Elevated prostacyclin biosynthesis in mice impacts memory and anxiety-like behavior.

Prostacyclin is an endogenous lipid metabolite with properties of vasodilation and anti-platelet aggregation. While the effects of prostacyclin on the vascular protection have been well-documented, the role of this eicosanoid in the central nervous system has not been extensively studied. Recently, a transgenic mouse containing a hybrid enzyme, of cyclooxygenase-1 linked to prostacyclin synthase, was developed that produces elevated levels of prostacyclin in vivo. The goal of this study was to investigate whether increased prostacyclin biosynthesis could affect behavioral phenotypes in mice. Our results uncovered that elevated levels of prostacyclin broadly affect both cognitive and non-cognitive behaviors, including decreased anxiety-like behavior and improved learning in the fear-conditioning memory test. This study demonstrates that prostacyclin plays an important, but previously unrecognized, role in central nervous system function and behavior.

A novel function for proSAAS as an amyloid anti-aggregant in Alzheimer's disease.

Neurodegenerative diseases such as Alzheimer's disease (AD) are characterized by an abnormal aggregation of misfolded beta-sheet rich proteins such as ß-amyloid (Aß). Various ubiquitously expressed molecular chaperones control the correct folding of cellular proteins and prevent the accumulation of harmful species. We here describe a novel anti-aggregant chaperone function for the neuroendocrine protein proSAAS, an abundant secretory polypeptide that is widely expressed within neural and endocrine tissues and which has previously been associated with neurodegenerative disease in various proteomics studies. In the brains of 12-month-old APdE9 mice, and in the cortex of a human AD-affected brain, proSAAS immunoreactivity was highly colocalized with amyloid pathology. Immunoreactive proSAAS co-immunoprecipitated with Aß immunoreactivity in lysates from APdE9 mouse brains. In vitro, proSAAS efficiently prevented the fibrillation of Aß(1-42) at molar ratios of 1 : 10, and this anti-aggregation effect was dose dependent. Structure-function studies showed that residues 97-180 were sufficient for the anti-aggregation function against Aß. Finally, inclusion of recombinant proSAAS in the medium of Neuro2a cells, as well as lentiviral-mediated proSAAS over-expression, blocked the neurocytotoxic effect of Aß(1-42) in Neuro2a cells. Taken together, our results suggest that proSAAS may play a role in Alzheimer's disease pathology.

Inhibitory neuron and hippocampal circuit dysfunction in an aged mouse model of Alzheimer's disease.

In Alzheimer's disease (AD), a decline in explicit memory is one of the earliest signs of disease and is associated with hippocampal dysfunction. Amyloid protein exerts a disruptive impact on neuronal function, but the specific effects on hippocampal network activity are not well known. In this study, fast voltage-sensitive dye imaging and extracellular and whole-cell electrophysiology were used on entorhinal cortical-hippocampal slice preparations to characterize hippocampal network activity in 12-16 month old female APPswe/PSEN1DeltaE9 (APdE9 mice) mice. Aged APdE9 mice exhibited profound disruptions in dentate gyrus circuit activation. High frequency stimulation of the perforant pathway in the dentate gyrus (DG) area of APdE9 mouse tissue evoked abnormally large field potential responses corresponding to the wider neural activation maps. Whole-cell patch clamp recordings of the identified inhibitory interneurons in the molecular layer of DG revealed that they fail to reliably fire action potentials. Taken together, abnormal DG excitability and an inhibitory neuron failure to generate action potentials are suggested to be important contributors to the underlying cellular mechanisms of early-stage Alzheimer's disease pathophysiology.

The neuroendocrine protein 7B2 suppresses the aggregation of neurodegenerative disease-related proteins.

Neurodegenerative diseases such as Alzheimer (AD) and Parkinson (PD) are characterized by abnormal aggregation of misfolded ß-sheet-rich proteins, including amyloid-ß (Aß)-derived peptides and tau in AD and α-synuclein in PD. Correct folding and assembly of these proteins are controlled by ubiquitously expressed molecular chaperones; however, our understanding of neuron-specific chaperones and their involvement in the pathogenesis of neurodegenerative diseases is limited. We here describe novel chaperone-like functions for the secretory protein 7B2, which is widely expressed in neuronal and endocrine tissues. In in vitro experiments, 7B2 efficiently prevented fibrillation and formation of Aß(1-42), Aß(1-40), and α-synuclein aggregates at a molar ratio of 1:10. In cell culture experiments, inclusion of recombinant 7B2, either in the medium of Neuro-2A cells or intracellularly via adenoviral 7B2 overexpression, blocked the neurocytotoxic effect of Aß(1-42) and significantly increased cell viability. Conversely, knockdown of 7B2 by RNAi increased Aß(1-42)-induced cytotoxicity. In the brains of APP/PSEN1 mice, a model of AD amyloidosis, immunoreactive 7B2 co-localized with aggregation-prone proteins and their respective aggregates. Furthermore, in the hippocampus and substantia nigra of human AD- and PD-affected brains, 7B2 was highly co-localized with Aß plaques and α-synuclein deposits, strongly suggesting physiological association. Our data provide insight into novel functions of 7B2 and establish this neural protein as an anti-aggregation chaperone associated with neurodegenerative disease.