Hyperglycemia Induces Oxidative Stress and Impairs Axonal Transport Rates in Mice

studies to determine the effect of hyperglycemia on the neurons in the central nervous system (CNS). While olfactory dysfunction is indicated in diabetes, the effect of hyperglycemia on olfactory receptor neurons (ORNs) remains unknown. In this study, we utilized manganese enhanced MRI (MEMRI) to assess the impact of hyperglycemia on axonal transport rates in ORNs. We hypothesize that (i) hyperglycemia induces oxidative stress and is associated with reduced axonal transport rates in the ORNs and (ii) hyperglycemia-induced oxidative stress activates the p38 MAPK pathway in association with phosphorylation of tau protein leading to the axonal transport deficits.-weighted MEMRI imaging was used to determine axonal transport rates post-streptozotocin injection in wildtype (WT) and superoxide dismutase 2 (SOD2) overexpressing C57Bl/6 mice. SOD2 overexpression reduces mitochondrial superoxide load. Dihydroethidium staining was used to quantify the reactive oxygen species (ROS), specifically, superoxide (SO). Protein and gene expression levels were determined using western blotting and Q-PCR analysis, respectively.STZ-treated WT mice exhibited significantly reduced axonal transport rates and significantly higher levels of ROS, phosphorylated p38 MAPK and tau protein as compared to the WT vehicle treated controls and STZ-treated SOD2 mice. The gene expression levels of p38 MAPK and tau remained unchanged.Increased oxidative stress in STZ-treated WT hyperglycemic mice activates the p38 MAPK pathway in association with phosphorylation of tau and attenuates axonal transport rates in the olfactory system. In STZ-treated SOD-overexpressing hyperglycemic mice in which superoxide levels are reduced, these deficits are reversed

Impact of arginase II on CBF in experimental cortical impact injury in mice using MRI

Traumatic brain injury (TBI) results in reduced cerebral blood flow (CBF) and low levels of the vasodilator nitric oxide (NO) may be involved. Arginase II negatively regulates NO production through competition for the substrate -arginine. We determined whether arginase II-deficient (ArgII−/−) mice would show improved CBF after TBI through arterial spin-labeling magnetic resonance imaging (MRI). The ArgII−/− mice exhibit a significantly improved CBF recovery after trauma in the perilesional brain (P=0.0015) and in various other brain regions. In conclusion, arginase II deficiency leads to a better CBF recovery after TBI and implicates arginase II in hemodynamic processes

STZ- WT mice depict significantly increased ROS levels that decrease in]SOD2-STZ mice.

<p>(A) The images depict nasal cavity sections showing genotypic differences in DHE fluorescence. (B) The graph depicts ratio of DHE and corresponding DAPI fluorescence, which was measured with ImageJ software. Significance was assessed by one way ANOVA with Dunnett's post-test. For WT, WT-STZ, SOD2, and SOD2-STZ n = 4, 6, 4, 4 respectively. ** p<0.01, * p<0.05 Bar = 20 µm.</p

MEMRI experiments demonstrate that the axonal transport deficits in WT-STZ mice recover in SOD2-STZ mice.

<p>(A) Pseudo-color MRI images depicting changes in Mn²⁺ signal intensities (yellow color) at the beginning (2minutes) and at the end of the imaging session (32 minutes) at a region of interest (ROI) identified as a circle on the outer olfactory neuronal layer (ONL). Note that the WT, SOD and SOD2-STZ mice exhibit a change from green (2 minute time point) to yellow (32 minute time point) whereas the WT-STZ animals exhibit a light green color at both time points indicating that Mn²⁺ has not traveled to these areas at the same rate. (B) Gray-Scale Image of the same data set in (A). (C) The graph depicts normalized axonal transport rates (% control) in the WT and SOD2 mice treated with vehicle or STZ for a week before <i>in vivo</i> axonal transport studies. Twelve mice were used in the WT group and four mice were used in each of WT-STZ, SOD2, and SOD2-STZ groups. Statistical analysis: One way ANOVA, Dunnett's post-test. * p<0.05. SOD2  =  SOD-2 overexpressing mice; SOD2-STZ  =  SOD-2 overexpressing mice treated with STZ.</p

Phosphorylated Tau significantly increase in WT-STZ mice and recovers in SOD2-STZ mice, despite hyperglycemia.

<p>Western blotting analysis of OB tissues from WT, WT-STZ, SOD2, SOD2-STZ mice show: (A) changes in site-specific phosphorylation of tau (p-tau) at threonine 205, (seven mice in WT, WT-STZ groups and six in SOD2 and SOD2-STZ groups) (B) changes in total levels of tau protein, (seven mice in WT, WT-STZ groups and six in SOD2 and SOD2-STZ groups) (C) QPCR of brain homogenates depict relative changes in mRNA levels of tau, (six mice used in each of the four groups) and (D) representative western blot from OB homogenates from 1 week vehicle or STZ treated 2-4-month-old mice. The results are normalized to β-actin. Statistical analysis: One way ANOVA followed by Dunnett's post test. ** p<0.01, *p<0.05.</p

STZ-induced hyperglycemia impairs axonal transport in the olfactory receptor neurons.

<p>(A) Graph depicts axonal transport rates (depicted as Mn²⁺ ΔSI/t on Y axis, where “SI” is signal intensity and “t” is time) of Mn²⁺at 1 week post-STZ treatment for WT(n = 3) and WT-STZ with fasting glucose levels 200–399 mg/dl (n = 3), and >400 mg/dl (n = 5). (B) Graph depicts the changes in axonal transport rates for WT (n = 4), WT-STZ (n = 3), and WT-STZ+insulin treated mice (n = 4). (C) The graph represents changes in axonal transport rates in a mouse model of WT-STZ (n = 5) as compared to WT mice (n = 4). Statistical analysis: One way ANOVA, Tukey's post test for more than 2 groups and Students t test to compare 2 groups. * p<0.05, ** p<0.01, *** p<0.001/WT  =  wildtype control. WT-STZ  =  Wildtype treated with streptozotocin.</p

Antioxidant Carbon Particles Improve Cerebrovascular Dysfunction Following Traumatic Brain Injury

Injury to the neurovasculature is a feature of brain injury and must be addressed to maximize opportunity for improvement. Cerebrovascular dysfunction, manifested by reduction in cerebral blood flow (CBF), is a key factor that worsens outcome after traumatic brain injury (TBI), most notably under conditions of hypotension. We report here that a new class of antioxidants, poly(ethylene glycol)-functionalized hydrophilic carbon clusters (PEG-HCCs), which are nontoxic carbon particles, rapidly restore CBF in a mild TBI/hypotension/resuscitation rat model when administered during resuscitationa clinically relevant time point. Along with restoration of CBF, there is a concomitant normalization of superoxide and nitric oxide levels. Given the role of poor CBF in determining outcome, this finding is of major importance for improving patient health under clinically relevant conditions during resuscitative care, and it has direct implications for the current TBI/hypotension war-fighter victims in the Afghanistan and Middle East theaters. The results also have relevancy in other related acute circumstances such as stroke and organ transplantation