Dendritic cells are abundant in non-lesional gray matter in multiple sclerosis

We have analyzed the localization of dendritic cells (DCs) in non-lesional gray matter (NLGM) in comparison to non-lesional white matter (NLWM) and acute or chronic active multiple sclerosis (MS) lesions. Immunohistochemistry was performed on cryostat sections for DCs markers (CD209, CD205, CD83) and other markers for inflammatory cells (CD68, CD8, CD4, CD3, CCR7, CCR5). We found cells expressing CD209 and containing myelin basic protein in both perivascular and parenchymal areas of NLGM. Our findings showing the expression of CD209(+) cells in NLGM parenchymal areas are surprising relative to the previous literature which reported the presence of CD209(+) DCs only in MS plaque perivascular areas. Although less numerous than CD209(+) cells, NLGM cells expressing mature DCs marker CD205 were consistently detected in perivascular cuffs of most lesions. In double labeling experiments, some but not all of the CD209(+) cells also expressed CD68 and CCR5. We also found CD209(+) cells in close contact with CD3(+) lymphocytes suggesting that DCs might contribute to the local activation of pathogenic T cells in the NLGM. Since injury to the NLGM is one of the key factors associated with disability accumulation, targeting DCs may represent a possible new therapeutic approach in MS to prevent disease progression.

The neurobiology of aggression and rage: role of cytokines

Recent studies have suggested an important relationship linking cytokines, immunity and aggressive behavior. Clinical reports describe increasing levels of hostility, anger, and irritability in patients who receive cytokine immunotherapy, and there are reports of a positive correlation between cytokine levels and aggressive behavior in non-patient populations. On the basis of these reports and others describing the presence or actions of different cytokines in regions of the brain associated with aggressive behavior, our laboratory embarked upon a program of research designed to identify and characterize the role of IL-1 and IL-2 in the hypothalamus and midbrain periaqueductal gray (PAG)--two regions functionally linked through reciprocal anatomical connections--in the regulation of feline defensive rage. A paradigm involved cytokine microinjections into either medial hypothalamus and elicitation of defensive rage behavior from the PAG or vice versa. These studies have revealed that both cytokines have potent effects in modulating defensive rage behavior. With respect to IL-1, this cytokine facilitates defensive rage when microinjected into either the medial hypothalamus or PAG and these potentiating effects are mediated through 5-HT2 receptors. In contrast, the effects of IL-2 are dependent upon the anatomical locus. IL-2 microinjected into the medial hypothalamus suppresses defensive rage and this suppression is mediated through GABA(A) receptors, while microinjections of IL-2 in the PAG potentiate defensive rage, in which these effects are mediated through NK-1 receptors. Present research is designed to further delineate the roles of cytokines in aggressive behavior and to begin to unravel the possible signaling pathways involved this process.

Major histocompatibility complex class II expression by activated microglia caudal to lesions of descending tracts in the human spinal cord is not associated with a T cell response

Lesion-induced microglial/macrophage responses were investigated in post-mortem human spinal cord tissue of 20 patients who had died at a range of survival times after spinal trauma or brain infarction. Caudal to the spinal cord injury or brain infarction, a strong increase in the number of activated microglial cells was observed within the denervated intermediate grey matter and ventral horn of patients who died shortly after the insult (4-14 days). These cells were positive for the leucocyte common antigen (LCA) and for the major histocompatibility complex class II antigen (MHC II), with only a small proportion staining for the CD68 antigen. After longer survival times (1-4 months), MHC II-immunoreactivity (MHC II-IR) was clearly reduced in the grey matter but abundant in the white matter, specifically within the degenerating corticospinal tract, co-localising with CD68. In this fibre tract, elevated MHC II-IR and CD68-IR were still detectable 1 year after trauma or stroke. It is likely that the subsequent expression of CD68 on MHC II-positive microglia reflects the conversion to a macrophage phenotype, when cells are phagocytosing degenerating presynaptic terminals in grey matter target regions at early survival times and removing axonal and myelin debris in descending tracts at later survival times. No T or B cell invasion or involvement of co-stimulatory B7 molecules (CD80 and CD86) was observed. It is possible that the up-regulation of MHC II on microglia that lack the expression of B7 molecules may be responsible for the prevention of a T cell response, thus protecting the spinal cord from secondary tissue damage.

Effect of intrathecal morphine and electro-acupuncture on cellular immune function of rats and increment of mu-opioid receptor mRNA expression in PAG following intrathecal morphine

The present study was to investigate the dynamic changes of cellular immune function of rats with intrathecal injection of (ith) morphine and the regulatory effect of electroacupuncture(EA) stimulation on "Zusanli" (St.36) and "Lanwei" (Extra 37) points. The results showed that ConA-induced rat spleen lymphocyte proliferation was significantly decreased on 2h, 4h, 8h, 12h, 24h, 48h after ith morphine(40microg/50microL). The proliferative response was recovered to nearly normal on 72h. EA on corresponding periods could prevent the decrease of lymphocyte proliferative response of rats induced by ith morphine. The same tendency was observed on the induction of IL-2 production. Further study continued to explore the mechanism of the potentiating effect of mu-opioid receptor in periaqueductal gray (PAG) and hippocampus on the immunosuppression induced by ith morphine at molecular level with in situ hybridization histochemistry technique. The results showed that ith morphine could increase the expression of mu-opioid receptor mRNA.

Suppression of splenic macrophage functions following acute morphine action in the rat mesencephalon periaqueductal gray

Morphine action in the periaqueductal gray (PAG) matter of the mesencephalon suppresses T cell proliferation and NK cell activity through actions at mu opioid receptors. We investigated the effect of acute microinjection of morphine in the rat PAG on macrophage function. We found that morphine injection in the PAG significantly (p <.01) suppressed nitric oxide production by untreated (82 +/- 23% suppression), IFN-gamma-primed (57 +/- 11% suppression), and LPS-activated (50 +/- 7% suppression) splenic macrophages and did not alter macrophage viability. In contrast, IFN-gamma- and LPS-activated macrophages from PAG-injected saline rats generated an increased output of nitric oxide, which was associated with significant (p <.01) reduction in cell viability. Morphine significantly (p <.01) inhibited TNF-alpha production by LPS-activated macrophages (28 +/- 8% inhibition compared with PAG-injected saline rats). In addition, morphine significantly (p <. 05) inhibited phagocytosis of Candida albicans by resident macrophages (40 +/- 20% inhibition compared with that of macrophages from PAG-injected saline rats). Responses of resident or activated macrophages from PAG-injected saline and untreated control groups did not differ significantly. The results of this ex vivo study suggest that suppressive effects of morphine on macrophage functions may contribute to increased susceptibility to infectious diseases and cancer associated with drug abuse.

Substance P receptor (NK1)-immunoreactive neurons projecting to the periaqueductal gray: distribution in the spinal trigeminal nucleus and the spinal cord of the rat

Substance P receptor (SPR)-immunoreactive neurons projecting to the periaqueductal gray (PAG) were examined in the rat spinal trigeminal nucleus and spinal cord by a retrograde tracing method combined with immunofluorescence histochemistry. After injection of Fluoro-gold (FG) into the PAG, SPR-immunoreactive neurons labeled with FG were observed mainly in the lateral spinal nucleus and lamina I of the medullary and spinal dorsal horns and additionally in laminae V and X of the spinal cord.

Transcription factor NF-kappaB and inhibitor I kappaBalpha are localized in macrophages in active multiple sclerosis lesions

NF-kappaB is a transcription factor family which on translocation to the nucleus regulates gene expression during cell activation. As such, NF-kappaB may play a role in the microglial response to myelin damage in multiple sclerosis (MS) lesions. Here the cellular localization of NF-kappaB and expression of the inhibitory I kappaBalpha were examined by immunocytochemistry on central nervous system (CNS) tissue from MS and control cases. In normal control white matter, the active form of the NF-kappaB subunit RelA (p65) was localized in microglial nuclei, while the c-Rel and p50 subunits and the inhibitory I kappaBalpha were restricted to the cytoplasm. In contrast, in actively demyelinating plaques, the RelA, c-Rel, and p50 subunits of NF-kappaB and I kappaBalpha were all present in macrophage nuclei in both parenchymal and perivascular areas. RelA was also found in the nuclei of a subset of hypertrophic astrocytes. Only c-Rel had a nuclear localization in lymphocytes in perivascular inflammatory cuffs. Our results suggest that constitutive activation of the RelA subunit in the nuclei of resting microglia may facilitate a rapid response to pathological stimuli in the CNS. Activation of the inducible NF-kappaB pool in macrophages in MS lesions could amplify the inflammatory reaction through upregulation of NF-kappaB-controlled adhesion molecules and cytokines.

Immunomodulating effects of morphine microinjected into periaqueductal gray

AIM

To study the effects of morphine on immune system through rat brain periaqueductal gray (PAG).

METHODS

Three hours after microinjection of morphine through the implanted steel tubes to PAG, splenic cytokines interleukin 2 (IL-2), interleukin 6 (IL-6), tumor necrosis factor (TNF), and natural killer cells (NK) activity were measured.

RESULTS

Microinjection of morphine (0.5 microL, 3672 ng) into PAG region had no influence on IL-6 and TNF-alpha (production of splenic macrophages, suppressed the natural killer cell (NK) activity and enhanced T-lymphocyte functions, including concanavalin A (Con A)-induced T-cell proliferation, IL-2 and TNF-beta production. Both the suppressive and stimulating actions were blocked by PAG preinjection of the mu opioid receptor antagonist naloxone (0.5 microL, 1 microgram), which alone showed the contrary effect to morphine.

CONCLUSION

Morphine affected immunofunctions through opioid receptors in PAG, and the influences on various immunocompetent cells were different.

Increased fos-like immunoreactivity in the periaqueductal gray of anaesthetised rats during opiate withdrawal

Staining of c-fos-like-immunoreactivity (CFIR) in neurones was used to study neuronal activation within subdivisions of periaqueductal gray (PAG), and in locus coeruleus and ventral tegmental area during opiate withdrawal in awake and anaesthetised, morphine-dependent rats. The number of CFIR containing neurones was significantly increased during naloxone-precipitated withdrawal in lateral and ventrolateral, particularly the caudal ventrolateral PAG. No changes were observed in dorsal-intermediate or dorsal-caudal PAG. In awake rats, a similar but more generalised increase in CFIR was observed in PAG following naloxone-precipitated withdrawal. Increases in ventral tegmental area and locus coeruleus during naloxone-precipitated withdrawal under anaesthesia varied greatly between animals. Induction of c-fos in lateral and ventrolateral PAG during withdrawal is consistent with known functions of these regions, involving the integration of autonomic and somatic components of defensive and escape behaviours which are characteristic signs of opiate withdrawal.

Noxious mechanical stimulation of the hind paws of the anaesthetized rat fails to elicit release of immunoreactive beta-endorphin in the periaqueductal grey matter

As a test of the hypothesis that an animal responds to a severe peripheral painful stimulus by a central release of beta-endorphin, antibody microprobes were inserted stereotactically into the midbrain of urethane anesthetized rats. These microprobes bore antibodies to beta-endorphin immobilized to their outer surfaces. While microprobes were in the brain for periods of 10 to 30 min either no stimulus was delivered or alligator clamps were applied to both hind paws. Microprobes were then incubated with 125I-beta-endorphin. Quantitative image analysis of microprobe autoradiographs showed no differences between the no-stimulus and noxious-stimulus groups. Thus these experiments found no evidence for beta-endorphin release following a severe peripheral painful stimulus.

Projections from serotonin- and substance P-like immunoreactive neurons in the midbrain periaqueductal gray onto the nucleus reticularis gigantocellularis pars alpha in the rat

Serotonin- and substance P-like immunoreactive (5HT-LI and SP-LI) neurons in the midbrain periaqueductal gray (PAG) of the rat were observed to send their axons to the nucleus reticularis gigantocellularis pars alpha (Rgc alpha) by the retrograde horseradish peroxidase (HRP)-tracing method combined with the 5HT- or SP-immunohistochemical technique. These 5HT- or SP-LI PAG neurons were distributed mainly in the ventrolateral subdivision and ventral portion of the medial subdivision at the middle and caudal levels of the PAG, and additionally in the nucleus raphe dorsalis (DR).

Molecular, cellular, and pathologic characterization of HLA-DR immunoreactivity in normal elderly and Alzheimer's disease brain

Previous studies have suggested that markers of immune function may be present in brain. We have characterized one of the most important of these markers, the human major histocompatibility complex antigen HLA-DR, at molecular, cellular, and pathologic levels. The results show that an antigen with the correct molecular weight for HLA-DR and the appropriate immunoreactivity for HLA-DR monoclonal antibodies is present in nondemented elderly (ND) and Alzheimer's disease (AD) brain tissue. HLA-DR immunoreactivity is profusely expressed by brain microglia, often expressed by lymphocytes within the neuropil, rarely expressed by astrocytes, and not expressed by neurons or oligodendrocytes. Pathologically, HLA-DR-like staining in ND patients is confined primarily to white matter nonreactive or resting microglia. In AD patients, both white matter and gray matter are stained, and HLA-DR-positive reactive microglia predominate. Virtually all senile or neuritic plaques are densely HLA-DR immunoreactive: at the plaque core staining intensity is elevated as much as 50-fold, dropping to background at the plaque margin.

Long-lasting neurochemical and functional changes in rats induced by neonatal administration of substance P antiserum

Substance P (SP) antiserum was administered to rats on the second day of life. Three months later, the content of SP was significantly decreased in the dorsal part of the spinal cord and in the periaqueductal gray matter of these animals, as compared to control rats receiving a neonatal treatment of non-specific immunoglobulins. Further, the levels of Met-enkephalin and 5-hydroxyindole acetic acid (5-HIAA) were concomitantly increased in the same regions. SP receptor binding sites and opioid receptors, which appear earlier in development, were not modified in the two regions studied. On the other hand, the antinociceptive response to intracerebroventricular (i.c.v.) injection of SP or of the synthetic enkephalin analog D-Ala2,D-Leu5-enkephalin, as well as the hypertensive response to i.c.v. SP were blocked. The results suggest that, after administration to newborn rats, the antiserum is able to penetrate into SP neurons, producing a long-lasting SP suppression and a subsensitivity to the pharmacological effects of the neuropeptide. The modifications in the content of Met-enkephalin and 5-HIAA are possibly compensatory changes which subserve the functionality of central cardiovascular and pain regulatory systems after the immunolesion.

Somatostatin-like immunoreactivity in the midbrain of the cat

Somatostatin (SS) immunoreactivity was localized in cat brain sections with an immunoperoxidase technique. Cell bodies in the midbrain containing SS immunoreactivity were found in the superficial and intermediate gray layers of the superior colliculus, the interpeduncular nucleus, the raphe, the inferior colliculus and nucleus of its brachium, the nucleus of the optic tract, and the lateral tegmental field. Additional positive neurons were seen in the parabigeminal nucleus and in the dorsal periaqueductal gray in kitten material. Immunoreactive fibers were observed in the periaqueductal gray and in the midbrain tegmentum, with particularly dense labeling just dorsal to the substantia nigra and in the parabrachial nuclei. This is the first report of the distribution of SS immunoreactivity in the midbrain of the cat. It is concluded that somatostatin has a distribution compatible with a role as a major neurotransmitter/neuromodulator within certain midbrain nuclei, especially the interpeduncular nucleus and the superior colliculus.

Localization of Met-enkephalin-like immunoreactivity within pain-related nuclei of cervical spinal cord, brainstem and midbrain in the cat

Met-enkephalin immunoreactivity was investigated with an indirect immunoperoxidase technique in the cervical spinal cord, brainstem and midbrain of the cat, paying special attention to pain-related nuclei. Different technical conditions were used to reveal preferentially met-enkephalin-containing fibres and terminals or perikarya. Immunoreactive fibres and terminals were revealed optimally in sections from control animals incubated with detergent (Triton X-100). Immunoreactive perikarya were revealed in colchicine treated animals. Comparison between different routes of administration showed that local injections of colchicine are needed to reveal optimally immunoreactive perikarya in nuclei located far from the ventricles. Met-enkephalin-containing fibres and terminals are widely distributed in the posterior brain and spinal cord. The densest network of immunoreactive fibers are observed in the superficial layers of the cervical spinal cord and the caudal trigeminal nucleus, in the nucleus of the solitary tract, the nucleus of the facial nerve, the nucleus of the prepositus hypoglossi, the nucleus raphe pallidus, the medial vestibular nucleus, the interpedoncular nucleus and the substantia nigra. A moderate staining of fibres is observed in various nuclei including the ventral horn of the spinal cord and caudal trigeminal nucleus, the brainstem and midbrain reticular formation, the inferior olivary complex, the nucleus of the descending trigeminal tract and the periaqueductal grey. Met-enkephalin-containing perikarya are present in all the nuclei cited before, except in the inferior olivary complex. The densest aggregation of enkephalin-like perikarya is observed in the nucleus raphe magnus, nucleus raphe obscurus, nucleus raphe pallidus, nucleus reticularis gigantocellularis pars alpha and nucleus reticularis lateralis. The general distribution of enkephalin-containing structures in the cervical spinal cord, brainstem and midbrain of the cat appears very similar to that of the rat except in the substantia nigra where met-enkephalin cell bodies are found in the cat but not in the rat. In particular the pain-related nuclei present a similar distribution of the peptide in the two species; however, met-enkephalin-containing cell bodies are much more numerous in the cat than in the rat (notably in the reticular formation). Similar types of met-enkephalin innervation occur in the dorsal and intermediate grey of the spinal cord and of the caudal trigeminal nucleus supporting further that the functional organizations of these regions are closely related.