The amyloid hypothesis of Alzheimer's disease (AD) postulates that amyloid-␤ (A␤) deposition and neurotoxicity play a causative role in AD; oxidative injury is thought to be central in the pathogenesis. An endogenous defense system against oxidative stress is induced by binding of the transcription factor nuclear factor E2-related factor 2 (Nrf2) to the antioxidant response element (ARE) enhancer sequence. The Nrf2-ARE pathway is activated in response to reactive oxygen species to trigger the simultaneous expression of numerous protective enzymes and scavengers. To exploit the Nrf2-ARE pathway therapeutically, we delivered Nrf2 bilaterally into the hippocampus of 9-month-old transgenic AD mice (APP/PS1 mice) using a lentiviral vector encoding human Nrf2. The data indicate that significant reductions in spatial learning deficits of aged APP/PS1 mice in a Morris Water Maze can be achieved by modulating levels of Nrf2 in the brain. Memory improvement in APP/PS1 mice after Nrf2 transduction shifts the balance between soluble and insoluble A␤ toward an insoluble A␤ pool without concomitant change in total brain A␤ burden. Nrf2 gene transfer is associated with a robust reduction in astrocytic but not microglial activation and induction of Nrf2 target gene heme oxygenase 1, indicating overall activation of the Nrf2-ARE pathway in hippocampal neurons 6 months after injection. Results warrant further exploration of the Nrf2-ARE pathway for treatment of AD and suggest that the Nrf2-ARE pathway may represent a potential therapeutic strategy to pursue in AD in humans, particularly in view of the multiple mechanisms by which Nrf2 can exert its protective effects.amyloid-beta ͉ astrocyte ͉ heme oxygenase-1 ͉ microglia ͉ oxidative stress

Accumulation of amyloid β (Aβ) is a major hallmark in Alzheimer’s disease (AD). Bone marrow derived monocytic cells (BMM) have been shown to reduce Aβ burden in mouse models of AD, alleviating the AD pathology. BMM have been shown to be more efficient phagocytes in AD than the endogenous brain microglia. Because BMM have a natural tendency to infiltrate into the injured area, they could be regarded as optimal candidates for cell-based therapy in AD. In this study, we describe a method to obtain monocytic cells from BM-derived haematopoietic stem cells (HSC). Mouse or human HSC were isolated and differentiated in the presence of macrophage colony stimulating factor (MCSF). The cells were characterized by assessing the expression profile of monocyte markers and cytokine response to inflammatory stimulus. The phagocytic capacity was determined with Aβ uptake assay in vitro and Aβ degradation assay of natively formed Aβ deposits ex vivo and in a transgenic APdE9 mouse model of AD in vivo. HSC were lentivirally transduced with enhanced green fluorescent protein (eGFP) to determine the effect of gene modification on the potential of HSC-derived cells for therapeutic purposes. HSC-derived monocytic cells (HSCM) displayed inflammatory responses comparable to microglia and peripheral monocytes. We also show that HSCM contributed to Aβ reduction and could be genetically modified without compromising their function. These monocytic cells could be obtained from human BM or mobilized peripheral blood HSC, indicating a potential therapeutic relevance for AD.

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BackgroundNumerous clinical trials in stroke have failed, most probably partially due to preclinical studies using young, healthy male rodents with little relevance to the heterogenic conditions of human stroke. Co-morbid conditions such as atherosclerosis and infections coupled with advanced age are known to contribute to increased risk of cerebrovascular diseases. Clinical and preclinical studies have shown that the E4 allele of human apolipoprotein (ApoE4) is linked to poorer outcome in various conditions of brain injury and neurodegeneration, including cerebral ischemia. Since ApoE is a known regulator of lipid homeostasis, we studied the impact of a high-cholesterol diet in aged mice in the context of relevant human ApoE isoforms on the outcome of focal brain ischemia.MethodsAged mice expressing human E3 and E4 isoforms of ApoE in C57BL/6J background and C57BL/6J mice fed on either a high-fat diet or a normal diet underwent permanent middle cerebral artery occlusion. The impact of a high-cholesterol diet was assessed by measuring the serum cholesterol level and the infarction volume was determined by magnetic resonance imaging. Sensorimotor deficits were assessed using an adhesive removal test and the findings were correlated with inflammatory markers.ResultsWe show that expression of human ApoE4 renders aged mice fed with a western-type diet more susceptible to sensorimotor deficits upon stroke. These deficits are not associated with atherosclerosis but are accompanied with altered astroglial activation, neurogenesis, cyclooxygenase-2 immunoreactivity and increased plasma IL-6.ConclusionsOur results support the hypothesis that ApoE alleles modify the inflammatory responses in the brain and the periphery, thus contributing to altered functional outcome following stroke.

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) modulates gene expression in response to oxidative damage in neurodegenerative diseases, including spinal cord injury (SCI). We noticed that activation of Nrf2 pathway persists for an extended time after clinically relevant contusion model of SCI. Injured Nrf2(-/-) mice were impaired in hindlimb function, exhibited increased atrophy, demyelination, and astrogliosis of the SC concomitant with altered expression of genes controlling apoptosis, inflammation, and neurotrophic factors suggesting the importance of Nrf2 for recovery. We used lentiviral gene transfer to increase Nrf2 expression and improve functional recovery after SCI. Although the transferred Nrf2 was expressed in neurons and astrocytes, we noticed hindlimb function impairment and elevated expression of pro-inflammatory cytokines as an adverse effect. These toxic effects were not reduced by including Nrf2 in the lentiviral vector. Augmenting the amount of delivered Nrf2 gene diminished toxic effects of the lentivirus, yet was not sufficient to improve functional recovery. Results of this study lead to the hypothesis that Nrf2 plays a crucial and multifaceted role in recovery from SCI, but even high overexpression of Nrf2 in injured SC may not offer extra benefit, providing protection only against lentivirus-induced toxicity that is manifested in the SC.