Genomic and biochemical approaches in the discovery of mechanisms for selective neuronal vulnerability to oxidative stress

Background: Oxidative stress (OS) is an important factor in brain aging and neurodegenerative diseases. Certain neurons in different brain regions exhibit selective vulnerability to OS. Currently little is known about the underlying mechanisms of this selective neuronal vulnerability. The purpose of this study was to identify endogenous factors that predispose vulnerable neurons to OS by employing genomic and biochemical approaches. Results: In this report, using in vitro neuronal cultures, ex vivo organotypic brain slice cultures and acute brain slice preparations, we established that cerebellar granule (CbG) and hippocampal CA1 neurons were significantly more sensitive to OS (induced by paraquat) than cerebral cortical and hippocampal CA3 neurons. To probe for intrinsic differences between in vivo vulnerable (CA1 and CbG) and resistant (CA3 and cerebral cortex) neurons under basal conditions, these neurons were collected by laser capture microdissection from freshly excised brain sections (no OS treatment), and then subjected to oligonucleotide microarray analysis. GeneChip-based transcriptomic analyses revealed that vulnerable neurons had higher expression of genes related to stress and immune response, and lower expression of energy generation and signal transduction genes in comparison with resistant neurons. Subsequent targeted biochemical analyses confirmed the lower energy levels (in the form of ATP) in primary CbG neurons compared with cortical neurons. Conclusion: Low energy reserves and high intrinsic stress levels are two underlying factors for neuronal selective vulnerability to OS. These mechanisms can be targeted in the future for the protection of vulnerable neurons

Genomic and biochemical approaches in the discovery of mechanisms for selective neuronal vulnerability to oxidative stress

<p>Abstract</p> <p>Background</p> <p>Oxidative stress (OS) is an important factor in brain aging and neurodegenerative diseases. Certain neurons in different brain regions exhibit selective vulnerability to OS. Currently little is known about the underlying mechanisms of this selective neuronal vulnerability. The purpose of this study was to identify endogenous factors that predispose vulnerable neurons to OS by employing genomic and biochemical approaches.</p> <p>Results</p> <p>In this report, using <it>in vitro </it>neuronal cultures, <it>ex vivo </it>organotypic brain slice cultures and acute brain slice preparations, we established that cerebellar granule (CbG) and hippocampal CA1 neurons were significantly more sensitive to OS (induced by paraquat) than cerebral cortical and hippocampal CA3 neurons. To probe for intrinsic differences between <it>in vivo </it>vulnerable (CA1 and CbG) and resistant (CA3 and cerebral cortex) neurons under basal conditions, these neurons were collected by laser capture microdissection from freshly excised brain sections (no OS treatment), and then subjected to oligonucleotide microarray analysis. GeneChip-based transcriptomic analyses revealed that vulnerable neurons had higher expression of genes related to stress and immune response, and lower expression of energy generation and signal transduction genes in comparison with resistant neurons. Subsequent targeted biochemical analyses confirmed the lower energy levels (in the form of ATP) in primary CbG neurons compared with cortical neurons.</p> <p>Conclusion</p> <p>Low energy reserves and high intrinsic stress levels are two underlying factors for neuronal selective vulnerability to OS. These mechanisms can be targeted in the future for the protection of vulnerable neurons.</p

Implications of Oxybate Dosing Regimen for Sleep, Sleep Architecture, and Disrupted Nighttime Sleep in Patients with Narcolepsy: A Commentary

Abstract Narcolepsy is associated with disrupted nighttime sleep (DNS). Sodium oxybate (SXB; Xyrem®), administered twice nightly, is indicated for the treatment of cataplexy and excessive daytime sleepiness in patients 7 years or older with narcolepsy. Recently, low-sodium oxybate (LXB, Xywav®; for people 7 years of age and older), which contains 92% less sodium than SXB and is dosed twice nightly, and sodium oxybate for extended release (SXB-ER; Lumryz™; for adults), which contains equal sodium to SXB and is dosed once nightly, have also been approved to treat cataplexy or excessive daytime sleepiness in narcolepsy. This paper reviews the evidence regarding the overall impact of oxybate administration, and impact of different oxybate dosing regimens (once nightly, SXB-ER; twice nightly, SXB), on DNS in narcolepsy utilizing polysomnographic data from five clinical trials (three assessing SXB in adults [referred to here as SXB trials 1, 2, and 3], one assessing SXB in children [referred to as the pediatric SXB trial], and one assessing SXB-ER in adults [REST-ON]). Both once-nightly and twice-nightly oxybate regimens similarly improved symptoms of DNS. Regardless of dosing regimen, people with narcolepsy treated with oxybate experience roughly 42–53 arousals and 9–38 awakenings each night, with one of these awakenings on twice-nightly oxybate being due to the second dosing requirement in studies of SXB. Additionally, for SXB, but not SXB-ER, polysomnographic data has been analyzed by half of the night, demonstrating a greater positive impact on sleep architecture in the second half of the night, which might be related to its nonlinear pharmacokinetic profile. We conclude that while once-nightly and twice-nightly oxybate dosing regimens differ in their pharmacokinetic profiles, both improve DNS in patients with narcolepsy to a similar degree

Apixaban versus warfarin in patients with atrial fibrillation

BACKGROUND: Vitamin K antagonists are highly effective in preventing stroke in patients with atrial fibrillation but have several limitations. Apixaban is a novel oral direct factor Xa inhibitor that has been shown to reduce the risk of stroke in a similar population in comparison with aspirin. METHODS: In this randomized, double-blind trial, we compared apixaban (at a dose of 5 mg twice daily) with warfarin (target international normalized ratio, 2.0 to 3.0) in 18,201 patients with atrial fibrillation and at least one additional risk factor for stroke. The primary outcome was ischemic or hemorrhagic stroke or systemic embolism. The trial was designed to test for noninferiority, with key secondary objectives of testing for superiority with respect to the primary outcome and to the rates of major bleeding and death from any cause. RESULTS: The median duration of follow-up was 1.8 years. The rate of the primary outcome was 1.27% per year in the apixaban group, as compared with 1.60% per year in the warfarin group (hazard ratio with apixaban, 0.79; 95% confidence interval [CI], 0.66 to 0.95; P<0.001 for noninferiority; P = 0.01 for superiority). The rate of major bleeding was 2.13% per year in the apixaban group, as compared with 3.09% per year in the warfarin group (hazard ratio, 0.69; 95% CI, 0.60 to 0.80; P<0.001), and the rates of death from any cause were 3.52% and 3.94%, respectively (hazard ratio, 0.89; 95% CI, 0.80 to 0.99; P = 0.047). The rate of hemorrhagic stroke was 0.24% per year in the apixaban group, as compared with 0.47% per year in the warfarin group (hazard ratio, 0.51; 95% CI, 0.35 to 0.75; P<0.001), and the rate of ischemic or uncertain type of stroke was 0.97% per year in the apixaban group and 1.05% per year in the warfarin group (hazard ratio, 0.92; 95% CI, 0.74 to 1.13; P = 0.42). CONCLUSIONS: In patients with atrial fibrillation, apixaban was superior to warfarin in preventing stroke or systemic embolism, caused less bleeding, and resulted in lower mortality. Copyright © 2011 Massachusetts Medical Society. All rights reserved