Role of C/EBP homologous protein in retinal ganglion cell death after ischemia/reperfusion injury.

Abstract

PURPOSE:

To investigate the role of C/EBP homologous protein (CHOP), a proapoptotic protein, and the unfolded protein response (UPR) marker that is involved in endoplasmic reticulum (ER) stress-mediated apoptosis in mouse retinal ganglion cell (RGC) death following ischemia/reperfusion (I/R) injury.

METHODS:

Retinal I/R injury was induced in adult C57BL/6J wild-type (WT) and CHOP knockout (Chop(-/-)) mice by raising IOP to 120 mm Hg for 60 minutes. Expression of CHOP and other UPR markers was studied by Western blot and immunohistochemistry. Retinal ganglion cell counts were performed in retinal flat mounts stained with an RGC marker. Retinal ganglion cell function was evaluated by scotopic threshold response (STR) electroretinography.

RESULTS:

In WT mice, retinal CHOP was upregulated by 30% in I/R-injured eyes compared to uninjured eyes 3 days after injury (P < 0.05). Immunohistochemistry confirmed CHOP upregulation specifically in RGCs. CHOP knockout did not affect baseline RGC density or STR amplitude. Ischemia/reperfusion injury decreased RGC densities and STR amplitudes in both WT and Chop(-/-) mice. However, survival of RGCs in I/R-injured Chop(-/-) mouse was 48% higher (P < 0.05) than that in I/R-injured WT mouse 3 days after I/R injury. Similarly, RGC density was significantly higher in Chop(-/-) eyes at 7, 14, and 28 days after I/R injury. Scotopic threshold response amplitudes of Chop(-/-) mice were significantly higher at 3 and 7 days after I/R than those of WT mice.

CONCLUSIONS:

Absence of CHOP partially protects against RGC loss and reduction in retinal function after I/R injury, indicating that CHOP and, thus, ER stress play an important role in RGC apoptosis in retinal I/R injury.

• Authors: Sonali Nashine, Yang Liu, Byung-Jin Kim, Abbot F Clark, Iok-Hou Pang
• Journal: Investigative ophthalmology & visual science (Invest Ophthalmol Vis Sci) Vol. 56 Issue 1 Pg. 221-31 (Nov 20 2014) ISSN: 1552-5783 [Electronic] United States
• PMID: 25414185 (Publication Type: Journal Article, Research Support, U.S. Gov't, Non-P.H.S.)
• Copyright: Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Chemical References

• DDIT3 protein, human
• Transcription Factor CHOP
• RNA

Topics

• Animals
• Blotting, Western
• Cell Death
• Cells, Cultured
• Disease Models, Animal
• Electroretinography
• Endoplasmic Reticulum Stress
• Gene Expression Regulation
• Genotype
• Immunohistochemistry
• Mice
• Mice, Inbred C57BL
• RNA (genetics)
• Real-Time Polymerase Chain Reaction
• Reperfusion Injury (genetics, metabolism, pathology)
• Retinal Ganglion Cells (metabolism, pathology)
• Transcription Factor CHOP (biosynthesis, genetics)