Increased Phosphorylation Of JNK Research Articles

The effects of ginsenoside Rb1 on JNK in oxidative injury in cardiomyocytes

Reactive oxygen species (ROS) can induce oxidative injury via iron interactions (i.e. Fenton chemistry and hydroxyl radical formation). Our prior work suggested that American ginseng berry extract and ginsenoside Re were highly cardioprotective against oxidant stress. To extend this study, we evaluated the protective effect of protopanaxadiol-type ginsenoside Rb1 (gRb1) on H(2)O(2)-induced oxidative injury in cardiomyocytes and explored the ROS-mediated intracellular signaling mechanism. Cultured embryonic chick cardiomyocytes (4-5 day) were used. Cell death was assessed by propidium iodide and lactate dehydrogenase release. Pretreatment with gRb1 (0.01, 0.1, or 1 μM) for 2 h and concurrent treatment with H(2)O(2) (0.5 mM) for 2 h resulted in a dose-dependent reduction of cell death, 36.6 ± 2.9% (n = 12, p < 0.05), 30.5 ± 5.1% (n = 12, p < 0.05) and 28.6 ± 3.1% (n = 12, p < 0.01) respectively, compared to H(2)O(2)-exposed cells (48.2 ± 3.3%, n = 12). This cardioprotective effect of gRb1 was associated with attenuated intracellular ROS generation as measured by 6-carboxy-2', 7'-dichlorodihydrofluorescein diacetate, preserved the mitochondrial membrane potential as determined using JC-1. In the ESR study, gRb1 exhibited the scavenging DPPH and hydroxyl radical activities. Furthermore, our data showed the increased JNK phosphorylation (p-JNK) in H(2)O(2)-exposed cells was suppressed by the pretreatment with gRb 1 (1 μM) (p < 0.01). Co-treatment of gRb1 with a specific inhibitor of JNK SP600125 (10 μM) further reduced the p-JNK and enhanced the cell survival after H(2)O(2) exposure. Collectively, our results suggest that gRb1 conferred cardioprotection that was mediated via attenuating ROS and suppressing ROS-induced JNK activation.

Inhibition of Hydrogen peroxide signaling by 4-hydroxynonenal due to differential regulation of Akt1 and Akt2 contributes to decreases in cell survival and proliferation in hepatocellular carcinoma cells

Dysregulation of cell signaling by electrophiles such as 4-hydroxynonenal (4-HNE) is a key component in the pathogenesis of chronic inflammatory liver disease. Another consequence of inflammation is the perpetuation of oxidative damage by the production of reactive oxidative species such as hydrogen peroxide. Previously, we have demonstrated Akt2 as a direct target of 4-HNE in hepatocellular carcinoma cells. In the present study, we used the hepatocellular carcinoma cell line HepG2 as model to understand the combinatorial effects of 4-HNE and hydrogen peroxide. We demonstrate that 4-HNE inhibits hydrogen peroxide-mediated phosphorylation of Akt1 but not Akt2. Pretreatment of HepG2 cells with 4-HNE prevented hydrogen peroxide stimulation of Akt-dependent phosphorylation of downstream targets and intracellular Akt activity compared with untreated control cells. Using biotin hydrazide capture, it was confirmed that 4-HNE treatment resulted in carbonylation of Akt1, which was not observed in untreated control cells. Using a synthetic GSK3α/β peptide as a substrate, treatment of recombinant human myristoylated Akt1 (rAkt1) with 20 or 40μΜ 4-HNE inhibited rAkt1 activity by 29 and 60%, respectively. We further demonstrate that 4-HNE activates Erk via a PI3 kinase and PP2A-dependent mechanism leading to increased Jnk phosphorylation. At higher concentrations, 4-HNE decreased both cell survival and proliferation as evidenced by MTT assays and EdU incorporation as well as decreased expression of cyclin D1 and β-catenin, an effect only moderately increased by the addition of hydrogen peroxide. The ability of 4-HNE to exert combinatorial effects on Erk, Jnk, and Akt-dependent cell survival pathways provides additional insight into the mechanisms of cellular damage associated with chronic inflammation.

Abstract 1468: Cerium oxide nanoparticles sensitize pancreatic cancer cells to radiation by modulating the JNK pathway

Abstract Pancreatic cancer, one of the most lethal cancers, has a poor prognosis and a high mortality rate. Currently, the absence of effective therapies increases reliance on radiation therapy (RT) to treat pancreatic cancer. We have previously reported that Cerium Oxide Nanoparticles (CONPs) are selectively toxic to cancer cells and possess the ability to selectively sensitize pancreatic cancer cells to radiation-induced cell death. Radiation-induced H2O2 production was significantly increased in the presence of less than or equal to 10 µM of CONPs and radiation-induced ROS production was increased in human L3.6pl pancreatic cancer cells pre-treated with 10 µM CONPs, which correlated with a significant decrease in cell viability and clonogenicity as compared to radiation alone. Conversely, ROS production was decreased in normal hTERT-HPNE pancreatic cells without impacting cell viability. The volume of pancreatic tumors was reduced by 48% in mice treated with combination therapy compared to radiation alone. Immunohistochemical (IHC) analysis revealed that combination therapy resulted in a significant increase in tumor cell apoptosis. In the most recent study, we determined the mechanism responsible for the increase in apoptosis as a result of increased ROS levels. L3.6pl cells (radiation sensitive), PANC-1 (radiation resistant) and HPNE (normal pancreatic cells) were treated with 5 Gy radiation in the presence or absence of 10 µM CONPs. CONPs selectively increased RT-induced Thioredoxin (TRX) oxidation in the cancer cells (L3.6pl: 14.2%, p&amp;lt;0.001; PANC-1: 23.5%, p&amp;lt;0.005) which correlated with a 35-40% increase in ASK-1 phosphorylation in both cell lines. Excitingly, western blot analyses showed a selective increase in JNK phosphorylation in both radiation sensitive (L3.6pl: JNK1 at 15%, JNK2 at 20%) and radiation resistant (PANC-1: JNK1 at 36%, JNK2 at 37%) cells which correlated with an increase in Caspase 3/7 activity (L3.6pl: 36.4%, p&amp;lt;0.05; PANC-1: 43.1%, p&amp;lt;0.05) compared to radiation alone. Knockdown of JNK expression by siRNA resulted in abrogation of Caspase 3/7 activity and corresponding cell death. Combination therapy of CONPs and radiation in an orthotopic murine model produced significant increases in JNK phosphorylation and Caspase 3 cleavage shown by IHC analysis. These data suggest that CONPs may act as a radiosensitizer in treatment of pancreatic cancer through the induction of JNK activation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1468. doi:1538-7445.AM2012-1468

Abstract 248: JNK-FoxO3a dependent apoptosis in quercetin treated MDA-MB-231 human breast cancer cells

Abstract FoxO transcription factors are well known as key tumor suppressors in mammalian cells. The suppression of FoxOs in cancer cells is thought to be mainly due to activation of multiple onco-kinases, such as Akt and SGK, by a phosphorylation-ubiquitylation-mediated cascade. On the other hand, phosphorlyation of FoxO by JNK relocalizes it from the cytoplasm to the nucleus allowing transcription of FoxO target genes. In this study, we applied human breast cancer cells to determine whether the activity of FoxO3a is regulated during the quercetin mediated apoptosis. After treatment with the indicated amount of quercetin (5-80uM) for 5days, the growth of human breast cancer cell lines including MDA-MB-231, MDA-MB-486 and MCF-7 cells was reduced in dose- and time-dependent manner. FACS analysis with AnnexinV/PI double staining showed that the proportion of early apoptotic cancer cells were significantly increased in quercetin treated cells. It represents the potent apoptotic effect of quercetin in breast cancer cells. Furthermore, a marked elevation of FoxO3a transcriptional activity was detected at 20μM of quercetin using FHRE-reporter assay, as well as increased protein level of FoxO3a was detected by western blotting. And also it was determined that the activation of FoxO3a lead to the upregulation of FasL expression during the apoptotic process. To identify the signaling mechanism of FoxO3a regulation, we examined the activation of several well known upstream kinases such as Akt, Erk, IKKβ, AMPK and JNK. Notably, a significant increase of JNK phosphorylation was observed in quercetin treated cells. In addition, the inhibition study with pharmacological inhibitor (SP600125) showed that the involvement of JNK for the regulation of FoxO3a activity is critical in quercetin treated breast cancer cells. These results demonstrate that quercetin induces FoxO3a-related apoptosis by activation of JNK in MDA-MB-231 cells, and suggest the possibility that JNK-FoxO3a signaling pathway contributes mainly to the apoptotic process of breast cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 248. doi:1538-7445.AM2012-248

Induction of a Mesenchymal Expression Program in Lung Epithelial Cells by Wingless Protein (Wnt)/β-Catenin Requires the Presence of c-Jun N-Terminal Kinase–1 (JNK1)

Recent studies suggest the importance of the transition of airway epithelial cells (EMT) in pulmonary fibrosis, and also indicate a role for Wingless protein (Wnt)/β-catenin signaling in idiopathic pulmonary fibrosis. We investigated the possible role of the Wnt signaling pathway in inducing EMT in lung epithelial cells, and sought to unravel the role of c-Jun-N-terminal-kinase-1 (JNK1). The exposure of C10 lung epithelial cells or primary mouse tracheal epithelial cells (MTECs) to Wnt3a resulted in increases in JNK phosphorylation and nuclear β-catenin content. Because the role of β-catenin as a transcriptional coactivator is well established, we investigated T-cell factor/lymphocyte-enhancement factor (TCF/LEF) transcriptional activity in C10 lung epithelial cells after the activation of Wnt. TCF/LEF transcriptional activity was enhanced after the activation of Wnt, and this increase in TCF/LEF transcriptional activity was diminished after the small interfering (si)RNA-mediated ablation of JNK. The activation of the Wnt pathway by Wnt3a, or the expression of either wild-type or constitutively active β-catenin (S37A), led to the activation of an EMT transcriptome, manifested by the increased mRNA expression of CArG box-binding factor-A, fibroblast-specific protein (FSP)-1, α-smooth muscle actin (α-SMA), and vimentin, increases in the content of α-SMA and FSP1, and the concomitant loss of zona occludens-1. The siRNA-mediated ablation of β-catenin substantially decreased Wnt3a-induced EMT. The siRNA ablation of JNK1 largely abolished Wnt3a, β-catenin, and β-catenin S37a-induced EMT. In MTECs lacking Jnk1, Wnt3a-induced increases in nuclear β-catenin, EMT transcriptome, and the content of α-SMA or FSP1 were substantially diminished. These data show that the activation of the Wnt signaling pathway is capable of inducing an EMT program in lung epithelial cells through β-catenin, and that this process is controlled by JNK1.

Impaired inflammatory responses to multiple Toll-like receptor ligands in alveolar macrophages of streptozotocin-induced diabetic mice

To investigate the effect of hyperglycemic state on the activation of alveolar macrophages (AMs) mediated via Toll-like receptors (TLRs) typically associated with bacterial infection. AMs obtained from normoglycemic control mice and streptozotocin-induced diabetic mice were stimulated ex vivo with the following: a TLR2 ligand, peptidoglycan (PGN); a TLR4 ligand, lipopolysaccharide (LPS); or a TLR5 ligand, flagellin (FLG). Cytokine production and mRNA expression were measured by ELISA and real-time PCR, respectively. TLR expression was assessed by real-time PCR and flow cytometry. AMs from diabetic mice produced significantly less TNF-α after PGN or FLG stimulation, and less IL-6 after FLG stimulation, compared with AMs from control mice. The decrease in the production of these cytokines was associated with reduced mRNA expression of the corresponding cytokines. In contrast, production of TNF-α and IL-6 after LPS stimulation did not differ between groups. Furthermore, there was no substantial difference in the expression of TLR2, TLR4, and TLR5 in AMs between the groups. The increased JNK phosphorylation induced by PGN or FLG stimulation was downregulated in AMs from diabetic mice. Hyperglycemic state impairs the reactivity of AMs to multiple TLR ligands. This effect might result from hyperglycemia-induced alteration of intracellular signaling and is unlikely due to the modulation of TLR expression.

Abstract P148: Urotensin II Impairs Cardiac Functions and Proliferation of Cardiac Side Population Cells in Mice During Chronic Pressure Overload.

Urotensin II (UII), a potent vasoactive “somatostatin-like” peptide, has been known to play a role in cardiovascular diseases including cardiac hypertrophy and heart failure. But its effect on cardiac side population cells (CSPs), one of somatic stem cells in the heart potentially participating in cardiac protection after injury, is unclear. The present study was therefore conducted to examine influences of UII on the differentiation, proliferation and function of CSPs. CSPs were isolated from neonatal rat hearts by fluorescence-activated cell sorting (FACS) and cultured in the absence or at the presence of UII. The expressions of alpha-cardiac myosin heavy chain, alpha-smooth muscle actin and Von Willebrand factor at mRNAs and protein levels were analyzed by reverse transcriptional PCR (RT-PCR) and immunofluoresence to evaluate the differentiation of CSPs into cardiomyocytes, smooth muscle cells and endothelial cells, respectively. The proliferation of CSPs was assessed by Luminescent Cell Viability Assay. The influence of UII on the proliferation of CSPs in vivo was also evaluated by FACS. Our results revealed that UII did inhibit the proliferation of CSPs through up-regulation of phosphorylated c-Jun N-terminal protein kinase (JNK), although it didn’t affect the differentiation of cultured CSPs into cardiaomyocytes, smooth muscle cells and endothelial cells. In vivo experiments also showed that injection of UII reduced the number of CSPs and impaired cardiac functions compared with vehicle injection in mice subjected to a chronic pressure overload, and an UII antagonist urantide induced a preserved cardiac function with an increased number of CSPs. These data indicate that UII reduces the number of CSPs by inhibiting the proliferation of CSPs possibly through increase of JNK phosphorylation, and blockage of UII may be a useful strategy for cardiac protection in the hypertensive.

Abstract P220: Anthrax Receptor Regulation of FAK and JNK Activation in Cardiac Myocytes

We previously demonstrated that anthrax lethal toxin (LT, protective antigen [PA] + lethal factor [LF]) produces acute systolic heart failure, characterized by increased left ventricular (LV) end-diastolic volume, reduced ejection fraction and decreased contractility in male Sprague-Dawley (SD) rats. The molecular basis for the cardiac dysfunction observed in either an animal model or clinical setting of anthrax toxicity remains to be examined. Previously, we tested LT dose-response effects on isolated neonatal rat ventricular myocytes (NRVM) at a dose of 0.05 ng/mL PA + 0.025 ng/mL LF diminished PLB and JNK phosphorylation from 1h to 4 h. During the LT+PA time-course, Akt phosphorylation at both Thr 308 and Ser 473 were also significantly reduced at all time points from 30 min to 4 h, accompanied by elevated B56α total protein and intracellular Ca 2+ , and reduced PLB phosphorylation. This response is mediated by translocation of LF into the cell through the anthrax receptors 1 and 2 (ATR1/2), which are structurally similar to integrins. In this study, we tested whether stimulation of ATR1/2 by PA alone can induce activation of the integrin effectors, FAK and JNK. Cardiac myocytes were treated time dependently (5 sec - 30 min) by PA at 0.25 ng/mL, and activation of FAK protein at different residues was determined. PA induced phosphorylation of FAK-Tyr 861 at 15 sec (p&lt;0.05), whereas there was no effect on FAK-Tyr 397 or FAK-Tyr 925 phosphorylation for any of the time points. Furthermore, we found that PA alone maximally increased JNK phosphorylation at 15 min of treatment (p&lt;0.05). This response was not blocked with either Losartan (10 µM) or AG1479 (100 nM) indicating that neither angiotensin type I receptor (AT1) or epidermal growth factor receptor (EGFR) transactivation was involved. In summary, this study suggests a key role of ATR1/2 in mediating of signal transduction across membrane of cardiac myocytes in response to B. anthracis PA stimulation and involvement in acute responses in regulation of FAK and JNK activation in independent of AT1 and EGFR pathway.

Infusion with the antioxidant N‐acetylcysteine attenuates early adaptive responses to exercise in human skeletal muscle

Production of reactive oxygen species (ROS) in skeletal muscle is markedly increased during exercise and may be essential for exercise adaptation. We, therefore, investigated the effects of infusion with the antioxidant N-acetylcysteine (NAC) on exercise-induced activation of signalling pathways and genes involved in exercise adaptation in human skeletal muscle. Subjects completed two exercise tests, 7 days apart, with saline (control, CON) or NAC infusion before and during exercise. Exercise tests comprised of cycling at 71% VO(2peak) for 45 min, and then 92% VO(2peak) to fatigue, with vastus lateralis biopsies at pre-infusion, after 45-min cycling and at fatigue. Analysis was conducted on the mitogen-activated protein kinase signalling pathways, demonstrating that NAC infusion blocked the exercise-induced increase in JNK phosphorylation, but not ERK1/2, or p38 MAPK. Nuclear factor-κB p65 phosphorylation was unaffected by exercise; however, it was reduced in NAC at fatigue by 14% (P < 0.05) compared with pre-infusion. Analysis of exercise and/or ROS-sensitive genes demonstrated that exercise-induced mRNA expression is ROS dependent of MnSOD, but not PGC-1α, interleukin-6, monocyte chemotactic protein-1, or heat-shock protein 70. These results suggest that inhibition of ROS attenuates some skeletal muscle cell signalling pathways and gene expression involved in adaptations to exercise.

Protein Phosphatase 2A and Neutral Sphingomyelinase 2 Regulate IRAK-1 Protein Ubiquitination and Degradation in Response to Interleukin-1β

The IL-1β signaling cascade is initiated by the phosphorylation of IL-1β receptor-associated kinase-1 (IRAK-1), followed by its ubiquitination and degradation. This paper investigates the regulation of IRAK-1 degradation in primary hepatocytes and in HEK cells overexpressing the IL-1β receptor. We provide evidence that protein phosphatase 2A (PP2A) is a negative regulator of the phosphorylation, Lys(48)-linked ubiquitination, and degradation of IRAK-1. PP2A catalytic activity increased within 30 min of stimulation with IL-1β. siRNA against PP2A catalytic subunit (PP2Ac) or treatment with pharmacological inhibitor, okadaic acid, enhanced IRAK-1 Lys(48)-linked ubiquitination and degradation. Direct interaction between PP2Ac and IRAK-1 was observed, suggesting that IRAK-1 might be a PP2A substrate. The mechanisms of PP2A activation by IL-1β involved neutral sphingomyelinase-2 (NSMase-2) and an accumulation of ceramide. Overexpression of NSMase-2 delayed IRAK-1 degradation in a PP2A-dependent manner, whereas NSMase-2 silencing had the opposite effect. The addition of sphingomyelinase, ceramide, or a proteasome inhibitor all led to retention of IRAK-1 at the cell membrane and to increased JNK phosphorylation. This study suggests that NSMase-2- and PP2A-dependent regulation of IRAK-1 degradation is a novel mechanism to fine tune the magnitude of IL-1β response.

Resistin Promotes Cardiac Hypertrophy via the AMP-activated Protein Kinase/Mammalian Target of Rapamycin (AMPK/mTOR) and c-Jun N-terminal Kinase/Insulin Receptor Substrate 1 (JNK/IRS1) Pathways

Resistin has been suggested to be involved in the development of diabetes and insulin resistance. We recently reported that resistin is expressed in diabetic hearts and promotes cardiac hypertrophy; however, the mechanisms underlying this process are currently unknown. Therefore, we wanted to elucidate the mechanisms associated with resistin-induced cardiac hypertrophy and myocardial insulin resistance. Overexpression of resistin using adenoviral vector in neonatal rat ventricular myocytes was associated with inhibition of AMP-activated protein kinase (AMPK) activity, activation of tuberous sclerosis complex 2/mammalian target of rapamycin (mTOR) pathway, and increased cell size, [(3)H]leucine incorporation (i.e. protein synthesis) and mRNA expression of the hypertrophic marker genes, atrial natriuretic factor, brain natriuretic peptide, and β-myosin heavy chain. Activation of AMPK with 5-aminoimidazole-4-carbozamide-1-β-D-ribifuranoside or inhibition of mTOR with rapamycin or mTOR siRNA attenuated these resistin-induced changes. Furthermore, resistin increased serine phosphorylation of insulin receptor substrate (IRS1) through the activation of the apoptosis signal-regulating kinase 1/c-Jun N-terminal Kinase (JNK) pathway, a module known to stimulate insulin resistance. Inhibition of JNK (with JNK inhibitor SP600125 or using dominant-negative JNK) reduced serine 307 phosphorylation of IRS1. Resistin also stimulated the activation of p70(S6K), a downstream kinase target of mTOR, and increased phosphorylation of the IRS1 serine 636/639 residues, whereas treatment with rapamycin reduced the phosphorylation of these residues. Interestingly, these in vitro signaling pathways were also operative in vivo in ventricular tissues from adult rat hearts overexpressing resistin. These data demonstrate that resistin induces cardiac hypertrophy and myocardial insulin resistance, possibly via the AMPK/mTOR/p70(S6K) and apoptosis signal-regulating kinase 1/JNK/IRS1 pathways.

Abstract 859: EGCG inhibits pancreatic cancer growth and stem cell characteristics in xenografts and KrasG12D transgenic mice models

Abstract FoxO (forkhead box O) transcription factors are crucial regulators of cell fate. This function of FoxO proteins relies on their ability to control diverse functions such as proliferation, differentiation, DNA repair and apoptosis. Constitutively active AKT and ERK in cancer cells have been shown to phosphorylate FoxO transcription factors (FKHR, FKHRL1 and AFX), which bind to protein 14-3-3 and sequester in the cytoplasm. In the absence of survival signals, FoxO proteins dephosphorylate, translocate to the nucleus and upregulate a series of target genes, thereby promoting cell cycle arrest and apoptosis. EGCG, a component of green tea, exerts antiproliferative and proapoptotic actions on a number of different cancer cell lines through diverse mechanisms. However, the mechanisms by which EGCG inhibits cell proliferation and induces apoptosis are poorly understood. EGCG inhibited viability and induced apoptosis in human pancreatic cancer cell lines. EGCG induces PTEN expression and inhibits Akt phosphorylation in pancreatic cancer Hs766T, AsPC-1, MIA PaCa-2 and PANC-1 cells. Treatment of PANC-1 cells with EGCG caused a decrease in ERK phosphorylation, and an increase in JNK phosphorylation. Overexpression of FOXO1, FOXO3a, and FOXO4 inhibited cell viability in PANC-1 cells. The inhibitory effects of EGCG on cell viability were further enhanced when cells were transfected with FOXO1, FOXO3a, and FOXO4. EGCG enhanced FOXO-DNA binding and transcriptional activities. Interestingly, EGCG inhibited pancreatic cancer growth and/or development in xenograft, orthotopic and KrasG12D transgenic mice models. EGCG also inhibited pancreatic cancer stem cell characteristics. In conclusion, our data demonstrate that EGCG can inhibit pancreatic cancer growth and/or development through multiple mechanisms and thus can be used for the management of pancreatic cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 859. doi:10.1158/1538-7445.AM2011-859

Effects of endurance training on apoptotic susceptibility in striated muscle

An increase in the production of reactive oxygen species occurs with muscle disuse, ischemic cardiomyopathy, and conditions that arise with senescence. The resulting oxidative stress is associated with apoptosis-related myopathies. Recent research has suggested that chronic exercise is protective against mitochondrially mediated programmed cell death. To further investigate this, we compared soleus (Sol) and cardiac muscles of voluntary wheel-trained (T; 10 wk) and untrained (C) animals. Training produced a 52% increase in muscle cytochrome c oxidase (COX) activity. Sol and left ventricle (LV) strips were isolated and incubated in vitro with H2O2 for 4 h. Strips were then fractionated into cytosolic and mitochondrial fractions. Whole muscle apoptosis-inducing factor (AIF) and Bax/Bcl-2 levels were reduced in both the Sol and LV from T animals. H2O2 treatment induced increases in JNK phosphorylation, cofilin-2 localization to the mitochondria, as well as cytosolic AIF in both Sol and LV of T and C animals, respectively. Mitochondrial Bax and cytosolic cytochrome c were augmented under oxidative stress in the LV only. The H2O2-induced increases in P-JNK, mitochondrial Bax, and cytosolic AIF were ablated in the LV of T animals. These data suggest that short-term oxidative stress can induce apoptotic signaling in striated muscles in vitro. In addition, training can attenuate oxidative stress-induced apoptotic signaling in a tissue-specific manner, with an effect that is most prominent in cardiac muscle.

Urotensin II inhibits the proliferation but not the differentiation of cardiac side population cells

Urotensin II (UII) induces the development of cardiac remodeling and atherosclerosis by promoting hypertrophy of cardiomyocytes and mitogenesis of fibroblasts and vascular smooth muscle cells. But its effect on cardiac side population cells (CSPs), one of somatic stem cells, is unclear. The present study examined the influences of UII on the differentiation and proliferation of CSPs. CSPs were isolated from neonatal rat hearts by fluorescence-activated cell sorting (FACS) and cultured with or without the presence of UII (10 −8, 10 −7 , 10 −6 mol/l). The expressions of α-cardiac myosin heavy chain (α-MHC), α-smooth muscle actin (SMA) and Von Willebrand factor (vWF) mRNAs and proteins were analyzed by reverse transcriptional PCR (RT-PCR) and immunofluoresence to evaluate the differentiation of CSPs into cardiomyocytes, smooth muscle cells and endothelial cells, respectively. The proliferation of CSPs was assessed by Luminescent Cell Viability Assay. The influence of UII on the proliferation of CSPs in vivo was also evaluated by FACS. Our results revealed that UII did inhibit the proliferation of CSPs through up-regulation of phosphorylated c-Jun N-terminal protein kinase (JNK), although it didn’t affect the differentiation of cultured CSPs. Experiments in vivo also showed that UII reduced the number of CSPs in mice compared with control group. These data indicate that UII reduces the number of CSPs by inhibiting the proliferation of CSPs possibly through increase of JNK phosphorylation.

Heat shock transcription factor-1 inhibits H2O2-induced apoptosis via down-regulation of reactive oxygen species in cardiac myocytes

Heat shock transcription factor-1 (HSF1) protects against cardiac diseases such as ischemia/reperfusion injury and myocardial infarction. However, the mechanisms have not yet been fully characterized. In this study, we investigated the effects of reactive oxygen species (ROS) and apoptosis signal-regulating kinase-1 (ASK1) in HSF1-regulated cardiomyocyte protection. Cultured cardiomyocytes of neonatal rats were transfected with HSF1, ASK1 or both of them before exposure to H(2)O(2), and the ROS generation, c-Jun N-terminal kinase (JNK) activity and apoptosis were examined. H(2)O(2) significantly increased intracellular ROS generation and apoptotic cells as expected, and all these cellular events were greatly inhibited by overexpression of HSF1. However, H(2)O(2)-induced increases in JNK phosphorylation and cell apoptosis were largely enhanced by ASK1 overexpression whereas the similar transfection did not affect the ROS generation in the cells. Moreover, inhibition of H(2)O(2)-increased ROS generation, JNK phosphorylation, and cellular apoptosis by overexpression of HSF1 tended to be disappeared, when the cells were co-transfected with ASK1. These results suggest that HSF1 protects cardiomyocytes from apoptosis under oxidative stress via down-regulation of intracellular ROS generation and inhibition of JNK phosphorylation. Although ASK1 itself has no effect on intracellular ROS generation, it may affect the inhibitory effects of HSF1 on ROS generation, JNK activity, and cardiomyocyte injury.

Neuronal nitric oxide synthase protects the pancreatic beta cell from glucolipotoxicity-induced endoplasmic reticulum stress and apoptosis

Cytokines stimulate nitric oxide production in pancreatic beta cells, leading to endoplasmic reticulum (ER) stress and apoptosis. Treatment of beta cells with glucose and NEFA induces nitric oxide synthase (NOS) as well as ER stress. However, the role of NO in glucolipotoxicity-induced ER stress in beta cells is not clear. We studied the effect of high glucose and palmitate levels on NOS isoform production in rat and Psammomys obesus islets and in insulinoma-1E beta cells. The effects of neuronal NOS (nNOS) inhibition by small interfering RNA or by N (omega)-nitro-L-arginine methyl ester (L-NAME) on beta cell function, ER stress and apoptosis under conditions of glucolipotoxicity were investigated. Overnight incubation of rat and P. obesus islets at 22.2 mmol/l glucose with 0.5 mmol/l palmitate induced the production of nNOS but not inducible NOS (iNOS), in contrast with the robust stimulation of iNOS by cytokines. NOS inhibition by L-NAME did not prevent the decrease in glucose-stimulated insulin secretion and proinsulin biosynthesis or the depletion of islet insulin content observed under conditions of glucolipotoxicity. Moreover, treatment of beta cells with palmitate and L-NAME together resulted in marked activation of the IRE1alpha and PERK pathways of the unfolded protein response. This was associated with increased JNK phosphorylation and apoptosis in islets and beta cells. Moreover, partial nNos knockdown increased JNK phosphorylation and CHOP production, leading to apoptosis. In beta cells subjected to glucolipotoxic conditions, chronic inhibition of NOS exacerbates ER stress and activates JNK. Therefore, induction of nNOS is an adaptive response to glucolipotoxicity that protects beta cells from stress and apoptosis.

Abstract 2868: EGCG inhibits pancreatic cancer growth in xenografts and KrasG12D transgenic mice models

Abstract FoxO (forkhead box O) transcription factors are crucial regulators of cell fate. This function of FoxO proteins relies on their ability to control diverse functions such as proliferation, differentiation, DNA repair and apoptosis. Constitutively active AKT and ERK in cancer cells have been shown to phosphorylate FoxO transcription factors (FKHR, FKHRL1 and AFX), which bind to protein 14-3-3 and sequester in the cytoplasm. In the absence of survival signals, FoxO proteins dephosphorylate, translocate to the nucleus and upregulate a series of target genes, thereby promoting cell cycle arrest and apoptosis. EGCG, a component of green tea, exerts antiproliferative and proapoptotic actions on a number of different cancer cell lines through diverse mechanisms. However, the mechanisms by which EGCG inhibits cell proliferation and induces apoptosis are poorly understood. EGCG inhibited viability and induced apoptosis in human pancreatic cancer cell lines. EGCG induces PTEN expression and inhibits Akt phosphorylation in pancreatic cancer Hs766T, AsPC-1, MIA PaCa-2 and PANC-1 cells. Treatment of PANC-1 cells with EGCG caused a decrease in ERK phosphorylation, and an increase in JNK phosphorylation. Overexpression of FOXO1, FOXO3a, and FOXO4 inhibited cell viability in PANC-1 cells. The inhibitory effects of EGCG on cell viability were further enhanced when cells were transfected with FOXO1, FOXO3a, and FOXO4. EGCG enhances FOXO-DNA binding activity. EGCG-induced FOXO transcriptional activity was further enhanced in the presence of FOXO1-TM, FOXO3a-TM, and FOXO4-TM. Interestingly, EGCG inhibited pancreatic cancer growth in xenograft, orthotopic and KrasG12D transgenic mice models. In conclusion, our data demonstrate that EGCG can inhibit pancreatic cancer growth through multiple mechanisms and thus can be used for the pancreatic cancer prevention. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 2868.

Voluntary aerobic exercise attenuates oxidative stress‐induced apoptotic signalling in cardiac muscle

An increase in the production of reactive oxygen species occurs with aging, and the resulting oxidative stress has been associated with apoptosis‐related cardiomyopathy. Recent research has indicated that chronic exercise is protective against mitochondrially‐mediated programmed cell death. To further investigate this in the heart we compared voluntary wheel trained (T, 9 weeks) and untrained (C) animals. Training increased heart weight to body weight ratio, and produced a 54% increase in muscle COX activity. Left ventricle (LV) strips were isolated and incubated in vitro with H2O2 for 4 hours. LV strips were then fractionated into cytosolic and mitochondrial fractions. H2O2 treatment induced increases in JNK phosphorylation, Bax localization to the mitochondria, as well as cytosolic AIF by 73%, 106% and 38% in C animals respectively, all of which were attenuated in T animals. Interestingly, H2O2 induced a 2.5‐fold increase in cofilin‐2 localization to the mitochondria, as well as a 64% increase in cytochrome c release which were unaltered by training. These data suggest that regular exercise can attenuate apoptotic signalling via reduced JNK phophorylation, Bax translocation and mitochondrial AIF release. Thus, endurance exercise training has the potential to reduce oxidative stress‐induced programmed cell death in the heart.

Insulin potentiates FcɛRI-mediated signaling in mouse bone marrow-derived mast cells

Factors contained in physiological microenvironments in tissues where mast cells differentiate and reside may influence mast cell responsiveness and modify antigen-dependent activation. A possible direct or indirect role of mast cell responses in diabetes mellitus prompted us to study the impact of insulin treatment on antigen triggered signaling pathways downstream of FcɛRI in bone marrow-derived mouse mast cells (BMMCs). We found that insulin alone stimulates tyrosine phosphorylation of tyrosine kinases Lyn, Syk, Fyn, the adapter protein Gab2 (Grb2-associated binding protein 2), Akt and activates ERK, JNK and p38 kinase. Effect of insulin on FcɛRI signaling pathways was marked by enhanced phosphorylation of Lyn, Fyn, Gab2 and Akt. Furthermore, BMMC stimulated with antigen in the presence of insulin responded with enhanced protein kinase θ (PKCθ) activity and increased JNK phosphorylation when compared to BMMC triggered with antigen alone. Functional studies reveal enhanced degranulation and altered cytoskeletal rearrangement when BMMCs were treated simultaneously with insulin and antigen. Our results suggest that insulin tunes antigen-mediated responses of mast cells.

Abstract B67: Thapsigargin sensitizes multidrug-resistant human ovarian carcinoma cells to doxorubicin

Abstract Chemoresistance to anticancer drugs is a common and troublesome occurrence in ovarian cancer patients. Despite advances in surgical and chemotherapeutic modalities, survival rates remain alarmingly low. Hence, it has been suggested that strategies for reversing multidrug resistance (MDR) are top priorities for reducing cancer mortality. Thapsigargin (TG), a sesquiterpene lactone isolated from the roots of Thapsia garganica, has been demonstrated to possess anticancer properties. The impact of TG, however, on chemoresistance has not been fully elucidated. Here, we report the effects of combining TG with doxorubicin (DOX), since DOX forms part of the standard treatment for women with advanced ovarian cancer. Multidrug-resistant A2780/MDR human ovarian carcinoma cells were treated with TG in combination with a clinically relevant concentration of DOX (10 µM) and assessed for cell proliferation using the MTT assay. A2780/MDR cells were 100-fold more resistant to DOX than parental A2780 cells on the basis of MTT assay. The IC50 of DOX decreased from 8.02 µM to 0.07 µM, in the presence of 1 µMTG, after 24 h of continuous drug combination exposure, producing a 115-fold reversal of MDR. Flow cytometric analysis of cells treated for 24 h with 10 µM DOX with and without 5 µMTG demonstrated significantly increased apoptosis in the presence of TG. TG by itself had little effect on the viability of A2780/MDR cells, as evident by less than 5% cell death after 24-h TG treatment. The activation of caspases-3 and -9 and PARP cleavage were enhanced in combination therapy relative to single agent treatments. Combined treatment with TG and DOX also increased JNK phosphorylation in A2780/MDR cells and pretreatment with JNK inhibitor SP600125 partially rescued apoptosis. Our data demonstrated that addition of TG at subtoxic concentration restored the sensitivity to DOX-induced apoptosis in A2780/MDR cells via JNK pathway. Taken together, these data support the concurrent use of DOX and TG in ovarian cancer therapeutics. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):B67.