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El pdf del artículo es la versión pre-print.-- et al. ; Alzheimer's disease (AD) is a devastating age-related neurodegenerative disease. Age is the main risk factor for sporadic AD, which is the most prevalent type. Amyloid-β peptide (Aβ) neurotoxicity is the proposed first step in a cascade of deleterious events leading to AD pathology and dementia. Glial cells play an important role in these changes. Astrocytes provide vital support to neurons and modulate functional synapses. Therefore, the toxic effects of Aβ on astrocytes might promote neurodegenerative changes that lead to AD. Aging reduces astrocyte antioxidant defenses and induces oxidative stress. We studied the effects of Aβ {42} on cultures of human astrocytes in the presence or absence of the following pro-oxidant agents: buthionine sulfoximine (BSO), a glutathione synthesis inhibitor, and FeSO{4}, which liberates redox active iron. Pro-oxidant conditions potentiated Aβ toxicity, as shown by the generation of free radicals, inflammatory changes, and apoptosis. Similar treatments were assessed in rats in vivo. A combination of Aβ {40} and Aβ {42} or Aβ {42} alone was infused intracerebroventricularly for 4 weeks. Other animal groups were also infused with BSO and FeSO{4}. A long-term analysis that ended 4 months later showed greater cognitive impairment in the Morris water maze task, which was induced by Aβ plus pro-oxidant agent treatments. Pro-oxidant agents also potentiated brain tissue pathology. This was demonstrated in histological studies that showed highly increased astrocyte reactivity in AD-vulnerable areas, Aβ deposits, and oxidative damage of AD-sensitive hippocampal neurons. To increase our understanding of AD, experimental models should be used that mimic age-related brain changes, in which age-related oxidative stress potentiates the effects of Aβ. © 2010 - IOS Press and the authors. ; This study was supported by grants SAF200613092-C02-02 from the Spanish Ministerio de Ciencia e Innovación, RD06/0013/1004 (RETICEF) from the Instituto de Salud Carlos III, 062931 from Fundació La Marató de TV3 and by the European Network of Excellence DiMI (LSHB-CT-2005-512146). S. García-Matas received a Generalitat (Autonomous Government of Catalonia) fellowship. ; Peer Reviewed

Neuronal death can be preceded by progressive dysfunction of axons. Several pathological conditions such as ischemia can disrupt the neuronal cytoskeleton. Microtubules are basic structural components of the neuronal cytoskeleton that regulate axonal transport and neuronal function. Up-to-date, high-resolution observation of microtubules in living neuronal cells is usually accomplished using fluorescent-based microscopy techniques. However, this needs exogenous fluorescence markers to produce the required contrast. This is an invasive procedure that may interfere with the microtubule dynamics. In this work, we show, for the first time to our knowledge, that by using the endogenous (label-free) contrast provided by second harmonic generation (SHG) microscopy, it is possible to identify early molecular changes occurring in the microtubules of living neurons under ischemic conditions. This is done by measuring the intensity modulation of the SHG signal as a function of the angular rotation of the incident linearly polarized excitation light (technique referred to as PSHG). Our experiments were performed in microtubules from healthy control cultured cortical neurons and were compared to those upon application of several periods of oxygen and glucose deprivation (up to 120 min) causing ischemia. After 120-min oxygen and glucose deprivation, a change in the SHG response to the polarization was measured. Then, by using a three-dimensional PSHG biophysical model, we correlated this finding with the structural changes occurring in the microtubules under oxygen and glucose deprivation. To our knowledge, this is the first study performed in living neuronal cells that is based on direct imaging of axons and that provides the means of identifying the early symptoms of ischemia. Live observation of this process might bring new insights into understanding the dynamics and the mechanisms underlying neuronal degeneration or mechanisms of protection or regeneration. ; This work is supported by the Spanish government through the Ministry of Economy and Competitiveness, grants No. TEC2009-09698 and No. FIS2009-09928; the Ministerio de Sanidad, grant No. FIS PI081932; the Laserlab-Europe Cont. grant No. JRA4:Optobio 212025; and the Photonics for Life Networks of Excellence. This research has also been partially supported by Fundació Cellex Barcelona and partially conducted at the Institute of Photonic Sciences' Super-Resolution Light Nanoscopy Facility. ; Peer reviewed