Microglial activation in the right amygdala-entorhinal-hippocampal complex is associated with preserved spatial learning in App(NL-G-F) mice.

In Alzheimer`s disease (AD), regional heterogeneity of β-amyloid burden and microglial activation of individual patients is a well-known phenomenon. Recently, we described a high incidence of inter-individual regional heterogeneity in terms of asymmetry of plaque burden and microglial activation in β-amyloid mouse models of AD as assessed by positron-emission-tomography (PET). We now investigate the regional associations between amyloid plaque burden, microglial activation, and impaired spatial learning performance in transgenic mice in vivo. In 30 AppNL-G-F mice (15 female, 15 male) we acquired cross-sectional 18 kDa translocator protein (TSPO-PET, 18F-GE-180) and β-amyloid-PET (18F-florbetaben) scans at ten months of age. Control data were obtained from age- and sex-matched C57BI/6 wild-type mice. We assessed spatial learning (i.e. Morris water maze) within two weeks of PET scanning and correlated the principal component of spatial learning performance scores with voxel-wise β-amyloid and TSPO tracer uptake maps in AppNL-G-F mice, controlled for age and sex. In order to assess the effects of hemispheric asymmetry, we also analyzed correlations of spatial learning performance with tracer uptake in bilateral regions of interest for frontal cortex, entorhinal/piriform cortex, amygdala, and hippocampus, using a regression model. We tested the correlation between regional asymmetry of PET biomarkers with individual spatial learning performance. Voxel-wise analyses in AppNL-G-F mice revealed that higher TSPO-PET signal in the amygdala, entorhinal and piriform cortices, the hippocampus and the hypothalamus correlated with spatial learning performance. Region-based analysis showed significant correlations between TSPO expression in the right entorhinal/piriform cortex and the right amygdala and spatial learning performance, whereas there were no such correlations in the left hemisphere. Right lateralized TSPO expression in the amygdala predicted better performance in the Morris water maze (β = -0.470, p = 0.013), irrespective of the global microglial activation and amyloid level. Region-based results for amyloid-PET showed no significant associations with spatial learning. Elevated microglial activation in the right amygdala-entorhinal-hippocampal complex of AppNL-G-F mice is associated with better spatial learning. Our findings support a protective role of microglia on cognitive function when they highly express TSPO in specific brain regions involved in spatial memory.

Biechele G ，Wind K ，Blume T ，Sacher C ，Beyer L ，Eckenweber F ，Franzmeier N ，Ewers M ，Zott B ，Lindner S ，Gildehaus FJ ，von Ungern-Sternberg B ，Tahirovic S ，Willem M ，Bartenstein P ，Cumming P ，Rominger A ，Herms J ，Brendel M ... -  《-》

Longitudinal PET Monitoring of Amyloidosis and Microglial Activation in a Second-Generation Amyloid-β Mouse Model.

Nonphysiologic overexpression of amyloid-β (Aβ) precursor protein in common transgenic Aβ mouse models of Alzheimer disease likely hampers their translational potential. The novel AppNL-G-F mouse incorporates a mutated knock-in, potentially presenting an improved model of Alzheimer disease for Aβ-targeting treatment trials. We aimed to establish serial small-animal PET of amyloidosis and neuroinflammation in AppNL-G-F mice as a tool for therapy monitoring. Methods:AppNL-G-F mice (20 homozygous and 21 heterogeneous) and 12 age-matched wild-type mice were investigated longitudinally from 2.5 to 10 mo of age with 18F-florbetaben Aβ PET and 18F-GE-180 18-kDa translocator protein (TSPO) PET. Voxelwise analysis of SUV ratio images was performed using statistical parametric mapping. All mice underwent a Morris water maze test of spatial learning after their final scan. Quantification of fibrillar Aβ and activated microglia by immunohistochemistry and biochemistry served for validation of the PET results. Results: The periaqueductal gray emerged as a suitable pseudo reference tissue for both tracers. Homozygous AppNL-G-F mice had a rising SUV ratio in cortex and hippocampus for Aβ (+9.1%, +3.8%) and TSPO (+19.8%, +14.2%) PET from 2.5 to 10 mo of age (all P < 0.05), whereas heterozygous AppNL-G-F mice did not show significant changes with age. Significant voxelwise clusters of Aβ deposition and microglial activation in homozygous mice appeared at 5 mo of age. Immunohistochemical and biochemical findings correlated strongly with the PET data. Water maze escape latency was significantly elevated in homozygous AppNL-G-F mice compared with wild-type at 10 mo of age and was associated with high TSPO binding. Conclusion: Longitudinal PET in AppNL-G-F knock-in mice enables monitoring of amyloidogenesis and neuroinflammation in homozygous mice but is insensitive to minor changes in heterozygous animals. The combination of PET with behavioral tasks in AppNL-G-F treatment trials is poised to provide important insights in preclinical drug development.

Sacher C ，Blume T ，Beyer L ，Peters F ，Eckenweber F ，Sgobio C ，Deussing M ，Albert NL ，Unterrainer M ，Lindner S ，Gildehaus FJ ，von Ungern-Sternberg B ，Brzak I ，Neumann U ，Saito T ，Saido TC ，Bartenstein P ，Rominger A ，Herms J ，Brendel M ... -  《-》

Pre-therapeutic microglia activation and sex determine therapy effects of chronic immunomodulation.

Modulation of the innate immune system is emerging as a promising therapeutic strategy against Alzheimer's disease (AD). However, determinants of a beneficial therapeutic effect are ill-understood. Thus, we investigated the potential of 18 kDa translocator protein positron-emission-tomography (TSPO-PET) for assessment of microglial activation in mouse brain before and during chronic immunomodulation. Methods: Serial TSPO-PET was performed during five months of chronic microglia modulation by stimulation of the peroxisome proliferator-activated receptor (PPAR)-γ with pioglitazone in two different mouse models of AD (PS2APP, AppNL-G-F ). Using mixed statistical models on longitudinal TSPO-PET data, we tested for effects of therapy and sex on treatment response. We tested correlations of baseline with longitudinal measures of TSPO-PET, and correlations between PET results with spatial learning performance and β-amyloid accumulation of individual mice. Immunohistochemistry was used to determine the molecular source of the TSPO-PET signal. Results: Pioglitazone-treated female PS2APP and AppNL-G-F mice showed attenuation of the longitudinal increases in TSPO-PET signal when compared to vehicle controls, whereas treated male AppNL-G-F mice showed the opposite effect. Baseline TSPO-PET strongly predicted changes in microglial activation in treated mice (R = -0.874, p < 0.0001) but not in vehicle controls (R = -0.356, p = 0.081). Reduced TSPO-PET signal upon pharmacological treatment was associated with better spatial learning despite higher fibrillar β-amyloid accumulation. Immunohistochemistry confirmed activated microglia to be the source of the TSPO-PET signal (R = 0.952, p < 0.0001). Conclusion: TSPO-PET represents a sensitive biomarker for monitoring of immunomodulation and closely reflects activated microglia. Sex and pre-therapeutic assessment of baseline microglial activation predict individual immunomodulation effects and may serve for responder stratification.

Biechele G ，Blume T ，Deussing M ，Zott B ，Shi Y ，Xiang X ，Franzmeier N ，Kleinberger G ，Peters F ，Ochs K ，Focke C ，Sacher C ，Wind K ，Schmidt C ，Lindner S ，Gildehaus FJ ，Eckenweber F ，Beyer L ，von Ungern-Sternberg B ，Bartenstein P ，Baumann K ，Dorostkar MM ，Rominger A ，Cumming P ，Willem M ，Adelsberger H ，Herms J ，Brendel M ... -  《Theranostics》

Longitudinal TSPO expression in tau transgenic P301S mice predicts increased tau accumulation and deteriorated spatial learning.

Eckenweber F ，Medina-Luque J ，Blume T ，Sacher C ，Biechele G ，Wind K ，Deussing M ，Briel N ，Lindner S ，Boening G ，von Ungern-Sternberg B ，Unterrainer M ，Albert NL ，Zwergal A ，Levin J ，Bartenstein P ，Cumming P ，Rominger A ，Höglinger GU ，Herms J ，Brendel M ... -  《-》

Glial activation is moderated by sex in response to amyloidosis but not to tau pathology in mouse models of neurodegenerative diseases.

Biechele G ，Franzmeier N ，Blume T ，Ewers M ，Luque JM ，Eckenweber F ，Sacher C ，Beyer L ，Ruch-Rubinstein F ，Lindner S ，Gildehaus FJ ，von Ungern-Sternberg B ，Cumming P ，Bartenstein P ，Rominger A ，Höglinger GU ，Herms J ，Brendel M ... -  《Journal of Neuroinflammation》