bluuebunny/crossref_metadata_2025 huggingface dataset:
Sympathetic Abnormalities during Autoimmune Processes
Authors: Del REY ADRIANA , KABIERSCH ALEXA , PETZOLDT SIGRID , BESEDOVSKY HUGO O.
Published: July 2009

Abstract:The sympathetic nervous system is one of the major pathways involved in immune‐neuroendocrine interactions. Disturbances in these interactions are likely to have consequences during lymphoproliferative diseases. Work derived from our group as well as from several others led us to the hypothesis that the overstimulation of the immune system that characterizes this type of pathology results in decreased sympathetic nerve activity in lymphoid organs. To explore this possibility, we used as a model lpr/lpr mice, which develop a genetically determined autoimmune, lupus‐like lymphoproliferative disease. We show that 18‐week‐old female C57Bl/6J lpr/lpr mice, which do not show overt symptoms of the disease but already have increased IgM and IgG2a levels in the blood, have decreased noradrenaline (NA) concentration and content in the spleen, but not in the kidney, as compared to normal C57Bl/6J littermates. Lpr/lpr mice do not express normal Fas, and therefore apoptosis cannot be triggered through this receptor. The defects in sympathetic innervation in the spleen of lpr/lpr mice prompted us to evaluate whether NA could influence lymphoid cell mass by inducing apoptosis. We found that NA can directly induce apoptosis in normal lymphoid cells via β‐adrenergic receptors. From the reported results we propose that reduction in sympathetic nerve function in lpr/lpr mice contributes to aggravation of the disease and suggest that in addition to the incapacity to mount Fas‐mediated apoptosis, a second proapoptotic mechanism, namely, that triggered by NA, is defective in these animals because of reduced availability of the neurotransmitter.
Antimicrobial Chromogranins and Proenkephalin‐A—Derived Peptides
Authors: METZ‐BOUTIGUE M. H. , GOUMON Y. , STRUB J. M. , LUGARDON K. , AUNIS D.
Published: July 2009

Abstract: The secretory granules from adrenal medullary chromaffin cells contain a complex mixture of low‐molecular mass constituents such as catecholamines, ascorbate, nucleotides, calcium, peptides, and several high‐molecular mass water‐soluble proteins including chromogranins and proenkephalin‐A. These proteins are sequestered into secretory granules in which processing yields a large variety of peptides. These fragments are released into the extracellular space upon cell stimulation and are recovered in blood, lymph, cerebrospinal fluid, and synovial fluid. Some of them have biological activity on cells in an autocrine, paracrine, or endocrine fashion. In addition, we have shown that peptides with antimicrobial activity are present with the secretory chromaffin granules and demonstrated that they are released from stimulated chromaffin cells. We have shown that posttranslational modifications modulate the antimicrobial activities. For some peptides, using confocal laser microscopy, we have examined the interaction of the rhodaminated peptides with biological membranes. In addition, we have shown that chromofungin, the antifungal peptide corresponding to chromogranin A47–66, can bind calmodulin in the presence of calcium and induce inhibition of calcineurin, a calmodulin‐dependent enzyme. Because these antibacterial peptides are colocalized with catecholamines, they may be activated during stress, playing a role as a first protective barrier against bacterial infection, and thus act as factors of the innate immunity shortly after infection and before the induction and mobilization of an adaptative immune system.
Integrating Systemic Information at the Molecular Level
Authors: REFOJO DAMIÁN , LIBERMAN ANA C. , GIACOMINI DAMIANA , NAGASHIMA ALBERTO CARBIA , GRACIARENA MARIANA , ECHENIQUE CARLOS , PEREDA MARCELO PAEZ , STALLA GÜNTER , HOLSBOER FLORIAN , ARZT EDUARDO
Published: July 2009

Abstract: An essential event in immune activation is the increase of cytokines in both plasma and immune tissues. Steroid hormones influence several adaptive responses in both health and disease. Cytokines and steroids have an intimate cross‐communication in many systems, making possible a satisfactory adaptive response to environmental changes. The ultimate level of integration of the cytokine‐steroids cross‐talk is the molecular level. We have demonstrated this in four types of cross‐talk mechanisms on different cells in which steroids have major roles: (1) The tumor necrosis factor (TNF)‐glucocorticoid receptor (GR) transcriptional interaction in cellular targets of TNF‐induced cytotoxicity. TNF potentiates the transactivation activity of GR and the priming with TNF increases the protective action of GR on TNF‐induced cytotoxicity. (2) The GR‐T cell receptor (TCR) antagonism in GR‐TCR‐induced T cell apoptosis and its modulation by cAMP. cAMP inhibits the TCR‐induced apoptosis through a PKA‐CREB‐dependent mechanism and potentiates glucocorticoid‐induced apoptosis by means of a CREB‐independent mechanism. (3) The GR influence on Th1‐Th2 cytokine expression and differentiation. Glucocorticoids inhibit the induction of GATA‐3 and T‐bet transcription factors. (4) The influence of ER/Smad‐4 signaling cross‐communication on prolactinoma pathogenesis. Physical and functional interactions between Smad‐4 and estrogen receptors take place in prolactinoma cells, providing a molecular explanation to link the tumorigenic action of these two important players of prolactinoma pathogenesis. The molecular cross‐talk between steroids and transcription factors is the mechanism that provides the basis for the outcome of adaptive responses integrating the systemic information provided by hormones and cytokines.
The Role of Neural Inflammation in Asthma and Chronic Obstructive Pulmonary Disease
Authors: JOOS GUY F. , De SWERT KATELIJNE O. , SCHELFHOUT VANESSA , PAUWELS ROMAIN A.
Published: July 2009

Abstract:The tachykinins substance P and neurokinin A are found within airway nerves and immune cells. They have various effects on the airways that can contribute to the changes observed in asthma and chronic obstructive pulmonary disease. Both tachykinin NK1and NK2receptors have been involved in the bronchoconstriction and the proinflammatory changes induced by substance P and neurokinin A. Tachykinin NK1and NK2receptor antagonists have activity in various animal models of allergic asthma and chronic bronchitis. It is suggested that dual NK1/NK2and triple NK1/NK2/NK3tachykinin receptor antagonists have potential in the treatment of obstructive airway diseases.
Neurotrophins in Allergic Airway Dysfunction
Authors: LOMMATZSCH MAREK , BRAUN ARMIN , RENZ HARALD
Published: July 2009

Abstract: Neurotrophins such as nerve growth factor (NGF) and brain‐derived neurotrophic factor (BDNF) are potent mediators of neuronal plasticity in the adult. There is increasing evidence that they regulate a variety of immune functions as well. Thus, neurotrophins are candidate molecules for neuroimmune interactions in allergic bronchial asthma, where elevated neurotrophin levels have been reported. In a mouse model of allergic airway inflammation we have identified macrophages and lymphocytes as additional cellular sources of NGF and BDNF in the inflamed lung. There was an unusual time course of BDNF in bronchoalveolar lavage fluid. BDNF levels peaked 1 week after the last allergen challenge, and did not correlate with the time course of the inflammatory response. In a series of experiments using blocking anti‐NGF and anti‐BDNF antibodies, we have shown that NGF specifically enhances inflammation and the allergic early‐phase response. In contrast, BDNF influenced chronic airway obstruction and local neuronal hyperreactivity without affecting inflammation. Using transgenic mice overexpressing NGF in the airway epithelium, we have confirmed the data obtained from anti‐NGF experiments. Allergen‐challenged NGF overexpressors displayed a markedly augmented airway inflammation, early‐phase response, and sensory irritation compared to wild‐type mice. Studies with p75‐NTR (−/−) knockout mice showed that these NGF effects are at least in part mediated by the low‐affinity neurotrophin receptor. Thus, our experiments suggest that NGF and BDNF have a profound, but differential impact on allergic airway dysfunction.
Molecular Mechanism of Agonism and Inverse Agonism in the Melanocortin Receptors
Authors: HOLST BIRGITTE , SCHWARTZ THUE W.
Published: July 2009

Abstract: Among the rhodopsin‐like 7TM receptors, the MC receptors are functionally unique because their high constitutive signaling activity is regulated not only by endogenous peptide agonists—MSH peptides—but also by endogenous inverse agonists, namely, the proteins agouti and AGRP. Moreover, the metal‐ion Zn2+ increases the signaling activity of at least the MC1 and MC4 receptors in three distinct ways: (1) by directly functioning as an agonist; (2) by potentiating the action of the endogenous agonist; and (3) by inhibiting the binding of the endogenous inverse agonist. Structurally the MC receptors are part of a small subset of 7TM receptors in which the main ligand‐binding crevice, and especially extracellular loops 2 and 3, appear to be specially designed for easy ligand access and bias towards an active state of the receptor—i.e., constitutive activity. Thus, in the MC receptors extracellular loop 2 is ultrashort because TM‐IV basically connects directly into TM‐V, whereas extracellular loop 3 appears to be held in a particular, constrained conformation by a putative, internal disulfide bridge. The interaction mode for the small and well‐defined zinc‐ion between a third, free Cys residue in extracellular loop 3 and conceivably an Asp residue located at the inner face of TM‐III gives important information concerning the activation mechanism for the MC receptors.
Syndecan‐3 Modulates Food Intake by Interacting with the Melanocortin/AgRP Pathway
Authors: REIZES OFER , BENOIT STEPHEN C. , STRADER APRIL D. , CLEGG DEBORAH J. , AKUNURU SHAILAJA , SEELEY RANDY J.
Published: July 2009

Abstract: Syndecan‐3, expressed in the developing nervous system and adult brain, alters feeding behavior through its interaction with the CNS melanocortin system, which provides critical tonic inhibition of both food intake and body adipose stores. A variety of both in vitro and transgenic data supports the hypothesis that syndecan‐3 modulates melanocortin activity via syndecan‐3 facilitation of agouti‐related protein (AgRP), a competitive antagonist of α‐melanocyte‐stimulating hormone (α‐MSH) at the melanocortin‐3 and ‐4 receptors. Consistent with this hypothesis, mice lacking syndecan‐3, which therefore would be predicted to have less effective AgRP, are more sensitive to inhibition of food intake by the melanocortin agonist MTII. Additionally, we took advantage of the fact that syndecan‐3 facilitation of AgRP is limited to when it is bound to the cell membrane. Pharmacologic inhibition of the enzyme that cleaves syndecan‐3 from the cell membrane leads to increased food intake in fasted rats, which have elevated levels of AgRP. Furthermore, the shedding process appears to be regulated under physiologic conditions, because a putative inhibitor of the shedding process, tissue inhibitor of metalloprotease‐3 (TIMP‐3), is increased by food deprivation. These observations contribute to the hypothesis that syndecan‐3 regulation of melanocortin signaling contributes to the normal control of energy balance. Collectively, the data suggest that the modulation of melanocortin regulation of energy balance by syndecan‐3 is modulated by the action of a TIMP‐3‐sensitive metalloprotease.
Functional Role, Structure, and Evolution of the Melanocortin‐4 Receptor
Authors: SCHIÖTH HELGI B. , LAGERSTRÖM MALIN C. , WATANOBE HAJIME , JONSSON LOGI , VERGONI ANNA VALERIA , RINGHOLM ANETA , SKARPHEDINSSON JON O. , SKULADOTTIR GUDRUN V. , KLOVINS JANIS , FREDRIKSSON ROBERT
Published: July 2009

Abstract: The melanocortin (MC)‐4 receptor participates in regulating body weight homeostasis. We demonstrated early that acute blockage of the MC‐4 receptor increases food intake and relieves anorexic conditions in rats. Our recent studies show that 4‐week chronic blockage of the MC‐4 receptor leads to robust increases in food intake and development of obesity, whereas stimulation of the receptor leads to anorexia. Interestingly, the food conversion ratio was clearly increased by MC‐4 receptor blockage, whereas it was decreased in agonist‐treated rats in a transient manner. Chronic infusion of an agonist caused a transient increase in oxygen consumption. Our studies also show that the MC‐4 receptor plays a role in luteinizing hormone and prolactin surges in female rats. The MC‐4 receptor has a role in mediating the effects of leptin on these surges. The phylogenetic relation of the MC‐4 receptor to other GPCRs in the human genome was determined. The three‐dimensional structure of the protein was studied by construction of a high‐affinity zinc binding site between the helices, using two histidine residues facing each other. We also cloned the MC‐4 receptor from evolutionary important species and showed by chromosomal mapping a conserved synteny between humans and zebrafish. The MC‐4 receptor has been remarkably conserved in structure and pharmacology for more than 400 million years, implying that the receptor participated in vital physiological functions early in vertebrate evolution.
Identification of a Serine Protease Involved with the Regulation of Adrenal Growth
Authors: BICKNELL ANDREW B.
Published: July 2009

Abstract: The adrenal cortex is a dynamic organ in which the cells of the outer cortex continually divide. It is well known that this cellular proliferation is dependent on constant stimulation from peptides derived from the ACTH precursor pro‐opiomelanocortin (POMC) because disruption of pituitary corticotroph function results in rapid atrophy of the gland. Previous results from our laboratory have suggested that the adrenal mitogen is a fragment derived from the N‐terminal of POMC not containing the γ‐MSH sequence. Because such a peptide is not generated during processing of POMC in the pituitary, we proposed that the mitogen is generated from circulating pro‐γ‐MSH by an adrenal protease. Using degenerate oligonucleotides, we identified a secreted serine protease expressed by the adrenal gland that we named adrenal secretory protease (AsP). In the adrenal cortex, expression of AsP is limited to the outer zona glomerulosa/fasciculata, the region where cortical cells are believed to be derived, and is significantly up‐regulated during compensatory growth. Y1 adrenocortical cells transfected with a vector expressing an antisense RNA (and thus having reduced levels of endogenous AsP) were found to grow slower than sense controls while also losing their ability to utilize exogenous pro‐γ‐MSH in the media supporting a role for AsP in adrenal growth. Digestion of an N‐POMC peptide substrate encompassing the residues around the dibasic cleavage site at positions 49/50 with affinity‐purified AsP showed cleavage not to occur at the dibasic site but two residues downstream leading us to propose the identity of the adrenal mitogen to be N‐POMC (1–52).
New Insights into the Functions of α‐MSH and Related Peptides in the Immune System
Authors: LUGER THOMAS A. , SCHOLZEN THOMAS E. , BRZOSKA THOMAS , BÖHM MARKUS
Published: July 2009

Abstract: There is a substantial body of evidence that the tridecapeptide α‐melanocyte‐stimulating hormone (α‐MSH) functions as a mediator of immunity and inflammation. The immunomodulating capacity of α‐MSH is primarily because of its effects on melanocortin receptor (MC‐1R)‐expressing monocytes, macrophages, and dendritic cells (DCs). α‐MSH down‐regulates the production of proinflammatory and immunomodulating cytokines (IL‐1, IL‐6, TNF‐α, IL‐2, IFN‐γ, IL‐4, IL‐13) as well as the expression of costimulatory molecules (CD86, CD40, ICAM‐1) on antigen‐presenting DCs. In contrast, the production of the cytokine synthesis inhibitor IL‐10 is up‐regulated by α‐MSH. At the molecular level, these effects of α‐MSH are mediated via the inhibition of the activation of transcription factors such as NFκB. Not only α‐MSH but also its C‐terminal tripeptide (α‐MSH 11–13, KPV) was able to bind to MC‐1R and to modulate the function of APCs. In vivo, using a mouse model of contact hypersensitivity (CHS) systemic and topical application of α‐MSH or KPV inhibited the sensitization and the elicitation phase of CHS and was able to induce hapten‐specific tolerance. To investigate the underlying mechanisms of tolerance induction, we have performed in vivo transfer experiments. Treatment of naive mice with bone marrow‐derived immature haptenized and α‐MSH‐pulsed DCs resulted in a significant inhibition of CHS. Furthermore, tolerance induction was found to be mediated by the generation of CTLA4+ and IL‐10‐producing T lymphocytes. The potent capacity of α‐MSH to modulate the function of antigen‐presenting cells (APCs) has been further supported in another experimental approach. In vitro, by activating APCs, α‐MSH has been shown to modulate IgE production by IL‐4 and anti‐CD40 stimulated B lymphocytes. Moreover, in a murine model of allergic airway inflammation, systemic treatment with α‐MSH resulted in a significant reduction of allergen‐specific IgE production, eosinophil influx, and IL‐4 production. These effects were mediated via IL‐10 production, because IL‐10 knockout mice were resistant to α‐MSH treatment. Therefore, therapeutic application of α‐MSH or related peptides (KPVs) as well as α‐MSH/KPV‐pulsed DCs may be a useful approach for the treatment of inflammatory, autoimmune, and allergic diseases in the future.
Electrophysiological Actions of Peripheral Hormones on Melanocortin Neurons
Authors: COWLEY MICHAEL A. , CONE ROGER D. , ENRIORI PABLO , LOUISELLE INGRID , WILLIAMS SARAH M. , EVANS ANNE E.
Published: July 2009

Abstract:Neurons of the arcuate nucleus of the hypothalamus (ARH) appear to be sites of convergence of central and peripheral signals of energy stores, and profoundly modulate the activity of the melanocortin circuits, providing a strong rationale for pursuing these circuits as therapeutic targets for disorders of energy homeostasis. Recently, tremendous advances have been made in identifying genes and pathways important to regulating energy homeostasis, particularly the hormone leptin and its receptor. This hormone/receptor pair is expressed at high levels in the so‐called satiety centers in the hypothalamus, and at lower levels elsewhere in the body. Recent studies in our lab and those of our collaborators have shown that leptin modulates different populations of hypothalamic cells in different ways, rapidly activating POMC neurons and inhibiting NPY/AgRP neurons.

In this report, we outline an integrated model of leptin's action in the arcuate nucleus of the hypothalamus, derived from our electrophysiological studies of brain slice preparations taken from transgenic mice that have been bred to express a variety of fluorescent proteins in specific cell types. We also discuss the recently withdrawn obesity drug fenfluramine, which appears to act on POMC neurons via the serotonin 2C receptor. Nutrient‐sensing serotonin neurons may project from the raphe nuclei in the brainstem to the hypothalamus; within the arcuate nucleus, serotonin signals are integrated with others such as leptin, ghrelin, and peptide YY3–36from the gut, to produce a coordinated response to nutrient state. Finally, we review the current inquiries into the ability of the hormone ghrelin to stimulate appetite by its action of NPY neurons and inhibition of POMC neurons.
State‐Dependent Modulation of Feeding Behavior by Proopiomelanocortin‐Derived β‐Endorphin
Authors: LOW MALCOLM J. , HAYWARD MICHAEL D. , APPLEYARD SUZANNE M. , RUBINSTEIN MARCELO
Published: July 2009

Abstract:Feeding behavior can be divided into appetitive and consummatory phases, differing in neural substrates and effects of deprivation. Opioids play an important role in the appetitive aspects of feeding, but they also have acute stimulatory effects on food consumption. Because the opioid peptide β‐endorphin is co‐synthesized and released with melanocortins from proopiomelanocortin (POMC) neuronal terminals, we examined the physiological role of β‐endorphin in feeding and energy homeostasis using a strain of mutant mice with a selective deficiency of β‐endorphin. Male β‐endorphin‐deficient mice unexpectedly became obese with ad libitum access to rodent chow. Total body weight increased by 15% with a 50–100% increase in the mass of white fat. The mice were hyperphagic with a normal metabolic rate. Despite the absence of endogenous β‐endorphin, the mutant mice did not differ from wild‐type mice in their acute feeding responses to β‐endorphin or neuropeptide Y administered intracerebroventricularly or naloxone administered intraperitoneally. Additional mice were studied using an operant behavioral paradigm to examine their acquisition of food reinforcers under increasing work demands. Food‐deprived, β‐endorphin‐deficient male mice emitted the same number of lever presses under a progressive ratio schedule compared to wild‐type mice. However, the mutant mice worked significantly less than did the wild‐type mice for food reinforcers under nondeprived conditions. Controls for nonspecific effects on acquisition of conditioned learning, activity, satiety, and resistance to extinction revealed no genotype differences, supporting our interpretation that β‐endorphin selectively affects a motivational component of reward behavior under nondeprived conditions. Therefore, we propose that β‐endorphin may function in at least two primary modes to modulate feeding. In the appetitive phase, β‐endorphin release increases the incentive value of food as a primary reinforcer. In contrast, it appears that endogenous β‐endorphin may inhibit food consumption in parallel with melanocortins and that the orexigenic properties previously ascribed to it may actually be due to other classes of endogenous opioid peptides.
Oxytocin Released from Magnocellular Dendrites
Authors: SABATIER NANCY , CAQUINEAU CÉLINE , DOUGLAS ALISON J. , LENG GARETH
Published: July 2009

Abstract: α‐Melanocyte‐stimulating hormone (α‐MSH) is implicated in a variety of behavioral processes that are remarkably similar to those behaviors in which centrally acting oxytocin has been implicated. Central oxytocin derives in part from centrally projecting parvocellular neurons of the paraventricular nucleus, but large amounts of oxytocin are also released from dendrites of magnocellular oxytocin neurons in the supraoptic and paraventricular nuclei of the hypothalamus. Oxytocin release from dendrites is semi‐independent of electrical activity and can be modulated by peptidergic signals independently of release from nerve terminals. Oxytocin is released from dendrites by stimuli that mobilize intracellular calcium stores, and such stimuli also prime dendritic stores of oxytocin, making them available for subsequent activity‐dependent secretion. Evidence exists for efferent projections to the supraoptic nucleus from the arcuate nucleus where α‐MSH neurons are located, and the supraoptic and paraventricular nuclei show high levels of expression of mRNA for the melanocortin receptor MC4R. These projections may be involved specifically in the regulation of dendritic oxytocin release.
Knockout Studies Defining Different Roles for Melanocortin Receptors in Energy Homeostasis
Authors: BUTLER ANDREW A. , CONE ROGER D.
Published: July 2009

Abstract: Proopiomelanocortin (POMC) is expressed in the arcuate nucleus of the hypothalamus (ARC) and the commissural nucleus of the solitary tract (cNTS). Post‐translational processing of POMC produces two melanocortin receptor ligands, α‐ and γ‐melanocyte‐stimulating hormone (MSH). Two melanocortin receptors (MC3R, MC4R) are expressed in brain regions receiving projections of POMC fibers, most of which also receive projections from a population of ARC neurons that co‐express neuropeptide Y (NPY) and the MC3R/MC4R antagonist agouti‐related peptide (AgRP). MC4R haploinsufficient humans and MC4R knockout (MC4RKO) mice exhibit increased adiposity and linear growth. MC4RKO mice exhibit hyperleptinemia and hyperinsulinemia and sometimes, but not always, develop type 2 diabetes (T2D). Individually housed MC4RKO mice fed low‐fat diets are not hyperphagic when food intake is corrected for lean mass, whereas hyperphagia is observed after the introduction of diets with increased fat content. POMC knockout (POMCKO) mice are similar in that the severity of hyperphagia increases with the introduction of high‐fat diets. By contrast, targeted deletion of the MC3R in the mouse results in increased adiposity despite the absence of hyperphagia. MC3RKO mice also exhibit reduced linear growth and lean mass; while MC3RKO mice are hyperleptinemic and hyperinsulinemic, the development of T2D has not been reported. The MC4R, but not the MC3R, is required for the stimulation of energy expenditure in response to melanocortin agonists and voluntary hyperphagia. Evidence for altered physical activity has also been reported for both knockout models. Analysis of MC4RKO mice indicates that this receptor is involved in rapidly coordinating energy consumption with energy expenditure through diet‐induced thermogenesis and activity.
α‐Melanocyte‐Stimulating Hormone Is a Peripheral, Integrative Regulator of Glucose and Fat Metabolism
Authors: BRENNAN MILES B. , COSTA JESSICA LYNN , FORBES STACY , REED PEGGY , BUI STEPHANIE , HOCHGESCHWENDER UTE
Published: July 2009

Abstract: Melanocortins are known to affect feeding and probably insulin activity through the central nervous system. It was also recently shown that peripheral α‐melanocyte‐stimulating hormone (α‐MSH) administration can reduce weight gain in both genetic and diet‐induced obese mice. As obesity is often associated with disregulation of glucose and insulin, we investigated the nature of glucose homeostasis in the obese pro‐opiomelanocortin (POMC) knockout mouse. Here we report that though they are obese, mice deficient in POMC (and, thereby, deficient in α‐MSH) are euglycemic throughout their lives. While these mice are euinsulinemic, they are hypersensitive to exogenous insulin. This defect can be reversed through administration of α‐MSH. We demonstrate that the actions of α‐MSH in the periphery, known from our work to include lipid metabolism effects, are also involved in glucose homeostasis. These findings substantiate a pivotal role of the POMC gene products in integrating metabolism.
Evolutionary Genetics of the Melanocortin‐1 Receptor in Vertebrates
Authors: MUNDY NICHOLAS I. , KELLY JOANNE , THERON EMMALIZE , HAWKINS KIM
Published: July 2009

Abstract: The molecular genetic basis of adaptive change in phenotype is a major outstanding issue in evolutionary biology. Evolutionary change in coat and plumage color is a promising system for making progress in this field. Most notably, recent work on the molecular genetic basis of hair and feather color has identified several genes which are candidates for involvement in evolutionary color change in mammals and birds. We have investigated the evolution of one of these candidate genes, the melanocortin‐1 receptor (MC1R) gene, in relation to changes in melanin distribution among a wide variety of primate species, and in bananaquits (Coereba flaveola), which are a classic case of melanic plumage polymorphism in birds. In primates, a role of the MC1R coding region in coat color evolution can be ruled out in several cases in which closely related species have drastically different distributions of eumelanin and/or pheomelanin. However, reconstruction of MC1R sequences over primate evolution shows the presence of mutations at important functional sites in several lineages. Most notably, the lion tamarins (Leontopithecus) show a striking pattern of MC1R evolution, including deletions and several nonconservative amino acid changes. In the bananaquit, an E92K substitution in the MC1R is strongly associated with melanism, and this is likely to be the causative mutation. Reconstruction of the evolution of bananaquit MC1R alleles shows that melanism is a derived trait in this species. These results confirm the utility of a candidate gene approach to color evolution in vertebrates and open the way for extensive future research.
Pigmentary Switches in Domestic Animal Species
Authors: KLUNGLAND H. , VÅGE D. I.
Published: July 2009

Abstract: Although homogeneous pigmentation usually is observed in wild animals, most domestic animal species display a wide variety of coat colors. In fur animals, the coat color is an important production trait, and in other species such as cattle and sheep, the coat color is a major breed characteristic. Variability in coat color is seen both within and between breeds, and makes domesticated species unique for studying gene function and gene regulation of loci affecting pigmentation. In several species, mutations in the MC1‐R gene have been shown to cause the dominant expression of black pigment. In fox, alleles of both the agouti and the MC1‐R gene could cause eumelanin synthesis. In addition, a nonepistatic interaction between MC1‐R and agouti has been observed, resulting in several different coat color phenotypes expressing a mixture of red and black pigmentation. Also in cattle and sheep, amino acid substitutions within the MC1‐R explain the dominant inheritance of black pigmentation. Unlike the constitutively activated MC1‐R found in the Alaska silver fox, dominant variants of the MC1‐R found in cattle and sheep seem to be completely dominant with no antagonizing effect of agouti. MC1‐R variants with premature stop codons are widespread in several cattle populations, indicating that this well‐conserved gene has no other fundamental function beside pigmentation. Other well‐established breed characteristics include distinct coat color patterns in which the distribution of melanocytes, partly regulated by the c‐kit gene, seems to be involved.
P‐Locus Is a Target for the Melanogenic Effects of MC‐1R Signaling
Authors: ANCANS JANIS , FLANAGAN NIAMH , HOOGDUIJN MARTIN J. , THODY ANTHONY J.
Published: July 2009

Abstract: Melanocortin receptor type 1 (MC‐1R) is an important control point for ultraviolet ray (UVR)‐induced tanning response in the skin. In this study, we show that p‐locus is a downstream target for MC‐1R signaling. The expression of p‐locus was up‐regulated by α‐MSH as well as db‐cAMP, a syn‐thetic analogue of cAMP that mimics activation of MC‐1R. Furthermore, p‐locus transcript abundance was significantly increased in epidermal melanocytes of white skin with facultative (UVR‐induced) pigmentation. Because p‐locus product is essential for pigmentation and also has been shown to be highly polymorphic in human population, we propose that the pigmentary response to the melanocortin peptides/UVR would be affected not only by MC‐1R mutations but also by the functionality of p‐locus product. These factors together could account for the many different levels of tanning ability seen in the white population.
TACE/ADAM17 Processing of EGFR Ligands Indicates a Role as a Physiological Convertase
Authors: LEE DAVID C. , SUNNARBORG SUSAN WOHLER , HINKLE C. LEANN , MYERS TIMOTHY J. , STEVENSON MARY , RUSSELL WILLIAM E. , CASTNER BEVERLY J. , GERHART MARY J. , PAXTON RAYMOND J. , BLACK ROY A. , CHANG AILEEN , JACKSON LESLIE F.
Published: July 2009

Abstract: EGF family growth factors, including transforming growth factor‐alpha (TGFα), amphiregulin (AR), and heparin‐binding EGF (HB‐EGF), are invariably expressed as transmembrane precursors that are cleaved at one or more sites in the extracellular domain to release soluble growth factor. Considerable attention has focused on the identification of proteases responsible for these processing events. We previously implicated tumor necrosis factor‐alpha converting enzyme (TACE/ADAM17) in the generation of soluble TGFα from its transmembrane precursor, proTGFα. Here, we review our findings that primary keratinocytes from TaceΔZn/ΔZn mice, which express a nonfunctional TACE, released dramatically lower levels of soluble TGFα compared to their normal counterparts, even though TGFα mRNA and cell‐associated protein levels were similar in the two cell populations. Restoration of TACE activity in TaceΔZn/ΔZn cells increased shedding of TGFα species, including the mature, 6‐kDa protein. Further, exogenous TACE enzyme accurately cleaved the N‐terminal processing site of proTGFα in cell lysates, as well as both physiologic sites of a soluble proTGFα ectodomain. TACE also accurately cleaved peptide substrates corresponding to the processing sites of several additional EGF family members, and restoration of TACE activity enhanced the shedding of soluble AR and HB‐EGF proteins from TaceΔZn/ΔZn cells. Finally, reduction of functional TACE gene dosage greatly exacerbated the open‐eye defect of Egfrwa‐2/wa‐2 newborns, which is regulated by redundant actions of several EGF family ligands. The implications of these results for the biology of the EGF family and TACE are discussed.
Chorioallantoic Morphogenesis and Formation of the Placental Villous Tree
Authors: CROSS JAMES C. , SIMMONS DAVID G. , WATSON ERICA D.
Published: July 2009

Abstract: The placenta is a highly specialized organ whose primary function is to promote the exchange of nutrients and oxygen between maternal and fetal blood, essential for survival and growth of the baby. The surface area for nutrient transport is a highly convoluted villous structure that forms by branching morphogenesis. In mice, this process begins after embryonic day 8.5, following attachment of allantoic mesoderm to the chorion, and continues through the end of gestation. Gene targeting studies in mice have identified a large number of genes that are essential for chorioallantoic development to give rise to the layer of the placenta called the labyrinth. Collectively, these studies reveal that a number of signaling pathways regulate four distinct phases of labyrinth development: chorioallantoic attachment (involving VCAM1 and its receptor α4 integrin, Bmp5/7, and Wnt7b, as well as the cochaperone Mrj), initiation of branching (involving the Gcm1 transcription factor to select sites of branch initiation), extension of villous branching (involving FGF, EGF, and HGF/Met signaling, through the Grb2/Sos1/Mek1/p38α MAPK pathway), followed by vascularization of the villous tree. The restricted expression and/or action of the signaling components indicate that a series of intercellular interactions regulate chorioallantoic development.
Remodeling of the Microenvironment by Aggressive Melanoma Tumor Cells
Authors: HENDRIX MARY J. C. , SEFTOR ELISABETH A. , KIRSCHMANN DAWN A. , QUARANTA VITO , SEFTOR RICHARD E. B.
Published: July 2009

Abstract: A necessity for development and tumor progression is a blood supply formed by vasculogenic and/or angiogenic events, involving the cooperative interactions of cells with their microenvironment. Based on the recent characterization of vasculogenic mimicry by aggressive melanoma cells, particularly their ability to express VE (vascular endothelial)‐cadherin, TIE‐1, and EphA2, current studies have focused on the molecular signals deposited by these cells as they remodel their microenvironment. The experimental approach utilizes unique three‐dimensional collagen matrices preconditioned by metastatic melanoma cells, which contain laminin 5 γ2 chain‐enriched tracks with promigratory cleavage fragments produced by cooperative interactions with specific matrix metalloproteinases (MMPs). The results demonstrate that the collagen matrices preconditioned by the metastatic cells induce poorly aggressive melanoma cells to express, for the first time, key angiogenic/vasculogenic/matrix‐remodeling genes. Treatment of aggressive melanoma cells with an MMP inhibitor resulted in the inhibition of vasculogenic mimicry‐associated genes in these tumor cells and abrogation of the inductive effects of the preconditioned matrix on poorly aggressive melanoma cells. These observations illustrate the remarkable influence of the microenvironment on the phenotype of melanoma cells and may provide new perspectives on tumor cell plasticity and unique treatment strategies.
Macrophage Migration Inhibitory Factor (MIF)
Authors: NISHIHIRA JUN , ISHIBASHI TERUO , FUKUSHIMA TSUYOSHI , SUN BAILONG , SATO YUJI , TODO SATORU
Published: July 2009

Abstract: Macrophage migration inhibitory factor (MIF) functions as a pluripotent cytokine involved in broad‐spectrum pathophysiological events in association with inflammation and immune responses. Several reports, including ours, have suggested that MIF is also involved in tumorigenesis; however, its precise role has not been fully investigated. We examined the effectiveness of anti‐MIF antibodies on tumor growth and tumor‐associated angiogenesis using murine colon cancer cell line, colon 26. We observed a significant inhibition of growth of tumors embedded on the back of BALB/c mice by treatment with anti‐MIF antibodies. Next, we implanted a Millipore chamber filled with colon cancer cells in the subcutaneous fascia of the flanks of mice and then treated them with anti‐MIF antibodies. We found that angiogenesis was markedly suppressed within the region of the subcutaneous fascia that was in contact with the chamber. To further assess the role of MIF in tumorigenesis, we established MIF transgenic mice, which demonstrated that tumor growth and the associated angiogenesis were significantly enhanced in comparison with control mice.
Hypomethylation: One Side of a Larger Picture
Authors: DUNN BARBARA K.
Published: July 2009

Abstract: Hypomethylation signifies one end of a spectrum of DNA methylation states. In most cases hypomethylation refers to a relative state that represents a change from the ‘normal’ methylation level. Hypomethylation, when approached from a topographical perspective, has been used to describe either overall decreases in the methylation status of the entire genome (global hypomethylation) or more localized relative demethylation of specific subsets of the genome, such as the promoter regions of protooncogenes or normally highly methylated repetitive sequences. Global hypomethylation accompanied by gene‐specific hypermethylation is observed in at least two important settings: cancer and aging. Global hypomethylation is generally reflective of decreased methylation in CpGs dispersed throughout repetitive sequences as well as the bodies of genes. Hypomethylation of repetitive and parasitic DNA sequences correlates with a number of adverse outcomes. For example, decreased methylation of repetitive sequences in the satellite DNA of the pericentric region of chromosomes is associated with increased chromosomal rearrangements, a hallmark of cancer. Decreased methylation of proviral sequences can lead to reactivation and increased infectivity. However, hypomethylation in cancer can also affect the CpGs in the promoters of specific genes—namely, protooncogenes—leading to their overexpression and resulting in the functional outcome of increased cell proliferation. Thus, hypomethylation, in a variety of settings in which it represents a deviation from ‘normal,’ appears to correlate with progression to cancer and offers potential mechanisms to explain the carcinogenic process.
Epigenetics: The Role of Methylation in the Mechanism of Action of Tumor Suppressor Genes
Authors: JAIN PAWAN K.
Published: July 2009

Abstract:Epigenetics is the study of mitotically heritable changes in gene expression without any changes in the primary DNA sequence. The major step in epigenetic gene regulation is gene inactivation by hypermethylation of CpG islands located in the promoter region. Specific enzymes and methylated DNA binding proteins play a major role in causing reduced expression of tumor suppressor genes, resulting in tumor formation and its progression. Prevention approaches are needed to avoid tumor formation. One approach to inhibiting inactivation of tumor suppressor genes is to use chemical agents such as 5‐azacytidine to prevent hypermethylation of DNA. Increased understanding of the mechanism of epigenetic silencing and the identification of additional molecular mechanisms (e.g., histone methylases) that may be targeted by pharmaceutical interventions may lead to more preventive strategies. The current status of the epigenetic regulation of tumor suppressor genes is discussed in this review article.
Sensitive Detection of DNA Methylation
Authors: COTTRELL SUSAN E. , LAIRD PETER W.
Published: July 2009

Abstract:In recent years, many molecular biomarkers have been discovered that are capable of distinguishing tumors from normal tissue. Among the different types of markers, DNA methylation markers stand out for their potential to provide a unique combination of specificity, sensitivity, high information content, and applicability to a wide variety of clinical specimens. Methylation markers are particularly suited for situations where sensitive detection is necessary, such as when tumor DNA is either scarce or diluted by excess normal DNA. One of the most widely used methods for measuring methylation levels, methylation‐specific PCR (MSP), has been proved to be a very effective tool in situations requiring sensitive detection. The addition of fluorogenic probes makes these assays more informative, quantitative, and suitable for a clinical format. The field of sensitive detection is not limited to MSP; hence, an alternative methylation‐sensitive amplification is discussed. PCR‐based methylation assays have been applied to the detection of tumor DNA in a variety of body fluids, including serum, plasma, urine, sputum, and lavage fluids. In many cases, the sensitivity and specificity of these detection assays has been impressive, but important technological issues remain in areas such as sample preparation, assay design, and marker selection. Once these technical concerns have been addressed, the sensitive detection of methylation will provide a powerful diagnostic and prognostic tool, especially for the early detection of preneoplastic and neoplastic lesions.
Cancer Biomarker Validation: Standards and Process
Authors: BARKER PETER E.
Published: July 2009

Abstract: Rigorous validation of biomarkers for early detection of cancer differs at the National Institute of Standards and Technology (NIST) from similar processes common among research laboratories. As a newly discovered biomarker assay makes the transition from a research setting to the clinical diagnostic laboratory, it should progress through defined stages of assay confirmation. The first task of a validation laboratory is evaluation of research assay technology, performance, and specifications (analytical validation). However, the ultimate goal is initial validation of the test to identify early stage cancer (clinical validation). Upon technical and clinical confirmation, assays are moved systematically toward a standardized, reproducible, high‐throughput format for clinical diagnostic implementation. With laboratory performance rigorously established, the clinical variables can subsequently be analyzed to define limitations, applications, and clinical utility. The role of NIST in technology evaluation for early cancer testing is described in the context of similar programs and prior experience at NIST. Here we conceptualize the validation steps of cancer test development and examine how NIST activities impact health care through institutional focus on measurement, technology, and standards development programs.
Viral Genes and Methylation
Authors: VERMA MUKESH
Published: July 2009

Abstract: Epigenetics represents a new frontier in cancer research. Methylation is the best studied of the epigenetic mechanisms that regulate gene expression. Regulation of gene expression by means of methylation has been reported for tumor suppressor genes, oncogenes, viral promoters, and age‐related genes. In this review, the regulation of viral gene expression by methylation is discussed, with particular emphasis on: (1) the virus‐specific factors that bind to promoter regions; (2) the implications of this knowledge for designing viral vectors that can be used to deliver genes for the purpose of gene therapy; and (3) the use of this knowledge for the early detection and prevention of cancer. Since methylation can be reversed by a variety of exogenous agents, great potential exists to develop interventions that target cancer‐associated aberrant methylation in an effort to reverse or prevent carcinogenesis.
Epigenetics in Carcinogenesis and Cancer Prevention
Authors: JONES PETER A.
Published: July 2009

Abstract: Carcinogenesis is a stepwise process of accumulation of genetic and epigenetic abnormalities that can lead to cellular dysfunction. It has become clear that epigenetic changes are equally important for this multistep process to produce its results. This article describes the different roles that epigenetic modulation may play during carcinogenesis and how an early detection and chemopreventive intervention strategy that takes both sides of the equation into account would be advantageous.
Histone Acetylation and Gastrointestinal Carcinogenesis
Authors: YASUI WATARU , OUE NAOHIDE , ONO SHIGEHIRO , MITANI YOSHITSUGU , ITO REIKO , NAKAYAMA HIROFUMI
Published: July 2009

Abstract: The importance of altered histone acetylation in gastrointestinal carcinogenesis, especially in relation to invasion and metastasis, is described. Histone acetylation and chromatin remodeling linked with CpG island methylation play a major role in epigenetic regulation of gene expression. Acetylation of histones through an imbalance of histone acetyltransferases and deacetylases disrupts nucleosome structure, which leads to DNA relaxation and subsequent increase in accessibility to transcription factors. The expression of acetylated histone H4 is reduced in a majority of gastric and colorectal cancers, indicating the low level of global histone acetylation in tumor cells. Moreover, reduced histone acetylation is significantly associated with depth of tumor invasion and nodal metastasis of gastrointestinal cancers. A histone deacetylase inhibitor, trichostatin A (TSA), induces growth arrest and apoptosis and suppresses invasion of cancer cells. Treatment with TSA, which is followed by increased histone acetylation in the promoters, induces the expression of many genes that are suppressors of invasion and metastasis, including tissue inhibitors of metalloproteinase and nm23H1/H2, in addition to negative cell cycle regulators and apoptosis‐related molecules. Our approach, serial analysis of gene expression (SAGE), enabled us to identify a gene that is a novel candidate for a metastasis suppressor, whose expression is induced by histone acetylation. These findings suggest that, by modifying gene expression, histone deacetylation may participate not only in tumorigenesis but also in invasion and metastasis. Therefore, histone acetylation should be a promising target for cancer therapy, especially against invasive and metastatic disease, but also for cancer prevention.
DNA Methylation, a Biomarker for Colorectal Cancer
Authors: JUBB ADRIAN M. , QUIRKE PHIL , OATES ADAM J.
Published: July 2009

Abstract: Currently up to one‐third of colorectal cancer patients present with locally advanced or metastatic disease that precludes a surgical cure. Performance limitations and low uptake of current screening tools have fueled research to develop minimally invasive approaches that can detect early‐stage neoplasms. The observation that altered DNA can be amplified from the stool or circulation has stimulated research on its use as a biomarker of occult neoplasia. De novo methylation of CpG islands 5′ to certain tumor suppressor genes has been associated with epigenetic silencing. At certain loci this phenomenon is specific for neoplastic populations, and it is frequently detected at early stages in colorectal tumorigenesis. Accordingly, hypermethylation events have been proposed by researchers as ideal targets for the basis of a screening panel to detect peripheral tumor DNA. This critique reviews research findings on the use of epigenetic biomarkers in screening for occult neoplasia. In addition, the authors consider the pathological utility of epigenetic testing in refining tumor staging and predicting disease recurrence.