241.
NEUROGLOBIN INHIBITS NA+ K+-ATPASE ACTIVITY: A POTENTIAL MECHANISM
OF NEUROPROTECTION. Xu Wei-Lin
1
, Hu Bing
1
, Fan Ming
2
, Qian Ling-Jia
3
, Zhang Cheng-
Gang
1
. Beijing Institute of Radiation Medicine, Beijing, P. R. China
1
, Beijing Institute of Basic
Medical Sciences, Beijing, P. R. China
2
, Tianjin Institute of Hygiene and Environmental
Medicine, Tianjin, P. R. China
3
.
Neuroglobin (NGB) is a newly discovered nervous system specific O2-binding protein and
promotes the survival of neuronal cells upon hypoxia. However, the mechanism underlying
neural protection is not known. To better understand the molecular mechanism of neuroprotective
effects of NGB, we used yeast two-hybrid technique to screen for proteins interacting with NGB
from a human fetal brain cDNA library using NGB as bait. A clone coding the C-terminal portion
of Na+, K+-ATPase b2 subunit (NKA1b2) was identified. Full-length cDNA sequence of coding
region for NKA1b2 was then obtained from a human fetal brain cDNA library by PCR. The
interaction of NGB and NKA1b2 was confirmed by GST-pull down and by co-
immunoprecipitation. Moreover, NGB and NKA1b2 were colocalized both in the cytoplasm and
in the varicosity of nerve fibers in cultured neuronal cells detected by indirect fluorescence
immunocytochemistry. The structure integrity of NGB was found to be essential for the
interaction between NGB and NKA1b2 as assayed by yeast two-hybrid experiments with a serial
of NGB truncated mutants. Consistent with binding to NKA1b2, NGB inhibits the enzymatic
activity of Na+, K+-ATPase in a dose dependent manner. Partial inhibition of Na+, K+-ATPase
activity is a potential survival strategy for neuronal cells in early stage of hypoxia. These studies
reveal a novel function of NGB, and identify the interaction with Na+, K+-ATPase as a potential
mechanism of neuroprotection by NGB.
242.
PROTECTIVE EFFECTS OF IPTAKALIM A NOVEL KATP CHANNEL OPENER ON
NEURONAL APOPTOSIS IN CEREBRAL CORTEX OF CHRONIC HYPOXIC RATS. Xie
Weiping
1
, Wang Hong
2
, Hu Gang
1
. Department of Pulmonology, The First Affiliated Hospital,
Nanjing Medical University, Nanjing
1
, Department of Pharmacology & Neurobiology, Nanjing
Medical University, Nanjing, China
2
.
Objectives: To investigate the protective effect of iptakalim, a novel KATP channel opener,
on neuronal apoptosis induced by chronic hypoxia in cerebral cortex of rats. Methods: Rats were
fed in hypoxic and normobaric environment (10%±0.5% O2,8h/day and 6day/week) and divided
into control group(rats treated with ig NS 5.0ml/kg/day), hypoxia group(hypoxic rats treated with
ig NS 5.0ml/kg/day), treated group (hypoxic rats treated with ig Ipt 0.75 mg/kg/day), treated
group (hypoxic rats treated with ig Ipt 1.5 mg/kg/day). After 4 weeks, neuronal apoptosis in
cerebral cortex of rats was detected with transmission electronic microscope, TdT-mediated
dUTP nick end labeling (TUNEL), flow cytometry. Results: There were apoptosis-associated
changes in neuronal morphology in the cerebral cortex of rats. The cell size was obviously
reduced, cytoplasm shrinked but the plasma membrane was integral. The nuclei were pyknotic
and heterochromatin marginated to the periphery of membrane which indicated condensation of
chromatin. Some nuclei were divided into several pieces and the apoptotic bodies appeared. The
neuronal apoptosis in chronic hypoxic rats was more prominent than that in control rats (P<0.01).
Chronic iptakalim treatment could reversed these changes in dose-dependent manner, in which
the higher dose of iptakalim reversed more effectively than the lower dose did. Conclusions:
Chronic hypoxia induces neuronal apoptosis in cerebral cortex of rats. Administration of
iptakalim before hypoxia exposure had a protective effect on neuronal apoptosis associated with
chronic hypoxia in rats in dose-dependent manner. It was confirmed that iptakalim can pass
through blood-brain-barrier and activate KATP channels in the neuron of cerebral cortex.
Iptakalim might be promising drugs in the treatment of patients with chronic hypoxic pulmonary
hypertension for it could not only ameliorate hypoxic pulmonary hypertension, but also protect
the neuron of cerebral cortex from apoptosis.
