Metabotyping of docosahexaenoic acid - Treated alzheimer's disease cell model

10.1371/journal.pone.0090123PLoS ONE92-POLN

LDLR Expression and Localization Are Altered in Mouse and Human Cell Culture Models of Alzheimer's Disease

Alzheimer's disease (AD) is a chronic neurodegenerative disorder and the most common form of dementia. The major molecular risk factor for late-onset AD is expression of the ε-4 allele of apolipoprotein E (apoE), the major cholesterol transporter in the brain. The low-density lipoprotein receptor (LDLR) has the highest affinity for apoE and plays an important role in brain cholesterol metabolism.Using RT-PCR and western blotting techniques we found that over-expression of APP caused increases in both LDLR mRNA and protein levels in APP transfected H4 neuroglioma cells compared to H4 controls. Furthermore, immunohistochemical experiments showed aberrant localization of LDLR in H4-APP neuroglioma cells, Aβ-treated primary neurons, and in the PSAPP transgenic mouse model of AD. Finally, immunofluorescent staining of LDLR and of γ- and α-tubulin showed a change in LDLR localization preferentially away from the plasma membrane that was paralleled by and likely the result of a disruption of the microtubule-organizing center and associated microtubule network.These data suggest that increased APP expression and Aβ exposure alters microtubule function, leading to reduced transport of LDLR to the plasma membrane. Consequent deleterious effects on apoE uptake and function will have implications for AD pathogenesis and/or progression

A thalamic reticular networking model of consciousness

<p>Abstract</p> <p>[Background]</p> <p>It is reasonable to consider the thalamus a primary candidate for the location of consciousness, given that the thalamus has been referred to as the gateway of nearly all sensory inputs to the corresponding cortical areas. Interestingly, in an early stage of brain development, communicative innervations between the dorsal thalamus and telencephalon must pass through the ventral thalamus, the major derivative of which is the thalamic reticular nucleus (TRN). The TRN occupies a striking control position in the brain, sending inhibitory axons back to the thalamus, roughly to the same region where they receive afferents.</p> <p>[Hypotheses]</p> <p>The present study hypothesizes that the TRN plays a pivotal role in dynamic attention by controlling thalamocortical synchronization. The TRN is thus viewed as a functional networking filter to regulate conscious perception, which is possibly embedded in thalamocortical networks. Based on the anatomical structures and connections, modality-specific sectors of the TRN and the thalamus appear to be responsible for modality-specific perceptual representation. Furthermore, the coarsely overlapped topographic maps of the TRN appear to be associated with cross-modal or unitary conscious awareness. Throughout the latticework structure of the TRN, conscious perception could be accomplished and elaborated through accumulating intercommunicative processing across the first-order input signal and the higher-order signals from its functionally associated cortices. As the higher-order relay signals run cumulatively through the relevant thalamocortical loops, conscious awareness becomes more refined and sophisticated.</p> <p>[Conclusions]</p> <p>I propose that the thalamocortical integrative communication across first- and higher-order information circuits and repeated feedback looping may account for our conscious awareness. This TRN-modulation hypothesis for conscious awareness provides a comprehensive rationale regarding previously reported psychological phenomena and neurological symptoms such as blindsight, neglect, the priming effect, the threshold/duration problem, and TRN-impairment resembling coma. This hypothesis can be tested by neurosurgical investigations of thalamocortical loops via the TRN, while simultaneously evaluating the degree to which conscious perception depends on the severity of impairment in a TRN-modulated network.</p

Particulate forms of APP in the extracellular milieu of cultured cells

The principle externalized forms of amyloid precursor protein (APP) are soluble and well-characterized, but some evidence has suggested the additional presence of externalized APP in a nonsoluble form. To further assess this possibility, the current study has applied high resolution microscopy protocols in addition to immunoprecipitation to characterize externalized APP in three commonly used cell culture models (SH-SY5Y human neuroblastoma cells, fetal rat brain cells, and HEK 293 human embryonic kidney cells). Confocal immunofluorescence microscopy, using an antiserum against the c-terminal domain of APP, showed typical cell-associated APP, but hot spots of APP also were evident in cell-free areas, apparently associated with the culture substrata. These hot-spots were examined for evidence of cellular deterioration by whole mount transmission electron microscopy. Neither cell debris nor disrupted cells were present. Instead, the hot spots of substratum-bound APP comprised discrete microparticles, approximately 50-100 nm across. These microparticles also could be found near cells and in some cases were attached to cell surface fibrils. Substratum-bound APP also could be found clustered within the extracellular matrix made by primary cell cultures. Occurrence of APP in extracellular microparticles was verified by centrifugation-immunoprecipitation analysis of media conditioned by APP-transfected cells. Radiolabeling data showed that particulate APP was from metabolically active cells. Metabolic labeling of particle-associated APP, as well as the absence of cellular debris near the APP-containing particles, suggests that the occurrence of nonsoluble APP in the extracellular milieu derives from a physiologically active process

Upregulation of iron regulatory proteins and divalent metal transporter-1 isoforms in the rat hippocampus after kainate induced neuronal injury

10.1007/s00221-005-0220-xExperimental Brain Research1703376-38