The accumulation of aggregated amyloid-β (Aβ) in amyloid plaques is a neuropathological hallmark of Alzheimer's disease (AD). Reactive astrocytes are intimately associated with amyloid plaques; however, their role in AD pathogenesis is unclear. We deleted the genes encoding two intermediate filament proteins required for astrocyte activation-glial fibrillary acid protein (Gfap) and vimentin (Vim)-in transgenic mice expressing mutant human amyloid precursor protein and presenilin-1 (APP/PS1). The gene deletions increased amyloid plaque load: APP/PS1 Gfap(-/-)Vim(-/-) mice had twice the plaque load of APP/PS1 Gfap(+/+)Vim(+/+) mice at 8 and 12 mo of age. APP expression and soluble and interstitial fluid Aβ levels were unchanged, suggesting that the deletions had no effect on APP processing or Aβ generation. Astrocyte morphology was markedly altered by the deletions: wild-type astrocytes had hypertrophied processes that surrounded and infiltrated plaques, whereas Gfap(-/-)Vim(-/-) astrocytes had little process hypertrophy and lacked contact with adjacent plaques. Moreover, Gfap and Vim gene deletion resulted in a marked increase in dystrophic neurites (2- to 3-fold higher than APP/PS1 Gfap(+/+)Vim(+/+) mice), even after normalization for amyloid load. These results suggest that astrocyte activation limits plaque growth and attenuates plaque-related dystrophic neurites. These activities may require intimate contact between astrocyte and plaque.

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α-Synuclein (αSyn) histopathology defines several neurodegenerative disorders, including Parkinson's disease, Lewy body dementia, and Alzheimer's disease (AD). However, the functional link between soluble αSyn and disease etiology remains elusive, especially in AD. We, therefore, genetically targeted αSyn in APP transgenic mice modeling AD and mouse primary neurons. Our results demonstrate bidirectional modulation of behavioral deficits and pathophysiology by αSyn. Overexpression of human wild-type αSyn in APP animals markedly reduced amyloid deposition but, counter-intuitively, exacerbated deficits in spatial memory. It also increased extracellular amyloid-β oligomers (AβOs), αSyn oligomers, exacerbated tau conformational and phosphorylation variants associated with AD, and enhanced neuronal cell cycle re-entry (CCR), a frequent prelude to neuron death in AD. Conversely, ablation of the SNCA gene encoding for αSyn in APP mice improved memory retention in spite of increased plaque burden. Reminiscent of the effect of MAPT ablation in APP mice, SNCA deletion prevented premature mortality. Moreover, the absence of αSyn decreased extracellular AβOs, ameliorated CCR, and rescued postsynaptic marker deficits. In summary, this complementary, bidirectional genetic approach implicates αSyn as an essential mediator of key phenotypes in AD and offers new functional insight into αSyn pathophysiology.

Accumulation of amyloid β (Aβ) in the brain is a key pathological hallmark of Alzheimer’s disease (AD). Because aging is the most prominent risk factor for AD, understanding the molecular changes during aging is likely to provide critical insights into AD pathogenesis. However, studies on the role of miRNAs in aging and AD pathogenesis have only recently been initiated. Identifying miRNAs dysregulated by the aging process in the brain may lead to novel understanding of molecular mechanisms of AD pathogenesis. Here, we identified that miR-186 levels are gradually decreased in cortices of mouse brains during aging. In addition, we demonstrated that miR-186 suppresses β-site APP-cleaving enzyme 1 (BACE1) expression by directly targeting the 3′UTR of Bace1 mRNA in neuronal cells. In contrast, inhibition of endogenous miR-186 significantly increased BACE1 levels in neuronal cells. Importantly, miR-186 overexpression significantly decreased Aβ level by suppressing BACE1 expression in cells expressing human pathogenic mutant APP. Taken together, our data demonstrate that miR-186 is a potent negative regulator of BACE1 in neuronal cells and it may be one of the molecular links between brain aging and the increased risk for AD during aging.

Schwann cell (SC) grafts promote axon regeneration in the injured spinal cord, but transplant efficacy is diminished by a high death rate in the first 2–3 days postimplantation. Both hypoxic preconditioning and pharmacological induction of the cellular hypoxic response can drive cellular adaptations and improve transplant survival in a number of disease/injury models. Hypoxia‐inducible factor 1 alpha (HIF‐1α), a regulator of the cellular response to hypoxia, is implicated in preconditioning‐associated protection. HIF‐1α cellular levels are regulated by the HIF‐prolyl hydroxylases (HIF‐PHDs). Pharmacological inhibition of the HIF‐PHDs mimics hypoxic preconditioning and provides a method to induce adaptive hypoxic responses without direct exposure to hypoxia. In this study, we show that hypoxia‐mimetics, deferoxamine (DFO) and adaptaquin (AQ), enhance HIF‐1α stability and HIF‐1α target gene expression. Expression profiling of hypoxia‐related genes demonstrates that HIF‐dependent and HIF‐independent expression changes occur. Analyses of transcription factor binding sites identify several candidate transcriptional co‐regulators that vary in SCs along with HIF‐1α. Using an in vitro model system, we show that hypoxia‐mimetics are potent blockers of oxidative stress‐induced death in SCs. In contrast, traditional hypoxic preconditioning was not protective. The robust protection induced by pharmacological preconditioning, particularly with DFO, indicates that pharmacological induction of hypoxic adaptations could be useful for promoting transplanted SC survival. These agents may also be more broadly useful for protecting SCs, as oxidative stress is a major pathway that drives cellular damage in the context of neurological injury and disease, including demyelinating diseases and peripheral neuropathies.

There is considerable indirect evidence that growth factor induced changes in the intracellular concentration of calcium play an important role in the regulation of the mammalian cell cycle. However, the precise mechanism by which this may be achieved remains unclear. Here we show that SKF-96365, an inhibitor of growth factor induced capacitative calcium entry (CCE), inhibits cell cycle progression by preventing entry into S phase. SKF-96365 changes the temporal profile of growth factor induced calcium signalling and recent studies have shown that alterations in the temporal and spatial patterns of calcium signalling can differentially regulate gene expression. We have therefore sought to examine the effect of inhibition of CCE on growth factor induced gene expression during G1. To achieve this we have initiated a combined transcriptomic and proteomic approach to measure CCE regulated gene expression using cDNA arrays and two-dimensional polyacrylamide gel electrophoresis, respectively. The initial results of this on-going analysis are reported here. They reveal that inhibition of CCE influences the expression of 29 genes at the mRNA level and 22 genes at the protein level. We report the identification of the mRNAs whose expression is altered by inhibition of CCE and describe the potential functional significance of some of these changes. The value of integrating a transcriptomic and two-dimensional gel electrophoresis based proteomic approach to studies of gene expression is discussed.

Summary We report findings from a new survey of US public attitudes toward human-animal chimeric embryo (HACE) research, designed to compare with recently reported Japanese survey data. We find that 59% of the US public can personally accept the process of injecting human induced pluripotent stem cells into genetically modified swine embryos and having human tissues produced in a pig's body transplanted into a human. This is greater acceptance than in Japan, and there is even strong acceptance among those with strong religious affiliations and who self-identify as conservatives. We argue that strong public support for HACE research, as well as the emerging literature suggesting that humanization of research animals is very unlikely, should compel the NIH to lift its current moratorium on HACE research.

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