SLEEP 2011 Abstract Supplement

A. Basic Science II. Cell and Molecular Biology and Genetics
0036
NADPH OXIDASE 2 ACTIVATION IN MOUSE BRAIN
DURING INTERMITTENT HYPOXIA PROMOTES
EXCESSIVE MITOCHONDRIAL ROS PRODUCTION AND
DYSFUNCTION
Zhang S, Qiao Z, Gozal D, Wang Y
University of Chicago, Chicago, IL, USA
Introduction: We recently showed that intermittent hypoxia during
sleep (IH)-induced neuronal oxidative stress and neurocognitive deficits
in mice were closely related to increased reactive oxygen species (ROS)
content and impaired respiratory function in cortical and hippocampal
mitochondria. On the other hand, these IH-induced pathological changes
were shown to be abolished or attenuated in mice in which NADPH
oxidase was genetically inactivated or pharmacologically inhibited. The
interaction between the NADPH oxidase pathway and pathways underlying
excessive mitochondrial ROS production is however unclear.
Methods: C57BL/6 and gp91phox-/- mice were exposed to IH (alternating
5.7% and 21% O2 every 90 seconds 12 hours/day for 2 months).
Cortical mitochondria were isolated for assessment of ROS content,
membrane potential, and electron transport chain complex activities.
Results: IH elicited significant increases in ROS content in cortical
mitochondria isolated from C57BL/6 mice, especially when respiration
was supported by a complex II substrate. Addition of ADP reduced
mitochondrial ROS content in both control and IH-treated animals and
completely abolished the difference between the two groups. Cortical
mitochondria from IH-treated C57BL/6 mice were also characterized
by decreased complex I activity and reduced inner mitochondrial
membrane potential. In contrast, IH-induced increases in cortical mitochondrial
ROS content were significantly attenuated in gp91phox-/-
mice lacking NADPH oxidase 2 activities due to disruption of the gene
encoding the catalytic subunit of the enzyme. Furthermore, IH-induced
impairment of complex I activity and inner mitochondrial membrane
potential were abrogated in gp91phox-/- mice.
Conclusion: Our findings suggest the presence of a cross-talk between
the NADPH oxidase 2 and mitochondrial ROS production pathways,
in which the former triggers the latter to generate excessive amounts of
ROS. Excess ROS production in turn, leads to mitochondrial oxidative
stress and dysfunction in cortical mitochondria of mice exposed to IH,
promoting apoptosis and cellular dysfunction.
Support (If Any): Supported by NIH grants HL-074369 and HL-
086662.
0037
CORTICAL WHITE MATTER IS VULNERABLE TO
INTERMITTENT HYPOXIA IN NKX6.2 NULL MICE
Cai J 1 , Tuong C 2 , Gozal D 3
1
Pediatrics/KCH Res. Inst., Anatomical Sciences and Neurobiology,
University of Louisville School of Medicine, Louisville, KY, USA,
2
Pediatrics/KCH Res. Inst., University of Louisville School of
Medicine, Louisville, KY, USA, 3 Pediatrics, University of Chicago,
Chicago, IL, USA
Introduction: Recent studies demonstrate that white matter is extensively
affected in brains of obstructive sleep apnea (OSA) patients. We
hypothesize that developmental myelin defect or breakdown underlies
the vulnerability of brain white matter to sleep apnea-associated IH. To
test this hypothesis, we examined the molecules relevant to myelin architecture
and oligodendrocytes in the mouse model of sleep apnea-associated
intermittent hypoxia (IH) using Nkx6.2-null mutant mice with
characteristics of mild abnormal paranodes and slight hypomyelination.
Methods: 12-week C57BL wild-type and Nkx6.2-null mice were exposed
to intermittent hypoxia (IH, 8% / 20.9% O2 /120s each cycle/12hrs)
or intermittent air (IA) during the light phase. After two-week IA or IH
exposure, prefrontal cortex, cortex, CA1 region and cerebellum were
dissected and collected. Myelin-related proteins, structural molecules of
paranode/node of Ranvier, and adult oligodendrocyte progenitor cells
(aOPCs) were examined in different brain regions between IA- and IHtreated
young adult wild-type or Nkx6.2 null mice.
Results: The expressions of myelin-relevant molecules including MBP
and CNPase were significant decreased in cortex, especially in prefrontal
area, in Nkx6.2-null brains after 2-week IH exposure. The NG2+/
pdgfrα+ aOPCs proliferated in response to IH insult. However, no obvious
phenotype of myelin was observed in IH-insulted wild-type brains.
Conclusion: The white matter in region of cortex with myelin deficiency
is vulnerable and sensitive to short-term IH insult, which may further
lead to neurological disorders. Intact and compact myelin laminate may
protect axons against short-term IH insult.
Support (If Any): Sleep Research Society Foundation/J. Christian Gillin
M.D. Research Grant (J.C.), University of Louisville SOM Basic
Grant (J.C.), and NIH HL-086662 (D.G.)
0038
EFFECTS OF STRESSOR CONTROLLABILITY ON NEURAL
PLASTICITY ASSOCIATED MRNA LEVELS IN MOUSE
AMYGDALA AND MEDIAL PREFRONTAL CORTEX (MPFC)
Machida M, Lonart G, Yang L, Sanford LD
Pathology & Anatomy, Eastern Virginia Medical School, Norfolk, VA,
USA
Introduction: Controllable and uncontrollable stress, modeled by escapable
and inescapable shock (ES and IS), produce different alterations
in post-stress rapid eye movement sleep (REM; ES increases whereas IS
decreases). Conditioned reminders of ES and IS also produce increases
and decreases in REM similar to those seen with the original stressors.
The mPFC assesses stressor controllability and interacts with the amygdala
which regulates post-stress sleep and conditioned changes in sleep.
We examined the expression of genes linked to neural plasticity in the
mPFC and amygdala after training with ES and IS.
Methods: Male BALB/cJ mice were trained in a shuttlebox using
a yoked design such that pairs of ES and IS mice received identical
amounts of shock (20 shocks: 0.5 mA, 5.0 sec maximum duration, 1.0
min intervals), but only ES mice could terminate shock. Control animals
(NS) were treated identically, but did not receive shock. Immediately or
2 hour after training, animals were sacrificed, total RNA was isolated,
then reverse transcription and real-time quantitative PCR (RT 2 qPCR)
was performed to assess mRNA levels of RIM1, BDNF, NGF-β, TNFα,
FGF-2, Arc, c-Fos, zif268, GRPR, spinophilin and GluR1 genes in the
amygdala, mPFC and somatosensory cortex, a control region. Corticosterone
was examined at each time point as an index of the stress
response.
Results: ES produced a significant up-regulation of BDNF mRNA levels
at 2 hour post-training in both regions. ES also significantly elevated
zif268 and GluR1 mRNA levels in mPFC whereas IS significantly elevated
Arc and GRPR mRNA levels in the amygdala. ES and IS did not
differentially alter mRNA levels in the somatosensory cortex. Corticosterone
was similarly increased by ES and IS compared to NS.
Conclusion: The observed differences in zif268, GluR1, Arc, and
GRPR mRNA levels after ES and IS may be due to differential expression
of neuronal plasticity related genes in the mPFC and amygdala.
Activation of divergent cellular pathways may underlie differences in
behavior and sleep produced by controllable and uncontrollable stress
and their associated memories.
Support (If Any): Supported by NIH research grants MH61716 and
MH64827.
SLEEP, Volume 34, Abstract Supplement, 2011
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