Inhibition of neuroretinal cell death by insulin-like growth factor-1 and its analogs.
OBJECTIVE
Visual loss secondary to retinal ischemia/hypoxia can be a serious complication of diabetic retinopathy, as well as other vascular insults. We used R28 retinal precursor cells, as well as primary rat retinal cell cultures, to test whether the neuroprotective growth factor IGF-1 would protect retinal cells from dying under conditions of hypoxia or serum-starvation. We also utilized three IGF-1 analogs ([LongR3], [Ala31], and [Leu24][Ala31]) with altered affinities for the IGF-1 receptor and/or IGF-1 binding proteins in order to address the mechanism(s) of IGF-1 neuroprotection.


METHODS
Retinal cultures were subjected to hypoxia (95% N2/5% CO2 for 0-8 h), or serum-starvation (0% serum for 48 h). Experimental cultures were pre-treated for 24 h with 0-100 ng/ml of IGF-1 or its analogs. Retinal cultures were analyzed for the extent of cell death by trypan blue exclusion assay, TUNEL in situ, as well as ssDNA analysis specific for apoptosis.


RESULTS
IGF-1 and all three IGF-1 analogs tested were able to inhibit neuroretinal cell death at a concentration of 50 ng/ml. Neuroprotection was evident under conditions of hypoxia or serum-starvation.


CONCLUSIONS
IGF-1, as well as IGF-1 analogs, improves survival of neuroretinal cells in vitro, under conditions of hypoxia or serum-starvation. Since all three IGF-1 analogs inhibit cell death to some degree, we interpret these results to mean that IGF-1-mediated inhibition of cell death does not depend upon strong affinities for the IGF-1 receptor or IGF-1 binding proteins. Further studies will reveal additional information as to the pathways responsible for IGF-1-mediated neuroprotection of retinal cells.
Seigel
G M
GM
Department of Neurobiology and Anatomy, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA. GAIL_SEIGEL@urmc.rochester.edu
Chiu
L
L
Paxhia
A
A
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D002478:Cells, Cultured; D016895:Culture Media, Serum-Free; D000860:Hypoxia / Q000150:complications; D020287:In Situ Nick-End Labeling; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000378:metabolism / Q000494:pharmacology*; D009924:Organ Culture Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D017526:Receptor, IGF Type 1 / Q000378:metabolism; D012160:Retina / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D014343:Trypan Blue
D016895:Culture Media, Serum-Free; D018970:Insulin-Like Growth Factor Binding Protein 1; D018696:Neuroprotective Agents; D007334:Insulin-Like Growth Factor I; D017526:Receptor, IGF Type 1; D014343:Trypan Blue