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Bone morphogenetic protein-4 interacts with activin and GnRH to modulate gonadotrophin secretion in LbetaT2 gonadotrophs.

Nicol L, Faure MO, McNeilly JR, Fontaine J, Taragnat C, McNeilly AS - J. Endocrinol. (2008)

Bottom Line: BMP-4 reduced LHbeta mRNA up-regulation in response to GnRH (+/-activin) and decreased GnRH receptor expression, which would favour FSH, rather than LH, synthesis and secretion.This was associated with increased FSHbeta mRNA levels and FSH secretion, but decreased LHbeta mRNA levels.These results confirm 1.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Reproductive Sciences Unit, The Queen's Medical Research Institute, Centre for Reproductive Biology, 47 Little France Crescent, Edinburgh, EH16 4TJ UK. l.nicol@hrsu.mrc.ac.uk

ABSTRACT
We have shown previously that, in sheep primary pituitary cells, bone morphogenetic proteins (BMP)-4 inhibits FSHbeta mRNA expression and FSH release. In contrast, in mouse LbetaT2 gonadotrophs, others have shown a stimulatory effect of BMPs on basal or activin-stimulated FSHbeta promoter-driven transcription. As a species comparison with our previous results, we used LbetaT2 cells to investigate the effects of BMP-4 on gonadotrophin mRNA and secretion modulated by activin and GnRH. BMP-4 alone had no effect on FSH production, but enhanced the activin+GnRH-induced stimulation of FSHbeta mRNA and FSH secretion, without any effect on follistatin mRNA. BMP-4 reduced LHbeta mRNA up-regulation in response to GnRH (+/-activin) and decreased GnRH receptor expression, which would favour FSH, rather than LH, synthesis and secretion. In contrast to sheep pituitary gonadotrophs, which express only BMP receptor types IA (BMPRIA) and II (BMPRII), LbetaT2 cells also express BMPRIB. Smad1/5 phosphorylation induced by BMP-4, indicating activation of BMP signalling, was the same whether BMP-4 was used alone or combined with activin+/-GnRH. We hypothesized that activin and/or GnRH pathways may be modulated by BMP-4, but neither the activin-stimulated phosphorylation of Smad2/3 nor the GnRH-induced ERK1/2 or cAMP response element-binding phosphorylation were modified. However, the GnRH-induced activation of p38 MAPK was decreased by BMP-4. This was associated with increased FSHbeta mRNA levels and FSH secretion, but decreased LHbeta mRNA levels. These results confirm 1. BMPs as important modulators of activin and/or GnRH-stimulated gonadotrophin synthesis and release and 2. important species differences in these effects, which could relate to differences in BMP receptor expression in gonadotrophs.

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Effects of BMP-4 on gonadotrophin secretion and FSHβ and LHβ mRNA expression. (A) FSH and (C) LH secreted on day 3 from LβT2 cells cultured with 0 or 50 ng/ml BMP-4 in the presence and absence of 50 ng/ml activin A±a daily 1 h pulse of 10 nM GnRH for 3 days were measured by RIA. Results represent total hormone secreted during the 1 h GnRH treatment and the subsequent overnight incubation; n=5. (B) FSHβ and (D) LHβ mRNA levels on day 4 in LβT2 cells, cultured as described, were measured by Taqman quantitative RT-PCR; n=3. Different letters indicate significant differences between treatment groups. Values represent means±s.e.m. from one representative experiment. Five experiments were performed with similar results.
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fig2: Effects of BMP-4 on gonadotrophin secretion and FSHβ and LHβ mRNA expression. (A) FSH and (C) LH secreted on day 3 from LβT2 cells cultured with 0 or 50 ng/ml BMP-4 in the presence and absence of 50 ng/ml activin A±a daily 1 h pulse of 10 nM GnRH for 3 days were measured by RIA. Results represent total hormone secreted during the 1 h GnRH treatment and the subsequent overnight incubation; n=5. (B) FSHβ and (D) LHβ mRNA levels on day 4 in LβT2 cells, cultured as described, were measured by Taqman quantitative RT-PCR; n=3. Different letters indicate significant differences between treatment groups. Values represent means±s.e.m. from one representative experiment. Five experiments were performed with similar results.

Mentions: To determine whether BMP-4 was capable of modifying gonadotrophin production and secretion in LβT2 gonadotrophs, cells given activin ±a daily 1 h pulse of GnRH for three days were also treated with BMP-4. Secretion profiles for FSH and LH, representing the total protein secreted during day 3 GnRH treatment and the subsequent overnight incubation, and the corresponding day 4 β-subunit mRNA levels are shown in Fig. 2. As expected, FSH secretion increased (P<0·001) in response to activin and this effect was increased synergistically (P<0·001) in the presence of GnRH, although GnRH alone had no effect (Fig. 2A). While BMP-4 alone had no effect on FSH secretion, it increased the release of FSH in response to activin and activin+GnRH (P<0·01 and P<0·001 respectively). Similarly, the FSHβ mRNA expression was up-regulated by activin (P<0·05) and this effect was also increased synergistically by GnRH (P<0·001; Fig. 2B). BMP-4 alone, or in combination with activin or GnRH, had no effect on FSHβ mRNA, but it further increased activin+GnRH-stimulated mRNA levels (P<0·01).


Bone morphogenetic protein-4 interacts with activin and GnRH to modulate gonadotrophin secretion in LbetaT2 gonadotrophs.

Nicol L, Faure MO, McNeilly JR, Fontaine J, Taragnat C, McNeilly AS - J. Endocrinol. (2008)

Effects of BMP-4 on gonadotrophin secretion and FSHβ and LHβ mRNA expression. (A) FSH and (C) LH secreted on day 3 from LβT2 cells cultured with 0 or 50 ng/ml BMP-4 in the presence and absence of 50 ng/ml activin A±a daily 1 h pulse of 10 nM GnRH for 3 days were measured by RIA. Results represent total hormone secreted during the 1 h GnRH treatment and the subsequent overnight incubation; n=5. (B) FSHβ and (D) LHβ mRNA levels on day 4 in LβT2 cells, cultured as described, were measured by Taqman quantitative RT-PCR; n=3. Different letters indicate significant differences between treatment groups. Values represent means±s.e.m. from one representative experiment. Five experiments were performed with similar results.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2262182&req=5

fig2: Effects of BMP-4 on gonadotrophin secretion and FSHβ and LHβ mRNA expression. (A) FSH and (C) LH secreted on day 3 from LβT2 cells cultured with 0 or 50 ng/ml BMP-4 in the presence and absence of 50 ng/ml activin A±a daily 1 h pulse of 10 nM GnRH for 3 days were measured by RIA. Results represent total hormone secreted during the 1 h GnRH treatment and the subsequent overnight incubation; n=5. (B) FSHβ and (D) LHβ mRNA levels on day 4 in LβT2 cells, cultured as described, were measured by Taqman quantitative RT-PCR; n=3. Different letters indicate significant differences between treatment groups. Values represent means±s.e.m. from one representative experiment. Five experiments were performed with similar results.
Mentions: To determine whether BMP-4 was capable of modifying gonadotrophin production and secretion in LβT2 gonadotrophs, cells given activin ±a daily 1 h pulse of GnRH for three days were also treated with BMP-4. Secretion profiles for FSH and LH, representing the total protein secreted during day 3 GnRH treatment and the subsequent overnight incubation, and the corresponding day 4 β-subunit mRNA levels are shown in Fig. 2. As expected, FSH secretion increased (P<0·001) in response to activin and this effect was increased synergistically (P<0·001) in the presence of GnRH, although GnRH alone had no effect (Fig. 2A). While BMP-4 alone had no effect on FSH secretion, it increased the release of FSH in response to activin and activin+GnRH (P<0·01 and P<0·001 respectively). Similarly, the FSHβ mRNA expression was up-regulated by activin (P<0·05) and this effect was also increased synergistically by GnRH (P<0·001; Fig. 2B). BMP-4 alone, or in combination with activin or GnRH, had no effect on FSHβ mRNA, but it further increased activin+GnRH-stimulated mRNA levels (P<0·01).

Bottom Line: BMP-4 reduced LHbeta mRNA up-regulation in response to GnRH (+/-activin) and decreased GnRH receptor expression, which would favour FSH, rather than LH, synthesis and secretion.This was associated with increased FSHbeta mRNA levels and FSH secretion, but decreased LHbeta mRNA levels.These results confirm 1.

View Article: PubMed Central - PubMed

Affiliation: MRC Human Reproductive Sciences Unit, The Queen's Medical Research Institute, Centre for Reproductive Biology, 47 Little France Crescent, Edinburgh, EH16 4TJ UK. l.nicol@hrsu.mrc.ac.uk

ABSTRACT
We have shown previously that, in sheep primary pituitary cells, bone morphogenetic proteins (BMP)-4 inhibits FSHbeta mRNA expression and FSH release. In contrast, in mouse LbetaT2 gonadotrophs, others have shown a stimulatory effect of BMPs on basal or activin-stimulated FSHbeta promoter-driven transcription. As a species comparison with our previous results, we used LbetaT2 cells to investigate the effects of BMP-4 on gonadotrophin mRNA and secretion modulated by activin and GnRH. BMP-4 alone had no effect on FSH production, but enhanced the activin+GnRH-induced stimulation of FSHbeta mRNA and FSH secretion, without any effect on follistatin mRNA. BMP-4 reduced LHbeta mRNA up-regulation in response to GnRH (+/-activin) and decreased GnRH receptor expression, which would favour FSH, rather than LH, synthesis and secretion. In contrast to sheep pituitary gonadotrophs, which express only BMP receptor types IA (BMPRIA) and II (BMPRII), LbetaT2 cells also express BMPRIB. Smad1/5 phosphorylation induced by BMP-4, indicating activation of BMP signalling, was the same whether BMP-4 was used alone or combined with activin+/-GnRH. We hypothesized that activin and/or GnRH pathways may be modulated by BMP-4, but neither the activin-stimulated phosphorylation of Smad2/3 nor the GnRH-induced ERK1/2 or cAMP response element-binding phosphorylation were modified. However, the GnRH-induced activation of p38 MAPK was decreased by BMP-4. This was associated with increased FSHbeta mRNA levels and FSH secretion, but decreased LHbeta mRNA levels. These results confirm 1. BMPs as important modulators of activin and/or GnRH-stimulated gonadotrophin synthesis and release and 2. important species differences in these effects, which could relate to differences in BMP receptor expression in gonadotrophs.

Show MeSH
Related in: MedlinePlus