Cognitive decline, Aß pathology, and blood-brain barrier function in aged 5xFAD mice.

BACKGROUND: Patients with Alzheimer's disease (AD) develop blood-brain barrier dysfunction to varying degrees. How aging impacts Aß pathology, blood-brain barrier function, and cognitive decline in AD remains largely unknown. In this study, we used 5xFAD mice to investigate changes in Aß levels, barrier function, and cognitive decline over time. METHODS: 5xFAD and wild-type (WT) mice were aged between 9.5 and 15.5 months and tested for spatial learning and reference memory with the Morris Water Maze (MWM). After behavior testing, mice were implanted with acute cranial windows and intravenously injected with fluorescent-labeled dextrans to assess their in vivo distribution in the brain by two-photon microscopy. Images were processed and segmented to obtain intravascular intensity, extravascular intensity, and vessel diameters as a measure of barrier integrity. Mice were sacrificed after in vivo imaging to isolate brain and plasma for measuring Aß levels. The effect of age and genotype were evaluated for each assay using generalized or cumulative-linked logistic mixed-level modeling and model selection by Akaike Information Criterion (AICc). Pairwise comparisons were used to identify outcome differences between the two groups. RESULTS: 5xFAD mice displayed spatial memory deficits compared to age-matched WT mice in the MWM assay, which worsened with age. Memory impairment was evident in 5xFAD mice by 2-threefold higher escape latencies, twofold greater cumulative distances until they reach the platform, and twice as frequent use of repetitive search strategies in the pool when compared with age-matched WT mice. Presence of the rd1 allele worsened MWM performance in 5xFAD mice at all ages but did not alter the rate of learning or probe trial outcomes. 9.5-month-old 15.5-month-old 5xFAD mice had twofold higher brain Aß40 and Aß42 levels (p < 0.001) and 2.5-fold higher (p = 0.007) plasma Aß40 levels compared to 9.5-month-old 5xFAD mice. Image analysis showed that vessel diameters and intra- and extravascular dextran intensities were not significantly different in 9.5- and 15.5-month-old 5xFAD mice compared to age-matched WT mice. CONCLUSION: 5xFAD mice continue to develop spatial memory deficits and increased Aß brain levels while aging. Given in vivo MP imaging limitations, further investigation with smaller molecular weight markers combined with advanced imaging techniques would be needed to reliably assess subtle differences in barrier integrity in aged mice.

Potential links between platelets and amyloid-ß in the pathogenesis of Alzheimer's disease: Evidence from in vitro, in vivo, and clinical studies.

Cerebral amyloid angiopathy (CAA) is a prevalent comorbidity among patients with Alzheimer's disease (AD), present in up to 80% of cases with varying levels of severity. There is evidence to suggest that CAA might intensify cognitive deterioration in AD patients, thereby accelerating the development of AD pathology. As a source of amyloids, it has been postulated that platelets play a significant role in the pathogenesis of both AD and CAA. Although several studies have demonstrated that platelet activation plays an important role in the pathogenesis of AD and CAA, a clear understanding of the mechanisms involved in the three steps: platelet activation, platelet adhesion, and platelet aggregation in AD pathogenesis still remains elusive. Moreover, potential therapeutic targets in platelet-mediated AD pathogenesis have not been explicitly addressed. Therefore, the aim of this review is to collate and discuss the in vitro, in vivo, and clinical evidence related to platelet dysfunction, including associated activation, adhesion, and aggregation, with specific reference to amyloid-related AD pathogenesis. Potential therapeutic targets of platelet-mediated AD pathogenesis are also discussed. By enriching the understanding of the intricate relationship between platelet dysfunction and onset of AD, researchers may unveil new therapeutic targets or strategies to tackle this devastating neurodegeneration.

Intracellular nickel accumulation induces apoptosis and cell cycle arrest in human astrocytic cells.

Nickel, a heavy metal found in electronic wastes and fume from electronic cigarettes, induces neuronal cell death and is associated with neurocognitive impairment. Astrocytes are the first line of defense against nickel after entering the brain; however, the effects of nickel on astrocytes remain unknown. Herein, we investigated the effect of nickel exposure on cell survival and proliferation and the underlying mechanisms in U-87 MG human astrocytoma cells and primary human astrocytes. Intracellular nickel levels were elevated in U-87 MG cells in a dose- and time-dependent manner after exposure to nickel chloride. The median toxic concentrations of nickel in astrocytoma cells and primary human astrocytes were 600.60 and >1000 µM at 48 h post-exposure, respectively. Nickel exposure triggered apoptosis in concomitant with the decreased expression of anti-apoptotic B-cell lymphoma protein (Bcl-2) and increased caspase-3/7 activity. Nickel induced reactive oxygen species formation. Additionally, nickel suppressed astrocyte proliferation in a dose- and time-dependent manner by delaying G2 to M phase transition through the upregulation of cyclin B1 and p27 protein expression. These results indicate that nickel-induced cytotoxicity of astrocytes is mediated by the activation of apoptotic pathway and disruption of cell cycle regulation.

Cadmium induces CCL2 production in glioblastoma cells via activation of MAPK, PI3K, and PKC pathways.

Cadmium (Cd) is accumulated in human astrocytes and induces the production of interleukin (IL)-6 and IL-8. Astrocytes are one of the major sources of chemokine C-C motif ligand 2 (CCL2; known as monocyte chemoattractant protein-1 [MCP-1]), in the brain. Elevated CCL2 levels are associated with cognitive impairment as well as the migration and invasion of glioblastoma cells. The present study hypothesized that non-toxic concentrations of Cd (as cadmium chloride [CdCl2]) could up-regulate CCL2 production in U-87 MG human glio-blastoma cells. The results showed that after exposure of the U-87 MG cells to CdCl2 at 1 and 10 µM, there was an up-regulation of CCL2 mRNA expression after 3 h of exposure and increased CCL2 secretion after 6 and 24 h. The study also found that inhibition of MAPK pathways, including ERK1/2, p38, and JNK by U0126, SB203580 and SP600125, respectively, reduced Cd-induced CCL2 secretion by the cells. Moreover, when cells were pretreated with Ro 32-0432 (an inhibitor of calcium-dependent PKC) and LY294002 (a PI3K inhibitor), this also resulted in a down-regulation of any Cd-induced CCL2 expression. Taken together, the results of this study allow for the conclusion to be made that CCL2 up-regulation in U-87 MG cells induced by Cd is mediated, in part, by an activation of MAPK, PI3K/Akt, and PKC pathways.

Leukotriene Receptor Antagonists Inhibit Mitogenic Activity in Triple Negative Breast Cancer Cells

Despite a discovery of hormonal pathways regulating breast cancer, a definitive cure for the disease requires further identification of alternative targets that provide a hormone-independent support. Apart from their role in inflammatory diseases, cysteinyl leukotriene (CysLT) receptor antagonists (LTRAs) decrease the risk of lung cancer in asthma patients and inhibit tumor progression in several malignancies. In the present study, we evaluate the effects of two chemically different, clinically relevant LTRAs (montelukast and zafirlukast) in a triple negative breast cancer cell line, MDAMB- 231. We found that these two LTRAs reduced breast cancer cell viability in a dose-dependent manner with the 50% inhibitory concentration (IC50) between 5-10 µM. Although both LTRAs have several pharmacological properties in common, we noticed that montelukast mainly induced apoptosis, while zafirlukast mainly exerted its action on cell cycle. However, the precise mechanisms responsible for such different effects remain unclear. In summary, our results suggest that CysLT plays a role in proliferation and survivability of breast cancer cells in the absence of hormonal stimuli.