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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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NMDA damage induces expression of Id1, a known target of BMP-Smad1/5/8 signaling.A. Representative images from at least 3 animals per treatment are shown. Injection of 100 mM NMDA induced Id1 expression (red) in Hes5-GFP+ Müller cells (green). Id1 expression was blocked by coinjection of BMP inhibitors, LDN-193189 (LDN) or dorsomorphin (DM). Scale bar: 50 µm. B. Representative Western blot showing the level of Id1 expression 2 days after injection of the indicated factors. C. Quantification of the Western blots. More than a 2 fold increase in Id1 expression was observed after NMDA damage, and this increase was blocked effectively by LDN or DM. The level of Id1 expression was normalized to beta-actin. *p<0.05 (t-test; n = 3 retinas).
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pone-0038690-g003: NMDA damage induces expression of Id1, a known target of BMP-Smad1/5/8 signaling.A. Representative images from at least 3 animals per treatment are shown. Injection of 100 mM NMDA induced Id1 expression (red) in Hes5-GFP+ Müller cells (green). Id1 expression was blocked by coinjection of BMP inhibitors, LDN-193189 (LDN) or dorsomorphin (DM). Scale bar: 50 µm. B. Representative Western blot showing the level of Id1 expression 2 days after injection of the indicated factors. C. Quantification of the Western blots. More than a 2 fold increase in Id1 expression was observed after NMDA damage, and this increase was blocked effectively by LDN or DM. The level of Id1 expression was normalized to beta-actin. *p<0.05 (t-test; n = 3 retinas).

Mentions: To verify that the increase in BMP signaling we observe with the pSmad1/5/8 antibody is able to activate known targets of this pathway, we assayed Id1, a well-characterized downstream target of BMP/Smad1/5/8 (Figure 3) [28], [29]. Id1 is not detectable in the undamaged retina, but NMDA damage induces robust labeling of Id1 two days after the NMDA treatment. As for the pSmad1/5/8, the Id1 expression is present in the nuclei of Hes5-GFP+ Müller glia (Figure 3A). The addition of either of two different well-characterized BMP receptor inhibitors, LDN-193189 (LDN) or dorsomorphin (DM), substantially reduced the NMDA-induced expression of Id1 in Müller glia. Western blot analysis supported the results we observed in retinal sections (Figure 3B–C). NMDA treatment caused a significant increase in the level of Id1 in the retina (approximately 2.5 fold increase compared to NT) (Figure 3C) and this was almost completely blocked by co-injection of either LDN-193189 or DM.


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

Ueki Y, Reh TA - PLoS ONE (2012)

NMDA damage induces expression of Id1, a known target of BMP-Smad1/5/8 signaling.A. Representative images from at least 3 animals per treatment are shown. Injection of 100 mM NMDA induced Id1 expression (red) in Hes5-GFP+ Müller cells (green). Id1 expression was blocked by coinjection of BMP inhibitors, LDN-193189 (LDN) or dorsomorphin (DM). Scale bar: 50 µm. B. Representative Western blot showing the level of Id1 expression 2 days after injection of the indicated factors. C. Quantification of the Western blots. More than a 2 fold increase in Id1 expression was observed after NMDA damage, and this increase was blocked effectively by LDN or DM. The level of Id1 expression was normalized to beta-actin. *p<0.05 (t-test; n = 3 retinas).
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Related In: Results  -  Collection

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pone-0038690-g003: NMDA damage induces expression of Id1, a known target of BMP-Smad1/5/8 signaling.A. Representative images from at least 3 animals per treatment are shown. Injection of 100 mM NMDA induced Id1 expression (red) in Hes5-GFP+ Müller cells (green). Id1 expression was blocked by coinjection of BMP inhibitors, LDN-193189 (LDN) or dorsomorphin (DM). Scale bar: 50 µm. B. Representative Western blot showing the level of Id1 expression 2 days after injection of the indicated factors. C. Quantification of the Western blots. More than a 2 fold increase in Id1 expression was observed after NMDA damage, and this increase was blocked effectively by LDN or DM. The level of Id1 expression was normalized to beta-actin. *p<0.05 (t-test; n = 3 retinas).
Mentions: To verify that the increase in BMP signaling we observe with the pSmad1/5/8 antibody is able to activate known targets of this pathway, we assayed Id1, a well-characterized downstream target of BMP/Smad1/5/8 (Figure 3) [28], [29]. Id1 is not detectable in the undamaged retina, but NMDA damage induces robust labeling of Id1 two days after the NMDA treatment. As for the pSmad1/5/8, the Id1 expression is present in the nuclei of Hes5-GFP+ Müller glia (Figure 3A). The addition of either of two different well-characterized BMP receptor inhibitors, LDN-193189 (LDN) or dorsomorphin (DM), substantially reduced the NMDA-induced expression of Id1 in Müller glia. Western blot analysis supported the results we observed in retinal sections (Figure 3B–C). NMDA treatment caused a significant increase in the level of Id1 in the retina (approximately 2.5 fold increase compared to NT) (Figure 3C) and this was almost completely blocked by co-injection of either LDN-193189 or DM.

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