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Lipopolysaccharide modulates astrocytic S100B secretion: a study in cerebrospinal fluid and astrocyte cultures from rats.

Guerra MC, Tortorelli LS, Galland F, Da Ré C, Negri E, Engelke DS, Rodrigues L, Leite MC, Gonçalves CA - J Neuroinflammation (2011)

Bottom Line: However, lower levels of LPS in astrocyte cultures were able to induce a decrease in S100B secretion after 24 h, without significant change in intracellular content of S100B.Together, these data contribute to the understanding of the effects of LPS on astrocytes, particularly on S100B secretion, and help us to interpret cerebrospinal fluid and serum changes for this protein in neuroinflammatory diseases.Moreover, non-brain S100B-expressing tissues may be differentially regulated, since LPS administration did not lead to increased serum levels of S100B.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, Porto Alegre, Brazil.

ABSTRACT

Background: Inflammatory responses in brain are primarily mediated by microglia, but growing evidence suggests a crucial importance of astrocytes. S100B, a calcium-binding protein secreted by astrocytes, has properties of a neurotrophic or an inflammatory cytokine. However, it is not known whether primary signals occurring during induction of an inflammatory response (e.g. lipopolysaccharide, LPS) directly modulate S100B.

Methods: In this work, we evaluated whether S100B levels in cerebrospinal fluid (CSF) and serum of Wistar rats are affected by LPS administered by intraperitoneal (IP) or intracerebroventricular (ICV) injection, as well as whether primary astrocyte cultures respond directly to lipopolysaccharide.

Results: Our data suggest that S100B secretion in brain tissue is stimulated rapidly and persistently (for at least 24 h) by ICV LPS administration. This increase in CSF S100B was transient when LPS was IP administered. In contrast to these S100B results, we observed an increase in in TNFα levels in serum, but not in CSF, after IP administration of LPS. In isolated astrocytes and in acute hippocampal slices, we observed a direct stimulation of S100B secretion by LPS at a concentration of 10 μg/mL. An involvement of TLR4 was confirmed by use of specific inhibitors. However, lower levels of LPS in astrocyte cultures were able to induce a decrease in S100B secretion after 24 h, without significant change in intracellular content of S100B. In addition, after 24 h exposure to LPS, we observed a decrease in astrocytic glutathione and an increase in astrocytic glial fibrillary acidic protein.

Conclusions: Together, these data contribute to the understanding of the effects of LPS on astrocytes, particularly on S100B secretion, and help us to interpret cerebrospinal fluid and serum changes for this protein in neuroinflammatory diseases. Moreover, non-brain S100B-expressing tissues may be differentially regulated, since LPS administration did not lead to increased serum levels of S100B.

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The LPS-induced decrease in S100B secretion is abolished by inhibition of TLR4. Rat cortical astrocytes were cultured in DMEM containing 10% FCS. After confluence, the medium was replaced by DMEM without serum in the presence or absence of 0.1 μg/mL LPS and 1 μM CLI-095, an inhibitor of TLR4. S100B was measured by ELISA at 24 h. Each value is a mean (± standard error) of at least 5 independent experiments performed in triplicate. Means indicated by different letters are significantly different (one way ANOVA followed by Duncan's test, with a significance level of p < 0.05).
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Figure 3: The LPS-induced decrease in S100B secretion is abolished by inhibition of TLR4. Rat cortical astrocytes were cultured in DMEM containing 10% FCS. After confluence, the medium was replaced by DMEM without serum in the presence or absence of 0.1 μg/mL LPS and 1 μM CLI-095, an inhibitor of TLR4. S100B was measured by ELISA at 24 h. Each value is a mean (± standard error) of at least 5 independent experiments performed in triplicate. Means indicated by different letters are significantly different (one way ANOVA followed by Duncan's test, with a significance level of p < 0.05).

Mentions: In order to investigate whether this effect was attributable to a direct effect of LPS on astrocytes, we added different concentrations of LPS (from 0.01 to 30 μg/mL) to primary astrocyte cultures and extracellular S100B was measured at 1 h (Figure 2A) and 24 h (Figure 2B). At 1 h, LPS (at concentrations from 10 μg/mL upwards) increased S100B secretion (p < 0.001, ANOVA). Conversely, at 24 h, LPS caused a decrease in S100B secretion, even with LPS concentrations as low as 0.01 μg/mL (p < 0.001). Acute hippocampal slices were also exposed to LPS for 1 h (Figure 2C) and a decrease in S100B secretion was observed at LPS concentrations from 0.1 to 1 μg/mL (p < 0.001). However, LPS at 10 μg/mL produced an increase in S100B secretion (p < 0.001). In order to characterize whether the effect of LPS is mediated by TLR4, we incubated astrocytes with specific inhibitors for this receptor (Cli-095 and OxPAPC, at 1 μM and 30 μg/mL, respectively). Both CLI-095 (Figure 3) and OxPAPC (data not shown) abolished the effect of LPS. It is important to mention that OxPAPC per se increased S100B secretion and therefore it is difficult to affirm that this inhibitor prevented the effect induced by LPS.


Lipopolysaccharide modulates astrocytic S100B secretion: a study in cerebrospinal fluid and astrocyte cultures from rats.

Guerra MC, Tortorelli LS, Galland F, Da Ré C, Negri E, Engelke DS, Rodrigues L, Leite MC, Gonçalves CA - J Neuroinflammation (2011)

The LPS-induced decrease in S100B secretion is abolished by inhibition of TLR4. Rat cortical astrocytes were cultured in DMEM containing 10% FCS. After confluence, the medium was replaced by DMEM without serum in the presence or absence of 0.1 μg/mL LPS and 1 μM CLI-095, an inhibitor of TLR4. S100B was measured by ELISA at 24 h. Each value is a mean (± standard error) of at least 5 independent experiments performed in triplicate. Means indicated by different letters are significantly different (one way ANOVA followed by Duncan's test, with a significance level of p < 0.05).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198930&req=5

Figure 3: The LPS-induced decrease in S100B secretion is abolished by inhibition of TLR4. Rat cortical astrocytes were cultured in DMEM containing 10% FCS. After confluence, the medium was replaced by DMEM without serum in the presence or absence of 0.1 μg/mL LPS and 1 μM CLI-095, an inhibitor of TLR4. S100B was measured by ELISA at 24 h. Each value is a mean (± standard error) of at least 5 independent experiments performed in triplicate. Means indicated by different letters are significantly different (one way ANOVA followed by Duncan's test, with a significance level of p < 0.05).
Mentions: In order to investigate whether this effect was attributable to a direct effect of LPS on astrocytes, we added different concentrations of LPS (from 0.01 to 30 μg/mL) to primary astrocyte cultures and extracellular S100B was measured at 1 h (Figure 2A) and 24 h (Figure 2B). At 1 h, LPS (at concentrations from 10 μg/mL upwards) increased S100B secretion (p < 0.001, ANOVA). Conversely, at 24 h, LPS caused a decrease in S100B secretion, even with LPS concentrations as low as 0.01 μg/mL (p < 0.001). Acute hippocampal slices were also exposed to LPS for 1 h (Figure 2C) and a decrease in S100B secretion was observed at LPS concentrations from 0.1 to 1 μg/mL (p < 0.001). However, LPS at 10 μg/mL produced an increase in S100B secretion (p < 0.001). In order to characterize whether the effect of LPS is mediated by TLR4, we incubated astrocytes with specific inhibitors for this receptor (Cli-095 and OxPAPC, at 1 μM and 30 μg/mL, respectively). Both CLI-095 (Figure 3) and OxPAPC (data not shown) abolished the effect of LPS. It is important to mention that OxPAPC per se increased S100B secretion and therefore it is difficult to affirm that this inhibitor prevented the effect induced by LPS.

Bottom Line: However, lower levels of LPS in astrocyte cultures were able to induce a decrease in S100B secretion after 24 h, without significant change in intracellular content of S100B.Together, these data contribute to the understanding of the effects of LPS on astrocytes, particularly on S100B secretion, and help us to interpret cerebrospinal fluid and serum changes for this protein in neuroinflammatory diseases.Moreover, non-brain S100B-expressing tissues may be differentially regulated, since LPS administration did not lead to increased serum levels of S100B.

View Article: PubMed Central - HTML - PubMed

Affiliation: Departamento de Bioquímica, Instituto de Ciências Básicas da Saúde, Universidade Federal do Rio Grande do Sul, Ramiro Barcelos, Porto Alegre, Brazil.

ABSTRACT

Background: Inflammatory responses in brain are primarily mediated by microglia, but growing evidence suggests a crucial importance of astrocytes. S100B, a calcium-binding protein secreted by astrocytes, has properties of a neurotrophic or an inflammatory cytokine. However, it is not known whether primary signals occurring during induction of an inflammatory response (e.g. lipopolysaccharide, LPS) directly modulate S100B.

Methods: In this work, we evaluated whether S100B levels in cerebrospinal fluid (CSF) and serum of Wistar rats are affected by LPS administered by intraperitoneal (IP) or intracerebroventricular (ICV) injection, as well as whether primary astrocyte cultures respond directly to lipopolysaccharide.

Results: Our data suggest that S100B secretion in brain tissue is stimulated rapidly and persistently (for at least 24 h) by ICV LPS administration. This increase in CSF S100B was transient when LPS was IP administered. In contrast to these S100B results, we observed an increase in in TNFα levels in serum, but not in CSF, after IP administration of LPS. In isolated astrocytes and in acute hippocampal slices, we observed a direct stimulation of S100B secretion by LPS at a concentration of 10 μg/mL. An involvement of TLR4 was confirmed by use of specific inhibitors. However, lower levels of LPS in astrocyte cultures were able to induce a decrease in S100B secretion after 24 h, without significant change in intracellular content of S100B. In addition, after 24 h exposure to LPS, we observed a decrease in astrocytic glutathione and an increase in astrocytic glial fibrillary acidic protein.

Conclusions: Together, these data contribute to the understanding of the effects of LPS on astrocytes, particularly on S100B secretion, and help us to interpret cerebrospinal fluid and serum changes for this protein in neuroinflammatory diseases. Moreover, non-brain S100B-expressing tissues may be differentially regulated, since LPS administration did not lead to increased serum levels of S100B.

Show MeSH
Related in: MedlinePlus