In vitro and in vivo neuroprotective effects of cJun N-terminal kinase inhibitors on retinal ganglion cells.
BACKGROUND
The c-Jun N-terminal kinase (JNK) signaling pathway plays an important role in neuronal pathophysiology. Using JNK inhibitors, we examined involvement of the JNK pathway in cultured rat retinal ganglion cell (RGC) death and in mouse retinal ischemia/reperfusion (I/R) injury of the visual axis. The in vitro effects of JNK inhibitors were evaluated in cultured adult rat retinal cells enriched in RGCs. Retinal I/R was induced in C57BL/6J mice through elevation of intraocular pressure to 120 mmHg for 60 min followed by reperfusion. SP600125 was administered intraperitoneally once daily for 28 days. Phosphorylation of JNK and c-Jun in the retina was examined by immunoblotting and immunohistochemistry. The thickness of retinal layers and cell numbers in the ganglion cell layer (GCL) were examined using H&E stained retinal cross sections and spectral domain optical coherence tomography (SD-OCT). Retinal function was measured by scotopic flash electroretinography (ERG). Volumetric measurement of the superior colliculus (SC) as well as VGLUT2 and PSD95 expression were studied.


RESULTS
JNK inhibitors SP600125 and TAT-JNK-III, dose-dependently and significantly (p < 0.05) protected against glutamate excitotoxicity and trophic factor withdrawal induced RGC death in culture. In the I/R model, phosphorylation of JNK (pJNK) in the retina was significantly (p < 0.05) increased after injury. I/R injury significantly (p < 0.05) decreased the thickness of retinal layers, including the whole retina, inner plexiform layer, and inner nuclear layer and cell numbers in the GCL. Administration of SP600125 for 28 days protected against all these degenerative morphological changes (p < 0.05). In addition, SP600125 significantly (p < 0.05) protected against I/R-induced reduction in scotopic ERG b-wave amplitude at 3, 7, 14, 21 and 28 days after injury. SP600125 also protected against the I/R-induced losses in volume and levels of synaptic markers in the SC. Moreover, the protective effects of SP600125 in the retina and SC were also detected even with only 7 days (Days 1-7 after I/R) of SP600125 treatment.


CONCLUSIONS
Our results demonstrate the important role the JNK pathway plays in retinal degeneration in both in vitro and in vivo models and suggest that JNK inhibitors may be a useful therapeutic strategy for neuroprotection of RGCs in the retina.
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA.|Department of Pharmaceutical Sciences, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.|Present Address: Department of Ophthalmology, Johns Hopkins University School of Medicine, 400 N. Broadway, Baltimore, MD, 21231, USA.
Byung-Jin
BJ
Kim
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA.|Department of Cell Biology & Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.
Sean M
SM
Silverman
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA.|Department of Pharmaceutical Sciences, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.|Department of Cell Biology & Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.
Yang
Y
Liu
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA.|Department of Cell Biology & Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.
Robert J
RJ
Wordinger
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA.|Department of Pharmaceutical Sciences, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA.
Iok-Hou
IH
Pang
North Texas Eye Research Institute, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76109, USA. abe.clark@unthsc.edu.|Department of Cell Biology & Immunology, University of North Texas Health Science Center, Fort Worth, TX, 76107, USA. abe.clark@unthsc.edu.
Abbot F
AF
Clark
D000818:Animals; D000873:Anthracenes / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D004195:Disease Models, Animal; D005260:Female; D007429:Intraocular Pressure / Q000502:physiology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018696:Neuroprotective Agents / Q000494:pharmacology*; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000378:metabolism; D012160:Retina / Q000378:metabolism*; D012164:Retinal Diseases / Q000378:metabolism*; D012165:Retinal Ganglion Cells / Q000378:metabolism*
D000873:Anthracenes; D018696:Neuroprotective Agents; C432165:pyrazolanthrone; D048031:JNK Mitogen-Activated Protein Kinases
Electroretinography; JNK inhibitors; Retinal ganglion cells; Retinal ischemia; c-Jun N-terminal kinase (JNK)