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PubMed2003

Balancing gastroprotection and cardioprotection with selective cyclo-oxygenase-2 inhibitors: clinical implications.

NSAIDs have been the mainstay of treatment in the management of pain and inflammation associated with chronic inflammatory disorders. They are effective. However, complications arising from chronic NSAID use are common and are primarily due to gastrointestinal (GI) toxicity in the form of gastritis, peptic erosions and ulceration and GI bleeds. GI toxicity has been attributed to the blockade of the cyclo-oxygenase (COX)-1-mediated generation of the cytoprotective prostanoids, such as prostaglandin (PG) E2 and PGI2 (prostacyclin). More recently, selective COX-2 inhibitors ('coxibs') were designed to inhibit the production of COX-2-dependent inflammatory prostanoids and to leave intact the cytoprotective COX-1 products. The coxibs, while exhibiting similar efficacy to traditional NSAIDs in controlled clinical trials of their efficacy in chronic inflammatory conditions, such as osteoarthritis and rheumatoid arthritis, have been associated with a reduced incidence of surrogate or actual indices of GI toxicity. However, concerns regarding cardiovascular safety in high-risk patients have evolved. These concerns were driven initially by the concept that inhibition of COX-2-derived endothelial PGI2 without concomitant inhibition of platelet thromboxane A2 would result in increased cardiovascular risk. This was borne out in the Vioxx Gastrointestinal Outcomes Research study of rofecoxib, but not demonstrated in the Celecoxib Long Term Arthritis Safety Study trial. Further elucidation of the relative roles of COX-1- and COX-2-generated prostanoids has enabled a greater understanding of the biology of these pathways. However, it is still not completely clear how this understanding may be appropriately translated into clinical medicine.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1996

Management of asthma with zafirlukast. Clinical experience and tolerability profile.

This article reviews the literature on the use of zafirlukast in the treatment of asthma, with particular focus on its ability to attenuate the asthma-causing effects of leukotrienes. Leukotrienes produced by the 5-lipoxygenase enzyme pathway have various biological activities. These include the specific inflammatory effects associated with asthma, such as increased vascular permeability, enhanced mucus production and decreased mucociliary transport. Leukotriene receptors in the airways also mediate a potent bronchoconstriction and this is particularly important in asthma. Zafirlukast was developed with the goal of attenuating the inflammatory effects of leukotrienes in asthma. Zafirlukast attenuates the responses to inhaled leukotrienes and allergen challenges, and produces beneficial effects in cold air- and exercise-induced asthma. Zafirlukast has been compared with placebo and sodium cromoglycate in clinical trials involving asthma patients. Zafirlukast brings about a significant bronchodilation within 1 hour of administration that is additive to the effects of beta 2 agonists. These studies showed that zafirlukast improves pulmonary function and reduces the symptoms of asthma. Zafirlukast is well tolerated with an incidence of adverse events similar to that seen with the use of placebo. As an oral twice-daily formulation, zafirlukast may improve patient adherence to therapy. As an anti-inflammatory agent, zafirlukast may in the future find a role in the treatment of a variety of diverse inflammatory conditions.

Anti-Asthmatic Agents↗
PubMed2003

How much gets there and what does it do?: The need for better pharmacokinetic and pharmacodynamic endpoints in contemporary drug discovery and development.

Drug discovery is an expensive, slow and high risk enterprise. Only one in ten of the agents that enter clinical development is successful, with an average cost of US dollars 500-800 million and a typical time-scale of 10-15 years from preclinical discovery research to regulatory approval. On the other hand, many new targets are emerging from genome sequencing and the improved understanding of molecular pathology. Also, new technologies are increasing the speed and improving the efficiency of drug discovery. These new advances should facilitate progress towards the development of personalised therapies that are targeted to the genetics and molecular pathology of individual patients. The availability of pharmacokinetic (PK) and pharmacodynamic (PD) endpoints is absolutely critical to modern drug development. They allow us to understand how much of the drug gets there (into the body and ideally to the target cells) and what it does (with respect to modulation of the molecular target and the cognate biochemical pathways and downstream biological effects). PK and PD endpoints allow us to construct a pharmacological audit trail, so that all of the successive stages from drug administration through to biological effects and clinical outcome can be monitored and interpreted. This in turn provides a rational basis for decision making, e.g. stop/go, during development. An understanding of PK/PD relationships also gives us s basis for selecting the optimal drug dose and schedule. Better, less invasive methods are required. Developments in molecular/functional imaging show promise and current examples are provided.

Costs and Cost Analysis↗
PubMed2004

Role of progastrins and gastrins and their receptors in GI and pancreatic cancers: targets for treatment.

Accumulating evidence in literature suggests that amidated and non-amidated gastrins (gastrin precursors) may play an important role in the proliferation and carcinogenesis of gastrointestinal and pancreatic cancers, especially in the presence of DNA damaging agents and/or infectious agents. Amidated gastrins appear to have a protective role, while progastrins exert growth promoting effects in cancers. Several receptor subtypes and signal transduction pathways mediate the biological effects of the gastrin peptides. Progastrin and gastrins also exert anti-apoptotic effects, which may additionally contribute to the growth and co-carcinogenic effects of these peptides on GI mucosal cells in vivo. Amidated gastrins additionally play an important role in the migration of GI epithelial cells, and in glandular morphogenesis, while progastrins may play an important role in invasion and metastasis. Therefore, targeting progastrins, gastrins, and their cognate receptors may provide a therapeutic tool for treating GI and pancreatic cancers. Targeting CCK2-receptors has, so far, not provided optimal beneficial effects. However, targeting gastrins via a vaccine approach has provided some encouraging results for treating GI and pancreatic cancers. It is expected that targeting precursor gastrins (progastrins and gly-gastrins), exclusively rather than amidated gastrins, may be more effective for treating GI cancers. Since GI cancers at advanced stages are largely responsive to autocrine and intracrine progastrins, down-regulation of intracellular progastrins will likely be more effective at this stage.

Animals↗
PubMed1999

Expression of the JAK and STAT superfamilies in human meningiomas.

OBJECT: The goal of this study was to investigate whether the janus kinase/signal transducer and activator of transcription (JAK/STAT) signal transduction pathway is present and active in meningiomas. The results of these investigations are important for all meningioma therapies that, similar to interferon-alpha-2B (IFNalpha-2B), depend on activation of this pathway for their effect. The authors were interested in evaluating the importance, if any, of the JAK/STAT pathway in the biology and therapy for these tumors. METHODS: Total proteins were extracted from 17 meningioma samples and the levels of JAKs and STATs were determined by using Western blot analysis. Levels of these proteins in meningiomas were compared with those found in normal dura. The JAKs and STATs (with the exception of Jak3 and Tyk2) were present both in the dura and in the meningiomas studied. In tumors JAK and STAT levels were always significantly higher than those found in normal dura. Differences in relative levels were found when meningiomas were subdivided according to the current neuropathological criteria and the highest levels were found in transitional meningiomas. The authors also investigated, using tyrosine-phosphorylated Statl and Stat3 antibodies, whether STATs were activated in meningiomas and normal dura in vivo. Their results indicate that both Statl and Stat3 are phosphorylated in vivo in meningiomas and in the dura. Furthermore, in vitro experiments in which two independent short-term cultures obtained from freshly dissected meningioma samples were used indicated that Statl and Stat3 are phosphorylated in response to treatment with IFNalpha-2B. Exposure of meningioma cells to IFNalpha-2B leads to nuclear translocation of tyrosine-phosphorylated Statl and Stat3, as demonstrated by immunocytochemical analysis. CONCLUSIONS: The results of this study indicate that the JAK and STAT families of proteins are important effectors in brain tumors and support the idea that the effects of IFNalpha in vivo are direct and not mediated by the immune system. This suggests a role for modulation of STAT transcription factors in inhibiting meningioma cell proliferation.

Acute-Phase Proteins↗
PubMed1995

Endocrine activity of plant-derived compounds: an evolutionary perspective.

Although plants have long been known to have important pharmacological effects in humans, the mechanism by which plant-derived compounds act in humans is still being elucidated. Two important pathways for the biological actions of plant-derived compounds involved binding either to hormone receptors or to enzymes that metabolize hormones. What are the origins of this interaction between plant-derived compounds and animals? And what insights can we gain from investigating this question? Some answers come from recent sequence analyses, revealing that 17 beta-hydroxysteroid dehydrogenase, which regulates estrogen and androgen levels in humans, and 15-hydroxyprostaglandin dehydrogenase, which regulates prostaglandin E2 and F2 alpha levels in humans, have a common ancestor with proteins in rhizobia that are important in forming nitrogen-fixing nodules in legume roots, and 3 beta-hydroxysteroid dehydrogenase, which regulates progestin and androgen levels in humans, has a common ancestor with enzymes important in the synthesis of anthocyanins. This evolutionary kinship, when combined with the structural similarities between flavonoids, licorice-derived compounds, and steroid hormones, provides another perspective on the hormone-like activity of flavonoids and other plant-derived compounds in humans: some of the hormone-like activity of plant-derived compounds is due to binding to steroid and prostaglandin dehydrogenases.

Alcohol Oxidoreductases↗
PubMed2004

Gene expression profiling of fibroblasts from a human progeroid disease (mandibuloacral dysplasia, MAD #248370) through cDNA microarrays.

Mandibuloacral dysplasia (MAD) is a rare autosomal recessive disorder caused basically by a missense mutation within the LMNA gene, which encodes for lamin A/C. We have used gene expression profiling to characterize the specificity of molecular changes induced by the prevalent MAD mutation (R527H). A total of 5531 transcripts expressed in human dermis were investigated in two MAD patients, both carrying the R527H mutation, and three control subjects (age and sex matched). Transcription profiles revealed a differential expression in MAD vs. control fibroblasts in at least 1992 genes. Sixty-seven of these genes showed a common altered pattern in both patients with a threshold expression level >+/-2. Nevertheless, a large number of these genes (43.3%) are ESTs or encode for protein with unknown function; the other genes are involved in biological processes or pathways such as cell adhesion, cell cycle, cellular metabolism, and transcription. Quantitative RT-PCR was applied to validate the microarray results (R2= 0.76). Analysis of the effect of the prevalent MAD mutation (R527H) over the transcriptional pattern of genes expressed in the human dermis showed that this LMNA gene mutation has pleiotropic effects on a limited number of genes. Further characterization of these effects might contribute to understanding the molecular pathogenesis of this disorder.

Abnormalities, Multiple↗
PubMed2006

A membrane form of TNF-alpha presented by exosomes delays T cell activation-induced cell death.

In common with many other cell types, synovial fibroblasts produce exosomes. In this study, we show that the exosomes produced by synovial fibroblasts obtained from individuals with rheumatoid arthritis (RASF), but not exosomes produced by synovial fibroblasts obtained from individuals with osteoarthritis, contain a membrane bound form of TNF-alpha as demonstrated by colloidal gold immunostaining of TNF-alpha and confirmed by both Western blot and mass spectrometry. The RASF-derived exosomes, but not exosomes derived from fibroblasts obtained from individuals with osteoarthritis, are cytotoxic for the L929 cell, a TNF-alpha-sensitive cell line, and stimulate activation of NF-kappaB and induction of collagenase-1 in RASF. These effects are blocked by addition of soluble TNFR1 (sTNFbp), suggesting that a TNF-alpha-signaling pathway mediates these biological activities. sTNFbp also reduced the production of exosomes by RASF, suggesting the interruption of a positive amplification loop. Exosomes can transmit signals between cells, and RASF exosomes, effectively taken up by anti-CD3-activated T cells, activated AKT and NF-kappaB and rendered these activated T cells resistant to apoptosis. Neutralization of exosomal membrane TNF-alpha by sTNFbp partially reversed this resistance, suggesting that not only TNF-alpha but also additional exosomal proteins may contribute to the development of apoptosis resistance.

Aged↗
PubMedDate not supplied

Duplication of the genome in normal and cancer cell cycles.

It is critical to discover the mechanisms of normal cell cycle regulation if we are to fully understand what goes awry in cancer cells. The normal eukaryotic cell tightly regulates the activity of origins of DNA replication so that the genome is duplicated exactly once per cell cycle. Over the last ten years much has been learned concerning the cell cycle regulation of origin activity. It is now clear that the proteins and cell cycle mechanisms that control origin activity are largely conserved from yeast to humans. Despite this conservation, the composition of origins of DNA replication in higher eukaryotes remains ill defined. A DNA consensus for predicting origins has yet to emerge, and it is of some debate whether primary DNA sequence determines where replication initiates. In this review we outline what is known about origin structure and the mechanism of once per cell cycle DNA replication with an emphasis on recent advances in mammalian cells. We discuss the possible relevance of these regulatory pathways for cancer biology and therapy.

Animals↗
PubMed2004

siRNAs: mechanism of RNA interference, in vivo and potential clinical applications.

Small interfering RNAs are currently the most widely used nucleic acid-based sequence-specific gene silencing molecules. These molecules mediate RNA interference--a natural post-transcriptional gene-silencing pathway. Given the high reliability and higher efficiency of small interfering RNA-mediated RNA interference, compared to earlier reverse genetic technologies, this is now the preferred technique in functional genomics. Furthermore, the exquisite specificity and exceptional gene-silencing potency of small interfering RNAs has resulted in intense research related to potential target-specific therapeutic applications of these molecules. This review will discuss the mechanism of RNA interference and applications of the pathway in molecular biology including functional genomics will be overviewed. The article will outline in vivo and potential clinical applications of small interfering RNA molecules.

Gene Targeting↗
PubMed2004

The gene expression profile of cyst epithelial cells in autosomal dominant polycystic kidney disease patients.

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder characterized by the formation of fluid-filled cysts in the kidney and progressive renal failure. Other manifestations of ADPKD include the formation of cysts in other organs (liver, pancreas, and spleen), hypertension, cardiac defects, and cerebral aneurysms. The loss of function of the polycystin -1 and -2 results in the formation of epithelium-lined cysts, a process that depends on initial epithelial proliferation. cDNA microarrays powerfully monitor gene expression and have led to the discoveries of pathways regulating complex biological processes. We undertook to profile the gene expression patterns of epithelial cells derived from the cysts of ADPKD patients using the cDNA microarray technique. Candidate genes that were differently expressed in cyst tissues were identified. 19 genes were up-regulated, and 6 down-regulated. Semi-quantitative RT-PCR results were consistent with the microarray findings. To distinguish between normal and epithelial cells, we used the hierarchical method. The results obtained may provide a molecular basis for understanding the biological meaning of cytogenesis.

Cells, Cultured↗
PubMed2002

Methods in molecular surgical pathology.

Nucleic acids (DNA and RNA) contain the basic information for the transcription and translation of the genetic information into the functional cell protein products. To obtain tissue materials for suitable extraction of these cellular components, proper preservation and storage are necessary for both fresh and archival materials. Techniques for nucleic acid analysis are fundamentally based on complementarity between target and probe nucleotide sequences called hybridization. These are aided by the discovery of polymerase chain reaction that allow for specific amplification of target nucleic acid sequences for detection and enhancing yields from small and precious specimens. These techniques, along with protein analysis by Western blotting, require validation, optimization, laboratory quality control, and assurance for competency. Interpretative criteria for each test according to accepted guidelines are necessary for clinical diagnostic purposes. High throughput technologies of nucleic acid and protein analyses for the discovery of new markers and understanding biological processes and pathways are also highlighted for their potential impact on surgical pathology practice.

Humans↗
PubMed2002

Methyltransferase: an enzyme assay for microbial methylmercury formation in acidic soils and sediments.

Methylmercury (MeHg) is a highly toxic form of mercury that bioaccumulates in aquatic food chains. However, methods to reliably identify sites of MeHg formation or to quantify MeHg production require the use of isotopic tracers, which limits their use. In this paper, a method is presented to quantify the methylation of mercury by a methyltransferase pathway. This methyltransferase pathway is one of the biochemical pathways responsible for biological mercury methylation. Protein is extracted from environmental samples, and mercury methyltransferase (HgMT) activity of soil extracts is calculated by assessing increases in methyltransferase activity induced by Hg addition. In enzyme extracts from pure cultures or soil samples, HgMT activity correlated with net MeHg production and Hg consumption, suggesting that HgMT activity can be used to estimate MeHg production in field samples. Over the course of a three-month period in a freshwater wetland, HgMT activity correlated with net MeHg concentrations (r2 = 0.55; p < 0.057). Furthermore, HgMT activity predicted (r2 = 0.80; p < 0.01) gross MeHg formation in freshwater wetlands as well as in laboratory microcosms calculated using previously published rate constants. Our results show that a methyltransferase assay, in combination with demethylation estimates, accurately predicts MeHg formation under field and laboratory conditions. This assay does not require the use of mercury added to field samples to estimate activity but rather estimates the biological activity present in the soil by quantifying the amount of enzyme present in the soil. Such an assay is well suited for use in field surveillance programs assessing MeHg formation in a variety of environments.

Animals↗
PubMed2004

Dynamics of neutral lipid storage in yeast.

Since energy storage is a basic metabolic process, the synthesis of neutral lipids occurs in all kingdoms of life. The yeast, Saccharomyces cerevisiae, widely accepted as a model eukaryotic cell, contains two classes of neutral lipids, namely steryl esters and triacylglycerols. Triacylglycerols are synthesized through two pathways governed by the acyl-CoA diacylglycerol acyltransferase Dga1p and the phospholipid diacylglycerol acyltransferase Lro1p, respectively. Steryl esters are formed by the two steryl ester synthases Are1p and Are2p, two enzymes with overlapping function which also catalyze triacylglycerol formation, although to a minor extent. Storage of neutral lipids is tightly linked to the biogenesis of so called lipid particles. The role of this compartment in lipid homeostasis and its interplay with other organelles involved in neutral lipid dynamics, especially the endoplasmic reticulum and the plasma membrane, are subject of current investigations. In contrast to neutral lipid formation, mobilization of triacylglycerols and steryl esters in yeast are less characterized at the molecular level. Only recently, the triacylglycerol lipase Tgl3p was identified as the first yeast enzyme of this kind by function. Genes and gene products governing steryl ester mobilization still await identification. Besides biochemical properties of enzymes involved in yeast neutral lipid synthesis and degradation, regulatory aspects of these pathways and cell biological consequences of neutral lipid depletion will be discussed in this minireview.

Acyltransferases↗
PubMed1990

Nucleoplasmin: the archetypal molecular chaperone.

Nucleoplasmin was the first protein to be described as a molecular chaperone. Studies of nucleoplasmin have resulted in advances in two areas of cell biology. Firstly, the pathway of nucleosome assembly in Xenopus oocytes and eggs has been elucidated and is the only assembly pathway known in detail. Nucleosome assembly represents the major chaperoning function of nucleoplasmin. Secondly, nucleoplasmin has been used to elucidate the transport of proteins into the nucleus, revealing a selective entry mechanism for nuclear proteins, passage through the nuclear pore complex, and a two-step mechanism of transport. The properties and functions of nucleoplasmin are reviewed, together with other proteins which are related either structurally or functionally to nucleoplasmin.

Animals↗
PubMed1988

Leukotriene generation and metabolism in isolated human lung macrophages.

We studied the generation and metabolism of leukotrienes (LTs) in human lung macrophages obtained from lung tissue of patients with central bronchial carcinoma. By counterflow centrifugation macrophages were enriched with a purity of more than 95-100%. A time and dose dependent generation of LTB4 and LTC4 was determined by specific radioimmunoassays after stimulation with the Ca-ionophore and anti-IgE. The amount of LTB4 exceeded the amount of LTC4. The concentrations of leukotrienes in the macrophage fraction amounted to 4.3 +/- 2.2 ng LTB4 and 0.6 +/- 0.05 ng LTC4/1 x 10(7) cells after 5 min of incubation with the Ca-ionophore. The LTB4 levels decreased to 3.0 +/- 0.6 ng after 60 min indicating the metabolism of the generated LTB4 by human lung macrophages. This was confirmed by incubation of the cells with exogenously added [3H]LTB4. LTB4 was converted into unpolar products as was identified by thin-layer chromatography and high-performance liquid chromatography; a comparison with the fibroblast cell line L929 which is known to convert LTB4 into the dihydro-LTB4 metabolite (5,12-dihydroxyeicosatrienoic acid) indicates that human lung macrophages use the same pathway of metabolization. Biological inactivation as determined by chemotaxis and cross-reaction with the LTB4 antiserum correlates with the degree of LTB4 metabolism. Moreover, the macrophages convert LTC4 into LTD4 and LTE4 by the enzymatic activity of the gamma-glutamyltranspeptidase and dipeptidase. Our data emphasize that the human alveolar macrophage not only produces arachidonic acid metabolites but modulates the local inflammatory potential by its metabolizing capacity for leukotrienes.

Antibodies, Anti-Idiotypic↗
PubMed1985

Intrinsic connections of macaque striate cortex: afferent and efferent connections of lamina 4C.

We have studied the intrinsic organization of macaque striate cortex by tracing the pattern of horseradish peroxidase (HRP)-labeled axons and cell bodies produced by microinjections of HRP into single cortical laminae. Both anterograde and retrograde transport results were used to examine: (1) the pattern of projections from lamina 4C to the superficial layers; (2) the projection from lamina 4C to deeper cortical layers; and (3) the projections to lamina 4C from other cortical laminae. Laminae 4C alpha and 4C beta differ in their pattern of projections to the superficial layers of striate cortex. Axons from neurons in lamina 4C beta ascend through lamina 4B without giving off collaterals and terminate in lamina 4A and in the base of lamina 3. By contrast, axons from neurons in lamina 4C alpha terminate in lamina 4B and less densely in the 4A/3B region. The projection from lamina 4C beta to lamina 4A is particularly dense and is distributed in a patchy fashion immediately above each injection site. The projection from lamina 4C beta to lamina 3B appears less dense and more widespread; we estimate that individual 4C beta axons may spread laterally for more than 400 micron. Furthermore, the pattern of HRP-labeled cell bodies in lamina 4C beta following injections into laminae 4A and 3B provides evidence for a subdivision within 4C beta. These injections always produce a large number of labeled neurons in the upper part of lamina 4C beta, whereas the lower portion contains few labeled neurons that are located immediately under the center of the injection site. Both lamina 4C alpha and lamina 4C beta also contribute less dense projections to the deeper layers of cortex. Lamina 4C beta projects mainly to lamina 6, whereas lamina 4C alpha contributes axon terminals to both lamina 5A and lamina 6. Neurons in lamina 6 provide the bulk of the intracortical projections to lamina 4C. The axons of these neurons are fine in caliber and have a delicate side-spine morphology that is quite distinct from lateral geniculate axon arbors. Neurons in lamina 5A also project onto lamina 4C, but the projections of these neurons appear concentrated in lamina 4C alpha. These results confirm or refine many conclusions about intrinsic connections of striate cortex drawn from Golgi material and suggest new patterns of connections not suspected from previous work.

Afferent Pathways↗
PubMed1985

Generation of nitric oxide by enzymatic oxidation of N-hydroxy-N-nitrosamines.

The nitric oxide (N = O) free radical exhibits potent cytocidal, mutagenic and vasodilatory properties. We have examined the hypothesis that the hydroxynitrosamino functionality (see sequence in text), which occurs naturally in antineoplastic and antihypertensive agents, will directly generate N = O following peroxidatic 1-electron oxidation. Cupferron (see sequence in text) is indeed an excellent (k greater than 10(7) m-1 s-1) substrate for horseradish peroxidase. The products are N = O and nitrosobenzene (phi - N = O) which are generated and consumed as follows. First, cupferron is oxidized by the classical peroxidatic mechanism to form an unstable nitroxide free radical (see sequence in text) which then forms N = O and phi - N = O spontaneously (see sequence in text). The N = O then reacts with phi - N = O to reform cupferron (see sequence in text) or with the enzyme to generate the characteristic peroxidase--N = O chromophore. Simultaneously, in a competitive reaction with O2, the N = O is converted to NO-2 (4N = O + O2 + 2H2O------------4NO-2 + 4H+). The reactivity of hydroxynitrosamino compounds with horseradish peroxidase is in the order cupferron greater than hydroxynitrosaminomethane greater than alanosine. These model reactions, involving direct oxidation of the hydroxynitrosamino moiety, comprise a novel pathway for the biological production of N = O.

Chemical Phenomena↗