Manganese Superoxide Dismutase Deficiency Exacerbates Ischemic Brain Damage Under Hyperglycemic Conditions by Altering A
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ORIGINAL ARTICLE
Manganese Superoxide Dismutase Deficiency Exacerbates Ischemic Brain Damage Under Hyperglycemic Conditions by Altering Autophagy Suresh L. Mehta & Yanling Lin & Wenge Chen & Fengshan Yu & Luyi Cao & Qingping He & Pak H. Chan & P. Andy Li
Published online: 8 June 2010 # Springer Science+Business Media, LLC 2010
Abstract Both preischemic hyperglycemia and suppression of SOD2 activity aggravate ischemic brain damage. This study was undertaken to assess the effect of SOD2 mutation on ischemic brain damage and its relation to the factors involved in autophagy regulation in hyperglycemic wild-type (WT) and heterozygous SOD2 knockout (SOD2–/+) mice subjected to 30-min transient focal ischemia. The brain samples were analyzed at 5 and 24 h after recirculation for ischemic lesion volume, superoxide production, and oxidative DNA damage and protein levels of Beclin 1, damageregulated autophagy modulator (DRAM), and microtubuleassociated protein 1 light chain 3 (LC3). The results revealed a significant increase in infarct volume in hyperglycemic SOD2–/+ mice, and this was accompanied with an early Suresh L. Mehta, Yanling Lin and Wenge Chen contributed equally S. L. Mehta : W. Chen : L. Cao : Q. He : P. A. Li (*) Department of Pharmaceutical Sciences, Biomanufacturing Research Institute and Technology Enterprise (BRITE), North Carolina Central University, BRITE Building, 302 East Lawson Street, Durham, NC 27707, USA e-mail: [email protected] Y. Lin Reproductive Biogenesis Institute, University of Hawaii School of Medicine, Honolulu, HI, USA W. Chen Department of Laser Therapeutics, Affiliated Hospital, College of Clinical Sciences, Ningxia Medical University, Ningxia, People’s Republic of China F. Yu : P. H. Chan Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, USA
(5 h) significant rise in superoxide production and reduced SOD2 activity in SOD2–/+ mice as compared to WT mice. The superoxide production is associated with oxidative DNA damage as indicated by colocalization of the dihydroethidium (DHE) signal with 8-OHdG fluorescence in SOD2–/+ mice. In addition, while ischemia in WT hyperglycemics increased the levels of autophagy markers Beclin 1, DRAM, and LC3, ischemia in hyperglycemic, SOD2-deficient mice suppressed the levels of autophagy stimulators. These results suggest that SOD2 knockdown exacerbates ischemic brain damage under hyperglycemic conditions via increased oxidative stress and DNA oxidation. Such effect is associated with suppression of autophagy regulators. Keywords Cerebral ischemia . SOD2 . Hyperglycemia . Oxidative stress . Autophagy
Introduction Hyperglycemia (HG) increases the extent of brain damage after transient cerebral ischemia (for review, see Ref. [1]). The underlying mechanism for this phenomenon is not fully understood. It has been suggested that oxidative stress produced by generation of excessive reactive oxygen species (ROS) in hyperglycemic conditions is associated with the progression of neuronal damage [2, 3]. Mitochondrial superoxide anion
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