Effect of GDNF on neuroblast proliferation and photoreceptor survival: additive protection with docosahexaenoic acid.
OBJECTIVE
In a previous study, it was reported that docosahexaenoic acid (DHA) is essential to postpone apoptosis and to promote differentiation of rat retina photoreceptors in vitro. In the current study, the protective effects of GDNF on photoreceptor cells during development in vitro and its action when combined with DHA were investigated.


METHODS
Rat retina neuronal cultures were incubated in a chemically defined medium, either without photoreceptor survival factors or supplemented with GDNF, DHA, or GDNF plus DHA. Evolution of survival, apoptosis, opsin expression, mitochondrial functioning, and cell proliferation were investigated at different times of development in vitro.


RESULTS
Incubation with GDNF selectively increased the number of surviving photoreceptors, reduced their apoptosis, and augmented opsin expression. Proliferative cell nuclei antigen (PCNA) determination and addition of [(3)H]-thymidine or bromodeoxyuridine showed that GDNF promoted neuroblast proliferation during the first hours of development in vitro. The combined addition of GDNF and DHA enhanced opsin expression and photoreceptor survival in an additive manner. The advance of photoreceptor apoptosis in cultures without trophic factors correlated with an increased impairment in mitochondrial functionality. Addition of GDNF and DHA significantly diminished the loss of mitochondrial activity.


CONCLUSIONS
These results show that GDNF stimulated the cell cycle progression, leading to neuroblast proliferation at early stages of development, and delayed the onset of apoptosis later on, improving differentiation and acting as a trophic factor for photoreceptors. The combination of GDNF with DHA had an additive effect both on photoreceptor survival and on opsin expression. Preservation of mitochondrial function may be involved in the antiapoptotic effect of both factors.
Politi
L E
LE
Instituto de Investigaciones Bioquímicas de Bahía Blanca and Universidad Nacional del Sur Buenos Aires, Argentina. inpoliti@criba.edu.ar
Rotstein
N P
NP
Carri
N G
NG
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002453:Cell Cycle / Q000187:drug effects; D002454:Cell Differentiation / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D056746:Cyclin G; D056766:Cyclin G1; D016213:Cyclins / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004281:Docosahexaenoic Acids / Q000494:pharmacology*; D004338:Drug Combinations; D004357:Drug Synergism; D051100:Glial Cell Line-Derived Neurotrophic Factor; D008928:Mitochondria / Q000502:physiology; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins / Q000494:pharmacology*; D020419:Photoreceptor Cells, Vertebrate / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017299:Rod Opsins / Q000378:metabolism
C534704:Ccng1 protein, rat; D056746:Cyclin G; D056766:Cyclin G1; D016213:Cyclins; D004338:Drug Combinations; C495041:Gdnf protein, rat; D051100:Glial Cell Line-Derived Neurotrophic Factor; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D018809:Proliferating Cell Nuclear Antigen; D017299:Rod Opsins; D004281:Docosahexaenoic Acids; D004247:DNA