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Biomedical subjects

Heikki Rauvala

Publications and source records attributed to Heikki Rauvala.

At least 19 recordsLinked to original sources
PubMed2005

Persistent elevation of high mobility group box-1 protein (HMGB1) in patients with severe sepsis and septic shock.

OBJECTIVE: To study the systemic release and kinetics of high mobility group box-1 protein (HMGB1) in relation to clinical features in a population of patients with severe sepsis or septic shock and to compare these with the kinetics of the cytokines interleukin-6, interleukin-8, interleukin-10, and tumor necrosis factor-alpha. DESIGN: Prospective study of two cohorts of patients. SETTING: Intensive care unit and infectious disease clinic at Karolinska University Hospital Huddinge. PATIENTS: Twenty-six patients with severe sepsis, 33 patients with septic shock, and a reference group of five patients with sepsis. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Sixty-four patients were included, ten of whom died within 28 days. Cytokine levels were measured at five time points during the first week after admission and were correlated to Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment scores. Two HMGB1 assays were used. Both demonstrated delayed kinetics for HMGB1 with high levels on inclusion that remained high throughout the study period. Serum concentration at 144 hrs, the last sampling point, was 300 times higher, 34,000 +/- 76,000 pg/mL (mean +/- sd), than any of the other cytokines. This study, however, found no predictable correlation between serum levels of HMGB1 and severity of infection. We did quite unexpectedly find significantly lower levels of HMGB1 in nonsurvivors compared with survivors as measured by our main assay, but the other showed no difference between the two groups. Levels of interleukin-6, interleukin-8, interleukin-10, and tumor necrosis factor-alpha correlated significantly with severity of disease, and all were significantly higher in patients with septic shock compared with those with severe sepsis. Neither of these comparisons showed significant correlations for HMGB1. CONCLUSIONS: This is the first prospective study assessing the release over time of HMGB1 in a population of patients with sepsis, severe sepsis, or septic shock. Levels remained high in the majority of patients up to 1 wk after admittance, indicating that the cytokine indeed is a downstream and late mediator of inflammation. Further studies are required to fully define the relationship of HMGB1 to severity of disease.

Biomarkers↗
PubMed2005

Behavioural phenotypes of hypomorphic KCC2-deficient mice.

Hyperpolarizing fast inhibitory neurotransmission by gamma-aminobutyric acid and glycine requires an efficient chloride extrusion mechanism in postsynaptic neurons. A major effector of this task in adult animals is the potassium-chloride co-transporter KCC2 that is selectively and abundantly expressed postsynaptically in most CNS neurons. Yet, the role of KCC2 in adult brain at the systems level is poorly known. Here, we characterize the behaviour of mice doubly heterozygous for KCC2 null and hypomorphic alleles that retain 15-20% of normal KCC2 protein levels in the brain. These hypomorphic KCC2-deficient mice were viable and fertile but weighed 15-20% less than wild-type littermates at 2 weeks old and thereafter. The mice displayed increased anxiety-like behaviour in several tests including elevated plus-maze and were more susceptible to pentylenetetrazole-induced seizures. Moreover, the mice were impaired in water maze learning and showed reduced sensitivity to tactile and noxious thermal stimuli in von Frey hairs, hot plate and tail flick tests. In contrast, the mice showed normal spontaneous locomotor activity in open field and Y-maze tests, and intact motor coordination in rotarod and beam tests. The results suggest that requirements for KCC2-dependent fast hyperpolarizing inhibition may differ among various functional systems of the CNS. As shunting inhibition is expected to be intact in KCC2-deficient neurons, these mice may provide a useful tool to study the specific functions and relative importance of hyperpolarizing fast synaptic inhibition in adult CNS that may have implications for human neuropsychiatric disorders, such as epilepsy, pain and anxiety.

Analysis of Variance↗
PubMed2004

Essential and separable roles for Syndecan-3 and Syndecan-4 in skeletal muscle development and regeneration.

Syndecan-3 and syndecan-4 function as coreceptors for tyrosine kinases and in cell adhesion. Syndecan-3(-/-) mice exhibit a novel form of muscular dystrophy characterized by impaired locomotion, fibrosis, and hyperplasia of myonuclei and satellite cells. Explanted syndecan-3(-/-) satellite cells mislocalize MyoD, differentiate aberrantly, and exhibit a general increase in overall tyrosine phosphorylation. Following induced regeneration, the hyperplastic phenotype is recapitulated. While there are fewer apparent defects in syndecan-4(-/-) muscle, explanted satellite cells are deficient in activation, proliferation, MyoD expression, myotube fusion, and differentiation. Further, syndecan-4(-/-) satellite cells fail to reconstitute damaged muscle, suggesting a unique requirement for syndecan-4 in satellite cell function.

Animals↗
PubMed2004

Regulation of monocyte migration by amphoterin (HMGB1).

Amphoterin (HMGB1) is a 30-kD heparin-binding protein involved in process extension and migration of cells by a mechanism involving the receptor for advanced glycation end products (RAGE). High levels of amphoterin are released to serum during septic shock. We have studied the expression of amphoterin in monocytes and the role of amphoterin and RAGE in monocyte transendothelial migration. Un-activated monocytes in suspension did not reveal amphoterin on their surface, but adherent monocytes exported amphoterin to the cell surface. Immunohistochemical staining of arterial thrombi in vivo revealed amphoterin in mononuclear cells and in surrounding extracellular matrix. Amphoterin was secreted from phorbol ester and interferon-gamma (IFN-gamma)-activated macrophages, and the secretion was inhibited by blocking the adenosine 5'-triphosphate (ATP)-binding cassette transporter-1, a member of the multidrug resistance protein family. Amphoterin was specifically adhesive for monocytes in peripheral blood leukocyte adhesion assay. Adhesion caused an extensive spreading of cells, which was inhibited by the dominant-negative RAGE receptor (soluble ectodomain of RAGE), and adhesion up-regulated chromogranin expression in monocytes, also suggesting a RAGE-dependent interaction. Monocyte transendothelial migration was efficiently inhibited by anti-amphoterin and anti-RAGE antibodies and by the soluble RAGE. We suggest that amphoterin is an autocrine/paracrine regulator of monocyte invasion through the endothelium.

Animals↗
PubMed2004

The role of ECM molecules in activity-dependent synaptic development and plasticity.

Growth and guidance of neurites (axons and dendrites) during development is the prerequisite for the establishment of functional neural networks in the adult organism. In the adult, mechanisms similar to those used during development may regulate plastic changes that underlie important nervous system functions, such as memory and learning. There is now ever-increasing evidence that extracellular matrix (ECM)-associated factors are critically involved in the formation of neuronal connections during development, and their plastic changes in the adult. Here, we review the current literature on the role of ECM components in activity-dependent synaptic development and plasticity, with the major focus on the thrombospondin type I repeat (TSR) domain-containing proteins. We propose that ECM components may modulate neuronal development and plasticity by: 1) regulating cellular motility and morphology, thus contributing to structural alterations that are associated with the expression of synaptic plasticity, 2) coordinating transsynaptic signaling during plasticity via their cell surface receptors, and 3) defining the physical parameters of the extracellular space, thereby regulating diffusion of soluble signaling molecules in the extracellular space (ECS).

Animals↗
PubMed2004

Transgenic mice overexpressing the full-length neurotrophin receptor trkB exhibit increased activation of the trkB-PLCgamma pathway, reduced anxiety, and facilitated learning.

We have investigated the biochemical, physiological, and behavioral properties of transgenic mice overexpressing the full-length neurotrophin receptor trkB (trkB.TK+). The highest trkB.TK+ mRNA overexpression was achieved in the cerebral cortex and hippocampal subfields, both areas also showing strongly increased trkB.TK+ receptor protein expression and phosphorylation. Furthermore, as a result of trkB.TK+ overexpression, partial activation of trkB downstream signaling was observed. Phosphorylation of phospholipaseCgamma-1 was increased but unexpectedly, the expression and phosphorylation levels of signaling molecules Shc and mitogen-activated protein kinase (MAPK) were unaltered. Behavioral studies revealed improved learning and memory in the water maze, contextual fear conditioning, and conditioned taste aversion tests, and reduced anxiety in the elevated plus maze (EPM) and light-dark exploration tests in trkB.TK+ transgenic mice. Electrophysiological studies revealed a reduced long-term potentiation (LTP) at the Schaffer collateral-CA1 synapse in trkB.TK+ mice. Altogether, overexpression of the trkB.TK+ receptor postnatally leads to selective activation of trkB signaling pathways and enhanced learning and memory.

Animals↗
PubMed2004

HB-GAM inhibits proliferation and enhances differentiation of neural stem cells.

Proliferation of neural stem cells in the embryonic cerebral cortex is regulated by many growth factors and their receptors. Among the key molecules stimulating stem cell proliferation are FGF-2 and the FGF receptor-1. This ligand-receptor system is highly dependent on the surrounding heparan sulfates. We have found that heparin-binding growth-associated molecule (HB-GAM, also designated as pleiotrophin) regulates neural stem cell proliferation in vivo and in vitro. Deficiency of HB-GAM results in a pronounced, up to 50% increase in neuronal density in the adult mouse cerebral cortex. This phenotype arises during cortical neurogenesis, when HB-GAM knockout embryos display an enhanced proliferation rate as compared to wild-type embryos. Further, our in vitro studies show that exogenously added HB-GAM inhibits formation and growth of FGF-2, but not EGF, stimulated neurospheres, restricts the number of nestin-positive neural stem cells, and inhibits FGF receptor phosphorylation. We propose that HB-GAM functions as an endogenous inhibitor of FGF-2 in stem cell proliferation in the developing cortex.

Animals↗
PubMed2004

Increased expression of beta6-integrin in skin leads to spontaneous development of chronic wounds.

Integrin alphavbeta6 is an epithelial cell-specific receptor that is not normally expressed by resting epithelium but its expression is induced during wound healing. The function of alphavbeta6-integrin in wound repair is not clear. In the present study, we showed that beta6-integrin expression was strongly up-regulated in the epidermis in human chronic wounds but not in different forms of skin fibrosis. To test whether increased beta6-integrin expression plays a role in abnormal wound healing we developed four homozygous transgenic mouse lines that constitutively expressed human beta6-integrin in the epithelium. The mice developed normally and did not show any histological abnormalities in the skin. The rate of experimental skin wound closure was unaltered and the wounds healed without significant scar formation. However, during breeding program 16.1 to 27.0% of transgenic mice developed spontaneous, progressing fibrotic chronic ulcers. None of the wild-type animals developed these lesions. The chronic lesions had areas with severe fibrosis and numerous activated macrophages and fibroblasts expressing transforming growth factor (TGF)-beta. The level of TGF-beta1 was significantly increased in the lesions as compared with normal skin. The findings suggest that increased alphavbeta6-integrin in keratinocytes plays an active part in abnormal wound healing possibly through a mechanism involving increased activation of TGF-beta.

Animals↗
PubMed2004

Impaired behavioural flexibility and memory in mice lacking GDNF family receptor alpha2.

The glial cell line-derived neurotrophic factor (GDNF) family receptor GFRalpha2 is the binding receptor for neurturin (NRTN). The main biological responses of GFRalpha2 are mediated via the Ret receptor tyrosine kinase, although it may also signal independently of Ret via the neural cell adhesion molecule NCAM. GFRalpha2 is expressed in many neurons of both the central and peripheral nervous system. Mice lacking GFRalpha2 receptors do not exhibit any gross defects in the central nervous system structure. However, they display profound deficits in the parasympathetic and enteric nervous system, accompanied by significant reduction in body weight after weaning. Here we present the results of behavioural analysis of the GFRalpha2-knockout mice. The knockout mice did not differ from wild-type mice in basic tests of motor and exploratory activity. However, differences were established in several memory tasks. The knockout mice were not impaired in the acquisition of spatial escape strategy. However, the deficit in flexibility in establishing a new strategy was revealed during reversal learning with the platform in the opposite quadrant of the pool. Furthermore, the knockout mice displayed significant impairment in contextual fear conditioning and conditioned taste aversion tests of memory. The results suggest that GFRalpha2 signalling plays a role in the development or maintenance of cognitive abilities that help in solving complex learning tasks.

Animals↗
PubMed2003

Vascular endothelial growth factor C is required for sprouting of the first lymphatic vessels from embryonic veins.

Lymphatic vessels are essential for immune surveillance, tissue fluid homeostasis and fat absorption. Defects in lymphatic vessel formation or function cause lymphedema. Here we show that the vascular endothelial growth factor C (VEGF-C) is required for the initial steps in lymphatic development. In Vegfc-/- mice, endothelial cells commit to the lymphatic lineage but do not sprout to form lymph vessels. Sprouting was rescued by VEGF-C and VEGF-D but not by VEGF, indicating VEGF receptor 3 specificity. The lack of lymphatic vessels resulted in prenatal death due to fluid accumulation in tissues, and Vegfc+/- mice developed cutaneous lymphatic hypoplasia and lymphedema. Our results indicate that VEGF-C is the paracrine factor essential for lymphangiogenesis, and show that both Vegfc alleles are required for normal lymphatic development.

Animals↗
PubMed2003

Merlin links to the cAMP neuronal signaling pathway by anchoring the RIbeta subunit of protein kinase A.

The cAMP-protein kinase A (PKA) pathway, important in neuronal signaling, is regulated by molecules that bind and target PKA regulatory subunits. Of four regulatory subunits, RIbeta is most abundantly expressed in brain. The RIbeta knockout mouse has defects in hippocampal synaptic plasticity, suggesting a role for RIbeta in learning and memory-related functions. Molecules that interact with or regulate RIbeta are still unknown. We identified the neurofibromatosis 2 tumor suppressor protein merlin (schwannomin), a molecule related to the ezrin-radixin-moesin family of membrane-cytoskeleton linker proteins, as a binding partner for RIbeta. Merlin and RIbeta demonstrated a similar expression pattern in central nervous system neurons and an overlapping subcellular localization in cultured hippocampal neurons and transfected cells. The proteins were coprecipitated from brain lysates by cAMP-agarose and coimmunoprecipited from cellular lysates with specific antibodies. In vitro binding studies verified that the interaction is direct. The interaction appeared to be under conformational regulation and was mediated via the alpha-helical region of merlin. Sequence comparison between merlin and known PKA anchoring proteins identified a conserved alpha-helical PKA anchoring protein motif in merlin. These results identify merlin as the first neuronal binding partner for PKA-RIbeta and suggest a novel function for merlin in connecting neuronal cytoskeleton to PKA signaling.

Amino Acid Sequence↗
PubMed2003

AMIGO, a transmembrane protein implicated in axon tract development, defines a novel protein family with leucine-rich repeats.

Ordered differential display identified a novel sequence induced in neurons by the neurite-promoting protein amphoterin. We named this gene amphoterin-induced gene and ORF (AMIGO), and also cloned two other novel genes homologous to AMIGO (AMIGO2 and AMIGO3). Together, these three AMIGOs form a novel family of genes coding for type I transmembrane proteins which contain a signal sequence for secretion and a transmembrane domain. The deduced extracellular parts of the AMIGOs contain six leucine-rich repeats (LRRs) flanked by cysteine-rich LRR NH2- and COOH-terminal domains and by one immunoglobulin domain close to the transmembrane region. A substrate-bound form of the recombinant AMIGO ectodomain promoted prominent neurite extension in hippocampal neurons, and in solution, the same AMIGO ectodomain inhibited fasciculation of neurites. A homophilic and heterophilic binding mechanism is shown between the members of the AMIGO family. Our results suggest that the members of the AMIGO protein family are novel cell adhesion molecules among which AMIGO is specifically expressed on fiber tracts of neuronal tissues and participates in their formation.

Animals↗
PubMed2003

Activity blockade increases the number of functional synapses in the hippocampus of newborn rats.

During development neuronal circuitries are refined by activity. Here we studied the role of spontaneous electrical activity in the regulation of synapse formation in the intact newborn (Postnatal Day 3; P3) rat hippocampus in vitro. The blockade of the spontaneous network activity with TTX led to an increase in the number of functional excitatory synapses in the CA3 area of the developing hippocampus. In parallel, there was a substantial increase in the expression levels of the presynaptic markers synaptophysin, synaptotagmin, and synapsin I and of GluR1 AMPA receptor subunits. These changes were associated with an increase in the frequency and amplitude of AMPA receptor-mediated miniature excitatory postsynaptic currents (mEPSCs). Our correlated immunocytochemical, electronmicroscopical, and electrophysiological experiments indicate that in the developing hippocampus spontaneous network activity controls the number of functional synapses.

Action Potentials↗
PubMed2002

Effects of targeted overexpression of pleiotrophin on postnatal bone development.

Pleiotrophin (PTN) is an extracellular matrix-associated growth/differentiation factor that, in post-natal life, is found mainly in bone and brain. Bone development was investigated in ptn-overexpressing mice between 1 and 30 weeks. In transgenics and controls, PTN (and its receptor syndecan-3) was synthesized by osteoblasts and was present in striated muscle. ptn over-expression enhanced intramembranous bone formation and had multiple effects on long-term bone growth. The pubertal growth spurt did not take place in transgenic mice, in which the growth trajectory was steady and continuous until 25 weeks. By 30 weeks, transgenic and control mice were of the same size, but the calcium content/mg bone was approximately 10% higher in the transgenics. PTN was also localized in growth plate and articular chondrocytes, but only in transgenic mice. In these, synthesis of type I collagen by articular chondrocytes was observed, as well as an encroachment of subchondral bone into the articular cartilage. The results suggest that PTN has multiple roles during in vivo bone formation and remodeling, probably acting as a co-factor or accessory protein that modulates the effects of primary signaling molecules.

Animals↗
PubMed2002

Receptor for advanced glycation end products-binding COOH-terminal motif of amphoterin inhibits invasive migration and metastasis.

Amphoterin has been suggested to regulate invasive process extension and cell migration in tumor cells and embryonic neurons through binding to receptor for advanced glycation end products (RAGE), a multiligand transmembrane receptor belonging to the immunoglobulin superfamily. In this study, we identify a COOH-terminal motif in amphoterin (amino acids 150-183) that is responsible for RAGE binding. We show that as a surface-bound ligand, this part of amphoterin is sufficient to induce RAGE-dependent process extension, suggesting a role in the regulation of cell motility. When applied in solution, the RAGE-binding COOH-terminal motif of amphoterin efficiently inhibits process extension and transendothelial migration of tumor cells. Furthermore, in an in vivo model, the corresponding synthetic peptide significantly suppresses formation of lung metastases. Taken together, these results suggest that amphoterin binds to RAGE through a COOH-terminal motif that can be used as an efficient inhibitor to block invasive migration of tumor cells.

Amino Acid Motifs↗
PubMed2002

Receptor for advanced glycation end products (RAGE) signaling induces CREB-dependent chromogranin expression during neuronal differentiation.

Receptor for advanced glycation end products (RAGE) mediates neurite outgrowth and cell migration upon stimulation with its ligand, amphoterin. We show here that RAGE-dependent changes in cell morphology are associated with proliferation arrest and changes in gene expression in neuroblastoma cells. Chromogranin B, a component of secretory vesicles in endocrine cells and neurons, was found to be up-regulated by RAGE signaling during differentiation of neuroblastoma cells along with the two other members of the chromogranin family, chromogranin A and secretogranin II. Ligation of RAGE by amphoterin lead to rapid phosphorylation and nuclear localization of cyclic AMP response element-binding protein (CREB), a major regulator of chromogranin expression. Furthermore, inhibition of ERK1/2-Rsk2-dependent CREB phosphorylation efficiently inhibited up-regulation of chromogranin gene expression upon RAGE activation. To further study the effects of RAGE and amphoterin on cellular differentiation, we stimulated embryonic stem cells expressing RAGE or a signaling-deficient mutant of RAGE with amphoterin. Amphoterin was found to promote RAGE-dependent neuronal differentiation of embryonic stem cells characterized by up-regulation of neuronal markers light neurofilament protein and beta-III-tubulin, activation of CREB, and increased expression of chromogranins A and B. These data suggest that RAGE signaling is capable of driving neuronal differentiation involving CREB activation and induction of chromogranin expression.

Animals↗
PubMed2002

Cognitive deficit and development of motor impairment in a mouse model of Niemann-Pick type C disease.

Niemann-Pick disease type C (NPC) is a fatal, autosomal recessive lipidosis characterized by a unique error in cellular trafficking of cholesterol. In the disease, unesterified cholesterol as well as sphingolipids accumulate in the late endosomes/lysosomes due to mutations in either of two recently isolated genes, NPC1 or NPC2. A metabolic and neurological disorder reminiscent of human NPC disease has been described in Balb/C mice, and it was recently shown that the mutation in the NPC mice resides in the orthologous murine Npc1 gene. Here we have followed the growth rate and applied behavioural methods in order to establish the onset and development of the major symptoms in the NPC mouse model. Wild type and NPC mice were studied during 28-59 days of age. Both male and female NPC mice displayed retarded growth at the age between 25 and 35 days. At the age of 35-45 days the weight was similar to controls and thereafter very rapidly decreased. The battery of coordination tests (vertical screen, beam balancing, coat hanger and rotating rod) established motor impairment of the NPC mice already at the age of 28-42 days, well before the onset of visually detectable ataxia. Decreased exploratory activity and lack of habituation was revealed in the NPC mice by open field test. The diseased mice were unable to learn and remember the location of the hidden escape platform in spatial water maze task suggesting cognitive impairment. In several tests the male NPC mice were more affected than the females. The present study represents the first behavioural analysis of the NPC mice. The battery of behavioural tests employed here should be valuable in the assessment of effective approaches to treat NPC, for which no preventive or curative measures have so far been established.

Animals↗