Abstract Cortical circuits rely on a precise balance of inhibitory and excitatory neurotransmission to encode information reliably and prevent pathology. Metabotropic GABA B receptors (GABA B Rs) are key regulators of inhibitory signalling in mammalian neurons. In GABAergic interneurons (INs), GABA B R activation reduces inhibition overall, leading to disinhibitory mechanisms. In the hippocampus, somatostatin-expressing (SST) INs form a major subtype that provides feedback inhibition to the distal dendrites of principal cells (PCs) and other INs. Plasticity of SST INs is well established as a mechanism controlling hippocampal circuit function through both inhibitory and disinhibitory pathways and depends on metabotropic glutamate receptors (mGluRs) and GABA B Rs. However, whether activation of GABABRs induces metaplastic changes in SST INs, and how this influences circuit function and behaviour, remains unclear. Here, we combined quantitative SDS-digested freeze-fracture replica immunoelectron microscopy, ex vivo electrophysiology, in vivo behavioural testing, and pharmacological manipulation of GABA B Rs. We show that receptor activation directly regulates SST IN plasticity via protein phosphatase 2A (PP2A)-dependent internalisation. GABA B R activation not only controls its own surface expression but also regulates membrane levels of mGluR1α and high-voltage-activated Ca v 1.2 (L-type) Ca 2+ channels. This GABA B R-dependent metaplasticity shifts circuit plasticity toward greater enhancement of long-range inputs to the CA1 region and disrupts contextual memory formation. These findings demonstrate that receptor-mediated surface dynamics in SST INs are critical for maintaining physiological neurotransmission and proper hippocampal microcircuit function.

Inflammation, aberrant proteostasis, and energy depletion are hallmarks of neurodegenerative diseases such as multiple sclerosis (MS). However, the interplay between inflammation, proteasomal dysfunction in neurons, and its consequences for neuronal integrity remains unclear. Using transcriptional, proteomic, and functional analyses of proteasomal subunits in inflamed neurons, we found that interferon-γ-mediated induction of the immunoproteasome subunit, proteasome 20S beta 8 (PSMB8) impairs the proteasomal balance, resulting in reduced proteasome activity. This reduction causes the accumulation of phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), a key metabolic regulator, leading to enhanced neuronal glycolysis, reduced pentose phosphate pathway activity, oxidative injury, and ferroptosis. Neuron-specific genetic and systemic pharmacological targeting of PSMB8 or PFKFB3 protected neurons in vitro and in a mouse model of MS. Our findings provide a unifying explanation for proteasomal dysfunction in MS and possibly other neurodegenerative diseases, linking inflammation to metabolic disruption, and presenting an opportunity for targeted neuroprotective therapies.

Abstract Background Dysregulated interferon-alpha/beta-receptor 1 (IFNAR1) signaling was recently identified to contribute to the development of sporadic Parkinson’s disease (PD) into PD with Dementia (PDD). The molecular, cellular, and phenotypic impacts of brain IFNAR1 loss in aging have not been explored in vivo, which may reveal novel disease mechanisms and therapeutic targets. Methods Single nuclei RNA sequencing (snRNA-seq), liquid chromatography tandem mass spectrometry (LC–MS/MS), functional metabolic mapping, flow cytometry, quantitative PCR (qPCR), in situ hybridization, immunofluorescence and immunohistochemistry, Western blotting, and behavior analyses were used to investigate the molecular, cellular, and phenotypic impacts of IFNAR1 loss in vivo. Results Baseline IFNAR1 expression varies among major brain cell types, including neurons and astrocytes, and is differentially affected in PD and Lewy Body Dementia patients compared to unaffected controls. Neuron- and astrocyte-specific transcriptomic and proteomic alterations in Ifnar1 –/– mice implicate mitochondrial defects, defective mitophagy, and synergistic dysfunctional neurotransmission upon IFNAR1 loss, leading to glucose hypermetabolism measured by functional metabolic analysis. Consequently, Ifnar1 –/– mice exhibited PDD-like pathogenesis, including dopaminergic cell loss in the substantia nigra, cortical neurodegeneration, Lewy-body-like inclusions, neuroinflammation, and progressive PDD-like behavior deficits. Brain cell-specific IFNAR1 loss examined in vivo revealed delayed but distinct development of PDD-like phenotypes, where neuropathology, motor, and cognitive behavior deficits were recapitulated only in mice lacking neuronal IFNAR1, and behavior resembling neuropsychiatric abnormalities recapitulated only in mice lacking astrocytic IFNAR1. Conclusions IFNAR1 plays a crucial role in brain and mitochondrial homeostasis, loss of which results in neurodegeneration and neuropathology resembling PDD. Differential neuropathology and behavioral outcomes upon neuronal vs astrocytic IFNAR1 loss emphasizes a need for understanding neurodegenerative pathophysiology in cell-specific contexts. Trial registration Not applicable as the study does not include a clinical trial.

Podocytes, highly specialized epithelial cells located in the glomerulus of the kidney, are essential to the filtration barrier that ensures separation of blood and urine. These cells exhibit a unique architecture, characterized by an intricate network of foot processes interconnected by slit diaphragms, which serve as a critical selective filter for plasma ultrafiltration. This review focusses on synthesizing current knowledge on podocyte physiology, emphasizing the roles of key proteins, signaling pathways, and environmental factors that influence their function. Publications featuring current advances in molecular biology and imaging techniques were used to summarize new insights into the regulatory pathways governing podocyte homeostasis, as well as the mechanisms of injury and repair. The biology of podocytes encompasses diverse processes, including cytoskeletal dynamics, cellular signaling, and interactions with neighboring cells and the extracellular matrix. Disruption of podocyte structure or function is fundamental to a variety of glomerular diseases, which can lead to proteinuria and progressive kidney failure. Understanding the intricate mechanisms involved in maintaining podocyte homeostasis offers potential therapeutic strategies to protect and restore podocyte integrity, addressing a critical need in nephrology. By highlighting the intricate balance required for podocyte survival, we reinforce their significance as both a cornerstone of renal filtration and a focal point in kidney disease research.

Circulating tumor cells (CTCs) play an important role in metastasis formation. Aberrant signaling of oncogenic pathways (e.g., PI3K/AKT/mTOR pathway) drives tumor progression. In this work, the susceptibility of the colon cancer CTC-derived cell line CTC-MCC-41 to AKT and mammalian target of rapamycin (mTOR) inhibitors was evaluated. Additionally, the functional role of the expressed AKT isoforms was characterized in this cell line. The efficacy of the AKT inhibitor MK2206, the mTOR inhibitor RAD001, and the combination was examined in CTC-MCC-41 cells in a murine intracardiac xenotransplantation model. Furthermore, stable isoform-specific AKT1 or AKT2 knockdowns (KDs) as well as AKT1/AKT2 double-KD cells were generated. Differentially regulated proteins and phospho-peptides were identified using liquid chromatography coupled mass spectrometry (LC-MS). CTC-MCC-41 cells showed a high susceptibility for dual targeting of AKT and mTOR in vivo, indicating that selective eradication of CTCs by AKT/mTOR inhibitors may be considered a new treatment option in cancer. KD of AKT1 or AKT2 significantly reduced the proliferation of CTC-MCC-41 cells. AKT KDs share commonly regulated proteins and phospho-proteins, but also regulate a large number uniquely. AKT1/AKT2 double-KD cells show a strongly dysregulated replication machinery, as well as a decrease in cell cycle activity and stem-cell-associated processes, underlining the non-redundant role of AKT isoforms.

INTRODUCTION:Podocytes are terminally differentiated cells of the kidney filtration barrier. Their network of interdigitating foot processes embraces the glomerular capillaries and is likely remodeled by cleavage of podocyte surface proteins. The metalloproteinase ADAM10 is a major regulator of such surface protein shedding and was recently implicated in the pathophysiology of antibody-mediated podocyte injury. METHODS:Here, we studied the contribution of ADAM10 in podocyte biology in health and disease and analyzed prominently expressed and disease-relevant podocyte membrane proteins in detail. We used genetically deficient mice, ADAM10-inhibited pig glomeruli, and various in vitro experimental systems in which detailed biochemical and imaging techniques were performed. RESULTS:We found that thrombospondin type 1 domain-containing 7A (THSD7A) and phospholipase A2 receptor 1 (PLA2R1), both of which are primary membranous nephropathy antigens, accumulated upon ADAM10 inhibition/deficiency. Moreover, increased protein levels of the foot process adhesion protein β-dystroglycan (β-DG) were found. Detailed biochemical analyses in different experimental systems revealed that THSD7A, PLA2R1, and β-DG are genuine ADAM10 substrates and subject to γ-secretase-mediated intramembrane proteolysis. These substrates co-localize and interact with the protease in podocytes and their shedding regulates filopodogenesis (THSD7A and β-DG) and cell matrix adhesion (β-DG). ADAM10 substrate usage, but also the stability of the podocyte cell surface proteins, is regulated by tetraspanin (Tspan) 15, which is likewise present at podocyte foot processes. A tricomponent complex of THSD7A/ADAM10/Tspan15 was found, with THSD7A acting as both an ADAM10 substrate and regulator. CONCLUSIONS:Altogether, our data emphasize the importance of ADAM10/Tspan15-mediated regulation of podocyte foot process surface proteins that serve as antigens in primary membranous nephropathy and impact cytoskeletal dynamics.

Chronic kidney disease affects 1 in 10 people worldwide, with damage to specialized blood filter cells of the kidney, called podocytes, playing a critical role. In membranous nephropathy (MN), a major cause of nephrotic syndrome, circulating autoantibodies attack proteins on podocyte foot processes (FPs), damaging the kidney's filtration barrier. Our study shows that these autoantibodies trigger the formation of antigen-autoantibody aggregates on the podocyte FP plasma membrane. These aggregates bud off as stalked vesicles, termed autoimmunoglobulin-triggered extracellular vesicles (AIT-EVs), which are released into the urine. AIT-EVs carry disease-causing autoantibodies, their target antigens, essential FP proteins, and disease-associated stressors representing a mechanism for removing immune complexes (ICs) and waste. However, their excessive release leads to FP effacement and podocyte dysfunction. In MN patients, urinary AIT-EVs correspond to glomerular urinary-space aggregates. Enriching AIT-EVs enables detection and monitoring of pathogenic autoantibodies, suggesting a non-invasive approach for autoimmune kidney disease diagnosis and therapy.

Ubiquitination influences a myriad of biological processes, such as the trafficking or degradation of ubiquitin-tagged target proteins. This posttranslational modification can be reversed by deubiquitinating enzymes (DUBs) that counterbalance the action of E3 ubiquitin ligases. We investigated the impact of PR-619, a membrane-permeable and broad-spectrum DUB inhibitor, on the entry of Ca2+ through native voltage-gated Ca2+ channels (VGCCs) of cultured embryonic cortical neurons. Fura-2-based Ca2+ imaging experiments showed that PR-619 reduced the cytosolic Ca2+ rises induced by depolarization by affecting mainly dihydropyridine-sensitive (L-type) VGCCs. This inhibition was sensitive to dynamin inhibitor Myr-Dip and lysosomal agents chloroquine and bafilomycin-A. PR-619 also reduced the amount of Cav1.2 proteins. A pharmacological approach was set out to better delineate the identity of the DUB responsible for this inhibitory action of PR-619. Since UCH-L1 and USP19 are two highly expressed neuronal DUBs, we investigated the effects of selective UCH-L1 (IMP1710, GK13S) and USP19 (ADC141) inhibitors. IMP1710 and GK13S depressed the Ca2+ uptake through L-type VGCCs, whereas ADC141 and the UCH-L3 inhibitor TCID had no effects. In addition, UCH-L1 inhibition impaired the neuronal Ca2+ storage capacities of neurons and reduced the Cav1.2 protein levels. Thus, UCH-L1 influences the neuronal uptake and storage of Ca2+, which is likely to have important physiological implications. Altogether, these results posit UCH-L1, the main DUB of the brain, as an important regulator of neuronal Ca2+ homeostasis and add to our understanding of its cellular functions.

BACKGROUND:Metastasis is the leading cause of cancer-related death in non-small cell lung cancer (NSCLC) patients. We previously showed that low HERC5 expression predicts early tumor dissemination and a dismal prognosis in NSCLC patients. Here, we performed functional studies to unravel the mechanism underlying the "metastasis-suppressor" effect of HERC5, with a focus on mitochondrial metabolism pathways.METHODS:We assessed cell proliferation, colony formation potential, anchorage-independent growth, migration, and wound healing in NSCLC cell line models with HERC5 overexpression (OE) or knockout (KO). To study early tumor cell dissemination, we used these cell line models in zebrafish experiments and performed intracardial injections in nude mice. Mass spectrometry (MS) was used to analyze protein changes in whole-cell extracts. Furthermore, electron microscopy (EM) imaging, cellular respiration, glycolytic activity, and lactate production were used to investigate the relationships with mitochondrial energy metabolism pathways.RESULTS:Using different in vitro NSCLC cell line models, we showed that NSCLC cells with low HERC5 expression had increased malignant and invasive properties. Furthermore, two different in vivo models in zebrafish and a xenograft mouse model showed increased dissemination and metastasis formation (in particular in the brain). Functional enrichment clustering of MS data revealed an increase in mitochondrial proteins in vitro when HERC5 levels were high. Loss of HERC5 leads to an increased Warburg effect, leading to improved adaptation and survival under prolonged inhibition of oxidative phosphorylation.CONCLUSIONS:Taken together, these results indicate that low HERC5 expression increases the metastatic potential of NSCLC in vitro and in vivo. Furthermore, HERC5-induced proteomic changes influence mitochondrial pathways, ultimately leading to alterations in energy metabolism and demonstrating its role as a new potential metastasis suppressor gene.

Kidney filtration is ensured by the interaction of podocytes, endothelial and mesangial cells. Immunoglobulin accumulation at the filtration barrier is pathognomonic for glomerular injury. The mechanisms that regulate filter permeability are unknown. Here, we identify a pivotal role for the proteasome in a specific cell type. Combining genetic and inhibitor-based human, pig, mouse, and Drosophila models we demonstrate that the proteasome maintains filtration barrier integrity, with podocytes requiring the constitutive and glomerular endothelial cells the immunoproteasomal activity. Endothelial immunoproteasome deficiency as well as proteasome inhibition disrupt the filtration barrier in mice, resulting in pathologic immunoglobulin deposition. Mechanistically, we observe reduced endocytic activity, which leads to altered membrane recycling and endocytic receptor turnover. This work expands the concept of the (immuno)proteasome as a control protease orchestrating protein degradation and antigen presentation and endocytosis, providing new therapeutic targets to treat disease-associated glomerular protein accumulations.

ABSTRACTBackgroundMembranous nephropathy (MN) is caused by autoantibody binding to podocyte foot process antigens such as THSD7A and PLA2R1. The mechanisms of the glomerular antigen/autoantibody deposition and clearance are unknown.MethodsWe explore the origin and significance of glomerular accumulations in (1) diagnostic and follow-up biospecimens from THSD7A+and PLA2R1+-MN patients compared to nephrotic non-MN patients, and (2) in experimental models of THSD7A+-MN.ResultsWe discovered podocyte exophers as correlates of histological antigen/autoantibody aggregates found in the glomerular urinary space of MN patients. Exopher vesicle formation represents a novel form of toxic protein aggregate removal inCaenorhabditis elegansneurons. In MN patients, podocytes released exophers to the urine. Enrichment of exophers from MN patient urines established them as a glomerular exit route for antigens and bound autoantibody. Exophers also carried disease-associated proteins such as complement and provided a molecular imprint of podocyte injury pathways. In experimental THSD7A+-MN, exophers were formed from podocyte processes and cell body. Their formation involved the translocation of antigen/autoantibody from the subepithelial to the urinary side of podocyte plasma membranes. Urinary exopher-release correlated with lower albuminuria and lower glomerular antigen/autoantibody burden. In MN patients the prospective monitoring of urinary exopher abundance and of exopher-bound autoantibodies was additive in the assessment of immunologic MN activity.ConclusionsExopher-formation and release is a novel pathomechanism in MN to remove antigen/autoantibody aggregates from the podocyte. Tracking exopher-release will add a non-invasive diagnostic tool with prognostic potential to clinical diagnostics and follow-up of MN patients.

Little is known about the mechanistic significance of the ubiquitin proteasome system (UPS) in a kidney autoimmune environment. In membranous nephropathy (MN), autoantibodies target podocytes of the glomerular filter resulting in proteinuria. Converging biochemical, structural, mouse pathomechanistic, and clinical information we report that the deubiquitinase Ubiquitin C-terminal hydrolase L1 (UCH-L1) is induced by oxidative stress in podocytes and is directly involved in proteasome substrate accumulation. Mechanistically, this toxic gain-of-function is mediated by non-functional UCH-L1, which interacts with and thereby impairs proteasomes. In experimental MN, UCH-L1 becomes non-functional and MN patients with poor outcome exhibit autoantibodies with preferential reactivity to non-functional UCH-L1. Podocyte-specific deletion of UCH-L1 protects from experimental MN, whereas overexpression of non-functional UCH-L1 impairs podocyte proteostasis and drives injury in mice. In conclusion, the UPS is pathomechanistically linked to podocyte disease by aberrant proteasomal interactions of non-functional UCH-L1.

Significance Statement Membranous nephropathy (MN) is an autoimmune kidney disease characterized by immune deposits in the glomerular basement membrane. Circulating anti-phospholipase A2 receptor 1 (PLA2R1) antibodies are detectable in 70%–80% of patients with MN, but experimental evidence of pathogenicity has been lacking. This study demonstrates the pathogenicity of human anti-PLA2R1 antibodies in minipigs, a model for MN that intrinsically expresses PLA2R1 on podocytes. After passive transfer of human anti-PLA2R1 antibody-containing plasma from patients with PLA2R1-associated MN to minipigs, antibodies were detected in the minipig glomeruli, but not in response to plasma from healthy controls. The minipigs developed histomorphological characteristics of MN, local complement activation in the glomeruli, and low-level proteinuria within 7 days, showing that human anti-PLA2R1 antibodies are pathogenic. Background Primary membranous nephropathy (MN) is an autoimmune kidney disease in which immune complexes are deposited beneath the epithelium in the glomeruli. The condition introduces a high risk for end-stage kidney disease. Seventy percent to 80% of patients with MN have circulating antibodies against phospholipase A2 receptor 1 (PLA2R1), and levels correlate with treatment response and prognosis. However, experimental evidence that human anti-PLA2R1 antibodies induce MN has been elusive. Methods In passive transfer experiments, minipigs received plasma or purified IgG from patients with PLA2R1-associated MN or from healthy controls. Anti-PLA2R1 antibodies and proteinuria were monitored using Western blot, ELISA, and Coomassie staining. Kidney tissues were analyzed using immunohistochemistry, immunofluorescence, electron microscopy, and proteomic analyses. Results Minipigs, like humans, express PLA2R1 on podocytes. Human anti-PLA2R1 antibodies bound to minipig PLA2R1 in vitro and in vivo. Passive transfer of human anti-PLA2R1 antibodies from patients with PLA2R1-associated MN to minipigs led to histological characteristics of human early-stage MN, activation of components of the complement cascade, and low levels of proteinuria. We observed development of an autologous, later phase of disease. Conclusions A translational approach from humans to minipigs showed that human anti-PLA2R1 antibodies are pathogenic in MN, although in the heterologous phase of disease only low-level proteinuria developed.

OPINION article Front. Cell. Neurosci., 23 March 2023Sec. Cellular Neurophysiology Volume 17 - 2023 | https://doi.org/10.3389/fncel.2023.1149954

Background: Bone is the main metastatic site for breast cancer. Single disseminated tumor cells (DTCs), the seeds of metastases detected in the bone marrow, can be found still years after the primary diagnosis. We have shown that the presence of DTCs in the bone marrow at both the time of diagnosis and after chemotherapy is an independent predictor of poor prognosis in primary non-metastatic breast cancer. We identified retinoic acid-induced 2 (RAI2) as a novel metastasis suppressor gene significantly associated with both positive DTC status and poor prognosis, especially among hormone-receptor positive breast cancer patients. RAI2 sustains differentiation of ER-positive tumor cells, whereas loss of RAI2 induces hormone independent growth and activation of AKT signalling as an important mediator of dormancy control. Methods: Xenograft models were established by injecting orthotopically RAI2 KO (CRISPR/Cas9 mediated RAI2 depletion) and parental KPL1 cells in immune deficient SCID/J mice. A transgenic RAI2 KO (RAIKO) mouse was established with the CRISPR/Cas9 system. The in vitro effect of RAI2 on the bone marrow cells was studied with osteoblast and osteoclast differentiation assays either with conditioned media from parental and RAI2 KO (MCF7 and KPL1) cells or with extracellular vesicles (EVs) isolated by ultracentrifugation from the supernatant fractions. miRNA content of the EVs from the different cell line models was assessed by next generation sequencing (NGS). NGS data was validated in plasma from a cohort of bone and brain metastatic breast cancer patients, non-metastatic breast cancer patients and in healthy donors. Results: Xenograft experiments in SCID/J mice showed an increased early tumor dissemination (increased numbers of CTCs and DTCs) when RAI2 KO cells were injected orthotopically versus the parental cell line, whereas the RAIKO mouse model showed that RAI2 is not involved in initial tumor development. Besides, both conditioned media as well as the EV fraction from RAI2 KO cells significantly increase osteoclast differentiation. Five miRNA candidates were identified to be involved in the RAI2-mediated crosstalk between tumor and bone cells. Validation assays on clinical samples identified miR-135a-5p to be lower expressed on EVs from bone metastatic patients compared to heathy donors and non-metastatic patients. Conclusions: RAI2 is a novel inhibitor of breast cancer tumor cells dissemination in the bone marrow thereby attenuating the vicious cycle of tumor crosstalk with the bone microenvironment. Citation Format: Thais Pereira Veiga, Stefan Werner, Desiree Loreth, Michael Horn, Melanie Groninger, Moritz Grabe, Anke Baranowsky, Hanna Taipaleenmäki, Laura Brylka, Jolanthe Kropidlowski, Thorsten Schinke, Klaus Pantel, Harriet Wikman. RAI2 is a novel bone metastasis-associated gene, mediating a vicious cross talk between breast cancer cells and osteoclasts [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1295.

Vascularization plays an important role in the microenvironment of the tumor. Therefore, it should be a key element to be considered in the development of in vitro cancer assays. In this study, we decellularized in vitro capillaries to remove genetic material and optimized the medium used to increase the robustness and versatility of applications. The growth pattern and drug responses of cancer cell lines and patient-derived primary cells were studied on decellularized capillaries. Interestingly, two distinct growth patterns were seen when cancer cells were grown on decellularized capillaries: "network" and "cluster". Network formation correlated with the metastatic properties of the cells and cluster formation was observed in non-metastatic cells. Drug responses of patient-derived cells correlated better with clinical findings when cells were cultured on decellularized capillaries compared with those cultured on plastic. Decellularized capillaries provide a novel method for cancer cell culture applications. It bridges the gap between complex 3D culture methods and traditional 2D culture methods by providing the ease and robustness of 2D culture as well as an in vivo-like microenvironment and scaffolding for 3D cultures.

Neuropathologically, Alzheimer’s disease (AD) is characterized by the accumulation of amyloid-beta peptide (Aβ) and subsequent formation of the so-called Aβ plaques. Along with neuronal loss, previous studies report white matter anomalies and corpus callosum (CC) atrophy in AD patients. Notably, perturbations in the white matter can be observed years before expected disease onset, suggesting that early stages of disease progression play a role in AD-associated loss of myelin integrity. Through seed-induced deposition of Aβ, we are able to examine alterations of central nervous system (CNS) integrity during the initial stages of plaque formation. In this study, we investigate the impact of Aβ seeding in the CC utilizing various imaging techniques as well as quantitative gene expression analysis and demonstrate that Aβ deposits result in an imbalance of glial cells in the CC. We found increased amounts of phagocytic microglia and reactive astrocytes, while oligodendrocyte progenitor cell (OPC) numbers were reduced. Moreover, white matter aberrations adjacent to the Aβ seeding were observed together with an overall decline in callosal myelination. This data indicate that the initial stages of plaque formation induce oligodendrocyte dysfunction, which might ultimately lead to myelin loss.

Several degenerative brain disorders such as Alzheimer's disease (AD), Parkinson's disease (PD) and Dementia with Lewy bodies (DLB) are characterized by the simultaneous appearance of amyloid-beta (A beta) and alpha-synuclein (alpha-syn) pathologies and symptoms that are similar, making it difficult to differentiate between these diseases. Until now, an accurate diagnosis can only be made by postmortem analysis. Furthermore, the role of alpha-syn in A beta aggregation and the arising characteristic olfactory impairments observed during the progression of these diseases is still not well understood. Therefore, we assessed A beta load in olfactory bulbs of APP-transgenic mice expressing APP695(KM670/671NL) and PSEN1(L166P) under the control of the neuron-specific Thy-1 promoter (referred to here as APPPS1) and APPPS1 mice co-expressing SNCA(A30P) (referred to here as APPPS1 x [A30P]aSYN). Furthermore, the olfactory capacity of these mice was evaluated in the buried food and olfactory avoidance test. Our results demonstrate an age-dependent increase in A beta load in the olfactory bulb of APP-transgenic mice that go along with exacerbated olfactory performance. Our study provides clear evidence that the presence of alpha-syn significantly diminished the endogenous and seed-induced A beta deposits and significantly ameliorated olfactory dysfunction in APPPS1 x [A30P]aSYN mice.

Alzheimer's disease (AD) is characterized by the accumulation of amyloid-β (Aβ) which ultimately forms plaques. These Aβ deposits can be induced in APP transgenic mouse models by prion-like seeding. It has been widely accepted that anosmia and hyposmia occur during the early stages of AD, even before cognitive deficits are present. In order to determine the impact of seed-induced Aβ deposits on olfaction, we performed intracerebral injections of seed-competent brain homogenate into the olfactory bulb of young pre-depositing APP transgenic mice. Remarkably, we observed a dramatic olfactory impairment in those mice. Furthermore, the number of newborn neurons as well as the activity of cells in the mitral cell layer was decreased. Notably, exposure to an enriched environment reduced Aβ seeding, vivified neurogenesis and most importantly reversed olfactory deficits. Based on our findings, we conclude that altered neuronal function as a result of induced Aβ pathology might contribute to olfactory dysfunction in AD.