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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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BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells in vivo after NMDA damage.A. Retinas were collected 2 days after NMDA injection (10 mM or 100 mM) with or without indicated factors, and then immunostained for Brn3, a marker for retinal ganglion cells. Representative images of retinal flatmouts are shown. Scale bar: 100 µm. B. Brn3+ cells were counted in random flatmount fields. In 10 mM NMDA damage, there were significantly more Brn3+ cells when BMP4 was co-injected with NMDA. On the other hand, co-injection of BMP inhibitors (NMDA+DM+Noggin) showed a significant reduction in Brn3+ cells compared to NMDA injection alone. The same trend was observed for the more severe NMDA damage (100 mM). *p<0.01 (t-test). Number of retinas analyzed for each treatment is shown in B.
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pone-0038690-g006: BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells in vivo after NMDA damage.A. Retinas were collected 2 days after NMDA injection (10 mM or 100 mM) with or without indicated factors, and then immunostained for Brn3, a marker for retinal ganglion cells. Representative images of retinal flatmouts are shown. Scale bar: 100 µm. B. Brn3+ cells were counted in random flatmount fields. In 10 mM NMDA damage, there were significantly more Brn3+ cells when BMP4 was co-injected with NMDA. On the other hand, co-injection of BMP inhibitors (NMDA+DM+Noggin) showed a significant reduction in Brn3+ cells compared to NMDA injection alone. The same trend was observed for the more severe NMDA damage (100 mM). *p<0.01 (t-test). Number of retinas analyzed for each treatment is shown in B.

Mentions: The increase in BMP signaling in the inner retina after retinal injury is similar to previously reported changes in other neuroprotective growth factors, such as CNTF [2], [3], [4], [5]. Therefore, we assessed whether BMP could also act as a neuroprotectant in the retina. We tested this possibility for BMP after NMDA induced ganglion cell death (Figure 6). Mice received intravitreal injections of mild or high doses of NMDA: 10 mM or 100 mM. Some animals also received co-injections of BMP4, DM, or the combination of DM and noggin. As noted above, intravitreal injection of 100 mM NMDA caused the death of almost 90% of the Brn3+ ganglion cells (276.5±29.6 Brn3+ cells/mm2 for 100 mM NMDA and 2409.5±149.9 Brn3+ cells/mm2 for untreated control) (Figure 6B). Although 10 mM NMDA injection resulted in less damage, approximately 80% of the Brn3+ cells were lost with the lower dose (560.8±84.3 Brn3+ cells/mm2 for 10 mM NMDA), Nevertheless, co-injection of BMP4 with either concentration of NMDA protected ganglion cells (Figure 6 A–B). In the higher dose of NMDA, the protection afforded by the BMP4 was more variable (940.8±398.9 Brn3+ cells/mm2), and did not reach statistical significance; however, the neuroprotective effect of BMP4 was statistically significant in the 10 mM treatment group (1107.0±167.7 Brn3+ cells/mm2) (Figure 6B).


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

Ueki Y, Reh TA - PLoS ONE (2012)

BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells in vivo after NMDA damage.A. Retinas were collected 2 days after NMDA injection (10 mM or 100 mM) with or without indicated factors, and then immunostained for Brn3, a marker for retinal ganglion cells. Representative images of retinal flatmouts are shown. Scale bar: 100 µm. B. Brn3+ cells were counted in random flatmount fields. In 10 mM NMDA damage, there were significantly more Brn3+ cells when BMP4 was co-injected with NMDA. On the other hand, co-injection of BMP inhibitors (NMDA+DM+Noggin) showed a significant reduction in Brn3+ cells compared to NMDA injection alone. The same trend was observed for the more severe NMDA damage (100 mM). *p<0.01 (t-test). Number of retinas analyzed for each treatment is shown in B.
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Related In: Results  -  Collection

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pone-0038690-g006: BMP-Smad1/5/8 signaling promotes survival of retinal ganglion cells in vivo after NMDA damage.A. Retinas were collected 2 days after NMDA injection (10 mM or 100 mM) with or without indicated factors, and then immunostained for Brn3, a marker for retinal ganglion cells. Representative images of retinal flatmouts are shown. Scale bar: 100 µm. B. Brn3+ cells were counted in random flatmount fields. In 10 mM NMDA damage, there were significantly more Brn3+ cells when BMP4 was co-injected with NMDA. On the other hand, co-injection of BMP inhibitors (NMDA+DM+Noggin) showed a significant reduction in Brn3+ cells compared to NMDA injection alone. The same trend was observed for the more severe NMDA damage (100 mM). *p<0.01 (t-test). Number of retinas analyzed for each treatment is shown in B.
Mentions: The increase in BMP signaling in the inner retina after retinal injury is similar to previously reported changes in other neuroprotective growth factors, such as CNTF [2], [3], [4], [5]. Therefore, we assessed whether BMP could also act as a neuroprotectant in the retina. We tested this possibility for BMP after NMDA induced ganglion cell death (Figure 6). Mice received intravitreal injections of mild or high doses of NMDA: 10 mM or 100 mM. Some animals also received co-injections of BMP4, DM, or the combination of DM and noggin. As noted above, intravitreal injection of 100 mM NMDA caused the death of almost 90% of the Brn3+ ganglion cells (276.5±29.6 Brn3+ cells/mm2 for 100 mM NMDA and 2409.5±149.9 Brn3+ cells/mm2 for untreated control) (Figure 6B). Although 10 mM NMDA injection resulted in less damage, approximately 80% of the Brn3+ cells were lost with the lower dose (560.8±84.3 Brn3+ cells/mm2 for 10 mM NMDA), Nevertheless, co-injection of BMP4 with either concentration of NMDA protected ganglion cells (Figure 6 A–B). In the higher dose of NMDA, the protection afforded by the BMP4 was more variable (940.8±398.9 Brn3+ cells/mm2), and did not reach statistical significance; however, the neuroprotective effect of BMP4 was statistically significant in the 10 mM treatment group (1107.0±167.7 Brn3+ cells/mm2) (Figure 6B).

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