A novel mouse model of Alzheimer's disease with chronic estrogen deficiency leads to glial cell activation and hypertrophy.

The role of estrogens in Alzheimer's disease (AD) involving ß-amyloid (Aß) generation and plaque formation was mostly tested in ovariectomized mice with or without APP mutations. The aim of the present study was to explore the abnormalities of neural cells in a novel mouse model of AD with chronic estrogen deficiency. These chimeric mice exhibit a total FSH-R knockout (FORKO) and carry two transgenes, one expressing the ß-amyloid precursor protein (APPsw, Swedish mutation) and the other expressing presenilin-1 lacking exon 9 (PS1Δ9). The most prominent changes in the cerebral cortex and hippocampus of these hypoestrogenic mice were marked hypertrophy of both cortical neurons and astrocytes and an increased number of activated microglia. There were no significant differences in the number of Aß plaques although they appeared less compacted and larger than those in APPsw/PS1Δ9 control mice. Similar glia abnormalities were obtained in wild-type primary cortical neural cultures treated with letrozole, an aromatase inhibitor. The concordance of results from APPsw/PS1Δ9 mice with or without FSH-R deletion and those with letrozole treatment in vitro (with and without Aß treatment) of primary cortical/hippocampal cultures suggests the usefulness of these models to explore molecular mechanisms involved in microglia and astrocyte activation in hypoestrogenic states in the central nervous system.

Tieg1/Klf10 is upregulated by NGF and attenuates cell cycle progression in the pheochromocytoma cell line PC12.

The transcription factor Tieg1/Klf10 belongs to a family of Sp1/Klf proteins that have been shown to play important roles during development and maintenance of various tissues and cell types. Upregulation of Tieg1/Klf10 has been reported for TGF-beta, BMP2, BMP4, ActivinA and GDNF as members of the TGF-beta superfamily. Moreover, estrogen, the cytostatic drugs homoharringtonine and velcade as well as nitric oxide are also able to trigger Tieg1/Klf10 transcription. Recent studies suggest a role for members of the neurotrophin family in regulating Tieg1/Klf10 transcriptional upregulation. Using semi-quantitative RT-PCR and immunoblotting, we present data describing that nerve growth factor (NGF) regulates the expression of Tieg1/Klf10 in the pheochromocytoma cell line PC12 in a TrkA-dependent manner. Moreover, we provide evidence for the existence of NGF-responsive elements in the 5'-regulatory region of Tieg1/Klf10 that contain binding sites for the transcription factors Sp1 and CREB. After treatment with NGF PC12 cells exit the cell cycle and start to differentiate towards a neuron-like phenotype indicated by neurite outgrowth. Using flow cytometry and differentiation assays we demonstrate that Tieg1/Klf10 reduces cell cycle progression in PC12 cells but fails to promote their terminal differentiation. Together, our results identify Tieg1/Klf10 as a new NGF target gene and substantiate its anti-proliferative function in the NGF signaling pathway in PC12 cells.

Imaging and organelle distribution of fluorescent InGaP/ZnS nanoparticles in glial cells.

AIM: To assess the effects of oleic acid treatment on subcellular distribution of indium gallium phosphide-zinc sulfide (InGaP/ZnS) nanoparticles in microglia and astrocytes. MATERIALS & METHODS: The extent of colocalization between the nanoparticles and organelles was assessed by confocal microscopy, spectrofluorometry and cell sorting. RESULTS: Cell treatment with a common fatty acid (oleic acid) within the range of physiological concentrations markedly enhanced the InGaP/ZnS uptake by microglia and afforded their colocalization within lipid droplets/lysosomes but not with mitochondria. CONCLUSION: These results suggest that the availability of mono-unsaturated fatty acids, such as oleic acid, in different cells could significantly alter nanoparticle uptake and localization, which can in turn affect the functions of cells and tissues coexposed to nanoparticles.

Nanoparticles can induce changes in the intracellular metabolism of lipids without compromising cellular viability.

There is growing concern about the safety of engineered nanoparticles, which are produced for various industrial applications. Quantum dots are colloidal semiconductor nanoparticles that have unique luminescence characteristics and the potential to become attractive tools for medical imaging. However, some of these particles can cause oxidative stress and induce cell death. The objective of this study was to explore quantum dot-induced metabolic changes, which could occur without any apparent cellular damage. We provide evidence that both uncoated and ZnS-coated quantum dots can induce the accumulation of lipids (increase in cytoplasmic lipid droplet formation) in two cell culture models: glial cells in primary mouse hypothalamic cultures and rat pheochromocytoma PC12 cells. Glial cells treated with CdTe quantum dots accumulated newly synthesized lipids in a phosphoinositide 3-kinase-dependent manner, which was consistent with the growth factor-dependent accumulation of lipids in PC12 cells treated with CdTe and CdSe/ZnS quantum dots. In PC12 cells, quantum dots, as well as the hypoxia mimetic CoCl(2), induced the up-regulation of hypoxia-inducible transcription factor-1alpha and the down-regulation of the beta-oxidation of fatty acids, both of which could contribute to the accumulation of lipids. On the basis of our results, we propose a model illustrating how nanoparticles, such as quantum dots, could trigger the formation of intracellular lipid droplets, and we suggest that metabolic measurements, such as the determination of fat oxidation in tissues, which are known sites of nanoparticle accumulation, could provide useful measures of nanoparticle safety. Such assays would expand the current platform of tests for the determination of the biocompatibility of nanomaterials.

Real-time imaging of astrocyte response to quantum dots: in vivo screening model system for biocompatibility of nanoparticles.

Astrocytes are the principle macroglial brain cells. They are activated by different stressors and brain injuries. Quantum dots (QDs) can cause oxidative stress. This study shows a real-time imaging of primary cortical cultures and assessment of QD-induced activation of astrocytes in the brains of transgenic mice with the luciferase gene driven by the murine astrocyte promoter. This approach may be widely applicable for assessing the astroglia/tissue response to nanoparticles in live animals.