Plasma Exchange Reduces Aß Levels in Plasma and Decreases Amyloid Plaques in the Brain in a Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is the most common type of dementia, characterized by the abnormal accumulation of protein aggregates in the brain, known as neurofibrillary tangles and amyloid-ß (Aß) plaques. It is believed that an imbalance between cerebral and peripheral pools of Aß may play a relevant role in the deposition of Aß aggregates. Therefore, in this study, we aimed to evaluate the effect of the removal of Aß from blood plasma on the accumulation of amyloid plaques in the brain. We performed monthly plasma exchange with a 5% mouse albumin solution in the APP/PS1 mouse model from 3 to 7 months old. At the endpoint, total Aß levels were measured in the plasma, and soluble and insoluble brain fractions were analyzed using ELISA. Brains were also analyzed histologically for amyloid plaque burden, plaque size distributions, and gliosis. Our results showed a reduction in the levels of Aß in the plasma and insoluble brain fractions. Interestingly, histological analysis showed a reduction in thioflavin-S (ThS) and amyloid immunoreactivity in the cortex and hippocampus, accompanied by a change in the size distribution of amyloid plaques, and a reduction in Iba1-positive cells. Our results provide preclinical evidence supporting the relevance of targeting Aß in the periphery and reinforcing the potential use of plasma exchange as an alternative non-pharmacological strategy for slowing down AD pathogenesis.

Tau Loss of Function, by Deletion or Aggregation, Contributes to Peripheral Insulin Resistance.

BACKGROUND: Several epidemiological data revealed an association between Alzheimer's disease (AD) and type 2 diabetes. Researchers concentrated on brain insulin resistance with little emphasis on the link between systemic insulin resistance and AD, despite the fact that the incidence of type 2 diabetes is higher in AD patients and that impairment in insulin signaling is a risk factor for AD. OBJECTIVE: The goal of this study is to determine the role of systemic insulin resistance in the pathogenesis of Alzheimer's disease by evaluating the consequences of tau loss-of-function on peripheral insulin sensitivity. METHODS: Primary hepatocytes isolated from transgenic mouse models (Tau KO, P301 L) and wild type mice (C57BL/6) were evaluated for their insulin sensitivity using glucose uptake assays as well as biochemical analysis of insulin signaling markers. RESULTS: Our data show that tau deletion or loss of function promotes peripheral insulin resistance as seen in primary hepatocytes isolated from Tau KO and P301 L mice, respectively. Furthermore, exposure of wild-type primary hepatocytes to sub-toxic concentrations of tau oligomers results in a dose-dependent inhibition of glucose uptake, associated with downregulation of insulin signaling. Tau oligomers-induced inactivation of insulin signaling proteins was rescued by inhibition of p38 MAPK, suggesting the involvement of p38 MAPK. CONCLUSIONS: This is the first study testing tau role in peripheral insulin resistance at the cellular level using multiple transgenic mouse models. Moreover, this study suggests that tau should be functional for insulin sensitivity, therefore, any loss of function by deletion or aggregation would result in insulin resistance.

Lewy Body-like Pathology and Loss of Dopaminergic Neurons in Midbrain Organoids Derived from Familial Parkinson's Disease Patient.

Progressive accumulation of α-Synuclein (αSyn) in Lewy bodies (LBs) and loss of dopaminergic (DA) neurons are the hallmark pathological features of Parkinson's disease (PD). Although currently available in vitro and in vivo models have provided crucial information about PD pathogenesis, the mechanistic link between the progressive accumulation of αSyn into LBs and the loss of DA neurons is still unclear. To address this, it is critical to model LB formation and DA neuron loss, the two key neuropathological aspects of PD, in a relevant in vitro system. In this study, we developed a human midbrain-like organoid (hMBO) model of PD. We demonstrated that hMBOs generated from induced pluripotent stem cells (hiPSCs), derived from a familial PD (fPD) patient carrying αSyn gene (SNCA) triplication accumulate pathological αSyn over time. These cytoplasmic inclusions spatially and morphologically resembled diverse stages of LB formation and were composed of key markers of LBs. Importantly, the progressive accumulation of pathological αSyn was paralleled by the loss of DA neurons and elevated apoptosis. The model developed in this study will complement the existing in vitro models of PD and will provide a unique platform to study the spatiotemporal events governing LB formation and their relation with neurodegeneration. Furthermore, this model will also be beneficial for in vitro screening and the development of therapeutic compounds.

Passive Immunotherapy Targeting Tau Oligomeric Strains Reverses Tauopathy Phenotypes in Aged Human-Tau Mice in a Mouse Model-Specific Manner.

BACKGROUND: Tau oligomers are one of the most toxic species, displaying prion-like strains which have different conformations resulting in different tauopathies. Passive immunotherapy targeting different tau species is a promising therapeutic approach. Age is one of the greatest risk factors; however, most immunotherapy studies are done in young to middle-aged mice tauopathy models, which is not representative of the many clinical trials done with older humans with established tauopathies. OBJECTIVE: We utilized two different clones of tau oligomer monoclonal antibodies (TOMAs) in aged Htau and JNPL3 mouse models to investigate the potential of passive immunotherapy. METHODS: Aged mice received a single intravenous injection of 120 µg/animal of either TOMA1, TOMA3 clones or a non-specific IgG. Their cognitive functions were assessed one-week post-injection using Y-maze and novel object recognition tests. Brain tissues were analyzed using biochemical and immunological assays. RESULTS: TOMA 1 and 3 rescues cognitive phenotypes in aged animals in a mouse model-specific manner, indicative by a reduction in tau oligomers levels. The TOMAs were shown to have strong reactivity with different tau oligomeric species in the different mouse models in vitro and ex vivo. CONCLUSION: This is the first study testing tau passive immunotherapy in aged animals and supports our previous reports on of the role of oligomeric tau in disease progression further validating the potential of TOMAs to rescue the late-stage disease pathology and phenotype. Moreover, this study suggests that multiple tau oligomeric strains exist in aged animals; therefore, it is of great importance to further characterize these strains.

Identification of Multicolor Fluorescent Probes for Heterogeneous Aß Deposits in Alzheimer's Disease.

Accumulation of amyloid-beta (Aß) into amyloid plaques and hyperphosphorylated tau into neurofibrillary tangles (NFTs) are pathological hallmarks of Alzheimer's disease (AD). There is a significant intra- and inter-individual variability in the morphology and conformation of Aß aggregates, which may account in part for the extensive clinical and pathophysiological heterogeneity observed in AD. In this study, we sought to identify an array of fluorescent dyes to specifically probe Aß aggregates, in an effort to address their diversity. We screened a small library of fluorescent probes and identified three benzothiazole-coumarin derivatives that stained both vascular and parenchymal Aß deposits in AD brain sections. The set of these three dyes allowed the visualization of Aß deposits in three different colors (blue, green and far-red). Importantly, two of these dyes specifically stained Aß deposits with no apparent staining of hyperphosphorylated tau or α-synuclein deposits. Furthermore, this set of dyes demonstrated differential interactions with distinct types of Aß deposits present in the same subject. Aß aggregate-specific dyes identified in this study have the potential to be further developed into Aß imaging probes for the diagnosis of AD. In addition, the far-red dye we identified in this study may serve as an imaging probe for small animal imaging of Aß pathology. Finally, these dyes in combination may help us advance our understanding of the relation between the various Aß deposits and the clinical diversity observed in AD.

Role of the efflux transporters BCRP and MRP1 in human placental bio-disposition of pravastatin.

The expression and activity of human placental transporters during pregnancy could be altered by several factors including pathological changes associated with preeclampsia. The aims of this study were to identify the placental efflux transporters involved in the bio-disposition of pravastatin, determine the protein expression of these transporters and their encoding genes as well as the activity of pravastatin uptake in placentas obtained from patients with preeclampsia. ATP-dependent uptake of [3H]-pravastatin by trophoblast tissue apical and basal membrane vesicles exhibited sigmoidal kinetics. The curved shapes of Eadie-Hofstee plots indicate that more than one placental transporter are involved in the uptake of pravastatin. ATP-dependent uptake of [3H]-pravastatin into vesicles expressing MRP1-5, BCRP, and P-gp, as well as the results of inhibition studies suggest that BCRP and MRP1 are the major placental efflux transporters responsible for the in vitro uptake of pravastatin. Compared to placentas from healthy pregnancies, preeclamptic placentas had increased number of syncytial knots with increased expression of BCRP in their apical membrane and increased expression of MRP1 in the cytoplasm of the syncytiotrophoblast and in cytoplasm of syncytial knots. There was a concomitant increase in ABCC1 but not in ABCG2 gene expressions in preeclamptic placentas. ATP-dependent uptake of [3H]-pravastatin by vesicles prepared from apical membranes of preeclamptic placentas was similar to the uptake by vesicles prepared from placentas obtained after uncomplicated pregnancies (13.9 ±â€¯6.5 vs 14.1 ±â€¯5.8 pmol·mg protein-1 min-1). The transporter-specific changes in the expression of BCRP and MRP1 in preeclamptic placentas did not affect the efflux activity of transporters localized on the apical membrane of the syncytiotrophoblast.

Mitochondrial-generated ROS down regulates insulin signaling via activation of the p38MAPK stress response pathway.

Impairment of insulin signaling and hepatic insulin resistance has been attributed to ROS-mediated activation of p38MAPK stress response signaling. Our research focused on whether (a) ROS generated by mitochondrial electron transport chain complex I (ETC-CI) dysfunction, via the use of Rotenone, inactivates insulin signaling; and (b) the p38MAPK pathway is involved in the ROS-induced impairment of insulin signaling. Our results show that in primary mouse hepatocytes the CI inhibitor, Rotenone, (a) induces IRS-1 Ser(307) phosphorylation that is blocked by the anti-oxidant NAC or by the p38MAPK inhibitors, SB203580 and SB202190; (b) inhibits insulin-stimulated AKT-Ser(473) and GSK3ß-Ser(9) phosphorylations, in a manner that is not responsive to reversal by the anti-oxidant NAC or by the p38MAPK inhibitors, SB203580 and SB202190. We conclude that rotenone-induced insulin resistance involves a p38MAPK-dependent mechanism for the inhibition of the proximal end of insulin signaling (IRS1), and a p38MAPK-independent mechanism for the inhibition of the distal end (AKT and GSK3ß). Our study suggests that ROS generated by inhibition of ETC CI, promotes hepatic insulin resistance partly via activation of the p38MAPK stress-response pathway.