Mitochondrial DNA polymorphisms specifically modify cerebral ß-amyloid proteostasis.

Several lines of evidence link mutations and deletions in mitochondrial DNA (mtDNA) and its maternal inheritance to neurodegenerative diseases in the elderly. Age-related mutations of mtDNA modulate the tricarboxylic cycle enzyme activity, mitochondrial oxidative phosphorylation capacity and oxidative stress response. To investigate the functional relevance of specific mtDNA polymorphisms of inbred mouse strains in the proteostasis regulation of the brain, we established novel mitochondrial congenic mouse lines of Alzheimer's disease (AD). We crossed females from inbred strains (FVB/N, AKR/J, NOD/LtJ) with C57BL/6 males for at least ten generations to gain specific mitochondrial conplastic strains with pure C57BL/6 nuclear backgrounds. We show that specific mtDNA polymorphisms originating from the inbred strains differentially influence mitochondrial energy metabolism, ATP production and ATP-driven microglial activity, resulting in alterations of cerebral ß-amyloid (Aß) accumulation. Our findings demonstrate that mtDNA-related increases in ATP levels and subsequently in microglial activity are directly linked to decreased Aß accumulation in vivo, implicating reduced mitochondrial function in microglia as a causative factor in the development of age-related cerebral proteopathies such as AD.

Comprehensive Characterization of the Pyroglutamate Amyloid-ß Induced Motor Neurodegenerative Phenotype of TBA2.1 Mice.

Alzheimer's disease (AD) is the most common neurodegenerative disorder and is being intensively investigated using a broad variety of animal models. Many of these models express mutant versions of human amyloid-ß protein precursor (AßPP) that are associated with amyloid-ß protein (Aß)-induced early onset familial AD. Most of these models, however, do not develop bold neurodegenerative pathology and the respective phenotypes. Nevertheless, this may well be essential for their suitability to identify therapeutically active compounds that have the potential for a curative or at least disease-modifying therapy in humans. In this study, the new transgenic mouse model TBA2.1 was explored in detail to increase knowledge about the neurodegenerative process induced by the presence of pyroglutamate modified human Aß3-42 (pEAß3-42). Analysis of the sensorimotor phenotype, motor coordination, Aß pathology, neurodegeneration, and gliosis revealed formation and progression of severe pathology and phenotypes including massive neuronal loss in homozygous TBA2.1 mice within a few months. In contrast, the start of a slight phenotype was observed only after 21 months in heterozygous mice. These data highlight the role of pEAß3-42 in the disease development and progression of AD. Based on the findings of this study, homozygous TBA2.1 mice can be utilized to gain deeper understanding in the underlying mechanisms of pEAß3-42 and might be suitable as an animal model for treatment studies targeting toxic Aß species, complementary to the well described transgenic AßPP mouse models.

Aß oligomer eliminating compounds interfere successfully with pEAß(3-42) induced motor neurodegenerative phenotype in transgenic mice.

Currently, there are no causative or disease modifying treatments available for Alzheimer's disease (AD). Previously, it has been shown that D3, a small, fully d-enantiomeric peptide is able to eliminate low molecular weight Aß oligomers in vitro, enhance cognition and reduce plaque load in AD transgenic mice. To further characterise the therapeutic potential of D3 towards N-terminally truncated and pyroglutamated Aß (pEAß(3-42)) we tested D3 and its head-to-tail tandem derivative D3D3 both in vitro and in vivo in the new mouse model TBA2.1. These mice produce human pEAß(3-42) leading to a strong, early onset motor neurodegenerative phenotype. In the present study, we were able to demonstrate 1) strong binding affinity of both D3 and D3D3 to pEAß(3-42) in comparison to Aß(1-42) and 2) increased affinity of the tandem derivative D3D3 in comparison to D3. Subsequently we tested the therapeutic potentials of both peptides in the TBA2.1 animal model. Truly therapeutic, non-preventive treatment with D3 and D3D3 clearly slowed the progression of the neurodegenerative TBA2.1 phenotype, indicating the strong therapeutic potential of both peptides against pEAß(3-42) induced neurodegeneration.

QIAD assay for quantitating a compound's efficacy in elimination of toxic Aß oligomers.

Strong evidence exists for a central role of amyloid ß-protein (Aß) oligomers in the pathogenesis of Alzheimer's disease. We have developed a fast, reliable and robust in vitro assay, termed QIAD, to quantify the effect of any compound on the Aß aggregate size distribution. Applying QIAD, we studied the effect of homotaurine, scyllo-inositol, EGCG, the benzofuran derivative KMS88009, ZAß3W, the D-enantiomeric peptide D3 and its tandem version D3D3 on Aß aggregation. The predictive power of the assay for in vivo efficacy is demonstrated by comparing the oligomer elimination efficiency of D3 and D3D3 with their treatment effects in animal models of Alzheimer´s disease.

ABC transporters B1, C1 and G2 differentially regulate neuroregeneration in mice.

BACKGROUND: ATP-binding cassette (ABC) transporters are essential regulators of organismic homeostasis, and are particularly important in protecting the body from potentially harmful exogenous substances. Recently, an increasing number of in vitro observations have indicated a functional role of ABC transporters in the differentiation and maintenance of stem cells. Therefore, we sought to determine brain-related phenotypic changes in animals lacking the expression of distinct ABC transporters (ABCB1, ABCG2 or ABCC1). METHODOLOGY AND PRINCIPAL FINDINGS: Analyzing adult neurogenesis in ABC transporter-deficient animals in vivo and neuronal stem/progenitor cells in vitro resulted in complex findings. In vivo, the differentiation of neuronal progenitors was hindered in ABC transporter-deficient mice (ABCB1(0/0)) as evidenced by lowered numbers of doublecortin(+) (-36%) and calretinin(+) (-37%) cells. In vitro, we confirmed that this finding is not connected to the functional loss of single neural stem/progenitor cells (NSPCs). Furthermore, assessment of activity, exploratory behavior, and anxiety levels revealed behavioral alterations in ABCB1(0/0) and ABCC1(0/0) mice, whereas ABCG2(0/0) mice were mostly unaffected. CONCLUSION AND SIGNIFICANCE: Our data show that single ABC transporter-deficiency does not necessarily impair neuronal progenitor homeostasis on the single NSPC level, as suggested by previous studies. However, loss of distinct ABC transporters impacts global brain homeostasis with far ranging consequences, leading to impaired neurogenic functions in vivo and even to distinct behavioral phenotypes. In addition to the known role of ABC transporters in proteopathies such as Parkinson's disease and Alzheimer's disease, our data highlight the importance of understanding the general function of ABC transporters for the brain's homeostasis and the regeneration potential.