Modulation Of Signal Transduction Pathways Research Articles

The ISG15/USP18 ubiquitin-like pathway (ISGylation system) in Hepatitis C Virus infection and resistance to interferon therapy

The ISG15/USP18 pathway modulates cellular functions and is important for the host innate immune response to chronic viral infections such as Hepatitis C Virus (HCV). Interferon stimulated gene 15 (ISG15) was the first ubiquitin-like protein modifier identified. As in ubiquitination, ISG15 conjugates to target proteins (ISGylation) through the sequential enzymatic action of activating E1, conjugating E2, and ligating E3 enzymes. ISGylation modulates signal transduction pathways and host anti-viral response. The ISGylation process is reversible through the action of an ISG15 protease, USP18. Ubiquitin-like specific protease 18 (USP18) has functions that are both ISG15-dependent and ISG15-independent; the importance of the ISG15/USP18 pathway to chronic HCV infection is illustrated by the consistent finding of increased levels of ISG15 and USP18 in the liver tissue of patients who do not respond to interferon-based treatments. Mechanistically, HCV seems to exploit the ISG15/USP18 pathway to promote viral replication and evade innate anti-viral immune responses.

Manipulating tissue metabolism by amino acids

Protein metabolism is considered to be regulated by amino acids, with major consequences on tissue development. There is evidence that lysine greatly affects carcass composition and muscle growth. In particular, a drastic effect of dietary provision of lysine has been observed on breast muscle development in chickens. Other essential amino acids, such as threonine and valine, do not have as pronounced an effect as lysine on body composition. Increasing lysine can also improve chicken breast muscle quality by increasing its ultimate pH and water holding capacity, but the underlying mechanisms are still unknown. Studies conducted over the last ten years indicate that, in addition to being substrates for protein synthesis, amino acids act as modulators of signal transduction pathways that control metabolism and cell functions. For instance, certain amino acids can modulate the activity of the intracellular protein kinases involved in the control of mRNA translation. Interestingly, enhanced responses to amino acids have been reported during the neonatal period, suggesting that early protein nutrition impacts on the development of broiler chicks. Methionine and cysteine have a very significant place among amino acids because they have several additional roles: they are precursors of essential molecules, for example cysteine is used for the synthesis of the antioxidant glutathione, and thus participates in the control of oxidative status, methionine is a source of the methyl groups needed for all biological methylation reactions, including methylation of DNA and histones, etc. These findings together indicate the importance of optimizing amino acid nutrition and providing a rationale for nutritional advice.

FKBPs in chromatin modification and cancer

FK506-binding proteins (FKBPs) are intracellular receptors for FK506 and rapamycin, immunosuppressants that have recently been utilized as anticancer drugs. In the cytoplasm, FKBPs and these drugs modulate signal transduction pathways. However, recent reports reveal novel functions of FKBPs in the nucleus, which include regulation of transcription factors, histone chaperone activity, and modifications of chromatin structure. These activities are known to affect gene expression, DNA repair, and DNA replication. Therefore, elucidation of the nuclear functions of FKBPs will help researchers and clinicians better understand how immunosuppressants work as anticancer drugs, which might in turn lead to novel designs of cancer therapy.

Challenges in the Management of Severe Asthma: Role of Current and Future Therapies

Severe asthma is a complex and heterogeneous phenotype characterized by persistent symptoms and poor control. While some patients respond to high doses of inhaled corticosteroids in combination with long-acting beta-agonists, a significant subset require oral corticosteroids to achieve symptom control. This issue has led to the development of alternative therapeutic strategies for severe asthma. This article provides an overview of current therapeutic strategies and suggests how they can be best applied to the treatment of severe asthma. The article then reviews alternative therapeutic strategies including macrolide antibiotics, biologic agents, modulators of signal transduction pathways and bronchial thermoplasty. The challenge remains to determine the appropriate phenotype for each therapeutic strategy in view of the heterogeneity of severe asthma.

Anesthetic Modulation of Signal Transduction Pathways in the α4β2 nAchR Revealed by the Perturbation-Based Markovian Transmission Model

The gating mechanism of ligand-gated ion channels and anesthetic modulation of channel gating remain to be determined. In this study, we used the perturbation-based Markovian transmission model to investigate the time-dependent signal propagation in the neuronal nicotinic acetylcholine receptor (α4β2 nAChR) under initial perturbations by agonist binding. Both open- and closed-channel α4β2 nAChR conformations in the presence and absence of the anesthetic halothane, from our previous computational studies, were examined. We found that signal transduction in α4β2 resembles the conformation wave mechanism. In all systems, the perturbation signal flows from the agonist-binding sites up toward the main immunogenic region, then down to the bottom of the beta barrel, followed by the extracellular (EC)/transmembrane (TM) interface, and finally to the transmembrane domain, as measured by the time dependence of the maximum probability flux. The EC domain of the open- and closed-channel α4β2 conformations showed different dynamic responses to the perturbation at the agonist-binding site: many more residues in the EC domain of the open-channel α4β2 nAChR exhibited frequent fluctuation. In the system with halothane, the signal transduction within pre-TM1 (R207), Cys-loop (F137, P138, F139), and TM2-TM3 linker (L271) slowed down in some of the subunits, but speeded up in others. The changes in signal transduction at the EC/TM interface may underlie the effects of anesthetics on the α4β2 nAChR. Supported by NIH (R01GM066358, R01GM056257, R37GM049202).

Two faces of lipid peroxidation products: the -Yin and Yang- principles of oxidative stress

Oxidants and antioxidants, like many other things, have two faces. Lipids, important biological substances of aerobic organisms, are oxidized by reactive oxygen and nitrogen species formed inevitably in vivo to give diverse products. The emerging evidence suggests that lipid peroxidation products have also two faces. Lipid peroxidation products alter biological membrane organization and modify proteins and nucleic acids, which result in a number of dysfunctional states in vivo. Many studies show that the levels of lipid peroxidation products increase with the development of acute and chronic diseases. Lipid peroxidation products may modulate signal transduction pathways and mediate biological processes through receptors or receptor-independent pathways. At the same time, it has been shown that the lipid peroxidation products induce adaptive response and increase tolerance against forthcoming oxidative stress by upregulating defense capacity. In this brief review, the examples of such dual opposite effects of lipid peroxidation products are shown and the underlying mechanisms are suggested.

Dietary flavonoids as cancer-preventive and therapeutic biofactors

Flavonoids are present in many plants, and hence, in foods and ingredients derived from them. These polyphenolic compounds have attracted renewed attention as potential anticarcinogens, and the molecular mechanisms of their anticarcinogenic effects and their bioavailability have been extensively explored. In this review, we focus on the major dietary flavonoids; flavones, flavonols, and flavan-3-ols (catechins), and evaluate their roles in cancer prevention. After absorption with or without metabolic conjugation, flavonoids are transported to target organs where they exert their anticarcinogenic activity. The molecular mechanisms of the anticarcinogenic effects of flavonoids include their antagonistic effect on the aryl hydrocarbon receptor (AhR), and regulation of phase I and II drug metabolizing enzymes and phase III transporters. Experimental evidence suggests that flavonoids modulate signal transduction pathways at each stage of carcinogenesis. The interactions between flavonoids and biomolecules in vivo must be investigated in detail to identify specific targets. In addition, the potential side effects should be considered when flavonoid supplements are used for cancer prevention. Therefore, the use of flavonoids as chemopreventive agents should be further investigated to establish safe levels of flavonoid intake.

New deals on the transcriptional and post-transcriptional regulation of TRP channel target genes during the angiogenesis of glioma

Tumor angiogenesis isn’t only the result of physiological adaptation to hypoxia in response to an increasing tumor mass, but it is also the result of critical genetic mutations that activate a transcriptional program for angiogenesis. Calcium (Ca 2+ ) is an important second messenger and its entry through plasma membrane affects angiogenesis. Several reports indicate that Ca 2+ permeable transient receptor potential (TRP) channels belonging to the TRPC, TRPV and TRPM represent target genes, down-stream to Notch1, PTEN, NFAT and Hif-1 transcriptional factors are activated during tumor angiogenesis. Several reports indicate that angiogenic growth factors such as vascular endothelial growth factor (VEGF) and basic firoblast growth factor (bFGF) may activate TRP channels at transcriptional and post-transcriptional levels, causing a subsequent rise in endothelial [Ca 2+ ]i, which modulates signal transduction pathways regulating the angiogenesis. Conversely, Ca2+ influx through TRP channel activation may stimulate endothelial cells to trigger transcription, production and release of angiogenic growth factors such as VEGF and platelet-derived growth factor (PDGF) that stimulate angiogenesis. Thus for example, hypoxia by inducing Notch1 activation, increases the expression of a member of TRPC family, TRPC6 and induces [Ca 2+ ]i that is coupled to activation of calcineurin-NFAT pathway that results in glioma angiogenesis. TRP channels might be a promising target for new therapeutic agents to anti-angiogenic therapy. However, we are only at the beginning to considering endothelial TRP channels as targets for novel anti-angiogenic therapeutic intervention. Further studies on the role of the different members of this ion channel family in physiology and pathology are required to understand the involvement of TRP channels in glioma angiogenesis.

Modulation of protein kinase signaling cascades by palytoxin

Although known for its acutely toxic action, palytoxin has also been identified as a type of carcinogenic agent called a tumor promoter. In general tumor promoters do not damage DNA, but instead contribute to carcinogenesis by disrupting the regulation of cellular signaling. The identification of palytoxin as a tumor promoter, together with the recognition that the Na +, K +-ATPase is its receptor, led to research on how palytoxin triggers the modulation of signal transduction pathways. This review focuses on mitogen activated protein (MAP) kinases as mediators of palytoxin-stimulated signaling. MAP kinases are a family of serine/threonine kinases that relay a variety of signals to the cellular machinery that regulates cell fate and function. The studies discussed in this review investigated how palytoxin stimulates MAP kinase activity and, in turn, how MAP kinases mediate the response of cells to palytoxin.

Antioxidants Induce Apoptosis of Rat Ovarian Theca-Interstitial Cells1

Regulation of growth of ovarian theca-interstitial tissues is essential for normal ovarian development and function. Reactive oxygen species are involved in modulation of signal transduction pathways, including regulation of tissue growth and apoptosis. Previously, we have demonstrated that antioxidants inhibit proliferation of theca-interstitial cells. This report evaluates the effects of antioxidants on apoptosis of rat theca-interstitial cells. The cells were cultured in chemically defined media without or with vitamin E succinate and ebselen. Apoptosis was evaluated by cytochemical assessment of nuclear morphology, activity of executioner caspases 3 and 7, and determination of staining with annexin V in combination with propidium iodide. Both tested antioxidants induced significant morphological changes consistent with apoptosis, including chromatin condensation, nuclear shrinkage, and pyknosis. Antioxidants also induced other hallmarks of apoptosis including increased activity of caspases 3/7 as well as increased staining with annexin V. The present findings demonstrate that antioxidants with distinctly different mechanisms of action induce a series of events consistent with the process of apoptosis in ovarian mesenchyme. These observations may be of translational-clinical relevance, providing mechanistic support for the use of antioxidants in the treatment of PCOS, a condition associated with excessive growth and activity of theca-interstitial cells.

Tomato Lycopene and Inflammatory Cascade: Basic Interactions and Clinical Implications

Lycopene, a natural carotenoid found in tomato, has been reported to possess various health benefits, such as cardiovascular and cancer preventive properties. However, the experimental basis for such health benefits is not fully understood. One of the possible mechanisms for its protective activities is by down-regulation of the inflammatory response. That includes the inhibition of pivotal pro-inflammatory mediators, such as the reduction of reactive oxygen species, the inhibition of synthesis and release of pro-inflammatory cytokines, changes in the expression of cyclooxygenase and lipoxygenase, modifications of eicosanoid synthesis, and modulation of signal transduction pathways, including that of the inducible nitric oxide synthase via its inhibitory effects on Nuclear Factor-kB (NF-kB), Activated protein-1 (AP-1) and mitogen-activated protein kinase (MAPK) signaling. Recent data suggest that lycopene also exhibits anti-inflammatory activity through induction of programmed cell death in activated immune cells. This review will discuss recent data on the control of inflammatory signaling exerted by tomato lycopene in isolated cells, in animal models and in clinical trials, focusing on the dose of the carotenoid and the biological environment in which it acts. A clear understanding of the molecular mechanisms of action of lycopene is crucial in the valuation of this molecule as a potential preventive and therapeutic agent.

Glutathione transferases as mediators of signaling pathways involved in cell proliferation and cell death

Glutathione transferases (GSTs) are enzymes that catalyze the conjugation of glutathione (GSH) to a variety of electrophilic substances. Their best known role is as cell housekeepers engaged in the detoxification of xenobiotics. Recently, GSTs have also been shown to act as modulators of signal transduction pathways that control cell proliferation and cell death. Their involvement in cancer cell growth and differentiation, and in the development of resistance to anticancer agents, has made them attractive drug targets. This review is focused on the inhibition of GSTs, in particular GSTP1-1, as a potential therapeutic approach for the treatment of cancer and other diseases associated with aberrant cell proliferation.

Bitter Melon (Momordica charantia) Extract Inhibits Breast Cancer Cell Proliferation by Modulating Cell Cycle Regulatory Genes and Promotes Apoptosis

Breast cancer is one of the most common cancers among women in the United States. Although there are effective drugs for treating advanced stages of breast cancers, women eventually develop resistance. One of the approaches to control breast cancer is prevention through diet, which inhibits one or more neoplastic events and reduces cancer risk. In this study, we have used human breast cancer cells, MCF-7 and MDA-MB-231, and primary human mammary epithelial cells as an in vitro model to assess the efficacy of bitter melon (Momordica charantia) extract (BME) as an anticancer agent. BME treatment of breast cancer cells resulted in a significant decrease in cell proliferation and induced apoptotic cell death. Apoptosis of breast cancer cells was accompanied by increased poly(ADP-ribose) polymerase cleavage and caspase activation. Subsequent studies showed that BME treatment of breast cancer cells inhibited survivin and claspin expression. Fluorescence-activated cell sorting analysis suggested that MCF-7 cells treated with BME accumulated during the G2-M phase of the cell cycle. Further studies revealed that BME treatment enhanced p53, p21, and pChk1/2 and inhibited cyclin B1 and cyclin D1 expression, suggesting an additional mechanism involving cell cycle regulation. Together, these results show that BME modulates signal transduction pathways for inhibition of breast cancer cell growth and can be used as a dietary supplement for prevention of breast cancer.

Darinaparsin a Novel Organic Arsenic Molecule Active in Lymphoma: Development of An Oral Form.

Abstract 4759 IntroductionDarinaparsin is an organic arsenic molecule constructed of dimethylated arsenic linked to glutathione (N-[S-(dimethylarsino)-N-L-gamma-glutamyl-L-cysteinyl]-glycine). It has a multifaceted mechanism of action, inducing G2/M cell cycle arrest and apoptosis mediated through disruption of mitochondrial functions, increased reactive oxygen species production, and modulation of signal transduction pathways. In addition, darinaparsin has anti-angiogenic activity. It has significant activity in a broad spectrum of hematologic and solid tumors in preclinical models, including human cell lines resistant to arsenic trioxide. It is active in heavily treated patients with refractory lymphoma when administered IV 300 mg/m2 for 5 days on a 28 day cycle, and is very well tolerated. Preclinically it is orally highly bioavailable. Oral administration may be of importance in potential utility in lymphoma in continuous metronomic dosing. MethodsTwo Phase I studies of oral darinaparsin are being conducted in patients diagnosed with relapsed or refractory advanced tumors. The first protocol is a Phase I, dose-escalation, oral administration study designed to determine the MTD of darinaparsin capsules. The dosing schedule is a regimen of 2 doses per week for 3 weeks followed by 1 week of rest, starting at 300 mg twice weekly. A second Phase I study, having a similar design and objective, evaluates several dosing regimens, including dosing capsules three times per week increasing dosing frequency to daily dosing for 3 weeks, with 1 week of rest. For each study 28 days constitutes one cycle. Standard methods for evaluation of toxicity, escalation and efficacy are being used. ResultsThese two studies have thus far enrolled 19 and 17 patients, respectively. In total there are 24 male and 12 female patients. The median age is 59 years, with a range from 38 to 82 years. To date, MTD has not been reached in either study. The dose continues to be escalated and is currently at 900mg / day twice weekly in the 1st study, and 300 mg daily every day in the 2nd study. Bioavailability has been very high (>75%). All patients were heavily pretreated and refractory. Of 27 evaluable patients thus far in the two trials, 2 had a partial response and 15 had prolonged stable disease, including lymphoma (NHL), head and neck, colon, and pancreatic cancers. The duration of responses has been 3 – 8 + months. Safety and tolerability has been very good and comparable to that of IV darinaparsin. SAEs were atrial fibrillation and congestive heart failure, each occurring in one patient, and dyspnea, occurring in two patients. No QT prolongation has been observed. Dose escalation continues in both studies and updated results will be presented. ConclusionDarinaparsin is a novel organic arsenic molecule that has demonstrated clinical activity in refractory lymphoma when given IV. When given orally by capsule, the drug is well tolerated and demonstrates early signs of activity. Disclosures:Buck:ZIOPHARM Oncology: Employment. Wallner:ZIOPHARM Oncology: Employment. Lewis:ZIOPHARM Oncology: Employment, Membership on an entity's Board of Directors or advisory committees.

The Janus‐faced role of ezrin in “linking” cells to either normal or metastatic phenotype

In the majority of eukaryotic cells, the ezrin, radixin and moesin (ERM) proteins are involved in many physiologic functions including regulation of actin cytoskeleton, control of cell shape, adhesion, motility and modulation of signal transduction pathways. In a previous study, we used a dominant negative ezrin-mutant to address ezrin involvement in remodeling of actin cytoskeleton and subsequently we depicted ezrin key role in melanoma cell migration and progression. Herein, we highlight recent advances on ezrin involvement in the metastatic phenomenon, including also some more neglected ezrin-related functions. Novel molecular processes driven by ezrin activation include: phagocytosis, acquisition of resistance to chemotherapeutics and triggering of programmed cell death signals. Recent data support an integrated role of ezrin also in development of tumor malignancy. On one hand, ezrin may be responsible of deranged execution of specific known functions such as adhesion and motility and on the other, it may also participate to unique metastatic determinants, through the establishment of aberrant linkages with tumor-related proteins. For instance, ezrin misslocalization, absence or deranged activity has started to be correlated with tumor progression in many tumors of different species, including humans. Concomitantly, ezrin may act simultaneously as a regulatory or deregulatory chaperon in both normal and tumor cells. It is still to be established whether this Janus-faced feature of ezrin is due to some unknown transforming Zelig-like property or to the fact that a tumor-associated molecule preferentially links to ezrin thus distracting it from its normal connections. However, the contribution of ezrin functional deregulation to the acquisition of the metastatic phenotype appears clear and ezrin or ezrin aberrant associations may represent good candidates for future anti-tumor therapies.

Physiological and toxicological transcriptome changes in HepG2 cells exposed to copper

Copper is an essential trace element; however, at supraphysiological levels, it can be extremely toxic. Microarray data from HepG2 cells exposed to 100, 200, 400, and 600 microM copper for 4, 8, 12 and 24 h were generated and analyzed. Principal components, K-means, and hierarchical clustering, interactome, and pathway mapping analyses indicated that these exposure conditions induce physiological and toxicological changes in the HepG2 transcriptome. As a general trend, when the level of toxicity increases, the number and diversity of affected genes, Gene Ontology categories, regulatory pathways, and complexity of interactomes increase. Physiological responses to copper include transition metal ion binding and responses to stress/stimulus, whereas toxicological responses include apoptosis, morphogenesis, and negative regulation of biomolecule metabolism. The global gene expression profile was overlaid onto biomolecular interaction networks and signal transduction cascades using pathway mapping and interactome identification. This analysis indicated that copper modulates signal transduction pathways associated with MAPK, NF-kappaB, death receptor, IGF-I, hypoxia, IL-10, IL-2, IL-6, EGF, Toll-like receptor, protein ubiquitination, xenobiotic metabolism, leukocyte extravasation, complement and coagulation, and sonic hedgehog signaling. These results provide insights into the global and molecular mechanisms regulating the physiological and toxicological responses to metal exposure.

Phospholipid transfer protein reduces phosphorylation of tau in human neuronal cells

Tau function is regulated by phosphorylation, and abnormal tau phosphorylation in neurons is one of the key processes associated with development of Alzheimer's disease and other tauopathies. In this study we provide evidence that phospholipid transfer protein (PLTP), one of the main lipid transfer proteins in the brain, significantly reduces levels of phosphorylated tau and increases levels of the inactive form of glycogen synthase kinase-3beta (GSK3 beta) in HCN2 cells. Furthermore, inhibition of phosphatidylinositol-3 kinase (PI3K) reversed the PLTP-induced increase in levels of GSK3 beta phosphorylated at serine 9 (pGSK3 beta(Ser9)) and partially reversed the PLTP-induced reduction in tau phosphorylation. We provide evidence that the PLTP-induced changes are not due to activation of Disabled-1 (Dab1), insofar as PLTP reduced levels of total and phosphorylated Dab1 in HCN2 cells. We have also shown that inhibition of tyrosine kinase activity of insulin receptor (IR) and/or insulin-like growth factor 1 (IGF1) receptor (IGFR) reverses the PLTP-induced increase in levels of phosphorylated Akt (pAkt(Thr308) and pAkt(Ser473)), suggesting that PLTP-mediated activation of the PI3K/Akt pathway is dependent on IR/IGFR receptor tyrosine kinase activity. Our study suggests that PLTP may be an important modulator of signal transduction pathways in human neurons.

Cancer Prevention and Treatment with Resveratrol: From Rodent Studies to Clinical Trials

Resveratrol (3,4',5-trihydroxy-trans-stilbene) is a dietary polyphenol derived from grapes, berries, peanuts, and other plant sources. During the last decade, resveratrol has been shown to possess a fascinating spectrum of pharmacologic properties. Multiple biochemical and molecular actions seem to contribute to resveratrol effects against precancerous or cancer cells. Resveratrol affects all three discrete stages of carcinogenesis (initiation, promotion, and progression) by modulating signal transduction pathways that control cell division and growth, apoptosis, inflammation, angiogenesis, and metastasis. The anticancer property of resveratrol has been supported by its ability to inhibit proliferation of a wide variety of human tumor cells in vitro. These in vitro data have led to numerous preclinical animal studies to evaluate the potential of this drug for cancer chemoprevention and chemotherapy. This review provides concise, comprehensive data from preclinical in vivo studies in various rodent models of human cancers, highlighting the related mechanisms of action. Bioavailability, pharmacokinetic, and potential toxicity studies of resveratrol in humans and ongoing interventional clinical trials are also presented. The conclusion describes directions for future resveratrol research to establish its activity and utility as a human cancer preventive and therapeutic drug.

Are We Hitting the Right Combination for Hormonally Sensitive Breast Cancer?

Are We Hitting the Right Combination for Hormonally Sensitive Breast Cancer?

Modulators of signal transduction pathways can promote axonal regeneration in entorhino-hippocampal slice cultures

Axonal regeneration after lesions is usually not possible in the adult central nervous system but can occur in the embryonic and young postnatal nervous system. In this study we used the model system of mouse entorhino-hippocampal slice cultures to assess the potential of pharmacological treatments with compounds targeting signal transduction pathways to promote growth of entorhinal fibers after mechanical lesions across the lesion site to their target region in the dentate gyrus. Compounds acting on the cyclic AMP-system, protein kinase C and G-proteins have been shown before to be able to promote regeneration. In this study we have confirmed the potential of drugs affecting these systems to promote axonal regeneration in the central nervous system. In addition we have found that inhibition of the phosphoinositide 3-kinase pathway and of the inositol triphosphate receptor also promoted axonal growth across the lesion site and are thus potential novel drug targets for promoting axonal regeneration after central nervous system lesions. Our findings demonstrate that slice culture models can be used to evaluate compounds for their potential to promote axonal regeneration and that the pharmacological modulation of signal transduction pathways is a promising approach for promoting axonal repair.