RESUMEN
Experimental allergic encephalomyelitis (EAE) is an animal model for the human demyelinating disease multiple sclerosis (MS). Increased permeability of the blood-brain barrier (BBB) precedes the development of clinical or pathologic findings in MS and may be induced by perivascular brain mast cells secreting vasoactive and proinflammatory molecules. Brain mast cells were investigated ultrastructurally in acute EAE of the non-human primate common marmoset Callithrix jacchus, which develops a mild neurologic relapsing-remitting course. Control diencephalic samples contained perivascular mast cells with mostly intact electron dense granules. In contrast, EAE samples had marked demyelination and mast cells with numerous altered secretory granules; their electron dense content varied in amount and texture with a "honeycomb" or "target" appearance, but without degranulation. These changes were evident even before the development of any clinical symptoms and suggest that brain mast cells may be involved in EAE, and possibly MS, through a unique process that may involve selective secretion of molecules able to disrupt the BBB.
Asunto(s)
Encéfalo/ultraestructura , Degranulación de la Célula , Encefalomielitis Autoinmune Experimental/metabolismo , Encefalomielitis Autoinmune Experimental/patología , Mastocitos/metabolismo , Mastocitos/ultraestructura , Animales , Encéfalo/irrigación sanguínea , Encéfalo/metabolismo , Encéfalo/patología , Callithrix , Gránulos Citoplasmáticos/metabolismo , Gránulos Citoplasmáticos/patología , Gránulos Citoplasmáticos/ultraestructura , Diencéfalo/irrigación sanguínea , Diencéfalo/metabolismo , Diencéfalo/patología , Diencéfalo/ultraestructura , Exocitosis , Humanos , Masculino , Mastocitos/patología , Vaina de Mielina/patología , Vaina de Mielina/ultraestructuraRESUMEN
Mast cells derive from a distinct bone marrow precursor and mature in tissues under the influence of stem cell factor, nerve growth factor (NGF) and certain interleukins. Intracranial mast cells first appear in the meninges and are located perivascularly close to neurons. They can be activated by antidromic stimulation of the trigeminal nerve, as well as by acute immobilization stress. Substance P (SP) and corticotropin-releasing hormone (CRH) are particularly potent in stimulating mast cell release of vasoactive, inflammatory and nociceptive molecules. These findings have suggested that mast cells may be involved in neuroinflammatory conditions, such as migraines. In this study, dura mast cells were shown to have characteristics of connective tissue mast cells (CTMC) as they contained histamine, heparin and rat mast cell protease I (RMCP-I). Mast cells were localized close to SP-positive neurons immunocytochemically and mast cell-neuron contacts were also documented using scanning electron microscopy. Dura stimulated by SP and carbachol in situ released histamine. Preincubation of dura with estradiol slightly augmented histamine release by SP, an effect possibly mediated through estrogen receptors identified on dura mast cells. Acute stress by immobilization led to dura mast cell degranulation which was prevented by pretreatment with a neutralizing antibody to CRH or a CRH receptor antagonist. The present results further clarify the biology of intracranial mast cells and support their involvement in the pathophysiology of migraines which are precipitated or worsened by stress.
Asunto(s)
Duramadre/fisiología , Mastocitos/fisiología , Neuronas/fisiología , Animales , Animales Recién Nacidos , Comunicación Celular , Células Cultivadas , Colinesterasas/análisis , Quimasas , Células del Tejido Conectivo/citología , Células del Tejido Conectivo/fisiología , Duramadre/citología , Histamina/análisis , Inmunohistoquímica , Masculino , Mastocitos/citología , Mastocitos/ultraestructura , Microscopía Electrónica de Rastreo , Neuronas/citología , Neuronas/efectos de los fármacos , Neuropéptidos/farmacología , Ratas , Ratas Sprague-Dawley , Receptores de Estrógenos/análisis , Restricción Física , Serina Endopeptidasas/análisis , Estrés Psicológico , Sustancia P/análisisRESUMEN
The activation of presynaptic histamine 3 (H(3)) receptors inhibits the release of histamine and other neurotransmitters from central nervous system neurons. Rat brain mast cells (MCs) release histamine and 5-hydroxytryptamine (5-HT) in response to neuropeptides and neurotransmitters secreted from adjacent neurons. Dura MCs also degranulate in response to antidromic trigeminal nerve stimulation and with acute psychological stress. Such findings have implicated brain MCs in certain neuroinflammatory disorders, such as migraines. We investigated the ultrastructural appearance of control and stimulated thalamic/hypothalamic (brain) MCs before and after treatment with the H(3) receptor agonist N(alpha)-methylhistamine (N(alpha)-mH) and the H(3) receptor antagonist thioperamide (Th). Ultrastructural investigation of brain MCs stimulated with compound 48/80 revealed extensive intragranular changes that paralleled 5-HT secretion but without degranulation by exocytosis typical of connective tissue MCs. N(alpha)-mH significantly reduced these morphological changes, as well as 5-HT release from brain MCs and neurons stimulated with KCl; conversely, Th augmented both histamine and 5-HT release from brain neurons and MCs. Neither N(alpha)-mH nor Th had any effect on peritoneal MCs. Simultaneous addition of both drugs largely antagonized each other's effects on brain MC activation and 5-HT secretion. Ultrastructural observations and lack of lactic dehydrogenase release in the perfusate excluded any cytotoxic effect. The ability of H(3) agonists to inhibit brain MC activation, as well as secretion of 5-HT from both brain MCs and neurons, may be useful in the management of migraines.
Asunto(s)
Encéfalo/citología , Encéfalo/efectos de los fármacos , Agonistas de los Receptores Histamínicos/farmacología , Antagonistas de los Receptores Histamínicos/farmacología , Mastocitos/efectos de los fármacos , Metilhistaminas/farmacología , Cavidad Peritoneal/citología , Piperidinas/farmacología , Receptores Histamínicos H3/fisiología , Animales , Encéfalo/metabolismo , Supervivencia Celular/efectos de los fármacos , Liberación de Histamina/efectos de los fármacos , Masculino , Mastocitos/fisiología , Mastocitos/ultraestructura , Neuronas/metabolismo , Ratas , Ratas Sprague-Dawley , Serotonina/metabolismoRESUMEN
Migraine may affect as many as 9% of all schoolchildren and often presents with abdominal symptoms of pain, nausea, and vomiting. Even though the pathophysiology of migraine remains unknown, self-regulation techniques appear to be more effective in prevention of childhood migraine than conventional pharmacotherapy which is often associated with adverse effects. Mast cells have been implicated in the pathogenesis of migraine in adults, but have not been previously studied in children with migraine. Mast cells are found close to the vessels and nerves in the meninges where they can release multiple vasoactive, neurosensitizing, and pro-inflammatory mediators. Therefore, we investigated whether children with migraine may have increased urinary levels of mast cell mediators and whether practicing relaxation imagery exercises has an effect on the frequency of headache, as well as on mast cell activation. Urine was collected for 24 hours from children with and without migraine after a 5-day amine-restricted diet. Children with migraine also collected urine during migraine episodes. The mean levels of urinary histamine, its main metabolite, methylhistamine, and the mast cell enzyme, tryptase, were higher in children than generally found in adults, but they did not differ statistically in any of the categories studied. However, in 8 of 10 children who practiced relaxation imagery techniques and successfully reduced the number of migraines, the urine tryptase levels were also significantly lower. There was no relationship between successful practice and sex or age of the child. These results suggest that stress may activate mast cells which could be involved in the pathophysiology of migraine.
Asunto(s)
Mastocitos/fisiología , Trastornos Migrañosos/prevención & control , Trastornos Migrañosos/fisiopatología , Terapia por Relajación , Controles Informales de la Sociedad , Niño , Preescolar , Femenino , Humanos , Masculino , Mastocitos/enzimología , Metilhistaminas/orina , Trastornos Migrañosos/orina , Resultado del Tratamiento , Triptasas/orinaRESUMEN
Mast cells have previously been identified in mammalian brain by histochemistry and histamine fluorescence, particularly in the rat thalamus and hypothalamus. However, the nature of brain mast cells has continued to be questioned, especially because the electron microscopic appearance often shows secretory granule morphology distinct from that of typical connective tissue mast cells. Here we report that mast cells in the rat hypothalamus, identified based on metachromatic staining with Toluidine Blue, fluoresced after staining with berberine sulfate, indicating the presence of heparin. These cells were also positive immunohistochemically for histamine, as well as for rat mast cell protease I, an enzyme characteristically present in rat connective tissue mast cells. In addition, these same cells showed a very strong signal with in situ hybridization for immunoglobulin E binding protein messenger RNA. However, use of antibodies directed towards immunoglobulin E or its binding protein did not label any cells, which may mean either the binding protein is below the level of detection of the techniques used or that it is not expressed except in pathological conditions when the blood-brain barrier becomes permeable. At the ultrastructural level, perivascular mast cells contained numerous, intact, electron-dense granules which were labeled by gold-labeled anti-rat mast cell protease I. These results clearly demonstrate the presence of perivascular mast cells in the rat hypothalamus, where they may participate in homeostatic processes.
Asunto(s)
Hipotálamo/química , Hipotálamo/fisiología , Mastocitos/fisiología , Animales , Inmunohistoquímica , Hibridación in Situ , Masculino , Mastocitos/ultraestructura , Microscopía Electrónica , Ratas , Ratas Sprague-DawleyRESUMEN
Stress is known to precipitate or worsen a number of disorders, such as migraines, in which mast cells are suspected of being involved by releasing vasoactive, nociceptive, and proinflammatory mediators. However, no functional association has been demonstrated yet between a migraine trigger and brain mast cell activation. Nontraumatic immobilization (restrain) stress has been shown to stimulate the hypothalamic-pituitary-adrenal axis and to cause redistribution of immune cells. Here, restrain stress caused degranulation in 70% of rat dura mast cells within 30 min, as shown both by light and electron microscopy. These morphologic findings were accompanied by cerebrospinal fluid elevation of rat mast cell protease I, but not II, indicating secretion from connective tissue type mast cells. Mast cell activation due to stress was abolished in animals that had been treated neonatally with capsaicin, indicating that neuropeptides in sensory nerve endings are involved in this response. Complete inhibition was also achieved by pretreating the animals ip with polyclonal antiserum to CRH. Mast cells in the dura were localized close to nerve processes containing substance P, but no CRH-positive fibers were identified even though these were found close to mast cells in the median eminence. This is the first time that stress is shown to activate intracranial mast cells; apparently through the sequential action of CRH and sensory neuropeptides. These findings may have implications for the pathophysiology and possible therapy of neuroinflammatory disorders such as migraines, which are induced or exacerbated by stress.
Asunto(s)
Encéfalo/ultraestructura , Degranulación de la Célula , Hormona Liberadora de Corticotropina/fisiología , Mastocitos/fisiología , Estrés Fisiológico/patología , Animales , Masculino , Mastocitos/ultraestructura , Trastornos Migrañosos/etiología , Ratas , Ratas Sprague-Dawley , Restricción FísicaRESUMEN
Multiple sclerosis (MS) lesions are associated with infiltration of T lymphocytes and macrophages that appear to mediate myelin destruction and gliosis (scarring). Mast cells are located perivascularly in the brain, are juxtaposed to neurons, and have been shown to secrete vasoactive and inflammatory mediators in response to neuropeptides and direct nerve stimulation. Mast cells have been previously identified in MS lesions, are activated by myelin basic protein, and can participate in the regulation of blood-brain barrier permeability, as well as in myelin destruction. Here, cerebrospinal fluid from MS patients and controls with other neurologic diseases was assayed for histamine, its major metabolite methylhistamine, and the specific mast cell marker tryptase. Histamine and methylhistamine were not elevated in MS. However, the mast cell specific proteolytic enzyme tryptase was significantly elevated in MS, suggesting that mast cell activation may be involved in the pathophysiology of this disease.
Asunto(s)
Mastocitos/enzimología , Esclerosis Múltiple/enzimología , Serina Endopeptidasas/líquido cefalorraquídeo , Adulto , Quimasas , Femenino , Histamina/líquido cefalorraquídeo , Humanos , Masculino , Metilhistaminas/líquido cefalorraquídeo , Persona de Mediana Edad , Esclerosis Múltiple/líquido cefalorraquídeo , Esclerosis Múltiple/inmunología , TriptasasRESUMEN
Mast cells are known for their participation in immediate and, more recently, delayed hypersensitivity reactions. They have been found in the meninges and certain brain areas where they are strictly perivascular, in close apposition to neurons, and they are activated by direct nerve stimulation or by neuropeptides. Intracranial mast cells contain many vasoactive substances which can increase the permeability of the blood-brain barrier, proteolytic enzymes which can degrade myelin in vitro, as well as chemotactic molecules which can attract inflammatory molecules in vivo. Connective tissue mast cells, with which intracranial mast cells share many characteristics, contain cytokines which can cause inflammation directly. Multiple sclerosis is a human demyelinating disease of unknown etiology, with a high prevalence in women which results in penetration of blood-borne immune cells within the brain parenchyma and subsequent destruction of myelin. Here, we report that 17 beta-estradiol and myelin basic protein, a major suspected immunogen in multiple sclerosis, had a synergistic action on inducing mast cell secretion. This effect was more pronounced in Lewis rats, which are susceptible to the development of experimental allergic encephalomyelitis, an animal model for multiple sclerosis, than in Sprague-Dawley rats, which are fairly resistant. Moreover, 18 h incubation of purified peritoneal mast cells with homogeneic slices of brain white matter in the presence of 17 beta-estradiol and myelin basic protein resulted in myelin changes resembling early stages of brain demyelination, which were also more evident in Lewis rats than in Sprague-Dawley rats. These results support the notion that mast cells could participate in the pathophysiology of demyelinating diseases.
Asunto(s)
Encéfalo/metabolismo , Enfermedades Desmielinizantes/metabolismo , Estradiol/farmacología , Mastocitos/metabolismo , Proteína Básica de Mielina/farmacología , Vaina de Mielina/metabolismo , Animales , Sinergismo Farmacológico , Procesamiento de Imagen Asistido por Computador , Técnicas In Vitro , Masculino , Microscopía Electrónica , Ratas , Ratas Endogámicas Lew , Ratas Sprague-DawleyRESUMEN
W/Wv mice have been extensively used as an important model to study the maturation/differentiation and pathophysiology of mast cells. These albino mice have been shown to have less than 1% of the mast cells found in the skin of their +/+ controls or other normal mice. Moreover, no mast cells are detected in other organs even though they apparently have an adequate number of mast cell precursors. Presumably, these precursors do not respond appropriately to microenvironmental growth factors, while 'normal' precursors from the +/+ controls of S1/S1d-deficient mice mature appropriately in the tissue microenvironment of the W/Wv mice. Female W/Wv mice and +/+ controls were immunized with allogeneic spinal cord homogenate in complete Freund's adjuvant and Mycobacterium tuberculosis in order to induce experimental allergic encephalomyelitis. All W/Wv mice developed extensive dermatitis with mastocytosis at the injection sites about 4 months after inoculation. Mast cells were identified by light microscopy following staining with toluidine blue and berberine sulfate as well as electron microscopy. They were also found to be functional since they secreted serotonin and histamine in response to either compound 48/80 or carbachol. The majority of these mast cells were, therefore, considered to be mature, connective tissue like, but many of them were in different stages of granule maturation as seen with electron microscopy. These findings imply that W/Wv mice may not always be appropriate as models of mast cell deficiency. Moreover, these results suggest that the 'defect' in W/Wv mast cell precursors can be overcome by factors produced during immunization and/or development of dermatitis. These findings may, therefore, help elucidate what regulates mast cell maturation/differentiation as well as their pathophysiology.
Asunto(s)
Dermatitis/inmunología , Inmunización , Mastocitos/efectos de los fármacos , Mastocitosis/inmunología , Animales , Recuento de Células , Dermatitis/patología , Enfermedad , Encefalomielitis Autoinmune Experimental/inmunología , Femenino , Liberación de Histamina/inmunología , Mastocitos/inmunología , Mastocitos/ultraestructura , Mastocitosis/patología , Ratones , Ratones Endogámicos C57BL , Ratones Mutantes , Serotonina/biosíntesis , Piel/inmunología , Piel/ultraestructuraRESUMEN
Mast cells have been studied extensively for their involvement in allergic reactions, where they secrete numerous powerful mediators in response to immunoglobulin E and specific antigens. However, they are also triggered by neuropeptides, they have been found in close contact with neurons, and they are activated in diseases such as angioedema, interstitial cystitis and irritable bowel disease, the prevalence of which is much higher in women. When tested on purified rat peritoneal mast cells, 17 beta-estradiol augmented secretion of histamine and serotonin, starting at 1 microM and in a dose-dependent manner, whether stimulated by the mast cell secretagogue compound 48/80 or the neuropeptide substance P. However, 17 beta-estradiol did not augment mast cell secretion stimulated by immunoglobulin E and specific antiserum indicating that immunologic stimulation is under different regulation. Testosterone inhibited secretion induced by compound 48/80. Tamoxifen, an estrogen receptor antagonist used in the treatment of breast cancer, inhibited serotonin and histamine release from purified rat peritoneal mast cells triggered by compound 48/80 or substance P. Tamoxifen also inhibited the increase in intracellular free Ca2+ originating from an influx of extracellular Ca2+ in response to compound 48/80. Moreover, tamoxifen antagonized the synergistic effect of phorbol myristate and the cation ionophore A23187 on mast cell secretion, suggesting that tamoxifen's inhibition may be due to regulation of protein kinase C activity. Tamoxifen may, therefore, have a beneficial effect in other neuroimmunoendocrine disorders both through estrogen receptor blockade and inhibition of mast cell secretion.