Biology Reference
In-Depth Information
4
20
3
2
10
1
0
60
50
40
30
20
10
0
1.0
0.5
0.0
1
10 100
HMGB1 concentration (nM)
1000
1
10
100
1000
HMGB1 concentration (nM)
8h HMGB1
24 h HMGB1
24 h HMGB1+PD098059
Figure 3.5 Quantification of CC chemokines released by astrocytes stimulated with
HMGB1.
Astrocytes were cultured in the presence of the indicated amounts of HMGB1,
and quantification of each chemokine in the conditioned media was carried out by ELISA.
Where indicated, 50 M PD098059 was added to the cell culture 15 minutes before HMGB1.
Experiments were performed twice. *
p
0.05; #
p
0.01 versus cells stimulated for 24 hours
with 40 nM HMGB1.
Source: Ref. [46]. Copyright 2007. The American Association of Immunologists, Inc.
can directly activate astrocytes, through autocrine or paracrine mechanisms, stimu-
lating reactive gliosis but also promoting migration and activation of effector cells
in demyelinating lesions. Of note, previous observations showed that cortical injec-
tion of HMGB1 in mouse brain did not increase the level of pro-inflammatory
mediators such as iNOS and IL-1, but did increase the sensitivity to ischemic injury
[29]
. Hence, HMGB1 seems to require the presence of substimulatory concentra-
tions of other glia-activating factors to display neuroinflammatory properties
in vivo
.
Recently, we demonstrated that HMGB1 elicits the release of excitatory amino acids
from astrocyte-derived subcellular particles (gliosomes), but not from nerve endings
(synaptosomes), by altering the activity of the glutamate-aspartate transporter
[41]
.
It has been proposed that glial CCL5 facilitates the spontaneous release of glutamate
from human nerve endings
[66]
; hence, we hypothesize that the concomitant increase
of glutamate and CCL5 release from astrocytes exposed to extracellular HMGB1 can
contribute to the amplification of both neurodegenerative and neuroinflammatory
processes in acute and chronic CNS diseases.
To assess the role of the MAPK-ERK1/2 cascade in the induction of astrocyte CC
chemokines, cells were stimulated with 40 nM HMGB1 for 24 hours in the presence
of the MEK inhibitor PD095058. In this condition, the release of the various CC
