Proteomic profiling of the phosphoproteins in the rat thalamus, hippocampus and frontal lobe after propofol anesthesia.

2.1 MB·English

by  Tang, Jing

Tangetal.BMCAnesthesiology2014,14:3
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RESEARCH ARTICLE Open Access
Proteomic profiling of the phosphoproteins in the
rat thalamus, hippocampus and frontal lobe after
propofol anesthesia
Jing Tang1†, Qiong Xue1,2†, Hong Ding1, Zaisheng Qin1, Jinfang Xiao1, Chunshui Lin1, Youtan Liu3* and Tao Tao1*
Abstract
Background: Propofol is a safe and effective intravenous anesthetic thatis widely used for theinduction and
maintenance of anesthesia during surgery. However, the mechanism by which propofol exerts itsanestheticeffect
remains unknown.The rapidonset ofphosphorylation modifications coincides with that of propofolanesthesia.
Methods: Propofol-anesthetizedrat models were built and phosphorylated proteins inthe thalamus, hippocampus
and frontal lobe were enrichedthe to analyze thechanges inthese phosphoproteins after propofol anesthesia.
Results: Sixteen of thesephosphoprotein spots were successfully identifiedusing MALDI-TOF MSand a subsequent
comparative sequence search in theMascot database.Of these proteins, keratin 18 and the tubulin 2c chain are
cytoskeletal proteins;keratin18 and gelsolin are relevantto alcohol drowsiness. Based on Western blotanalysis, we
also confirmed that thephosphorylation of these proteins is directly induced by propofol, indicating that propofol
anesthesia may be relevantto cytoskeletal proteins and alcohol drowsiness.
Conclusions: These identifiedpropofol-induced phosphorylations of proteinsprovide meaningful contributions for
further studying the anesthetic mechanism of propofol.
Keywords: 2D-gel electrophoresis, Anesthesia, Phosphorylation, Propofol,Rats
Background ion channels in the membrane [4]. Both the neurotrans-
Propofol is widely used in medical procedures such as mitters that play an important role in synaptic transmis-
gastrointestinal endoscopy in outpatient clinics [1], sion and ion channels are mostly proteins. Protein
pediatric MRI examinations [2] and pediatric radiother- modifications, especially phosphorylation and dephos-
apy [3] because of its rapid onset, controllable delivery phorylation, play key roles in various cellular functions,
and rapid recovery. Because of its various advantages and such as cell differentiation [5], cell growth and apoptosis
wide range of applications, the mechanism of propofol as [6]. Kondratyuk et al. [7] confirmed that depolarization
a general anesthetic has been the focus of increasing can increase the phosphorylation ofsodiumchannels ina
scientific research and much attention from anesthesi- study conducted in rat brain synaptosomes. In addition,
ologists. Nevertheless, the specific mechanism remains abnormalphosphorylationcancauseabnormalcellularac-
unclear. tivities. Studies suggested that abnormal phosphorylation
Thus far, anesthetic drugs have been known to exert of tau in brain tissue precedes the formation of neurofib-
their effect mainly by regulating both the synaptic trans- rillary tangles in Alzheimer’s disease [8]. Furthermore, in-
mission of key parts of the central nervous system and creasedtauphosphorylationhasbeenreportedinanimals
subjected to isoflurane and desflurane inhalation, which
may contribute to the short-term cognitive dysfunction
*Correspondence:[email protected];[email protected]
†Equalcontributors following anesthetic administration [9,10]. Therefore, de-
3DepartmentofAnesthesiology,TheUniversityofHongkongShenzhen tecting the changes in phosphorylation after propofol in-
Hospital,Shenzhen,China
fusion will be of great help in exploring the underlying
1DepartmentofAnesthesia,NanfangHospital,SouthernMedicalUniversity,
Guangzhou,Guangdong,China mechanismofthegeneralanestheticactionofpropofol.
Fulllistofauthorinformationisavailableattheendofthearticle
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The brain is a highly interactive entity, in which a PhosphoProtein Purification column (QIAGEN, Valencia,
numberofseparatebrainareascooperatetoexecutebio- CA) according to the manufacturer’s protocol. Briefly,
logical functions[11].Thethalamus maybethoughtasa 30mgoftissuefromthethreebrainregionswerehomog-
type of relay and is believed to act as the switchboard of enized in 350 μl of lysis buffer containing 0.25% (w/v)
information between a variety of subcortical areas and CHAPS, protease/phosphatase inhibitors, and benzonase
the cerebral cortex [12]. Additionally, functional brain as described inthe manufacturer’s protocol.Theobtained
imaging also confirmed that the thalamus is the key tar- phosphorylated proteins were purified with a 2D Clean-
get for anesthetic action [13]. Studies have shown that Up Kit (GE Healthcare). Next, the phosphoprotein yield
the hippocampus is responsible for mental behaviors wasdeterminedwitha2DQUANTKit(GEHealthcare).
such as initial learning and memory as well as for con-
scious behavior[14]. Wei Het al. [15] reported thatpro- Two-dimensionalelectrophoresis(2-DE)
pofol affects LTD expression in hippocampal CA1 An Immobiline Dry strip (pH 3–10 in the thalamus or
dendrites in rats, which was assumed to be the reason pH 4–7 in the hippocampus and frontal lobe, 24 cm
for propofol-induced learning and memory damage. The length, GE Healthcare) was rehydrated with 400 μg of
cerebral cortex is the final target of arousal systems, and phosphoprotein in 450 μl of rehydration buffer contain-
the dorsolateral prefrontal cortex is one of most import- ing 4% CHAPS, 7 M urea, 2 M thiourea, 20 mM Trizma
ant parts of the cerebral cortex, participating in activities base, 65 mM DTT, 1% IPG buffer and 0.002% bromo-
such as emotion recognition, voluntary movements and phenol blue for 14 hr at room temperature. Isoelectric
working memory [16] as well as the maintenance of the focusing (IEF) was performed using the Ettan IPGphor 3
arousal state in mammals [17]. Thus, phosphorylated IEF System (GEHealthcare) for atotalof70kVh.For the
proteins in the thalamus, hippocampus and frontal lobes second dimension, SDS-PAGE was performed using an
were extracted in an animal model induced by propofol Ettan DALTsix Large Vertical system (Amersham, USA)
anesthesia, and the proteins that were differentially according to the following procedures: 45 min at a con-
expressed before and after anesthesia were identified stant power of 5 watts followed by 20 watts per gel until
using two-dimensional electrophoresis and mass spec- thebromophenolbluereachedthebottomofthegel.The
trometry in an attempt to uncover meaningful clues gelswerethenstainedwith0.12%w/vCoomassieBrilliant
about theanesthetic mechanismofpropofol. Blue G250. The 2D gels were analyzed with the DeCyder
softwarepackage(GEHealthcare,USA).
Methods
Experimentalanimalsandtreatment MALDI-TOFMSidentificationanddatabasesearching
Forty-eight male Sprague–Dawley (SD) rats (180–220 g) ThepeptidemixtureswereidentifiedonaBrukerUltraflex
were randomly separated into two groups: the control III MALDI-TOF/TOF MS (Bruker Daltonics, Germany)
group(Cgroup,n=24) and the propofolgroup (Pgroup, operating in reflectron mode with 20 kVaccelerating volt-
n=24). To decrease the individual difference, every 4 ageand23kVreflectingvoltage.Peptidemassfingerprints
rats were divided into a sub-group and tissues from the (PMFs)weresearchedagainsttheSwissProtdatabaseusing
same sub-group were mixed together for one gel of 2D- the program Mascot 2.1 (Matrix Science Ltd). The search
electrophoresis. All animal procedures were approved and parameters were as follows: trypsin digestion with one
conducted in accordance with the guidelines for the care missedcleavage;carbamidomethylmodificationofcysteine
and use of animals of the ethics committee of Southern as a fixed modification; oxidation of methionine as a vari-
Medical University. Rats in the propofol group were ablemodification;peptidetolerancemaximumof±0.5Da;
assigned to receive a 10 mg/kg bolusinjection of propofol MS/MS tolerance maximum of ±100 ppm; peptide charge
(Astrazeneca,UK)deliveredin1minandacontinuousin- of+1;andp<0.05foralocalPMFsearch.
jection of 24 mg/kg/h propofol via a tail vein. The rats in
the control group received an equivalent volume of 10% GeneontologyanalysisusingGOMiner
Intralipid(Sino-SwedenPharmaceuticalCorp.,Ltd.,China) Differentially expressed phosphoproteins were further
viaatailvein.After20min,allratswereanesthetizedwith classifiedusingtheGoMinersoftware[18]incombination
urethane and sacrificed immediately by decapitation. with the GO database, which relies on a controlled vo-
Threebrainregionswerecollectedandfrozeninliquidni- cabulary to describe a protein in terms of its subcellular
trogen. The samples were stored at −80°C until further localization,molecularfunction,orbiologicalprocess.
processing.
Westernblotanalysis
Enrichmentforphosphorylatedproteinsfromtissues A total of 18 SD rats were randomly divided into three
Phosphoproteins from the thalamus, hippocampus and groups: the control group (C group), propofol anesthesia
frontal lobe of the rats were enriched on a QIAGEN for 20 min group (P1 group) and propofol anesthesia
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20 min followed by an arousal state for 1 h group (P2 like protein 1, ATP synthase subunit alpha, metastasis-
group). The rats of the C and P groups were treated in associated protein MTA1 and actin, which were derived
the same manner as described above. The rats of the P2 from the frontal lobe, were decreased in the propofol
group were exposed to the propofol anesthesia used in group.
the P group for 20 min and were sacrificed 1 h post-
anesthesia. Equal amounts of total protein (40 μg) and Geneontologyanalysisofpropofol-responsive
phosphoprotein (40 μg) were loaded and run on 12% phosphoproteins
SDS/polyacrylamide gels and transferred onto polyvi- The list of differentially expressed phosphoproteins was
nylidene difluoride membranes (PVDF) (Amersham preparedforuse intheGoMiner softwareincombination
Pharmacia Biotech, Piscataway, NJ). To detect keratin with the GO database. As seen in Tables 2, 3 and 4, the
18 and phospho-keratin 18, the membranes were probed identified proteins were mainly distributed in the cyto-
with anti-cytokeratin 18 mouse monoclonal antibodies plasm (12/16) and cytoskeleton (6/16), with functions in
(1:500; Santa Cruz Biotechnology, Heidelberg, Germany). metabolism (10/16), regulation (8/16), stimulus response
To detect gelsolin and phospho-gelsolin, the membranes (6/16)andresponsetoethanol(5/16).
were probed with anti-gelsolin mouse monoclonal anti-
bodies (1:500; Santa Cruz Biotechnology, Heidelberg, Westernblotconfirmation
Germany). To detect apolipoprotein E and phospho- To verify the 2D results, keratin 18 and gelsolin from the
apolipoprotein E, the membranes were probed with anti- thalamus and apolipoprotein E from the hippocampus
apolipoprotein E goat polyclonal antibodies (1:500; Santa were analyzed using Western blots. These proteins were
CruzBiotechnology,Heidelberg,Germany).Theimmuno- selected because of interest in the components of the
reactive bands were visualized using a Kodak 2000 M cytoskeleton.Thecorrespondingdifferentialkeratin18ex-
camerasystem(EastmanKodak,Rochester,NY)according pression patterns that were identified using 2D electro-
totheinstructionsofthemanufacturer. phoresis and the MALDI-TOF massspectraare shown in
Figure 2A-B and Figure 3A, respectively. To more rigor-
Statisticalanalysis ously study the effect of propofol on the protein phos-
All the data were tested for a normal distribution before phorylation,18ratsweredividedintothreegroups:theC,
statistical analysis, and the statistical analysis was per- P1 and P2 groups. The amounts of phosphorylated and
formedusingSPSS 13.0. Thestatistical significance of the total keratin 18 were determined using Western blots. As
difference among groups was evaluated using variance shown in Figure 4A-B, the amount of total keratin 18
(ANOVA) followed by the Student-Newman-Keuls post showed no significant difference among the three groups
hocprocedure.SignificancewasdefinedasP<0.05. (P=0.823).However,comparedwiththeamountintheC
and P2 groups, the level of phospho-keratin 18 in the P1
Results group decreased dramatically in accordance with our 2D
Quantitativecomparisonandidentificationof gelsresults(P=0.000).Thecorrespondingdifferentialgel-
phosophoproteinspotson2Dgels solin and apolipoprotein E expression patterns that were
To determine the change in the phosphoprotein profiles identified using 2D electrophoresis and the MALDI-TOF
ofthethalamus,hippocampusandfrontallobeinresponse mass spectra are shown in Figure 2C-E and Figure 3B-C,
to propofol, gel-based comparative proteomic analyses respectively. As shown in Figure 4C-E, there were no
were performed. As shown in Figure 1, 21 phosophopro- observable changes in total gelsolin (P=0.084) and total
tein spots were found to be significantly altered among apolipoprotein E (P=0.139). The amount of phospho-
the three brain regions. Sixteen of these phosphoprotein gelsolin in the P1 group significantly increased compared
spots were successfully identified using MALDI-TOF MS totheamountintheCandP2groups(Figure4C-D).(P=
and the subsequent comparative sequence search in the 0.000). The amount of phospho-apolipoprotein E in the
Mascot database (Table 1). Derived from the thalamus, P1 group significantly decreased compared to that in the
gelsolin and hemoglobin were substantially up-regulated, C and P2 groups (Figure 4E-F) (P=0.000). These results
but keratin 18 was down-regulated in the propofol group. indicated that propofol can affect the extent of protein
Derived from the hippocampus, glutathione peroxidase 3, phosphorylation.
betaine-homocysteine S-methyltransferase 1, SET domain-
containingprotein6andcytochromecoxidasesubunit5A Discussion
were significantly overexpressed in the propofol group, Althoughtheanestheticeffectofpropofolhasbeenexten-
while macrophage-capping protein, tubulin beta-2c chain sivelystudiedbyanesthesiologists,themolecularmechan-
and apolipoprotein E were expressed at a lower level than ismviawhichpropofolexertsitsanestheticeffectremains
in the control group. The levels of delta-aminolevulinic unknown. Research has demonstrated that decreasing the
acid dehydratase,40SribosomalproteinSA,thioredoxin- infusion speed of propofol could effectively decrease the
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Figure1Representativetwo-dimensionalgels.Controlgroup(C),Propofolgroup(P).Thephosphoproteinspotsdifferentiallyexpressedinthe
thalamus(A),hippocampus(B)andfrontallobe(C).
side effects resulting from propofol anesthesia [19]. identified, and their correlation with cognitive dysfunction
Larssonetal.[20]alsofoundthattheminimumamountof after anesthesia was further explored by Xuena Zhang
hemodynamic fluctuations and the most stable anesthetic etal.[23].Theseexperimentalresultsprovidedanewclue
effect occurred when propofol was delivered at a speed of forexplainingthemolecularmechanismsofpostoperative
10mg/kg/min.Becausetheanesthetizedratsinthisexperi- cognitive dysfunction after anesthesia. However, these
mentwerenotsubjectedtoanysurgicalprocedures,thein- studiesexaminedtotal proteins,and proteinsynthesis isa
fusion speed could be set a lower level (24 mg/kg/h), with time-consuming process. In contrast, protein phosphoryl-
whichastableanimalmodelwasestablished. ationisafastand reversible process that is involved in
Futter et al. [21] indicated that 7, 14 and 10 proteins a wide variety of crucial cellular activities [6], in which
spotswerefoundtobedifferentiallyexpressedinratbrain the transcription and synthesis of new proteins are not
tissues 3 h, 24 h and 72 h after propofol anesthesia, re- involved. In all post-translational modification, phos-
spectively.Uniformdifferentiallyexpressedproteinprofiles phorylation anddephosphorylationisthemostimportant
werenoticedinthebraintissuesofratsexposedtopropo- which regulate all activites of life including cellular signal
folorsevoflurane,andsomeproteinsevenshowedatrend transduction, cell differentiation, cell growth and apop-
with the opposite change, indicating that the mechanism tosis [5-7]. In addition, the rapid onset of phosphoryl-
ofactionofinhaled anestheticswasnot completelyidenti- ationmodificationscoincideswiththeonsetofthepropofol
cal to that of intravenous anesthesia [22]. The insoluble anesthesia. Therefore, the profile of phosphorylated pro-
protein profiles in the rat hippocampus were successfully teins in the thalamus, hippocampus and frontal lobes was
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Table1MALDI-TOFMSidentificationofdifferentiallyexpressedprotein
Spota Proteinname Uniprotaccession TheoreticalMr(kDa)b Totalscorec QueriesMachedd P/Ce
1 Keratin18 Q5BJY9 47.76 72 100% ↓
2 Gelsolin Q68FP1 86.07 24 99.96% ↑
3 Hemoglobin P02091 15.85 30 99.95% ↑
4 Macrophage-cappingprotein Q6AYC4 28.80 148 100% ↓
6 Tubulinbeta-2Cchain Q6P9T8 49.80 43 99.96% ↓
7 ApolipoproteinE P02650 35.75 29 99.92% ↓
9 Glutathioneperoxidase3 P23764 25.27 87 100% ↑
10 Betaine-homocysteineS-methyltransferase1 O96171 44.98 62 100% ↑
11 SETdomain-containingprotein6 D3ZSK5 54.55 76 100% ↑
12 Cytochromecoxidasesubunit5A P11240 16.20 29 99.91% ↑
13 Delta-aminolevulinicaciddehydratase P06214 36.03 33 99.95% ↓
15 40SribosomalproteinSA P38983 42.91 150 100% ↓
16 Thioredoxin-likeprotein1 Q920J4 32.25 156 100% ↓
18 ATPsynthasesubunitalpha P31399 59.75 23 99.95% ↓
19 Metastasis-associatedproteinMTA1 Q62599 79.41 52 100% ↓
21 Actin,aorticsmoothmuscle P62738 42.01 62 100% ↓
aThenumbersindicatethespotpositionsin2DgelasshowninFigure1.
bCaculatedfromthedatabaseentrywithoutanyprocessing.
cByMALDI-TOFMSanalysis.
dByMALDI-TOFMSanalysis.
eP/Cpropofolgroupcomparedwithcontrolgroup.
determined using proteomics in this study. Using mass levels of the three proteins were verified using Western
spectrometry, sixteen proteins were found to be differen- blots, suggesting that propofol anesthesia can cause
tially expressed after propofol anesthesia, and the phos- changesincytoskeletalproteinsinbraintissue.
phorylation of keratin 18, gelsolin and apolipoprotein E The cytoskeleton mainly consists of microtubules, mi-
wasmeasuredusingWesternblottoverifythe2Delectro- crofilaments and intermediate filaments. The tubulin 2c
phoresisresults. chain is the main structural component of microtubules,
The identified differentially expressed phosphorylated and actin is the main constituent of microfilaments. In
proteins were subjected to bioinformatics analysis. Six addition to maintaining the stability of cell shape and
proteins, including keratin 18, gelsolin, tubulin 2c chain, structure, cytoskeletal proteins also regulate various mo-
macrophage-capping protein, actin and apolipoprotein E lecularactivitiessuchasintracellulartransport[24],energy
were identified. These proteins form cytoskeletal struc- and information transfer [25], and signal transduction.
turesorparticipateinstabilizingthecytoskeletalstructure.
Additionally, the changing trends in the phosphorylation
Table3Themolecularfunctionoftheidentifiedproteins
afteranesthesiabypropofol
Table2Thesubcellulardistributionoftheidentified Molecular Proteinname
function
proteinsafteranesthesiabypropofol
Binding MTA1,actin,ApolipoproteinE,ATPsynthasesubunit
Subcellular Proteinname
alpha,gelsolin,Macrophage-cappingprotein,
Cytoplasm Keratin18,gelsolin,MTA1,actin,ApolipoproteinE, Betaine-homocysteineS-methyltransferase1,
M-cappingprotein,tubulin2cchain,thioredoxin-like Hemoglobin,40SribosomalproteinSA,
protein1,Betaine-homocysteineS-methyltransferase1, Delta-aminolevulinicaciddehydratase
40SribosomalproteinSA,ATPsynthasesubunitalpha,
Catalytic gelsolin,Glutathioneperoxidase3,tubulin2cchain,
Delta-aminolevulinicaciddehydratase
Hemoglobin,Cytochromecoxidasesubunit5A,
Nucleus keratin18,M-cappingprotein,SETdomain-containing ApolipoproteinE,SETdomain-containingprotein6
protein6,40SribosomalproteinSA,MTA1
Antioxidant Glutathioneperoxidase3,ApolipoproteinE,Delta-
Cytoskeleton keratin18,gelsolin,tubulin2cchain,M-cappingprotein, aminolevulinicaciddehydratase,thioredoxin-like
actin,ApolipoproteinE protein1
Mitochondrion Cytochromecoxidasesubunit5A,ATPsynthase Responseto gelsolin,ApolipoproteinE,Delta-aminolevulinic
subunitalpha ethanol aciddehydratase,actin,Keratin18
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Table4Thebiologicalprocessesbeingparticipatedinby Alterations in cytoskeletal architecture can result in
theidentifiedproteinsafteranesthesiabypropofol changes in ion channels and account for the occurrence
Biological Proteinname and development of brain-related disorders, which was
processes first found in neurocytes. In 1981, Fukuda et al. [26] re-
Metabolic Keratin18,Hemoglobin,ATPsynthasesubunit ported for the first time that cytoskeletal architecture
process alpha,actin,thioredoxin-likeprotein1,SET
disruption could inhibit the excitatory functions of sevr-
domain-containingprotein6,Betaine-homocysteine
S-methyltransferase1,Glutathioneperoxidase3, ral central nervous systems (CNS) component. In 1988,
ApolipoproteinE,MTA1 Srinivasan et al., using the voltage-clamp technique [27],
Biological Keratin18,gelsolin,ApolipoproteinE,Macrophage- confirmed that the cytoskeleton was capable of modu-
regulation cappingprotein,tubulin2cchain,Betaine-homocysteine lating sodium channels in neurocytes. Propofol-induced
S-methyltransferase1,SETdomain-containingprotein6
amnesiamayberelatedtothedown-regulationofactivity-
Developmental Keratin18,ATPsynthasesubunitalpha,tubulin2c regulated cytoskeleton-associated protein (Arc) in the
process chain
hippocampus. In contrast, the Arc mRNA level does not
Stimulus Keratin18,gelsolin,thioredoxin-likeprotein1,
change significantly, indicating that propofol may exert
reponse Delta-aminolevulinicaciddehydratase,ApolipoproteinE,
SETdomain-containingprotein6 its function by affecting protein modification [28].
Figure2Thechangeintheamountsofphospho-keratin18,phospho-gelsolinandphospho-apolipoproteinEinthepropofolgroup.
Controlgroup(C),Propofolgroup(P).Thegelsinthecontrolandpropofol groups have been enlarged to show the low expression of
phospho-keratin 18 (A) and the high expression of phospho-gelsolin (C) and phospho-apolipoprotein E (E) in the propofol group. The
corresponding gray intensityanalysisofthe2Dresults(B,D,F).Thedensitometricanalysisofeachproteinwascalculatedfrom6differentgelsusing
PDQuestsoftware.Eachbarrepresentsthemean±SD(*P<0.05,comparedwiththecontrolgroup).
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Figure3Identificationofkeratin18,gelsolinandapolipoproteinEusingMALDI-TOFMS.Massspectrometryofin-geltrypsindigestsof
theproteinsandanalysisofthedepictedpeptidespectrumresultedintheidentificationofkeratin18(A),gelsolin(B)andapolipoproteinE(C).
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Figure4Confirmationoftheexpressionofphospho-keratin18,phospho-gelsolinandphospho-apolipoproteinEwithWesternblot
analysis.Controlgroup(Cgroup),propofolanesthesiafor20mingroup(P1group)andpropofolanesthesia20minfollowedbyanarousalstate
for1hgroup(P2group).Westernblotanalysisofphosphoproteinandtotalproteinsamplesfromtheindividualrats(A,C,E).Thecorresponding
grayintensityanalysisoftheWesternblotresultsofthe3groups(B,D,F).Eachbarrepresentsthemean±SD(*P<0.05,n=6,comparedwith
theother2groups).
Microtubule-associated proteins (MAPs) bind to the [8]. Sevoflurane, isoflurane and propofol can induce
tubulin subunits that form microtubules. Tau proteins tau hyperphosphorylation, which may account for the
are type II MAPs that are abundant in neurons in the occurrenceofpostoperativecognitivedysfunction[10,29].
central nervous system, and their phosphorylation state Reduced apolipoprotein E phosphorylation caused by
can be modulated by a specific set of phosphatases and anesthetic propofol was demonstrated and was later con-
phosphokinases, which play a vital role in maintaining firmed using Western blot in this experiment. Apolipo-
neuronal function and development. Hyperphosphoryla- protein E is synthesized and secreted predominantly by
tion of the tau protein is assumed to be involved in the astrocytesandmicrogliainthebrain,whichparticipatesin
neuropathogenesis of several types of dementia, such as neuronrepairafterinjury,dendriticgrowthandthemain-
Alzheimer’sdiseaseandpostoperativecognitivedysfunction tenance of synaptic plasticity [30]. Apolipoprotein E also
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playsavitalroleinthepathogenesisofAlzheimer’sdisease, Abbreviations
where apolipoprotein E is found in the amyloid plaques SD:Sprague–Dawley;IEF:Isoelectricfocusing;PMFs:Peptidemass
and neurofibrillary tangles characteristic of Alzheimer’s fingerprints;PVDF:Polyvinylidenedifluoridemembranes;CNS:Central
nervoussystems;Arc:Activity-regulatedcytoskeleton-associatedprotein;
disease[31]. MAPs:Microtubule-associatedproteins;GABA:Gamma-aminobutyricacid;
The deposition of monomers and polymers of hyper- NMDA:N-methyl-D-aspartate;Glu:Glutamicacid.
phosphorylated tau protein in the brain of a trans-
Competinginterests
genic mice expressing apolipoprotein E4 (C112R) [32,33] Allauthorsdeclarethattheyhavenocompetinginterests.
suggested that apolipoprotein E affected tau phosphoryl-
ation. We speculate that the postoperative cognitive dys- Authors’contributions
JT,conductingofthestudyandeditinglanguageofthemanuscript,
function induced by anesthetic propofol may result from
approvedthefinalmanuscriptandattestedtotheintegrityoftheoriginal
alterationsinserum apolipoprotein Elevels.Nevertheless, dataandtheanalysisreportedinthismanuscript.QX,conductingofthe
the interwoven relationship between these factors and studyandpreparingthemanuscript,isthearchivalauthorandapprovedthe
finalmanuscript.HD,datacollection,attestedtotheintegrityoftheoriginal
whether apolipoprotein E phosphorylation is involved in
dataandtheanalysisreportedinthismanuscript.ZQ,dataanalysis,
thisprocessmustbefurtherexplored. approvedthefinalmanuscript.JX,dataanalysis,approvedthefinal
Bioinformatics analysis indicated that gelsolin and kera- manuscript.CL,dataanalysis,approvedthefinalmanuscript.YL,study
design,approvedthefinalmanuscriptandattestedtotheintegrityofthe
tin 18 exhibit responses to ethanol. Ethanol can weaken
originaldataandtheanalysisreportedinthismanuscript.TT,studydesign,
ourbody’sreactions tooutsidestimulation,whichis simi- approvedthefinalmanuscriptandattestedtotheintegrityoftheoriginal
lar to the behavioral changes that emerge after propofol dataandtheanalysisreportedinthismanuscript.Allauthorsreadand
approvedthefinalmanuscript.
anesthesia.Aminoacidneurotransmitterreceptorsplayan
importantroleinalcoholdependence[34].Ethanolisboth Acknowledgements
agamma-aminobutyricacid(GABA)receptoragonistand We thank Dr. Mingzhe Zhao and Hui Li for the help of MALDI-TOF MS
identification and database searching.
an N-methyl-D-aspartate (NMDA) receptor antagonist,
which results in degenerative alterations of the nervous
Funding
systemduringbraindevelopmentbyinhibitingERKphos- ThisworkwassupportedbytheNationalNaturalScienceFoundationof
phorylation[35,36].Theeffectofethanolissimilartothat China(81301664)andtheNaturalScienceFoundationofGuangdong
Province(S2012010008120,andS2013010014312)andMedicalScientific
of propofol on brain stem cell apoptosis during brain de-
ResearchFoundationofGuangdongProvince(B2011202)andtheMajor
velopment.Glutamicacid(Glu)servesasthemainneuro- ProgramofShenzhenTechnologyandInnovationCommittee(201201018).
transmitter for the inputs and outputs as well as the
Authordetails
intrinsic circuitry of the hippocampus, which appears to 1DepartmentofAnesthesia,NanfangHospital,SouthernMedicalUniversity,
be the brain region that is most sensitive to alcohol Guangzhou,Guangdong,China.2DepartmentofAnesthesia,TheFirst
damage [37] and is the target of the anesthetic effect of AffiliatedHospitalofZhengzhouUniversity,Zhengzhou,Henan,China.
3DepartmentofAnesthesiology,TheUniversityofHongkongShenzhen
propofol. In summary, the targets of and transmitters in
Hospital,Shenzhen,China.
general anesthetic agents are similar tothose of the effect
of alcohol on the brain. Furthermore, studies have af- Received:14October2013Accepted:3January2014
Published:10January2014
firmedthatethanolwas able to induce the dephosphor-
ylation of keratin 18 in the liver and kidney [38]. In our References
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