No abstract

We assessed baseline and KCl‐stimulated glutamate release by using microdialysis in freely moving young adult (7 months) and middle‐aged (17 months) transgenic mice carrying mutated human amyloid precursor protein and presenilin genes (APdE9 mice) and their wild‐type littermates. In addition, we assessed the age‐related development of amyloid pathology and spatial memory impaired in the water maze and changes in glutamate transporters. APdE9 mice showed gradual spatial memory impairment between 6 and 15 months of age. The stimulated glutamate release declined very robustly in 17‐month‐old APdE9 mice as compared to 7‐month‐old APdE9 mice. This age‐dependent decrease in stimulated glutamate release was also evident in wild‐type mice, although it was not as robust as in APdE9 mice. When compared to individual baselines, all aged wild‐type mice showed 25% or greater increase in glutamate release upon KCl stimulation, but none of the aged APdE9 mice. There was an age‐dependent decline in VGLUT1 levels, but not in the levels of VGLUT2, GLT‐1 or synaptophysin. Astrocyte activation as measured by glial acidic fibrillary protein was increased in middle‐aged APdE9 mice. Blunted pre‐synaptic glutamate response may contribute to memory deficit in middle‐aged APdE9 mice.

Pyrrolidine dithiocarbamate (PDTC) is a clinically tolerated inhibitor of nuclear factor-B (NF-B), antioxidant and antiinflammatory agent, which provides protection in brain ischemia models. In neonatal hypoxia-ischemia model, PDTC activates Akt and reduces activation of glycogen synthase kinase 3␤ (GSK-3␤). Because chronic inflammation, oxidative stress, and increased GSK-3␤ activity are features of Alzheimer's disease (AD) pathology, we tested whether PDTC reduces brain pathology and improves cognitive function in a transgenic animal model of AD. A 7 month oral treatment with PDTC prevented the decline in cognition in AD mice without altering ␤-amyloid burden or gliosis. Moreover, marked oxidative stress and activation of NF-B were not part of the brain pathology. Instead, the phosphorylated form of GSK-3␤ was decreased in the AD mouse brain, and PDTC treatment increased the phosphorylation of Akt and GSK-3␤. Also, PDTC treatment increased the copper concentration in the brain. In addition, PDTC rescued cultured hippocampal neurons from the toxicity of oligomeric A␤ and reduced tau phosphorylation in the hippocampus of AD mice. Finally, astrocytic glutamate transporter GLT-1, known to be regulated by Akt pathway, was decreased in the transgenic AD mice but upregulated back to the wild-type levels by PDTC treatment. Thus, PDTC may improve spatial learning in AD by interfering with Akt-GSK pathway both in neurons and astrocytes. Because PDTC is capable of transferring external Cu 2ϩ into a cell, and, in turn, Cu 2ϩ is able to activate Akt, we hypothesize that PDTC provides the beneficial effect in transgenic AD mice through Cu 2ϩ -activated Akt pathway.

This work demonstrates how increased activity of copperzinc superoxide dismutase (SOD1) paradoxically boosts production of toxic reactive oxygen species (ROS) in the intermembrane space (IMS) of mitochondria. Even though SOD1 is a cytosolic enzyme, a fraction of it is found in the IMS, where it is thought to provide protection against oxidative damage. We found that SOD1 controls cytochrome c-catalyzed peroxidation in vitro when superoxide is available. The presence of SOD1 significantly increased the rate of ROS production in mitoplasts, which are devoid of outer membrane and IMS. In response to inhibition of respiration with antimycin A, isolated mouse wildtype mitochondria increased ROS production, but the mitochondria from mice lacking SOD1 (SOD1 ؊/؊ ) did not. Also, lymphocytes isolated from SOD1 ؊/؊ mice produced significantly less ROS than did wild-type cells and were more resistant to apoptosis induced by inhibition of respiration. Moreover, an increased amount of the toxic mutant G93A SOD1 in the IMS increased ROS production. The mitochondrial dysfunction and cell damage paradoxically induced by SOD1-mediated ROS production may be implicated in chronic degenerative diseases.

Neuroinflammation is strongly induced by cerebral ischemia. The early phase after the onset of ischemic stroke is characterized by acute neuronal injury, microglial activation, and subsequent infiltration of blood-derived inflammatory cells, including macrophages. Therefore, modulation of the microglial/macrophage responses has increasingly gained interest as a potential therapeutic approach for the ischemic stroke. In our study, we investigated the effects of peripherally administered interleukin 13 (IL-13) in a mouse model of permanent middle cerebral artery occlusion (pMCAo). Systemic administration of IL-13 immediately after the ischemic insult significantly reduced the lesion volume, alleviated the infiltration of CD45 + leukocytes, and promoted the microglia/macrophage alternative activation within the ischemic region, as determined by arginase 1 (Arg1) immunoreactivity at 3 days post-ischemia (dpi). Moreover, IL-13 enhanced the expression of M2a alternative activation markers Arg1 and Ym1 in the peri-ischemic (PI) area, as well as increased plasma IL-6 and IL-10 levels at 3 dpi. Furthermore, IL-13 treatment ameliorated gait disturbances at day 7 and 14 and sensorimotor deficits at day 14 post-ischemia, as analyzed by the CatWalk gait analysis system and adhesive removal test, respectively. Finally, IL-13 treatment decreased neuronal cell death in a coculture model of neuroinflammation with RAW 264.7 macrophages. Taken together, delivery of IL-13 enhances microglial/macrophage antiinflammatory responses in vivo and in vitro, decreases ischemia-induced brain cell death, and improves sensory and motor functions in the pMCAo mouse model of cerebral ischemia.