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Leptin-dependent neurotoxicity via induction of apoptosis in adult rat neurogenic cells.

Segura S, Efthimiadi L, Porcher C, Courtes S, Coronas V, Krantic S, Moyse E - Front Cell Neurosci (2015)

Bottom Line: Leptin-dependent withdrawal of neural stem cells from the cell cycle was associated with increased apoptosis, as detected by TUNEL, which was preceded by cyclin D1 induction.Cyclin-D1 silencing by specific shRNA prevented leptin-induced decrease of the cell number per neurosphere thus pointing to the causal relationship between leptin actions on apoptosis and cyclin D1 induction.The inhibition of neural stem cell expansion via ERK/cyclin D1-triggered apoptosis defines novel biological action of leptin which may be involved in adiposity-dependent neurotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Physiologie de la Reproduction et des Comportements, UMR 85 Institut National de la Recherche Agronomique, Centre INRA de Tours, Université François Rabelais de Tours Nouzilly, France.

ABSTRACT
Adipocyte-derived hormone leptin has been recently implicated in the control of neuronal plasticity. To explore whether modulation of adult neurogenesis may contribute to leptin control of neuronal plasticity, we used the neurosphere assay of neural stem cells derived from the adult rat subventricular zone (SVZ). Endogenous expression of specific leptin receptor (ObRb) transcripts, as revealed by RT-PCR, is associated with activation of both ERK and STAT-3 pathways via phosphorylation of the critical ERK/STAT-3 amino acid residues upon addition of leptin to neurospheres. Furthermore, leptin triggered withdrawal of neural stem cells from the cell cycle as monitored by Ki67 labeling. This effect was blocked by pharmacological inhibition of ERK activation thus demonstrating that ERK mediates leptin effects on neural stem cell expansion. Leptin-dependent withdrawal of neural stem cells from the cell cycle was associated with increased apoptosis, as detected by TUNEL, which was preceded by cyclin D1 induction. Cyclin D1 was indeed extensively colocalized with TUNEL-positive, apoptotic nuclei. Cyclin-D1 silencing by specific shRNA prevented leptin-induced decrease of the cell number per neurosphere thus pointing to the causal relationship between leptin actions on apoptosis and cyclin D1 induction. Leptin target cells in SVZ neurospheres were identified by double TUNEL/phenotypic marker immunocytofluorescence as differentiating neurons mostly. The inhibition of neural stem cell expansion via ERK/cyclin D1-triggered apoptosis defines novel biological action of leptin which may be involved in adiposity-dependent neurotoxicity.

No MeSH data available.


Related in: MedlinePlus

Leptin triggers STAT3 pathway activation in SVZ-derived neurospheres. (A–P) Immunocytochemical assay of leptin effects on STAT3 (C,D,G,H,K,L,O,P) and its active phosphorylated form (Phospho-STAT3; A,B,E,F,I,J,M,N) in MAP2-labeled neuronal cell subpopulation of in SVZ neurospheres. SVZ neurospheres were assayed in the absence (Control) or in the presence of 6.2 M leptin for the indicated time periods. ***significantly different from control at p < 0.001. (Q) Proportions (%) of activated Phospho-STAT3 immunoreactive among total STAT3 cells; the numbers in brackets indicate the number of STAT-3 cells quantified for each duration of leptin exposure.
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Figure 2: Leptin triggers STAT3 pathway activation in SVZ-derived neurospheres. (A–P) Immunocytochemical assay of leptin effects on STAT3 (C,D,G,H,K,L,O,P) and its active phosphorylated form (Phospho-STAT3; A,B,E,F,I,J,M,N) in MAP2-labeled neuronal cell subpopulation of in SVZ neurospheres. SVZ neurospheres were assayed in the absence (Control) or in the presence of 6.2 M leptin for the indicated time periods. ***significantly different from control at p < 0.001. (Q) Proportions (%) of activated Phospho-STAT3 immunoreactive among total STAT3 cells; the numbers in brackets indicate the number of STAT-3 cells quantified for each duration of leptin exposure.

Mentions: To explore whether detected ObRb mRNA expression corresponds to the presence of functional leptin receptors, we first studied if leptin could alter STAT3 expression and phosphorylation in SVZ neurospheres by double immunocytochemistry and confocal microscopy. In both control and leptin-treated neurospheres, unphosphorylated (inactive) STAT3 was expressed only in MAP2-immunoreactive, i.e., neuronal cells; reciprocally all neuronal cells displayed STAT3 immunoreactivity (Figures 2 C,D,G,H,K,L,O,P). In the absence of leptin, the phosphorylated form of STAT3 (pSTAT3) was almost undetectable in neurosphere cultures (Figures 2A,B). However, leptin triggered rapid and transient STAT3 phosphorylation which peaked 10 min after its addition (Figures 2 E,I,M,Q) and was restricted to MAP2-labeled neuronal cells (Figures 2 E,F,I,J,M,N).


Leptin-dependent neurotoxicity via induction of apoptosis in adult rat neurogenic cells.

Segura S, Efthimiadi L, Porcher C, Courtes S, Coronas V, Krantic S, Moyse E - Front Cell Neurosci (2015)

Leptin triggers STAT3 pathway activation in SVZ-derived neurospheres. (A–P) Immunocytochemical assay of leptin effects on STAT3 (C,D,G,H,K,L,O,P) and its active phosphorylated form (Phospho-STAT3; A,B,E,F,I,J,M,N) in MAP2-labeled neuronal cell subpopulation of in SVZ neurospheres. SVZ neurospheres were assayed in the absence (Control) or in the presence of 6.2 M leptin for the indicated time periods. ***significantly different from control at p < 0.001. (Q) Proportions (%) of activated Phospho-STAT3 immunoreactive among total STAT3 cells; the numbers in brackets indicate the number of STAT-3 cells quantified for each duration of leptin exposure.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4561523&req=5

Figure 2: Leptin triggers STAT3 pathway activation in SVZ-derived neurospheres. (A–P) Immunocytochemical assay of leptin effects on STAT3 (C,D,G,H,K,L,O,P) and its active phosphorylated form (Phospho-STAT3; A,B,E,F,I,J,M,N) in MAP2-labeled neuronal cell subpopulation of in SVZ neurospheres. SVZ neurospheres were assayed in the absence (Control) or in the presence of 6.2 M leptin for the indicated time periods. ***significantly different from control at p < 0.001. (Q) Proportions (%) of activated Phospho-STAT3 immunoreactive among total STAT3 cells; the numbers in brackets indicate the number of STAT-3 cells quantified for each duration of leptin exposure.
Mentions: To explore whether detected ObRb mRNA expression corresponds to the presence of functional leptin receptors, we first studied if leptin could alter STAT3 expression and phosphorylation in SVZ neurospheres by double immunocytochemistry and confocal microscopy. In both control and leptin-treated neurospheres, unphosphorylated (inactive) STAT3 was expressed only in MAP2-immunoreactive, i.e., neuronal cells; reciprocally all neuronal cells displayed STAT3 immunoreactivity (Figures 2 C,D,G,H,K,L,O,P). In the absence of leptin, the phosphorylated form of STAT3 (pSTAT3) was almost undetectable in neurosphere cultures (Figures 2A,B). However, leptin triggered rapid and transient STAT3 phosphorylation which peaked 10 min after its addition (Figures 2 E,I,M,Q) and was restricted to MAP2-labeled neuronal cells (Figures 2 E,F,I,J,M,N).

Bottom Line: Leptin-dependent withdrawal of neural stem cells from the cell cycle was associated with increased apoptosis, as detected by TUNEL, which was preceded by cyclin D1 induction.Cyclin-D1 silencing by specific shRNA prevented leptin-induced decrease of the cell number per neurosphere thus pointing to the causal relationship between leptin actions on apoptosis and cyclin D1 induction.The inhibition of neural stem cell expansion via ERK/cyclin D1-triggered apoptosis defines novel biological action of leptin which may be involved in adiposity-dependent neurotoxicity.

View Article: PubMed Central - PubMed

Affiliation: Physiologie de la Reproduction et des Comportements, UMR 85 Institut National de la Recherche Agronomique, Centre INRA de Tours, Université François Rabelais de Tours Nouzilly, France.

ABSTRACT
Adipocyte-derived hormone leptin has been recently implicated in the control of neuronal plasticity. To explore whether modulation of adult neurogenesis may contribute to leptin control of neuronal plasticity, we used the neurosphere assay of neural stem cells derived from the adult rat subventricular zone (SVZ). Endogenous expression of specific leptin receptor (ObRb) transcripts, as revealed by RT-PCR, is associated with activation of both ERK and STAT-3 pathways via phosphorylation of the critical ERK/STAT-3 amino acid residues upon addition of leptin to neurospheres. Furthermore, leptin triggered withdrawal of neural stem cells from the cell cycle as monitored by Ki67 labeling. This effect was blocked by pharmacological inhibition of ERK activation thus demonstrating that ERK mediates leptin effects on neural stem cell expansion. Leptin-dependent withdrawal of neural stem cells from the cell cycle was associated with increased apoptosis, as detected by TUNEL, which was preceded by cyclin D1 induction. Cyclin D1 was indeed extensively colocalized with TUNEL-positive, apoptotic nuclei. Cyclin-D1 silencing by specific shRNA prevented leptin-induced decrease of the cell number per neurosphere thus pointing to the causal relationship between leptin actions on apoptosis and cyclin D1 induction. Leptin target cells in SVZ neurospheres were identified by double TUNEL/phenotypic marker immunocytofluorescence as differentiating neurons mostly. The inhibition of neural stem cell expansion via ERK/cyclin D1-triggered apoptosis defines novel biological action of leptin which may be involved in adiposity-dependent neurotoxicity.

No MeSH data available.


Related in: MedlinePlus