ORIGINAL ARTICLE

Effects of propofol on P2X7 receptors and the secretion of tumornecrosis factor-a in cultured astrocytes

Jia Liu • Xiao-Fei Gao • Wen Ni • Jin-Bao Li

Received: 20 October 2010 / Accepted: 6 May 2011 / Published online: 24 May 2011

� Springer-Verlag 2011

Abstract Upon CNS injury, adenosine-50-triphosphate is

released and acts on P2X7 receptors, which might influence

many cytokines secretion from glial cells and, in turn,

affects the survival of neurons. Propofol, an intravenous

anesthetic, has been shown to provide neuroprotective

effect. However, the effect of propofol on astrocyte-asso-

ciated processes remains to be clarified. In this study, we

investigated the effects of propofol on P2X7 activity in

astrocytes and tumor necrosis factor-a (TNF-a) secretion

from these cells and thereby to infer the possible role(s) of

glial P2X7 receptors in propofol neural protective effects.

Whole-cell patch clamp results showed that in clinically

relevant concentrations (3.3, 10 or 33 lM), propofol

increased the P2X7 current amplitudes significantly and

propofol in 10 lM extended the inactivation times of P2X7

receptors. Enzyme-linked immunosorbent assay showed

that propofol increased the secretion of TNF-a from

astrocytes in high concentration (300 lM), while inhibited

in clinically relevant concentration (10 lM). Both of these

effects were not influenced by Brilliant blue G. These

results suggest that in clinically relevant concentrations,

propofol increases the activity of P2X7 receptors in

activated astrocytes, but this does not contribute to the

downregulation of the secretion of TNF-a.

Keywords Astrocytes � Propofol � Purinergic P2X7

receptor � Tumor necrosis factor-a

Introduction

In the central nervous system (CNS), extracellular adeno-

sine-50-triphosphate (ATP) has physiological roles in neu-

rotransmission, glial communication, neurite outgrowth,

and proliferation [1]. Extracellular ATP derived from

injured cells or astrocytes is one of the most important key

messengers for mediating pathological conditions of the

CNS. Massive amounts of ATP are released from damaged

tissue after ischemia and trauma, resulting in sustained

elevation of ATP levels in the areas surrounding the injured

zone [2–4]. P2X7 receptor is a purinergic P2 receptor and

functions as an ion channel in response to extracellular

ATP and is permeable to several small cations such as

Ca2?, K?, and Na? [5]. Through the activation of P2X7

receptor, ATP influences the secretion of pro-inflammatory

cytokines and chemokines such as tumor necrosis factor-a(TNF-a), interleukin-1b (IL-1b), and CC chemokine ligand

3 [6–8] and also stimulates the production of superoxide

and nitric oxide in microglial cells [9, 10]. In these cases,

ATP is a potent immunomodulator regulating the activa-

tion, migration, phagocytosis, and release of pro-inflam-

matory factors in immune and glial cells.

Astrocytes are the most abundant glial cells in the brain

and have a critical role in maintaining neuronal activities

and alteration of their functions. Upon CNS injury, astro-

cytes will be activated by ATP and produce TNF-a, IL-1b,

and glutamate that can impede or promote neuron survival

J. Liu � W. Ni (&) � J.-B. Li (&)

Department of Anesthesiology, Changhai Hospital,

Second Military Medical University, 168 Changhai Road,

Shanghai 200433, China

e-mail: ni_wen2010@yahoo.cn

J.-B. Li

e-mail: li_jinbao2010@yahoo.cn

X.-F. Gao

Department of Neurobiology, Institute of Neuroscience,

Second Military Medical University,

800 Xiangyin Road, Shanghai 200433, China

123

Clin Exp Med (2012) 12:31–37

DOI 10.1007/s10238-011-0139-4

[11]. P2X7 receptor has been reported in astrocytes [12].

Both 1 mM ATP and 30-O-(4-benzoyl)benzoyl-ATP

(BzATP), a P2X7 receptor agonist, attenuated TNF-arelease in lipopolysaccharide (LPS)-stimulated astrocytes

[13].

Propofol (2, 6-diiospropyl phenol) is a potent intrave-

nous hypnotic agent widely used for the induction and

maintenance of anesthesia and for sedation in the intensive

care unit [14]. Much attention has been given to the neu-

roprotective effect of propofol in ischemic brain damage

[15–24]. However, the effect of propofol on astrocyte-

associated processes remains to be clarified. In the present

study, we investigated the effects of propofol on P2X7

receptor and TNF-a secretion in cultured astrocytes and

thereby to infer the possible role(s) of glial P2X7 receptors

in propofol neural protective effects.

Materials and methods

Astrocyte-purified cultures

Astrocytes were harvested from neonatal rats (P2–3) as

previously described [25, 26]. The cerebral cortices were

removed, demembranated, chopped, and then incubated

with 0.125% trypsin at 37�C for 30 min. The mixture was

then triturated in triturating solution and the cells were

centrifuged, resuspended in serum, and then plated onto

poly-D-lysine-coated culture flasks and incubated in

DMEM containing 10% FBS. After 6–10 days, as soon as a

monolayer of astrocytes was formed, microglia and cells of

the oligodendrocyte lineage were removed by shaking the

culture at 150 rpm at 37�C overnight. This protocol

resulted in highly pure astrocyte cultures ([96%) as

assessed by immunocytochemical staining using primary

antibodies raised against GFAP. Finally, astrocytes were

harvested by treating the culture flasks with 0.125% trypsin

solution. Collected cells were plated at a density of

1 9 103/cm2 onto coverslips in 24-well plates and cultured

for 24 h before electrophysiological recordings.

Electrophysiological recordings

A whole-cell patch clamp technique was used to record

ionic currents. The pipette solution contained 130 mM

KCl, 1 mM CaCl2, 2 mM MgCl2, 10 mM EGTA, and

10 mM HEPES. The pH was adjusted to 7.2 with KOH.

The external solution contained 140 mM NaCl, 5 mM KCl,

2.5 mM CaCl2, 1 mM MgCl2, 10 mM glucose, and 10 mM

HEPES. The pH was adjusted to 7.4 with NaOH. The

pipette resistance was 6–8 MX. Whole-cell voltage-clamp

recordings were performed at room temperature (21–24�C)

with a MultiClamp 700A amplifier (Axon Instruments,

Foster City, California, USA). A membrane potential was

held at -70 mV, and those recordings with series resis-

tance above 20 MX were rejected. Analog signals were

filtered at 2 kHz, sampled at 10 kHz. Drug solutions were

delivered by OCTAFLOW system (ALA scientific Instru-

ments Inc, Westbury, New York, USA). BzATP was

applied for 5 s. The peak currents during drug application

were measured. One barrel was used to apply a drug-free

solution to enable rapid termination of the drug application.

Experiments were controlled by clampex 8.1 software

(Axon Instruments).

ELISA

Astrocytes were cultured at a density of 1 9 105/cm2. LPS

(10 lg/ml) was added to the culture medium. After treat-

ment of the cells, they were grown in 24-well plates, with

the indicated concentrations of drugs for the times indi-

cated, in triplicate. The culture media was collected from

each well and centrifuged at 600 g for 10 min. Superna-

tants were assayed for TNF-a by ELISA according to the

manufacturer’s instructions (R&D Systems Europe, Ltd.).

The sensitivity limit for this procedure is 15 pg TNF-a/ml.

The absorbance at 450 nm was read with a Bio-Rad model

680 microplate spectrophotometer (Bio-Rad, California,

USA).

Reagents

Propofol, LPS, BzATP, and Brilliant blue G (BBG) were

purchased from Sigma (Shanghai, China). All chemicals

were dissolved in water or dimethyl sulfoxide and then

diluted in the recording physiological solution or cell cul-

ture medium just before use.

Statistical analysis

Data were analyzed by clampfit 8.1 software (Axon

Instruments) and Origin 7.02 (OriginLab Corporation,

Northampton, Massachusetts, USA). All results are

expressed as mean ± SEM. A Fisher’s least significance

difference t test was used. A difference was accepted as

significant if the probability was less than 5% (P \0.05).

Results

Propofol increases BzATP-sensitive current

in astrocytes

Recordings from astrocytes were made within 2 days after

secondary plating. Application of BzATP (300 lM) to the

astrocytes, voltage clamped at -70 mV, evoked an inward

32 Clin Exp Med (2012) 12:31–37

123

current in 185 of 201 cells tested. The current rapidly

ceased after removal of the agonist. The currents amplitude

varied greatly, from 73 to 1309pA, and the currents were

blocked by 10uM BBG (Fig. 1B). BzATP failed to induce

any inward current in flat and polygonal cells, while large

amplitude currents were always detected in the hypertro-

phy cells with long processes. In the following electro-

physiological experiments, we mainly investigated the

P2X7 receptor currents in these reactive astrocytes char-

acterized by long processes.

In order to investigate whether propofol influenced the

P2X7 receptor currents of astrocytes, we first treated the

cells with 300 lM BzATP for 5 s, then washed with

the external solution for 2 min, and finally treated the cells

with 300 lM BzATP along with 0.33, 1, 3.3, 10, 33, 100,

or 300 lM prpofol for 5 s. P2X7 receptor current

amplitudes were increased by propofol (Fig. 1A). The

percentage of enhancement increased as the propofol

concentration increased and reached the maximum at

10 lM, then the percentage went down while the propofol

concentration continue increased (Fig. 1C1). By taking the

current increase induced by 10 lM propofol (maximal

effect) as 100% of effect, the data of the enhancement of

propofol were fitted by a sigmoidal equation (Eq. 1), where

A1 is the highest effect level, A2 is the lowest effect level,

x0 is IC50, and p is the slope of the curve (Fig. 1C2). The

IC50 of propofol is 1.7 lM.

We also investigated whether the kinetic characteristics

of the P2X7-activated current was affected by propofol.

The best approximation of the deactivating current

(Ideact(t)) during washout of BzATP was achieved using a

bi-exponentially decaying function (Eq. 2), where I0 is the

steady-state current, Ideact,1 and Ideact,2 are the initial

amplitudes, and sdeact,1 and sdeact,2 are the time constants of

the slow and fast deactivating component, respectively

[27]. According to our results (Table 1), in a relatively

low concentration range (from 0.33 to 10 lM), propofol

increased sdeact,1 in a dose-dependent manner. As the

concentration of propofol is higher than 10 lM (from 33 to

300 lM), the degree of increase was gradually reduced.

Propofol (from 0.33 to 300 lM) did not show any signif-

icant influence on sdeact,2.

Propofol influences secretion of TNF-a

According to the previous electrophysiological results, the

P2X7 receptor currents were not increased significantly

when astrocytes were treated with high concentration

Fig. 1 Concentration–response relationships of propofol for BzATP-

sensitive currents. A1–A7, Sample traces of the inward currents

induced by 300 lM BzATP (control, left) and, after 2 min of external

solution perfusion, the currents (right) induced by 0.33 lM (A1),1 lM (A2), 3.3 lm (A3), 10 lM (A4), 33 lm (A5), 100 lM (A6), and

300 lM (A7) propofol. B The inward current evoked by 300 lM

BzATP was blocked by 10uM BBG. C1. Linear chart of P2X7

receptor current co-treated with different concentrations of propofol.

Ordinate represents the current amplitude as percentages of the

control. Asterisks indicate significant difference in the control. C2.

Concentration–response curve of propofol-mediated effects on P2X7

currents

Clin Exp Med (2012) 12:31–37 33

123

propofol (300–100 lM). While the P2X7 receptor currents

were enhanced significantly by relatively low concentra-

tion (10 lM) propofol. Therefore, in the ELISA experi-

ments, we chose 300 and 10 lM as the working

concentrations of propofol and collected the supernatant

after 48 h treatment. In addition, the P2X7 receptor agonist

BzATP (100 lM), and the antagonists BBG (10 lM) were

used to investigate the action of propofol (Fig. 2). When

BzATP or BBG was applied alone with LPS, the TNF-aconcentration was decreased or reversed, respectively.

Propofol (300 lM) significantly increased the TNF-aconcentration in the culture supernatant. Addition of

BzATP decreased the TNF-a concentration significantly,

while addition of BBG did not further affect the TNF-aconcentration significantly. When propofol was applied in

a low concentration (10 lM), the TNF-a concentration in

the culture supernatant was not increased, but decreased.

Addition of BzATP further decreased the TNF-a concen-

tration, while addition of BBG did not further affect the

TNF-a concentration significantly either (Fig. 2; Table 2)..

Discussion

In order to study the influence of propofol on P2X7

receptors in astrocytes of the cerebral cortex, we treated

the cells with different concentrations of propofol. We

Ta

ble

1S

val

ues

of

the

dea

ctiv

atin

gcu

rren

to

fP

2X

7re

cep

tors

du

rin

gw

ash

ou

to

fB

zAT

P

s(m

s)C

on

tro

l0

.33

lM

1lM

3.3

lM1

0l

M3

3lM

10

0lM

30

0l

M

Dea

ct,1

11

20

.47

±6

21

.64

11

55

.47

±1

15

2.0

71

70

1.7

0±

10

99

.12

23

98

.09

±5

64

.73

45

10

.66

±1

94

0.4

0*

25

64

.43

±1

22

4.2

12

02

8.7

7±

18

78

.77

95

7.8

5±

83

6.4

9

Dea

ct,2

44

0.1

3±

38

.45

41

6.2

8±

13

8.3

04

41

.43

±7

3.4

52

80

.46

±1

15

.89

50

9.1

1±

89

.69

33

4.2

9±

97

.68

42

0.4

2±

62

.05

30

9.3

4±

67

.80

ms

mil

lise

con

d.s d

eact,

1an

ds d

eact,

2ar

eth

eti

me

con

stan

tso

fth

esl

ow

and

fast

dea

ctiv

atin

gco

mp

on

ent,

resp

ecti

vel

y.

*P

10l

Mvs.

contr

ol\

0.0

5

Fig. 2 Propofol influences secretion of TNF-a from astrocytes. The

cells of all groups were treated with 10 lg/ml LPS for 48 h along with

respective treatments. Control, LPS alone; propofol, 300nM or

10 lM; BBG, 10 lM; BzATP, 100 lM. No statistical difference

was found between group 300 lM propofol ? BBG and group

300 lM propofol; between group 10 lM propofol ? BBG

and group 10 lM propofol. *P300lM propofol versus control \0.05;�P300lM propofol?BzATP versus 300lM propofol \0.05; *P10lM propofol versus

control \0.05; }P10lM propofol?BzATP versus 10lM propofol \0.05; *P BzATP

versus control \0.05

34 Clin Exp Med (2012) 12:31–37

123

chose 0.33, 1, 3.3, 10, 33, 100, and 300 lM as working

concentrations. It has been reported that the blood con-

centration of propofol required for minor surgery is

1.5–4.5 lg/ml (8.43–25.28 lM), while for major surgery is

2.5–6 lg/ml (14.04–33.71 lM) [28]. In this clinically rel-

evant concentration range, BzATP-sensitive current

amplitudes were increased by 3.3, 10, and 33 lM propofol.

This is consistent with the effect reported in a rat mi-

croglial cell line [29]. However, in that report, P2X7 cur-

rent amplitudes were increased more highly as the

concentration of propofol was higher. In our study, when

the concentration was relatively low (lower than 10 lM),

propofol enhanced the P2X7 current in a concentration-

dependent manner. If the concentration was higher than

10 lM, the effect of propofol went down. When the cells

were treated with higher concentration (100–300 lM) of

propofol, the BzATP-sensitive current amplitudes showed

a trend of increasing, but were not increased significantly.

This may be the composite result of the following actions:

firstly, this may be due to the difference in cell types used,

respectively. Secondly, in our study, BzATP, a P2X7 ago-

nist, was used to induce inward currents, while Nakanishi

and his colleagues used ATP, an endogenous ligand of

P2X7 receptor, which might also activated P2Y receptors to

influence P2X7 currents. However, both Nakanishi’s and

our results indicated that P2X7 current amplitudes were

increased by propofol of clinically relevant concentration.

Thirdly, it has been reported that long-time treatment of

10 lM propofol caused PKC activation in astrocytes [30].

Activation of PKC decreased P2X7 receptor-mediated

calcium signaling in type-2 astrocyte cell line, RBA-2 [31].

These implied that propofol at high concentration would

activate PKC more quickly and then inhibit P2X7 receptor

activity. This might neutralize the effect of propofol on

P2X7-mediated currents in astrocytes.

In addition, we compared the inactivation rate of P2X7

receptors treated with propofol in different concentrations.

In clinically relevant concentrations (10 lM), propofol

extended the slow deactivating component of P2X7-med-

iated current. These results implied that during clinical

surgery propofol enhanced the activity of P2X7 receptors

in astrocytes.

TNF-a plays an important role in neuron apoptosis [32].

Thus, we carried out ELISA experiments to investigate

whether the enhancement of P2X7 receptor activity by

propofol would affect the secretion of TNF-a in astrocytes.

Our results showed that propofol at lower concentration

(10 lM) inhibited the TNF-a secretion. This suggests that

inhibition of the TNF-a secretion from astrocytes might be

one of the mechanisms for propofol at clinically relevant

concentrations to protect neurons in brain injury. However,

300 lM propofol increased the TNF-a concentration in

culture medium significantly. This implies that high doseTa

ble

2T

NF

-aco

nce

ntr

atio

nin

the

cult

ure

sup

ern

atan

to

fas

tro

cyte

s

pg

/ml

Co

ntr

ol

BzA

TP

BB

G3

00

lM

pro

po

fol

10

lMp

rop

ofo

l

Bla

nk

BzA

TP

BB

GB

lan

kB

zAT

PB

BG

C6

6.5

6±

7.1

93

2.6

0±

3.6

2*

*8

0.3

7±

8.5

61

90

.73

±1

0.9

4*

90

.39

±1

3.3

6�

18

6.9

4±

36

.50

50

.23

±7

.32

*2

5.9

4±

2.8

05

6.4

3±

6.4

7

Bla

nk

,3

00

lMo

r1

0l

Mp

rop

ofo

lw

asap

pli

edal

on

e.N

ost

atis

tica

ld

iffe

ren

cew

asfo

un

db

etw

een

gro

up

30

0lM

pro

po

fol

?B

BG

and

gro

up

30

0lM

pro

po

fol;

bet

wee

ng

rou

p1

0l

M

pro

po

fol

?B

BG

and

gro

up

10

lM

pro

po

fol

*P

300l

Mpro

pofo

lvers

us

contr

ol\

0.0

5;

�P

300l

Mpro

pofo

l?B

zA

TP

vers

us

300l

Mpro

pofo

l\

0.0

5;

*P

10l

Mpro

pofo

lvers

us

contr

ol\

0.0

5;}

P10l

Mpro

pofo

l?B

zA

TP

vers

us

10l

Mpro

pofo

l\

0.0

5;

**

PB

zA

TP

vers

us

contr

ol\

0.0

1

Clin Exp Med (2012) 12:31–37 35

123

of propofol would damage neurons through promoting the

TNF-a secretion. It has been reported that 30–300 lM

propofol did not influence LPS-induced TNF-a production

in mixed glial cells [33]. But this research work cannot rule

out the influence of microglia, which is another important

source of TNF-a.

P2X7 receptors play a regulatory role in the secretion of

many cytokines [34]. For example, activation of P2X7

receptors in astrocytes inhibits TNF-a secretion [13]. In our

study, BzATP inhibited the TNF-a secretion in addition to the

effect of propofol, but BBG did not increase the secretion of

TNF-a from astrocytes treated with propofol only (both

300–10 lM). This implied that the influence of propofol to

TNF-a concentration might not be related with P2X7 recep-

tors. Recently, a new study reported that propofol suppressed

TNF-abiosynthesis in LPS-stimulated macrophages [35]. The

propofol was used in 1, 10, 25, and 50 lM. Their results are in

consistent with ours. According to Wu and his colleagues’

theory [35], downregulation of nuclear factor-j B-mediated

toll-like receptor 4 gene expression might be a candidate

explanation for the mechanism of propofol inhibition.

Conclusions

Our results indicate that in clinically relevant concentra-

tions, propofol increases the activity of P2X7 receptors in

activated astrocytes, but this does not contribute to the

downregulation of the secretion of TNF-a.

Math formulae

y ¼ A2þ A1� A2

1þ xx0

� �p ð1Þ

Ideact tð Þ ¼ Ideact;1 � e� t

sdeact;1 þ Ideact;2 � e� t

sdeact;2 þ I0 ð2Þ

Conflict of interest None.

References

1. Burnstock G (2008) Purinergic signalling and disorders of the

central nervous system. Nat Rev Drug Discov 7:575–590

2. Wang X, Arcuino G, Takano T, Lin J, Peng WG, Wan P, Li P, Xu

Q, Liu QS, Goldman SA, Nedergaard M (2004) P2X7 receptor

inhibition improves recovery after spinal cord injury. Nat Med

10:821–827

3. Phillis JW, O’Regan MH, Perkins LM (1993) Adenosine 50-tri-phosphate release from the normoxic and hypoxic in vivo rat

cerebral cortex. Neurosci Lett 151:94–96

4. Melani A, Turchi D, Vannucchi MG, Cipriani S, Gianfriddo M,

Pedata F (2005) ATP extracellular concentrations are increased

in the rat striatum during in vivo ischemia. Neurochem Int

47:442–448

5. North RA (2002) Molecular physiology of P2X receptors. Physiol

Rev 82:1013–1067

6. Suzuki T, Hide I, Ido K, Kohsaka S, Inoue K, Nakata Y (2004)

Production and release of neuroprotective tumor necrosis factor

by P2X7 receptor-activated microglia. J Neurosci 24:1–7

7. Ferrari D, Pizzirani C, Adinolfi E, Lemoli RM, Curti A, Idzko M,

Panther E, Di Virgilio F (2006) The P2X7 receptor: a key player

in IL-1 processing and release. J Immunol 176:3877–3883

8. Kataoka A, Tozaki-Saitoh H, Koga Y, Tsuda M, Inoue K (2009)

Activation of P2X7 receptors induces CCL3 production in mi-

croglial cells through transcription factor NFAT. J Neurochem

108:115–125

9. Gendron FP, Chalimoniuk M, Strosznajder J, Shen S, Gonzalez FA,

Weisman GA, Sun GY (2003) P2X7 nucleotide receptor activation

enhances IFN gamma-induced type II nitric oxide synthase activity

in BV-2 microglial cells. J Neurochem 87:344–352

10. Parvathenani LK, Tertyshnikova S, Greco CR, Roberts SB,

Robertson B, Posmantur R (2003) P2X7 mediates superoxide

production in primary microglia and is up-regulated in a trans-

genic mouse model of Alzheimer’s disease. J Biol Chem 278:

13309–13317

11. Neary JT, Kang Y, Shi YF, Tran MD, Wanner IB (2006) P2

receptor signalling, proliferation of astrocytes, and expression of

molecules involved in cell-cell interactions. Novartis Found

Symp 276:131–143

12. Duan S, Anderson CM, Keung EC, Chen Y, Chen Y, Swanson

RA (2003) P2X7 receptor-mediated release of excitatory amino

acids from astrocytes. J Neurosci 23:1320–1328

13. Kucher BM, Neary JT (2005) Bi-functional effects of ATP/P2

receptor activation on tumor necrosis factor-alpha release in lipo-

polysaccharide-stimulated astrocytes. J Neurochem 92:525–535

14. Fulton B, Sorkin EM (1995) Propofol: an overview of its phar-

macology and a review of its clinical efficacy in intensive care

sedation. Drugs 50:636–657

15. Kochs E, Hoffman WE, Werner C, Thomas C, Albrecht RF,

Schulte am Esch J (1992) The effects of propofol on brain electrical

activity, neurologic outcome, and neuronal damage following

incomplete ischemia in rats. Anesthesiology 76:245–252

16. Ito H, Watanabe Y, Isshiki A, Uchino H (1999) Neuroprotective

properties of propofol and midazolam, but not pentobarbital, on

neuronal damage induced by forebrain ischemia, based on the

GABAA receptors. Acta Anaesthesiol Scand 43:153–162

17. Buggy DJ, Nicol B, Rowbotham DJ, Lambert DG (2000) Effects

of intravenous anesthetic agents on glutamate release: a role for

GABAA receptor-mediated inhibition. Anesthesiology 92:1067–

1073

18. Yamakura T, Sakimura K, Shimoji K, Mishina M (1995) Effects

of propofol on various AMPA-, kainate- and NMDA-selective

glutamate receptor channels expressed in Xenopus oocytes.

Neurosci Lett 188:187–190

19. Orser BA, Bertlik M, Wang LY, MacDonald JF (1995) Inhibition

by propofol (2, 6 di-isopropylphenol) of the N-methyl-D-aspar-

tate subtype of glutamate receptor in cultured hippocampal neu-

rones. Br J Pharmacol 116:1761–1768

20. Lingamaneni R, Birch ML, Hemmings HC Jr (2001) Widespread

inhibition of sodium channel-dependent glutamate release from

isolated nerve terminals by isoflurane and propofol. Anesthesi-

ology 95:1460–1466

21. Sitar SM, Hanifi-Moghaddam P, Gelb A, Cechetto DF, Siu-

shansian R, Wilson JX (1999) Propofol prevents peroxide-

induced inhibition of glutamate transport in cultured astrocytes.

Anesthesiology 90:1446–1453

22. Murphy PG, Myers DS, Davies MJ, Webster NR, Jones JG

(1992) The antioxidant potential of propofol (2, 6-diisopropyl-

phenol). Br J Anaesth 68:613–618

36 Clin Exp Med (2012) 12:31–37

123

23. Tsuchiya M, Asada A, Maeda K, Ueda Y, Sato EF, Shindo M,

Inoue M (2001) Propofol versus midazolam regarding their

antioxidant activities. Am J Respir Crit Care Med 163:26–31

24. Adembri C, Venturi L, Tani A, Chiarugi A, Gramigni E, Cozzi A,

Pancani T, De Gaudio RA, Pellegrini-Giampietro DE (2006)

Neuroprotective effects of propofol in models of cerebral ische-

mia: inhibition of mitochondrial swelling as a possible mecha-

nism. Anesthesiology 104:80–89

25. McNaught KS, Jenner P (2000) Extracellular accumulation of

nitric oxide, hydrogen peroxide, and glutamate in astrocytic

cultures following glutathione depletion, complex I inhibition,

and/or lipopolysaccharide-induced activation. Biochem Pharma-

col 60:979–988

26. McCarthy KD, de Vellis J (1980) Preparation of separate as-

troglial and oligodendroglial cell cultures from rat cerebral tissue.

J Cell Biol 85:890–902

27. Becker D, Woltersdorf R, Boldt W, Schmitz S, Braam U, Sch-

malzing G, Markwardt F (2008) The P2X7 carboxyl tail is a

regulatory module of P2X7 receptor channel activity. J Biol

Chem 283:25725–25734

28. Miller RD (2005) Miller’s Anesthesia: Churchill Livingstone

29. Nakanishi M, Mori T, Nishikawa K, Sawada M, Kuno M, Asada

A (2007) The effects of general anesthetics on P2X7 and P2Y

receptors in a rat microglial cell line. Anes Anal 104:1136–1144

30. Zhu SM, Xiong XX, Zheng YY, Pan CF (2009) Propofol inhibits

aquaporin 4 expression through a protein kinase C-dependent

pathway in an astrocyte model of cerebral ischemia/reoxygena-

tion. Anesth Analg 109:1493–1499

31. Hung AC, Chu YJ, Lin YH, Weng JY, Chen HB, Au YC, Sun SH

(2005) Roles of protein kinase C in regulation of P2X7 receptor-

mediated calcium signalling of cultured type-2 astrocyte cell line,

RBA-2. Cell Signal 17:1384–1396

32. Lorz C, Mehmet H (2009) The role of death receptors in neural

injury. Front Biosci 14:583–595

33. Shibakawa YS, Sasaki Y, Goshima Y, Echigo N, Kamiya Y,

Kurahashi K, Yamada Y, Andoh T (2005) Effects of ketamine

and propofol on inflammatory responses of primary glial cell

cultures stimulated with lipopolysaccharide. Br J Anaesth

95:803–810

34. Mingam R, De Smedt V, Amedee T, Bluthe RM, Kelley KW,

Dantzer R, Laye S (2008) In vitro and in vivo evidence for a role

of the P2X7 receptor in the release of IL-1 beta in the murine

brain. Brain Behav Immun 22:234–244

35. Wu GJ, Chen TL, Chang CC, Chen RM (2009) Propofol sup-

presses tumor necrosis factor-alpha biosynthesis in lipopoly-

saccharide-stimulated macrophages possibly through

downregulation of nuclear factor-kappa B-mediated toll-like

receptor 4 gene expression. Chem Biol Interact 180:465–471

Clin Exp Med (2012) 12:31–37 37

123