Fell–Muir Lecture: Heparan sulphate and the art of cell regulation: a polymer chain conducts the protein orchestra

Heparan sulphate (HS) sits at the interface of the cell and the extracellular matrix. It is a member of the glycosaminoglycan family of anionic polysaccharides with unique structural features designed for protein interaction and regulation. Its client proteins include soluble effectors (e.g. growth factors, morphogens, chemokines), membrane receptors and cell adhesion proteins such as fibronectin, fibrillin and various types of collagen. The protein-binding properties of HS, together with its strategic positioning in the pericellular domain, are indicative of key roles in mediating the flow of regulatory signals between cells and their microenvironment. The control of transmembrane signalling is a fundamental element in the complex biology of HS. It seems likely that, in some way, HS orchestrates diverse signalling pathways to facilitate information processing inside the cell. A dictionary definition of an orchestra is ‘a large group of musicians who play together on various instruments …’ to paraphrase, the HS orchestra is ‘a large group of proteins that play together on various receptors’. HS conducts this orchestra to ensure that proteins hit the right notes on their receptors but, in the manner of a true conductor, does it also set ‘the musical pulse’ and create rhythm and harmony attractive to the cell? This is too big a question to answer but fun to think about as you read this review.     

Biochemical changes in the cervical tissue of rabbit induced by interleukin-8, interleukin-1{beta}dehydroepiandrosterone sulphate and prostaglandin E2: a comparative study

The aim of this research was to study and compare the mechanismof action of interieukin (IL)-8, IL-1 dehydro-epiandrosteronesulphate (DHEA-S) and prostaglandin (PG)E2 on the cervix. Fiveequal groups of pregnant rabbits (n = 45) were tested by eitherplacebo or tested drugs in the form of vaginal suppositoriesonce daily for 3 days. The suppositories contained human recombinantIL-8 (100 ng), IL-1 (200 ng), DHEA-S (10 mg) or PGE2 (1 mg).All rabbits were tested by one dose, two doses or three doses.Consistency, dilatation and water contents were estimated 24h after the last dose of treatment Leukocyte infiltration ofthe cervices was studied after staining the cervical tissuesections with antirabbit RT2 monoclonal antibodies. Relativecollagen concentration was assessed after staining with PicrosiriusRed. Collagenase, gelatinase and elastase activities were measuredin 100 mg of homogenized cervical connective tissue. Water contentswere significantly increased in all tested cervices. Neutrophilnumbers were increased in IL-8 and IL-1 groups after the seconddose of treatment (P < 0.0005 and 0.001 respectively). Inthe PGE2 group, neutrophils were increased after the third doseof treatment, whereas in DHEA-S group no significant changeswere observed. Collagen content was significantly decreasedin IL-8, IL-1 and PGE2 groups after the first dose of treatment(P < 0.004, and 0.005 and 0.03 respectively). In the DHEA-Sgroup, the decrease in collagen content occurred after the thirddose (P < 0.05). Collagenase activity was markedly increasedin IL-8, IL-1, and DHEA-S groups after the second dose of treatment(P < 0.001, 0.003 and 0.007 respectively). No significantincrease in collagenase activity was found in PGE2 group. Gelatinaseactivity was significantly increased in IL-8, IL-1, PGE2 andDHEA-S groups after the second dose of treatment (P < 0.008,0.01, 0.003 and 0.05 respectively). Also, elastase activitywas increased after the second dose of treatment in all groups(P < 0.001, 0.001 0.001 and 0.006 respectively). Our datasuggest that ripening of the cervix in rabbit can be initiatedby different mechanisms. Cytokines play a vital role in cervicalripening, especially IL-8 and IL-1. IL-8 is one of the factorswhich could ripen the cervix in a manner similar to the physiologicalprocess at term.     

Gene expression patterns in melanocytic cells: candidate markers for early stage and malignant transformation.

Different stages of differentiation of human melanocytic cells, such as normal melanocytes, naevus and melanoma cells, reflect distinct gene expression patterns. A PCR-based subtractive hybridization and display method was applied to identify genes that are differentially expressed in melanocytic cells in relation to early stage and malignant transformation. This resulted in the identification of a number of candidate cDNAs differentially expressed among melanocytes, naevus cells, and (non)-metastatic melanoma cells. Out of this collection of cDNAs, 16 clones were screened that comprised 12 novel genes, one previously identified expressed sequence tag related to vesicular trafficking (Ras-related protein Rab5b). The other three were also known genes that were either related to cell motility (beta-tubulin), pre-mRNA splicing (small nuclear protein U1A), or of unknown function (the human TI227-H gene). The differential expression patterns of Rab5b and two novel gene fragments (pCMa1, pCMn2) were further assessed in melanocytic cells. pCMa1 was expressed more in metastatic melanoma than in primary melanoma cells. In contrast, pCMn2 was expressed in both non-metastatic and metastatic melanoma cells, but was not detectable in either normal melanocytes or naevus cells. The Ras-related protein Rab5b showed lower levels of expression in highly metastatic than in other melanoma cells. These three cDNAs may therefore be involved in the early stage and malignant transformation of melanocytes.     

Oxygen, genes, and development: An analysis of the role of hypoxic gene regulation during murine vascular development

Development of the mammalian cardiovascular system is a complex process guided by both genetic and environmental components. Significant advances in the genetics of vascular development have been accomplished most recently by the analysis of multiple ”knockout” and transgenic mice which exhibit varying degrees of impaired vascularity. This review focuses on the potential of the environment of the developing embryo to affect its development. In particular we analyze the evidence implicating the ability of physiological parameters such as oxygen and glucose concentrations within and surrounding the embryo to affect the expression of genes critical for vascular development. We conclude that the vascularization of a developing mammalian embryo is a plastic process dependent on the dynamic interaction between fundamental genetic and physiological factors. Received: 15 October 1997 / Accepted: 27 January 1998     

Macrophages: Supportive cells for tissue repair and regeneration

Macrophages, and more broadly inflammation, have been considered for a long time as bad markers of tissue homeostasis. However, if it is indisputable that macrophages are associated with many diseases in a deleterious way, new roles have emerged, showing beneficial properties of macrophages during tissue repair and regeneration. This discrepancy is likely due to the high plasticity of macrophages, which may exhibit a wide range of phenotypes and functions depending on their environment. Therefore, regardless of their role in immunity, macrophages play a myriad of roles in the maintenance and recovery of tissue homeostasis. They take a major part in the resolution of inflammation. They also exert various effects of parenchymal cells, including stem and progenitor cell, of which they regulate the fate. In the present review, few examples from various tissues are presented to illustrate that, beyond their specific properties in a given tissue, common features have been described that sustain a role of macrophages in the recovery and maintenance of tissue homeostasis.     

Semaphorins in development and adult brain: Implication for neurological diseases

As a group, Semaphorins are expressed in most tissues and this distribution varies considerably with age. Semaphorins are dynamically expressed during embryonic development and their expression is often associated with growing axons. This expression decreases with maturity and several observations support the idea that in adult brain the expression of secreted Semaphorins is sensitive to electrical activity and experience. The functional role of Semaphorins in guiding axonal projections is well established and more recent evidence points to additional roles in the development, function and reorganization of synaptic complexes. Semaphorins exert the majority of their effects by binding to cognate receptor proteins through their extracellular domains. A common theme is that Semaphorin-triggered signalling induces the rearrangement of the actin and microtubule cytoskeleton. Mutations in Semaphorin genes are linked to several human diseases associated with neurological changes, but their actual influence in the pathogenesis of these diseases remains to be demonstrated. In addition, Semaphorins and their receptors are likely to mediate cross-talk between neurons and other cell types, including in pathological situations where their influence can be damaging or favourable depending on the context. We discuss how the manipulation of Semaphorin function might be crucial for future clinical studies.