Peripheral nerve induces macrophage neurotrophic activities: regulation of neuronal process outgrowth, intracellular signaling and synaptic function

Plasma levels of IL-1Ra are associated with schizophrenia

AIM

Although peripheral low-grade inflammation and brain-derived neurotrophic factor (BDNF) levels have been implicated in schizophrenia (SCZ), the interactions between them remain to be fully revealed. We aimed to compare BDNF and cytokines in patients with SCZ and healthy controls (HC). Additionally, we aimed to investigate the association between peripheral levels of cytokines and BDNF in patients with SCZ.

METHODS

Plasma levels of BDNF, interferon gamma, interleukin (IL)-10, IL-12, IL-1, IL-6, IL-8, tumor necrosis factor alpha, macrophage migration inhibitory factor, IL-1 receptor antagonist (IL-1Ra), and CD40 Ligand were compared in 45 SCZ patients and 38 HC using Luminex technology.

RESULTS

Compared to HC, patients had significantly higher IL-1Ra levels (P = 0.031). We found a strong positive association between BDNF and CD40 Ligand in the patient group (rho = 0.858, P < 0.001) as well as in the HC group (rho = 0.822, P < 0.001), respectively. Furthermore, there was a negative association between BDNF and tumor necrosis factor alpha in patients (rho = -0.429, P = 0.030) as well as in HC (rho = -0.649, P < 0.001).

CONCLUSION

These results suggest that the cytokine IL-1Ra may play a role in SCZ pathophysiology. Additionally, the interaction between cytokines and BDNF levels further indicated the diverse actions of these cytokines.

Immune-inflammatory predictors of the pelvic pain syndrome associated with adenomyosis

The aim of the study was the analysis of immune inflammatory processes in the development of the pelvic pain syndrome associated with adenomyosis. For morphological examination were used 54 fragments of the myometrium obtained from patients after hysterectomy with pelvic pain on a background of diffuse adenomyosis of II-III degree, and 20 patients with painless form of adenomyosis. The identification of the macrophages distribution was held by means of an immune-hysto-chemical analysis of MAT (monoclonal antibody) for CD68. (Clone PG-M1, 'Diagnostic BioSystems', USA). The results of the study showed a significantly higher expression of CD68 (49.3 ± 2.3 vs. 21.2 ± 1.7 units. p < .01) in patients with painful adenomyosis form in areas of the ectopic endometrium, in the perivascular regions of the myometrium, as compared to those areas in women with painless group. We assume that these factors increase neurogenic inflammation and sensitivity of nociceptors in myometrium, activation of peripheral nerve fibers and, can act as triggers of the pelvic pain syndrome associated with adenomyosis.

(-)-Epigallocatechin-3-gallate (EGCG) modulates neurological function when intravenously infused in acute and, chronically injured spinal cord of adult rats

Spinal cord injury (SCI) causes severe and long lasting motor and sensory deficits, chronic pain, and autonomic dysreflexia. (-)-epigallocatechin-3-gallate (EGCG) has shown to produce neuroprotective effect in a broad range of neurodegenerative disease animal models. This study designed to test the efficacy of intravenous infusion of EGCG for 36 h, in acutely injured rats' spinal cord: within first 4 h post-injury and, in chronically SC injured rats: after one year of injury. Functional outcomes measured using standard BBB scale, The Louisville Swim Scale (LSS) and, pain behavior assessment tests. 72 Female adult rats subjected to moderate thoracic SCI using MASCIS Impactor, blindly randomized as the following: (I) Acute SCI + EGCG (II) Acute SCI + saline. (III) Chronic SCI + EGCG. (IV) Chronic SCI + saline and, sham SCI animals. EGCG i.v. treatment of acute and, chronic SCI animals resulted in significantly better recovery of motor and sensory functions, BBB and LSS (P < 0.005) and (P < 0.05) respectively. Tactile allodynia, mechanical nociception (P < 0.05) significantly improved. Paw withdrawal and, tail flick latencies increase significantly (P < 0.05). Moreover, in the EGCG treated acute SCI animals the percentage of lesion size area significantly reduced (P < 0.0001) and, the number of neurons in the spinal cord increased (P < 0.001). Percent areas of GAP-43 and GFAP immunohistochemistry showed significant (P < 0.05) increase. We conclude that the therapeutic window of opportunity for EGCG to depict neurological recovery in SCI animals, is viable up to one year post SCI when intravenously infused for 36 h.

The role of neurotrophins in multiple sclerosis-pathological and clinical implications

Multiple sclerosis (MS) is a chronic inflammatory demyelinating and neurodegenerative disease of the central nervous system (CNS) with unknown etiology. It was recently suggested that autoimmunity, which had long been considered to be destructive in MS, might also play a protective role in the CNS of MS patients. Neurotrophins are polypeptides belonging to the neurotrophic factor family. While neurotrophins mediate cell survival and proliferation in the nervous system, they are also expressed within peripheral blood mononuclear cells fraction (PBMCs) of immunological system. In MS additional neurotrophic support from PBMCs might compensate relative neurotrophins deficiency in the damaged CNS tissue that needs to be repaired. Failure to produce the adequate neurotrophins concentrations might result in decreased protection of the CNS, consequently leading to increased atrophy, which is the main determinant of MS patients' end-point disability. There are several lines of evidence, both from clinical research and animal models, suggesting that neurotrophins play a pivotal role in neuroprotective and neuroregenerative processes that are often defective in the course of MS. It seems that neuroprotective strategies might be used as potentially valuable add-on therapies, alongside traditional immunomodulatory treatment in multiple sclerosis.

The role of tumor necrosis factor receptor superfamily members in mammalian brain development, function and homeostasis

Tumor necrosis factor receptor superfamily (TNFRSF) members were initially identified as immunological mediators, and are still commonly perceived as immunological molecules. However, our understanding of the diversity of TNFRSF members' roles in mammalian physiology has grown significantly since the first discovery of TNFRp55 (TNFRSF1) in 1975. In particular, the last decade has provided evidence for important roles in brain development, function and the emergent field of neuronal homeostasis. Recent evidence suggests that TNFRSF members are expressed in an overlapping regulated pattern during neuronal development, participating in the regulation of neuronal expansion, growth, differentiation and regional pattern development. This review examines evidence for non-immunological roles of TNFRSF members in brain development, function and maintenance under normal physiological conditions. In addition, several aspects of brain function during inflammation will also be described, when illuminating and relevant to the non-immunological role of TNFRSF members. Finally, key questions in the field will be outlined.

Acid fibroblast growth factor and peripheral nerve grafts regulate Th2 cytokine expression, macrophage activation, polyamine synthesis, and neurotrophin expression in transected rat spinal cords

Spinal cord injury elicits an inflammatory response that recruits macrophages to the injured spinal cord. Quantitative real-time PCR results have shown that a repair strategy combining peripheral nerve grafts with acidic fibroblast growth factor (aFGF) induced higher interleukin-4 (IL-4), IL-10, and IL-13 levels in the graft areas of rat spinal cords compared with transected spinal cords at 10 and 14 d. This led to higher arginase I-positive alternatively activated macrophage (M2 macrophage) responses. The gene expression of several enzymes involved in polyamine biosynthesis pathways was also upregulated in the graft areas of repaired spinal cords. The treatment induced a twofold upregulation of polyamine levels at 14 d, as confirmed by HPLC. Polyamines are important for the repair process, as demonstrated by the observation that treatment with inhibitors of arginase I and ornithine decarboxylase attenuates the functional recoveries of repaired rats. After 14 d, the treatment also induced the expression of neurotrophin nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), as well as M2 macrophages within grafted nerves expressing BDNF. IL-4 was upregulated in the injury sites of transected rats that received aFGF alone compared with those that received nerve grafts alone at 10 d. Conversely, nerve graft treatment induced NGF and BDNF expression at 14 d. Macrophages expressing polyamines and BDNF may benefit axonal regeneration at 14 d. These results indicate that aFGF and nerve grafts regulate different macrophage responses, and M2 macrophages may play an important role in axonal regeneration after spinal cord injury in rats.

Psychotropic drugs on in vitro brain-derived neurotrophic factor production in whole blood cell cultures from healthy subjects

The aim of this study was to evaluate the effects of certain antidepressant and antipsychotic drugs on the in vitro production of brain-derived neurotrophic factor (BDNF) in whole blood cell culture from healthy volunteers. Whole blood cells from 41 healthy volunteers were stimulated with or without phytohemagglutinin and lipopolysaccharides with treatments of amitriptyline, paroxetine, mirtazapine, and venlafaxine, which are antidepressant drugs, and haloperidol and clozapine, which are antipsychotic drugs. Brain-derived neurotrophic factor levels were measured in supernatants of unstimulated and stimulated whole blood cell cultures. When the effects of each antidepressant agent at the therapeutic concentration were compared with the effects in control subjects using the Wilcoxon test, the in vitro BDNF production was significantly enhanced in the stimulated cultures treated with amitriptyline (P = 0.021). When analyzing the change in the BDNF productions by each of the drugs using the Friedman test, amitriptyline significantly increased the BDNF production in stimulated cultures (P = 0.002), whereas paroxetine, mirtazapine, and venlafaxine did not stimulate the BDNF production (P > 0.05). However, BDNF production by amitriptyline was only increased by 12% to 17%. Haloperidol and clozapine at therapeutic concentrations did not significantly alter the BDNF production in unstimulated and stimulated whole blood cells (P > 0.05). Our study suggests that some antidepressant and antipsychotic agents do not have a direct effect on increasing the BDNF production in whole blood cells during immediate treatment. Thus, the level of BDNF production in human blood cells may not influence the plasma or serum BDNF levels of subjects in clinical studies.

Neuroproteomics approaches to decipher neuronal regeneration and degeneration

Given the complexity of brain and nerve tissues, systematic approaches are essential to understand normal physiological conditions and functional alterations in neurological diseases. Mass spectrometry-based proteomics is increasingly used in neurosciences to determine both basic and clinical differential protein expression, protein-protein interactions, and post-translational modifications. Proteomics approaches are especially useful to understand the mechanisms of nerve regeneration and degeneration because changes in axons following injury or in disease states often occur without the contribution of transcriptional events in the cell body. Indeed, the current understanding of axonal function in health and disease emphasizes the role of proteolysis, local axonal protein synthesis, and a broad range of post-translational modifications. Deciphering how axons regenerate and degenerate has thus become a postgenomics problem, which depends in part on proteomics approaches. This review focuses on recent proteomics approaches designed to uncover the mechanisms and molecules involved in neuronal regeneration and degeneration. It emerges that the principal degenerative mechanisms converge to oxidative stress, dysfunctions of axonal transport, mitochondria, chaperones, and the ubiquitin-proteasome systems. The mechanisms regulating nerve regeneration also impinge on axonal transport, cytoskeleton, and chaperones in addition to changes in signaling pathways. We also discuss the major challenges to proteomics work in the nervous system given the complex organization of the brain and nerve tissue at the anatomical, cellular, and subcellular levels.

The effect of OTK18 upregulation in U937 cells on neuronal survival

The intent of this study was to characterize the effect OTK18 upregulation in monocytic cells had on neuronal survival. The human monocytic cell line, U937, was differentiated into macrophages or left as an undifferentiated monocyte. These cells were transfected with a plasmid containing the enhanced green fluorescent protein and OTK18 (pEGFP-OTK18) or an empty control vector (pEGFP-N3). The supernatants from the transfected U937 cells were used to culture rat neuronal cells (PC12). A live/dead assay was performed to determine the effect of culturing on cell survival. The protein levels of the neurotoxin, tumor necrosis factor alpha (TNF-alpha), and the neurotrophin, neurotrophin three (NT3), were determined by enzyme linked immunosorbent assay. The results of the live/dead assay showed differential cell survival between conditions with pEGFP-OTK18 when compared to the control empty vector. Quantitative real-time polymerase chain reaction assays demonstrated that OTK18 had an increased expression level when compared to the control. Lastly, NT3 protein levels were upregulated in treated cells with increased OTK18 expression, suggesting that OTK18 may play a role in neurotrophin production and consequently support neuronal survival.

Protective autoimmunity in the nervous system

The immune system can play both detrimental and beneficial roles in the nervous system. Multiple arms of the immune system, including T cells, B cells, NK cells, mast cells, macrophages, dendritic cells, microglia, antibodies, complement and cytokines participate in limiting damage to the nervous system during toxic, ischemic, hemorrhagic, infective, degenerative, metabolic and immune-mediated insults and also assist in the process of repair after injury has occurred. Immune cells have been shown to produce neurotrophic growth factors and interact with neurons and glial cells to preserve them from injury and stimulate growth and repair. The immune system also appears to participate in proliferation of neural progenitor stem cells and their migration to sites of injury. Neural stem cells can also modify the immune response in the central and peripheral nervous system to enhance neuroprotective effects. Evidence for protective and reparative functions of the immune system has been found in diverse neurologic diseases including traumatic injury, ischemic and hemorrhagic stroke, multiple sclerosis, infection, and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis). Existing therapies including glatiramer acetate, interferon-beta and immunoglobulin have been shown to augment the protective and regenerative aspects of the immune system in humans, and other experimental interventions such as vaccination, minocycline, antibodies and neural stem cells, have shown promise in animal models of disease. The beneficent aspects of the immune response in the nervous system are beginning to be appreciated and their potential as pharmacologic targets in neurologic disease is being explored.

Low and dysregulated BDNF secretion from immune cells of MS patients is related to reduced neuroprotection

Multiple sclerosis (MS) is characterized by lesions with inflammatory infiltration, demyelination and axonal damage in the CNS white matter that correlates with the extent of disease disability. Knowledge of up-regulatory triggers of neuroprotective pathways in the CNS is essential for the development of the next generation of disease therapies. Recent studies have suggested a neuroprotective activity of the lesion-infiltrating immune cells. We studied the secretion of brain-derived neurotrophic factor (BDNF) from the immune cells of untreated patients with relapsing remitting (RR) MS with mild to moderate disability and sought immune factors that regulate the BDNF levels and affect the survival of neuronal cells in vitro. We found lower than normal secreted levels of BDNF from the immune cells of these patients. The normal effect of CD40 stimulation that up-regulates BDNF secretion levels and induces neuroprotection was absent in the MS patients, while the expression of CD40 on their monocytes was elevated. The failure of BDNF availability from immune cells in patients with RR-MS and the loss of a neuroprotective effect by these cells may be related to a more widespread phenomenon of deviated immunity in MS, and may be linked to the continuous CNS neuronal tissue loss during the course of this disease.

Axon growth across a lesion site along a preformed guidance pathway in the brain

Our previous studies showed that axonal outgrowth from dorsal root ganglia (DRG) transplants in the adult rat brain could be directed toward a specific target location using a preformed growth-supportive pathway. This pathway induced axon growth within the corpus callosum across the midline to the opposite hemisphere. In this study, we examined whether such pathways would also support axon growth either through or around a lesion of the corpus callosum. Pathways expressing GFP, NGF, or FGF2/NGF were set up by multiple injections of adenovirus along the corpus callosum. Each pathway included the transplantation site in the left corpus callosum, 2.8 mm away from the midline, and a target site in the right corpus callosum, 2.5 mm from the midline. At the same time, a 1 mm lesion was made through the corpus callosum at the midline in an anteroposterior direction. A group of control animals received lesions and Ad-NGF injections only at the transplant and target sites, without a bridging pathway. DRG cell suspensions from postnatal day 1 or 2 rats were injected at the transplantation site three to four days later. Two weeks after transplantation, brain sections were stained using an anti-CGRP antibody. The CGRP+ axons were counted at 0.5 mm and 1.5 mm from the lesion site in both hemispheres. Few axons grew past the lesion in animals with control pathways, but there was robust axon growth across the lesion site in the FGF2/NGF and NGF-expressing pathways. This study indicated that preformed NGF and combination guidance pathways support more axon growth past a lesion in the adult mammalian brain.

Macrophage depletion in the murine olfactory epithelium leads to increased neuronal death and decreased neurogenesis

Apoptosis of olfactory sensory neurons (OSNs) induced by olfactory bulbectomy (OBX) leads to the activation of resident macrophages within the olfactory epithelium (OE). These macrophages phagocytose degenerating OSNs and secrete chemokines, which recruit additional macrophages into the OE, and cytokines/growth factors, which regulate basal cell proliferation and differentiation and maturation of OSNs. In this study we apply for the first time the use of liposome-encapsulated clodronate to selectively deplete macrophages during the OSN degeneration/regeneration cycle in order to elucidate the role(s) of macrophages in regulating cellular mechanisms that lead to apoptosis and neurogenesis. Mice were injected intranasally and intravenously with either liposome-encapsulated clodronate or empty liposomes prior to and after OBX or sham OBX. At 48 hours after surgery the numbers of macrophages in the OE of both sham and OBX clodronate-treated mice were significantly reduced compared to liposome-treated controls (38% and 35%, respectively, P < 0.05). The reduction in macrophage numbers was accompanied by significant decreases in OE thickness (22% and 21%, P < 0.05), the number of mOSNs (1.2- and 1.9-fold, P < 0.05), and basal cell proliferation (7.6- and 3.8-fold, P < 0.005) in sham and OBX mice, respectively, compared to liposome-treated controls. In OBX mice there was also increased immunoreactivity for active caspase-3 in the OE and olfactory nerves of clodronate-treated OBX mice compared to liposome-treated controls. These results indicate that macrophages modulate the OSN population in the normal and target-ablated murine OE by influencing neuronal survival and basal cell proliferation, resulting in neurogenesis and replacement of mature OSNs.

Genomic and proteomic microglial profiling: pathways for neuroprotective inflammatory responses following nerve fragment clearance and activation

Microglia, a primary immune effector cell of the central nervous system (CNS) affects homeostatic, neuroprotective, regenerative and degenerative outcomes in health and disease. Despite these broad neuroimmune activities linked to specific environmental cues, a precise cellular genetic profile for microglia in the context of disease and repair has not been elucidated. To this end we used nucleic acid microarrays, proteomics, immunochemical and histochemical tests to profile microglia in neuroprotective immune responses. Optic and sciatic nerve (ON and SN) fragments were used to stimulate microglia in order to reflect immune consequences of nervous system injury. Lipopolysaccharide and latex beads-induced microglial activation served as positive controls. Cytosolic and secreted proteins were profiled by surface enhanced laser desorption ionization-time of flight (SELDI-TOF) ProteinChip, 1D and 2D difference gel electrophoresis. Proteins were identified by peptide sequencing with tandem mass spectrometry, ELISA and western blot tests. Temporal expression of pro-inflammatory cytokines, antioxidants, neurotrophins, and lysosomal enzyme expression provided, for the first time, a unique profile of secreted microglia proteins with neuroregulatory functions. Most importantly, this molecular and biochemical signature supports a broad range of microglial functions for debris clearance and promotion of neural repair after injury.

Delayed GM‐CSF treatment stimulates axonal regeneration and functional recovery in paraplegic rats via an increased BDNF expression by endogenous macrophages

Macrophages (monocytes/microglia) could play a critical role in central nervous system repair. We have previously found a synchronism between the regression of spontaneous axonal regeneration and the deactivation of macrophages 3-4 wk after a compression-injury of rat spinal cord. To explore whether reactivation of endogenous macrophages might be beneficial for spinal cord repair, we have studied the effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in the same paraplegia model and in cell cultures. There was a significant, though transient, improvement of locomotor recovery after a single delayed intraperitoneal injection of 2 microg GM-CSF, which also increased significantly the expression of Cr3 and brain-derived neurotrophic factor (BDNF) by macrophages at the lesion site. At longer survival delays, axonal regeneration was significantly enhanced in GM-CSF-treated rats. In vitro, BV2 microglial cells expressed higher levels of BDNF in the presence of GM-CSF and neurons cocultured with microglial cells activated by GM-CSF generated more neurites, an effect blocked by a BDNF antibody. These experiments suggest that GM-CSF could be an interesting treatment option for spinal cord injury and that its beneficial effects might be mediated by BDNF.

Chronic stress induces upregulation of brain-derived neurotrophic factor (BDNF) mRNA and integrin alpha5 expression in the rat pineal gland

Chronic stress affects brain areas involved in learning and emotional responses. These alterations have been related with the development of cognitive deficits in major depression. Moreover, stress induces deleterious actions on the epithalamic pineal organ, a gland involved in a wide range of physiological functions. The aim of this study was to investigate whether the stress effects on the pineal gland are related with changes in the expression of neurotrophic factors and cell adhesion molecules. Using reverse transcription-polymerase chain reaction (RT-PCR) and Western blot, we analyzed the effect of chronic immobilization stress on the BDNF mRNA and integrin alpha5 expression in the rat pineal gland. We found that BDNF is produced in situ in the pineal gland. Chronic immobilization stress induced upregulation of BDNF mRNA and integrin alpha5 expression in the rat pineal gland but did not produce changes in beta-actin mRNA or in GAPDH expression. Stressed animals also evidenced an increase in anxiety-like behavior and acute gastric lesions. These results suggest that BDNF and integrin alpha5 may have a counteracting effect to the deleterious actions of immobilization stress on functionally stimulated pinealocytes. Furthermore, this study proposes that the pineal gland may be a target of glucocorticoid damage during stress.

Immune-Based Therapy for Spinal Cord Repair: Autologous Macrophages and Beyond

Spinal cord injury is a devastating condition of the central nervous system (CNS), often resulting in severe loss of tissue, functional impairment, and only limited repair. Studies over the last few years have shown that response to the insult and spontaneous attempts at repair are multiphasic processes, with varying and sometimes conflicting requirements. This knowledge has led to novel strategies of therapeutic intervention. Our view is that a pivotal role in repair, maintenance, healing, and cell renewal in the CNS, as in other tissues, is played by the immune system. The mode and timing of intervention must be carefully selected, however, as the capacity of the CNS to tolerate local repair mechanisms is limited. Studies have shown that the spontaneously evoked early innate response to CNS injury is characterized by invasion of neutrophils and is unfavorable for cell survival. This is followed by a response of the resident innate immune cells (microglia), which however cannot supply all the needs of the damaged tissue; moreover, once evoked, and for as long as the damage persists, the microglial response remains beyond the capacity of the CNS to tolerate it. Immune-based clinical intervention is most effective in improving functional and morphological recovery when delayed for a certain period. Effective intervention might be in the form of (1) local injection of "alternatively activated" macrophages, (2) systemic injection of dendritic cells specific to CNS antigens, or (3) T-cell-based vaccination. The treatment of choice depends on the severity of the insult, the site of injury, the therapeutic window, and safety considerations.

Classification of HIV-1-mediated neuronal dendritic and synaptic damage using multiple criteria linear programming

The ability to identify neuronal damage in the dendritic arbor during HIV-1-associated dementia (HAD) is crucial for designing specific therapies for the treatment of HAD. To study this process, we utilized a computer-based image analysis method to quantitatively assess HIV-1 viral protein gp120 and glutamate-mediated individual neuronal damage in cultured cortical neurons. Changes in the number of neurites, arbors, branch nodes, cell body area, and average arbor lengths were determined and a database was formed (http://dm.ist.unomaha. edu/database.htm). We further proposed a two-class model of multiple criteria linear programming (MCLP) to classify such HIV-1-mediated neuronal dendritic and synaptic damages. Given certain classes, including treatments with brain-derived neurotrophic factor (BDNF), glutamate, gp120 or non-treatment controls from our in vitro experimental systems, we used the two-class MCLP model to determine the data patterns between classes in order to gain insight about neuronal dendritic damages. This knowledge can be applied in principle to the design and study of specific therapies for the prevention or reversal of neuronal damage associated with HAD. Finally, the MCLP method was compared with a well-known artificial neural network algorithm to test for the relative potential of different data mining applications in HAD research.

Neuroregulatory events follow adaptive immune-mediated elimination of HIV-1-infected macrophages: studies in a murine model of viral encephalitis

HIV-1-specific cellular immunity serves to eliminate infected cells and disease. However, how this process specifically affects the CNS is poorly understood. To mirror the regulatory events that occur in human brain after HIV-1 infection, a murine model of viral encephalitis was used to study relationships, over time, among lymphocyte-mediated infected cell elimination, innate immune responses, and neuropathology. Nonobese diabetic SCID mice were reconstituted with human PBL and a focal encephalitis induced by intracranial injection of autologous HIV-1-infected, monocyte-derived macrophages (MDM). On days 7, 14, and 21 after MDM injection into the basal ganglia, the numbers of human lymphocytes and mouse monocytes, virus-infected MDM, glial (astrocyte and microglial) responses, cytokines, inducible NO (iNOS), neurotrophic factors, and neuronal Ags were determined in brain by immunohistochemistry, real-time PCR, and Western blot assays. Microglia activation, astrocytosis, proinflammatory cytokines, and iNOS expression accompanied the loss of neuronal Ags. This followed entry of human lymphocytes and mouse monocytes into the brain on days 7 and 14. Elimination of virus-infected human MDM, expression of IL-10, neurotropins, and a down-regulation of iNOS coincided with brain tissue restoration. Our results demonstrate that the degree of tissue damage and repair parallels the presence of infected macrophages and effectors of innate and adaptive immunity. This murine model of HIV-1 encephalitis can be useful in elucidating the role played by innate and adaptive immunity in disease progression and resolution.

Rapid disease development in scrapie-infected mice deficient for CD40 ligand

The inhibition of CD40-CD40L interaction-mediated signalling was suggested as a therapeutic strategy for the treatment of Alzheimer's disease. Conversely, CD40-deficient neurons were reported to be more vulnerable to stress associated with ageing as well as nerve growth factor-beta and serum withdrawal. We studied the scrapie infection of CD40L-deficient (CD40L(-/-)) mice to see whether ablation of the CD40L gene would be beneficial or detrimental in this model of a neurodegenerative amyloidosis. CD40L(-/-) mice died on average 40 days earlier than wild-type control mice and exhibited a more pronounced vacuolation of the neuropil and an increased microglia activation. The experimental model indicates that a deficiency for CD40L is highly detrimental in prion diseases and reinforces the neuroprotective function of intact CD40-CD40L interactions. The stimulation of neuroprotective pathways may represent a possibility to delay therapeutically the disease onset in prion infections of the central nervous system.