Heparan Sulfate Proteoglycans Are Involved in Opiate Receptor-Mediated Cell Migration

Research progress on the conformational properties of comb-like polymers in dilute solutions

As a special type of branched polymers, comb-like polymers simultaneously possess the structural characteristics of a linear backbone profile and crowded sidechain branches/grafts, and such structural uniqueness leads to reduced interchain entanglement, enhanced molecular orientation, and unique stimulus-response behavior, which greatly expands the potential applications in the fields of super-soft elastomers, molecular sensors, lubricants, photonic crystals, etc. In principle, all these molecular features can be traced back to three structural parameters, i.e., the degree of polymerization of the backbone (Nb), the degree of polymerization of the graft sidechain (Ng), and the grafting density (σ). Consequently, it is of great importance to understand the correlation mechanism between the structural characteristics and physicochemical properties, among which, the conformational properties in dilute solution have received the most attention due to its central position in polymer science. In the past decades, the development of synthetic chemistry and characterization techniques has greatly stimulated the progress of this field, and a number of experiments have been executed to verify the conformational properties; however, due to the complexity of the structural parameters and the diversity of the chemical design, the achieved experimental progress displays significant controversies compared with the theoretical predictions. This review aims to provide a full picture of recent research progress on this topic, specifically, (1) first, a few classical theoretical models regarding the chain conformation are introduced, and the quasi-two-parameter (QTP) theory for the conformation analysis is highlighted; (2) second, the research progress of the static conformation of comb-like polymers in dilute solution is discussed; (3) third, the research progress of the dynamic conformation in dilute solution is further discussed. The key issues, existing controversies and future research directions are also highlighted. We hope that this review can provide insightful information for the understanding of the conformational properties of comb-like polymers, open a new door for the regulation of conformational behavior in related applications, and promote related theoretical and experimental research in the community.

Long-term intrathecal administration of morphine vs. baclofen: Differences in CSF glycoconjugate profiles using multiglycomics

Opioid use for treatment of persistent pain has increased dramatically over the past two decades, but it has not resulted in improved pain management outcomes. To understand the molecular mechanisms of opioids, molecular signatures that arise from opioid exposure are often sought after, using various analytical methods. In this study, we performed proteomics, and multiglycomics via sequential analysis of polysialic acids, glycosaminoglycans, N-glycans and O-glycans, using the same cerebral spinal fluid (CSF) sample from patients that had long-term (>2 years), intrathecal morphine or baclofen administered via an indwelling pump. Proteomics and N-glycomics signatures between the two treatment groups were highly conserved, while significant differences were observed in polysialic acid, heparan sulfate glycosaminoglycan and O-glycan profiles between the two treatment groups. This represents the first study to investigate the potential relationships between diverse CSF conjugated glycans and long-term intrathecal drug exposure. The unique changes, observed by a sequential analytical workflow, reflect previously undescribed molecular effects of opioid administration and pain management.

Drug-selected population in melanoma A2058 cells as melanoma stem-like cells retained angiogenic features - the potential roles of heparan-sulfate binding ANGPTL4 protein

Malignant cancer may contain highly heterogeneous populations of cells, including stem-like cells which were resistant to chemotherapy agents, radiation, mechanical stress, and immune surveillance. The characterization of these specific subpopulations might be critical to develop novel strategy to remove malignant tumors. We selected and enriched small population of human melanoma A2058 cells by repetitive selection cycles (selection, restoration, and amplification). These subpopulation of melanoma cells persisted the characteristics of slower cell proliferation, enhanced drug-resistance, elevated percentage of side population as analyzed by Hoechst33342 exclusion, in vitro sphere formation, and in vivo xenograft tumor formation by small amount of tumor cells. The selected populations would be melanoma stem-like cells with high expression of stem cell markers and altered kinase activation. Microarray and bioinformatics analysis highlighted the high expression of angiopoietin-like 4 protein in drug-selected melanoma stem-like cells. Further validation by specific shRNA demonstrated the role of angiopoietin-like 4 protein in drug-selected subpopulation associated with enhanced drug-resistance, sphere formation, reduced kinase activation, in vitro tube-forming ability correlated with heparan-sulfate proteoglycans. Our finding would be applicable to explore the mechanism of melanoma stemness and use angiopoietin-like 4 as potential biomarkers to identify melanoma stem-like cells.

Conformations of polyelectrolyte molecular brushes: A mean-field theory

We present a mean-field theory for the solution properties of polyelectrolyte molecular brushes, comprising multiple ionically charged side chains tethered to the main chain (backbone). The power-law dependences for local and large-scale conformational properties, i.e., the brush thickness, extension of spacers between the grafts, and end-to-end distance for the main chain macromolecule, are derived as a function of architectural parameters (the lengths of the main chain and of the grafts, grafting density). We demonstrate that at high grafting density or/and a large fraction of charged monomer units in the grafts, the localization of counterions in the intra-molecular volume occurs and we specify the onset of this transition. We prove that such localization of the counterions is accompanied by full extension of the main chain of the polyelectrolyte molecular brush in salt-free solution. This stretching of the main chain is relaxed upon an increase in the salt concentration. The dependence of the macromolecular dimensions of the polyelectrolyte molecular brush on the salt concentration is derived, and multiple power-law exponents valid in different salt concentration ranges are predicted.

Angle-independent pH-sensitive composites with natural gyroid structure

pH sensor is an important and practical device with a wide application in environmental protection field and biomedical industries. An efficient way to enhance the practicability of intelligent polymer composed pH sensor is to subtilize the three-dimensional microstructure of the materials, adding measurable features to visualize the output signal. In this work, C. rubi wing scales were combined with pH-responsive smart polymer polymethylacrylic acid (PMAA) through polymerization to achieve a colour-tunable pH sensor with nature gyroid structure. Morphology and reflection characteristics of the novel composites, named G-PMAA, are carefully investigated and compared with the original biotemplate, C. rubi wing scales. The most remarkable property of G-PMAA is a single-value corresponding relationship between pH value and the reflection peak wavelength (λmax), with a colour distinction degree of 18 nm/pH, ensuring the accuracy and authenticity of the output. The pH sensor reported here is totally reversible, which is able to show the same results after several detection circles. Besides, G-PMAA is proved to be not influenced by the detection angle, which makes it a promising pH sensor with superb sensitivity, stability, and angle-independence.

Fabrications and Applications of Stimulus-Responsive Polymer Films and Patterns on Surfaces: A Review

In the past two decades, we have witnessed significant progress in developing high performance stimuli-responsive polymeric materials. This review focuses on recent developments in the preparation and application of patterned stimuli-responsive polymers, including thermoresponsive layers, pH/ionic-responsive hydrogels, photo-responsive film, magnetically-responsive composites, electroactive composites, and solvent-responsive composites. Many important new applications for stimuli-responsive polymers lie in the field of nano- and micro-fabrication, where stimuli-responsive polymers are being established as important manipulation tools. Some techniques have been developed to selectively position organic molecules and then to obtain well-defined patterned substrates at the micrometer or submicrometer scale. Methods for patterning of stimuli-responsive hydrogels, including photolithography, electron beam lithography, scanning probe writing, and printing techniques (microcontact printing, ink-jet printing) were surveyed. We also surveyed the applications of nanostructured stimuli-responsive hydrogels, such as biotechnology (biological interfaces and purification of biomacromoles), switchable wettability, sensors (optical sensors, biosensors, chemical sensors), and actuators.

Opioids and clonidine modulate cytokine production and opioid receptor expression in neonatal immune cells

OBJECTIVE

Opioids and clonidine, used in for sedation, analgesia and control of opioid withdrawal in neonates, directly or indirectly activate opioid receptors (OPRs) expressed in immune cells. Therefore, our objective is to study how clinically relevant concentrations of different opioids and clonidine change cytokine levels in cultured whole blood from preterm and full-term infants.

STUDY DESIGN

Using blood from preterm (≤ 30 weeks gestational age (GA), n=7) and full-term ( ≥ 37 weeks GA, n=19) infants, we investigated the changes in cytokine profile (IL-1β, IL-6, IL-8, IL-10, IL-12p70 and TNF-α), cyclic adenosine monophosphate (cAMP) levels and μ-, δ- and κ- opioid receptor (OPR) gene and protein expression, following in-vitro exposure to morphine, methadone, fentanyl or clonidine at increasing concentrations ranging from 0 to 1 mM.

RESULT

Following lipopolysaccharide activation, IL-10 levels were 146-fold greater in cultured blood from full-term than from preterm infants. Morphine and methadone, but not fentanyl, at >10(-5) M decreased all tested cytokines except IL-8. In contrast, clonidine at <10(-9) M increased IL-6, while at >10(-5) M increased IL-1β and decreased TNF-α levels. All cytokine changes followed the same patterns in preterm and full-term infant cultured blood and matched increases in cAMP levels. All three μ-, δ- and κ-OPR genes were expressed in mononuclear cells (MNC) from preterm and full-term infants. Morphine, methadone and clonidine, but not fentanyl, at >10(-5)M decreased the expression of μ-OPR, but not δ- or κ-OPRs.

CONCLUSION

Generalized cytokine suppression along with downregulation of μ-OPR expression observed in neonatal MNC exposed to morphine and methadone at clinically relevant concentrations contrast with the modest effects observed with fentanyl and clonidine. Therefore, we speculate that fentanyl and clonidine may be safer therapeutic choices for sedation and control of opioid withdrawal and pain in neonates.

Surface induced self-organization of comb-like macromolecules

We present a review of the theoretical and experimental evidence for the peculiar properties of comb copolymers, demonstrating the uniqueness of these materials among other polymer architectures. These special properties include an increase in stiffness upon increasing side-chain length, the spontaneous curvature of adsorbed combs, rod-globule transition, and specific intramolecular self-assembly. We also propose a theory of chemically heterogeneous surface nanopattern formation in ultrathin films of comblike macromolecules containing two different types (A and B) of incompatible side chains (so-called binary combs). Side chains of the binary combs are strongly adsorbed on a surface and segregated with respect to the backbone. The thickness of surface domains formed by the B side chains is controlled by the interaction with the substrate. We predict the stability of direct and inverse disc-, torus- and stripelike nanostructures. Phase diagrams of the film are constructed.

Analysis of the cluster formation in two-component cylindrical bottle-brush polymers under poor solvent conditions: a simulation study

Two-component bottle-brush polymers, where flexible side chains containing N = 20, 35 and 50 effective monomers are grafted alternatingly to a rigid backbone, are studied by Molecular Dynamics simulations, varying the grafting density [Formula: see text] and the solvent quality. Whereas for poor solvents and large enough [Formula: see text] the molecular brush is a cylindrical object with monomers of different type occupying locally the two different halves of the cylinder, for intermediate values of [Formula: see text] an axially inhomogeneous structure of "pearl-necklace" type is formed, where microphase separation between monomers of different type within a cluster takes place. These "pearls" have a strongly non-spherical ellipsoidal shape, due to the fact that several side chains cluster together in one "pearl". We discuss the resulting structures in detail and we present a comparison with the single-component bottle-brush case.

A role for S1P signalling in axon guidance in the Xenopus visual system

Sphingosine 1-phosphate (S1P), a lysophospholipid, plays an important chemotactic role in the migration of lymphocytes and germ cells, and is known to regulate aspects of central nervous system development such as neurogenesis and neuronal migration. Its role in axon guidance, however, has not been examined. We show that sphingosine kinase 1, an enzyme that generates S1P, is expressed in areas surrounding the Xenopus retinal axon pathway, and that gain or loss of S1P function in vivo causes errors in axon navigation. Chemotropic assays reveal that S1P elicits fast repulsive responses in retinal growth cones. These responses require heparan sulfate, are sensitive to inhibitors of proteasomal degradation, and involve RhoA and LIM kinase activation. Together, the data identify downstream components that mediate S1P-induced growth cone responses and implicate S1P signalling in axon guidance.

Endogenous opiates and behavior: 2004

This paper is the 27th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over 30 years of research. It summarizes papers published during 2004 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Autocrine and Paracrine Transcriptional Regulation of Type IIA Secretory Phospholipase A2 Gene in Vascular Smooth Muscle Cells

Objective— The inflammation that occurs during the development of atherosclerosis is characterized by a massive release of sPLA2-IIA (group IIA secretory phospholipase A2) from vascular smooth muscle cells (VSMCs). We have investigated the autocrine function of sPLA2-IIA in rat aortic and human VSMCs.

Methods and Results— We found that the transcription of the endogenous sPLA2-IIA gene increased by adding a cell supernatant containing human sPLA2-IIA proteins. We show that this effect was independent of the sPLA2 activity using sPLA2-IIA proteins lacking enzyme activity. Transient transfections with various sPLA2-IIA rat promoter-luciferase constructs demonstrated that the C/EBP, NK-κB, and Ets transcription factors are involved in the increase in sPLA2-IIA gene transcription. We also found the M-type sPLA2 receptor mRNA in VSMCs, and we showed that the sPLA2-luciferase reporter gene was induced by the specific agonist of the sPLA2 receptor, aminophenylmannopyranoside (APMP), and that this induction was mediated by the same transcription factor-binding sites. Finally, we used a sPLA2-IIA mutant unable to bind heparan-sulfate proteoglycans to show that the binding of wild-type sPLA2-IIA to proteoglycans is essential for the induction of an autocrine loop.

Conclusions— We have thus identified new autocrine and paracrine pathways activating sPLA2-IIA gene expression in rat and human VSMCs.

Specific structural features of heparan sulfate proteoglycans potentiate neuregulin-1 signaling

Neuregulins are a family of growth and differentiation factors that act through activation of cell-surface erbB receptor tyrosine kinases and have essential functions both during development and on the growth of cancer cells. One alternatively spliced neuregulin-1 form has a distinct heparin-binding immunoglobulin-like domain that enables it to adhere to heparan sulfate proteoglycans at key locations during development and substantially potentiates its activity. We examined the structural specificity needed for neuregulin-1-heparin interactions using a gel mobility shift assay together with an assay that measures the ability of specific oligosaccharides to block erbB receptor phosphorylation in L6 muscle cells. Whereas the N-sulfate group of heparin was most important, the 2-O-sulfate and 6-O-sulfate groups also contributed to neuregulin-1 binding in these two assays. Optimal binding to neuregulin-1 required eight or more heparin disaccharides; however, as few as two disaccharides were still able to bind neuregulin-1 to a lesser extent. The physiological importance of this specificity was shown both by chemical and siRNA treatment of cultured muscle cells. Pretreatment of muscle cells with chlorate that blocks all sulfation or with an siRNA that selectively blocks N-sulfation significantly reduced erbB receptor activation by neuregulin-1 but had no effect on the activity of neuregulin-1 that lacks the heparin-binding domain. These results suggest that the regulation of glycosaminoglycan sulfation is an important biological mechanism that can modulate both the localization and potentiation of neuregulin-1 signaling.

Coregulation of fibronectin signaling and matrix contraction by tenascin-C and syndecan-4

Syndecan-4 is a ubiquitously expressed heparan sulfate proteoglycan that modulates cell interactions with the extracellular matrix. It is transiently up-regulated during tissue repair by cells that mediate wound healing. Here, we report that syndecan-4 is essential for optimal fibroblast response to the three-dimensional fibrin-fibronectin provisional matrix that is deposited upon tissue injury. Interference with syndecan-4 function inhibits matrix contraction by preventing cell spreading, actin stress fiber formation, and activation of focal adhesion kinase and RhoA mediated-intracellular signaling pathways. Tenascin-C is an extracellular matrix protein that regulates cell response to fibronectin within the provisional matrix. Syndecan-4 is also required for tenascin-C action. Inhibition of syndecan-4 function suppresses tenascin-C activity and overexpression of syndecan-4 circumvents the effects of tenascin-C. In this way, tenascin-C and syndecan-4 work together to control fibroblast morphology and signaling and regulate events such as matrix contraction that are essential for efficient tissue repair.