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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 inhibits proliferation and triggers cell death of SVZ neurospheres. (A) Photomicrographs of DAPI staining (top row) and Ki-67 green immunocytofluorescence (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. (B) Photomicrographs of DAPI staining (top row) and TUNEL green cytofluorescent staining (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. Histograms represent the proportions of Ki-67 (A) or TUNEL (B) positive nuclei expressed as % of the total cell number (as determined by DAPI staining) by taking as a reference 100% the values obtained for the control condition. Data are expressed as mean percent of control ± SEM. Statistical significancies at *p < 0.05 or ***p < 0.001.
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Figure 5: Leptin inhibits proliferation and triggers cell death of SVZ neurospheres. (A) Photomicrographs of DAPI staining (top row) and Ki-67 green immunocytofluorescence (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. (B) Photomicrographs of DAPI staining (top row) and TUNEL green cytofluorescent staining (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. Histograms represent the proportions of Ki-67 (A) or TUNEL (B) positive nuclei expressed as % of the total cell number (as determined by DAPI staining) by taking as a reference 100% the values obtained for the control condition. Data are expressed as mean percent of control ± SEM. Statistical significancies at *p < 0.05 or ***p < 0.001.

Mentions: The observed leptin-mediated increase of cyclin D1 (Figure 4) appeared paradoxical in the light of our findings concerning the inhibition of neurosphere neural cell proliferation by leptin (Figure 1). To understand the mechanism behind such paradoxical effect of leptin, we checked directly leptin effects on the cell cycle by immunocytochemical analysis of Ki-67 labeling. This marker is expressed by cycling cells in any phase of the cell cycle but not by quiescent cells (Scholzen and Gerdes, 2000). In the absence of leptin, the majority of cells (about 60% of the total cell population as identified by DAPI-staining of their nuclei) were in the cell division cycle (Figure 5A). Addition of leptin resulted in a significant decrease in the proportion of the Ki-67-positive cells as compared to control cultures (Figure 5A).


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 inhibits proliferation and triggers cell death of SVZ neurospheres. (A) Photomicrographs of DAPI staining (top row) and Ki-67 green immunocytofluorescence (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. (B) Photomicrographs of DAPI staining (top row) and TUNEL green cytofluorescent staining (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. Histograms represent the proportions of Ki-67 (A) or TUNEL (B) positive nuclei expressed as % of the total cell number (as determined by DAPI staining) by taking as a reference 100% the values obtained for the control condition. Data are expressed as mean percent of control ± SEM. Statistical significancies at *p < 0.05 or ***p < 0.001.
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Related In: Results  -  Collection

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Figure 5: Leptin inhibits proliferation and triggers cell death of SVZ neurospheres. (A) Photomicrographs of DAPI staining (top row) and Ki-67 green immunocytofluorescence (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. (B) Photomicrographs of DAPI staining (top row) and TUNEL green cytofluorescent staining (lower row) in control (no leptin) and 6.2 nM leptin-treated neurosphere cultures at 5 DIV. Histograms represent the proportions of Ki-67 (A) or TUNEL (B) positive nuclei expressed as % of the total cell number (as determined by DAPI staining) by taking as a reference 100% the values obtained for the control condition. Data are expressed as mean percent of control ± SEM. Statistical significancies at *p < 0.05 or ***p < 0.001.
Mentions: The observed leptin-mediated increase of cyclin D1 (Figure 4) appeared paradoxical in the light of our findings concerning the inhibition of neurosphere neural cell proliferation by leptin (Figure 1). To understand the mechanism behind such paradoxical effect of leptin, we checked directly leptin effects on the cell cycle by immunocytochemical analysis of Ki-67 labeling. This marker is expressed by cycling cells in any phase of the cell cycle but not by quiescent cells (Scholzen and Gerdes, 2000). In the absence of leptin, the majority of cells (about 60% of the total cell population as identified by DAPI-staining of their nuclei) were in the cell division cycle (Figure 5A). Addition of leptin resulted in a significant decrease in the proportion of the Ki-67-positive cells as compared to control cultures (Figure 5A).

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