Nitric oxide dynamics and dependent neurovascular coupling in a triple-transgenic mouse model of Alzheimer’s disease

were highly reproducible between multiple experiments (N>4). Conclusion: DJ-1 shows a complex and dynamic redoxdependent response which regulates its interaction with target proteins in the cytosol and membrane fractions. We speculate these interactions may be important during redox signalling and in the protective role of DJ-1 against oxidative stress. Keywords: DJ-1, cysteine oxidation, cardiomyocytes, heart doi:10.1016/j.freeradbiomed.2012.08.548 Neuroscience and Nitric Oxide 8: Nitric oxide dynamics and dependent neurovascular coupling in a triple-transgenic mouse model of Alzheimer’s disease C.F. Lourenço*1, R.M. Barbosa1 ,2, E. Cadenas3, R. Radi4, J. Laranjinha1 ,2 1 Center for Neuroscience and Cell Biology, Coimbra, Portugal, 2University of Coimbra, Portugal, 3University of Southern California, Los Angeles, CA, USA, 4Center for Free Radical and Biomedical Research, Facultad de Medicina, Universidad de la Republica, Montevideo, Uruguay Alzheimer's disease (AD) is a common and complex neurodegenerative disorder in which nitric oxide(•NO)related pathways and cerebrovascular dysfunction have been implicated. However, the ascertainment of the exact role of each one of these factors is not fully understood. Recently, by simultaneously measuring •NO dynamics and CBF in hippocampus in vivo, we collected evidences that, upon glutamatergic activaction, neuronal-derived-•NO mediates the local increase in cerebral blood flow (CBF) in response to rising metabolic demands imposed by neuronal activation, i.e., the neurovascular coupling process. In this work, by using a similar approach, we investigate whether glutamateinduced •NO production is altered in AD and whether the coupling of both dynamics, •NO and CBF, is compromised. By using a triple transgenic mouse model of Alzheimer's disease (3xTgAD mice), we observed that glutamate-induced •NO dynamics were not significantly affected in AD mice up to 12-months of age, although markers of oxidative stress were observed from 6 month-old. In turn, in older mice (18 month-old), glutamate induced higher •NO peaks in 3xTgAD, which correlated with increased nNOS expression found at this age in hippocampus. A striking observation is that CBF changes coupled to •NO dynamics were impaired in the 12 month-old mice in the absence of significant

S62

reduction in •NO dynamics, declining hereafter with aging in both 3xTgAD and control mice. Data supports that the observed impairment in neurovascular coupling in the AD animals is primarily due to cerebrovascular dysfunction, rather than a dysfunctional signaling from neurons to blood vessels. Globally, by means of direct measuring •NO concentration dynamics and CBF changes in a mouse model of AD, this work highlights the critical role of vascular responses to neuronal derived-•NO signaling, thus providing functional insights that support an impaired cerebrovascular function in AD. CFL acknowledges Posdoctoral fellowship SFRH/BPD/82436/2011 from FCT. Work supported by FCT grant PTDC/SAU-NEU/108992/2008 Keywords: Nitric oxide dynamics, Hippocampus, Neurovascular coupling, Alzheimer's Disease doi:10.1016/j.freeradbiomed.2012.08.549

Oxidation of Macromolecules Oral Presentations Oxidation of Macromolecules 1: Generation and Accumulation of Cellular 5Hydroxymethylcytosine by Redox-active Quinones B-Z. Zhu* Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, China The recently identified sixth nuclear DNA base 5hydroxymethylcytosine (5hmC) is an important epigenetic marker and may be involved in DNA demethylation and pluripotency in mammals. Currently, the most commonly accepted mechanism for the generation of 5hmC is through enzymatic oxidation of 5methylcytosine (5mC) by ten-eleven translocation (TET) family proteins in mammalian cells. 5hmC has been detected in various tissues with a wide disparity in abundance. However, the conversion of 5mC to 5hmC by TET proteins has only been identified in several 5hmC-abundant mammalian cells and tissues. Here we show an unprecedented non-enzymatic pathway for cellular generation of 5hmC induced by redox-active quinones, which may cause 0.35% 5mC to be oxidized and dramatically change epigenome. Interestingly, the formation of 5hmC is persistent and accumulative, which is in contrast to 8-oxo-7,8-dihydro-2'-deoxyguanosine, another well-known biomarker for oxidatively generated DNA damage. The mechanism is found to be due to the redox-cycling of quinones, leading to the production of high levels of reactive oxygen species, which in turn undergo intracellular labile iron-catalyzed conversion to