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Publikation

Krohn, M.; Zoufal, V.; Mairinger, S.; Wanek, T.; Paarmann, K.; Brüning, T.; Eiriz, I.; Brackhan, M.; Langer, O.; Pahnke, J.; Generation and Characterization of an Abcc1 Humanized Mouse Model (hABCC1flx/flx) with Knockout Capability Mol. Pharmacol. 96, 138-147, (2019) DOI: 10.1124/mol.119.115824

ATP-binding cassette (ABC) transporters such as ABCB1 (P-glycoprotein), ABCC1 (MRP1), and ABCG2 (BCRP) are well known for their role in rendering cancer cells resistant to chemotherapy. Additionally, recent research provided evidence that, along with other ABC transporters (ABCA1 and ABCA7), they might be cornerstones to tackle neurodegenerative diseases. Overcoming chemoresistance in cancer, understanding drug-drug interactions, and developing efficient and specific drugs that alter ABC transporter function are hindered by a lack of in vivo research models, which are fully predictive for humans. Hence, the humanization of ABC transporters in mice has become a major focus in pharmaceutical and neurodegenerative research. Here, we present a characterization of the first Abcc1 humanized mouse line. To preserve endogenous expression profiles, we chose to generate a knockin mouse model that leads to the expression of a chimeric protein that is fully human except for one amino acid. We found robust mRNA and protein expression within all major organs analyzed (brain, lung, spleen, and kidney). Furthermore, we demonstrate the functionality of the expressed human ABCC1 protein in brain and lungs using functional positron emission tomography imaging in vivo. Through the introduction of loxP sites, we additionally enabled this humanized mouse model for highly sophisticated studies involving cell type–specific transporter ablation. Based on our data, the presented mouse model appears to be a promising tool for the investigation of cell-specific ABCC1 function. It can provide a new basis for better translation of preclinical research.
Publikation

Paarmann, K.; Prakash, S. R.; Krohn, M.; Möhle, L.; Brackhan, M.; Brüning, T.; Eiriz, I.; Pahnke, J.; French maritime pine bark treatment decelerates plaque development and improves spatial memory in Alzheimer's disease mice Phytomedicine 57, 39-48, (2019) DOI: 10.1016/j.phymed.2018.11.033

BackgroundPlant extracts are increasingly investigated as potential drugs against Alzheimer's disease (AD) and dementia in general. Pycnogenol is an extract from the bark of the French maritime pine (Pinus pinaster Aiton subsp. atlantica) with known anti-oxidative and neuroprotective effects.Hypothesis/PurposePycnogenol is thought to improve cognitive functions in elderly. We wanted to investigate and quantify these effects in a model system of cerebral ß-amyloidosis/AD.Study design/methodsThis study experimentally assessed the effects of Pycnogenol on AD-related pathology in a ß-amyloidosis mouse model. APP-transgenic mice and controls were treated orally in a pre-onset and post-onset treatment paradigm. The effects of Pycnogenol were characterized by analysing ß-amyloid (Aß) plaques, number of neurons, glia coverage, myelination pattern, and cortical coverage with axons using immunohistochemistry. Aß levels were quantified using ELISA and gene expression levels of APP-processing enzymes ADAM10, BACE1 and IDE protein levels were determined by Western blot. Behavioural changes in circadian rhythm were monitored and spatial memory / cognition was assessed using a water maze test.ResultsPycnogenol significantly decreased the number of plaques in both treatment paradigms but did not alter levels of soluble Aß or the gene expression of APP-processing enzymes. The morphological analyses revealed no changes in the number of neurons, astrocytes, microglia, the myelination pattern, or the morphology of axons. Behavioural testing revealed an improvement of the spatial memory in the pre-onset treatment paradigm only.ConclusionOur results suggest to evaluate clinically a potential use of Pycnogenol in the prevention or in early stages of mild cognitive impairment (MCI) and AD.
Publikation

Steffen, J.; Krohn, M.; Schwitlick, C.; Brüning, T.; Paarmann, K.; Pietrzik, C. U.; Biverstål, H.; Jansone, B.; Langer, O.; Pahnke, J.; Expression of endogenous mouse APP modulates β-amyloid deposition in hAPP-transgenic mice Acta Neuropathol. Commun. 5, 49, (2017) DOI: 10.1186/s40478-017-0448-2

Amyloid-β (Aβ) deposition is one of the hallmarks of the amyloid hypothesis in Alzheimer’s disease (AD). Mouse models using APP-transgene overexpression to generate amyloid plaques have shown to model only certain parts of the disease. The extent to which the data from mice can be transferred to man remains controversial. Several studies have shown convincing treatment results in reducing Aβ and enhancing cognition in mice but failed totally in human. One model-dependent factor has so far been almost completely neglected: the endogenous expression of mouse APP and its effects on the transgenic models and the readout for therapeutic approaches.Here, we report that hAPP-transgenic models of amyloidosis devoid of endogenous mouse APP expression (mAPP-knockout / mAPPko) show increased amounts and higher speed of Aβ deposition than controls with mAPP. The number of senile plaques and the level of aggregated hAβ were elevated in mAPPko mice, while the deposition in cortical blood vessels was delayed, indicating an alteration in the general aggregation propensity of hAβ together with endogenous mAβ. Furthermore, the cellular response to Aβ deposition was modulated: mAPPko mice developed a pronounced and age-dependent astrogliosis, while microglial association to amyloid plaques was diminished. The expression of human and murine aggregation-prone proteins with differing amino acid sequences within the same mouse model might not only alter the extent of deposition but also modulate the route of pathogenesis, and thus, decisively influence the study outcome, especially in translational research.
Publikation

Sike, ?.; Wengenroth, J.; Upīte, J.; Brüning, T.; Eiriz, I.; Sántha, P.; Biverstål, H.; Jansone, B.; Haugen, H. J.; Krohn, M.; Pahnke, J.; Improved method for cannula fixation for long-term intracerebral brain infusion J. Neurosci. Meth. 290, 145-150, (2017) DOI: 10.1016/j.jneumeth.2017.07.026

BackgroundImplanted osmotic minipumps are commonly used for long-term, brain-targeted delivery of a wide range of experimental agents by being connected to a catheter and a cannula. During the stereotactical surgery procedure, the cannula has to be placed correctly in the x-y directions and also with respect to the injection point in the z-direction (deepness). However, the flat fixation base of available cannula holders doesn’t allow an easy, secure fixation onto the curve-shaped skull.New methodWe have developed a modified method for a better fixation of the cannula holder by using an easy-to-produce, skull-shaped silicone spacer as fixation adapter.ResultsWe describe the application and its fast and reliable production in the lab.Comparison with existing method(s)Superglue or cement is currently being used as the method of choice. However, the curve-shaped skull surface does not fit well with the flat and rigid cannula adapter which leads to fixation problems over time causing wide infusion channels and often also to leakage problems from intracerebrally applied agents towards the surface meninges. As another consequence of the inappropriate fixation, the cannula may loosen from the skull before the end of the experiment or it causes damage to the brain tissue, harming the animals with leading to a failure of the whole experiment.ConclusionsThe easy-to-produce spacer facilitates the crucial step of long-term, stereotactic brain infusion experiments with intracerebral catheters in a highly secure and reproducible way.
Publikation

Fröhlich, C.; Zschiebsch, K.; Gröger, V.; Paarmann, K.; Steffen, J.; Thurm, C.; Schropp, E.-M.; Brüning, T.; Gellerich, F.; Radloff, M.; Schwabe, R.; Lachmann, I.; Krohn, M.; Ibrahim, S.; Pahnke, J.; Activation of Mitochondrial Complex II-Dependent Respiration Is Beneficial for α-Synucleinopathies Mol. Neurobiol. 53, 4728-4744, (2016) DOI: 10.1007/s12035-015-9399-4

Parkinson’s disease and dementia with Lewy bodies are major challenges in research and clinical medicine world-wide and contribute to the most common neurodegenerative disorders. Previously, specific mitochondrial polymorphisms have been found to enhance clearance of amyloid-β from the brain of APP-transgenic mice leading to beneficial clinical outcome. It has been discussed whether specific mitochondrial alterations contribute to disease progression or even prevent toxic peptide deposition, as seen in many neurodegenerative diseases. Here, we investigated α-synuclein-transgenic C57BL/6J mice with the A30P mutation, and a novel A30P C57BL/6J mouse model with three mitochondrial DNA polymorphisms in the ND3, COX3 and mtRNAArg genes, as found in the inbred NOD/LtJ mouse strain. We were able to detect that the new model has increased mitochondrial complex II-respiration which occurs in parallel to neuronal loss and improved motor performance, although it exhibits higher amounts of high molecular weight species of α-synuclein. High molecular weight aggregates of different peptides are controversially discussed in the light of neurodegeneration. A favourable hypothesis states that high molecular weight species are protective and of minor importance for the pathogenesis of neurodegenerative disorders as compared to the extreme neurotoxic monomers and oligomers. Summarising, our results point to a potentially protective and beneficial effect of specific mitochondrial polymorphisms which cause improved mitochondrial complex II-respiration in α-synucleinopathies, an effect that could be exploited further for pharmaceutical interventions.
Publikation

Steffen, J.; Krohn, M.; Paarmann, K.; Schwitlick, C.; Brüning, T.; Marreiros, R.; Müller-Schiffmann, A.; Korth, C.; Braun, K.; Pahnke, J.; Revisiting rodent models: Octodon degus as Alzheimer’s disease model? Acta Neuropathol. Commun. 4, 91, (2016) DOI: 10.1186/s40478-016-0363-y

Alzheimer’s disease primarily occurs as sporadic disease and is accompanied with vast socio-economic problems. The mandatory basic research relies on robust and reliable disease models to overcome increasing incidence and emerging social challenges. Rodent models are most efficient, versatile, and predominantly used in research. However, only highly artificial and mostly genetically modified models are available. As these ‘engineered’ models reproduce only isolated features, researchers demand more suitable models of sporadic neurodegenerative diseases. One very promising animal model was the South American rodent Octodon degus, which was repeatedly described as natural ‘sporadic Alzheimer’s disease model’ with ‘Alzheimer’s disease-like neuropathology’. To unveil advantages over the ‘artificial’ mouse models, we re-evaluated the age-dependent, neurohistological changes in young and aged Octodon degus (1 to 5-years-old) bred in a wild-type colony in Germany. In our hands, extensive neuropathological analyses of young and aged animals revealed normal age-related cortical changes without obvious signs for extensive degeneration as seen in patients with dementia. Neither significant neuronal loss nor enhanced microglial activation were observed in aged animals. Silver impregnation methods, conventional, and immunohistological stains as well as biochemical fractionations revealed neither amyloid accumulation nor tangle formation. Phosphoepitope-specific antibodies against tau species displayed similar intraneuronal reactivity in both, young and aged Octodon degus.In contrast to previous results, our study suggests that Octodon degus born and bred in captivity do not inevitably develop cortical amyloidosis, tangle formation or neuronal loss as seen in Alzheimer’s disease patients or transgenic disease models.
Publikation

Krohn, M.; Bracke, A.; Avchalumov, Y.; Schumacher, T.; Hofrichter, J.; Paarmann, K.; Fröhlich, C.; Lange, C.; Brüning, T.; von Bohlen und Halbach, O.; Pahnke, J.; Accumulation of murine amyloid-β mimics early Alzheimer’s disease Brain 138, 2370-2382, (2015) DOI: 10.1093/brain/awv137

Amyloidosis mouse models of Alzheimer’s disease are generally established by transgenic approaches leading to an overexpression of mutated human genes that are known to be involved in the generation of amyloid-β in Alzheimer’s families. Although these models made substantial contributions to the current knowledge about the ‘amyloid hypothesis’ of Alzheimer’s disease, the overproduction of amyloid-β peptides mimics only inherited (familiar) Alzheimer’s disease, which accounts for <1% of all patients with Alzheimer’s disease. The inherited form is even regarded a ‘rare’ disease according to the regulations for funding of the European Union (www.erare.eu). Here, we show that mice that are double-deficient for neprilysin (encoded by Mme), one major amyloid-β-degrading enzyme, and the ABC transporter ABCC1, a major contributor to amyloid-β clearance from the brain, develop various aspects of sporadic Alzheimer’s disease mimicking the clinical stage of mild cognitive impairment. Using behavioural tests, electrophysiology and morphological analyses, we compared different ABC transporter-deficient animals and found that alterations are most prominent in neprilysin × ABCC1 double-deficient mice. We show that these mice have a reduced probability to survive, show increased anxiety in new environments, and have a reduced working memory performance. Furthermore, we detected morphological changes in the hippocampus and amygdala, e.g. astrogliosis and reduced numbers of synapses, leading to defective long-term potentiation in functional measurements. Compared to human, murine amyloid-β is poorly aggregating, due to changes in three amino acids at N-terminal positions 5, 10, and 13. Interestingly, our findings account for the action of early occurring amyloid-β species/aggregates, i.e. monomers and small amyloid-β oligomers. Thus, neprilysin × ABCC1 double-deficient mice present a new model for early effects of amyloid-β-related mild cognitive impairment that allows investigations without artificial overexpression of inherited Alzheimer’s disease genes.

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