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PubMed2001

Use of muscarinic agonists in the treatment of Sjögren's syndrome.

Two muscarinic agonists (pilocarpine and cevimeline) have recently been approved for the treatment of symptoms of xerostomia in Sjögren's syndrome (SS). These agents stimulate the M1 and M3 receptors present on salivary glands, leading to increased secretory function. The use of these agents emphasizes the importance of neuroendocrine mechanisms in SS, which is considered an autoimmune disorder. We review recent studies on the release of cytokines and metalloproteinases in SS-affected glands and their influence on the release of and response to neurotransmitters. Also, we review the structure and function of muscarinic receptors as they may relate to SS and the potential use of novel muscarinic agonists in SS.

Humans↗
PubMed2002

In vivo activation of myelin oligodendrocyte glycoprotein-specific T cells in healthy control subjects.

Autoreactive T cells are present in healthy subjects but are assumed not to induce overt disease due to lack of exposure to autoantigen or because of immune regulation. In EAE, activation of myelin protein-specific T cells is a crucial step in disease induction. In this study, we evaluated whether myelin oligodendrocyte glycoprotein (MOG)-reactive T cells had been activated in vivo using peripheral blood mononuclear cells from neurologically healthy subjects. In vitro assays used either memory, CD45RO(+), or naïve, CD45RA(+) T-cell populations. MOG-reactive T cells were isolated from 7 of 10 subjects. Unexpectedly, a substantial number of MOG-reactive T cells were isolated from the CD45RO(+), memory T-cell subset in 6 subjects. The majority of these T cells generated gamma interferon in excess of IL-4, expressed VLA-4, and produced nerve growth factor. These findings demonstrate that a substantial proportion of MOG-reactive T cells from some subjects have been activated in vivo without resulting in clinical disease.

Adult↗
PubMed1999

IL-1alpha but not IL-1beta-induced prostaglandin synthesis is inhibited by corticotropin-releasing factor.

Interleukin (IL)-1alpha and IL-1beta share low amino acid homology, but exhibit a very similar array of biological activities. The authors previously showed negative regulation of IL-1alpha-induced prostaglandin (PG) production by corticotropin releasing factor (CRF). In this study, the authors compared the effect of CRF on IL-1alpha- and IL-1beta-induced PG synthesis. IL-1alpha (100 U/ml) increased prostacyclin (PGI2) (measured as 6-keto PGF1alpha[6K]) synthesis in endothelial cells and the production of PGE2in fibroblasts. The PG response to IL-1alpha was suppressed by simultaneous exposure to CRF (2.5x10(-11)-2.5x10(-8) M) in both cell types. IL-1alpha enhanced both phospholipase A2(PLA2) and prostaglandin H synthase (PGHS) activities, and the two effects were completely abrogated by CRF. IL- 1beta (100 U/ml) was as active as IL-1alpha in triggering release of PGI2 from endothelial cells and PGE2 from fibroblasts. However, CRF (2.5x10(-11)-2.5x10(-8) M) failed to alter the IL-1beta-induced PG synthesis in both cell types. Following IL-1beta PGHS activity, and to a lesser extent PLA2 activity, were enhanced, however CRF only inhibited PGHS and not PLA2 activity. It is concluded that although IL-1alpha and IL-1beta usually produce similar biological effects, here they seem to act via different mechanisms. The different regulation of IL-1alpha and IL-1beta pro-inflammatory activities by CRF may attribute special precision and specificity to the neuroendocrine-immune control of inflammatory processes.

Animals↗
PubMed1998

Distribution and temporal regulation of the immune response in the rat brain to intracerebroventricular injection of interferon-gamma.

The response to intracerebroventricular administration of interferon (IFN)-gamma was examined in the adult Wistar rat brain: major histocompatibility complex (MHC) antigens class I and II, CD8 and CD4 antigens, and the macrophage/microglia antigen OX42 were analyzed in respect to saline-injected cases over 1 week. The glial cell type expressing MHC antigens was characterized with double labeling. IFN-gamma was thus found to induce MHC class I and II expression in microglia, identified by tomato lectin histochemistry, and not in GFAP-immunostained astrocytes. MHC antigen-expressing microglia was detected in the periventricular parenchyma, several fields of the cerebral cortex, cerebellum, major fiber tracts, and brainstem superficial parenchyma. Different gradients of density and staining intensity of the MHC-immunopositive elements were observed in these regions, in which MHC class I antigens persisted up to 1 week, when MHC class II induction had declined. Quantitative analysis pointed out the proliferation of OX42-immunoreactive cells in periventricular and basal brain regions. CD8+ T cells were observed in periventricular regions, basal forebrain, and fiber tracts 3 days after IFN-gamma injection and their density markedly increased by 7 days. CD4+ T cells were also seen and they were fewer than CD8+ ones. However, numerous CD4+ microglial cells were observed in periventricular and subpial regions, especially 1 week after IFN-gamma injection. Our data indicate that this proinflammatory cytokine mediates in vivo microglia activation and T cell infiltration in the brain and that the cells involved in this immune response display a regional selectivity and a different temporal regulation of antigen expression.

Animals↗
PubMed1994

Prolactin and the immune system.

Prolactin (PRL) is involved in a wide range of physiological effects in several species and its immunoregulatory role has already been well documented. The PRL receptor has been cloned from various species. There are at least two receptor isoforms (short and long) in rats and mice, which differ only in their cytoplasmic domains, generated by alternative splicing of a single gene, although in human only the long form exists. Using the reverse transcriptase-polymerase chain reaction (RT-PCR), we detected transcripts encoding both forms of PRL receptor in all lymphoid tissues examined in human, mouse, and rat, but in mouse and rat the ratio between the two forms was variable from animal to animal. Concerning the transcript encoding the PRL itself, a clear signal was always found in human lymphocytes and occasionally in rat thymus. We also developed a quantitative PCR (Q-PCR) in order to measure the absolute number of transcripts in thymus and spleen from rats at two stages of estrous cycle. The level of expression of the two forms was about equal. Finally, we identified the tyrosine kinase JAK2, which is constitutively associated with the PRLR, using the Nb2 rat lymphoma cell line as a model system with which to study the action of PRL on cell mitogenesis. We also showed that, after stimulation by PRL, the dimerization process is a prerequisite step for the phosphorylation of the PRLR and JAK2, which represents the earliest event in the signal transduction pathway.

Animals↗
PubMed1994

Substance P receptors and signal transduction in leukocytes.

In this paper we demonstrate several aspects of the mechanisms of action of the neurotransmitter Substance P in the immune system. We describe how Substance P can activate T cells, B cells, monocytes, and granulocytes to, respectively, proliferation, immunoglobulin synthesis, cytokine production, and chemotaxis. However, the neurotransmitter does not trigger cells of the immune system only via the well-characterized neurokinin-1 receptor, which mediates the signaling by Substance P in the neuroendocrine system. We show that Substance P can activate T cells receptor-independently. The receptor-independent activation of T cells leads to the activation of heterotrimeric G proteins and calcium-influx into the T cell, followed by an increase in proliferation of the cell. Apart from the receptor-independent activation pathway, Substance P can also activate monocytes and B cells via a nonneurokinin Substance P receptor. Activation of this novel receptor leads to the activation of MAP kinase, which is an important second messenger in the cascade leading to cytokine production by monocytes. In contrast to the non-neurokinin Substance P receptor, triggering of the NK-1 receptor, transfected in Jurkat cells, or triggering of T cells via receptor-independent pathways does not lead to activation of MAP kinase. Combining the data, we can conclude that the interaction between the neuroendocrine system and the immune system with regard to Substance P clearly indicates that the immune system does not necessarily mirror the communication pathways that are used in the neuroendocrine system. Substance P is capable of signaling the immune system via multiple activation pathways.

Calcium↗
PubMed1994

The enteric nervous and immune systems: interactions for mucosal immunity and inflammation.

A number of anatomical studies have demonstrated the presence of peptidergic nerve fibers infiltrating mucosal lymphoid tissues. The exact mechanisms of how neuropeptides are released to affect these lymphoid sites are unclear, but radiolabeled binding studies have shown that mucosal leukocytes bear a number of neuropeptide receptors on their cell surfaces capable of responding to neural signals. The presence of neuropeptide-containing fibers and the ability to receive neural signals suggest that mucosal lymphocytes can be influenced by neurogenic mediators. The objectives set forth in this review are to provide what is currently known about the ability of substance P and vasoactive intestinal peptide to promote mucosal IgA responses in the gastrointestinal tract via Th2 mechanisms and to discuss how these neuropeptides contribute to the exacerbation of the inflammatory diseases of the gastrointestinal tract. We describe how immune responses develop in the gastrointestinal immune system and emphasize how neuropeptides may influence the differentiation of lymphocytes in mucosal inductive tissues and their subsequent expression in mucosal effector sites. Finally, we discuss new techniques developed by the Mucosal Immunization Research Group that have enabled the study of mucosal immune responses.

Animals↗
PubMed1994

The role of the hypothalamic-pituitary-adrenal axis in susceptibility to autoimmune/inflammatory disease.

The central nervous system (CNS) affects the immune system through endocrine, paracrine, and neuronal mechanisms. The immune system in turn communicates with the CNS through many of the same mechanisms. Evidence that this bidirectional communication plays a vital role in susceptibility to inflammatory and infectious disease is derived largely from animal models in which the communication has been interrupted or reconstituted surgically, pharmacologically, or on a preexisting genetic basis. The advantage of animal models for studying the pathophysiologic relevance of such connections is that the systems can be manipulated at several levels and at different times in relation to development of the inflammatory disease and the outcome of the manipulation can be quantified. While in vitro studies may be used to further define the subcellular and molecular mechanisms of these interactions, only an intact organism, in which the central nervous system is connected to the immune system, can be used to fully define the nature of these interconnections. This review describes approaches to studying CNS-immune system interactions, using relatively inflammatory-susceptible and inflammatory-resistant Lewis and Fischer rats as models for evaluating the role of the HPA axis in susceptibility to inflammatory disease.

Animals↗
PubMed1994

Negative regulatory molecules in the neuroendocrine and immune systems: suppressin as an example.

The early foundations of both neuroendocrinology and immunology were established by studies that linked the production, secretion, and action of circulating factors to the physiological state of an organism. These studies ultimately identified the cells of the neuroendocrine and immune systems as a rich source of such homeostatic regulatory molecules, and currently they are referred to as neuroendocrine hormones, peptides, and cytokines. More recently, two additional concepts have been added to this model. The first was that immune cells produce neuroendocrine hormones and peptides and that neuroendocrine cells produce cytokines. The second was the notion that both positive and negative factors control a variety of physiological processes. Recently, we have identified a new polypeptide negative regulator of cell proliferation that we have named suppressin (SPN). This negative regulatory molecule is also produced by both neuroendocrine and immune cells. The objective of this article is to provide an example of the biochemical, cellular, and molecular approaches used to characterize SPN and that could be used to characterize similar molecules from neuroendocrine and immune sources.

Animals↗
PubMed2002

Genetic and immunologic considerations in autism.

According to recent epidemiological surveys, autistic spectrum disorders have become recognized as common childhood psychopathologies. These life-lasting conditions demonstrate a strong genetic determinant consistent with a polygenic mode of inheritance for which several autism susceptibility regions have been identified. Parallel evidence of immune abnormalities in autistic patients argues for an implication of the immune system in pathogenesis. This review summarizes advances in the molecular genetics of autism, as well as recently emerging concerns addressing the disease incidence and triggering factors. The neurochemical and immunologic findings are analyzed in the context of a neuroimmune hypothesis for autism. Studies of disorders with established neuroimmune nature indicate multiple pathways of the pathogenesis; herein, we discuss evidence of similar phenomena in autism.

Autistic Disorder↗
PubMed1999

MLT and the immune-hematopoietic system.

It is now well recognized that a main actor in the continuous interaction between the nervous and immune systems is the pineal hormone MLT. T-helper cells bear G-protein coupled MLT cell membrane receptors and, perhaps, MLT nuclear receptors. Activation of MLT receptors enhances the release of T-helper cell type 1 (Th1) cytokines, such as gamma-interferon and interleukin-2 (IL-2), as well as of novel opioid cytokines which crossreact immunologically with both interleukin-4 (IL-4) and dynorphin B. MLT has been reported also to enhance the production of interleukin-1 (IL-1), interleukin-6 (IL-6) and interleukin-12 (IL-12) in human monocytes. These mediators may counteract stress-induced immunodepression and other secondary immunodeficiencies, protect mice against lethal viral and bacterial diseases, synergize with IL-2 in cancer patients and influence hematopoiesis. In cancer patients, MLT seems to be required for the effectiveness of low dose IL-2 in those neoplasias that are generally resistant to IL-2 alone. Hematopoiesis is apparently influenced by the action of the MLT-induced-opioids (MIO) on kappa-opioid receptors present on stromal bone marrow macrophages. Most interestingly, gamma-interferon and colony stimulating factors (CSFs) may modulate the production of MLT in the pineal gland. A hypothetical pineal-immune-hematopoietic network is, therefore, taking shape. From the immunopharmacological and ethical point of view, clinical studies on the effect of MLT in combination with IL-2 or other cytokines in viral disease including human immunodeficiency virus-infected patients and cancer patients are needed. In conclusion, MLT seems to play a crucial role in the homeostatic interactions between the brain and the immune-hematopoietic system and deserves to be further studied to identify its therapeutic indications and its adverse effects.

Animals↗
PubMed2001

Genetic factors involved in central nervous system/immune interactions.

Analysis of several inbred rat strains has led us to hypothesize that HPA axis abnormalities may contribute, in part, to susceptibility to both autoimmune disease and addiction. In this article we review the evidence for this hypothesis and describe our ongoing efforts to genetically characterize these traits. We have mapped the locations of 23 loci that regulate autoimmune disease in rats, and are currently constructing QTL congenic lines in which a genomic region from the resistant strain is transferred to the susceptible strain or vice versa. These QTL congenic lines will be valuable to test whether genes encoding autoimmune regulation also control neuroendocrine traits. Further genetic dissection and identification of the underlying genes will be necessary to infer a mechanistic link between autoimmune and neuroendocrine traits.

Animals↗
PubMed2025

Mouse Testing Methods in Psychoneuroimmunology: Measuring Behavioral Responses.

The field of psychoneuroimmunology (PNI) aims to uncover the processes and consequences of nervous, immune, and endocrine system relationships. Behavior is a consequence of such interactions and manifests from a complex interweave of factors including immune-to-neural and neural-to-immune communication. Often the signaling molecules involved during a particular episode of neuroimmune activation are not known, but behavioral response provides evidence that bioactives such as neurotransmitters and cytokines are perturbed. Immunobehavioral phenotyping is a first-line approach when examining the neuroimmune system and its reaction to immune stimulation or suppression. Behavioral response is significantly more sensitive than direct measurement of a single specific bioactive and can quickly and efficiently rule in or out relevance of a particular immune challenge or therapeutic to neuroimmunity. Classically, immunobehavioral research was focused on sickness symptoms related to bacterial infection, but neuroimmune activation is now a recognized complication of diseases and disorders ranging from cancer to diabesity to Alzheimer's. Immunobehaviors include lethargy, loss of appetite, and disinterest in social activity/surrounding environment. In addition, neuroimmune activation can diminish physical activity, precipitate feelings of depression and anxiety, and impair cognitive and executive function. Provided is a detailed overview of behavioral tests frequently used to examine neuroimmune activation in mice with a special emphasis on pre-experimental conditions that can confound or prevent successful immunobehavioral experimentation.

Animals↗