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FGF-2 released from degenerating neurons exerts microglial-induced neuroprotection via FGFR3-ERK signaling pathway.

Noda M, Takii K, Parajuli B, Kawanokuchi J, Sonobe Y, Takeuchi H, Mizuno T, Suzumura A - J Neuroinflammation (2014)

Bottom Line: Fibroblast growth factor-2 is secreted by neurons when damaged by glutamate or oligomeric amyloid β 1-42.FGF-2 enhances microglial migration and phagocytosis of neuronal debris, and is neuroprotective against glutamate toxicity through FGFR3-extracellular signal-regulated kinase (ERK) signaling pathway, which is directly controlled by Wnt signaling in microglia.FGF-2 secreted from degenerating neurons may act as a 'help-me' signal toward microglia by inducing migration and phagocytosis of unwanted debris.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. tmizuno@riem.nagoya-u.ac.jp.

ABSTRACT

Background: The accumulation of activated microglia is a hallmark of various neurodegenerative diseases. Microglia may have both protective and toxic effects on neurons through the production of various soluble factors, such as chemokines. Indeed, various chemokines mediate the rapid and accurate migration of microglia to lesions. In the zebra fish, another well-known cellular migrating factor is fibroblast growth factor-2 (FGF-2). Although FGF-2 does exist in the mammalian central nervous system (CNS), it is unclear whether FGF-2 influences microglial function.

Methods: The extent of FGF-2 release was determined by ELISA, and the expression of its receptors was examined by immunocytochemistry. The effect of several drug treatments on a neuron and microglia co-culture system was estimated by immunocytochemistry, and the neuronal survival rate was quantified. Microglial phagocytosis was evaluated by immunocytochemistry and quantification, and microglial migration was estimated by fluorescence-activated cell sorting (FACS). Molecular biological analyses, such as Western blotting and promoter assay, were performed to clarify the FGF-2 downstream signaling pathway in microglia.

Results: Fibroblast growth factor-2 is secreted by neurons when damaged by glutamate or oligomeric amyloid β 1-42. FGF-2 enhances microglial migration and phagocytosis of neuronal debris, and is neuroprotective against glutamate toxicity through FGFR3-extracellular signal-regulated kinase (ERK) signaling pathway, which is directly controlled by Wnt signaling in microglia.

Conclusions: FGF-2 secreted from degenerating neurons may act as a 'help-me' signal toward microglia by inducing migration and phagocytosis of unwanted debris.

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Related in: MedlinePlus

The detection of FGF-2 in primary neurons and glial cells. (A) Neurons were treated with glutamate (Glu) or oligomeric amyloid β1-42 (oAβ) at the indicated concentrations. FGF-2 concentrations in the neuronal culture supernatants were measured using ELISAs at each time point. Results show the means with SEM (n = 3). Significant differences compared with untreated samples. *: P < 0.05, **: P < 0.01 (one-way ANOVA with Dunnett’s post-hoc test). (B) Astrocytes, microglia and neurons were treated with Glu (20 μM) or oAβ (5 μM) for 6 h. Other treatments of astrocytes (6 h) were LPS (1 μg/ml), TNF-α (20 ng/ml), IFN-γ (10 ng/ml), and a combination of all three. ELISA was then performed to detect FGF-2 concentration in the culture supernatants. The results show the means with SEM (n = 3). Significant differences compared with untreated samples in each cell type. *: P < 0.05, ***: P < 0.001, n.s.: not significant (one-way ANOVA with Dunnett’s post-hoc test).
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Figure 2: The detection of FGF-2 in primary neurons and glial cells. (A) Neurons were treated with glutamate (Glu) or oligomeric amyloid β1-42 (oAβ) at the indicated concentrations. FGF-2 concentrations in the neuronal culture supernatants were measured using ELISAs at each time point. Results show the means with SEM (n = 3). Significant differences compared with untreated samples. *: P < 0.05, **: P < 0.01 (one-way ANOVA with Dunnett’s post-hoc test). (B) Astrocytes, microglia and neurons were treated with Glu (20 μM) or oAβ (5 μM) for 6 h. Other treatments of astrocytes (6 h) were LPS (1 μg/ml), TNF-α (20 ng/ml), IFN-γ (10 ng/ml), and a combination of all three. ELISA was then performed to detect FGF-2 concentration in the culture supernatants. The results show the means with SEM (n = 3). Significant differences compared with untreated samples in each cell type. *: P < 0.05, ***: P < 0.001, n.s.: not significant (one-way ANOVA with Dunnett’s post-hoc test).

Mentions: FGF-2 is widely expressed in the CNS, especially in astrocytes, while FGF-5, FGF-8, and FGF-9 are synthesized by neurons [33]. FGF-2 is reported to be produced by cerebellar granule neurons in co-cultures with microglia, and to abrogate quinolinic acid–mediated neurotoxicity [31]. In this study, we investigated whether cortical neurons could produce FGF-2 in response to neurotoxic stimuli. We found that treatment for 6 h and 24 h with 20 μM glutamate or 5 μM oAβ significantly induced FGF-2 release from cortical neurons (Figure 2A). Astrocytes typically secrete FGF-2; however, various stimuli including glutamate, oAβ, lipopolysaccharide (LPS), and other proinflammatory cytokines did not enhance FGF-2 secretion by astrocytes (Figure 2B). Furthermore, FGF-2 secretion by microglia was barely detectable (Figure 2B).


FGF-2 released from degenerating neurons exerts microglial-induced neuroprotection via FGFR3-ERK signaling pathway.

Noda M, Takii K, Parajuli B, Kawanokuchi J, Sonobe Y, Takeuchi H, Mizuno T, Suzumura A - J Neuroinflammation (2014)

The detection of FGF-2 in primary neurons and glial cells. (A) Neurons were treated with glutamate (Glu) or oligomeric amyloid β1-42 (oAβ) at the indicated concentrations. FGF-2 concentrations in the neuronal culture supernatants were measured using ELISAs at each time point. Results show the means with SEM (n = 3). Significant differences compared with untreated samples. *: P < 0.05, **: P < 0.01 (one-way ANOVA with Dunnett’s post-hoc test). (B) Astrocytes, microglia and neurons were treated with Glu (20 μM) or oAβ (5 μM) for 6 h. Other treatments of astrocytes (6 h) were LPS (1 μg/ml), TNF-α (20 ng/ml), IFN-γ (10 ng/ml), and a combination of all three. ELISA was then performed to detect FGF-2 concentration in the culture supernatants. The results show the means with SEM (n = 3). Significant differences compared with untreated samples in each cell type. *: P < 0.05, ***: P < 0.001, n.s.: not significant (one-way ANOVA with Dunnett’s post-hoc test).
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4022102&req=5

Figure 2: The detection of FGF-2 in primary neurons and glial cells. (A) Neurons were treated with glutamate (Glu) or oligomeric amyloid β1-42 (oAβ) at the indicated concentrations. FGF-2 concentrations in the neuronal culture supernatants were measured using ELISAs at each time point. Results show the means with SEM (n = 3). Significant differences compared with untreated samples. *: P < 0.05, **: P < 0.01 (one-way ANOVA with Dunnett’s post-hoc test). (B) Astrocytes, microglia and neurons were treated with Glu (20 μM) or oAβ (5 μM) for 6 h. Other treatments of astrocytes (6 h) were LPS (1 μg/ml), TNF-α (20 ng/ml), IFN-γ (10 ng/ml), and a combination of all three. ELISA was then performed to detect FGF-2 concentration in the culture supernatants. The results show the means with SEM (n = 3). Significant differences compared with untreated samples in each cell type. *: P < 0.05, ***: P < 0.001, n.s.: not significant (one-way ANOVA with Dunnett’s post-hoc test).
Mentions: FGF-2 is widely expressed in the CNS, especially in astrocytes, while FGF-5, FGF-8, and FGF-9 are synthesized by neurons [33]. FGF-2 is reported to be produced by cerebellar granule neurons in co-cultures with microglia, and to abrogate quinolinic acid–mediated neurotoxicity [31]. In this study, we investigated whether cortical neurons could produce FGF-2 in response to neurotoxic stimuli. We found that treatment for 6 h and 24 h with 20 μM glutamate or 5 μM oAβ significantly induced FGF-2 release from cortical neurons (Figure 2A). Astrocytes typically secrete FGF-2; however, various stimuli including glutamate, oAβ, lipopolysaccharide (LPS), and other proinflammatory cytokines did not enhance FGF-2 secretion by astrocytes (Figure 2B). Furthermore, FGF-2 secretion by microglia was barely detectable (Figure 2B).

Bottom Line: Fibroblast growth factor-2 is secreted by neurons when damaged by glutamate or oligomeric amyloid β 1-42.FGF-2 enhances microglial migration and phagocytosis of neuronal debris, and is neuroprotective against glutamate toxicity through FGFR3-extracellular signal-regulated kinase (ERK) signaling pathway, which is directly controlled by Wnt signaling in microglia.FGF-2 secreted from degenerating neurons may act as a 'help-me' signal toward microglia by inducing migration and phagocytosis of unwanted debris.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Neuroimmunology, Research Institute of Environmental Medicine, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8601, Japan. tmizuno@riem.nagoya-u.ac.jp.

ABSTRACT

Background: The accumulation of activated microglia is a hallmark of various neurodegenerative diseases. Microglia may have both protective and toxic effects on neurons through the production of various soluble factors, such as chemokines. Indeed, various chemokines mediate the rapid and accurate migration of microglia to lesions. In the zebra fish, another well-known cellular migrating factor is fibroblast growth factor-2 (FGF-2). Although FGF-2 does exist in the mammalian central nervous system (CNS), it is unclear whether FGF-2 influences microglial function.

Methods: The extent of FGF-2 release was determined by ELISA, and the expression of its receptors was examined by immunocytochemistry. The effect of several drug treatments on a neuron and microglia co-culture system was estimated by immunocytochemistry, and the neuronal survival rate was quantified. Microglial phagocytosis was evaluated by immunocytochemistry and quantification, and microglial migration was estimated by fluorescence-activated cell sorting (FACS). Molecular biological analyses, such as Western blotting and promoter assay, were performed to clarify the FGF-2 downstream signaling pathway in microglia.

Results: Fibroblast growth factor-2 is secreted by neurons when damaged by glutamate or oligomeric amyloid β 1-42. FGF-2 enhances microglial migration and phagocytosis of neuronal debris, and is neuroprotective against glutamate toxicity through FGFR3-extracellular signal-regulated kinase (ERK) signaling pathway, which is directly controlled by Wnt signaling in microglia.

Conclusions: FGF-2 secreted from degenerating neurons may act as a 'help-me' signal toward microglia by inducing migration and phagocytosis of unwanted debris.

Show MeSH
Related in: MedlinePlus