Biomedical subjects

Patricia Parnet

Publications and source records attributed to Patricia Parnet.

9 recordsLinked to original sources

PubMed2005

ATP binding cassette transporter ABC1 is required for the release of interleukin-1beta by P2X7-stimulated and lipopolysaccharide-primed mouse Schwann cells.

Schwann cells are best known as myelinating glial cells of the peripheral nervous system, but they also participate actively in the sphere of immunity by producing pro-inflammatory cytokines, such as interleukin-1beta (IL-1beta). In a previous study, we demonstrated that posttranslational processing of IL-1beta by immune-challenged Schwann cells required the P2X7 receptor. Remarkably, the release of IL-1beta was not associated with cell death, indicating the involvement of an active mechanism. ATP binding cassette (ABC) transporters are known to transport leaderless secretory proteins, such as IL-1beta; therefore, we investigated whether such transporters were at work in Schwann cells. Mouse Schwann cells expressed ABC1 transporter mRNA and displayed the functional protein. Glybenclamide and diisothiocyanato-stilbene-disulfonic acid (DIDS), two blockers of chloride fluxes that drive the export activity of ABC1 transporters, inhibited IL-1beta release without altering its intracellular processing. Enhancing chloride efflux potentiated the release of IL-1beta, while decreasing it led to a strong reduction in its release. Because the stimulation of the P2X7 receptor also activates a chloride conductance, we investigated the possibility of a sole anionic pathway mobilized by the P2X7 receptor and ABC1. Glybenclamide and DIDS had no significant effects on the P2X7-activated chloride current suggesting therefore the existence of two different pathways. In summary, ABC1 transporters are required for the release of IL-1beta by mouse Schwann cells. Being associated together with chloride conductance, P2X7 receptors and ABC1 transporters delineate a subtle and complex regulation of IL-1beta production in mammalian Schwann cells. Furthermore, ABC1 transporters could be a target of therapeutic interest for regulating IL-1beta activity in neuroinflammation disorders.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2005

NFkappaB activates in vivo the synthesis of inducible Cox-2 in the brain.

Interleukin-1beta (IL-1beta) induces cyclooxygenase-2 (Cox-2) expression in many of its cellular targets resulting in production and release of prostaglandins. Although IL-1beta-induced Cox-2 expression most likely requires activation of nuclear transcription factor kappa B (NFkappaB) pathway, this has never been formally demonstrated in vivo. We tested this using a specific inhibitor of NFkappaB activation, the NEMO binding domain (NBD) peptide, that has been shown previously to be effective in various in vivo models of acute inflammation. Incubation of rat glioma cells with the NBD peptide blocked IL-1beta-induced NFkappaB nuclear translocation. Furthermore, after injection of a biotinylated version of the NBD peptide into the lateral ventricle of the brain, we found that it readily diffused to its potential cellular targets in vivo. To test the effects of the peptide on NFkappaB activation and Cox-2 expression in the brain, we injected it intracerebroventricularly (36 microg/rat) into rats before intraperitoneal injection of IL-1beta (60 microg/kg). Treatment with NBD peptide completely abolished IL-1beta-induced NFkappaB activation and Cox-2 synthesis in microvasculature. In contrast, the peptide had no effect on constitutive neuronal Cox-2. These findings strongly support the hypothesis that IL-1beta-induced NFkappaB activation plays a major role in transmission of immune signals from the periphery to the brain.

Animals↗

PubMed2005

Inactivation of the cerebral NFkappaB pathway inhibits interleukin-1beta-induced sickness behavior and c-Fos expression in various brain nuclei.

The behavioral effects of peripherally administered interleukin-1beta (IL-1beta) are mediated by the production of cytokines and other proinflammatory mediators at the level of the blood-brain interface and by activation of neural pathway. To assess whether this action is mediated by NFkappaB activation, rats were injected into the lateral ventricle of the brain with a specific inhibitor of NFkappaB activation, the NEMO Binding Domain (NBD) peptide that has been shown previously to abolish completely IL-1beta-induced NFkappaB activation and Cox-2 synthesis in the brain microvasculature. NFkappaB pathway inactivation significantly blocked the behavioral effects of intraperitoneally administered IL-1beta in the form of social withdrawal and decreased food intake, and dramatically reduced IL-1beta-induced c-Fos expression in various brain regions as paraventricular nucleus, supraoptic nucleus, and lateral part of the central amygdala. These findings strongly support the hypothesis that IL-1beta-induced NFkappaB activation at the blood-brain interface is a crucial step in the transmission of immune signals from the periphery to the brain that underlies further events responsible of sickness behavior.

Analysis of Variance↗

PubMed2003

Maturation and release of interleukin-1beta by lipopolysaccharide-primed mouse Schwann cells require the stimulation of P2X7 receptors.

The P2X7 receptor, mainly expressed by immune cells, is a ionotropic receptor activated by high concentration of extracellular ATP. It is involved in several processes relevant to immunomodulation and inflammation. Among these processes, the production of extracellular interleukin-1beta (IL-1beta), a pro-inflammatory cytokine, plays a major role in the activation of the cytokine network. We have investigated the role of P2X7 receptor and of an associated calcium-activated potassium conductance (BK channels) in IL-1beta maturation and releasing processes by Schwann cells. Lipopolysaccharide-primed Schwann cells synthesized large amounts of pro-IL-1beta but did not release detectable amounts of pro or mature IL-1beta. ATP on its own had no effect on the synthesis of pro-IL-1beta, but a co-treatment with lipopolysaccharide and ATP led to the maturation and the release of IL-1beta by Schwann cells. Both mechanisms were blocked by oxidized ATP. IL-1beta-converting enzyme (ICE), the caspase responsible for the maturation of pro-IL-1beta in IL-1beta, was activated by P2X7 receptor stimulation. The specific inhibition of ICE by the caspase inhibitor Ac-Tyr-Val-Ala-Asp-aldehyde blocked the maturation of IL-1beta. In searching for a link between the P2X7 receptor and the activation of ICE, we found that enhancing potassium efflux from Schwann cells upregulated the production of IL-1beta, while strongly reducing potassium efflux led to opposite effects. Blocking BK channels actually modulated IL-1beta release. Taken together, these results show that P2X7 receptor stimulation and associated BK channels, through the activation of ICE, leads to the maturation and the release of IL-1beta by immune-challenged Schwann cells.

Adenosine Triphosphate↗

PubMed2003

Nuclear factor kappaB nuclear translocation as a crucial marker of brain response to interleukin-1. A study in rat and interleukin-1 type I deficient mouse.

The signalling pathways that mediate early central effects of interleukin-1 (IL-1) during the acute phase reaction have been poorly elucidated. Interaction of IL-1beta to its specific receptor interleukin-1 receptor type I (IL-1RI) leads to nuclear factor kappa B (NuFkappaB) nuclear translocation and a robust transcriptional activation of inhibitor of kappa B alpha (IkappaBalpha) within the rat brain. Indeed, we demonstrated that IL-1RI expressed in blood brain barrier (BBB) cells and in circumventricular organs (CVOs) is crucial for p65-NFkappaB translocation induced by peripheral injection of IL-1beta. Moreover, it has been previously shown that monitoring IkappaBalpha mRNA synthesis is an effective tool to investigate the activity of the transcription factor NFkappaB into the CNS. However in the present study we observed time-related and cell-type differences between IkappaBalpha mRNA synthesis and p65-NFkappaB translocation. This indicates that the expression of IkappaBalpha mRNA does not strictly parallel p65-NFkappaB nuclear translocation, suggesting that these markers are not interchangeable to investigate NFkappaB activity but must be studied together. Thus, we hypothesize that IL-1beta reached the brain across the CVOs that lack a BBB and endothelial cells all over the brain and interacted with its receptors to induce NFkappaB translocation. The study of the consequences of the impairment of NFkappaB pathway activation in in vivo experimentation should bring important clues about the precise role of this transcription factor.

Active Transport, Cell Nucleus↗

PubMed2003

[The immune status of Schwann cells: what is the role of the P2X7 receptor?].

The peripheral nervous system (PNS) displays structural barriers and a lack of lymphatic drainage which strongly limit the access of molecules and cells from the immune system. In addition, the PNS has the ability to set up some specific mechanisms of immune protection to limit the pathogenicity of inflammation processes following insults by pathogens or inflammatory autoimmune diseases like the Guillain-Barré syndrome. Schwann cells are among the most prominent cells which can display immune capabilities in the PNS. Numerous in vitro studies have shown that Schwann cells were indeed able to display a large repertoire of properties, ranging from the participation to antigen presentation, to secretion of pro- and anti-inflammatory cytokines, chemokines and neurotrophic factors. In vivo studies have confirmed the immune capabilities of Schwann cells. The aim of this review is to present how Schwann cells can participate to the initiation, the regulation and the termination of the immune response in the light of the recent discovery of the Schwann cell expression of purinergic P2X7 receptors.

Animals↗

PubMed2002

Expression and regulation of interleukin-1 receptors in the brain. Role in cytokines-induced sickness behavior.

Sickness behavior refers to the coordinated set of behavior changes that develop in sick individuals during the course of an infection. At the molecular level, these changes are due to the effects of proinflammatory cytokines as interleukin-1 on the brain. The purpose of this article is not to review the entire field of cytokines and behavior, but rather to address the role of interleukin-1 receptors (IL-1Rs) in sickness behavior. We briefly describe the notion of sickness behavior and present the distribution of IL-1Rs in the central nervous system of the human, mouse and rat. We then bring arguments in favor of the functionality of the various subtypes of receptors and evaluate the nature of the signaling pathways activated by brain IL-1Rs to initiate central modifications leading to symptoms of sickness. Finally, modulation of IL-1 action on its receptor by various opposing factors including glucocorticoids and anti-inflammatory cytokines is discussed.

Brain↗

PubMed2002

Cytokine-induced sickness behaviour: mechanisms and implications.

Sickness behaviour represents the expression of the adaptive reorganization of the priorities of the host during an infectious episode. This process is triggered by pro-inflammatory cytokines produced by peripheral phagocytic cells in contact with invading micro-organisms. The peripheral immune message is relayed to the brain via a fast neural pathway and a slower humoral pathway, resulting in the expression of pro-inflammatory cytokines in macrophage-like cells and microglia in the brain. The cellular and molecular components of this previously unsuspected system are being progressively identified. These advances are opening new avenues for understanding brain disorders, including depression.

Animals↗

PubMed1998

Molecular basis of sickness behavior.

Peripheral and central injections of lipopolysaccharide (LPS), a cytokine inducer, and recombinant proinflammatory cytokines such as interleukin-1 beta (IL-1 beta) induce sickness behavior in the form of reduced food intake and decreased social activities. Mechanisms of the behavioral effects of cytokines have been the subject of much investigation during the last 3 years. At the behavioral level, the profound depressing effects of cytokines on behavior are the expression of a highly organized motivational state. At the molecular level, sickness behavior is mediated by an inducible brain cytokine compartment that is activated by peripheral cytokines via neural afferent pathways. Centrally produced cytokines act on brain cytokine receptors that are similar to those characterized on peripheral immune and nonimmune cells, as demonstrated by pharmacologic experiments using cytokine receptor antagonists, neutralizing antibodies to specific subtypes of cytokine receptors, and gene targeting techniques. Evidence exists that different components of sickness behavior are mediated by different cytokines and that the relative importance of these cytokines is not the same in the peripheral and central cytokine compartments.

Animals↗