Cornelis P. Tensen

Expression of MCP-1 by Reactive Astrocytes in Demyelinating Multiple Sclerosis Lesions

The pathology of multiple sclerosis (MS) is characterized by breakdown of the blood-brain barrier (BBB), accompanied by infiltration of macrophages and T lymphocytes into the central nervous system (CNS). The migration of these cells into the CNS parenchyma may be partly regulated by chemokines. The aim of this study was therefore to investigate the cellular localization of the potent monocyte- and T-cell-attracting chemokine monocyte chemoattractant protein (MCP)-1 by immunohistochemistry on postmortem brain tissue from MS and normal control cases. Brain tissue samples of six MS patients and four patients without a history of brain disease were neuropathologically classified according to characteristic (immuno)histochemical staining patterns. Frozen tissue sections of active demyelinating MS lesions, chronic active demyelinating MS lesions, and normal control brain were immunohistochemically stained with a monoclonal antibody directed against MCP-1. In active demyelinating MS lesions as well as in chronic active MS lesions, reactive hypertrophic astrocytes were strongly immunoreactive for MCP-1, whereas perivascular and parenchymal foamy macrophages did not express MCP-1 protein. These results suggest a significant role for the beta-chemokine MCP-1, synthesized in vivo by reactive hypertrophic astrocytes, in the recruitment and activation of myelin-degrading macrophages and thereby contributing to the evolution of MS lesions.

The antipsoriatic drug dimethylfumarate strongly suppresses chemokine production in human keratinocytes and peripheral blood mononuclear cells.

Backgroundu2003The effectiveness of systemic treatment of psoriasis with fumaric acid esters has been proven, but their mode of action at the cellular and molecular level has not yet been fully elucidated.

A NOVEL G PROTEIN-COUPLED RECEPTOR MEDIATING BOTH VASOPRESSIN- AND OXYTOCIN-LIKE FUNCTIONS OF LYS-CONOPRESSIN IN LYMNAEA STAGNALIS

We have cloned a receptor, named LSCPR, for vasopressin-related Lys-conopressin in Lymnaea stagnalis. Lys-conopressin evokes Ca(2+)-dependent Cl- currents in Xenopus oocytes injected with LSCPR cRNA. Expression of LSCPR mRNA was detected in central neurons and peripheral muscles associated with reproduction. Upon application of Lys-conopressin, both neurons and muscle cells depolarize owing to an enhancement of voltage-dependent Ca2+ currents and start firing action potentials. Some neurons coexpress LSCPR and Lys-conopressin, suggesting an autotransmitter-like function for this peptide. Lys-conopressin also induces a depolarizing response in LSCPR-expressing neuroendocrine cells that control carbohydrate metabolism. Thus, in addition to oxytocin-like reproductive functions, LSCPR mediates vasopressin-like metabolic functions of Lys-conopressin as well.

Genomic organization, sequence and transcriptional regulation of the human CXCL 11 gene

CXCL 11, encoded by the cDNA sequences designated beta-R1, H-174, or I-TAC, is a CXC chemokine ligand for CXCR3 and assumed to be involved in inflammatory diseases characterized by the presence of activated T-cells. We here describe the genomic organization (four exons interrupted by three introns of 585, 98 and 230 bp) and sequence including 960 bp from the immediate 5-upstream region of the human CXCL 11 gene. Within the promoter region, consensus sequences for regulatory elements (ISRE, GAS, NF-kappaB) important for cytokine-induced gene transcription were identified. The effect of (pro)inflammatory cytokines on CXCL 11 mRNA expression in monocytic cell lines (THP-1, U937) and primary cultures of dermal fibroblasts and endothelial cells were examined using Northern blot analysis. For these cell types, IFN-gamma was a potent inducer of CXCL 11 transcription, which was synergistically enhanced by TNF-alpha.

Parasites flicking the NPY gene on the host’s switchboard: why NPY?

It was investigated whether up‐regulation of the NPY gene by the schistosome Trichobilharzia ocellata in its snail host Lymnaea stagnalis redirects the hosts energy flows. We cloned the cDNA encoding Lymnaea NPY (LyNPY), purified and sequenced the peptide, and used synthesized peptide for physiological and morphological studies. Increasing the LyNPY titer in nonparasitized snails (mimicking parasitosis) by 1) implantation of slow‐release pellets and 2) injections suppressed reproductive activity and reduced growth in a dose‐ and time‐dependent manner without affecting food intake. When the LyNPY titer was back to normal, reproduction and growth were resumed, coinciding with a transient increase of food intake serving to replenish glycogen stores. Observations on double‐immunostained whole mount preparations of brains support these data. A close association was found between LyNPY‐positive axons and axons both from ovulation hormone‐producing neurons and molluscan insulin‐like peptide‐producing neurons involved in regulation of growth. As no synaptic(‐like) contacts were observed, it is supposed that LyNPY acts nonsynaptically. No morphological interaction was found between LyNPY‐positive axons and motoneurons innervating the feeding apparatus. Our data explain why it is an advantageous strategy for endoparasites to up‐regulate the highly conserved NPY gene in their host.—de Jong‐Brink, M., Reid, C. N., Tensen, C. P., Ter Maat, A. Parasites flicking the NPY gene on the hosts switchboard: why NPY? FASEB J. 13, 1972–1984 (1999)

Transmitter identification in neurons involved in male copulation behavior in Lymnaea stagnalis

In this paper, we have mapped the cellular localization of various transmitters onto the central neurons which are involved in male copulation behavior in Lymnaea stagnalis, by combining retrograde tracing with immunocytochemistry and in situ hybridization. Evidence is provided that neurons which were backfilled from the penis nerve, the sole nerve to innervate the male copulatory organ, synthesize a multitude of neuropeptides (APGWamide, Lymnaea neuropeptide tyrosin [LNPY], conopressin, pedal peptide, SEEPLY, DEILSR, myomodulin, and Lymnaea inhibitory peptide [LIP]) as well as the classical neurotransmitter, serotonin. In the anterior lobe, the backfilled neurons mainly contain the tetrapeptide APGWamide and conopressin, and not LNPY or pedal peptide. The results suggest a central role in the regulation of copulation activity for the anterior lobe neurons that produce APGWamide and conopressin. Immunostainings of backfilled nervous systems revealed immunopositive axons originating from these neurons to form varicosities on the cell somata of neurons in the other clusters contributing to the innervation of the male sexual system. Neurons from the right parietal ganglion projecting into the penis nerve were electrophysiologically and morphologically identified by simultaneously recording from the cell body intracellularly and the penis nerve extracellularly and subsequently filling them with an anterograde tracer and subjecting them to immunocytochemistry. This method has provided links between morphology, physiology, and the transmitter contents of these neurons. J. Comp. Neurol. 395:440–449, 1998.

Molecular Cloning and Neuronal Expression of a Novel Type of a G-Protein-Coupled Receptor With Ldl Binding Motifs From the Pond Snail Lymnaea Stagnalis

We have isolated and characterized a cDNA encoding a novel type of receptor from the central nervous system (CNS) of the pond snail Lymnaea stagnalis. This receptor appears to be a natural hybrid between two classes of receptor proteins. The N-terminal part of the protein contains two types of repeated sequences; the first displays a high degree of sequence similarity with the extracellular binding domains of the low density lipoprotcin (LDL) receptor, which binds, internalizes, and releases cholesterol containing apolipoproteins. The second type of repeat, and the C-tcrminal part of this receptor arc homologous to specific regions of a class of G-protein-coupled receptors, the mammalian glycoprotein hormone receptor family. The mRNA encoding the receptor is predominantly located in the CNS in a small cluster of 90 neurons within the pedal ganglia, and to a lesser extent in the heart. The discovery of this chimeric receptor and its neuronal expression indicates the presence of a new subclass of G-protein-coupled receptors that may be involved in the transduction of signals carried by lipoproteins into neuronal events via G-proteins.