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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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Intravitreal injection of NMDA results in death of retinal ganglion cells and amacrine cells by 2 days.A. Images of retinal cross sections (left column) and flatmounts (right 3 columns) are shown. Neurotoxic damage induced by 100 mM NMDA injection caused a reduction in Brn3+ (red) retinal ganglion cells and HuC/D+ amacrine (green) cells compared to untreated (NT) or vehicle injected (PBS) retinas by 2 days after injection. GFAP, a marker for retinal damage, was also upregulated at 2 days. Scale bars: 100 µm. B. Brn3+ cells were counted in random flatmount fields. At 2 days after NMDA injection, there was a significant reduction in Brn3+ cells (276.5±29.6 Brn3+ cells/mm2) compared to NT retinas (2409.5±149.9 Brn3+ cells/mm2). No further reduction in Brn3+ cells was observed at 5d after NMDA injection (273.7±29.6 Brn3+ cells/mm2). Therefore, we collected eyes 2 days after injection for the rest of the study. *p<0.005 with t-test.
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pone-0038690-g001: Intravitreal injection of NMDA results in death of retinal ganglion cells and amacrine cells by 2 days.A. Images of retinal cross sections (left column) and flatmounts (right 3 columns) are shown. Neurotoxic damage induced by 100 mM NMDA injection caused a reduction in Brn3+ (red) retinal ganglion cells and HuC/D+ amacrine (green) cells compared to untreated (NT) or vehicle injected (PBS) retinas by 2 days after injection. GFAP, a marker for retinal damage, was also upregulated at 2 days. Scale bars: 100 µm. B. Brn3+ cells were counted in random flatmount fields. At 2 days after NMDA injection, there was a significant reduction in Brn3+ cells (276.5±29.6 Brn3+ cells/mm2) compared to NT retinas (2409.5±149.9 Brn3+ cells/mm2). No further reduction in Brn3+ cells was observed at 5d after NMDA injection (273.7±29.6 Brn3+ cells/mm2). Therefore, we collected eyes 2 days after injection for the rest of the study. *p<0.005 with t-test.

Mentions: Previous studies have shown that intravitreal injections of NMDA cause rapid death of retinal ganglion cells [25], [26]. To confirm these earlier studies, we made injections of high dose of NMDA (100 mM) into the vitreal chamber of adult mice, and analyzed the retinas 2–5 days later in sections and flatmounts. We found that by 2 days after the NMDA treatment, there was already a substantial reduction in the number of Brn3+ retinal ganglion cells (276.5±29.6 Brn3+ cells/mm2), when compared with uninjected (2409.5±149.9 Brn3+ cells/mm2) or PBS injected control retinas (2277.6±59.0 Brn3+ cells/mm2) (Figure 1A–B). There was a similar reduction in the number of another marker of ganglion and amacrine cells, HuC/D [27], in the NMDA treated retinas. Both Brn3 and HuC/D showed similar declines after 5 days (273.7±29.6 Brn3+ cells/mm2) (Figure 1A–B). The reduction in the number of ganglion cells was paralleled by an increase in the expression of GFAP, a marker for retinal damage, in the Müller glial cells (Figure 1A). These results indicate that intravitreal injections of 100 mM NMDA induce rapid death of retinal ganglion cells in adult mice.


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

Ueki Y, Reh TA - PLoS ONE (2012)

Intravitreal injection of NMDA results in death of retinal ganglion cells and amacrine cells by 2 days.A. Images of retinal cross sections (left column) and flatmounts (right 3 columns) are shown. Neurotoxic damage induced by 100 mM NMDA injection caused a reduction in Brn3+ (red) retinal ganglion cells and HuC/D+ amacrine (green) cells compared to untreated (NT) or vehicle injected (PBS) retinas by 2 days after injection. GFAP, a marker for retinal damage, was also upregulated at 2 days. Scale bars: 100 µm. B. Brn3+ cells were counted in random flatmount fields. At 2 days after NMDA injection, there was a significant reduction in Brn3+ cells (276.5±29.6 Brn3+ cells/mm2) compared to NT retinas (2409.5±149.9 Brn3+ cells/mm2). No further reduction in Brn3+ cells was observed at 5d after NMDA injection (273.7±29.6 Brn3+ cells/mm2). Therefore, we collected eyes 2 days after injection for the rest of the study. *p<0.005 with t-test.
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Related In: Results  -  Collection

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pone-0038690-g001: Intravitreal injection of NMDA results in death of retinal ganglion cells and amacrine cells by 2 days.A. Images of retinal cross sections (left column) and flatmounts (right 3 columns) are shown. Neurotoxic damage induced by 100 mM NMDA injection caused a reduction in Brn3+ (red) retinal ganglion cells and HuC/D+ amacrine (green) cells compared to untreated (NT) or vehicle injected (PBS) retinas by 2 days after injection. GFAP, a marker for retinal damage, was also upregulated at 2 days. Scale bars: 100 µm. B. Brn3+ cells were counted in random flatmount fields. At 2 days after NMDA injection, there was a significant reduction in Brn3+ cells (276.5±29.6 Brn3+ cells/mm2) compared to NT retinas (2409.5±149.9 Brn3+ cells/mm2). No further reduction in Brn3+ cells was observed at 5d after NMDA injection (273.7±29.6 Brn3+ cells/mm2). Therefore, we collected eyes 2 days after injection for the rest of the study. *p<0.005 with t-test.
Mentions: Previous studies have shown that intravitreal injections of NMDA cause rapid death of retinal ganglion cells [25], [26]. To confirm these earlier studies, we made injections of high dose of NMDA (100 mM) into the vitreal chamber of adult mice, and analyzed the retinas 2–5 days later in sections and flatmounts. We found that by 2 days after the NMDA treatment, there was already a substantial reduction in the number of Brn3+ retinal ganglion cells (276.5±29.6 Brn3+ cells/mm2), when compared with uninjected (2409.5±149.9 Brn3+ cells/mm2) or PBS injected control retinas (2277.6±59.0 Brn3+ cells/mm2) (Figure 1A–B). There was a similar reduction in the number of another marker of ganglion and amacrine cells, HuC/D [27], in the NMDA treated retinas. Both Brn3 and HuC/D showed similar declines after 5 days (273.7±29.6 Brn3+ cells/mm2) (Figure 1A–B). The reduction in the number of ganglion cells was paralleled by an increase in the expression of GFAP, a marker for retinal damage, in the Müller glial cells (Figure 1A). These results indicate that intravitreal injections of 100 mM NMDA induce rapid death of retinal ganglion cells in adult mice.

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