Effect of naturally occurring α-synuclein-antibodies on toxic α-synuclein-fragments.

Alpha-synuclein (α-Syn) is a soluble protein primarily expressed in presynaptic terminals in the central nervous system (CNS). Aggregates of fibrillated α-Syn are the major component of Lewy bodies (LB), a pathologic hallmark of idiopathic Parkinson's disease (PD). Recently, naturally occurring autoantibodies against human α-Syn (nAbs α-Syn) were detected in the peripheral blood of PD patients and controls. Here, we investigated the inhibitory effects of nAbs α-Syn on distinct α-Syn fragments, as well as inflammatory responses and cytotoxicity evoked by nAbs α-Syn in primary microglia. All α-Syn fragments induced the release of the pro-inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) from microglia in primary culture. Cotreatment with nAbs α-Syn alleviated the release of pro-inflammatory cytokines induced by α-Syn fragments α-Syn 1-95, α-Syn 61-140, α-Syn 96-140 and α-Syn 112. Treatment with the α-Syn fragments α-Syn 1-95, α-Syn 61-140 and α-Syn 112 impaired the viability of primary microglia. This effect could not be counteracted by cotreatment with nAbs α-Syn. Data suggest an important role of nAbs α-Syn in the α-Syn-induced inflammation cascade, and indicate the potential importance of nAbs in the pathogenesis of PD. This could provide an experimental therapeutic target for patients with PD.

The multi-target effects of CNI-1493: convergence of anti-amylodogenic and anti-inflammatory properties in animal models of Alzheimer's disease.

After several decades of Alzheimer's disease (AD) research and failed clinical trials, one can speculate that targeting a single pathway is not sufficient. However, a cocktail of novel therapeutics will constitute a challenging clinical trial. A more plausible approach will capitalize on a drug that has relevant and synergistic multiple-target effects in AD. We have previously demonstrated the efficacy of CNI-1493 in the CRND8 transgenic AD mouse model. Similar to many anti-inflammatory drugs that were tested in preclinical model of AD, it was speculated that the significant effect of CNI-1493 is due to its established anti-inflammatory properties in rodents and humans. In the present study, we set out to elucidate the protective mechanism of CNI-1493 as a drug simultaneously targeting several aspects of AD pathology. Using C1213, a highly similar analogue of CNI-1493 that lacks anti-inflammatory properties, we show that both compounds directly interact with soluble and insoluble Amyloid ß (Aß) aggregates and attenuate Aß cytotoxicity in vitro. Additionally, CNI-1493 and C1213 ameliorated Aß-induced behavioral deficits in nematodes. Finally, C1213 reduced Aß plaque burden and cognitive deficits in transgenic CRND8 mice to a similar extent as previously shown with CNI-1493. Taken together, our findings suggest anti-amyloidogenic activity as a relevant component for the in-vivo efficacy of CNI-1493 and its analogue C1213. Thus, CNI-1493, a drug with proven safety in humans, is a viable candidate for novel multi-target therapeutic approaches to AD.

Glucocerebrosidase deficiency and mitochondrial impairment in experimental Parkinson disease.

Gaucher disease is an autosomal recessive disease, caused by a lack or functional deficiency of the lysosomal enzyme, glucocerebrosidase (GCase). Recently, mutations in the glucocerebrosidase gene (GBA) have been associated with Parkinson's disease (PD) and GBA mutations are now considered the most important genetic vulnerability factor for PD. In this study, we have investigated (i) in vivo whether inhibition of the enzyme glucosylceramide synthase by miglustat may protect C57Bl/6 mice against subchronic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication and (ii) in vitro whether a decrease of GCase activity may render dopaminergic neurons susceptible to MPP(+) (1-methyl-4-phenylpyridinium) or alpha-synuclein (α-Syn) toxicity and amenable to miglustat treatment. We could demonstrate that reduction of glucocerebroside by inhibition of glucosylceramide synthase partially protects mice against MPTP-induced toxicity. Conversely, we could show that inhibition of GCase activity with conduritol-B-epoxide (CBE) enhances both α-Syn and MPP(+) induced toxicity in vitro. However, only CBE-induced enhancement of MPP(+) toxicity could be reversed by miglustat. Moreover, we were unable to reveal any alterations of complex I activity or cell respiration upon treatment with either CBE or miglustat. Our findings suggest that the reduction of GCase activity rather than an accumulation of glucocerebroside increases aSyn toxicity.

Heat shock protein 60: an endogenous inducer of dopaminergic cell death in Parkinson disease.

BACKGROUND: Increasing evidence suggests that inflammation associated with microglial cell activation in the substantia nigra (SN) of patients with Parkinson disease (PD) is not only a consequence of neuronal degeneration, but may actively sustain dopaminergic (DA) cell loss over time. We aimed to study whether the intracellular chaperone heat shock protein 60 (Hsp60) could serve as a signal of CNS injury for activation of microglial cells. METHODS: Hsp60 mRNA expression in the mesencephalon and the striatum of C57/BL6 mice treated with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) and the Hsp60/TH mRNA ratios in the SN of PD patients and aged-matched subjects were measured. To further investigate a possible link between the neuronal Hsp60 response and PD-related cellular stress, Hsp60 immunoblot analysis and quantification in cell lysates from SH-SY5Y after treatment with 100 µM MPP+ (1-methyl-4-phenylpyridinium) at different time points (6, 12, 24 and 48 hours) compared to control cells were performed. Additional MTT and LDH assay were used. We next addressed the question as to whether Hsp60 influences the survival of TH+ neurons in mesencephalic neuron-glia cultures treated either with MPP+ (1 µM), hHsp60 (10 µg/ml) or a combination of both. Finally, we measured IL-1ß, IL-6, TNF-α and NO-release by ELISA in primary microglial cell cultures following treatment with different hHsp60 preparations. Control cultures were exposed to LPS. RESULTS: In the mesencephalon and striatum of mice treated with MPTP and also in the SN of PD patients, we found that Hsp60 mRNA was up-regulated. MPP+, the active metabolite of MPTP, also caused an increased expression and release of Hsp60 in the human dopaminergic cell line SH-SY5Y. Interestingly, in addition to being toxic to DA neurons in primary mesencephalic cultures, exogenous Hsp60 aggravated the effects of MPP+. Yet, although we demonstrated that Hsp60 specifically binds to microglial cells, it failed to stimulate the production of pro-inflammatory cytokines or NO by these cells. CONCLUSIONS: Overall, our data suggest that Hsp60 is likely to participate in DA cell death in PD but via a mechanism unrelated to cytokine release.

The α7 nAChR agonist PNU-282987 reduces inflammation and MPTP-induced nigral dopaminergic cell loss in mice.

BACKGROUND: Parkinson's disease (PD) is associated with neurodegeneration of dopaminergic neurons and an accompanying neuroinflammatory process in the substantia nigra (SN). The cholinergic anti-inflammatory signalling pathway allows the autonomic nervous system to modulate immunologic stimuli and inflammatory processes. A major component of this pathway is the α7 nicotinic acetylcholine receptor (α7 nACh receptor), which is expressed on immune cells such as microglia. OBJECTIVE: To determine the role of this cholinergic anti-inflammatory signalling pathway, we investigated the effects of the selective α7 nACh agonist PNU-282987 and of the non-competitive nACh antagonist mecamylamine on microglia-induced neuroinflammation and toxin-induced degeneration of dopaminergic neurons in a mouse model of PD. METHODS: PNU-282987, mecamylamine or placebo administration was started one day before MPTP intoxication and repeated daily until sacrifice after MPTP intoxication. C57Bl/6 mice were injected intraperitoneally four times at 2 h intervals with either 20 mg/kg MPTP-HCl or a corresponding volume of saline. Two or seven days after the end of the MPTP intoxication, the animals were killed and their brains were processed for further analysis. RESULTS: Treatment with PNU-282987 resulted in an attenuation of neuroinflammation in the MPTP-lesioned SN. Furthermore, PNU-282987 attenuated MPTP-induced dopaminergic cell loss in the SN and reduced striatal dopamine depletion. Unexpectedly, mecamylamine lowered neuroinflammation as well, though it did not show a neuroprotective potential at the nigral level. CONCLUSIONS: Our results demonstrate the therapeutic potential of the selective α7 nicotinic acetylcholine agonist PNU-282987 in attenuating neuroinflammation and toxin-induced loss of dopaminergic neurons in the acute MPTP mouse model of PD.

Probenecid potentiates MPTP/MPP+ toxicity by interference with cellular energy metabolism.

The uricosuric agent probenecid is co-administered with the dopaminergic neurotoxin MPTP to produce a chronic mouse model of Parkinson's disease. It has been proposed that probenecid serves to elevate concentrations of MPTP in the brain by reducing renal elimination of the toxin. However, this mechanism has never been formally demonstrated to date and is questioned by our previous data showing that intracerebral concentrations of MPP(+), the active metabolite of MPTP, are not modified by co-injection of probenecid. In this study, we investigated the potentiating effects of probenecid in vivo and in vitro arguing against the possibility of altered metabolism or impaired renal elimination of MPTP. We find that probenecid (i) is toxic in itself to several neuronal populations apart from dopaminergic neurons, and (ii) that it also potentiates the effects of other mitochondrial complex I inhibitors such as rotenone. On a mechanistic level, we show that probenecid is able to lower intracellular ATP concentrations and that its toxic action on neuronal cells can be reversed by extracellular ATP. Probenecid can potentiate the effect of mitochondrial toxins due to its impact on ATP metabolism and could therefore be useful to model atypical parkinsonian syndromes.

Bee venom and its component apamin as neuroprotective agents in a Parkinson disease mouse model.

Bee venom has recently been suggested to possess beneficial effects in the treatment of Parkinson disease (PD). For instance, it has been observed that bilateral acupoint stimulation of lower hind limbs with bee venom was protective in the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. In particular, a specific component of bee venom, apamin, has previously been shown to have protective effects on dopaminergic neurons in vitro. However, no information regarding a potential protective action of apamin in animal models of PD is available to date. The specific goals of the present study were to (i) establish that the protective effect of bee venom for dopaminergic neurons is not restricted to acupoint stimulation, but can also be observed using a more conventional mode of administration and to (ii) demonstrate that apamin can mimic the protective effects of a bee venom treatment on dopaminergic neurons. Using the chronic mouse model of MPTP/probenecid, we show that bee venom provides sustained protection in an animal model that mimics the chronic degenerative process of PD. Apamin, however, reproduced these protective effects only partially, suggesting that other components of bee venom enhance the protective action of the peptide.

Toll like receptor 4 mediates cell death in a mouse MPTP model of Parkinson disease.

In mammalians, toll-like receptors (TLR) signal-transduction pathways induce the expression of a variety of immune-response genes, including inflammatory cytokines. It is therefore plausible to assume that TLRs are mediators in glial cells triggering the release of cytokines that ultimately kill DA neurons in the substantia nigra in Parkinson disease (PD). Accordingly, recent data indicate that TLR4 is up-regulated by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in a mouse model of PD. Here, we wished to evaluate the role of TLR4 in the acute mouse MPTP model of PD: TLR4-deficient mice and wild-type littermates control mice were used for the acute administration way of MPTP or a corresponding volume of saline. We demonstrate that TLR4-deficient mice are less vulnerable to MPTP intoxication than wild-type mice and display a decreased number of Iba1+ and MHC II+ activated microglial cells after MPTP application, suggesting that the TLR4 pathway is involved in experimental PD.

CNI-1493 attenuates neuroinflammation and dopaminergic neurodegeneration in the acute MPTP mouse model of Parkinson's disease.

BACKGROUND: Parkinson's disease (PD) is associated with neurodegeneration of dopaminergic neurons in the substantia nigra. Neuroinflammatory processes have been shown to be a key component of this neurodegeneration and, as such, small molecule compounds which inhibit these inflammatory events are a critical research focus. OBJECTIVE: CNI-1493 is an anti-inflammatory compound that strongly inhibits macrophages and also stimulates the cholinergic anti-inflammatory pathway. We have examined whether CNI-1493 has a neuroprotective effect in the acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD. METHODS: CNI-1493 (8 mg/kg i.p.) or placebo administration was started 1 day before MPTP intoxication and repeated daily until sacrifice after MPTP intoxication. C57/Bl6 mice - either treated with CNI-1493 or with placebo - were injected intraperitoneally 4 times at 2-hour intervals with either 20 mg/kg MPTP-HCl or a corresponding volume of saline. Two or 7 days after the end of the MPTP intoxication, the animals were killed and their brains were processed for further analysis. RESULTS: Administration of CNI-1493 markedly protected tyrosine hydroxylase-positive substantia nigra neurons against MPTP neurotoxicity. CNI-1493 treatment in the MPTP model was also accompanied by a profound reduction of activated microglia within the substantia nigra, as measured by ionized calcium-binding adapter molecule-1 staining. CONCLUSIONS: These findings support that CNI-1493 could reduce the MPTP-induced toxicity likely by inhibition of neuroinflammatory responses. The neuroprotective effect of CNI-1493 suggests that CNI-1493 might be a valuable neuroprotective candidate in the future treatment of PD.

Naturally occurring α-synuclein autoantibody levels are lower in patients with Parkinson disease.

OBJECTIVE: Biomarkers are required for the diagnosis and monitoring of disease progression in Parkinson disease (PD). To date, most studies have concentrated on α-synuclein (α-Syn), a protein involved in Parkinson disease pathogenesis, as a potential biomarker, with inconsistent outcomes. Recently, naturally occurring autoantibodies against α-Syn (α-Syn-nAbs) have been detected in the serum of patients with PD. They represent a putative diagnostic marker for PD. METHODS: We established and validated an ELISA to quantify α-Syn-nAbs in serum samples. We analyzed serum samples from 62 patients with PD, 46 healthy controls (HC), and 42 patients with Alzheimer disease (AD) using this newly established ELISA. Additionally, serum levels of endogenous α-Syn were measured. RESULTS: There was a significant difference in α-Syn-nAbs levels between the investigated groups (p = 0.005; Kruskal-Wallis test). Levels of α-Syn-nAbs were significantly lower in patients with PD compared to HC (p < 0.05; Dunn multiple comparison post hoc test) or patients with AD (p < 0.05). Furthermore, we detected no difference between patients with AD and HC. The sensitivity and specificity of the assay for patients with PD vs. HC were 85% and 25%, respectively. The α-Syn-nAbs levels did not correlate with age, Hoehn & Yahr status, or duration of disease. Endogenous α-Syn had no influence on α-Syn-nAbs levels in sera. CONCLUSIONS: Using a well-validated assay, we detected reduced α-Syn-nAbs levels in patients with PD compared to patients with AD and HC. The assay did not achieve criteria for use as a diagnostic tool to reliably distinguish PD from HC. Further studies are needed to assess α-Syn-nAbs as a biomarker in PD.

Differentially expressed gene profile in the 6-hydroxy-dopamine-induced cell culture model of Parkinson's disease.

Parkinson's disease (PD) is a chronic neurodegenerative disorder characterized by progressive loss of dopaminergic (DA) neurons of the substantia nigra pars compacta with unknown aetiology. 6-Hydroxydopamine (6-OHDA) treatment of neuronal cells is an established in vivo model for mimicking the effect of oxidative stress found in PD brains. We examined the effects of 6-OHDA treatment on human neuroblastoma cells (SH-SY5Y) and primary mesencephalic cultures. Using a reverse arbitrarily primed polymerase chain reaction (RAP-PCR) approach we generated reproducible genetic fingerprints of differential expression levels in cell cultures treated with 6-OHDA. Of the resulting sequences, 23 showed considerable homology to known human coding sequences. The results of the RAP-PCR were validated by reverse transcription PCR, real-time PCR and, for selected genes, by Western blot analysis and immunofluorescence. In four cases, [tomoregulin-1 (TMEFF-1), collapsin response mediator protein 1 (CRMP-1), neurexin-1, and phosphoribosylaminoimidazole synthetase (GART)], a down-regulation of mRNA and protein levels was detected. Further studies will be necessary on the physiological role of the identified proteins and their impact on pathways leading to neurodegeneration in PD.

Blood-based protein biomarkers for diagnosis and classification of neurodegenerative diseases: current progress and clinical potential.

Biomarker research is a rapidly advancing field in medicine. Recent advances in genomic, genetic, epigenetic, neuroscientific, proteomic, and metabolomic knowledge and technologies have opened the way to thriving research. In the most general sense, a biomarker refers to any useful characteristic that can be measured and used as an indicator of a normal biologic process, a pathogenic process, or a pharmacologic response to a therapeutic agent. Despite the extensive resources concentrated on this area, there are very few biomarkers currently available that qualify and are satisfactorily validated for mental disorders, and there is still a major lack of biomarkers for typifying neurodegenerative disorders such as Alzheimer's disease and Parkinson's disease. This article provides an overview of this field of research and focuses on recent advances in biomarker research in Alzheimer's disease and Parkinson's disease.

Naturally occurring autoantibodies against beta-amyloid: investigating their role in transgenic animal and in vitro models of Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative disorder primarily affecting regions of the brain responsible for higher cognitive functions. Immunization against ß-amyloid (Aß) in animal models of AD has been shown to be effective on the molecular level but also on the behavioral level. Recently, we reported naturally occurring autoantibodies against Aß (NAbs-Aß) being reduced in Alzheimer's disease patients. Here, we further investigated their physiological role: in epitope mapping studies, NAbs-Aß recognized the mid-/C-terminal end of Aß and preferentially bound to oligomers but failed to bind to monomers/fibrils. NAbs-Aß were able to interfere with Aß peptide toxicity, but NAbs-Aß did not readily clear senile plaques although early fleecy-like plaques were reduced. Administration of NAbs-Aß in transgenic mice improved the object location memory significantly, almost reaching performance levels of wild-type control mice. These findings suggest a novel physiological mechanism involving NAbs-Aß to dispose of proteins or peptides that are prone to forming toxic aggregates.

Role of macrophage migration inhibitory factor in primary glioblastoma multiforme cells.

Macrophage migration inhibitory factor (MIF) is a protein that is overexpressed in many tumors, such as colon and prostate cancer, melanoma, and glioblastoma multiforme (GBM). In its function as a cytokine, MIF induces angiogenesis, promotes cell cycle progression, and inhibits apoptosis. Recently, the molecular signal transduction has been specified: MIF has been found to be a ligand to the CD74/CD44-receptor complex and to activate the ERK1/2 MAPK cascade. In addition MIF binds to the chemokine receptors CXCR2 and CXCR4. This effects an integrin-dependent leukocyte arrest and mediates leukocyte chemotaxis. Recent work has described a clearer role of MIF in GBM tumor cell lines. The current study used human primary GBM cells. We show that inhibition of MIF with ISO-1, an inhibitor of the D-dopachrome tautomerase site of MIF, reduced the growth rate of primary GBM cells in a dose-dependent manner, and in addition ISO-1 increased protein expression of MIF and its receptors CD74, CXCR2, and CXCR4 in vitro but decreased expression of CD44. Furthermore, hypoxia as cell stressor increases the protein expression of MIF in primary GBM cells. These results underscore the importance of MIF in GBM and show that MIF and its receptors may be a promising target for the treatment of malignant gliomas.

Intravenous immunoglobulins as a treatment for Alzheimer's disease: rationale and current evidence.

Current treatment options for Alzheimer's disease (AD) exert only a short-lived effect on disease symptoms. Active and passive immunotherapy have both been shown to be effective in clearing plaques, removing beta-amyloid (Abeta) and improving behaviour in animal models of AD. Although the first active immunization trial in humans was discontinued because of severe adverse effects, several new approaches are currently being investigated in clinical trials. Recently, commercially available intravenous immunoglobulins (IVIG) have been used in small pilot trials for the treatment of patients with AD, based on the hypothesis that IVIG contains naturally occurring autoantibodies (nAbs-Abeta) that specifically recognize and block the toxic effects of Abeta. Furthermore, these nAbs-Abeta are reduced in AD patients compared with healthy controls, supporting the notion of replacement with IVIG. Beyond the occurrence of nAbs-Abeta, evidence for several other mechanisms associated with IVIG in AD has been reported in preclinical experiments and clinical studies. In 2009, a phase III clinical trial involving more than 360 AD patients was initiated and may provide conclusive evidence for the effect of IVIG as a treatment option for AD in 2011. In this article, we review the current knowledge and scientific rationale for using IVIG in patients with AD and other neurodegenerative disorders.

Midregional Proenkephalin A and N-terminal Protachykinin A are decreased in the cerebrospinal fluid of patients with dementia disorders and acute neuroinflammation.

Midregional Proenkephalin A (MR-PENK A) and N-terminal Protachykinin A (NT-PTA) are stable fragments of the precursor peptides for enkephalins and substance P, respectively. We measured MR-PENK A and NT-PTA concentrations by sensitive chemiluminescence immunoassays in cerebrospinal fluid (CSF) of 19 neurologically healthy controls (NHC), 28 patients with other neurologic disorders (OND), 70 patients with dementia disorders (38 Alzheimer's disease [AD], 8 dementia with Lewy bodies [DLB], 12 frontotemporal dementia [FTD], and 12 patients with vascular dementia [VD]), and 16 patients with acute neuroinflammation (AN). Median concentrations of NT-PTA were decreased in all patient groups compared to NHC showing significant differences between patients with NHC and AN (p<0.001), OND and AN (p<0.001), FTD and AN (p<0.01) and pAD and AN (p<0.05). Median MR-PENK A levels were lower in patients with OND, dementia disorders (including AD, FTD, DLB and VD) and AN compared to NHC subjects, although this differences did not reach statistical significance (p>0.05). A maximum difference of both proneuropeptide fragments was found between NHC subjects and patients with AN, with a more than 2fold decrease in median NT-PTA and a 1.5fold decrease in median MR-PENK A levels. Concentrations of both proneuropeptide fragments were positively correlated in all patients (r=0.77, p<0.001). Our results indicate alterations of the cerebral PENK A- and PTA-system in both, dementia and acute neuroinflammatory disorders. These neuropeptide systems seem to be highly correlated in healthy and pathological status.

The role of macrophage migration inhibitory factor in Alzheimer's disease.

Previous studies have shown that amyloid beta protein (Abeta ), the essential molecule for the formation of toxic oligomers and, subsequently, Alzheimer plaques, has been associated in vivo with the immune modulator, macrophage migration inhibitory factor (MIF) (17). To further investigate this association in vivo we used the APP transgenic mouse model. Serial brain sections of transgenic APP mice were stained for Abeta plaques and MIF and we observed MIF immunolabeling in microglial cells in association with Abeta plaques in the transgenic mouse brain sections. In addition, functional studies in murine and human neuronal cell lines revealed that Abeta-induced toxicity could be reversed significantly by a small molecule inhibitor of MIF (ISO-1). Finally, to elucidate the role of MIF in Alzheimer's Disease (AD) we measured MIF levels in the brain cytosol and cerebrospinal fluid (CSF) of AD patients and age-matched controls. Our results demonstrate a marked increase of MIF levels within the CSF of AD patients compared with controls. Combined, our results indicate a strong role for MIF in the pathogenesis of AD and furthermore suggest that inhibition of MIF may provide a valuable avenue of investigation for the prevention of disease onset, progression and/or severity.

Copper deficiency associated with severe neurological disorder--a genetic work-up of possible mutations in copper transport proteins.

BACKGROUND: Copper deficiency has been described as resulting in severe neurological impairment. However, mechanisms underlying a copper deficiency are presently unknown. PATIENTS AND METHODS: We describe three patients suffering from severe spasticity, ataxia and hyperreflexia and had laboratory evidence of copper deficiency. RESULTS: Genetic analysis of six copper transporters/chaperones revealed no mutations, but two SNPs in one copper transporter protein and one copper chaperone. CONCLUSIONS: Owing to the severity of the disease further research is required to elucidate the mechanisms leading to copper deficiency.

Peripheral and central biodistribution of (111)In-labeled anti-beta-amyloid autoantibodies in a transgenic mouse model of Alzheimer's disease.

Active as well as passive immunization against beta-amlyoid (Abeta) has been proposed as a treatment to lower cerebral amyloid burden and stabilize cognitive decline in Alzheimer's disease (AD). To clarify the mechanism of action underlying passive immunization, the in vivo distribution (and sites of degradation) of peripherally administered radiolabeled human and mouse anti-Abeta antibodies were analyzed in a transgenic mouse model of AD. In APP23 mice, a model in which mutated human amyloid precursor protein is overexpressed, the biodistribution of intravenously applicated (111)indium-conjugated affinity-purified human polyclonal autoantibodies (NAbs-Abeta) was compared to that of monoclonal anti-Abeta(1-17) (6E10), anti-Abeta(17-24) antibodies (4G8) and anti-CD-20 (Rituximab), a non-Abeta targeting control. Blood clearance half-lives were 50+/-6h for Rituximab, 20-30h for NAbs-Abeta, 29+/-5h for 4G8 and 27+/-3h for 6E10. Blood activity was higher for 6E10 at 4h as compared to 4G8, Rituximab and NAbs-Abeta. At the 96h time point, Rituximab had the highest blood activity among the antibodies tested. As expected, all antibodies displayed hepatobiliary clearance. Additionally, NAbs-Abeta was excreted in the urinary tract. Liver and kidney uptake of NAbs-Abeta increased over time and was higher than in the monoclonal antibodies at 48h/96h. The brain-to-blood radioactivity ratio for NAbs-Abeta at later time points (>48h) was higher than that of 6E10, 4G8 and Rituximab. In addition, the distribution varied, with highest values found in the hippocampus. Our data indicate a cerebral accumulation of human NAbs-Abeta in the APP23 model. Further studies with human immunoglobulins and particularly with those that recognize different Abeta-epitopes are required in order to delineate in more detail the mode of action of NAbs-Abeta.