Molecular Events (molecular + event)

Distribution by Scientific Domains
Distribution within Life Sciences

Kinds of Molecular Events

  • early molecular event
  • key molecular event

  • Terms modified by Molecular Events

  • molecular event underlying

  • Selected Abstracts

    Focal Adhesion Kinase pp125FAK Interacts With the Large Conductance Calcium-Activated hSlo Potassium Channel in Human Osteoblasts: Potential Role in Mechanotransduction,

    Roger Rezzonico
    Abstract Molecular events of mechanotransduction in osteoblasts are poorly defined. We show that the mechanosensitive BK channels open and recruit the focal adhesion kinase FAK in osteoblasts on hypotonic shock. This could convert mechanical signals in biochemical events, leading to osteoblast activation. Introduction: Mechanical strains applied to the skeleton influence bone remodeling and architecture mainly through the osteoblast lineage. The molecular mechanisms involved in osteoblastic mechanotransduction include opening of mechanosensitive cation channels and the activation of protein tyrosine kinases, notably FAK, but their interplay remains poorly characterized. The large conductance K+ channel (BK) seems likely as a bone mechanoreceptor candidate because of its high expression in osteoblasts and its ability to open in response to membrane stretch or hypotonic shock. Propagation of the signals issued from the mechanosensitivity of BK channels inside the cell likely implies complex interactions with molecular partners involved in mechanotransduction, notably FAK. Methods: Interaction of FAK with the C terminus of the hSlo ,-subunit of BK was investigated using the yeast two-hybrid system as well as immunofluorescence microscopy and coimmunoprecipitation experiments with a rabbit anti-hslo antibody on MG63 and CAL72 human osteosarcoma cell lines and on normal human osteoblasts. Mapping of the FAK region interacting with hSlo was approached by testing the ability of hSlo to recruit mutated ot truncated FAK proteins. Results: To the best of our knowledge, we provide the first evidence of the physical association of FAK with the intracellular part of hslo. We show that FAK/hSlo interaction likely takes place through the Pro-1-rich domain situated in the C-terminal region of the kinase. FAK/hSlo association occurs constitutively at a low, but appreciable, level in human osteosarcoma cells and normal human osteoblasts that express endogenous FAK and hSlo. In addition, we found that application of an hypo-osmotic shock to these cells induced a sustained activation of BK channels associated to a marked increase in the recruitment of FAK on hSlo. Conclusions: Based on these data, we propose that BK channels might play a triggering role in the signaling cascade induced by mechanical strains in osteoblasts. [source]

    The elusive intermediate on the folding pathway of the prion protein

    FEBS JOURNAL, Issue 6 2008
    David C. Jenkins
    A key molecular event in prion diseases is the conversion of the cellular conformation of the prion protein (PrPC) to an altered disease-associated form, generally denoted as scrapie isoform (PrPSc). The molecular details of this conformational transition are not fully understood, but it has been suggested that an intermediate on the folding pathway of PrPC may be recruited to form PrPSc. In order to investigate the folding pathway of PrP we designed and expressed two mutants, each possessing a single strategically located tryptophan residue. The secondary structure and folding properties of the mutants were examined. Using conventional analyses of folding transition data determined by fluorescence and CD, and novel phase-diagram analyses, we present compelling evidence for the presence of an intermediate species on the folding pathway of PrP. The potential role of this intermediate in prion conversion is discussed. [source]

    Interpretation of biological activity data of bacterial endotoxins by simple molecular models of mechanism of action

    FEBS JOURNAL, Issue 3 2000
    Vladimir Frecer
    Lipid A moiety has been identified as the bioactive component of bacterial endotoxins (lipopolysaccharides). However, the molecular mechanism of biological activity of lipid A is still not fully understood. This paper contributes to understanding of the molecular mechanism of action of bacterial endotoxins by comparing molecular modelling results for two possible mechanisms with the underlying experimental data. Mechanisms of action involving specific binding of lipid A to a protein receptor as well as nonspecific intercalation into phospholipid membrane of a host cell were modelled and analysed. As the cellular receptor for endotoxin has not been identified, a model of a peptidic pseudoreceptor was proposed, based on molecular structure, symmetry of the lipid A moiety and the observed character of endotoxin-binding sites in proteins. We have studied the monomeric form of lipid A from Escherichia coli and its seven synthetic analogues with varying numbers of phosphate groups and correlated them with known biological activities determined by the Limulus assay. Gibbs free energies associated with the interaction of lipid A with the pseudoreceptor model and intercalation into phospholipid membrane calculated by molecular mechanics and molecular dynamics methods were used to compare the two possible mechanisms of action. The results suggest that specific binding of lipid A analogues to the peptidic pseudoreceptor carrying an amphipathic cationic binding pattern BHPHB (B, basic; H, hydrophobic; P, polar residue, respectively) is energetically more favourable than intercalation into the phospholipid membrane. In addition, binding affinities of lipid A analogues to the best minimum binding sequence KFSFK of the pseudoreceptor correlated with the experimental Limulus activity parameter. This correlation enabled us to rationalize the observed relationship between the number and position of the phosphate groups in the lipid A moiety and its biological activity in terms of specific ligand,receptor interactions. If lipid A,receptor interaction involves formation of phosphate-ammonium ion-pair(s) with cationic amino-acid residues, the specific mechanism of action was fully consistent with the underlying experimental data. As a consequence, recognition of lipid A variants by an amphipathic binding sequence BHPHB of a host-cell protein receptor might represent the initial and/or rate-determining molecular event of the mechanism of action of lipid A (or endotoxin). The insight into the molecular mechanism of action and the structure of the lipid A-binding pattern have potential implications for rational drug design strategies of endotoxin-neutralizing agents or binding factors. [source]

    Gq/11-induced intracellular calcium mobilization mediates Per2 acute induction in Rat-1 fibroblasts

    GENES TO CELLS, Issue 9 2006
    Naoyuki Takashima
    Phase resetting is one of the essential properties of circadian clocks that is required for the adjustment to a particular environment and the induction of Per1 and Per2 clock genes is believed to be a primary molecular event during this process. Although the intracellular signal transduction pathway underlying Per1 gene activation has been well characterized, the mechanisms that control Per2 up-regulation have not yet been elucidated. In our present study, we demonstrate that Gq/11 coupled receptors mediate serum-induced immediate rat Per2 (rPer2) transactivation in Rat-1 fibroblasts via intracellular Ca2+ mobilization. Stimulation of these cells with a high concentration of serum was found to rapidly increase the intracellular Ca2+ levels and strongly up-regulated rPer2 gene. rPer2 induction by serum stimulation was abrogated by intracellular Ca2+ chelation and depletion of intracellular Ca2+ store, which suggests that the calcium mobilization is necessary for the up-regulation of rPer2 gene. In addition, suppression of Gq/11 function was observed to inhibit both Ca2+ mobilization and rPer2 induction. Further, we demonstrated that endothelin-induced acute rPer2 transactivation via Gq/11-coupled endothelin receptors is also suppressed by a Gq/11 specific inhibitor. These findings together suggest that serum and endothelin utilize a common Gq/11-PLC mediated pathway for the transactivation of rPer2, which involves the mobilization of calcium from the intracellular calcium store. [source]

    Genetics of dermatofibrosarcoma protuberans family of tumors: From ring chromosomes to tyrosine kinase inhibitor treatment

    Nicolas Sirvent
    Dermatofibrosarcoma protuberans (DP) is a rare, slow-growing, infiltrating dermal neoplasm of intermediate malignancy, made up of spindle-shaped tumor cells often positive for CD34. The preferred treatment is wide surgical excision with pathologically negative margins. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes, which have been shown by using fluorescence in situ hybridization techniques to be derived from chromosome 22 and to contain low-level amplified sequences from 17q22-qter and 22q10,q13.1, or t(17;22), that are most often unbalanced. Both the rings and linear der(22) contain a specific fusion of COL1A1 with PDGFB. Similar to other tumors, the COL1A1-PDGFB fusion is occasionally cryptic, associated with complex chromosomal rearrangements. Although rings have been mainly observed in adults, translocations have been reported in all pediatric cases. DP is therefore a unique example of a tumor in which (i) the same molecular event occurs either on rings or linear translocation derivatives, (ii) the chromosomal abnormalities display an age-related pattern, and (iii) the presence of the specific fusion gene is associated with the gain of chromosomal segments, probably taking advantage of gene dosage effects. In all DP cases that underwent molecular investigations, the breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the ,-helical coding region (exons 6,49). No preferential COL1A1 breakpoint and no correlation between the breakpoint location and the age of the patient or any clinical or histological particularity have been described. The COL1A1-PDGFB fusion is detectable by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer from PDGFB exon 2. Recent studies have determined the molecular identity of "classical" DP, giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma, and the granular cell variant of DP. In approximately 8% of DP cases, the COL1A1-PDGFB fusion is not found, suggesting that genes other than COL1A1 or PDGFB might be involved in a subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. It is encouraging that inhibitory effects of the PDGF receptor tyrosine kinase antagonist imatinib mesylate have been demonstrated in vivo; such targeted therapies might be warranted in the near future for treatment of the few DP cases not manageable by surgery. © 2003 Wiley-Liss, Inc. [source]

    Long-lasting up-regulation of orexin receptor type 2 protein levels in the rat nucleus accumbens after chronic cocaine administration

    Guo-Chi Zhang
    Abstract Hypothalamic orexin (hypocretin) neurons project to the key structures of the limbic system and orexin receptors, both orexin receptor type 1 (OXR1) and type 2 (OXR2), are expressed in most limbic regions. Emerging evidence suggests that orexin is among important neurotransmitters that regulate addictive properties of drugs of abuse. In this study, we examined the effect of psychostimulant cocaine on orexin receptor protein abundance in the rat limbic system in vivo. Intermittent administration of cocaine (20 mg/kg, i.p., once daily for 5 days) caused a typical behavioral sensitization response to a challenge cocaine injection at a 14-day withdrawal period. Repeated cocaine administration at the same withdrawal time also increased OXR2 protein levels in the nucleus accumbens while repeated cocaine had no effect on OXR1 and orexin neuropeptide (both orexin-A and orexin-B) levels in this region. In contrast to the nucleus accumbens, OXR2 levels in the frontal cortex, the ventral tegmental area, the hippocampus, and the dorsal striatum (caudate putamen) were not altered by cocaine. Remarkably, the up-regulated OXR2 levels in the nucleus accumbens showed a long-lasting nature as it persisted up to 60 days after the discontinuation of repeated cocaine treatments. In contrast to chronic cocaine administration, an acute cocaine injection was insufficient to modify levels of any orexin receptor and peptide. Our data identify the up-regulation of OXR2 in the nucleus accumbens as an enduring molecular event that is correlated well with behavioral plasticity in response to chronic psychostimulant administration. This OXR2 up-regulation may reflect a key adaptation of limbic orexinergic transmission to chronic drug exposure and may thus be critical for the expression of motor plasticity. [source]

    Chloroquine resistance in the malarial parasite, Plasmodium falciparum

    Lyann M.B. Ursos
    Abstract Malarial parasites remain a health problem of staggering proportions. Worldwide, they infect about 500 million, incapacitate tens of millions, and kill approximately 2.5 million (mostly children) annually. Four species infect humans, but most deaths are caused by one particular species, Plasmodium falciparum. The rising number of malarial deaths is due in part to increased drug resistance in P. falciparum. There are many varieties of antimalarial drug resistance, and there may very well be several molecular level contributions to each variety. This is because there are a number of different drugs with different mechanisms of action in use, and more than one molecular event may sometimes be relevant for resistance to any one class of drugs. Thus, "multidrug" resistance in a clinical setting likely entails complex combinations of overlapping resistance pathways, each specific for one class of drug, that then add together to confer the particular multidrug resistance phenotype. Nonetheless, rapid progress has been made in recent years in elucidating mechanisms of resistance to specific classes of antimalarial drugs. As one example, resistance to the antimalarial drug chloroquine, which has been the mainstay therapy for decades, is becoming well understood. This article focuses on recent advances in determining the molecular mechanism of chloroquine resistance, with particular attention to the biochemistry and biophysics of the P. falciparum digestive vacuole, wherein changes in pH have recently been found to be associated with chloroquine resistance. © 2002 Wiley Periodicals, Inc. Med Res Rev, 22, No. 5, 465,491, 2002; Published online in Wiley InterScience ( DOI 10.1002/med.10016 [source]

    Extrarenal rhabdoid tumors of soft tissue: Clinicopathological and molecular genetic review and distinction from other soft-tissue sarcomas with rhabdoid features

    Yoshinao Oda
    Malignant rhabdoid tumor (MRT) of the soft tissue is a rare and highly aggressive tumor that occurs in infancy or childhood. It predominantly involves a deep axial location such as the neck or paraspinal region. Microscopically, the tumor is composed of a diffuse proliferation of rounded or polygonal cells with eccentric nuclei, prominent nucleoli and glassy eosinophilic cytoplasm containing hyaline-like inclusion bodies, arranged in sheets and nests. These characteristic ,rhabdoid cells' are also present in certain soft-tissue sarcomas such as synovial sarcoma, extraskeletal myxoid chondrosarcoma and leiomyosarcoma. The existence of rhabdoid cells in these other sarcomas is correlated with a worse prognosis for the patients. Cytogenetic and molecular analyses have shown abnormalities in the long arm of chromosome 22 and alteration of the hSNF5/INI1 (SMARCB1) gene in renal, extrarenal and intracranial MRT. This gene alteration has been considered to be a specific molecular event in MRT, but a recent study has also demonstrated frequent alteration of this gene in proximal-type epithelioid sarcoma (ES). Both MRT of soft tissue and proximal-type ES show immunoreactivity for vimentin, cytokeratin and epithelial membrane antigen. The tumor cells of proximal-type ES are also occasionally positive for CD34 and ,-catenin, whereas MRT of soft tissue has no immunoreaction for these markers. Detailed clinicopathological and immunohistochemical evaluations are necessary to distinguish MRT of soft tissue from proximal-type ES, because these tumors demonstrated a similar morphology and the same gene alteration. [source]

    Hapten,protein binding: from theory to practical application in the in vitro prediction of skin sensitization

    CONTACT DERMATITIS, Issue 4 2005
    Maja Divkovic
    In view of the forthcoming European Union ban on in vivo testing of cosmetic and toiletry ingredients, following the publication of the 7th amendment to the Cosmetics Directive, the search for practical, alternative, non-animal approaches is gathering pace. For the end-point of skin sensitization, the ultimate goal, i.e. the development and validation of alternative in vitro/in silico assays by 2013, may be achieved through a better understanding of the skin sensitization process on the cellular and molecular levels. One of the key molecular events in skin sensitization is protein haptenation, i.e. the chemical modification of self-skin protein(s) thus forming macromolecular immunogens. This concept is widely accepted and in theory can be used to explain the sensitizing capacity of many known skin sensitizers. Thus, the principle of protein or peptide haptenation could be used in in vitro assays to predict the sensitization potential of a new chemical entity. In this review, we consider some of the theoretical aspects of protein haptenation, how mechanisms of protein haptenation can be investigated experimentally and how we can use such knowledge in the development of novel, alternative approaches for predicting skin sensitization potential in the future. [source]

    Guest Lecture 9.00,9.45 Wednesday 17 September 2003

    CYTOPATHOLOGY, Issue 2003
    Peter A. Hall MD PhD FRCPath
    The past decades have seen an explosion in our knowledge of the molecular events underpinning the pathogenesis of many disease processes. Furthermore, there have been enormous technical advances with the ability to identify, clone and sequence genes and to characterize their protein products now being common place in research settings. However, despite many claims as to the utility of molecular and biochemical methods in pathology only very few laboratories employ such methods in a clinical setting. Indeed the impact of molecular medicine has been more talked about than real. Why is this? The goal of this presentation is to address this question and present some perspectives on the future of Molecular Pathology. I shall overview, for the BSCC, the current state of the technology available for gene analysis and to explore the developments needed before the mirage of molecular pathology becomes a clinical reality. [source]

    The heel and toe of the cell's foot: A multifaceted approach for understanding the structure and dynamics of focal adhesions

    CYTOSKELETON, Issue 11 2009
    Haguy Wolfenson
    Abstract Focal adhesions (FAs) are large clusters of transmembrane receptors of the integrin family and a multitude of associated cytoplasmic "plaque" proteins, which connect the extracellular matrix-bound receptors with the actin cytoskeleton. The formation of nearly stationary FAs defines a boundary between the dense and highly dynamic actin network in lamellipodium and the sparser and more diverse cytoskeletal organization in the lamella proper, creating a template for the organization of the entire actin network. The major "mechanical" and "sensory" functions of FAs; namely, the nucleation and regulation of the contractile, myosin-II-containing stress fibers and the mechanosensing of external surfaces depend, to a major extent, on the dynamics of molecular components within FAs. A central element in FA regulation concerns the positive feedback loop, based on the most intriguing feature of FAs; that is, their dependence on mechanical tension developing by the growing stress fibers. FAs grow in response to such tension, and rapidly disassemble upon its relaxation. In this article, we address the mechanistic relationships between the process of FA development, maturation and dissociation and the dynamic molecular events, which take place in different regions of the FA, primarily in the distal end of this structure (the "toe") and the proximal "heel," and discuss the central role of local mechanical forces in orchestrating the complex interplay between FAs and the actin system. Cell Motil. Cytoskeleton 66: 1017,1029, 2009. © 2009 Wiley-Liss, Inc. [source]

    Cardiac hypertrophy and failure: lessons learned from genetically engineered mice

    ACTA PHYSIOLOGICA, Issue 1 2001
    Y. Takeishi
    Congestive heart failure is a major and growing public health problem. Because of improved survival of myocardial infarction patients produced by thrombolytic therapy or per-cutaneous revascularization it represents the only form of cardiovascular disease with significantly increased incidence and prevalence. Clinicians view this clinical syndrome as the final common pathway of diverse pathologies such as myocardial infarction and haemodynamic overload. Insights into mechanisms for heart failure historically derived from physiological and biochemical studies which identified compensatory adaptations for the haemodynamic burden associated with the pathological condition including utilization of the Frank Starling mechanism, augmentation of muscle mass, and neurohormonal activation to increase contractility. Therapy has largely been phenomenological and designed to prevent or limit the deleterious effects of these compensatory processes. More recently insights from molecular and cell biology have contributed to a more mechanistic understanding of potential causes of cardiac hypertrophy and failure. Many different analytical approaches have been employed for this purpose. These include the use of conventional animal models which permit serial observation of the onset and progression of heart failure and a sequential analysis of underlying biochemical and molecular events. Neonatal murine cardiomyocytes have been a powerful tool to examine in vitro subcellular mechanisms devoid of the confounding functional effects of multicellular preparations and heterogeneity of cell type. Finally, significant progress has been made by utilizing tissue from human cardiomyopathic hearts explanted at the time of orthotopic transplantation. Each of these methods has significant advantages and disadvantages. Arguably the greatest advance in our understanding of cardiac hypertrophy and failure over the past decade has been the exploitation of genetically engineered mice as biological reagents to study in vivo the effects of alterations in the murine genome. The power of this approach, in principle, derives from the ability to precisely overexpress or ablate a gene of interest and examine the phenotypic consequences in a cardiac specific post-natal manner. In contrast to conventional animal models of human disease which employ some form of environmental stress, genetic engineering involves a signal known molecular perturbation which produces the phenotype. [source]

    Early molecular events in the assembly of the focal adhesion-stress fiber complex during fibroblast spreading

    CYTOSKELETON, Issue 3 2004
    Baruch Zimerman
    Cell adhesion to the extracellular matrix triggers the formation of integrin-mediated contact and reorganization of the actin cytoskeleton. Examination of nascent adhesions, formed during early stages of fibroblast spreading, reveals a variety of forms of actin-associated matrix adhesions. These include: (1) small (,1 ,m), dot-like, integrin-, vinculin-, paxillin-, and phosphotyrosine-rich structures, with an F-actin core, broadly distributed over the ventral surfaces of the cells; (2) integrin-, vinculin-, and paxillin-containing "doublets" interconnected by short actin bundles; (3) arrays of actin-vinculin complexes. Such structures were formed by freshly plated cells, as well as by cells recovering from latrunculin treatment. Time-lapse video microscopy of such cells, expressing GFP-actin, indicated that long actin cables are formed by an end-to-end lining-up and apparent fusion of short actin bundles. All these structures were prominent during cell spreading, and persisted for up to 30,60 min after plating. Upon longer incubation, they were gradually replaced by stress fibers, associated with focal adhesions at the cell periphery. Direct examination of paxillin and actin reorganization in live cells revealed alignment of paxillin doublets, forming long and highly dynamic actin bundles, undergoing translocation, shortening, splitting, and convergence. The mechanisms underlying the assembly and reorganization of actin-associated focal adhesions and the involvement of mechanical forces in regulating their dynamic properties are discussed. Cell Motil. Cytoskeleton 58:143,159, 2004. © 2004 Wiley-Liss, Inc. [source]

    Rapid accumulation of nucleostemin in nucleolus during newt regeneration

    Nobuyasu Maki
    Abstract In newt regeneration, differentiated cells can revert to stem cell,like cells in which the proliferative ability and multipotentiality are restored after dedifferentiation. However, the molecular events that occur during the dedifferentiation still remain obscure. Nucleostemin has been identified in mammals as a nucleolar protein specific to stem cells and cancer cells. In this study, a newt nucleostemin homologue was cloned and its regulation was analyzed. During lens regeneration, the expression of nucleostemin was activated and nucleostemin rapidly accumulated in the nucleoli of dedifferentiating pigmented epithelial cells 2 days before cell cycle reentry. During limb regeneration, nucleostemin also accumulated in the nucleoli of degenerating multinucleate muscle fibers before blastema formation. These findings suggest that nucleostemin plays a role in the dedifferentiation of newt cells and can provide crucial clues for addressing the molecular events at early steps of cellular dedifferentiation in newts. Developmental Dynamics 236:941,950, 2007. © 2006 Wiley-Liss, Inc. [source]

    Molecular characterization of conditionally immortalized cell lines derived from mouse early embryonic inner ear

    John A. Germiller
    Abstract Inner ear sensory hair cells (HCs), supporting cells (SCs), and sensory neurons (SNs) are hypothesized to develop from common progenitors in the early embryonic otocyst. Because little is known about the molecular signals that control this lineage specification, we derived a model system of early otic development: conditionally immortalized otocyst (IMO) cell lines from the embryonic day 9.5 Immortomouse. This age is the earliest stage at which the otocyst can easily be separated from surrounding mesenchymal, nervous system, and epithelial cells. At 9.5 days post coitum, there are still pluripotent cells in the otocyst, allowing for the eventual identification of both SN and HC precursors,and possibly an elusive inner ear stem cell. Cell lines derived from primitive precursor cells can also be used as blank canvases for transfections of genes that can affect lineage decisions as the cells differentiate. It is important, therefore, to characterize the "baseline state" of these cell lines in as much detail as possible. We characterized seven representative "precursor-like" IMO cell populations and the uncloned IMO cells, before cell sorting, at the molecular level by polymerase chain reaction (PCR) and immunocytochemistry (IHC), and one line (IMO-2B1) in detail by real-time quantitative PCR and IHC. Many of the phenotypic markers characteristic of differentiated HCs or SCs were detected in IMO-2B1 proliferating cells, as well as during differentiation for up to 30 days in culture. These IMO cell lines represent a unique model system for studying early stages of inner ear development and determining the consequences of affecting key molecular events in their differentiation. Developmental Dynamics 231:815,827, 2004. © 2004 Wiley-Liss, Inc. [source]

    Recent development and potential use of µ- and ,-opioid receptor ligands in positron emission tomography studies

    Gjermund Henriksen
    Abstract Quantitative non-invasive imaging of target structures in the human central nervous system provided by positron emission tomography (PET) permits investigation of the relationship between molecular events and pharmacological effects in living humans. Due to their prominent role in opiate and stimulant drug misuse and dependence, as well as in nociceptive signaling, µ- and ,-opioid receptors are potential targets for advances in neuro(psycho)pharmacological treatment of these illnesses and syndromes. In this review, we describe recent developments in specific positron emitting radiopharmaceuticals for these opioid receptor subclasses. Implications for further advances and clinical applications of the labeled ligands are discussed. Drug Dev. Res. 67:890,904, 2006. © 2007 Wiley-Liss, Inc. [source]

    Interstrand crosslink inducing agents in pretransplant conditioning therapy for hematologic malignancies

    Benigno C. Valdez
    Abstract Despite successful molecularly targeted, highly specific, therapies for hematologic malignancies, the DNA interstrand crosslinking agents, which are among the oldest and least specific cytotoxic drugs, still have an important role. This is particularly true in stem cell transplantation, where virtually every patient receives conditioning therapy with a DNA-alkylating agent-based program. However, due to concern about serious additive toxicities with combinations of different alkylating drugs, the last several years have seen nucleoside analogs, whose cytotoxic action follows vastly different molecular pathways, introduced in combination with alkylating agents. The mechanistic differences paired with different metabolic pathways for the respective drugs have clinically translated into increased safety without appreciable loss of antileukemic activity. In this report, we review pre-clinical evidence for synergistic antileukemic activity when nucleoside analog(s) and DNA-alkylating agent(s) are combined in the most appropriate manner(s), without a measurable decrease in clinical efficacy compared with the more established alkylating agent combinations. Data from our own laboratory using combinations of fludarabine, clofarabine, and busulfan as prototype representatives for these respective classes of cytotoxic agents are combined with information from other investigators to explain how the observed molecular events will result in greatly enhanced synergistic cytotoxicity. We further present possible mechanistic pathways for such desirable cytotoxic synergism. Finally, we propose how this information-backed hypothesis can be incorporated in the design of the next generation conditioning therapy programs in stem cell transplantation to optimize antileukemic efficacy while still safeguarding patient safety. Environ. Mol. Mutagen., 2010. © 2010 Wiley-Liss, Inc. [source]

    Activation of Epstein-Barr virus/C3d receptor (gp140, CR2, CD21) on human cell surface triggers pp60src and Akt-GSK3 activities upstream and downstream to PI 3-kinase, respectively

    Monique Barel
    Abstract We previously demonstrated that CR2 activation on human B lymphocyte surface specifically triggered tyrosine phosphorylation of the 95-kDa nucleolin, this leading to its binding on SH2 domainsof p85 sub-unit of PI 3-kinase and to activation of this enzyme. The specificity of CR2 pathway was clearly demonstrated as neither CD19 nor BCR could induce tyrosine phosphorylation of nucleolin in normal B lymphocytes. These data led us to investigate herein additional molecular events, which were triggered by CR2 activation, upstream and downstream to PI 3-kinase activation. Upstream, we demonstrated that pp60src, a tyrosine kinase of the src family, was involved in tyrosine phosphorylation of nucleolin, while syk tyrosine kinase was not. We also demonstrated a direct protein-proteininteraction of pp60src with nucleolin in a CR2-dependent and CD19-independent pathway. Downstream, we demonstrated that CR2 activation also triggered Akt and GSK3 enzyme activation, this pathway being under the control of pp60src tyrosine kinase activation. These regulatory functions of activated CR2 were specific as independent of syk tyrosine kinase and of CD19 and BCR activation. Thus, CR2 activation recruits a specific mechanism to activate PI 3-kinase and its subsequent pathways, this mechanism being different to those recruited by CD19 and BCR. [source]

    Expression of functional NR1/NR2B-type NMDA receptors in neuronally differentiated SK-N-SH human cell line

    Marina Pizzi
    Abstract The present study demonstrates that human SK-N-SH neuroblastoma cells, differentiated by retinoic acid (RA), express functional NMDA receptors and become vulnerable to glutamate toxicity. During exposure to RA, SK-N-SH cells switched from non-neuronal to neuronal phenotype by showing antigenic changes typical of postmitotic neurons together with markers specific for cholinergic cells. Neuronally differentiated cells displayed positive immunoreactivity to the vesicular acetylcholine transporter and active acetylcholine release in response to depolarizing stimuli. The differentiation correlated with the expression of NMDA receptors. RT-PCR and immunoblotting analysis identified NMDA receptor subunits NR1 and NR2B, in RA-differentiated cultures. The NR1 protein immunolocalized to the neuronal cell population and assembled with the NR2B subunit to form functional N -methyl- d -aspartate (NMDA) receptors. Glutamate or NMDA application, concentration-dependently increased the intracellular Ca2+ levels and acetylcholine release in differentiated cultures, but not in undifferentiated SK-N-SH cells. Moreover, differentiated cultures became vulnerable to NMDA receptor-mediated excitotoxicity. The glutamate effects were enhanced by glycine application and were prevented by the NMDA receptor blocker MK 801, as well as by the NR2B selective antagonist ifenprodil. These data suggest that SK-N-SH cells differentiated by brief treatment with RA may represent an unlimited source of neuron-like cells suitable for studying molecular events associated with activation of human NR1/NR2B receptors. [source]

    Hair growth inhibition by psychoemotional stress: a mouse model for neural mechanisms in hair growth control

    Eva M. J. Peters
    Abstract:, Stress has long been discussed controversially as a cause of hair loss. However, solid proof of stress-induced hair growth inhibition had long been missing. If psychoemotional stress can affect hair growth, this must be mediated via definable neurorendocrine and/or neuroimmunological signaling pathways. Revisiting and up-dating relevant background data on neural mechanisms of hair growth control, we sketch essentials of hair follicle (HF) neurobiology and discuss the modulation of murine hair growth by neuropeptides, neurotransmitters, neurotrophins, and mast cells. Exploiting an established mouse model for stress, we summarize recent evidence that sonic stress triggers a cascade of molecular events including plasticity of the peptidergic peri- and interfollicular innervation and neuroimmune crosstalk. Substance P (SP) and NGF (nerve growth factor) are recruited as key mediators of stress-induced hair growth-inhibitory effects. These effects include perifollicular neurogenic inflammation, HF keratinocyte apoptosis, inhibition of proliferation within the HF epithelium, and premature HF regression (catagen induction). Intriguingly, most of these effects can be abrogated by treatment of stressed mice with SP-receptor neurokinin-1 receptor (NK-1) antagonists or NGF-neutralizing antibodies , as well as, surprisingly, by topical minoxidil. Thus there is now solid in vivo -evidence for the existence of a defined brain- HF axis. This axis can be utilized by psychoemotional and other stressors to prematurely terminate hair growth. Stress-induced hair growth inhibition can therefore serve as a highly instructive model for exploring the brain-skin connection and provides a unique experimental model for dissecting general principles of skin neuroendocrinology and neuroimmunology well beyond the HF. [source]

    Cellular and molecular mechanisms of bleomycin-induced murine scleroderma: current update and future perspective

    Toshiyuki Yamamoto
    Abstract:, Scleroderma is a fibrotic condition characterized by immunologic abnormalities, vascular injury and increased accumulation of matrix proteins in the skin. Although the aetiology of scleroderma is not fully elucidated, a growing body of evidence suggests that extracellular matrix overproduction by activated fibroblasts results from complex interactions among endothelial cells, lymphocytes, macrophages and fibroblasts, via a number of mediators. Cytokines, chemokines and growth factors secreted by inflammatory cells and mesenchymal cells (fibroblasts and myofibroblasts) play an important role in the fibrotic process of scleroderma. Recently, we established a murine model of scleroderma by repeated local injections of bleomycin. Dermal sclerosis was induced in various mouse strains, although the intensity of dermal sclerosis varied among various strains. Histopathological and biochemical analysis demonstrated that this experimental murine scleroderma reflected a number of aspects of human scleroderma. Further investigation of the cellular and molecular mechanisms of inflammatory reaction, fibroblast activation and extracellular matrix deposition following dermal injury by bleomycin treatment will lead to the better understanding of the pathophysiology and the exploration of effective treatment against scleroderma. This review summarizes recent progress of the cellular and molecular events in the pathogenesis of bleomycin-induced scleroderma; moreover, further perspective by using this mouse model has been discussed. [source]

    Hypoxia-inducible factor as a physiological regulator

    Patrick H. Maxwell
    Hypoxia-inducible factor (HIF) is a transcription complex which responds to changes in oxygen, providing cells with a master regulator that coordinates changes in gene transcription. HIF operates in all mammalian cell types and is ancient in evolutionary terms, being conserved in C. elegans and D. melanogaster. This review summarizes recent insights into the molecular events that link reduced oxygenation to HIF activation and emerging insights into the extensive role of HIF in a broad range of physiological processes. [source]

    Regulation of Human Myometrial Contractility During Pregnancy and Labour: Are Calcium Homeostatic Pathways Important?

    Rachel M. Tribe
    If we are to develop new strategies for the treatment and management of preterm and dysfunctional term labour, it is imperative that we improve current understanding of the control of human uterine activity. Despite many studies of animal pregnancy, there is a paucity of knowledge relating to the complex control of human myometrium during pregnancy. It is hypothesized that human myometrium is relatively quiescent during the majority of pregnancy and that as term approaches there is cascade of molecular events that prepare the uterus for labour. This review will consider the cellular mechanisms involved in the regulation of human myometrial activity and the modulation of these by hormonal and mechanical signals. In particular, the contribution of calcium homeostatic pathways to the control of human myometrial contractility during gestation will be discussed. [source]

    Effect of 5-lipoxygenase inhibitor MK591 on early molecular and signaling events induced by staphylococcal enterotoxin B in human peripheral blood mononuclear cells

    FEBS JOURNAL, Issue 12 2008
    Chanaka Mendis
    Staphylococcal enterotoxin B (SEB) has been the focus of a number of studies due to its ability to promote septic shock and a massive impact on the human immune system. Even though symptoms and pathology associated with SEB is well known, early molecular events that lead to lethality are still poorly understood. Our approach was to utilize SEB induced human peripheral blood mononuclear cells (PBMCs) as a prototype module to further investigate the complexity of signaling cascades that may ultimately lead to lethal shock. Our study revealed the activation of multiple divergent intracellular pathways within minutes of SEB induction including components that interconnect investigated pathways. A series of performed inhibitor studies identified a specific inhibitor of 5-LO (MK591), which has the ability to block JNK, MAPK, p38kinase and 5-LO signaling-cascades and drastically reducing the activity of pro-inflammatory cytokine TNF-,. Further evaluation of MK591 utilizing cell proliferation assays in PBMCs, human proximal tubule cells and in vivo studies (monkey) showed a decrease in cell proliferation. The inhibitory effect of MK591 was reconfirmed at a genetic level through the utilization of a set of SEB specific genes. Signaling activities, inhibitor studies, cellular analysis and gene expression analysis in unison illustrated the significance of pathway interconnectors such as 5-LO as well as inhibiting such inter-connectors (using MK591) in SEB induced human PBMCs. [source]

    Biochemical characterization of MI-ENG1, a family 5 endoglucanase secreted by the root-knot nematode Meloidogyne incognita

    FEBS JOURNAL, Issue 11 2000
    Christel Béra-Maillet
    A ,-1,4-endoglucanase named MI-ENG1, homologous to the family 5 glycoside hydrolases, was previously isolated from the plant parasitic root-knot nematode Meloidogyne incognita. We describe here the detection of the enzyme in the nematode homogenate and secretion and its complete biochemical characterization. This study is the first comparison of the enzymatic properties of an animal glycoside hydrolase with plant and microbial enzymes. MI-ENG1 shares many enzymatic properties with known endoglucanases from plants, free-living or rumen-associated microorganisms and phytopathogens. In spite of the presence of a cellulose-binding domain at the C-terminus, the ability of MI-ENG1 to bind cellulose could not be demonstrated, whatever the experimental conditions used. The biochemical characterization of the enzyme is a first step towards the understanding of the molecular events taking place during the plant,nematode interaction. [source]

    Multiple cell death programs: Charon's lifts to Hades

    FEMS YEAST RESEARCH, Issue 2 2004
    Wilfried Bursch
    Abstract Cells use different pathways for active self-destruction as reflected by different morphology: while in apoptosis (or "type I") nuclear fragmentation associated with cytoplasmic condensation but preservation of organelles is predominant, autophagic degradation of cytoplasmic structures preceding nuclear collapse is a characteristic of a second type of programmed cell death (PCD). The diverse morphologies can be attributed , at least to some extent , to distinct biochemical and molecular events (e.g. caspase-dependent and -independent death programs; DAP-kinase activity, Ras-expression). However, apoptosis and autophagic PCD are not mutually exclusive phenomena. Rather, diverse PCD programs emerged during evolution, the conservation of which apparently allows cells a flexible response to environmental changes, either physiological or pathological. [source]

    TGF-, signaling potentiates differentiation of embryonic stem cells to Pdx-1 expressing endodermal cells

    GENES TO CELLS, Issue 6 2005
    Nobuaki Shiraki
    Embryonic stem (ES) cells have the capacity to differentiate to every cell type that constitutes fetal or adult tissues. To trace and quantitatively assess the differentiation of ES cells into gut endodermal cells, we used an ES cell line with the lacZ gene inserted into the pdx-1 locus. Targeted mutations of pdx-1 in mice demonstrate that pdx-1 is required for pancreatic and rostral duodenal development; therefore, pdx-1 serves as an excellent early gut regional specific marker. When these ES cells were differentiated by removal of leukemia inhibitory factor (LIF), only fractional cells turned into lacZ positive, which indicates pancreatic-duodenal differentiation. Co-cultivation of ES cells with pancreatic rudiments induced a significant increase in the proportion of lacZ positive cell numbers and this increase was further enhanced by forced expression of a chick putative endoderm inducer gene, cmix. Transforming growth factor (TGF)-,2 mimicked the effects of pancreatic rudiments and this effect was enhanced by cmix expression. Expression analysis showed over-expression of cmix induced endodermal marker genes. These data indicate that one can make use of this knowledge on molecular events of embryonic development to drive ES cells to differentiate into pdx-1 expressing endodermal cells in vitro. [source]

    Developmental and activity-dependent genomic occupancy profiles of CREB in monkey area V1

    J. Lalonde
    The mammalian neocortex displays significant plastic rearrangement in response to altered sensory input, especially during early postnatal development. It is believed that cyclic AMP-response element-binding (CREB) plays an important role in orchestrating the molecular events that guide neuroplastic change, although the details of its genomic targets during normal postnatal development or in response to sensory deprivation remain unknown. Here, we performed CREB chromatin immunoprecipitation (ChIP) from monkey area V1 tissue and hybridized enriched DNA fragments to promoter microarrays (ChIP chip analysis). Our goal was to determine and categorize the CREB regulon in monkey area V1 at two distinct developmental stages (peak of critical period vs. adulthood) and after 5 days of monocular enucleation (ME) at both ages. Classification of enriched candidates showed that the majority of isolated promoter loci (n = 795) were common to all four conditions. A particularly interesting group of candidates (n = 192) was specific to samples derived from enucleated infant area V1. Gene ontology analysis of CREB targets during early postnatal development showed a subgroup of genes implicated in cytoskeleton-based structural modification. Analysis of messenger RNA expression (quantitative real-time,polymerase chain reaction) of candidate genes showed striking differences in expression profiles between infant and adult area V1 after ME. Our study represents the first extensive genomic analysis of CREB DNA occupancy in monkey neocortex and provides new insight into the multifaceted transcriptional role of CREB in guiding neuroplastic change. [source]

    Detection of unidentified chromosome abnormalities in human neuroblastoma by spectral karyotyping (SKY)

    Ninette Cohen
    Spectral karyotyping (SKY) is a novel technique based on the simultaneous hybridization of 24 fluorescently labeled chromosome painting probes. It provides a valuable addition to the investigation of many tumors that can be difficult to define by conventional banding techniques. One such tumor is neuroblastoma, which is often characterized by poor chromosome morphology and complex karyotypes. Ten primary neuroblastoma tumor samples initially analyzed by G-banding were analyzed by SKY. In 8/10 tumors, we were able to obtain additional cytogenetic information. This included the identification of complex rearrangements and material of previously unknown origin. Structurally rearranged chromosomes can be identified even in highly condensed metaphase chromosomes. Following the SKY results, the G-banding findings were reevaluated, and the combination of the two techniques resulted in a more accurate karyotype. This combination allows identification not only of material gained and lost, but also of breakpoints and chromosomal associations. The use of SKY is therefore a powerful tool in the genetic characterization of neuroblastoma and can contribute to a better understanding of the molecular events associated with this tumor. © 2001 Wiley-Liss, Inc. [source]

    Peripheral T-cell lymphoma gene expression profiles

    B. Martinez-Delgado
    Abstract Expression profiling using DNA microarrays has been very helpful to improve our knowledge of the pathobiology of many tumour types, including lymphomas. Peripheral T-cell lymphomas (PTCL) constitute an heterogeneous group of tumours with different morphologic, immunophenotypic, and clinical characteristics. Their complexity and their low frequency in the western countries have made difficult the identification of molecular events responsible of the development of these tumours. The first studies on expression profiling of PTCL have also revealed heterogeneity at this level, mainly regarding the PTCL NOS subgroup. Different molecular subgroups within PTCL unspecified have been identified associated to different expression profiles. However, the clinical significance of this molecular sub-classification remains to be probed in studies involving larger number of samples. In addition, the expression level of NF-kB pathway genes allowed to differentiate two PTCL subgroups, and this difference could have clinical interest. In general, PTCL expression profiles are difficult to interpret due to the significant proportion of other infiltrating cells accompanying the tumour. However, microarrays are being a helpful tool in the initial task of dissecting the PTCL expression profile. Copyright © 2006 John Wiley & Sons, Ltd. [source]