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Activation of BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells after damage in vivo.

Ueki Y, Reh TA - PLoS ONE (2012)

Bottom Line: During this period, BMP2, -4 and -7 were upregulated, leading to phosphorylation of the downstream effector, Smad1/5/8 in the inner retina, including in retinal ganglion cells.Co-injection of BMP inhibitors with NMDA effectively blocked the damage-induced BMP-Smad1/5/8 activation and led to further cell death of retinal ganglion cells, when compared with NMDA injection alone.Moreover, treatment of the retina with exogenous BMP4 along with NMDA damage led to a significant rescue of retinal ganglion cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Structure, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
While the essential role of bone morphogenetic protein (BMP) signaling in nervous system development is well established, its function in the adult CNS is poorly understood. We investigated the role of BMP signaling in the adult mouse retina following damage in vivo. Intravitreal injection of N-methyl-D-aspartic acid (NMDA) induced extensive retinal ganglion cell death by 2 days. During this period, BMP2, -4 and -7 were upregulated, leading to phosphorylation of the downstream effector, Smad1/5/8 in the inner retina, including in retinal ganglion cells. Expression of Inhibitor of differentiation 1 (Id1; a known BMP-Smad1/5/8 target) was also upregulated in the retina. This activation of BMP-Smad1/5/8 signaling was also observed following light damage, suggesting that it is a general response to retinal injuries. Co-injection of BMP inhibitors with NMDA effectively blocked the damage-induced BMP-Smad1/5/8 activation and led to further cell death of retinal ganglion cells, when compared with NMDA injection alone. Moreover, treatment of the retina with exogenous BMP4 along with NMDA damage led to a significant rescue of retinal ganglion cells. These data demonstrate that BMP-Smad1/5/8 signaling is neuroprotective for retinal ganglion cells after damage, and suggest that stimulation of this pathway can serve as a potential target for neuroprotective therapies in retinal ganglion cell diseases, such as glaucoma.

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Injection of BMP4 or inhibitors of BMP along with NMDA potentiates or decreases, respectively, Smad1/5/8 activation without affecting Smad2/3 signaling.Smad1/5/8 and Smad2/3 activation was detected 2 days after the injection of indicated factors by immunohistochemistry. A lower dose of NMDA (10 mM) sufficiently activates both Smad1/5/8 and Smad2/3 in the inner retina. Injection of BMP4 along with NMDA caused a small increase in pSmad1/5/8 over the NMDA alone. When NMDA was co-injected with DM, Smad1/5/8 phosphorylation was blocked effectively without affecting Smad2/3 activation. Co-injection with an additional BMP signaling inhibitor, noggin (Nog), completely blocked Smad1/5/8 activation, and caused slight reduction in pSmad2/3. ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganclion cell layer. Scale bars: 30 µm. Representative images from at least 3 animals per treatment are shown.
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pone-0038690-g005: Injection of BMP4 or inhibitors of BMP along with NMDA potentiates or decreases, respectively, Smad1/5/8 activation without affecting Smad2/3 signaling.Smad1/5/8 and Smad2/3 activation was detected 2 days after the injection of indicated factors by immunohistochemistry. A lower dose of NMDA (10 mM) sufficiently activates both Smad1/5/8 and Smad2/3 in the inner retina. Injection of BMP4 along with NMDA caused a small increase in pSmad1/5/8 over the NMDA alone. When NMDA was co-injected with DM, Smad1/5/8 phosphorylation was blocked effectively without affecting Smad2/3 activation. Co-injection with an additional BMP signaling inhibitor, noggin (Nog), completely blocked Smad1/5/8 activation, and caused slight reduction in pSmad2/3. ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganclion cell layer. Scale bars: 30 µm. Representative images from at least 3 animals per treatment are shown.

Mentions: To assess the specificity of the BMP receptor inhibitors, we analyzed sections of retinas for pSmad1/5/8 and pSmad2/3 after intravitreal injections of NMDA alone, BMP4 co-injection with NMDA, or NMDA treatment with co-injection of the BMP receptor blocker, DM and the natural BMP inhibitor, noggin (Figure 5). In untreated retinas, there is typically a low level of pSmad1/5/8 labeling in the ganglion cell layer (Figure 5), but cells in the inner nuclear layer are not labeled. Either a low dose (10 mM; Figure 5) or a high dose (100 mM; Figure 2A) of NMDA treatment induced robust labeling of both pSmad1/5/8 and pSmad2/3 after 2 days, particularly in cells of the inner nuclear layer (Figure 5, arrows). Co-injection with BMP4 caused a small, but reproducible increase in the pSmad1/5/8 labeled cells, but no change in pSmad2/3. Co-injection of NMDA with either DM or the combination of DM and noggin, led to a marked inhibition in the number of pSmad1/5/8 labeled cells in the INL, but this treatment had only a slight effect on the pSmad 2/3 labeling. These data confirm the specificity of the BMP inhibitors for this pathway, and also demonstrate that the combination of DM and noggin is most effective for complete inhibition of BMP signaling after NMDA damage.


Activation of BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells after damage in vivo.

Ueki Y, Reh TA - PLoS ONE (2012)

Injection of BMP4 or inhibitors of BMP along with NMDA potentiates or decreases, respectively, Smad1/5/8 activation without affecting Smad2/3 signaling.Smad1/5/8 and Smad2/3 activation was detected 2 days after the injection of indicated factors by immunohistochemistry. A lower dose of NMDA (10 mM) sufficiently activates both Smad1/5/8 and Smad2/3 in the inner retina. Injection of BMP4 along with NMDA caused a small increase in pSmad1/5/8 over the NMDA alone. When NMDA was co-injected with DM, Smad1/5/8 phosphorylation was blocked effectively without affecting Smad2/3 activation. Co-injection with an additional BMP signaling inhibitor, noggin (Nog), completely blocked Smad1/5/8 activation, and caused slight reduction in pSmad2/3. ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganclion cell layer. Scale bars: 30 µm. Representative images from at least 3 animals per treatment are shown.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3368846&req=5

pone-0038690-g005: Injection of BMP4 or inhibitors of BMP along with NMDA potentiates or decreases, respectively, Smad1/5/8 activation without affecting Smad2/3 signaling.Smad1/5/8 and Smad2/3 activation was detected 2 days after the injection of indicated factors by immunohistochemistry. A lower dose of NMDA (10 mM) sufficiently activates both Smad1/5/8 and Smad2/3 in the inner retina. Injection of BMP4 along with NMDA caused a small increase in pSmad1/5/8 over the NMDA alone. When NMDA was co-injected with DM, Smad1/5/8 phosphorylation was blocked effectively without affecting Smad2/3 activation. Co-injection with an additional BMP signaling inhibitor, noggin (Nog), completely blocked Smad1/5/8 activation, and caused slight reduction in pSmad2/3. ONL, outer nuclear layer; INL, inner nuclear layer; GCL, ganclion cell layer. Scale bars: 30 µm. Representative images from at least 3 animals per treatment are shown.
Mentions: To assess the specificity of the BMP receptor inhibitors, we analyzed sections of retinas for pSmad1/5/8 and pSmad2/3 after intravitreal injections of NMDA alone, BMP4 co-injection with NMDA, or NMDA treatment with co-injection of the BMP receptor blocker, DM and the natural BMP inhibitor, noggin (Figure 5). In untreated retinas, there is typically a low level of pSmad1/5/8 labeling in the ganglion cell layer (Figure 5), but cells in the inner nuclear layer are not labeled. Either a low dose (10 mM; Figure 5) or a high dose (100 mM; Figure 2A) of NMDA treatment induced robust labeling of both pSmad1/5/8 and pSmad2/3 after 2 days, particularly in cells of the inner nuclear layer (Figure 5, arrows). Co-injection with BMP4 caused a small, but reproducible increase in the pSmad1/5/8 labeled cells, but no change in pSmad2/3. Co-injection of NMDA with either DM or the combination of DM and noggin, led to a marked inhibition in the number of pSmad1/5/8 labeled cells in the INL, but this treatment had only a slight effect on the pSmad 2/3 labeling. These data confirm the specificity of the BMP inhibitors for this pathway, and also demonstrate that the combination of DM and noggin is most effective for complete inhibition of BMP signaling after NMDA damage.

Bottom Line: During this period, BMP2, -4 and -7 were upregulated, leading to phosphorylation of the downstream effector, Smad1/5/8 in the inner retina, including in retinal ganglion cells.Co-injection of BMP inhibitors with NMDA effectively blocked the damage-induced BMP-Smad1/5/8 activation and led to further cell death of retinal ganglion cells, when compared with NMDA injection alone.Moreover, treatment of the retina with exogenous BMP4 along with NMDA damage led to a significant rescue of retinal ganglion cells.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Structure, University of Washington, Seattle, Washington, United States of America.

ABSTRACT
While the essential role of bone morphogenetic protein (BMP) signaling in nervous system development is well established, its function in the adult CNS is poorly understood. We investigated the role of BMP signaling in the adult mouse retina following damage in vivo. Intravitreal injection of N-methyl-D-aspartic acid (NMDA) induced extensive retinal ganglion cell death by 2 days. During this period, BMP2, -4 and -7 were upregulated, leading to phosphorylation of the downstream effector, Smad1/5/8 in the inner retina, including in retinal ganglion cells. Expression of Inhibitor of differentiation 1 (Id1; a known BMP-Smad1/5/8 target) was also upregulated in the retina. This activation of BMP-Smad1/5/8 signaling was also observed following light damage, suggesting that it is a general response to retinal injuries. Co-injection of BMP inhibitors with NMDA effectively blocked the damage-induced BMP-Smad1/5/8 activation and led to further cell death of retinal ganglion cells, when compared with NMDA injection alone. Moreover, treatment of the retina with exogenous BMP4 along with NMDA damage led to a significant rescue of retinal ganglion cells. These data demonstrate that BMP-Smad1/5/8 signaling is neuroprotective for retinal ganglion cells after damage, and suggest that stimulation of this pathway can serve as a potential target for neuroprotective therapies in retinal ganglion cell diseases, such as glaucoma.

Show MeSH
Related in: MedlinePlus