adaptation to stress induced by anticancer drugs, cancer cells are often able to become resistant to single or multiple anticancer agents. However, it remains largely unknown how paclitaxel resistance happens. In this study, we generated a cell line of acquired resistance to paclitaxel therapy, A2780T, which is cross-resistant to other antimitotic drugs, such as PLK1 inhibitor or AURKA inhibitor. Immunoblotting revealed significant alterations in cell-cycle-related and apoptotic-related proteins involved in key signaling pathways. In particular, phosphorylation of p38, which activates H2AX, was significantly decreased in A2780T cells compared to the parental A2780 cells. Geldanamycin (GA), an inhibitor of Hsp90, sustained activation of the p38/H2AX axis, and A2780T cells were shown to be more sensitive to GA compared to A2780 cells. Furthermore, treatment of A2780 and A2780T cells with GA significantly enhanced sensitivity to paclitaxel. Meanwhile, GA cooperated with paclitaxel to suppress tumor growth in a mouse ovarian cancer xenograft model. In conclusion, GA may sensitize a subset of ovarian cancer to paclitaxel, particularly those tumors in which resistance is driven by inactivation of p38/H2AX axis.

p38 mitogen-activated protein kinase inhibition modulates nucleus pulposus cell apoptosis in spontaneous resorption of herniated intervertebral discs: An experimental study in rats

The present study was performed to investigate the role of p38 mitogen‑activated protein kinase (MAPK) in the resorption of herniated intervertebral discs in 30 rats. In the non‑contained and p38 MAPK inhibition (p38i) groups, two coccygeal intervertebral discs (IVDs) were removed and wounded prior to relocation into the subcutaneous space of the skin of the back. In the contained group, the cartilage endplates maintained their integrity. Furthermore, SB203580 was injected intraperitoneally into the p38i group, whereas saline was injected into the other two groups. In the non‑contained group, the weight of the relocated IVDs decreased to a greater extent over time when compared with the contained and p38i groups. Phosphorylated p38, tumor necrosis factor‑α, and interleukin‑1β were observed to exhibit higher expression levels in the non‑contained group compared with the contained and p38i groups, at weeks 1 and 4 post‑surgery. The expression level of caspase‑3 and the densities of apoptotic disc cells were significantly higher in the non‑contained group compared with the contained and p38i groups at 4 weeks post‑surgery. In conclusion, p38 MAPK induces apoptosis in IVDs, while also accelerating the resorption of the relocated IVDs. Thus, p38 MAPK may be important in spontaneous resorption of IVDs.

Estradiol and Estrogen Receptor Agonists Oppose Oncogenic Actions of Leptin in HepG2 Cells

Obesity is a significant risk factor for certain cancers, including hepatocellular carcinoma (HCC). Leptin, a hormone secreted by white adipose tissue, precipitates HCC development. Epidemiology data show that men have a much higher incidence of HCC than women, suggesting that estrogens and its receptors may inhibit HCC development and progression. Whether estrogens antagonize oncogenic action of leptin is uncertain. To investigate potential inhibitory effects of estrogens on leptin-induced HCC development, HCC cell line HepG2 cells were treated with leptin in combination with 17 β-estradiol (E2), estrogen receptor-α (ER-α) selective agonist PPT, ER-β selective agonist DPN, or G protein-coupled ER (GPER) selective agonist G-1. Cell number, proliferation, and apoptosis were determined, and leptin- and estrogen-related intracellular signaling pathways were analyzed. HepG2 cells expressed a low level of ER-β mRNA, and leptin treatment increased ER-β expression. E2 suppressed leptin-induced HepG2 cell proliferation and promoted cell apoptosis in a dose-dependent manner. Additionally E2 reversed leptin-induced STAT3 and leptin-suppressed SOCS3, which was mainly achieved by activation of ER-β. E2 also enhanced ERK via activating ER-α and GPER and activated p38/MAPK via activating ER-β. To conclude, E2 and its receptors antagonize the oncogenic actions of leptin in HepG2 cells by inhibiting cell proliferation and stimulating cell apoptosis, which was associated with reversing leptin-induced changes in SOCS3/STAT3 and increasing p38/MAPK by activating ER-β, and increasing ERK by activating ER-α and GPER. Identifying roles of different estrogen receptors would provide comprehensive understanding of estrogenic mechanisms in HCC development and shed light on potential treatment for HCC patients.

Activation of mitochondrial transient receptor potential vanilloid 1 channel contributes to microglial migration

Microglia, the resident immune cells in the brain, survey the environment of the healthy brain. Microglial migration is essential for many physiological and pathophysiological processes. Although microglia express some members of the transient receptor potential (TRP) channel family, there is little knowledge regarding the physiological roles of TRP channels in microglia. Here, we explored the role of TRP vanilloid 1 (TRPV1), a channel opened by capsaicin, heat, protons, and endovanilloids, in microglia. We found that application of capsaicin induced concentration-dependent migration in microglia derived from wild-type mice but not in those derived from TRPV1 knockout (TRPV1-KO) mice. Capsaicin-induced microglial migration was significantly inhibited by co-application of the TRPV1 blocker SB366791 and the Ca(2+) chelator BAPTA-AM. Using RT-PCR and immunocytochemistry, we validated that TRPV1 was expressed in microglia. Electrophysiological recording, intracellular Ca(2+) imaging, and immunocytochemistry indicated that TRPV1 was localized primarily in intracellular organelles. Treatment with capsaicin induced an increase in intramitochondrial Ca(2+) concentrations and mitochondrial depolarization. Furthermore, microglia derived from TRPV1-KO mice showed delayed Ca(2+) efflux compared with microglia derived from wild-type mice. Capsaicin-induced microglial migration was inhibited by membrane-permeable antioxidants and MAPK inhibitors, suggesting that mitochondrial TRPV1 activation induced Ca(2+) -dependent production of ROS followed by MAPK activation, which correlated with an augmented migration of microglia. Moreover, a mixture of three endovanilloids augmented microglial migration via TRPV1 activation. Together, these results indicate that mitochondrial TRPV1 plays an important role in inducing microglial migration. Activation of TRPV1 triggers an increase in intramitochondrial Ca(2+) concentration and following depolarization of mitochondria, which results in mtROS production, MAPK activation, and enhancement of chemotactic activity in microglia.

Attenuation of mitochondrial and nuclear p38α signaling: a novel mechanism of estrogen neuroprotection in cerebral ischemia

P38 mitogen-activated protein kinase (MAPK) is a pro-apoptotic and pro-inflammatory protein that is activated in response to cellular stress. While p38 is known to be activated in response to cerebral ischemia, the precise role of p38 and its isoforms in ischemia-induced neuronal apoptosis remains unclear. In the current study, we examined the differential activation and functional roles of p38α and p38β MAPK isoforms in short-term ovariectomized female rats treated with either the neuroprotective ovarian hormone 17beta-estradiol (E2) or placebo in a model of global cerebral ischemia (GCI). GCI induced biphasic activation of total p38 in the hippocampal CA1, with peaks at 30 min and 1 day after 10-min ischemia-reperfusion. Further study demonstrated that activated p38α, but not p38β, translocated to the nucleus 30 min and 3 h post reperfusion, and that this event coincided with increased phosphorylation of activating transcription factor 2 (ATF2), a p38 target protein. Intriguingly, activated p38α was also enhanced in mitochondrial fractions of CA1 neurons 1 day after GCI, and there was loss of mitochondrial membrane potential, as well as enhanced cytochrome c release and caspase-3 cleavage at 2 days post GCI. Importantly, E2 prevented the biphasic activation of p38, as well as both nuclear and mitochondrial translocation of p38α after GCI, and these findings correlated with attenuation of mitochondrial dysfunction and delayed neuronal cell death in the hippocampal CA1. Furthermore, administration of a p38 inhibitor was able to mimic the neuroprotective effects of E2 in the hippocampal CA1 region by preventing nuclear and mitochondrial translocation of p38α, loss of mitochondrial membrane potential, and neuronal apoptosis. As a whole, this study suggests that changes in subcellular localization of the activated p38α isoform are required for neuronal apoptosis following GCI, and that E2 exerts robust neuroprotection, in part, through dual inhibition of activation and subcellular trafficking of p38α.

Modulated mechanism of phosphatidylserine on the catalytic activity of Naja naja atra phospholipase A2 and Notechis scutatus scutatus notexin

Phosphatidylserine (PS) externalization is a hallmark for apoptotic death of cells. Previous studies showed that Naja naja atra phospholipase A2 (NnaPLA2) and Notechis scutatus scutatus notexin induced apoptosis of human cancer cells. However, NnaPLA2 and notexin did not markedly disrupt the integrity of cellular membrane as evidenced by membrane permeability of propidium iodide. These findings reflected that the ability of NnaPLA2 and notexin to hydrolyze membrane phospholipids may be affected by PS externalization. To address that question, this study investigated the membrane-interacted mode and catalytic activity of NnaPLA2 and notexin toward outer leaflet (phosphatidylcholine/sphingomyelin/cholesterol, PC/SM/Chol) and inner leaflet (phosphatidylserine/phosphatidylethanolamine/cholesterol, PS/PE/Chol) of plasma membrane-mimicking vesicles. PS incorporation promoted enzymatic activity of NnaPLA2 and notexin on PC and PC/SM vesicles, but suppressed NnaPLA2 and notexin activity on PC/SM/Chol and PE/Chol vesicles. PS incorporation increased the membrane fluidity of PC vesicles but reduced membrane fluidity of PC/SM, PC/SM/Chol and PE/Chol vesicles. PS increased the phospholipid order of all the tested vesicles. Moreover, PS incorporation did not greatly alter the binding affinity of notexin and NnaPLA2 with phospholipid vesicles. Acrylamide quenching studies and trinitrophenylation of Lys residues revealed that membrane-bound mode of notexin and NnaPLA2 varied with the targeted membrane compositions. The fine structure of catalytic site in NnaPLA2 and notexin in all the tested vesicles showed different changes. Collectively, the present data suggest that membrane-inserted PS modulates PLA2 interfacial activity via its effects on membrane structure and membrane-bound mode of NnaPLA2 and notexin, and membrane compositions determine the effect of PS on PLA2 activity.

Taiwan cobra phospholipase A2 suppresses ERK-mediated ADAM17 maturation, thus reducing secreted TNF-α production in human leukemia U937 cells

The goal of this study was to explore the signaling pathway regulating the processing of proADAM17 into ADAM17 in Taiwan cobra phospholipase A2 (PLA2)-treated human leukemia U937 cells. PLA2 induced reactive oxygen species (ROS)-elicited p38 MAPK activation and ERK inactivation in U937 cells. Catalytically inactive bromophenacylated PLA2 (BPB-PLA2) and PLA2 mutants evoked Ca(2+)-mediated p38 MAPK activation, and the level of phosphorylated ERK remained unchanged. PLA2 treatment reduced mature ADAM17 expression and secreted TNF-α (sTNF-α) production. Co-treatment of SB202190 (p38 MAPK inhibitor) and catalytically inactive PLA2 increased ERK phosphorylation, ADAM17 maturation and sTNF-α production. Nevertheless, mRNA levels of ADAM17 and TNF-α were insignificantly altered after PLA2 and SB202190/BPB-PLA2 treatment. ADAM17 activity assay and knock-down of ADAM17 revealed that ADAM17 was involved in sTNF-α production. Restoration of ERK activation increased the processing of proADAM17 into ADAM17 in PLA2-treated cells, while inactivation of ERK reduced ADAM17 maturation in untreated and SB202190/BPB-PLA2-treated cells. Removal of cell surface heparan sulfate abrogated PLA2 and SB202190/BPB-PLA2 effect on ADAM17 maturation. Taken together, the present data reveal that PLA2 suppresses ERK-mediated ADAM17 maturation, thus reducing sTNF-α production in U937 cells. Moreover, the binding with heparan sulfate is crucial for the PLA2 effect.

Design and discovery of novel quinazolinedione-based redox modulators as therapies for pancreatic cancer

BACKGROUND

Altered cellular bioenergetics and oxidative stress are emerging hallmarks of most cancers including pancreatic cancer. Elevated levels of intrinsic reactive oxygen species (ROS) in tumors make them more susceptible to exogenously induced oxidative stress. Excessive oxidative insults overwhelm their adaptive antioxidant capacity and trigger ROS-mediated cell death. Recently, we have discovered a novel class of quinazolinediones that exert their cytotoxic effects by modulating ROS-mediated signaling.

METHODS

Cytotoxic potential was determined by colorimetric and colony formation assays. An XF24 Extracellular Flux Analyzer, and colorimetric and fluorescent techniques were used to assess the bioenergetics and oxidative stress effects, respectively. Mechanism was determined by Western blots.

RESULTS

Compound 3a (6-[(2-acetylphenyl)amino]quinazoline-5,8-dione) was identified through a medium throughput screen of ~1000 highly diverse in-house compounds and chemotherapeutic agents for their ability to alter cellular bioenergetics. Further structural optimizations led to the discovery of a more potent analog, 3b (6-[(3-acetylphenyl)amino]quinazoline-5,8-dione) that displayed anti-proliferative activities in low micromolar range in both drug-sensitive and drug-resistant cancer cells. Treatment with 3b causes Akt activation resulting in increased cellular oxygen consumption and oxidative stress in pancreatic cancer cells. Moreover, oxidative stress induced by 3b promoted activation of stress kinases (p38/JNK) resulting in cancer cell death. Treatment with antioxidants was able to reduce cell death confirming ROS-mediated cytotoxicity.

CONCLUSION

In conclusion, our novel quinazolinediones are promising lead compounds that selectively induce ROS-mediated cell death in cancer cells and warrant further preclinical studies.

GENERAL SIGNIFICANCE

Since 3b (6-[(3-acetylphenyl)amino]quinazoline-5,8-dione) exerts Akt-dependent ROS-mediated cell death, it might provide potential therapeutic options for chemoresistant and Akt-overexpressing cancers.

L-type voltage-dependent calcium channel is involved in the snake venom group IA secretory phospholipase A2-induced neuronal apoptosis

Snake venom group IA secretory phospholipase A2 (sPLA2-IA) is known as a neurotoxin. Snake venom sPLA2s are neurotoxic in vivo and in vitro, causing synergistic neurotoxicity to cortical cultures when applied with toxic concentrations of glutamate. However, it has not yet been cleared sufficiently how sPLA2-IA exerts neurotoxicity. Here, we found sPLA2-IA induced neuronal cell death in a concentration-dependent manner. This death was a delayed response requiring a latent time for 6h. sPLA2-IA-induced neuronal cell death was accompanied with apoptotic blebbing, condensed chromatin, and fragmented DNA, exhibiting apoptotic features. NMDA receptor blockers suppressed the neurotoxicity of sPLA2-IA, but an AMPA receptor blocker did not. Interestingly, L-type voltage-dependent Ca(2+) channel (L-VDCC) blocker significantly protected neurons from the sPLA2-IA-induced apoptosis. On the other hand, neither N-VDCC blockers nor P/Q-VDCC blocker did. In conclusion, we demonstrated that sPLA2-IA induced neuronal cell death via apoptosis. Furthermore, the present study suggests that not only NMDA receptor but also L-VDCC contributed to the neurotoxicity of snake venom sPLA2-IA.

Redox regulation of MAPK phosphatase 1 controls monocyte migration and macrophage recruitment

Monocytic adhesion and chemotaxis are regulated by MAPK pathways, which in turn are controlled by redox-sensitive MAPK phosphatases (MKPs). We recently reported that metabolic disorders prime monocytes for enhanced recruitment into vascular lesions by increasing monocytes' responsiveness to chemoattractants. However, the molecular details of this proatherogenic mechanism were not known. Here we show that monocyte priming results in the S-glutathionylation and subsequent inactivation and degradation of MKP-1. Chronic exposure of human THP-1 monocytes to diabetic conditions resulted in the loss of MKP-1 protein levels, the hyperactivation of ERK and p38 in response to monocyte chemoattractant protein-1 (MCP-1), and increased monocyte adhesion and chemotaxis. Knockdown of MKP-1 mimicked the priming effects of metabolic stress, whereas MKP-1 overexpression blunted both MAPK activation and monocyte adhesion and migration induced by MCP-1. Metabolic stress promoted the S-glutathionylation of MKP-1, targeting MKP-1 for proteasomal degradation. Preventing MKP-1 S-glutathionylation in metabolically stressed monocytes by overexpressing glutaredoxin 1 protected MKP-1 from degradation and normalized monocyte adhesion and chemotaxis in response to MCP-1. Blood monocytes isolated from diabetic mice showed a 55% reduction in MKP-1 activity compared with nondiabetic mice. Hematopoietic MKP-1 deficiency in atherosclerosis-prone mice mimicked monocyte priming and dysfunction associated with metabolic disorders, increased monocyte chemotaxis in vivo, and accelerated atherosclerotic lesion formation. In conclusion, we identified MKP-1 as a central redox-sensitive regulator of monocyte adhesion and migration and showed that the loss of MKP-1 activity is a critical step in monocyte priming and the metabolic stress-induced conversion of blood monocytes into a proatherogenic phenotype.

Fas-associated phosphatase 1 mediates Fas resistance in myeloid progenitor cells expressing the Bcr-abl oncogene

The interferon consensus sequence binding protein (Icsbp) is a transcription factor that influences multiple aspects of myelopoiesis. Expression of Icsbp is decreased in the bone marrow of human subjects with chronic myeloid leukemia (CML), and studies in murine models suggest that Icsbp functions as an anti-oncogene for CML. We previously identified a set of Icsbp target genes that may contribute to this anti-oncogene effect. The set includes PTPN13, the gene encoding Fas-associated phosphatase 1 (Fap1, a Fas antagonist). We previously demonstrated that myeloid progenitor cells from Icsbp-knockout mice exhibit Fap1-dependent Fas resistance. In the present study, we determined that the Fas resistance of Bcr-abl+cells is Icsbp- and Fap1-dependent. We also found that treatment of Bcr-abl bone marrow cells with a Fap1-blocking peptide prevents in vitro selection of a tyrosine kinase inhibitor (TKI)-resistant population. Therefore, these results have implications for therapeutic targeting of the Fas-resistant leukemia stem cell population and addressing TKI resistance in CML.

Recombinant TFPI-2 enhances macrophage apoptosis through upregulation of Fas/FasL

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine proteinase inhibitor with inhibitory activity toward activated factor XI, plasma kallikrein, plasmin, certain matrix metalloproteinases, and the tissue factor-activated factor VII complex. In addition, TFPI-2 has other functions such as promoting cell migration and inducing apoptosis. In the present study, we investigated if TFPI-2 induced apoptosis in cultured U937-derived macrophages and the possible signal pathways that involved in the apoptotic process. Apoptotic DNA fragment detection and caspase-3,9 activity measurements indicated that rTFPI-2 promoted U937-derived macrophage apoptosis. Hoechst 33342 assay and flow cytometry further showed that rTFPI-2 induced apoptosis in cultured macrophages in a dose-dependent manner. Because death receptors of the TNF family such as Fas are the best-understood death pathways that recruit Fas-associated death domain (FADD) and procaspase-8 to the receptor in macrophages, we investigated the expression of Fas and its ligand (FasL) and downstream signal caspase-8 by Western blot analysis. The results indicated that the process of apoptosis triggered by rTFPI-2 was, at least in part, actively conducted by U937-derived macrophages possibly through Fas/FasL signal pathway. In brief, rTFPI-2 may have the potential usefulness in inducing macrophages apoptosis, which suggest TFPI-2 might have antiatherogenic effects.

Mechanical impact induces cartilage degradation via mitogen activated protein kinases

OBJECTIVE

To determine the activation of Mitogen activated protein (MAP) kinases in and around cartilage subjected to mechanical damage and to determine the effects of their inhibitors on impaction-induced chondrocyte death and cartilage degeneration.

DESIGN

The phosphorylation of MAP kinases was examined with confocal microscopy and immunoblotting. The effects of MAP kinase inhibitors on impaction-induced chondrocyte death and proteoglycan (PG) loss were determined with fluorescent microscopy and 1, 9-Dimethyl-Methylene Blue (DMMB) assay. The expression of catabolic genes at mRNA levels was examined with quantitative real-time PCR.

RESULTS

Early p38 activation was detected at 20 min and 1h post-impaction. At 24h, enhanced phosphorylation of p38 and extracellular signal-regulated protein kinase (ERK)1/2 was visualized in chondrocytes from in and around impact sites. The phosphorylation of p38 was increased by 3.0-fold in impact sites and 3.3-fold in adjacent cartilage. The phosphorylation of ERK-1 was increased by 5.8-fold in impact zone and 5.4-fold in adjacent cartilage; the phosphorylation of ERK-2 increased by 4.0-fold in impacted zone and 3.6-fold in adjacent cartilage. Furthermore, the blocking of p38 pathway did not inhibit impaction-induced ERK activation. The inhibition of p38 or ERK pathway significantly reduced injury-related chondrocyte death and PG losses. Quantitative Real-time PCR analysis revealed that blunt impaction significantly up-regulated matrix metalloproteinase (MMP)-13, Tumor necrosis factor (TNF)-α, and ADAMTS-5 expression.

CONCLUSION

These findings implicate p38 and ERK mitogen activated protein kinases (MAPKs) in the post-injury spread of cartilage degeneration and suggest that the risk of post-traumatic osteoarthritis (PTOA) following joint trauma could be decreased by blocking their activities, which might be involved in up-regulating expressions of MMP-13, ADAMTS-5, and TNF-α.

Oxidative stress induced by urban fine particles in cultured EA.hy926 cells

It has been reported that vascular endothelia cell damage is an important precursor to the morbidity and mortality associated with cardiovascular disease exposed to airborne particulate matter (PM). The present study investigated the hypothesis that urban fine (PM(2.5)) particles could cause cytotoxicity via oxidative stress in human umbilical vein endothelial cells, EA.hy926. The concentrations of metal elements (Cr, Fe, Ni, Cu, Zn, Mo, Cd and Pb) in PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) were determined by inductively coupled plasma - mass spectrometry (ICP-MS). Iron (Fe), Zn and Pb were highly enriched in all the samples. Exposure of the cultured EA.hy926 cells to PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) led to cell death, reactive oxygen species (ROS) increase, mitochondrial transmembrane potential (ΔΨm) disruption and NF-κB activation, respectively. The ROS increase by exposure to PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) triggered the activation of nuclear factor (NF)-κB, which means that PM(2.5) particles exert cytotoxicity by an apopotic process. However, the induction of cytotoxicity by PM(2.5) suspension, water-soluble and water-insoluble fractions of PM(2.5) was reversed by pretreatment with superoxide dismutase (SOD). These results suggest that each fraction of PM(2.5) has a potency to cause oxidative stress in endothelial cells. ROS was generated through PM(2.5)-mediated mitochondrial apoptotic pathway, which may induce direct interaction between metal elements and endothelia cells.

Taiwan cobra phospholipase A2-elicited JNK activation is responsible for autocrine fas-mediated cell death and modulating Bcl-2 and Bax protein expression in human leukemia K562 cells

Phospholipase A(2) (PLA(2)) from Naja naja atra venom induced apoptotic death of human leukemia K562 cells. Degradation of procaspases, production of tBid, loss of mitochondrial membrane potential, Bcl-2 degradation, mitochondrial translocation of Bax, and cytochrome c release were observed in PLA(2)-treated cells. Moreover, PLA(2) treatment increased Fas and FasL protein expression. Upon exposure to PLA(2), activation of p38 MAPK (mitogen-activated protein kinase) and JNK (c-Jun NH(2)-terminal kinase) was found in K562 cells. SB202190 (p38 MAPK inhibitor) pretreatment enhanced cytotoxic effect of PLA(2) and led to prolonged JNK activation, but failed to affect PLA(2)-induced upregulation of Fas and FasL protein expression. Sustained JNK activation aggravated caspase8/mitochondria-dependent death pathway, downregulated Bcl-2 expression and increased mitochondrial translocation of Bax. SP600125 (JNK inhibitor) abolished the cytotoxic effect of PLA(2) and PLA(2)-induced autocrine Fas death pathway. Transfection ASK1 siRNA and overexpression of dominant negative p38alpha MAPK proved that ASK1 pathway was responsible for PLA(2)-induced p38 MAPK and JNK activation and p38alpha MAPK activation suppressed dynamically persistent JNK activation. Downregulation of FADD abolished PLA(2)-induced procaspase-8 degradation and rescued viability of PLA(2)-treated cells. Taken together, our results indicate that JNK-mediated autocrine Fas/FasL apoptotic mechanism and modulation of Bcl-2 family proteins are involved in PLA(2)-induced death of K562 cells.

Involvement of p38 MAPK- and JNK-modulated expression of Bcl-2 and Bax in Naja nigricollis CMS-9-induced apoptosis of human leukemia K562 cells

CMS-9, a phospholipase A(2) (PLA(2)) isolated from Naja nigricollis venom, induced apoptosis of human leukemia K562 cells, characterized by mitochondrial depolarization, modulation of Bcl-2 family members, cytochrome c release and activation of caspases 9 and 3. Moreover, an increase in intracellular Ca2+ concentration and the production of reactive oxygen species (ROS) was noted. Pretreatment with BAPTA-AM (Ca2+ chelator) and N-acetylcysteine (NAC, ROS scavenger) proved that Ca2+ was an upstream event in inducing ROS generation. Upon exposure to CMS-9, activation of p38 MAPK and JNK was observed in K562 cells. BAPTA-AM or NAC abrogated CMS-9-elicited p38 MAPK and JNK activation, and rescued viability of CMS-9-treated K562 cells. SB202190 (p38 MAPK inhibitor) and SP600125 (JNK inhibitor) suppressed CMS-9-induced dissipation of mitochondrial membrane potential, Bcl-2 down-regulation, Bax up-regulation and increased mitochondrial translocation of Bax. Inactivation of PLA(2) activity reduced drastically the cytotoxicity of CMS-9, and a combination of lysophosphatidylcholine and stearic acid mimicked the cytotoxic effects of CMS-9. Taken together, our data suggest that CMS-9-induced apoptosis of K562 cells is catalytic activity-dependent and is mediated through mitochondria-mediated death pathway triggered by Ca2+/ROS-evoked p38 MAPK and JNK activation.

Suppression of ERK signaling evokes autocrine Fas-mediated death in arachidonic acid-treated human chronic myeloid leukemia K562 cells

Arachidonic acid (AA)-induced apoptotic death of K562 cells (human chronic myeloid leukemic cells) was characteristic of reactive oxygen species (ROS) generation and mitochondrial depolarization. N-Acetylcysteine pretreatment rescued viability of AA-treated cells and abolished mitochondrial depolarization. In contrast to no significant changes in phospho-JNK and phospho-ERK levels, AA evoked notable activation of p38 MAPK. Unlike that of JNK and p38 MAPK, ERK suppression further reduced the viability of AA-treated cells. Increases in Fas/FasL protein expression, caspase-8 activation, the production of tBid and the loss of mitochondrial membrane potential were noted with K562 cells that were treated with a combination of U0126 and AA. Down-regulation of FADD attenuated U0126-evoked degradation of procaspase-8 and Bid. Abolition of p38 MAPK activation abrogated U0126-elicited Fas/FasL up-regulation in AA-treated cells. U0126 pretreatment suppressed c-Fos phosphorylation but increased p38 MAPK-mediated c-Jun phosphorylation. Knock-down of c-Fos and c-Jun protein expression by siRNA suggested that c-Fos counteracted the effect of c-Jun on Fas/FasL up-regulation. Taken together, our data indicate that AA induces the ROS/mitochondria-dependent death pathway and blocks the ERK pathway which enhances the cytotoxicity of AA through additionally evoking an autocrine Fas-mediated apoptotic mechanism in K562 cells.

Novel cationic lipid that delivers siRNA and enhances therapeutic effect in lung cancer cells

We have developed lipid-polycation-DNA (LPD) nanoparticles containing DOTAP and targeted with polyethylene glycol (PEG) tethered with anisamide (AA) to specifically deliver siRNA to H460 human lung carcinoma cells which express the sigma receptor. A novel non-glycerol based cationic lipid which contains both a guanidinium and a lysine residue as the cationic headgroup, i.e. DSGLA, downregulated pERK more efficiently in H460 cells than DOTAP. As demonstrated by using fluorescently labeled siRNA, LPD-PEG-AA prepared with DSGLA efficiently delivered siRNA to the cytoplasm of the H460 cells. Although the siRNA delivered by LPD-PEG-AA containing either DOTAP or DSGLA could effectively silence EGFR expression, a synergistic cell killing effect in promoting cellular apoptosis was only observed with DSGLA. The fluorescently labeled siRNA was efficiently delivered into the cytoplasm of H460 xenograft tumor by the LPD-PEG-AA containing either DOTAP or DSGLA 4 h after intravenous injection. Three daily injections (0.6 mg/kg) of siRNA formulated in the LPD-PEG-AA containing either DOTAP or DSGLA could effectively silence the epidermal growth factor receptor (EGFR) in the tumor, but the formulation containing DSGLA could induce more cellular apoptosis. A significant improvement in tumor growth inhibition was observed after dosing with LPD-PEG-AA containing DSGLA. Thus, DSGLA served as both a formulation component as well as a therapeutic agent which synergistically enhanced the activity of siRNA.