We suggest for the first time, a dual role for γ-secretase in Alzheimer's disease. One role is the cleavage of the amyloid precursor protein for pathologic β-amyloid production and the other is to regulate microglia activity that is important for clearing neurotoxic β-amyloid deposits. Further studies of γ-secretase-mediated cellular pathways in microglia may provide useful insights into the development of Alzheimer's disease and other neurodegenerative diseases, providing future avenues for therapeutic intervention.

No abstract

Blood-borne brain metastases are associated with poor prognosis, but little is known about the interplay between cerebral blood flow, surgical stress responses, and the metastatic process. The intra-carotid inoculation approach, traditionally used in animal studies, involves permanent occlusion of the common carotid artery (CCA). Herein we introduce a novel intra-carotid inoculation approach that avoids CCA ligation, namely – assisted external carotid artery inoculation (aECAi) – and compared it to the traditional approach in C57/BL6 mice, assessing cerebral blood flow; particle distribution; blood-brain barrier (BBB) integrity; stress, inflammatory and immune responses; and tumor brain retention and growth. Doppler flowmetry and two-photon imaging confirmed that only in the traditional approach regional and capillary cerebral blood flux were significantly reduced. Corticosterone and plasma IL-6 levels were higher in the traditional approach, splenic numbers of NK, CD3+, granulocytes, and dendritic cells were lower, and many of these indices were more profoundly affected by surgical stress in the traditional approach. BBB integrity was unaffected. Administration of spherical beads indicated that CCA ligation significantly limited brain distribution of injected particles, and inoculation of D122-LLC syngeneic tumor cells resulted in 10-fold lower brain tumor-cell retention in the traditional approach. Last, while most of the injected tumor cells were arrested in extra-cranial head areas, our method improved targeting of brain-tissue by 7-fold. This head versus brain distribution difference, commonly overlooked, cannot be detected using in vivo bioluminescent imaging. Overall, it is crucial to maintain unperturbed cerebral blood flow while studying brain metastasis and interactions with stress and inflammatory responses.

Nanoparticles (NPs) have great potential to increase the diagnostic capacity of many imaging modalities. MRI is currently regarded as the method of choice for the imaging of deep tissues, and metal ions, such as calcium ions (Ca(2+)), are essential ingredients for life. Despite the tremendous importance of Ca(2+) for the well-being of living systems, the noninvasive determination of the changes in Ca(2+) levels in general, and extracellular Ca(2+) levels in particular, in deep tissues remains a challenge. Here, we describe the preparation and contrast mechanism of a flexible easy to prepare and selective superparamagnetic iron oxide (SPIO) NPs for the noninvasive determination of changes in extracellular Ca(2+) levels using conventional MRI. We show that SPIO NPs coated with monodisperse and purified alginate, having a specific molecular weight, provide a tool to selectively determine Ca(2+) concentrations in the range of 250 µm to 2.5 mm, even in the presence of competitive ions. The alginate-coated magnetic NPs (MNPs) aggregate in the presence of Ca(2+) , which, in turn, affects the T2 relaxation of the water protons in their vicinity. The new alginate-coated SPIO NP formulations, which have no effect on cell viability for 24 h, allow the detection of Ca(2+) levels secreted from ischemic cell cultures and the qualitative examination of the change in extracellular Ca(2+) levels in vivo. These results demonstrate that alginate-coated MNPs can be used, at least qualitatively, as a platform for the noninvasive MRI determination of extracellular Ca(2+) levels in myriad in vitro and in vivo biomedical applications.

Ataxia-telangiectasia is a multifaceted syndrome caused by null mutations in the ATM gene, which encodes the protein kinase ATM, a key participant in the DNA damage response. Retinal neurons are highly susceptible to DNA damage because they are terminally differentiated and have the highest metabolic activity in the central nervous system. In this study, we characterized the retina in young and aged Atmdeficient mice (Atm ؊/؊ ). At 2 months of age, angiography revealed faint retinal vasculature in Atm ؊/؊ animals relative to wild-type controls. This finding was accompanied by increased expression of vascular endothelial growth factor protein and mRNA. Fibrinogen, generally absent from wild-type retinal tissue, was evident in Atm ؊/؊ retinas, whereas mRNA of the tight junction protein occludin was significantly decreased. Immunohistochemistry labeling for occludin in 6-month-old mice showed that this decrease persists in advanced stages of the disease. Some brain disorders may have a vascular origin, 1,2 and vascular diseases can be directly linked to neuronal and synaptic dysfunction through changes in the blood flow, increase in blood-brain barrier permeability, and in nutrient supply. 3 A healthy brain relies on the proper function and communication of all cells comprising the neurovascular unit: neurons, astrocytes, brain endothelium, and vascular smooth muscle cells. 4 Impaired genomic stability interferes with cellular homeostasis and poses a constant threat to cellular viability. 5 The cell combats this threat by activating the DNA damage response (DDR), a complex signaling network that detects the DNA lesions, promotes their repair, and temporarily modulates cellular metabolism while the damage is being repaired. 6 The DDR is vigorously activated by DNA double-strand breaks (DSBs), a particularly cytotoxic DNA lesion induced by ionizing radiation, radiomimetic chemicals, and oxygen radicals. 7,8 The DNA damage response is a hierarchical process executed by sensor/mediator proteins that accumulate at DSB sites and by protein kinases that serve as transducers of the DNA damage alarm to numerous downstream effectors. 6 The primary transducer of the cellular response to DSBs is the protein kinase ATM, which phosphorylates many key players in the various branches of the DDR. 9 Ataxia-telangiectasia (A-T) is an autosomal recessive disorder caused by mutations in the ATM gene that encodes the ATM protein. 10 A-T is characterized by progressive neurodegeneration affecting mainly the cerebellum, which develops into severe neuromotor dysfunction;

No abstract

Activation of the minute virus of mice (MVM) P4 promoter is a key step in the life cycle of the virus and is completely dependent on host transcription factors. Since transcription-factor composition varies widely in different cell types, there is the possibility that only some cell types in the host organism have the capacity to initiate expression from the P4 promoter and therefore that the promoter may be a factor in determining the tropism of MVM. In this study, the ability of various cell types to activate P4, independent of the other virus-host interactions, was examined in transgenic mouse lines bearing a beta-galactosidase reporter sequence driven by the P4 promoter. It was found that lacZ was expressed during embryogenesis and in the adult in a cell-type-specific and differentiation-dependent pattern. The data are consistent with cell-type and stage-specific activation of the P4 promoter having a role in determining the host cell-type range of MVM. The ability of some parvoviruses to replicate in, and kill oncogenically transformed cells, and to destroy induced tumors in laboratory animals is the basis of recent approaches to use MVM-based vectors in cancer gene therapy. Since these vectors rely on the activation of the P4 promoter by the target tissues, understanding the promoter dependence on cell-type and differentiation status is important for their design and potential use.