Neurochemical plasticity in the enteric nervous system of a primate animal model of experimental Parkinsonism

Emerging evidences suggest that the enteric nervous system (ENS) is affected by the degenerative process in Parkinson's disease (PD). In addition lesions in the ENS could be associated with gastrointestinal (GI) dysfunctions, in particular constipation, observed in PD. However, the precise alterations of the ENS and especially the changes in the neurochemical phenotype remain largely unknown both in PD and experimental Parkinsonism. The aim of our study was thus to characterize the neurochemical coding of the ENS in the colon of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys, a well-characterized model of PD. In the myenteric plexus, there was a significant increase in the number of neurons per ganglia (identified with Hu), especially nitric oxide synthase immunoreactives (IR) neurons in MPTP-treated monkeys compared to controls. A concomitant 72% decrease in the number of tyrosine hydroxylase-IR neurons was observed in MPTP-treated monkeys compared to controls. In contrast no change in the cholinergic or vasoactive intestinal peptide-IR population was observed. In addition, the density of enteric glial cells was not modified in MPTP-treated monkeys. Our results demonstrate that MPTP induces major changes in the myenteric plexus and to a lesser extent in the submucosal plexus of monkeys. They further reinforce the observation that lesions of the ENS occur in the course of PD that might be related to the GI dysfunction observed in this pathology.

Activity-dependent regulation of tyrosine hydroxylase expression in the enteric nervous system

The regulation of neuromediator expression by neuronal activity in the enteric nervous system (ENS) is currently unknown. Using primary cultures of ENS derived from rat embryonic intestine, we have characterized the regulation of tyrosine hydroxylase (TH), a key enzyme involved in the synthesis of dopamine. Depolarization induced either by 40 mm KCl, veratridine or by electrical field stimulation produced a robust and significant increase in the proportion of TH immunoreactive (TH-IR) neurons (total neuronal population was identified with PGP9.5 or Hu) compared to control. This increase in the proportion of TH-IR neurons was significantly reduced by the sodium channel blocker tetrodotoxin (0.5 microm), demonstrating that neuronal activity was critically involved in the effects of these depolarizing stimuli. KCl also increased the proportion of VIP-IR but not nNOS-IR enteric neurons. The KCl-induced increase in TH expression was partly reduced in the presence of the nicotinic receptor antagonist hexamethonium (100 microm), of noradrenaline (1 microm) and of the alpha(2)-adrenoreceptor agonist clonidine (1 microm). Combining pharmacological and calcium imaging studies, we have further shown that L-type calcium channels were involved in the increase of TH expression induced by KCl. Finally, using specific inhibitors, we have shown that both protein kinases A and C as well as the extracellular signal-regulated kinases were required for the increase in the proportion of TH-IR neurons induced by KCl. These results are the first demonstration that TH phenotype of enteric neurons can be regulated by neuronal activity. They could also set the basis for the study of the pathways and mechanisms involved in the neurochemical plasticity observed both during ENS development and in inflammatory enteric neuropathies.

Emotional facial palsy following striato-capsular infarction

Emotional facial palsy (EFP) is a rare condition in which facial paresis is only apparent during reflex movements of the hemiface, such as smiling and laughter. We report the case of a 32-year-old man presenting with EFP as the main symptom of a small striatocapsular infarction. Our case strongly suggests that the anterior arm of the internal capsule is part of the corticonuclear tract that is involved in emotional facial motility.

Myélite aiguë transverse idiopathique : application des nouveaux critères diagnostiques à une cohorte de 17 patients

INTRODUCTION

Idiopathic Acute Transverse Myelitis (ATM) is an inflammatory and immune-mediated disorder, distinct from infectious ATM, ATM of systemic lupus erythematosus or Sjögren's syndrome, and medullary manifestation of multiple sclerosis. Prognosis is not well-known.

OBJECTIVE

To evaluate clinical, paraclinical and pronognosis data in patients selected with new diagnosis criteria, classically described in idiopathic ATM.

METHODS

Seventeen patients with diagnosis criteria were retrospectively (1996-2005) studied. A telephone investigation was conducted in 2005 to obtained data on the clinical course.

RESULTS

Seven men and 10 women, ranging in age from 15 to 75 years (mean: 39.8 years) met these new criteria. Our study showed that epidemiological and clinical findings as well as laboratory results were in agreement with those presented in the literature. Conversely, prognosis was better since 76p.cent of the patients could walk without assistance. The clinical presentation of some of our patients and/or their progression towards other multifocal inflammatory disorders, suggests there might be links between ATM, neuromyelitis optica (NMO) and Acute Dissemined Encephalomyelitis (ADEM).

CONCLUSION

Patients with idiopathic ATM, selected with new criteria, have a rather good prognosis. ATM seems to be part of a continuum of neuroimmunologic disorders including NMO or ADEM although reasons explaining distinct focal disorders remain unclear.

Cannabis et récepteurs cannabinoïdes : de la physiopathologie aux possibilités thérapeutiques

BACKGROUND

Although cannabis has been used as a medicine for several centuries, the therapeutic properties of cannabis preparations (essentially haschich and marijuana) make them far most popular as a recreational drugs.

STATE OF THE ART

Scientific studies on the effects of cannabis were advanced considerably by the identification in 1964 of cannabinoid D9-tetrahydrocannadinol (THC), recognized as the major active constituent of cannabis. Cloning of the centrally located CB1 receptor in 1990 and the identification of the first endogenous ligand of the CB1 receptor, anandamide, in 1992 further advanced our knowledge.

PERSPECTIVE AND CONCLUSIONS

Progress has incited further research on the biochemistry and pharmacology of the cannabinoids in numerous diseases of the central nervous system. In the laboratory animal, cannabinoids have demonstrated potential in motion disorders, demyelinizing disease, epilepsy, and as anti-tumor and neuroprotector agents. Several clinical studies are currently in progress, but therapeutic use of cannabinoids in humans couls be hindered by undesirable effects, particularly psychotropic effects. CB1 receptor antagonists also have interesting therapeutic potential.

[L-DOPA-induced dyskinesia]

L-DOPA-induced dyskinesias are a common problem, occurring in about one third of parkinsonian patients after five years of treatment. Young age of onset, disease severity, duration of therapy and total dose of L-DOPA are the variables that best correlate with the development of dyskinesias. The first manifestations of dyskinesia are usually dystonic and involve the foot homolateral to the side most affected by Parkinson's disease. With time, dyskinesias may be classified in three main categories: off dystonia, diphasic dyskinesias also called onset and end of dose dyskinesia and peak dose dyskinesia. Although this classification is very useful in clinical practice, the different types of dyskinesia frequently overlap in a single patient when the disease progresses. Other types of involuntary movements such as myoclonus, a tremor with an increased amplitude and akathisia have been described. The physiopathology of L-DOPA-induced dyskinesias remains unclear but synaptic plasticity in striatal neurons seems to be a major phenomenon in the development of dyskinesias. Some rating scales have been developed to assess the intensity and severity of dyskinesias but their usefulness is still matter of debate.

[Dyskinesia caused by L-DOPA]

L-DOPA-induced dyskinesias are a common problem, occurring in about one third of parkinsonian patients after five years of treatment. Young age of onset, disease severity, duration of therapy and total dose of L-DOPA are the variables that best correlate with the development of dyskinesias. The first manifestations of dyskinesia are usually dystonic and involve the foot homolateral to the side most affected by Parkinson's disease. With time, dyskinesias may be classified in three main categories: off dystonia, diphasic dyskinesias also called "onset and end of dose dyskinesia" and peak dose dyskinesia. Although this classification is very useful in clinical practice, the different types of dyskinesia frequently overlap in a single patient when the disease progresses. Other types of involuntary movements such as myoclonus, a tremor with an increased amplitude and akathisia have been described. The physiopathology of L-DOPA-induced dyskinesias remains unclear but synaptic plasticity in striatal neurons seems to be a major phenomenon in the development of dyskinesias. Some rating scales have been developed to assess the intensity and severity of dyskinesias but their usefulness is still matter of debate.

Dual role of Fyn in the regulation of FAK+6,7 by cannabinoids in hippocampus

In hippocampus endocannabinoids modulate synaptic function and plasticity and increase tyrosine phosphorylation of several proteins, including focal adhesion kinase (FAK). Autophosphorylation of FAK on Tyr-397 is generally a critical step for its activation, allowing the recruitment of Src family kinases, and phosphorylation of FAK and associated proteins. We have examined the mechanisms of the regulation of FAK by cannabinoids in rat and mouse hippocampal slices. Anandamide and 2-arachidonoylglycerol, two endocannabinoids, and Delta9-tetrahydrocannabinol, stimulated tyrosine phosphorylation of FAK+6,7, a neuronal splice isoform of FAK, on several residues including Tyr-397. Cannabinoids increased phosphorylation of p130-Cas, a protein associated with FAK, but had no effect on PYK2, a tyrosine kinase related to FAK and enriched in hippocampus. Pharmacological experiments and the use of knockout mice demonstrated that the effects of cannabinoids were mediated through CB1 receptors. These effects were sensitive to manipulation of cAMP-dependent protein kinase, suggesting that they were mediated by inhibition of a cAMP pathway. PP2, an Src family kinase inhibitor, prevented the effects of cannabinoids on p130-Cas and on FAK+6,7 tyrosines 577 and 925, but not 397, indicating that FAK autophosphorylation was upstream of Src family kinases in response to CB1-R stimulation. Endocannabinoids increased the association of Fyn, but not Src, with FAK+6,7. In hippocampal slices from Fyn -/- mice, the levels of p130-Cas were increased, and the effects of endocannabinoids on tyrosine phosphorylation, including of Tyr-397, were completely abolished. These results demonstrate the specific functional association of Fyn with FAK+6,7 in a pathway regulated by endocannabinoids, in which Fyn may play roles dependent and independent of its catalytic activity.

Post-infectious ophtalmoparesis associated with anti-GM1 but not with anti-GQ1b antibodies

Acute paresis of extraocular muscles has been described following infection or immunization. It is usually associated with the presence of anti-GQ1b antibodies. We report a case of post-infectious ophtalmoparesis that was negative for anti-GQ1b antibodies and positive for anti-GM1 antibodies.

Effects of riluzole on N-methyl-D-aspartate-induced tyrosine phosphorylation in the rat hippocampus

Since increased tyrosine phosphorylation has been observed in response to brain ischemia, we investigated whether riluzole (an inhibitor of glutamate neurotransmission with neuroprotective properties) affects tyrosine phosphorylation stimulated by N-methyl-D-aspartate (NMDA) in rat hippocampal slices. Riluzole produced an extremely potent concentration-related inhibition of NMDA (1 mM)-stimulated protein tyrosine phosphorylation (IC(50)=0.5+/-0.03 microM, mean+/-S.D.), but failed to affect that evoked by phorbol 12-myristate 13-acetate (PMA, an activator of protein kinase C, 0.1 and 1 microM). These results suggest that inhibition of tyrosine phosphorylation may contribute to the neuroprotective effects of riluzole against excitotoxic injury.

Cannabinoids activate p38 mitogen-activated protein kinases through CB1 receptors in hippocampus

Cannabinoid receptors (CB1-R) are the target of a novel class of neuromodulators, the endocannabinoids. Yet, their signalling mechanisms in adult brain are poorly understood. We report that, in rat and mouse hippocampal slices, anandamide and 2-arachidonoylglycerol, synthetic cannabinoids, and delta(9)-tetrahydrocannabinol activated p38 mitogen-activated protein kinases (MAPK), but not c-Jun N-terminal kinase (JNK). In contrast, lysophosphatidic acid (LPA), a lipid messenger acting on different receptors, increased both p38-MAPK and JNK phosphorylation. The effects of cannabinoids on p38-MAPK were mediated through activation of CB1-R because they were blocked in the presence of SR 141716 A and absent in CB1-R knockout mice, two conditions that did not alter the effects of LPA. The activation of p38-MAPK by cannabinoids was insensitive to inhibitors of SRC: These results provide new insights into the cellular mechanisms by which cannabinoids exert their effects in hippocampus.

Echistatin inhibits pp125FAK autophosphorylation, paxillin phosphorylation and pp125FAK-paxillin interaction in fibronectin-adherent melanoma cells

Echistatin, a snake-venom RGD-containing protein, was previously shown to disrupt cell-matrix adhesion by a mechanism that involves the reduction of pp125FAK tyrosine phosphorylation levels. The aim of this study was to establish the sequence of events downstream pp125FAK dephosphorylation that could be responsible for echistatin-induced disassembly of actin cytoskeleton and focal adhesions in fibronectin-adherent B16-BL6 melanoma cells. The results obtained show that echistatin induces a decrease of both autophosphorylation and kinase activity of pp125FAK. One hour of cell exposure to echistatin caused a 39% decrease of pp125FAK Tyr397 phosphorylation and a 31% reduction of pp125FAK autophosphorylation activity as measured by immune-complex kinase assay. Furthermore, 1 h of cell treatment by echistatin produced a 63% decrease of paxillin phosphorylation, as well as a reduction in the amount of paxillin bound to pp125FAK. Immunofluorescence analysis of echistatin treated cells showed the concomitant disappearance of both paxillin and pp125FAK from focal adhesions. The reduction of paxillin phosphorylation may represent a critical step in the pathway by which disintegrins exert their biological activity, including the inhibition of experimental metastasis in vivo.

Spondylodiscitis and epidural abscess due to Candida albicans

A 32-year-old woman, addicted to heroin, presented with a dorsal spondylodiscitis due to Candida albicans associated with epidural abscess. Antimycotic treatment was successful, and no neurosurgical decompression was necessary. To our knowledge, this is the first case of documented epidural involvement in candidal spondylodiscitis. The diagnosis of candidal spondylodiscitis should be considered in cases of para- or tetraplegia occurring in intravenous drug abusers.

FAK and PYK2/CAKbeta in the nervous system: a link between neuronal activity, plasticity and survival?

A major aim of neurobiology today is to improve understanding of the signaling pathways that couple rapid events, such as the action potential and neurotransmitter release, to long-lasting changes in synaptic strength and increased neuronal survival. These adaptations involve interactions of neurons with other cells and with the extracellular matrix. They use, in part, the same molecular machinery that controls adhesion, motility or survival in non-neuronal cells. This machinery includes two homologous non-receptor tyrosine kinases, FAK and PYK2/CAKbeta, and the associated SRC-family tyrosine kinases. Specific brain isoforms of FAK with distinct properties are regulated by neurotransmitters, whereas PYK2/CAKbeta is highly sensitive to depolarization. The multiplicity of the pathways that can be activated by these tyrosine kinases indicates their importance in signal transduction in the adult brain.