J Korean Ophthalmol Soc.  2012 Aug;53(8):1150-1156. 10.3341/jkos.2012.53.8.1150.

Neuroprotective Effect of Rapamycin in Optic Nerve Transection Model

• Kim SH
• Han YK
• Park KH
• Kim YJ

• KMID: 2215959
• DOI: http://doi.org/10.3341/jkos.2012.53.8.1150

Abstract

PURPOSE
The present study investigated whether rapamycin activated autophagy in retinal ganglion cells (RGC) and evaluated its effect on RGC survival following optic nerve transection (ONT).
METHODS
The activation of autophagy in RGCs after intravitreal injection of rapamycin was evaluated with the immunohistochemical staining of phospho-S6 ribosomal protein. Rapamycin or 0.1% DMSO was injected intravitreally immediately after ONT. At 1 and 2 weeks after ONT, the RGCs were counted. Rapamycin and autophagy inhibitors, 3-methyladenine or Wortmannin were co-injected intravitreally after ONT and the RGCs were counted 1 week later.
RESULTS
Expression of phospho-S6 ribosomal protein was decreased in RGCs after intravitreal injection of rapamycin. The RGC number was significantly higher in the rapamycin group than in the control group 1 week after ONT. However, the RGC number was not different between the 2 groups 2 weeks after ONT. Repeated intravitreal injection of rapamycin at 1-week intervals showed neuroprotection 2 weeks after ONT. The RGC number was not different between the control group and the co-injection group of rapamycin-autophagy inhibitor.
CONCLUSIONS
Activated autophagy by rapamycin was neuroprotective in RGC after ONT.

Keyword

Autophagy; Neuroprotection; Optic nerve transaction; Rapamycin; Retinal ganglion cells

MeSH Terms

Adenine
Androstadienes
Autophagy
Dimethyl Sulfoxide
Intravitreal Injections
Neuroprotective Agents
Optic Nerve
Optic Nerve Injuries
Retinal Ganglion Cells
Ribosomal Proteins
Sirolimus
Adenine
Androstadienes
Dimethyl Sulfoxide
Neuroprotective Agents
Ribosomal Proteins
Sirolimus

Figure

• 

  Figure 1 Immunohistochemistry of phospho-S6 ribosomal protein in retinal ganglion cells. (A) Phospho-S6 ribosomal protein was predominantly expressed in retinal ganglion cells of normal rat retina. (B) Expression of phospho-S6 ribosomal protein was markedly reduced in retinal ganglion cells after intravitreal injection of rapamycin (5 ng/µl).

• 

  Figure 2 Retinal ganglion cells (RGCs) survival 1 week after optic nerve transection (ONT). (A) Intravitreal injection of rapamycin showed neuroprotective effect after ONT (*Mann-Whitney test, p < 0.01). RGCs were retrogradely labeled in the control group (B) and the rapamycin injection group (C).

• 

  Figure 3 Effect of rapamycin for retinal ganglion cells (RGC) survival 2 weeks after optic nerve transaction (ONT). (A) Repeated intravitreal injection of rapamycin showed neuroprotection at 2 weeks after ONT (*One-way ANOVA, post Hoc Tukey test, p < 0.05). RGCs were retrogradely labeled in the control group (B), the rapamycin single injection group (C), and the rapamycin additional injection group (D).

• 

  Figure 4 Retinal ganglion cells survival 1 week after optic nerve transection (ONT) and co-injection of rapamycin and autophagy inhibitors; 3-methyladenine (3-MA) or Wortmannin (A). RGCs were retrogradely labeled in the control group (B), the co-injection group of rapamycin and 3-MA (C) and the co-injection group of rapamycin and Wortmannin (D).

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