- Email: [email protected]
P3-364
S482
Poster P3:: Tuesday Posters
and AB42 levels in the well-characterized mouse model of AD (Tg2576 mice, N⬎14/group). We then genetically combined the Tg2576 mice with heterozygous sod2 mice (n⫽15) to study the interactions between mitochondrial oxidative stress and cerebral AB load. We found that mitochondrial SOD2 deficiency exacerbates plaque load and significantly alters the AB40:AB42 ratio in favour of decreased AB40 levels and increased AB42 levels. This was associated with a significant elevation in APP protein, a modulation of both total tau and phosphorylated tau and a significant reduction in metal levels (e.g. Cu, Fe and Zn) in the brain. Conclusions: There is an interaction between APP and mitochondrial oxidative stress that results in a perturbation of two key neurochemical hallmarks of AD, and impacts upon brain metal homeostasis. P3-363
SYNCHROTRON X-RAY STUDY OF ALZHEIMER’S TISSUE DEMONSTRATES MIXEDVALENCE IRON OXIDE ACCUMULATIONS IN SUPERIOR FRONTAL GYRUS
Joanna F. Collingwood1, Mark R. Davidson2, Albina Mikhaylova2, Christopher Batich2, Jon Dobson1, 1Keele University, Stoke On Trent, United Kingdom; 2University of Florida, Gainesville, FL, USA. Contact e-mail: [email protected] Background: The form and distribution of brain iron in neurodegeneration is significant for pathogenesis, chelation therapy, and as a potential biomarker. Iron easily changes valence state in-vivo, ensuring that it is present in a variety of forms. Disrupted iron metabolism is a common feature in neurodegeneration, and redox-active Fe(II) is understood to drive excess free radical generation via the Fenton reaction and thereby contribute to oxidative stress damage. Storage typically involves Fe(II) being taken up and stored in ferritin as Fe(III)-based ferrihydrite-like core. However, recent work has demonstrated unusual iron oxide accumulations associated with Alzheimer’s disease pathology. Objective(s): We are utilizing a powerful mapping/characterization approach with synchrotron X-rays to study autopsy tissue. This enables micronresolution location and identification of iron deposits in situ, and their correlation with disease pathology. This is contributing to our understanding of the role of unusual iron accumulations in disease pathogenesis, and should inform developments in metal chelation therapy and optimize the potential of iron as a biomarker for early detection and diagnosis. Methods: Iron fluorescence was mapped in Alzheimer’s tissue from the superior frontal gyrus. Anomalous iron concentrations were identified and characterized using X-ray absorption spectroscopy. Standards (including ferritin, hemoglobin, and a variety of iron oxide standards) were fitted to the individual traces using linear combination fitting routines, allowing the relative proportions to be determined in micron-scale regions exhibiting a variety of iron compounds. Conclusions: Concentrations of both ferritin and magnetite, a mixed-valence magnetic iron oxide potentially indicating disrupted brain-iron metabolism, were evident. Most significantly, deposits including a predominantly Fe(II)-based oxide were identified in-situ at several sites within the tissue. This is evidence that redox-active iron is concentrated and stabilized in Alzheimer’s tissue, which is particularly important in the context of oxidative stress damage. The presence of Fe(II) may indicate a failure to fully oxidise iron during uptake and storage, or may be a consequence of reduction by amyloid as has been recently shown in vitro. Overall, these results demonstrate a practical means of correlating iron compounds and disease pathology in-situ and have clear implications for disease pathogenesis and potential therapies. P3-364
IRON AND ALZHEIMER’S DISEASE: NEW INSIGHTS FROM NOVEL IMAGING TECHNIQUES
Jon Dobson1,2, Joanna F. Collingwood1, Mark R. Davidson2, Quentin A. Pankhurst3, Albina Mikhaylova2, Dimitri Hautot1, Rafal Dunin-Borkowski4, Mihaly Posfai4, Takeshi Kasama5,4, RKK Chong4, Christopher Batich2, 1Keele University, Stoke-on-Trent, United Kingdom; 2University of Florida, Gainesville, FL, USA;
3 University College London, London, United Kingdom; 4Cambridge University, Cambridge, United Kingdom; 5RIKEN, Saitama, Japan. Contact e-mail: [email protected]
Background: Abnormal accumulations of iron have been known to be associated with Alzheimer’s disease (AD) for over 50 years. In the intervening time, however, very little progress has been made in understanding the origin, nature and role of iron compounds in neurodegeneration. We have recently developed novel techniques which, when combined, allow us to not only locate and map the distribution of anomalous iron compounds in situ in AD tissue but also to identify and quantify the specific compounds present. Objective(s): (i) To modify and develop physics-based methods for imaging, locating and characterizing anomalous iron compounds in Alzheimer’s Disease. (ii) To use information obtained from these studies to inform the development of MRI-based early diagnosis techniques and to understand the possible role of iron and other metals in AD pathology. Methods: Synchrotron ⫻-ray analysis, Superconducting Quantum Interference Device magnetometry and transmission electron microscopy/electron tomography were employed to map and characterize iron compounds in AD and control tissue samples. Conclusions: Using these novel techniques, we have identified specific, anomalous iron compounds associated with Alzheimer’s tissue in general and plaque cores in particular. High concentrations of magnetite (a mix-valence iron oxide) appear to be dominant in the plaque core with levels also raised in bulk tissue samples from AD females. A second, ferrous iron oxide is also present in some anomalies. Both of these compounds may promote oxidative damage by providing a source of ferrous iron and via triplet state stabilization due to the magnetic fields they generate. In addition, electron microscopy analysis indicates a potential malfunction of ferritin within AD plaque cores. The results of these studies will shed light on the potential role of iron in AD pathogenesis and help to inform the development of early detection techniques and new investigations of chelation therapies.
FIG. 1: Electron tomographic reconstruction of an AD plaque core. P3-365
ROLE OF MITOCHONDRIAL ALDEHYDE DEHYDROGENASE IN THE ONSET OF ALZHEIMER’S DISEASE
Ikuroh Ohsawa, Kiyomi Nishimaki, Yayoi Murakami, Yuko Suzuki, Masahiro Ishikawa, Shigeo Ohta, Nippon Medical School, Kawasaki, Japan. Contact e-mail: [email protected]
Poster P3:: Tuesday Posters
and AB42 levels in the well-characterized mouse model of AD (Tg2576 mice, N⬎14/group). We then genetically combined the Tg2576 mice with heterozygous sod2 mice (n⫽15) to study the interactions between mitochondrial oxidative stress and cerebral AB load. We found that mitochondrial SOD2 deficiency exacerbates plaque load and significantly alters the AB40:AB42 ratio in favour of decreased AB40 levels and increased AB42 levels. This was associated with a significant elevation in APP protein, a modulation of both total tau and phosphorylated tau and a significant reduction in metal levels (e.g. Cu, Fe and Zn) in the brain. Conclusions: There is an interaction between APP and mitochondrial oxidative stress that results in a perturbation of two key neurochemical hallmarks of AD, and impacts upon brain metal homeostasis. P3-363
SYNCHROTRON X-RAY STUDY OF ALZHEIMER’S TISSUE DEMONSTRATES MIXEDVALENCE IRON OXIDE ACCUMULATIONS IN SUPERIOR FRONTAL GYRUS
Joanna F. Collingwood1, Mark R. Davidson2, Albina Mikhaylova2, Christopher Batich2, Jon Dobson1, 1Keele University, Stoke On Trent, United Kingdom; 2University of Florida, Gainesville, FL, USA. Contact e-mail: [email protected] Background: The form and distribution of brain iron in neurodegeneration is significant for pathogenesis, chelation therapy, and as a potential biomarker. Iron easily changes valence state in-vivo, ensuring that it is present in a variety of forms. Disrupted iron metabolism is a common feature in neurodegeneration, and redox-active Fe(II) is understood to drive excess free radical generation via the Fenton reaction and thereby contribute to oxidative stress damage. Storage typically involves Fe(II) being taken up and stored in ferritin as Fe(III)-based ferrihydrite-like core. However, recent work has demonstrated unusual iron oxide accumulations associated with Alzheimer’s disease pathology. Objective(s): We are utilizing a powerful mapping/characterization approach with synchrotron X-rays to study autopsy tissue. This enables micronresolution location and identification of iron deposits in situ, and their correlation with disease pathology. This is contributing to our understanding of the role of unusual iron accumulations in disease pathogenesis, and should inform developments in metal chelation therapy and optimize the potential of iron as a biomarker for early detection and diagnosis. Methods: Iron fluorescence was mapped in Alzheimer’s tissue from the superior frontal gyrus. Anomalous iron concentrations were identified and characterized using X-ray absorption spectroscopy. Standards (including ferritin, hemoglobin, and a variety of iron oxide standards) were fitted to the individual traces using linear combination fitting routines, allowing the relative proportions to be determined in micron-scale regions exhibiting a variety of iron compounds. Conclusions: Concentrations of both ferritin and magnetite, a mixed-valence magnetic iron oxide potentially indicating disrupted brain-iron metabolism, were evident. Most significantly, deposits including a predominantly Fe(II)-based oxide were identified in-situ at several sites within the tissue. This is evidence that redox-active iron is concentrated and stabilized in Alzheimer’s tissue, which is particularly important in the context of oxidative stress damage. The presence of Fe(II) may indicate a failure to fully oxidise iron during uptake and storage, or may be a consequence of reduction by amyloid as has been recently shown in vitro. Overall, these results demonstrate a practical means of correlating iron compounds and disease pathology in-situ and have clear implications for disease pathogenesis and potential therapies. P3-364
IRON AND ALZHEIMER’S DISEASE: NEW INSIGHTS FROM NOVEL IMAGING TECHNIQUES
Jon Dobson1,2, Joanna F. Collingwood1, Mark R. Davidson2, Quentin A. Pankhurst3, Albina Mikhaylova2, Dimitri Hautot1, Rafal Dunin-Borkowski4, Mihaly Posfai4, Takeshi Kasama5,4, RKK Chong4, Christopher Batich2, 1Keele University, Stoke-on-Trent, United Kingdom; 2University of Florida, Gainesville, FL, USA;
3 University College London, London, United Kingdom; 4Cambridge University, Cambridge, United Kingdom; 5RIKEN, Saitama, Japan. Contact e-mail: [email protected]
Background: Abnormal accumulations of iron have been known to be associated with Alzheimer’s disease (AD) for over 50 years. In the intervening time, however, very little progress has been made in understanding the origin, nature and role of iron compounds in neurodegeneration. We have recently developed novel techniques which, when combined, allow us to not only locate and map the distribution of anomalous iron compounds in situ in AD tissue but also to identify and quantify the specific compounds present. Objective(s): (i) To modify and develop physics-based methods for imaging, locating and characterizing anomalous iron compounds in Alzheimer’s Disease. (ii) To use information obtained from these studies to inform the development of MRI-based early diagnosis techniques and to understand the possible role of iron and other metals in AD pathology. Methods: Synchrotron ⫻-ray analysis, Superconducting Quantum Interference Device magnetometry and transmission electron microscopy/electron tomography were employed to map and characterize iron compounds in AD and control tissue samples. Conclusions: Using these novel techniques, we have identified specific, anomalous iron compounds associated with Alzheimer’s tissue in general and plaque cores in particular. High concentrations of magnetite (a mix-valence iron oxide) appear to be dominant in the plaque core with levels also raised in bulk tissue samples from AD females. A second, ferrous iron oxide is also present in some anomalies. Both of these compounds may promote oxidative damage by providing a source of ferrous iron and via triplet state stabilization due to the magnetic fields they generate. In addition, electron microscopy analysis indicates a potential malfunction of ferritin within AD plaque cores. The results of these studies will shed light on the potential role of iron in AD pathogenesis and help to inform the development of early detection techniques and new investigations of chelation therapies.
FIG. 1: Electron tomographic reconstruction of an AD plaque core. P3-365
ROLE OF MITOCHONDRIAL ALDEHYDE DEHYDROGENASE IN THE ONSET OF ALZHEIMER’S DISEASE
Ikuroh Ohsawa, Kiyomi Nishimaki, Yayoi Murakami, Yuko Suzuki, Masahiro Ishikawa, Shigeo Ohta, Nippon Medical School, Kawasaki, Japan. Contact e-mail: [email protected]