Peripheral injections of Freund's adjuvant in mice provoke leakage of serum proteins through the blood-brain barrier without inducing reactive gliosis

Absence of functional alternative complement pathway alleviates lupus cerebritis

The complement inhibitor, Crry, which blocks both the classical and alternative pathways, alleviates CNS disease in the lupus model, MRL/MpJ-Tnfrsf6lpr (MRL/lpr) mice. To understand the role of the alternative pathway, we studied mice deficient in a key alternative pathway protein, complement factor B (fB). Immune deposits (IgG and C3) were reduced in the brains of MRL/lpr fB-deficient (fB-/-MRL/lpr) compared to fB-sufficient (MRL/lpr) mice, indicating reduced complement activation. Reduced neutrophil infiltration (22% of MRL/lpr mice) and apoptosis (caspase-3 activity was reduced to 33% of MRL/lpr mice) in these mice indicates that the absence of the alternative pathway was neuroprotective. Furthermore, expression of phospho (p)-Akt (0.16+/-0.02 vs. 0.35+/-0.13, p<0.03) was increased, while expression of p-PTEN (0.40+/-0.06 vs. 0.11+/-0.07, p<0.05) was decreased in fB-/-MRL/lpr mice compared to their MRL/lpr counterparts. The expression of fibronectin, laminin and collagen IV was significantly decreased in fB-/-MRL/lpr mice compared to MRL/lpr mice, indicating that in the lupus setting, tissue integrity was maintained in the absence of the alternative pathway. Absence of fB reduced behavioral alterations in MRL/lpr mice. Our results suggest that in lupus, the alternative pathway may be the key mechanism through which complement activation occurs in brain, and therefore it might serve as a therapeutic target for lupus cerebritis.

Microglial activation in the hippocampus of hypercholesterolemic rabbits occurs independent of increased amyloid production

Background

Rabbits maintained on high-cholesterol diets are known to show increased immunoreactivity for amyloid beta protein in cortex and hippocampus, an effect that is amplified by presence of copper in the drinking water. Hypercholesterolemic rabbits also develop sporadic neuroinflammatory changes. The purpose of this study was to survey microglial activation in rabbits fed cholesterol in the presence or absence of copper or other metal ions, such as zinc and aluminum.

Methods

Vibratome sections of the rabbit hippocampus and overlying cerebral cortex were examined for microglial activation using histochemistry with isolectin B₄ from Griffonia simplicifolia. Animals were scored as showing either focal or diffuse microglial activation with or without presence of rod cells.

Results

Approximately one quarter of all rabbits fed high-cholesterol diets showed evidence of microglial activation, which was always present in the hippocampus and not in the cortex. Microglial activation was not correlated spatially with increased amyloid immunoreactivity or with neurodegenerative changes and was most pronounced in hypercholesterolemic animals whose drinking water had been supplemented with either copper or zinc. Controls maintained on normal chow were largely devoid of neuroinflammatory changes, but revealed minimal microglial activation in one case.

Conclusion

Because the increase in intraneuronal amyloid immunoreactivity that results from administration of cholesterol occurs in both cerebral cortex and hippocampus, we deduce that the microglial activation reported here, which is limited to the hippocampus, occurs independent of amyloid accumulation. Furthermore, since neuroinflammation occurred in the absence of detectable neurodegenerative changes, and was also not accompanied by increased astrogliosis, we conclude that microglial activation occurs because of metabolic or biochemical derangements that are influenced by dietary factors.

P2X3 receptor involvement in pain states

The understanding of how pain is processed at each stage in the peripheral and central nervous system is the precondition to develop new therapies for the selective treatment of pain. In the periphery, ATP can be released from various cells as a consequence of tissue injury or visceral distension and may stimulate the local nociceptors. The highly selective distribution of P2X(3) and P2X(2/3) receptors within the nociceptive system has inspired a variety of approaches to elucidate the potential role of ATP as a pain mediator. Depolarization by ATP of neurons in pain-relevant neuronal structures such as trigeminal ganglion, dorsal root ganglion, and spinal cord dorsal horn neurons are well investigated. P2X receptor-mediated afferent activation appears to have been implicated in visceral and neuropathic pain and even in migraine and cancer pain. This article reviews recently published research describing the role that ATP and P2X receptors may play in pain perception, highlighting the importance of the P2X(3) receptor in different states of pain.

Mouse model mimics multiple sclerosis in the clinico-radiological paradox

The value of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis, in deriving novel diagnostic and therapeutic input has been subject to recent debate. This study is the first to report a disseminated distribution of plaques including cranial nerves, prior to or at early stages of disease in murine adoptive transfer EAE, irrespective of the development of clinical symptoms. We induced EAE by adoptive proteolipid protein-specific T-cell transfer in 26 female SJL/J mice, and applied high-field-strength magnetic resonance imaging (MRI) scans longitudinally, assessing blood-brain barrier (BBB) disruption by gadopentate dimeglumine enhancement. We visualized inflammatory nerve injury by gadofluorine M accumulation, and phagocytic cells in inflamed tissue by very small anionic iron oxide particles (VSOP-C184). MRI was correlated with immunohistological sections. In this study, we discovered very early BBB breakdown of white and grey brain matter in 25 mice; one mouse developed exclusively spinal cord inflammation. Widely disseminated contrast-enhancing lesions preceded the onset of disease in 10 animals. Such lesions were present despite the absence of any clinical disease formation in four mice, and coincided with the first detectable symptoms in others. Cranial nerves, predominantly the optic and trigeminal nerves, showed signal intensity changes in nuclei and fascicles of 14 mice. At all sites of MRI lesions we detected cellular infiltrates on corresponding histological sections. The discrepancy between the disease burden visualized by MRI and the extent of disability indeed mimics the human clinico-radiological paradox. MRI should therefore be implemented into evaluational in vivo routines of future therapeutic EAE studies.

Fusion antibody for Alzheimer's disease with bidirectional transport across the blood-brain barrier and abeta fibril disaggregation

Delivery of monoclonal antibody therapeutics across the blood-brain barrier is an obstacle to the diagnosis or therapy of CNS disease with antibody drugs. The immune therapy of Alzheimer's disease attempts to disaggregate the amyloid plaque of Alzheimer's disease with an anti-Abeta monoclonal antibody. The present work is based on a three-step model of immune therapy of Alzheimer's disease: (1) influx of the anti-Abeta monoclonal antibody across the blood-brain barrier in the blood to brain direction, (2) binding and disaggregation of Abeta fibrils in brain, and (3) efflux of the anti-Abeta monoclonal antibody across the blood-brain barrier in the brain to blood direction. This is accomplished with the genetic engineering of a trifunctional fusion antibody that binds (1) the human insulin receptor, which mediates the influx from blood to brain across the blood-brain barrier, (2) the Abeta fibril to disaggregate amyloid plaque, and (3) the Fc receptor, which mediates the efflux from brain to blood across the blood-brain barrier. This fusion protein is a new antibody-based therapeutic for Alzheimer's disease that is specifically engineered to cross the human blood-brain barrier in both directions.

Adenosine and ATP receptors

Adenosine and ATP, via P1 and P2 receptors respectively, can modulate pain transmission under physiological, inflammatory, and neuropathic pain conditions. Such influences reflect peripheral and central actions and effects on neurons as well as other cell types. In general, adenosine A1 receptors produce inhibitory effects on pain in a number of preclinical models and are a focus of attention. In humans, i.v. infusions of adenosine reduce some aspects of neuropathic pain and can reduce postoperative pain. For P2X receptors, there is a significant body of information indicating that inhibition of P2X3 receptors may be useful for relieving inflammatory and neuropathic pain. More recently, data have begun to emerge implicating P2X4, P2X7 and P2Y receptors in aspects of pain transmission. Both P1 and P2 receptors may represent novel targets for pain relief.

Blood-brain barrier delivery

Neuropharmaceutics is the largest potential growth sector of the pharmaceutical industry. However, this growth is blocked by the problem of the blood-brain barrier (BBB). Essentially 100% of large-molecule drugs and >98% of small-molecule drugs do not cross the BBB. The BBB can be traversed because there are multiple endogenous transporters within this barrier. Therefore, brain drug development programs of the future need to be re-configured so that drugs are formulated to enable transport into the brain via endogenous BBB transporters.

Peripheral inflammation and neuroprotection: systemic pretreatment with complete Freund's adjuvant reduces 6-hydroxydopamine toxicity in a rodent model of Parkinson's disease

Complete Freund's adjuvant (CFA), a pro-inflammatory agent, was inoculated, subcutaneously, to Sprague-Dawley rats prior to the intrastriatal injection of 6-hydroxydopamine (6-OHDA). Animals were sacrificed 7 and 28 days following 6-OHDA injection; neuronal damage, glial activation and cytokine levels, within the nigrostriatal system, were then investigated. Nigrostriatal degeneration induced by 6-OHDA was accompanied by early microglial and astroglial activation, which preceded the onset of dopaminergic cell loss, in the SNc, without significant changes in cytokine levels. CFA pretreatment markedly reduced the SNc neuronal loss and associated microglial activation, as well as the rotational response to apomorphine. These changes were associated with moderate, transient increases in the nigrostriatal levels of glial-cell-derived neurotrophic factor (GDNF) and pro-inflammatory cytokines, including interleukin (IL)-1alpha, IL-1beta and IL-6. Our results show that prior delivery of a peripheral, pro-inflammatory stimulus induces neuroprotection, in a rodent model of Parkinson's disease, possibly through the modulation of cytokine production at the nigrostriatal level.

Mouse brain IgG-like immunoreactivity: strain-specific occurrence in microglia and biochemical identification of IgG

Unlike the brains of most mammals, the mouse brain appears unique in the massive appearance of cells showing IgG-like immunoreactivity, which has repeatedly been shown via immunohistochemistry. In the present study, we first examined possible species differences in IgG-like immunohistochemical staining in the brains of various rodents, including mice. In four of six mouse strains examined (ICR, Balb/c, C57BL/6, and AKR/J), antibodies against mouse IgG revealed positive staining in many brain microglia. However, no such positive staining was detected in brains of the rat, hamster, guinea pig, or two other mouse strains (CBA/N and CBA/J). We purified IgG-like-immunoreactive molecule(s) biochemically from brain of the ICR mouse as a representative mouse strain. Our amino-acid-sequence analysis proved that the purified protein was identical to serum IgG. The possibility of IgG synthesis by brain microglia in the ICR mouse was denied by our RT-PCR experiments and in situ hybridization histochemistry. In addition, Fcgamma-receptor-deficient double-knockout mice of the C57BL/6 genetic background contained no IgG-immunoreactive microglia in the brain. These results clearly indicate that microglial IgG staining is due to the uptake of serum IgG through Fcgamma receptors. However, the strain-specific mechanisms resulting in microglial IgG uptake remain to be elucidated, in that Fcgamma receptors are omnipresent in microglia of all rodents examined here.

The blood-brain barrier: bottleneck in brain drug development

The blood-brain barrier (BBB) is formed by the brain capillary endothelium and excludes from the brain approximately 100% of large-molecule neurotherapeutics and more than 98% of all small-molecule drugs. Despite the importance of the BBB to the neurotherapeutics mission, the BBB receives insufficient attention in either academic neuroscience or industry programs. The combination of so little effort in developing solutions to the BBB problem, and the minimal BBB transport of the majority of all potential CNS drugs, leads predictably to the present situation in neurotherapeutics, which is that there are few effective treatments for the majority of CNS disorders. This situation can be reversed by an accelerated effort to develop a knowledge base in the fundamental transport properties of the BBB, and the molecular and cellular biology of the brain capillary endothelium. This provides the platform for CNS drug delivery programs, which should be developed in parallel with traditional CNS drug discovery efforts in the molecular neurosciences.

Immunization with myelin oligodendrocyte glycoprotein and complete Freund adjuvant partially protects dopaminergic neurons from 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced damage in mouse model of Parkinson's disease

The concept of neuroprotective immunity identifies a new role of autoimmune cells in the CNS pathology. Specifically, immune cells infiltrating the CNS during an injury may help in a regeneration process and prevent the secondary degeneration of neurons. The objectives of our study were to determine the role of autoimmune and peripheral immune enhancement in neurodegeneration process, and to compare the results between young adult and aging animals. C57Bl mice were immunized with either myelin oligodendrocyte glycoprotein (MOG) 35-55 combined with complete Freund adjuvant (CFA), or CFA alone. Following 6 days, the animals were injected with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to produce a damage of the nigrostriatal dopaminergic system. Although immunization with MOG 35-55 combined with CFA resulted in autoimmune encephalomyelosis, it substantially enhanced neuronal survival after the toxic insult. The immunization with CFA alone was also effective in preventing neuronal cell death, but the magnitude of the neuroprotective effect was smaller. Interestingly, the neuroprotective effect of MOG 35-55 and CFA was more pronounced in aging (i.e. 10-month-old) compared with young (i.e. 2-month-old) mice. Our results indicate that an increased immune activation may be beneficial for neurodegenerative processes following the CNS injury, but the mechanisms of such immune neuroprotection and of age differences need further investigation.

Chronic inflammatory pain leads to increased blood-brain barrier permeability and tight junction protein alterations

The blood-brain barrier (BBB) maintains brain homeostasis by limiting entry of substances to the central nervous system through interaction of transmembrane and intracellular proteins that make up endothelial cell tight junctions (TJs). Recently it was shown that the BBB can be modulated by disease pathologies including inflammatory pain. This study examined the effects of chronic inflammatory pain on the functional and molecular integrity of the BBB. Inflammatory pain was induced by injection of complete Freund's adjuvant (CFA) into the right plantar hindpaw in female Sprague-Dawley rats under halothane anesthesia; control animals were injected with saline. Edema and hyperalgesia were assessed by plethysmography and infrared paw-withdrawal latency. At 72 h postinjection, significant edema formation and hyperalgesia were noted in the CFA-treated rats. Examination of permeability of the BBB by in situ perfusion of [14C]sucrose while rats were under pentobarbital anesthesia demonstrated that CFA treatment significantly increased brain sucrose uptake. Western blot analysis of BBB TJ proteins showed no change in expression of zonula occludens-1 (an accessory protein) or actin (a cytoskeletal protein) with CFA treatment. Expression of the transmembrane TJ proteins occludin and claudin-3 and -5 significantly changed with CFA treatment with a 60% decrease in occludin, a 450% increase in claudin-3, and a 615% increase in claudin-5 expression. This study demonstrates that during chronic inflammatory pain, alterations in BBB function are associated with changes in specific transmembrane TJ proteins.

Extravasation of blood-borne immunoglobulin G through blood-brain barrier during adrenaline-induced transient hypertension in the rat

The effect of transient hypertension on blood-brain barrier (BBB) permeability, particularly on extravasation of immunoglobulin G (IgG), has not been fully understood. In the present experiment, we investigated the time course of endogenous albumin and IgG extravasation through BBB and the localization of extravasated IgG in brain parenchyma during adrenaline(AD)-induced transient hypertension in the rat by using Evans blue fluorescence, immunohistochemistry, and Western blot. The results showed that a bolus injection of AD (10 microg/kg) induced a transient elevation of arterial pressure lasting about 1 min. The endogenous albumin and IgG entered the brain parenchyma via BBB only when hypertension occurred. Electron microscopically, the IgG-like immunoreactivities were predominantly seen in the cytoplasm of endothelia of capillaries, pericytes, extracellular space of parenchyma, and the cytoplasm of glial cells. The results suggest that circulating IgG or antibodies might contact the structures of brain parenchyma through passage of BBB when its permeability is temporally changed by transient hypertension. This phenomenon implies a possible mechanism of pathogenesis for immune-mediated diseases in the brain.

Induction of experimental autoimmune encephalomyelitis in Dark Agouti rats without adjuvant

Experimental autoimmune encephalomyelitis (EAE) is a well-recognized model for multiple sclerosis (MS) in humans. However, adjuvants used with encephalitogens to induce EAE produce non-specific effects interfering with the mechanisms involved in the autoimmune response to the central nervous system (CNS) tissue. It is therefore important to establish a more suitable model of EAE for analysis of autoimmune phenomena resembling those operative in MS. Here we report that EAE can be induced regularly in Dark Agouti (DA) strain of rats with spinal cord tissue without any adjuvant, as judged by both clinical and histological parameters. The incidence and severity of EAE depended on the origin of the encephalitogen, the rat versus guinea pig spinal cord homogenate being more efficient. Furthermore, EAE could be reinduced in animals which had recovered from disease that had been induced actively with encephalitogen alone, suggesting the role of adjuvant-generated non-specific mechanisms in resistance to reinduction of EAE. Thus, EAE induced in DA rats with encephalitogen alone provides a reproducible model for defining pathogenically relevant events in CNS autoimmunity devoid of the potentially misleading effects of adjuvants.

A murine model for neuropsychiatric disorders associated with group A beta-hemolytic streptococcal infection

A syndrome of motoric and neuropsychiatric symptoms comprising various elements, including chorea, hyperactivity, tics, emotional lability, and obsessive-compulsive symptoms, can occur in association with group A beta-hemolytic streptococcal (GABHS) infection. We tested the hypothesis that an immune response to GABHS can result in behavioral abnormalities. Female SJL/J mice were immunized and boosted with a GABHS homogenate in Freund's adjuvant, whereas controls received Freund's adjuvant alone. When sera from GABHS-immunized mice were tested for immunoreactivity to mouse brain, a subset was found to be immunoreactive to several brain regions, including deep cerebellar nuclei (DCN), globus pallidus, and thalamus. GABHS-immunized mice having serum immunoreactivity to DCN also had increased IgG deposits in DCN and exhibited increased rearing behavior in open-field and hole-board tests compared with controls and with GABHS-immunized mice lacking serum anti-DCN antibodies. Rearing and ambulatory behavior were correlated with IgG deposits in the DCN and with serum immunoreactivity to GABHS proteins in Western blot. In addition, serum from a GABHS mouse reacted with normal mouse cerebellum in nondenaturing Western blots and immunoprecipitated C4 complement protein and alpha-2-macroglobulin. These results are consistent with the hypothesis that immune response to GABHS can result in motoric and behavioral disturbances and suggest that anti-GABHS antibodies cross-reactive with brain components may play a role in their pathophysiology.

DNA vaccination against mutant huntingtin ameliorates the HDR6/2 diabetic phenotype

Immunization against extracellular neurotoxic proteins has shown promise in the treatment of several neurodegenerative disorders. We sought to determine whether immunization against mutant huntingtin, the intracellular protein that causes Huntington's disease (HD), could slow disease progression in the HD mouse model HDR6/2. DNA vaccination was used to present the mutant intracellular antigen to the immune system in a physiological context. Assay of a peripheral biomarker, pancreatic insufficiency, was used as an initial test of efficacy. DNA vaccination with a 5' fragment of the HD cDNA prevented development of the HDR6/2 diabetic phenotype. Insulin staining demonstrated that HDR6/2 diabetes may be caused by a severe pancreatic insulin deficiency. Immunoresponsive HDR6/2 mice showed increased insulin staining more closely resembling wild-type levels. These observations suggest that DNA vaccination against toxic intracellular proteins may be therapeutic.

Mechanisms of Disease: The Blood-Brain Barrier

OBJECTIVE

The blood-brain barrier (BBB) is often perceived as a passive membrane. However, evidence has demonstrated that the BBB plays an active role in normal homeostasis and in certain disease processes.

METHODS

Approximately 300 peer-reviewed publications that discussed normal or abnormal BBB function were reviewed.

RESULTS

The role of the BBB and how it contributes to disorders of the central nervous system vary, depending on the specific disease process.

CONCLUSION

In health and disease and extending to old age, endothelial cells, neurons, and glia constitute a neurovascular unit that regulates the BBB. Advances toward penetrating the BBB must account for both normal and abnormal functions of the neurovascular unit.

Pertussis toxin-induced reversible encephalopathy dependent on monocyte chemoattractant protein-1 overexpression in mice

In this report we describe pertussis toxin-induced reversible encephalopathy dependent on monocyte chemoattractant protein-1 (MCP-1) overexpression (PREMO), a novel animal model that exhibits features of human encephalopathic complications of inflammatory disorders such as viral meningoencephalitis and Lyme neuroborreliosis as well as the mild toxic encephalopathy that commonly precedes relapses of multiple sclerosis (MS). Overexpression of the mouse MCP-1 gene product (classically termed JE) in astrocytes, the major physiological CNS cellular source of MCP-1, failed to induce neurological impairment. Unexpectedly, transgenic (tg) mice overexpressing MCP-1 at a high level (MCP-1(hi)) manifested transient, severe encephalopathy with high mortality after injections of pertussis toxin (PTx) plus complete Freund's adjuvant (CFA). Surviving mice showed markedly improved function and did not relapse during a prolonged period of observation. Tg mice that expressed lower levels of MCP-1 were affected minimally after CFA/PTx injections, and tg expression of other chemokines failed to elicit this disorder. The disorder was significantly milder in mice lacking T-cells, which therefore play a deleterious role in this encephalopathic process. Disruption of CC chemokine receptor 2 (CCR2) abolished both CNS inflammation and encephalopathy, identifying CCR2 as a relevant receptor for this disorder. Proinflammatory and type 1 cytokines including TNF-alpha, IL-1beta, IFN-gamma, IL-2, RANTES, and IP-10 were elevated in CNS tissues from mice with PREMO. These studies characterize a novel model of reversible inflammatory encephalopathy that is dependent on both genetic and environmental factors.

Acute experimental allergic encephalomyelitis increases lumbar spinal cord incorporation of epidurally administered [(3)H]-D-mannitol and [(14)C]-carboxyl-inulin in rabbits

We sought to determine whether acute experimental allergic encephalomyelitis (EAE) alters the incorporation of epidurally administered [(3)H]-D-mannitol and [(14)C]-carboxyl-inulin into the lumbar spinal cord in rabbits. Acute EAE is an experimental model for demyelinating spinal cord diseases such as multiple sclerosis. It was induced in rabbits by footpad inoculation with rabbit spinal cord homogenate, resulting in hind limb paresis or paralysis. Animals were classified into four study groups: Control, Paraparesis, 1-Day Paraplegia, and 5-Day Paraplegia. Ten microCi each of [(3)H]-D-mannitol and [(14)C]-carboxyl-inulin were administered epidurally for 90 min. After infusion, animals were perfused with saline. The lumbar cord was dissected and divided into 11 segments. Compared with other groups, animals in the 5-Day Paraplegia group had greater incorporation of [(3)H]-D-mannitol and [(14)C]-carboxyl-inulin in lumbar segment 8, corresponding to the location of the epidural catheter tip. Compared with the Control group, EAE animals had increased [(3)H]-D-mannitol incorporation in various lumbar segments. Increases in the spinal cord incorporation of epidural drugs with EAE suggest that demyelination may render the spinal cord susceptible to larger amounts of substances administered in the epidural space. These findings may have implications regarding neurotoxicity in association with demyelinating spinal cord disease.

IMPLICATIONS

Acute experimental allergic encephalomyelitis, a disease model for multiple sclerosis, increased spinal cord incorporation of radioactive drugs administered in the epidural space. We conclude that demyelinating disease processes may expose the spinal cord to larger amounts of substances administered neuraxially.

Induction of type 1 immune pathology in the brain following immunization without central nervous system autoantigen in transgenic mice with astrocyte-targeted expression of IL-12

IL-12, a cytokine produced by microglia, may regulate cellular immunity at a localized level in the CNS. To investigate this further, we examined the consequences of peripheral immune stimulation without specific autoantigen in wild-type or transgenic (termed GF-IL12) mice with astrocyte production of the bioactive IL-12 p75 heterodimer. Active immunization with CFA and pertussis toxin, a procedure known to stimulate a robust type 1-biased immune response, produced CNS immune pathology from which GF-IL12 but not wild-type mice developed signs of clinical disease consisting of loss of activity, piloerection, mild tremor, and motor change. All immunized mice had some degree of mononuclear cell infiltration into the brain; however, the severity of this was markedly increased in GF-IL12 mice where leukocytes accumulated in perivascular and parenchymal locations. Accumulating cells consisted of CD4(+) and CD8(+) T cells and macrophage/microglia. Moreover, expression of cytokines (IFN-gamma and TNF), chemokines (IFN-inducible protein-10 and RANTES), the immune accessory molecules, MHC class II, B7.2, ICAM-1 and VCAM-1, and NO synthase-2 was induced in the CNS of the GF-IL12 mice. Therefore, peripheral immunization of GF-IL12 but not wild-type mice can provoke active type 1 immunity in the brain-a process that does not require CNS-specific immunizing autoantigen. These findings indicate that the cytokine milieu of a tissue can dramatically influence the development of intrinsic immune responses and associated pathology.

Amyloid beta peptide as a vaccine for Alzheimer's disease involves receptor-mediated transport at the blood-brain barrier

Much research is now focused on a potential vaccine for Alzheimer's disease (AD). Current studies involve administering the amyloid beta peptide (Abeta) in Freund's complete adjuvant, which cannot be used in humans. Our studies show that the immune complex of Abeta is taken up by a receptor-mediated process at the blood-brain barrier (BBB). The success of immunization for AD, therefore, may be critically dependent on circulating Abeta levels which are lower in AD patients compared to AD transgenic mice. Moreover, we have found that modifying the antibody with polyamine increases its BBB permeability and may provide a better approach to passive immunization for Alzheimer's disease.

Astrogliosis in the adult and developing CNS: is there a role for proinflammatory cytokines?

Astrogliosis, characterized by the enhanced expression of GFAP, represents a remarkably homotypic response of astrocytes to all types of injuries of the CNS, including injuries of the developing CNS. As such, astrocytes serve as microsensors of the injured microenvironment regardless of their location in the CNS. The diversity of insults that engender astrogliosis and the brain-wide nature of the astrocytic response suggest that common injury factors serve as the trigger of this cellular reaction. One prominent theme that has emerged in recent years is that proinflammatory cytokines and chemokines serve as a stimulus for induction of astrogliosis. Here we present a brief critique of this hypothesis based on a review of literature and some of our own recentfindings. Studies of astrocytes, in vitro, clearly indicate that these cell types are responsive to a variety of growth factors, including cytokines and chemokines. A somewhat different picture, however, can be seen from data obtained in vivo. It is true that trauma and diseases of the nervous system, as well as some exposures to neurotoxic chemicals, can be associated with the expression in brain of large varieties of cytokines and chemokines. That these same conditions result in astrogliosis has fostered the circumstantial link between cytokine/chemokine expression and the induction of astrogliosis. Several lines of evidence argue against this view, including (a) suppression of cytokine expression does not suppress gliosis, (b) gliosis can occur in the absence of enhanced expression of cytokines, (c) elevations in brain cytokines can occur in the absence of gliosis and (d) the patterns of cytokine expression in the adult and developing CNS are more consistent with a trophic role for these chemical messengers rather than a role in the induction of inflammation. Enhanced expression of cytokines and chemokines after brain injury appear to be signal transduction events unrelated to the induction of astrogliosis.

Distribution of albumin nanoparticles in animals induced with the experimental allergic encephalomyelitis

Experimental allergic encephalomyelitis (EAE) is an autoimmune disease characterised by a disruption of the blood-brain barrier (BBB), demyelination and a relevant inflammatory reaction with an intense infiltration of macrophages. These neurological disorders are similar to those observed in the multiple sclerosis (MS) disease. The use of different liposomes and adeno-associated virus has been proposed for improving the treatment of this pathogenesis. The aim of this work was to evaluate the potential and capacity of albumin nanoparticles to reach the central nervous system (CNS) in EAE-induced rats. For this purpose, the distribution of biotinylated nanoparticles within the CNS was studied. Albumin carriers were mainly found in the lumbar portion of the spinal cord, overlying the meningeal and perivascular areas. The optic chiasma, iris and the area of the Purkinje cells of the cerebellum revealed also an intense presence of these carriers. Finally, immunohistochemical studies also revealed that circulating macrophages (ED1), which migrate to damaged sites, and resident activated microglial cells (OX42) were involved in the distribution of albumin nanoparticles. In summary, the use of nanoparticles may be useful for the design of new pharmaceutical dosage forms able to target the lesions associated with alterations of the BBB.